Oxytocin Revisited - Its Role in Cardiovascular Regulation

REVIEW ARTICLE

Oxytocin Revisited: Its Role in Cardiovascular RegulationJ. Gutkowska and M. Jankowski

Laboratory of Cardiovascular Biochemistry, Centre de recherche, Centre hospitalier de l’Universite de Montreal (CRCHUM) – Hotel-Dieu and Department of

Medicine, Universite de Montreal, Montreal, Quebec, Canada.

Historical background

Interest in the cardiovascular action of pituitary extracts dates back

more than 100 years. Oliver and Schafer (1) demonstrated the

vasoconstrictive and hypertensive effects of pituitary extracts in

1895. Howell (2) concluded that glycerine and saline extracts of the

pituitary anterior lobe produced little or no change in blood pres-

sure (BP) and heart rate, and that the data of Oliver and Schafer

were a result of substance(s) residing in the gland’s posterior lobe.

Later, in 1906, Sir Henry Dale (3) determined that i.v. injection of

ox posterior pituitary gland extracts into cats caused uterine con-

tractions. Further studies, by Dale (4), extended these observations

on posterior pituitary extract properties and suggested that: ‘It does

not seem justifiable ... to draw the conclusion that the principle

acting on the plain muscle of the uterus is different from that

which acts on the arteries’.

Kamm et al. (5), Gaddum (6) and Fraser (7) reported a wide

diversity of physiological effects of neurohypophyseal extracts and

presented conclusive evidence with fractional precipitation of two

active ‘principles’: one producing BP elevation in dogs and the other

stimulating uterine muscle contractions in guinea-pigs. These hor-

mones were later isolated as vasopressin (AVP) and oxytocin (OT),

respectively. A few years later, Ott and Scott (8) established that,

besides their impact on the uterus, posterior pituitary extracts pro-

moted milk flow by mammary myo-epithelial cell contraction in lac-

tating goats, both considered as principal properties of OT. The

molecular structures of OT and AVP were elucidated by Du Vig-

neaud et al. in the 1950s (9). Since these early studies, it has been

widely accepted that AVP and OT, known as neurohypophyseal hor-

mones, are not only important to the central nervous system (CNS),

but also have physiological actions in peripheral organs. Several

other investigations have disclosed that OT is an ubiquitous hor-

mone, occurring also in males. A similar number of OTergic neuro-

nes have been detected in the brains of males and females, and

stimuli, such as heightened osmotic pressure, gastric distention,

and mating-induced OT release, occur in both genders. These obser-

vations suggested physiological functions of this hormone in addi-

tion to its role in female reproduction.

Journal ofNeuroendocrinology

Correspondence to:

J. Gutkowska, Laboratory of

Cardiovascular Biochemistry, Centre

de recherche, Centre hospitalier de

l’Universite de Montreal (CRCHUM) –

Hotel-Dieu and Department of

Medicine, Universite de Montreal,

3850 St. Urbain Street, Masson

Pavilion, Montreal, Quebec H2W 1T8,

Canada (e-mail:

[email protected]).

Traditionally associated with female reproduction, oxytocin (OT) was revisited recently and was

revealed to have several new roles in the cardiovascular system. Functional OT receptors have

been discovered in the rat and human heart, as well as in vascular beds. The cardiovascular

activities of OT include: (i) lowering blood pressure; (ii) negative cardiac inotropy and chronotro-

py; (iii) parasympathetic neuromodulation; (iv) vasodilatation; (v) anti-inflammatory; (vi) antioxi-

dative; and (vii) metabolic effects. These outcomes are mediated, at least in part, by stimulating

cardioprotective mediators, such as nitric oxide and atrial natriuretic peptide. OT and its

extended form OT-Gly-Lys-Arg have been shown to be abundant in the foetal mouse heart. OT

has the capacity to generate cardiomyocytes from various types of stem cells, including the car-

diac side population. Mesenchymal cells transfected with OT-Gly-Lys-Arg, or preconditioned with

OT, are resistant to apoptosis and express endothelial cell markers. OT increases glucose uptake

in cultured cardiomyocytes from newborn and adult rats, in normal, hypoxic and even insulin

resistance conditions. In rats with experimentally-induced myocardial infarction, continuous in

vivo OT delivery improves the cardiac healing process, as well as cardiac work, reduces inflam-

mation and stimulates angiogenesis. Therefore, in pathological conditions, OT exerts anti-inflam-

matory and cardioprotective properties, and improves vascular and metabolic functions. Thus, OT

has potential for therapeutic use.

Key words: oxytocin, natriuretic peptides, heart, cardiomyogenesis.

doi: 10.1111/j.1365-2826.2011.02235.x

Journal of Neuroendocrinology, 2012, 24, 599–608

ª 2011 The Authors.

Journal of Neuroendocrinology ª 2011 Blackwell Publishing Ltd

In the 1940–1950s, OT was associated with the cardiovascular

system, and it has been shown that OT exerts depressor activity in

various species, including humans (10). It was reported that BP

reduction, after OT, weakens cardiac contraction, an effect consid-

ered to be secondary to vasodilatation (10–12). Several studies

determined that posterior pituitary extracts elicit chloruretic and

natriuretic actions, modifying renal haemodynamics (13). However,

the data obtained were conflicting because the impact of OT on the

urine flow rate was not similar in all species, depending on the

position of subjects, seated or upright, and the doses tested. For a

long time, there was no explanation of the mechanism by which OT

may regulate kidney functions. An important point in these studies

was reported by Sedlakova et al. (14) who investigated the effects

of OT injected into the systemic circulation and into the renal vein

of dogs. Their findings indicated that the renal outcomes of OT

were not a result of its direct action on the kidneys but rather to

the release of some intracranial natriuretic substance, which directly

increases tubular sodium excretion. Parallel to these studies, several

groups of researchers observed that the brain plays a role in the

regulation of kidney functions.

OT was revisited at the turn of the millennium. New techniques,

such as gene deletion, have been developed, and it has become

clear that OT is essential for milk ejection but not for parturition or

reproductive behaviour. Females, with a deleted OT gene, manifest

no deficit in fertility or reproduction; they demonstrate maternal

behaviour, although their offspring cannot survive because of the

dams’ inability to nurse (15). New evidence has been presented that

OT is involved in a complex range of behaviours, such as maternal,

social, sexual and feeding behaviours, memory, learning, pair bond-

ing and immunological processes. At the same time, new data point

to mechanisms of OT involvement in cardiovascular regulation

(16,17).

Neural control of hydromineral homeostasis

The role of the CNS in the control of body fluid homeostasis has

been studied by several groups. In the early 1950s, Anderson and

McCann (18) reported that microinjection of hypertonic saline into

the hypothalamus of goats induced polydipsia. A similar effect was

observed with electrical stimulation of the same area. Subsequently,

Andersson et al. (19) determined that saline microinjection into the

third ventricle (3V) and its anteroventral portion (AV3V) evoked

marked natriuresis. Therefore, various transmitters in the control of

water, salt and food intake were investigated in the brain. All these

studies provided clear evidence that the 3V area is part of the neu-

ronal circuitry involved in the regulation of renal water and sodium

intake and excretion. The hypothalamic-neurohypophyseal system is

important in the maintenance of body fluid homeostasis by secret-

ing AVP and OT in response to osmotic and non-osmotic stimuli.

Low blood volume and hypernatraemia are major stimuli that gen-

erate AVP in supraoptic and paraventricular nuclei of the hypothal-

amus. Hypothalamic osmoreceptors sense rising extracellular

osmolarity and evoke AVP release, as occurs with dehydration.

Peripheral osmoreceptors are found in the portal veins. Barorecep-

tors located in the left atrium, carotid sinus and aortic arch detect

arterial underfilling, which stimulates neurones in supraoptic and

paraventricular nuclei to produce AVP. Unlike osmoreceptors, baro-

receptors must be suppressed to stimulate AVP release, and this

inhibition in turn comes after a fall in BP. By contrast, after blood

volume expansion (BVE), which activates baroreceptors, several neu-

ral, behavioural and hormonal mechanisms work in concert to inhi-

bit water and salt ingestion and to increase natriuresis and urine

flow. The mechanism of this control was not, however, well-under-

stood until the discovery of natriuretic peptides (NPs) provided a

potent defence mechanism against volume overload in mammals,

including humans (20).

Natriuretic peptides

During the 1960s, much attention was paid to the possible exis-

tence of natriuretic hormones. The idea emerged from the experi-

ments of DeWardener and Clarkson (21), disclosing that natriuresis

during BVE occurs without an increase in the glomerular filtration

rate or changes in aldosterone secretion. This was later confirmed

by Davis and Freeman (22). Cort et al. (23) reported the purification

of a hypothalamic natriuretic factor and claimed it was an OT ana-

logue. Subsequently, evidence was obtained that a natriuretic factor

resides in the hypothalamus and could be related to OT. Morris

et al. (24) evaluated the effects of median eminence lesions on

natriuretic responses to volume expansion and pharmacological

stimulation of the 3V area. Indeed, median eminence lesions

blocked the natriuretic and kaliuretic responses to volume expan-

sion and other 3V area stimulations. Median eminence destruction

interrupted the supraoptic-hypophyseal tract and, consequently,

eliminated the secretion of both neurohypophyseal hormones, AVP

and OT. These experiments suggested that the lesions interrupted

the release of natriuretic hormones involved in centrally-induced

natriuresis. Still, no explanation is forthcoming as to how kidney

functions are regulated centrally.

The breakthrough came from the discovery in 1981 of atrial

natriuretic peptide (ANP) by De Bold et al. (20). ANP is a potent

diuretic and natriuretic hormone isolated from the heart. The dis-

covery of natriuretic hormones was preceded by the pioneering

experiments of Gauer and Henry (25) showing that atrial dilatation

produces diuresis. Water head-out immersion has been known to

trigger diuresis since ancient times. Immersion in water most prob-

ably increases venous return to the heart and dilates the atria, sub-

sequently augmenting ANP release and diuresis.

After the discovery of ANP, other NPs were isolated: brain natri-

uretic peptide (BNP) from porcine brain tissues (26) and C-type

natriuretic peptide, mainly synthesised in the CNS (27). The NP sys-

tem consists of three main ligands and three receptor types. These

peptides evoke a wide variety of physiological responses, such as

diuresis, natriuresis, vasodilatation, renin-angiotensin and aldoste-

rone system inhibition, and thereby regulate BP as well as blood

volume (28). Both ANP and BNP control vasculature permeability,

suppress smooth muscle cell, mesangial cell and cardiac fibroblast

proliferation, and curb cardiac hypertrophy. They are released into

the circulation in response to BP elevation, volume expansion and

some pharmacological agents (28). Accumulating evidence indicates

600 J. Gutkowska and M. Jankowski

ª 2011 The Authors. Journal of Neuroendocrinology, 2012, 24, 599–608


that they act as autocrine and ⁄ or paracrine factors at the site of

synthesis.

Moreover, NPs, through inhibition of various hypertrophic signal-

ling pathways in cardiac cells, protect against myocardial injury and

heart failure. HS-142-1, an antagonist of ANP-transducing recep-

tors, increases basal and phenylephrine-stimulated protein synthe-

sis, augments cardiomyocyte (CM) size and enhances the expression

level of genes coding for skeletal actin, b-myosin heavy chain and

ANP, which are all markers of cardiac hypertrophy, in cultured neo-

natal rat ventricular myocytes (29). NPs inhibit DNA synthesis in fi-

broblasts under pathological conditions (30).

NPs are ubiquitous hormones expressed in many tissues, includ-

ing the brain. It is interesting that the brain area involved in cen-

trally-induced natriuresis is also rich in ANP-secreting neurones

(31). Therefore, it was hypothesised that, during mechanical and

pharmacological stimulation of the AV3V area, ANP release is

responsible for diuresis and natriuresis. Indeed, stimulation of the

AV3V region by carbachol, a cholinergic drug, had an expected

diuretic effect, accompanied by a 25-fold rise in plasma ANP con-

centration, which was still significant after 40 min. Carbachol stim-

ulation increased ANP content in several neuronal structures, such

as the medial basal hypothalamus, neurohypophysis and anterior

hypophysis, without any effect on ANP content in the lungs or

heart. Conversely, plasma ANP declined dramatically at both 24

and 120 h after AV3V lesions. The changes in plasma ANP were

accompanied by reduced ANP content in several brain structures:

medial basal hypothalamus, median eminence, neurohypophysis,

anterior hypophysis-choroid plexus and olfactory bulbs (32). All

these structures in the CNS, related to water and electrolyte bal-

ance, expressed ANP and its receptors. However, the amount of

ANP found in such tissues was far too low to induce its major

secretion into plasma. Therefore, we postulated that neural control

of electrolyte secretion might be mediated by hypothalamic natri-

uretic hormones from the neurohypophysis responsible for ANP

release from the heart and subsequent diuresis. To substantiate

this hypothesis, we tested the rat BVE model because it is already

known that volume expansion is the most effective stimulus of

ANP efflux.

Neuronal circuit

Our studies on stimulation and destruction of the AV3V, the site of

perikarya of ANP neurones, and median eminence, indicated that

CNS participation is critical to ANP release in response to BVE (33).

During BVE, we observed neuronal circuitry activation involving car-

diac-aortic and renal baroreceptors, muscarinic and a-adrenergic

synapses, ANPnergic neurones and the ascending serotonergic sys-

tem, leading to ANP release, represented diagrammatically in Fig. 1.

The role of baroreceptors has been evaluated in the ANP

response to BVE. Plasma ANP was significantly decreased 1 week

after the de-afferentation of carotid-aortic baroreceptors, and the

response to BVE was greatly reduced compared to sham-operated

controls. Similar results were obtained in rats that underwent renal

de-afferentation: the ANP reaction to BVE was suppressed. Bilateral

vagotomy did not interfere with ANP responses to BVE. These data

suggested that carotid-aortic and renal baroreceptor impulses are

important pathways that mediate ANP release (34). Blockade of

cholinergic-muscarinic synapses with atrophine sulphate, and a1

receptors with phentolamine, before BVE, markedly suppressed ANP,

indicating that muscarinic and a-adrenergic synapses are essential

to ANP liberation (35).

To determine the possible role of the serotoninergic system,

because the AV3V region receives important afferent input from

ascending serotoninergic axons, BVE was performed in rats in

which the dorsal raphe nucleus, the site of perikarya of serotonin-

ergic (5-HT) neurones, was destroyed by electrolytic lesions or

depleted of 5-HT with lateral ventricular injection of p-chlorophe-

nylalanine (36). In the absence of the serotonergic system, anti-

natriuresis occurred with no ANP release, suggesting that the

5-HTergic pathway to AV3V participates in controlling BVE-induced

ANP liberation and the ensuing natriuresis. One possible pathway is

stimulatory 5-HT input into the ANPnergic neuronal system, which,

consequently, could activate OTergic neurones in supraoptic nuclei

projecting to the neural lobe. Hypophysectomy and posterior lobec-

tomy completely inhibited ANP responses to BVE, indicating that a

factor originating in the posterior hypophysis is responsible for ANP

release (33). Intraperitoneal or i.v. injection of OT into rats not only

increased sodium excretion, but also concomitantly elevated plasma

ANP (37,38). Thus, it became clear that, during BVE, activation of

the neuronal circuitry elicited OT secretion into the circulation,

ANPn

ACHn

RN

H2O

NEn

PPAP

OT

OTR

ANP

AoBr

Na+

K+

NTS

KBr

5-HTn

LC

ATBr

OTn

Fig. 1. Discovery of the cardiac oxytonin (OT) system: experiments in vol-

ume-expanded animals indicated the role of OT in atrial natriuretic peptide

(ANP) release. AoBr, aortic baroreceptors; ATBr, atrial baroreceptors; KBr, kid-

ney baroreceptors; NEn, norepinephrinergic neurones; DRN, dorsal raphe

nucleus; 5-HTn, serotoninergic neurones; LC, locus ceruleus; NTS, nucleus

tractus solitarius; ACHn, cholinergic neurones; ANPn, ANPergic neurones;

ONn, oxytocinergic neurones; AP, anterior pituitary; PP, posterior pituitary;

OTR, oxytocin receptors.

Role of OT in cardiovascular regulation 601

Journal of Neuroendocrinology, 2012, 24, 599–608 ª 2011 The Authors.


where it reached the atria, invoking atrial OT receptors (OTR) and

ANP release from the heart.

OT system in the heart

Both OT and its receptors are found in the heart and large vessels

(39–41). The OTR gene is expressed at various sites of the reproduc-

tive tract, which is considered to be the main action of OT, although

it has also been demonstrated in other tissues, such as the kidneys,

mammary glands, thymus and several brain areas (42). OTR have

been cloned and shown to be a member of the subclass of G-pro-

tein-coupled receptors (43). OTR in the rat heart appear to be identi-

cal to those in the uterus and other organs (39). The presence of OTR

in rat and human hearts was detected by a reverse transcriptase-

polymerase chain reaction (PCR) and by in situ hybridisation, autora-

diography of atrial and ventricular sections, and confirmed by a

competitive binding assay (39,44). The functionality of heart OTR was

demonstrated by the ability of OT to release ANP from the isolated,

perfused rat heart (40). The addition of OT (10)6M) to perfusion

buffer resulted in enhanced ANP liberation. The heart rate was

decreased significantly by 10)6M OT during perfusion, and this

decline was reversed by OT antagonist (OTA) 10)6M.

Interestingly, the addition of 10)6M OTA to perfusion buffer

inhibited OT-stimulated ANP release, making it lower than in con-

trol animals and indicating OT synthesis in the heart (39,45). The

ability of OTA to reduce basal ANP liberation from atria incubated

in vitro (45) and from perfused hearts supports the hypothesis that

these effects could be physiologically relevant.

An OT gene transcript has been detected by amplification of rat

cDNA by PCR of all heart chambers. The highest OT concentration,

measured by radioimmunoassay (RIA), was found in the right

atrium and was comparable to the OT concentration in the hypo-

thalamus (40), whereas the lowest levels in the heart occurred in

the ventricles. Amplified fragments of OT gene from the rat heart

were identical in size to those in the uterus. Furthermore, in vitro

studies showed OT release from rat atrial CMs.

Cardiovascular effects of OT

Systemic administration of OT has significant outcomes on BP, vas-

cular tone and cardiovascular regulation. Conversely, the absence of

either OT or its receptors in knockout mice has not been reported

to produce cardiac insufficiency (46). Although OT knockout mice

have a normal heart structure, experiments have recorded aug-

mented intrinsic heart rates in these animals, indicating that an

intracardiac OT system controls cardiac electrical activity (47).

Accumulating evidence points to multiple beneficial effects in

the heart and vasculature. To date, the cardiovascular properties of

OT include: (i) natriuresis (38) and decreased BP, possibly secondary

to ANP release (16,39); (ii) negative inotrophic and chronotrophic

effects (45,48), as well as parasympathetic neuromodulation (49);

(iii) vasodilatation via the OTR-induced nitric oxide (NO) pathway

and endothelial cell (EC) growth (50,51); (iv) altered insulin (INS)

liberation (52) and anti-diabetic actions (53,54). At the cellular level,

protective OT outcomes comprise: (i) antioxidant actions (55,56); (ii)

inhibition of inflammation (57,58); (iii) potentiation of glucose

uptake in CMs exposed to hypoxia and conditions of insulin resis-

tance (54); (iv) stimulation of endothelial markers in mesenchymal

cells (59) and stem cells, including these isolated from the heart as

a side population (60).

Central, intraventricular infusion of OT is accompanied by BP ele-

vation, an action that is probably associated with the stimulation

of substance P forebrain receptors by OT (61). By contrast, periph-

eral OT administration lowers mean arterial pressure in rats and

does not affect heart rate (16). On the other hand, in the absence

of a central regulatory influence, OT can reduce heart rate and con-

traction strength of the isolated atrium during rat heart perfusion

(45,49). In addition, intracardiac OT stimulating ANP release may

control cardiovascular homeostasis and the body’s internal environ-

ment (39,45).

Recent data indicate that the negative chronotrophic properties

of OT participate in its protective effects on ischaemia-reperfusion-

induced myocardial injury (48). Beneficial cardiac actions could also

be attributed to the fact that OT stimulates ANP release (39), result-

ing in an improvement of hydromineral homeostasis, cardiac hyper-

trophy and balance of anti-inflammatory and pro-inflammatory

cytokines within the injured heart (62). Different cardioprotective

mechanisms of OT were demonstrated recently in animal models of

myocardial infarction. In rat and rabbit models of ischaemic heart

disease, OT treatment significantly reduced infarct size and

improved parameters of heart function (48,59,62–65).

Several OT signalling pathways in cardiac cells have been postu-

lated in conjunction with specific functions in the heart. Figure 2

illustrates hypothetical pathways in the heart that are coupled with

OT-mediated cardioprotection, such as the prevention of apoptosis,

CM hypertrophy and fibrosis, with stimulation of glucose uptake, cell

proliferation and differentiation. In the cardiovascular system, OTR

are associated with the ANP-cGMP and NO-cGMP pathways, which

reduce the force and rate of contraction and increase vasodilatation.

We reported recently that OT augments glucose uptake in CMs via

phosphoinositide-3-kinase (PI3K) and potentiates the glucose uptake

effect of 2,4-dinitrophenol, an uncoupler of oxidative phosphoryla-

tion targeting the mitochondria (54). PI3K pathways are considered

beneficial during myocardial injuries (66–68). The calcium-calmodulin

kinase kinase and AMP-activated protein kinase (AMPK) pathways are

also involved in OT-mediated glucose uptake in CMs (54). AMPK acti-

vation in the heart after ischemia and reperfusion is recognised as

cardioprotective because it limits both apoptosis and cell damage

(68–70). We should also consider p38 MAPK and extracellular signal-

regulated kinase 1 ⁄ 2 (ERK1 ⁄ 2) phosphorylation, which may contrib-

ute to the proliferative activity of OT (71). Recently, in a rabbit model

of myocardial ischaemia-reperfusion, OT treatment induced ERK1 ⁄ 2,

AKT and eNOS phosphorylation in cardiac tissues (65). Therefore, OT,

similar to other G-protein-coupled ligands, can act by PI3K ⁄ AKT acti-

vation and projection onto downstream kinases. Recent studies have

revealed that the cardioprotective effects of OT are mediated through

opening of mitochondrial ATP-dependent potassium channels in the

rat heart (63).

OTR are present in several major cell types that are important in

the progression of vascular pathologies, including vascular smooth




muscle cells, ECs, macrophages and adipocytes (58,62,72,73).

In vitro studies have discerned that OT modulates processes critical

to early lesion formation within vascular and immune tissues (58).

Specifically, OT exerts antioxidant effects on vascular smooth mus-

cle cells, aortic ECs and macrophages through attenuation of

NADPH-oxidase-dependent superoxide production. In vivo, periph-

eral OT administration inhibits atherosclerotic lesions in the thoracic

aorta (73). In addition, OT promotes the migration of human dermal

microvascular endothelial cells, human breast tumour-derived endo-

thelial cells (74) and human umbilical vein endothelial cells (50,75).

The pro-migratory impact of OT requires OTR activation of the

PI3K ⁄ AKT ⁄ eNOS pathway (50). Moreover, OT increases EC prolifera-

tion and alters the gene expression of adhesion molecules as well

as matrix metalloproteinases, contributing to improved cell motility

and growth (74). Angiogenic and anti-apoptotic OT effects are indi-

cated by increased number of cardiac CD31+-expressing microves-

sels (76). In this way, OT can control blood flow to the heart.

OT as natural cardiomyogen

Several studies have proposed a role for OT as a growth and differ-

entiation ⁄ maturation factor in a gestational ⁄ perinatal context.

Accordingly, OT can induce mammalian stem cells into a special cell

type that retains the ability to self-renew indefinitely (i.e. undergo

cell division in an undifferentiated state) and differentiate into

specialised cells. Several observations brought us to the concept

that the OT system could participate in activation of the stem cell

pool residing in the heart and contribute to cardiac regeneration.

Because OT system activation was seen in foetal and newborn

hearts at a stage of intense cardiac hyperplasia (77), we hypothes-

ised a function for OT in CM differentiation.

Initial experiments showed that OT induces CM differentiation of

the mouse embryonal carcinoma P19 cell line, an established cell

model for studying early heart differentiation (78). P19 cells, derived

from a teratocarcinoma in CH3 ⁄ He mice, can differentiate into all

three germ layers (79). Culture and differentiation of cells are sim-

ple: they remain undifferentiated without the help of feeder cells or

inhibitory factors, and, unlike embryonic stem cells, they do not

spontaneously generate CMs. The efficient differentiation of P19

cells depends on the previous formation of non-adhering cell

aggregates (79). Traditionally, cell aggregation in culture suspension

under 0.5–1.0% dimethyl sulfoxide (DMSO) has served to induce

CM differentiation of P19 cells (80). The efficiency of cardiac P19

cell differentiation in vitro is still not optimal in response to various

agents, with yields between 5% and 20% of CMs (78,81–84). In the

P19 cell model, the order of cardiomyogenesis efficiency is OT

OTR

Ras

arrestin

Gαq/11

Raf-1+

MEK 1/2

MEK5

DAG

Calcineurin

PIP2

IP3

PI3K/AKT

CaM

eNOS

sGCNO

EC migration

VasodilatationAnti-apoptoticAnti-hypertrophic

Anti-hypertrophic

Proteinsynthesis

Cellularresponses

Anti-fibrotic

Anti-apoptotic

Proliferation,cardiomyocyte differentiation

Glucose uptake

CaMANP

CaMKK

NPR-A

AMP

ERK5ERK1/2

NFAT-P

NFAT

NFAT,NKx2.5,Gata4,MEF-2C

AMPKAMPK

cGMP

PKC

Ca+2

cyclin D1

eEF2c-jun, c-fos,elk-1

PLC

RTKs

AC

Gs

OTR

cAMP

PKAeEF2 kinase,eEF2 phosphatase

Fig. 2. Schematic diagram of potential signalling pathways of oxytocin receptors (OTRs) in cardiac cells. AC, adenylate cyclase; AMPK, AMP-activated protein

kinase; AKT, serine ⁄ threonine protein kinase Akt; ANP, atrial natriuretic peptide; CaM, calmodulin; CaMKK, Ca2+ ⁄ calmodulin-dependent protein kinase kinase;

CaMK, Ca2+ ⁄ calmodulin-dependent protein kinase; DAG, diacylglycerol; EC, endothelial cells; eEF2, elongation factor-2; ERK, extracellular signal-regulated kinas-

es; IP3, inositol 1,4,5-trisphosphate; MEK5, mitogen-activated protein kinase kinase 5; NFAT, nuclear factor of activated T-cells; NOS, nitric oxide synthase;

PIP2, phosphatidylinositol 4,5-bisphosphate; PKA, protein kinase A; PKC, protein kinase C; PLC, phospholipase C; PI3K, phosphatidyl-3 kinase; TKs, receptor tyro-

sine kinases.




(10)7M) ‡ DMSO > retinoic acid (10)8–10)7

M) when these agents

are added to cultures during the entire period of cell aggregation

(77,78). It is noteworthy that P19 cell exposure to higher retinoic

acid concentration (10)6M) over the aggregation period generates

neurones but not muscle cells. In embryonic D3 stem cells, sponta-

neously-beating cell colonies develop upon aggregation; the meso-

dermal derivatives formed in embryoid bodies include subtypes of

cardiac cells (atrial CMs, ventricular CMs and pacemaker cells),

which are potently enhanced by treatment with OT, as identified by

histological, molecular and electrophysiological criteria (82).

The idea that OT has cardioregenerative capacities derives from

the observation that the hormone induces the differentiation of

cultured resident cardiac stem cells (CSCs) in mice (85) and rats

(60). In the adult heart, CSCs maintain balanced survival, prolifera-

tion and self-renewal to replace mature cells lost during injury or

turnover. Matsuura et al. (85) group discovered the presence of a

Sca-1+ stem cell population in adult mouse hearts expressing telo-

merase reverse transcriptase, which has been associated with self-

renewal potential. These cells, lacking haematopoietic markers, are

easily distinguished from haematopoietic stem cells of bone marrow

origin and, when treated with OT, differentiate into functional CMs.

Although the cells present the early cardiac markers GATA-4 and

mycocyte enhancer factor 2 (MEF2), they do not express Nkx2.5 or

genes encoding cardiac sarcomeric proteins. When exposed to OT, a

small population of Sca-1+ cells manifests sarcomeric structures

and forms spontaneously-beating CMs. In addition, after i.v. deliv-

ery, Sca-1+ CSCs can be recruited to the myocardium injured by

ischemia ⁄ reperfusion and can functionally differentiate in situ (85).

Importantly, these cells express positive ionotropic responses to iso-

proterenol via b1-adrenergic receptor signalling. The apparently

small number of CMs generated in vitro by OT stimulation raises

the question whether or not OT-mediated cardiomyogenesis is a

default pathway for CSCs. Matsuura et al. (85) reported that OT

induced approximately 0.5–1% of Sca-1POS, ckitNEG, CD45NEG cells

from the adult murine heart to differentiate into functional, spon-

taneously-beating, immature CMs. In this regard, cardiac differenti-

ation of Sca-1+ cells does not require cell aggregation for the

process to proceed (85). On the other hand, a study by the same

group in another CSC type isolated from the rat heart (60) dis-

closed that OT treatment resulted in the generation of 5% CMs.

These cells, termed cardiac side population cells (CSPs), but not cor-

responding side population cells isolated from bone marrow, differ-

entiated into CMs in response to OT treatment. Therefore, OT

possesses more powerful cardiogenic activity against CSCs than

reported previously. CSPs have the ability to efflux Hoechst dye, a

process dependent on ABC transporters. CSCs, especially ABCG-2-

dependent CSPs, have been linked with stem ⁄ progenitor cells, which

are positive for ABCG2, Sca-1, ckit (low), CD34 (low), CD45 (low)

and negative for CD31 (57,86). A possible role for CSCs in heart

healing is indicated by increased numbers of ABCG2-expressing

cells in the border zone adjacent to myocardial infarcts (57). Stimu-

lation of CM differentiation could be concomitant with neovascu-

larisation because OT stimulates EC growth (51) and angiogenesis

(75).

Mechanism of OT-induced cardiomyogenesis

Some observations point to a mechanism involved in OT-mediated

stem cell differentiation into CMs. Ca2+ mobilisation in response to

OT treatment has been detected in D3 embryonic stem cells differ-

entiating into CMs (82). It has also been shown that OT-induced

differentiation of P19 stem cells into CMs was suppressed by the

NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). The NO

donor S-nitroso-N-acetylpenicillamine was able to reverse L-NAME-

mediated inhibition of P19 cell differentiation into CMs (81). This

study clearly indicates a role for NO and NOS enzymes in stem cell

differentiation. However, the fact that NOS suppression by L-NAME

also increases the number of stem and progenitor cells differentiat-

ing into CMs highlights the complexity of the phenomenon (81).

Another study has reported that exposure of D3 stem cells to AVP

augments the number of beating embryoid bodies and heightens

GATA-4 expression. These AVP effects on cells were also found to

be antagonised by L-NAME (84), again suggesting a positive role for

NO in stem cell differentiation into CMs. This investigation high-

lighted the expression of AVP receptors in undifferentiated D3 cells,

with the AVP expression profile changing during the differentiation

process (84). It has been observed in the P19 cell model that AVP

not only increases spontaneously-occurring cardiomyogenesis, but

also initiates the process (84,87).

The OTR-NO-cGMP pathway, that is essential for OT-elicited dif-

ferentiation of P19 stem cells into CMs, is associated with GATA-4

and MEF2c elevation (81). GATA-4 regulates the expression of genes

that are critical for CM differentiation as well as for cardioprotec-

tive peptides in the adult heart. MEF2c is a member of the MEF2

family that is involved in cardiac, skeletal and smooth muscle

development. Partial GATA-4 gene targeting in cardiac and noncar-

diac cells indicates that even modest variations in GATA-4 gene

level or activity can participate in the maintenance of normal car-

diac function (88). GATA-4 has also been implicated in intercellular

cross-talk by inducing hypertrophy-associated angiogenesis via vas-

cular endothelial growth factor release and targeting the endothe-

lium (89). The upstream sequence of OTR contains putative binding

sites for GATA-4 and Nkx2.5, and GATA-4 serves as a key transcrip-

tional regulator of numerous cardiac peptides, including ANP, BNP

and OTR (90). GATA-4 has been identified in stem and progenitor

cells of the heart in combination with OT-mediated CM differentia-

tion (60,85). A recent study has demonstrated that undifferentiated

murine embryonic stem express BNP and its receptors, with its sig-

nalling being essential for cell survival and clonal growth (91). This

finding suggests possible interaction of the OT and NP systems in

embryonic stem during cardiomyogenesis.

Biological role of carboxyl terminally-extended OT

Accumulated, intermediate OT precursor peptides, termed OT-Gly-

Lys-Arg (OT-GKR), OT-Gly-Lys (OT-GK) and OT-G (OT-Gly), gener-

ally referred to as carboxyl-extended forms of OT (OT-X), occur

during post-translational processing and proteolytic cleavage of

OT gene products (89). These forms are further cleaved and ami-




dated to yield OT nonapeptide. OT-X forms have been detected in

the developing brain of animals and in foetal plasma. Interest-

ingly, the concentration of these molecules in foetal sheep

plasma was 35-fold higher than hormonally-active OT in the

early stages of development (92). Similarly, the amidated OT form

is not detectable in the foetal rat brain until embryonic day 21,

despite abundant expression of the principal intermediate form,

OT-GKR, during the same time period (92). The plasma OT-X ele-

vation reported during early foetal development in sheep (92) is

reduced in late gestation, when OT begins to predominate in the

circulation. Our previous data indicated that OT-X forms could be

produced in the developing heart because OT synthesis is seen in

CM cultures from newborn rats (40) and in EC P19 cells (78,82).

High-performance liquid chromatography of newborn rat hearts

and immunocytochemistry of whole mouse embryos revealed that

OT-GKR is abundant in developing rodent hearts. The selectivity

of OT-GKR antibodies and the lack of their reaction to OT nona-

peptide have already been demonstrated by RIA cross-reactivity

analysis (82). As observed in this study, localisation of the OT

system in mouse somites, embryonic vertebral precursors, is con-

sistent with findings that OT is involved in osteogenesis and is

important in skeleton mineralisation (93).

Recently, we reported that the OT precursor molecule OT-GKR

has a profound cardiomyogenic action on the D3 stem cell line that

could be of physiological importance in cardiac development. We

noted a profound increase of cardiomyogenesis after both exoge-

nously-applied OT-GKR into the cell medium and OT-GKR precursor

peptide were delivered by OT-GKR gene transfer to D3 cells (82).

Further reports (94) provide new evidence of the biological activity

of OT-X, notably OT-GKR, during the induction of cardiomyogenic

differentiation of the P19 cells.

At present, we are providing proof that, besides the differentia-

tion ability of OT ⁄ OT-GKR, such molecules have a substantial effect

on metabolism. Glucose, the principal energy substrate for the foe-

tus and newborn, is essential for normal foetal metabolism and

growth (95). Fetal glucose utilisation is increased by INS produced

in growing amounts by the developing foetal pancreas as gestation

proceeds, enhancing glucose utilisation among insulin-sensitive tis-

sues, such as the heart, which grow in mass and thus need glucose

during late gestation (96). Our data suggest a possible role of OT in

this process because OT molecules have a synergistic action on glu-

cose uptake stimulated by INS. We have also determined that OT

enhances glucose uptake stimulated by hypoxia. This observation

points to a potential role of OT in providing enhanced glucose sup-

ply to the foetal heart in conditions of impaired placental function

(97) and its possible application in the development of therapeutic

strategies against heart disease.

Cardiac tissue expresses ABCG2-positive cells involved in the dif-

ferentiation of cardiac stem cells (98). These cells are potentially

important in healing myocardial damage (99). Myocardial tissue,

presumably incapable of self-repairing cardiac insults, has some

regeneration capacity through the activation of putative cardiac

progenitor cells (100,101). The observation that OT ⁄ OT-GKR stimu-

late glucose uptake in ABCG2-positive cells, more significantly than

in nonselected CMs, indicates a role for OT in the metabolism of

progenitor cells (54). We established that OT could augment glucose

uptake in CMs in normal physiology and during hypoxic conditions,

which could improve cell survival and, consequently, heart perfor-

mance.

Conclusions

From the pioneering work of Oliver, Schafer, Howell and Dale to the

most recent findings, it is evident that OT is a pleiotrophic hormone

acting in classical endocrine fashion as well as via paracrine and

autocrine mechanisms. Indeed, OT is a key hormone of a system

within cardiac muscle that regulates basic cardiac function, such as

stem cell differentiation, CM survival and regeneration after ischae-

mic stress. OT also acts peripherally by controlling hydromineral bal-

ance and vascular reactivity. Its role in regulating energy metabolism

in isolated tissues, including the heart, is particularly relevant in con-

ditions of insulin resistance and hyperglycaemic states because OT

operates, at least in part, through activation of the INS pathway but

through different receptors. OT and its post-translational gene pre-

cursor, namely OT-GKR, stimulate glucose uptake in CMs under both

normal physiological conditions and hypoxia, which could clearly

improve cell survival and, consequently, heart performance.

Acknowledgements

This study was supported in part by the Canadian Institutes of Health

Research and the Canadian Heart and Stroke Foundation. The authors thank

Alexandria Aubourg for secretarial work, Ovid Da Silva for manuscript edit-

ing, and the Research Support Office, Research Centre, CHUM, for logistical

assistance. The authors report that they have no conflicts of interest.

Received 10 August 2011,

revised 23 September 2011,

accepted 3 October 2011

References

1 Oliver G, Schafer EA. On the physiological action of extracts of pitui-

tary body and certain other glandular organs: preliminary communica-

tion. J Physiol 1895; 18: 277–279.

2 Howell WH. A contribution to the physiology of sleep, based upon ple-

thysmographic experiments. J Exp Med 1897; 2: 313–345.

3 Dale HH. On some physiological actions of ergot. J Physiol 1906; 34:

163–206.

4 Dale HH. The actions of extracts of pituitary body. Biochem J 1910; 4:

427–447.

5 Kamm O, Aldrich TB, Grote IW, Rowe LW, Bugbee EP. Active principles

of the posterior lobe of the pituitary gland. J Am Chem Soc 1928; 50:

573–601.

6 Gaddum JH. Some properties of the separated active principles of the

pituitary (posterior lobe). J Physiol 1928; 65: 434–440.

7 Fraser AM. The action of the oxytocin hormone of the pituitary gland

on urine secretion. J Physiol 1942; 101: 236–251.

8 Ott I, Scott JC. The action of infundibulin upon the mammary secre-

tion. Proc Soc Exp Biol Med 1910; 8: 48–49.

9 Du Vigneaud V, Ressler C, Trippett S. The sequence of amino acids in

oxytocin, with a proposal for the structure of oxytocin. J Biol Chem

1953; 205: 949–957.




10 Woodbury RA, Abreu BE. Influence of oxytocin (pitocin) upon the

heart and blood pressure of the chicken, rabbit, cat, dog and turtle.

Am J Physiol 1944; 142: 114–120.

11 Kitchin AH, Lloyd SM, Pickford M. Some actions of oxytocin on the

cardiovascular system in man. Clin Sci 1959; 18: 399–406.

12 Nakano J, Fisher RD. Studies on the cardiovascular effects of synthetic

oxytocin. J Pharmacol Exp Ther 1963; 142: 206–214.

13 Cross RB, Dicker SE, Kitchin AH, Lloyd S, Pickford M. The effect of oxy-

tocin on the urinary excretion of water and electrolytes in man. J

Physiol 1960; 153: 553–561.

14 Sedlakova E, Lichardus B, Cort JH. Plasma saluretic activity: its nature

and relation to oxytocin analogs. Science 1969; 164: 580–582.

15 Nishimori K, Young LJ, Guo Q, Wang Z, Insel TR, Matzuk MM. Oxytocin

is required for nursing but is not essential for parturition or reproduc-

tive behavior. Proc Natl Acad Sci USA 1996; 93: 11699–11704.

16 Petersson M. Cardiovascular effects of oxytocin. Prog Brain Res 2002;

139: 281–288.

17 Gutkowska J, Jankowski M, Mukaddam-Daher S, McCann SM. Oxytocin

is a cardiovascular hormone. Braz J Med Biol Res 2000; 33: 625–633.

18 Andersson B, McCann SM. The effect of hypothalamic lesions on the

water intake of the dog. Acta Physiol Scand 1956; 35: 313–320.

19 Andersson B, Jobin M, Olsson K. Stimulation of urinary salt excretion

following injections of hypertonic NaCl-solution into the 3rd brain

ventricle. Acta Physiol Scand 1966; 67: 127–128.

20 De Bold AJ, Borenstein HB, Veress AT, Sonnenberg H. A rapid and

potent natriuretic response to intravenous injection of atrial myocar-

dial extract in rats. Life Sci 1981; 28: 89–94.

21 DeWardener HE, Clarkson EL. Natriuretic Hormone. New York, NY:

Raven Press, 1985: 1013–1031.

22 Davis JO, Freeman RH. Mechanisms regulating renin release. Physiol

Rev 1976; 56: 1–56.

23 Cort JH, Lichardus B, Pliska V, Barth T, Uhrin V, Rudinger J. In:Margou-

lies J, eds.Protein and polypeptide hormones. Amsterdam: Excerpta

Medica, 1969; 939.

24 Morris M, McCann SM, Orias R. Evidence for hormonal participation in

the natriuretic and kaliuretic responses to intraventricular hypertonic

saline and norepinephrine. Proc Soc Exp Biol Med 1976; 152: 95–98.

25 Gauer OH, Henry JP. Circulatory basis of fluid volume control. Physiol

Rev 1963; 43: 423–481.

26 Sudoh T, Minamino N, Kangawa K, Matsuo H. Brain natriuretic pep-

tide-32: N-terminal six amino acid extended form of brain natriuretic

peptide identified in porcine brain. Biochem Biophys Res Commun

1988; 155: 726–732.

27 Suga S, Nakao K, Itoh H, Komatsu Y, Ogawa Y. Endothelial production

of C-type natriuretic peptide and its marked augmentation by trans-

forming growth factor b. Possible existence of vascular natriuretic

peptide system. J Clin Invest 1992; 90: 1145–1149.

28 Ruskoaho H. Atrial natriuretic peptide: synthesis, release, and metabo-

lism. Pharmacol Rev 1992; 44: 479–602.

29 Horio T, Nishikimi T, Yoshihara F, Matsuo H, Takishita S, Kangawa K.

Inhibitory regulation of hypertrophy by endogenous atrial natriuretic

peptide in cultured cardiac myocytes. Hypertension 2000; 35: 19–24.

30 Cao L, Gardner DG. Natriuretic peptides inhibit DNA synthesis in car-

diac fibroblasts. Hypertension 1995; 25: 227–234.

31 Palkovits M, Eskay RL, Antoni FA. Atrial natriuretic peptide in the med-

ian eminence is of paraventricular nucleus origin. Neuroendocrinology

1987; 46: 542–544.

32 Baldissera S, Menani JW, Sotero dos Santos LF, Favaretto AL, Gut-

kowska J, Turrin MQ, McCann SM, Antunes-Rodrigues J. Role of the

hypothalamus in the control of atrial natriuretic peptide release. Proc

Natl Acad Sci USA 1989; 86: 9621–9625.

33 Antunes-Rodrigues J, Ramalho MJ, Reis LC, Menani JV, Turrin MQ,

Gutkowska J, McCann SM. Lesions of the hypothalamus and pituitary

inhibit volume-expansion-induced release of atrial natriuretic peptide.

Proc Natl Acad Sci USA 1991; 88: 2956–2960.

34 Antunes-Rodrigues J, Machado BH, Andrade HA, Mauad H, Ramalho

MJ, Reis LC, Silva-Netto CR, Favaretto AL, Gutkowska J, McCann SM.

Carotid-aortic and renal baroreceptors mediate the atrial natriuretic

peptide release induced by blood volume expansion. Proc Natl Acad

Sci USA 1992; 89: 6828–6831.

35 Antunes-Rodrigues J, Marubayashi U, Favaretto AL, Gutkowska J, McC-

ann SM. Essential role of hypothalamic muscarinic and a-adrenergic

receptors in atrial natriuretic peptide release induced by blood volume

expansion. Proc Natl Acad Sci USA 1993; 90: 10240–10244.

36 Reis LC, Ramalho MJ, Favaretto AL, Gutkowska J, McCann SM, An-

tunes-Rodrigues J. Participation of the ascending serotonergic system

in the stimulation of atrial natriuretic peptide release. Proc Natl Acad

Sci USA 1994; 91: 12022–12026.

37 Haanwinckel MA, Elias LK, Favaretto AL, Gutkowska J, McCann SM,

Antunes-Rodrigues J. Oxytocin mediates atrial natriuretic peptide

release and natriuresis after volume expansion in the rat. Proc Natl

Acad Sci USA 1995; 92: 7902–7906.

38 Soares TJ, Coimbra TM, Martins AR, Pereira AG, Carnio EC, Branco LG,

Albuquerque-Araujo WI, De Nucci G, Favaretto AL, Gutkowska J, McCann

SM, Antunes-Rodrigues J. Atrial natriuretic peptide and oxytocin induce

natriuresis by release of cGMP. Proc Natl Acad Sci USA 1999; 96: 278–

283.

39 Gutkowska J, Jankowski M, Lambert C, Mukaddam-Daher S, Zingg HH,

McCann SM. Oxytocin releases atrial natriuretic peptide by combining

with oxytocin receptors in the heart. Proc Natl Acad Sci USA 1997;

94: 11704–11709.

40 Jankowski M, Hajjar F, Al Kawas S, Mukaddam-Daher S, Hoffman G,

McCann SM, Gutkowska J. Rat heart: a site of oxytocin production

and action. Proc Natl Acad Sci USA 1998; 95: 14558–14563.

41 Jankowski M, Wang D, Hajjar F, Mukaddam-Daher S, McCann SM,

Gutkowska J. Oxytocin and its receptors are synthesized in the rat

vasculature. Proc Natl Acad Sci USA 2000; 97: 6207–6211.

42 Adan RA, Van Leeuwen FW, Sonnemans MA, Brouns M, Hoffman G,

Verbalis JG, Burbach JP. Rat oxytocin receptor in brain, pituitary,

mammary gland, and uterus: partial sequence and immunocytochemi-

cal localization. Endocrinology 1995; 136: 4022–4028.

43 Adan RA, Van Leeuwen FW, Sonnemans MA, Hoffman G, Verbalis JG,

Burbach JP. The rat oxytocin receptor. cDNA cloning and immunocyto-

chemical localization in brain, pituitary, mammary gland and uterus.

Adv Exp Med Biol 1995; 395: 345–346.

44 Cicutti NJ, Smyth CE, Rosaeg OP, Wilkinson M. Oxytocin receptor bind-

ing in rat and human heart. Can J Cardiol 1999; 15: 1267–1273.

45 Favaretto AL, Ballejo GO, Albuquerque-Araujo WI, Gutkowska J, An-

tunes-Rodrigues J, McCann SM. Oxytocin releases atrial natriuretic

peptide from rat atria in vitro that exerts negative inotropic and chro-

notropic action. Peptides 1997; 18: 1377–1381.

46 Nishimori K, Takayanagi Y, Yoshida M, Kasahara Y, Young LJ, Kawa-

mata M. New aspects of oxytocin receptor function revealed by

knockout mice: sociosexual behaviour and control of energy balance.

Prog Brain Res 2008; 170: 79–90.

47 Bernatova I, Rigatto KV, Key MP, Morris M. Stress-induced pressor and

corticosterone responses in oxytocin-deficient mice. Exp Physiol 2004;

89: 549–557.

48 Ondrejcakova M, Ravingerova T, Bakos J, Pancza D, Jezova D. Oxytocin

exerts protective effects on in vitro myocardial injury induced by

ischemia and reperfusion. Can J Physiol Pharmacol 2009; 87: 137–

142.




49 Mukaddam-Daher S, Lin YL, Roy J, Gutkowska J, Cardinal R. Negative

inotropic and chronotropic effects of oxytocin. Hypertension 2001;

38: 292–296.

50 Cattaneo MG, Lucci G, Vicentini LM. Oxytocin stimulates in vitro

angiogenesis via a Pyk-2 ⁄ Src-dependent mechanism. Exp Cell Res

2009; 315: 3210–3219.

51 Thibonnier M, Conarty DM, Preston JA, Plesnicher CL, Dweik RA, Erzu-

rum SC. Human vascular endothelial cells express oxytocin receptors.

Endocrinology 1999; 140: 1301–1309.

52 Sirotkin AV, Florkovicova I, Makarevich AV, Schaeffer HJ, Kotwica J,

Marnet PG, Sanislo P. Oxytocin mediates some effects of insulin-like

growth factor-I on porcine ovarian follicles. J Reprod Dev 2003; 49:

141–149.

53 Gutkowska J, Broderick TL, Bogdan D, Wang D, Lavoie JM, Jankowski

M. Downregulation of oxytocin and natriuretic peptides in diabetes:

possible implications in cardiomyopathy. J Physiol 2009; 587: 4725–

4736.

54 Florian M, Jankowski M, Gutkowska J. Oxytocin increases glucose

uptake in neonatal rat cardiomyocytes. Endocrinology 2010; 151:

482–491.

55 Iseri SO, Sener G, Saglam B, Gedik N, Ercan F, Yegen BC. Oxytocin

ameliorates oxidative colonic inflammation by a neutrophil-dependent

mechanism. Peptides 2005; 26: 483–491.

56 Iseri SO, Sener G, Saglam B, Gedik N, Ercan F, Yegen BC. Oxytocin pro-

tects against sepsis-induced multiple organ damage: role of neutroph-

ils. J Surg Res 2005; 126: 73–81.

57 Pfister O, Mouquet F, Jain M, Summer R, Helmes M, Fine A, Colucci

WS, Liao R. CD31) but not CD31+ cardiac side population cells exhibit

functional cardiomyogenic differentiation. Circ Res 2005; 97: 52–61.

58 Szeto A, Nation DA, Mendez AJ, Dominguez-Bendala J, Brooks LG,

Schneiderman N, McCabe PM. Oxytocin attenuates NADPH-dependent

superoxide activity and IL-6 secretion in macrophages and vascular

cells. Am J Physiol Endocrinol Metab 2008; 295: E1495–E1501.

59 Kim YS, Kwon JS, Hong MH, Kim J, Song CH, Jeong MH, Cho JG, Park

JC, Kang JC, Ahn Y. Promigratory activity of oxytocin on umbilical cord

blood-derived mesenchymal stem cells. Artif Organs 2010; 34: 453–

461.

60 Oyama T, Nagai T, Wada H, Naito AT, Matsuura K, Iwanaga K, Takah-

ashi T, Goto M, Mikami Y, Yasuda N, Akazawa H, Uezumi A, Takeda S,

Komuro I. Cardiac side population cells have a potential to migrate

and differentiate into cardiomyocytes in vitro and in vivo. J Cell Biol

2007; 176: 329–341.

61 McCann SM, Antunes-Rodrigues J, Jankowski M, Gutkowska J. Oxyto-

cin, vasopressin and atrial natriuretic peptide control body fluid

homeostasis by action on their receptors in brain, cardiovascular sys-

tem and kidney. Prog Brain Res 2002; 139: 309–328.

62 Jankowski M, Bissonauth V, Gao L, Gangal M, Wang D, Danalache B,

Wang Y, Stoyanova E, Clouthier G, Blaise G, Gutkowska J. Anti-inflam-

matory effect of oxytocin in rat myocardial infarction. Basic Res Car-

diol 2010; 105: 205–218.

63 Alizadeh AM, Faghihi M, Sadeghipour HR, Mohammadghasemi F, Imani

A, Houshmand F, Khori V. Oxytocin protects rat heart against ische-

mia-reperfusion injury via pathway involving mitochondrial ATP-

dependent potassium channel. Peptides 2010; 31: 1341–1345.

64 Houshmand F, Faghihi M, Zahediasl S. Biphasic protective effect of

oxytocin on cardiac ischemia ⁄ reperfusion injury in anaesthetized rats.

Peptides 2009; 30: 2301–2308.

65 Kobayashi H, Yasuda S, Bao N, Iwasa M, Kawamura I, Yamada Y, Ya-

maki T, Sumi S, Ushikoshi H, Nishigaki K, Takemura G, Fujiwara T, Fu-

jiwara H, Minatoguchi S. Post-infarct treatment with oxytocin

improves cardiac function and remodeling via activating cell-survival

signals and angiogenesis. J Cardiovasc Pharmacol 2009; 54: 510–519.

66 Cantley LC. The phosphoinositide 3-kinase pathway. Science 2002;

296: 1655–1657.

67 Fujio Y, Nguyen T, Wencker D, Kitsis RN, Walsh K. Akt promotes sur-

vival of cardiomyocytes in vitro and protects against ischemia-reper-

fusion injury in mouse heart. Circulation 2000; 101: 660–667.

68 Miike T, Kunishiro K, Kanda M, Azukizawa S, Kurahashi K, Shirahase H.

Impairment of endothelium-dependent ACh-induced relaxation in

aorta of diabetic db ⁄ db mice – possible dysfunction of receptor

and ⁄ or receptor-G protein coupling. Naunyn Schmiedebergs Arch

Pharmacol 2008; 377: 401–410.

69 Lee ES, Uhm KO, Lee YM, Kwon J, Park SH, Soo KH. Oxytocin stimu-

lates glucose uptake in skeletal muscle cells through the calcium-

CaMKK-AMPK pathway. Regul Pept 2008; 151: 71–74.

70 Russell RR III, Li J, Coven DL, Pypaert M, Zechner C, Palmeri M, Giord-

ano FJ, Mu J, Birnbaum MJ, Young LH. AMP-activated protein kinase

mediates ischemic glucose uptake and prevents postischemic cardiac

dysfunction, apoptosis, and injury. J Clin Invest 2004; 114: 495–503.

71 Devost D, Wrzal P, Zingg HH. Oxytocin receptor signalling. Prog Brain

Res 2008; 170: 167–176.

72 Gimpl G, Fahrenholz F. The oxytocin receptor system: structure, func-

tion, and regulation. Physiol Rev 2001; 81: 629–683.

73 Nation DA, Szeto A, Mendez AJ, Brooks LG, Zaias J, Herderick EE,

Gonzales J, Noller CM, Schneiderman N, McCabe PM. Oxytocin attenu-

ates atherosclerosis and adipose tissue inflammation in socially iso-

lated ApoE) ⁄ ) mice. Psychosom Med 2010; 72: 376–382.

74 Cassoni P, Marrocco T, Bussolati B, Allia E, Munaron L, Sapino A,

Bussolati G. Oxytocin induces proliferation and migration in immortal-

ized human dermal microvascular endothelial cells and human breast

tumor-derived endothelial cells. Mol Cancer Res 2006; 4: 351–359.

75 Cattaneo MG, Chini B, Vicentini LM. Oxytocin stimulates migration

and invasion in human endothelial cells. Br J Pharmacol 2008; 153:

728–736.

76 Jankowski M, Wang D, Danalache B, Gangal M, Gutkowska J. Cardiac

oxytocin receptor blockade stimulates adverse cardiac remodeling in

ovariectomized spontaneously hypertensive rats. Am J Physiol Heart

Circ Physiol 2010; 299: H265–H274.

77 Jankowski M, Danalache B, Wang D, Bhat P, Hajjar F, Marcinkiewicz

M, Paquin J, McCann SM, Gutkowska J. Oxytocin in cardiac ontogeny.

Proc Natl Acad Sci USA 2004; 101: 13074–13079.

78 Paquin J, Danalache BA, Jankowski M, McCann SM, Gutkowska J. Oxy-

tocin induces differentiation of P19 embryonic stem cells to cardio-

myocytes. Proc Natl Acad Sci USA 2002; 99: 9550–9555.

79 van der Heyden MA, Defize LH. Twenty-one years of P19 cells: what

an embryonal carcinoma cell line taught us about cardiomyocyte dif-

ferentiation. Cardiovasc Res 2003; 58: 292–302.

80 McBurney MW. P19 embryonal carcinoma cells. Int J Dev Biol 1993;

37: 135–140.

81 Danalache BA, Paquin J, Donghao W, Grygorczyk R, Moore JC, Mum-

mery CL, Gutkowska J, Jankowski M. Nitric oxide signaling in oxyto-

cin-mediated cardiomyogenesis. Stem Cells 2007; 25: 679–688.

82 Gassanov N, Devost D, Danalache B, Noiseux N, Jankowski M, Zingg

HH, Gutkowska J. Functional activity of the carboxyl-terminally

extended oxytocin precursor peptide during cardiac differentiation of

embryonic stem cells. Stem Cells 2008; 26: 45–54.

83 Gassanov N, Er F, Zagidullin N, Jankowski M, Gutkowska J, Hoppe UC.

Retinoid acid-induced effects on atrial and pacemaker cell differentia-

tion and expression of cardiac ion channels. Differentiation 2008; 76:

971–980.

84 Gassanov N, Jankowski M, Danalache B, Wang D, Grygorczyk R, Hoppe

UC, Gutkowska J. Arginine vasopressin-mediated cardiac differentia-

tion: insights into the role of its receptors and nitric oxide signaling. J

Biol Chem 2007; 282: 11255–11265.




85 Matsuura K, Nagai T, Nishigaki N, Oyama T, Nishi J, Wada H, Sano M,

Toko H, Akazawa H, Sato T, Nakaya H, Kasanuki H, Komuro I. Adult

cardiac Sca-1-positive cells differentiate into beating cardiomyocytes.

J Biol Chem 2004; 279: 11384–11391.

86 Mouquet F, Pfister O, Jain M, Oikonomopoulos A, Ngoy S, Summer R,

Fine A, Liao R. Restoration of cardiac progenitor cells after myocardial

infarction by self-proliferation and selective homing of bone marrow-

derived stem cells. Circ Res 2005; 97: 1090–1092.

87 Gutkowska J, Miszkurka M, Danalache B, Gassanov N, Wang D, Jan-

kowski M. Functional arginine-vasopressin system in early heart matu-

ration. Am J Physiol Heart Circ Physiol 2007; 293: H2262–H2270.

88 Bisping E, Ikeda S, Kong SW, Tarnavski O, Bodyak N, McMullen JR, Ra-

jagopal S, Son JK, Ma Q, Springer Z, Kang PM, Izumo S, Pu WT. Gata4

is required for maintenance of postnatal cardiac function and protec-

tion from pressure overload-induced heart failure. Proc Natl Acad Sci

USA 2006; 103: 14471–14476.

89 Heineke J, Auger-Messier M, Xu J, Oka T, Sargent MA, York A, Klevitsky

R, Vaikunth S, Duncan SA, Aronow BJ, Robbins J, Crombleholme TM,

Molkentin JD. Cardiomyocyte GATA4 functions as a stress-responsive

regulator of angiogenesis in the murine heart. J Clin Invest 2007;

117: 3198–3210.

90 Uchida S, Fuke S, Tsukahara T. Upregulations of Gata4 and oxytocin

receptor are important in cardiomyocyte differentiation processes of

P19CL6 cells. J Cell Biochem 2007; 100: 629–641.

91 Abdelalim EM, Tooyama I. BNP signaling is crucial for embryonic stem

cell proliferation. PLoS ONE 2009; 4: e5341.

92 Morris M, Castro M, Rose JC. Alterations in oxytocin prohormone pro-

cessing during early development in the fetal sheep. Am J Physiol

1992; 263: R738–R740.

93 Tamma R, Colaianni G, Zhu LL, DiBenedetto A, Greco G, Montemurro

G, Patano N, Strippoli M, Vergari R, Mancini L, Colucci S, Grano M,

Faccio R, Liu X, Li J, Usmani S, Bachar M, Bab I, Nishimori K, Young

LJ, Buettner C, Iqbal J, Sun L, Zaidi M, Zallone A. Oxytocin is an ana-

bolic bone hormone. Proc Natl Acad Sci USA 2009; 106: 7149–7154.

94 Danalache BA, Gutkowska J, Slusarz MJ, Berezowska I, Jankowski M.

Oxytocin-Gly-Lys-Arg: a novel cardiomyogenic peptide. PLoS ONE

2010; 5: e13643.

95 Lopaschuk GD, Spafford MA, Marsh DR. Glycolysis is predominant

source of myocardial ATP production immediately after birth. Am J

Physiol 1991; 261: H1698–H1705.

96 Hay WW Jr. Recent observations on the regulation of fetal metabolism

by glucose. J Physiol 2006; 572: 17–24.

97 Sakuragawa N, Matsui A, Matsuzaka T, Kono Y, Ido T, Ishiwata K, Ka-

washima K. Enhanced glucose metabolism and impaired placental

function in hypoxic pregnant rats. Int J Rad Appl Instrum B 1988; 15:

645–650.

98 Martin CM, Meeson AP, Robertson SM, Hawke TJ, Richardson JA, Bates

S, Goetsch SC, Gallardo TD, Garry DJ. Persistent expression of the

ATP-binding cassette transporter, Abcg2, identifies cardiac SP cells in

the developing and adult heart. Dev Biol 2004; 265: 262–275.

99 Scobioala S, Klocke R, Kuhlmann M, Tian W, Hasib L, Milting H, Koenig

S, Stelljes M, El Banayosy A, Tenderich G, Michel G, Breithardt G, Nikol

S. Up-regulation of nestin in the infarcted myocardium potentially

indicates differentiation of resident cardiac stem cells into various lin-

eages including cardiomyocytes. FASEB J 2008; 22: 1021–1031.

100 Laflamme MA, Myerson D, Saffitz JE, Murry CE. Evidence for cardio-

myocyte repopulation by extracardiac progenitors in transplanted

human hearts. Circ Res 2002; 90: 634–640.

101 Quaini F, Urbanek K, Beltrami AP, Finato N, Beltrami CA, Nadal-Ginard

B, Kajstura J, Leri A, Anversa P. Chimerism of the transplanted heart.

N Engl J Med 2002; 346: 5–15.




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Oxytocin Revisited - Its Role in Cardiovascular Regulation