Strategies for Engineered Negligible Senescence (SENS), Second Conference

Queens' College, Cambridge, England7-11 September 2005

Zinc homeostasis in aging: two elusive faces of the same “metal”

Immunology Centre (Section: Nutrition, Immunity and Aging) Res. Department Italian National Research Centres on Aging (INRCA), Ancona Italy

I.N.R.C.A.“N. Masera” Gerontol. Res. Dept.

Dr. Eugenio Mocchegiani

A) INDIRECTImmunoresistance to infections by zinc

involving MTs, iNOS, PARP homeostasis

B) DIRECTImmunoresistance by zinc involving

cell-mediated immune responses

ZINC

IL-12ZnFTS

Balance

M NK

Host defence

Th3 IL-2, IFN

IL- 1, IL-6 rIL-1, rIL-6

PKC

iNOS

Immune cell

NO

Sequester of intracellular zinc by MTs for their biological functions.

ZnMTs

PARP

Zinc release of MTs by NO to antioxidant enzyme

NAD+ Nucleus

Antioxidant enzyme activation (SOD)

DNA- repair

Protection of MTs by oxidative damage

DNA strand breakage

MTmRNA

(cGMP)

(cAMP)

Th2 Th1/Th2/Th3paradigm

Th1

Mocchegiani E. et al., TiPS, 2000

Stressor agent

Zinc dependentAntioxidant enzymes

Zinc dependentTranscription factors

Stress induced response

Protein and DNA repairing enzymes

DNA and protein damage

MT

Intracellular zinc signals (response to stress)

Sulfur ligand

Zinc

Metallothioneins (MT) are proteins constituted by two sub-units, alpha and beta domains, which can bind 4 and 3 zinc ions into clusters involving 20 cysteine residues which bind zinc through sulfur ligands.

Mocchegiani E. et al., MAD, 1998

NK ACTIVITY IN HUMANS

0

10

20

30

40

50

60

70

80

90

NK

(L

.U. 2

0/1

07)

young adult adult infected old old infected nonagen. nonagen. inf.

*

*p<0.01 when compared to adults and nonagenarians Mocchegiani E. et al., MAD, 2003

MT-IIA-mRNA (RT-PCR) in human MT-IIA-mRNA (RT-PCR) in human lymphocyteslymphocytes

You

ng

Old

Old

est

(non

ag

en

ary

)

Old

in

fecte

d

200 bp

245 bp

MT-II A-mRNA

ß-actin

youngold

centenarians

old infected

0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

Mt2

A/

acti

n

Plasma IL-6 Plasma IL-6 (pg/ml)(pg/ml)

0

5

10

15

20

25

30

35

Pla

sm

a I

L-6

(p

g/m

l)

*

* * Mocchegiani E. et al.,MAD, 2003

Zinc binding with MT in the liver from young and old miceZinc binding with MT in the liver from young and old mice

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 3 5 7 9 11 13 15 17 19 21 23 25

Fractions

Meta

l (µ

g/m

l)

YOUNG (Zn binding with MT)

OLD (Zn binding with MT)

OLD (Cu binding with MT)

YOUNG (Cu binding with MT)

HP

MT

I.N.R.C.A.“N. Masera” Gerontol. Res. Dept.

Mocchegiani E. et al., MAD, 2002

Zinc homeostasis in neuronal cells

-The release of Zn++ from “zinc enriched neurons” seems to exert a protective action against excessive release and extracellular accumulation of glutamate

- Zinc binding is required for NGF activity and for the zinc-fingers mediated transcription of other growth factors

- Zinc is required for the regulation of of many relevant enzymes involved in neuronal function

(E. Mocchegiani et al., Progress in Neurobiology, 75, 367, 2005)

Consequences of a possible zinc deficiency in the aged brain

?

Mocchegiani E, Bertoni-Freddari C, Marcellini F, Malavolta M. Brain, aging and neurodegeneration: role of zinc ion availability. Prog Neurobiol. 2005;75(6):367-90.

Neurotoxicity of zinc for the brain

- Excessive increase of intracellular zinc have been reported in degenerating neurons in the hippocampal hilus and CA1, as well as in the cerebral cortex, thalamus, striatum, and amygdala after transient forebrain ischemia in rats (Koh et al., 1996).- Evidences indicate that zinc also enters into postsynaptic neurons in toxic excess during seizures and traumatic brain injury (Frederickson et al., 2005).

MT-Zn Mithocondrial Zn pool

Vescicular zinc

Excessive release of zinc

neurotrophin receptor p75NTR

p75NTR-associated death executor (NADE)

Mithocondrial release of cytochrome c and AIF

Caspases

PARP-1 overactivation

drastic depletion of NAD+ and ATP

Apoptosis Necrosis

Age (months) of mice

Young-adult age Ageing Very old age0 2 15 24

Accelerated switching on =death of aged

Delayed switching on =increased longevity

IL-6Free zinc ions

Genetic background ?

Stress

MTmRNA

gp130

MTmRNA(lamp)

SUCCESSFUL AGING

IL-6(hand to press switch)

gp 130 (switch)

Immune plasticity

(spring)= normal immune response

Absence of immune plasticity = immune decrement

Maintenance of immune plasticity =satisfactory immune plasticity

free zinc ions

Mocchegiani E. et al., Exp. Gerontol, 2002

General conclusions From the data reported may be stressed the following points:

 1) The zinc ion bioavailability, via MT homeostasis, is crucial for the entire efficiency of many body homeostatic mechanisms, including immune and brain functions, with however different effects strictly dependent by the inflammatory status mediated by IL-6 and gp130

2) Zinc transporters are involved in zinc ion bioavailability. Their determination is crucial in order to clarify the zinc homeostasis in ageing

3) An excessive release of zinc can lead to zinc toxicosis in the brain with subsequent neuronal death and beta-amyloid accumulation and formation of senile plaques

4) The genetic polymorphisms of IL-6 may be the background for a correct zinc ion bioavailability and the subsequent successful ageing

 All these points are the main tasks of Zincage project, in which zinc supplementation is foreseen following the genetic background from each old recruited subject in order to discriminate the real zinc deficiency and to clarify old people who need zinc supply for healthy ageing.

I.N.R.C.A.“N. Masera” Gerontol. Res. Dept.

SIXTH FRAMEWORK PROGRAMMESIXTH FRAMEWORK PROGRAMMEPRIORITY 5PRIORITY 5

FOOD QUALITY AND SAFETYFOOD QUALITY AND SAFETY

Contract for:  

SPECIFIC TARGETED RESEARCH PROJECTSPECIFIC TARGETED RESEARCH PROJECT

Annex 1 - “Description of Work”

Project acronym: ZINCAGE

Project full title: NUTRITIONAL ZINC, OXIDATIVE STRESS AND IMMUNOSENESCENCE: BIOCHEMICAL, GENETIC AND LIFESTYLE IMPLICATIONS FOR HEALTHY AGEING.

Contract no.: FOOD-CT-2004-506850. Total contribution 3.000.000 Euro

Scientific Coordinator: Dr. Eugenio Mocchegiani Immunology Ctr. Res. Dept. INRCA, Ancona, Italy (e.mocchegiani@inrca.it)

Date of preparation of Annex 1: 25/8/2003Operative start date of the contract: 1 February 2004

Duration of the project : 3 years www.zincage.org

I.N.R.C.A.“N. Masera” Gerontol. Res. Dept.