DETOXICATION ROLE OF THE PLACENTA:
EFFECT OF EFFLUX TRANSPORTERS AND BIOTRANSFORMATION ENZYMES
František ŠtaudKatedra farmakologie a toxikologie
Univerzita Karlova v PrazeFarmaceutická fakulta v Hradci Králové
Placenta
EFFLUXTRANSPORTERS
ENZYMES?
Efflux transporters and enzymesof the placenta
Several ABC transporters have been localized in placenta: MDR1, BCRP, MRPs
Protection of fetus against xenobiotics from mother.
Efflux transporters and enzymesof the placenta – expression of P-glycoprotein
Novotna M, et al. Reprod Tox, 2004
RT-PCR
Western blotting
Efflux transporters and enzymesof the placenta
Enzymes of phase one (CYP1,2,3 families)phase two (GST, UDP-glucuronosyltransferase, sulphotransferase, N-acetyl transferase).
Clinical significance??
Mainly metabolism of steroid hormones (11-HSD).
Efflux transporters and enzymesof the placenta – expression of 11-HSD2
Staud F, et al. Placenta, 2005
RT-PCR
Western blotting
Dual perfusion of the rat placenta
Conversion capacity
100*metaboliteparent
metabolite
M>F clearance
pma
ffvmf wC
QCCl
.
.
F>M clearance
p
ffm w
QERCl
.
Pla
cen
ta
PK analysis of efflux transporter activity (in placenta)
MaternalCirculation
FetalCirculation
Passive clearance (Clpd)
famamefflux CK
VCl
/
max
Capacity limited clearance (Clefflux)
effluxpdT ClClCl Total clearance (ClT)
mampdTmf CK
VClCl
max
M>F transport
fampdTfm CK
VClCl
max
F>M transport
ABC
F > M
M > F
Effect of P-gp on placental transport of Rhodamine 123
Pavek P, Staud F, et al. J Pharmacol Exp Ther, 2003
Transplacental transport of Rho123
0
0,1
0,2
0,3
0,4
0,5
M>F F>M
Cle
aran
ce (
ml/
min
)
Effect of BCRP on transplacental PK of cimetidine
8.7116.7Km
2.47 7.14Vmax
0.0420.042CLpd
inhibitorcontrolF>M
0.028 0.77 Km
0.00057 0.013 Vmax
0.043 0.041CLpd
inhibitorcontrol M>F
M-F clearance
0,000
0,010
0,020
0,030
0,040
0,050
0,060
0,001 0,01 0,1 1 10 100 1000
Maternal cim etidine concentration (uM)
Cle
aran
ce (
ml/m
in/w
)
control
inhibitor
mampdTmf CK
VClCl
max
F-M clearance
0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,001 0,01 0,1 1 10 100 1000
Fetal cimetidine concentration (uM )
CL
(m
l/m
in/w
)
control
inhibitor
fampdTfm CK
VClCl
max
~ 0.042 ml/min
Effect of BCRP on fetomaternal efflux of cimetidine
Cimetidine (100nM) present in both circulations – fetal perfusate recirculated
Active efflux of cimetidine from fetal compartment
80
85
90
95
100
0 5 10 15 20 25 30
Time (min)
Con
cent
ratio
n (%
of t
ime
0)
Cimetidine concentration dropped by 13% over 30 min
Effect of BCRP/Pgp on transplacental PK
ABC
11-hydroxysteroid dehydrogenase (11-HSD2) in placenta
• Regulates transport of maternal glucocorticoids – conversion to inactive 11-keto form
• cortisol cortison (human)
• corticosterone 11-dehydrocorticosterone (rat)
11-HSD2 saturability
(M>F corticosterone 3-200nM)
Staud F, Mazancova K, Miksik I, et al. Placenta, 2005
corticosterone
11-dehydrocorticosterone
Conversion of fetal corticosterone
Inhibition and saturation
Staud F, Mazancova K, Miksik I, et al. Placenta, 2005
Conclusions
Efflux transporters in the trophoblast can remove substrates from fetus to mother.
Similarly, some enzymes may metabolize molecules in the fetal circulation.
Transporters and enzymes play a key role in detoxication of the fetus.
Acknowledgements
Current PhD students:Mgr. Martina ČečkováMgr. Antonín LibraMgr. Lukáš ČervenýMgr. Zuzana VackováMgr. Leoš FuksaMgr. Lenka CygalováMgr. Lucie ŠvecováMgr. Eva BrčákováColleagues:RNDr. Jiří Pácha, DrScMUDr. Stanislav Mičuda, PhDPharmDr. Petr Pávek, PhDProf. MUDr. Zdeněk Fendrich, CSc
Financial support:GAUKFRVŠ
Technical assistance:A. KunováD. Součková