title: Pro-inflammatory cytokine regulation of P-glycoprotein in the developing blood-brain barrier.
abstract: Placental P-glycoprotein (P-gp) acts to protect the developing fetus from exogenous compounds. This protection declines with advancing gestation leaving the fetus and fetal brain vulnerable to these compounds and potential teratogens in maternal circulation. This vulnerability may be more pronounced in pregnancies complicated by infection, which is common during pregnancy. Pro-inflammatory cytokines (released during infection) have been shown to be potent inhibitors of P-gp, but nothing is known regarding their effects at the developing blood-brain barrier (BBB). We hypothesized that P-gp function and expression in endothelial cells of the developing BBB will be inhibited by pro-inflammatory cytokines. We have derived brain endothelial cell (BEC) cultures from various stages of development of the guinea pig: gestational day (GD) 50, 65 (term ~68 days) and postnatal day (PND) 14. Once these cultures reached confluence, BECs were treated with various doses (10(0)-10(4 )pg/mL) of pro-inflammatory cytokines: interleukin-1β (IL-1β), interleukin-6 (IL-6) or tumor necrosis factor- α (TNF-α). P-gp function or abcb1 mRNA (encodes P-gp) expression was assessed following treatment. Incubation of GD50 BECs with IL-1β, IL-6 or TNF-α resulted in no change in P-gp function. GD65 BECs displayed a dose-dependent decrease in function with all cytokines tested; maximal effects at 42%, 65% and 34% with IL-1β, IL-6 and TNF-α treatment, respectively (P<0.01). Inhibition of P-gp function by IL-1β, IL-6 and TNF-α was even greater in PND14 BECs; maximal effects at 36% (P<0.01), 84% (P<0.05) and 55% (P<0.01), respectively. Cytokine-induced reductions in P-gp function were associated with decreased abcb1 mRNA expression. These data suggest that BBB P-gp function is increasingly responsive to the inhibitory effects of pro-inflammatory cytokines, with increasing developmental age. Thus, women who experience infection and take prescription medication during pregnancy may expose the developing fetal brain to greater amounts of exogenous compounds - many of which are considered potentially teratogenic.
authors.affiliation: Department of Physiology, University of Toronto, Toronto, Ontario, Canada. majid.iqbal@utoronto.ca
authors.forename: Majid
authors.initials: M
authors.lastname: Iqbal
authors.forename: Hay Lam
authors.initials: HL
authors.lastname: Ho
authors.forename: Sophie
authors.initials: S
authors.lastname: Petropoulos
authors.forename: Vasilis G
authors.initials: VG
authors.lastname: Moisiadis
authors.forename: William
authors.initials: W
authors.lastname: Gibb
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Matthews
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000378:metabolism*; D016207:Cytokines / Q000494:pharmacology*; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D006168:Guinea Pigs; D053583:Interleukin-1beta / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D008297:Male; D011247:Pregnancy; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D016207:Cytokines; D053583:Interleukin-1beta; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha