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 (100–104 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.

Acute Effects of Viral Exposure on P-Glycoprotein Function in the Mouse Fetal Blood-Brain Barrier

“…Indirect actions would likely be mediated by induction of pro-inflammatory cytokines. Indeed, pro-inflammatory cytokines such as IL-6 can reduce P-gp activity in the developing BBB [17]. IL-6 had the most potent effect inhibiting P-gp activity in BECs when compared to other pro-inflammatory cytokines [17].…”

“…Indeed, pro-inflammatory cytokines such as IL-6 can reduce P-gp activity in the developing BBB [17]. IL-6 had the most potent effect inhibiting P-gp activity in BECs when compared to other pro-inflammatory cytokines [17]. Importantly, increased maternal levels of IL-6 temporally matched the decline in P-gp function at the developing BBB.…”

“…Further, we have shown that human placental explants exposed to LPS and polyinosinic:polycytidylic acid (PolyI:C), a synthetic analog of double stranded RNA (dsRNA) that stimulates TLR-3-viral immunological responses [15], exhibit reduced expression of P-gp [16]. Additionally, brain endothelial cell (BEC) cultures exposed to the pro-inflammatory cytokines interleukin (IL)-1β, IL-6 or tumor necrosis factor (TNF)-α displayed impaired P-gp function [17]. Together, these results suggest that both bacterial and viral infections have the potential to decrease fetal protection and increase exposure to xenobiotics and environmental toxins that may have teratogenic consequences.…”

Specific Increase in MDR1 Mediated Drug-Efflux in Human Brain Endothelial Cells following Co-Exposure to HIV-1 and Saquinavir

“…It was observed that increase in chemokines in humans may increase the MDR1 expression in BBB endothelial cells through different signaling pathways, mainly the protein kinase-C (PKC) pathway [6], [29]. However, recent studies on rat brain capillaries indicated that there is a network of signaling mechanisms that modulate MDR1 activity involving TNF-α and IL-6 [29], [30]. On the other hand, HIV-1 Tat protein was also found to play an important role in overexpressing MDR1 in rodent BBB by activating NF-κB [31].…”

Regulation of ABC efflux transporters at blood-brain barrier in health and neurological disorders

“…A previous study showed that treatment of the brain endothelial cell derived from various stages of development of the guinea pig with the pro-inflammatory cytokines, IL-1β, IL-6 and TNF-α has a different effect on expression of P-gp. At late gestational stage and at postnatal stage, IL-1β, IL-6 and TNF-α exposure resulted in a dose-dependent decrease in P-gp function (Iqbal et al, 2012). Cytokine-induced reductions in P-gp function were associated with decreased ABCB1 mRNA expression (Iqbal et al, 2012).…”