Role Of Tumor Necrosis Factor Alpha On Lipopolysaccharide (LPS)-induced Down-regulation Of Cytochrome P450 3A In Mouse Fetal Liver

Objective To investigate the role of tumor necrosis factor alpha (TNF-α) on lipopolysaccharide (LPS)-induced downregulation of cytochrome P450 3A (CYP3A) in mouse fetal liver and to explore the effects of a low dose LPS pretreatment on maternal LPS exposure induced downregulation of CYP3A in mouse fetal liver.Methods The present study included five separate experiments. In experiment 1, the pregnant mice were sacrificed on gestational day 14, 16, 18 and pups were sacrificed on postnatal day 4, 21, 70. In experiment 2, the pregnant mice were administered with a single dose of LPS (500μg/kg, ip) on gestational day 17 and sacrificed at 2 or 12 h after LPS treatment. In experiment 3, the pregnant mice were administered with different doses of LPS (200 or 500μg/kg, ip) on gestational day 17 and sacrificed at 12 h after LPS treatment. In experiment 4, the pregnant mice were pretreated with PTX (100 mg/kg, ip) at 30 min before LPS and sacrificed at 12 h after LPS administration. In experiment 5, the pregnant mice were pretreated with a low dose of LPS (10μg/kg, ip) at 24 h before high-dose LPS and sacrificed at 1.5 h or 12 h after high-dose LPS administration. Cyp3a11 and TNF-αmRNA in maternal liver, placenta and fetal liver was measured by reverse transcription polymerase chain reaction (RT-PCR). The expressions of CYP3A protein in mouse fetal liver were determined using Western blot. Enzyme-linked immunosorbent assay (ELISA) was used to determine the levels of TNF-α, IL-1βand IL-6 in maternal serum, amniotic fluid and mouse fetal liver.Results With embryonic development, fetal hepatocytes gradually expressed various types of cytochromes P450 (CYPs) and on postnatal day 4 the level of CYP3A was about 80% of that in adult liver. Maternal LPS exposure significantly downregulated Cyp3a11 mRNA and CYP3A protein in fetal liver in a time- and dose- dependent manner. PTX, an inhibitor of TNF-αsynthesis, pretreatment significantly attenuated LPS-induced downregulation of CYP3A in fetal liver. Additional experiment showed that a low dose LPS pretreatment decreased the level of TNF-αin maternal serum and amniotic fluid and counteracted LPS-induced expression of TNF-αmRNA in maternal liver and placenta. Although a low dose LPS pretreatment alleviated LPS-induced increase in TNF-αin fetal liver, it had little effect on TNF-αmRNA in fetal liver. These results suggested that a low dose LPS pretreatment protected fetuses against LPS-induced downregulation of hepatic CYP3A expression through the repression of maternally-sourced TNF-αproduction. Correspondingly, a low dose LPS pretreatment attenuated LPS-induced downregulation of CYP3A in fetal liver.Conclusion LPS-induced downregulation of CYP3A in fetal liver is mediated, at least in part, by TNF-α. The increased level of TNF-αprotein in fetal liver, transferred from either the maternal circulation or amniotic fluid, seems to be associated with LPS-induced downregulation of CYP3A in fetal liver. And a low dose LPS pretreatment protects fetuses against LPS-induced downregulation of hepatic CYP3A through the repression of maternally-sourced TNF-αproduction.