Shah Pranav, Omoluabi Ozozoma, Moorthy Bhagavatula, Ghose Romi
Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston (P.S, O.O., R.G.), and Department of Pediatrics, Baylor College of Medicine (B.M.), Houston, Texas.
Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston (P.S, O.O., R.G.), and Department of Pediatrics, Baylor College of Medicine (B.M.), Houston, Texas
Drug Metab Dispos. 2016 Jan;44(1):61-7. doi: 10.1124/dmd.115.066761. Epub 2015 Oct 15.
The expressions and activities of hepatic drug-metabolizing enzymes and transporters (DMETs) are altered during infection and inflammation. Inflammatory responses in the liver are mediated primarily by Toll-like receptor (TLR)-signaling, which involves recruitment of Toll/interleukin (IL)-1 receptor (TIR) domain containing adaptor protein (TIRAP) and TIR domain containing adaptor inducing interferon (IFN)-β (TRIF) that eventually leads to induction of proinflammatory cytokines and mitogen-activated protein kinases (MAPKs). Lipopolysaccharide (LPS) activates the Gram-negative bacterial receptor TLR4 and polyinosinic:polycytidylic acid (polyI:C) activates the viral receptor TLR3. TLR4 signaling involves TIRAP and TRIF, whereas TRIF is the only adaptor protein involved in the TLR3 pathway. We have shown previously that LPS-mediated downregulation of DMETs is independent of TIRAP. To determine the role of TRIF, we treated TRIF(+/+) and TRIF(-/-) mice with LPS or polyI:C. LPS downregulated (∼40%-60%) Cyp3a11, Cyp2a4, Ugt1a1, Mrp2 mRNA levels, whereas polyI:C downregulated (∼30%-60%) Cyp3a11, Cyp2a4, Cyp1a2, Cyp2b10, Ugt1a1, Mrp2, and Mrp3 mRNA levels in TRIF(+/+) mice. This downregulation was not attenuated in TRIF(-/-) mice. Induction of cytokines by LPS was observed in both TRIF(+/+) and TRIF(-/-) mice. Cytokine induction was delayed in polyI:C-treated TRIF(-/-) mice, indicating that multiple mechanisms mediating polyI:C signaling exist. To assess the role of MAPKs, primary hepatocytes were pretreated with specific inhibitors before treatment with LPS/polyI:C. We found that only the c-jun-N-terminal kinase (JNK) inhibitor attenuated the down-regulation of DMETs. These results show that TRIF-independent pathways can be involved in the downregulation of DMETs through TLR4 and 3. JNK-dependent mechanisms likely mediate this downregulation.
在感染和炎症过程中，肝脏药物代谢酶和转运体（DMETs）的表达及活性会发生改变。肝脏中的炎症反应主要由Toll样受体（TLR）信号介导，该信号涉及募集含Toll/白细胞介素（IL）-1受体（TIR）结构域的接头蛋白（TIRAP）和含TIR结构域的接头蛋白诱导干扰素（IFN）-β（TRIF），最终导致促炎细胞因子和丝裂原活化蛋白激酶（MAPKs）的诱导。脂多糖（LPS）激活革兰氏阴性细菌受体TLR4，聚肌苷酸:聚胞苷酸（polyI:C）激活病毒受体TLR3。TLR4信号传导涉及TIRAP和TRIF，而TRIF是TLR3途径中唯一涉及的接头蛋白。我们之前已经表明，LPS介导的DMETs下调与TIRAP无关。为了确定TRIF的作用，我们用LPS或polyI:C处理TRIF(+/+)和TRIF(-/-)小鼠。LPS下调了（约40%-60%）Cyp3a11、Cyp2a4、Ugt1a1、Mrp2的mRNA水平，而polyI:C下调了（约30%-60%）TRIF(+/+)小鼠中Cyp3a11、Cyp2a4、Cyp1a2、Cyp2b10、Ugt1a1、Mrp2和Mrp3的mRNA水平。这种下调在TRIF(-/-)小鼠中并未减弱。在TRIF(+/+)和TRIF(-/-)小鼠中均观察到LPS诱导的细胞因子。在polyI:C处理的TRIF(-/-)小鼠中，细胞因子诱导延迟，表明存在多种介导polyI:C信号传导的机制。为了评估MAPKs的作用，在用LPS/polyI:C处理之前，先用特异性抑制剂预处理原代肝细胞。我们发现只有c-jun氨基末端激酶（JNK）抑制剂减弱了DMETs的下调。这些结果表明，不依赖TRIF的途径可通过TLR4和3参与DMETs的下调。JNK依赖的机制可能介导了这种下调。
