School of Pharmacy, Sungkyunkwan University, Suwon, Korea.
J Pineal Res. 2012 Aug;53(1):67-76. doi: 10.1111/j.1600-079X.2012.00972.x. Epub 2012 Jan 31.
The cytoprotective mechanisms of melatonin in hepatic ischemia/reperfusion (I/R) injury associated with heme oxygenase-1 (HO-1) induction and type 1 interferon (IFN) signaling pathway downstream of toll-like receptor 4 (TLR4) were investigated. Rats were subjected to 60min of ischemia followed by 5-hr reperfusion. Melatonin (10mg/kg) or vehicle (5% ethanol in saline) was administered intraperitoneally 15min prior to ischemia and immediately before reperfusion. Rats were pretreated with zinc protoporphyrin (ZnPP, 10mg/kg, i.p.), a HO-1 inhibitor, at 16 and 3hr prior to ischemia. Melatonin attenuated the I/R-induced increase in serum alanine aminotransferase activity, and ZnPP reversed this attenuation. Melatonin augmented the levels of HO activity and HO-1 protein and mRNA expression, and this enhancement was reversed by ZnPP. Melatonin enhanced the level of NF-E2-related factor-2 (Nrf2) nuclear translocation, and ZnPP reversed this increase. Overexpression of TLR4 and its adaptor proteins, toll-receptor-associated activator of interferon (TRIF), and myeloid differentiation factor 88 (MyD88), induced by I/R, was attenuated by melatonin; ZnPP reversed the effect of melatonin on TLR4 and TRIF expression. Melatonin suppressed the increased interaction between TLR4/TRIF and TLR4/MyD88, which was reversed by ZnPP. Melatonin attenuated the increased levels of JAK2 and STAT1 activation as well as IFN-β, and ZnPP reversed these inhibitory effects of melatonin. Melatonin inhibited the level of chemokine (C-X-C motif) ligand 10 (CXCL-10), and ZnPP reversed this inhibition. Our findings suggest that melatonin protects the liver against I/R injury by HO-1 overexpression, which suppresses the type 1 IFN signaling pathway downstream of TLR4.
研究了褪黑素通过诱导血红素加氧酶-1（HO-1）和 Toll 样受体 4（TLR4）下游的 1 型干扰素（IFN）信号通路在肝缺血/再灌注（I/R）损伤中的细胞保护机制。大鼠接受 60 分钟缺血，然后再灌注 5 小时。褪黑素（10mg/kg）或载体（5%乙醇生理盐水）在缺血前 15 分钟和再灌注前立即腹腔内给药。大鼠在缺血前 16 小时和 3 小时预先用血红素加氧酶-1 抑制剂锌原卟啉（ZnPP，10mg/kg，腹腔内）预处理。褪黑素减轻了 I/R 引起的血清丙氨酸氨基转移酶活性升高，而 ZnPP 逆转了这种减弱。褪黑素增强了 HO 活性和 HO-1 蛋白和 mRNA 的表达，而 ZnPP 则逆转了这种增强。褪黑素增强了 NF-E2 相关因子-2（Nrf2）核易位，而 ZnPP 则逆转了这种增加。I/R 诱导的 TLR4 及其衔接蛋白，干扰素相关激活物（TRIF）和髓样分化因子 88（MyD88）的过表达被褪黑素减弱；ZnPP 逆转了褪黑素对 TLR4 和 TRIF 表达的影响。褪黑素抑制了 TLR4/TRIF 和 TLR4/MyD88 之间相互作用的增加，而 ZnPP 则逆转了这种作用。褪黑素减弱了 JAK2 和 STAT1 激活以及 IFN-β的增加，而 ZnPP 逆转了褪黑素的这些抑制作用。褪黑素抑制趋化因子（C-X-C 基序）配体 10（CXCL-10）的水平，而 ZnPP 则逆转了这种抑制作用。我们的研究结果表明，褪黑素通过 HO-1 的过表达来保护肝脏免受 I/R 损伤，从而抑制 TLR4 下游的 1 型 IFN 信号通路。
