脂氧素A4诱导PPARγ/HO-1过表达在保护肾缺血/再灌注损伤中的信号机制研究

Prevention of renal ischemia/reperfusion injury is important for management of acute renal failure and renal transplantation. Oxygen free radicals play a major role in renal ischemia/reperfusion injury. Heme oxygenase-1(HO-1) is key enzyme of antioxidation. Lipoxin A4 (LXA4) is a novel potent anti-inflammatory mediator in human body. Besides, LXA4 acts as an antioxidation agent. Our previous pilot studies have found that LXA4 inhibits murine renal ischemia/reperfusion injury and induced the expressions of peroxisome proliferator-activated receptor-γ (PPARγ) /HO-1 in renal tubular epithelial cells. However, the mechanisms remian unclear. It can be speculated that those effects of LXA4 may be mediated by the signal pathways via nuclear factor-E2-related factor 2(Nrf2) and PPARγ downstream kinases PI-3K, NF-kB, AP-1, JNK and STATs. The present studies will confirm above speculation and be undertaken with animal models, cell culture and methods of molecular biology, reveal the signal transduction pathways by which LXA4 induces overexpressions of PPARγ/HO-1 in renal tubular epithelial cells. The understanding of above mechanisms chould provide the theoretical and experimental basis for application of LXA4 analogues in treatment of renal ischemia/reperfusion injury.

肾缺血/再灌注损伤的防治对于急性肾衰竭的治疗、提高肾移植成功率有重要意义，而氧自由基是造成该损伤的主要原因，血红素加氧酶-1(HO-1)是减轻氧自由基损伤的抗氧化关键酶。新抗炎介质脂氧素A4(LXA4)除了具有抗炎作用外，近来发现有抗氧化作用。我们在预实验中发现，LXA4可抑制肾缺血/再灌注损伤，并诱导肾小管上皮细胞高表达过氧化物酶体增殖子活化受体γ(PPARγ)/HO-1，其机制有待研究。我们推测LXA4诱导的PPARγ/HO-1过表达在抑制该损伤中起重要作用，其信号通路可能涉及核因子E2 相关因子2(Nrf2)和PI3-K、NF-kB、AP-1、JNK和STATs。本课题应用动物模型、细胞培养和分子生物学有关方法，证实上述推测。阐明LXA4诱导肾小管上皮细胞PPARγ/HO-1高表达的信号转导通路，将为应用LXA4防治肾缺血/再灌注损伤、开发国家一类创新药物提供实验依据并奠定理论基础。

我们在预实验中发现，脂氧素A4(LXA4)可抑制鼠肾缺血/再灌注损伤，并诱导肾小管上皮细胞高表达过氧化物酶体增殖子活化受体(PPAR)/血红素加氧酶-1(HO-1)，推测LXA4诱导的PPAR/HO-1过表达在抑制该损伤中起重要作用，其信号通路可能涉及核因子E2 相关因子2 (Nrf2)和其他信号分子。本课题应用动物模型、细胞培养和分子生物学有关方法，证实上述推测。研究发现，LXA4受体激动剂BML-111可抑制肾缺血/再灌注导致的组织学损伤，抑制该损伤导致的肾脏髓过氧化物酶、丙二醛、血尿素氮和肌酐、尿氨基葡萄糖苷酶和亮氨酸氨基肽酶的升高，BML-111通过活化肾小管上皮细胞p38MAPK刺激PPARα表达，后者通过与HO-1启动子的PPRE区域结合，活化HO-1，从而抑制肾缺血/再灌注损伤。另外，LXA4抑制缺氧/复氧导致的肾小管上皮细胞损伤，活化肾小管上皮细胞p38MAPK，不活化Akt或ERK1/2，刺激PPARγ表达，后者促进Nrf2转位至细胞核，与HO-1的E1增强子的抗氧化反应元件(ARE)相结合，从而活化HO-1，抑制肾小管上皮细胞缺氧/复氧损伤。总之，本研究阐明LXA4防治肾缺血/再灌注损伤的信号通路，为开发国家一类创新药物提供实验依据并奠定理论基础。