The effect of immunosuppressant FK506 on hepatic function of graft

探讨免疫抑制剂FK506和环孢素A是否直接影响IL-1β诱导的肝细胞诱导型一氧化氮合酶基因表达。方法：用IL-1β处理原代培养的大鼠肝细胞，比较两种药物对培养上清液中亚硝酸盐的释放、诱导型一氧化氮合酶蛋白和基因表达水平以及对核因子-κB的激活作用。结果：IL-1β可增加培养肝细胞诱导型一氧化氮合酶蛋白和诱导型一氧化氮合酶基因的表达，增加一氧化氮的产生。NF-κB是炎症反应中诱导型一氧化氮合酶基因表达的重要转录因子，加入IL-1β后，肝细胞核中也有表达。FK506可明显抑制IL-1β诱导的一氧化氮生成、诱导型一氧化氮合酶蛋白合成和诱导型一氧化氮合酶基因表达，而环孢素A对此无明显影响。此外，FK506抑制了NF-κB的激活，并降低了NF-κB p50/p65亚基的基因表达水平。结论：这些结果表明，FK506而不是环孢素A抑制了NF-κB激活过程中诱导型一氧化氮合酶的诱导表达。

Studies were performed to determine whether the immunosuppressants FK506 and cyclosporin A directly influence gene expression of inducible nitric oxide synthase by IL-1β in hepatocytes. Methods : Primary cultures of rat hepatocytes were treated with IL-1β in the presence and absence of FK506 or cyclosporin A. Release of nitrite into culture medium, levels of inducible nitric oxide synthase protein and mRNA, and activation of NF-κB were compared with the two drugs. Results : IL-1β increased levels of inducible nitric oxide synthase protein and inducible nitric oxide synthase mRNA, as well as nitric oxide production, in the cultured hepatocytes. NF-κB, an important transcription factor in inducible nitric oxide synthase gene expression in response to inflammation, also appeared in the nuclear fraction of hepatocytes after addition of IL-1β. FK506 markedly inhibited the nitric oxide formation, inducible nitric oxide synthase protein synthesis and inducible nitric oxide synthase mRNA expression induced by IL-1β, but cyclosporin A had no effects. Furthermore, FK506 inhibited NF-κB activation and decreased mRNA levels of the p50/p65 subunits of NF-κB. Conclusions : These results demonstrate that FK506, but not cyclosporin A, inhibits the induction of inducible nitric oxide synthase expression during NF-κB activation