Williams Lynn M, Lali Ferdinand, Willetts Kate, Balague Cristina, Godessart Nuria, Brennan Fionula, Feldmann Marc, Foxwell Brian M J
Kennedy Institute of Rheumatology Division, Imperial College London, Hammersmith, London W6 8LH, United Kingdom.
Mol Immunol. 2008 May;45(9):2446-54. doi: 10.1016/j.molimm.2007.12.011. Epub 2008 Feb 6.
TNF is a key factor in a variety of inflammatory diseases. Here we report that TNF induced pro-inflammatory cytokine synthesis of IL-6 and IL-8 is mediated by the Rho GTPase Rac. TNF induces p42/p44, p54 and p38 MAPK kinase; these kinases have been implicated in control of cytokine synthesis. However, over-expression of a dominant negative form of Rac strongly inhibited TNF-induced p42/44 MAPK kinase activation, but had little effect upon JNK and no effect upon p38 MAPK activity. Another key signalling pathway controlling cytokine expression is NF-kappaB. When analyzing TNF-induced NF-kappaB activity via luciferase-reporter assays or via EMSA, we were able to show that the dominant negative version of Rac could completely abrogate TNF-induced NF-kappaB activity. In addition, we also observed that inhibition of the ERK pathway led to a reduction in TNF-induced NF-kappaB transcriptional activity; this was accompanied by an ablation of TNF-induced p65 phosphorylation at serine 276. This would suggest that TNF-induced activation of Rac, lies upstream of NF-kappaB activation, and that the inhibition of this pathway results in inhibition of cytokine production.
肿瘤坏死因子（TNF）是多种炎症性疾病中的关键因子。在此我们报告，TNF诱导的白细胞介素-6（IL-6）和白细胞介素-8（IL-8）促炎细胞因子合成是由Rho鸟苷三磷酸酶（GTPase）Rac介导的。TNF诱导p42/p44、p54和p38丝裂原活化蛋白激酶（MAPK）激酶；这些激酶与细胞因子合成的调控有关。然而，Rac显性负性形式的过表达强烈抑制TNF诱导的p42/44 MAPK激酶活化，但对应激活化蛋白激酶（JNK）影响很小，对p38 MAPK活性无影响。另一个控制细胞因子表达的关键信号通路是核因子κB（NF-κB）。当通过荧光素酶报告基因检测或电泳迁移率变动分析（EMSA）分析TNF诱导的NF-κB活性时，我们能够表明Rac的显性负性形式可完全消除TNF诱导的NF-κB活性。此外，我们还观察到细胞外信号调节激酶（ERK）通路的抑制导致TNF诱导的NF-κB转录活性降低；这伴随着TNF诱导的p65丝氨酸276磷酸化的消除。这表明TNF诱导的Rac活化位于NF-κB活化的上游，并表明该通路的抑制导致细胞因子产生的抑制。
