Mechanism for the release of IL-8 from A549 cells treated with alpha-toxin.

产气荚膜梭菌（C. perfringens）引起的气性坏疽的一个特征是感染区域内缺乏中性粒细胞，并且中性粒细胞在边缘的血管内皮上大量积聚。给小鼠静脉注射产气荚膜梭菌α毒素导致中性粒细胞在肺和肝的血管内皮上积聚，并释放GRO/KC。 α-毒素触发信号转导途径的激活，导致 mRNA 表达和 IL-8 的产生，从而激活 A549 细胞中中性粒细胞的迁移和结合。 K252a（一种酪氨酸激酶 A (TrkA) 抑制剂）和 TrkA 的 siRNA 抑制毒素诱导的 TrkA 磷酸化和 IL-8 的产生。此外，K252a 抑制毒素诱导的 ERK1/2 和 p38 MAPK 磷酸化。 PD98059（一种 ERK1/2 抑制剂）可抑制 ERK1/2 的磷酸化和 NF-κB p65 的核转位，但 SB203580（一种 p38 MAPK 抑制剂）则不会。另一方面，PD98059和SB203580抑制毒素诱导的IL-8产生。用PD98059处理细胞导致毒素诱导的IL-8 mRNA表达受到抑制，而用SB203580处理细胞导致IL-8 mRNA稳定性降低。这些结果表明，α-毒素通过激活两个独立的途径（ERK1/2/NF-κB 和 p38 MAPK 途径）诱导 IL-8 的产生。

A characteristic feature of gas gangrene with Clostridium perfringens(C. perfringens) is the absence of neutrophils within the infected area and the massive accumulation of neutrophils on the vascular endothelium at the margins. Intravenous injection of C. perfringens alpha-toxin into mice resulted in accumulation of neutrophils on the vascular endothelium in lung and liver, and release of GRO/KC. Alpha-toxin triggered activation of signal transduction pathways causing mRNA expression and production of IL-8, which activates migration and binding of neutrophils, in A549 cells. K252a, a tyrosine kinase A(TrkA) inhibitor, and siRNA for TrkA inhibited the toxin-induced phosphorylation of TrkA and production of IL-8.In addition, K252a inhibited the toxin-induced phosphorylation of ERK1/2 and p38 MAPK. PD98059, an ERK1/2 inhibitor, depressed phosphorylation of ERK1/2 and nuclear translocation of NF-κB p65, but SB203580, a p38 MAPK inhibitor, did not. On the other hand, PD98059 and SB203580 suppressed the toxin-induced production of IL-8.Treatment of the cells with PD98059 resulted in inhibition of IL-8 mRNA expression induced by the toxin and that with SB203580 led to a decrease in the stabilization of IL-8 mRNA. These results suggest that alpha-toxin induces production of IL-8 through the activation of two separate pathways, the ERK1/2/NF-κB and p38 MAPK pathways.