自噬对鼠伤寒沙门菌所致的巨噬细胞凋亡的影响

The Influence of Autophagy on Apoptosis of Macrophage Induced by Salmonella typhimurium

摘要:

为探讨鼠伤寒沙门菌与巨噬细胞共作用时细胞自噬对凋亡的影响, 用加入自噬诱导剂雷帕霉素(Rapamycin, RAPA)和未加RAPA的RPMI 1640过夜培养小鼠腹腔巨噬细胞J774A.1, 以携带一分子量为100 kb毒力质粒的鼠伤寒沙门菌标准毒株SR-11为受试菌。首先测定RAPA对菌量及细胞活性的影响, 然后建立细胞感染模型, 在细菌与细胞共作用后动态观察24 h, 不同时间点检测细胞超微结构变化、自噬泡的形成、Beclin-1和Bcl-2的表达、细胞存活率和胞内活菌计数以及细胞凋亡情况。结果显示, RAPA单独作用于细菌或细胞时菌量及细胞活性均无变化; 而对细胞感染模型而言, RAPA作用与否细胞内的细菌数及细胞存活率均有显著改变, RAPA可明显降低细胞内活菌数及其所致的巨噬细胞凋亡率(P < 0.05); RAPA干预组在细菌与细胞共作用早期, 部分细菌可被双层膜包裹形成自噬泡, 细胞超微结构正常; Beclin-1的表达量增加, 而Bcl-2的表达量降低; 后期细胞破坏程度明显轻于未用RAPA组。以上结果提示, 通过调控细胞自噬水平以减轻宿主细胞凋亡, 可作为防治某些感染性疾病的新途径。

Abstract:

In the present study, the influence of autophagy on apoptosis of macrophage induced by Salmonella typhimurium was investigated. Murine macrophage-like cell line J774A.1 was cultivated with RPMI 1640 containing autophagy inducer rapamycin (RAPA) or not overnight, the standard Salmonella typhimurium virulent strain SR-11 was used as the test bacterium. First, the influence of RAPA on bacteria growth and J774A.1 cells survival were detected, then the incubation of J774A.1 and SR-11 were dynamically tracked 24 h. Cell ultrastructure, the formation of autophagic vesicles, Beclin-1 and Bcl-2 expression, cell survival rate, the number of intracellular viable bacteria and cell apoptosis were detected at different time. The results showed that RAPA didn’t affect bacteria growth and the survival of J774A.1 cells. However, in cellular infectious model, RAPA could significantly reduce the number of intracellular viable bacteria and the rate of macrophage apoptosis, thereby increasing cell survival (P < 0.05). Some bacteria was wrapped in the autophagic vacuoles of J774A.1 cells during inchoate infectious stage, and cellular ultrastructure was normal after RAPA treatment. Moreover, the expression of Beclin-1 was increased while the expression of Bcl-2 was declined, and cells damage were significantly lighter in the late stage. All these results suggested that the regulation of cellular autophagy to lower the level of host cells apoptosis may be used as new ways of the prevention and control for some infectious diseases.