Mantis N, Prévost M C, Sansonetti P
Unité de Pathogénie Microbienne Moléculaire, INSERM U389, Paris, France.
Infect Immun. 1996 Jul;64(7):2474-82. doi: 10.1128/iai.64.7.2474-2482.1996.
Shigella flexneri-infected macrophage cells undergo an apoptotic-like death as early as one hour after infection (A. Zychlinsky, M. C. Prévost, and P. J. Sansonetti, Nature [London] 358:167-168, 1992). To determine the fate of infected epithelial cells, we characterized the viability, morphology, and several metabolic activities of HeLa cells after treatment with M90T, an invoffve isolate of S. flexneri serotype 5, or BS176, a noninvasive isolate cured of the 220-kb virulence plasmid. Using standard assays, we found that for at least 4 h after infection with M90T, HeLa cells remained viable and did not detach or lyse. The ultrastructural morphology of HeLa cells heavily infected with M90T was free of hallmarks associated with cells undergoing apoptosis. Consistent with the idea that intracellular bacterial growth is metabolically stressful to the host cell, we observed that, compared with BS176 treated-HeLa cells, M90T-treated HeLa cells showed (i) a significant decrease in the total pool size of nucleoside triphosphates, (ii) a reduced ability to incorporate extracellular radiolabeled methionine into the soluble and insoluble cell fractions, and (iii) a stimulation of glucose uptake. However, there was no detectable increase in expression of the stress-inducible hsp70 gene in M90T-infected HeLa cells or activation of the anaerobic metabolic pathway as determined by measuring total lactate levels. These results demonstrate clearly that the fate of S.flexneri-infected cells can vary dramatically between cell types and agree with the hypothesis that the destruction of epithelial cells observed in experimental models of shigellosis is due to the host inflammatory response and probably not bacterial intracellular multiplication per se.
福氏志贺菌感染的巨噬细胞早在感染后一小时就会经历类似凋亡的死亡（A. 齐克林斯基、M. C. 普雷沃斯特和P. J. 桑索尼蒂，《自然》[伦敦]358:167 - 168，1992）。为了确定受感染上皮细胞的命运，我们对HeLa细胞在用M90T（福氏志贺菌血清型5的侵袭性分离株）或BS176（去除了220 kb毒力质粒的非侵袭性分离株）处理后的活力、形态和几种代谢活性进行了表征。使用标准检测方法，我们发现用M90T感染后至少4小时，HeLa细胞仍保持活力，没有脱落或裂解。被M90T严重感染的HeLa细胞的超微结构形态没有与正在经历凋亡的细胞相关的特征。与细胞内细菌生长对宿主细胞造成代谢压力的观点一致，我们观察到，与用BS176处理的HeLa细胞相比，用M90T处理的HeLa细胞表现出：（i）三磷酸核苷的总库大小显著降低；（ii）将细胞外放射性标记的甲硫氨酸掺入可溶性和不溶性细胞组分的能力降低；（iii）葡萄糖摄取增加。然而，在用M90T感染的HeLa细胞中，未检测到应激诱导型hsp70基因的表达增加，也未通过测量总乳酸水平确定厌氧代谢途径的激活。这些结果清楚地表明，福氏志贺菌感染细胞的命运在不同细胞类型之间可能有很大差异，这与志贺菌病实验模型中观察到的上皮细胞破坏是由于宿主炎症反应而可能不是细菌本身在细胞内繁殖的假设一致。
