Department of Physiology, Faculty of Medicine, Kaohsiung Medical University Hospital, Taiwan.
Shock. 2012 Mar;37(3):289-96. doi: 10.1097/SHK.0b013e318240b52a.
Severe sepsis associated with overproduction of tumor necrosis factor α and reactive oxygen species leads to energy depletion and cellular damage. Both reactive oxygen species and damaged organelles induce autophagy for recycling nutrients to combat pathological stress. To study whether autophagy plays a beneficial role in the pathogenesis of renal failure during sepsis, rats were subjected to cecal ligation and puncture (CLP) or sham operation. Temporal relationship of autophagy and renal dysfunction were examined in vivo. The results showed that the level of lipidated microtubule-associated protein light chain 3 (LC3-II), a marker of autophagy, elevated transiently at 3 h but declined at 9 h until 18 h after CLP. Light chain 3 aggregation in renal tissue showed a similar trend to the change of LC3-II protein. High levels of blood urea nitrogen and creatinine as well as low tubular sodium reabsorption occurred at 18 h after CLP. The distribution of autophagy located primarily in angiotensin-converting enzyme-positive, which is concentrated in proximal tubule, but calbindin D28k (calcium-binding protein D28K, a marker of distal tubule)-negative cells in renal cortex. Therefore, NRK-52E (proximal tubule epithelial cell line) cells were used to further examine cell viability and DNA fragmentation after silencing or inducing autophagy. We found that knockdown of Atg7 (autophagy-related gene 7) exaggerates, whereas preincubation of rapamycin (an autophagy inducer) diminishes tumor necrosis factor α-induced cell death. These results suggest that the decline of sepsis-induced autophagy contributes to the proximal tubular dysfunction, and maintenance of sufficient autophagy prevents cell death. These data open prospects for therapies that activate autophagy during sepsis.
严重脓毒症与肿瘤坏死因子-α和活性氧物质的过度产生有关，导致能量耗竭和细胞损伤。活性氧物质和受损细胞器都会诱导自噬，以回收营养物质来对抗病理性应激。为了研究自噬在脓毒症相关肾衰竭发病机制中是否发挥有益作用，我们对大鼠进行了盲肠结扎穿孔（CLP）或假手术。在体内检测了自噬和肾功能障碍的时间关系。结果表明，自噬标志物微管相关蛋白轻链 3（LC3-II）的脂质化水平在 CLP 后 3 h 短暂升高，但在 9 h 时下降，并持续至 18 h。肾组织中 LC3 聚集的变化趋势与 LC3-II 蛋白相似。CLP 后 18 h 出现血尿素氮和肌酐水平升高以及肾小管钠重吸收降低。自噬的分布主要位于血管紧张素转换酶阳性细胞中，这些细胞集中在近端小管，但在肾皮质中钙结合蛋白 D28k（钙结合蛋白 D28K，远端小管的标志物）阴性细胞中。因此，我们使用 NRK-52E（近端肾小管上皮细胞系）细胞进一步研究沉默或诱导自噬后细胞活力和 DNA 片段化的变化。我们发现，Atg7（自噬相关基因 7）的敲低会加重，而雷帕霉素（自噬诱导剂）的预孵育会减轻肿瘤坏死因子-α诱导的细胞死亡。这些结果表明，脓毒症诱导的自噬下降导致近端小管功能障碍，维持足够的自噬可以防止细胞死亡。这些数据为在脓毒症期间激活自噬的治疗方法开辟了前景。
