Institute of Developmental Biology, School of Life Science, Shandong University, Jinan, China.
J Cell Physiol. 2010 Oct;225(1):174-9. doi: 10.1002/jcp.22210.
Lipopolysaccharide (LPS), as an important proinflammatory agent, targets the endothelium. However, almost all in vitro experiments of the effect of LPS on vascular endothelial cells (VECs) were performed under an artificially decreased concentration of serum that was not enough to maintain the cell growth for a long time. The mechanism underlying LPS action on VECs cultured in a nutrient-rich condition is not clear. To address this question and mimic the in vivo condition, we investigated the effect of LPS on VEC autophagy, which is involved in numerous physiological processes. The effect of LPS on microtubule-associated protein 1 light chain 3 (LC3) distribution, LC3-II accumulation and p62 degradation showed that LPS effectively induced autophagy in VECs cultured in the presence of 20% serum. To understand the mechanism by which LPS triggers the cell autophagy, we first investigated the effects of LPS on the expression of BIRC2 (cIAP1), a well-known apoptosis inhibitor, and on the kinase activity of mammalian target of rapamycin (mTOR) and nuclear translocation of p53. LPS increased BIRC2 expression in a dose- and time-dependent manner and elevated the intranuclear level of p53 but had no effect on the mTOR pathway when it triggered VEC autophagy. Furthermore, knockdown of BIRC2 by RNA interference inhibited the autophagy and the translocation of p53 to nuclei induced by LPS. These data suggest a novel role for BIRC2 in LPS-induced autophagy in VECs.
脂多糖（LPS）作为一种重要的促炎剂，作用于血管内皮细胞。然而，几乎所有 LPS 对血管内皮细胞（VEC）作用的体外实验都是在人为降低血清浓度下进行的，这种血清浓度不足以维持细胞的长期生长。在富含营养的条件下 LPS 对 VEC 作用的机制尚不清楚。为了解决这个问题并模拟体内条件，我们研究了 LPS 对参与多种生理过程的 VEC 自噬的影响。LPS 对微管相关蛋白 1 轻链 3（LC3）分布、LC3-II 积累和 p62 降解的影响表明，LPS 可有效诱导在 20%血清存在的情况下培养的 VEC 发生自噬。为了了解 LPS 触发细胞自噬的机制，我们首先研究了 LPS 对 BIRC2（cIAP1）表达的影响，BIRC2 是一种众所周知的凋亡抑制剂，以及对哺乳动物雷帕霉素靶蛋白（mTOR）激酶活性和 p53 核转位的影响。LPS 以剂量和时间依赖的方式增加 BIRC2 的表达，并升高核内 p53 水平，但在触发 VEC 自噬时对 mTOR 途径没有影响。此外，RNA 干扰敲低 BIRC2 抑制了 LPS 诱导的自噬和 p53 向核内的转位。这些数据表明 BIRC2 在 LPS 诱导的 VEC 自噬中具有新的作用。
