Adiponectin is protective against endoplasmic reticulum stress-induced apoptosis of endothelial cells in sepsis

Endoplasmic reticulum (ER) stress is a critical molecular mechanism involved in the pathogenesis of sepsis. Hence, strategies for alleviating this stress may be essential for preventing cardiovascular injuries under sepsis. Adiponectin is secreted by adipocytes and its levels are decreased in sepsis. The purpose of this study was to investigate the protective effects of adiponectin treatment on endothelial cells and its mechanism. Male Wistar rats underwent cecal ligation and puncture (CLP) before being treated with adiponectin (72 and 120 μg/kg). The levels of malondialdehyde (MDA) in plasma, histological structure, and apoptosis of endothelial cells were evaluated. In vitro, human umbilical vein endothelial cells (HUVECs) were treated with adiponectin at 10 and 20 μg/mL for 24 h after stimulation by lipopolysaccharide (LPS). The levels of reactive oxygen species (ROS), ultrastructure, rate of apoptosis, the expression of inositol-requiring enzyme 1α (IRE1α) protein, and its downstream molecules (78 kDa glucose-regulated protein (GRP78), C/EBP homologous protein (CHOP), and caspase-12) were detected. The results showed that the levels of MDA and ROS induced by CLP or LPS stimulation were increased. Furthermore, endothelial cell apoptosis was increased under sepsis. The IRE1α pathway was initiated, as evidenced by activated IRE1α, increased GRP78, and up-regulated CHOP and caspase-12 in HUVECs. Following treatment with adiponectin, the number of apoptotic endothelial cells was markedly decreased. These findings demonstrated that treatment with adiponectin decreased apoptosis of endothelial cells caused by sepsis by attenuating the ER stress IRE1α pathway activated by oxidative stress.内质网（Endoplasmic reticulum, ER）应激是参与脓毒症（sepsis）发病机制的关键分子机制。因此，缓解此类应激的策略或对预防脓毒症相关心血管损伤至关重要。脂联素（adiponectin）由脂肪细胞分泌，其在脓毒症患者体内的表达水平显著降低。本研究旨在探讨脂联素干预对内皮细胞的保护作用及其潜在分子机制。雄性Wistar大鼠先接受盲肠结扎穿刺术（cecal ligation and puncture, CLP）造模，随后分别以72 μg/kg与120 μg/kg的剂量给予脂联素干预。检测各组大鼠血浆丙二醛（malondialdehyde, MDA）水平、内皮细胞组织学结构及凋亡情况。体外实验中，人脐静脉内皮细胞（human umbilical vein endothelial cells, HUVECs）先经脂多糖（lipopolysaccharide, LPS）刺激，再分别以10 μg/mL、20 μg/mL的脂联素处理24小时。随后检测细胞内活性氧（reactive oxygen species, ROS）水平、超微结构、细胞凋亡率，以及肌醇需求酶1α（inositol-requiring enzyme 1α, IRE1α）蛋白及其下游分子（78kDa葡萄糖调节蛋白（78 kDa glucose-regulated protein, GRP78）、C/EBP同源蛋白（C/EBP homologous protein, CHOP）与半胱天冬酶-12（caspase-12））的表达水平。研究结果显示，CLP造模或LPS刺激可显著升高机体与细胞内MDA及ROS水平；同时，脓毒症状态下内皮细胞凋亡率明显上调。IRE1α通路被激活，具体表现为HUVECs中IRE1α活化、GRP78表达上调，以及CHOP与caspase-12的转录水平升高。经脂联素干预后，凋亡的内皮细胞数量显著减少。上述结果表明，脂联素可通过减轻氧化应激介导的ER应激IRE1α通路激活，进而抑制脓毒症诱导的内皮细胞凋亡。