Calpain-mediated lung endothelial barrier modulation in acute lung injury

总结 急性肺损伤（ALI）的特征是肺血管内皮（EC）屏障受损，导致 EC渗透性增加和肺水肿。革兰氏阴性菌感染占主要 因为阿里。关于革兰氏阴性内毒素（即脂多糖，LPS）如何诱导 EC屏障破坏。我们发现LPS激活人肺微血管内皮细胞内的内肽酶，钙蛋白酶， （HLMVEC）和特异性钙蛋白酶抑制剂防止LPS诱导的EC屏障功能的破坏， ALI中HLMVECs和LPS诱导的肺水肿钙蛋白酶是一个钙依赖性非溶酶体家族 中性半胱氨酸内肽酶通过哺乳动物细胞中底物蛋白的有限蛋白水解起作用， 包括HLMVECs。我们的初步数据表明，LPS诱导talin切割成头和杆结构域， HLMVECs中talin磷酸化和钙蛋白酶过表达引起talin切割和RhoA激活 和肌球蛋白轻链磷酸酶（MLCP）磷酸化，导致MLCP抑制和肌球蛋白轻链 (MLC)磷酸化塔林蛋白通过塔林蛋白裂解或磷酸化被激活。塔林裂解分离 从而消除自身抑制并刺激talin头部与整联蛋白结合， 诱导FA活化，导致RhoA活化和MLCP抑制和MLC磷酸化，并增加 肺EC通透性。通过Ser-425磷酸化的Talin活化可以通过细胞周期蛋白依赖性 激酶5（CDK 5）。我们的数据表明钙蛋白酶抑制剂减弱LPS诱导的CDK 5活性的增加， MLCP参与了talin的去磷酸化。本研究旨在探讨钙蛋白酶/MLCP 协调调节talin活化（切割/磷酸化），导致ALI中内皮屏障破坏。 我们将确定是否革兰氏阴性内毒素LPS，E。大肠杆菌和铜绿假单胞菌诱导钙蛋白酶激活 钙蛋白酶导致肺微血管内皮屏障破坏和Rho介导的MLCP 在ALI中的MLC磷酸化/抑制和MLC磷酸化。我们将定义LPS、E. coli和P. 铜绿假单胞菌诱导talin活化（裂解/磷酸化）和FA加强，导致肺 体外和体内微血管内皮屏障破坏。我们将研究钙蛋白酶是否调节 talin激活（裂解/磷酸化）在肺微血管内皮屏障破坏中的作用 LPS、E.大肠杆菌和铜绿假单胞菌。我们将评估来自革兰氏阴性脓毒症ALI患者的血浆是否 通过calpain-talin-FA-MLCP途径诱导HLMVEC屏障受损。这一提议是新颖的，因为它将 鉴定钙蛋白酶作为肺EC屏障损害介质，钙蛋白酶通过调节新的talin发挥这一作用 切割/磷酸化、RhoA活化和MLCP活性。更好地理解机械 洞察力将提供一个框架，新的钙蛋白酶抑制和MLCP激活策略， 用于干预和治疗ALI。

Summary Acute lung injury (ALI) is characterized by lung vascular endothelial (EC) barrier compromise resulting in increased EC permeability and pulmonary edema. The infections of Gram negative bacteria compose the major cause for ALI. Little has been known about how Gram negative endotoxins (i.e. lipopolysaccharides, LPS) induce EC barrier disruption. We found that LPS activates endopeptidase, calpain, in human lung microvascular ECs (HLMVECs) and the specific calpain inhibition prevents LPS-induced disruption of EC barrier function of HLMVECs and LPS-induced pulmonary edema in ALI. Calpain is a family of calcium-dependent non-lysosomal neutral cysteine endopeptidases that act via limited proteolysis of substrate proteins in mammalian cells, including HLMVECs. Our preliminary data show that LPS induces talin cleavage into head and rod domain and talin phosphorylation in HLMVECs and that overexpression of calpain causes talin cleavage and RhoA activation and myosin light chain phosphatase (MLCP) phosphorylation resulting in MLCP inhibition and myosin light chain (MLC) phosphorylation. Talin is activated through talin cleavage or phosphorylation. Talin cleavage separates head from rod domain thus removing auto-inhibition and stimulating talin head binding to integrin and thus induces FA activation, leading to RhoA activation and MLCP inhibition and MLC phosphorylation and increased lung EC permeability. Talin activation through phosphorylation at Ser-425 can be through cyclin-dependent kinase 5 (CDK5). Our data show that calpain inhibition attenuates LPS-induced increase in CDK5 activity and that MLCP is involved in talin dephosphorylation. This proposal is to study a novel hypothesis that calpain/MLCP coordination regulates talin activation (cleavage/phosphorylation) leading to endothelial barrier disruption in ALI. We will determine whether Gram negative endotoxin LPS, E. coli and P. aeruginosa induce calpain activation and calpain leads to lung microvascular endothelial barrier disruption and Rho-mediated MLCP phosphorylation/inhibition and MLC phosphorylation in ALI. We will define whether LPS, E. coli and P. aeruginosa induce talin activation (cleavage/phosphorylation) and FA strengthening, leading to lung microvascular endothelial barrier disruption in vitro and in vivo. We will investigate whether calpain regulates talin activation (cleavage/phosphorylation) in lung microvascular endothelial barrier disruption in ALI induced by LPS, E. coli and P. aeruginosa. We will assess whether plasma from ALI patients with Gram negative sepsis induces HLMVEC barrier compromise via calpain-talin-FA-MLCP pathway. This proposal is novel because it will identify calpain as mediators in lung EC barrier compromise and calpain serves this role by regulating novel talin cleavage/phosphorylation, RhoA activation and MLCP activity in ALI. A better understanding of the mechanistic insight will provide a framework from which novel calpain inhibition and MLCP activation strategies can be developed for intervention and treatment of ALI.