Wu Yong, Yang Huan, Cheng Ming, Shi Jialin, Zhang Weichen, Liu Shaojun, Zhang Minmin
Department of Nephrology, Huashan Hospital and Nephrology Institute, Fudan University, Shanghai, China.
Front Med (Lausanne). 2022 Jan 28;9:811980. doi: 10.3389/fmed.2022.811980. eCollection 2022.
Renal ischemia/reperfusion injury is a major contributor of acute kidney injury (AKI), leading to renal cell necrosis, apoptosis, and inflammation. Calpains, a family of Ca-dependent cysteine proteases, play a pivotal role in the pathogenesis of renal diseases. Several studies have reported calpain inhibitors showing remarkable reno-protective effects against proteinuria and α-klotho deficiency-induced renal aging symptoms, particularly against glomerulus injury. However, little is known about the role of the calpain inhibitor calpeptin in acute kidney injury. The present study aims to investigate the potential mechanism of downregulation of Calpain 1 and 2 activity by calpeptin in the ischemia/reperfusion (IR)-induced AKI model. Firstly, we observed that the contents of Calpain 1 and 2 were significantly increased in the renal biopsy of clinical AKI patients, especially in the diseased tubules space. To investigate the impacts of calpain activity inhibition, we further pretreated with calpeptin in both the IR mouse model and in the HK-2 cells hypoxia model. We found that the calpain inhibitor calpeptin improved renal functional deterioration, attenuated pathological structure damage, and decreased tubular cell apoptosis in the IR injury-induced AKI mice model. Mechanistically, calpeptin significantly suppressed the AIM2 (absent in melanoma 2) and NLRP3 (NOD-like receptor protein 3) inflammasome signaling pathways and increased Klotho protein levels. Furthermore, immunofluorescence assays demonstrated that the application of calpeptin effectively inhibited Calpain 1 activation and gasdermin D (GSDMD) cleavage in the renal tubules of IR mice. Taken together, our both and experiments suggest that calpeptin conveyed reno-protection in AKI might be mediated by the inhibition of AIM2 inflammasome activation and upregulation of Klotho protein. As such, we provide new evidence that Calpain 1 and 2 activation may be closely associated with the pathogenesis of clinical AKI. The calpain-mediated AIM2 inflammasome signaling pathway and distinct interaction between calpain and Klotho may provide a potential novel preventative and therapeutic target for acute kidney injury.
肾缺血/再灌注损伤是急性肾损伤（AKI）的主要原因，可导致肾细胞坏死、凋亡和炎症。钙蛋白酶是一类钙依赖性半胱氨酸蛋白酶，在肾脏疾病的发病机制中起关键作用。多项研究报道，钙蛋白酶抑制剂对蛋白尿和α-klotho缺乏引起的肾脏衰老症状具有显著的肾保护作用，尤其是对肾小球损伤。然而，关于钙蛋白酶抑制剂钙肽素在急性肾损伤中的作用知之甚少。本研究旨在探讨钙肽素下调钙蛋白酶1和2活性在缺血/再灌注（IR）诱导的AKI模型中的潜在机制。首先，我们观察到临床AKI患者肾活检中钙蛋白酶1和2的含量显著增加，尤其是在病变肾小管区域。为了研究抑制钙蛋白酶活性的影响，我们在IR小鼠模型和HK-2细胞缺氧模型中均用钙肽素进行了预处理。我们发现，钙蛋白酶抑制剂钙肽素可改善IR损伤诱导的AKI小鼠模型的肾功能恶化，减轻病理结构损伤，并减少肾小管细胞凋亡。机制上，钙肽素显著抑制AIM2（黑色素瘤缺失2）和NLRP3（NOD样受体蛋白3）炎性小体信号通路，并增加Klotho蛋白水平。此外，免疫荧光分析表明，应用钙肽素可有效抑制IR小鼠肾小管中钙蛋白酶1的激活和gasdermin D（GSDMD）的裂解。综上所述，我们的体内和体外实验表明，钙肽素在AKI中发挥肾保护作用可能是通过抑制AIM2炎性小体激活和上调Klotho蛋白介导的。因此，我们提供了新的证据，表明钙蛋白酶1和2的激活可能与临床AKI的发病机制密切相关。钙蛋白酶介导的AIM2炎性小体信号通路以及钙蛋白酶与Klotho之间独特的相互作用可能为急性肾损伤提供一个潜在的新型预防和治疗靶点。
