Melatonin alleviates chronic stress-induced hippocampal microglia pyroptosis and subsequent depression-like behaviors by inhibiting Cathepsin B/NLRP3 signaling pathway in rats

Melatonin improves chronic stress-induced hippocampal damage and depression-like behaviors, but the mechanism needs further study. This study was to explore the mechanism of melatonin inhibiting microglia pyroptosis. In virtro experiments, melatonin improved corticosterone-induced the ultrastructure and microstructure damage of HAPI cells by inhibiting pyroptosis, thereby increasing cell survival rate. Protein-protein interaction network and molecular autodocking predicted that Cathespin B might be the target of melatonin inhibition of NLRP3-mediated pyroptosis. Melatonin inhibited corticosterone-induced Cathespin B expression. Both Cathepsin B inhibitor CA-074Me and NLRP3 knockout inhibited the HAPI cells pyroptosis. Similarly, melatonin inhibited Cathepsin B agonist Pazopanib-induced activation of Cathepsin B/NLRP3 signaling pathway and HAPI cells pyroptosis. In vivo studies, melatonin inhibited chronic restraint stress (CRS)-induced activation of Cathepsin B/NLRP3 signaling pathway and alleviated hippocampal microglia pyroptosis in rats. Inhibition of microglia pyroptosis improved CRS-induced depression-like behaviors of rats. In addition, inhibition of Cathepsin B and NLRP3 alleviated hippocampal pyroptosis. Melatonin inhibited Pazopanib-induced activation of Cathepsin B/NLRP3 signaling pathway and hippocampal pyroptosis. These results demonstrated that melatonin could alleviate CRS-induced hippocampal microglia pyroptosis by inhibiting Cathepsin B/NLRP3 signaling pathway, thereby improving depression-like behaviors in rats. This study reveals the molecular mechanism of melatonin in the prevention and treatment of chronic stress-related encephalopathy.