Downregulation of HSPA12A protects heart against sepsis through suppressing mTOR-mediated inflammatory response in cardiomyocytes.

Abstract

Objective: Over-activated immune response in hearts is the main pathological feature of septic cardiomyopathy, a fatal complication of sepsis with high mortality. Autophagy is capable to limit immune response by removing inflammatory mediators. Heat shock protein A12A (HSPA12A) encodes an atypical member of HSP70 family. This study aimed to investigate the role of HSPA12A in septic cardiomyopathy.

Methods: Sepsis was induced by cecal ligation and puncture (CLP) for 6 h in mice in vivo or by LPS treatment for 24 h in primary cardiomyocytes in vitro. HSPA12A knockout (Hspa12a^-/-) mice were generated by cre-loxp system. Echocardiography was performed to assess cardiac function. TUNEL and propidium iodide (PI) staining was used to indicate cardiomyocyte death. Inflammation-related factors were examined by qPCR and immunoblotting. Autophagy was evaluated by levels of LC3-II and p62.

Results: Sepsis decreased HSPA12A expression in hearts and cardiomyocytes, while HSPA12A knockout in mice attenuated sepsis-induced cardiomyocyte death and cardiac dysfunction. Sepsis-induced activation of TLR4/MyD88/NF-κB-mediated inflammation was inhibited in hearts by HSPA12A knockout whereas was enhanced by HSPA12A overexpression in cardiomyocytes. Moreover, HSPA12A overexpression activated mTOR and inhibited autophagy in cardiomyocytes, while inhibition of mTOR by rapamycin diminished the HSPA12A-induced autophagy inhibition, inflammation activation, and cardiomyocyte death in septic cardiomyocytes.

Conclusion: Downregulation of HSPA12A inhibited mTOR to activated autophagy, thereby suppressed inflammatory response, and ultimately attenuated septic cardiomyopathy. Our findings identified HSPA12A as a driver for septic cardiomyopathy development, and strategies that inhibit HSPA12A in cardiomyocytes might be a potential therapeutic intervention.