Cardio Lipotoxicity Induces Diabetic Cardiomyopathy Through CGAS-STING Mediated Cardiomyocyte Pyroptosis

Objective: Diabetic cardiomyopathy(DCM)is a diabetes-induced heart disease.It is a common clinical complication of diabetes that currently lacks specific treatment.Cyclic GMP-AMP synthase(c GAS)-stimulator of interferon genes(STING)signaling pathway has been proved to contribute to the pathogenesis of cardiovascular diseases.However,whether it has a regulatory effect on the pathological process of DCM and its mechanism of action have not yet been elucidated.The present study aimed to determine the role of c GAS-STING on the initiation of nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3(NLRP3)inflammasome-induced cardiac pyroptosis and chronic inflammation during the pathogenesis of DCM.Methods: For in vitro experiments,cardiomyocytes were treated with palmitic acid(PA)to simulate cardiolipotoxicity,and treated with the DNA-depleting agent ethidium bromide(Et Br),or transfected with small interfering RNA(si RNA)to silence the expression of c GAS or STING to inhibit the activation of c GAS-STING signaling pathway.And through flow cytometry,cell immunofluorescence,Western blot,quantitative realtime polymerase chain reaction(q RT-PCR),PI staining and LDH release test to explore the activation and mechanism of c GAS-STING signaling pathway in cardiomyocytes.For in vivo experiments,C57BL/6 mice were pre-injected with adenoassociated virus 9(AAV-9)into the tail vein to specifically knock out cardiac sting1 gene expression.After 4 weeks,mice were intraperitoneally injected with streptozotocin(STZ,50 mg/kg)for five consecutive days,and fed with high-fat diet to induce a diabetic mouse model.The regulatory role of c GAS-STING in cardiac hypertrophy and cardiac dysfunction was explored by echocardiographic detection,immune-histochemical analysis,wheat germ agglutinin(WGA)staining and western blot analysis.Results: In this study,we found that PA-induced lipotoxicity disrupts mitochondrial homeostasis,leading to excessive accumulation of mitochondrial reactive oxygen species(mt ROS),which in turn triggers oxidative damage to mitochondrial DNA(mt DNA)and is released into the cytoplasm,promoting c GAS-STING activation and mediating induce cardiomyocyte pyroptosis,thereby aggravating myocardial hypertrophy in diabetic cardiomyopathy.At the same time,we found that activation of the c GAS-STING signaling pathway in diabetic hearts induced the activation of the NLRP3 inflammasome and promoted the release of cellular inflammatory factors into the blood.Furthermore,knockdown of sting1 gene expression by AAV-9 in diabetic mouse hearts attenuated pyroptosis and inflammatory responses in the hearts,thereby inhibiting diabetesinduced cardiac hypertrophy and improving cardiac function.Conclusion: Our study demonstrated that the activation of c GAS-STING pathway caused by mitochondria oxidative damage and mt DNA escape which induced by free fatty acid promoted pyroptosis and proinflammatory response in cardiomyocytes in a NLRP3 inflammasome dependent way,hence promoted the myocardial hypertrophy during the progress of DCM.