Research On The Role Of Stress Granules Activation In Sepsis-induced Myocardial Dysfunction

Background: Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection.It is associated with high morbidity and mortality rates among patients in the intensive care unit.Sepsis-induced myocardial dysfunction(SIMD)is the most common and serious organ dysfunction.Myocardial dysfunction in patients with sepsis is associated with multiple organ failure and poor outcomes.Given that the mechanism underlying septic cardiomyopathy has not been fully elucidated,effective treatment approaches are lacking.Stress granules(SG)are cytoplasmic membrane-less compartments that form in response to cellular stress and play important roles in various cell signaling pathways.The role of SG in sepsis-induced myocardial dysfunction has not been determined.Methods: Neonatal cardiomyocytes(CMs)were treated with lipopolysaccharide(LPS).SG activation was visualized by immunofluorescence staining to detect the co-localization of GTPase-activating protein SH3 domain binding protein 1(G3BP1)and T cell-restricted intracellular antigen 1(TIA-1).Eukaryotic translation initiation factor alpha(e IF2α)phosphorylation,an indicator of classical SG formation,was assessed by western blotting.Tumor necrosis factor alpha(TNF-α)production was assessed by PCR and enzyme-linked immunosorbent assays.CM function was evaluated by intracellular cyclic adenosine monophosphate(c AMP)levels in response to dobutamine.Pharmacological inhibition(ISRIB),a G3BP1 CRISPR activation plasmid,and a G3BP1 KO plasmid were employed to modulate SG activation.The fluorescence intensity of JC-1 was used to evaluate mitochondrial membrane potential.Results: LPS challenge in CMs induced SG activation and resulted in e IF2α phosphorylation,increased TNF-α production,and decreased intracellular c AMP in response to dobutamine.The pharmacological inhibition of SG(ISRIB)increased TNF-α expression and decreased intracellular c AMP levels in CMs treated with LPS.The overexpression of G3BP1 increased SG activation,attenuated the LPS-induced increase in TNF-α expression,and improved CM contractility(as evidenced by increased intracellular c AMP).Furthermore,SG connected with LPS-induced mitochondrial membrane potential dissipation in CMs.The results of Western blot assays showed that PERK-I could down-regulate LPS-induced e IF2 a phosphorylation,further confirming the role of PERK in LPS-induced stress response in CMs.Conclusion: SG formation plays a protective role in CM with sepsis.