<p>Mitochondrial dysfunction is a key contributor to septic cardiomyopathy, driving myocardial inflammation and apoptosis. This study found that Sushi-repeat containing protein X-linked 2 (Srpx2) is associated with mitochondrial damage and is downregulated in the myocytes of lipopolysaccharide (LPS)-treated rats. Sprague Dawley rats were intraperitoneally injected with LPS (10&#xa0;mg/kg) to establish a septic cardiomyopathy model. Adeno-associated viruses (8.5 × 10¹¹ vg/mL) containing Srpx2-overexpressing plasmids were injected into rats through their tail vein. Srpx2 overexpression improved hemodynamics and decreased myocardial damage in LPS-treated rats. H9C2 cells were treated with LPS (10&#xa0;μg/mL) to establish an in vitro septic model. The cells were then transfected with Srpx2-overexpressing plasmids. Srpx2 overexpression ameliorated mitochondrial damage, which was evidenced by restoring mitochondrial morphology, enhancing the complex activities, and elevating ATP and mitochondrial membrane potential levels in cardiomyocytes. Srpx2 overexpression reduced mitochondrial reactive oxygen species levels and superoxide generation in cardiomyocytes. Srpx2 overexpression decreased cleaved caspase-3 and 9 protein levels. Tumor necrosis factor-α and interleukin-1 beta levels were also reduced in cardiomyocytes with Srpx2 overexpression, suggesting reversal of inflammation. The RNA-sequencing data indicated that Srpx2 might regulate the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway to protect cardiomyocytes. Srpx2 overexpression increased the p-PI3K and p-AKT protein levels. The treatment of H9C2 cells with 10&#xa0;μM LY294002, a PI3K/AKT pathway inhibitor, reversed the protective effects of Srpx2 against mitochondrial damage and apoptosis. In conclusion, Srpx2 alleviates mitochondrial damage by activating the PI3K/AKT pathway, thereby reducing apoptosis and inflammation in septic cardiomyopathy.</p> Graphical abstract <p></p>