TNF-α down-regulates sarcoplasmic reticulum Ca2+ ATPase expression and leads to left ventricular diastolic dysfunction through binding of NF-κB to promoter response element

TNF-alpha (TNF-alpha) causes left ventricular diastolic dysfunction. Down-regulation of sarcoplasmic reticulum Ca2+-ATPase 2a protein (SERCA2a) expression is one of the major mechanisms underlying diastolic dysfunction. We investigated whether TNF-alpha modulates SERCA2a expression and alters cardiac diastolic function, and its detailed signalling pathway. We used both in vitro cellular cardiomyocyte model and in vivo rat model to address this issue. We found that TNF-alpha decreased the levels of both SERCA2a mRNA and protein in the cardiomyocytes, with corresponding impairment of diastolic calcium reuptake, a cellular phenotype of cardiac diastolic function. An similar to 2 kb promoter of the SERCA2a gene (atp2a2) along with its serial deletions was cloned into the luciferase reporter system. TNF-alpha significantly decreased the promoter activity, and truncation of the SERCA2a gene promoter with the putative nuclear factor kappa-B (NF-kappa B) response element abolished TNF-alpha-induced SERCA2a gene suppression. Chromatin immunoprecipitation and gel retardation also confirmed the binding of NF-kappa B to this putative-binding site. TNF-alpha increased the phosphorylation of IKK and the degradation of I kappa B, resulted in NF-kappa B nuclear translocation, and decreased SERCA2a gene promoter activity. This process was attenuated by NF-kappa B blockers and simvastatin. In the in vivo rat model, lipopolysaccharide treatment significantly elevated the serum TNF-alpha level, as well as phosphorylation of IKK, resulting in a decrease in myocardial SERCA2a expression, diastolic calcium reuptake, and diastolic dysfunction. Oral treatment with simvastatin led to an increase in SERCA2a expression, alleviation, and prevention of the diastolic dysfunction. TNF-alpha suppresses SERCA2a gene expression via the IKK/I kappa B/NF-kappa B pathway and binding of NF-kappa B to the SERCA2a gene promoter, and its effect is blocked by simvastatin, demonstrating the potential therapeutic effect of statins in treating inflammation-related diastolic dysfunction.