Leukemia inhibitory factor and interleukin-6 downregulate sarcoplasmic reticulum Ca2+ ATPase (SERCA2) in cardiac myocytes

Alterations in gene expression are a hallmark of cardiac hypertrophy and he art failure. Among these, the decreased expression of the sarcoplasmic reti culum calcium ATPase (SERCA2) has been described. Elevated levers of cytoki nes in particular, Leukemia Inhibitory Factor (LIF) and Interleukin-6 (IL-6 ) have been shown to have the capacity to elicit hypertrophic responses in cultured cardiac myocytes. In this study, we investigated the effects of th ese cytokines (LIF & IL-6) on the regulation of SERCA2 levels in cardiac my ocytes. Cultured neonatal rat ventricular myocytes were transfected with a 3.2 kb promoter plasmid construct containing the SERCA2 promoter linked to a chloramphenicol acetyltransferase (CAT) reporter gene, and subsequently t reated with 10 ng/ml LIF or 10 ng/ml IL-6. LIF and IL-6 independently cause d a significant (p less than or equal to 0.05) 23-36 % inhibition in SERCA2 promoter activity. LIF and IL-6 induced inhibition was also evident in SER CA2 mRNA levels as assessed by Northern analysis. Time course of inhibition of SERCA2 mRNA levels showed the most prominent decrease occurring after 4 8 hours of treatment, with both cytokines having a dose dependent effect on the inhibitory response. Western analysis using a polyclonal antibody to S ERCA2 protein indicate a significant, 60 % decrease in the amount of total SERCA2 protein in cultured myocytes treated with 10 ng/ml LIF or IL-6. In c onclusion, the cytokines LIF and IL-6 downregulate SERCA2 gene expression a nd protein levels. The molecular mechanism responsible for cytokine induced downregulation of SERCA2 is at least partly transcriptional.