Abstract 18443: Early Inflammation in βII-Spectrin Deficient Hearts Promote Cardiac Remodeling and Heart Failure

Abstract

Background: Dysregulation of cardiac cytoskeletal proteins such as βII-spectrin has been recognized to promote accelerated heart failure (HF) and arrhythmias in human and mouse models. However, the mechanism by which βII-spectrin dysregulation underlies HF is poorly understood. Hypothesis: We hypothesized that cardiomyocyte loss of βII-spectrin leads to recruitment of inflammatory macrophages that augment cardiac remodeling by promoting arrhythmogenesis and increased susceptibility to HF. Methods: Cardiomyocyte-specific βII-spectrin knockout (βII-cKO) and control mice (βII-flox) were generated and harvested for RNA-sequencing (RNA-seq), qRT-PCR (to validate candidate inflammatory genes), immunohistochemistry, immunoblotting, and flow cytometry. siRNA was also used to knockdown βII-spectrin in cultured cells to validate that direct loss of βII-spectrin contributes to immune cell recruitment. Transaortic constriction (TAC) was used to induce pressure overload. Results: RNA-seq demonstrated an early significant increase of inflammatory macrophages and T cell markers following βII-spectrin loss. Consistent with RNA-seq and qRT-PCR results, immunohistochemistry demonstrated an increase in CD45 positive cells in juvenile βII-cKO mouse hearts compared to control. siRNA targeted depletion of βII-spectrin in cultured cardiomyocyte led to increased expression and secretion of TGFβ-1 protein, which can promote infiltrating of immune cells. Notably, accelerated HF at two weeks was observed in βII-cKO mice compared to controls after TAC. Conclusions: These data suggest that βII-spectrin loss may mediate inflammation via the TGFβ-1 pathway, which in part contributes to βII-spectrin-mediated accelerated HF. Furthermore, these are the first data implicating βII-spectrin in the TGFβ1-immune signaling pathway in cardiomyocytes.