Tumor Necrosis Factor‐alpha Mediated Changes in Cardiomyocyte Adhesion

Abstract

We have established that myocardial levels of tumor necrosis factor‐a (TNF) are acutely elevated in the aortocaval fistula model of heart failure. Furthermore, the elevations in TNF coincide with the initial development of ventricular dilatation induced by the sustained volume overload. It was our hypothesis that TNF induced alterations in integrin mediated cardiomyocyte adhesion contribute to this adverse myocardial remodeling. To test this supposition, left ventricular cardiomyocytes were isolated from normal adult hearts (n = 6) by perfusion with collagenase. Aliquots of 5×104 calcium tolerant isolated cardiomyocytes were incubated for 0.5 hr in DMEN media containing TNF (50 ng/ml), TNF + PP2 (Src kinase inhibitor), TNF + SB203580 (p38 MAP kinase inhibitor), or media alone. The cardiomyocytes were then plated on laminin coated wells for 2 hr, after which the wells were washed and the percentage of adherent cells determined. Incubation with TNF produced a significant 45% reduction in cardiomyocyte adhesion to laminin. This decrease was markedly attenuated by the Src kinase inhibitor PP2, whereas the p38 MAP kinase inhibitor did not prevent the TNF mediated decrease in adhesion. This study implicates reductions in integrin mediated cardiomyocyte adhesion induced by TNF signaling via Src kinase dependent pathways in the adverse myocardial contributing to alterations in ventricular structure and function.