Cyclic AMP induces necroptotic cell death in cardiac fibroblasts

Abstract

Increased levels of the second messenger cyclic AMP (cAMP) can promote cell loss of a variety of cell types. The precise mechanism(s) for this loss is/are not clearly defined, although cAMP can promote apoptosis of certain types of cells (Insel et al, Acta Physiol in press). In the present study, we used adult rat cardiac fibroblasts (rCFs) to test the hypothesis that cAMP induces necroptosis. Our results from morphological and biochemical studies provide evidence that cAMP induces necroptosis in rCFs and is mediated by protein kinase A and not Epac, another cAMP effector. The findings include destruction of the plasma membrane of rCFs, which differs from apoptotic shrinking of the membrane, and a prominent increase in expression of HMGB1, a marker of necrosis, following treatment with cAMP‐elevating agents. In addition, such agents induce death in a caspase‐PARP independent manner. The pan‐caspase inhibitor, z‐VAD‐fmk increases cell death induced by CPT‐cAMP but the necroptosis inhibitors necrostatin‐1 and cyclosporine A reduce this effect. Taken together, these findings lead us to conclude that cAMP induces necroptosis in rCFs and that this occurs via a PKA‐mediated mechanism. cAMP/PKA‐promoted necroptosis may contribute to decrease in number of CFs in vivo and may be a mechanism of cAMP‐promoted cell death in other types of cells. (Supported by research and training grants from NIH).