Loss of ADAM15 Exacerbates Transition to Decompensated Myocardial Hypertrophy and Dilation Through Activation of the Calcineurin Pathway.

Background: Myocardial hypertrophy and dilation are key features of cardiomyopathies and involve several cellular and molecular events. ADAMs (a disintegrin and metalloproteinases) are membrane-bound proteinases with diverse functions whose role in heart disease remains underexplored. ADAM15 is expressed in the heart and is downregulated in the failing human heart. We investigated the role ADAM15 in pressure overload cardiomyopathy.
Methods: We assessed ADAM15 levels in myocardial specimens from patients. Its direct role in pressure overload was investigated by subjecting wildtype and Adam15 -deficient mice to transverse aortic constriction (TAC).
Results: ADAM15 levels did not change in patients with concentric hypertrophy, but markedly decreased in eccentric hypertrophy and heart failure. Loss of ADAM15 alone did not cause cardiomyopathy in mice (1 year old). After TAC, Adam15 ^-/- mice exhibited worsened eccentric hypertrophy and dilation with greater increase in hypertrophy markers (pJNK, pERK1/2; Nppb, Nppa , Myh7 , Acta1 ) compared with wildtype-TAC. Expression of integrin-α7 (but not integrin β1) increased significantly more in Adam15 ^-/- -TAC hearts, while the interaction of these integrins with basement membrane (laminin), decreased consistent with worsened left ventricle dilation. In vitro, ADAM15 knockdown increased cardiomyocyte hypertrophy in response to mechanical stretch. Adam15 ^-/- -TAC hearts exhibited increased calcineurin activity and de-phosphorylation of nuclear factor of activated T cells. Calcineurin inhibition (cyclosporin-A) blocked the excess hypertrophy and dilation in Adam15 ^-/- -TAC mice. Proteome profiling demonstrated the increased abundance of the key proteins linked to worsened DCM in Adam15 ^-/- -TAC.
Conclusion: This is the first report demonstrating that ADAM15 can suppress hypertrophy through regulating the integrin-laminin interaction and the calcineurin pathway.