Mechanism of fibrotic cardiomyopathy in mice expressing truncated Rho‐associated coiled‐coil protein kinase 1

Abstract

We have previously found that in failing human hearts, Rho-associated coiled-coil protein kinase 1 (ROCK1) is processed by caspase-3 into an active isoform, ROCKΔ1. The purpose of the current investigation was to elucidate the pathological consequences of truncated ROCK1 accumulation in the heart, the associated molecular mechanism of ROCKΔ1-mediated cardiac phenotype, and the molecular signaling between Rho kinase activation in cardiomyocytes and extracellular matrix response. We generated transgenic mice expressing ROCKΔ1 in cardiomyocytes to mimic the situation observed in human heart disease, whereas an additional kinase-deficient mouse was generated as a control. The ROCKΔ1 transgenic mice developed fibrotic cardiomyopathy with diastolic dysfunction. Transgenic hearts displayed activated TGFβ1 and NF-κB signaling and a release of a subset of cytokines and were susceptible to angiotensin II stress. Treatment with a Rho kinase inhibitor attenuated the fibrotic phenotype. Cardiac fibroblasts differentiated into myofibroblasts when cocultured with transgenic cardiomyocytes but not with wild-type cardiomyocytes. Inhibitors of Rho kinase as well as TGFβR1 and NF-κB decreased these effects. The serum response factor-dependent TGFβ1 regulation was shown to be responsible for the Rho kinase-mediated activation of TGFβ1 signaling. We conclude that ROCKΔ1 is a novel fibrotic factor. Activation of TGFβ1 and NF-κB signaling contributes to the Rho kinase-mediated pathological fibrosis.

Small G Proteins in the Cardiovascular System: Physiological and Pathological Aspects

“…This decreased fibrosis is associated with a reduced expression of markers of fibrosis including transforming growth factor-␤ (TGF-␤), CTGF, and type III collagen. Similar reduction of fibrosis has been observed in Rock1 knockout mice (582), together with a decreased cardiomyocyte apoptosis following pressure overload by aortic banding (563). These results thus indicate that in vivo, Rock1 contributes to the development of cardiac fibrosis but not hypertrophy in response to various pathological conditions.…”

“…These results thus indicate that in vivo, Rock1 contributes to the development of cardiac fibrosis but not hypertrophy in response to various pathological conditions. This was recently confirmed in a transgenic mice expressing a truncated activate form of Rock1 in cardiomyocytes (563) These mice displayed extensive cardiac fibrosis due to upregulation of TGF-␤ and cytokine release in cardiomyocytes that promoted myofibroblast differentiation (563).…”

Rnd3/RhoE Modulates Hypoxia-Inducible Factor 1α/Vascular Endothelial Growth Factor Signaling by Stabilizing Hypoxia-Inducible Factor 1α and Regulates Responsive Cardiac Angiogenesis

“…Treatment with Rho kinase inhibitor reversed the cardiac phenotype and improved cardiac functions. 29 Therefore, it wa logical to assume that the Rnd3 deficiency-mediated cardiac dysfunction was through the augmentation of ROCK1 activity. However, by taking the approaches of genetic deletion of ROCK1 and the utilization of a Rho kinase inhibitor, we recently found that Rho kinase activation was partially, but not entirely, responsible for Rnd3 deficiency-induced cardiomyopathy, suggesting that there was a Rho kinase-independent mechanism regulated by Rnd3.…”

Signaling Pathways in Cardiac Myocyte Apoptosis

“…When expressed in cardiomyocytes, the truncated ROCK1 by itself induced caspase 3 activation and apoptosis in vitro and myocardial fibrosis in vivo [42, 195]. Interestingly, global deficiency of ROCK1 also inhibited myocyte apoptosis, and transgenic expression of ROCK1 enhanced apoptosis following pressure overload or in a pathological hypertrophy mouse model overexpressing G α q [42, 159].…”