Abstract 19098: Beta-Adrenergic Receptor Stimulation Transactivates the Protease-Activated Receptor 1 via Mmp-13 in Heart
Introduction: Chronic beta-adrenergic receptor (b-AR) overstimulation, a hallmark of heart failure (HF), elicits increased cardiac expression of matrix metalloproteinases (MMPs). MMP-1 was found to cleave and activate PAR1 in human tumor cells. We recently reported a role for excess cardiac PAR1 activity in HF pathogenesis. We hypothesized that chronic β-AR overstimulation would effect myocardial MMP-dependent PAR1 transactivation.
Results: β-AR stimulation of neonatal rat cardiomyocytes (NRVM) with isoproterenol (ISO) increased cleavage of alkaline phosphatase-tagged PAR1, which was ablated by the general MMP inhibitor GM6001 (10 microM), thus implicating MMPs in β-AR-dependent PAR1 cleavage (n=6). Two separate specific MMP-13 inhibitors (1 microM) blocked this ISO-mediated PAR1 cleavage, and MMP-13 dose-dependently cleaved PAR1 in cardiac cells (n=5), specifically implicating MMP-13 in cardiac beta-AR-PAR1 transactivation. Interestingly, conditioned medium from ISO-stimulated cardiac fibroblasts (CF) highly induced AP-PAR1 cleavage in myocytes: this intercellular transactivation was reduced by MMP-13 pharmacologic inhibition (n=5). MMP-13 (10 nM) also induced Erk1/2 activation in both NRVM and CF that was significantly reduced by PAR1 antagonists (1 microM) (n=4). In addition, we found that MMP-13 induced inositol phosphates generation in cardiac cells (n=4) and infection of NRVM or CF with the inhibitory GalphaqI peptide reduced MMP-13/PAR1/ERK1/2 activation (n=4). MMP-13 stimulation also caused GRK2-dependent PAR1 internalization, which was blocked by the Gβγ/GRK2 peptide inhibitor βARKct (n=5). Finally, WT or PAR1 knockout mice were exposed to chronic ISO infusion (30mg/kg/day) for 7 days. Importantly, cardiac MMP-13 activity was increased, concomitant with reduced cardiac function in WT mice, determined by echocardiography. However, cardiac function was fully conserved in PAR1 KO mice (WT FS: 43.2%±2.0, n=7. PAR-1 KO FS: 50.5%±1.9, n=6).
Conclusion: These data suggest that chronic β-AR overstimulation contributes to cardiac dysfunction in part through CF and CM-derived transactivation of a novel, pathologic MMP-13-dependent PAR1 signaling.
- © 2010 by American Heart Association, Inc.