G Protein-coupled Receptor Kinase-2 Is a Novel Regulator of Collagen Synthesis in Adult Human Cardiac Fibroblasts

Abstract

Cardiac fibroblasts (CF) make up 60 -70% of the total cell number in the heart and play a critical role in regulating normal myocardial function and in adverse remodeling following myocardial infarction and the transition to heart failure. Recent studies have shown that increased intracellular cAMP can inhibit CF transformation and collagen synthesis in adult rat CF; however, mechanisms by which cAMP production is regulated in CF have not been elucidated. We investigated the potential role of G protein-coupled receptor kinase-2 (GRK2) in modulating collagen synthesis by adult human CF isolated from normal and failing left ventricles. Baseline collagen synthesis was elevated in failing CF and was not inhibited by ␤-agonist stimulation in contrast to normal controls. ␤-adrenergic receptor (␤-AR) signaling was markedly uncoupled in the failing CF, and expression and activity of GRK2 were increased 3-fold. Overexpression of GRK2 in normal CF recapitulated a heart failure phenotype with minimal inhibition of collagen synthesis following ␤-agonist stimulation. In contrast, knockdown of GRK2 expression in normal CF enhanced cAMP production and led to greater ␤-agonist-mediated inhibition of basal and TGF␤-stimulated collagen synthesis versus control. Inhibition of GRK2 activity in failing CF by expression of the GRK2 inhibitor, GRK2ct, or siRNA-mediated knockdown restored ␤-agoniststimulated inhibition of collagen synthesis and decreased collagen synthesis in response to TGF␤ stimulation. GRK2 appears to play a significant role in regulating collagen synthesis in adult human CF, and increased activity of this kinase may be an important mechanism of maladaptive ventricular remodeling as mediated by cardiac fibroblasts.

SIRT3 Blocks Aging-Associated Tissue Fibrosis in Mice by Deacetylating and Activating Glycogen Synthase Kinase 3β

“…Failing heart specimens were obtained from diseased hearts that were removed during orthotopic heart transplantation. The detailed protocols for the isolation and culture of failing cardiac fibroblasts were described previously (15). Adult human nonfailing left ventricular control cardiac fibroblasts were purchased from Cell Applications, Inc. (San Diego, CA).…”

“…Mice with cardiac tissue-restricted expression of Sirt3 and the infusion of Ang-II in mice to develop hypertrophy and fibrosis were described previously (12). Cardiac fibroblasts from 6-month-old wild-type (WT) and Sirt3-knockout (KO) mice were isolated and cultured as previously described (15). SB-505124 (S4696; Sigma) was dissolved in dimethyl sulfoxide (DMSO), which was further diluted with peanut oil and administered at a dose of 10 mg per kg body weight, intraperitoneally (i.p.…”

“…Six different human fibroblast cultures were obtained as controls. Cultured fibroblasts were used within a few passages of culturing to ensure preservation of the control or failing phenotype (15).…”

Medicinal plants with wound healing potential

“…Rho family GTPase like Rac-1, Rho-A, and Cdc-42 plays a pivotal role in fibroblast cell proliferation and migration (D'Souza et al, 2011). Cell cycle regulators such as cyclins, and cyclin-dependent kinase 1 and 2 are involved in cytoskeleton formation in fibroblasts (Yoshizaki et al, 2004).…”

Developmental and tumoral vascularization is regulated by G protein–coupled receptor kinase 2

“…Besides regulating chemokine GPCRs, GRK2 phosphorylates PDGF receptors (10) and also modulates TGF-β signaling in epithelial cells (11) or cardiac fibroblasts (12). GRK2 inhibits PDGF-dependent chemotactic signaling in VSMCs (13) and modulates both vasoconstrictory and vasodilatory responses of VSMCs (14,15), whereas increased GRK2 attenuates NO production by sinusoidal ECs in the context of liver injury (16).…”