Arginine Vasopressin Enhances Cell Survival via a G Protein-Coupled Receptor Kinase 2/β-Arrestin1/Extracellular-Regulated Kinase 1/2-Dependent Pathway in H9c2 Cells

Circulating levels of arginine vasopressin (AVP) are elevated during hypovolemia and during cardiac stress. AVP activates arginine vasopressin type 1A (V-1A)/G alpha(q)-coupled receptors in the heart and vasculature and V2/G alpha(s)-coupled receptors in the kidney. However, little is known regarding the signaling pathways that influence the effects of V-1A receptor (V1AR) activation during cellular injury. Using hypoxia-reoxygenation (H/R) as a cell injury model, we evaluated cell survival and caspase 3/7 activity in H9c2 myoblasts after treatment with AVP. Pretreatment of H9c2 cells with AVP significantly reduced H/R-induced cell death and caspase 3/7 activity, effects that were blocked via both selective V1AR inhibition and mitogen-activated protein kinase (MEK1/2) inhibition. AVP increased extracellular-regulated kinase 1/2 (ERK1/2) phosphorylation in a concentration-dependent manner that was sensitive to MEK1/2 inhibition and V1AR inhibition, but not V1BR or V2R inhibition. Discrete elements of the V-1A/G alpha(q)-protein kinase C (PKC) and V-1A/G protein-coupled receptor kinase (GRK)/beta-arrestin signaling cascades were inhibited to dissect the pathways responsible for the protective effects of V1AR signaling: G alpha(q) (overexpression of Gq-I-ires-green fluorescent protein), PKC (administration of Ro 31-82425; 2-[8-(aminomethyl)6,7,8,9- tetrahydropyrido[1,2-a] indol-3-yl]-3-(1-methyl-1H-indol-3yl) maleimide, HCl, bisindolylmaleimide X, HCl), GRK2 [C-terminal GRK2 peptide overexpression and small interfering RNA (siRNA) knockdown], GRK5 (siRNA knockdown), and beta-arrestin1 (siRNA knockdown). These studies demonstrated that both Gaq/PKC- and GRK2/beta-arrestin1-dependent V1AR signaling were capable of inducing ERK1/2 phosphorylation in response to AVP stimulation. However, AVP-mediated protection against H/R was elicited only via GRK2- and beta-arrestin1-dependent signaling. These results suggest that activation of the V1AR in H9c2 cells mediates protective signaling via a GRK2/beta 2 arrestin1/ERK1/2-dependent mechanism that leads to decreased caspase 3/7 activity and enhanced survival under conditions of ischemic stress.