Effects of hypoxia on regulators of G‐protein signaling 2 (RGS2) regulation of pulmonary arterial constriction

Abstract

RGS2 protein inhibits Gq‐coupled G protein coupled receptor (GPCR) signaling. Our goal was to determine whether hypoxia reduces RGS2 in pulmonary arterial smooth muscle causing enhanced GPCR agonist calcium (Ca) signaling and constriction. Human pulmonary arterial smooth muscle cells (SMC) and RGS2 KO and WT mice were used. RGS2 protein was knocked down by RGS2 siRNA. SMC were incubated in hypoxia (1% O2) or normoxia (21% O2) for 1–48 hrs. We measured RGS2 expression by western blotting, Ca mobilization with Ca dyes and constriction of pulmonary arteries and SMC by video morphometry. RGS2 siRNA caused knockdown (KD) of RGS2 by 68%±1 in SMC. Ca mobilization for U46619 and endothelin1 (ET‐1) was 2‐fold higher for RGS2 KD compared to control and constriction by ET‐1 and U46619 was increased by 21%±2 and 14%±2, respectively. Pulmonary arteries of lung slices from RGS2 KO mice had increased constriction to serotonin (26%±4) and U46619 (20%±4) compared to WT. Hypoxia significantly reduced RGS2 at 8 (54%±9), 24 (59%±8) and 48 (71%±6) hours in SMC. 48 hours of hypoxia increased constriction for ET‐1 and U46619 by 19%±3 and 21%±2, respectively while Ca was increased 2‐fold for both agonists. We found that RGS2 plays a role in GPCR constriction of SMC and pulmonary arteries. Hypoxia downregulates RGS2 causing augmented Ca signaling and constriction which may contribute to pulmonary hypertension. Support: Am Heart Asso; Am Asthma Fdn