Silencing regulator of G protein signaling-2 (RGS-2) increases angiotensin II signaling: insights into hypertension from findings in Bartter's/Gitelman's syndromes.

OBJECTIVE: Regulator of G-protein signaling (RGS)-2 is a regulator of angiotensin II (Ang II) signaling. In Bartter's syndrome/Gitelman's syndrome (BS/GS), we have demonstrated increased RGS-2 levels and blunted Ang II signaling which contribute to their reduced vasomotor tone and remodeling.The present study investigates the effect of silencing RGS-2 in fibroblasts from six BS/GS patients on intracellular Ca ((Equation is included in full-text article.)) mobilization and extracellular signal-regulated kinase (ERK) 1/2 phosphorylation, established Ang II-mediated responses. METHODS: Fibroblasts were RGS-2 silenced by transfecting chemically synthesized small interfering RNA. Silencing efficiency and Ang II-induced ERK 1/2 phosphorylation were evaluated by western blot and Ang II-induced(Equation is included in full-text article.)using Fura-2 AM. RESULTS: RGS-2 expression in not silenced BS/GS fibroblasts from patients is increased compared with healthy controls [0.34 ± 0.02 vs. 0.19 ± 0.01 densitometric units (d.u.), P = 0.0005]. Silencing RGS-2 in BS/GS patients was achieved to the level of controls. Ang II-induced(Equation is included in full-text article.)release and ERK 1/2 phosphorylation were reduced in not silenced cells from BG/GS patients compared with controls (112.16 ± 13.2 vs. 130.33 ± 13.64 mmol/l, P = 0.011 and 0.64 ± 0.08 vs. 0.91 ± 0.03 mmol/l, P < 0.006, respectively). Silencing RGS-2 in BS/GS patients increased Ang II-induced(Equation is included in full-text article.)release and ERK 1/2 phosphorylation in silenced cells compared with not silenced cells [59.3 ± 10.8 (peak-basal) vs. 40.5 ± 14.1 nmol/l, P = 0.017 and 0.84 ± 0.06 vs. 0.64 ± 0.08 nmol/l, P < 0.03, respectively], whereas they were not different compared with controls (60.1 ± 4.3 and 0.91 ± 0.03 nmol/l). Integrating the(Equation is included in full-text article.)response over time showed increased(Equation is included in full-text article.)area under the curve (AUC) of BS/GS silenced cells compared with that of not silenced cells (P = 0.013). CONCLUSION: This is the first report of silencing RGS-2 effect on Ang II signaling in a human clinical condition of altered vascular tone regulation and remodeling and establishes RGS-2 as a key regulatory element of Ang II signaling in humans. © 2008 Lippincott Williams & Wilkins, Inc.