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Regulator of G protein signaling 2 deficiency causes endothelial dysfunction and impaired endothelium-derived hyperpolarizing factor-mediated relaxation by dysregulating Gi/o signaling.

ABSTRACT: Regulator of G protein signaling 2 (RGS2) is a GTPase-activating protein for G(q/11)? and G(i/o)? subunits. RGS2 deficiency is linked to hypertension in mice and humans, although causative mechanisms are not understood. Because endothelial dysfunction and increased peripheral resistance are hallmarks of hypertension, determining whether RGS2 regulates microvascular reactivity may reveal mechanisms relevant to cardiovascular disease. Here we have determined the effects of systemic versus endothelium- or vascular smooth muscle-specific deletion of RGS2 on microvascular contraction and relaxation. Contraction and relaxation of mesenteric resistance arteries were analyzed in response to phenylephrine, sodium nitroprusside, or acetylcholine with or without inhibitors of nitric oxide (NO) synthase or K(+) channels that mediate endothelium-derived hyperpolarizing factor (EDHF)-dependent relaxation. The results showed that deleting RGS2 in vascular smooth muscle had minor effects. Systemic or endothelium-specific deletion of RGS2 strikingly inhibited acetylcholine-evoked relaxation. Endothelium-specific deletion of RGS2 had little effect on NO-dependent relaxation but markedly impaired EDHF-dependent relaxation. Acute, inducible deletion of RGS2 in endothelium did not affect blood pressure significantly. Impaired EDHF-mediated vasodilatation was rescued by blocking G(i/o)? activation with pertussis toxin. These findings indicated that systemic or endothelium-specific RGS2 deficiency causes endothelial dysfunction resulting in impaired EDHF-dependent vasodilatation. RGS2 deficiency enables endothelial G(i/o) activity to inhibit EDHF-dependent relaxation, whereas RGS2 sufficiency facilitates EDHF-evoked relaxation by squelching endothelial G(i/o) activity. Mutation or down-regulation of RGS2 in hypertension patients therefore may contribute to endothelial dysfunction and defective EDHF-dependent relaxation. Blunting G(i/o) signaling might improve endothelial function in such patients.

SUBMITTER: Osei-Owusu P

PROVIDER: S-EPMC3321003 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature

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Regulator of G protein signaling 2 deficiency causes endothelial dysfunction and impaired endothelium-derived hyperpolarizing factor-mediated relaxation by dysregulating Gi/o signaling.

Osei-Owusu Patrick P Sabharwal Rasna R Kaltenbronn Kevin M KM Rhee Man-Hee MH Chapleau Mark W MW Dietrich Hans H HH Blumer Kendall J KJ

The Journal of biological chemistry 20120221 15

Regulator of G protein signaling 2 (RGS2) is a GTPase-activating protein for G(q/11)α and G(i/o)α subunits. RGS2 deficiency is linked to hypertension in mice and humans, although causative mechanisms are not understood. Because endothelial dysfunction and increased peripheral resistance are hallmarks of hypertension, determining whether RGS2 regulates microvascular reactivity may reveal mechanisms relevant to cardiovascular disease. Here we have determined the effects of systemic versus endothel ...[more]

PMID: 22354966

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Project description:Arterial hyperpolarization to acetylcholine (ACh) reflects coactivation of K(Ca)3.1 (IK(Ca)) channels and K(Ca)2.3 (SK(Ca)) channels in the endothelium that transfers through myoendothelial gap junctions and diffusible factor(s) to affect smooth muscle relaxation (endothelium-derived hyperpolarizing factor [EDHF] response). However, ACh can differentially activate K(Ca)3.1 and K(Ca)2.3 channels, and we investigated the mechanisms responsible in rat mesenteric arteries. K(Ca)3.1 channel input to EDHF hyperpolarization was enhanced by reducing external [Ca(2+)](o) but blocked either with forskolin to activate protein kinase A or by limiting smooth muscle [Ca(2+)](i) increases stimulated by phenylephrine depolarization. Imaging [Ca(2+)](i) within the endothelial cell projections forming myoendothelial gap junctions revealed increases in cytoplasmic [Ca(2+)](i) during endothelial stimulation with ACh that were unaffected by simultaneous increases in muscle [Ca(2+)](i) evoked by phenylephrine. If gap junctions were uncoupled, K(Ca)3.1 channels became the predominant input to EDHF hyperpolarization, and relaxation was inhibited with ouabain, implicating a crucial link through Na(+)/K(+)-ATPase. There was no evidence for an equivalent link through K(Ca)2.3 channels nor between these channels and the putative EDHF pathway involving natriuretic peptide receptor-C. Reconstruction of confocal z-stack images from pressurized arteries revealed K(Ca)2.3 immunostain at endothelial cell borders, including endothelial cell projections, whereas K(Ca)3.1 channels and Na(+)/K(+)-ATPase alpha(2)/alpha(3) subunits were highly concentrated in endothelial cell projections and adjacent to myoendothelial gap junctions. Thus, extracellular [Ca(2+)](o) appears to modify K(Ca)3.1 channel activity through a protein kinase A-dependent mechanism independent of changes in endothelial [Ca(2+)](i). The resulting hyperpolarization links to arterial relaxation largely through Na(+)/K(+)-ATPase, possibly reflecting K(+) acting as an EDHF. In contrast, K(Ca)2.3 hyperpolarization appears mainly to affect relaxation through myoendothelial gap junctions. Overall, these data suggest that K(+) and myoendothelial coupling evoke EDHF-mediated relaxation through distinct, definable pathways.

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Dataset Information

Regulator of G protein signaling 2 deficiency causes endothelial dysfunction and impaired endothelium-derived hyperpolarizing factor-mediated relaxation by dysregulating Gi/o signaling.

Publications

Regulator of G protein signaling 2 deficiency causes endothelial dysfunction and impaired endothelium-derived hyperpolarizing factor-mediated relaxation by dysregulating Gi/o signaling.

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