Biphasic effect of hydrogen peroxide on skeletal muscle arteriolar tone via activation of endothelial and smooth muscle signaling pathways

Abstract

We hypothesized that hydrogen peroxide (H2O2) has a role in the local regulation of skeletal muscle blood flow, thus significantly affecting the myogenic tone of arterioles. In our study, we investigated the effects of exogenous H2O2 on the diameter of isolated, pressurized (at 80 mmHg) rat gracilis skeletal muscle arterioles (diameter of approximately 150 microm). Lower concentrations of H2O2 (10(-6)-3 x 10(-5) M) elicited constrictions, whereas higher concentrations of H2O2 (6 x 10(-5)-3 x 10(-4) M), after initial constrictions, caused dilations of arterioles (at 10(-4) M H2O2, -19 +/- 1% constriction and 66 +/- 4% dilation). Endothelium removal reduced both constrictions (to -10 +/- 1%) and dilations (to 33 +/- 3%) due to H2O2. Constrictions due to H2O2 were completely abolished by indomethacin and the prostaglandin H2/thromboxane A2 (PGH2/TxA2) receptor antagonist SQ-29548. Dilations due to H2O2 were significantly reduced by inhibition of nitric oxide synthase (to 38 +/- 7%) but were unaffected by clotrimazole or sulfaphenazole (inhibitors of cytochrome P-450 enzymes), indomethacin, or SQ-29548. In endothelium-denuded arterioles, clotrimazole had no effect, whereas H2O2-induced dilations were significantly reduced by charybdotoxin plus apamin, inhibitors of Ca(2+)-activated K+ channels (to 24 +/- 3%), the selective blocker of ATP-sensitive K+ channels glybenclamide (to 14 +/- 2%), and the nonselective K(+)-channel inhibitor tetrabutylammonium (to -1 +/- 1%). Thus exogenous administration of H2O2 elicits 1) release of PGH2/TxA2 from both endothelium and smooth muscle, 2) release of nitric oxide from the endothelium, and 3) activation of K+ channels, such as Ca(2+)-activated and ATP-sensitive K+ channels in the smooth muscle resulting in biphasic changes of arteriolar diameter. Because H2O2 at low micromolar concentrations activates several intrinsic mechanisms, we suggest that H2O2 contributes to the local regulation of skeletal muscle blood flow in various physiological and pathophysiological conditions.

Oxidative Stress Induces Vascular Calcification through Modulation of the Osteogenic Transcription Factor Runx2 by AKT Signaling

“…In the present study we demonstrated that H 2 O 2 , at concentrations of 0.1 to 0.4 mM, induces osteogenic differentiation and calcificationofVSMCinaconcentrationdependent manner. These levels of H 2 O 2 are consistent with the amounts generated by the increased levels of oxidant enzymes associated with atherosclerosis including xanthine oxidase and NAD(P)H oxidases (14). Furthermore, previous reports have shown that the viability of VSMC is not affected by H 2 O 2 concentrations up to 800 M (49).…”

“…Increased vascular formation of H 2 O 2 , a highly diffusible ROS capable of initiating redox cell signaling, is known to play an important role in the pathogenesis of atherosclerosis (14). In the present study we demonstrated that H 2 O 2 , at concentrations of 0.1 to 0.4 mM, induces osteogenic differentiation and calcificationofVSMCinaconcentrationdependent manner.…”

“…Under normal conditions constitutive oxidase activities and endogenous scavenger systems, including catalase and glutathione peroxidases, maintain steady-state H 2 O 2 levels in vascular tissue (10). Upon stimulation, these oxidases in the endothelium, media, and adventitia can produce H 2 O 2 and contribute to increased exposure of VSMC to this oxidant (10,14).VSMC exhibit an extraordinary capacity to undergo phenotypic change during development in cultures and in association with diseases (15). Emerging evidence supports the concept that vascular calcification, like mineralization of bones and teeth, is a cell-regulated process (16).…”

“…Under normal conditions constitutive oxidase activities and endogenous scavenger systems, including catalase and glutathione peroxidases, maintain steady-state H 2 O 2 levels in vascular tissue (10). Upon stimulation, these oxidases in the endothelium, media, and adventitia can produce H 2 O 2 and contribute to increased exposure of VSMC to this oxidant (10,14).…”

Preserved coronary arteriolar dilatation in patients with type 2 diabetes mellitus: Implications for reactive oxygen species

“…Thus, in addition to inhibiting endothelial generation of NO, H 2 O 2 may actively participate in endothelium-dependent vasodilation mechanisms in type 2 diabetes mellitus. The mechanism of H 2 O 2 -mediated dilation is not completely understood, but studies have shown that, by activating calcium-activated potassium channels, H 2 O 2 hyperpolarizes vascular smooth muscle cells and therefore potentially acts as an EDHF [13,33,34]. Other studies have demonstrated that H 2 O 2 -induced vasodilation is mediated through the release of NO from the endothelium [25] or is partially mediated by cGMP release [20].…”