Sepiapterin enhances angiogenesis and functional recovery in mice after myocardial infarction.
ABSTRACT Uncoupling of nitric oxide synthase (NOS) has been implicated in left ventricular (LV) remodeling and dysfunction after myocardial infarction (MI). We hypothesized that inducible NOS (iNOS) plays a crucial role in LV remodeling after MI, depending on its coupling status. MI was created in wild-type, iNOS-knockout (iNOS(-/-)), endothelial NOS-knockout (eNOS(-/-)), and neuronal NOS-knockout (nNOS(-/-)) mice. iNOS and nNOS expressions were increased after MI associated with an increase in nitrotyrosine formation. The area of myocardial fibrosis and LV end-diastolic volume and ejection fraction were more deteriorated in eNOS(-/-) mice compared with other genotypes of mice 4 wk after MI. The expression of GTP cyclohydrolase was reduced, and tetrahydrobiopterin (BH(4)) was depleted in the heart after MI. Oral administration of sepiapterin after MI increased dihydrobiopterin (BH(2)), BH(4), and BH(4)-to-BH(2) ratio in the infarcted but not sham-operated heart. The increase in BH(4)-to-BH(2) ratio was associated with inhibition of nitrotyrosine formation and an increase in nitrite plus nitrate. However, this inhibition of NOS uncoupling was blunted in iNOS(-/-) mice. Sepiapterin increased capillary density and prevented LV remodeling and dysfunction after MI in wild-type, eNOS(-/-), and nNOS(-/-) but not iNOS(-/-) mice. N(ω)-nitro-L-arginine methyl ester abrogated sepiapterin-induced increase in nitrite plus nitrate and angiogenesis and blocked the beneficial effects of sepiapterin on LV remodeling and function. These results suggest that sepiapterin enhances angiogenesis and functional recovery after MI by activating the salvage pathway for BH(4) synthesis and increasing bioavailable nitric oxide predominantly derived from iNOS.
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ABSTRACT: The core region of a myocardial infarction is notoriously unsupportive of cardiomyocyte survival. However, there has been less investigation of the potentially beneficial spontaneous recruitment of endogenous bone marrow progenitor cells (BMPCs) within infarcted areas. In the current study we examined the role of tissue oxygenation and derived toxic species in the control of BMPC engraftment during postinfarction heart remodeling. For assessment of cellular origin, local oxygenation, redox status, and fate of cells in the infarcted region, myocardial infarction in mice with or without LacZ(+) bone marrow transplantation was induced by coronary ligation. Sham-operated mice served as controls. After 1 week, LacZ(+) BMPC-derived cells were found inhomogeneously distributed into the infarct zone, with a lower density at its core. Electron paramagnetic resonance (EPR) oximetry showed that pO2 in the infarct recovered starting on day 2 post-myocardial infarction, concomitant with wall thinning and erythrocytes percolating through muscle microruptures. Paralleling this reoxygenation, increased generation of reactive oxygen/nitrogen species was detected at the infarct core. This process delineated a zone of diminished BMPC engraftment, and at 1 week infiltrating cells displayed immunoreactive 3-nitrotyrosine and apoptosis. In vivo treatment with a superoxide dismutase mimetic significantly reduced reactive oxygen species formation and amplified BMPC accumulation. This treatment also salvaged wall thickness by 43% and left ventricular ejection fraction by 27%, with significantly increased animal survival. BMPC engraftment in the infarct inversely mirrored the distribution of reactive oxygen/nitrogen species. Antioxidant treatment resulted in increased numbers of engrafted BMPCs, provided functional protection to the heart, and decreased the incidence of myocardial rupture and death.Journal of the American Heart Association. 01/2014; 3(1):e000471.
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ABSTRACT: Increased levels of the sugar metabolite methylglyoxal (MG) in vivo were shown to participate in the pathophysiology of vascular complications in diabetes. Alterations of endothelial nitric oxide synthase (eNOS) activity by hypophosphorylation of the enzyme and enhanced monomerization are found in the diabetic milieu, and the regulation of this still remains undefined. Using various pharmacological approaches, we elucidate putative mechanisms by which MG modulates eNOS-associated functions of MG-stimulated superoxide (O2[bullet]-) production, phosphorylation status and eNOS uncoupling in EA.hy926 human endothelial cells. In cultured EA.hy926 endothelial cells, the effects of MG treatment, tetrahydrobiopterin (BH4; 100 muM) and sepiapterin (20 muM) supplementation, NOS inhibition by NG-nitro-L-arginine methyl ester (L-NAME; 50 muM), and inhibition of peroxynitrite (ONOO-) formation (300 muM Tempol plus 50 muM L-NAME) on eNOS dimer/monomer ratios, Ser-1177 eNOS phosphorylation and 3-nitrotyrosine (3NT) abundance were quantified using immunoblotting. O2[bullet]--dependent fluorescence was determined using a commercially available kit and tissue biopterin levels were measured by fluorometric HPLC analysis. In EA.hy926 cells, MG treatment significantly enhanced O2[bullet]- generation and 3NT expression and reduced Ser-1177 eNOS phosphorylation, eNOS dimer/monomer ratio and cellular biopterin levels indicative of eNOS uncoupling. These effects were significantly mitigated by administration of BH4, sepiapterin and suppression of ONOO- formation. L-NAME treatment significantly blunted eNOS-derived O2[bullet]- generation but did not modify eNOS phosphorylation or monomerization. MG triggers eNOS uncoupling and hypophosphorylation in EA.hy926 endothelial cells associated with O2[bullet]- generation and biopterin depletion. The observed effects of the glycolysis metabolite MG presumably account, at least in part, for endothelial dysfunction in diabetes.Cardiovascular Diabetology 09/2013; 12(1):134. · 4.21 Impact Factor
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ABSTRACT: AIMS: HSPA12B is a newly discovered and endothelial-cell-specifically expressed heat shock protein. We have reported recently that overexpression of HSPA12B increased endothelial nitric oxide synthase (eNOS) expression in mouse cardiac tissues during endotoxemia. Endothelial NOS has been shown to protect heart from ischemic injury. We hypothesized that overexpression of HSPA12B will attenuate cardiac dysfunction and remodeling after myocardial infarction (MI) through an eNOS-dependant mechanism. METHODS AND RESULTS: MI was induced by permanent ligation of the left anterior descending coronary artery in the transgenic mice (Tg) overexpressing hspa12b gene and its wild type littermates (WT). Echocardiographic analysis revealed that Tg mice exhibited improvements in cardiac dysfunction and remodeling at 1 and 4 week(s) after MI. These improvements were accompanied by a significant decrease in cardiomyocyte apoptosis and increase in capillary and arteriolar densities. Significant upregulation of eNOS, VEGF, Ang-1 and Bcl-2 was also observed in Tg hearts compared to WT hearts after MI. However, pharmacological inhibition of eNOS abolished the HSPA12B-induced decrease in cardiomyocyte apoptosis and increase in capillary formation after MI. Most importantly, inhibition of eNOS abrogated the protection of HSPA12B against cardiac dysfunction and remodeling after MI. CONCLUSION: These data demonstrate for the first time that the overexpression of HSPA12B attenuates cardiac dysfunction and remodeling after MI. This action of HSPA12B was mediated, at least in part, by prevention of cardiomyocyte apoptosis and promotion of myocardial angiogenesis via an eNOS-dependent mechanism. HSPA12B could be a novel target for the management of patients with post-MI cardiac dysfunction and remodeling.Cardiovascular Research 05/2013; · 5.81 Impact Factor