Sepiapterin enhances angiogenesis and functional recovery in mice after myocardial infarction
Second Department of Internal Medicine, Kansai Medical University, Moriguchi City, Japan. AJP Heart and Circulatory Physiology
(Impact Factor: 3.84).
09/2011; 301(5):H2061-72. DOI: 10.1152/ajpheart.00525.2011
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.
Available from: Leni Moldovan
- "These observations suggest that NOS2 is another major source of superoxide in this tissue, most likely via “uncoupling.” Recently we42 and others43 have demonstrated that NOS uncoupling with a switch from NO generation to superoxide production occurs in ischemic myocardium. Because the DHE signal in 1‐day ischemic hearts did not respond to the above inhibitors (Figure 5C), one may assume a different origin of early ROS formation. "
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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.
Available from: Lixin Liu
- "eNOS uncoupling is associated with increased eNOS monomerization, tyrosine nitration and formation of dihydrobiopterin (BH2) and decreased cellular BH4
[16,17]. Sepiapterin is a stable precursor of BH4 and serves as a valuable pharmacological agent for the study of eNOS uncoupling due to its high cell permeability as compared to BH4
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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.
Available from: jpet.aspetjournals.org
- "None of the supplements affected the amount of water consumed by the animals, which was on average 4 ml per day. The dose of SP, approximately 0.64 mg/kg per day, was significantly less than that used in previous studies on vascular function, whether provided in food pellets (Pannirselvam et al., 2002) or in the drinking water (Shimazu et al., 2011). This dosage was selected on the basis of preliminary experiments, demonstrating that it increased the BH4:BH2 levels in and was cytotoxic to different tumor cell lines grown as xenografts or in tissue culture (C. S. Rabender and R. B. Mikkelsen, unpublished data). "
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ABSTRACT: The effects of modulating tetrahydrobiopterin (BH4) levels with a metabolic precursor, sepiapterin (SP), on dextran sodium sulfate (DSS) induced colitis and azoxymethane (AOM) induced colorectal cancer were studied. SP in the drinking water blocks DSS-induced colitis measured as decreased disease activity index (DAI), morphological criteria and recovery of Ca2+-induced contractility responses lost as a consequence of DSS treatment. SP reduces inflammatory responses measured as decreased numbers of infiltrating inflammatory macrophages and neutrophils and decreased expression of pro-inflammatory cytokines IL-1β, IL-6 and IL-17A. HPLC analyses of colonic BH4 and its oxidized derivative, dihydrobiopterin (BH2), are inconclusive although there is a trend for lower BH4:BH2 with DSS treatment that was reversed with SP. Reduction of colonic cGMP levels by DSS is reversed with SP by a mechanism sensitive to 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), a specific inhibitor of the NO-sensitive soluble guanylate cyclase (sGC). ODQ abrogates the protective effects of SP on colitis. This plus the finding that SP reduces DSS enhanced protein Tyr nitration are consistent with DSS induced uncoupling of NOS. The results agree with previous studies demonstrating inactivation of sGC in DSS-treated animals as being important in recruitment of inflammatory cells and in altered cholinergic signaling and colon motility. SP also reduces the number of colon tumors in the DSS/AOM treated mice from 7 to 1 per unit colon length. Thus pharmacological modulation of BH4 with currently available drugs may provide a mechanism for alleviating some forms of colitis and potentially minimizing the potential for colorectal cancer in patients with colitis.
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