Saradhadevi Varadharaj

The Ohio State University, Columbus, Ohio, United States

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Publications (22)130.34 Total impact

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    ABSTRACT: Nitric oxide (NO) derived from eNOS is mostly responsible for the maintenance of vascular homeostasis where decrease in its bioavailability is characteristic of ROS-induced endothelial dysfunction (ED). Since 5,5-Dimethyl-1-pyrroline-N-oxide (DMPO), a commonly used spin trap, has been shown to control intracellular nitroso-redox balance by scavenging ROS and donating NO it was employed as cardio-protective agent against ED but the mechanism of its protection is still not clear. This study elucidates the mechanism of protection imparted by DMPO against SIN-1-induced oxidative injury to bovine aortic endothelial cells (BAEC). BAEC were treated with SIN-1 as ONOO(-) donor and post-incubated with DMPO. MTT assay was employed to assess cytotoxicity by SIN-1 and cytoprotection by DMPO. Levels of ROS and NO generation from HEK293 cells transfected with wild type and mutant eNOS cDNAs, BH4 bioavailability, eNOS activity, eNOS and Akt kinase phosphorylation were determined. Post-treatment of cells with DMPO attenuated SIN-1-mediated cytotoxicity and ROS generation, restoration of NO levels via increased in eNOS activity and phospho-eNOS levels. Treatment with DMPO alone significantly increased NO levels and induced phosphorylation of eNOS S1179 via Akt kinase. Transfection studies with wild type and mutant human eNOS confirmed a dual role of eNOS as O2 (●-) with SIN-1 treatment and NO producer in the presence of DMPO. This study demonstrates that post-treatment with DMPO of oxidatively challenged cells can impart reversal of eNOS dysfunction and can have pharmacological implications in the treatment of cardiovascular diseases.
    British Journal of Pharmacology 01/2014; · 5.07 Impact Factor
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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: AIMS: The role of endothelial nitric oxide synthase (eNOS)/NO signaling is well-documented in late ischemic preconditioning (IPC); however, the role of eNOS and its activation in early IPC remains controversial. This study investigates the role of eNOS in early IPC and the signaling pathways and molecular interactions that regulate eNOS activation during early IPC.Methods and ResultsRat hearts were subjected to 30-min global ischemia and reperfusion (I/R) with or without IPC (3 cycles 5-min I and 5-min R) in the presence or absence of the NOS inhibitor (L-NAME), phosphatidylinositol 3-kinase (PI3K) inhibitor (LY294002/LY), protein kinase A (PKA) inhibitor (H89) during IPC induction or prior endothelial permeablization. IPC improved postischemic contractile function and reduced infarction compared to I/R with this abrogated by L-NAME or endothelial permeablization. eNOS(Ser1176), Akt(Ser473), and PKA(Thr197) phosphorylation was increased following IPC. I/R decreased eNOS(Ser1176) phosphorylation, while IPC increased it. Mass spectroscopy confirmed eNOS(Ser1176) phosphorylation and quantitative Western blots showed ~24 % modification of eNOS(Ser1176) following IPC. Immunoprecipitation demonstrated eNOS, Akt and PKA complexation. Immunohistology showed IPC-induced Akt and PKA phosphorylation in cardiomyocytes and endothelium. With eNOS activation, IPC increased NO production as measured by EPR spin trapping and fluorescence microscopy. LY or H89 not only decreased Akt(Ser473) or PKA(Thr197) phosphorylation, respectively; but also abolished IPC-induced preservation of eNOS and eNOS(Ser1176) phosphorylation as well as cardioprotection. CONCLUSION: Thus, Akt- and PKA-mediated eNOS activation, with phosphorylation near the C-terminus, is critical for early IPC-induced cardioprotection with eNOS-derived NO from the endothelium serving a critical role.
    Cardiovascular Research 09/2012; · 5.81 Impact Factor
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    ABSTRACT: Inheritable missense mutations in small molecular weight heat-shock proteins (HSP) with chaperone-like properties promote self-oligomerization, protein aggregation, and pathologic states such as hypertrophic cardiomyopathy in humans. We recently described that human mutant αB-crystallin (hR120GCryAB) overexpression that caused protein aggregation cardiomyopathy (PAC) was genetically linked to dysregulation of the antioxidant system and reductive stress (RS) in mice. However, the molecular mechanism that induces RS remains only partially understood. Here we define a critical role for the regulatory nuclear erythroid 2-related factor 2 (Nrf2)-Kelch-like ECH-associated protein (Keap1) pathway--the master transcriptional controller of antioxidants, in the pathogenesis of PAC and RS. In myopathic mice, increased reactive oxygen species signaling during compensatory hypertrophy (i.e., 3 months) was associated with upregulation of key antioxidants in a manner consistent with Nrf2/antioxidant response element (ARE)-dependent transactivation. In transcription factor assays, we further demonstrate increased binding of Nrf2 to ARE during the development of cardiomyopathy. Of interest, we show that the negative regulator Keap1 was predominantly sequestrated in protein aggregates (at 6 months), suggesting that sustained nuclear translocation of activated Nrf2 may be a contributing mechanism for RS. Our findings implicate a novel pathway for therapeutic targeting and abrogating RS linked to experimental cardiomyopathy in humans. Antioxid.
    Antioxidants & Redox Signaling 03/2011; 14(6):957-71. · 8.20 Impact Factor
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    ABSTRACT: Human saphenous veins (HSVs) are widely used for bypass grafts despite their relatively low long-term patency. To evaluate the role of reactive oxygen species (ROS) signaling in intima hyperplasia (IH), an early stage pathology of vein-graft disease, and to explore the potential therapeutic effects of up-regulating endogenous antioxidant enzymes, we studied segments of HSV cultured ex vivo in an established ex vivo model of HSV IH. Results showed that HSV cultured ex vivo exhibit an ~3-fold increase in proliferation and ~3.6-fold increase in intimal area relative to freshly isolated HSV. Treatment of HSV during culture with Protandim, a nutritional supplement known to activate Nrf2 and increase the expression of antioxidant enzymes in several in vitro and in vivo models, blocks IH and reduces cellular proliferation to that of freshly isolated HSV. Protandim treatment increased the activity of SOD, HO-1, and catalase 3-, 7-, and 12-fold, respectively, and decreased the levels of superoxide (O(2)(•-)) and the lipid peroxidation product 4-HNE. Blocking catalase activity by cotreating with 3-amino-1,2,4-triazole abrogated the protective effect of Protandim on IH and proliferation. In conclusion, these results suggest that ROS-sensitive signaling mediates the observed IH in cultured HSV and that up-regulation of endogenous antioxidant enzymes can have a protective effect.
    Free Radical Biology and Medicine 03/2011; 50(6):700-9. · 5.27 Impact Factor
  • Journal of The American College of Cardiology - J AMER COLL CARDIOL. 01/2011; 57(14).
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    ABSTRACT: Endothelial nitric oxide synthase (eNOS) is critical in the regulation of vascular function, and can generate both nitric oxide (NO) and superoxide (O(2)(•-)), which are key mediators of cellular signalling. In the presence of Ca(2+)/calmodulin, eNOS produces NO, endothelial-derived relaxing factor, from l-arginine (l-Arg) by means of electron transfer from NADPH through a flavin containing reductase domain to oxygen bound at the haem of an oxygenase domain, which also contains binding sites for tetrahydrobiopterin (BH(4)) and l-Arg. In the absence of BH(4), NO synthesis is abrogated and instead O(2)(•-) is generated. While NOS dysfunction occurs in diseases with redox stress, BH(4) repletion only partly restores NOS activity and NOS-dependent vasodilation. This suggests that there is an as yet unidentified redox-regulated mechanism controlling NOS function. Protein thiols can undergo S-glutathionylation, a reversible protein modification involved in cellular signalling and adaptation. Under oxidative stress, S-glutathionylation occurs through thiol-disulphide exchange with oxidized glutathione or reaction of oxidant-induced protein thiyl radicals with reduced glutathione. Cysteine residues are critical for the maintenance of eNOS function; we therefore speculated that oxidative stress could alter eNOS activity through S-glutathionylation. Here we show that S-glutathionylation of eNOS reversibly decreases NOS activity with an increase in O(2)(•-) generation primarily from the reductase, in which two highly conserved cysteine residues are identified as sites of S-glutathionylation and found to be critical for redox-regulation of eNOS function. We show that eNOS S-glutathionylation in endothelial cells, with loss of NO and gain of O(2)(•-) generation, is associated with impaired endothelium-dependent vasodilation. In hypertensive vessels, eNOS S-glutathionylation is increased with impaired endothelium-dependent vasodilation that is restored by thiol-specific reducing agents, which reverse this S-glutathionylation. Thus, S-glutathionylation of eNOS is a pivotal switch providing redox regulation of cellular signalling, endothelial function and vascular tone.
    Nature 12/2010; 468(7327):1115-8. · 38.60 Impact Factor
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    ABSTRACT: Cigarette smoking is a major independent risk factor for cardiovascular disease. While the association between chronic smoking and cardiovascular disease is well established, the underlying mechanisms are incompletely understood, partly due to the lack of adequate in vivo animal models. Here, we report a mouse model of chronic smoking-induced cardiovascular pathology. Male C57BL/6J mice were exposed to whole body mainstream cigarette smoke (CS) using a SCIREQ "InExpose" smoking system (48 min/day, 5 days/wk) for 16 or 32 wk. Age-matched, air-exposed mice served as nonsmoking controls. Blood pressure was measured, and cardiac MRI was performed. In vitro vascular ring and isolated heart experiments were performed to measure vascular reactivity and cardiac function. Blood from control and smoking mice was studied for the nitric oxide (NO) decay rate and reactive oxygen species (ROS) generation. With 32 wk of CS exposure, mice had significantly less body weight gain and markedly higher blood pressure. At 32 wk of CS exposure, ACh-induced vasorelaxation was significantly shifted to the right and downward, left ventricular mass was significantly larger along with an increased heart-to-body weight ratio, in vitro cardiac function tended to be impaired with high afterload, white blood cells had significantly higher ROS generation, and the blood NO decay rate was significantly faster. Thus, smoking led to blunted weight gain, hypertension, endothelial dysfunction, leukocyte activation with ROS generation, decreased NO bioavailability, and mild cardiac hypertrophy in mice that were not otherwise predisposed to disease. This mouse model is a useful tool to enable further elucidation of the molecular and cellular mechanisms of smoking-induced cardiovascular diseases.
    AJP Heart and Circulatory Physiology 11/2010; 300(1):H388-96. · 4.01 Impact Factor
  • Free Radical Biology and Medicine - FREE RADICAL BIOL MED. 01/2010; 49.
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    ABSTRACT: Stem cell therapy for myocardial tissue repair is limited by the poor survival of transplanted cells, possibly because of inadequate supply of oxygen and nutrients. The purpose of this study was to assess the oxygenation level and functional recovery after allogenic transplantation of mesenchymal stem cells (MSC) in a rat model of myocardial infarction (MI). Myocardial oxygen tension (Po(2)) was measured by electron paramagnetic resonance oximetry using an implantable oxygen-sensing spin probe (OxySpin). MSCs incubated with OxySpins showed substantial uptake of the probe without affecting its oxygen sensitivity or calibration. The cells internalized with OxySpins were able to differentiate into osteogenic, adipogenic, cardiomyocyte, and endothelial cell lineages. The labeled cells tested positive for CD44 and CD29 markers and negative for the hematopoietic markers CD14 and CD45. For the in vivo studies, MI was induced in rats by permanently ligating the left anterior descending coronary artery. MSCs with OxySpins were transplanted in the infarct region of hearts. A significant increase in Po(2) was observed in the MSC group compared with the untreated MI group (18.1 +/- 2.6 vs. 13.0 +/- 1.8 mmHg, n = 4, P < 0.05) at 4 wk after transplantation. Echocardiography showed a significant improvement in ejection fraction and fraction shortening, which inversely correlated with the magnitude of fibrosis in the treated hearts. The cell-transplanted hearts also showed an increase in vascular endothelial growth factor level and capillary density in the infarct region. The study established our ability to measure and correlate changes in myocardial tissue oxygenation with cardiac function in infarcted rat hearts treated with MSCs.
    AJP Heart and Circulatory Physiology 04/2009; 296(5):H1263-73. · 4.01 Impact Factor
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    ABSTRACT: Bovine aortic endothelial cells (ECs) respond to nitric oxide (NO) donors by activating the redox-sensitive NF-E2-related factor 2/antioxidant response element pathway and up-regulating heme oxygenase (HO)-1 expression. EC exposure to steady laminar shear stress causes a sustained increase in NO, a transient increase in reactive oxygen species (ROS), and activation of the HO-1 gene. Because steady laminar flow increases the mitochondrial superoxide (O(2)(*-)) production, we hypothesized that mitochondria-derived ROS play a role in shear-induced HO-1 expression. Flow (10 dynes/cm(2), 6 h)-induced expression of HO-1 protein was abolished when BAECs were preincubated and sheared in the presence of either N(G)-nitro-L-arginine methyl ester or N-acetyl-L-cysteine, suggesting that either NO or ROS up-regulates HO-1. Ebselen and diphenylene iodonium blocked HO-1 expression, and uric acid had no effect. The mitochondrial electron transport chain inhibitors, myxothiazol, rotenone, or antimycin A, and the mitochondria-targeted antioxidant peptide, Szeto-Schiller (SS)-31, which scavenges O(2)(*-), hydrogen peroxide (H(2)O(2)), peroxynitrite, and hydroxyl radicals, markedly inhibited the increase in HO-1 expression. These data collectively suggest that mitochondrial H(2)O(2) mediates the HO-1 induction. MitoSOX and 2',7'-dichlorofluorescin (DCF) fluorescence showed that mitochondrial O(2)(*-) levels and intracellular peroxides, respectively, are higher in sheared ECs compared with static controls and, in part, dependent on NO. SS-31 significantly inhibited both the shear-induced MitoSOX and DCF fluorescence signals. Either phosphatidylinositol 3-kinase or mitogen-activated protein kinase cascade inhibitors blocked the HO-1 induction. In conclusion, under shear, EC mitochondria-derived H(2)O(2) diffuses to the cytosol, where it initiates oxidative signaling leading to HO-1 up-regulation and maintenance of the atheroprotective EC status.
    Journal of Pharmacology and Experimental Therapeutics 02/2009; 329(1):94-101. · 3.89 Impact Factor
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    ABSTRACT: Increased O(2)* and NO production is a key mechanism of mitochondrial dysfunction in myocardial ischemia/reperfusion injury. A crucial segment of the mitochondrial electron transport chain is succinate ubiquinone reductase (SQR or Complex II). In SQR, oxidative impairment and deglutathionylation of the 70-kDa flavin protein occurs in the post-ischemic heart ( Chen, Y. R., Chen, C. L., Pfeiffer, D. R., and Zweier, J. L. (2007) J. Biol. Chem. 282, 32640-32654 ). To gain insights into the oxidative modification of the 70-kDa protein in the post-ischemic myocardium, we used the identified S-glutathionylated peptide ((77)AAFGLSEAGFNTACVTK(93)) of the 70-kDa protein as a chimeric epitope incorporating a "promiscuous" T cell epitope to generate a high titer polyclonal antibody, AbGSC90. Purified AbGSC90 showed a high binding affinity to isolated SQR. Antibodies of AbGSC90 moderately inhibited the electron transfer and superoxide generation activities of SQR. To test for protein nitration, rats were subjected to 30 min of coronary ligation followed by 24 h of reperfusion. Tissue homogenates were immunoprecipitated with AbGSC90 and probed with antibodies against 3-nitrotyrosine. Enhancement of protein tyrosine nitration was detected in the post-ischemic myocardium. Isolated SQR was subjected to in vitro protein nitration with peroxynitrite, leading to site-specific nitration at the 70-kDa polypeptide and impairment of SQR electron transfer activity. Protein nitration of SQR further impaired its protein-protein interaction with Complex III. Liquid chromatography/tandem mass spectrometry analysis indicated that Tyr-56 and Tyr-142 were involved in protein tyrosine nitration. When the isolated SQR was subjected to in vitro S-glutathionylation, oxidative modification and impairment mediated by peroxynitrite were significantly decreased, thus confirming the protective effect of S-glutathionylation from the oxidative damage of nitration.
    Journal of Biological Chemistry 09/2008; 283(41):27991-8003. · 4.65 Impact Factor
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    ABSTRACT: Cultured vascular endothelial cell (EC) exposure to steady laminar shear stress results in peroxynitrite (ONOO(-)) formation intramitochondrially and inactivation of the electron transport chain. We examined whether the "hyperoxic state" of 21% O(2), compared with more physiological O(2) tensions (Po(2)), increases the shear-induced nitric oxide (NO) synthesis and mitochondrial superoxide (O(2)(*-)) generation leading to ONOO(-) formation and suppression of respiration. Electron paramagnetic resonance oximetry was used to measure O(2) consumption rates of bovine aortic ECs sheared (10 dyn/cm(2), 30 min) at 5%, 10%, or 21% O(2) or left static at 5% or 21% O(2). Respiration was inhibited to a greater extent when ECs were sheared at 21% O(2) than at lower Po(2) or left static at different Po(2). Flow in the presence of an endothelial NO synthase (eNOS) inhibitor or a ONOO(-) scavenger abolished the inhibitory effect. EC transfection with an adenovirus that expresses manganese superoxide dismutase in mitochondria, and not a control virus, blocked the inhibitory effect. Intracellular and mitochondrial O(2)(*-) production was higher in ECs sheared at 21% than at 5% O(2), as determined by dihydroethidium and MitoSOX red fluorescence, respectively, and the latter was, at least in part, NO-dependent. Accumulation of NO metabolites in media of ECs sheared at 21% O(2) was modestly increased compared with ECs sheared at lower Po(2), suggesting that eNOS activity may be higher at 21% O(2). Hence, the hyperoxia of in vitro EC flow studies, via increased NO and mitochondrial O(2)(*-) production, leads to enhanced ONOO(-) formation intramitochondrially and suppression of respiration.
    AJP Cell Physiology 08/2008; 295(1):C180-91. · 3.71 Impact Factor
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    ABSTRACT: In the vasculature, nitric oxide (NO) is generated by endothelial NO synthase (eNOS) in a calcium/calmodulin-dependent reaction. With oxidative stress, the critical cofactor BH(4) is depleted, and NADPH oxidation is uncoupled from NO generation, leading to production of (O(2)*). Although phosphorylation of eNOS regulates in vivo NO generation, the effects of phosphorylation on eNOS coupling and O(2)* generation are unknown. Therefore, we phosphorylated recombinant BH(4)-free eNOS in vitro using native kinases and determined O(2)* generation using EPR spin trapping. Phosphorylation of Ser-1177 by Akt led to an increase (>50%) in maximal O(2)* generation from eNOS. Moreover, Ser-1177 phosphorylation greatly altered the Ca(2+) sensitivity of eNOS, such that O(2)* generation became largely Ca(2+)-independent. In contrast, phosphorylation of eNOS at Thr-495 by protein kinase Calpha (PKCalpha) had no effect on maximum activity or calcium sensitivity but decreased calmodulin binding and increased association with caveolin. In endothelial cells, eNOS-dependent O(2)* generation was stimulated by vascular endothelial growth factor that induced phosphorylation of Ser-1177. With PKC activation that led to phosphorylation of Thr-495, no inhibition of O(2)* generation occurred. As such, phosphorylation of eNOS at Ser-1177 is pivotal in the direct regulation of O(2)* and NO generation, altering both the Ca(2+) sensitivity of the enzyme and rate of product formation, whereas phosphorylation of Thr-495 indirectly affects this process through regulation of the calmodulin and caveolin interaction. Thus, Akt-mediated phosphorylation modulates eNOS uncoupling and greatly increases O(2)* generation from the enzyme at low Ca(2+) concentrations, and PKCalpha-mediated phosphorylation alters the sensitivity of the enzyme to other negative regulatory signals.
    Journal of Biological Chemistry 07/2008; 283(40):27038-47. · 4.65 Impact Factor
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    ABSTRACT: Any clinical intervention (e.g., coronary angioplasty, thrombolysis) used to reintroduce blood flow to an ischemic region of the myocardium is accompanied by a complex enzymatic cascade of reactions resulting in severe injury to the heart, termed myocardial ischemia/reperfusion (I/R) injury. In this study, we evaluated the ability of H-3010 (1-hydroxy-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole-3-carboxylic acid (2-(3,4-dimethoxyphenyl)-5-([2-(3,4-dimethoxyphenyl)ethyl]-methylamino)-2-isopropylpentyl)-amide), a pyrroline modification of verapamil (2-(3,4-dimethoxyphenyl)-5-[2-(3,4-dimethoxyphenyl)ethylmethyl-amino]-2-(1-methylethyl)pentanenitrile), to protect the heart against I/R-mediated injury. Isolated perfused rat hearts pretreated with verapamil and H-3010 were subjected to 30 min of global no-flow ischemia followed by 45 min of reperfusion. The recovery (expressed as a percentage of preischemic baseline) in contractile function (left ventricular developed pressure) of hearts subjected to I/R was significantly higher in hearts treated with H-3010 at 5 microM (51.0 +/- 6.4%) as well as at 50 microM (75.1 +/- 7.4%) as compared with verapamil at 5 microM (32.2 +/- 3.7%) or untreated control hearts (18.1 +/- 2.8%). Creatine kinase release was significantly attenuated in hearts treated with H-3010 (45.7 +/- 4.5 U/liter) as compared with untreated controls (131.5 +/- 6.4 U/liter). Similar trends were also observed for lactate dehydrogenase release as well. A marked reduction in percent area of infarction was observed in the H-3010 group (11.7 +/- 1.6%) compared with verapamil (25.1 +/- 2.9%) and control (41.3 +/- 1.9%) groups. Additional in vitro studies showed a marked decrease in reactive oxygen species generation with H-3010. In conclusion, our data clearly demonstrated that the verapamil derivative, H-3010, significantly decreased I/R-induced cardiac dysfunction. This can be attributed to the combined benefits of the pyrroline moiety (antioxidant) and the parent verapamil component (antiarrhythmic) in the protection of the heart from I/R-induced injury.
    Journal of Pharmacology and Experimental Therapeutics 11/2007; 323(1):119-27. · 3.89 Impact Factor
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    ABSTRACT: Our earlier studies have shown that vitamin C at pharmacological doses (mM) induces loss of redox-dependent viability in bovine lung microvascular endothelial cells (BLMVECs) that is mediated by oxidative stress. Therefore, here, we investigated the vitamin C-induced activation of the lipid signaling enzyme, phospholipase D (PLD) in BLMVECs. Monolayer cultures of BLMVECs were treated with vitamin C (0-10 mM) for different time periods (0-2 h) and the activity of PLD was determined. Vitamin C induced activation of PLD in BLMVECs in a time- and dose-dependent fashion that was significantly attenuated by antioxidants, p38 mitogen-activated protein kinase (p38 MAPK)-specific inhibitor (SB203580), extracellular signal-regulated protein kinase (ERK)-specific inhibitor (PD98059), and transient transfection of cells with dominant-negative (DN)-p38 MAPK and DN-ERK1/ERK2. Vitamin C also induced phosphorylation and enhanced the activities of p38 MAPK and ERK in BLMVECs in a time-dependent fashion. It was also evident that vitamin C induced translocation of PLD(1) and PLD(2), association of p38 MAPK and ERK with PLD(1) and PLD(2), threonine phosphorylation of PLD(1) and PLD(2) and SB203580- and PD98059-inhibitable threonine phosphorylation of PLD(1) in BLMVECs. Transient transfection of BLMVECs with DN-p38 MAPK and DN-ERK1/ERK2 resulted in marked attenuation of vitamin C-induced phosphorylation of threonine in PLD(1) and PLD(2). We, for the first time, showed that vitamin C at pharmacological doses, activated PLD in the lung microvascular ECs through oxidative stress and MAPK activation.
    Cellular Signalling 10/2006; 18(9):1396-407. · 4.47 Impact Factor
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    ABSTRACT: The aim of this study was to determine whether prolonged loss of NO activity, in endothelial NO synthase knockout (eNOS(-/-)) mice, influences endothelin (ET) ETA receptor-mediated smooth muscle contraction and, if so, to define the underlying mechanism(s). In isolated endothelium-denuded abdominal aortas, contractions to the selective ETA receptor agonist ET-1(1-31) were significantly increased in aortas from eNOS(-/-) compared with wild-type (WT) mice. In contrast, contractions to the alpha1-adrenergic agonist phenylephrine or the thromboxane (TX) A2 analog U-46619 were similar between eNOS(-/-) and WT mice. Immunofluorescent and Western blot analysis demonstrated that the aortic expression of ETA receptors was decreased in eNOS(-/-) compared with WT mice. Contractions evoked by ET-1(1-31), but not phenylephrine, were reduced by inhibition of cyclooxygenase-2 (COX-2) (indomethacin or celecoxib) or of TXA2/prostaglandin H2 receptors (SQ-29548). After COX inhibition, contractions to ET-1(1-31) were no longer increased and were actually decreased in eNOS(-/-) compared with WT aortas. Western blot analysis revealed that endothelium-denuded abdominal aortas express COX-2, but not COX-1, and that expression of COX-2 was significantly increased in eNOS(-/-) compared with WT mice. Contractions to the COX substrate arachidonic acid were also increased in eNOS(-/-) aortas. Furthermore, ET-1(1-31) but not phenylephrine stimulated production of the TXA2 metabolite TXB2, which was increased in eNOS(-/-) compared with WT aortas. Therefore, COX-2 plays a crucial and selective role in ETA-mediated smooth muscle contraction. Furthermore, COX-2 expression is increased in eNOS(-/-) mice, which overcomes a reduced expression of ETA receptors and enables a selective increase in contraction to ETA receptor stimulation.
    Circulation Research 07/2006; 98(11):1439-45. · 11.86 Impact Factor
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    ABSTRACT: We previously showed that C-phycocyanin (PC), an antioxidant biliprotein pigment of Spirulina platensis (a blue-green alga), effectively inhibited doxorubicin-induced oxidative stress and apoptosis in cardiomyocytes. Here we investigated the cardioprotective effect of PC against ischemia-reperfusion (I/R)-induced myocardial injury in an isolated perfused Langendorff heart model. Rat hearts were subjected to 30 min of global ischemia at 37 degrees C followed by 45 min of reperfusion. Hearts were perfused with PC (10 microM) or Spirulina preparation (SP, 50 mg/l) for 15 min before the onset of ischemia and throughout reperfusion. After 45 min of reperfusion, untreated (control) hearts showed a significant decrease in recovery of coronary flow (44%), left ventricular developed pressure (21%), and rate-pressure product (24%), an increase in release of lactate dehydrogenase and creatine kinase in coronary effluent, significant myocardial infarction (44% of risk area), and TdT-mediated dUTP nick end label-positive apoptotic cells compared with the preischemic state. PC or SP significantly enhanced recovery of heart function and decreased infarct size, attenuated lactate dehydrogenase and creatine kinase release, and suppressed I/R-induced free radical generation. PC reversed I/R-induced activation of p38 MAPK, Bax, and caspase-3, suppression of Bcl-2, and increase in TdT-mediated dUTP nick end label-positive apoptotic cells. However, I/R also induced activation of ERK1/2, which was enhanced by PC treatment. Overall, these results for the first time showed that PC attenuated I/R-induced cardiac dysfunction through its antioxidant and antiapoptotic actions and modulation of p38 MAPK and ERK1/2.
    AJP Heart and Circulatory Physiology 06/2006; 290(5):H2136-45. · 4.01 Impact Factor
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    ABSTRACT: Doxorubicin (DOX), a potent antineoplastic agent, poses limitations for its therapeutic use due to the associated risk of developing cardiomyopathy and congestive heart failure. The cardiotoxicity of doxorubicin is associated with oxidative stress and apoptosis. We have recently shown that Spirulina, a blue-green alga with potent antioxidant properties, offered significant protection against doxorubicin-induced cardiotoxicity in mice. The aim of the present study was to establish the possible protective role of C-phycocyanin, one of the active ingredients of Spirulina, against doxorubicin-induced oxidative stress and apoptosis. The study was carried out using cardiomyocytes isolated from adult rat hearts. Doxorubicin significantly enhanced the formation of reactive oxygen species (ROS) in cells as measured by the 2',7'-dichlorodihydrofluorescein diacetate and dihydroethidium fluorescence. The doxorubicin-induced reactive oxygen species formation was significantly attenuated in cells pretreated with C-phycocyanin. It was further observed that the doxorubicin-induced DNA fragmentation and apoptosis, as assayed by TUNEL assay and flow cytometry coupled with BrdU-FITC/propidium iodide staining, were markedly attenuated by C-phycocyanin. C-phycocyanin also significantly attenuated the doxorubicin-induced increase in the expression of Bax protein, release of cytochrome c, and increase in the activity of caspase-3 in cells. In summary, C-phycocyanin ameliorated doxorubicin-induced oxidative stress and apoptosis in cardiomyocytes. This study further supports the crucial role of the antioxidant nature of C-phycocyanin in its cardioprotection against doxorubicin-induced oxidative stress and apoptosis.
    Journal of Cardiovascular Pharmacology 02/2006; 47(1):9-20. · 2.38 Impact Factor
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    ABSTRACT: The goal of this study was to determine whether acetylcholine evokes endothelium-dependent contraction in mouse arteries and to define the mechanisms involved in regulating this response. Arterial rings isolated from wild-type (WT) and endothelial nitric oxide (NO) synthase knockout (eNOS(-/-)) mice were suspended for isometric tension recording. In abdominal aorta from WT mice contracted with phenylephrine, acetylcholine caused a relaxation that reversed at the concentration of 0.3-3 microM. After inhibition of NO synthase [with N(omega)-nitro-l-arginine methyl ester (l-NAME), 1 mM], acetylcholine (0.1-10 microM) caused contraction under basal conditions or during constriction to phenylephrine, which was abolished by endothelial denudation. This contraction was inhibited by the cyclooxygenase inhibitor indomethacin (1 muM) or by a thromboxane A(2) (TxA(2)) and/or prostaglandin H(2) receptor antagonist SQ-29548 (1 microM) and was associated with endothelium-dependent generation of the TxA(2) metabolite TxB(2.) Also, SQ-29548 (1 microM) abolished the reversal in relaxation evoked by 0.3-3 microM acetylcholine and subsequently enhanced the relaxation to the agonist. The magnitude of the endothelium-dependent contraction to acetylcholine (0.1-10 microM) was similar in aortas from WT mice treated in vitro with l-NAME and from eNOS(-/-) mice. In addition, we found that acetylcholine (10 microM) also caused endothelium-dependent contraction in carotid and femoral arteries of eNOS(-/-) mice. These results suggest that acetylcholine initiates two competing responses in mouse arteries: endothelium-dependent relaxation mediated predominantly by NO and endothelium-dependent contraction mediated most likely by TxA(2).
    AJP Heart and Circulatory Physiology 10/2005; 289(3):H1027-32. · 4.01 Impact Factor