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Subodh Verma

Publications and source records attributed to Subodh Verma.

At least 109 records · Page 6Linked to original sources
PubMed2002

A self-fulfilling prophecy: C-reactive protein attenuates nitric oxide production and inhibits angiogenesis.

BACKGROUND: Given the central importance of nitric oxide (NO) in the development and clinical course of cardiovascular diseases, we sought to determine whether the powerful predictive value of C-reactive protein (CRP) might be explained through an effect on NO production. METHODS AND RESULTS: Endothelial cells (ECs) were incubated with recombinant CRP (0 to 100 microg/mL, 24 hours), and NO and cyclic guanosine monophosphate (cGMP) production was assessed. The effects of CRP on endothelial NO synthase (eNOS) protein, mRNA expression, and mRNA stability were also examined. In a separate study, the effects of CRP (25 microg/mL) on EC cell survival, apoptosis, and in vitro angiogenesis were evaluated. Incubation of ECs with CRP resulted in a significant inhibition of basal and stimulated NO release, with concomitant reductions in cGMP production. CRP caused a marked downregulation of eNOS mRNA and protein expression. Actinomycin D studies suggested that eNOS downregulation was related to decreased mRNA stability. In conjunction with a decrease in NO production, CRP inhibited both basal and vascular endothelial growth factor-stimulated angiogenesis as assessed by EC migration and capillary-like tube formation. CRP did not induce EC survival but did, however, promote apoptosis in a NO-dependent fashion. CONCLUSIONS: CRP, at concentrations known to predict adverse vascular events, directly quenches the production of the NO, in part, through posttranscriptional effect on eNOS mRNA stability. Diminished NO bioactivity, in turn, inhibits angiogenesis, an important compensatory mechanism in chronic ischemia. Through decreasing NO synthesis, CRP may facilitate the development of diverse cardiovascular diseases. Risk reduction strategies designed to lower plasma CRP may be effective by improving NO bioavailability.

Apoptosis↗
PubMed2002

Endothelin antagonism and interleukin-6 inhibition attenuate the proatherogenic effects of C-reactive protein.

BACKGROUND: C-reactive protein (CRP) has been suggested to actively participate in the development of atherosclerosis. In the present study, we examined the role of the potent endothelium-derived vasoactive factor endothelin-1 (ET-1) and the inflammatory cytokine interleukin-6 (IL-6) as mediators of CRP-induced proatherogenic processes. METHODS AND RESULTS: Saphenous vein endothelial cells (HSVECs) were incubated with human recombinant CRP (25 microg/mL, 24 hours) and the expression of vascular cell adhesion molecule (VCAM-1), intracellular adhesion molecule (ICAM-1), and monocyte chemoattractant chemokine-1 was determined. The effects of CRP on LDL uptake were assessed in macrophages using immunofluorescent labeling of CD32 and CD14. In each study, the effect of endothelin antagonism (bosentan) and IL-6 inhibition (monoclonal anti-IL-6 antibodies) was examined. The effects of CRP on the secretion of ET-1 and IL-6 from HSVECs were also evaluated. Incubation of HSVECs with recombinant human CRP resulted in a marked increase in ICAM-1 and VCAM-1 expression (P<0.001). Likewise, CRP caused a significant increase in monocyte chemoattractant chemokine-1 production, a key mediator of leukocyte transmigration (P<0.001). CRP caused a marked and sustained increase in native LDL uptake by macrophages (P<0.05). These proatherosclerotic effects of CRP were mediated, in part, via increased secretion of ET-1 and IL-6 (P<0.01) and were attenuated by both bosentan and IL-6 antagonism (P<0.01). CONCLUSIONS: CRP actively promotes a proatherosclerotic and proinflammatory phenotype. These effects are mediated, in part, via the production of ET-1 and IL-6 and are attenuated by mixed ET(A/B) receptor antagonism and IL-6 inhibition. Bosentan may be useful in decreasing CRP-mediated vascular disease.

Antibodies↗
PubMed2002

Endothelin blockade potentiates endothelial protective effects of ACE inhibitors in saphenous veins.

BACKGROUND: Angiotensin II and endothelin-1 are potent endothelium-derived contracting factors. The effects of acute endothelin antagonism on endothelial function in saphenous vein from patients treated with and without angiotensin-converting enzyme inhibitors were compared. METHODS: Vascular segments of saphenous vein were obtained perioperatively from 14 patients on angiotensin-converting enzyme inhibitors and 29 controls. In vitro endothelium-dependent and -independent responses to acetylcholine and sodium nitroprusside were assessed by constructing isometric dose-response curves in precontracted rings in the presence and absence of bosentan (endothelinA/B receptor antagonist) and BQ-123 (endothelinA antagonist) using isolated organ baths. Percent maximum relaxation and sensitivity were compared between interventions. RESULTS: Endothelium-dependent relaxation to acetylcholine was augmented in the angiotensin-converting enzyme inhibitor-treated group (p < 0.005). Both specific and mixed endothelin receptor blockade improved acetylcholine-mediated relaxation in the angiotensin-converting enzyme inhibitor-treated and untreated groups (p < 0.02). The effects of these antagonists were endothelium specific as endothelium-independent responses to sodium nitroprusside remain unaltered. CONCLUSIONS: These data demonstrate that (1) chronic angiotensin-converting enzyme inhibition improves endothelial function in saphenous veins, and (2) this effect can be further augmented by acute endothelin blockade. These data suggest that antagonism of both angiotensin II and endothelin may be important in attenuating saphenous vein arteriosclerosis.

Acetylcholine↗
PubMed2002

Cellular basis of endothelial dysfunction in small mesenteric arteries from spontaneously diabetic (db/db -/-) mice: role of decreased tetrahydrobiopterin bioavailability.

1. Endothelium-dependent and -independent regulation of vascular tone in small mesenteric arteries (SMA) from control (db/db +/?) and diabetic (db/db -/-) mice was compared. 2. Phenylephrine-induced maximum contraction, but not sensitivity, of SMA in db/db -/- compared to db/db +/? was enhanced. 3. Acetylcholine (ACh), but not sodium nitroprusside (SNP), -induced relaxation was reduced in SMA from db/db -/- compared to db/db +/?. 4. ACh-induced relaxation of SMA was inhibited by a combination of N(omega)-nitro-L-arginine and indomethacin in db/db +/?, but not in db/db -/-. 5. Acute incubation of SMA with tetrahydrobiopterin (BH(4), 10 microM) and sepiapterin (100 microM) enhanced ACh-induced relaxation in SMA from db/db -/-, but not from db/db +/? 2,4-diamino-6-hydroxypyrimidine, an inhibitor of GTP cyclohydrolase I, (10 mM), impaired the sensitivity of SMA from db/db +/? to ACh, which was restored by co-incubation with BH(4) (10 microM). 6. BH(4) and superoxide dismutase (SOD, 150 u ml(-1)), either alone or in combination, had no effect on either ACh or SNP-induced relaxation in SMA from eNOS -/- mice. 7. Incubation of SMA with SOD (150 iu ml(-1)), catalase (200 iu ml(-1)) and L-arginine (1 mM) had no effect on ACh-induced relaxation of SMA. However, the combination of polyethylene glycol-SOD (200 iu ml(-1)) and catalase (80 u ml(-1)) improved the sensitivity of ACh-induced relaxation in db/db -/-, but not in db/db +/?. 8. These data suggest that increased production of superoxide anions and decreased availability of BH(4) result in an 'uncoupling' of nitric oxide synthase and endothelial dysfunction in SMA from db/db -/- mice.

Animals↗
PubMed2002

Novel cardioprotective effects of tetrahydrobiopterin after anoxia and reoxygenation: Identifying cellular targets for pharmacologic manipulation.

OBJECTIVES: Contemporary cardioprotective strategies to prevent perioperative ischemia-reperfusion injury have focused on the l-arginine nitric oxide pathway. Tetrahydrobiopterin is an absolute cofactor required for the enzyme nitric oxide synthase and is thus a critical determinant of nitric oxide production. We hypothesized that ischemia-reperfusion results in diminished levels of tetrahydrobiopterin, which might represent a key cellular defect underlying endothelial and myocyte dysfunction after ischemia-reperfusion. To this aim, we examined the effects of tetrahydrobiopterin supplementation in (1) an in vivo experimental model of global ischemia-reperfusion and (2) an in vitro human ventricular heart cell model of simulated ischemia-reperfusion. Measures of endothelial function, oxidant production, cell survival, and cardiac function were used to assess outcome. METHODS: In study 1 Wistar rats were divided into one of 2 groups (n = 10 per group). One group received tetrahydrobiopterin (25 mg x kg(-1) x d(-1) for 7 days), and the other group served as the control group. Hearts were subjected to 30 minutes of ischemia followed by 30 minutes of reperfusion, and left ventricular developed pressure, left ventricular systolic pressure, and left ventricular end-diastolic pressure were determined by using the modified Langendorff technique. In study 2 we quantitated myocardial malondialdehyde, a marker of lipid peroxidation, in ventricular tissues from both groups of animals using butanol phase extraction and spectrophotometric analysis. In study 3 coronary vascular responses were determined in vascular segments of the left coronary artery in both groups of animals after ischemia-reperfusion. Endothelium-dependent and endothelium-independent vasodilatation to acetylcholine and sodium nitroprusside, respectively, were compared between groups. In study 4, using a human ventricular heart cell model of simulated ischemia-reperfusion, we studied the effects of tetrahydrobiopterin (20 micromol/L) on cellular injury (as assessed by means of trypan blue uptake). RESULTS: After ischemia-reperfusion, myocardial dysfunction was evidenced by a decrease in left ventricular developed pressure and an increase in left ventricular end-diastolic pressure (P =.01 compared with baseline). Hearts from tetrahydrobiopterin-treated rats exhibited protection against ischemia-reperfusion injury (left ventricular developed pressure: 74 +/- 4 vs control 42 +/- 8 mm Hg, P =.01; left ventricular end-diastolic pressure: 12 +/- 3 vs 34 +/- 7 mm Hg, P =.01). Furthermore, tetrahydrobiopterin treatment attenuated the rise in malondialdehyde levels after ischemia-reperfusion (P =.01). After reperfusion, coronary endothelial function to acetylcholine was attenuated (P =.003 vs sham-treated mice), whereas responses to sodium nitroprusside remained unchanged. Tetrahydrobiopterin-treated rats exhibited an improvement in acetylcholine-mediated vasorelaxation (P =.01 vs ischemia-reperfusion group). Cellular injury, as assessed by means of trypan blue uptake, was higher in human ventricular heart cells subjected to simulated ischemia-reperfusion; this effect was prevented with tetrahydrobiopterin treatment (P =.001). CONCLUSIONS: Supplemental tetrahydrobiopterin provides a novel cardioprotective effect on left ventricular function, endothelial-vascular reactivity, oxidative damage, and cardiomyocyte injury after ischemia-reperfusion injury and might represent an important cellular target for future operative myocardial protection strategies.

Adolescent↗
PubMed2002

Increased endothelin-1 production in diabetic patients after cardioplegic arrest and reperfusion impairs coronary vascular reactivity: reversal by means of endothelin antagonism.

OBJECTIVES: Evidence has accrued to suggest that diabetic patients face an increased risk of ischemic events and low output syndrome and might mount an inordinate response to ischemia and reperfusion. Because hyperglycemia is a potent stimulus for endothelin-1 production, we hypothesized that increased production, action, or both of endothelin-1 in diabetes might represent an important mediator of endothelial dysfunction in patients with that disease. To this aim, we compared the effects of cardioplegic arrest and reperfusion on coronary sinus effluent endothelin-1 levels and atrial arteriolar vascular responses in diabetic and case-matched nondiabetic patients undergoing coronary artery bypass grafting. METHODS: In study 1 coronary sinus effluent endothelin-1 levels were assessed at baseline and at 1 and 10 minutes after reperfusion in 13 diabetic and 12 nondiabetic patients matched for age, ejection fraction, Parsonnet score, and crossclamp time. In study 2 vascular responses of atrial arterioles subjected to perioperative ischemia-reperfusion were evaluated with videomicroscopy. Atrial microvessels (from appendages) were obtained before and after removal of the aortic crossclamp, and vascular responses to exogenously administered endothelin-1 (10(-10) mol/L) and substance P (10(-8) mol/L) were studied in the presence or absence of BQ-123, an endothelin A receptor antagonist. RESULTS: Diabetic patients elaborated more endothelin-1 at 1 and 10 minutes after reperfusion (P =.01). Endothelin-1-mediated vasoconstriction was similar in diabetic and nondiabetic atrial microvessels before cardioplegic arrest and cardiopulmonary bypass. After cardiopulmonary bypass and reperfusion, endothelin-1-mediated vasoconstriction was enhanced in both groups; however, this response was greater in microvessels from diabetic patients (P =.02). BQ-123, the endothelin A antagonist, attenuated the effects of bypass and reperfusion on endothelin-1-mediated vasoconstriction in both groups (P =.01). Substance P-mediated vasodilatation was similar in diabetic and nondiabetic atrial microvessels before bypass. After bypass and reperfusion, substance P-mediated vasodilatation was diminished in both groups; however, this response was more pronounced in the diabetic group (P =.003). BQ-123 coincubation restored substance P-mediated vasodilatation in both groups. CONCLUSIONS: We determined the following: (1) the coronary effluent release of endothelin-1 is higher in diabetic than in nondiabetic patients after cardiopulmonary bypass and reperfusion; (2) diabetic coronary microvessels respond to bypass and reperfusion with greater endothelin-1-mediated vasoconstriction and diminished nitric oxide-mediated vasodilatation; and (3) these effects are attenuated by endothelin antagonism. Endothelin-1 might be an important mediator of ischemia-reperfusion injury in patients with diabetes. Furthermore, use of endothelin receptor antagonists might be a novel strategy for improving the resistance of the diabetic heart to cardioplegic arrest and reperfusion.

Aged↗
PubMed2002

Hyperglycemia exaggerates ischemia-reperfusion-induced cardiomyocyte injury: reversal with endothelin antagonism.

OBJECTIVES: We have previously demonstrated an importance of endothelin-1 in diabetic patients undergoing bypass surgery. Recent evidence suggests that cardiomyocytes might also produce endothelin-1, which might directly impair myocyte contractility by increasing intracellular calcium levels. Because hyperglycemia is a potent stimulus of endothelin-1 production, we hypothesized that increased production, action, or both of endothelin-1 might be a mediator of direct cardiomyocyte injury in diabetes. Therefore we studied the effects of endothelin receptor blockers (BQ-123 and bosentan) on hyperglycemia-induced endothelin-1 production and cellular injury after ischemia-reperfusion. METHODS: Using a human ventricular heart cell model of simulated ischemia-reperfusion, we studied the effects of normoglycemia (5 mmol/L, 48 hours) and hyperglycemia (25 mmol/L, 48 hours) on cellular injury and endothelin-1 production. Furthermore, the effects of selective endothelin-A and mixed endothelin-A/B receptor antagonism (with BQ-123 and bosentan, respectively) were evaluated. RESULTS: Cellular injury, as assessed by means of trypan blue uptake, was higher in human ventricular heart cells subjected to hyperglycemia and simulated ischemia-reperfusion injury (P =.01); this effect was prevented with both BQ-123 and bosentan (P =.01). In addition, heart cells from the hyperglycemic group elaborated more endothelin-1 after ischemia-reperfusion (P =.02). CONCLUSIONS: Endothelin-1 production and cellular injury were greater in human ventricular heart cells subjected to hyperglycemic conditions and simulated ischemia-reperfusion. These effects are mediated by endothelin-A receptors because both BQ-123 and bosentan exerted similar degrees of protection. Endothelin receptor blockade is a novel strategy to improve the resistance of the diabetic heart to cardioplegic arrest and reperfusion.

Antihypertensive Agents↗
PubMed2002

Exaggerated coronary reactivity to endothelin-1 in diabetes: reversal with bosentan.

We previously demonstrated that chronic endothelin receptor blockade (with bosentan) improved functional cardiac performance in streptozotocin-diabetic rats, suggesting a novel role of endothelin-1 (ET-1) in modulating diabetic heart dysfunction. To gain insight into the mechanism(s) underlying this effect, we examined the coronary vascular responses to ET-1 in hearts from diabetic and control rats treated with or without bosentan. Rats were divided into control, control-treated, diabetic, and diabetic-treated groups. The control-treated and diabetic-treated groups received bosentan (100 mg x kg(-1) x d(-1)) for 8 weeks. Following treatment, hearts were isolated and perfused, and coronary reactivity to ET-1 was assessed by measuring the changes in coronary perfusion pressure in response to ET-1 (50 and 100 pM). Additionally, maximal coronary blood flow (assessed with 10(-5) M adenosine) was measured in isolated perfused hearts. The key observation is that coronary reactivity to ET-1 was significantly higher in the diabetic than the control rats. This effect was normalized in diabetic rats chronically receiving bosentan. Maximal coronary vasodilation did not differ between the four groups. In conclusion, the reactivity of ET-1 is altered in the isolated perfused coronary vascular bed from diabetic rats, and chronic ET receptor blockade restores this reactivity to control values. These observations provide a possible mechanism for the improvement in diabetic heart function observed after chronic bosentan treatment.

Animals↗
PubMed2002

Female rats are protected against fructose-induced changes in metabolism and blood pressure.

The objective of this study was to determine whether the effects of a fructose diet, which causes hyperinsulinemia, insulin resistance, and hypertension in male rats, are dependent on sex. Blood pressure was measured via the tail-cuff method, and oral glucose tolerance tests were performed to assess insulin sensitivity. Blood pressure in female rats did not differ between fructose-fed and control rats at any time point (126 +/- 5 and 125 +/- 3 mmHg at week 9 for fructose-fed and control rats, respectively) nor was there a difference in any metabolic parameter measured. Furthermore, the vascular insulin resistance that is present in male fructose-fed rats was not observed. After ovariectomy, fructose caused a significant change in systolic blood pressure from baseline compared with fructose-fed ovary-intact rats (change of 21 +/- 5 vs. -2 +/- 4 mmHg). The results demonstrate that females do not develop hypertension or hyperinsulinemia upon fructose feeding except after ovariectomy, suggesting that female sex hormones may confer protection against the effects of a fructose diet.

Animals↗
PubMed2002

L-arginine protects human heart cells from low-volume anoxia and reoxygenation.

Protective effects of L-arginine were evaluated in a human ventricular heart cell model of low-volume anoxia and reoxygenation independent of alternate cell types. Cell cultures were subjected to 90 min of low-volume anoxia and 30 min of reoxygenation. L-Arginine (0-5.0 mM) was administered during the preanoxic period or the reoxygenation phase. Nitric oxide (NO) production, NO synthase (NOS) activity, cGMP levels, and cellular injury were assessed. To evaluate the effects of the L-arginine on cell signaling, the effects of the NOS antagonist N(G)-nitro-L-arginine methyl ester, NO donor S-nitroso-N-acetyl-penicillamine, guanylate cyclase inhibitor methylene blue, cGMP analog 8-bromo-cGMP, and ATP-sensitive K+ channel antagonist glibenclamide were examined. Our data indicate that low-volume anoxia and reoxygenation increased NOS activity and facilitated the conversion of L-arginine to NO, which provided protection against cellular injury in a dose-dependent fashion. In addition, L-arginine cardioprotection was achieved by the activation of guanylate cyclase, leading to increased cGMP levels in human heart cells. This action involves a glibenclamide-sensitive, NO-cGMP-dependent pathway.

Arginine↗
PubMed2002

Interaction of 5-methyltetrahydrofolate and tetrahydrobiopterin on endothelial function.

The present study was designed to investigate the interaction between 5-methyltetrahydrofolate and tetrahydrobiopterin in modulating endothelial function. Tetrahydrobiopterin is a critical cofactor for nitric oxide synthase and maintains this enzyme as a nitric oxide- versus superoxide-producing enzyme. The structure of 5-methyltetrahydrofolate is similar to tetrahydrobiopterin and both agents have been shown to improve endothelium-dependent vasodilatation. We hypothesized that 5-methyltetrahydrofolate interacts with nitric oxide synthase in a fashion analogous, yet independent, of tetrahydrobiopterin to improve endothelial function. We demonstrate that 5-methyltetrahydrofolate binds the active site of nitric oxide synthase and mimics the orientation of tetrahydrobiopterin. Furthermore, 5-methyltetrahydrofolate attenuates superoxide production (induced by inhibition of tetrahydrobiopterin synthesis) and improves endothelial function in aortae isolated from tetrahydrobiopterin-deficient rats. We suggest that 5-methyltetrahydrofolate directly interacts with nitric oxide synthase to promote nitric oxide (vs. superoxide) production and improve endothelial function. 5-Methyltetrahydrofolate may represent an important strategy for intervention aimed at improving tetrahydrobiopterin bioavailability.

Acetylcholine↗
PubMed2002

The T-786-->C mutation in endothelial nitric oxide synthase is associated with hypertension.

Although the pathogenic mechanisms involved in predisposing individuals to hypertension are not well defined, evidence is accumulating that suggests a strong genetic transmission. Animal studies and some clinical investigations have revealed that aberrant NO production may be an important contributing factor. Indeed, a missense mutation in the endothelial NO gene caused by a Glu298Asp alteration has been strongly associated with essential hypertension, coronary artery spasm, and myocardial infarction. Recently, another point mutation caused by a T-786-->C transition in the 5'-flanking region of the endothelial NO synthase gene has been identified and, like the Glu298Asp mutation, is associated with coronary artery spasm. The present study was conducted to determine the effect of the T-786-->C point mutation on hypertension. We investigated the interaction between the endothelial NO synthase T-786-->C polymorphism and blood pressure in a large (n=705) clinically healthy population. Allele frequencies for the T and C alleles were 62% and 38%, translating into 39%, 46% and 15% of the population having the T/T, T/C, and C/C genotypes, respectively, for the T-786-->C point mutation. Subjects with the C/C genotype had significantly higher systolic blood pressures and were 2.16(95% confidence interval, 1.3 to 3.7) more likely to be hypertensive. Therefore, the -786 C/C genotype in NO synthase is a significant contributing factor for increasing the risk of essential hypertension.

Adult↗
PubMedDate not supplied

Cardiac remodeling and failure: from molecules to man (Part I).

The process of heart failure appears to be a common and coordinated response to cardiac injury and dysfunction. The contemporary mechanistic viewpoint that predictable, shared, highly regulated events underlie the complex heart failure process implies that an improved understanding of these mechanisms is fundamental to the advancement of cardiovascular biology and the subsequent development of targeted, effective treatment strategies for patients with congestive heart failure (CHF). Cardiac remodeling (CR) is the restructuring and reshaping of the heart that underlies heart failure progression. CR is a major determinant of the clinical course of CHF, irrespective of its etiology. The traditional concepts of cellular remodeling in the failing heart are based on well-established data indicating characteristic alterations in cell size, shape, and the ability to perform contractile work. The role of programmed cell death and the exciting possibility of cardiomyocyte regeneration are areas of intense investigation. Notably, the accumulating data in both animal and human hearts suggesting cardiomyocyte regeneration and renewal indicate that cellular remodeling is a complex and dynamic process that is not completely understood. For the development of new treatments to regenerate and restore failing myocardium, the possibilities offered by controlling cell death and enhancing cell renewal as a therapeutic target are unprecedented. Based on a critical review of the available literature, the traditional concepts and mechanisms describing the regulation of remodeling are largely inadequate. The neurohormonal (RAAS and adrenergic systems) and innovative cytokine hypothesis (TNF-alpha and others) of remodeling and failure do not account for all the cellular and molecular changes that result in the progression of CHF. Given that these contemporary concepts serve as the basis for the majority of our current heart failure treatments, it is not surprising that CHF is an emerging epidemic in our society. To define new therapeutic targets and to control the process of remodeling, novel biomolecules and mechanisms for the coordinated control of CR must be further defined.

Heart Failure↗