Showing papers by "Dipak K. Das published in 2002"

Pharmacological preconditioning with resveratrol: role of nitric oxide

Abstract: Resveratrol (trans-3,4′,5-trihydroxystilbene), a recently described grape-derived polyphenolic antioxidant, has been found to protect the heart from ischemic-reperfusion injury. The present study s...

Pharmacological preconditioning with resveratrol: an insight with iNOS knockout mice.

Abstract: Resveratrol, a natural antioxidant and polyphenol found in grapes and wine, has been found to pharmacologically precondition the heart through the upregulation of nitric oxide (NO). To gain further...

Activin, a Grape Seed-derived Proanthocyanidin Extract, Reduces Plasma Levels of Oxidative Stress and Adhesion Molecules (ICAM-1, VCAM-1 and E-selectin) in Systemic Sclerosis

Abstract: This study evaluated whether a new generation antioxidant Activin derived from the grape seed proanthocyanidins, could reduce the induction of the adhesion molecules as a result of inflammatory response in the plasma of systemic sclerosis (SSc) patients. SSc patients were divided into two groups: one group was treated with Activin, a grape seed-derived proanthocyanidins, while the other group served as control. Patients were given Activin 100 mg/day orally for one month after which the blood samples were withdrawn from both groups of the patients. Blood was also taken from normal human volunteers. Plasma was obtained in fasting state between 8 to 9 A.M. from two groups of SSc patients and controls. Soluble adhesion molecules including ICAM-1, VCAM-1, E-selectin and P-selectin as well as malonaldehyde, a marker for oxidative stress, were measured. The results of our study demonstrated up-regulation of these soluble adhesion molecules except for P-selectin, in the plasma of the SSc patients compared to those obtained from human volunteers. Activin significantly attenuated the increased expression of these adhesion molecules. In addition, there was a significant increase in the amount of malondialdehyde formation in the plasma of the SSc patients, which was also attenuated by Activin. The results of this study demonstrated that Activin could reduce the inflammatory response and the oxidative stress developed in SSc patients.

Cardioprotection with sildenafil, a selective inhibitor of cyclic 3',5'-monophosphate-specific phosphodiesterase 5.

Abstract: The effects of sildenafil (Viagra R ), a specific inhibitor of phosphodiesterase 5, on ischemic myocardium was examined using an isolated rat heart model. Rats were pretreated with sildenafil at doses ranging from 0.001 mg to 0.5 mg/kg body weight. After 60 min, isolated hearts were subjected to ischemia for 30 min followed by 2 h of reperfusion. The results demonstrated that at 0.05 mg/kg (and to some extent at 0.01 mg/kg), sildenafil provided significant cardioprotection as evidenced by improved ventricular recovery, a reduced incidence of ventricular fibrillation and decreased myocardial infarction. At higher doses, it caused a significant increase in the incidence of ventricular fibrillation while at very low doses it had no effect on cardiac function. As expected, sildenafil increased cyclic 3',5'-monophosphate (cGMP) content in the heart. The results demonstrate for the first time that within a narrow dose range, sildenafil can protect the heart from ischemia/reperfusion injury, probably through a cGMP-signaling pathway.

Resveratrol, a component of wine and grapes, in the prevention of kidney disease.

Abstract: Ischemia is an inciting factor in 50% of incidences of acute renal failure, and it increases the risk of organ rejection after renal transplantation. We have previously demonstrated that resveratrol (RSV) reduces ischemia-reperfusion (I/R) injury of rat kidney both by antioxidant and anti-inflammatory mechanisms. However, a clear morphological demonstration of this activity has not been made. To answer this question we have performed a new set of experiments following the experimental protocol reported below to investigate the effects of I/R injury and RSV pretreatment on kidney morphology by computerized morphometric analysis. Both renal arteries were clamped for 40 minutes in 40 male Wistar rats (b.w. 220 +/- 20 g); 20 rats were pretreated with RSV 1 microM e.v. 40 minutes before clamping. All animals were reperfused for 24 hours and then sacrificed. Histological examination showed tissue conservation in treated rats. I/R-induced glomerular collapse (as revealed by mean glomerular volume and glomerular shape factor) was significantly reduced by RSV pretreatment. Capillary tuft/Bowman's capsule area ratio was enhanced in the I/R group suggesting tubular hypertension. RSV pre-treatments significantly reduced this parameter to the control value. The number of platelet clots in the capillary tuft and tubular necrosis were also reduced by RSV versus I/R group. L-NAME administration worsened both functional and structural damage. Finally, cGMP urinary levels were markedly reduced from 12.1 +/- 8.4 nmol/day to 0.10 +/- 0.10 nmol/day in the I/R group. RSV provided cGMP (5.01 +/- 1.5 nmol/day, P < 0.05). As expected, L-NAME administration significantly reduced cGMP in urine (0.71 +/- 0.6 nmol/day). The present study confirms the protective effect of RSV pretreatment in I/R injury of rat kidney and suggests multiple mechanisms of action.

Potentiation of angiogenic response by ischemic and hypoxic reconditioning of the heart

Abstract: This review is intended to discuss the newly discovered role of preconditioning which should make it an attractive therapeutic stimulus for repairing the injured myocardium. We recently found that apart from rendering the myocardium tolerant to ischemic reperfusion injury, preconditioning also potentiates angiogenesis. Our study demonstrated for the first time that both ischemic and hypoxic preconditioning triggered myocardial angiogenesis at the capillary and arteriolar levels which nicely corroborated with the improved myocardial contractile function. Hypoxic preconditioning resulted in the stimulation of VEGF, the most potent angiogenic factor known to date. In concert, endothelial cell specific tyrosine kinase receptors, Tie 1, Tie 2 and Flt-1 and Flk-1 were also significantly enhanced in the preconditioned myocardium. The redox-regulated transcription factor NF kappa B was found to play an essential role in the preconditioning regulation of angiogenesis.

Reduction of Myocardial Ischemia Reperfusion Injury with Regular Consumption of Grapes

Abstract: Recently several polyphenolic antioxidants derived from grape seeds and skins have been implicated in cardioprotection. This study was undertaken to determine if the grapes were equally cardioprotective. Sprague Dawley male rats were given (orally) standardized grape extract (SGE) for a period of three weeks. Time-matched control experiments were performed by feeding the animals 45 microg/100 of glucose plus 45 microg/100 g fructose per day for three weeks. After 30 days, rats were sacrificed, hearts excised and perfused via working-mode. Hearts were made ischemic for 30 min followed by two hours of reperfusion. At 100 mg/kg and at 200 mg/kg, SGE provided significant cardioprotection as evidenced by improved post-ischemic ventricular recovery and reduced amount of myocardial infarction. No cardioprotection was apparent when rats were given grape samples at a dose of 50 mg/100 g/day. In vitro studies demonstrated that the SGE could directly scavenge superoxide and hydroxyl radicals which are formed in the ischemic reperfused myocardium. The results demonstrate that the heats of the rats fed SGE reduced myocardial ischemia reperfusion injury by functioning as in vivo antioxidant.

The role of heme oxygenase signaling in various disorders.

Abstract: Modern methods of cell and molecular biology, augmented by molecular technology, have great potential for helping to unravel the complex mechanisms of various diseases. They also have the potential to help us try to dissect the events which follow the altered physiological conditions. Thus, there is every reason to believe that some of the potential mechanisms will be translated sooner or later into the clinic. Heme oxygenase (HO)-related mechanisms play an important role in several aspects of different diseases. In the past several years, significant progress has been made in our understanding of the function and regulation of HO. The objective of this article is to review current knowledge relating to the importance of HO mechanism in various diseases including myocardial ischemia/reperfusion, hypertension, cardiomyopathy, organ transplantation, endotoxemia, lung diseases, and immunosuppression. The morbidity and mortality of these diseases remain high even with optimal medical management. Furthermore, in this review, we consider various factors influencing the HO system and finally assess current pharmacological approaches to their control.