Arpad Tosaki

Grape seed proanthocyanidin reduces cardiomyocyte apoptosis by inhibiting ischemia/reperfusion-induced activation of JNK-1 and C-JUN

The mechanism of cardioprotection with red wine consumption was studied by examining the antideath signaling cascade of one of the principle components of red wine, proanthocyanidins. Grape seed proanthocyanidin extract (GSPE) was administered orally (100 mg/kg/d) supplemented with regular diet for 3 weeks to a group of rats while the other group was given the regular diet only for the same period of time. After 3 weeks, rats were sacrificed, hearts excised, and perfused via Langendorff mode. After stabilization, hearts were perfused in the working mode for baseline measurement of contractile function. Hearts were then made globally ischemic for 30 min followed by 2 h of reperfusion. Contractile function was continuously monitored during reperfusion, and free radical production was examined by electron spin resonance (ESR) technique. Cardiomyocyte apoptosis was examined by TUNEL staining in conjunction with an antibody against myocin heavy chain to specifically detect myocytes. Induction of JNK-1 and c-fos proteins was studied by Western blot analysis using respective antibodies followed by densitometric scanning. The results indicated significant induction of JNK-1 and c-fos proteins in the ischemic/reperfused myocardium, which was inhibited by the proanthocyanidin extract. In concert, GSPE significantly reduced the appearance of apoptotic cardiomyocytes in the ischemic/reperfused hearts. GSPE also significantly reduced the appearance of the reactive oxygen species in the hearts. Improved postischemic contractile recovery was achieved with GSPE suggesting its cardioprotective action. The results of this study indicated that GSPE functioned as an in vivo antioxidant, and its cardioprotective properties may be at least partially attributed to its ability to block antideath signal through the inhibition of proapoptotic transcription factor and gene, JNK-1 and c-Jun.

The evolution of diabetic response to ischemia/reperfusion and preconditioning in isolated working rat hearts

OBJECTIVEnStudies have shown that the diabetic heart exhibits abnormalities in cellular ion transport, which can affect susceptibility to reperfusion-induced ventricular fibrillation (VF), tachycardia (VT) and functional derangements. It has been shown that preconditioning renders the heart very resistant to a subsequent prolonged ischemic episode. This phenomenon has been extensively studied in healthy myocardium, but such a study has not been previously done in diseased (hypertrophic or myopathic) hearts.nnnMETHODSnWe studied the incidence of reperfusion-induced VF, VT, cardiac function, and ion shifts (Na+, K+, Ca2+, and Mg2+) induced by ischemia/reperfusion in isolated hearts from rats with streptozotocin-induced diabetes. Following 2, 4, 6, and 8 weeks of diabetes, hearts were isolated and subjected to 30 min global ischemia followed by reperfusion.nnnRESULTSnIn the 2-week diabetic group the total incidence of VF and VT was reduced from their non-diabetic age-matched control value of 100 and 100% to 42 (P < 0.05) and 42% (P < 0.05), respectively. Such a reduction in the incidence of VF and VT was not observed with progressive diabetes (4, 6, and 8 weeks). In the 2-week diabetics, the reduction in the VF and VT was reflected in the improvement of postischemic function, the reduction of ischemia and reperfusion-induced Na+ and Ca2+ gains, and the prevention in K+ and Mg2+ loss. This diabetes-induced initial protection was not seen in the 4- and 6-week diabetics, and a deterioration of postischemic function was observed in the 8-week diabetics. Four cycles of preconditioning, each consisting of 5 min ischemia followed by 10 min reperfusion, failed to reduce the incidence of VF and VT, improve cardiac function, and prevent ion shifts induced by 30 min ischemia followed by 30 min reperfusion in 4- and 8-week diabetics.nnnCONCLUSIONSnIn the early phase of diabetes the heart is more resistant to ischemia/reperfusion than the non-diabetic heart. Preconditioning does not afford protection against a prolonged period of ischemia in diabetics, indicating that preconditioning may be a healthy heart phenomenon.

Adenosine triphosphate-sensitive potassium channel blocking agent ameliorates, but the opening agent aggravates, ischemia/reperfusion-induced injury: Heart function studies in nonfibrillatingt isolated hearts

OBJECTIVESnThis study was conducted to elucidate the role of the adenosine triphosphate (ATP)-sensitive potassium channel blocking agent glibenclamide and the opener cromakalim in the mechanism of reperfusion-induced injury.nnnBACKGROUNDnRecently, ATP-sensitive potassium channel openers have been proposed to reduce ischemia/reperfusion-induced injury, including arrhythmias and heart function. Thus, one might hypothesize that pharmacologic agents that enhance the loss of potassium ions in the myocardium through ATP-sensitive potassium channels would be arrhythmogenic, and agents that interfere with tissue potassium ion loss would be antiarrhythmic.nnnMETHODSnIsolated working guinea pig hearts and phosphorus-31 nuclear magnetic resonance spectroscopy were used to study the recovery of myocardial function and phosphorus compounds after 30, 40 and 50 min of normothermic global ischemia followed by reperfusion in untreated control and glibenclamide- and cromakalim-treated groups.nnnRESULTSnAfter 30 min of ischemia, 1, 3, 10 and 30 mumol/liter of glibenclamide dose-dependently reduced the incidence of reperfusion-induced ventricular fibrillation (total) from its control value of 92% to 75%, 33% (p < 0.05), 33% (p < 0.05) and 42% (p < 0.05), respectively. The incidence of ventricular tachycardia followed the same pattern. A reduction of arrhythmias was also observed after 40 and 50 min of ischemia followed by reperfusion in the glibenclamide-treated hearts. Cromakalim, at the same concentrations, did not reduce the incidence of reperfusion-induced arrhythmias. During reperfusion, glibenclamide (3 and 10 mumol/liter) improved the recovery of coronary blood flow, aortic flow, myocardial contractility and tissue ATP and creatine phosphate content, but cromakalim failed to ameliorate the recovery of postischemic myocardium compared with that in the drug-free control hearts.nnnCONCLUSIONSnThe preservation of myocardial potassium ions and phosphorus compounds by glibenclamide can improve the recovery of postischemic function, but the use of ATP-sensitive potassium channel openers as antihypertensive or antiarrhythmic agents may be of particular concern in those postinfarction patients who are known to be at high risk for sudden cardiac death.

Cardioprotective abilities of white wine

Abstract: To study if white wines, like red wine, can also protect the heart from ischemia reperfusion injury, ethanol‐free extracts of three different white wines (WW1, WW2 and WW3) (100 mg/100 g body weight) were given orally to Sprague Dawley rats (200 g body weight) for three weeks. Control rats were given water only for the same period of time. After three weeks, rats were anesthetized and sacrificed, and the hearts excised for the preparation of isolated working rat heart. All hearts were subjected to 30 min global ischemia followed by two hours of reperfusion. The results demonstrated that among the three different white wines, only WW2 showed cardioprotection as evidenced by improved post‐ischemic ventricular recovery compared to control. The amount of malonaldehyde production in white wine‐fed rat hearts were lower compared to that found in control hearts indicating reduced formation of the reactive oxygen species. In vitro studies using chemiluminescence technique revealed that these white wines scavenged both superoxide anions and hydroxyl radicals. The results of our study demonstrated that only WW2 white wine provided cardioprotection as evidenced by the improved the post‐ischemic contractile recovery and reduced myocardial infarct size. The cardioprotective effect of this white wine may be attributed, at least in part, from its ability to function as an in vivo antioxidant.

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 μg/100 of glucose plus 45 μg/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.

ROLE OF NITRIC OXIDE AND TPEN, A POTENT METAL CHELATOR, IN ISCHAEMIC AND REPERFUSED RAT ISOLATED HEARTS

1. The role of nitric oxide (NO) was studied in the control of ischaemic/reperfused cardiac function and the effect of N, N, N, N‐tetrakis‐[2‐pyridylmethyl]‐ethylenediamine(TPEN), a potent metal chelator, on the regulation of cardiac NO formation.

Myocardial Salvage by Chimyl Alcohol: Possible Role of Peroxisomal Dysfunction in Reperfusion Injury

The results of this study suggest that reperfusion of ischemic myocardium may lead to the peroxisomal disorder both functionally and biochemically. An alkyl glycerol such as chimyl alcohol can protect the ischemic heart from the reperfusion injury probably by enhancing the plasmalogen synthesis.

Lanthanum Provides Cardioprotection by Modulating Na+-Ca2+ Exchangea

Intracellular Ca2+ overloading is a well-recognized feature in myocardial ischemic and reperfusion injury. The exact mechanism for Caz+ influx into the cell remains controversial, but it is generally accepted that both Ca2+ slow channels and Nat-Ca2+ exchangers play a role in the pathophysiology of myocardial ischemic and reperfusion injury.2 It is known that acidosis induced by anaerobic metabolism leads to enhanced exchange of intracellular H+ for Nat which in turn becomes instrumental for the intracellular Ca2+ accumulation. This hypothesis is well supported by the observations that inhibitors of Na+-H+exchangers such as amiloride can inhibit the accumulation of Ca2+. Approximately 41% of the total exchangeable Ca2 is localized in a kinetic compartment defined by rapid compartment, and this Ca2 pool is rapidly displaced by lanthanum (La3+), a known inhibitor of Ca2+-binding protein^.^ La3+ is also a potent inhibitor of CaZf entry into mitochondria via the uniport ~ y s t e m . ~ La3+ has also been found to nonspecifically block the Ca2+ channels. In this study, we examined the effects of La3+ on myocardial rhythm disturbances associated with ischemia and reperfusion. In an attempt to examine its mechanism of actions, we also examined the myocardial contents of Na+, K+, Ca2* and Mg2+.

Extracellular magnesium manipulation reduces reperfusion arrhythmias and ion shifts in isolated rat hearts.

Clinical reports of the successful treatment of cardiac arrhythmias with magnesium salts began to appear in the scientific literature some 50 years ago1 but it is only in the last few years that the necessary electrophysiological studies have been carried out to shed light on these empirical observations.2 We used the in mtro rat heart preparation with regional and global ischemia to examine the relationship between the incidence of reperfusion-induced arrhythmias and the manipulation of extracellular Mg. Changes in myocardial Na, K, Ca, and Mg during ischemia and reperfusion were measured. Our experiments were designed to provide insights into the mechanisms responsible for the initiation of ventricular fibrillation (VF) and tachycardia (VT), and to assess the antiarrhythmic effects of Mg.