Glibenclamide, an antagonist of ATP sensitive K+ channels, blocks free radical generation in the rat myocardium

Antioxidant effect of pomegranate against streptozotocin-nicotinamide generated oxidative stress induced diabetic rats

Oxidative stress attributes a crucial role in chronic complication of diabetes. The aim of this study was to determine the most effective part of pomegranate on oxidative stress markers and antioxidant enzyme activities against streptozotocin-nicotinamide (STZ-NA)-induced diabetic rats. Male Sprague-Dawley rats were randomly divided into six groups. Experimental diabetes was induced by a single intraperitoneal injection (i.p), 15 min after the i.p administration of NA. Diabetic rats showed significant increase in plasma glucose level, and the significant decrease in plasma insulin level. The activities of antioxidant enzymes such as total antioxidant status (TAS), superoxide dismutase (SOD), and catalase (CAT) reduced while the levels of biomarkers of oxidative stress such as gamma-glutamyle transferase (GGT), and malondialdehyde (MDA) increased in diabetic control rats as compared to normal control rats. Oral treatment with pomegranate seed-juice for 21 days demonstrated significant protective effects on all the biochemical parameters studied. Besides, biochemical findings were supported by histopathological study. These results revealed that pomegranate has potential protective effect against oxidative stress induced diabetic rats.

Comparing the effects of ginger and glibenclamide on dihydroxybenzoic metabolites produced in stz-induced diabetic rats

BACKGROUND

The aim of the present study was to investigate the effect of ginger and glibenclamide on oxidative stress markers. Oxidative stress is caused by an unbalance between a relative overload of oxidants and depletion of antioxidants, as implicated in the pathogenesis of several chronic diseases, including atherosclerosis and diabetes mellitus. Regarding the role of oxidative stress in the pathogenesis of diabetes mellitus, we investigated the effect of ginger and glibenclamide in diabetic rats induced bystreptozocin (STZ).

OBJECTIVES

This study assessed the effects of ginger and glibenclamide on dihydroxybenzoic acid metabolites in diabetic rats.

MATERIALS AND METHODS

In this study 30 Wistar strain male rats were divided into five groups: Group 1: Normal control receiving normal saline (0.9 0/0), Group 2: control DMSO (Dimethyl sulfoxide) (as solvent of glibenclamide), Group 3: Diabetic control receiving Streptozocin (STZ ) (50 mg/kg) ,Group 4: diabetic+ Ginger Extract: this group received ginger ethanolic extract (200 mg/kg) via IP (Intraperitoneally) injection for 30 days, and Group 5 diabetic rats received glibenclamide (0.5 m/kg). Production of hydroxyl radicals was examined in the diabetic rats induced by streptozocin. Hydroxyl radicals were generated in plasma of the hyperglycemic rats, and were quantitatively assayed by trapping hydroxyl radicals with salicylic acid so as to produce 2,3-and 2,5-dihydroxybenzoic acid.

RESULTS

Production of hydroxyl radicals increased; therefore, by using salicylic acid, hydroxyl radicals were trapped and 2,3dihydroxybenzoic acid and 2,5dihydroxybenzoic acid metabolites were formed then measured by HPLC and spectrophotometer. Rats receiving ginger extract and glibenclamide showed decreased level of metabolites compared to the diabetic controls (P <0/001). This means that antioxidants act as scavenger of free radicals.

CONCLUSIONS

Comparative effect of ginger and glibenclamide also showed that glibenclamide has antioxidant effect as a scavenger of free radical, but ginger is more capable of eliminating them.

Protective role of glibenclamide against nicotinamide-streptozotocin induced nuclear damage in diabetic Wistar rats

Objective:

To evaluate the protective effect of glibenclamide against the experimental diabetes-induced nuclear damage in Wistar rats.

Materials and Methods:

The anti-mutagenic effect of glibenclamide (0.5, 5 and 50 mg/kg, p.o daily for 4 weeks) was evaluated against the nicotinamide (NA)-streptozotocin (STZ) induced type-2 diabetes mellitus using bone marrow micronucleus and sperm abnormalities tests. The antioxidant status was tested by estimating the serum levels of lipid peroxidation (LPO), catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx).

Results:

The results indicated that glibenclamide at 50 mg/kg decreased the frequency of micronuclei in erythrocytes (P < 0.05) and sperm shape abnormality (P < 0.01) besides enhancing the antioxidant status (P < 0.05) in the diabetic rats. However, glibenclamide treatment did not enhance the polychromatic and normochromatic erythrocytes (P/N) ratio and sperm count in the diabetic condition.

Conclusion:

The observations indicate that the glibenclamide has anti-mutagenic potential which could be related to the antioxidant effect and might also possess anti-proliferative property.

The mechanisms of inhibitory actions of gliclazide on neutrophils-endothelial cells adhesion and surface expression of endothelial adhesion molecules mediated by a high glucose concentration

BACKGROUND

We previously reported that culture of endothelial cells in the presence of high glucose concentrations (27.8 and 55.5 mM) increase neutrophils adhesion because of the increase in endothelial adhesion molecules expression via activation of a protein kinase C (PKC) pathway. The antidiabetic sulfonylurea gliclazide, but not glibenclamide, inhibited these events, but the mechanisms involved were not clarified then. We present hereafter the results of further investigations of that effect with special reference to PKC activation.

METHODS

Human umbilical vein endothelial cells (HUVEC) were cultured for 48 h in a glucose-rich medium and neutrophils from healthy volunteers were then added and allowed to adhere for 30 min. Adhered neutrophils were quantified by measuring myeloperoxidase (MPO) activities and the surface expression of endothelial adhesion molecules was determined by enzyme immunoassay.

RESULTS

Culture in the presence of a high glucose concentration (27.8 mM for 48 h) increased neutrophils-endothelial cells adhesion and the surface expression of intercellular adhesion molecule-1 (ICAM-1), P-selectin, and E-selectin on the endothelial cells. These phenomena were significantly inhibited by gliclazide (20 microM). On the other hand, phorbol 12-myristate 13-acetate (PMA), a PKC activator, had an effect similar to a high glucose concentration and that effect was also inhibited by gliclazide.

CONCLUSIONS

These data suggest that gliclazide inhibits high glucose-mediated neutrophils-endothelial cells adhesion and expression of endothelial adhesion molecules through inhibition of a PKC pathway.

Participation of high glucose concentrations in neutrophil adhesion and surface expression of adhesion molecules on cultured human endothelial cells: effect of antidiabetic medicines

BACKGROUND

Atherosclerosis and vascular inflammation induced by hyperglycemia are important factors in the promotion of diabetic complications. One of the earliest events in the inflammatory process is increased binding of neutrophils to endothelial cells. Since vascular inflammation has been recently reported to be crucial for the onset of atherosclerosis-mediated serious diseases (acute myocardial infarction, stroke), in this study, we examined the effects of high glucose concentrations on endothelial-neutrophil cell adhesion and surface expression of endothelial adhesion molecules. We also evaluated the effects of various antidiabetic medicines on these events.

METHODS

Human umbilical vein endothelial cells (HUVECs) were first cultured for 48 h in the glucose-rich medium, and neutrophils from healthy volunteers were then added and allowed to adhere for 30 min. Adhered neutrophils were quantified by measuring myeloperoxidase (MPO) activities, and surface expression of endothelial adhesion molecules was determined using an enzyme immunoassay.

RESULTS

High glucose concentrations (over 27.8 mM) increased endothelial-neutrophil cell adhesion and expression of endothelial adhesion molecules (intercellular adhesion molecule-1 (ICAM-1), P-selectin, E-selectin). These events were protein kinase C (PKC) dependent, because PKC inhibitors, but not other intracellular second messenger inhibitors, significantly blocked them. Among antidiabetic medicines, a sulfonylurea, gliclazide (but not glibenclamide or glimepiride), and an aldose reductase inhibitor, epalrestat, significantly inhibited these events; however, a new K(ATP)-channel blocker, netegulinide, a biguanide, metformine, or an insulin sensitizer, troglitazone, did not.

CONCLUSIONS

Our data is consistent with hyperglycemia-mediated vascular inflammation through increases in neutrophil adhesion and expression of endothelial adhesion molecules. These events might lead to the onset of atherosclerosis-mediated serious diseases, but could be inhibited by something perhaps, such as gliclazide and epalrestat.

Nucleoside transport inhibition in ischemic myocardium results in enhanced taurine efflux

We measured with the microdialysis technique energy-related metabolites in ischemic myocardium over time in an experimental pig model. Emphasis was put on the dipyridamole effect when administered in the microdialysis probe inserted in ischemic myocardium. Not only adenosine but also taurine and pyruvate concentrations were significantly higher in the microdialysate during the periods of ischemia and extracorporeal circulation with cardioplegia. The enhanced efflux of taurine in ischemic myocardium induced by dipyridamole is a new finding. A mechanistic role of taurine in the prevention of Ca(2+) overload in ischemic myocytes is discussed. Also, taurine may have stimulatory effects on glycolysis in ischemic heart.

Block of cardiac ATP-sensitive K(+) channels reduces hydroxyl radicals in the rat myocardium

The present study examined whether opening of an ATP-sensitive K(+) (K(ATP)) channel can induce hydroxyl free radical ((*)OH) generation in the rat myocardium. Sodium salicylate in Ringer's solution (0.5 nmol/microl/min) was infused directly through a microdialysis probe to detect the generation of (*)OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (DHBA). Induction of cromakalim (100 microM), a K(ATP) channel opener, through the microdialysis probe significantly increased the level of 2,3-DHBA. Another K(ATP) channel opener, nicorandil, also increased the level of 2,3-DHBA. When iron(II) was administered to cromakalim-pretreated animals, a marked elevation of DHBA was observed, compared with iron(II) only-treated animals. A positive linear correlation between iron(II) and formation of (*)OH, trapped as DHBA in the dialysate, was shown (r(2) = 0.988). When corresponding experiments were performed with nicorandil-treated animals, a positive linear correlation between iron(II) and DHBA in the dialysate was shown (r(2) = 0.988). However, the presence of glibenclamide (1-50 microM) decreased the cromakalim-induced 2,3-DHBA formation in a concentration-dependent manner (IC(50) = 9.1 microM). 5-Hydroxydecanoate (5-HD; 100 microM), another K(ATP) channel antagonist, also decreased cromakalim-induced (*)OH formation. The IC(50) value for 5-HD against cromakalim-evoked increase in 2,3-DHBA was 107.2 microM. In the presence of glibenclamide (10 microM), the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery (LAD). When the heart was reperfused, the normal elevation of 2,3-DHBA in the heart dialysate was not observed in animals pretreated with glibenclamide (10 microM). When corresponding experiments were performed with 5-HD (100 microM) pretreated animals, the same results were obtained. These results suggest that opening of cardiac K(ATP) channels may cause (*)OH generation.