Histopathological and biochemical effects of nebivolol on short term hyperhomocysteinemia induced endothelial dysfunction in rats

Objective: Homocysteine has a potent mitogenic effect on vascular smooth muscle cells. Additionally homocysteine, decreases endothelial derived nitric oxide synthase and nitric oxide formation. As a result of degradation the endothelial production of nitric oxide, endothel is subjected to oxidative stress and endothelial dysfunction occurs. Also homocysteine increases lipid peroxidation. Nebviolol which is highly selective third generation β1-boker, shows its effect by vasodilatation, through L-arginine/NO pathway. Endothelial derived NO plays an important role on nebviolol induced vasodilation, has been shown in the experimental studies. Nebivolol reduces cell proliferation. Nebivolol prevents intima against damages. Nebivolol reduces intimal hyperplasia and the possibility of restenosis which occurs after endothelial injury. In this study, we aimed to uncover the nebivolol's inhibitor effect on endothelial dysfunction, with pathology sections whichs are taken from rats' heart and thoracic aorta, and biochemical analysis results of blood serum. Materiel And Method: Male wistar albino rats were divided into 4 groups randomly and equally (n=7). 1) Control Group (n=7): The animals in this group, did not receive any medication for 4 weeks. Every day, once a day we gave 1 ml drinking water by orogastric gavage. 2) Nebivolol Group (n=7): The animals in this group, 10 mg/kg/day nebivolol was given by orogastric gavage every day, once a day, for 4 weeks. 3) Methionine group (n=7): The animals in this group, 1gr/kg/day methionine was given by orogastric gavage every day, once a day, for 4 weeks. 4) Methionine+nebivolol group (n=7): The animals in this group, 1gr/kg/day methionine and 10 mg/kg/day nebivolol was given at the same day two hours later by orogastric gavage every day, once a day, for 4 weeks. Before the study begins, weights of rats were measured. Throughout the study, in all groups of rats were fed by standard rat silage and urban drinking water without limitation. For drug dosage adjustment, weights of the rats were measured every week. And then the amount of drug was determined for each rat. L-methionine (M9625 Sigma-Aldrich L-Methionine reagent grade, ≥98% (TLC) ) which dissolved in pH 7.4 phosphate buffer solution, was given 1gr/kg/day dosage by orogastric gavage every day, once a day, for 4 weeks. Nebivolol was obtained from Nexivol ready tablets which was produced by Abdi Ibrahim Company. And then dissolved in 10% dimethylsulfoxide solution. Nebivolol was given 10mg/kg/day dosage by orogastric gavage every day, once a day, for 4 weeks. At the end of the study, rats were sacrificed under ether anesthesia, and then blood samples were taken in EDTA hemogram tubes and flat biochemistry tubes. Then the rat aorta and heart were dissected and placed in 10% formaldehyde solution for histochemical and immunohistochemical examination. Results: In our study hyperhomocysteinemia was found to be significantly in the group which received methionine. In line with this finding in the biochemical analysis of antioxidants catalase, glutathione, glutathione peroxidase, glutathione reductase, superoxide dismutase levels were decreased and oxidants ADMA, homocysteine and MDA levels were increased. The animals in the group, which was given methionine and nebivolol at the same time, antioxidant catalase, glutathione, glutathione peroxidase, glutathione reductase, superoxide dismutase levels were observed decrease and oxidant ADMA, homocysteine and MDA levels were observed increase. When we make comparison of the animals in the group, which was given methionine and nebivolol at the same time and the animals in the group which was given methionine only, the difference of the Glutathione reductase and SOD results was not statistically significant. All other comparison of biochemical results were obtained statistically significant. From the histopathological findings, only in TGF β-1 aorta staining groups and the cardiomyocyte degeneration groups, were detected statistically significant differences between the groups. But when we make comparison of the animals in the group, which was given methionine and nebivolol at the same time and the animals in the group which was given methionine only, the difference of results was not statistically significant. Conclusion: In this study which was done on the rats, we were able to shown biochemical results that we could avoid from short-term hyperhomocysteinemia induced endothelial dysfunction by giving nebivolol molecule, for the first time in the literature. In addition, for the first time we showed nebivolol may prevent from increase in Hcy levels, if we gave oral methionine with nebivolol in two hours later on the same day. Previously in the literature to the absence of a similar study makes our work unique. We believed that we can avoid from short-term hyperhomocysteinemia induced endothelial dysfunction by giving nebivolol molecule based on our biochemical findings. When we compared histopathological findings in our study, cardiomyocyte degeneration was observed more in the methionine group. But in the short term administration of nebivolol, did not cause a statistically significant difference on histopathological findings. We believe that more clinical trials which will use more rats and long treatment periods are needed in order to generalize these results, also revealed histopathological changes clearly. Keywords: Hyperhomocysteinemia, nebivolol, asymmetric dimethyl arginine, nitric oxide, antioxidant, endothelial dysfunction, cardiomyocyte degeneration, histopathology, malondialdehyde, glutathione, glutathione peroxidase, glutathione reductase, superoxide dismutase, catalase, transforming growth factor beta-1, vascular endothelial growth factor. Contact address: Adnan Menderes Üniversitesi Tıp Fakültesi Hastanesi Kardiyoloji Anabilim Dalı, Merkez/Aydın, Phone:00905352013420