Efeitos do tratamento com sildenafil na hipertensão experimental renovascular

• Autor(a) principal: Moreira, Ananda Tissianel Dias
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/7989
• topic: Renovascular hypertension; Angiotensin II; Endotelial dysfunction; Stenotic kidney; Oxidative stress; DNA damage; Hipertensão renovascular; Sildenafil; Angiotensina II; Disfunção endotelial; Rim estenótico; Estresse oxidativo; Dano ao DNA; Fisiologia; 612

Hypertension is a major worldwide health issue. The aim of the present study was to evaluate the beneficial effects of sildenafil on hemodynamics, endothelial function, and on oxidative stress and DNA damage in the stenotic kidney in the mouse model of renovascular hypertension, type two-kidney, one clip (2K1C). Considering our previous report indicating that the chronic blockade of phosphodiesterase 5 with sildenafil (Viagra ®) has marked beneficial effects improve endothelial function and on oxidative stress and DNA damage in a model of spontaneous atherosclerosis, we tested the hypothesis that sildenafil could also reduce the endothelial dysfunction and protect the stenotic kidneys of 2K1C hypertensive mice against oxidative stress and DNA genotoxicity. This drug increases the bioavailability of the intracellular second messenger of NO (cGMP) by inhibition of phosphodiesterase 5. Male C57BL/6 mice were subjected to 2K1C hypertension. After 14 days, sildenafil (40 mg/kg/day) or vehicle was administrated, during a period of 14 days. At the end of experimental period, animals were anesthetized and catheterized for direct arterial pressure measurements. In the studies about endothelial function, the mesenteric arteriolar bed (MAB) was removed and studied its responsiveness through dose-response curves to acetylcholine (ACh) in vitro and precontracted with norepinephrine. The renal levels of angiotensin II in the stenotic kidneys were determined by a blind examiner in another laboratory. The stenotic kidney cells were isolated by enzymatic approaches for evaluation of cell viability and oxidative stress through flow cytometry and for evaluation of DNA damage through the comet assay. Measurements of intracellular superoxide anions and hydrogen peroxide levels as well as nitric oxide bioavailability were also obtained. Data are mean ± SEM. The statistical analysis was through one-way ANOVA followed by Bonferroni post hoc test.* p<0.05 and **p<0.01 vs. 2K1C and & p<0,05 e &&p<0,01 was considered as statistically significant. As expected, blood pressure and heart rate was higher in 2K1C than in sham mice (sham 107 ± 2 vs. 2K1C 125 ± 2* mmHg, 451± 18 vs. 516±2 bpm, respectively). Sildenafil treatment significantly reduced mean arterial blood pressure (112 ± 2* mmHg) and heart rate (471 ± 12* bpm). The renal levels of angiotensin II showed elevation in 2K1C (179 ± 32*pmol/g tissue) when compared to sham group (70 ± 7 pmol/g tissue). However, sildenafil prevented this elevation in the hypertensive animals treated with this drug (94±6* pmol/g tissue). 2K1C mice showed markedly vascular dysfunction in the ACh test (Rmax: 48,7 ± 1,8**) when compared to sham (Rmax: 76,13 ± 2), which was reversed by sildenafil treatment (Rmax: 67,48 ± 4 ##).This dysfunction was not due to reduction in vascular smooth muscle sensitivity to NO, once no differences were found in SNP responses. The role of NO and COXderived prostanoids (PGI2) in relaxation of 2K1C was diminished (dAUC: NO: 51 ± 5*, PGI2: 9,0 ± 3,8# a.u) when compared to sham (dAUC: NO: 77 ± 5; PGI2: 32,7 ± 4,7 a.u) but were restored by sildenafil (NO:74 ± 6# ; PGI2: 29,6 ± 6,5# a.u). The participation of ROS was evaluated by blockage of NAPH oxidase and it was observed that there was greater participation of ROS in 2K1C (dAUC: 76,0 ± 4* a.u) when compared to sham and 2K1C sildenafil ( dAUC 48,7 ± 5,9, 56,8 ± 5# a.u) and that sildenafil caused a significant reduction of oxidative stress. In stenotic kidney from 2K1C mice there was an increase in oxidative stress and reactive oxygen species production (•O2: 887 ± 41, H2O2: 308 ± 22 a.u.) when compared to sham (•O2:700 ± 21, H2O2: 214 ± 7,7 a.u.), and sildenafil caused a remarkable decrease in these levels in treated animals ( •O2: 765 ± 32, H2O2 : 235 ± 20 a.u). On the other hand, sildenafil increased nitric oxide levels (350 ± 33 a.u.) relative to those in the nontreated 2K1C mice and sham (217 ± 10, 260 ± 21 a.u., respectively). Similarly, treatment with sildenafil significantly reduced the high level of kidney DNA damage that is a characteristic of renovascular hypertensive mice. In stenotic kidney from 2K1C mice there was an increased DNA fragmentation (tail moment: 38 ± 5,7%, % tail DNA: 52,2 ± 10 a.u.) when compared to sham (tail moment: 21 ± 2,1%, % tail DNA: 21,5 ± 3,2 a.u.), and sildenafil caused a remarkable decrease in these parameters (tail moment:17 ± 3,4%, % tail DNA: 17,3 ± 3,5 a.u.). Therefore, this study show revealed a beneficial cardiovascular effects, such as restoring endothelial function. Our data, suggest that the main mechanism of its action is restoring NO and PGI2 and reducing the increased oxidative stress. In the stenotic kidneys of 2K1C mice sildenafil was able to reduce ROS production, increase NO bioavailability inhibit DNA damage and markedly reduced the levels de angiotensin II. Thus, these data contributes with important that for a future use of phosphodiesterase 5 inhibitors aiming the amelioration of endothelial function and renoprotection against the DNA damage in individuals with renovascular hypertension