Exposição aguda ao cádmio induz lesão endotelial em aorta de ratos: papel do estresse oxidativo, da angiotensina II e dos prostanóides da via da ciclooxigenase

• Autor(a) principal: Angeli, Jhuli Keli
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/8058
• topic: renin angiotensin system location; ROS; COX-2; Sistema renina angiotensina local; Fisiologia; 612

The Cadmium (Cd) is a toxic metal, widely used in industry and is a constant component of agricultural fertilizers, which has increased the environmental contamination by this metal. It has a close connection with cardiovascular diseases such as atherosclerosis and hypertension, and in addition, it can induce an increase in oxidative stress. One of the main locations affected by oxidative stress are conductance arteries, which consequently, increases the risk for development of atherosclerosis. However, there are few reports evaluating acute effects of cadmium in the aorta. The objective of this study was to evaluate the effects of exposure "in vitro" by Cadmium Chloride on the vascular reactivity and the putative mechanisms involved in this process. Male Wistar rats (250-300g) were used. The animals were anesthetized and then the thoracic aorta was removed and dissected to obtain rings with 3 to 5 mm in length. Control rings and those previously incubated with 10 uM Cd underwent concentration-response curve to phenylephrine (10-10 -10-4M, FE). We evaluated the effects of L-NAME (100µM), apocynin (0,3mM), superoxide Dismutase (SOD, 150 U/ml), catalase (1000 U ml-1), co-incubation (catalase + SOD), enalapril (10 µM), losartan (10 µM), indomethacin (10μM), NS 398 (1 μM), SQ 29,548 (1 μM), SC 19,220 (10 μM) e furegrelato (10 μM) in controls and after Cd incubation. Rings without endothelium were also evaluated. Rings incubated with control and Cd were also subjected to mechanical removal of the vascular endothelium; to increased concentrations of acetylcholine (10-11 a 10-5M, Ach) and sodium nitroprusside (10-11 a 10-5M, NPS). In addition, protein expression of the endothelial nitric oxide synthase (eNOS) isoform, eNOS phosphorylated and AT1 receptor was measured. Results were expressed as mean ± SEM and differences in the area under the curve (dAUC%) or the maximum response (Emax) were evaluated by Student's t-test and analysis of variance (ANOVA) one way, repeated measures or completely randomized, followed by post-hoc Tukey test when necessary (p<0.05). The Emax for FE was greater in rings incubated with Cd when compared to controls (Emax,Ct: 102,5 ± 3,4; Cd: 156,1 ± 4,7). Incubation with L-NAME increased the reactivity of the rings in both groups, but to a lesser extent in rings incubated with Cd (dAUC% Ct x Ct + L-NAME: 117,0 ± 15,3 vs Cd x Cd + L-NAME: 59,7 ± 11,05). Apocynin reduced reactivity in both groups, but with a greater magnitude in rings incubated with Cd (dAUC% Ct x Apo: 26,72 ± 9,41 vs Cd x apo + Cd: 62,47 ± 6,13). Catalase did not significantly alter the vascular response in the presence of Cd, the co-incubation and SOD SOD + Catalase reduced reactivity in rings incubated with Cd (Emax, Ct: 90,6 ± 8,1; Cd : 113,6 ± 6,4; SOD + Cd: 72,7 ± 8,4; SOD+ Cd+ Cata 71,46 ± 10,56). Losartan did not modify the response to phenylephrine compared to control values, but caused greater decrease in response in rings losartan + Cd compared to rings incubated with only Cd (Emax,Ct: 103,2 ± 6,2; LOS+ Cd: 111,4 ± 8,2). The same response was observed after incubation with enalapril. Indomethacin did not modify the response to phenylephrine compared to the control values, but caused greater decrease in response of rings Indo + Cd compared to rings incubated with only Cd (Emax,Ct: 88,4 ± 3,6; Indo + Cd: 76,7 ± 5,8). The same response was observed with the other inhibitors: NS 398 (Emax,Ct: 92,7 ± 5,4; NS + Cd: 84,0 ± 6,3), SQ 29,548 (Emax,Ct: 97,2 ± 6,8; SQ + Cd 79,0 ± 7,2), SC 19,220 (Emax,Ct 97,2 ± 6,8; SC + Cd 102,9 ± 7,6) furegrelato (Emax,Ct 86,6 ± 6,1; FURE + Cd 70,8 ± 7,3). The absence of endothelium (E-) caused an increase in response to FE compared to rings with intact endothelium (E+) in both groups. This increase was smaller in magnitude in rings (E-) incubated with Cd when compared to E+ incubated with metal (% dAUC, CT;E+/E- 147,95 ± 21,9 Cd; E+/E- 67,63 ± 19,04). Cd did not alter the vasodilator response to ACh, or the response to NPS. Protein expression was similar in both control and cadmium treated groups. Our results suggest that Cd increases Emax to FE acting on the vascular endothelium. Furthermore, the mechanisms responsible for this process appear to involve: increased bioavailability of angiotensin II and COX product; decreased release of NO induced by the increased production of free radicals.