Sildenafil diminui a hiperreatividade de aneis isolados de traqueia de ratos e altera a expressão genica de proteínas Canonical transient receptor potential após desafio antigênico

Abstract

Sildenafil (Viagra ®) is a selective inhibitor of cyclic guanosinamonofosfato (cGMP) a specific phosphodiesterase-5 (PDE5) useful in the treatment of erectile dysfunction and pulmonary arterial hypertension. The increase in intracellular cGMP levels caused by inhibition of PDE5 causes several cellular events such as airway smooth muscle relaxation and inhibition of cellular inflammation. The aim of this study was to evaluate the mechanism of action of sildenafil in tracheas of naive animals and challenged to ovalbumin, evaluate the effect of sildenafil on the expression and function of calcium channels operated by stock in tracheas of naive animals, sensitized and challenged with ovalbumin. In this work male rats of Wistar species were used, animals were actively sensitized by intraperitoneal injections of ovalbumin (three application on alternate days - 1, 3 and 5), the antigenic challenge (bronchoprovocation) occurred during the period between the 21 and 50 days post-sensitization, exactly 24 hours before the experiments in vitro. After removing the tracheal rings form chambers mounted on isolated bath and performed the concentration effect curves. When comparing the relaxing effect of sildenafil IC50 in animals with intact epithelium 27.2 [17.5 to 42.1] microM (n = 12), whereas the IC50 for the preparations without epithelium (n = 7) was of 232.25 [129.58 to 416.23] microM, (p <0.05 Kruskal-Wallis). In preparations not treated with L-NAME IC50 was 27.2 [17.5 to 42.1] microM (n = 12), while in preparations treated with L-NAME (n = 7) was 348.1 [248 to 488.5] microM (p <0.05 Kruskal-Wallis). We observed in naive animals an increase in the EC50 for carbachol contraction produced by 0.22 [0.17 to 0.30] microM (n = 8) in the absence of sildenafil for 2.01 [1.21 to 3.33 ] microM (n = 7) in the presence of 30 microM of sildenafil for 2.85 [2.09 to 3.87] microM in the presence of 100 mM of sildenafil, and 2.45 [1.67 to 3.6 ] microM (n = 10) in the presence of 300 mM of sildenafil. In animals sensitized and challenged with ovalbumin, sildenafil 30μM inhibited bronchial hyperactivity. Concerning the entrance of capacitative calcium, the sildenafi decreased the contraction produced by the replacement of calcium by 42.9 ± 7.3% in naive animals to 10.8 ± 3.7% in presence of 30 mM of sildenafil (p <0, 05). In the animals challenged sildenafi decreased the contraction produced by the replacement of calcium (98.0 ± 11.8%, n = 6) without the presence of sildenafil in 22.7 ± 5.4% in the presence of sildenafil 30 microM (p <0.05). Correlating gene expression with animals sensitized and challenged with ovalbumin treated with sildenafil a significant increase in gene expression TRPC1 TRPC6 (p <0.05, test HolmSidak) occurred. In contrast TRPC5 expression, expressed no changes after antigenic challenge, but decreased significantly after the treatment with sildenafil (p <0.05, test HolmSidak). In this study, we found that the myorelaxant effect of sildenafil involves NO, cGMP, potassium channels and calcium channels operated by stock. The presence of sildenafil was also able to significantly reduce the response to antigen in tissues from mice sensitized and challenged, and to alter the expression of genes belonging to the subfamily of TRPC, linking the involvement of phosphodiesterase 5 via the cellular expression of genes in TRPC tracheal smooth muscle.