Effect of tobacco smoke on hydrogen sulfide-induced rat thoracic aorta relaxation

Levels of hydrogen sulfide (H(2)S), a gaseous signaling molecule, are reduced in the serum of individuals who smoke. We hypothesized that tobacco smoke influenced smooth muscle relaxation by decreasing H(2)S levels and this effect could also influence expression of cystathionine γ-lyase (CSE) and sulfonylurea receptor-2 (SUR-2). The aim of this study was to explore the effect of tobacco smoke on H(2)S-mediated rat thoracic aorta relaxation and its possible mechanism. Thirty-two Sprague-Dawley rats were divided into four groups: control (C) group, short-term smoker (SS) group, mid-term smoker (MS) group, and long-term smoker (LS) group. H(2)S concentrations in serum, action of H(2)S on rat aortic vascular relaxation, and expression of CSE and SUR-2 in thoracic aortic smooth muscle were measured. Although there was no significant difference in H(2)S between the C and the SS groups, concentration of H(2)S was significantly reduced in both the LS and MS groups compared to control (P<0.01). Furthermore, H(2)S was significantly lower in the LS than in the MS group (P<0.05). Rat aortic vascular relaxation was lower in all three treatment groups compared to the control, with the most significant decrease observed in the LS group (P<0.05 compared to the MS group). Expression of CSE and SUR-2 was reduced in the LS and MS groups compared to control (P<0.05), with the lowest levels observed in the LS group (P<0.05). Therefore, tobacco smoke reduced expression of CSE and SUR-2 in rat thoracic aorta, which may inhibit H(2)S production and vascular dilation.