THROMBOXANE-DEPENDENT CORONARY VASOCONSTRICTION IN OBESE MICE: ROLE OF PEROXYNITRITE

Abstract

Objective: Obesity leads to chronic oxidative stress promoting the development of cardiovascular diseases including endothelial dysfunction, which might occur through the cyclooxygenase (COX) pathway. This study aimed to investigate the role of peroxynitrite in the generation of COX-derived products and its role in coronary vascular responses. Design and method: We evaluated arachidonic acid (AA)-dependent coronary vascular responses in isolated hearts from control and obese C57BL/6 mice and explored COX metabolism using the COX-2 inhibitor indomethacin and 1-benzylimidazole, inhibitor of thromboxane synthase (TXS). COX, TXS, and TXA2 receptor (TP) protein expression was assessed in heart homogenates. The release of TXA2 in the coronary circulation was also evaluated. In addition, the possible involvement of peroxynitrite on increased coronary response was explored by detecting peroxynitrite by coumarin boronic acid (CBA) and 3-nitrotyrosine protein expression. Alterations in TXS, and TP receptor protein expression were also evaluated in heart homogenates from obese mice treated with the peroxynitrite scavenger FeTMPyP. Results: Arachidonic acid (AA) dependent coronary vasoconstriction in isolated hearts, increased from 31.06 ± 2.67 mmHg in control mice to 88.99 ± 6.09 mmHg in obese mice. Both, indomethacin and 1-benzylimidazole reduced the vasoconstriction response in control and obese mice. TXA2 released during AA-induced vasoconstriction phase was increased in heart perfusates from 76.1 ± 18.42 pg/mL in control mice to 203.6 ± 29.8 pg/mL in obese mice. COX- 2, TXS and TP receptor protein expression was increased in hearts from obese mice (1.96 ± 0.25, 0.70 ± 0.07, 1.22 ± 0.19 arbitrary units, respectively) compared with control mice (0.17 ± 0.02; 0.06 ± 0.02; and 0.29 ± 0.06 arbitrary units, respectively). Moreover, nitrotyrosine and peroxynitrite levels were higher in obese mice, compared with control mice. Increase in coronary vasoconstriction, TXA2 release as well as protein expression was prevented with FeTMPyP treatment in obese mice. Conclusions: Peroxynitrite-dependent induction of COX-2 and TXS protein expression in heart tissue from obese mice may lead to increased TXA2 coronary circulation, thereby increasing coronary vasoconstriction.