Peroxisome proliferator-activated receptor-γ activation reduces cyclooxygenase-2 expression in vascular smooth muscle cells from hypertensive rats by interfering with oxidative stress

Aims: Hypertension is associated with increased plasma inflammatory markers such as cytokines and increased vascular cyclooxygenase-2 (COX-2) expression. The ability of peroxisome proliferator-activated receptor-gamma (PPAR gamma) agonists to reduce oxidative stress seems to contribute to their anti-inflammatory properties. This study analyzes the effect of pioglitazone, a PPAR gamma agonist, on interleukin-1 beta-induced COX-2 expression and the role of reactive oxygen species (ROS) on this effect. Methods and results: Vascular smooth muscle cells from hypertensive rats stimulated with interleukin-1 beta (10 ng/ml, 24 h) were used. Interleukin-1 beta increased: 1) COX-2 protein and mRNA levels; 2) protein and mRNA levels of the NADPH oxidase subunit NOX-1, NADPH oxidase activity and ROS production; and 3) phosphorylation of inhibitor of nuclear factor kappa B (I kappa B) kinase (IKK) nuclear expression of the p65 nuclear factor kappa B (NF-kappa B) subunit and cell proliferation, all of which were reduced by apocynin (30 mu mol/l). Interleukin-1 beta-induced COX-2 expression was reduced by apocynin, tempol (10 mu mol/l), catalase (1000 U/ml) and lactacystin (5 mu mol/l). Moreover, H2O2 (50 mu mol/l, 90 min) induced COX-2 expression, which was reduced by lactacystin. Pioglitazone (10 mu mol/l) reduced the effects of interleukin-1 beta on: 1) COX-2 protein and mRNA levels; 2) NOX-1 protein and mRNA levels, NADPH oxidase activity and ROS production; and 3) p-IKK, p65 expressions and cell proliferation. Pioglitazone also reduced the H2O2-induced COX-2 expression and increased Cu/Zn and Mn-superoxide dismutase protein expression. PPAR gamma small interfering RNA (5 nmol/l) further increased interleukin-1 beta-induced COX-2 and NOX-1 mRNA levels. In addition, pioglitazone increased the interleukin-1 beta-induced PPAR gamma mRNA levels. Conclusion: PPAR gamma activation with pioglitazone reduces interleukin-1 beta-induced COX-2 expression by interference with the redox-sensitive transcription factor NF-kappa B.