Peroxisome Proliferator-Activated Receptor-γ Ameliorates Pulmonary Arterial Hypertension by Inhibiting 5-Hydroxytryptamine 2B Receptor

An elevated plasma level of 5-hydroxytryptamine (5-HT) or upregulation of 5-HT receptor signaling or both is implicated in vascular contraction and remodeling in pulmonary arterial hypertension (PAH). Recently, peroxisome proliferator-activated receptor-gamma (PPAR gamma) agonists have been shown to ameliorate PAH. However, their effects on the 5-HT-induced contraction of pulmonary arteries remain unknown. Here, we examined the role of PPAR gamma in inhibiting 5-HT2B receptor (5-HT2BR) to ameliorate PAH. Pulmonary arteries from PAH rats induced by monocrotaline or chronic hypoxia showed an enhanced vasoconstriction in response to BW723C86, a specific agonist for 5-HT2BR. Expression of 5-HT2BR was also increased in pulmonary arteries from the PAH rats, accompanied by vascular remodeling and right ventricular hypertrophy. Treatment with the PPAR gamma agonist rosiglitazone in vivo reversed the expression and the vasocontractive effect of 5-HT2BR as well as the thickening of pulmonary arteries. In pulmonary artery smooth muscle cells, 5-HT induced the gene expression of 5-HT2BR, which was inhibited by rosiglitazone, pioglitazone, or adenovirus-mediated overexpression of constitutively activated PPAR gamma. The pharmacological effect of PPAR gamma was through the suppression of the 5-HT-induced activator protein-1 activity. These results demonstrated the beneficial effect of PPAR gamma on 5-HT2BR-mediated vasocontraction, providing a new mechanism for the potential use of PPAR gamma agonists in PAH. (Hypertension. 2012;60:1471-1478.)