Peroxisome proliferator-activated receptor-β/δ, the acute signaling factor in prostacyclin-induced pulmonary vasodilation.

As powerful vasodilators, prostacyclin analogues are presently the mainstay in the treatment of severe pulmonary arterial hypertension. Although the hemodynamic effects of prostacyclin analogues are well known, the molecular mechanism of their acute effects on pulmonary vascular tone and systemic vascular tone remains poorly understood. Peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) was previously identified as a putative receptor responsible for the modulation of target gene expression in response to prostacyclin analogues. The present study investigated the signaling pathway of prostacyclin in human pulmonary arterial smooth muscle cells (PASMCs), and sought to define the role of PPARβ/δ in the acute vasodilating effect. In human PASMCs, prostacyclin rapidly activated TWIK-related acid-sensitive K channel 1 (TASK-1) and calcium-dependent potassium channels (K(Ca)). This pathway was mediated via the prostanoid I receptor-protein kinase A pathway. The silencing of PPARβ/δ demonstrated that the downstream K(Ca) activation was exclusively dependent on PPARβ/δ signaling, whereas the activation of TASK-1 was not. In addition, the PPARβ/δ-induced activation of K(Ca) was independent of NO. The acute prostacyclin-induced K(Ca) activation is critically dependent on PPARβ/δ as a rapid signaling factor. This accounts in part for the vasodilating effect of prostacyclin in pulmonary arteries, and provides insights into a new molecular explanation for the effects of prostanoids.