Loss of DP1 Aggravates Vascular Remodeling in Pulmonary Arterial Hypertension via mTORC1 Signaling.

RATIONALE: Vascular remodeling, including smooth muscle cell hypertrophy and proliferation, is the key pathological feature of pulmonary arterial hypertension (PAH). Prostaglandin (PG) I2 analogs (baraprost, iloprost, and treprostinil) are effective in the treatment of PAH. Of note, the clinically favorable effects of treprostinil in severe PAH may be attributable to concomitant activation of PGD2 receptor subtype 1 (DP1).

OBJECTIVES: To study the role of DP1 in the progression of PAH and its underlying mechanism.

METHODS AND RESULTS: DP1 expression was downregulated in hypoxia-treated PASMCs and in pulmonary arteries (PAs) from rodent PAH models and idiopathic PAH patients. DP1 deletion exacerbated PA remodeling in hypoxia-induced PAH, whereas pharmacological activation or forced expression of DP1 receptor had the opposite effect in different rodent models. DP1 deficiency promoted PASMC hypertrophy and proliferation in response to hypoxia via induction of mammalian target of rapamycin complex (mTORC) 1 activity. Rapamycin, an inhibitor of mTORC1, alleviated the hypoxia-induced exacerbation of PAH in DP1-/- mice. DP1 activation facilitated raptor dissociation from mTORC1 complex and suppressed mTORC1 activity through protein kinase A (PKA)-dependent phosphorylation of raptor at Ser791. Moreover, treprostinil treatment blocked the progression of hypoxia-induced PAH in mice in part by targeting DP1 receptor.

CONCLUSION: DP1 activation attenuates hypoxia-induced PA remodeling and PAH through PKA-mediated dissociation of raptor from the mTORC1 complex. These results suggest that DP1 receptor may serve as a therapeutic target for the management of PAH.