H₂S Donor Therapy Reverses Established Pulmonary Arterial Hypertension and Pulmonary Vascular Structural Remodeling...

Objectives: Downregulation of the endogenous gasotransmitter hydrogen sulfide (H₂S) contributes to the pathogenesis of pulmonary arterial hypertension (PAH). While prophylactic H₂S supplementation prevents PAH initiation in different rat models, its ability to reverse fully established PAH and pulmonary vascular structural remodeling is unknown. In this study, we aimed to test whether H₂S donor therapy can reverse the existing PAH in a chronic-hypoxia rat model. Methods: After 3 weeks of hypoxia exposure, rats with established hypoxia-induced pulmonary hypertension (HPH) were randomized to receive either continued hypoxia alone or hypoxia plus the H₂S donor NaHS (56 μmol/kg·d, ip) for an additional 6 weeks. Pulmonary artery pressure, pulmonary artery muscularization, and right ventricular hypertrophy were assessed. Furthermore, the cell proliferation (Ki-67 and PCNA), ERK1/2 phosphorylation, and persulfidation of the endothelin type A receptor (ETAR) were examined and detected in rat lung tissues and pulmonary artery smooth muscle cells (PASMCs). Results: H₂S therapy effectively reversed established HPH and pulmonary artery structural remodeling, reducing RVSP, mPAP, and the proportion of fully muscularized small pulmonary arteries by 13.8%, 12.0%, and 62.7%, respectively. Moreover, the PAT/PET ratio was normalized to normoxic levels. The right ventricular hypertrophy index decreased by 29.2%. Mechanistically, H₂S therapy suppressed PASMC proliferation, reduced ERK1/2 phosphorylation, and enhanced ETAR persulfidation. Furthermore, dithiothreitol-mediated reduction of ETAR persulfidation abrogated these antiproliferative effects of H₂S therapy, establishing persulfidation as an obligatory mechanism. Conclusions: H₂S donor therapy effectively reverses established HPH and pulmonary vascular structural remodeling by inhibiting PASMC proliferation, which is linked to enhanced ETAR persulfidation. These data provide preclinical proof-of-concept for H₂S-based interventions in patients with manifest PAH.