Background <p>Pulmonary hypertension is a severe vascular disease characterised by pulmonary arterial remodeling and right heart failure. However, the role of the glycolytic protein P4HA1 in its pathogenesis remains elusive.</p> Methods <p>RNA-seq analysis was performed on hypoxic human pulmonary artery endothelial cells, and P4HA1 expression was validated in PH animal models. In vitro, P4HA1 knockdown was used to assess its effects on glycolysis, proliferation, and migration. Mechanistic studies included HIF1α transcriptional regulation and P4HA1-mediated HIF1α stabilization via reduced ubiquitination. AAV9-shP4HA1 was employed to assess P4HA1’s function in pulmonary vascular remodeling in vivo.</p> Results <p>P4HA1 was significantly upregulated in human pulmonary arterial endothelial cells (HPAECs) exposed to hypoxia. Mechanistic investigations revealed that HIF1α transcriptionally activates P4HA1 expression, while P4HA1 reciprocally stabilizes HIF1α by attenuating its ubiquitin-mediated degradation, thereby establishing a self-amplifying signaling loop. Functional studies demonstrated that P4HA1 knockdown effectively suppressed hypoxia-induced glycolytic reprogramming, inhibited cellular proliferation, and impaired migratory capacity in HPAECs. Consistent with these in vitro findings, endothelial-specific P4HA1 knockdown in vivo significantly attenuated hypoxia-induced pulmonary vascular remodeling and improved right ventricular function in a mouse PH model.</p> Conclusions <p>Our studty identify P4HA1 as a novel contributor to PH pathogenesis and suggest that targeting the P4HA1/HIF1α axis may offer a promising therapeutic approach for pulmonary hypertension.</p>