BACKGROUND: Pulmonary hypertension, characterized by vascular remodeling, currently lacks curative therapeutic options. The dysfunction of pulmonary artery endothelial cells plays a pivotal role in the initiation and progression of pulmonary hypertension (PH). ErbB3 (human epidermal growth factor receptor 3), also recognized as HER3, is a member of the ErbB family of receptor tyrosine kinases. METHODS: Microarray, immunofluorescence, and Western blotting analyses were conducted to investigate the pathological role of ErbB3. Blood samples were collected for biomarker examination from healthy donors or patients with hypoxic PH. The pathological functions of ErbB3 were further validated in rodents subjected to chronic hypoxia- and Sugen-induced PH, with or without adeno-associated virus-mediated ErbB3 overexpression, systemic deletion, or endothelial cell–specific ErbB3 knockdown. Primary human pulmonary artery endothelial cells and pulmonary artery smooth muscle cells were used to elucidate the underlying mechanisms. RESULTS: ErbB3 exhibited significant upregulation in the serum, lungs, distal pulmonary arteries, and pulmonary artery endothelial cells isolated from patients with PH compared with those from healthy donors. ErbB3 overexpression stimulated hypoxia-induced endothelial cell proliferation, exacerbated pulmonary artery remodeling, elevated systolic pressure in the right ventricle, and promoted right ventricular hypertrophy in murine models of PH. Conversely, systemic deletion or endothelial cell–specific knockout of ErbB3 yielded opposite effects. Coimmunoprecipitation and proteomic analysis identified YB-1 (Y-box binding protein 1) as a downstream target of ErbB3. ErbB3 induced nuclear translocation of YB-1 and subsequently promoted hypoxia-inducible factor 1/2α transcription. A positive loop involving ErbB3-periostin-hypoxia–inducible factor 1/2α was identified to mediate the progressive development of this disease. MM-121, a human anti-ErbB3 monoclonal antibody, exhibited both preventive and therapeutic effects against hypoxia-induced PH. CONCLUSIONS: Our study reveals, for the first time, that ErbB3 serves as a novel biomarker and a promising target for the treatment of PH.

Pulmonary hypertension (PH) is characterized by vascular remodeling caused by marked proliferation of pulmonary artery smooth muscle cells (PASMCs). Andrographolide (ANDRO) is a potent anti-inflammatory agent which possesses antioxidant, and has anticarcinogenic activity. The present study examined potential therapeutic effects of ANDRO on PH in both chronic hypoxia and Sugen5416/hypoxia mouse PH models. Effects of ANDRO were also studied in cultured human PASMCs isolated from either healthy donors or PH patients. In vivo, ANDRO decreased distal pulmonary arteries (PAs) remodeling, mean PA pressure and right ventricular hypertrophy in chronic hypoxia- and Sugen/hypoxia-induced PH in mice. ANDRO reduced cell viability, proliferation and migration, but increased cell apoptosis in the PASMCs isolated from PH patients. ANDRO also reversed the dysfunctional bone morphogenetic protein receptor type-2 (BMPR2) signaling, suppressed [Ca2⁺]_i elevation, reactive oxygen species (ROS) generation, and the upregulated expression of IL-6 and IL-8, ET-1 and VEGF in PASMCs from PH patients. Moreover, ANDRO significantly attenuated the activation of TLR4/NF-κB, ERK- and JNK-MAPK signaling pathways and reversed the inhibition of p38-MAPK in PASMCs of PH patients. Further, ANDRO blocked hypoxia-triggered ROS generation by suppressing NADPH oxidase (NOX) activation and augmenting nuclear factor erythroid 2-related factor 2 (Nrf2) expression both in vitro and in vivo. Conventional pulmonary vasodilators have limited efficacy for the treatment of severe PH. We demonstrated that ANDRO may reverse pulmonary vascular remodeling through modulation of NOX/Nrf2-mediated oxidative stress and NF-κB-mediated inflammation. Our findings suggest that ANDRO may have therapeutic value in the treatment of PH.

BACKGROUND: Pulmonary hypertension (PH) is a life-threatening cardiovascular disorder characterized by irreversible pulmonary vascular remodeling and poor prognosis. RNA pseudouridylation, the most evolutionarily conserved RNA epigenetic modification, and its catalytic enzyme pseudouridine synthase 7 (PUS7) remained uncharacterized in PH, representing a major gap in the understanding of the epigenetic pathogenesis of the disease. METHODS: We generated the first single-base resolution pseudouridine (Ψ) landscape in lung tissues of patients with PH using bisulfite-induced deletion sequencing. PUS7 expression was analyzed in hypoxic pulmonary artery endothelial cells, the lung tissues of patients with PH, and SU5416-hypoxia rodent model. The functional roles of PUS7 were investigated through genetic manipulation (PUS7-deficiency cells, adeno-associated virus serotype–mediated overexpression, endothelial cell–specific knockdown, and heterozygous knockout mice) and pharmacological inhibition with NSC107512. RESULTS: Bisulfite-induced deletion sequencing revealed global Ψ dysregulation in the lung tissues of patients with PH. Among PUS family members, PUS7 was the most markedly upregulated in these tissues and in the hypoxic pulmonary artery endothelial cells. Both gene knockdown and pharmacological inhibition with NSC107512 ameliorated PH, whereas adeno-associated virus serotype–mediated PUS7 overexpression exacerbated disease progression. RNA immunoprecipitation sequencing and mutagenesis studies demonstrated that PUS7 bound to and catalyzed Ψ at position 688 of TGFBI (transforming growth factor β–induced protein) mRNA, thereby stabilizing TGFBI and activating phosphatidylinositol 3-kinase–protein kinase B signaling pathway. Furthermore, hypoxia-inducible factor 2α bound directly to the PUS7 promoter, establishing a hypoxia-inducible factor 2α/PUS7/TGFBI/phosphatidylinositol 3-kinase–protein kinase B positive feedback loop that drives PH pathogenesis. CONCLUSIONS: PUS7-mediated pseudouridylation serves as a novel epigenetic driver of PH through the hypoxia-inducible factor 2α/PUS7/TGFBI/phosphatidylinositol 3-kinase–protein kinase B axis, positioning PUS7 as a promising therapeutic target for this devastating disease.