Bioactive Compounds Combination from Rhodiola tangutica Alleviates Pulmonary Vascular Remodeling in High-Altitude Pulmonary Hypertension Rat through PI3K-AKT Pathway

Na Yang^1,2Meiduo Huayu^1,2Shanshan Su³Bin Hou^1,2Zhanting Yang^1,2Xingmei Nan^1,2Zhanqiang Li^1,2*

• ¹Research Center for High Altitude Medicine, Qinghai University, Xining, China
• ²Research Center for High Altitude Medicine, Key Laboratory for High Altitude Medicine , Key Laboratory of Application and Foundation for High Altitude Medicine Research in Qinghai Province., Xining, Qinghai Province, China
• ³Xining Customs Technical Center, Key Laboratory of Food Safety Research in Qinghai Province, Xining, Qinghai Province, China

Background: Hypoxia-induced pulmonary vascular remodeling is central to the development of highaltitude pulmonary hypertension (HAPH). Rhodiola tangutica has traditionally been used to prevent chronic mountain sickness. While its active fraction (ACRT) shows therapeutic potential for HAPH, the main pharmacodynamic substances remain unclear due to the complex composition.Aims: This study aimed to identify bioactive equivalent combinatorial components (BECCs) of ACRT that alleviate pulmonary vascular remodeling in HAPH rats and to explore the underlying pharmacological mechanisms.Methods: Seventy adult Sprague-Dawley rats were divided into control, hypoxia, hypoxia+ACRT (150 mg/kg), hypoxia+BECCs (25, 50 and 100mg/kg) and hypoxia+Sildenafil (30 mg/kg) group. A HAPH rat model was induced using hypobaric hypoxia chamber simulating 5000-meter altitude. The effects of BECCs on pulmonary vascular remodeling in HAPH rats were evaluated based on hemodynamic indexes and histopathological changes, alongside antioxidant properties.Phosphoproteomics and Western blotting were performed to analyze AKT1-related protein expression in lung tissues. In vitro, 3% O2-induced pulmonary artery smooth muscle cells (PASMCs) models were utilized to evaluate the anti-proliferative effects of BECCs and identify the dominant components. The underlying mechanisms were explored using Western blotting and drug affinity responsive target stability test (DARTS) assay for binding affinity.Results: HAPH rat models were successfully established as evidenced by changes in physiological parameters. The BECCs showed the comparable efficacy as ACRT in recovering hemodynamic indexes and histopathological changes. Mechanistically, BECCs modulated AKT phosphorylation and related protein expression. In vitro, BECCs inhibited hypoxia-induced PASMCs proliferation.Particularly flavonoids (Fla) in BECCs exhibited stronger anti-proliferative activity than others, acting as the dominant contributors by regulating PI3K rather than PDPK or mTOR pathways to inhibit AKT phosphorylation. Within Fla, eriodictyol and quercetin were found to inhibit PASMC proliferation by targeting PI3K.BECCs demonstrated comparable efficacy to ACRT in alleviating HAPH progression, reversing hypoxia-induced vascular remodeling, inhibiting oxidative stress and PASMCs proliferation by targeting AKT protein. Flavonoids were identified as the key bioactive components contributing to the holistic effects of BECCs by regulating PI3K/AKT pathways. These findings could be extended to improve quality control and clarify bioactive components of R. tangutica, while inspiring development of combinatorial therapies for HAPH treatment.