CH25H/25-HC promotes pulmonary fibrosis via AMPK/STAT6 pathway-dependent M2 macrophage polarization in COPD

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OBJECTIVE: Chronic obstructive pulmonary disease (COPD) is intricately linked to pulmonary fibrosis, yet the underlying mechanisms remain unclear. This study investigates whether CH25H/25-hydroxycholesterol (25-HC) promotes pulmonary fibrosis in COPD by modulating AMPK/STAT6-dependent M2 macrophage polarization. METHODS: Using GEO datasets and a cigarette smoke-induced COPD mouse model, we analyzed CH25H expression and fibrotic pathology. CH25H was silenced via adeno-associated virus (AAV)-delivered shRNA. Histopathology, flow cytometry, qPCR, and Western blotting assessed fibrosis, macrophage polarization (M1/M2), and AMPK/STAT6 pathway activity. Bone marrow-derived macrophages (BMDMs) were employed to validate polarization mechanisms. The role of the AMPK/STAT6 pathway was investigated using the specific activator. RESULTS: Analysis of the GEO database and experimental verification showed significantly increased CH25H expression in both lung tissues and macrophages from COPD mice. CH25H knockdown alleviated alveolar damage, airway remodeling, and pulmonary fibrosis in COPD mice, evidenced by reduced expression of fibrosis-related proteins, improved lung function, and attenuated inflammatory responses. Moreover, CH25H knockdown inhibited M2 macrophage polarization and decreased the proportion of M2-type macrophages. Importantly, decreased levels of 25-HC following CH25H knockdown were asso ciated with suppressed activation of the AMPK/STAT6 pathway. Rescue experiments demonstrated that the protective effects of CH25H knockdown could be reversed by adding the AMPKα activator GSK621. CONCLUSION: Our findings demonstrate that CH25H/25-HC exacerbates COPD-associated pulmonary fibrosis by promoting AMPK/STAT6-dependent M2 macrophage polarization. Targeting CH25H may represent a novel therapeutic strategy for mitigating fibrosis in COPD.