MD2 mediates COPD pathogenesis by inducing airway inflammation and ferroptosis through the TLR4/MyD88 pathway.

Abstract

BACKGROUND: Chronic obstructive pulmonary disease (COPD), the third leading cause of death worldwide, is a chronic inflammatory respiratory disease characterized by airflow limitation. Myeloid differentiation protein 2 (MD2), an important accessory protein of toll like receptor 4 (TLR4), plays a crucial role in mediating lung disease pathogenesis, however, its functional contribution to COPD progression remains poorly understood. METHODS: In vivo, MD2 knockout mice were utilized to establish cigarette smoke -induced COPD or combined with lipopolysaccharide-induced acute exacerbation COPD (AECOPD). L6H21 was used as a pharmacological inhibitor of MD2. In vitro, cellular model was established by stimulating human bronchial epithelial cells (BEAS-2B) with cigarette smoke extract (CSE). Immunoprecipitation assay was used to elucidate MD2/TLR4/MyD88 complex formation. The changes of inflammation and ferroptosis-related indicators were detected by several molecular biology techniques. RESULTS: MD2 expression was upregulated in COPD patients and mouse lungs. Genetic knockout of MD2 significantly alleviated airway inflammation and pulmonary ferroptosis in COPD mice. In vitro studies demonstrated that MD2 silencing or L6H21 mitigated CSE-induced NF-κB activation, pro-inflammatory gene expression, and changes in ferroptosis-related markers in BEAS-2B cells. Mechanistically, MD2 could form complex with TLR4/MyD88 upon CSE stimulation in BEAS-2B cells. Additionally, MD2 knockout or L6H21 significantly attenuated airway inflammation and lung ferroptosis in AECOPD mice. CONCLUSION: These results indicated that MD2 promotes ferroptosis in airway epithelial cells by forming a complex with TLR4/MyD88, activating NF-κB-mediated inflammatory responses to exacerbate COPD pathogenesis. These findings identify MD2 as a potential therapeutic target and provide novel insights for COPD intervention strategies.