Mechanism of action of miR-15b-5p in alleviating asthma airway remodeling through the HMGB1/TLR4/IL-33 signaling axis

The pathophysiologic processes of asthma are characterized not only by significant changes in miRNA expression but also by the modulation of HMGB1 and its downstream effectors. However, the specific roles of miR-15b-5p and HMGB1 in asthma remain poorly understood. This study explores the regulatory role of miR-15b-5p in asthma by targeting HMGB1. We utilized HMGB1-conditioned knockout mice (Sftpc-cre; HMGB1flox/flox) in type II alveolar epithelial cells (AT2), induced with house dust mite (HDM), to establish a mouse model of asthma. Results demonstrated that AT2 cell-specific deletion of HMGB1 attenuated allergen-induced airway hyperresponsiveness and reduced airway inflammation. Concurrently, miR-15b-5p levels were significantly reduced in wild-type (WT) asthmatic mice, while HMGB1, TLR4, and IL-33 levels were elevated. Administration of miR-15b5p agomir mirrored the effects of HMGB1 knockdown, reducing peribronchiolar inflammatory cells and ameliorating airway inflammation and remodeling. A luciferase reporter gene assay system was employed to predict and verify HMGB1 as a direct target of miR-15b-5p. Overexpression of miR-15b-5p significantly inhibited apoptosis and activation of HMGB1, TLR4, and IL-33, and decreased NLRP3, Caspase-1, and IL-1 beta expression. In vitro, miR-15b-5p overexpression and HMGB1 knockdown attenuated HDM-induced cellular inflammation and production of Cleaved-caspase-9, Cleaved-caspase-3, and Bax, while enhancing mitochondrial membrane potential. This study suggests that miR-15b-5p acts as a protective mechanism against allergic airway inflammation by inhibiting the HMGB1/TLR4/IL-33 signaling pathway in AT2 cells. Targeting the HMGB1/TLR4/IL-33 signaling by miR-15b-5p may offer a potential therapeutic strategy for asthma.