Trained Immunity Attenuates Bleomycin-Induced Pulmonary Fibrosis by Promoting AMPK-Mediated Autophagy in Alveolar Macrophages

Trained immunity (TI) represents a form of immune memory in innate immune cells, driven by sustained epigenetic and metabolic reprogramming that potentiates innate immune responses. Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease characterized by persistent alveolar injury and pathological tissue remodeling. Given the central role of macrophages in IPF pathogenesis, we hypothesized that inducing TI could functionally reprogram these cells and attenuate fibrosis. In a murine model of pulmonary fibrosis induced by bleomycin, prior induction of TI via β-glucan enhanced autophagic activity in macrophages and reduced pathological collagen deposition. This trained response restricted bleomycin-triggered mitochondrial DNA release and suppressed the mitochondrial apoptosis pathway, thereby promoting macrophage survival. The protective effects were diminished by administration of the AMPK inhibitor Compound C. Our findings indicate that TI promotes mitophagy correlating with the AMPK-ULK1 signaling axis, thereby reducing alveolar macrophage apoptosis and uncovering a potential therapeutic strategy for pulmonary fibrosis.