Irisin in airway remodeling in COPD: Regulatory mechanisms from epithelial barrier to smooth muscle.

This review synthesizes the emerging evidence positioning irisin, a myokine released during physical activity, as a critical molecular link in chronic obstructive pulmonary disease (COPD) airway remodeling. Clinically, irisin deficiency is consistently observed in COPD and correlates with key features including reduced physical activity, respiratory muscle weakness, sarcopenia, emphysema severity, and exacerbation risk, supporting a hypothesis of a "muscle-lung crosstalk" axis. At the cellular level, irisin exerts direct protective effects on airway structural cells by preserving epithelial barrier integrity via anti-apoptotic and antioxidant mechanisms, while modulating airway smooth muscle tone, proliferation, and extracellular matrix dynamics. Mechanistically, these actions converge on core signaling networks centered on AMPK activation, coordinating downstream pathways such as PGC-1α-mediated mitochondrial regulation, mTOR-dependent autophagy, and SIRT1-driven anti-inflammatory cascades. Emerging layers of complexity involve non-coding RNAs, extracellular vesicles, integrin αVβ5 receptor signaling, and intracellular interactions like Enolase 1 (ENO1) ubiquitination. Collectively, these findings form an "exercise/pharmacology-irisin-airway structural cell-signaling pathway-airway remodeling" framework. Beyond irisin, other adipomyokines (leptin, adiponectin, BDNF, and erythropoietin) exhibit distinct-often opposing-inflammatory and immune profiles in COPD, underscoring a broader multi-hormone network. Future directions should focus on validating irisin as a clinical biomarker and exploring irisin-based therapeutic interventions, which represent a promising avenue for improving COPD management.