The lung-gut axis and airway inflammation in COPD

OBJECTIVE: Chronic obstructive pulmonary disease (COPD) is a common lung disease characterized by multiple persistent respiratory symptoms and decreased lung function. Despite extensive research exploring the complex pathogenic mechanisms and signaling pathways underlying COPD, there are currently no effective disease-modifying drugs capable of halting or reversing progressive lung damage, standard interventions including bronchodilators, long-term oxygen therapy and pulmonary rehabilitation merely alleviate clinical symptoms while failing to arrest disease progression, accompanied by unavoidable adverse effects. Against this backdrop, microbiota-targeted interventions emerge as a promising alternative therapeutic strategy. This drives the urgent need to dissect unrecognized pathogenic pathways and develop novel prevention and treatment strategies. METHODS: This narrative review summarizes recent data on gut microbiota dysregulation and gut-lung crosstalk in COPD, highlighting immune-mediated gut-lung crosstalk mechanisms, including the shared mucosal immune system and metabolite-induced modulation of pulmonary structure and function. RESULTS: In addition to immune inflammation and hypoxia, COPD patients usually have gastrointestinal complications and gut microbiota (GM) dysregulation. Role of GM in regulating the functional development of the host immune system, and the "gut-lung axis" established by GM and the lung also plays a crucial role in regulating lung inflammation and airway function. This may be attributed to the shared mucosal immune system between the gut and lungs, as well as the ability of metabolites to influence lung structure and function. However, the specific pathway of this gut-lung communication in COPD is still unclear. CONCLUSIONS: This article reviews the changes of GM related to COPD, and focuses on the mechanism of GM and its metabolites in the occurrence and development of COPD from the immune pathway, so as to find new intervention targets, and highlight the emerging potential of GM interventions (diet, probiotics and prebiotics) for future clinical research and treatment of COPD.