Luteolin mitigates region-specific gut microbiota dysbiosis and microbial network remodeling during Mycoplasma gallisepticum infection.

Mycoplasma gallisepticum (MG), a major cause of chronic respiratory disease in chickens, is increasingly recognized to induce pathological changes beyond the respiratory tract. However, current knowledge of MG-associated gut dysbiosis is based largely on fecal samples and does not resolve microbial responses along the intestinal tract. In this study, we characterized segment-specific alterations in the intestinal microbiota of MG-infected chickens and evaluated the protective effects of luteolin. MG infection induced marked spatial heterogeneity in gut microbial communities. The duodenum and jejunum showed relatively limited compositional changes, whereas the ileum displayed pronounced taxonomic shifts and extensive remodeling of microbial interaction networks, suggesting increased ecological instability. The cecum exhibited substantial taxonomic turnover but retained a more modular network structure. Across intestinal segments, MG infection was associated with enrichment of Lactobacillus and Limosilactobacillus and depletion of Ligilactobacillus, Weissella, and Enterococcus, accompanied by villus-crypt disruption, reduced expression of tight junction-related genes, systemic inflammatory imbalance, and aggravated lung injury. Luteolin partially reversed these alterations in a region-dependent manner by limiting infection-associated taxa, restoring depleted commensals, and reorganizing microbial networks. These changes were accompanied by improved intestinal morphology, enhanced barrier integrity, reduced pulmonary MG burden, and attenuated lung apoptosis. In primary alveolar epithelial cells (AEC II), luteolin also suppressed MG adhesion, oxidative stress, inflammation, and apoptosis through activation of the KEAP1-NRF2-NQO1 pathway. Collectively, these findings identify the ileum as a particularly MG-responsive intestinal niche and show that luteolin alleviates MG-associated pathology by modulating gut microbiota and preserving barrier function.