Formononetin Alleviates Cigarette Smoke Extract-Induced Lung Injury in Mice with Gut Microbiota and Taurine/SLC6A6/NF-κB Modulation.

Cigarette smoke exposure is a major preventable risk factor for respiratory disease and drives oxidative and inflammatory lung injury, highlighting the urgent need for safe, multi-target interventions beyond conventional anti-inflammatory therapy. Formononetin (FMN), a naturally occurring isoflavone with antioxidant, anti-inflammatory, and microbiota-modulating potential, may offer a dietary-botanical strategy against smoke-related pulmonary damage. This study evaluated FMN against cigarette smoke extract (CSE)-induced lung injury and explored its associations with intestinal barrier integrity, gut microbiota, taurine metabolism, SLC6A6 expression, and NF-κB activation. In a CSE-challenged mouse model, oral FMN, particularly at 70 mg/kg, improved body weight gain, reduced the lung index, attenuated pulmonary histopathological injury, restored GSH/GSSG and SOD, decreased MDA, and suppressed TNF-α, IL-1β, and IL-6 expression. FMN also ameliorated colonic injury and restored ZO-1 and occludin expression. Exploratory 16S rRNA sequencing and fecal metabolomics indicated FMN-associated alterations in gut microbial composition and metabolic profiles, with taurine and hypotaurine metabolism identified as a candidate pathway for further investigation. FMN further restored lung taurine content and SLC6A6 expression while inhibiting NF-κB activation. These findings suggest that FMN alleviates CSE-induced lung injury and that this improvement is associated with coordinated changes in gut microbiota composition, taurine metabolism, SLC6A6 expression, and NF-κB activation.