Modulation of Gut Microbiota Mediates the Anti-Inflammatory Effect of Chi-Ju-Di-Huang-Wan against Dry Eye Disease

Abstract Objective: Chi-Ju-Di-Huang-Wan (CJDHW) is commonly prescribed for the treatment of dry eye disease (DED) with well-documented effectiveness. However, the underlying mechanism remains unclear. Our study aimed to elucidate its potential mechanism by using in vivo and in vitro models. Methodology: Benzalkonium chloride (BAC)-induced DED rats and human corneal epithelial cells (HCEC) were employed to investigate the therapeutic actions of CJDHW. Results: In DED rats, tear production was reduced by over 50% compared to control but was gradually restored by Cyclosporine A (CsA) and CJDHW after 14 days of treatment. An additional 14-day treatment fully restored tear production to control level. Slit-lamp examination revealed severe corneal damage in DED rats, characterized by extensive fluorescein staining. CsA-treated rats showed minimal staining, while CJDHW-treated rats exhibited reduced staining, indicating corneal repair supported by promoted cell proliferation and wound healing in HCEC cells. Comparably to CsA, CJDHW notably decreased the pro-inflammatory cytokines in both tear fluid and corneal tissue of DED rats. This was supported by in vitro study that CJDHW significantly down-regulated pro-inflammatory cytokines in HCEC cells. Microbial analysis showed that CJDHW induced changes in microbial composition at Phylum level, with a significant higher community richness and diversity in CJDHW-treated DED rats. Principal Co-ordinate Analysis revealed a distinct separation in gut microbiota between DED rats and those treated with CJDHW (moderate dosage). Conclusions: CJDHW restores tear production and enhances corneal repair by suppressing inflammatory response in ocular surface via modulating gut microbiota, providing mechanistic understanding of the beneficial actions of CJDHW in DED treatment.