Cynaroside attenuates uropathogenic Escherichia coli adhesion and invasion by suppressing bacterial virulence and down-modulating urothelial Caveolin-1 signaling.

Abstract

BACKGROUND: Uropathogenic Escherichia coli (UPEC) constitutes a primary pathogen responsible for urinary tract infections (UTIs), characterized predominantly by colonization initiated through adhesion, persistence via biofilm formation, and invasion facilitated by lipid rafts. Cynaroside (Cyn), a natural flavonoid, emerges as a potential anti-virulence compound; nonetheless, the involvement of Caveolin-1 (CAV1) in UPEC adhesion and invasion processes has yet to be fully elucidated. PURPOSE: To investigate the effects and mechanisms of Cyn on UPEC adhesion and invasion in bladder epithelial cells and in a rat UTI model. METHODS: We evaluated Cyn across bacterial, human bladder epithelial (5637), and rat UTI models using standard microbiological assays, imaging, and transcriptomics with quantitative PCR validation. Adhesion/invasion, barrier function, and cytokines were measured in 5637 cells, with CAV1 dependence tested by small interfering RNA (siRNA) and rescue experiments. Oral efficacy was assessed by urinary colony-forming units (CFU), inflammatory indices, histopathology, and bladder tissue protein expression. RESULTS: No direct bacteriostasis was observed, yet UPEC motility and biofilm formation declined, fimbrial/flagellar ultrastructure was disrupted, and virulence genes (fimH, papG, fliC) were downregulated. In 5637 cells, Cyn decreased adhesion and invasion, restored barrier function, and lowered IL-6 and TNF-α; these effects were attenuated in the CAV1 knockdown condition, but in the rescue experiment, reconstitution of CAV1-Mut partially restored these effects. In rats, oral Cyn reduced urinary CFU, improved inflammatory indices and bladder pathology, and decreased adhesion-related proteins (Uroplakin Ia, Uroplakin Ib, Uroplakin III, integrin alpha-3, integrin beta-1, and CAV1). CONCLUSIONS: Cyn functions as an anti-virulence natural product that mitigates UPEC pathogenesis by inhibiting bacterial virulence programs and modulating CAV1-mediated epithelial processes, supporting its potential for UTI management.