Increased Urothelial Cell Apoptosis and Chronic Inflammation Are Associated with Recurrent Urinary Tract Infection in Women

OBJECTIVE This study was designed to investigate whether increased urothelial cell apoptosis and chronic inflammation might contribute to recurrent urinary tract infection (UTI) in women. METHODS The bladder biopsy specimens were collected from thirty women with recurrent UTI and ten controls. The bladder biopsies were performed at one to two months after UTI episode had been completely resolved and urine analysis and urine culture all showed negative. Immunofluorescence staining of the adhesive protein E-cadherin, mast cell and TUNEL were performed in all the bladder specimens. In addition, western blots were also performed to analyze the inflammatory proteins (phospho-p38, tryptase) and apoptotic protein (Bax) in the bladder mucosa specimens between patients with recurrent UTI and controls. RESULTS Immunofluorescence staining showed significantly lower E-cadherin in the recurrent UTI bladder tissue compared with the controls (25.4±8.9 v 42.4±16.7, p<0.0001). The mast cell expression was significantly stronger in the recurrent UTI bladder tissue compared with the controls (2.5±1.8 v 1.3±1.2, p = 0.046). TUNEL staining revealed a significantly higher numbers of apoptotic cells in the recurrent UTI bladder tissue compared with the control bladder tissue (1.5±1.8 v 0.08±0.3, p<0.0001). Western blot analysis also showed that the expressions of tryptase and Bax increased in five recurrent UTI specimens compared with two normal control specimens. CONCLUSION Chronic inflammation, urothelial cell apoptosis and impairment of barrier function of urothelial cells might contribute to recurrent UTI in women.