Radiation‐induced variations in urothelial expression of intercellular adhesion molecule 1 (ICAM‐1): association with changes in urinary bladder function

Abstract

Purpose: To assess the effect of single‐dose irradiation on intercellular adhesion molecule 1 (ICAM‐1) expression in the urothelium of mouse urinary bladder and to correlate ICAM‐1 variations with fluctuations in storage capacity during the early and late radiation response.Materials and methods: Groups of female C3H mice were subjected to irradiation with either 20 or 0 Gy. The intensity of immunohistochemical ICAM‐1 staining in the urothelium was assessed in a semiquantitative way applying an arbitrary score (0–5). Changes in bladder storage function were assessed by transurethral cystometry.Results: For the early radiation response phase, a reduction in bladder capacity by >50%, i.e. a positive functional radiation response, was seen in 40% of the irradiated animals between days 0 and 15, and in 64% of animals during days 16–30. During the late response phase, 71% of the animals sacrificed after day 180 developed a positive functional response. Urothelial cells were found to express ICAM‐1 constitutively. Irradiation resulted in an early rise in staining signal by day 2, with a maximum on day 4 and a return to control values on day 13. A permanent increase in ICAM‐1 staining signal was observed in the late phase, from day 90 to 360 after irradiation. The expression of ICAM‐1 in animals with a positive late response was 4.2±1.2 (mean±standard deviation), compared with 2.6±1.0 in non‐responders (p=0.0009).Conclusion: Irradiation induces significant acute and chronic changes in urothelial ICAM‐1 expression indicating that the urothelium contributes to the pathogenesis of both acute and late radiation effects in the urinary bladder.