Effects of Cyclooxygenase on the Urothelium of the Urinary Bladder of Mice Exposed to Pelvic Radiation.

OBJECTIVE: To determine the role of cyclooxygenase (COX) expression in the urothelium of the urinary bladder during radiation injury caused by pelvic radiotherapy for cancer therapy.

STUDY DESIGN: Twenty-four male Swiss Albino mice were separated into 4 groups. The first group was the control group (Group 1) and the second, third, and fourth groups were euthanized after 24 hours (Group 2), 48 hours (Group 3), and 7 days (Group 4), respectively. A single-fractioned 10 Gy of ionizing radiation was applied to all mice's pelvic zone with Co-60. Bladders were removed completely from the pelvic region. Histochemical analysis using hematoxylin and eosin and immunohistochemical analysis using anti-COX-1 and COX-2 antibodies were performed on tissue samples. The immunoreactivities of the urinary bladder were quantified using H-score measurement, and statistical comparison was performed.

RESULTS: In the immunohistochemical examination the COX-1 immunoreactivities were found to be higher in the urothelium of the bladder in the radiation exposed groups than in the normal control group (group 1) (p < 0.005). Additionally, high immunoreactivity of COX-2 molecule was established in groups 2, 3, and 4 of radiation groups as compared to group 1 (p < 0.005) in examination of the urothelium. COX-1 and COX-2 immunoreactivities in the submucosa were detected higher in group 4 than in the other groups (p < 0.005).

CONCLUSION: COX-1 and COX-2 expressions in the urothelium and subepithelium of the urinary bladder were investigated in mice during the acute radiation response. The expression of COX-1 and COX-2 in the urothelium seems to prevent bladder damage from radiation, supplying differentiation and restoration of the urothelium.