Up-regulation of protease activated receptors in bladder after cyclophosphamide induced cystitis and colocalization with capsaicin receptor (VR1) in bladder nerve fibers.
PURPOSE: Studies suggest that protease activated receptors (PARs) are mediators of inflammation and repair. Studies suggest a neurogenic mechanism for PAR2 in inflammation and the fact that interaction between PAR2 and transient receptor vanilloid receptor (TRPV1 or VR1) are important for the induction and maintenance of inflammatory pain. MATERIALS AND METHODS: We examined the expression of PAR2 to 4 in bladder urothelium and detrusor muscle whole mounts in controls, female rats and those treated with cyclophosphamide (CYP) acutely (4 and 48 hours) or chronically (every third day for 10 days) using Western blot and immunohistochemical techniques. Colocalization of PARs in nerve fibers and VR1 immunoreactive nerve fibers was determined by double labeling techniques for protein gene product and capsaicin receptor (VR1). RESULTS: Western blot revealed up-regulation (1.5 to 9.4-fold) of PAR2 to 4 in bladder after cystitis. Immunohistochemistry revealed PAR2 to 4 expression in urothelial and detrusor muscle cells, and in nerve fibers in the subepithelial bladder layer. Confocal microscopy revealed colocalization of PAR2 to 4 with protein gene product 9.5 and VR1, suggesting that PARs are distributed in C-fiber bladder nerves. CONCLUSIONS: These studies demonstrate that 1) CYP induced cystitis up-regulates PAR2 to 4 expression in the bladder, 2) PAR2 to 4 is expressed in urothelium, detrusor muscle and bladder nerve fibers in control and CYP treated rats, and 3) bladder C-fibers and bladder afferent cells in dorsal root ganglia express PAR2 to 4. These results suggest the involvement of PARs in bladder inflammation that contributes to altered sensory processing and reflex function.