The Effects of Neurokinin-1 Receptor Antagonist in an Experimental Autoimmune Cystitis Model Resembling Bladder Pain Syndrome/Interstitial Cystitis.

To identify the effects of the neurokinin-1 receptor (NK1R) antagonist aprepitant in treating pelvic pain, micturition symptoms, and bladder inflammation in mice with experimental autoimmune cystitis (EAC) similar to bladder pain syndrome/interstitial cystitis (BPS/IC). Female C57BL/6 mice were divided into the following three groups: normal control, EAC, and EAC plus aprepitant. EAC was induced in mice by duplicate immunization with bladder homogenate. In the EAC model group, EAC mice were given PBS by gavage once a day during the fourth week. In the EAC plus aprepitant group, aprepitant was administered instead of PBS in the same way. After 4 weeks, pelvic pain threshold and urination habits of mice were analyzed, as well as the bladder weight to body weight ratio, and histologic assessment of the expression of IL-1β, TNF-α, intercellular adhesion molecule 1 (ICAM-1), and NK1R in bladder tissue. EAC mice mimicked the phenotype and pathophysiologic lesions of BPS/IC well. Compared to PBS-treated EAC mice, the mice treated with aprepitant exhibited higher pain threshold values, less number of total urine spots or small urine spots, lower bladder weight to body weight ratio, and reduced bladder inflammation with less mast cell infiltration and decreased expressions of IL-1β, TNF-α, and ICAM-1 in bladder tissue. There was no difference in NK1R expression in bladders treated with or without aprepitant. The NK1R antagonist aprepitant relieved pelvic pain, urinary symptoms, and bladder inflammation in EAC mice. This indicated that NK1R may be a novel therapeutic target in BPS/IC treatment.