Antagonism of macrophage migration inhibitory factor decreases cyclophosphamide cystitis in mice

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine found pre-formed in the urothelium. During inflammation, MIF is released into the bladder lumen and bladder MIF mRNA is upregulated. Since MIF also has tautomerase activity and blocking tautomerase activity also blocks MIF's biological activity, we hypothesized that blocking MIF's tautomerase activity would prevent bladder inflammation. Therefore, we examined the effects of a MIF tautomerase inhibitor (ISO-1; also blocks biological activity) on cyclophosphamide (CYP)-induced cystitis in mice.

Mice receiving CYP (300 mg/kg; i.p.) to induce cystitis or saline (control) were treated either with ISO-1 (20 mg/kg; i.p.; daily) or vehicle (20% DMSO; i.p.; daily) for 2 days. After 2 days, micturition volume and frequency in awake mice were recorded and also mechanical sensitivity to abdominal stimulation using von Frey monofilaments. Bladders were collected under anesthesia and examined histologically, nerve growth factor levels were assayed in bladder homogenates, and production of inflammatory cytokines in the bladder was determined using a targeted array.

CYP treatment resulted in decreased micturition volume, increased frequency, decreased threshold, increased histological signs of cystitis, increased bladder NGF levels and production of inflammatory cytokines when compared to the control group. Treatment with ISO-1 prevented or greatly decreased all these changes.

Antagonizing MIF's activity with a systemic MIF tautomerase inhibitor was able to prevent or greatly reduced chemical cystitis in mice, thus indicating the MIF mediates bladder inflammation in this model. MIF represents a novel and important modulator of cystitis.