Macrophage migration inhibitory factor mediates protease‐activated receptor 4‐induced bladder pain through urothelial high mobility group box 1

摘要

Macrophage migration inhibitory factor (MIF) mediates pain although the mechanisms are not well understood. Urothelial activation of protease activated receptor 4 (PAR4) results in urothelial MIF release, urothelial high mobility group box 1 (HMGB1) release and bladder pain in mice without bladder inflammation. All three effects are prevented by MIF inhibition while intravesical disulfide HMGB1 alone can induce bladder pain. This study utilizes genetic MIF deletion to determine whether MIF mediates PAR4‐induced bladder pain and is upstream of HMGB1‐induced bladder pain. Wild type (C57/BL6) and MIF knockout (KO) mice were treated with intravesical PAR4 activating peptide or disulfide HMGB1 and tested for abdominal mechanical hypersensitivity at baseline (before treatment) and 24 h after injection. Micturition parameters and bladder histology were examined after behavioral test. Real‐time PCR and western blotting measured style="fixed-case">HMGB1 m style="fixed-case">RNA and protein levels in the bladders of naïve wild type and style="fixed-case">MIF KO mice, while immunofluorescence measured style="fixed-case">HMGB1 protein levels in the urothelium of both strains. Intravesical style="fixed-case">PAR4 activation resulted in abdominal mechanical hypersensitivity in wild‐type mice but not style="fixed-case">MIF KO mice. Intravesical disulfide style="fixed-case">HMGB1 induced abdominal mechanical hypersensitivity in both strains. Neither treatment resulted in significant changes in micturition or bladder histology in either strain. style="fixed-case">HMGB1 m style="fixed-case">RNA and protein levels were higher in style="fixed-case">MIF KO mouse bladders and the urothelium of style="fixed-case">MIF KO bladder had greater immunostaining than the wild‐type strain. style="fixed-case">MIF is a pivotal molecule mediating style="fixed-case">PAR4‐induced bladder pain and regulating urothelial style="fixed-case">HMGB1 production and release to elicit bladder pain.