• Mengmeng Zhao, Lei Liu, Zhenghao Chen, Ning Ding, Jiliang Wen, Jiaxin Liu, Nan Ge, and Xiulin Zhang.
• Department of Urology, The Second Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China.
• Pain. 2022 Nov 1; 163 (11): 2200-2212.

AbstractThe transient receptor potential cation channel subfamily M member-3 (TRPM3) channel is a recently recognized noxious heat sensor that is involved in inflammatory thermal hyperalgesia. To examine its involvement in the development of hyperalgesia in interstitial cystitis/painful bladder syndrome (IC/PBS), rats with cyclophosphamide (CYP)-induced chronic cystitis were used as a model of IC/PBS. Mechanical and thermal hyperalgesia in lower abdominal region overlying the bladder in CYP rats were measured using von Frey filaments and radiant heat, respectively. Transient receptor potential cation channel subfamily M member-3 expression at the mRNA, protein, and functional levels in dorsal root ganglion neurons innervating the bladder was detected using RNA in situ hybridization (RNAscope), Western blotting, immunohistochemistry, and Ca 2+ imaging, respectively. Transient receptor potential cation channel subfamily M member-3 channels were expressed on most of the bladder primary afferent nerve terminals containing calcitonin gene-related peptide and their cell bodies in L6-S1 dorsal root ganglion. Activation of TRPM3 in the bladder wall by its specific agonist pregnenolone sulphate or CIM0216 induced spontaneous bladder pain, calcitonin gene-related peptide release, and neurogenic inflammation that was evidenced by edema, plasma extravasation, inflammatory cell accumulation, and mast cell infiltration. In CYP rats, pretreatment with the TRPM3 antagonist primidone (2 mg/kg, i.p.) significantly alleviated the mechanical and thermal hyperalgesia, bladder submucosal edema, mast cell infiltration, and bladder hyperactivity. Cyclophosphamide-induced cystitis was associated with TRPM3 upregulation at the mRNA, protein, and functional levels in bladder afferent neurons. Our results suggest that upregulation of TRPM3 channels is involved in the development of chronic pain in CYP-induced cystitis, and targeting TRPM3 may be a pharmacological strategy for treating bladder pain in IC/PBS.Copyright © 2022 International Association for the Study of Pain.

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