Endogenous HS sensitizes PAR4-induced bladder pain.

Bladder pain is a prominent symptom of interstitial cystitis/painful bladder syndrome. Hydrogen sulfide (HS) generated by cystathionine β-synthase (CBS) or cystathionine γ-lyase (CSE) facilitates bladder hypersensitivity. We assessed involvement of the HS pathway in protease-activated receptor 4 (PAR4)-induced bladder pain. A bladder pain model was induced by intravesical instillation of PAR4-activating peptide in mice. The role of HS in this model was evaluated by intraperitoneal preadministration of d,l-propargylglycine (PAG), aminooxyacetic acid (AOAA), or S-adenosylmethionine or the preintravesical administration of NaHS. SV-HUC-1 cells were treated in similar manners. Assessments of CBS, CSE, and macrophage migration inhibitory factor (MIF) expression, bladder voiding function, bladder inflammation, HS production, and referred bladder pain were performed. The CSE and CBS pathways existed in both mouse bladders and SV-HUC-1 cells. HS signaling was upregulated in PAR4-induced bladder pain models, and HS-generating enzyme activity was upregulated in human bladders, mouse bladders, and SV-HUC-1 cells. Pretreatment with AOAA or NaHS inhibited or promoted PAR4-induced mechanical hyperalgesia, respectively; however, PAG only partially inhibited PAR4-induced bladder pain. Treatment with PAG or AOAA decreased HS production in both mouse bladders and SV-HUC-1 cells. Pretreatment with AOAA increased MIF protein levels in bladder tissues and cells, whereas pretreatment with NaHS lowered MIF protein levels. Bladder pain triggered by the HS pathway was not accompanied by inflammation or altered micturition behavior. Thus endogenous HS generated by CBS or CSE caused referred hyperalgesia mediated through MIF in mice with PAR4-induced bladder pain, without causing bladder injury or altering micturition behavior.