title: Protease-Activated Receptor 4 Induces Bladder Pain through High Mobility Group Box-1.
abstract: Pain is the significant presenting symptom in Interstitial Cystitis/Painful Bladder Syndrome (IC/PBS). Activation of urothelial protease activated receptor 4 (PAR4) causes pain through release of urothelial macrophage migration inhibitory factor (MIF). High Mobility Group Box-1 (HMGB1), a chromatin-binding protein, mediates bladder pain (but not inflammation) in an experimental model (cyclophosphamide) of cystitis. To determine if PAR4-induced bladder hypersensitivity depends on HMGB1 downstream, we tested whether: 1) bladder PAR4 stimulation affected urothelial HMGB1 release; 2) blocking MIF inhibited urothelial HMGB1 release; and 3) blocking HMGB1 prevented PAR4-induced bladder hypersensitivity. HMGB1 release was examined in immortalized human urothelial cultures (UROtsa) exposed to PAR4-activating peptide (PAR4-AP; 100 μM; 2 hours) or scrambled control peptide. Female C57BL/6 mice, pretreated with a HMGB1 inhibitor (glycyrrhizin: 50 mg/kg; i.p.) or vehicle, received intravesical PAR4-AP or a control peptide (100 μM; 1 hour) to determine 1) HMGB1 levels at 1 hour in the intravesical fluid (released HMGB1) and urothelium, and 2) abdominal hypersensitivity to von Frey filament stimulation 24 hours later. We also tested mice pretreated with a MIF blocker (ISO-1: 20 mg/kg; i.p.) to determine whether MIF mediated PAR4-induced urothelial HMGB1 release. PAR4-AP triggered HMGB1 release from human (in vitro) and mice (in vivo) urothelial cells. Intravesical PAR4 activation elicited abdominal hypersensitivity in mice that was prevented by blocking HMGB1. MIF inhibition prevented PAR4-mediated HMGB1 release from mouse urothelium. Urothelial MIF and HGMB1 represent novel targets for therapeutic intervention in bladder pain conditions.
authors.affiliation: Research and Development, Lexington Veterans Affairs Medical Center, Lexington, Kentucky, United States of America.|Saha Cardiovascular Research Center, University of Kentucky, Lexington, Kentucky, United States of America.
authors.forename: Dimitrios E
authors.initials: DE
authors.lastname: Kouzoukas
authors.affiliation: Research and Development, Lexington Veterans Affairs Medical Center, Lexington, Kentucky, United States of America.|Department of Physiology, University of Kentucky, Lexington, Kentucky, United States of America.
authors.forename: Fei
authors.initials: F
authors.lastname: Ma
authors.affiliation: Department of Natural Sciences, St. Petersburg College, St. Petersburg, Florida, United States of America.
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Meyer-Siegler
authors.affiliation: Research and Development, Lexington Veterans Affairs Medical Center, Lexington, Kentucky, United States of America.|Department of Physiology, University of Kentucky, Lexington, Kentucky, United States of America.
authors.forename: Karin N
authors.initials: KN
authors.lastname: Westlund
authors.affiliation: Research and Development, Lexington Veterans Affairs Medical Center, Lexington, Kentucky, United States of America.
authors.forename: David E
authors.initials: DE
authors.lastname: Hunt
authors.affiliation: Research and Development, Lexington Veterans Affairs Medical Center, Lexington, Kentucky, United States of America.|Department of Physiology, University of Kentucky, Lexington, Kentucky, United States of America.|Department of Surgery, University of Kentucky, Lexington, Kentucky, United States of America.
authors.forename: Pedro L
authors.initials: PL
authors.lastname: Vera
mesh_terms: D000818:Animals; D002460:Cell Line; D005260:Female; D024243:HMGB1 Protein / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D008263:Macrophage Migration-Inhibitory Factors / Q000037:antagonists & inhibitors / Q000378:metabolism; D008810:Mice, Inbred C57BL; D017699:Pelvic Pain / Q000378:metabolism* / Q000473:pathology / Q000517:prevention & control; D018179:Receptors, Thrombin / Q000378:metabolism*; D001743:Urinary Bladder / Q000378:metabolism / Q000473:pathology*
chemical_list: D024243:HMGB1 Protein; D008263:Macrophage Migration-Inhibitory Factors; D018179:Receptors, Thrombin; C112908:protease-activated receptor 4