A Role for Bradykinin Signaling in Chronic Vulvar Pain

Abstract

Chronic vulvar pain is alarmingly common in women of reproductive age and is often accompanied by psychological distress, sexual dysfunction, and a significant reduction in quality of life. Localized provoked vulvodynia (LPV) is associated with intense vulvar pain concentrated in the vulvar vestibule (area surrounding vaginal opening). To date, the origins of vulvodynia are poorly understood, and treatment for LPV manages pain symptoms, but does not resolve the root causes of disease. Until recently, no definitive disease mechanisms had been identified; our work indicates LPV has inflammatory origins, although additional studies are needed to understand LPV pain. Bradykinin signaling is one of the most potent inducers of inflammatory pain and is a candidate contributor to LPV. We report that bradykinin receptors are expressed at elevated levels in LPV patient versus healthy control vestibular fibroblasts, and patient vestibular fibroblasts produce elevated levels of proinflammatory mediators with bradykinin stimulation. Inhibiting expression of one or both bradykinin receptors significantly reduces proinflammatory mediator production. Finally, we determined that bradykinin activates NFκB signaling (a major inflammatory pathway), while inhibition of NFκB successfully ablates this response. These data suggest that therapeutic agents targeting bradykinin sensing and/or NFκB may represent new, more specific options for LPV therapy. Perspective: There is an unmet need for the development of more effective vulvodynia therapies. As we explore the mechanisms by which human vulvar fibroblasts respond to proinflammatory/pro-pain stimuli, we move closer to understanding the origins of chronic vulvar pain and identifying new therapeutic targets, knowledge which could significantly improve patient care.

Pharmacological Effects of a Novel Bradykinin-Related Peptide (RR-18) from the Skin Secretion of the Hejiang Frog (Ordorrana hejiangensis) on Smooth Muscle

“…In particular, peptides, such as bombesin and bradykinin, act as myotropic peptides and are critical to protecting amphibians from predators [ 8 , 18 ]. At the same time, BK and BRPs are associated with many diseases, such as chronic pain and cancer [ 13 , 19 ]. Recently, very few peptides from the Hejiang frog have been reported [ 9 , 20 , 21 ].…”

Toll-Like Receptor Signaling Contributes to Proinflammatory Mediator Production in Localized Provoked Vulvodynia

“…TLR1-9 mRNA expression was evaluated in three LPV case and two paired control fibroblast strains using reverse transcriptase quantitative PCR (RT-qPCR) 4, 7 . TLR expression was determined using previously published methods 17–20 .…”

“…Paired strains from a prototypical case 5 were challenged with stimuli that activate the full range of human TLRs using the Human TLR1-9 Agonist Kit (InvivoGen USA, San Diego, CA). IL-6 was analyzed by ELISA 4, 7 ; IL-6 is a measure of TLR pro-inflammatory activity 8, 9, 12–15 .…”

“…Protein levels of TLR-7 were measured by Western blotting in three paired case strains 4, 7 using a primary antibody specific for TLR-7 (GeneTex Inc., Irvine, CA). TLR-7 expression levels were quantified by densitometric analysis and normalized to a control protein (β-tubulin; Cell Signaling Technology, Danvers, MA).…”

“…We have subsequently identified receptors (e.g. Bradykinin Receptors 1 and 2 and Dectin-1) that contribute to this maladaptive inflammation response 4, 7 . However, inactivating one or more of these receptors does not completely disrupt proinflammatory mediator production, pointing to the existence of other co-existing receptors/mechanisms 4, 7 .…”