(111) Oxidative Stress and Lipid Response in Localized Provoked Vulvodynia

Abstract Introduction Vulvar pain affects as 16-28% of women at some point in their lives, and the chronic vulvar pain disorder vulvodynia affects almost 10% of US women annually. One of the most common causes of dyspareunia, or pain with intercourse, in pre-menopausal women is the vulvodynia subtype most prevalent in this population: localized provoked vulvodynia (LPV), defined as pain disproportionate to stimuli applied to the vulvar vestibule. Recent advances have established inflammation as a major disease instigator, demonstrated by an increase in inflammatory lipids and a decrease in pro-resolving lipids. However, the exact etiology remains unclear, and treatment focuses on pain palliation rather than treating the underlying pathophysiology. Objective Oxidative stress, which is present in LPV samples, can both be caused by and contribute to inflammation, suggesting it may be another key player in LPV. Our goal is to examine the effects of oxidative stress in LPV patient tissue samples by examining lipid responses and inflammatory signal production. Methods We used a validated fibroblast model from patient tissue samples and tissue biopsy directly for both cases and controls. Each patient serves as their own control because samples are taken from both the affected painful vestibule and an unaffected pain-free vulvar site a few millimeters away. Non LPV patients have the same sites sampled. In the model, both inflammatory response and lipidomic signatures correlate with LPV pain thresholds. Whole tissue samples and the derived fibroblast strains treated with hydrogen peroxide (oxidative stress) were sent for lipidomics analysis. Fibroblast cultures treated with oxidative stress and/or inflammatory stimuli underwent inflammatory signal quantification via IL-6, IL-8 & PGE-2 ELISAs. Results We found evidence of oxidative stress in the tissue and that oxidative stress exposure increased inflammation in our cellular model. Coupled with observed deficits in the mRNA expression of genes implicated in oxidative stress defense, we hypothesized that painful case vestibules would be enriched for oxidized lipids. However, 8-iso-prostaglandin E2 & ent-prostaglandin E2 were actually lower in cases than controls, at both vestibular and vulvar sites, and 9- & 13-hydroxyoctadecadienoic acid were lower just in the case vestibule. When testing oxidative response in the fibroblasts using hydrogen peroxide for 6 hours, there was again no consistent increase in oxidized lipids. However, case vestibular samples were generally less responsive to the oxidative stress. When hydrogen peroxide and inflammatory stimuli were added together to the fibroblasts over a longer time period, additional inflammatory cytokine secretion compared to inflammation alone was inconsistent for both controls and cases. Conclusions Many of these oxidized lipids are important for recruiting immune cells like Tregs which help clear inflammation, so the failure of case vestibules to produce these may contribute to the previously demonstrated failed resolution of inflammation in LPV. The healthy vulvovaginal microbiome often exhibits an abundance of Lactobacilli that produce hydrogen peroxide, so examining further how oxidative stress, lipid oxidation, and inflammation interact to resolve or continue symptoms is an important next step to understanding the pathophysiology of this painful disorder. Disclosure No.