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Yaseen Awad-Igbaria,1,2 Shilo Dadon,1,2 Alon Shamir,3,4 Alejandro Livoff,5 Mark Shlapobersky,5 Jacob Bornstein,1,2,* Eilam Palzur2,* 1Faculty of Medicine in the Galilee, Bar-Ilan University, Safed, Israel; 2The Research Institute of Galilee Medical Center, Nahariya, Israel; 3Psychobiology Research Laboratory, Mazor Mental Health Center, Akko, Israel; 4The Ruth and Bruce Rappaport Faculty of Medicine, Technion – Israel Institute of Technology, Haifa, Israel; 5Pathology Department, Barzilai University Medical Center, Ashkelon, Israel*These authors contributed equally to this workCorrespondence: Yaseen Awad-Igbaria, The Research Institute of Galilee Medical Center, PO Box 21, Nahariya, 22100, Israel, Tel +972 50-4500101, Email Yaseenawad123@gmail.comBackground: Provoked vulvodynia (PV) is the main cause of vulvar pain and dyspareunia. The etiology of PV has not yet been elucidated. However, PV is associated with a history of recurrent inflammation, and its often accompanied by increases in the numbers of mast cells (MCs) and sensory hyperinnervation in the vulva. Therefore, this study aimed to examine the role of MCs and the early inflammatory events in the development of chronic vulvar pain in a rat model of PV.Methods: Mechanical and thermal vulvar sensitivity was measured for 5 months following zymosan vulvar challenges. Vulvar changes in glutamate and nerve growth factor (NGF) were analyzed using ELISA. Immunofluorescence (IF) staining of the vulvar section after 20, 81, and 160 days of the zymosan challenge were performed to test MCs accumulation, hyperinnervation, and expression of pain channels (transient receptor potential vanilloid/ankyrin-1-TRPV1 & TRPA1) in vulvar neurons. Changes in the development of vulvar pain were evaluated following the administration of the MCs stabilizer ketotifen fumarate (KF) during zymosan vulvar challenges.Results: Zymosan-challenged rats developed significant mechanical and thermal vulvar sensitivity that persisted for over 160 days after the zymosan challenge. During inflammation, increased local concentrations of NGF and glutamate and a robust increase in MCs degranulation were observed in zymosan-challenged rats. In addition, zymosan-challenged rats displayed sensory hyperinnervation and an increase in the expression of TRPV1 and TRPA1. Treatment with KF attenuated the upregulated level of NGF during inflammation, modulated the neuronal modifications, reduced MCs accumulation, and enhanced mechanical hypersensitivity after repeated inflammation challenges.Conclusion: The present findings suggest that vulvar hypersensitivity is mediated by MCs accumulation, nerve growth, and neuromodulation of TRPV1 and TRPA1. Hence, KF treatment during the critical period of inflammation contributes to preventing chronic vulvar pain development.Keywords: provoked vulvodynia, inflammation, mast cell, nerve growth factor, glutamate, hyperinnervation

© The Author(s) 2022. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/., This short opinion aimed to present the evidence to support our hypothesis that vulvodynia is a neuroinflammatory pain syndrome originating in the pelvic visceral nerve plexuses caused by the failure of weakened uterosacral ligaments (USLs) to support the pelvic visceral nerve plexuses, i.e., T11-L2 sympathetic and S2-4 parasympathetic plexuses. These are supported by the USLs, 2 cm from their insertion to the cervix. They innervate the pelvic organs, glands, and muscles. If the USLs are weak or lax, gravitational force or even the muscles may distort and stimulate the unsupported plexuses. Inappropriate afferent signals could then be interpreted as originating from an end-organ site. Activation of sensory visceral nerves causes a neuro-inflammatory response in the affected tissues, leading to neuroproliferation of small peripheral sensory nerve fibers, which may cause hyperalgesia and allodynia in the territory of the damaged innervation. Repair of the primary abnormality of USL laxity, responsible for mechanical stimulation of the pelvic sensory plexus, may lead to resolution of the pain syndrome.

The opening of the mitochondrial permeability transition pore (mPTP) has emerged as a pivotal event following traumatic brain injury (TBI). Evidence showing the impact of the translocator protein (TSPO) over mPTP activity has prompted several studies exploring the effect of TSPO ligands, including etifoxine, on the outcome of traumatic brain injury (TBI). Mitochondrial respiration was assessed by respirometry in isolated rat brain mitochondria (RBM) by measurements of oxidative phosphorylation capacity (OXPHOS). The addition of calcium to RBM was used to induce mitochondrial injury and resulted in significant OXPHOS reduction that could be reversed by preincubation of RBM with etifoxine. Sensorimotor and cognitive functions were assessed following controlled cortical impact and compared in vehicle and etifoxine-treated animals. There was no difference between the vehicle and etifoxine groups for sensorimotor functions as assessed by rotarod. In contrast, etifoxine resulted in a significant improvement of cognitive functions expressed by faster recovery in Morris water maze testing. The present findings show a significant neuroprotective effect of etifoxine in TBI through restoration of oxidative phosphorylation capacity associated with improved behavioral and cognitive outcomes. Since etifoxine is a registered drug used in common clinical practice, implementation in a phase II study may represent a reasonable step forward.

Experimental studies have shown that ligands of the 18 kDa translocator protein can reduce neuronal damage induced by traumatic brain injury by protecting mitochondria and preventing metabolic crisis. Etifoxine, an anxiolytic drug and 18 kDa translocator protein ligand, has shown beneficial effects in the models of peripheral nerve neuropathy. The present study investigates the potential effect of etifoxine as a neuroprotective agent in traumatic brain injury (TBI). For this purpose, the effect of etifoxine on lesion volume and modified neurological severity score at 4 weeks was tested in Sprague&ndash, Dawley adult male rats submitted to cortical impact contusion. Effects of etifoxine treatment on neuronal survival and apoptosis were also assessed by immune stains in the perilesional area. Etifoxine induced a significant reduction in the lesion volume compared to nontreated animals in a dose-dependent fashion with a similar effect on neurological outcome at four weeks that correlated with enhanced neuron survival and reduced apoptotic activity. These results are consistent with the neuroprotective effect of etifoxine in TBI that may justify further translational research.

Cerebral edema represents a major threat following traumatic brain injury. However, therapeutic measures for control of intracranial pressure alone have failed to restore cerebral metabolism and improve neurological outcome. Since mitochondrial damage results in ATP depletion and deactivation of membrane ionic pumps, we hypothesized that modulation of ATP bioavailability may directly affect cytotoxic edema. Intracranial pressure measurements were performed in Sprague-Dawley rats treated by intraperitoneal injection of dimethylsulfoxide (vehicle), cyclosporine A (CsA), or Oligomycin B (OligB) following cortical contusion and further correlated with water content, mitochondrial damage, and electron microscopic assessment of neuronal and axonal edema. As hypothesized, ultra-structural figures of edema closely correlated with intracranial pressure elevation, increased water content and mitochondrial membrane permeabilization expressed by loss of transmembrane mitochondrial potential. Further, mitochondrial damage evidenced ultra-structurally by figures of swollen mitochondria with severely distorted cristae correlated with both cytotoxic edema and mitochondrial dysfunction. Importantly, cerebral edema and mitochondrial impairment were significantly worsened by treatment with OligB, whereas a noticeable improvement could be observed in animals that received injections of CsA. Since OligB and CsA are responsible for symmetrical and opposite effects on oxidative metabolism, these findings support the hypothesis of a causative relationship between edema and mitochondrial function.

Traumatic brain injury (TBI) is a leading cause of death and functional disability in western countries, affecting mostly young patients. Despite intense and sustained efforts deployed for the development of new therapeutic strategies, no clinical benefit has been shown by any of the investigated compounds. Increasing attention has been drawn during the past two decades to the neuroprotective effects of estrogens, although most of the available data relate to ischemic brain injury. The purpose of the present study was to investigate the potential neuroprotective value of estrogens in TBI as a therapeutic modality. For this purpose, a contusion was created in the parietal cortex by dynamic cortical deformation in two groups of 10 Sprague-Dawley male rats. Following the injury, treated animals received conjugated estrogens for 3 days, using a subcutaneously implanted osmotic pump. Animals were then sacrificed, and TUNEL, anti-active Caspase 3, bcl-2, and bax labeling were performed in paraffin-embedded brain sections, allowing for comparative and quantitative analysis. In estrogen-treated animals, there was a marked and significant reduction of apoptosis in comparison with non-treated animals. The reduction in TUNEL and active Caspase 3 staining was similar and close to 50%. Optical analysis of histological slides prepared by bcl-2 labeling showed a significant increase in bcl-2 expression in estrogen-treated animals compared to non-treated animals. On the contrary, bax expression was not influenced by hormonal treatment, and no difference could be noticed between the two groups. These results support the potential therapeutic value of estrogens in TBI and further clarify their mode of action.

Cerebral contusions are one the most frequent traumatic lesions and the most common indication for secondary surgical decompression. The purpose of this study was to investigate the physiology of perilesional secondary brain damage and evaluate the value of hyperbaric oxygen therapy (HBOT) in the treatment of these lesions. Five groups of five Sprague-Dawley rats each were submitted to dynamic cortical deformation (DCD) induced by negative pressure applied to the cortex. Cerebral lesions produced by DCD at the vacuum site proved to be reproducible. The study protocol entailed the following: (1) DCD alone, (2) DCD and HBOT, (3) DCD and post-operative hypoxia and HBOT, (4) DCD, post-operative hypoxia and HBOT, and (5) DCD and normobaric hyperoxia. Animals were sacrificed after 4 days. Histological sections showed localized gross tissue loss in the cortex at injury site, along with hemorrhage. In all cases, the severity of secondary brain damage was assessed by counting the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and caspase 3-positive cells in successive perilesional layers, each 0.5 mm thick. Perilesional TUNEL positive cells suggested the involvement of apoptosis in group 1 (12.24% of positive cells in layer 1). These findings were significantly enhanced by post-operative hypoxia (31.75%, p < 0.001). HBOT significantly reduced the severity and extent of secondary brain damage expressed by the number of TUNEL positive cells in each layer and the volume of the lesion (4.7% and 9% of TUNEL positive cells in layer 1 in groups 2 and 4 respectively, p < 0.0001 and p < 0.003). Normobaric hyperoxia also proved to be beneficial although in a lesser extent. This study demonstrates that the vacuum model of brain injury is a reproducible model of cerebral contusion. The current findings also suggest that HBOT may limit the growth of cerebral contusions and justify further experimental studies.