Background: Peripheral nerve injury can cause neuroinflammation and neuromodulation that lead to mitochondrial dysfunction and neuronal apoptosis in the dorsal root ganglion (DRG) and spinal cord, contributing to neuropathic pain and motor dysfunction. Hyperbaric oxygen therapy (HBOT) has been suggested as a potential therapeutic tool for neuropathic pain and nerve injury. However, the specific cellular and molecular mechanism by which HBOT modulates the development of neuropathic pain and motor dysfunction through mitochondrial protection is still unclear. Methods: Mechanical and thermal allodynia and motor function were measured in rats following sciatic nerve crush (SNC). The HBO treatment (2.5 ATA) was performed 4 h after SNC and twice daily (12 h intervals) for seven consecutive days. To assess mitochondrial function in the spinal cord (L2–L6), high-resolution respirometry was measured on day 7 using the OROBOROS-O2k. In addition, RT-PCR and Immunohistochemistry were performed at the end of the experiment to assess neuroinflammation, neuromodulation, and apoptosis in the DRG (L3–L6) and spinal cord (L2–L6). Results: HBOT during the early phase of the SNC alleviates mechanical and thermal hypersensitivity and motor dysfunction. Moreover, HBOT modulates neuroinflammation, neuromodulation, mitochondrial stress, and apoptosis in the DRG and spinal cord. Thus, we found a significant reduction in the presence of macrophages/microglia and MMP-9 expression, as well as the transcription of pro-inflammatory cytokines (TNFa, IL-6, IL-1b) in the DRG and (IL6) in the spinal cord of the SNC group that was treated with HBOT compared to the untreated group. Notable, the overexpression of the TRPV1 channel, which has a high Ca²⁺ permeability, was reduced along with the apoptosis marker (cleaved-Caspase3) and mitochondrial stress marker (TSPO) in the DRG and spinal cord of the HBOT group. Additionally, HBOT prevents the reduction in mitochondrial respiration, including non-phosphorylation state, ATP-linked respiration, and maximal mitochondrial respiration in the spinal cord after SNC. Conclusion: Mitochondrial dysfunction in peripheral neuropathic pain was found to be mediated by neuroinflammation and neuromodulation. Strikingly, our findings indicate that HBOT during the critical period of the nerve injury modulates the transition from acute to chronic pain via reducing neuroinflammation and protecting mitochondrial function, consequently preventing neuronal apoptosis in the DRG and spinal cord.

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality in young adults, characterized by primary and secondary injury. Primary injury is the immediate mechanical damage, while secondary injury results from delayed neuronal death, often linked to mitochondrial damage accumulation. Hyperbaric oxygen therapy (HBOT) has been proposed as a potential treatment for modulating secondary post-traumatic neuronal death. However, the specific molecular mechanism by which HBOT modulates secondary brain damage through mitochondrial protection remains unclear. Spatial learning, reference memory, and motor performance were measured in rats before and after Controlled Cortical Impact (CCI) injury. The HBOT (2.5 ATA) was performed 4 h following the CCI and twice daily (12 h intervals) for four consecutive days. Mitochondrial functions were assessed via high-resolution respirometry on day 5 following CCI. Moreover, IHC was performed at the end of the experiment to evaluate cortical apoptosis, neuronal survival, and glial activation. The current result indicates that HBOT exhibits a multi-level neuroprotective effect. Thus, we found that HBOT prevents cortical neuronal loss, reduces the apoptosis marker (cleaved-Caspase3), and modulates glial cell proliferation. Furthermore, HBO treatment prevents the reduction in mitochondrial respiration, including non-phosphorylation state, oxidative phosphorylation, and electron transfer capacity. Additionally, a superior motor and spatial learning performance level was observed in the CCI group treated with HBO compared to the CCI group. In conclusion, our findings demonstrate that HBOT during the critical period following the TBI improves cognitive and motor damage via regulating glial proliferation apoptosis and protecting mitochondrial function, consequently preventing cortex neuronal loss.

Background: 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.

Provoked vulvodynia (PV) is characterized by localized chronic vulvar pain. It is associated with a history of recurrent inflammation, mast cell (MC) accumulation and neuronal sprouting in the vulva. However, the mechanism of how vulvar-inflammation promotes neuronal sprouting and gene-expression adaptation in the spinal cord, leading to hypersensitivity and painful sensations, is unknown. Here, we found that vulvar tissue from women with PV (n = 8) is characterized by MC accumulation and neuronal sprouting compared to women without PV (n = 4). In addition, we observed these changes in an animal study of PV. Thus, we found that repeated vulvar zymosan-inflammation challenges lead to long-lasting mechanical and thermal vulvar hypersensitivity, which is mediated by MC accumulation, neuronal sprouting, overexpression of the pain channels (TRPV1 and TRPA1) in vulvar neurons, as well as a long-term increase of gene expression related to neuroplasticity, neuroinflammation and nerve growth factor (NGF) in the spinal cord/dorsal root ganglia (DRG) (L6–S3). However, regulation of the NGF pathway by stabilization of MC activity with ketotifen fumarate (KF) during vulvar inflammation attenuates the local increase of NGF and histamine, as well as the elevated transcription of pro-inflammatory cytokines and NGF pathway in the spinal cord. Additionally, KF treatment during inflammation modulates MC accumulation, neuronal hyperinnervation and overexpression of the TRPV1 and TRPA1 channels in the vulvar neurons, consequently preventing the development of vulvar pain. A thorough examination of the NGF pathway during inflammation revealed that blocking NGF activity by using an NGF-non-peptide-inhibitor (Ro08-2750) regulates the upregulation of genes related to neuroplasticity and the NGF pathway in the spinal cord, as well as modulating neuronal sprouting and overexpression of the pain channels, resulting in a reduced level of vulvar hypersensitivity. On the other hand, stimulation of the NGF pathway in the vulvar promotes neuronal sprouting, overexpression of pain channels and increase of gene expression related to neuroplasticity, neuroinflammation and NGF in the spinal cord, resulting in long-lasting vulvar hypersensitivity. In conclusion, our findings suggest that vulvar allodynia induced by inflammation is mediated by MC accumulation, neuronal sprouting and neuromodulation in the vulvar. Additionally, chronic vulvar pain may involve a long-term adaptation in gene expression in the spinal cord, which probably plays a critical role in central sensitization and pain maintenance. Strikingly, regulating the NGF pathway during the critical period of inflammation prevents vulvar pain development via modulating the neuronal changes in the vestibule and spinal cord, suggesting a fundamental role for the NGF pathway in PV development.

Maternal obesity in pregnancy and lactation is linked to metabolic disturbances and neurodevelopmental problems in offspring, increasing the risk of psychiatric disorders in adulthood. We proposed that maternal N-acetyl cysteine (NAC) supplementation during lactation, a critical period for neurodevelopment, potentially protects offspring from developing cognitive impairment in adulthood. Fifteen young female ICR mice were randomly allocated to different experimental groups: high-fat diet (HFD; 60.3% fat before mating, during pregnancy and lactation), HFD-NAC of 300 mg/kg/day during lactation, CD (high-fat diet before mating, during pregnancy, and regular chow control diet of 8.2% fat during lactation), CD-NAC of 300 mg/kg/day during lactation and control group consuming regular chow diet. The serum inflammatory markers of the offspring were evaluated post-weaning, while metabolic markers, microglial density, and cognitive performance were assessed in adulthood using the novel Object Recognition and Morris Water Maze tests. Our results demonstrate maternal obesity during gestation and lactation increased body weight, hepatic steatosis, and microglial cell density in the dentate gyrus (DG) and cortex. Furthermore, these offspring exhibited reduced spatial learning abilities in adulthood, regardless of sex. However, maternal NAC administration during lactation and maternal diet intervention significantly reduced brain microglial density and improved both male and female offspring metabolic profiles. More importantly, NAC supplementation during lactation, regardless of maternal diet, enhanced male offspring's learning ability in adulthood. Our findings indicate that administering NAC to obese mothers during the critical lactation period may offer protection against metabolic disturbances and cognitive deficits in adult offspring previously exposed to maternal obesity.