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Postherpetic neuralgia (PHN) is a notorious neuropathic pain featuring persistent profound mechanical hyperalgesia with significant negative impact on patients' life quality. CDDO can regulate inflammatory response and programmed cell death. Its derivative also protects neurons from damages by modulating microglia activities. As a consequence of central and peripheral sensitization, applying neural blocks may benefit to minimize the risk of PHN. This study aimed to explore whether CDDO could generate analgesic action in a PHN-rats' model. The behavioural test was determined by calibrated forceps testing. The number of apoptotic neurons and degree of glial cell reaction were assessed by immunofluorescence assay. Activation of PKC-δ and the phosphorylation of Akt were measured by western blots. CDDO improved PHN by decreasing TRPV1-positive nociceptive neurons, the apoptotic neurons, and reversed glial cell reaction in adult rats. It also suppressed the enhanced PKC-δ and p-Akt signalling in the sciatic nerve, dorsal root ganglia (DRG) and spinal dorsal horn. Our research is the promising report demonstrating the analgesic and neuroprotective action of CDDO in a PHN-rat's model by regulating central and peripheral sensitization targeting TRPV1, PKC-δ and p-Akt. It also is the first study to elucidate the role of oligodendrocyte in PHN., (© 2024 The Authors. Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd.)

Neuropathic pain following nerve injury is a complex condition, which often puts a negative impact on life and remains a sustained problem. To make pain management better is of great significance and unmet need. RTA 408 (Omaveloxone) is a traditional Asian medicine with a valid anti-inflammatory property. Thus, we aim to investigate the therapeutic effect of RTA-408 on mechanical allodynia in chronic constriction injury (CCI) rats as well as the underlying mechanisms. Neuropathic pain was induced by using CCI of the rats' sciatic nerve (SN) and the behavior testing was measured by calibrated forceps testing. Activation of Nrf-2, the phosphorylation of nuclear factor-κB (NF-κB), and the inflammatory response were assessed by western blots. The number of apoptotic neurons and degree of glial cell reaction were examined by immunofluorescence assay. RTA-408 exerts an analgesic effect on CCI rats. RTA-408 reduces neuronal apoptosis and glial cell activation by increasing Nrf-2 expression and decreasing the inflammatory response (TNF-α/ p-NF-κB/ TSLP/ STAT5). These data suggest that RTA-408 is a candidate with potential to reduce nociceptive hypersensitivity after CCI by targeting TSLP/STAT5 signaling., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Neuropathic pain is a debilitating chronic disorder, significantly causing personal and social burdens, in which activated neuroinflammation is one major contributor. Thymic stromal lymphopoietin (TSLP) and interleukin (IL)-33 is important for chronic inflammation. Linalyl acetate (LA) is main component of lavender oil with an anti-inflammatory property through TSLP signaling. The aim of the study is to investigate how LA regulates mechanical hyperalgesia after sciatic nerve injury (SNI). Adult Sprague-Dawley male rats were separated into 3 groups: control group, SNI group and SNI with LA group. LA was administrated intraperitoneally one day before SNI. Pain behavior test was evaluated through calibration forceps testing. Ipsilateral sciatic nerves (SNs), dorsal root ganglions (DRGs) and spinal cord were collected for immunofluorescence staining and Western blotting analyses. SNI rats were more sensitive to hyperalgesia response to mechanical stimulus since operation, which was accompanied by spinal cord glial cells reactions and DRG neuro-glial interaction. LA could relieve the pain sensation, proinflammatory cytokines and decrease the expression of TSLP/TSLPR complex. Also, LA could reduce inflammation through reducing IL-33 signaling. This study is the first to indicate that LA can modulate pain through TSLP/TSLPR and IL-33 signaling after nerve injury., (© 2022. The Author(s).)

Resiniferatoxin is an ultrapotent capsaicin analog that mediates nociceptive processing; treatment with resiniferatoxin can cause an inflammatory response and, ultimately, neuropathic pain. Hepatoma-derived growth factor, a growth factor related to normal development, is associated with neurotransmitters surrounding neurons and glial cells. Therefore, the study aims to investigate how blocking hepatoma-derived growth factor affects the inflammatory response in neuropathic pain. Serum hepatoma-derived growth factor protein expression was measured via ELISA. Resiniferatoxin was administrated intraperitoneally to induce neuropathic pain in 36 male Sprague-Dawley rats which were divided into three groups (resiniferatoxin+recombinant hepatoma-derived growth factor antibody group, resiniferatoxin group, and control group) ( n = 12/group). The mechanical threshold response was tested with calibration forceps. Cell apoptosis was measured by TUNEL assay. Immunofluorescence staining was performed to detect apoptosis of neuron cells and proliferation of astrocytes in the spinal cord dorsal horn. RT-PCR technique and western blot were used to measure detect inflammatory factors and protein expressions. Serum hepatoma-derived growth factor protein expression was higher in the patients with sciatica compared to controls. In resiniferatoxin-group rats, protein expression of hepatoma-derived growth factor was higher than controls. Blocking hepatoma-derived growth factor improved the mechanical threshold response in rats. In dorsal root ganglion, blocking hepatoma-derived growth factor inhibited inflammatory cytokines. In the spinal cord dorsal horn, blocking hepatoma-derived growth factor inhibited proliferation of astrocyte, apoptosis of neuron cells, and attenuated expressions of pain-associated proteins. The experiment showed that blocking hepatoma-derived growth factor can prevent neuropathic pain and may be a useful alternative to conventional analgesics., Competing Interests: All the authors declare they have no conflicts of interest., (Copyright © 2021 Chieh-Hsin Wu et al.)

Thymic stromal lymphopoietin (TSLP) is a well-known cytokine for T helper 2 inflammatory responses. A nerve injury activates the neuroinflammation cascade and neuron–glia interaction in dorsal root ganglions (DRG)s, leading to neuropathic pain. Therefore, this study was to investigate the role of TSLP after nerve injury. Male Sprague-Dawley rats were divided as an experimental group with chronic constriction injury (CCI) to the sciatic nerve and a control group. The mechanical pain threshold response was determined by calibration forceps. After assessment of mechanical allodynia, the ipsilateral spinal cord, DRG, sciatic nerve and skin were harvested. Immunofluorescence staining was performed to identify cell types with various markers. Western blot analyses were performed to evaluate protein expressions. Mechanical allodynia developed after CCI and persisted for the next 14 days. Astrocyte reactions occurred and continued until day 14, too. After CCI, DRG and the sciatic nerve also had significantly increased expressions of TSLP/TSLP-R/STAT5. The TSLPR was localized to sensory neuronal endings innervating the skin. This study is the first to demonstrate that the TSLP complex and the STAT5 pathway in nerve are potential therapeutic targets because of their roles in pain regulation after nerve injury. [ABSTRACT FROM AUTHOR]