Molecular Pain最新文献

Calcineurin inhibitors, including tacrolimus (FK506), are used as immunosuppressive agents and can cause unexplained calcineurin inhibitor-induced pain syndrome (CIPS). We investigated how FK506 affects the expression of Na_V1.7, a voltage-gated Na⁺ channel implicated in pain perception that is upregulated in dorsal root ganglion (DRG) neurons in several pain disorders. We generated a model of FK506-induced pain by administering FK506 to Na_V1.7-ChR2 mice, which exhibit light-responsive pain. To evaluate nociceptive responses, paw withdrawal threshold (PWT) was measured using the von Frey test. The optogenetic place aversion (OPA) and light irradiation paw withdrawal tests were also performed. On the 11th day of initial injection, DRGs were dissected from mice under anesthesia and analyzed for Na_V1.7 expression using quantitative reverse transcription PCR (RT-qPCR). PWT was also measured for mice that received the selective Na_V1.7 inhibitor or vehicle. PWT was lower in FK506-treated mice than in those administered the vehicle on the 8th and 12th days after initial FK506 injection (p < 0.05). Mechanical hypersensitivity was reversible and peaked at around 10 days after FK506 administration. OPA and light irradiation paw withdrawal test results corroborated the hypersensitivity to light-responsivity. Na_V1.7 mRNA levels in DRG were higher in FK506-treated mice than in those administered the vehicle on the 11th day (p < 0.05). A selective Na_V1.7 inhibitor reversed FK506-induced pain. Increased Na_V1.7 expression in DRG neurons may be responsible for FK506-induced peripheral neuropathy. Our findings suggest that endogenous calcineurin regulates Na_V1.7 expression. Thus, selective Na_V1.7 inhibition could be a potential therapeutic strategy for CIPS.

Inflammatory pain is a major global health challenge, significantly affecting quality of life and emotional well-being. Current treatment options are limited and often accompanied by adverse effects. Caffeic acid phenethyl ester (CAPE), a natural compound with notable anti-inflammatory properties, has not yet been fully elucidated for its efficacy in inflammatory pain. This work examined the role of CAPE in modulating inflammatory pain. Inflammatory pain was induced in mice by administration of Complete Freund's Adjuvant (CFA), and pain relief was assessed through mechanical and thermal sensitivity tests. Combined with network pharmacology and molecular docking analysis, the PI3K/Akt/NF-κB pathway was identified as a potential therapeutic target. Further validation was performed using Western blot, immunofluorescence, qRT-PCR, toe thickness measurement, and H&E staining of the plantar skin sections. CAPE administration produced significant reductions in CFA-induced pain and anxiety-like behaviors. Intraperitoneal administration of CAPE significantly suppressed the phosphorylation of PI3K, Akt, and NF-κB in microglia, reduced the expression of M1 microglial marker CD86 and pro-inflammatory cytokines (TNF-α, IL-1β, IL-6), and increased the expression of M2 marker CD206 and anti-inflammatory cytokines (IL-4, IL-10). Additionally, CAPE reduced paw edema and inflammatory factor levels in toe tissue. In vitro experiments further confirmed that CAPE induced the polarization of microglia from the M1 to M2 phenotype. Our results demonstrate that CAPE facilitates the transition of microglia to the M2 phenotype mediated by the PI3K/Akt/NF-κB pathway, which attenuates peripheral inflammation and subsequently diminishes inflammation-induced hypersensitivity. These results offer novel perspectives on the possible therapeutic applications of CAPE in the management of inflammatory pain.

Paclitaxel (PTX) treatment induces a pathological pain state that is often associated with neuroinflammation in the central nervous system. The available interventions for PTX-induced pathological pain encounter adverse effects and limited efficacies. Recent studies have shown the significant effectiveness of Electroacupuncture (EA) in pain management as a simple and safe alternative medical treatment. Here, we evaluated the analgesic effect of EA on pain behaviors in PTX-treated rats and investigated its potential analgesic mechanisms. In this study, a pathological pain model was established in SD rats via intraperitoneal (i.p.) injection of PTX. EA or Sham EA treatments were applied every other day for PTX-treated rats. Pain behaviors of mechanical allodynia and thermal hyperalgesia in rats were measured, followed by analysis of the spinal cord tissue via using molecular biology methods. Here, we show that EA treatment is capable to alleviate PTX-induced mechanical allodynia and thermal hyperalgesia in rats. In addition, EA regulated the abnormal protein expression of astrocytes, microglia, neurons, TLR4-MyD88/TRIF signaling pathway and cytokines in the lumbar spinal cord of PTX-treated rats. Furthermore, we investigated the spinal co-expressions of TLR4 in astrocytes, microglia, and neurons respectively in rats and the regulatory effect of EA on TLR4 and cells mentioned above. In summary, EA shows analgesic properties as it ameliorates PTX-induced mechanical allodynia and thermal hyperalgesia probably by reducing central neuroinflammation. Therefore, we consider EA as a potential therapeutic candidate for the treatment of PTX-induced pathologic pain. Notably, this study provides the first morphological evidence that EA may concurrently influence TLR4-mediated neuroimmune interactions across multiple spinal cell types, suggesting a potential central mechanism distinct from previously reported peripheral actions.

Paclitaxel (PTX) is a drug commonly used in cancer chemotherapy despite its neurotoxicity. TRPA1 channels are essential mediators of sensory transduction and nociception. These cation channels are linked to PTX-induced neurotoxicity, which Li⁺ prevents. This study aimed to examine the effects of Li+ on PTX-induced neurotoxicity and on TRPA1 channels. We utilized the SH-SY5Y cell line to assess cell viability via the MTT assay. Intracellular Ca²⁺ concentration in Fura-2-loaded cells was measured using spectrofluorometry. TRPA1 channel activity was evaluated with whole-cell patch-clamp recordings. The effects of PTX, Li⁺, and TRPA1 agonists and antagonists were tested. Motor function, thermal response, and cognitive performance were assessed in adult Wistar rats with neuropathy induced by PTX. PTX (100 nM) significantly reduced cell viability, and Li⁺ (10 mM) alleviated this effect. AITC (300 µM), a TRPA1-selective agonist, decreased cell viability, with a more pronounced impact when PTX was present. A967079 (10 µM), a selective TRPA1 antagonist, significantly lessened the cytotoxicity caused by PTX. Li⁺ reduced the cytotoxic effects of TRPA1 activation both with and without PTX. PTX increased TRPA1 currents and amplified TRPA1-mediated intracellular Ca²⁺ increase, while Li⁺ neutralized both effects. Additionally, PTX causes sensorimotor and cognitive neuropathy, which was reversed by Li⁺ treatment. These findings suggest that Li⁺ may act as a neuroprotective agent, preventing neuronal damage caused by PTX via TRPA1 channel pathways.

Background: Paclitaxel (PTX), a widely administered chemotherapeutic drug, is known to cause neuropathic pain as a severe adverse effect. Elevated calpain expression in tumor tissues not only mediates chemoresistance but may also participate in the paclitaxel-induced neuropathic pain (PINP). There is still controversy over whether Calpain-1 (CAPN1), a subtype of calpain protease, exerts neuroprotective effects or nociceptive effects. The role and underlying mechanism of calpain1 in PINP remain unclear.

Results: To clarify the contribution of calpain to CIPN, we examined the protein expressions of CAPN1, CAPN2, Neuronal Calcium Sensor-1(NCS-1), and Transient Receptor Potential Vanilloid 4 (TRPV4) in the DRGs and spinal dorsal horn (SDH) of PTX-treated rats. Results showed no significant changes in CAPN1 and CAPN2 protein levels in the DRGs, but marked upregulation in the SDH, along with heightened calpain activity, as evidenced by the accumulation of spectrin degradation products (a known substrate of calpain). The abnormal enhancement of CAPN1 in PTX-treated rats, contrasting with its reduced expression in most chronic pain models, prompted further investigation into its potential involvement in chronic pain. Immunofluorescence double-staining confirmed that CAPN1 localization was predominantly neuronal. Intraspinal CAPN1 overexpression restricted to CaMKII neurons in the naive rats effectively reproduced paclitaxel-induced neuropathic pain (PINP) with a comparable extent and duration of pain threshold reduction. Western blot analysis revealed that CAPN1 overexpression in spinal CaMKII neurons elevated NCS-1 expression, a calcium-binding protein essential for maintaining calcium homeostasis, which in turn strengthen the expression of CAPN2 as well as the calpain enzymatic activity. These data indicate that CAPN1 does not confer neuroprotective effects in paclitaxel-induced pain models. Rather, its overexpression in spinal CaMKII neurons directly promotes nociceptive signaling, most likely through disruption of plasma membrane calcium dynamics. Collectively, the results identify CAPN1 as a candidate therapeutic target for the clinical treatment and prevention of PINP.

The role of T cells in chemotherapy-induced peripheral neuropathy (CIPN) is complex and shaped by biological and experimental factors, including sex, hormonal status, genetic background, and cancer model. This complexity has contributed to inconsistent findings among studies, limiting therapeutic progress. In this study, we investigate how T cells contribute to painful paclitaxel (PTX)-induced peripheral neuropathy (PIPN). Adult male T cell-competent (RNU^+/-) and T cell-deficient (RNU^-/-) rats were subcutaneously inoculated with tumor cells and subsequently treated with intraperitoneal PTX (8 mg/kg total dose). Reflexive (mechanical, heat, cold) and non-reflexive (burrowing, gait) pain behaviors were assessed from baseline through week 6. Immunohistochemistry (CD68, CX3CR1, CD206) and flow cytometry (CD163, CD86, CD11b/c, CD3, CD161a, CD45RA) were used to assess macrophage and lymphocyte populations. T cell-competent, but not -deficient, rats developed and maintained cold hypersensitivity following PTX. T cells also reduced the onset intensity of PTX-induced mechanical hypersensitivity. In T cell-competent rats, PTX reduced T and B cell counts and increased the CD4+/CD8+ T cell ratio across DRG, sciatic nerve, and spleen. PTX shifted macrophage polarization toward the M1 phenotype and reduced the M2/M1 ratio, independent of T cells. However, M2 macrophages (M2γ and M2a) increased specifically in the sciatic nerves of T cell-deficient rats. Additionally, natural killer (NK) cells decreased in PTX-treated, T cell-deficient rats but remained unchanged in T cell-competent rats. These findings highlight the complex role of T cells in PIPN. In PIPN, T cells play a critical role in driving PTX-induced cold hypersensitivity. A decrease in their number worsens pain intensity, possibly by altering the CD4+/CD8+ T cell balance. In contrast, NK cell reductions in T cell-deficient rats may contribute to hypersensitivity in the absence of T cells.

Noxious chemicals like chlorine induce extreme distress, pain, and irritation in exposed individuals, yet methods to evaluate pain-related behavioral responses are absent. It is also unknown whether analgesics would alleviate pain and physical discomfort induced by such noxious chemicals. The grimace scale (GS), which evaluates facial expression features such as orbital tightening (OT), is a valuable indicator of pain and distress in animals. However, conventional GS approaches are labor-intensive, prone to subjectivity, and lack quantitative precision. In this study, we employed machine learning with DeepLabCut to annotate key facial landmarks in video recordings of chlorine-exposed rats. Focusing on the superior and inferior eyelid margins and the medial and lateral canthi, we quantified eyelid distance and palpebral fissure width as measures of OT. Rigorous inclusion and exclusion criteria for annotated images were established to ensure accuracy and reproducibility. The quantitative GS in rats subjected to chlorine exposure was validated. Significant reductions in eyelid distance and palpebral fissure width were observed upon chlorine exposure as compared to unexposed control animals. Administration of the opioid analgesic buprenorphine significantly reduced the OT caused by chlorine. This study establishes a robust, quantitative method for assessing OT in chlorine-exposed rats using DeepLabCut, providing a scalable, objective tool for assessing pain induced by noxious chemicals in preclinical research. This study also suggests that opioids can alleviate pain and physical discomfort induced by inhalation of noxious chemicals, providing a new therapeutic strategy for managing the respiratory hazard of noxious chemicals.

Although 5-hydroxytryptamine (5-HT) contributes to pruritus associated with allergic contact dermatitis (ACD), the role of 5-HT derived from mast cells (MC) in chronic pruritus induced by squaric acid dibutyl ester (SADBE), and the expression and distribution of 5-HT2A receptor (HTR2A) in sensory neurons remain unclear. In this study, a SADBE-induced ACD mouse model was established to evaluate pruritus behavior, MC activation, and 5-HTproduction. The mechanism was verified through pharmacological intervention (MC stabilizer cromolyn, HTR2A antagonist Ketanserin) and FcεRIα-KO mice. It was found that SADBE triggered time-dependent MC recruitment (peaking at Day 14-21) and Mc-derived 5-HT release, which were associated with persistent pruritus. The intervention of MC stabilizer cromolyn and FcεRIα-KO mice confirmed MC/IgE-dependent 5-HT release, and inhibiting MC degranulation could reduce pruritus. Single-cell RNA sequencing and RNAscope in situ hybridization techniques revealed that HTR2A was mainly expressed in the NF3/PEP2/NP3 subsets of DRG neurons. The co-expression level of HTR2A and Nppb was relatively high, partially overlapping with TRPV1/TRPA1. HTR2A antagonists can relieve SADBE-induced pruritus. In conclusion, we have determined that the MC-5-HT-HTR2A axis is involved in chronic pruritus in SADBE-induced ACD, and targeting this axis provides a very promising therapeutic strategy.

Neuropathic pain (NP) is a refractory chronic pain disorder with a complex pathogenesis and limited effective treatment options. In recent years, exosomes derived from mesenchymal stem cells (MSC-Exos) have attracted attention as promising therapeutic agents due to their anti-inflammatory, neuroregenerative, and immunomodulatory properties. This study aimed to investigate the therapeutic effects and underlying mechanisms of human umbilical cord mesenchymal stem cell-derived exosomes (hUC-MSC-Exos) in a rat model of neuropathic pain induced by chronic constriction injury (CCI) of the sciatic nerve. hUC-MSC-Exos were isolated via ultracentrifugation and administered to CCI rats. Behavioral tests demonstrated that hUC-MSC-Exos significantly ameliorated both mechanical allodynia and thermal hyperalgesia in CCI rats. Further mechanistic investigations indicated that hUC-MSC-Exos downregulated the expression of pro-inflammatory cytokines (NF-κB, TNF-α, IL-6) and modulated astrocyte activation and polarization, thereby contributing to neuropathic pain relief. These findings elucidate the potential mechanisms through which hUC-MSC-Exos alleviate NP and provide an experimental foundation for their future clinical application.

Migraine is a very common and incapacitating condition. We chose to assess the therapeutic effect of Botulinum toxin injection on migraine and tension-type headache patients in an effort to measure salivary alpha amylase for these groups before and after treatment with Botulinum toxin injection because stress appears to be a significant provoking factor of this disorder.There were twenty patients with chronic tension-type headaches and twenty-five patients with chronic migraines among the forty-five individuals. Enzyme-linked immunosorbent assay (ELISA) kits were used to test the salivary biomarker (salivary cortisol and salivary alpha amylase). The PREEMPT (Onabotulinum toxinS AntIpOde for chronic migraiNe) treatment protocol, a systematic procedure for treating chronic migraines, was administered to the patients. Biomarkers measured during the study were analyzed as surrogate measures of stress to shed light on potential physiological action of the intervention. Context In patients with chronic migraine and tension-type headaches, the effect of Nabota (Botulinum toxin type A) on specific stress-related indicators was evaluated.The results demonstrated a statistically significant (p<0.05) rise in salivary cortisol and a statistically significant (p<0.05) decrease in salivary alpha amylase following Botulinum toxin intervention for both research groups (chronic migraine, chronic tension headaches).