Downregulation of metallothionein-2 contributes to oxaliplatin-induced neuropathic pain

Sanqi Qushi formula ameliorates renal injury in experimental membranous nephropathy rats by inhibiting the MEK/ERK signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Sanqi Qushi Formula (SQQS), a clinically validated derivative of the Sanqi oral solution, integrates principles of traditional Chinese medicine (TCM) to treat membranous nephropathy (MN). Its efficacy in reducing proteinuria and preserving renal function has been observed in clinical practice.

AIM OF THE STUDY

This study aims to elucidate the therapeutic mechanisms, active components, and pathway-specific effects of SQQS in MN, providing a scientific foundation for its clinical use.

MATERIALS AND METHODS

The components of SQQS were analyzed using UHPLC-MS/MS. A passive Heymann nephritis (PHN) rat model was induced by intravenous injection of anti-Fx1A serum. Rats received oral SQQS for 3 weeks, and urine/serum samples were collected to evaluate renal function and chemokine levels. Renal histopathology was assessed via immunofluorescence, PASM staining, and CD68 immunostaining. Network pharmacology integrated target prediction for SQQS compounds and differentially expressed genes from the Gene Expression Omnibus (GEO) database (MN patient glomeruli). Mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway proteins and epithelial-mesenchymal transition (EMT) markers were analyzed by western blotting (WB). Molecular docking and molecular dynamics simulations evaluated compound-MEK interactions. Human glomerular podocytes were treated with SQQS-derived compounds; viability and migration were assessed using cell counting kit-8 assay and scratch assays.

RESULTS

UHPLC-MS/MS identified 129 compounds in SQQS. SQQS treatment significantly reduced renal injury markers, glomerular IgG deposition, and basement membrane thickening in PHN rats. GEO database analysis revealed 839 upregulated and 166 downregulated genes in MN glomeruli. Network pharmacology implicated the tumor necrosis factor (TNF) pathway, with 10 upregulated targets (e.g., MAP2K1, MMP3, CXCL10). WB confirmed SQQS suppressed MEK/ERK phosphorylation and decreased MMP3 and α-SMA levels. Renal CD68+ macrophages and associated chemokines (CXCL10, CCL20) were reduced by SQQS. Methylnissolin-3-O-glucoside, a flavonoid from Astragalus mongholicus Bunge, dose-dependently inhibited TNF-α-induced MEK/ERK activation and migration. MEK agonists reversed methylnissolin-3-O-glucoside-mediated MEK/ERK suppression.

CONCLUSION

SQQS ameliorates MN progression by inhibiting the MEK/ERK pathway, suppressing EMT, and reducing macrophage recruitment, with methylnissolin-3-O-glucoside as a key bioactive component.

Mesencephalic astrocyte-derived neurotrophic factor (MANF): A novel therapeutic target for chemotherapy-induced peripheral neuropathy via regulation of integrated stress response and neuroinflammation

Chemotherapy-induced peripheral neuropathy (CIPN) represents a severe complication, impacting up to 90% of cancer patients administered with chemotherapeutic agents such as oxaliplatin. The purpose of our study was to examine the potential role and therapeutic efficacy of Mesencephalic Astrocyte-derived Neurotrophic Factor (MANF), given its recognized neuroprotective and immunomodulatory properties in diverse neurological disorders. Utilizing an oxaliplatin-induced CIPN mouse model, we investigated MANF expression in the dorsal root ganglia (DRG) and spinal cord, and evaluated the impacts of AAV-mediated MANF overexpression on CIPN. Our findings revealed substantial downregulation of MANF expression in both the DRG and spinal cord of CIPN inflicted mice, with MANF majorly localized in neurons as opposed to glial cells. Intrathecal administration of AAV-MANF preceding oxaliplatin treatment yielded several beneficial results. MANF overexpression diminished mechanical hypersensitivity and decreased Calcitonin Gene-Related Peptide (CGRP) expression in DRG and the spinal dorsal horn. These enhancements were concomitant with modulation of the integrated stress response (ISR) and neuroinflammation. Intervention with AAV-MANF effectively regulated ISR markers (BiP, CHOP, and p-eIF2α), mitigated activation of microglia and astrocytes in the DRG and spinal dorsal horn, and inhibited NFκB and ERK inflammatory signaling pathways. To conclude, our study underscores the potential of MANF as a viable therapeutic target for CIPN, manifesting its ability to modulate ISR and neuroinflammation. These insights recommend that continued exploration of MANF-centered approaches could facilitate the advancement of more efficacious interventions for this incapacitating chemotherapy complication.

Ozone promotes macrophage efferocytosis and alleviates neuropathic pain by activating the AMPK/Gas6-MerTK/SOCS3 signaling pathway

Background

Neuropathic pain (NPP) is a multifaceted pain syndrome that occurs as a consequence of physical injury or underlying diseases, with an incidence rate of 7%-10%, NPP poses a significant clinical challenge as current treatment options are ineffective. The accumulation of apoptotic cells and neuroinflammation play crucial roles in the pathological mechanisms of NPP. Here, we aim to investigate strategies for effectively clearing apoptotic cells and provide therapeutic interventions for NPP.

Methods

CCI mice were treated with different concentrations of ozone (15μg, 30μg, 45μg) to investigate the effects on the accumulation of apoptotic cells and neuroinflammation. In vitro, the phagocytic function of BMDM towards apoptotic neutrophils after ozone treatment was examined.

Results

We found ozone at a concentration of 30μg significantly alleviated mechanical hypersensitivity in CCI mice and ozone significantly upregulates the phagocytic activity of BMDM. Furthermore, we investigated the mechanisms and found ozone could activate AMPK, upregulate Gas6 (but not Protein S), activate MerTK (a key receptor involved in apoptosis), and enhance the phagocytic function of BMDM towards apoptotic neutrophils. It caused the promotion of SOCS3 expression and the suppression of inflammatory factors IL-1β, IL-6, and TNF-a. Interestingly, the effect of ozone in alleviating CCI-induced pain was abolished by the AMPK inhibitor CC and the MerTK receptor inhibitor UNC2541.

Conclusion

Ozone facilitated macrophage clearance of apoptotic cells, decreased neuroinflammation by activation of p-AMPK/Gas6/MerTK/SOCS3 signaling pathway, which may become an effective therapeutic approach for neuropathic pain after further clinical validation.

Compensatory upregulation of MT2A alleviates neurogenic intermittent claudication through inhibiting activated p38 MAPK-mediated neuronal apoptosis

Neurogenic intermittent claudication (NIC), a classic symptom of lumbar spinal stenosis (LSS), is associated with neuronal apoptosis. To explore the novel therapeutic target of NIC treatment, we constructed the rat model of NIC by cauda equina compression (CEC) method and collected dorsal root ganglion (DRG) tissues, a region responsible for sensory and motor function, for mRNA sequencing. Bioinformatic analysis of mRNA sequencing indicated that upregulated metallothionein 2A (MT2A), an apoptosis-regulating gene belonging to the metallothionein family, might participate in NIC progression. Activated p38 MAPK mediated motor dysfunction following LSS and it was also found in DRG tissues of rats with NIC. Therefore, we supposed that MT2A might affect NIC progression by regulating p38 MAPK pathway. Then the rat model of NIC was used to explore the exact role of MT2A. Rats at day 7 post-CEC exhibited poorer motor function and had two-fold MT2A expression in DRG tissues compared with rats with sham operation. Co-localization analysis showed that MT2A was highly expressed in neurons, but not in microglia or astrocytes. Subsequently, neurons isolated from DRG tissues of rats were exposed to hypoxia condition (3% O2, 92% N2, 5% CO2) to induce cell damage. Gain of MT2A function in neurons was performed by lentivirus-mediated overexpression. MT2A overexpression inhibited apoptosis by inactivating p38 MAPK in hypoxia-exposed neurons. Our findings indicated that high MT2A expression was related to NIC progression, and MT2A overexpression protected against NIC through inhibiting activated p38 MAPK-mediated neuronal apoptosis in DRG tissues.

MIF-Modulated Spinal Proteins Associated with Persistent Bladder Pain: A Proteomics Study

Bladder pain is a prominent symptom in Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS). We studied spinal mechanisms of bladder pain in mice using a model where repeated activation of intravesical Protease Activated Receptor-4 (PAR4) results in persistent bladder hyperalgesia (BHA) with little or no bladder inflammation. Persistent BHA is mediated by spinal macrophage migration inhibitory factor (MIF), and is associated with changes in lumbosacral proteomics. We investigated the contribution of individual spinal MIF receptors to persistent bladder pain as well as the spinal proteomics changes associated with relief of persistent BHA by spinal MIF antagonism. Female mice with persistent BHA received either intrathecal (i.t.) MIF monoclonal antibodies (mAb) or mouse IgG1 (isotype control antibody). MIF antagonism temporarily reversed persistent BHA (peak effect: 2 h), while control IgG1 had no effect. Moreover, i.t. antagonism of the MIF receptors CD74 and C-X-C chemokine receptor type 4 (CXCR4) partially reversed persistent BHA. For proteomics experiments, four separate groups of mice received either repeated intravesical scrambled peptide and sham i.t. injection (control, no pain group) or repeated intravesical PAR4 and: sham i.t.; isotype IgG1 i.t. (15 μg); or MIF mAb (15 μg). L6-S1 spinal segments were excised 2 h post-injection and examined for proteomics changes using LC-MS/MS. Unbiased proteomics analysis identified and relatively quantified 6739 proteins. We selected proteins that showed significant changes compared to control (no pain group) after intravesical PAR4 (sham or IgG i.t. treatment) and showed no significant change after i.t. MIF antagonism. Six proteins decreased during persistent BHA (V-set transmembrane domain-containing protein 2-like confirmed by immunohistochemistry), while two proteins increased. Spinal MIF antagonism reversed protein changes. Therefore, spinal MIF and MIF receptors mediate persistent BHA and changes in specific spinal proteins. These novel MIF-modulated spinal proteins represent possible new targets to disrupt spinal mechanisms that mediate persistent bladder pain.

The toxicity assessment of phosmet on development, reproduction, and gene expression in Daphnia magna

The use of pesticides to control pests, weeds, and diseases or to regulate plant growth is indispensable in agricultural production. However, the excessive use of these chemicals has led to significant concern about their potential negative impacts on health and the environment. Phosmet is one such pesticide that is commonly used on plants and animals against cold moth, aphids, mites, suckers, and fruit flies. Here, we investigated the effects of phosmet on a model organism, Daphnia magna using acute and chronic toxicity endpoints such as lethality, mobility, genotoxicity, reproduction, and gene expression. We performed survival experiments in six-well plates at seven different concentrations (0.01, 0.1, 1, 10, 25, 50, 100 μM) as well as the control in three replicates. We observed statistically significant mortality rates at 25 µM and above upon 24 h of exposure, and at 1 µM and above following 48 h of exposure. Genotoxicity analysis, reproduction assay and qPCR analysis were carried out at concentrations of 0.01 and 0.1 μM phosmet as these concentrations did not show any lethality. Comet assay showed that exposure to phosmet resulted in significant DNA damage in the cells. Interestingly, 0.1 μM phosmet produced more offspring per adult compared to the control group indicating a hormetic response. Gene expression profiles demonstrated several genes involved in different physiological pathways, including oxidative stress, detoxification, immune system, hypoxia and iron homeostasis. Taken together, our results indicate that phosmet has negative effects on Daphnia magna in a dose- and time-dependent manner and could also induce lethal and physiological toxicities to other aquatic organisms.

NMDA Receptors Regulate Oxidative Damage in Keratinocytes during Complex Regional Pain Syndrome in HaCaT Cells and Male Rats

Complex regional pain syndrome (CRPS), a type of primary chronic pain, occurs following trauma or systemic disease and typically affects the limbs. CRPS-induced pain responses result in vascular, cutaneous, and autonomic nerve alterations, seriously impacting the quality of life of affected individuals. We previously identified the involvement of keratinocyte N-methyl-d-asparagic acid (NMDA) receptor subunit 2 B (NR2B) in both peripheral and central sensitizations in CRPS, although the mechanisms whereby NR2B functions following activation remain unclear. Using an in vivo male rat model of chronic post-ischemia pain (CPIP) and an in vitro oxygen-glucose deprivation/reoxygenation (OGD/R) cell model, we discovered that oxidative injury occurs in rat keratinocytes and HaCaT cells, resulting in reduced cell viability, mitochondrial damage, oxidative damage of nucleotides, and increased apoptosis. In HaCaT cells, OGD/R induced increases in intracellular reactive oxygen species levels and disrupted the balance between oxidation and antioxidation by regulating a series of antioxidant genes. The activation of NMDA receptors via NMDA exacerbated these changes, whereas the inhibition of the NR2B subunit alleviated them. Co-administration of ifenprodil (an NR2B antagonist) and NMDA (an NMDA receptor agonist) during the reoxygenation stage did not result in any significant alterations. Furthermore, intraplantar injection of ifenprodil effectively reversed the altered gene expression that was observed in male CPIP rats, thereby revealing the potential mechanisms underlying the therapeutic effects of peripheral ifenprodil administration in CRPS. Collectively, our findings indicate that keratinocytes undergo oxidative injury in CRPS, with NMDA receptors playing regulatory roles.

Tetrandrine alleviates oxaliplatin-induced mechanical allodynia via modulation of inflammation-related genes

Oxaliplatin, a platinum-based chemotherapy drug, causes neuropathic pain, yet effective pharmacological treatments are lacking. Previously, we showed that tetrandrine (TET), with anti-inflammatory properties, reduces mechanical allodynia in nerve-injured mice. This study explores the effect of TET on oxaliplatin-induced mechanical allodynia and gene changes in mice. Male C57BL/6J mice received oxaliplatin intraperitoneally to induce mechanical allodynia. Post-treatment with TET or vehicle, the mechanical withdrawal threshold (WMT) was assessed using von Frey filaments. TET alleviated oxaliplatin-induced mechanical allodynia. RNA sequencing identified 365 differentially expressed genes (DEGs) in the Control vs. Oxaliplatin group and 229 DEGs in the Oxaliplatin vs. TET group. Pearson correlation analysis of co-regulated DEGs and inflammation-related genes (IRGs) revealed 104 co-regulated inflammation-related genes (Co-IRGs) (|cor| > 0.8, P < 0.01). The top 30 genes in the PPI network were identified. Arg2, Cxcl12, H2-Q6, Kdr, and Nfkbia were highlighted based on ROC analysis. Subsequently, Arg2, Cxcl12, Kdr, and Nfkbia were further verified by qRCR. Immune infiltration analysis indicated increased follicular CD4 T cell infiltration in oxaliplatin-treated mice, reduced by TET. Molecular docking showed strong binding affinity between TET and proteins encoded by Arg2, Cxcl12, Kdr, and Nfkbia. In summary, TET may alleviate oxaliplatin-induced peripheral neuropathy in clinical conditions.

Monoclonal Antibody Targeting CGRP Relieves Cisplatin-Induced Neuropathic Pain by Attenuating Neuroinflammation

Chemotherapy-induced neuropathic pain (CIPN) is a common side effect of antitumor chemotherapeutic agents. It describes a pathological state of pain related to the cumulative dosage of the drug, significantly limiting the efficacy of antitumor treatment. Sofas strategies alleviating CIPN still lack. Calcitonin gene-related peptide (CGRP) is a neuropeptide involved in many pathologic pains. In this study, we explored the effects of CGRP blocking on CIPN and potential mechanisms. Total dose of 20.7 mg/kg cisplatin was used to establish a CIPN mouse model. Mechanical and thermal hypersensitivity was measured using von Frey hairs and tail flick test. Western blot and immunofluorescence were utilized to evaluate the levels of CGRP and activated astrocytes in mouse spinal cord, respectively. In addition, real-time quantitative PCR (RT-qPCR) was used to detect the level of inflammatory cytokines such as IL-6, IL-1β, and NLRP3 in vitro and in vivo. There are markedly increased CGRP expression and astrocyte activation in the spinal cord of mice following cisplatin treatment. Pretreatment with a monoclonal antibody targeting CGRP (ZR8 mAb) effectively reduced cisplatin-induced mechanical hypersensitivity and thermal nociceptive sensitization and attenuated neuroinflammation as marked by downregulated expression of IL-6, IL-1β, and NLRP3 in the mice spinal cord and spleen. Lastly, ZR8 mAb does not interfere with the antitumor effects of cisplatin in tumor-bearing mice. Our findings indicate that neutralizing CGRP with monoclonal antibody could effectively alleviate CIPN by attenuating neuroinflammation. CGRP is a promising therapeutic target for CIPN.

Lumbosacral spinal proteomic changes during PAR4-induced persistent bladder pain

Repeated intravesical activation of protease-activated receptor-4 (PAR4) in mice results in persistent bladder hyperalgesia (BHA). We investigated spinal proteomic changes associated with persistent BHA. Persistent BHA was induced in female mice by repeated (3x; days 0,2,4; n = 9) intravesical instillation of PAR4 activating peptide (PAR4-AP) while scrambled peptide served as the control (no pain; n = 9) group. The threshold to lower abdominal von Frey stimulation was recorded prior to and during treatment. On day 7, L6-S1 spinal segments were excised and examined for proteomic changes using LC-MS/MS. In-depth, unbiased proteomic tandem-mass tag (TMT) analysis identified and relatively quantified 6739 proteins. We identified significant changes with 29 decreasing and 51 increasing proteins in the persistent BHA group and they were associated with neuroprotection, redox modulation, mitochondrial factors, and neuronal-related proteins. In an additional experiment, decreases in protein levels were confirmed by immunohistochemistry for metallothionein 1/2. Our results show that persistent bladder pain is associated with central (spinal) protein changes. Previous work showed that PAR4-induced bladder pain is mediated, at least in part by spinal MIF. Further functional studies of these top changing proteins may lead to the discovery of novel potential therapeutic targets at the spinal level to modulate persistent bladder pain. Future studies will examine the effect of spinal MIF antagonism on PAR4-induced spinal proteomics associated with persistent bladder pain.

Pancreatic ductal adenocarcinoma induces neural injury that promotes a transcriptomic and functional repair signature by peripheral neuroglia

Perineural invasion (PNI) is the phenomenon whereby cancer cells invade the space surrounding nerves. PNI occurs frequently in epithelial malignancies, but is especially characteristic of pancreatic ductal adenocarcinoma (PDAC). The presence of PNI portends an increased incidence of local recurrence, metastasis and poorer overall survival. While interactions between tumor cells and nerves have been investigated, the etiology and initiating cues for PNI development is not well understood. Here, we used digital spatial profiling to reveal changes in the transcriptome and to allow for a functional analysis of neural-supportive cell types present within the tumor-nerve microenvironment of PDAC during PNI. We found that hypertrophic tumor-associated nerves within PDAC express transcriptomic signals of nerve damage including programmed cell death, Schwann cell proliferation signaling pathways, as well as macrophage clearance of apoptotic cell debris by phagocytosis. Moreover, we identified that neural hypertrophic regions have increased local neuroglial cell proliferation which was tracked using EdU tumor labeling in KPC mice, as well as frequent TUNEL positivity, suggestive of a high turnover rate. Functional calcium imaging studies using human PDAC organotypic slices confirmed nerve bundles had neuronal activity, as well as contained NGFR+ cells with high sustained calcium levels, which are indicative of apoptosis. This study reveals a common gene expression pattern that characterizes solid tumor-induced damage to local nerves. These data provide new insights into the pathobiology of the tumor-nerve microenvironment during PDAC as well as other gastrointestinal cancers.

Somatostatin Neurons from Periaqueductal Gray to Medulla Facilitate Neuropathic Pain in Male Mice

Projections from the periaqueductal gray (PAG) to the rostral ventromedial medulla (RVM) are known to engage in descending pain modulation, but how the neural substrates of the PAG-RVM projections contribute to neuropathic pain remains largely unknown. In this study, we showed somatostatin-expressing glutamatergic neurons in the lateral/ventrolateral PAG that facilitate mechanical and thermal hypersensitivity in a mouse model of chemotherapy-induced neuropathic pain. We found that these neurons form direct excitatory connections with neurons in the RVM region. Inhibition of this PAG-RVM projection alleviates mechanical and thermal hypersensitivity associated with neuropathy, whereas its activation enhances hypersensitivity in the mice. Thus, our findings revealed that somatostatin neurons within the PAG-RVM axial are crucial for descending pain facilitation and can potentially be exploited as a useful therapeutic target for neuropathic pain. PERSPECTIVE: We report the profound contribution of somatostatin neurons within the PAG-RVM projections to descending pain facilitation underlying neuropathic pain. These results may help to develop central therapeutic strategies for neuropathic pain.

Neuroprotective mechanism of Ajugarin-I against Vincristine-Induced neuropathic pain via regulation of Nrf2/NF-κB and Bcl2 signalling

Vincristine (VCR) is a well-known chemotherapeutic agent that frequently triggers neuropathic pain. Ajugarin-I (Aju-I) isolated from Ajuga bracteosa exerts antioxidant, anti-inflammatory, and neuroprotective properties. The present study was designed to investigate the ameliorative potential of Aju-I against VCR-induced neuropathic pain and explored the underlying mechanism involved. The neuroprotective potential of Aju-I was first confirmed against hydrogen peroxide (H₂O₂)-induced cytotoxicity and oxidative stress in PC12 cells. For neuropathic pain induction, vincristine was given intraperitoneally (i.p.) into adult male albino mice (BALB/c) of the same age (8-12 weeks old) for 10 days (days 1-10). Aju-I (1 and 5 mg/kg) doses were administered from day 11 to 21 intraperitoneally (i.p.) after the neuropathic induction. Initially, behavioral tests such as thermal hyperalgesia, mechanical allodynia, and cold allodynia were performed to investigate the antinociceptive potential of Ajugarin-I (1 and 5 mg/kg, b.w). The nuclear factor-erythroid factor 2-related factor 2(Nrf2), nuclear factor-κB (NF-κB), BCL2-associated × protein (Bax), and B-cell-lymphoma-2 (Bcl-2) signaling proteins were determined by immunohistochemistry and western blot. Additionally, inflammatory cytokines, antioxidant, and oxidative stress parameters were also measured in the spinal cord and sciatic nerve. The behavioral results demonstrated that Aju-I (5 mg/kg) markedly alleviated VCR-induced neuropathic pain behaviors including hyperalgesia and allodynia. It reversed the histological alterations caused by VCR in the sciatic nerve, spinal cord, and brain. It significantly alleviated oxidative stress and inflammation by regulating the immunoreactivity of Nrf2/NF-κB signaling. It suppressed apoptosis by regulating the immunoreactivity of Bcl-2/Bax and Caspase-3. The flow cytometry and comet analysis also confirmed its anti-apoptotic potential. It considerably improved the antioxidant status and mitigated VCR-induced inflammatory cytokines. High-performance liquid chromatography (HPLC) analysis indicated that Aju-I crosses the blood-brain barrier (BBB) and penetrated the brain tissue. These findings suggest that Aju-I treatment inhibited vincristine-induced neuropathy via regulation of Nrf2/NF-κB and Bcl2 signaling.

Pancreatic Ductal Adenocarcinoma Induces Neural Injury that Promotes a Transcriptomic and Functional Repair Signature by Peripheral Neuroglia

Perineural invasion (PNI) is the phenomenon whereby cancer cells invade the space surrounding nerves. PNI occurs frequently in epithelial malignancies, but is especially characteristic of pancreatic ductal adenocarcinoma (PDAC). The presence of PNI portends an increased incidence of local recurrence, metastasis and poorer overall survival. While interactions between tumor cells and nerves have been investigated, the etiology and initiating cues for PNI development is not well understood. Here, we used digital spatial profiling to reveal changes in the transcriptome and to allow for a functional analysis of neural-supportive cell types present within the tumor-nerve microenvironment of PDAC during PNI. We found that hypertrophic tumor-associated nerves within PDAC express transcriptomic signals of nerve damage including programmed cell death, Schwann cell proliferation signaling pathways, as well as macrophage clearance of apoptotic cell debris by phagocytosis. Moreover, we identified that neural hypertrophic regions have increased local neuroglial cell proliferation which was tracked using EdU tumor labeling in KPC mice. This study reveals a common gene expression pattern that characterizes solid tumor-induced damage to local nerves. These data provide new insights into the pathobiology of the tumor-nerve microenvironment during PDAC as well as other gastrointestinal cancers.

Metallothionein-2: An emerging target in inflammatory diseases and cancers

Metallothionein-2 (MT-2) was originally discovered as a mediator of zinc homeostasis and cadmium detoxification. However, MT-2 has recently received increased attention because altered expression of MT-2 is closely related to various diseases such as asthma and cancers. Several pharmacological strategies have been developed to inhibit or modify MT-2, revealing its potential as drug target in diseases. Therefore, a better understanding of the mechanisms of MT-2 action is warranted to improve drug development for potential clinical applications. In this review, we highlight recent advances in determining the protein structure, regulation, binding partners, and new functions of MT-2 in inflammatory diseases and cancers.

Animal models of chemotherapy-induced peripheral neuropathy for hematological malignancies: A review

Chemotherapy is one of the main treatments for hematologic malignancies. However, chemotherapy-induced peripheral neuropathy (CIPN) is one of the most common long-term toxic reactions in chemotherapy, and the occurrence of CIPN affects patients' quality of life and can cause interruption of chemotherapy in severe cases, thus reducing the efficacy of chemotherapy. We currently summarize the existing CIPN animal models, including the characteristics of several common animal models such as bortezomib-induced peripheral neuropathy, vincristine-induced peripheral neuropathy, and oxaliplatin-induced peripheral neuropathy. It was found that CIPN may lead to behavioral, histopathological, and neurophysiological changes inducing peripheral neuropathy. However, the mechanism of CIPN has not been fully elucidated, especially the prevention and treatment protocols need to be improved. Therefore, this review article summarizes the progress of research on CIPN animal models and the possible mechanisms and treatment of CIPN.

Positive interaction between GPER and β-alanine in the dorsal root ganglion uncovers potential mechanisms: mediating continuous neuronal sensitization and neuroinflammation responses in neuropathic pain

Background

The pathogenesis of neuropathic pain and the reasons for the prolonged unhealing remain unknown. Increasing evidence suggests that sex oestrogen differences play a role in pain sensitivity, but few studies have focused on the oestrogen receptor which may be an important molecular component contributing to peripheral pain transduction. We aimed to investigate the impact of oestrogen receptors on the nociceptive neuronal response in the dorsal root ganglion (DRG) and spinal dorsal horn using a spared nerve injury (SNI) rat model of chronic pain.

Methods

We intrathecally (i.t.) administered a class of oestrogen receptor antagonists and agonists intrathecal (i.t.) administrated to male rats with SNI or normal rats to identify the main receptor. Moreover, we assessed genes identified through genomic metabolic analysis to determine the key metabolism point and elucidate potential mechanisms mediating continuous neuronal sensitization and neuroinflammatory responses in neuropathic pain. The excitability of DRG neurons was detected using the patch-clamp technique. Primary culture was used to extract microglia and DRG neurons, and siRNA transfection was used to silence receptor protein expression. Immunofluorescence, Western blotting, RT-PCR and behavioural testing were used to assess the expression, cellular distribution, and actions of the main receptor and its related signalling molecules.

Results

Increasing the expression and function of G protein-coupled oestrogen receptor (GPER), but not oestrogen receptor-α (ERα) and oestrogen receptor-β (ERβ), in the DRG neuron and microglia, but not the dorsal spinal cord, contributed to SNI-induced neuronal sensitization. Inhibiting GPER expression in the DRG alleviated SNI-induced pain behaviours and neuroinflammation by simultaneously downregulating iNOS, IL-1β and IL-6 expression and restoring GABAα2 expression. Additionally, the positive interaction between GPER and β-alanine and subsequent β-alanine accumulation enhances pain sensation and promotes chronic pain development.

Conclusion

GPER activation in the DRG induces a positive association between β-alanine with iNOS, IL-1β and IL-6 expression and represses GABAα2 involved in post-SNI neuropathic pain development. Blocking GPER and eliminating β-alanine in the DRG neurons and microglia may prevent neuropathic pain development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02524-9.