Overexpression of suppressor of cytokine signaling 3 in dorsal root ganglion attenuates cancer-induced pain in rats

GluR2 overexpression in ACC glutamatergic neurons alleviates cancer-induced bone pain in rats

BACKGROUND

Cancer-induced bone pain (CIBP) is a complex chronic pain with poorly understood mechanisms. The anterior cingulate cortex (ACC) plays a critical role in processing and modulating chronic pain. This study investigates how the GluR2 receptors (calcium impermeable AMPA receptors) in ACC glutamatergic neurons regulate CIBP.

METHODS

The CIBP models were established by injecting Walker 256 cells into the tibia of SD rats. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) were used as indicators of hyperalgesia. The immunofluorescence staining was employed to detect the expression of c-Fos in ACC and identify the subtypes of co-labeled c-Fos+ neurons. Real-time monitoring of calcium activity in ACC glutamatergic neurons was achieved through the fiber photometry. The excitability of glutamatergic neurons in ACC was modulated using chemicalgenetics and optogenetics techniques. The expression of GluR2 at the mRNA and protein level in ACC were assessed using RT-qPCR and Western blotting.

RESULTS

There were significant reductions in PWT and PWL of CIBP rats after Walker 256 cell injection. The ACC of CIBP rats showed increased c-Fos expression compared to sham rats, with mainly activated c-Fos co-localized with glutamatergic neurons. Optogenetic or chemogenetic activation of ACC glutamatergic neurons led to increased hyperalgesia in sham rats, while suppression of their activity alleviated hyperalgesia in CIBP rats. Calcium activity in ACC glutamatergic neurons of CIBP rats was increased with suprathreshold stimulation of von Frey filament. Notably, surface GluR2 protein and mRNA were reduced in ACC of CIBP rats. Furthermore, overexpression of GluR2 by AAV-CaMKII-GluR2 injection was decreased c-Fos expression in ACC and alleviated hyperalgesia in CIBP rats.

CONCLUSIONS

These findings suggest that decreased surface GluR2 receptors in ACC glutamatergic neurons contribute to calcium activity and excessive excitability, thereby inducing CIBP in rats. Conversely, GluR2 overexpression in ACC glutamatergic neurons alleviates CIBP in rats. This study provides a new potential therapeutic approach for targeting the GluR2 receptor to alleviate CIBP for cancer patients.

Molecular targets in bone cancer pain: a systematic review of inflammatory cytokines

Bone cancer pain (BCP) profoundly impacts patient's quality of life, demanding more effective pain management strategies. The aim of this systematic review was to investigate the role of inflammatory cytokines as potential molecular targets in BCP. A systematic search for animal rodent models of bone cancer pain studies was conducted in PubMed, Scopus, and Web of Science. Methodological quality and risk of bias were assessed using the SYRCLE RoB tool. Twenty-five articles met the inclusion criteria, comprising animal studies investigating molecular targets related to inflammatory cytokines in BCP. A low to moderate risk of bias was reported. Key findings in 23 manuscripts revealed upregulated classic pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-17, IL-18, IL-33) and chemokines in the spinal cord, periaqueductal gray, and dorsal root ganglia. Interventions targeting these cytokines consistently mitigated pain behaviors. Additionally, it was demonstrated that glial cells, due to their involvement in the release of inflammatory cytokines, emerged as significant contributors to BCP. This systematic review underscores the significance of inflammatory cytokines as potential molecular targets for alleviating BCP. It emphasizes the promise of targeted interventions and advocates for further research to translate these findings into effective therapeutic strategies. Ultimately, this approach holds the potential to enhance the patient's quality of life.

Neuropathic pain development following nerve injury is mediated by SOX11-ARID1A-SOCS3 transcriptional regulation in the spinal cord

BACKGROUND

Neuropathic pain, a complex condition originating from nervous system damage, remains a significant clinical challenge due to limited understanding of its underlying mechanisms. Recent research highlights the SOX11 transcription factor, known for its role in nervous system development, as a crucial player in neuropathic pain development and maintenance. This study investigates the role of the SOX11-ARID1A-SOCS3 pathway in neuropathic pain modulation within the spinal cord.

METHODS AND RESULTS

Using a spinal nerve ligation (SNL) model in mice, we observed a significant upregulation of Sox11 in the spinal cord dorsal horn post-injury. Intrathecal administration of Sox11 shRNA mitigated SNL-induced neuropathic pain behaviors, including mechanical allodynia and heat hyperalgesia. Further, we demonstrated that Sox11 regulates neuropathic pain via transcriptional control of ARID1A, with subsequent modulation of SOCS3 expression. Knockdown of ARID1A and SOCS3 via shRNA resulted in alleviation of Sox11-induced pain sensitization. Additionally, Sox11 overexpression led to an increase in ARID1A binding to the SOCS3 promoter, enhancing chromatin accessibility and indicating a direct regulatory relationship. These findings were further supported by in vitro luciferase reporter assays and chromatin accessibility analysis.

CONCLUSIONS

The SOX11-ARID1A-SOCS3 pathway plays a pivotal role in the development and maintenance of neuropathic pain. Sox11 acts as a master regulator, modulating ARID1A, which in turn influences SOCS3 expression, thereby contributing to the modulation of neuropathic pain. These findings provide a deeper understanding of the molecular mechanisms underlying neuropathic pain and highlight potential therapeutic targets for its treatment. The differential regulation of this pathway in the spinal cord and dorsal root ganglia (DRG) underscores its complexity and the need for targeted therapeutic strategies.

LncRNA NONRATT014888.2 contributes to cancer-induced bone pain through downregulation of natriuretic peptide receptor 3 in rats

Long noncoding RNA (lncRNA) is implicated in both cancer development and pain process. However, the role of lncRNA in the development of cancer-induced bone pain (CIBP) is unclear. LncRNA NONRATT014888.2 is highly expressed in tibia related dorsal root ganglions (DRGs) in CIBP rats which function is unknown. CIBP was induced by injection of Walker 256 mammary gland tumor cells into the tibia canal of female SD rats. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) of rats were measured. Down-regulation of NONRATT014888.2 by siRNA in CIBP rats markedly attenuated hind-paw mechanical pain hypersensitivity. LncRNA-predicted target mRNAs analysis and mRNA sequencing results cued Socs3, Npr3 were related with NONRATT014888.2. Intrathecal injection of NONRATT014888.2-siR206 upregulated Npr3 both in mRNA and protein level. Npr3 was co-expressed in NONRATT014888.2-positive DRGs neurons and mainly located in cytoplasm, but not in Glial fibrillary acidic protein (GFAP)-positive cells. Intrathecal injection of ADV-Npr3 upregulated Npr3 expression and enhanced the PWT of CIBP rats. Our results suggest that upregulated lncRNA NONRATT014888.2 contributed to hyperalgesia in CIBP rats, and the mechanism may through downregulation of Npr3.

Oral Cancer Cells Release Vesicles that Cause Pain

Oral cancer pain is attributed to the release from cancers of mediators that sensitize and activate sensory neurons. Intraplantar injection of conditioned media (CM) from human tongue cancer cell line HSC-3 or OSC-20 evokes nociceptive behavior. By contrast, CM from noncancer cell lines, DOK, and HaCaT are non-nociceptive. Pain mediators are carried by extracellular vesicles (EVs) released from cancer cells. Depletion of EVs from cancer cell line CM reverses mechanical allodynia and thermal hyperalgesia. CM from non-nociceptive cell lines become nociceptive when reconstituted with HSC-3 EVs. Two miRNAs (hsa-miR-21-5p and hsa-miR-221-3p) are identified that are present in increased abundance in EVs from HSC-3 and OSC-20 CM compared to HaCaT CM. The miRNA target genes suggest potential involvement in oral cancer pain of the toll like receptor 7 (TLR7) and 8 (TLR8) pathways, as well as signaling through interleukin 6 cytokine family signal transducer receptor (gp130, encoded by IL6ST) and colony stimulating factor receptor (G-CSFR, encoded by CSF3R), Janus kinase and signal transducer and activator of transcription 3 (JAK/STAT3). These studies confirm the recent discovery of the role of cancer EVs in pain and add to the repertoire of algesic and analgesic cancer pain mediators and pathways that contribute to oral cancer pain.

The optimized drug delivery systems of treating cancer bone metastatic osteolysis with nanomaterials

Some cancers such as human breast cancer, prostate cancer, and lung cancer easily metastasize to bone, leading to osteolysis and bone destruction accompanied by a complicated microenvironment. Systemic administration of bisphosphonates (BP) or denosumab is the routine therapy for osteolysis but with non-negligible side effects such as mandibular osteonecrosis and hypocalcemia. Thus, it is imperative to exploit optimized drug delivery systems, and some novel nanotechnology and nanomaterials have opened new horizons for scientists. Targeted and local drug delivery systems can optimize biodistribution depending on nanoparticles (NPs) or microspheres (MS) and implantable biomaterials with the controllable property. Drug delivery kinetics can be optimized by smart and sustained/local drug delivery systems for responsive delivery and sustained delivery. These delicately fabricated drug delivery systems with special matrix, structure, morphology, and modification can minimize unexpected toxicity caused by systemic delivery and achieve desired effects through integrating multiple drugs or multiple functions. This review summarized recent studies about optimized drug delivery systems for the treatment of cancer metastatic osteolysis, aimed at giving some inspiration in designing efficient multifunctional drug delivery systems.

Identification of lncRNA and mRNA expression profiles in dorsal root ganglion in rats with cancer-induced bone pain

BACKGROUND

Cancer-induced bone pain (CIBP) is one of the most severe types of chronic pain which the involved mechanisms are largely unknown. LncRNA has been found to play critical roles in chronic pain. However, its function in peripheral nervous system in CIBP remains unknown. Identifying the different lncRNA expression pattern is essential for understanding the genetic mechanisms underlying the pathogenesis of CIBP.

METHODS

The model was induced by injection of Walker 256 cells into the rat tibia canal. Behavior tests and X-ray microtomography (MicroCT) analysis were performed to verify the model's establishment. L2-L5 DRGs were harvested at 14-day post operation and the differential lncRNA and mRNA expression patterns were investigated by microarray analyses. RT-qPCR analysis and RNA interference were performed for expression and function verifications. Bioinformatics analysis was conducted for further function study.

RESULTS

CIBP rats showed hyperalgesia and the MicroCT analysis showed tibia destruction. A total of 73 lncRNAs and 187 mRNAs were dysregulated. The expressions of several lncRNAs and mRNAs were validated by RT-qPCR experiment. Biological analyses showed that the changed mRNAs were mainly related to cellular and single-organism process, cell and cell part, binding function and immune system pathway. The top 30 lncRNA-predicted mRNAs are mainly related to peroxisome, DNA-dependent DNA replication, double-stranded RNA binding, tuberculosis and purine metabolism. 56 lncRNAs (30 downregulated and 26 upregulated) and 179 DEGs (35 downregulated and 144 upregulated) have a significant correlation and constructed a co-expression network. Downregulation of lncRNA NONRATT021203.2 by siRNA intrathecal injection increased PWL and WBD in CIBP rats, alleviating cancer induced bone hyperalgesia.

CONCLUSION

LncRNA played important roles in regulation of CIBP or mRNA expression in peripheral neuropathy in CIBP. These alterd mRNAs and lncRNAs might be potential therapeutic targets for the treatment of CIBP.

Usefulness of the measurement of neurite outgrowth of primary sensory neurons to study cancer-related painful complications

Abnormal outgrowth of sensory nerves is one of the important contributors to pain associated with cancer and its treatments. Primary neuronal cultures derived from dorsal root ganglia (DRG) have been widely used to study pain-associated signal transduction and electrical activity of sensory nerves. However, there are only a few studies using primary DRG neuronal culture to investigate neurite outgrowth alterations due to underlying cancer-related factors and chemotherapeutic agents. In this study, primary DRG sensory neurons derived from mouse, non-human primate, and human were established in serum and growth factor-free conditions. A bovine serum albumin gradient centrifugation method improved the separation of sensory neurons from satellite cells. The purified DRG neurons were able to maintain their heterogeneous subpopulations, and displayed an increase in neurite growth when exposed to cancer-derived conditioned medium, while they showed a reduction in neurite length when treated with a neurotoxic chemotherapeutic agent. Additionally, a semi-automated quantification method was developed to measure neurite length in an accurate and time-efficient manner. Finally, these exogenous factors altered the gene expression patterns of murine primary sensory neurons, which are related to nerve growth, and neuro-inflammatory pain and nociceptor development. Together, the primary DRG neuronal culture in combination with a semi-automated quantification method can be a useful tool for further understanding the impact of exogenous factors on the growth of sensory nerve fibers and gene expression changes in sensory neurons.

Distinct Gene Expression Patterns of Ion Channels and Cytokines in Rat Primary Sensory Neurons During Development of Bone Cancer and Cancer Pain

Cancer and cancer pain processes a major clinical challenge and the underlined mechanisms of pathogenesis remain elusive. We examined the specific changes in the transcriptomic profiles in the dorsal root ganglion (DRG) neurons of rats with bone cancer and bone cancer pain (BCP) using RNA sequencing technology. The bone cancer and BCP was induced by tumor cells implantation (TCI) into the tibia bone cavity in adult female rats. One week after treatment, TCI caused up- and down-regulation of thousands of genes in DRG. These genes were mainly involved in the immune process, inflammatory response, and intracellular signaling transduction of carbohydrate and cytokine. The cAMP and calcium signaling pathways were the major processes in the initial responses. Differentially expressed gene (DEG) analysis further showed that the genes for ion channels increased during day 1-7, while the genes for cytokine signaling pathways sustainedly increased during day 7-14 after TCI. The time courses of gene expression for ion channels and cytokines support their distinct roles in the early induction and late maintenance of BCP development. In addition, among the top 500 up- and down-regulated genes, 80-90% were unique for bone cancer pain as well as neuropathic and inflammatory pain, while less than 2% were shared among the three different forms of pain. This study reveals the uniqueness of mechanisms underlying bone cancer with pain, which is, to a large extent, differently from pain after acute inflammatory and nerve injury and provides novel potential targets of DEGs for bone cancer with pain.

Transcriptomic sex differences in sensory neuronal populations of mice

Many chronic pain conditions show sex differences in their epidemiology. This could be attributed to sex-dependent differential expression of genes (DEGs) involved in nociceptive pathways, including sensory neurons. This study aimed to identify sex-dependent DEGs in estrous female versus male sensory neurons, which were prepared by using different approaches and ganglion types. RNA-seq on non-purified sensory neuronal preparations, such as whole dorsal root ganglion (DRG) and hindpaw tissues, revealed only a few sex-dependent DEGs. Sensory neuron purification increased numbers of sex-dependent DEGs. These DEG sets were substantially influenced by preparation approaches and ganglion types [DRG vs trigeminal ganglia (TG)]. Percoll-gradient enriched DRG and TG neuronal fractions produced distinct sex-dependent DEG groups. We next isolated a subset of sensory neurons by sorting DRG neurons back-labeled from paw and thigh muscle. These neurons have a unique sex-dependent DEG set, yet there is similarity in biological processes linked to these different groups of sex-dependent DEGs. Female-predominant DEGs in sensory neurons relate to inflammatory, synaptic transmission and extracellular matrix reorganization processes that could exacerbate neuro-inflammation severity, especially in TG. Male-selective DEGs were linked to oxidative phosphorylation and protein/molecule metabolism and production. Our findings catalog preparation-dependent sex differences in neuronal gene expressions in sensory ganglia.

Upregulation of lncRNA-NONRATT021203.2 in the dorsal root ganglion contributes to cancer-induced pain via CXCL9 in rats

Cancer-induced pain (CIP) is a kind of chronic pain that occurs during cancer progression over time. However, the mechanisms are largely unknown, and clinical treatment remains challenging. LncRNAs have been reported to play critical roles in various biological processes, including chronic pain. The aim of our study was to investigate whether lncRNAs participate in the development of CIP by regulating the expression levels of some molecules related to pain modulation. The CIP model was established by injecting Walker 256 mammary gland tumor cells into the tibial canal of rats. In this study, we found that lncRNA-NONRATT021203.2 was increased in the CIP rats and that lncRNA-NONRATT021203.2-siRNA could relieve hyperalgesia in these rats. For elucidation of the underlying mechanism, we showed that lncRNA-NONRATT021203.2 could target C-X-C motif chemokine ligand 9 (CXCL9), which was increased in the CIP rats, and that CXCL9-siRNA could relieve hyperalgesia. At the same time, silencing lncRNA-NONRATT021203.2 expression decreased the mRNA and protein levels of CXCL9. Immunofluorescence analysis showed that CXCL9 was mainly expressed in the CGRP-positive and IB4-positive DRG neurons. Further research showed that lncRNA-NONRATT021203.2 and CXCL9 were colocalized in the DRG neurons. Our data suggested that lncRNA-NONRATT021203.2 participated in the CIP in rats and likely mediates the upregulation of CXCL9. The present study provided us with a new potential target for the clinical treatment of cancer-induced pain.

Lidocaine Potentiates SOCS3 to Attenuate Inflammation in Microglia and Suppress Neuropathic Pain

Lidocaine is one of the typical local anesthetics that are frequently used in the peripheral nerve blocks and pain management. Emerging evidence have shown that lidocaine may exert anti-inflammatory effect involving neuropathic pain. However, the effect and underlying mechanism of lidocaine in suppressing neuroinflammation in neuropathic pain are incompletely revealed. In this study, effects of lidocaine on the suppressors of cytokine-signaling protein 3 (SOCS3) in microglia are investigated in chronic constriction injury (CCI) rat model and lipopolysaccharide (LPS)-stimulated BV-2 cells. It was shown that intrathecal injection of lidocaine substantially alleviated CCI-induced neuropathic pain, as reflected by the decreased thermal latency and mechanical threshold. Lidocaine reduced the CCI-evoked spinal injury and cell apoptosis. CCI induced an significant increase of IBA1+ microglia accompanied by the increase of inflammatory cytokines IL-6 and IL-1β, which were suppressed after lidocaine administration. SOCS3 expression in IBA1+ microglia was notably upregulated in response to lidocaine injection, which presented in a similar pattern in LPS-activated BV-2 cells. Furthermore, lidocaine upregulated SOCS3 expression dependent of pCREB, and CREB silencing greatly discounted this effect. The intrathecal injection of lentiviral vectors LV-SOCS3 efficiently alleviated CCI-evoked neuropathic pain and reduced spinal IBA1+ microglia. SOCS3 overexpression contributed to the inhibition of neuroinflammation by decreasing the expression and activation of p38 MAPK and NF-κB stimulated by LPS. Collectively, lidocaine promoted the SOCS3 expression in microglia, in turn leading to suppression of IBA1+ microglia accumulation and p38 MAPK and NF-κB, which may expand our understanding on lidocaine in suppressing neuroinflammation and neuropathic pain.

Upregulation of bone morphogenetic protein 2 ( Bmp2) in dorsal root ganglion in a rat model of bone cancer pain

Bone cancer pain is one of the most severe and intractable complications in patients suffering from primary or metastatic bone cancer and profoundly compromises the quality of life. Emerging evidence indicates that the dorsal root ganglion play an integral role in the modulation of pain hypersensitivity. However, the underlying molecular mechanisms during dorsal root ganglion-mediated bone cancer pain remain elusive. In this study, RNA-sequencing was used to detect the differentially expressed genes in dorsal root ganglion neurons of a rat bone cancer pain model established by intratibial inoculation of Walker 256 breast cancer cells. Gene ontology and Kyoto Encyclopedia of Genes and Genomes analysis showed that the differentially expressed genes (fold change > 1.5; false discovery rate < 0.05) were enriched in the bone morphogenetic protein (BMP) signaling pathway, transforming growth factor-β signaling pathway, and positive regulation of cartilage development. Importantly, serum deprivation-response protein (Sdpr), hephaestin (Heph), transthyretin (Ttr), insulin receptor substrate 1 (Irs1), connective tissue growth factor (Ctgf ), and Bmp2 genes were associated with bone pain and degeneration. Of note, Bmp2, a pleiotropic and secreted molecule mediating pain and inflammation, was one of the most significantly upregulated genes in dorsal root ganglion neurons in this bone cancer pain model. Consistent with these data, upregulation of Bmp2 in the bone cancer pain model was validated by immunohistochemistry, real-time quantitative polymerase chain reaction, and western blotting. Importantly, intrathecal administration of siRNA significantly reduced Bmp2 transcription and ameliorated bone cancer pain in rat as shown by paw withdrawal mechanical threshold and spontaneous and movement-evoked pain-like behaviors. In conclusion, we have characterized the comprehensive gene expression profile of dorsal root ganglion from a bone cancer pain rat model by RNA-sequencing and identified Bmp2 as a potential therapeutic target for bone cancer pain treatment.

Expression profiles of TRPV1, TRPV4, TLR4 and ERK1/2 in the dorsal root ganglionic neurons of a cancer-induced neuropathy rat model

Background

The spread of tumors through neural routes is common in several types of cancer in which patients suffer from a moderate-to-severe neuropathy, neural damage and a distorted quality of life. Here we aim to examine the expression profiles of transient receptor potential vanilloid 1 (TRPV1) and of transient receptor potential vanilloid 4 (TRPV4), toll-like receptor 4 (TLR4) and extracellular signal-regulated kinase (ERK1/2), and to assess the possible therapeutic strategies through blockade of transient receptor potential (TRP) channels.

Methods

Cancer was induced within the sciatic nerves of male Copenhagen rats, and tissues from dorsal root ganglia (DRG) were collected and used for measurements of immunofluorescence and Western blotting. The TRPV1 antagonist capsazepine, the selective TRPV4 antagonist HC-067047 and the calcium ions inhibitor ruthenium red were used to treat thermal and/or mechanical hyperalgesia.

Results

Transient receptor potential vanilloid 1 showed a lower expression in DRGs on days 7 and 14. The expression of TRPV4, TLR4 and ERK1/2 showed an increase on day 3 then a decrease on days 7 and 14. TRPV1 and TLR4 as well as TRPV4 and ERK1/2 co-existed on the same neuronal cells. The neuropathic pain was reversed in dose-dependent manners by using the TRP antagonists and the calcium ions inhibitor.

Conclusion

The decreased expression of TRPV1 and TRPV4 is associated with high activation. The increased expression of TLR4 and ERK1/2 reveals earlier immune response and tumor progression, respectively, and their ultimate decrease is an indicator of nerve damage. We studied the possible role of TRPV1 and TRPV4 in transducing cancer-induced hyperalgesia. The possible treatment strategies of cancer-induced thermal and/or mechanical hyperalgesia using capsazepine, HC-067047 and ruthenium red are examined.

Prenatal maternal stress induces visceral hypersensitivity of adult rat offspring through activation of cystathionine-β-synthase signaling in primary sensory neurons

Irritable bowel syndrome is a disorder of unknown etiology characterized by widespread, chronic abdominal pain associated with altered bowel movements. Increasing amounts of evidence indicate that stressors presented during gestational periods could have long-term effects on the offspring's tissue structure and function, which may predispose to gastrointestinal diseases. The aim of the present study is to determine whether prenatal maternal stressis a adverse factor affecting gastrointestinal sensitivity and to investigate possible mechanisms underlying prenatal maternal stress-induced visceral hypersensitivity in adult offspring. Prenatal maternal stress was induced in pregnant Sprague-Dawley rats by exposure to heterotypic intermitent stress from gestational day 7 to delivery. Prenatal maternal stress significantly increased visceromotor response to colorectal distention in adult offspring from the age of 6 weeks to 10 weeks. Prenatal maternal stress also enhanced neuronal excitability including depolarization of resting membrane potentials, reduction in rheobase, and an increase in the number of action potentials evoked by 2× and 3× rheobase current stimultion of colon-specific dorsal root ganglion neurons. Prenatal maternal stress remarkably enhanced expression of cystathionine-β-synthase and Nav1.7 in T13-L2 thoracolumbar dorsal root ganglions both at protein and mRNA levels. Intraperitoneal injection of aminooxyacetic acid, an inhibitor of cystathionine-β-synthase, attenuated prenatal maternal stress-induced visceral hypersensitivity in a dose-dependent manner. A consecutive seven-day administration of aminooxyacetic acid reversed the hyperexcitability of colon-specific dorsal root ganglion neurons and markedly reduced Nav1.7 expression. These results indicate that the presence of multiple psychophysical stressors during pregnancy is associated with visceral hypersensitivity in offspring, which is likely mediated by an upregualtion of cystathionine-β-synthase and Nav1.7 expression. Prenatal maternal stress might be a significant contributor to irritable bowel syndrome, and cystathionine-β-synthase might be a potential target for treatment for chronic visceral hypersensitivity in patients with irritable bowel syndrome.

Upregulation of Spinal Voltage-Dependent Anion Channel 1 Contributes to Bone Cancer Pain Hypersensitivity in Rats

Voltage-dependent anion channel 1 (VDAC1) is thought to contribute to the progression of tumor development. However, whether VDAC1 contributes to bone cancer pain remains unknown. In this study, we found that the expression of VDAC1 was upregulated in the L2-5 segments of the spinal dorsal horn at 2 and 3 weeks after injection of tumor cells into the tibial cavity. Intrathecal injection of a VDAC1 inhibitor significantly reversed the pain hypersensitivity and reduced the over-expression of Toll-like receptor 4 (TLR4). Intrathecal injection of minocycline, an inhibitor of microglia, also attenuated the pain hypersensitivity of rat models of bone cancer pain. These results suggest that VDAC1 plays a significant role in the development of complicated cancer pain, possibly by regulating the expression of TLR4.