Spinal IFN-γ-induced protein-10 (CXCL10) mediates metastatic breast cancer-induced bone pain by activation of microglia in rat models

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.

Targeting Members of the Chemokine Family as a Novel Approach to Treating Neuropathic Pain

Neuropathic pain is a debilitating condition that affects millions of people worldwide. Numerous studies indicate that this type of pain is a chronic condition with a complex mechanism that tends to worsen over time, leading to a significant deterioration in patients' quality of life and issues like depression, disability, and disturbed sleep. Presently used analgesics are not effective enough in neuropathy treatment and may cause many side effects due to the high doses needed. In recent years, many researchers have pointed to the important role of chemokines not only in the development and maintenance of neuropathy but also in the effectiveness of analgesic drugs. Currently, approximately 50 chemokines are known to act through 20 different seven-transmembrane G-protein-coupled receptors located on the surface of neuronal, glial, and immune cells. Data from recent years clearly indicate that more chemokines than initially thought (CCL1/2/3/5/7/8/9/11, CXCL3/9/10/12/13/14/17; XCL1, CX3CL1) have pronociceptive properties; therefore, blocking their action by using neutralizing antibodies, inhibiting their synthesis, or blocking their receptors brings neuropathic pain relief. Several of them (CCL1/2/3/7/9/XCL1) have been shown to be able to reduce opioid drug effectiveness in neuropathy, and neutralizing antibodies against them can restore morphine and/or buprenorphine analgesia. The latest research provides irrefutable evidence that chemokine receptors are promising targets for pharmacotherapy; chemokine receptor antagonists can relieve pain of different etiologies, and most of them are able to enhance opioid analgesia, for example, the blockade of CCR1 (J113863), CCR2 (RS504393), CCR3 (SB328437), CCR4 (C021), CCR5 (maraviroc/AZD5672/TAK-220), CXCR2 (NVPCXCR220/SB225002), CXCR3 (NBI-74330/AMG487), CXCR4 (AMD3100/AMD3465), and XCR1 (vMIP-II). Recent research has shown that multitarget antagonists of chemokine receptors, such as CCR2/5 (cenicriviroc), CXCR1/2 (reparixin), and CCR2/CCR5/CCR8 (RAP-103), are also very effective painkillers. A multidirectional strategy based on the modulation of neuronal-glial-immune interactions by changing the activity of the chemokine family can significantly improve the quality of life of patients suffering from neuropathic pain. However, members of the chemokine family are still underestimated pharmacological targets for pain treatment. In this article, we review the literature and provide new insights into the role of chemokines and their receptors in neuropathic pain.

Cyclin D1 mediates pain behaviour in a rat model of breast cancer-induced bone pain by a mechanism involving regulation of the proliferation of spinal microglia

Aims

The involvement of cyclin D1 in the proliferation of microglia, and the generation and maintenance of bone cancer pain (BCP), have not yet been clarified. We investigated the expression of microglia and cyclin D1, and the influences of cyclin D1 on pain threshold.

Methods

Female Sprague Dawley (SD) rats were used to establish a rat model of BCP, and the messenger RNA (mRNA) and protein expression of ionized calcium binding adaptor molecule 1 (IBA1) and cyclin D1 were detected by reverse transcription-polymerase chain reaction (RT-PCR) and western blot, respectively. The proliferation of spinal microglia was detected by immunohistochemistry. The pain behaviour test was assessed by quantification of spontaneous flinches, limb use, and guarding during forced ambulation, mechanical paw withdrawal threshold, and thermal paw withdrawal latency.

Results

IBA1 and cyclin D1 in the ipsilateral spinal horn increased in a time-dependent fashion. Spinal microglia proliferated in BCP rats. The microglia inhibitor minocycline attenuated the pain behaviour in BCP rats. The cyclin-dependent kinase inhibitor flavopiridol inhibited the proliferation of spinal microglia, and was associated with an improvement in pain behaviour in BCP rats.

Conclusion

Our results revealed that the inhibition of spinal microglial proliferation was associated with a decrease in pain behaviour in a rat model of BCP. Cyclin D1 acts as a key regulator of the proliferation of spinal microglia in a rat model of BCP. Disruption of cyclin D1, the restriction-point control of cell cycle, inhibited the proliferation of microglia and attenuated the pain behaviours in BCP rats. Cyclin D1 and the proliferation of spinal microglia may be potential targets for the clinical treatment of BCP.

Cite this article: Bone Joint Res 2022;11(11):803–813.

Chemokine CXCL10 regulates pain behaviors via PI3K-AKT signaling pathway in mice

The analgesic efficacy of morphine can be affected by a variety of factors. Our previous studies demonstrated that chemokine (CXC motif) ligand 10 (CXCL10) could induce algesia directly and attenuate the analgesic effect produced by a single dose of morphine. However, the underlying mechanism remains unclear. In the present study, we aimed to further investigate the mechanism of CXCL10-mediated inhibition on morphine analgesic effect. According to our findings, recombinant CXCL10 protein (rmCXCL10) could increase the phosphorylation of serine-threonine kinase AKT reduced by morphine in spinal cord. Blocking AKT activation by phosphoinositide 3-kinase (PI3K) inhibitor could effectively attenuate CXCL10-induced algesia, and reverse the decrease of paw withdrawal thresholds caused by the co-administration of morphine and rmCXCL10. Furthermore, rmCXCL10 could enhance the spinal expression of pro-inflammatory cytokines, including TNF-α, IL-6, and IL-1β, which could be blocked by PI3K inhibitor. In summary, these findings suggest that PI3K-AKT signaling pathway mediates the effect of CXCL10 on the regulation of morphine analgesia and the release of cytokines in spinal cord. Our study provides a new insight into the mechanism of chemokine-relative pain regulation.

RGMa signal in Macrophages Induces Neutrophil-related Astrocytopathy in NMO

OBJECTIVE

Repulsive guidance molecule-a (RGMa) is a glycosylphosphatidylinositol-linked glycoprotein which has multiple functions including axon growth inhibition and immune regulation. However, its role in the pathophysiology of neuromyelitis optica (NMO) is poorly understood. Perivascular astrocytopathy, which is induced by the leakage of aquaporin-4 (AQP4)-specific IgG into the central nervous system parenchyma, is a key feature of NMO pathology. We investigated the RGMa involvement in the pathology of NMO astrocytopathy, and tested a therapeutic potential of humanized anti-RGMa monoclonal antibody (RGMa-mAb).

METHODS

Using a clinically relevant NMO rat model, we evaluated the therapeutic effect of a RGMa-mAb by behavioral testing, immunohistochemistry, and gene expression assay. We further performed in vitro experiments to address the RGMa-signaling in macrophages.

RESULTS

In both NMO rats and an NMO-autopsied sample, RGMa was expressed by the spared neurons and astrocytes, whereas its receptor neogenin was expressed by infiltrating macrophages. AQP4-IgG-induced astrocytopathy and clinical exacerbation in NMO rats were ameliorated by RGMa-mAb treatment. RGMa-mAb treatment significantly suppressed neutrophil infiltration, and decreased the expression of neutrophil chemoattractants. Interestingly, neogenin-expressing macrophages accumulated in the lesion expressed CXCL2, a strong neutrophil chemoattractant, and further analysis revealed that RGMa directly regulated CXCL2 expression in macrophages. Finally, we found that our NMO rats developed neuropathic pain, and RGMa-mAb treatment effectively ameliorated the severity of neuropathic pain.

INTERPRETATION

RGMa signaling in infiltrated macrophages is a critical driver of neutrophil-related astrocytopathy in NMO lesions, and RGMa-mAb may provide an efficient therapeutic strategy for NMO-associated neuropathic pain and motor deficits in patients with NMO. This article is protected by copyright. All rights reserved.

Pathogenic Roles of CXCL10 in Experimental Autoimmune Prostatitis by Modulating Macrophage Chemotaxis and Cytokine Secretion

Chronic prostatitis and chronic pelvic pain syndrome (CP/CPPS) is an inflammatory immune disease characterized by intraprostatic leukocyte infiltration and pelvic or perineal pain. Macrophages play vital roles in the pathogenesis of CP/CPPS. However, the mechanisms controlling the activation and chemotaxis of macrophages in CP/CPPS remain unclear. This study aimed to investigate the roles of the CXCL10/CXCR3 pathway in the activation and chemotaxis of macrophages in CP/CPPS patients. The serums of CP/CPPS patients and healthy volunteers were collected and measured. Results showed that CXCL10 expression was significantly elevated and correlated with the severity of CP/CPPS patients. The experimental autoimmune prostatitis (EAP) model was generated, and adeno-associated virus and CXCR3 inhibitors were used to treat EAP mice. Immunofluorescence, flow cytometry, and Western blotting were used to analyze the functional phenotype and regulation mechanism of macrophages. Results showed that CXCL10 deficiency ameliorates EAP severity by inhibiting infiltration of macrophages to prostate. Moreover, CXCL10 could induce macrophage migrations and secretions of proinflammatory mediators via CXCR3, which consequently activated the downstream Erk1/2 and p38 MAPK signaling pathways. We also showed that prostatic stromal cell is a potential source of CXCL10. Our results indicated CXCL10 as an important mediator involved in inflammatory infiltration and pain symptoms of prostatitis by promoting the migration of macrophages and secretion of inflammatory mediators via CXCR3-mediated ERK and p38 MAPK activation.

CXCR3 signalling partially contributes to the pathogenesis of neuropathic pain in male rodents

BACKGROUND

Currently, there is a lack of effective therapy for chronic pain. Increasing evidence has shown that chemokines and their correlative receptors involved in the neuron-glial cell cross-talk could contribute to the pathogenesis of neuropathic pain. Our previous studies suggested that CXCR3 expression was elevated in the spinal dorsal horn after nerve injury.

OBJECTIVES

In this study, we aimed to explore the role of CXCR3 signalling in chronic pain modulation.

METHODS

Reverse transcription quantitative PCR and Western blotting were used to measure the expression of CXCR3 and its ligands in the spinal cord following chronic constriction injury (CCI) of the sciatic nerve. Cxcr3 -knockout mice were used to observe the effect of the receptor on pain-related behaviour and microglial activation. Immunohistochemistry was used to investigate the expression of two activation markers for spinal microglia, Iba-1 and phosphorylated-p38 (p-p38) in these mice.

RESULTS

The expression of CXCR3 and its ligand CXCL11 was upregulated in the lumbar dorsal horn of the spinal cord in CCI models. In Cxcr3 -knockout mice, CCI-induced tactile allodynia and thermal hyperalgesia were observed to be alleviated during the early stage of pain processing. Meanwhile, the expression of the glial activation markers, namely, Iba-1 and p-p38, was decreased.

CONCLUSION

Our results demonstrate that CXCR3 could be a key modulator involved in pain modulation of the spinal cord; therefore, CXCR3-related signalling pathways could be potential targets for the treatment of intractable pathological pain.

Brief relaxation training is associated with long-term endocrine therapy adherence among women with breast cancer: post hoc analysis of a randomized controlled trial

PURPOSE

Despite life-saving potential, many women struggle to adhere to adjuvant endocrine therapy (AET) for their breast cancer (BCa). Prior research has demonstrated that emotional distress is a barrier to AET adherence. We followed women from a trial to test the long-term effects of two 5-week post-surgical group-based stress management interventions, cognitive behavioral therapy (CBT), and relaxation training versus an attention-matched health education control, on AET adherence.

METHODS

We conducted a long-term follow-up (median = 8 years) of women randomized to CBT, relaxation training, or health education after surgery for stage 0-3 BCa. We measured adherence with the Endocrine Therapy Medication Usage Questionnaire (ETMUQ). First, we established factors on the ETMUQ via confirmatory factor analysis. We then used Bayesian structural equation modeling to regress these factors on study arm, controlling for age and treatments received.

RESULTS

Of those who completed long-term follow-up (n = 59, 44.7%), over half (n = 33; 55.9%) reported problems with adherence generally. Women receiving relaxation training (n = 15) had better adherence than those receiving health education (n = 24) on the Forgetfulness/Inconsistency [B(SE) = 0.25(0.14), p = 0.049] and Intentional Nonadherence [B(SE) = 0.31(0.14), p = 0.018] factors of the ETMUQ. Similar results were observed for those receiving relaxation training compared to CBT (n = 20): Forgetfulness/Inconsistency [B(SE) = - 0.47(0.25), p = 0.031]; Intentional Nonadherence [B(SE) = - 0.31(0.15), p = 0.027].

CONCLUSION

Women receiving relaxation training were less likely to (1) forget to take their AET and (2) intentionally miss doses of AET in the long term compared to women receiving health education or CBT. This is evidence for the need of randomized trials that aim to improve adherence by incorporating theoretically based behavioral change techniques.

TRIAL REGISTRATION AND DATES

Trial 2R01-CA-064710 was registered March 26, 2006.

Decreased pain sensitivity and alterations of cerebrospinal fluid and plasma inflammatory mediators after total hip arthroplasty in patients with disabling osteoarthritis

BACKGROUND

Proinflammatory mechanisms are implicated in pain states. Recent research indicates that patients with osteoarthritis (OA) with signs of central sensitization exhibit elevated cerebrospinal fluid (CSF) levels of interferon gamma-induced protein 10 (IP-10), Fms-related tyrosine kinase 1 (Flt-1), and monocyte chemoattractant protein 1 (MCP-1).

METHODS

The current prospective cohort study, including 15 patients with OA, primarily aimed to evaluate associations among alterations in CSF IP-10, Flt-1, MCP-1, and pain sensitization following total hip arthroplasty (THA). Participants provided CSF and blood samples for analysis of 10 proinflammatory mediators, and underwent detailed clinical examination and quantitative sensory testing, immediately preoperative and 18 months after surgery.

RESULTS

Neurophysiological measures of pain showed markedly reduced pain sensitivity long-term postoperative. Increases in remote site pressure pain detection thresholds (PPDTs) and decreased temporal summation indicated partial resolution of previous central sensitization. Compared to preoperative, CSF concentrations of IP-10 were increased (p = 0.041), whereas neither Flt-1 (p = 0.112) nor MCP-1 levels changed (p = 0.650). Compared to preoperative, plasma concentrations of IP-10 were increased (p = 0.006), whereas interleukin (IL)-8 was decreased (p = 0.023). Subjects who exhibited increases in arm PPDTs above median showed greater increases in CSF IP-10 compared to those with PPDT increases below median (p = 0.028). Analyses of plasma IP-10 and IL-8 indicated higher levels of peripheral inflammation were linked to decreased pressure pain thresholds (unadjusted β = -0.79, p = 0.006, and β = -118.1, p = 0.014, respectively).

CONCLUSIONS

THA leads to long-term decreases in pain sensitivity, indicative of resolution of sensitization processes. Changes in CSF and plasma levels of IP-10, and plasma IL-8, may be associated with altered pain phenotype.

Differential expression of cerebrospinal fluid neuroinflammatory mediators depending on osteoarthritis pain phenotype

Supplemental Digital Content is Available in the Text.

Distinct cerebrospinal fluid neuroinflammatory profiles may be associated with different objective characteristics of persistent pain in osteoarthritis patients undergoing total hip arthroplasty.

Neuroinflammation is implicated in the development and maintenance of persistent pain states, but there are limited data linking cerebrospinal fluid (CSF) inflammatory mediators with neurophysiological pain processes in humans. In a prospective observational study, CSF inflammatory mediators were compared between patients with osteoarthritis (OA) who were undergoing total hip arthroplasty due to disabling pain symptoms (n = 52) and pain-free comparison controls (n = 30). In OA patients only, detailed clinical examination and quantitative sensory testing were completed. Cerebrospinal fluid samples were analyzed for 10 proinflammatory mediators using Meso Scale Discovery platform. Compared to controls, OA patients had higher CSF levels of interleukin 8 (IL-8) (P = 0.002), intercellular adhesion molecule 1 (P = 0.007), and vascular cell adhesion molecule 1 (P = 0.006). Osteoarthritis patients with central sensitization possibly indicated by arm pressure pain detection threshold <250 kPa showed significantly higher CSF levels of Fms-related tyrosine kinase 1 (Flt-1) (P = 0.044) and interferon gamma-induced protein 10 (IP-10) (P = 0.024), as compared to subjects with PPDT above that threshold. In patients reporting pain numerical rating scale score ≥3/10 during peripheral venous cannulation, Flt-1 was elevated (P = 0.025), and in patients with punctate stimulus wind-up ratio ≥2, CSF monocyte chemoattractant protein 1 was higher (P = 0.011). Multiple logistic regression models showed that increased Flt-1 was associated with central sensitization, assessed by remote-site PPDT and peripheral venous cannulation pain, and monocyte chemoattractant protein-1 with temporal summation in the area of maximum pain. Multiple proinflammatory mediators measured in CSF are associated with persistent hip OA-related pain. Pain phenotype may be influenced by specific CSF neuroinflammatory profiles.

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.

Hsa_circ_0000515 is a novel circular RNA implicated in the development of breast cancer through its regulation of the microRNA-296-5p/CXCL10 axis

Cancer metastasis is a major cause of death among women afflicted with breast cancer (BC) and understanding the molecular processes involved is a major focus in BC research. Circular RNAs (circRNAs) have emerged as genomic regulatory molecules in carcinogenesis and metastasis; however, their role in BC is unclear. We characterized a novel circRNA, hsa_circ_0000515, in context of BC. We collected 340 cancerous tissues surgically resected from BC patients and found hsa_circ_0000515 was upregulated in BC tissues and associated with poor prognosis of BC. Silencing of hsa_circ_0000515 impaired cell cycle progression, cell proliferation, and invasion, attenuated inflammatory response, and reduced the proangiogenetic potential of BC cells. RNA pull-down and dual-luciferase reporter gene assays showed that hsa_circ_0000515 binds miR-296-5p, preventing it from repressing CXCL10 expression. We also observed that miR-296-5p inhibition or CXCL10 overexpression promoted cell cycle progression, restored proliferative, invasive and proangiogenetic abilities, and increased inflammatory response in MCF-7 cells in the absence of hsa_circ_0000515. In vivo analyses showed that partial loss of hsa_circ_0000515 reduced the tumor growth of MCF-7 cells in nude mice. The key findings from this study revealed that targeting hsa_circ_0000515 might be an effective strategy to combat BC.

The circular RNA circSlc7a11 promotes bone cancer pain pathogenesis in rats by modulating LLC-WRC 256 cell proliferation and apoptosis

Treatment of bone cancer pain (BCP) caused by bone metastasis in advanced cancers remains a challenge in clinical oncology, and the underlying mechanisms of BCP are poorly understood. This study aimed to investigate the pathogenic roles of circular RNAs (circRNAs) in regulating cancer cell proliferation and BCP development. Eight differentially expressed circRNAs in the rat spinal cord were validated by agarose gel electrophoresis and Sanger sequencing. Expression of circRNAs and mRNAs was detected by quantitative RT-PCR. MTS assay and flow cytometry were performed to analyze cell proliferation and apoptosis, respectively. Differentially expressed mRNA profiles were characterized by deep RNA sequencing, hierarchical clustering, and functional categorization. The interactions among circRNAs, microRNAs (miRNAs), and mRNAs were predicted using TargetScan. Additionally, western blot was performed to determine the protein levels of Pax8, Isg15, and Cxcl10. Multiple circRNAs were differentially expressed in the spinal cords of BCP model rats; of these, circSlc7a11 showed the greatest increase in expression. The overexpression of circSlc7a11 significantly promoted cell proliferation and repressed apoptosis of LLC-WRC 256 and UMR-106 cells, whereas circSlc7a11 silencing produced the opposite effects. Altered expression of circSlc7a11 also induced substantial changes in the mRNA expression profiles of LLC-WRC 256 cells; these changes were linked to multiple apoptotic processes and signaling pathways, such as the chemokine signaling pathway, and formed a complex circRNA/miRNA/mRNA network. Additionally, Pax8, Isg15, and Cxc110 protein level in LLC-WRC 256 cells was consistent with the mRNA results. The circRNA circSlc7a11 regulates rat BCP development by modulating LLC-WRC 256 cell proliferation and apoptosis through multiple-signaling mechanisms.

Comparison of regulatory networks of E74-like factor 1 and cold-shock domain-containing E1 in breast cancer cell lines using ChIP datasets

In the present study, differences in the expression of target genes between chromatin immunoprecipitation sequencing (ChIP-seq) datasets of breast cancer MCF-7 cells treated with antibodies to E74-like factor 1 (ELF1) and cold-shock domain-containing E1 (CSDE1) were analyzed and gene regulatory networks were established. The datasets were downloaded from the Gene Expression Omnibus (GEO) database. ELF1-associated target genes and CSDE1-associated target genes were analyzed for functional prediction and protein-protein interaction (PPI) networks. The ELF1 ChIP-seq dataset contained 95 ELF1-associated target genes, while the CSDE1 ChIP-seq dataset contained 826 CSDE1-associated target genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that the ELF1- and CSDE1-associated target genes had different potential functions and signaling pathways. The ELF1-associated target genes were mainly enriched in the GO terms of molecular transducer activity, catalytic activity, cellular processes and response to sensitivity, and in the KEGG pathways of olfactory transduction, the chemokine signaling pathway, carbohydrate digestion and absorption, and starch and sucrose metabolism. The CSDE1-associated target genes were mainly enriched in the GO terms of binding, transcription regulator activity, cellular processes and metabolic processes, and in the KEGG pathways of ribosome, metabolic pathways, endocytosis, oxidative phosphorylation and transcriptional misregulation in cancer. PPI network analysis revealed that the ELF1 regulatory network primarily regulated chemokine-mediated malignant tumor cells, while the CSDE1 regulatory network mainly regulated ribosomes, metabolic pathways and oxidative phosphorylation. Reverse transcription-quantitative PCR indicated that ELF1 overexpression led to significant downregulation of C-X-C motif chemokine-8 and -6 expression levels in MCF-7 cells, while overexpression of CSDE1 significantly induced the mRNA expression of CSDE1-associated target genes, which included mitochondrial ribosomal protein L4, NADH: ubiquinone oxidoreductase subunit B7, small nuclear ribonucleoprotein polypeptide E, ribosomal protein S26 (RPS26), RPS11 and RPS6, in the MCF-7 cells. In breast cancer MCF-7 cells, the target genes and regulatory pathways of ELF1 and CSDE1 were different. Understanding these regulatory pathways may help to develop strategies for personalized breast cancer treatment.

Evaluating the Role of CXCR3 in Pain Modulation: A Literature Review

CXCR3 is a well-known receptor involved in immune cell recruitment and inflammation. Pathological inflammation leads to pain stimulation and hence nociception. Therefore, we decided to review the recent research on CXCR3 to identify its precise role in the modulation of pain in a variety of clinical conditions targeting various regions of the body. Studies were selected from PubMed Medline, which relate CXCR3 to the progression of diseases with either bone cancer pain, neuropathic pain, cystitis pain, osteoarthritis and rheumatoid arthritis pain, dental pain, in particular, periodontitis and pulpitis. In all the diseases studied, a high prevalence of CXCR3 and/or its ligand were identified where CXCR3 is a key player in the pathophysiological process of many inflammatory conditions. CXCR3 and its ligands, particularly CXCL10, modulate nociception via actions in the dorsal root ganglia and dorsal horn of the spinal cord, in cases of bone cancer pain, neuropathic, and joint pain. However, with the other studied disease, no direct link to pain has been made, although it contributes to the pathological progression of the diseases and hence would be a causal factor for the pain. Furthermore, CXCR3 appears to play a role in desensitizing the opioid receptor in the descending modulatory pathway within the brain stem as well as modulating opioid-induced hyperalgesia in the dorsal horn of the spinal cord. Further research is required for understanding the exact mechanisms of CXCR3 in pain modulation centrally and peripherally. A greater understanding of the immunological activities and pharmacological consequence of CXCR3 and its ligands could help in the discovery of newer drugs for modulating pain arising from pathogenic or inflammatory sources. Given the significance of the CXCR3 for nociception, its utilization may prove to be beneficial as a target for analgesia.

Spinal microglia-neuron interactions in chronic pain

Current deficiency in our understanding of acute-to-chronic pain transition remains a hurdle for developing effective treatments against chronic pain. Whereas neurocentric mechanisms alone are insufficient to provide satisfactory explanation for such transition, neuro-immune crosstalk has attracted attention in recent pain research. In contrast to brain microglia, spinal microglia are activated immediately in various pain states. The fast-responsive enrichment and activation of spinal microglia among different pain conditions have highlighted the crucial role of neuroinflammation caused by microglia-neuron crosstalk in pain initiation. Recent studies have revealed spinal microglia-neuron interactions are also involved in chronic pain maintenance, albeit, with different anatomic distribution, cellular and molecular mechanisms, and biologic functions. Delineating the exact temporal discrepancies of spinal microglia distribution and functions along acute-to-chronic pain transition may provide additional mechanistic insights for drug development to prevent deterioration of acute pain into the chronic state. This narrative review summerizes the longitudinal alterations of spinal microglia-neuron interactions in the initiation of pain hypersensitivity, acute-to-chronic pain progression, and chronic pain maintenance, followed by an overview of current clinical translation of preclinical studies on spinal microglia. This review highlights the crucial role of the interaction between spinal microglia and neighboring neurons in the initiation and maintenance of pain hypersensitivity, in relation to the release of cytokines, chemokines, and neuroactive substances, as well as the modulation of synaptic plasticity. Further exploration of the uncharted functions of spinal microglia-neuron crosstalk may lead to the design of novel drugs for preventing acute-to-chronic pain transition.

C-X-C Motif Chemokine 10 Contributes to the Development of Neuropathic Pain by Increasing the Permeability of the Blood-Spinal Cord Barrier

Neuropathic pain is among the most debilitating forms of chronic pain. Studies have suggested that chronic pain pathogenesis involves neuroimmune interactions and blood-spinal cord barrier (BSCB) disruption. However, the underlying mechanisms are poorly understood. We modeled neuropathic pain in rats by inducing chronic constriction injury (CCI) of the sciatic nerve and analyzed the effects on C-X-C motif chemokine 10 (CXCL10)/CXCR3 activation, BSCB permeability, and immune cell migration from the circulation into the spinal cord. We detected CXCR3 expression in spinal neurons and observed that CCI induced CXCL10/CXCR3 activation, BSCB disruption, and mechanical hyperalgesia. CCI-induced BSCB disruption enabled circulating T cells to migrate into the spinal parenchyma. Intrathecal administration of an anti-CXCL10 antibody not only attenuated CCI-induced hyperalgesia, but also reduced BSCB permeability, suggesting that CXCL10 acts as a key regulator of BSCB integrity. Moreover, T cell migration may play a critical role in the neuroimmune interactions involved in the pathogenesis of CCI-induced neuropathic pain. Our results highlight CXCL10 as a new potential drug target for the treatment of nerve injury-induced neuropathic pain.

The endocannabinoid system: Novel targets for treating cancer induced bone pain

Treating Cancer-induced bone pain (CIBP) continues to be a major clinical challenge and underlying mechanisms of CIBP remain unclear. Recently, emerging body of evidence suggested the endocannabinoid system (ECS) may play essential roles in CIBP. Here, we summarized the current understanding of the antinociceptive mechanisms of endocannabinoids in CIBP and discussed the beneficial effects of endocannabinoid for CIBP treatment. Targeting non-selective cannabinoid 1 receptors or selective cannabinoid 2 receptors, and modulation of peripheral AEA and 2-AG, as well as the inhibition the function of fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) have produced analgesic effects in animal models of CIBP. Management of ECS therefore appears to be a promising way for the treatment of CIBP in terms of efficacy and safety. Further clinical studies are encouraged to confirm the possible translation to humans of the very promising results already obtained in the preclinical studies.

Long Non-Coding RNA (LncRNA) UFC1/miR-34a Contributes to Proliferation and Migration in Breast Cancer

Background

At present, a number of long non-coding RNAs (lncRNAs) have been realized as the critical regulators of breast cancers. Current evidence indicates that dysregulation of UFC1 contributes to the tumorigenesis and progression of various types of human cancer. However, the roles of UFC1 in breast cancer are still unclear.

Material/Methods

Firstly, we measured the expression of UFC1 in breast cancer tissues and cells lines compared with corresponding controls. Then, cell functional assays were performed to determine the roles of UFC1 in breast cancer progression in vitro. Moreover, the correlation between UFC1 and miR-34a was determined by luciferase reporter assays. Further, the role of miR-34a in regulating biological function of breast cancer and its downstream target CXCL10 was applied by a series of functional assays.

Results

In present study, we found that UFC1 was highly expressed in breast tissue and cells lines compared with normal tissues and cell lines. Silenced UFC1 suppressed multiple biological activities of breast cancer cells, which also functioned as a miR-34a sponge in breast cancer. Furthermore, over-expressing miR-34a could prominently suppress cell growth, invasion, migration and inducing apoptosis in breast cancer cells. In addition, we verified that miR-34a was a target of CXCL10 by bioinformatics analysis and luciferase reporter assay.

Conclusions

LncRNA UFC1 regulated biological activity of breast cancer via miR-34a/CXCL10 axis, providing a novel diagnosis biomarker and potential therapeutic target for breast cancer.

Transcriptomic characterisation of the optimised rat model of Walker 256 breast cancer cell-induced bone pain

In patients with breast cancer, metastases of cancer cells to the axial skeleton may cause excruciating pain, particularly in the advanced stages. The current drug treatments available to alleviate this debilitating pain condition often lack efficacy and/or produce undesirable side effects. Preclinical animal models of cancer-induced bone pain are key to studying the mechanisms that cause this pain and for the success of drug discovery programs. In a previous study conducted in our laboratory, we validated and characterised the rat model of Walker 256 cell-induced bone pain, which displayed several key resemblances to the human pain condition. However, gene level changes that occur in the pathophysiology of cancer-induced bone pain in this preclinical model are unknown. Hence, in this study, we performed the transcriptomic characterisation of the Walker 256 cell line cultured in vitro to predict the molecular genetic profile of this cell line. We also performed transcriptomic characterisation of the Walker 256 cell-induced bone pain model in rats using the lumbar spinal cord and lumbar dorsal root ganglia tissues. Here we show that the Walker 256 cell line resembles the basal-B molecular subtype of human breast cancer cell lines. We also identify several genes that may underpin the progression of pain hypersensitivities in this condition, however, this needs further confirmatory studies. These transcriptomic insights have the potential to direct future studies aimed at identifying various mechanisms underpinning pain hypersensitivities in this model that may also assist in discovery of novel pain therapeutics for breast cancer-induced bone pain.

Crosstalk between Cdk5/p35 and ERK1/2 signalling mediates spinal astrocyte activity via the PPARγ pathway in a rat model of chronic constriction injury

The specific mechanisms underlying cyclin-dependent kinase 5 (Cdk5)-mediated neuropathic pain at the spinal cord level remain elusive. The aim of the present study was to explore the role of crosstalk between Cdk5/p35 and extracellular signal-regulated kinase 1/2 (ERK1/2) signalling in mediating spinal astrocyte activity via the PPARγ pathway in a rat model of chronic constriction injury (CCI). Here, we quantified pain behaviour after CCI; detected the localization of p35, Cdk5, phosphorylated ERK1/2 (pERK1/2), phosphorylated peroxisome proliferator-activated receptor γ (pPPARγ), neuronal nuclei (a neuronal marker), glial fibrillary acidic protein (GFAP, an activated astrocyte marker) and ionized calcium binding adaptor molecule 1 (a microglial marker) in the dorsal horn using immunofluorescence; measured the protein levels of Cdk5, p35, pERK1/2, pPPARγ and GFAP using western blot analysis; and gauged the enzyme activity of Cdk5/p35 kinase using a Cdk5/p35 kinase activity assay kit. Tumour necrosis factor-α, interleukin (IL)-1β and IL-6 levels were measured using enzyme-linked immunosorbent assay (ELISA). Ligation of the right sciatic nerve induced mechanical allodynia; thermal hyperalgesia; and the time-dependent upregulation of p35, pERK1/2 and GFAP and downregulation of pPPARγ. p35 colocalized with Cdk5, pERK1/2, pPPARγ, neurons and astrocytes but not microglia. Meanwhile, intrathecal injection of the Cdk5 inhibitor roscovitine, the mitogen-activated ERK kinase (MEK) inhibitor U0126 and the PPARγ agonist pioglitazone prevented or reversed behavioural allodynia, increased pPPARγ expression, inhibited astrocyte activation and alleviated proinflammatory cytokine (tumour necrosis factor-α, IL-1β, and IL-6) release from activated astrocytes. Furthermore, crosstalk between the Cdk5/p35 and ERK1/2 pathways was observed with CCI. Blockade of either Cdk5/p35 or ERK1/2 inhibited Cdk5 activity. These findings indicate that spinal crosstalk between the Cdk5/p35 and ERK1/2 pathways mediates astrocyte activity via the PPARγ pathway in CCI rats and that targeting this crosstalk could be an effective strategy to attenuate CCI and astrocyte-derived neuroinflammation.

Development of chronic pain in males with traumatic spinal cord injury: role of circulating levels of the chemokines CCL2 and CXCL10 in subacute stage

STUDY DESIGN

Longitudinal study.

OBJECTIVES

To assess the impact of spinal cord injury (SCI) on circulating levels of chemokines (CCL2 and CXCL10) and its relation with pain development.

SETTING

National Hospital for SCI patients.

METHODS

We longitudinally studied changes in the circulating levels of CCL2 and CXCL10 in 27 male patients with complete SCI who were evaluated in the early subacute phase and indeed 3 and 6 months after injury measuring at each time-point serum levels of CCL2 and CXCL10. Patients were telephonically interviewed about pain 1 year after SCI.

RESULTS

In the early subacute phase, patients with pain showed higher CXCL10 and similar CCL2 levels as opposed to those without pain. Moreover, CCL2 concentrations were positively associated with pain intensity. The results obtained by analysing the temporal profile of the chemokines suggested that CXCL10 was inclined to decrease over time, while CCL2 increased over time.

CONCLUSION

The results of this preliminary study, the first performed in humans with traumatic SCI, suggest a link between changes in the circulating chemokine profile and pain development in subacute SCI stage as well as with severity in a more chronic stage. Large series studies will evaluate whether the circulating chemokine status can be useful as a biomarker for assessing the patients' risk for pain development.

Spinal microglia contribute to cancer-induced pain through system xC --mediated glutamate release

Introduction:

Microglial cells, the resident macrophages of the central nervous system, are a key contributor to the generation and maintenance of cancer-induced pain (CIP). In healthy organisms, activated microglia promote recovery through the release of trophic and anti-inflammatory factors to clear toxins and pathogens and support neuronal survival. Chronically activated microglia, however, release toxic substances, including excess glutamate, causing cytotoxicity. Accordingly, rising attention is given to microglia for their role in abnormal physiology and in mediating neurotoxicity.

Objectives:

To examine the nociceptive relationship between peripherally-released glutamate and microglial xCT.

Methods:

A validated murine model of 4T1 carcinoma cell–induced nociception was used to assess the effect of peripheral tumour on spinal microglial activation and xCT expression. Coculture systems were then used to investigate the direct effect of glutamate released by wildtype and xCT knockdown MDA-MB-231 carcinoma cells on microglial activation, functional system x_C⁻ activity, and protein levels of interferon regulatory factor 8 (IRF8), a transcription factor implicated in microglia-mediated nociception.

Results:

Blockade of system x_C⁻ with sulfasalazine (SSZ) in vivo attenuated nociception in a 4T1 murine model of CIP and attenuates tumour-induced microglial activation in the dorsal horn of the spinal cord. Furthermore, knockdown of xCT in MDA-MB-231 cells mitigated tumour cell–induced microglial activation and functional system x_C⁻ activity in vitro.

Conclusions:

These data collectively demonstrate that the system xCT antiporter is functionally implicated in CIP and may be particularly relevant to pain progression through microglia. Upregulated xCT in chronically activated spinal microglia may be one pathway to central glutamate cytotoxicity. Microglial xCT may therefore be a valuable target for mitigating CIP.

The Role of CXCR3 in Neurological Diseases

BACKGROUND

Neurological diseases have become an obvious challenge due to insufficient therapeutic intervention. Therefore, novel drugs for various neurological disorders are in desperate need. Recently, compelling evidence has demonstrated that chemokine receptor CXCR3, which is a G protein-coupled receptor in the CXC chemokine receptor family, may play a pivotal role in the development of neurological diseases. The aim of this review is to provide evidence for the potential of CXCR3 as a therapeutic target for neurological diseases.

METHODS

English journal articles that focused on the invovlement of CXCR3 in neurological diseases were searched via PubMed up to May 2017. Moreover, reference lists from identified articles were included for overviews.

RESULTS

The expression level of CXCR3 in T cells was significantly elevated in several neurological diseases, including multiple sclerosis (MS), glioma, Alzheimer's disease (AD), chronic pain, human T-lymphotropic virus type 1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and bipolar disorder. CXCR3 antagonists showed therapeutic effects in these neurological diseases.

CONCLUSION

These studies provided hard evidence that CXCR3 plays a vital role in the pathogenesis of MS, glioma, AD, chronic pain, HAM/TSP and bipolar disorder. CXCR3 is a crucial molecule in neuroinflammatory and neurodegenerative diseases. It regulates the activation of infiltrating cells and resident immune cells. However, the exact functions of CXCR3 in neurological diseases are inconclusive. Thus, it is important to understand the topic of chemokines and the scope of their activity in neurological diseases.

Antinociceptive effects of Ginsenoside Rb1 in a rat model of cancer-induced bone pain

Ginsenoside Rb1 (GRb1) is a major ingredient of ginseng, a traditional medicine that has been used for thousands of years. Previous studies have reported that GRb1 had anti-inflammatory, antioxidant and neuroprotective effects. The current study aimed to evaluate the antinociceptive effects of GRb1 in a rat model of cancer-induced bone pain (CIBP) established by intratibial injection of Walker 256 cells. Intraperitoneal injection (i.p.) of GRb1 (5 and 10 mg/kg, but not 1 mg/kg) partially and transiently reversed the mechanical allodynia and thermal hyperalgesia in CIBP rats at 14 days following surgery when the pain behavior is established. Furthermore, repeated administration of GRb1 demonstrated persistent analgesic effect. Additionally, the protein expression and immunoreactivity of iba1, which is the maker of microglia, was significantly suppressed in CIBP rats treated with GRb1 (i.p., 10 mg/kg) from day 12 for three consecutive days compared with CIBP rats treated with a vehicle. Furthermore, upregulation of spinal interleukin (IL)-1β, IL-6 and tumor necrosis factor-α were also significantly inhibited by the treatment of GRb1 (i.p., 10 mg/kg) from day 12 for three consecutive days. Together, these results indicated that GRb1 may attenuate CIBP via inhibiting the activation of microglia and glial-derived proinflammatory cytokines.

Activation of hippocampal microglia in a murine model of cancer-induced pain

Introduction

Pain is a common and debilitating comorbidity of metastatic breast cancer. The hippocampus has been implicated in nociceptive processing, particularly relating to the subjective aspect of pain. Here, a syngeneic mouse model was used to characterize the effects of peripheral tumors on hippocampal microglial activation in relation to cancer-induced pain (CIP).

Materials and methods

Mice were systemically treated with the colony-stimulating factor 1 receptor inhibitor Pexidartinib prior to intrafemoral (IF) or subcutaneous 4T1 carcinoma cell inoculation. Spontaneous and evoked nociceptive responses were quantitated throughout tumor development, and contralateral hippocampi were collected via endpoint microdissection for RNA analysis. Additionally, IF tumor-bearing animals were sacrificed on days 5, 10, 15, and 20 post 4T1 cell inoculation, and brain sections were immunofluorescently stained for Iba1, a marker of activated microglia.

Results

Ablation of these neuroimmune cells with the CSF1R inhibitor Pexidartinib delayed the onset and severity of cancer-induced nociceptive behaviors in IF tumor-bearing animals, adding to the body of literature that demonstrates microglial contribution to the development and maintenance of CIP. Furthermore, in untreated IF tumor-bearing mice, nociceptive behaviors appeared to progress in parallel with microglial activation in hippocampal regions. Immunofluorescent Iba1+ microglia increased in the dentate gyrus and cornu ammonis 1 hippocampal regions in IF tumor-bearing animals over time, which was confirmed at the mRNA level using relevant microglial markers.

Conclusion

This is the first experimental evidence to demonstrate the effects of peripheral tumor-induced nociception on hippocampal microglial activation. The increase in hippocampal microglia observed in the present study may reflect the emotional and cognitive deficits reported by patients with CIP.

The Roles of Chemokine CXCL13 in the Development of Bone Cancer Pain and the Regulation of Morphine Analgesia in Rats

Chemokines are important regulators of immune, inflammatory, and neuronal responses in peripheral and central pain pathway. The aim of this study was to investigate whether chemokine (C-X-C motif) ligand 13 (CXCL13) and its receptor (C-X-C chemokine receptor type 5, CXCR5) involve in the development of bone cancer pain (BCP) and the regulation of morphine analgesia in rats. The change of pain behaviors in BCP rats were measured by testing paw withdrawal threshold (PWT). The levels of CXCL13, CXCR5 and signal pathway proteins (p-p38, p-ERK and p-AKT etc.) in the spinal cord were measured via western blots. The expression of CXCL13 and CXCR5 in spinal cord was increased in BCP rats. The BCP rats showed decrease of PWTs, which was relieved by CXCR5i. Intrathecally injection of murine recombinant CXCL13 (mrCXCL13) decreased the PWTs of BCP rats and opposed morphine-induced analgesia in BCP rats. In BCP rats, the signal pathway proteins (p38, ERK and AKT) in the spinal cord were activated. CXCL13 and morphine had contrary effect on the phosphorylation of these proteins. MrCXCL13 directly increased the levels of p-p38, p-ERK and p-AKT in BCP rats. However, morphine decreased the levels of these proteins in BCP rats. While blocking the activation of p-p38, p-ERK and p-AKT, morphine analgesia was enhanced. These results suggest CXCL13 participated in bone cancer pain and opposed morphine analgesia via p38, ERK and AKT pathways. It may be a target to enhance pain management in cancer pain patients.

Dehydrocorydaline attenuates bone cancer pain by shifting microglial M1/M2 polarization toward the M2 phenotype

Bone cancer pain remains a major challenge in patients with primary or metastatic bone cancer due to a lack of understanding the mechanisms. Previous studies have revealed the two distinct functional polarization states of microglia (classically activated M1 and alternatively activated M2) in the spinal cord in nerve injury–induced neuropathic pain. However, whether microglia in the spinal cord polarize to M1 and M2 phenotypes and contribute to the development of bone cancer pain remains unclear. In this study, we used a mouse model with bone cancer to characterize the M1/M2 polarization of microglia in the spinal cord during the development of bone cancer pain, and investigated the antinociceptive effects of dehydrocorydaline, an alkaloidal component isolated from Rhizoma corydalis on bone cancer pain. Our results show that microglia in the spinal cord presented increased M1 polarization and decreased M2 polarization, while overproduction of IL-1β and inhibited expression of IL-10 was detected during bone cancer pain development. Intraperitoneal administration of dehydrocorydaline (10 mg/kg) had significant antinociceptive effects on day 14 after osteosarcoma cell implantation, accompanied by suppressed M1 phenotype and upregulated M2 phenotype of microglia in the spinal cord, while alleviated inflammatory response was observed then. These results suggest that the imbalanced polarization of microglia toward the M1 phenotype in the spinal cord may contribute to the development of bone cancer pain, while dehydrocorydaline helps to attenuate bone cancer pain, with microglial polarization shifting toward the M2 phenotype in the spinal cord.

Altered Expression of Differential Genes in Thoracic Spinal Cord Involved in Experimental Cholestatic Itch Mouse Model

The spinal origin of cholestatic itch in experimental obstructive jaundice mouse model remains poorly understood. In this study, the jaundice model was established by bile duct ligation (BDL) in mice, and differential gene expression patterns were analyzed in the lower thoracic spinal cord involved in cholestatic pruritus after BDL operation using high-throughput RNA sequencing. At 21st day after BDL, the expression levels of ENSRNOG00000060523, ENSRNOG00000058405 and ENSRNOG00000055193 mRNA were significantly up-regulated, and those of ENSRNOG00000042197, ENSRNOG00000008478, ENSRNOGOOOOOO19607, ENSRNOG00000020647, ENSRNOG00000046289, Gemin8, Serpina3n and Trim63 mRNA were significantly down-regulated in BDL group. The RNAseq data of selected mRNAs were validated by RT-qPCR. The expression levels of ENSRNOG00000042197, ENSRNOG00000008478, ENSRNOGOOOOOO 19607, ENSRNOG00000020647, ENSRNOG00000046289 and Serpina3n mRNA were significantly down-regulated in BDL group. This study suggested that cholestatic pruritus in experimental obstructive jaundice mouse model is related with in the changes of gene expression profiles in spinal cord.

Pharmacological blockade of CXCR3 by (±)-NBI-74330 reduces neuropathic pain and enhances opioid effectiveness - Evidence from in vivo and in vitro studies

It has been suggested that CXCR3 is important for nociception. Our experiments were conducted to evaluate involvement of CXCR3 and its ligands (CXCL4, CXCL9, CXCL10, CXCL11/CCL21) in neuropathic pain. Our studies give new evidence that intrathecal administration of each CXCR3 ligand induces pain-like behaviour in naive mice that occurs shortly after injection due to its location of neurons, which is confirmed by immunofluorescent staining. Moreover, intrathecal administrations of CXCL9, CXCL10, CCL21 neutralizing antibodies diminished pain-related behaviour. RT-PCR/Western blot analysis unprecedentedly showed spinal elevated levels of CXCR3 after chronic constriction injury of the sciatic nerve in rats in parallel with different time-course changes of its endogenous ligands. Initially, on day 2 we observed spinal increased levels of CXCL10 and CXCL11 indicating that these chemokines have important roles in triggering neuropathy. Then, on day 7, we observed increased levels of CXCL4, CXCL9, CXCL10. Interestingly, changes in CXCL9 level persisted until day 28, suggesting that these chemokines are responsible for long-term, persistent neuropathy. Additionally, in DRG the CXCL4, CXCL9 were elevated. The results obtained from primary glial cultures, suggests that all CXCR3 ligands can be produced in microglia, but also, except for CXCL4, in astrocytes. We provide the first evidence that in neuropathy chronic intrathecal administration of CXCR3 antagonist, (±)-NBI-74330, attenuates hypersensitivity with concomitant occurrence of microglial and some of CXCR3 ligands activation observed in the spinal cord and/or DRG level. This paper underlies the significance of CXCR3 in neuropathic pain and shows therapeutic potential of its blockade for enhancement of morphine analgesia as the major novelty of this work.

Minocycline as a promising therapeutic strategy for chronic pain

Chronic pain remains to be a clinical challenge due to insufficient therapeutic strategies. Minocycline is a member of the tetracycline class of antibiotics, which has been used in clinic for decades. It is frequently reported that minocycline may has many non-antibiotic properties, among which is its anti-nociceptive effect. The results from our lab and others suggest that minocycline exerts strong analgesic effect in animal models of chronic pain including visceral pain, chemotherapy-induced periphery neuropathy, periphery injury induced neuropathic pain, diabetic neuropathic pain, spinal cord injury, inflammatory pain and bone cancer pain. In this review, we summarize the mechanisms underlying the analgesic effect of minocycline in preclinical studies. Due to a good safety record when used chronically, minocycline may become a promising therapeutic strategy for chronic pain in clinic.

The Chemokine CCL4 (MIP-1β) Evokes Antinociceptive Effects in Mice: a Role for CD4+ Lymphocytes and Met-Enkephalin

In the present study, we characterize the antinociceptive effects produced by the chemokine CCL4 in mice. The intraplantar administration of very low doses of CCL4 (0.1-3 pg) produced bilateral antinociception assessed by the unilateral hot-plate test (UHP) without evoking chemotactic responses at the injection site. Moreover, the subcutaneous administration of CCL4 (3-100 pg/kg) also yielded bilateral antinociception in the UHP and the paw pressure test and reduced the number of spinal neurons that express Fos protein in response to noxious stimulation. The implication of peripheral CCR5 but not CCR1 in CCL4-evoked antinociception was deduced from the inhibition produced by systemic but not intrathecal, administration of the CCR5 antagonist DAPTA, and the inefficacy of the CCR1 antagonist J113863. Besides, the inhibition observed after subcutaneous but not intrathecal administration of naloxone demonstrated the involvement of peripheral opioids and the efficacy of naltrindole but not cyprodime or nor-binaltorphimine supported the participation of δ-opioid receptors. In accordance, plasma levels of met-enkephalin, but not β-endorphin, were augmented in response to CCL4. Likewise, CCL4-evoked antinociception was blocked by the administration of an anti-met-enk antibody. Leukocyte depletion experiments performed with cyclophosphamide, anti-Ly6G, or anti-CD3 antibodies indicated that the antinociceptive effect evoked by CCL4 depends on circulating T lymphocytes. Double immunofluorescence experiments showed a four times more frequent expression of met-enk in CD4⁺ than in CD8⁺ T lymphocytes. CCL4-induced antinociception almost disappeared upon CD4⁺, but not CD8⁺, lymphocyte depletion with selective antibodies, thus supporting that the release of met-enk from CD4⁺ lymphocytes underlies the opioid antinociceptive response evoked by CCL4.

The Somatostatin Receptor-4 Agonist J-2156 Alleviates Mechanical Hypersensitivity in a Rat Model of Breast Cancer Induced Bone Pain

In the majority of patients with breast cancer in the advanced stages, skeletal metastases are common, which may cause excruciating pain. Currently available drug treatments for relief of breast cancer-induced bone pain (BCIBP) include non-steroidal anti-inflammatory drugs and strong opioid analgesics along with inhibitors of osteoclast activity such as bisphosphonates and monoclonal antibodies such as denosumab. However, these medications often lack efficacy and/or they may produce serious dose-limiting side effects. In the present study, we show that J-2156, a somatostatin receptor type 4 (SST4 receptor) selective agonist, reverses pain-like behaviors in a rat model of BCIBP induced by unilateral intra-tibial injection of Walker 256 breast cancer cells. Following intraperitoneal administration, the ED₅₀ of J-2156 for the relief of mechanical allodynia and mechanical hyperalgesia in the ipsilateral hindpaws was 3.7 and 8.0 mg/kg, respectively. Importantly, the vast majority of somatosensory neurons in the dorsal root ganglia including small diameter C-fibers and medium-large diameter fibers, that play a crucial role in cancer pain hypersensitivities, expressed the SST4 receptor. J-2156 mediated pain relief in BCIBP-rats was confirmed by observations of a reduction in the levels of phosphorylated extracellular signal-regulated kinase (pERK), a protein essential for central sensitization and persistent pain, in the spinal dorsal horn. Our results demonstrate the potential of the SST4 receptor as a pharmacological target for relief of BCIBP and we anticipate the present work to be a starting point for further mechanism-based studies.

Digital gene expression profiling analysis and its application in the identification of genes associated with improved response to neoadjuvant chemotherapy in breast cancer

BACKGROUND

This study aimed to screen sensitive biomarkers for the efficacy evaluation of neoadjuvant chemotherapy in breast cancer.

METHODS

In this study, Illumina digital gene expression sequencing technology was applied and differentially expressed genes (DEGs) between patients presenting pathological complete response (pCR) and non-pathological complete response (NpCR) were identified. Further, gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were then performed. The genes in significant enriched pathways were finally quantified by quantitative real-time PCR (qRT-PCR) to confirm that they were differentially expressed. Additionally, GSE23988 from Gene Expression Omnibus database was used as the validation dataset to confirm the DEGs.

RESULTS

After removing the low-quality reads, 715 DEGs were finally detected. After mapping to KEGG pathways, 10 DEGs belonging to the ubiquitin proteasome pathway (HECTD3, PSMB10, UBD, UBE2C, and UBE2S) and cytokine-cytokine receptor interactions (CCL2, CCR1, CXCL10, CXCL11, and IL2RG) were selected for further analysis. These 10 genes were finally quantified by qRT-PCR to confirm that they were differentially expressed (the log2 fold changes of selected genes were - 5.34, 7.81, 6.88, 5.74, 3.11, 19.58, 8.73, 8.88, 7.42, and 34.61 for HECTD3, PSMB10, UBD, UBE2C, UBE2S, CCL2, CCR1, CXCL10, CXCL11, and IL2RG, respectively). Moreover, 53 common genes were confirmed by the validation dataset, including downregulated UBE2C and UBE2S.

CONCLUSION

Our results suggested that these 10 genes belonging to these two pathways might be useful as sensitive biomarkers for the efficacy evaluation of neoadjuvant chemotherapy in breast cancer.

Serum and synovial fluid cytokine profiling in hip osteoarthritis: distinct from knee osteoarthritis and correlated with pain

Background

Inflammation is associated with the onset and progression of osteoarthritis in multiple joints. It is well known that mechanical properties differ between different joints, however, it remains unknown if the inflammatory process is similar/distinct in patients with hip vs. knee OA. Without complete understanding of the role of any specific cytokine in the inflammatory process, understanding the ‘profile’ of inflammation in a given patient population is an essential starting point. The aim of this study was to identify serum cytokine profiles in hip Osteoarthritis (OA), and investigate the association between cytokine concentrations and clinical measurements within this patient population and compare these findings to knee OA and healthy control cohorts.

Methods

In total, 250 serum samples (100 knee OA, 50 hip OA and 100 control) and 37 synovial fluid samples (8 knee OA, 14 hip OA and 15 control) were analyzed using a multiplex ELISA based approach. Synovial biopsies were also obtained and examined for specific cytokines. Pain, physical function and activity within the hip OA cohort were examined using the HOOS, SF-36, HHS and UCLA outcome measures.

Results

The three cohorts showed distinct serum cytokine profiles. EGF, FGF2, MCP3, MIP1α, and IL8 were differentially expressed between hip and knee OA cohorts; while FGF2, GRO, IL8, MCP1, and VEGF were differentially expressed between hip OA and control cohorts. Eotaxin, GRO, MCP1, MIP1β, VEGF were differentially expressed between knee OA and control cohorts. EGF, IL8, MCP1, MIP1β were differentially expressed in synovial fluid from a sub-set of patients from each cohort. Specifically within the hip OA cohort, IL-6, MDC and IP10 were associated with pain and were also found to be present in synovial fluid and synovial membrane (except IL-6) of patients with hip OA.

Conclusion

OA may include different inflammatory subtypes according to affected joints and distinct inflammatory processes may drive OA in these joints. IL6, MDC and IP10 are associated with hip OA pain and these proteins may be able to provide additional information regarding pain in hip OA patients.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-1955-4) contains supplementary material, which is available to authorized users.

Sinomenine attenuates cancer-induced bone pain via suppressing microglial JAK2/STAT3 and neuronal CAMKII/CREB cascades in rat models

Cancer-induced bone pain is one of the most severe types of pathological pain, which often occurs in patients with advanced prostate, breast, and lung cancer. It is of great significance to improve the therapies of cancer-induced bone pain due to the opioids' side effects including addiction, sedation, pruritus, and vomiting. Sinomenine, a traditional Chinese medicine, showed obvious analgesic effects on a rat model of chronic inflammatory pain, but has never been proven to treat cancer-induced bone pain. In the present study, we investigated the analgesic effect of sinomenine after tumor cell implantation and specific cellular mechanisms in cancer-induced bone pain. Our results indicated that single administration of sinomenine significantly and dose-dependently alleviated mechanical allodynia in rats with cancer-induced bone pain and the effect lasted for 4 h. After tumor cell implantation, the protein levels of phosphorylated-Janus family tyrosine kinase 2 (p-JAK2), phosphorylated-signal transducers and activators of transcription 3 (p-STAT3), phosphorylated-Ca2+/calmodulin-dependent protein kinase II (p-CAMKII), and phosphorylated-cyclic adenosine monophosphate response element-binding protein (p-CREB) were persistently up-regulated in the spinal cord horn. Chronic intraperitoneal treatment with sinomenine markedly suppressed the activation of microglia and effectively inhibited the expression of JAK2/STAT3 and CAMKII/CREB signaling pathways. We are the first to reveal that up-regulation of microglial JAK2/STAT3 pathway are involved in the development and maintenance of cancer-induced bone pain. Moreover, our investigation provides the first evidence that sinomenine alleviates cancer-induced bone pain by inhibiting microglial JAK2/STAT3 and neuronal CAMKII/CREB cascades.

Altered expression of differential gene and lncRNA in the lower thoracic spinal cord on different time courses of experimental obstructive jaundice model accompanied with altered peripheral nociception in rats

The spinal origin of jaundice-induced altered peripheral nociceptive response poorly understood. In the current study, we aimed to first validate rats with bile duct ligation (BDL) as a jaundice model accompanied by altered peripheral nociceptive response, and then to analyze differential gene and lncRNA expression patterns in the lower thoracic spinal cord on different time courses after BDL operation by using high-throughput RNA sequencing. The differentially expressed genes (DEGs) identified using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis, followed by clustering analysis, Gene Ontology analysis and pathway analysis. As a result, a total of 2033 lncRNAs were differentially expressed 28d after BDL, in which 1545 probe sets were up-regulated and 488 probe sets were down-regulated, whereas a total of 2800 mRNAs were differentially expressed, in which 1548 probe sets were up-regulated and 1252 probe sets were down-regulated. The RNAseq data of select mRNAs and lncRNAs was validated by RT-qPCR. 28d after BDL, the expressions of lncRNA NONRATT002335 and NONRATT018085 were significantly up-regulated whereas the expression of lncRNA NONRATT025415, NONRATT025388 and NONRATT025409 was significantly down-regulated. 14d after BDL, the expressions of lncRNA NONRATT002335 and NONRATT018085 were significantly up-regulated; the expression of lncRNA NONRATT025415, NONRATT025388 and NONRATT025409 was significantly down-regulated. In conclusion, the present study showed that jaundice accompanied with decreased peripheral nociception involved in the changes of gene and lncRNA expression profiles in spinal cord. These findings extend current understanding of spinal mechanism for obstructive jaundice accompanied by decreased peripheral nociception.

Reactive oxygen species scavengers ameliorate mechanical allodynia in a rat model of cancer-induced bone pain

Cancer-induced bone pain (CIBP) is a frequent complication in patients suffering from bone metastases. Previous studies have demonstrated a pivotal role of reactive oxygen species (ROS) in inflammatory and neuropathic pain, and ROS scavengers exhibited potent antinociceptive effect. However, the role of spinal ROS remains unclear. In this study, we investigated the analgesic effect of two ROS scavengers in a well-established CIBP model. Our results found that intraperitoneal injection of N-tert-Butyl-α-phenylnitrone (PBN, 50 and 100 mg/kg) and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol, 100 and 200 mg/kg) significantly suppressed the established mechanical allodynia in CIBP rats. Moreover, repeated injection of PBN and Tempol showed cumulative analgesic effect without tolerance. However, early treatment with PBN and Tempol failed to prevent the development of CIBP. Naive rats received repetitive injection of PBN and Tempol showed no significant change regarding the nociceptive responses. Finally, PBN and Tempol treatment notably suppressed the activation of spinal microglia in CIBP rats. In conclusion, ROS scavengers attenuated established CIBP by suppressing the activation of microglia in the spinal cord.

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PBN and Tempol could suppress established mechanical allodynia in CIBP rats.

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Repeated injection of PBN and Tempol showed cumulative analgesic effect.

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PBN and Tempol failed to prevent the development of CIBP.

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PBN and Tempol could suppress the microglia activation in CIBP rats.

Potential role of CXCL10/CXCR3 signaling in the development of morphine tolerance in periaqueductal gray

Tolerance to morphine antinociception hinders its long-term use in clinical practice. Interaction between neuron and microglia has been proved to play critical role in the mechanism of morphine tolerance, while CXCL10/CXCR3 signaling has been implicated in neuron-glia signaling and morphine analgesia. This study aims to investigate whether CXCL10/CXCR3 signaling in periaqueductal gray (PAG) contributes to the development of morphine tolerance by modulating neuron-microglia interaction. The results showed that the expressions of CXCR3 and CXCL10 were gradually increased in parallel with repeated morphine administration and activation of microglia. CXCR3 was co-localized with neuronal marker NeuN, while CXCL10 was derived from microglia. Microglia inhibitor minocycline significantly attenuated the expression of CXCL10, besides, both minocycline and CXCR3 inhibitor alleviated the development of morphine tolerance. Taken together, our study provided the evidence that CXCL10/CXCR3 signaling in PAG is involved in the development of morphine analgesic tolerance via neuron-microglia interaction.

Exosome secretome and mediated signaling in breast cancer patients with nontuberculous mycobacterial disease

Bronchiectasis Nontuberculous mycobacterium (NTM_nb) infection is an emerging health problem in breast cancer (BCa) patients. We measured sera exosome proteome in BCa-NTM_nb subjects and controls by Mass Spectroscopy. Extracellular matrix protein 1 (ECM1) was detected exclusively in the circulating exosomes of 82% of the BCa-NTM_nb cases. Co-culture of ECM1⁺ exosomes with normal human mammary epithelial cells induced epithelial to mesenchymal transition accompanied by increased Vimentin/CDH1 expression ratio and Glutamate production. Co-culture of the ECM1⁺ exosomes with normal human T cells modulated their cytokine production. The ECM1⁺ exosomes were markedly higher in sera obtained from BCa-NTM_nb subjects. Exclusive expression of APN, APOC4 and AZGP1 was evident in the circulating exosomes of these BCa-NTM_nb cases, which predicts disease prevalence independent of the body max index in concert with ECM1. Monitoring ECM1, APN, APOC4 and AZGP1 in the circulating exosomes could be beneficial for risk assessment, monitoring and surveillance of BCa-NTM_nb.

Altered expression of target genes of spinal cord in different itch models compared with capsaicin assessed by RT-qPCR validation

Spinal cord plays a central role in the development and progression of pathogenesis of obstinate pruritus. In the current study, four groups of adult male C57Bl/6 mice were investigated; one group treated with saline, while the other groups intradermally injected with compound 48/80, histamine, α-Me-5-HT and capsaicin (algogenic substance), respectively. The intradermal microinjection of pruritic and algogenic compound resulted in a dramatic increase in the itch/algogenic behavior. Analysis of the microarray data showed that 15 genes in spinal cord (C5-C8) were differentially expressed between control group and 48/80 group, in which 9 genes were up-regulated and 6 genes were down-regulated. Furthermore, the results of RT-qPCR validation studies in C5-C8 spinal cord revealed that the 9 mRNA (Sgk1, Bag4, Fos, Ehd2, Edn3, Wdfy, Corin, 4921511E18Rik and 4930423020Rik) showed very different patterns for these different drugs, especially when comparing α-Me-5-HT and capsaicin. In three itch models, Fos and Ehd2 were up-regulated whereas Corin, 4921511E18Rik and 4930423020Rik were down-regulated. Furthermore, Corin and 4930423020Rik were down-regulated in itch model group compared to capsaicin group. Thus the application of microarray technique, coupled with RT-qPCR validation, further explain the mechanism behind itching evoked by pruritic compounds. It can contribute to our understanding of pharmacological methods for prevention or treatment of obstinate pruritus.

Optimization and In Vivo Profiling of a Refined Rat Model of Walker 256 Breast Cancer Cell-Induced Bone Pain Using Behavioral, Radiological, Histological, Immunohistochemical and Pharmacological Methods

In the majority of patients with advanced breast cancer, there is metastatic spread to bones resulting in pain. Clinically available drug treatments for alleviation of breast cancer-induced bone pain (BCIBP) often produce inadequate pain relief due to dose-limiting side-effects. A major impediment to the discovery of novel well-tolerated analgesic agents for the relief of pain due to bony metastases is the fact that most cancer-induced bone pain models in rodents relied on the systemic injection of cancer cells, causing widespread formation of cancer metastases and poor general animal health. Herein, we have established an optimized, clinically relevant Wistar Han female rat model of breast cancer induced bone pain which was characterized using behavioral assessments, radiology, histology, immunohistochemistry and pharmacological methods. In this model that is based on unilateral intra-tibial injection (ITI) of Walker 256 carcinoma cells, animals maintained good health for at least 66 days post-ITI. The temporal development of hindpaw hypersensitivity depended on the initial number of Walker 256 cells inoculated in the tibiae. Hindpaw hypersensitivity resolved after approximately 25 days, in the continued presence of bone tumors as evidenced by ex vivo histology, micro-computed tomography scans and immunohistochemical assessments of tibiae. A possible role for the endogenous opioid system as an internal factor mediating the self-resolving nature of BCIBP was identified based upon the observation that naloxone, a non-selective opioid antagonist, caused the re-emergence of hindpaw hypersensitivity. Bolus dose injections of morphine, gabapentin, amitriptyline and meloxicam all alleviated hindpaw hypersensitivity in a dose-dependent manner. This is a first systematic pharmacological profiling of this model by testing standard analgesic drugs from four important diverse classes, which are used to treat cancer induced bone pain in the clinical setting. Our refined rat model more closely mimics the pathophysiology of this condition in humans and hence is well-suited for probing the mechanisms underpinning breast cancer induced bone pain. In addition, the model may be suitable for efficacy profiling of new molecules from drug discovery programs with potential to be developed as novel agents for alleviation of intractable pain associated with disseminated breast cancer induced bony metastases.

STAT1 as a downstream mediator of ERK signaling contributes to bone cancer pain by regulating MHC II expression in spinal microglia

Major histocompatibility class II (MHC II)-specific activation of CD4⁺ T helper cells generates specific and persistent adaptive immunity against tumors. Emerging evidence demonstrates that MHC II is also involved in basic pain perception; however, little is known regarding its role in the development of cancer-induced bone pain (CIBP). In this study, we demonstrate that MHC II expression was markedly induced on the spinal microglia of CIBP rats in response to STAT1 phosphorylation. Mechanical allodynia was ameliorated by either pharmacological or genetic inhibition of MHC II upregulation, which was also attenuated by the inhibition of pSTAT1 and pERK but was deteriorated by intrathecal injection of IFNγ. Furthermore, inhibition of ERK signaling decreased the phosphorylation of STAT1, as well as the production of MHC II in vivo and in vitro. These findings suggest that STAT1 contributes to bone cancer pain as a downstream mediator of ERK signaling by regulating MHC II expression in spinal microglia.

Designing small molecule CXCR3 antagonists

INTRODUCTION

By virtue of its specificity for chemokines induced in Th1-associated pathologies, CXCR3 has attracted considerable attention as a target for therapeutic intervention. Several pharmacologically distinct small molecules with in vitro and in vivo potency have been described in the literature, although to date, none have shown efficacy in clinical trials. Areas covered: In this article, the author outlines the rationale for targeting CXCR3 and discusses the potential pitfalls in targeting receptors in poorly understood areas of chemokine biology. Furthermore, they cover emerging therapeutic areas outside of the 'traditional' Th1 arena in which CXCR3 antagonists may ultimately bear fruit. Finally, they discuss the design of recently discovered small molecules targeting CXCR3. Expert opinion: CXCR3 and its ligands appear to play roles in a multitude of diverse diseases in humans. In vitro studies suggest that CXCR3 is inherently 'druggable' and that potent, efficacious small molecules targeting CXCR3 antagonists will find a clinical niche. However, the well-trodden path to failure of small molecule chemokine receptor antagonists in clinical trials suggests that a cautious approach should be undertaken. Ideally, unequivocal evidence elucidating the precise role of CXCR3 should be obtained before targeting the receptor in a particular disease cohort.

Upregulation of (C-X-C motif) Ligand 13 (CXCL13) Attenuates Morphine Analgesia in Rats with Cancer-Induced Bone Pain

Background

The aim of this study was to investigate the role of chemokine (C-X-C motif) ligand 13 (CXCL13) in morphine tolerance in rats with cancer-induced bone pain (CIBP).

Material/Methods

We established a rat CIBP model and a rat CIBP-morphine tolerance (BM) model. BM rats were intrathecally administered rmCXCL13, neutralizing anti-CXCL13, and normal saline, while the control group rats underwent a sham operation and were injected with normal saline. The morphine analgesia was assessed by measuring mechanical withdrawal threshold (MWT) and mechanical withdrawal duration (MWD) at various time points. The co-expressions of CXCL13 and NeuN were measured by immunofluorescence double-staining. CXCL13 protein and mRNA expressions were detected by Western blot and quantitative real-time polymerase chain reaction (RT-qPCR), respectively.

Results

Compared to the sham-operation (S) group, the BM group showed obviously decreased MWT and increased MWD on Day 9 after CIBP, but obviously increased MWT and decreased MWD on Day 3 after morphine administration; subsequently, the MWT was decreased and MWD was increased (all P<0.05). In comparison with the S+saline group, increased MWT and decreased MWD were observed in BM rats on Day 3 after anti-CXCL13 administration, and obviously decreased MWT and increased MWD were found in BM rats on Day 3 after rmCXCL13 administration (all P<0.05).

Conclusions

Up-regulated CXCL13 has a negative role in morphine analgesia in relief of CIBP, which may provide a new target for the management of CIBP.