CXCR4 antagonist AMD3100 elicits analgesic effect and restores the GlyRα3 expression against neuropathic pain

Elevated plasma CXCL12 leads to pain chronicity via positive feedback upregulation of CXCL12/CXCR4 axis in pain synapses

BACKGROUND

Chronic pain poses a clinical challenge due to its associated costly disability and treatment needs. Determining how pain transitions from acute to chronic is crucial for effective management. Upregulation of the chemokine C-X-C motif ligand 12 (CXCL12) in nociceptive pathway is associated with chronic pain. Our previous study has reported that elevated plasma CXCL12 mediates intracerebral neuroinflammation and the comorbidity of cognitive impairment in neuropathic pain, but whether it is also involved in the pathogenesis of pathologic pain has not been investigated.

METHODS

Intravenous or intrathecal injection (i.v. or i.t.) of recombinant mouse CXCL12, neutralizing antibody (anti-CXCL12) or AMD3100 [an antagonist of its receptor C-X-C chemokine receptor type 4 (CXCR4)] was used to investigate the role of CXCL12 signaling pathway in pain chronicity. Two behavioral tests were used to examine pain changes. ELISA, immunofluorescence staining, Western blot, quantitative Real Time-PCR and Cytokine array were applied to detect the expressions of different molecules.

RESULTS

We found that increased plasma CXCL12 was positively correlated with pain severity in both chronic pain patients and neuropathic pain model in mice with spared nerve injury (SNI). Neutralizing plasma CXCL12 mitigated SNI-induced hyperalgesia. A single i.v. injection of CXCL12 induced prolonged mechanical hyperalgesia and activation of the nociceptive pathway. Multiple intravenous CXCL12 caused persistent hypersensitivity, enhanced structural plasticity of nociceptors and up-regulation of the CXCL12/CXCR4 axis in the dorsal root ganglion (DRG) and spinal dorsal horn (SDH). However, intrathecal blocking of CXCL12/CXCR4 pathway by CXCL12 antibody or CXCR4 antagonist AMD3100 significantly alleviated CXCL12-induced pain hypersensitivity and pathological changes.

CONCLUSIONS

Our study provides strong evidence that a sustained increase in plasma CXCL12 contributes to neuropathic pain through a positive feedback loop that enhances nociceptor plasticity, and suggests that targeting CXCL12/CXCR4 axis in plasma or nociceptive pathways has potential value in regulating pain chronicity.

Esketamine inhibits the c-Jun N-terminal kinase pathway in the spinal dorsal horn to relieve bone cancer pain in rats

Cancer-induced bone pain (CIBP) is one of the most common and feared symptoms in patients with advanced tumors. The X-C motif chemokine ligand 12 (CXCL12) and the CXCR4 receptor have been associated with glial cell activation in bone cancer pain. Moreover, mitogen-activated protein kinases (MAPKs), as downstream CXCL12/CXCR4 signals, and c-Jun, as activator protein AP-1 components, contribute to the development of various types of pain. However, the specific CIBP mechanisms remain unknown. Esketamine is a non-selective N-methyl-d-aspartic acid receptor (NMDA) inhibitor commonly used as an analgesic in the clinic, but its analgesic mechanism in bone cancer pain remains unclear. We used a tumor cell implantation (TCI) model and explored that CXCL12/CXCR4, p-MAPKs, and p-c-Jun were stably up-regulated in the spinal cord. Immunofluorescence images showed activated microglia in the spinal cord on day 14 after TCI and co-expression of CXCL12/CXCR4, p-MAPKs (p-JNK, p-ERK, p-p38 MAPK), and p-c-Jun in microglia. Intrathecal injection of the CXCR4 inhibitor AMD3100 reduced JNK and c-Jun phosphorylations, and intrathecal injection of the JNK inhibitor SP600125 and esketamine also alleviated TCI-induced pain and reduced the expression of p-JNK and p-c-Jun in microglia. Overall, our data suggest that the CXCL12/CXCR4-JNK-c-Jun signaling pathway of microglia in the spinal cord mediates neuronal sensitization and pain hypersensitivity in cancer-induced bone pain and that esketamine exerts its analgesic effect by inhibiting the JNK-c-Jun pathway.

Progress in Pathological and Therapeutic Research of HIV-Related Neuropathic Pain

HIV-related neuropathic pain (HRNP) is a neurodegeneration that gradually develops during the long-term course of acquired immune deficiency syndrome (AIDS) and manifests as abnormal sock/sleeve-like symmetrical pain and nociceptive hyperalgesia in the extremities, which seriously reduces patient quality of life. To date, the pathogenesis of HRNP is not completely clear. There is a lack of effective clinical treatment for HRNP and it is becoming a challenge and hot spot for medical research. In this study, we conducted a systematic review of the progress of HRNP research in recent years including (1) the etiology, classification and clinical symptoms of HRNP, (2) the establishment of HRNP pathological models, (3) the pathological mechanisms underlying HRNP from three aspects: molecules, signaling pathways and cells, (4) the therapeutic strategies for HRNP, and (5) the limitations of recent HRNP research and the future research directions and prospects of HRNP. This detailed review provides new and systematic insight into the pathological mechanism of HRNP, which establishes a theoretical basis for the future exploitation of novel target drugs. HIV infection, antiretroviral therapy and opioid abuse contribute to the etiology of HRNP with symmetrical pain in both hands and feet, allodynia and hyperalgesia. The pathogenesis involves changes in cytokine expression, activation of signaling pathways and neuronal cell states. The therapy for HRNP should be patient-centered, integrating pharmacologic and nonpharmacologic treatments into multimodal intervention.

CXCR4 antagonists disrupt leukaemia-meningeal cell adhesion and attenuate chemoresistance

The effective prophylaxis and treatment of central nervous system (CNS) involvement in acute lymphoblastic leukaemia (ALL) remains a significant clinical challenge. Developing novel and more effective CNS-directed therapies has been hampered, in part, by our limited understanding of the leukaemia niche in the CNS relative to the bone marrow. Accordingly, defining the molecular and cellular components critical for the establishment and maintenance of the CNS leukaemia niche may lead to new therapeutic opportunities. In prior work we showed that direct intercellular interactions between leukaemia and meningeal cells enhance leukaemia chemoresistance in the CNS. Herein, we show that the CXCR4/CXCL12 chemokine axis contributes to leukaemia-meningeal cell adhesion. Importantly, clinically tested CXCR4 antagonists, which are likely to cross the blood-brain and blood-cerebral spinal fluid barriers and penetrate the CNS, effectively disrupted leukaemia-meningeal cell adhesion. Moreover, by disrupting these intercellular interactions, CXCR4 antagonists attenuated leukaemia chemoresistance in leukaemia-meningeal cell co-culture experiments and enhanced the efficacy of cytarabine in targeting leukaemia cells in the meninges in vivo. This work identifies the CXCR4/CXCL12 axis as an important regulator of intercellular interactions within the CNS leukaemia niche and supports further testing of the therapeutic efficacy of CXCR4 antagonists in overcoming CNS niche-mediated chemoresistance.

miR-185-5p alleviates CCI-induced neuropathic pain by repressing NLRP3 inflammasome through dual targeting MyD88 and CXCR4

MicroRNAs (miRNAs) are important modulators in the evolvement and progression of neuropathic pain (NP). According to reports, miR-185-5p contributes to various diseases and inflammatory responses. However, it is not clear whether miR-185-5p mediates neuroinflammation and NP following chronic constrictive injury (CCI). The CCI model was constructed in rats to induce NP. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) were employed to evaluate pain threshold in CCI rats. The expression of miR-185-5p, GFAP, Iba1, Caspase-3-positive cells, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)-labeled apoptotic neurons, inflammatory mediators, including interleukin (IL)-6, IL-1β and tumor necrosis factor-α (TNF-α) in lumbar portion (L4-L6) of CCI rats were determined. Furthermore, the targets of miR-185-5p were predicted by the Starbase, and the binding association between miR-185-5p and MyD88, miR-185-5p and CXCR4 was verified by the dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. As shown by the data, miR-185-5p was distinctly reduced in L4-L6 spinal cord tissues of rats after CCI. Up-regulating miR-185-5p alleviated mechanical and thermal hyperalgesia, inactivated microglia and astrocytes accumulation, and abated the contents of IL-1β, IL-6 and TNF-α in L4-L6 spinal cord tissues of CCI rats. Bioinformatics analysis suggested that MyD88 and CXCR4 were potential target genes of miR-185-5p. Increasing miR-185-5p expression notably impeded the expression of MyD88, CXCR4 and NLRP3 inflammasome in BV2 microglia, while attenuating miR-185-5p expression exerted the opposite effects. Notably, down-regulating MyD88 and CXCR4 significantly enhanced the miR-185-5p-mediated anti-inflammatory effects, and reversed miR-185-5p inhibitor-mediated proinflammatory effects. Additionally, up-regulating miR-185-5p repressed BV2-induced neuronal apoptosis and increased neuronal viability. In conclusion, this study suggested that miR-185-5p chokes CCI-induced NP and neuroinflammation by targeting MyD88 and CXCR4, indicating that miR-186-5p is an underlying therapeutic target for NP.

Upregulating miR-130a-5p relieves astrocyte over activation-induced neuropathic pain through targeting C-X-C motif chemokine receptor 12/C-X-C motif chemokine receptor 4 axis

OBJECTIVES

This study intends to explore the role and specific mechanism of miR-130a-5p in neuropathic pain through regulating the C-X-C motif chemokine receptor 12 (CXCL12)-C-X-C motif chemokine receptor 4 (CXCR4) pathway.

METHODS

First, mouse neuropathic pain model was constructed by spinal nerve ligation. MiR-130a-5p mimics were used to upregulate miR-130a-5p in vivo. The behaviour and pain scores of the spinal cord injury (SCI) mice were assessed. In addition, astrocytic activation as well as inflammatory response in the spinal lesions was determined.

RESULTS

The results manifested miR-130a-5p was notably downregulated in neuropathic pain model and reached the lowest point at 3 days after injury. Besides, tail vein injection of miR-130a-5p mimics inhibited the activation and inflammatory response of astrocytes, thus alleviating chronic constriction injury-induced neuropathic pain. Moreover, miR-130a-5p inactivated CXCR4 and its downstream Rac1, nuclear factor-κB (NF-κB) and extracellular regulated protein kinases signalling pathways by attenuating CXCL12.

CONCLUSION

MiR-130a-5p inactivated astrocytes by targeting CXCL12/CXCR4, thus alleviating SCI-induced neuropathic pain.

[HMGB1 as a target for prevention of chemotherapy-induced peripheral neuropathy]

Chemotherapy-induced peripheral neuropathy (CIPN) considerably impairs cancer patients' QOL, and may lead to discontinuation of drug treatment of cancer. Currently, there is no effective strategy against CIPN. Therefore, it is an urgent issue to develop clinically available drugs that prevent or treat CIPN. We have shown that high mobility group box 1 (HMGB1), a damage-associated molecular pattern (DAMP) molecule, plays an essential role in the development of CIPN. Most interestingly, thrombomodulin α, approved as a medicine for treatment of disseminated intravascular coagulation (DIC) in Japan, causes thrombin-dependent degradation of extracellular HMGB1 that is released in response to chemotherapeutics, and prevents CIPN. Thus, we expect that targeting HMGB1 or its receptors would lead to prevention of CIPN in cancer patients in near future.

Targeting Neuropathic Pain: Pathobiology, Current Treatment and Peptidomimetics as a New Therapeutic Opportunity

There is a huge need for pharmaceutical agents for the treatment of chronic Neuropathic Pain (NP), a complex condition where patients can suffer from either hyperalgesia or allodynia originating from central or peripheral nerve injuries. To date, the therapeutic guidelines include the use of tricyclic antidepressants, serotonin-noradrenaline reuptake inhibitors and anticonvulsants, beside the use of natural compounds and non-pharmacological options. Unfortunately, these drugs suffer from limited efficacy and serious dose-dependent adverse effects. In the last decades, the heptapeptide SP1-7, the major bioactive metabolite produced by Substance P (SP) cleavage, has been extensively investigated as a potential target for the development of novel peptidomimetic molecules to treat NP. Although the physiological effects of this SP fragment have been studied in detail, the mechanism behind its action is not fully clarified and the target for SP1-7 has not been identified yet. Nevertheless, specific binding sites for the heptapeptide have been found in brain and spinal cord of both mouse and rats. Several Structure-Affinity Relationship (SAR) studies on SP1-7 and some of its synthetic analogues have been carried out aiming to developing more metabolically stable and effective small molecule SP1-7-related amides that could be used as research tools for a better understanding of the SP1-7 system and, in a longer perspective, as potential therapeutic agents for future treatment of NP.

Mozobil® (Plerixafor, AMD3100), 10 years after its approval by the US Food and Drug Administration

AMD3100 (plerixafor, Mozobil®) was first identified as an anti-HIV agent specifically active against the T4-lymphotropic HIV strains, as it selectively blocked the CXCR4 receptor. Through interference with the interaction of CXCR4 with its natural ligand, SDF-1 (also named CXCL12), it also mobilized the CD34⁺stem cells from the bone marrow into the peripheral blood stream. In December 2008, AMD3100 was formally approved by the US FDA for autologous transplantation in patients with Non-Hodgkin’s Lymphoma or multiple myeloma. It may be beneficially used in various other malignant diseases as well as hereditary immunological disorders such as WHIM syndrome, and physiopathological processes such as hepatopulmonary syndrome.

Thrombin-Responsive, Brain-Targeting Nanoparticles for Improved Stroke Therapy

Current treatments for ischemic stroke are insufficient. The lack of effective pharmacological approaches can be mainly attributed to the difficulty in overcoming the blood-brain barrier. Here, we report a simple strategy to synthesize protease-responsive, brain-targeting nanoparticles for the improved treatment of stroke. The resulting nanoparticles respond to proteases enriched in the ischemic microenvironment, including thrombin or matrix metalloproteinase-9, by shrinking or expanding their size. Targeted delivery was achieved using surface conjugation of ligands that bind to proteins that were identified to enrich in the ischemic brain using protein arrays. By screening a variety of formulations, we found that AMD3100-conjugated, size-shrinkable nanoparticles (ASNPs) exhibited the greatest delivery efficiency. The brain targeting effect is mainly mediated by AMD3100, which interacts with CXCR4 that is enriched in the ischemic brain tissue. We showed that ASNPs significantly enhanced the efficacy of glyburide, a promising stroke therapeutic drug whose efficacy is limited by its toxicity. Due to their high efficiency in penetrating the ischemic brain and low toxicity, we anticipate that ASNPs have the potential to be translated into clinical applications for the improved treatment of stroke patients.

miRNA-23a/CXCR4 regulates neuropathic pain via directly targeting TXNIP/NLRP3 inflammasome axis

BACKGROUND

Chemokine CXC receptor 4 (CXCR4) in spinal glial cells has been implicated in neuropathic pain. However, the regulatory cascades of CXCR4 in neuropathic pain remain elusive. Here, we investigated the functional regulatory role of miRNAs in the pain process and its interplay with CXCR4 and its downstream signaling.

METHODS

miRNAs and CXCR4 and its downstream signaling molecules were measured in the spinal cords of mice with sciatic nerve injury via partial sciatic nerve ligation (pSNL). Immunoblotting, immunofluorescence, immunoprecipitation, and mammal two-hybrid and behavioral tests were used to explore the downstream CXCR4-dependent signaling pathway.

RESULTS

CXCR4 expression increased in spinal glial cells of mice with pSNL-induced neuropathic pain. Blocking CXCR4 alleviated the pain behavior; contrarily, overexpressing CXCR4 induced pain hypersensitivity. MicroRNA-23a-3p (miR-23a) directly bounds to 3' UTR of CXCR4 mRNA. pSNL-induced neuropathic pain significantly reduced mRNA expression of miR-23a. Overexpression of miR-23a by intrathecal injection of miR-23a mimics or lentivirus reduced spinal CXCR4 and prevented pSNL-induced neuropathic pain. In contrast, knockdown of miR-23a by intrathecal injection of miR-23a inhibitor or lentivirus induced pain-like behavior, which was reduced by CXCR4 inhibition. Additionally, miR-23a knockdown or CXCR4 overexpression in naïve mice could increase the thioredoxin-interacting protein (TXNIP), which was associated with induction of NOD-like receptor protein 3 (NLRP3) inflammasome. Indeed, CXCR4 and TXNIP were co-expressed. The mammal two-hybrid assay revealed the direct interaction between CXCR4 and TXNIP, which was increased in the spinal cord of pSNL mice. In particular, inhibition of TXNIP reversed pain behavior elicited by pSNL, miR-23a knockdown, or CXCR4 overexpression. Moreover, miR-23a overexpression or CXCR4 knockdown inhibited the increase of TXNIP and NLRP3 inflammasome in pSNL mice.

CONCLUSIONS

miR-23a, by directly targeting CXCR4, regulates neuropathic pain via TXNIP/NLRP3 inflammasome axis in spinal glial cells. Epigenetic interventions against miR-23a, CXCR4, or TXNIP may potentially serve as novel therapeutic avenues in treating peripheral nerve injury-induced nociceptive hypersensitivity.