Characterisation of Immune and Neuroinflammatory Changes Associated with Chemotherapy-Induced Peripheral Neuropathy

Modeling mechanisms of chemotherapy-induced peripheral neuropathy and chemotherapy transport using induced pluripotent stem cell-derived sensory neurons

BACKGROUND

and Purpose: Chemotherapy-induced peripheral neuropathy (CIPN) constitutes a significant health problem due to the increasing prevalence and lack of therapies for treatment and prevention. While pivotal for routine cancer treatment, paclitaxel and vincristine frequently cause CIPN and impact the quality of life among cancer patients and survivors. Here, we investigate molecular mechanisms and drug transport in CIPN.

EXPERIMENTAL APPROACH

Human sensory neurons were derived from induced pluripotent stem cells (iPSC-SNs), which were characterized using flow cytometry and immunolabeling. These iPSC-SNs were exposed to different concentrations of the two microtubule-targeting agents, paclitaxel and vincristine, with and without pre-exposure to inhibitors and inducers of efflux transporters. Neuronal networks were quantified via fluorescent staining against sensory neuron markers. Transcriptional effects of the chemotherapeutics were examined using quantitative polymerase chain reactions (qPCR).

KEY RESULTS

Paclitaxel exposure resulted in axonal retraction and thickening, while vincristine caused fragmentation and abolishment of axons. Both agents increased the mRNA expression of the pain receptor, transient receptor potential vanilloid (TRPV1), and highly induced neuronal damage, as measured by activating transcription factor 3 (ATF3) mRNA. iPSC-SNs express the efflux transporters, P-glycoprotein (P-gp, encoded by ABCB1) and multidrug resistance-associated protein 1 (MPR1, encoded by ABCC1). Modulation of efflux transporters indicate that P-gp and MRP1 play a role in modulating neuronal accumulation and neurotoxicity in preliminary experiments.

CONCLUSION

and Implications: iPSC-SNs are a valuable and robust model to study the role of efflux transporters and other mechanistic targets in CIPN. Efflux transporters may play a role in CIPN pathogenesis as they regulate the disposition of chemotherapy to the peripheral nervous system, and they may present potential therapeutic targets for CIPN.

The role of the gut microbiome in neuroinflammation and chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most debilitating adverse effects caused by chemotherapy drugs such as paclitaxel, oxaliplatin and vincristine. It is untreatable and often leads to the discontinuation of cancer therapy and a decrease in the quality of life of cancer patients. It is well-established that neuroinflammation and the activation of immune and glial cells are among the major drivers of CIPN. However, these processes are still poorly understood, and while many chemotherapy drugs alone can drive the activation of these cells and consequent neuroinflammation, it remains elusive to what extent the gut microbiome influences these processes. In this review, we focus on the peripheral mechanisms driving CIPN, and we address the bidirectional pathways by which the gut microbiome communicates with the immune and nervous systems. Additionally, we critically evaluate literature addressing how chemotherapy-induced dysbiosis and the consequent imbalance in bacterial products may contribute to the activation of immune and glial cells, both of which drive neuroinflammation and possibly CIPN development, and how we could use this knowledge for the development of effective treatment strategies.

Functional and structural neurodegenerative activities of Ankaferd BloodStopper in a mouse sciatic nerve model

Traumatic and postoperative hemorrhages are life-threatening complications. Ankaferd BloodStopper (ABS) is a potent topical hemostatic agent to stop bleeding. However, ABS is associated with nerve toxicity. The present study aimed to investigate the functional and structural neurodegenerative effects of ABS in a mouse model. A total of 30 male BALB/c mice, aged 6-8 weeks, were randomly divided into control group (no treatment), a sham group (treated with saline) and an experimental group (treated with ABS). In the saline and the ABS groups, the right sciatic nerve was surgically exposed and treated with saline or ABS, respectively. No surgical procedure was performed in the control group. On day 7 post-treatment, functional changes of the sciatic nerve were evaluated by a horizontal ladder rung walking task. Structural changes were assessed with immunohistochemistry. In the horizontal ladder rung walking test, the gait impairment was proportional to the severity of sciatic nerve damage, with the ABS group showing a significantly higher rate of errors than the control and saline groups. Immunohistochemistry demonstrated extensive degeneration and deformation in the axons and myelin sheath of the sciatic nerve in the ABS group. The results provide compelling evidence for the neurotoxicity of ABS.

Acupuncture-related interventions improve chemotherapy-induced peripheral neuropathy: A systematic review and network meta-analysis

BACKGROUND

The previous effects of acupuncture-related interventions in improving chemotherapy-induced peripheral neuropathy (CIPN) symptoms and quality of life (QoL) remain unclear in terms of pairwise comparisons.

AIMS

This systematic review and network meta-analysis aimed to determine the hierarchical effects of acupuncture-related interventions on symptoms, pain, and QoL associated with CIPN in cancer patients undergoing chemotherapy.

METHODS

Nine electronic databases were searched, including PubMed, Embase, Cochrane Library, EBSCO, Medline Ovid, Airiti Library, China National Knowledge Infrastructure (CNKI), China Journal full-text database (CJFD), and Wanfang. Medical subject heading terms and text words were used to search for eligible randomized controlled trials published from database inception to May 2023.

RESULTS

A total of 33 studies involving 2,027 participants were included. Pairwise meta-analysis revealed that acupuncture-related interventions were superior to usual care, medication, or dietary supplements in improving CIPN symptoms, CIPN pain, and QoL. Furthermore, network meta-analysis indicated that acupuncture plus electrical stimulation (acupuncture-E) had the greatest overall effect among the various interventions. The surface under the cumulative ranking curve (SUCRA) revealed that acupuncture-E ranked the highest in improving CINP symptoms. Acupuncture alone was most effective in reducing CIPN pain, and acupuncture plus moxibustion (acupuncture-M) ranked highest in enhancing QoL.

CONCLUSION

This finding suggests that acupuncture-related interventions can provide patients with benefits in improving CIPN symptoms, pain, and QoL. In particular, acupuncture-E could be the most effective approach in which the provided evidence offers diverse options for cancer patients and healthcare professionals.

IMPLICATION FOR THE PROFESSION AND/OR PATIENT CARE

These findings provide valuable insights into the potential benefits of acupuncture-related interventions for managing symptoms, pain, and QoL associated with CIPN in patients undergoing chemotherapy. Among the various interventions studied, overall, acupuncture-E had the most significant impact and was effective for a minimum duration of 3 weeks. On the other hand, transcutaneous electrical acupoint/nerve stimulation (TEAS) was identified as a noninvasive and feasible alternative for patients who had concerns about needles or the risk of bleeding. It is recommended that TEAS interventions should be carried out for a longer period, preferably lasting 4 weeks, to achieve optimal outcomes.

TRIAL REGISTRATION

The study protocol was registered in the International Prospective Register of Systematic Reviews.

REGISTRATION NUMBER

CRD42022319871.

Persistent changes in nociceptor translatomes govern hyperalgesic priming in mouse models

Hyperalgesic priming is a model system that has been widely used to understand plasticity in painful stimulus-detecting sensory neurons, called nociceptors. A key feature of this model system is that following priming, stimuli that do not normally cause hyperalgesia now readily provoke this state. We hypothesized that hyperalgesic priming occurs due to reorganization of translation of mRNA in nociceptors. To test this hypothesis, we used paclitaxel treatment as the priming stimulus and translating ribosome affinity purification (TRAP) to measure persistent changes in mRNA translation in Nav1.8+ nociceptors. TRAP sequencing revealed 161 genes with persistently altered mRNA translation in the primed state. We identified Gpr88 as upregulated and Metrn as downregulated. We confirmed a functional role for these genes, wherein a GPR88 agonist causes pain only in primed mice and established hyperalgesic priming is reversed by Meteorin. Our work demonstrates that altered nociceptor translatomes are causative in producing hyperalgesic priming.

Communicating pain: emerging axonal signaling in peripheral neuropathic pain

Peripheral nerve damage often leads to the onset of neuropathic pain (NeuP). This condition afflicts millions of people, significantly burdening healthcare systems and putting strain on families' financial well-being. Here, we will focus on the role of peripheral sensory neurons, specifically the Dorsal Root Ganglia neurons (DRG neurons) in the development of NeuP. After axotomy, DRG neurons activate regenerative signals of axons-soma communication to promote a gene program that activates an axonal branching and elongation processes. The results of a neuronal morphological cytoskeleton change are not always associated with functional recovery. Moreover, any axonal miss-targeting may contribute to NeuP development. In this review, we will explore the epidemiology of NeuP and its molecular causes at the level of the peripheral nervous system and the target organs, with major focus on the neuronal cross-talk between intrinsic and extrinsic factors. Specifically, we will describe how failures in the neuronal regenerative program can exacerbate NeuP.

Efficacy and safety of traditional plant-based medicines for preventing chronic oxaliplatin-induced peripheral neurotoxicity in patients with colorectal cancer: A systematic review and meta-analysis with core herb contribution

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional plant-based medicines (TMs) have been widely used to prevent chronic oxaliplatin-induced peripheral neurotoxicity (OIPN). However, the prevention and safety of TMs for chronic OIPN remain ambiguous. Furthermore, diverse TM prescriptions and complicated components limit in-depth research on the mechanisms of TMs.

AIM OF THIS STUDY

To determine core TMs and potential pharmacological pathways on the basis of a thorough investigation into the preventive benefits and safety of oral TMs for chronic OIPN in colorectal cancer (CRC).

METHODS

A search of the PubMed, Cochrane, Embase, CNKI, VIP, and Wanfang databases for RCTs reporting on TMs for chronic OIPN was conducted through December 1, 2022. Subgroup analysis, sensitivity analysis and meta-regression were applied to assess the impacts of influencing variables. The assessment of Risk of Bias was relied on Cochrane Risk of Bias tool. The funnel plot, Egger's test, and the Trim and Fill method were applied to identify potential publication bias. Trial sequential analyses (TSA) were carried out by the TSA tool to increase the robustness. The assessment of the quality of evidence was according to the GRADE system. System pharmacology analysis was employed to screen core herbal combinations to elucidate possible mechanisms for preventing chronic OIPN in CRC.

RESULTS

The pooled effect estimate with robustness increased by TSA analysis demonstrated that oral TMs appeared to significantly decrease the incidence of chronic OIPN (RR = 0.66, 95% CI (0.56, 0.78); P＜0.00001), leukocytopenia (RR = 0.65, 95% CI (0.54,0.79); P＜0.00001), and nausea and vomiting (RR = 0.72, 95% CI (0.61,0.84); P＜0.0001) as well as improve the Objective Response Rate (ORR) (RR = 1.31, 95% CI (1.09,1.56); P = 0.003). The incidence of severe chronic OIPN was revealed a significant reduction, particularly when chemotherapy was administered for periods of time shorter than six months (RR = 0.33, 95% CI (0.15,0.71); P = 0.005; actuation duration＜3 months; RR = 0.33, 95% CI (0.17,0.62); P = 0.0007; actuation duration≥3 months, ＜6 months). The considerable heterogeneity among studies may be attributable to the severity of dysfunction categorized by grade and accumulated dosage. Using core TMs consisting of Astragalus membranaceus (Fisch.) Bunge, Atractylodes Macrocephala Koidz., Poria cocos (Schw.) Wolf, and Codonopsis pilosula (Franch.) Nannf. To regulate nuclear factor-kappa B against inflammation caused by activation of microglia might be an approach to preventing chronic OIPN.

CONCLUSIONS

TMs appear to be effective and safe in the prevention of chronic OIPN, especially severe chronic OIPN. Additionally, core TMs consisting of Astragalus membranaceus (Fisch.) Bunge, Atractylodes Macrocephala Koidz., Poria cocos (Schw.) Wolf, and Codonopsis pilosula (Franch.) Nannf were presumably responsible for reducing the incidence of chronic OIPN, and the mechanism may be related to relieving inflammation. However, quality-assured trials with long-term follow-up for exploring inflammatory factors and preliminary research on core TMs and pharmacological pathways are needed.

Paeoniflorin ameliorates oxaliplatin-induced peripheral neuropathy via inhibiting neuroinflammation through influence on gut microbiota

Oxaliplatin (OXA)-induced peripheral neuropathy (OIPN) is a severe side effect that greatly limits OXA clinical use and threatens patients' life and health. Paeoniflorin exhibits extensive anti-inflammatory and neuroprotective effects, but whether it can protect against OIPN and the underlying mechanisms remain unclear. This study aimed to investigate the effects of paeoniflorin on OIPN and probe into the underlying mechanisms. The OIPN model was established through oxaliplatin injection in rats. The ameliorative effects of paeoniflorin on OIPN was assessed by nociceptive hypersensitivities through pain behavioral methods. Neuroinflammation were examined by measuring the levels of inflammatory cytokines and immune cells infiltration. The signaling pathway of TLR4/MyD88/NF-κB was evaluated by Western blotting. Gut microbial changes were detected by 16S rDNA sequencing technology. In addition, antibiotics-induced microbiota eradication and fecal microbial transplantation (FMT) were applied for exploring the function of gut microbiota in the protective effects of paeoniflorin. The results revealed that paeoniflorin significantly alleviated mechanical and cold hypersensitivity, mitigated neuroinflammation and influenced gut microbial composition in OIPN rats. Fecal microbiota transplantation further verified that gut microbiota was required for paeoniflorin ameliorating OIPN and that the underlying mechanism involved downregulation of TLR4/MyD88/NF-κB signaling. Specifically, Akkermansia, Dubosiella and Corynebacterium might serve as crucial genera regulated by paeoniflorin in the treatment of OIPN. In summary, our investigations delineate paeoniflorin's ameliorative effects on OIPN by alleviating neuroinflammation through regulations of gut microbiota. This suggests that paeoniflorin may serve as a new potential strategy for treatment of OIPN in clinical practice.

NT-3 contributes to chemotherapy-induced neuropathic pain through TrkC-mediated CCL2 elevation in DRG neurons

Cancer patients undergoing treatment with antineoplastic drugs often experience chemotherapy-induced neuropathic pain (CINP), and the therapeutic options for managing CINP are limited. Here, we show that systemic paclitaxel administration upregulates the expression of neurotrophin-3 (Nt3) mRNA and NT3 protein in the neurons of dorsal root ganglia (DRG), but not in the spinal cord. Blocking NT3 upregulation attenuates paclitaxel-induced mechanical, heat, and cold nociceptive hypersensitivities and spontaneous pain without altering acute pain and locomotor activity in male and female mice. Conversely, mimicking this increase produces enhanced responses to mechanical, heat, and cold stimuli and spontaneous pain in naive male and female mice. Mechanistically, NT3 triggers tropomyosin receptor kinase C (TrkC) activation and participates in the paclitaxel-induced increases of C-C chemokine ligand 2 (Ccl2) mRNA and CCL2 protein in the DRG. Given that CCL2 is an endogenous initiator of CINP and that Nt3 mRNA co-expresses with TrkC and Ccl2 mRNAs in DRG neurons, NT3 likely contributes to CINP through TrkC-mediated activation of the Ccl2 gene in DRG neurons. NT3 may be thus a potential target for CINP treatment.

Knockdown siRNA Targeting GPR55 Reveals Significant Differences Between the Anti-inflammatory Actions of KLS-13019 and Cannabidiol

KLS-13019 was reported previously to reverse paclitaxel-induced mechanical allodynia in a mouse model of chemotherapy-induced peripheral neuropathy (CIPN). Recent studies demonstrated that paclitaxel-induced increases in inflammatory markers (GPR55, NLRP3, and IL-1β) of dorsal root ganglion (DRG) cultures were shown to be reversed by KLS-13019 treatment. The mechanism of action for KLS-13019-mediated reversal of paclitaxel-induced neuroinflammation now has been explored using GPR55 siRNA. Pre-treatment of DRG cultures with GPR55 siRNA produced a 21% decrease of immunoreactive (IR) area for GPR55 in cell bodies and a 59% decrease in neuritic IR area, as determined by high-content imaging. Using a 24-h reversal treatment paradigm, paclitaxel-induced increases in the inflammatory markers were reversed back to control levels after KLS-3019 treatment. Decreases in these inflammatory markers produced by KLS-13019 were significantly attenuated by GPR55 siRNA co-treatment, with mean IR area responses being attenuated by 56% in neurites and 53% in cell bodies. These data indicate that the percentage decreases in siRNA-mediated attenuation of KLS-13019-related efficacy on the inflammatory markers were similar to the percentage knockdown observed for neuritic GPR55 IR area. Similar studies conducted with cannabidiol (CBD), the parent compound of KLS-13019, produced low efficacy (25%) reversal of all inflammatory markers that were poorly attenuated (29%) by GPR55 siRNA. CBD was shown previously to be ineffective in reversing paclitaxel-induced mechanical allodynia. The present studies indicated significant differences between the anti-inflammatory properties of KLS-13019 and CBD which may play a role in their observed differences in the reversibility of mechanical allodynia in a mouse model of CIPN.

Current understanding of the molecular mechanisms of chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is the most common off-target adverse effects caused by various chemotherapeutic agents, such as cisplatin, oxaliplatin, paclitaxel, vincristine and bortezomib. CIPN is characterized by a substantial loss of primary afferent sensory axonal fibers leading to sensory disturbances in patients. An estimated of 19-85% of patients developed CIPN during the course of chemotherapy. The lack of preventive measures and limited treatment options often require a dose reduction or even early termination of life-saving chemotherapy, impacting treatment efficacy and patient survival. In this Review, we summarized the current understanding on the pathogenesis of CIPN. One prominent change induced by chemotherapeutic agents involves the disruption of neuronal cytoskeletal architecture and axonal transport dynamics largely influenced by the interference of microtubule stability in peripheral neurons. Due to an ineffective blood-nerve barrier in our peripheral nervous system, exposure to some chemotherapeutic agents causes mitochondrial swelling in peripheral nerves, which lead to the opening of mitochondrial permeability transition pore and cytochrome c release resulting in degeneration of primary afferent sensory fibers. The exacerbated nociceptive signaling and pain transmission in CIPN patients is often linked the increased neuronal excitability largely due to the elevated expression of various ion channels in the dorsal root ganglion neurons. Another important contributing factor of CIPN is the neuroinflammation caused by an increased infiltration of immune cells and production of inflammatory cytokines. In the central nervous system, chemotherapeutic agents also induce neuronal hyperexcitability in the spinal dorsal horn and anterior cingulate cortex leading to the development of central sensitization that causes CIPN. Emerging evidence suggests that the change in the composition and diversity of gut microbiota (dysbiosis) could have direct impact on the development and progression of CIPN. Collectively, all these aspects contribute to the pathogenesis of CIPN. Recent advances in RNA-sequencing offer solid platform for in silico drug screening which enable the identification of novel therapeutic agents or repurpose existing drugs to alleviate CIPN, holding immense promises for enhancing the quality of life for cancer patients who undergo chemotherapy and improve their overall treatment outcomes.

Molecular and Cellular Involvement in CIPN

Many anti-cancer drugs, such as taxanes, platinum compounds, vinca alkaloids, and proteasome inhibitors, can cause chemotherapy-induced peripheral neuropathy (CIPN). CIPN is a frequent and harmful side effect that affects the sensory, motor, and autonomic nerves, leading to pain, numbness, tingling, weakness, and reduced quality of life. The causes of CIPN are not fully known, but they involve direct nerve damage, oxidative stress, inflammation, DNA damage, microtubule dysfunction, and altered ion channel activity. CIPN is also affected by genetic, epigenetic, and environmental factors that modulate the risk and intensity of nerve damage. Currently, there are no effective treatments or prevention methods for CIPN, and symptom management is mostly symptomatic and palliative. Therefore, there is a high demand for better understanding of the cellular and molecular mechanisms involved in CIPN, as well as the development of new biomarkers and therapeutic targets. This review gives an overview of the current knowledge and challenges in the field of CIPN, focusing on the biological and molecular mechanisms underlying this disorder.

CC Chemokine Family Members' Modulation as a Novel Approach for Treating Central Nervous System and Peripheral Nervous System Injury-A Review of Clinical and Experimental Findings

Despite significant progress in modern medicine and pharmacology, damage to the nervous system with various etiologies still poses a challenge to doctors and scientists. Injuries lead to neuroimmunological changes in the central nervous system (CNS), which may result in both secondary damage and the development of tactile and thermal hypersensitivity. In our review, based on the analysis of many experimental and clinical studies, we indicate that the mechanisms occurring both at the level of the brain after direct damage and at the level of the spinal cord after peripheral nerve damage have a common immunological basis. This suggests that there are opportunities for similar pharmacological therapeutic interventions in the damage of various etiologies. Experimental data indicate that after CNS/PNS damage, the levels of 16 among the 28 CC-family chemokines, i.e., CCL1, CCL2, CCL3, CCL4, CCL5, CCL6, CCL7, CCL8, CCL9, CCL11, CCL12, CCL17, CCL19, CCL20, CCL21, and CCL22, increase in the brain and/or spinal cord and have strong proinflammatory and/or pronociceptive effects. According to the available literature data, further investigation is still needed for understanding the role of the remaining chemokines, especially six of them which were found in humans but not in mice/rats, i.e., CCL13, CCL14, CCL15, CCL16, CCL18, and CCL23. Over the past several years, the results of studies in which available pharmacological tools were used indicated that blocking individual receptors, e.g., CCR1 (J113863 and BX513), CCR2 (RS504393, CCX872, INCB3344, and AZ889), CCR3 (SB328437), CCR4 (C021 and AZD-2098), and CCR5 (maraviroc, AZD-5672, and TAK-220), has beneficial effects after damage to both the CNS and PNS. Recently, experimental data have proved that blockades exerted by double antagonists CCR1/3 (UCB 35625) and CCR2/5 (cenicriviroc) have very good anti-inflammatory and antinociceptive effects. In addition, both single (J113863, RS504393, SB328437, C021, and maraviroc) and dual (cenicriviroc) chemokine receptor antagonists enhanced the analgesic effect of opioid drugs. This review will display the evidence that a multidirectional strategy based on the modulation of neuronal-glial-immune interactions can significantly improve the health of patients after CNS and PNS damage by changing the activity of chemokines belonging to the CC family. Moreover, in the case of pain, the combined administration of such antagonists with opioid drugs could reduce therapeutic doses and minimize the risk of complications.

A toxicological review of alkaloids

Alkaloids are naturally occurring compounds with complex structures found in natural plants. To further improve the understanding of plant alkaloids, this review focuses on the classification, toxicity and mechanisms of action, providing insight into the occurrence of alkaloid-poisoning events and guiding the safe use of alkaloids in food, supplements and clinical applications. Based on their chemical structure, alkaloids can be divided into organic amines, diterpenoids, pyridines, isoquinolines, indoles, pyrrolidines, steroids, imidazoles and purines. The mechanisms of toxicity of alkaloids, including neurotoxicity, hepatoxicity, nephrotoxicity, cardiotoxicity and cytotoxicity, have also been reviewed. Some cases of alkaloid poisoning have been introduced when used as food or clinically, including accidental food poisoning, excessive consumption, and poisoning caused by the improper use of alkaloids in a clinical setting, and the importance of safety evaluation was illustrated. This review summarizes the toxicity and mechanism of action of alkaloids and provides evidence for the need for the safe use of alkaloids in food, supplements and clinical applications.

Knockdown siRNA targeting GPR55 reveals significant differences between the anti-inflammatory actions of KLS-13019 and cannabidiol

KLS-13019 was reported previously to reverse paclitaxel-induced mechanical allodynia in a mouse model of chemotherapy-induced peripheral neuropathy (CIPN). Recent studies demonstrated that paclitaxel-induced increases in inflammatory markers (GPR55, NLRP3 and IL-1b) of dorsal root ganglion (DRG) cultures were shown to be reversed by KLS-13019 treatment. The mechanism of action for KLS-13019-mediated reversal of paclitaxel-induced neuroinflammation now has been explored using GPR55 siRNA. Pretreatment of DRG cultures with GPR55 siRNA produced a 21% decrease of immunoreactive (IR) area for GPR55 in cell bodies and a 59% decrease in neuritic IR area, as determined by high content imaging. Using a 24-hour reversal treatment paradigm, paclitaxel-induced increases in the inflammatory markers were reversed back to control levels after KLS-3019 treatment. Decreases in these inflammatory markers produced by KLS-13019 were significantly attenuated by GPR55 siRNA co-treatment, with mean IR area responses being attenuated by 56% in neurites and 53% in cell bodies. These data indicate that the percentage decreases in siRNA-mediated attenuation of KLS-13019-related efficacy on the inflammatory markers were similar to the percentage knockdown observed for neuritic GPR55 IR area. Similar studies conducted with cannabidiol (CBD), the parent compound of KLS-13019, produced low efficacy (25%) reversal of all inflammatory markers that were poorly attenuated (29%) by GPR55 siRNA. CBD was shown previously to be ineffective in reversing paclitaxel-induced mechanical allodynia. The present studies indicated significant differences between the anti-inflammatory properties of KLS-13019 and CBD which may play a role in their observed differences in the reversibility of mechanical allodynia in a mouse model of CIPN.

Phosphosulindac (OXT-328) prevents and reverses chemotherapy induced peripheral neuropathy in mice

Background

Chemotherapy-induced peripheral neuropathy (CIPN), a side effect of chemotherapy, is particularly difficult to treat. We explored whether phosphosulindac (PS), a modified NSAID, could treat CIPN.

Methods

CIPN was induced in male C57BL/6 J mice by paclitaxel, vincristine or oxaliplatin. Mechanical allodynia was measured with the von Frey test and cold allodynia with the acetone test. To determine the preventive effect of PS, it was administered 2 days before the induction of CIPN. Mouse Lewis lung carcinoma xenografts were used to determine if PS altered the chemotherapeutic efficacy of paclitaxel. Cultured cell lines were used to evaluate the effect of PS on neuroinflammation.

Results

Treatment with each of the three chemotherapeutic agents used to induce CIPN lowered the mechanical allodynia scores by 56 to 85% depending on the specific agent. PS gel was applied topically 3x/day for 16-22 days to the hind paws of mice with CIPN. This effect was dose-dependent. Unlike vehicle, PS returned mechanical allodynia scores back to pre-CIPN levels. PS had a similar effect on paclitaxel-induced CIPN cold allodynia. Sulindac, a metabolite of PS, had no effect on CIPN. PS significantly prevented CIPN compared to vehicle. Given concomitantly with paclitaxel to mice with lung cancer xenografts, PS relieved CIPN without affecting the anticancer effect of paclitaxel. The enantiomers of PS were equally efficacious against CIPN, suggesting the therapeutic suitability of the racemate PS. There were no apparent side effects of PS. PS suppressed the levels of IL-6, IL-10, CXCL1, and CXCL2 induced by paclitaxel in a neuroblastoma cell line, and macrophage activation to the M1 proinflammatory phenotype.

Conclusion

Topically applied PS demonstrated broad therapeutic and preventive efficacy against CIPN, preserved the anticancer effect of paclitaxel, and was safe. Its anti-CIPN effect appears to be mediated, in part, by suppression of neuroinflammation. These data support further evaluation of topical PS for the control of CIPN.

Exercise for reducing chemotherapy-induced peripheral neuropathy: a systematic review and meta-analysis of randomized controlled trials

Background

More than half of cancer patients develop severe chemotherapy-induced peripheral neuropathy (CIPN), resulting in low quality of life, negative effects on function, and challenges in treatment compliance. Most recent studies have shown that exercise therapy has a positive impact on reducing CIPN symptoms and can also improve quality of life, balance, and activity levels. The aim of this meta-analysis was to evaluate the effect of exercise therapy on the efficacy of CIPN.

Methods

Computerized search of Embase, Web of Science, CNKI, Wan Fang Data, VIP, CBM for RCTs on exercise therapy for CIPN from database creation to November 2022, without language restriction. The Cochrane Handbook 5.3 risk of bias assessment tool was used to evaluate the quality of the included studies. Then Revman 5.3 software was used to evaluate the quality of the included studies. The heterogeneity of the research results is tested by I2, continuous variables were presented as weighted mean difference or standard mean difference, and confidence intervals were set at 95%. Stata15.0 was utilized to conduct a meta-analysis.

Results

A total of 15 RCTs with 1,124 patients were included. Meta-analysis showed that the test group was superior to the control group in terms of total symptom score (SMD: -0.62; 95% Cl: -0.99, -0.24), numbness, tingling, quality of life score (total score, physical, function), pain, balance, and neurotoxicity function assessment (FACT/GOG-NTX) questionnaire (p < 0.05).

Limitations

The duration and frequency of treatment are different every week, which may have some impact on the results.

Conclusion

Exercise therapy can be effective in treating CIPN by improving symptom score (total symptom score, numbness, tingling), quality of life score (total score, physical function), pain, balance, and FACT/GOG-NTX questionnaires. It still needs to be refined and validated by more high-quality, multicenter, large-sample RCTs in the future.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022373131, identifier: CRD42022373131.

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

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

Complement Receptor C3aR1 Contributes to Paclitaxel-Induced Peripheral Neuropathic Pain in Mice and Rats

Cancer chemotherapy-induced neuropathic pain is a devastating pain syndrome without effective therapies. We previously reported that rats deficient in complement C3, the central component of complement activation cascade, showed a reduced degree of paclitaxel-induced mechanical allodynia (PIMA), suggesting that complement is integrally involved in the pathogenesis of this model. However, the underlying mechanism was unclear. Complement activation leads to the production of C3a, which mediates inflammation through its receptor C3aR1. In this article, we report that the administration of paclitaxel induced a significantly higher expression level of C3aR1 on dorsal root ganglion (DRG) macrophages and expansion of these macrophages in DRGs in wild-type (WT) compared with in C3aR1 knockout (KO) mice. We also found that paclitaxel induced less severe PIMA, along with a reduced DRG expression of transient receptor potential channels of the vanilloid subtype 4 (TRPV4), an essential mediator for PIMA, in C3aR1 KO than in WT mice. Treating WT mice or rats with a C3aR1 antagonist markedly attenuated PIMA in association with downregulated DRG TRPV4 expression, reduced DRG macrophages expansion, suppressed DRG neuron hyperexcitability, and alleviated peripheral intraepidermal nerve fiber loss. Administration of C3aR1 antagonist to TRPV4 KO mice further protected them from PIMA. These results suggest that complement regulates PIMA development through C3aR1 to upregulate TRPV4 on DRG neurons and promote DRG macrophage expansion. Targeting C3aR1 could be a novel therapeutic approach to alleviate this debilitating pain syndrome.

Traditional Chinese Medicine syndrome analysis on oxaliplatin-induced peripheral neuropathy and clinical efficacy of Bushen Yiqi formula: a prospective randomized controlled study

OBJECTIVES

To analyze the distribution characteristics of Traditional Chinese Medicine (TCM) syndromes in patients with oxaliplatin-induced peripheral neuropathy (OIPN) and observe the clinical efficacy of Bushen Yiqi formula (, BSYQF) in treating patients with OIPN.

METHODS

A total of 89 patients with OIPN were enrolled in this study. The TCM syndrome characteristics were investigated by frequency analysis methodology after collecting and analyzing the TCM syndrome elements of the patients with the OIPN TCM syndrome element scale. Further, 62 cases of cold-dampness obstruction syndrome and kidney-Qi deficiency and cold syndrome were selected and randomly divided into the control group (n = 31) and the treatment group (n = 31). The patients in the treatment group were treated with modified BSYQF, while those in the control group were treated with mecobalamin tablets for 3 weeks. The Levi sensory neurotoxicity score and the neuro-electrophysiological changes were observed before and after the treatment in both groups.

RESULTS

The distribution of TCM syndrome types in 89 patients with OIPN were in order of kidney-Qi deficiency and cold syndrome (44 cases), cold-dampness obstruction syndrome (18 cases), Yin deficiency of liver and kidney syndrome (11 cases), blood stasis obstruction syndrome (7 cases), and dampness-heat obstruction syndrome (5 cases). Improvement in Levi sensory neurotoxicity score: After 3-week treatment, the total effective rate in the treatment group was higher than that in the control group (P < 0.05). The subgroup analysis showed that the total effective rate in the treatment group of patients with kidney-Qi deficiency and cold syndrome was higher than that in the control group before and after treatment (P < 0.05). Improvement in nerve conduction velocity: The sensory nerve conduction velocity of bilateral ulnar nerves improved in the control group after treatment compared with that before treatment (P < 0.05). The sensory and motor nerve conduction velocities of the bilateral ulnar and bilateral peroneal nerves improved in the treatment group compared with those before treatment and after treatment in the control group (P < 0.05).

CONCLUSIONS

The modified BSYQF had a definite therapeutic effect on the OIPN in patients with kidney-Qi deficiency and cold syndrome and those with cold-dampness obstruction syndrome. It could effectively reduce the grade of peripheral nerve toxicity and improve nerve conduction velocity, and its curative effect was better than that of mecobalamin tablets.

Huangqi Guizhi Wuwu decoction alleviates oxaliplatin-induced peripheral neuropathy via the gut-peripheral nerve axis

BACKGROUND

Oxaliplatin-induced peripheral neurotoxicity (OIPN) limits the dose of chemotherapy and seriously affects the quality of life. Huangqi Guizhi Wuwu Decoction (HGWD) is a classical Traditional Chinese Medicine (TCM) formula for the prevention of OIPN. However, its specific pharmacological mechanism of action remains unknown. Our study found that HGWD can effectively alleviate chronic OIPN and regulate intestinal flora. Therefore, we explored the mechanism of action of HGWD in alleviating chronic OIPN from the perspective of intestinal flora.

METHODS

In this study, we established an OIPN model in C57BL/6 mice treated with different concentrations of HGWD. Mechanical pain and cold pain were assessed at certain time points, and samples of mice colon, dorsal root ganglion (DRG), serum, and feces were collected. Associated inflammation levels in the colon and DRG were detected using immunohistochemical techniques; the serum lipopolysaccharide (LPS) levels and associated inflammation were assessed using the appropriate kits; and 16S rRNA sequencing was used to examine the dynamic changes in gut microorganisms. Finally, established fecal microbiota transplantation (FMT) and antibiotic (ABX) pretreatment models were used to validate flora's role in HGWD for chronic OIPN by pain scoring and related pathological analysis.

RESULTS

HGWD treatment significantly alleviated pain sensitivity in chronic OIPN mice. Pathological results showed that HGWD treatment improved intestinal ZO-1 expression and reduced serum LPS levels and associated inflammatory factors in the colon, serum, and DRG. The 16S rRNA results showed that HGWD restored the composition of the intestinal flora in a time-dependent manner to alleviate OIPN. FMT and ABX experiments demonstrated that HGWD can alleviate chronic OIPN by regulating intestinal flora homeostasis.

CONCLUSIONS

HGWD prevents chronic OIPN by dynamically regulating intestinal flora homeostasis, thereby ameliorating intestinal barrier damage and reducing serum LPS and relevant inflammatory factor levels in the colon, serum, and DRG.

Skin Extracellular Matrix Breakdown Following Paclitaxel Therapy in Patients with Chemotherapy-Induced Peripheral Neuropathy

The chemotherapeutic agent paclitaxel causes peripheral neuropathy, a dose-limiting side effect, in up to 68% of cancer patients. In this study, we investigated the impact of paclitaxel therapy on the skin of breast cancer patients with chemotherapy-induced peripheral neuropathy (CIPN), building upon previous findings in zebrafish and rodents. Comprehensive assessments, including neurological examinations and quality of life questionnaires, were conducted, followed by intraepidermal nerve fiber (IENF) density evaluations using skin punch biopsies. Additionally, RNA sequencing, immunostaining for Matrix-Metalloproteinase 13 (MMP-13), and transmission electron microscopy provided insights into molecular and ultrastructural changes in this skin. The results showed no significant difference in IENF density between the control and CIPN patients despite the presence of patient-reported CIPN symptoms. Nevertheless, the RNA sequencing and immunostaining on the skin revealed significantly upregulated MMP-13, which is known to play a key role in CIPN caused by paclitaxel therapy. Additionally, various genes involved in the regulation of the extracellular matrix, microtubules, cell cycle, and nervous system were significantly and differentially expressed. An ultrastructural examination of the skin showed changes in collagen and basement membrane structures. These findings highlight the presence of CIPN in the absence of IENF density changes and support the role of skin remodeling as a major contributor to CIPN.

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.

Scientific and Regulatory Policy Committee Technical Review: Biology and Pathology of Ganglia in Animal Species Used for Nonclinical Safety Testing

Dorsal root ganglia (DRG), trigeminal ganglia (TG), other sensory ganglia, and autonomic ganglia may be injured by some test article classes, including anti-neoplastic chemotherapeutics, adeno-associated virus-based gene therapies, antisense oligonucleotides, nerve growth factor inhibitors, and aminoglycoside antibiotics. This article reviews ganglion anatomy, cytology, and pathology (emphasizing sensory ganglia) among common nonclinical species used in assessing product safety for such test articles (TAs). Principal histopathologic findings associated with sensory ganglion injury include neuron degeneration, necrosis, and/or loss; increased satellite glial cell and/or Schwann cell numbers; and leukocyte infiltration and/or inflammation. Secondary nerve fiber degeneration and/or glial reactions may occur in nerves, dorsal spinal nerve roots, spinal cord (dorsal and occasionally lateral funiculi), and sometimes the brainstem. Ganglion findings related to TA administration may result from TA exposure and/or trauma related to direct TA delivery into the central nervous system or ganglia. In some cases, TA-related effects may need to be differentiated from a spectrum of artifactual and/or spontaneous background changes.

Understanding the initiation, delivery and processing of bone cancer pain from the peripheral to the central nervous system

Bone cancer pain is a complex condition characterized by persistent, sudden, spontaneous pain accompanied by hyperalgesia that typically arises from bone metastases or primary bone tumors, causing severe discomfort and significantly diminishing cancer patients' quality of life and confidence in their ability to overcome the disease. It is widely known that peripheral nerves are responsible for detecting harmful stimuli, which are then transmitted to the brain via the spinal cord, resulting in the perception of pain. In the case of bone cancer, tumors and stromal cells within the bone marrow release various chemical signals, including inflammatory factors, colony-stimulating factors, chemokines, and hydrogen ions. Consequently, the nociceptors located at the nerve endings within the bone marrow sense these chemical signals, generating electrical signals that are then transmitted to the brain through the spinal cord. Subsequently, the brain processes these electrical signals in a complex manner to create the sensation of bone cancer pain. Numerous studies have investigated the transmission of bone cancer pain from the periphery to the spinal cord. However, the processing of pain information induced by bone cancer within the brain remains unclear. With the continuous advancements in brain science and technology, the brain mechanism of bone cancer pain would become more clearly understood. Herein, we focus on summarizing the peripheral nerve perception of the spinal cord transmission of bone cancer pain and provide a brief overview of the ongoing research regarding the brain mechanisms involved in bone cancer pain.

SAFit2 ameliorates paclitaxel-induced neuropathic pain by reducing spinal gliosis and elevating pro-resolving lipid mediators

BACKGROUND

Chemotherapy-induced neuropathic pain (CIPN) describes a pathological pain state that occurs dose-dependently as a side effect and can limit or even impede an effective cancer therapy. Unfortunately, current treatment possibilities for CIPN are remarkably confined and mostly inadequate as CIPN therapeutics themselves consist of low effectiveness and may induce severe side effects, pointing out CIPN as pathological entity with an emerging need for novel treatment targets. Here, we investigated whether the novel and highly specific FKBP51 inhibitor SAFit2 reduces paclitaxel-induced neuropathic pain.

METHODS

In this study, we used a well-established multiple low-dose paclitaxel model to investigate analgesic and anti-inflammatory properties of SAFit2. For this purpose, the behavior of the mice was recorded over 14 days and the mouse tissue was then analyzed using biochemical methods.

RESULTS

Here, we show that SAFit2 is capable to reduce paclitaxel-induced mechanical hypersensitivity in mice. In addition, we detected that SAFit2 shifts lipid levels in nervous tissue toward an anti-inflammatory and pro-resolving lipid profile that counteracts peripheral sensitization after paclitaxel treatment. Furthermore, SAFit2 reduced the activation of astrocytes and microglia in the spinal cord as well as the levels of pain-mediating chemokines. Its treatment also increased anti-inflammatory cytokines levels in neuronal tissues, ultimately leading to a resolution of neuroinflammation.

CONCLUSIONS

In summary, SAFit2 shows antihyperalgesic properties as it ameliorates paclitaxel-induced neuropathic pain by reducing peripheral sensitization and resolving neuroinflammation. Therefore, we consider SAFit2 as a potential novel drug candidate for the treatment of paclitaxel-induced neuropathic pain.

Scientific and Regulatory Policy Committee Points to Consider: Sampling, Processing, Evaluation, Interpretation, and Reporting of Test Article-Related Ganglion Pathology for Nonclinical Toxicity Studies

Certain biopharmaceutical products consistently affect dorsal root ganglia, trigeminal ganglia, and/or autonomic ganglia. Product classes targeting ganglia include antineoplastic chemotherapeutics, adeno-associated virus-based gene therapies, antisense oligonucleotides, and anti-nerve growth factor agents. This article outlines "points to consider" for sample collection, processing, evaluation, interpretation, and reporting of ganglion findings; these points are consistent with published best practices for peripheral nervous system evaluation in nonclinical toxicity studies. Ganglion findings often occur as a combination of neuronal injury (e.g., degeneration, necrosis, and/or loss) and/or glial effects (e.g., increased satellite glial cell cellularity) with leukocyte accumulation (e.g., mononuclear cell infiltration or inflammation). Nerve fiber degeneration and/or glial reactions may be seen in nerves, dorsal spinal nerve roots, spinal cord, and occasionally brainstem. Interpretation of test article (TA)-associated effects may be confounded by incidental background changes or experimental procedure-related changes and limited historical control data. Reports should describe findings at these sites, any TA relationship, and the criteria used for assigning severity grades. Contextualizing adversity of ganglia findings can require a weight-of-evidence approach because morphologic changes of variable severity occur in ganglia but often are not accompanied by observable overt in-life functional alterations detectable by conventional behavioral and neurological testing techniques.

miR-4433a-3p promotes granulosa cell apoptosis by targeting peroxisome proliferator-activated receptor alpha and inducing immune cell infiltration in polycystic ovarian syndrome

BACKGROUND

Granulosa cell (GC) proliferation and apoptosis are critical events of the ovum energy supply, which lead to follicular growth retardation or atresia, and various ovulatory obstacles, eventually resulting in the development of ovarian disorders such as polycystic ovarian syndrome (PCOS). Apoptosis and dysregulated miRNA expression in GCs are manifestations of PCOS. miR-4433a-3p has been reported to be involved in apoptosis. However, there is no study reporting the roles of miR-4433a-3p in GC apoptosis and PCOS progression.

METHODS

miR-4433a-3p and peroxisome proliferator-activated receptor alpha (PPAR-α) levels in GCs of PCOS patients or in tissues of a PCOS rat model were examined by quantitative polymerase chain reaction and immunohistochemistry. Bioinformatics analyses and luciferase assays were used to examine the association between miR-4433a-3p and PPAR-α, as well as PPAR-α and immune cell infiltration, in PCOS patients.

RESULTS

miR-4433a-3p expression in GCs of PCOS patients was increased. miR-4433a-3p overexpression inhibited the growth of the human granulosa-like tumor cell line (KGN) and promoted apoptosis, while co-treatment with PPAR-α and miR-4433a-3p mimic rescued miR-4433a-3p-induced apoptosis. PPAR-α was a direct target of miR-4433a-3p and its expression was decreased in PCOS patients. PPAR-α expression was also positively correlated with the infiltration of activated CD4+ T cells, eosinophils, B cells, gamma delta T cells, macrophages, and mast cells, but negatively correlated with the infiltration of activated CD8+ T cells, CD56+ bright natural killer cells, immature dendritic cells, monocytes, plasmacytoid dendritic cells, neutrophils, and type 1 T helper cells in PCOS patients.

CONCLUSION

The miR-4433a-3p/PPAR-α/immune cell infiltration axis may function as a novel cascade to alter GC apoptosis in PCOS.

Neuropathic-like Nociception and Spinal Cord Neuroinflammation Are Dependent on the TRPA1 Channel in Multiple Sclerosis Models in Mice

Background: Transient receptor potential ankyrin 1 (TRPA1) activation is implicated in neuropathic pain-like symptoms. However, whether TRPA1 is solely implicated in pain-signaling or contributes to neuroinflammation in multiple sclerosis (MS) is unknown. Here, we evaluated the TRPA1 role in neuroinflammation underlying pain-like symptoms using two different models of MS. Methods: Using a myelin antigen, Trpa1+/+ or Trpa1-/- female mice developed relapsing-remitting experimental autoimmune encephalomyelitis (RR-EAE) (Quil A as adjuvant) or progressive experimental autoimmune encephalomyelitis (PMS)-EAE (complete Freund's adjuvant). The locomotor performance, clinical scores, mechanical/cold allodynia, and neuroinflammatory MS markers were evaluated. Results: Mechanical and cold allodynia detected in RR-EAE, or PMS-EAE Trpa1+/+ mice, were not observed in Trpa1-/- mice. The increased number of cells labeled for ionized calcium-binding adapter molecule 1 (Iba1) or glial fibrillary acidic protein (GFAP), two neuroinflammatory markers in the spinal cord observed in both RR-EAE or PMS-EAE Trpa1+/+ mice, was reduced in Trpa1-/- mice. By Olig2 marker and luxol fast blue staining, prevention of the demyelinating process in Trpa1-/- induced mice was also detected. Conclusions: Present results indicate that the proalgesic role of TRPA1 in EAE mouse models is primarily mediated by its ability to promote spinal neuroinflammation and further strengthen the channel inhibition to treat neuropathic pain in MS.

Rosuvastatin Synergistically Enhances the Antinociceptive Efficacy of Duloxetine in Paclitaxel-Induced Neuropathic Pain in Mice

Paclitaxel, a widely used cancer chemotherapeutic agent, has high incidence of neurotoxicity associated with the production of neuropathic pain, for which only duloxetine has shown significant but moderate analgesic effect. Since statins, classically used to reduce hypercholesterolemia, have shown antinociceptive effect in preclinical studies on neuropathic pain, we studied whether the antinociceptive efficacy of duloxetine could be synergistically potentiated by rosuvastatin in a model of paclitaxel-induced neuropathy in mice. The astrocytic and microglial responses in the spinal cord of paclitaxel-treated mice were also assessed by measuring GFAP and CD11b proteins, respectively. Paclitaxel treatment did not impair motor coordination and balance in rotarod testing. Rosuvastatin, duloxetine, and the rosuvastatin/duloxetine combination (combined at equieffective doses) dose-dependently decreased mechanical allodynia (ED₃₀, von Frey testing) and thermal hyperalgesia (ED₅₀, hot plate testing) in paclitaxel-treated mice. Isobolographic analysis showed a superadditive interaction for rosuvastatin and duloxetine, as both the ED₃₀ and ED₅₀ for the rosuvastatin/duloxetine combination contained only a quarter of each drug compared to the individual drugs. The rosuvastatin/duloxetine combination reversed paclitaxel-induced GFAP overexpression, indicating that such effects might depend in part on astrocyte inactivation. Results suggest that statins could be useful in synergistically enhancing the efficacy of duloxetine in some chemotherapy-induced neuropathic conditions.

G protein-coupled P2Y12 receptor is involved in the progression of neuropathic pain

The pathological mechanism of neuropathic pain is complex, which seriously affects the physical and mental health of patients, and its treatment is also difficult. The role of G protein-coupled P2Y12 receptor in pain has been widely recognized and affirmed. After nerve injury, stimulated cells can release large amounts of nucleotides into the extracellular matrix, act on P2Y12 receptor. Activated P2Y12 receptor activates intracellular signal transduction and is involved in the development of pain. P2Y12 receptor activation can sensitize primary sensory neurons and receive sensory information. By transmitting the integrated information through the dorsal root of the spinal cord to the secondary neurons of the posterior horn of the spinal cord. The integrated information is then transmitted to the higher center through the ascending conduction tract to produce pain. Moreover, activation of P2Y12 receptor can mediate immune cells to release pro-inflammatory factors, increase damage to nerve cells, and aggravate pain. While inhibits the activation of P2Y12 receptor can effectively relieve pain. Therefore, in this article, we described P2Y12 receptor antagonists and their pharmacological properties. In addition, we explored the potential link between P2Y12 receptor and the nervous system, discussed the intrinsic link of P2Y12 receptor and neuropathic pain and as a potential pharmacological target for pain suppression.

Meteorin Alleviates Paclitaxel-Induced Peripheral Neuropathic Pain in Mice

Chemotherapy-induced peripheral neuropathy is a challenging condition to treat, and arises due to severe, dose-limiting toxicity of chemotherapeutic drugs such as paclitaxel. This often results in debilitating sensory and motor deficits that are not effectively prevented or alleviated by existing therapeutic interventions. Recent studies have demonstrated the therapeutic effects of Meteorin, a neurotrophic factor, in reversing neuropathic pain in rodent models of peripheral nerve injury induced by physical trauma. Here, we sought to investigate the potential antinociceptive effects of recombinant mouse Meteorin (rmMeteorin) using a paclitaxel-induced peripheral neuropathy model in male and female mice. Paclitaxel treatment (4 × 4 mg/kg, i.p.) induced hind paw mechanical hypersensitivity by day 8 after treatment. Thereafter, in a reversal dosing paradigm, five repeated injections of rmMeteorin (.5 and 1.8 mg/kg s.c. respectively) administered over 9 days produced a significant and long-lasting attenuation of mechanical hypersensitivity in both sexes. Additionally, administration of rmMeteorin ( .5 and 1.8 mg/kg), initiated before and during paclitaxel treatment (prevention dosing paradigm), reduced the establishment of hind paw mechanical hypersensitivity. Repeated systemic administration of rmMeteorin in both dosing paradigms decreased histochemical signs of satellite glial cell reactivity as measured by glutamine synthetase and connexin 43 protein expression in the dorsal root ganglion. Additionally, in the prevention administration paradigm rmMeteorin had a protective effect against paclitaxel-induced loss of intraepidermal nerve fibers. Our findings indicate that rmMeteorin has a robust and sustained antinociceptive effect in the paclitaxel-induced peripheral neuropathy model and the development of recombinant human Meteorin could be a novel and effective therapeutic for chemotherapy-induced peripheral neuropathy treatment. PERSPECTIVE: Chemotherapy neuropathy is a major clinical problem that decreases quality of life for cancer patients and survivors. Our experiments demonstrate that Meteorin treatment alleviates pain-related behaviors, and signs of neurotoxicity in a mouse model of paclitaxel neuropathy.

Inducible co-stimulatory molecule (ICOS) alleviates paclitaxel-induced neuropathic pain via an IL-10-mediated mechanism in female mice

Chemotherapy-induced peripheral neuropathy (CIPN) is a primary dose-limiting side effect caused by antineoplastic agents, such as paclitaxel. A primary symptom of this neuropathy is pain. Currently, there are no effective treatments for CIPN, which can lead to long-term morbidity in cancer patients and survivors. Neuro-immune interactions occur in CIPN pain and have been implicated both in the development and progression of pain in CIPN and the resolution of pain in CIPN. We investigated the potential role of inducible co-stimulatory molecule (ICOS) in the resolution of CIPN pain-like behaviors in mice. ICOS is an immune checkpoint molecule that is expressed on the surface of activated T cells and promotes proliferation and differentiation of T cells. We found that intrathecal administration of ICOS agonist antibody (ICOSaa) alleviates mechanical hypersensitivity caused by paclitaxel and facilitates the resolution of mechanical hypersensitivity in female mice. Administration of ICOSaa reduced astrogliosis in the spinal cord and satellite cell gliosis in the DRG of mice previously treated with paclitaxel. Mechanistically, ICOSaa intrathecal treatment promoted mechanical hypersensitivity resolution by increasing interleukin 10 (IL-10) expression in the dorsal root ganglion. In line with these observations, blocking IL-10 receptor (IL-10R) activity occluded the effects of ICOSaa treatment on mechanical hypersensitivity in female mice. Suggesting a broader activity in neuropathic pain, ICOSaa also partially resolved mechanical hypersensitivity in the spared nerve injury (SNI) model. Our findings support a model wherein ICOSaa administration induces IL-10 expression to facilitate neuropathic pain relief in female mice. ICOSaa treatment is in clinical development for solid tumors and given our observation of T cells in the human DRG, ICOSaa therapy could be developed for combination chemotherapy-CIPN clinical trials.

Microglia are implicated in the development of paclitaxel chemotherapy-associated cognitive impairment in female mice

Chemotherapy remains a mainstay in the treatment of many types of cancer even though it is associated with debilitating behavioral side effects referred to as "chemobrain," including difficulty concentrating and memory impairment. The predominant hypothesis in the field is that systemic inflammation drives these cognitive impairments, although the brain mechanisms by which this occurs remain poorly understood. Here, we hypothesized that microglia are activated by chemotherapy and drive chemotherapy-associated cognitive impairments. To test this hypothesis, we treated female C57BL/6 mice with a clinically-relevant regimen of a common chemotherapeutic, paclitaxel (6 i.p. doses at 30 mg/kg), which impairs memory of an aversive stimulus as assessed via a contextual fear conditioning (CFC) paradigm. Paclitaxel increased the percent area of IBA1 staining in the dentate gyrus of the hippocampus. Moreover, using a machine learning random forest classifier we identified immunohistochemical features of reactive microglia in multiple hippocampal subregions that were distinct between vehicle- and paclitaxel-treated mice. Paclitaxel treatment also increased gene expression of inflammatory cytokines in a microglia-enriched population of cells from mice. Lastly, a selective inhibitor of colony stimulating factor 1 receptor, PLX5622, was employed to deplete microglia and then assess CFC performance following paclitaxel treatment. PLX5622 significantly reduced hippocampal gene expression of paclitaxel-induced proinflammatory cytokines and restored memory, suggesting that microglia play a critical role in the development of chemotherapy-associated neuroinflammation and cognitive impairments. This work provides critical evidence that microglia drive paclitaxel-associated cognitive impairments, a key mechanistic detail for determining preventative and intervention strategies for these burdensome side effects.

Role of tubulin post-translational modifications in peripheral neuropathy

Peripheral neuropathy is a common disorder that results from nerve damage in the periphery. The degeneration of sensory axon terminals leads to changes or loss of sensory functions, often manifesting as debilitating pain, weakness, numbness, tingling, and disability. The pathogenesis of most peripheral neuropathies remains to be fully elucidated. Cumulative evidence from both early and recent studies indicates that tubulin damage may provide a common underlying mechanism of axonal injury in various peripheral neuropathies. In particular, tubulin post-translational modifications have been recently implicated in both toxic and inherited forms of peripheral neuropathy through regulation of axonal transport and mitochondria dynamics. This knowledge forms a new area of investigation with the potential for developing therapeutic strategies to prevent or delay peripheral neuropathy by restoring tubulin homeostasis.

Prevention of Chemotherapy-Induced Peripheral Neuropathy by Inhibiting C-X-C Motif Chemokine Receptor 2

Chemotherapy-induced peripheral neuropathy (CIPN) is a major drawback in the use of chemotherapeutic agents for patients with cancer. Although studies have investigated a broad number of molecules that might be related to CIPN, the differences in the chemokine pathways between various chemotherapeutic agents, such as vincristine and oxaliplatin, which are some of the most widely used treatments, have not been fully elucidated. We confirmed that the administration (intraperitoneal injections for seven days) of vincristine (0.1 mg/kg) and oxaliplatin (3 mg/kg) induced pain by using the von Frey behavioral test. Subsequent applications with vincristine and oxaliplatin led to mechanical allodynia that lasted more than one week from the fifth day. After the induction of mechanical allodynia, the mRNA expression of CXCR2, CXCL1, CXCL3, and CXCL5 was examined in the dorsal root ganglia (DRG) and spinal cord of the CIPN models. As a result, the mRNA expression of CXCR2 robustly increased in the lumbar spinal cord in the oxaliplatin-treated mice. Next, to evaluate the involvement of CXCR2 in CIPN, reparixin, a CXCR1/2 inhibitor, was administered intrathecally or intraperitoneally with vincristine or oxaliplatin and was further verified by treatment with ruxolitinib, which inhibits Janus kinase 2 downstream of the CXCR1/2 pathway. Reparixin and ruxolitinib blocked oxaliplatin-induced allodynia but not vincristine-induced allodynia, which suggests that CXCR2-related pathways are associated with the development of oxaliplatin-induced neuropathy. Together with the above results, this suggests that the prevention of oxaliplatin-induced neuropathy by CXCR2 inhibition can lead to successful chemotherapy, and it is important to provide appropriate countermeasures against CIPN development for each specific chemotherapeutic agent.

Pharmacological Evidence of the Important Roles of CCR1 and CCR3 and Their Endogenous Ligands CCL2/7/8 in Hypersensitivity Based on a Murine Model of Neuropathic Pain

Neuropathic pain treatment remains a challenging issue because the therapies currently used in the clinic are not sufficiently effective. Moreover, the mechanism of neuropathy is still not entirely understood; however, much evidence indicates that chemokines are important factors in the initial and late phases of neuropathic pain. To date, the roles of CCR1, CCR3 and their endogenous ligands have not been extensively studied; therefore, they have become the subject of our research. In the present comprehensive behavioral and biochemical study, we detected significant time-dependent and long-lasting increases in the mRNA levels of CCR1 and/or CCR3 ligands, such as CCL2/3/4/5/6/7/8/9, in the murine spinal cord after chronic constriction injury of the sciatic nerve, and these increases were accompanied by changes in the levels of microglial/macrophage, astrocyte and neutrophil cell markers. ELISA results suggested that endogenous ligands of CCR1 and CCR3 are involved in the development (CCL2/3/5/7/8/9) and persistence (CCL2/7/8) of neuropathic pain. Moreover, intrathecal injection of CCL2/3/5/7/8/9 confirmed their possible strong influence on mechanical and thermal hypersensitivity development. Importantly, inhibition of CCL2/7/8 production and CCR1 and CCR3 blockade by selective/dual antagonists effectively reduced neuropathic pain-like behavior. The obtained data suggest that CCL2/7/8/CCR1 and CCL7/8/CCR3 signaling are important in the modulation of neuropathic pain in mice and that these chemokines and their receptors may be interesting targets for future investigations.

Neurophysiopathological Aspects of Paclitaxel-induced Peripheral Neuropathy

Chemotherapy is widely used as a primary treatment or adjuvant therapy for cancer. Anti-microtubule agents (such as paclitaxel and docetaxel) are used for treating many types of cancer, either alone or in combination. However, their use has negative consequences that restrict the treatment's ability to continue. The principal negative effect is the so-called chemotherapy-induced peripheral neuropathy (CIPN). CIPN is a complex ailment that depends on diversity in the mechanisms of action of the different chemotherapy drugs, which are not fully understood. In this paper, we review several neurophysiological and pathological characteristics, such as morphological changes, changes in ion channels, mitochondria and oxidative stress, cell death, changes in the immune response, and synaptic control, as well as the characteristics of neuropathic pain produced by paclitaxel.

The role of the neuronal microenvironment in sensory function and pain pathophysiology

The high prevalence of pain and the at times low efficacy of current treatments represent a significant challenge to healthcare systems worldwide. Effective treatment strategies require consideration of the diverse pathophysiologies that underlie various pain conditions. Indeed, our understanding of the mechanisms contributing to aberrant sensory neuron function has advanced considerably. However, sensory neurons operate in a complex dynamic microenvironment that is controlled by multidirectional interactions of neurons with non-neuronal cells, including immune cells, neuronal accessory cells, fibroblasts, adipocytes, and keratinocytes. Each of these cells constitute and control the microenvironment in which neurons operate, inevitably influencing sensory function and the pathology of pain. This review highlights the importance of the neuronal microenvironment for sensory function and pain, focusing on cellular interactions in the skin, nerves, dorsal root ganglia, and spinal cord. We discuss the current understanding of the mechanisms by which neurons and non-neuronal cells communicate to promote or resolve pain, and how this knowledge could be used for the development of mechanism-based treatments.

RgIA4 Prevention of Acute Oxaliplatin-Induced Cold Allodynia Requires α9-Containing Nicotinic Acetylcholine Receptors and CD3+ T-Cells

Chemotherapy-induced neuropathic pain is a debilitating and dose-limiting side effect. Oxaliplatin is a third-generation platinum and antineoplastic compound that is commonly used to treat colorectal cancer and commonly yields neuropathic side effects. Available drugs such as duloxetine provide only modest benefits against oxaliplatin-induced neuropathy. A particularly disruptive symptom of oxaliplatin is painful cold sensitivity, known as cold allodynia. Previous studies of the Conus regius peptide, RgIA, and its analogs have demonstrated relief from oxaliplatin-induced cold allodynia, yielding improvement that persists even after treatment cessation. Moreover, underlying inflammatory and neuronal protection were shown at the cellular level in chronic constriction nerve injury models, consistent with disease-modifying effects. Despite these promising preclinical outcomes, the underlying molecular mechanism of action of RgIA4 remains an area of active investigation. This study aimed to determine the necessity of the α9 nAChR subunit and potential T-cell mechanisms in RgIA4 efficacy against acute oxaliplatin-induced cold allodynia. A single dose of oxaliplatin (10 mg/kg) was utilized followed by four daily doses of RgIA4. Subcutaneous administration of RgIA4 (40 µg/kg) prevented cold allodynia in wildtype mice but not in mice lacking the α9 nAChR-encoding gene, chrna9. RgIA4 also failed to reverse allodynia in mice depleted of CD3⁺ T-cells. In wildtype mice treated with oxaliplatin, quantitated circulating T-cells remained unaffected by RgIA4. Together, these results show that RgIA4 requires both chrna9 and CD3⁺ T-cells to exert its protective effects against acute cold-allodynia produced by oxaliplatin.

Multiplex immunohistochemistry reveals cochlear macrophage heterogeneity and local auditory nerve inflammation in cisplatin-induced hearing loss

Inner ear macrophages play a vital role in cochlear homeostasis. Recent studies have demonstrated the existence of macrophages at different sites of the cochlea, with increased cochlear infiltration as an inflammatory response mechanism to injury. However, current methods, such as conventional immunohistochemistry and flow cytometry, provide limited information about the diversity of cochlear macrophages. Recently, multiplex immunohistochemistry (mIHC) successfully identified the heterogeneity of immune cells in cancer tissue and thereby improved our understanding of the disease prognosis. In this study, we modified the mIHC technique for cochlear tissue and utilized it to investigate cochlear macrophage behavior and heterogeneity before and after exposure to ototoxic drugs such as cisplatin. Four-week-old C57BL/6N female mice were intraperitoneally injected with cisplatin at 5 mg/kg/day consecutively for 6 days. Their hearing levels were assessed before and after the injection. Their cochleae were harvested before (day 0) and on days 8 and 15 after the cisplatin injection. Paraffin-embedded sections were sequentially immunostained using macrophage surface markers to identify the different categories of macrophages. Each immunostaining cycle included incubation with primary antibody, incubation with secondary antibody, chromogenic staining, and image scanning. Thereafter, all antibodies were stripped out, and antigen retrieval was performed to prepare the tissue for the next cycle. The results revealed that activated cochlear macrophages were not entirely differentiated into M1 or M2 categories but into multi-marker M1/M2 mixed macrophages. Furthermore, the ratio of these mixed (M1/M2) macrophages to Iba1+ macrophages increased in the auditory nerve after cisplatin exposure, suggesting local auditory nerve inflammation. The increase in the population of activated macrophages in the auditory nerve region was concomitant with the temporary shift of hearing threshold on day 8 post-cisplatin injection. The findings of this study indicate the effectiveness of mIHC in identifying cochlear macrophage heterogeneity both in the resting state and after cisplatin exposure. Therefore, mIHC could be a powerful tool in cochlear immunology research. Our findings may provide new insights into the co-relation between the cochlear macrophage and cisplatin exposure.

Chemotherapy-induced peripheral neuropathy in children and adolescent cancer patients

Brain cancer and leukemia are the most common cancers diagnosed in the pediatric population and are often treated with lifesaving chemotherapy. However, chemotherapy causes severe adverse effects and chemotherapy-induced peripheral neuropathy (CIPN) is a major dose-limiting and debilitating side effect. CIPN can greatly impair quality of life and increases morbidity of pediatric patients with cancer, with the accompanying symptoms frequently remaining underdiagnosed. Little is known about the incidence of CIPN, its impact on the pediatric population, and the underlying pathophysiological mechanisms, as most existing information stems from studies in animal models or adult cancer patients. Herein, we aim to provide an understanding of CIPN in the pediatric population and focus on the 6 main substance groups that frequently cause CIPN, namely the vinca alkaloids (vincristine), platinum-based antineoplastics (cisplatin, carboplatin and oxaliplatin), taxanes (paclitaxel and docetaxel), epothilones (ixabepilone), proteasome inhibitors (bortezomib) and immunomodulatory drugs (thalidomide). We discuss the clinical manifestations, assessments and diagnostic tools, as well as risk factors, pathophysiological processes and current pharmacological and non-pharmacological approaches for the prevention and treatment of CIPN.

Antinociceptive effect of plant-based natural products in chemotherapy-induced peripheral neuropathies: A systematic review

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most prevalent and difficult-to-treat symptoms in cancer patients. For this reason, the explore for unused helpful choices able of filling these impediments is essential. Natural products from plants stand out as a valuable source of therapeutic agents, being options for the treatment of this growing public health problem. Therefore, the objective of this study was to report the effects of natural products from plants and the mechanisms of action involved in the reduction of neuropathy caused by chemotherapy. The search was performed in PubMed, Scopus and Web of Science in March/2021. Two reviewers independently selected the articles and extracted data on characteristics, methods, study results and methodological quality (SYRCLE). Twenty-two studies were selected, describing the potential effect of 22 different phytochemicals in the treatment of CIPN, with emphasis on terpenes, flavonoids and alkaloids. The effect of these compounds was demonstrated in different experimental protocols, with several action targets being proposed, such as modulation of inflammatory mediators and reduction of oxidative stress. The studies demonstrated a predominance of the risk of uncertain bias for randomization, baseline characteristics and concealment of the experimental groups. Our findings suggest a potential antinociceptive effect of natural products from plants on CIPN, probably acting in several places of action, being strategic for the development of new therapeutic options for this multifactorial condition.

Mechanisms underlying paclitaxel-induced neuropathic pain: Channels, inflammation and immune regulations

Paclitaxel is a chemotherapeutic agent widely used for many types of malignancies. However, when paclitaxel is used to treat tumors, patients commonly experience severe neuropathic pain that is difficult to manage. The mechanism underlying paclitaxel-induced neuropathic pain remains unclear. Evidence demonstrates correlations between mechanisms of paclitaxel-mediated pain and associated actions of ion channels, neuroinflammation, mitochondrial damage, and other factors. This review provides a comprehensive analysis of paclitaxel-induced neuropathic pain mechanisms and suggestions for effective interventions.

Emerging Approaches for the Management of Chemotherapy-Induced Peripheral Neuropathy (CIPN): Therapeutic Potential of the C5a/C5aR Axis

Chemotherapy-induced peripheral neuropathy (CIPN) is the most common neurologic complication of chemotherapy, resulting in symptoms like pain, sensory loss, and numbness in the hands and feet that cause lots of uneasiness in patients with cancer. They often suffer from pain so severe that it interrupts the treatment, thus invalidating the entire chemotherapy-based healing process, and significantly reducing their quality of life. In this paper, we underline the role of the complement system in CIPN, highlighting the relevance of the C5a fragment and its receptor C5aR1, whose activation is thought to be involved in triggering a cascade of events that can lead to CIPN onset. Recent experimental data showed the ability of docetaxel and paclitaxel to specifically bind and activate C5aR1, thus shining light on one of the molecular mechanisms by which taxanes may activate a cascade of events leading to neuropathy. According to these new evidence, it was possible to suggest new mechanisms underlying the pathophysiology of CIPN. Hence, the C5a/C5aR1 axis may represent a new target for CIPN treatment, and the use of C5aR1 inhibitors can be proposed as a potential new therapeutic option to manage this high unmet medical need.

Anti-Inflammatory Properties of KLS-13019: a Novel GPR55 Antagonist for Dorsal Root Ganglion and Hippocampal Cultures

KLS-13019, a novel devised cannabinoid-like compound, was explored for anti-inflammatory actions in dorsal root ganglion cultures relevant to chemotherapy-induced peripheral neuropathy (CIPN). Time course studies with 3 µM paclitaxel indicated > 1.9-fold increases in immunoreactive (IR) area for cell body GPR55 after 30 min as determined by high content imaging. To test for reversibility of paclitaxel-induced increases in GPR55, cultures were treated for 8 h with paclitaxel alone and then a dose response to KLS-13019 added for another 16 h. This "reversal" paradigm indicated established increases in cell body GPR55 IR areas were decreased back to control levels. Because GPR55 had previously reported inflammatory actions, IL-1β and NLRP3 (inflammasome-3 marker) were also measured in the "reversal" paradigm. Significant increases in all inflammatory markers were produced after 8 h of paclitaxel treatment alone that were reversed to control levels with KLS-13019 treatment. Accompanying studies using alamar blue indicated that decreased cellular viability produced by paclitaxel treatment was reverted back to control levels by KLS-13019. Similar studies conducted with lysophosphatidylinositol (GPR55 agonist) in DRG or hippocampal cultures demonstrated significant increases in neuritic GPR55, NLRP3 and IL-1β areas that were reversed to control levels with KLS-13019 treatment. Studies with a human GPR55-β-arrestin assay in Discover X cells indicated that KLS-13019 was an antagonist without agonist activity. These studies indicated that KLS-13019 has anti-inflammatory properties mediated through GPR55 antagonist actions. Together with previous studies, KLS-13019 is a potent neuroprotective, anti-inflammatory cannabinoid with therapeutic potential for high efficacy treatment of neuropathic pain.

Cellular Pathogenesis of Chemotherapy-Induced Peripheral Neuropathy: Insights From Drosophila and Human-Engineered Skin Models

Chemotherapy-induced peripheral neuropathy (CIPN) is a highly prevalent and complex condition arising from chemotherapy cancer treatments. Currently, there are no treatment or prevention options in the clinic. CIPN accompanies pain-related sensory functions starting from the hands and feet. Studies focusing on neurons in vitro and in vivo models significantly advanced our understanding of CIPN pathological mechanisms. However, given the direct toxicity shown in both neurons and non-neuronal cells, effective in vivo or in vitro models that allow the investigation of neurons in their local environment are required. No single model can provide a complete solution for the required investigation, therefore, utilizing a multi-model approach would allow complementary advantages of different models and robustly validate findings before further translation. This review aims first to summarize approaches and insights from CIPN in vivo models utilizing small model organisms. We will focus on Drosophila melanogaster CIPN models that are genetically amenable and accessible to study neuronal interactions with the local environment in vivo. Second, we will discuss how these findings could be tested in physiologically relevant vertebrate models. We will focus on in vitro approaches using human cells and summarize the current understanding of engineering approaches that may allow the investigation of pathological changes in neurons and the skin environment.

Gut microbiota depletion by antibiotics ameliorates somatic neuropathic pain induced by nerve injury, chemotherapy, and diabetes in mice

Background

Gut microbiota has been found involved in neuronal functions and neurological disorders. Whether and how gut microbiota impacts chronic somatic pain disorders remain elusive.

Methods

Neuropathic pain was produced by different forms of injury or diseases, the chronic constriction injury (CCI) of the sciatic nerves, oxaliplatin (OXA) chemotherapy, and streptozocin (STZ)-induced diabetes in mice. Continuous feeding of antibiotics (ABX) cocktail was used to cause major depletion of the gut microbiota. Fecal microbiota, biochemical changes in the spinal cord and dorsal root ganglion (DRG), and the behaviorally expressed painful syndromes were assessed.

Results

Under condition of gut microbiota depletion, CCI, OXA, or STZ treatment-induced thermal hyperalgesia or mechanical allodynia were prevented or completely suppressed. Gut microbiota depletion also prevented CCI or STZ treatment-induced glial cell activation in the spinal cord and inhibited cytokine production in DRG in OXA model. Interestingly, STZ treatment failed to induce the diabetic high blood glucose and painful hypersensitivity in animals with the gut microbiota depletion. ABX feeding starting simultaneously with CCI, OXA, or STZ treatment resulted in instant analgesia in all the animals. ABX feeding starting after establishment of the neuropathic pain in CCI- and STZ-, but not OXA-treated animals produced significant alleviation of the thermal hyeralgesia or mechanical allodynia. Transplantation of fecal bacteria from SPF mice to ABX-treated mice partially restored the gut microbiota and fully rescued the behaviorally expressed neuropathic pain, of which, Akkermansia, Bacteroides, and Desulfovibrionaceae phylus may play a key role.

Conclusion

This study demonstrates distinct roles of gut microbiota in the pathogenesis of chronic painful conditions with nerve injury, chemotherapy and diabetic neuropathy and supports the clinical significance of fecal bacteria transplantation.

The Role of Vascular-Immune Interactions in Modulating Chemotherapy Induced Neuropathic Pain

Chemotherapy causes sensory disturbances in cancer patients that results in neuropathies and pain. As cancer survivorships has dramatically increased over the past 10 years, pain management of these patients is becoming clinically more important. Current analgesic strategies are mainly ineffective and long-term use is associated with severe side effects. The issue being that common analgesic strategies are based on ubiquitous pain mediator pathways, so when applied to clinically diverse neuropathic pain and neurological conditions, are unsuccessful. This is principally due to the lack of understanding of the driving forces that lead to chemotherapy induced neuropathies. It is well documented that chemotherapy causes sensory neurodegeneration through axonal atrophy and intraepidermal fibre degeneration causing alterations in pain perception. Despite the neuropathological alterations associated with chemotherapy-induced neuropathic pain being extensively researched, underlying causes remain elusive. Resent evidence from patient and rodent studies have indicated a prominent inflammatory cell component in the peripheral sensory nervous system in effected areas post chemotherapeutic treatment. This is accompanied by modulation of auxiliary cells of the dorsal root ganglia sensory neurons such as activation of satellite glia and capillary dysfunction. The presence of a neuroinflammatory component was supported by transcriptomic analysis of dorsal root ganglia taken from mice treated with common chemotherapy agents. With key inflammatory mediators identified, having potent immunoregulatory effects that directly influences nociception. We aim to evaluate the current understanding of these immune-neuronal interactions across different cancer therapy drug classes. In the belief this may lead to better pain management approaches for cancer survivors.

Synergistic Antinociceptive Effects of Indomethacin-Pregabalin and Meloxicam-Pregabalin in Paclitaxel-Induced Neuropathic Pain

Neuropathic pain is often closely associated with nerve injury or inflammation, and the role of traditional nonsteroidal anti-inflammatory drugs as adjuvants for treating chemotherapy-induced peripheral neuropathic pain remains unclear. In this study, the potential synergistic antinociceptive effects of indomethacin–pregabalin and meloxicam–pregabalin were evaluated in paclitaxel-induced neuropathic pain and carrageenan-induced inflammatory pain in rodents. Although indomethacin and meloxicam alone only slightly relieved mechanical allodynia in the above two models, isobolographic analysis showed that the combination of indomethacin or meloxicam with pregabalin produced significant synergistic antinociceptive effects for paclitaxel-induced neuropathic pain (IN-PGB, experimental ED₂₅ = [4.41 (3.13–5.82)] mg/kg, theoretical ED₂₅ = [8.50 (6.62–10.32)] mg/kg; MEL-PGB, experimental ED₂₅ = [3.96 (2.62–5.46)] mg/kg, theoretical ED₂₅ = [7.52 (5.73–9.39)] mg/kg). In addition, MEL-PGB dosed via intraplantar injection into the left paw, intragastric injection, or intraperitoneal injection reversed paclitaxel-induced allodynia, indicating that they may act at multiple sites in the neuroaxis and periphery. However, indomethacin–pregabalin and meloxicam–pregabalin exerted antagonistic antiallodynic interactions in carrageenan-induced inflammatory pain in rats. Taken together, coadministration of indomethacin or meloxicam with pregabalin may possess potential therapeutic advantages for treating chemotherapy-induced neuropathic pain.