Chemotherapy-induced peripheral neuropathy: where are we now?

In vitro neurotoxicity testing: lessons from chemotherapy-induced peripheral neurotoxicity

INTRODUCTION

Chemotherapy induced peripheral neurotoxicity (CIPN) is a long-lasting, or even permanent, late toxicity caused by largely used anticancer drugs. CIPN affects a growing population of cancer survivors and diminishes their quality of life since there is no curative/preventive treatment. Among several reasons for this unmet clinical need, there is an incomplete knowledge on mechanisms leading to CIPN. Therefore, bench side research is still greatly needed: in vitro studies are pivotal to both evaluate neurotoxicity mechanisms and potential neuroprotection strategies.

AREAS COVERED

Advantages and disadvantages of in vitro approaches are addressed with respect to their applicability to the CIPN field. Different cell cultures and techniques to assess neurotoxicity/neuroprotection are described. PubMed search-string: (chemotherapy-induced) AND (((neuropathy) OR neurotoxicity) OR neuropathic pain) AND (in vitro) AND (((((model) OR SH-SY5Y) OR PC12) OR iPSC) OR DRG neurons); (chemotherapy-induced) AND (((neuropathy) OR neurotoxicity) OR neuropathic pain) AND (model) AND (((neurite elongation) OR cell viability) OR morphology). No articles published before 1990 were selected.

EXPERT OPINION

CIPN is an ideal experimental setting to test axonal damage and, in general, peripheral nervous system mechanisms of disease and neuroprotection. Therefore, starting from robust preclinical data in this field, potentially, relevant biological rationale can be transferred to other human spontaneous diseases of the peripheral nervous system.

Microbiome contributions to pain: a review of the preclinical literature

ABSTRACT

Over the past 2 decades, the microbiome has received increasing attention for the role that it plays in health and disease. Historically, the gut microbiome was of particular interest to pain scientists studying nociplastic visceral pain conditions given the anatomical juxtaposition of these microorganisms and the neuroimmune networks that drive pain in such diseases. More recently, microbiomes both inside and across the surface of the body have been recognized for driving sensory symptoms in a broader set of diseases. Microbiomes have never been a more popular topic in pain research, but to date, there has not been a systematic review of the preclinical microbiome pain literature. In this article, we identified all animal studies in which both the microbiome was manipulated and pain behaviors were measured. Our analysis included 303 unique experiments across 97 articles. Microbiome manipulation methods and behavioral outcomes were recorded for each experiment so that field-wide trends could be quantified and reported. This review specifically details the animal species, injury models, behavior measures, and microbiome manipulations used in preclinical pain research. From this analysis, we were also able to conclude how manipulations of the microbiome alter pain thresholds in naïve animals and persistent pain intensity and duration in cutaneous and visceral pain models. This review summarizes by identifying existing gaps in the literature and providing recommendations for how to best plan, implement, and interpret data collected in preclinical microbiome pain experiments.

Challenges and Complications in the Management of Advanced Oropharyngeal Carcinoma: Role of Post-Mortem Diagnosis and Future Perspectives

Oropharyngeal squamous-cell carcinoma (OPSCC) poses significant challenges in diagnosis, treatment, and management and has important medico-legal and forensic implications. In particular, the management of OPSCC and its treatment-related complications can often be challenging. In cases with advanced OPSCC, a loco-regional extension of the tumor can contribute to the destruction of oral cavity tissues, while the radiotherapy treatment can induce profound changes in tissue morphology and structure. These changes, which resemble tumor neoplasms and endovascular effects, are related to a higher risk of fatal bleeding, as reported in the case study illustrated, in which a hemorrhage occurred from a lingual artery, originating from an ulcerative, necrotic, hemorrhagic lesion on the tongue. Bleeding complications in OPSCC and prolonged radiotherapy are associated with high mortality and require comprehensive management strategies to improve survival and quality of life. Autopsy investigations, contributing to the definition of post-mortem diagnosis, can provide valuable insights into the pathogenetic mechanisms underlying bleeding and guide therapeutic decisions and preventive measures. The integration of autopsy and histopathological investigation into clinical practice should be considered as a necessary support to optimize the management of complications in advanced OPSCC patients, emphasizing the importance of a patient-centered approach and continued research.

Factors affecting peripheral neuropathy induced by nanoparticle albumin-bound paclitaxel in patients with pancreatic cancer

AIM

Chemotherapy-induced peripheral neuropathy (CIPN) is a major toxicity limiting the use of nab-paclitaxel (Nab-P) in treating patients with pancreatic cancer. The aim of this study was to identify the factors affecting CIPN using patient-reported outcome measures and the minimally invasive volumetric absorptive microsampling (VAMS) technique.

METHODS

The maximum concentrations of paclitaxel (Cmax) were measured from 81 VAMS samples collected from 44 participants with pancreatic cancer. The association between CIPN development and demographic, clinical and pharmacokinetic factors was determined using univariable and multivariable logistic regression. The association between CIPN severity and the factors was evaluated using Spearman's rank correlation. The impact of Cmax and the number of treatment cycles on the severity was assessed using multivariable linear regression.

RESULTS

The development of CIPN was significantly associated with cumulative dose (odds ratio 1.005, 95% confidence interval [CI] 1.003-1.007), treatment cycles (3.47, 2.25-5.85), alkaline phosphate (0.992, 0.985-0.998) and age (1.092, 1.020-1.179), with an area under the receiver operating characteristic curve of 0.89 (95% CI 0.83-0.95). The severity of CIPN significantly worsened with increasing cumulative dose (coefficient 0.58, 95% CI 0.44-0.69), treatment cycles (0.57, 0.44-0.68) and age (0.18, 0.00-0.35). The severity of CIPN was predictable from treatment cycles (P = .0002) and Cmax (P = .01).

CONCLUSION

The higher the cumulative dose of Nab-P, treatment cycles and age, the more frequently and severely do the patients experience CIPN. In predicting the severity of CIPN using Cmax, minimally invasive VAMS is a feasible alternative to venous blood sampling.

FTY720/Fingolimod mitigates paclitaxel-induced Sparcl1-driven neuropathic pain and breast cancer progression

Paclitaxel is among the most active chemotherapy drugs for the aggressive triple negative breast cancer (TNBC). Unfortunately, it often induces painful peripheral neuropathy (CIPN), a major debilitating side effect. Here we demonstrate that in naive and breast tumor-bearing immunocompetent mice, a clinically relevant dose of FTY720/Fingolimod that targets sphingosine-1-phosphate receptor 1 (S1PR1), alleviated paclitaxel-induced neuropathic pain. FTY720 also significantly attenuated paclitaxel-stimulated glial fibrillary acidic protein (GFAP), a marker for activated astrocytes, and expression of the astrocyte-secreted synaptogenic protein Sparcl1/Hevin, a key regulator of synapse formation. Notably, the formation of excitatory synapses containing VGluT2 in the spinal cord dorsal horn induced by paclitaxel was also inhibited by FTY720 treatment, supporting the involvement of astrocytes and Sparcl1 in CIPN. Furthermore, in this TNBC mouse model that mimics human breast cancer, FTY720 administration also enhanced the anti-tumor effects of paclitaxel, leading to reduced tumor progression and lung metastasis. Taken together, our findings suggest that targeting the S1P/S1PR1 axis with FTY720 is a multipronged approach that holds promise as a therapeutic strategy for alleviating both CIPN and enhancing the efficacy of chemotherapy in TNBC treatment.

Chemotherapy-Induced Peripheral Neuropathy: A Recent Update on Pathophysiology and Treatment

Chemotherapy-induced peripheral neuropathy (CIPN) is a major long-lasting side effect of some chemotherapy drugs, which threatens cancer survival rate. CIPN mostly affects sensory neurons and occasionally motor neurons, causing numbness, tingling, discomfort, and burning pain in the upper and lower extremities. The pathophysiology of CIPN is not completely understood; however, it is believed that chemotherapies induce peripheral neuropathy via directly damaging mitochondria, impairing the function of ion channels, triggering immunological mechanisms, and disrupting microtubules. The treatment of CIPN is a medical challenge, and there are no approved pharmacological options. Currently, duloxetine and other antidepressants, antioxidant, anti-inflammatory, and ion-channel targeted therapies are commonly used in clinics to relieve the symptoms of CIPN. Several other types of drugs, such as cannabinoids, sigma-1 receptor antagonists, and nicotinamides ribose, are being evaluated in preclinical and clinical studies. This paper summarizes the information related to the physiology of CIPN and medicines that could be used for treating this condition.

An Immune-Enhancing Injectable Hydrogel Loaded with Esketamine and DDP Promotes Painless Immunochemotherapy to Inhibit Breast Cancer Growth

Chemotherapy is the cornerstone of triple-negative breast cancer. The poor effectiveness and severe neuropathic pain caused by it have a significant impact on the immune system. Studies confirmed that immune cells in the tumor microenvironment (TME), have critical roles in tumor immune regulation and prognosis. In this study, it is revealed that the painless administration of Esketamine, combined with Cisplatin (DDP), can exert an anti-tumor effect, which is further boosted by the hydrogel delivery system. It is also discovered that Esketamine combined with DDP co-loaded in Poloxamer Hydrogel (PDEH) induces local immunity by increasing mature Dendritic Cells (mDCs) and activated T cells in PDEH group while the regulatory T cells (Tregs) known as CD4+CD25+FoxP3+decreased significantly. Finally, , CD8+ and CD4+ T cells in the spleen exhibited a significant increase, suggesting a lasting immune impact of PDEH. This study proposes that Esketamine can serve as a painless immune modulator, enhancing an anti-tumor effect while co-loaded in poloxamer hydrogel with DDP. Along with improving immune cells in the microenvironment, it can potentially alleviate anxiety and depression. With its outstanding bio-safety profile, it offers promising new possibilities for painless clinical therapy.

The Efficacy of Ketamine for Acute and Chronic Pain in Patients with Cancer: A Systematic Review of Randomized Controlled Trials

Managing cancer-related pain poses significant challenges, prompting research into alternative approaches such as ketamine. This systematic review aims to analyze and summarize the impact of ketamine as an adjuvant to opioid therapy for cancer-related pain. We conducted a literature review in MEDLINE, EMBASE, and Scopus from 1 January 1982 to 20 October 2023. Abstracts were screened against inclusion criteria, and eligible studies underwent a full-text review. Data was extracted from the included studies, and a framework analysis approach summarized the evidence regarding ketamine's use in patients with cancer. A total of 21 randomized clinical trials were included, and the quality of all the included studies was good or fair. Significant improvements in pain scores and reduced morphine consumption were consistently observed with intravenous ketamine administration for postoperative pain control, particularly when combined with other analgesics such as morphine. Ketamine was less effective when used as an analgesic for chronic pain management, with several studies on neuropathic pain or chemotherapy-induced neuropathy finding minimal significant effect on reduction of pain scores or morphine requirements. The efficacy of ketamine in pain management appears to depend on factors such as dosage, route of administration, and patient population.

Impact of exercise on chemotherapy-induced peripheral neuropathy in survivors with post-treatment primary breast cancer

PURPOSE

Chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating side effect of neurotoxic chemotherapy. Exercise activates neuromuscular function and may improve CIPN. We examined the association between exercise and CIPN symptoms in breast cancer survivors.

METHODS

In a retrospective cross-sectional study, we included patients completing a survey assessing exercise exposure and neuropathy symptoms in a tertiary cancer center survivorship clinic. We evaluated exercise duration and intensity using a standardized questionnaire quantified in metabolic equivalent tasks (MET-h/wk). We defined exercisers as patients meeting the National Physical Activity Guidelines' criteria. We used multivariable logistic regressions to examine the relationship between exercise and CIPN and if this differed as a function of chemotherapy regimen adjusting for age, gender, and race.

RESULTS

We identified 5444 breast cancer survivors post-chemotherapy (median age 62 years (interquartile range [IQR]: 55, 71); median 4.7 years post-chemotherapy (IQR: 3.3, 7.6)) from 2017 to 2022. CIPN overall prevalence was 34% (95% confidence interval [CI]: 33%, 36%), 33% for non-taxane, and 37% for taxane-based chemotherapy. CIPN prevalence was 28% (95% CI: 26%, 30%) among exercisers and 38% (95% CI: 37%, 40%) among non-exercisers (difference 11%; 95% CI: 8%, 13%; p < 0.001). Compared to patients with low (<6 MET-h/wk) levels of exercise (42%), 11% fewer patients with moderate (6-20.24 MET-h/wk) to high (>20.25 MET-h/wk) levels of exercise reported CIPN. Exercise was associated with reduced prevalence of all CIPN symptoms regardless of chemotherapy type.

CONCLUSION

CIPN may persist several years following chemotherapy among patients with breast cancer but is significantly reduced by exercise in a dose-dependent manner.

HDAC inhibitors as a potential therapy for chemotherapy-induced neuropathic pain

Cancer, a chronic disease characterized by uncontrolled cell development, kills millions of people globally. The WHO reported over 10 million cancer deaths in 2020. Anticancer medications destroy healthy and malignant cells. Cancer treatment induces neuropathy. Anticancer drugs cause harm to spinal cord, brain, and peripheral nerve somatosensory neurons, causing chemotherapy-induced neuropathic pain. The chemotherapy-induced mechanisms underlying neuropathic pain are not fully understood. However, neuroinflammation has been identified as one of the various pathways associated with the onset of chemotherapy-induced neuropathic pain. The neuroinflammatory processes may exhibit varying characteristics based on the specific type of anticancer treatment delivered. Neuroinflammatory characteristics have been observed in the spinal cord, where microglia and astrocytes have a significant impact on the development of chemotherapy-induced peripheral neuropathy. The patient's quality of life might be affected by sensory deprivation, loss of consciousness, paralysis, and severe disability. High cancer rates and ineffective treatments are associated with this disease. Recently, histone deacetylases have become a novel treatment target for chemotherapy-induced neuropathic pain. Chemotherapy-induced neuropathic pain may be treated with histone deacetylase inhibitors. Histone deacetylase inhibitors may be a promising therapeutic treatment for chemotherapy-induced neuropathic pain. Common chemotherapeutic drugs, mechanisms, therapeutic treatments for neuropathic pain, and histone deacetylase and its inhibitors in chemotherapy-induced neuropathic pain are covered in this paper. We propose that histone deacetylase inhibitors may treat several aspects of chemotherapy-induced neuropathic pain, and identifying these inhibitors as potentially unique treatments is crucial to the development of various chemotherapeutic combination treatments.

Navigating Preclinical Models and Medications for Peripheral Neuropathy: A Review

Peripheral neuropathy (PN) is a multifaceted disorder characterised by peripheral nerve damage, manifesting in symptoms like pain, weakness, and autonomic dysfunction. This review assesses preclinical models in PN research, evaluating their relevance to human disease and their role in therapeutic development. The Streptozotocin (STZ)-induced diabetic rat model is widely used to simulate diabetic neuropathy but has limitations in faithfully replicating disease onset and progression. Cisplatin-induced PN models are suitable for studying chemotherapy-induced peripheral neuropathy (CIPN) and closely resemble human pathology. However, they may not fully replicate the spectrum of sensory and motor deficits. Paclitaxel-induced models also contribute to understanding CIPN mechanisms and testing neuroprotective agents. Surgical or trauma-induced models offer insights into nerve regeneration and repair strategies. Medications such as gabapentin, pregabalin, duloxetine, and fluoxetine have demonstrated promise in these models, enhancing our understanding of their therapeutic efficacy. Despite progress, developing models that accurately mirror human PN remains imperative due to its complex nature. Continuous refinement and innovative approaches are critical for effective drug discovery. This review underscores the strengths and limitations of current models and advocates for an integrated approach to address the complexities of PN better and optimise treatment outcomes.

Topical menthol for chemotherapy-induced peripheral neuropathy: a randomised controlled trial in breast cancer

OBJECTIVES

Chemotherapy-induced peripheral neuropathy (CIPN) symptom is one of the side effects of paclitaxel in breast cancer patients. This randomised controlled study was conducted to investigate the effect of topical menthol applied on the hands and feet of breast cancer patients receiving chemotherapy on CIPN symptoms.

METHODS

60 breast cancer patients receiving chemotherapy were randomly assigned to an intervention group (n=30), which received topical menthol treatment, or a control group (n=30), which received standard care. Both groups continued their routine pharmacological treatments throughout the study. The intervention group applied 1% menthol topically to their hands and feet two times a day. The effect of the intervention on CIPN symptoms was evaluated 3 weeks and 6 weeks after the intervention.

RESULTS

The intervention group showed a significantly greater improvement in CIPN symptoms over time compared with the control group, with an effect size of η2=0.214 for the group×time interaction. Additionally, the intervention group exhibited a notable positive change in the exposure subscale of the CIPN rating scale, with an effect size of η2=0.114.

CONCLUSIONS

Topical application of menthol significantly mitigates the symptoms of CIPN in breast cancer patients. This study supports the use of menthol as an effective adjunctive treatment for CIPN.

TRIAL REGISTRATION NUMBER

NCT05429814.

An investigation on the role of oxytocin in chronic neuropathic pain in a Wistar rat model

Introduction Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting side effect with ineffective preventative and curative treatment. Currently, only Duloxetine has been recommended as effective treatment for CIPN, which has shown individual-dependent, short-term analgesic effects, with limiting adverse effects and poor bioavailability. The neuropeptide, oxytocin, may offer significant analgesic and anxiolytic potential, as it exerts central and peripheral attenuating effects on nociception. However, it is unknown whether the intervention administered in a model of CIPN is an effective therapeutic alternative or adjuvant. Materials and Methods The intervention was divided into two phases. Phase 1 aimed to induce CIPN in adult Wistar rats using the chemotherapeutic agent Paclitaxel. Mechanical (electronic von Frey filament) and thermal (acetone evaporation test and Hargreaves test) hypersensitivity testing were used to evaluate changes due to the neuropathic induction. Phase 2 consisted of a 14-day intervention period with saline (o.g.), duloextine (o.g.), or oxytocin (i.n.) administered as treatment. Following the intervention, anxiety-like behaviour was assessed using the elevated plus maze (EPM) and light-dark box protocols. Analysis of peripheral plasma corticosterone, peripheral plasma oxytocin, and hypothalamic oxytocin concentrations were assessed using ELISA assays. Results The findings showed that we were able to successfully establish a model of chemotherapy-induced peripheral neuropathy during Phase 1, determined by the increase in mechanical and thermal nociceptive responses following Paclitaxel administration. Furthermore, the animals treated with oxytocin displayed a significant improvement in mechanical sensitivity over the intervention phase, indicative of an improvement in nociceptive sensitivity in the presence of neuropathic pain. Animals that received Paclitaxel and treated with oxytocin also displayed significantly greater explorative behaviour during the EPM, indicative of a reduced presence of anxiety-like behaviour. Conclusion Our results support the hypothesis that intranasally administered oxytocin may augment the analgesic and anxiolytic effects of duloxetine in a chemotherapy induced peripheral neuropathy model in a Wistar rat. Future studies should consider administering the treatments in combination to observe the potential synergistic effects.

Efficacy of Mirogabalin for Taxane-associated Chemotherapy-induced Peripheral Neuropathy in Perioperative Chemotherapy for Early Breast Cancer

BACKGROUND/AIM

Treatment with taxanes can result in chemotherapy-induced peripheral neuropathy (CIPN). We investigated the efficacy and safety of mirogabalin for the treatment of CIPN in patients who had been administered perioperative chemotherapy including taxane-based agents for breast cancer.

PATIENTS AND METHODS

We retrospectively analyzed the case of 43 patients with early breast cancer who received a taxane as perioperative chemotherapy and were administered mirogabalin at the diagnosis of CIPN.

RESULTS

Thirty-six patients (83.7%) had grade 1 CIPN and the other seven patients (16.3%) had grade 2 CIPN. The median mirogabalin dose was 10 mg (5-30 mg). CIPN improved from grade 1 to 0 in 12 patients (27.9%) and from grade 2 to 1 in one patient (2.3%); 13 (30.2%) patients thus had an objective therapeutic response. There were no cases in which chemotherapy was reduced or discontinued due to CIPN. Adverse events were evaluated by Common Terminology Criteria for Adverse Events and included five cases of dizziness (11.7%), three of somnolence (7.0%), and two of nausea (4.7%), all of which were grade ≤2. There were no cases of serious (grade ≥3) adverse effects.

CONCLUSION

Mirogabalin may be effective and safe for treating CIPN of patients who receive a taxane in a perioperative breast cancer setting.

Centralizing the Knowledge and Interpretation of Pain in Chemotherapy-Induced Peripheral Neuropathy: A Paradigm Shift towards Brain-Centric Approaches

Chemotherapy-induced peripheral neuropathy (CIPN) is a side effect of cancer treatment, often linked with pain complaints. Patients report mechanical and thermal hypersensitivity that may emerge during chemotherapy treatment and may persist after cancer remission. Whereas the latter situation disturbs the quality of life, life itself may be endangered by the appearance of CIPN during cancer treatment. The causes of CIPN have almost entirely been ascribed to the neurotoxicity of chemotherapeutic drugs in the peripheral nervous system. However, the central consequences of peripheral neuropathy are starting to be unraveled, namely in the supraspinal pain modulatory system. Based on our interests and experience in the field, we undertook a review of the brain-centered alterations that may underpin pain in CIPN. The changes in the descending pain modulation in CIPN models along with the functional and connectivity abnormalities in the brain of CIPN patients are analyzed. A translational analysis of preclinical findings about descending pain regulation during CIPN is reviewed considering the main neurochemical systems (serotoninergic and noradrenergic) targeted in CIPN management in patients, namely by antidepressants. In conclusion, this review highlights the importance of studying supraspinal areas involved in descending pain modulation to understand the pathophysiology of CIPN, which will probably allow a more personalized and effective CIPN treatment in the future.

Roles of Thermosensitive Transient Receptor Channels TRPV1 and TRPM8 in Paclitaxel-Induced Peripheral Neuropathic Pain

Paclitaxel, a microtubule-stabilizing chemotherapy drug, can cause severe paclitaxel-induced peripheral neuropathic pain (PIPNP). The roles of transient receptor potential (TRP) ion channel vanilloid 1 (TRPV1, a nociceptor and heat sensor) and melastatin 8 (TRPM8, a cold sensor) in PIPNP remain controversial. In this study, Western blotting, immunofluorescence staining, and calcium imaging revealed that the expression and functional activity of TRPV1 were upregulated in rat dorsal root ganglion (DRG) neurons in PIPNP. Behavioral assessments using the von Frey and brush tests demonstrated that mechanical hyperalgesia in PIPNP was significantly inhibited by intraperitoneal or intrathecal administration of the TRPV1 antagonist capsazepine, indicating that TRPV1 played a key role in PIPNP. Conversely, the expression of TRPM8 protein decreased and its channel activity was reduced in DRG neurons. Furthermore, activation of TRPM8 via topical application of menthol or intrathecal injection of WS-12 attenuated the mechanical pain. Mechanistically, the TRPV1 activity triggered by capsaicin (a TRPV1 agonist) was reduced after menthol application in cultured DRG neurons, especially in the paclitaxel-treated group. These findings showed that upregulation of TRPV1 and inhibition of TRPM8 are involved in the generation of PIPNP, and they suggested that inhibition of TRPV1 function in DRG neurons via activation of TRPM8 might underlie the analgesic effects of menthol.

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.

Treatment Complications of Head and Neck Cancers and Rehabilitation Measures: A Narrative Review

Head and neck cancers (HNCs) are malignant tumors mainly from squamous cells in the head and neck tissues. Treatment involves a multidisciplinary approach with surgery, radiotherapy, and chemotherapy. However, the long-term prognosis for patients with advanced-stage tumors is guarded, with a median survival time of approximately 24 months. HNC patients have very high rates of depression and anxiety and the highest suicide rate among all cancers due to the intense and challenging nature of the treatment, underscoring the importance of our collective efforts. Rehabilitation success depends on various factors, including tumor, patient, and treatment-related factors. Patients may require post-treatment oral rehabilitation measures, including implants, obturators, and flexible dentures. These measures are crucial, but they often need to be more utilized. Patients may face challenges in maintaining oral hygiene and managing mucositis. Additionally, it is essential to address other intricacies such as trismus, xerostomia, gustatory dysfunctions, neuropathy, speech impairments, and psychological disturbances. Unfortunately, there is little literature on post-treatment rehabilitative measures. Despite its crucial role in improving patients' quality of life, rehabilitation often receives inadequate attention compared to treatment. Our narrative review, which covers various factors that affect rehabilitation, including oral rehabilitation measures and post-treatment complications, is anticipated to deliver practical insights to professionals and inspire positive changes in their regular practice.

Bortezomib-induced peripheral neuropathy: Clinical features, molecular basis, and therapeutic approach

Bortezomib is the first-line standard and most effective chemotherapeutic for multiple myeloma; however, bortezomib-induced peripheral neuropathy (BIPN) severely affects the chemotherapy regimen and has long-term impact on patients under maintenance therapy. The pathogenesis of BIPN is poorly understood, and basic research and development of BIPN management drugs are in early stages. Besides chemotherapy dose reduction and regimen modification, no recommended prevention and treatment approaches are available for BIPN apart from the International Myeloma Working Group guidelines for peripheral neuropathy in myeloma. An in-depth exploration of the pathogenesis of BIPN, development of additional therapeutic approaches, and identification of risk factors are needed. Optimizing effective and standardized BIPN treatment plans and providing more decision-making evidence for clinical diagnosis and treatment of BIPN are necessary. This article reviews the recent advances in BIPN research; provides an overview of clinical features, underlying molecular mechanisms, and therapeutic approaches; and highlights areas for future studies.

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.

Effect of Melissa officinalis on Chemotherapy-Induced Peripheral Neuropathy in Cancer Patients: A Randomized Trial

Background: Chemotherapy-induced peripheral neuropathy (CIPN) is a significant cancer treatment side effect that can influence both quality of life and treatment course. Melissa Officinalis (MO), due to its high content of flavonoids, has antioxidant, anti-inflammatory, and neuroprotective properties.  Materials and Methods: The cancer patients diagnosed with CIPN attended a referral center in Sari (Iran). The hydroalcoholic extract of MO leaves was extracted by the maceration method. The control group received a placebo along with gabapentin as the standard treatment, and the intervention group received 500 mg Melissa officinalis 2 times daily for 3 months plus gabapentin. Patients were evaluated at the baseline and 3 months later, according to Common Terminology Criteria for Adverse Effects (CTCAE) and EORTC QLQ-C30 (Integrated System for Quality of Life Assessment).  Results: A total of 40 patients were considered as group D (intervention group), and 35 patients completed the study. Out of 40 subjects in the placebo group (P), 3 patients could not tolerate the drug due to gastrointestinal disturbances. The final values of CTCAE showed a statistically significant difference (p=0.010). Indicators related to the quality of life in both groups showed a significant improvement. In the intervention group, the pain perception and diarrhea experience were significantly reduced. Conclusion: Quality of life indicators were improved by prescribing gabapentin with and without Melissa officinalis. The addition of Melissa officinalis to the chemotherapy regimen may improve diarrhea and pain perception.

Risk factors for taxane-induced peripheral neuropathy in patients with breast cancer

PURPOSE

This study investigated the clinical risk factors for peripheral neuropathy induced by docetaxel and albumin-bound paclitaxel (AP) in patients with breast cancer.

METHODS

This prospective observational study recruited 268 patients between March 2019 and December 2020. Patient information was obtained through the query system for laboratory test results, patient consultations, and scale evaluations. Neuropathic symptoms were followed up throughout and until 3 months after taxane chemotherapy. Univariate and multivariate analyses were used to find the risk factors for overall and moderate-severe taxane-induced peripheral neuropathy (TIPN).

RESULTS

Cumulative dose (odds ratio [OR] = 3.533, 95% confidence interval [CI]: 1.797-6.944, p < 0.001), body mass index (BMI) (OR = 2.926, 95% CI: 1.621-5.281, p < 0.001), body surface area (BSA) (OR = 1.724, 95% CI: 1.011-2.941, p = 0.045), and hypocalcemia (OR = 4.899, 95% CI: 1.518-15.811, p = 0.008) all increased the risk of TIPN. Only cumulative dose (OR = 2.577, 95% CI: 1.161-5.719, p = 0.020) and BSA (OR = 2.040, 95% CI: 1.073-3.877, p = 0.030) were independent risk factors for moderate-severe TIPN.

CONCLUSION

Cumulative dose, BMI, BSA, and hypocalcemia are all risk factors for overall TIPN, whereas cumulative dose and BSA are risk factors for moderate-severe TIPN. Patients with breast cancer who have high BMI, large BSA, hypocalcemia, and large cumulative dose may be at risk of TIPN, and intervention measures must be actively carried out for them.

Transient Receptor Potential Channels: Multiple Modulators of Peripheral Neuropathic Pain in Several Rodent Models

Neuropathic pain, a prevalent chronic condition in clinical settings, has attracted widespread societal attention. This condition is characterized by a persistent pain state accompanied by affective and cognitive disruptions, significantly impacting patients' quality of life. However, current clinical therapies fall short of addressing its complexity. Thus, exploring the underlying molecular mechanism of neuropathic pain and identifying potential targets for intervention is highly warranted. The transient receptor potential (TRP) receptors, a class of widely distributed channel proteins, in the nervous system, play a crucial role in sensory signaling, cellular calcium regulation, and developmental influences. TRP ion channels are also responsible for various sensory responses including heat, cold, pain, and stress. This review highlights recent advances in understanding TRPs in various rodent models of neuropathic pain, aiming to uncover potential therapeutic targets for clinical management.

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.

Effect of Silybum Marianum on Reduction of Chemotherapy-Induced Peripheral Neurotoxicity with Cisplatin

Background

Chemotherapy-induced peripheral neurotoxicity (CIPN) is one of the major complications of chemotherapy regimens commonly used in the treatment of solid and hematologic cancers. Given the high incidence of CIPN in antitumor therapies in patients and limited studies on antioxidants, this study was aimed to investigate the effect of Silybum marianum (SM) on cisplatin-induced peripheral neuropathy.

Materials and Methods

This double-blind randomized clinical trial study was performed on 60 cancer patients treated with cisplatin chemotherapy at Seyyed-o-Shohada Hospital of Isfahan during 2019-2020. The patients were divided into two parallel groups as intervention (treated by SM) and placebo, and DN4 (Douleur neuropathique 4 questions) and CIPNAT (chemotherapy-induced peripheral neuropathy assessment tool) were completed for patients in the before and after intervention groups and compared between the two groups.

Results

The mean of DN4 score in the before and after study in the intervention group was in 1.76 ± 1.24 and 2.07 ± 2.03, respectively (P = 0.38), and in the control group was 1.41 ± 1.28 ± 3.11 ± 2.86, respectively (P = 0.012). The mean CIPNAT score in the intervention groups was 5.93 ± 3.65 and 4.20 ± 3.23 (P = 0.01), and in the control group was 4.20 ± 4.22 and 4.16 ± 4.03 (P = 0.39).

Conclusion

Based on our data, SM is an effective agent in reducing peripheral neuropathy. The use of SM was associated with decreased scores of peripheral neuropathy and was helpful in patients undergoing chemotherapy with cisplatin.

Dysregulation of sphingolipid metabolism in pain

Pain is a clinical condition that is currently of great concern and is often caused by tissue or nerve damage or occurs as a concomitant symptom of a variety of diseases such as cancer. Severe pain seriously affects the functional status of the body. However, existing pain management programs are not fully satisfactory. Therefore, there is a need to delve deeper into the pathological mechanisms underlying pain generation and to find new targets for drug therapy. Sphingolipids (SLs), as a major component of the bilayer structure of eukaryotic cell membranes, also have powerful signal transduction functions. Sphingolipids are abundant, and their intracellular metabolism constitutes a huge network. Sphingolipids and their various metabolites play significant roles in cell proliferation, differentiation, apoptosis, etc., and have powerful biological activities. The molecules related to sphingolipid metabolism, mainly the core molecule ceramide and the downstream metabolism molecule sphingosine-1-phosphate (S1P), are involved in the specific mechanisms of neurological disorders as well as the onset and progression of various types of pain, and are closely related to a variety of pain-related diseases. Therefore, sphingolipid metabolism can be the focus of research on pain regulation and provide new drug targets and ideas for pain.

Glioma-targeted oxaliplatin/ferritin clathrate reversing the immunosuppressive microenvironment through hijacking Fe2+ and boosting Fenton reaction

Glioma is easy to develop resistance to temozolomide (TMZ). TMZ-resistant glioma secretes interleukin-10 (IL-10) and transforming growth factor-β (TGF-β), recruiting regulatory T cell (Treg) and inhibiting the activity of T cells and natural killer cell (NK cell), subsequently forming an immunosuppressive microenvironment. Oxaliplatin (OXA) greatly inhibits the proliferation of TMZ-resistant glioma cells, but the ability of OXA to cross blood-brain barrier (BBB) is weak. Thus, the therapeutic effect of OXA on glioma is not satisfactory. Transferrin receptor 1 (TfR1) is highly expressed in brain capillary endothelial cells and TMZ-resistant glioma cells. In this study, OXA was loaded into ferritin (Fn) to prepare glioma-targeted oxaliplatin/ferritin clathrate OXA@Fn. OXA@Fn efficiently crossed BBB and was actively taken up by TMZ-resistant glioma cells via TfR1. Then, OXA increased the intracellular H2O2 level and induced the apoptosis of TMZ-resistant glioma cells. Meanwhile, Fn increased Fe2+ level in TMZ-resistant glioma cells. In addition, the expression of ferroportin 1 was significantly reduced, resulting in Fe2+ to be locked up inside the TMZ-resistant glioma cells. This subsequently enhanced the Fenton reaction and boosted the ferroptosis of TMZ-resistant glioma cells. Consequently, T cell mediated anti-tumor immune response was strongly induced, and the immunosuppressive microenvironment was significantly reversed in TMZ-resistant glioma tissue. Ultimately, the growth and invasion of TMZ-resistant glioma was inhibited by OXA@Fn. OXA@Fn shows great potential in the treatment of TMZ-resistant glioma and prospect in clinical transformation.

Role of pattern recognition receptors in chemotherapy-induced neuropathic pain

Progress in the development of effective chemotherapy is producing a growing population of patients with acute and chronic painful chemotherapy-induced peripheral neuropathy (CIPN), a serious treatment-limiting side effect for which there is currently no US Food and Drug Administration-approved treatment. CIPNs induced by diverse classes of chemotherapy drugs have remarkably similar clinical presentations, leading to the suggestion they share underlying mechanisms. Sensory neurons share with immune cells the ability to detect damage associated molecular patterns (DAMPs), molecules produced by diverse cell types in response to cellular stress and injury, including by chemotherapy drugs. DAMPs, in turn, are ligands for pattern recognition receptors (PRRs), several of which are found on sensory neurons, as well as satellite cells, and cells of the immune system. In the present experiments, we evaluated the role of two PRRs, TLR4 and RAGE, present in dorsal root ganglion (DRG), in CIPN. Antisense (AS)-oligodeoxynucleotides (ODN) against TLR4 and RAGE mRNA were administered intrathecally before ('prevention protocol') or 3 days after ('reversal protocol') the last administration of each of three chemotherapy drugs that treat cancer by different mechanisms (oxaliplatin, paclitaxel and bortezomib). TLR4 and RAGE AS-ODN prevented the development of CIPN induced by all three chemotherapy drugs. In the reversal protocol, however, while TLR4 AS-ODN completely reversed oxaliplatin- and paclitaxel-induced CIPN, in rats with bortezomib-induced CIPN it only produced a temporary attenuation. RAGE AS-ODN, in contrast, reversed CIPN induced by all three chemotherapy drugs. When a TLR4 antagonist was administered intradermally to the peripheral nociceptor terminal, it did not affect CIPN induced by any of the chemotherapy drugs. However, when administered intrathecally, to the central terminal, it attenuated hyperalgesia induced by all three chemotherapy drugs, compatible with a role of TLR4 in neurotransmission at the central terminal but not sensory transduction at the peripheral terminal. Finally, since it has been established that cultured DRG neurons can be used to study direct effects of chemotherapy on nociceptors, we also evaluated the role of TLR4 in CIPN at the cellular level, using patch-clamp electrophysiology in DRG neurons cultured from control and chemotherapy-treated rats. We found that increased excitability of small-diameter DRG neurons induced by in vivo and in vitro exposure to oxaliplatin is TLR4-dependent. Our findings suggest that in addition to the established contribution of PRR-dependent neuroimmune mechanisms, PRRs in DRG cells also have an important role in CIPN.

Complementary and alternative medicine in relation to chemotherapy-induced peripheral neuropathy: A narrative review

PURPOSE

To summarizes the available evidence on the effectiveness, safety, and feasibility of complementary and alternative medicine (CAM) in the management of chemotherapy-induced peripheral neuropathy (CIPN).

METHODS

We searched for systematic reviews, and meta-analyzes published up to April 2023 in the Pubmed and Web of Science databases. The latest original research on related topics was also reviewed. The search was restricted to English-language papers. Two independent reviewers performed a quality assessment of the identified literature.

RESULTS

The results of 35 systematic reviews and meta-analyzes were included in this study. Preliminary evidence suggests that CAM, including acupuncture, physical activity (PA), herbal and nutritional supplements, mind-body therapies, touch therapy, and non-invasive neuromodulation techniques, have shown tremendous potential for the prevention and treatment of CIPN. Of these, there is strong evidence supporting acupuncture, PA, and herbal medicine. However, existing clinical studies are also limited by the heterogeneity of study methods, insufficient sample size, and poor study design. Further studies are needed to validate the efficacy of CAM in patients with CIPN and to elucidate potential therapeutic mechanisms.

CONCLUSIONS

Current research has reached a preliminary conclusion suggesting the potential efficacy of certain CAMs in the management of CIPN. Future clinical trials should incorporate more robust study design protocols and larger sample sizes to enhance the validity of findings.

Effect of vitamin E on doxorubicin and paclitaxel-induced memory impairments in male rats

PURPOSE

In addition to peripheral neuronal dysfunction, conventional chemotherapy can be associated with other neurological treatment-limiting adverse effects, including cognitive dysfunction, memory impairment, and anxiety, which are referred to as "chemobrain". This study aimed to investigate the effects of doxorubicin (DOX) and paclitaxel (PAC) on learning and memory in rats using radial arm water maze (RAWM) and investigated a potential beneficial effect of vitamin E (Vit. E).

METHODS

Adult male rats were injected with four doses of 2 mg/kg/week DOX, or 2 mg/kg PAC every other day intraperitoneally. Vit. E was co-administered with these drugs in other groups to study its antioxidative effects. Using the RAWM, each rat was assessed for learning and memory performance through two sets of six trials separated by a 5-min rest period evaluating both short- and long-term effects on memory.

RESULTS

There was no deficit in learning or long-term memory in both drug groups compared to control. However, rats in both drug groups made significantly more errors in all short-term memory trials. This effect was mitigated when Vit. E was co-administered with either drug. Moreover, PAC (but not DOX) induced hippocampal lipid peroxidation by increasing the levels of standard biomarker thiobarbituric acid reactive substances (TBARS). Interestingly, Vit. E prevented PAC-induced hippocampal oxidative stress. Furthermore, both DOX and PAC were correlated with reduction in Brain-Derived Neurotrophic Factor (BDNF) expression levels in the hippocampus, which was overcome by the co-administration of Vit. E.

CONCLUSION

There is a potential role of Vit. E in alleviating short-term memory impairment in rats exposed to chemotherapy, possibly by reducing hippocampal oxidative stress and neurodegeneration.

Spinal HMGB1 participates in the early stages of paclitaxel-induced neuropathic pain via microglial TLR4 and RAGE activation

Introduction

Chemotherapy-induced neuropathic pain (CINP) is one of the main adverse effects of chemotherapy treatment. At the spinal level, CINP modulation involves glial cells that upregulate Toll-like receptor 4 (TLR4) and signaling pathways, which can be activated by pro-inflammatory mediators as the high mobility group box-1 (HMGB1).

Objective

To evaluate the spinal role of HMGB1 in the paclitaxel-induced neuropathic pain via receptor for advanced glycation end products (RAGE) and TLR4 activation expressed in glial cells.

Methods

Male C57BL/6 Wild type and TLR4 deficient mice were used in the paclitaxel-induced neuropathic pain model. The nociceptive threshold was measured using the von Frey filament test. In addition, recombinant HMGB1 was intrathecally (i.t.) injected to confirm its nociceptive potential. To evaluate the spinal participation of RAGE, TLR4, NF-kB, microglia, astrocytes, and MAPK p38 in HMGB1-mediated nociceptive effect during neuropathic pain and recombinant HMGB1-induced nociception, the drugs FPS-ZM1, LPS-RS, PDTC, minocycline, fluorocitrate, and SML0543 were respectively administrated by i.t. rout. Microglia, astrocytes, glial cells, RAGE, and TLR4 protein expression were analyzed by Western blot. ELISA immunoassay was also used to assess HMGB1, IL-1β, and TNF-α spinal levels.

Results

The pharmacological experiments demonstrated that spinal RAGE, TLR4, microglia, astrocytes, as well as MAPK p38 and NF-kB signaling are involved with HMGB1-induced nociception and paclitaxel-induced neuropathic pain. Furthermore, HMGB1 spinal levels were increased during the early stages of neuropathic pain and associated with RAGE, TLR4 and microglial activation. RAGE and TLR4 blockade decreased spinal levels of pro-inflammatory cytokines during neuropathic pain.

Conclusion

Taken together, our findings indicate that HMGB1 may be released during the early stages of paclitaxel-induced neuropathic pain. This molecule activates RAGE and TLR4 receptors in spinal microglia, upregulating pro-inflammatory cytokines that may contribute to neuropathic pain.

IUPHAR review: Navigating the role of preclinical models in pain research

Chronic pain is a complex and challenging medical condition that affects millions of people worldwide. Understanding the underlying mechanisms of chronic pain is a key goal of preclinical pain research so that more effective treatment strategies can be developed. In this review, we explore nociception, pain, and the multifaceted factors that lead to chronic pain by focusing on preclinical models. We provide a detailed look into inflammatory and neuropathic pain models and discuss the most used animal models for studying the mechanisms behind these conditions. Additionally, we emphasize the vital role of these preclinical models in developing new pain-relief drugs, focusing on biologics and the therapeutic potential of NMDA and cannabinoid receptor antagonists. We also discuss the challenges of TRPV1 modulation for pain treatment, the clinical failures of neurokinin (NK)- 1 receptor antagonists, and the partial success story of Ziconotide to provide valuable lessons for preclinical pain models. Finally, we highlight the overall success and limitations of current treatments for chronic pain while providing critical insights into the development of more effective therapies to alleviate the burden of chronic pain.

Spinal Neuronal miR-124 Inhibits Microglial Activation and Contributes to Preventive Effect of Electroacupuncture on Chemotherapy-Induced Peripheral Neuropathy in Mice

Chemotherapy-induced peripheral neuropathy (CIPN) is a persistent and irreversible side effect of antineoplastic agents. Patients with CIPN usually show chronic pain and sensory deficits with glove-and-stocking distribution. However, whether spinal neuronal microRNA (miR)-124 is involved in cisplatin-induced peripheral neuropathy remains to be studied. In this study, miR-124 was significantly reduced in the spinal dorsal horn in CIPN mice. Overexpression of neuronal miR-124 induced by injecting adeno-associated virus with neuron-specific promoter into the spinal cord of mice prevented the development of mechanical allodynia, sensory deficits, and the loss of intraepidermal nerve fibers induced by cisplatin. Meanwhile, cisplatin-induced M1 microglia activation and the release of proinflammatory cytokines were significantly inhibited by overexpression of neuronal miR-124. Furthermore, electroacupuncture (EA) treatment upregulated miR-124 expression in the spinal dorsal horn of CIPN mice. Interestingly, downregulation of spinal neuronal miR-124 significantly inhibited the regulatory effect of EA on CIPN and microglia activity as well as spinal neuroinflammation induced by cisplatin. These results demonstrate that spinal neuronal miR-124 is involved in the prevention and treatment of EA on cisplatin-induced peripheral neuropathy in mice. Our findings suggest that spinal neuronal miR-124 might be a potential target for EA effect, and we provide, to our knowledge, a new experimental basis for EA prevention of CIPN.

Gut Microbiota Modulation and Its Implications on Neuropathic Pain: A Comprehensive Literature Review

Neuropathic pain (NP) is a chronic pain disorder arising from somatosensory nervous system impairment. Extensive evidence supports the notion that the gut microbiota (GM) is crucial in maintaining human health by performing vital tasks. At the same time, its disruption has been linked to the emergence and advancement of an expanding range of disorders, including NP, in which GM could play a role in its pathophysiology. The crosstalk between the nervous system and GM happens through immune mediators, metabolites, and nervous structures and involves both central and peripheral nervous systems. This literature review aims to thoroughly investigate the function of modulating GM in the treatment of NP. It will achieve this by integrating existing knowledge, identifying underlying mechanisms, and evaluating the possible clinical consequences of exploiting the gut-brain axis. We will cover the main therapeutic applications of the described GM-modulators, such as probiotics, faecal microbiota transplantation, dietary supplements and emotional support, to the main kinds of NP in which any evidence, even if only pre-clinical, has been unravelled in recent years. The explored NP areas include chemotherapy-induced peripheral neuropathy, diabetic neuropathy, trauma-induced neuropathic pain, trigeminal neuralgia, postherpetic neuralgia and low back pain.

Cisplatin Provokes Peripheral Nociception and Neuronal Features of Therapy-Induced Senescence and Calcium Dysregulation in Rats

Therapy-Induced Senescence (TIS) is a form of senescence that is typically described in malignant cells in response to the exposure of cancer chemotherapy or radiation but can also be precipitated in non-malignant cells. TIS has been shown to contribute to the development of several cancer therapy-related adverse effects; however, evidence on its role in mediating chemotherapy-induced neurotoxicity, such as Chemotherapy-induced Peripheral Neuropathy (CIPN), is limited. We here show that cisplatin treatment over two cycles (cumulative dose of 23 mg/kg) provoked mechanical allodynia and thermal hyperalgesia in Sprague-Dawley rats. Isolation of dorsal root ganglia (DRG) from the cisplatin-treated rats demonstrated robust SA-β-gal upregulation at both day 8 (after the first cycle) and day 18 (after the second cycle), decreased lmnb1 expression, increased expression of cdkn1a and cdkn2a, and of several factors of the Senescence-associated Secretory Phenotype (SASP) (Il6, Il1b, and mmp9). Moreover, single-cell calcium imaging of cultured DRGs revealed a significant increase in terms of the magnitude of KCl-evoked calcium responses in cisplatin-treated rats compared to vehicle-treated rats. No significant change was observed in terms of the magnitude of capsaicin-evoked calcium responses in cisplatin-treated rats compared to vehicle-treated rats but with decreased area under the curve of the responses in cisplatin-treated rats. Further evidence to support the contribution of TIS to therapy adverse effects is required but should encourage the use of senescence-modulating agents (senotherapeutics) as novel palliative approaches to mitigate chemotherapy-induced neurotoxicity.

G Protein-Coupled Receptors and Ion Channels Involvement in Cisplatin-Induced Peripheral Neuropathy: A Review of Preclinical Studies

Cisplatin is a platinum-based chemotherapy drug widely used to treat various solid tumours. Although it is effective in anti-cancer therapy, many patients develop peripheral neuropathy during and after cisplatin treatment. Peripheral neuropathy results from lesions or diseases in the peripheral somatosensory nervous system and is a significant cause of debilitation and suffering in patients. In recent years, preclinical studies have been conducted to elucidate the mechanisms involved in chemotherapy-induced peripheral neuropathic pain, as well as to promote new therapeutic targets since current treatments are ineffective and are associated with adverse effects. G-protein coupled receptors and ion channels play a significant role in pain processing and may represent promising targets for improving the management of cisplatin-induced neuropathic pain. This review describes the role of G protein-coupled receptors and ion channels in cisplatin-induced pain, analysing preclinical experimental studies that investigated the role of each receptor subtype in the modulation of cisplatin-induced pain.

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.

Netazepide, an Antagonist of Cholecystokinin Type 2 Receptor, Prevents Vincristine-Induced Sensory Neuropathy in Mice

Among the vinca-alkaloid class, vincristine is a potent chemotherapeutic agent with significant neurotoxic effects and is employed to address a wide spectrum of cancer types. Recently, the therapeutic potential of the cholecystokinin type 2 receptor (CCK2R) as a target for vincristine-induced peripheral neuropathy (VIPN) was demonstrated. In this study, the impact of preventive CCK2R blockade using netazepide (Trio Medicines Ltd., London, UK) was investigated in a mouse model of vincristine-induced peripheral neuropathy. Netazepide is a highly selective CCK2R antagonist under development for the treatment of patients with gastric neuroendocrine tumors caused by hypergastrinemia secondary to chronic autoimmune atrophic gastritis. Vincristine-induced peripheral neuropathy was induced by intraperitoneal injections of vincristine at 100 µg/kg/d for 7 days (D0 to D7). Netazepide (2 mg/kg/d or 5 mg/kg/d, per os) was administered one day before vincristine treatment until D7. Vincristine induced a high tactile allodynia from D1 to D7. VIPN was characterized by dorsal root ganglion neuron (DRG) and intraepidermal nerve fiber (IENF) loss, and enlargement and loss of myelinated axons in the sciatic nerve. Netazepide completely prevented the painful symptoms and nerve injuries induced by vincristine. In conclusion, the fact that netazepide protected against vincristine-induced peripheral neuropathy in a mouse model strongly supports the assessment of its therapeutic potential in patients receiving such chemotherapy.

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.

Targeting therapy-induced senescence as a novel strategy to combat chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a treatment-limiting adverse effect of anticancer therapy that complicates the lifestyle of many cancer survivors. There is currently no gold-standard for the assessment or management of CIPN. Subsequently, understanding the underlying mechanisms that lead to the development of CIPN is essential for finding better pharmacological therapy. Therapy-induced senescence (TIS) is a form of senescence that is triggered in malignant and non-malignant cells in response to the exposure to chemotherapy. Recent evidence has also suggested that TIS develops in the dorsal root ganglia of rodent models of CIPN. Interestingly, several components of the senescent phenotype are commensurate with the currently established primary processes implicated in the pathogenesis of CIPN including mitochondrial dysfunction, oxidative stress, and neuroinflammation. In this article, we review the literature that supports the hypothesis that TIS could serve as a holistic mechanism leading to CIPN, and we propose the potential for investigating senotherapeutics as means to mitigate CIPN in cancer survivors.

Gadolinium Presence in Rat Skin: Assessment of Histopathologic Changes Associated with Small Fiber Neuropathy

Background The presence of gadolinium traces in the skin after administration of gadolinium-based contrast agents (GBCAs) raised safety concerns regarding a potential association with small fiber neuropathy (SFN). Purpose To investigate signs of SFN in rat foot pads by quantification of the intraepidermal nerve fiber density (IENFD) after multiple GBCA administrations and to evaluate gadolinium concentration, chemical species, and clearance. Materials and Methods Fifty rats received eight intravenous injections of either gadodiamide, gadobutrol, gadoterate, gadoteridol (8 × 0.6 mmol per kilogram of body weight), or saline (1.2 mL per kilogram of body weight), within 2 weeks and were sacrificed 5 days or 5 weeks after the last injection. IENFD was determined with protein gene product (PGP) 9.5 immunofluorescent staining and blinded and automated image analysis. The gadolinium and GBCA concentrations were measured with inductively coupled plasma mass spectrometry (ICP-MS), laser ablation ICP-MS, and matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI). P values were calculated using linear contrasts of model analysis. Results The IENFD (measured as geometric mean [SD] and in number of nerve fibers per millimeter of epidermis) was not significantly altered after 5 days (saline, 8.4 [1.1]; gadobutrol, 9.7 [1.2]; gadoterate, 9.2 [1.2]; gadoteridol, 9.9 [1.3]; gadodiamide, 10.5 [1.2]) or 5 weeks (saline, 19.7 [1.4]; gadobutrol, 16.4 [1.6]; gadoterate, 14.3 [1.6]; gadoteridol, 22.2 [1.8]; gadodiamide, 17.9 [1.4]). Gadolinium skin concentrations were highest for gadodiamide after 5 days (16.0 nmol/g [1.1]) and 5 weeks (10.6 nmol/g [1.2], -33%). Macrocyclic agents were lower at 5 days (gadoteridol, 2.6 nmol/g [1.2]; gadobutrol, 2.7 nmol/g [1.1]; and gadoterate, 2.3 nmol/g [1.2]) and efficiently cleared after 5 weeks (gadoteridol, -95%; gadobutrol and gadoterate, -96%). The distribution of gadolinium and IENF did not visually overlap. For macrocyclic agents, gadolinium was found in sweat glands and confirmed to be intact chelate. Conclusion There were no signs of SFN in rat foot pads using multiple dosing regimens at two time points after administration of GBCAs. Macrocyclic GBCAs exhibited lower levels of gadolinium in the skin and were effectively eliminated within 5 weeks compared with linear gadodiamide, and intact macrocyclic GBCA was detected in sweat glands. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Clement in this issue.

Role of TRPA1 in Painful Cold Hypersensitivity

Transient receptor potential ankyrin 1 (TRPA1) is a polymodal cation channel that plays a pivotal role in pain generation after exposure to irritant chemicals and is involved in the sensation of a wide variety of pathological pain. TRPA1 was first reported to be sensitive to noxious cold, but its intrinsic cold sensitivity still remains under debate. To address this issue, we focused on cold hypersensitivity induced by oxaliplatin, a platinum-based chemotherapeutic drug, as a peculiar adverse symptom of acute peripheral neuropathy. We and other groups have shown that oxaliplatin enhances TRPA1 sensitivity to its chemical agonists and reactive oxygen species (ROS). Our in vitro and animal model studies revealed that oxaliplatin, or its metabolite oxalate, inhibits hydroxylation of a proline residue within the N-terminus of human TRPA1 (hTRPA1) via inhibition of prolyl hydroxylase domain-containing protein (PHD), which induces TRPA1 sensitization to ROS. Although hTRPA1 is insensitive to cold, PHD inhibition endows hTRPA1 with cold sensitivity through sensing the small amount of ROS produced after exposure to cold. Hence, we propose that PHD inhibition can unveil the cold sensitivity of hTRPA1 by converting ROS signaling into cold sensitivity. Furthermore, in this review, we summarize the role of TRPA1 in painful cold hypersensitivity during peripheral vascular impairment.

Preclinical research in paclitaxel-induced neuropathic pain: a systematic review

Introduction

Chemotherapy-induced peripheral neuropathy (CIPN) is a common consequence of cancer treatment and pain is a frequent complaint of the patients. Paclitaxel, a cytostatic drug, generates a well-described peripheral nerve injury and neuroinflammation, which may be experimentally mimicked in animal models. We conducted a systematic review analyzing the experimental design, reporting and mechanisms underlying paclitaxel-induced neuropathy in the included studies to establish the perspectives of translation of the current literature in models of CIPN.

Methods

We elected studies published in Pubmed and Scopus between 1 January 2018 and 3 December 2022.

Results

According to a defined mesh of keywords searched, and after applying exclusion and inclusion criteria, 70 original studies were included and analyzed in detail. Most studies used male Sprague-Dawley rats to induce paclitaxel-induced neuropathy, used low doses of paclitaxel, and the analyzed studies mainly focused at 14-28 days of CIPN. Mechanical nociceptive tests were preferred in the behavioral evaluation. The mechanisms under study were mainly neuroinflammation of peripheral nerves. The overall methodological quality was considered moderate, and the risk of bias was unclear.

Discussion

Despite the ample preclinical research in paclitaxel-induced neuropathy, this systematic review alerts to some flaws in the experimental design along with limitations in reporting, e.g., lack of representation of both sexes in experimental work and the lack of reporting of the ARRIVE guidelines. This may limit the reproducibility of preclinical studies in CIPN. In addition, the clinical features of CIPN should be considered when designing animal experiments, such as sex and age of the CIPN patients. In this way the experimental studies aiming to establish the mechanisms of CIPN may allow the development of new drugs to treat CIPN and translation in the research of CIPN could be improved.

An In Vitro Assessment Method for Chemotherapy-Induced Peripheral Neurotoxicity Caused by Anti-Cancer Drugs Based on Electrical Measurement of Impedance Value and Spontaneous Activity

Chemotherapy-induced peripheral neurotoxicity (CIPN) is a major adverse event of anti-cancer drugs, which still lack standardized measurement and treatment methods. In the present study, we attempted to evaluate neuronal dysfunctions in cultured rodent primary peripheral neurons using a microelectrode array system. After exposure to typical anti-cancer drugs (i.e., paclitaxel, vincristine, oxaliplatin, and bortezomib), we successfully detected neurotoxicity in dorsal root ganglia neurons by measuring electrical activities, including impedance value and spontaneous activity. The impedance value decreased significantly for all compounds, even at low concentrations, which indicated cell loss and/or neurite degeneration. The spontaneous activity was also suppressed after exposure, which suggested neurotoxicity again. However, an acute response was observed for paclitaxel and bortezomib before toxicity, which showed different mechanisms based on compounds. Therefore, MEA measurement of impedance value could provide a simple assessment method for CIPN, combined with neuronal morphological changes.

Incidence and Resolution of Eribulin-Induced Peripheral Neuropathy (IRENE) in Locally Advanced or Metastatic Breast Cancer: Prospective Cohort Study

BACKGROUND

Eribulin, a halichondrin-class microtubule dynamics inhibitor, is a preferred treatment option for patients with advanced breast cancer who have been pretreated with an anthracycline and a taxane. Peripheral neuropathy (PN) is a common side effect of chemotherapies for breast cancer and other tumors. The Incidence and Resolution of Eribulin-Induced Peripheral Neuropathy (IRENE) noninterventional postauthorization safety study assessed the incidence and severity of PN in patients with breast cancer treated with eribulin.

PATIENTS AND METHODS

IRENE is an ongoing observational, single-arm, prospective, multicenter, cohort study. Adult patients (≥18 years of age) with locally advanced or metastatic breast cancer and disease progression after 1-2 prior chemotherapeutic regimen(s) for advanced disease were treated with eribulin. Patients with eribulin-induced PN (new-onset PN or worsening of preexisting PN) were monitored until death or resolution of PN. Primary endpoints included the incidence, severity, and time to resolution of eribulin-induced PN. Secondary endpoints included time to disease progression and safety.

RESULTS

In this interim analysis (data cutoff date: July 1, 2019), 67 (32.4%) patients experienced any grade eribulin-induced PN, and 12 (5.8%) patients experienced grade ≥3 eribulin-induced PN. Median time to resolution of eribulin-induced PN was not reached. Median time to disease progression was 4.6 months (95% CI, 4.0-6.5). Treatment-emergent adverse events (TEAEs) occurred in 195 (93.8%) patients and serious TEAEs occurred in 107 (51.4%) patients.

CONCLUSION

The rates of any grade and grade ≥3 eribulin-induced PN observed in this real-world study were consistent with those observed in phase III randomized clinical trials. No new safety findings were observed.

A bibliometric analysis of chemotherapy and pain in pediatric patients over the last decade

Background

Chemotherapy is an important treatment for children with cancer, and chemotherapy-induced pain is an important role in affecting patients' quality of life. In our study, bibliometric analysis was used to identify current research hotspots and future research trends of chemotherapy and pain in children over the last decade. Our findings can provide a reference for the research in the field of chemotherapy and pain in children.

Method

Publications of chemotherapy and pain in children were collected from the Web of Science Core Collection database. CiteSpace was used to analyze publication characteristics from 2013 to 2022.

Results

We identified 1,130 eligible publications in the field of chemotherapy and pain in children, with an increasing trend of publications over the last decade. In the field of chemotherapy and pain in children, the United States had the most publication with 346, followed by China with 135. The author with the most published papers was Pamela S Hinds (n = 8) from the United States. The journals that published the most papers were the Journal of pediatric hematology oncology (n = 44) and Medicine (n = 44). The Journal of Clinical Oncology was cited the most frequency (n = 422). St. Jude Children's Research Hospital had the most publication (n = 23). The specific keywords related to the field of chemotherapy and pain in children were "children", "chemotherapy", "management", "childhood cancer", "randomized controlled trial" and "efficacy". Emerging research focuses predominantly on symptomatic and supportive interventions for chemotherapy and pain in children.

Conclusion

Attention to chemotherapy and pain in children with cancer was insufficient. This bibliometric analysis showed the upward trend of chemotherapy and pain in children over the last decade. More studies are needed to improve the quality of life in children with chemotherapy-induced pain. This study may provide useful information to guide future research on chemotherapy and pain in children.

Ropivacaine-loaded hydrogels for prolonged relief of chemotherapy-induced peripheral neuropathic pain and potentiated chemotherapy

Chemotherapy can cause severe pain for patients, but there are currently no satisfactory methods of pain relief. Enhancing the efficacy of chemotherapy to reduce the side effects of high-dose chemotherapeutic drugs remains a major challenge. Moreover, the treatment of chemotherapy-induced peripheral neuropathic pain (CIPNP) is separate from chemotherapy in the clinical setting, causing inconvenience to cancer patients. In view of the many obstacles mentioned above, we developed a strategy to incorporate local anesthetic (LA) into a cisplatin-loaded PF127 hydrogel for painless potentiated chemotherapy. We found that multiple administrations of cisplatin-loaded PF127 hydrogels (PFC) evoked severe CIPNP, which correlated with increased pERK-positive neurons in the dorsal root ganglion (DRG). However, incorporating ropivacaine into the PFC relieved PFC-induced CIPNP for more than ten hours and decreased the number of pERK-positive neurons in the DRG. Moreover, incorporating ropivacaine into the PFC for chemotherapy is found to upregulate major histocompatibility complex class I (MHC-I) expression in tumor cells and promote the infiltration of cytotoxic T lymphocytes (CD8+ T cells) in tumors, thereby potentiating chemotherapy efficacy. This study proposes that LA can be used as an immunemodulator to enhance the effectiveness of chemotherapy, providing new ideas for painless cancer treatment.

Topical coapplication of hyaluronan with transdermal drug delivery enhancers attenuates inflammatory and neuropathic pain

ABSTRACT

We have previously shown that intradermal injection of high-molecular-weight hyaluronan (500-1200 kDa) produces localized antihyperalgesia in preclinical models of inflammatory and neuropathic pain. In the present experiments, we studied the therapeutic effect of topical hyaluronan, when combined with each of 3 transdermal drug delivery enhancers (dimethyl sulfoxide [DMSO], protamine or terpene), in preclinical models of inflammatory and neuropathic pain. Topical application of 500 to 1200 kDa hyaluronan (the molecular weight range used in our previous studies employing intradermal administration), dissolved in 75% DMSO in saline, markedly reduced prostaglandin E 2 (PGE 2 ) hyperalgesia, in male and female rats. Although topical 500- to 1200-kDa hyaluronan in DMSO vehicle dose dependently, also markedly, attenuated oxaliplatin chemotherapy-and paclitaxel chemotherapy-induced painful peripheral neuropathy (CIPN) in male rats, it lacked efficacy in female rats. However, following ovariectomy or intrathecal administration of an oligodeoxynucleotide antisense to G-protein-coupled estrogen receptor (GPR30) mRNA, CIPN in female rats was now attenuated by topical hyaluronan. Although topical coadministration of 150 to 300, 300 to 500, or 1500 to 1750 kDa hyaluronan with DMSO also attenuated CIPN, a slightly lower-molecular-weight hyaluronan (70-120 kDa) did not. The topical administration of a combination of hyaluronan with 2 other transdermal drug delivery enhancers, protamine and terpene, also attenuated CIPN hyperalgesia, an effect that was more prolonged than with DMSO vehicle. Repeated administration of topical hyaluronan prolonged the duration of antihyperalgesia. Our results support the use of topical hyaluronan, combined with chemically diverse nontoxic skin penetration enhancers, to induce marked antihyperalgesia in preclinical models of inflammatory and neuropathic pain.

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.