Peripheral and central oxidative stress in chemotherapy-induced neuropathic pain

The effects of the GLP1 analog liraglutide on allodynia and motor coordination in peripheral neuropathy induced by a chemotherapeutic agent, cisplatin

Peripheral neuropathy is one of the dose-limiting side effects of cisplatin (CIS) and still has no effective treatment. In this study, we aimed to investigate the potential protective effects of liraglutide, a Glucagon-like peptide-1 (GLP-1) analogue against CIS-induced peripheral neuropathy. For this purpose, female Sprague Dawley rats (n = 32) were randomly allocated into 4 groups: control, CIS, CIS + liraglutide (once weekly) and CIS + liraglutide (daily). Neuropathic pain was induced by CIS 3 mg/kg/week for 5 weeks. The potential effects of liraglutide were investigated by behavior tests (von Frey, tail flick and footprint analysis), biochemical analysis and histopathological analyses of sciatic nerves and dorsal root ganglions. In the von Frey and tail flick tests, liraglutide demonstrated anti-neuropathic effects. Liraglutide also ameliorated motor coordination which was impaired by CIS. Liraglutide was shown to have beneficial effects against CIS-induced peripheral neuropathy by parameters demonstrating reduction of histopathological damage (stained by toluidine blue) of the sciatic nerves and dorsal root ganglions, suppression of oxidative stress parameters (SOD, CAT and GPx), and inflammatory load (NO, IL-6 and IL-10). Weekly dosing regimen was more effective than daily administration of liraglutide in this study. As a result, liraglutide seems to be the candidate agent for the effective treatment of CIS-induced peripheral neuropathy.

Discovering genetically-supported drug targets for multisite chronic pain through multi-omics Mendelian randomization and single-cell RNA-sequencing

Multisite chronic pain (MCP) is a highly prevalent disorder with substantial unmet therapeutic needs.We conducted multi-omics Mendelian randomization and Bayesian colocalization to identify potential therapeutic targets for MCP. Summary-level data of gene expressions and protein abundance levels were obtained from corresponding quantitative trait loci studies, respectively. Summary-level data for MCP was leveraged from the UK Biobank. The transcriptome-wide association study (TWAS), Mendelian randomization, and Bayesian colocalization approaches were applied to investigate the potential causal effects of gene expressions and protein levels on MCP in both blood and brain tissues. Phenome-wide Mendelian randomization analysis (MR-PheWAS), single-cell sequencing data, protein-protein interaction (PPI), and reaction pathway analysis were further conducted to digging the underlying mechanisms. Our analysis identified and validated two plasma targets for MCP, namely KLC1 and LANCL1, at both gene expression levels and protein levels across multi-methodologies. Moreover, MR-PheWAS observed additional benefits associated with these two targets. Through analyses based on single-cell sequencing data, we identified critical cell types for KLC1, primarily megakaryocytes, and neurons, notably linked to the axon guidance pathway, while LANCL1 showed associations with B lymphocytes, neurons, and the electron transport pathway. In dorsal root ganglions, we identified enrichments of both LANCL1 and KLC1 in putative silent nociceptors. The effects are possibly mediated through axonal transport and the activation of NMDARs, supported by PPI and reaction pathway analysis. Our multi-dimensional analysis suggests that genetically determined KLC1 and LANCL1 are causally linked to MCP risk, holding promise as appealing drug targets for MCP.

The Integrated Transcriptome Bioinformatics Analysis of Energy Metabolism-Related Profiles for Dorsal Root Ganglion of Neuropathic Pain

Neuropathic pain (NP) is a debilitating disease and is associated with energy metabolism alterations. This study aimed to identify energy metabolism-related differentially expressed genes (EMRDEGs) in NP, construct a diagnostic model, and analyze immune cell infiltration and single-cell gene expression characteristics of NP. GSE89224, GSE123919, and GSE134003 were downloaded from the Gene Expression Omnibus. Differentially expressed genes (DEGs) analysis and an intersection with highly energy metabolism-related modules in weighted gene co-expression network analysis (WGCNA) was performed in GSE89224. Least absolute shrinkage and selection operator (LASSO), random forest, and logistic regression were used for model genes selection. NP samples were divided into high- and low-risk groups and different disease subtypes based on risk score of LASSO algorithm and consensus clustering analysis, respectively. Immune cell composition was estimated in different risk groups and NP subtypes. Datasets 134,003 were performed for identification of single-cell DEGs and functional enrichment. Cell-cell communications and pseudo-time analysis to reveal the expression profile of NP. A total of 38 EMRDEGs were obtained and are majorly enriched in metabolism about glioma and inflammation. LASSO, random forest, and logistic regression identified 6 model genes, which were Itpr1, Gng8, Socs3, Fscn1, Cckbr, and Camk1. The nomogram, based on six model genes, had a good predictive ability, concordance, and diagnostic value. The comparisons between different risk groups and NP subtypes identified important pathways and different immune cells component. The immune infiltration results majorly associated with inflammation and energy metabolism. Single-cell analysis revealed cell-cell communications and cells differentiation characteristics of NP. In conclusion, our results not only elucidate the involvement of energy metabolism in NP but also provides a robust diagnostic tool with six model genes. These findings might give insight into the pathogenesis of NP and provide effective therapeutic regimens for the treatment of NP.

Metformin Protects Human Induced Pluripotent Stem Cell (hiPSC)-Derived Neurons from Oxidative Damage Through Antioxidant Mechanisms

The antidiabetic drug metformin possesses antioxidant and cell protective effects including in neuronal cells, suggesting its potential use for treating neurodegenerative diseases. This study aimed to assess metformin's effects on viability and antioxidant activity in human-induced pluripotent stem cell (hiPSC)-derived neurons under varying concentrations and stress conditions. Six lines of hiPSC-derived neuronal progenitors derived from healthy human iPSCs were treated with metformin (1-500 µM) on day 18 of differentiation. For mature neurons (day 30), three concentrations (10 µM, 50 µM, and 100 µM) were used to assess cytotoxicity. MG132 proteasomal inhibitor and sodium arsenite (NaArs) were used to investigate oxidative stress, and 50 µM of metformin was tested for its protective effects against oxidative stress in hiPSC-derived neurons. Metformin treatment did not affect cell viability, neuronal differentiation, or trigger reactive oxygen species (ROS) generation in healthy hiPSC-derived motor neurons. Additionally, mitochondrial membrane potential (MMP) loss was not observed at 50 µM metformin. Metformin effectively protected neurons from stress agents and elevated the expression of antioxidant genes when treated with MG132. However, an interplay between MG132 and metformin resulted in lower expression of Nrf2 and NQO1 compared to the MG132 group alone, indicating reduced JC-1 aggregate levels due to MG132 proteasomal inhibition. Metformin upregulated antioxidant genes in hiPSC-derived neurons under stress conditions and protected the cells from oxidative damage.

Links Between Cellular Energy Metabolism and Pain Sensation

One of the functions of organism cells is to maintain energy homeostasis to promote metabolism and adapt to the environment. The 3 major pathways of cellular energy metabolism are glycolysis, the tricarboxylic acid (TCA) cycle, and oxidative phosphorylation (OXPHOS). Neurons, astrocytes, and microglia are crucial in allodynia, hyperalgesia, and sensitization in nociceptive pathways. This review focused on these 3 major cellular energy metabolism pathways, aiming to elucidate the relationship between neurocyte and pain sensation and present the reprogramming of energy metabolism on pain, as well as the cellular and molecular mechanism underlying various forms of pain. The clinical and preclinical drugs involved in pain treatment and molecular mechanisms via cellular energy metabolism were also discussed.

Characterisation of periorbital mechanical allodynia in the reserpine-induced fibromyalgia model in mice: The role of the Schwann cell TRPA1/NOX1 signalling pathway

Fibromyalgia (FM) is a complex and multifaceted condition characterized by a range of clinical symptoms, including widespread pain and a strong association with migraine headaches. Recent findings have underscored the role of oxidative stress and transient receptor potential ankyrin 1 (TRPA1) channel in migraine and FM. However, the precise mechanisms underlying the comorbidity between migraine and FM are unclear. Periorbital mechanical allodynia (PMA), which recapitulates one of the major symptoms of migraine, and the feed-forward mechanism driven by reactive oxygen species and TRPA1, were investigated in a reserpine-induced FM model in C57BL/6J mice, employing pharmacological interventions and genetic approaches. Reserpine-treated mice developed PMA (which was alleviated by antimigraine drugs) and increased endoneurial macrophages and oxidative stress markers in the trigeminal nerve tissues (neuroinflammation). These responses were absent upon macrophage depletion and by pharmacological inhibition or global genetic deletion of the TRPA1 channel. Furthermore, selective silencing of TRPA1 in Schwann cells attenuated both reserpine-induced PMA and neuroinflammation, while selective silencing of TRPA1 in sensory neurons reduced PMA but not neuroinflammation. In reserpine-treated mice, Schwann cell TRPA1 promoted NADPH oxidase 1-mediated reactive oxygen species generation and macrophage density increase in the mouse trigeminal nerve, which sustains PMA. Targeting TRPA1 channels in Schwann cells could offer a novel therapeutic strategy for FM-related headaches.

Double-Layer Microneedle Patch Loaded with HA-PBA-QCT for Management of Paclitaxel-Induced Peripheral Neuropathic Pain

Chemotherapy-induced neuropathic pain (CINP) is a common adverse effect of antineoplastic drugs, often leading to dose reduction, treatment delays, or cessation of chemotherapy. Chemotherapy agents, like paclitaxel (PTX), damage the somatosensory nervous system by inducing neuroinflammation and oxidative stress, resulting in the sensitization of sensory neurons. Quercetin (QCT), known for its anti-inflammatory, antioxidant, and neuroprotective properties, is investigated for various neurological disorders. This work creates phenylboronic acid-modified hyaluronic acid (HA-PBA) gels with incorporated QCT and fabricates a double-layer microneedle (MN) patch using an HA-PBA-QCT complex in the needles and HA/polyvinyl alcohol (PVA) as the substrate. The crosslinking between PVA and HA-PBA-QCT enables a controlled, sustained release of QCT upon application. This work applies these QCT-loaded microneedle (QMN) patches to the instep skin of PTX-treated mice, which exhibits mechanical allodynia and cold hyperalgesia. Biweekly applications of the QMN patches significantly reduce pain responses. This analgesic effect is associated with the modulation of satellite glial cell activity, decreased macrophage infiltration, and reduced TNF-α and IL-6 levels in dorsal root ganglia (DRGs). Additionally, the treatment improves cellular antioxidant capacity, indicated by upregulated Nrf2 and catalase in DRGs. Overall, these findings suggest that double-layer QMN patches offer long-term anti-inflammatory and antioxidant benefits, potentially alleviating CINP in patients.

Animal models of cisplatin-induced neuropathic pain

Cisplatin chemotherapy has been used as the main treatment for different types of cancer. However, cisplatin chemotherapy-induced peripheral neuropathic pain (CIPNP) seriously affects the treatment process and quality of life of patients. In addition, it impacts the underlying mechanism and prevention and treatment strategies, indicating that drug selection and efficacy evaluation need to be further investigated. Furthermore, an animal model that is more consistent with the pathological mechanism needs to be developed. In this study, we describe and discuss the methods of developing and detecting CIPNP models in rats and mice induced by cisplatin chemotherapy. The aim was to improve the modeling rate and develop animal models that are more consistent with the developmental pattern of the disease. In addition, the study provides ideal reference animal models for clinical research and drug discovery and development.

Long-Term Effects of Ozone Treatment in Patients with Persistent Numbness and Tingling Secondary to Chemotherapy-Induced Peripheral Neuropathy. A Retrospective Study

BACKGROUND

Numbness and tingling secondary to chemotherapy-induced peripheral neuropathy (CIPN) are frequent side effects that limit chemotherapy treatment and quality of life. Successful treatments for CIPN are limited. This preliminary report shows the potential long-term effects of ozone treatment in the management of persistent numbness and tingling secondary to CIPN.

METHODS

Ozone treatment was administered by rectal insufflation in 15 patients (female/male: 8/7, age: 66 years old) suffering from persistent numbness and tingling secondary to grade-2 or grade-3 CIPN. Planned ozone treatment consisted of 40 sessions over 4 months. The initial concentration of 10 μg/mL was progressively increased to 30 μg/mL. The initial gas volume of 180 mL/session was progressively increased to 300 mL/session if tolerated. Before and after ozone treatment, and at 3- and 6- months after the end of treatment, they were assessed (i) the grade of CIPN-toxicity, and (ii) the self-reported decrease in numbness and tingling.

RESULTS

After ozone treatment, 47% of patients experienced a decrease in the grade of CIPN-toxicity (P = .016), and 67% of patients reported a decrease in numbness and tingling ≥50% (P = .002). These effects were maintained at 3- and 6- months after the end of O3T.

CONCLUSIONS

In this retrospective report, patients with persistent numbness and tingling secondary to CIPN showed clinically relevant and long-term improvements after ozone treatment. The magnitude and duration of the observed effects merit further research and support our ongoing clinical trials.

An emerging aspect of cancer neuroscience: A literature review on chemotherapy-induced peripheral neuropathy

The nervous system governs both ontogeny and oncology. Foundational discoveries have clarified the direct communication of neurotransmitters with tumors and indirect interactions through neural effects on the immune system and the tumor microenvironment. Meantime, the nervous system is susceptible to cancer and its treatment. Chemotherapy-induced peripheral neuropathy (CIPN) is the most common side effects that significantly reduce the efficacy of anti-cancer treatment and patients' quality of life by leading to dose reduction or early cessation of chemotherapy. However, there are no effective strategies to reverse or treat CIPN. A better understanding of the mechanisms is expected to enable the development of the next generation of therapies. Here, we summarize the recent important studies on clinical manifestations, risk factors, prediction, pathogenesis, prevention, and treatment of CIPN. We also provide perspectives and insights regarding the rationales of bidirectional interactions between cancer and the nervous system.

DNA Damage Response Network and Intracellular Redox Status in the Clinical Outcome of Patients with Lung Cancer

Background/Objectives: DNA damage response (DDR) is a network of molecular pathways associated with the pathogenesis and progression of several diseases, as well as the outcome of chemotherapy. Moreover, the intracellular redox status is essential for maintaining cell viability and controlling cellular signaling. Herein, we analyzed DDR signals and redox status in peripheral blood mononuclear cells (PBMCs) from patients with lung cancer with different response rates to platinum-based chemotherapy. Methods: Several DDR-associated signals and redox status, expressed as the GSH/GSSG ratio, were measured in two lung cancer cell lines (A549, H1299), two normal fibroblast cell lines (WS1, 1BR3hT), and PBMCs from 20 healthy controls and 32 patients with lung cancer at baseline (17 responders and 15 non-responders to subsequent platinum-based chemotherapy). Results: Higher levels of endogenous/baseline DNA damage, decreased GSH/GSSG ratios, and augmented apurinic/apyrimidinic sites, as well as lower nucleotide excision repair (NER) and increased interstrand cross-links (ICLs) repair efficiencies, were observed in lung cancer cell lines compared with normal ones (all p < 0.05). Moreover, PBMCs from patients with lung cancer showed reduced GSH/GSSG ratios, augmented apurinic/apyrimidinic sites, decreased NER and ICL repair capacities, and lower apoptosis rates, compared with healthy controls (all p < 0.001). Interestingly, PBMCs from patients who are responders are characterized by reduced GSH/GSSG ratios, augmented apurinic/apyrimidinic sites, decreased NER and ICL repair capacities, and higher apoptosis rates compared with patients who are non-responders (all p < 0.01). Conclusions: Together, DDR-associated parameters and redox status measured in PBMCs from patients with lung cancer at baseline are associated with the therapeutic benefit of platinum-based chemotherapy.

Endoplasmic reticulum stress: The underlying mechanism of chronic pain

Chronic pain (CP) affects over 30 % of the global population, imposing significant financial burdens on individuals and society. However, existing treatments for CP offer limited efficacy and troublesome side effects, primarily owing to a lack of knowledge of its precise underlying mechanism. Pathological stimuli disrupt the intricate process of protein folding and endoplasmic reticulum (ER) homeostasis. This disruption leads to the accumulation of misfolded or unfolded proteins in the ER, generating a condition termed ER stress. Emerging data have indicated that ER stress, occurring in the peripheral and central nervous systems, contributes to the development and maintenance of CP. This review aimed to comprehensively explore the intersection of ER stress and CP within the lower and upper nervous systems and highlight the cell-specific contributions of the unfolded protein response in different CP types. We provide a comprehensive synthesis of evidence from animal models, examining neuronal and non-neuronal mechanisms and discuss the damaging ER stress-linked inflammation, autophagy, oxidative stress, and apoptosis, which collectively drive disease progression and contribute to a neurotoxic environment. However, the mechanisms through which ER stress influences the most advanced centre-of-pain projections in the brain remain unclear. Further investigation in this area is crucial to elucidate the relationship between ER stress and CP and facilitate the development of novel therapeutic drugs for this intractable dilemma.

H. pectinata (L.) Poit - Traditional uses, phytochemistry and biological-pharmacological activities in preclinical studies: A systematic review

ETHNOPHARMACOLOGICAL RELEVANCE

H. pectinata (L.) Poit, popularly known as "sambacaitá" or "canudinho", is a plant endemic to north-eastern Brazil. Its aerial parts, leaves and flowers have traditionally been used to treat gastrointestinal disorders, rhinopharyngitis, nasal congestion, bacterial and fungal infections, fever, colic, inflammation, and pain.

AIM OF THE STUDY

The aim of this review was to provide information on the botanical characteristics, ethnomedicinal uses, phytochemistry and biological-pharmacological activities of H. pectinata.

MATERIALS AND METHODS

This systematic review followed the Cochrane Handbook Collaboration and the PRISMA guidelines. The review question was what are the biological-pharmacological activities of H. pectinata presented in non-clinical studies. The search for articles was conducted in the Medline (via PubMed), Embase, Web of Science, Scopus, Virtual Health Library, SciELO, Google Scholar and the Brazilian Digital Library of Theses and Dissertations databases. Two reviewers independently selected the studies that met the inclusion criteria, extracted the data, and assessed the risk of bias of the included studies.

RESULTS

39 articles were included in this review, of which 19 reported in vitro experiments, 16 in vivo studies and 4 in vivo and in vitro experiments. H. pectinata is a plant widely used in folk medicine in north-eastern Brazil for the treatment of various ailments, such as respiratory diseases, gastrointestinal disorders, bacterial and fungal infections, and general inflammation. Supporting its popular use, several in vitro and in vivo pharmacological investigations of the essential oil and extract of H. pectinata have demonstrated their anti-inflammatory, antinociceptive, antioxidant, antidepressant, anticancer, hepatoregenerative, healing, and antimicrobial activities. H. pectinata has been reported to contain 75 bioactive constituents, comprising 9 flavonoids, 54 terpenes, and 12 other compounds.

CONCLUSION

H. pectinata is a plant commonly used in traditional medicine. Phytochemically, it contains several bioactive constituents, including terpenes and flavonoids, and has been shown to have antinociceptive, anti-inflammatory, antimicrobial and antitumour activity, as well as hepatorregenerative and healing effects, and low toxicity.

Nicotinamide riboside activates SIRT3 to prevent paclitaxel-induced peripheral neuropathy

Paclitaxel (PTX) is a microtubule stabilizer that disrupts the normal cycle of microtubule depolymerization and repolymerization, leading to cell cycle arrest and cancer cell death. It is commonly used as a first-line chemotherapeutics for various malignancies, such as breast cancer, non-small cell lung cancer, and ovarian cancer. However, PTX chemotherapy is associated with common and serious side effects, including chemotherapy-induced peripheral neuropathy (CIPN). As cancer treatment advances and survival rates increase, the impact of CIPN on patients' quality of life has become more significant. To date, there is no effective treatment strategy for CIPN. Surtuin3 (SIRT3) is a nicotinamide adenine dinucleotide (NAD+) dependent protein deacetylase located on mitochondria. It transfers the acetyl group of the lysine side chain of acetylated substrate proteins to NAD+, producing deacetylated proteins to regulate mitochondrial energy metabolic processes. SIRT3 has been found to play an important role in various diseases, including aging, neurodegenerative diseases, cancer, heart disease, metabolic diseases, etc. However, the role of SIRT3 in CIPN is still unknown. This study found for the first time that activating SIRT3 helps to improve paclitaxel-induced CIPN. Nicotinamide riboside (NR) can protect dorsal root ganglion (DRG) mitochondria against oxidative damage caused by paclitaxel through activating SIRT3-MnSOD2 and SIRT3-Nrf2 pathway. Moreover, NR can enhance the anticancer activity of paclitaxel. Together, our research provides new strategy and candidate drug for the treatment of CIPN.

The dual role of TRPV1 in peripheral neuropathic pain: pain switches caused by its sensitization or desensitization

The transient receptor potential vanilloid 1 (TRPV1) channel plays a dual role in peripheral neuropathic pain (NeuP) by acting as a "pain switch" through its sensitization and desensitization. Hyperalgesia, commonly resulting from tissue injury or inflammation, involves the sensitization of TRPV1 channels, which modulates sensory transmission from primary afferent nociceptors to spinal dorsal horn neurons. In chemotherapy-induced peripheral neuropathy (CIPN), TRPV1 is implicated in neuropathic pain mechanisms due to its interaction with ion channels, neurotransmitter signaling, and oxidative stress. Sensitization of TRPV1 in dorsal root ganglion neurons contributes to CIPN development, and inhibition of TRPV1 channels can reduce chemotherapy-induced mechanical hypersensitivity. In diabetic peripheral neuropathy (DPN), TRPV1 is involved in pain modulation through pathways including reactive oxygen species and cytokine production. TRPV1's interaction with TRPA1 channels further influences chronic pain onset and progression. Therapeutically, capsaicin, a TRPV1 agonist, can induce analgesia through receptor desensitization, while TRPV1 antagonists and siRNA targeting TRPV1 show promise in preclinical studies. Cannabinoid modulation of TRPV1 provides another potential pathway for alleviating neuropathic pain. This review summarizes recent preclinical research on TRPV1 in association with peripheral NeuP.

Schwann cell TRPA1 elicits reserpine-induced fibromyalgia pain in mice

BACKGROUND AND PURPOSE

Fibromyalgia is a complex clinical disorder with an unknown aetiology, characterized by generalized pain and co-morbid symptoms such as anxiety and depression. An imbalance of oxidants and antioxidants is proposed to play a pivotal role in the pathogenesis of fibromyalgia symptoms. However, the precise mechanisms by which oxidative stress contributes to fibromyalgia-induced pain remain unclear. The transient receptor potential ankyrin 1 (TRPA1) channel, known as both a pain sensor and an oxidative stress sensor, has been implicated in various painful conditions.

EXPERIMENTAL APPROACH

The feed-forward mechanism that implicates reactive oxygen species (ROS) driven by TRPA1 was investigated in a reserpine-induced fibromyalgia model in C57BL/6J mice employing pharmacological interventions and genetic approaches.

KEY RESULTS

Reserpine-treated mice developed pain-like behaviours (mechanical/cold hypersensitivity) and early anxiety-depressive-like disorders, accompanied by increased levels of oxidative stress markers in the sciatic nerve tissues. These effects were not observed upon pharmacological blockade or global genetic deletion of the TRPA1 channel and macrophage depletion. Furthermore, we demonstrated that selective silencing of TRPA1 in Schwann cells reduced reserpine-induced neuroinflammation (NADPH oxidase 1-dependent ROS generation and macrophage increase in the sciatic nerve) and attenuated fibromyalgia-like behaviours.

CONCLUSION AND IMPLICATIONS

Activated Schwann cells expressing TRPA1 promote an intracellular pathway culminating in the release of ROS and recruitment of macrophages in the mouse sciatic nerve. These cellular and molecular events sustain mechanical and cold hypersensitivity in the reserpine-evoked fibromyalgia model. Targeting TRPA1 channels on Schwann cells could offer a novel therapeutic approach for managing fibromyalgia-related behaviours.

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.

The Combination of Molecular Hydrogen and Heme Oxygenase 1 Effectively Inhibits Neuropathy Caused by Paclitaxel in Mice

Chemotherapy-provoked peripheral neuropathy and its associated affective disorders are important adverse effects in cancer patients, and its treatment is not completely resolved. A recent study reveals a positive interaction between molecular hydrogen (H2) and a heme oxygenase (HO-1) enzyme inducer, cobalt protoporphyrin IX (CoPP), in the inhibition of neuropathic pain provoked by nerve injury. Nevertheless, the efficacy of CoPP co-administered with hydrogen-rich water (HRW) on the allodynia and emotional disorders related to paclitaxel (PTX) administration has not yet been assessed. Using male C57BL/6 mice injected with PTX, we examined the effects of the co-administration of low doses of CoPP and HRW on mechanical and thermal allodynia and anxiodepressive-like behaviors triggered by PTX. Moreover, the impact of this combined treatment on the oxidative stress and inflammation caused by PTX in the amygdala (AMG) and dorsal root ganglia (DRG) were studied. Our results indicated that the antiallodynic actions of the co-administration of CoPP plus HRW are more rapid and higher than those given by each of them when independently administered. This combination inhibited anxiodepressive-like behaviors, the up-regulation of the inflammasome NLRP3 and 4-hydroxynonenal, as well as the high mRNA levels of some inflammatory mediators. This combination also increased the expression of NRF2, HO-1, superoxide dismutase 1, glutathione S-transferase mu 1, and/or the glutamate-cysteine ligase modifier subunit and decreased the protein levels of BACH1 in the DRG and/or AMG. Thus, it shows a positive interaction among HO-1 and H2 systems in controlling PTX-induced neuropathy by modulating inflammation and activating the antioxidant system. This study recommends the co-administration of CoPP plus HRW as an effective treatment for PTX-provoked neuropathy and its linked emotive deficits.

Silencing of FTO inhibits oxidative stress to relieve neuropathic pain by m6A modification of GPR177

BACKGROUND

Neuropathic pain (NP) is a challenging health condition owing to its complex nature and associated multiple etiologies. The occurrence of NP involves the abnormal activity of neurons mediated by oxidative stress (OS). Previous research has demonstrated that m6A methylation plays a role in the regulatory pathway of NP. This study aimed to investigate the specific molecular pathways through which m6A methylation modifiers alleviate NP.

METHODS

For this purpose, an NO rat model was developed via spared nerve injury (SNI), followed by quantifying the animal's pain assessment via paw withdrawal threshold (PWT) and paw withdrawal latency (PWL). The OS in SNI rats was evaluated by measuring reactive oxygen species, superoxide dismutase, and catalase (CAT) in spinal cord tissues. Moreover, quantitative-real-time polymerase chain reaction and western blot analysis were employed for detecting fat mass and obesity-associated (FTO) and GPR177 levels, while m6A levels of GPR117 were analyzed via MeRIP.

RESULTS

The results indicated an enhanced OS with highly expressed FTO in spinal cord tissue samples, where knocking down Fto effectively relieved NP and OS in SNI rats. Mechanistic investigations revealed that Fto-mediated reduction of Grp177 m6A modification was involved in the WNT5a/TRPV1 axis-mediated OS remission of NP. Moreover, in vitro experiment results indicated that YTHDF2 was an important m6A methylated reading protein for this process.

CONCLUSIONS

Fto silencing leads to increased m6A methylation of Grp177 through a YTHDF2-dependent mechanism, resulting in decreased Grp177 stability and ultimately reducing NP in rats by OS suppression.

Evaluation of the Therapeutic Potential of Amantadine in a Vincristine-Induced Peripheral Neuropathy Model in Rats

This study aimed to evaluate the therapeutic potential of amantadine in a vincristine-induced peripheral neuropathy model in rats. Forty-eight male Wistar rats were used. The treated groups received oral amantadine at doses of 2, 5, 12, 25 and 50 mg/kg, with daily applications for 14 days. The mechanical paw withdrawal threshold was measured using a digital analgesimeter. Immunohistochemical analysis of IL-6, TNFα, MIP1α, IL-10, CX3CR1, CXCR4, SOD, CAT and GPx, and enzymatic activity analysis of CAT, SOD and GPx were performed, in addition to quantitative PCR of Grp78, Chop, Ho1, Perk, Bax, Bcl-xL, Casp 3, Casp 9, IL-6, IL-10, IL-18 and IL-1β. The results showed an increase in nociceptive thresholds in animals that received 25 mg/kg and 50 mg/kg amantadine. Immunohistochemistry showed a decrease in the immunostaining of IL-6, TNFα, MIP1α and CX3CR1, and an increase in IL-10. CAT and SOD showed an increase in both immunochemistry and enzymatic analysis. qPCR revealed a reduced expression of genes related to endoplasmic reticulum stress and regulation in the expression of immunological and apoptotic markers. Amantadine demonstrated antinociceptive, anti-inflammatory and antioxidant effects in the vincristine-induced peripheral neuropathy model in rats, suggesting that amantadine may be considered an alternative approach for the treatment of vincristine-induced peripheral neuropathic pain.

Protective Effects of Glatiramer Acetate Against Paclitaxel-Induced Peripheral Neuropathy in Rats: A Role for Inflammatory Cytokines and Oxidative Stress

Chemotherapy-induced peripheral neuropathy (CIPN) is a major challenge for cancer patients who undergo chemotherapy with paclitaxel. Therefore, finding effective therapies for CIPN is crucial. Glatiramer acetate is used to treat multiple sclerosis that exerts neuroprotective properties in various studies. We hypothesized that glatiramer acetate could also improve the paclitaxel-induced peripheral neuropathy. We used a rat model of paclitaxel (2 mg/kg/every other day for 7 doses)-induced peripheral neuropathy. Rats were treated with either different doses of glatiramer acetate (1, 2, 4 mg/kg/day) or its vehicle for 14 days in separate groups. The mechanical and thermal sensitivity of the rats by using the Von Frey test and the Hot Plate test, respectively, were assessed during the study. The levels of oxidative stress (malondialdehyde and superoxide dismutase), inflammatory markers (TNF-α, IL-10, NF-kB), and nerve damage (H&E and S100B staining) in the sciatic nerves of the rats were also measured at the end of study. Glatiramer acetate (2 and 4 mg/kg) exerted beneficial effects on thermal and mechanical allodynia tests. It also modulated the inflammatory response by reducing TNF-α and NF-κB levels, enhancing IL-10 production, and improving the oxidative stress status by lowering malondialdehyde and increasing superoxide dismutase activity in the sciatic nerve of the rats. Furthermore, glatiramer acetate enhanced nerve conduction velocity in all treatment groups. Histological analysis revealed that glatiramer acetate (2 and 4 mg/kg) prevented paclitaxel-induced damage to the nerve structure. These results suggest that glatiramer acetate can alleviate the peripheral neuropathy induced by paclitaxel.

Pegylated nanoliposomal cisplatin ameliorates chemotherapy-induced peripheral neuropathy

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a serious adverse effect of cisplatin. The current study aimed to determine whether PEGylated nanoliposomal cisplatin can limit CIPN in an animal model.

METHODS

Cisplatin-loaded PEGylated liposome nanoparticles (Cis-PL) were produced as a combination of lecithin, cholesterol, and DSPE-mPEG2000 in a molar ratio of 50:45:5 and were characterized by polydispersity index (PDI), zeta potential, Field emission scanning electron microscopy (FESEM) analysis, as well as encapsulation efficiency (EE). Fifteen male rats were provided and randomly divided into 3 groups including Cis-PL group, cisplatin group, and control group. Behavioural tests (hot-plate test and acetone drop test) were used for evaluating CIPN. Moreover, oxidative stress markers and histopathological analysis were applied. Treatment-related toxicity was assessed by haematological analysis as well as liver and renal function tests.

RESULTS

Cis-PL had an average particle size of 125.4, PDI of 0.127, and zeta potential of -40.9 mV. Moreover, the Cis-PL exhibited a high EE as well as low levels of leakage rate at 25 °C. In a hot-plate test, paw withdrawal latency was longer in Cis-PL group in comparison to rats treated with cisplatin. A lower number of withdrawal responses was detected during acetone drop test in Cis-PL group than in cisplatin-treated rats. Assessment of oxidative stress markers showed that Cis-PL could improve oxidative stress. Additionally, histopathological assessment demonstrated that the number of satellite cells was significantly reduced in the dorsal root ganglion (DRG) of Cis-PL-treated rats compared with those treated with cisplatin. The cisplatin group had elevated white blood cells counts, reduced platelet counts, and higher levels of bilirubin, ALT (alanine aminotransferase, and AST (aspartate aminotransferase), and creatinine compared with the control group, which was ameliorated in Cis-PL group.

CONCLUSIONS

Data from the current study support the previous hypothesis that Cisplatin-loaded PEGylated liposome could be a promising solution for CIPN in the future by modulating oxidative stress and preventing glial cell activation in DRG, suggesting further clinical studies to investigate the efficacy of this agent and its potential application in clinical practice.

Xenon ameliorates chronic post-surgical pain by regulating mitophagy in microglia and rats mediated by PINK1/Parkin pathway

Background

Chronic post-surgical pain (CPSP) is one of the important causes of poor postoperative outcomes, the activation of microglia in the spinal cord is closely related to the generation, transmission and maintenance of CPSP. Xenon (Xe), an anesthetic gas, has been reported to be able to significantly reduce intraoperative analgesia and postoperative pain sensation at low doses. However, the mechanism of the regulatory effect of xenon on activated microglia after CPSP remains unclear.

Methods

In this study, CPSP model rats were treated with 50% Xe inhalation for 1 h following skin/muscle incision and retraction (SMIR), once a day for 5 consecutive days, and then the painbehavioraltests (pain behavior indexes paw withdrawal mechanical threshold, PWMT and thermal withdrawal latency, TWL), microglial activation, oxidative stress-related indexes (malondialdehyde, MDA; superoxide dismutase, SOD; hydrogen peroxide, H2O2; and catalase, CAT), mitophagy and PINK1/Parkin pathway were examined.

Results

The present results showed that a single dose of Xe treatment in SMIR rat model could significantly improve PWMT and TWL in the short-term at a single treatment and long-term at multiple treatments. Xe treatment inhibited microglia activation and oxidative stress in the spinal dorsal horn of SMIR rats, as indicated by the decrease of Iba1 and MDA/H2O2 levels and the increase of SOD/CAT levels. Compared with the control group, Xe further increased the CPSP promoted Mito-Tracker (a mitochondrial marker) and LC3 (an autophagy marker) co-localization positive spots and PINK1/Parkin/ATG5/BECN1 (autophagy-related proteins) protein expression levels, and inhibited the Mito-SOX (a mitochondrial reactive oxygen species marker) positive signal, indicating that Xe promoted microglia mitophagy and inhibited oxidative stress in CPSP. Mechanistically, we verified that Xe promoted PINK1/Parkin signaling pathway activation.

Conclusion

Xe plays a role in ameliorating chronic post-surgical pain by regulating the PINK1/Parkin pathway mediated microglial mitophagy and provide new ideas and targets for the prevention and treatment of CPSP.

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.

Role of parthenolide in paclitaxel-induced oxidative stress injury and impaired reproductive function in rat testicular tissue

The chemotherapeutic agent paclitaxel (PTX) causes testicular toxicity due to oxidative stress. Parthenolide (PTL), the active ingredient of the Tanacetum parthenium plant, is used to treat inflammation, dizziness, and spasms. In the present study, we evaluated the therapeutic effect of PTL on PTX-induced testicular toxicity in rats and its role in reproductive function. To this end, 6 groups were formed: control, PTX, sham, T1, T2, and T3. After testicular toxicity was induced in rats with 8 mg/kg PTX, the rats were treated with 1 mg/kg, 2 mg/kg, and 4 mg/kg PTL for 14 days. GSH and MDA levels were measured in rat testicular tissue after the last dose of PTL was administered. To determine the damage caused by PTX to testicular tissue by detecting 8-OHdG and iNOS, sections were prepared and examined histopathologically and immunohistochemically. Furthermore, the gene expressions and enzymatic activities of SOD, CAT, GPx, GST, and GR were investigated in all groups. After PTL treatment, MDA, 8-OHdG, and iNOS levels decreased while GSH levels increased in testicular tissue. Increased levels of antioxidant genes and enzymes also reduced oxidative stress. Additionally, the expression levels of the Dazl, Ddx4, and Amh genes, which are involved in gametogenesis and sperm production, decreased in case of toxicity and increased with PTL treatment. The data from this study show that PTL may have a therapeutic effect in the treatment of testicular damage by eliminating the oxidative stress-induced damage caused by PTX in testicular tissue, providing an effective approach to alleviating testicular toxicity, and playing an important role in reproduction/sperm production, especially at a dose of 4 mg/kg.

Applications of Cannabinoids in Neuropathic Pain: An Updated Review

Neuropathic pain is experienced due to injury to the nerves, underlying disease conditions or toxicity induced by chemotherapeutics. Multiple factors can contribute to neuropathic pain such as central nervous system (CNS)-related autoimmune and metabolic disorders, nerve injury, multiple sclerosis and diabetes. Hence, development of pharmacological interventions to reduce the drawbacks of existing chemotherapeutics and counter neuropathic pain is an urgent unmet clinical need. Cannabinoid treatment has been reported to be beneficial for several disease conditions including neuropathic pain. Cannabinoids act by inhibiting the release of neurotransmitters from presynaptic nerve endings, modulating the excitation of postsynaptic neurons, activating descending inhibitory pain pathways, reducing neural inflammation and oxidative stress and also correcting autophagy defects. This review provides insights on the various preclinical and clinical therapeutic applications of cannabidiol (CBD), cannabigerol (CBG), and cannabinol (CBN) in various diseases and the ongoing clinical trials for the treatment of chronic and acute pain with cannabinoids. Pharmacological and genetic experimental strategies have well demonstrated the potential neuroprotective effects of cannabinoids and also elaborated their mechanism of action for the therapy of neuropathic pain.

Chemotherapy for pain: reversing inflammatory and neuropathic pain with the anticancer agent mithramycin A

ABSTRACT

The persistence of inflammatory and neuropathic pain is poorly understood. We investigated a novel therapeutic paradigm by targeting gene networks that sustain or reverse persistent pain states. Our prior observations found that Sp1-like transcription factors drive the expression of TRPV1, a pain receptor, that is blocked in vitro by mithramycin A (MTM), an inhibitor of Sp1-like factors. Here, we investigate the ability of MTM to reverse in vivo models of inflammatory and chemotherapy-induced peripheral neuropathy (CIPN) pain and explore MTM's underlying mechanisms. Mithramycin reversed inflammatory heat hyperalgesia induced by complete Freund adjuvant and cisplatin-induced heat and mechanical hypersensitivity. In addition, MTM reversed both short-term and long-term (1 month) oxaliplatin-induced mechanical and cold hypersensitivity, without the rescue of intraepidermal nerve fiber loss. Mithramycin reversed oxaliplatin-induced cold hypersensitivity and oxaliplatin-induced TRPM8 overexpression in dorsal root ganglion (DRG). Evidence across multiple transcriptomic profiling approaches suggest that MTM reverses inflammatory and neuropathic pain through broad transcriptional and alternative splicing regulatory actions. Mithramycin-dependent changes in gene expression following oxaliplatin treatment were largely opposite to and rarely overlapped with changes in gene expression induced by oxaliplatin alone. Notably, RNAseq analysis revealed MTM rescue of oxaliplatin-induced dysregulation of mitochondrial electron transport chain genes that correlated with in vivo reversal of excess reactive oxygen species in DRG neurons. This finding suggests that the mechanism(s) driving persistent pain states such as CIPN are not fixed but are sustained by ongoing modifiable transcription-dependent processes.

Research hotspots and trends on neuropathic pain-related mood disorders: a bibliometric analysis from 2003 to 2023

Introduction

Neuropathic Pain (NP) is often accompanied by mood disorders, which seriously affect the quality of life of patients. This study aimed to analyze the hotspots and trends in NP-related mood disorder research using bibliometric methods and to provide valuable predictions for future research in this field.

Methods

Articles and review articles on NP-related mood disorders published from January 2003 to May 2023 were retrieved from the Web of Science Core Collection. We used CiteSpace to analyze publications, countries, institutions, authors, cited authors, journals, cited journals, references, cited references, and keywords. We also analyzed collaborative network maps and co-occurrence network maps.

Results

A total of 4,540 studies were collected for analysis. The number of publications concerning NP-related mood disorders every year shows an upward trend. The United States was a major contributor in this field. The University of Toronto was the most productive core institution. C GHELARDINI was the most prolific author, and RH DWORKIN was the most frequently cited author. PAIN was identified as the journal with the highest productivity and citation rate. The current research hotspots mainly included quality of life, efficacy, double-blind methodology, gabapentin, pregabalin, postherpetic neuralgia, and central sensitization. The frontiers in research mainly focused on the mechanisms associated with microglia activation, oxidative stress, neuroinflammation, and NP-related mood disorders.

Discussion

In conclusion, the present study provided insight into the current state and trends in NP-related mood disorder research over the past 20 years. Consequently, researchers will be able to identify new perspectives on potential collaborators and cooperative institutions, hot topics, and research frontiers in this field.

An up-to-date view of paclitaxel-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN),referring to the damage to the peripheral nerves caused by exposure to a neurotoxic chemotherapeutic agent, is a common side effect amongst patients undergoing chemotherapy. Paclitaxel-induced peripheral neuropathy (PIPN) can lead to dose reduction or early cessation of chemotherapy, which is not conducive to patients'survival. Even after treatment is discontinued, PIPN symptoms carried a greater risk of worsening and plagued the patient's life, leading to long-term morbidity in survivors. Here, we summarize the research progress for clinical manifestations, risk factors, pathogenesis, prevention and treatment of PIPN, so as to embark on the path of preventing PIPN with prolongation of patient's life quality on a long-term basis.

A Novel Therapy for Cisplatin-Induced Allodynia and Dysfunctional and Emotional Impairments in Male and Female Mice

Patients undergoing chemotherapy with cisplatin (CIS) develop neuropathy in addition to other symptoms such as, anxiety, depression, muscle wasting and body weight loss. This symptomatology greatly weakens patients and may even lead to adjournment of chemotherapy. The protecting actions of molecular hydrogen in many neurological illnesses have been described, but its effect on the functional and emotional deficiencies caused by CIS has not been assessed. In C57BL/6J male and female mice injected with CIS, we examined the impact of the prophylactic treatment with hydrogen-rich water (HRW) on: (i) the tactile and cold allodynia, (ii) the deficits of grip strength and weight loss, (iii) the anxiodepressive-like behaviors and (iv) the inflammatory and oxidative reactions incited by CIS in the dorsal root ganglia (DRG) and prefrontal cortex (PFC). The results demonstrate that the mechanical allodynia and the anxiodepressive-like comportment provoked by CIS were similarly manifested in both sexes, whereas the cold allodynia, grip strength deficits and body weight loss produced by this chemotherapeutic agent were greater in female mice. Nonetheless, the prophylactic treatment with HRW prevented the allodynia and the functional and emotional impairments resulting from CIS in both sexes. This treatment also inhibited the inflammatory and oxidative responses activated by CIS in the DRG and PFC in both sexes, which might explain the therapeutic actions of HRW in male and female mice. In conclusion, this study revealed the plausible use of HRW as a new therapy for the allodynia and physical and mental impairments linked with CIS and its possible mechanism of action.

Involvement of Oxidative Stress and Nutrition in the Anatomy of Orofacial Pain

Pain is a very important problem of our existence, and the attempt to understand it is one the oldest challenges in the history of medicine. In this review, we summarize what has been known about pain, its pathophysiology, and neuronal transmission. We focus on orofacial pain and its classification and features, knowing that is sometimes purely subjective and not well defined. We consider the physiology of orofacial pain, evaluating the findings on the main neurotransmitters; in particular, we describe the roles of glutamate as approximately 30-80% of total peripheric neurons associated with the trigeminal ganglia are glutamatergic. Moreover, we describe the important role of oxidative stress and its association with inflammation in the etiogenesis and modulation of pain in orofacial regions. We also explore the warning and protective function of orofacial pain and the possible action of antioxidant molecules, such as melatonin, and the potential influence of nutrition and diet on its pathophysiology. Hopefully, this will provide a solid background for future studies that would allow better treatment of noxious stimuli and for opening new avenues in the management of pain.

Microbiota and Mitochondrial Sex-Dependent Imbalance in Fibromyalgia: A Pilot Descriptive Study

Fibromyalgia is a widespread chronic condition characterized by pain and fatigue. Among the long list of physiological disturbances linked to this syndrome, mitochondrial imbalance and oxidative stress stand out. Recently, the crosstalk between mitochondria and intestinal microbiota has caught the attention of biomedical researchers, who have found connections between this axis and several inflammatory and pain-related conditions. Hence, this pilot descriptive study focused on characterizing the mitochondrial mass/mitophagy ratio and total antioxidant capacity in PBMCs, as well as some microbiota components in feces, from a Peruvian cohort of 19 females and 7 males with FM. Through Western blotting, electrochemical oxidation, ELISA, and real-time qPCR, we determined VDAC1 and MALPLC3B protein levels; total antioxidant capacity; secretory immunoglobulin A (sIgA) levels; and Firmicutes/Bacteroidetes, Bacteroides/Prevotella, and Roseburia/Eubacterium ratios; as well as Ruminococcus spp., Pseudomonas spp., and Akkermansia muciniphila levels, respectively. We found statistically significant differences in Ruminococcus spp. and Pseudomonas spp. levels between females and males, as well as a marked polarization in mitochondrial mass in both groups. Taken together, our results point to a mitochondrial imbalance in FM patients, as well as a sex-dependent difference in intestinal microbiota composition.

Kinin B2 Receptor Mediates Cisplatin-Induced Painful Peripheral Neuropathy by Intracellular Kinase Pathways and TRPA1 Channel Sensitisation

Chemotherapy-induced peripheral neuropathy is a severe clinical problem frequently associated with cisplatin use. Although its pathophysiology is poorly understood, it is known that kinin receptors and the transient receptor potential ankyrin 1 (TRPA1) channel play a significant role in the peripheral neuropathy induced by cisplatin in rodents. However, the role of signalling pathways downstream from B₂ kinin receptors activation and sensitisation of the TRPA1 channel remains unknown in this model. The cisplatin-induced neuropathy model caused mechanical and cold allodynia in male Swiss mice. Antagonists for kinin B₂ and B₁ receptors and the TRPA1 channel attenuated the painful parameters. Local sub-nociceptive doses of kinin B₂ receptor (bradykinin) and TRPA1 channel (allyl isothiocyanate; AITC) agonists enhanced the painful parameters in cisplatin-treated mice, which their respective antagonists attenuated. Furthermore, we demonstrated the interaction between the kinin B₂ receptor and the TRPA1 channel in cisplatin-induced peripheral neuropathy since phospholipase C (PLC) and protein kinase C epsilon (PKCε) inhibitors attenuated the increase in mechanical and cold allodynia evoked by bradykinin and AITC in cisplatin-treated mice. Therefore, regulating the activation of signalling pathways downstream from the kinin B₂ receptors activation and TRPA1 channel sensitisation can mitigate the painful peripheral neuropathy decurrent of the oncology treatment with cisplatin.

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.

Magnolin Inhibits Paclitaxel-Induced Cold Allodynia and ERK1/2 Activation in Mice

Chemotherapy-induced peripheral neuropathy (CIPN) is a common side effect of anti-cancer drugs. The main symptoms often include sensory disturbances and neuropathic pain, and currently there is no effective treatment for this condition. This study aimed to investigate the suppressive effects of magnolin, an extracellular signal-regulated kinase (ERK) inhibitor substance derived from a 95% EtOH extract of the seeds of Magnolia denudata, on the symptoms of CIPN. A taxol-based anti-cancer drug paclitaxel (PTX) was repeatedly injected (2 mg/kg/day, total 8 mg/kg) into mice to induce CIPN. A neuropathic pain symptom was assessed using a cold allodynia test that scores behaviors of licking and shaking paw after plantar administration of acetone drop. Magnolin was administered intraperitoneally (0.1, 1, or 10 mg/kg) and behavioral changes to acetone drop were measured. The effect of magnolin administration on ERK expression in the dorsal root ganglion (DRG) was investigated using western blot analysis. The results showed that the repeated injections of PTX induced cold allodynia in mice. Magnolin administration exerted an analgesic effect on the PTX-induced cold allodynia and inhibited the ERK phosphorylation in the DRG. These results suggest that magnolin could be developed as an alternative treatment to suppress paclitaxel-induced neuropathic pain symptoms.

H2S Alleviates Neuropathic Pain in Mice by Nrf2 Signaling Pathway Activation

Neuropathic pain is a chronic pain caused by direct damage to the peripheral or central nervous system, characterized by hyperalgesia, allodynia, and spontaneous pain. Hydrogen sulfide (H2S) therapy has been applied for neuropathic pain treatment, although the underlying mechanisms remain unknown. In this study, we sought to ascertain whether H2S therapy could alleviate neuropathic pain in a model of chronic constriction injury (CCI) and, if so, the potential mechanism. A CCI model was established in mice through a spinal nerve ligation method. Intrathecal injection of NaHS was used to treat CCI model mice. The thermal paw withdrawal latency (TPWL) and mechanical paw withdrawal threshold (MPWT) were used for pain threshold evaluation in mice. A series of experiments including immunofluorescence, enzyme-linked immunosorbent assay, electrophysiological test, mitochondrial DNA (mtDNA) quantification, measurement of ATP content, demethylase activity, and western blot were performed to investigate the specific mechanism of H2S treatment in neuropathic pain. Mice with CCI exposure exhibited a decrease in MPWT and TPWL, an increase in IL-1β and TNF-α expressions, elevated eEPSP amplitude, an upregulation of mtDNA, and a reduction in ATP production, whereas H2S treatment significantly reversed these changes. Furthermore, CCI exposure induced a remarkable increase in vGlut2- and c-fos-positive as well as vGlut2- and Nrf2-positive cells, an increase in Nrf2 located in the nucleus, and an upregulation of H3K4 methylation, and H2S treatment further enhanced these changes. In addition, ML385, a selective Nrf2 inhibitor, reversed the neuroprotective effects of H2S. H2S treatment mitigates CCI-induced neuropathic pain in mice. This protective mechanism is possibly linked to the activation of the Nrf2 signaling pathway in vGlut2-positive cells.

Intraganglionic reactive oxygen species mediate inflammatory pain and hyperalgesia through TRPA1 in the rat

Reactive oxygen species (ROS) are generated in nociceptive pathways in response to inflammation and injury. ROS are accumulated within the sensory ganglia following peripheral inflammation, but the functional role of intraganlionic ROS in inflammatory pain is not clearly understood. The aims of this study were to investigate whether peripheral inflammation leads to prolonged ROS accumulation within the trigeminal ganglia (TG), whether intraganglionic ROS mediate pain hypersensitivity via activation of TRPA1, and whether TRPA1 expression is upregulated in TG during inflammatory conditions by ROS. We demonstrated that peripheral inflammation causes excess ROS production within TG during the period when inflammatory mechanical hyperalgesia is most prominent. Additionally, scavenging intraganglionic ROS attenuated inflammatory mechanical hyperalgesia and a pharmacological blockade of TRPA1 localized within TG also mitigated inflammatory mechanical hyperalgesia. Interestingly, exogenous administration of ROS into TG elicited mechanical hyperalgesia and spontaneous pain-like responses via TRPA1, and intraganglionic ROS induced TRPA1 upregulation in TG. These results collectively suggest that ROS accumulation in TG during peripheral inflammation contributes to pain and hyperalgesia in a TRPA1 dependent manner, and that ROS further exacerbate pathological pain responses by upregulating TRPA1 expression. Therefore, any conditions that exacerbate ROS accumulation within somatic sensory ganglia can aggravate pain responses and treatments reducing ganglionic ROS may help alleviate inflammatory pain.

Drug-induced oxidative stress in cancer treatments: Angel or devil?

Oxidative stress (OS), defined as redox imbalance in favor of oxidant burden, is one of the most significant biological events in cancer progression. Cancer cells generally represent a higher oxidant level, which suggests a dual therapeutic strategy by regulating redox status (i.e., pro-oxidant therapy and/or antioxidant therapy). Indeed, pro-oxidant therapy exhibits a great anti-cancer capability, attributing to a higher oxidant accumulation within cancer cells, whereas antioxidant therapy to restore redox homeostasis has been claimed to fail in several clinical practices. Targeting the redox vulnerability of cancer cells by pro-oxidants capable of generating excessive reactive oxygen species (ROS) has surfaced as an important anti-cancer strategy. However, multiple adverse effects caused by the indiscriminate attacks of uncontrolled drug-induced OS on normal tissues and the drug-tolerant capacity of some certain cancer cells greatly limit their further applications. Herein, we review several representative oxidative anti-cancer drugs and summarize their side effects on normal tissues and organs, emphasizing that seeking a balance between pro-oxidant therapy and oxidative damage is of great value in exploiting next-generation OS-based anti-cancer chemotherapeutics.

Water extract of Notopterygium incisum alleviates cold allodynia in neuropathic pain by regulation of TRPA1

ETHNOPHARMACOLOGICAL RELEVANCE

Neuropathic pain can be debilitating and drastically affects the quality of life of those patients suffering from this condition. The Chinese herb Notopterygium incisum Ting ex H.T. Chang has long been used to disperse "cold". One under examined clinical feature of neuropathic pain is sensitivity to cold. Patients with neuropathic pain or arthritis usually describe a worsening of symptoms during the winter.

AIMS OF THIS STUDY

We proposed to test the hypothesis that Notopterygium incisum has a positive effect on the cold sensitivity found in neuropathic pain.

MATERIALS AND METHODS

In this study, we established chronic constriction injury (CCI) and cisplatin induced neuropathic pain mice models. Behavioral experiments and physiological examination methods were employed to investigate the effect of water extract of Notopterygium incisum (WN) on cold pain.

RESULTS

We found WN reduced cold pain and allyl isothiocyanate (AITC, Transient Receptor Potential A1 (TRPA1 agonist)) induced pain. WN inhibited AITC induced calcium response in HEK 293 cells transfected with TRPA1 and dorsal root ganglion (DRG) neurons. Moreover, we found that oral administration of WN reduced cold allodynia and mechanical allodynia caused by (CCI) and cisplatin induced neuropathic pain. We also observed that oral administration of WN decreased responses to AITC in DRG neurons as well as expression of TRPA1 in the WN treated neuropathic pain model.

CONCLUSIONS

The present study provide evidence that Notopterygium incisum alleviates cold allodynia in CCI and cisplatin induced neuropathic pain mouse models. WN alleviated neuropathic pain induced cold allodynia via directly modulating TRPA1. Our findings identify WN as a promising candidate for treating neuropathic pain that highlights a new mechanism of Notopterygium incisum on 'disperse cold'.

PGC1α: an emerging therapeutic target for chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN)-mediated paresthesias are a common complication in cancer patients undergoing chemotherapy. There are currently no treatments available to prevent or reverse CIPN. Therefore, new therapeutic targets are urgently needed to develop more effective analgesics. However, the pathogenesis of CIPN remains unclear, and the prevention and treatment strategies of CIPN are still unresolved issues in medicine. More and more studies have demonstrated that mitochondrial dysfunction has become a major factor in promoting the development and maintenance of CIPN, and peroxisome proliferator-activated receptor gamma (PPARγ) coactivator 1α (PGC1α) plays a significant role in maintaining the mitochondrial function, protecting peripheral nerves, and alleviating CIPN. In this review, we highlight the core role of PGC1α in regulating oxidative stress and maintaining normal mitochondrial function and summarize recent advances in its therapeutic effects and mechanisms in CIPN and other forms of peripheral neuropathy. Emerging studies suggest that PGC1α activation may positively impact CIPN mitigation by modulating oxidative stress, mitochondrial dysfunction, and inflammation. Therefore, novel therapeutic strategies targeting PGC1α could be a potential therapeutic target in CIPN.

Management of pain in patients with bone metastases

Cancer-induced bone pain (CIBP) has a considerable impact on patients’ quality of life as well as physical and mental health. At present, patients with CIBP are managed according to the three-step analgesic therapy algorithm proposed by the World Health Organization. Opioids are commonly used as the first-line treatment for moderate-to-severe cancer pain but are limited due to addiction, nausea, vomiting and other gastrointestinal side effects. Moreover, opioids have a limited analgesic effect in some patients. In order to optimize the management of CIBP, we must first identify the underlying mechanisms. In some patients, surgery, or surgery combined with radiotherapy or radiofrequency ablation is the first step in the management of CIBP. Various clinical studies have shown that anti-nerve growth factor (NGF) antibodies, bisphosphonates, or RANKL inhibitors can reduce the incidence and improve the management of cancer pain. Herein, we review the mechanisms of cancer pain and potential therapeutic strategies to provide insights for optimizing the management of CIBP.

Resolvin D1/N-formyl peptide receptor 2 ameliorates paclitaxel-induced neuropathic pain through the activation of IL-10/Nrf2/HO-1 pathway in mice

Introduction

Paclitaxel is a chemotherapy drug that is commonly used to treat cancer, but it can cause paclitaxel-induced neuropathic pain (PINP) as a side effect. Resolvin D1 (RvD1) has been shown to be effective in promoting the resolution of inflammation and chronic pain. In this study, we evaluated the effects of RvD1 on PINP and its underlying mechanisms in mice.

Methods

Behavioral analysis was used to assess the establishment of the PINP mouse model and to test the effects of RvD1 or other formulations on mouse pain behavior. Quantitative real-time polymerase chain reaction analysis was employed to detect the impact of RvD1 on 12/15 Lox, FPR2, and neuroinflammation in PTX-induced DRG neurons. Western blot analysis was used to examine the effects of RvD1 on FPR2, Nrf2, and HO-1 expression in DRG induced by PTX. TUNEL staining was used to detect the apoptosis of DRG neurons induced by BMDM conditioned medium. H2DCF-DA staining was used to detect the reactive oxygen species level of DRG neurons in the presence of PTX or RvD1+PTX treated BMDMs CM.

Results

Expression of 12/15-Lox was decreased in the sciatic nerve and DRG of mice with PINP, suggesting a potential involvement of RvD1 in the resolution of PINP. Intraperitoneal injection of RvD1 promoted pain resolution of PINP in mice. Intrathecal injection of PTX-treated BMDMs induced mechanical pain hypersensitivity in naïve mice, while pretreatment of RvD1 in BMDMs prevented it. Macrophage infiltration increased in the DRGs of PINP mice, but it was not affected by RvD1 treatment. RvD1 increased IL-10 expression in the DRGs and macrophages, while IL-10 neutralizing antibody abolished the analgesic effect of RvD1 on PINP. The effects of RvD1 in promoting IL-10 production were also inhibited by N-formyl peptide receptor 2 (FPR2) antagonist. The primary cultured DRG neurons apoptosis increased after stimulation with condition medium of PTX-treated BMDMs, but decreased after pretreatment with RvD1 in BMDMs. Finally, Nrf2-HO1 signaling was additionally activated in DRG neurons after stimulation with condition medium of RvD1+PTX-treated BMDMs, but these effects were abolished by FPR2 blocker or IL-10 neutralizing antibody.

Discussion

In conclusion, this study provides evidence that RvD1 may be a potential therapeutic strategy for the clinical treatment of PINP. RvD1/FPR2 upregulates IL-10 in macrophages under PINP condition, and then IL-10 activates the Nrf2- HO1 pathway in DRG neurons, relieve neuronal damage and PINP.

P66shc in the spinal cord is an important contributor in complete Freund's adjuvant induced inflammatory pain in mice

PURPOSE

The aim of this study is to investigate whether p66shc is involved in inflammatory pain and the potential molecular mechanisms of p66shc in inflammatory pain.

METHODS

Inflammatory pain model was established by complete Freund's adjuvant (CFA) injection. Paw withdrawal latency (PWL) and paw withdrawal frequency (PWF) was recorded. The expression of spinal p66shc were determined by immunohistochemical staining, immunofluorescence staining. P66shc knockdown was performed by an adeno-associated virus (AAV) vector infusion. NLRP3 inflammasome complexes were determined by Western blot. DHE staining was used to evaluate reactive oxygen species (ROS) generation.

RESULTS

P66Shc expression was progressively elevated in spinal cord of inflammatory pain mice, and p66Shc knockdown in vivo significantly attenuated CFA injection triggers hyperalgesia. Furthermore, knockdown of p66Shc significantly inhibited ROS production and NOD-like receptor protein 3 (NLRP3) inflammasome activation, which were reversed by a ROS donor (t-BOOH). However, post-treatment with nigericin, a agonist of NLRP3, reversed AAV-shP66shc analgesic effect.

CONCLUSION

Spinal p66shc may facilitate the development of inflammatory pain by promoting the activation of NLRP3 inflammasome through ROS.

Ozone in Chemotherapy-Induced Peripheral Neuropathy—Current State of Art, Possibilities, and Perspectives

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most detrimental toxicity to a patient’s quality of life. Pathophysiological mechanisms involved in CIPN pathogenesis are complex, multifactorial, and only partially examined. They are suspected to be associated with oxidative stress (OS), mitochondrial dysfunction, ROS-induced apoptosis, myelin sheath and DNA damage, and immunological and inflammatory processes. Unfortunately, medications commonly used for the management of other neuropathic pain syndromes, including gabapentinoids, opioids, and tricyclic antidepressants (such as desipramine and nortriptyline), do not bring satisfactory results in CIPN. The aim of this review is to evaluate the existing literature on the potential use of medical ozone as a treatment for CIPN. This paper would explore the potential therapeutic benefits of medical ozone. The review would evaluate the existing literature on the use of medical ozone in other contexts, as well as its potential application in treating CIPN. The review would also suggest possible research methods, such as randomized controlled trials, to evaluate the efficacy of medical ozone as a treatment for CIPN. Medical ozone has been used to disinfect and treat diseases for over 150 years. The effectiveness of ozone in treating infections, wounds, and a variety of diseases has been well documented. Ozone therapy is also documented to inhibit the growth of human cancer cells and has antioxidative and anti-inflammatory effects. Due to its ability to modulate oxidative stress, inflammation, and ischemia/hypoxia, ozone may have a potentially valuable effect on CIPN.

The Therapeutic Potential of Antioxidants in Chemotherapy-Induced Peripheral Neuropathy: Evidence from Preclinical and Clinical Studies

As cancer therapies advance and patient survival improves, there has been growing concern about the long-term adverse effects that patients may experience following treatment, and concerns have been raised about such persistent, progressive, and often irreversible adverse effects. Chemotherapy is a potentially life-extending treatment, and chemotherapy-induced peripheral neuropathy (CIPN) is one of its most common long-term toxicities. At present, strategies for the prevention and treatment of CIPN are still an open problem faced by medicine, and there has been a large amount of previous evidence that oxidative damage is involved in the process of CIPN. In this review, we focus on the lines of defense involving antioxidants that exert the effect of inhibiting CIPN. We also provide an update on the targets and clinical prospects of different antioxidants (melatonin, N-acetylcysteine, vitamins, α-lipoic acid, mineral elements, phytochemicals, nutritional antioxidants, cytoprotectants and synthetic compounds) in the treatment of CIPN with the help of preclinical and clinical studies, emphasizing the great potential of antioxidants as adjuvant strategies to mitigate CIPN.

Gonadal hormone-dependent nociceptor sensitization maintains nociplastic pain state in female mice

ABSTRACT

Nociplastic pain conditions develop predominantly in women. We recently established a murine nociplastic pain model by applying postinjury thermal (40°C) stimulation to an injured (capsaicin-injected) area, triggering a transition to a nociplastic pain state manifesting as persistent mechanical hypersensitivity outside of the previously injured area. The nociplastic pain state was centrally maintained by spinal microglia in males but peripherally by ongoing afferent activity at the previously injured area in females. Here, we investigated whether gonadal hormones are critical for the development of this peripherally maintained nociplastic pain state in females. Although the transition to a nociplastic pain state still occurred in ovariectomized females, the pain state was maintained neither by ongoing afferent activity at the previously injured area nor by spinal microglia. Estradiol reconstitution a week before the injury plus postinjury stimulation, but not after the transition had already occurred, restored the development of peripherally maintained nociplastic mechanical hypersensitivity in ovariectomized females. G protein-coupled estrogen receptor antagonism during the transition phase mimicked ovariectomy in gonad-intact females, whereas the receptor antagonism after the transition gradually alleviated the nociplastic mechanical hypersensitivity. At the previously injured area, afferents responsive to allyl isothiocyanate (AITC), a TRPA1 agonist, contributed to the maintenance of nociplastic mechanical hypersensitivity in gonad-intact females. In ex vivo skin-nerve preparations, only AITC-responsive afferents from the nociplastic pain model in gonad-intact females showed ongoing activities greater than control. These results suggest that gonadal hormones are critical for peripherally maintained nociplastic pain state in females by sensitizing AITC-responsive afferents to be persistently active.

Soluble epoxide hydrolase inhibition alleviates chemotherapy induced neuropathic pain

Chemotherapy induced peripheral neuropathy (CIPN) is a particularly pernicious form of neuropathy and the associated pain is the primary dose-limiting factor of life-prolonging chemotherapy treatment. The prevalence of CIPN is high and can last long after treatment has been stopped. Currently, late in the COVID-19 pandemic, there are still increased psychological pressures on cancer patients as well as additional challenges in providing analgesia for them. These include the risks of nonsteroidal anti-inflammatory drug (NSAID) analgesics potentially masking early infection symptoms and the immunosuppression of steroidal and opiate based approaches. Even without these concerns, CIPN is often inadequately treated with few therapies that offer significant pain relief. The experiments we report use soluble epoxide hydrolase inhibitors (sEHI) which relieved this intractable pain in preclinical models. Doses of EC5026, an IND candidate intended to treat neuropathic pain, elicited dose dependent analgesic responses in multiple models including platinum-based, taxane, and vinca alkaloid-based CIPN pain in Sprague Dawley rats. At the same time as a class, the sEHI are known to result in fewer debilitating side effects of other analgesics, likely due to their novel mechanism of action. Overall, the observed dose-dependent analgesia in both male and female rats across multiple models of chemotherapy induced neuropathic pain holds promise as a useful tool when translated to the clinic.

Neuropathy, its Profile and Experimental Nerve Injury Neuropathic Pain Models: A Review

Neuropathy is a terrible disorder that has a wide range of etiologies. Drug-induced neuropathy, which happens whenever a chemical agent damages the peripheral nerve system, has been linked here to the iatrogenic creation of some drugs. It is potentially permanent and causes sensory impairments and paresthesia that typically affects the hands, feet, and stockings; motor participation is uncommon. It might appear suddenly or over time, and the long-term outlook varies. The wide range of chronic pain conditions experienced by people has been one of the main obstacles to developing new, more effective medications for the treatment of neuropathic pain. Animal models can be used to examine various neuropathic pain etiologies and symptoms. Several models investigate the peripheral processes of neuropathic pain, whereas some even investigate the central mechanisms, such as drug induce models like vincristine, cisplatin, bortezomib, or thalidomide, etc., and surgical models like sciatic nerve chronic constriction injury (CCI), sciatic nerve ligation through spinal nerve ligation (SNL), sciatic nerve damage caused by a laser, SNI (spared nerve injury), etc. The more popular animal models relying on peripheral nerve ligatures are explained. In contrast to chronic sciatic nerve contraction, which results in behavioral symptoms of less reliable stressful neuropathies, (SNI) spared nerve injury generates behavioral irregularities that are more feasible over a longer period. This review summarizes the latest methods models as well as clinical ideas concerning this mechanism. Every strongest current information on neuropathy is discussed, along with several popular laboratory models for causing neuropathy.

Quercetin Ameliorates Neuropathic Pain after Brachial Plexus Avulsion via Suppressing Oxidative Damage through Inhibition of PKC/MAPK/ NOX Pathway

BACKGROUND

Brachial plexus avulsion (BPA) animally involves the separation of spinal nerve roots themselves and the correlative spinal cord segment, leading to formidable neuropathic pain of the upper limb.

METHODS

The right seventh cervical (C7) ventral and dorsal roots were avulsed to establish a neuropathic pain model in rats. After operation, rats were treated with quercetin (QCN) by intragastric administration for 1 week. The effects of QCN were evaluated using mechanical allodynia tests and biochemical assay kits.

RESULTS

QCN treatment significantly attenuated the avulsion-provoked mechanical allodynia, elevated the levels of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) and total antioxidant capacity (TAC) in the C7 spinal dorsal horn. In addition, QCN administration inhibited the activations of macrophages, microglia and astrocytes in the C6 dorsal root ganglion (DRG) and C6-8 spinal dorsal horn, as well as attenuated the release of purinergic 2X (P2X) receptors in C6 DRG. The molecular mechanism underlying the above alterations was found to be related to the suppression of the PKC/MAPK/NOX signal pathway. To further study the anti-oxidative effects of QCN, we applied QCN on the H2O2-induced BV-2 cells in vitro, and the results attested that QCN significantly ameliorated the H2O2-induced ROS production in BV-2 cells, inhibited the H2O2-induced activation of PKC/MAPK/NOX pathway.

CONCLUSION

Our study for the first time provided evidence that QCN was able to attenuate pain hypersensitivity following the C7 spinal root avulsion in rats, and the molecular mechanisms involve the reduction of both neuro-inflammatory infiltration and oxidative stress via suppression of P2X receptors and inhibition of the activation of PKC/MAPK/NOX pathway. The results indicate that QCN is a natural compound with great promise worthy of further development into a novel therapeutic method for the treatment of BPA-induced neuropathic pain.

A mechanistic understanding of the relationship between skin innervation and chemotherapy-induced neuropathic pain

Neuropathic pain is a frequent complication of chemotherapy-induced peripheral neurotoxicity (CIPN). Chemotherapy-induced peripheral neuropathies may serve as a model to study mechanisms of neuropathic pain, since several other common causes of peripheral neuropathy like painful diabetic neuropathy may be due to both neuropathic and non-neuropathic pain mechanisms like ischemia and inflammation. Experimental studies are ideally suited to study changes in morphology, phenotype and electrophysiologic characteristics of primary afferent neurons that are affected by chemotherapy and to correlate these changes to behaviors reflective of evoked pain, mainly hyperalgesia and allodynia. However, hyperalgesia and allodynia may only represent one aspect of human pain, i.e., the sensory-discriminative component, while patients with CIPN often describe their pain using words like annoying, tiring and dreadful, which are affective-emotional descriptors that cannot be tested in experimental animals. To understand why some patients with CIPN develop neuropathic pain and others not, and which are the components of neuropathic pain that they are experiencing, experimental and clinical pain research should be combined. Emerging evidence suggests that changes in subsets of primary afferent nerve fibers may contribute to specific aspects of neuropathic pain in both preclinical models and in patients with CIPN. In addition, the role of cutaneous neuroimmune interactions is considered. Since obtaining dorsal root ganglia and peripheral nerves in patients is problematic, analyses performed on skin biopsies from preclinical models as well as patients provide an opportunity to study changes in primary afferent nerve fibers and to associate these changes to human pain. In addition, other biomarkers of small fiber damage in CIPN, like corneal confocal microscope and quantitative sensory testing, may be considered.