The chemotherapeutic oxaliplatin alters voltage-gated Na(+) channel kinetics on rat sensory neurons

Schwann cell transient receptor potential ankyrin 1 (TRPA1) ortholog in zebrafish larvae mediates chemotherapy-induced peripheral neuropathy

BACKGROUND AND PURPOSE

The oxidant sensor transient receptor potential ankyrin 1 (TRPA1) channel expressed by Schwann cells (SCs) has recently been implicated in several models of neuropathic pain in rodents. Here we investigate whether the pro-algesic function of Schwann cell TRPA1 is not limited to mammals by exploring the role of TRPA1 in a model of chemotherapy-induced peripheral neuropathy (CIPN) in zebrafish larvae.

EXPERIMENTAL APPROACH

We used zebrafish larvae and a mouse model to test oxaliplatin-evoked nociceptive behaviours. We also performed a TRPA1 selective silencing in Schwann cells both in zebrafish larvae and mice to study their contribution in oxaliplatin-induced CIPN model.

KEY RESULTS

We found that zebrafish larvae and zebrafish TRPA1 (zTRPA1)-transfected HEK293T cells respond to reactive oxygen species (ROS) with nociceptive behaviours and intracellular calcium increases, respectively. TRPA1 was found to be co-expressed with the Schwann cell marker, SOX10, in zebrafish larvae. Oxaliplatin caused nociceptive behaviours in zebrafish larvae that were attenuated by a TRPA1 antagonist and a ROS scavenger. Oxaliplatin failed to produce mechanical allodynia in mice with Schwann cell TRPA1 selective silencing (Plp1+-Trpa1 mice). Comparable results were observed in zebrafish larvae where TRPA1 selective silencing in Schwann cells, using the specific Schwann cell promoter myelin basic protein (MBP), attenuated oxaliplatin-evoked nociceptive behaviours.

CONCLUSION AND IMPLICATIONS

These results indicate that the contribution of the oxidative stress/Schwann cell/TRPA1 pro-allodynic pathway to neuropathic pain models seems to be conserved across the animal kingdom.

Ion Channel and Transporter Involvement in Chemotherapy-Induced Peripheral Neurotoxicity

The peripheral nervous system can encounter alterations due to exposure to some of the most commonly used anticancer drugs (platinum drugs, taxanes, vinca alkaloids, proteasome inhibitors, thalidomide), the so-called chemotherapy-induced peripheral neurotoxicity (CIPN). CIPN can be long-lasting or even permanent, and it is detrimental for the quality of life of cancer survivors, being associated with persistent disturbances such as sensory loss and neuropathic pain at limb extremities due to a mostly sensory axonal polyneuropathy/neuronopathy. In the state of the art, there is no efficacious preventive/curative treatment for this condition. Among the reasons for this unmet clinical and scientific need, there is an uncomplete knowledge of the pathogenetic mechanisms. Ion channels and transporters are pivotal elements in both the central and peripheral nervous system, and there is a growing body of literature suggesting that they might play a role in CIPN development. In this review, we first describe the biophysical properties of these targets and then report existing data for the involvement of ion channels and transporters in CIPN, thus paving the way for new approaches/druggable targets to cure and/or prevent CIPN.

Single and Combined Effects of Cannabigerol (CBG) and Cannabidiol (CBD) in Mouse Models of Oxaliplatin-Associated Mechanical Sensitivity, Opioid Antinociception, and Naloxone-Precipitated Opioid Withdrawal

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most prevalent and dose-limiting complications in chemotherapy patients, with estimates of at least 30% of patients experiencing persistent neuropathy for months or years after treatment cessation. An emerging potential intervention for the treatment of CIPN is cannabinoid-based pharmacotherapies. We have previously demonstrated that treatment with the psychoactive CB1/CB2 cannabinoid receptor agonist Δ9-tetrahydrocannabinol (Δ9-THC) or the non-psychoactive, minor phytocannabinoid cannabidiol (CBD) can attenuate paclitaxel-induced mechanical sensitivity in a mouse model of CIPN. We then showed that the two compounds acted synergically when co-administered in the model, giving credence to the so-called entourage effect. We and others have also demonstrated that CBD can attenuate several opioid-associated behaviors. Most recently, it was reported that another minor cannabinoid, cannabigerol (CBG), attenuated cisplatin-associated mechanical sensitivity in mice. Therefore, the goals of the present set of experiments were to determine the single and combined effects of cannabigerol (CBG) and cannabidiol (CBD) in oxaliplatin-associated mechanical sensitivity, naloxone-precipitated morphine withdrawal, and acute morphine antinociception in male C57BL/6 mice. Results demonstrated that CBG reversed oxaliplatin-associated mechanical sensitivity only under select dosing conditions, and interactive effects with CBD were sub-additive or synergistic depending upon dosing conditions too. Pretreatment with a selective α2-adrenergic, CB1, or CB2 receptor selective antagonist significantly attenuated the effect of CBG. CBG and CBD decreased naloxone-precipitated jumping behavior alone and acted synergistically in combination, while CBG attenuated the acute antinociceptive effects of morphine and CBD. Taken together, CBG may have therapeutic effects like CBD as demonstrated in rodent models, and its interactive effects with opioids or other phytocannabinoids should continue to be characterized.

DRG Explant Model: Elucidating Mechanisms of Oxaliplatin-Induced Peripheral Neuropathy and Identifying Potential Therapeutic Targets

Oxaliplatin triggered chemotherapy induced peripheral neuropathy (CIPN) is a common and debilitating side effect of cancer treatment which limits the efficacy of chemotherapy and negatively impacts patients quality of life dramatically. For better understanding the mechanisms of CIPN and screen for potential therapeutic targets, it is critical to have reliable in vitro assays that effectively mirror the neuropathy in vivo . In this study, we established a dorsal root ganglia (DRG) explant model. This model displayed dose-dependent inhibition of neurite outgrowth in response to oxaliplatin, while oxalic acid exhibited no significant impact on the regrowth of DRG. The robustness of this assay was further demonstrated by the inhibition of OCT2 transporter, which facilitates oxaliplatin accumulation in neurons, fully restoring the neurite regrowth capacity. Using this model, we revealed that oxaliplatin triggered a substantial increase of oxidative stress in DRG. Notably, inhibition of TXNIP with verapamil significantly reduced oxidative stress level. Our results demonstrated the use of DRG explants as an efficient model to study the mechanisms of CIPN and screen for potential treatments.

Neuromuscular blockade characteristics of cisatracurium in patients receiving chemotherapy: A preliminary study in breast cancer patients

Background and Aims

Cancer chemotherapeutic agents cause alteration in the response to neuromuscular blocking drugs, which can have serious perioperative implications. Magnesium, commonly found to be deficient in these patients, plays an indispensable role in neuromuscular transmission. This study aimed to understand the effect of neoadjuvant chemotherapy on the neuromuscular blocking properties of cisatracurium.

Material and Methods

One hundred female patients scheduled for breast cancer surgery were divided into two groups (n = 50 each). Group B received neoadjuvant chemotherapy with taxane, adriamycin, and cyclophosphamide, and Group A did not receive neoadjuvant chemotherapy. Neuromuscular block following cisatracurium 0.15 mg/kg was measured using peripheral nerve stimulator at the ulnar nerve. Onset time, duration of intense block, clinical duration of action, time to TOF4 after the last dose of cisatracurium, along with preoperative serum magnesium concentration were measured. Correlation and multiple regression were run to analyze the relationship between history of neoadjuvant chemotherapy, preoperative magnesium, and the abovementioned time points. Mediation analysis was done to ascertain if magnesium was mediating the observed effects.

Results

Onset time was prolonged by nearly 18% in Group B compared to Group A (P = 0.001). The duration of intense block was 35.27 ± 8.9 min in Group B and 42.07 ± 10.99 min in Group A (P < 0.001). The clinical duration of action of cisatracurium was significantly shorter in Group B (46.06 ± 8.68 min) compared to Group A (55.87 ± 11.04 min, P < 0.001). The time to TOF4 was 32.86 ± 5.66 min in Group B and 36.57 ± 8.49 min in Group A (P < 0.05). Preoperative serum magnesium levels were significantly lower in Group B (P < 0.001).

Conclusion

Patients who had received neoadjuvant chemotherapy had a delayed onset, shorter duration of action, and faster recovery for cisatracurium. Although preoperative magnesium levels were lower in Group B, it was found to be an independent predictor rather than a mediator of these effects.

The elusive Nav1.7: From pain to cancer

Voltage-gated sodium channels (Nav) are protein complexes that play fundamental roles in the transmission of signals in the nervous system, at the neuromuscular junction and in the heart. They are mainly present in excitable cells where they are responsible for triggering action potentials. Dysfunctions in Nav ion conduction give rise to a wide range of conditions, including neurological disorders, hypertension, arrhythmia, pain and cancer. Nav family 1 is composed of nine members, named numerically from 1 to 9. A Nax family also exists and is involved in body-fluid homeostasis. Of particular interest is Nav1.7 which is highly expressed in the sensory neurons of the dorsal root ganglions, where it is involved in the propagation of pain sensation. Gain-of-function mutations in Nav1.7 cause pathologies associated with increased pain sensitivity, while loss-of-function mutations cause reduced sensitivity to pain. The last decade has seen considerable effort in developing highly specific Nav1.7 blockers as pain medications, nonetheless, sufficient efficacy has yet to be achieved. Evidence is now conclusively showing that Navs are also present in many types of cancer cells, where they are involved in cell migration and invasiveness. Nav1.7 is anomalously expressed in endometrial, ovarian and lung cancers. Nav1.7 is also involved in Chemotherapy Induced Peripheral Neuropathy (CIPN). We propose that the knowledge and tools developed to study the role of Nav1.7 in pain can be exploited to develop novel cancer therapies. In this chapter, we illustrate the various aspects of Nav1.7 function in pain, cancer and CIPN, and outline therapeutic approaches.

Statins enhances antitumor effect of oxaliplatin in KRAS-mutated colorectal cancer cells and inhibits oxaliplatin-induced neuropathy

BACKGROUND

KRAS mutations are fraught with the progression of colorectal cancer and resistance to chemotherapy. There are pathways such as extracellular regulated protein kinase 1/2 (ERK1/2) and Akt downstream and farnesylation and geranylgeranylation upstream that are activated upon mutated KRAS. Previous studies have shown that statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, are effective to treat KRAS mutated colorectal cancer cells. Increased doses of oxaliplatin (L-OHP), a well-known alkylating chemotherapeutic drug, causes side effects such as peripheral neuropathy due to ERK1/2 activation in spinal cords. Hence, we examined the combinatorial therapeutic efficacy of statins and L-OHP to reduce colorectal cancer cell growth and abrogate neuropathy in mice.

METHODS

Cell survival and confirmed apoptosis was assessed using WST-8 assay and Annexin V detection kit. Detection of phosphorylated and total proteins was analyzed the western blotting. Combined effect of simvastatin and L-OHP was examined the allograft mouse model and L-OHP-induced neuropathy was assessed using cold plate and von Frey filament test.

RESULTS

In this study, we examined the effect of combining statins with L-OHP on induction of cell death in colorectal cancer cell lines and improvement of L-OHP-induced neuropathy in vivo. We demonstrated that combined administration with statins and L-OHP significantly induced apoptosis and elevated the sensitivity of KRAS-mutated colorectal cancer cells to L-OHP. In addition, simvastatin suppressed KRAS prenylation, thereby enhancing antitumor effect of L-OHP through downregulation of survivin, XIAP, Bcl-xL, and Bcl-2, and upregulation of p53 and PUMA via inhibition of nuclear factor of κB (NF-κB) and Akt activation, and induction of c-Jun N-terminal kinase (JNK) activation in KRAS-mutated colorectal cancer cells. Moreover, simvastatin enhanced the antitumor effects of L-OHP and suppressed L-OHP-induced neuropathy via ERK1/2 activation in vivo.

CONCLUSION

Therefore, statins may be therapeutically useful as adjuvants to L-OHP in KRAS-mutated colorectal cancer and may also be useful in the treatment of L-OHP-induced neuropathy.

Effect of cisplatin on respiratory activity in neonatal rats

One side effect of cisplatin, a cytotoxic platinum anticancer drug, is peripheral neuropathy; however, its central nervous system effects remain unclear. We monitored respiratory nerve activity from the C4 ventral root in brainstem and spinal cord preparations from neonatal rats (P0-3) to investigate its central effects. Bath application of 10-100 μM cisplatin for 15-20 min dose-dependently decreased the respiratory rate and increased the amplitude of C4 inspiratory activity. These effects were not reversed after washout. In separate perfusion experiments, cisplatin application to the medulla decreased the respiratory rate, and application to the spinal cord increased the C4 burst amplitude without changing the burst rate. Application of other platinum drugs, carboplatin or oxaliplatin, induced no change of respiratory activity. A membrane potential analysis of respiratory-related neurons in the rostral medulla showed that firing frequencies of action potentials in the burst phase tended to decrease during cisplatin application. In contrast, in inspiratory spinal motor neurons, cisplatin application increased the peak firing frequency of action potentials during the inspiratory burst phase. The increased burst amplitude and decreased respiratory frequency were partially antagonized by riluzole and picrotoxin, respectively. Taken together, cisplatin inhibited respiratory rhythm via medullary inhibitory system activation and enhanced inspiratory motor nerve activity by changing the firing property of motor neurons.

Neurological Complications of Conventional and Novel Anticancer Treatments

Various neurological complications, affecting both the central and peripheral nervous system, can frequently be experienced by cancer survivors after exposure to conventional chemotherapy, but also to modern immunotherapy. In this review, we provide an overview of the most well-known adverse events related to chemotherapy, with a focus on chemotherapy induced peripheral neurotoxicity, but we also address some emerging novel clinical entities related to cancer treatment, including chemotherapy-related cognitive impairment and immune-mediated adverse events. Unfortunately, efficacious curative or preventive treatment for all these neurological complications is still lacking. We provide a description of the possible mechanisms involved to drive future drug discovery in this field, both for symptomatic treatment and neuroprotection.

Sodium-Calcium Exchanger 2: A Pivotal Role in Oxaliplatin Induced Peripheral Neurotoxicity and Axonal Damage?

Oxaliplatin (OHP)-induced peripheral neurotoxicity (OIPN) is a frequent adverse event of colorectal cancer treatment. OIPN encompasses a chronic and an acute syndrome. The latter consists of transient axonal hyperexcitability, due to unbalance in Na+ voltage-operated channels (Na+VOC). This leads to sustained depolarisation which can activate the reverse mode of the Na+/Ca2+ exchanger 2 (NCX2), resulting in toxic Ca2+ accumulation and axonal damage (ADa). We explored the role of NCX2 in in vitro and in vivo settings. Embryonic rat Dorsal Root Ganglia (DRG) organotypic cultures treated with SEA0400 (SEA), a NCX inhibitor, were used to assess neuroprotection in a proof-of-concept and pilot study to exploit NCX modulation to prevent ADa. In vivo, OHP treated mice (7 mg/Kg, i.v., once a week for 8 weeks) were compared with a vehicle-treated group (n = 12 each). Neurophysiological and behavioural testing were performed to characterise acute and chronic OIPN, and morphological analyses were performed to detect ADa. Immunohistochemistry, immunofluorescence, and western blotting (WB) analyses were also performed to demonstrate changes in NCX2 immunoreactivity and protein expression. In vitro, NCX inhibition was matched by ADa mitigation. In the in vivo part, after verifyingboth acute and chronic OIPN had ensued, we confirmed via immunohistochemistry, immunofluorescence, and WB that a significant NCX2 alteration had ensued in the OHP group. Our data suggest NCX2 involvement in ADa development, paving the way to a new line of research to prevent OIPN.

Arrhythmic Complications Associated with Cancer Therapies

Over the last several decades, advancements in cancer screening and treatment have significantly improved cancer mortality and overall quality of life. Unfortunately, non-cancer-related side effects, including cardiovascular toxicities can impact the continued delivery of these treatments. Arrhythmias are an increasingly recognized class of cardiotoxicity that can occur as a direct consequence of the treatment or secondary to another type of toxicity such as heart failure, myocarditis, or ischemia. Atrial arrhythmias, particularly atrial fibrillation (AF) are most commonly encountered, however, ventricular- and bradyarrhythmias can also occur, albeit at lower rates. Treatment strategies tailored to patients with cancer are essential to allow for the safe delivery of the cancer treatment without affecting short- or long-term oncologic or cardiovascular outcomes.

Antioxidant and Neuroprotective Effect of a Grape Pomace Extract on Oxaliplatin-Induced Peripheral Neuropathy in Rats: Biochemical, Behavioral and Histopathological Evaluation

Oxaliplatin is a widely used chemotherapeutic agent. Despite its many beneficial aspects in fighting many malignancies, it shares an aversive effect of neuropathy. Many substances have been used to limit this oxaliplatin-driven neuropathy in patients. This study evaluates the neuroprotective role of a grape pomace extract (GPE) into an oxaliplatin induced neuropathy in rats. For this reason, following the delivery of the substance into the animals prior to or simultaneously with oxaliplatin, their performance was evaluated by behavioral tests. Blood tests were also performed for the antioxidant activity of the extract, along with a histological and pathological evaluation of dorsal root ganglion (DRG) cells as the major components of the neuropathy. All behavioral tests were corrected following the use of the grape pomace. Oxidative stressors were also limited with the use of the extract. Additionally, the morphometrical analysis of the DRG cells and their immunohistochemical phenotype revealed the fidelity of the animal model and the changes into the parvalbumin and GFAP concentration indicative of the neuroprotective role of the pomace. In conclusion, the grape pomace extract with its antioxidant properties alleviates the harmful effects of the oxaliplatin induced chronic neuropathy in rats.

Characterization of Patients With and Without Painful Peripheral Neuropathy After Receiving Neurotoxic Chemotherapy: Traditional Quantitative Sensory Testing vs C-Fiber and Aδ-Fiber Selective Diode Laser Stimulation

Painful chemotherapy induced peripheral neuropathy (CIPN) is a common complication of chemotherapy with drugs such as taxanes and platinum compounds. Currently, no methods are available for early detection of sensory changes that are associated with painful CIPN, nor are there biomarkers that are specific to painful CIPN. This study aimed to compare Diode Laser fiber type-selective stimulator (DLss), a method to selectively stimulate cutaneous C and Aδ fibers, to traditional quantitative sensory testing (QST) in determining psychophysical differences between patients with painful CIPN and a control group. Sensory testing was performed on the dorsal mid-foot of 20 patients with painful neuropathy after taxane- or platinum-based chemotherapy, and 20 patients who received similar neurotoxic chemotherapy, without painful CIPN. In a multivariable analysis, C-fiber to Aδ fiber detection threshold ratio, measured by DLss, was significantly different between the groups (P <.05). While QST parameters such as warmth detection threshold were different between the groups in univariate analyses, these findings were likely attributable to group differences in patient age and cumulative chemotherapy dose. PERSPECTIVE: In this study, fiber-specific DLss test showed potential in identifying sensory changes that are specific for painful neuropathy, encouraging future testing of this approach as a biomarker for early detection of painful CIPN. TRIAL REGISTRATION: The study was approved by the Washington University Institutional Review Board (#201807162) and registered at ClinicalTrials.gov (NCT03687970).

Dorsal root ganglion toll-like receptor 4 signaling contributes to oxaliplatin-induced peripheral neuropathy

ABSTRACT

Activation of toll-like receptor 4 (TLR4) in the dorsal root ganglion (DRG) and spinal cord contributes to the generation of paclitaxel-related chemotherapy-induced peripheral neuropathy (CIPN). Generalizability of TLR4 signaling in oxaliplatin-induced CIPN was tested here. Mechanical hypersensitivity developed in male SD rats by day 1 after oxaliplatin treatment, reached maximum intensity by day 14, and persisted through day 35. Western blot revealed an increase in TLR4 expression in the DRG of oxaliplatin at days 1 and 7 after oxaliplatin treatment. Cotreatment of rats with the TLR4 antagonist lipopolysaccharide derived from Rhodobacter sphaeroides ultrapure or with the nonspecific immunosuppressive minocycline with oxaliplatin resulted in significantly attenuated hyperalgesia on day 7 and 14 compared with rats that received oxaliplatin plus saline vehicle. Immunostaining of DRGs revealed an increase in the number of neurons expressing TLR4, its canonical downstream signal molecules myeloid differentiation primary response gene 88 (MyD88) and TIR-domain-containing adapter-inducing interferon-β, at both day 7 and day 14 after oxaliplatin treatment. These increases were blocked by cotreatment with either lipopolysaccharide derived from Rhodobacter sphaeroides or minocycline. Double staining showed the localization of TLR4, MyD88, and TIR-domain-containing adapter-inducing interferon-β in subsets of DRG neurons. Finally, there was no significant difference in oxaliplatin-induced mechanical hypersensitivity between male and female rats when observed for 2 weeks. Furthermore, upregulation of TLR4 was detected in both sexes when tested 14 days after treatment with oxaliplatin. These findings suggest that the activation of TLR4 signaling in DRG neurons is a common mechanism in CIPN induced by multiple cancer chemotherapy agents.

Oxaliplatin-induced neuropathy and colo-rectal cancer patient’s quality of life: Practical lessons from a prospective cross-sectional, real-world study

BACKGROUND

Colon cancer is one the most common forms of cancer in both sexes. Due to important progress in the field of early detection and effective treatment, colon and rectal cancer survivors currently account for 10% of cancer survivors worldwide. However, the effects of anti-cancer treatments, especially oxaliplatin-based chemotherapy, on the quality of life (QoL) have been less evaluated. Although the incidence of severe chemotherapy-induced neuropathy (CIPN) in clinical studies is below 20%, data from real-world studies is scarce, and CIPN is probably under-reported due to patient selection and the patients’ fear that reporting side-effects might lead to treatment cessation.

AIM

To determine the impact of CIPN on QoL in colorectal cancer patients with a recent history of oxaliplatin-based chemotherapy.

METHODS

We performed a prospective cross-sectional study in two major Romanian oncology tertiary hospitals—the Regional Institute of Oncology Iași (Iasi, Romania) and the Fundeni Clinical Oncology Institute (Bucharest, Romania). All consecutive patients with colon or rectal cancer, undergoing Oxaliplatin-based chemotherapy that consented to enroll in the study, were assessed by means of two questionnaires—the EORTC QQ-CR29 (quality of life in colon and rectal cancer patients) and the QLQ-CIPN20 (assessment of neuropathy). Several demographical, social, clinical and treatment data were also collected. Statistical analysis was performed by means of SPSS v20. The student t test was used to assess the relationship between the QLQ-CIPN20 and QLQ-CR29 results. Kaplan Meyer-curves were used to report 3-year progression-free survival (PFS) in patients that discontinued chemotherapy vs those that completed the recommended course.

RESULTS

Of the 267 patients that fulfilled the inclusion criteria in the pre-specified time frame, 101 (37.8%) agreed to participate in the clinical study. At the time of the enrolment in the study, over 50% of the patients had recently interrupted their oxaliplatin-based chemotherapy, most often due to neuropathy. Almost 85% of the responders reported having tingling or numbness in their fingers or hands, symptoms that were associated with pain in over 20% of the cases. When comparing the scores in the two questionnaires, a statistically significant relationship (P < 0.001) was found between the presence of neuropathic symptoms and a decreased quality of life. This correlation was consistent when the patients were stratified by sex, disease stage, comorbidities and the presence of stoma or treatment type, suggesting that neuropathy in itself may be a reason for a decreased quality of life. At the 3 year final assessment, median recurrence-free survival in stage III patients was 26.88 mo. When stratified by completion of chemotherapy, median recurrence free-survival of stage III patients that completed chemotherapy was 28.27 mo vs 24.33 mo in patients that discontinued chemotherapy due to toxicity, a difference that did not reach statistical significance.

CONCLUSION

CIPN significantly impacts QoL in colorectal cancer patients. CIPN is also the most frequent reason for treatment discontinuation. Physicians should actively assess for CIPN in order to prevent chronic neuropathy.

Severe Generalized Weakness, Paraplegia following administration of Oxaliplatin in a patient with refractory T-cell non-Hodgkin lymphoma: A case report

INTRODUCTION

Oxaliplatin is a third-generation platinum compound that used extensively for the treatment of various types of cancer especially gastrointestinal neoplasms. The main dose-limiting toxicities of oxaliplatin are hematological toxicity and peripheral sensory neuropathy.

CASE REPORT

A 42-year-old man with refractory peripheral T-cell lymphoma (PTCL) was admitted to receive GEMOX chemotherapy regimen (gemcitabine, oxaliplatin). Three days after receiving his third cycle of chemotherapy regimen, he was re-admitted to the emergency department with complaint of severe generalized weakness, and paraplegia in the lower extremities. According to clinical and para-clinical findings, chronic sensorimotor polyneuropathy with ongoing axonal loss was confirmed.

MANAGEMENT & OUTCOME

Intravenous dexamethasone 8 mg three times daily was started at the time of admission for the patient. Muscle weakness and sensory impairment improved dramatically within 10 days and the patient was able to walk with assistance.

DISCUSSION

Several cases of neuropathy following oxaliplatin and only one case with gemcitabine-based chemotherapy regimen have been previously reported. However, motor symptoms are rare unless in the setting of acute neuropathy due to oxaliplatin. The most striking finding of our study was the incidence of a chronic sensorimotor axonaldemyelinating polyneuropathy in a patient who were subjected to oxaliplatin therapy. In conclusion, we report a case of severe generalized weakness and paraplegia following administration of Oxaliplatin.

OUP accepted manuscript

In vitro models of the peripheral nervous system would benefit from further refinements to better support studies on neuropathies. In particular, the assessment of pain-related signals is still difficult in human cell cultures. Here, we harnessed induced pluripotent stem cells (iPSCs) to generate peripheral sensory neurons enriched in nociceptors. The objective was to generate a culture system with signaling endpoints suitable for pharmacological and toxicological studies. Neurons generated by conventional differentiation protocols expressed moderate levels of P2X3 purinergic receptors and only low levels of TRPV1 capsaicin receptors, when maturation time was kept to the upper practically useful limit of 6 weeks. As alternative approach, we generated cells with an inducible NGN1 transgene. Ectopic expression of this transcription factor during a defined time window of differentiation resulted in highly enriched nociceptor cultures, as determined by functional (P2X3 and TRPV1 receptors) and immunocytochemical phenotyping, complemented by extensive transcriptome profiling. Single cell recordings of Ca²⁺-indicator fluorescence from >9000 cells were used to establish the “fraction of reactive cells” in a stimulated population as experimental endpoint, that appeared robust, transparent and quantifiable. To provide an example of application to biomedical studies, functional consequences of prolonged exposure to the chemotherapeutic drug oxaliplatin were examined at non-cytotoxic concentrations. We found (i) neuronal (allodynia-like) hypersensitivity to otherwise non-activating mechanical stimulation that could be blocked by modulators of voltage-gated sodium channels; (ii) hyper-responsiveness to TRPV1 receptor stimulation. These findings and several other measured functional alterations indicate that the model is suitable for pharmacological and toxicological studies related to peripheral neuropathies.

Renin-angiotensin-aldosterone system inhibitors prevent the onset of oxaliplatin-induced peripheral neuropathy: A retrospective multicenter study and in vitro evaluation

Oxaliplatin (OXA) is used in chemotherapy for various cancer types and is associated with acute and chronic neurotoxicity. However, a preventive strategy for OXA-induced peripheral neuropathy (OIPN) and its underlying mechanism remain unclear. We examined the effects of renin-angiotensin-aldosterone system inhibitors (RAASIs) on OIPN by performing a retrospective multicenter study and an in vitro assay. We retrospectively evaluated electronic medical records of 976 patients who underwent one or more courses of OXA-containing regimens at Ehime, Okayama, and Tokushima University Hospitals. The primary endpoint was the incidence of OIPN during or after OXA administration. The effects of RAASIs and OXA on the neurite length in PC12 cells were determined. The combined administration of an OXA-containing regimen and RAASI significantly inhibited the cumulative incidence grade-2 or higher OIPN (log-rank test; P=0.0001). RAASIs markedly suppressed the development of both acute and chronic OIPN (multivariate analysis; P=0.017 and P=0.011). In an in vitro assay, 10 µM OXA suppressed the neurite length; treatment with 1 μM aliskiren, spironolactone, 10 μM candesartan, and enalapril significantly restored neurite length to the control level. Moreover, 1 μM SCH772984 (a selective inhibitor of extracellular signal-regulated kinase, ERK1/2) and 500 μM SQ22536 (a cell-permeable adenylate cyclase [AC] inhibitor) markedly abolished neuroprotective effects of candesartan and enalapril. These results indicate that RAASIs possess preventive or therapeutic effects in acute and chronic OIPN, candesartan and enalapril may directly increase in the activity of ERK1/2 and AC in PC12 cells.

Considerations for a Reliable In Vitro Model of Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is widely recognized as a potentially severe toxicity that often leads to dose reduction or discontinuation of cancer treatment. Symptoms may persist despite discontinuation of chemotherapy and quality of life can be severely compromised. The clinical symptoms of CIPN, and the cellular and molecular targets involved in CIPN, are just as diverse as the wide variety of anticancer agents that cause peripheral neurotoxicity. There is an urgent need for extensive molecular and functional investigations aimed at understanding the mechanisms of CIPN. Furthermore, a reliable human cell culture system that recapitulates the diversity of neuronal modalities found in vivo and the pathophysiological changes that underlie CIPN would serve to advance the understanding of the pathogenesis of CIPN. The demonstration of experimental reproducibility in a human peripheral neuronal cell system will increase confidence that such an in vitro model is clinically useful, ultimately resulting in deeper exploration for the prevention and treatment of CIPN. Herein, we review current in vitro models with a focus on key characteristics and attributes desirable for an ideal human cell culture model relevant for CIPN investigations.

Toxicity in Peripheral Nerves: An Overview

Introduction to a collection. This article is intended to introduce a collection of papers on toxic neuropathies. Toxic neuropathies can be caused by a variety of substances and by different mechanisms. Toxic agents are numerous and can be distinguished between drugs, recreational agents, heavy metals, industrial agents, pesticides, warfare agents, biologic substances and venoms. Toxic agents reach the nervous system by ingestion, transcutaneously, via the mucous membranes, parenterally and by aerosols. The most frequent types are cumulative toxicities. Other types are acute or delayed toxicities. Pathogenetic mechanisms range from a specific toxic substance profile causing axonal or demyelinating lesions, towards ion channel interferences, immune-mediated mechanisms and a number of different molecular pathways. In addition, demyelination, focal lesions and small fiber damage may occur. Clinically, neurotoxicity presents most frequently as axonal symmetric neuropathies. In this work, we present a panoramic view of toxic neuropathy, in terms of symptoms, causes, mechanisms and classification.

Effects of route of administration on neural exposure to platinum-based chemotherapy treatment: a pharmacokinetic study in rat

The persisting need for effective clinical treatment of chemotherapy-induced neurotoxicity (CIN) motivates critical evaluation of preclinical models of CIN for their translational relevance. The present study aimed to provide the first quantitative evaluation of neural tissue exposed in vivo to a platinum-based anticancer compound, oxaliplatin (OX) during and after two commonly used dosing regimens: slow IV infusion used clinically and bolus IP injection used preclinically. Inductively-coupled plasma mass spectrometry analysis of dorsal root ganglia indicated that while differences in the temporal dynamics of platinum distribution exist, key drivers of neurotoxicity, e.g. peak concentrations and exposure, were not different across the two routes of administration. We conclude that the IP route of OX administration achieves clinically relevant pharmacokinetic exposure of neural tissues in a rodent model of CIN.

Spontaneous, Voluntary, and Affective Behaviours in Rat Models of Pathological Pain

In pain patients affective and motivational reactions as well as impairment of daily life activities dominate the clinical picture. In contrast, many rodent pain models have been established on the basis of mechanical hypersensitivity testing. Up to today most rodent studies on pain still rely on reflexive withdrawal responses only. This discrepancy has likely contributed to the low predictive power of preclinical pain models for novel therapies. Here, we used a behavioural test array for rats to behaviourally evaluate five aetiologically distinct pain models consisting of inflammatory-, postsurgical-, cephalic-, neuropathic- and chemotherapy-induced pain. We assessed paralleling clinical expressions and comorbidities of chronic pain with an array of behavioural tests to assess anxiety, social interaction, distress, depression, and voluntary/spontaneous behaviours. Pharmacological treatment of the distinct pain conditions was performed with pathology-specific and clinically efficacious analgesics as gabapentin, sumatriptan, naproxen, and codeine. We found that rats differed in their manifestation of symptoms depending on the pain model and that pathology-specific analgesics also reduced the associated behavioural parameters. Based on all behavioural test performed, we screened for tests that can discriminate experimental groups on the basis of reflexive as well as non-sensory, affective parameters. Together, we propose a set of non-evoked behaviours with a comparable predictive power to mechanical threshold testing for each pain model.

Drug-Induced Peripheral Neuropathy: A Narrative Review

Background

Peripheral neuropathy is a painful condition deriving from many and varied etiologies. Certain medications have been implicated in the iatrogenic development of Drug Induced Peripheral Neuropathy (DIPN) and include chemotherapeutic agents, antimicrobials, cardiovascular drugs, psychotropic, anticonvulsants, among others. This review synthesizes current clinical concepts regarding the mechanism, common inciting medications, and treatment options for drug-induced peripheral neuropathy.

Methods

The authors undertook a structured search of bibliographic databases for peer-reviewed research literature using a focused review question and inclusion/exclusion criteria. The most relevant and up to date research was included.

Results

Drug-induced peripheral neuropathy is a common and painful condition caused by many different and frequently prescribed medications. Most often, DIPN is seen in chemotherapeutic agents, antimicrobials, cardiovascular drugs, psychotropic, and anticonvulsant drugs. Certain drugs exhibit more consistent neuropathic side effects, such as the chemotherapeutic compounds, but others are more commonly prescribed by a larger proportion of providers, such as the statins. DIPN is more likely to occur in patients with concomitant risk factors such as preexisting neuropathy, diabetes, and associated genetically predisposing diseases. DIPN is often difficult to treat, however medications including duloxetine, and gabapentin are shown to reduce neuropathic pain. Advanced techniques of neuromodulation offer promise though further randomized and controlled studies are needed to confirm efficacy.

Conclusion

Awareness of the drugs covered in this review and their potential for adverse neuropathic effect is important for providers caring for patients who report new onset symptoms of pain, paresthesia, or weakness. Prevention of DIPN is especially important because treatment often proves challenging. While many pharmacologic therapies have demonstrated analgesic potential in the pain caused by DIPN, many patients remain refractive to treatment. More studies are needed to elucidate the effectiveness of interventional, neuromodulating therapies.

AAAPT Diagnostic Criteria for Acute Neuropathic Pain

OBJECTIVE

Acute neuropathic pain is a significant diagnostic challenge, and it is closely related to our understanding of both acute pain and neuropathic pain. Diagnostic criteria for acute neuropathic pain should reflect our mechanistic understanding and provide a framework for research on and treatment of these complex pain conditions.

METHODS

The Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION) public-private partnership with the U.S. Food and Drug Administration (FDA), the American Pain Society (APS), and the American Academy of Pain Medicine (AAPM) collaborated to develop the ACTTION-APS-AAPM Pain Taxonomy (AAAPT) for acute pain. A working group of experts in research and clinical management of neuropathic pain was convened. Group members used literature review and expert opinion to develop diagnostic criteria for acute neuropathic pain, as well as three specific examples of acute neuropathic pain conditions, using the five dimensions of the AAAPT classification of acute pain.

RESULTS

AAAPT diagnostic criteria for acute neuropathic pain are presented. Application of these criteria to three specific conditions (pain related to herpes zoster, chemotherapy, and limb amputation) illustrates the spectrum of acute neuropathic pain and highlights unique features of each condition.

CONCLUSIONS

The proposed AAAPT diagnostic criteria for acute neuropathic pain can be applied to various acute neuropathic pain conditions. Both the general and condition-specific criteria may guide future research, assessment, and management of acute neuropathic pain.

Therapeutic Agents for Oxaliplatin-Induced Peripheral Neuropathy; Experimental and Clinical Evidence

Oxaliplatin is an essential drug in the chemotherapy of colorectal, gastric, and pancreatic cancers, but it frequently causes peripheral neuropathy as a dose-limiting factor. So far, animal models of oxaliplatin-induced peripheral neuropathy have been established. The mechanisms of development of neuropathy induced by oxaliplatin have been elucidated, and many drugs and agents have been proven to have neuroprotective effects in basic studies. In addition, some of these drugs have been validated in clinical studies for their inhibitory effects on neuropathy. In this review, we summarize the basic and clinical evidence for the therapeutic effects of oxaliplatin. In basic research, there are many reports of neuropathy inhibitors that target oxidative stress, inflammatory response, sodium channel, transient receptor potential (TRP) channel, glutamate nervous system, and monoamine nervous system. Alternatively, very few drugs have clearly demonstrated the efficacy for oxaliplatin-induced peripheral neuropathy in clinical trials. It is important to activate translational research in order to translate basic research into clinical research.

Therapeutic Agents for Oxaliplatin-Induced Peripheral Neuropathy; Experimental and Clinical Evidence

Oxaliplatin is an essential drug in the chemotherapy of colorectal, gastric, and pancreatic cancers, but it frequently causes peripheral neuropathy as a dose-limiting factor. So far, animal models of oxaliplatin-induced peripheral neuropathy have been established. The mechanisms of development of neuropathy induced by oxaliplatin have been elucidated, and many drugs and agents have been proven to have neuroprotective effects in basic studies. In addition, some of these drugs have been validated in clinical studies for their inhibitory effects on neuropathy. In this review, we summarize the basic and clinical evidence for the therapeutic effects of oxaliplatin. In basic research, there are many reports of neuropathy inhibitors that target oxidative stress, inflammatory response, sodium channel, transient receptor potential (TRP) channel, glutamate nervous system, and monoamine nervous system. Alternatively, very few drugs have clearly demonstrated the efficacy for oxaliplatin-induced peripheral neuropathy in clinical trials. It is important to activate translational research in order to translate basic research into clinical research.

Therapeutic Agents for Oxaliplatin-Induced Peripheral Neuropathy; Experimental and Clinical Evidence

Oxaliplatin is an essential drug in the chemotherapy of colorectal, gastric, and pancreatic cancers, but it frequently causes peripheral neuropathy as a dose-limiting factor. So far, animal models of oxaliplatin-induced peripheral neuropathy have been established. The mechanisms of development of neuropathy induced by oxaliplatin have been elucidated, and many drugs and agents have been proven to have neuroprotective effects in basic studies. In addition, some of these drugs have been validated in clinical studies for their inhibitory effects on neuropathy. In this review, we summarize the basic and clinical evidence for the therapeutic effects of oxaliplatin. In basic research, there are many reports of neuropathy inhibitors that target oxidative stress, inflammatory response, sodium channel, transient receptor potential (TRP) channel, glutamate nervous system, and monoamine nervous system. Alternatively, very few drugs have clearly demonstrated the efficacy for oxaliplatin-induced peripheral neuropathy in clinical trials. It is important to activate translational research in order to translate basic research into clinical research.

Addressing the Need of a Translational Approach in Peripheral Neuropathy Research: Morphology Meets Function

Peripheral neuropathies (PNs) are a type of common disease that hampers the quality of life of affected people. Treatment, in most cases, is just symptomatic and often ineffective. To improve drug discovery in this field, preclinical evidence is warranted. In vivo rodent models allow a multiparametric approach to test new therapeutic strategies, since they can allow pathogenetic and morphological studies different from the clinical setting. However, human readouts are warranted to promptly translate data from the bench to the bedside. A feasible solution would be neurophysiology, performed similarly at both sides. We describe a simple protocol that reproduces the standard clinical protocol of a neurophysiology hospital department. We devised the optimal montage for sensory and motor recordings (neurography) in mice, and we also implemented F wave testing and a short electromyography (EMG) protocol at rest. We challenged this algorithm by comparing control animals (BALB/c mice) with a model of mild neuropathy to grasp even subtle changes. The neurophysiological results were confirmed with neuropathology. The treatment group showed all expected alterations. Moreover, the neurophysiology matched the neuropathological analyses. Therefore, our protocol can be suggested to promptly translate data from the bench to the bedside and vice versa.

An overview of ongoing clinical trials assessing pharmacological therapeutic strategies to manage chemotherapy-induced peripheral neuropathy, based on preclinical studies in rodent models

Chemotherapy-induced peripheral neuropathy (CIPN) is a major dose-limiting side effect induced by a variety of chemotherapeutic agents. Symptoms are mainly sensory: pain, tingling, numbness, and temperature sensitivity. They may require the tapering of chemotherapy regimens or even their cessation; thus, the prevention/treatment of CIPN is critical to increase effectiveness of cancer treatment. However, CIPN management is mainly based on conventional neuropathic pain treatments, with poor clinical efficacy. Therefore, significant effort is made to identify new pharmacological targets to prevent/treat CIPN. Animal modeling is a key component in predicting human response to drugs and in understanding the pathophysiological mechanisms underlying CIPN. In fact, studies performed in rodents highlighted several pharmacological targets to treat/prevent CIPN. This review provides updated information about ongoing clinical trials testing drugs for the management of CIPN and presents some of their proof-of-concept studies conducted in rodent models. The presented drugs target oxidative stress, renin-angiotensin system, glutamatergic neurotransmission, sphingolipid metabolism, neuronal uptake transporters, nicotinamide adenine dinucleotide metabolism, endocannabinoid system, transient receptor potential channels, and serotoninergic receptors. As some clinical trials focus on the effect of the drugs on pain, others evaluate their efficacy by assessing general neuropathy. Moreover, based on studies conducted in rodent models, it remains unclear if some of the tested drugs act in an antinociceptive fashion or have neuroprotective properties. Thus, further investigations are needed to understand their mechanism of action, as well as a global standardization of the methods used to assess efficacy of new therapeutic strategies in the treatment of CIPN.

Bee Venom Acupuncture Attenuates Oxaliplatin-Induced Neuropathic Pain by Modulating Action Potential Threshold in A-Fiber Dorsal Root Ganglia Neurons

Oxaliplatin is a third-generation platinum-based chemotherapeutic drug widely used in colorectal cancer treatment. Although potent against this tumor, it can induce cold and mechanical allodynia even after a single injection. The currently used drugs to attenuate this allodynia can also cause unwanted effects, which limit their use. Bee venom acupuncture (BVA) is widely used in Korean medicine to treat pain. Although the effect of BVA on oxaliplatin-induced neuropathic pain has been addressed in many studies, its action on dorsal root ganglia (DRG) neurons has never been investigated. A single oxaliplatin injection (6 mg/kg, intraperitoneally) induced cold and mechanical allodynia, and BVA (0.1 and 1 mg/kg, subcutaneous, ST36) dose-dependently decreased allodynia in rats. On acutely dissociated lumbar 4-6 DRG neurons, 10 min application of oxaliplatin (100 μM) shifted the voltage-dependence of sodium conductance toward negative membrane potentials in A- but not C-fibers. The resting membrane potential remained unchanged, but the action potential threshold decreased significantly compared to that of the control (p < 0.05). However, 0.1 μg/mL of BVA administration increased the lowered action potential threshold. In conclusion, these results suggest that BVA may attenuate oxaliplatin-induced neuropathic pain by altering the action potential threshold in A-fiber DRG neurons.

Platinum accumulation in the brain and alteration in the central regulation of cardiovascular and respiratory functions in oxaliplatin-treated rats

Oxaliplatin is a platinum-based alkylating chemotherapeutic agent used for cancer treatment. Neurotoxicity is one of its major adverse effects that often demands dose limitation. However, the effects of chronic oxaliplatin on the toxicity of the autonomic nervous system regulating cardiorespiratory function and adaptive reflexes are unknown. Male Sprague Dawley rats were treated with intraperitoneal oxaliplatin (3 mg kg^-1 per dose) 3 times a week for 14 days. The effects of chronic oxaliplatin treatment on baseline mean arterial pressure (MAP); heart rate (HR); splanchnic sympathetic nerve activity (sSNA); phrenic nerve activity (PNA) and its amplitude (PNamp) and frequency (PNf); and sympathetic reflexes were investigated in anaesthetised, vagotomised and artificially ventilated rats. The same parameters were evaluated after acute oxaliplatin injection, and in the chronic treatment group following a single dose of oxaliplatin. The amount of platinum in the brain was determined with atomic absorption spectrophotometry. Chronic oxaliplatin treatment significantly increased MAP, sSNA and PNf and decreased HR and PNamp, while acute oxaliplatin had no effects. Platinum was accumulated in the brain after chronic oxaliplatin treatment. In the chronic oxaliplatin treatment group, further administration of a single dose of oxaliplatin increased MAP and sSNA. The baroreceptor sensitivity and somatosympathetic reflex were attenuated at rest while the sympathoexcitatory response to hypercapnia was increased in the chronic treatment group. This is the first study to reveal oxaliplatin-induced alterations in the central regulation of cardiovascular and respiratory functions as well as reflexes that may lead to hypertension and breathing disorders which may be mediated via accumulated platinum in the brain.

Efficacy of Oral Cryotherapy During Oxaliplatin Infusion in Preventing Oral Thermal Hyperalgesia: A Randomized Trial

BACKGROUND

Chemotherapy-induced oral thermal hyperalgesia (OTH) is a common and debilitating side effect of platinum-based anticancer agents. This study evaluated the efficacy of oral cryotherapy in preventing OTH during oxaliplatin chemotherapy infusion.

METHODS

Patients with gastrointestinal cancer treated with biweekly oxaliplatin (85 mg/m2 over 120 minutes) at Abramson Cancer Center at the University of Pennsylvania were randomized to receive oral cryotherapy (ice chips) during oxaliplatin infusion or standard-of-care treatment. All patients completed baseline questionnaires regarding oral and peripheral symptoms and on-treatment questionnaires on day 1 of each subsequent chemotherapy cycle. Those in the treatment arm were asked to document how long they kept the ice chips in their mouths (0, <30, 30, 60, 90, or 120 minutes) and to report their discomfort associated with oral cryotherapy. Evaluable patients were those who had completed at least 2 cycles of oxaliplatin therapy.

RESULTS

Of 62 randomized patients with a variety of gastrointestinal malignancies, 50 (25 per treatment arm) were evaluable for efficacy. The rate of patients with oral symptoms after the first treatment cycle was significantly lower in the intervention arm (n=8; 32%) than in the control arm (n=18; 72%), meeting the primary study objective (P=.01). The magnitude of difference in symptom scores before versus after the first treatment cycle was significantly less in the intervention versus control arm (P=.001). No difference in oral symptoms over time was seen between the intervention and control groups (P=.20), although a high attrition rate was noted. Duration of ice chip exposure was associated with improved oral symptoms over time (P=.02).

CONCLUSIONS

Oral cryotherapy is a tolerable and cost-effective method of diminishing OTH in patients receiving oxaliplatin chemotherapy, and seems to be most effective in the early stages of treatment.

Acute Peripheral Motor Neuropathy Induced by Oxaliplatin-Correlated Hypokalaemia

Neurotoxicity is one of the most common side effects of oxaliplatin-based therapy. Most patients who receive at least 3–4 months of treatment suffer from peripheral sensory neurotoxicity (PSN), characterised by the loss or impairment of tactile and proprioceptive sensory function. Motor impairment, such as muscle weakness or palsy, has been rarely described, and the physiopathology of PSN, as well as the motor symptoms due to oxaliplatin-based treatment, are not adequately understood. Here we report the case of a patient who experienced severe acute peripheral motor neuropathy as a side effect of oxaliplatin-based treatment. We also review other cases of PSN published in the literature and suggest a novel hypothesis on the physiopathology of this particular event. Take-away lessons: Not all of the neurological symptoms observed during oxaliplatin-based treatment can be traced back directly to the oxaliplatin itself, and other factors, such as electrolyte imbalances, may contribute to the symptoms. Patients with gastro-intestinal malignancies are the patients most affected by neurotoxicity due to the side effects of chemotherapy and the disease itself.

Neu-horizons: neuroprotection and therapeutic use of riluzole for the prevention of oxaliplatin-induced neuropathy-a randomised controlled trial

TRIAL DESIGN

Peripheral neuropathy is a commonly reported adverse effect of oxaliplatin treatment, representing a significant limitation which may require discontinuation of effective therapy. The present study investigated the neuroprotective potential of riluzole in patients undergoing oxaliplatin treatment in a randomised-controlled trial comparing riluzole and placebo-control.

METHODS

Fifty-two patients (17 females, 58.1 ± 12.7 years) receiving oxaliplatin treatment were randomised into either a treatment (50 mg riluzole) or lactose placebo group. The primary outcome measure was the total neuropathy score-reduced (TNSr). Secondary outcome measures include nerve excitability measures, 9-hole pegboard and FACT-GOG NTX questionnaire. Patients were assessed at baseline, pre-cycle 10 or 12, 4-week and 12-week post-treatment.

RESULTS

Both the treatment and placebo groups developed objective and patient reported evidence of neurotoxicity over the course of oxaliplatin treatment, although there were no significant differences across any parameters between the two groups. However, across follow-up assessments, the treatment group experienced greater neuropathy, represented by a higher TNSr score at 4-week post-chemotherapy of 8.3 ± 2.7 compared with 4.6 ± 3.6 (p = 0.032) which was sustained at 12-week post-treatment (p = 0.089). Similarly, patients in the treatment group reported worse symptoms with a FACT-GOG NTX score of 37.4 ± 10.2 compared with 43.3 ± 7.4 (p = 0.02) in the placebo group at 4-week post-treatment.

CONCLUSION

This study is the first to provide an objective clinical investigation of riluzole in oxaliplatin-induced peripheral neuropathy employing both functional and neurophysiological measures. Although the recruitment target was not reached, the results do not show any benefit of riluzole in minimising neuropathy and may suggest that riluzole worsens neuropathy associated with oxaliplatin treatment.

Acute changes in nerve excitability following oxaliplatin treatment in mice

Oxaliplatin chemotherapy produces acute changes in peripheral nerve excitability in humans by modulating voltage-gated Na⁺ channel activity. However, there are few animal studies of oxaliplatin-induced neuropathy that demonstrate similar changes in excitability. In the present study, we measured the excitability of motor and sensory caudal nerve in C57BL/6 mice after oxaliplatin injections either systemically (intraperitoneal) or locally (intramuscular at the base of the tail). As opposed to intraperitoneal administration of oxaliplatin, a single intramuscular injection of oxaliplatin produced changes in both motor and sensory axons. In motor axons, oxaliplatin caused a greater change in response to long-lasting depolarization and an upward shift in the recovery cycle, particularly at 24 h [depolarizing threshold electrotonus (TEd) 10-20 ms, P = 0.0095; TEd 90-100 ms, P = 0.0056) and 48 h (TEd 10-20 ms, P = 0.02; TEd 90-100 ms, P = 0.04) posttreatment. Oxaliplatin treatment also stimulated the production of afterdischarges in motor axons. These changes were transient and showed dose dependence. Mathematical modeling demonstrated that these changes could be accounted for by slowing inactivation of voltage-gated Na⁺ channels by 73.3% and reducing fast K⁺ conductance by 47% in motor axons. In sensory axons, oxaliplatin caused an increase in threshold, a reduction in peak amplitude, and greater threshold changes to strong hyperpolarizing currents on days 4 and 8. Thus, local administration of oxaliplatin produced clinically relevant changes in nerve excitability in mice and may provide an alternative approach for the study of acute oxaliplatin-induced neurotoxicity.NEW & NOTEWORTHY We present a novel mouse model of acute oxaliplatin-induced peripheral neurotoxicity that is comparable to clinical observations. Intramuscular injection of oxaliplatin produced acute changes in motor nerve excitability that were attributable to alterations in Na⁺ and K⁺ channel activity. Conversely, we were unable to show any significant changes in nerve excitability with systemic intraperitoneal injections of oxaliplatin. This study suggests that local intramuscular injection is a valid approach for modelling oxaliplatin-induced peripheral neuropathy in animals.

Effect of Oxaliplatin on Voltage-Gated Sodium Channels in Peripheral Neuropathic Pain

Oxaliplatin is a chemotherapeutic drug widely used to treat various types of tumors. However, it can induce a serious peripheral neuropathy characterized by cold and mechanical allodynia that can even disrupt the treatment schedule. Since the approval of the agent, many laboratories, including ours, have focused their research on finding a drug or method to decrease this side effect. However, to date no drug that can effectively reduce the pain without causing any adverse events has been developed, and the mechanism of the action of oxaliplatin is not clearly understood. On the dorsal root ganglia (DRG) sensory neurons, oxaliplatin is reported to modify their functions, such as the propagation of the action potential and induction of neuropathic pain. Voltage-gated sodium channels in the DRG neurons are important, as they play a major role in the excitability of the cell by initiating the action potential. Thus, in this small review, eight studies that investigated the effect of oxaliplatin on sodium channels of peripheral neurons have been included. Its effects on the duration of the action potential, peak of the sodium current, voltage–response relationship, inactivation current, and sensitivity to tetrodotoxin (TTX) are discussed.

Management of Oxaliplatin-Induced Peripheral Sensory Neuropathy

Oxaliplatin-induced peripheral neurotoxicity (OIPN) is a severe and potentially permanent side effect of cancer treatment affecting the majority of oxaliplatin-treated patients, mostly with the onset of acute symptoms, but also with the establishment of a chronic sensory loss that is supposed to be due to dorsal root ganglia neuron damage. The pathogenesis of acute as well as chronic OIPN is still not completely known, and this is a limitation in the identification of effective strategies to prevent or limit their occurrence. Despite intense investigation at the preclinical and clinical levels, no treatment can be suggested for the prevention of OIPN, and only limited evidence for the efficacy of duloxetine in the treatment setting has been provided. In this review, ongoing neuroprotection clinical trials in oxaliplatin-treated patients will be analyzed with particular attention paid to the hypothesis leading to the study, to the trial strengths and weaknesses, and to the outcome measures proposed to test the efficacy of the therapeutic approach. It can be concluded that (1) prevention and treatment of OIPN still remains an important and unmet clinical need, (2) further, high-quality research is mandatory in order to achieve reliable and effective results, and (3) dose and schedule modification of OHP-based chemotherapy is currently the most effective approach to limit the severity of OIPN.

Taxane-induced sensory peripheral neuropathy is associated with an SCN9A single nucleotide polymorphism in Japanese patients

Background

Sodium channels located in the dorsal root ganglion, particularly Nav1.7 and Nav1.8, encoded by SCN9A and SCN10A, respectively, act as molecular gatekeepers for pain detection. Our aim was to determine the association between TIPN and SCN9A and SCN10A polymorphisms.

Methods

Three single nucleotide polymorphisms (SNPs) in SCN9A and two in SCN10A were investigated using whole-genome genotyping data from 186 Japanese breast or ovarian cancer patients classified into two groups as follows: cases that developed taxane-induced grade 2–3 neuropathy (N = 108) and controls (N = 78) with grade 0–1 neuropathy. Multiple logistic regression analyses were conducted to evaluate associations between TIPN and SNP genotypes.

Results

SCN9A-rs13017637 was a significant predictor of grade 2 or higher TIPN (odds ratio (OR) = 3.463; P = 0.0050) after correction for multiple comparisons, and precision was improved when only breast cancer patients were included (OR 5.053, P = 0.0029). Moreover, rs13017637 was a significant predictor of grade 2 or higher TIPN 1 year after treatment (OR 3.906, P = 0.037), indicating its contribution to TIPN duration.

Conclusion

SCN9A rs13017637 was associated with the severity and duration of TIPN. These findings are highly exploratory and require replication and validation prior to any consideration of clinical use.

Semi-Mechanism-Based Pharmacokinetic-Toxicodynamic Model of Oxaliplatin-Induced Acute and Chronic Neuropathy

Oxaliplatin (L-OHP) is widely prescribed for treating gastroenterological cancer. L-OHP-induced peripheral neuropathy is a critical toxic effect that limits the dosage of L-OHP. An ideal chemotherapeutic strategy that does not result in severe peripheral neuropathy but confers high anticancer efficacy has not been established. To establish an optimal evidence-based dosing regimen, a pharmacokinetic-toxicodynamic (PK-TD) model that can characterize the relationship between drug administration regimen and L-OHP-induced peripheral neuropathy is required. We developed a PK-TD model of L-OHP for peripheral neuropathy using Phoenix^® NLME™ Version 8.1. Plasma concentration of L-OHP, the number of withdrawal responses in the acetone test, and the threshold value in the von Frey test following 3, 5, or 8 mg/kg L-OHP administration were used. The PK-TD model consisting of an indirect response model and a transit compartment model adequately described and simulated time-course alterations of onset and grade of L-OHP-induced cold and mechanical allodynia. The results of model analysis suggested that individual fluctuation of plasma L-OHP concentration might be a more important factor for individual variability of neuropathy than cell sensitivity to L-OHP. The current PK-TD model might contribute to investigation and establishment of an optimal dosing strategy that can reduce L-OHP-induced neuropathy.

Toxic Peripheral Neuropathies: Agents and Mechanisms

Toxic peripheral neuropathies are an important form of acquired polyneuropathy produced by a variety of xenobiotics and different exposure scenarios. Delineating the mechanisms of neurotoxicants and determining the degenerative biological pathways triggered by peripheral neurotoxicants will facilitate the development of sensitive and specific biochemical-based methods for identifying neurotoxicants, designing therapeutic interventions, and developing structure-activity relationships for predicting potential neurotoxicants. This review presents an overview of the general concepts of toxic peripheral neuropathies with the goal of providing insight into why certain agents target the peripheral nervous system and produce their associated lesions. Experimental data and the main hypotheses for the mechanisms of selected agents that produce neuronopathies, axonopathies, or myelinopathies including covalent or noncovalent modifications, compromised energy or protein biosynthesis, and oxidative injury and disruption of ionic gradients across membranes are presented. The relevance of signaling between the main components of peripheral nerve, that is, glia, neuronal perikaryon, and axon, as a target for neurotoxicants and the contribution of active programmed degenerative pathways to the lesions observed in toxic peripheral neuropathies is also discussed.

A Comparative Review of Chemotherapy-Induced Peripheral Neuropathy in In Vivo and In Vitro Models

Chemotherapy-induced peripheral neuropathy (CIPN) is an adverse effect caused by several classes of widely used anticancer therapeutics. Chemotherapy-induced peripheral neuropathy frequently leads to dose reduction or discontinuation of chemotherapy regimens, and CIPN symptoms can persist long after completion of chemotherapy and severely diminish the quality of life of patients. Differences in the clinical presentation of CIPN by widely diverse classifications of anticancer agents have spawned multiple mechanistic hypotheses that seek to explain the pathogenesis of CIPN. Despite its clinical relevance, common occurrence, and extensive investigation, the pathophysiology of CIPN remains unclear. Furthermore, there is no unequivocal gold standard for the prevention and treatment of CIPN. Herein, we review in vivo and in vitro models of CIPN with a focus on histopathological changes and morphological features aimed at understanding the pathophysiology of CIPN and identify gaps requiring deeper exploration. An elucidation of the underlying mechanisms of CIPN is imperative to identify potential targets and approaches for prevention and treatment.

Pathogenesis of platinum-induced peripheral neurotoxicity: Insights from preclinical studies

One of the most relevant dose-limiting adverse effects of platinum drugs is the development of a sensory peripheral neuropathy that highly impairs the patients' quality of life. Nowadays there are no available efficacy strategies for the treatment of platinum-induced peripheral neurotoxicity (PIPN), and the only way to prevent its development and progression is by reducing the dose of the cytostatic drug or even withdrawing the chemotherapy regimen. This clinical issue has been the main focus of hundreds of preclinical research works during recent decades. As a consequence, dozens of in vitro and in vivo models of PIPN have been developed to elucidate the molecular mechanisms involved in its development and to find neuroprotective targets. The apoptosis of peripheral neurons has been identified as the main mechanism involved in PIPN pathogenesis. This mechanism of DRG sensory neurons cell death is triggered by the nuclear and mitochondrial DNA platination together with the increase of the oxidative cellular status induced by the depletion of cytoplasmic antioxidant mechanisms. However, since there has been no successful transfer of preclinical results to clinical practise in terms of therapeutic approaches, some mechanisms of PIPN pathogenesis still remain to be elucidated. This review is focused on the pathogenic mechanisms underlying PIPN described up to now, provided by the critical analysis of in vitro and in vivo models.

Topiramate prevents oxaliplatin-related axonal hyperexcitability and oxaliplatin induced peripheral neurotoxicity

Oxaliplatin (OHP) Induced Peripheral Neurotoxicity (OIPN) is one of the dose-limiting toxicities of the drug and these adverse effects limit cancer therapy with L-OHP, used for colorectal cancer treatment. Acute neurotoxicity consists of symptoms that are the hallmarks of a transient axonal hyperexcitability; chronic neurotoxicity has a clinical picture compatible with a length-dependent sensory neuropathy. Acute OIPN pathogenesis has been linked to sodium voltage-operated channels (Na + VOC) dysfunction and it has been advocated as a possible predisposing factor to chronic neurotoxicity. We tested if topiramate (TPM), a well-known Na + VOC modulator, was able to modify acute as well as chronic OIPN. The project was divided into two parts. In Experiment 1 we tested by means of Nerve Excitability Testing (NET) a cohort of female Wistar rats to assess TPM effects after a single OHP administration (5 mg/kg, iv). In Experiment 2 we assessed TPM effects after chronic OHP treatment (5 mg/kg, 2qw4ws, iv) using NET, nerve conduction studies (NCS), behavioral tests and neuropathology (caudal nerve morphometry and morphology and Intraepidermal Nerve Fiber [IENF] density). In Experiment 1 TPM was able to prevent OHP effects on Na + VOC: OHP treatment induced a highly significant reduction of the sensory nerve's threshold, during the superexcitability period (p-value = 0.008), whereas TPM co-administration prevented this effect. In Experiment 2 we verified that TPM was able to prevent not only acute phenomena, but also to completely prevent chronic OIPN. This latter observation was supported by a multimodal approach: in fact, only OHP group showed altered findings compared to CTRL group at a neurophysiological (proximal caudal nerve sensory nerve action potential [SNAP] amplitude, p-value = 0.001; distal caudal nerve SNAP amplitude, p-value<0.001, distal caudal nerve sensory conduction velocity, p-value = 0.04), behavioral (mechanical threshold, p-value 0.003) and neuropathological levels (caudal nerve fibers density, p-value 0.001; IENF density, p-value <0.001). Our data show that TPM is a promising drug to prevent both acute and chronic OIPN. These findings have a high translational potential, since they were obtained using outcome measures that match clinical practice and TPM is already approved for clinical use being free from detrimental interaction with OHP anticancer properties.

Upregulation of ERK phosphorylation in rat dorsal root ganglion neurons contributes to oxaliplatin-induced chronic neuropathic pain

Oxaliplatin is the first-line chemotherapy for metastatic colorectal cancer. Unlike other platinum anticancer agents, oxaliplatin does not result in significant renal impairment and ototoxicity. Oxaliplatin, however, has been associated with acute and chronic peripheral neuropathies. Despite the awareness of these side-effects, the underlying mechanisms are yet to be clearly established. Therefore, in this study, we aimed to understand the factors involved in the generation of chronic neuropathy elicited by oxaliplatin treatment. We established a rat model of oxaliplatin-induced neuropathic pain (4 mg kg^-1 intraperitoneally). The paw withdrawal thresholds were assessed at different time-points after the treatment, and a significant decrease was observed 3 and 4 weeks after oxaliplatin treatment as compared to the vehicle treatment (4.4 ± 1.0 vs. 16.0 ± 4.1 g; P < 0.05 and 4.4 ± 0.7 vs. 14.8 ± 3.1 g; P < 0.05, respectively). We further evaluated the role of different mitogen-activated protein kinases (MAPKs) pathways in the pathophysiology of neuropathic pain. Although the levels of total extracellular signal-regulated kinase (ERK) 1/2 in the dorsal root ganglia (DRG) were not different between oxaliplatin and vehicle treatment groups, phosphorylated ERK (p-ERK) 1/2 was up-regulated up to 4.5-fold in the oxaliplatin group. Administration of ERK inhibitor PD98059 (6 μg day^-1 intrathecally) inhibited oxaliplatin-induced ERK phosphorylation and neuropathic pain. Therefore, upregulation of p-ERK by oxaliplatin in rat DRG and inhibition of mechanical allodynia by an ERK inhibitor in the present study may provide a better understanding of intracellular molecular alterations associated with oxaliplatin-induced neuropathic pain and help in the development of potential therapeutics.

Prevention and Treatment for Chemotherapy-Induced Peripheral Neuropathy: Therapies Based on CIPN Mechanisms

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a progressive, enduring, and often irreversible adverse effect of many antineoplastic agents, among which sensory abnormities are common and the most suffering issues. The pathogenesis of CIPN has not been completely understood, and strategies for CIPN prevention and treatment are still open problems for medicine.

OBJECTIVES

The objective of this paper is to review the mechanism-based therapies against sensory abnormities in CIPN.

METHODS

This is a literature review to describe the uncovered mechanisms underlying CIPN and to provide a summary of mechanism-based therapies for CIPN based on the evidence from both animal and clinical studies.

RESULTS

An abundance of compounds has been developed to prevent or treat CIPN by blocking ion channels, targeting inflammatory cytokines and combating oxidative stress. Agents such as glutathione, mangafodipir and duloxetine are expected to be effective for CIPN intervention, while Ca/Mg infusion and venlafaxine, tricyclic antidepressants, and gabapentin display limited efficacy for preventing and alleviating CIPN. And the utilization of erythropoietin, menthol and amifostine needs to be cautious regarding to their side effects.

CONCLUSIONS

Multiple drugs have been used and studied for decades, their effect against CIPN are still controversial according to different antineoplastic agents due to the diverse manifestations among different antineoplastic agents and complex drug-drug interactions. In addition, novel therapies or drugs that have proven to be effective in animals require further investigation, and it will take time to confirm their efficacy and safety.

Electrophysiologic evaluation of facial nerve functions after oxaliplatin treatment

PURPOSE

This study analyzes the effect of oxaliplatin treatment on the facial nerve. The facial nerve is the most commonly paralyzed cranial motor nerve because it advances through a long, curved bone canal. Electroneurography and blink reflex are the electrophysiological measurements used for evaluating facial nerve function. Oxaliplatin is a cytotoxic agent used in adjuvant or palliative systemic therapy for colorectal cancer treatment.

METHODS

This study was performed on 20 individuals who were at least 18 years old at Hacettepe University Ear Nose Throat Department, Audiology and Speech Disorders Unit, and Neurology Division EMG Laboratory as they received oxaliplatin treatment from Hacettepe University Oncology Hospital. Electroneurography and blink-reflex values were recorded and examined. The parameters taken during the second and fourth months were compared for this purpose.

RESULTS

This study shows that the prolongation of distal latencies of compound muscle action potential is statistically significant, the amplitudes showed no difference. The ENoG results were analyzed, the prolongation of latency measurements between pre-treatment and the fourth month after treatment were statistically significant. The blink-reflex results showed that comparison with the baseline values, the prolongation of latencies in R1 measurements between pre-treatment, the second month, and the fourth month were significant.

CONCLUSIONS

The facial nerve is affected asymptomatically by oxaliplatin treatment. During oxaliplatin treatment, the evaluation of facial nerve function could be beneficial for patients by improving their quality of life. Electroneurography and blink-reflex tests can be used in the early evaluations of different medicines to determine their neurotoxicity.

Mechanisms of Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most frequent side effects caused by antineoplastic agents, with a prevalence from 19% to over 85%. Clinically, CIPN is a mostly sensory neuropathy that may be accompanied by motor and autonomic changes of varying intensity and duration. Due to its high prevalence among cancer patients, CIPN constitutes a major problem for both cancer patients and survivors as well as for their health care providers, especially because, at the moment, there is no single effective method of preventing CIPN; moreover, the possibilities of treating this syndrome are very limited. There are six main substance groups that cause damage to peripheral sensory, motor and autonomic neurons, which result in the development of CIPN: platinum-based antineoplastic agents, vinca alkaloids, epothilones (ixabepilone), taxanes, proteasome inhibitors (bortezomib) and immunomodulatory drugs (thalidomide). Among them, the most neurotoxic are platinum-based agents, taxanes, ixabepilone and thalidomide; other less neurotoxic but also commonly used drugs are bortezomib and vinca alkaloids. This paper reviews the clinical picture of CIPN and the neurotoxicity mechanisms of the most common antineoplastic agents. A better understanding of the risk factors and underlying mechanisms of CIPN is needed to develop effective preventive and therapeutic strategies.

Simple surface EMG recording as a noninvasive screening method for the detection of acute oxaliplatin-induced neurotoxicity: a feasibility pilot study

OBJECTIVES

Oxaliplatin-induced neurotoxicity can be a dose-limiting side effect to effective chemotherapy. Acute hyperexcitability causes cold-evoked sensory and motor symptoms, which resemble neuromyotonia. An accessible and non-invasive technique for early detection could help select patients for potential treatments. We assessed the use of a simple surface electromyography (sEMG) in patients directly after oxaliplatin infusion.

METHODS

In patients with colorectal cancer, acute neurotoxicity was evaluated by means of a physical examination, a questionnaire, and sEMG directly after the second and fourth cycle of oxaliplatin. Questionnaires were also assessed 1 day after infusion.

RESULTS

14 patients were measured after the second cycle and 8 patients were also measured after the fourth cycle of oxaliplatin. All patients reported to a variable degree oxaliplatin induced neurotoxicity symptoms: sensitivity to touching cold or swallowing cold items were reported as most severe. Clinical signs of hyperexcitability were observed in 55% of the measurements. Spontaneous activity compatible with neuromyotonia was observed in 82% of the sEMG recordings.

CONCLUSIONS

Patient reported symptoms, physical examination and simple sEMG are complementary measurements to detect acute oxaliplatin induced neurotoxicity. After further validation, sEMG recording can be used as a simple objective screenings tool to detect nerve hyperexcitability directly after oxaliplatin administration.

Preventive action of benztropine on platinum-induced peripheral neuropathies and tumor growth

The endogenous cholinergic system plays a key role in neuronal cells, by suppressing neurite outgrowth and myelination and, in some cancer cells, favoring tumor growth. Platinum compounds are widely used as part of first line conventional cancer chemotherapy; their efficacy is however limited by peripheral neuropathy as a major side-effect. In a multiple sclerosis mouse model, benztropine, that also acts as an anti-histamine and a dopamine re-uptake inhibitor, induced the differentiation of oligodendrocytes through M1 and M3 muscarinic receptors and enhanced re-myelination. We have evaluated whether benztropine can increase anti-tumoral efficacy of oxaliplatin, while preventing its neurotoxicity.We showed that benztropine improves acute and chronic clinical symptoms of oxaliplatin-induced peripheral neuropathies in mice. Sensory alterations detected by electrophysiology in oxaliplatin-treated mice were consistent with a decreased nerve conduction velocity and membrane hyperexcitability due to alterations in the density and/or functioning of both sodium and potassium channels, confirmed by action potential analysis from ex-vivo cultures of mouse dorsal root ganglion sensory neurons using whole-cell patch-clamp. These alterations were all prevented by benztropine. In oxaliplatin-treated mice, MBP expression, confocal and electronic microscopy of the sciatic nerves revealed a demyelination and confirmed the alteration of the myelinated axons morphology when compared to animals injected with oxaliplatin plus benztropine. Benztropine also prevented the decrease in neuronal density in the paws of mice injected with oxaliplatin. The neuroprotection conferred by benztropine against chemotherapeutic drugs was associated with a lower expression of inflammatory cytokines and extended to diabetic-induced peripheral neuropathy in mice.Mice receiving benztropine alone presented a lower tumor growth when compared to untreated animals and synergized the anti-tumoral effect of oxaliplatin, a phenomenon explained at least in part by benztropine-induced ROS imbalance in tumor cells.This report shows that blocking muscarinic receptors with benztropine prevents peripheral neuropathies and increases the therapeutic index of oxaliplatin. These results can be rapidly transposable to patients as benztropine is currently indicated in Parkinson's disease in the United States.