The effects of oxaliplatin, an anticancer drug, on potassium channels of the peripheral myelinated nerve fibres of the adult rat

The incidence rate of allergic reactions induced by oxaliplatin is higher in patients with rectal cancer compared with colon cancer

AIM

To explore the diverse profiles of adverse reactions caused by oxaliplatin between colon and rectal cancer, we investigated the toxicity of oxaliplatin in patients with colon and rectal cancer.

METHODS

From January 2017 to December 2021, 200 cases of sporadic CRC patients with adverse reactions after oxaliplatin were collected from Harbin Medical University Cancer Hospital, Harbin, China. All patients received a chemotherapy regimen containing oxaliplatin (100 colon cancer and 100 rectal cancer). We reviewed the adverse reactions induced by oxaliplatin in patients with colon and rectal cancer.

RESULTS

We found there was no significant difference in gastrointestinal toxicity, hematotoxicity, neurotoxicity, hepatotoxicity, respiratory toxicity, and cardiotoxicity caused by oxaliplatin between patients with colon cancer and patients with rectal cancer, but patients with rectal cancer were more prone to allergic reactions than patients with colon cancer after oxaliplatin. In addition, we found neutrophil-to-lymphocyte ratios (NLR) and platelet-to-lymphocyte ratios (PLR) were higher in patients with colon cancer than in patients with rectal cancer. This may reflect differences in immune status and inflammatory responses between colon cancer and rectal cancer, which might be the reason for more allergic reactions caused by oxaliplatin in colon cancer patients compared to rectal cancer patients.

CONCLUSION

Except for a higher incidence of allergic reactions in patients with rectal cancer, no significant difference in the incidence of adverse drug reactions associated with oxaliplatin was noted between patients with colon cancer and rectal cancer. Our results suggested more attention should be paid to the allergic reaction caused by oxaliplatin in patients with colon cancer.

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.

Oxaliplatin-induced peripheral neurotoxicity in colorectal cancer patients: mechanisms, pharmacokinetics and strategies

Oxaliplatin-based chemotherapy is a standard treatment approach for colorectal cancer (CRC). However, oxaliplatin-induced peripheral neurotoxicity (OIPN) is a severe dose-limiting clinical problem that might lead to treatment interruption. This neuropathy may be reversible after treatment discontinuation. Its complicated mechanisms are related to DNA damage, dysfunction of voltage-gated ion channels, neuroinflammation, transporters, oxidative stress, and mitochondrial dysfunction, etc. Several strategies have been proposed to diminish OIPN without compromising the efficacy of adjuvant therapy, namely, combination with chemoprotectants (such as glutathione, Ca/Mg, ibudilast, duloxetine, etc.), chronomodulated infusion, dose reduction, reintroduction of oxaliplatin and topical administration [hepatic arterial infusion chemotherapy (HAIC), pressurized intraperitoneal aerosol chemotherapy (PIPAC), and hyperthermic intraperitoneal chemotherapy (HIPEC)]. This article provides recent updates related to the potential mechanisms, therapeutic strategies in treatment of OIPN, and pharmacokinetics of several methods of oxaliplatin administration in clinical trials.

Serum sodium ions and chloride ions associated with taxane-induced peripheral neuropathy in Chinese patients with early-stage breast cancer: A nation-wide multicenter study

BACKGROUND

Taxane-induced peripheral neuropathy (TIPN) is a debilitating adverse effect of cancer treatments with taxanes which may require a reduction or discontinuation chemotherapy and affect clinical and survival outcomes. A number of factors have contributed to the increasing prevalence of TIPN. Nonetheless, limited knowledge exists of potential prechemotherapy blood-based biochemical factors associated with TIPN development.

METHODS

We recruited breast cancer patients at seven cancer institutions in China. Participants aged 18 years or older with stage I to III breast cancer who scheduled to undergo primary neoadjuvant and adjuvant chemotherapy with taxanes were eligible. Eligible patients underwent patient-reported neuropathy assessments using the EORTC-CIPN20 questionnaire. Patients completed the questionnaire before commencing treatment and after every cycle. For every patient, we selected the highest TIPN toxicity score for analysis since the first cycle. The posttreatment TIPN severity was compared with blood-based biochemical factors within 30 days before commencing treatment. Independent samples t tests, Mann-Whitney U tests and linear regression were used to identify blood-based and clinical associations with TIPN development.

RESULTS

The study included 873 breast cancer participants who received paclitaxel, docetaxel or nanoparticle albumin-bound (nab)-paclitaxel. In the whole cohort, factors associated with higher TIPN toxicity scores were higher cumulative chemotherapy dose (β = 0.005; 95% CI, 0.004 to 0.006; P < .001), lower sodium ions (β = -0.24; 95% CI, -0.39 to -0.09; P = .002) and higher chloride ions (β = 0.30; 95% CI, 0.16 to 0.44; P < .001).

CONCLUSIONS

The findings suggest that breast cancer patients with a higher cumulative chemotherapy dose, lower pretreatment sodium ions, and higher pretreatment chloride ions receiving taxanes should receive closer monitoring to mitigate the development of short-term and long-term TIPN.

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.

Chemotherapy-induced peripheral neuropathy in children and adolescent cancer patients

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

Leukocytoclastic vasculitis presenting clinically as bullous pyoderma gangrenosum following leucovorin, fluorouracil and oxaliplatin chemotherapy: a rare case report and literature review

There are no published cases about bullous pyoderma gangrenosum induced by leucovorin, fluorouracil and oxaliplatin (FOLFOX) chemotherapy. With the increasing incidence of gastric and colorectal cancers and the increased usage of targeted therapies, some cutaneous adverse effects may become common. An 84-year-old male presented to our clinic with multiple ulcerative plaques covered with hemorrhagic crusts on both extremities after several FOLFOX chemotherapy sessions for gastric cancer and liver metastasis. Two weeks later, multiple bullae also appeared, especially on the acral areas. The histopathology examination was compatible with acute leukocytoclastic vasculitis. The FOLFOX chemotherapy regimen is increasingly administered considering the rising incidence of gastrointestinal cancers. Hence, our understanding of its possible side effects and complications must be heightened.

Protective effect of naringin against oxaliplatin-induced peripheral neuropathy in rats: A behavioral and molecular study

Oxaliplatin (OXL) is a chemotherapeutic drug used for metastatic and other types of cancer, but it causes peripheral neuropathy as a dose-limiting side effect. Herein, we used the rat model of OXL-induced peripheral neuropathy to demonstrate the protective effects of naringin (NRG) in this neuropathy. In this study, rats were injected with OXL (4 mg/kg, body weight, i.p.) in 5% glucose solution 30 min after oral administration of NRG (50 and 100 mg/kg, body weight) on the 1st, 2nd, 5th, and 6th days. OXL caused sensory and motor neuropathy (as revealed by the hot plate, tail flick, rota-rod, and cold hyperalgesia tests) in the sciatic nerve of rats. Coadministration of oral NRG alleviated OXL-induced sensory and motor neuropathy. Levels of superoxide dismutase, catalase, glutathione peroxidase, nuclear factor erythroid 2-related factor 2, Heme oxygenase-1, nuclear factor-κ B, tumor necrosis factor-α, interleukin-1β, Bax, Bcl-2, caspase-3, paraoxonase, mitogen-activated protein kinase 14, neuronal nitric oxide synthase (nNOS), acetylcholinesterase, and arginase 2 in the sciatic nerve tissues were assessed by real-time polymerase chain reaction. Moreover, the protein levels of caspase-3, Bax, Bcl-2, intercellular adhesion molecules-1, glial fibrillary acidic protein, and nNOS were examined by Western blot analysis. NRG treatment significantly improved all the above-mentioned parameters and reduced OXL-induced oxidative stress, inflammation, and apoptosis in the sciatic nerve tissue. In conclusion, this study demonstrated that NRG significantly attenuated OXL-induced peripheral neuropathy and might be considered as a new protective agent to prevent the OXL-induced peripheral neuropathy.

Prevention of anticancer therapy-induced neurotoxicity: putting DNA damage in perspective

Chemotherapy-induced peripheral neuropathy (CIPN) is a severe side effect of conventional cancer therapeutics (cAT) that significantly impacts the quality of life of tumor patients. The molecular mechanisms of CIPN are incompletely understood and there are no effective preventive or therapeutic measures available to date. Here, we present a brief overview of the current knowledge about mechanisms underlying CIPN and discuss DNA damage-related stress responses as feasible targets for the prevention of CIPN. In addition, we discuss that the nematode Caenorhabditis elegans is a useful 3R-conform model organism to further elucidate molecular mechanisms of CIPN and to identify novel lead compounds protecting from cAT-triggered neuropathy.

Application Potential of Plant-Derived Medicines in Prevention and Treatment of Platinum-Induced Peripheral Neurotoxicity

As observed with other chemotherapeutic agents, the clinical application of platinum agents is a double-edged sword. Platinum-induced peripheral neuropathy (PIPN) is a common adverse event that negatively affects clinical outcomes and patients’ quality of life. Considering the unavailability of effective established agents for preventing or treating PIPN and the increasing population of cancer survivors, the identification and development of novel, effective interventions are the need of the hour. Plant-derived medicines, recognized as ideal agents, can not only help improve PIPN without affecting chemotherapy efficacy, but may also produce synergy. In this review, we present a brief summary of the mechanisms of platinum agents and PIPN and then focus on exploring the preventive or curative effects and underlying mechanisms of plant-derived medicines, which have been evaluated under platinum-induced neurotoxicity conditions. We identified 11 plant extracts as well as 17 plant secondary metabolites, and four polyherbal preparations. Their effects against PIPN are focused on oxidative stress and mitochondrial dysfunction, glial activation and inflammation response, and ion channel dysfunction. Also, ten clinical trials have assessed the effect of herbal products in patients with PIPN. The understanding of the molecular mechanism is still limited, the quality of clinical trials need to be further improved, and in terms of their efficacy, safety, and cost effectiveness studies have not provided sufficient evidence to establish a standard practice. But plant-derived medicines have been found to be invaluable sources for the development of natural agents with beneficial effects in the prevention and treatment of PIPN.

Targeting strategies for oxaliplatin-induced peripheral neuropathy: clinical syndrome, molecular basis, and drug development

Oxaliplatin (OHP)-induced peripheral neurotoxicity (OIPN) is a severe clinical problem and potentially permanent side effect of cancer treatment. For the management of OIPN, accurate diagnosis and understanding of significant risk factors including genetic vulnerability are essential to improve knowledge regarding the prevalence and incidence of OIPN as well as enhance strategies for the prevention and treatment of OIPN. The molecular mechanisms underlying OIPN are complex, with multi-targets and various cells causing neuropathy. Furthermore, mechanisms of OIPN can reinforce each other, and combination therapies may be required for effective management. However, despite intense investigation in preclinical and clinical studies, no preventive therapies have shown significant clinical efficacy, and the established treatment for painful OIPN is limited. Duloxetine is the only agent currently recommended by the American Society of Clinical Oncology. The present article summarizes the most recent advances in the field of studies on OIPN, the overview of the clinical syndrome, molecular basis, therapy development, and outlook of future drug candidates. Importantly, closer links between clinical pain management teams and oncology will advance the effectiveness of OIPN treatment, and the continued close collaboration between preclinical and clinical research will facilitate the development of novel prevention and treatments for OIPN.

Silent cold-sensing neurons contribute to cold allodynia in neuropathic pain

Patients with neuropathic pain often experience innocuous cooling as excruciating pain. The cell and molecular basis of this cold allodynia is little understood. We used in vivo calcium imaging of sensory ganglia to investigate how the activity of peripheral cold-sensing neurons was altered in three mouse models of neuropathic pain: oxaliplatin-induced neuropathy, partial sciatic nerve ligation, and ciguatera poisoning. In control mice, cold-sensing neurons were few in number and small in size. In neuropathic animals with cold allodynia, a set of normally silent large diameter neurons became sensitive to cooling. Many of these silent cold-sensing neurons responded to noxious mechanical stimuli and expressed the nociceptor markers Nav1.8 and CGRPα. Ablating neurons expressing Nav1.8 resulted in diminished cold allodynia. The silent cold-sensing neurons could also be activated by cooling in control mice through blockade of Kv1 voltage-gated potassium channels. Thus, silent cold-sensing neurons are unmasked in diverse neuropathic pain states and cold allodynia results from peripheral sensitization caused by altered nociceptor excitability.

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.

Zingiber officinale Roscoe Rhizomes Attenuate Oxaliplatin-Induced Neuropathic Pain in Mice

Oxaliplatin is a platinum derivative chemotherapeutic drug widely used against cancers, but even a single treatment can induce a severe allodynia that requires treatment interruption and dose diminution. The rhizome of Zingiber officinale roscoe (Z. officinale, ginger), has been widely used in traditional medicine to treat various diseases causing pain; however, its effect against oxaliplatin-induced neuropathic pain has never been assessed. In mice, a single oxaliplatin (6 mg/kg, i.p.) treatment induced significant cold and mechanical allodynia. Cold and mechanical allodynia were assessed by acetone drop and von Frey filament tests, respectively. Water extracts of Z. officinale (100, 300, and 500 mg/kg, p.o.) significantly attenuated both cold and mechanical allodynia induced by oxaliplatin. Intrathecal pre-treatment with the antagonist 5-HT1A (NAN-190, i.t., 1 μg), but not with the antagonist 5-HT2A (ketanserin, i.t., 1 μg), significantly blocked the analgesic effect of Z. officinale against both cold and mechanical allodynia. However, 5-HT3 antagonist (MDL-72222, i.t., 15 μg) administration only blocked the anti-allodynic effect of Z. officinale against cold allodynia. Real-time PCR analysis demonstrated that Z. officinale significantly increased the mRNA expression of the spinal 5-HT1A receptor that was downregulated after oxaliplatin injection. These results suggest that Z. officinale may be a viable treatment option for oxaliplatin-induced neuropathic pain.

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.

The active second-generation proteasome inhibitor oprozomib reverts the oxaliplatin-induced neuropathy symptoms

Oxaliplatin-induced neuropathy (OXAIN) is a major adverse effect of this antineoplastic drug, widely used in the treatment of colorectal cancer. Although its molecular mechanisms remain poorly understood, recent evidence suggest that maladaptive neuroplasticity and oxidative stress may participate to the development of this neuropathy. Given the role played on protein remodeling by ubiquitin-proteasome system (UPS) in response to oxidative stress and in neuropathic pain, we investigated whether oxaliplatin might cause alterations in the UPS-mediated degradation pathway, in order to identify new pharmacological tools useful in OXAIN. In a rat model of OXAIN (2.4 mg kg^-1 i.p., daily for 10 days), a significant increase in chymotrypsin-(β5) like activity of the constitutive proteasome 26S was observed in the thalamus (TH) and somatosensory cortex (SSCx). In addition, the selective up-regulation of β5 and LMP7 (β5i) subunit gene expression was assessed in the SSCx. Furthermore, this study revealed that oprozomib, a selective β5 subunit proteasome inhibitor, is able to normalize the spinal prodynorphin gene expression upregulation induced by oxaliplatin, as well as to revert mechanical allodynia and thermal hyperalgesia observed in oxaliplatin-treated rats. These results underline the relevant role of UPS in the OXAIN and suggest new pharmacological targets to counteract this severe adverse effect. This preclinical study reveals the involvement of the proteasome in the oxaliplatin-induced neuropathy and adds useful information to better understand the molecular mechanism underlying this pain condition. Moreover, although further evidence is required, these findings suggest that oprozomib could be a therapeutic option to counteract chemotherapy-induced neuropathy.

Neurotoxicity of antineoplastic drugs: Mechanisms, susceptibility, and neuroprotective strategies

This review summarizes the adverse effects on the central and/or peripheral nervous systems that may occur in response to antineoplastic drugs. In particular, we describe the neurotoxic side effects of the most commonly used drugs, such as platinum compounds, doxorubicin, ifosfamide, 5-fluorouracil, vinca alkaloids, taxanes, methotrexate, bortezomib and thalidomide. Neurotoxicity may result from direct action of compounds on the nervous system or from metabolic alterations produced indirectly by these drugs, and either the central nervous system or the peripheral nervous system, or both, may be affected. The incidence and severity of neurotoxicity are principally related to the dose, to the duration of treatment, and to the dose intensity, though other factors, such as age, concurrent pathologies, and genetic predisposition may enhance the occurrence of side effects. To avoid or reduce the onset and severity of these neurotoxic effects, the use of neuroprotective compounds and/or strategies may be helpful, thereby enhancing the therapeutic effectiveness of antineoplastic drug.

Chronic defects in intraspinal mechanisms of spike encoding by spinal motoneurons following chemotherapy

Chemotherapy-induced sensorimotor disabilities, including gait and balance disorders, as well as physical fatigue often persist for months and sometimes years into disease free survival from cancer. While associated with impaired sensory function, chronic sensorimotor disorders might also depend on chemotherapy-induced defects in other neuron types. In this report, we extend consideration to motoneurons, which, if chronically impaired, would necessarily degrade movement behavior. The present study was undertaken to determine whether motoneurons qualify as candidate contributors to chronic sensorimotor disability independently from sensory impairment. We tested this possibility in vivo from rats 5 weeks following human-scaled treatment with one of the platinum-based compounds, oxaliplatin, widely used in chemotherapy for a variety of cancers. Action potential firing of spinal motoneurons responding to different fixed levels of electrode-current injection was measured in order to assess the neurons' intrinsic capacity for stimulus encoding. The encoding of stimulus duration and intensity corroborated in untreated control rats was severely degraded in oxaliplatin treated rats, in which motoneurons invariably exhibited erratic firing that was unsustained, unpredictable from one stimulus trial to the next, and unresponsive to changes in current strength. Direct measurements of interspike oscillations in membrane voltage combined with computer modeling pointed to aberrations in subthreshold conductances as a plausible contributor to impaired firing behavior. These findings authenticate impaired spike encoding as a candidate contributor to, in the case of motoneurons, deficits in mobility and fatigue. Aberrant firing also becomes a deficit worthy of testing in other CNS neurons as a potential contributor to perceptual and cognitive disorders induced by chemotherapy in patients.

Oral administration of Cystine and Theanine ameliorates oxaliplatin-induced chronic peripheral neuropathy in rodents

Oxaliplatin frequently causes severe peripheral neuropathy as a dose-limiting toxicity. However, this toxicity lacks a strategy for prevention. Cystine/Theanine is a supplement, which includes precursors for the biosynthesis of glutathione. In this study, we investigated the effects of Cystine/Theanine on oxaliplatin-induced peripheral neuropathy using an in vivo model. Repeated injection of oxaliplatin (4 mg/kg intraperitoneally twice a week for 2 weeks) caused mechanical allodynia, cold hyperalgesia and axonal degeneration of the sciatic nerve in rats. Mechanical allodynia and axonal degeneration, but not cold hyperalgesia, were ameliorated by daily co-administration of Cystine [200 mg/kg orally (p.o.)] and Theanine (80 mg/kg p.o.). Moreover, co-administration of Cystine and Theanine to rats significantly increased the glutathione level in the sciatic nerve compared with the oxaliplatin group. Furthermore, Cystine and Theanine did not attenuate the tumour cytotoxicity of oxaliplatin in C-26 tumour cell-bearing mice. These findings suggest that Cystine and Theanine may be beneficial for preventing oxaliplatin-induced peripheral neuropathy.

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.

Oxaliplatin-induced peripheral neuropathy: clinical features, mechanisms, prevention and treatment

Oxaliplatin (OXA) is a commonly used platinum-based chemotherapy drug for colorectal cancer. OXA-induced peripheral neurotoxcity (OIPN) is a comprehensive adverse reaction of OXA. OIPN can be divided into acute and chronic types according to clinical features and different mechanisms. The main clinical features of acute OIPN are cold-sensitive sensory symptoms and neuropathic pain in limbs. In addition to the above symptoms, chronic OIPN also produces autonomic nerve dysfunction. The most important mechanism involved in acute OIPN is the alteration of voltage-gated Na + channels, and nuclear DNA damage in chronic OIPN. There are some methods like reducing exposure to cold, calcium and magnesium salts, amifostine could be beneficial in acute OIPN prevention and dose modification, changing in schedule glutathione, duloxetine, selective serotonin reuptake inhibitors, carbonic anhydrase inhibitor in chronic OIPN prevention. Recent updates are provided in this article in relation to the clinical features, potential mechanisms, prevention and treatment of OIPN.

Neuroprotective effect of alogliptin on oxaliplatin-induced peripheral neuropathy in vivo and in vitro

Oxaliplatin is a platinum-based antineoplastic drug commonly used for treating colorectal, gastric, and pancreatic cancer. However, it frequently causes peripheral neuropathy as dose-limiting toxicity and is lacking a strategy for prevention. Alogliptin, a dipeptidyl peptidase 4 (DPP-4) inhibitor, is an oral antidiabetic drug. Previous studies have shown that DPP-4 inhibitors have pleiotropic effects, including neuroprotection. In this study, we investigated the effects of alogliptin on oxaliplatin-induced peripheral neuropathy using in vitro and in vivo models. In PC12 cells, alogliptin attenuated neurite disorders induced by oxaliplatin and cisplatin. The repeated injection of oxaliplatin caused mechanical allodynia and axonal degeneration of the sciatic nerve in rats. These neuropathies were ameliorated by co-administration of alogliptin. Moreover, alogliptin did not attenuate tumor cytotoxicity of oxaliplatin in the cultured colon, gastric, or pancreatic cancer cell lines and tumor-bearing mice. These findings suggest that alogliptin may be beneficial for preventing oxaliplatin-induced peripheral neuropathy.

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.

Characterization in Dual Activation by Oxaliplatin, a Platinum-Based Chemotherapeutic Agent of Hyperpolarization-Activated Cation and Electroporation-Induced Currents

Oxaliplatin (OXAL) is regarded as a platinum-based anti-neoplastic agent. However, its perturbations on membrane ionic currents in neurons and neuroendocrine or endocrine cells are largely unclear, though peripheral neuropathy has been noted during its long-term administration. In this study, we investigated how the presence of OXAL and other related compounds can interact with two types of inward currents; namely, hyperpolarization-activated cation current (I_h) and membrane electroporation-induced current (I_MEP). OXAL increased the amplitude or activation rate constant of I_h in a concentration-dependent manner with effective EC₅₀ or K_D values of 3.2 or 6.4 μM, respectively, in pituitary GH₃ cells. The stimulation by this agent of I_h could be attenuated by subsequent addition of ivabradine, protopine, or dexmedetomidine. Cell exposure to OXAL (3 μM) resulted in an approximately 11 mV rightward shift in I_h activation along the voltage axis with minimal changes in the gating charge of the curve. The exposure to OXAL also effected an elevation in area of the voltage-dependent hysteresis elicited by long-lasting triangular ramp. Additionally, its application resulted in an increase in the amplitude of I_MEP elicited by large hyperpolarization in GH₃ cells with an EC₅₀ value of 1.3 μM. However, in the continued presence of OXAL, further addition of ivabradine, protopine, or dexmedetomidine always resulted in failure to attenuate the OXAL-induced increase of I_MEP amplitude effectively. Averaged current-voltage relation of membrane electroporation-induced current (I_MEP) was altered in the presence of OXAL. In pituitary R1220 cells, OXAL-stimulated I_h remained effective. In Rolf B1.T olfactory sensory neurons, this agent was also observed to increase I_MEP in a concentration-dependent manner. In light of the findings from this study, OXAL-mediated increases of I_h and I_MEP may coincide and then synergistically act to increase the amplitude of inward currents, raising the membrane excitability of electrically excitable cells, if similar in vivo findings occur.

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.

Liability of the voltage-gated potassium channel KCNN3 repeat polymorphism to acute oxaliplatin-induced peripheral neurotoxicity

Thus far, there are conflicting results on the causal role of K+ channels in the pathogenesis of acute oxaliplatin-induced peripheral neurotoxicity (OXAIPN). As such, we tested the hypothesis that the voltage-gated K+ channel KCNN3 repeat polymorphism confers liability to acute OXAIPN. DNA from 151 oxaliplatin-treated patients for colorectal cancer was extracted and genotyped. The incidence of acute OXIPN was measured by the OXA-neuropathy questionnaire, while the severity of acute OXAIPN was scored basing on the number of symptoms reported by the patients at each clinical assessment. The increased number of acute symptoms was considered as being suggestive of an increased severity of acute OXAIPN. A total of 130/151 (86.1%) patients developed any grade of acute OXAIPN. Grade I acute neurotoxicity was revealed in 43 (28.5%) patients; grade II in 34 (22.5%); and grade III in 53 (53.1%) patients. Genotyping revealed alleles carrying 11 to 20 CAG repeats. The majority of patients were heterozygous (131; 89.4%). The most common numbers of CAG repeats were 15 (n = 46), 16 (n = 53), and 17 (n = 95). Patients carrying alleles with either 15 to 17 CAG repeats (P = .601) did not experience a higher incidence of grade III (treatment-emergent) acute OXAIPN. Likewise, no increased incidence of acute treatment-emergent OXAIPN was noted in heterozygous patients carrying either two short alleles (<19 CAG repeats) or one short and one long (≥19 CAG repeats) allele (P = .701). Our results do not support a causal relationship between the KCNN3CAG repeat polymorphism and acute OXΑIPN.

Rational treatment of chemotherapy-induced peripheral neuropathy with capsaicin 8% patch: from pain relief towards disease modification

Purpose

Chemotherapy-induced peripheral neuropathy (CIPN) with associated chronic pain is a common and disabling condition. Current treatments for neuropathic pain in CIPN are largely ineffective, with unfavorable side-effects. The capsaicin 8% patch (capsaicin 179 mg patch) is approved for the treatment of neuropathic pain: a single topical cutaneous application can produce effective pain relief for up to 12 weeks. We assessed the therapeutic potential of capsaicin 8% patch in patients with painful CIPN, and its mechanism of action.

Patients and methods

16 patients with chronic painful CIPN (mean duration 2.5 years), in remission for cancer and not receiving chemotherapy, were treated with 30 min application of capsaicin 8% patch to the feet. Symptoms were monitored using the 11-point numerical pain rating scale (NPRS), and questionnaires. Investigations were performed at baseline and three months after patch application, including skin biopsies with a range of markers, and quantitative sensory testing (QST).

Results

Patients reported significant reduction in spontaneous pain (mean NPRS: −1.27; 95% CI 0.2409 to 2.301; p=0.02), touch-evoked pain (−1.823; p=0.03) and cold-evoked pain (−1.456; p=0.03). Short-Form McGill questionnaire showed a reduction in neuropathic (p=0.0007), continuous (p=0.01) and overall pain (p=0.004); Patient Global Impression of Change showed improvement (p=0.001). Baseline skin biopsies showed loss of intra-epidermal nerve fibers (IENF), and also of sub-epidermal nerve fibers quantified by image analysis. Post-patch application skin biopsies showed a significant increase towards normalization of intra-epidermal and sub-epidermal nerve fibers (for IENF: structural marker PGP9.5, p=0.009; heat receptor TRPV1, p=0.027; regenerating nerve marker GAP43, p=0.04). Epidermal levels of Nerve Growth Factor (NGF), Neurotrophin-3 (NT-3), and Langerhans cells were also normalized. QST remained unchanged and there were no systemic side-effects, as in previous studies.

Conclusion

Capsaicin 8% patch provides significant pain relief in CIPN, and may lead to regeneration and restoration of sensory nerve fibers ie, disease modification.

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.

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.

Synthesis and encapsulation of V(IV,V) compounds in silica nanoparticles targeting development of antioxidant and antiradical nanomaterials

The quest for effective treatments of oxidative stress has concentrated over the years on new nanomaterials with improved antioxidant and antiradical activity, thereby attracting broad research interest. In that regard, research efforts in our lab were launched to pursue such hybrid materials involving a) synthesis of silica gel matrices, b) evaluation of the suitability of atoxic matrices as potential carriers for the controlled release of V(IV)(VOSO₄), V(V)(NaVO₃) compounds and a newly synthesized heterometallic lithium-vanadium(IV,V) tetranuclear compound containing vanadium-bound hydroxycarboxylic 1,3-diamine-2-propanol-N,N,N',N'-tetraacetic acid (DPOT), and c) investigation of structural and textural properties of silica nanoparticles (NPs) by different and complementary characterization techniques, inquiring into the nature of the encapsulated vanadium species and their interaction with the siloxane matrix, collectively targeting novel antioxidant and antiradical nanomaterials biotechnology. The physicochemical characterization of the vanadium-loaded SiO₂ NPs led to the formulation of optimized material configuration linked to the delivery of the encapsulated antioxidant-antiradical load. Entrapment and drug release studies showed a) the competence of hybrid nanoparticles with respect to encapsulation efficiency of the vanadium compound (concentration dependence), b) congruence with the physicochemical features determined, and c) a well-defined release profile of NP load. Antioxidant properties and the free radical scavenging capacity of the new hybrid materials (containing VOSO₄, NaVO₃, and V-DPOT) were demonstrated through a) 2-diphenyl-1-picrylhydrazyl (DPPH) free radical, and b) intracellular-extracellular reactive oxygen species (ROS) assays, through UV-Visible spectroscopy techniques, collectively showing that the hybrid silica NPs (empty-loaded) could serve as an efficient platform for nanodrug formulations counteracting oxidative stress.

Identification of drug transporters contributing to oxaliplatin-induced peripheral neuropathy

Oxaliplatin is widely used as a key drug in the treatment of colorectal cancer. However, its administration is associated with the dose-limiting adverse effect, peripheral neuropathy. Platinum accumulation in the dorsal root ganglion (DRG) is the major mechanism responsible for oxaliplatin-induced neuropathy. Some drug transporters have been identified as platinum complex transporters in kidney or tumor cells, but not yet in DRG. In the present study, we investigated oxaliplatin transporters and their contribution to peripheral neuropathy. We identified 12 platinum transporters expressed in DRG with real-time PCR, and their transiently overexpressing cells were established. After exposure to oxaliplatin, the accumulation of platinum in these overexpressing cells was evaluated using a coupled plasma mass spectrometer. Octn1/2- and Mate1-expressing cells showed the intracellular accumulation of oxaliplatin. In an animal study, peripheral neuropathy developed after the administration of oxaliplatin (4 mg/kg, intravenously, twice a week) to siRNA-injected rats (0.5 nmol, intrathecally, once a week) was demonstrated with the von Frey test. The knockdown of Octn1 in DRG ameliorated peripheral neuropathy, and decreased platinum accumulation in DRG, whereas the knockdown of Octn2 did not. Mate1 siRNA-injected rats developed more severe neuropathy than control rats. These results indicate that Octn1 and Mate1 are involved in platinum accumulation at DRG and oxaliplatin-induced peripheral neuropathy.

Effect of certain trimethoxy flavones on paclitaxel - induced peripheral neuropathy in mice

BACKGROUND

The anti - nociceptive effect of 7, 2', 3' - trimethoxy flavone, 7, 2', 4' - trimethoxy flavone, 7, 3', 4' - trimethoxy flavone and 7, 5, 4' - trimethoxy flavone against inflammatory, neurogenic and thermal pain in mice was reported earlier. The present study was designed to investigate the effect of the above trimethoxy flavones in amelioration of peripheral neuropathy induced by paclitaxel.

METHODS

Peripheral neuropathy was induced in mice by administration of a single i.p. dose (10 mg/kg) of paclitaxel. The manifestations of peripheral neuropathy such as tactile allodynia, cold allodynia and thermal hyperalgesia were assessed 24 h later by employing hair aesthesiometer test, acetone bubble test and hot water tail immersion test respectively. Further, the role of inflammatory cytokines like TNF - α, IL - 1β and free radicals in the action of trimethoxy flavones was investigated using in vitro assays.

RESULTS

The test compounds dose dependently attenuated paclitaxel - induced tactile allodynia, cold allodynia and thermal hyperalgesia in mice. The test compounds inhibited TNF - α, IL - 1β and free radicals in a concentration dependent manner.

CONCLUSION

The investigated trimethoxy flavones attenuated paclitaxel - induced peripheral neuropathy in mice. The inhibition of cytokines and free radicals in addition to many neuronal mechanisms reported earlier may contribute to this beneficial effect.

Possible association of CAG repeat polymorphism in KCNN3 encoding the potassium channel SK3 with oxaliplatin-induced neurotoxicity

INTRODUCTION

Data suggest a role of the potassium channel SK3 (KCNN3 gene) in oxaliplatin-induced neurotoxicity (OIN). Length variations in the polymorphic CAG repeat of the KCNN3 gene may be associated with the risk of OIN.

MATERIALS AND METHODS

We performed patch-clamp experiments on HEK293 cell lines, expressing SK3 channel isoforms with short (11) or long (24) CAG repetitions, to measure intracellular calcium concentrations to test the effects of oxaliplatin on current density. A retrospective study was carried out on patients with colorectal cancer who had received oxaliplatin-based chemotherapy. DNA for KCNN3 genotyping was extracted from leukocytes. The region containing the CAG repeats was amplified by PCR and the products separated by capillary electrophoresis for length analysis. The patients were divided into three groups depending on whether they carried two short alleles, one short allele and one long allele, or two long alleles. The primary endpoint was the onset of grade 2 or 3 neuropathy to oxaliplatin.

RESULTS

There was no difference in current density, but oxaliplatin induced a differential effect on apamin-sensitive current density between the two isoforms expressed in the HEK cell lines. There was a significant reduction of store-operated calcium entry into cells expressing the short and more active isoform only after high concentration of oxaliplatin exposition. Eighty-six patients were included in the clinical study. There was no significant association between OIN and KCNN3 polymorphism for the three groups.

CONCLUSION

We observed a slight association between OIN and CAG repeat polymorphisms of the KCNN3 gene in a preclinical model, but not a clinical study.

Roles of Transient Receptor Potential Ankyrin 1 in Oxaliplatin-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN), characterized by symptoms of paresthesia, dysesthesia, numbness, and pain, is a common adverse effect of several chemotherapeutic agents, including platinum-based agents, taxanes, and vinca alkaloids. However, no effective prevention or treatment strategies exist for CIPN because the mechanisms underpinning this neuropathy are poorly understood. Recent accumulating evidence suggests that some transient receptor potential (TRP) channels functioning as nociceptors in primary sensory neurons are responsible for CIPN. In this review, we focus on the specific roles of redox-sensitive TRP ankyrin 1 (TRPA1), which was first reported to be a cold nociceptor, in acute cold hypersensitivity induced by oxaliplatin, a platinum-based agent, because it induces a peculiar cold-triggered CIPN during or within hours after its infusion. Oxaliplatin-induced rapid-onset cold hypersensitivity is ameliorated by TRPA1 blockade or deficiency in mice. Consistent with this, oxaliplatin enhances the responsiveness of TRPA1 stimulation, but not of TRP melastatin 8 (TRPM8) and TRP vanilloid 1 (TRPV1), in mice and cultured mouse dorsal root ganglion neurons. These responses are mimicked by an oxaliplatin metabolite, oxalate. In human TRPA1 (hTRPA1)-expressing cells, oxaliplatin or oxalate causes TRPA1 sensitization to reactive oxygen species (ROS) by inhibiting prolyl hydroxylases (PHDs). Inhibition of PHD-mediated hydroxylation of a proline residue within the N-terminal ankyrin repeat of hTRPA1 endows TRPA1 with cold sensitivity by its sensing of cold-evoked ROS. This review discusses these findings and summarizes the evidence demonstrating that oxaliplatin-induced acute cold hypersensitivity is caused by TRPA1 sensitization to ROS via PHD inhibition, which enables TRPA1 to convert ROS signaling into cold sensitivity.

Triggering receptor expressed on myeloid cells 2 (TREM2) dependent microglial activation promotes cisplatin-induced peripheral neuropathy in mice

Chemotherapy-induced peripheral neuropathy (CIPN) is a common adverse side effect of many antineoplastic agents. Patients treated with chemotherapy often report pain and paresthesias in a "glove-and-stocking" distribution. Diverse mechanisms contribute to the development and maintenance of CIPN. However, the role of spinal microglia in CIPN is not completely understood. In this study, cisplatin-treated mice displayed persistent mechanical allodynia, sensory deficits and decreased density of intraepidermal nerve fibers (IENFs). In the spinal cord, activation of microglia, but not astrocyte, was persistently observed until week five after the first cisplatin injection. Additionally, mRNA levels of inflammation related molecules including IL-1β, IL-6, tumor necrosis factor (TNF)-α, inducible nitric oxide synthase (iNOS) and CD16, were increased after cisplatin treatment. Intraperitoneal (i.p.) or intrathecal (i.t.) injection with minocycline both alleviated cisplatin-induced mechanical allodynia and sensory deficits, and prevented IENFs loss. Furthermore, cisplatin enhanced triggering receptor expressed on myeloid cells 2 (TREM2) /DNAX-activating protein of 12 kDa (DAP12) signaling in the spinal cord microglia. The blockage of TREM2 by i.t. injecting anti-TREM2 neutralizing antibody significantly attenuated cisplatin-induced mechanical allodynia, sensory deficits and IENFs loss. Meanwhile, anti-TREM2 neutralizing antibody prominently suppressed the spinal IL-6, TNF-α, iNOS and CD16 mRNA level, but it dramatically up-regulated the anti-inflammatory cytokines IL-4 and IL-10. The data demonstrated that cisplatin triggered persistent activation of spinal cord microglia through strengthening TREM2/DAP12 signaling, which further resulted in CIPN. Functional blockage of TREM2 or inhibition of microglia both benefited for cisplatin-induced peripheral neuropathy. Microglial TREM2/DAP12 may serve as a potential target for CIPN intervention.

Axonal excitability changes and acute symptoms of oxaliplatin treatment: In vivo evidence for slowed sodium channel inactivation

OBJECTIVE

Neurotoxicity is the most frequent dose-limiting side effect of the anti-cancer agent oxaliplatin, but the mechanisms are not well understood. This study used nerve excitability testing to investigate the pathophysiology of the acute neurotoxicity.

METHODS

Questionnaires, quantitative sensory tests, nerve conduction studies and nerve excitability testing were undertaken in 12 patients with high-risk colorectal cancer treated with adjuvant oxaliplatin and in 16 sex- and age-matched healthy controls. Examinations were performed twice for patients: once within 3 days after oxaliplatin treatment (post-infusion examination) and once shortly before the following treatment (recovery examination).

RESULTS

The most frequent post-infusion symptoms were tingling paresthesias and cold allodynia. The most prominent nerve excitability change was decreased superexcitability of motor axons which correlated with the average intensity of abnormal sensations (Spearman Rho = 0.80, p < .01). The motor nerve excitability changes were well modeled by a slowing of sodium channel inactivation, and were proportional to dose/m² with a half-life of about 10d.

CONCLUSIONS

Oxaliplatin induces reversible slowing of sodium channel inactivation in motor axons, and these changes are closely related to the reversible cold allodynia. However, further studies are required due to small sample size in this study.

SIGNIFICANCE

Nerve excitability data provide an index of sodium channel dysfunction: an objective biomarker of acute oxaliplatin neurotoxicity.

Platinum-induced neurotoxicity: A review of possible mechanisms

Patients treated with platinum-based chemotherapy frequently experience neurotoxic symptoms, which may lead to premature discontinuation of therapy. Despite discontinuation of platinum drugs, these symptoms can persist over a long period of time. Cisplatin and oxaliplatin, among all platinum drugs, have significant neurotoxic potential. A distal dose-dependent symmetrical sensory neuropathy is the most common presentation of platinum neurotoxicity. DNA damage-induced apoptosis of dorsal root ganglion (DRG) neurons seems to be the principal cause of neurological symptoms. However, DRG injury alone cannot explain some unique symptoms such as cold-aggravated burning pain affecting distal extremities that is observed with oxaliplatin administration. In this article, we briefly reviewed potential mechanisms for the development of platinum drugs-associated neurological manifestations.

Pathophysiology of Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced neuropathy is a common, dose-dependent adverse effect of several antineoplastics. It can lead to detrimental dose reductions and discontinuation of treatment, and severely affects the quality of life of cancer survivors. Clinically, chemotherapy-induced peripheral neuropathy presents as deficits in sensory, motor, and autonomic function which develop in a glove and stocking distribution due to preferential effects on longer axons. The pathophysiological processes are multi-factorial and involve oxidative stress, apoptotic mechanisms, altered calcium homeostasis, axon degeneration and membrane remodeling as well as immune processes and neuroinflammation. This review focusses on the commonly used antineoplastic substances oxaliplatin, cisplatin, vincristine, docetaxel, and paclitaxel which interfere with the cancer cell cycle-leading to cell death and tumor degradation-and cause severe acute and chronic peripheral neuropathies. We discuss drug mechanism of action and pharmacokinetic disposition relevant to the development of peripheral neuropathy, the epidemiology and clinical presentation of chemotherapy-induced neuropathy, emerging insight into genetic susceptibilities as well as current understanding of the pathophysiology and treatment approaches.

Ion channels and neuronal hyperexcitability in chemotherapy-induced peripheral neuropathy; cause and effect?

Abstract

Cancer is the second leading cause of death worldwide and is a major global health burden. Significant improvements in survival have been achieved, due in part to advances in adjuvant antineoplastic chemotherapy. The most commonly used antineoplastics belong to the taxane, platinum, and vinca alkaloid families. While beneficial, these agents are frequently accompanied by severe side effects, including chemotherapy-induced peripheral neuropathy (CPIN). While CPIN affects both motor and sensory systems, the majority of symptoms are sensory, with pain, tingling, and numbness being the predominant complaints. CPIN not only decreases the quality of life of cancer survivors but also can lead to discontinuation of treatment, thereby adversely affecting survival. Consequently, minimizing the incidence or severity of CPIN is highly desirable, but strategies to prevent and/or treat CIPN have proven elusive. One difficulty in achieving this goal arises from the fact that the molecular and cellular mechanisms that produce CPIN are not fully known; however, one common mechanism appears to be changes in ion channel expression in primary afferent sensory neurons. The processes that underlie chemotherapy-induced changes in ion channel expression and function are poorly understood. Not all antineoplastic agents directly affect ion channel function, suggesting additional pathways may contribute to the development of CPIN Indeed, there are indications that these drugs may mediate their effects through cellular signaling pathways including second messengers and inflammatory cytokines. Here, we focus on ion channelopathies as causal mechanisms for CPIN and review the data from both pre-clinical animal models and from human studies with the aim of facilitating the development of appropriate strategies to prevent and/or treat CPIN.

Niclosamide Inhibits Oxaliplatin Neurotoxicity while Improving Colorectal Cancer Therapeutic Response

Neuropathic pain is a limiting factor of platinum-based chemotherapies. We sought to investigate the neuroprotective potential of niclosamide in peripheral neuropathies induced by oxaliplatin. Normal neuron-like and cancer cells were treated in vitro with oxaliplatin associated or not with an inhibitor of STAT3 and NF-κB, niclosamide. Cell production of reactive oxygen species and viability were measured by 2',7'-dichlorodihydrofluorescein diacetate and crystal violet. Peripheral neuropathies were induced in mice by oxaliplatin with or without niclosamide. Neurologic functions were assessed by behavioral and electrophysiologic tests, intraepidermal innervation, and myelination by immunohistochemical, histologic, and morphologic studies using confocal microscopy. Efficacy on tumor growth was assessed in mice grafted with CT26 colon cancer cells. In neuron-like cells, niclosamide downregulated the production of oxaliplatin-mediated H₂O₂, thereby preventing cell death. In colon cancer cells, niclosamide enhanced oxaliplatin-mediated cell death through increased H₂O₂ production. These observations were explained by inherent lower basal levels of GSH in cancer cells compared with normal and neuron-like cells. In neuropathic mice, niclosamide prevented tactile hypoesthesia and thermal hyperalgesia and abrogated membrane hyperexcitability. The teniacide also prevented intraepidermal nerve fiber density reduction and demyelination in oxaliplatin mice in this mixed form of peripheral neuropathy. Niclosamide prevents oxaliplatin-induced increased levels of IL6, TNFα, and advanced oxidized protein products. Niclosamide displayed antitumor effects while not abrogating oxaliplatin efficacy. These results indicate that niclosamide exerts its neuroprotection both in vitro and in vivo by limiting oxaliplatin-induced oxidative stress and neuroinflammation. These findings identify niclosamide as a promising therapeutic adjunct to oxaliplatin chemotherapy. Mol Cancer Ther; 16(2); 300-11. ©2016 AACR.