Cisplatin neuropathy. Clinical, electrophysiologic, morphologic, and toxicologic studies

Sensory neuronopathies, diagnostic criteria and causes

PURPOSE OF REVIEW

To stress on the diagnostic strategy of sensory neuronopathies (SNN), including new genes and antibodies.

RECENT FINDING

SNN involve paraneoplastic, dysimmune, toxic, viral and genetic mechanisms. About one-third remains idiopathic. Recently, new antibodies and genes have reduced this proportion. Anti-FGFR3 and anti-AGO antibodies are not specific of SNN, although SNN is predominant and may occur with systemic autoimmune diseases. These antibodies are the only marker of an underlying dysimmune context in two-thirds (anti-FGFR3 antibodies) and one-third of the cases (anti-AGO antibodies), respectively. Patients with anti-AGO antibodies may improve with treatment, which is less clear with anti-FGFR3 antibodies. A biallelic expansion in the RFC1 gene is responsible for the cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) in which SNN is a predominant manifestation. Most of the patients have an adult onset and are sporadic. The RFC1 mutation may represent one-third of idiopathic sensory neuropathies. Finally, the criteria for the diagnosis of paraneoplastic SNN have recently been updated.

SUMMARY

The diagnostic of SNN relies on criteria distinguishing SNN from other neuropathies. The strategy in search of their cause now needs to include these recent findings.

Role of inflammation and oxidative stress in chemotherapy-induced neurotoxicity

Chemotherapeutic agents may adversely affect the nervous system, including the neural precursor cells as well as the white matter. Although the mechanisms are not completely understood, several hypotheses connecting inflammation and oxidative stress with neurotoxicity are now emerging. The proposed mechanisms differ depending on the class of drug. For example, toxicity due to cisplatin occurs due to activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), which alters hippocampal long-term potentiation. Free radical injury is also involved in the cisplatin-mediated neurotoxicity as dysregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) has been seen which protects against the free radical injury by regulating glutathione S-transferases and hemeoxygenase-1 (HO-1). Thus, correcting the imbalance between NF-κB and Nrf2/HO-1 pathways may alleviate cisplatin-induced neurotoxicity. With newer agents like bortezomib, peripheral neuropathy occurs due to up-regulation of TNF-α and IL-6 in the sensory neurons. Superoxide dismutase dysregulation is also involved in bortezomib-induced neuropathy. This article reviews the available literature on inflammation and oxidative stress in neurotoxicity caused by various classes of chemotherapeutic agents. It covers the conventional medicines like platinum compounds, vinca alkaloids, and methotrexate, as well as the newer therapeutic agents like immunomodulators and immune checkpoint inhibitors. A better understanding of the pathophysiology will lead to further advancement in strategies for management of chemotherapy-induced neurotoxicity.

The Future of Neurotoxicology: A Neuroelectrophysiological Viewpoint

Neuroelectrophysiology is an old science, dating to the 18th century when electrical activity in nerves was discovered. Such discoveries have led to a variety of neurophysiological techniques, ranging from basic neuroscience to clinical applications. These clinical applications allow assessment of complex neurological functions such as (but not limited to) sensory perception (vision, hearing, somatosensory function), and muscle function. The ability to use similar techniques in both humans and animal models increases the ability to perform mechanistic research to investigate neurological problems. Good animal to human homology of many neurophysiological systems facilitates interpretation of data to provide cause-effect linkages to epidemiological findings. Mechanistic cellular research to screen for toxicity often includes gaps between cellular and whole animal/person neurophysiological changes, preventing understanding of the complete function of the nervous system. Building Adverse Outcome Pathways (AOPs) will allow us to begin to identify brain regions, timelines, neurotransmitters, etc. that may be Key Events (KE) in the Adverse Outcomes (AO). This requires an integrated strategy, from in vitro to in vivo (and hypothesis generation, testing, revision). Scientists need to determine intermediate levels of nervous system organization that are related to an AO and work both upstream and downstream using mechanistic approaches. Possibly more than any other organ, the brain will require networks of pathways/AOPs to allow sufficient predictive accuracy. Advancements in neurobiological techniques should be incorporated into these AOP-base neurotoxicological assessments, including interactions between many regions of the brain simultaneously. Coupled with advancements in optogenetic manipulation, complex functions of the nervous system (such as acquisition, attention, sensory perception, etc.) can be examined in real time. The integration of neurophysiological changes with changes in gene/protein expression can begin to provide the mechanistic underpinnings for biological changes. Establishment of linkages between changes in cellular physiology and those at the level of the AO will allow construction of biological pathways (AOPs) and allow development of higher throughput assays to test for changes to critical physiological circuits. To allow mechanistic/predictive toxicology of the nervous system to be protective of human populations, neuroelectrophysiology has a critical role in our future.

Cisplatin Mouse Models: Treatment, Toxicity and Translatability

Cisplatin is one of the most widely used chemotherapeutic drugs in the treatment of a wide range of pediatric and adult malignances. However, it has various side effects which limit its use. Cisplatin mouse models are widely used in studies investigating cisplatin therapeutic and toxic effects. However, despite numerous promising results, no significant improvement in treatment outcome has been achieved in humans. There are many drawbacks in the currently used cisplatin protocols in mice. In the paper, the most characterized cisplatin protocols are summarized together with weaknesses that need to be improved in future studies, including hydration and supportive care. As demonstrated, mice respond to cisplatin treatment in similar ways to humans. The paper thus aims to illustrate the complexity of cisplatin side effects (nephrotoxicity, gastrointestinal toxicity, neurotoxicity, ototoxicity and myelotoxicity) and the interconnectedness and interdependence of pathomechanisms among tissues and organs in a dose- and time-dependent manner. The paper offers knowledge that can help design future studies more efficiently and interpret study outcomes more critically. If we want to understand molecular mechanisms and find therapeutic agents that would have a potential benefit in clinics, we need to change our approach and start to treat animals as patients and not as tools.

Drug-Induced Peripheral Neuropathy: Diagnosis and Management

Peripheral neuropathy comes in all shapes and forms and is a disorder which is found in the peripheral nervous system. It can have an acute or chronic onset depending on the multitude of pathophysiologic mechanisms involving different parts of nerve fibers. A systematic approach is highly beneficial when it comes to cost-effective diagnosis. More than 30 causes of peripheral neuropathy exist ranging from systemic and auto-immune diseases, vitamin deficiencies, viral infections, diabetes, etc. One of the major causes of peripheral neuropathy is drug induced disease, which can be split into peripheral neuropathy caused by chemotherapy or by other medications. This review deals with the latest causes of drug induced peripheral neuropathy, the population involved, the findings on physical examination and various workups needed and how to manage each case.

Modulation of Glutamate Transporter EAAT1 and Inward-Rectifier Potassium Channel Kir4.1 Expression in Cultured Spinal Cord Astrocytes by Platinum-Based Chemotherapeutics

Platinum-based chemotherapeutics still play an essential role in cancer treatment. Despite their high effectiveness, severe side effects such as chemotherapy-induced neuropathy (CIPN) occur frequently. The pathophysiology of CIPN by platinum-based chemotherapeutics is not fully understood yet, but primarily the disturbance of dorsal root ganglion cells is discussed. However, there is increasing evidence of central nervous system involvement with activation of spinal cord astrocytes after treatment with chemotherapeutics. We investigated the influence of cis- or oxaliplatin on the functionality of cultured rat spinal cord astrocytes by using immunocytochemistry and patch-clamp electrophysiology. Cis- or oxaliplatin activated spinal astrocytes and led to downregulation of the excitatory amino acid transporter 1 (EAAT1) expression. Furthermore, the expression and function of potassium channel Kir4.1 were modulated. Pre-exposure to a specific Kir4.1 blocker in control astrocytes led to a reduced immune reactivity (IR) of EAAT1 and a nearly complete block of the current density. When spinal astrocytes were pre-exposed to antibiotic minocycline, all effects of cis- or oxaliplatin were abolished. Taken together, the modulation of Kir4.1 and EAAT1 proteins in astrocytes could be linked to the direct impact of cis- or oxaliplatin, identifying spinal astrocytes as a potential target in the prevention and treatment of chemotherapy-induced neuropathy.

Anticancer Drugs and the Nervous System

PURPOSE OF REVIEW

This article reviews the clinical features, prognosis, and treatment of neurotoxicity from anticancer drugs, including conventional cytotoxic chemotherapy, biologics, and targeted therapies, with a focus on the newer immunotherapies (immune checkpoint inhibitors and chimeric antigen receptor T cells).

RECENT FINDINGS

Whereas neurologic complications from traditional chemotherapy are widely recognized, newer cancer therapies, in particular immunotherapies, have unique and distinct patterns of neurologic adverse effects. Anticancer drugs may cause central or peripheral nervous system complications. Neurologic complications of therapy are being seen with increasing frequency as patients with cancer are living longer and receiving multiple courses of anticancer regimens, with novel agents, combinations, and longer duration. Neurologists must know how to recognize treatment-related neurologic toxicity since discontinuation of the offending agent or dose adjustment may prevent further or permanent neurologic injury. It is also imperative to differentiate neurologic complications of therapy from cancer progression into the nervous system and from comorbid neurologic disorders that do not require treatment dose reduction or discontinuation.

SUMMARY

Neurotoxicity from cancer therapy is common, with effects seen on both the central and peripheral nervous systems. Immune checkpoint inhibitor therapy and chimeric antigen receptor T-cell therapy are new cancer treatments with distinct patterns of neurologic complications. Early recognition and appropriate management are essential to help prevent further neurologic injury and optimize oncologic management.

Comparative Analysis of Chemotherapy-Induced Peripheral Neuropathy in Bioengineered Sensory Nerve Tissue Distinguishes Mechanistic Differences in Early-Stage Vincristine-, Cisplatin-, and Paclitaxel-Induced Nerve Damage

Chemotherapy-induced peripheral neuropathy (CIPN) is a well-known, potentially permanent side effect of widely used antineoplastic agents. The mechanisms of neuropathic progression are poorly understood, and the need to test efficacy of novel interventions to treat CIPN continues to grow. Bioengineered microphysiological nerve tissue ("nerve on a chip") has been suggested as an in vitro platform for modeling the structure and physiology of in situ peripheral nerve tissue. Here, we find that length-dependent nerve conduction and histopathologic changes induced by cisplatin, paclitaxel, or vincristine in rat dorsal root ganglion-derived microphysiological sensory nerve tissue recapitulate published descriptions of clinical electrophysiological changes and neuropathologic biopsy findings in test animals and human patients with CIPN. We additionally confirm the postulated link between vincristine-induced axoplasmic transport failure and functional impairment of nerve conduction, the postulated paclitaxel-induced somal toxicity, and identify a potential central role of gliotoxicity in cisplatin-induced sensory neuropathy. Microphysiological CIPN combines the tight experimental control afforded by in vitro experimentation with clinically relevant functional and structural outputs that conventionally require in vivo models. Microphysiological nerve tissue provides a low-cost, high-throughput alternative to conventional nonclinical models for efficiently and effectively investigating lesions, mechanisms, and treatments of CIPN. Neural microphysiological systems are capable of modeling complex neurological disease at the tissue level offering unique advantages over conventional methodology for both testing and generating hypotheses in neurological disease modeling. Impact Statement Recapitulation of distinct hallmarks of clinical CIPN in microphysiological sensory nerve validates a novel peripheral neurotoxicity model with unique advantages over conventional model systems.

Neuronal uptake transporters contribute to oxaliplatin neurotoxicity in mice

Peripheral neurotoxicity is a debilitating condition that afflicts up to 90% of patients with colorectal cancer receiving oxaliplatin-containing therapy. Although emerging evidence has highlighted the importance of various solute carriers to the toxicity of anticancer drugs, the contribution of these proteins to oxaliplatin-induced peripheral neurotoxicity remains controversial. Among candidate transporters investigated in genetically engineered mouse models, we provide evidence for a critical role of the organic cation transporter 2 (OCT2) in satellite glial cells in oxaliplatin-induced neurotoxicity, and demonstrate that targeting OCT2 using genetic and pharmacological approaches ameliorates acute and chronic forms of neurotoxicity. The relevance of this transport system was verified in transporter-deficient rats as a secondary model organism, and translational significance of preventive strategies was demonstrated in preclinical models of colorectal cancer. These studies suggest that pharmacological targeting of OCT2 could be exploited to afford neuroprotection in cancer patients requiring treatment with oxaliplatin.

Involvement of selective GABA-A receptor subtypes in amelioration of cisplatin-induced neuropathic pain by 2'-chloro-6-methyl flavone (2'-Cl-6MF)

Cisplatin-induced peripheral neuropathic pain is a common adverse effect of chemotherapy. The present study evaluated the effects of 2'-chloro-6-methylflavone (2'-Cl-6MF) at recombinant α1β2γ2L, α2β1-3γ2L, and α3β1-3γ2L GABA-A receptor subtypes expressed in Xenopus oocytes and subsequently evaluated its effectiveness in cisplatin-induced neuropathic pain. The results showed that 2'-Cl-6MF potentiated GABA-elicited currents at α2β2/3γ2L and α3β2/3γ2L GABA-A receptor subtypes. The potentiation was blocked by the co-application of flumazenil (a benzodiazepine (BDZs) site antagonist). In behavioral studies, mechanical allodynia was induced by intraplantar injection of cisplatin (40 μg/paw) in Sprague Dawley rats, and behavioral assessments were made 24 h after injection. 2'-Cl-6MF (1, 10, 30, and 100 mg/kg, i.p.), was administered 1 h before behavioral evaluation. Administration of 2'-Cl-6MF (30 and 100 mg/kg, i.p) significantly enhanced the paw withdrawal threshold and decreased mechanical allodynia. The standard drugs, gabapentin (GBP) at the dose of 70 mg/kg, and HZ 166 (16 mg/kg), i.p. also significantly enhanced the paw withdrawal threshold in mechanical allodynia. Pretreatment with pentylenetetrazole (PTZ) (15 mg/kg, i.p.) and flumazenil reversed the antinociceptive effect of 2'-Cl-6MF in mechanical allodynia indicating GABAergic mechanisms. Moreover, the binding mechanism of 2'-Cl-6MF was rationalized by in silico modeling tools. The 3D-coordinates of α2β2γ2L and α2β3γ2L were generated after homology modeling of the α2 subtype and 2'-Cl-6MF was at predicted binding sites of the developed models. The α2 model was compared with the α1 and α3 subunits via structural and sequence alignment. Molecular docking depicted that the compound binds efficiently at the neuromodulator binding site of the receptors. The findings of this study revealed that 2'-Cl-6MF ameliorated the manifestations of cisplatin-induced neuropathic pain in rats. Furthermore, we also conclude that GABAergic mechanisms may contribute to the antinociceptive effect of 2'-Cl-6MF. The molecular docking studies also confirm the involvement of the BDZs site of GABA-A receptors. It was observed that Ile230 of α2 stabilize the chlorophenyl ring of 2'-Cl-6MF through hydrophobic interactions, which is replaced by Val203 in α1 subunit. However, the smaller side chain of Val203 does not provide hydrophobic interaction to the compound due to high conformational flexibility of α1 subunit.

Platinum-Based Drugs Cause Mitochondrial Dysfunction in Cultured Dorsal Root Ganglion Neurons

Cisplatin and oxaliplatin are treatment options for a variety of cancer types. While highly efficient in killing cancer cells, both chemotherapeutics cause severe side effects, e.g., peripheral neuropathies. Using a cell viability assay, a mitochondrial stress assay, and live-cell imaging, the effects of cis- or oxaliplatin on the mitochondrial function, reactive oxygen species (ROS) production, and mitochondrial and cytosolic calcium concentration of transient receptor potential ankyrin 1 (TRPA1)- or vanilloid 1 (TRPV1)-positive dorsal root ganglion (DRG) neurons of adult Wistar rats were determined. Mitochondrial functions were impaired after exposure to cis- or oxaliplatin by mitochondrial respiratory chain complex I-III inhibition. The basal respiration, spare respiratory capacity, and the adenosine triphosphate (ATP)-linked respiration were decreased after exposure to 10 µM cis- or oxaliplatin. The ROS production showed an immediate increase, and after reaching the peak, ROS production dropped. Calcium imaging showed an increase in the cytosolic calcium concentration during exposure to 10 µM cis- or oxaliplatin in TRPA1- or TRPV1-positive DRG neurons while the mitochondrial calcium concentration continuously decreased. Our data demonstrate a significant effect of cis- and oxaliplatin on mitochondrial function as an early event of platinum-based drug exposure, suggesting mitochondria as a potential target for preventing chemotherapy-induced neuropathy.

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.

Impact of peripheral neuropathy induced by platinum in first-line chemotherapy on second-line chemotherapy with paclitaxel for advanced gastric cancer

BACKGROUND

Fluoropyrimidine plus platinum, followed by paclitaxel (PTX) plus ramucirumab is a recommended treatment strategy for advanced gastric cancer (AGC). We investigated how peripheral neuropathy (PN), induced by platinum in first-line chemotherapy, affected the tolerability of second-line chemotherapy with PTX (2nd-PTX).

METHODS

The subjects were AGC patients who received second-line chemotherapy with PTX (2nd-PTX) after the failure of platinum-based chemotherapy between March 2015 and June 2018. We retrospectively reviewed PN severity, and dose reduction and/or discontinuation due to PN during 2nd-PTX, and compared the cumulative incidence of grade 2 PN between the two groups according to first-line chemotherapy containing oxaliplatin (L-OHP) or cisplatin (CDDP).

RESULTS

The L-OHP and CDDP groups consisted of 50 patients each. PN severity before 2nd-PTX was grade 1/2 in 46/12% of patients in the L-OHP group, and 100/0% in the CDDP group. The worst grades of chemotherapy-induced PN during 2nd-PTX were grades 1/2/3 in 40/34/14% of patients in the L-OHP group, and 36/18/0% in the CDDP group. Median time to grade 2 PN after starting second-PTX was 2.5 months in the L-OHP group and 8.6 months in the CDDP group (hazard ratio 3.34, p = 0.002). The frequencies of a PN-related dose reduction and/or discontinuation of PTX were 18% in the L-OHP group and 8% in the CDDP group (p = 0.234).

CONCLUSIONS

The severity of PN and tolerability of 2nd-PTX may be affected by first-line chemotherapy with L-OHP or CDDP for AGC.

Recent advances in understanding chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a common cause of pain and poor quality of life for those undergoing treatment for cancer and those surviving cancer. Many advances have been made in the pre-clinical science; despite this, these findings have not been translated into novel preventative measures and treatments for CIPN. This review aims to give an update on the pre-clinical science, preventative measures, assessment and treatment of CIPN.

Changes in long term peripheral nerve biophysical properties in childhood cancer survivors following neurotoxic chemotherapy

OBJECTIVE

In the context of increasing numbers of childhood cancer survivors (CCS), this study aimed to enhance understanding of the biophysical basis for long term chemotherapy induced peripheral neuropathy from different chemotherapy agents in CCS.

METHODS

Detailed cross-sectional neurophysiological examination, using median nerve axonal excitability studies, alongside clinical assessments, in 103 long term CCS (10.5 ± 0.6 years post-treatment).

RESULTS

Cisplatin treated CCS (n = 16) demonstrated multiple sensory axonal excitability changes including increased threshold (P < 0.05), alterations in depolarising and hyperpolarising threshold electrotonus (P < 0.05) and reduction in resting and minimum IV slope (P < 0.01). Vincristine treated CCS (n = 73) were comparable to controls, except for prolonged distal motor latency (P = 0.001). No differences were seen in the non-neurotoxic chemotherapy group (n = 14). Abnormalities were more evident in the cisplatin subgroup with greater clinical neuropathy manifestations.

CONCLUSION

Persistent long term changes in axonal biophysical properties vary with different chemotherapy agents, most evident after cisplatin exposure. Longitudinal studies of nerve function during chemotherapy treatment are required to further evaluate these differences and their mechanistic basis.

SIGNIFICANCE

This study provides a unique biophysical perspective for persistent cisplatin related neurotoxicity in children, previously under recognised.

Treating Patients With Locally Advanced Squamous Cell Carcinoma of the Head and Neck Unsuitable to Receive Cisplatin-Based Therapy

Concurrent chemoradiotherapy with high-dose cisplatin (100 mg/m² every 3 weeks) is the preferred regimen with curative intent for patients with unresected locally advanced squamous cell carcinoma of the head and neck (LA SCCHN). This treatment is associated with acute and late toxicities, including myelosuppression, severe nausea/vomiting, irreversible renal failure, hearing loss, and neurotoxicity. Because of cisplatin's safety profile, treatment adherence to high-dose cisplatin can be suboptimal. Patients commonly receive less than the total cumulative target dose of 300 mg/m² or the minimum recommended dose of 200 mg/m², which can have a negative impact on locoregional control and survival. Alternatively, cetuximab plus radiotherapy may be most suitable for patients at high risk of non-adherence to high-dose cisplatin. We discuss the baseline characteristics dictating the unsuitability/borderline unsuitability of cisplatin and the available alternative evidence-based treatment regimens for patients with LA SCCHN. We non-systematically reviewed published phase II and III trials and retrospective analyses of high-dose cisplatin-based chemoradiation in LA SCCHN conducted between 1987 and 2018, focusing on recent key phase III studies. We defined the baseline characteristics and associated prescreening tests to determine unsuitability and borderline unsuitability for high-dose cisplatin in combination with radiotherapy in patients with LA SCCHN. Patients with any pre-existing comorbidities that may be exacerbated by high-dose cisplatin treatment can be redirected to a non-cisplatin-based option to minimize the risk of treatment non-adherence. High-dose cisplatin plus radiotherapy remains the preferred treatment for fit patients with unresected LA SCCHN; patients who are unsuitable or borderline unsuitable for high-dose cisplatin could be identified using available tests for potential comorbidities and should be offered alternative treatments, such as cetuximab plus radiotherapy.

Solute Carrier Transportome in Chemotherapy-Induced Adverse Drug Reactions

Members of the solute carrier (SLC) family of transporters are responsible for the cellular influx of a broad range of endogenous compounds and xenobiotics. These proteins are highly expressed in the gastrointestinal tract and eliminating organs such as the liver and kidney, and are considered to be of particular importance in governing drug absorption and elimination. Many of the same transporters are also expressed in a wide variety of organs targeted by clinically important anticancer drugs, directly affect cellular sensitivity to these agents, and indirectly influence treatment-related side effects. Furthermore, targeted intervention strategies involving the use of transport inhibitors have been recently developed, and have provided promising lead candidates for combinatorial therapies associated with decreased toxicity. Gaining a better understanding of the complex interplay between transporter-mediated on-target and off-target drug disposition will help guide the further development of these novel treatment strategies to prevent drug accumulation in toxicity-associated organs, and improve the safety of currently available treatment modalities. In this report, we provide an update on this rapidly emerging field with particular emphasis on anticancer drugs belonging to the classes of taxanes, platinum derivatives, nucleoside analogs, and anthracyclines.

Overview of cisplatin-induced neurotoxicity and ototoxicity, and the protective agents

Cisplatin has dramatically improved the survival rate of cancer patients, but it has also increased the prevalence of hearing and neurological deficits in this population. Cisplatin induces ototoxicity, peripheral (most prevalent) and central (rare) neurotoxicity. This review addresses the ototoxicity and the neurotoxicity associated with cisplatin-based chemotherapy, providing an integrated view of the potential protective agents that have been evaluated in vitro, in vivo and in clinical trials, their targets and mechanisms of protection and their effects on the antitumor activity of cisplatin. So far, the findings are insufficient to support the use of any oto- or neuroprotective agent before, during or after cisplatin chemotherapy. Despite their promising effects in vitro and in animal studies, many agents have not been evaluated in clinical trials. Additionally, the clinical trials have limitations concerning the sample size, controls, measurement, heterogeneous groups, several arms of treatment, short follow-up or no blinding. Besides that, for most agents, the effects on the antitumor activity of cisplatin have not been evaluated in tumor-bearing animals, which discourages clinical trials. Further well-designed randomized controlled clinical trials are necessary to definitely demonstrate the effectiveness of the oto- or neuroprotective agents proposed by animal and in vitro studies.

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.

Time-to-Event Modeling of Peripheral Neuropathy: Platform Analysis of Eight Valine-Citrulline-Monomethylauristatin E Antibody-Drug Conjugates

Peripheral neuropathy (PN) is a common long-term debilitating toxicity of antimicrotubule agents. PN was the most frequent adverse event resulting in dose modifications and/or discontinuation of treatment for valine-citrulline-monomethylauristatin E antibody-drug conjugates (ADCs) developed at Genentech. A pooled time-to-event analysis across eight ADCs (~700 patients) was performed to evaluate the relationship between the ADC exposure and the risk for developing a clinically significant (grade ≥ 2) PN. In addition, the impact of demographic and pathophysiological risk factors on the risk for PN was explored. The time-to-event analysis suggested that the development of PN risk increased with ADC exposure, treatment duration, body weight, and previously reported PN. This model can be used to inform clinical strategies such as adaptations to dosing regimen and/or treatment duration as well as inform clinical eligibility to reduce the incidence of grade ≥ 2 PN.

Mitochondrial dysfunction in the pathogenesis of chemotherapy-induced peripheral neuropathy

Several first-line chemotherapeutic agents, including taxanes, platinum agents and proteasome inhibitors, are associated with the dose-limiting side effect of chemotherapy-induced peripheral neuropathy (CIPN). CIPN predominantly manifests as sensory symptoms, which are likely due to drug accumulation within peripheral nervous tissues rather than the central nervous system. No treatment is currently available to prevent or reverse CIPN. The causal mechanisms underlying CIPN are not yet fully understood. Mitochondrial dysfunction has emerged as a major factor contributing to the development and maintenance of CIPN. This chapter will provide an overview of both clinical and preclinical data supporting this hypothesis. We will review the studies reporting the nature of mitochondrial dysfunction evoked by chemotherapy in terms of changes in mitochondrial morphology, bioenergetics and reactive oxygen species (ROS) generation. Furthermore, we will discuss the in vivo effects of pharmacological interventions that counteract chemotherapy-evoked mitochondrial dysfunction and ameliorate pain-like behavior.

Intramuscular administration of hexachloroplatinate reverses cyanide-induced metabolic derangements and counteracts severe cyanide poisoning

Cyanide is a highly toxic industrial chemical that is widely used by manufactures. Smoke inhalation during household fires is the most common source of cyanide poisoning while additional risks to civilians include industrial accidents and terrorist attacks. Despite the risks to large numbers of individuals, an antidote capable of administration at scale adequate for a mass casualty, prehospital scenario does not yet exist. Previously, we demonstrated that intravenous cisplatin analogues accelerate recovery from cyanide poisoning in mice and rabbits. Of the dozens of platinum‐based organometallic complexes tested, hexachloroplatinate (HCP) emerged as a promising lead compound, exhibiting strong affinity for cyanide and efficacy across model systems. Here, we show HCP is an antidote to lethal cyanide exposure and is importantly effective when delivered intramuscularly. The pharmacokinetic profile of HCP exhibited bioavailability in the systemic circulation 2.5 minutes post‐treatment and subsequent renal clearance of HCP‐cyanide. HCP restored parameters of cellular physiology including cytochrome c oxidase redox state and TCA cycle metabolism. We next validated these findings in a large animal model (swine). Finally, preclinical safety studies in mice revealed minimal toxicity. Cumulatively, these findings demonstrate that HCP is a promising lead compound for development of an intramuscular injectable cyanide antidote for mass casualty scenarios.

Minimizing Risk of Cancer Therapeutics

Cancer treatments continue to advance the management and survival of patients. However, use of these regimens can lead to significant side effects both temporary and permanent. Neuromuscular side effects include chemotherapy-induced peripheral neuropathy and radiation fibrosis syndrome. At this time, the only way to resolve the neurotoxicity is reduction or discontinuation of the offending agent. In an attempt to limit interference with a patient's chemotherapy regimen and mitigate chronic disability, efforts for early detection through subjective clinical evaluations and objective measurement with electrodiagnostics can help to improve symptom management and minimize alteration in treatment.

Cannabinoids and agmatine as potential therapeutic alternatives for cisplatin-induced peripheral neuropathy

Cisplatin is a widely used antineoplastic agent in the treatment of various cancers. Peripheral neuropathy is a well-known side effect of cisplatin and has the potential to result in limiting and/or reducing the dose, decreasing the quality of life. Unfortunately, the mechanism for cisplatin-induced neuropathy has not been completely elucidated. Currently, available treatments for neuropathic pain (NP) are mostly symptomatic, insufficient and are often linked with several detrimental side effects; thus, effective treatments are needed. Cannabinoids and agmatine are endogenous modulators that are implicated in painful states. This review explains the cisplatin-induced neuropathy and antinociceptive effects of cannabinoids and agmatine in animal models of NP and their putative therapeutic potential in cisplatin-induced neuropathy.

Peripheral Neurotoxicity following High-Dose Cisplatin with Glutathione: Clinical and Neurophysiological Assessment

The use of high-dose cisplatin is limited by development of severe peripheral neurotoxicity and gradual worsening of renal function. In an ongoing study of high-dose cisplatin glutathione has been employed with the aim of preventing major cisplatin-induced toxicities. Neurotoxicity was examined in detail in 32 patients with ovarian cancer treated with cisplatin (160 mg/m2) and cyclophosphamide (600 mg/m2) every 3-4 weeks for five courses. In addition to serial complete neurological examination, sensory action potentials (SAPs) and motor conduction velocities (MCVs) were also assessed. We confirmed the development of a predominant sensory involvement, characterized by mild distal paresthesias and decrease in vibratory sensibility and in deep tendon reflexes, with a slight reduction of SAPs, observed after three courses of treatment. After five courses, distal paresthesias and disesthesias, decreased proprioception and loss of vibratory sensibility with ataxic signs, absence of deep tendon reflexes, unobtainable SAPs and only moderately reduced MCVs were seen. We did not observe any case of disabling neuropathy. There was a tendency to a more severe involvement of peripheral nerves in patients aged more than fifty. The 3 patients presenting the most serious neuropathy were the oldest in the whole group. Low degree of neurotoxicity observed in this study supports a glutathione protection against cisplatin-induced neurotoxicity. As the urinary excretion of platinum indicated no changes in the renal clearance of cisplatin following repeated courses, the lack of drug accumulation and high plasma peak due to preserved renal function might explain the reduced neurotoxicity observed.

A micellar cisplatin prodrug simultaneously eliminates both cancer cells and cancer stem cells in lung cancer

Platinum-based chemotherapy as first-line treatment for lung cancers encounters insufficient selectivity, severe side effects and drug resistance in clinics. In this study, we developed an amphiphilic prodrug of cisplatin-poly(ethylene glycol)-block-polycaprolactone and demonstrated that the prodrug formed micellar nanoparticles, NP_Pt(IV), with an average diameter of ∼100 nm. NP_Pt(IV) released platinum in response to the intracellular acidic and reductive environment, and in turn induced significant anti-proliferative activity in lung cancer cells. More importantly, NP_Pt(IV) exhibited a prominent inhibitory effect on CD133⁺ lung cancer stem cells (CSCs) and suppressed tumor growth in vivo. Unlike cisplatin treatment which eventually enriches CSCs, NP_Pt(IV) treatment prevents the accumulation of CD133⁺ lung CSCs in tumors. Therefore, NP_Pt(IV) simutaneously targeting CSCs and non-CSCs might represent a superior strategy to improve conventional anticancer therapy directed predominantly to tumor bulk populations.

Cisplatin alters the function and expression of N-type voltage-gated calcium channels in the absence of morphological damage of sensory neurons

Platinum-based chemotherapeutic agents, such as cisplatin, are still frequently used for treating various types of cancer. Besides its high effectiveness, cisplatin has several serious side effects. One of the most common side effects is dorsal root ganglion (DRG) neurotoxicity. However, the mechanisms underlying this neurotoxicity are still unclear and controversially discussed. Cisplatin-mediated modulation of voltage-gated calcium channels (VGCCs) in the DRG neurons has been shown to alter intracellular calcium homeostasis, a process critical for the induction of neurotoxicity. Using the whole-cell patch-clamp technique, immunostaining, behavioural experiments and electron microscopy (EM) of rat DRGs, we here demonstrate that cisplatin-induced neurotoxicity is due to functional alteration of VGCC, but not due to morphological damage. In vitro application of cisplatin (0.5 µM) increased N-type VGCC currents (I_Ca(V)) in small DRG neurons. Repetitive in vivo administration of cisplatin (1.5 mg/kg, cumulative 12 mg/kg) increased the protein level of N-type VGCC over 26 days, with the protein level being increased for at least 14 days after the final cisplatin administration. Behavioural studies revealed that N-type VGCCs are crucial for inducing symptoms of cisplatin-related neuropathic pain, such as thermal and mechanical hyperalgesia. EM and histology showed no evidence of any structural damage, apoptosis or necrosis in DRG cells after cisplatin exposure for 26 days. Furthermore, no nuclear DNA damage in sensory neurons was observed. Here, we provide evidence for a mainly functionally driven induction of neuropathic pain by cisplatin.

Toxic Effects of Metallopharmaceuticals

Discovery of the metallopharmaceutical cisplatin and its use in antitumour therapy has initiated the rational design and screening of metal-based anticancer agents as potential chemotherapeutics. In addition to the achievements of cisplatin and its therapeutic analogues, there are significant drawbacks to its use: resistance and toxicity. Over the past four decades, numerous transition metal complexes have been synthesized and investigated in vitro and in vivo. The most studied metals among these complexes are platinum and ruthenium. The key features of these investigations is to find novel metal complexes that could potentially exert less toxicity and equal or higher antitumour potency and to overcome other pharmacological deficiencies. Ru complexes have a different mode of action than cisplatin does, some of which are under clinical trials for treating metastatic or cisplatin-resistant tumours. This review consists of the current knowledge, published and unpublished, related to the toxicity of metallopharmaceuticals, and special attention is given to platinum [Pt(II) and Pt(IV)] and ruthenium [Ru(II) and Ru(III)] complexes.

The Role of Transporters in the Toxicity of Chemotherapeutic Drugs: Focus on Transporters for Organic Cations

The introduction of chemotherapy in the treatment of cancer is one of the most important achievements of modern medicine, even allowing the cure of some lethal diseases such as testicular cancer and other malignant neoplasms. The number and type of chemotherapeutic agents available have steadily increased and have developed until the introduction of targeted tumor therapy. It is now evident that transporters play an important role for determining toxicity of chemotherapeutic drugs not only against target but also against nontarget cells. This is of special importance for intracellularly active hydrophilic drugs, which cannot freely penetrate the plasma membrane. Because many important chemotherapeutic agents are substrates of transporters for organic cations, this review discusses the known interaction of these substances with these transporters. A particular focus is given to the role of transporters for organic cations in the development of side effects of chemotherapy with platinum derivatives and in the efficacy of recently developed tyrosine kinase inhibitors to specifically target cancer cells. It is evident that specific inhibition of uptake transporters may be a possible strategy to protect against undesired side effects of platinum derivatives without compromising their antitumor efficacy. These transporters are also important for efficient targeting of tyrosine kinase inhibitors to cancer cells. However, in order to achieve the aims of protecting from undesired toxicities and improving the specificity of uptake by tumor cells, an exact knowledge of transporter expression, function, regulation under normal and pathologic conditions, and of genetically and epigenetically regulation is mandatory.

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.

Neurophysiological and clinical outcomes in chemotherapy-induced neuropathy in cancer

Chemotherapy induced peripheral neuropathy (CIPN) is a significant toxicity of cancer treatment, with the potential to affect long-term function and quality of life in cancer survivors. There remains a lack of consensus around optimal assessment techniques. While current approaches to CIPN assessment are focused on clinical grading scales, it is becoming increasingly evident that a more comprehensive multimodal assessment package is necessary to accurately characterise the impact of CIPN as well as gauge the utility of neuroprotective mechanisms. Neurophysiological techniques provide objective biomarkers and may enable early detection of toxicity while patient reported outcomes are necessary to determine the significance of symptoms to individual patients. In addition to providing an objective assessment, clinical neurophysiological techniques provide important insights into the contributory pathophysiological mechanisms of CIPN with different chemotherapy agents. There is a paucity of implementation of these techniques in the clinical trial setting. The present Review aims to facilitate the use of neurophysiological studies as part of comprehensive assessment packages for the monitoring of CIPN by summarising current understanding of neurophysiological changes that underlie the development of neuropathy, clinical presentations and patient reported outcomes as well as advantages and limitations of current techniques for the neurophysiological assessment of CIPN.

An in vivo mechanism for the reduced peripheral neurotoxicity of NK105: a paclitaxel-incorporating polymeric micellar nanoparticle formulation

In our previous rodent studies, the paclitaxel (PTX)-incorporating polymeric micellar nanoparticle formulation NK105 had showed significantly stronger antitumor effects and reduced peripheral neurotoxicity than PTX dissolved in Cremophor^® EL and ethanol (PTX/CRE). Thus, to elucidate the mechanisms underlying reduced peripheral neurotoxicity due to NK105, we performed pharmacokinetic analyses of NK105 and PTX/CRE in rats. Among neural tissues, the highest PTX concentrations were found in the dorsal root ganglion (DRG). Moreover, exposure of DRG to PTX (C_{max_PTX} and AUC_{0-inf._PTX}) in the NK105 group was almost half that in the PTX/CRE group, whereas exposure of sciatic and sural nerves was greater in the NK105 group than in the PTX/CRE group. In histopathological analyses, damage to DRG and both peripheral nerves was less in the NK105 group than in the PTX/CRE group. The consistency of these pharmacokinetic and histopathological data suggests that high levels of PTX in the DRG play an important role in the induction of peripheral neurotoxicity, and reduced distribution of PTX to the DRG of NK105-treated rats limits the ensuing peripheral neurotoxicity. In further analyses of PTX distribution to the DRG, Evans blue (Eb) was injected with BODIPY^®-labeled NK105 into rats, and Eb fluorescence was observed only in the DRG. Following injection, most Eb dye bound to albumin particles of ~8 nm and had penetrated the DRG. In contrast, BODIPY^®–NK105 particles of ~90 nm were not found in the DRG, suggesting differential penetration based on particle size. Because PTX also circulates as PTX–albumin particles of ~8 nm following injection of PTX/CRE, reduced peripheral neurotoxicity of NK105 may reflect exclusion from the DRG due to particle size, leading to reduced PTX levels in rat DRG (275).

Depletion of Mitofusin-2 Causes Mitochondrial Damage in Cisplatin-Induced Neuropathy

Sensory neuropathy is a relevant side effect of the antineoplastic agent cisplatin. Mitochondrial damage is assumed to play a critical role in cisplatin-induced peripheral neuropathy, but the pathomechanisms underlying cisplatin-induced mitotoxicity and neurodegeneration are incompletely understood. In an animal model of cisplatin-induced neuropathy, we determined in detail the extent and spatial distribution of mitochondrial damage during cisplatin treatment. Changes in the total number of axonal mitochondria during cisplatin treatment were assessed in intercostal nerves from transgenic mice that express cyan fluorescent protein. Further, we explored the impact of cisplatin on the expression of nuclear encoded molecules of mitochondrial fusion and fission, including mitofusin-2 (MFN2), optic atrophy 1 (OPA1), and dynamin-related protein 1 (DRP1). Cisplatin treatment resulted in a loss of total mitochondrial mass in axons and in an abnormal mitochondrial morphology including atypical enlargement, increased vacuolization, and loss of cristae. These changes were observed in distal and proximal nerve segments and were more prominent in axons than in Schwann cells. Transcripts of fusion and fission proteins were reduced in distal nerve segments. Significant reduced expression levels of the fusion protein MFN2 was detected in nerves of cisplatin-exposed animals. In summary, we provide for the first time an evidence that cisplatin alters mitochondrial dynamics in peripheral nerves. Loss of MFN2, previously implicated in the pathogenesis of other neurodegenerative diseases, also contributes to the pathogenesis in cisplatin-induced neuropathy.

Synthesis, spectral characterization of novel Pd(II), Pt(II) π-coordination compounds based on N-allylthioureas. Cytotoxic properties and DNA binding ability

Four novel Pd²⁺ and Pt²⁺ mononuclear π-coordination compounds with general formula [M(HL)^1,2Cl₂], M=Pd²⁺, Pt²⁺ have been synthesized by reaction of [PdCl₄]^2-, [PtCl₄]^2- anions with N-allyl-4-morpholinethiocarboxamide (HL¹) and N-Allyl-N'-tert-butylthiourea (HL²). All complexes have been characterized by single-crystal X-ray diffraction study and ¹H, ¹³C NMR spectroscopy. Cytotoxic, cytostatic and proapoptotic activities of compounds have been determined in vitro on HeLa cell line and compared with cisplatin as etalon drug. All complex compounds possessed pronounced cytotoxic activity with IC₅₀ indexes in range of 2·10^-6-1.5·10^-4М (IC₅₀ of cisplatin is 5.7∙10^-5М) and showed proapoptotic, cytostatic and antisyntetic influence higher or comparable with cisplatin. The comparative influence of cisplatin and synthesized metal complexes on pTZ19R* plasmid DNA was monitored by agarose gel electrophoresis. All compounds showed high affinity to DNA that correlates with observed cytostatic and proapoptotic levels. In general Pd(II) compounds showed higher activity than Pt(II) ones.

Cisplatin-induced neuropathic pain is mediated by upregulation of N-type voltage-gated calcium channels in dorsal root ganglion neurons

Cisplatin is important in the treatment of various types of cancer. Although it is highly effective, it also has severe side effects, with neurotoxicity in dorsal root ganglion (DRG) neurons being one of the most common. The key mechanisms of neurotoxicity are still controversially discussed; however, disturbances of the calcium homeostasis in DRG neurons have been suggested to mediate cisplatin neurotoxicity. By using the whole-cell patch-clamp technique, immunostaining and behavioral experiments with Sprague-Dawley rats, we examined the influence of short- and long-term exposure to cisplatin on voltage-gated calcium channel (VGCC) currents (I_Ca(V)) in small DRG neurons. In vitro exposure to cisplatin reduced I_Ca(V) in a concentration-dependent manner (0.01-50μM; 13.8-77.3%; IC₅₀ 5.07μM). Subtype-specific measurements of VGCCs showed differential effects on I_Ca(V). While the I_Ca(V) of P/Q-, L- and T-type VGCCs were reduced, I_Ca(V) of N-type VGCCs were increased by 30.3% during depolarization to 0mV. Exposure of DRG neurons to cisplatin (0.5 or 5μM) for 24-48h in vitro significantly increased a CaMK II-mediated I_Ca(V) current density. Immunostaining and western blot analysis revealed an increase of N-type VGCC protein level in DRG neurons 24h after cisplatin exposure. Cisplatin-mediated activation of caspase-3 was prevented by inhibition of N-type VGCCs using Ɯ-conotoxin MVIIA. Behavioral experiments showed that Ɯ-conotoxin MVIIA treatment prevented neuropathic syndromes in vivo by inhibiting upregulation of the N-type protein level. Here we show evidence for the first time for a crucial role of N-type VGCC in the genesis of cisplatin-induced polyneuropathy.

Cisplatin induces mitochondrial deficits in Drosophila larval segmental nerve

Cisplatin is an effective chemotherapy drug that induces peripheral neuropathy in cancer patients. In rodent dorsal root ganglion neurons, cisplatin binds nuclear and mitochondrial DNA (mtDNA) inducing DNA damage and apoptosis. Platinum-mtDNA adducts inhibit mtDNA replication and transcription leading to mitochondrial degradation. Cisplatin also induces climbing deficiencies associated with neuronal apoptosis in adult Drosophila melanogaster. Here we used Drosophila larvae that express green fluorescent protein in the mitochondria of motor neurons to observe the effects of cisplatin on mitochondrial dynamics and function. Larvae treated with 10μg/ml cisplatin had normal survival with deficiencies in righting and heat sensing behavior. Behavior was abrogated by, the pan caspase inhibitor, p35. However, active caspase 3 was not detected by immunostaining. There was a 27% decrease in mitochondrial membrane potential and a 42% increase in reactive oxygen species (ROS) in mitochondria along the axon. Examination of mitochondrial axonal trafficking showed no changes in velocity, flux or mitochondrial length. However, cisplatin treatment resulted in a greater number of stationary organelles caused by extended pausing during axonal motility. These results demonstrate that cisplatin induces behavior deficiencies in Drosophila larvae, decreased mitochondrial activity, increased ROS production and mitochondrial pausing without killing the larvae. Thus, we identified particular aspects of mitochondrial dynamics and function that are affected in cisplatin-induced peripheral neuropathy and may represent key therapeutic targets.

Neurologic Complications of Commonly Used Drugs in the Hospital Setting

This chapter reviews the neurologic complications of medications administered in the hospital setting, by class, introducing both common and less common side effects. Detail is devoted to the interaction between pain, analgesia, sedation, and their residual consequences. Antimicrobials are given in nearly every hospital setting, and we review their capacity to produce neurologic sequelae with special devotion to cefepime and the antiviral treatment of human immunodeficiency virus. The management of hemorrhagic stroke has become more complex with the introduction of novel oral anticoagulants, and we provide an update on what is known about reversal of the new oral anticoagulants. Both central and peripheral nervous system complications of immunosuppressants and chemotherapies are reviewed. Because diagnosis is generally based on clinical acumen, alone, neurotoxic syndromes resulting from psychotropic medications may be easily overlooked until severe dysautonomia develops. We include a practical approach to the diagnosis of serotonin syndrome and neuroleptic malignant syndrome.

Modulation of the metabolism of cis-platin in blood plasma by glutathione

The anticancer drug cis-platin (CP) is in worldwide clinical use to treat a variety of cancers, but is inherently associated with severe toxic side effects. Previous animal studies revealed that its neurotoxicity can be significantly reduced by the coadministration of l-glutathione (GSH) without affecting the anticancer effect. The underlying molecular mechanism, however, has remained elusive. Since the bloodstream is a likely biological compartment where CP-derived hydrolysis products may react with GSH, we have employed a recently developed metallomics tool to gain insight into the interaction of CP and GSH in rabbit plasma in vitro. After the addition of increasing GSH/CP molar ratios to plasma (25:1, 50:1, and 100:1), the determination of the Pt distribution 5 min and 2 h later revealed the formation of a Pt–GSH complex that did not bind to plasma proteins. The simultaneously obtained Zn distribution in plasma revealed a progressively more pronounced perturbation of the Zn metalloproteome with increasing GSH/CP molar ratios at the 5 min time point, which partially reversed at the 2 h time point. The formation of Pt–GSH species in plasma is therefore likely to be directly involved in the process by which GSH protects mammalian organisms from CP-induced neurotoxicity, nephrotoxicity, and possibly other organ-based toxicities.

Unilateral Cervical Polyneuropathies following Concurrent Bortezomib, Cetuximab, and Radiotherapy for Head and Neck Cancer

We report a constellation of cervical polyneuropathies in a patient treated with concurrent bortezomib, cetuximab, and cisplatin alongside intensity modulated radiotherapy for carcinoma of the tonsil with neck metastasis. The described deficits include brachial plexopathy, cervical sensory neuropathy, and oculosympathetic, recurrent laryngeal, and phrenic nerve palsies within the ipsilateral radiation field. Radiation neuropathy involving the brachial plexus is typically associated with treatment of breast or lung cancer; however, increased awareness of this entity in the context of investigational agents with potential neuropathic effects in head and neck cancer has recently emerged. With this report, we highlight radiation neuropathy in the setting of investigational therapy for head and neck cancer, particularly since these sequelae may present years after therapy and entail significant and often irreversible morbidity.

Nerve growth factor alters microtubule targeting agent-induced neurotransmitter release but not MTA-induced neurite retraction in sensory neurons

Peripheral neuropathy is a dose-limiting side effect of anticancer treatment with the microtubule-targeted agents (MTAs), paclitaxel and epothilone B (EpoB); however, the mechanisms by which the MTAs alter neuronal function and morphology are unknown. We previously demonstrated that paclitaxel alters neuronal sensitivity, in vitro, in the presence of nerve growth factor (NGF). Evidence in the literature suggests that NGF may modulate the neurotoxic effects of paclitaxel. Here, we examine whether NGF modulates changes in neuronal sensitivity and morphology induced by paclitaxel and EpoB. Neuronal sensitivity was assessed using the stimulated release of calcitonin gene-related peptide (CGRP), whereas morphology of established neurites was evaluated using a high content screening system. Dorsal root ganglion cultures, maintained in the absence or presence of NGF, were treated from day 7 to day 12 in culture with paclitaxel (300nM) or EpoB (30nM). Following treatment, the release of CGRP was stimulated using capsaicin or high extracellular potassium. In the presence of NGF, EpoB mimicked the effects of paclitaxel: capsaicin-stimulated release was attenuated, potassium-stimulated release was slightly enhanced and the total peptide content was unchanged. In the absence of NGF, both paclitaxel and EpoB decreased capsaicin- and potassium-stimulated release and the total peptide content, suggesting that NGF may reverse MTA-induced hyposensitivity. Paclitaxel and EpoB both decreased neurite length and branching, and this attenuation was unaffected by NGF in the growth media. These differential effects of NGF on neuronal sensitivity and morphology suggest that neurite retraction is not a causative factor to alter neuronal sensitivity.

Feasibility and safety of a modified outpatient regimen with intravenous/intraperitoneal chemotherapy for optimally debulked stage III ovarian cancer

OBJECTIVE

Intraperitoneal (i.p.) chemotherapy improves survival in optimally debulked ovarian cancer patients. However, the need for inpatient administration and the perceived higher toxicity rates compared with standard intravenous chemotherapy have limited its widespread application. Several modified outpatient schemes, such as the Spanish Ovarian Cancer Research Group (GEICO) regimen, have been tested and have reported overall better tolerance with an improvement in completion treatment rates. The aim of our study was to assess the toxicity of the GEICO regimen in patients treated at our institution.

METHODS

We reviewed clinical records of stage III ovarian cancer patients with optimally debulked primary cytoreduction surgery that were treated from June 2009 to April 2013 with the GEICO regimen. Patients received intravenous paclitaxel (175 mg/m2) for 3 hours on day 1, i.p. cisplatin (100 mg/m2) on day 2, and i.p. paclitaxel (60 mg/m2) on day 8 every 21 days for a maximum of 6 cycles.

RESULTS

Twenty-one patients were identified. In 67% of the patients, i.p. port placement was performed at the primary surgery. The most common grade 3-to-4 toxicities seen were abdominal pain (14.3%) and neurotoxicity (9.5%). Eighteen patients (85.7%) completed the 6 cycles. Three patients stopped chemotherapy because of treatment-related toxicity. There were no serious port-related complications. With a median follow-up of 46 months, median progression-free survival was 23 months (95% confidence interval [11.8-34.6]). Nine patients (42.9%) have relapsed; most relapses were multifocal and extraperitoneal.

CONCLUSION

The administration of the GEICO outpatient modified regimen was feasible with a good safety profile. It seems to show less toxicity than previously reported IP chemotherapy regimens. In our institution, port-related complications were infrequent and easily managed. However, further studies are warranted to establish the optimal i.p. regimen in a prospective manner and to validate it in a larger phase 3 trial.

APE1, the DNA base excision repair protein, regulates the removal of platinum adducts in sensory neuronal cultures by NER

Peripheral neuropathy is one of the major side effects of treatment with the anticancer drug, cisplatin. One proposed mechanism for this neurotoxicity is the formation of platinum adducts in sensory neurons that could contribute to DNA damage. Although this damage is largely repaired by nuclear excision repair (NER), our previous findings suggest that augmenting the base excision repair pathway (BER) by overexpressing the repair protein APE1 protects sensory neurons from cisplatin-induced neurotoxicity. The question remains whether APE1 contributes to the ability of the NER pathway to repair platinum-damage in neuronal cells. To examine this, we manipulated APE1 expression in sensory neuronal cultures and measured Pt-removal after exposure to cisplatin. When neuronal cultures were treated with increasing concentrations of cisplatin for two or three hours, there was a concentration-dependent increase in Pt-damage that peaked at four hours and returned to near baseline levels after 24h. In cultures where APE1 expression was reduced by ∼ 80% using siRNA directed at APE1, there was a significant inhibition of Pt-removal over eight hours which was reversed by overexpressing APE1 using a lentiviral construct for human wtAPE1. Overexpressing a mutant APE1 (C65 APE1), which only has DNA repair activity, but not its other significant redox-signaling function, mimicked the effects of wtAPE1. Overexpressing DNA repair activity mutant APE1 (226 + 177APE1), with only redox activity was ineffective suggesting it is the DNA repair function of APE1 and not its redox-signaling, that restores the Pt-damage removal. Together, these data provide the first evidence that a critical BER enzyme, APE1, helps regulate the NER pathway in the repair of cisplatin damage in sensory neurons.

Role of transporters in the distribution of platinum-based drugs

Platinum derivatives used as chemotherapeutic drugs such as cisplatin and oxaliplatin have a potent antitumor activity. However, severe side effects such as nephro-, oto-, and neurotoxicity are associated with their use. Effects and side effects of platinum-based drugs are in part caused by their transporter-mediated uptake in target and non target cells. In this mini review, the transport systems involved in cellular handling of platinum derivatives are illustrated, focusing on transporters for cisplatin. The copper transporter 1 seems to be of particular importance for cisplatin uptake in tumor cells, while the organic cation transporter (OCT) 2, due to its specific organ distribution, may play a major role in the development of undesired cisplatin side effects. In polarized cells, e.g., in renal proximal tubule cells, apically expressed transporters, such as multidrug and toxin extrusion protein 1, mediate secretion of cisplatin and in this way contribute to the control of its toxic effects. Specific inhibition of cisplatin uptake transporters such as the OCTs may be an attractive therapeutic option to reduce its toxicity, without impairing its antitumor efficacy.