Current View in Platinum Drug Mechanisms of Peripheral Neurotoxicity

Platinum-based chemotherapy: trends in organic nanodelivery systems

Despite the investment in platinum drugs research, cisplatin, carboplatin and oxaliplatin are still the only Pt-based compounds used as first line treatments for several cancers, with a few other compounds being approved for administration in some Asian countries. However, due to the severe and worldwide impact of oncological diseases, there is an urge for improved chemotherapeutic approaches. Furthermore, the pharmaceutical application of platinum complexes is hindered by their inherent toxicity and acquired resistance. Nanodelivery systems rose as a key strategy to overcome these challenges, with recognized versatility and ability towards improving the safety, bioavailability and efficacy of the available drugs. Among the known nanocarriers, organic systems have been widely applied, taking advantage of their potential as drug vehicles. Researchers have mainly focused on the development of lipidic and polymeric carriers, including supramolecular structures, with an overall improvement of encapsulated platinum complexes. Herein, an overview of recent trends and strategies is presented, with the main focus on the encapsulation of platinum compounds into organic nanocarriers, showcasing the evolution in the design and development of these promising systems. This comprehensive review highlights formulation methods as well as characterization procedures, providing insights that may be helpful for the development of novel platinum nanocarriers aiming at future pharmaceutical applications.

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.

Applications of Cannabinoids in Neuropathic Pain: An Updated Review

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

Cancer survivors post-chemotherapy exhibit unimpaired short-latency stretch reflexes in the proximal upper extremity

Oxaliplatin (OX) chemotherapy can lead to long-term sensorimotor impairments in cancer survivors. The impairments are often thought to be caused by OX-induced progressive degeneration of sensory afferents known as length-dependent dying-back sensory neuropathy. However, recent preclinical work has identified functional defects in the encoding of muscle proprioceptors and in motoneuron firing. These functional defects in the proprioceptive sensorimotor circuitry could readily impair muscle stretch reflexes, a fundamental building block of motor coordination. Given that muscle proprioceptors are distributed throughout skeletal muscle, defects in stretch reflexes could be widespread, including in the proximal region where dying-back sensory neuropathy is less prominent. All previous investigations on chemotherapy-related reflex changes focused on distal joints, leading to results that could be influenced by dying-back sensory neuropathy rather than more specific changes to sensorimotor circuitry. Our study extends this earlier work by quantifying stretch reflexes in the shoulder muscles in 16 cancer survivors and 16 healthy controls. Conduction studies of the sensory nerves in hand were completed to detect distal sensory neuropathy. We found no significant differences in the short-latency stretch reflexes (amplitude and latency) of the shoulder muscles between cancer survivors and healthy controls, contrasting with the expected differences based on the preclinical work. Our results may be linked to differences between the human and preclinical testing paradigms including, among many possibilities, differences in the tested limb or species. Determining the source of these differences will be important for developing a complete picture of how OX chemotherapy contributes to long-term sensorimotor impairments.NEW & NOTEWORTHY Our results showed that cancer survivors after oxaliplatin (OX) treatment exhibited stretch reflexes that were comparable with age-matched healthy individuals in the proximal upper limb. The lack of OX effect might be linked to differences between the clinical and preclinical testing paradigms. These findings refine our expectations derived from the preclinical study and guide future assessments of OX effects that may have been insensitive to our measurement techniques.

An update on neurobiological mechanisms involved in the development of chemotherapy-induced cognitive impairment (CICI)

Cancer is the second leading cause of death worldwide despite efforts in early diagnosis of the disease and advances in treatment. The use of drugs that exert toxic effects on tumor cells or chemotherapy is one of the most widely used treatments against cancer. However, its low toxic selectivity affects both healthy cells and cancer cells. It has been reported that chemotherapeutic drugs may generate neurotoxicity that induces deleterious effects of chemotherapy in the central nervous system. In this sense, patients report decreased cognitive abilities, such as memory, learning, and some executive functions after chemotherapy. This chemotherapy-induced cognitive impairment (CICI) develops during treatment and persists even after chemotherapy. Here we present a review of the literature on the main neurobiological mechanisms involved in CICI using a Boolean formula following the steps of the PRISMA guidelines that were used to perform statements searches in various databases. The main mechanisms described in the literature to explain CRCI include direct and indirect mechanisms that induce neurotoxicity by chemotherapeutic agents. Therefore, this review provides a general understanding of the neurobiological mechanisms of CICI and the possible therapeutic targets to prevent it..

Red Blood Cell Membrane-Camouflaged Gold Nanoparticles for Treatment of Melanoma

Background

Patients with melanoma have poor response and low long-term survival to conventional cisplatin (CP). Recently, biomimetic nanoparticles have played a significant role in tumor therapy. The purpose of this study was to mechanistically evaluate the effect of red blood cell membrane camouflaged gold nanoparticles loaded with CP (RBCm@AuNPs-CP) on enhancing chemotherapy in melanoma.

Methods

Treated B16-F10 cells with RBCm@AuNPs-CP, the antimelanoma effect in vitro was explored by detecting cell viability, apoptosis rate, level of reactive oxygen species (ROS), and singlet oxygen. RBCm@AuNPs-CP was injected into the melanoma-bearing mice via tail vein, and the target-ability, therapeutic effect, and toxicity were detected in melanoma tumor-bearing mice.

Results

RBCm@AuNPs-CP had an antiproliferation and apoptosis-inducing effect on B16-F10 cells, which might be mediated by oxidative stress of ROS, and its effect was significantly enhanced compared with the CP treatment group. In vivo experiments suggested the same outcome, with better target-ability of RBCm@AuNPs-CP.

Conclusion

The erythrocyte camouflage nanosystem RBCm@AuNPs-CP exhibited well passive tumor target-ability and promoted apoptosis of melanocytes by inducing ROS. RBCm@AuNPs-CP as a novel safe and effective targeted drug delivery system may provide a promising choice for the treatment of melanoma.

Neuroprotective Potential of Intranasally Delivered Sulforaphane-Loaded Iron Oxide Nanoparticles Against Cisplatin-Induced Neurotoxicity

Cisplatin (CIS) is a platinum-based chemotherapeutic drug that is widely used to treat cancer. However, its therapeutic efficiency is limited due to its potential to provoke neurotoxicity. Sulforaphane (SF) is a natural phytochemical that demonstrated several protective activities. Iron oxide nanoparticles (Fe₃O₄-NPs) could be used as drug carriers. This study aimed to explore the nanotoxic influence of SF-loaded within Fe₃O₄-NPs (N.SF), and to compare the neuroprotective potential of both N.SF and SF against CIS-induced neurotoxicity. N.SF or SF was administrated intranasally for 5 days before and 3 days after a single dose of CIS (12 mg/kg/week, i.p.) on the 6^th day. Neuromuscular coordination was assessed using hanging wire and tail-flick tests. Acetylcholinesterase (AChE) activities and markers of oxidative stress were measured in the brain. In addition, the brain iron (Fe) content was estimated. CIS significantly induced a significant increase in AChE activities and lipid peroxides, and a significant decrement in glutathione (GSH) and nitric oxide (NO) contents. CIS elicited impaired neuromuscular function and thermal hyperalgesia. CIS-induced brains displayed a significant reduction in Fe content. Histopathological examination of different brain regions supported the biochemical and behavioral results. Contradict, treatment of CIS-rats with either N.SF or SF significantly decreased AChE activity, mitigated oxidative stress, and ameliorated the behavioral outcome. The histopathological features supported our results. Collectively, N.SF demonstrated superior neuroprotective activities on the behavioral, biochemical, and histopathological (striatum and cerebral cortex) aspects. N.SF could be regarded as a promising “pre-clinical” neuroprotective agent. Furthermore, this study confirmed the safe toxicological profile of Fe₃O₄-NPs.

Pro-Inflammatory Signalling PRRopels Cisplatin-Induced Toxicity

Cisplatin is a platinum-based chemotherapeutic that has long since been effective against a variety of solid-cancers, substantially improving the five-year survival rates for cancer patients. Its use has also historically been limited by its adverse drug reactions, or cisplatin-induced toxicities (CITs). Of these reactions, cisplatin-induced nephrotoxicity (CIN), cisplatin-induced peripheral neuropathy (CIPN), and cisplatin-induced ototoxicity (CIO) are the three most common of several CITs recognised thus far. While the anti-cancer activity of cisplatin is well understood, the mechanisms driving its toxicities have only begun to be defined. Most of the literature pertains to damage caused by oxidative stress that occurs downstream of cisplatin treatment, but recent evidence suggests that the instigator of CIT development is inflammation. Cisplatin has been shown to induce pro-inflammatory signalling in CIN, CIPN, and CIO, all of which are associated with persisting markers of inflammation, particularly from the innate immune system. This review covered the hallmarks of inflammation common and distinct between different CITs, the role of innate immune components in development of CITs, as well as current treatments targeting pro-inflammatory signalling pathways to conserve the use of cisplatin in chemotherapy and improve long-term health outcomes of cancer patients.

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.

Mechanisms of Chemotherapy-Induced Neurotoxicity

Since the first clinical trials conducted after World War II, chemotherapeutic drugs have been extensively used in the clinic as the main cancer treatment either alone or as an adjuvant therapy before and after surgery. Although the use of chemotherapeutic drugs improved the survival of cancer patients, these drugs are notorious for causing many severe side effects that significantly reduce the efficacy of anti-cancer treatment and patients’ quality of life. Many widely used chemotherapy drugs including platinum-based agents, taxanes, vinca alkaloids, proteasome inhibitors, and thalidomide analogs may cause direct and indirect neurotoxicity. In this review we discuss the main effects of chemotherapy on the peripheral and central nervous systems, including neuropathic pain, chemobrain, enteric neuropathy, as well as nausea and emesis. Understanding mechanisms involved in chemotherapy-induced neurotoxicity is crucial for the development of drugs that can protect the nervous system, reduce symptoms experienced by millions of patients, and improve the outcome of the treatment and patients’ quality of life.

Identification of prophylactic drugs for oxaliplatin-induced peripheral neuropathy using big data

BACKGROUND

Drug repositioning is a cost-effective method to identify novel disease indications for approved drugs; it requires a shorter developmental period than conventional drug discovery methods. We aimed to identify prophylactic drugs for oxaliplatin-induced peripheral neuropathy by drug repositioning using data from large-scale medical information and life science information databases.

METHODS

Herein, we analyzed the reported data between 2007 and 2017 retrieved from the FDA's database of spontaneous adverse event reports (FAERS) and the LINCS database provided by the National Institute of Health. The efficacy of the drug candidates for oxaliplatin-induced peripheral neuropathy obtained from the database analysis was examined using a rat model of peripheral neuropathy. Additionally, we compared the incidence of peripheral neuropathy in patients who received oxaliplatin at the Tokushima University Hospital, Japan. The effects of statins on the animal model were examined in six-week-old male Sprague-Dawley rats and seven or eight-week-old male BALB/C mice. Retrospective medical chart review included clinical data from Tokushima University Hospital from April 2009 to March 2018.

RESULTS

Simvastatin, indicated for dyslipidemia, significantly reduced the severity of peripheral neuropathy and oxaliplatin-induced hyperalgesia. In the nerve tissue of model rats, the mRNA expression of Gstm1 increased with statin administration. A retrospective medical chart review using clinical data revealed that the incidence of peripheral neuropathy decreased with statin use.

CONCLUSION AND RELEVANCE

Thus, drug repositioning using data from large-scale basic and clinical databases enables the discovery of new indications for approved drugs with a high probability of success.

Cancer survivors post-chemotherapy exhibit unique proprioceptive deficits in proximal limbs

BACKGROUND

Oxaliplatin (OX) chemotherapy for colorectal cancer is associated with adverse neurotoxic effects that can contribute to long-term sensorimotor impairments in cancer survivors. It is often thought that the sensorimotor impairments are dominated by OX-induced dying-back sensory neuropathy that primarily affects the distal regions of the limb. Recent preclinical studies have identified encoding dysfunction of muscle proprioceptors as an alternative mechanism. Unlike the dying-back sensory neuropathy affecting distal limbs, dysfunction of muscle proprioceptors could have more widespread effects. Most investigations of chemotherapy-induced sensorimotor impairments have considered only the effects of distal changes in sensory processing; none have evaluated proximal changes or their influence on function. Our study fills this gap by evaluating the functional use of proprioception in the shoulder and elbow joints of cancer survivors post OX chemotherapy. We implemented three multidirectional sensorimotor tasks: force matching, target reaching, and postural stability tasks to evaluate various aspects of proprioception and their use. Force and kinematic data of the sensorimotor tasks were collected in 13 cancer survivors treated with OX and 13 age-matched healthy controls.

RESULTS

Cancer survivors exhibited less accuracy and precision than an age-matched control group when they had to rely only on proprioceptive information to match force, even for forces that required only torques about the shoulder. There were also small differences in the ability to maintain arm posture but no significant differences in reaching. The force deficits in cancer survivors were significantly correlated with self-reported motor dysfunction.

CONCLUSIONS

These results suggest that cancer survivors post OX chemotherapy exhibit proximal proprioceptive deficits, and that the deficits in producing accurate and precise forces are larger than those for producing unloaded movements. Current clinical assessments of chemotherapy-related sensorimotor dysfunction are largely limited to distal symptoms. Our study suggests that we also need to consider changes in proximal function. Force matching tasks similar to those used here could provide a clinically meaningful approach to quantifying OX-related movement dysfunction during and after chemotherapy.

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.

Cisplatin-induced neurotoxicity involves the disruption of serotonergic neurotransmission

Neurotoxicity is a frequent side effect of cisplatin (CisPt)-based anticancer therapy whose pathophysiology is largely vague. Here, we exploited C. elegans as a 3R-compliant in vivo model to elucidate molecular mechanisms contributing to CisPt-induced neuronal dysfunction. To this end, we monitored the impact of CisPt on various sensory functions as well as pharyngeal neurotransmission by recording electropharyngeograms (EPGs). CisPt neither affected food and odor sensation nor mechano-sensation, which involve dopaminergic and glutaminergic neurotransmission. However, CisPt reduced serotonin-regulated pharyngeal pumping activity independent of changes in the morphology of related neurons. CisPt-mediated alterations in EPGs were fully rescued by addition of serotonin (5-HT) (≤ 2 mM). Moreover, the CisPt-induced pharyngeal injury was prevented by co-incubation with the clinically approved serotonin re-uptake inhibitory drug duloxetine. A protective effect of 5-HT was also observed with respect to CisPt-mediated impairment of another 5-HT-dependent process, the egg laying activity. Importantly, CisPt-induced apoptosis in the gonad and learning disability were not influenced by 5-HT. Using different C. elegans mutants we found that CisPt-mediated (neuro)toxicity is independent of serotonin biosynthesis and re-uptake and likely involves serotonin-receptor subtype 7 (SER-7)-related functions. In conclusion, by measuring EPGs as a surrogate parameter of neuronal dysfunction, we provide first evidence that CisPt-induced neurotoxicity in C. elegans involves 5-HT-dependent neurotransmission and SER-7-mediated signaling mechanisms and can be prevented by the clinically approved antidepressant duloxetine. The data highlight the particular suitability of C. elegans as a 3R-conform in vivo model in molecular (neuro)toxicology and, moreover, for the pre-clinical identification of neuroprotective candidate drugs.

Ruthenium Complexes: An Alternative to Platinum Drugs in Colorectal Cancer Treatment

Colorectal cancer (CRC) is one of the intimidating causes of death around the world. CRC originated from mutations of tumor suppressor genes, proto-oncogenes and DNA repair genes. Though platinum (Pt)-based anticancer drugs have been widely used in the treatment of cancer, their toxicity and CRC cells' resistance to Pt drugs has piqued interest in the search for alternative metal-based drugs. Ruthenium (Ru)-based compounds displayed promising anticancer activity due to their unique chemical properties. Ru-complexes are reported to exert their anticancer activities in CRC cells by regulating different cell signaling pathways that are either directly or indirectly associated with cell growth, division, proliferation, and migration. Additionally, some Ru-based drug candidates showed higher potency compared to commercially available Pt-based anticancer drugs in CRC cell line models. Meanwhile Ru nanoparticles coupled with photosensitizers or anticancer agents have also shown theranostic potential towards CRC. Ru-nanoformulations improve drug efficacy, targeted drug delivery, immune activation, and biocompatibility, and therefore may be capable of overcoming some of the existing chemotherapeutic limitations. Among the potential Ru-based compounds, only Ru (III)-based drug NKP-1339 has undergone phase-Ib clinical trials in CRC treatment.

Redox-sensitive TRP channels: a promising pharmacological target in chemotherapy-induced peripheral neuropathy

INTRODUCTION

Chemotherapy-induced peripheral neuropathy (CIPN) and its related pain is a major side effect of certain chemotherapeutic agents used in cancer treatment. Available analgesics are mostly symptomatic, and on prolonged treatment, patients become refractive to them. Hence, the development of improved therapeutics that act on novel therapeutic targets is necessary. Potential targets include the redox-sensitive TRP channels [e.g. TRPA1, TRPC5, TRPC6, TRPM2, TRPM8, TRPV1, TRPV2, and TRPV4] which are activated under oxidative stress associated with CIPN.

AREAS COVERED

We have examined numerous neuropathy-inducing cancer chemotherapeutics and their pathophysiological mechanisms. Oxidative stress and its downstream targets, the redox-sensitive TRP channels, together with their potential pharmacological modulators, are discussed. Finally, we reflect upon the barriers to getting new therapeutic approaches into the clinic. The literature search was conducted in PubMed upto and including April 2021.

EXPERT OPINION

Redox-sensitive TRP channels are a promising target in CIPN. Pharmacological modulators of these channels have reduced pain in preclinical models and in clinical studies. Clinical scrutiny suggests that TRPA1, TRPM8, and TRPV1 are the most promising targets because of their pain-relieving potential. In addition to the analgesic effect, TRPV1 agonist-Capsaicin possesses a disease-modifying effect in CIPN through its restorative property in damaged sensory nerves.

Piceatannol ameliorates behavioural, biochemical and histological aspects in cisplatin-induced peripheral neuropathy in rats

Peripheral neurotoxicity is a dose-limiting and a potentially lifelong persistent toxicity of cisplatin. This study investigated the possible protective effect of piceatannol (PIC) in a model of cisplatin-induced peripheral neuropathy in rats. PIC (10 mg/kg, i.p.) was given for 7 days, starting 2 days before cisplatin single injection (7 mg/kg, i.p.). Behavioural, biochemical and histological examinations were conducted. Cisplatin administration resulted in thermal hypoalgesia evidenced by increased paw and tail withdrawal latency times in the hotplate and tail flick tests, respectively, and reduced the abdominal constrictions in response to the acetic acid injection. Moreover, cisplatin treatment decreased rat locomotor activity and grip strength. These behavioural alterations were reversed by PIC coadministration. In addition, PIC decreased cisplatin-induced elevation in serum neurotensin and platinum accumulation in sciatic nerve. Also, PIC reversed, to a large extent, cisplatin-induced microscopical alterations in nerve axons and restored normal myelin thickness. Therefore, PIC may protect against cisplatin-induced peripheral neuropathy.

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.

A comparative analysis of the mutagenicity of platinum-containing chemotherapeutic agents reveals direct and indirect mutagenic mechanisms

Platinum-based drugs are a mainstay of cancer chemotherapy. However, their mutagenic effect can increase tumour heterogeneity, contribute to the evolution of treatment resistance and also induce secondary malignancies. We coupled whole genome sequencing with phenotypic investigations on two cell line models to compare the magnitude and examine the mechanism of mutagenicity of cisplatin, carboplatin and oxaliplatin. Cisplatin induced significantly more base substitution mutations than carboplatin or oxaliplatin when used at equitoxic concentrations on human TK6 or chicken DT40 cells, and also induced the highest number of short insertions and deletions. The analysis of base substitution spectra revealed that all three tested platinum drugs elicit both a direct mutagenic effect at purine dinucleotides, and an indirect effect of accelerating endogenous mutagenic processes, whereas the direct mutagenic effect appeared to correlate with the level of DNA damage caused as assessed through histone H2AX phosphorylation and single-cell agarose gel electrophoresis, the indirect mutagenic effects were equal. The different mutagenicity and DNA-damaging effect of equitoxic platinum drug treatments suggest that DNA damage independent mechanisms significantly contribute to their cytotoxicity. Thus, the comparatively high mutagenicity of cisplatin should be taken into account in the design of chemotherapeutic regimens.

Use of C. elegans as a 3R-compliant in vivo model for the chemoprevention of cisplatin-induced neurotoxicity

Anticancer therapeutics can provoke severe side effects that impair the patient's quality of life. A frequent dose-limiting side effect of platinum-based anticancer therapy is neurotoxicity. Its pathophysiology is poorly understood, and effective preventive or therapeutic measures are missing. Therefore, elucidation of the molecular mechanism of platinating drug-induced neurotoxicity and the development of preventive strategies is urgently needed. To this end, we aim to use C. elegans as a 3R-compliant in vivo model. The 3R principles were conceived for animal welfare in science concerning animal experiments, which should be replaced, reduced or refined. We can analytically demonstrate dose-dependent uptake of cisplatin (CisPt) in C. elegans, as well as genotoxic and cytotoxic effects based on DNA adduct formation (i.e., 1,2-GpG intrastrand crosslinks), induction of apoptosis, and developmental toxicity. Measuring the impairment of pharyngeal pumping as a marker of neurotoxicity, we found that especially CisPt reduces the pumping frequency at concentrations where basal and touch-provoked movement were not yet affected. CisPt causes glutathione (GSH) depletion and RNAi-mediated knockdown of the glutamate-cysteine ligase GCS-1 aggravates the CisPt-induced inhibition of pharyngeal pumping. Moreover, N-acetylcysteine (NAC) mitigated CisPt-triggered toxicity, indicating that GSH depletion contributes to the CisPt-induced pharyngeal damage. In addition to NAC, amifostine (WR1065) also protected the pharynx of C. elegans from the toxic effects of CisPt. Measuring pharyngeal activity by the electrophysiological recording of neurotransmission in the pharynx, we confirmed that CisPt is neurotoxic in C. elegans and that NAC is neuroprotective in the nematode. The data support the hypothesis that monitoring the pharyngeal activity of C. elegans is a useful surrogate marker of CisPt-induced neurotoxicity. In addition, a low GSH pool reduces the resistance of neurons to CisPt treatment, and both NAC and WR1065 are capable of attenuating platinum-induced neurotoxicity during post-incubation in C. elegans. Overall, we propose C. elegans as a 3R-compliant in vivo model to study the molecular mechanisms of platinum-induced neurotoxicity and to explore novel neuroprotective therapeutic strategies to alleviate respective side effects of platinum-based cancer therapy.

Platinum accumulation in oxaliplatin-induced peripheral neuropathy

Oxaliplatin-induced peripheral neuropathy (OIPN) is a common and dose-limiting toxic effect that markedly limits the use of oxaliplatin and affects the quality of life. Although it is common, the underlying mechanisms of OIPN remain ambiguous. Recent studies have shown that the platinum accumulation in peripheral nervous system, especially in dorsal root ganglion, is a significant mechanism of OIPN. Several specific transporters, including organic cation transporters, high-affinity copper uptake protein1 (CTR1), ATPase copper transporting alpha (ATP7A) and multidrug and toxin extrusion protein 1 (MATE1), could be associated with this mechanism. This review summarizes the current research progress about the relationship between platinum accumulation and OIPN, as well as suggests trend for the future research.

Protection against oxaliplatin-induced mechanical and thermal hypersensitivity in Sarm1-/- mice

Chemotherapy-induced peripheral neuropathy (CIPN) is a common dose-limiting side effect of cancer treatment, often associated with degeneration of sensory axons or their terminal regions. Presence of the slow Wallerian degeneration protein (WLD^S), or genetic deletion of sterile alpha and TIR motif containing protein 1 (SARM1), which strongly protect axons from degeneration after injury or axonal transport block, alleviate pain in several CIPN models. However, oxaliplatin can cause an acute pain response, suggesting a different mechanism of pain generation. Here, we tested whether the presence of WLD^S or absence of SARM1 protects against acute oxaliplatin-induced pain in mice after a single oxaliplatin injection. In BL/6 and Wld^S mice, oxaliplatin induced significant mechanical and cold hypersensitivities which were absent in Sarm1^-/- mice. Despite the presence of hypersensitivity there was no significant loss of intraepidermal nerve fibers (IENFs) in the footpads of any mice after oxaliplatin treatment, suggesting that early stages of pain hypersensitivity could be independent of axon degeneration. To identify other changes that could underlie the pain response, RNA sequencing was carried out in DRGs from treated and control mice of each genotype. Sarm1^-/- mice had fewer gene expression changes than either BL/6 or Wld^S mice. This is consistent with the pain measurements in demonstrating that Sarm1^-/- DRGs remain relatively unchanged after oxaliplatin treatment, unlike those in BL/6 and Wld^S mice. Changes in levels of four transcripts - Alas2, Hba-a1, Hba-a2, and Tfrc - correlated with oxaliplatin-induced pain, or absence thereof, across the three genotypes. Our findings suggest that targeting SARM1 could be a viable therapeutic approach to prevent oxaliplatin-induced acute neuropathic pain.

Early Physiological and Cellular Indicators of Cisplatin-Induced Ototoxicity

Cisplatin chemotherapy often causes permanent hearing loss, which leads to a multifaceted decrease in quality of life. Identification of early cisplatin-induced cochlear damage would greatly improve clinical diagnosis and provide potential drug targets to prevent cisplatin's ototoxicity. With improved functional and immunocytochemical assays, a recent seminal discovery revealed that synaptic loss between inner hair cells and spiral ganglion neurons is a major form of early cochlear damage induced by noise exposure or aging. This breakthrough discovery prompted the current study to determine early functional, cellular, and molecular changes for cisplatin-induced hearing loss, in part to determine if synapse injury is caused by cisplatin exposure. Cisplatin was delivered in one to three treatment cycles to both male and female mice. After the cisplatin treatment of three cycles, threshold shift was observed across frequencies tested like previous studies. After the treatment of two cycles, beside loss of outer hair cells and an increase in high-frequency hearing thresholds, a significant latency delay of auditory brainstem response wave 1 was observed, including at a frequency region where there were no changes in hearing thresholds. The wave 1 latency delay was detected as early cisplatin-induced ototoxicity after only one cycle of treatment, in which no significant threshold shift was found. In the same mice, mitochondrial loss in the base of the cochlea and declining mitochondrial morphometric health were observed. Thus, we have identified early spiral ganglion-associated functional and cellular changes after cisplatin treatment that precede significant threshold shift.

Early Stimulation of TREK Channel Transcription and Activity Induced by Oxaliplatin-Dependent Cytosolic Acidification

Oxaliplatin-induced peripheral neuropathy is characterized by an acute hyperexcitability syndrome triggered/exacerbated by cold. The mechanisms underlying oxaliplatin-induced peripheral neuropathy are unclear, but the alteration of ion channel expression and activity plays a well-recognized central role. Recently, we found that oxaliplatin leads to cytosolic acidification in dorsal root ganglion (DRG) neurons. Here, we investigated the early impact of oxaliplatin on the proton-sensitive TREK potassium channels. Following a 6-h oxaliplatin treatment, both channels underwent a transcription upregulation that returned to control levels after 42 h. The overexpression of TREK channels was also observed after in vivo treatment in DRG cells from mice exposed to acute treatment with oxaliplatin. Moreover, both intracellular pH and TREK channel transcription were similarly regulated after incubation with amiloride, an inhibitor of the Na⁺/H⁺ exchanger. In addition, we studied the role of oxaliplatin-induced acidification on channel behavior, and, as expected, we observed a robust positive modulation of TREK channel activity. Finally, we focused on the impact of this complex modulation on capsaicin-evoked neuronal activity finding a transient decrease in the average firing rate following 6 h of oxaliplatin treatment. In conclusion, the early activation of TREK genes may represent a mechanism of protection against the oxaliplatin-related perturbation of neuronal excitability.

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.

Antioxidant Supplementation with N-Acetylcysteine as a Protection Against Cisplatin-Induced Motor Impairment in Rats

The aim of this study was to estimate a potential beneficial influence of N-acetylcysteine (NAC) in the treatment of cisplatin-induced motor impairment. We included 32 male Wistar albino rats, divided into 4 equal groups: control (received saline on the 1st and 5th day), cisplatin – CIS (received saline on the 1st and cisplatin 7.5 mg/kg i.p. on the 5th day), NAC (received NAC on the 1st and 5th day, 500 mg/kg i.p.), and CIS+NAC (received NAC on the 1st and 5th day, 500 mg/kg i.p. and cisplatin 7.5 mg/kg i.p. on the 5th day) group. Motor performance was estimated by rotarod, grip wire, open field (OF), elevated plus maze (EPM) and beam-walking (BW) tests on the 10th day. Cisplatin administration resulted in decreased motor performance in all tests, except for BW test, compared to the control group. NAC supplementation on its own had no significant effect on motor performance parameters. However, simultaneous administration of NAC along with cisplatin reversed negative impact of cisplatin in rotarod, OF and EPM tests, with no significant effect on the results obtained in grip wire test. The results of this study confirmed numerous motoric manifestations of cisplatin-induced neurotoxicity in rats. However, the decline in most of the estimated parameters was successfully prevented by antioxidant supplementation with NAC.

Toxic Peripheral Neuropathies: Agents and Mechanisms

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

Insights into platinum-induced peripheral neuropathy-current perspective

Cancer is a global health problem that is often successfully addressed by therapy, with cancer survivors increasing in numbers and living longer world around. Although new cancer treatment options are continuously explored, platinum based chemotherapy agents remain in use due to their efficiency and availability. Unfortunately, all cancer therapies affect normal tissues as well as cancer, and more than 40 specific side effects of platinum based drugs documented so far decrease the quality of life of cancer survivors. Chemotherapy-induced peripheral neuropathy is a frequent side effects of platinum-based chemotherapy agents. This cluster of complications is often so debilitating that patients occasionally have to discontinue the therapy. Sensory neurons of dorsal root ganglia are at the core of chemotherapy-induced peripheral neuropathy symptoms. In these postmitotic cells, DNA damage caused by platinum chemotherapy interferes with normal functioning. Accumulation of DNA-platinum adducts correlates with neurotoxic severity and development of sensation of pain. While biochemistry of DNA-platinum adducts is the same in all cell types, molecular mechanisms affected by DNA-platinum adducts are different in cancer cells and non-dividing cells. This review aims to raise awareness about platinum associated chemotherapy-induced peripheral neuropathy as a medical problem that has remained unexplained for decades. We emphasize the complexity of this condition both from clinical and mechanistical point of view and focus on recent findings about chemotherapy-induced peripheral neuropathy in in vitro and in vivo model systems. Finally, we summarize current perspectives about clinical approaches for chemotherapy-induced peripheral neuropathy treatment.

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.

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.

Neuroprotective Role of Selected Antioxidant Agents in Preventing Cisplatin-Induced Damage of Human Neurons In Vitro

Chemotherapy-induced peripheral neuropathy (CIPN) is a side effect of platinum-based chemotherapy and decreases the quality of life of cancer patients. We compared neuroprotective properties of several agents using an in vitro model of terminally differentiated human cells NT2-N derived from cell line NT2/D1. Sodium azide and an active metabolite of amifostine (WR1065) increase cell viability in simultaneous treatment with cisplatin. In addition, WR1065 protects the non-dividing neurons by decreasing cisplatin caused oxidative stress and apoptosis. Accumulation of Pt in cisplatin-treated cells was heterogeneous, but the frequency and concentration of Pt in cells were lowered in the presence of WR1065 as shown by X-ray fluorescence microscopy (XFM). Transition metals accumulation accompanied Pt increase in cells; this effect was equally diminished in the presence of WR1065. To analyze possible chemical modulation of Pt-DNA bonds, we examined the platinum L_III near edge spectrum by X-ray absorption spectroscopy. The spectrum found in cisplatin-DNA samples is altered differently by the addition of either WR1065 or sodium azide. Importantly, a similar change in Pt edge spectra was noted in cells treated with cisplatin and WR1065. Therefore, amifostine should be reconsidered as a candidate for treatments that reduce or prevent CIPN.

Peripheral neuropathy in children and adolescents treated for cancer

Peripheral neuropathy is a well recognised treatment-related toxicity in children with cancer, associated with exposure to neurotoxic chemotherapy agents. Acute damage can occur in sensory, motor, or autonomic neurons, with symptoms that are rarely life threatening, but often severe enough to interfere with function during therapy and after treatment ends. The type of neuropathy and specific symptoms are associated with multiple factors including age at time of therapy, genetic predisposition, chemotherapy type and cumulative dose, and exposure to other agents during therapy. In this Review, we describe the peripheral neuropathy phenotype in children during cancer therapy and among survivors who have completed therapy, to summarise genetic and treatment-related risk factors for neuropathy, and to outline strategies to monitor and detect neuropathy during and after therapy. Additionally, we outline strategies for medical management of neuropathy during treatment and potential rehabilitation interventions to prevent or remediate functional loss.

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.

Toxicities of Therapeutic Agents Used in Medicine

This Special Issue on "Toxicities of Therapeutic Agents Used in Medicine" reports on some peculiar cases of toxicities related to widely and commonly employed drugs.[...].