Oxaliplatin Modulates the Characteristics of Voltage-Gated Calcium Channels and Action Potentials in Small Dorsal Root Ganglion Neurons of Rats

Contribution of T-type calcium channel isoforms to cold and mechanical sensitivity in naïve and oxaliplatin-treated mice of both sexes

BACKGROUND AND PURPOSE

The chemotherapy agent oxaliplatin can give rise to oxaliplatin-induced peripheral neuropathy (OIPN). Here, we investigated whether T-type calcium channels (Cav3) contribute to OIPN.

EXPERIMENTAL APPROACH

We chronically treated mice with oxaliplatin and assessed pain responses and changes in expression of Cav3.2 calcium channels. We also tested the effects of T-type channel blockers on cold sensitivity in wild-type and Cav3.2 null mice.

KEY RESULTS

Oxaliplatin treatment led to mechanical and cold hypersensitivity in male and female mice. Mechanical hypersensitivity persisted in Cav3.2 null mice of both sexes. Intraperitoneal or intrathecal delivery of pan T-type channel inhibitors attenuated mechanical hypersensitivity in wild-type but not Cav3.2 null mice. Remarkably cold hypersensitivity occurred in female but not male Cav3.2 null mice even without oxaliplatin treatment. Unexpectedly, intrathecal, intraplantar or intraperitoneal delivery of T-type channel inhibitors Z944 or TTA-P2 transiently induced cold hypersensitivity in both male and female wild-type mice. Acute knockdown of specific Cav3 isoforms revealed that the depletion of Cav3.1 in males and depletion of either Cav3.1 or Cav3.2 in females triggered cold hypersensitivity. Finally, reducing Cav3.2 expression by disrupting the interactions between Cav3.2 and the deubiquitinase USP5 with the small organic molecule II-2 reversed oxaliplatin-induced mechanical and cold hypersensitivity and importantly did not trigger cold allodynia.

CONCLUSION AND IMPLICATIONS

Altogether, our data indicate that T-type channels differentially contribute to the regulation of cold and mechanical hypersensitivity, and raise the possibility that T-type channel blockers could promote cold allodynia.

Oxaliplatin-associated shock in stage III colorectal cancer patients: real-world evidence in Taiwan

Background

Oxaliplatin-associated shock (referred to as shock) is a rare but life-threatening adverse event.

Objectives

This pioneering cohort study aimed to quantitatively investigate the association between oxaliplatin use and shock in patients with stage III colorectal cancer (CRC), identify potential independent risk factors for shock, and assess the cycle-to-shock during oxaliplatin treatment.

Design

The study utilized a nested case-control (NCC) design to assess the association between oxaliplatin and shock and employed a case-crossover approach to address unmeasured confounders.

Methods

All newly diagnosed stage III CRC patients were identified from the CRC Health Database (2012-2016). Conditional logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CIs) for oxaliplatin's link to shock incidence.

Results

Among 6932 oxaliplatin recipients, 331 suffered shock. In all, 3309 controls were selected via risk-set sampling for the shock cases. Oxaliplatin use is associated with a doubled risk of shock (adjusted OR: 2.08, 95% CI: 1.23-3.52). Two independent risk factors were male sex (adjusted OR: 1.33, 95% CI: 1.05-1.69) and heart diseases (adjusted OR: 1.65, 95% CI: 1.17-2.32). The case-crossover analysis revealed a more than fourfold risk (OR: 4.4, 95% CI: 1.67-11.62). In total, 22 of 331 shock cases were exposed to oxaliplatin within 2 days of shock onset, with a median cycle-to-shock time at the seventh cycle.

Conclusion

Oxaliplatin use significantly increased shock risk in stage III CRC patients. Male sex and heart disease are two independent risk factors.

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.

Cisplatin Provokes Peripheral Nociception and Neuronal Features of Therapy-Induced Senescence and Calcium Dysregulation in Rats

Therapy-Induced Senescence (TIS) is a form of senescence that is typically described in malignant cells in response to the exposure of cancer chemotherapy or radiation but can also be precipitated in non-malignant cells. TIS has been shown to contribute to the development of several cancer therapy-related adverse effects; however, evidence on its role in mediating chemotherapy-induced neurotoxicity, such as Chemotherapy-induced Peripheral Neuropathy (CIPN), is limited. We here show that cisplatin treatment over two cycles (cumulative dose of 23 mg/kg) provoked mechanical allodynia and thermal hyperalgesia in Sprague-Dawley rats. Isolation of dorsal root ganglia (DRG) from the cisplatin-treated rats demonstrated robust SA-β-gal upregulation at both day 8 (after the first cycle) and day 18 (after the second cycle), decreased lmnb1 expression, increased expression of cdkn1a and cdkn2a, and of several factors of the Senescence-associated Secretory Phenotype (SASP) (Il6, Il1b, and mmp9). Moreover, single-cell calcium imaging of cultured DRGs revealed a significant increase in terms of the magnitude of KCl-evoked calcium responses in cisplatin-treated rats compared to vehicle-treated rats. No significant change was observed in terms of the magnitude of capsaicin-evoked calcium responses in cisplatin-treated rats compared to vehicle-treated rats but with decreased area under the curve of the responses in cisplatin-treated rats. Further evidence to support the contribution of TIS to therapy adverse effects is required but should encourage the use of senescence-modulating agents (senotherapeutics) as novel palliative approaches to mitigate chemotherapy-induced neurotoxicity.

TRPM3 as a novel target to alleviate acute oxaliplatin-induced peripheral neuropathic pain

ABSTRACT

Chemotherapy-induced peripheral neuropathic pain (CIPNP) is an adverse effect observed in up to 80% of patients of cancer on treatment with cytostatic drugs including paclitaxel and oxaliplatin. Chemotherapy-induced peripheral neuropathic pain can be so severe that it limits dose and choice of chemotherapy and has significant negative consequences on the quality of life of survivors. Current treatment options for CIPNP are limited and unsatisfactory. TRPM3 is a calcium-permeable ion channel functionally expressed in peripheral sensory neurons involved in the detection of thermal stimuli. Here, we focus on the possible involvement of TRPM3 in acute oxaliplatin-induced mechanical allodynia and cold hypersensitivity. In vitro calcium microfluorimetry and whole-cell patch-clamp experiments showed that TRPM3 is functionally upregulated in both heterologous and homologous expression systems after acute (24 hours) oxaliplatin treatment, whereas the direct application of oxaliplatin was without effect. In vivo behavioral studies using an acute oxaliplatin model for CIPNP showed the development of cold and mechano hypersensitivity in control mice, which was lacking in TRPM3 deficient mice. In addition, the levels of protein ERK, a marker for neuronal activity, were significantly reduced in dorsal root ganglion neurons derived from TRPM3 deficient mice compared with control after oxaliplatin administration. Moreover, intraperitoneal injection of a TRPM3 antagonist, isosakuranetin, effectively reduced the oxaliplatin-induced pain behavior in response to cold and mechanical stimulation in mice with an acute form of oxaliplatin-induced peripheral neuropathy. In summary, TRPM3 represents a potential new target for the treatment of neuropathic pain in patients undergoing chemotherapy.

Pretreatment with Zonisamide Mitigates Oxaliplatin-Induced Toxicity in Rat DRG Neurons and DRG Neuron–Schwann Cell Co-Cultures

Oxaliplatin (OHP) is a platinum-based agent that can cause peripheral neuropathy, an adverse effect in which the dorsal root ganglion (DRG) neurons are targeted. Zonisamide has exhibited neuroprotective activities toward adult rat DRG neurons in vitro and therefore, we aimed to assess its potential efficacy against OHP-induced neurotoxicity. Pretreatment with zonisamide (100 μM) alleviated the DRG neuronal death caused by OHP (75 μM) and the protective effects were attenuated by a co-incubation with 25 μM of the mitogen-activated protein kinase (MAPK; MEK/ERK) inhibitor, U0126, or the phosphatidyl inositol-3′-phosphate-kinase (PI3K) inhibitor, LY294002. Pretreatment with zonisamide also suppressed the OHP-induced p38 MAPK phosphorylation in lined DRG neurons, ND7/23, while the OHP-induced DRG neuronal death was alleviated by pretreatment with the p38 MAPK inhibitor, SB239063 (25 μM). Although zonisamide failed to protect the immortalized rat Schwann cells IFRS1 from OHP-induced cell death, it prevented neurite degeneration and demyelination-like changes, as well as the reduction of the serine/threonine-specific protein kinase (AKT) phosphorylation in DRG neuron–IFRS1 co-cultures exposed to OHP. Zonisamide’s neuroprotection against the OHP-induced peripheral sensory neuropathy is possibly mediated by a stimulation of the MEK/ERK and PI3K/AKT signaling pathways and suppression of the p38 MAPK pathway in DRG neurons. Future studies will allow us to solidify zonisamide as a promising remedy against the neurotoxic adverse effects of OHP.

Quantitative proteomic analysis of oxaliplatin induced peripheral neurotoxicity

Oxaliplatin (OXA)-induced peripheral neurotoxicity (OIPN) is a high-incidence and dose-dependent adverse reaction during OXA treatment. Its underlying mechanisms remain unclear, and no effective treatment or prevention therapies are currently available. Here, we employed a data independent acquisition (DIA)-based quantitative proteomic strategy to investigate the global proteome alterations in the dorsal root ganglion (DRG) tissues from mice injected with OXA for different periods. We identified 1128 differentially regulated proteins that were divided into six subclusters according to their alteration trends. Interestingly, these proteins were involved in cellular processes such as cell cycle, ribosomal stress, metabolism, and ion transport. In addition, OXA administration induced abundance changes of ion channels and proteins associated with mitochondrial function and reactive oxygen species production. Furthermore, we investigated the effects of diroximel fumarate (DRF), an FDA-approved oral fumarate drug for the treatment of relapsing forms of multiple sclerosis. Our findings showed that DRF could effectively ameliorate symptoms of OIPN and reduce the level of oxidative stress in mice. Taken together, our study systematically mapped the proteome alteration associated with the neural toxicity of OXA, and the findings could be leveraged to better understand the mechanisms of OIPN and to develop more effect treatment therapies. SIGNIFICANCE: Oxaliplatin (OXA)-induced peripheral neurotoxicity (OIPN) is a high-incidence and dose-dependent adverse reaction with unclear mechanism. Here we employed a data independent acquisition (DIA)-based quantitative proteomic strategy to explore the proteome changes in dorsal root ganglion (DRG) tissues from mice treated by OXA. The findings provided novel insights regarding the mechanisms of OIPN. For example, our data showed that OXA induced a broad disturbance in metabolism, particularly in glycolysis and amino acid metabolism. Additionally, we observed abundance changes of many ion channels and proteins associated with mitochondrial function and reactive oxygen species production. Furthermore, this study provided the first evidence for the possibility of repositioning diroximel fumarate (DRF) for treating OIPN.

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

ABSTRACT

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

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

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

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

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

Cisplatin-induced activation and functional modulation of satellite glial cells lead to cytokine-mediated modulation of sensory neuron excitability

Cisplatin plays an essential role in the treatment of various cancers. Cisplatin exhibits high efficacy, but it often leads to severe neurotoxic side effects, such as chemotherapy-induced polyneuropathy (CIPN). The pathophysiology of CIPN is not fully understood. There is increasing evidence for damage to satellite glial cells (SGC) and dorsal root ganglion (DRG) neurons. We investigated the influence of cisplatin on the function of SGCs and the direct influence on DRGs. Satellite glial cells were isolated from DRG and exposed to 0.1, 1, 10, or 100 μM cisplatin for 2 h, 4 h, and 24 h. Using immunocytochemical staining and Western blot analysis, the expression of the glial fibrillary acid protein (GFAP), reactive oxygen species (ROS), and inward rectifier potassium channel 4.1 (K_ir4.1) was determined. An increase in the immune reactivity (IR) and protein levels of GFAP and ROS was measured, and a reduction of IR and protein level of K_ir4.1 was detected. A decrease in these channels' current density was observed using the whole-cell patch-clamp recording. The interleukin-6 (IL-6) and tumor necrosis factor α (TNFα) release of SGCs increased after cisplatin exposure as measured using ELISA, and interleukin-1β (IL-1β) decreased. The SGC-secreted factors in the supernatant after cisplatin treatment led to a modulation of cultured DRG neurons' excitability. Taken together, the modulation and function of different SGC proteins could be linked to a direct impact of cisplatin. Further, SGC-secreted factors influenced the excitability of sensory neurons. Overall, SGCs could be a potential target in preventing and treating chemotherapy-induced neuropathic pain.

Sexual dimorphism in the contribution of neuroendocrine stress axes to oxaliplatin-induced painful peripheral neuropathy

ABSTRACT

Although clinical studies support the suggestion that stress is a risk factor for painful chemotherapy-induced peripheral neuropathy (CIPN), there is little scientific validation to support this link. Here, we evaluated the impact of stress on CIPN induced by oxaliplatin, and its underlying mechanisms, in male and female rats. A single dose of oxaliplatin produced mechanical hyperalgesia of similar magnitude in both sexes, still present at similar magnitude in both sexes, on day 28. Adrenalectomy mitigated oxaliplatin-induced hyperalgesia, in both sexes. To confirm the role of neuroendocrine stress axes in CIPN, intrathecal administration of antisense oligodeoxynucleotide targeting β₂-adrenergic receptor mRNA both prevented and reversed oxaliplatin-induced hyperalgesia, only in males. By contrast, glucocorticoid receptor antisense oligodeoxynucleotide prevented and reversed oxaliplatin-induced hyperalgesia in both sexes. Unpredictable sound stress enhanced CIPN, in both sexes. The administration of stress hormones, epinephrine, corticosterone, and their combination, at stress levels, mimicked the effects of sound stress on CIPN, in males. In females, only corticosterone mimicked the effect of sound stress. Also, a risk factor for CIPN, early-life stress, was evaluated by producing both stress-sensitive (produced by neonatal limited bedding) and stress-resilient (produced by neonatal handling) phenotypes in adults. Although neonatal limited bedding significantly enhanced CIPN only in female adults, neonatal handling significantly attenuated CIPN, in both sexes. Our study demonstrates a sexually dimorphic role of the 2 major neuroendocrine stress axes in oxaliplatin-induced neuropathic pain.

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.

Examining Sodium and Potassium Channel Conductances Involved in Hyperexcitability of Chemotherapy-Induced Peripheral Neuropathy: A Mathematical and Cell Culture-Based Study

Chemotherapy-induced peripheral neuropathy (CIPN) is a prevalent, painful side effect which arises due to a number of chemotherapy agents. CIPN can have a prolonged effect on quality of life. Chemotherapy treatment is often reduced or stopped altogether because of the severe pain. Currently, there are no FDA-approved treatments for CIPN partially due to its complex pathogenesis in multiple pathways involving a variety of channels, specifically, voltage-gated ion channels. One aspect of neuropathic pain in vitro is hyperexcitability in dorsal root ganglia (DRG) peripheral sensory neurons. Our study employs bifurcation theory to investigate the role of voltage-gated ion channels in inducing hyperexcitability as a consequence of spontaneous firing due to the common chemotherapy agent paclitaxel. Our mathematical investigation of a reductionist DRG neuron model comprised of sodium channel Nav1.7, sodium channel Nav1.8, delayed rectifier potassium channel, A-type transient potassium channel, and a leak channel suggests that Nav1.8 and delayed rectifier potassium channel conductances are critical for hyperexcitability of small DRG neurons. Introducing paclitaxel into the model, our bifurcation analysis predicts that hyperexcitability is highest for a medium dose of paclitaxel, which is supported by multi-electrode array (MEA) recordings. Furthermore, our findings using MEA reveal that Nav1.8 blocker A-803467 and delayed rectifier potassium enhancer L-alpha-phosphatidyl-D-myo-inositol 4,5-diphosphate, dioctanoyl (PIP2) can reduce paclitaxel-induced hyperexcitability of DRG neurons. Our approach can be readily extended and used to investigate various other contributors of hyperexcitability in CIPN.

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

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

Chemotherapy-induced peripheral neuropathy: part 1-current state of knowledge and perspectives for pharmacotherapy

Background

Despite the increasing knowledge of the etiology of neuropathic pain, this type of chronic pain is resistant to available analgesics in approximately 50% of patients and therefore is continuously a subject of considerable interest for physiologists, neurologists, medicinal chemists, pharmacologists and others searching for more effective treatment options for this debilitating condition.

Materials and methods

The present review article is the first of the two articles focused on chemotherapy-induced peripheral neuropathy (CIPN).

Results

CIPN is regarded as one of the most common drug-induced neuropathies and is highly pharmacoresistant. The lack of efficacious pharmacological methods for treating CIPN and preventing its development makes CIPN-related neuropathic pain a serious therapeutic gap in current medicine and pharmacotherapy. In this paper, the most recent advances in the field of studies on CIPN caused by platinum compounds (namely oxaliplatin and cisplatin), taxanes, vinca alkaloids and bortezomib are summarized.

Conclusions

The prevalence of CIPN, potential causes, risk factors, symptoms and molecular mechanisms underlying this pharmacoresistant condition are discussed.

Graphic abstract

Activation and functional modulation of satellite glial cells by oxaliplatin lead to hyperexcitability of sensory neurons in vitro

Platinum-based chemotherapeutics still play an important role in cancer therapy, however, severe side effects, such as painful neuropathy, occur frequently. The pathophysiologic mechanisms depend on the applied chemotherapeutic agent and are still controversial. In addition to neuronal damage, disturbance of glial cell activity may contribute to neurotoxicity. Here, we focused on the effect of oxaliplatin on satellite glial cell (SGC) function and on the activity of the dorsal root ganglion (DRG) neurons. SGCs were isolated as high-purity cultures and treated with 1 and 10 μM oxaliplatin for 2, 4 and 24 h. Subsequently, glial fibrillary acid protein (GFAP), reactive oxygen species (ROS), Connexin-43 (Cx-43), and inward rectifier potassium channel 4.1 (K_ir4.1) expression was determined by immunocytochemical staining (ICC) and Western blot analyses. Immunochemical staining and Western blot analysis showed an increase in the immune reactivity (IR) and protein levels of ROS, GFAP, and Cx-43. Furthermore, reduction of the IR and protein levels and current density were demonstrated using patch-clamp measurements, of K_ir4.1 channels after oxaliplatin exposure. Cytokine release in SGCs was measured using enzyme-linked immunosorbent assays (ELISA) after oxaliplatin exposure and indicated an increased release of IL-6 and TNFα, while IL-1β was decreased. The direct influence of SGC-secreted factors in the supernatant after oxaliplatin treatment led to the hyperexcitability of cultured DRG neurons. In summary, oxaliplatin has a direct impact on the modulation and function of different SGC proteins. Furthermore, SGC-released factors influence the excitability of sensory neurons, qualifying SGCs as potential targets for the prevention and treatment of oxaliplatin-induced polyneuropathy.

Inhibitory Effects of Columbianadin on Nociceptive Behaviors in a Neuropathic Pain Model, and on Voltage-Gated Calcium Currents in Dorsal Root Ganglion Neurons in Mice

Radix angelicae pubescentis (RAP) has been used in Chinese traditional medicine to treat painful diseases such as rheumatism and headache. A previous study has reported that columbianadin (CBN), a major coumarin in RAP inhibits acute and inflammatory pain behaviors. However, the effects of CBN on neuropathic pain behaviors, and the potential underlying mechanism have not been reported. In the present study, the effects of CBN, compared to another major coumarin of RAP osthole (OST), on oxaliplatin-induced neuropathic pain behaviors and on the voltage-gated calcium currents in small dorsal root ganglion (DRG) neurons were studied in mice. It was found that CBN and OST inhibited both mechanical and cold hypersensitivity induced by oxaliplatin. Moreover, CBN and OST might preferentially inhibit T- and L-type calcium currents (Ica). The inhibitory effects of CBN and OST on the oxaliplatin-induced mechanical allodynia were prevented by gabapentin. These results suggest that CBN, as well as OST might inhibit neuropathic pain behaviors through an inhibition of T- and L-type calcium currents in nociceptive DRG neurons.

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.

Repurposing antipsychotics of the diphenylbutylpiperidine class for cancer therapy

The recent development of high throughput compound screening has allowed drug repurposing to emerge as an effective avenue for discovering novel treatments for cancer. FDA-approved antipsychotic drugs fluspirilene, penfluridol, and pimozide are clinically used for the treatment of psychotic disorders, primarily schizophrenia. These compounds, belong to diphenylbutylpiperidine class of antipsychotic drugs, are the potent inhibitors of dopamine D2 receptor and calcium channel. A correlation has been found that patients treated for schizophrenia have lower incidences of certain types of cancer, such as respiratory, prostate, and bladder cancers. These compounds have also been shown to inhibit cancer proliferation in a variety of cancer cells, including melanoma, lung carcinoma, breast cancer, pancreatic cancer, glioma, and prostate cancer, among others. Antipsychotic drugs induce apoptosis and suppress metastasis in in vitro and in vivo models through mechanisms involving p53, STAT3, STAT5, protein phosphatase 2A, cholesterol homeostasis, integrins, autophagy, USP1, wnt/β-catenin signaling, and DNA repair. Additionally, pre-clinical evidence suggests that penfluridol and pimozide act synergistically with existing chemotherapeutic agents, such as dasatinib, temozolomide, and cisplatin. Some studies have also reported that the cytotoxic activity of the antipsychotics is selective for dividing cells. Based on this growing body of evidence and the availability and previous FDA-approval of the drugs, the compounds appear to be promising anti-cancer agents.

[Effect of cinobufagin on transient outward potassium current in dorsal root ganglion cells of rats with cancer-induced bone pain]

OBJECTIVE

To observe the effect of cinobufagin on transient outward potassium current (IA) in rat dorsal root ganglion cells of cancer-induced bone pain (CIBP) and explore the possible analgesic mechanism of cinobufagin.

METHODS

Whole cell patch clamp technique was used to examine the effect of cionbufagin on IA in acutely isolated dorsal root ganglion (DRG) cells from normal SD rats and rats with bone cancer pain.

RESULTS

The DRG cells from rats with CIBP showed obviously decreased IA current density, an activation curve shift to the right, and an inactivation curve shift to the left. Cinobufagin treatment significantly increased the IA current density and reversed the changes in the activation and inactivation curves in the DRG cells.

CONCLUSIONS

IA current is decreased in DRG neurons from rats with CIBP. Cinobufagin can regulate the activation and inactivation of IA current in the DRG cells, which may be related to its analgesic mechanism.