Nrf2 inhibits oxaliplatin-induced peripheral neuropathy via protection of mitochondrial function

Pt(IV) Complexes as Anticancer Drugs and Their Relationship with Oxidative Stress

Despite continuous research, cancer is still a leading cause of death worldwide; therefore, new methods of cancer management improvement are emerging. It is well known that in the pathophysiology of cancer, oxidative stress (OS) is a significant factor. Nevertheless, there is currently no quick or easy way to identify OS in cancer patients using blood tests. Currently, in cancer treatments, Pt(IV) complexes are preferred to Pt(II) complexes in terms of adverse effects, drug resistance, and administration methods. Intracellular reductants convert Pt(IV) complexes to their Pt(II) analogs, which are Pt compounds with anti-carcinogenic effects. Our aim was to find out if Pt(IV) complexes could be used to assess blood oxidative stress indicators and, consequently, monitor the development of cancer. In this review, we analyzed previous research using the PubMed and Google Scholar public databases to verify the potential use of Pt(IV) complexes in cancer management. We found that two main serum antioxidants, glutathione and ascorbic acid, which are easily measured using conventional methods, react favorably with Pt(IV) complexes. Our research results suggest Pt(IV) complexes as therapeutic anticancer drugs and potential diagnosis agents. However, further research must be conducted to verify this hypothesis.

Platinum Deposition in the Central Nervous System: A Novel Insight into Oxaliplatin-induced Peripheral Neuropathy in Young and Old Mice

Numerous factors can contribute to the incidence or exacerbation of peripheral neuropathy induced by oxaliplatin (OXA). Recently, platinum accumulation in the spinal cord of mice after OXA exposure, despite the efficient defenses of the central nervous system, has been demonstrated by our research group, expanding the knowledge about its toxicity. One hypothesis is platinum accumulation in the spinal cord causes oxidative damage to neurons and impairs mitochondrial function. Thus, the main aim of this study was to investigate the relationship between aging and OXA-induced neuropathic pain and its comorbidities, including anxious behavior and cognitive impairment. By using an OXA-induced peripheral neuropathy model, platinum and bioelement concentrations and their influence on oxidative damage, neuroprotection, and neuroplasticity pathways were evaluated in Swiss mice, and our findings showed that treatment with OXA exacerbated pain and anxious behavior, albeit not age-induced cognitive impairment. Platinum deposition in the spinal cord and, for the first time, in the brain of mice exposed to OXA, regardless of age, was identified. We found that alterations in bioelement concentration, oxidative damage, neuroprotection, and neuroplasticity pathways induced by aging contribute to OXA-induced peripheral neuropathy. Our results strive to supply a basis for therapeutic interventions for OXA-induced peripheral neuropathy considering age specificities.

Trace elements and metal nanoparticles: mechanistic approaches to mitigating chemotherapy-induced toxicity-a review of literature evidence

Anticancer chemotherapy (ACT) remains a cornerstone in cancer treatment, despite significant advances in pharmacology over recent decades. However, its associated side effect toxicity continues to pose a major concern for both oncology clinicians and patients, significantly impacting treatment protocols and patient quality of life. Current clinical strategies to mitigate ACT-induced toxicity have proven largely unsatisfactory, leaving a critical unmet need to block toxicity mechanisms without diminishing ACT's therapeutic efficacy. This review aims to document the molecular mechanisms underlying ACT toxicity and highlight research efforts exploring the protective effects of trace elements (TEs) and their nanoparticles (NPs) against these mechanisms. Our literature review reveals that the primary driver of ACT toxicity is redox imbalance, which triggers oxidative inflammation, apoptosis, endoplasmic reticulum stress, mitochondrial dysfunction, autophagy, and dysregulation of signaling pathways such as PI3K/mTOR/Akt. Studies suggest that TEs, including zinc, selenium, boron, manganese, and molybdenum, and their NPs, can potentially counteract ACT-induced toxicity by inhibiting oxidative stress-mediated pathways, including NF-κB/TLR4/MAPK/NLRP3, STAT-3/NLRP3, Bcl-2/Bid/p53/caspases, and LC3/Beclin-1/CHOP/ATG6, while also upregulating protective signaling pathways like Sirt1/PPAR-γ/PGC-1α/FOXO-3 and Nrf2/HO-1/ARE. However, evidence regarding the roles of lncRNA and the Wnt/β-catenin pathway in ACT toxicity remains inconsistent, and the impact of TEs and NPs on ACT efficacy is not fully understood. Further research is needed to confirm the protective effects of TEs and their NPs against ACT toxicity in cancer patients. In summary, TEs and their NPs present a promising avenue as adjuvant agents for preventing non-target organ toxicity induced by ACT.

Biological Mediators and Partial Regulatory Mechanisms on Neuropathic Pain Associated With Chemotherapeutic Agents

One of the most common issues caused by antineoplastic agents is chemotherapy-induced peripheral neuropathy (CIPN). In patients, CIPN is a sensory neuropathy accompanied by various motor and autonomic changes. With a high prevalence of cancer patients, CIPN is becoming a major problem for both cancer patients and for their health care providers. Nonetheless, there are lacking effective interventions preventing CIPN and treating the CIPN symptoms. A number of studies have demonstrated the cellular and molecular signaling pathways leading to CIPN using experimental models and the beneficial effects of some interventions on the CIPN symptoms related to those potential mechanisms. This review will summarize results obtained from recent human and animal studies, which include the abnormalities in mechanical and temperature sensory responses following chemotherapy such as representative bortezomib, oxaliplatin and paclitaxel. The underlying mechanisms of CIPN at cellular and molecular levels will be also discussed for additional in-depth studies needed to be better explored. Overall, this paper reviews the basic picture of CIPN and the signaling mechanisms of the most common antineoplastic agents in the peripheral and central nerve systems. A better understanding of the risk factors and fundamental mechanisms of CIPN is needed to develop effective preventive and therapeutic strategies.

Mitotherapy prevents peripheral neuropathy induced by oxaliplatin in mice

Oxaliplatin (OXA) is an antineoplastic agent used for the treatment of cisplatin-resistant tumours, presenting lower incidence of nephrotoxicity and myelotoxicity than other platinum-based drugs. However, OXA treatment is highly associated with painful peripheral neuropathy, a well-known and relevant side effect caused by mitochondrial dysfunction. The transfer of functional exogenous mitochondria (mitotherapy) is a promising therapeutic strategy for mitochondrial diseases. We investigated the effect of mitotherapy on oxaliplatin-induced painful peripheral neuropathy (OIPN) in male mice. OIPN was induced by i.p. injections of oxaliplatin (3 mg/kg) over 5 consecutive days. Mechanical (von Frey test) and cold (acetone drop test) allodynia were evaluated between 7 and 17 days after the first OXA treatment. Mitochondria was isolated from donor mouse livers and mitochondrial oxidative phosphorylation was assessed with high resolution respirometry. After confirming that the isolated mitochondria were functional, the organelles were administered at the dose of 0.5 mg/kg of mitochondrial protein on days 1, 3 and 5. Treatment with OXA caused both mechanical and cold allodynia in mice that were significant 7 days after the initial injection of OXA and persisted for up to 17 days. Mitotherapy significantly prevented the development of both sensory alterations, and attenuated body weight loss induced by OXA. Mitotherapy also prevented spinal cord ERK1/2 activation, microgliosis and the increase in TLR4 mRNA levels. Mitotherapy prevented OIPN by inhibiting neuroinflammation and the consequent cellular overactivity in the spinal cord, presenting a potential therapeutic strategy for pain management in oncologic patients undergoing OXA treatment.

Current understanding and future directions of cruciferous vegetables and their phytochemicals to combat neurological diseases

Neurological disorders incidences are increasing drastically due to complex pathophysiology, and the nonavailability of disease-modifying agents. Several attempts have been made to identify new potential chemicals to combat these neurological abnormalities. At present, complete abolishment of neurological diseases is not attainable except for symptomatic relief. However, dietary recommendations to help brain development or improvement have increased over the years. In recent times, cruciferous vegetables and their phytochemicals have been identified from preclinical and clinical investigations as potential neuroprotective agents. The present review highlights the beneficial effects and molecular mechanisms of phytochemicals such as indole-3-carbinol, diindolylmethane, sulforaphane, kaempferol, selenium, lutein, zeaxanthin, and vitamins of cruciferous vegetables against neurological diseases including Parkinson's disease, Alzheimer's disease, stroke, Huntington's disease, autism spectra disorders, anxiety, depression, and pain. Most of these cruciferous phytochemicals protect the brain by eliciting antioxidant, anti-inflammatory, and antiapoptotic properties. Regular dietary intake of cruciferous vegetables may benefit the prevention and treatment of neurological diseases. The present review suggests that there is a lacuna in identifying the clinical efficacy of these phytochemicals. Therefore, high-quality future studies should firmly establish the efficacy of the above-mentioned cruciferous phytochemicals in clinical settings.

Topical Oxaliplatin Produces Gain- and Loss-of-Function in Multiple Classes of Sensory Afferents

The platinum chemotherapeutic oxaliplatin produces dose-limiting pain, dysesthesia, and cold hypersensitivity in most patients immediately after infusion. An improved understanding of the mechanisms underlying these symptoms is urgently required to facilitate the development of symptomatic or preventative therapies. In this study, we have used skin-saphenous nerve recordings in vitro and behavioral experiments in mice to characterize the direct effects of oxaliplatin on different types of sensory afferent fibers. Our results confirmed that mice injected with oxaliplatin rapidly develop mechanical and cold hypersensitivities. We further noted profound changes to A fiber activity after the application of oxaliplatin to the receptive fields in the skin. Most oxaliplatin-treated Aδ- and rapidly adapting Aβ-units lost mechanical sensitivity, but units that retained responsiveness additionally displayed a novel, aberrant cold sensitivity. Slowly adapting Aβ-units did not display mechanical tachyphylaxis, and a subset of these fibers was sensitized to mechanical and cold stimulation after oxaliplatin treatment. C fiber afferents were less affected by acute applications of oxaliplatin, but a subset gained cold sensitivity. Taken together, our findings suggest that direct effects on peripheral A fibers play a dominant role in the development of acute oxaliplatin-induced cold hypersensitivity, numbness, and dysesthesia. PERSPECTIVE: The chemotherapeutic drug oxaliplatin rapidly gives rise to dose-limiting cold pain and dysesthesia. Here, we have used behavioral and electrophysiological studies of mice to characterize the responsible neurons. We show that oxaliplatin directly confers aberrant cold responsiveness to subsets of A-fibers while silencing other fibers of the same type.

NRF2 and the Moirai: Life and Death Decisions on Cell Fates

Significance: The transcription factor NRF2 (NF-E2-related factor 2) plays an important role as a master regulator of the cellular defense system by activating transcriptional programs of NRF2 target genes encoding multiple enzymes related to cellular redox balance and xenobiotic detoxication. Comprehensive transcriptional analyses continue to reveal an ever-broadening range of NRF2 target genes, demonstrating the sophistication and diversification of NRF2 biological signatures beyond its canonical cytoprotective roles. Recent Advances: Accumulating evidence indicates that NRF2 has a strong association with the regulation of cell fates by influencing key processes of cellular transitions in the three major phases of the life cycle of the cell (i.e., cell birth, cell differentiation, and cell death). The molecular integration of NRF2 signaling into this regulatory program occurs through a wide range of NRF2 target genes encompassing canonical functions and those manipulating cell fate pathways. Critical Issues: A singular focus on NRF2 signaling for dissecting its actions limits in-depth understanding of its intersection with the molecular machinery of cell fate determinations. Compensatory responses of downstream pathways governed by NRF2 executed by a variety of transcription factors and multifactorial signaling crosstalk require further exploration. Future Directions: Further investigations using optimized in vivo models and active engagement of overarching approaches to probe the interplay of widespread pathways are needed to study the properties and capabilities of NRF2 signaling as a part of a large network within the cell fate regulatory domain. Antioxid. Redox Signal. 38, 684-708.

Reactive oxygen species as mediators of disease progression and therapeutic response in colorectal cancer

Significance Reactive oxygen species (ROS) are critical to normal cellular function with redox homeostasis achieved by balancing ROS production with removal through detoxification mechanisms. Many of the conventional chemotherapies used to treat colorectal cancer (CRC) derive a proportion of their cytotoxicity from ROS generation and resistance to chemotherapy is associated with elevated detoxification mechanisms. Furthermore, cancer stem cells demonstrate elevated detoxification mechanisms making definitive treatment with existing chemotherapy challenging. In this article we review the roles of ROS in normal and malignant colonic cell biology and how existing and emerging therapies might harness ROS for therapeutic benefit. Recent advances Recent publications have elucidated the contribution of ROS to the cytotoxicity of conventional chemotherapy alongside the emerging approaches of photodynamic therapy (PDT), sonodynamic therapy (SDT) and radiodynamic therapy (RDT) in which ROS are generated in response to excitatory light, sound or X-ray stimuli to promote cancer cell apoptosis. Critical issues The majority of patients with metastatic CRC have a very poor prognosis with 5-year survival of approximately 13% making the need for new or more effective treatments an imperative. Future Directions Modulation of ROS through a combination of new and emerging therapies may improve the efficacy of current chemotherapy providing novel approaches to treat otherwise resistant disease.

Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating side effect of many common anti-cancer agents that can lead to dose reduction or treatment discontinuation, which decrease chemotherapy efficacy. Long-term CIPN can interfere with activities of daily living and diminish the quality of life. The mechanism of CIPN is not yet fully understood, and biomarkers are needed to identify patients at high risk and potential treatment targets. Metabolomics can capture the complex behavioral and pathophysiological processes involved in CIPN. This chapter is to review the CIPN metabolomics studies to find metabolic pathways potentially involved in CIPN. These potential CIPN metabolites are then investigated to determine whether there is evidence from studies of other neuropathy etiologies such as diabetic neuropathy and Leber hereditary optic neuropathy to support the importance of these pathways in peripheral neuropathy. Six potential biomarkers and their putative mechanisms in peripheral neuropathy were reviewed. Among these biomarkers, histidine and phenylalanine have clear roles in neurotransmission or neuroinflammation in peripheral neuropathy. Further research is needed to discover and validate CIPN metabolomics biomarkers in large clinical studies.

SIRT1-Enriched Exosomes Derived from Bone Marrow Mesenchymal Stromal Cells Alleviate Peripheral Neuropathy via Conserving Mitochondrial Function

Diabetic peripheral neuropathy (DPN) is a highly prevalent diabetic complication characterized at the molecular level by mitochondrial dysfunction and deleterious oxidative damage. No effective treatments for DPN are currently available. The present study was developed to examine the impact of exosomes derived from bone marrow mesenchymal stromal cells (BMSCs) overexpressing sirtuin 1 (SIRT1) on DPN through antioxidant activity and the preservation of mitochondrial homeostasis. A DPN model was established using 20-week-old diabetic model mice (db/db). Exosomes were prepared from control BMSCs (exo-control) and BMSCs that had been transduced with a SIRT1 lentivirus (exo-SIRT1). Sensory and motor nerve conduction velocity values were measured to assess neurological function, and mechanical and thermal sensitivity were analyzed in these animals. Exo-SIRT1 preparations exhibited a high loading capacity and readily accumulated within peripheral nerves following intravenous administration, whereupon they were able to promote improved neurological recovery relative to exo-control treatment. DPN mice exhibited significantly improved nerve conduction velocity following exo-SIRT1 treatment. Relative to exo-control-treated mice, those that underwent exo-SIRT1 treatment exhibited significantly elevated TOMM20 and Nrf2/HO-1 expression, reduced MDA levels, increased GSH and SOD activity, and increased MMP. Together, these results revealed that both exo-control and exo-SIRT1 administration was sufficient to reduce the morphological and behavioral changes observed in DPN model mice, with exo-SIRT1 treatment exhibiting superior therapeutic efficacy. These data thus provide a foundation for future efforts to explore other combinations of gene therapy and exosome treatment in an effort to alleviate DPN.

Preconditioning by voluntary wheel running attenuates later neuropathic pain via nuclear factor E2-related factor 2 antioxidant signaling in rats

ABSTRACT

Animal and human studies have shown that exercise prior to nerve injury prevents later chronic pain, but the mechanisms of such preconditioning remain elusive. Given that exercise acutely increases the formation of free radicals, triggering antioxidant compensation, we hypothesized that voluntary running preconditioning would attenuate neuropathic pain by supporting redox homeostasis after sciatic nerve injury in male and female rats. We show that 6 weeks of voluntary wheel running suppresses neuropathic pain development induced by chronic constriction injury across both sexes. This attenuation was associated with reduced nitrotyrosine immunoreactivity-a marker for peroxynitrite-at the sciatic nerve injury site. Our data suggest that prior voluntary wheel running does not reduce the production of peroxynitrite precursors, as expression levels of inducible nitric oxide synthase and NADPH oxidase 2 were unchanged. Instead, voluntary wheel running increased superoxide scavenging by elevating expression of superoxide dismutases 1 and 2. Prevention of neuropathic pain was further associated with the activation of the master transcriptional regulator of the antioxidant response, nuclear factor E2-related factor 2 (Nrf2). Six weeks of prior voluntary wheel running increased Nrf2 nuclear translocation at the sciatic nerve injury site; in contrast, 3 weeks of prior wheel running, which failed to prevent neuropathic pain, had no effect on Nrf2 nuclear translocation. The protective effects of prior voluntary wheel running were mediated by Nrf2, as suppression was abolished across both sexes when Nrf2 activation was blocked during the 6-week running phase. This study provides insight into the mechanisms by which physical activity may prevent neuropathic pain. Preconditioning by voluntary wheel running, terminated prior to nerve injury, suppresses later neuropathic pain in both sexes, and it is modulated through the activation of Nrf2-antioxidant signaling.

TRPV1 channel in spermatozoa is a molecular target for ROS-mediated sperm dysfunction and differentially expressed in both natural and ART pregnancy failure

Bi-directional crosstalk between Ca2+ signaling and ROS modulates physiological processes as a part of a regulatory circuit including sperm function. The role of transient receptor potential vanilloid 1 (TRPV1) in this regard cannot be undermined. This is the first report demonstrating the Ca2+-sensitive TRPV1 channel to be under-expressed in spermatozoa of subfertile men, idiopathic infertile men, and normozoospermic infertile males with high ROS (idiopathic infertility and unilateral varicocele). To study the effect of TRPV1 in determining the fertility outcome, we compared the expression profile of TRPV1 in spermatozoa of male partners who achieved pregnancy by natural conception (NC+, n = 10), IVF (IVF+, n = 23), or ICSI (ICSI +, n = 9) and their respective counterparts with failed pregnancy NC (n = 7), IVF (n = 23), or ICSI (n = 10), by both immunocytochemistry and flow-cytometry. Reduced expression of TRPV1 in sperm of IVF ± and ICSI ± men with respect to that NC+ men imply its role in mediating successful fertilization. Unsuccessful pregnancy outcome with an underexpression of TRPV1 in sperm of NC-/IVF-/ICSI-men suggests its role in conception and maintenance of pregnancy. Since ROS is regarded as one of the major contributors to sperm dysfunction, the effect of H2O2 +/- TRPV1 modulators (RTX/iRTX) on acrosomal reaction and calcium influx was evaluated to confirm TRPV1 as a redox sensor in human sperm. A significant increment in the percentage of acrosome reacted spermatozoa along with augmented Ca2+-influx was observed after H2O2 treatment, both in the presence or absence of TRPV1 agonist resiniferatoxin (RTX). The effect was attenuated by the TRPV1 antagonist iodoresiniferatoxin (iRTX), indicating the involvement of TRPV1 in mediating H2O2 response. Enhancement of motility and triggering of acrosomal reaction post TRPV1 activation suggested that disruption of these signaling cascades in vivo, possibly due to down-regulation of TRPV1 in these subfertile males. Bioinformatic analysis of the crosstalk between TRPV1 with fertility candidate proteins (reported to influence IVF outcome) revealed cell death and survival, cellular compromise, and embryonic development to be the primary networks affected by anomalous TRPV1 expression. We therefore postulate that TRPV1 can act as a redox sensor, and its expression in spermatozoa may serve as a fertility marker.

Nox, Nox, Are You There? The Role of NADPH Oxidases in the Peripheral Nervous System

Significance: Reactive oxygen species (ROS) contribute to multiple aspects of peripheral nervous system (PNS) biology ranging from physiological processes (e.g., axonal outgrowth and regeneration) to pathophysiology (e.g., nerve degeneration). Although ROS are derived from multiple sources, NADPH oxidase (Nox) family members are dedicated to ROS generation. Noxs are expressed in the PNS, and their overexpression is associated with detrimental effects on nerve function and contributes, at least in part, to peripheral neuropathies. Recent Advances: Of the seven members, studies mostly focused on Nox1, Nox2, and Nox4, which are expressed in the PNS in a cell-specific manner. We have also recently identified human Nox5 in sural nerve biopsies. When maintained at homeostatic levels, Noxs regulate several aspects of peripheral nerve health, most notably neurite outgrowth and axonal regeneration following nerve lesion. While Nox2 and Nox4 dysregulation is a major source of oxidative stress in PNS disorders, including neuropathic pain and diabetic peripheral neuropathy, recent evidence also implicates Nox1 and Nox5. Critical Issues: Although there is compelling evidence for a direct role of Noxs on nerve function, little is known about their subcellular localization, intercellular regulation, and interaction. These, together with redox signaling, are considered crucial components of nerve redox status. In addition, the lack of isoform-specific inhibitors limits conclusions about the physiological role of Noxs in the PNS and their therapeutic potential in peripheral neuropathies. Future Directions: Future research using isoform-specific genetic and pharmacological approaches are therefore needed to better understand the significance of Nox enzymes in PNS (patho) physiology. Antioxid. Redox Signal. 37, 613-630.

Sensory neuron dysfunction in orthotopic mouse models of colon cancer

Reports of neurological sequelae related to colon cancer are largely restricted to rare instances of paraneoplastic syndromes, due to autoimmune reactions. Systemic inflammation associated with tumor development influences sensory neuron function in other disease models, though the extent to which this occurs in colorectal cancer is unknown. We induced orthotopic colorectal cancer via orthotopic injection of two colorectal cancer cell lines (MC38 and CT26) in two different mouse strains (C57BL/6 and Balb/c, respectively). Behavioral tests of pain sensitivity and activity did not detect significant alterations in sensory sensitivity or diminished well-being throughout tumor development. However, immunohistochemistry revealed widespread reductions in intraepidermal nerve fiber density in the skin of tumor-bearing mice. Though loss of nerve fiber density was not associated with increased expression of cell injury markers in dorsal root ganglia, lumbar dorsal root ganglia neurons of tumor-bearing animals showed deficits in mitochondrial function. These neurons also had reduced cytosolic calcium levels in live-cell imaging and reduced spontaneous activity in multi-electrode array analysis. Bulk RNA sequencing of DRGs from tumor-bearing mice detected activation of gene expression pathways associated with elevated cytokine and chemokine signaling, including CXCL10. This is consistent with the detection of CXCL10 (and numerous other cytokines, chemokines and growth factors) in MC38 and CT26 cell-conditioned media, and the serum of tumor-bearing mice. Our study demonstrates in a pre-clinical setting that colon cancer is associated with latent sensory neuron dysfunction and implicates cytokine/chemokine signaling in this process. These findings may have implications for determining risk factors and treatment responsiveness related to neuropathy in colorectal cancer.

Identification of the NRF2 transcriptional network as a therapeutic target for trigeminal neuropathic pain

Trigeminal neuralgia, historically dubbed the "suicide disease," is an exceedingly painful neurologic condition characterized by sudden episodes of intense facial pain. Unfortunately, the only U.S. Food and Drug Administration (FDA)-approved medication for trigeminal neuralgia carries substantial side effects, with many patients requiring surgery. Here, we identify the NRF2 transcriptional network as a potential therapeutic target. We report that cerebrospinal fluid from patients with trigeminal neuralgia accumulates reactive oxygen species, several of which directly activate the pain-transducing channel TRPA1. Similar to our patient cohort, a mouse model of trigeminal neuropathic pain also exhibits notable oxidative stress. We discover that stimulating the NRF2 antioxidant transcriptional network is as analgesic as inhibiting TRPA1, in part by reversing the underlying oxidative stress. Using a transcriptome-guided drug discovery strategy, we identify two NRF2 network modulators as potential treatments. One of these candidates, exemestane, is already FDA-approved and may thus be a promising alternative treatment for trigeminal neuropathic pain.

Resveratrol Glycosides Impede Microglial Apoptosis and Oxidative Stress in Rats for Spinal Cord Injury

Spinal cord injury (SCI) usually occurs after severe trauma, which can lead to detrimental and unpredictable secondary diseases, including dyskinesia, paraplegia and even quadriplegia, resulting in seriously reduced quality of life among these patients. Oxidative damage is one of the major pathogenic factors of SCI. Resveratrol biologically exerts a significant antioxidant activity by increasing the levels of antioxidants and sequentially scavenging free radicals, so as to protect multiple organs from damage. This study investigates whether resveratrol can function as a protective mediator in SCI and the underlying mechanisms, aiming to provide a theoretical hint for the treatment of SCI. After establishment of SCI model in rats, serial doses of resveratrol were administrated. Afterwards, the therapeutic effects of resveratrol glycosides were evaluated by analyzing the motor function, spinal cord edema, cellular apoptosis and oxidative reaction in rats. Eventually, the potential mechanisms of resveratrol glycosides were studied via Western blotting. Our results showed that the pro-apoptosis proteins were highly expressed in the spinal cord tissue of rats after SCI. In comparison with healthy rats, those with SCI exhibited significant widespread dead neurons, glial cell apoptosis, oxidative stress and more serious functional defects. Nevertheless, resveratrol glycosides can ameliorate oxidative stress, inhibit the apoptosis of glial cells and neuronal death after SCI. Importantly, it can induce the activation of the Nrf2/HO-1 signal transduction pathway that mediated the alleviation of SCI in rats. Resveratrol can improve motor dysfunction after SCI, which may be a result of its anti-oxidation and anti-apoptotic effects via modulating the Nrf2 signal transduction pathway of microglia, which provides a new idea for the treatment of SCI.

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.

Protective Mechanism of Electroacupuncture on Peripheral Neurotoxicity Induced by Oxaliplatin in Rats

OBJECTIVE

To study the effect of electroacupuncture (EA) on oxaliplatin-induced peripheral neuropathy (OIPN) in rats.

METHODS

Male Sprague-Dawley rats were equally divided into 3 groups using a random number table: the control group, the OIPN group, and the EA (OIPN + EA) group, with 10 rats in each. The time courses of mechanical, cold sensitivity, and microcirculation blood flow intensity were determined. The morphology of the dorsal root ganglion (DRG) was observed by electron microscopic examination. The protein levels of nuclear factor E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and the transient receptor potential (TRP) protein family in DRGs were assayed by Western blot.

RESULTS

EA treatment significantly reduced mechanical allodynia and cold allodynia in OIPN rats (P<0.01). Notably, oxaliplatin treatment resulted in impaired microcirculatory blood flow and pathomorphological defects in DRGs (P<0.01). EA treatment increased the microcirculation blood flow and attenuated the pathological changes induced by oxaliplatin (P<0.01). In addition, the expression levels of Nrf2 and HO-1 were down-regulated, and the TRP protein family was over-expressed in the DRGs of OIPN rats (P<0.01). EA increased the expression levels of Nrf2 and HO-1 and decreased the level of TRP protein family in DRG (P<0.05 or P<0.01).

CONCLUSION

EA may be a potential alternative therapy for OIPN, and its mechanism may be mainly mediated by restoring the Nrf2/HO-1 signaling pathway.

Duloxetine alleviates oxaliplatin-induced peripheral neuropathy by regulating p53-mediated apoptosis

Oxaliplatin (OXA) is a key platinum-based chemotherapeutic agent for treatment of metastatic colorectal cancer, but the side effects of acute and chronic neuropathies limit its clinical application. Duloxetine has been found to have the potential to prevent OXA-induced peripheral neuropathy in several studies, but the underlying mechanisms remain unclear. The purpose of this study was to evaluate the effects of duloxetine on OXA-induced peripheral neuropathy and to find the potential mechanisms. The neuropathic pain mice model was used to explore the role of duloxetine on OXA-induced peripheral neuropathy by measuring the change of thermal withdrawal latency (TWL), paw withdrawal threshold (PWT), and intraepidermal nerve fiber density (IENFD). Moreover, to explore molecular mechanisms, effects of duloxetine on OXA-induced changes in mRNA and protein expression of components of the p53-related pathways in cultured rat dorsal root ganglion (DRG) neurons were measured. In vivo, we found duloxetine treatment could significantly prevent the changes in the TWL, PWT to mechanical stimulation, and the IENFD of mice caused by OXA. In vitro, we found duloxetine notably inhibits the relative mRNA and protein expression levels of p53, Bax/Bcl2, caspase-3, and caspase-9 in DRG neurons, which may indicate duloxetine protected the DRG neuron by inhibiting p53-related pathways. These results suggest that duloxetine could alleviate the OXA-induced peripheral neuropathy. Duloxetine deserves further consideration as a potential protective agent against peripheral neuropathy.

Paeoniflorin Ameliorates BiPN by Reducing IL6 Levels and Regulating PARKIN-Mediated Mitochondrial Autophagy

Background

Bortezomib-induced peripheral neuropathy (BiPN) is a common complication of multiple myeloma (MM) treatment that seriously affects the quality of life of patients. The purpose of the present study was to explore the therapeutic effect of paeoniflorin on BiPN and its possible mechanism.

Methods

ELISA was used to measure the level of interleukin-6 (IL6) in the plasma of MM patients, and bioinformatics analysis was used to predict the mechanism underlying the effect of paeoniflorin on peripheral neuropathy. Cell and animal models of BiPN were constructed to evaluate mitochondrial function by measuring cell viability and mitochondrial quality and labeling mitochondria with MitoTracker Green. Nerve injury in mice with BiPN was assessed by behavioral tests, evaluation of motor nerve conduction velocity, hematoxylin-eosin (HE) staining, electron microscopy and analysis of the levels of reactive oxygen species (ROS). Western blotting and immunohistochemistry (IHC) were used to assess the expression of autophagy-related proteins.

Results

In MM patients, IL6 levels were positively correlated with the degree of PN. The results of bioinformatics analysis suggested that paeoniflorin ameliorated PN by altering inflammation levels and mitochondrial autophagy. Paeoniflorin increased PC12 cell viability and mitochondrial autophagy levels, alleviated mitochondrial damage, and reduced IL6 levels. In addition, paeoniflorin effectively improved the behavior of mice with BiPN, relieved sciatic nerve injury in mice, increased the expression of LC3II/I, beclin-1, and Parkin in sciatic nerve cells, and increased the expression of LC3B and Parkin in the nerve tissue.

Conclusion

The present study confirmed that paeoniflorin significantly ameliorated peripheral neuropathy (PN) caused by bortezomib, possibly by reducing IL6 levels to regulate PARKIN-mediated mitochondrial autophagy and mitochondrial damage.

Biological mechanisms and clinical efficacy of sulforaphane for mental disorders

Current clinical management of major mental disorders, such as autism spectrum disorder, depression and schizophrenia, is less than optimal. Recent scientific advances have indicated that deficits in oxidative and inflammation systems are extensively involved in the pathogenesis of these disorders. These findings have led to expanded considerations for treatment. Sulforaphane (SFN) is a dietary phytochemical extracted from cruciferous vegetables. It is an effective activator of the transcription factor nuclear erythroid-2 like factor-2, which can upregulate multiple antioxidants and protect neurons against various oxidative damages. On the other hand, it can also significantly reduce inflammatory response to pathological states and decrease the damage caused by the immune response via the nuclear factor-κB pathway and other pathways. In this review, we introduce the biological mechanisms of SFN and the pilot evidence from its clinical trials of major mental disorders, hoping to promote an increase in psychiatric clinical studies of SFN.

Selenium Attenuates TBHP-Induced Apoptosis of Nucleus Pulposus Cells by Suppressing Mitochondrial Fission through Activating Nuclear Factor Erythroid 2-Related Factor 2

Intervertebral disc (IVD) degeneration (IDD), the leading cause of low back pain (LBP), remains intractable due to a lack of effective therapeutic strategies. Several lines of studies have documented that nucleus pulposus cell (NPC) death induced by excessive oxidative stress is a crucial contributor to IDD. However, the concrete role and regulation mechanisms have not been fully clarified. Selenium (Se), a vital prosthetic group of antioxidant enzymes, is indispensable for maintaining redox homeostasis and promoting cell survival. However, no light was shed on the role of Se on IDD progression, especially regulation on mitochondrial dynamics and homeostasis. To fill this research gap, the current study focuses on the effects of Se, including sodium selenite (SS) and selenomethionine (Se-Met), on IDD progression and the underlying mechanisms. In vitro, we found that both SS and Se-Met alleviated tert-butyl hydroperoxide- (TBHP-) induced oxidative stress, protected mitochondrial function, and inhibited apoptosis of NPCs. Further experiments indicated that Se suppressed TBHP-induced mitochondrial fission and rescued the imbalance of mitochondrial dynamics. Promoting mitochondrial fission by carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP) partially counteracted the cytoprotective effects of Se. Moreover, blocking nuclear factor erythroid 2-related factor 2 (Nrf2) with ML385 proved that the effect of Se on regulating mitochondrial dynamics was attributed to the activation of the Nrf2 pathway. In the puncture-induced rat IDD model, a supplement of Se-Met ameliorated degenerative manifestations. Taken together, our results demonstrated that Se suppressed TBHP-induced oxidative stress and mitochondrial fission by activating the Nrf2 pathway, thereby inhibiting the apoptosis of NPCs and ameliorating IDD. Regulation of mitochondrial dynamics by Se may have a potential application value in attenuating the pathological process of IDD.

The Effects of Nuclear Factor Erythroid 2 (NFE2)-Related Factor 2 (Nrf2) Activation in Preclinical Models of Peripheral Neuropathic Pain

Oxidative stress, resulting from an imbalance between the formation of damaging free radicals and availability of protective antioxidants, can contribute to peripheral neuropathic pain conditions. Reactive oxygen and nitrogen species, as well as products of the mitochondrial metabolism such as superoxide anions, hydrogen peroxide, and hydroxyl radicals, are common free radicals. Nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf2) is a transcription factor encoded by the NFE2L2 gene and is a member of the cap 'n' collar subfamily of basic region leucine zipper transcription factors. Under normal physiological conditions, Nrf2 remains bound to Kelch-like ECH-associated protein 1 in the cytoplasm that ultimately leads to proteasomal degradation. During peripheral neuropathy, Nrf2 can translocate to the nucleus, where it heterodimerizes with muscle aponeurosis fibromatosis proteins and binds to antioxidant response elements (AREs). It is becoming increasingly clear that the Nrf2 interaction with ARE leads to the transcription of several antioxidative enzymes that can ameliorate neuropathy and neuropathic pain in rodent models. Current evidence indicates that the antinociceptive effects of Nrf2 occur via reducing oxidative stress, neuroinflammation, and mitochondrial dysfunction. Here, we will summarize the preclinical evidence supporting the role of Nrf2 signaling pathways and Nrf2 inducers in alleviating peripheral neuropathic pain.

Probable Mechanisms of Doxorubicin Antitumor Activity Enhancement by Ginsenoside Rh2

Ginsenoside Rh2 increases the efficacy of doxorubicin (DOX) treatment in murine models of solid and ascites Ehrlich’s adenocarcinoma. In a solid tumor model (treatment commencing 7 days after inoculation), DOX + Rh2 co-treatment was significantly more efficacious than DOX alone. If treatment was started 24 h after inoculation, the inhibition of tumor growth of a solid tumor for the DOX + Rh2 co-treatment group was complete. Furthermore, survival in the ascites model was dramatically higher for the DOX + Rh2 co-treatment group than for DOX alone. Mechanisms underlying the combined DOX and Rh2 effects were studied in primary Ehrlich’s adenocarcinoma-derived cells and healthy mice’s splenocytes. Despite the previously established Rh2 pro-oxidant activity, DOX + Rh2 co-treatment revealed no increase in ROS compared to DOX treatment alone. However, DOX + Rh2 treatment was more effective in suppressing Ehrlich adenocarcinoma cell adhesion than either treatment alone. We hypothesize that the benefits of DOX + Rh2 combination treatment are due to the suppression of tumor cell attachment/invasion that might be effective in preventing metastatic spread of tumor cells. Ginsenoside Rh2 was found to be a modest activator in a Neh2-luc reporter assay, suggesting that Rh2 can activate the Nrf2-driven antioxidant program. Rh2-induced direct activation of Nrf2 might provide additional benefits by minimizing DOX toxicity towards non-cancerous cells.

Tmem160 contributes to the establishment of discrete nerve injury-induced pain behaviors in male mice

Chronic pain is a prevalent medical problem, and its molecular basis remains poorly understood. Here, we demonstrate the significance of the transmembrane protein (Tmem) 160 for nerve injury-induced neuropathic pain. An extensive behavioral assessment suggests a pain modality- and entity-specific phenotype in male Tmem160 global knockout (KO) mice: delayed establishment of tactile hypersensitivity and alterations in self-grooming after nerve injury. In contrast, Tmem160 seems to be dispensable for other nerve injury-induced pain modalities, such as non-evoked and movement-evoked pain, and for other pain entities. Mechanistically, we show that global KO males exhibit dampened neuroimmune signaling and diminished TRPA1-mediated activity in cultured dorsal root ganglia. Neither these changes nor altered pain-related behaviors are observed in global KO female and male peripheral sensory neuron-specific KO mice. Our findings reveal Tmem160 as a sexually dimorphic factor contributing to the establishment, but not maintenance, of discrete nerve injury-induced pain behaviors in male mice.

The potential roles of Nrf2/Keap1 signaling in anticancer drug interactions

Nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2), together with its suppressive binding partner Kelch-like ECH-associated protein 1 (Keap1), regulates cellular antioxidant response and drug metabolism. The roles of Nrf2/Keap1 signaling in the pathology of many diseases have been extensively investigated, and small molecules targeting Nrf2/Keap1 signaling have been developed to prevent or treat diseases such as multiple sclerosis, chronic kidney disease and cancer. Notably, Nrf2 plays dual roles in cancer development and treatment. Activation of Nrf2/Keap1 signaling in cancer cells has been reported to promote cancer progression and result in therapy resistance. Since cancer patients are often suffering comorbidities of other chronic diseases, anticancer drugs could be co-administrated with other drugs and herbs. Nrf2/Keap1 signaling modulators, especially activators, are common in drugs, herbs and dietary ingredients, even they are developed for other targets. Therefore, drug-drug or herb-drug interactions due to modulation of Nrf2/Keap1 signaling should be considered in cancer therapies. Here we briefly summarize basic biochemistry and physiology functions of Nrf2/Keap1 signaling, Nrf2/Keap1 signaling modulators that cancer patients could be exposed to, and anticancer drugs that are sensitive to Nrf2/Keap1 signaling, aiming to call attention to the potential drug-drug or herb-drug interactions between anticancer drugs and these Nrf2/Keap1 signaling modulators.

Pathological Mechanisms and Preventive Strategies of Oxaliplatin-Induced Peripheral Neuropathy

Oxaliplatin, which is widely used in treating cancers such as colorectal cancer, frequently causes peripheral neuropathy. It not only significantly reduces the patient's quality of life due to physical distress but may also result in a change or discontinuation of cancer treatment. Oxaliplatin-induced peripheral neuropathy (OIPN) is classified as acute or chronic depending on the onset time of side effects; however, the prevention and treatment of OIPN has not been established. As these peripheral neuropathies are side effects that occur due to treatment, the administration of effective prophylaxis can effectively prevent their onset. Although transient relief of symptoms such as pain and numbness enable the continuation of cancer treatment, it may result in the worsening of peripheral neuropathy. Thus, understanding the pathological mechanisms of OIPN and finding better preventative measures are important. This review focuses on animal models to address these issues, clarifies the pathological mechanisms of OIPN, and summarizes various approaches to solving OIPN, including targets for preventing OIPN.

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.

Dexmedetomidine alleviates inflammation in neuropathic pain by suppressing NLRP3 via Nrf2 activation

The aim of the present study was to investigate the mechanism by which dexmedetomidine (DEX) alleviates neuropathic pain in a chronic constriction injury (CCI) model in rats. A CCI rat model was established through sciatic nerve ligation. CCI rats were treated with DEX, the nuclear factor erythroid 2-related factor 2 (Nrf2) inhibitor ML385, the NLR family pyrin domain containing 3 (NLRP3) antagonist MCC950 and/or the NLRP3 activator nigericin. The mechanical withdrawal threshold (MWT) was measured to assess the pain sensitivity of CCI rats. Hematoxylin and eosin staining and TUNEL staining were used to examine spinal injury and apoptosis, respectively. ELISA was used to quantify the levels of inflammatory factors. The expression levels of Nrf2 and NLRP3 were also examined. The results indicated that a decrease in MWT and increases in spinal cord injury, apoptosis and inflammatory factors were detected in CCI rats compared with control rats. Spinal inflammation was abrogated in DEX-treated CCI rats. Compared with the model group, an increase in MWT and decreases in spinal cord injury, apoptosis and inflammatory factors were detected in rats treated with MCC950, while the opposite effects were observed in rats treated with nigericin. The opposite effects on these indicators were observed in the DEX + ML385 and MCC950 + ML385 groups compared with the DEX and MCC950 groups, respectively. MWT was increased, while spinal cord injury, apoptosis and inflammation decreased in the nigericin + DEX group compared with the nigericin group. In summary, the results of the present study indicated that DEX reduced neuropathic pain in CCI rats by suppressing NLRP3 through Nrf2 activation.

Antioxidants Improve Oxaliplatin-Induced Peripheral Neuropathy in Tumor-Bearing Mice Model: Role of Spinal Cord Oxidative Stress and Inflammation

Chemotherapy-Induced Peripheral Neuropathy (CIPN) is a common, difficult-to-treat, and dose-limiting side effect associated with Oxaliplatin (OXA) treatment. In this study, we evaluated the effect of three antioxidants - namely N-acetylcysteine, α-lipoic acid and vitamin E - upon nociceptive parameters and antitumor efficacy of OXA in a tumor-bearing Swiss mice model. Oral treatment with antioxidants inhibited both mechanical and cold allodynia when concomitantly administrated with OXA (preventive protocol), as well as in animals with previously established CIPN (therapeutic protocol). OXA increased Reactive Oxygen Species (ROS) production and lipoperoxidation, and augmented the content of pro-inflammatory cytokines (IL-1β and TNF-α) and expression of the astrocytic marker Gfap mRNA in the spinal cord. Antioxidants decreased ROS production and lipoperoxidation, and abolished neuroinflammation in OXA-treated animals. Toll-like receptor 4 (Tlr4) and inflammasome enzyme caspase-1/11 knockout mice treated with OXA showed reduced levels of pro-inflammatory cytokines (but not oxidative stress) in the spinal cord, which were associated with resistance to OXA-induced mechanical allodynia. Lastly, antioxidants affected neither antitumor activity nor hematological toxicity of OXA in vivo. The herein presented results are provocative for further evaluation of antioxidants in clinical management of chemotherapy-induced peripheral neuropathy. PERSPECTIVE: This study reports preventive and therapeutic efficacy of orally administrated antioxidants (N-acetylcysteine, α-lipoic-acid and Vitamin-E) in alleviating oxaliplatin-induced peripheral neuropathy in tumor-bearing mice. Antioxidants' anti-nociceptive effects are associated with inhibition of ROS-dependent neuroinflammation, and occur at no detriment of OXA antitumor activity, therefore indicating a translational potential of these compounds.

Pregabalin reduces oxaliplatin-induced oxidative neurotoxicity through modulation of TRPV1 channels in DBTRG neuronal cell line

As a member of the platinum drug group, oxaliplatin (OXAL) is used to treat brain tumors, although its use is limited through excessive calcium ion (Ca) influx and reactive oxygen species (ROS) production in neurons. The Ca permeable transient receptor potential vanilloid 1 (TRPV1) channel is activated by ROS, and its activity might be reduced by the antioxidant property of pregabalin (PREGAB). This study aimed to investigate the protective action of PREGAB against OXAL-induced oxidative neurotoxicity in human glioblastoma (DBTRG) cells. The DBTRG cells were divided into four treatment groups: control, PREGAB (500 µM for 1 h), OXAL (25 µM for 24 h), and PREGAB + OXAL. In the laser confocal microscope and plate reader analyses, apoptosis, mitochondrial membrane depolarization (JC-1), cell death (propidium iodide/Hoechst rate), and ROS-level production increased by activating TRPV1 in the cells using the OXAL treatment, although the cell viability values decreased. However, these values were recovered in the PREGAB + OXAL group using PREGAB and TRPV1 inhibitor (capsazepine) treatments. In the patch-clamp analyses, OXAL-induced TRPV1 channel activation in the OXAL group also decreased in the PREGAB + OXAL group using the PREGAB and capsazepine treatments. In conclusion, the apoptosis and oxidant actions of OXAL were increased by activation of the TRPV1 channel, but this effect was diminished by the PREGAB treatment. PREGAB treatment has the potential to be an effective strategy in the treatment of OXAL-induced oxidative neurotoxicity.

Role of Oxidative Stress in the Pathogenesis of Amyotrophic Lateral Sclerosis: Antioxidant Metalloenzymes and Therapeutic Strategies

Amyotrophic lateral sclerosis (ALS) affects motor neurons in the cerebral cortex, brainstem and spinal cord and leads to death due to respiratory failure within three to five years. Although the clinical symptoms of this disease were first described in 1869 and it is the most common motor neuron disease and the most common neurodegenerative disease in middle-aged individuals, the exact etiopathogenesis of ALS remains unclear and it remains incurable. However, free oxygen radicals (i.e., molecules containing one or more free electrons) are known to contribute to the pathogenesis of this disease as they very readily bind intracellular structures, leading to functional impairment. Antioxidant enzymes, which are often metalloenzymes, inactivate free oxygen radicals by converting them into a less harmful substance. One of the most important antioxidant enzymes is Cu²⁺Zn²⁺ superoxide dismutase (SOD1), which is mutated in 20% of cases of the familial form of ALS (fALS) and up to 7% of sporadic ALS (sALS) cases. In addition, the proper functioning of catalase and glutathione peroxidase (GPx) is essential for antioxidant protection. In this review article, we focus on the mechanisms through which these enzymes are involved in the antioxidant response to oxidative stress and thus the pathogenesis of ALS and their potential as therapeutic targets.

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.

Peripheral Neuropathy under Oncologic Therapies: A Literature Review on Pathogenetic Mechanisms

Peripheral neurologic complications are frequent adverse events during oncologic treatments and often lead to dose reduction, administration delays with time elongation of the therapeutic plan and, not least, worsening of patients' quality of life. Experience skills are required to recognize symptoms and clinical evidences and the collaboration between different health professionals, in particular oncologists and hospital pharmacists, grants a correct management of this undesirable occurrence. Some classes of drugs (platinates, vinca alkaloids, taxanes) typically develop this kind of side effect, but the genesis of chemotherapy-induced peripheral neuropathy is not linked to a single mechanism. This paper aims from one side at summarizing and explaining all the scattering mechanisms of chemotherapy-induced peripheral neuropathy through a detailed literature revision, on the other side at finding new approaches to possible treatments, in order to facilitate the collaboration between oncologists, hematologists and hospital pharmacists.

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

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

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

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

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

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

Drug Repositioning for the Prevention and Treatment of Chemotherapy-Induced Peripheral Neuropathy: A Mechanism- and Screening-Based Strategy

Chemotherapy-induced peripheral neuropathy (CIPN) is a severe adverse effect observed in most patients treated with neurotoxic anti-cancer drugs. Currently, there are no therapeutic options available for the prevention of CIPN. Furthermore, few drugs are recommended for the treatment of existing neuropathies because the mechanisms of CIPN remain unclear. Each chemotherapeutic drug induces neuropathy by distinct mechanisms, and thus we need to understand the characteristics of CIPN specific to individual drugs. Here, we review the known pathogenic mechanisms of oxaliplatin- and paclitaxel-induced CIPN, highlighting recent findings. Cancer chemotherapy is performed in a planned manner; therefore, preventive strategies can be planned for CIPN. Drug repositioning studies, which identify the unexpected actions of already approved drugs, have increased in recent years. We have also focused on drug repositioning studies, especially for prevention, because they should be rapidly translated to patients suffering from CIPN.

Reestablishment of Redox Homeostasis in the Nociceptive Primary Afferent as a Mechanism of Antinociception Promoted by Mesenchymal Stem/Stromal Cells in Oxaliplatin-Induced Chronic Peripheral Neuropathy

Painful neuropathy is a common adverse effect of oxaliplatin (OXL), a platinum-derivative chemotherapeutic agent. Oxidative stress and mitochondrial dysfunction are key factors contributing to the development of OXL-induced peripheral neuropathy (OIPN). Based on the antioxidant and antinociceptive properties of mesenchymal stem/stromal cells (MSC), the present study tested the hypothesis that MSC induce antinociceptive effects during OIPN by promoting regulation of redox environment and mitochondrial homeostasis in the nociceptive primary afferents. C57Bl/6 mice submitted to the OXL-chronic neuropathy induction protocol by repeated intravenous administration of OXL (1 mg/kg) were evaluated to determine the paw mechanical and thermal nociceptive thresholds using the von Frey filaments and cold plate tests, respectively. Two weeks after the neuropathy induction, mice were treated with bone marrow-derived MSC (1 × 106), vehicle, or gabapentin (GBP, 70 mg/kg). Four weeks later, mitochondrial morphology, gene expression profile, and oxidative stress markers in the sciatic nerve and dorsal root ganglia (DRG) were evaluated by transmission electron microscopy, RT-qPCR, and biochemical assays, respectively. OXL-treated mice presented behavioral signs of sensory neuropathy, such as mechanical allodynia and thermal hyperalgesia. The behavioral painful neuropathy was completely reverted by a single administration of MSC, while the daily treatment with GBP induced only a short-lived antinociceptive effect. The ultrastructural analysis of the sciatic nerve and DRG of OIPN mice revealed a high proportion of atypical mitochondria in both myelinated and unmyelinated fibers. Importantly, this mitochondrial atypia was strongly reduced in MSC-treated neuropathic mice. Moreover, MSC-treated neuropathic mice showed upregulation of Sod and Nrf2 mRNA in the sciatic nerve and DRG. In line with this result, MSC reduced markers of nitrosative stress and lipid peroxidation in the sciatic nerve and DRG from OIPN mice. Our data suggest that the reestablishment of redox homeostasis in the nociceptive primary afferents is a mechanism by which MSC transplantation reverts the OXL-induced chronic painful neuropathy.

Mitoquinone attenuates vascular calcification by suppressing oxidative stress and reducing apoptosis of vascular smooth muscle cells via the Keap1/Nrf2 pathway

Oxidative stress and apoptosis of vascular smooth muscle cells (VSMCs) are key to vascular calcification in patients with chronic kidney disease (CKD). The mitochondria-targeted antioxidant, mitoquinone (MitoQ), which reduces oxidative stress and apoptosis, has a protective effect in acute models of renal injury but whether MitoQ can attenuate vascular calcification in CKD patients is unknown. This study was conducted to investigate whether MitoQ can prevent calcification, both in vitro and in vivo. Adenine was used to induce calcification in rats, and inorganic phosphate was used to induce calcification in VSMCs. To elucidate the underlying molecular mechanism, a specific inhibitor of Nrf2, ML385, was used 1 h before MitoQ administration. Histological staining, ELISA, flow cytometry, alizarin red staining and western blotting were used to test this hypothesis. Administration of MitoQ alleviated calcification and oxidative stress. The anti-apoptotic effect of MitoQ was associated with upregulation of Bcl-2, downregulation of Bax, and increased Nrf2 expression. The effects of MitoQ were reversed by treatment with ML385. This study offers evidence that MitoQ attenuates vascular calcification by suppressing oxidative stress and apoptosis of VSMCs through the Keap1/Nrf2 pathway. MitoQ should be further investigated as a potential therapy to prevent vascular calcification in CKD patients.

The Neuroimmunology of Chronic Pain: From Rodents to Humans

Chronic pain, encompassing conditions, such as low back pain, arthritis, persistent post-surgical pain, fibromyalgia, and neuropathic pain disorders, is highly prevalent but remains poorly treated. The vast majority of therapeutics are directed solely at neurons, despite the fact that signaling between immune cells, glia, and neurons is now recognized as indispensable for the initiation and maintenance of chronic pain. This review highlights recent advances in understanding fundamental neuroimmune signaling mechanisms and novel therapeutic targets in rodent models of chronic pain. We further discuss new technological developments to study, diagnose, and quantify neuroimmune contributions to chronic pain in patient populations.

Nuclear Factor Erythroid 2-Related Factor 2 in Regulating Cancer Metabolism

Significance: Nuclear factor erythroid 2 (NFE2)-related factor 2 (NFE2L2, or NRF2) is a transcription factor predominantly affecting the expression of antioxidant genes. NRF2 plays a significant role in the control of redox balance, which is crucial in cancer cells. NRF2 activation regulates numerous cancer hallmarks, including metabolism, cancer stem cell characteristics, tumor aggressiveness, invasion, and metastasis formation. We review the molecular characteristics of the NRF2 pathway and discuss its interactions with the cancer hallmarks previously listed. Recent Advances: The noncanonical activation of NRF2 was recently discovered, and members of this pathway are involved in carcinogenesis. Further, cancer-related changes (e.g., metabolic flexibility) that support cancer progression were found to be redox- and NRF2 dependent. Critical Issues: NRF2 undergoes Janus-faced behavior in cancers. The pro- or antineoplastic effects of NRF2 are context dependent and essentially based on the specific molecular characteristics of the cancer in question. Therefore, systematic investigation of NRF2 signaling is necessary to clarify its role in cancer etiology. The biggest challenge in the NRF2 field is to determine which cancers can be targeted for better clinical outcomes. Further, large-scale genomic and transcriptomic studies are missing to correlate the clinical outcome with the activity of the NRF2 system. Future Directions: To exploit NRF2 in a clinical setting in the future, the druggable members of the NRF2 pathway should be identified. In addition, it will be important to study how the modulation of the NRF2 system interferes with cytostatic drugs and their combinations.

Based on Systematic Pharmacology: Molecular Mechanism of Siwei Jianbu Decoction in Preventing Oxaliplatin-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting side effect caused by chemotherapy drugs, and its existence seriously affects the quality of life of patients. We first established an oxaliplatin-induced peripheral neuropathy (OIPN) model and then measured and evaluated mechanical hyperalgesia, thermal nociception, cold allodynia, and intraepidermal nerve fiber (IENF) density to determine Siwei Jianbu Decoction's role in preventing OIPN. Then, we conducted a systematic pharmacological study that revealed important roles for the MAPK signaling pathway and proinflammatory immune pathway and confirmed these roles by western blot, immunofluorescence, and qPCR. The data show that Siwei Jianbu Decoction can effectively prevent oxaliplatin-induced neuroinflammation by inhibiting an increase in NF-κB expression via downregulation of p-ERK1/2 and p-p38. The present study showed that SWJB may be beneficial in preventing oxaliplatin-induced peripheral neuropathy.

Formononetin ameliorates oxaliplatin-induced peripheral neuropathy via the KEAP1-NRF2-GSTP1 axis

Management of oxaliplatin-induced peripheral neuropathy (OIPN) has proven challenging owing to the concern that any OIPN-preventing agents may also decrease the efficacy of the chemotherapeutic agent and fail to reverse established neuronal damage. Nevertheless, targeting redox signaling pathways constitutes a promising therapy in OIPN and we have previously demonstrated the protective role of nuclear factor erythroid-2 related factor 2 (NRF2) in this disorder. Here, we investigated the protective properties of formononetin (FN), a clinical preparation extract, in OIPN. RNA interference experiments revealed that FN protects against OIPN directly through activation of the NRF2 pathway. Further expression profile sequencing showed that FN exerts its protective effect via the NRF2 downstream-oxaliplatin metabolism enzyme, GSTP1. We also demonstrated that FN does not influence the chemotherapeutic function of oxaliplatin, as NRF2 exhibits a different drug metabolic enzyme activation state downstream in colorectal cell lines than that in neurons. Following synthesis of Bio-FN to screen the target binding proteins, we found that FN selectively binds to His129 and Lys131 in the BTB domain of KEAP1. In vivo experiments revealed that FN-induced activation of the NRF2 signaling pathway alleviated the nociceptive sensations in mice. Our findings highlight a new binding mechanism between KEAP1 and isoflavones for activation of the NRF2 system and suggest that pharmacological or therapeutic activation of the NRF2-GSTP1 axis may serve as an effective strategy to prevent or attenuate the progression of OIPN.

•

FN prevents oxaliplatin-induced peripheral neuropathy via KEAP1-NRF2-GSTP1 axis.

•

FN retains oxaliplatin in vitro antitumor activity in cancer cells.

•

FN selectively binds His129 and Lys131 in the Keap1 BTB domain.

Lycopene protects against central and peripheral neuropathy by inhibiting oxaliplatin-induced ATF-6 pathway, apoptosis, inflammation and oxidative stress in brains and sciatic tissues of rats

The fact that oxaliplatin (OXL), a platinum-based chemotherapeutic drug, causes severe neuropathy greatly limits its clinical use. This study investigated the effects of lycopene, a potent antioxidant, on OXL-induced central and peripheral neuropathy. In this study, 30 min after oral administration of LY at a dose of 2 mg/kg b.w./day and 4 mg/kg b.w./day on 1 st, 2nd, 4th and 5th days, rats were given 4 mg/kg b.w./day of OXL intraperitoneally. It was detected that LY decreased OXL-induced lipid peroxidation and increased the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) and the levels of glutathione (GSH) in brain tissue. LY showed anti-inflammatory effects by decreasing levels of mitogen-activated protein kinase-14 (MAPK14), nuclear factor kappa-B (NF-κB) and tumor necrosis factor-α (TNF-α) in brain and sciatic tissue. It was determined that OXL-induced endoplasmic reticulum stress (ERS) decreased because LY administration reduced the expressions of activating transcription factor-6 (ATF6), glucose-regulated protein-78 (GRP78), RNA-activated protein kinase (PKR)-like ER kinase and inositol-requiring enzyme-1 (IRE1). LY administration also reduced the damage of OXL-induced brain and sciatic tissue by increasing NCAM levels and decreasing GFAP levels. It was determined that caspase-3 immunopositivity markedly decreased by OXL and LY in combination. It was also observed that LY provided neuronal protection by increasing brain-derived neurotrophic factor (BDNF) levels, which decreased with OXL administration in sciatic tissue. The results demonstrate that LY can be beneficial in ameliorating OXL-induced central and peripheral nerve injuries by showing antioxidant, anti-inflammatory and anti-apoptotic properties in the brain and sciatic tissue.

The mitochondria-targeted anti-oxidant MitoQ protects against intervertebral disc degeneration by ameliorating mitochondrial dysfunction and redox imbalance

Objective

Mitochondrial dysfunction, oxidative stress and nucleus pulposus (NP) cell apoptosis are important contributors to the development and pathogenesis of intervertebral disc degeneration (IDD). Here, we comprehensively evaluated the effects of mitochondrial dynamics, mitophagic flux and Nrf2 signalling on the mitochondrial quality control, ROS production and NP cell survival in in vitro and ex vivo compression models of IDD and explored the effects of the mitochondria‐targeted anti‐oxidant MitoQ and its mechanism.

Material and methods

Human NP cells were exposed to mechanical compression to mimic pathological conditions.

Results

Compression promoted oxidative stress, mitochondrial dysfunction and NP cell apoptosis. Mechanistically, compression disrupted the mitochondrial fission/fusion balance, inducing fatal fission. Concomitantly, PINK1/Parkin‐mediated mitophagy was activated, whereas mitophagic flux was blocked. Nrf2 anti‐oxidant pathway was insufficiently activated. These caused the damaged mitochondria accumulation and persistent oxidative damage. Moreover, MitoQ restored the mitochondrial dynamics balance, alleviated the impairment of mitophagosome‐lysosome fusion and lysosomal function and enhanced the Nrf2 activity. Consequently, damaged mitochondria were eliminated, redox balance was improved, and cell survival increased. Additionally, MitoQ alleviated IDD in an ex vivo rat compression model.

Conclusions

These findings suggest that comodulation of mitochondrial dynamics, mitophagic flux and Nrf2 signalling alleviates sustained mitochondrial dysfunction and oxidative stress and represents a promising therapeutic strategy for IDD; furthermore, our results provide evidence that MitoQ might serve as an effective therapeutic agent for this disorder.

Oral Dimethyl Fumarate Reduces Peripheral Neuropathic Pain in Rodents via NFE2L2 Antioxidant Signaling

BACKGROUND

Available treatments for neuropathic pain have modest efficacy and significant adverse effects, including abuse potential. Because oxidative stress is a key mechanistic node for neuropathic pain, the authors focused on the master regulator of the antioxidant response-nuclear factor erythroid 2-related factor 2 (NFE2L2; Nrf2)-as an alternative target for neuropathic pain. The authors tested whether dimethyl fumarate (U.S. Food and Drug Administration-approved treatment for multiple sclerosis) would activate NFE2L2 and promote antioxidant activity to reverse neuropathic pain behaviors and oxidative stress-dependent mechanisms.

METHODS

Male Sprague Dawley rats, and male and female wild type and Nfe2l2 mice were treated with oral dimethyl fumarate/vehicle for 5 days (300 mg/kg; daily) after spared nerve injury/sham surgery (n = 5 to 8 per group). Allodynia was measured in von Frey reflex tests and hyperalgesia in operant conflict-avoidance tests. Ipsilateral L4/5 dorsal root ganglia were assayed for antioxidant and cytokine/chemokine levels, and mitochondrial bioenergetic capacity.

RESULTS

Dimethyl fumarate treatment reversed mechanical allodynia (injury-vehicle, 0.45 ± 0.06 g [mean ± SD]; injury-dimethyl fumarate, 8.2 ± 0.16 g; P < 0.001) and hyperalgesia induced by nerve injury (injury-vehicle, 2 of 6 crossed noxious probes; injury-dimethyl fumarate, 6 of 6 crossed; P = 0.013). The antiallodynic effect of dimethyl fumarate was lost in nerve-injured Nfe2l2 mice, but retained in nerve-injured male and female wild type mice (wild type, 0.94 ± 0.25 g; Nfe2l2, 0.02 ± 0.01 g; P < 0.001). Superoxide dismutase activity was increased by dimethyl fumarate after nerve injury (injury-vehicle, 3.96 ± 1.28 mU/mg; injury-dimethyl fumarate, 7.97 ± 0.47 mU/mg; P < 0.001). Treatment reduced the injury-dependent increases in cytokines and chemokines, including interleukin-1β (injury-vehicle, 13.30 ± 2.95 pg/mg; injury-dimethyl fumarate, 6.33 ± 1.97 pg/mg; P = 0.022). Injury-impaired mitochondrial bioenergetics, including basal respiratory capacity, were restored by dimethyl fumarate treatment (P = 0.025).

CONCLUSIONS

Dimethyl fumarate, a nonopioid and orally-bioavailable drug, alleviated nociceptive hypersensitivity induced by peripheral nerve injury via activation of NFE2L2 antioxidant signaling. Dimethyl fumarate also resolved neuroinflammation and mitochondrial dysfunction-oxidative stress-dependent mechanisms that drive nociceptive hypersensitivity after nerve injury.

Targeting CARD6 attenuates spinal cord injury (SCI) in mice through inhibiting apoptosis, inflammation and oxidative stress associated ROS production

Spinal cord injury (SCI) causes long-term and severe disability, influencing the quality of life and triggering serious socioeconomic consequences. Lack of effective pharmacotherapies for SCI is largely attributable to an incomplete understanding of its pathogenesis. Caspase recruitment domain family member 6 (CARD6) was initially suggested to be a protein playing significant role in NF-κB activation. However, the effects of CARD6 on SCI progression remain unknown. In this study, the wild type (CARD6+/+), CARD6 knockout (CARD6-/-) and CARD6 transgenic (TG) mice were subjected to a SCI model in vivo, and in vitro experiments were conducted by treating microglia cells with lipopolysaccharide (LPS). Here, we identified CARD6 as a suppressor of SCI in mice. CARD6 knockout significantly accelerated functional deficits, neuron death and glia activation, whereas CARD6 overexpression resulted in the opposite effects. Both in vivo and in vitro SCI models suggested that CARD6 knockout markedly promoted apoptosis by increasing Cyto-c release to cytosol from mitochondria and activating Caspase-3 signaling. In addition, CARD6 knockout mice exhibited stronger inflammatory response after SCI, as evidenced by the significantly elevated expression of pro-inflammatory cytokines TNF-α, IL-1β and IL-6, which was largely through enhancing the activation of NF-κB signaling.