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

Mesenchymal stem cells in chemotherapy-induced peripheral neuropathy: A new challenging approach that requires further investigations

Chemotherapeutic drugs may disrupt the nervous system and cause chemotherapy-induced peripheral neuropathy (CIPN) as side effects. There are no completely successful medications for the prevention or treatment of CIPN. Many drugs such as tricyclic antidepressants and anticonvulsants have been used for symptomatic treatment of CIPN. Unfortunately, these drugs often give only partial relief or have dose-limiting side effects. Thus, the treatment of CIPN becomes a challenge because of failure to regenerate and repair the injured neurons. Mesenchymal stem cell (MSC) therapy is a new attractive approach for CIPN. Evidence has demonstrated that MSCs play important roles in reducing oxidative stress, neuroinflammation, and apoptosis, as well as mediating axon regeneration after nerve damage in several experimental studies and some clinical trials. We will briefly review the pathogenesis of CIPN, traditional therapies used and their drawbacks as well as therapeutic effects of MSCs, their related mechanisms, future challenges for their clinical application, and the additional benefit of their combination with pharmacological agents. MSCs-based therapies may provide a new therapeutic strategy for patients suffering from CIPN where further investigations are required for studying their exact mechanisms. Combined therapy with pharmacological agents can provide another promising option for enhancing MSC therapy success while limiting its adverse effects.

Dimethyl Fumarate Attenuates Oxaliplatin-Induced Peripheral Neuropathy without Affecting the Anti-tumor Activity of Oxaliplatin in Rodents

Oxaliplatin has been used as a first choice for colorectal, gastric and pancreatic cancer, but it induces peripheral neuropathies. Dimethyl fumarate (DMF) is an oral drug for multiple sclerosis with neuroprotective effects on oxidative stress. Using both in vivo and in vitro models, we investigated the effects of DMF on oxaliplatin-induced peripheral neuropathy and other side effects, as well as on the anti-tumor activity of oxaliplatin. Repeated intraperitoneal injection of 4 mg/kg oxaliplatin (twice per week for 4 weeks) caused mechanical allodynia (as revealed by the von Frey tests), cold hyperalgesia (as revealed by the acetone tests), and axonal degeneration in the sciatic nerve of rats. Co-administration of oral DMF (200 mg/kg, five times per week for 4 weeks) relieved oxaliplatin-induced mechanical allodynia but not cold hyperalgesia, and ameliorated axonal degeneration. In addition, DMF did not exacerbate oxaliplatin-induced body weight loss or bone marrow suppression, such as reduction in red blood cells, white blood cells, neutrophils and lymphocytes. Furthermore, DMF did not inhibit the anti-tumor activity of oxaliplatin in any cultured cancer cell line (C26, mouse colon carcinoma; HCT116, human colon carcinoma; MKN45, human gastric adenocarcinoma; MIA PaCa-2, human pancreatic carcinoma) or C26-bearing mice. These results suggest that DMF prevents oxaliplatin-induced mechanical allodynia and axonal degeneration without affecting the anti-tumor activity of oxaliplatin. Therefore, DMF may be useful for managing oxaliplatin-induced chronic peripheral neuropathy.

Analgesic and Antidepressant Effects of Oltipraz on Neuropathic Pain in Mice by Modulating Microglial Activation

Nerve injury provokes microglial activation, contributing to the sensory and emotional disorders associated with neuropathic pain that do not completely resolve with treatment. In C57BL/6J mice with neuropathic pain induced by chronic constriction of the sciatic nerve (CCI), we evaluated the effects of oltipraz, an antioxidant and anticancer compound, on (1) allodynia and hyperalgesia, (2) microglial activation and pain signaling pathways, (3) oxidative stress, and (4) depressive-like behaviors. Twenty-eight days after surgery, we assessed the effects of oltipraz on the expression of CD11b/c (a microglial marker), phosphoinositide 3-kinase (PI3K)/ phosphorylated protein kinase B (p-Akt), nuclear factor-κB (NF-κB) transcription factor, and mitogen activated protein kinases (MAPK) in the spinal cord, hippocampus, and prefrontal cortex. Our results show that oltipraz alleviates neuropathic pain by inhibiting microglial activation and PI3K/p-Akt, phosphorylated inhibitor of κBα (p-IκBα), and MAPK overexpression, and by normalizing and/or enhancing the expression of antioxidant proteins, nuclear factor erythroid derived-2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1), and NAD(P)H:quinone oxidoreductase-1 (NQO1) in the spinal cord. The inhibition of microglial activation and induction of the Nrf2/HO-1/NQO1 signaling pathway in the hippocampus and/or prefrontal cortex may explain the antidepressant effects of oltipraz during neuropathic pain. These data demonstrate the analgesic and antidepressant effects of oltipraz and reveal its protective and antioxidant properties during chronic pain.

The neuroprotective mechanisms and effects of sulforaphane

Sulforaphane (SFN) is a phytochemical found in cruciferous vegetables. It has been shown to have many protective effects against many diseases, including multiple types of cancer. SFN is a potent activator of the nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant response element (ARE) genetic pathway. Upregulation of Nrf2-ARE increases the availability of multiple antioxidants. A substantial amount of preclinical research regarding the ability of SFN to protect the nervous system from many diseases and toxins has been done, but only a few small human trials have been completed. Preclinical data suggest that SFN protects the nervous system through multiple mechanisms and may help reduce the risk of many diseases and reduce the burden of symptoms in existing conditions. This review focuses on the literature regarding the protective effects of SFN on the nervous system. A discussion of neuroprotective mechanisms is followed by a discussion of the protective effects elicited by SFN administration in a multitude of neurological diseases and toxin exposures. SFN is a promising neuroprotective phytochemical which needs further human trials to evaluate its efficacy in preventing and decreasing the burden of many neurological diseases.

Mechanisms of Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most frequent side effects caused by antineoplastic agents, with a prevalence from 19% to over 85%. Clinically, CIPN is a mostly sensory neuropathy that may be accompanied by motor and autonomic changes of varying intensity and duration. Due to its high prevalence among cancer patients, CIPN constitutes a major problem for both cancer patients and survivors as well as for their health care providers, especially because, at the moment, there is no single effective method of preventing CIPN; moreover, the possibilities of treating this syndrome are very limited. There are six main substance groups that cause damage to peripheral sensory, motor and autonomic neurons, which result in the development of CIPN: platinum-based antineoplastic agents, vinca alkaloids, epothilones (ixabepilone), taxanes, proteasome inhibitors (bortezomib) and immunomodulatory drugs (thalidomide). Among them, the most neurotoxic are platinum-based agents, taxanes, ixabepilone and thalidomide; other less neurotoxic but also commonly used drugs are bortezomib and vinca alkaloids. This paper reviews the clinical picture of CIPN and the neurotoxicity mechanisms of the most common antineoplastic agents. A better understanding of the risk factors and underlying mechanisms of CIPN is needed to develop effective preventive and therapeutic strategies.

Resveratrol alleviates chemotherapy-induced oogonial stem cell apoptosis and ovarian aging in mice

Chemotherapy-induced ovarian aging not only increases the risk for early menopause-related complications but also results in infertility in young female cancer survivors. Oogonial stem cells have the ability to generate new oocytes and thus provide new opportunities for treating ovarian aging and female infertility. Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a natural phenol derived from plants, that has been shown to have positive effects on longevity and redox flow in lipid metabolism and a preventive function against certain tumors. To evaluate whether resveratrol could promote the repair of oogonial stem cells damage in a busulfan/cyclophosphamide (Bu/Cy)-induced accelerated ovarian aging model, female mice were administered 30 and 100 mg/kg/d resveratrol through a gavage for 2 weeks. We demonstrated that resveratrol (30 mg/kg/d) relieved oogonial stem cells loss and showed an attenuating effect on Bu/Cy-induced oxidative apoptosis in mouse ovaries, which may be attributed to the attenuation of oxidative levels in ovaries. Additionally, we also showed that Res exerted a dose-dependent effect on oogonial stem cells and attenuated H2O2-induced cytotoxicity and oxidative stress injury by activating Nrf2 in vitro. Therefore, resveratrol could be of a potential therapeutic drug used to prevent chemotherapy-induced ovarian aging.

γ-glutamylcysteine exhibits anti-inflammatory effects by increasing cellular glutathione level

Sepsis is a life-threatening organ dysfunction caused by dysregulated host response to infection and characterized by redox imbalance and severe oxidative stress. Glutathione (GSH) serves several vital functions, including scavenging free radicals and maintaining intracellular redox balance. Extracellular GSH is unable to be taken into the majority of human cells, and the GSH prodrug N-acetyl-l-cysteine (NAC) does not exhibit promising clinical effects. γ-glutamylcysteine (γ-GC), an intermediate dipeptide of the GSH-synthesis pathway and harboring anti-inflammatory properties, represents a relatively unexplored option for sepsis treatment. The anti-inflammatory efficiency of γ-GC and the associated molecular mechanism need to be explored. In vivo investigation showed that γ-GC reduced sepsis lethality and attenuated systemic inflammatory responses in mice, as well as inhibited lipopolysaccharide (LPS)-stimulated production of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), high-mobility group box 1 (HMGB1), and nitric oxide (NO) and the expression of inducible NO synthase and cyclooxygenase 2 in RAW264.7 cells. Moreover, both in vivo and in vitro experiments demonstrated that γ-GC exhibited better therapeutic effects against inflammation compared with N-acetyl-L-cysteine (NAC) and GSH. Mechanistically, γ-GC suppressed LPS-induced reactive oxygen species accumulation and GSH depletion. Inflammatory stimuli, such as LPS treatment, upregulated the expression of glutathione synthetase via activating nuclear factor-erythroid 2-related factor (Nrf2) and nuclear factor kappa B (NF-κB) pathways, thereby promoting synthesis of GSH from γ-GC. These findings suggested that γ-GC might represent a potential therapeutic agent for sepsis treatment.

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γ-GC reduces sepsis lethality and attenuates inflammatory responses in BALB/c mice.

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γ-GC suppresses LPS-induced inflammation, ROS accumulation, and GSH depletion.

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Nrf2 and NF-κB pathways are essential for upregulating GSS level to promote GSH synthesis from γ-GC.

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γ-GC is more effective in attenuation inflammation than NAC and GSH.