Nicotinamide riboside, a form of vitamin B3 and NAD+ precursor, relieves the nociceptive and aversive dimensions of paclitaxel-induced peripheral neuropathy in female rats

Promises of natural products as clinical applications for cancer

Cancer represents a substantial threat to human health and mortality, necessitating the development of novel pharmacological agents with innovative mechanisms of action. Consequently, extensive research has been directed toward discovering new anticancer compounds derived from natural sources, including plants, microbes, and marine organisms. This review offers a comprehensive analysis of natural anticancer agents that are either currently undergoing clinical trials or have been integrated into clinical practice. A comprehensive understanding of the historical origins of natural anticancer agents, alongside traditional targets for tumor treatment and the distinct characteristics of cancer, can significantly facilitate researchers in the discovery and development of innovative anticancer drugs for clinical use. Furthermore, the exploration of microbial and marine sources is currently a prominent area of focus in the clinical application and advancement of new anticancer therapies. Detailed classification and elucidation of the functions and antitumor properties of these natural products are essential. It is imperative to comprehensively summarize and comprehend the natural anticancer drugs that have been and continue to be utilized in clinical settings.

Chemotherapy-Induced Peripheral Neuropathy: A Recent Update on Pathophysiology and Treatment

Chemotherapy-induced peripheral neuropathy (CIPN) is a major long-lasting side effect of some chemotherapy drugs, which threatens cancer survival rate. CIPN mostly affects sensory neurons and occasionally motor neurons, causing numbness, tingling, discomfort, and burning pain in the upper and lower extremities. The pathophysiology of CIPN is not completely understood; however, it is believed that chemotherapies induce peripheral neuropathy via directly damaging mitochondria, impairing the function of ion channels, triggering immunological mechanisms, and disrupting microtubules. The treatment of CIPN is a medical challenge, and there are no approved pharmacological options. Currently, duloxetine and other antidepressants, antioxidant, anti-inflammatory, and ion-channel targeted therapies are commonly used in clinics to relieve the symptoms of CIPN. Several other types of drugs, such as cannabinoids, sigma-1 receptor antagonists, and nicotinamides ribose, are being evaluated in preclinical and clinical studies. This paper summarizes the information related to the physiology of CIPN and medicines that could be used for treating this condition.

Augustus Waller's foresight realized: SARM1 in peripheral neuropathies

Peripheral neuropathy is a common neurodegenerative condition characterized by numbness, tingling, pain, and weakness that frequently starts in the distal limbs. Arising from multiple etiologies, many peripheral neuropathies exhibit a slowly progressive course due to axon degeneration for which no effective treatments exist. During the past decade, numerous crucial insights into mechanisms of axon degeneration in peripheral neuropathies emerged from experiments involving nerve-cutting procedures, revealing the central role of the SARM1 axon degeneration pathway in both. Here I review commonalities and differences in the role of SARM1 after nerve cut and in several acquired and inherited peripheral neuropathies. This new knowledge now paves the way for the development of therapeutics that directly address root causes of various kinds of neuropathies.

HDAC inhibitors as a potential therapy for chemotherapy-induced neuropathic pain

Cancer, a chronic disease characterized by uncontrolled cell development, kills millions of people globally. The WHO reported over 10 million cancer deaths in 2020. Anticancer medications destroy healthy and malignant cells. Cancer treatment induces neuropathy. Anticancer drugs cause harm to spinal cord, brain, and peripheral nerve somatosensory neurons, causing chemotherapy-induced neuropathic pain. The chemotherapy-induced mechanisms underlying neuropathic pain are not fully understood. However, neuroinflammation has been identified as one of the various pathways associated with the onset of chemotherapy-induced neuropathic pain. The neuroinflammatory processes may exhibit varying characteristics based on the specific type of anticancer treatment delivered. Neuroinflammatory characteristics have been observed in the spinal cord, where microglia and astrocytes have a significant impact on the development of chemotherapy-induced peripheral neuropathy. The patient's quality of life might be affected by sensory deprivation, loss of consciousness, paralysis, and severe disability. High cancer rates and ineffective treatments are associated with this disease. Recently, histone deacetylases have become a novel treatment target for chemotherapy-induced neuropathic pain. Chemotherapy-induced neuropathic pain may be treated with histone deacetylase inhibitors. Histone deacetylase inhibitors may be a promising therapeutic treatment for chemotherapy-induced neuropathic pain. Common chemotherapeutic drugs, mechanisms, therapeutic treatments for neuropathic pain, and histone deacetylase and its inhibitors in chemotherapy-induced neuropathic pain are covered in this paper. We propose that histone deacetylase inhibitors may treat several aspects of chemotherapy-induced neuropathic pain, and identifying these inhibitors as potentially unique treatments is crucial to the development of various chemotherapeutic combination treatments.

CORRECTION OF PATHOLOGICAL CHANGES IN SALIVARY GLANDS OF ANIMALS WITH PACLITAXEL-INDUCED NEUROPATHY

BACKGROUND

Paclitaxel is a highly effective chemotherapeutic agent used to treat breast, ovarian, and other cancers. At the same time, paclitaxel causes peripheral neuropathy as a side effect in 45%-70% of patients.

AIM

The aim of the study was to investigate the effect of paclitaxel-induced peripheral neuropathy on the development of pathological changes in the salivary glands of animals and to explore the possibility of correction of the identified changes with vitamin B/ATP complex.

MATERIALS AND METHODS

To simulate toxic neuropathy, animals were injected i/p with paclitaxel 2 mg/kg for 4 days. In order to correct the identified changes, rats were injected i/m with vitamin B/ATP complex (1 mg/ kg) for 9 days. In the homogenate of the submandibular salivary glands, α-amylase activity, total proteolytic activity, total antitryptic activity, the content of medium mass molecules, thiobarbituric acid reactive substances (TBARS), oxidatively modified proteins, and catalase activity were determined.

RESULTS

A significant increase in the content of oxidatively modified proteins, medium mass molecules, and the content of TBARS and significant decrease in the activity of catalase and amylase were determined in the salivary glands of animals with toxic neuropathy compared to these parameters in intact animals. Administration of vitamin B/ATP complex for 9 days against the background of paclitaxel-induced neuropathy led to normalization of antitryptic activity and amylase activity, a significant decrease in the content of oxidatively modified proteins, medium mass molecules, and TBARS along with a significant increase in catalase activity in the salivary glands of animals compared to the untreated rats with neuropathy.

CONCLUSION

Paclitaxel-induced neuropathy caused the development of pathological changes in the salivary glands of rats, which was evidenced by a carbonyl- oxidative stress and impaired protein synthetic function. The correction with vitamin B/ATP complex restored the protein-synthetic function and the proteinase-inhibitor balance, suppressed the oxidative stress and normalized free radical processes in the salivary glands of rats.

NAMPT/NAD+/PARP1 Pathway Regulates CFA-Induced Inflammatory Pain via NF-κB Signaling in Rodents

Emerging evidence has implicated nicotinamide adenine dinucleotide (NAD+) metabolism in various inflammatory diseases. In the study, the role of NAD+ metabolism in Complete Freund's Adjuvant (CFA)-evoked inflammatory pain and the underlying mechanisms are investigated. The study demonstrated that CFA induced upregulation of nicotinamide phosphoribosyltransferase (NAMPT) in dorsal root ganglia (DRG) without significant changes in the spinal cord. Inhibition of NAMPT expression by intrathecal injection of NAMPT siRNA alleviated CFA-induced pain-like behavior, decreased NAD+ contents in DRG, and lowered poly-(ADP-ribose) polymerase 1 (PARP1) activity levels. These effects are all reversed by the supplement of nicotinamide mononucleotide (NMN). Inhibition of PARP1 expression by intrathecal injection of PARP1 siRNA alleviated CFA-induced pain-like behavior, while elevated NAD+ levels of DRG. The analgesic effect of inhibiting NAMPT/NAD+/PARP1 axis can be attributed to the downregulation of the NF-κB/IL-1β inflammatory pathway. Double immunofluorescence staining showed that the expression of NAMPT/NAD+/PARP1 axis is restricted to DRG neurons. In conclusion, PARP1 activation in response to CFA stimulation, fueled by NAMPT-derived NAD+, mediates CFA-induced inflammatory pain through NF-κB/IL-1β inflammatory pathway.

Bortezomib-induced peripheral neuropathy: Clinical features, molecular basis, and therapeutic approach

Bortezomib is the first-line standard and most effective chemotherapeutic for multiple myeloma; however, bortezomib-induced peripheral neuropathy (BIPN) severely affects the chemotherapy regimen and has long-term impact on patients under maintenance therapy. The pathogenesis of BIPN is poorly understood, and basic research and development of BIPN management drugs are in early stages. Besides chemotherapy dose reduction and regimen modification, no recommended prevention and treatment approaches are available for BIPN apart from the International Myeloma Working Group guidelines for peripheral neuropathy in myeloma. An in-depth exploration of the pathogenesis of BIPN, development of additional therapeutic approaches, and identification of risk factors are needed. Optimizing effective and standardized BIPN treatment plans and providing more decision-making evidence for clinical diagnosis and treatment of BIPN are necessary. This article reviews the recent advances in BIPN research; provides an overview of clinical features, underlying molecular mechanisms, and therapeutic approaches; and highlights areas for future studies.

SLC25A51 decouples the mitochondrial NAD+/NADH ratio to control proliferation of AML cells

SLC25A51 selectively imports oxidized NAD+ into the mitochondrial matrix and is required for sustaining cell respiration. We observed elevated expression of SLC25A51 that correlated with poorer outcomes in patients with acute myeloid leukemia (AML), and we sought to determine the role SLC25A51 may serve in this disease. We found that lowering SLC25A51 levels led to increased apoptosis and prolonged survival in orthotopic xenograft models. Metabolic flux analyses indicated that depletion of SLC25A51 shunted flux away from mitochondrial oxidative pathways, notably without increased glycolytic flux. Depletion of SLC25A51 combined with 5-azacytidine treatment limits expansion of AML cells in vivo. Together, the data indicate that AML cells upregulate SLC25A51 to decouple mitochondrial NAD+/NADH for a proliferative advantage by supporting oxidative reactions from a variety of fuels. Thus, SLC25A51 represents a critical regulator that can be exploited by cancer cells and may be a vulnerability for refractory AML.

Chemotherapy-Induced Peripheral Neuropathy: Diagnosis, Agents, General Clinical Presentation, and Treatments

PURPOSE OF REVIEW

This review aims to discuss pathophysiology, diagnosis, clinical presentation, and treatment of chemotherapy-induced peripheral neuropathy. Agent-specific presentation and pathophysiology is also being discussed.

RECENT FINDINGS

As new systemic oncological treatments continue to be developed, the number of cancer survivors continues to grow. Survivors are living longer with the long-term side effects of oncological treatments. We reviewed the pathophysiology of agent-specific chemotherapy-induced peripheral neuropathy and the updates in its treatment and preventative tools. Chemotherapy-induced peripheral neuropathy is a debilitating long-term side effect that often impairs cancer survivors' function and quality of life. The increasing life expectancy of cancer survivors has resulted in increased prevalence of this condition. Understanding its intricacies can provide physicians with better treatment tools and research opportunities to develop or identify new therapeutic agents.

Elevation of NAD+ by nicotinamide riboside spares spinal cord tissue from injury and promotes locomotor recovery

Spinal cord injury (SCI)-induced tissue damage spreads to neighboring spared cells in the hours, days, and weeks following injury, leading to exacerbation of tissue damage and functional deficits. Among the biochemical changes is the rapid reduction of cellular nicotinamide adenine dinucleotide (NAD+), an essential coenzyme for energy metabolism and an essential cofactor for non-redox NAD+-dependent enzymes with critical functions in sensing and repairing damaged tissue. NAD+ depletion propagates tissue damage. Augmenting NAD+ by exogenous application of NAD+, its synthesizing enzymes, or its cellular precursors mitigates tissue damage. Nicotinamide riboside (NR) is considered to be one of the most promising NAD+ precursors for clinical application due to its ability to safely and effectively boost cellular NAD+ synthesis in rats and humans. Moreover, various preclinical studies have demonstrated that NR can provide tissue protection. Despite these promising findings, little is known about the potential benefits of NR in the context of SCI. In the current study, we tested whether NR administration could effectively increase NAD+ levels in the injured spinal cord and whether this augmentation of NAD+ would promote spinal cord tissue protection and ultimately lead to improvements in locomotor function. Our findings indicate that administering NR (500 mg/kg) intraperitoneally from four days before to two weeks after a mid-thoracic contusion-SCI injury, effectively doubles NAD+ levels in the spinal cord of Long-Evans rats. Moreover, NR administration plays a protective role in preserving spinal cord tissue post-injury, particularly in neurons and axons, as evident from the observed gray and white matter sparing. Additionally, it enhances motor function, as evaluated through the BBB subscore and missteps on the horizontal ladderwalk. Collectively, these findings demonstrate that administering NR, a precursor of NAD+, increases NAD+ within the injured spinal cord and effectively mitigates the tissue damage and functional decline that occurs following SCI.

Nicotinamide Riboside, a Promising Vitamin B3 Derivative for Healthy Aging and Longevity: Current Research and Perspectives

Many studies have suggested that the oxidized form of nicotinamide adenine dinucleotide (NAD+) is involved in an extensive spectrum of human pathologies, including neurodegenerative disorders, cardiomyopathy, obesity, and diabetes. Further, healthy aging and longevity appear to be closely related to NAD+ and its related metabolites, including nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN). As a dietary supplement, NR appears to be well tolerated, having better pharmacodynamics and greater potency. Unfortunately, NR is a reactive molecule, often unstable during its manufacturing, transport, and storage. Recently, work related to prebiotic chemistry discovered that NR borate is considerably more stable than NR itself. However, immediately upon consumption, the borate dissociates from the NR borate and is lost in the body through dilution and binding to other species, notably carbohydrates such as fructose and glucose. The NR left behind is expected to behave pharmacologically in ways identical to NR itself. This review provides a comprehensive summary (through Q1 of 2023) of the literature that makes the case for the consumption of NR as a dietary supplement. It then summarizes the challenges of delivering quality NR to consumers using standard synthesis, manufacture, shipping, and storage approaches. It concludes by outlining the advantages of NR borate in these processes.

Oral supplementation of nicotinamide riboside alters intestinal microbial composition in rats and mice, but not humans

The gut microbiota impacts systemic levels of multiple metabolites including NAD⁺ precursors through diverse pathways. Nicotinamide riboside (NR) is an NAD⁺ precursor capable of regulating mammalian cellular metabolism. Some bacterial families express the NR-specific transporter, PnuC. We hypothesized that dietary NR supplementation would modify the gut microbiota across intestinal sections. We determined the effects of 12 weeks of NR supplementation on the microbiota composition of intestinal segments of high-fat diet-fed (HFD) rats. We also explored the effects of 12 weeks of NR supplementation on the gut microbiota in humans and mice. In rats, NR reduced fat mass and tended to decrease body weight. Interestingly, NR increased fat and energy absorption but only in HFD-fed rats. Moreover, 16S rRNA gene sequencing analysis of intestinal and fecal samples revealed an increased abundance of species within Erysipelotrichaceae and Ruminococcaceae families in response to NR. PnuC-positive bacterial strains within these families showed an increased growth rate when supplemented with NR. The abundance of species within the Lachnospiraceae family decreased in response to HFD irrespective of NR. Alpha and beta diversity and bacterial composition of the human fecal microbiota were unaltered by NR, but in mice, the fecal abundance of species within Lachnospiraceae increased while abundances of Parasutterella and Bacteroides dorei species decreased in response to NR. In conclusion, oral NR altered the gut microbiota in rats and mice, but not in humans. In addition, NR attenuated body fat mass gain in rats, and increased fat and energy absorption in the HFD context.

Nicotinamide riboside alleviates cisplatin-induced peripheral neuropathy via SIRT2 activation

Background

Chemotherapy-induced peripheral neuropathy represents a major impairment to the quality of life of cancer patients and is one of the most common dose-limiting adverse effects of cancer treatment. Despite its prevalence, no effective treatment or prevention strategy exists. We have previously provided genetic evidence that the NAD⁺-dependent deacetylase, SIRT2, protects against cisplatin-induced peripheral neuronal cell death and neuropathy by enhancing nucleotide excision repair. In this study, we aimed to examine whether pharmacologic activation of SIRT2 would provide effective prevention and treatment of cisplatin-induced peripheral neuropathy (CIPN) without compromising tumor cell cytotoxic response to cisplatin.

Methods

Using von Frey and dynamic hot plate tests, we studied the use of nicotinamide riboside (NR) to prevent and treat CIPN in a mouse model. We also performed cell survival assays to investigate the effect of NAD⁺ supplementation on cisplatin toxicity in neuronal and cancer cells. Lewis lung carcinoma model was utilized to examine the effect of NR treatment on in vivo cisplatin tumor control.

Results

We show that NR, an NAD⁺ precursor and pharmacologic activator of SIRT2, effectively prevents and alleviates CIPN in mice. We present in vitro and in vivo genetic evidence to illustrate the specific dependence on SIRT2 of NR-mediated CIPN mitigation. Importantly, we demonstrate that NAD⁺ mediates SIRT2-dependent neuroprotection without inhibiting cisplatin cytotoxic activity against cancer cells. NAD⁺ may, in fact, further sensitize certain cancer cell types to cisplatin.

Conclusions

Together, our results identify SIRT2-targeted activity of NR as a potential therapy to alleviate CIPN, the debilitating and potentially permanent toxicity.

SIRT1: A promising therapeutic target for chronic pain

Chronic pain remains an unresolved problem. Current treatments have limited efficacy. Thus, novel therapeutic targets are urgently required for the development of more effective analgesics. An increasing number of studies have proved that sirtuin 1 (SIRT1) agonists can relieve chronic pain. In this review, we summarize recent progress in understanding the roles and mechanisms of SIRT1 in mediating chronic pain associated with peripheral nerve injury, chemotherapy-induced peripheral neuropathy, spinal cord injury, bone cancer, and complete Freund's adjuvant injection. Emerging studies have indicated that SIRT1 activation may exert positive effects on chronic pain relief by regulating inflammation, oxidative stress, and mitochondrial dysfunction. Therefore, SIRT1 agonists may serve as potential therapeutic drugs for chronic pain.

Emerging evidence for compromised axonal bioenergetics and axoglial metabolic coupling as drivers of neurodegeneration

Impaired bioenergetic capacity of the nervous system is thought to contribute to the pathogenesis of many neurodegenerative diseases (NDD). Since neuronal synapses are believed to be the major energy consumers in the nervous system, synaptic derangements resulting from energy deficits have been suggested to play a central role for the development of many of these disorders. However, long axons constitute the largest compartment of the neuronal network, require large amounts of energy, are metabolically and structurally highly vulnerable, and undergo early injurious stresses in many NDD. These stresses likely impose additional energy demands for continuous adaptations and repair processes, and may eventually overwhelm axonal maintenance mechanisms. Indeed, pathological axon degeneration (pAxD) is now recognized as an etiological focus in a wide array of NDD associated with bioenergetic abnormalities. In this paper I first discuss the recognition that a simple experimental model for pAxD is regulated by an auto-destruction program that exhausts distressed axons energetically. Provision of the energy substrate pyruvate robustly counteracts this axonal breakdown. Importantly, energy decline in axons is not only a consequence but also an initiator of this program. This opens the intriguing possibility that axon dysfunction and pAxD can be suppressed by preemptively energizing distressed axons. Second, I focus on the emerging concept that axons communicate energetically with their flanking glia. This axoglial metabolic coupling can help offset the axonal energy decline that activates the pAxD program but also jeopardize axon integrity as a result of perturbed glial metabolism. Third, I present compelling evidence that abnormal axonal energetics and compromised axoglial metabolic coupling accompany the activation of the pAxD auto-destruction pathway in models of glaucoma, a widespread neurodegenerative condition with pathogenic overlap to other common NDD. In conclusion, I propose a novel conceptual framework suggesting that therapeutic interventions focused on bioenergetic support of the nervous system should also address axons and their metabolic interactions with glia.

An important link between the gut microbiota and the circadian rhythm: imply for treatments of circadian rhythm sleep disorder

Currently, gut microbiota living in the gastrointestinal tract, plays an important role in regulating host's sleep and circadian rhythms. As a tool, gut microbiota has great potential for treating circadian disturbance and circadian insomnia. However, the relationship between gut microbiota and circadian rhythms is still unclear, and the mechanism of action has still been the focus of microbiome research. Therefore, this article summarizes the current evidences associating gut microbiota with factors that impact host circadian rhythms neurology sleep disorder. Moreover, we discuss the changes to these systems in sleep disorder and the potential mechanism of intestinal microbiota in regulating circadian rhythms neurology sleep disorder via microbial metabolites. Meanwhile, based on the role of intestinal flora, it is provided a novel insight into circadian related insomnia and will be benefit the dietary treatment of circadian disturbance and the circadian related insomnia.

Nicotinamide Riboside Alleviates Corneal and Somatic Hypersensitivity Induced by Paclitaxel in Male Rats

Purpose

Patients receiving chemotherapy may experience ocular discomfort and dry eye-like symptoms; the latter may be neuropathic in nature. This study assessed corneal and somatic hypersensitivity in male rats treated with paclitaxel and whether it was relieved by nicotinamide riboside (NR).

Methods

Corneal sensitivity to tactile and chemical stimulation, basal tear production, and sensitivity of the hindpaw to tactile and cool stimuli were assessed before and after paclitaxel in the absence and presence of sustained treatment with 500 mg/kg per os NR. Corneal nerve density and hindpaw intraepidermal nerve fiber (IENF) density were also examined.

Results

Paclitaxel-treated rats developed corneal hypersensitivity to tactile stimuli, enhanced sensitivity to capsaicin but not hyperosmolar saline, and increased basal tear production. Corneal nerve density visualized with anti-β-tubulin or calcitonin gene-related peptide (CGRP) was unaffected. Paclitaxel induced tactile and cool hypersensitivity of the hindpaw and a loss of nonpeptidergic hindpaw IENFs visualized with anti-protein gene product (PGP) 9.5 and CGRP. NR reversed tactile hypersensitivity of the cornea without suppressing tear production or chemosensitivity; it did not alter corneal afferent density. NR also reversed tactile and cool hypersensitivity of the hindpaw without reversing the loss of hindpaw IENFs.

Conclusions

These findings suggest that paclitaxel may be a good translational model for chemotherapy-induced ocular discomfort and that NR may be useful for its relief. The ability of NR to relieve somatic tactile hypersensitivity independent of changes in sensory nerve innervation suggests that reversal of terminal arbor degeneration is not critical to the actions of NR.

Nicotinamide Riboside for the Prevention and Treatment of Doxorubicin Cardiomyopathy. Opportunities and Prospects

Despite the progress in the development of new anticancer strategies, cancer is rapidly spreading around the world and remains one of the most common diseases. For more than 40 years, doxorubicin has been widely used in the treatment of solid and hematological tumors. At the same time, the problem of its cardiotoxicity remains unresolved, despite the high efficiency of this drug. Symptomatic therapy is used as a treatment for side-effects of doxorubicin or pathological conditions that have already appeared in their background. To date, there are no treatment methods for doxorubicin cardiomyopathy as such. A drug such as nicotinamide riboside can play an important role in solving this problem. Nicotinamide riboside is a pyridine nucleoside similar to vitamin B3 that acts as a precursor to NAD+. There is no published research on nicotinamide riboside effects on cardiomyopathy, despite the abundance of works devoted to the mechanisms of its effects in various pathologies. The review analyzes information about the effects of nicotinamide riboside on various experimental models of pathologies, its role in the synthesis of NAD+, and also considers the possibility and prospects of its use for the prevention of doxorubicin cardiomyopathy.

Preclinical and Clinical Evidence of Therapeutic Agents for Paclitaxel-Induced Peripheral Neuropathy

Paclitaxel is an essential drug in the chemotherapy of ovarian, non-small cell lung, breast, gastric, endometrial, and pancreatic cancers. However, it frequently causes peripheral neuropathy as a dose-limiting factor. Animal models of paclitaxel-induced peripheral neuropathy (PIPN) have been established. The mechanisms of PIPN development 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 PIPN effects. This review summarizes the basic and clinical evidence for therapeutic or prophylactic effects for PIPN. In pre-clinical research, many reports exist of neuropathy inhibitors that target oxidative stress, inflammatory response, ion channels, transient receptor potential (TRP) channels, cannabinoid receptors, and the monoamine nervous system. Alternatively, very few drugs have demonstrated PIPN efficacy in clinical trials. Thus, enhancing translational research to translate pre-clinical research into clinical research is important.

Nicotinamide riboside relieves paclitaxel-induced peripheral neuropathy and enhances suppression of tumor growth in tumor-bearing rats

Nicotinamide riboside (NR) is a vitamin B3 precursor of NAD that blunts diabetic and chemotherapy-induced peripheral neuropathy in preclinical models. This study examined whether NR also blunts the loss of intraepidermal nerve fibers induced by paclitaxel, which is associated with peripheral neuropathy. The work was conducted in female rats with N-methyl-nitrosourea (MNU)-induced tumors of the mammary gland to increase its translational relevance, and to assess the interaction of NR with paclitaxel and NR's effect on tumor growth. Once daily oral administration of 200 mg/kg NR p.o. beginning with the first of 3 i.v. injections of 6.6 mg/kg paclitaxel to tumor-bearing rats significantly decreased paclitaxel-induced hypersensitivity to tactile and cool stimuli, as well as place-escape avoidance behaviors. It also blunted the loss of intraepidermal nerve fibers in tumor-bearing rats, as well as a separate cohort of tumor-naive rats. Unexpectedly, concomitant administration of NR during paclitaxel treatment further decreased tumor growth; thereafter, tumor growth resumed at the same rate as vehicle-treated controls. Administration of NR also decreased the percentage of Ki67-positive tumor cells in these rats. Once daily administration of NR did not seem to alter tumor growth or the percentage of Ki67-positive tumor cells in rats that were not treated with paclitaxel and followed for 3 months. These results further support the ability of NR to play a protective role after nerve injury. They also suggest that NR may not only alleviate peripheral neuropathy in patients receiving taxane chemotherapy, but also offer an added benefit by possibly enhancing its tumor-suppressing effects.

The Role of Nucleotide Excision Repair in Cisplatin-Induced Peripheral Neuropathy: Mechanism, Prevention, and Treatment

Platinum-based chemotherapy-induced peripheral neuropathy (CIPN) is one of the most common dose-limiting effects of cancer treatment and results in dose reduction and discontinuation of life-saving chemotherapy. Its debilitating effects are often permanent and lead to lifelong impairment of quality of life in cancer patients. While the mechanisms underlying the toxicity are not yet fully defined, dorsal root ganglia sensory neurons play an integral role in symptom development. DNA-platinum adducts accumulate in these cells and inhibit normal cellular function. Nucleotide excision repair (NER) is integral to the repair of platinum adducts, and proteins involved in its mechanism serve as potential targets for future therapeutics. This review aims to highlight NER’s role in cisplatin-induced peripheral neuropathy, summarize current clinical approaches to the toxicity, and discuss future perspectives for the prevention and treatment of CIPN.

NAD+ metabolism and its roles in cellular processes during ageing

Nicotinamide adenine dinucleotide (NAD+) is a coenzyme for redox reactions, making it central to energy metabolism. NAD+ is also an essential cofactor for non-redox NAD+-dependent enzymes, including sirtuins, CD38 and poly(ADP-ribose) polymerases. NAD+ can directly and indirectly influence many key cellular functions, including metabolic pathways, DNA repair, chromatin remodelling, cellular senescence and immune cell function. These cellular processes and functions are critical for maintaining tissue and metabolic homeostasis and for healthy ageing. Remarkably, ageing is accompanied by a gradual decline in tissue and cellular NAD+ levels in multiple model organisms, including rodents and humans. This decline in NAD+ levels is linked causally to numerous ageing-associated diseases, including cognitive decline, cancer, metabolic disease, sarcopenia and frailty. Many of these ageing-associated diseases can be slowed down and even reversed by restoring NAD+ levels. Therefore, targeting NAD+ metabolism has emerged as a potential therapeutic approach to ameliorate ageing-related disease, and extend the human healthspan and lifespan. However, much remains to be learnt about how NAD+ influences human health and ageing biology. This includes a deeper understanding of the molecular mechanisms that regulate NAD+ levels, how to effectively restore NAD+ levels during ageing, whether doing so is safe and whether NAD+ repletion will have beneficial effects in ageing humans.

Vincristine- and bortezomib-induced neuropathies - from bedside to bench and back

Vincristine and bortezomib are effective chemotherapeutics widely used to treat hematological cancers. Vincristine blocks tubulin polymerization, whereas bortezomib is a proteasome inhibitor. Despite different mechanisms of action, the main non-hematological side effect of both is peripheral neuropathy that can last long after treatment has ended and cause permanent disability. Many different cellular and animal models of various aspects of vincristine and bortezomib-induced neuropathies have been generated to investigate underlying molecular mechanisms and serve as platforms to develop new therapeutics. These models revealed that bortezomib induces several transcriptional programs in dorsal root ganglia that result in the activation of different neuroinflammatory pathways and secondary central sensitization. In contrast, vincristine has direct toxic effects on the axon, which are accompanied by changes similar to those observed after nerve cut. Axon degeneration following both vincristine and bortezomib is mediated by a phylogenetically ancient, genetically encoded axon destruction program that leads to the activation of the Toll-like receptor adaptor SARM1 (sterile alpha and TIR motif containing protein 1) and local decrease of nicotinamide dinucleotide (NAD+). Here, I describe current in vitro and in vivo models of vincristine- and bortezomib induced neuropathies, present discoveries resulting from these models in the context of clinical findings and discuss how increased understanding of molecular mechanisms underlying different aspects of neuropathies can be translated to effective treatments to prevent, attenuate or reverse vincristine- and bortezomib-induced neuropathies. Such treatments could improve the quality of life of patients both during and after cancer therapy and, accordingly, have enormous societal impact.

Resistance of Food-Maintained Operant Responding to Mechanical Punishment in Rats: Further Evidence for Weak "Affective/Motivational Pain" in Rat Models of Inflammatory and Neuropathic Pain

Clinically relevant chronic pain is often associated with functional impairment and behavioral depression as an “affective/motivational” sign of pain; however preclinical animal models of inflammatory and neuropathic pain often produce weak evidence of impaired function. We hypothesized that hindpaw mechanical stimulation produced by a requirement to rear on a textured “NOX” plate would punish operant responding in rats treated with intraplantar complete Freund’s adjuvant (CFA, a model of inflammatory pain) or the chemotherapeutic paclitaxel (PTX, a model of neuropathic pain) and produce sustained pain-related depression of operant behavior. Male Sprague–Dawley rats were trained under a progressive-ratio (PR) schedule of food-maintained operant responding, then treated with CFA (100 µL in left hindpaw), PTX (2.0 mg/kg IP on alternate days for four total injections; 6.6 mg/kg IV on alternate days for three total injections), or saline vehicle. PR break points and mechanical thresholds for paw withdrawal from von Frey filaments were then tracked for 28 days. Subsequently, rats were tested with the opioid receptor antagonist naltrexone to assess latent sensitization and with the kappa opioid receptor (KOR) agonist U69593 to assess KOR function. CFA produced significant mechanical hypersensitivity for 3 weeks but decreased PR breakpoints for only 1 day. Both IP and IV PTX produced mechanical hypersensitivity for at least three weeks; however, only IV PTX decreased PR breakpoints, and this decrease was not alleviated by morphine. After recovery, naltrexone reinstated mechanical hypersensitivity in CFA- but not PTX-treated rats, and it did not reinstate depression of breakpoints in any group. U69593 dose-dependently decreased PR breakpoints in all groups with no difference between control vs. CFA/PTX groups. These results suggest that rearing on a textured NOX plate was not sufficient to punish operant responding in CFA- and PTX-treated rats despite the presence of sustained mechanical hypersensitivity. The rapid recovery of operant responding could not be attributed to latent sensitization, KOR downregulation, or behavioral tolerance. These results extend the range of conditions under which putative chronic pain manipulations produce weak evidence for depression of operant responding as a sign of the “affective/motivational” component of pain in rats.

Pathological Mechanisms of Bortezomib-Induced Peripheral Neuropathy

Bortezomib, a first-generation proteasome inhibitor widely used in chemotherapy for hematologic malignancy, has effective anti-cancer activity but often causes severe peripheral neuropathy. Although bortezomib-induced peripheral neuropathy (BIPN) is a dose-limiting toxicity, there are no recommended therapeutics for its prevention or treatment. One of the most critical problems is a lack of knowledge about pathological mechanisms of BIPN. Here, we summarize the known mechanisms of BIPN based on preclinical evidence, including morphological abnormalities, involvement of non-neuronal cells, oxidative stress, and alterations of transcriptional programs in both the peripheral and central nervous systems. Moreover, we describe the necessity of advancing studies that identify the potential efficacy of approved drugs on the basis of pathological mechanisms, as this is a convincing strategy for rapid translation to patients with cancer and BIPN.

Effect of nicotinamide riboside on lipid metabolism and gut microflora-bile acid axis in alcohol-exposed mice

Alcoholic liver disease (ALD) is the most common complication of alcohol abuse, while we lack safe and effective treatment for ALD. This study aimed to explore the effects of nicotinamide riboside (NR) on lipid metabolism and gut microflora-bile acid axis in alcohol-exposed mice. NR significantly improved liver histopathological damage and abnormal liver function. NR as a provider of nicotinamide adenine dinucleotide (NAD+) increased the NAD+/NADH ratio. Meanwhile, NR inhibited the activation of the protein phosphatase 1 signaling pathway, decreased the liver triglyceride and total bile acid levels, and reduced lipid accumulation. According to the results of gut microflora species analysis, NR intervention changed the microbial community structure at the phylum, family and genus levels, and the species abundances returned to a level similar to these of the normal control group. Besides, the results of high-performance liquid chromatograph-mass spectrometry showed that NR intervention resulted in fecal bile acid levels tending to be normal with decreased chenodeoxycholic acid level and increased deoxycholic acid and hyocholic acid levels. Spearman's correlation analysis showed a correlation between gut microflora and bile acids. Therefore, NR supplementation has the potential to prevent ALD, and its mechanism may be related to regulating lipid metabolism disorders and the gut microflora-bile acid axis.

Wolfram syndrome: new pathophysiological insights and therapeutic strategies

Wolfram Syndrome (WS) is an ultra-rare, progressive neurodegenerative disease characterized by early-onset diabetes mellitus and irreversible loss of vision, secondary to optic nerve degeneration. Visual loss in WS is an important cause of registrable blindness in children and young adults and the pathological hallmark is the preferential loss of retinal ganglion cells within the inner retina. In addition to optic atrophy, affected individuals frequently develop variable combinations of neurological, endocrinological, and psychiatric complications. The majority of patients carry recessive mutations in the WFS1 (4p16.1) gene that encodes for a multimeric transmembrane protein, wolframin, embedded within the endoplasmic reticulum (ER). An increasingly recognised subgroup of patients harbor dominant WFS1 mutations that usually cause a milder phenotype, which can be limited to optic atrophy. Wolframin is a ubiquitous protein with high levels of expression in retinal, neuronal, and muscle tissues. It is a multifunctional protein that regulates a host of cellular functions, in particular the dynamic interaction with mitochondria at mitochondria-associated membranes. Wolframin has been implicated in several crucial cellular signaling pathways, including insulin signaling, calcium homeostasis, and the regulation of apoptosis and the ER stress response. There is currently no cure for WS; management remains largely supportive. This review will cover the clinical, genetic, and pathophysiological features of WS, with a specific focus on disease models and the molecular pathways that could serve as potential therapeutic targets. The current landscape of therapeutic options will also be discussed in the context of the latest evidence, including the pipeline for repurposed drugs and gene therapy.

Plain language summary

Wolfram syndrome - disease mechanisms and treatment options Wolfram syndrome (WS) is an ultra-rare genetic disease that causes diabetes mellitus and progressive loss of vision from early childhood. Vision is affected in WS because of damage to a specialized type of cells in the retina, known as retinal ganglion cells (RGCs), which converge at the back of the eye to form the optic nerve. The optic nerve is the fast-conducting cable that transmits visual information from the eye to the vision processing centers within the brain. As RGCs are lost, the optic nerve degenerates and it becomes pale in appearance (optic atrophy). Although diabetes mellitus and optic atrophy are the main features of WS, some patients can develop more severe problems because the brain and other organs, such as the kidneys and the bladder, are also affected. The majority of patients with WS carry spelling mistakes (mutations) in the WFS1 gene, which is located on the short arm of chromosome 4 (4p16.1). This gene is highly expressed in the eye and in the brain, and it encodes for a protein located within a compartment of the cell known as the endoplasmic reticulum. For reasons that still remain unclear, WFS1 mutations preferentially affect RGCs, accounting for the prominent visual loss in this genetic disorder. There is currently no effective treatment to halt or slow disease progression and management remains supportive, including the provision of visual aids and occupational rehabilitation. Research into WS has been limited by its relative rarity and the inability to get access to eye and brain tissues from affected patients. However, major advances in our understanding of this disease have been made recently by making use of more accessible cells from patients, such as skin cells (fibroblasts), or animal models, such as mice and zebrafish. This review summarizes the mechanisms by which WFS1 mutations affect cells, impairing their function and eventually leading to their premature loss. The possible treatment strategies to block these pathways are also discussed, with a particular focus on drug repurposing (i.e., using drugs that are already approved for other diseases) and gene therapy (i.e., replacing or repairing the defective WFS1 gene).

Hyperglycemia-reduced NAD+ biosynthesis impairs corneal epithelial wound healing in diabetic mice

OBJECTIVE

Nicotinamide adenine dinucleotide (NAD) is an essential molecule participating in multiple physiological and pathophysiological processes. In diabetic cornea, the NAD⁺-consuming enzyme SIRT1 was down-regulated and contributed to the delayed wound healing. However, the impact of hyperglycemia on corneal NAD⁺ biosynthesis remained elusive. This study was to investigate the relationship of NAD⁺ biosynthesis and the delayed corneal wound healing in diabetic mice.

METHODS

Type 1 diabetes mellitus (DM) mice were induced by streptozotocin and corneal epithelial wound healing models were constructed by epithelial scraping. The NAD⁺ contents of corneal epithelium were measured using the NAD/NADH quantification kit. Expression of key enzymes involved in the NAD⁺ biosynthesis in type 1 DM mice and type 2 DM patients were analyzed. The nicotinamide phosphoribosyltransferase (NAMPT)-specific siRNA and the selective inhibitor FK866 were used to achieve the blockade of NAMPT, whereas exogenous NAD⁺ and its precursors were replenished to the corneal epithelial cells and DM mice.

RESULTS

Hyperglycemia attenuated NAD⁺ content and NAMPT expression in the corneal epithelium of both type 1 DM mice and type 2 DM patients. Local knockdown of NAMPT by siRNA or FK866 consistently recapitulated the delayed corneal epithelial wound healing in normal mice. Moreover, NAD⁺ replenishment recovered the impaired proliferation and migration capacity by either FK866 or high glucose treatment in cultured corneal epithelial cells. Furthermore, in DM mice, NAD⁺ and its precursors nicotinamide mononucleotide and nicotinamide riboside also facilitated corneal epithelial and nerve regeneration, accompanied with the recovered expression of SIRT1 and phosphorylated EGFR, AKT, and ERK1/2 in epithelium and corneal sensitivity.

CONCLUSION

Hyperglycemia-reduced NAD⁺ biosynthesis and contributed to the impaired epithelial wound healing in DM mice. The replenishment of NAD⁺ and its precursors facilitated diabetic corneal wound healing and nerve regeneration, which may provide a novel therapeutic strategy for the treatment of diabetic corneal complications.

An overview of ongoing clinical trials assessing pharmacological therapeutic strategies to manage chemotherapy-induced peripheral neuropathy, based on preclinical studies in rodent models

Chemotherapy-induced peripheral neuropathy (CIPN) is a major dose-limiting side effect induced by a variety of chemotherapeutic agents. Symptoms are mainly sensory: pain, tingling, numbness, and temperature sensitivity. They may require the tapering of chemotherapy regimens or even their cessation; thus, the prevention/treatment of CIPN is critical to increase effectiveness of cancer treatment. However, CIPN management is mainly based on conventional neuropathic pain treatments, with poor clinical efficacy. Therefore, significant effort is made to identify new pharmacological targets to prevent/treat CIPN. Animal modeling is a key component in predicting human response to drugs and in understanding the pathophysiological mechanisms underlying CIPN. In fact, studies performed in rodents highlighted several pharmacological targets to treat/prevent CIPN. This review provides updated information about ongoing clinical trials testing drugs for the management of CIPN and presents some of their proof-of-concept studies conducted in rodent models. The presented drugs target oxidative stress, renin-angiotensin system, glutamatergic neurotransmission, sphingolipid metabolism, neuronal uptake transporters, nicotinamide adenine dinucleotide metabolism, endocannabinoid system, transient receptor potential channels, and serotoninergic receptors. As some clinical trials focus on the effect of the drugs on pain, others evaluate their efficacy by assessing general neuropathy. Moreover, based on studies conducted in rodent models, it remains unclear if some of the tested drugs act in an antinociceptive fashion or have neuroprotective properties. Thus, further investigations are needed to understand their mechanism of action, as well as a global standardization of the methods used to assess efficacy of new therapeutic strategies in the treatment of CIPN.

Deletion of CD38 and supplementation of NAD+ attenuate axon degeneration in a mouse facial nerve axotomy model

Following facial nerve axotomy, nerve function is not fully restored even after reconstruction. This may be attributed to axon degeneration/neuronal death and sustained neuroinflammation. CD38 is an enzyme that catalyses the hydrolysis of nicotinamide adenine dinucleotide (NAD+) and is a candidate molecule for regulating neurodegeneration and neuroinflammation. In this study, we analyzed the effect of CD38 deletion and NAD+ supplementation on neuronal death and glial activation in the facial nucleus in the brain stem, and on axon degeneration and immune cell infiltration in the distal portion of the facial nerve after axotomy in mice. Compared with wild-type mice, CD38 knockout (KO) mice showed reduced microglial activation in the facial nucleus, whereas the levels of neuronal death were not significantly different. In contrast, the axon degeneration and demyelination were delayed, and macrophage accumulation was reduced in the facial nerve of CD38 KO mice after axotomy. Supplementation of NAD+ with nicotinamide riboside slowed the axon degeneration and demyelination, although it did not alter the level of macrophage infiltration after axotomy. These results suggest that CD38 deletion and supplementation of NAD+ may protect transected axon cell-autonomously after facial nerve axotomy.

Deletion of CD38 and supplementation of NAD+ attenuate axon degeneration in a mouse facial nerve axotomy model

Following facial nerve axotomy, nerve function is not fully restored even after reconstruction. This may be attributed to axon degeneration/neuronal death and sustained neuroinflammation. CD38 is an enzyme that catalyses the hydrolysis of nicotinamide adenine dinucleotide (NAD⁺) and is a candidate molecule for regulating neurodegeneration and neuroinflammation. In this study, we analyzed the effect of CD38 deletion and NAD⁺ supplementation on neuronal death and glial activation in the facial nucleus in the brain stem, and on axon degeneration and immune cell infiltration in the distal portion of the facial nerve after axotomy in mice. Compared with wild-type mice, CD38 knockout (KO) mice showed reduced microglial activation in the facial nucleus, whereas the levels of neuronal death were not significantly different. In contrast, the axon degeneration and demyelination were delayed, and macrophage accumulation was reduced in the facial nerve of CD38 KO mice after axotomy. Supplementation of NAD⁺ with nicotinamide riboside slowed the axon degeneration and demyelination, although it did not alter the level of macrophage infiltration after axotomy. These results suggest that CD38 deletion and supplementation of NAD⁺ may protect transected axon cell-autonomously after facial nerve axotomy.

Nicotinamide riboside alleviates alcohol-induced depression-like behaviours in C57BL/6J mice by altering the intestinal microbiota associated with microglial activation and BDNF expression

The gut microbiota play an important role in many central nervous system diseases through the gut microbiota-brain axis. Recent studies suggest that nicotinamide riboside (NR) has neuroprotective properties. However, it is unknown whether NR can prevent or protect against alcohol-induced depression. Furthermore, it is unclear whether its therapeutic action involves changes in the composition of the gut microbiome. Here, we investigated the effects of NR in the mouse model of alcohol-induced depression. Treatment with NR improved the alcohol-induced depressive behaviour in mice. In addition, NR decreased the number of activated microglia in the hippocampus, and it reduced the levels of pro-inflammatory (IL-1β, IL-6, and TNF-α) and anti-inflammatory (IL-10 and TGF-β) cytokines in the brain of mice with alcohol-induced depression. Furthermore, NR significantly upregulated BDNF and diminished the inhibition of the AKT/GSK3β/β-catenin signalling pathway in the hippocampus of these mice. 16S rRNA sequencing revealed that, compared with control and NR-treated mice, the gut microbiome richness and composition were significantly altered in the depressed mice. Spearman's correlation analysis showed that differential gut bacterial genera correlated with the levels of inflammation-related cytokines and BDNF in the brain. After faecal microbiota transplantation, cognitive behaviours, microglial activity, levels of cytokines and BDNF, and activation state of the AKT/GSK3β/β-catenin signalling pathway (which is downstream of the BDNF receptor, TrkB) in recipient mice were similar to those in donor mice. Collectively, our findings show that NR dietary supplementation protects against alcohol-induced depression-like behaviours, possibly by altering the composition of the gut microbiota.

Emerging pharmacological strategies for the management of chemotherapy-induced peripheral neurotoxicity (CIPN), based on novel CIPN mechanisms

INTRODUCTION

Based on results of available clinical trials, the treatment and prevention of chemotherapy-induced peripheral neurotoxicity (CIPN) largely remains an unmet clinical need. However, new approaches have emerged in the last few years, attempting to modify the natural history of acute and late CIPN effects through a better knowledge of the pathogenic process on the molecular level.

AREAS COVERED

Clinical results of recently published (last 5 years) or ongoing emerging therapeutic/preventive pharmacological approaches based on novel CIPN mechanisms have been identified from Pubmed and ClinicalTrials.gov. Results are reviewed and discussed, in order to assess the trend of new clinical studies but also to infer the role novel approaches may have in the future.

EXPERT OPINION

The large heterogeneity of disease-causing mechanisms prevents researchers from identifying a reliable approach to effectively and safely treat or prevent CIPN. Understanding of novel pathophysiologic processes is leading the way to novel therapies, which, through targeting the sphingosine 1-phosphate receptor or pharmacologically inhibiting axonal degeneration might achieve in the future both treatment and prevention of CIPN. Toward this end, a multi-targeting approach, combining drugs to target different CIPN pathomechanisms seems to be a rational approach that warrants testing.

Systemic Treatment With Nicotinamide Riboside Is Protective in a Mouse Model of Light-Induced Retinal Degeneration

Purpose

Maintaining levels of nicotinamide adenine dinucleotide (NAD+), a coenzyme critical for cellular energetics and biosynthetic pathways, may be therapeutic in retinal disease because retinal NAD+ levels decline during retinal damage and degeneration. The purpose of this study was to investigate whether systemic treatment with nicotinamide riboside (NR), a NAD+ precursor that is orally deliverable and well-tolerated by humans, is protective in a mouse model of light-induced retinal degeneration.

Methods

Mice were injected intraperitoneally with vehicle or NR the day before and the morning of exposure to degeneration-inducing levels of light. Retinal function was assessed by electroretinography and in vivo retinal morphology and inflammation was assessed by optical coherence tomography. Post mortem retina sections were assessed for morphology, TUNEL, and inflammatory markers Iba1 and GFAP. Retinal NAD+ levels were enzymatically assayed.

Results

Exposure to degeneration-inducing levels of light suppressed retinal NAD+ levels. Mice undergoing light-induced retinal degeneration exhibited significantly suppressed retinal function, severely disrupted photoreceptor cell layers, and increased apoptosis and inflammation in the outer retina. Treatment with NR increased levels of NAD+ in retina and prevented these deleterious outcomes.

Conclusions

This study is the first to report the protective effects of NR treatment in a mouse model of retinal degeneration. The positive outcomes, coupled with human tolerance to NR dosing, suggest that maintaining retinal NAD+ via systemic NR treatment should be further explored for clinical relevance.

Nicotinamide riboside supplementation corrects deficits in oxytocin, sociability and anxiety of CD157 mutants in a mouse model of autism spectrum disorder

Oxytocin (OT) is a critical molecule for social recognition and memory that mediates social and emotional behaviours. In addition, OT acts as an anxiolytic factor and is released during stress. Based on the activity of CD38 as an enzyme that produces the calcium-mobilizing second messenger cyclic ADP-ribose (cADPR), CD157, a sister protein of CD38, has been considered a candidate mediator for the production and release of OT and its social engagement and anti-anxiety functions. However, the limited expression of CD157 in the adult mouse brain undermined confidence that CD157 is an authentic and/or actionable molecular participant in OT-dependent social behaviour. Here, we show that CD157 knockout mice have low levels of circulating OT in cerebrospinal fluid, which can be corrected by the oral administration of nicotinamide riboside, a recently discovered vitamin precursor of nicotinamide adenine dinucleotide (NAD). NAD is the substrate for the CD157- and CD38-dependent production of cADPR. Nicotinamide riboside corrects social deficits and fearful and anxiety-like behaviours in CD157 knockout males. These results suggest that elevating NAD levels with nicotinamide riboside may allow animals with cADPR- and OT-forming deficits to overcome these deficits and function more normally.

SIRT2 protects peripheral neurons from cisplatin-induced injury by enhancing nucleotide excision repair

Platinum-based chemotherapy-induced peripheral neuropathy is one of the most common causes of dose reduction and discontinuation of life-saving chemotherapy in cancer treatment; it often causes permanent impairment of quality of life in cancer patients. The mechanisms that underlie this neuropathy are not defined, and effective treatment and prevention measures are not available. Here, we demonstrate that SIRT2 protected mice against cisplatin-induced peripheral neuropathy (CIPN). SIRT2 accumulated in the nuclei of dorsal root ganglion sensory neurons and prevented neuronal cell death following cisplatin treatment. Mechanistically, SIRT2, an NAD+-dependent deacetylase, protected neurons from cisplatin cytotoxicity by promoting transcription-coupled nucleotide excision repair (TC-NER) of cisplatin-induced DNA cross-links. Consistent with this mechanism, pharmacological inhibition of NER using spironolactone abolished SIRT2-mediated TC-NER activity in differentiated neuronal cells and protection of neurons from cisplatin-induced cytotoxicity and CIPN in mice. Importantly, SIRT2's protective effects were not evident in lung cancer cells in vitro or in tumors in vivo. Taken together, our results identified SIRT2's function in the NER pathway as a key underlying mechanism of preventing CIPN, warranting future investigation of SIRT2 activation-mediated neuroprotection during platinum-based cancer treatment.

Nicotinamide Riboside-The Current State of Research and Therapeutic Uses

Nicotinamide riboside (NR) has recently become one of the most studied nicotinamide adenine dinucleotide (NAD+) precursors, due to its numerous potential health benefits mediated via elevated NAD+ content in the body. NAD+ is an essential coenzyme that plays important roles in various metabolic pathways and increasing its overall content has been confirmed as a valuable strategy for treating a wide variety of pathophysiological conditions. Accumulating evidence on NRs' health benefits has validated its efficiency across numerous animal and human studies for the treatment of a number of cardiovascular, neurodegenerative, and metabolic disorders. As the prevalence and morbidity of these conditions increases in modern society, the great necessity has arisen for a rapid translation of NR to therapeutic use and further establishment of its availability as a nutritional supplement. Here, we summarize currently available data on NR effects on metabolism, and several neurodegenerative and cardiovascular disorders, through to its application as a treatment for specific pathophysiological conditions. In addition, we have reviewed newly published research on the application of NR as a potential therapy against infections with several pathogens, including SARS-CoV-2. Additionally, to support rapid NR translation to therapeutics, the challenges related to its bioavailability and safety are addressed, together with the advantages of NR to other NAD+ precursors.

Maternal Nicotinamide Riboside Enhances Postpartum Weight Loss, Juvenile Offspring Development, and Neurogenesis of Adult Offspring

Conditions of metabolic stress dysregulate the NAD metabolome. By restoring NAD, nicotinamide riboside (NR) provides resistance to such conditions. We tested the hypotheses that postpartum might dysregulate maternal NAD and that increasing systemic NAD with NR might benefit mothers and offspring. In postpartum mothers, the liver NAD metabolome is depressed while blood increases circulation of NAD metabolites to enable a >20-fold increase in mammary NAD⁺ and NADP⁺. Lactation and NR synergize in stimulating prolactin synthesis and mammary biosynthetic programs. NR supplementation of new mothers increases lactation and nursing behaviors and stimulates maternal transmission of macronutrients, micronutrients, and BDNF into milk. Pups of NR-supplemented mothers are advantaged in glycemic control, size at weaning, and synaptic pruning. Adult offspring of mothers supplemented during nursing retain advantages in physical performance, anti-anxiety, spatial memory, delayed onset of behavioral immobility, and promotion of adult hippocampal neurogenesis. Thus, postgestational maternal micronutrition confers lasting advantages to offspring.

Acute sources of mitochondrial NAD+ during respiratory chain dysfunction

It is a textbook definition that in the absence of oxygen or inhibition of the mitochondrial respiratory chain by pharmacologic or genetic means, hyper-reduction of the matrix pyridine nucleotide pool ensues due to impairment of complex I oxidizing NADH, leading to reductive stress. However, even under these conditions, the ketoglutarate dehydrogenase complex (KGDHC) is known to provide succinyl-CoA to succinyl-CoA ligase, thus supporting mitochondrial substrate-level phosphorylation (mSLP). Mindful that KGDHC is dependent on provision of NAD⁺, hereby sources of acute NADH oxidation are reviewed, namely i) mitochondrial diaphorases, ii) reversal of mitochondrial malate dehydrogenase, iii) reversal of the mitochondrial isocitrate dehydrogenase as it occurs under acidic conditions, iv) residual complex I activity and v) reverse operation of the malate-aspartate shuttle. The concept of NAD⁺ import through the inner mitochondrial membrane as well as artificial means of manipulating matrix NAD⁺/NADH are also discussed. Understanding the above mechanisms providing NAD⁺ to KGDHC thus supporting mSLP may assist in dampening mitochondrial dysfunction underlying neurological disorders encompassing impairment of the electron transport chain.

NAD+ in sulfur mustard toxicity

Sulfur mustard (SM) is a toxicant and chemical warfare agent with strong vesicant properties. The mechanisms behind SM-induced toxicity are not fully understood and no antidote or effective therapy against SM exists. Both, the risk of SM release in asymmetric conflicts or terrorist attacks and the usage of SM-derived nitrogen mustards as cancer chemotherapeutics, render the mechanisms of mustard-induced toxicity a highly relevant research subject. Herein, we review a central role of the abundant cellular molecule nicotinamide adenine dinucleotide (NAD⁺) in molecular mechanisms underlying SM toxicity. We also discuss the potential beneficial effects of NAD⁺ precursors in counteracting SM-induced damage.

NAD+ therapy in age-related degenerative disorders: A benefit/risk analysis

Nicotinamide adenine dinucleotide (NAD+) is an essential pyridine nucleotide that is present in all living cells. NAD+ acts as an important cofactor and substrate for a multitude of biological processes including energy production, DNA repair, gene expression, calcium-dependent secondary messenger signalling and immunoregulatory roles. The de novo synthesis of NAD+ is primarily dependent on the kynurenine pathway (KP), although NAD+ can also be recycled from nicotinic acid (NA), nicotinamide (NAM) and nicotinamide riboside (NR). NAD+ levels have been reported to decline during ageing and age-related diseases. Recent studies have shown that raising intracellular NAD+ levels represents a promising therapeutic strategy for age-associated degenerative diseases in general and to extend lifespan in small animal models. A systematic review of the literature available on Medline, Embase and Pubmed was undertaken to evaluate the potential health and/or longevity benefits due to increasing NAD+ levels. A total of 1545 articles were identified and 147 articles (113 preclinical and 34 clinical) met criteria for inclusion. Most studies indicated that the NAD+ precursors NAM, NR, nicotinamide mononucleotide (NMN), and to a lesser extent NAD+ and NADH had a favourable outcome on several age-related disorders associated with the accumulation of chronic oxidative stress, inflammation and impaired mitochondrial function. While these compounds presented with a limited acute toxicity profile, evidence is still quite limited and long-term human clinical trials are still nascent in the current literature. Potential risks in raising NAD+ levels in various clinical disorders using NAD+ precursors include the accumulation of putative toxic metabolites, tumorigenesis and promotion of cellular senescence. Therefore, NAD+ metabolism represents a promising target and further studies are needed to recapitulate the preclinical benefits in human clinical trials.

Nicotinamide Riboside Enhances Mitochondrial Proteostasis and Adult Neurogenesis through Activation of Mitochondrial Unfolded Protein Response Signaling in the Brain of ALS SOD1G93A Mice

Amyotrophic lateral sclerosis (ALS) is caused by the progressive degeneration of motor neurons in the spinal cord, the brain stem, and the motor cortex. So far, there is still a lack of effective drugs. Nicotinamide adenine dinucleotide (NAD+) takes part in redox reactions and the NAD-dependent signaling pathway. The NAD+ decline is related with many neurological diseases, leading to the accumulation of neurotoxic protein in the central nervous system. Moreover, the NAD+ supplementation is shown to promote neural stem cells/neuronal precursor cells (NSCs/NPCs) pool maintenance. Regulatory mechanisms and functions of NAD+ metabolism in ALS are still unknown. Thus, we hypothesized the aggregation of human SOD1 toxic protein and the fate of NSCs/NPCs in the ALS disease could be improved by the administration of nicotinamide riboside (NR), an NAD+ precursor. In this study, we treated SOD1G93A transgenic and wild-type mice by the oral administration of 20 mg/ml NR starting at 50 days of age. Effects of NR on the body weight, the motor function, the onset and the survival were assessed during the experiment. The expression of mutant hSOD1 protein, mitochondrial unfolded protein response (UPRmt) related protein, mitophagy markers and NAD+ metabolism related protein were detected by immunoblotting. Effects of NR on the NSCs/NPCs in neurogenic niches of brain were identified by the immunofluorescence staining. Our investigation elucidated that the NR treatment exhibited better hanging wire endurance but did not postpone the onset or extend the life span of SOD1G93A mice. Besides, we observed that the NR repletion promoted the clearance of mitochondrial hSOD1 neurotoxic protein. Meanwhile, the mitochondrial function pathway was disrupted in the brain of SOD1G93A mice. What's more, we demonstrated that the inadequate function of NAD+ salvage synthesis pathway was the primary explanation behind the decline of NAD+, and the NR treatment enhanced the proliferation and migration of NSCs/NPCs in the brain of SOD1G93A mice. At last, we found that levels of UPRmt related protein were significantly increased in the brain of SOD1G93A mice after the NR treatment. In summary, these findings reveal that the administration of NR activates UPRmt signaling, modulates mitochondrial proteostasis and improves the adult neurogenesis in the brain of SOD1G93A mice.

NAD+ homeostasis in health and disease

The conceptual evolution of nicotinamide adenine dinucleotide (NAD⁺) from being seen as a simple metabolic cofactor to a pivotal cosubstrate for proteins regulating metabolism and longevity, including the sirtuin family of protein deacylases, has led to a new wave of scientific interest in NAD⁺. NAD⁺ levels decline during ageing, and alterations in NAD⁺ homeostasis can be found in virtually all age-related diseases, including neurodegeneration, diabetes and cancer. In preclinical settings, various strategies to increase NAD⁺ levels have shown beneficial effects, thus starting a competitive race to discover marketable NAD⁺ boosters to improve healthspan and lifespan. Here, we review the basics of NAD⁺ biochemistry and metabolism, and its roles in health and disease, and we discuss current challenges and the future translational potential of NAD⁺ research.

Targeting the programmed axon degeneration pathway as a potential therapeutic for Charcot-Marie-Tooth disease

The programmed axon degeneration pathway has emerged as an important process contributing to the pathogenesis of several neurological diseases. The most crucial events in this pathway include activation of the central executioner SARM1 and NAD⁺ depletion, which leads to an energetic failure and ultimately axon destruction. Given the prevalence of this pathway, it is not surprising that inhibitory therapies are currently being developed in order to treat multiple neurological diseases with the same therapy. Charcot-Marie-Tooth disease (CMT) is a heterogeneous group of neurological diseases that may also benefit from this therapeutic approach. To evaluate the appropriateness of this strategy, the contribution of the programmed axon degeneration pathway to the pathogenesis of different CMT subtypes is being actively investigated. The subtypes CMT1A, CMT1B and CMT2D are the first to have been examined. Based on the results from these studies and advances in developing therapies to block the programmed axon degeneration pathway, promising therapeutics for CMT are now on the horizon.

Efficient separation of vitamins mixture in aqueous solution using a stable zirconium-based metal-organic framework

High-efficiency separation of niacin (NIA) and nicotinamide (NIC) still faces large challenge up to date. In this work, a stable zirconium-based metal-organic framework (DUT-67) was used to adsorb and separate NIA and NIC in aqueous solutions. The adsorption capacities for NIA and NIC at the concentration ratio of 1:1 were 110.2 mg g^-1 and 11.2 mg g^-1, respectively. Further study indicates that low ratio of NIA/ NIC is in favor of the separation. High temperature can restrain the adsorptions of NIA and NIC but promote the separation. Besides, DUT-67 can be well regenerated via a simple method. Mechanism analysis indicates that electrostatic interaction plays a critical role in the separation of these vitamins.

Vincristine and bortezomib use distinct upstream mechanisms to activate a common SARM1-dependent axon degeneration program

Chemotherapy-induced peripheral neuropathy is one of the most prevalent dose-limiting toxicities of anticancer therapy. Development of effective therapies to prevent chemotherapy-induced neuropathies could be enabled by a mechanistic understanding of axonal breakdown following exposure to neuropathy-causing agents. Here, we reveal the molecular mechanisms underlying axon degeneration induced by 2 widely used chemotherapeutic agents with distinct mechanisms of action: vincristine and bortezomib. We showed previously that genetic deletion of SARM1 blocks vincristine-induced neuropathy and demonstrate here that it also prevents axon destruction following administration of bortezomib in vitro and in vivo. Using cultured neurons, we found that vincristine and bortezomib converge on a core axon degeneration program consisting of nicotinamide mononucleotide NMNAT2, SARM1, and loss of NAD+ but engage different upstream mechanisms that closely resemble Wallerian degeneration after vincristine and apoptosis after bortezomib. We could inhibit the final common axon destruction pathway by preserving axonal NAD+ levels or expressing a candidate gene therapeutic that inhibits SARM1 in vitro. We suggest that these approaches may lead to therapies for vincristine- and bortezomib-induced neuropathies and possibly other forms of peripheral neuropathy.

Why Is Mom Stressed: Homeorhesis as the Potential Problem and Nicotinamide Riboside as the Potential Solution

The remodeling of female mammalian physiology to support the development of a fertilized egg into an externally breathing individual and then to provide all the nutrition to this individual while remodeling back to nearly her pregestational state is without parallel in male mammalian physiological transitions. While it is common parlance to refer to postpartum depression as a not infrequent stress in women, the postpartum physiological changes after every birth constitute profound metabolic stresses that are understudied and have important nutritional, behavioral, and neurodevelopmental implications for the maternal and neonatal health of every mammalian species. We discovered that the postpartum liver of a lactating female mouse has a depressed nicotinamide adenine dinucleotide (NAD) metabolome linked to circulation of higher levels of NAD metabolites in support of a >20-fold increase in NAD coenzymes in the mammary. Furthermore, by supporting a new mother’s apparent higher demand for NAD precursors, we increased circulation of prolactin, superinduced mammary biosynthetic programs, increased her time of arched-back nursing, enhanced mammary production of brain-derived neurotrophic factor, promoted postgestational weight loss, advanced the neurobehavioral development of her offspring, and allowed them to mature as stronger and more resilient adults with advantages in hippocampal neurogenesis and body composition. These results show that a new mother’s capacity for biosynthesis and functionally important nurturing is apparently limited by NAD. Here, we discuss homeorhetic flow of resources from a new mother to her offspring in the context of NAD metabolism and suggest avenues for future investigation.

Bortezomib-induced aerobic glycolysis contributes to chemotherapy-induced painful peripheral neuropathy

Chemotherapy-induced painful peripheral neuropathy (CIPN) is the most common toxicity associated with widely used chemotherapeutics. CIPN is the major cause of dose reduction or discontinuation of otherwise life-saving treatment. Unfortunately, CIPN can persist in cancer survivors, which adversely affects their quality of life. Moreover, available treatments are vastly inadequate, warranting a better understanding of the biochemical and metabolic mechanisms that occur in response to chemotherapeutics which would be critical for the development of novel therapies for CIPN. Using extracellular flux analysis, this study demonstrated that the proteasome inhibitor, bortezomib, enhanced glycolysis while suppressing oxidative phosphorylation in the sensory neurons of mice. This metabolic phenotype is known as aerobic glycolysis. Bortezomib upregulated lactate dehydrogenase A and pyruvate dehydrogenase kinase 1, which consequently enhanced the production of lactate and repressed pyruvate oxidation, respectively. Moreover, lactate dehydrogenase A- and pyruvate dehydrogenase kinase 1-driven aerobic glycolysis was associated with increased extracellular acidification, augmented calcium responses, and pain in bortezomib-induced CIPN. Remarkably, pharmacological blockade and in vivo knockdown of lactate dehydrogenase A or pyruvate dehydrogenase kinase 1 reversed the metabolic phenotype, attenuated calcium responses, and alleviated pain induced by bortezomib. Collectively, these results elucidate the mechanisms by which bortezomib induces aerobic glycolysis. Moreover, these findings establish aerobic glycolysis as a metabolic phenotype that underpins bortezomib-induced CIPN.

Safety and Metabolism of Long-term Administration of NIAGEN (Nicotinamide Riboside Chloride) in a Randomized, Double-Blind, Placebo-controlled Clinical Trial of Healthy Overweight Adults

Nicotinamide riboside (NR) is a newly discovered nicotinamide adenine dinucleotide (NAD+) precursor vitamin. A crystal form of NR chloride termed NIAGEN is generally recognized as safe (GRAS) for use in foods and the subject of two New Dietary Ingredient Notifications for use in dietary supplements. To evaluate the kinetics and dose-dependency of NR oral availability and safety in overweight, but otherwise healthy men and women, an 8-week randomized, double-blind, placebo-controlled clinical trial was conducted. Consumption of 100, 300 and 1000 mg NR dose-dependently and significantly increased whole blood NAD+ (i.e., 22%, 51% and 142%) and other NAD+ metabolites within 2 weeks. The increases were maintained throughout the remainder of the study. There were no reports of flushing and no significant differences in adverse events between the NR and placebo-treated groups or between groups at different NR doses. NR also did not elevate low density lipoprotein cholesterol or dysregulate 1-carbon metabolism. Together these data support the development of a tolerable upper intake limit for NR based on human data.