Effect of cyanide ions (CN-) extracted from cassava (Manihotesculenta Crantz) on Alveolar Epithelial Cells (A549 cells).

Cassava (Manihotesculenta Crantz) is one of the most important root crops in tropical countries. It is a major source of cyanogenic glycosides viz. linamarin and lotaustralin, and these on breakdown liberate HCN and ketone. Cassava cyanide extract (CCE) from cassava leaves and tuber rinds were formulated as a biopesticide against certain borer insect pests of horticultural crops. Adenocarcinomic human alveolar basal epithelial cells (A549) were treated with three different concentrations (100, 200, 400 ppm) of CCE. The MTT and NRU assays showed dose-dependent cytotoxicity. The DCFH-DA assay does not show any free radical scavenging activity, whereas the NRR assay showed a reduction in the nitrile radicals with an increase in the concentration of the bioactive compound. A negative correlation was found between the concentration of the bioactive principles and mitochondrial and lysosomal functions. Various cellular assays demonstrated the cellular response of the CCE, and it was found that at higher concentration (400 ppm), the CCE exert a significant necrotic cell death rather than apoptosis. The results of the study indicated that the CCE have a remarkable tendency of anti-proliferative ability.

Local Targeting of NAD+ Salvage Pathway Alters the Immune Tumor Microenvironment and Enhances Checkpoint Immunotherapy in Glioblastoma.

The aggressive primary brain tumor glioblastoma (GBM) is characterized by aberrant metabolism that fuels its malignant phenotype. Diverse genetic subtypes of malignant glioma are sensitive to selective inhibition of the NAD+ salvage pathway enzyme nicotinamide phosphoribosyltransferase (NAMPT). However, the potential impact of NAD+ depletion on the brain tumor microenvironment has not been elaborated. In addition, systemic toxicity of NAMPT inhibition remains a significant concern. Here we show that microparticle-mediated intratumoral delivery of NAMPT inhibitor GMX1778 induces specific immunologic changes in the tumor microenvironment of murine GBM, characterized by upregulation of immune checkpoint PD-L1, recruitment of CD3+, CD4+, and CD8+ T cells, and reduction of M2-polarized immunosuppressive macrophages. NAD+ depletion and autophagy induced by NAMPT inhibitors mediated the upregulation of PD-L1 transcripts and cell surface protein levels in GBM cells. NAMPT inhibitor modulation of the tumor immune microenvironment was therefore combined with PD-1 checkpoint blockade in vivo, significantly increasing the survival of GBM-bearing animals. Thus, the therapeutic impacts of NAMPT inhibition extended beyond neoplastic cells, shaping surrounding immune effectors. Microparticle delivery and release of NAMPT inhibitor at the tumor site offers a safe and robust means to alter an immune tumor microenvironment that could potentiate checkpoint immunotherapy for glioblastoma. SIGNIFICANCE: Microparticle-mediated local inhibition of NAMPT modulates the tumor immune microenvironment and acts cooperatively with anti-PD-1 checkpoint blockade, offering a combination immunotherapy strategy for the treatment of GBM.

Biomonitoring Equivalents for cyanide.

Exposure to cyanide is widespread in human populations due to a variety of natural and anthropogenic sources. The potential health risks of excess cyanide exposure are dose-dependent and include effects on the thyroid, the male reproductive system, developmental effects, neuropathies and death. Many organizations have derived exposure guideline values for cyanide, which represent maximum recommended exposure levels for inhalation and oral routes of exposure. Biomonitoring Equivalents (BEs) are estimates of the average biomarker concentrations that correspond to these reference doses. Here, we determine BE values for cyanide. The literature on the pharmacokinetics of cyanide was reviewed to identify a biomarker of exposure. Despite issues with biomarker specificity, thiocyanate (SCN-) in the urine or plasma was identified as the most practical biomarker. BE values were produced that correspond to previously published critical effect levels. These BE values range from 0.0008 to 0.8 mg/L and 0.0005-2.5 mg/L for SCN- in urine and plasma, respectively. Confidence in these BE values varies, depending on route of exposure, biomarker, and health endpoint of interest. We anticipate that these BE values will be useful for lower tier (screening level) chemical risk assessment; however due to issues with biomarker specificity and uncertainty in background levels of SCN-, this approach requires refinement to be useful at higher tiers.

DMTS is an effective treatment in both inhalation and injection models for cyanide poisoning using unanesthetized mice.

CONTEXT: Cyanide (CN) is a metabolic poison, halting ATP synthesis by inhibiting complex IV of the electron transport chain. If exposed at high enough concentrations, humans and most animals can die within minutes. Because time is a crucial factor in survival of CN poisoning, a rapidly bioavailable, nontoxic, easy to administer CN medical countermeasure could improve morbidity/mortality in a mass CN exposure scenario. The most likely route of exposure to CN is via inhalation. OBJECTIVE: This study examined the efficacy of a new formulation for dimethyl trisulfide (DMTS), a countermeasure which has shown promise as a treatment for CN poisoning, using both inhalation and injection models of CN exposure. METHODS: We developed a model of acute CN inhalation intoxication, using the highly toxic agent system from CH Technologies for nose-only exposure. Both continuous and discontinuous HCN exposure paradigms were implemented. For comparison, we also utilized a potassium cyanide (KCN) injection model. In all experiments, DMTS was administered as a cyanide countermeasure via intramuscular injection in unanesthetized mice. RESULTS: We found DMTS administration to be highly protective against both subcutaneous KCN and HCN inhalation toxicity. In the KCN injection model, DMTS afforded protection against 3.73 times the LD50 dose of KCN. In our HCN inhalation exposure model, mice challenged with LC50 HCN doses for the duration of either 10- or 40-minute exposure paradigms demonstrated improved survival in the presence of DMTS treatment (87.5% and 90.0% survival, respectively). Animals in the DMTS treatment groups of both lethal exposure models similarly exhibited improvement in observed toxic signs. CONCLUSION: We show that a newly developed formulation of DMTS is efficacious within two lethal CN exposure mouse models (inhalation and injection) and is highly effective by intramuscular injection. Within these HCN studies, we demonstrate efficacy of DMTS in both continuous and discontinuous inhalation exposure models.

Identification of novel resistance mechanisms to NAMPT inhibition via the de novo NAD+ biosynthesis pathway and NAMPT mutation.

Cancer cells have an unusually high requirement for the central and intermediary metabolite nicotinamide adenine dinucleotide (NAD+), and NAD+ depletion ultimately results in cell death. The rate limiting step within the NAD+ salvage pathway required for converting nicotinamide to NAD+ is catalyzed by nicotinamide phosphoribosyltransferase (NAMPT). Targeting NAMPT has been investigated as an anti-cancer strategy, and several highly selective small molecule inhibitors have been found to potently inhibit NAMPT in cancer cells, resulting in NAD+ depletion and cytotoxicity. To identify mechanisms that could cause resistance to NAMPT inhibitor treatment, we generated a human fibrosarcoma cell line refractory to the highly potent and selective NAMPT small molecule inhibitor, GMX1778. We uncovered novel and unexpected mechanisms of resistance including significantly increased expression of quinolinate phosphoribosyl transferase (QPRT), a key enzyme in the de novo NAD+ synthesis pathway. Additionally, exome sequencing of the NAMPT gene in the resistant cells identified a single heterozygous point mutation that was not present in the parental cell line. The combination of upregulation of the NAD+ de novo synthesis pathway through QPRT over-expression and NAMPT mutation confers resistance to GMX1778, but the cells are only partially resistant to next-generation NAMPT inhibitors. The resistance mechanisms uncovered herein provide a potential avenue to continue exploration of next generation NAMPT inhibitors to treat neoplasms in the clinic.

Broad AOX expression in a genetically tractable mouse model does not disturb normal physiology.

Plants and many lower organisms, but not mammals, express alternative oxidases (AOXs) that branch the mitochondrial respiratory chain, transferring electrons directly from ubiquinol to oxygen without proton pumping. Thus, they maintain electron flow under conditions when the classical respiratory chain is impaired, limiting excess production of oxygen radicals and supporting redox and metabolic homeostasis. AOX from Ciona intestinalis has been used to study and mitigate mitochondrial impairments in mammalian cell lines, Drosophila disease models and, most recently, in the mouse, where multiple lentivector-AOX transgenes conferred substantial expression in specific tissues. Here, we describe a genetically tractable mouse model in which Ciona AOX has been targeted to the Rosa26 locus for ubiquitous expression. The AOXRosa26 mouse exhibited only subtle phenotypic effects on respiratory complex formation, oxygen consumption or the global metabolome, and showed an essentially normal physiology. AOX conferred robust resistance to inhibitors of the respiratory chain in organello; moreover, animals exposed to a systemically applied LD50 dose of cyanide did not succumb. The AOXRosa26 mouse is a useful tool to investigate respiratory control mechanisms and to decipher mitochondrial disease aetiology in vivo.

Broadband near-infrared spectroscopy can detect cyanide-induced cytochrome aa3 inhibition in rats: a proof of concept study.

PURPOSE: Clinically available near-infrared spectroscopy (NIRS) devices use two to five wavelengths of light to measure the relative amounts of oxyhemoglobin and deoxyhemoglobin in tissue to determine tissue hemoglobin oxygen saturation (StO2). In addition to StO2, broadband NIRS devices (using hundreds of wavelengths of light) may be able to measure the oxidation state of mitochondrial cytochrome aa3 (Cytox) which reflects the subcellular energetic state. We hypothesize that broadband NIRS devices can measure Cytox independent of changes in hemoglobin saturation. METHODS: In this prospective non-randomized study, 20 male Sprague-Dawley rats (300 g) were anesthetized with isoflurane, tracheally intubated, and ventilated with 100% O2 containing 2% isoflurane. They were subsequently instrumented with a broadband NIRS device that used a halogen light source coupled to an emitting fibreoptic cable. Three receiving fibreoptic cables were utilized; one analyzed the light source and the other two were directed at the base of the skull. Each receiving fibre was connected to a spectrometer to measure light intensity. Sodium cyanide (NaCN) 5 mg·kg-1 iv was injected in order to produce cytochrome aa3 reduction. Two to three minutes after injection, oxygen was eliminated and 100% nitrogen (i.e., anoxia) was used for ventilation in order to induce a reduction in both cytochrome aa3 and hemoglobin desaturation. Changes in the cytochrome oxidation state and hemoglobin oxygenation were calculated using a broadband algorithm and compared before and after both the NaCN and anoxia interventions. RESULTS: The NaCN injection resulted in a decrease in median [interquartile range (IQR)] deoxyhemoglobin (-0.014 [-0.29 to -0.005] arbitrary units [AU]; P < 0.001), an increase in oxyhemoglobin (0.013 [-0.011 to 0.031] AU; P < 0.001), and a reduction in cytochrome aa3 (-0.015 [-0.020 to -0.011] AU; P < 0.001). Anoxia resulted in an increase in median [IQR] deoxyhemoglobin (0.13 [0.11 to 0.18] AU; P < 0.001), a decrease in oxyhemoglobin (-0.17 [-0.22 to -0.15] AU; P < 0.001), and a reduction in cytochrome aa3 (-0.04 [-0.06 to -0.03] AU; P < 0.001). CONCLUSION: Broadband NIRS can effectively measure the directionality of changes in both Cytox and StO2 by uncoupling the cytochrome and hemoglobin signals through inhibition of the electron transport chain and anoxia.

NAMPT Inhibitor GMX1778 Enhances the Efficacy of 177Lu-DOTATATE Treatment of Neuroendocrine Tumors.

Neuroendocrine tumors (NETs) can be treated by peptide receptor radionuclide therapy using radiolabeled somatostatin analogs. However, the efficacy of such treatment is low and needs to be optimized. Our study evaluated the potential radiosensitizing effects of inhibition of nicotineamide phosphoribosyltransferase on 177Lu-DOTATATE treatment in a NET model. METHODS: Nude mice xenografted with the human NET cell line GOT1 were treated with semiefficient doses of 177Lu-DOTATATE (7.5 MBq, intravenously) or the nicotineamide phosphoribosyltransferase inhibitor GMX1778 (100 mg/kg/wk, orally). RESULTS: Median time to tumor progression (tumor volume larger than at day 0) was 3 d for controls, 7 d for single-dose GMX1778, 28 d for single-dose 177Lu-DOTATATE, 35 d for 3 weekly doses of GMX1778, and 98 d for combined treatment with 177Lu-DOTATATE and GMX1778 × 1. After 177Lu-DOTATATE and 3 weekly doses of GMX1778, none of the tumors progressed within 120 d. CONCLUSION: GMX1778 enhances the efficacy of 177Lu-DOTATATE treatment and induces a prolonged antitumor response.

Determinants of cognitive performance in children relying on cyanogenic cassava as staple food.

While risk factors for konzo are known, determinants of cognitive impairment in konzo-affected children remain unknown. We anchored cognitive performance (KABC-II scores) to serum levels of free-thyroxine (free-T4), thyroid-stimulating hormone (TSH), albumin, and motor proficiency (BOT-2 scores) in 40 children including 21 with konzo (median age: 9 years) and 19 without konzo (median age: 8 years). A multiple regression model was used to determine variables associated with changes in KABC-II scores. Age (ß: -0.818, 95% CI: -1.48, -0.152) (p = 0.018), gender (ß: -5.72; 95% CI: -9.87, -1.57 for females) (p = 0.009), BOT-2 score (ß: 0.390; 95% CI: 0.113, 0.667) (p = 0.008), and free-T4 (ß: 1.88; 95% CI: 0.009, 3.74) (p = 0.049) explained 61.1 % of variation in KABC-II scores. Subclinical hypothyroidism was not associated with poor cognition. A crude association was found between serum albumin and KABC-II scores (ß: 1.26; 95 % CI: 0.136, 2.39) (p = 0.029). On spot urinary thiocyanate reached 688 µmol/l in children without konzo and 1,032 µmol/L in those with konzo. Female gender and low serum albumin are risk factors common to cognitive and proportionally associated motor deficits in children exposed to cassava cyanogens. The two types of deficits may share common mechanisms.

Normative concentrations of urine thiocyanate in cassava eating communities in Nigeria.

Exposure to cyanide is a major public health problem where highly cyanogenic cassava foods are consumed. Thiocyanate (SCN), the biomarker of exposure to cyanide is present in several foods, and produced endogenously. Concentrations of urine SCN were measured in endemic and non-endemic areas of ataxic polyneuropathy in Nigeria. Cassava food consumption in the endemic area was twice that of non-endemic areas. Geometrical mean (95% CI) urine SCN was 20 µmol/l (18-24) for no consumption of cassava foods, 56 µmol/l (49-64) for daily consumption, 56 µmol/l (48-65) for twice daily consumption and 85 µmol/l (62-117) for thrice daily consumption. 95th percentile reference limit was 125 µmol/l for no consumption of cassava food, but 360 µmol/l for thrice daily consumption. Urine SCN is a useful biomarker of exposure to cyanide from cassava foods. There is strong ecological association of exposure to cyanide and endemicity of ataxic polyneuropathy.

Hydroxocobalamin in cyanide poisoning.

INTRODUCTION: On theoretical grounds, hydroxocobalamin is an attractive antidote for cyanide poisoning as cobalt compounds have the ability to bind and detoxify cyanide. This paper reviews the pharmacokinetic and pharmacodynamic aspects of hydroxocobalamin, its efficacy in human cyanide poisoning and its adverse effects. METHODS: PubMed was searched for the period 1952 to April 2012. A total of 71 papers were identified in this way; and none was excluded. PHARMACOKINETICS AND PHARMACODYNAMICS: Pharmacokinetic studies in dogs and humans suggest a two-compartment model, with first order elimination kinetics. Pharmacodynamic studies in animals suggest that hydroxocobalamin would be a satisfactory antidote for human cyanide poisoning. EFFICACY IN HUMAN POISONING: There is limited evidence that hydroxocobalamin alone is effective in severe poisoning by cyanide salts. The evidence for the efficacy of hydroxocobalamin in smoke inhalation is complicated by lack of evidence for the importance of cyanide exposure in fires and the effects of other chemicals as well as confounding effects of other therapeutic measures, including hyperbaric oxygen. Evidence that hydroxocobalamin is effective in poisoning due to hydrogen cyanide alone is lacking; extrapolation of efficacy from poisoning by ingested cyanide salts may not be valid. The rate of absorption may be greater with inhaled hydrogen cyanide and the recommended slow intravenous administration of hydroxocobalamin may severely limit its clinical effectiveness in these circumstances. ADVERSE EFFECTS: Both animal and human data suggest that hydroxocobalamin is lacking in clinically significant adverse effects. However, in one human volunteer study, delayed but prolonged rashes were observed in one-sixth of subjects, appearing 7 to 25 days after administration of 5 g or more of hydroxocobalamin. Rare adverse effects have included dyspnoea, facial oedema, and urticaria. CONCLUSIONS: Limited data on human poisonings with cyanide salts suggest that hydroxocobalamin is an effective antidote; data from smoke inhalation are less clear-cut. Although clinically important reactions to hydroxocobalamin have not been seen, some, non-life threatening, adverse reactions can occur.

Amygdalin inhibits angiogenesis in the cultured endothelial cells of diabetic rats.

BACKGROUND: Angiogenesis contributes to different physiological and pathological conditions. The aim of this study was to investigate for the first time the antiangiogenic effects of amygdalin on the cultured endothelial cells of diabetic rats. MATERIALS AND METHODS: A total of 20 streptozotocin-induced diabetic rats were divided into two equal groups of control and amygdalin-treated animals. Eight weeks after the induction of diabetes, amygdalin was injected intraperitoneally (3 mg/kg) to the rats of the treatment group. One day later, rats were sacrificed; the aortic arteries were excised and cut as 2 mm rings. Each aortic ring was incubated in a cell-culture well for 7 days. The process of angiogenesis was monitored by counting the number of microvessels and primary microtubules in each well. RESULTS: Optic microscopy showed proliferation and migration of new endothelial cells to the fibrin gels. The endothelial cells produced primary microtubules which gradually made several branches and finally made a vascular matrix. The number of the primary microtubules and microvessels were significantly lower in the amygdalin-treated vs. control group (P < 0.01). CONCLUSION: Therefore, amygdalin exerts inhibitory effects on angiogenesis in aortic rings of diabetic rats and may pave a new way for treatment of unfavorable angiogenic conditions.

Therapy mediated by mitophagy abrogates tumor progression.

Autophagy is mainly a cellular recycling process that promotes survival, but it can also cause cell death if cell injury persists. The role of mitophagy in tumorigenesis remains uncertain. Other cell death types, such as apoptosis or necrosis, are often altered during tumor development and therefore are not ideal targets to generate efficient antitumor therapies. We have used the system linamarase/linamarin/glucose oxidase (lis/lin/GO) to eliminate tumor cells. This therapeutic strategy is based on the combination of cyanide and oxidative stress to abrogate tumor growth. After severe mitochondrial insult by lis/lin/GO, the electron transport chain is blocked and hydrogen peroxide production increased. This triggers a degradative phase of these damaged organelles inducing mitophagy that finally leads to cell death. This death process depends on the vacuole generation, BNIp3 and the formation of autolysosomes. Importantly, evasion of apoptosis is known to result in resistance to anti-cancer therapies but this inhibition also augments sensitivity to autophagy, which could be used to promote tumor regression. We explored the potential of this powerful mitophagy-inducing system in vitro and in vivo to eradicate human malignant tumors.

Succinate is the controller of O2-/H2O2 release at mitochondrial complex I : negative modulation by malate, positive by cyanide.

Mitochondrial production of H(2)O(2) is low with NAD substrates (glutamate/pyruvate, 3 and 2 mM) (G/P) and increases over ten times upon further addition of succinate, with the formation of a sigmoidal curve (semimaximal value at 290 microM, maximal H(2)O(2) production at 600 microM succinate). Malate counteracts rapidly the succinate induced increased H(2)O(2) release and moves the succinate dependent H(2)O(2) production curve to the right. Nitric oxide (NO) and carbon monoxide (CO) are cytochrome c oxidase inhibitors which increase mitochondrial ROS production. Cyanide (CN(-)) was used to mimic NO and CO. In the presence of G/P and succinate (300 microM), CN(-) progressively increased the H(2)O(2) release rate, starting at 1.5 microM. The succinate dependent H(2)O(2) production curve was moved to the left by 30 microM CN(-). The V(max) was little modified. We conclude that succinate is the controller of mitochondrial H(2)O(2) production, modulated by malate and CN(-). We propose that succinate promotes an interaction between Complex II and Complex I, which activates O(2)(-) production.

Which cyanide antidote?

Cyanide has several antidotes, with differing mechanisms of action and diverse toxicological, clinical, and risk-benefit profiles. The international medical community lacks consensus about the antidote or antidotes with the best risk-benefit ratio. Critical assessment of cyanide antidotes is needed to aid in therapeutic and administrative decisions that will improve care for victims of cyanide poisoning (particularly poisoning from enclosed-space fire-smoke inhalation), and enhance readiness for cyanide toxic terrorism and other mass-casualty incidents. This paper reviews preclinical and clinical data on available cyanide antidotes and considers the profiles of these antidotes relative to properties of a hypothetical ideal cyanide antidote. Each of the antidotes shows evidence of efficacy in animal studies and clinical experience. The data available to date do not suggest obvious differences in efficacy among antidotes, with the exception of a slower onset of action of sodium thiosulfate (administered alone) than of the other antidotes. The potential for serious toxicity limits or prevents the use of the Cyanide Antidote Kit, dicobalt edetate, and 4-dimethylaminophenol in prehospital empiric treatment of suspected cyanide poisoning. Hydroxocobalamin differs from these antidotes in that it has not been associated with clinically significant toxicity in antidotal doses. Hydroxocobalamin is an antidote that seems to have many of the characteristics of the ideal cyanide antidote: rapid onset of action, neutralizes cyanide without interfering with cellular oxygen use, tolerability and safety profiles conducive to prehospital use, safe for use with smoke-inhalation victims, not harmful when administered to non-poisoned patients, easy to administer.

Preclinical development of the nicotinamide phosphoribosyl transferase inhibitor prodrug GMX1777.

GMX1778 was recently shown to function as a potent inhibitor of nicotinamide phosphoribosyl transferase. To translate the discovery of GMX1778 mechanism of action into optimal clinical use of its intravenously administered prodrug, GMX1777, the efficacy of GMX1777 was evaluated in xenograft models and the pharmacokinetic profile of GMX1778 and its effect on nicotinamide adenine dinucleotide cellular levels was measured by liquid chromatography/mass spectrometry. Consistent with the requirement for a prolonged exposure for cytotoxicity in vitro, a dose of 75 mg/kg of GMX1777 administered as two bolus intravenous injections in 1 day were not effective at reducing the growth of multiple myeloma (IM-9) tumors, whereas the same dose of GMX1777 administered over a 24 h intravenous infusion caused tumor regression in the IM-9 model, a small-cell lung cancer (SHP-77) model, and a colon carcinoma (HCT-116) model. A 72 h continuous intravenous infusion of GMX1777 was also effective in the IM-9 model, but was associated with a smaller therapeutic index. GMX1777 at a dose of 75 mg/kg administered over a 24 h intravenous infusion produced GMX1778 steady-state plasma levels of approximately 1 microg/ml and caused nicotinamide adenine dinucleotide levels to decrease significantly in tumors. Consistent with the GMX1778 mechanism of action, nicotinic acid protected mice treated with a lethal dose of GMX1777. These data support the design of an open-label, dose-escalation trial, in which patients with refractory solid tumors and lymphomas receive 24 h infusions of GMX1777 as a single agent in 3-week cycles. Furthermore, these results indicate that nicotinic acid is a potent antidote to treat GMX1777 overdose.

Role of hydroxocobalamin in acute cyanide poisoning.

OBJECTIVE: To review the recently approved cyanide antidote, hydroxocobalamin, and describe its role in therapy. DATA SOURCES: Relevant publications were identified through a systematic search of PubMed using the MeSH terms and key words hydroxocobalamin and cyanide. This search was then limited to human studies published since 2000. Systematic searches were conducted through January 2008. References from identified articles were reviewed for additional pertinent human studies. STUDY SELECTION AND DATA EXTRACTION: The literature search retrieved 7 studies on the safety and/or efficacy of hydroxocobalamin in humans. Four new studies were identified by the search and 3 studies were identified from the references. DATA SYNTHESIS: Studies of antidote efficacy in humans are ethically and logistically difficult. A preclinical study demonstrated that intravenous doses of hydroxocobalamin 5 g are well tolerated by volunteer subjects. Hydroxocobalamin has been shown to reduce cyanide concentrations in controlled studies of nitroprusside therapy and in heavy smokers. A retrospective study of 14 acute cyanide poisonings also demonstrated hydroxocobalamin's safety and efficacy. Two studies examining hydroxocobalamin for smoke inhalation-associated cyanide poisoning indicated a possible benefit, but they are insufficient to establish definitive criteria for use in this setting. Randomized controlled trials of hydroxocobalamin and traditional cyanide antidotes (nitrites/thiosulfate) are lacking. CONCLUSIONS: Cyanide poisoning can rapidly cause death. Having an effective antidote readily available is essential for facilities that provide emergency care. In cases of cyanide ingestion, both the nitrite/thiosulfate combination and hydroxocobalamin are effective antidotes. Hydroxocobalamin offers an improved safety profile for children and pregnant women. Hydroxocobalamin also appears to have a better safety profile in the setting of cyanide poisoning in conjunction with smoke inhalation. However, current data are insufficient to recommend the empiric administration of hydroxocobalamin to all victims of smoke inhalation.

D-Erythroascorbic acid activates cyanide-resistant respiration in Candida albicans.

Higher plants, protists and fungi possess cyanide-resistant respiratory pathway, which is mediated by alternative oxidase (AOX). The activity of AOX has been found to be dependent on several regulatory mechanisms including gene expression and posttranslational regulation. In the present study, we report that the presence of cyanide in culture medium remarkably retarded the growth of alo1/alo1 mutant of Candida albicans, which lacks d-arabinono-1,4-lactone oxidase (ALO) that catalyzes the final step of d-erythroascorbic acid (EASC) biosynthesis. Measurement of respiratory activity and Western blot analysis revealed that increase in the intracellular EASC level induces the expression of AOX in C. albicans. AOX could still be induced by antimycin A, a respiratory inhibitor, in the absence of EASC, suggesting that several factors may act in parallel pathways to induce the expression of AOX. Taken together, our results suggest that EASC plays important roles in activation of cyanide-resistant respiration in C. albicans.

Anticancer agent CHS-828 inhibits cellular synthesis of NAD.

Malignant cells display increased demands for energy production and DNA repair. Nicotinamide adenine dinucleotide (NAD) is required for both processes and is also continuously degraded by cellular enzymes. Nicotinamide phosphoribosyltransferase (Nampt) is a crucial factor in the resynthesis of NAD, and thus in cancer cell survival. Here, we establish the cytotoxic mechanism of action of the small molecule inhibitor CHS-828 to result from impaired synthesis of NAD. Initially, we detected cross-resistance in cells between CHS-828 and a known inhibitor of Nampt, FK866, a compound of a structurally different class. We then showed that nicotinamide protects against CHS-828-mediated cytotoxicity. Finally, we observed that treatment with CHS-828 depletes cellular NAD levels in sensitive cancer cells. In conclusion, these results strongly suggest that, like FK866, CHS-828 kills cancer cells by depleting NAD.