Anaerobic cyanides oxidation with bimetallic modulation of biological toxicity and activity for nitrite reduction.

Cyanide is a typical toxic reducing agent prevailing in wastewater with a well-defined chemical mechanism, whereas its exploitation as an electron donor by microorganisms is currently understudied. Given that conventional denitrification requires additional electron donors, the cyanide and nitrogen can be eliminated simultaneously if the reducing HCN/CN- and its complexes are used as inorganic electron donors. Hence, this paper proposes anaerobic cyanides oxidation for nitrite reduction, whereby the biological toxicity and activity of cyanides are modulated by bimetallics. Performance tests illustrated that low toxicity equivalents of iron-copper composite cyanides provided higher denitrification loads with the release of cyanide ions and electrons from the complex structure by the bimetal. Both isotopic labeling and Density Functional Theory (DFT) demonstrated that CN--N supplied electrons for nitrite reduction. The superposition of chemical processes reduces the biotoxicity and enhances the biological activity of cyanides in the CN-/Fe3+/Cu2+/NO2- coexistence system, including complex detoxification of CN- by Fe3+, CN- release by Cu2+ from [Fe(CN)6]3-, and NO release by nitrite substitution of -CN groups. Cyanide is the smallest structural unit of C/N-containing compounds and serves as a probe to extend the electron-donating principle of anaerobic cyanides oxidation to more electron-donor microbial utilization.

A benzothiophene-based fluorescent probe with dual-functional to polarity and cyanide for practical applications in living cells and real water samples.

Polarity is a significant intracellular environmental parameter associated with cancer, while cyanide (CN-) is known to be highly toxic to humans. In this work, we designed a dual-functional fluorescent probe (TPABT) for simultaneous detection of polarity and CN-. As a polarity sensor, the probe exhibits NIR emission at 766 nm in 1,4-dioxane (non-polar solvent), whose emission intensity is 71-fold stronger than that in water (polar solvent). Meanwhile, the fluorescence intensity and quantum yield are linearly related to solvent polarity, confirming the polarity response ability of TPABT. For cell polarity detection, low cytotoxicity and polarity sensitivity of probe enable the applications for differentiating cancer cells (HeLa, 4TI) from normal cells (HUV, 3 T3) and monitoring the polarity changes of 4TI cells. As a CN- sensor, TPABT displays a turn-on fluorescence at 640 nm upon the addition of CN-, with advantages of anti-interference, response in aqueous media and low detection limit (22 nM). Additionally, we further explored the practical applications of TPABT for CN- determination in three types of real water samples (drinking water, tap water and lake water) and living cells. Notably, TPABT responses to polarity and CN- in two independent fluorescence channels of 766 and 640 nm, respectively, ensuring the dual functions for polarity and CN- sensing. Consequently, this multi-responsive fluorescent probe TPABT is promising to diagnose polarity-related diseases and detect CN- in real environments.

Bacterial tolerance and detoxification of cyanide, arsenic and heavy metals: Holistic approaches applied to bioremediation of industrial complex wastes.

Cyanide is a highly toxic compound that is found in wastewaters generated from different industrial activities, such as mining or jewellery. These residues usually contain high concentrations of other toxic pollutants like arsenic and heavy metals that may form different complexes with cyanide. To develop bioremediation strategies, it is necessary to know the metabolic processes involved in the tolerance and detoxification of these pollutants, but most of the current studies are focused on the characterization of the microbial responses to each one of these environmental hazards individually, and the effect of co-contaminated wastes on microbial metabolism has been hardly addressed. This work summarizes the main strategies developed by bacteria to alleviate the effects of cyanide, arsenic and heavy metals, analysing interactions among these toxic chemicals. Additionally, it is discussed the role of systems biology and synthetic biology as tools for the development of bioremediation strategies of complex industrial wastes and co-contaminated sites, emphasizing the importance and progress derived from meta-omic studies.

The stability of cyanide in human biological samples. A systematic review, meta-analysis and determination of cyanide (GC-QqQ-MS/MS) in an authentic casework 7 years after fatal intoxication.

A 30 year old man was found with no signs of life in front of the house. The cyanide concentration in blood and urine was determined five years after the man's death. What is more, a stability study was conducted for 730 days in an authentic casework blood sample. Sample preparation procedure included precipitation with methanol:water mixture, solid phase extraction (SPE) and derivatization with the use of PFB-Br (pentafluorobenzyl bromide). The sample was analyzed using GC-QqQ-MS/MS (gas chromatopraphy coupled with tandem mass spectrometry) isotope dilution method. Separation was done using a SH-RXI-5MS column (30 m x 0.25 mm, 0.25 µm). Detection of PFB-CN and PFB-13CN was achieved using a triple-quadrupole mass spectrometer with an electron ionization (EI) ion source in multiple reaction monitoring (MRM) mode. After 5 years from the man's death, cyanide concentration was: 1900 ng/mL in blood and 500 ng/mL in urine. Stability study performed in an authentic blood sample 6 and 7 years after the man's death revealed cyanide concentrations of 1898.2 ng/mL and 1618.7 ng/mL, respectively. While spectrophotometric and colorimetric methods recorded both decrease and increase in cyanide concentration over time, newer chromatographic methods mainly indicate a decrease. The studies presented in this paper seem to confirm this trend. However, in order to interpretate the results of cyanide concentration in biological material reliably, more research is still necessary.

Mercury cyanide complexes and their relevance as environmental contaminants.

This review addresses the formation and relevance of mercury cyanide complexes as environmental contaminants. Gold extraction is traditionally carried out through the process of mercury amalgamation (Hg) due to its simplicity and low cost. However, this process is inefficient, capturing only about 30% of the gold present in the processed material. Additionally, mercury is toxic, mobile, and capable of accumulating in aquatic ecosystems, leading to its prohibition in several countries. As an alternative, cyanidation has been widely used in gold extraction. However, the frequent combination of Hg amalgamation with cyanidation can result in the formation of mercury cyanide complexes, which can be released into local water bodies, potentially impacting human health and the environment. This article reviews the existing knowledge of these complexes and highlights the remaining gaps in understanding their environmental behavior. It also emphasizes the need to address concerns related to the formation of these complexes and seek solutions to minimize their negative impacts. Furthermore, the article highlights the lack of updates in the literature regarding the impacts of cyanidation and the limited availability of comprehensive information on the topic. It is essential to conduct updated research in this area to advance knowledge and promote safer and more responsible practices in the mining industry.

Elucidating the binding properties of methemoglobin in red blood cell to cyanide, hydrosulfide, and azide ions using artificial red blood cell.

Methemoglobin (metHb), the oxidized form of hemoglobin, lacks the ability of reversible oxygen binding; however, it has a high binding affinity to toxic substances such as cyanide, hydrosulfide, and azide. This innate property of metHb offers the clinical option to treat patients poisoned with these toxins, by oxidizing the endogenous hemoglobin in the red blood cells (RBCs). The binding properties of naked metHb (isolated from RBC) with these toxins has been studied; however, the binding behaviors of metHb under the intracellular conditions of RBC are unclear because of the difficulty in detecting metHb status changes in RBC. This study aimed to elucidate the binding properties of metHb in RBC under physiological and poisoned conditions using artificial RBC, which was hemoglobin encapsulated in a liposome. The mimic-circumstances of metHb in RBC (metHb-V) was prepared by oxidizing the hemoglobin in artificial RBC. Spectroscopic analysis indicated that the metHb in metHb-V exhibited a binding behavior different from that of naked metHb, depending on the toxic substance: When the pH decreased, (i) the cyanide binding affinity of metHb-V remained unchanged, but that of naked metHb decreased (ii) the hydrosulfide binding affinity was increased in metHb-V but was decreased in naked metHb. (iii) Azide binding was increased in metHb-V, which was similar to that in naked metHb, irrespective of the pH change. Thus, the binding behavior of intracellular metHb in the RBC with cyanide, hydrosulfide, and azide under physiological and pathological conditions were partly elucidated using the oxidized artificial RBC.

Exogenous thiocyanate inhibits sulfurtransferase pathway and induces ß-cyanoalanine synthase pathway to enhance exogenous cyanide assimilation in rice plants.

Cyanide (CN-) assimilation in plants takes place by ß-cyanoalanine synthase (ß-CAS) and sulfurtransferase (ST), in which the ST pathway converts CN- into thiocyanate (SCN-). Both chemicals (CN- and SCN-) are frequently detected in the effluent of gold mining operations. In this connection, exogenous SCN- was applied to rice plants with CN- and compared with CN- alone to investigate its effects on CN- assimilation and degradation pathways. Interestingly, the CN- and SCN- content in both roots and shoots were increased with the increase in "CN-" treatments, but surprisingly their content under "SCN-+CN-" treatments did not show the similar trend. The increasing trend remained the same for CN- but the SCN- content was constant with increasing CN- concentrations in comparison with the control (SCN- alone). Additionally, the assimilation rates of CN- in rice plants under "SCN-+CN-" treatments were significantly higher than "CN-" treatments. The application of SCN- with CN- mostly alters the expression of both ß-CAS and ST-associated genes. On one side, the application of SCN- significantly repressed the expression of genes encoded with ST in rice plants, but on the other side, it significantly up-regulated the expression of the ß-CAS gene located in mitochondria. These results reveal that the application of exogenous SCN- increases CN- assimilation rates by inhibiting the ST pathway and stimulating the ß-CAS pathway. This study would provide new insight into the positive effects of exogenous SCN- in increasing CN- assimilation by altering the degradation pathways in rice plants.

Acute ecotoxicological effects of Hg(CN)2 in Danio rerio (zebrafish).

Artisanal and small-scale gold mining (ASGM) is the largest source of anthropogenic Hg emissions on the planet. In addition, Hg-contaminated tailings are often reprocessed with sodium cyanide (NaCN) to extract the residual gold remaining in the material. This leads to the formation of mercury cyanide (Hg(CN)2) complexes, which are often discharged in untreated form into local drainages, leading to large amounts of free cyanide being released. However, data on mercury-cyanide interactions are scarce. In this study, we investigated the impact of cyanide and Hg bioavailability in zebrafish when added as Hg(CN)2. Different concentrations of Hg(CN)2 and NaCN were used, leading to an LC50 of 0.53 mg.L-1 for NaCN and 0.16 mg.L-1 for Hg(CN)2. Analyzing free cyanide concentrations in aquarium water, >40% dissociation was observed for NaCN and about 5% for Hg(CN)2. The accumulation of total Hg (THg) in the brain, gills, muscle and kidney was quantified. All fish exposed to Hg(CN)2 had higher THg levels than their controls and kidney was the tissue with higher Hg(CN)2 accumulation. Histological effects on the kidney and gills of both cyanides in D. rerio tissues were investigated, suggesting renal alterations in fish exposed to Hg(CN)2 and showing hyperplasia in the gills of animals exposed to NaCN and Hg(CN)2. The results alert to the risks of the presence of these complexes in aquatic environments.

A synthetic porphyrin as an effective dual antidote against carbon monoxide and cyanide poisoning.

Simultaneous poisoning by carbon monoxide (CO) and hydrogen cyanide is the major cause of mortality in fire gas accidents. Here, we report on the invention of an injectable antidote against CO and cyanide (CN-) mixed poisoning. The solution contains four compounds: iron(III)porphyrin (FeIIITPPS, F), two methyl-ß-cyclodextrin (CD) dimers linked by pyridine (Py3CD, P) and imidazole (Im3CD, I), and a reducing agent (Na2S2O4, S). When these compounds are dissolved in saline, the solution contains two synthetic heme models including a complex of F with P (hemoCD-P) and another one of F with I (hemoCD-I), both in their iron(II) state. hemoCD-P is stable in its iron(II) state and captures CO more strongly than native hemoproteins, while hemoCD-I is readily autoxidized to its iron(III) state to scavenge CN- once injected into blood circulation. The mixed solution (hemoCD-Twins) exhibited remarkable protective effects against acute CO and CN- mixed poisoning in mice (~85% survival vs. 0% controls). In a model using rats, exposure to CO and CN- resulted in a significant decrease in heart rate and blood pressure, which were restored by hemoCD-Twins in association with decreased CO and CN- levels in blood. Pharmacokinetic data revealed a fast urinary excretion of hemoCD-Twins with an elimination half-life of 47 min. Finally, to simulate a fire accident and translate our findings to a real-life scenario, we confirmed that combustion gas from acrylic cloth caused severe toxicity to mice and that injection of hemoCD-Twins significantly improved the survival rate, leading to a rapid recovery from the physical incapacitation.

Revisiting the testicular toxicity of cyanide: Assessment of the new and existing literature.

BACKGROUND: Based on new testing, we re-assess U.S. EPA and California OEHHA conclusions regarding male reproductive toxicity associated with cyanide exposure. METHODS: Literature identified by ATSDR, ECETOC and EPA was complemented by studies conducted after 2006. Relevant studies were scored for quality using ToxRTool. RESULTS: Eleven pertinent animal investigations were identified; five with quality scores of 1 were evaluated in-depth. The NTP 13-week drinking water study of NaCN in rats reported significantly decreased water intakes and reduced cauda epididymal weights; altered sperm parameters occurred in high-dose rats. When compared to contemporaneous historical control data (HCD), the mean cauda epididymal weights of cyanide-treated rats in the NTP study were within HCD, whereas control weights exceeded HCD. A new 13-week drinking water study used the same design with additional features (individually caged rats, "paired water" controls, thyroid hormone determinations, post-treatment recovery) and found a smaller decrease in water consumption (11% versus 18% at 300 ppm) and no treatment-related changes in male reproductive measures. Although thyroid/parathyroid weights were increased at 300 ppm, histopathology and thyroid hormone levels were unaffected. The remaining high-quality cyanide studies reported no adverse findings in male reproductive organs. Unconfounded sperm measures were not adversely affected in any quality 1 studies. CONCLUSIONS: Changes in the male reproductive system reported after cyanide exposure in the NTP study were not reproducible, unlikely to be treatment-related, and should not be used as the sole basis for human health assessments.

New gold (III) cyanide complex TGS 121 induces ER stress, proteasome inhibition and death of Ras-hyperactivated cells.

Metal-based agents in cancer therapy, like cisplatin and its derivates, have established clinical applications but also can induce serious side effects. Thus, metallotherapeutic alternatives for platinum derivatives are developed and intensively studied. Platinum is replaced by several transition metals including gold. Especially gold (III) complexes can have the same square-planar structure and are isoelectric with platinum (II). Hence, they are developed as potential anti-cancer drugs. Thus, our group projected and developed a group of novel cyanide-based gold (III) complexes. Within this work, we aimed to characterize the safety and effectivity of one of them, TGS 121. TGS 121 in our preliminary work was selective for Ras-hyperactivated cells. Here we studied the effects of the novel complex in cancerous Ras-3 T3 and non-cancerous NIH-3 T3 cells. The complex TGS 121 turned out to be non-toxic for NIH-3 T3 cells and to induce death and alternations in Ras-hyperactivated cells. We found induction of ER stress, mitochondria swelling, proteasome inhibition, and cell cycle block. Moreover, TGS 121 inhibited cell migration and induced the accumulation of perinuclear organelles that was secondary to proteasome inhibition. Results presented in this report suggest that stable gold-cyanide TGS 121 complex is non-toxic, with a targeted mechanism of action and it is promising in anticancer drug discovery.

Spatial-temporal variations of proline and related amino acids reveal distinct nitrogenous utilization strategies in rice during detoxification of exogenous cyanide.

Cyanide (CN-) pollution in agricultural systems impairs amino acid metabolism in rice plants, hence decreasing their quality and yield. Meanwhile, little is known about the effects of CN- assimilation on the innate pool of proline (Pro) and its synthesis-related amino acids (Pro-AAs) in rice plants. In this study, a hydroponic experiment was carried out to investigate the effect of exogenous KCN on indigenous levels of Pro-AAs, i.e., Pro, glutamate (Glu), arginine (Arg), and ornithine (Orn) in rice seedlings fertilized with either nitrate (NO3-) or ammonium (NH4+) through the biochemical and RT-qPCR analysis. At the same KCN treatment concentration, the relative growth rate of NH4+-fed rice seedlings was considerably higher than that of NO3--fed rice seedlings, but the residual concentration of CN- in NH4+-fed rice tissues was lower than that of NO3--fed rice tissues. Based on the UPLC and stoichiometry molar ratio calculations, it is evident that the Glu pathway contributed significantly to Pro synthesis in rice under KCN + NO3- treatments; whereas the Orn pathway governed the synthesis of Pro in rice under KCN + NH4+ treatments. Moreover, transcriptional and bioinformatics analysis revealed that NH4+ fertilization resulted in spatial-temporal differences in the genetic response in rice tissue during detoxification of CN- compared with KCN + NO3- treatments. These findings suggested that the innate level of Pro serves as "a fishing float" to balance the flux between Pro and Pro-AAs in exogenous KCN-treated rice plants under different nitrogenous nutritional conditions.

A fully water-soluble Calix[4]arene probe for fluorometric and colorimetric detection of toxic hydrosulfide and cyanide ions: Practicability in living cells and food samples.

Although hydrosulfide and cyanide anions play important roles in daily life that they are available in a lot of foods. However, their excess amounts contaminate water, land, and food and cause serious problems to human health. Herein, we introduce a water-soluble macrocyclic sensor based-on Calix[4]arene (MPI-Calix[4]) with dual response sites for fluorescence recognizing cyanide (CN-) and hydrogen sulfide (HS-) under longwave light. MPI-Calix[4] exhibits a high selectivity and sensitivity in the detection of CN- and HS-, where the limits of detection were as low as 0.115 and 8.12 µmol/L, respectively. The cell imaging studies shows that this probe can be easily used in the detection of CN- and HS- on living cells. Full understanding of these results paved a fruitful system to improve an applicable analytical process for food safety and quality.

Intramuscular administration of glyoxylate rescues swine from lethal cyanide poisoning and ameliorates the biochemical sequalae of cyanide intoxication.

Cyanide-a fast-acting poison-is easy to obtain given its widespread use in manufacturing industries. It is a high-threat chemical agent that poses a risk of occupational exposure in addition to being a terrorist agent. FDA-approved cyanide antidotes must be given intravenously, which is not practical in a mass casualty setting due to the time and skill required to obtain intravenous access. Glyoxylate is an endogenous metabolite that binds cyanide and reverses cyanide-induced redox imbalances independent of chelation. Efficacy and biochemical mechanistic studies in an FDA-approved preclinical animal model have not been reported. Therefore, in a swine model of cyanide poisoning, we evaluated the efficacy of intramuscular glyoxylate on clinical, metabolic, and biochemical endpoints. Animals were instrumented for continuous hemodynamic monitoring and infused with potassium cyanide. Following cyanide-induced apnea, saline control or glyoxylate was administered intramuscularly. Throughout the study, serial blood samples were collected for pharmacokinetic, metabolite, and biochemical studies, in addition, vital signs, hemodynamic parameters, and laboratory values were measured. Survival in glyoxylate-treated animals was 83% compared with 12% in saline-treated control animals (p < .01). Glyoxylate treatment improved physiological parameters including pulse oximetry, arterial oxygenation, respiration, and pH. In addition, levels of citric acid cycle metabolites returned to baseline levels by the end of the study. Moreover, glyoxylate exerted distinct effects on redox balance as compared with a cyanide-chelating countermeasure. In our preclinical swine model of lethal cyanide poisoning, intramuscular administration of the endogenous metabolite glyoxylate improved survival and clinical outcomes, and ameliorated the biochemical effects of cyanide.

Evaluating the significance of amino acids (AAs) in cyanide-treated rice plants under different nitrogen fertilization using the relative importance index of AA.

The biosynthesis of amino acids (AAs) in plants is affected by different nitrogen (N) sources. The effects of exogenous cyanide (KCN) on the concentrations and profiles of AAs in rice seedlings were carried out in the presence of nitrate (+NO3-)/ammonium (+NH4+) or N deficiency (-N). Targeted metabolomics analysis indicated that the highest accumulation of AAs in CN--treated rice seedlings was detected in the "CN-+NH4+" treatments than in other treatments, wherein the doses of exogenous KCN did not significantly affect the total amount of AAs in rice seedlings at the same N fertilized condition. The total content of AAs in rice shoots under "CN-+NH4+" treatments was higher than other treatments, while the total content of AAs in rice roots under "CN-+NO3-" treatments was higher than other treatments. Also, the profiles of 21 AAs in CN--treated rice seedlings showed tissue-specific under different N fertilization. The relative importance index (RII) of AA was used to evaluate the importance of AAs in CN--treated rice seedlings under different N fertilization. The common AAs with higher RII values were compared between three different treatments of KCN (e.g., 0, 1, and 2 mg CN/L). Under "CN-+(-N)" treatments, Ala, Asp, Glu, Val, and Gly (Ala, Gly, Val, and Lys) were the common AAs in rice roots (shoots). Under "CN-+NO3-" treatments, Ala, Glu, Asp, Ser, and Thr (Asp, Ala, Thr, Ser, and Asn) were the common AAs with higher RII values in rice roots (shoots) between all CN- treatments. Under "CN-+NH4+" treatments, Asp, Gln, Asn, and Ala (Asp, Glu, and Thr) were the common AAs with higher RII values in rice roots (shoots) between all CN- treatments. These results suggested that using the RII to describe the change and fluctuation of AAs in rice plants may reflect the different N utilization strategies in response to exogenous CN- exposure.

Development of AIEE active fluorescent and colorimetric probe for the solid, solution, and vapor phase detection of cyanide: smartphone and food applications.

Apart from environmental implications, the extreme toxicity of cyanide can lead to sudden human death upon prolonged exposure to it. Hence, rapid and low-level on-site detection of cyanide has earned paramount significance in the present era. Therefore, an AIEE active and piezofluorochromic Schiff base (probe 2) was synthesized which exhibited highly selective fluorescence enhancement based nanoscale (LOD; 6.17 nM) detection of CN-. The interaction mode was attributed to the deprotonation of the probe by the cyanide that was confirmed through 1H NMR titration, pH, theoretical studies, and switchable fluorescence response upon the addition of HCl. Advantageously, probe 2 displayed solid and vapor phase recognition of cyanide which is the first of its kind as far as we know. The excellent sensing potential of the probe was satisfactorily applied for the detection of cyanide in food, natural soil, and industrial wastewater. Additionally, probe 2 showed an immediate colorimetric response towards cyanide which was favorably integrated through a smartphone. Finally, the switchable fluorescence response of the probe was used to design an INHIBIT logic gate. Therefore, the multifunctional probe 2 displayed excellent practical potential for cyanide detection which was the ultimate goal of our work.

Evaluation of interactions in chemical mixtures containing cyanides.

Cyanides are highly toxic chemicals found indoors and outdoors, in air, water, and soil. Environmental exposures often are to mixtures of cyanides with other environmental pollutants. Interactive toxicology is the study of the toxicity of a chemical when it occurs with other chemicals or stressors. Such interactions can modify the joint toxicity of a given mixture. Several binary mixtures of cyanides have been studied in humans and animals to develop antidotes, and their mechanism of action is well understood. We used this limited binary weight of evidence to evaluate the toxicity of untested mixtures, extended it, and applied it to complex environmental mixtures to advance methods for joint toxicity assessment. Federal agencies and local entities provide guidance to evaluate such exposures in the absence of specific data. The objective of this paper is to illustrate use and applicability of ATSDR's framework for evaluation of environmental mixtures, specifically the use of weight of evidence in Tier III, using cyanide mixtures as examples. The results show, for certain cyanide mixtures for which data are available, interactions can be evaluated with a high degree of confidence. For complex mixtures that contain unidentified components, such as found in fires, similarity-based grouping risk assessment is proposed.

Peptide-based colorimetric and fluorescent dual-functional probe for sequential detection of copper(â ¡) and cyanide ions and its application in real water samples, test strips and living cells.

A novel dual-functional peptide probe FLH based on fluorescent "on-off-on" strategy and colorimetric visualization method was designed and synthesized. This new probe exhibited highly selective and rapid detection of Cu2+ with significant fluorescent "turn-off" response, with a visible colorimetric change from yellow to orange. The combination ratio of FLH to Cu2+ (1:1) was determined using ESI-HRMS spectra and Job's plot. The fluorescent emission showed a good linear response (R2 = 0.9986) with a low detection limit of 1.5 nM. In addition, the FLH-Cu2+ complex displayed colorimetric changes and a fluorescent "off-on" response toward CN- over a wide pH range from 7 to 12. This detection behavior was observed within 20 s, with a limit of detection (LOD) for CN- at 12.7 nM. Based on stability and accuracy, FLH was next developed as dual-functional test strips, and was also successfully applied to detect Cu2+ and CN- in two actual water samples. More importantly, the cytotoxicity studies indicated that FLH had good biocompatibility and low toxicity, and was successfully utilized for monitoring Cu2+ and CN- in living cells through fluorescence imaging.

Glyoxylate protects against cyanide toxicity through metabolic modulation.

Although cyanide's biological effects are pleiotropic, its most obvious effects are as a metabolic poison. Cyanide potently inhibits cytochrome c oxidase and potentially other metabolic enzymes, thereby unleashing a cascade of metabolic perturbations that are believed to cause lethality. From systematic screens of human metabolites using a zebrafish model of cyanide toxicity, we have identified the TCA-derived small molecule glyoxylate as a potential cyanide countermeasure. Following cyanide exposure, treatment with glyoxylate in both mammalian and non-mammalian animal models confers resistance to cyanide toxicity with greater efficacy and faster kinetics than known cyanide scavengers. Glyoxylate-mediated cyanide resistance is accompanied by rapid pyruvate consumption without an accompanying increase in lactate concentration. Lactate dehydrogenase is required for this effect which distinguishes the mechanism of glyoxylate rescue as distinct from countermeasures based solely on chemical cyanide scavenging. Our metabolic data together support the hypothesis that glyoxylate confers survival at least in part by reversing the cyanide-induced redox imbalances in the cytosol and mitochondria. The data presented herein represent the identification of a potential cyanide countermeasure operating through a novel mechanism of metabolic modulation.

A novel aqueous dimethyl trisulfide formulation is effective at low doses against cyanide toxicity in non-anesthetized mice and rats.

BACKGROUND: Cyanide (CN) is a metabolic poison that is capable of intoxicating individuals through accidental or intentional means. With high concentration exposures, death can occur in minutes. In cases of mass casualty exposures, there is a need for a rapid-acting countermeasure capable of being administered in a short period of time in a pre-hospital setting to treat victims. OBJECTIVE: These studies evaluate the safety and efficacy of a novel aqueous formulation of dimethyl trisulfide (DMTS) as an intramuscular (IM) CN countermeasure using non-anesthetized rodent models. METHODS: Non-anesthetized rodents (mice and rats) were exposed to hydrogen cyanide (HCN) or potassium cyanide (KCN) along with immediate IM 10% DMTS treatment or vehicle treatment. Survival and other parameters, such as the time to recovery and assessment of clinical toxic signs (e.g., gasping, loss of righting reflex, convulsions, etc.), were quantified to determine the effectiveness of 10% DMTS treatment (12.5, 25, 75 mg/kg IM) compared to vehicle control treatment. A rat KCN delayed-treatment model with a 15-minute treatment delay was also utilized to simulate a real-life exposure/treatment scenario with 10% DMTS treatment. The stability of the 10% DMTS formulation was also assessed. RESULTS: A 25 mg/kg IM dose of 10% DMTS exhibits potent efficacy against subcutaneous (SC) KCN challenge in both mice and rats and inhalational HCN exposure in mice. 10% DMTS treatment also shortens the time to recovery in rats using a delayed-treatment model. CONCLUSION: IM treatment with 10% DMTS improves survival and clinical outcomes in non-anesthetized rodent models of acute CN toxicity. Additionally, the use of an SC KCN delayed-treatment model in rats is advised to assess the performance of a candidate CN countermeasure in a more realistic exposure/treatment scenario.