Toxicokinetic Profiles of α-ketoglutarate Cyanohydrin, a Cyanide Detoxification Product, Following Exposure to Potassium Cyanide

Poisoning by cyanide can be verified by analysis of the cyanide detoxification product, α-ketoglutarate cyanohydrin (α-KgCN), which is produced from the reaction of cyanide and endogenous α-ketoglutarate. Although α-KgCN can potentially be used to verify cyanide exposure, limited toxicokinetic data in cyanide-poisoned animals are available. We, therefore, studied the toxicokinetics of α-KgCN and compared its behavior to other cyanide metabolites, thiocyanate and 2-amino-2-thiazoline-4-carboxylic acid (ATCA), in the plasma of 31 Yorkshire pigs that received KCN (4 mg/mL) intravenously (IV) (0.17 mg/kg/min). α-KgCN concentrations rose rapidly during KCN administration until the onset of apnea, and then decreased over time in all groups with a half-life of 15 min. The maximum concentrations of α-KgCN and cyanide were 2.35 and 30.18 μM, respectively, suggesting that only a small fraction of the administered cyanide is converted to α-KgCN. Although this is the case, the α-KgCN concentration increased \u3e100-fold over endogenous concentrations compared to only a three-fold increase for cyanide and ATCA. The plasma profile of α-KgCN was similar to that of cyanide, ATCA, and thiocyanate. The results of this study suggest that the use of α-KgCN as a biomarker for cyanide exposure is best suited immediately following exposure for instances of acute, high-dose cyanide poisoning

Simultaneous Determination of 3-mercaptopyruvate and Cobinamide in Plasma by Liquid Chromatography–tandem Mass Spectrometry

The current suite of Food and Drug Administration (FDA) approved antidotes (i.e., sodium nitrite, sodium thiosulfate, and hydroxocobalamin) are effective for treating cyanide poisoning, but individually, each antidote has major limitations (e.g., large effective dosage or delayed onset of action). To mitigate these limitations, next-generation cyanide antidotes are being investigated, including 3-mercaptopyruvate (3-MP) and cobinamide (Cbi). Analytical methods capable of detecting these therapeutics individually and simultaneously (for combination therapy) are essential for the development of 3-MP and Cbi as potential cyanide antidotes. Therefore, a liquid chromatography–tandem mass-spectrometry method for the simultaneous analysis of 3-MP and Cbi was developed. Sample preparation of 3-MP consisted of spiking plasma with an internal standard (13C3-3-MP), precipitation of plasma proteins, and derivatizing 3-MP with monobromobimane to produce 3-mercaptopyruvate-bimane. Preparation of Cbi involved denaturing plasma proteins with simultaneous addition of excess cyanide to convert each Cbi species to dicyanocobinamide (Cbi(CN)2). The limits of detection for 3-MP and Cbi were 0.5 μM and 0.2 μM, respectively. The linear ranges were 2–500 μM for 3-MP and 0.5–50 μM for Cbi. The accuracy and precision for 3-MP were 100 ± 9% and \u3c8.3% relative standard deviation (RSD), respectively. For Cbi(CN)2, the accuracy was 100 ± 13% and the precision was \u3c9.5% RSD. The method presented here was used to determine 3-MP and Cbi from treated animals and may ultimately facilitate FDA approval of these antidotes for treatment of cyanide poisoning

Aortic pathology from protein kinase G activation is prevented by an antioxidant vitamin B12 analog.

People heterozygous for an activating mutation in protein kinase G1 (PRKG1, p.Arg177Gln) develop thoracic aortic aneurysms and dissections (TAAD) as young adults. Here we report that mice heterozygous for the mutation have a three-fold increase in basal protein kinase G (PKG) activity, and develop age-dependent aortic dilation. Prkg1R177Q/+ aortas show increased smooth muscle cell apoptosis, elastin fiber breaks, and oxidative stress compared to aortas from wild type littermates. Transverse aortic constriction (TAC)-to increase wall stress in the ascending aorta-induces severe aortic pathology and mortality from aortic rupture in young mutant mice. The free radical-neutralizing vitamin B12-analog cobinamide completely prevents age-related aortic wall degeneration, and the unrelated anti-oxidant N-acetylcysteine ameliorates TAC-induced pathology. Thus, increased basal PKG activity induces oxidative stress in the aorta, raising concern about the widespread clinical use of PKG-activating drugs. Cobinamide could be a treatment for aortic aneurysms where oxidative stress contributes to the disease, including Marfan syndrome

Noninvasive monitoring of treatment response in a rabbit cyanide toxicity model reveals differences in brain and muscle metabolism

Noninvasive near infrared spectroscopy measurements were performed to monitor cyanide (CN) poisoning and recovery in the brain region and in foreleg muscle simultaneously, and the effects of a novel CN antidote, sulfanegen sodium, on tissue hemoglobin oxygenation changes were compared using a sub-lethal rabbit model. The results demonstrated that the brain region is more susceptible to CN poisoning and slower in endogenous CN detoxification following exposure than peripheral muscles. However, sulfanegen sodium rapidly reversed CN toxicity, with brain region effects reversing more quickly than muscle. In vivo monitoring of multiple organs may provide important clinical information regarding the extent of CN toxicity and subsequent recovery, and facilitate antidote drug development

Antidotal efficacies of the cyanide antidote candidate dimethyl trisulfide alone and in combination with cobinamide derivatives

Formulation optimization and antidotal combination therapy are the two important tools to enhance the antidotal protection of the cyanide (CN) antidote dimethyl trisulfide (DMTS). The focus of this study is to demonstrate how the formulation with polysorbate 80 (Poly80), an excipient used in pharmaceutical technology, and the combinations with other CN antidotes having different mechanisms of action enhance the antidotal efficacy of the unformulated (neat) DMTS. The LD50 for CN was determined by the statistical Dixon up-and-down method on mice. Antidotal efficacy was expressed as antidotal potency ratio (APR). CN was injected subcutaneously one minute prior to the antidotes’ injection intramuscularly. The APR values of 1.17 (dose: 25 mg/kg bodyweight) and 1.45 (dose: 50 mg/kg bodyweight) of the neat DMTS were significantly enhanced by the Poly80 formulation at both investigated doses to 2.03 and 2.33, respectively. The combination partners for the Poly80 formulated DMTS (DMTS-Poly80; 25 and 50 mg/kg bodyweight) were 4-nitrocobinamide (4NCbi) (20 mg/kg bodyweight) and aquohydroxocobinamide (AHCbi; 50, 100, and 250 mg/kg bodyweight). When DMTS-Poly80 (25 and 50 mg/kg bodyweight; APR = 2.03 and 2.33, respectively) was combined with 4NCbi (20 mg/kg bodyweight; APR = 1.35), significant increase in the APR values were noted at both DMTS doses (APR = 2.38 and 3.12, respectively). AHCbi enhanced the APR of DMTS-Poly80 (100 mg/kg bodyweight; APR = 3.29) significantly only at the dose of 250 mg/kg bodyweight (APR = 5.86). These studies provided evidence for the importance of the formulation with Poly80 and the combinations with cobinamide derivatives with different mechanisms of action for DMTS as a CN antidote candidate

Acute rotenone poisoning: A scoping review

ContextRotenone is a toxic chemical found in various plants, including some used as food. Rotenone poisoning can be fatal and there is no antidote. Mechanistically, rotenone inhibits mitochondrial complex I, leading to reduced ATP production, compensatory glycolytic upregulation and secondary lactate production, and oxidative stress. Our literature review examined acute rotenone poisoning in humans, including exposure scenarios, clinical presentations, and treatments.MethodsWe searched five databases for relevant literature from database inception through the search date: July 12, 2022, pairing controlled vocabulary and keywords for "rotenone" with terms relating to human exposures and outcomes, such as "ingestion," "exposure," and "poisoning." We included all peer-reviewed reports found using the search terms where the full English text was available. Data abstracted included the number, age, weight, and sex of the exposed person(s), country where exposure happened, exposure scenario, ingestion context, estimated dose, clinical features, whether hospitalization occurred, treatments, and outcomes.ResultsAfter removing non-qualifying sources from 2,631 publications, we identified 11 case reports describing 18 victims, 15 of whom were hospitalized and five died. Most cases occurred in private quarters where victims unknowingly consumed rotenone-containing plants. Vomiting and metabolic acidosis occurred most commonly. Some patients exhibited impaired cardiopulmonary function. Supportive treatment addressed symptoms and included gastric lavage and/or activated charcoal to remove rotenone from the stomach, vasopressors for hypotension, mechanical ventilation for respiratory insufficiency, and sodium bicarbonate for acidosis. Some patients received N-acetylcysteine to counter oxidative stress.ConclusionsRotenone poisoning, though rare, can be fatal. Exposure prevention is impractical since rotenone is found in some plants used as food or pesticides. Cases may be under-diagnosed because symptoms are non-specific and under-reported in English-language journals since most cases occurred in non-English speaking countries. Treatments are supportive. Exploring antioxidant therapy in animal models of rotenone poisoning may be indicated considering rotenone's mechanism of toxicity

and Reversal by Homocysteine

Abstract. Purine nucleosides, which accumulate in adenosine deaminase and purine nucleoside phosphorylase deficiency, are toxic to lymphoid cells. Since adenine nucleosides inhibit S-adenosylhomocysteine hydrolase, they could potentially decrease intracellular methionine synthesis. To test this hypothesis, we measured methionine synthesis by the use of ['4C]formate as a radioactive precursor in cultured human T and B lymphoblasts treated with varying concentrations of purine nucleosides; 2'-deoxycoformycin and 8-aminoguanosine were added to inhibit adenosine deaminase and purine nucleoside phosphorylase, respectively. In the T lymphoblasts methionine synthesis was inhibited-50 % by 10 MAM of 2'-deoxyadenosine, adenine arabinoside, or 2'-deoxyguanosine. By contrast, in the B lymphoblasts methionine synthesis was considerably less affected by these nucleosides, with 50 % inhibition occurring at 100,uM of 2'-deoxyadenosine and adenine arabinoside; 100 uM of2'-deoxyguanosine yielded <10% inhibition. Adenosine and guanosine were considerably less potent inhibitors of methionine synthesis in both the T and B lymphoblasts. An adenosine deaminasedeficient and a purine nucleoside phosphorylase-deficient cell line, both of B cell origin, exhibited sensitivities to the nucleosides similar to those of the normal B cell lines. In both the T and B cell lines homocysteine reversed the methionine synthesis inhibition induced by the adenine nucleosides and guanosine and largely reversed that induced by 2'-deoxyguanosine. Methionin

Cobinamide chemistries for photometric cyanide determination. A merging zone liquid core waveguide cyanide analyzer using cyanoaquacobinamide

Diaquacobinamide (H2O)(2)Cbi(2+) or its conjugate base hydroxyaquacobinamide (OH(H2O)Cbi(+))) can bind up to two cyanide ions, making dicyanocobinamide. This transition is accompanied by a significant change in color, previously exploited for cyanide determination. The reagent OH(H2O)Cbi(+) is used in excess; when trace amounts of cyanide are added, CN(H2O)Cbi(+) should be formed. But the spectral absorption of CN(H2O)Cbi(+) is virtually the same as that of OH(H2O)Cbi(+). It has been inexplicable how trace amounts of cyanide are sensitively measured by this reaction. it is shown here that even with excess OH(H2O)Cbi(+), (CN)(2)Cbi is formed first due to kinetic reasons; this only slowly forms CN(H2O)Cbi(+). This understanding implies that CN(H2O)Cbi(+) will itself be a better reagent. We describe a single valve merging zone flow analyzer that allows both sample and reagent economy. With a 50 cm liquid core waveguide (LCW) flow cell and an inexpensive fiber optic - charge coupled device array spectrometer, a S/N = 3 limit of detection of 8 nM, a linear dynamic range to 6 mu M, and excellent precision (RSD 0.49% and 1.07% at 50 and 100 nM, respectively, n = 5 each) are formed. At 1% carryover, sample throughput is 40 h(-1). The setup is readily used to measure thiocyanate with different reagents. We demonstrate applicability to real samples by analyzing human saliva samples and hydrolyzed extracts of apple seeds, peach pits, and almonds