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Clinical Toxicology (Philadelphia, Pa.) Mar 2020Dicobalt edetate and hydroxocobalamin are widely used to treat hydrogen cyanide poisoning. However, comparative and quantitative efficacy data are lacking. Although...
Dicobalt edetate and hydroxocobalamin are widely used to treat hydrogen cyanide poisoning. However, comparative and quantitative efficacy data are lacking. Although post-exposure treatment is typical, it may be possible to administer these antidotes before exposure to first attenders entering a known site of cyanide release, as supplementary protection to their personal protective equipment. We established an anaesthetised Gottingen minipig model of lethal bolus potassium cyanide (KCN) injection to simulate high dose hydrogen cyanide inhalation. Doses were similar to human lethal doses of KCN. Dicobalt edetate and hydroxocobalamin were administered shortly before KCN and their effect on metabolic and cardiovascular variables and survival time were measured. Increases in arterial lactate were similar after 0.08 and 0.12 mmol/kg KCN. KCN 0.08 mmol/kg was survived by 4/4 animals with moderate cardiovascular effects, while the 0.12 mmol/kg dose was lethal in 4/4 animals, with a mean time to euthanasia of 28.3 (SEM: 13.9) min. Administration of dicobalt edetate (0.021 mmol/kg, 8.6 mg/kg) or hydroxocobalamin (0.054 mmol/kg, 75 mg/kg) at clinically licenced doses had modest effect on lactate concentrations but increased survival after administration of KCN 0.12 mmol/kg (survival: dicobalt edetate 4/4, hydroxocobalamin 2/4) but not 0.15 mmol/kg (0/4 and 0/4, respectively). In a subsequent larger study, doubling the dose of hydroxocobalamin (0.108 mmol/kg, 150 mg/kg) was associated with a modest but inconsistent increased survival after 0.15 mmol/kg KCN (survival: control 0/8, 75 mg/kg 1/10, 150 mg/kg 3/10) likely due to variable pharmacokinetics. In this porcine study of cyanide exposure, with pre-exposure antidote administration, licenced doses of dicobalt edetate and hydroxocobalamin were effective at just lethal doses but ineffective at less than twice the estimated LD. The efficacy of a rapidly-administered double-dose of hydroxocobalamin was limited by variable pharmacokinetics. In clinical poisoning scenarios, with delayed administration, the antidotes are likely to be even less effective. New antidotes are required for treatment of cyanide exposures appreciably above the minimum lethal dose.
Topics: Animals; Antidotes; Chelating Agents; Cyanides; Disease Models, Animal; Dose-Response Relationship, Drug; Edetic Acid; Hydroxocobalamin; Male; Pre-Exposure Prophylaxis; Swine; Swine, Miniature
PubMed: 31389254
DOI: 10.1080/15563650.2019.1628969 -
Journal of Bacteriology Jul 2022Staphylococcus aureus Tet38 efflux pump has multiple functions, including conferring resistance to tetracycline and other compounds and enabling internalization and...
Staphylococcus aureus Tet38 efflux pump has multiple functions, including conferring resistance to tetracycline and other compounds and enabling internalization and survival within epithelial cells. In this study, we evaluated the effects of sodium and potassium on expression. These monovalent cations are known to play a role in transport by the related S. aureus TetK and B. subtilis TetL transporters. transcription decreased with increasing sodium concentrations by means of direct repression by the salt stress-dependent KdpD/E regulator. transcription increased 20-fold and tetracycline minimum inhibitory concentration (MIC) increased 4-fold in a Δ mutant. KdpE bound specifically to the promoter. Under extreme salt stress, the survival of S. aureus with intact was reduced compared to that of a Δ mutant. To study the effect of sodium on Tet38 function, we generated constructs overexpressing and and introduced them into Escherichia coli TO114, which is deficient in major sodium transporters. Tet38 tetracycline efflux was directly demonstrated in a fluorescence assay, and tetracycline efflux of both Tet38 and TetK was abolished by the protonophore carbonyl cyanide 3-chlorophenylhydrazone (CCCP). In contrast, NaCl inhibited efflux by Tet38 but not TetK, whereas KCl inhibited efflux by TetK but not Tet38. Cell-associated Na increased with heterologous overexpression of Tet38. These data indicate that S. aureus Tet38 is a tetracycline efflux pump regulated by the KdpD/E regulator. Under salt stress, S. aureus adjusted its survival in part by reducing the expression of through KdpD/E. The mechanisms by which Tet38 is detrimental to salt tolerance in S. aureus and inhibited by sodium remain to be determined. This study shows that S. aureus Tet38 is a tetracycline efflux pump regulated by KdpD/E regulator. These findings are the first direct demonstration of Tet38-mediated tetracycline efflux, which had previously been inferred from its ability to confer tetracycline resistance. Under salt stress, S. aureus adjusts its survival in part by reducing the expression of through KdpD/E. We demonstrated the differences in the respective functions of S. aureus Tet38 and other tetracycline efflux transporters (S. aureus TetK, B. subtilis TetL) regarding their transport of tetracycline and Na/K. Notably, sodium selectively reduced tetracycline efflux by Tet38, and potassium selectively reduced tetracycline efflux by TetK. The multiple functions of Tet38 emphasize its importance in bacterial adaptation to and survival in diverse environments.
Topics: Anti-Bacterial Agents; Bacterial Proteins; Escherichia coli; Escherichia coli Proteins; Membrane Transport Proteins; Microbial Sensitivity Tests; Potassium; Protein Kinases; Salt Stress; Sodium; Staphylococcus aureus; Tetracycline
PubMed: 35699453
DOI: 10.1128/jb.00142-22 -
Experimental Physiology Sep 2019What is the central question of this study? The traditional surgical approach for sino-aortic denervation in rats leads to simultaneous carotid baroreceptor and...
NEW FINDINGS
What is the central question of this study? The traditional surgical approach for sino-aortic denervation in rats leads to simultaneous carotid baroreceptor and chemoreceptor deactivation, which does not permit their individual study in different situations. What is the main finding and its importance? We have described a new surgical approach capable of selective denervation of the arterial (aortic and carotid) baroreceptors, keeping the carotid bodies (chemoreceptors) intact. It is understood that this technique might be a useful tool for investigating the relative role of the baro- and chemoreceptors in several physiological and pathophysiological conditions.
ABSTRACT
Studies have demonstrated that the traditional surgical approach for sino-aortic denervation in rats leads to simultaneous carotid baroreceptor and chemoreceptor deactivation. The present study reports a new surgical approach to denervate the aortic and the carotid baroreceptors selectively, keeping the carotid bodies (peripheral chemoreceptors) intact. Wistar rats were subjected to specific aortic and carotid baroreceptor denervation (BAROS-X) or sham surgery (SHAM). Baroreflex activation was achieved by i.v. administration of phenylephrine, whereas peripheral chemoreflex activation was produced by i.v. administration of potassium cyanide. The SHAM and BAROS-X rats displayed significant hypertensive responses to phenylephrine administration. However, the reflex bradycardia following the hypertensive response caused by phenylephrine was remarkable in SHAM, but not significant in the BAROS-X animals, confirming the efficacy of the surgical procedure to abolish the baroreflex. In addition, the baroreflex activation elicited by phenylephrine increased carotid sinus nerve activity only in SHAM, but not in the BAROS-X animals, providing support to the notion that the baroreceptor afferents were absent. Instead, the classical peripheral chemoreflex hypertensive and bradycardic responses to potassium cyanide were similar in both groups, suggesting that the carotid body chemoreceptors were preserved after BAROS-X. In summary, we describe a new surgical approach in which only the baroreceptors are eliminated, while the carotid chemoreceptors are preserved. Therefore, it is understood that this procedure is potentially a useful tool for examining the relative roles of the arterial baroreceptors versus the chemoreceptors in several pathophysiological conditions, for instance, arterial hypertension and heart failure.
Topics: Animals; Aorta; Arteries; Baroreflex; Blood Pressure; Carotid Body; Chemoreceptor Cells; Denervation; Heart Rate; Hypertension; Male; Phenylephrine; Pressoreceptors; Rats; Rats, Wistar
PubMed: 31161612
DOI: 10.1113/EP087764 -
Drug and Chemical Toxicology Nov 2019Cyanide-induced chemical hypoxia is responsible for pronounced oxidative damage in the central nervous system. The disruption of mitochondrial oxidative metabolism has...
Cyanide-induced chemical hypoxia is responsible for pronounced oxidative damage in the central nervous system. The disruption of mitochondrial oxidative metabolism has been associated with upregulation of uncoupling proteins (UCPs). The present study addresses the dose- and time-dependent effect of sub-acute cyanide exposure on various non-enzymatic and enzymatic oxidative stress markers and their correlation with inducible-nitric oxide synthase (iNOS) and uncoupling protein-2 (UCP-2) expression. Animals received (oral) triple distilled water (vehicle control), 0.25 LD50 potassium cyanide (KCN) or 0.50 LD50 KCN daily for 21 d. Animals were sacrificed on 7, 14 and 21 d post-exposure to measure serum cyanide and nitrite, and brain malondialdehyde (MDA), reduced glutathione (GSH), glutathione disulfide (GSSG), cytochrome oxidase (CCO), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) and catalase (CA) levels, together with iNOS and UCP-2 expression, and DNA damage. The study revealed that a dose- and time-dependent increase in cyanide concentration was accompanied by corresponding CCO inhibition and elevated MDA levels. Decrease in GSH levels was not followed by reciprocal change in GSSG levels. Diminution of SOD, GPx, GR and CA activity was congruent with elevated nitrite levels and upregulation of iNOS and UCP-2 expression, without any DNA damage. It was concluded that long-term cyanide exposure caused oxidative stress, accompanied by upregulation of iNOS. The upregulation of UCP-2 further sensitized the cells to cyanide and accentuated the oxidative stress, which was independent of DNA damage.
Topics: Animals; Brain; DNA Damage; Dose-Response Relationship, Drug; Female; Lethal Dose 50; Nitric Oxide Synthase Type II; Oxidative Stress; Potassium Cyanide; Rats; Rats, Wistar; Superoxide Dismutase; Time Factors; Uncoupling Protein 2; Up-Regulation
PubMed: 29609494
DOI: 10.1080/01480545.2018.1451876 -
Canadian Journal of Physiology and... Oct 2020This study aims to investigate the mechanisms through which fructose diphosphate (FDP) causes anti-hypoxia and anti-fatigue effects and improves learning and memory....
This study aims to investigate the mechanisms through which fructose diphosphate (FDP) causes anti-hypoxia and anti-fatigue effects and improves learning and memory. Mice were divided into three groups: low-dose FDP (FDP-L), high-dose FDP (FDP-H), and a control group. Acute toxic hypoxia induced by carbon monoxide, sodium nitrite, and potassium cyanide and acute cerebral ischemic hypoxia were used to investigate the anti-hypoxia ability of FDP. The tests of rod-rotating, mouse tail suspension, and swimming endurance were used to explore the anti-fatigue effects of FDP. The Morris water maze experiment was used to determine the impact of FDP on learning and memory ability. Poisoning-induced hypoxic tests showed that mouse survival time was significantly prolonged in the FDP-L and FDP-H groups compared with the control group ( < 0.05). In the exhaustive swimming test, FDP significantly shortened struggling time and prolonged the time of mass-loaded swimming; the rod-rotating test showed that endurance time was significantly prolonged by using FDP ( < 0.05). FDP significantly decreased lactate and urea nitrogen levels and increased hepatic and muscle glycogen and glucose transporter-4 and Na-K-ATPase ( < 0.05). To conclude, FDP enhances hypoxia tolerance and fatigue resistance and improves learning and memory ability through regulating glucose and energy metabolism.
Topics: Animals; Behavior, Animal; Disease Models, Animal; Energy Metabolism; Fatigue; Fructosediphosphates; Hypoxia; Hypoxia-Ischemia, Brain; Learning; Locomotion; Memory; Mice; Morris Water Maze Test; Rotarod Performance Test; Swimming
PubMed: 32551885
DOI: 10.1139/cjpp-2019-0690 -
Journal of the American Chemical Society Jul 2021The stereoselective cyanoalkylation of electron-deficient olefins with potassium cyanide and alkyl halides was developed based on the utilization of modular chiral...
The stereoselective cyanoalkylation of electron-deficient olefins with potassium cyanide and alkyl halides was developed based on the utilization of modular chiral 1,2,3-triazolium salts featuring a hydrogen bond-donor ability as catalysts. The reaction involving multiple carbon-carbon bond formations proceeds via the enantioselective conjugate addition of a cyanide ion and the consecutive catalyst-controlled diastereoselective alkylation of intermediary chiral triazolium enolates. Control experiments revealed that the use of a properly tuned chiral triazolium ion as a catalyst and the presence of the cyano functionality in the intermediary enolate are of crucial importance for achieving high levels of acyclic absolute and relative stereocontrol.
PubMed: 34270904
DOI: 10.1021/jacs.1c05380 -
Molecules (Basel, Switzerland) May 2023Fenebrutinib is an orally available Bruton tyrosine kinase inhibitor. It is currently in multiple phase III clinical trials for the management of B-cell tumors and...
Fenebrutinib is an orally available Bruton tyrosine kinase inhibitor. It is currently in multiple phase III clinical trials for the management of B-cell tumors and autoimmune disorders. Elementary in-silico studies were first performed to predict susceptible sites of metabolism and structural alerts for toxicities by StarDrop WhichP450™ module and DEREK software; respectively. Fenebrutinib metabolites and adducts were characterized in-vitro in rat liver microsomes (RLM) using MS3 method in Ion Trap LC-MS/MS. Formation of reactive and unstable intermediates was explored using potassium cyanide (KCN), glutathione (GSH) and methoxylamine as trapping nucleophiles to capture the transient and unstable iminium, 6-iminopyridin-3()-one and aldehyde intermediates, respectively, to generate a stable adducts that can be investigated and analyzed using mass spectrometry. Ten phase I metabolites, four cyanide adducts, five GSH adducts and six methoxylamine adducts of fenebrutinib were identified. The proposed metabolic reactions involved in formation of these metabolites are hydroxylation, oxidation of primary alcohol to aldehyde, n-oxidation, and n-dealkylation. The mechanism of reactive intermediate formation of fenebrutinib can provide a justification of the cause of its adverse effects. Formation of iminium, iminoquinone and aldehyde intermediates of fenebrutinib was characterized. N-dealkylation followed by hydroxylation of the piperazine ring is proposed to cause the bioactivation to iminium intermediates captured by cyanide. Oxidation of the hydroxymethyl group on the pyridine moiety is proposed to cause the generation of reactive aldehyde intermediates captures by methoxylamine. N-dealkylation and hydroxylation of the pyridine ring is proposed to cause formation of iminoquinone reactive intermediates captured by glutathione. FBB and several phase I metabolites are bioactivated to fifteen reactive intermediates which might be the cause of adverse effects. In the future, drug discovery experiments utilizing this information could be performed, permitting the synthesis of new drugs with better safety profile. Overall, in silico software and in vitro metabolic incubation experiments were able to characterize the FBB metabolites and reactive intermediates using the multistep fragmentation capability of ion trap mass spectrometry.
Topics: Rats; Animals; Chromatography, Liquid; Chromatography, High Pressure Liquid; Tandem Mass Spectrometry; Piperazines; Pyridones; Glutathione; Cyanides; Aldehydes; Microsomes, Liver
PubMed: 37241965
DOI: 10.3390/molecules28104225 -
Drug Metabolism and Disposition: the... May 2022We recently established the mechanism-based inactivation (MBI) of cytochrome P450 3A (CYP3A) by the fibroblast growth factor receptor (FGFR) inhibitors erdafitinib and...
We recently established the mechanism-based inactivation (MBI) of cytochrome P450 3A (CYP3A) by the fibroblast growth factor receptor (FGFR) inhibitors erdafitinib and infigratinib. Serendipitously, our preliminary data have also revealed that pemigatinib (PEM), another clinically approved FGFR1-3 inhibitor, similarly elicited time-dependent inhibition of CYP3A. This was rather unexpected, as it was previously purported that PEM did not pose any metabolism-dependent liabilities due to the absence of glutathione-related conjugates in metabolic profiling experiments conducted in human liver microsomes. Here, we confirmed that PEM inhibited both CYP3A isoforms in a time-, concentration-, and cofactor-dependent manner consistent with MBI, with inactivator concentration at half-maximum rate constant, maximum inactivation rate constant, and partition ratio of 8.69 and 11.95 M, 0.108 and 0.042 min, and approximately 44 and approximately 47 for CYP3A4 and CYP3A5, respectively. Although the rate of inactivation was diminished by coincubation with an alternative substrate or direct inhibitor of CYP3A, the inclusion of nucleophilic trapping agents afforded no such protection. Furthermore, the lack of catalytic activity recovery following dialysis and oxidation with potassium ferricyanide coupled with the absence of a spectrally resolvable peak in the Soret region collectively implied that the underlying mechanism of inactivation was not elicited via the formation of pseudo-irreversible metabolite-intermediate complexes. Finally, utilizing cyanide trapping and high-resolution mass spectrometry, we illuminated the direct and sequential oxidative bioactivation of PEM and its major -desmethylated metabolite at its distal morpholine moiety to reactive iminium ion hard electrophilic species that could covalently inactivate CYP3A via MBI. SIGNIFICANCE STATEMENT: This study reports for the first time the covalent MBI of CYP3A by PEM and deciphered its bioactivation pathway involving the metabolic activation of PEM and its major -desmethylated metabolite to reactive iminium ion intermediates. Following which, a unique covalent docking methodology was harnessed to unravel the structural and molecular determinants underpinning its inactivation. Findings from this study lay the foundation for future investigation of clinically relevant drug-drug interactions between PEM and concomitant substrates of CYP3A.
Topics: Cytochrome P-450 CYP3A; Cytochrome P-450 CYP3A Inhibitors; Humans; Microsomes, Liver; Morpholines; Pyrimidines; Pyrroles; Renal Dialysis
PubMed: 35153194
DOI: 10.1124/dmd.121.000804 -
RSC Advances Jul 2022Zorifertinib (AZD-3759; ZFB) is a potent, novel, oral, small molecule used for the treatment of non-small cell lung cancer (NSCLC). ZFB is Epidermal Growth Factor...
Zorifertinib (AZD-3759; ZFB) is a potent, novel, oral, small molecule used for the treatment of non-small cell lung cancer (NSCLC). ZFB is Epidermal Growth Factor Receptor (EGFR) inhibitor that is characterized by good permeability of the blood-brain barrier for (NSCLC) patients with EGFR mutations. The present research reports the profiling of , and reactive metabolites of ZFB. Prediction of vulnerable metabolic sites and reactivity pathways (cyanide and GSH) of ZFB were performed by WhichP450™ module (StarDrop software package) and XenoSite reactivity model (XenoSite Web Predictor-Home), respectively. ZFB metabolites were done by incubation with isolated perfused rat liver hepatocytes and rat liver microsomes (RLMs). Extraction of ZFB and its related metabolites from the incubation matrix was done by protein precipitation. metabolism was performed by giving ZFB (10 mg kg) through oral gavage to Sprague Dawley rats that were housed in metabolic cages. Urine was collected at specific time intervals (0, 6, 12, 18, 24, 48, 72, 96 and 120 h) from ZFB dosing. The collected urine samples were filtered then stored at -70 °C. -Methyl piperazine ring of ZFB undergoes phase I metabolism forming iminium intermediates that were stabilized using potassium cyanide as a trapping agent. Incubation of ZFB with RLMs were performed in the presence of 1.0 mM KCN and 1.0 mM glutathione to check reactive intermediates as it is may be responsible for toxicities associated with ZFB usage. For metabolites there were six phase I metabolites, three phase II metabolites, seven reactive intermediates (four GSH conjugates and three cyano adducts) of ZFB were detected by LC-IT-MS. For metabolites there were six phase I and three phase II metabolites of ZFB were detected by LC-IT-MS. and phase I metabolic pathways were -demethylation, -demethylation, hydroxylation, reduction, defluorination and dechlorination. phase II metabolic reaction was direct sulphate and glucuronic acid conjugation with ZFB.
PubMed: 35919181
DOI: 10.1039/d2ra02848d -
Clinical Toxicology (Philadelphia, Pa.) Jan 2022Cyanide (CN) is a metabolic poison that is capable of intoxicating individuals through accidental or intentional means. With high concentration exposures, death can...
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.
Topics: Animals; Antidotes; Cyanides; Humans; Mice; Potassium Cyanide; Rats; Sulfides
PubMed: 34219566
DOI: 10.1080/15563650.2021.1935991