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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 -
Pathophysiology : the Official Journal... Sep 2014Vascular occlusion and cyanide neurotoxicity induces oxidative stress and degeneration in the brain. This oxidant induced stress changes the vascular dynamics of...
BACKGROUND
Vascular occlusion and cyanide neurotoxicity induces oxidative stress and degeneration in the brain. This oxidant induced stress changes the vascular dynamics of cerebral blood vessels, and participates in homeostatic response mechanisms which balance oxygen supply to hypoxic stress-sensitive neurons. The associated changes in vascular morphology include remodeling of the microvasculature and endothelial changes, alterations in regional circulation and variations in the blood brain barrier (BBB). This study compares alterations in physiology of the cerebral artery after a short-term oxidative stress induced by cyanide toxicity and vascular occlusion.
METHOD
Adult Wistar rats (N=30) were divided into three groups; vascular occlusion (VO) (n=12), potassium cyanide administration (CN) (n=12) and Control-CO (n=6). The CN rates were treated with 30mg/kg of orally administered KCN while the VO was subjected to global vascular occlusion, both for a duration of 10 days, described as the treatment phase. Control animals were fed on normal rat chow and water for 10 days. At the end of the treatment phase, n=6 animals in each of the VO, CN and VO groups were anesthetized with sodium pentobarbital (50IP) and the CCA exposed, after which pin electrodes were implanted to record the spikes form the tunica media of the CCA. After day 10, treatment was discontinued for these animals, each remaining in the VO and CN groups (VO-I and CN-I) until day 20 (withdrawal phase) following which the spikes were recorded using the procedure described above.
RESULTS/DISCUSSION
Vascular occlusion and cyanide toxicity increased vascular resistance in the MCA (reduced lumen thickness ratio) and increased the diameter of the CCA after the treatment phase of 10 days. After 10 days of withdrawal, the VO group showed a reduction in resistance and an increase in the lumen width/wall thickness ratio (LWR) while the CN group showed increased resistance and a reduction in LWR.
CONCLUSION
Cyanide toxicity increased vascular resistance by inducing degenerative changes in the wall of the artery while vascular occlusion increased resistance through mechanical stress and increased thickness of arterial wall. After the withdrawal phase, vascular resistance diminished in the VO to a significantly greater extent than the CN.
PubMed: 25156812
DOI: 10.1016/j.pathophys.2014.08.002 -
Food Chemistry Jan 2018This study determined nutrients, chemical contaminants, (insecticide residues and heavy metals), and natural toxic substances (nitrate, nitrite, cyanide, oxalate,...
This study determined nutrients, chemical contaminants, (insecticide residues and heavy metals), and natural toxic substances (nitrate, nitrite, cyanide, oxalate, phytate, and trypsin inhibitor) in tubers of Jerusalem artichokes-Kaentawan in the Thai language-grown in four major provinces in Thailand. They were purchased, prepared, homogenized, and freeze-dried for further analysis using standard methods. All Kaentawan samples contained considerable amounts of fructans and dietary fiber (15.4±0.2gand3.2±0.8g/100gfresh weight [FW], respectively), as well as potassium and iron (339±61and0.32±0.05mg/100gFW, respectively). All samples had very low amounts of insecticide residues (37 compounds), cyanide, and trypsin inhibitor, as well as Pb, Cd, nitrate, and nitrite (0.82±0.09, 0.10±0.02, 1.9-17.5, and 0.01-0.24mgkgFW, respectively), in addition to oxalate and phytate (14±9and0.17±0.02mg/100gFW, respectively). This study's data can be used for food composition databases and for safety consumption.
Topics: Food; Fructans; Helianthus; Plant Tubers
PubMed: 28867090
DOI: 10.1016/j.foodchem.2016.09.116 -
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 -
International Journal of Toxicology Sep 2016Potassium cyanide (KCN) is an inhibitor of cytochrome C oxidase causing rapid death due to hypoxia. A well-characterized model of oral KCN intoxication is needed to test...
Potassium cyanide (KCN) is an inhibitor of cytochrome C oxidase causing rapid death due to hypoxia. A well-characterized model of oral KCN intoxication is needed to test new therapeutics under the Food and Drug Administration Animal Rule. Clinical signs, plasma pH and lactate concentrations, biomarkers, histopathology, and cyanide and thiocyanate toxicokinetics were used to characterize the pathology of KCN intoxication in adult and juvenile mice. The acute oral LD50s were determined to be 11.8, 11.0, 10.9, and 9.9 mg/kg in water for adult male, adult female, juvenile male, and juvenile female mice, respectively. The time to death was rapid and dose dependent; juvenile mice had a shorter mean time to death. Juvenile mice displayed a more rapid onset and higher incidence of seizures. The time to observance of respiratory signs and prostration was rapid, but mice surviving beyond 2 hours generally recovered fully within 8 hours. At doses up to the LD50, there were no gross necropsy or microscopic findings clearly attributed to administration of KCN in juvenile or adult CD-1 mice from 24 hours to 28 days post-KCN challenge. Toxicokinetic analysis indicated rapid uptake, metabolism, and clearance of plasma cyanide. Potassium cyanide caused a rapid, dose-related decrease in blood pH and increase in serum lactate concentration. An increase in fatty acid-binding protein 3 was observed at 11.5 mg/kg KCN in adult but not in juvenile mice. These studies provide a characterization of KCN intoxication in adult and juvenile mice that can be used to screen or conduct preclinical efficacy studies of potential countermeasures.
Topics: Animals; Biomarkers; Body Weight; Disease Models, Animal; Drug Evaluation, Preclinical; Fatty Acid-Binding Proteins; Female; Hydrogen-Ion Concentration; Lactic Acid; Lethal Dose 50; Male; Mice; Mice, Inbred Strains; Potassium Cyanide; Thiocyanates; Toxicokinetics
PubMed: 27170682
DOI: 10.1177/1091581816646973 -
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