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Abstract
Flavonoids are plant pigments that are synthesised from phenylalanine, generally display marvelous colors known from flower petals, mostly emit brilliant fluorescence when they are excited by UV light, and are ubiquitous to green plant cells. The flavonoids are used by botanists for taxonomical classification. They regulate plant growth by inhibition of the exocytosis of the auxin indolyl acetic acid, as well as by induction of gene expression, and they influence other biological cells in numerous ways. Flavonoids inhibit or kill many bacterial strains, inhibit important viral enzymes, such as reverse transcriptase and protease, and destroy some pathogenic protozoans. Yet, their toxicity to animal cells is low. Flavonoids are major functional components of many herbal and insect preparations for medical use, e.g., propolis (bee's glue) and honey, which have been used since ancient times. The daily intake of flavonoids with normal food, especially fruit and vegetables, is 1-2 g. Modern authorised physicians are increasing their use of pure flavonoids to treat many important common diseases, due to their proven ability to inhibit specific enzymes, to simulate some hormones and neurotransmitters, and to scavenge free radicals.
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Siegal DM, Curnutte JT, Connolly SJ, Lu G, Conley PB, Wiens BL, Mathur VS, Castillo J, Bronson MD, Leeds JM, Mar FA, Gold A, Crowther MA. Andexanet Alfa for the Reversal of Factor Xa Inhibitor Activity. N Engl J Med 2015; 373:2413-24. [PMID: 26559317 DOI: 10.1056/nejmoa1510991] [Citation(s) in RCA: 744] [Impact Index Per Article: 74.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND Bleeding is a complication of treatment with factor Xa inhibitors, but there are no specific agents for the reversal of the effects of these drugs. Andexanet is designed to reverse the anticoagulant effects of factor Xa inhibitors. METHODS Healthy older volunteers were given 5 mg of apixaban twice daily or 20 mg of rivaroxaban daily. For each factor Xa inhibitor, a two-part randomized placebo-controlled study was conducted to evaluate andexanet administered as a bolus or as a bolus plus a 2-hour infusion. The primary outcome was the mean percent change in anti-factor Xa activity, which is a measure of factor Xa inhibition by the anticoagulant. RESULTS Among the apixaban-treated participants, anti-factor Xa activity was reduced by 94% among those who received an andexanet bolus (24 participants), as compared with 21% among those who received placebo (9 participants) (P<0.001), and unbound apixaban concentration was reduced by 9.3 ng per milliliter versus 1.9 ng per milliliter (P<0.001); thrombin generation was fully restored in 100% versus 11% of the participants (P<0.001) within 2 to 5 minutes. Among the rivaroxaban-treated participants, anti-factor Xa activity was reduced by 92% among those who received an andexanet bolus (27 participants), as compared with 18% among those who received placebo (14 participants) (P<0.001), and unbound rivaroxaban concentration was reduced by 23.4 ng per milliliter versus 4.2 ng per milliliter (P<0.001); thrombin generation was fully restored in 96% versus 7% of the participants (P<0.001). These effects were sustained when andexanet was administered as a bolus plus an infusion. In a subgroup of participants, transient increases in levels of d-dimer and prothrombin fragments 1 and 2 were observed, which resolved within 24 to 72 hours. No serious adverse or thrombotic events were reported. CONCLUSIONS Andexanet reversed the anticoagulant activity of apixaban and rivaroxaban in older healthy participants within minutes after administration and for the duration of infusion, without evidence of clinical toxic effects. (Funded by Portola Pharmaceuticals and others; ANNEXA-A and ANNEXA-R ClinicalTrials.gov numbers, NCT02207725 and NCT02220725.).
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Randomized Controlled Trial |
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744 |
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Schnider TW, Minto CF, Gambus PL, Andresen C, Goodale DB, Shafer SL, Youngs EJ. The influence of method of administration and covariates on the pharmacokinetics of propofol in adult volunteers. Anesthesiology 1998; 88:1170-82. [PMID: 9605675 DOI: 10.1097/00000542-199805000-00006] [Citation(s) in RCA: 679] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Unresolved issues with propofol include whether the pharmacokinetics are linear with dose, are influenced by method of administration (bolus vs. infusion), or are influenced by age. Recently, a new formulation of propofol emulsion, containing disodium edetate (EDTA), was introduced in the United States. Addition of EDTA was found by the manufacturer to significantly reduce bacterial growth. This study investigated the influences of method of administration, infusion rate, patient covariates, and EDTA on the pharmacokinetics of propofol. METHODS Twenty-four healthy volunteers aged 26-81 yr were given a bolus dose of propofol, followed 1 h later by a 60-min infusion. Each volunteer was randomly assigned to an infusion rate of 25, 50, 100, or 200 microg x kg(-1) x min(-1). Each volunteer was studied twice under otherwise identical circumstances: once receiving propofol without EDTA and once receiving propofol with EDTA. The influence of the method of administration and of the volunteer covariates was explored by fitting a three-compartment mamillary model to the data. The influence of EDTA was investigated by direct comparison of the measured concentrations in both sessions. RESULTS The concentrations of propofol with and without EDTA were not significantly different. The concentration measurements after the bolus dose were significantly underpredicted by the parameters obtained just from the infusion data. The kinetics of propofol were linear within the infusion range of 25-200 microg x kg(-1) x min(-1). Age was a significant covariate for Volume2 and Clearance2, as were weight, height, and lean body mass for the metabolic clearance. CONCLUSIONS These results demonstrate that method of administration (bolus vs. infusion), but not EDTA, influences the pharmacokinetics of propofol. Within the clinically relevant range, the kinetics of propofol during infusions are linear regarding infusion rate.
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Abstract
The present review discusses the structure of the anticholinesterase organophosphates (OPs), which are used predominantly as insecticides. OP poisoning can occur in a variety of situations and can be accidental or suicidal. It is common in developing countries. The cholinergic syndrome is caused by acetylcholinesterase inhibition, and diagnosis is based on the clinical signs and symptoms as well as the measurement of inhibition of erythrocyte acetylcholinesterase and/or plasma cholinesterase activity. Antidotal treatment is with atropine, an enzyme reactivator such as pralidoxime and diazepam. Anticholinesterase OPs may produce effects other than the acute cholinergic syndrome, including the intermediate syndrome. Later effects may include organophosphorus-induced delayed neuropathy. Certain OPs are exploited for their anticholinesterase effects, including defoliants such as 'DEF', herbicides such as glyphosate, fire retardants and industrial intermediates. The toxicology of this group is heterogeneous and they may or may not possess anticholinesterase activity.
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Rusconi CP, Scardino E, Layzer J, Pitoc GA, Ortel TL, Monroe D, Sullenger BA. RNA aptamers as reversible antagonists of coagulation factor IXa. Nature 2002; 419:90-4. [PMID: 12214238 DOI: 10.1038/nature00963] [Citation(s) in RCA: 393] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Many therapeutic agents are associated with adverse effects in patients. Anticoagulants can engender acute complications such as significant bleeding that increases patient morbidity and mortality. Antidote control provides the safest means to regulate drug action. For this reason, despite its known limitations and toxicities, heparin use remains high because it is the only anticoagulant that can be controlled by an antidote, the polypeptide protamine. To date, no generalizable strategy for developing drug-antidote pairs has been described. We investigated whether drug-antidote pairs could be rationally designed by taking advantage of properties inherent to nucleic acids to make antidote-controlled anticoagulant agents. Here we show that protein-binding oligonucleotides (aptamers) against coagulation factor IXa are potent anticoagulants. We also show that oligonucleotides complementary to these aptamers can act as antidotes capable of efficiently reversing the activity of these new anticoagulants in plasma from healthy volunteers and from patients who cannot tolerate heparin. This generalizable strategy for rationally designing a drug-antidote pair thus opens up the way for developing safer regulatable therapeutics.
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Silva R, Vilas-Boas V, Carmo H, Dinis-Oliveira RJ, Carvalho F, de Lourdes Bastos M, Remião F. Modulation of P-glycoprotein efflux pump: induction and activation as a therapeutic strategy. Pharmacol Ther 2015; 149:1-123. [PMID: 25435018 DOI: 10.1016/j.pharmthera.2014.11.013] [Citation(s) in RCA: 260] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 11/19/2014] [Indexed: 01/03/2023]
Abstract
P-glycoprotein (P-gp) is an ATP-dependent efflux pump encoded by the MDR1 gene in humans, known to mediate multidrug resistance of neoplastic cells to cancer therapy. For several decades, P-gp inhibition has drawn many significant research efforts in an attempt to overcome this phenomenon. However, P-gp is also constitutively expressed in normal human epithelial tissues and, due to its broad substrate specificity, to its cellular polarized expression in many excretory and barrier tissues, and to its great efflux capacity, it can play a crucial role in limiting the absorption and distribution of harmful xenobiotics, by decreasing their intracellular accumulation. Such a defense mechanism can be of particular relevance at the intestinal level, by significantly reducing the intestinal absorption of the xenobiotic and, consequently, avoiding its access to the target organs. In this review, the current knowledge on this important efflux pump is summarized, and a new focus is brought on the therapeutic interest of inducing and/or activating P-gp for limiting the toxicity caused by its substrates. Several in vivo and in vitro studies validating the use of such a therapeutic strategy are discussed. An extensive literature search for reported P-gp inducers/activators and for the experimental models used in their characterization was conducted. Those studies demonstrate that effective antidotal pathways can be achieved by efficiently promoting the P-gp-mediated efflux of deleterious xenobiotics, resulting in a significant reduction in their intracellular levels and, consequently, in a significant reduction of their toxicity.
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Review |
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260 |
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Baliga R, Zhang Z, Baliga M, Ueda N, Shah SV. In vitro and in vivo evidence suggesting a role for iron in cisplatin-induced nephrotoxicity. Kidney Int 1998; 53:394-401. [PMID: 9461098 DOI: 10.1046/j.1523-1755.1998.00767.x] [Citation(s) in RCA: 234] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Cisplatin is a widely used antineoplastic agent that has nephrotoxicity as a major side effect. The underlying mechanism of this nephrotoxicity is still not well known. Iron has been implicated to play an important role in several models of tissue injury, presumably through the generation of hydroxyl radicals via the Haber-Weiss reaction or other highly toxic free radicals. In the present study we examined the catalytic iron content and the effect of iron chelators in an in vitro model of cisplatin-induced cytotoxicity in LLC-PK1 cells (renal tubular epithelial cells) and in an in vivo model of cisplatin-induced acute renal failure in rats. Exposure of LLC-PK1 cells to cisplatin resulted in a significant increase in bleomycin-detectable iron (iron capable of catalyzing free radical reactions) released into the medium. Concurrent incubation of LLC-PK1 cells with iron chelators including deferoxamine and 1,10-phenanthroline significantly attenuated cisplatin-induced cytotoxicity as measured by lactate dehydrogenase (LDH) release. Bleomycin-detectable iron content was also markedly increased in the kidney of rats treated with cisplatin. Similarly, administration of deferoxamine in rats provided marked functional (as measured by blood urea nitrogen and creatinine) and histological protection against cisplatin-induced acute renal failure. In a separate study, we examined the role of hydroxyl radical in cisplatin-induced nephrotoxicity. Incubation of LLC-PK1 cells with cisplatin caused an increase in hydroxyl radical formation. Hydroxyl radical scavengers, dimethyl sulfoxide, mannitol and benzoic acid, significantly reduced cisplatin-induced cytotoxicity and, treatment with dimethyl sulfoxide or dimethylthiourea provided significant protection against cisplatin-induced acute renal failure. Taken together, our data strongly support a critical role for iron in mediating tissue injury via hydroxyl radical (or a similar oxidant) in this model of nephrotoxicity.
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Casida JE, Gammon DW, Glickman AH, Lawrence LJ. Mechanisms of selective action of pyrethroid insecticides. Annu Rev Pharmacol Toxicol 1983; 23:413-38. [PMID: 6347050 DOI: 10.1146/annurev.pa.23.040183.002213] [Citation(s) in RCA: 232] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Review |
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Weinbroum AA, Flaishon R, Sorkine P, Szold O, Rudick V. A risk-benefit assessment of flumazenil in the management of benzodiazepine overdose. Drug Saf 1997; 17:181-96. [PMID: 9306053 DOI: 10.2165/00002018-199717030-00004] [Citation(s) in RCA: 225] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The worldwide expansion in the use of benzodiazepines has led to their frequent, and often inappropriate, use and to increase in their involvement in self-induced poisoning and iatrogenic overdosing. Flumazenil is a specific and competitive antagonist at the central benzodiazepine receptor, reversing all effects of benzodiazepine agonists without tranquillising or anticonvulsant actions. Incremental intravenous bolus injections of flumazenil 0.1 to 0.3 mg are the most effective and well tolerated in the diagnosis and treatment of pure benzodiazepine overdose; additional boluses or an infusion (0.3 to 0.5 mg/h) can be given to prevent patients from relapsing into coma. Intravenous flumazenil 10 to 20 micrograms/kg is effective in neonates and small children. Intramuscular, oral (20 to 25 mg 3 times daily or as required) and rectal administration may be used as alternatives in long term regimens. Patients with mixed-drug overdose require higher doses (up to 2 mg bolus, approximately equal to 1 mg/h infusion) to regain consciousness. Children and the elderly, chronically ill patients, and pregnant women and their fetuses all respond satisfactorily to flumazenil, but the usefulness of the drug in patients with hepatic encephalopathy and alcohol overdose is debatable. The use of flumazenil results in complete awakening with restoration of upper airway protective reflexes, thus enabling gastric lavage to be performed and transfer of the patient from the emergency room to another hospital department. Resumption of effective spontaneous respiration allows for expeditious extubation, weaning off mechanical ventilation or the avoidance of endotracheal intubation. While flumazenil is not associated with haemodynamic adverse effects, caution should be exercised when using this agent in patients who have co-ingested chloral hydrate to carbamazepine or whose ECG shows abnormalities typical to those seen after overdose with tricyclic antidepressants (TCAs); the use of flumazenil in the presence of these drugs can sometimes induce treatable cardiac dysrrhythmia. Flumazenil per se does not induce adverse effects. Coma reversal by flumazenil may cause mild, short-lived reactions caused by sudden awakening. Withdrawal symptoms in long term benzodiazepine users and seizures in patients who have taken an overdose of TCA or carbamazepine and a benzodiazepine can occur with flumazenil; these symptoms are avoidable by utilising slow flumazenil dose titration.
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Review |
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Kim SH, Henry EC, Kim DK, Kim YH, Shin KJ, Han MS, Lee TG, Kang JK, Gasiewicz TA, Ryu SH, Suh PG. Novel compound 2-methyl-2H-pyrazole-3-carboxylic acid (2-methyl-4-o-tolylazo-phenyl)-amide (CH-223191) prevents 2,3,7,8-TCDD-induced toxicity by antagonizing the aryl hydrocarbon receptor. Mol Pharmacol 2006; 69:1871-8. [PMID: 16540597 DOI: 10.1124/mol.105.021832] [Citation(s) in RCA: 225] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a widespread environmental pollutant with many toxic effects, including endocrine disruption, reproductive dysfunction, immunotoxicity, liver damage, and cancer. These are mediated by TCDD binding to and activating the aryl hydrocarbon receptor (AhR), a basic helix-loop-helix transcription factor. In this regard, targeting the AhR using novel small molecule inhibitors is an attractive strategy for the development of potential preventive agents. In this study, by screening a chemical library composed of approximately 10,000 compounds, we identified a novel compound, 2-methyl-2H-pyrazole-3-carboxylic acid (2-methyl-4-o-tolylazo-phenyl)-amide (CH-223191), that potently inhibits TCDD-induced AhR-dependent transcription. In addition, CH-223191 blocked the binding of TCDD to AhR and inhibited TCDD-mediated nuclear translocation and DNA binding of AhR. These inhibitory effects of CH-223191 prevented the expression of cytochrome P450 enzymes, target genes of the AhR. Unlike many known antagonists of AhR, CH-223191 did not have detectable AhR agonist-like activity or estrogenic potency, suggesting that CH-223191 is a specific antagonist of AhR. It is noteworthy that CH-223191 potently prevented TCDD-elicited cytochrome P450 induction, liver toxicity, and wasting syndrome in mice. Taken together, these results demonstrate that this novel compound, CH-223191, may be a useful agent for the study of AhR-mediated signal transduction and the prevention of TCDD-associated pathology.
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Research Support, N.I.H., Extramural |
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225 |
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Abstract
Nerve agents (sarin, soman, cyclosarin, tabun and VX agent) and pesticides (paraoxon, chlorpyrifos, TEPP) represent extremely toxic group of organophosphorus compounds (OPCs). These compounds inhibit enzyme acetylcholinesterase (AChE, EC 3.1.1.7) via its phosphorylation or phosphonylation at the serine hydroxy group in its active site. Afterwards, AChE is not able to serve its physiological function and intoxicated organism is died due to overstimulation of cholinergic nervous system. The current standard treatment of poisoning with highly toxic OPCs usually consists of the combined administration of anticholinergic drugs (preferably atropine) and AChE reactivators (called "oximes"). Anticholinergic drugs block effects of accumulated neurotransmitter acetylcholine at nicotinic and muscarinic receptor sites, while oximes reactivate AChE inhibited by OPCs. Unfortunately, none from the currently used oximes is sufficiently effective against all known nerve agents and pesticides. Therefore, to find new oximes able to sufficiently reactivate inhibited AChE (regardless of the type of OPCs) is still very important task for medicinal chemistry with the aim to improve the efficacy of antidotal treatment of the acute poisonings mentioned. In this paper, the relationship between chemical structure of AChE reactivators and their ability to reactivate AChE inhibited by several nerve agents and pesticides is summarized. It is shown that there are several structural fragments possibly involving in the structure of proposed AChE reactivators. Finally, an attempt of a future course of new AChE reactivators development is discussed.
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Abstract
Flumazenil is a benzodiazepine receptor antagonist. It is currently used mainly in the anaesthetic and emergency rooms to reverse the effect of exogenous benzodiazepines. Its use in a variety of experimental animal models and in human neuropsychiatric disorders continues to generate a wealth of information on the possible role of the benzodiazepine-GABA(A) receptor complex in their pathogenesis. In addition, labelled with carbon-11, flumazenil has proved to be one of the most successful positron emission tomography ligands stimulating research on the role of the benzodiazepine receptor in these disorders. This review focuses on the current state of play of flumazenil as a therapeutic or investigative agent in neuropsychiatry, citing also the relevant animal models.
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Review |
30 |
170 |
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Blanc EM, Bruce-Keller AJ, Mattson MP. Astrocytic gap junctional communication decreases neuronal vulnerability to oxidative stress-induced disruption of Ca2+ homeostasis and cell death. J Neurochem 1998; 70:958-70. [PMID: 9489715 DOI: 10.1046/j.1471-4159.1998.70030958.x] [Citation(s) in RCA: 169] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We investigated the effect of uncoupling astrocytic gap junctions on neuronal vulnerability to oxidative injury in embryonic rat hippocampal cell cultures. Mixed cultures (neurons growing on an astrocyte monolayer) treated with 18-alpha-glycyrrhetinic acid (GA), an uncoupler of gap junctions, showed markedly enhanced generation of intracellular peroxides (2,7-dichlorofluorescein fluorescence), impairment of mitochondrial function [(dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction], and cell death (lactate dehydrogenase release) following exposure to oxidative insults (FeSO4 and 4-hydroxynonenal). GA alone had little or no effect on basal levels of peroxides, mitochondrial function, or neuronal survival. Intercellular dye transfer analyses revealed extensive astrocyte-astrocyte coupling but no astrocyte-neuron or neuron-neuron coupling in the mixed cultures. Studies of pure astrocyte cultures and microscope analyses of neurons in mixed cultures showed that the increased oxidative stress and cell death in GA-treated cultures occurred only in neurons and not in astrocytes. Antioxidants (propyl gallate and glutathione) blocked the death of neurons exposed to FeSO4/GA. Elevations of neuronal intracellular calcium levels ([Ca2+]i) induced by FeSO4 were enhanced in neurons in mixed cultures exposed to GA. Removal of extracellular Ca2+ and the L-type Ca2+ channel blocker nimodipine prevented impairment of mitochondrial function and cell death induced by FeSO4 and GA, whereas glutamate receptor antagonists were ineffective. Finally, GA exacerbated kainate- and FeSO4-induced injury to pyramidal neurons in organotypic hippocampal slice cultures. The data suggest that interastrocytic gap junctional communication decreases neuronal vulnerability to oxidative injury by a mechanism involving stabilization of cellular calcium homeostasis and dissipation of oxidative stress.
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Xia L, Nordman T, Olsson JM, Damdimopoulos A, Björkhem-Bergman L, Nalvarte I, Eriksson LC, Arnér ESJ, Spyrou G, Björnstedt M. The mammalian cytosolic selenoenzyme thioredoxin reductase reduces ubiquinone. A novel mechanism for defense against oxidative stress. J Biol Chem 2003; 278:2141-6. [PMID: 12435734 DOI: 10.1074/jbc.m210456200] [Citation(s) in RCA: 160] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The selenoprotein thioredoxin reductase (TrxR1) is an essential antioxidant enzyme known to reduce many compounds in addition to thioredoxin, its principle protein substrate. Here we found that TrxR1 reduced ubiquinone-10 and thereby regenerated the antioxidant ubiquinol-10 (Q10), which is important for protection against lipid and protein peroxidation. The reduction was time- and dose-dependent, with an apparent K(m) of 22 microm and a maximal rate of about 12 nmol of reduced Q10 per milligram of TrxR1 per minute. TrxR1 reduced ubiquinone maximally at a physiological pH of 7.5 at similar rates using either NADPH or NADH as cofactors. The reduction of Q10 by mammalian TrxR1 was selenium dependent as revealed by comparison with Escherichia coli TrxR or selenium-deprived mutant and truncated mammalian TrxR forms. In addition, the rate of reduction of ubiquinone was significantly higher in homogenates from human embryo kidney 293 cells stably overexpressing thioredoxin reductase and was induced along with increasing cytosolic TrxR activity after the addition of selenite to the culture medium. These data demonstrate that the selenoenzyme thioredoxin reductase is an important selenium-dependent ubiquinone reductase and can explain how selenium and ubiquinone, by a combined action, may protect the cell from oxidative damage.
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Lewin M, Samuel S, Merkel J, Bickler P. Varespladib (LY315920) Appears to Be a Potent, Broad-Spectrum, Inhibitor of Snake Venom Phospholipase A2 and a Possible Pre-Referral Treatment for Envenomation. Toxins (Basel) 2016; 8:toxins8090248. [PMID: 27571102 PMCID: PMC5037474 DOI: 10.3390/toxins8090248] [Citation(s) in RCA: 157] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 08/11/2016] [Accepted: 08/15/2016] [Indexed: 01/07/2023] Open
Abstract
Snakebite remains a neglected medical problem of the developing world with up to 125,000 deaths each year despite more than a century of calls to improve snakebite prevention and care. An estimated 75% of fatalities from snakebite occur outside the hospital setting. Because phospholipase A2 (PLA2) activity is an important component of venom toxicity, we sought candidate PLA2 inhibitors by directly testing drugs. Surprisingly, varespladib and its orally bioavailable prodrug, methyl-varespladib showed high-level secretory PLA2 (sPLA2) inhibition at nanomolar and picomolar concentrations against 28 medically important snake venoms from six continents. In vivo proof-of-concept studies with varespladib had striking survival benefit against lethal doses of Micrurus fulvius and Vipera berus venom, and suppressed venom-induced sPLA2 activity in rats challenged with 100% lethal doses of M. fulvius venom. Rapid development and deployment of a broad-spectrum PLA2 inhibitor alone or in combination with other small molecule inhibitors of snake toxins (e.g., metalloproteases) could fill the critical therapeutic gap spanning pre-referral and hospital setting. Lower barriers for clinical testing of safety tested, repurposed small molecule therapeutics are a potentially economical and effective path forward to fill the pre-referral gap in the setting of snakebite.
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Research Support, Non-U.S. Gov't |
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Fu W, Luo H, Parthasarathy S, Mattson MP. Catecholamines potentiate amyloid beta-peptide neurotoxicity: involvement of oxidative stress, mitochondrial dysfunction, and perturbed calcium homeostasis. Neurobiol Dis 1998; 5:229-43. [PMID: 9848093 DOI: 10.1006/nbdi.1998.0192] [Citation(s) in RCA: 142] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Oxidative stress and mitochondrial dysfunction are implicated in the neuronal cell death that occurs in physiological settings and in neurodegenerative disorders. In Alzheimer's disease (AD) degenerating neurons are associated with deposits of amyloid beta-peptide (A beta), and there is evidence for increased membrane lipid peroxidation and protein oxidation in the degenerating neurons. Cell culture studies have shown that A beta can disrupt calcium homeostasis and induce apoptosis in neurons by a mechanism involving oxidative stress. We now report that catecholamines (norepinephrine, epinephrine, and dopamine) increase the vulnerability of cultured hippocampal neurons to A beta toxicity. The catecholamines were effective in potentiating A beta toxicity at concentrations of 10-200 microM, with the higher concentrations (100-200 microM) themselves inducing cell death. Serotonin and acetylcholine were not neurotoxic and did not modify A beta toxicity. Levels of membrane lipid peroxidation, and cytoplasmic and mitochondrial reactive oxygen species, were increased following exposure to neurons to A beta, and catecholamines exacerbated the oxidative stress. Subtoxic concentrations of catecholamines exacerbated decreases in mitochondrial energy charge and transmembrane potential caused by A beta, and higher concentrations of catecholamines alone induced mitochondrial dysfunction. Antioxidants (vitamin E, glutathione, and propyl gallate) protected neurons against the damaging effects of A beta and catecholamines, whereas the beta-adrenergic receptor antagonist propanolol and the dopamine (D1) receptor antagonist SCH23390 were ineffective. Measurements of intracellular free Ca2+ ([Ca2+]i) showed that A beta induced a slow elevation of [Ca2+]i which was greatly enhanced in cultures cotreated with catecholamines. Collectively, these data indicate a role for catecholamines in exacerbating A beta-mediated neuronal degeneration in AD and, when taken together with previous findings, suggest roles for oxidative stress induced by catecholamines in several different neurodegenerative conditions.
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Mahfoud R, Maresca M, Garmy N, Fantini J. The mycotoxin patulin alters the barrier function of the intestinal epithelium: mechanism of action of the toxin and protective effects of glutathione. Toxicol Appl Pharmacol 2002; 181:209-18. [PMID: 12079430 DOI: 10.1006/taap.2002.9417] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Patulin is a mycotoxin mainly found in apple and apple products. In addition to being toxic for animals, mutagenic, carcinogenic and teratogenic, patulin induces intestinal injuries, including epithelial cell degeneration, inflammation, ulceration, and hemorrhages. In a study of the cellular mechanisms associated with the intestinal toxicity of patulin, two human epithelial intestinal cell lines (HT-29-D4 and Caco-2-14) were exposed to the mycotoxin. Micromolar concentrations of patulin were found to induce a rapid and dramatic decrease of transepithelial resistance (TER) in both cell lines without major signs of toxicity as assessed by the LDH release assay. Since TER reflects the organization of tight junctions, these data indicate that patulin affected the barrier function of the intestinal epithelium. The inhibitory effect of patulin on TER was closely associated with its reactivity for SH groups: (i) cysteine and glutathione prevented the cells from patulin injury; (ii) patulin toxicity was potentiated by buthionine sulfoximine, a specific glutathione-depleting agent; (iii) treatment of the cells with N-ethylmaleimide, a compound known to react with SH groups, resulted in a marked decrease of TER. Moreover, the inhibitory effect of patulin on TER was mimicked and potentiated by phenylarsine oxide, a specific inhibitor of protein tyrosine phosphatase (PTP). This cellular enzyme is a key regulator of intestinal epithelial barrier function. The active site of PTP contains a cysteine residue (Cys215) that is essential for phosphatase activity. Sulfhydryl-reacting compounds such as acetaldehyde decrease TER through covalent modification of Cys215 of PTP. We propose that the toxicity of patulin for intestinal cells involves, among other potential mechanisms, an inactivation of the active site of PTP.
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Nachon F, Brazzolotto X, Trovaslet M, Masson P. Progress in the development of enzyme-based nerve agent bioscavengers. Chem Biol Interact 2013; 206:536-44. [PMID: 23811386 DOI: 10.1016/j.cbi.2013.06.012] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 06/15/2013] [Accepted: 06/18/2013] [Indexed: 11/17/2022]
Abstract
Acetylcholinesterase is the physiological target for acute toxicity of nerve agents. Attempts to protect acetylcholinesterase from phosphylation by nerve agents, is currently achieved by reversible inhibitors that transiently mask the enzyme active site. This approach either protects only peripheral acetylcholinesterase or may cause side effects. Thus, an alternative strategy consists in scavenging nerve agents in the bloodstream before they can reach acetylcholinesterase. Pre- or post-exposure administration of bioscavengers, enzymes that neutralize and detoxify organophosphorus molecules, is one of the major developments of new medical counter-measures. These enzymes act either as stoichiometric or catalytic bioscavengers. Human butyrylcholinesterase is the leading stoichiometric bioscavenger. Current efforts are devoted to its mass production with care to pharmacokinetic properties of the final product for extended lifetime. Development of specific reactivators of phosphylated butyrylcholinesterase, or variants with spontaneous reactivation activity is also envisioned for rapid in situ regeneration of the scavenger. Human paraoxonase 1 is the leading catalytic bioscavenger under development. Research efforts focus on improving its catalytic efficiency toward the most toxic isomers of nerve agents, by means of directed evolution-based strategies. Human prolidase appears to be another promising human enzyme. Other non-human efficient enzymes like bacterial phosphotriesterases or squid diisopropylfluorophosphatase are also considered though their intrinsic immunogenic properties remain challenging for use in humans. Encapsulation, PEGylation and other modifications are possible solutions to address this problem as well as that of their limited lifetime. Finally, gene therapy for in situ generation and delivery of bioscavengers is for the far future, but its proof of concept has been established.
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Review |
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van Helden HP, Busker RW, Melchers BP, Bruijnzeel PL. Pharmacological effects of oximes: how relevant are they? Arch Toxicol 1996; 70:779-86. [PMID: 8911635 DOI: 10.1007/s002040050340] [Citation(s) in RCA: 123] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The increased international concern about the threat of military and terroristic use of nerve agents, prompted us to critically consider the expected value of the currently available oxime treatment of nerve agent poisoning. Although oximes have been designed to reactivate the inhibited acetylcholinesterase (AChE), clinical experience has indicated that they are not always very effective as reactivators and at this very moment none of them can be regarded as a broad-spectrum antidote. In spite of this drawback, oximes are worth further investigating, since recent data derived from soman or tabun lethally intoxicated non-human primates suggest that the oxime HI-6 may exert a pharmacological effect that is not related to reactivation of inhibited AChE, but still leads to survival. This pharmacological effect causes recovery of neuronal transmission in the respiratory centres of the brain and recovery of neuromuscular transmission in the diaphragm. These findings have stimulated research to reveal the pharmacological basis of these effects in order to find drugs which could be more effective and less toxic than the available oximes. Since cholinergic drugs were able to exert this effect, a new concept for further treatment is suggested: maintenance of neuronal transmission in spite of continued AChE-inhibition by pharmacological manipulation of the cholinergic receptor. This should renew interest in the diverse pharmacological effects of oximes to reach a more effective treatment in the future.
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Review |
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Abbès S, Ouanes Z, ben Salah-Abbès J, Houas Z, Oueslati R, Bacha H, Othman O. The protective effect of hydrated sodium calcium aluminosilicate against haematological, biochemical and pathological changes induced by Zearalenone in mice. Toxicon 2006; 47:567-74. [PMID: 16563452 DOI: 10.1016/j.toxicon.2006.01.016] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2005] [Revised: 01/12/2006] [Accepted: 01/12/2006] [Indexed: 11/28/2022]
Abstract
Hydrated sodium calcium aluminosilicate (HSCAS), an anticaking agent for mixed feed, was added alone or simultaneously with a toxic Zearalenone (ZEN) dose to balb/c mice and was evaluated for its ability to restore damages induced by ZEN. The latter is a mycotoxin produced by fusarium genera; it is mainly known to induce several toxic effects such as hepatotoxicity, immunotoxicity and nephrotoxicity on animals and humans. The experimental approach consisted of eight treatments of six mice each by 400 mg/kg bw or 5 g/kg bw of HSCAS. Two experimental groups have received respectively ZEN alone at 40 (8% of LD50) and at 500 mg/kg bw (LD50). Two other groups have received ZEN at 40 or 500 mg/kg bw combined respectively with HSCAS at 400 mg/kg bw and 5 g/kg bw. The control groups received water or olive oil. Forty-eight hours after treatment, blood samples were collected for haematological and serum biochemical parameters measurements. ZEN treatment significantly increased hematocrit, haemoglobin, white blood cells: lymphocytes, eosinophils, neutrophils, monocytes and the most of biochemical serum parameters; it significantly reduced platelets and induced degenerative changes in the hepatic and renal tissues; while, the mixture of HSCAS with ZEN induced a reestablishment of haematological parameters, levels of serum biochemical enzyme activities and histological pictures of both liver and kidney. It also prevented general toxicity of ZEN. This was observed by the shift of LD50 for this toxin. Thus, our data strongly suggested that deleterious effects of ZEN could be overcome or, at least, significantly were diminished by HSCAS. Moreover, this sorbent by itself did not show any toxic effects.
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Aaseth J, Skaug MA, Cao Y, Andersen O. Chelation in metal intoxication--Principles and paradigms. J Trace Elem Med Biol 2015; 31:260-6. [PMID: 25457281 DOI: 10.1016/j.jtemb.2014.10.001] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 08/14/2014] [Accepted: 10/06/2014] [Indexed: 01/19/2023]
Abstract
The present review provides an update of the general principles for the investigation and use of chelating agents in the treatment of intoxications by metals. The clinical use of the old chelators EDTA (ethylenediamine tetraacetate) and BAL (2,3-dimercaptopropanol) is now limited due to the inconvenience of parenteral administration, their own toxicity and tendency to increase the neurotoxicity of several metals. The hydrophilic dithiol chelators DMSA (meso-2,3-dimercaptosuccinic acid) and DMPS (2,3-dimercapto-propanesulphonate) are less toxic and more efficient than BAL in the clinical treatment of heavy metal poisoning, and available as capsules for oral use. In copper overload, DMSA appears to be a potent antidote, although d-penicillamine is still widely used. In the chelation of iron, the thiols are inefficient, since iron has higher affinity for ligands with nitrogen and oxygen, but the new oral iron antidotes deferiprone and desferasirox have entered into the clinical arena. Comparisons of these agents and deferoxamine infusions are in progress. General principles for research and development of new chelators are briefly outlined in this review.
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Review |
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105 |
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Koplovitz I, Stewart JR. A comparison of the efficacy of HI6 and 2-PAM against soman, tabun, sarin, and VX in the rabbit. Toxicol Lett 1994; 70:269-79. [PMID: 8284794 DOI: 10.1016/0378-4274(94)90121-x] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
This study compared the efficacy of HI6 and 2-PAM against nerve agent (soman, tabun, sarin, and VX)-induced lethality in the atropinesterase-free rabbits pretreated with vehicle (controls) or pyridostigmine. Treatment was administered at signs or 2 min after agent challenge and consisted of oxime (100 mumol/kg) + atropine (13 mg/kg) (alone or together with diazepam). Twenty-four-h LD50 values were calculated for soman- and tabun-intoxicated animals, whereas 24-h survival was noted in animals given 10 LD50s of sarin or VX. In pyridostigmine and control rabbits intoxicated with soman and treated with oxime + atropine (alone or together with diazepam), HI6 was 3-5 times more effective than 2-PAM. In contrast, HI6 was less effective than 2-PAM against tabun poisoning. In pyridostigmine-pretreated animals exposed to tabun, efficacy was increased more than 3-fold when compare to tabun-challenged animals treated with atropine + HI6 alone. Both oximes were highly effective against sarin and VX. These findings suggest that HI6 could replace 2-PAM as therapy for nerve agent poisoning, because it is superior to 2-PAM against soman, and when used in pyridostigmine-pretreated animals, it affords excellent protection against all four nerve agents when used in combination with atropine (alone or together with diazepam) therapy.
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Clement JG. Toxicology and pharmacology of bispyridium oximes--insight into the mechanism of action vs Soman poisoning in vivo. FUNDAMENTAL AND APPLIED TOXICOLOGY : OFFICIAL JOURNAL OF THE SOCIETY OF TOXICOLOGY 1981; 1:193-202. [PMID: 6897946 DOI: 10.1016/s0272-0590(81)80058-9] [Citation(s) in RCA: 101] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
HI-6 was the least toxic and the most efficacious oxime examined against Soman poisoning with a high safety ratio between 26-30. Reactivation of peripheral acetylcholinesterase following Soman poisoning was more important in the beneficial therapeutic action of HI-6 than reactivation of central acetylcholinesterase. HI-6 reactivated Sarin-inhibited but not Tabun-inhibited acetylcholinesterase both peripherally and centrally. HI-6 passes the blood brain barrier as evidenced by its reactivation centrally of Sarin-inhibited acetylcholinesterase. Soman-inhibited enzyme was not aged in vivo by 30 min. In vivo diaphragm acetylcholinesterase was inhibited to a greater extent by Soman, Sarin and Tabun than intercostal muscle acetylcholinesterase. In vitro diaphragm and intercostal muscle acetylcholinesterase had similar IC50 values for Soman. HI-6 has antimuscarinic and antinicotinic activity in addition to its previously reported ganglion blocking activity (Lundy and Tremblay, 1979). These additional pharmacological actions of HI-6 may play a role in the therapeutic action of HI-6 (at the higher concentrations). The results suggest that peripheral acetylcholinesterase in the rat diaphragm is the primary lesion in Soman poisoning. The beneficial action of HI-6 in rats versus Soman poisoning is due to reactivation of diaphragm acetylcholinesterase.
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Donohue TM, Osna NA, Clemens DL. Recombinant Hep G2 cells that express alcohol dehydrogenase and cytochrome P450 2E1 as a model of ethanol-elicited cytotoxicity. Int J Biochem Cell Biol 2006; 38:92-101. [PMID: 16181800 DOI: 10.1016/j.biocel.2005.07.010] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2005] [Accepted: 07/27/2005] [Indexed: 02/08/2023]
Abstract
HepG2 cells were transfected with recombinant plasmids, one carrying the murine alcohol dehydrogenase (ADH) gene and the other containing the gene encoding human cytochrome P450 2E1 (CYP2E1). One of recombinant clones called VL-17A exhibited ADH and CYP2E1 specific activities comparable to those in isolated rat hepatocytes. VL-17A cells oxidized ethanol and generated acetaldehyde, the levels of which depended upon the initial ethanol concentration. Compared with unexposed VL-17A cells, ethanol exposure increased the cellular redox (lactate:pyruvate ratio) and caused cell toxicity, indicated by increased leakage of lactate dehydrogenase into the medium,. Exposure of VL-17A cells to 100mM ethanol significantly elevated caspase 3 activity, an indicator of apoptosis, but this ethanol concentration did not affect caspase 3 activity in parental HepG2 cells. Because ethanol consumption causes a decline in hepatic protein catabolism, we examined the influence of ethanol exposure on proteasome activity in HepG2, VL-17A, E-47 (CYP2E1(+)) and VA-13 (ADH(+)) cells. Exposure to 100mM ethanol caused a 25% decline in the chymotrypsin-like activity of the proteasome in VL-17A cells, but the enzyme was unaffected in the other cell types. This inhibitory effect on the proteasome was blocked when ethanol metabolism was blocked by 4-methyl pyrazole. We conclude that recombinant VL-17A cells, which express both ADH and CYP2E1 exhibit hepatocyte-like characteristics in response to ethanol. Furthermore, the metabolism of ethanol by these cells via ADH and CYP2E1 is sufficient to bring about an inhibition of proteasome activity that may lead to apoptotic cell death.
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Comparative Study |
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100 |