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Frontiers in Plant Science 2017Arbuscular mycorrhizal fungi (AMF) are crucial components of fertile soils, able to provide several ecosystem services for crop production. Current economic, social and...
Arbuscular mycorrhizal fungi (AMF) are crucial components of fertile soils, able to provide several ecosystem services for crop production. Current economic, social and legislative contexts should drive the so-called "second green revolution" by better exploiting these beneficial microorganisms. Many challenges still need to be overcome to better understand the mycorrhizal symbiosis, among which (i) the biotrophic nature of AMF, constraining their production, while (ii) phosphate acts as a limiting factor for the optimal mycorrhizal inoculum application and effectiveness. Organism fitness and adaptation to the changing environment can be driven by the modulation of mitochondrial respiratory chain, strongly connected to the phosphorus processing. Nevertheless, the role of the respiratory function in mycorrhiza remains largely unexplored. We hypothesized that the two mitochondrial respiratory chain components, alternative oxidase (AOX) and cytochrome oxidase (COX), are involved in specific mycorrhizal behavior. For this, a complex approach was developed. At the pre-symbiotic phase (axenic conditions), we studied phenotypic responses of spores with two AOX and COX inhibitors [respectively, salicylhydroxamic acid (SHAM) and potassium cyanide (KCN)] and two growth regulators (abscisic acid - ABA and gibberellic acid - Ga3). At the symbiotic phase, we analyzed phenotypic and transcriptomic (genes involved in respiration, transport, and fermentation) responses in biosystem (glasshouse conditions): we monitored the effects driven by ABA, and explored the modulations induced by SHAM and KCN under five phosphorus concentrations. KCN and SHAM inhibited spore germination while ABA and Ga3 induced differential spore germination and hyphal patterns. ABA promoted mycorrhizal colonization, strong arbuscule intensity and positive mycorrhizal growth dependency (MGD). In ABA treated plants, induced down-regulation of gene isoforms and up-regulation of genes involved in plant COX pathway. In all phosphorus (P) concentrations, blocking AOX or COX induced opposite mycorrhizal patterns : KCN induced higher -type arbuscule density, positive MGD but lower root colonization compared to SHAM, which favored -type formation and negative MGD. Following our results and current state-of-the-art knowledge, we discuss metabolic functions linked to respiration that may occur within mycorrhizal behavior. We highlight potential connections between AOX pathways and fermentation, and we propose new research and mycorrhizal application perspectives.
PubMed: 28424712
DOI: 10.3389/fpls.2017.00417 -
Nigerian Journal of Physiological... Dec 2018Cyanide is a potent neurotoxic substance that can initiate series of intracellular reactions leading to oxidativestress. To evaluate effect of sublethal administration...
Cyanide is a potent neurotoxic substance that can initiate series of intracellular reactions leading to oxidativestress. To evaluate effect of sublethal administration of potassium cyanide (KCN) on sensorimotor functions and long termvisuo-spatial learning and memory in adult Swiss mice and possible ameliorative role of vitamins A and E. These vitaminsA and E (dietary) are antioxidants that have scavenging properties against free radicals and reactive oxygen species as aresult of oxidative stress induced by cyanide. Thirty-five mice weighing between 18-22 g were used for the study. Theanimals were randomly divided into five groups (n = 7) and exposed to sublethal concentration of potassium cyanide (10%LD50; 1.5 mg/kg). KCN was administered orally while vitamin A (25 mg/kg) and vitamin E (50 mg/kg) were administeredintra-peritoneal (IP) once daily for 28 days. Potassium cyanide (KCN) was first administered and after 10 minutes intervals,followed by vitamin A and then E after 5 minutes, vitamin E were administered across the different treatment groups. Micewere examined for signs of toxicity. Vitamins pre-treatment ameliorated toxic signs. In the dynamics of wire grid, coathanger and stationary beam test, the latency to fall in weeks 2 and 4 were statistically significant. In acquisition and retention,using elevated plus maze (EPM), KCN treated group recorded high transfer latencies in seconds (50.40±1.72 secs) and(57.60±0.93 secs) as compared to group IV (29.40±0.68 secs; 5.60±0.60 secs). Cyanide is a neurotoxin that affects motorfunctions with progressive decline in motor strength and coordination. KCN affects acquisition and retention memory whilepre-treatment with antioxidant vitamins A and E ameliorated these deficits.
Topics: Animals; Antioxidants; Memory; Mice; Neurotoxicity Syndromes; Oxidative Stress; Potassium Cyanide; Reactive Oxygen Species; Vitamin A; Vitamin E
PubMed: 30837773
DOI: No ID Found -
Shock (Augusta, Ga.) Mar 2017Our objective was to determine how circulatory failure develops following systemic administration of potassium cyanide (KCN). We used a noninhaled modality of...
Our objective was to determine how circulatory failure develops following systemic administration of potassium cyanide (KCN). We used a noninhaled modality of intoxication, wherein the change in breathing pattern would not influence the diffusion of CN into the blood, akin to the effects of ingesting toxic levels of CN. In a group of 300 to 400 g rats, CN-induced coma (CN i.p., 7 mg/kg) produced a central apnea within 2 to 3 min along with a potent and prolonged gasping pattern leading to autoresuscitation in 38% of the animals. Motor deficits and neuronal necrosis were nevertheless observed in the surviving animals. To clarify the mechanisms leading to potential autoresuscitation versus asystole, 12 urethane-anesthetized rats were then exposed to the lowest possible levels of CN exposure that would lead to breathing depression within 7 to 8 min; this dose averaged 0.375 mg/kg/min i.v. At this level of intoxication, a cardiac depression developed several minutes only after the onset of the apnea, leading to cardiac asystole as PaO2 reached value approximately 15 Torr, unless breathing was maintained by mechanical ventilation or through spontaneous gasping. Higher levels of KCN exposure in 10 animals provoked a primary cardiac depression, which led to a rapid cardiac arrest by pulseless electrical activity (PEA) despite the maintenance of PaO2 by mechanical ventilation. These effects were totally unrelated to the potassium contained in KCN. It is concluded that circulatory failure can develop as a direct consequence of CN-induced apnea but in a narrow range of exposure. In this "low" range, maintaining pulmonary gas exchange after exposure, through mechanical ventilation (or spontaneous gasping), can reverse cardiac depression and restore spontaneous breathing. At higher level of intoxication, cardiac depression is to be treated as a specific and spontaneously irreversible consequence of CN exposure, leading to a PEA.
Topics: Animals; Apnea; Blood Gas Analysis; Cyanides; Male; Potassium Chloride; Pulmonary Gas Exchange; Rats; Rats, Sprague-Dawley; Shock
PubMed: 27513083
DOI: 10.1097/SHK.0000000000000732 -
Biology Sep 2022Recombinant DNA technology offered the creation of new combinations of DNA segments that are not found together in nature. The present study aimed to produce an...
Recombinant DNA technology offered the creation of new combinations of DNA segments that are not found together in nature. The present study aimed to produce an ecofriendly bioremediation model to remediate cyanide pollution from a polluted marine system. Cyanide is a known toxic compound produced through natural and anthropogenic activities. An -mediated genetic transformation technique was used to generate transformed using plant expression vector pTRA-K-cTp carries isolated coding sequence of the cyanobacterial cyanase gene () isolated from (PCC6803). qRT-PCR analysis showed the overexpression of in transgenic , as compared with the respective wild type. Growth parameters and biochemical analyses were performed under cyanide stress conditions using transgenic and wild for evaluating the effect of the presence of the cyanobacterial cyanase gene in algae. The transgenic strain () showed promising results for cyanide bioremediation in polluted water samples. Cyanide depletion assays and algal growth showed a significant resistance in the transgenic type against cyanide stress, as compared to the wild type. Genetically modified alga showed the ability to phytoremediate a high level of potassium cyanide (up to150 mg/L), as compared to the wild type. The presence of the gene has induced a protection response in , which was shown in the results of growth parameter analyses. Therefore, the present study affirms that transgenic the coding gene is a potential effective ecofriendly bioremediator model for the remediation of cyanide pollutants in fresh water.
PubMed: 36290324
DOI: 10.3390/biology11101420 -
Medicinal Research Reviews Nov 2019Tyrosine kinase inhibitors (TKI) are small heterocyclic molecules targeting transmembrane and cytoplasmic tyrosine kinases that have met with considerable success in... (Review)
Review
Tyrosine kinase inhibitors (TKI) are small heterocyclic molecules targeting transmembrane and cytoplasmic tyrosine kinases that have met with considerable success in clinical oncology. TKI are associated with toxicities including liver injury that may be serious and even life-threatening. Many of them require warnings in drug labeling against liver injury, and five of them have Black Box Warning (BBW) labels. Although drug-induced liver injury is a matter of clinical and industrial concern, little is known about the underlying mechanisms that likely involve reactive metabolites (RM). RM are electrophiles or radicals originating from the metabolic activation of particular functional groups, known as structural alerts or toxicophores. RM are able to covalently bind to proteins and macromolecules, causing cellular damage and even cell death. If the adducted protein is the enzyme involved in RM formation, time-dependent inhibition of the enzyme-also called mechanism-based inhibition (MBI) or inactivation-can occur and lead to pharmacokinetic drug-drug interactions. To mitigate RM liabilities, common practice in drug development includes avoiding structural alerts and assessing RM formation via RM trapping screens with soft and hard nucleophiles (glutathione, potassium cyanide, and methoxylamine) in liver microsomes. RM-positive derivatives are further optimized to afford drug candidates with blocked or minimized bioactivation potential. However, different structural alerts are still commonly used scaffolds in drug design, including in TKI structures. This review focuses on the current state of knowledge of the relations among TKI structures, bioactivation pathways, RM characterization, and hepatotoxicity and cytochrome P450 MBI in vitro.
Topics: Animals; Chemical and Drug Induced Liver Injury; Cytochrome P-450 Enzyme System; Drug Interactions; Glucuronosyltransferase; Humans; Protein Kinase Inhibitors; Time Factors
PubMed: 31111528
DOI: 10.1002/med.21577 -
International Journal of Molecular... Jun 2021A novel cytoplasmic dye-decolorizing peroxidase from was investigated that oxidizes anthraquinone dyes, lignin model compounds, and general peroxidase substrates such...
A novel cytoplasmic dye-decolorizing peroxidase from was investigated that oxidizes anthraquinone dyes, lignin model compounds, and general peroxidase substrates such as ABTS efficiently. Unlike related enzymes, an aspartate residue replaces the first glycine of the conserved GXXDG motif in DyPA. In solution, DyPA exists as a stable dimer with the side chain of Asp146 contributing to the stabilization of the dimer interface by extending the hydrogen bond network connecting two monomers. To gain mechanistic insights, we solved the DyPA structures in the absence of substrate as well as in the presence of potassium cyanide and veratryl alcohol to 1.7, 1.85, and 1.6 Å resolution, respectively. The active site of DyPA has a hexa-coordinated heme iron with a histidine residue at the proximal axial position and either an activated oxygen or CN molecule at the distal axial position. Asp149 is in an optimal conformation to accept a proton from HO during the formation of compound I. Two potential distal solvent channels and a conserved shallow pocket leading to the heme molecule were found in DyPA. Further, we identified two substrate-binding pockets per monomer in DyPA at the dimer interface. Long-range electron transfer pathways associated with a hydrogen-bonding network that connects the substrate-binding sites with the heme moiety are described.
Topics: Catalysis; Catalytic Domain; Coloring Agents; Crystallography, X-Ray; Dictyostelium; Heme; Hydrogen Bonding; Hydrogen Peroxide; Oxidation-Reduction; Peroxidase
PubMed: 34200865
DOI: 10.3390/ijms22126265 -
Methods in Molecular Biology (Clifton,... 2024Various bacterial species are associated with plant roots. However, symbiotic and free-living plant growth-promoting bacteria (PGPB) can only help plants to grow and...
Various bacterial species are associated with plant roots. However, symbiotic and free-living plant growth-promoting bacteria (PGPB) can only help plants to grow and develop under normal and stressful conditions. Several biochemical and in vitro assays were previously designed to differentiate between the PGPB and other plant-associated bacterial strains. This chapter describes and summarizes some of these assays and proposes a strategy to screen for PGPB. To determine the involvement of the PGPB in abiotic stress tolerance, assays for the ability to produce 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, ammonium, gibberellic acid (GA), indole acetic acid (IAA), and microbial volatile organic compounds (mVOCs) are described in this chapter. Additionally, assays to show the capacity to solubilize micronutrients such as potassium, phosphorus, and zinc by bacteria were also summarized in this chapter. To determine the contribution of the PGPB in biotic stress tolerance in plants, Fe-siderophore, hydrogen cyanide, and antibiotic and antifungal metabolites production assays were described. Moreover, assays to investigate the growth-promotion activities of a bacterium strain on plants, using the gnotobiotic root elongation, in vitro, and pots assays, were explained. Finally, an assay for the localization of endophytic bacterium in plant tissues was also presented in this chapter. Although the assays described in this chapter can give evidence of the nature of the mechanism behind the PGPB actions, other unknown growth-promoting means are yet to decipher, and until then, new methodologies will be developed.
Topics: Stress, Physiological; Bacteria; Plant Roots; Plant Growth Regulators; Plant Development; Indoleacetic Acids; Symbiosis; Plants; Soil Microbiology; Gibberellins; Volatile Organic Compounds
PubMed: 38869802
DOI: 10.1007/978-1-0716-3973-3_19 -
Plant, Cell & Environment Nov 2021Flooding is a major environmental constraint that obliges plants to adopt plastic responses in order to cope with it. When partially submerged, tomato plants undergo...
Flooding is a major environmental constraint that obliges plants to adopt plastic responses in order to cope with it. When partially submerged, tomato plants undergo profound changes involving rearrangements in their morphology and metabolism. In this work, we observed that partial submergence markedly dampens root respiration and halts root growth. However, the flooded hypocotyl surprisingly enhances oxygen consumption. Previous results demonstrated that aerenchyma formation in the submerged tomato stem re-establishes internal oxygen tension, making aerobic respiration possible. Indeed, potassium cyanide abruptly stops oxygen uptake, indicating that the cytochrome c pathway is likely to be engaged. Furthermore, we found out that leaf-derived sugars accumulate in large amounts in hypocotyls of flooded plants. Girdling and feeding experiments point to sucrose as the main carbon source for respiration. Consistently, submerged hypocotyls are characterized by high sucrose synthase activity, indicating that sucrose is cleaved and channelled into respiration. Since inhibition of hypocotyl respiration significantly prevents sugar build-up, it is suggested that a high respiration rate is required for sucrose unloading from phloem. As substrate availability increases, respiration is fuelled even more, leading to a maintained allocation of sugars to flooded hypocotyls.
Topics: Floods; Hypocotyl; Solanum lycopersicum; Plant Roots; Plant Stems; Sucrose
PubMed: 34268805
DOI: 10.1111/pce.14152 -
Drug Metabolism and Bioanalysis Letters Dec 2023Everolimus, an allosteric mechanistic target of rapamycin (mTOR) inhibitor, recently demonstrated the therapeutic value of mTOR inhibitors for Central Nervous System...
BACKGROUND
Everolimus, an allosteric mechanistic target of rapamycin (mTOR) inhibitor, recently demonstrated the therapeutic value of mTOR inhibitors for Central Nervous System (CNS) indications driven by hyperactivation of mTOR. A newer, potent brain-penetrant analog of everolimus, referred to as (1) in this manuscript [(S)-3-methyl-4-(7-((R)-3-methylmorpholino)-2-(thiazol-4-yl)-3H-imidazo[4,5-b]pyridin-5-yl)morpholine,(1)] catalytically inhibits mTOR function in the brain and increases the lifespan of mice with neuronal mTOR hyperactivation.
INTRODUCTION
Early evaluation of the safety of 1 was conducted in cynomolgus monkeys in which oral doses were administered to three animals in a rising-dose fashion (from 2 to 30 mg/kg/day). 1 produced severe toxicity including the evidence of hepatic toxicity, along with non-dose proportional increases in drug exposure. Investigations of cross-species hepatic bioactivation of 1 were conducted to assess whether the formation of reactive drug metabolites was associated with the mechanism of liver toxicity.
METHOD
1 contained two morpholine rings known as structural alerts and can potentially form reactive intermediates through oxidative metabolism. Bioactivation of 1 was investigated in rat, human and monkey liver microsomes fortified with trapping agents such as methoxylamine or potassium cyanide.
RESULTS
Our results suggest that bioactivation of the morpholine moieties to reactive intermediates may have been involved in the mechanism of liver toxicity observed with 1. Aldehyde intermediates trappable by methoxylamine were identified in rat and monkey liver microsomal studies. In addition, a total of four cyano conjugates arising from the formation of iminium ion intermediates were observed and identified. These findings may potentially explain the observed monkey toxicity. Interestingly, methoxylamine or cyano adducts of 1 were not observed in human liver microsomes.
CONCLUSION
The bioactivation of 1 appears to be species-specific. Circumstantial evidence for the toxicity derived from 1 point to the formation of iminium ion intermediates trappable by cyanide in monkey liver microsomes. The cyano conjugates were only observed in monkey liver microsomes, potentially pointing to cause at least the hepatotoxicity observed in monkeys. In contrast, methoxylamine conjugates were detected in both rat and monkey liver microsomes, with only a trace amount in human liver microsomes. Cyano conjugates were not observed in human liver microsomes, challenging the team on the drugability and progressivity of 1 through drug development. The mechanisms for drug-induced liver toxicity are multifactorial. These results are highly suggestive that the iminium ion may be an important component in the mechanism of liver toxicity 1 observed in the monkey.
PubMed: 38047363
DOI: 10.2174/0118723128260455231104180653 -
Scientific Reports Feb 2016Hydrogen sulfide is a highly toxic gas-second only to carbon monoxide as a cause of inhalational deaths. Its mechanism of toxicity is only partially known, and no...
Hydrogen sulfide is a highly toxic gas-second only to carbon monoxide as a cause of inhalational deaths. Its mechanism of toxicity is only partially known, and no specific therapy exists for sulfide poisoning. We show in several cell types, including human inducible pluripotent stem cell (hiPSC)-derived neurons, that sulfide inhibited complex IV of the mitochondrial respiratory chain and induced apoptosis. Sulfide increased hydroxyl radical production in isolated mouse heart mitochondria and F2-isoprostanes in brains and hearts of mice. The vitamin B12 analog cobinamide reversed the cellular toxicity of sulfide, and rescued Drosophila melanogaster and mice from lethal exposures of hydrogen sulfide gas. Cobinamide worked through two distinct mechanisms: direct reversal of complex IV inhibition and neutralization of sulfide-generated reactive oxygen species. We conclude that sulfide produces a high degree of oxidative stress in cells and tissues, and that cobinamide has promise as a first specific treatment for sulfide poisoning.
Topics: Animals; Antidotes; Apoptosis; Brain; Cell Differentiation; Cobamides; Drosophila melanogaster; Electron Transport Complex IV; F2-Isoprostanes; Fibroblasts; Humans; Hydrogen Sulfide; Hydroxyl Radical; Induced Pluripotent Stem Cells; Male; Mice; Mice, Inbred C57BL; Mitochondria, Heart; Myocardium; Neurons; Oxidative Stress; Potassium Cyanide; Rats; Sulfides
PubMed: 26877209
DOI: 10.1038/srep20831