RESUMO
Arsenicosis, a syndrome caused by ingestion of arsenic contaminated drinking water, currently affects millions of people in South-East Asia and elsewhere. Previous animal studies revealed that the toxicity of arsenite essentially can be abolished if selenium is co-administered as selenite. Although subsequent studies have provided some insight into the biomolecular basis of this striking antagonism, many details of the biochemical pathways that ultimately result in the detoxification and excretion of arsenic using selenium supplements have yet to be thoroughly studied. To this end and in conjunction with the recent Phase III clinical trial "Selenium in the Treatment of Arsenic Toxicity and Cancers", we have applied synchrotron X-ray techniques to elucidate the mechanisms of this arsenic-selenium antagonism at the tissue and organ levels using an animal model. X-ray fluorescence imaging (XFI) of cryo-dried whole-body sections of laboratory hamsters that had been injected with arsenite, selenite, or both chemical species, provided insight into the distribution of both metalloids 30 minutes after treatment. Co-treated animals showed strong co-localization of arsenic and selenium in the liver, gall bladder and small intestine. X-ray absorption spectroscopy (XAS) of freshly frozen organs of co-treated animals revealed the presence in liver tissues of the seleno bis-(S-glutathionyl) arsinium ion, which was rapidly excreted via bile into the intestinal tract. These results firmly support the previously postulated hepatobiliary excretion of the seleno bis-(S-glutathionyl) arsinium ion by providing the first data pertaining to organs of whole animals.
Assuntos
Intoxicação por Arsênico/metabolismo , Arsênio/metabolismo , Mamíferos/metabolismo , Selênio/metabolismo , Animais , Arsênio/farmacocinética , Intoxicação por Arsênico/diagnóstico , Feminino , Mesocricetus , Especificidade de Órgãos , Selênio/farmacocinética , Espectrometria por Raios X/métodos , Síncrotrons , Distribuição Tecidual , Espectroscopia por Absorção de Raios XRESUMO
Defective lysosomal acidification contributes to virtually all lysosomal storage disorders (LSDs) and to common neurodegenerative diseases like Alzheimer's and Parkinson's. Despite its fundamental importance, the mechanism(s) underlying this defect remains unclear. The v-ATPase, a multisubunit protein complex composed of cytosolic V1-sector and lysosomal membrane-anchored V0-sector, regulates lysosomal acidification. Mutations in the CLN1 gene, encoding PPT1, cause a devastating neurodegenerative LSD, INCL. Here we report that in Cln1-/- mice, which mimic INCL, reduced v-ATPase activity correlates with elevated lysosomal pH. Moreover, v-ATPase subunit a1 of the V0 sector (V0a1) requires palmitoylation for interacting with adaptor protein-2 (AP-2) and AP-3, respectively, for trafficking to the lysosomal membrane. Notably, treatment of Cln1-/- mice with a thioesterase (Ppt1)-mimetic, NtBuHA, ameliorated this defect. Our findings reveal an unanticipated role of Cln1 in regulating lysosomal targeting of V0a1 and suggest that varying factors adversely affecting v-ATPase function dysregulate lysosomal acidification in other LSDs and common neurodegenerative diseases.
Assuntos
Hidroxilaminas/uso terapêutico , Doenças por Armazenamento dos Lisossomos/enzimologia , Lisossomos/metabolismo , Tioléster Hidrolases/metabolismo , ATPases Vacuolares Próton-Translocadoras/metabolismo , Complexo 2 de Proteínas Adaptadoras/metabolismo , Animais , Modelos Animais de Doenças , Avaliação Pré-Clínica de Medicamentos , Endossomos/enzimologia , Células HEK293 , Humanos , Lipoilação , Doenças por Armazenamento dos Lisossomos/tratamento farmacológico , Camundongos , Distribuição AleatóriaRESUMO
The assessment of the microbial diversity of the entire community of a given habitat requires the extraction of the total environmental DNA. Metagenomic investigations of a petroleum-polluted habitat have its unique challenges. The specific methods were developed for the extraction of high-quality metagenome in good quantity from the petroleum-polluted saline and non-saline sites in Gujarat (India). The soil samples were washed to remove the toxic, hazardous organic pollutants which might interfere with the recovery of the metagenomic DNA. The metagenomic DNA extraction results were encouraging with the mechanical bead beating, soft lysis, and combination of both. The extracted DNA was assessed for its purity and yield followed by its application in the amplification of the 16S rRNA region. The amplicons were used for judging the molecular diversity by the denaturing gradient gel electrophoresis (DGGE). The microbial diversity was also analyzed statistically by calculating various diversity indices and principal component analysis (PCA). The results on the metagenomic diversity of the bacterial population among the three cohorts based on the culture-independent technique exhibited significant difference among the PAH sites and Okha-Madhi and Porbandar Madhavpur habitats.
Assuntos
Bactérias/genética , Variação Genética , Poluição por Petróleo , Microbiologia do Solo , Bactérias/classificação , Biodegradação Ambiental , DNA Bacteriano , Eletroforese em Gel de Gradiente Desnaturante , Ecossistema , Monitoramento Ambiental/métodos , Índia , Petróleo/análise , RNA Ribossômico 16S/genética , Solo/química , Poluentes do Solo/análiseRESUMO
Human exposure to potentially neurotoxic methylmercury species is a public-health concern for many populations worldwide. Both fish and whale are known to contain varying amounts of methylmercury species. However studies of populations that consume large quantities of fish or whale have provided no clear consensus as to the extent of the risk. The toxicological profile of an element depends strongly on its chemical form. We have used X-ray absorption spectroscopy to investigate the comparative chemical forms of mercury and selenium in fish and whale skeletal muscle. The predominant chemical form of mercury in whale is found to closely resemble that found in fish. In the samples of skeletal muscle studied, no involvement of selenium in coordination of mercury is indicated in either whale or fish, with no significant inorganic HgSe or HgS type phases being detected. The selenium speciation in fish and whale shows that similar chemical types are present in each, but in significantly different proportions. Our results suggest that for equal amounts of Hg in skeletal muscle, the direct detrimental effects arising from the mercury content from consuming skeletal muscle from whale and fish should be similar if the effects of interactions with other components in the meat are not considered.
Assuntos
Mercúrio/química , Músculo Esquelético/química , Selênio/química , Poluentes Químicos da Água/química , Baleias/anatomia & histologia , Animais , Feminino , Peixes , Humanos , Análise dos Mínimos Quadrados , Mercúrio/toxicidade , Selênio/toxicidade , Espectroscopia por Absorção de Raios XRESUMO
A chelator is a molecule which binds a metal or metalloid ion by two or more functional groups to form a stable ring complex known as a chelate. Despite the widespread clinical use of so-called chelation therapy to remove mercury, none of the drugs currently in use have been shown to chelate mercury. Mercury can adopt three common coordination environments: linear diagonal, trigonal planar, and tetrahedral. We have previously discussed some of the structural criteria for optimal binding of mercury in linear-diagonal coordination with thiolate donors (George et al. in Chem. Res. Toxicol. 17:999-1006, 2004). Here we employed density functional theory and X-ray absorption spectroscopy to evaluate the ideal chain length for simple alkane dithiolate chelators of Hg(2+). We have also extended our previous calculations of the optimum coordination geometries to the three-coordinate [Hg(SR)(3)](-) case. Finally, we propose a new chelator "tripod" molecule, benzene-1,3,5-triamidopropanethiolate, or "Trithiopod," which is expected to bind Hg(2+) in three-coordinate geometry with very high affinity.
Assuntos
Quelantes/química , Mercúrio/química , Modelos Moleculares , Compostos Organomercúricos/química , Alcanos/química , Estrutura Molecular , Teoria Quântica , Compostos de Sulfidrila/química , Espectroscopia por Absorção de Raios XRESUMO
Methylmercury is among the most potentially toxic species to which human populations are exposed, both at high levels through poisonings and at lower levels through consumption of fish and other seafood. However, the molecular mechanisms of methylmercury toxicity in humans remain poorly understood. We used synchrotron X-ray absorption spectroscopy (XAS) to study mercury chemical forms in human brain tissue. Individuals poisoned with high levels of methylmercury species showed elevated cortical selenium with significant proportions of nanoparticulate mercuric selenide plus some inorganic mercury and methylmercury bound to organic sulfur. Individuals with a lifetime of high fish consumption showed much lower levels of mercuric selenide and methylmercury cysteineate. Mercury exposure did not perturb organic selenium levels. These results elucidate a key detoxification pathway in the central nervous system and provide new insights into the appropriate methods for biological monitoring.
Assuntos
Química Encefálica , Poluentes Ambientais/intoxicação , Intoxicação do Sistema Nervoso por Mercúrio/metabolismo , Mercúrio/análise , Compostos de Metilmercúrio/intoxicação , Absorciometria de Fóton , Acidentes de Trabalho , Idoso , Animais , Criança , Cisteína/análogos & derivados , Cisteína/análise , Exposição Ambiental , Poluentes Ambientais/farmacocinética , Feminino , Peixes , Contaminação de Alimentos , Humanos , Inativação Metabólica , Masculino , Carne/análise , Mercúrio/química , Compostos de Mercúrio/análise , Intoxicação do Sistema Nervoso por Mercúrio/patologia , Compostos de Metilmercúrio/análise , Compostos de Metilmercúrio/farmacocinética , Pessoa de Meia-Idade , Modelos Moleculares , Estrutura Molecular , Nanopartículas , New York , Imagem Óptica , Selênio/análise , Compostos de Selênio/análise , Seicheles , SuínosRESUMO
Fish is a major dietary source of potentially neurotoxic methylmercury compounds for humans. It is also a rich source of essential selenium. We have used in situ mercury L(III)-edge and selenium K-edge X-ray absorption spectroscopy to chemically characterize the methylmercury and selenium in both fresh fish and fish digested with simulated gastric fluid. For the mercury, we confirm our earlier finding [ Harris et al. ( 2003 ) Science 301 , 1203 ] that the methylmercury is coordinated by a single thiolate donor, which resembles cysteine, and for the selenium, we find a mixture of organic forms that resemble selenomethionine and an aliphatic selenenyl sulfide such as Cys-S-Se-Cys. We find that local chemical environments of mercury and selenium do not change upon digestion of the fish with simulated gastric fluid. We discuss the toxicological implications for humans consuming fish.
Assuntos
Digestão , Peixes/metabolismo , Mucosa Gástrica/metabolismo , Compostos de Metilmercúrio/química , Selênio/química , Poluentes Químicos da Água/química , Animais , Contaminação de Alimentos , Compostos de Metilmercúrio/metabolismo , Compostos de Metilmercúrio/toxicidade , Selênio/metabolismo , Selênio/toxicidadeRESUMO
Soil amendments can be used to cost-effectively reduce the bioavailability and mobility of toxic metals in contaminated soils. In this study a field demonstration was conducted at a Pb-contaminated site to evaluate the effectiveness of P-induced Pb immobilization. Phosphate was applied at a 4.0 molar ratio of P to Pb with three treatments: T1, 100% of P from H3PO4; T2, 50% P from H3PO4 + 50% P from Ca(H2PO4)2; and T3, 50% P from H3PO4 + 5% phosphate rock. Phosphate amendments effectively transformed soil Pb from the nonresidual (sum of exchangeable, carbonate, Fe/Mn, and organic) to the residual fraction, with residual Pb increase by 19-48% for T1, 22-50% for T2, and 11-55% for T3, respectively. Lead immobilization was attributed to the P-induced formation of chloropyromorphite [Pb10(PO4)6Cl2], which was identified in the surface soil, subsurface soil, and plant rhizosphere soil. Occurrence of chloropyromorphite was evident 220 days after P addition for T1 and T2 treatments and 330 days for T3. Visual MINTEQ model and activity-ratio diagram indicated that lead phosphate minerals controlled Pb2+ activities in the P-treated soils. Phosphate treatments significantly reduced Pb translocation from the roots to the shoots in the St. Augustine grass (Stenotaphrum secundatum), possibly via the formation of chloropyromorphite on the cell walls of roots. This field observation suggested that P amendments are efficient in reducing Pb mobility via in situ formation of insoluble chloropyromorphite minerals at a field setting. Lead immobilization shows a long-term stability. A mixture of H3PO4 and phosphate rock yields the best overall results for in situ Pb immobilization, with less soil pH change and less P leaching. Application of combined H3PO4 with phosphate rock may provide an effective alternative to the current phosphate remediation technologies for contaminated soils.