RESUMEN
Letter by Gopalan et al. on article by Singh and Moodley (Singh JA, Moodley K. Critical care triaging in the shadow of COVID-19: Ethics considerations. S Afr Med J 2020;110(5):355-359. https://doi.org/10.7196/SAMJ.2020.v110i5.14778); and response by Singh and Moodley.
Asunto(s)
Infecciones por Coronavirus , Cuidados Críticos , Pandemias , Neumonía Viral , Salud Pública , África Austral , Betacoronavirus , COVID-19 , Humanos , Asignación de Recursos , SARS-CoV-2 , SudáfricaRESUMEN
Bisphenol A (BPA) and bisphenol F (BPF) are widely used to manufacture plastics and epoxy resins. Both compounds have been shown to be present in the environment and are food contaminants, with, as a result, a low but chronic exposure of humans. However, the fate and possible bioactivation of these compounds at the level of human cell lines was not completely elucidated yet. In this study, we investigated the ability of human cells (intestinal cell line: LS174T, hepatoma cell line: HepG2, and renal cell line: ACHN) to biotransform BPA and BPF, and focused on the cytotoxicity and genotoxicity of these two bisphenols, through the use of a novel and efficient genotoxic assay based on the detection of histone H2AX phosphorylation. BPA and BPF were extensively metabolized in HepG2 and LS174T cell lines, with stronger biotransformation capabilities in intestinal cells than observed in liver cells. Both cell lines produced the glucuronide as well as the sulfate conjugates of BPA. Conversely, the ACHN cell line was found to be devoid of any metabolic capabilities for the two examined bisphenols. Cytotoxicity was tested for BPA, BPF, as well as one metabolite of BPF produced in vivo in rat, namely dihydroxybenzophenone (DHB). In the three cell lines used, we observed similar ranges of toxicity, with DHB being weakly cytotoxic, BPF exhibiting an intermediary cytotoxicity, and BPA being the most cytotoxic compound tested. BPA and DHB were not found to be genotoxic, whatever the cell line examined. BPF was clearly genotoxic in HepG2 cells. These results demonstrate that some human cell lines extensively metabolize bisphenols and establish the genotoxic potential of bisphenol F.
Asunto(s)
Compuestos de Bencidrilo/farmacocinética , Compuestos de Bencidrilo/toxicidad , Daño del ADN/efectos de los fármacos , Histonas/análisis , Fenoles/farmacocinética , Fenoles/toxicidad , Animales , Biotransformación , Línea Celular , Cromatografía Líquida de Alta Presión/métodos , Células Hep G2 , Histonas/metabolismo , Humanos , Intestinos/citología , Intestinos/efectos de los fármacos , Hígado/citología , Hígado/efectos de los fármacos , Fosforilación , RatasRESUMEN
Trans-4-hydroxy-2-nonenal (HNE) is a potent cytotoxic and genotoxic compound originating from the peroxidation of n-6 polyunsaturated fatty acids. Its metabolism has been previously studied in the rat (Alary et al. 1995. Chem. Res. Toxicol., 8: 35-39). In addition to major urinary mercapturic derivatives, some polar urinary metabolites were isolated and could correspond to hydroxylated compounds. 4-Hydroxynonenoic acid (HNA), resulting from the oxidation of the HNE carbonyl group, is a medium chain fatty acid and its omega-hydroxylation might be hypothesized. Therefore, the involvement of the CYP 4A family isoenzymes in the metabolism of [3H]HNE has been investigated in vivo using inducer treatments (fibrates) in wild-type or in peroxisome proliferator-activated receptor alpha (PPARalpha)-deficient mice. In wild-type mice, but not in PPARalpha (-/-) mice, fibrate treatments resulted in an increase of two urinary metabolites characterized, after HPLC purifications and mass spectrometry analyses, as the omega-hydroxylated metabolite of HNA, i.e., 4,9-dihydroxy-2-nonenoic acid, and its oxidized form, 4-hydroxy-2-nonene-1,9-dicarboxylic acid. The formation of the latter is correlated accurately to laurate hydroxylase activity studied concurrently in microsomes prepared from the liver of these animals. Basal levels of these two metabolites were measured in urine of normal and PPARalpha-deficient mice. These results are in accord with an implication of the P450 4A family in the extended oxidative metabolism of 4-HNE.
Asunto(s)
Aldehídos/metabolismo , Sistema Enzimático del Citocromo P-450/metabolismo , Oxigenasas de Función Mixta/metabolismo , Receptores Citoplasmáticos y Nucleares/deficiencia , Factores de Transcripción/deficiencia , Animales , Cromatografía Líquida de Alta Presión , Clofibrato/farmacología , Citocromo P-450 CYP4A , Sistema Enzimático del Citocromo P-450/genética , Femenino , Fenofibrato/farmacología , Hidroxilación , Hipolipemiantes/farmacología , Peroxidación de Lípido , Masculino , Espectrometría de Masas , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Microcuerpos/efectos de los fármacos , Microsomas Hepáticos/enzimología , Oxigenasas de Función Mixta/genética , Oxidación-Reducción , ARN Mensajero/genética , ARN Mensajero/metabolismo , Ratas , Receptores Citoplasmáticos y Nucleares/genética , Factores de Transcripción/genéticaRESUMEN
Following iv administration of 4-hydroxy-2-nonenal (HNE) and [4-3H]HNE to rats, 15 polar urinary metabolites accounting for about 50% of the urinary radioactivity were separated by HPLC. Among them, eight major compounds and tritiated water were quantified. The metabolites were unequivocally characterized using GC/MS and ESI/MS/MS/MS. Most of "HNE polar metabolites" originate from omega-oxidation of 4-hydroxy-2-nonenoic acid (HNA): 9-hydroxy-HNA, its mercapturic acid conjugate, and two diastereoisomers of the corresponding lactone. The oxidation of 9-hydroxy-HNA by alcohol and aldehyde dehydrogenases leads to the excretion of 9-carboxy-HNA and of the corresponding lactone mercapturic acid conjugate. 1, 4-Dihydroxy-2-nonene (DHN) originating from the reduction of HNE by alcohol dehydrogenase was to a lesser extent omega-hydroxylated, leading to 9-hydroxy-DHN which was excreted as a mercapturic acid conjugate (two diastereoisomers).
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Aldehídos/orina , Inhibidores de Cisteína Proteinasa/orina , Aldehídos/metabolismo , Animales , Biotransformación , Cromatografía Líquida de Alta Presión , Inhibidores de Cisteína Proteinasa/metabolismo , Cromatografía de Gases y Espectrometría de Masas , Concentración de Iones de Hidrógeno , Técnicas In Vitro , Peroxidación de Lípido , Masculino , Microsomas Hepáticos/efectos de los fármacos , Microsomas Hepáticos/metabolismo , Ratas , Ratas Wistar , Espectrometría de Masa Bombardeada por Átomos VelocesRESUMEN
Residues of estradiol-17 beta (E2 beta) in the kidney fat of one milk-fed calf were studies using radiometric methodologies. A three-month old Friesian male veal calf was injected intramuscularly daily for 3 d with 333 mg of [6,7(n)-3H]-E2 beta (specific activity: 7.55 MBq mmol-1) dissolved in 2 ml of propylene glycol and slaughtered 3 h after the last administration. Total estrogens were about 280 ng g-1 in perirenal fat. After a de-lipidation step, the relatively polar metabolites that were extractable with dichloromethane represented the main fraction of the metabolites, which accounts for almost 50% of the total radioactivity of the tissue, of which E2 beta was the major metabolite (19.7%) and E1 and E2 alpha represented only 7.7 and 3.2%, respectively. Conjugated estrogens accounted for only 15.2% of the total estrogen content. Non-polar estrogens (about 25% of total estrogens) were removed specifically with isooctane during the de-lipidation step and were further purified on silica and alumina columns before being chromatographed by normal-phase HPLC. The radioactive metabolites were eluted as estrogen-17 esters. The HPLC analysis of the estrogens released following hydrolysis of the esters indicated that E2 beta was the main estrogen acylated by long-chain fatty acids in the fraction of lipoidal estrogens. The presence of such a class of estrogens in fat could be of interest for the detection of estrogens a considerable time after estradiol administration.
Asunto(s)
Tejido Adiposo/química , Estradiol/metabolismo , Tejido Adiposo/metabolismo , Animales , Bovinos , Cromatografía Líquida de Alta Presión/métodos , Estradiol/análogos & derivados , Estradiol/análisis , Estrógenos/análisis , Riñón , Masculino , Técnica de Dilución de Radioisótopos , TritioRESUMEN
In all egg laying vertebrates, synthesis and use of vitellogenin (Vg) are intimately bound to the active phase of reproduction. In the liver of the rainbow trout (Salmo gairdnerii), Vg synthesis is influenced by estradiol (E2) which, we believe, acts through the classical mechanism of steroid hormone action. After binding of the hormone to a soluble specific receptor protein, the estradiol-receptor complex can interact with chromatin and modulate the expression of Vg genes, leading to increased synthesis of specific mRNA and Vg. We show here: (i) the presence of specific oestrogen receptors (dissociation constant KD congruent to 1.5 X 10(-9) M for E2) in the cytosol of the male trout liver. (ii) The male liver, offering, an ideal experimental control of "zero" background, we followed-in the liver of male trout--the kinetics of induction of Vg mRNA by hybridization with Vg cDNA, after E2 stimulation, and (iii) the apparition of Vg in the serum by using an original rocket immuno-electrophoretic technique. The male trout liver vitellogenin model and the original techniques we developed will be very useful to study the influence of endogenous and exogenous factors on the different steps (receptors, transcription, translation) of vitellogenesis regulation.