E2 potentializes benzo(a)pyrene-induced hepatic cytochrome P450 enzyme activities in Nile tilapia at high concentrations

In the aquatic environment, biotransformation enzymes are established biomarkers for assessing PAH exposure in fish, but little is known about the effect of 17β-estradiol (E2) on these enzymes during exposure to benzo(a)pyrene (BaP). In this study, Nile tilapia (Oreochromis niloticus) were exposed for 3, 5, and 10 days to BaP (300 μg L(-1)) and E2 (5 μg L(-1)). These substances were applied isolated or mixed. In the mixture experiment, fish were analyzed pre- and postexposure in order to better understand whether preexposure to the hormone masks the responses activated by PAH or vice versa. Phase I enzymes ethoxyresorufin-O-deethylase (EROD), pentoxyresorufin-O-depenthylase (PROD), and benzyloxyresorufin-O-debenzylase (BROD) activities as well as the phase II enzyme glutathione S-transferase (GST) were analyzed. Isolated E2 treatment decreased EROD activity after 3 days, but this enzyme activity returned to control values after 5 and 10 days of exposure. Isolated BaP treatment significantly induced EROD activity after 3 and 5 days, and the activity returned to control levels after ten exposure days. Combined treatment (E2 + Bap) significantly increased EROD activity, both in the pre- and postexposure. This increase was even higher than in the isolated BaP treatment, suggesting a synergism between these two compounds. When E2 and BaP were used singly, they did not change BROD and PROD activities. However, combined treatment (E2 + Bap) significantly increased PROD activity. Isolated BaP treatment increased GST activity after 10 days. However, this response was not observed in the mixture treatment, suggesting that E2 suppressed the GST induction modulated by BaP. The results put together indicated that E2 altered the biotransformation pathway regarding enzymes activated by BaP in Nile tilapia.

Microarray analysis of cytochrome P450 mediated insecticide resistance in Drosophila

Insecticide resistance in laboratory selected Drosophila strains has been associated with upregulation of a range of different cytochrome P450s, however in recent field isolates of D. melanogaster resistance to DDT and other compounds is conferred by one P450 gene, Cyp6g1. Using microarray analysis of all Drosophila P450 genes, here we show that different P450 genes such as Cyp12d1 and Cyp6a8 can also be selected using DDT in the laboratory. We also show, however, that a homolog of Cyp6g1 is over-expressed in a field resistant strain of D. simulans. In order to determine why Cyp6g1 is so widely selected in the field we examine the pattern of cross-resistance of both resistant strains and transgenic flies over-expressing Cyp6g1 alone. We show that all three DDT selected P450s can confer resistance to the neonicotinoid imidacloprid but that Cyp6a8 confers no cross-resistance to malathion. Transgenic flies over-expressing Cyp6g1 also show cross-resistance to other neonicotinoids such as acetamiprid and nitenpyram. We suggest that the broad level of cross-resistance shown by Cyp6g1 may have facilitated its selection as a resistance gene in natural Drosophila populations. (C) 2003 Elsevier B.V. Ltd. All rights reserved.

Cellular localization of androgen synthesis in equine granulosa-theca cell tumors: Immunohistochemical expression of 17α-hydroxylase/17,20-lyase cytochrome P450

Elevated blood testosterone concentrations, often accompanied by male-typical behaviors, is a common signalment of mares with granulosa-theca cell tumors (GCTCs), but no definitive information exists regarding the cellular differentiation of tumors associated with androgen secretion. This study was conducted to localize and thereby define the cellular expression of 17α-hydroxylase/17,20-lyase cytochrome P450 (P450c17), the enzyme most directly responsible for androgen synthesis, in 30 GTCTs and control tissues (gonads and adrenal glands) using immuno-histochemistry (IHC). Immuno-reactivity for P450c17 was evident in approximately half of 30 specimens examined, was most consistent in the interstitial cells surrounding existing or developing cysts, and was less intense in cells within cysts in the smaller proportion of specimens where this was observed. In control tissues, the expression of P450c17 was localized primarily in theca interna of normal ovarian follicles, in theca-lutein cells of some corpora lutea, but not in granulosa-lutein cells. Testicular interstitial cells and islands of adreno-cortical cells located in the adrenal medulla of the adrenal cortex further established the specificity of the antisera used. These data provided the first substantive evidence that polyhedral cells identified previously in GTCTs by histopathology have the potential to synthesize and secrete androgens, similar to theca interna and theca lutein cells in normal equine ovaries. © 2010 Elsevier Inc.

Advances in prodrug design

The background of prodrug design is presented herein as the basis for introducing new and advanced latent systems, taking into account mainly the versatility of polymers and other macromolecules as carriers. PDEPT (Polymer-Directed Enzyme Prodrug Therapy); PELT (Polymer-Enzyme Liposome Therapy); CDS (Chemical Delivery System); ADEPT(Antibody-Directed Enzyme Prodrug Therapy); GDEPT/VDEPT (Gene-Directed Enzyme Prodrug Therapy/Virus-Directed Enzyme Prodrug Therapy); ODDS (Osteotropic Drug Delivery System) and LEAPT (Lectin-directed enzyme-activated prodrug therapy) are briefly described and some examples are given. © 2005 Bentham Science Publishers Ltd.

The role of mitochondria and biotransformation in abamectin-induced cytotoxicity in isolated rat hepatocytes

Abamectin (ABA), which belongs to the family of avermectins, is used as a parasiticide; however, ABA poisoning can impair liver function. In a previous study using isolated rat liver mitochondria, we observed that ABA inhibited the activity of adenine nucleotide translocator and FoF1-ATPase. The aim of this study was to characterize the mechanism of ABA toxicity in isolated rat hepatocytes and to evaluate whether this effect is dependent on its metabolism. The toxicity of ABA was assessed by monitoring oxygen consumption and mitochondrial membrane potential, intracellular ATP concentration, cell viability, intracellular Ca2+ homeostasis, release of cytochrome c, caspase 3 activity and necrotic cell death. ABA reduces cellular respiration in cells energized with glutamate and malate or succinate. The hepatocytes that were previously incubated with proadifen, a cytochrome P450 inhibitor, are more sensitive to the compound as observed by a rapid decrease in the mitochondrial membrane potential accompanied by reductions in ATP concentration and cell viability and a disruption of intracellular Ca2+ homeostasis followed by necrosis. Our results indicate that ABA biotransformation reduces its toxicity, and its toxic action is related to the inhibition of mitochondrial activity, which leads to decreased synthesis of ATP followed by cell death. © 2012 Elsevier Ltd.

Effects of β-glucan extracted from Agaricus blazei on the expression of ERCC5, CASP9, and CYP1A1 genes and metabolic profile in HepG2 cells

The polysaccharide β-glucan has biological properties that stimulate the immune system and can prevent chronic pathologies, including cancer. It has been shown to prevent damage to DNA caused by the chemical and physical agents to which humans are exposed. However, the mechanism of β-glucan remains poorly understood. The objective of the present study was to verify the protective effect of β-glucan on the expression of the genes ERCC5 (involved in excision repair of DNA damage), CASP9 (involved in apoptosis), and CYP1A1 (involved in the metabolism of xenobiotics) using real-time polymerase chain reaction and perform metabolic profile measurements on the HepG2 cells. Cells were exposed to only benzo[a]pyrene (B[a]P), β-glucan, or a combination of B[a]P with β-glucan. The results demonstrated that 50 μg/mL β-glucan significantly repressed the expression of the ERCC5 gene when compared with the untreated control cells in these conditions. No change was found in the CASP9 transcript level. However, the CYP1A1 gene expression was also induced by HepG2 cells exposed to B[a]P only or in association with β-glucan, showing its effective protector against damage caused by B[a]P, while HepG2 cells exposed to only β-glucan did not show CYP1A1 modulation. The metabolic profiles showed moderate bioenergetic metabolism with an increase in the metabolites involved in bioenergetic metabolism (alanine, glutamate, creatine and phosphocholine) in cells treated with β-glucan and to a lesser extent treated with B[a]P. Thus, these results demonstrate that the chemopreventive activity of β-glucan may modulate bioenergetic metabolism and gene expression. © 2013 The Author(s).

Aspectos metabolômico, biológico e proteômico de Maytenus ilicifolia e Salacia campestris (Celastraceae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Enzimas de biotransformação em tilápia (Oreochromis niloticus) exposta ao hormônio natural 17b-estradiol

Among the sexual hormones the estrogens are receiving major attention due to their biological activity. Such biological response is atributed to the best conformation recognized by their receptors, resulting in maximum responses. The estrogens are also considered responsible for most of disruptor´s effects caused by their presence in aquatic ecosystems. The 17β-estradiol hormone is produced by vertebrates during the reproductive phase of their lives and its presence has been detected in superficial waters. The objective of this study was to evaluate the cause-effect of tilapia exposition to the hormone 17β-estradiol through the analysis of biotransformation enzymes in liver and gills, complemented with the quantification of 17β-estradiol and estrone in water samples collected from fish ponds integrated to swine production. The present study was conducted under laboratory conditions, in a randomized experimental design with three levels of 17β-estradiol (E2) (0, 5, 15 µg L-1), with three replicates. After 7 days of exposure time, liver and gills were extracted to analyze three isoforms of cytochrome P450: EROD, BROD, PROD and the activity of Glutathione S-Transferase (GST). The results showed that the EROD activity (CYP1A), normally induced by the metabolism of aromatic compounds, did not present statistical differences among the treatments exposed to E2, what means that the hormone did not induce isoform 1A in fish under these particular experimental conditions. PROD activity was significantly altered in both concentrations, by means of 5 and 15 µg L-1, when compared to control. This result can indicate an important role of PROD on the metabolism of E2 present in water. Regarding to the BROD activity, it could be observed differences statistically significant between control and both groups of treatments. Two or more CYP isoforms can contribute to the metabolism of the same compound, what makes BROD a candidate as a next bioindicator of the exposure to E2 in aquatic ecosystems. Analysis of variance could confirm the effect of E2 statistically significant on the GST activity in liver tissues with >90% of significance (Prob>F = 0.0753). Furthermore, it was possible to observe that the values of GSTs activities in liver and gills in both, control and treatments, follow a tendency, that means, enzymatic activity in gills increase as the increasing of the activity in the liver tissues. In this study, the 17β–estradiol was found in measurable concentrations in three sampled points, and these values were similar to the findings of other authors at different locations in Brazil. In addition, those values are much higher than the minimum concentration that presented observable effects (10 ng L-1).

Mecanismos de toxicidade do fipronil em hepatócitos isolados de rato

Pós-graduação em Ciência e Tecnologia Animal - FEIS

CYP1A2*1C, CYP2E1*5B, and GSTM1 polymorphisms are predictors of risk and poor outcome in head and neck squamous cell carcinoma patients

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Genetic polymorphism and their contribution to cancer susceptibility

Uma vez que a maioria dos carcinogênicos químicos não é capaz de causar efeitos danosos per se, o metabolismo desses compostos é a parte crucial da resposta inicial à exposição ambiental. Os distúrbios causados no balanço entre os processos de ativação e destoxificação podem, assim, explicar as variações individuais em resposta à exposição aos carcinogênicos. A quantidade de compostos carcinogênicos finais produzida depende da ação competitiva entre os passos de ativação e destoxificação, envolvendo as enzimas do citocromo P450 e das S-glutatião transferases.

GSTT1, GSTM1 and CYP2E1 genetic polymorphisms in gastric cancer and chronic gastritis in a Brazilian population

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Doença arterial coronariana: Um novo paradigma na AIDS

The HIV-infected individuals have been identified as a peculiar group whose propensity to the development of abnormalities in lipids metabolism supports the hypothesis that AIDS itself can be considered as an independent risk factor for the occlusive diseases development. The AIDS progression, as well as the therapy against HIV has been capable to show an array of metabolic disturbances that HIV-infected patients are prone to. These metabolic alterations affect the fate of plasmatic lipids and homocysteine as a result of three factor mainly: (i) the viral infection per se which triggers the development of hypertriglyceridemia and hipocholesterolemia; (ii) multiple vitamins and micronutrients deficiencies, that favors an onset of hyperhomocysteinemia; (iii) the state-of-the-art therapy for HIV infection, which is accompanied to idiosyncratic effects encompassing the lipid metabolism. In this context, a variety of risk factors to atherosclerosis can be identified in the HIV-infected individual. Of note, it must be considered that once life expectancy of these patients has been expanded due to the effective therapy, on the other hand they can accelerate atherosclerotic disease or its pathological appearance in the same extent.