Efeito do esqualeno em ratos Wistar submetidos ao modelo de hepatocarcinogênese do Hepatócito Resistente

No presente estudo foi avaliado o eventual efeito quimiopreventivo do esqualeno, um triterpeno intermediário na biossíntese de esteróides em plantas e animais e constituinte do óleo de oliva, quando administrado a ratos Wistar durante 8 semanas consecutivas em período compreendendo as etapas de iniciação e seleção/promoção do modelo de hepatocarcinogênese do “hepatócito resistente” (RH). Animais tratados apenas com óleo de milho ou água e submetidos ao modelo do RH foram utilizados como controles. A análise estatística de nódulos visíveis macroscopicamente e de lesões pré-neoplásicas GST-P positivas, não revelou efeito quimiopreventivo significante por parte do esqualeno. Os índices de proliferação celular e de apoptose foram semelhantes entre os grupos. Da mesma forma, a análise de danos no DNA mostrou ausência de proteção por parte do esqualeno. Por outro lado, o aumento dos níveis plasmáticos de colesterol total sugere que o esqualeno foi absorvido. Assim, nossos dados não demonstram atividade quimiopreventiva digna de nota por parte do esqualeno, quando administrado durante as etapas iniciais da hepatocarcinogênese em ratos Wistar submetidos ao modelo do RH.Not available

Ação do licopeno na proteção contra danos induzidos no DNA in vivo e in vitro

O licopeno e um pigmento natural sintetizado por plantas e microorganismos, e encontrado principalmente no tomate. E um isomero aciclico do À-caroteno sem atividade pro-vitaminica-A, sendo um dos mais potentes agentes antioxidantes. Diversos pesquisadores tem demonstrado o efeito protetor do licopeno contra danos no DNA e sobre a carcinogenese quimicamente induzida, embora os mecanismos envolvidos nesses processos nao estejam, ainda, totalmente esclarecidos. Assim, o presente estudo objetivou avaliar o potencial quimioprotetor do licopeno contra danos no DNA e sobre a hepaticarcinogenese em roedores. O efeito anticarcinogenico do licopeno em figado de ratos foi avaliado utilizando-se os focos GST-P positivos (modelo de hepatocarcinogenese de media duracao proposto por Ito et al., 1988) como biomarcadores de lesoes pre-neoplasicas. Para avaliacao do efeito antigenotoxico e antimutagenico do carotenoide, bem como de seu possivel mecanismo de acao, foram utilizados, respectivamente, o teste do cometa e o teste do micronucleo em duas linhagens celulares in vitro: celulas de ovario de hamster chines (CHO) e celulas de hepatoma humano (HepG2). Mutagenos de acao direta (peroxido de hidrogenio, oxido de 4-nitroquinolina - 4NQO e metil metanosulfonato - MMS) e indireta (dietilnitrosamina -DEN), foram utilizados como indutores de danos no DNA in vitro. Os resultados mostraram que o licopeno, na concentracao 300 ppm, reduziu significativamente os danos no DNA induzidos pela DEN na etapa de iniciacao da hepatocarcinogenese de rato, embora nao tenha sido observada reducao do numero e area dos focos GST-P-positivos. Os resultados dos experimentos in vitro mostraram que o tratamento previo e simultaneo com licopeno (10, 25, e 50 ÊM) foi eficaz em reduzir os niveis de danos no DNA induzidos pelo H2O2 e pela DEN em celulas HepG2, quando avaliados tanto teste do cometa como do micronucleo.Lycopene is a natural pigment synthesized by plants and microorganisms, and mainly found in tomatoes. It is an acyclic isomer of â-carotene with no vitamin A activity, and one of the most potent antioxidants. Several studies have showed the chemopreventive effect of lycopene on chemically-induced DNA damage and on chemical hepatocarcinogenesis, however its mechanism of action needs to be clarified. The present study aimed to evaluate the protective activity of lycopene on chemically-induced DNA damage and on rodent hepatocarcinogenesis. Anticarcinogenic potential of lycopene was evaluated using GST-P positive foci (medium-term hepatocarcinogenesis model described by Ito et al., 1988) as a biomarker of preneoplasic lesion. Lycopene antigenotoxicity and antimutagenicity, as well as its mechanism of action were investigated in two cell lines (CHO and human hepatoma cell HepG2) using the comet assay and micronucleus test, respectively. Direct-acting (hydrogen peroxide; 4-nitroquinoline 1-oxide - 4NQO; methyl methanesulphonate - MMS) and indirect-acting (n-nitrosodiethylamine DEN) mutagens were used to induce in vitro DNA damage. The results showed that lycopene (300 ppm) reduced DEN-induced DNA damage at the initiation step of in vivo hepatocarcinogenesis, although no effect was observed on the number and area of GST-P positive foci in liver of rats. Data from in vitro experiments showed that lycopene (10, 25 and 50 ìM) was effective in reducing DNA damage induced by H2O2 and DEN in HepG2 cells, both in comet assay and in micronucleus test. In CHO cells the chemopreventive acitivity of lycopene was visualized only for primary DNA damage in the comet assay. In conclusion our data confirmed the chemopreventive effect of lycopene on chemically-induced DNA damage, although such activity depends on the treatment schedule used. On the other hand, no protective action of this carotenoid on DEN-induced preneoplasic lesion in liver of rats was detected.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Fluoride does not induce DNA breakage in Chinese hamster ovary cells in vitro.

Fluoride has been widely used in dentistry because it is a specific and effective caries prophylactic agent. However, excess fluoride may represent a hazard to human health, especially by causing injury to genetic material. Genotoxicity tests represent an important part of cancer research to assess the risk of potential carcinogens. In the current study, the potential DNA damage associated with exposure to fluoride was assessed by the single cell gel (comet) assay in vitro. Chinese hamster ovary cells were exposed to sodium fluoride (NaF) at final concentration ranging from 7 to 100 micro/ml for 3 h, at 37 dgrees C. The results pointed out that NaF in all concentrations tested did not contribute to DNA damage as depicted by the mean tail moment and tail intensity. These findings are clinically important since they represent an important contribution to a correct evaluation of the potential health risk associated with the exposure to dental agents

Tomato oleoresin inhibits DNA damage but not diethylnitrosamine-induced rat hepatocarcinogenesis

Various studies have shown that lycopene, a non-provitamin A carotenoid, exerts antioxidant, antimutagenic and anticarcinogenic activities in different in vitro and in vivo systems. However, the results concerning its chemopreventive potential on rat hepatocarcinogenesis are ambiguous. The aim of the present study was to investigate the antigenotoxic and anticarcinogenic effects of dietary tomato oleoresin adjusted to lycopene concentration at 30, 100 or 300ppm (administered 2 weeks before and during or 8 weeks after carcinogen exposure) on liver of male Wistar rats treated with a single intraperitoneal dose of 20 or 100 mg/kg of diethylnitrosamine (DEN), respectively. The level of DNA damage in liver cells and the development of putative preneoplastic single hepatocytes, minifoci and foci of altered hepatocytes (FHA) positive for glutathione S-transferase (GST-P) were used as endpoints. Significant reduction of DNA damage was detected when the highest lycopene concentration was administered before and during the DEN exposure (20 mg/kg). However, the results also showed that lycopene consumption did not reduce cell proliferation in normal hepatocytes or the growth of initiated hepatocytes into minifoci positive for GST-P during early regenerative response after 70% partial hepatectomy, or the number and area of GST-P positive FHA induced by DEN (100 mg/ kg) at the end of week 10. Taken together, the data suggest a chemopreventive effect of tomato oleoresin against DNA damage induced by DEN but no clear effectiveness in initiating or promoting phases of rat hepatocarcinogenesis. (c) 2008 Elsevier GmbH. All rights reserved

Lycopene activity against chemically induced DNA damage in Chinese hamster ovary cells

Lycopene is a natural pigment synthesized by plants and microorganisms, and it is mainly found in tomatoes. It is an acyclic isomer of P-carotene and one of the most potent antioxidants. Several studies have demonstrated the ability of lycopene to prevent chemically induced DNA damage; however, the mechanisms involved are still not clear. in the present study, we investigated the antigenotoxic/antimutagenic effects of lycopene in Chinese Hamster Ovary Cells (CHO) treated with hydrogen peroxide, methylmethanesulphonate (MMS), or 4-nitroquinoline-1-oxide (4-NQO). Lycopene (97%), at final concentrations of 10, 25, and 50 M, was tested under three different protocols: before, simultaneously, and after the treatment with the mutagens. Comet and cytokinesis-block micronucleus assays were used to evaluate the level of DNA damage. Data showed that lycopene reduced the frequency of micronucleated cells induced by the three mutagens. However, this chemopreventive activity was dependent on the concentrations and treatment schedules used. Similar results were observed in the comet assay, although some enhancements of primary DNA damage were detected when the carotenoid was administered after the mutagens. in conclusion, our findings confirmed the chemopreventive activity of lycopene, and showed that this effect occurs under different mechanisms. (c) 2007 Elsevier B.V. All rights reserved.São Paulo State Univ, Botucatu Med Sch, Dept Pathol, BR-18518000 São Paulo, BrazilSão Paulo State Univ, Inst Biosci, Botucatu, SP, BrazilSão Paulo State Univ, Botucatu Med Sch, Dept Clin Med, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Hlth Sci, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Hlth Sci, São Paulo, BrazilWeb of Scienc

Chemoprevention of rat hepatocarcinogenesis with histone deacetylase inhibitors: Efficacy of tributyrin, a butyric acid prodrug

Hepatocellular carcinoma (HCC) ranks in prevalence and mortality among top 10 cancers worldwide. Butyric acid (BA), a member of histone deacetylase inhibitors (HDACi) has been proposed as an anticareinogenic agent. However, its short half-life is a therapeutical limitation. This problem could be circumvented with tributyrin (TB), a proposed BA prodrug. To investigate TB effectiveness for chemoprevention, rats were treated with the compound during initial phases of ""resistant hepatocyte"" model of hepatocarcinogenesis, and cellular and molecular parameters were evaluated. TB inhibited (p < 0.05) development of hepatic preneoplastic lesions (PNL) including persistent ones considered HCC progression sites. TB increased (p < 0.05) PNL remodeling, a process whereby they tend to disappear. TB did not inhibit cell proliferation in PNL, but induced (p < 0.05) apoptosis in remodeling ones. Compared to controls, rats treated with TB presented increased (P < 0.05) hepatic levels of BA indicating its effectiveness as a prodrug. Molecular mechanisms of TB-induced hepatocarcinogenesis chemoprevention were investigated. TB increased (p < 0.05) hepatic nuclear histone H3K9 hyperacetylation specifically in PNL and p21 protein expression, which could be associated with inhibitory HDAC effects. Moreover, it reduced (p < 0.05) the frequency of persistent PNL with aberrant cytoplasmic p53 accumulation, an alteration associated with increased malignancy. Original data observed in our study support the effectiveness of TB as a prodrug of BA and as an HDACi in hepatocarcinogenesis chemoprevention. Besides histone acetylation and p21 restored expression, molecular mechanisms involved with TB anticarcinogenic actions could also be related to modulation of p53 pathways. (C) 2008 Wiley-Liss, Inc.FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo)CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior)CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico

Chemopreventive effects of beta-ionone and geraniol during rat hepatocarcinogenesis promotion: distinct actions on cell proliferation, apoptosis, HMGCoA reductase, and RhoA

Chemopreventive activities of the dietary isoprenoids beta-ionone (beta I) and geraniol (GOH) were evaluated during the promotion phase of hepatocarcinogenesis. Over 5 consecutive weeks, rats received daily 16 mg/100 g body weight (b.w.) of beta I (beta I group), 25 mg/100 g b.w. of GOH (GOH group), or only corn oil (CO group, controls). Compared to the CO group, the following was observed: only the beta I group showed a decrease in the mean number of visible hepatocyte nodules (P<.05); beta I and GOH groups had reduced mean number of persistent preneoplastic lesions (pPNLs) (P<.05), but no differences regarding number of remodeling PNL (rPNLs) were observed; only the beta I group exhibited smaller rPNL size and percentage of liver sections occupied by pPNLs (P<.05), whereas the GOH group displayed a smaller percentage of liver sections occupied by rPNLs (P<.05); a trend was observed in the beta I group, which showed reduced cell proliferation of pPNLs (P<.10), and the GOH group had increased apoptosis in pPNLs and rPNLs (P<.05); only the beta I group displayed reduced total plasma cholesterol concentrations (P<.05) and increased hepatic 3-hydroxy-3-methylglutaryl coenzyme A (HMGCoA) reductase mRNA levels (P<.05): only the GOH group had lower hepatic membrane RhoA protein levels (P<.05); both the beta I- and GOH-treated groups had higher hepatic concentrations of beta I and GOH, respectively (P<.05). Given these data, beta I and GOH show promising chemopreventive effects during promotion of hepatocarcinogenesis by acting through distinct mechanism of actions: beta I may inhibit cell proliferation and modulate HMGCoA reductase, and GOH can induce apoptosis and inhibit RhoA activation. (C) 2011 Elsevier Inc. All rights reserved.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq