ß-ionone modulates the expression of miRNAs and genes involved in the metastatic phenotype of microdissected persistent preneoplastic lesions in rats submitted to hepatocarcinogenesis.

MicroRNAs (miRNAs) are post-transcriptional gene expression regulators which expression is frequently altered in hepatocellular carcinoma (HCC). ß-ionone (ßI) is noted for its ability to inhibit persistent preneoplastic lesions (pPNLs) in liver rats. We evaluated the expression of miRNAs involved in carcinogenesis and possible targets modulated by ßI, in pPNLs and surrounding of microdissected tissues. Rats subjected to resistant hepatocyte model were treated during promotion stage with ßI (16 mg/100 g body weight) or corn oil (CO; 0.25 mL/100 g body weight; controls). Five animals receive no treatment (NT). In CO group, 38 and 29 miRNAs showed reduced expression relative to NT (P < 0.05) in pPNLs and surrounding, respectively. No miRNAs showed increased expression in surrounding of the CO compared to NT group; however, 30 miRNAs showed increased expression (P ≤ 0.05) in pPNLs of the CO group. There was no difference between ßI and CO groups (P > 0.05) in the expression of miRNAs in surrounding. In pPNLs ßI increased expression of miR-122 and miR-34a (P ≤ 0.05) and reduced of Igf2 (P ≤ 0.05), target of the latter, compared to CO. Additionally, ßI decreased the expression of miR-181c and its target Gdf2 (P ≤ 0.05). ßI reduced the expression of miR-181b and miR-708 (P ≤ 0.05) and increased the expression of their respective target mRNAs Timp3 and Mtss1 (P ≤ 0.05), relative to CO group. Modulation of miRNAs target genes by ßI was confirmed in vitro. ßI is a promising chemopreventive agent in the initial stages of hepatocarcinogenesis, as it modulates the expression of the miRNAs and target genes that can alter the metastatic phenotype of HCC. © 2016 Wiley Periodicals, Inc.

ß-ionone inhibits persistent preneoplastic lesions during the early promotion phase of rat hepatocarcinogenesis: TGF-α, NF-κB, and p53 as cellular targets.

Dietary isoprenic derivatives such as ß-ionone (ßI) are a promising class of chemopreventive agents. In this study, cellular aspects of ßI protective activities during early hepatocarcinogenesis were evaluated. Male Wistar rats were submitted to "resistant hepatocyte" model and then received daily 16 mg/100 g body weight (b.w.) of ßI (ßI group) or only 0.25 mL/100 g b.w. of corn oil (vehicle, control group [CO]) during 4 wk, specifically during early promotion phase. Compared to controls, ßI inhibited (P < 0.05) the development of persistent preneoplastic lesions (pPNL), considered to be potential hepatocellular carcinoma (HCC) progression sites, and increased remodeling PNL (rPNL) (P < 0.05) that tend to regress to a normal phenotype. Increased ßI hepatic levels (P < 0.05), in the ßI group, were associated with its chemopreventive actions. Compared to control rats, ßI reduced the frequency of both pPNL and rPNL positive for tumor growth factor (TGF)-α (P < 0.05), reduced the frequency of pPNL stained for p65 (nuclear factor-kappaB; NF-κB) (P < 0.05), and reduced the frequency of pPNL positive for cytoplasmic p53 (P < 0.05). Our data demonstrated that ßI targets TGF-α, NF-κB, and p53 in initial phases of hepatocarcinogenesis and specifically inhibits PNL with increased probability to progress to HCC. This isoprenoid may represent a chemopreventive agent of choice for HCC control.

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 anticarcinogenic 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.

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 300 ppm (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 100mg/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 (20mg/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 (100mg/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.

Effects of crude extracts of Agaricus blazei on DNA damage and on rat liver carcinogenesis induced by diethylnitrosamine.

The effects of crude extracts of the mushroom Agaricus blazei Murrill (Agaricaceae) on both DNA damage and placental form glutathione S-transferase (GST-P)-positive liver foci induced by diethylnitrosamine (DEN) were investigated. Six groups of adult male Wistar rats were used. For two weeks, animals of groups 3 to 6 were treated with three aqueous solutions of A. blazei (mean dry weight of solids being 1.2, 5.6, 11.5 and 11.5 mg/ml, respectively). After this period, groups 2 to 5 were given a single ip injection 200 mg/kg DEN and groups 1 and 6 were treated with 0.9% NaCl. All animals were subjected to 70% partial hepatectomy at week five and sacrificed 4, 24 and 48 h or 8 weeks after DEN or 0.9% NaCl treatments (10th week after the beginning of the experiment). The alkaline comet assay and GST-P-positive liver foci development were used to evaluate the influence of the mushroom extracts on liver cell DNA damage and on the initiation of liver carcinogenesis, respectively. Previous treatment with the highest concentration of A. blazei (11.5 mg/ml) significantly reduced DNA damage, indicating a protective effect against DEN-induced liver cytotoxicity/genotoxicity. However, the same dose of mushroom extract significantly increased the number of GST-P-positive liver foci.

Chemopreventive effects of the dietary histone deacetylase inhibitor tributyrin alone or in combination with vitamin A during the promotion phase of rat hepatocarcinogenesis.

The chemopreventive effects of tributyrin (TB) and vitamin A (VA), alone or in combination, were investigated during the promotion phase of rat hepatocarcinogenesis. Compared to diethylnitrosamine control rats, TB and TB+VA-treated rats, but not VA-treated rats, presented a lower incidence and mean number of hepatocyte nodules and a smaller size of persistent preneoplastic lesions (pPNLs). In addition, TB and TB+VA-treated rats exhibited a higher apoptotic body index in pPNL and remodeling PNL, whereas VA-treated rats presented only a higher apoptotic body index in remodeling PNL. None of the treatments inhibited cell proliferation in PNL. TB and TB+VA-treated rats, but not VA-treated rats, exhibited higher levels of H3K9 acetylation and p21 protein expression. TB and VA-treated rats exhibited increased hepatic concentrations of butyric acid and retinoids, respectively. Compared to normal rats, diethylnitrosamine control animals exhibited lower retinyl palmitate hepatic concentrations. All groups had similar expression levels and exhibited similar unmethylated CRBP-I promoter region in microdissected pPNL, indicating that epigenetic silencing of this gene was not involved in alteration of retinol metabolism in early hepatocarcinogenesis. Data support the effectiveness of TB as a dietary histone deacetylase inhibitor during the promotion phase of hepatocarcinogenesis, which should be considered for chemoprevention combination strategies.

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

Chemopreventive activities of the dietary isoprenoids ß-ionone (ßI) 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 ßI (ßI 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 ßI group showed a decrease in the mean number of visible hepatocyte nodules (P<.05); ßI 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 ßI 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 ßI 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 ßI 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 ßI- and GOH-treated groups had higher hepatic concentrations of ßI and GOH, respectively (P<.05). Given these data, ßI and GOH show promising chemopreventive effects during promotion of hepatocarcinogenesis by acting through distinct mechanism of actions: ßI may inhibit cell proliferation and modulate HMGCoA reductase, and GOH can induce apoptosis and inhibit RhoA activation.

Absence of chemopreventive influence of propolis on the rat liver altered foci development.

Propolis (bee glue) is a complex mixture of natural substances that exhibits a broad spectrum of biological activities. As the possibility exists that it may exert a chemopreventive role against cancer development, the present study aimed to evaluate the chemopreventive influence of a Brazilian aqueous propolis extract (APE) in a rat two-stage (initiation-promotion) medium-term bioassay for chemical liver carcinogenesis. Male Wistar rats were sequentially initiated with diethylnitrosamine (DEN, 200mg/kgb.w.) and, 2 weeks later, exposed to a diet containing hexachlorobenzene (HCB, 100ppm) and to APE 0.1% through drinking water for 6 weeks. Appropriate control groups were also established. The animals were sacrificed at the weeks 8th and 30th when liver samples were processed to evaluate the development of altered hepatocyte foci (AHF) identified under hematoxylin and eosin (H&E) staining and by the immunohistochemical expression of the enzyme glutathione S-transferase placental form (GST-P). The results indicate that APE 0.1% did not protect against the development of any of the differentially identified putative preneoplastic foci in DEN-initiated animals, exposed or not to the promoting agent HCB. Also, APE 0.1% by itself did not significantly induce any AHF, what is in line with its already known absence of genotoxic potential. Our results indicate that an aqueous extract of Brazilian propolis did not exert chemoprevention on the hepatocarcinogenesis process chemically induced in the rat.

Genotoxicity of antimicrobial endodontic compounds by single cell gel (comet) assay in Chinese hamster ovary (CHO) cells.

OBJECTIVE: In the current study, the potential DNA damage associated with exposure to a number of antimicrobial endodontic compounds was assessed by the single cell gel (comet) assay in vitro. STUDY DESIGN: Chinese hamster ovary (CHO) cells were exposed to formocresol, paramonochlorophenol, calcium hydroxide, or chlorhexidine at final concentration ranging from 0.01% to 1%. RESULTS: Formocresol, paramonochlorophenol, and calcium hydroxide, as well as chlorhexidine in all concentrations tested did not contribute to the DNA damage. CONCLUSION: These findings are clinically relevant since they represent an important contribution to the correct evaluation of the potential health risk associated with exposure to dental agents.

Squalene does not exhibit a chemopreventive activity and increases plasma cholesterol in a Wistar rat hepatocarcinogenesis model.

The eventual chemopreventive effect of squalene (SQ), a triterpene present in olive oil, was evaluated when administered to Wistar rats during a period comprising the initiation and selection/promotion of the "resistant hepatocyte" (RH) model of hepatocarcinogenesis. During 8 consecutive wk, animals received by gavage SQ (100 or 150 mg/100 g body weight) dissolved in corn oil (CO) daily. Animals treated with only CO and submitted to the RH model were used as controls. Treatments with SQ did not result in inhibition of macroscopically visible hepatocyte nodules (P > 0.05) or of hepatic placental glutathione S-transferase- positive preneoplastic lesions (PNL; P > 0.05). Hepatic cell proliferation and apoptosis indexes were not different (P > 0.05) among the different experimental groups, both regarding PNL and surrounding normal tissue areas. There were no significant differences (P > 0.05) among comets presented by rats treated with the two SQ doses or with CO. On the other hand, SQ increased total plasma cholesterol levels when administered at both doses (P < 0.05). This indicates that the isoprenoid was absorbed. Thus, SQ did not present chemopreventive activity during hepatocarcinogenesis and had a hypercholesterolemic effect, suggesting caution when considering its use in chemoprevention of cancer.

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.

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

O flúor tem sido amplamente usado na Odontologia, pois é um agente profilático efetivo e específico contra a cárie dentária. Entretanto, o flúor em excesso pode representar perigos à saúde humana, especialmente por causar agressão ao material genético. Testes de genotoxicidade representam uma importante parte da pesquisa do câncer para a avaliação de risco de possíveis carcinógenos. Neste presente estudo, danos ao DNA associados à exposição ao flúor foram avaliados pelo teste de células individualizadas em gel de agarose (teste do cometa) in vitro. Células de ovário de hamster chinês foram expostas ao fluoreto de sódio (NaF) nas concentrações finais de 7 a 100 µg/ml, durante 3 h, a 37ºC. Os resultados mostraram que o NaF não contribuiu para os danos no DNA em todas as concentrações testadas, conforme demonstrado pelas médias do momento da cauda e da intensidade da cauda dos cometas. Esses achados são clinicamente importantes, uma vez que representam uma importante contribuição para a correta avaliação do potencial risco à saúde associada à exposição aos agentes odontológicos.

Ação do licopeno na proteção contra danos induzidos no DNA in vivo e in vitro / Action of lycopene in the protection against damage induced in DNA in vivo and in vitro

O licopeno é um pigmento natural sintetizado por plantas e microorganismos, e encontrado principalmente no tomate. É um isômero acíclico do beta-caroteno sem atividade pró-vitamínica­-A, sendo um dos mais potentes agentes antioxidantes. Diversos pesquisadores têm demonstrado o efeito protetor do licopeno contra danos no DNA e sobre a carcinogênese quicamente induzida, embora os mecanismos envolvidos nesses processos não estejam, ainda totalmente esclarecidos. Assim, o presente estudo objetivou avaliar o potencial quimioprotetor do licopeno contra danos no DNA e sobre a hepaticarcinogênese em roedores. O efeito anticarcinogênico do licopeno em figado de ratos foi avaliado utilizando-se os focos GST-P positivos (modelo de hepatocarcinogênese de média duração proposto por Ito et al., 1988) como biomarcadores de lesões pré-neoplásicas. Para avaliação do efeito antigenotóxico e antimutagênico do carotenóide, bem como de seu possível mecanismo de ação, foram utilizados, respectivamente, o teste do cometa e o teste do micronúcleo em duas linhagens celulares in vitro: células de ovário de hamster chinês (CHO) e células de hepatoma humano (HepG2). Mutágenos de ação direta (peróxido de hidrogênio, oxido de 4-nitroquinolina - 4NQO e metil metanosulfonato - MMS) e indireta (dietilnitrosamina -DEN), foram utilizados 10 indutores de danos no DNA in vitro. Os resultados mostraram que o licopeno, na concentração 300 ppm, reduziu significativamente os danos no DNA induzidos pela DEN na etapa de iniciação da hepatocarcinogênese de rato, embora não tenha sido observada redução do número e área dos focos GST-P-positivos. Os resultados dos experimentos in vitro mostraram que o tratamento prévio e simultâneo com licopeno (10, 25, e 50 miuM) foi eficaz em reduzir os níveis de danos no DNA induzidos pelo H202 e pela DEN em células HepG2, quando avaliados tanto teste do cometa como do micronúcleo.