Assessment of no-observed-effect-levels for DNA adducts formation by genotoxic carcinogens in fetal turkey livers.

For genotoxic carcinogens, covalent binding to DNA is a critical initiating event in tumorigenesis. The present research investigated dose-effect relationships of three genotoxic carcinogens representing different structural classes, 2-acetylaminofluorene (2-AAF), benzo[a]pyrene (B[a]P) and quinoline (QUI), to assess the existence of no-observed-effect-levels (NOELs) for the formation of DNA adducts. Carcinogens were administered into the air sac of fertilized turkey eggs over wide dose ranges in three daily injections on days 22 to 24 of incubation. DNA adducts were measured in the fetal turkey livers by the 32P-nucleotide postlabeling (NPL) assay. B[a]P and QUI produced DNA adducts in a dosage-related manner and exhibited NOELs at 0.65 and 0.35 mg/kg bw/day, respectively. In contrast, 2-AAF formed DNA adducts at all tested dosages down to 0.005 mg/kg bw/day. Benchmark dose (BMD) analysis identified the potencies of 2-AAF and QUI to be similar, while B[a]P was the least potent compound. Overall, findings in fetal turkey livers demonstrated that exposure levels to genotoxic compounds that do not result in DNA adducts can exist but are not evident with all carcinogens of this type. The use of mechanistic dose-effect studies for genotoxic endpoints can provide critical information for prioritization of concerns for risk assessment.

Chronic Administration of Diethylnitrosamine and 2-Acetylaminofluorene Induces Hepatocellular Carcinoma in Wistar Rats.

This study aimed to analyze the biochemical, histological, and gene expression alterations produced in a hepatocarcinogenesis model induced by the chronic administration of diethylnitrosamine (DEN) and 2-acetylaminofluorene (2-AAF) in Wistar rats. Thirteen rats weighing 180 to 200 g were divided into two groups: control and treated. Rats in the treated group were administered an intraperitoneal (i.p.) injection of DEN (50 mg/kg/week) and an intragastric (i.g.) dose of 2-AAF (25 mg/kg/week) for 18 weeks. The treated group had significant increases in their total cholesterol, HDL-C, AST, ALT, ALKP, and GGT levels. Furthermore, a histological analysis showed the loss of normal liver architecture with nuclear pleomorphism in the hepatocytes, atypical mitosis, and fibrous septa that were distributed between the portal triads and collagen fibers through the hepatic sinusoids. The gene expressions of 24 genes related to fibrosis, inflammation, apoptosis, cell growth, angiogenesis, lipid metabolism, and alpha-fetoprotein (AFP) were analyzed; only TGFß, COL1α1, CYP2E1, CAT, SOD, IL6, TNF-α, and ALB showed significant differences when both groups were compared. Additionally, lung histopathological alterations were found in the treated group, suggesting metastasis. In this model, the chronic administration of DEN+2-AAF induces characteristic alterations of hepatocellular carcinoma in Wistar rats without AFP gene expression changes, highlighting different signatures in hepatocellular carcinoma heterogeneity.

Quercetin and naringenin abate diethylnitrosamine/acetylaminofluorene-induced hepatocarcinogenesis in Wistar rats: the roles of oxidative stress, inflammation and cell apoptosis.

This study was designed to assess the preventive effects and to suggest the probable mechanisms of action of quercetin and naringein in diethylnitrosamine (DEN)/2-acetylaminofluorene (2AAF)-induced hepatocarcinogenesis in Wistar male rats. The chemical-induction of hepatocarcinogenesis was performed by injection of DEN intraperitoneally at 150 mg/kg body weight (b.w.) twice/week for two weeks, followed by oral administration of 2AAF at 20 mg/kg body weight (b.w.) 4 times/week for 3 weeks. The DEN/2AAF-administered rats were co-treated with quercetin and naringenin at dose level of 10 mg/kg b. w. by oral gavage for 20 weeks. The treatment of DEN/2AAF-administered rats with quercetin and naringenin significantly prevented the elevations in serum levels of liver function indicators (ALT, AST, ALP, γ-GT, total bilirubin and albumin) and liver tumor biomarkers including AFP, CEA and CA19.9. The cancerous histological lesions and inflammatory cells infiltration in liver of DEN/2AAF-administered rats were remarkably suppressed by treatments with quercetin and naringenin. The hepatic oxidative stress markers including NO level and lipid peroxidation significantly decreased while the SOD, GPx and CAT activities and GSH content significantly increased in DEN/2AAF-administered rats treated with quercetin and naringenin when compared to DEN/2AFF-administered control rats. Furthermore, the lowered mRNA expression of liver IL-4, P53 and Bcl-2 in of DEN/2AAF-administered rats were significantly counteracted by treatment with quercetin and naringenin. Taken together, our results demonstrate that quercetin and naringenin may abate hepatocarcinogenesis via enhancement of anti-inflammatory, anti-oxidant and apoptotic actions.

Enrichment of progenitor cells by 2-acetylaminofluorene accelerates liver carcinogenesis induced by diethylnitrosamine in vivo.

The potential role of hepatocytes versus hepatic progenitor cells (HPC) on the onset and pathogenesis of hepatocellular carcinoma (HCC) has not been fully clarified. Because the administration of 2-acetylaminofluorene (2AAF) followed by a partial hepatectomy, selectively induces the HPC proliferation, we investigated the effects of chronic 2AAF administration on the HCC development caused by the chronic administration of the carcinogen diethylnitrosamine (DEN) for 16 weeks in the rat. DEN + 2AAF protocol impeded weight gain of animals but promoted prominent hepatomegaly and exacerbated liver alterations compared to DEN protocol alone. The tumor areas detected by γ-glutamyl transferase, prostaglandin reductase-1, and glutathione S-transferase Pi-1 liver cancer markers increased up to 80% as early as 12 weeks of treatment, meaning 6 weeks earlier than DEN alone. This protocol also increased the number of Ki67-positive cells and those of CD90 and CK19, two well-known progenitor cell markers. Interestingly, microarray analysis revealed that DEN + 2AAF protocol differentially modified the global gene expression signature and induced the differential expression of 30 genes identified as HPC markers as early as 6 weeks of treatment. In conclusion, 2AAF induces the early appearance of HPC markers and as a result, accelerates the hepatocarcinogenesis induced by DEN in the rat. Thus, since 2AAF simultaneously administrated with DEN enriches HPC during hepatocarcinogenesis, we propose that DEN + 2AAF protocol might be a useful tool to investigate the cellular origin of HCC with progenitor features.

Investigation of the Effects of Octreotide Agent on Oxidative Stress, 8-Hydroxy Deoxyguanosine in Experimental Hepatic Carcinogenesis Rat Model.

INTRODUCTION: 2-AAF and DEN are well-known liver toxicants commonly used to stimulate tumors in laboratory animals. AIM: The aim of this study was to investigate the effect of octreotide on DEN-induced and 2-AAF-supplemented hepatocarcinogenesis in Wistar albino rats. MATERIALS AND METHODS: In this study, 64 Wistar albino rats were divided into 8 groups. DEN (175 mg/kg) initiated and 2-AAF (20 mg/kg) promoted liver carcinogenesis in rats. The tumor growth inhibitor octreotide (300 µg/kg) was used. Rats were sacrificed at the end of experiment and their liver tissues were taken for the study. SOD, GSH-Px, CAT activities, NO and MDA levels were measured spectrophotometrically. Also, Hsp70 and 8-OHdG was measured by the ELISA method. RESULTS: In group 7, MDA, 8-OHdG, and Hsp70 levels were significantly increased. In addition, SOD, GSH-Px activity was significantly reduced in this group. MDA, 8-OHdG and Hsp70 levels were significantly reduced in Group 8, which received octreotide for treatment. CONCLUSION: DEN and 2-AAF cause very serious liver damage. Octreotide protects the liver from carcinogenesis, increases the activity of cellular antioxidant enzymes and helps reduce DNA damage. Therefore, octreotide may be an inhibitor in tumor cells and may reduce oxidative stress.

Diwu Yanggan Modulates the Wnt/ß-catenin Pathway and Inhibits Liver Carcinogenesis Signaling in 2-AAF/PH Model Rats.

The activation of the Wnt/ß-catenin signaling pathway in oval cells after liver injury is implicated in hepatocarcinogenesis. Diwu Yanggan capsule is a Chinese herbal medicine that has been used for treating liver disorder. The present study aimed to examine the mechanism by which Diwu Yanggan inhibits liver carcinogenesis, and the involvement of the Wnt/ß-catenin signaling pathway. Diwu Yanggan capsule was administered to 2-acetaminofluorene/partial hepatectomy (2-AAF/PH) rats, a murine model of liver injury. The biomarkers of oval cells and key proteins in the Wnt/ß-catenin signaling pathway were assessed on postoperative day 8, 10, 14, 17, 19 and 22. The results showed that treatment with Diwu Yanggan was associated with reduced expression of oval cell and stem cell biomarkers in the 2-AAF/PH animals. The expression pattern of key proteins in the Wnt/ß-catenin pathway was altered in Diwu Yanggan-treated animals, indicating that the Diwu Yanggan treatment accelerated the activation of the Wnt/ß-catenin pathway in the initial stage and contributed to its deactivation in the later stage. Histological findings indicated that hepatocyte proliferation was suppressed in Diwu Yanggan-treated animals, compared with untreated 2-AAF/PH animals. Taken together, Diwu Yanggan capsule may reduce the risk of hepatocarcinogenesis by modulating the Wnt/ß-catenin signaling pathway.

Pantoprazole attenuates tumorigenesis via inhibition of exosomal secretion in a rat model of hepatic precancerous lesion induced by diethylnitrosamine and 2-acetamidofluorene.

The present study aimed to evaluate the potential therapeutic effect of pantoprazole, a proton-pump inhibitor, on precancerous lesion (PCL) in rats. diethylnitrosamine and 2-acetylaminofluorene were used to induce PCL in rats, in vivo. The rats were treated with three doses of pantoprazole (100, 50, and 25  mg/kg; three times weekly) during the last 4 weeks of the total 10 weeks of the experiment. Blood and liver tissue samples were collected for measurement of the exosomal abundance and exosomal competing endogenous RNA markers. Results revealed that pantoprazole administration had an ameliorating effect on liver function tests and microscopic features of the liver; and decreased exosome abundance in the liver tissue samples and sera of the rats. Meanwhile, the treatment also resulted in a dose-dependent decrease in exosomal RAB11A mRNA and long noncoding RNA RP11-513I15.6, which is an important participant in th exosomal secretion process with an increase in exosomal miRNA-1262. Based on these results, we postulated that pantoprazole has the potential to attenuate liver tumorigenesis in this rat model.

Abnormal expression of HMGB-3 is significantly associated with malignant transformation of hepatocytes.

AIM: To explore the relationship between dynamic expression of high mobility group box-3 (HMGB3) and malignant transformation of hepatocytes. METHODS: Expression of HMGB family proteins were observed in rat hepatocarcinogenesis models induced with 2-acetylaminofluorene. Alterations of HMGB3 were analyzed at the mRNA level by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and at the protein level by immunohistochemistry or Western blotting. HMGB3 in human liver cancer tissues were evaluated using bioinformatics databases from GEO, TCGA, and Oncomine. A specific HMGB3-shRNA was used to knock down HMGB3 expression in order to investigate its effects on proliferation and cell cycle in vitro and in vivo. RESULTS: Elevated HMGB3 levels were first reported in hepatocarcinogenesis, with increasing expression from normal liver to cancer. Bioinformatic databases showed that HMGB3 expression in hepatocellular carcinoma tissues was significantly higher than that in normal liver tissues. Higher HMGB3 expression was discovered in liver cancer cells compared with LO2 cells in vitro. According to gene set enrichment analysis, HMGB3 mRNA levels were correlated with cell cycle and DNA replication pathways. Knocking down HMGB3 by specific shRNA significantly inhibited proliferation of HepG2 cells by cell cycle arrest and downregulating DNA replication related genes (cyclin B1, FEN1, and PCNA) at the mRNA and protein level. Furthermore, silencing HMGB3 significantly inhibited xenograft tumor growth (measured by Ki67) in vivo. CONCLUSION: HMGB3 is involved in malignant transformation of hepatocytes and could be a useful biomarker for diagnosis and a potential target for therapy of liver cancer.

Selective Cytotoxicity of Luteolin and Kaempferol on Cancerous Hepatocytes Obtained from Rat Model of Hepatocellular Carcinoma: Involvement of ROS-Mediated Mitochondrial Targeting.

To evaluate the cytotoxicity effects of luteolin (LUT) and kaempferol (KAE) via reactive oxygen species (ROS) mediated mitochondrial targeting on hepatocytes obtained from the liver of hepatocellular carcinoma (HCC) rats. In this study, HCC induced by diethylnitrosamine (DEN) and 2-acetylaminofluorene (2-AAF). In the following, rat liver hepatocytes and mitochondria were isolated and tested for every eventual apoptotic and anti-HCC effects of LUT and KAE. The results of MTT assay showed that LUT and KAE were able to induce selective cytotoxicity in hepatocytes of HCC group in a dose- and time-dependent manner. Treatment of mitochondria from hepatocytes of HCC group with LUT and KAE were accompanied by loss of mitochondrial membrane potential (MMP) and mitochondrial swelling and release of cytochrome c (P < 0.001) via reactive oxygen species (ROS) generation before cytotoxicity ensued. LUT and KAE also increased activation of caspase-3 (P < 0.001 and P < 0.01, respectively). Flow-cytometry analysis indicated that the mode of cell death induced by these flavonoids were mostly apoptosis. Importantly, LUT and KAE were nontoxic for healthy hepatocytes and mitochondria. Therefore, we suggest that LUT and KAE are a good candidate for the complementary therapeutic agent against HCC.

Strong carcinogenic stress response induction of preneoplastic cells positive for GST-P in the rat liver: Physiological mechanism for initiation.

AIMS: To identify experimental conditions that induce preneoplastic cells positive for glutathione S-transferase P-form (GST-P) in the rat liver by new approaches, and analysis of the mechanism of cancer initiation based on the findings. MAIN METHODS: The experimental protocols employed to induce GST-P+ preneoplastic cells in rat liver were as follows. Protocol 1: adult rats were fed basal diet containing 2-acetylaminofluorene (AAF, 0.02% by wt) and high concentrations of N-acetyl-l-cysteine (0.5%) over 10 weeks. Protocol 2: rats were subjected to partial hepatectomy (2/3PH), followed by an AAF (0.04%) diet for two more weeks. Vibratome-prepared liver sections were then immunostained for GST-P. KEY FINDINGS: GST-P was inducible in the rat liver in response to the strong carcinogenic stress by AAF in the two experimental protocols. When examined immunocytochemically with vibratome sections, the biliary tracts of hepatocytes, GST-P+ single hepatocytes and foci were heavily positive for the marker enzyme in addition to ordinary cytosolic staining of preneoplastic cell populations. The biliary tracts of hepatocytes were severely injured, and the excretory portions of GST-P+ single hepatocytes were significantly injured. SIGNIFICANCE: The cytotoxic action of AAF that give rise to the GST-P+ single hepatocytes was suggested to be an injury to the excretory pump(s) and the duct of hepatocytes. A new physiological mechanism was hypothesized for the induction of preneoplastic cell populations in the rat liver instead of a genetic mechanism.

Molecular characterization of the grape seeds extract's effect against chemically induced liver cancer: In vivo and in vitro analyses.

The purpose of this study was to investigate the anti-cancer property of grape seed extract (GSE) during early stages of developing liver cancer using a two-stage carcinogenic model combining diethylnitrosamine (DEN) and 2-Acetyl Aminofluorene (2-AAF). Administration of GSE at doses 25, 50 and 100 mg/kg per day started at the beginning of promotion periods and continued for 14 weeks. GSE dramatically inhibited pre-neoplastic foci formation as well as significantly decreased the number and the area of placental glutathione-S-transferase in livers of DEN-2AAF-treated rats by approximately 4 & 10 fold deductions, respectively. GSE's effects were associated with induced apoptosis, reduced cell proliferation, decreased oxidative stress and down regulation of histone deacetylase activity and inflammation makers, such as cyclooxygenase 2, inducible nitric oxide synthase, nuclear factor-kappa B-p65 and p- phosphorylated tumor necrosis factor receptor expressions in liver. GSE treatment also decreased the viability of HepG2 cells and induced early and late apoptosis through activating caspase-3 and Bax. Furthermore, GSE induced G2/M and G1/S cell cycle arrest. The present study provides evidence that the GSE's anticancer effect is mediated through the inhibition of cell proliferation, induction of apoptosis, modulating oxidative damage and suppressing inflammatory response.

Identification of (Z)-2,3-Diphenylacrylonitrileas Anti-Cancer Molecule in Persian Gulf Sea Cucumber Holothuria parva.

Hepatocellular carcinoma (HCC), also named cancerous hepatoma, is the most common type of malignant neoplasia of the liver. In this research, we screened the Persian Gulf sea cucumber Holothuria parva (H. parva) methanolic sub-fractions for the possible existence of selective toxicity on liver mitochondria isolated from an animal model of HCC. Next, we purified the most active fraction. Thus the structure of the active molecule was identified. HCC was induced by diethylnitrosamine (DEN) and 2-acetylaminofluorene (2-AAF) protocol. Rat liver mitochondria for evaluation of the selective cytotoxic effects of sub-fractions of H. parva were isolated and then mitochondrial parameters were determined. Our results showed that C1 sub-fraction of methanolic extract of H. parva considerably increased reactive oxygen species (ROS) generation, collapse of mitochondrial membrane potential (MMP), swelling in mitochondria and cytochrome c release only on HCC liver mitochondria. Furthermore, the methanolic extract of H. parva was investigated furthermore and the active fraction was extracted. In this fraction, (Z)-2,3-diphenylacrylonitrile molecule, which is also known as α-cyanostilbene, was identified by mass analysis. This molecule increased ROS generation, collapse of MMP, swelling in mitochondria and finally cytochrome c release only on HCC liver mitochondria. The derivatives of (Z)-2,3-diphenylacrylonitrile in other natural products were also reported as an anti-cancer agent. These results suggest the eligibility of the (Z)-2,3-diphenylacrylonitrile as a complementary therapeutic agent for patients with HCC.

[Dynamic expression of carnitine palmitoyltransferase II in the mitochondrial inner membrane during hepatocyte malignant transformation induced by lipid accumulation].

Objective: To investigate the dynamic expression of hepatic carnitine palmitoyltransferase-II (CPT-II) in the mitochondrial inner membrane during hepatocyte malignant transformation induced by lipid accumulation. Methods: Male Sprague-Dawley rats were divided randomly into control, fatty liver, and induced cancer groups, which were fed with normal, high-fat (HF), and HF containing 2-fluorenylacetamide (0.05%, 2-FAA) diets, respectively, for 14 weeks. One rat from each group was sacrificed every two weeks and the blood and liver samples were collected. Liver morphological changes were evaluated with hematoxylin and eosin staining, and the liver tissue samples were divided into control, fatty liver, degeneration, precancerous, and cancerous groups accordingly. Hepatic lipids were dyed by the oil red O method. The CPT-II expression was measured by immunohistochemistry and compared with the specific CPT-II concentration (ng/mg liver protein, ng/mg P) among different groups. Serum levels of circulating total cholesterol (Tch), triglyceride (TG), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) were quantitatively analyzed. Results: Massive lipid accumulation hepatocytes was seen in rats on HF and HF containing 2-FAA diets. The lipid levels in the control group were significantly lower than those in the fatty liver (t = -11.556, P < 0.001), degeneration (t = -4.847, P = 0.04), precancerous (t = -13.652, P = 0.005), and cancerous groups (t = -10.896, P = 0.008). The serum TG and Tch levels in the degeneration, precancerous, and cancerous groups were 2-3 times higher than those in the control group (P < 0.05). After 2-FAA treatment, the morphological changes of rat hepatocytes showed the progression from degeneration and precancerosis to cancerosis, with hepatocyte injury. The serum AST and ALT levels in the degeneration, precancerous, and cancerous groups were significantly higher (4-8 times) than those in the control group (P < 0.05). The specific concentration of liver CPT-II expression was significantly reduced during hepatocyte malignant transformation, as confirmed by immunohistochemistry, with the CPT-II levels significantly lower in the cancerous group than in any of other groups (P < 0.05). Conclusion: Low hepatic CPT-II expression might lead to abnormal lipid accumulation in hepatocytes, which should promote the malignant transformation of hepatocytes.

Mitochondrial carnitine palmitoyl transferase-II inactivity aggravates lipid accumulation in rat hepatocarcinogenesis.

AIM: To investigate the dynamic alteration of mitochondrial carnitine palmitoyl transferase II (CPT-II) expression during malignant transformation of rat hepatocytes. METHODS: Sprague-Dawley male rats were fed with normal, high fat (HF), and HF containing 2-fluorenylacetamide (2-FAA) diet, respectively. According to the Hematoxylin and Eosin staining of livers, rats were divided into control, fatty liver, degeneration, precancerous, and cancerous groups. Liver lipids were dyed with Oil Red O, CPT-II alterations were analyzed by immunohistochemistry, and compared with CPT-II specific concentration (µg/mg protein). Levels of total cholesterol (Tch), triglyceride (TG), and amino-transferases [alanine aminotransferase (ALT), aspartate aminotransferase (AST)] were determined by the routine methods. RESULTS: After intake of HF and/or HF+2-FAA diets, the rat livers showed mass lipid accumulation. The lipid level in the control group was significantly lower than that in other groups. The changes of serum TG and Tch levels were abnormally increasing, 2-3 times more than those in the controls (P < 0.05). During the rat liver morphological changes from normal to cancer development process with hepatocyte injury, serum AST and ALT levels were significantly higher (4-8 times, P < 0.05) than those in the control group. The specific concentration of CPT-II in liver tissues progressively decreased during hepatocyte malignant transformation, with the lowest CPT-II levels in the cancer group than in any of the other groups (P < 0.05). CONCLUSION: Low CPT-II expression might lead to abnormal hepatic lipid accumulation, which should promote the malignant transformation of hepatocytes.

Results of rat Pig-a/PIGRET assay with a single dose regimen of 1,3-propane sultone and 2-acetyl aminofluorene.

The Pig-a assay is a useful in vivo mutation detecting test and is easier to perform than the in vivo transgenic mutation assay. This assay is now recognized to be able to detect a number of mutagenic chemicals administered to rats in sub-acute or sub-chronic dose studies. The present investigation was conducted to evaluate the usefulness of peripheral blood Pig-a assays with total red blood cells (RBC Pig-a assay) and with reticulocytes (PIGRET assay) using two genotoxic rodent carcinogens, 1,3-propane sultone (1,3-PS) and 2-acetylaminofluorene (2-AAF). Male rats were orally administered a single dose of each test compound, and both the RBC Pig-a and PIGRET assays were performed using flow cytometry to measure the Pig-a mutant frequency (MF) before and after dosing on Days 8, 15 and 29. In the experiment with 1,3-PS, significant increases in Pig-a MF were observed from Day 15 and Day 8 in the RBC Pig-a and PIGRET assays, respectively. The results of both assays demonstrated that the increases in Pig-a MF were detectable after a single treatment with 1,3-PS. Furthermore, the difference in the kinetics of the increase in Pig-a MF between the RBC Pig-a and PIGRET assays with 1,3-PS suggests that the PIGRET assay has an advantage in detecting the mutant erythrocytes earlier than the RBC Pig-a assay. In contrast, no significant increases were observed in the Pig-a assays using either RBC or reticulocytes with 2-AAF. The negative results in both assays with 2-AAF may indicate the limitation of the single dose method; however, further investigation at higher doses is necessary to determine limitation of the single dose method.

Myricetin Selectively Induces Apoptosis on Cancerous Hepatocytes by Directly Targeting Their Mitochondria.

Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related death. In patients for whom HCC could not be detected early, current treatments show poor tolerance and low efficacy. So, alternative therapies with good efficacy are urgently needed. The aim of this research was to evaluate the selective apoptotic effects of myricetin (MYR), a flavonoid compound, on hepatocytes and mitochondria obtained from the liver of HCC rats. In this study, HCC induced by diethylnitrosamine (DEN), as an initiator, and 2-acetylaminofluorene (2-AAF), as a promoter. To confirm the HCC induction, serum levels of alpha-fetoprotein (AFP), AST, AST and ALP and histopathological changes in the liver tissue were evaluated. Rat liver hepatocytes and mitochondria for evaluation of the selective cytotoxic effects of MYR were isolated, and mitochondrial and cellular parameters related to apoptosis signalling were then determined. Our results showed that MYR was able to induce cytotoxicity only in hepatocytes from the HCC but not from the untreated control group. Besides, MYR (12.5, 25 and 50 µM) induced a considerable increase in reactive oxygen species (ROS) level, mitochondrial swelling, mitochondrial membrane permeabilization (MMP) and cytochrome c release only in cancerous but not in untreated normal hepatocyte mitochondria. MYR selectively increased caspase-3 activation and apoptotic phenotypes in HCC, but not untreated normal hepatocytes. Finally, our finding underlines MYR as a promising therapeutic candidate against HCC and recommends the compound for further studies.

Chemoprotective effect of Vernonia amygdalina Del. (Astereacea) against 2-acetylaminofluorene-induced hepatotoxicity in rats.

Natural products possessing antioxidant properties play a very crucial role in ameliorating deleterious effects of reactive oxygen species. This study investigated the chemoprotective properties of methanolic extract of Vernonia amygdalina (MEVA) in an experimental model of hepatic oxidative damage induced by 2-acetylaminofluorene (2-AAF). Rats were divided into six groups. Groups 1 and 2 received saline and dimethyl sulfoxide, respectively, and served as controls. Group 3 received MEVA at a dose of 250 mg/kg, while groups 5 and 6 were pretreated for 14 days with MEVA at 250 mg/kg and 500 mg/kg doses before coadministration with 2-AAF at 100 mg/kg for another 7 days. 2-AAF was administered to group 4 for the last 7 days. Animals were killed 24 h after the last administration of 2-AAF. 2-AAF significantly (p < 0.05) induced marked hepatic damage as revealed by increased activities of serum enzymes such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and γ-glutamyl transferase and bilirubin concentration. 2-AAF also elicited decrease in the activities of antioxidant enzymes such as superoxide dismutase, catalase, glutathione-S-transferase, and glutathione peroxidase, depletion of reduced glutathione, and increase in malondialdehyde levels. The activities of glucose-6-phosphatase and 5'-nucleotidase were also depleted. MEVA at 250 mg/kg and 500 mg/kg significantly (p < 0.05) ameliorated the oxidative damage, functional impairments, and histopathological changes associated with 2-AAF toxicity by reducing the activities of serum enzymes, upregulating the antioxidant defense enzymes and glutathione with decrease in malondialdehyde level. In this study, the revealed ameliorative and hepatoprotective effects of MEVA against 2-AAF-induced toxicity may be due to its antioxidant and free-radical scavenging activities, thus suggesting its usefulness as a possible chemoprophylactic agent.

Sex differences in DNA damage produced by the carcinogen 2-acetylaminofluorene in cultured human hepatocytes compared to rat liver and cultured rat hepatocytes.

Male rats are more susceptible to the induction of liver cancer by the aromatic amine 2-acetylaminofluorene (AAF) than are females. To assess the basis for this difference and to determine whether sex differences in susceptibility to AAF are present in human liver cells, the DNA reactivity of AAF was measured in livers of male and female Sprague-Dawley (SD) rats and in cultured SD rat and human hepatocytes of both sexes. In livers of rats administered oral doses of AAF, the total levels of adducts measured by nucleotide postlabelling at up to 8 weeks were about twofold greater in males than in females. Similarly, the level of AAF-DNA adducts formed in cultured male rat hepatocytes dosed with AAF was about twofold greater than in female rat hepatocytes. Also, the level of DNA repair synthesis was about threefold greater in AAF-dosed cultured male rat hepatocytes compared with female, indicating that the greater adduct levels in males was not due to lesser repair. In contrast, in cultured human hepatocytes of both sexes, AAF produced similar levels of adducts and DNA repair synthesis, which were intermediate between those produced in male and female rat hepatocytes. Thus, the greater susceptibility of male rats to AAF hepatocarcinogenicity is due at least in part to greater bioactivation and formation of AAF-DNA adducts in hepatocytes. Moreover, the data from human hepatocytes suggest that human liver could be less susceptible than male rat liver to the carcinogenic effects of aromatic amine carcinogens of the AAF type.

Alternative Multiorgan Initiation-Promotion Assay for Chemical Carcinogenesis in the Wistar Rat.

The medium-term multiorgan initiation-promotion chemical bioassay (diethylnitrosamine, methyl-nitrosourea, butyl-hydroxybutylnitrosamine, dihydroxypropylnitrosamine, dimethylhydrazine [DMBDD]) with the Fischer 344 rat was proposed as an alternative to the conventional 2-year carcinogenesis bioassay for regulatory purposes. The acronym DMBDD stands for the names of five genotoxic agents used for initiation of multiorgan carcinogenesis. The Brazilian Agency for the Environment officially recognized a variation of this assay (DMBDDb) as a valid method to assess the carcinogenic potential of agrochemicals. Different from the original protocol, this DMBDDb is 30-week long, uses Wistar rats and two positive control groups exposed to carcinogenesis promoters sodium phenobarbital (PB) or 2-acetylaminofluorene (2-AAF). This report presents the experience of an academic laboratory with the DMBDDb assay and contributes to the establishment of this alternative DMBDD bioassay in a different rat strain. Frequent lesions observed in positive groups to evaluate the promoting potential of pesticides and the immunohistochemical expressions of liver cytochrome P450 (CYP) 2B1/2B2 and CYP1A2 enzymes were assessed. Commonly affected organs were liver, kidney, intestines, urinary bladder, and thyroid. PB promoting activity was less evident than that of 2-AAF, especially in males. This study provides a repository of characteristic lesions occurring in positive control animals submitted to a modified alternative 2-stage multiorgan protocol for carcinogenesis in Wistar rat.

MicroRNA-152-mediated dysregulation of hepatic transferrin receptor 1 in liver carcinogenesis.

Over-expression of transferrin receptor 1 (TFRC) is observed in hepatocellular carcinoma (HCC); however, there is a lack of conclusive information regarding the mechanisms of this dysregulation. In the present study, we demonstrated a significant increase in the levels of TFRC mRNA and protein in preneoplastic livers from relevant experimental models of human hepatocarcinogenesis and in human HCC cells. Additionally, using the TCGA database, we demonstrated an over-expression of TFRC in human HCC tissue samples and a markedly decreased level of microRNA-152 (miR-152) when compared to non-tumor liver tissue. The results indicated that the increase in levels of TFRC in human HCC cells and human HCC tissue samples may be attributed, in part, to a post-transcriptional mechanism mediated by a down-regulation of miR-152. This was evidenced by a strong inverse correlation between the level of TFRC and the expression of miR-152 in human HCC cells (r = -0.99, p = 4. 7 × 10-9), and was confirmed by in vitro experiments showing that transfection of human HCC cell lines with miR-152 effectively suppressed TFRC expression. This suggests that miR-152-specific targeting of TFRC may provide a selective anticancer therapeutic approach for the treatment of HCC.