Inhibition of N-nitrosodiethylamine-induced hepatocarcinogenesis by Picroliv

Picroliv, an iridoid glycoside mixture prepared from the roots and rhizomes of Picrorhiza kurroa was found to be an effective inhibitor of hepatocarcinogenesis induced by N-Nitrosodiethylamine (NDEA) in rats. Animals administered with NDEA had large hepatic nodules and the liver weight was increased to 6.17 +/- 1.0 g/100 g.b.wt. as compared to the normal liver weight 2.84 +/- 0.08 g/100 g.b.wt. Picroliv administration (200 mg/Kg.b.wt) reduced the liver weight to 3.30 +/- 0.23 g/100 g.b.wt. Oral administration of Picroliv reduced NDEA-induced elevation of gamma-glutamyltranspeptidase (gamma-GT) in serum and liver to that of normal rats. Moreover, elevated levels of bilirubin, alkaline phosphatase (ALP), glutamatepyruvate transaminase (GPT) and serum peroxides were also found to be significantly reduced by Picroliv administration. Similar observations were noticed in glutathione (GSH) and glutathione S-transferase (GST) levels. Histopathological analysis of the Picroliv treated rat liver resembles that of a normal liver except for a few alterations such as hepatocytomegalia and karyomegalia in some focii. The results are indicative of the chemopreventive potential of Picroliv against chemically-induced liver tumours.     

Long term administration of granulocyte-macrophage colony stimulating factor decreases development of 1-2 dimethylhydrazine-induced colon cancer in rats

BACKGROUND AND OBJECTIVES: The antitumoral activities of granulocyte-macrophage colony stimulating factor (GM-CSF) were shown earlier. In this study, the effects of GM-CSF were investigated on colon cancer induced by 18 weeks of 1-2 dimethylhydrazine (DMH) administration in rats. METHODS: Four groups received subcutaneous saline (n = 20), 15 mg/kg DMH (n = 30), DMH +6 microg/kg GM-CSF (n = 30), and DMH +12 microg/kg (n = 30) GM-CSF. RESULTS: The average number of tumors (2.8 vs. 1.5) and mean tumor volume (179 +/- 36 vs. 27 +/- 9 mm(3); means +/- SEM) were reduced in DMH + GM-CSF groups as compared to the DMH group (n = 30, P < 0.01). DMH-induced enhancement of free radicals and lipid peroxidation were decreased in DMH + GM-CSF group (n = 8-12, P < 0.05). The magnitude of DMH-induced alterations in superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities was lowered in the DMH + GM-CSF group (n = 12-16, P < 0.05). DMH-induced increases in the total nitrite/nitrate levels and the nitric oxide synthase (NOS) activity (n = 10-12, P < 0.05) were also reduced in the DMH + GM-CSF group (n = 8-9, P < 0.05). CONCLUSIONS: The results indicate that GM-CSF inhibits the development of DMH-induced colon cancer in rats and suggest that inhibition of oxidative stress and NO pathway are involved in the observed antitumoral effects.     

Chemopreventive Effect of Amorphophallus campanulatus (Roxb.) Blume Tuber Against Aberrant Crypt Foci and Cell Proliferation in 1, 2-Dimethylhydrazine Induced Colon Carcinogenesis

Colorectal cancer is one of the leading causes of cancer death, both in men and women. This study investigatedthe effects of Amorphophallus campanulatus tuber methanolic extract (ACME) on aberrant crypt foci (ACF)formation, colonic cell proliferation, lipid peroxidative damage and the antioxidant status in a long term preclinicalmodel of 1, 2-dimethylhydrazine (DMH) induced colon carcinogenesis in rats. Male Wistar rats were dividedinto six groups, viz., group I rats served as controls; group II rats treated as drug controls receiving 250 mg/kg body weight of ACME orally; group III rats received DMH (20 mg/kg body weight) subcutaneously once aweek for the first 15 weeks; groups IV, V and VI rats received ACME along with DMH during the initiation,post- initiation stages and the entire period of the study, respectively. All the rats were sacrificed at the end of 30weeks and the intestinal and colonic tissues from different groups were subjected to biochemical and histologicalstudies. Administration of DMH resulted in significant (p≤0.05) intestinal and colonic lipid peroxidation (MDA)and reduction of antioxidants such as catalase, glutathione peroxidase, glutathione reductase, glutathione-Stransferaseand reduced glutathione. Whereas the supplementation of ACME significantly (p≤0.05) improvedthe intestinal and colonic MDA and reduced glutathione levels and the activities of antioxidant enzymes inDMH intoxicated rats. ACME administration also significantly suppressed the formation and multiplicity ofACF. In addition, the DMH administered rats showed amplified expression of PCNA in the colon and decreasedexpression of this proliferative marker was clearly noted with initiation, post-initiation and entire period ofACME treatment regimens. These results indicate that ACME could exert a significant chemopreventive effecton colon carcinogenesis induced by DMH.     

Effect of thymoquinone on 1,2-dimethyl-hydrazine-induced oxidative stress during initiation and promotion of colon carcinogenesis

We evaluated pre- and post-thymoquinone (TQ) treatment on 1,2-dimethyl-hydrazine (DMH)-induced oxidative stress during initiation and promotion of colon carcinogenesis. Wistar rats were induced with DMH (20 mg/kg) for 10 or 20 weeks, and treated with TQ (5 mg/kg). Following sacrifice, the colons were analysed for tumour development, reactive oxygen species (ROS) generation, lipid peroxidation [conjugated diene (CD) and malondialdehyde (MDA)], antioxidants [glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD) and reduced glutathione (GSH)], and histological changes. Increased ROS levels and lipid peroxidation were seen during tumour initiation and promotion. All ROS-scavenging enzyme activities were increased upon shorter DMH treatment but not following longer treatment, while GSH amount was increased upon both treatments. Oxidative state perturbations were associated with moderate colon dysplasia and 30% tumour incidence at initiation and marked dysplasia and 100% tumour incidence at promotion. TQ pre-treatment restored completely DMH-induced oxidative stress at initiation and established histological changes and tumour development. It also abrogated oxidative status aggravation at promotion, and significantly reduced tumour incidence (67%). By comparison, TQ post-treatment corrected oxidative status and attenuated tumour development at initiation. It slightly reduced MDA and antioxidant level at promotion, with a slight reduction in tumour state and dysplasia degree. TQ is efficacious in protecting and curing DMH-induced initiation phase of colon cancer, while exerting a protective role at promotion. TQ effect seems to be related to its capacity in preventing DMH-induced oxidative stress. These in vivo results support the notion that TQ may be of value as a chemo-preventive alternative in colorectal cancer patients.     

A protective role of 1,25-dihydroxyvitamin D3 in chemically induced rat colon carcinogenesis.

The intriguing observation has been made that 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] receptors are present in tissues not involved in calcium homeostasis and that 1,25(OH)2D3 exerts an antiproliferative, differentiation-promoting action in a variety of cancer cell lines, including cells of the large intestine. It was therefore deemed of interest to study 1,25(OH)2D3 expression and biological activity in a murine model of colon carcinogenesis. Colon carcinogenesis was induced in male rats by the sequential administration of 1,2-dimethylhydrazine dihydrochloride (DMH). Levels and binding characteristics of 1,25(OH)2D3 receptors were assessed in control and DMH-treated rat colonic mucosal high-speed supernatants. In concurrent studies, 1,25(OH)2D3 was administered (s.c., 400 ng/rat) prior to, together with and after DMH challenge and the activity of ornithine decarboxylase (ODC), a growth-related DMH-induced enzyme, was determined in colonic cytosols. Serum Ca2+ levels were measured concurrently. Rats submitted to identical treatment schedules were killed 10 weeks after termination of DMH administration and the whole colon was opened and examined for tumors. The results show that (i) rat colonic mucosa possesses a single class of high-affinity 1,25(OH)2D3 receptors; (ii) DMH administration provokes a marked reduction (50%) in 1,25(OH)2D3 binding sites without affecting Kd values; (iii) DMH administered concurrently with 1,25(OH)2D3 suppressed the vitamin D-induced hypercalcemia and restored serum Ca2+ concentrations to basal levels; and (iv) 1,25(OH)2D3 delivered prior to DMH challenge obliterated the typical DMH-induced early colonic ODC activity peak and markedly reduced (50%) the number of colon adenocarcinomas. The present findings indicate that a colon-specific potent carcinogen interferes with the biological expression of 1,25(OH)2D3 and that vitamin D administered prior to a carcinogenic insult is able to reduce significantly the incidence of colon tumors, presumably acting as an antiproliferative or differentiation-promoting agent.     

Selenium as a chemopreventive agent in experimentally induced colon carcinogenesis

AIM: To elucidate the chemopreventive efficacy of selenium during experimentally induced colon carcinogenesis.METHODS: Thirty-two male wistar rats were divided into four groups: group I (normal control); group II [1,2-dimethylhydrazine (DMH) treated]; group III (selenium treated); and group IV (DMH + selenium treated). Groups II and IV were given subcutaneous injections of DMH (30 mg/kg body weight) every week for 20 wk. Selenium, in the form of sodium selenite, was given to groups III and IV at 1 ppm in drinking water ad libitum for 20 wk. At the end of the study, rats were sacrificed and their colons were analyzed for the development of tumors, antioxidant enzyme levels and histological changes.RESULTS: 100% of the DMH treated rats developed tumors, which was reduced to 60% upon simultaneous selenium supplementation. Similarly, tumor multiplicity decreased to 1.1 following selenium supplementation to DMH treated rats. Levels of lipid peroxidation, glutathione-S-transferase, superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx) decreased following DMH treatment, whereas levels of glutathione (GSH) and glutathione reductase (GR) significantly increased in DMH treated rats. Selenium administration to DMH treated rats led to an increase in the levels of lipid peroxidation, SOD, catalase, glutathione-S-transferase and GPx, but decreased the levels of GSH and GR. Histopathological studies on DMH treated rats revealed dysplasia of the colonic histoarchitecture, which showed signs of improvement following selenium treatment.CONCLUSION: The study suggests the antioxidative potential of selenium is a major factor in providing protection from development of experimentally induced colon carcinogenesis.     

Chemoprevention of 1,2-dimethylhydrazine-induced colon cancer in mice by naturally occurring organosulfur compounds

Organosulfur compounds (OSCs) present in garlic and onion oil have been shown to inhibit chemical carcinogenesis. In this study, we compared the chemopreventive efficacy of five lipid- and four water-soluble OSCs using the murine nuclear aberration assay. Administration of diallyl sulfide and S-allyl cysteine p.o. at a dose of 200 mg/kg 3 h prior to i.p. 1,2-dimethylhydrazine (DMH) injection (20 mg/kg) significantly inhibited colonic nuclear damage in female C57Bl/6J mice by 47% and 36%, respectively. The inhibitory effect of S-allyl cysteine was found to be dose dependent. The other OSCs did not affect the level of DMH-induced nuclear toxicity. Furthermore, the incidence and frequency of colonic tumors induced by DMH (20 mg/kg, 10 weekly i.p. injections) in female CF-1 mice were significantly inhibited by S-allyl cysteine pretreatment, given 3 h prior to each carcinogen injection. These data indicate that the allyl group coupled to a single sulfur atom might play an important structural role in inhibition of DMH-induced colonic nuclear toxicity and carcinogenesis. OSCs containing allyl groups stimulated glutathione S-transferase activity in both the liver and colon. However, their saturated analogues stimulated little or no hepatic and colonic glutathione S-transferase activity. Induction of hepatic and colonic glutathione S-transferase might assist in detoxification of carcinogens and could be necessary for some aspects of chemoprevention.     

芥菜籽通过抗氧化和免疫偏移预防大肠肿瘤的实验研究

背景与目的：近年来有关十字花科植物预防肿瘤的研究,主要探讨其抗氧化、抗突变作用、调节免疫功能及诱导细胞凋亡等。芥菜籽(mustard seeds,MS)是十字花科植物的种子。本研究旨在探讨MS对1,2-二甲基肼(1,2-dimethylhydrazine,DMH)诱导的大鼠大肠肿瘤的抗氧化和免疫偏移作用机制。方法：将48只Wistar雄性大鼠随机均分为4组：DMH模型组(模型组)、DMH+5%MS干预组(5%MS干预组)、DMH+7.5%MS干预组(7.5%MS干预组)和正常对照组。模型组和MS干预组每周按30 mg/kg剂量给予DMH腹腔注射1次,连续20周,均于32周时处死大鼠观察大肠肿瘤发生率并HE染色确定肿瘤的组织分型,检测血清脂质过氧化产物丙二醛(malondialdehyde,MDA)水平、抗氧化酶活力、Th1和Th2亚群细胞因子含量。结果：正常对照组大鼠无肿瘤发生。模型组总成瘤率为100%,5%MS干预组和7.5%MS干预组总成瘤率分别降低33.3%和58.3%(P<0.05)。DMH诱导大鼠形成肿瘤的过程中,模型组MDA水平和Th2亚群细胞因子含量均显著高于正常对照组(P<0.05);而抗氧化酶活力明显低于正常对照组(P<0.05)。经MS干预后MDA呈显著下降趋势(P<0.05),而抗氧化酶活力和Th1亚群细胞因子含量均呈显著升高趋势(P<0.05)。结论：芥菜籽显著降低DMH化学诱导的大鼠大肠肿瘤的发生,作用机制可能与其抗氧化作用和免疫平衡偏移有关。     

Inhibition of hepatocarcinogenic responses to 1,2-dimethylhydrazine by diallyl sulfide, a component of garlic oil

The mechanisms by which diallyl sulfide (DAS), a component ofgarlic oil, inhibits hepatocarcinogenicity of 1,2-dimethylhydrazine(DMH) were examined in male Fischer 344 rats. Rats were subjectedto partial hepatectomy to stimulate hepatocellular proliferationrequired for initiation by DMH (50–200 mg/kg i.p.) given12 h later. Initiation was assessed by the numbers of foci andnodules of hepatocytes that were positive for -glutamyl transpeptidase(-GT) or glutathione-S-transferase-P (GST-P) after 6 weeks promotionby orotic acid (1% in semi-purified diet). DAS at doses above50 mg/kg (by gavage) administered 1 h before DMH (50 mg/kg)partially reduced the numbers of -GT and GST-P-positive foci.By comparison, all doses of DAS (25–100 mg/kg) completelyprevented liver necrosis by DMH (200 mg/kg). DAS substantiallyreduced macromolecular binding of [¹⁴C]DMH in cultured livercells, but had no effect on their levels of gluta-thione-S-transferase,glutathione reductase or glutathione peroxidase at 18 h. Thesefindings suggest that low dosages of DAS which reduce DMH bindingappear more likely to inhibit hepatocarcinogenicity by reducingthe promoting influences of post-necrotic regeneration thanby preventing initiation.     

Chemopreventive effect of trans-resveratrol--a phytoalexin against colonic aberrant crypt foci and cell proliferation in 1,2-dimethylhydrazine induced colon carcinogenesis

Prevention of cancer remains a primary need and new chemopreventive agents must be developed for this purpose. Towards this goal, a chemoprevention study was conducted to evaluate the activity of resveratrol (Res), a phytoalexin, as an inhibitor of colon carcinogenesis. Wistar male rats were divided into six groups, group 1 were control rats, group 2 were control rats that received Res (8 mg/kg body wt p.o. everyday), rats in groups 3-6 were treated weekly with 1,2-dimethylhydrazine (DMH, 20 mg/kg body wt, s.c. x 15 times). In addition, groups 4, 5 and 6 received Res as in group 2. Modifying effects were assessed using aberrant crypt foci (ACF) and the extent of histopathological lesions as end point markers. At the end of 30 weeks, Res markedly reduced tumor incidence, the degree of histological lesions and also the size of tumors significantly (P < 0.05) as compared with the rats treated with unsupplemented DMH. The number of ACF consisting of more than six aberrant crypts per rat was observed in group 6 (6.2 +/- 1.4), group 5 (7.7 +/- 1.0) and group 4 (8.2 +/- 1.4) which were significantly lower than that of group 3 (22.3 +/- 2.4) (P < 0.05). The most pronounced inhibition of ACF development was noted in rats fed Res for the entire period and also during the post-initiation period. Also, Res administration lowered the number of argyrophilic nucleolar organizing region-associated proteins (AgNORs) per nucleus in non-lesional colonic crypts, which reflects the cell proliferation activity. Oxidative imbalance in DMH-treatment was significantly (P < 0.01) modulated on Res supplementation as indicated by optimal concentration of thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH). The results of our study suggest Res to be an effective chemopreventive agent, which suppresses DMH-induced colon carcinogenesis at various stages.     

Chemoprevention of 2-amino-1-methyl-6-phenylimidazo- [4,5-b]pyridine-induced colon carcinogenesis by 1-O-hexyl-2,3,5-trimethylhydroquinone after initiation with 1,2-dimethylhydrazine in F344 rats

The aim of this study is to investigate the chemopreventive effects of the synthetic phenolic antioxidant 1-O-hexyl-2,3, 5-trimethylhydroquinone (HTHQ) on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-associated colon carcinogenesis in rats after initiation with 1,2-dimethylhydrazine (DMH) in male F344 rats. Groups of 20-22, 6-week-old male F344 rats were given four subcutaneous injections of 40 mg/kg body wt of DMH during the initial 4 weeks. They were then maintained on powdered basal diet containing 0.03% PhIP alone, PhIP together with 0.5 or 0.125% HTHQ, 0.5 or 0.125% HTHQ alone or basal diet for 32 weeks. A small number (1.1 +/- 1.1/rat) of colon tumors were induced by DMH treatment alone. After initiation with DMH, the number of colon tumors was greatly increased to 8.3 +/- 5.6 by the administration of PhIP. Additional treatment with HTHQ dose-dependently decreased the multiplicity of colon adenocarcinomas to 4.9 +/- 2.8 and 2.6 +/- 1.4 with 0.125 and 0.5%, respectively. This treatment similarly reduced atypical hyperplasias of the ventral prostate. Furthermore, HTHQ significantly reduced the multiplicity of duodenal adenocarcinomas induced by DMH + PhIP or DMH alone. Immunohistochemically, HTHQ was revealed to suppress PhIP-DNA adduct formation in the epithelial cells of the colon and prostate in a separate 2 weeks experiment. The present results clearly showed that HTHQ has chemopreventive potential for PhIP-associated colon and prostate carcinogenesis. The observed inhibition may largely be due to interference with PhIP-DNA adduct formation. In addition, HTHQ has been demonstrated to inhibit duodenal carcinogenesis in the post-initiation stage.     

Rapid induction of colorectal tumors in rats initiated with 1,2-dimethylhydrazine followed by dextran sodium sulfate treatment

To establish a rapid bioassay system with neoplastic end-points for detection of colorectal carcinogenesis modifiers, we evaluated the effects of dextran sodium sulfate (DSS) treatment on the different stages of carcinogenesis in rats initiated with 1,2-dimethylhydrazine (DMH). F344 male rats were given three subcutaneous injections of DMH (40 mg/kg body weight) in a week, and were administered drinking water containing 1.0% DSS ad libitum either during or after the initiation period for a week, or both during and after initiation periods for 2 weeks. At the 10th week of the experiment, although the numbers of aberrant crypt foci were significantly decreased in all groups treated with DSS and given DMH-initiation as compared with DMH alone, dysplastic foci/adenomas/adenocarcinomas were increased. The incidences and multiplicities of these lesions were highest in rats treated with DSS after DMH-initiation period. At the 26th week, the incidences of adenocarcinomas (100 vs. 20% in DMH alone) and their multiplicities (6.6 +/- 0.8/rat vs. 0.2 +/- 0.4/rat in DMH alone) were also highest in this group. These results indicate that short-term DSS-treatment in the post-initiation period significantly accelerates DMH-induced colorectal tumor development in rats, so that this protocol may effective for establishment of a rapid bioassay system with neoplastic end-points.     

Anticarcinogenic activity of nanoencapsulated quercetin in combating diethylnitrosamine-induced hepatocarcinoma in rats

Hepatocellular carcinoma is the most common primary hepatic malignancy worldwide. N-Nitroso compounds act as strong carcinogens in various animals, including primates. Diethylnitrosamine (DEN) is a well known carcinogenic substance, which induces hepatic carcinoma. The theme of the study was to evaluate the therapeutic efficacy of nanoencapsulated flavonoidal quercetin (3,5,7,3',4'-pentahydroxy flavone, QC) in combating DEN-induced hepatocarcinogenesis in rats. DEN induced a substantial increase in relative liver weights with proliferation and development of hyperplastic nodules. A significant increase in hepatocellular and nephrotoxicity indicated by serum alkaline phosphatase, aspartate transaminase, alanine transaminase, urea, and creatinine was observed in DEN-treated animals. Maximum protection from such toxicity was provided by nanoparticulated QC. Elevated levels of conjugated diene in DEN-treated rats were lowered significantly by nanoparticulated QC. Antioxidant levels in hepatic cells were reduced significantly by the induction of DEN. Nanoparticulated QC was found most potent for complete prevention of DEN-induced reduction in antioxidant levels in the liver. Upregulation of glutathione-S-transferase activity by DEN induction was reduced maximally by nanoencapsulated QC. Nanoencapsulated QC completely protected the mitochondrial membrane of the liver from carcinoma mediated by DEN injection. A significant correlation could be drawn between DEN-induced tissue reactive oxygen species generation and cytochrome C expression in the liver. Nanoencapsulated QC completely prevented the DEN-induced cytochrome C expression in the liver significantly.     

Spermidine/spermine N-1-acetyltransferase as a marker of dimethylhydrazine-induced colonic carcinogenesis in the rat

We investigated whether spermidine/spermine N-1-acetyltransferase (SSAT) might be a useful marker of 1,2-dimethylhydrazine (DMH)-induced colorectal tumors in rats. Male Wistar rats were given DMH weekly for 5 weeks (150 mg/kg/dose), and then sacrificed 5, 10, 15 or 20 weeks after the first dose. Tumors were detected in 2 of 6 rats sacrificed at 10 weeks. Colorectal mucosal SSAT activity was 25.8+/-2.4 pmoles/mg/min before dosing, and only slightly higher at 5 weeks (36.8+/-10.0). From week 5 onward, activity rose sharply and significantly, reaching 87.2+/-29.0 by week 20. These results indicate that SSAT is an excellent marker of DMH-induced colonic carcinogenesis.     

Effects of mycophenolate mofetil on cisplatin-induced renal dysfunction in rats

Purpose Inflammation and oxidative stress are important events among the plethora of mechanisms involved in cisplatin (CDDP)-induced nephrotoxicity. The aim of this study was to evaluate the effect of mycophenolate mofetil (MMF), an immunosuppressive, in the protection against CDDP-induced renal dysfunction. Methods Rats were divided into four groups; untreated-control group, CDDP-treated group (7 mg/kg, single intraperitoneal dose), MMF-treated group (40 mg/kg/day orally for 5 successive days) and the fourth group was treated with both drugs and MMF treatment was started 1 day prior to CDDP administration. Nephrotoxicity was assessed 7 days after the CDDP treatment by measuring serum indices of nephrotoxicity, kidney weight as a percentage of total body weight, kidney’s tissue peroxidative alterations and total nitrate/nitrite concentration (NOx) and the results were confirmed histopathologically. Results Rats treated with CDDP showed marked nephrotoxicity as evidenced from the significant increase in serum creatinine and urea levels and decrease in serum calcium and albumin levels. Kidneys of CDDP-treated rats showed significant increases in kidney weight and malondialdehyde (MDA) production level and decreases in total NOx concentration, glutathione peroxidase (GPx) activity and reduced glutathione (GSH) content levels. Histopathological assessment of kidneys of CDDP-treated rats revealed extensive tubular necrosis with “sloughing off” of the renal tubular lining cells, intratubular hyaline casts and mononuclear cell infiltration. Treatment with MMF significantly protected the rats against CDDP-induced nephrotoxicity. The rise in serum creatinine and urea levels, kidney weight and kidney tissue MDA production, depletion of “endogenous antioxidant reserve” including GPx activity and reduced GSH content levels and the deleterious histopathological changes induced by CDDP treatment were significantly mitigated by MMF treatment. Conclusions MMF treatment dramatically ameliorates CDDP-induced renal dysfunction.     

Inhibitory Effects of High Temperature- and Pressure-Treated Garlic on Formation of 1,2-Dimethylhydrazine-Induced Mucin-Depleted Foci and O6-Methylguanine DNA Adducts in the Rat Colorectum

High temperature- and pressure-treated garlic (HTPG) has been reported to have enhanced antioxidativeand cytotoxic activities. However, there have been no reports on chemopreventive effects using animal cancermodels. This study first examined the modifying effects of HTPG on 1,2-dimethylhydrazine (DMH)-inducedmucin-depleted foci (MDF) and aberrant crypt foci (ACF), preneoplastic lesions in the rat colorectum. MaleF344 rats (5 weeks old) were fed basal diet, or experimental diets containing 1% or 3% HTPG for 5 weeks. Oneweek later, all rats were injected s.c. with DMH (40 mg/kg, once weekly for 2 weeks). At 10 weeks of age, all therats were sacrificed, and the colorectum was evaluated for MDF and ACF. In rats given DMH and 3% HTPG,the numbers of MDF were decreased significantly as compared with those of rats given DMH alone (p<0.01),and the numbers of ACF showed a tendency to decrease, although not significantly. Next, the effects of HTPGon the formation of DMH-induced O6-methylguanine (O6-MeG) DNA adducts in rats were studied. Male F344rats (5 weeks old) were fed the basal diet or 10% HTPG diet for 5 weeks. All rats were injected i.p. once with 40mg/kg DMH at the end of week 5. The animals were sacrificed 6 hours after DMH injection to analyze the O6-MeG DNA adducts in the colorectal mucosa and liver. Dietary administration of HTPG significantly reducedthe adduct levels in the colorectal mucosa and liver, compared with the controls (both p<0.01). The activities ofsome detoxification enzymes in the liver of DMH-treated rats were also measured. HTPG significantly reducedthe activity of cytochrome P450 (CYP) 2E1, known to be responsible for activation of DMH in rat liver (p<0.05).In contrast, HTPG significantly enhanced the activities of phase 2 enzymes, quinone reductase (QR) andglutathione S-transferase (GST), in rat liver (both p<0.05). These results suggested that HTPG might havechemopreventive effects against colon carcinogenesis, at least in the initiation stage.     

Summation of initiation activities of low doses of the non-hepatocarcinogen 1,2-dimethylhydrazine in the liver after carbon tetrachloride administration

Summation of initiation by low doses of the indirect-acting non-hepatocarcinogen, 1,2-dimethylhydrazine (DMH) after proliferative stimulation with a necrogenic dose of carbon tetrachloride (CCl4) was investigated in terms of the induction of glutathione S-transferase placental form (GST-P) positive liver cell foci. Cell kinetics of liver after CCl4 i.g. treatment were examined with bromodeoxyuridine (BrdU) labeling (experiment I). To assess the correlation between cell proliferation and induction of liver cell foci, DMH (10 mg/kg i.g.) was administrated to 7-week-old male F344 rats at 12, 24, 36, 48, 60, 96 h after CCl4 i.g. and initiated populations expanded using the resistant hepatocyte model (experiment IIA). Subsequently, effects of repeated administration (10 mg/kg, four times, i.g.) of DMH were compared with the results of a single administration (40 mg/ kg, i.g.) with the same total dose (experiment IIB). In experiments I and IIA, the numbers and areas of GST-P-positive foci increased with the BrdU labeling index at the time of DMH treatment (maximum after 60 h). In experiment HB, repeated exposure of DMH at 10 mg/kg, four times resulted in significant (P<0.05) increase in number and area of GST-P-positive foci compared with the single administration (40 mg/kg). Thus, multiple low dose treatments during cell proliferation might be most effective for detection of weak initiation activity.     

Grapefruit juice intake does not enhance but rather protects against aflatoxin B1-induced liver DNA damage through a reduction in hepatic CYP3A activity

Influence of grapefruit juice intake on aflatoxin B1 (AFB1)-induced liver DNA damage was examined using a Comet assay in F344 rats given 5 mg/kg AFB1 by gavage. Rats allowed free access to grapefruit juice for 5 days prior to AFB1 administration resulted in clearly reduced DNA damage in liver, to 65% of the level in rats that did not receive grapefruit juice. Furthermore, rats treated with grapefruit juice extract (100 mg/kg per os) for 5 days prior to AFB1 treatment also reduced the DNA damage to 74% of the level in rats that did not receive grapefruit juice. No significant differences in the portal blood and liver concentrations of AFB1 were observed between grapefruit juice intake rats and the controls. In an Ames assay with AFB1 using Salmonella typhimurium TA98, lower numbers of revertant colonies were detected with hepatic microsomes prepared from rats administered grapefruit juice, compared with those from control rats. Microsomal testosterone 6beta-hydroxylation was also lower with rats given grapefruit juice than with control rats. Immunoblot analyses showed a significant decrease in hepatic CYP3A content, but not CYP1A and CYP2C content, in microsomes of grapefruit juice-treated rats than in non-treated rats. No significant difference in hepatic glutathione S-transferase (GST) activity and glutathione content was observed in the two groups. GSTA5 protein was not detected in hepatic cytosol of the two groups. In microsomal systems, grapefruit juice extract inhibited AFB1-induced mutagenesis in the presence of a microsomal activation system from livers of humans as well as rats. These results suggest that grapefruit juice intake suppresses AFB1-induced liver DNA damage through inactivation of the metabolic activation potency for AFB1 in rat liver.     

Chemopreventive efficacy of Moringa oleifera pods against 7, 12-dimethylbenz[a]anthracene induced hepatic carcinogenesis in mice

Oxidative stress is a common mechanism contributing to initiation and progression of hepatic damage in a variety of liver disorders. Hence there is a great demand for the development of agents with potent antioxidant effect. The aim of the present investigation is to evaluate the efficacy of Moringa oleifera as a hepatoprotective and an antioxidant against 7, 12-dimethylbenz[a]anthracene induced hepatocellular damage. Single oral administration of DMBA (15 mg/kg) to mice resulted in significantly (p<0.001) depleted levels of xenobiotic enzymes like, cytochrome P450 and b5. DMBA induced oxidative stress was confirmed by decreased levels of reduced glutathione (GSH) and glutathione-S-transferase (GST) in the liver tissue. The status of hepatic aspartate transaminase (AST), alanine transaminase (ALT), and alkaline phosphatase (ALP) which is indicative of hepatocellular damage were also found to be decreased in DMBA administered mice. Pretreatment with the Moringa oleifera (200 and 400 mg/kg) orally for 14 days significantly reversed the DMBA induced alterations in the liver tissue and offered almost complete protection. The results from the present study indicate that Moringa oleifera exhibits good hepatoprotective and antioxidant potential against DMBA induced hepatocellular damage in mice that might be due to decreased free radical generation.