Inhibitory Effect of Epigallocatechin Gallate, Epigallocatechin, and Gallic Acid on the Formation of N-Nitrosodiethylamine In Vitro.

This study investigated the inhibitory effect of epigallocatechin gallate (EGCG), epigallocatechin (EGC), and gallic acid (GA) on the formation of N-nitrosodiethylamine (NDEA) in vitro. Results show that the three polyphenols are capable to block NDEA formation when the molar ratio of phenols to nitrite is higher than 0.8, and a more acidic environment is prone to promote the inhibitory potential of phenols. It is also found that the inhibitory effect tends to decrease in the order: EGCG, EGC, GA, which is in accordance with the order of their DPPH scavenging activity, suggesting that the inhibitory effect of polyphenols on NDEA formation may work through a free radical way. Kinetic study further revealed the three polyphenols react with nitrite at a much faster rate than diethylamine does (P < 0.05). By scavenging nitrite at a faster rate than the nitrosation of diethylamine, polyphenols at high concentration can significantly block NDEA formation. These observations may promote a possible application of polyphenol compounds to inhibit the formation of nitrosamines in food processing. PRACTICAL APPLICATION: The presence of N-nitrosamines in human diet should be an etiological risk factor for human cancers. This work may provide a useful guideline for phenolic compounds to inhibit the formation of nitrosamines in food processing, such as in the process of curing meats. Polyphenols have been proved to block NDEA formation under normal gastric juice condition, suggesting the intake of polyphenols is a potential way to prevent diseases caused by nitrite.

Acteoside-mediates chemoprevention of experimental liver carcinogenesis through STAT-3 regulated oxidative stress and apoptosis.

In the absence of an effective therapy against Hepatocellular Carcinoma (HCC), chemoprevention remains an important strategy to circumvent morbidity and mortality. Here, we examined chemopreventive potential of Acteoside (ACT), a plant derived phenylethanoid glycoside against an environmental and dietary carcinogen, diethylnitrosamine (DEN)-induced rat hepatocarcinogenesis. ACT treatment (0.1 and 0.3% supplemented with diet) started 2 weeks before DEN challenge and continued for 18 weeks thereafter, showed a remarkable chemopreventive activity. ACT treatment resulted in reduced HCC nodules. Histopathology showed progressive tissue damage, necrosis (5 weeks), hepatocytic injury (10 weeks), anisonucleosis with presence of prominent nucleoli, sinusidal dilations, and lymphomono nuclear inflammation (18 weeks). Biochemical analysis showed hepatocytic injury (raised ALT, p < 0.001), inflammation [IL-6, IFN-γ (p < 0.05), and TNF-α (p < 0.001)], apoptosis [elevated Caspase-3 (p < 0.001)]. ACT at 0.1 and 0.3% ameliorated DEN-induced pre-hepatocarcinogenic manifestations. Mechanistic studies of ACT chemoprevention was elucidated using Hep3B cells with an aim to develop an in vitro DEN-induced toxicity model. Hep3B was found to be a reliable and more sensitive towards DEN toxicity compared to HepG2 and HuH7 cells. ACT prevented DEN-induced cytotoxicity (p < 0.001), DNA damage, and genotoxicity (micronuclei test, DNA ladder test, Hoechst staining, cell cycle analysis). ACT significantly (p < 0.001) scavenged DEN-induced reactive oxygen species (ROS) levels and prevented mitochondrial membrane potential (MMP) loss. Immunoblotting showed ACT treatment reversed DEN-induced NF-κB, Bax, Cytochrome C, Bcl-2, and Stat-3 levels. We conclude that chemoprotective effect of ACT is mediated by STAT-3 dependent regulation of oxidative stress and apoptosis and ACT has potential to be developed as a chemopreventive agent. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 782-798, 2016.

Effects of carnosine, taurine, and betaine pretreatments on diethylnitrosamine-induced oxidative stress and tissue injury in rat liver.

Several chemicals such as N-diethylnitrosamine (DEN) promote hepatocellular cancer in rodents and induce hepatocyte injury. DEN affects the initiation stage of carcinogenesis together with enhanced cell proliferation accompanied by hepatocellular necrosis. DEN-induced hepatocellular necrosis is reported to be related to enhanced generation of reactive oxygen species. Carnosine (CAR), taurine (TAU), and betaine (BET) are known to have powerful antioxidant properties. We aimed to investigate the effects of CAR, TAU, and BET pretreatments on DEN-induced oxidative stress and liver injury in male rats. Rats were given CAR (2 g L-1 in drinking water), TAU (2.5% in chow), and BET (2.5% in chow) for 6 weeks and DEN (200 mg kg-1 intraperitoneally) was given 2 days before the end of this period. Serum alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and γ-glutamyl transferase activities were determined and a histopathologic evaluation was performed on the liver tissue. Oxidative stress was detected in the liver by measuring malondialdehyde, diene conjugate, protein carbonyl and nitrotyrosine levels, glutathione and glutathione peroxidase levels, and superoxide dismutase and glutathione transferase activities. Pretreatments with CAR, TAU, and BET decreased liver prooxidant status without remarkable changes in antioxidant parameters in DEN-treated rats. Pretreatments with TAU and BET, but not CAR, were also found to be effective to reduce liver damage in DEN-treated rats. In conclusion, TAU, BET, and possibly CAR may have an ameliorating effect on DEN-induced hepatic injury by reducing oxidative stress in rats.

Molecular mechanisms of nano-selenium in mitigating hepatocellular carcinoma induced by N-nitrosodiethylamine (NDEA) in rats.

The possible molecular mechanisms of Nano-selenium (nano-se) in attenuating hepatocellular carcinoma (HCC) was investigated in this study. To achieve this target, the apoptotic/necrotic rate in hepatic cells was investigated morphologically by double staining with acridine orange/ethidium bromide to address the type of cell death induced by nano-Se in HCC-bearing rats. To predict the oxidative stress and DNA damage, the generation of 8-hydroxy-2-deoxyguanosine (8-OHdG) and 2-deoxyguanosine (2-dG) was examined. Moreover, the expression of some HCC-related genes was investigated such as aldo-keto reductase 1B10 (Akr1b10), ING3 and Foxp1 genes. As well as the histopathological study of liver tissue sections was performed. The results obtained from this study revealed that (HCC+Nano Se) group shows the highest number of damaged cancerous cells. Furthermore, the necrotic/apoptotic rate was significantly higher in (nano-Se+HCC), (HCC+Doxo) and (HCC+Doxo+nano-se) compared to that in the untreated HCC group. Treatment of HCC group with nano-se decreased the ratio of 8-OHdG/2-dG generation significantly with respect to the untreated HCC group. The opposite was observed regarding the gene expression of AKr1b10 and ING3. The treatment of HCC group with nano-se elicited significant increase in the expression of Akr1b10 and ING3 genes compared with untreated HCC group. On the other hand, the expression of Foxp1 gene was significantly decreased in HCC group treated with nano-se in comparison with the untreated HCC group. The histopathological study provided a supportive evidence for the molecular genetics study. Our data shed light on the molecular mechanisms of nano-se in attenuating HCC in the experimental model.

Myrtenal ameliorates diethylnitrosamine-induced hepatocarcinogenesis through the activation of tumor suppressor protein p53 and regulation of lysosomal and mitochondrial enzymes.

Myrtenal is a novel class of compound belongs to monoterpenes found predominantly in mint, pepper, etc., and it was shown to have excellent pharmacological activities against many diseases among which cancer is imperative. Hepatocellular carcinoma is a primary malignancy of the hepatocytes, which rapidly leads to death in short periods. The aim of this study was to investigate the possible therapeutic efficiency of myrtenal against diethylnitrosamine-induced experimental hepatocarcinogenesis by analyzing the key enzymes of carbohydrate metabolism, lysosomal and mitochondrial TCA cycle enzymes, and also the possible role of tumor suppressor protein p53, and scanning electron microscopic studies. The results revealed that myrtenal significantly ameliorated the altered enzymes of carbohydrate metabolism, lysosomal and mitochondrial enzymes, and interestingly the tumor suppressor protein p53 was found to be significantly accumulated in myrtenal-treated animals, which inevitably confirms that myrtenal has a prominent role in preventing the liver cancer during treatment. Furthermore, the antineoplastic property was well evidenced by the mRNA expression of p53 protein by the reverse-transcriptase polymerase chain reaction and immunoblot analysis. The observed anticancer property of myrtenal may be due to the involvement and expression of p53 and influence in the mitochondrial and lysosomal membrane integrity and also interference in the gluconeogenesis process of cancer cells. Our results suggest that myrtenal is very efficient and useful compound in the treatment of liver cancer in future.

Beetroot juice protects against N-nitrosodiethylamine-induced liver injury in rats.

Red beetroot, a common ingredient of diet, is a rich source of a specific class of antioxidants, betalains. Our previous studies have shown the protective role of beetroot juice against carcinogen induced oxidative stress in rats. The aim of this study was to examine the effect of long term feeding (28 days) with beetroot juice on phase I and phase II enzymes, DNA damage and liver injury induced by hepatocarcinogenic N-nitrosodiethylamine (NDEA). Long term feeding with beetroot juice decreased the activities of enzymatic markers of cytochrome P450, CYP1A1/1A2 and CYP2E1. NDEA treatment also reduced the activities of these enzymes, but increased the activity of CYP2B. Moreover, combined treatment with beetroot juice and NDEA enhanced significantly CYP2B only. Modulation of P450 enzyme activities was accompanied by changes in the relevant proteins levels. Increased level and activity of NQO1 was the most significant change among phase II enzymes. Beetroot juice reduced the DNA damage increased as the result of NDEA treatment, as well as the biomarkers of liver injury. Collectively, these results confirm the protective effect of beetroot juice against oxidative damage shown in our previous studies and indicate that metabolic alterations induced by beetroot feeding may protect against liver damage.

[O-aminoazotoluene inhibits DENA-induced hepatocarcinogenesis when used together in mice].

When used separately, diethylnitrosamine (DENA) initiates 4-6 times more neoplastic lesions in the liver of suckling mice than ortho-aminoazotoluene (OAT) lower. However, after combined treatment with either carcinogen the total number of hepatic lesions was significantly than that in mice injected with DENA only. Similar inhibition of DENA-induced hepatocarcinogenesis was observed when OAT was administered 8-12 hrs after DENA. Our findings cannot be adequately explained except by competition of the carcinogens for supposedly target molecules of protein origin, presumably, transcription factors, which contribute to generation of genetic information. They have different affinities for different compounds and, therefore, suffer different damage from the latter functioning.

Chemopreventive effect of bacoside A on N-nitrosodiethylamine-induced hepatocarcinogenesis in rats.

PURPOSE: Chemoprevention is an effective approach to control hepatocarcinogenesis. Bacoside A, the active constituent of Bacopa monniera Linn., is anticipated to play a role in chemoprevention of liver cancer. METHODS: In the present study, we investigated the chemopreventive effect of bacoside A against N-nitrosodiethylamine-induced hepatocarcinogenesis in an animal model. RESULTS: Administration of carcinogen showed a significant elevation in the levels of lipid peroxidation, serum tumor marker enzymes and liver injury marker enzymes with subsequent decrease in the levels of both hemolysate and liver antioxidant status. Bacoside A co-treatment maintained the N-nitrosodiethylamine-induced alterations at near normal level. Histopathological and electron microscopic study of the liver tissue also supports the above biochemical observations. CONCLUSIONS: From our findings we conclude that bacoside A is effective to prevent DEN-induced hepatocellular carcinoma by quenching lipid peroxidation and enhancing antioxidant status through free radical scavenging mechanism and having potential of protecting endogenous enzymatic and non-enzymatic antioxidant activity.

Maté attenuates DNA damage and carcinogenesis induced by diethylnitrosamine and thermal injury in rat esophagus.

Drinking hot maté has been associated with risk for esophageal cancer in South America. Thus, the aims of this study were to evaluate the modifying effects of maté intake on DNA damage and esophageal carcinogenesis induced by diethylnitrosamine (DEN) and thermal injury (TI) in male Wistar rats. At the initiation phase of carcinogenesis, rats were treated with DEN (8 x 80 mg/kg) and submitted to TI (water at 65 degrees C, 1 ml/rat, instilled into the esophagus). Concomitantly, the animals received maté (2.0%w/v) for 8 weeks. Samples of peripheral blood were collected 4h after the last DEN application for DNA damage analysis. At weeks 8 and 20, samples from esophagus and liver were also collected for histological and immunohistochemical analysis. Maté significantly decreased DNA damage in leukocytes, cell proliferation rates in both esophagus and liver and the number of preneoplastic liver lesions from DEN/TI-treated animals at week 8. A significant lower incidence of esophageal papillomas and liver adenomas and tumor multiplicity was observed in the animals previously treated with maté at week 20. Thus, maté presented protective effects against DNA damage and esophageal and liver carcinogenesis induced by DEN.

Vesicular flavonoid in combating diethylnitrosamine induced hepatocarcinoma in rat model.

Reactive oxygen species (O2(*-), OH(-), H2O2) are known to play an important role in tumor initiation in hepatocarcinoma. Hepatocarcinoma was developed in the Swiss Albino rats by administration three doses of diethylnitrosamine (DEN) (200 mg/kg b. wt.) (i.p.) at 15 days interval. Quercetin (QC), herbal polyphenolic compound, is a potent anticancer drug. Clinical trials are difficult for its hydrophobic nature. To overcome this problem, our study was aimed to formulate soluble liver specific, galactosylated liposomal QC and to investigate its efficacy against hepatocarcinoma in rat model. Galactosylated liposomal QC was formulated and the suspension was introduced intravenously to rats (8.98 microM/kg) once in a week for 16 weeks. Hepatocarcinoma in rat model and its pathological improvement were evaluated histopathologically, histochemically and electron microscopically. Severe oxidative damage was noticed in the whole liver and its microsomal fraction of DEN treated rats. Huge numbers of hyperplastic nodules (HNs) with pre-neoplastic lesions appeared in rat liver by DEN administration. Galactosylated liposomal QC injections prevented DEN mediated development of hepatocarcinoma and oxidative damage in rat liver. Quercetin in liver specific galactosylated liposomal drug delivery system may be recommended as a potent therapeutic formulation against DEN-induced hepatocarcinoma.

Anticarcinogenic effects of hexaamminecobalt(III) chloride in mice initiated with diethylnitrosamine.

Hexaamminecobalt(III) chloride ([Co(NH3)6]Cl3) was investigated for its antineoplastic role in relation to tumor marker enzymes, drug metabolizing enzymes, oxidative stress-related parameters, and histopathological analysis of liver and lung tissues of mice. Initiation was performed using a single intraperitoneal injection of diethylnitrosamine (DENA) at a carcinogenic dose of 90 mg/kg body weight. The cobalt complex supplementation at a dose of 100 ppm in drinking water was given ad libitum throughout the experimental period of 14 weeks. In comparison to lung, the cobalt complex supplementation was found to reverse DENA-induced biochemical changes more effectively in liver. Histological examination of liver and lung from DENA-initiated and cobalt-complex-supplemented mice showed considerable protection in the case of liver compared to that of lung. The involvement of the [Co(NH3)6]Cl3 in modulating several factors associated with carcinogenesis induced by DENA thus showed its anticarcinogenic potential against chemically induced hepatocarcinogenesis.

Impediment of diethylnitrosamine induced hepatotoxicity in male Balb/c mice by pretreatment with aqueous Azadirachta indica leaf extract.

Considering the hepatoprotective properties of Azadirachta indica, the present study was designed to evaluate its preventive effects against diethylnitrosamine (NDEA) induced hepatotoxicity in male Balb/c mice. Exposure of NDEA caused a significant increase in micronucleated cell score, lipid peroxidation levels (LPO) and activity of lactate dehydrogenase (LDH). A significant decrease in reduced glutathione (GSH) contents and activity of glutathione-S-transferase (GST) was also observed upon NDEA treatment, whereas their activities of cytochrome P450 and cytochrome b5 showed non-significant alterations. Aqueous A. indica leaf extract (AAILE) pretreatment showed protective effects against NDEA induced toxicity by decreasing the frequency of micronucleated cell, levels of LPO and LDH activity. Also, a decreased activity of GST, cytochrome P450 and an increased activity of cytochrome b5, GSH contents was observed when AAILE pretreated mice were injected with NDEA. Only AAILE treatment caused a noticeable decrease in the frequency of micronuclei, activity of cytochrome P450 and cytochrome b5, but a significant increase in the activity of GST and GSH contents, whereas, non significant alterations were observed in the activity of LDH and levels of LPO. Significance of these observations with respect to hepatoprotective efficacy of A. indica has been discussed in the present manuscript.

Evaluation of possible mechanisms of protective role of Tamarix gallica against DEN initiated and 2-AAF promoted hepatocarcinogenesis in male Wistar rats.

We have previously reported that Tamarix gallica caused a marked inhibition of thioacetamide-induced hepatotoxicity, oxidative damage and early tumor promotion related events in the liver. These results strongly indicates that T. gallica may have chemopreventive potential. Therefore, in the present study, we examined the inhibitory effects of T. gallica methanolic extract on diethylnitrosamine (DEN) initiated and 2-acetyl aminofluorene (2-AAF) promoted liver carcinogenesis in male Wistar rats. Interestingly, it was found that T. gallica (25 and 50 mg/kg body wt.) resulted in a marked reduction of the incidence of liver tumors. The study was further histologically confirmed. Furthermore to understand the underlying mechanisms of chemopreventive action by T. gallica we evaluated the levels activities of hepatic antioxidant defense enzymes, ornithine decarboxylase activity and hepatic DNA synthesis as a marker for tumor promotion since direct correlation between these marker parameters and carcinogenicity have been well documented. Treatment of male Wistar rats for five consecutive days with 2-AAF i.p. induced significant hepatic toxicity, oxidative stress and hyperproliferation. Pretreatment of T. gallica extract (25 and 50 mg/kg body wt.) prevented oxidative stress by restoring the levels of antioxidant enzymes and also prevented toxicity at both the doses. The promotion parameters induced (ornithine decarboxylase activity and DNA synthesis) by 2-AAF administration in diet with partial hepatectomy (PH) were also significantly suppressed dose-dependently by T. gallica. Therefore, we can conclude that ultimately the protection against liver carcinogenesis by T. gallica methanolic extract might be mediated by multiple actions, which include restoration of cellular antioxidant enzymes, detoxifying enzymes, ODC activity and DNA synthesis.

Low dose DDT inhibition of hepatocarcinogenesis initiated by diethylnitrosamine in male rats: possible mechanisms.

Previously we reported a tendency for reduction of the development of glutathione-S-transferase placental form (GST-P) positive foci, recognized as preneoplastic changes in rat liver, by a low dose of 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT), which belongs to the same group of hepatic cytochrome P-450 inducers as phenobarbital and is itself a non-genotoxic hepatocarcinogen. In order to clarify the biological significance of this phenomenon, we investigated the reproducibility and changes in other parameters using an initiation-promotion model in which male F344 rats were treated with DDT at doses of 0, 0.005, 0.5, 500 ppm in the diet for 11 or 43 weeks after initiation of hepatocarcinogenesis with N-diethylnitrosamine (DEN). When 500 ppm DDT was applied, the formation of GST-P positive foci and tumor were markedly elevated. In contrast, induction of GST-P positive foci and liver tumors tended to be inhibited at a dose of 0.005 ppm, correlating with protein levels of cytochrome P450 2B1 and 3A2 (CYP2B1 and 3A2) and generation of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative DNA damage. mRNA levels for 8-oxoguanine glycosylase 1 (OGG1), an 8-OHdG repair enzyme, connexin 32 (Cx32), a major component of Gap junctions, and hepatic nuclear factor 1alpha (HNF-1alpha), a Cx32 regulator, were inversely correlated with GST-P positive foci and tumor formation. These results indicate that low dose DDT may indeed exhibit inhibitory effects on chemically initiated-rat hepatocarcinogenicity, in contrast to the promotion observed with high doses, and that this is related to changes in metabolizing enzymes, cell communication, and DNA damage and its repair.

Chemoprevention of preneoplastic liver foci development by dietary mushroom Agaricus blazei Murrill in the rat.

The chemopreventive potential of an Agaricus blazei (Ab) Murrill mushroom meal was investigated in a medium-term rat liver carcinogenesis assay. Male Wistar rats initiated for hepatocarcinogenesis with diethylnitrosamine (DEN, 200 mg/kg i.p.) were fed during a 6-week period with the dry powdered mushroom strains Ab 29 or 26, each one with opened (OB) or closed basidiocarp (CB), mixed at 10% level in a basal diet. All experimental animals and controls were subjected to partial hepatectomy at week 3 and killed at week 8. Chemopreventive activity of the mushroom meal was observed for the Ab 29 (OB and CB) and Ab 26 (CB) strains in terms of the number of putative preneoplastic altered foci of hepatocytes which express either the enzyme glutathione S-transferase, placental form (GST-P+) or the transforming growth factor-alpha, and for the Ab 29 (OB) and Ab 26 (CB) strains on the size of GST-P+ foci. This was associated with inhibition of foci cell proliferation in the animals fed the Ab 29 (OB) and Ab 26 (CB) strains. The results suggest that the protective influence of the Ab meal against the DEN potential for rat liver carcinogenicity depends on both the strain and period of mushroom harvest.

Inhibition of nitrosodiethylamine-induced hepatocarcinogenesis by dietary turmeric in rats.

Turmeric, widely used in food and medicine has been shown to prevent benzo(a)pyrene [B(a)P] or dimethylbenz(a)anthracene (DMBA)-induced forestomach, skin and mammary tumors in mice and/or rats. In this study we examine the modulatory effects of turmeric on nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis in rats. Female Wistar rats were administered NDEA (200 ppm) through drinking water (5 days per week) for 4 weeks. Control and/or NDEA-treated rats received 0, 0.2, 1.0 or 5.0% turmeric diet (w/w) either before (2 weeks), during (4 weeks) and after NDEA exposure (10 weeks) or starting from 24 h after NDEA exposure for 10 weeks. NDEA-treated rats receiving 1 or 5% turmeric before, during and after carcinogen exposure showed significant decrease in number of gamma glutamyl transpeptidase (GGT) positive foci measuring >500 or >1000 microm and decrease in the incidence of NDEA-induced focal dysplasia (FD) and hepatocellularcarcinomas. Decrease in the number of GGT positive foci measuring >1000 microm was also observed in NDEA-treated rats receiving 0.2% turmeric, although no decrease in tumor incidence was noted. On the other hand, similar levels of turmeric treatment (0.2, 1 and 5%) after exposure to NDEA did not show any protective effects. The underlying mechanism(s) of chemoprevention of NDEA-induced hepatocarcinogenesis need to be explored.

Chemoprevention of DMBA-induced UV-B promoted, NOR-1-induced TPA promoted skin carcinogenesis, and DEN-induced phenobarbital promoted liver tumors in mice by extract of beetroot.

Our previous studies identified the extract of Beta vulgaris (beetroot), commercially also known as betanin, as a potent cancer chemopreventive agent in both in vitro Epstein-Barr early antigen activation assay and in an in vivo two-stage mouse lung and skin carcinogenesis. To explore this issue further, we have now investigated its cancer chemopreventive potentials in three different chemical carcinogen initiation-promotion experimental tumor models in mice. Following tumor initiation with 390 nmol of 7,12-dimethylbenz(a)anthracene (DMBA) in 100 microl of acetone, the mouse skin tumor promotion with 3430 J/m(2) of ultraviolet light-B (UV-B) as well as splenomegaly was significantly inhibited by oral administration of 0.0025% betanin. At the same dose, betanin also afforded significant protection in the mouse skin cancer model following the topical application of 390 nmol of (+/-)-(E)-4-methyl-2-[(E)-hydroxyamino]-5-nitro-6-methoxy-3-hexanamide (NOR-1) in 100 microl of acetone and promoted by topical administration of 1.7 nmol of 12-O-tetradecanoylphorbol-13-acetate (TPA). In the two-stage model of hepatocarcinogenesis in mice with N-nitrosodiethylamine (DEN, 30 mg/kg) as the initiator and phenobarbital as the promoter, oral administration of 0.0025% betanin also showed a very significant inhibition of both the incidence and multiplicity of the liver tumors. These findings along with our initial reports suggest that betanin which is a regularly consumed natural product colorant is an effective cancer chemopreventive agent in mice. The most interesting observation is that the cancer chemopreventive effect was exhibited at a very low dose used in the study and thus indicating that beetroot warrants more attention for possible human applications in the control of malignancy.

Inhibition of diethylnitrosamine-induced rat liver chromosomal aberrations and DNA-strand breaks by synergistic supplementation of vanadium and 1alpha,25-dihydroxyvitamin D(3).

Vanadium (V) has recently been found to possess potent anti-neoplastic activity in rat hepatocarcinogenesis. Recent studies have suggested that the active metabolite of vitamin D(3), 1alpha, 25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], can inhibit growth and/or induce differentiation of a variety of cell types. In the present study, attempts have been made to investigate the combination effects on chromosomal aberrations (CAs) and DNA-strand breaks during the early preneoplastic stage of diethylnitrosamine (DEN)-induced rat liver carcinogenesis in male Sprague-Dawley rats. V (0.5 ppm ad libitum) and/or 1,25(OH)(2)D(3) (0.3 microg/0.1 ml propylene glycol per os twice weekly) either alone or in combination were given to DEN-treated and control rats 4 weeks prior to DEN injection. Under these experimental conditions it was observed that, when given in combination, V and 1,25(OH)(2)D(3) offered maximum protection against DEN-induced structural aberrations 96 h (66.7%, P<0.05), 15 days (44.9%, P<0.005) and 30 days (63.8%, P<0.001) after DEN injection. Synergistic supplementation of both V and 1, 25(OH)(2)D(3) 4 weeks before DEN injection was found to offer significant (64.1%, P<0.001) protection against generation of single-strand breaks when compared with the DEN control. Thus, the combination effect of V, an essential trace element, and of 1, 25(OH)(2)D(3), a dietary micronutrient, appears beneficial in preventing genetic damage in liver cells upon alkylation induced by DEN.

Combined supplementation of vanadium and 1alpha,25-dihydroxyvitamin D(3) inhibit diethylnitrosamine-induced rat liver carcinogenesis.

A combination of a differentiation-inducing agent like 1alpha, 25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] with a compound that blocks entry of calcium into cells like vanadium (V) may offer a new approach to differentiation therapy and address the problem of hypercalcemia. Initiation of hepatocarcinogenesis was performed by a single intraperitoneal injection of diethylnitrosamine (DEN) (200 mg/kg b.wt.) in male Sprague-Dawley rats. Supplementation of V, 1, 25(OH)(2)D(3), or both V and 1,25(OH)(2)D(3) were started 4 weeks prior to DEN injection and continued thereafter till 20th week. It was observed that supplementation of V (0.5 ppm) in drinking water ad libitum or 1,25(OH)(2)D(3) (3 microg/ml propylene glycol) per os twice weekly for the entire period of the experiment significantly reduces the number and size of hyperplastic nodules while the combination treatment offered an additive effect in reducing it to 37.5% from 83.3%. V-1,25(OH)(2)D(3) combination was also effective in elevating the level of hepatic microsomal cytochrome P-450 (Cyt. P-450) (P<0.001). Moreover, A significant reduced level of cytosolic glutathione (GSH) (P<0.001) and glutathione S-transferase (GST) (P<0.001) activity as well as reduction in the appearance of gamma-glutamyltranspeptidase (GGT)-positive foci (P<0.001) as compared to carcinogen control were observed in V plus 1, 25(OH)(2)D(3) treated group. These results suggest that V may be useful in combination with 1,25(OH)(2)D(3) in the inhibition of experimental rat hepatocarcinogenesis.

Prevention of N-nitrosodiethylamine-induced lung tumorigenesis by ellagic acid and quercetin in mice.

The polyphenolic antioxidants, consumed as an integral part of vegetables, fruits and beverages, are suggested as possessing anticarcinogenic properties. In the present study we have looked into the anticarcinogenic potential of plant polyphenols ellagic acid (EA) and quercetin against N-nitrosodiethylamine-induced lung tumorigenesis in mice. Ellagic acid was able to significantly reduce tumour incidence to 20% from the control value of 72.2%. Similarly, tumour burden was also decreased, although not significantly, from 3.15 to 2.5. Quercetin (QR) caused the tumour incidence to decrease from 76.4% to 44.4% when fed until the third dose of carcinogen. Both of the polyphenols suppressed the tumour incidence mainly by acting at the initiation phase of the carcinogenesis, since continuing the feeding of polyphenols until the termination of the experiment did not cause any apparent change in tumour incidence or tumour burden. Besides this, ellagic acid was found to be a better chemopreventor than quercetin. In order to search for their mechanism of action, the effect of feeding of these compounds on reduced glutathione (GSH), an important endogenous antioxidant, and on lipid peroxidation was investigated. Both ellagic acid and QR caused a significant increase in GSH and decrease in NADPH- and ascorbate-dependent lipid peroxidation. Ellagic acid was found to be more effective in decreasing the lipid peroxidation and increasing the GSH. This may be one of the reasons for its observed better anticarcinogenic property as compared to quercetin.