Valerian inhibits rat hepatocarcinogenesis by activating GABA(A) receptor-mediated signaling.

Valerian is widely used as a traditional medicine to improve the quality of sleep due to interaction of several active components with the γ-aminobutyric acid (GABA) A receptor (GABA(A)R) system. Recently, activation of GABA signaling in stem cells has been reported to suppress cell cycle progression in vivo. Furthermore, possible inhibitory effects of GABA(A)R agonists on hepatocarcinogenesis have been reported. The present study was performed to investigate modulating effects of Valerian on hepatocarcinogenesis using a medium-term rat liver bioassay. Male F344 rats were treated with one of the most powerful Valerian species (Valeriana sitchensis) at doses of 0, 50, 500 and 5000 ppm in their drinking water after initiation of hepatocarcinogenesis with diethylnitrosamine (DEN). Formation of glutathione S-transferase placental form positive (GST-P(+)) foci was significantly inhibited by Valerian at all applied doses compared with DEN initiation control rats. Generation of 8-hydroxy-2'-deoxyguanosine in the rat liver was significantly suppressed by all doses of Valerian, likely due to suppression of Nrf2, CYP7A1 and induction of catalase expression. Cell proliferation was significantly inhibited, while apoptosis was induced in areas of GST-P(+) foci of Valerian groups associated with suppression of c-myc, Mafb, cyclin D1 and induction of p21(Waf1/Cip1), p53 and Bax mRNA expression. Interestingly, expression of the GABA(A)R alpha 1 subunit was observed in GST-P(+) foci of DEN control rats, with significant elevation associated with Valerian treatment. These results indicate that Valerian exhibits inhibitory effects on rat hepatocarcinogenesis by inhibiting oxidative DNA damage, suppressing cell proliferation and inducing apoptosis in GST-P(+) foci by activating GABA(A)R-mediated signaling.

Lack of carcinogenicity of enzymatically modified isoquercitrin in F344/DuCrj rats.

The present study was conducted to evaluate the potential carcinogenicity of enzymatically modified isoquercitrin, administered in the diet at doses of 0.5% or 1.5% to groups of 50 male and female F344/DuCrj rats. Control males and females (50 rats each) were maintained on basal diet. Animals were observed for 104 weeks. There were no treatment-related clinical signs of toxicity in the treated groups. Body weights, feed consumption, survival rates and hematological findings for exposed rats of both sexes showed no variations among the groups. There was a slight but significant dose-dependent decrease in relative spleen weights in all treated groups, albeit with no histopathological variation. Overall histopathological evaluation of neoplasms and all tissues after 2 years showed that tumors developed in all groups including the controls. There was a non-significant tendency for increase in the incidence of pituitary gland adenomas in the high dose-treated females (45.5%) as compared to controls (27.7%), with a slight increase in hemorrhage incidences, but values for males were low and similar in both control and treated rats. There were no apparent effects of isoquercitrin on development of kidney neoplasms, hyperplasias or chronic nephropathy. Parathyroid adenomas or hyperplasias were found not affected by isoquercitrin treatment, and there were no differences in mammary gland fibroadenomas or hyperplasias between treated and control rats. Various tumors were found in other organs with no significant differences between the groups. In conclusion, under the conditions of this 2-year feeding experiment, no evidence was obtained of carcinogenicity of enzymatically modified isoquercitrin in male or female F344 rats.

Lack of preventive efficacy of FK228, a histone deacetylase inhibitor, against N-butyl-N-(4-hydroxybutyl) nitrosamine-induced urinary bladder carcinogenesis in p53+/- and p53+/+ mice.

BACKGROUND: The efficacy of FK228, a histone deacetylase inhibitor that is currently under early clinical trials for cancer therapy, against N-butyl-N-(4-hydroxybutyl)- nitrosamine (BBN) -induced mouse urinary bladder carcinogenesis was examined. MATERIALS AND METHODS: Heterozygous p53-deficient (p53+/-) and wild-type (p53+/+) mice were given FK228 (0, 0.01 and 0.1 mg/kg i.p., 3 times/week, respectively) after 10 weeks of 0.05% BBN treatment, and were sacrificed at 22 and 24 weeks after the start, respectively. RESULTS: There was no significant difference in the incidence of urinary bladder tumors among groups in the p53+/- or p53+/+ mice, although the high dose of FK228 increased the p21WAF1 mRNA expression in urinary bladder cancers in animals of both genotypes. CONCLUSION: The present data indicate a lack of any inhibitory effects of FK228 on BBN-induced mouse urinary bladder carcinogenesis under the present conditions.

No inhibition of urinary bladder carcinogenesis in rats with intravesical instillation of alpha-galactosylceramide.

The immunostimulatory a-galactosylceramide, KRN 7000 ((2S,3S,4R)-1-O-(a-D-galactopyranosyl)-2-(N-hexacosnoylamino)-1,3,4-octadecatrienol), may be anticipated to have antitumor activity in vivo apart from any direct toxicity to cancer cells. In this experiment, inhibition of rat bladder carcinogenesis by intravesically instillated KRN7000 was investigated. Male Fischer 344 rats, 6-weeks-old at the start, were divided into 4 groups, all first receiving the carcinogen, 0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine, in their drinking water for 12 weeks. Then groups 1 and 2 respectively were administered 500 and 50 mg/kg of KRN7000 intravesically once weekly for 17 weeks. Group 3 similarly received only 0.3 micro/l of saline (vehicle control). Group 4 did not undergo bladder catheterization. On macroscopic examination at 30 weeks, multiplicities and sizes of bladder tumors in the KRN 7000 high and low-dose groups were not significantly different from those of the vehicle control group. Histologic examination confirmed no significant variation in incidences of carcinomas or preneoplastic lesions in the bladder among groups 1 to 4. Thus the results indicate that intravesical instillation of KRN7000 does not inhibit bladder carcinogenesis in rats.

Induction of tumors in the colon and liver of the immunodeficient (SCID) mouse by 2-amino-3-methylimidazo[4,5-f ]quinoline (IQ)-modulation by long-chain fatty acids.

We have recently shown that immunodeficient (SCID) mice, which lack functional T and B cells, are highly susceptible to low dose site specific induction of colon aberrant crypt foci (ACF), surrogates for colon tumors, by 2-amino-3-methylimidazo[4,5-f ]quinoline (IQ). To test whether long-term exposure to a high dose in the diet might prove carcinogenic to the SCID mouse colon, in contrast to other mice strains tested to date, the compound was administered at 300 p.p.m. in the diet to female 6-7-week-old SCID mice for 32 weeks. IQ induced high numbers of ACF, hyperplastic polyps, dysplasia, and colon adenomas, as well as hepatocellular altered foci and liver adenomas. Induction of colon tumors did not correlate with the main sites where ACF developed, the proximal colon, however, being seen mainly in the mid and distal colon. Induction of colon tumors correlated significantly with the incidence of dysplasia, crypt height, the mitotic index, cell proliferation and numbers of 8-hydroxydeoxyguanosine (8-OHdG)-positive cells in the colon crypt, particularly in mid and distal colon. Administration of 20% omega-6 polyunsaturated fatty acids (corn oil), omega-3 polyunsaturated fatty acids (perilla oil), or monounsaturated fatty acids (olive oil) simultaneously with IQ in the diet resulted in: (i) inhibition of colon and liver tumor induction by corn and perilla oil, whereas olive oil showed no effects; (ii) no reduction in total numbers of ACF by corn oil or perilla oil but significant suppression in the olive oil treated group; (iii) inhibition of tumor development particularly by omega-3 polyunsaturated fatty acids in perilla oil, correlating significantly with decreased cell proliferation in both colon and liver and a marked decrease in crypt heights and mitotic indices. Selective reduction in the numbers of 8-OHdG-positive nuclei, mainly in the middle and distal colon crypts, was also found to correlate with tumor inhibition. Thus, the results indicate carcinogenicity of IQ in the colon of the SCID mouse and preventive effects of polyunsaturated fatty acids.

Lack of modification of rat hepatocarcinogenesis by fernane-type triterpenoids, isolated from a Euphorbia genus.

Inhibitors of topoisomerases, enzymes that produce an unusual type of DNA damage, are considered as antitumor agents. Recently it has been reported that the fernane-type triterpenoid EC-2 and its hydroxyl derivative, isolated from Euphorbia, are potent topoisomerase II inhibitors. In this study, the modifying effects of EC-2 and EC-4 on the development of putative preneoplastic lesions, glutathione S-transferase placental form (GST-P)-positive foci, in the liver of rats were investigated using a medium-term bioassay system. Fisher 344 male, 6-week-old rats were given a single intraperitoneal injection (200 mg/kg b.w.) of diethylnitrosamine or saline at the beginning of the experiment and subjected to 2/3 partial hepatectomy at the 3rd week. The test compounds were administered five times/week by i.g. gavage at a dose of 1 mg/kg b.w. from 2 to 8 weeks. Quantitation of the numbers and areas per cm(2) of induced GST-P positive foci did not demonstrated any significant differences among the groups and no variation in cell proliferation as indicated by 5-bromo- 2'-deoxyuridine (BrdU) labeling. Our results suggest that EC-2 and EC-4 have no modifying effects on rat hepatocarcinogenesis.