Role of beta-carotene on the changes in activity patterns and levels of biotransforming enzymes in transplantable murine lymphoma

Phytochemical regulation of UDP-glucuronosyltransferases: implications for cancer prevention

Uridine 5'-diphospho-glucuronosyltransferases (UGTs) are Phase II biotransformation enzymes that metabolize endogenous and exogenous compounds, some of which have been associated with cancer risk. Many phytochemicals have been shown to induce UGTs in humans, rodents, and cell culture systems. Because UGTs maintain hormone balance and facilitate excretion of potentially carcinogenic compounds, regulation of their expression and activity may affect cancer risk. Phytochemicals regulate transcription factors such as the nuclear factor-erythroid 2-related factor 2 (Nrf2), aryl hydrocarbon, and pregnane X receptors as well as proteins in several signal transduction cascades that converge on Nrf2 to stimulate UGT expression. This induction can be modified by several factors, including phytochemical dose and bioavailability and interindividual variation in enzyme expression. In this review, we summarize the knowledge of dietary modulation of UGTs, particularly by phytochemicals, and discuss the potential mechanisms by which phytochemicals regulate UGT transcription.

Beta-carotene prolongs survival, decreases lipid peroxidation and enhances glutathione status in transplantable murine lymphoma

Carotenoids of dietary origin have recently been the subject of renewed research interest because of epidemiological evidence indicating an inverse relationship between intake of carotenoids-rich plant substances and risk of certain cancers. This study was attempted to understand the biological actions of dietary beta-carotene (BC) on Dalton's lymphoma (DL), a rapidly proliferating transplantable tumor, in effecting the survival of the lymphoma-bearing mice. The glutathione (GSH) level and the extent of lipid peroxidation in the liver, kidney and brain were monitored in BC-treated (100 mg/kg food) mice transplanted with DL. These markers showed substantial alterations during the whole length of tumor progression in lymphoma-bearing mice without BC supplementation. When treated with BC, both malondialdehyde contents (evidence of lipid peroxidation) and the GSH levels in different organs were found to be closer to normal values in the initial period of tumor progression. BC-mediated protection against lipid peroxidation was maximally found to be in hepatic tissue throughout the study following DL transplantation. This was fairly reflected in the higher BC concentration in hepatic tissue of BC-treated lymphoma group compared to untreated lymphoma control. Significantly higher survival time (51-55 days) was observed in BC-treated animals in comparison to their untreated DL counterparts (35-38 days). The prolonged survival observed in the BC-supplemented animals may be attributed to the higher resistance offered by animals receiving BC towards lipid peroxidation-related tissue injury.

Novel implications of the potential role of selenium on antioxidant status in streptozotocin-induced diabetic mice

Levels of blood glucose, lipid peroxidation, glutathione (GSH), glutathione peroxidase (GPx), glutathione S-transferase (GST) activities and blood selenium levels were determined in streptozotocin (STZ)-induced diabetic mice. The effect of oral administration of sodium selenite was studied on the above parameters. Diabetes caused hyperglycemia (2.8-fold increase) with a significant increase in the malondialdehyde levels (89% in liver and 83% in blood) and GST activity (55%) and marked decreases in GSH levels (approximately 73% in blood and 79% in liver) in the 5th week after STZ treatment as compared to normal control animals. Treatment of STZ-induced diabetic mice with sodium selenite changed these parameters to near control values in almost all cases. These results suggest that selenium plays a role in reducing the oxidative stress associated with diabetes.

Antitumor effect of an oral administration of canthaxanthin on BALB/c mice bearing thymoma cells

The antitumor effect of canthaxanthin in BALB/c mice bearing a transplantable thymoma was investigated. Male or female mice received two different doses of canthaxanthin (7 or 14 micrograms/g body wt/day) starting 15 days before tumor inoculation (7 x 10(7) cells i.p.). Canthaxanthin treatment delayed the appearance of macroscopic ascites and prolonged animal survival. This effect was dose dependent and more evident in females than in males. It appeared only when the carotenoid was administered before tumor transplantation. The antitumor efficacy of the carotenoid was related to its tissue incorporation. Canthaxanthin was incorporated in a dose-dependent manner in liver and thymoma cells and to a larger extent in females than in males. Our study shows the antitumor efficacy of canthaxanthin in vivo against a transplantable murine thymoma and points out the importance of dose, administration timing, and sex in the antitumor efficacy of this compound.