Biomedical subjects

H T Huynh

Publications and source records attributed to H T Huynh.

21 records · Page 2Linked to original sources

PubMedDate not supplied

Effects of intragastrically administered Pycnogenol on NNK metabolism in F344 rats.

NNK is a tobacco-specific nitrosamine that requires metabolic activation by cytochrome P450 enzymes. NNK may be metabolized via carbonyl reduction, N-oxidation, and alpha-carbon hydroxylation. Pycnogenol is a mixture of flavonoid compounds extracted from pine tree bark and is available as a dietary supplement. We have previously shown that Pycnogenol inhibits the in vitro metabolism of NNK in lung and liver microsomes of F344 rats in a concentration-dependent manner. In this report, intragastrically administered Pycnogenol in saline affected NNK metabolism in lung microsomes differently than in liver microsomes of F344 rats. The administered Pycnogenol was inhibitory toward NNK activation in lung microsomes but not in liver microsomes suggesting that Pycnogenol may afford chemoprotection toward NNK-induced lung tumorigenesis when administered orally but not toward NNK-induced liver tumorigenesis. The effects of intragastrically administered Pycnogenol on NNK metabolism in lung and liver microsomes were similar in 6 mo and 20 mo old rats although the level of NNK metabolism was less in the 20 mo old animals.

Administration, Oral↗

PubMedDate not supplied

Selective induction of apoptosis in human mammary cancer cells (MCF-7) by pycnogenol.

Breast cancer is the second leading cause of cancer death in women in the United States. The 1999 Cancer Facts and Figures, published by the American Cancer Society, estimates that almost 43,700 women and men will die of breast cancer in the United States. In this study, we compared the response of human breast cancer cells (MCF-7) and normal human mammary cells (MCF-10) to apoptosis in the presence of pycnogenol. Pycnogenol is a mixture of flavonoid compounds extracted from the bark of pine trees. MCF-7 and MCF-10 cells were plated out in culture dishes and grown in medium containing 0, 40, or 80 micrograms pycnogenol/ml culture medium. Cells were harvested at confluency, incubated with DAPI for 15 min and viewed microscopically for evidence of apoptosis. Apoptosis is detectable by morphology, chromatin condensation, nuclear DNA fragmentation, DNA strand breakage or apoptotic bodies. DAPI is a DNA-binding fluorescent dye used to visualize DNA fragmentation. Apoptosis, as detected by DAPI staining, was significantly higher in MCF-7 cells treated with pycnogenol than the untreated cells. The presence of pycnogenol did not significantly alter the number of apoptotic cells in MCF-10 samples. These results suggest that pycnogenol selectively induced death in human mammary cancer cells (MCF-7) and not in normal human mammary MCF-10 cells.

Antineoplastic Agents↗

PubMedDate not supplied

Effects of plant-derived phenols on rat liver cytochrome P450 2B1 activity.

Dietary constituents contain a variety of compounds that are known to modulate liver enzyme activity. In this report, the plant-derived phenols catechin, chlorogenic acid, diosmin, epigallo-catechin gallate (EGCG), naringenin, quercetin and resveratrol were studied for their effects on the activity of cytochrome P450 2B1 in liver microsomes from 6- and 20-month male Fisher F344 rats. The compounds at two concentrations (0.1 and 0.25 mM) were incubated with 0.2 mg liver microsomal protein and 50 microM 7-ethoxy-4-trifluoromethyl coumarin (EFC). O-deethylation of EFC to the fluorescence product 7-hydroxy-4-trifluoromethyl coumarin (HFC) is catalyzed by CYP450 2B1. EGCG, naringenin, quercetin and resveratrol inhibited the in vitro O-deethylation of EFC in liver microsomes from both 6- and 20-month rats. Quercetin was the most effective inhibitor. Catechin inhibited the in vitro O-deethylation of EFC only in microsomes from 6-month-old rats whereas diosmin inhibited the reaction only in microsomes from 20-month-old rats. Chlorogenic acid inhibited the in vitro O-deethylation of EFC in microsomes from both age groups at the 0.25 mM concentration only. These results suggest that plant phenols have varied effects on liver microsomal cytochrome P450 2B1 activity that may be influenced by the age of the animal.

Alkylation↗