Biomedical subjects

Heekyung Chung

Publications and source records attributed to Heekyung Chung.

3 recordsLinked to original sources

PubMed2004

Vitamin E supplementation reverses the age-associated decrease in effective immune synapse formation in CD4+ T cells.

Aging is associated with impairment of T cell function. We demonstrate here that age-associated declines in T cell signaling are due to the inability to form effective immune synapses at the site of the T cell receptor and antigen interaction. On the basis of our previous research with vitamin E (VE), we hypothesized that VE supplementation of old CD4(+) T cells enhances effective immune synapse formation through increased translocation of signaling proteins. Using confocal microscopy, we found that when exposed to antigen-presenting cells, CD4(+) T cells from old mice have a lower percentage of effective immune synapses compared to those from young mice. Furthermore, we show that in vitro and in vivo VE supplementation increases the percentage of old CD4(+) T cells capable of forming a functional immune synapse. Further studies are under way to determine the mechanisms of age and VE-induced enhancement of effective immune synapse formation.

Aging↗

PubMed2003

Effect of age on susceptibility to azoxymethane-induced colonic aberrant crypt foci formation in C57BL/6JNIA mice.

To determine the effect of age on susceptibility to azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) formation and its underlying mechanism, young and old mice were injected with AOM weekly for 4 or 5 weeks and euthanized 5 or 6 weeks later. Given the same (12 or 15) mg/kg body weight dose of AOM, old mice had significantly more ACF than young mice. However, given the same total dose of AOM (to avoid confounding effect of higher dose to heavier old mice), at a low total dose (1.5 mg) there was no age difference, but at higher total doses (1.8 and 2.2 mg) young mice had significantly more ACF than old mice. These results indicate that the age-related susceptibility to AOM differs depending on whether administration of the carcinogen is based on weight or total dose. These age differences are not due to variations in cyclooxygenase-2 expression, cell proliferation, or AOM hydroxylase activity.

Age Factors↗

PubMed2003

Vitamin E supplementation does not alter azoxymethane-induced colonic aberrant crypt foci formation in young or old mice.

Vitamin E, part of the body's primary lipid-soluble defense against free radicals and reactive oxygen molecules, has been suggested to reduce the risk for some cancers. However, the role of vitamin E in the etiology and prevention of colon cancer, especially in the highest risk group, the aged, is not clear. Thus, this study was conducted to elucidate the effect of vitamin E supplementation on susceptibility to colon cancer by examining azoxymethane (AOM)-induced aberrant crypt foci (ACF) formation, a surrogate biomarker of colon cancer. Young (3-4 mo) and old (19-20 mo) C57BL/6JNIA mice were fed either a control diet (30 mg dl-alpha-tocopheryl acetate/kg diet) or a vitamin E-supplemented diet (500 mg dl-alpha-tocopheryl acetate/kg diet) for 16 wk. After 6 wk of dietary supplementation, young and old mice were injected with saline or AOM weekly for 5 wk to receive the same total dose of AOM (2.2 mg) and killed 10 wk after the first AOM injection. Vitamin E supplementation had no effect on the number of AOM-induced ACF in young or old mice. In addition, vitamin E supplementation did not have an effect on splenocyte interferon-gamma, interluekin-6 and tumor necrosis factor-alpha levels, natural killer cell killing activity or colonic cell proliferation in young or old mice. Thus, alpha-tocopherol does not seem to affect the initiation and early promotion stages of AOM-induced colon carcinogenesis in young or old mice. Whether vitamin E supplementation might be effective in reducing AOM-induced colon tumors is unclear.

Aging↗