Oxidative damage to Hs68 cells induced by UVA and NO and protection by food, cosmetic and cellular components

• Main Authors: Shih-Mei Lin, 林詩玫
• Other Authors: Miao-Lin Hu
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/12259464970793231080

碩士 === 國立中興大學 === 食品科學系 === 88 === It is well known that cumulative exposure of human skin to UVA results in increased risk of skin cancer. Some studies indicated that cellular lesion induced by UVA was due to reactive oxygen species (ROS; 1O2, O2.-, H2O2 or .OH). In UVA treated cells, the simultaneous production of NO and ROS might result in the formation of ONOO.- and increasing cellular damage. Therefore, this thesis work was divided into two parts. One was to investigate oxidative damage to human foreskin fibroblasts (Hs68 cells) by UVA and iron ions, the other was to study protective effect of food, cosmetic and cellular components against UVA- or NO-induced oxidative damage in Hs68 cells. PartⅠ Oxidative damage to Hs68 cells induced by UVA and iron ions This part of study was to investigate effect of ferrous ion (Fe2+) and nitrilotriacetate (NTA) on cytotoxicity induced by UVA. The results show that Fe2+ and Fe2+-NTA significantly promoted membrane lipid peroxidation (the generation of TBARS was increased), DNA oxidative damage (DNA strand breakage and the generation of 8-hydroxyguanosine (8-OH-dG)) and cytotoxicity (reduction of cellular viability)(p＜0.05). Lipid peroxidation may be caused by singlet oxygen (1O2 ) generated from cells during UVA irradiation, which reacted with membrane lipid (LH) to form lipid hydroxyperoxide (LOOH). The role of iron ions in lipid peroxidation is likely in the breakdown of LOOH according to reaction (1): LOOH + Fe2+→LO. + .OH + Fe3+ (1) Fe3+ is thought to be reduced by UVA to Fe2+, which induces the generation of free radical continuously to increase lipid peroxidation. DNA oxidative damage may be caused by reaction of Fe2+ with H2O2 generated from UVA irradiated cells to produce .OH, which induces DNA strand breakage and the formation of 8-OH-dG, leading to necrosis. In the experimental model, NTA significantly promoted DNA oxidative damage in Hs68 cells induced by Fe2+, possibly by chelation of iron ions, leading to changes of distribution and redox potential of cellular iron ions. The result also shows that DNA damage is not a result of lipid peroxidation in this UVA/Fe2+-NTA/cell system. Part Ⅱ Protective effect of food, cosmetic and cellular components against UVA- or NO-induced oxidative damage in Hs68 cells This part of study was to investigate the effects of several components of food (maltol), cosmetics (benzophenone, butyl methoxydibenzoylmethane (BM-DBM) and boldine) and mammalian cells (dimethylglycine (DMG) and diphosphoglycerate (DPG)) on oxidative damage induced by UVA or NO. In cellular damage induced by UVA, none of the six compounds inhibited lipid peroxidation. In fact, matol and BM-DBM enhanced lipid peroxidation. DMG, 2,3-DPG and boldine inhibited DNA oxidative damage induced by UVA, but maltol and BM-DBM could enhance it. Cellular damage induced by NO: in the present study, we only investigated DNA oxidative damage induced by NO because NO might not intiate lipid peroxidation. The result shows that 2,3-DPG, benzophenone, BM-DBM and boldine could inhibit DNA strand breakage induced by NO. Among them, BM-DBM had better inhibitory effect. According to it, we suggest that 2,3-DPG and boldine may protect against oxidative stress induced by UVA and NO. Conclusion The present results show that Fe2+-NTA strongly enhanced lipid peroxidation and DNA oxidative damage induced by UVA; the mechanism may be that NTA changed the distribution and redox potential of cellular iron ions. Such damage leads to cell death - necrosis, and can increase the risk of mutation of DNA and carcinogenesis. UVA radiation may induce the generation of NO, which may stimulate melanocytes to generate and accumulate melanin. NO may induce inflammatory response and result in the formation of erythema. 2,3-DPG and boldine can inhibit DNA oxidative damage induced by UVA and NO, and they may have potentials to be sunscreens.