A Fluorometric Assay ofL-Aspartate: 2-oxoglutarate Aminotransferase in Human Serum with N-(9-Acridinyl) maleimide

Glutathione isopropyl ester reduces UVB-induced skin damage in hairless mice

The protective effect of administration of glutathione (GSH) isopropyl ester on photodamage, such as lipid peroxidation, inflammation and tumorigenesis induced by UV exposure (290-400 nm, max. 312 nm), was investigated using hairless mice. Pretreatment with 20 mg/kg GSH isopropyl ester prevented the increases of thiobarbituric acid-reactive substance (TBARS) formation in skin and serum sialic acid, indices of lipid peroxidation and inflammatory reaction, respectively, which were caused by a single dose (15 kJ/m2) of UV irradiation. The level of epidermal GSH in skins of the GSH ester-treated mice was maintained within normal limits. When mice were exposed to UV at a dose of 2 kJ/m2, three times weekly, skin tumors developed in all of them after 25 weeks. The formation of skin tumors was significantly inhibited by administration of 10 mg/kg GSH ester prior to each UV irradiation for 25 weeks. Moreover, the increases of cutaneous TBARS and serum sialic acid in the tumor-bearing mice were also prevented by continuous pretreatment with GSH ester. Even after 24 weeks, the epidermal GSH content of the pretreated mice was mostly retained compared to nonirradiated mice. However, administration of GSH prior to acute or chronic UV irradiation had no effect on the UV-induced damage. The present results suggest that the protection from photodamage afforded by pretreatment with GSH ester is due to maintenance of a normal GSH level.

Possible role of metallothionein in the cellular defense mechanism against UVB irradiation in neonatal human skin fibroblasts

The role of metallothionein (MT) in protecting skin cells against UVB irradiation was investigated. Fibroblast strains from normal adult (HS-K) and neonatal (NB1RGB) human skins as well as keratinocyte strains from human skin (SV40-HSK) and newborn Balb/c mouse skin (Pam 212) were exposed to UVB irradiation. The sensitivity of HS-K and NB1RGB cells to UVB irradiation was similar; those of SV40-HSK and Pam 212 cells were two- and six-fold as sensitive to UVB irradiation as HS-K cells, respectively. The HS-K cells contained the greatest cellular reduced form of glutathione (GSH) levels compared to the three other skin cells: the levels were 13-, 7- and 6-fold of those in NB1RGB, SV40-HSK and Pam 212 cells, respectively. These results indicated that the sensitivity of skin cells to UVB irradiation was not always associated with their endogenous GSH levels. In particular, despite the fact that NB1RGB cells contained a relatively small amount of GSH, they were less sensitive to UVB irradiation. NB1RGB cells contained 4-30 times more MT than those in other skin cells examined. The sulfhydryl residues of MT molecules in the NB1RGB cells were estimated to be mostly unoccupied by metals, suggesting they act in a similar way to those of GSH. Moreover, NB1RGB cells in which the MT content was elevated by dexamethasone (1 microM) or Zn2+ (7 micrograms/mL) treatment were more resistant to UVB irradiation than nontreated ones. These results suggest that, at least in neonatal human skin fibroblasts, MT may play a role in protection against UVB irradiation.