ANTIOXIDANT ACTIVITY OF EGT 25 mRNA expression. Thus, we examined the effect of EGT on MMP-1 mRNA expression in cultured normal human fibroblasts exposed to UVA. MMP-1 mRNA in human fibroblasts was elevated 1.25-fold at 24 h post UV A irradiation. EGT reduced MMP-1 mRNA expression levels in a dose-dependent manner (Figure 6). The results indicated that EGT down-regulated MMP-1 mRNA expression of fibroblasts induced by UVA irradiation. DISCUSSION EGT has structural similarities to histidine, urocanic acid, and carnitine, none of which are substantial antioxidants. EGT has strong and unusual antioxidant activity due to its sulfur in thione form, which converts to the sulfhydryl form to scavenge oxygen radicals. A recent study showed the protective abilities of EGT on cell damage induced by H202 and ONOO- (26). In addition, it suppressed NF-KB activation stimulated by H20 2 (27). Therefore, we focused on the antioxidative effects of EGT against •0 2 - and 1 0 2 , and examined whether it reduced the markers of skin aging. We show here that EGT scavenged •0 2 - and 1 0 2 and inhibited the lipid peroxidation initiated by these ROS. UV-irradiated fibroblasts secrete several proteins, including TNF-a, which is a pro­ inflammatory cytokine, and MMP-1, which degrades the collagen matrix. EGT inhib­ ited DVB-induced up-regulation of TNF-a gene expression and suppressed MMP-1 gene transcription in human dermal fibroblasts exposed to UV A. These data suggest that ROS can initiate these changes in gene expression. Cutaneous damage induced by UV irradiation may lead to premature skin aging, called photoaging (4). The relationship between wrinkle formation and dermal matrix alter­ ation has been actively studied by many researchers. It has been proposed that UV irradiation causes photoaging in skin by induction of an imbalance of dermal matrix metabolism, including reduction of collagen synthesis and enhancement of MMP-1 production. Recently, Chung et al. (28) proposed a theory on the dermal alterations in MMP-1 G3PDH EGT (mg/ml) UVA (J/cm2) 0 0 0 0.5 1.0 20 20 20 Figure 6. EGT-suppressed MMP-1 up-regulation by UVA irradiation. Human fibroblasts were exposed to UVA at a dose of 20 J/cm2 in the presence of various concentrations of EGT in HBS. Total RNA was extracted at 6 h after UVA irradiation. The expression of MMP-1 was evaluated by RT-PCR.

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