Yc. Fu et al., Ultraviolet radiation and reactive oxygen generation as inducers of keratinocyte apoptosis: Protective role of tea polyphenols, J TOX E H A, 61(3), 2000, pp. 177-188
Citations number
49
Categorie Soggetti
Environment/Ecology,"Pharmacology & Toxicology
Journal title
JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH-PART A
Ultraviolet A ( UVA) radiation produces serious damage to skin, especially
to dermis, but its damage to epidermis and responsible mechanisms are not f
ully understood. Studies were thus undertaken to investigate the effects of
UVA or reactive oxygen species (ROS) on lipid peroxidation, cell cycle, an
d apoptosis in primary cultured rat keratinocytes and to determine the poss
ible protect ive effects of tea polyphenols (TPP). UVA or ROS increased the
release of plasma enzyme lactate dehydrogenase (LDH), and increased lipid
peroxidation production (malondialdehyde, MDA), but decreased the activity
of glutathione peroxidase (GSH-Px), indicating that UVA or ROS were cytosta
tic and peroxidizing to keratinocytes. TPP stabilized and protected cell me
mbranes from ROS or UVA by inhibiting the release of LDH, lowering MDA leve
ls, and increasing GSH-Px activity. Flow cytometry ( FCM) analysis revealed
that UVA or ROS decreased the proliferative index (PI); hence the cell gro
wth was blocked in the S/G2 phase, with an increase in the percentage of ap
optosis in primary keratinocytes. TPP modified the UVA or ROS-induced chang
es in PI and apoptosis. TPP may be useful to protect keratinocytes from UVA
irradiation. In summary, these data demonstrated that UVA damage to skin k
eratinocytes in vitro was similar to that for ROS and that TPP protects aga
inst UVA-induced cytotoxicity by inhibiting lipid peroxidation and apoptosi
s.