Chronic exposure to solar UV radiation damages skin, increasing its thickness and reducing its elasticity, and causes
skin cancer. Our aim in this study was to examine the effects of an
olive leaf extract and its component
oleuropein on skin damage and the incidence of skin
tumors caused by long-term UVB irradiation in hairless mice. Male hairless mice (5 wk old) were divided into 6 groups, including a non-UVB group, a vehicle-treated UVB group (control), 2
olive leaf extract-treated UVB groups, and 2
oleuropein-treated UVB groups. Five groups were UVB irradiated (36-180 mJ/
cm(2)) 3 times each week for 30 wk and skin thickness and elasticity after UVB irradiation were measured every week.
Olive leaf extract (300 and 1000 mg/kg) and
oleuropein (10 and 25 mg/kg) were administered orally twice daily every day for 30 wk. The extract and
oleuropein significantly inhibited increases in skin thickness and reductions in skin elasticity, and skin
carcinogenesis and
tumor growth. Furthermore, they prevented increases in the expression of
matrix metalloproteinase (MMP)-2, MMP-9, and MMP-13 as well as in levels of
vascular endothelial growth factor (
VEGF) and
cyclooxygenase-2 (COX-2) in the skin. Based on histological evaluation, they prevented increases in the expression of Ki-67 and CD31-positive cells induced by the irradiation. These results suggest that the preventative effects of the
olive leaf extract and
oleuropein on chronic UVB-induced skin damage and
carcinogenesis and
tumor growth may be due to inhibition of the expression of
VEGF, MMP-2, MMP-9, and MMP-13 through a reduction in COX-2 levels.