2.7. MMP-1 and MMP-9 activity assays
The cells were planted in 6-well plates, exposed to UVB irradiation, and incubated
with various concentrations of samples for 24 h. The amount of active
MMP-1 and MMP-9 in the cells after UVB exposure was measured using the Human
Active MMP-1 Fluorescent Assay Kit and Human Active MMP-9 Fluorescent Assay
Kit (R&D Systems, Inc., USA) according to manufacturer protocols. The fluorescence
(emission, 405 nm; excitation, 320 nm) was measured using a microplate reader
(Thermo Electron Corporation, Finland).