FIGURE 4

Cysteinyl-DOPA-melanin but not DOPA-melanin acts as a photosensitizing agent in the induction of charge modification of Cat after UVA and His is able to counteract the phenomenon. U937 cells were irradiated with UVA (20 J/cm²) or UVB (0.45 J/cm²) through CDM (4 g/ml) or DM (4 g/ml) in the presence or absence of His (30 mM) in the cell suspension (see Figure 3). Thereafter, cells were processed for zymographic analysis. (a) CDM acts as a photosensitizing agent in the induction of charge modification of Cat in U937 after UVA, and His, a quencher of singlet oxygen, is able to counteract the phenomenon. CTR=non-irradiated cells; CDM=non-irradiated cells with CDM put onto the filter; UVA=cells irradiated with UVA; CDM UVA=cells irradiated with UVA through CDM; His=non-irradiated cells in the presence of His in the cell suspension; His UVA=cells irradiated with UVA in the presence of His in the cell suspension; His CDM UVA=cells irradiated with UVA through CDM in the presence of His in the cell suspension. (b) UVA irradiation through DM does not modify charge properties of Cat in U937. CTR=non-irradiated cells; DM=non-irradiated cells with DM put onto the filter; UVA=cells irradiated with UVA; DM UVA=cells irradiated with UVA through DM. (c) UVB irradiation through CDM does not modify the charge properties of Cat. CTR=non-irradiated cells; CDM=non-irradiated cells with CDM put onto the filter; UVB=cells irradiated with UVB; CDM UVB=cells irradiated with UVB through CDM. (d) UVB irradiation through DM does not modify the charge properties of Cat. CTR=non-irradiated cells; DM=non-irradiated cells with DM put onto the filter; UVB=cells irradiated with UVB; DM UVB=cells irradiated with UVB through DM.