Fig. 4

M1/M2 macrophage polarization was changed by treatment with exosomes (UVB + ZnONPs) from HaCaT cells. A Characterization of HaCaT cell-secreted exosomes. Exosomes were isolated from HaCaT cell culture medium, and exosome markers, including CD63, TSG101, and Flotillin-1, were identified by western blotting. The number of particles isolated from HaCaT cells was determined by nanoparticle tracking analysis (NTA). B Representative TEM images of exosomes obtained from untreated HaCaT cells (scale bar represents 100 nm). C DioC18 fluorescence-labeled HaCaT cells and THP-1-derived macrophages were cocultured in a transwell manner, as depicted schematically. Representative data showing the presence of DioC18-labeled exosomes that were internalized by macrophages after HaCaT cells were exposed to UVB + ZnONPs for 24 h (scale bar represents 100 μm). D Flow cytometry showed an increase in the amount of fluorescence-labeled exosomes released and taken up by macrophages in the UVB + ZnONP-treated group (*p < 0.05 compared with control). E Exosomes purified from HaCaT cells exposed to UVB + ZnONPs were added to THP-1-derived macrophages for 24 h. An increase in the M1 macrophage population was observed by flow cytometry when THP-1-derived macrophages were exposed to LPS (100 ng/ml) and exosomes (UVB + ZnONPs). PMA stimulates THP-1-derived macrophages. To mitigate the potential impact of PMA on macrophage polarization, we employed PMA as an internal control. (*p < 0.05 compared with control). F Western blot analysis was conducted to assess the protein expression of inducible nitric oxide synthase (iNOS, M1) and arginase-1 (ARG1, M2) in PMA-derived macrophages, LPS (100 ng/ml), and exosomes (UVB + ZnONPs). The histograms illustrate the relative expression levels of iNOS and ARG1 (*p < 0.05 compared with control). G The iNOS/ ARG1 ratio in the LPS and exosome exposure groups was normalized to that of the PMA group. (*p < 0.05 compared with control). H Mouse skin biopsies were collected from the different experimental groups after treatment for 72 h. Immunofluorescence analysis of CD86 (M1 macrophage marker) and CD206 (M2 macrophage marker) was performed to distinguish the M1/M2 macrophage populations (scale bar represents 100 μm). The quantification of CD86⁺ and CD206⁺ cells was evaluated by ImageJ software (***p < 0.001 compared with control). DAPI staining labeled the nuclear DNA of cells