[The modulation of low-level laser on polarization of mouse bone marrow-derived macrophages]

Objective To investigate the influence of 810 nm low-level laser of different energy on the polarization of macrophages. Methods The macrophages were isolated from the bone borrow of BALB/c mice and cultured in macrophage colony stimulating factor (M-CSF) conditioned cultural medium. The expression of F4/80 was examined by flow cytometry for identification. After lipopolysaccharide-γ interferon (LPS-IFN-γ) induced polarization status in the macrophages, the mRNA expressions of inducible nitric oxide synthase (iNOS), arginase 1 (Arg1) and CD86 were detected by reverse transcription PCR, and the protein expressions of iNOS and Arg1 were tested by Western blotting. Thereafter, the M1 macrophages were exposed to 810 nm low-level laser of (1, 2, 3, 4) J/cm(2), and then the cell viability was evaluated by MTT assay; the expressions of iNOS and Arg1 were observed by immunofluorescent cytochemical staining; the mRNA and protein levels of iNOS and Arg1 were studied by reverse transcription PCR and Western blotting. Results Flow cytometry showed that the percentage of F4/80 positive cells cultured with M-CSF conditioned medium was 99.9%. The mRNA and protein levels of iNOS and CD86 in macrophages were both significantly raised after induction by LPS-IFN-γ. Compared with the control cells, the viability of M1 cells significantly decreased when the energy of the low-level laser exposure was 4 J/cm(2), while the viability remained unchanged when the energy was 1, 2 or 3 J/cm(2). Immunocytochemistry revealed that the percentage of Arg1 positive cells that represent M2 macrophages was not significantly different from the control group when the irradiation dose was 1 or 2 J/cm(2), however, the Arg1 positive cells significantly increased and the iNOS positive cells that represent M1 macrophages significantly decreased when the irradiation dose was 3 or 4 J/cm(2). When the irradiation dose was 1 or 2 J/cm(2), the mRNA and protein levels of iNOS and Arg1 remained unchanged compared with the control group. When the irradiation dose was 3 or 4 J/cm(2), the mRNA and protein levels of iNOS significantly decreased and Arg1 significantly increased. Conclusion The 810 nm low-level laser with the energy of 1 or 2 J/cm(2) have no significant influence on the polarization and viability of macrophages. M1 macrophages can be polarized into M2 macrophages while there is no significant difference in the cell viability when the energy was 3 J/cm(2). When the energy was 4 J/cm(2), M1 cells can be polarized into M2 cells and the cell viability significantly decreased.