The M1/M2 Pattern and the Oxidative Stress are Modulated by Low- Level Laser in Human Macrophage

Abstract

Objective: This study investigated the phototherapy (PhT) effect on U937 cells activated by lipopolysaccharide (LPS) from E. coli. PhT has been reported to control the release of inflammatory mediators from different cells activated by LPS. It is unknown if the macrophage M1/M2 pattern as well as the reactive oxygen species (ROS) generation and the pro- and anti-inflammatory cytokines secretion from U937 cells can be influenced by PhT. Methods: The U937 cells, a human monocytic cell line, were cultured and matured to macrophages in a medium with LPS and irradiated (660 nm) at 4.5 J/cm2. Apoptosis was standardized with Annexin-V and propidie iodate (PI) and the cytotoxicity assay evaluated by MTT. ROS was measured by DCFH-DA. The cytokines, chemokines, NF-κB and Sp1 activity were measured by ELISA. PhT was studied in the presence of a Sp1 inhibitor, mithramycin. Results: The pro-inflammatory cytokines and chemokines, ROS and NF-κB were downregulated by PhT. On the contrary, IL-10, arginase, PGC-1β and glutathione were upregulated. The Sp1 activity was increased after PhT to values higher than those from cells only LPS-treated; oppositely the mithramycin abrogated this effect. Conclusion: The PhT restored the macrophage polarization toward M2 pattern as well as balanced the oxidative stress and modulated the immune response upregulating the IL-10 secretion by a mechanism in which Sp1 transcription factor has a crucial role.