Efeito da fotobiomodulação no reparo de membrana, metabolismo lipídico e resposta inflamatória: implicações na infecção por Trypanosoma cruzi

Abstract

Low-level laser therapy (LLLT), also known as photobiomodulation (PBM), involves applying a light source to a specific area using low power and energy levels to enhance regenerative processes and regulate functional disorders. However, the impact of LLLT on molecular and cellular mechanisms, as well as on the immune response triggered by intracellular pathogens, remains largely unelucidated. In this context, it is crucial to elucidate how LBP modulates key cellular mechanisms, such as membrane repair (MR), T. cruzi infection, and lipid metabolism. One of the main MR mechanisms in cells injured by chemical or mechanical stimuli involves the repair process through endocytosis, mediated by calcium influx and lysosomal exocytosis, leading to endocytic removal of the damaged area and resealing of the plasma membrane (PM). Pathogens such as the protozoan T. cruzi can exploit endocytic vesicles formed during the activation of this MR process to invade host cells. Additionally, this parasite manipulates the biogenesis of lipid bodies (LBs), biologically active organelles involved in lipid metabolism and the modulation of inflammatory responses. Considering the crucial role of MR mechanisms and LBs in cellular responses during infection, this study aimed to investigate, in vitro, the effects of LLLT on PM integrity, MR, the progression of T. cruzi infection, and lipid metabolism. C2C12 myoblasts were irradiated with LLLT at a dose of 30 J/cm² (output power: 100 mW, exposure time: 8 s, continuous emission, single session) and subsequently infected, or not, with T. cruzi trypomastigotes (Dm28c strain). Afterward, the cells were fixed and processed, and the supernatants collected for fluorescence assays, immunolabeling, Western Blot, Transmission Electron Microscopy (TEM), and quantification of PGE₂ and cytokines. Photobiomodulation did not alter cell viability but affected PM permeability. Preirradiation with LLLT promoted calcium influx, lysosomal recruitment, and caveolae formation, cellular events associated with MR via endocytosis, as well as modulated T. cruzi infection, favoring parasite invasion, replication, and survival. Both photobiomodulation and T. cruzi infection increased LB biogenesis, a process modulated by PPARγ and SREBP-1 expression, leading to elevated PGE₂ levels under both conditions. Pre-irradiation with LLLT also exhibited a modulatory effect on inflammatory mediators, reducing IL-6 and TNF-α while increasing IL-10, whereas infection alone elevated IL-6, TNF-α, IL-12, and IL-10. Altogether, these findings indicate that LLLT induces microlesions in the PM capable of activating MR via endocytosis, while also regulating lipid metabolism and immune responses, thereby directly influencing the course of T. cruzi infection.