Photobiomodulation can alter mRNA levels cell death-related

Photobiomodulation (PBM) by low-level laser has demonstrated excellent results for inflammatory treatments, promoting repair of injured tissues. Knowledge regarding the molecular mechanisms involved in this process has been increasing, but its effect on cell death/survival-related gene expression after laser irradiation with different doses is not well understood. So, it is important to know these effects in order to guarantee the safety of therapeutic protocols based on PBM. This study aimed to investigate the mRNA levels of genes related to proteins involved in cell death/survival pathways of healthy tissues from talocrural joint of mice after PBM. Mice were divided into three groups: control, PBM at 3 J cm⁻², and PBM at 30 J cm⁻². Laser irradiation was performed on talocrural joint during four consecutive days. Morphological analyses, immunocytochemistry, FasL, Fas, Bax, Apaf1, Caspase9, Caspase3, Caspase6, Bcl2 mRNA levels, and DNA fragmentation were performed to verify cell death induction after laser irradiation. PBM can increase mRNA levels of almost genes pro-apoptotic. On the other hand, mRNA level of anti-apoptotic protein Bcl-2 gene was not significantly altered. Bcl-2/Bax ratio (indicator of protective molecular response) was decreased after PBM at 30 J cm⁻², trending to DNA fragmentation. Results obtained in this study indicate that PBM by low-level infrared laser alters mRNA relative levels of genes involved in cell death pathways. However, these molecular alterations were not able to cause DNA fragmentation in cells in talocrural joint tissues, indicating that infrared laser was not enough to cause cell death.