Laser photobiomodulation of pro-inflammatory mediators on Walker Tumor 256 induced rats

Laser photobiomodulation or low-level laser therapy (LLLT) is recognized worldwide for its expansive use in medicine. LLLT has been reported to increase enzymatic activity, increasing the mitochondrial transmembrane potential, leading to an increased energy availability and signal transduction. Nevertheless, an inhibitory effect is also observed by the production of excessive ROS which can result the shutdown of mitochondrial energy production, and finally to apoptosis. However, the mechanism of apoptosis induced by LLLT is still not well understood. The main objective of the present study was to investigate the hypothesis that LLLT induces oxidative stress and stimulates the generation of pro-inflammatory markers interfering in tumor progression. Methods: Seventy-two female Walker Tumor induced Wistar rats (eight weeks of age, 200 g body weight) were used for this study. TW-256 cells were suspended in phosphate buffered saline and then subcutaneously inoculated at 1 x 107 viable tumor cells/ml per rat into the right flank (tumor-bearing rats). After a period of 14 days in order to assess the development of the solid tumor mass, the animals were randomized and distributed in four groups (n = 8 animals/group): (1) Control or irradiated by LLLT (2) Laser 1J - 35,7 J/cm(2), (3) Laser 3 J - 107,14 J/cm(2) and (4) Laser 6 J - 214,28 J/cm(2); (Thera Laser - 660 nm, 100 mW DMC (R), Sao Carlos, Brazil) at four equidistant points according to their respective treatment groups, conducted three times on alternate days. The regulation and expression of inflammatory mediators IL-1 beta, IL-6, IL-10, TNF-alpha was assessed by ELISA and gene expression of COX-1, COX-2, iNOS, eNOS was analyzed by RT-PCR. Results: We found that the 1 Joule (J) treated group promoted a significant increase in the levels of different inflammatory markers IL-1 beta, the gene expression of COX-2, iNOS, which was statistically different (p < 0.05) when compared among different treatment and control groups. With Respect IL-6, IL-10, TNF-alpha levels statistically significant reduce was observed in 1 Joule treated group when comparing to different energies groups and control group. Conclusion: Our results suggest the evidence 1 J-35,7 J/cm(2) treatment was able to produce cytotoxic effects by generation of ROS causing acute inflammation and thus may be employed as the best energy dose associated with Photodynamic Therapy. (AU)