Influence of neodymium-doped yttrium aluminum garnet laser exposure time on cytokine secretion in lipopolysaccharide-challenged rat peripheral blood mononuclear cells

Multiple investigators have suggested that infrared laser energy facilitates hard and soft tissue wound healing through various mechanisms, including the suppression of inflammation. This study investigated the influence of neodymium-doped yttrium aluminum garnet (Nd:YAG) laser exposure time on pro-inflammatory cytokine/chemokine concentrations in lipopolysaccharide (LPS)-stimulated rat peripheral blood mononuclear cells (PBMCs). Cultured rat PBMCs were stimulated with various LPS concentrations (0, 10, 100, or 1000 ng/mL) and treated with Nd:YAG laser irradiation for 0 (control), 30, 45, or 60 s. For these experiments, the average power, pulse duration, and repetition rate remained constant at 5 W, 100 μs, and 20 Hz, respectively. Luminex magnetic microsphere immunoassays were used to compare the secretion of 27 inflammatory mediators from LPS-stimulated PBMCs in laser-irradiated versus control groups. Two-way analysis of variance was used to compare the main effects of laser exposure time and LPS concentration on cytokine/chemokine concentrations and evaluate the potential interaction between these factors. Four pro-inflammatory cytokines – tumor necrosis factor-α, macrophage inflammatory protein (MIP)-1α, MIP-2, and interferon gamma-induced protein-10 – exhibited a trend of reduced secretion in laser-irradiated cultures. The effect appeared more pronounced at longer exposure times (45 and 60 s). However, none of the 27 inflammatory mediators exhibited statistically significant reductions in concentrations in laser-irradiated cultures versus control cultures. These observations do not support a robust anti-inflammatory effect of Nd:YAG laser irradiation. Further studies should explore the potential impact of Nd:YAG laser irradiation on cytotoxicity and cellular growth kinetics and extend across a range of irradiation parameters and cell types.