Photobiomodulation modulates peripheral and central expression of inflammation-related genes following carrageenan-induced inflammation in rats

Abstract Peripheral inflammation can induce molecular changes in central nervous system through immune–brain communication. This study investigated whether photobiomodulation (PBM) modulates the temporal mRNA expression of pro- and anti-inflammatory cytokines and receptors involved in prostacyclin and kinin signaling in peripheral and central tissues following carrageenan-induced inflammation in rats. Male Wistar rats received subplantar carrageenan injections (1 mg/paw) and were treated or not with PBM (660 nm) 1 h after carrageenan administration. Animals were euthanized at 1, 3, or 6 h, and mRNA expression of IL-6, IL-10, prostacyclin receptor (IP), and kinin B1 and B2 receptors was quantified by qRT-PCR in subplantar and brain tissues. IL-6 and IP receptor mRNA expression showed their highest levels at 6 h among the carrageenan-treated groups and were reduced by PBM at this time point in both subplantar and brain tissues. In the paw, B1 receptor expression showed its highest level at 3 h among the time points evaluated and was reduced by PBM, whereas B2 receptor expression showed its greatest increase at 6 h. In the brain, PBM reduced B1 and B2 receptor expression at 6 h. IL-10 expression increased in the paw, remaining elevated in PBM-treated animals. In the brain, IL-10 expression was higher at 3 h than at 6 h following carrageenan administration, whereas PBM maintained elevated IL-10 expression at 6 h. Carrageenan-induced peripheral inflammation was accompanied by time-dependent changes in inflammation- and nociception-related gene expression in brain tissue. Localized PBM modulated these peripheral and central transcriptional responses by reducing IL-6, IP, and kinin receptor expression at specific time points while maintaining elevated IL-10 expression. These findings extend previous observations by showing modulation of cytokine, prostacyclin, and kinin signaling-related gene expression following localized PBM.