Gene expression profiling reveals aryl hydrocarbon receptor as a possible target for photobiomodulation when using blue light (24h time point)

Photobiomodulation (PBM) with blue light induces a biphasic dose response curve in proliferation of immortalized human keratinocytes (HaCaT), with a maximum anti-proliferative effect reached with 30min (41.4J/cm²). The aim of this study was to test the photobiomodulatory effect of 41.4J/cm2 blue light irradiation on ROS production, apoptosis and gene expression at different time points after irradiation of HaCaT cells in vitro. ROS concentration was increased 30min after irradiation. However, already 1h after irradiation, cells were able to reduce ROS and balance the concentration to a normal level. The sudden increase in ROS did not damage the cells, which was demonstrated with FACS analysis where HaCaT cells did not show any sign of apoptosis after blue light irradiation. Furthermore, a time course could be seen in gene expression analysis after blue light, with an early response of stimulated genes already 1h after blue light irradiation, leading to the discovery of the aryl hydrocarbon receptor as possible target for blue light irradiation. 10,000 HaCaT cells per well were plated in black 96 well plates. After seeding, cells were incubated 24h at 37°C with 5% CO2. Medium was renewed and cells were irradiated for 30 min with blue light (452nm). The right half of the plate was taped with black foil for the no light negative control. After defined time point (24h) cells were harvested