Photobiomodulation by blue light induces a dose dependent biphasic proliferation curve in human keratinocytes [exp2]

Photobiomodulation (PBM) with blue light induces a biphasic dose response curve in proliferation of immortalized human keratinocytes (HaCaT), with a maximum proliferative effect reached with 7.5min (10.35J/cm2). The aim of this study was to test the photobiomodulatory effect of 10.35J/cm2 blue light irradiation on cell proliferation, ROS production and gene expression at different time points after irradiation of HaCaT cells in vitro and to compare the results with the anti-proliferative phase of PBM using blue light with 41.4J/cm2. For 10.35J/cm2 cell proliferation was increased for all measured harvesting time points up to at least 24h after irradiation. ROS concentration was increased 30min after irradiation. However, already 1h after irradiation, cells were able to decrease ROS and stabilize the concentration to the basal level. The sudden increase in ROS was even higher when compared to 41.4J/cm2. However, gene expression analysis did not indicate any sign of apoptosis and even indicated an activation of cell survival mechanisms. Furthermore, comparable to 41.4J/cm2, aryl hydrocarbon receptor (AHR) “battery genes” showed a deregulation after blue light irradiation strengthening the hypothesis of AHR as possible target for blue light irradiation. 6 samples: 3x 96 well plates per experiment, each plate contains irradiated cells and not light control cells to exclude a plate effect (systematic error), therefore there are 3 replicates for irradiated cells and 3 replicates of no light conotrol cells