Blue light is known for its anti-microbial, anti-proliferative and anti-inflammatory effects. Furthermore, it is already used
for the treatment of neonatal jaundice and acne. However, little is known about the exact mechanisms of action on gene
The aim of this study was to assess the impact of blue LED irradiation on the proliferation and gene expression in
immortalized human keratinocytes (HaCaT) in vitro. Furthermore its safety was assessed.
XTT-tests revealed a decrease in cell proliferation in blue light irradiated cells depending on the duration of light
irradiation. Moreover, gene expression analysis demonstrated deregulated genes already 3 hours after blue light
irradiation. 24 hours after blue light irradiation the effects seemed to be even more pronounced. The oxidative stress
response was significantly increased, pointing to increased ROS production due to blue light, as well as steroid hormone
biosynthesis. Downregulated pathways or biological processes were connected to anti-inflammatory response.
Interestingly, also the melanoma pathway contained significantly downregulated genes 24 hours after blue light
irradiation, which stands in accordance to literature that blue light can also inhibit proliferation in cancer cells. First tests
with melanoma cells revealed a decrease in cell proliferation after blue light irradiation. In conclusion, blue light
irradiation might open avenues to new therapeutic regimens; at least blue light seems to have no effect that induces
cancer growth or formation.