Characterization of UVB and UVA‐340 Lamps and Determination of Their Effects on ER Stress and DNA Damage

Ultraviolet B-light (UVB) has been often used as a "physiological" UV in photobiology studies. How representative and equivalent these studies are compared to the effect of the sunlight is always of great interest. We now characterized the spectrum and intensity of two commonly used UV sources, a UVB lamp and a UVA-340 lamp which simulate the solar spectrum in the UVB/UVA range in the presence or absence of a UVB band pass filter that reduces >80% UVA from the UVA-340 lamp. The spectrum of each lamp was used in computational modeling for skin penetration. The effects of the lamps on endoplasmic reticulum (ER)-stress response and DNA damage in cultured keratinocytes HaCaT cells were analyzed. Our data show that the UVB lamp is a better inducer for both eIF2α phosphorylation and PERK modification, as well as a better reducer of ATF6 expression. The UVB lamp is also the best inducer of gamma-H2AX expression and cyclobutane pyrimidine dimers formation. However, the UVA-340 lamp is a better inducer for ATF4 expression. Our results indicate that different spectral characteristics of UV lamps can produce different results for the activation of the ER-stress responses and the differences do not always follow a defined pattern.