Insight into the redox status of inflammatory skin equivalents as determined by EPR spectroscopy

Atopic dermatitis (AD) is a chronic inflammatory skin disease whose pathogenesis is still not fully understood. Since inflammatory processes correlate with oxidative stress, the redox status may play a key role in AD. In this study, electron paramagnetic resonance (EPR) spectroscopy was mainly used to investigate the redox status in normal and inflammatory skin equivalents mimicking characteristics of AD in vitro using EPR spin probes (TEMPO, PCA) and a spin trap (DMPO). The total antioxidant status in the hydrophilic and lipophilic compartments of skin (microenvironment) showed no differences between the skin equivalents. In the inflammatory skin equivalents, a decreased glutathione concentration in the epidermis and an increased metabolic radical production could be observed compared to normal skin equivalents. The induction of external stress by simulated solar irradiation (UVB-NIR) resulted in the same amount and type of radicals in normal and inflammatory skin equivalents. For the first time, the antioxidant and oxidant status of inflammatory in vitro skin equivalents was analyzed by EPR to elucidate their redox status using different methods which focus on various microenvironments. Our investigations suggested that the redox status in atopic skin could be different, but this should be investigated more comprehensively, because the results can vary depending on the used methods and where the investigations take place.