The Effect of UVB Irradiation and Oxidative Stress on the Skin Barrier—A New Method to Evaluate Sun Protection Factor Based on Electrical Impedance Spectroscopy

Abstract

Sunlight is vital for several biochemical processes of the skin organ. However, acute or chronic exposure to ultraviolet radiation (UVR) has several harmful effects on the skin structure and function, especially in the case of the failing function of antioxidative enzymes, which may lead to substantial tissue damage due to the increased presence of reactive oxygen species (ROS). The aim of this work was to investigate the combined effect of ultraviolet B (UVB) irradiation and oxidative stress on the skin barrier integrity. For this, we employed electrical impedance spectroscopy (EIS) to characterize changes of the electrical properties of excised pig skin membranes after various exposure conditions of UVB irradiation, oxidative stress, and the inhibition of antioxidative enzymatic processes. The oxidative stress was regulated by adding hydrogen peroxide (H2O2) as a source of ROS, while sodium azide (NaN3) was used as an inhibitor of the antioxidative enzyme catalase, which is naturally present throughout the epidermis. By screening for the combined effect of UVB and oxidative stress on the skin membrane electrical properties, we developed a new protocol for evaluating these parameters in a simple in vitro setup. Strikingly, the results show that exposure to extreme UVB irradiation does not affect the skin membrane resistance, implying that the skin barrier remains macroscopically intact. Likewise, exposure to only oxidative stress conditions, without UVB irradiation, does not affect the skin membrane resistance. In contrast to these observations, the combination of UVB irradiation and oxidative stress conditions results in a drastic decrease of the skin membrane resistance, indicating that the integrity of the skin barrier is compromised. Further, the skin membrane effective capacitance remained more or less unaffected by UVB exposure, irrespective of simultaneous exposure of oxidative stress. The EIS results were concluded to be associated with clear signs of macroscopic tissue damage of the epidermis as visualized with microscopy after exposure to UVB irradiation under oxidative stress conditions. Finally, the novel methodology was tested by performing an assessment of cosmetic sunscreen formulations with varying sun protection factor (SPF), with an overall successful outcome, showing good correlation between SPF value and protection capacity in terms of skin resistance change. The results from this study allow for the development of new skin sensors based on EIS for the detection of skin tissue damage from exposure to UVB irradiation and oxidative stress and provide a new, more comprehensive methodology, taking into account both the influence of UVB irradiation and oxidative stress, for in vitro determination of SPF in cosmetic formulations.

Non-invasive skin sampling of tryptophan/kynurenine ratio in vitro towards a skin cancer biomarker

“…For this, an equivalent circuit comprised of a resistor, for solution resistance, connected in series with the skin membrane impedance was used. The skin membrane impedance was modelled by a parallel combination of a resistor for the skin membrane resistance, R mem , and a so-called constant phase element, CPE, which here represents the capacitive properties of the skin membrane [20][21][22] . A more detailed description of Franz cell equipped with four electrodes for measurement of skin membrane resistance can be found elsewhere 20 .…”

Skin hydration dynamics investigated by electrical impedance techniques in vivo and in vitro

“…This caveat should be kept in mind for the 1 kHz data obtained with the NE. Still, it was decided to use this parameter due to the fact that it can be straightforwardly compared with the data obtained with the 4E methodology, where the 1 kHz data represent the skin membrane resistance in a consistent and well established manner 9,39,40 . Further, previous measurements performed with a noninvasive Nevisense probe showed that the NE impedance data can be expressed as the ratio of the impedance magnitudes at two particular frequencies of 20 and 500 kHz, which greatly reduces the complexity of the experimental data 38 .…”

Antioxidant and Anti-inflammatory Effect of Cannabidiol Contributes to the Decreased Lipid Peroxidation of Keratinocytes of Rat Skin Exposed to UV Radiation

“…One potential candidate is the pharmacologically active-but nonpsychoactive-antioxidant and anti-inflammatory phytocannabinoid-cannabidiol (CBD, Figure 1) found in the Cannabis sativa L. plant [8][9][10]. Assessment of the antioxidant activity of CBD has shown that it can regulate the redox state directly by influencing redox components and indirectly interacting with other molecular targets related to redox balance [11].…”