Imaging of metabolic activity adaptations to UV stress, drugs and differentiation at cellular resolution in skin and skin equivalents – Implications for oxidative UV damage

• Published in: Redox biology 2020-10, Vol.37, p.101583-101583, Article 101583
• Main Authors: Kremslehner, Christopher, Miller, Anne, Nica, Robert, Nagelreiter, Ionela-Mariana, Narzt, Marie-Sophie, Golabi, Bahar, Vorstandlechner, Vera, Mildner, Michael, Lachner, Julia, Tschachler, Erwin, Ferrara, Francesca, Klavins, Kristaps, Schosserer, Markus, Grillari, Johannes, Haschemi, Arvand, Gruber, Florian
• Format: Article
• Language: English
• Subjects: from the Special Issue on Impact of environmental pollution and stress on redox signaling and oxidative stress pathways; Edited by Thomas Münzel and Andreas Daiber
• ISSN: 2213-2317; 2213-2317
• DOI: 10.1016/j.redox.2020.101583

The epidermis is a multi-layered epithelium that consists mainly of keratinocytes which proliferate in its basal layer and then differentiate to form the stratum corneum, the skin's ultimate barrier to the environment. During differentiation keratinocyte function, chemical composition, physical properties, metabolism and secretion are profoundly changed. Extrinsic or intrinsic stressors, like ultraviolet (UV) radiation thus may differently affect the epidermal keratinocytes, depending on differentiation stage. Exposure to UV elicits the DNA damage responses, activation of pathways which detoxify or repair damage or induction of programmed cell death when the damage was irreparable. Recently, rapid diversion of glucose flux into the pentose phosphate pathway (PPP) was discovered as additional mechanism by which cells rapidly generate reduction equivalents and precursors for nucleotides – both being in demand after UV damage. There is however little known about the correlation of such metabolic activity with differentiation state, cell damage and tissue localization of epidermal cells. We developed a method to correlate the activity of G6PD, the first and rate-limiting enzyme of this metabolic UV response, at cellular resolution to cell type, differentiation state, and cell damage in human skin and in organotypic reconstructed epidermis. We thereby could verify rapid activation of G6PD as an immediate UVB response not only in basal but also in differentiating epidermal keratinocytes and found increased activity in cells which initiated DNA damage responses. When keratinocytes had been UVB irradiated before organotypic culture, their distribution within the skin equivalent was abnormal and the G6PD activity was reduced compared to neighboring cells. Finally, we found that the anti-diabetic and potential anti-aging drug metformin strongly induced G6PD activity throughout reconstructed epidermis. Activation of the protective pentose phosphate pathway may be useful to enhance the skin's antioxidant defense systems and DNA damage repair capacity on demand. [Display omitted] •Automated whole tissue histocytometry localizes enzymatic activity of G6PD within the epidermis at cell resolution.•Keratinocytes in the tissue context react to UVB radiation with immediate activation of G6PD.•Highest induction of G6PD was observed in cells undergoing DNA damage repair.•The drug Metformin strongly induces epidermal G6PD activity.