Cellular senescence is an irreversible growth arrest caused by oxidative stress and DNA damage and ultraviolet (UV) radiation mediated cellular damage is responsible for skin photoaging. Type 17 collagen (COL17) is crucial for preventing skin aging. Apocynin, a NADPH oxidase inhibitor can chemically induce COL17 protein synthesis and promote stem cell survival. Our unpublished data showed that klotho mutant (kl/kl) mice, which is a premature aging model, displayed increased senescence-associated-β-galactosidase (Sa-β-Gal) activity, increased production of p16, phosphorylated histone H2AX (γH2AX), matrix metallopeptidase 9 and 1 (MMP-9, MMP-1), increased activation of mitogen-activated kinase (MAPK) along with deceased COL17 production in the skin. Our study aimed to investigate whether induction of COL17 by apocynin can decrease UVB-induced cell senescence or not. In our experimental model hTert/KER-CT keratinocytes were pretreated with apocynin (10 µM, 20 µM, 40 µM) for 24 hours and exposed to UVB (100 J/m2). Immunohistochemistry, immunofluorescence, qRT-PCR, and western blot were used to measure the expression of COL17, MAPK, MMP-9, MMP-1, p16, and γH2AX, cellular senescence was measured by SA-β-gal staining, and propidium iodide ((PI)/RNase solution was used to measure cell cycle. In our study, UVB exposure decreased COL17 (P<0.05), increased activation of MAPK, and Sa-β-Gal activity (P<0.001), increased G1 arrest (P<0.001), increased production of MMP-9, p16 (P<0.001), and γH2AX (P<0.001). Apocynin restored the COL17 production (P<0.01) and reduced senescence (P<0.001), cell cycle arrest (P<0.01), and suppressed increased production of MMP-9, γH2AX, and p16 in human keratinocytes (P<0.001). The change at the protein level was in parallel to mRNA expression. Taken together, our results suggest that apocynin reduced DNA damage, senescence, and cell cycle arrest and it also restored the COL17 production and thereby protected skin stem cells from aging.

ESDR520 - The protective effects of Apocynin against ultraviolet B-induced cellular senescence in human keratinocytes

The scientific meeting of the European Society for Dermatological Research (ESDR) is held yearly, usually in September. With an international attendance of more than 1000 skin scientists from around the globe, the four-day event includes short oral presentations from peer-reviewed abstracts, keynote lectures from international experts, sponsored symposia, satellite programs, educational events as well as an important focus on posters, networking and building collaborations amongst scientists. For more information about this year’s meeting visit our website.