Melanocytes differential reactivity to prolonged oxidative stress in relation to pigmentation levels: A senescence model

Summary: Abstract Body: Understanding how oxidative stress drives melanocyte aging is essential for advancing research on skin aging and its associated disorders. These pigment-producing cells are particularly prone to oxidative damage due to their high metabolic activity and melanin production, which can increase reactive oxygen species (ROS). However, there is limited research on how prolonged oxidative stress affects melanocyte function and senescence, especially regarding the role pigmentation levels might play in their response. This study aimed to develop the SenMel model that induces senescence of human epidermal melanocytes by chronic hydrogen peroxide (H2O2) exposure. Melanocytes from three donors with different pigmentation levels underwent six H2O2 treatments over two weeks (week 1: 100 µM; week 2: 500 µM). Several parameters were assessed, including cell proliferation (BrdU assay), β-galactosidase (β-gal) activity, melanin content, and the expression of key melanocyte markers at both the gene and protein levels (e.g., MITF, tyrosinase, p16, TRP1, TRP2). Results revealed that chronic exposure to H2O2 significantly elevated β-gal activity (up to +95%, depending on the donor) while reducing cell proliferation (up to -75%, depending on the donor) within the SenMel model. Highly pigmented cells showed greater melanin production (+55%), while in medium-pigmented cells trends for inhibition were observed. Interestingly, lightly pigmented SenMel exhibited negligible changes in melanin synthesis. Molecular analysis indicated elevated p16 (up to +50%, depending on the donor) and higher tyrosinase/TRP2 levels in highly pigmented SenMel, though MITF and TRP1 expression remained unchanged across pigmentation groups. These findings emphasize that baseline pigmentation affects melanocyte responses to oxidative stress, positioning this model as a valuable tool for studying senescence mechanisms in melanocytes. Samuel Guenin¹, Julie Gerbaud¹, Fabienne Guyard¹, Aline Larrignon¹, Eglantine Siret¹, Fabien Ah-Thione¹, Laure Pasquer¹, Julien Oré¹, Nathalie Pedretti¹, Nicolas Amalric¹, Valérie Hamon de Almeida¹ 1. QIMA Bioalternatives, QIMA Life Sciences, Gençay, France. Pigmentation, Melanoma, and Melanoma Immune Surveillance