Photoprotective Effect of Hydroxychloroquine on Human Keratinocytes

Hydroxychloroquine (HCQ), an antimalarial commonly used in autoimmune and dermatological conditions, may exert photoprotective effects, though its role against high-energy visible light (HEVL) remains underexplored. This study evaluated HCQ’s impact on cell viability and oxidative stress in human keratinocytes (HaCat cells) exposed to HEVL blue light. Cells were treated with HCQ (1, 2.5, or 5 µM) and irradiated with blue light doses (4.5–72 J/cm2). Assays assessed cell viability (XTT), reactive oxygen species (ROS) production, and the expression of oxidative stress-related enzymes: superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT). Results showed that low blue light doses triggered endogenous protective responses, which HCQ enhanced, potentially via SOD activation. However, higher irradiation levels caused extensive cellular damage that overwhelmed HCQ’s protective capacity. These findings suggest HCQ may confer in vitro photoprotection against sublethal HEVL exposure by modulating oxidative stress responses, although this effect diminishes beyond a certain damage threshold.