Scyllo-Inositol Attenuates Blue Light-Induced Oxidative Stress and Cellular Injury in Caenorhabditis elegans and HaCaT Cells

Background: Blue light can cause oxidative stress and cellular injury. We tested whether scyllo-inositol (SI) could reduce these changes in Caenorhabditis elegans and HaCaT cells. Methods: We measured worm survival, movement, body size, autofluorescence, and ROS-associated signals. In HaCaT cells, we measured proliferation, cell-cycle distribution, apoptosis, mitochondrial membrane potential, and γH2AX fluorescence. We also performed RNA sequencing and qRT-PCR. Supplementary experiments examined SI-only conditions, cell-free ABTS responses, irradiated medium, and the daf-16 mutant CF1038. Results: SI improved several outcomes in blue light-exposed worms. The 25 mmol·L−1 concentration showed the largest response among the tested doses. In HaCaT cells, 100 μmol·L−1 SI given after irradiation improved viability and DNA synthesis and reduced apoptosis and stress-associated signals. Transcriptomic results identified stress-response and FOXO-related pathways. SI produced only limited improvement in the daf-16 mutant CF1038. The ABTS samples were below the calibrated Trolox range. Conclusions: SI treatment was associated with reduced injury under the tested blue light conditions. The findings support further study of stress-response mechanisms. They do not establish direct radical scavenging, a specific intracellular target, or clinical protection from everyday light exposure.