High-Color-Temperature Lighting Is Associated With Activation of MAPK/ERK–nNOS Signaling and MMP-2–Related Pathways in Ocular Tissues

Purpose: To investigate whether exposure to artificial lighting with different correlated color temperatures (CCTs) affects ocular structure and myopia-related molecular signaling pathways before axial elongation in a murine model. Methods: C57BL/6 mice were exposed to standard lighting (control) or artificial lighting at 3000, 4000, or 6000 K under a 12-hour light/12-hour dark cycle for 21 days. Spectral power distribution and illuminance were recorded. Histological analyses were performed to assess corneal epithelial thickness, retinal outer and inner nuclear layers (ONL and INL), and sclera thickness. Western blotting was used to evaluate phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2), neuronal nitric oxide synthase (nNOS), matrix metalloproteinase-2 (MMP-2), TNF-α, and IL-6. Immunohistochemistry was performed to assess ionized calcium-binding adapter molecule 1 (Iba-1) immunoreactivity in retinal tissues. Results: Exposure to different CCTs did not affect systemic growth, axial length, or ocular structural integrity. Axial length was comparable across groups (P = 0.431), and no significant differences were observed in sclera thickness, ONL, INL, or corneal epithelial thickness. In contrast, molecular analyses revealed CCT-dependent alterations. Exposure to 6000 K lighting increased p-ERK1/2, nNOS, MMP-2, TNF-α, and IL-6 expression and elevated Iba-1 immunoreactivity in retinal tissues. Conclusions: High-CCT lighting is associated with alterations in myopia-related molecular signaling in the absence of detectable structural or axial changes. These findings highlight early, pre-structural molecular responses to spectral light environments and suggest that CCT influences myopia-relevant pathways before overt ocular remodeling occurs.