Exploring the biometric and retinal proteomic changes in normal growing chicks after repeated low-level red-light treatment-a pilot study

Purpose : Although recent clinical evidence suggests that repeated low-level red-light (RLRL) therapy might effectively control eyeball elongation, the underlying mechanisms remain elusive. This study aims to explore the effect and mechanism of RLRL retinal protein alterations in normal chicks.

Methods : At postnatal day 5, six chicks received RLRL treatment of LED source (650 nm, 30 minutes, twice daily, 600 lux) as treated, while five chicks received normal white light with the same lumination served as controls(12/12h). Refractive error (Rx), choroidal thickness (CT), vitreous chamber depth (VCD), and axial length (AXL) were measured before and after treatment for 3, 8, and 10 days. Retinal tissues after 10 days of treatment were digested with EasyPep MS sample prep kit. One microgram of peptide was analyzed using a novel ZenoTOF™ 7600 mass spectrometry (MS) system (SCIEX, US) and quantified by Spectronaut™. Protein interactions and pathway analysis were investigated using the Metascape and Ingenuity Pathway Analysis (IPA).

Results : RLRL treatment resulted in significant decreases in VCD, with reductions of 100±70 µm (8 days) and 80±26 µm (10 days) respectively. Significant reduction in AXL (80±58 µm) was only detected after 10 days treatment (p < 0.05, unpaired t-test). Differences in Rx and CT were not significant at all time points. A total of 10 up-regulated and 239 down-regulated proteins were identified when compared to the control group (Fold change cutoff 1.20 and p < 0.05; FDR 1%). Protein-protein interaction enrichment analysis with Metascape found the regulated proteins were significantly enriched in mitochondrial translation initiation, mitochondrial translation elongation and mitochondrial translation termination. Furthermore, IPA analysis indicated the two most enriched pathways were mitochondrial translation and protein kinase A (PKA) signaling.

Conclusions : Our preliminary data, obtained by a novel label-free MS approach utilizing data-independent acquisition, indicate that RLRL treatment may modulate ocular elongation during the process of emmetropization in normal chicks, accompanied by significant regulation of retinal proteins. Bioinformatics analysis suggests that mitochondrial functions are crucially involved in the response to RLRL treatment. However, further investigation is required to confirm the effects of RLRL in the myopia model.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.