Aging retinal function is improved by near infrared light (670 nm) that is associated with corrected mitochondrial decline

Abstract

Aging is associated with cellular decline and reduced function, partly mediated by mitochondrial compromise. However, aged mitochondrial function is corrected with near infrared light (670 nm) that improves their membrane potentials and adenosine triphosphate production and also reduces age-related inflammation. We ask if 670 nm light can also improve declining retinal function. Electroretinograms were measured in 2-, 7-, and 12-month old C57BL/6 mice. Significant age-related declines were measured in the photoreceptor generated a-wave and the postreceptoral b-wave. Seven- and 12-month-old mice were exposed to 670 nm for 15 minutes daily over 1 month. These showed significant improved retinal function in both waves of approximately 25% but did not reach levels found in 2-month-old animals. Our data suggest, 670 nm light can significantly improve aged retinal function, perhaps by providing additional adenosine triphosphate production for photoreceptor ion pumps or reduced aged inflammation. This may have implications for the treatment of retinal aging and age-related retinal disease, such as macular degeneration.

Keywords: Aging; Mitochondria; Retina.

Fig. 1

Examples of ERG recordings from 2-, 7-, and 12-month-old mice and the impact of treatment with 670 nm light. (A) Panel shows the waveforms of the ERGs. The waves from 2-month-old mice are shown twice, once in the first row with 7-month animals and again in the second row with 12-month animals for direct comparison. Reductions with age are apparent in untreated aged mice. Improvements on this are apparent in both treated groups in the right hand column. (B) Panel shows the analysis of waveforms with statistical comparisons of aged decline and improvements following 670 nm light treatment. Significant improvements in signal amplitude were found following treatment in all groups except for the photopic response at 7 months. Abbreviations and symbols: M, month. ^∗p < 0.05, ^∗∗p < 0.01, and ^∗∗∗p < 0.001. Error bars are standard error of the mean. Analysis at progressive light intensities between the 3 groups (1 way ANOVA) revealed for scotopic a-wave at 2 m versus 7 m, NS for the first 2 intensities and p < 0.05 for the final. Scotopic b-wave 2 m versus 7 m NS for the first 3 intensities and p < 0.05 for the subsequent 4. Photopic b-wave 2 m versus 7 m each NS. Scotopic a-wave 2 m versus 12 m, first 2 intensities NS, final intensity p < 0.05. Scotopic b-wave 2 m versus 12 m, first 3 intensities NS, subsequent intensities all p < 0.05. Photopic b-wave 2 m versus 12 m, first 2 intensities p < 0.05, final intensity NS.

Fig. 2

COX immunohistochemistry in experimental and untreated mice at 7 m (A and B). Higher levels were found in experimental animals compared to controls (C). Similar data at 12 m (D and E), which were again significantly different with greater levels in 670 nm exposed mice (F). ^∗p < 0.05 and ^∗∗p < 0.01. Abbreviations: IHC-Fr, immunohistochemistry frozen section; ONL, outer nuclear layer; OPL, outer plexiform layer; PR, photoreceptor inner segments.