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Neurobiology of Aging 52 (2017) 66e70 Contents lists available at ScienceDirect Neurobiology of Aging journal homepage: www.elsevier.com/locate/neuaging Aging retinal function is improved by near infrared light (670 nm) that is associated with corrected mitochondrial decline Chrishne Sivapathasuntharam a, Sobha Sivaprasad b, Christopher Hogg b, Glen Jeffery a, * a University College London Institute of Ophthalmology, London, UK b Moorfields Eye Hospital, London, UK articleinfo Article history: Received 20 September 2016 Received in revised form 1 January 2017 Accepted 2 January 2017 Available online 10 January 2017 Keywords: Retina Aging Mitochondria 1. Introduction Aging is associated with declining mitochondrial function, with reductions in mitochondrial membrane potentials and adenosine triphosphate production (ATP) (Gkotsi et al., 2014; Harman, 1972; Kokkinopoulos et al., 2013; Kujoth et al., 2005; Lane, 2005). The pace of aging is linked to metabolic rate, with high rates associated with faster aging (Speakman, 2005; Wang et al., 2010). The retina is a key example of this as photoreceptors have the greatest energy demand in the body (Linsenmeier and Padnick-Silver, 2000). Here, ATP declines significantly by 3e4 months in mice. At the same time, mitochondrial membrane potentials decline (Kokkinopoulos et al., 2013), chronic inflammation becomes established (Catchpole et al., 2013; Hoh Kam et al., 2013; Xu et al., 2009), and retinal function declines (Kolesnikov et al., 2010; Li et al., 2001). These events herald a 30% photoreceptor loss in both mouse and man (Cunea and Jeffery, 2007; Cunea et al., 2014; Curcio, 2001). Some of these features can be corrected. Specific long wave- lengths of light are absorbed by cytochrome c oxidase in mito- chondria (Fitzgerald et al., 2013), and this is associated with * Corresponding author at: University College London, Institute of Ophthal- mology, 11-43 Bath St., London EC1V9EL, UK. Tel.: þ442076086837; fax: þ442076086909. E-mail address: g.jeffery@ucl.ac.uk (G. Jeffery). 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. Electro- retinograms 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 signif- icant 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. ! 2017 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). improved respiration, increased membrane potentials and improved ATP production (Gkotsi et al., 2014; Kokkinopoulos et al., 2013), and reductions in key markers of age-related retinal inflammation (Begum et al., 2013). In Drosophila, long wavelength light also increases mean lifespan and mobility (Begum et al., 2015), and in bumble bees, it has similar impact but also improves the electroretinogram in normal animals and those in which mito- chondrial function has been undermined by insectiside exposure (Powner et al., 2016). Here, we ask if 670 nm light exposure that is associated with corrected mitochondrial function and reduced inflammation translates to improved retinal function in aged mice. 2. Materials and methods 2.1. Mice Thirty-five female C57BL/6 mice were used at 3 different ages (n 1⁄4 4 at 2 months, n 1⁄4 18 at 7 months, and n 1⁄4 13 at 12 months). Mice at 7 and 12 months were divided into treated (7 months n 1⁄4 8, 12 months n 1⁄4 7) and untreated (7 months n 1⁄4 10, 12 months n 1⁄4 6). All animals were maintained under identical standard laboratory conditions. Experimental mice were exposed for 15 min/d to 670 nm light (40 mW/cm2, 36 J in total) via LEDs (CH Electronics, UK) at approximately 10 AM. Light exposures and light environment 0197-4580/! 2017 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). http://dx.doi.org/10.1016/j.neurobiolaging.2017.01.001PDF Image | Aging retinal function is improved by near infrared (670 nm
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