Low-Intensity Blue Light Exposure Reduces Melanopsin Expression in Intrinsically Photosensitive Retinal Ganglion Cells and Damages Mitochondria in Retinal Ganglion Cells in Wistar Rats

Abstract

This study investigated the effect of low-intensity blue light on the albino Wistar rat retina, including intrinsically photosensitive retinal ganglion cells (ipRGCs). Three groups of nine albino Wistar rats were used. One group was continuously exposed to blue light (150 lx) for 2 d (STE); one was exposed to 12 h of blue light and 12 h of darkness for 10 d (LTE); one was maintained in 12 h of white light (150 lx) and 12 h of darkness for 10 d (control). Melanopsin (Opn4) was immunolabelled on retinal whole-mounts. To count and measure Opn4-positive ipRGC somas and dendrites (including Sholl profiles), Neuron J was used. Retinal cryosections were immunolabeled for glial fibrillary acid protein (GFAP) and with terminal deoxynucleotidyl transferase dUTP nick-end labelling for apoptosis detection. LTE reduced the length of Opn4-positive ipRGC dendrites (p = 0.03) and decreased Opn4-immunoreactivity in ipRGC outer stratifying dendrites. LTE and STE decreased the complexity of dendritic arborization (Sholl profile; p < 0.001, p = 0.03, respectively), increased retinal GFAP immunoreactivity (p < 0.001, p = 0.002, respectively), and caused outer segment vesiculation and outer nuclear layer apoptosis. Ultrastructural analysis showed that LTE damaged mitochondria in retinal ganglion cells and in the inner plexiform layer. Thus, LTE to low-intensity blue light harms the retinas of albino Wistar rats.

Light Pollution and Oxidative Stress: Effects on Retina and Human Health

“…Exposure to blue light-emitting LEDs has been shown to decrease melanopsin expression and damage ipRGCs [ 126 ]. LED exposure in animal models has led to mitochondrial damage, reduced dendritic arborization of ipRGCs, increased retinal GFAP immunoreactivity, and apoptosis in the outer nuclear retinal layer [ 127 ].…”

“…In addition to the previously discussed effects of light, sunlight is well-recognized as a human carcinogen. Both natural and artificial light directly affect the skin, with blue light, in particular, having the capacity to penetrate more deeply (0.07 to 1 mm) than ultraviolet rays (UV) [ 126 , 127 , 133 , 134 ]. Notably, the epidermis expresses melanopsins OPN2, OPN3, and OPN4, which are activated by blue light.…”

“…Moreover, apart from UV-induced damage, blue light is associated with accelerated skin aging, increased hyperpigmentation of skin melanocytes, and the development of dark spots [ 126 , 127 , 128 , 129 , 133 , 134 , 135 , 136 , 137 ].…”