Blue light exposure in vitro causes toxicity to trigeminal neurons and glia through increased superoxide and hydrogen peroxide generation

Abstract

Today the noxiousness of blue light from natural and particularly artificial (fluorescent tubes, LED panels, visual displays) sources is actively discussed in the context of various ocular diseases. Many of them have an important neurologic component and are associated with ocular pain. This neuropathic signal is provided by nociceptive neurons from trigeminal ganglia. However, the phototoxicity of blue light on trigeminal neurons has not been explored so far. The aim of the present in vitro study was to investigate the cytotoxic impact of various wavebands of visible light (410-630 nm) on primary cell culture of mouse trigeminal neural and glial cells. Three-hour exposure to narrow wavebands of blue light centered at 410, 440 and 480 nm of average 1.1 mW/ cm 2 irradiance provoked cell death, altered cell morphology and induced oxidative stress and inflammation. These effects were not observed for other tested visible wavebands. We observed that neurons and glial cells processed the light signal in different manner, in terms of resulting superoxide and hydrogen peroxide generation, inflammatory biomarkers expression and phototoxic mitochondrial damage. We analyzed the pathways of photic signal reception, and we proposed that, in trigeminal cells, in addition to widely known mitochondriamediated light absorption, light could be received by means of non-visual opsins, melanopsin (opn4) and neuropsin (opn5). We also investigated the mechanisms underlying the observed phototoxicity, further suggesting an important role of the endoplasmic reticulum in neuronal transmission of blue-light-toxic message. Taken together, our results give some insight into circuit of tangled pain and photosensitivity frequently observed in patients consulting for these ocular symptoms.

Blue light-induced gene expression alterations in cultured neurons are the result of phototoxic interactions with neuronal culture media

“…Previous reports have found that culture media and its supplements can react with light to generate ROS, and recent efforts to overcome this have resulted in the generation of photostable culture media which prevents a decay in cell health during sustained light exposure 12,14,15,18 . Importantly, we report that blue light-induced alterations in IEGs such as Fos are prevented when neuronal culture media is transitioned to photostable solution supplemented with antioxidants before light exposure.…”

“…While the phototoxic effects of both ambient and targeted light on cell viability in vitro has been noted for decades [12][13][14] , recent reports documenting blue light-induced gene expression alterations both in vitro and in vivo have emphasized deleterious effects of blue light on cellular function 15,16 . Multiple reports have documented robust effects of blue light exposure in vitro, including upregulation of genes such as Fos (aka cFos) that are often used as markers of neuronal activity but which can also be induced in response to cellular stress [15][16][17] . Others have noted that cellular phototoxicity is often the result of reactive oxygen species (ROS) generated in culture media during photostimulation, which can be prevented by utilizing a non-light-reactive media instead of the typical media utilized in neuronal cultures 18 .…”

“…In the present work, we characterized the effects of blue light on gene expression and cell viability in vitro using a rat primary neuronal culture model. As recent reports indicate that ROS are generated when culture media is exposed to blue waveform light 14,15 , we hypothesized that light-induced alterations in gene expression would be dependent on the neuronal cell culture media utilized in these experiments. We replicated and extended previous literature by demonstrating that blue light exposure induces multiple IEGs in neuronal cultures, and characterized the duration, frequency, and temporal properties of this effect.…”

Blue Light-Induced Gene Expression Alterations in Cultured Neurons Are the Result of Phototoxic Interactions with Neuronal Culture Media

“…While the phototoxic effects of both ambient and targeted light on cell viability in vitro has been noted for decades (Wang, 1976;Dixit and Cyr, 2003;Carlton et al, 2010), recent reports documenting blue light-induced gene expression alterations both in vitro and in vivo have emphasized deleterious effects of blue light on cellular function (Marek et al, 2019;Tyssowski and Gray, 2019). Multiple reports have documented robust effects of blue light exposure in vitro, including upregulation of genes such as Fos (also known as cFos) that are often used as markers of neuronal activity but which can also be induced in response to cellular stress (Bahrami and Drabløs, 2016;Marek et al, 2019;Tyssowski and Gray, 2019). Others have noted that cellular phototoxicity is often the result of reactive oxygen species (ROS) generated in culture media during photostimulation, which can be prevented by using a non-light-reactive media instead of the typical media used in neuronal cultures (Stockley et al, 2017).…”

“…In the present work, we characterized the effects of blue light on gene expression and cell viability in vitro using a rat primary neuronal culture model. As recent reports indicate that ROS are generated when culture media is exposed to blue wavelength light (Dixit and Cyr, 2003;Marek et al, 2019), we hypothesized that lightinduced alterations in gene expression would be dependent on the neuronal cell culture media used in these experiments. We replicated and extended previous literature by demonstrating that blue light exposure induces multiple immediate early genes (IEGs) in neuronal cultures, and characterized the duration, frequency, and temporal properties of this effect.…”