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Isabelle Ranchon-Cole, christine Cercy, Marjolaine Vareille, Michel Doly; Ceramide And Cytokine In Light-induced Retinal Degeneration. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5312.
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Recent studies have defined the sphingomyelin signal transduction pathway as an upstream mechanism for mediating apoptosis for several cell surface receptors and environmental stresses. In addition, ceramide accumulation mediates inflammation and cell death. In the present study, we have evaluated the level of ceramide and cytokines during light-induced retinal degeneration with a particular interest at 4 hours of light exposure which is the last time point before apoptotic nuclei can be detected in the retina.
Albinos Wistar rats were raised in dim cyclic light. At the age of 7-8 weeks they were dark-adapted overnight before being exposed to 3400 lux for up to 24 hours. Retinas were harvested before exposure to the damaging light, at 4 hours of light exposure, at the end of light exposure and 1 or 3 days after the end of light exposure. Neutral lipids molecular species and ceramide-sphingomyelin were analysed by gas-liquid chromatography. IL-6, IL-23 and TNF-α were quantified by ELISA Kit.
At 4 hours of light-exposure, there was a significant decrease of the total neutral lipids compared to unexposed retinas. The total monoglycerides, cholesterol, total diacylglycerol, sphingomyelin and ceramide were significantly decreased but there was no significant variation in the total esterified-cholesterol or total triglycerides. IL-6 could not be detected in the retina except at the end of the 24 hours of light-exposure with 3 ± 2 pg/mg proteins. TNF-α did not vary significantly at any experimental time point. In contrary, IL-23 was detected in the un-exposed retinas and significantly increased by 256% at the end of light-exposure (24h) and stay at a high level up to 7 days after light exposure.
Ceramide or cytokines do not seem to play a role in the initiation of apoptosis but IL-23 may be involved in the sustained of the process.
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