The possible protective effect of curcumin on monosodium glutamate-induced retinal changes in adult male albino rats

Abstract

Introduction Monosodium glutamate (MSG) is widely used as a flavor-enhancing food additive for its unique taste. It is added to fast foods, children’s foods, snacks, soups, and many other canned foods all over the world. Recently, it has been proved that MSG has neurotoxic effects, including retinal degeneration. Curcumin is a naturally occurring compound with known antioxidative activity. Experimentally, it has been observed that curcumin has a significant retinal neuroprotective effect. Aim The present study was carried out to investigate the possible protective effect of curcumin against the retinal toxicity of MSG. Materials and methods Thirty adult male albino rats were used. The animals were divided as follows: group I was the control group; group II received curcumin at a dose of 150 mg/kg body weight; group III received MSG at a dose of 1 g/kg body weight; and group IV received MSG concomitantly with curcumin at the same previous doses. Both curcumin and MSG were given orally once daily for 4 weeks. Retinal sections were stained with H&E and immunohistochemically stained to detect glial fibrillary acidic protein (GFAP) and caspase-3 antibodies. Retinal thickness and area% of GFAP staining were measured. Results MSG caused several histological retinal changes, including separation of pigment epithelium, distortion and disorganization of photoreceptors, pyknosis in many nuclei of the outer nuclear layer, degeneration in the cells of the inner nuclear layer and the ganglion cell layer, dilatation and congestion of some blood vessels, and interruption of the internal limiting membrane. A statistically significant decrease in the retinal thickness and increase in area% reaction with GFAP antibodies were also detected. Such abnormalities were, to a large extent, prevented with the use of curcumin. Conclusion Several histological alterations were observed in the retinas of rats treated with MSG, and coadministration of curcumin with MSG improved these alterations to a large extent.