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Takahiro Kurose, Tsubasa Takezawa, Shuu Shiratori, Mariyo Kato, Yoko Mitsuguchi, Yoshihiro Takai, Yoichi Honma, Eriko Sugano, Hiroshi Tomita; Neuroprotective effect of a dietary supplement against glutamate-induced cytotoxicity in experimental glaucoma models. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2567.
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© ARVO (1962-2015); The Authors (2016-present)
Glaucoma is characterized by retinal ganglion cell (RGC) death and a progressive loss of vision. Glutamate toxicity has been proposed as a mechanism of RGC death in recent studies. In this study, we evaluated the neuroprotective effect of ClearVision EX® (CV, Rohto Pharmaceutical), which is a dietary supplement containing lutein, anti-oxidants, vitamins, and minerals, on glutamate toxicity.
RGC damage in 8-week-old male Sprague—Dawley rats (N=6) was induced by intravitreal injection of N-Methyl-D-aspartate (NMDA) (5 nmol/eye). CV (30, 100, or 300 mg/kg) or vehicle was orally administered once daily. RGC function was evaluated by determining the amplitude of the scotopic threshold response (STR) of ERG at 2 days after NMDA injection. To assess retinal structure, the ratio of the thickness of the whole retinal layer (WR) and the inner plexiform layer (IPL) in histological sections was calculated (IPL/WR). To elucidate the mechanism underlying these effects, HT22 cell line was used to evaluate the neuroprotective effect against non-receptor-mediated oxidative glutamate toxicity. HT22 cells were plated at a density of 1.0 × 104 cells/well in a 96–well plate, and incubated with glutamic acid (2.5 mM) and CV (0.6–60 µg/mL). Cell viability was evaluated by the MTS assay 24 h later (N=5).
Intravitreal injection of NMDA decreased the STR amplitude, while the 300 mg/kg CV group retained a significantly higher amplitude compared to the vehicle group (48.4±8.8 µV vs. 33.8±16.7 µV, p<0.05). For structure analysis, IPL/WR was significantly higher in the 300 mg/kg CV group than in the vehicle group (15.7±2.9% vs. 12.0±0.9%, p<0.05). Glutamate treatment significantly decreased the viability of HT22 cells to 50.7±3.0%, and CV showed a concentration-dependent cytoprotective effect. At the highest concentration, the viability of HT22 cells was 98.9±3.2% (p<0.001).
CV showed a neuroprotective effect in the NMDA-induced glaucoma model by suppressing excitotoxicity and/or oxidative stress. Since CV suppressed glutamate toxicity in HT22 cells, these findings suggest that CV shows a neuroprotective effect against glutamate-induced cytotoxicity by inhibiting oxidative stress.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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