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S. Agarwal, N. Agarwal, B.J. Tripathi, R.C. Tripathi, K.V. Chalam; Influence of Ciliary Neurotrophic Factor (CNTF) on Apoptotic Retinal Ganglion Cell Death Induced By Glutamate Excitoxicity . Invest. Ophthalmol. Vis. Sci. 2006;47(13):892.
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Neuronal damage and degeneration following acute ischemic injury and chronic oxidative stress are believed to be mediated by excitoxicity of over–stimulated neurotransmitters. Glutamate, a major excitatory amino acid neurotransmitter of the central nervous system (CNS), has been implicated in many of these neurological disorders. In this study, we investigated the neuroprotective effects of ciliary neurotrophic factor (CNTF) in over–stimulated concentrations of L–Glutamic acid (glutamate) on transfected rat–retinal ganglion cells (RGC–5). Cellular toxicity and death was accessed by neutral red dye assay and western blot for proapoptotic gene bax.
Transformed rat RGC (RGC–5 cells) were used. RGC–5 cells were pre–incubated with either Delbecco's minimum essential medium (10% fetal calf serum, 1% penicillin/streptomycin) or DMEM with CNTF (100 ng/ml) for 24 hours, and exposed to 2.5, 3.5, and 5.5 (mM) L–glutamic acid. Cells without glutamate administration served as control. Cell viability was determined with the neutral red dye uptake assay. Levels of bax were monitored by western blot analysis.
Glutamate treatment resulted in RGC–5 cell death, and CNTF aided in cell survival from glutamate cytotoxicity. Excitotoxic death was averted (27 ± 0.89 for 2.5 mM; 33 ± 0.23 for 3.5 mM; 38 ± 0.18 for 5.5 mM) in cells pretreated with ciliary neurotrophic factor. Cells deficient of CNTF showed a time and concentration dependent correlation for toxic damage. Levels of bax showed change in response to glutamate exposure, with and without pretreatment of CNTF.
Ciliary neurotrophic factor aided in the survival of RGC–5 against glutamate cytotoxicity. The neuroprotective effects of CNTF likely arise from the activation of signaling pathways coupled to trkB receptors present on neurons. These results suggest that CNTF may provide a valuable benefit that could prove valuable in the cellular survivability and possible regeneration after excitoxicity.
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