Abstract
Purpose: :
Retinal degeneration in glaucoma has been suggested to be due to several factors including high ocular pressure, oxidative stress, hypoxia and growth factor deprivation. Wnt signaling is an essential pathway that is involved in the regulation of cell proliferation and differentiation in the retina. Our previous work showed that the Wnt pathway is involved in retinal degeneration and that its activation confers protection to photoreceptors challenged with oxidative stress. In this study we investigate the effect of activation of the Wnt signaling pathway on retinal ganglion cells (RGCs) challenged with elevated pressure, oxidative stress and hypoxia.
Methods: :
Cultures of a rat ganglion cell line (RGC-5) were plated at cell densities which preliminary experiments concluded were optimal for induction of apoptosis following treatment. Cultures were incubated in growth medium only, growth medium plus Wnt3a conditioned media or growth medium plus control conditioned media. Cultures were subjected to elevated pressure, hypoxia and oxidative stress. Cells were then harvested and RNA and protein analysis followed. Caspase activity assays and quantitative PCR analysis were performed to detect apoptosis.
Results: :
Caspase activity was detected in all cultures exposed to elevated pressure but when Wnt3a was present the caspase activity observed in cell lysates was lower than in cell lysates from cultures incubated in control media. Quantitative PCR analysis on cells exposed to elevated pressure showed that the expression of the pro-apoptotic protein Bax was lower when cells were treated with Wnt3a relative to cultures incubated in control media. Similar results were observed in cultures exposed to oxidative stress in which cells treated with Wnt3a had lower caspase activity and lower expression of Bax compared to cells incubated in control media.
Conclusions: :
Our data suggests Wnt3a conditioned media conferred protection from apoptosis as shown by the decrease in caspase activity levels and reduction in Bax expression compared to values obtained from cells incubated in control media. These results suggest that activation of the Wnt signaling pathway by Wnt3a could be a tool to develop therapeutic strategies for the prevention of RGC death.
Keywords: neuroprotection • ganglion cells • cell survival