Decreased glutathione transferase levels in rd1/rd1 mouse retina: Replenishment protects photoreceptors in retinal explants

Abstract

Currently much attention is focused on glutathione S transferase (GST)-induced suppression of apoptosis. The objective of our studies was therefore to see if GST isoenzymes rescue photoreceptors in retinal explants from rd1/rd1 mice, in which photoreceptors degenerate rapidly. Eyes from C3H rd1/rd1 and +/+ mice were collected at various time points between postnatal day (PN) 2 and PN28. Localization and content of α-GST and μ-GST was investigated by immunofluorescence and semi-quantitative Western blot analysis, respectively. In addition, PN2 and PN7 retinal explants were cultured till PN28, during which they were treated with 10 ng/ml α-GST or μ-GST. The spatiotemporal expression of both GST isoforms was closely similar: early presence in ganglion cell layer after which staining became restricted to Müller cells (particularly in the endfeet) and horizontal cell fibers in both rd1/rd1 and +/+. Doublets of α-GST and μ-GST were detected by Western blot analysis. Densitometry of these bands indicated steady reduction of α-GST content in rd1/rd1 retina starting from the second postnatal week. When α-GST and μ-GST were added exogenously to rd1/rd1 explants, photoreceptor rescue was produced that was more prominent in PN2 than in PN7 explants and more effective by α-GST than μ-GST. We propose that α-GST neuroprotection is mediated by reduction of tissue oxidative stress.