Abstract
Purpose::
We have previously demonstrated that the expression of heat shock protein 72 (Hsp72) is up-regulated in retinal ganglion cells in response to intravitreal injection of N-methyl-D-aspartate (NMDA). In this study we investigate the expression of heat shock factors 1 (HSF1) and 2 (HSF2) in retina and their relationship with Hsp72 and Hsc70.
Methods::
Adult male Wistar rats weighing 300-350g were used to examine the expression of retinal HSF1 and HSF2 with Western blotting (n=36; 4 per time point) and the expression of Hsp72 and Hsc70 in the retinal ganglion cell layer with immunohistochemistry (n=36; 4 per time point) at 0, 1, 3, 6, 9, 12, 18, 24 and 48 hours after intravitreal injection of 8 nmoles of NMDA. To confirm specificity to retinal ganglion cells, retrograde labeling of Fluoro-gold injected in the superior colliculi was performed and the expression of HSFs were examined by immunohistochemistry.
Results::
Counting of immuno-positive cells and quantification of immuno-reactivity in the retinal ganglion cell layer showed an up-regulation of Hsp72 at 12, 18 and 24 hours post-injection but no difference in the expression of Hsc70 at all time points. Western blotting demonstrated up-regulation of HSF1 and HSF2 as early as 3 hours. The up-regulation of HSF1 and HSF2 was sustained up to 24 hours post-injection and decreased at 48 hours post-injection. Positive immuno-reactivity corresponding to HSF1 and HSF2 was localized predominantly in the inner retina and most of Fluoro-gold labeled cells were HSF1 and HSF2 immuno-positive.
Conclusions::
The up-regulation of both HSF1 and HSF2 is linked to the induction of Hsp72 in retinal ganglion cells after exposure to excitotoxic stress.
Keywords: ganglion cells • stress response • excitatory neurotransmitters