Induction of heat shock proteins 27 and 72 in  retinal ganglion cells after acute pressure-induced  ischaemia.
BACKGROUND
We wanted to investigate whether heat shock protein (HSP) 27 and HSP 72 are induced in retinal ganglion cells (RGCs) after acute intraocular pressure (IOP)-induced ischaemia.


METHODS
Retinal ischaemia was induced by acutely increasing IOP to 100-110 mmHg for 30 or 90 min unilaterally in Sprague Dawley rats. A fluorescent tracer (fluorogold, FG) was applied to the superior colliculi to label RGCs. Twenty-four hours, 1 week or 2 weeks after of IOP elevation, rats were killed, RGCs counted, and immunohistochemical labelling of the retina was performed. HSP-positive RGCs were counted and normalized HSP RGC counts determined.


RESULTS
The ratio of FG-positive labelled RGCs in the experimental to the contralateral eye as a marker of RGC survival remained unchanged after 30 min of ischaemia: 1.09 +/- 0.11 at 1 week, and 0.94 +/- 0.28 at 2 weeks. After 90 min of ischaemia RGC survival decreased to 0.19 +/- 0.14 at 1 week, and 0.20 +/- 0.14 at 2 weeks. After 30 min of ischaemia, the normalized HSP 27- and HSP 72-positive RGC count was detected at highest levels (HSP 27: 5.42 +/- 1.18; HSP 72: 12.23 +/- 1.24) at 2 weeks compared with controls,whereas after 90 min ischaemia it was detected at higher levels at 1 week (HSP 27: 52.63 +/- 3.65; HSP 72: 206.84 +/- 60.38), as well as at 2 weeks (HSP 27: 89.00 +/- 17.21; HSP 72: 191.00 +/- 50.05).


CONCLUSIONS
These results demonstrate an enhanced induction of HSP 27 and HSP 72 after 90 min acute IOP-induced ischaemia. In contrast to 30 min ischaemia, we showed time-dependent loss of RGCs after 90 min of ischaemia after 1 week or 2 weeks.
Windisch
Bettina K
BK
Retina and Optic Nerve Research Laboratory, Dalhousie University, Halifax, Nova Scotia, Canada.
LeVatte
Terry L
TL
Archibald
Michele L
ML
Chauhan
Balwantray C
BC
D000818:Animals; D002452:Cell Count; D002470:Cell Survival; D055551:HSP27 Heat-Shock Proteins / Q000096:biosynthesis*; D050884:HSP72 Heat-Shock Proteins / Q000096:biosynthesis*; D007150:Immunohistochemistry; D007429:Intraocular Pressure; D007511:Ischemia / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000378:metabolism* / Q000473:pathology; D013194:Staining and Labeling; D013997:Time Factors
D055551:HSP27 Heat-Shock Proteins; D050884:HSP72 Heat-Shock Proteins