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Abstract #8203 Published in IGR 4-3
Loss of retinal ganglion cells following retinal ischemia: the role of inducible nitric oxide synthase
Neufeld AH; Kawai S; Das S; Vora S; Gachie E; Connor JR; Manning PTExperimental Eye Research 2002; 75: 521-528
Following experimental, transient, retinal ischemia in the rat, there is loss of retinal neurons, which occurs over several weeks. Retinal ganglion cells (RGCs) are particularly susceptible and there is early, massive degeneration of these neurons after ischemia. The authors determined the early mechanisms by which RGCs are killed following ischemia. Retinal ischemia/reperfusion was produced in rats by transient unilateral elevation of intraocular pressure above systolic blood pressure. Retinas were studied by immunohistochemistry for the presence of inducible nitric oxide synthase (NOS-2) at several time points post-ischemia and specific cell types were identified. Rats were also treated orally with -N6 -(1-iminoethyl)lysine 5-tetrazole amide (SC-51), a prodrug of an inhibitor of NOS-2 or with aminoguanidine (AG) for a period of 14 days. Retrograde labelling with Fluoro-Gold quantitated the loss of RGCs. NOS-2 was not present in the normal retina and was not present in the eyes that were contralateral to the ischemic eyes. Within 24 hours after ischemia, polymorphonuclear leukocytes containing NOS-2 had entered the ganglion cell layer and surrounded RGCs. Within five days after ischemia, NOS-2 was present in many inner retina cells and in invading monocytes in the vitreous. Between seven and 14 days post-ischemia, there were few hematogenous cells in the retina but NOS-2 was sparsely detectable in microglia and other cells of the inner retina. Two weeks after ischemia, rat eyes lost approximately 50% of the RGCs. Treatment with AG for 14 days following ischemia was partially neuroprotective; approximately 28% of the RGCs were lost. Treatment with SC-51 for 14 days following ischemia almost completely prevented the loss of RGCs. Thus, within 24 hours following ischemia, polymorphonuclear leukocytes containing NOS-2 attack and kill neurons in the ganglion cell layer. For two weeks after ischemia, NOS-2 appears transiently in the retina in several different cell types at different times. Continuous pharmacological treatment with inhibitors of NOS-2 activity during the two weeks post-ischemia period provides significant neuroprotection against the loss of RGCs.
A.H. Neufeld, MD, Department of Ophthalmology and Visual Sciences, Washington University of Medicine, 660 South Euclid Avenue, Box 8096, St Louis, MO 63110, USA. neufeld@vision.wustl.edu
Classification:
1.3 Pathogenesis (Part of: 1 General aspects)
5 Experimental glaucoma; animal models