ABSTRACT
Sodium nitroprusside (SNP), an NO donor, was studied for its effects on apoptosis in rat retinal neurons. TUNEL-positive cells were observed in the outer nuclear layer (ONL), but not in the inner retina after SNP treatment. Inner retinal neurons died by necrosis. No photoreceptor cells were found in the ONL after seven days. Immunoblotting confirmed that neurnal NO synthase expression increased up to 5 days (approximately 170% of control levels), and then declined by 7 days, suggesting that NO induces apoptosis in the ONL, and that inner retinal neurons die by necrosis due to glutamate from damaged photoreceptors.
Subject(s)
Apoptosis/drug effects , Nitric Oxide Donors/pharmacology , Nitroprusside/pharmacology , Retina/cytology , Animals , Blotting, Western , In Situ Nick-End Labeling , Male , Nitric Oxide/metabolism , Nitric Oxide Synthase/analysis , Nitric Oxide Synthase Type I , Rats , Rats, Sprague-Dawley , Retina/growth & developmentABSTRACT
We investigated the expression and cellular localization of neuronal nitric oxide synthase (nNOS) in the rat retina, following ischemic injury induced by transient increase of intraocular pressure. In the normal retina, nNOS immunoreactivity was localized to certain populations of amacrine cells, displaced amacrine cells and a few bipolar cells. Following transient ischemia, retinal neurons expressing the immunoreactivity increased and peaked three days after reperfusion. Quantitative evaluation using immunoblotting confirmed that nNOS expression showed a peak value (500% of control levels) at 3 days, and then decreased again to 150% of controls by 4 weeks after reperfusion. Our findings suggest that this over-produced NO may act as a neurotoxic agent in the ischemic rat retina.
Subject(s)
Brain Ischemia/enzymology , Cell Death/physiology , Neurons/enzymology , Nitric Oxide Synthase/metabolism , Nitric Oxide/metabolism , Reperfusion Injury/enzymology , Retina/enzymology , Animals , Brain Ischemia/physiopathology , Disease Models, Animal , Immunohistochemistry , Intraocular Pressure/physiology , Male , Nerve Degeneration/enzymology , Nerve Degeneration/physiopathology , Neurons/pathology , Rats , Rats, Sprague-Dawley , Reperfusion Injury/physiopathology , Retina/injuries , Retina/physiopathology , Up-Regulation/physiologyABSTRACT
Using immunoblot analysis and immunocytochemistry, we investigated expression and cellular localization of endothelial nitric oxide synthase (eNOS) and proliferating cell nuclear antigen (PCNA) in the l-arginine treated ischemic rat retina. In parallel, we tested whether the blood-retinal barrier was intact by immunocytochemistry using an antiserum against IgG. In the l-arginine-treated ischemic retina, the magnitude of the increased eNOS was higher, and PCNA was expressed in endothelial cells as well as in neurons in the inner retina during the whole experimental period. Finally, IgG leakage was not detectable in the l-arginine-treated ischemic retina. Our results clearly suggest that the increased NO production by eNOS may be essential for the survival of endothelial cells in the rat retina following transient ischemia.
