The Effect Of Nitric Oxide Synthetase (nos) On The Retinal Nerve Cell Apoptosis In Early Diabetic Mice

Objective To determine the expression of nitric oxide synthetase(NOS) in retina ofearly diabeti mice and to investigate the effect of NOS on the apoptosis of retinalneuronal cell.Methods Diabetic mice model was induced by injected with streptozotoc(STZ).Saline was injected in the controls. The retinal was excised and studied 2w (DM1group) and 20w(DM2 group) after the establishment of the experimental model andthe controls(C group): (1) The retina was paraffin imbedded and sliced. To showneuroepithelial layer of the retina by general hematoxylin-eosin staining(HE); (2) Thenerve cell apoptosis on retina was detected using TUNEL; (3) Retinal 3-nitrotyrosine(3－NT) were quantified by a competitive ELISA; (4)Retinal protein was extrated inorder to determined the expression of nitric oxide synthetase (iNOS, nNOS) bywestern blot.Results (1) The retina constitution in sections for HE in DM1 were not differentcompared with those in C group in light microscopy. The retinal thickness of DM2group was thinner than other groups obviously. And ganglion cells were decreasedand disorder in MD2 group.(2) Rare TUNEL positive cells was in C group. Little apoptosis cells were showed in ganglin cell layer in DM1 group. TUNEL positive cells in retinal wereincreased significantly in ganglion cell layer and inner nuclear layer, also in outernuclear layer.(3) Compared to control animals, NT levels were significantly increased in rat retinaswith diabetes. Also, NT levels in rat retinas with diates for 20 weeks were higher thanin those for 2 weeks.(4) The expression of nNOS was significantly lower in diabetic retinas than in controlrats as determined by western blot. The nNOS level of 20w diabetic rats was alsolower than in 2W diabetic rats. The diabetic treatment induced a significant increasedof iNOS expression in rat retinas, but no significant difference was found between 2and 20 weeks diabetic retinas.ConclusiConclusion The cellular apoptosis happened earlier than the changes of retinalappearance in early diabetic mice retina. This report has demonstrated that NTincreases in rat retinas in the early stages of diabetes. NO production by the neuronalform of NOS may be the rate-limiting step in NT formation, as supported by thereduced nNOS expression in the diabetic retinas. The nitric oxide sythetase,especially a loss of nNOS activity is possible contribute to apoptosis of retinal nervecells in early diabetic retinopathy.