Nitric Oxide Inhibits NMDA-Induced Activation of NF-kB in Rat Retina

Abstract

Abstract: : Purpose: In nervous systems, nuclear factor-kB (NF-kB) is inducted by several stimuli and has been reported to have both neuroprotective and neurotoxic functions. NO also has a controversial role in neuronal cell death. Thus, we investigated whether NMDA alters NF-kB and whether NO inhibits NMDA-induced changes in rat retina. Methods: Anesthetized male Wistar rats (8-weeks-olds) were used in this study. A single 5 µl injection of 4×10^-2 M NMDA in PBS with or without 10^-4 M NOC 18 (NO donor) was administered intravitreally into one eye. PBS was injected to the opposite eye as a control. The eyes were enucleated at 1 and 5 days after injection. Nuclear and cytosolic extracts of retinas were used for analysis of NF-kB p65 protein levels by Western blot analysis. NF-kB DNA binding activity of retinas was analyzed by electrophoretic mobility shift assay (EMSA). Moreover, morphological changes were evaluated. Results: Western blot analysis showed that intravitreal injection of NMDA increased in NF-kB p65 protein levels of cytosolic extracts at 1 and 5 days after injection. EMSA showed that NMDA increased in NF-kB DNA binding activity of nuclear extracts. The NMDA-induced increment of NF-kB DNA binding activity was inhibited by concomitant injection of NOC 18. In addition, morphological analysis showed that NO prevented NMDA-induced neurotoxicity. Conclusions:These results suggest that activated NF-kB may be involved in the NMDA-induced neurotoxicity. Inhibition of NF-kB DNA binding activity by NO may lead to neuroprotective effects in rat retina.

Keywords: transcription factors • nitric oxide • neuroprotection