Enhanced Expression of Activator Protein–1 (AP–1) in N–Methyl–D–Aspartate (NMDA)–Induced Apoptotic Cell Death

Abstract

Purpose: : N–methyl–D–aspartate (NMDA)–mediated neurotoxicity of retina is a model system widely used to investigate intracellular mechanisms that lead to apoptotic cell death in ocular diseases. Activator protein–1 (AP–1) is known to be involved in apoptotic pathways for the various stimuli. We examined expression of AP–1 in NMDA–induced neurotoxicity in the rat retina.

Methods: : Male Wistar rats (8–weeks–old) were used in this study. A single 5 micro litter injection of 4×10^–2 M NMDA was administered intravitreally into one eye of anesthetized rat. Phosphate–buffered saline (PBS) was injected as a control. The eyes were enucleated at 24 hours after injection. AP–1 DNA binding activity in NMDA or PBS–treated retinas were assessed by electrophoretic mobility shift assay (EMSA). Immunohistochemistry was performed with an antibody against c–Jun/AP–1. Double–labeling with TUNEL staining and c–Jun/AP–1 was performed to examine the relation between apoptotic cells and c–Jun/AP–1 positive cells.

Results: : EMSA showed an increase of AP–1 DNA binding activity in NMDA–tread retinas. Immunohistochemistry provided the NMDA induced a substantial increase in c–Jun/AP–1 immunoreactivity in the ganglion cell layer (GCL) and the inner nuclear layer (INL). Co–localization of TUNEL positive cells with c–Jun/AP–1 were also observed in the GCL and the INL.

Conclusions: : Increase of AP–1 DNA binding activity and c–Jun/AP–1 immunoreactivity may participate in NMDA–induced retinopathy.

Keywords: apoptosis/cell death • retina • ganglion cells