Endogenous and inducible Nuclear Factor (NF)–B transcriptional activity in adult transgenic mice retina.

Abstract

Abstract: : Purpose: The Nuclear Factor (NF)–ΚB is an essential transcriptional regulator of genes involved in cell death. The role of endogenous NF–ΚB in the mechanisms that control the survival of retinal neurons remains undefined. To address this issue, we examined the retinas of adult transgenic mice containing the NF–ΚB promoter/enhancer sequence upstream of the ß–galactosidase (ß–gal) reporter gene. Methods: NF–ΚB transcriptional activity in adult transgenic retinas was examined using standard histochemical analysis of ß–gal expression in retinal sections. Changes in the cellular localization and levels of endogenous NF–ΚB/ß–gal expression were investigated after intravitreal injection of tumor necrosis factor α (TNF–α, 0.4 µg), a well–established NF–ΚB activator, or N–Methyl–D–Aspartate (NMDA, 20 mM) to induce excitotoxic retinal ganglion cell (RGC) death. Results: Basal levels of NF–ΚB activity were observed in few RGCs and Müller glial cells in intact transgenic retinas. Intravitreal injection of TNFα induced a striking increase in the number of ß–gal positive RGCs and cells in Müller cells. The pattern of ß–gal expression in retinas treated with NMDA was as follows: i) prior to RGC death (3 hrs post–NMDA injection) only few RGCs and Müller cells expressed the NF–ΚB/ß–gal transgene; ii) at the onset of RGC death (6 hrs post–NMDA injection) an increase in ß–gal staining was observed in Müller cells, but not in RGCs, and iii) during massive RGC death (18 hrs post–NMDA injection) robust ß–gal staining was observed in Müller cells while reporter gene expression was absent from surviving RGCs. Conclusions: Endogenous NF–ΚB activity was readily induced following stimulation with TNFα or NMDA in the adult retina. Our data indicate that NMDA, a stimulus that induced RGC death, correlated with selective increase of NF–ΚB activity in glial cells.

Keywords: transcription factors • cell death/apoptosis • Muller cells