Glutamate-Induced NFκB Activation in the Retina

PURPOSE. To determine the distribution and glutamate-mediated activation of nuclear factor (NF) kappa B members in the retina and pan-purified retinal ganglion cells (RGCs) and to characterize steps in the signal transduction events that lead to NF kappa B activation. METHODS. Retinal expression patterns and RGCs were evaluated for five NF kappa B proteins with the aid of immunohistochemistry. Retinal explants or RGCs were treated with glutamate with or without the presence of the NDMA receptor antagonist memantine, the calcium chelator EGTA, or a specific inhibitor for calcium/calmodulin-dependent protein kinase-II (CaMKII). Characterizations of NF kappa B activation were performed with the aid of electrophoretic mobility shift assays and supershift assays. RESULTS. All five NF kappa B proteins were present in the retina and in the pan-purified RGCs. In response to a glutamate stimulus, all NF kappa B proteins except c-Rel were activated. P65 was unique in that it was not constitutively active but showed a glutamate-inducible activation in the retina and in the cultured RGCs. Memantine, EGTA, or autocamtide-2-related inhibitory peptide (AIP) inhibited NF kappa B activation in the retina. Furthermore, AIP significantly reduced the level of glutamate-induced degradation of I kappa Bs. CONCLUSIONS. These data indicate that glutamate activates distinct NF kappa B proteins in the retina. P65 activation may be especially important with regard to RGC responses to glutamate given that its activity is induced by conditions known to lead to the death of these cells. The NMDA receptor-Ca2+-CaMKII signaling pathway is involved in glutamate-induced NF kappa B activation. Because AIP blocks the degradation of I kappa B, its regulation is clearly downstream of CaMKII. (Invest Ophthalmol Vis Sci. 2009; 50: 917-925) DOI:10.1167/iovs.08-2555