Transcription factor NF‐κB activation after in vivo perforant path LTP in mouse hippocampus

Abstract

There is increasing evidence that transcription factors (TFs) play a critical role in maintaining later phases of hippocampal long-term potentiation (LTP). We have been led to study the role in synaptic plasticity of the powerful, yet generally unheralded, NF-kappaB TF because it may serve as both a signaling molecule after its activation at the synapse and then a transcription initiator upon reaching the nucleus. In the present study, we show that LTP activates NF-kappaB in the intact mouse hippocampus. Mice were sacrificed 15 min after one of three treatments: tetanization (high-frequency stimulation [HFS]), low-frequency stimulation (LFS), or no stimulated control animals (CT). In a first study, nuclear NF-kappaB activity from hippocampus was estimated by electrophoretic mobility shift assays (EMSAs). A higher level of hippocampal TF binding to the NF-kappaB recognition element was found in the HFS group compared with LFS or CT. In a second study, NF-kappaB activity was evaluated by immunohistochemistry with a specific antibody that recognizes the activated form of NF-kappaB. This antibody binds to the exposed nuclear location sequence on the p65 subunit of NF-kappaB consequent to its dissociation from the inhibitory IkappaB molecule. In the four subfields of hippocampus examined--granule cell layer, hilus of the dentate gyrus, CA3 and CA1 pyramidal fields of the hippocampal gyrus--the highest levels of activated NF-kappaB, statistically significant in all cases were found after HFS. In certain comparisons, LFS animals also showed significant elevation with respect to CT. These results support the role of NF-kappaB as part of the synaptic signaling and transcriptional regulation mechanism required in long-term plasticity, emphasizing the combinatorial nature of TF function.

NF-κB activity in distinct neural subtypes of the rat hippocampus: Influence of time and GABA antagonism in acute slice preparations

“…Furthermore, recent studies have indicated the requirement of active NF-B for LTP, LTD, and spatial memory (Kaltschmidt et al 2006;Romano et al 2006). Moreover, employ-ing the same antibody approach as adapted in the present studies, Freudenthal et al (2004) demonstrated that NF-B is upregulated in the hippocampus following both high-frequency and low-frequency stimulation in vivo. Along with the recent identification of p65-containing protein complexes in synaptic terminals and their activity-mediated retrograde transport to the cell body, these properties of NF-B position this transcription factor ideally to translate synaptic activity into a transcriptional program driving subsequent plasticity (Kaltschmidt et al 1993;Meberg et al 1996;Mattson and Camandola 2001;Wellmann et al 2001;Meffert et al 2003).…”

“…Recent studies have implicated the transcription factor NF-B in hippocampal LTP, LTD, and spatial memory (Freudenthal et al 2004;Kaltschmidt et al 2006;O'Mahony et al 2006;Romano et al 2006;Vernon et al 2006). Thus, differential basal activities of this cardinal transcription factor in distinct neuronal subpopulations of the hippocampus have important implications for the nature of plasticity mobilized in each area.…”

“…In vivo studies have clearly indicated activation of NF-B accompanies LTP, LTD, and learning in the hippocampus in the absence of the confounding issues encountered in the acute slice preparation (Freudenthal et al 2004;Kaltschmidt et al 2006;Romano et al 2006). In particular, Freudenthal et al (2004), using precisely the same antibody marker, demonstrated increased activity of NF-B following both high-and low-frequency stimulation of the perforant path in vivo.…”

“…Here, we have adapted the active p65-specific antibody approach used by Freudenthal et al (2004) to allow the imaging of NF-B activity in distinct neuronal subfields of the hippocampus in the acute slice. We focused on the three primary neuronal cell populations of the hippocampal excitatory loop, namely the dentate granule cells and the CA3 and CA1 pyramidal cells.…”

Chronic CXCL10 alters the level of activated ERK1/2 and transcriptional factors CREB and NF-κB in hippocampal neuronal cell culture

“…Activation of NF-κB has been shown to be triggered by a wide variety of stimuli, such as glutamate depolarization, increase in intracellular Ca 2+ , neuropeptides, neural cell adhesion molecule, and cytokines (e.g., interleukin-1) (Freudenthal et al, 2004). NF-κB is activated in neurons and glial cells in a variety of acute and chronic neurodegenerative conditions (Epstein and Gelbard, 1999;Mattson, 2005).…”