Modulator Effects of Interleukin-1β and Tumor Necrosis Factor-α on AMPA-Induced Excitotoxicity in Mouse Organotypic Hippocampal Slice Cultures

Abstract

The inflammatory cytokines interleukin-1␤ and tumor necrosis factor-␣ (TNF-␣) have been identified as mediators of several forms of neurodegeneration in the brain. However, they can produce either deleterious or beneficial effects on neuronal function. We investigated the effects of these cytokines on neuronal death caused by exposure of mouse organotypic hippocampal slice cultures to toxic concentrations of AMPA. Either potentiation of excitotoxicity or neuroprotection was observed, depending on the concentration of the cytokines and the timing of exposure. A relatively high concentration of mouse recombinant TNF-␣ (10 ng/ml) enhanced excitotoxicity when the cultures were simultaneously exposed to AMPA and to this cytokine. Decreasing the concentration of TNF-␣ to 1 ng/ml resulted in neuroprotection against AMPA-induced neuronal death independently on the application protocol. By using TNF-␣ receptor (TNFR) knock-out mice, we demonstrated that the potentiation of AMPA-induced toxicity by TNF-␣ involves TNF receptor-1, whereas the neuroprotective effect is mediated by TNF receptor-2. AMPA exposure was associated with activation and proliferation of microglia as assessed by macrophage antigen-1 and bromodeoxyuridine immunohistochemistry, suggesting a functional recruitment of cytokineproducing cells at sites of neurodegeneration. Together, these findings are relevant for understanding the role of proinflammatory cytokines and microglia activation in acute and chronic excitotoxic conditions.

Rapid Tumor Necrosis Factor α-Induced Exocytosis of Glutamate Receptor 2-Lacking AMPA Receptors to Extrasynaptic Plasma Membrane Potentiates Excitotoxicity

“…The application of TNF␣ in our in vitro assay for 18 h did not itself increase neuron death, suggesting that programmed apoptotic death did not contribute to the kainate plus TNF␣ potentiation of neuron death. These results are in agreement with previous in vitro hippocampal slice studies showing that AMPAinduced excitotoxicity was dependent on the TNF␣ receptor TNFR1 but not the TNF␣ receptor TNFR2 (Bernardino et al, 2005). These results in combination with our data demonstrating TNF␣-induced trafficking through TNFR1 activation (Stellwagen et al, 2005) fit the hypothesis that TNFR1 activation may contribute to excitotoxic death, whereas TNFR2 may signal for neuroprotection (Fontaine et al, 2002).…”

“…Neurons pretreated with the AMPAR/KA receptorspecific antagonist CNQX (10 M) before exposure to kainate were completely protected from excitotoxicity (97 Ϯ 5% compared with control) (data not shown), indicating that the cell death produced by kainate requires AMPAR/KA receptor activity. These results are in agreement with previous in vitro hippocampal studies showing the AMPAR dependence of TNF␣-potentiated neuron death (Bernardino et al, 2005).…”

“…CP-AMPARs are important functionally because they have stronger current passing capabilities compared with GluR2-containing AMPARs and are Ca 2ϩ -permeable (Hollmann et al, 1991;Burnashev et al, 1992). When neurons are exposed to excess glutamate after neuronal damage, excessive surface expression of CP-AMPARs induced by increased TNF␣ levels may lead to the abnormal influx of Ca 2ϩ and overactivation of AMPARs resulting in potentiated excitotoxicity (Gelbard et al, 1993;Chao and Hu, 1994;Hermann et al, 2001;Bernardino et al, 2005).…”

Excitotoxic Death of Retinal NeuronsIn VivoOccurs via a Non-Cell-Autonomous Mechanism

“…We focused on TNF␣ as a major effector in this pathway because the TNF␣ gene is tightly regulated by NF-B, and previous studies have indicated that TNF␣ can facilitate excitotoxic damage (Chao and Hu, 1994;Hermann et al, 2001;Bernardino et al, 2005;Noh et al, 2005;Ferguson et al, 2008;Kaushal and Schlichter, 2008;Leonoudakis et al, 2008). We showed that TNF␣ in Mü ller glia was dramatically increased by NMDA exposure, and our loss of function experiments confirmed that TNF␣ plays an obligatory role in the loss of retinal neurons induced by NMDA.…”

Inflammation Triggers Synaptic Alteration and Degeneration in Experimental Autoimmune Encephalomyelitis

“…Previous experiments, in fact, showed that TNF␣ was able to modulate AMPA receptor-mediated synaptic transmission (Beattie et al, 2002;Stellwagen et al, 2005;Stellwagen and Malenka, 2006) and excitotoxicity (Bernardino et al, 2005) by inducing the upregulation of the GluR1 subunit in vitro.…”