Human T lymphocytes express both ionotropic and metabotropic glutamate receptors that control immune responses, cell activation, maturation and death. In this study, we examined the effect of N-methyl-D-aspartate (NMDA) and σ1-receptor ligands on the secretion of the proinflammatory chemokine interleukin 8 (IL-8) and the anti-inflammatory cytokine interleukin 10 (IL-10) in human leukemia Jurkat cells and peripheral blood lymphocytes (PBLs). We have shown that NMDA increased IL-8 and decreased IL-10 secretion and that σ-ligands modulated the action of NMDA. Moreover, the effects of NMDA and σ-ligands were interrelated with the nitric oxide (NO) content, suggesting that the intracellular concentration of NO could play a major role in the synthesis of cytokines. Western blots against the NR2A and NR2B subunits of the NMDA glutamate receptor revealed that long-term (48 h) treatment of PBLs with glutamate at concentrations within normal plasma levels (1 × 10^–5M), in contrast to low concentrations (0.3 × 10^–6M), downregulates the NR2A subunit, probably by internalization. Furthermore, we found that PBLs with noninternalized NR2A secreted less IL-10 than lymphocytes with downregulated NR2A; under these conditions, the transcriptional activity of NF-κB was increased whereas the transcriptional activity of c-Fos was decreased. These findings implicate that the activities of NF-κB and c-Fos control the expression of the IL8 and IL10 genes, depending on the subunit composition of the NMDA receptor. In conclusion, we suggest that lymphocytes express an active NMDA receptor only in a low-glutamate milieu.

BackgroundMacrophages are a functionally heterogeneous cell population and depending on microenvironments they polarize in two main groups: M1 and M2. Glutamic acid and glutamate receptors may participate in the regulation of macrophage plasticity. To investigate the role of glutamatergic systems in macrophages physiology, we performed the transfection of mGluR5 cDNAs into RAW-264.7 cells.ResultsComparative analysis of modified (RAW-mGluR5 macrophages) and non-modified macrophages (RAW-macrophages) has shown that the RAW-mGluR5 macrophages absorbed more glutamate than control cells and the amount of intracellular glutamate correlated with the expression of excitatory amino acid transporters -2 (EAAT-2). Besides, our results have shown that RAW-mGluR5 macrophages expressed a higher level of peroxisome proliferator-activated receptor γ (PPAR-γ) and secreted more IL-10, high mobility group box 1 proteins (HMGB1) and Galectin-3 than control RAW-macrophages.ConclusionsWe propose that elevation of intracellular glutamate and expression of mGluR5 may initiate the metabolic rearrangement in macrophages that could contribute to the formation of an immunosuppressive phenotype.

IL-10 provides trophic and survival effects directly on neurons, promotes axonal outgrowth, and stimulates neuroregeneration. In this study, we analyzed the activities of arginase and nitric oxide synthase (NOS) in synaptoneurosomes derived from brain cortex of C57BL/6 IL-10 gene-knockout (KO) and wild-type (Wt) mice and determined that the synaptoneurosomes derived from KO mice present lower arginase II activity and lower spermine content than those derived from Wt mice, whereas the basal NOS activity in the KO synaptoneurosomes was higher than that observed in the control synaptoneurosomes. Moreover, our results indicate that the plasma membranes isolated from the KO mice brain exhibit significantly lower spermine-induced enhancement of [ 3 H] MK-801 binding than the plasma membranes from the brain of Wt mice. Glutamate increases the production of nitric oxide (NO) in Wt synaptoneurosomes in a dose-dependent manner, whereas in the KO synaptoneurosomes, this amino acid does not affect the synthesis of NO. The glutamate-dependent acceleration of NO synthesis in Wt synaptoneurosomes was abrogated by LY367385, an antagonist of mGluR1a/b. The western blot analysis of the synaptoneurosomal proteins demonstrates that the expression of the subunits of NMDAR (NMDAR2A and NMDAR2B), the level of NMDAR-bound nNOS and the expression of iNOS are not changed in KO mice and that only the level of mGluR1a/b is markedly reduced in the synaptoneurosomes of KO mice. We conclude that a neuroprotective and neuroregenerative property of IL-10, in addition to its effects on polyamine metabolism and the spermine-dependent modulation of NMDAR, may involve the regulation of mGluR1a/b expression.

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