Metabotropic glutamate receptor 5 may be involved in macrophage plasticity

Background: Macrophages 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. Results: Comparative analysis of modified (RAW-mGluR5 macrophages) and non-modified macrophages (RAWmacrophages) 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 proliferatoractivated receptor gamma(PPAR-gamma) and secreted more IL-10, high mobility group box 1 proteins (HMGB1) and Galectin-3 than control RAW-macrophages. Conclusions: We 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.