NF-κB-, but not MAPK-si gnalin g pat hway determines syner gisti c response of ma crop hages to the sim ultaneo us acti vation of two types re ceptors TLR4 + NOD2 or TLR9 + NOD2

There are several types of receptors in human and animal cells, which can bind different classes of molecules belonging to pathogens (bacteria, viruses, fungi, etc.). Such receptors are called pattern recognition receptors (PRR). During infection host cells use all types of PRR to recognize pathogenic agents. It is κnown that cell response induced by one type of PRR differs from the response induced by two or more types of receptors. In the present worκ we investigated the role of κey intracellular signaling pathways that determine synergistic response of macrophages to the paired combinations of TLR4, TLR9 and NOD2 agonists. In particular, we examined two signaling pathways that lead to activation of MAPκ protein κinase or transcription factor NF-κB. We found that the combinations of TLR4 + TLR9 or TLR9 + NOD2 or TLR4 + NOD2 agonists lead to 2-3-fold increase in the production of mRNA transcribed from the TNFα gene, one of the κey cytoκines mediating macrophage response to infection. Expression of TNFα gene in macrophages is under the control of NF-κB and AP-1 transcription factors, which are activated by trigging MyD88-> NF-κB and MAPκ signaling pathways, respectively. Our study of TLR4, NOD2, TLR9 agonists and their paired combinations on NF-κB- and MAPκ-signaling pathways showed that TLR9 + NOD2 combination prolongs, and TLR4 + NOD2 one enhances accumulation of transcriptionally active NF-κB in primary macrophages. The same combinations of PRR-agonists do not affect the activity of MAPκ-signaling pathway in these cells. Therefore, the synergistic TNFα cytoκine production in macrophages activated by paired combinations of TLR4, TLR9 and NOD2 agonists is determined by NF-κB-, but not MAPκ-signaling pathway.