Immune system protects our body from various pathogens. We can roughly divide it in two groups: innate and adaptive immune system. Although the innate immune system is not capable of antigen-specific differentiation of pathogens, it can still recognize foreign molecules using the pattern recognition receptors (PRR), which recognize pathogen associated molecular patterns (PAMPs) and danger associated molecular patterns (DAMPs). NOD1 and NOD2 receptors belong to NLRs, which are one of the PRR families. NOD1 and NOD2 receptors are cytosolic receptors that recognize cytoplasmic PAMPs. In the case of NOD1 receptor that PAMP is iE-DAP, whereas MDP is the smallest fragment recognized by NOD2 receptor. After ligand recognition, the receptors activate NF-κB, IRF and MAPK signaling pathways, which triggers inflammatory response. NOD2 receptor is encoded by CARD15 gene. Different polymorphisms and mutations on that particular gene can change the NOD2 function, which can lead to chronic inflammatory and autoimmune diseases or cancer. Therefore, NOD2 antagonists have a therapeutic potential in treating diseases that occur as a result of an increased NOD2 signaling. In this master’s thesis, we synthesized 10 novel NOD2 antagonists. We used N-(2-(1-(2,3-dihydro-1H-inden-5-yl)amino)-2-oxoethyl)-1H-benzo[d]imidazol-2-yl)methyl)benzamide as our lead compound. We replaced the benzoyl moiety of the lead compound with various substituents, affecting the receptor binding and/or physicochemical properties. The Chair of Clinical Biochemistry, University Ljubljana, Faculty of pharmacy performed the cytotoxicity assay, NOD1 antagonistic activity evaluation and NOD2 antagonistic activity evaluation on newly synthesized antagonists. The results showed that three compounds (compounds 5, 9 and 20) expressed increased antagonistic activity compared to that of the lead compound with compound 20 being the best NOD2 antagonist of our compound series. Most of the newly synthesized NOD2 antagonists possessed similar NOD1 antagonistic activity. Based on the results, we were able to gather some information regarding the structure-activity relationship of our final compounds. The replacement of our lead compound’s benzoyl moiety with arylsulfonyl (compounds 5 in 9) or benzyl moiety (compound 20) improved the NOD2 antagonistic activity, while the presence of basic center in compounds 7, 11, 14, 16, 18 and 21 showed negative effect on the NOD2 antagonistic activity.
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