Characterization of the immunosuppressant activity of the novel biogenic amine 3HKA and its analog derivatives

Abstract Tryptophan (Trp) is an essential amino acid which in mammalian cells 90% is processed through the kynurenine pathway. Kynurenine metabolites are among the most potent regulators of immune responses. Herein we report the characterization of a novel immunosuppressant biogenic amine, 3-hydroxy-L-kynurenamine (3HKA), generated through an uncharacterized lateral pathway of Trp catabolism, involving its decarboxylation by the aromatic amino acid decarboxylase. 3HKA is generated by both professional (Dendritic Cells, DC) and non-professional (Lymphatic Endothelial Cells) APC. Quantitative phosphoproteomic analysis of human-monocytes (CD14 +) derived DCs, identified key signaling transduction receptors, IFNR1, and signaling molecules from the JAK/STAT and cAMP mediated PKA pathways, regulated by 3HKA. Cell-based assays coupled with ELISA platforms showed that 3-HKA inhibited the IFN-g-mediated STAT1/NF-kB pathway in human DCs, and consequent decreased the release of pro-inflammatory chemokines and cytokines IL-1, TNFa, IL-6, and IL12p70. In vivo, 3-HKA reduced the intestinal inflammation in a model of dextran sodium sulfate-induced colitis. Furthermore, flow cytometry analysis revealed that 3-HKA increased the number of T-cells expressing 2, 3 or 4 exhaustion markers (PD-1, CTLA4, LAG3 or TIM3), exclusively in CD8 +CD4 −cells. We used, in silico approaches for ligand and pharmacophore-based drug discovery and developed 30 novel 3-HKA analogues with ADMET predicted drug-like properties. Structure-activity relationships studies, leaded to identify compounds with improved anti-inflammatory profiles. The novel anti-inflammatory 3-HKA analogues showed promising activity for the treatment of autoimmune diseases