Identification of Human S100A9 as a Novel Target for Treatment of Autoimmune Disease via Binding to Quinoline-3-Carboxamides

Abstract

Despite more than 25 years of research, the molecular targets of quinoline-3-carboxamides have been elusive although these compounds are currently in Phase II and III development for treatment of autoimmune/inflammatory diseases in humans. Using photoaffinity cross-linking of a radioactively labelled quinoline-3-carboxamide compound, we could determine a direct association between human S100A9 and quinoline-3-carboxamides. This interaction was strictly dependent on both Zn++ and Ca++. We also show that S100A9 in the presence of Zn++ and Ca++ is an efficient ligand of receptor for advanced glycation end products (RAGE) and also an endogenous Toll ligand in that it shows a highly specific interaction with TLR4/MD2. Both these interactions are inhibited by quinoline-3-carboxamides. A clear structure-activity relationship (SAR) emerged with regard to the binding of quinoline-3-carboxamides to S100A9, as well as these compounds potency to inhibit interactions with RAGE or TLR4/MD2. The same SAR was observed when the compound's ability to inhibit acute experimental autoimmune encephalomyelitis in mice in vivo was analysed. Quinoline-3-carboxamides would also inhibit TNFα release in a S100A9-dependent model in vivo, as would antibodies raised against the quinoline-3-carboxamide–binding domain of S100A9. Thus, S100A9 appears to be a focal molecule in the control of autoimmune disease via its interactions with proinflammatory mediators. The specific binding of quinoline-3-carboxamides to S100A9 explains the immunomodulatory activity of this class of compounds and defines S100A9 as a novel target for treatment of human autoimmune diseases.

Transcriptome Assessment Reveals a Dominant Role for TLR4 in the Activation of Human Monocytes by the Alarmin MRP8

“…Although MRP8 has been unequivocally demonstrated to be an active component for phagocyte stimulation in vitro (9), the biologically relevant complex forms of MRP8/MRP14 in vivo, however, are still to be defined. Furthermore, it is not clear whether MRP8/MRP14 interacts directly with certain amino acids within the RAGE receptor or to carboxylated glycans covalently attached to RAGE (16,19). For isolated MRP14, similar findings were found.…”

“…Similar MRP8/MRP14-RAGE interactions were observed in a study done by Boyd et al (23) on purified cardiomyocytes, during which RAGE was coimmunoprecipitated with MRP8/ MRP14. Binding of MRP8 and/or MRP14 to both TLR4 (9,19) and RAGE (18,19) has been demonstrated in BIAcore studies, and strong binding constants in the low nanomolar range could be calculated for both receptors. Although MRP8 has been unequivocally demonstrated to be an active component for phagocyte stimulation in vitro (9), the biologically relevant complex forms of MRP8/MRP14 in vivo, however, are still to be defined.…”

“…For isolated MRP14, similar findings were found. Although it could be shown that MRP14 binds to both receptors TLR4 as well as RAGE (19), cytokine induction could only be observed for MRP14-TLR4-dependent activation in a cell line culturing model (39). Studies on phagocytes from TLR4 mutant mice clearly indicate that TLR4 is mainly responsible for MRP8-dependent activation in these cells (9).…”

“…RAGE has been described as the receptor for several S100 proteins, including MRP8 and MRP14 (16,17). In vitro studies have demonstrated that MRP8/MRP14 binds to immobilized RAGE (18,19), and that RAGE but not TLR4 associates with MRP8/ MRP14 in colon tumor cells (20). However, studies using TLR4 or RAGE knockout mouse strains indicate that TLR4 is the main receptor that functions during activation of murine phagocytes (9).…”

Specific effect of immunomodulatory quinoline-3-carboxamide ABR-215757 in GM-CSF stimulated bone marrow cell cultures: Block of initiation of proliferation of Gr-1+ cells

“…Along these lines, we have detected a profound reduction of T cell priming in treated mice (our unpublished data). Further, LPS-induced production of the inflammatory cytokine TNF was significantly reduced in 5757-treated mice [5], suggesting that early steps in T cell activation involving interactions between T cells and antigen-presenting cells might be targeted by 5757-treatment.…”