Function of the A2A receptor-mediated IL-10 regulation

Our current experimental data strongly suggest the adenosine A2A receptor (A2AR) signaling in myeloid immune cell biology to be an attractive target for pharmaceutical manipulation for treating autoimmune diseases, on the one hand and augmenting anti-tumor responses on the other. The proposed research should help fill several important gaps in our knowledge of the immunosuppressive mechanisms of A2AR signaling pathway in an inflamed microenvironment. The IL-10 promoter contains binding sites for the NF-B, CREB, STAT and NFAT:AP-1 transcription factors, and it has been suggested that NF-B, AP-1:NFAT (but not yet CREB1) activate these promoter in immune cells. Employing EMSA analysis we have shown that CREB1 shows A2AR-induced binding activity to the CRE- consensus oligonucleotide in wild-type but not A2AR-deficient cells. In this context, we have first experimental evidence that A2AR may indeed selectively regulate LPS-mediated IL-10 (but not TNF , IL-6 and IL-12p40) transactivation in vivo, at least suggesting one level of regulation represented by the A2AR:CREB1 signaling in TLR4+ myeloid cells. Since this transcriptional regulation under the influence of A2AR:CREB1 appears to be rate limiting for MDSC responses at least in vitro, it is worthwhile to define the relevance of this candidate A2AR:CREB1:IL-10 pathway in MDSC in vivo. Therefore, we aim to determine by ChIP analysis and electrophoretic mobility shift assays whether aberrant CREB1 signaling contributes to the altered expression of IL-10 in these A2AR-/- myeloid cells. Our work thus may demonstrate that A2AR signaling through cAMP:CREB- 1:C:EBPß activation in the myeloid cell subset can control MDSC polarization and/or immunosuppression in autoimmunity and, potentially, other immune disorders. Base on our proof-of-concept validation employing mouse in vivo and immune cell ex vivo analyses clearly confirm a myeloid cell-type specific A2AR:CREB1:IL-10 signaling axis as a non-redundant and essential immune checkpoint candidate in autoimmunity. Thus, the academic mission of this project is the identification of molecular signatures of the A2AR function of MDSC biology during inflammation and autoimmunity employing our established research tools and interdisciplinary state-of-the-art genetic, immunological, biochemical as well as proteomic and genome-wide transcriptomic technologies. This concept, once validated, would demonstrate that targeting A2AR with a selective agonist can reshape the immune microenvironment in inflamed CNS tissue and attenuate autoreactive T cell-mediated tissue damage without targeting the effector T cells directly. This project is therefore ground-breaking for its important basic science implications as fundamental new mechanistic knowledge of key aspects. In this context, a detailed understanding of the underlying molecular mechanisms of immune system control that is governed by adenosine in autoimmunity and, potentially, other immune disorders may represent a promising way to therapeutically modulate signaling thresholds particularly in myeloid cells.

"Pathomechanism of the adenosine 2a receptor (A2aR) revealed in cerebral malaria" Univ.-Prof. Gottfried Baier; http://www.baierlab.com/ The novelty of our FWF research results is based on the preclinical validation of a key role of the A2aR signaling pathway in severe courses of cerebral malaria (CM). Our project success is based on mechanistic insights into the molecular and cellular processes of the lymphatic A2aR and its downstream signaling pathway during a Plasmodium infection. Our successful elaboration of the underlying molecular mechanisms closed the gaps in our knowledge of the A2aR signaling pathway. Our careful research therefore has the potential to be groundbreaking as it has uncovered important basic scientific implications of the A2aR lymphatic axis as a contributor to CD8+ T cell dysfunction in CM. Our current A2aR-centered study complements the ongoing research on CM around the world and could enable innovative strategies to develop new preventive and therapeutic treatment options for CM and thereby reduce the future mortality or neurological impairment of CM-surviving children in malaria-endemic countries, for example mitigate in East Africa. The next logical step is to develop an immunotherapy scheme for CM by repurposing existing A2aR antagonists. Taken together, our research results show a novel role of the A2aR in the cerebral malaria pathogenesis. Thus, cerebral malaria appears to be an easily treatable process and particularly highlights A2aR as an attractive target for pharmaceutical medication in order to significantly reduce the socio-economic burden of cerebral malaria.