Hypoxia suppresses the production of MMP-9 by human monocyte-derived dendritic cells and requires activation of adenosine receptor A2b via cAMP/PKA signaling pathway

The migration of dendritic cells (DCs) from the site of antigen-encounter to regional lymphoid organs is crucial for DCs to function as potent antigen-presenting cells. Matrix metalloproteinase-9 (MMP-9) is critically for DCs migration across extracellular matrix (ECM). We verified in previous studies that hypoxia diminished the production of MMP-9 in human monocyte-derived DCs via an unknown mechanism. In this study, we found, for the first time to our knowledge, that hypoxia altered the expression of adenosine receptors on matured DCs (mDCs) toward the predominant expression of adenosine receptor A2b. MRS1754 (an A2b-receptor specific antagonist) was able to counteract the inhibition of hypoxia on MMP-9 by mDCs. We also found that forskolin (a direct adenylate cyclase activator) can mimic the action of hypoxia on the production of MMP-9 by DCs, whereas the adenylate cyclase inhibitor SQ22536 and the PKA inhibitor H89 can abrogate the inhibition of MMP-9 produce by mDCs under hypoxia. The results herein provide initial evidence that the inhibitory effect of hypoxia on MMP-9 by mDCs requires the activation of A2b in a cAMP/PKA-dependent pathway. These data offer new insights into our understanding of the molecular mechanisms underlying the migratory function of DCs in local-tissue hypoxic microenvironments.