Extracellular Adenosine (eAdo) - A2B Receptor Axis Inhibits in Nlrp3 Inflammasome-dependent Manner Trafficking of Hematopoietic Stem/progenitor Cells

Abstract

We postulated that mobilization, homing, and engraftment of hematopoietic stem/progenitor cells (HSCPs) is facilitated by a state of sterile inflammation induced in bone marrow (BM) after administration of pro-mobilizing drugs or in response to pre-transplant myeloablative conditioning. An important role in this phenomenon plays purinergic signaling that by the release of extracellular adenosine triphosphate (eATP) activates in HSPCs and in cells in the hematopoietic microenvironment an intracellular pattern recognition receptor (PPR) known as Nlrp3 inflammasome. We reported recently that its deficiency results in defective trafficking of HSPCs. Moreover, it is known that eATP after release into extracellular space is processed by cell surface expressed ectonucleotidases CD39 and CD73 to extracellular adenosine (eAdo) that in contrast to eATP shows an anti-inflammatory effect. Based on data that the state of sterile inflammation promotes trafficking of HSPCs, and since eAdo is endowed with anti-inflammatory properties we become interested in how eAdo will affect the mobilization, homing, and engraftment of HSPCs and which of eAdo receptors are involved in these processes. As expected, eAdo impaired HSPCs trafficking and this occurred in autocrine- and paracrine-dependent manner by direct stimulation of these cells or by affecting cells in the BM microenvironment. We report herein for the first time that this defect is mediated by activation of the A2B receptor and a specific inhibitor of this receptor improves eAdo-aggravated trafficking of HSPCs. To explain this at the molecular level eAdo-A2B receptor interaction upregulates in HSPCs in NF-kB-, NRF2- and cAMP-dependent manner heme oxygenase-1 (HO-1), that is Nlrp3 inflammasome inhibitor. This corroborated with our analysis of proteomics signature in murine HSPCs exposed to eAdo that revealed that A2B inhibition promotes cell migration and proliferation. Based on this we postulate that blockage of A2B receptor may accelerate the mobilization of HSPCs as well as their hematopoietic reconstitution and this approach could be potentially considered in the future to be tested in the clinic. Graphical Abstract

Murine and human-purified very small embryonic-like stem cells (VSELs) express purinergic receptors and migrate to extracellular ATP gradient.

“…Since the chemotactic responsiveness of several cell types to eATP is regulated negatively by eAdo and VSELs express P1 receptors, we evaluated chemotaxis to eATP alone and in the presence of added eAdo. As expected, chemotactic response was inhibited in the presence of eAdo [19]. Our previous research also demonstrated that cell migration to the eATP gradient depends on activating intracellular pattern recognition receptor -Nlrp3 in ammasome [20].…”

ADA2 regulates inflammation and hematopoietic stem cell emergence via the A2bR pathway in zebrafish

“…To delve deeper into the molecular mechanisms involved in the generation of such phenotypes, we explored the interplay between the A 2b R/PKA pathway and inflammation, and we successfully rescued the inflammatory phenotype observed in cecr1b -deficient zebrafish embryos by inhibiting it. A 2b R-mediated purinergic signaling also inhibits the mobilization, homing, and engraftment of cultured HSPCs 54 , 79 , 80 . This process involves the inflammasome, a multiprotein complex responsible for activating pro-inflammatory cytokines, such as IL-1β and IL-18, thus leading to an inflammatory response that negatively affects HSPC migration and integration into the target tissue 54 , 79 , 80 .…”

“…Moreover, A 2b R has been associated with several pathological mechanisms, such as inflammation, leukocyte and endothelial function, and specification and maintenance of hematopoietic stem progenitor cells (HSPCs) 48 – 54 . For instance, A 2b R mediates the pro-inflammatory action of eAdo in monocytes and endothelial cells and reduces HSPC proliferation and mobilization 49 – 52 , 54 , 55 .…”

External Liver-Derived Complement and Intrinsic Present in Hematopoietic Stem/Progenitor Cells Complosome Modulate Cell Metabolism and Response to Stress

“…Recent evidence indicates that a state of sterile inflammation is triggered in BM mainly by complement cascade (ComC) cleavage fragments C3a and C5a with the participation of an important mediator of purinergic signaling that is extracellular adenosine triphosphate (eATP) [6,10]. HSCPs that reside in hematopoietic tissues, to respond appropriately to pro-inflammatory mediators, must adjust their metabolism to meet new challenges.…”