title: Adenosine A3 receptors negatively regulate the engulfment-dependent apoptotic cell suppression of inflammation.
abstract: Timed initiation of apoptotic cell death followed by efficient removal mediated by professional macrophages is a key mechanism in maintaining tissue homeostasis. Besides phagocytosis, clearance of apoptotic cells also involves suppression of inflammatory responses by apoptotic cells mediated by both direct inhibition of pro-inflammatory cytokine production and release of soluble anti-inflammatory factors, which act in a paracrine or autocrine fashion to amplify or sustain the anti-inflammatory response. Previous work has demonstrated that during engulfment of apoptotic cells adenosine is produced in sufficient amounts to trigger both adenosine A2A receptors (A2ARs) and A3 receptors (A3Rs). Adenosine bound to A2ARs of macrophages activated the adenylate cyclase pathway to suppress the apoptotic-cell induced, NO-dependent formation of neutrophil migration factors. Here we show by using A3R null engulfing macrophages that the adenosine produced triggers the A3Rs as well, which attenuate the A2AR signaling by inhibiting adenylate cyclase. As a result, the balance in the activation of A2ARs and A3Rs determines the amounts of NO and consequently the levels of neutrophil chemoattractants formed. Since during phagocytosis of apoptotic cells the expression of A2ARs increases, while that of A3Rs decreases, on long term adenosine suppresses the proinflammatory responses in engulfing macrophages.
authors.affiliation: Department of Dental Biochemistry, Research Center of Molecular Medicine, University of Debrecen, Debrecen H-4012, Hungary.
authors.forename: Edina
authors.initials: E
authors.lastname: Duró
authors.affiliation: Department of Dental Biochemistry, Research Center of Molecular Medicine, University of Debrecen, Debrecen H-4012, Hungary.
authors.forename: Anna
authors.initials: A
authors.lastname: Pallai
authors.affiliation: Department of Dental Biochemistry, Research Center of Molecular Medicine, University of Debrecen, Debrecen H-4012, Hungary.
authors.forename: Krisztina
authors.initials: K
authors.lastname: Köröskényi
authors.affiliation: Department of Biochemistry and Molecular Biology, Research Center of Molecular Medicine, University of Debrecen, Debrecen H-4012, Hungary.
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Sarang
authors.affiliation: Department of Dental Biochemistry, Research Center of Molecular Medicine, University of Debrecen, Debrecen H-4012, Hungary. Electronic address: szondy@med.unideb.hu.
authors.forename: Zsuzsa
authors.initials: Z
authors.lastname: Szondy
mesh_terms: D000241:Adenosine / Q000235:genetics / Q000276:immunology*; D000262:Adenylyl Cyclases / Q000235:genetics / Q000276:immunology; D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000276:immunology*; D019898:Autocrine Communication / Q000502:physiology; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D009504:Neutrophils / Q000166:cytology / Q000276:immunology; D019899:Paracrine Communication / Q000502:physiology; D010587:Phagocytosis / Q000502:physiology*; D043705:Receptor, Adenosine A2A / Q000235:genetics / Q000276:immunology; D043684:Receptor, Adenosine A3 / Q000235:genetics / Q000276:immunology*
chemical_list: D043705:Receptor, Adenosine A2A; D043684:Receptor, Adenosine A3; D000262:Adenylyl Cyclases; D000241:Adenosine
keywords: Adenosine; Apoptosis; Inflammation; Macrophages; Phagocytosis; Signal transduction