title: Cross-regulation of carbon monoxide and the adenosine A2a receptor in macrophages.
abstract: Adenosine and heme oxygenase-1 (HO-1) exert a wide range of anti-inflammatory and immunomodulatory actions, making them crucial regulatory molecules. Despite the diversity in their modes of action, the similarity of biological effects of adenosine and HO-1 led us to hypothesize a possible interrelationship between them. We assessed a potential role for HO-1 in the ability of adenosine or 5'-N-ethylcarboxamidoadenosine (NECA), a stable adenosine analog, to modify the response of LPS-stimulated macrophages. Adenosine and NECA markedly induced HO-1 and blocked LPS-induced TNF-alpha production via adenosine A2aR-mediated signaling; blocking of HO-1 by RNA interference abrogated the effects of adenosine and NECA on TNF-alpha. HO-1 overexpression or exposure to carbon monoxide (CO), a product of HO-1 enzymatic activity, resulted in augmented A2aR mRNA and protein levels in RAW264.7 cells and primary macrophages. The induction of A2aR expression by HO-1 or CO resulted in an increase in the sensitivity to the anti-inflammatory effects of adenosine and NECA, which was lost in macrophages isolated from A2aR-deficient mice. Moreover, a decrease in cAMP levels upon NECA stimulation of naive macrophages was counterbalanced by CO exposure to up-regulate A2aR levels. This implies adenosine receptor isoform switch as a selective modification in macrophage phenotype. Taken together, these data suggest the existence of a positive feedback loop among adenosine, HO-1, CO, and the A2aR in the chronological resolution of the inflammatory response.
authors: Transplant and Immunobiology Research Centers, Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, 99 Brookline Avenue, Boston, MA 02215, USA.
authors: Arvand
authors: A
authors: Haschemi
authors: Oswald
authors: O
authors: Wagner
authors: Rodrig
authors: R
authors: Marculescu
authors: Barbara
authors: B
authors: Wegiel
authors: Simon C
authors: SC
authors: Robson
authors: Nicola
authors: N
authors: Gagliani
authors: David
authors: D
authors: Gallo
authors: Jiang-Fan
authors: JF
authors: Chen
authors: Fritz H
authors: FH
authors: Bach
authors: Leo E
authors: LE
authors: Otterbein
mesh_terms: D000241:Adenosine / Q000378:metabolism* / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology; D000818:Animals; D002248:Carbon Monoxide / Q000378:metabolism*; D002478:Cells, Cultured; D015536:Down-Regulation; D051547:Heme Oxygenase-1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D016753:Interleukin-10 / Q000378:metabolism; D018664:Interleukin-12 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D043705:Receptor, Adenosine A2A / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D008070:Lipopolysaccharides; D012333:RNA, Messenger; D043705:Receptor, Adenosine A2A; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D018664:Interleukin-12; D019830:Adenosine-5'-(N-ethylcarboxamide); D002248:Carbon Monoxide; D051547:Heme Oxygenase-1; D000241:Adenosine