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Background & Aims: During progression of liver disease, inflammation affects survival of hepatocytes. Endogenous release of adenosine triphosphate (ATP) in the liver activates purinergic P2 receptors (P2R), which regulate inflammatory responses, but little is known about the roles of these processes in the development of acute hepatitis. Methods: We induced acute hepatitis in C57BL/6 mice by intravenous injection of concanavalin A and then analyzed liver concentrations of ATP and expression of P2R. We assessed P2Y 2 R −/− mice and C57BL/6 wild-type mice injected with suramin, a pharmacologic inhibitor of P2YR. Toxic liver failure was induced in mice by intraperitoneal injection of acetaminophen. Hepatocyte-specific functions of P2R signaling were analyzed in primary mouse hepatocytes. Results: Induction of acute hepatitis in wild-type C57BL/6 mice released large amounts of ATP from livers and induced expression of P2Y2R. Liver damage and necrosis were greatly reduced in P2Y 2 R −/− mice and C57BL/6 mice given injections of suramin. Acetaminophen-induced liver damage was reduced in P2Y 2 R −/− mice. Analysis of liver-infiltrating immune cells during acute hepatitis revealed that expression of P2Y2R in bone marrow−derived cells was required for liver infiltration by neutrophils and subsequent liver damage. Hepatic expression of P2Y2R interfered with expression of genes that regulate cell survival, and promoted tumor necrosis factor−α-mediated cell death, in a cell-autonomous manner. Conclusions: Extracellular ATP and P2Y2R have cell-type specific, but synergistic functions during liver damage that regulate cellular immune responses and promote hepatocyte death. Reagents designed to target P2Y2R might be developed to treat inflammatory liver disease. [ABSTRACT FROM AUTHOR]

Idiopathic pulmonary fibrosis (IPF) is a disease with a poor prognosis and very few available treatment options. The involvement of the purinergic receptor subtypes P2Y 2 and P2X 7 in fibrotic lung disease has been demonstrated recently. In this study, we investigated the role of P2Y 6 receptors in the pathogenesis of IPF in humans and in the animal model of bleomycin-induced lung injury. P2Y 6 R expression was upregulated in lung structural cells but not in bronchoalveolar lavage (BAL) cells derived from IPF patients as well as in animals following bleomycin administration. Furthermore, BAL fluid levels of the P2Y 6 R agonist uridine-5'-diphosphate were elevated in animals with bleomycin-induced pulmonary fibrosis. Inflammation and fibrosis following bleomycin administration were reduced in P2Y 6 R-deficient compared to wild-type animals confirming the pathophysiological relevance of P2Y 6 R subtypes for fibrotic lung diseases. Experiments with bone marrow chimeras revealed the importance of P2Y 6 R expression on lung structural cells for pulmonary inflammation and fibrosis. Similar effects were obtained when animals were treated with the P2Y 6 R antagonist MRS2578. In vitro studies demonstrated that proliferation and secretion of the pro-inflammatory/pro-fibrotic cytokine IL-6 by lung fibroblasts are P2Y 6 R-mediated processes. In summary, our results clearly demonstrate the involvement of P2Y 6 R subtypes in the pathogenesis of pulmonary fibrosis. Thus, blocking pulmonary P2Y 6 receptors might be a new target for the treatment of IPF.

Purinergic receptor activation via extracellular ATP is involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). Nucleoside triphosphate diphosphohydrolase-1/CD39 hydrolyses extracellular ATP and modulates P2 receptor signalling.We aimed to investigate the expression and function of CD39 in the pathogenesis of cigarette smoke-induced lung inflammation in patients and preclinical mouse models. CD39 expression and soluble ATPase activity were quantified in sputum and bronchoalveolar lavage fluid (BALF) cells in nonsmokers, smokers and COPD patients or mice with cigarette smoke-induced lung inflammation. In mice, pulmonary ATP and cytokine concentrations, inflammation and emphysema were analysed in the presence or absence of CD39.Following acute cigarette smoke exposure CD39 was upregulated in BALF cells in smokers with further increases in COPD patients. Acute cigarette smoke exposure induced CD39 upregulation in murine lungs and BALF cells, and ATP degradation was accelerated in airway fluids. CD39 inhibition and deficiency led to augmented lung inflammation; treatment with ATPase during cigarette smoke exposure prevented emphysema.Pulmonary CD39 expression and activity are increased in COPD. CD39 deficiency leads to enhanced emphysema in mice, while external administration of a functional CD39 analogue partially rescues the phenotype. The compensatory upregulation of pulmonary CD39 might serve as a protective mechanism in cigarette smoke-induced lung damage., (Copyright ©ERS 2016.)

Objective: Nucleotides such as ATP, ADP, UTP, and UDP serve as proinflammatory danger signals via purinergic receptors on their release to the extracellular space by activated or dying cells. UDP binds to the purinergic receptor Y6 (P2Y6) and propagates vascular inflammation by inducing the expression of chemokines such as monocyte chemoattractant protein 1, interleukin-8, or its mouse homologsCCL1 (chemokine [C-C motif] ligand 1)/keratinocyte chemokine, CXCL2 (chemokine [C-X-C motif] ligand 2)/macrophage inflammatory protein 2, and CXCL5 (chemokine [C-X-C motif] ligand 5)/LIX, and adhesion molecules such as vascular cell adhesion molecule 1 and intercellular cell adhesion molecule 1. Thus, P2Y6 contributes to leukocyte recruitment and inflammation in conditions such as allergic asthma or sepsis. Because atherosclerosis is a chronic inflammatory disease driven by leukocyte recruitment to the vessel wall, we hypothesized a role of P2Y6 in atherogenesis., Approach and Results: Intraperitoneal stimulation of wild-type mice with UDP induced rolling and adhesion of leukocytes to the vessel wall as assessed by intravital microscopy. This effect was not present in P2Y6-deficient mice. Atherosclerotic aortas of low-density lipoprotein receptor-deficient mice consuming high-cholesterol diet for 16 weeks expressed significantly more transcripts and protein of P2Y6 than respective controls. Finally, P2Y6 (-/-)/low-density lipoprotein receptor-deficient mice consuming high-cholesterol diet for 16 weeks developed significantly smaller atherosclerotic lesions compared with P2Y6 (+/+)/low-density lipoprotein receptor-deficient mice. Bone marrow transplantation identified a crucial role of P2Y6 on vascular resident cells, most likely endothelial cells, on leukocyte recruitment and atherogenesis. Atherosclerotic lesions of P2Y6-deficient mice contained fewer macrophages and fewer lipids as determined by immunohistochemistry. Mechanistically, RNA expression of vascular cell adhesion molecule 1 and interleukin-6 was decreased in these lesions and P2Y6-deficient macrophages took up less modified low-density lipoprotein cholesterol., Conclusions: We show for the first time that P2Y6 deficiency limits atherosclerosis and plaque inflammation in mice., (© 2014 American Heart Association, Inc.)