title: The atrial natriuretic peptide as a regulator of Kupffer cell functions.
abstract: Kupffer cells (KCs), the resident macrophages of the liver, contribute prominently to liver injury by inflammatory mediators. Pre-conditioning with the atrial natriuretic peptide (ANP), known also as a regulator of macrophage functions, attenuates hepatic ischemia-reperfusion injury. Therefore, the aim of this study was to determine the presence of functional ANP receptors on isolated KCs and to investigate whether this hepatoprotective hormone influences the activation of KCs. KCs were isolated by collagenase/pronase digestion followed by elutrial centrifugation and cultured for 1 to 3 days. Intracellular cyclic guanosine 3'5'-monophosphate (cGMP) concentrations were measured by radioimmunoassay after treating the cells with sodium nitroprusside or ANP. KCs were stimulated with bacterial lipopolysaccharide in the presence or absence of ANP, and inflammatory mediators were determined. Phagocytosis was assayed using Coumarin-labeled latex particles and flow cytometric analysis. Treatment of KCs with ANP but not with sodium nitroprusside resulted in a significant elevation of intracellular cGMP levels indicating functional type A natriuretic peptide receptors (NPR-As). ANP significantly reduced lipopolysaccharide (LPS)-induced tumor necrosis factor alpha (TNFalpha) secretion, paralleled by an increased cell-associated TNFalpha. LPS-induced TNFalpha mRNA expression was not affected. ANP significantly increased phagocytotic activity of KCs via NPR-A. No effect of ANP on LPS-activated inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 protein levels, iNOS mRNA expression, nitric oxide, and PGE2-production was observed. We demonstrated functional cGMP-dependent ANP receptors in isolated rat KCs. ANP reduced TNFalpha release possibly by influencing post-translational processing of TNFalpha in LPS-activated KCs. In addition, we demonstrated that ANP enhances phagocytosis in KCs. These effects may contribute to the hepatoprotective actions of ANP.
authors.affiliation: Department of Pharmacy, Center of Drug Research, Munich, Germany.
authors.forename: Alexandra K
authors.initials: AK
authors.lastname: Kiemer
authors.forename: Andreas
authors.initials: A
authors.lastname: Baron
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Gerbes
authors.forename: Manfred
authors.initials: M
authors.lastname: Bilzer
authors.forename: Angelika M
authors.initials: AM
authors.lastname: Vollmar
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism* / Q000494:pharmacology; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000096:biosynthesis; D006162:Guanylate Cyclase / Q000187:drug effects / Q000378:metabolism; D007527:Isoenzymes / Q000187:drug effects / Q000378:metabolism; D007728:Kupffer Cells / Q000187:drug effects / Q000502:physiology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000187:drug effects / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017461:Receptors, Atrial Natriuretic Factor / Q000187:drug effects / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D000099242:Atrial Natriuretic Factor Receptor B
chemical_list: D009320:Atrial Natriuretic Factor; D006152:Cyclic GMP; D051546:Cyclooxygenase 2; D015232:Dinoprostone; D006162:Guanylate Cyclase; D007527:Isoenzymes; D008070:Lipopolysaccharides; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D011451:Prostaglandin-Endoperoxide Synthases; D012333:RNA, Messenger; D017461:Receptors, Atrial Natriuretic Factor; D014409:Tumor Necrosis Factor-alpha; D000099242:Atrial Natriuretic Factor Receptor B; C016276:8-bromocyclic GMP; C496318:Nos2 protein, rat; C091715:atrial natriuretic factor receptor A