Acute-phase protein alpha1-antitrypsin--a novel regulator of angiopoietin-like protein 4 transcription and secretion
SourceJournal of Immunology, 192, 11, (2014), pp. 5354-62
Article / Letter to editor
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Journal of Immunology
SubjectRadboudumc 4: lnfectious Diseases and Global Health RIMLS: Radboud Institute for Molecular Life Sciences
The angiopoietin-like protein 4 (angptl4, also known as peroxisome proliferator-activated receptor [PPAR]gamma-induced angiopoietin-related protein) is a multifunctional protein associated with acute-phase response. The mechanisms accounting for the increase in angptl4 expression are largely unknown. This study shows that human alpha1-antitrypsin (A1AT) upregulates expression and release of angplt4 in human blood adherent mononuclear cells and in primary human lung microvascular endothelial cells in a concentration- and time-dependent manner. Mononuclear cells treated for 1 h with A1AT (from 0.1 to 4 mg/ml) increased mRNA of angptl4 from 2- to 174-fold, respectively, relative to controls. In endothelial cells, the maximal effect on angptl4 expression was achieved at 8 h with 2 mg/ml A1AT (11-fold induction versus controls). In 10 emphysema patients receiving A1AT therapy (Prolastin), plasma angptl4 levels were higher relative to patients without therapy (nanograms per milliliter, mean [95% confidence interval] 127.1 [99.5-154.6] versus 76.8 [54.8-98.8], respectively, p = 0.045) and correlated with A1AT levels. The effect of A1AT on angptl4 expression was significantly diminished in cells pretreated with a specific inhibitor of ERK1/2 activation (UO126), irreversible and selective PPARgamma antagonist (GW9662), or genistein, a ligand for PPARgamma. GW9662 did not alter the ability of A1AT to induce ERK1/2 phosphorylation, suggesting that PPARgamma is a critical mediator in the A1AT-driven angptl4 expression. In contrast, the forced accumulation of HIF-1alpha, an upregulator of angptl4 expression, enhanced the effect of A1AT. Thus, acute-phase protein A1AT is a physiological regulator of angptl4, another acute-phase protein.
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