Search

Background and Aims: We have previously found increased levels of the cysteine protease legumain in plasma and plaques from patients with carotid atherosclerosis. This study further investigated legumain during acute cardiovascular events., Methods: Circulating levels of legumain from patients and legumain released from platelets were assessed by enzyme-linked-immunosorbent assay. Quantitative PCR and immunoblotting were used to study expression, while localization was visualized by immunohistochemistry., Results: In the SUMMIT Malmö cohort (n = 339 with or without type 2 diabetes and/or cardiovascular disease [CVD], and 64 healthy controls), the levels of circulating legumain were associated with the presence of CVD in non-diabetics, with no relation to outcome. In symptomatic carotid plaques and in samples from both coronary and intracerebral thrombi obtained during acute cardiovascular events, legumain was co-localized with macrophages in the same regions as platelets. In vitro, legumain was shown to be present in and released from platelets upon activation. In addition, THP-1 macrophages exposed to releasate from activated platelets showed increased legumain expression. Interestingly, primary peripheral blood mononuclear cells stimulated with recombinant legumain promoted anti-inflammatory responses. Finally, in a STEMI population (POSTEMI; n = 272), patients had significantly higher circulating legumain before and immediately after percutaneous coronary intervention compared with healthy controls (n = 67), and high levels were associated with improved outcome., Conclusions: Our data demonstrate for the first time that legumain is upregulated during acute cardiovascular events and is associated with improved outcome., Competing Interests: Declaration of competing interest The authors declared they do not have anything to disclose regarding conflict of interest with respect to this manuscript., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

Background and Aims: The cysteine protease legumain has been shown to be up-regulated in unstable atherosclerotic plaques. This study aims to further elucidate legumain in atherosclerosis, by examining legumain in plasma and carotid plaques from patients with carotid stenosis. Furthermore, legumain secretion from monocyte-derived macrophages treated with atherogenic lipids during macrophage polarization was studied., Methods: Plasma levels of legumain from patients with carotid stenosis (n = 254), healthy controls (n = 91), and secreted from monocyte-derived macrophages were assessed by enzyme-linked-immunosorbent assay. Quantitative PCR and immunoblotting of legumain were performed on isolated plaques and legumain localization was visualized by immunohistochemistry and fluorescence microscopy. Monocyte-derived macrophages polarized to M1 or M2 macrophages were treated with VLDL, oxLDL or cholesterol crystals (CC) and the level of legumain analysed., Results: Patients with carotid stenosis had significantly higher levels of plasma legumain compared with healthy controls (median 2.0 versus 1.5 ng/ml, respectively; p = 0.003), although there was no correlation between the level of legumain and the degree of stenosis, and legumain was not an independent factor to identify patients with carotid plaques. Moreover, patients with symptoms the last 2 months had higher expressions of mature legumain, cystatin C and E/M, and the macrophage markers CD80 (M1) and CD163 (M2). Legumain co-localized with both M1 and M2 macrophages within plaques, whereas legumain mRNA expression was significantly higher (p < 0.0001) in plaques compared to non-atherosclerotic arteries (controls). Furthermore, in vitro studies showed significantly increased secretion of legumain from pro-inflammatory M1 compared to pro-resolving M2 macrophages (p = 0.014), and particularly in M1 treated with CC. In plaques, legumain was localized to structures resembling foam cells., Conclusions: Legumain is increased in both plasma and plaques of patients with carotid stenosis and might be a new and early biomarker of atherosclerosis., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Macrophages express several lysosomal cysteine proteases such as cathepsins and legumain. In this study, we assessed the expression, activity and secretion of legumain in cellular models of monocytes/macrophages. Macrophages were derived from M-CSF- or GM-CSF/IFNγ-stimulated human primary monocytes (M2 and M1, respectively), PMA-treated human THP-1 cells, or murine RAW264.7 macrophages. In both primary monocytes and THP-1 cells, monocyte-to-macrophage differentiation caused highly increased cellular expression and activity of legumain. Also, secretion of legumain from macrophages, but not from monocytes, was observed. Notably, M2 macrophages expressed significantly higher levels of active legumain than M1 macrophages, which are not previously reported. Legumain mRNA has been shown to be down-regulated in monocytes isolated from patients treated with the HMG-CoA reductase inhibitor atorvastatin. Interestingly, in our study, the active legumain produced by M2 macrophages was found to be inhibited by atorvastatin, which was reflected in aberrant cellular expression and processing.