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Hepatokine ?1-Microglobulin Signaling Exacerbates Inflammation and Disturbs Fibrotic Repair in Mouse Myocardial Infarction.

ABSTRACT: Acute cardiac rupture and adverse left ventricular (LV) remodeling causing heart failure are serious complications of acute myocardial infarction (MI). While cardio-hepatic interactions have been recognized, their role in MI remains unknown. We treated cultured cardiomyocytes with conditioned media from various cell types and analyzed the media by mass spectrometry to identify ?1-microglobulin (AM) as an Akt-activating hepatokine. In mouse MI model, AM protein transiently distributed in the infarct and border zones during the acute phase, reflecting infiltration of AM-bound macrophages. AM stimulation activated Akt, NF?B, and ERK signaling and enhanced inflammation as well as macrophage migration and polarization, while inhibited fibrogenesis-related mRNA expression in cultured macrophages and cardiac fibroblasts. Intramyocardial AM administration exacerbated macrophage infiltration, inflammation, and matrix metalloproteinase 9 mRNA expression in the infarct and border zones, whereas disturbed fibrotic repair, then provoked acute cardiac rupture in MI. Shotgun proteomics and lipid pull-down analysis found that AM partly binds to phosphatidic acid (PA) for its signaling and function. Furthermore, systemic delivery of a selective inhibitor of diacylglycerol kinase ?-mediated PA synthesis notably reduced macrophage infiltration, inflammation, matrix metalloproteinase activity, and adverse LV remodeling in MI. Therefore, targeting AM signaling could be a novel pharmacological option to mitigate adverse LV remodeling in MI.

SUBMITTER: Hakuno D

PROVIDER: S-EPMC6233179 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Hepatokine α1-Microglobulin Signaling Exacerbates Inflammation and Disturbs Fibrotic Repair in Mouse Myocardial Infarction.

Hakuno Daihiko D Kimura Masahiro M Ito Shinji S Satoh Junko J Nakashima Yasuhiro Y Horie Takahiro T Kuwabara Yasuhide Y Nishiga Masataka M Ide Yuya Y Baba Osamu O Nishi Hitoo H Nakao Tetsushi T Nishino Tomohiro T Nakazeki Fumiko F Koyama Satoshi S Hanada Ritsuko R Randolph Ruiz R RR Endo Jin J Kimura Takeshi T Ono Koh K

Scientific reports 20181113 1

Acute cardiac rupture and adverse left ventricular (LV) remodeling causing heart failure are serious complications of acute myocardial infarction (MI). While cardio-hepatic interactions have been recognized, their role in MI remains unknown. We treated cultured cardiomyocytes with conditioned media from various cell types and analyzed the media by mass spectrometry to identify α1-microglobulin (AM) as an Akt-activating hepatokine. In mouse MI model, AM protein transiently distributed in the infa ...[more]

PMID: 30425314

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Project description:BackgroundPreclinical data suggest that an acute inflammatory response following myocardial infarction (MI) accelerates systemic atherosclerosis. Using combined positron emission and computed tomography, we investigated whether this phenomenon occurs in humans.Methods and resultsOverall, 40 patients with MI and 40 with stable angina underwent thoracic 18F-fluorodeoxyglucose combined positron emission and computed tomography scan. Radiotracer uptake was measured in aortic atheroma and nonvascular tissue (paraspinal muscle). In 1003 patients enrolled in the Global Registry of Acute Coronary Events, we assessed whether infarct size predicted early (≤30 days) and late (>30 days) recurrent coronary events. Compared with patients with stable angina, patients with MI had higher aortic 18F-fluorodeoxyglucose uptake (tissue-to-background ratio 2.15±0.30 versus 1.84±0.18, P<0.0001) and plasma C-reactive protein concentrations (6.50 [2.00 to 12.75] versus 2.00 [0.50 to 4.00] mg/dL, P=0.0005) despite having similar aortic (P=0.12) and less coronary (P=0.006) atherosclerotic burden and similar paraspinal muscular 18F-fluorodeoxyglucose uptake (P=0.52). Patients with ST-segment elevation MI had larger infarcts (peak plasma troponin 32 300 [10 200 to >50 000] versus 3800 [1000 to 9200] ng/L, P<0.0001) and greater aortic 18F-fluorodeoxyglucose uptake (2.24±0.32 versus 2.02±0.21, P=0.03) than those with non-ST-segment elevation MI. Peak plasma troponin concentrations correlated with aortic 18F-fluorodeoxyglucose uptake (r=0.43, P=0.01) and, on multivariate analysis, independently predicted early (tertile 3 versus tertile 1: relative risk 4.40 [95% CI 1.90 to 10.19], P=0.001), but not late, recurrent MI.ConclusionsThe presence and extent of MI is associated with increased aortic atherosclerotic inflammation and early recurrent MI. This finding supports the hypothesis that acute MI exacerbates systemic atherosclerotic inflammation and remote plaque destabilization: MI begets MI.Clinical trial registrationURL: https://www.clinicaltrials.gov. Unique identifier: NCT01749254.

Project description:In adult mammals, massive sudden loss of cardiomyocytes after infarction overwhelms the limited regenerative capacity of the myocardium, resulting in the formation of a collagen-based scar. Necrotic cells release danger signals, activating innate immune pathways and triggering an intense inflammatory response. Stimulation of toll-like receptor signaling and complement activation induces expression of proinflammatory cytokines (such as interleukin-1 and tumor necrosis factor-?) and chemokines (such as monocyte chemoattractant protein-1/ chemokine (C-C motif) ligand 2 [CCL2]). Inflammatory signals promote adhesive interactions between leukocytes and endothelial cells, leading to extravasation of neutrophils and monocytes. As infiltrating leukocytes clear the infarct from dead cells, mediators repressing inflammation are released, and anti-inflammatory mononuclear cell subsets predominate. Suppression of the inflammatory response is associated with activation of reparative cells. Fibroblasts proliferate, undergo myofibroblast transdifferentiation, and deposit large amounts of extracellular matrix proteins maintaining the structural integrity of the infarcted ventricle. The renin-angiotensin-aldosterone system and members of the transforming growth factor-? family play an important role in activation of infarct myofibroblasts. Maturation of the scar follows, as a network of cross-linked collagenous matrix is formed and granulation tissue cells become apoptotic. This review discusses the cellular effectors and molecular signals regulating the inflammatory and reparative response after myocardial infarction. Dysregulation of immune pathways, impaired suppression of postinfarction inflammation, perturbed spatial containment of the inflammatory response, and overactive fibrosis may cause adverse remodeling in patients with infarction contributing to the pathogenesis of heart failure. Therapeutic modulation of the inflammatory and reparative response may hold promise for the prevention of postinfarction heart failure.

Project description:Rationale: The transformation of fibroblasts into activated myofibroblasts is a critical step that results in cardiac fibrosis upon myocardial infarction (MI). Leucine-rich repeat-containing protein-8A (LRRC8A) is a multi-functional protein involved in cell survival, growth, and proliferation, whereas its role in regulating myofibroblast phenotypes and myocardial fibrosis remains unknown. Methods: Conditional myofibroblast-specific Lrrc8a knockout mouse models were established by crossing the Lrrc8a flox/flox mice with the tamoxifen-inducible periostin-Cre transgenic mice. The involvement of LRRC8A in regulating cardiac fibrosis post-MI and myofibroblast phenotypes induced by transforming growth factor-β1 (TGF-β1) was comprehensively evaluated. The mechanisms underlying LRRC8A regulation of myofibroblast phenotypes were determined by RNA sequencing-driven analysis followed by cause-effect experiments. Results: LRRC8A expression was significantly elevated in the fibrotic tissues and the fibroblasts isolated from the post-MI hearts. Compared with the wild-type (WT) littermates, the specific knockout of LRRC8A in myofibroblasts greatly attenuated myofibroblast transformation, fibrotic remodeling, and ventricular dysfunction after MI. Silencing of LRRC8A expression suppressed, whereas overexpression of LRRC8A enhanced, the pro-fibrotic myofibroblast phenotypes in isolated cardiac fibroblasts upon stimulation with TGF-β1. LRRC8A participated in TGF-β1-induced myofibroblast transformation via activating JAK2-STAT3 signaling. Furthermore, LRRC8A activated the JAK2-STAT3 pathway via its C-terminal leucine-rich repeat-domain (LRRD), directly interacting with growth factor receptor-bound protein 2 (GRB2), an adaptor protein associated with and necessary for tyrosine-phosphorylated JAK2. Conclusions: LRRC8A regulates myofibroblast transformation and cardiac fibrosis following MI. LRRC8A inhibition might be a promising strategy for cardiac fibrosis and heart failure.

Dataset Information

Hepatokine ?1-Microglobulin Signaling Exacerbates Inflammation and Disturbs Fibrotic Repair in Mouse Myocardial Infarction.

Publications

Hepatokine α1-Microglobulin Signaling Exacerbates Inflammation and Disturbs Fibrotic Repair in Mouse Myocardial Infarction.

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