Search

Interferon regulatory factor 2 binding protein 2 (Irf2bp2), a co-repressor of Irf2, is required for fetal hepatic erythropoiesis through the expansion of erythromyeloid progenitors. Mice with germline ablation of the entire Irf2bp2 transcript produced no viable Irf2bp2-null pups in first litters. In subsequent litters, fewer than 1/3 of the expected Irf2bp2-null pups were born and half survived to adulthood. As in humans with somatic mutations in IRF2BP2, adult Irf2bp2- null mice developed lymphoma. Transcriptome profiling of liver, heart, and skeletal muscle from Irf2bp2-null adult mice revealed a predominant upregulation of interferon-responsive genes. Of interest, hematopoietic stem cell-enriched transcription factors (Etv6, Fli1, Ikzf1, and Runx1) were also elevated in Irf2bp2-null livers. Intriguingly, Irf2bp2-positive myeloid (but not lymphoid) cells were detected in the livers of adult Irf2bp2-null mice. In female Irf2bp2-null mice, these cells carried a Y chromosome while in male Irf2bp2-null livers, no cells with Barr bodies (inactivated X chromosomes) were detected, indicating that Irf2bp2-positive erythromyeloid cells might be acquired only from male siblings of prior litters by transmaternal microchimerism. These cells likely rescue the deficit in fetal erythropoiesis, but not adult-onset lymphomagenesis, caused by Irfb2p2 ablation. [ABSTRACT FROM AUTHOR]

Objective: Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a circulating protein that promotes degradation of the low density lipoprotein (LDL) receptor. Mutations that block PCSK9 secretion reduce LDL-cholesterol and the incidence of myocardial infarction (MI). However, it remains unclear whether elevated plasma PCSK9 associates with coronary atherosclerosis (CAD) or more directly with rupture of the plaque causing MI. Methods and Results: Plasma PCSK9 was measured by ELISA in 645 angiographically defined controls (<30% coronary stenosis) and 3,273 cases of CAD (>50% stenosis in a major coronary artery) from the Ottawa Heart Genomics Study. Because lipid lowering medications elevated plasma PCSK9, confounding association with disease, only individuals not taking a lipid lowering medication were considered (279 controls and 492 with CAD). Replication was sought in 357 controls and 465 with CAD from the Emory Cardiology Biobank study. PCSK9 levels were not associated with CAD in Ottawa, but were elevated with CAD in Emory. Plasma PCSK9 levels were elevated in 45 cases with acute MI (363.5±140.0 ng/ml) compared to 398 CAD cases without MI (302.0±91.3 ng/ml, p = 0.004) in Ottawa. This finding was replicated in the Emory study in 74 cases of acute MI (445.0±171.7 ng/ml) compared to 273 CAD cases without MI (369.9±139.1 ng/ml, p = 3.7×10−4). Since PCSK9 levels were similar in CAD patients with or without a prior (non-acute) MI, our finding suggests that plasma PCSK9 is elevated either immediately prior to or at the time of MI. Conclusion: Plasma PCSK9 levels are increased with acute MI. [ABSTRACT FROM AUTHOR]

Background: Interferon Regulatory Factor 2 Binding Protein 2 (IRF2BP2) is an anti-inflammatory transcription co-factor in innate immunity. A 9 nucleotide deletion polymorphism in the 3'UTR of IRF2BP2 associates with coronary artery disease risk through an unknown mechanism. Hypothesis: The deletion disrupts regulation of IRF2BP2 mRNA translation and protein levels. Methods: The indel's effect on innate immune activation was evaluated following LPS stimulation of primary human aortic smooth muscle cells (HAoSMC) either homozygous non-risk (HNR) or heterozygous (HET) carrying 1 copy of the risk allele. The same experiment was carried out in HNR THP-1 macrophages. Western blots evaluated IRF2BP2 protein expression. RNA gel shifts using cytoplasmic extracts from THP-1 cells with risk and non-risk probes evaluated binding of RNA-binding proteins in response to LPS. Various antibodies for RNA-binding proteins and to IRF2BP2 as a control were tested for their ability to supershift or compete for binding to the RNA probes. Results: IRF2BP2 levels increase at 24 and 48hrs after LPS treatment in HNR HAoSMCs, but decrease within 4 hours and stay down at 48 hours in HNR THP-1 macrophages. HET HAoSMCs show reduced IRF2BP2 by 48 hours. RNA gel shift revealed selective binding to the non-risk probe using LPS-stimulated THP-1 cell extracts. While none of the antibodies to known RNA-binding proteins affected binding of the LPS-activated complex to the non-risk RNA probe, the IRF2BP2 antibody competed for binding, revealing a novel putative auto-regulatory RNA-binding function for IRF2BP2 that is disrupted by the deletion (risk) polymorphism. Conclusions: Regulation of IRF2BP2 is tissue-specific. Reduced expression of IRF2BP2 in HAoSMCs that carry the deletion allele may promote inflammation, foam cell and atherosclerotic lesion formation by disrupting an auto-regulatory control mechanism. [ABSTRACT FROM AUTHOR]

Interferon regulatory factor 2 binding protein 2 (IRF2BP2) suppresses the innate inflammatory response of macrophages. A 9-nucleotide deletion (rs3045215) in the 3' untranslated region (3'-UTR) of human IRF2BP2 mRNA confers risk of coronary artery disease (CAD) in the Ottawa Heart Genomics Study (OHGS). Here, we sought to identify regulatory mechanisms that may contribute to this risk. We tested how lipopolysaccharides (LPS) affects IRF2BP2 expression in human THP-1 macrophages and primary aortic smooth muscle cells (HAoSMC) genotyped for the deletion allele. Both cell types are implicated in coronary atherosclerosis. We also examined how the deletion affects interaction with RNA binding proteins (RBPs) to regulate IRF2BP2 expression. LPS altered allele-specific binding of RBPs in RNA gel shift assays with the THP-1 macrophage protein extracts. The RBP ELAVL1 suppressed the expression of a luciferase reporter carrying the 3'UTR of IRF2BP2 with the deletion allele. Other RBPs AUF1 or KHSRP did not confer such allele specific regulation. Since it is co-inherited with a risk variant for osteoporosis, a condition tied to arterial calcification, we examined the association of the deletion allele with coronary artery calcification in individuals who had undergone computed tomography angiography in the OHGS. In 323 individuals with a minimal burden of atherosclerosis (<30% coronary stenosis) and 138 CAD cases (>50% stenosis), Mendelian randomization revealed that the rs3045215 deletion allele significantly increased coronary artery calcification in men with minimal coronary stenosis. Thus, not only does the rs3045215 deletion allele predict atherosclerosis, but it also predisposes to early-onset calcification in men., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Vilmundarson, Duong, Soheili, Chen and Stewart.)

Background: Genetic variation at chromosome 9p21 is a recognized risk factor for coronary heart disease (CHD). However, its effect on disease progression and subsequent events is unclear, raising questions about its value for stratification of residual risk., Methods: A variant at chromosome 9p21 (rs1333049) was tested for association with subsequent events during follow-up in 103 357 Europeans with established CHD at baseline from the GENIUS-CHD (Genetics of Subsequent Coronary Heart Disease) Consortium (73.1% male, mean age 62.9 years). The primary outcome, subsequent CHD death or myocardial infarction (CHD death/myocardial infarction), occurred in 13 040 of the 93 115 participants with available outcome data. Effect estimates were compared with case/control risk obtained from the CARDIoGRAMplusC4D consortium (Coronary Artery Disease Genome-wide Replication and Meta-analysis [CARDIoGRAM] plus The Coronary Artery Disease [C4D] Genetics) including 47 222 CHD cases and 122 264 controls free of CHD., Results: Meta-analyses revealed no significant association between chromosome 9p21 and the primary outcome of CHD death/myocardial infarction among those with established CHD at baseline (GENIUS-CHD odds ratio, 1.02; 95% CI, 0.99-1.05). This contrasted with a strong association in CARDIoGRAMPlusC4D odds ratio 1.20; 95% CI, 1.18-1.22; P for interaction <0.001 compared with the GENIUS-CHD estimate. Similarly, no clear associations were identified for additional subsequent outcomes, including all-cause death, although we found a modest positive association between chromosome 9p21 and subsequent revascularization (odds ratio, 1.07; 95% CI, 1.04-1.09)., Conclusions: In contrast to studies comparing individuals with CHD to disease-free controls, we found no clear association between genetic variation at chromosome 9p21 and risk of subsequent acute CHD events when all individuals had CHD at baseline. However, the association with subsequent revascularization may support the postulated mechanism of chromosome 9p21 for promoting atheroma development.

Background: The Genetics of Subsequent Coronary Heart Disease (GENIUS-CHD) consortium was established to facilitate discovery and validation of genetic variants and biomarkers for risk of subsequent CHD events, in individuals with established CHD., Methods: The consortium currently includes 57 studies from 18 countries, recruiting 185 614 participants with either acute coronary syndrome, stable CHD, or a mixture of both at baseline. All studies collected biological samples and followed-up study participants prospectively for subsequent events., Results: Enrollment into the individual studies took place between 1985 to present day with a duration of follow-up ranging from 9 months to 15 years. Within each study, participants with CHD are predominantly of self-reported European descent (38%-100%), mostly male (44%-91%) with mean ages at recruitment ranging from 40 to 75 years. Initial feasibility analyses, using a federated analysis approach, yielded expected associations between age (hazard ratio, 1.15; 95% CI, 1.14-1.16) per 5-year increase, male sex (hazard ratio, 1.17; 95% CI, 1.13-1.21) and smoking (hazard ratio, 1.43; 95% CI, 1.35-1.51) with risk of subsequent CHD death or myocardial infarction and differing associations with other individual and composite cardiovascular endpoints., Conclusions: GENIUS-CHD is a global collaboration seeking to elucidate genetic and nongenetic determinants of subsequent event risk in individuals with established CHD, to improve residual risk prediction and identify novel drug targets for secondary prevention. Initial analyses demonstrate the feasibility and reliability of a federated analysis approach. The consortium now plans to initiate and test novel hypotheses as well as supporting replication and validation analyses for other investigators.

Enhanced postnatal care (EPC) increases resilience to adversity in adulthood. Since microglia participate in shaping neural circuits, we asked how ablation of an inflammation-suppressing factor IRF2BP2 (Interferon Regulatory Factor 2 Binding Protein 2) in microglia would affect the responses to EPC. Mice lacking IRF2BP2 in microglia (KO) and littermate controls (WT) were subjected to EPC during the first 3 weeks after birth. EPC reduced anxiety in WT but not KO mice. This was associated with reduced inflammatory cytokine expression in the hypothalamus. Whole genome RNAseq profiling of the hypothalamus identified 101 genes whose expression was altered by EPC: 95 in WT, 11 in KO, with 5 in common that changed in opposite directions. Proteoglycan 4 (Prg4), prostaglandin D2 synthase (Ptgds) and extracellular matrix protease inhibitor Itih2 were suppressed by EPC in WT but elevated in KO mice. On the other hand, the glutamate transporter VGLUT1 (Slc17a7) was increased by EPC in WT but not KO mice. Prostaglandin D2 (PGD2) is known to enhance microglial inflammation and promote Gfap expression. ELISA confirmed reduced PGD2 in the hypothalamus of WT mice after EPC, associated with reduced Gfap expression. Our study suggests that the anxiety-reducing effect of EPC operates by suppressing microglial inflammation, likely by reducing neuronal prostaglandin D2 production.

Rationale: Inflammation impairs macrophage cholesterol clearance from vascular tissues and promotes atherosclerosis. Inflammatory macrophages suppress expression of the transcription cofactor interferon regulatory factor 2-binding protein 2 (IRF2BP2), and genetic variants near IRF2BP2 associate with ischemic heart disease progression in humans., Objectives: To test whether IRF2BP2 in macrophages affects atherosclerosis in mice and humans., Methods and Results: We generated mice that delete IRF2BP2 in macrophages. IRF2BP2-deficient macrophages worsened atherosclerosis in irradiated low-density lipoprotein receptor null-recipient mice and in apolipoprotein E null mice. IRF2BP2-deficient macrophages were inflammatory and had impaired cholesterol efflux because of their inability to activate the cholesterol transporter ABCA1 in response to cholesterol loading. Their expression of the anti-inflammatory transcription factor Krüppel-like factor 2 was markedly reduced. Promoter studies revealed that IRF2BP2 is required for MEF2-dependent activation of Krüppel-like factor 2. Importantly, restoring Krüppel-like factor 2 in IRF2BP2-deficient macrophages attenuated M1 inflammatory and rescued M2 anti-inflammatory gene activation and improved the cholesterol efflux deficit by restoring ABCA1 activation in response to cholesterol loading. In a cohort of 1066 angiographic cases and 1011 controls, homozygous carriers of a deletion polymorphism (rs3045215) in the 3' untranslated region sequence of human IRF2BP2 mRNA had a higher risk of coronary artery disease (recessive model, odds ratio [95% confidence interval]=1.560 [1.179-2.065], P=1.73E-03) and had lower IRF2BP2 (and Krüppel-like factor 2) protein levels in peripheral blood mononuclear cells. The effect of this deletion polymorphism to suppress protein expression was confirmed in luciferase reporter studies., Conclusion: Ablation of IRF2BP2 in macrophages worsens atherosclerosis in mice, and a deletion variant that lowers IRF2BP2 expression predisposes to coronary artery disease in humans., (© 2015 American Heart Association, Inc.)