Alu elements in ANRIL non-coding RNA at chromosome 9p21 modulate atherogenic cell functions through trans-regulation of gene networks.

The chromosome 9p21 (Chr9p21) locus of coronary artery disease has been identified in the first surge of genome-wide association and is the strongest genetic factor of atherosclerosis known today. Chr9p21 encodes the long non-coding RNA (ncRNA) antisense non-coding RNA in the INK4 locus (ANRIL). ANRIL expression is associated with the Chr9p21 genotype and correlated with atherosclerosis severity. Here, we report on the molecular mechanisms through which ANRIL regulates target-genes in trans, leading to increased cell proliferation, increased cell adhesion and decreased apoptosis, which are all essential mechanisms of atherogenesis. Importantly, trans-regulation was dependent on Alu motifs, which marked the promoters of ANRIL target genes and were mirrored in ANRIL RNA transcripts. ANRIL bound Polycomb group proteins that were highly enriched in the proximity of Alu motifs across the genome and were recruited to promoters of target genes upon ANRIL over-expression. The functional relevance of Alu motifs in ANRIL was confirmed by deletion and mutagenesis, reversing trans-regulation and atherogenic cell functions. ANRIL-regulated networks were confirmed in 2280 individuals with and without coronary artery disease and functionally validated in primary cells from patients carrying the Chr9p21 risk allele. Our study provides a molecular mechanism for pro-atherogenic effects of ANRIL at Chr9p21 and suggests a novel role for Alu elements in epigenetic gene regulation by long ncRNAs.

Effect of macrophage overexpression of murine liver X receptor-alpha (LXR-alpha) on atherosclerosis in LDL-receptor deficient mice.

UNLABELLED: Background- The nuclear liver X receptor-alpha (LXR-alpha) has been implicated in the regulation of intracellular cholesterol homeostasis, inflammatory response, and atherosclerosis susceptibility. The aim of the present study was to test whether transgenic expression of LXR-alpha might affect these mechanisms and result in a reduction of atherosclerosis. METHODS AND RESULTS: We generated mice with macrophage overexpression of mouse LXR-alpha, evidenced by significantly elevated expression levels of LXR-target genes (ABCA1, ABCG1) in these cells. For atherosclerosis studies, mice were crossed onto the LDL-receptor deficient background. Plasma lipids and lipoproteins as well as liver triglycerides were not significantly different between transgenic animals and nontransgenic controls. However, lesion area at the brachiocephalic artery (BCA) was significantly reduced (-83%, P=0.02) in male LXR-alpha transgenic mice. This was associated with a significantly increased cholesterol efflux to acceptor-free media (+24%, P=0.002) and ApoA1 containing media (+20%, P<0.0001) as well as reduced lipopolysaccharide (LPS)-induced NO-release from macrophages of transgenic animals, providing a potential mechanism for the reduction of atherosclerosis. CONCLUSIONS: Our data show for the first time that transgenic overexpression of LXR-alpha in macrophages has significant antiatherogenic properties. We conclude that overexpression of LXR-alpha in macrophages might be useful as a therapeutic principle for the prevention of atherosclerosis.

Identification of macrophage arginase I as a new candidate gene of atherosclerosis resistance.

OBJECTIVE: Our laboratory has previously created 2 strains of rabbits with genetically determined high-atherosclerotic response (HAR) and low-atherosclerotic response (LAR). The aim of the present study was to identify new genes of atherosclerosis susceptibility in macrophages from the 2 strains. METHODS AND RESULTS: Suppression subtractive hybridization was used to screen for genes with higher expression in macrophages from LAR rabbits. We identified a cDNA fragment with high homology to human arginase I (AI; 91%) and subsequently cloned the full-length cDNA of the rabbit homologue. Quantitative RT-PCR revealed a significantly higher macrophage AI mRNA expression in LAR rabbits than in HAR rabbits (77428+/-10941 versus 34344+/-4538; P=0.002; copies/10(6) copies beta-actin), which also correlated with a significantly higher arginase enzyme activity. Northern blot analysis led to the identification of a size polymorphism of AI mRNA. This was because of a 413 bp C-repeat insertion in the 3' untranslated region. The shorter transcript variant was predominantly expressed in LAR rabbits and associated with significantly higher AI mRNA expression levels. Transfection experiments indicated decreased mRNA stability of the long AI variant. CONCLUSIONS: High expression of arginase I in macrophages may contribute to atherosclerosis resistance of LAR rabbits, possibly by conferring antiinflammatory effects in the vessel wall.

Detection of disseminated pancreatic cells by amplification of cytokeratin-19 with quantitative RT-PCR in blood, bone marrow and peritoneal lavage of pancreatic carcinoma patients.

AIM: To evaluate the diagnostic potential of cytokeratin-19 (CK-19) mRNA for the detection of disseminated tumor cells in blood, bone marrow and peritoneal lavage in patients with ductal adenocarcinoma of the pancreas. METHODS: Sixty-eight patients with pancreatic cancer (n = 37), chronic pancreatitis (n = 16), and non-pancreatic benign surgical diseases (n = 15, control group) were included in the study. Venous blood was taken preoperatively, intraoperatively and at postoperative d 1 and 10. Preoperative bone marrow aspirates and peritoneal lavage taken before mobilization of the tumor were analyzed. All samples were evaluated for disseminated tumor cells by CK-19-specific nested-PCR and quantitative fluorogenic RT-PCR. RESULTS: CK-19 mRNA expression was increased in 24 (64%) blood samples and 11 (30%) of the peritoneal lavage samples in the patients with pancreatic cancer. In 15 (40%) of the patients with pancreatic cancer, disseminated tumor cells were detected in venous blood and bone marrow and/or peritoneal lavage. In the peritoneal lavage, the detection rates were correlated with the tumor size and the tumor differentiation. CK-19 levels were increased in pT3/T4 and moderately/poorly differentiated tumors (G2/G3). Pancreatic cancer patients with at least one CK-19 mRNA-positive sample showed a trend towards shorter survival. Pancreatic cancer patients showed significantly increased detection rates of disseminated tumor cells in blood and peritoneal lavage compared to the controls and the patients with chronic pancreatitis. CONCLUSION: Disseminated tumor cells can be detected in patients with pancreatic ductal adenocarcinoma by CK-19 fluorogenic RT-PCR. In peritoneal lavage, detection rate is correlated with tumor stage and differentiation. In the clinical use, CK-19 is suitable for the distinction between malignant and benign pancreatic disease in combination with other tumor-specific markers.

Molecular Fingerprint for Terminal Abdominal Aortic Aneurysm Disease.

BACKGROUND: Clinical decision making in abdominal aortic aneurysms (AAA) relies completely on diameter. At this point, improved decision tools remain an unmet medical need. Our goal was to identify changes at the molecular level specifically leading up to AAA rupture. METHODS AND RESULTS: Aortic wall tissue specimens were collected during open elective (eAAA; n=31) or emergency repair of ruptured AAA (rAAA; n=17), and gene expression was investigated using microarrays. Identified candidate genes were validated with quantitative real-time polymerase chain reaction in an independent sample set (eAAA: n=46; rAAA: n=18). Two gene sets were identified, 1 set containing 5 genes linked to terminal progression, that is, positively associated with progression of larger AAA, and with rupture (HILPDA, ANGPTL4, LOX, SRPX2, FCGBP), and a second set containing 5 genes exclusively upregulated in rAAA (ADAMTS9, STC1, GFPT2, GAL3ST4, CCL4L1). Genes in both sets essentially associated with processes related to impaired tissue remodeling, such as angiogenesis and adipogenesis. In gene expression experiments we were able to show that upregulated gene expression for identified candidate genes is unique for AAA. Functionally, the selected upregulated factors converge at processes coordinated by the canonical HIF-1α signaling pathway and are highly expressed in fibroblasts but not inflammatory cells of the aneurysmatic wall. Histological quantification of angiogenesis and exploration of the HIF-1α network in rAAA versus eAAA shows enhanced microvessel density but also clear activation of the HIF-1α network in rAAA. CONCLUSIONS: Our study shows a specific molecular fingerprint for terminal AAA disease. These changes appear to converge at activation of HIF-1α signaling in mesenchymal cells. Aspects of this cascade might represent targets for rupture risk assessment.

Circular non-coding RNA ANRIL modulates ribosomal RNA maturation and atherosclerosis in humans.

Circular RNAs (circRNAs) are broadly expressed in eukaryotic cells, but their molecular mechanism in human disease remains obscure. Here we show that circular antisense non-coding RNA in the INK4 locus (circANRIL), which is transcribed at a locus of atherosclerotic cardiovascular disease on chromosome 9p21, confers atheroprotection by controlling ribosomal RNA (rRNA) maturation and modulating pathways of atherogenesis. CircANRIL binds to pescadillo homologue 1 (PES1), an essential 60S-preribosomal assembly factor, thereby impairing exonuclease-mediated pre-rRNA processing and ribosome biogenesis in vascular smooth muscle cells and macrophages. As a consequence, circANRIL induces nucleolar stress and p53 activation, resulting in the induction of apoptosis and inhibition of proliferation, which are key cell functions in atherosclerosis. Collectively, these findings identify circANRIL as a prototype of a circRNA regulating ribosome biogenesis and conferring atheroprotection, thereby showing that circularization of long non-coding RNAs may alter RNA function and protect from human disease.

Rapid detection of the prion protein M129V polymorphism with the LightCycler.

The common single nucleotide polymorphism at codon 129 of the prion protein gene is a key determinant of the genetic susceptibility to Creutzfeldt-Jakob disease (CJD). Recently, a molecular classification of sporadic CJD based on the M129V genotype in conjunction with other determinants was proposed. In the present study, we describe the development and evaluation of a rapid fluorescent-based assay to detect this polymorphism using the LightCycler system. The two polymorphic alleles could be clearly distinguished by their melting points at 52.1 and 60.4 degrees C, representing the 129V and 129M alleles, respectively. These results were confirmed by DNA sequencing. We evaluated our test in 400 patient samples and found no deviations from the expected melting patterns. The calculated allele frequency for the M-allele was 0.66. Thus, we have established a rapid, reliable fluorescent assay for high-throughput detection of the prion protein M129V polymorphism.

Identification of mutations in the lipoprotein lipase (LPL) and apolipoprotein C-II (APOC2) genes using denaturing high performance liquid chromatography (DHPLC).

BACKGROUND: Endothelial lipoprotein lipase (LPL) hydrolyzes triglycerides of chylomicrons and very low density lipoproteins, releasing free fatty acids for local and systemic use. Mutations in the LPL gene or its cofactor APOC2 may result in a decrease or complete loss of enzyme function and subsequently to type I hyperlipoproteinemia. METHODS: We used PCR to amplify all exons and the promoter region of LPL and APOC2. Nine blinded DNA samples with known LPL mutations were used as positive controls. In addition, nine patients from our lipid clinic and twelve healthy subjects were analyzed. DNA was screened for sequence variants by denaturing HPLC (DHPLC) followed by direct sequencing of PCR fragments showing distinct elution profiles. RESULTS: All LPL sequence variants in the positive controls (D9N, V69L, delAACTG386, I225T, N291S, and S447X) were correctly identified. In the remaining patients, additional variants were detected in LPL and APOC2. These variants were also present in healthy subjects, indicating that they constituted silent variation with no relevant effect on plasma triglycerides, at least in the heterozygous state. CONCLUSIONS: A semi-automated DHPLC screening method was developed for the detection of sequence variants in the LPL and APOC2 genes. Our results demonstrate that the method was robust and sensitive.

Genetic regulation of serum phytosterol levels and risk of coronary artery disease.

BACKGROUND: Phytosterols are plant-derived sterols that are taken up from food and can serve as biomarkers of cholesterol uptake. Serum levels are under tight genetic control. We used a genomic approach to study the molecular regulation of serum phytosterol levels and potential links to coronary artery disease (CAD). METHODS AND RESULTS: A genome-wide association study for serum phytosterols (campesterol, sitosterol, brassicasterol) was conducted in a population-based sample from KORA (Cooperative Research in the Region of Augsburg) (n=1495) with subsequent replication in 2 additional samples (n=1157 and n=1760). Replicated single-nucleotide polymorphisms (SNPs) were tested for association with premature CAD in a metaanalysis of 11 different samples comprising 13 764 CAD cases and 13 630 healthy controls. Genetic variants in the ATP-binding hemitransporter ABCG8 and at the blood group ABO locus were significantly associated with serum phytosterols. Effects in ABCG8 were independently related to SNPs rs4245791 and rs41360247 (combined P=1.6 x 10(-50) and 6.2 x 10(-25), respectively; n=4412). Serum campesterol was elevated 12% for each rs4245791 T-allele. The same allele was associated with 40% decreased hepatic ABCG8 mRNA expression (P=0.009). Effects at the ABO locus were related to SNP rs657152 (combined P=9.4x10(-13)). Alleles of ABCG8 and ABO associated with elevated phytosterol levels displayed significant associations with increased CAD risk (rs4245791 odds ratio, 1.10; 95% CI, 1.06 to 1.14; P=2.2 x 10(-6); rs657152 odds ratio, 1.13; 95% CI, 1.07 to 1.19; P=9.4 x 10(-6)), whereas alleles at ABCG8 associated with reduced phytosterol levels were associated with reduced CAD risk (rs41360247 odds ratio, 0.84; 95% CI, 0.78 to 0.91; P=1.3 x 10(-5)). CONCLUSION: Common variants in ABCG8 and ABO are strongly associated with serum phytosterol levels and show concordant and previously unknown associations with CAD.

Effect of macrophage ApoE on atherosclerosis in LDL-receptor deficient mice.

Apolipoprotein E (ApoE) plays an important role in the development of atherosclerosis. Previous studies provide evidence for an atheroprotective role of ApoE in mouse models on the ApoE deficient (ApoE-/-) background. However, it is not clear whether this is also true on the LDL-receptor deficient (LDLR-/-) background. Transgenic mice carrying hApoE coding sequences in a chicken lysozyme expression cassette were generated. Transgene expression was directed into macrophages, expressing low levels of hApoE. Expression of the hApoE transgene was not sufficient to correct hypercholesterolemia. However, lesion area at the brachiocephalic artery (BCA) was significantly reduced (-72%) in female hApoE transgenic mice on the LDLR-/- background. This was associated with increased cholesterol efflux in macrophages of transgenic animals on the ApoE-/- background. We conclude that over-expression of ApoE in macrophages might be useful as a therapeutic principle for the prevention of atherosclerosis.