Aortic Gene Expression Research Articles

Short-term hyperglycaemia causes non-reversible changes in arterial gene expression in a fully ‘switchable’ in vivo mouse model of diabetes

Irreversible arterial damage due to early effects of hypo- or hyperglycaemia could account for the limited success of glucose-lowering treatments in preventing cardiovascular disease (CVD) events. We hypothesised that even brief hypo- or hyperglycaemia could adversely affect arterial gene expression and that these changes, moreover, might not be fully reversible. By controlled activation of a 'switchable' c-Myc transgene in beta cells, adult pIns-c-MycER(TAM) mice were rendered transiently hypo- and then hyperglycaemic, after which they were allowed to recover for up to 3 months. Immediate and sequential changes in aortic global gene expression from normal glycaemia through hypo- and hyperglycaemia to recovery were assessed. Gene expression was compared with that of normoglycaemic transgenic and tamoxifen-treated wild-type controls. Overall, expression of 95 genes was significantly affected by moderate hypoglycaemia (glucose down to 2.5 mmol/l), whereas over 769 genes were affected by hyperglycaemia. Genes and pathways activated included several involved in atherogenic processes, such as inflammation and arterial calcification. Although expression of many genes recovered to initial pre-exposure levels when hyperglycaemia was corrected (74.9%), in one in four genes this did not occur. Quantitative reverse transcriptase PCR and immunohistochemistry verified the gene expression patterns of key molecules, as shown by global gene arrays. Short-term exposure to hyperglycaemia can cause deleterious and persistent changes in arterial gene expression in vivo. Brief hypoglycaemia also adversely affects gene expression, although less substantially. Together, these results suggest that early correction of hyperglycaemia and avoidance of hypoglycaemia may both be necessary to avoid excess CVD risk in diabetes.

In Utero Exposure to Maternal Diabetes Impairs Vascular Expression of Prostacyclin Receptor in Rat Offspring

OBJECTIVETo evaluate modifications of arterial structure, gene expression, and function in our model of rats exposed to maternal diabetes.RESEARCH DESIGN AND METHODSMorphometric analyses of elastic vessels structure and determination of thoracic aortic gene expression profile with oligonucleotide chips (Agilent, G4130, 22k) were performed before the onset of established hypertension (3 months).RESULTSArterial parameters of in situ fixed thoracic aorta were not significantly different between control mother offspring and diabetic mother offspring (DMO). The aortic gene expression profile of DMO is characterized by modifications of several members of the arachidonic acid metabolism including a twofold underexpression of prostacyclin receptor, which could contribute to decreased vasodilatation. This was confirmed by ex vivo experiments on isolated aortic rings. Pharmacological studies on conscious rats showed that systolic blood pressure decline in response to a PGI2 analog was impaired in DMO rats.CONCLUSIONSThese results suggest an abnormal vascular fetal programming of prostacyclin receptor in rats exposed in utero to maternal hyperglycemia that is associated with impaired vasodilatation and may be involved in the pathophysiology of hypertension in this model.

Hyperglycemia modulates plasminogen activator inhibitor-1 expression and aortic diameter in experimental aortic aneurysm disease

Extracellular matrix degradation is a sentinel pathologic feature of abdominal aortic aneurysm (AAA) disease. Diabetes mellitus, a negative risk factor for AAA, may impair aneurysm progression through its influence on the fibrinolytic system. We hypothesize that hyperglycemia limits AAA progression through effects on endogenous plasminogen activator inhibitor-1 (PAI-1) levels and subsequent reductions in plasmin generation. Experimental AAAs were induced in diabetic and control mice via the intra-aortic elastase infusion method. Serial transabdominal high-frequency ultrasound examinations were performed to monitor aortic diameter following elastase infusion. Circulating PAI-1 and plasmin alpha2-antiplasmin (PAP) complex concentrations were determined by ELISA and local expression of PAI-1 levels was examined by RT-PCR and immunohistochemistry. Hyperglycemia was associated with reduced AAA diameter, increased plasma PAI-1 concentration and reduced plasmin generation. Aneurysmal aortic PAI-1 gene expression increased in parallel with plasma concentration, with peak expression occurring early after aneurysm initiation. Hyperglycemia increases PAI-1 expression and attenuates AAA diameter in experimental AAA disease. These results emphasize the role of the fibrinolytic pathway in AAA pathophysiology, and suggest a candidate mechanism for hyperglycemic inhibition of AAA disease.

The Mouse Atherosclerosis Locus at Chromosome 10 ( Ath11 ) Acts Early in Lesion Formation With Subcongenic Strains Delineating 2 Narrowed Regions

Ath11, an atherosclerosis susceptibility locus on proximal chromosome 10 (0 to 21 cM) revealed in a cross between apolipoprotein E deficient C57BL/6 (B6) and FVB mice, was recently confirmed in congenic mice. The objectives of this study were to assess how Ath11 affects lesion development and morphology, to determine aortic gene expression in congenics, and to narrow the congenic interval. Assessing lesion area over time in congenic mice showed that homozygosity for the FVB allele increased lesion area at 6 weeks persisting through to 24 weeks of age. Staining of aortic root sections at 16 weeks did not reveal obvious differences between congenics. Aortic expression-array analysis at 6 weeks revealed 97 genes that were >2-fold regulated, including 1 gene in the quantitative trait locus interval, Aldh8a1, and 2 gene clusters regulated by Hnf4alpha and Esr1. Analysis of lesion area in 11 subcongenic strains revealed 2 narrowed regions, 10a (21 genes), acting in females, and 10b (7 genes), acting in both genders. Ath11 appears to act early in lesion formation, with significant effects on aortic gene expression. This quantitative trait locus is genetically complex, containing a female-specific region 10a from 0 to 7.3 megabases (21 genes) and a gender-independent region 10b from 20.1 to 21.9 megabases (7 genes).

Secretory Phospholipase A2, Group IIA Is a Novel Serum Amyloid A Target Gene: ACTIVATION OF SMOOTH MUSCLE CELL EXPRESSION BY AN INTERLEUKIN-1 RECEPTOR-INDEPENDENT MECHANISM

Atherosclerosis is a multifactorial vascular disease characterized by formation of inflammatory lesions. Elevated circulating acute phase proteins indicate disease risk. Serum amyloid A (SAA) is one such marker but its function remains unclear. To determine the role of SAA on aortic smooth muscle cell gene expression, a preliminary screen of a number of genes was performed and a strong up-regulation of expression of secretory phospholipase A(2), group IIA (sPLA(2)) was identified. The SAA-induced increase in sPLA(2) was validated by real time PCR, Western blot analysis, and enzyme activity assays. Demonstrating that SAA increased expression of sPLA(2) heteronuclear RNA and that inhibiting transcription eliminated the effect of SAA on sPLA(2) mRNA suggested that the increase was transcriptional. Transient transfections and electrophoretic mobility shift assays identified CAAT enhancer-binding protein (C/EBP) and nuclear factor kappaB (NFkappaB) as key regulatory sites mediating the induction of sPLA(2). Moreover, SAA activated the inhibitor of NF-kappaB kinase (IKK) in cultured smooth muscle cells. Previous reports showed that interleukin (IL)-1beta up-regulates Pla2g2a gene transcription via C/EBPbeta and NFkappaB. Interestingly, SAA activated smooth muscle cell IL-1beta mRNA expression, however, blocking IL-1 receptors had no effect on SAA-mediated activation of sPLA(2) expression. Thus, the observed changes in sPLA(2) expression were not secondary to SAA-induced IL-1 receptor activation. The association of SAA with high density lipoprotein abrogated the SAA-induced increase in sPLA(2) expression. These data suggest that during atherogenesis, SAA can amplify the involvement of smooth muscle cells in vascular inflammation and that this can lead to deposition of sPLA(2) and subsequent local changes in lipid homeostasis.

Growth Hormone-Releasing Peptide-2 Suppresses Vascular Oxidative Stress in ApoE−/− Mice But Does Not Reduce Atherosclerosis

GH-releasing peptide-2 (GHRP-2) is a synthetic peptide that increases circulating GH and IGF-I levels. It also binds to CD36, a scavenger receptor for oxidized low-density lipoprotein (OxLDL), and may prevent cellular uptake of this proatherogenic complex. To determine its potential antiatherogenic effects, GHRP-2 (20 microg twice daily) was administered sc to ApoE(-/-) mice for 12 wk. GHRP-2 increased circulating IGF-I 1.2- to 1.6-fold and decreased circulating interferon-gamma by 66%. Although GHRP-2 did not alter atherosclerotic plaque area, it decreased aortic production of superoxide as assessed by dihydroethidium staining. GHRP-2 decreased aortic gene expression of 12/15-lipoxygenase by 92% and reduced the aortic expression of interferon-gamma and macrophage migration inhibitory factor. In cultured aortic smooth muscle cells, GHRP-2 prevented the OxLDL-induced generation of peroxides, down-regulation of IGF-I receptor, and apoptosis. In macrophages, GHRP-2 reduced lipid accumulation with OxLDL exposure. In summary, GHRP-2 exerts antioxidant effects in vivo and in vitro but does not reduce plaque burden. The lack of an antiatherogenic effect may be due to GH-dependent effects in vivo, thereby blunting the effect of increased IGF-I.

High phosphorus diet induces vascular calcification, a related decrease in bone mass and changes in the aortic gene expression

In chronic kidney disease, hyperphosphatemia has been associated to vascular calcifications. Moreover, the rate and progression of vascular calcification have been related with the reduction of bone mass and osteoporotic fractures, hereby suggesting a strong link between vascular calcification and bone loss. Our aim was to prospectively study the effects of high phosphorus diet on bone mass, vascular calcification and gene expression profile of the arterial wall. A rat model of 7/8 nephrectomy fed with normal (0.6%) and moderately high (0.9%) phosphorus diet was used. Biochemical parameters, bone mineral density and vascular calcifications were assessed. A microarray analysis of the aortic tissue was also performed to investigate the gene expression profile. After 20 weeks, the rats fed with a high phosphorus diet showed a significant increase in serum phosphorus, PTH, and creatinine, together with aortic calcification and a decrease in bone mass. The histological analysis of the vascular calcifications showed areas with calcified tissue and the gene expression profile of this calcified tissue showed repression of muscle-related genes and overexpression of bone-related genes, among them, the secreted frizzled related proteins, well-known inhibitors of the Wnt pathway, involved in bone formation. The study demonstrated prospectively the inverse and direct relationship between vascular calcification and bone mass. In addition, the microarrays findings provide new information on the molecular mechanisms that may link this relationship.

Counter-regulation by atorvastatin of gene modulations induced by L-NAME hypertension is associated with vascular protection

Statins, 3-hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, protect against deleterious effects of chronic nitric oxide inhibition. We aimed at determining the genes and pathways involved in the protective effect of statin treatment during hypertension. Chronic inhibition of nitric oxide synthesis by Nω-nitro- l-arginine methyl ester (L-NAME) induced accelerated hypertension which was slightly reduced by cotreatment with atorvastatin (100 mg/kg/day). Gene expression profile of aortic media was strongly modified by atorvastatin cotreatment which prevented modulation of many genes regulated by L-NAME administration (described in Dupuis, M., Soubrier, F., Brocheriou, I., Raoux, S., Haloui, M., Louedec, L., Michel, J.B., Nadaud, S., 2004. Profiling of aortic smooth muscle cell gene expression in response to chronic inhibition of nitric oxide synthase in rats. Circulation 110, 867–873). The functional classification of these genes highlighted several major biological pathways modulated in aortic media by atorvastatin: effectors involved in smooth muscle tone; extracellular matrix; intracellular mediators of cell proliferation. Moreover, atorvastatin partially prevented arterial wall thickening, TGF-β pathway activation, MCP-1 induction and smooth muscle cell proliferation induced by L-NAME treatment although blood pressure was only slightly reduced, suggesting mechanisms independent of blood pressure levels. The induction of PPARalpha mRNA expression by atorvastatin in L-NAME treated rats also suggests that this pathway could participate in the protective effect. In conclusion, our data show that atorvastatin specifically antagonizes a set of genes modulated by L-NAME-induced accelerated hypertension.

Insulin‐like growth factor I downregulates proatherogenic 12/15‐lipoxygenase in vivo and in vitro

We have shown that 12/15‐lipoxygenase (LOX) mediates important proatherogenic oxidized low density lipoprotein (OxLDL)‐induced effects in smooth muscle cells (SMC), namely, apoptosis and downregulation of the insulin‐like growth factor (IGF‐1) receptor, and that infusion of IGF‐1 into Apolipoprotein E‐null (ApoE‐/‐) mice suppresses macrophage (MF) plaque infiltration and atherosclerosis. To determine molecular mechanisms mediating IGF‐1's anti‐atherogenic effects ApoE‐\‐ mice were injected with IGF‐1 (0.7 mg/kg/day, 7d). IGF‐1 decreased LOX aortic gene expression by 64±6% (RT‐PCR). IGF‐1 dose‐dependently decreased LOX gene expression in THP‐1 derived MF, while no significant effect was seen in SMC. To examine IGF‐1's effects on LOX activity, SMC or MF were pre‐treated with IGF‐1 (10 or 50 ng/ml, 24h), and then exposed to OxLDL or control. 14,15‐leukotriene (a product of LOX‐specific enzymatic reaction) levels were measured in conditioned media by ELISA. OxLDL induced a five‐fold increase in LOX activity levels in MF, and a smaller increase in LOX activity in SMC. IGF‐1 partially blocked OxLDL‐induced LOX upregulation by 27±4%. In summary, IGF‐1 suppresses vascular LOX expression in ApoE‐\‐ mice and induces LOX downregulation in MΦ and SMC. Our data suggests that the ability of IGF‐1 to downregulate LOX plays an important role in its anti‐atherogenic effect.Study supported by NIH HL 70241

Developmental programming of sex-dependent alterations in lipid metabolism: a role for long-term, sex-specific alterations in LDL-receptor expression. Focus on “Developmental programming of lipid metabolism and aortic vascular function in C57BL/6 mice: a novel study suggesting an involvement of LDL-receptor”

the nobel prize in physiology or medicine was awarded to Brown and Goldstein in 1985 for their discovery of the low-density lipoprotein (LDL) receptor and its importance in the regulation of cholesterol metabolism ([2][1]). Cholesterol, an essential component of the mammalian cell membrane, is

Effects of Chronic Mild Stress on the Development of Atherosclerosis and Expression of Toll‐Like Receptor 4 Signaling Pathway in Adolescent Apolipoprotein E Knockout Mice

Here, we investigated the effect of chronic mild stress (CMS) on the development of atherosclerosis as well as the expression of Toll-like receptors (TLRs) signaling pathway in adolescent apolipoprotein E knockout (apoE-/-) mice. Mice were subjected to daily CMS for 0, 4, and 12 weeks, respectively. To identify the expression of Toll-like receptor 4 signaling pathway in adolescent apolipoprotein E knockout mice subjected to CMS, we compared gene expression in aortas of stressed and unstressed mice using TLRs signaling pathway real-time PCR microarrays consisting of 87 genes. We found that atherosclerosis lesions both in aortic tress and sinuses of CMS mice were significantly increased linearly in response to duration of CMS exposure. Among 87 genes analyzed, 15 genes were upregulated in stressed mice, especially TLR4, myeloid differentiation factor 88 (MyD88), and IL-1β, and 28 genes were downregulated compared with nonstressed mice. CMS mice demonstrated markedly increased aortic atherosclerosis that were associated with significant increases in levels of expression of TLR4, MyD88, nuclear factor κB (NF-κB), MCP-1, IL-1β, TNF-α, and sICAM-1. Taken together, our results suggest an important role for TLR4 signaling pathway in atherosclerosis in a CMS mouse model.

Prenatal dexamethasone exposure in the common marmoset monkey enhances gene expression of antioxidant enzymes in the aorta of adult offspring

Human epidemiological studies have indicated that low birth weight associated with an adverse intrauterine environment is related to a greater incidence of cardiovascular disorders in later life. In the foetus, endogenous glucocorticoids generally increase if there is intrauterine nutrient deficiency. The consequent glucocorticoid hyperexposure has been hypothesised to cause in utero programming of atherogenic genes. We investigated the effect of oral treatment with the synthetic glucocorticoid dexamethasone during early or late pregnancy in marmoset monkeys on oxidative and antioxidant status in the offspring. Urinary concentrations of F2-isoprostanes were quantified as markers for in vivo oxidative stress. Expression of the mRNAs for the antioxidant enzymes cytosolic glutathione peroxidase (GPx-1), phospholipid hydroperoxide glutathione peroxidase (GPx-4), cytosolic Cu,Zn-superoxide dismutase (SOD1), mitochondrial Mn-superoxide dismutase (SOD2), glutathione reductase (GSR), modifier subunit of glutamate-cysteine ligase (GCLM) and catalase were determined in the aorta. Three groups of pregnant marmosets (10 animals per group) were treated orally for one week with vehicle, or with dexamethasone (5 mg/kg daily) during two gestation windows: early dexamethasone group, pregnancy day 42–48, and late dexamethasone group, pregnancy day 90–96. In one male sibling of each litter (10 males per group), aortas were taken at 2 years of age. In the late dexamethasone group a higher aortic mRNA expression for GPx-1 (p < 0.023), MnSOD (p < 0.016), GCLM (p < 0.019) and GSR (p < 0.014) in comparison to the controls was observed. Aortic expression in the early dexamethasone group was statistically significantly higher only for GSR mRNA (p < 0.038). No significant changes in urinary F2-isoprostane concentrations between controls, early and late dexamethasone groups at 2 years of age were observed. Hence, prenatal exposure to dexamethasone in the third trimester leads to increased mRNA expression of several aortic antioxidant enzymes in the offspring. This expression pattern was not temporally related to oxidative stress, and it may reflect in utero re-programming of aortic antioxidant gene expression during prenatal glucocorticoid exposure.

Abstract 1489: Vitamin D Receptor Activation Modulates the Effect of Uremia on Aortic Gene Expression and Endothelial Function

Vitamin D receptor (VDR) activation therapy is associated with cardiovascular/survival benefit in chronic kidney disease (CKD), but the mechanism of action is not well understood. The aim of this study is to investigate how uremia affects gene expression in aorta and whether VDR activation modulates the uremic effect. DNA microarray technology was used to assess the gene expression profile in aorta prepared from SHAM and 5/6 nephrectomized (NX) rat, a model of Stage 4/5 CKD, treated with or without 0.17 μg/kg paricalcitol, a VDR activator. As expected, paricalcitol at 0.17 μg/kg after two weeks of treatment effectively suppressed serum parathyroid hormone (PTH); no significant difference was observed in ionized calcium or serum phosphorus. Uremia exhibited a significant effect on the gene expression pattern in the aorta, affecting 468 sequences ( ≥1.5-fold changes with p&lt;0.01 vs. SHAM). When the criteria were tightened to ≥ 2-fold changes with p&lt;0.01, uremia still affected 135 target sequences in the rat aorta with 63 up-regulated and 72 down-regulated. Target genes fell into various categories including metabolism and cellular metabolism. Paricalcitol treatment normalized 95 out of the 135 sequences affected by uremia; many of the genes were related to mitochondrial function and oxidative stress. As a follow-up to the microarray analysis, endothelial function was examined. Uremia significantly affected aortic relaxation (−50.0 ± 7.4% in NX rats vs. −96.2 ± 5.3% in SHAM at 30 μM acetylcholine). The endothelial-dependent relaxation response to acetylcholine (Ach) at 30 μM was improved to −58.2 ± 6.0%, −77.5 ± 7.3% and −90.5 ± 4.0% in NX rats treated with paricalcitol at 0.021, 0.042 and 0.083 μg/kg for two weeks, respectively, while blood pressure and heart rate were not changed. PTH suppression alone didn’t improve endothelial function since cinacalcet, a calcimimetic targeting calcium sensing receptor, suppressed PTH without affecting endothelial-dependent vasorelaxation. In conclusion, VDR activation by paricalcitol modulates the effect of uremia on aortic gene expression and endothelial function independent of PTH and blood pressure control, which may be one of the mechanisms responsible for paricalcitol’s cardiovascular benefit in CKD.

Abstract 6147: A Tissue Stem Cell Niche Regulates Bicuspid Aortic Valve Disease

Bicuspid aortic valve disease is the most common congenital cardiac malformation and indication for surgery for aortic valve patients. The age of onset for the development of stenosis is earlier in bicuspid aortic valves than tricuspid aortic valves. Understanding the cellular mechanisms of this valve lesion, will help to develop novel approaches towards slowing disease progression. This study hypothesizes that bicuspid aortic valve disease develops secondary to a tissue stem cell niche to activate a cross-talk mechanism which induces Notch1 cleavage and Lrp5 mediated bone formation specific to the bicuspid aortic valve. Human ex vivo bicuspid valves versus control aortic valves were tested for Notch1 expression by RTPCR, Western Blot and Immunohistochemistry. eNOS null bicuspid mice: control (n=20), cholesterol (n=20), cholesterol + Atorvastatin (n=20), were tested for the development of aortic stenosis by Visual Sonics Echo, Immunohistochemistry for Notch1, Wnt, Lrp5, Osteocalcin, PCNA and RTPCR for Notch1, Lrp5, Cbfa1, Osteocalcin. In vitro studies were performed to characterize Wnt secretion from aortic valve endothelial cells and gene expression for Notch1, Lp5 and osteocalcin from the valve myofibroblast cells. This study characterizes the secretion of Wnt3a (&gt;300-fold, p&lt;0.01) from aortic valve endothelium in the presence of abnormal nitric oxide regulation and lipids as measured by eNOS enzymatic activity and tissue nitrite levels. Osteoblastogenesis in the adjacent myofibroblast cell is activated via Notch1 cleavage(p&lt;0.001) and upregulation of the Wnt3a/Lrp5 receptor. Human ex vivo valves express Notch1 cleavage as compared to normal valves from heart transplant(p&lt;0.01). Cholesterol treated eNOS mice develop severe stenosis with cleavage of Notch1, increase in Lrp5, Wnt3a, cyclin, Cbfa1, and Osteopontin,(3-fold increase(p&lt;0.01) which was not present in the controls and normalized in the statin treated valves. Targeting the Notch1/Wnt3a/Lrp5 pathway in bicuspid valvular calcification presents a novel approach towards treating this disease. The importance of this cross talk mechanism is demonstrated in three models of aortic valve disease and will have important clinical implications. This research has received full or partial funding support from the American Heart Association, AHA National Center.

Abstract 3693: Early Growth Response Gene-1 Deficiency In Bone-marrow-derived Cells Reduces Macrophage Accumulation And Atherosclerotic Lesion Formation In A Hyperlipidemic Mouse Model

Early growth response gene-1 (Egr-1), a prototype of a family of zinc-finger transcription factors, is a master regulator of many genes which play important roles in cardiovascular diseases. Within atherosclerotic lesions Egr-1 is expressed in several cell types, such as smooth muscle cells, endothelial cells and monocytes/macrophages. Since macrophages play a pivotal role in atherosclerotic lesion development, this study investigated the effects of Egr-1-deficiency within bone-marrow derived cells on the development of atherosclerosis in a hyperlipidemic mouse model. Therefore we transplanted bone-marrow from Egr-1 deficient mice and wild type controls into lethally irradiated low-density lipoprotein receptor deficient mice. After 20 weeks on a western diet atherosclerotic lesions within the aortic sinus and gene expression of inflammatory genes in the aortas of the recipients were evaluated. Mice receiving Egr-1 deficient bone-marrow had less atherosclerotic lesion development compared with mice receiving wild type bone-marrow (318 736 ± 98 910μm 2 vs. 404 539 ± 92 408μm 2 , p&lt;0.05). The size of the necrotic core within the lesions was also reduced. Immunohistochemistry revealed that mice receiving Egr-1 deficient bone-marrow had less macrophages in comparison to controls. Gene expression analysis in the aortas of the mice demonstrated reduced expression of Vascular Cell Adhesion Molecule (VCAM-1), an important adhesion molecule during the development of atherosclerosis. These results were validated with in vitro studies where Egr-1-deficient peritoneal macrophages revealed less VCAM-1 mRNA expression after stimulation with lipopolysaccharide in comparison to wildtype macrophages. This study demonstrates that bone-marrow derived Egr-1 promotes macrophage accumulation and atherosclerotic lesion development possible over an increased expression of VCAM-1.

Abstract 246: Global Analysis of Differentially Expressed Genes in the Aortae of Apoe-deficient Mice Infused with Insulin-like Growth Factor I: Novel Mechanisms of the Anti-atherogenic Effect of IGF-1

We have previously shown that insulin like growth factor-I (IGF-1) suppresses atherosclerosis progression in ApoE-null mice. To determine mechanisms, ApoE-null mice were chronically infused with IGF-1 (1.5 mg/kg/d, 12 weeks) or saline (control) or treated short-term with IGF-1 (0.4 mg/kg/d, i.p., 1 week) or saline (control). Aortic gene expression of 84 atherosclerosis-related genes-of-interest was analyzed with RT-PCR arrays. Chronic IGF-1 infusion decreased expression levels of pro-apoptotic molecules (Bax, 0.62, BID, 0.26), adhesion molecules (integrin β2, 0.32, integrin α2, 0.28, VCAM-1, 0.43), pro-inflammatory cytokines (TNFα, 0.22, interferon γ, 0.30) and lipoprotein lipase (LPL, an enzyme mediating lipid hydrolysis and tissue uptake of oxidized low density lipoprotein (OxLDL), 0.69). These changes in gene expression correlated with a reduction in atherosclerotic plaque burden (Oil Red-positive aortic valve lesion area, ×000 pixels 2 , IGF-1, 228±13, saline, 268±22), suppression of plaque apoptosis (% apoptotic cells per plaque, IGF-1, 3.4±0.7, saline, 5.8±0.5, P&lt;0.05, TUNEL assay), decrease in plaque TNFα levels (58% reduction vs. saline, P&lt;0.05, immunostaining), and inhibition of serum LPL activity (IGF-1, 1.1±0.2, saline, 3.7±0.4, P&lt;0.05, fluorescence assay). Short-term IGF-1 treatment similarly decreased mRNA levels of Bax (0.68), BID (0.61), integrin β2 (0.62), TNFα (0.50), interferon γ (0.37), LPL (0.42) and also downregulated a group of scavenger receptors (CD36, 0.44, MSR-1, 0.48, MSR-2, 0.52). To further characterize the effect of IGF-1 on LPL we exposed THP-1-derived macrophages to OxLDL (80 ug/ml, 16 h) in the presence or absence of IGF-1. OxLDL increased LPL activity in conditioned media (&gt;5 fold, P&lt;0.01), but pre-treatment with IGF-1 (25 ng/ml, 24 h) reversed LPL upregulation by 52% and suppressed lipid internalization by 88% (P&lt;0.05, Oil Red staining). In summary IGF-1 reduces pro-inflammatory cytokines, pro-apoptotic molecules, adhesion molecules, scavenger receptors, and lipoprotein lipase expression in ApoE-null mice and markedly blunts OxLDL-induced upregulation of LPL and lipid uptake in THP-derived macrophages. These data provide major insights into mechanisms whereby IGF-1 is atheroprotective.

High-Density Lipoproteins Affect Endothelial BMP-Signaling by Modulating Expression of the Activin-Like Kinase Receptor 1 and 2

High-density lipoproteins (HDL) have antiinflammatory effects on the vascular endothelium. Because bone morphogenetic proteins (BMPs) are known to be inflammatory mediators, we examined the effect of HDL on BMP signaling. Increasing concentrations of HDL progressively enhanced expression of the activin-like kinase receptor (ALK)1 and ALK2 in human aortic endothelial cells as determined by real-time polymerase chain reaction and immunoblotting. Induction of ALK1 was a result of enhanced ALK2 expression as determined by siRNA interference, and was associated with increased levels of vascular endothelial growth factor (VEGF) and matrix Gla protein (MGP). The HDL-induction of ALK2 was dependent on BMP-signaling, and affected coregulation of the ALK2 gene by the homeodomain proteins MSX2, DLX3, and DLX5, as determined by reporter gene assays, siRNA interference, and chromatin immunoprecipitation. Apolipoprotein A-I transgenic mice, known to have high HDL and inhibition of atherogenesis, exhibited similar changes in aortic gene expression as seen in endothelial cells treated with HDL in vitro. We conclude that HDL benefits the arterial wall by allowing for enhanced ALK1 and ALK2 signaling, resulting in an increase of VEGF and MGP, essential for endothelial cell survival and prevention of vascular calcification, respectively.

THE ROLE OF ANGIOGENESIS IN ABDOMINAL AORTIC ANEURYSM RUPTURE

Mechanisms underlying abdominal aortic aneurysm (AAA) rupture are poorly defined. This study investigated the extent of angiogenesis in AAA rupture site and the role of VEGF in experimental aneurysms. Methods and Results: Affymetrix microarray analysis of human AAA rupture site (n = 10), with paired anterior sac as controls, revealed overexpression of genes involved in angiogenesis, apoptosis, inflammation and proteolysis. QRT-PCR confirmed upregulation of 26 out of 32 selected genes. Using CD31 immunostaining, angiogenesis (microvessel density) was increased at AAA rupture site compared to anterior sac (p < 0.001). VEGF, a potent pro-angiogenic cytokine, was significantly overexpressed at both mRNA level and protein level. To investigate the role of VEGF, ApoE−/− mice were assigned to either: (1) saline infusion (placebo control), (2) AngII infusion (which induced aneurysm formation) or (3) AngII infusion plus 21 days 100 mcg VEGF. MRI scans revealed that VEGF treatment increased diameter and cross-sectional area of aneurysms (day 21, p < 0.002; day 28, p < 0.0005) and upregulated aortic MMP2 gene expression (p < 0.0009). Conclusions: Angiogenesis was increased at human AAA rupture site and VEGF treatment intensified formation of AngII-induced aneurysms. Whether anti-angiogenic therapy reduces aneurysm expansion and decreases risk of rupture merits further investigations.

Neuronatin: A New Inflammation Gene Expressed on the Aortic Endothelium of Diabetic Mice

OBJECTIVE—Identification of arterial genes and pathways altered in obesity and diabetes.RESEARCH DESIGN AND METHODS—Aortic gene expression profiles of obese and diabetic db/db, high-fat diet–fed C57BL/6J, and control mice were obtained using mouse Affymetrix arrays. Neuronatin (Nnat) was selected for further analysis. To determine the function of Nnat, a recombinant adenovirus (Ad-Nnat) was used to overexpress the Nnat gene in primary endothelial cells and in the mouse aorta in vivo.RESULTS—Nnat, a gene of unknown vascular function, was upregulated in the aortas of db/db and high-fat diet–fed mice. Nnat gene expression was increased in db/db mouse aorta endothelial cells. Nnat protein was localized to aortic endothelium and was selectively increased in the endothelium of db/db mice. Infection of primary human aortic endothelial cells (HAECs) with Ad-Nnat increased expression of a panel of nuclear factor-κB (NF-κB)-regulated genes, including inflammatory cytokines, chemokines, and cell adhesion molecules. Infection of mouse carotid arteries in vivo with the Ad-Nnat increased expression of vascular cell adhesion molecule 1 protein. Nnat activation of NF-κB and inflammatory gene expression in HAECs was mediated through pathways distinct from tumor necrosis factor-α. Nnat expression stimulated p38, Jun NH2-terminal kinase, extracellular signal–related kinase, and AKT kinase phosphorylation. Phosphatidylinositol 3-kinase and p38 inhibitors prevented Nnat-mediated activation of NF-κB–induced gene expression.CONCLUSIONS—Nnat expression is increased in endothelial cells of obese and diabetic mouse blood vessels. The effects of Nnat on inflammatory pathways in vitro and in vivo suggest a pathophysiological role of this new gene in diabetic vascular diseases.

Changes of noradrenaline-induced contractility and gene expression in aorta of rats acclimated to heat in two different modes

We investigated changes in responsiveness to noradrenaline (NA) and gene expression in aorta, and plasma nitrite/nitrate (NOx) levels in heat-acclimated rats. Male rats were exposed for 10 consecutive days to either 32 degrees C in the second half of the dark phase (HI) or to 32 degrees C constantly (HC). Controls were kept at 24 degrees C. After heat acclimation, thoracic aorta was excised and blood was taken in the first (Dark1) and second (Dark2) halves of the dark phase, and in the light phase. Contractile response to NA in HI was significantly depressed in Dark1 and Dark2, whereas in HC the contraction response to NA was significantly attenuated in all phases. Endothelial NO synthase (eNOS) mRNA expression was significantly enhanced in HI in Dark2. Inducible NOS mRNA was undetectable. mRNA expression of period2 was not modified by heat acclimation. Plasma NOx concentrations in HI were significantly elevated in Dark1 and Dark2, while in HC, the level was significantly raised in all phases. Our results suggest that in rats, heat acclimation improves distensibility of thoracic aorta due to attenuated responsiveness to NA, which might be attributable in part to an upregulated eNOS expression and an increase in circulating NO. The phases of the day when such changes occurred appear to be closely related to the periods when the animals were previously subjected to heat.