Regulation of aortic extracellular matrix synthesis via noradrenergic system and angiotensin II in juvenile rats.

CONTEXT: Extracellular matrix (ECM) synthesis regulation by sympathetic nervous system (SNS) or angiotensin II (ANG II) was widely reported, but interaction between the two systems on ECM synthesis needs further investigation. OBJECTIVE: We tested implication of SNS and ANG II on ECM synthesis in juvenile rat aorta. MATERIALS AND METHODS: Sympathectomy with guanethidine (50 mg/kg, subcutaneous) and blockade of the ANG II AT1 receptors (AT1R) blocker with losartan (20 mg/kg/day in drinking water) were performed alone or in combination in rats. mRNA and protein synthesis of collagen and elastin were examined by Q-RT-PCR and immunoblotting. RESULTS: Collagen type I and III mRNA were increased respectively by 62 and 43% after sympathectomy and decreased respectively by 31 and 60% after AT1R blockade. Combined treatment increased collagen type III by 36% but not collagen type I. The same tendency of collagen expression was observed at mRNA and protein levels after the three treatments. mRNA and protein level of elastin was decreased respectively by 63 and 39% and increased by 158 and 15% after losartan treatment. Combined treatment abrogates changes induced by single treatments. DISCUSSION AND CONCLUSION: The two systems act as antagonists on ECM expression in the aorta and combined inhibition of the two systems prevents imbalance of mRNA and protein level of collagen I and elastin induced by single treatment. Combined inhibition of the two systems prevents deposit or excessive reduction of ECM and can more prevent cardiovascular disorders.

Functional meta-analysis of double connectivity in gene coexpression networks in mammals.

In functional genomics, the high-throughput methods such as microarrays 1) allow analysis of the relationships between genes considering them as elements of a network and 2) lead to biological interpretations thanks to Gene Ontology. But up to now it has not been possible to find relationships between the functions and the connectivity of the genes in coexpression networks. To achieve this aim, we have defined a double connectivity for each gene by the numbers of its significant negative and positive correlations with the other genes within a given biological condition, or group. Here, based on the analysis of 1,260 DNA microarrays, we show that this double connectivity clearly separates two types of genes, those with a predominantly strong negative connectivity, hub- genes, and those with a predominantly strong positive connectivity, hub+ genes. Interestingly, the hub+ genes concerned transcription factors more often than by chance and, similarly, for the hub- genes concerning miRNA predicted targets. Furthermore, a meta-analysis of GO annotations carried out on 67 groups in humans and rats shows that these two types of genes correspond to a functional biological duality. The hub- genes were mainly involved in basic functions common to all eukaryote cells, whereas the hub+ genes were mainly involved in specialized functions related to cell differentiation and communication. The separation and the biological role of these hub- and hub+ genes provide a powerful new tool for a better understanding of the control and regulation of the key genes involved in cellular differentiation and physiopathological conditions.

Increased insulin-stimulated expression of arterial angiotensinogen and angiotensin type 1 receptor in patients with type 2 diabetes mellitus and atheroma.

OBJECTIVE: Because inhibition of the renin-angiotensin system (RAS) reduces the onset of type 2 diabetes (T2D) and prevents atherosclerosis, we investigated the expression of RAS in the arterial wall of T2D and nondiabetic (CTR) patients. METHODS AND RESULTS: mRNA and protein levels of angiotensinogen (AGT), angiotensin-converting enzyme (ACE) and AT1 receptor (AT1R) were determined in carotid atheroma plaque, nearby macroscopically intact tissue (MIT), and in vascular smooth muscle cells (VSMCs) before and after insulin stimulation from 21 T2D and 22 CTR patients. AGT and ACE mRNA and their protein levels were 2- to 3-fold higher in atheroma and in MIT of T2D patients. VSMCs from T2D patients had respectively 2.5- and 5-fold higher AGT and AT1R mRNA and protein contents. Insulin induced an increase in AGT and AT1R mRNA with similar ED50. These responses were blocked by PD98059, an inhibitor of MAP-kinase in the two groups whereas wortmannin, an inhibitor of PI3-kinase, partially prevented the response in CTR patients. Phosphorylated ERK1-2 was 4-fold higher in MIT from T2D than from CTR patients. CONCLUSIONS: The arterial RAS is upregulated in T2D patients, which can be partly explained by an hyperactivation of the ERK1-2 pathway by insulin.

Transcriptional alterations in the left ventricle of three hypertensive rat models.

Left ventricular hypertrophy (LVH) is commonly associated with hypertension and represents an independent cardiovascular risk factor. The aim of this study was to test the hypothesis that the cardiac overload related to hypertension is associated to a specific gene expression pattern independently of genetic background. Gene expression levels were obtained with microarrays for 15,866 transcripts from RNA of left ventricles from 12-wk-old rats of three hypertensive models [spontaneously hypertensive rat (SHR), Lyon hypertensive rat (LH), and heterozygous TGR(mRen2)27 rat] and their respective controls. More than 60% of the detected transcripts displayed significant changes between the three groups of normotensive rats, showing large interstrain variability. Expression data were analyzed with respect to hypertension, LVH, and chromosomal distribution. Only four genes had significantly modified expression in the three hypertensive models among which a single gene, coding for sialyltransferase 7A, was consistently overexpressed. Correlation analysis between expression data and left ventricular mass index (LVMI) over all rats identified a larger set of genes whose expression was continuously related with LVMI, including known genes associated with cardiac remodeling. Positioning the detected transcripts along the chromosomes pointed out high-density regions mostly located within blood pressure and cardiac mass quantitative trait loci. Although our study could not detect a unique reprogramming of cardiac cells involving specific genes at early stage of LVH, it allowed the identification of some genes associated with LVH regardless of genetic background. This study thus provides a set of potentially important genes contained within restricted chromosomal regions involved in cardiovascular diseases.

Induction of tissue kallikrein in human carotid atheroma does not lead to kallikrein-kinins pathway activation.

OBJECTIVE: The impairment of the tissue kallikrein-kinin system (KKS) may result in atheroma development. To determine the involvement of KKS in pathophysiology of human atherosclerosis, we examined the expression of all components of this system as well as angiotensinogen (another tissue kallikrein (TK) substrate), at messenger ribonucleic acid (mRNA) and protein levels in the human carotid artery with and without atheroma. METHODS: mRNA levels were compared with semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) between atheroma plaque and intact tissue obtained during carotid endarterectomy in 15 patients. The cellular localization of the transcripts and proteins was analyzed with in situ hybridization and immunohistochemistry. TK activity was measured using chromogenic substrate. RESULTS: The kininogen mRNA was not detected in carotid wall. The TK mRNA was increased four-fold and TK activity 23-fold in atheroma plaque compared with intact tissue. No difference was observed for B1, B2 receptors, kallistatin, angiotensinogen and protein-kinase G type 1alpha (PK-G) mRNAs. The TK and angiotensinogen transcripts as well as kininogen and angiotensinogen proteins were present in both intimal and medial cells. The kininogen immunoreactivity was weaker in atheroma. CONCLUSIONS: All KKS components were synthesized in arterial wall except kininogen probably coming from plasma. The absence of PK-G mRNA down-regulation in atheroma suggests that the kallikrein induction does not lead to KKS activation.

Involvement of cysteinyl leukotrienes in angiotensin II-induced contraction in isolated aortas from transgenic (mRen-2)27 rats.

OBJECTIVES: We have previously reported that 5-lipoxygenase-derived products, and particularly the cysteinyl leukotrienes (CysLTs), were involved in angiotensin II (Ang II)-induced contractions in isolated aortas from spontaneously hypertensive rats. DESIGN: The aim of this study was to assess the role of CysLTs in the vascular response to Ang II in an Ang II-dependent model of hypertension, the (mRen-2)27 transgenic rats (TGs). METHODS: Intact aortic rings from TG and normotensive Sprague-Dawley rats (SDs) were suspended in organ chambers for isometric tension development in response to Ang II. In addition, the release of CysLTs in response to Ang II (0.3 micromol/l) was measured by enzyme immunoassay. RESULTS: In isolated aortas from TG rats, pretreatment with the 5-lipoxygenase inhibitor (AA861, 10 micromol/l) or the CysLT1 receptor antagonist (MK571, 1 micromol/l) significantly (P < 0.05) reduced Ang II-induced contractions by 52 and 42%, respectively. In addition, Ang II induced a 2.6-fold increase in CysLT release (pg/mg dry weight tissue: 58.3 +/- 17.9 (Ang II, n = 7) versus 22.5 +/- 5.9 (basal, n = 7) P < 0.05), which was inhibited by the AT1 receptor antagonist losartan (1 micromol/l). In contrast, in aortas from SD rats, pretreatment with AA861 or MK571 did not alter Ang II-induced contraction and CysLT production remained unchanged after exposure to Ang II. CONCLUSION: These data suggest that CysLTs are involved in the contractile responses to Ang II in isolated aortas from TG but not from SD rats.

Cathepsin G is associated with atheroma formation in human carotid artery.

OBJECTIVE: To elucidate the organization of the tissue angiotensin system, we investigated the expression and cellular localization of angiotensin system components and cathepsins D and G, potentially involved in intraparietal angiotensin II formation and atheroma. METHODS: Total RNA was extracted from atheroma plaque, fatty streaks and macroscopically intact tissue obtained during carotid endarterectomy in 21 hypertensive patients. mRNA levels were compared between these tissues using a semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). In situ hybridization and immunohistochemistry were used to define the cellular localization of the transcripts and their respective proteins. RESULTS: Apart from renin and angiotensin type 2 (AT2) receptors, which were never detected, the studied mRNAs could be measured in all patients. Angiotensin-converting enzyme (ACE) mRNA was increased five-fold in atheroma, and angiotensin type 1 receptor (AT1) mRNA decreased 2.5-fold in atheroma and 1.4-fold in fatty streaks compared to intact tissue. A two-fold increase in cathepsin G mRNA was observed in atheroma plaque. In atheroma and intact tissue, significant positive correlations were found between cathepsin G and angiotensinogen, AT1 receptor and ACE mRNAs. Angiotensinogen and cathepsin mRNAs and proteins were detected in both arterial layers. AT1 immunoreactivity was mainly associated with alpha-actin-positive cells. CONCLUSION: All components required for angiotensin II formation are expressed locally in the arterial wall, where, in the absence of renin, cathepsin G could be a major angiotensin-generating enzyme. Overexpression of ACE and cathepsin G may lead to angiotensin II overproduction and contribute, with decreased number of differentiated smooth muscle cells, to the lower amount of AT1 receptor in atheroma.

Macroarray analysis in the hypertrophic left ventricle of renin-dependent hypertensive rats: identification of target genes for renin.

INTRODUCTION: The aim of this work was to identify new renin target genes in left ventricular hypertrophy during hypertension. MATERIALS AND METHODS: We compared left ventricle gene expression from four transgenic TGR(mRen2)27 (TG+/-) rats and four non-transgenic littermates (TG-/-) using cDNA macroarray. Hybridisation signals were quantified with a phosphorimager, and normalised to an external scale. Data analysis was performed with Statistical Analysis for Microarrays (SAM 1.21) software. The mRNA levels of candidate genes were determined by semi-quantitative RT-PCR in three different hypertensive rats: TG+/-, spontaneously hypertensive (SHR) and genetically Lyon hypertensive (LH) rats, compared to their respective controls (TG-/-, Wistar-Kyoto, Lyon low blood pressure rats). RESULTS: Out of 1,200 genes present on the macroarray, 233 were reliably measured and only three were overexpressed (Biglycan, beta1-adenosine monophosphate-activated protein kinase [AMPK] and amyloid precursor like protein 2 [APLP2]) and 19 were underexpressed in the left ventricle of TG+/- compared with TG-/-. APLP2 is a member of the amyloid precursor protein (APP) family. APLP2 and APP mRNA levels were increased in TGR(mRen2)27 but significantly decreased in LH rats, while only APP was increased in SHR rats. CONCLUSIONS: We report new genes associated with renin-dependent left ventricular hypertrophy. Moreover, this work shows for the first time that the APP family gene expression could be altered in response to high renin activity and this effect is independent of cardiac remodelling and hypertension.

Auto-amplification of cortisol actions in human carotid atheroma is linked to arterial remodeling and stroke.

High cortisol and aldosterone levels increase cardiovascular risk, but the respective roles of each hormone within the arterial wall remain controversial. We tested the hypothesis that cortisol production within the arterial wall may contribute to atherosclerotic remodeling and act through illicit activation of the mineralocorticoid receptor (MR). Gene expression studies of the corticoid system components and marker genes of the atherosclerotic process in human carotid atheroma plaque and nearby macroscopically intact tissue (MIT) were considered together with clinical data and compared with pharmacological stimulations of human vascular smooth muscle cells (VSMCs) in contractile or lipid-storing phenotypes. The components of corticoid production and action were present and active within the human carotid wall and VSMCs. Atheroma plaque and lipid-storing VSMCs expressed 11ß-hydroxysteroid deshydrogenase-1 (11ß-HSD1) at two- to tenfold higher levels than MIT or contractile VSMCs. The 11ß-HSD1 expression was stimulated by cortisol and cortisone, especially in lipid-storing VSMCs. MR mRNA level was lower in atheroma and lipid-storing VSMCs and downregulated via MR by fludrocortisone and cortisol. Cortisol upregulated collagen1 and MCP-1 mRNAs via the glucocorticoid receptor (GRα), in both VSMC phenotypes, whereas fludrocortisone stimulated the collagen1 expression only in lipid-storing VSMCs. The GRα mRNA level in MIT was higher in patients with previous stroke and correlated positively with the collagen1 mRNA but negatively with diastolic blood pressure. Local cortisol production by 11ß-HSD1, and its action via high parietal GRα could be relevant from the first step of atherosclerotic remodeling and auto-amplify with transdifferentiation of VSMCs during atheroma progression.

Physiological regulation of extracellular matrix collagen and elastin in the arterial wall of rats by noradrenergic tone and angiotensin II.

The interactions between the effects of the sympathetic nervous system (SNS) and angiotensin II (ANG II) on vascular extracellular matrix (ECM) synthesis were determined in rats. The mRNA and protein content of collagen I, collagen III and elastin in the abdominal aorta (AA) and femoral artery (FA) was investigated in Wistar-Kyoto rats treated for 5 weeks with guanethidine, a sympathoplegic, losartan, an ANG II AT1 receptor (AT1R) blocker, or both. The effects of noradrenaline (NE) and ANG II on collagen III and elastin mRNA, and the receptor involved, were tested in cultured vascular smooth muscle cells (VSMCs) in vitro. Guanethidine increased collagen types I and III and decreased elastin, while losartan had an opposite effect, although without effect on collagen III. The combination of treatments abrogated changes induced by simple treatment with collagen I and elastin, but increased collagen III mRNA in AA and not in FA. NE stimulated collagen III mRNA via ß receptors and elastin via α1 and α2 receptors. ANG II stimulated collagen III but inhibited elastin mRNA via AT1R. Overall, SNS and ANG II exert opposite and antagonistic effects on major components of ECM in the vascular wall. This may be of relevance for the choice of a therapeutic strategy in vascular diseases.

Physiological regulation of MMPs and tPA/PAI in the arterial wall of rats by noradrenergic tone and angiotensin II.

The interactions between the sympathetic nervous system (SNS) and angiotensin II (ANG II), and their direct effects in vitro on the enzymes involved in vascular extracellular matrix (ECM) degradation, were examined. Rats were treated with guanethidine, losartan or the combined treatments. mRNA, protein and activity of matrix metalloproteinase (MMP)-2 and MMP-9 and mRNA of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1) were quantified in abdominal aorta (AA) and femoral artery (FA). Norepinephrine (NE) or ANG II with adrenergic (ß, α1 and α2) or losartan antagonists was tested for MMP mRNA response in cultured vascular smooth muscle cells (VSMCs). Combined treatment enhances the inhibition of MMP-2 mRNA and protein level induced by simple treatment in AA. However MMP-9 in AA and MMP mRNA in FA were reduced in the same order by treatments. MMP activities were not affected by treatments. The t-PA/PAI-1 ratio, which reflects the fibrinolytic balance, remained higher after treatments. In cultured VSMCs, NE induced stimulation of MMP mRNA via α2 and ß adrenergic receptors and MMP-2 activity via ß adrenergic receptors, while ANG II-induced stimulation was abrogated by losartan. Overall, there is a synergic inhibition of both systems on the level of MMP-2 in AA.

Reduced atherosclerotic lesion size in P-selectin deficient apolipoprotein E-knockout mice fed a chow but not a fat diet.

P-selectin. We investigated the role of P-selectin on the development of vascular lesions in an ApoE(-/-) male mice. Double-knockout (ApoE(-/-), P-selectin(-/-); DKO) were compared to single-knockout (ApoE(-/-); SKO) mice. They were fed a chow or fat diet for 3, 6, 15, and 20 weeks, without any differences in cholesterol levels. DKO mice fed a chow diet exhibited a ratio of lesion area over media lower than SKO mice, for 3 (P < .03) , 6 (P < .001), and 15 (P < .02) weeks. DKO mice fed a fat diet showed a lower ratio only at 3 weeks. P-selectin deficiency in ApoE(-/-) mice has a protective effect in atherosclerotic lesions development. Reduction of lesion size depends on diet type and duration. A fat diet could neutralize the beneficial effects of P-selectin deficiency, inducing atherosclerotic lesions via probably other adhesion molecules.

Increased expression of IL-6 and LIF in the hypertrophied left ventricle of TGR(mRen2)27 and SHR rats.

Cytokines from the interleukin-6 (IL-6) family have been reported to play an important synergistic role with angiotensin II in the development of pathological cardiac hypertrophy. Whether their expression pattern changes in vivo, in an angiotensin I-dependent hypertrophied myocardium has not been reported. In this study, we addressed that issue using two animal models of angiotensin II-dependent cardiac hypertrophy. Heterozygous transgenic TGR(mRen2)27 (TGR) with an overactive cardiac renin angiotensin system and the closely related spontaneously hypertensive rats (SHR) were compared to their respective control rats. The mRNA levels of IL-6, leukemia inhibitory factor (LIF), ciliary neurotrophic factor (CNTF) and cardiotrophin-1 (CT-1) as well as their receptor subunits, glycoprotein 130 (gp130), IL-6 receptor (IL-6R), LIFR, and CNTFR, were measured by semi-quantitative RT-PCR. The protein levels of IL-6, LIF and CT-1 were investigated by western blot. TGR and SHR both displayed significant over expression of mRNA and protein levels for IL-6 and LIF. In TGR, the increased level of LIF was accompanied by a decrease in mRNA levels for LIFR and CNTFR. In SHR, a higher level of mRNA IL-6R was observed. By contrast, the mRNA and protein levels for CT-1 and the mRNA level for gp130 did not vary in these two models. These findings suggest that IL-6 and LIF, but not CT-1, contribute to angiotensin II-dependent left ventricular hypertrophy in the two hypertensive rat models, TGR(mRen2)27 and SHR.