Protease inhibitor 15, a candidate gene for abdominal aortic internal elastic lamina ruptures in the rat

The inbred Brown Norway (BN) rat develops spontaneous ruptures of the internal elastic lamina (RIEL) of the abdominal aorta (AA) and iliac arteries. Prior studies with crosses of the BN/Orl RJ (susceptible) and LOU/M (resistant) showed the presence of a significant QTL on chromosome 5 and the production of congenic rats proved the involvement of this locus. In this study, we further dissected the above-mentioned QTL by creating a new panel of LOU.BN(chr5) congenic and sub-congenic lines and reduced the locus to 5.2 Mb. Then 1002 HS rats were studied, whose phenotyping revealed a low prevalence and high variability for RIEL. High resolution mapping in the HS panel detected the major locus on chromosome 5 (log P>35) and refined it to 1.4Mb. Subsequently, RNA-seq analysis on AA of BN, congenics and LOU revealed expression differences for only protease inhibitor15 (Pi15) gene and a putative long intergenic noncoding RNA (lincRNA) within the linkage region. The high abundance of lincRNA with respect to reduced Pi15 expression, in conjunction with exertion of longitudinal strain, may be related to RIEL, indicating the potential importance of proteases in biological processes related to defective aortic IEL structure. Similar mechanisms may be involved in aneurysm initiation in the human AA

Increased microparticle production and impaired microvascular endothelial function in aldosterone-salt-treated rats: protective effects of polyphenols

We aimed to characterize circulating microparticles in association with arterial stiffness, inflammation and endothelial dysfunction in aldosterone-salt-induced hypertension in rats and to investigate the preventive effects of red wine polyphenols. Uninephrectomized male Sprague-Dawley rats were treated with aldosterone-salt (1 µg.h(-1)), with or without administration of either red wine polyphenols, Provinols™ (20 mg.kg(-1).day(-1)), or spironolactone (30 mg.kg(-1).day(-1)) for 4 weeks. Microparticles, arterial stiffness, nitric oxide (NO) spin trapping, and mesenteric arterial function were measured. Aldosterone-salt rats showed increased microparticle levels, including those originating from platelets, endothelium and erythrocytes. Hypertension resulted in enhanced aortic stiffness accompanied by increased circulating and aortic NO levels and an upregulation of aortic inducible NO-synthase, NFκB, superoxide anions and nitrotyrosine. Flow-induced dilatation was reduced in mesenteric arteries. These effects were prevented by spironolactone. Provinols™ did not reduce arterial stiffness or systolic hypertension but had effects similar to those of spironolactone on endothelial function assessed by flow-mediated vasodilatation, microparticle generation, aortic NO levels and oxidative stress and apoptosis in the vessel wall. Neither the contractile response nor endothelium-dependent relaxation in mesenteric arteries differed between groups. The in vivo effects of Provinols™ were not mediated by mineralocorticoid receptors or changes in shear stress. In conclusion, vascular remodelling and endothelial dysfunction in aldosterone-salt-mediated hypertension are associated with increased circulating microparticles. Polyphenols prevent the enhanced release of microparticles, macrovascular inflammation and oxidative stress, and microvascular endothelial dysfunction independently of blood pressure, shear stress and mineralocorticoid receptor activation in a model of hyperaldosteronism

Characteristics of the aortic elastic network and related phenotypes in seven inbred rat strains.

Extracellular matrix (ECM) molecules such as elastin and collagen provide mechanical support to the vessel wall and are essential for vascular function. Evidence that genetic factors influence aortic ECM composition and organization was concluded from our previous studies showing that the inbred Brown Norway (BN) rat differs significantly from the outbred Long-Evans (LE) and the inbred LOU rat with respect to both thoracic aortic elastin content and internal elastic lamina (IEL) rupture in the abdominal aorta and iliac arteries. Here, we measured aortic elastin and collagen contents as well as factors that may modulate these parameters [insulin growth factor (IGF)-I, transforming growth factor (TGF)-beta(1), and matrix metalloproteinase (MMP)-2] in seven inbred rat strains, including BN and LOU. We also investigated whether IEL ruptures occur in strains other than BN. We showed that LOU, LE, BN, and Fischer 344 (F344) rats were significantly different for aortic elastin content and elastin-to-collagen ratio, whereas LE, Lewis, WAG, and Wistar-Furth (WF) were similar for these parameters. BN and F344 had the lowest values. BN was the only strain to present numerous IEL ruptures, whereas F344, LE, and WF presented a few and the other strains presented none. In addition, IGF-I and TGF-beta(1) levels in the plasma and aorta differed significantly between strains, suggesting genetic control of their production. Because inbred rat strains provide interesting models for quantitative trait locus analysis, our results concerning elastin, collagen, IEL ruptures, and cytokines may provide a basis for the search for candidate genes involved in the control of these phenotypes

L005 Identification of genes involved in aortic elastic anomalies in the rat

The inbred Brown Norway (BN) rat presents several rare arterial phenotypes, including an aortic elastin deficit, a high incidence of PDA and the spontaneous formation of ruptures in the internal elastic lamina (RIEL) of the abdominal aorta (AA) and iliac arteries. Our previously performed genetic linkage study, using microsatellite markers, showed that these 3 arterial phenotypes do not correlate in the backcross population and so are independent, and are controlled by distinct genetic loci (Kota et al. Physiol. Genomics, 2007). The RIEL phenotype is of particular interest as it probably reflects a structural anomaly of the elastic network of the AA and the contiguous common iliac arteries. Since the human AA is highly susceptible to pathological alterations with aging, i.e. atherosclerosis and aneurysm formation, for reasons not entirely understood, the discovery of a gene influencing AA elastic network structure would be of interest. In the BN rat, RIEL is strongly linked to a locus on chromosome 5 (peak LOD score 27.4) but in this locus candidate genes are sparse and sequencing them gave negative results. We thus produced congenic rats, introgressing the chrom5 segment containing the RIEL locus from BN rats on a LOU (control) genetic background. These rats express the phenotype sufficiently (30 % of parental BN values) to permit further studies on recombinant offspring to try and locate the gene(s) responsible. We have analysed genotype-phenotype correlations in a large cohort of recombinants, obtained by crossing the congenic rat LOU.BN.D5Rat59-D5Rat131 with parental LOU and subsequent intercrossing, in order to further define the position of the gene(s) responsible. We also performed high-density SNP mapping on chosen, informative recombinants, using >5000 SNPs discriminative between BN and LOU, and demonstrated the purity of the LOU genetic background (>99.9 % outside the chr.5 congenic region). Further generations of recombinants produced from informative genitors and use of SNP genotyping in the congenic region has enabled us to locate the gene(s) responsible for a moderate RIEL phenotype in the first 6Mb region of chrom5. However, BN homozygosity down to 35 Mb causes increased severity of the phenotype