Polymorphism in gene coding for ACE determines different development of myocardial fibrosis in rats

Abstract

.-In humans, the effect of angiotensinconverting enzyme (ACE) gene polymorphisms in cardiovascular disease is still controversial. In the rat, a microsatellite marker in the ACE gene allows differentiation of the ACE gene polymorphism among strains with different ACE levels. We tested the hypothesis that this ACE gene polymorphism determines the extent of cardiac fibrosis induced by isoproterenol (Iso) in the rat. We used a male F2 generation (homozygous LL and BB ACE genotypes determined by polymerase chain reaction) derived from two rat strains [BrownNorway (BB) and Lewis (LL)] that differ with respect to their plasma ACE activities. For induction of left ventricular (LV) hypertrophy (LVH) and cardiac fibrosis, rats were infused with Iso (5 mg⅐kg Ϫ1 ⅐day Ϫ1 ) or saline (control) for 10 days and euthanized at day 1 after the last injection. The interstitial collagen volumetric fraction (ICVF), collagen I, and fibronectin content, but not collagen III content, were significantly higher in the homozygous BB rats than in homozygous LL rats. Differences in metalloprotease (MMP)-9, but not in MMP-2 activities as well as in cardiac cell proliferation, were also detected between LL and BB rats treated with Iso. LV ACE activity was higher in BB rats than LL rats and correlated with ICVF (r ϭ 0.61, P Ͻ 0.002). No changes were observed in plasma ACE activities, ANG II plasma or LV levels, plasma renin activity, and ACE and ANG II type 1 receptor (AT1R) mRNA levels in the LV of rats with the two different ACE polymorphisms. Iso induced a similar degree of LVH [assessed by an increase in LV weight 100 per body weight, LV-to-right ventricle (RV) ratio, and LV protein content] in LL and BB rats. We concluded that rats in the F2 generation with high plasma ACE activity developed more fibrosis but to a similar degree of LVH compared with rats with low plasma ACE activity. renin angiotensin system; fibrosis; hypertrophy; angiotensin-converting enzyme; angiotensin-converting enzyme gene polymorphism THE CELLULAR COMPARTMENT of the cardiac tissue is mainly represented by the cardiac myocytes, responsible for the contractile activity of the heart, and by interstitial cells, including resident fibroblasts, endothelial cells, vascular cells, and monocytes (47). Fibroblasts, the most abundant cell type in the heart, produce both extracellular matrix proteins (ECM) and metalloproteases (MMPs), thus playing a central role in the regulation of ECM (23, 48). The major ECM proteins are type I and III collagens, although other types of collagens as well as fibronectin are also present. Collagens are degraded by a family of MMPs capable of enzymatically digesting a wide variety of ECM proteins (41). The activity of MMPs is controlled at the transcriptional level as well as through activation and inhibition by other proteins, including tissue inhibitors of MMPs (12,23). The fibrillar collagen network ensures the structural integrity of the adjoining myocytes, provides the means by which myocyte shortening is translated into ventricular pump ...

Differential ACE expression among tissues in allele-specific Wistar rat lines

“…The difference between WU-B and WU-L rats was statistically significant (p \ 0.001), with more staining present in WU-B lines (a) cardiovascular tissue but with corresponding results. In follow-up studies between these two strains by Ocaranza et al (2004), higher left ventricular ACE activity was reported in connection to B homozygous ACE allele.…”

“…Challah et al (1998) demonstrated that ACE activity in cultured vascular cells and in neointima formation in the carotid artery after balloon injury was influenced by ACE levels. Moreover, Ocaranza et al (2002Ocaranza et al ( , 2004 showed that there is an enhanced hypertensive response and more fibrosis in response to myocardial infarction in the Brown Norway rat with higher ACE levels. When studying the effect of the B and L alleles and their difference in ACE expression on the phenotype, it is important to realize that the Brown Norway and Lou rat strains have completely different genetic backgrounds.…”

La sobreexpresión del gen de enzima convertidora de angiotensina homóloga (ECA2) revierte la hipertensión arterial y el remodelado cardíaco experimental

“…Además, la sobreexpresión de ECA2 regresó la fibrosis cardíaca en el modelo de HTA dependiente de Ang II, siendo la regresión de la fibrosis cardíaca mayor en las ratas LL AdECA2 respecto de las ratas BN. El modelo de ratas homocigotas LL y BN ha sido ampliamente utilizado en investigaciones previas del laboratorio 14,15,16 describiendo que en condiciones basales, las ratas BN presentan mayores niveles de ECA, renina y Ang II pero baja actividad de NEP y Ang-(1-7) 13,14 . En cambio, las ratas LL presentan características opuestas.…”

“…En cambio, las ratas LL presentan características opuestas. Por otra parte, el pinzamiento de la arteria renal izquierda (modelo Goldblatt, GB, 2K-1C) genera mayor HTA en las ratas BN que las LL [15] y mayor desarrollo de fibrosis miocárdica inducida por isoproterenol 16 , lo cual explica que la regresión de la fibrosis haya sido mayor en las ratas LL tratadas con AdECA2. Las principales limitaciones de este estudio es que desconocemos a la fecha si el efecto terapéutico de la ECA2 en la disminución de la HTA y la regresión de la hipertrofia y la fibrosis cardíaca se relaciona con mejoría de la función ventricular.…”

“…El tejido fue examinado bajo microscopio de luz, las imágenes fueron captadas con cámara Nikon y proyectadas a un monitor. Se utilizó el programa Matlab, con el cuál se midió el contenido de colágeno intersticial según el procedimiento descrito por Ocaranza et al 16 . 6-Análisis de resultados: Los datos obtenidos se expresaron como promedio ± S.E.M.…”