Endothelin-1 critically influences cardiac function via superoxide-MMP9 cascade

Abstract

We have generated low-expressing and high-expressing endothelin-1 genes (L and H) and have bred mice with four levels of expression: L/L, ∼20%; L/+, ∼65%; +/+ (wild type), 100%; and H/+, ∼350%. The hypomorphic L allele can be spatiotemporally switched to the hypermorphic H allele by Cre-loxP recombination. Young adult L/L and L/+ mice have dilated cardiomyopathy, hypertension, and increased plasma volumes, together with increased ventricular superoxide levels, increased matrix metalloproteinase 9 (Mmp9) expression, and reduced ventricular stiffness. H/+ mice have decreased plasma volumes and significantly heavy stiff hearts. Global or cardiomyocyte-specific switching expression from L to H normalized the abnormalities already present in young adult L/L mice. An epithelial sodium channel antagonist normalized plasma volume and blood pressure, but only partially corrected the cardiomyopathy. A superoxide dismutase mimetic made superoxide levels subnormal, reduced Mmp9 overexpression, and substantially improved cardiac function. Genetic absence of Mmp9 also improved cardiac function, but increased superoxide remained. We conclude that endothelin-1 is critical for maintaining normal contractile function, for controlling superoxide and Mmp9 levels, and for ensuring that the myocardium has sufficient collagen to prevent overstretching. Even a modest (∼35%) decrease in endothelin-1 gene (Edn1) expression is sufficient to cause cardiac dysfunction.amiloride | extracellular matrix | reactive oxygen species | sodium retention | tempol P revious studies have demonstrated that individuals with dilated cardiomyopathy have increased plasma levels of endothelin-1 (1) and elevated endothelin-1 mRNA levels in the heart (2). In addition, two polymorphisms in the endothelin type A receptor gene (EDNRA), G231A and C1363T, are associated with differences in the risk for pathogenesis and mortality in patients with idiopathic dilated cardiomyopathy (3, 4). These findings suggest endothelin-1 plays a causative and/or compensatory role in dilated cardiomyopathy.In animal studies, mice completely lacking endothelin-1 have severe anomalies in the heart and aorta with craniofacial abnormalities and die at age 10-12 d post coitum (5). Mice with a cardiomyocyte-specific deletion of endothelin-1 develop dilated cardiomyopathy as they age or if they are subjected to aortic banding when young (6). In the opposite direction, mice having a conditional ∼10-fold overexpression of endothelin-1 in the heart also develop dilated cardiomyopathy associated with increases in the expression of inflammatory cytokines (7).To gain a better understanding of the physiological role of endothelin-1 in mammals, we have used a method of altering the 3′ untranslated region (UTR) of a gene of interest without changing its 5′ transcriptional regulatory elements (8) to generate mice having four step-wise levels of expression of endothelin-1 covering physiologically likely ranges (from ∼20% normal to ∼350%). We here report that plasma volumes and blood pressure increas...

Global Overexpression of ET-1 Decreases Blood Pressure - A Systematic Review and Meta-Analysis of ET-1 Transgenic Mice

“…This fits very well with the observation that a decreased tissue concentration or a heterozygous knockout of the ET-1 gene is associated with an elevation of blood pressure [24]. Despite lower blood pressure, the heart/body weight ratio in older ET-1+/+ mice is clearly increased as compared to control littermates of the same age.…”

“…This fits well with the observation that a global heterozygous ET-1 knockout in mice causes hypertension (the complete knockout in homozygous ET-1 knockout mice is lethal due to craniofacial malformations [23]). This landmark study was recently confirmed by another independent study showing that a decrease in systemic ET-1 level of up to 35 % of that in the control mice causes hypertension [24]. Notably, in this model blood pressure could be normalized by epithelial sodium channel blockers, indicating that renal tubular sodium transport plays a key role in the pathogenesis of hypertension in these settings.…”

Plasma ET-1 Concentrations are Elevated in Patients with Hypertension – Meta-Analysis of Clinical Studies

“…This fits well with the observation that a global heterozygous ET-1 knockout in mice causes hypertension (the complete knockout in homozygous ET-1 knockout mice is lethal due to craniofacial malformations [23]). This landmark study was recently confirmed by another independent group showing that a decrease in systemic ET-1 level of up to 35 % of that in the control mice causes hypertension [33]. Notably, in this model blood pressure could be normalized by epithelial sodium channel blockers, indicating that renal tubular sodium transport plays a key role in the pathogenesis of hypertension in these settings.…”

Focal Adhesion Kinase-mediated Phosphorylation of Beclin1 Protein Suppresses Cardiomyocyte Autophagy and Initiates Hypertrophic Growth

“…Despite mounting evidence for a causal role of autophagy suppression in the promotion of compensatory hypertrophy (4,11,31,(42)(43)(44)(45)(46), the mechanistic links between pressure overload and adrenergic signaling-induced autophagic suppression have remained largely unsolved. A prior report indicated that endothelin-1 can suppress autophagy by inducing ubiquitination and degradation of Atg14L through ZBTB16-Cullin3-Rock1 E3 ubiquitin ligase complex (47).…”