The autosomal dominant mutation in the human alphaB-crystallin gene inducing a R120G amino acid exchange causes a multisystem, protein aggregation disease including cardiomyopathy. The pathogenesis of cardiomyopathy in this mutant (hR120GCryAB) is poorly understood. Here, we show that transgenic mice overexpressing cardiac-specific hR120GCryAB recapitulate the cardiomyopathy in humans and find that the mice are under reductive stress. The myopathic hearts show an increased recycling of oxidized glutathione (GSSG) to reduced glutathione (GSH), which is due to the augmented expression and enzymatic activities of glucose-6-phosphate dehydrogenase (G6PD), glutathione reductase, and glutathione peroxidase. The intercross of hR120GCryAB cardiomyopathic animals with mice with reduced G6PD levels rescues the progeny from cardiac hypertrophy and protein aggregation. These findings demonstrate that dysregulation of G6PD activity is necessary and sufficient for maladaptive reductive stress and suggest a novel therapeutic target for abrogating R120GCryAB cardiomyopathy and heart failure in humans.

Once thought to result from passive precipitation of calcium and phosphate, it now appears that vascular calcification is a consequence of tightly regulated processes that culminate in organized extracellular matrix deposition by osteoblast-like cells. These cells may be derived from stem cells (circulating or within the vessel wall) or differentiation of existing cells, such as smooth muscle cells (SMCs) or pericytes. Several factors induce this transition, including bone morphogenetic proteins, oxidant stress, high phosphate levels, parathyroid hormone fragments, and vitamin D. Once the osteogenic phenotype is induced, cells gain a distinctive molecular fingerprint, marked by the transcription factor core binding factor alpha1. Alternatively, loss of inhibitors of mineralization, such as matrix gamma-carboxyglutamic acid Gla protein, fetuin, and osteopontin, also contribute to vascular calcification. The normal balance between promotion and inhibition of calcification becomes dysregulated in chronic kidney disease, diabetes mellitus, atherosclerosis, and as a consequence of aging. Once the physiological determinants of calcification are perturbed, calcification may occur at several sites in the cardiovascular system, including the intima and media of vessels and cardiac valves. Here, calcification may occur through overlapping yet distinct molecular mechanisms, each with different clinical ramifications. A variety of imaging techniques are available to visualize vascular calcification, including fluoroscopy, echocardiography, intravascular ultrasound, and electron beam computed tomography. These imaging modalities vary in sensitivity and specificity, as well as clinical application. Through greater understanding of both the mechanism and clinical consequences of vascular calcification, future therapeutic strategies may be more effectively designed and applied.

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Vascular calcification is highly prevalent and, when present, is associated with major adverse cardiovascular events. Vascular smooth muscle cells play an integral role in mediating vessel calcification by undergoing differentiation to osteoblast-like cells and generating matrix vesicles that serve as a nidus for calcium-phosphate deposition in the vessel wall. Once believed to be a passive process, it is now recognized that vascular calcification is a complex and highly regulated process that involves activation of cellular signaling pathways, circulating inhibitors of calcification, genetic factors, and hormones. This review will examine several of the key mechanisms linking vascular smooth muscle cells to vessel calcification that may be targeted to reduce vessel wall mineralization and, thereby, reduce cardiovascular risk.

Hyperaldosteronism is associated with impaired vascular reactivity; however, the mechanisms by which aldosterone promotes endothelial dysfunction remain unknown. Glucose-6-phosphate dehydrogenase (G6PD) modulates vascular function by limiting oxidant stress to preserve bioavailable nitric oxide (NO(*)). Here we show that aldosterone (10(-9)-;10(-7) mol/l) decreased endothelial G6PD expression and activity in vitro, resulting in increased oxidant stress and decreased NO(*) levels-similar to what is observed in G6PD-deficient endothelial cells. Aldosterone decreased G6PD expression by increasing expression of the cyclic AMP-response element modulator (CREM) to inhibit cyclic AMP-response element binding protein (CREB)-mediated G6PD transcription. In vivo, infusion of aldosterone decreased vascular G6PD expression and impaired vascular reactivity. These effects were abrogated by spironolactone or vascular gene transfer of G6pd. These findings demonstrate that aldosterone induces a G6PD-deficient phenotype to impair endothelial function; aldosterone antagonism or gene transfer of G6pd improves vascular reactivity by restoring G6PD activity.

Background Pulmonary arterial hypertension (PAH) is characterized, in part, by decreased endothelial nitric oxide (NO•) production and elevated levels of endothelin-1. Endothelin-1 is known to stimulate endothelial nitric oxide synthase (eNOS) via the endothelin-B receptor (ETB), suggesting that this signaling pathway is perturbed in PAH. Endothelin-1 also stimulates adrenal aldosterone synthesis; in systemic blood vessels, hyperaldosteronism induces vascular dysfunction by increasing endothelial reactive oxygen species (ROS) generation and decreasing NO• levels. We hypothesized that aldosterone modulates PAH by disrupting ETB-eNOS signaling through a mechanism involving increased pulmonary endothelial oxidant stress. Methods and Results In rats with PAH, elevated endothelin-1 levels were associated with elevated aldosterone levels in plasma and lung tissue and decreased lung NO• metabolites in the absence of left heart failure. In human pulmonary artery endothelial cells (HPAECs), endothelin-1 increased aldosterone levels via PGC-1α/steroidogenesis factor-1-dependent upregulation of aldosterone synthase. Aldosterone also increased ROS production, which oxidatively modified cysteinyl thiols in the eNOS-activating region of ETB to decrease endothelin-1-stimulated eNOS activity. Substitution of ETB-Cys405 with alanine improved ETB-dependent NO• synthesis under conditions of oxidant stress, confirming that Cys405 is a redox sensitive thiol that is necessary for ETB-eNOS signaling. In HPAECs, mineralocorticoid receptor antagonism with spironolactone decreased aldosterone-mediated ROS generation and restored ETB-dependent NO• production. Spironolactone or eplerenone prevented or reversed pulmonary vascular remodeling and improved cardiopulmonary hemodynamics in two animal models of PAH in vivo. Conclusions Our findings demonstrate that aldosterone modulates an ETB cysteinyl thiol redox switch to decrease pulmonary endothelium-derived NO• and promote PAH.

Background Pulmonary hypertension (PH) is associated with increased morbidity across the cardiopulmonary disease spectrum. Based largely on expert consensus opinion, PH is defined by a mean pulmonary artery pressure (mPAP) ≥25 mmHg. Although mPAP levels below this threshold are common among populations at risk for PH, the relevance of mPAP <25 mmHg to clinical outcome is unknown. Methods and Results We analyzed retrospectively all US veterans undergoing right heart catheterization (RHC)(2007–2012) in the Veterans Affairs health care system (N=21,727; 908 day median follow-up). Cox proportional hazards models were used to evaluate the association between mPAP and outcomes of all-cause mortality and hospitalization, adjusted for clinical covariates. When treating mPAP as a continuous variable, the mortality hazard increased beginning at 19 mmHg (HR=1.183, 95% CI [1.004–1.393]) relative to 10 mmHg. Therefore, patients were stratified into three groups: referent (≤18 mmHg; N=4,207), borderline PH (19–24 mmHg; N=5,030), and PH (≥25 mmHg; N=12,490). The adjusted mortality hazard was increased for borderline PH (HR=1.23, 95% CI [1.12–1.36], P<0.0001) and PH (HR=2.16, 95% CI [1.96–2.38], P<0.0001) compared to the referent group. The adjusted hazard for hospitalization was also increased in borderline PH (HR=1.07, 95% CI [1.01–1.12], P=0.0149) and PH (HR=1.15, 95% CI [1.09–1.22], P<0.0001). The borderline PH cohort remained at increased risk for mortality after excluding the following high-risk subgroups: patients with pulmonary artery wedge pressure >15 mmHg, pulmonary vascular resistance ≥3.0 Wood units, or inpatient status at the time of RHC. Conclusions These data illustrate a continuum of risk according to mPAP level, and that borderline PH is associated with increased mortality and hospitalization. Future investigations are needed to test the generalizability of our findings to other populations and study the effect of treatment on outcome in borderline PH.

Acquired aortic valve disease and valvular calcification is highly prevalent in adult populations worldwide and is associated with significant cardiovascular morbidity and mortality. At present, there are no medical therapies that will prevent or regress aortic valve calcification or stenosis and surgical or transcatheter aortic valve replacement remain the only effective therapies for treating this disease. In the setting of valve injury as a result of exposure to biochemical mediators or hemodynamic forces, normal homeostatic processes are disrupted resulting in extracellular matrix degradation, aberrant matrix deposition and fibrosis, inflammatory cell infiltration, lipid accumulation, and neoangiogenesis of the valve tissue and, ultimately, calcification of the valve. Calcification of the aortic valve is now understood to be an active process that involves the coordinated actions of resident valve endothelial and interstitial cells, circulating inflammatory and immune cells, and bone marrow-derived cells. These cells may undergo a phenotype transition to become osteoblast-like cells and elaborate bone matrix, endothelial-to-mesenchymal transition, and form matrix vesicles that serve as a nidus for microcalcifications. Each of these mechanisms has been shown to contribute to aortic valve calcification suggesting that strategies that target these cellular events may lead to novel therapeutic interventions to halt the progression or reverse aortic valve calcification.