A therosclerosis is characterized with plaque formation in large and medium-sized blood vessels. The stiffened and narrowed blood vessels limit blood circulation and increase plaque thrombogenicity, which threatens the functionality of vital organs such as the heart and brain. [1][2][3] The development of atherosclerosis is a chronic pathological process. Vascular remodeling and inflammation, endothelial dysfunction, smooth muscle cell (SMC) proliferation and migration, and accumulation of cholesterol-rich lipoproteins in blood vessel walls are early events of atherogenesis, resulting in the recruitment of circulating monocytes, their adhesion to endothelium via adhesion molecules, and their differentiation into macrophages. 4 The subendothelial accumulation of cholesterol-laden macrophages is morphologically recognized as foam cells. In humans, these fatty streaks can progress to more advanced lesions characterized by a lipid-rich necrotic core and a fibrous cap consisting of SMCs and collagen.Lesion rupture can result from the decreased viability of SMCs that is necessary for collagen production and for the structural integrity of the fibrous cap following the release of matrix metalloproteinases from apoptotic macrophages. 4-8 Editorial see p 2472 Clinical Perspective on p 2534Hydrogen sulfide (H 2 S), a member of the gasotransmitter family, plays a number of important physiological roles within the body, including protection against cardiovascular disease.9-11 Cystathionine γ-lyase (CSE) endogenously produces H 2 S in the cardiovascular system, 12,13 and the deficiency of CSE in mice leads to decreased endogenous H 2 S level, age-dependent increase in blood pressure, impaired endothelium-dependent vasorelaxation, and accumulation of homocysteine in the blood.14 Administration of NaHS (a H 2 S donor) protects rat aortic SMCs from the cytotoxicity caused Background-Cystathionine γ-lyase (CSE) produces hydrogen sulfide (H 2 S) in the cardiovascular system. The deficiency of CSE in mice leads to a decreased endogenous H 2 S level, an age-dependent increase in blood pressure, and impaired endothelium-dependent vasorelaxation. To date, there is no direct evidence for a causative role of altered metabolism of endogenous H 2 S in atherosclerosis development. Methods and Results-Six-week-old CSE gene knockout and wild-type mice were fed with either a control chow or atherogenic paigen-type diet for 12 weeks. Plasma lipid profile and homocysteine levels, blood pressure, oxidative stress, atherosclerotic lesion size in the aortic roots, cell proliferation, and adhesion molecule expression were then analyzed. CSE-knockout mice fed with atherogenic diet developed early fatty streak lesions in the aortic root, elevated plasma levels of cholesterol and low-density lipoprotein cholesterol, hyperhomocysteinemia, increased lesional oxidative stress and adhesion molecule expression, and enhanced aortic intimal proliferation. Treatment of CSE-knockout mice with NaHS, but not N-acetylcysteine or ezetimibe, inhibited the acceler...

Abstract-Consomic rats (SS.BN13), in which chromosome 13 from normotensive inbred Brown Norway rats from a colony maintained at the Medical College of Wisconsin (BN/Mcw) was introgressed into the background of Dahl salt-sensitive (SS/Mcw) rats, also maintained in a colony at the Medical College of Wisconsin, were bred. The present studies determined the mean arterial pressure (MAP) responses to salt and renal and peripheral vascular responses to norepinephrine and angiotensin II; 24-hour protein excretion and histological analyses were used to assess renal pathology in rats that received a high salt (4% NaCl) diet for 4 weeks. MAP of rats measured daily during the fourth week averaged 170Ϯ3. Key Words: hypertension, sodium dependent Ⅲ rats Ⅲ sodium Ⅲ chromosome 13 Ⅲ blood pressure Ⅲ consomic D ahl salt-sensitive (SS) rats exhibit many of the abnormalities that occur with hypertension in African Americans, 1,2 including blood pressure salt sensitivity, 3,4 insulin resistance, 5 and hyperlipidemia. 6 They have a low renin form of hypertension 3 that is refractory to treatment with converting enzyme inhibitors 7,8 and is effectively treated with diuretics. 7,9 Moreover, these rats rapidly develop severe progressive hypertensive glomerulosclerosis that leads to end-stage renal disease, as is commonly also seen in African Americans with hypertension. 9,10 For these reasons, insights and findings of the studies in SS rats may provide valuable clues to the genetic basis of hypertension and related traits in African Americans.The explosion of genomic resources in the rat has led to remarkable advances in identifying the regions of the rat genome that contain blood pressure quantitative trait loci (QTLs), as reviewed by Hamet et al, 11 Zicha and Kunes,12 and Rapp. 13 We have recently completed a linkage analysis based on an intercross of SS and Brown Norway (BN) salt-insensitive rats in which total genome scans using 238 polymorphic markers, evenly distributed throughout the genome, were scored. All F2 rats (113 males and 99 females) were extensively phenotyped for 239 measured or derived traits. This linkage analysis indicated the existence of a broad range of traits related to pathways of functional importance in hypertension that mapped to 19 chromosomes. 14,15 The development of congenic strains has been used by a number of laboratories, including our own, to confirm and narrow QTL regions of interest. 16,17 Despite the usefulness of congenic rat models in the deconstruction of complex traits and the identification of candidate genes, this work has been hampered by the time and expense involved in producing these informative recombinant rats. Even with the use of markerassisted selection to identify the rats best suited for backcrossing in generations, 18 we have found that the process of developing an inbred congenic strain requires nearly 2 years and 5 to 7 generations of backcrosses to achieve rats that are sufficiently isogenic to make meaningful comparisons.To overcome these limitations, we have been developing ...

Hyperhomocysteinemia is an independent risk factor for cardiovascular disease and accelerates atherosclerosis in apoE ؊/؊ mice. Despite the observations that homocysteine causes endoplasmic reticulum (ER) stress and programmed cell death (PCD) in cultured human vascular endothelial cells, the cellular factors responsible for this effect and their relevance to atherogenesis have not been completely elucidated. We report here that homocysteine induces the expression of T-cell death-associated gene 51 (TDAG51), a member of the pleckstrin homology-related domain family, in cultured human vascular endothelial cells. This effect was observed for other ER stress-inducing agents, including dithiothreitol and tunicamycin. TDAG51 expression was attenuated in homozygous A/A mutant eukaryotic translation initiation factor 2␣ mouse embryonic fibroblasts treated with homocysteine or tunicamycin, suggesting that ER stress-induced phosphorylation of eukaryotic translation initiation factor 2␣ is required for TDAG51 transcriptional activation. Transient overexpression of TDAG51 elicited significant changes in cell morphology, decreased cell adhesion, and promoted detachmentmediated PCD. In support of these in vitro findings, TDAG51 expression was increased and correlated with PCD in the atherosclerotic lesions from apoE ؊/؊ mice fed hyperhomocysteinemic diets, compared with mice fed a control diet. Collectively, these findings provide evidence that TDAG51 is induced by homocysteine, promotes detachment-mediated PCD, and contributes to the development of atherosclerosis observed in hyperhomocysteinemia.

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Synthesis of transmembrane and secretory proteins occurs within the endoplasmic reticulum (ER) and isextremely important in the normal functioning of both the heart and kidney. The dysregulation of protein synthesis/processing within the ER causes the accumulation of unfolded proteins, thereby leading to ER stress and the activation of the unfolded protein response. Sarcoplasmic reticulum/ER Ca 2؉ disequilibrium can lead to cardiac hypertrophy via cytosolic Ca 2؉ elevation and stimulation of the Ca 2؉ /calmodulin, calcineurin, NF-AT3 pathway. Although cardiac hypertrophy may be initially adaptive, prolonged or severe ER stress resulting from the increased protein synthesis associated with cardiac hypertrophy can lead to apoptosis of cardiac myocytes and result in reduced cardiac output and chronic heart failure. The failing heart has a dramatic effect on renal function because of inadequate perfusion and stimulates the release of many neurohumoral factors that may lead to further ER stress within the heart, including angiotensin II and arginine-vasopressin. Renal failure attributable to proteinuria and uremia also induces ER stress within the kidney, which contributes to the transformation of tubular epithelial cells to a fibroblast-like phenotype, fibrosis, and tubular cell apoptosis, further diminishing renal function. As a consequence, cardiorenal syndrome may develop into a vicious circle with poor prognosis. New therapeutic modalities to alleviate ER stress through stimulation of the cytoprotective components of the unfolded protein response, including GRP78 upregulation and eukaryotic initiation factor 2␣ phosphorylation, may hold promise to reduce the high morbidity and mortality associated with cardiorenal syndrome. (Circ Res. 2011;106:629-642.) Key Words: angiotensin Ⅲ calcium Ⅲ cardiac failure Ⅲ cardiac hypertrophy Ⅲ ER stress H eart failure can be subdivided into 2 important categories, acute and chronic. Acute heart failure is primarily a manifestation of underlying vascular disease, including atherosclerosis, that leads to a sudden interruption of cardiac blood supply through thrombus formation and consequently myocardial infarction (MI). 1 To a lesser degree, MI may also result from coronary artery vasospasm and hyperreactivity of the underlying vascular smooth muscle layer caused by an imbalance between cellular factors that modulate vasoconstriction and vasodilation. 2 In both cases, cardiac myocyte hypoxia results in cell death through apoptosis or necrosis, 3 an acute inflammatory response and a chronic inflammatory response in the region of cell death. This results in scar tissue formation and the reduction of cardiac contractile capacity through myocyte cell loss.

Objective-Peroxynitrite, a potent oxidant generated by the reaction of NO with superoxide, has been implicated in the promotion of atherosclerosis. We designed this study to determine whether peroxynitrite induces its proatherogenic effects through induction of endoplasmic reticulum (ER) stress. Methods and Results-Human vascular endothelial cells treated with Sin-1, a peroxynitrite generator, induced the expression of the ER chaperones GRP78 and GRP94 and increased eIF2␣ phosphorylation. These effects were inhibited by the peroxynitrite scavenger uric acid. Sin-1 caused the depletion of ER-Ca 2ϩ , an effect known to induce ER stress, resulting in the elevation of cytosolic Ca 2ϩ and programmed cell death (PCD). Sin-1 treatment was also found, via 3-nitrotyrosine and GRP78 colocalization, to act directly on the ER. Adenoviral-mediated overexpression of GRP78 in endothelial cells prevented Sin-1-induced PCD. Consistent with these in vitro findings, 3-nitrotyrosine was observed and colocalized with GRP78 in endothelial cells of early atherosclerotic lesions from apolipoprotein E-deficient mice. Conclusions-Peroxynitrite is an ER stress-inducing agent. Its effects include the depletion of ER-Ca 2ϩ , a known mechanism of ER stress induction. The observation that 3-nitrotyrosine-containing proteins colocalize with markers of ER stress within early atherosclerotic lesions suggests that peroxynitrite contributes to atherogenesis through a mechanism involving ER stress. Key Words: endothelium Ⅲ nitric oxide Ⅲ endoplasmic reticulum Ⅲ atherosclerosis Ⅲ calcium E ndothelial dysfunction/injury represents a key early step in atherogenesis. The majority of risk factors for atherosclerosis, including, hyperlipidemia, hypertension, diabetes, and smoking, are associated with endothelial dysfunction. 1 A major function of the vascular endothelium is the regulation of vascular tone by NO through NO-induced smooth muscle relaxation. 2 Reduced NO bioavailability is a common feature in atherosclerosis and can result from oxidative stress. 3 In the apolipoprotein E-deficient (apoE Ϫ/Ϫ ) mouse model of atherosclerosis, endothelial dysfunction, as shown by decreased NO-mediated vasodilation to acetylcholine, correlates with increased atherosclerotic lesion size. 4 The availability of NO and superoxide (. O 2 -) within the atherosclerotic lesion creates the conditions for peroxynitrite formation because NO and . O 2 -react at physiological pH to form peroxynitrite. 5 A marker of peroxynitrite generation, 3-nitrotyrosine (3-NT) is elevated in human atherosclerotic lesions. 6,7 However, the mechanism by which reduced NO bioavailability and peroxynitrite formation contribute to atherosclerosis remains uncertain. See coverEndoplasmic reticulum (ER) stress, a cellular stress pathway induced by the accumulation of unfolded proteins in the ER, may offer an explanation for the contribution of peroxynitrite to atherosclerosis. ER stress results in an evolutionary conserved cellular response involving the upregulation of a set of genes, including ...

The course of hypertension development in young spontaneously hypertensive rats (SHR) was studied by the measurement of changes in systolic blood pressure (BP), body weight, and heart rate (HR) at 2, 3, 4, and 6 wk of age. To achieve this, we compared inbreeding lines of SHR and Wistar-Kyoto rats (WKY) to determine if differences in BP, body weight, or HR were present among inbreeding lines of the same strain or between strains. The effect of these differences on the eventual level of BP was then assessed. We found that BP began to diverge between SHR and WKY at 4 wk of age. Significant differences in systolic BP (24 mmHg) between SHR inbreeding lines at 4 wk of age did not affect the BP at 8 wk (172 vs. 170 mmHg). Pulse pressure was significantly higher in SHR than in WKY at 4 wk of age. HR was elevated in SHR over age-matched WKY at 3 wk of age and positively correlated to the level of BP attained by individual animals at 6 wk ( P = 0.037). Moreover, WKY inbreeding lines showing elevated HR developed higher BP (145 vs. 127 mmHg) at 10–12 and 20 wk of age. The prehypertensive tachycardia in SHR was investigated further and found to result from an increased intrinsic HR. Because HR at 3 wk is a genetic trait that can be partitioned into inbreeding lines, and inbreeding lines most expressive of this trait showed the highest eventual BP, we conclude that prehypertensive tachycardia may be an important first step during hypertension development in SHR. Moreover, early elevations in HR are highly predictive ( r = 0.41) of hypertension occurrence in the animal population studied.

Background:The integrated stress response (ISR) maintains cellular homeostasis during aberrant protein folding (ER stress). Results:The ISR enhances glutathione synthesis through up-regulation of cystathionine ␥-lyase via the eIF2␣-ATF4 pathway. Conclusion: Cells undergoing the ISR induce cystathionine ␥-lyase, thereby maintaining cellular homeostasis. Significance: These findings link the cells response to ER stress and redox homeostasis through the ISR.