Description: Background— Two endophenotypes of arterial calcification, calcification on arterial wall and calcification in atherosclerotic plaques, are associated with different types of cardiovascular events. Mgp -deficient mice showed matrix Gla protein (MGP) is strongly associated with calcification on arterial wall without atherosclerotic plaques, and MGP variants were not significantly associated with myocardial infarction. MGP may play different roles in the 2 endophenotypes. Methods and Results— We analyzed the associations of MGP variants rs4236, rs1800801, and rs1800802 with the 2 endophenotypes determined by multidetector computed tomography angiography. A total of 585 with calcification on coronary artery wall, 675 with calcification in coronary atherosclerotic plaques, 454 with calcification on aortic wall, and 725 controls were enrolled. After Bonferroni correction, rs4236 and rs1800801 were still associated with calcification on arterial wall, the odds ratios were 0.708 (95% confidence interval, 0.540–0.928) for rs4236 and 0.652 (95% confidence interval, 0.479–0.888) for rs1800801 in coronary artery wall calcification, and 0.699 (95% confidence interval, 0.525–0.931) for rs4236 and 0.650 (95% confidence interval, 0.467–0.905) for rs1800801 in aortic wall calcification, respectively. The variants were correlated with calcification severity by ln(CAC Agatston score+1) in coronary artery wall calcification but not in atherosclerotic plaque calcification. In accordance with their associations with calcification on arterial wall, rs4236C and rs1800801A were associated with higher MGP plasma levels, whereas rs1800802C was associated with lower MGP levels in normal controls. Because of the role of calcification in plaque vulnerability, their associations with acute myocardial infarction were also determined in 771 controls and 752 patients, no association was found. Conclusions— MGP genetic variants showed association with calcification on arterial wall but not with calcification in atherosclerotic plaques.

Description: Primary hypertension is a chronic disease with high morbidity, and the rate of controlled blood pressure is far from satisfactory, worldwide. Vaccination provides a promising approach for treatment of hypertension and improvement in compliance. Here, the ATRQβ-001 vaccine, a peptide (ATR-001) derived from human angiotensin II (Ang II) receptor type 1 conjugated with Qβ bacteriophage virus-like particles, was developed and evaluated in animal models of hypertension. The ATRQβ-001 vaccine significantly decreased the blood pressure of Ang II–induced hypertensive mice up to 35 mm Hg (143±4 versus 178±6 mm Hg; P =0.005) and that of spontaneously hypertensive rats up to 19 mm Hg (173±2 versus 192±3 mm Hg; P =0.003) and prevented remodeling of vulnerable hypertensive target organs. No obvious feedback activation of circulating or local renin-angiotensin system was observed. Additionally, no significant immune-mediated damage was detected in vaccinated hypertensive and nonhypertensive animals. The half-life of the anti-ATR-001 antibody was 14.4 days, surpassing that of existing chemical drugs. In vitro, the anti–ATR-001 antibody specifically bound to Ang II receptor type 1 and inhibited Ca 2+ -dependent signal transduction events, including protein kinase C-α translocation, extracellular signal-regulated kinase 1/2 phosphorylation (72% decrease; P =0.013), and elevation of intracellular Ca 2+ (68% decrease; P =0.017) induced by Ang II, but without inhibiting Ang II binding to the receptor. In conclusion, the ATRQβ-001 vaccine decreased the blood pressure of Ang II–induced hypertensive mice and spontaneously hypertensive rats effectively through diminishing the pressure response and inhibiting signal transduction initiated by Ang II. Thus, the ATRQβ-001 vaccine may provide a novel and promising method for the treatment of primary hypertension.

Description: Objective— The development of a murine model of spontaneous atherosclerotic plaque rupture with luminal thrombus. Methods and Results— Combined partial ligation of the left renal artery and left common carotid artery in 8-week-old apolipoprotein E–deficient mice induced endogenous renovascular hypertension and local low oscillatory shear stress in the left common carotid artery. After 8 weeks, a fresh left common carotid artery lumen thrombus associated with severe plaque burden was found in 50% (10/20) of the mice. Histological analyses indicated that all left common carotid artery lesions had vulnerable features, and 50% (5/10) of the mice showed plaque rupture with a lumen thrombus. Multiple layers with layering discontinuity and intraplaque hemorrhages were found in 80% (8/10) of the mice. Further experiments showed that both increased blood pressure, and angiotensin-II contributed to plaque progression and vulnerability. Decreased intimal collagen associated with increased collagenase activity and matrix metalloproteinase expression also resulted in plaque disruption. Conclusion— We demonstrate a murine model of spontaneous plaque rupture with a high incidence of luminal thrombus. The model not only nicely recapitulates the pathophysiological processes of human plaque rupture but it is also simple, fast, and highly efficient to generate.

Description: A multitude of evidence suggests that iodinated contrast material causes nephrotoxicity; however, there have been no previous studies that use arterial spin labeling (ASL) blood flow functional magnetic resonance imaging (fMRI) to investigate the alterations in effective renal plasma flow between normointensive and hypertensive rats following injection of contrast media. We hypothesized that FAIR-SSFSE arterial spin labeling MRI may enable noninvasive and quantitative assessment of regional renal blood flow abnormalities and correlate with disease severity as assessed by histological methods. Renal blood flow (RBF) values of the cortex and medulla of rat kidneys were obtained from ASL images postprocessed at ADW4.3 workstation 0.3, 24, 48, and 72 h before and after injection of iodinated contrast media (6 ml/kg). The H&E method for morphometric measurements was used to confirm the MRI findings. The RBF values of the outer medulla were lower than those of the cortex and the inner medulla as reported previously. Iodinated contrast media treatment resulted in decreases in RBF in the outer medulla and cortex in spontaneously hypertensive rats (SHR), but only in the outer medulla in normotensive rats. The iodinated contrast agent significantly decreased the RBF value in the outer medulla and the cortex in SHR compared with normotensive rats after injection of the iodinated contrast media. Histological observations of kidney morphology were also consistent with ASL perfusion changes. These results demonstrate that the RBF value can reflect changes of renal perfusion in the cortex and medulla. ASL-MRI is a feasible and accurate method for evaluating nephrotoxic drugs-induced kidney damage.

Description: Rationale: Transplantation of stem cells into damaged hearts has had modest success as a treatment for ischemic heart disease. One of the limitations is the poor stem cell survival in the diseased microenvironment. Prolyl hydroxylase domain protein 2 (PHD2) is a cellular oxygen sensor that regulates 2 key transcription factors involved in cell survival and inflammation: hypoxia-inducible factor and nuclear factor-B. Objective: We studied whether and how PHD2 silencing in human adipose-derived stem cells (ADSCs) enhances their cardioprotective effects after transplantation into infarcted hearts. Methods and Results: ADSCs were transduced with lentiviral short hairpin RNA against prolyl hydroxylase domain protein 2 (shPHD2) to silence PHD2. ADSCs, with or without shPHD2, were transplanted after myocardial infarction in mice. ADSCs reduced cardiomyocyte apoptosis, fibrosis, and infarct size and improved cardiac function. shPHD2-ADSCs exerted significantly more protection. PHD2 silencing induced greater ADSC survival, which was abolished by short hairpin RNA against hypoxia-inducible factor-1α. Conditioned medium from shPHD2-ADSCs decreased cardiomyocyte apoptosis. Insulin-like growth factor-1 (IGF-1) levels were significantly higher in the conditioned medium of shPHD2-ADSCs versus ADSCs, and depletion of IGF-1 attenuated the cardioprotective effects of shPHD2-ADSC–conditioned medium. Nuclear factor-B activation was induced by shPHD2 to induce IGF-1 secretion via binding to IGF-1 gene promoter. Conclusions: PHD2 silencing promotes ADSCs survival in infarcted hearts and enhances their paracrine function to protect cardiomyocytes. The prosurvival effect of shPHD2 on ADSCs is hypoxia-inducible factor-1α dependent, and the enhanced paracrine function of shPHD2-ADSCs is associated with nuclear factor-B–mediated IGF-1 upregulation. PHD2 silencing in stem cells may be a novel strategy for enhancing the effectiveness of stem cell therapy after myocardial infarction.

Description: Background and Purpose— A novel quantitative susceptibility mapping (QSM) processing technology has been developed to map tissue susceptibility property without blooming artifacts. We hypothesize that hematoma volume measurement on QSM is independent of imaging parameters, eliminating its echo time dependence on gradient echo MRI. Methods— Gradient echo MRI of 16 patients with intracerebral hemorrhage was processed with susceptibility-weighted imaging, R 2 * (=1/T2*) mapping, and QSM at various echo times. Hematoma volumes were measured from these images. Results— Linear regression of hematoma volume versus echo time showed substantial slopes for gradient echo magnitude (0.45±0.31 L/s), susceptibility-weighted imaging (0.52±0.46), and R 2 * (0.39±0.30) but nearly zero slope for QSM (0.01±0.05). At echo time=20 ms, hematoma volume on QSM was 0.80 x that on gradient echo magnitude image ( R 2 =0.99). Conclusions— QSM can provide reliable measurement of hematoma volume, which can be performed rapidly and accurately using a semiautomated segmentation tool.

Description: Objective— This study determined the role of angiotensin-converting enzyme (ACE) on the development of angiotensin I–induced atherosclerosis and the contribution of leukocyte-specific expression of this enzyme. Approach and Results— To define the contribution of ACE-dependent activity to angiotensin II synthesis in atherosclerotic development, male low-density lipoprotein receptor –/– mice were fed a fat-enriched diet and infused with either angiotensin I or angiotensin II. The same infusion rate of these peptides had equivalent effects on atherosclerotic development. Coinfusion of an ACE inhibitor, enalapril, ablated angiotensin I–augmented atherosclerosis but had no effect on angiotensin II–induced lesion development. ACE protein was detected in several cell types in atherosclerotic lesions, with a predominance in macrophages. This cell type secreted angiotensin II, which was ablated by ACE inhibition. To study whether leukocyte ACE contributed to atherosclerosis, irradiated male low-density lipoprotein receptor –/– mice were repopulated with bone marrow–derived cells from either ACE +/+ or ACE –/– mice and fed the fat-enriched diet for 12 weeks. Chimeric mice with ACE deficiency in bone marrow–derived cells had modestly reduced atherosclerotic lesions in aortic arches but had no effects in aortic roots. Conclusions— ACE mediates angiotensin I–induced atherosclerosis, and ACE expression in leukocytes modestly contributes to atherosclerotic development in hypercholesterolemic mice.

Description: Interferon regulatory factor 1 (IRF1), a critical member of the IRF family, was previously shown to be associated with the immune system and to be involved in apoptosis and tumor suppression. However, the role of IRF1 in pressure overload–induced cardiac remodeling has remained unclear. Using genetic approaches, we established a central role for the IRF1 transcription factor in the regulation of cardiac remodeling both in vivo and in vitro, and we determined the mechanism underlying this process. The expression level of IRF1 was remarkably altered in both failing human hearts and hypertrophic murine hearts. Transgenic mice with cardiac-specific IRF1 overexpression exacerbated aortic banding–induced cardiac hypertrophy, ventricular dilation, fibrosis, and dysfunction, whereas IRF1-deficient (knockout) mice exhibited a significant reduction in the hypertrophic response. Similar results were observed in a global IRF1-knockout rat model. Mechanistically, the prohypertrophic effects elicited by IRF1 in response to pathological stimuli were associated with the direct activation of inducible nitric oxide synthase (iNOS). Furthermore, we identified 1 IRF1-binding site in the promoter region of the iNOS gene, which was essential for its transcription. To examine the IRF1-iNOS axis in vivo, we generated IRF1-transgenic/iNOS-knockout mice. IRF1 exerted profoundly detrimental effects in these mice; however, these effects were nullified by iNOS ablation. These data suggest the IRF1–iNOS axis as a crucial regulator of cardiac remodeling and that IRF1 could be a potent therapeutic target for cardiac remodeling.

Description: Objective— Kindlin-3 is a critical supporter of integrin function in platelets. Lack of expression of kindlin-3 protein in patients impairs integrin αIIbβ3–mediated platelet aggregation. Although kindlin-3 has been categorized as an integrin-binding partner, the functional significance of the direct interaction of kindlin-3 with integrin αIIbβ3 in platelets has not been established. Here, we evaluated the significance of the binding of kindlin-3 to integrin αIIbβ3 in platelets in supporting integrin αIIbβ3–mediated platelet functions. Approach and Results— We generated a strain of kindlin-3 knockin (K3KI) mice that express a kindlin-3 mutant that carries an integrin-interaction defective substitution. K3KI mice could survive normally and express integrin αIIbβ3 on platelets similar to their wild-type counterparts. Functional analysis revealed that K3KI mice exhibited defective platelet function, including impaired integrin αIIbβ3 activation, suppressed platelet spreading and platelet aggregation, prolonged tail bleeding time, and absence of platelet-mediated clot retraction. In addition, whole blood drawn from K3KI mice showed resistance to in vitro thrombus formation and, as a consequence, K3KI mice were protected from in vivo arterial thrombosis. Conclusions— These observations demonstrate that the direct binding of kindlin-3 to integrin αIIbβ3 is involved in supporting integrin αIIbβ3 activation and integrin αIIbβ3-dependent responses of platelets and consequently contributes significantly to arterial thrombus formation.

Description: The cardiopulmonary baroreflex responds to an increase in central venous pressure (CVP) by decreasing total peripheral resistance and increasing heart rate (HR) in dogs. However, the direction of ventricular contractility change is not well understood. The aim was to elucidate the cardiopulmonary baroreflex control of ventricular contractility during normal physiological conditions via a mathematical analysis. Spontaneous beat-to-beat fluctuations in maximal ventricular elastance ( E max ), which is perhaps the best available index of ventricular contractility, CVP, arterial blood pressure (ABP), and HR were measured from awake dogs at rest before and after β-adrenergic receptor blockade. An autoregressive exogenous input model was employed to jointly identify the three causal transfer functions relating beat-to-beat fluctuations in CVP to E max (CVP -〉 E max ), which characterizes the cardiopulmonary baroreflex control of ventricular contractility, ABP to E max , which characterizes the arterial baroreflex control of ventricular contractility, and HR to E max , which characterizes the force-frequency relation. The CVP -〉 E max transfer function showed a static gain of 0.037 ± 0.010 ml –1 (different from zero; P 〈 0.05) and an overall time constant of 3.2 ± 1.2 s. Hence, E max would increase and reach steady state in ~16 s in response to a step increase in CVP, without any change to ABP or HR, due to the cardiopulmonary baroreflex. Following β-adrenergic receptor blockade, the CVP -〉 E max transfer function showed a static gain of 0.0007 ± 0.0113 ml –1 (different from control; P 〈 0.10). Hence, E max would change little in steady state in response to a step increase in CVP. Stimulation of the cardiopulmonary baroreflex increases ventricular contractility through β-adrenergic receptor system mediation.