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SummaryCellular senescence and organismal aging predispose age-related chronic diseases, such as neurodegenerative, metabolic, and cardiovascular disorders. These diseases emerge coincidently from elevated oxidative/electrophilic stress, inflammation, mitochondrial dysfunction, DNA damage, and telomere dysfunction and shortening. Mechanistic linkages are incompletely understood. Here, we show that ablation of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) accelerates vascular aging and atherosclerosis, coinciding with telomere dysfunction and shortening and DNA damage. PGC-1α deletion reduces expression and activity of telomerase reverse transcriptase (TERT) and increases p53 levels. Ectopic expression of PGC-1α coactivates TERT transcription and reverses telomere malfunction and DNA damage. Furthermore, alpha lipoic acid (ALA), a non-dispensable mitochondrial cofactor, upregulates PGC-1α-dependent TERT and the cytoprotective Nrf-2-mediated antioxidant/electrophile-responsive element (ARE/ERE) signaling cascades, and counteracts high-fat-diet-induced, age-dependent arteriopathy. These results illustrate the pivotal importance of PGC-1α in ameliorating senescence, aging, and associated chronic diseases, and may inform novel therapeutic approaches involving electrophilic specificity.

Background Lifestyle modifications are first‐line measures for cardiovascular disease prevention. Whether lifestyle intervention also preserves cardiovascular health is less clear. Our study examined the role of a Health Partner–administered lifestyle intervention on metrics of ideal cardiovascular health. Methods and Results A total of 711 university employees (48±11 years; 66% women, 72% Caucasian/22.5% African Americans) enrolled in a program that promoted healthier lifestyles at Emory University (Atlanta, GA). Anthropometric, laboratory, and physical activity measurements were performed at baseline and at 6 months, 1 year, and 2 years of follow‐up. Results were utilized by the Health Partner to generate a personalized plan aimed at meeting ideal health metrics. Compared to baseline, at each of the 6‐month, 1‐year, and 2‐year follow‐up visits, systolic blood pressure was lower by 3.6, 4.6, and 3.3 mm Hg ( P P 2 ( P P Conclusions A personalized, goal‐directed Health Partner intervention significantly improved the cardiometabolic risk profile and metrics of cardiovascular health. These effects were evident at 6 months following enrollment and were sustained for 2 years. Whether the Health Partner intervention improves long‐term morbidity and mortality and is cost‐effective needs further investigation.

Akt/protein kinase B (PKB) activation/phosphorylation by angiotensin II (Ang II) is a critical signaling event in hypertrophy of vascular smooth muscle cells (VSMCs). Conventional wisdom asserts that Akt activation occurs mainly in plasma membrane domains. Recent evidence that Akt activation may take place within intracellular compartments challenges this dogma. The spatial identity and mechanistic features of these putative signaling domains have not been defined. Using cell fractionation and fluorescence methods, we demonstrate that the early endosomal antigen-1 (EEA1)-positive endosomes are a major site of Ang II-induced Akt activation. Akt moves to and is activated in EEA1 endosomes. The expression of EEA1 is required for phosphorylation of Akt at both Thr-308 and Ser-473 as well as for phosphorylation of its downstream targets mTOR and S6 kinase, but not for Erk1/2 activation. Both Akt and phosphorylated Akt (p-Akt) interact with EEA1. We also found that PKC-α is required for organizing Ang II-induced, EEA1-dependent Akt phosphorylation in VSMC early endosomes. EEA1 expression enables PKC-α phosphorylation, which in turn regulates Akt upstream signaling kinases, PDK1 and p38 MAPK. Our results indicate that PKC-α is a necessary regulator of EEA1-dependent Akt signaling in early endosomes. Finally, EEA1 down-regulation or expression of a dominant negative mutant of PKC-α blunts Ang II-induced leucine incorporation in VSMCs. Thus, EEA1 serves a novel function as an obligate scaffold for Ang II-induced Akt activation in early endosomes.

Proton nuclear magnetic resonance (1H-NMR) spectroscopy of plasma provides a global metabolic profiling method that shows promise for clinical diagnostics. However, cross-sectional studies are complicated by a lack of understanding of intraindividual variation, and this limits experimental design and interpretation of data. The present study determined the diurnal variation detected by1H NMR spectroscopy of human plasma. Data reduction methods revealed three time-of-day metabolic patterns, which were associated with morning, afternoon, and night. Major discriminatory regions for these time-of-day patterns included the various kinds of lipid signals (-CH2- and -CH2OCOR), and the region between 3 and 4 ppm heavily overlapped with amino acids that had α-CH and α-CH2. The phasing and duration of time-of-day patterns were variable among individuals, apparently because of individual difference in food processing/digestion and absorption and clearance of macronutrient energy sources (fat, protein, carbohydrate). The times of day that were most consistent among individuals, and therefore most useful for cross-sectional studies, were fasting morning (0830–0930), postprandial afternoon (1430–1630), and nighttime samples (0430–0530). Importantly, the integrated picture of metabolism provided by1H-NMR spectroscopy of plasma suggests that this approach is suitable to study complex regulatory processes, including eating patterns/eating disorders, upper gastrointestinal functions (gastric emptying, pancreatic, biliary functions), and absorption/clearance of macronutrients. Hence,1H-NMR spectroscopy of plasma could provide a global metabolic tolerance test to assess complex processes involved in disease, including eating disorders and the range of physiological processes causing dysregulation of energy homeostasis.

Aims The purpose of this analysis was to determine whether the efficacy of adenosine vs. placebo was dependent on the timing of reperfusion therapy in the second Acute Myocardial Infarction Study of Adenosine (AMISTAD-II). Methods and results Patients presenting with ST-segment elevation anterior AMI were randomized to receive placebo vs. adenosine (50 or 70 µg/kg/min) for 3 h starting within 15 min of reperfusion therapy. In the present post hoc hypothesis generating study, the results were stratified according to the timing of reperfusion, i.e. ≥ or < the median 3.17 h, and by reperfusion modality. In patients receiving reperfusion

Objective— Angiotensin II (Ang II) is a potent mediator of vascular hypertrophy in vascular smooth muscle cells (VSMCs). These effects are mediated through the Ang II type 1 receptor (AT 1 R) and require its trafficking through caveolin-1 (Cav1)–enriched lipid rafts and reactive oxygen species (ROS) derived from Rac1-dependent NAD(P)H oxidase. The specific role(s) of Cav1 in AT 1 R signaling is incompletely understood. Methods and Results— Knockdown of Cav1 protein by small interfering RNA (siRNA) inhibits Ang II–stimulated Rac1 activation and membrane translocation, H 2 O 2 production, ROS-dependent epidermal growth factor receptor (EGF-R) transactivation, and subsequent phosphorylation of Akt without affecting ROS-independent extracellular signal-regulated kinase 1/2 phosphorylation. Ang II stimulates tyrosine phosphorylation of Sos-1, a Rac–guanine nucleotide exchange factor, which is inhibited by Cav1 siRNA, demonstrating involvement of Cav1 in Rac1 activation. Detergent-free fractionation showed that EGF-Rs are found basally in Cav1-enriched lipid raft membranes and associate with Cav1. Ang II stimulates AT 1 R movement into these microdomains contemporaneously with the egress of EGF-R. Both aspects of this bidirectional receptor trafficking are inhibited by Cav1 siRNA. Moreover, Cav1 siRNA inhibits Ang II–induced vascular hypertrophy. Conclusions— Cav1 plays an essential role in AT 1 R targeting into Cav1-enriched lipid rafts and Rac1 activation, which are required for proper organization of ROS-dependent Ang II signaling linked to VSMC hypertrophy.

ObjectivesThe purpose of this research was to determine the effect of intravenous adenosine on clinical outcomes and infarct size in ST-segment elevation myocardial infarction (STEMI) patients undergoing reperfusion therapy.BackgroundPrevious small studies suggest that adenosine may reduce the size of an evolving infarction.MethodsPatients (n = 2,118) with evolving anterior STEMI receiving thrombolysis or primary angioplasty were randomized to a 3-h infusion of either adenosine 50 or 70 μg/kg/min or of placebo. The primary end point was new congestive heart failure (CHF) beginning >24 h after randomization, or the first re-hospitalization for CHF, or death from any cause within six months. Infarct size was measured in a subset of 243 patients by technetium-99m sestamibi tomography.ResultsThere was no difference in the primary end point between placebo (17.9%) and either the pooled adenosine dose groups (16.3%) or, separately, the 50-μg/kg/min dose and 70-μg/kg/min groups (16.5% vs. 16.1%, respectively, p = 0.43). The pooled adenosine group trended toward a smaller median infarct size compared with the placebo group, 17% versus 27% (p = 0.074). A dose-response relationship with final median infarct size was seen: 11% at the high dose (p = 0.023 vs. placebo) and 23% at the low dose (p = NS vs. placebo). Infarct size and occurrence of a primary end point were significantly related (p < 0.001).ConclusionsClinical outcomes in patients with STEMI undergoing reperfusion therapy were not significantly improved with adenosine, although infarct size was reduced with the 70-μg/kg/min adenosine infusion, a finding that correlated with fewer adverse clinical events. A larger study limited to the 70-μg/kg/min dose is, therefore, warranted.

Objective— Angiotensin II has been implicated in the pathogenesis of the vascular complications of insulin resistance. Recently, serine phosphorylation and degradation of insulin receptor substrate-1 (IRS-1) were shown to inhibit Akt activation and reduce glucose uptake. Therefore, we examined the effects of chronic angiotensin II treatment on IRS-1 phosphorylation and protein expression in vascular smooth muscle cells (VSMCs). Methods and Results— Using Western analysis, we found that angiotensin II (100 nmol/L; 18 hours) caused a 61±5% degradation of IRS-1 and abolished insulin-induced activation of Akt. Phosphorylation of IRS-1 on Ser307, which leads to subsequent IRS-1 degradation, was stimulated by angiotensin II. This phosphorylation was blocked by the Src inhibitor PP1 and by the antioxidants N -acetylcysteine and ebselen. Stable overexpression of catalase abrogated angiotensin II–induced IRS-1 phosphorylation and IRS-1 degradation. Similarly, a mutant phosphoinositide-dependent kinase-1 (PDK1) that cannot associate with Src abolished IRS-1 phosphorylation and degradation induced by angiotensin II. Proteasome inhibitors also prevented IRS-1 degradation. Conclusions— Thus, angiotensin II decreases IRS-1 protein levels in VSMCs via Src, PDK1, and reactive oxygen species–mediated phosphorylation of IRS-1 on Ser307 and subsequent proteasome-dependent degradation. These events impair insulin signaling and provide a molecular basis for understanding the clinical observation that angiotensin II type 1 receptor antagonists improve insulin resistance and its associated vasculopathies.

We have previously demonstrated that both isoprenylcysteine carboxylmethyltransferase (ICMT) and one of its substrates, the RhoGTPase Rac1, are critical for the tumor necrosis factor α (TNFα) stimulation of vascular cell adhesion molecule-1 expression in endothelial cells (EC). Here, we have shown that ICMT regulates TNFα stimulation of Rac1 activity. TNFα stimulation of EC increased the membrane association of Rac1, an event that is essential for Rac1 activity. ICMT inhibitor N-acetyl-S-farnesyl-l-cysteine (AFC) blocked the accumulation of Rac1 into the membrane both in resting and TNFα-stimulated conditions. Similarly, the membrane-associated Rac1 was lower in Icmt-deficient versus wild-type mouse embryonic fibroblasts (MEFs). TNFα also increased the level of GTP-Rac1, the active form of Rac1, in EC. AFC completely suppressed the TNFα stimulation of increase in GTP-Rac1 levels. Confocal microscopy revealed resting EC Rac1 was present in the plasma membrane and also in the perinuclear region. AFC mislocalized Rac1, both from the plasma membrane and the perinuclear region. Mislocalization of Rac1 was also observed in Icmt-deficient versus wild-type MEFs. To determine the consequences of ICMT inhibition, we investigated the effect of AFC on p38 mitogen-activated protein (MAP) kinase phosphorylation, which is downstream of Rac1. AFC inhibited the TNFα stimulation of p38 MAP kinase phosphorylation in EC. TNFα stimulation of p38 MAP kinase phosphorylation was also significantly attenuated in Icmt-deficient versus wild-type MEFs. To understand the mechanism of inhibition of Rac1 activity, we examined the effect of ICMT inhibition on the interaction of Rac1 with its inhibitor, Rho guanine nucleotide dissociation inhibitor (RhoGDI). The association of Rac1 with its inhibitor RhoGDI was dramatically increased in the Icmt-deficient versus wild-type MEFs both in resting as well as in TNFα-stimulated conditions, suggesting that RhoGDI was involved in inhibiting Rac1 activity under the conditions of ICMT inhibition. These results suggest that ICMT regulates Rac1 activity by controlling the interaction of Rac1 with RhoGDI. We hypothesize that ICMT regulates the release of Rac1 from RhoGDI.

Angiogenesis, a process of new blood vessel growth, contributes to various pathophysiologies such as cancer, diabetic retinopathy and atherosclerosis. Accumulating evidence suggests that cardiovascular diseases are associated with increased oxidative stress in blood vessels. Reactive oxygen species (ROS) such as superoxide and H2O2 cause blood vessels to thicken, produce inflammation in the vessel wall, and thus are regarded as "risk factors" for vascular disease, whereas ROS also act as signaling molecules in many aspects of growth factor-mediated physiological responses. Recent reports suggest that ROS play an important role in angiogenesis; however, its underlying molecular mechanisms remain unknown. Vascular endothelial growth factor (VEGF) induces angiogenesis by stimulating endothelial cell (EC) proliferation and migration primarily through the receptor tyrosine kinase VEGF receptor2 (Flk1/KDR). VEGF binding initiates tyrosine phosphorylation of KDR, which results in activation of downstream signaling enzymes including ERK1/2, Akt and eNOS, which contribute to angiogenic-related responses in EC. Importantly, the major source of ROS in EC is a NAD(P)H oxidase and EC express all the components of phagocytic NAD(P)H oxidase including gp91phox, p22phox, p47phox, p67phox and the small G protein Rac1. We have recently demonstrated that ROS derived from NAD(P)H oxidase are critically important for VEGF signaling in vitro and angiogenesis in vivo. Furthermore, a peptide hormone, angiotensin II, a major stimulus for vascular NAD(P)H oxidase, also plays an important role in angiogenesis. Because EC migration and proliferation are primary features of the process of myocardial angiogenesis, we would like to focus on the recent progress that has been made in the emerging area of NAD(P)H oxidase-derived ROS-dependent signaling in ECs, and discuss the possible roles in angiogenesis. Understanding these mechanisms may provide insight into the components of NAD(P)H oxidase as potential therapeutic targets for treatment of angiogenesis-dependent diseases such as cancer and atherosclerosis and for promoting myocardial angiogenesis in ischemic heart diseases.

3-Phosphoinositide-dependent protein kinase 1 (PDK1) is a signal integrator that activates the AGC superfamily of serine/threonine kinases. PDK1 is phosphorylated on tyrosine by oxidants, although its regulation by agonists that stimulate G-protein-coupled receptor signaling pathways and the physiological consequences of tyrosine phosphorylation in this setting have not been fully identified. We found that angiotensin II stimulates the tyrosine phosphorylation of PDK1 in vascular smooth muscle in a calcium- and c-Src-dependent manner. The calcium-activated tyrosine kinase Pyk2 acts as a scaffold for Src-dependent phosphorylation of PDK1 on Tyr9, which permits phosphorylation of Tyr373 and -376 by Src. This critical function of Pyk2 is further supported by the observation that Pyk2 and tyrosine-phosphorylated PDK1 colocalize in focal adhesions after angiotensin II stimulation. Importantly, infection of smooth muscle cells with a Tyr9 mutant of PDK1 inhibits angiotensin II-induced tyrosine phosphorylation of paxillin and focal adhesion formation. These observations identify a novel interaction between PDK1 and Pyk2 that regulates the integrity of focal adhesions, which are major compartments for integrating signals for cell growth, apoptosis, and migration.

In 1998, the American Heart Association convened Prevention Conference V to examine strategies for the identification of high-risk patients who need primary prevention. Among the strategies discussed was the measurement of markers of inflammation.1 The Conference concluded that “many of these markers (including inflammatory markers) are not yet considered applicable for routine risk assessment because of: (1) lack of measurement standardization, (2) lack of consistency in epidemiological findings from prospective studies with endpoints, and (3) lack of evidence that the novel marker adds to risk prediction over and above that already achievable through the use of established risk factors.” The National Cholesterol Education Program Adult Treatment Panel III Guidelines identified these markers as emerging risk factors,1a which could be used as an optional risk factor measurement to adjust estimates of absolute risk obtained using standard risk factors. Since these publications, a large number of peer-reviewed scientific reports have been published relating inflammatory markers to cardiovascular disease (CVD). Several commercial assays for inflammatory markers have become available. As a consequence of the expanding research base and availability of assays, the number of inflammatory marker tests ordered by clinicians for CVD risk prediction has grown rapidly. Despite this, there has been no consensus from professional societies or governmental agencies as to how these assays of markers of inflammation should be used in clinical practice. On March 14 and 15, 2002, a workshop titled “CDC/AHA Workshop on Inflammatory Markers and Cardiovascular Disease: Applications to Clinical and Public Health Practice” was convened in Atlanta, Ga, to address these issues. The goals of this workshop were to determine which of the currently available tests should be used; what results should be used to define high risk; which patients should be tested; and the indications for which the tests would be most useful. These …

Angiotensin II (Ang II) induces transactivation of the epidermal growth factor (EGF) receptor (EGF-R), which serves as a scaffold for various signaling molecules in vascular smooth muscle cells (VSMCs). Cholesterol and sphingomyelin-enriched lipid rafts are plasma membrane microdomains that concentrate various signaling molecules. Caveolae are specialized lipid rafts that are organized by the cholesterol-binding protein, caveolin, and have been shown to be associated with EGF-Rs. Angiotensin II stimulation promotes a rapid movement of AT1 receptors to caveolae; however, their functional role in angiotensin II signaling has not been elucidated. Here we show that cholesterol depletion by β-cyclodextrin disrupts caveolae structure and concomitantly inhibits tyrosine phosphorylation of the EGF-R and subsequent activation of protein kinase B (PKB)/Akt induced by angiotensin II. Similar inhibitory effects were obtained with other cholesterol-binding agents, filipin and nystatin. In contrast, EGF-R autophosphorylation and activation of Akt/PKB in response to EGF are not affected by cholesterol depletion. The early Ang II-induced upstream signaling events responsible for transactivation of the EGF-R, such as the intracellular Ca2+ increase and c-Src activation, also remain intact. The EGF-R initially binds caveolin, but these two proteins rapidly dissociate following angiotensin II stimulation during the time when EGF-R transactivation is observed. The activated EGF-R is localized in focal adhesions together with tyrosine-phosphorylated caveolin. These findings suggest that 1) a scaffolding role of caveolin is essential for EGF-R transactivation by angiotensin II and 2) cholesterol-rich microdomains as well as focal adhesions are important signal-organizing compartments required for the spatial and temporal organization of angiotensin II signaling in VSMCs.

Abstract —Angiotensin II (Ang II) is a vasoactive hormone with critical roles in vascular smooth muscle cell growth, an important feature of hypertension and atherosclerosis. Many of these effects are dependent on the production of reactive oxygen species (ROS). Ang II induces phosphorylation of the epidermal growth factor (EGF) receptor (EGF-R), which serves as a scaffold for various signaling molecules. Here, we provide novel evidence that ROS are critical mediators of EGF-R transactivation by Ang II. Pretreatment of vascular smooth muscle cells with the antioxidants diphenylene iodonium, Tiron, N -acetylcysteine, and ebselen significantly inhibited (≈80% to 90%) tyrosine phosphorylation of the EGF-R by Ang II but not by EGF. Of the 5 autophosphorylation sites on the EGF-R, Ang II mainly phosphorylated Tyr1068 and Tyr1173 in a redox-sensitive manner. The Src family kinase inhibitor PP1, overexpression of kinase-inactive c-Src, or chelation of intracellular Ca 2+ attenuated EGF-R transactivation. Although antioxidants had no effects on the Ca 2+ mobilization or phosphorylation of Ca 2+ -dependent tyrosine kinase Pyk2, they inhibited c-Src activation by Ang II, suggesting that c-Src is 1 signaling molecule that links ROS and EGF-R phosphorylation. Furthermore, Ang II–induced tyrosine phosphorylation of the autophosphorylation site and the SH2 domain of c-Src was redox sensitive. These findings emphasize the importance of ROS in specific Ang II–stimulated growth-related signaling pathways and suggest that redox-sensitive EGF-R transactivation may be a potential target for antioxidant therapy in vascular disease.

It is now recognized that the mechanical environment of a cell has an influence on its structure and function. For the vascular endothelial cell that resides at the interface of the flowing blood and the underlying vessel wall, there is mounting evidence of the importance of flow and the associated wall shear stress in the regulation of endothelial biology. Not only is it a sensitive regulator of endothelial structure and function, but different flow environments will influence endothelial cell biology differently. Furthermore, there may be an interaction between the chemical environment of a cell and its mechanical environment. This is illustrated by the inhibition by steady laminar shear stress of the cytokine induction of VCAM-1. Results also are presented in which flow studies have been conducted using a co-culture model of the vessel wall. These experiments provide evidence of a quiescent endothelium; however, much more needs to be done to engineer the cell culture environment to make it more physiologic.

Activation of phospholipase C (PLC) is one of the earliest events in angiotensin II (Ang II) type 1 (AT1) receptor (R)-mediated signal transduction in vascular smooth muscle cells (VSMCs). The coupling mechanisms of AT1 Rs to PLC, however, are controversial, because both tyrosine phosphorylation of PLC-γ and G protein-dependent PLC-β activation pathways have been reported. The expression of PLC-β1, furthermore, has not been consistently demonstrated in VSMCs. Here we identified the PLC subtypes and subunits of heterotrimeric G proteins involved in AT1 R-PLC coupling using cultured rat VSMCs. Western analysis revealed the expression of PLC-β1, -γ1, and -δ1 in VSMCs. Ang II-stimulated inositol trisphosphate (IP3) formation measured at 15 s, which corresponds to the peak response, was significantly inhibited by electroporation of antibodies against PLC-β1, but not by anti-PLC-γ and -δ antibodies. Electroporation of anti-Gαq/11 and -Gα12 antibodies also showed significant inhibition of the Ang II-induced IP3 generation at 15 s, while anti-Gαi and Gα13 antibodies were ineffective. Furthermore, in VSMCs electroporated with anti-Gβ antibody and cells stably transfected with the plasmid encoding the Gβγ-binding region of the carboxyl terminus of β-adrenergic receptor kinase1, the peak Ang II-stimulated PLC activity (at 15 s) was significantly inhibited. The tyrosine kinase inhibitor, genistein, had no effect on the peak response to Ang II stimulation, but significantly inhibited IP3 production after 30 s, a time period which temporally correlated with PLC-γ tyrosine phosphorylation in response to Ang II. Moreover, electropor-ation of anti-PLC-γ antibody markedly inhibited the IP3production measured at 30 s, indicating that tyrosine phosphorylation of PLC-γ contributes mainly to the later phase of PLC activation. Thus, these results suggest that: 1) AT1receptors sequentially couple to PLC-β1 via a heterotrimeric G protein and to PLC-γ via a downstream tyrosine kinase; 2) the initial AT1 receptor-PLC-β1 coupling is mediated by Gαq/11βγ and Gα12βγ; 3) Gβγ acts as a signal transducer for activation of PLC in VSMCs. The sequential coupling of AT1 receptors to PLC-β1 and PLC-γ, as well as dual coupling of AT1 receptors to distinct Gα proteins, suggests a novel mechanism for a temporally controlled, highly organized and convergent Ang II-signaling network in VSMCs.

Angiotensin II induces an oxidant stress-dependent hypertrophy in cultured vascular smooth muscle cells. To investigate the growth-related molecular targets of H2O2, we examined the redox sensitivity of agonist-stimulated activation of the mitogen-activated protein kinase (MAPK) family. We show here that angiotensin II elicits a rapid increase in intracellular H2O2 and a rapid and robust phosphorylation of both p42/44MAPK (16-fold) and p38MAPK (15-fold). However, exogenous H2O2 activates only p38MAPK (14-fold), and diphenylene iodonium, an NADH/NADPH oxidase inhibitor, attenuates angiotensin II-stimulated phosphorylation of p38MAPK, but not p42/44MAPK. Furthermore, in cells stably transfected with human catalase, angiotensin II-induced intracellular H2O2 generation is almost completely blocked, resulting in inhibition of phosphorylation of p38MAPK, but not p42/44MAPK, and a subsequent partial decrease in angiotensin II-induced hypertrophy. Specific inhibition of either the p38MAPK pathway with SB203580 (4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole) or the p42/44MAPK pathway with PD98059 (2-(2′-amino-3′-methoxyphenyl)oxanaphthalen-4-one) also partially, but significantly, attenuates angiotensin II-induced hypertrophy; however, simultaneous blockade of both pathways has an additive inhibitory effect, indicating that the hypertrophic response to angiotensin II requires parallel, independent activation of both MAPK pathways. These results provide the first evidence that p38MAPK is a critical component of the oxidant stress (H2O2)-sensitive signaling pathways activated by angiotensin II in vascular smooth muscle cells and indicate that it plays a crucial role in vascular hypertrophy.

Increasing experimental evidence suggests that non-phagocytic cells express a potent superoxide (O2-.)-producing NADH oxidase that might be related to the phagocytic NADPH oxidase. Here we show that the cytokine tumour necrosis factor alpha (TNF-alpha) activates, in a time- and dose-dependent manner, a O2-.-producing NADH oxidase in cultured rat aortic smooth-muscle cells. Dose-response experiments for NADH showed an upward shift of the curve for TNF-alpha-treated cells, suggesting that TNF-alpha increased the amount of available enzyme. Using the anti-sense transfection technique, we further demonstrate that the molecular identity of this oxidase includes p22(phox) (the alpha subunit of cytochrome b558 and part of the electron transfer component of the phagocytic NADPH oxidase), which we recently cloned from a rat vascular smooth-muscle cell cDNA library. In addition, prolonged treatment with TNF-alpha increased p22phox mRNA expression without affecting p22phox mRNA stability, and only when transcriptional activity was intact. These findings identify a p22phox-containing NADH oxidase as a source for cytokine-induced free radical production in vascular smooth-muscle cells and clarify some of the mechanisms involved in the regulation of vascular oxidase activity.

Abstract Monocyte chemoattractant protein-1 (MCP-1), a potent monocyte chemoattractant synthesized by vascular cells and monocytes, has been proposed to be an important mediator of inflammatory responses in the arterial vasculature. It was recently demonstrated that hypertension is associated with an inflammatory response in the arterial wall. To determine the effect of hypertension on arterial MCP-1 expression, we induced hypertension in Sprague-Dawley rats by infusing angiotensin II (0.75 mg · kg −1 · d −1 SC) for 7 days. Using Northern blot analysis, we detected a 3.6-fold increase in MCP-1 mRNA in the aortas of hypertensive rats. When we normalized blood pressure in angiotensin II–treated rats through oral administration of the nonspecific vasodilator hydralazine (15 mg · kg −1 · d −1 ), aortic MCP-1 mRNA expression was significantly reduced. Similar results were obtained with a norepinephrine model of hypertension. Taken together, these data suggest that mechanical factors may be responsible in part for the upregulation of expression. Consistent with this interpretation, we found that cultured rat aortic vascular smooth muscle cells exposed to mechanical strain (20% peak deformation at 1 Hz) exhibited a marked increase in MCP-1 expression, suggesting the hemodynamic strain imparted onto arterial cells in hypertension is an important stimulus underlying this phenomenon. These results provide important insights into the in vivo regulation of MCP-1 and have potential implications for understanding the influence of hypertension on atherosclerosis.

GRK5, a recently cloned member of the G protein-coupled receptor kinase family, has been shown to phosphorylate and participate in the desensitization of angiotensin II (Ang II) type 1A (AT1A) receptors. In this study, the effect of angiotensin II on GRK5 expression was examined in cultured vascular smooth muscle cells and aortas of Ang II-infused hypertensive rats. In vascular smooth muscle cells, Ang II (100 nm) up-regulated GRK5 mRNA as early as 1 h, with a peak at 16 h. This up-regulation was dose- and calcium-dependent. The increase in GRK5 mRNA was reflected in a smaller increase in protein expression, which nonetheless had functional significance since AT1 receptor phosphorylation was increased and phospholipase C activation was decreased following prolonged incubation with Ang II. In aortas of Ang II-infused hypertensive rats, both GRK5 mRNA and protein levels increased ∼3-fold compared with sham-operated rats at 5 and 7 days, respectively. This up-regulation was blocked either by losartan or by the nonspecific vasodilator hydralazine. Since a subpressor dose of Ang II did not increase GRK5 mRNA levels and norepinephrine infusion also increased GRK5 mRNA expression, we conclude that Ang II-induced GRK5 up-regulation in rat aortas may be due to hypertension per se. Hormone- and hemodynamic stress-induced GRK5 regulation may provide a novel molecular basis for long-term regulation of agonist sensitivity of vascular cells.

Abstract Thrombin has been implicated as an important mediator of vascular lesion formation in atherosclerosis and restenosis. To investigate a potential role for thrombin signaling in the vascular response to hypertension, we have studied thrombin receptor (TR) expression and regulation in hypertensive rats. Aortic TR mRNA was upregulated by angiotensin II (Ang II)–induced hypertension (10.7±2.5 times control, P 1 receptor antagonist losartan normalized blood pressure and TR mRNA. Conversely, lowering blood pressure to the same degree with hydralazine did not abolish the upregulation of TR mRNA expression. When low-renin low–Ang II hypertension was induced in Dahl salt-sensitive rats, there was no detectable increase in the expression of aortic thrombin receptor mRNA. Finally, treatment with a chimeric heparin-binding form of the recombinant human Cu/Zn superoxide dismutase caused complete inhibition of TR mRNA upregulation, suggesting that an increased rate of superoxide anion production is an important signaling mechanism. Thus, increased TR expression via a redox-sensitive mechanism in the aortic smooth muscle of rats treated with Ang II represents a novel in vivo mechanism through which the hypertensive effects of Ang II are mediated.

Angiotensin II is a multifunctional hormone that affects both contraction and growth of vascular smooth muscle cells through a complex series of intracellular signaling events initiated by the interaction of angiotensin II with the AT 1 receptor. The cellular response to angiotensin II is multiphasic, involving stimulation within seconds of phospholipase C and Ca 2+ mobilization; activation within minutes of phospholipase D, A 2 , protein kinase C, and MAP kinase; and stimulation after a period of hours of gene transcription and NADH/NADPH oxidase activity. Angiotensin II also activates numerous intracellular tyrosine kinases. In this respect, it shares some aspects of signaling with growth factor and cytokine receptors, including activation of phospholipase C-γ, src, and ras; association of shc with grb2; and stimulation of the Jak/STAT pathway. The cellular events responsible for this unique series of events may involve receptor movement and the creation of a signaling domain. Elucidation of these pathways is important to our understanding of AT 1 receptor function as a final effector of the renin-angiotensin system.

The type 1A angiotensin II receptor (AT1A-R), which mediates cardiovascular effects of angiotensin II, has been shown to undergo rapid agonist-induced desensitization. We investigated the potential role of second messenger-activated kinases and G protein-coupled receptor kinases (GRKs) in the regulation of this receptor. In 293 cells transfected with the AT1A-R, a 3-min challenge with angiotensin II engendered a 46% decrease in subsequent angiotensin II-stimulated phosphoinositide hydrolysis in intact cells. This agonist-induced desensitization correlated temporally and dose-dependently with the phosphorylation of the receptor to a stoichiometry of 1 mol of phosphate/mol of receptor, as assessed by immunoprecipitation of receptors from cells metabolically labeled with 32Pi. Agonist-induced receptor phosphorylation was reduced by 40-50% by either overexpression of a dominant negative K220R mutant GRK2 or treatment of the cells with the protein kinase C (PKC) inhibitor staurosporine, in a virtually additive fashion. Cellular overexpression of GRK2K220R not only inhibited agonist-induced AT1A-R phosphorylation, but also prevented receptor desensitization, as assessed by angiotensin II-stimulated GTPase activity in membranes prepared from agonist-treated and control cells. In contrast, PKC inhibition by staurosporine did not affect homologous desensitization of the AT1A-R. Overexpression of GRKs 2, 3, or 5 significantly augmented the agonist-induced AT1A-R phosphorylation 1.5- to 1.7-fold (p < 0.001). These findings suggest a role for receptor phosphorylation by one or several GRKs in the rapid agonist-induced desensitization of the AT1A-R.

Although arterial bifurcations are frequent sites for obstructive atherosclerotic lesions, the optimal approach to these lesions remains unresolved. Benchtop models of arterial bifurcations were analyzed for flow disturbances known to correlate with vascular disease. These models possess an adaptable geometry capable of simulating the course of arterial disease and the effects of arterial interventions. Chronic in vivo studies evaluated the effect of flow disturbances on the pattern of neointimal hyperplasia. Acute in vivo studies helped propose a mechanism that bridges the early mechanical stimulus and the late tissue effect. Side-branch (SB) dilation adversely affected flow patterns in the main branch (MB) and, as a result, the long-term MB patency of stents implanted in pig arteries. Critical to this effect is chronic MB remodeling that seems to compensate for an occluded SB. Acute leukocyte recruitment was directly influenced by the changes in flow patterns, suggesting a link between flow disturbance on the one hand and leukocyte recruitment and intimal hyperplasia on the other. It is often impossible to simultaneously maximize the total cross-sectional area of both branches and to minimize flow disturbance in the MB. The apparent trade-off between these two clinically desirable goals may explain many of the common failure modes of bifurcation stenting.

The pathophysiologic basis for stable and unstable angina, as well as for myocardial infarction, has been clarified through clinical and pathologic studies. Only recently have we begun to understand these clinical syndromes in the context of biologic processes within the vessel wall. Atherosclerotic lesion formation is now characterized as an inflammatory response to both metabolic and physical injury. Oxidative modification of low-density lipoprotein (LDL) cholesterol is of central importance in the initiation of this inflammatory cascade. The endothelium, a site of LDL oxidation, regulates vessel tone, inflammatory activity within the vessel wall, and vascular smooth muscle growth. In addition, it provides a nonthrombogenic surface within the vasculature. Endothelial damage could drastically alter these functions, predisposing to vasoconstriction, thrombosis, inflammation, and smooth muscle growth, the key components of atherogenesis. All ischemic coronary syndromes (stable angina, unstable angina, and myocardial infarction) are characterized by alterations in normal endothelium-mediated relaxation. Considerable evidence suggests that free-radical mediated nitric oxide destruction accounts for these abnormalities. In the oxidative environment of the atherosclerotic vessel wall, these free-radical by-products are plentiful. In addition to vasospasm, unstable angina and myocardial infarction are associated with plaque rupture and mural thrombus formation. We currently have little understanding of this conversion from a stable plaque to a rupture-prone, “active” atherosclerotic plaque, although monocyte and lymphocyte products, oxygen-derived free radicals, and degradative enzymes probably contribute. This concept of the unstable coronary syndromes in an inflammatory context with “episodic” plaque activation alters our traditional view of atherosclerosis. The high-risk life-threatening coronary lesion is not necessarily the most severely stenotic but, rather, the lesion having the most active state of inflammation. The biologic state of the atherosclerotic plaque is therefore a more important determinant of clinical course than is the extent of stenosis. As our understanding of the pathogenesis of atherosclerosis evolves, even more effective and specific therapeutic approaches will emerge, diminishing the late and often catastrophic consequences of this disease.

Vascular injury mobilizes bone marrow–derived proangiogenic cells into the circulation, where these cells can facilitate vascular repair and new vessel formation. We sought to determine the relationship between a new biomarker of circulating bone marrow–derived proangiogenic cell activity, the presence of atherosclerotic cardiovascular disease (CVD) and its risk factors, and clinical outcomes. Circulating proangiogenic cell activity was estimated using a reproducible angiogenic colonyforming unit (CFU-A) assay in 532 clinically stable subjects aged 20 to 90 years and ranging in the CVD risk spectrum from those who are healthy without risk factors to those with active CVD. CFU-A counts increased with the burden of CVD risk factors (p < 0.001). CFU-A counts were higher in subjects with symptomatic CVD than in those without (p < 0.001). During follow-up of 232 subjects with CVD, CFU-A counts were higher in those with death, myocardial infarction, or stroke than in those without (110 [70–173] vs 84 [51–136], p = 0.01). Therefore, we conclude that circulating proangiogenic cell activity, as estimated by CFU-A counts, increases with CVD risk factor burden and in the presence of established CVD. Furthermore, higher circulating proangiogenic cell activity is associated with worse clinical outcome in those with CVD.

Heritable factors play a key role in the development of coronary heart disease.1 Early unbiased genome-wide approaches have led to the identification of more than a dozen novel risk loci for myocardial infarction (MI) in predominantly Caucasian cohorts.2–8 Many loci have replicated in large cohorts, yet of these only four appear to have a mechanistically relevant basis through lipid metabolism pathways (1p13, 1p32, 19p13, 6q26).9,10 The remaining loci span genomic regions that as yet have no clearly defined mechanism to explain MI risk. Valuable insights into the functions of these variants may be gleaned by studying their effects on related or intermediate phenotypes which may be causal in the pathway to developing MI. This is best illustrated by the initial association of 1p13 with MI and then with the intermediate phenotype of lipid levels, with subsequent functional studies identifying its role in cellular cholesterol transport through the sortillin protein.11 Another intermediate phenotype of interest in vascular disease is abnormal pressure wave reflection within the arterial tree. Abnormalities in these arterial tree properties occur due to complex composite changes in parameters such as arterial stiffness and vasomotor tone, ultimately leading to increased left ventricular after-load and cardiovascular events such as myocardial ischemia, MI, and stroke.12–15 We therefore investigated the association of variants at eight MI risk loci, whose mechanisms of action are currently unknown, with noninvasively derived pulse wave analysis (PWA) indexes including the magnitude and timing of reflected arterial pressure waveforms in two separate Caucasian populations. The first consisting of very healthy subjects, free of confounding risk factors to enable an assessment of direct genetic risk and the second, an unselected community-based population that allowed determination of genetic effects in the context of common risk factors. We hypothesized that some or all of these markers would demonstrate association with indexes of adverse arterial wave reflection.

Background Experimental and clinical observations suggest that lowering serum lipid levels may reduce the risk of restenosis after coronary angioplasty. We report the results of a prospective, randomized, double-blind trial evaluating whether lowering lipid levels with lovastatin can prevent or delay restenosis after angioplasty. Methods Seven to 10 days before angioplasty, we randomly assigned eligible patients to receive lovastatin (40 mg orally twice daily) or placebo. Patients who underwent successful, complication-free, first-time angioplasty of a native vessel (the index lesion) continued to receive therapy for six months, when a second coronary angiogram was obtained. The primary end point was the extent of restenosis of the index lesion, as assessed by quantitative coronary arteriography. Of 404 patients randomly assigned to study groups, 384 underwent angioplasty; 354 of the procedures were successful, and 321 patients underwent angiographic restudy at six months. Results At base line, the patien...

The bovine endothelial nitric oxide synthase gene plus 2.9 kilobases of 5'-flanking sequence has been isolated and characterized. The gene spans 20 kilobases and contains 26 exons and 25 introns. Two transcription start sites have been determined by primer extension analysis which are located 170 and 240 base pairs upstream, respectively, from the methionine translational initiation codon. Evidence supporting the upstream boundary region for transcriptional initiation was also obtained by reverse transcription-polymerase chain reaction. The 5'-flanking region lacks a typical TATA box but contains numerous putative transcription factor binding sites. These include consensus sequences for an AP-1 site, an NF-1 site, a tumor necrosis factor responsive element, two sterol regulatory elements, 3 acute-phase response element, two sterol regulatory elements, 3 acute-phase response elements, 6 GATA motifs, 16 CACCC boxes, 5 Sp1 sites, 15 estrogen half-palindromic motifs, and 9 fluid shear stress-responsive elements. The isolated gene promoter directs basal transcription of a luciferase reporter gene when transiently transfected into bovine aortic endothelial cells. High sequence homology of the promoter region to the human endothelial nitric oxide synthase gene promoter (75% nucleotide identity in 1.6 kilobases of 5'-flanking sequence) suggests evolutionary conservation of transcriptional regulation. Isolation and characterization of the bovine endothelial nitric oxide synthase gene should facilitate further investigation of mechanisms by which gene expression is regulated.

Arterial stiffening may lead to hypertension, greater left ventricular after-load and adverse clinical outcomes. The underlying mechanisms influencing arterial elasticity may involve oxidative injury to the vessel wall. We sought to examine the relationship between novel markers of oxidative stress and arterial elastic properties in healthy humans.We studied 169 subjects (mean age 42.6 ± 14 years, 51.6% male) free of traditional cardiovascular risk factors. Indices of arterial stiffness and wave reflections measured included carotid-femoral Pulse Wave Velocity (PWV), Augmentation Index (Aix) and Pulse Pressure Amplification (PPA). Non-free radical oxidative stress was assessed as plasma oxidized and reduced amino-thiol levels (cysteine/cystine, glutathione/GSSG) and their ratios (redox potentials), and free radical oxidative stress as derivatives of reactive oxygen metabolites (dROMs). Inflammation was assessed as hsCRP and interleukin-6 levels. The non-free radical marker of oxidative stress, cystine was significantly correlated with all arterial indices; PWV (r=0.38, p0.001), Aix (r=0.35, p0.001) and PPA (r=-0.30, p0.001). Its redox potential, was also associated with PWV (r=0.22, p=0.01), while the free radical marker of oxidative stress dROMS was associated with Aix (r=0.25, p0.01). After multivariate adjustment for age, gender, arterial pressure, height, weight, heart rate and CRP, of these oxidative stress markers, only cystine remained independently associated with PWV (p=0.03), Aix (p=0.01) and PPA (p=0.05).In healthy subjects without confounding risk factors or significant systemic inflammation, a high cystine level, reflecting extracellular oxidant burden, is associated with increased arterial stiffness and wave reflections. This has implications for understanding the role of oxidant burden in pre-clinical vascular dysfunction.

We found previously that stimulation of c-fos and c-myc mRNA expression are early events in hydrogen peroxide-induced growth in rat aortic smooth muscle (RASM) cells. In the present study, we investigated the role of phospholipase A2 (PLA2) and protein kinase C (PKC) in mediating hydrogen peroxide-induced c-fos mRNA expression in RASM cells. Mepacrine and p-bromophenacylbromide, potent inhibitors of PLA2 activity, blocked hydrogen peroxide-induced c-fos mRNA expression. Arachidonic acid, a product of PLA2 activity, stimulated the expression of c-fos mRNA with a time course similar to that of hydrogen peroxide. PKC down-regulation attenuated both hydrogen peroxide and arachidonic acid-induced c-fos mRNA expression by 50%. Nordihydroguaiaretic acid (a lipoxygenase-cytochrome P450 monooxygenase inhibitor) significantly inhibited both hydrogen peroxide and arachidonic acid-induced c-fos mRNA expression, whereas indomethacin (a cyclooxygenase inhibitor) had no effect. Together, these findings indicate that 1) hydrogen peroxide-induced c-fos mRNA expression is mediated by PLA2-dependent arachidonic acid release, 2) both PKC-dependent and independent mechanisms are involved in hydrogen peroxide-induced expression of c-fos mRNA and 3) arachidonic acid metabolism via the lipoxygenase-cytochrome P450 monooxygenase pathway appears to be required for hydrogen peroxide-induced expression of c-fos mRNA.

Forkhead transcription factor FoxO1 and the NAD(+)-dependent histone deacetylase SIRT1 are evolutionarily conserved regulators of the development of aging, oxidative stress resistance, insulin resistance, and metabolism in species ranging from invertebrates to mammals. SIRT1 deacetylates FoxO1 and enables activation of FoxO1 transcription in multiple systems. The functional consequences of the interactions between FoxO1 and SIRT1 remain incompletely understood. Here, we demonstrate that the 1.5-kb rat sirt1 promoter region contains a cluster of five putative FoxO1 core binding repeat motifs (5×IRS-1) and a forkhead-like consensus binding site (FKHD-L). Luciferase promoter assays demonstrate that FoxO1 directly activates SIRT1 promoter activity and that both the IRS-1 and FKHD-L enable FoxO1-dependent SIRT1 transcription. Electrophoretic mobility shift and chromatin immunoprecipitation assays show that FoxO1 binds to the IRS-1 and FKHD-L sites of the SIRT1 promoter. Consistently, FoxO1 overexpression increases SIRT1 expression, and FoxO1 depletion by siRNA reduces SIRT1 expression at both the messenger RNA and protein levels in vascular smooth muscle cells and HEK293 cells. Thus, endogenous FoxO1 is a positive transcriptional regulator of SIRT1. Conversely, SIRT1 promotes FoxO1-driven SIRT1 autotranscription through interacting with and deacetylating FoxO1. Moreover, resveratrol, a plant polyphenol activator of SIRT1, increases FoxO1-dependent SIRT1 transcription activity and thus induces its expression. These findings suggest that positive feedback mechanisms regulate FoxO1-dependent SIRT1 transcription and indicate a previously unappreciated function for FoxO1. This signaling network may coordinate multiple pathways acting upon immune, inflammatory, regenerative, and metabolic processes.

A rat vascular AT1 receptor cDNA has been stably expressed into Chinese Hamster Ovary cells and the resulting recombinant AT1a receptor has been functionally characterized. This receptor binds 125I Sar1-angiotensin II with an affinity of 0.9 nM and the displacement of this ligand by a series of peptidic and nonpeptidic analogs is shown. Binding of angiotensin II to this receptor causes a rapid increase in inositol phosphate production, whereas this effect is not observed in nontransfected cells. Des-aspartyl1 angiotensin II and at a lesser extent angiotensin I are also able to produce an increase in inositol phosphates. More importantly, the actions of angiotensin II on cell division were clearly demonstrated in this model, since angiotensin II is able to stimulate DNA synthesis by 400% and double the cell population of the transfected cells in 36 hours in the absence of any other growth factor, whereas no effect is observed in nontransfected cells.

Restenosis remains a critical limitation of percutaneous transluminal coronary angioplasty (PTCA). Recent experimental and clinical data have suggested that lovastatin, an hydroxymethylglutaryl coenzyme A reductase inhibitor, may reduce the rate of restenosis through reduction of low density-lipoprotein (LDL) cholesterol or possibly by direct effects. Lovastatin may therefore produce favorable alterations in endothelial healing, resulting in a decreased smooth muscle cell proliferative response to injury after angioplasty. Emory University, in conjunction with Merck Research Laboratories, has initiated a 10-center double-blinded, placebo-controlled, randomized trial to assess the effect of both pretreatment and aggressive lipid lowering with lovastatin in reducing the rate of restenosis. Lovastatin achieves approximately 75% of its effect on LDL cholesterol by 1 week. Thus, patients scheduled for PTCA are randomly assigned pretreatment with lovastatin, 40 mg twice daily, or placebo 7 to 10 days before PTCA. Therapy is continued for 6 months, at which time repeat coronary arteriography is performed. A detailed safety algorithm was designed, with patients receiving lovastatin and matching placebo back-titrated on a 1:1 basis for LDL cholesterol

I. Introduction THOUGH Tigerstedt described the ability of a kidney extract to influence blood pressure in 1898 (1), it is within this century that the remarkable physiology and medical significance of the renin-angiotensin system has been delineated. Within the last 5 yr, two new developments have taken place, the synthesis of nonpeptidic antagonists of angiotensin II and, most recently, the isolation of complementary DNA encoding the vascular form of the angiotensin II receptor. These two developments are intellectually linked and complementary; they foreshadow future directions in understanding and manipulating the renin-angiotensin system. Here, we describe our research that led to the isolation of cDNA encoding the rat vascular angiotensin II receptor (2). Until the development of nonpeptidic antagonists of angiotensin II, pharmacological studies of angiotensin II receptors employed angiotensin II or other peptide analogs. Such studies demonstrated a heterogeneity of apparent receptors based on pharm...

Angiotensin II (Ang II) is a pleuripotential hormone that is important in the pathophysiology of multiple conditions including aging, cardiovascular and renal diseases, and insulin resistance. Reactive oxygen species (ROS) are important mediators of Ang II-induced signaling generally and have a well defined role in vascular hypertrophy, which is inhibited by overexpression of catalase, inferring a specific role of H(2)O(2). The molecular mechanisms are understood incompletely. The transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1 alpha) is a key regulator of energy metabolism and ROS-scavenging enzymes including catalase. We show that Ang II stimulates Akt-dependent PGC-1 alpha serine 570 phosphorylation, which is required for the binding of the histone acetyltransferase GCN5 (general control nonderepressible 5) to PGC-1 alpha and for its lysine acetylation. These sequential post-translational modifications suppress PGC-1 alpha activity and prevent its binding to the catalase promoter through the forkhead box O1 transcription factor, thus decreasing catalase expression. We demonstrate that overexpression of the phosphorylation-defective mutant PGC-1 alpha (S570A) prevents Ang II-induced increases in H(2)O(2) levels and hypertrophy ([(3)H]leucine incorporation). Knockdown of PGC-1 alpha by small interfering RNA promotes basal and Ang II-stimulated ROS and hypertrophy, which is reversed by polyethylene glycol-conjugated catalase. Thus, endogenous PGC-1 alpha is a negative regulator of vascular hypertrophy by up-regulating catalase expression and thus reducing ROS levels. We provide novel mechanistic insights by which Ang II may mediate its ROS-dependent pathophysiologic effects on multiple cardiometabolic diseases.

To establish guidelines for more effectively incorporating part-time faculty into departments of internal medicine, a task force was convened in early 2007 by the Association of Specialty Professors. The task force used informal surveys, current literature, and consensus building among members of the Alliance for Academic Internal Medicine to produce a consensus statement and a series of recommendations. The task force agreed that part-time faculty could enrich a department of medicine, enhance workforce flexibility, and provide high-quality research, patient care, and education in a cost-effective manner. The task force provided a series of detailed steps for operationalizing part-time practice; to do so, key issues were addressed, such as fixed costs, malpractice insurance, space, cross-coverage, mentoring, career development, productivity targets, and flexible scheduling. Recommendations included (1) increasing respect for work-family balance, (2) allowing flexible time as well as part-time employment, (3) directly addressing negative perceptions about part-time faculty, (4) developing policies to allow flexibility in academic advancement, (5) considering part-time faculty as candidates for leadership positions, (6) encouraging granting agencies, including the National Institutes of Health and Veterans Administration, to consider part-time faculty as eligible for research career development awards, and (7) supporting future research in "best practices" for incorporating part-time faculty into academic departments of medicine.

Endothelial dysfunction is known to precede the development of atherosclerosis and results primarily from increased oxidative degradation of NO. We hypothesized that assessment of oxidative stress in the bloodstream will reliably predict endothelial function in healthy adults. A total of 124 healthy nonsmokers had endothelial function assessed using ultrasound measurement of brachial artery flow-mediated vasodilation. Plasma oxidative stress was estimated by measuring the levels of the reduced and oxidized forms of thiols, including glutathione (reduced glutathione and oxidized glutathione) and cysteine (cysteine and cystine), respectively, and the mixed disulfide. Among the traditional risk factors, there were significant and independent correlations between flow-mediated vasodilation and high-density lipoprotein level, body mass index, gender, and the Framingham risk score. Among the thiol markers, plasma cystine ( r =−0.23; P =0.009) and the mixed disulfide ( r =−0.23; P =0.01) levels correlated with endothelium-dependent but not endothelium-independent vasodilation, even after adjusting for the Framingham risk score and high-sensitivity C-reactive protein level. A higher level of oxidized metabolites was associated with worse endothelial function. In conclusion, the oxidative stress markers, cystine, and the mixed disulfide are independent predictors of endothelial function. These markers, in combination with the Framingham risk score, may help in the early identification of asymptomatic subjects with endothelial dysfunction who are at potentially increased risk for future atherosclerotic disease progression.

Angiotensin II (Ang II) is a pluripotent hormone in vascular smooth muscle cells (VSMCs) and stimulates arterial hypertrophy, a hallmark of remodeling in hypertension. These effects are mediated primarily through the G protein–coupled receptor Ang II type 1 receptor (AT1R).1 In VSMCs, AT1R-mediated signaling is biphasic, and internalization of the agonist/receptor complex into what we called a “signaling domain” is required for the tonic phase of signaling (initially characterized by phospholipase D activation) but not for the initial phospholipase C stimulation, which occurs at the cell surface.2 This evidence was consistent with the existence of spatially discrete Ang II signaling domains. We showed that sequential Ang II–induced phospholipase activation is mediated through ≥2 Gα subunits (Gαq and Gα12/13), as well as their associated Gβγ components.3,4 In addition, various nonreceptor tyrosine kinases, including cAbl and some from the Src family, as well as mitogen-activated protein kinases and Akt, are activated by Ang II and mediate VSMC hypertrophy and growth.5–7 Activation of these pathways is in part dependent on tyrosine phosphorylation (transmodulation) of the epidermal growth factor receptor (EGF-R), which serves as a “scaffold” for the assembly of cSrc and Pyk2, leading to downstream activation of extracellular-regulated kinase (ERK)1/2 and Akt.8,9 These results are consistent with a model that requires temporal dispersion and organization of the AT1R signaling repertoire in VSMCs.7,10 Accumulating evidence suggests that receptors and the signaling molecules with which they associate are not randomly distributed in the cell membrane but are localized in specialized signaling domains. Functionally distinct microdomains, formed by the lateral packing of glycosphingolipids and cholesterol within the membrane bilayer, have been identified in plasma membranes. These domains, called “lipid rafts,” have been implicated in membrane trafficking and cellular signaling mechanisms and serve …

Important output signals of the angiotensin subtype 1 receptor (AT 1 R) in vascular smooth muscle cells (VSMCs) are mediated by angiotensin II (Ang II)-stimulated transactivation of the epidermal growth factor receptor (EGF-R), which is critical for vascular hypertrophy. Ang II-induced EGF-R transactivation is mediated through cSrc, a proximal target of reactive oxygen species (ROS) derived from NAD(P)H oxidase (NOX) and is dependent on AT 1 R trafficking through caveolin1 (Cav1)-enriched lipid rafts. Underlying molecular mechanisms are incompletely understood. The nonreceptor tyrosine kinase, proto-oncogene cAbl is a substrate of Src and is a major mediator for ROS-dependent tyrosine phosphorylation of Cav1. We thus hypothesized that cAbl is important for ROS-, cSrc-, and Cav1-dependent growth-related AT 1 R signal transduction. Here we show that Ang II induces tyrosine phosphorylation of cAbl in rat VSMCs and mouse aorta, and that Ang II promotes association of cAbl with AT 1 R, both of which are Src-dependent. Pretreatment of rat VSMCs with the NOX inhibitor diphenylene iodonium or the antioxidants N-acetylcysteine or ebselen significantly inhibited Ang II-induced cAbl phosphorylation. Cell fractionation shows that both EGF-Rs and cAbl are found basally in Cav1-enriched membrane fractions. Knockdown of cAbl protein using small interference RNA inhibits Ang II-stimulated: (1) trafficking of AT 1 R into, and EGF-R out of, Cav1-enriched lipid rafts; (2) EGF-R transactivation; (3) appearance of the transactivated EGF-R and phospho-Cav1 at focal adhesions; and (4) vascular hypertrophy. These studies provide a novel role of cAbl in the spatial and temporal organization of growth-related AT 1 R signaling in VSMCs and suggest that cAbl may be generally important in signaling of G-protein coupled receptors.

Background— Neovascularization is potentially important for the treatment of ischemic heart and limb disease. We reported that reactive oxygen species (ROS) derived from gp91 phox (Nox2)-containing NAD(P)H oxidase are involved in angiogenesis in mouse sponge models as well as in vascular endothelial growth factor (VEGF) signaling in cultured endothelial cells. The role of gp91 phox -derived ROS in neovascularization in response to tissue ischemia is unknown, however. Methods and Results— Here, we show that neovascularization in the ischemic hindlimb is significantly impaired in gp91 phox−/− mice as compared with wild-type (WT) mice as evaluated by laser Doppler flow, capillary density, and microsphere measurements. In WT mice, inflammatory cell infiltration in the ischemic hindlimb was maximal at 3 days, whereas capillary formation was prominent at 7 days when inflammatory cells were no longer detectable. Increased O 2 ·− production and gp91 phox expression were present at both time points. The dihydroethidium staining of ischemic tissues indicates that O 2 ·− is mainly produced from inflammatory cells at 3 days and from neovasculature at 7 days after operation. Relative to WT mice, ischemia-induced ROS production in gp91 phox−/− mice at both 3 and 7 days was diminished, whereas VEGF expression was enhanced and the inflammatory response was unchanged. Infusion of the antioxidant ebselen into WT mice also significantly blocked the increase in blood flow recovery and capillary density after ischemia. Conclusions— gp91 phox -derived ROS play an important role in mediating neovascularization in response to tissue ischemia. NAD(P)H oxidases and their products are potential therapeutic targets for regulating angiogenesis in vivo.

Vascular endothelial growth factor (VEGF) stimulates endothelial cell (EC) migration and proliferation primarily through the VEGF receptor-2 (VEGFR2). We have shown that VEGF stimulates a Rac1-dependent NAD(P)H oxidase to produce reactive oxygen species (ROS) that are involved in VEGFR2 autophosphorylation and angiogenic-related responses in ECs. The small GTPase ARF6 is involved in membrane trafficking and cell motility; however, its roles in VEGF signaling and physiological responses in ECs are unknown. In this study, we show that overexpression of dominant-negative ARF6 [ARF6(T27N)] almost completely inhibits VEGF-induced Rac1 activation, ROS production, and VEGFR2 autophosphorylation in ECs. Fractionation of caveolae/lipid raft membranes demonstrates that ARF6, Rac1, and VEGFR2 are localized in caveolin-enriched fractions basally. VEGF stimulation results in the release of VEGFR2 from caveolae/lipid rafts and caveolin-1 without affecting localization of ARF6, Rac1, or caveolin-1 in these fractions. The egress of VEGFR2 from caveolae/lipid rafts is contemporaneous with the tyrosine phosphorylation of caveolin-1 (Tyr14) and VEGFR2 and with their association with each other. ARF6(T27N) significantly inhibits both VEGF-induced responses. Immunofluorescence studies show that activated VEGFR2 and phosphocaveolin colocalize at focal complexes/adhesions after VEGF stimulation. Both overexpression of ARF6(T27N) and mutant caveolin-1(Y14F), which cannot be phosphorylated, block VEGF-stimulated EC migration and proliferation. Moreover, ARF6 expression is markedly upregulated in association with an increase in capillary density in a mouse hindlimb ischemia model of angiogenesis. Thus, ARF6 is involved in the temporal-spatial organization of caveolae/lipid rafts– and ROS-dependent VEGF signaling in ECs as well as in angiogenesis in vivo.