Maria Carolina Gongora

Coronary Artery Calcium to Predict All-Cause Mortality in Elderly Men and Women

OBJECTIVES We sought to study the prognostic utility of coronary artery calcium (CAC) in the elderly. BACKGROUND The prognostic significance of CAC in the elderly is not well known. METHODS All-cause mortality was assessed in 35,388 patients (3,570 were >or=70 years old at screening, and 50% were women) after a mean follow-up of 5.8 +/- 3 years. RESULTS In older patients, risk factors and CAC were more prevalent. Overall survival was 97.9% at the end of follow-up. Mortality increased with each age decile with a relative hazard of 1.09 (95% confidence interval: 1.08 to 1.10, p < 0.0001), and rates were greater for men than women (hazard ratio: 1.53; 95% confidence interval: 1.32 to 1.77, p < 0.0001). Increasing CAC scores were associated with decreasing survival across all age deciles (p < 0.0001). Survival for a <40-year and >or=80-year-old man with a CAC score >or=400 was 88% and 19% (95% and 44% for a woman, p < 0.0001), respectively. Among the 20,562 patients with no CAC, annual mortality rates ranged from 0.3% to 2.2% for patients age 40 to 49 years or >or=70 years (p < 0.0001). The use of CAC allowed us to reclassify more than 40% of the patients >or=70 years old more often by excluding risk (i.e., CAC <400) in those with >3 risk factors. CONCLUSIONS Despite their limited life expectancy, the use of CAC discriminates mortality risk in the elderly. Furthermore, the use of CAC allows physicians to reclassify risk in the elderly.

Role of Extracellular Superoxide Dismutase in Hypertension

We previously found that angiotensin II–induced hypertension increases vascular extracellular superoxide dismutase (ecSOD), and proposed that this is a compensatory mechanism that blunts the hypertensive response and preserves endothelium-dependent vasodilatation. To test this hypothesis, we studied ecSOD-deficient mice. ecSOD−/− and C57Blk/6 mice had similar blood pressure at baseline; however, the hypertension caused by angiotensin II was greater in ecSOD−/− compared with wild-type mice (168 versus 147 mm Hg, respectively; P<0.01). In keeping with this, angiotensin II increased superoxide and reduced endothelium-dependent vasodilatation in small mesenteric arterioles to a greater extent in ecSOD−/− than in wild-type mice. In contrast to these findings in resistance vessels, angiotensin II paradoxically improved endothelium-dependent vasodilatation, reduced intracellular and extracellular superoxide, and increased NO production in aortas of ecSOD−/− mice. Whereas aortic expression of endothelial NO synthase, Cu/ZnSOD, and MnSOD were not altered in ecSOD−/− mice, the activity of Cu/ZnSOD was increased by 80% after angiotensin II infusion. This was associated with a concomitant increase in expression of the copper chaperone for Cu/ZnSOD in the aorta but not in the mesenteric arteries. Moreover, the angiotensin II–induced increase in aortic reduced nicotinamide-adenine dinucleotide phosphate oxidase activity was diminished in ecSOD−/− mice as compared with controls. Thus, during angiotensin II infusion, ecSOD reduces hypertension, minimizes vascular superoxide production, and preserves endothelial function in resistance arterioles. We also identified novel compensatory mechanisms involving upregulation of copper chaperone for Cu/ZnSOD, increased Cu/ZnSOD activity, and decreased reduced nicotinamide-adenine dinucleotide phosphate oxidase activity in larger vessels. These compensatory mechanisms preserve large vessel function when ecSOD is absent in hypertension.

Calcium-Dependent NOX5 Nicotinamide Adenine Dinucleotide Phosphate Oxidase Contributes to Vascular Oxidative Stress in Human Coronary Artery Disease

OBJECTIVES This study sought to examine the expression and activity of the calcium-dependent nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) in human atherosclerotic coronary arteries. BACKGROUND The NOX-based NADPH oxidases are major sources of reactive oxygen species (ROS) in human vessels. Several NOX homologues have been identified, but their relative contribution to vascular ROS production in coronary artery disease (CAD) is unclear; NOX5 is a unique homolog in that it is calcium dependent and thus could be activated by vasoconstrictor hormones. Its presence has not yet been studied in human vessels. METHODS Coronary arteries from patients undergoing cardiac transplantation with CAD or without CAD were studied; NOX5 was quantified and visualized using Western blotting, immunofluorescence, and quantitative real-time polymerase chain reaction. Calcium-dependent NADPH oxidase activity, corresponding greatly to NOX5 activity, was measured by electron paramagnetic resonance. RESULTS Both Western blotting and quantitative real-time polymerase chain reaction indicated a marked increase in NOX5 protein and messenger ribonucleic acid (mRNA) in CAD versus non-CAD vessels. Calcium-dependent NADPH-driven production of ROS in vascular membranes, reflecting NOX5 activity, was increased 7-fold in CAD and correlated significantly with NOX5 mRNA levels among subjects. Immunofluorescence showed that NOX5 was expressed in the endothelium in the early lesions and in vascular smooth muscle cells in the advanced coronary lesions. CONCLUSIONS These studies identify NOX5 as a novel, calcium-dependent source of ROS in atherosclerosis.

Upregulation of Nox1 in vascular smooth muscle leads to impaired endothelium-dependent relaxation via eNOS uncoupling

Recent work has made it clear that oxidant systems interact. To investigate potential cross talk between NADPH oxidase (Nox) 1 upregulation in vascular smooth muscle and endothelial function, transgenic mice overexpressing Nox1 in smooth muscle cells (Tg(SMCnox1)) were subjected to angiotensin II (ANG II)-induced hypertension. As expected, NADPH-dependent superoxide generation was increased in aortas from Nox1-overexpressing mice. Infusion of ANG II (0.7 mg x kg(-1) x day(-1)) for 2 wk potentiated NADPH-dependent superoxide generation and hydrogen peroxide production compared with similarly treated negative littermate controls. Endothelium-dependent relaxation was impaired in transgenic mice, and bioavailable nitric oxide was markedly decreased. To test the hypothesis that eNOS uncoupling might contribute to endothelial dysfunction, the diet was supplemented with tetrahydrobiopterin (BH(4)). BH(4) decreased aortic superoxide production, partially restored bioavailable nitric oxide in aortas of ANG II-treated Tg(SMCnox1) mice, and significantly improved endothelium-dependent relaxation in these mice. Western blot analysis revealed less dimeric eNOS in Tg(SMCnox1) mice compared with the wild-type mice; however, total eNOS was equivalent. Pretreatment of mouse aortas with the eNOS inhibitor N(G)-nitro-L-arginine methyl ester decreased ANG II-induced superoxide production in Tg(SMCnox1) mice compared with wild-type mice, indicating that uncoupled eNOS is also a significant source of increased superoxide in transgenic mice. Thus overexpression of Nox1 in vascular smooth muscle leading to enhanced production of reactive oxygen species in response to ANG II causes eNOS uncoupling and a decrease in nitric oxide bioavailability, resulting in impaired vasorelaxation.

Tumor Necrosis Factor-Like Weak Inducer of Apoptosis Increases the Permeability of the Neurovascular Unit through Nuclear Factor-κB Pathway Activation

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is a member of the tumor necrosis factor superfamily. TWEAK acts on responsive cells via binding to a small cell-surface receptor named fibroblast growth factor-inducible-14 (Fn14). TWEAK can stimulate numerous cellular responses including cell proliferation, migration, and proinflammatory molecule production. The present study investigated whether TWEAK plays a role in the regulation of the permeability of the neurovascular unit (NVU). We found that intracerebral injection of TWEAK in wild-type mice induces activation of the nuclear factor-κB (NF-κB) pathway and matrix metalloproteinase-9 (MMP-9) expression in the brain with resultant disruption in the structure of the NVU and increase in the permeability of the blood-brain barrier (BBB). TWEAK did not increase MMP-9 activity or BBB permeability when injected into mice genetically deficient in the NF-κB family member p50. Furthermore, we report that inhibition of TWEAK activity during cerebral ischemia with an Fn14-Fc decoy receptor results in significant preservation of the integrity of the NVU with attenuation of cerebral ischemia-induced increase in the permeability of the BBB. We conclude that the cytokine TWEAK plays a role in the disruption of the structure and permeability of the NVU during physiological and pathological conditions.

Loss of Extracellular Superoxide Dismutase Leads to Acute Lung Damage in the Presence of Ambient Air A Potential Mechanism Underlying Adult Respiratory Distress Syndrome

The extracellular superoxide dismutase 3 (SOD3) is highly expressed in both blood vessels and lungs. In different models of pulmonary injury, SOD3 is reduced; however, it is unclear whether this contributes to lung injury. To study the role of acute SOD3 reduction in lung injury, the SOD3 gene was deleted in adult mice by using the Cre-Lox technology. Acute reduction of SOD3 led to a fivefold increase in lung superoxide, marked inflammatory cell infiltration, a threefold increase in the arterial-alveolar gradient, respiratory acidosis, histological changes similar to those observed in adult respiratory distress syndrome, and 85% mortality. Treatment with the SOD mimetic MnTBAP and intranasal administration of SOD-containing polyketal microparticles reduced mortality, prevented the histological alterations, and reduced lung superoxide levels. To understand how mice with the SOD3 embryonic deletion survived without lung injury, gene array analysis was performed. These data demonstrated the up-regulation of 37 genes and down-regulation of nine genes, including those involved in cell signaling, inflammation, and gene transcription in SOD3-/- mice compared with either mice with acute SOD3 reduction or wild-type controls. These studies show that SOD3 is essential for survival in the presence of ambient oxygen and that acute loss of this enzyme can lead to severe lung damage. Strategies either to prevent SOD3 inactivation or to augment its levels might prove useful in the treatment of acute lung injury.

TWEAK-Fn14 pathway inhibition protects the integrity of the neurovascular unit during cerebral ischemia.

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is a member of the tumor necrosis factor superfamily. TWEAK acts via binding to a cell surface receptor named Fn14. To study the role of this cytokine in the regulation of the permeability of the neurovascular unit (NVU) during cerebral ischemia, TWEAK activity was inhibited in wild-type mice with a soluble Fn14-Fc decoy receptor administered either immediately or 1 h after middle cerebral artery occlusion (MCAO). Administration of Fn14-Fc decoy resulted in faster recovery of motor function and a 66.4%±10% decrease in Evans blue dye extravasation when treatment was administered immediately after MCAO and a 46.1%±13.1% decrease when animals were treated 1 h later (n=4, P<0.05). Genetic deficiency of Fn14 resulted in a 60%±12.8% decrease in the volume of the ischemic lesion (n=6, P<0.05), and a 87%±22% inhibition in Evans blue dye extravasation 48 h after the onset of the ischemic insult (n=6, P<0.005). Compared with control animals, treatment with Fn14-Fc decoy or genetic deficiency of Fn14 also resulted in a significant inhibition of nuclear factor-κB pathway activation, matrix metalloproteinase-9 activation and basement membrane laminin degradation after MCAO. These findings show that the cytokine TWEAK plays a role in the disruption of the structure of the NVU during cerebral ischemia and that TWEAK antagonism is a potential therapeutic strategy for acute cerebral ischemia.

Role of Menkes ATPase in Angiotensin II-Induced Hypertension: A Key Modulator for Extracellular Superoxide Dismutase Function

The extracellular superoxide dismutase (SOD3), a secretory copper-containing enzyme, regulates angiotensin II (Ang II)–induced hypertension by modulating levels of extracellular superoxide anion. The present study was designed to determine the role of the copper transporter Menkes ATPase (MNK) in Ang II–induced SOD3 activity and hypertension in vivo. Here we show that chronic Ang II infusion enhanced systolic blood pressure and vascular superoxide anion production in MNK mutant (MNKmut) mice as compared with those in wild-type mice, which are associated with impaired acetylcholine-induced endothelium-dependent vasorelaxation in MNKmut mice. These effects in MNKmut mice are rescued by infusion of the SOD mimetic Tempol. By contrast, norepinephrine-induced hypertension, which is not associated with an increase in vascular superoxide anion production, is not affected in MNKmut mice. Mechanistically, basal and Ang II infusion-induced increase in vascular SOD3-specific activity is significantly inhibited in MNKmut mice. Coimmunoprecipitation analysis reveals that Ang II stimulation promotes association of MNK with SOD3 in cultured vascular smooth muscle cell and in mouse aortas, which may contribute to SOD3-specific activity by increasing copper delivery to SOD3 through MNK. In summary, MNK plays an important role in modulating Ang II–induced hypertension and endothelial function by regulating SOD3 activity and vascular superoxide anion production and becomes a potential therapeutic target for oxidant stress-dependent cardiovascular diseases.

Cardiovascular Complications of Pregnancy

Pregnancy causes significant metabolic and hemodynamic changes in a woman’s physiology to allow for fetal growth. The inability to adapt to these changes might result in the development of hypertensive disorders of pregnancy (hypertension, preeclampsia or eclampsia), gestational diabetes and preterm birth. Contrary to previous beliefs these complications are not limited to the pregnancy period and may leave permanent vascular and metabolic damage. There is in addition, a direct association between these disorders and increased risk of future cardiovascular disease (CVD, including hypertension, ischemic heart disease, heart failure and stroke) and diabetes mellitus. Despite abundant evidence of this association, women who present with these complications of pregnancy do not receive adequate postpartum follow up and counseling regarding their increased risk of future CVD. The postpartum period in these women represents a unique opportunity to intervene with lifestyle modifications designed to reduce the development of premature cardiovascular complications. In some cases it allows early diagnosis and treatment of chronic hypertension or diabetes mellitus. The awareness of this relationship is growing in the medical community, especially among obstetricians and primary care physicians, who play a pivotal role in detecting these complications and assuring appropriate follow up.

Sad Heart From No SOD

The superoxide dismutases (SODs), which catalyze the dismutation of 2 superoxide anions to hydrogen peroxide and oxygen, represent major antioxidant mechanisms in single-cell organisms, plants, bacteria and eukaryotes. In mammalian cells, there are 3 forms of SOD that include the mitochondrial manganese SOD (MnSOD or SOD2), the cytoplasmic SOD that is a copper/zinc-containing enzyme (Cu/Zn SOD or SOD1), and an extracellular SOD that is also a copper/zinc-containing enzyme (ecSOD or SOD3). The ecSOD is unique in that it is actively secreted via the trans -Golgi network and binds to glycosaminoglycans in the vascular extracellular matrix and to the extracellular protein fibrillin 5.1 In most tissues, the amount of ecSOD is very small, on the order of 1% to 5% of the total SOD. In contrast, blood vessels, the lung, and to a lesser extent, the heart contain substantial amounts of this enzyme. The ecSOD is therefore of particular interest to investigators interested in cardiovascular and pulmonary biology. Overexpression of ecSOD protects mice against lung damage, and mice lacking ecSOD are predisposed to lung injury caused by hyperoxia. Between 30% and 50% of the total SOD in blood vessels is in this extracellular form, and mice lacking this enzyme have vascular dysfunction and are predisposed to hypertension.2 In cardiovascular tissues and, likely the lung, an important role of the SODs is to protect NO against oxidative inactivation by superoxide. Both NO and superoxide are free radicals with unpaired electrons in their outer orbitals and react with one another in a diffusion-limited fashion. Studies in which the Cu/ZnSODs (SOD1 and SOD3) have been pharmacologically inhibited have shown that NO cannot be released from the endothelium without being oxidatively degraded.3 Thus, these enzymes play a role in promoting vasodilatation and sustaining the protective roles of NO in the vascular wall. …