Nitric oxide-releasing aspirin decreases vascular injury by reducing inflammation and promoting apoptosis

Expression of soluble guanylate cyclase (sGC) and its ability to form a functional heterodimer are crucial for reviving the NO-sGC signaling in PAH

In order to determine the underpinnings of a dysfunctional NO-sGC signal pathway which occurs in pulmonary arterial hypertension (PAH), we investigated pulmonary arterial smooth muscle cells (PASMCs) derived from PAH patients. We found low expression of sGC, a poor sGCα1β1 heterodimer and this correlated with low expression of its facilitator chaperon, hsp90. Treating PASMCs overnight (16 h) with low micromolar doses of a slow release NO donor DETANONOate, reinstated the sGCα1β1 heterodimer and restored its NO-heme dependent activity. Transwell co-culture of HEK cells stably expressing eNOS with PAH PASMCs also restored the sGC heterodimer and its heme-dependent activity with sGC stimulator, BAY 41-2272. To determine whether the dysfunctionality in the NO-sGC pathway stems from a dysfunctional eNOS producing negligible NO, we did transwell co-cultures of pulmonary arterial endothelial cells (PAECs) with PASMCs. Our results indicated that PAECs from both control and PAH samples when activated for eNOS restored both sGC heterodimer and its heme-dependent sGC activity in the corresponding PASMCs, suggesting that PAECs from PAH can also generate NO. In line with these results expression of eNOS, its support chaperon hsp90, its specific kinase Akt, p-Akt or post-translational modifications (PTMs) like OGlcNAc or phospho-tyrosine were unchanged in PAH relative to controls. Additionally there was uniform expression of Hbα/β and Mb in PASMCs or PAECs in PAH or controls and these globins can effectively scavenge the eNOS generated NO, as there was evidence of strong eNOS-Hb/Mb interactions. Our studies suggest that factors such as globin NO scavenging along with vascular remodeling in PAH can cause hampered vasodilation which in the face of poor NO levels as occurs in PAH are additional impediments for effective vasodilation. However importantly our studies suggests that future therapies can use low doses of NO along with sGC stimulators as a potential drug for PAH subjects.

Anemoside B4 Inhibits Vascular Smooth Muscle Cell Proliferation, Migration, and Neointimal Hyperplasia

Vascular smooth muscle cell (VSMC) phenotypic transformation, proliferation, and migration play a pivotal role in developing neointimal hyperplasia after vascular injury, including percutaneous transluminal angioplasty and other cardiovascular interventions. Anemoside B4 (B4) is a unique saponin identified from the Pulsatilla chinensis (Bge.) Regel, which has known anti-inflammatory activities. However, its role in modulating VSMC functions and neointima formation has not been evaluated. Herein, we demonstrate that B4 administration had a potent therapeutic effect in reducing neointima formation in a preclinical mouse femoral artery endothelium denudation model. Bromodeoxyuridine incorporation study showed that B4 attenuated neointimal VSMC proliferation in vivo. Consistent with the in vivo findings, B4 attenuated PDGF-BB-induced mouse VSMC proliferation and migration in vitro. Moreover, quantitative RT-PCR and Western blot analysis demonstrated that B4 suppressed PDGF-BB-induced reduction of SM22α, SMA, and Calponin, suggesting that B4 inhibited the transformation of VSMCs from contractile to the synthetic phenotype. Mechanistically, our data showed B4 dose-dependently inhibited the activation of the phosphatidylinositol 3-kinase (PI3K)/AKT and p38 mitogen-activated protein kinase MAPK signaling pathways. Subsequently, we determined that B4 attenuated VSMC proliferation and migration in a p38 MAPK and AKT dependent manner using pharmacological inhibitors. Taken together, this study identified, for the first time, Anemoside B4 as a potential therapeutic agent in regulating VSMC plasticity and combating restenosis after the vascular intervention.

Klotho Protein Protects Human Keratinocytes from UVB-Induced Damage Possibly by Reducing Expression and Nuclear Translocation of NF-κB

Background

UV-related skin disease such as actinic keratosis is a major concern in public health. In view of the cell injury induced by UVB, Klotho protein it is an ideal therapy to eliminate UVB-induced cell damages and the associated signaling pathways.

Material/Methods

To gain insights into the potential role of Klotho and the underlying molecular mechanism, we constructed a Klotho-overexpress HaCaT cell line and assessed the protection against UVB insults. The effects of exposure to UVB radiation on the human keratinocyte HaCaT cells, including cell growth, apoptosis, and changes of selected biomarkers, were measured by CCK-8, flow cytometry, Quantitative real-time PCR, and Western blot analysis.

Results

We found that enhanced NF-κB activity was accompanied by decreased expression of the anti-aging protein Klotho upon UVB stimulation, which was further confirmed with in vivo experiments. Overexpression of Klotho was able to considerably alleviate the UVB-induced damages to cells and reversed the UVB-caused biomarker changes to a great extent, which was comparable to the effects of administration of NF-κB inhibitor PDTC, suggesting the inhibition of nuclear translocation and DNA-binding activity of NF-κB. Furthermore, Klotho overexpression was proved to decrease the nuclear expression of NF-κB as much as the treatment with PDTC, which provides support for the direct regulation of NF-κB by Klotho.

Conclusions

Collectively, our work provides new insight into the potential role of Klotho in the context of UVB-induced injuries in human keratinocytes, as well as providing the basis for future study of new therapies against UV-related skin disease.

Phosphorylation of GATA-6 is required for vascular smooth muscle cell differentiation after mTORC1 inhibition

Vascular smooth muscle cells (VSMCs) undergo transcriptionally regulated reversible differentiation in growing and injured blood vessels. This dedifferentiation also contributes to VSMC hyperplasia after vascular injury, including that caused by angioplasty and stenting. Stents provide mechanical support and can contain and release rapamycin, an inhibitor of the mechanistic target of rapamycin complex 1 (mTORC1). Rapamycin suppresses VSMC hyperplasia and promotes VSMC differentiation. We report that rapamycin-induced differentiation of VSMCs required the transcription factor GATA-6. Inhibition of mTORC1 stabilized GATA-6 and promoted the nuclear accumulation of GATA-6, its binding to DNA, its transactivation of promoters encoding contractile proteins, and its inhibition of proliferation. These effects were mediated by phosphorylation of GATA-6 at Ser(290), potentially by Akt2, a kinase that is activated in VSMCs when mTORC1 is inhibited. Rapamycin induced phosphorylation of GATA-6 in wild-type mice, but not in Akt2(-/-) mice. Intimal hyperplasia after arterial injury was greater in Akt2(-/-) mice than in wild-type mice, and the exacerbated response in Akt2(-/-) mice was rescued to a greater extent by local overexpression of the wild-type or phosphomimetic (S290D) mutant GATA-6 than by that of the phosphorylation-deficient (S290A) mutant. Our data indicated that GATA-6 and Akt2 are involved in the mTORC1-mediated regulation of VSMC proliferation and differentiation. Identifying the downstream transcriptional targets of mTORC1 may provide cell type-specific drug targets to combat cardiovascular diseases associated with excessive proliferation of VSMCs.

Ten-eleven translocation-2 (TET2) is a master regulator of smooth muscle cell plasticity

BACKGROUND

Smooth muscle cells (SMCs) are remarkably plastic. Their reversible differentiation is required for growth and wound healing but also contributes to pathologies such as atherosclerosis and restenosis. Although key regulators of the SMC phenotype, including myocardin (MYOCD) and KLF4, have been identified, a unifying epigenetic mechanism that confers reversible SMC differentiation has not been reported.

METHODS AND RESULTS

Using human SMCs, human arterial tissue, and mouse models, we report that SMC plasticity is governed by the DNA-modifying enzyme ten-eleven translocation-2 (TET2). TET2 and its product, 5-hydroxymethylcytosine (5-hmC), are enriched in contractile SMCs but reduced in dedifferentiated SMCs. TET2 knockdown inhibits expression of key procontractile genes, including MYOCD and SRF, with concomitant transcriptional upregulation of KLF4. TET2 knockdown prevents rapamycin-induced SMC differentiation, whereas TET2 overexpression is sufficient to induce a contractile phenotype. TET2 overexpression also induces SMC gene expression in fibroblasts. Chromatin immunoprecipitation demonstrates that TET2 coordinately regulates phenotypic modulation through opposing effects on chromatin accessibility at the promoters of procontractile versus dedifferentiation-associated genes. Notably, we find that TET2 binds and 5-hmC is enriched in CArG-rich regions of active SMC contractile promoters (MYOCD, SRF, and MYH11). Loss of TET2 and 5-hmC positively correlates with the degree of injury in murine models of vascular injury and human atherosclerotic disease. Importantly, localized TET2 knockdown exacerbates injury response, and local TET2 overexpression restores the 5-hmC epigenetic landscape and contractile gene expression and greatly attenuates intimal hyperplasia in vivo.

CONCLUSIONS

We identify TET2 as a novel and necessary master epigenetic regulator of SMC differentiation.

The effect of probiotic-fermented soy milk on enhancing the NO-mediated vascular relaxation factors

BACKGROUND

Soy milk is one of the common soy-based foods in Asia. In this study the effects of soy milk fermented with selected probiotics on nitric oxide (NO)-mediated vascular relaxation factors in cell model systems were investigated.

RESULTS

Soy milk fermented with Lactobacillus plantarum TWK10 or Streptococcus thermophilus BCRC 14085 for 48 h showed a greater transformation of glucoside isoflavones to aglycone isoflavones (P < 0.05). An increase in aglycone isoflavones in ethanol extracts from fermented soy milk stimulated NO production and endothelial NO synthase (eNOS) activity in human umbilical vein endothelial cells. It also had a stimulating effect on superoxide anion scavenging and prostaglandin E₂ production. In addition, it enhanced mRNA expression of the E-prostanoid 4 receptor in rat thoracic aorta smooth muscle cells. Moreover, a small amount of O₂⁻ induced by water extracts from fermented soy milk at low concentration (1 mg mL⁻¹) increased the content of calcium ions and activated eNOS, thereby promoting NO production and the coupling state of eNOS.

CONCLUSION

Soy milk fermented with selected probiotics promotes the relaxation factors of vascular endothelial cells and can be applied in the development of functional foods.

Phytoestrogen genistein protects against endothelial barrier dysfunction in vascular endothelial cells through PKA-mediated suppression of RhoA signaling

The soy-derived phytoestrogen genistein has received attention for its potential to improve vascular function, but its mechanism remains unclear. Here, we report that genistein at physiologically relevant concentrations (0.1-10 μM) significantly inhibited thrombin-induced increase in endothelial monolayer permeability. Genistein also reduced the formation of stress fibers by thrombin and suppressed thrombin-induced phosphorylation of myosin light chain (MLC) on Ser(19)/Thr(18) in endothelial cells (ECs). Genistein had no effect on resting intracellular [Ca(2+)] or thrombin-induced increase in Ca(2+) mobilization. Addition of the inhibitors of endothelial nitric oxide synthase or estrogen receptor did not alter the protective effect of genistein. RhoA is a small GTPase that plays an important role in actin-myosin contraction and endothelial barrier dysfunction. RhoA inhibitor blocked the protective effect of genistein on endothelial permeability and also ablated thrombin-induced MLC-phosphorylation in ECs. Inhibition of PKA significantly attenuated the effect of genistein on thrombin-induced EC permeability, MLC phosphorylation, and RhoA membrane translocation in ECs. Furthermore, thrombin diminished cAMP production in ECs, which were prevented by treatment with genistein. These findings demonstrated that genistein improves thrombin-induced endothelial barrier dysfunction in ECs through PKA-mediated suppression of RhoA signaling.

Effect on walking distance and atherosclerosis progression of a nitric oxide-donating agent in intermittent claudication

BACKGROUND

Peripheral arterial disease (PAD) is almost invariably associated with a generalized atherosclerotic involvement of the arterial tree and endothelial dysfunction. Previous short-term studies showed improvement of vascular reactivity and walking capacity in PAD patients by measures aimed at restoring nitric oxide (NO) production. NO is also known to prevent the progression of atherosclerosis. We wished to assess whether the prolonged administration of an NO-donating agent (NCX 4016) improves the functional capacity of PAD patients and affects the progression of atherosclerosis as assessed by carotid intima-media thickness (IMT).

METHODS

This prospective, double-blind, placebo-controlled study enrolled 442 patients with stable intermittent claudication who were randomized to NCX 4016 (800 mg, twice daily) or its placebo for 6 months. The primary study outcome was the absolute claudication distance on a constant treadmill test (10% incline, 3 km/h). The main secondary end point was the change of the mean far-wall right common carotid artery IMT.

RESULTS

The increase of absolute claudication distance at 6 months compared with baseline was 126±140 meters in the placebo-treated group and 117±137 meters in the NCX 4016-treated group, with no significant differences. Carotid IMT increased in the placebo-treated group (+0.01±0.01 mm; P=.55) and decreased in the NCX 4016-treated group (-0.03±0.01 mm; P=.0306). Other secondary end points did not differ between the two treatments.

CONCLUSIONS

Long-term NO donation does not improve the claudication distance but does reduce progression of atherosclerosis in patients with PAD. Further studies aimed at assessing whether long-term NO donation may prevent ischemic cardiovascular events are warranted.

NO-donating aspirin and aspirin partially inhibit age-related atherosclerosis but not radiation-induced atherosclerosis in ApoE null mice

BACKGROUND

We previously showed that irradiation to the carotid arteries of ApoE(-/-) mice accelerated the development of macrophage-rich, inflammatory atherosclerotic lesions, prone to intra-plaque hemorrhage. In this study we investigated the potential of anti-inflammatory and anti-coagulant intervention strategies to inhibit age-related and radiation-induced atherosclerosis.

METHODOLOGY/PRINCIPAL FINDINGS

ApoE(-/-) mice were given 0 or 14 Gy to the neck and the carotid arteries and aortic arches were harvested at 4 or 30 weeks after irradiation. Nitric oxide releasing aspirin (NCX 4016, 60 mg/kg/day) or aspirin (ASA, 30 or 300 mg/kg/day) were given continuously in the chow. High dose ASA effectively blocked platelet aggregation, while the low dose ASA or NCX 4016 had no significant effect on platelet aggregation. High dose ASA, but not NCX 4016, inhibited endothelial cell expression of VCAM-1 and thrombomodulin in the carotid arteries at 4 weeks after irradiation; eNOS and ICAM-1 levels were unchanged. After 30 weeks of follow-up, NCX 4016 significantly reduced the total number of lesions and the number of initial macrophage-rich lesions in the carotid arteries of unirradiated mice, but these effects were not seen in the brachiocephalic artery of the aortic arch (BCA). In contrast, high dose ASA lead to a decrease in the number of initial lesions in the BCA, but not in the carotid artery. Both high dose ASA and NCX 4016 reduced the collagen content of advanced lesions and increased the total plaque burden in the BCA of unirradiated mice. At 30 weeks after irradiation, neither NCX 4016 nor ASA significantly influenced the number or distribution of lesions, but high dose ASA lead to formation of collagen-rich "stable" advanced lesions in carotid arteries. The total plaque area of the irradiated BCA was increased after ASA, but the plaque burden was very low compared with the carotid artery.

CONCLUSIONS/SIGNIFICANCE

The development and characteristics of radiation-induced atherosclerosis varied between different arteries but could not be circumvented by anti-inflammatory and anti-coagulant therapies. This implicates other underlying mechanistic pathways compared to age-related atherosclerosis.

Vascular damage as an underlying mechanism of cardiac and cerebral toxicity in irradiated cancer patients

Radiation is an independent risk factor for cardiovascular and cerebrovascular disease in cancer patients. Modern radiotherapy techniques reduce the volume of the heart and major coronary vessels exposed to high doses, but some exposure is often unavoidable. Radiation damage to the myocardium is caused primarily by inflammatory changes in the microvasculature, leading to microthrombi and occlusion of vessels, reduced vascular density, perfusion defects and focal ischemia. This is followed by progressive myocardial cell death and fibrosis. Clinical studies also demonstrate regional perfusion defects in non-symptomatic breast cancer patients after radiotherapy. The incidence and extent of perfusion defects are related to the volume of left ventricle included in the radiation field. Irradiation of endothelial cells lining large vessels also increases expression of inflammatory molecules, leading to adhesion and transmigration of circulating monocytes. In the presence of elevated cholesterol, invading monocytes transform into activated macrophages and form fatty streaks in the intima, thereby initiating the process of atherosclerosis. Experimental studies have shown that radiation predisposes to the formation of inflammatory plaque, which is more likely to rupture and cause a fatal heart attack or stroke. This paper presents a brief overview of the current knowledge on mechanisms for development of radiation-induced cardiovascular and cerebrovascular damage. It does not represent a comprehensive review of the literature, but reference is made to several excellent recent reviews on the topic.

Platelet dense-granule secretion plays a critical role in thrombosis and subsequent vascular remodeling in atherosclerotic mice

BACKGROUND

Platelet aggregation plays a critical role in myocardial infarction and stroke; however, the role of platelet secretion in atherosclerotic vascular disease is poorly understood. Therefore, we examined the hypothesis that platelet dense-granule secretion modulates thrombosis, inflammation, and atherosclerotic vascular remodeling after injury.

METHODS AND RESULTS

Functional deletion of the Hermansky-Pudlak syndrome 3 gene (HPS3(-/-)) markedly reduces platelet dense-granule secretion. HPS3(-/-) mice have normal platelet counts, platelet morphology, and alpha-granule number, as well as maximal secretion of the alpha-granule marker P-selectin; however, their capacity to form platelet-leukocyte aggregates is significantly reduced (P<0.05). To examine the role of platelet dense-granule secretion in these processes, atherosclerosis-prone mice with combined genetic deficiency of apolipoprotein E and HPS3 (ApoE(-/-), HPS3(-/-)) were compared with congenic, atherosclerosis-prone mice with normal platelet secretion (ApoE(-/-), HPS3(+/+)). After 16 to 18 weeks on a high-fat diet, both groups of mice had similar fasting cholesterol levels and body weight. Carotid arteries of ApoE(-/-), HPS3(+/+) mice thrombosed rapidly after FeCl(3) injury, but ApoE(-/-), HPS3(-/-) mice were completely resistant to thrombotic arterial occlusion (P<0.01). Three weeks after injury, neointimal hyperplasia (from alpha-smooth muscle actin-positive cells) was significantly less (P<0.001) in arteries from ApoE(-/-), HPS3(-/-) mice. In ApoE(-/-), HPS3(-/-) mice, there were also pronounced reductions in arterial inflammation, as indicated by a 74% decrease in CD45-positive leukocytes (P<0.01) and a 73% decrease in Mac-3-positive macrophages (P<0.05).

CONCLUSIONS

In atherosclerotic mice, reduced platelet dense-granule secretion is associated with marked protection against the development of arterial thrombosis, inflammation, and neointimal hyperplasia after vascular injury.

Vascular disease in mice with a dysfunctional circadian clock

BACKGROUND

Cardiovascular disease is the leading cause of death for both men and women in the United States and the world. A profound pattern exists in the time of day at which the death occurs; it is in the morning, when the endothelium is most vulnerable and blood pressure surges, that stroke and heart attack most frequently happen. Although the molecular components of circadian rhythms rhythmically oscillate in blood vessels, evidence of a direct function for the "circadian clock" in the progression to vascular disease is lacking.

METHODS AND RESULTS

In the present study, we found increased pathological remodeling and vascular injury in mice with aberrant circadian rhythms, Bmal1-knockout and Clock mutant. In addition, naive aortas from Bmal1-knockout and Clock mutant mice exhibit endothelial dysfunction. Akt and subsequent nitric oxide signaling, a pathway critical to vascular function, was significantly attenuated in arteries from Bmal1-knockout mice.

CONCLUSIONS

Our data reveal a new role for the circadian clock during chronic vascular responses that may be of significance in the progression of vascular disease.

In vivo modulation of Nogo-B attenuates neointima formation

Nogo-B was recently identified as a novel vascular marker; the normally high vascular expression of Nogo-B is rapidly lost following vascular injury. Here we assess the potential therapeutic effects of Ad-Nogo-B delivery to injured vessels in vivo. Nogo-B overexpression following Ad-Ng-B infection of vascular smooth muscle cells (VSMCs) was shown to block proliferation and migration in a dose-dependent manner in vitro. We next assessed the effects of Ad-Ng-B treatment on neointima formation in two in vivo models of acute vascular injury. Adventitial delivery of Ad-Ng-B to wire-injured murine femoral arteries led to a significant decrease in the intimal area [0.014 mm(2) versus 0.030 mm(2) (P = 0.049)] and the intima:media ratio [0.78 versus 1.67 (P = 0.038)] as compared to the effects of Ad-beta-Gal control virus at 21 days after injury. Similarly, lumenal delivery of Ad-Ng-B to porcine saphenous veins prior to carotid artery grafting significantly reduced the intimal area [2.87 mm(2) versus 7.44 mm(2) (P = 0.0007)] and the intima:media ratio [0.32 versus 0.55 (P = 0.0044)] as compared to the effects following the delivery of Ad- beta-Gal, at 28 days after grafting. Intimal VSMC proliferation was significantly reduced in both the murine and porcine disease models. Gene delivery of Nogo-B exerts a positive effect on vascular injury-induced remodeling and reduces neointimal development in two arterial and venous models of vascular injury.

Pharmacologic Profile and Therapeutic Potential of NCX 4016, a Nitric Oxide-releasing Aspirin, for Cardiovascular Disorders

NCX 4016, 2-(acetyloxy)benzoic acid 3-[(nitrooxy)methyl]phenyl ester, is a new molecule in which a nitric oxide (NO)-releasing moiety is covalently linked to aspirin. After enzymatic metabolism, NCX 4016 releases both components. In vitro and in some animal models, these components exert their pharmacologic effects simultaneously. Nitric oxide (NO) is a small gaseous molecule that exerts several activities which may prevent atherothrombotic disorders. Moreover, it displays a protective activity on the gastric mucosa. NCX 4016 has been shown to inhibit platelet activation in vitro more effectively than aspirin, to inhibit smooth muscle cell proliferation, to exert an endothelial cell protective activity and to suppress the function of several inflammatory cells potentially involved in atherothrombosis. In animal models, NCX 4016 protected from platelet thromboembolism, prevented restenosis in atherosclerosis-prone animals, protected the heart from ischemia/reperfusion injury, and induced neoangiogenesis in critically ischemic limbs. Moreover, it displayed little or no gastric toxicity and appeared to protect stomach from noxious stimuli, including aspirin. NCX 4016 has been evaluated in healthy volunteers and found to inhibit platelet cyclo-oxygenase-1 (COX-1) similarly to or slightly less than aspirin, to raise the circulating levels of NO-degradation products, and to have little or no gastric toxicity in short term studies. In particular, in phase II studies, NCX 4016 had favorable effects on effort-induced endothelial dysfunction in intermittent claudication and on platelet-activation parameters elicited by short-term hyperglycemia in type II diabetics. In patients with type II diabetes the effects of NCX 4016 on microalbuminuria and on some hemodynamic parameters were promising. The pharmacokinetics of in vivo aspirin- and NO- released by NCX 4016, as well as the bioavailability of the two molecules, were not yet adequately studied. Also, the long-term tolerability of NCX 4016, as well as its possible effectiveness in preventing ischemic cardiovascular events and progression of atherosclerosis, should be explored.

Ionizing radiation accelerates the development of atherosclerotic lesions in ApoE-/- mice and predisposes to an inflammatory plaque phenotype prone to hemorrhage

After radiotherapy treatment, there is an increased incidence of localized atherosclerosis in patients with Hodgkin's disease, breast cancer, and head and neck cancer. Here, we established a mouse model to study the development and progression of radiation-induced atherosclerosis and to compare the phenotype of these lesions with age-related atherosclerosis. Atherosclerosis-prone ApoE-/- mice fed a regular chow diet received single radiation doses of 14 Gy or sham treatments (0 Gy) to the neck, including both carotid arteries. At 22, 28, and 34 weeks after irradiation, blood samples were taken, and the arterial tree was removed for histological examination. Cholesterol levels in irradiated mice were not significantly different from age-matched controls, and markers of systemic inflammation (soluble intercellular adhesion molecule-1, soluble vascular cell adhesion molecule-1, and C-reactive protein) were not elevated. The lesions in irradiated arteries were macrophage rich, with a remarkable influx of inflammatory cells, predominantly granulocytes. Intraplaque hemorrhage and erythrocyte-containing macrophages were seen only in lesions of irradiated arteries. Based on these data, we propose that irradiation accelerates the development of macrophage-rich, inflammatory atherosclerotic lesions prone to intraplaque hemorrhage.

Genistein acutely stimulates nitric oxide synthesis in vascular endothelial cells by a cyclic adenosine 5'-monophosphate-dependent mechanism

Genistein may improve vascular function, but the mechanism of this effect is unclear. We tested the hypothesis that genistein directly regulates vascular function through stimulation of endothelial nitric oxide synthesis. Genistein activated endothelial nitric oxide synthase (eNOS) in intact bovine aortic endothelial cells and human umbilical vein endothelial cells over an incubation period of 10 min. The maximal eNOS activity was at 1 microm genistein. Consistent with this activation pattern, 1 microm genistein maximally stimulated the phosphorylation of eNOS at serine 1179 at 10 min of incubation. The rapid activation of eNOS by genistein was not dependent on RNA transcription or new protein synthesis and was not blocked by a specific estrogen receptor antagonist. In addition, inhibition of MAPK or phosphatidylinositol 3-OH kinase/Akt kinase had no affect on eNOS activation by genistein. Furthermore, the genistein effect on eNOS was also independent of tyrosine kinase inhibition. However, inhibition of cAMP-dependent kinase [protein kinase A (PKA)] by H89 completely abolished the genistein-stimulated eNOS activation and phosphorylation, suggesting that genistein acted through a PKA-dependent pathway. These findings demonstrated that genistein had direct nongenomic effects on eNOS activity in vascular endothelial cells, leading to eNOS activation and nitric oxide synthesis. These effects were mediated by PKA and were unrelated to an estrogenic effect. This cellular mechanism may underlie some of the cardiovascular protective effects proposed for soy phytoestrogens.

Nitric oxide-releasing aspirin derivative, NCX 4016, promotes reparative angiogenesis and prevents apoptosis and oxidative stress in a mouse model of peripheral ischemia

BACKGROUND

Recently, nitric oxide (NO) donors have been developed that mimic the physiological intracellular release of NO. We evaluated whether one of these new compounds, consisting of aspirin coupled to an NO-releasing moiety (NCX 4016), would protect limbs from supervening arterial occlusion.

METHODS AND RESULTS

Mice were assigned to receive regular chow or chow containing NCX 4016 or aspirin (both at 300 mumol/kg body weight, daily) throughout the 3-week experimental period. One week after randomization, they underwent surgical excision of the left femoral artery. Limb blood flow recovery (laser Doppler flowmetry) was accelerated by NCX 4016 as compared with aspirin or vehicle (P<0.05). In controls, histological analysis revealed a 35% increase in the capillary density of ischemic muscles compared with contralateral ones, indicative of spontaneous angiogenesis. Neovascularization was enhanced by NCX 4016 (91%; P<0.05 versus vehicle), but not by aspirin (51%; P=NS versus vehicle). Furthermore, NCX 4016 reduced endothelial cell (EC) apoptosis (4.3+/-1.0 versus 8.7+/-2.0 in aspirin and 12.6+/-3.3 ECs/1000 cap in vehicle; P<0.05 for either comparison) as well as caspase-3 mRNA levels in ischemic muscles ([caspase-3/GAPDH]*100 = 0.09+/-0.04 versus 2.30+/-0.44 in aspirin and 2.30+/-0.32 in vehicle; P<0.01 for either comparison). Nitrite levels and the ratio of reduced to oxidized glutathione were selectively increased in ischemic muscles by NCX 4016. Vascular endothelial growth factor-A expression was reduced by aspirin, with this effect being blunted by NCX 4016.

CONCLUSIONS

Pretreatment with the new oral NO-releasing aspirin derivative stimulates reparative angiogenesis and prevents apoptosis and oxidative stress, thereby alleviating the consequences of supervening arterial occlusion.

A new role for Nogo as a regulator of vascular remodeling

Although Nogo-A has been identified in the central nervous system as an inhibitor of axonal regeneration, the peripheral roles of Nogo isoforms remain virtually unknown. Here, using a proteomic analysis to identify proteins enriched in caveolae and/or lipid rafts (CEM/LR), we show that Nogo-B is highly expressed in cultured endothelial and smooth muscle cells, as well as in intact blood vessels. The N terminus of Nogo-B promotes the migration of endothelial cells but inhibits the migration of vascular smooth muscle (VSM) cells, processes necessary for vascular remodeling. Vascular injury in Nogo-A/B-deficient mice promotes exaggerated neointimal proliferation, and adenoviral-mediated gene transfer of Nogo-B rescues the abnormal vascular expansion in those knockout mice. Our discovery that Nogo-B is a regulator of vascular homeostasis and remodeling broadens the functional scope of this family of proteins.