Transfection of inducible nitric oxide synthase gene causes apoptosis in vascular smooth muscle cells

Advancements in Omics and Breakthrough Gene Therapies: A Glimpse into the Future of Peripheral Artery Disease

Peripheral artery disease (PAD), a highly prevalent global disease, associates with significant morbidity and mortality in affected patients. Despite progress in endovascular and open revascularization techniques for advanced PAD, these interventions grapple with elevated rates of arterial restenosis and vein graft failure attributed to intimal hyperplasia (IH). Novel multiomics technologies, coupled with sophisticated analyses tools recently powered by advances in artificial intelligence, have enabled the study of atherosclerosis and IH with unprecedented single-cell and spatial precision. Numerous studies have pinpointed gene hubs regulating pivotal atherogenic and atheroprotective signaling pathways as potential therapeutic candidates. Leveraging advancements in viral and nonviral gene therapy (GT) platforms, gene editing technologies, and cutting-edge biomaterial reservoirs for delivery uniquely positions us to develop safe, efficient, and targeted GTs for PAD-related diseases. Gene therapies appear particularly fitting for ex vivo genetic engineering of IH-resistant vein grafts. This manuscript highlights currently available state-of-the-art multiomics approaches, explores promising GT-based candidates, and details GT delivery modalities employed by our laboratory and others to thwart mid-term vein graft failure caused by IH, as well as other PAD-related conditions. The potential clinical translation of these targeted GTs holds the promise to revolutionize PAD treatment, thereby enhancing patients' quality of life and life expectancy.

Enzyme Activity and Lipogenesis Inhibition by Fermented Grain Using Natural Enzymes

This study aims to compare the effects of three enzyme-rich foods, including one fermented (grain enzyme) and two non-fermented foods (enzyme foods 1 and 2), by investigating their antioxidant, anti-inflammatory, and anti-adipogenic properties. Grain enzyme exhibited the highest radical scavenging activity and was rich in antioxidant components, including total polyphenol and total flavonoid contents. Grain enzyme and enzyme foods 1 and 2 inhibited nitric oxide production by 27, 34, and 17%, respectively, at a concentration of 200 μg/mL in LPS-stimulated macrophages. Among the tested enzymes, grain enzyme demonstrated the strongest inhibition on the expression of inducible nitric oxide synthase (INOS), cyclooxygenase-2 (COX-2), and interleukin (IL)-1β, while Enzyme Food 2 exhibited the most significant suppression of IL-6 mRNA levels. Furthermore, Grain Enzyme demonstrated a stronger inhibitory effect compared to Enzyme Food 1 and 2. Grain Enzyme decreased the mRNA expression of peroxisome proliferator-activated receptor (PPAR)γ, CCAAT/enhancer-binding protein (C/EBP)α, and fatty acid-binding protein (FABP)4 by 28, 21, and 30%, respectively, at a concentration of 400 μg/mL. In summary, fermented grain enzymes outperformed non-fermented enzymes in suppressing inflammation and adipogenesis. This study highlights the anti-inflammatory and anti-adipogenic effects of grain enzyme, suggesting its potential as a valuable dietary supplement for managing metabolic disorders.

Human pulmonary microvascular endothelial cell DDAH1-mediated nitric oxide production promotes pulmonary smooth muscle cell apoptosis in co-culture

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease in preterm infants, and pulmonary hypertension (PH) develops in 25%-40% of patients with BPD, increasing morbidity and mortality. BPD-PH is characterized by vasoconstriction and vascular remodeling. Nitric oxide (NO) is a pulmonary vasodilator and apoptotic mediator made in the pulmonary endothelium by NO synthase (eNOS). Asymmetric dimethylarginine (ADMA) is an endogenous eNOS inhibitor, primarily metabolized by dimethylarginine dimethylaminohydrolase-1 (DDAH1). Our hypothesis is that DDAH1 knockdown in human pulmonary microvascular endothelial cells (hPMVEC) will result in lower NO production, decreased apoptosis, and greater proliferation of human pulmonary arterial smooth muscle cells (hPASMC), whereas DDAH1 overexpression will have the opposite effect. hPMVECs were transfected with small interfering RNA targeting DDAH1 (siDDAH1)/scramble or adenoviral vector containing DDAH1 (AdDDAH1)/AdGFP for 24 h and co-cultured for 24 h with hPASMC. Analyses included Western blot for cleaved and total caspase-3, caspase-8, caspase-9, β-actin; trypan blue exclusion for viable cell numbers; terminal deoxynucleotide transferase dUTP nick end labeling (TUNEL); and BrdU incorporation. Small interfering RNA targeting DDAH1 (siDDAH1) transfected into hPMVEC resulted in lower media nitrites, cleaved caspase-3 and caspase-8 protein expression, and TUNEL staining; and greater viable cell numbers and BrdU incorporation in co-cultured hPASMC. Adenoviral-mediated transfection of the DDAH1 gene (AdDDAH1) into hPMVEC resulted in greater cleaved caspase-3 and caspase-8 protein expression and lower viable cell numbers in co-cultured hPASMC. Partial recovery of hPASMC viable cell numbers after AdDDAH1-hPMVEC transfection was observed when media were treated with hemoglobin to sequester NO. In conclusion, hPMVEC-DDAH1-mediated NO production positively regulates hPASMC apoptosis, which may prevent/attenuate aberrant pulmonary vascular proliferation/remodeling in BPD-PH.NEW & NOTEWORTHY BPD-PH is characterized by vascular remodeling. NO is an apoptotic mediator made in the pulmonary endothelium by eNOS. ADMA is an endogenous eNOS inhibitor metabolized by DDAH1. EC-DDAH1 overexpression resulted in greater cleaved caspase-3 and caspase-8 protein expression and lower viable cell numbers in co-cultured SMC. After NO sequestration, SMC viable cell numbers partially recovered despite EC-DDAH1 overexpression. EC-DDAH1-mediated NO production positively regulates SMC apoptosis, which may prevent/attenuate aberrant pulmonary vascular proliferation/remodeling in BPD-PH.

An arginase-1 SNP that protects against the development of pulmonary hypertension in bronchopulmonary dysplasia enhances NO-mediated apoptosis in lymphocytes

Arginase and nitric oxide synthase (NOS) share a common substrate, l‐arginine, and have opposing effects on vascular remodeling. Arginase is the first step in polyamine and proline synthesis necessary for cellular proliferation, while NO produced from NOS promotes apoptosis. Previously, we identified a single nucleotide polymorphism (SNP) in the arginase‐1 (ARG1) gene, rs2781666 (T‐allele) that was associated with a decreased risk for developing pulmonary hypertension (PH) in a cohort of infants with bronchopulmonary dysplasia (BPD). In this study, we utilized lymphocytes from neonates (the only readily available cells from these patients expressing the two genotypes of interest) with either the rs2781666 SNP (TT) or wild type (GG) to test the hypothesis that the protection of the ARG1 SNP against the development of PH in BPD would involve augmented NO production leading to more apoptosis. Lymphocytes were stimulated with IL‐4, IL‐13, and phorbol myristate acetate (PMA). We found that TT lymphocytes had similar levels of arginase I and arginase II expression, but there was a tendency for lower urea production (a surrogate marker of arginase activity), than in the GG lymphocytes. The TT lymphocytes also had significantly greater NO production than did GG lymphocytes despite no differences in iNOS expression between genotypes. Furthermore, the TT lymphocytes had lower numbers of viable cells, and higher levels of cleaved caspase‐3 than did GG lymphocytes. Inhibiting NOS activity using N_ω‐Nitro‐l‐arginine methyl ester hydrochloride (l‐NAME) significantly decreased cleaved caspase‐3 levels in the TT lymphocytes. These data demonstrate that the TT genotype results in greater levels of NO production leading to more apoptosis, which is consistent with the concept that BPD patients with the TT genotype are protected against the development of PH by producing greater basal levels of endogenous NO.

Apoptosis and Nitrative Stress Associated with Phosphodiesterase Inhibitor-Induced Mesenteric Vasculitis in Rats

Nitric oxide may play a role in phosphodiesterase (PDE) inhibitor-induced rat mesenteric vasculitis. The present study was conducted to identify cellular sources of iNOS, determine the distribution of nitrotyrosine (NT) residues as a footprint of peroxynitrite (ONOO-) production, and evaluate their association with vascular apoptosis. To dissociate primary events from secondary changes associated with the inflammatory response, rats were given the PDE IV inhibitor CI-1018 orally at 750 mg/kg alone or concurrently with dexamethasone (DEX) intraperitoneally at 1 mg/kg for 4—5 days. Neutrophil (PMN) involvement in apoptosis was investigated in CI-1018 treated rats dosed with rabbit anti-rat PMN serum (APS). iNOS expression, NT residues, and caspase-3 were detected by immuno-histochemistry. Apoptosis was evaluated by TUNEL assay. CI-1018 induced vascular lesions were associated with iNOS expression in endothelial cells and inflammatory infiltrates; NT was evident only in the latter. Caspase-3 and TUNEL-positive staining were prominent only in medial smooth muscle cells (SMC) from CI-1018-treated rats and only when associated with active inflammation. iNOS- and NT-positive inflammatory cells were present in close proximity to SMC with caspase-3 staining. Inflammatory infiltrates were absent in rats given DEX with minimal SMC necrosis and hemorrhage remained. DEX eliminated apoptosis and immunoreactivity associated with caspase-3, iNOS, and NT. APS depletion of PMNs decreased the incidence and severity of vasculitis but failed to abolish completely caspase-3 immunoreactivity. Expression patterns for caspase-3, iNOS, and NT demonstrated that nitrative stress is a prominent feature of PDE inhibitor-induced vasculitis, with a possible role in medial SMC apoptosis. Further, medial SMC apoptosis may not be a primary event, but instead may be secondary to the inflammatory response.

Increased expression of bFGF is associated with carotid atherosclerotic plaques instability engaging the NF-κB pathway

Unstable atherosclerotic plaques of the carotid arteries are at great risk for the development of ischemic cerebrovascular events. The degradation of the extracellular matrix by matrix metalloproteinases (MMPs) and NO-induced apoptosis of vascular smooth muscle cells (VSMCs) contribute to the vulnerability of the atherosclerotic plaques. Basic fibroblast growth factor (bFGF) through its mitogenic and angiogenic properties has already been implicated in the pathogenesis of atherosclerosis. However, its role in plaque stability remains elusive. To address this issue, a panel of human carotid atherosclerotic plaques was analyzed for bFGF, FGF-receptors-1 and -2 (FGFR-1/-2), inducible nitric oxide synthase (iNOS) and MMP-9 expression. Our data revealed increased expression of bFGF and FGFR-1 in VSMCs of unstable plaques, implying the existence of an autocrine loop, which significantly correlated with high iNOS and MMP-9 levels. These results were recapitulated in vitro by treatment of VSMCs with bFGF. bFGF administration led to up-regulation of both iNOS and MMP-9 that was specifically mediated by nuclear factor-kappaB (NF-kappaB) activation. Collectively, our data demonstrate a novel NF-kappaB-mediated pathway linking bFGF with iNOS and MMP-9 expression that is associated with carotid plaque vulnerability.

Translational studies of A20 in atherosclerosis and cardiovascular disease

Cardiovascular disease (CVD) is the biggest killer in the Western World despite significant advances in understanding its molecular underpinnings. Chronic inflammation, the classical hallmark of atherogenesis is thought to play a key pathogenic role in the development of atherosclerotic lesions from initiation of fatty streaks to plaque rupture. Over-representation of mostly pro-inflammatory nuclear factor kappa B (NF-kappaB) target genes within atherosclerotic lesions has led to the common-held belief that excessive NF-kappaB activity promotes and aggravates atherogenesis. However, mouse models lacking various proteins involved in NF-kappaB signaling have often resulted in conflicting findings, fueling additional investigations to uncover the molecular involvement of NF-kappaB and its target genes in atherogenesis. In this chapter we will review the role of the NF-kappaB-regulated, yet potent NF-kappaB inhibitory and anti-inflammatory gene A20/TNFAIP3 in atherogenesis, and highlight the potential use of its atheroprotective properties for the prevention and treatment of cardiovascular diseases.

Synergistic apoptosis of CML cells by buthionine sulfoximine and hydroxychavicol correlates with activation of AIF and GSH-ROS-JNK-ERK-iNOS pathway

Background

Hydroxychavicol (HCH), a constituent of Piper betle leaf has been reported to exert anti-leukemic activity through induction of reactive oxygen species (ROS). The aim of the study is to optimize the oxidative stress –induced chronic myeloid leukemic (CML) cell death by combining glutathione synthesis inhibitor, buthionine sulfoximine (BSO) with HCH and studying the underlying mechanism.

Materials and Methods

Anti-proliferative activity of BSO and HCH alone or in combination against a number of leukemic (K562, KCL22, KU812, U937, Molt4), non-leukemic (A549, MIA-PaCa2, PC-3, HepG2) cancer cell lines and normal cell lines (NIH3T3, Vero) was measured by MTT assay. Apoptotic activity in CML cell line K562 was detected by flow cytometry (FCM) after staining with annexinV-FITC/propidium iodide (PI), detection of reduced mitochondrial membrane potential after staining with JC-1, cleavage of caspase- 3 and poly (ADP)-ribose polymerase proteins by western blot analysis and translocation of apoptosis inducing factor (AIF) by confocal microscopy. Intracellular reduced glutathione (GSH) was measured by colorimetric assay using GSH assay kit. 2′,7′-dichlorodihydrofluorescein diacetate (DCF-DA) and 4-amino-5-methylamino-2′,7′-difluorofluorescein (DAF-FM) were used as probes to measure intracellular increase in ROS and nitric oxide (NO) levels respectively. Multiple techniques like siRNA transfection and pharmacological inhibition were used to understand the mechanisms of action.

Results

Non-apoptotic concentrations of BSO significantly potentiated HCH-induced apoptosis in K562 cells. BSO potentiated apoptosis-inducing activity of HCH in CML cells by caspase-dependent as well as caspase-independent but apoptosis inducing factor (AIF)-dependent manner. Enhanced depletion of intracellular GSH induced by combined treatment correlated with induction of ROS. Activation of ROS- dependent JNK played a crucial role in ERK1/2 activation which subsequently induced the expression of inducible nitric oxide synthase (iNOS). iNOS- mediated production of NO was identified as an effector molecule causing apoptosis of CML cells.

Conclusion/Significance

BSO synergizes with HCH in inducing apoptosis of CML cells through the GSH-ROS-JNK-ERK-iNOS pathway.

Modulation of NO and ROS production by AdiNOS transduced vascular cells through supplementation with L-Arg and BH4: implications for gene therapy of restenosis

OBJECTIVE

Gene therapy with viral vectors encoding for NOS enzymes has been recognized as a potential therapeutic approach for the prevention of restenosis. Optimal activity of iNOS is dependent on the intracellular availability of L-Arg and BH4 via prevention of NOS decoupling and subsequent ROS formation. Herein, we investigated the effects of separate and combined L-Arg and BH4 supplementation on the production of NO and ROS in cultured rat arterial smooth muscle and endothelial cells transduced with AdiNOS, and their impact on the antirestenotic effectiveness of AdiNOS delivery to balloon-injured rat carotid arteries.

METHODS AND RESULTS

Supplementation of AdiNOS transduced endothelial and vascular smooth muscle cells with L-Arg (3.0 mM), BH4 (10 μM) and especially their combination resulted in a significant increase in NO production as measured by nitrite formation in media. Formation of ROS was dose-dependently increased following transduction with increasing MOIs of AdiNOS. Exposure of RASMC to AdiNOS tethered to meshes via a hydrolyzable cross-linker, modeling viral delivery from stents, resulted in increased ROS production, which was decreased by supplementation with BH4 but not L-Arg or L-Arg/BH4. Enhanced cell death, caused by AdiNOS transduction, was also preventable with BH4 supplementation. In the rat carotid model of balloon injury, intraluminal delivery of AdiNOS in BH4-, L-Arg-, and especially in BH4 and L-Arg supplemented animals was found to significantly enhance the antirestenotic effects of AdiNOS-mediated gene therapy.

CONCLUSIONS

Fine-tuning of iNOS function by L-Arg and BH4 supplementation in the transduced vasculature augments the therapeutic potential of gene therapy with iNOS for the prevention of restenosis.

Tumor cells upregulate normoxic HIF-1α in response to doxorubicin

Hypoxia-inducible factor 1 (HIF-1) is a master transcription factor that controls cellular homeostasis. Although its activation benefits normal tissue, HIF-1 activation in tumors is a major risk factor for angiogenesis, therapeutic resistance, and poor prognosis. HIF-1 activity is usually suppressed under normoxic conditions because of rapid oxygen-dependent degradation of HIF-1α. Here, we show that, under normoxic conditions, HIF-1α is upregulated in tumor cells in response to doxorubicin, a chemotherapeutic agent used to treat many cancers. In addition, doxorubicin enhanced VEGF secretion by normoxic tumor cells and stimulated tumor angiogenesis. Doxorubicin-induced accumulation of HIF-1α in normoxic cells was caused by increased expression and activation of STAT1, the activation of which stimulated expression of iNOS and its synthesis of nitric oxide (NO) in tumor cells. Mechanistic investigations established that blocking NO synthesis or STAT1 activation was sufficient to attenuate the HIF-1α accumulation induced by doxorubicin in normoxic cancer cells. To our knowledge, this is the first report that a chemotherapeutic drug can induce HIF-1α accumulation in normoxic cells, an efficacy-limiting activity. Our results argue that HIF-1α-targeting strategies may enhance doxorubicin efficacy. More generally, they suggest a broader perspective on the design of combination chemotherapy approaches with immediate clinical impact.

Janus-like role of fibroblast growth factor 2 in arteriosclerotic coronary artery disease: atherogenesis and angiogenesis

Angiogenic stimulation is a promising new strategy for treating patients with arteriosclerotic coronary artery disease. This strategy aims to ameliorate cardiac function by improving myocardial perfusion and lowering the risk of myocardial infarction. However, angiogenesis may contribute to the growth of atherosclerotic lesions. Atherogenesis is also a potential side effect of angiogenic therapy. Early clinical trials were performed using fibroblast growth factor 2 (FGF2) protein, which enhances the formation of new collateral vessels to reduce ischaemic symptoms. Conversely, angiogenic stimulation by FGF2 is a dilemma because it could cause negative angiogenic effects, such as atherosclerosis. Thus far, clinical trials in patients with recombinant FGF2 protein therapy have not yet yielded undisputable beneficial effects. Future trials should determine whether an improvement can be obtained in patients with coronary artery disease using a combination of FGF2 and other growth factors or a combination of the FGF2 gene and stem cell therapy. This review summarises the multiple roles of FGF2 in the progression of atherosclerosis, its effect on pro-angiogenesis and improvement of cardiac function in coronary artery disease, and the potentially unfavourable effect of angiogenesis on the prevention and treatment of atherogenesis.

Regulation of reactive oxygen species by p53: implications for nitric oxide-mediated apoptosis

Nitric oxide (NO) induces vascular smooth muscle cell (VSMC) apoptosis in part through activation of p53. Traditionally, p53 has been thought of as the gatekeeper, determining if a cell should undergo arrest and repair or apoptosis following exposure to DNA-damaging agents, depending on the severity of the damage. However, our laboratory previously demonstrated that NO induces apoptosis to a much greater extent in p53(-/-) compared with p53(+/+) VSMC. Increased reactive oxygen species (ROS) within VSMC has been shown to induce VSMC apoptosis, and recently it was found that the absence of, or lack of, functional p53 leads to increased ROS and oxidative stress within different cell types. This study investigated the differences in intracellular ROS levels between p53(-/-) and p53(+/+) VSMC and examined if these differences were responsible for the increased susceptibility to NO-induced apoptosis observed in p53(-/-) VSMC. We found that p53 actually protects VSMC from NO-induced apoptosis by increasing antioxidant protein expression [i.e., peroxiredoxin-3 (PRx-3)], thereby reducing ROS levels and cellular oxidative stress. We also observed that the NO-induced apoptosis in p53(-/-) VSMC was largely abrogated by pretreatment with catalase. Furthermore, when the antioxidant protein PRx-3 and its specific electron acceptor thioredoxin-2 were silenced within p53(+/+) VSMC with small-interfering RNA, not only did these cells exhibit greater ROS production, but they also exhibited increased NO-induced apoptosis similar to that observed in p53(-/-) VSMC. These findings suggest that ROS mediate NO-induced VSMC apoptosis and that p53 protects VSMC from NO-induced apoptosis by decreasing intracellular ROS. This research demonstrates that p53 has antioxidant functions in stressed cells and also suggests that p53 has antiapoptotic properties.

Isopropylamine NONOate (IPA/NO) moderates neointimal hyperplasia following vascular injury

OBJECTIVE

Isopropylamine NONOate (IPA/NO) is a nitroxyl (HNO) donor at physiologic pH. HNO is a positive inotrope and vasodilator, but little is known about its effect on neointimal hyperplasia. The aims of this study are to determine the effect of IPA/NO on endothelial and vascular smooth muscle cells (VSMC) in vitro and to determine if IPA/NO inhibits neointimal hyperplasia in vivo.

METHODS

VSMC were harvested from the abdominal aortas of male Sprague Dawley rats, and human umbilical vein endothelial cells were purchased from ATCC. In vitro, cellular proliferation was assessed by (3)H-thymidine incorporation, cell migration was assessed using the scrape assay, and cell death was assessed using Guava personal cell analysis (PCA). Cell cycle analysis was performed using propidium iodide staining and flow cytometry analysis. Protein expression was assessed using Western blot analysis. Phosphorylated proteins were assessed using immunoprecipitation and Western blot analysis. In vivo, the carotid artery injury model was performed on male Sprague Dawley rats treated with (n = 12) or without (n = 6) periadventitial IPA/NO (10 mg). Arteries harvested at 2 weeks were assessed for morphometrics using ImageJ. Inflammation was assessed using immunohistochemistry. Endothelialization was assessed by Evans blue staining of carotid arteries harvested 7 days after balloon injury from rats treated with (n = 6) or without (n = 3) periadventitial IPA/NO (10 mg).

RESULTS

In vitro, 1000 micromol/L IPA/NO inhibited both VSMC (38.7 +/- 4.5% inhibition vs control, P = .003) and endothelial cell proliferation (54.0 +/- 2.9% inhibition vs control, P < or = 0.001) without inducing cell death or inhibiting migration. In VSMC, this inhibition was associated with an S-phase cell cycle arrest and increased expression of cyclin A, cyclin D1, and the cyclin-dependent kinase inhibitor p21. No change was noted in the phosphorylation status of cdk2, cdk4, or cdk6 by IPA/NO. In rodents subjected to the carotid artery balloon injury model, IPA/NO caused significant reductions in neointimal area (298 +/- 20 vs 422 +/- 30, P < or = .001) and medial area (311 +/- 14 vs 449 +/- 16, P < or = .001) compared with injury alone, and reduced macrophage infiltration to 1.7 +/- 0.8 from 16.1 +/- 3.5 cells per high power field (P < or = .001). IPA/NO also prevented re-endothelialization compared with injury alone (55.9 +/- 0.5% nonendothelialized vs 21 +/- 4.4%, respectively, P = .001). Lastly, a 50% mortality rate was observed in the IPA/NO-treated groups.

CONCLUSIONS

In summary, while IPA/NO modestly inhibited neointimal hyperplasia by inhibiting VSMC proliferation and macrophage infiltration, it also inhibited endothelial cell proliferation and induced significant mortality in our animal model. Since HNO is being investigated as a treatment for congestive heart failure, our results raise some concerns about the use of IPA/NO in the vasculature and suggest that further studies be conducted on the safety of HNO donors in the cardiovascular system.

Influence of cholesterol and fish oil dietary intake on nitric oxide-induced apoptosis in vascular smooth muscle cells

Apoptosis of vascular smooth muscle cells (SMC) is critically involved in the progression of atherosclerosis. We previously reported that dietary cholesterol intake induces changes in SMC at molecular and gene expression levels. The objectives of the present study were to investigate the differential response to nitric oxide of vascular SMC obtained from chicks after cholesterol and fish oil dietary intake and to examine effects on the main pro-apoptotic and anti-apoptotic genes. Dietary cholesterol intake reduced the Bcl-2/Bax (anti-apoptotic/pro-apoptotic) protein ratio in SMC, making them more susceptible to apoptosis. When cholesterol was withdrawn and replaced with a fish oil-enriched diet, the Bcl-xl/Bax protein ratio significantly increased, reversing the changes induced by cholesterol. The decrease in c-myc gene expression after apoptotic stimuli and the increase in Bcl-xl/Bax ratio indicate that fish oil has a protective role against apoptosis in SMC. Nitroprussiate-like nitric oxide donors exerted an intensive action on vascular SMC cultures. However, SMC-C (isolated from animals fed with control diet) and SMC-Ch (isolated from animals fed with cholesterol-enriched diet) responded differently to nitric oxide, especially in their bcl-2 and bcl-xl gene expression. SMC isolated from animals fed with cholesterol-enriched and then fish oil-enriched diet (SMC-Ch-FO cultures) showed an intermediate apoptosis level (Bcl-2/Bax ratio) between SMC-C and SMC-Ch, induction of c-myc expression and elevated p53 expression. These findings indicate that fish oil protects SMC against apoptosis.

Evolving neurovascular relationships in the RCS rat with age

PURPOSE

To examine the course of development of vascular disorders in the Royal College of Surgeons (RCS) rat and how these may lead to retinal ganglion cell loss.

METHODS

Whole-mount retinae from RCS rats were first stained for neurofilament protein and then for NADPH-diaphorase staining. A separate group of RCS rats was injected with Type II Peroxidase and the retinae were subsequently processed for peroxidase histochemistry.

RESULTS

The first changes in the deep vascular plexus occur as the photoreceptor layer is lost and it comes into close proximity to the retinal pigment epithelial (RPE) cell layer. RPE cells migrate onto retinal vessels, and at such locations vascular complex develop. These are first found ventral to the optic nerve head and then gradually progress over most of the retina. The inner retinal vessels that supply the complexes cross the optic nerve fiber layer and appear to be under tension. They ligate axons, which leads to retinal ganglion cell loss.

CONCLUSIONS

These observations show vascular changes can have secondary repercussions for neurons distant from the primary lesion.

Evaluation of the effect of oxidative stress and vitamin E supplementation on renal function in rats with streptozotocin-induced Type 1 diabetes

We investigated the possible role of reactive oxygen species (ROS) on renal function in experimental diabetes.

MATERIALS AND METHODS

Seven groups of male rats were studied. Group I consisted of control animals. Diabetes was induced (by streptozotocin) in the animals in the other groups and they received either insulin or vitamin E (300 or 600 mg/kg), both insulin and vitamin E, or no treatment for 4 weeks. At the end of the study, blood pressure was measured and parameters of kidney function and oxidative stress were evaluated in serum and kidney tissue samples.

RESULTS

Diabetic animals had higher blood pressures; increased serum glucose, urea, creatinine, cyclic guanosine monophosphate (cGMP); increased kidney tissue levels of malondialdehyde and inducible nitric oxide synthetase (iNOS); and reduced serum glutathione peroxidase when compared with control animals. Blood glucose levels in diabetic animals were controlled by insulin and not by any dose of vitamin E alone. However, all other measured parameters improved towards control levels with either insulin or vitamin E in either dose. An additive beneficial effect was observed on the levels of iNOS and cGMP when both forms of treatment were used in diabetic animals.

CONCLUSIONS

We conclude that ROS may play an important role in diabetes-induced nephropathy in this rat model. Vitamin E supplementation in addition to insulin can have additive protective effects against deterioration of renal function in this model.

Gene therapy via inducible nitric oxide synthase: a tool for the treatment of a diverse range of pathological conditions

Nitric oxide (NO(.)) is a reactive nitrogen radical produced by the NO synthase (NOS) enzymes; it affects a plethora of downstream physiological and pathological processes. The past two decades have seen an explosion in the understanding of the role of NO(.) biology, highlighting various protective and damaging modes of action. Much of the controversy surrounding the role of NO(.) relates to the differing concentrations generated by the three isoforms of NOS. Both calcium-dependent isoforms of the enzyme (endothelial and neuronal NOS) generate low-nanomolar/picomolar concentrations of NO(.). By contrast, the calcium-independent isoform (inducible NOS (iNOS)) generates high concentrations of NO(.), 2-3 orders of magnitude greater. This review summarizes the current literature in relation to iNOS gene therapy for the therapeutic benefit of various pathological conditions, including various states of vascular disease, wound healing, erectile dysfunction, renal dysfunction and oncology. The available data provide convincing evidence that manipulation of endogenous NO(.) using iNOS gene therapy can provide the basis for future clinical trials.

Beneficial effect of a short-acting NO donor for the prevention of neointimal hyperplasia

Nitric oxide (NO)-based therapies effectively inhibit neointimal hyperplasia in animal models of arterial injury and bypass grafting, but are not available clinically. We created a simple, effective, locally applied NO-eluting therapy to prevent restenosis after vascular procedures. We investigated the efficacy of perivascular delivery of two distinctly different diazeniumdiolate NO donors, 1-[2-(carboxylato)pyrrolidin-1-yl]diazen-1-ium-1,2-diolate (PROLI/NO) (short half-life) and diazeniumdiolated poly(acrylonitrile) (PAN/NO) (long half-life), in powder or gel form (30% poloxamer 407), at inhibiting neointimal hyperplasia using the rat carotid artery injury model. Two weeks postinjury, all of the NO-eluting therapies successfully reduced neointimal hyperplasia. However, most dramatically, PROLI/NO powder reduced intimal area by 91.2% (p<0.05) versus injury alone. PROLI/NO powder was noted to reduce the medial area (40.2% vs injury alone, p<0.05), whereas other groups showed no such effect. Three days postinjury, each NO treatment group significantly reduced cellular proliferation. However, inflammatory markers revealed a distinct pattern: PAN/NO groups displayed increased leukocyte infiltration (p<0.05), whereas PROLI/NO groups displayed less macrophage infiltration (p<0.05). In conclusion, perivascular delivery of diazeniumdiolate NO donors in powder or gel form effectively inhibits neointimal hyperplasia. Application of short-acting PROLI/NO powder most effectively inhibited neointimal hyperplasia and inflammation and may represent a simple, clinically applicable NO-eluting therapy to prevent neointimal hyperplasia and restenosis after open vascular interventions.

Inhibition of nitric oxide-induced apoptosis by nicotine in oral epithelial cells

Development of oral cancer is clearly linked to the usage of smokeless tobacco. The molecular mechanisms involved in this process are however not well understood. Toward this goal, we investigated the effect of smokeless tobacco exposure on apoptosis of oral epithelial cells. Exposure of oral epithelial cells to smokeless tobacco extract (STE) induces apoptosis in a dose-dependent manner, until a threshold level of nicotine is achieved upon which apoptosis is inhibited. 1 mM of nicotine is able to inhibit apoptosis significantly induced by STE in these oral cells. Exposure of cells to nicotine alone has no effect on apoptosis, but nicotine inhibits apoptosis induced by other agents present in STE. In this study we show that, the anti-apoptotic action of nicotine is specifically associated with down-regulation of nitric oxide (NO) production. Using specific inducers of NO, we have demonstrated that inhibition of apoptosis by nicotine is through down-regulation of NO production. Further, we observed that nicotine clearly acts as a sink of NO radicals, shown using peroxynitrite generator (SIN-1) in conjunction or absence of radical scavengers. Nicotine thus causes most damage in transformed epithelial cells as depicted by accumulation of nitrotyrosine in a 3-NT ELISA assay. Inhibition of apoptosis is a hallmark in tumor progression and propels development of cancer. It may further result in functional loss of apoptotic effector mechanisms in the transformed cells. Thus, our data clearly indicates that inhibition of NO-induced apoptosis by nicotine may lead to tobacco-induced oral carcinogenesis, and implies careful development of modalities in tobacco cessation programs.

The role of nitric oxide in the pathophysiology of intimal hyperplasia

Since its discovery, nitric oxide (NO) has emerged as a biologically important molecule and was even named Molecule of the Year by Science magazine in 1992. Specific to our interests, NO has been implicated in the regulation of vascular pathology. This review begins with a summary of the molecular biology of NO, from its discovery to the mechanisms of endogenous production. Next, we turn our attention to describing the arterial injury response of neointimal hyperplasia, and we review the role of NO in the pathophysiology of neointimal hyperplasia. Finally, we review the literature regarding NO-based therapies. This includes the development of inhalational-based NO therapies, systemically administered L-arginine and NO donors, NO synthase gene therapy, locally applied NO donors, and NO-releasing prosthetic materials. By reviewing the current literature, we emphasize the tremendous clinical potential that NO-based therapies can have on the development of neointimal hyperplasia.

Adenoviral-mediated gene transfer of nitric oxide synthase isoforms and vascular cell proliferation

OBJECTIVE

Many vascular diseases are associated with reduced nitric oxide (NO) bioavailability. Nitric oxide synthase (NOS) gene therapy to the vasculature is a possible treatment for vascular disease as a means of increasing NO bioavailability, and this may be achieved using any of the NOS isoforms. The aim of our study was to compare the effects of adenoviral-mediated overexpression of the most commonly used NOS isoforms eNOS and iNOS on vascular cell proliferation.

METHODS

Human coronary artery smooth muscle cells (HCSMCs) and human umbilical vein endothelial cells (HUVECs) were transduced with adenoviral vectors encoding eNOS or iNOS at a multiplicity of infection of 100. Control cells were exposed to AdNull (empty vector) or diluent alone. Transgene expression was sought by Western blotting. The Greiss assay was used to measure nitrite levels. Cell proliferation was assessed by cell counting on days 0, 3 and 6. Apoptosis was sought using FACS analysis. Angiogenesis was measured using a commercially available in vitro kit.

RESULTS

Expression of both isoforms was detected in transduced cells by Western blot at all three time points. NOS transduction resulted in increased nitrite levels with higher levels seen in iNOS- compared to eNOS-transduced cells. Cell proliferation was diminished in AdeNOS- and AdiNOS-transduced cells compared with non-transduced cells on days 3 and 6 in both HCSMCs and HUVECs. Apoptosis was not detected in either cell line with either of the isoforms at any timepoint studied. Both eNOS and iNOS gene transfer caused a reduction in angiogenesis.

CONCLUSIONS

NOS gene transfer to both endothelial and vascular smooth muscle cells is antiproliferative and antiangiogenic. The biological effect is identical with both isoforms and there is no evidence to support a differential effect on endothelial and vascular smooth muscle cell biology.

A20, a modulator of smooth muscle cell proliferation and apoptosis, prevents and induces regression of neointimal hyperplasia

A20 is a NF-kappaB-dependent gene that has dual anti-inflammatory and antiapoptotic functions in endothelial cells (EC). The function of A20 in smooth muscle cells (SMC) is unknown. We demonstrate that A20 is induced in SMC in response to inflammatory stimuli and serves an anti-inflammatory function via blockade of NF-kappaB and NF-kappaB-dependent proteins ICAM-1 and MCP-1. A20 inhibits SMC proliferation via increased expression of cyclin-dependent kinase inhibitors p21waf1 and p27kip1. Surprisingly, A20 sensitizes SMC to cytokine- and Fas-mediated apoptosis through a novel NO-dependent mechanism. In vivo, adenoviral delivery of A20 to medial rat carotid artery SMC after balloon angioplasty prevents neointimal hyperplasia by blocking SMC proliferation and accelerating re-endothelialization, without causing apoptosis. However, expression of A20 in established neointimal lesions leads to their regression through increased apoptosis. This is the first demonstration that A20 exerts two levels of control of vascular remodeling and healing. A20 prevents neointimal hyperplasia through combined anti-inflammatory and antiproliferative functions in medial SMC. If SMC evade this first barrier and neointima is formed, A20 has a therapeutic potential by uniquely sensitizing neointimal SMC to apoptosis. A20-based therapies hold promise for the prevention and treatment of neointimal disease.

Comparative effects of azelnidipine and other Ca2+-channel blockers on the induction of inducible nitric oxide synthase in vascular smooth muscle cells

Overproduction of nitric oxide by inducible nitric oxide synthase contributes to the progression of cardiovascular disease. We investigated the effects of azelnidipine and other Ca2+-channel blockers on nitric oxide production by cultured aortic smooth muscle cells isolated from Wistar rats and human umbilical vein endothelial cells (HUVECs), using the Griess reaction and oxyhemoglobin method. Release of lactic dehydrogenase (LDH) was measured to evaluate cell damage, and immunohistochemistry was performed to examine the expression of inducible nitric oxide synthase and nitrotyrosine protein. Azelnidipine and other Ca2+-channel blockers inhibited the release of nitric oxide induced by lipopolysaccharide plus interferon-gamma. Azelnidipine inhibited it most potently among the Ca2+-channel blockers tested (azelnidipine, amlodipine, nifedipine, diltiazem, verapamil, and nicardipine) at a concentration of 10 microM. Longer stimulation with these agents induced the expression of inducible nitric oxide synthase and nitrotyrosine, with an increase of lactic dehydrogenase release, whereas azelnidipine suppressed these changes. In human umbilical vein endothelial cells, azelnidipine enhanced basal nitric oxide production by endothelial nitric oxide synthase. In conclusion, azelnidipine potently inhibited the induction of inducible nitric oxide synthase and then nitric oxide production in vascular smooth muscle cells, while enhancing constitutive nitric oxide production by endothelial cells. Azelnidipine may inhibit nitrotyrosine expression and cell damage caused by overproduction of nitric oxide, suggesting a mechanism for its cardiovascular protective effect.

Pulmonary arterial hypertension in systemic sclerosis: clinical manifestations, pathophysiology, evaluation, and management

It is increasingly recognized that significant pulmonary arterial hypertension (PAH) develops in more than 15% of patients with systemic sclerosis (SSc). As this complication of SSc may occur even in the absence of overt interstitial lung disease (isolated PAH), it has been likened to primary PAH and is attributable to intrinsic vascular pathology that is the hallmark of SSc. Deregulated activity of mediators controlling vasomotor tone has been implicated, and levels of endothelin-1 (ET-1) are elevated in the circulation and in the lungs. By causing enhanced vasoconstriction, vascular endothelial cell proliferation, smooth muscle hypertrophy, and irreversible vascular remodeling in the lungs, ET-1 appears to play a significant role in the pathogenesis of SSc-associated PAH. Although patients with the limited cutaneous form of SSc are more likely to develop PAH than those with the diffuse form, the true prevalence of PAH in SSc, and the risk factors for its development, are not yet known. Because the prognosis of patients with SSc-associated PAH is substantially worse than that of patients without this complication, intensive efforts are underway to develop sensitive screening strategies and effective treatments. Serial evaluation of SSc patients with Doppler echocardiography appears to be prudent. Antibodies against the centromere or fibrillarin proteins may be useful in identifying those patients with SSc at highest risk for developing PAH. The US FDA has approved a number of novel treatments, including long-acting oral ET-1 receptor antagonists such as bosentan and short-acting parenteral prostacyclin analogs, such as epoprostenol, for PAH. In particular, bosentan appear to be well tolerated, and short-term therapy results in improved exercise tolerance, improved hemodynamics, and possibly improved survival in patients with advanced PAH. These agents may be used alone, or possibly in combination with prostacyclin analogs. Therapeutic agents that modulate the synthesis of nitric oxide, and additional agents targeting the ET-1 signaling system are under preclinical development. Although the large-scale clinical trials that resulted in obtaining FDA approval for these agents were generally carried out in patients with primary PAH, it appears that patients with SSc-associated PAH respond similarly. Therefore, it is reasonable to conclude that ET-1 receptor antagonists and parenteral prostacyclin analogs should be used in SSc patients with moderate to severe PAH. The efficacy of these agents for treating patients with PAH who also experience significant interstitial lung disease, as occurs in many SSc patients, remains unknown. Additional important unresolved issues relate to the long-term efficacy of ET-1 receptor antagonists, and their effects on survival and progression of PAH. Additionally, it is not yet clear if early intervention for SSc patients with mild PAH is beneficial.

Bidirectional regulation of monocyte chemoattractant protein-1 gene at distinct sites of its promoter by nitric oxide in vascular smooth muscle cells

We have previously reported that chronic activation of phosphatidylinositol 3-kinase (PI3-kinase) by the overexpression of membrane-targeted p110CAAX induced proinflammatory gene expression in rat vascular smooth muscle cells (VSMCs) through the induction of CCAAT/enhancer binding protein-beta (C/EBP-beta) and C/EBP-delta. To examine the anti-inflammatory effect of nitric oxide (NO) on proinflammatory gene expression, we have investigated the effects of sodium nitroprusside (SNP) on the monocyte chemoattractant protein-1 (MCP-1) gene expression in VSMCs under chronic activation of PI3-kinase. At low concentrations (0.05 mM) of SNP, but not at high concentrations (0.5-1.0 mM), MCP-1 mRNA and protein expression as well as its transcriptional activity were significantly reduced. We found that SNP induced C/EBP homologous protein (CHOP) expression, which inhibited C/EBP binding activity and reduced the C/EBP activity induced by chronic activation of PI3-kinase in a dose-dependent manner up to 1.0 mM. Consistently, the increase in CHOP expression significantly reduced the MCP-1 promoter activity induced by PI3-kinase. However, the overexpression of CHOP alone upregulated MCP-1 promoter activity in a dose-dependent manner up to high concentrations. Deletion analysis of MCP-1 promoter and electrophoretic mobility shift assay identified the CHOP-response element (CHOP-RE) at the region between -190 and -179 bp of MCP-1 promoter. By using CHOP-RE as a decoy, we significantly suppressed the increase in promoter activity of MCP-1 induced by either CHOP or SNP. Thus CHOP induced by an NO donor has bidirectional effects on MCP-1 gene expression: it decreases gene expression by inhibition of C/EBPs, and it increases the gene expression through CHOP-RE.

Inducible nitric oxide synthase has divergent effects on vascular and metabolic function in obesity

Previous studies have suggested an involvement of inducible nitric oxide synthase (iNOS) in obesity, but the relation, if any, between this and mechanisms underlying endothelial dysfunction in obesity is unknown. We studied mice fed an obesogenic high-fat or standard diet for up to 8 weeks. Obesity was associated with elevated blood pressure; resistance to the glucoregulatory actions of insulin; resistance to the vascular actions of insulin, assessed as the reduction in phenylephrine constrictor response of aortic rings after insulin preincubation (lean -21.7 +/- 11.5 vs. obese 18.2 +/- 15.5%; P < 0.05); and evidence of reactive oxygen species (ROS)-dependent vasodilatation in response to acetylcholine in aortic rings (change in maximal relaxation to acetylcholine after exposure to catalase: lean -2.1 +/- 6.0 vs. obese -15.0 +/- 3.8%; P = 0.04). Obese mice had increased expression of iNOS in aorta, with evidence of increased vascular NO production, assessed as the increase in maximal constriction to phenylephrine after iNOS inhibition with 1400W (lean -3.5 +/- 9.1 vs. obese 42.1 +/- 11.2%; P < 0.001). To further address the role of iNOS in obesity-induced vascular and metabolic dysfunction, we studied the effect of a high-fat diet in iNOS knockout mice (iNOS KO). Obese iNOS KO mice were protected against the development of resistance to insulin's glucoregulatory and vascular effects (insulin-dependent reduction in maximal phenylephrine response: obese wild-type 11.2 +/- 15.0 vs. obese iNOS KO -20.0 +/- 7.7%; P = 0.02). However, obese iNOS KO mice remained hypertensive (124.0 +/- 0.7 vs. 114.9 +/- 0.5 mmHg; P < 0.01) and had evidence of increased vascular ROS production. Although these data support iNOS as a target to protect against the adverse effects of obesity on glucoregulation and vascular insulin resistance, iNOS inhibition does not prevent the development of raised blood pressure or oxidative stress.

The drug-based pipeline against restenosis

More than 1 million percutaneous coronary interventions (PCIs) are performed yearly worldwide. Restenosis is the recurrent narrowing that can occur within 6 months following an initially successful PCI. Although drug-eluting stents have accomplished remarkable success, restenosis has not been eliminated and optimisation of both the polymers and drugs associated with them is desirable. This article reviews the presently available and potential preventive approaches against restenosis, including the sirolimus and paclitaxel drug-eluting stents.

Nitric oxide-induced apoptosis is mediated by Bax/Bcl-2 gene expression, transition of cytochrome c, and activation of caspase-3 in rat vascular smooth muscle cells

BACKGROUND

In contrast to the anti-apoptotic action of nitric oxide (NO) on endothelial cells, NO exerts a pro-apoptotic effect on vascular smooth muscle cells (VSMCs). This study was designed to elucidate the mechanism underlying NO-induced apoptosis in rat VSMCs.

METHODS AND RESULTS

(1) Using the terminal deoxynucleotidyl transferase-mediated digoxigenin-11-dUTP nick end labeling (TUNEL) assay and fluorescence activated cell sorter (FACS) analyses, apoptosis of rat VSMCs were confirmed after exposure to sodium nitroprusside (SNP) (0.5 to 4 mmol/l), an exogenous NO donor. The effects of SNP were blocked by hemoglobin. (2) A universal caspase inhibitor, z-VAD-fmk, dose-dependently inhibited NO-induced apoptosis. VSMCs degraded Ac-DEVD-pNA rather than Ac-WHED-pNA after exposure to SNP, which suggested that the activation of caspase 3 rather than caspase 1 was involved in the process. Immunoblot analysis confirmed the activation of caspase-3. (3) Exposure to SNP induced the release of cytochrome c from the mitochondria to the cytosol, which was detected by immunoblot analysis of mitochondrial and cytosol fractions. (4) SNP exposure increased the ratio of Bax/Bcl-2 protein expression twofold by immunoblot analysis.

CONCLUSIONS

The mechanism of NO-induced apoptosis in rat VSMCs involves an increase in the ratio of Bax/Bcl-2 gene expression, which leads to the release of cytochrome c from the mitochondria to the cytosol, finally activating caspase-3 and resultant apoptosis.

p42/44 Mitogen-activated protein kinase regulated by p53 and nitric oxide in human pulmonary arterial smooth muscle cells

Although nitric oxide (NO) is known to inhibit vascular smooth muscle cell proliferation, the subcellular molecular mechanisms involved with the inhibitory signal transduction pathways are uncertain. We investigated the effect of exogenous NO on cell proliferation and the expression of p53, p21, and phosphorylated p42/44 mitogen-activated protein kinase (MAPK) in human pulmonary arterial smooth muscle cells (HPASMC). Both S-nitroso-N-acetyl penicillamine and diethylenetriaminelNONOate dose-dependently suppressed [3H]-thymidine incorporation in cultured HPASMC, and induced the expression of p53 and p21 protein. Further, the NO donors transiently increased the phosphorylation of p42/44 MAPK and then suppressed it. Although MAPK kinase inhibitors suppressed [3H]-thymidine incorporation by the cells, no significant change was observed in the expression of p53 and p21. The NO donors also suppressed the activation of p42/44 MAPK evoked by transient transfection of the wild-type p53 gene; however, they failed to suppress the activation of p42/44 MAPK in constitutive-active mutations of the Ras or Raf genes trasnsfected from HPASMC. These results indicate that exogenous NO is able to transiently activate p42/44 MAPK via the induction of p53, and then suppress it via inactivation of the Ras and Raf cascades.

Inducible nitric oxide synthase is present in human abdominal aortic aneurysm and promotes oxidative vascular injury

OBJECTIVE

Nitric oxide (NO), catalyzed by inducible NO synthase (iNOS), may be important in the pathophysiologic characteristics of many vascular diseases. Although there is indirect evidence to support the presence of iNOS in abdominal aortic aneurysm (AAA) in human beings, no definitive study has confirm this finding. The present study was designed to assess expression of iNOS in AAA in human beings. Furthermore, the activity of iNOS and the oxidative vascular injury initiated by iNOS were assessed with detection of nitrotyrosine, which is a marker indicative of formation and activity of the NO-derived oxidant peroxynitrite.

METHODS

We studied 25 patients with AAA and 10 patients with normal abdominal aortas. In situ hybridization and immunohistochemistry were used in tissue sections to localize iNOS messenger RNA (mRNA) and protein. Double staining with a combination of in situ hybridization and immunohistochemistry was used to simultaneously demonstrate iNOS mRNA expression and its cellular localization. The presence of peroxynitrite was indirectly assessed with immunostaining with anti-nitrotyrosine antibodies.

RESULTS

In situ hybridization and immunohistochemistry confirmed the presence of iNOS in media and adventitia of AAA in all 25 patients. Specific cell markers identified iNOS mRNA-positive cells mainly as T and B lymphocytes, macrophages, and smooth muscle cells. Positive immunostaining for nitrotyrosine was present in macrophages and smooth muscle cells. Normal abdominal aorta demonstrated virtually no iNOS or nitrotyrosine expression.

CONCLUSION

Stimulated expression of iNOS is associated with degeneration of AAA in human beings, and the activity of this enzyme under such conditions preferentially promotes formation and activity of peroxynitrite and further contributes to oxidative tissue and cellular injury in AAA. This may be important in the pathogenesis of AAA.

Prospective evaluation of hydroperoxide plasma levels and stable nitric oxide end products in patients subjected to angioplasty for coronary artery disease

BACKGROUND

Oxidative stress appears to be involved in several processes that contribute to atherogenesis and restenosis following vascular intervention.

METHODS

The aim of our study was to evaluate prospectively the plasma concentrations of a hydroperoxide (ROOH) and nitric oxide end product (NO(x)) in patients subjected to coronary angioplasty (PTCA) and routine control angiography 6 months after the initial procedure. We prospectively studied 48 consecutive patients (39 men, nine women, mean age 52 years) with stable angina who underwent successful elective angioplasty. A vascular segment was considered successfully treated when the residual luminal narrowing in the dilated segment immediately after angioplasty was <50%. Angiographic follow-up was obtained in all of the patients. Plasma samples were drawn at baseline (before angioplasty) and serially after angioplasty (1, 3 and 6 months afterwards). Hydroperoxides were determined by the FOX II assay (ferrous oxidation in xylenol orange, Pierce Rockford, IL). Nitrate was converted in the presence of NO3 reductase. The Griess reagent was used for the measurement of NO2.

RESULTS

The overall angiographic restenosis rate was 35%. There were no significant differences in clinical variables between the patients with or without restenosis. The baseline levels (0.8+/-0.09 vs. 0.6+/-0.2 micromol/l) as well as the concentrations of authentic lipid hydroperoxide in plasma after 1 month (0.7+/-0.09 vs. 1.0+/-0.2 micromol/l) and 6 months (0.8+/-0.1 vs. 1.0+/-0.2 micromol/l) were similar in both groups. Three months after the angioplasty a significant increase in the ROOH level was noticed in the patients with restenosis (0.9+/-0.1 vs. 1.4+/-0.2, P=0.04). Plasma levels of NO(x) were similar in both groups at baseline (23.6+/-2.1 vs. 22.7+/-2.6 micromol/l) and 1 month after procedure (24.4+/-2.2 vs. 23.4+/-3.3 micromol/l). However, in patients with restenosis significant decreases in stable NO end products were observed 3 and 6 months after PTCA (18.1+/-1.5 vs. 13.3+/-1.7, P=0.04; 14.2+/-1.0 vs. 8.7+/-1.3, P=0.02, respectively).

CONCLUSIONS

In patients with angiographic restenosis a significant increase in lipid peroxidation accompanied by a reduction in the stable end products of nitric oxide in plasma is observed several months after PTCA.

Inhibitory effects of ursodeoxycholic acid on the induction of nitric oxide synthase in vascular smooth muscle cells

The expression of inducible nitric oxide synthase (iNOS) and the resultant increased nitric oxide production are associated with endotoxemia and atherosclerotic lesions observed in transplant hearts or balloon-injured artery. Ursodeoxycholic acid has been shown to have cardiovascular protective effects, such as inhibition of the development of transplant arteriosclerosis, but its mechanism remains unclear. Here, we investigated the effects of ursodeoxycholic acid on nitric oxide production and the expression of iNOS in vascular smooth muscle cells isolated from adult rat aorta and rabbit coronary artery. Nitrite released from cells in the culture medium was measured with the Griess reaction. iNOS mRNA and protein were measured by Northern and Western blot analyses. Treatment with ursodeoxycholic acid (30-1000 microM) significantly inhibited lipopolysaccharide plus interferon-gamma-induced nitric oxide production in a concentration-dependent manner, but ursodeoxycholic acid showed only small inhibitory effects on nitric oxide production that had already been induced by lipopolysaccharide plus interferon-gamma. Ursodeoxycholic acid by itself did not affect basal nitric oxide production. Ursodeoxycholic acid also suppressed lipopolysaccharide plus interferon-gamma-induced expression of iNOS mRNA and protein. Ursodeoxycholic acid had the most potent inhibitory effect among various kinds of bile acids examined, i.e. chenodeoxycholic acid, deoxycholic acid, cholic acid and conjugated bile acids such as tauroursodeoxycholic acid. These results suggest that ursodeoxycholic acid inhibits the induction of iNOS and then nitric oxide production in aortic and coronary artery smooth muscle cells, suggesting a possible mechanism for the cardiovascular protective effect of ursodeoxycholic acid under various pathophysiological conditions such as endotoxemia and atherosclerosis.

Preclinical evaluation of inducible nitric oxide synthase lipoplex gene therapy for inhibition of stent-induced vascular neointimal lesion formation

Several reports have established the concept of nitric oxide synthase (NOS) gene transfer for inhibiting smooth muscle cell (SMC) proliferation after vascular injury. To minimize potential risks associated with viral gene transfer, we developed a liposome-based gene transfer approach employing inducible NOS (iNOS) overexpression for inhibition of stent-induced neointimal lesion formation. Therapeutic lipoplexes were transferred to femoral or coronary arteries of Goettingen minipigs, using the Infiltrator local drug delivery device. Efficiency of local iNOS lipoplex transfer was analyzed by iNOS-specific immunohistochemistry. NO-mediated inhibition of stent-induced neointimal lesion formation was analyzed by intravascular ultrasound (IVUS) and computerized morphometry. Gene transfer efficiency increased dose dependently to a maximum of 44.3 +/- 4.2% iNOS-positive vessel area (dose, 2 microg of iNOS lipoplex). Proliferating cell nuclear antigen (PCNA) expression of medial SMCs (immunohistochemistry) was inhibited significantly by transfer of 2 microg of iNOS lipoplexes (111 +/- 27 cells [iNOS] versus 481 +/- 67 cells [control; PCNA-positive medial cells]). IVUS analysis demonstrated that local transfer of iNOS lipoplexes resulted in a significant reduction of femoral in-stent plaque area (control, 40.85 +/- 6.37 mm(2); iNOS, 24.69 +/- 1.8 mm(2); p = 0.03). Coronary in-stent lesion formation was reduced by about 45% as determined by histologic morphometry (control, 4.0 +/- 0.29; iNOS, 2.2 +/- 0.30; p < 0.01). In conclusion, this study demonstrates that local intramural delivery of iNOS lipoplexes can exert therapeutic effects in inhibiting stent-induced neointimal lesion formation. Together with the nonviral character of this gene therapy approach, these findings may have important impact on the transition of NOS-based gene therapy to clinical practice.

Mitochondria, nitric oxide, and cardiovascular dysfunction

Cardiovascular diseases encompass a wide spectrum of abnormalities with diverse etiologies. The molecular mechanisms underlying these disorders include a variety of responses such as changes in nitric oxide- (NO) dependent cell signaling and increased apoptosis. An interesting aspect that has received little or no attention is the role mitochondria may play in the vascular changes that occur in both atherosclerosis and hypertension. With the changing perspective of the organelle from simply a role in metabolism to a contributor to signal transduction pathways, the role of mitochondria in cells with relatively low energy demands such as the endothelium has become important to understand. In this context, the definition of the NO-cytochrome c oxidase signaling pathway and the influence this has on cytochrome c release is particularly important in understanding apoptotic mechanisms involving the mitochondrion. This review examines the role of compromised mitochondrial function in a variety of vascular pathologies and the modulation of these effects by NO. The interaction of NO with the various mitochondrial respiratory complexes and the role NO plays in modulating mitochondrial-mediated apoptosis in these systems will be discussed.

Different contribution of apoptosis to the antiproliferative effects of L-arginine, enalapril and losartan on neointimal growth inhibition after balloon arterial injury

It remains to be clarified how angiotensin-converting enzyme inhibitor-induced function (ie, increased NO related action or the inhibition of angiotensin II AT1 receptor dependent action) affects apoptosis of smooth muscle cells in the neointima following arterial injury. Saline (control), enalapril, L-arginine, combined enalapril and L-arginine, or losartan was administered for 14 days to Sprague-Dawley rats after balloon carotid injury and the ratio of intima to media areas (I/M), inducible NO synthase (iNOS) concentrations and %TUNEL were measured. I/M decreased similarly in the enalapril, L-arginine and losartan groups, and the combination of enalapril and L-arginine resulted in the largest I/M decrease. TUNEL positivity was increased compared with controls in the following order: losartan, L-arginine, enalapril and combination of enalapril and L-arginine. The intensity of immunostaining for iNOS was increased approximately 1.9-fold compared with the control in the combined enarapril and L-arginine group as well as in the enalapril group. These data suggest that the apoptosis in the neointima is different for L-arginine, losartan and enalapril under similar conditions and was higher under treatment with enalapril, not only via the action of NO or blocking of the AT1, but also by upregulation of iNOS.

Endothelial cell apoptosis induced by antibodies against dengue virus nonstructural protein 1 via production of nitric oxide

The onset of vascular leakage and hemorrhagic diathesis is one of the life-threatening complications occurring in dengue patients, yet the pathogenic mechanisms are not well understood. In this study, we demonstrated that Abs against dengue virus nonstructural protein 1 (NS1) generated in mice cross-reacted with human endothelial cells and mouse vessel endothelium. After binding, mouse anti-NS1 Abs induced endothelial cell apoptosis in a caspase-dependent manner. Inducible NO synthase expression could be observed; it showed a time- and dose-dependent correlation with NO production. Endothelial cell apoptosis, characterized by exposure of phosphatidylserine on the cell surface and nuclear DNA fragmentation, was blocked by treatment with the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester. Further studies demonstrated that the expression of Bcl-2 and Bcl-x(L) decreased in both mRNA and protein levels, whereas p53 and Bax increased after anti-NS1 treatment. Cytochrome c release was also observed. All of these effects could be inhibited by N(omega)-nitro-L-arginine methyl ester. Taken together, anti-NS1 Abs act as autoantibodies that cross-react with noninfected endothelial cells and trigger the intracellular signaling leading to the production of NO and to apoptosis. Endothelial cell damage may cause vascular leakage that contributes to the pathogenesis of dengue disease.

Potentiation of nitric oxide-induced apoptosis in p53-/- vascular smooth muscle cells

The functional role of p53 in nitric oxide (NO)-mediated vascular smooth muscle cell (VSMC) apoptosis remains unknown. In this study, VSMC from p53-/- and p53+/+ murine aortas were exposed to exogenous or endogenous sources of NO. Unexpectedly, p53-/- VSMC were much more sensitive to the proapoptotic effects of NO than were p53+/+ VSMC. Furthermore, this paradox appeared to be specific to NO, because other proapoptotic agents did not demonstrate this differential effect on p53-/- cells. NO-induced apoptosis in p53-/- VSMC occurred independently of cGMP generation. However, mitogen-activated protein kinase (MAPK) pathways appeared to play a significant role. Treatment of the p53-/- VSMC with S-nitroso-N-acetylpenicillamine resulted in a marked activation of p38 MAPK and, to a lesser extent, of c-Jun NH(2)-terminal kinase, mitogen-activated protein kinase kinase (MEK) 1/2, and p42/44 (extracellular signal-regulated kinase, ERK). Furthermore, basal activity of the MEK-p42/44 (ERK) pathway was increased in the p53+/+ VSMC. Inhibition of p38 MAPK with SB-203580 or of MEK1/2 with PD-98059 blocked NO-induced apoptosis. Therefore, p53 may protect VSMC against NO-mediated apoptosis, in part, through differential regulation of MAPK pathways.

The genetics of the target tissue in rheumatoid arthritis

The genetic mechanisms that are complementary in predisposing and then establishing disease are yet to be fully elucidated. During a lifetime, the genetic composition of the host is not only hereditary but undergoes rearrangements, integrations, and more subtle single-base pair alterations. These changes can be inconsequential or lead to aberrant and deleterious pathologic changes. In a complex multifactorial disease such as RA, the relative roles of the dynamic versus germline elements of the disease have yet to be fully determined. Further studies of large populations are likely to segregate out factors affecting specific ethnic, clinical, and genetic subgroups.

Cytokine-activated Jak-2 is involved in inducible nitric oxide synthase expression independent from NF-kappaB activation in vascular smooth muscle cells

Inflammatory cytokines, such as interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha, activate nuclear factor-kappa B (NF-kappaB) which transactivates inducible nitric oxide synthase (iNOS) gene in vascular smooth muscle cells (VSMCs). However, it remains obscure whether cytokine-mediated iNOS expression in VSMCs requires signaling pathway(s) other than NF-kappaB activation. The present study was designed to elucidate whether protein tyrosine kinases (PTKs) are involved in the cytokine-induced NF-kappaB activation and iNOS expression in cultured rat VSMCs. Both IL-1beta and TNF-alpha stimulated NF-kappaB activity, iNOS mRNA and protein expression with massive nitrite/nitrate (NOx) production in rat VSMCs. PTK inhibitors (genistein, herbimycin A) dose-dependently inhibited the cytokine-stimulated NOx production and iNOS mRNA expression. However, neither genistein nor herbimycin A affected the cytokine-stimulated phosphorylation and degradation of IkappaB-alpha, or NF-kappaB activation, whereas they completely blocked the cytokine-stimulated iNOS transcriptional activity. Tyrphostin B42 (AG490), a Jak-2 tyrosine kinase inhibitor, similarly blocked the cytokine-induced NOx production, iNOS expression and its promoter activity without affecting NF-kappaB-dependent transcription. Transfection of a dominant-negative Jak-2 mutant antagonized the cytokine-induced NOx production and iNOS expression, while wild-type Jak-2 expressing construct was without effect. These data indicate that the cytokine-induced iNOS expression involves activation of Jak-2 signaling pathway independent from NF-kappaB activation in rat VSMCs.

Nitric oxide and cyclic guanosine monophosphate stimulate apoptosis via activation of the Fas-FasL pathway

BACKGROUND

Inappropriately exaggerated response of pulmonary vascular cells to inflammatory mediators may be one mechanism that leads to acute (or adult) respiratory distress syndrome. Nitric oxide (NO) is induced following such exaggerated responses and may have a variety of biological effects, including induction of apoptosis. The mechanism by which NO causes apoptosis is unknown; however, Fas (CD95) and Fas ligand (FasL) (CD95L) have been implicated. We hypothesized that NO-induced apoptosis in pulmonary vascular smooth muscle cells is mediated through a Fas-FasL pathway.

MATERIALS AND METHODS

Cultured human and rat pulmonary artery smooth muscle cells (PASMCs) were exposed to soluble FasL (0-5 ng/ml), the NO donor S(G)-nitroso-N-acetyl pencillamine (SNAP) (0-50 microg/ml), and/or anti-FasL (0-100 microg/ml) for 12 h. Apoptosis was measured using in situ DNA nick end labeling and flow cytometry. Changes in Fas and FasL protein levels were assessed via Western blot analysis. Messenger RNA (mRNA) abundance of apoptosis-related genes was determined using a ribonuclease protection assay.

RESULTS

Rat PASMCs exposed to FasL show a dose-dependent increase in apoptosis. Human PASMCs are less responsive to FasL. Addition of anti-FasL to rat PASMCs treated with 10(-5) M SNAP decreases apoptosis levels compared to SNAP treated alone. FasL and Fas receptor proteins are increased in response to 10(-3) to 10(-4) M SNAP or 10(-6) M 8-bromo-cyclic guanosine monophosphate (cGMP). The mRNA abundance of Fas, FasL, and other apoptosis-related genes is increased in response to 10(-6) M 8-bromo-cGMP but not 8-bromo-cyclic adenosine monophosphate.

CONCLUSIONS

Nitric oxide-induced apoptosis in rat and human PASMCs is mediated, at least in part, through the Fas-FasL pathway, with cGMP increasing the expression of Fas and FasL.

Nitric oxide: implications for vascular and endovascular surgery

Nitric oxide has a key role in vascular homeostasis. It plays a protective role by suppressing abnormal proliferation of vascular smooth muscle following various pathological situations including atherosclerosis and restenosis after vascular interventions such as balloon angioplasty, stent deployment and bypass grafting. It also has strong antiplatelet and anti-thrombogenic properties. In this review, possible applications to daily vascular and endovascular surgery practice, including systemic use of NO donors, enhancing endogenous production of NO by L-arginine and gene therapy, local delivery strategies and coating stents and grafts with NO-delivering/enhancing chemicals are reviewed.

The pathobiology of pulmonary hypertension. Endothelium

Dysfunctional endothelial cells have a central and critical role in the initiation and progression of severe pulmonary hypertension. The elucidation of the mechanisms involved in the control of endothelial cell proliferation and cell death in the pulmonary vasculature, therefore, is fundamentally important in the pathogenesis of severe pulmonary hypertension and of great interest for a better understanding of endothelial cell biology. Because the intravascular growth of endothelial cells resulting in tumorlets is unique to severe pulmonary hypertension, this phenomenon can teach researchers about the factors involved in the formation and maintenance of the normal endothelial cell monolayer. Clearly, in severe pulmonary hypertension, the "law of the endothelial cell monolayer" has been broken. The ultimate level of such a control is at the altered gene expression pattern that is conducive to endothelial cell growth and disruption of pulmonary blood flow. Secondary pulmonary hypertension certainly also is associated with proliferated pulmonary endothelial cells and plexiform lesions that are histologically indistinguishable from those in PPH. What is then the difference in the mechanisms of endothelial cell proliferation between primary and secondary pulmonary hypertension? The authors believe that PPH is a disease caused by somatic mutations in key angiogenesis- or apoptosis-related genes such as the TGF-beta receptor-2 and Bax. The loss of these important cell growth control mechanisms allows for the clonal expansion of endothelial cells from a single cell that has acquired a selective growth advantage. On the other hand, the proliferated endothelial cells in secondary pulmonary hypertension are polyclonal. It follows from this finding that local (vascular) factor(s) (such as increased shear stress), rather than mutations, play a major role in triggering endothelial cell proliferation. In PPH and secondary pulmonary hypertension, the researcher can postulate that the pulmonary vascular bed contains progenitor-like cells with the capacity of dysregulated growth. The main difference in the pathogenesis of primary and secondary pulmonary endothelial cell proliferation therefore may be the initial mechanism involved in the recruitment of an endothelial progenitor-like cell. In PPH, anorexigen-associated, and familial PPH, the proliferation of endothelial cells occurs from a mutated single cell, whereas in secondary pulmonary hypertension, several progenitor-like cells would be activated to grow. The abnormal endothelial cells in both forms of severe pulmonary hypertension expand because of the expression of angiogenesis-related molecules such as VEGF, VEGFR-2, HIF-1 alpha, and HIF-beta. Also important for the expansion of these cells is the down-regulation of expression of apoptosis-related mediators such as TGF-beta receptor-2 or Bax. The success of any therapy for severe pulmonary hypertension requires that the underlying process of endothelial cell proliferation could be controlled or reversed.

The regulatory role of nitric oxide in apoptosis

Nitric oxide (NO) is a multi-faceted molecule with dichotomous regulatory roles in many areas of biology. The complexity of its biological effects is a consequence of its numerous potential interactions with other molecules such as reactive oxygen species (ROS), metal ions, and proteins. The effects of NO are modulated by both direct and indirect interactions that can be dose-dependent and cell-type specific. For example, in some cell types NO can promote apoptosis, whereas in other cells NO inhibits apoptosis. In hepatocytes, NO can inhibit the main mediators of cell death-caspase proteases. Moreover, low physiological concentrations of NO can inhibit apoptosis, but higher concentrations of NO may be toxic. High NO concentrations lead to the formation of toxic reaction products like dinitrogen trioxide or peroxynitrite that induce cell death, if not by apoptosis, then by necrosis. Long-term exposure to nitric oxide in certain conditions like chronic inflammatory states may predispose cells to tumorigenesis through DNA damage, inhibition of DNA repair, alteration in programmed cell death, or activation of proliferative signaling pathways. Understanding the regulatory mechanisms of NO in apoptosis and carcinogenesis will provide important clues to the diagnosis and treatment of tissue damage and cancer. In this article we have reviewed recent discoveries in the regulatory role of NO in specific cell types, mechanisms of pro-apoptotic and anti-apoptotic induction by NO, and insights into the effects of NO on tumor biology.

Transcription factors p53 and HIF-1alpha as targets of nitric oxide

It is widely recognized that the production of nitric oxide (NO) from L-arginine metabolism is an essential determinate of diverse signalling cascades throughout the body, with a major impact during nonspecific host defence. Biological actions of NO and derived species comprise physiological as well as pathological entities, with an impressive and steadily growing number of signalling pathways and/or protein targets being involved. It is now appreciated that NO not only acts as an effector molecule but also as an autocrine as well as paracrine modulator of rapid and delayed cellular responses. Among multiple targets the tumour suppressor p53 and the hypoxia inducible factor-1alpha (HIF-1alpha) emerged. Accumulation of p53 in response to NO delivery may account for an interference in cell cycle progression and/or initiation of apoptosis that is found in close correlation with inducible NO synthase (NOS) expression. Quite similarly, accumulation of HIF-1alpha not only occurs during hypoxia, but also under conditions of NO delivery, thus mimicking a situation of reduced oxygen availability. Interestingly, p53 and HIF-1alpha share regulatory elements that cause protein stabilization in part as a result of impaired ubiquitin-evoked protein degradation. Here, we summarize current knowledge on the impact of NO on p53- and HIF-1alpha-stabilization and we will discuss pathophysiological consequences. These examples may help to shape and refine current concepts of NO action with an emphasis on transcription factor regulation.

Apoptosis in atherosclerosis: pathological and pharmacological implications

Normal embryonic development, tissue differentiation and repair in the eukaryote requires a tightly regulated apoptosis, or programmed cell death. Apoptosis also plays an essential role in different pathological processes including atherosclerosis, in which it affects all cell types in the atherosclerotic lesion, including endothelial cells, vascular smooth muscle cells, and macrophages. During atherosclerosis progression, pro- and anti-apoptotic signals abound in the evolving lesion. Apoptosis limits the number of a particular cell type that accumulates in the lesion and slows down the overall progression of the lesion. On the other hand, it contributes to the production of unstable plaques. Many pharmacological agents used to treat cardiovascular and lipid disorders have pro- or/and anti-apoptotic effects. Pharmaceuticals that modulate apoptosis in specific types of cell can potentially serve as anti-atherogenic agents. However, to develop agents for clinical use requires a thorough knowledge of the pathophysiology of apoptosis in atheromatous lesions, a highly cell-specific process. Here we review our current understanding of the process to provide a background for future pharmacological research in the area.

[Pro- and anti-apoptotic role of nitric oxide, NO]

NO displays both pro- and anti-apoptotic properties. The parameters governing these effects begin to be elucidated. Among these figure the nature of the cells, their redox state, the flow and concentration of NO, its possibility to react with superoxide generated at the level of mitochondria. The targets of NO include molecules involved in DNA repair, such as PARP, the DNA-dependent protein kinase (DNA-PK) and p53 which control the transcription of various genes involved in the apoptotic process (bax, cdk inhibitors), and the proteasome which control the degradation of several apoptotic proteins. The inhibition by NO of caspases through S-nitrosylation of their active sites provides a rationale for our understanding of the anti-apoptotic effect of NO, but other mechanisms are involved, such as a regulation of the mitochondrial permeability. A better knowledge of the various steps of the apoptotic process that are affected by NO would allow the design of new pharmacological tools.