Inducible NO Synthesis in the Vasculature

Impact of Zinc on Oxidative Signaling Pathways in the Development of Pulmonary Vasoconstriction Induced by Hypobaric Hypoxia

Hypobaric hypoxia is a condition that occurs at high altitudes (>2500 m) where the partial pressure of gases, particularly oxygen (PO2), decreases. This condition triggers several physiological and molecular responses. One of the principal responses is pulmonary vascular contraction, which seeks to optimize gas exchange under this condition, known as hypoxic pulmonary vasoconstriction (HPV); however, when this physiological response is exacerbated, it contributes to the development of high-altitude pulmonary hypertension (HAPH). Increased levels of zinc (Zn2+) and oxidative stress (known as the “ROS hypothesis”) have been demonstrated in the vasoconstriction process. Therefore, the aim of this review is to determine the relationship between molecular pathways associated with altered Zn2+ levels and oxidative stress in HPV in hypobaric hypoxic conditions. The results indicate an increased level of Zn2+, which is related to increasing mitochondrial ROS (mtROS), alterations in nitric oxide (NO), metallothionein (MT), zinc-regulated, iron-regulated transporter-like protein (ZIP), and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-induced protein kinase C epsilon (PKCε) activation in the development of HPV. In conclusion, there is an association between elevated Zn2+ levels and oxidative stress in HPV under different models of hypoxia, which contribute to understanding the molecular mechanism involved in HPV to prevent the development of HAPH.

Reactive Oxygen Species and Pulmonary Vasculature During Hypobaric Hypoxia

An increasing number of people are living or working at high altitudes (hypobaric hypoxia) and therefore suffering several physiological, biochemical, and molecular changes. Pulmonary vasculature is one of the main and first responses to hypoxia. These responses imply hypoxic pulmonary vasoconstriction (HPV), remodeling, and eventually pulmonary hypertension (PH). These events occur according to the type and extension of the exposure. There is also increasing evidence that these changes in the pulmonary vascular bed could be mainly attributed to a homeostatic imbalance as a result of increased levels of reactive oxygen species (ROS). The increase in ROS production during hypobaric hypoxia has been attributed to an enhanced activity and expression of nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase), though there is some dispute about which subunit is involved. This enzymatic complex may be directly induced by hypoxia-inducible factor-1α (HIF-1α). ROS has been found to be related to several pathways, cells, enzymes, and molecules in hypoxic pulmonary vasculature responses, from HPV to inflammation, and structural changes, such as remodeling and, ultimately, PH. Therefore, we performed a comprehensive review of the current evidence on the role of ROS in the development of pulmonary vasculature changes under hypoxic conditions, with a focus on hypobaric hypoxia. This review provides information supporting the role of oxidative stress (mainly ROS) in the pulmonary vasculature’s responses under hypobaric hypoxia and depicting possible future therapeutics or research targets. NADPH oxidase-produced oxidative stress is highlighted as a major source of ROS. Moreover, new molecules, such as asymmetric dimethylarginine, and critical inflammatory cells as fibroblasts, could be also involved. Several controversies remain regarding the role of ROS and the mechanisms involved in hypoxic responses that need to be elucidated.

Comparison between Flurbiprofen and its Nitric Oxide-Releasing Derivatives HCT-1026 and NCX-2216 on Aβ(1-42)-Induced Brain Inflammation and Neuronal Damage in the Rat

Brain inflammation is an underlying factor in the pathogenesis of Alzheimer's disease (AD) and epidemiological studies indicate that a sustained use of non-steroidal anti-inflammatory drugs (NSAIDs) has a protective effect on the disease. We investigated, in vivo, whether differences exist in the antiinflammatory and neuroprotective actions of flurbiprofen and its two nitric oxide-donor derivatives, HCT-1026 and NCX-2216, and the ability of these two derivatives to release nitric oxide in the brain. In adult rats injected into the nucleus basalis with preaggregated Aβ(1-42) we investigated by immunohistochemical methods glia reaction, the induction of inducible nitric oxide synthase (iNOS), the activation of p38 mitogen-activated protein kinase (p38MAPK) pathway and the number of choline acetyltransferase (ChAT)-positive neurons and, in naïve rats we investigated, by microdialysis, cortical extracellular levels of nitrite. Injection of Aβ(1-42) induced iNOS at the injection site, activated p38MAPK 7 days after injection and brought about an intense microglia and astrocyte reaction along with a marked reduction in the number of ChAT-positive neurones, persisting up to at least up to 21 days. Flurbiprofen, HCT-1026 and NCX-2216 (15 mg/kg) significantly attenuated the Aβ(1-42)-induced glia reaction, iNOS induction and p38MAPK activation 7 days after treatment and astrocytes reaction 21 days after treatment. On an equimolar basis, HCT-1026 resulted the most active agent in reducing the Aβ(1-42)-induced microglia reaction. The cholinergic cell loss was also significantly reduced by 21 days of HCT-1026 treatment. No differences in the body weight were found between the animals treated for 21 days with 15 mg/kg of either HCT-1026 or NCX-2216 and the controls. An oral administration of HCT-1026 (15 mg/kg) or NCX-2216 (100 mg/kg) to naiïve rats was followed by significant and long long -lasting increases in cortical nitrite levels. These findings indicate that the addition of a nitric oxide donor potentiates the anti-inflammatory activity of flurbiprofen in a model of brain inflammation.

[Cardiovascular manifestations in rheumatoid arthritis]

Rheumatoid arthritis (RA) is a chronic inflammatory disease, characterized by a polyarticular joint inflammation which eventually leads to joint destruction and general disability. Besides these polyarticular manifestations, several systemic immune phenomena have been described. An increased mortality in RA patients is evident and is mainly caused by an increased cardiovascular risk. The correlation between disease activity and mortality highlighted the important role of the systemic inflammatory reaction in induction and progression of vascular damaging processes. Endothelial dysfunction and vascular inflammation are important, mechanisms in atherosclerosis and induced by conventional risk factors and systemic inflammation. It has been shown that the deleterious influence of conventional risk factors is aggravated by inflammatory mediators, mainly by pro-inflammatory cytokines. In addition, certain inflammatory mediators exert damaging effects to blood vessels. Especially CRP, merely considered as a risk indicating parameter in the past, has attracted remarkable attention. Also certain RA specific immune phenomena are of considerable proatherosclerotic potential. At least in part, they could be responsible for the excess mortality in RA patients. The newer TNFalpha blocking agents interfere with different mechanisms responsible for induction and perpetuation of atherosclerotic processes. Time will show whether they make a remarkable impact on the cardiovascular mortality in RA patients.

Nitric Oxide Synthase Gene Transfer as a Tool to Study Biology of Endothelial Cells

During the past decade, the development of gene transfer technology provided a powerful and facile tool that afforded the genetic modification of vascular endothelial function. This development has coincided with molecular cloning and extensive accumulation of knowledge concerning the role of nitric oxide synthase isoforms in vascular homeostasis. Experimental evidence continues to accumulate that in vivo adenovirus-mediated gene transfer into the vessel wall is a very useful technique in studies designed to characterize function of a given gene or protein. In this review, we will use nitric oxide synthase gene transfer as a paradigm to illustrate how gene transfer technology can be used to address key issues in the vascular biology of endothelium.

Aldosteronism: an immunostimulatory state precedes proinflammatory/fibrogenic cardiac phenotype

Chronic inappropriate (relative to dietary Na+ intake) elevations in circulating aldosterone (ALDO), termed aldosteronism, are associated with remodeling of intramural arteries of the right and left heart. Lesions appear at week 4 of treatment with ALDO and 1% dietary NaCl in uninephrectomized rats (ALDOST) and include invading monocytes, macrophages and lymphocytes with intracellular evidence of oxidative and nitrosative stress, myofibroblasts, and perivascular fibrosis. In this study, we tested the hypothesis that an immunostimulatory state with activated circulating peripheral blood mononuclear cells (PBMCs) precedes this proinflammatory and profibrogenic cardiac phenotype and is initiated by reduction in the cytosolic free Mg2+ concentration ([Mg2+]i). At 1 and 4 wk of ALDOST (preclinical and clinical stages, respectively), we monitored serum Mg2+, PBMC [Mg2+]i and cytosolic free [Ca2+] (via fluorimetry), and expressed genes (via microchip array) as well as markers of oxidative and nitrosative stress in plasma [alpha1-antiproteinase activity (alpha1-AP)] and cardiac tissue (immunohistochemical detection of gp91phox subunit of NADPH oxidase and 3-nitrotyrosine). Age- and gender-matched unoperated and untreated (UO) rats and uninephrectomized salt-treated (UN) rats served as controls. Serum [Mg2+] was unchanged by ALDOST. In contrast with UO and UN, [Mg2+]i and plasma alpha1-AP were each reduced (P < 0.05) at weeks 1 and 4. The decline in PBMC [Mg2+]i was accompanied by Ca2+ loading. Differential (twofold and higher) expression (up- and downregulation) in PBMC transcriptomes was present at week 1 and progressed at week 4. Involved were genes for the alpha1-isoform of Na+-K+-ATPase, the ATP-dependent Ca2+ pump, antioxidant reserves, inducible nitric oxide synthase, and PBMC activation with autoimmune responses. Expression of 3-nitrotyrosine and activation of gp91phox were seen in inflammatory cells that invaded intramural arteries. Thus early in aldosteronism (preclinical stage), an immunostimulatory state featuring activated circulating PBMCs with reduced ionized [Mg2+]i and oxidative and nitrosative stress precedes and may even predispose to coronary vascular lesions that first appear at week 4.

Inhibitory effect of recombinant iNOS gene expression on vasomotor function of canine basilar artery

The present study was designed to determine the effect of recombinant inducible nitric oxide (NO) synthase (iNOS) gene expression on vasomotor function in cerebral arteries. Isolated canine basilar arteries were exposed ex vivo (30 min at 37 degrees C) to an adenoviral vector [10(7), 10(8), or 10(9) plaque-forming units (pfu)/ml] encoding either the iNOS gene or the beta-galactosidase reporter gene. Twenty-four hours after transduction, Western blot analysis demonstrated expression of iNOS protein only in iNOS (10(9) pfu/ml)-transduced arteries. Immunohistochemical analysis localized iNOS expression predominantly in adventitia. Vascular reactivity of isolated basilar arteries was studied by isometric force recording. Concentration-response curves to UTP (10(-9)-10(-3) M) and diethylaminodiazen-1-ium-1,2-dioate (10(-10)-10(-5) M) were significantly shifted to the right in iNOS gene (10(9) pfu/ml)-transduced rings compared with control and beta-galactosidase-transduced rings (P < 0.05, n = 5-6). Endothelium-dependent relaxation to bradykinin was significantly attenuated in iNOS-transduced rings (P < 0.001, n = 8). The basal level of cGMP and superoxide anion (O(2)(-).) production were elevated in iNOS-transduced rings (P < 0.05, n = 7 for cGMP; P < 0.01, n = 6-9 for O(2)(-). production). Our results suggest that expression of recombinant iNOS in cerebral arteries reduces vasomotor reactivity to both vasoconstrictor and vasodilator agonists. Attenuation of contractions is most likely due to functional antagonism between UTP and cGMP. Reduction of endothelium-dependent relaxation to bradykinin appears to be mediated in part by reduced reactivity of smooth muscle cells to NO.