Changes In Nitric Oxide Production Research Articles

Increasing tetrahydrobiopterin in cardiomyocytes adversely affects cardiac redox state and mitochondrial function independently of changes in NO production

Tetrahydrobiopterin (BH4) represents a potential strategy for the treatment of cardiac remodeling, fibrosis and/or diastolic dysfunction. The effects of oral treatment with BH4 (Sapropterin™ or Kuvan™) are however dose-limiting with high dose negating functional improvements. Cardiomyocyte-specific overexpression of GTP cyclohydrolase I (mGCH) increases BH4 several-fold in the heart. Using this model, we aimed to establish the cardiomyocyte-specific responses to high levels of BH4. Quantification of BH4 and BH2 in mGCH transgenic hearts showed age-based variations in BH4:BH2 ratios. Hearts of mice (<6 months) have lower BH4:BH2 ratios than hearts of older mice while both GTPCH activity and tissue ascorbate levels were higher in hearts of young than older mice. No evident changes in nitric oxide (NO) production assessed by nitrite and endogenous iron–nitrosyl complexes were detected in any of the age groups. Increased BH4 production in cardiomyocytes resulted in a significant loss of mitochondrial function. Diminished oxygen consumption and reserve capacity was verified in mitochondria isolated from hearts of 12-month old compared to 3-month old mice, even though at 12 months an improved BH4:BH2 ratio is established. Accumulation of 4-hydroxynonenal (4-HNE) and decreased glutathione levels were found in the mGCH hearts and isolated mitochondria. Taken together, our results indicate that the ratio of BH4:BH2 does not predict changes in neither NO levels nor cellular redox state in the heart. The BH4 oxidation essentially limits the capacity of cardiomyocytes to reduce oxidant stress. Cardiomyocyte with chronically high levels of BH4 show a significant decline in redox state and mitochondrial function.

Neuronal and inducible nitric oxide synthase upregulation in the rat medial prefrontal cortex following acute restraint stress: A dataset.

This data article provides additional evidence on gene expression changes in the neuronal and inducible isoforms of nitric oxide synthase in the medial prefrontal cortex following acute stress. Male Wistar rats aged 6–8 weeks were exposed to control or restraint stress conditions for up to four hours in the dark cycle after which the brain was removed and the medial prefrontal cortex isolated by cryodissection. Following RNA extraction and cDNA synthesis, gene expression data were measured using quantitative real-time PCR. The mRNA levels of the neuronal and inducible nitric oxide synthase isoforms, and the inhibitory subunit of NF-κB, I kappa B alpha were determined using the ΔΔCT method relative to control animals. This data article presents complementary results related to the research article entitled ‘Acute restraint stress induces specific changes in nitric oxide production and inflammatory markers in the rat hippocampus and striatum’ [1].

Featured Article: Differential regulation of endothelial nitric oxide synthase phosphorylation by protease-activated receptors in adult human endothelial cells.

Protease-activated receptors have been shown to regulate endothelial nitric oxide synthase through the phosphorylation of specific sites on the enzyme. It has been established that PAR-2 activation phosphorylates eNOS-Ser-1177 and leads to the production of the potent vasodilator nitric oxide, while PAR-1 activation phosphorylates eNOS-Thr-495 and decreases nitric oxide production in human umbilical vein endothelial cells. In this study, we hypothesize a differential coupling of protease-activated receptors to the signaling pathways that regulates endothelial nitric oxide synthase and nitric oxide production in primary adult human coronary artery endothelial cells. Using Western Blot analysis, we showed that thrombin and the PAR-1 activating peptide, TFLLR, lead to the phosphorylation of eNOS-Ser-1177 in human coronary artery endothelial cells, which was blocked by SCH-79797 (SCH), a PAR-1 inhibitor. Using the nitrate/nitrite assay, we also demonstrated that the thrombin- and TFLLR-induced production of nitric oxide was inhibited by SCH and L-NAME, a NOS inhibitor. In addition, we observed that TFLLR, unlike thrombin, significantly phosphorylated eNOS-Thr-495, which may explain the observed delay in nitric oxide production in comparison to that of thrombin. Activation of PAR-2 by SLIGRL, a PAR-2 specific ligand, leads to dual phosphorylation of both catalytic sites but primarily regulated eNOS-Thr-495 phosphorylation with no change in nitric oxide production in human coronary artery endothelial cells. PAR-3, known as the non-signaling receptor, was activated by TFRGAP, a PAR-3 mimicking peptide, and significantly induced the phosphorylation of eNOS-Thr-495 with minimal phosphorylation of eNOS-Ser-1177 with no change in nitric oxide production. In addition, we confirmed that PAR-mediated eNOS-Ser-1177 phosphorylation was Ca(2+)-dependent using the Ca(2+) chelator, BAPTA, while eNOS-Thr-495 phosphorylation was mediated via Rho kinase using the ROCK inhibitor, Y-27632, suggesting protease-activated receptor coupling to Gq and G12/13, respectively. These data suggest a vascular bed specific differential coupling of protease-activated receptors to the signaling pathways that regulate endothelial nitric oxide synthase and nitric oxide production that may be responsible for endothelial dysfunction associated with cardiovascular disease.

Laser-Based Methods for Detection of Nitric Oxide in Plants.

Nitric oxide (NO) plays an important role in plant signaling and in response to various stress conditions. Therefore, real-time measurements of NO production provide better insights into understanding plant processes and can help developing strategies to improve food production and postharvest quality. Using laser-based spectroscopic methods, sensitive, online, in planta measurements of plant-pathogen interactions are possible. This chapter introduces the basic principle of the optical detectors using different laser sources for accurate monitoring of fast dynamic changes of NO production. Several applications are also presented to demonstrate the suitability of these detectors for detection of NO in plants.

(-)-Epicatechin Prevents Blood Pressure Increase and Reduces Locomotor Hyperactivity in Young Spontaneously Hypertensive Rats.

This study investigated the effects of subchronic (−)-epicatechin (Epi) treatment on locomotor activity and hypertension development in young spontaneously hypertensive rats (SHR). Epi was administered in drinking water (100 mg/kg/day) for 2 weeks. Epi significantly prevented the development of hypertension (138 ± 2 versus 169 ± 5 mmHg, p < 0.001) and reduced total distance traveled in the open-field test (22 ± 2 versus 35 ± 4 m, p < 0.01). In blood, Epi significantly enhanced erythrocyte deformability, increased total antioxidant capacity, and decreased nitrotyrosine concentration. In the aorta, Epi significantly increased nitric oxide (NO) synthase (NOS) activity and elevated the NO-dependent vasorelaxation. In the left heart ventricle, Epi increased NOS activity without altering gene expressions of nNOS, iNOS, and eNOS. Moreover, Epi reduced superoxide production in the left heart ventricle and the aorta. In the brain, Epi increased nNOS gene expression (in the brainstem and cerebellum) and eNOS expression (in the cerebellum) but had no effect on overall NOS activity. In conclusion, Epi prevented the development of hypertension and reduced locomotor hyperactivity in young SHR. These effects resulted from improved cardiovascular NO bioavailability concurrently with increased erythrocyte deformability, without changes in NO production in the brain.

Acute restraint stress induces specific changes in nitric oxide production and inflammatory markers in the rat hippocampus and striatum

Chronic mild stress has been shown to cause hippocampal neuronal nitric oxide synthase (NOS) overexpression and the resultant nitric oxide (NO) production has been implicated in the etiology of depression. However, the extent of nitrosative changes including NOS enzymatic activity and the overall output of NO production in regions of the brain like the hippocampus and striatum following acute stress has not been characterized. In this study, outbred male Wistar rats aged 6–7 weeks were randomly allocated into 0 (control), 60, 120, or 240min stress groups and neural regions were cryodissected for measurement of constitutive and inducible NOS enzymatic activity, nitrosative status, and relative gene expression of neuronal and inducible NOS. Hippocampal constitutive NOS activity increased initially but was superseded by the inducible isoform as stress duration was prolonged. Interestingly, hippocampal neuronal NOS and interleukin-1β mRNA expression was downregulated, while the inducible NOS isoform was upregulated in conjunction with other inflammatory markers. This pro-inflammatory phenotype within the hippocampus was further confirmed with an increase in the glucocorticoid-antagonizing macrophage migration inhibitory factor, Mif, and the glial surveillance marker, Ciita. This indicates that despite high levels of glucocorticoids, acute stress sensitizes a neuroinflammatory response within the hippocampus involving both pro-inflammatory cytokines and inducible NOS while concurrently modulating the immunophenotype of glia. Furthermore, there was a delayed increase in striatal inducible NOS expression while no change was found in other pro-inflammatory mediators. This suggests that short term stress induces a generalized increase in inducible NOS signaling that coincides with regionally specific increased markers of adaptive immunity and inflammation within the brain.

C57BL/6N Mice Are More Resistant to Ehrlich Ascites Tumors Than C57BL/6J Mice: The Role of Macrophage Nitric Oxide.

BackgroundEffectiveness of the immune defense formed by the genotype often determines the predisposition to cancer. Nitric oxide (NO) produced by macrophages is an important element in this defense.Material/MethodsWe hypothesized that genetic characteristics of NO generation systems can predetermine the vulnerability to tumor development. The study was conducted on mice of 2 genetic substrains – C57BL/6J and C57BL/6N – with Ehrlich ascites carcinoma (EAC). NO production in the tumor was changed using ITU, an iNOS inhibitor; c-PTIO, a NO scavenger; and SNP, a NO donor. Macrophage NO production was estimated by nitrite concentration in the culture medium. iNOS content was measured by Western blot analysis. Macrophage phenotype was determined by changes in NO production, iNOS level, and CD markers of the phenotype.ResultsThe lifespan of C57BL/6N mice (n=10) with EAC was 25% longer (p<0.01) than in C57BL/6J mice (n=10). Decreased NO production 23% reduced the survival duration of C57BL/6N mice (p<0.05), which were more resistant to tumors. Elevated NO production 26% increased the survival duration of C57BL/6J mice (p<0.05), which were more susceptible to EAC. Both the NO production and the iNOS level were 1.5 times higher in C57BL/6N than in C57BL/6J mice (p<0.01). CD markers confirmed that C57BL/6N macrophages had the M1 and C57BL/6J macrophages had the M2 phenotype.ConclusionsThe vulnerability to the tumor development can be predetermined by genetic characteristics of the NO generation system in macrophages. The important role of NO in anti-EAC immunity should be taken into account in elaboration of new antitumor therapies.

Role of oxidative stress, inflammation, nitric oxide and transforming growth factor-beta in the protective effect of diosgenin in monocrotaline-induced pulmonary hypertension in rats

Pulmonary hypertension is a progressive disease of various origins that is associated with right ventricular dysfunction. In the present study, the protective effect of diosgenin was investigated in monocrotaline-induced pulmonary hypertension in rats. Pulmonary hypertension was induced by a single subcutaneous injection of monocrotaline (60mg/kg). Diosgenin (100mg/kg) was given by oral administration once daily for 3 weeks. At the end of the experiment, mean arterial blood pressure, electrocardiography and echocardiography were recorded. Rats were then sacrificed and serum was separated for determination of total nitrate/nitrite level. Right ventricles and lungs were isolated for estimation of oxidative stress markers, tumor necrosis factor-alpha, total nitrate/nitrite and transforming growth factor-beta contents. Myeloperoxidase and caspase-3 activities in addition to endothelial and inducible nitric oxide synthase protein expression were also determined. Moreover, histological analysis of pulmonary arteries and cardiomyocyte cross-sectional area was performed. Diosgenin treatment provided a significant improvement toward preserving hemodynamic changes and alleviating oxidative stress, inflammatory and apoptotic markers induced by monocrotaline in rats. Furthermore, diosgenin therapy prevented monocrotaline-induced changes in nitric oxide production, endothelial and inducible nitric oxide synthase protein expression as well as histological analysis. These findings support the beneficial effect of diosgenin in pulmonary hypertension induced by monocrotaline in rats.

Immediate effects of spinal manipulation on nitric oxide, substance P and pain perception

Previous studies have analyzed the effects of spinal manipulation on pain sensitivity by using several sensory modalities, but to our knowledge, no studies have focused on serum biomarkers involved in the nociceptive pathway after spinal manipulation. Our objectives were to determine the immediate effect of cervical and dorsal manipulation over the production of nitric oxide and substance P, and establishing their relationship with changes in pressure pain thresholds in asymptomatic subjects. In this single-blind randomized controlled trial, 30 asymptomatic subjects (16 men) were randomly distributed into 3 groups (n = 10 per group): control, cervical and dorsal manipulation groups. Blood samples were extracted to obtain serum. ELISA assay for substance P and chemiluminescence analysis for nitric oxide determination were performed. Pressure pain thresholds were measured with a pressure algometer at the C5–C6 joint, the lateral epicondyle and the tibialis anterior muscle. Outcome measures were obtained before intervention, just after intervention and 2 h after intervention. Our results indicated an increase in substance P plasma level in the cervical manipulation group (70.55%) when compared with other groups (p < 0.05). This group also showed an elevation in the pressure pain threshold at C5–C6 (26.75%) and lateral epicondyle level (21.63%) immediately after the intervention (p < 0.05). No changes in nitric oxide production were observed. In conclusion, mechanical stimulus provided by cervical manipulation increases substance P levels and pressure pain threshold but does not change nitric oxide concentrations. Part of the hypoalgesic effect of spinal manipulation may be due to the action of substance P.

An integrated microfluidic device for monitoring changes in nitric oxide production in single T-lymphocyte (Jurkat) cells.

A considerable amount of attention has been focused on the analysis of single cells in an effort to better understand cell heterogeneity in cancer and neurodegenerative diseases. Although microfluidic devices have several advantages for single cell analysis, few papers have actually demonstrated the ability of these devices to monitor chemical changes in perturbed biological systems. In this paper, a new microfluidic channel manifold is described that integrates cell transport, lysis, injection, electrophoretic separation, and fluorescence detection into a single device, making it possible to analyze individual cells at a rate of 10 cells/min in an automated fashion. The system was employed to measure nitric oxide (NO) production in single T-lymphocytes (Jurkat cells) using a fluorescent marker, 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM DA). The cells were also labeled with 6-carboxyfluorescein diacetate (6-CFDA) as an internal standard. The NO production by control cells was compared to that of cells stimulated using lipopolysaccharide (LPS), which is known to cause the expression of inducible nitric oxide synthase (iNOS) in immune-type cells. Statistical analysis of the resulting electropherograms from a population of cells indicated a 2-fold increase in NO production in the induced cells. These results compare nicely to a recently published bulk cell analysis of NO.

Peroxisome Proliferator-activated Receptor γ, Coactivator 1α Deletion Induces Angiotensin II–Associated Vascular Dysfunction by Increasing Mitochondrial Oxidative Stress and Vascular Inflammation

Peroxisome proliferator-activated receptor γ, coactivator 1α (PGC-1α) is an important mediator of mitochondrial biogenesis and function. Because dysfunctional mitochondria might be involved in the pathogenesis of vascular disease, the current study was designed to investigate the effects of in vivo PGC-1α deficiency during chronic angiotensin II (ATII) treatment. Although ATII infusion at subpressor doses (0.1 mg/kg per day for 7 days) did not cause vascular dysfunction in wild-type mice, it led to impaired endothelial-dependent and endothelial-independent relaxation in PGC-1α knockout mice. In parallel, oxidative stress was increased in aortic rings from ATII-treated PGC-1α knockout mice, whereas no change in nitric oxide production was observed. By using the mitochondrial-specific superoxide dye MitoSox and complex I inhibitor rotenone, we identified the mitochondrial respiratory chain as the major PGC-1α-dependent reactive oxygen species source in vivo, accompanied by increased vascular inflammation and cell senescence. In vivo treatment with the mitochondria-targeted antioxidant Mito-TEMPO partially corrected endothelial dysfunction and prevented vascular inflammation in ATII-treated PGC-1α mice, suggesting a causative role of mitochondrial reactive oxygen species in this setting. PGC-1α deletion induces vascular dysfunction and inflammation during chronic ATII infusion by increasing mitochondrial reactive oxygen species production.

In Silico Modeling of Shear-Stress-Induced Nitric Oxide Production in Endothelial Cells through Systems Biology

Nitric oxide (NO) produced by vascular endothelial cells is a potent vasodilator and an antiinflammatory mediator. Regulating production of endothelial-derived NO is a complex undertaking, involving multiple signaling and genetic pathways that are activated by diverse humoral and biomechanical stimuli. To gain a thorough understanding of the rich diversity of responses observed experimentally, it is necessary to account for an ensemble of these pathways acting simultaneously. In this article, we have assembled four quantitative molecular pathways previously proposed for shear-stress-induced NO production. In these pathways, endothelial NO synthase is activated 1), via calcium release, 2), via phosphorylation reactions, and 3), via enhanced protein expression. To these activation pathways, we have added a fourth, a pathway describing actual NO production from endothelial NO synthase and its various protein partners. These pathways were combined and simulated using CytoSolve, a computational environment for combining independent pathway calculations. The integrated model is able to describe the experimentally observed change in NO production with time after the application of fluid shear stress. This model can also be used to predict the specific effects on the system after interventional pharmacological or genetic changes. Importantly, this model reflects the up-to-date understanding of the NO system, providing a platform upon which information can be aggregated in an additive way.

Phosphorylation of argininosuccinate synthase at T131 correlates with changes in NO production

The citrulline‐nitric oxide cycle is a tightly regulated system for the production of nitric oxide (NO) in vascular endothelial cells. Argininosuccinate synthase (AS) acts as the rate‐limiting step in the cycle which converts citrulline back to arginine, providing the essential substrate for endothelial nitric oxide synthase. Previous work has demonstrated that AS is a phospho‐protein, a post‐translational modification that allows AS to support acute changes in NO production. Bioinformatic analysis identified a putative AS phosphorylation site at threonine 131, which was confirmed by LC‐MS analysis showing that phosphorylation at T131 increased upon treatment of endothelial cells with the serine/threonine phosphatase inhibitor okadaic acid. To investigate the role of phosphorylation of AS at T131, analysis was carried out comparing the overexpression of phospho‐null (T to A) and phospho‐mimetic (T to D) mutations to wild type AS. After knockdown of endogenous AS by siRNA, rescue of AS function was measured by the recovery of NO production in endothelial cells under conditions of limited arginine. Expression of the phospho‐null mutation showed similar levels of NO production to wild type AS. However, expression of the T131 phospho‐mimetic AS construct demonstrated reduced NO upon stimulation with VEGF confirming the physiological significance of T131 phosphorylation. (NIH RO1 HL083153‐01A2).

Hypothyroidism: age-related influence on cardiovascular nitric oxide system in rats

This study investigates whether changes in nitric oxide (NO) production participate in the cardiovascular manifestations of hypothyroidism and whether these changes are age-related. Sprague–Dawley rats aged 2 and 18 months old were treated with 0.02% methimazole (wt/vol) during 28 days. Left ventricular function was evaluated by echocardiography. Measurements of arterial blood pressure, heart rate, nitric oxide synthase (NOS) activity and NOS/caveolin-1 and -3 protein levels were performed. Hypothyroidism enhanced the age-related changes in heart function. Hypothyroid state decreased atrial NOS activity in both young and adult rats, associated with a reduction in protein levels of the three NOS isoforms in young animals and increased caveolin (cav) 1 expression in adult rats. Ventricle and aorta NOS activity increased in young and adult hypothyroid animals. In ventricle, changes in NOS activity were accompanied by an increase in inducible NOS isoform in young rats and by an increase in caveolins expression in adult rats. Greater aorta NOS activity level in young and in adult Hypo rats would derive from the inducible and the endothelial NOS isoform, respectively. Thyroid hormones would be one of the factors involved in the modulation of cardiovascular NO production and caveolin-1 and -3 tissue-specific abundance, regardless of age. Hypothyroidism appears to contribute in a differential way to aging-induced changes in the myocardium and aorta tissues. Low thyroid hormones levels would enhance the aging effect on the heart. Age-related changes in NO production participate in the cardiovascular manifestations of hypothyroidism.

Antioxidant and Anti-Apoptotic Activity of Vasoactive Intestinal Peptide (VIP) Against 6-Hydroxy Dopamine Toxicity in the Rat Corpus Striatum

6-Hydroxydopamine (6-OHDA) is an oxidative stress neurotoxin, which is oxidized in neurons, causes respiratory inhibition, and induces free radical formation and oxidative stress. Therefore, a 6-OHDA-induced Parkinson's disease (PD) experimental model can be used to test a candidate molecule for use as an antioxidant that could be a promising therapeutic for treating Parkinson's disease. Recent studies have shown that vasoactive intestinal peptide (VIP) might be a good candidate agent for the treatment of PD. In this study, the anti-apoptotic and antioxidant actions of VIP were investigated using the 6-OHDA-lesioned rat model for PD. Twenty-four young adult Sprague-Dawley rats were used. The rats were separated into the following groups: group I (n = 8), sham operated; group II (n = 8), 6-OHDA lesioned; group III (n = 8), 6-OHDA lesioned + i.p. VIP-injected (25 ng/kg) every 2 days for 15 days. The first i.p. injection of VIP was made 1 h after the intrastriatal 6-OHDA microinjection. Antioxidant enzymatic activity [super oxide dismutase (SOD) and catalase (CAT)], lipid peroxidation, nitric oxide and DNA fragmentation were measured from homogenates isolated from the corpus striatum. SOD, CAT, malondialdehyde, and DNA fragmentation were measured using a spectrophotometer, and nitric oxide (NO) levels were measured by capillary electrophoresis. 6-OHDA significantly induced oxidative stress, lipid peroxidation, and DNA fragmentation in the corpus striatum of rats. VIP significantly protected neuronal tissue from oxidative stress and apoptosis by reducing lipid peroxidation and DNA fragmentation. 6-OHDA toxicity did not cause significant changes in NO production in the corpus striatum. However, VIP treatment significantly reduced NO levels in brain tissue.

The changes of nitric oxide production during the growth of Microcystis aerugrinosa

This study characterized the changes of nitric oxide (NO) production during the growth of Microcystis aerugrinosa, a cyanobacterium which usually cause cyanobacterial blooms. Results showed a drastic NO release accompanying with cell density and Chl-a content sharp rises when M. aerugrinosa grew from fifth day to sixth day. Moreover, high N:P ratio accelerated the cyanobacterial growth and NO burst. Sodium nitroprusside, an exogenous NO donor, promoted M. aerugrinosa growth with the optimal concentration of 0.1 mg/L. Experiments by supplementing with sodium nitrite and l-arginine demonstrated NO production in M. aerugrinosa cells was mainly through nitrate reductase (NR) pathway while minorly through NO synthase pathway. All these data suggested M. aerugrinosa produced increasing NO during its growth mainly by NR pathway, during which NO positively regulated the growth of M. aerugrinosa.

Effects of aqueous saffron extract on nitric oxide production by two human carcinoma cell lines: Hepatocellular carcinoma (HepG2) and laryngeal carcinoma (Hep2)

Objective: A number of studies have demonstrated the potentia l antitumor effects of saffron and its constituents on different malignant cells in vitro. It has been reported that a novel glycoconjugate isolated from corms and callus of saffron possesses cytotoxic activity against different tumor cellswith nitric oxide (NO) production. These data suggest that the cytotoxic effect of saffron extract may be related to an effect on nitric oxide production. The aim of the study was to investigate the effect of whole saffron extract on NO production by the hepatocellular carcinoma cell line (HepG-2) and laryngeal carcinoma cell lin e (Hep-2). Materials and Methods: The cell lines were treated with a saffron extract . The morphologic changes were observed and recorded after 24, 48 and 72 of incubation. The MTT test was used to assess cell viability and the quantitative changes in NO production was evaluated using Griess test in the aforementioned time intervals. Results: The morphologic images showed qualitative changes in both cell lines. The MTT assay results indicated that there was an increase in cyt otoxic effect by adding the extract at concentrations of 0, 200, 400 and 800 µg/ml. However, the NO concentration decreased significantly after 6, 12, 18, 24, 48 and 72 hours of incubation, respectively. IC 50 of 400 µg/ml was obtained for HepG2 cells; however, Hep2 and L929 cells did not respond to any extract concentrations. Conclusion: This study suggested that the saffron extract had a cyto toxic effect on HepG-2 and Hep-2 cell lines. The cytotoxic effect was probably related to a decrease in the NO concentration.

3D network model of NO transport in tissue

We developed a mathematical model to simulate shear stress-dependent nitric oxide (NO) production and transport in a 3D microcirculatory network based on published data. The model consists of a 100 μm × 500 μm × 75 μm rectangular volume of tissue containing two arteriole-branching trees, and nine capillaries surrounding the vessels. Computed distributions for NO in blood, vascular walls, and surrounding tissue were affected by hematocrit (Hct) and wall shear stress (WSS) in the network. The model demonstrates that variations in the red blood cell (RBC) distribution and WSS in a branching network can have differential effects on computed NO concentrations due to NO consumption by RBCs and WSS-dependent changes in NO production. The model predicts heterogeneous distributions of WSS in the network. Vessel branches with unequal blood flow rates gave rise to a range of WSS values and therefore NO production rates. Despite increased NO production in a branch with higher blood flow and WSS, vascular wall NO was predicted to be lower due to greater NO consumption in blood, since the microvascular Hct increased with redistribution of RBCs at the vessel bifurcation. Within other regions, low WSS was combined with decreased NO consumption to enhance the NO concentration.

Molecular Mechanisms in Exercise-Induced Cardioprotection

Physical inactivity is increasingly recognized as modifiable behavioral risk factor for cardiovascular diseases. A partial list of proposed mechanisms for exercise-induced cardioprotection include induction of heat shock proteins, increase in cardiac antioxidant capacity, expression of endoplasmic reticulum stress proteins, anatomical and physiological changes in the coronary arteries, changes in nitric oxide production, adaptational changes in cardiac mitochondria, increased autophagy, and improved function of sarcolemmal and/or mitochondrial ATP-sensitive potassium channels. It is currently unclear which of these protective mechanisms are essential for exercise-induced cardioprotection. However, most investigations focus on sarcolemmal KATP channels, NO production, and mitochondrial changes although it is very likely that other mechanisms may also exist. This paper discusses current information about these aforementioned topics and does not consider potentially important adaptations within blood or the autonomic nervous system. A better understanding of the molecular basis of exercise-induced cardioprotection will help to develop better therapeutic strategies.

Using blood pressure telemetry to assess acute changes in arterial stiffness in rats after nitric oxide synthase inhibition or environmental tobacco smoke exposure

Although environmental tobacco smoke (ETS) exposure has been reported to acutely increase arterial stiffness in humans, understanding of the underlying mechanisms is unclear and few studies have measured these effects in experimental animals. One potential mechanism for the increased arterial stiffness is reduced nitric oxide (NO) bioactivity as a result of oxidative stress. Thus, the objective of this study was to determine whether acute changes in arterial stiffness could be detected using arterial pulse wave dP/dt in blood pressure telemetry implanted rats and to investigate the role of NO in regulating dP/dt. Intravenous injection of acetylcholine (0.91 ng/kg) decreased and norepinephrine (0.02 mg/kg) increased dP/dt compared to saline vehicle (0.5 mL/kg). Injection of the NO synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME; 30 mg/kg) decreased plasma nitrate/nitrite (NOx), but transiently increased dP/dt. ETS at low and high doses had no effect on dP/dt, but increased plasma NOx levels at high ETS exposure and increased plasma nitrotyrosine levels in both ETS groups. In conclusion, acute changes in NO production via acetylcholine or L-NAME alter the arterial pulse wave dP/dt consistently with the predicted changes in arterial stiffness. Although acute ETS appears to biologically inactivate NO, a concomitant increase in NO production at high ETS exposure may explain why dP/dt was not acutely altered by ETS in the current study.