Effect of aspirin on constitutive nitric oxide synthase and the biovailability of NO

Effect of aspirin on blood pressure in hypertensive patients: a systematic review and meta-analysis

INTRODUCTION

Aspirin is widely used for secondary prevention in patients with hypertension. However, previous studies mainly focused on the preventive effects of aspirin, and there has been a lack of reliable evidence on whether taking aspirin affects blood pressure This study aimed to investigate whether aspirin would affect the blood pressure in patients with hypertension.

METHODS

PubMed, Cochrane database, Embase, Scopus and Medline databases were searched until September 2023. For continuous variables (e.g., blood pressure reduction), the mean difference (MD) was selected as the effect magnitude indices. We used the Cochrane Collaboration's Risk of Bias tool to assess the risk of bias.

RESULT

A total of five studies were included, comprising 20,312 patients. We found that aspirin did not affect SBP (MD = -0.78, 95% CI: - 2.41, 0.84). A similar result was found for DBP (MD = -0.86, 95% CI: - 2.14, 0.42).

CONCLUSION

This study showed no significant difference in blood pressure between the aspirin and control groups, suggesting that aspirin does not affect blood pressure.

Changes in the Plasma and Platelet Nitric Oxide Biotransformation Metabolites during Ischemic Stroke-A Dynamic Human LC/MS Metabolomic Study

Despite improvement in the management of modifiable cardiovascular risk factors, ischemic stroke remains the leading cause of morbidity and mortality in the adult population. The aim of this study was to analyze the time-dependent dynamic differences in expression of the nitric oxide (NO) metabolic pathway in the platelet and plasma compartment between subjects with and without ischemic stroke. Additionally, the interplay between these parameters and platelet aggregation was investigated. A total of 418 patients in acute phase of non-cardioembolic stroke were investigated. Following the inclusion and exclusion criteria, finally 40 subjects with stroke and 39 demographically matched healthy participants were enrolled. Neurological physical examination, followed by assessment of the platelet and plasma levels of the nitric oxide synthase (NOS) inhibitors, including asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA), as well as NOS substrate-L-Arginine were performed dynamically three times within the first 24-h, then on the 3rd and 7th day after the stroke onset, which was compared with the healthy control. The platelet L-Arginine concentration was significantly higher on the 1st and 3rd day of stroke, while the plasma levels were significantly lower on exact days in comparison to the control. The competitive NOS-inhibitors in platelets were stably elevated in stroke subjects, whereas no significant differences in plasma compartment were noted. The arachidonic-acid-induced platelet aggregation was negatively associated with the platelet NOS substrate bioavailability, as assessed by the L−Arginine ADMA-ratio on the 3rd and 7th day. Subjects with non-cardioembolic ischemic stroke are characterized by elevated platelet levels of NOS inhibitors. Management of stroke results in increasing the platelet L-Arginine concentration and subsequent NO bioavailability in the platelet compartment.

Antioxidant and Anti-Inflammatory Effects of Bischofia javanica (Blume) Leaf Methanol Extracts through the Regulation of Nrf2 and TAK1

Bischofia javanica (Blume) has been traditionally used to treat inflammatory diseases such as tonsillitis and ulcers throughout Asia, including China, Indonesia, and the Philippines: however, the molecular mechanisms by which B. javanica exerts its antioxidant and anti-inflammatory properties remain largely unknown. In this study, we analyzed the antioxidant and anti-inflammatory mechanisms of methanol extracts of B. javanica leaves (MBJ) in vitro and in vivo. MBJ decreased nitric oxide (NO) production and the expression of pro-inflammatory cytokines, including interleukin (IL)-1β, IL-6, and tumor necrosis factor-α, in lipopolysaccharide (LPS)-treated RAW 264.7 cells. The observed suppression of inflammatory responses by MBJ was correlated with an inhibition of the nuclear factor-κB (NF-κB) and the mitogen-activated protein kinase (MAPK) pathways. Additionally, MBJ induced nuclear translocation of the nuclear factor erythroid 2-related factor 2 (Nrf2), a transcription factor that upregulates the expression of anti-inflammatory and antioxidant genes. Furthermore, MBJ exhibited antioxidant and anti-inflammatory effects in an acute hepatitis mouse model. In conclusion, our results confirm the medicinal properties of B. javanica, and therefore MBJ could be applied to improve inflammatory and redox imbalances in different types of pathologies.

The impact of acetylsalicylic acid dosed at bedtime on circadian rhythms of blood pressure in the high-risk group of cardiovascular patients-a randomized, controlled trial

Purpose

Time of drug administration may significantly influence its effect. The aim of the present study was to investigate the effect of ASA (administrated in the morning or in the evening) on the anti-hypertensive effect and diurnal blood pressure profile in the high-risk group of cardiovascular patients.

Methods

All patients (n = 114) had been diagnosed with coronary heart disease and arterial hypertension prior to the enrolment and had been treated with 75 mg per day of ASA in the morning. The patients were randomly assigned to one of the two study groups receiving 75 mg of ASA per day in a single antiplatelet therapy for 3 months in the morning (n = 58) or in the evening (n = 56). The control group (n = 61) consisted of patients with arterial hypertension but without coronary heart disease, not receiving ASA. In all the patients, during each visit, clinical blood pressure (BP) and ambulatory blood pressure measurements (ABPM) were performed.

Results

There was a significant reduction in 24-h BP and blood pressure at night in the ASA group evening group compared with the ASA morning group and the control group.

Conclusions

The present study demonstrated that compared with the use of ASA in the morning, its administration in the evening may lead to favourable drop in the ABPM and an improvement of the diurnal profile in the high-risk group of cardiovascular patients who are not naïve to ASA.

Electronic supplementary material

The online version of this article (10.1007/s00228-020-02997-8) contains supplementary material, which is available to authorized users.

[Antiplatelet therapy: resistance to traditional antiaggregation drugs and role of new antiplatelet agents]

Platelet aggregation plays a key role in the development of major cardiovascular events (MACE) related to atherothrombosis. Since the appearance of coronary stenting, the importance of measuring and modulating platelet activity has considerably increased in the scientific literature during the last decade. Double antiplatelet therapy with aspirin and clopidogrel administrated to stent carriers has widely demonstrated its efficacy in the prevention of MACE compared with aspirin alone. These benefits are also present when a conservatory approach is chosen for acute coronary syndrome management. However, there are an important number of patients who develop MACE despite optimal dual antiplatelet therapy, most likely related to an incomplete platelet activity inhibition. Many studies suggest an important inter-individual variability in the response to the drugs, maybe related, at least in part, to the use of different assessment techniques of platelet aggregation. Other authors suggest an incomplete platelet inhibition as a possible explanation for the presence of MACE in patients under optimal antiplatelet therapy. Resistance to usual drugs has become a clinically relevant issue that requires an individual approach where new antiplatelet agents, such as prasugrel or ticagrelor, could play an important role as stated in current consensus documents.

Leptin increases blood pressure and markers of endothelial activation during pregnancy in rats

Raised leptin levels have been reported in the placentae and serum of women with elevated blood pressure and proteinuria during pregnancy. The role of leptin in this however remains unknown. This study investigates the effect of leptin administration on systolic blood pressure (SBP) and proteinuria and serum markers of endothelial activation during pregnancy in Sprague Dawley rats. From day 1 of pregnancy, 24 rats were randomised into those given either saline (group 1) or leptin at 60 or 120 μ g/kg/body weight/day (groups 2 and 3 resp.). SBP was measured every 5 days and 24-h urinary protein was measured at days 0 and 20 of pregnancy. Animals were euthanised on day 20 of pregnancy, and serum was collected for estimation of E-selectin and ICAM-1. Compared to group 1, SBP during the latter part of the pregnancy was significantly higher in the leptin-treated group (P < 0.01). Urinary protein excretion, serum E-selectin, and ICAM-1 were significantly higher in leptin-treated rats (P < 0.05). It seems that leptin administration to normotensive Sprague Dawley rats during pregnancy significantly increases SBP, urinary protein excretion, and markers of endothelial activation. However, further studies are required to examine the underlying mechanism responsible for this and its relevance to preeclampsia in humans.

High glucose inhibits the aspirin-induced activation of the nitric oxide/cGMP/cGMP-dependent protein kinase pathway and does not affect the aspirin-induced inhibition of thromboxane synthesis in human platelets

Since hyperglycemia is involved in the "aspirin resistance" occurring in diabetes, we aimed at evaluating whether high glucose interferes with the aspirin-induced inhibition of thromboxane synthesis and/or activation of the nitric oxide (NO)/cGMP/cGMP-dependent protein kinase (PKG) pathway in platelets. For this purpose, in platelets from 60 healthy volunteers incubated for 60 min with 5-25 mmol/L d-glucose or iso-osmolar mannitol, we evaluated the influence of a 30-min incubation with lysine acetylsalicylate (L-ASA; 1-300 μmol/L) on 1) platelet function under shear stress; 2) aggregation induced by sodium arachidonate or ADP; 3) agonist-induced thromboxane production; and 4) NO production, cGMP synthesis, and PKG-induced vasodilator-stimulated phosphoprotein phosphorylation. Experiments were repeated in the presence of the antioxidant agent amifostine. We observed that platelet exposure to 25 mmol/L d-glucose, but not to iso-osmolar mannitol, 1) reduced the ability of L-ASA to inhibit platelet responses to agonists; 2) did not modify the L-ASA-induced inhibition of thromboxane synthesis; and 3) prevented the L-ASA-induced activation of the NO/cGMP/PKG pathway. Preincubation with amifostine reversed the high-glucose effects. Thus, high glucose acutely reduces the antiaggregating effect of aspirin, does not modify the aspirin-induced inhibition of thromboxane synthesis, and inhibits the aspirin-induced activation of the NO/cGMP/PKG pathway. These results identify a mechanism by which high glucose interferes with the aspirin action.

Cilostazol, not aspirin, reduces ischemic brain injury via endothelial protection in spontaneously hypertensive rats

BACKGROUND AND PURPOSE

It is well-established that hypertension leads to endothelial dysfunction in the cerebral artery. Recently, cilostazol has been used for the secondary prevention of ischemic stroke. Among antiplatelet drugs, phosphodiesterase inhibitors including cilostazol have been shown to have protective effects on endothelial cells. The aim of the present study is to investigate the effects of cilostazol and aspirin on endothelial nitric oxide synthase (eNOS) phosphorylation in the cerebral cortex, endothelial function, and infarct size after brain ischemia in spontaneously hypertensive rats (SHR).

METHODS

Five-week-old male SHR received a 5-week regimen of chow containing 0.1% aspirin, 0.1% cilostazol, 0.3% cilostazol, or the vehicle control. The levels of total and Ser(1177)-phosphorylated eNOS protein in the cerebral cortex were evaluated by Western blot. To assess the contribution of eNOS in maintaining cerebral blood flow, we monitored cerebral blood flow by laser-Doppler flowmetry after L-N(5)-(1-iminoethyl)ornithine infusion. Additionally, we evaluated residual microperfusion using fluorescence-labeled serum protein and infarct size after transient focal brain ischemia.

RESULTS

In SHR, the blood pressure and heart rate were similar among the groups. Cilostazol-treated SHR had a significantly higher ratio of phospho-eNOS/total eNOS protein than vehicle-treated and aspirin-treated SHR. Treating with cilostazol, but not aspirin, significantly improved cerebral blood flow response to L-N(5)-(1-iminoethyl)ornithine. Cilostazol also increased residual perfusion of the microcirculation and reduced brain damage after ischemia compared to vehicle control and aspirin.

CONCLUSIONS

These findings indicate that cilostazol, but not aspirin, can attenuate ischemic brain injury by maintaining endothelial function in the cerebral cortex of SHR.

Virgin olive oil administration improves the effect of aspirin on retinal vascular pattern in experimental diabetes mellitus

The aim of the present study is to evaluate the possible influence of virgin olive oil (VOO) on the effect of acetylsalicylic acid (ASA) in platelet aggregation, prostanoid and NO production and retinal vascular pattern in rats with experimental type 1-like diabetes. We used 100 male Wistar rats that were distributed into five groups: (1) non-diabetic rats (NDR); (2) untreated diabetic rats (DR); (3) DR treated with ASA (2 mg/kg per d per os (p.o.)); (4) DR treated with VOO (0·5 ml/kg per d p.o.); (5) DR treated with ASA plus VOO. The duration of diabetes was 3 months, and each treatment was administered from the first day of diabetes. Variables that were quantified were platelet aggregation (Imax), thromboxane B2 (TxB2), aortic prostacyclin (6-keto-PGF1α) and NO, and the percentage of retina with horseradish peroxidase-permeable vessels (HRP-PV). Diabetic rats showed a higher Imax (35 %) and TxB2 (63 %) than NDR, and a lower 6-keto-PGF1α, NO and HRP-PV than NDR ( − 74·6 %). ASA and VOO administration reduced these differences and prevented the percentage of HRP-PV ( − 59·7 % with ASA and − 46·7 % with VOO). The administration of ASA plus VOO showed a strong platelet inhibition (80·2 v. 23·4 % for VOO and 50·6 % for ASA+VOO, P < 0·0001), and reduced HRP-PV differences to − 31·6 % (P < 0·001 with respect to DR and P < 0·0001 with respect to DR treated with ASA). In conclusion, the administration of VOO to rats with type 1-like diabetes mellitus improves the pharmacodynamic profile of ASA, and increases its retinal anti-ischaemic effect.

eNOS gene influences platelet phenotype in acute coronary syndrome patients on dual antiplatelet treatment

Nitric Oxide (NO) plays a relevant role in regulating platelet recruitment and eNOS is the major isoform known to be expressed in platelets. Polymorphisms in the eNOS gene with a reduced NO availability might affect platelet phenotype. The aim of our study was to evaluate the role of eNOS-786T > C, 894G > T and 4a/4b polymorphisms in modulating platelet phenotype in 1442 acute coronary syndrome (ACS) patients on dual antiplatelet therapy, previously investigated in relation to platelet function. Platelet aggregation on platelet-rich plasma after collagen (2 microg/mL), ADP (10 microM) and arachidonic acid (AA) (1 mM) stimuli and the genetic analysis of eNOS polymorphisms were assessed. In subjects carrying the eNOS 4a and -786C alleles a significantly higher maximal platelet aggregation value after AA was found (p = 0.02 and p = 0.047, respectively). eNOS 4a but not -786C allele weakly influenced platelet aggregation after collagen stimulus (p = 0.05). eNOS 4a allele significantly and independently influenced AA-induced platelet aggregation (p = 0.01). A significantly higher percentage of patients with AA-induced high residual platelet reactivity (RPR) was found in subjects carrying both eNOS 4a and -786C allele (p = 0.03 and p = 0.04, respectively). At logistic multivariate analysis, the eNOS 4a allele significantly influenced the AA-induced high residual platelet reactivity (p = 0.02). This study evidences a role for eNOS gene in moderately, but significantly, modulating platelet phenotype in a high-risk population on dual antiplatelet treatment.

Ultraviolet B light-induced nitric oxide/peroxynitrite imbalance in keratinocytes--implications for apoptosis and necrosis

Elevation of nitric oxide (NO*) can either promote or inhibit ultraviolet B light (UVB)-induced apoptosis. In this study, we determined real-time concentration of NO* and peroxynitrite (ONOO(-)) and their role in regulation of membrane integrity and apoptosis. Nanosensors (diameter 300-500 nm) were used for direct in situ simultaneous measurements of NO* and ONOO(-) generated by UVB in cultured keratinocytes and mice epidermis. An exposure of keratinocytes to UVB immediately generated ONOO(-) at maximal concentration of 190 nm followed by NO(*) release with a maximal concentration of 91 nm. The kinetics of UVB-induced NO*/ONOO(-) was in contrast to cNOS agonist stimulated NO*/ONOO(-) from keratinocytes. After stimulating cNOS by calcium ionophore (CaI), NO* release from keratinocytes was followed by ONOO(-) production. The [NO*] to [ONOO(-)] ratio generated by UVB decreased below 0.5 indicating a serious imbalance between cytoprotective NO* and cytotoxic ONOO(-)-a main component of nitroxidative stress. The NO*/ONOO(-) imbalance increased membrane damage and cell apoptosis was partially reversed in the presence of free radical scavenger. The results suggest that UVB-induced and cNOS-produced NO* is rapidly scavenged by photolytically and enzymatically generated superoxide (O(2) (-)) to produce high levels of ONOO(-), which enhances oxidative injury and apoptosis of the irradiated cells.

Pre admission antithrombotics are associated with improved outcomes following ischaemic stroke: a cohort from the Registry of the Canadian Stroke Network

BACKGROUND

Several studies have attempted to identify predictors of outcome following ischaemic stroke. Reduced stroke severity has been reported with pre admission ASA use, and improved outcomes have been reported with pre admission statin treatment. The interaction between pre treatment medications and clinical response to tPA is less clear. The objective of our study was to assess clinical outcomes in patients with acute ischaemic stroke with respect to pre treatment medications.

METHODS

The Registry of the Canadian Stroke Network collected pre morbid and prospective outcome data on 5568 patients with ischaemic stroke. We applied multivariate analyses to correlate pre admission medications with stroke severity on presentation, in-hospital mortality, and modified Rankin at discharge. Analyses were adjusted for age, gender, medical history, tPA administration, blood pressure, and glucose on presentation.

RESULTS

Pre admission treatment with ASA and clopidogrel was associated with less severe stroke upon presentation. A similar trend was seen with dipyridamole and ticlopidine, but did not reach statistical significance. Pre treatment with ASA and warfarin was associated with improved Rankin scores at discharge. There was no interaction between tPA treatment and pre admission antiplatelets with respect to in-hospital mortality or disability at discharge, although tPA treatment was independently associated with improved Rankin at discharge. Pre treatment antiplatelet use did not result in increased intracerebral haemorrhage following tPA administration.

CONCLUSIONS

Patients with acute ischaemic stroke taking antithrombotic medications at hospital admission have improved functional outcomes. No interaction is noted between use of these medications and outcome following thrombolysis. This large prospective cohort study is consistent with previous published reports, and supports the notion that pre admission antithrombotics may mitigate brain injury during acute stroke.

Myeloperoxidase-mediated LDL oxidation and endothelial cell toxicity of oxidized LDL: attenuation by (−)-epicatechin

Recent data suggest an inverse epidemiological association between intake of flavanol-rich cocoa products and cardiac mortality. Potential beneficial effect of cocoa may be attributed to flavanol-mediated improvement of endothelial function, as well as to enhancement of bioavailability and bioactivity of nitric oxide in vivo. ( - )-Epicatechin is one bioactive flavanol found in cocoa. This review deals with protective actions of ( - )-epicatechin on two key processes in atherogenesis, oxidation of LDL and damage to endothelial cell by oxidized LDL (oxLDL), with emphasis on data from this laboratory. ( - )-Epicatechin not only abrogates or attenuates LDL oxidation but also counteracts deleterious actions of oxLDL on vascular endothelial cells. These protective actions are only partially shared by other vasoprotective agents such as vitamins C and E or aspirin. Thus, ( - )-epicatechin appears to be a pleiotropic protectant for both LDL and endothelial cells.

Aspirin acetylates nitric oxide synthase type 3 in platelets thereby increasing its activity

AIMS

Acute administration of aspirin increases nitric oxide (NO) synthesis by platelets, an effect not shared by other non-steroidal anti-inflammatory drugs. The aim of the present study was to determine the mechanism by which aspirin acutely increases the activity of NO synthase type 3 (NOS-3), the predominant NOS isoform expressed by platelets, and specifically whether this occurs through an increase in its acetylation.

METHODS AND RESULTS

Platelets isolated from the blood of healthy human subjects were exposed in vitro to vehicle or aspirin at different concentrations (5 micromol/L-4 mmol/L). Changes in intraplatelet Ca(2+) concentration were determined from fura-2 fluorescence. Following immunoprecipitation of NOS-3 from platelet lysates, its activity was determined from l-[(3)H]arginine to l-[(3)H]citrulline conversion, and its serine phosphorylation quantified by western blotting. Acetylation of NOS-3 in platelets was assessed by the incorporation of radioactivity into the immunoprecipitated enzyme from [acetyl-(14)C]aspirin. Following transfection of HeLa cells with NOS-3, NO biosynthesis in response to aspirin was determined from cyclic GMP measurement, and sites of NOS-3 acetylation were ascertained by liquid chromatography-tandem mass spectrometry. At all concentrations tested, aspirin increased the activity of NOS-3 from platelets. This was not associated with any measurable change in intraplatelet Ca(2+) concentration. Serine phosphorylation of NOS-3 in platelets was decreased, and this was especially marked for serine-1177 phosphorylation, whereas acetylation of NOS-3 was increased, by aspirin incubation. HeLa cells transfected with NOS-3 exhibited an increase in NO biosynthesis following aspirin exposure, and this was associated with acetylation of the enzyme on both serine-765 and serine-771.

CONCLUSION

Aspirin acetylates NOS-3 acutely in platelets, and this causes an increase in its activity as well as a decrease in its phosphorylation. It is also possible that aspirin indirectly affects NOS-3 activity by acetylating other substrates within the platelet, but this remains to be determined.

Augmentation of U46619 induced human platelet aggregation by aspirin

Aspirin is known to suppress platelet function markedly. However, aspirin at concentrations higher than 1 mM was observed to augment 1.3 microM U46619 (a stable thromboxane receptor (TP receptor) agonist) induced human platelet aggregation in this study. Moreover, at a concentration as low as 250 microM aspirin increased the aggregation induced by U46619 in 13% of normal and healthy individuals. The degree of platelet aggregation and the amount of ATP release were enhanced in U46619 stimulated platelet rich plasma by the addition of aspirin (>250 microM). U46619 was previously reported to inhibit forskolin-stimulated adenyl cyclase and to reduce the cAMP formation. Both of the augmentation effects of aspirin on U46619-induced aggregation and ATP release were blocked by MeSAMP, a P2Y(12) receptor antagonist. U46619 induced aggregation was suppressed by the addition of ADP scavenger (CP/CPK) with no significant change on ATP measured and the effect of CP/CPK could not be reversed by aspirin. In addition, aspirin augmented the inhibitory effect of U46619 on the cAMP production. Our present results suggested that the potentiation effect of aspirin on U46619 induced aggregation was related with the secreted ADP and the subsequent P2Y(12)/Gi related signaling.

Effects of hydroxytyrosol and hydroxytyrosol acetate administration to rats on platelet function compared to acetylsalicylic acid

Virgin olive oil (VOO) contains the polyphenols hydroxytyrosol (HT) and hydroxytyrosol acetate (HT-AC). This study investigated the antiplatelet effect of HT and HT-AC in healthy rats and compared their effects to acetylsalicylic acid (ASA). All compounds were administered orally for 7 days. HT and HT-AC inhibited platelet aggregation in whole blood, with a 50% inhibitory dose (ID50) of 48.25 mg/kg per day for HT, 16.05 mg/kg per day for HT-AC, and 2.42 mg/kg per day for ASA. Platelet synthesis of thromboxane B2 was inhibited by up to 30% by HT and 37% by HT-AC; the ID50 of this effect for ASA was 1.09 mg/kg per day. Vascular prostacyclin production was inhibited by up to 27.5% by HT and 32% by HT-AC; the ID50 of this effect for ASA was 6.75 mg/kg per day. Vascular nitric oxide production was increased by up to 34.2% by HT, 66% by HT-AC, and 64% by ASA. We conclude that HT and HT-AC administered orally inhibited platelet aggregation in rats and that a decrease in thromboxane synthesis along with an increase in nitric oxide production contributed to this effect.

Leptin-induced endothelial dysfunction in obesity

Hyperleptinemia accompanying obesity affects endothelial nitric oxide (NO) and is a serious factor for vascular disorders. NO, superoxide (O(2)(-)), and peroxynitrite (ONOO(-)) nanosensors were placed near the surface (5+/-2 microm) of a single human umbilical vein endothelial cell (HUVEC) exposed to leptin or aortic endothelium of obese C57BL/6J mice, and concentrations of calcium ionophore (CaI)-stimulated NO, O(2)(-), ONOO(-) were recorded. Endothelial NO synthase (eNOS) expression and L-arginine concentrations in HUVEC and aortic endothelium were measured. Leptin did not directly stimulate NO, O(2)(-), or ONOO(-) release from HUVEC. However, a 12-h exposure of HUVEC to leptin increased eNOS expression and CaI-stimulated NO (625+/-30 vs. 500+/-24 nmol/l control) and dramatically increased cytotoxic O(2)(-) and ONOO(-) levels. The [NO]-to-[ONOO(-)] ratio ([NO]/[ONOO(-)]) decreased from 2.0+/-0.1 in normal to 1.30+/-0.1 in leptin-induced dysfunctional endothelium. In obese mice, a 2.5-fold increase in leptin concentration coincided with 100% increase in eNOS and about 30% decrease in intracellular L-arginine. The increased eNOS expression and a reduced l-arginine content led to eNOS uncoupling, a reduction in bioavailable NO (250+/-10 vs. 420+/-12 nmol/l control), and an elevated concentration of O(2)(-) (240%) and ONOO(-) (70%). L-Arginine and sepiapterin supplementation reversed eNOS uncoupling and partially restored [NO]/[ONOO(-)] balance in obese mice. In obesity, leptin increases eNOS expression and decreases intracellular l-arginine, resulting in eNOS an uncoupling and depletion of endothelial NO and an increase of cytotoxic ONOO(-). Hyperleptinemia triggers an endothelial NO/ONOO(-) imbalance characteristic of dysfunctional endothelium observed in other vascular disorders, i.e., atherosclerosis and diabetes.

Leptin-induced endothelial dysfunction in obesity

Hyperleptinemia accompanying obesity affects endothelial nitric oxide (NO) and is a serious factor for vascular disorders. NO, superoxide (O(2)(-)), and peroxynitrite (ONOO(-)) nanosensors were placed near the surface (5+/-2 microm) of a single human umbilical vein endothelial cell (HUVEC) exposed to leptin or aortic endothelium of obese C57BL/6J mice, and concentrations of calcium ionophore (CaI)-stimulated NO, O(2)(-), ONOO(-) were recorded. Endothelial NO synthase (eNOS) expression and L-arginine concentrations in HUVEC and aortic endothelium were measured. Leptin did not directly stimulate NO, O(2)(-), or ONOO(-) release from HUVEC. However, a 12-h exposure of HUVEC to leptin increased eNOS expression and CaI-stimulated NO (625+/-30 vs. 500+/-24 nmol/l control) and dramatically increased cytotoxic O(2)(-) and ONOO(-) levels. The [NO]-to-[ONOO(-)] ratio ([NO]/[ONOO(-)]) decreased from 2.0+/-0.1 in normal to 1.30+/-0.1 in leptin-induced dysfunctional endothelium. In obese mice, a 2.5-fold increase in leptin concentration coincided with 100% increase in eNOS and about 30% decrease in intracellular L-arginine. The increased eNOS expression and a reduced l-arginine content led to eNOS uncoupling, a reduction in bioavailable NO (250+/-10 vs. 420+/-12 nmol/l control), and an elevated concentration of O(2)(-) (240%) and ONOO(-) (70%). L-Arginine and sepiapterin supplementation reversed eNOS uncoupling and partially restored [NO]/[ONOO(-)] balance in obese mice. In obesity, leptin increases eNOS expression and decreases intracellular l-arginine, resulting in eNOS an uncoupling and depletion of endothelial NO and an increase of cytotoxic ONOO(-). Hyperleptinemia triggers an endothelial NO/ONOO(-) imbalance characteristic of dysfunctional endothelium observed in other vascular disorders, i.e., atherosclerosis and diabetes.

Enhanced L-arginine-induced vasoreactivity suggests endothelial dysfunction in CADASIL

BACKGROUND

Mutations in the Notch3 gene are the cause of CADASIL, a hereditary small vessel disease leading to stroke and vascular dementia. The disease is characterized by ultrastructural granular deposits within small arterial vessels and degeneration of vascular smooth muscle cells. Yet, little is known about endothelial function in CADASIL. Vasoreactivity induced by L-arginine, which is the substrate for endothelial nitric oxide synthase, is a parameter of endothelial function and has been shown to be altered in patients with cerebrovascular disease.

METHODS

To assess endothelial function in CADASIL, L-arginine-induced vasoreactivity was studied in 25 CADASIL subjects and 24 non-CADASIL control subjects without previous history of cerebrovascular disease by transcranial Doppler sonography of the middle cerebral artery.

RESULTS

Resting mean flow velocity was significantly reduced in patients (43.7 +/- 14.5 cm/s) compared to controls (57.0 +/- 10.4 cm/s) [p < 0.001]. Patients exhibited a significantly higher pulsatility index (PI = 0.94 +/- 0.19) than control subjects (PI = 0.79 +/- 0.11) [p < 0.01]. L-arginine-induced vasoreactivity was significantly increased in patients (36.1 +/- 15.5 % ) versus controls (27.9 +/- 8.5 %) [p < 0.05]. In patients, there was a significant reduction of the PI following L-arginine application (PI = 0.86 +/- 0.13) compared to resting PI [p < 0.01].

CONCLUSIONS

Our results may indicate a pathogenic role of impaired cerebral hemodynamics and endothelial dysfunction in CADASIL. Our finding of enhanced L-arginine vasoreactivity might have therapeutic implications for CADASIL and sporadic small vessel disease.

The role of aspirin in cardiovascular prevention: implications of aspirin resistance

Aspirin is well recognized as an effective antiplatelet drug for secondary prevention in subjects at high risk of cardiovascular events. However, most patients receiving long-term aspirin therapy still remain at substantial risk of thrombotic events due to insufficient inhibition of platelets, specifically via the thromboxane A2 pathway. Although the exact prevalence is unknown, estimates suggest that between 5.5% and 60% of patients using this drug may exhibit a degree of "aspirin resistance," depending upon the definition used and parameters measured. To date, only a limited number of clinical studies have convincingly investigated the importance of aspirin resistance. Of these, few are of a sufficient scale, well designed, and prospective, with aspirin used at standard doses. Also, most studies do not sufficiently address the issue of noncompliance to aspirin as a frequent, yet easily preventable cause of resistance to this antiplatelet drug. This review article provides a comprehensive overview of aspirin resistance, discussing its definition, prevalence, diagnosis, and therapeutic approaches. Moreover, the clinical implications of aspirin resistance are explored in various cardiovascular disease states, including diabetes mellitus, hypertension, heart failure, and other similar disorders where platelet reactivity is enhanced.

Progress in clinical neurosciences: The 'antiplatelet' agents and the role of the endothelium

The antiplatelet drugs, commonly used in the prevention and treatment of cerebrovascular disease, possess a number of effects that are independent of direct antiplatelet actions. Beneficial and detrimental effects both occur. The endothelium is an important mediator of these non-antiplatelet effects. We performed a literature search to locate articles related to acetylsalicylic acid (aspirin), clopidogrel, ticlopidine, and dipyridamole and the interactions of these medications with the endothelium. The role of each of the above medications is explored in relation to vasodilation, inflammation, oxidation, platelet-leukocyte interactions, and thrombogenic tendency via platelet-vessel wall interactions.

Effects of low-dose aspirin on blood pressure and endothelial function of treated hypertensive hypercholesterolaemic subjects

The main objective of this study was to assess whether aspirin 100 mg QD can improve blood pressure (BP) control and endothelial function in subjects with arterial hypertension (AH) and hypercholesterolaemia. In total, 21 patients of both sexes (52.1+/-11.5 years) with treated AH and hypercholesterolaemia on antihypertensive and statin therapy were included in the treatment group. In the control group, 20 matched patients of both sexes (51.3+/-12.7 years), but without statin therapy, were recruited. Treatment group subjects received aspirin (100 mg QD) for a duration of 12 weeks at randomization (Treatment phase-1), followed by single blind matching placebo for 12 weeks (Placebo phase) and then again received aspirin (100 mg QD) for an additional 12 weeks (Treatment phase-2). The control group participated in Treatment phase-1, but did not continue Placebo phase and Treatment phase-2. At randomization and at the end of each study phase, mean 24-h systolic BP (SBP) and diastolic BP (DBP) were assessed by 24-h ambulatory blood pressure monitoring (ABPM) and endothelium-dependent (flow mediated, FMD) and -independent (nitroglycerin induced, NTG) vasodilatations of brachial artery were measured using high-resolution ultrasound. In Treatment phase-1, reduction of SBP and DBP (DeltaSBP 5.7+/-2.6 mmHg, P=0.008; DeltaDBP 3.8+/-1.7 mmHg, P=0.014) and improvement of FMD (4.1+/-0.6%, P=0.019), in Placebo phase an elevation of SBP and DBP (DeltaSBP -6.2+/-2.9 mmHg, P=0.002; DeltaDBP -4.2+/-1.9 mmHg, P=0.031) and worsening of FMD (-3.8+/-0.9%, P=0.027), and in Treatment phase-2 reduction of SBP and DBP (DeltaSBP 4.9+/-2.3 mmHg, P=0.005; DeltaDBP 4.1+/-1.3 mmHg, P=0.024) and improvement of FMD (4.5+/-1.3%, P=0.009) were observed in the treatment Group but not in the control group. Addition of low-dose aspirin to antihypertensive medications and statins in hypertensive and hypercholesterolaemic subjects can reduce both SBP and DBP by improvement of endothelial function.

Prostaglandins participate in the late phase of the vascular response to acetylcholine iontophoresis in humans

The participation of prostaglandins (PGs) in the cutaneous vasodilatation to acetylcholine (ACh) applied via iontophoresis is under debate. Using laser Doppler flowmetry, we studied the long lasting effect (20 min) of iontophoretic application (30 s; 0.1 mA) of ACh on the human forearm. Experiments were repeated (1) using deionized water instead of ACh to test the effect of current application, (2) after scopolamine treatment to inhibit muscarinic cholinergic receptors, and (3) 2 h, 3 days and 10 days following inhibition of PG synthesis with aspirin or a placebo control. Cutaneous vascular conductance (CVC) was calculated at rest (CVC(rest)), at peak vasodilatation in the first 5 min following ACh iontophoresis (CVC(peak)), and 20 min after iontophoresis (CVC(20)). The minimal CVC (CVC(min)) following iontophoresis was also determined. Cutaneous response to ACh displayed a biphasic pattern with an early and transient peak (CVC(peak): 62 +/- 8% of the maximal CVC induced by local heating (MVC)) followed by a long lasting slower vasodilatation (CVC(min): 44 +/- 6; CVC(20): 56 +/- 5%MVC). The current itself had no major effect. Scopolamine almost abolished both phases. The long lasting phase was aspirin sensitive but not the transient phase. At hour 2 post-aspirin, CVC(peak) was 61 +/- 10, CVC(min) 26 +/- 6 and CVC(20) 29 +/- 6%MVC. At day 3, CVC(peak) was 53 +/- 9, CVC(min) 22 +/- 3 and CVC(20) 25 +/- 4%MVC. At day 10, CVC(peak) was 67 +/- 10, CVC(min) 47 +/- 7 and CVC(20) 50 +/- 8%MVC. Placebo had no effect. We conclude that PGs participate in the vasodilator response following ACh iontophoresis. Previous non-steroidal anti-inflammatory drug treatments must be taken into account when studying the effect of ACh iontophoresis.