Chronic exercise reduces platelet activation in hypertension: upregulation of the L-arginine-nitric oxide pathway

The effect of physical activity intervention on blood pressure in 18 low and middle-income countries: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

In especially, low and middle-income nations (LMICs), where healthcare access may be restricted, high blood pressure (BP) is a major risk factor for cardiovascular disease and stroke, both of which can even lead to death. Altering one's lifestyle, in conjunction with medical therapy, has been demonstrated to be effective in lowering BP. Recent research has shown that physical activity (PA), in a variety of guises and to varying degrees, can be an effective means of lowering BP.

OBJECTIVE

The purpose of this meta-analysis and systematic review was to evaluate the impact that PA plays in the development of hypertension in LMICs nations.

METHODS

An exhaustive search of the available research was carried out in order to locate studies that were pertinent. We searched a number of online databases, such as SCOPUS, Medline, and Web of Science, looking for clinical trials that were published before March of 2023. Studies were only considered for inclusion if they were randomized controlled trials (RCTs), reported on the association between PA and BP, and were carried out in LMICs countries.

RESULTS

This meta-analysis incorporated a comprehensive collection of 60 studies, encompassing a total of 11,002 people, consisting of 5,630 cases and 5372 controls. The findings indicate that engaging in PA had a notable impact on decreasing systolic blood pressure (SBP), as seen by a weighted mean difference (WMD) of -7.70 mmHg, with a 95% confidence interval (CI) ranging from -9.50 to -5.91 (p < 0.001). Additionally, PA was found to have a significant influence on reducing diastolic blood pressure (DBP), as indicated by a WMD of -3.60 mmHg, with a 95% CI ranging from -4.48to -2.73(p < 0.001). The findings from subgroup analysis indicate that the observed results remained statistically significant when considering individuals with baseline SBP of 120 mmHg or lower and DBP of 80 mmHg or lower.

CONCLUSION

The incorporation of PA can significantly contribute to the mitigation of high BP within LMICs nations. Additional investigation is required to ascertain the most effective form and amount of PA in order to mitigate BP levels within these specific individuals.

Effects of exercise on whole-blood transcriptome profile in children with overweight/obesity

BACKGROUND

The current knowledge about the molecular mechanisms underlying the health benefits of exercise is still limited, especially in childhood. We set out to investigate the effects of a 20-week exercise intervention on whole-blood transcriptome profile (RNA-seq) in children with overweight/obesity.

METHODS

Twenty-four children (10.21 ± 1.33 years, 46% girls) with overweight/obesity, were randomized to either a 20-week exercise program (intervention group; n = 10), or to a no-exercise control group (n = 14). Whole-blood transcriptome profile was analyzed using RNA-seq by STRT technique with GlobinLock technology.

RESULTS

Following the 20-week exercise intervention program, 161 genes were differentially expressed between the exercise and the control groups among boys, and 121 genes among girls (p-value <0.05), while after multiple correction, no significant difference between exercise and control groups persisted in gene expression profiles (FDR >0.05). Genes enriched in GO processes and molecular pathways showed different immune response in boys (antigen processing and presentation, infections, and T cell receptor complex) and in girls (Fc epsilon RI signaling pathway) (FDR <0.05).

CONCLUSION

These results suggest that 20-week exercise intervention program alters the molecular pathways involved in immune processes in children with overweight/obesity.

Effects of exercise on platelet reactivity after myocardial infarction: a randomized clinical trial

Exercise training (ET) can lower platelet reactivity in patients with cardiovascular risk factors. However, the effects of ET on platelet reactivity in higher-risk patients is unknown. The aim of this study was to evaluate the effects of ET on platelet reactivity in patients with recent myocardial infarction (MI). Ninety patients were randomly assigned 1 month post-MI to the intervention (patients submitted to a supervised ET program) or control group. All patients were on dual antiplatelet therapy (DAPT). Platelet reactivity by VerifyNow-P2Y12 (measured by P2Y12 reaction units - PRUs) test was determined at baseline and at the end of 14 ± 2 weeks of follow-up at rest (primary endpoint), and multiplate electrode aggregometry (MEA) adenosine diphosphate (ADP) and aspirin (ASPI) tests were performed immediately before and after the maximal cardiopulmonary exercise test (CPET) at the same time points (secondary endpoints). Sixty-five patients (mean age 58.9 ± 10 years; 73.8% men; 60% ST elevation MI) completed follow-up (control group, n = 31; intervention group, n = 34). At the end of the follow-up, the mean platelet reactivity was 172.8 ± 68.9 PRUs and 166.9 ± 65.1 PRUs for the control and intervention groups, respectively (p = .72). Platelet reactivity was significantly increased after the CPET compared to rest at the beginning and at the end of the 14-week follow-up (among the intervention groups) by the MEA-ADP and MEA-ASPI tests (p < .01 for all analyses). In post-MI patients on DAPT, 14 weeks of supervised ET did not reduce platelet reactivity. Moreover, platelet reactivity was increased after high-intensity exercise (ClinicalTrials.gov: NCT02958657; https://clinicaltrials.gov/ct2/show/NCT02958657).

Resistance training reduces platelet activation in hypertensive women: the role of purinergic signaling

BACKGROUND AND AIM

Essential arterial hypertension is a risk factor for stroke, myocardial infarction, heart failure, and arterial aneurysm, which are related to the activation of platelets. Purinergic signaling has a central role in platelet aggregation. Although ATP and ADP can act as a proaggregant agent, adenosine inhibits platelet aggregation and reduces vascular injury. Physical exercise exhibits antiaggregant properties and can modulate purinergic system. The aim of this study was to evaluate the effect of 6 months of resistance training on purinergic system components in platelets and on platelet activation, hemodynamic and anthropometric parameters in hypertensive woman.

METHOD

A total of 31 hypertensive and 28 normotensive middle-aged sedentary women were submitted to 6 months of resistance training. Purinergic enzymes activities were assessed in platelets; ATP and Tromboxane B2 (TXB2) levels were measured in serum. Blood pressure (BP), BMI, and body fat were also measured. All variables were statistically analyzed, considering P value less than 0.05.

RESULTS

Six months of resistance training was able to significantly reduce BP, ATP, and TXB2 levels as well as NTPDase, ecto-5'nucleotidase, and ADA activities in hypertensive group. After 6 months of resistance training, purinergic system components and TXB2 of hypertensive group were similar to normotensive group in platelets, demonstrating that resistance training was able to modulate platelet activation. A positive correlation was found between BP, enzyme activities, and levels of ATP and TXB2.

CONCLUSION

Our findings demonstrated the relationship between purinergic signaling and platelet activation in hypertension and suggests that resistance training serve as tool to reduce platelet aggregation in hypertensive woman by modulating purinergic system.

Potential mechanisms of multimodal prehabilitation effects on surgical complications: a narrative review

Continuous advances in prehabilitation research over the past several decades have clarified its role in improving preoperative risk factors, yet the evidence demonstrating reduced surgical complications remains uncertain. Describing the potential mechanisms underlying prehabilitation and surgical complications represents an important opportunity to establish biological plausibility, develop targeted therapies, generate hypotheses for future research, and contribute to the rationale for implementation into the standard of care. In this narrative review, we discuss and synthesize the current evidence base for the biological plausibility of multimodal prehabilitation to reduce surgical complications. The goal of this review is to improve prehabilitation interventions and measurement by outlining biologically plausible mechanisms of benefit and generating hypotheses for future research. This is accomplished by synthesizing the available evidence for the mechanistic benefit of exercise, nutrition, and psychological interventions for reducing the incidence and severity of surgical complications reported by the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP). This review was conducted and reported in accordance with a quality assessment scale for narrative reviews. Findings indicate that prehabilitation has biological plausibility to reduce all complications outlined by NSQIP. Mechanisms for prehabilitation to reduce surgical complications include anti-inflammation, enhanced innate immunity, and attenuation of sympathovagal imbalance. Mechanisms vary depending on the intervention protocol and baseline characteristics of the sample. This review highlights the need for more research in this space while proposing potential mechanisms to be included in future investigations.

NEDD4 attenuates oxidized low‑density lipoprotein‑induced inflammation and dysfunction in vascular endothelial cells via regulating APEX1 expression

Atherosclerosis chiefly results from inflammation as well as vascular endothelial cell dysfunction. Methylation levels of neuronally expressed developmentally downregulated 4 (NEDD4) were found to be fortified in atherosclerosis patients and NEDD4 deficiency enhanced vascular calcification. However, the exact function of NEDD4 in inflammation and vascular endothelial dysfunction remains to be elucidated. In the present study, CCK-8 assay was used to estimate cell viability. Reverse transcription-quantitative PCR was adopted to examine the expression of NEDD4, inflammation-associated enzymes and apurinic/apyrimidinic endodeoxyribonuclease 1 (APEX1). Western blotting was used to test NEDD4, endothelial nitric oxide synthase, inducible nitric oxide synthase and APEX1 protein levels. Cytotoxicity was detected by a lactate dehydrogenase (LDH) kit. Reactive oxygen species level was tested by a corresponding kit. Vascular cell adhesion molecule 1 and intercellular adhesion molecule 1 contents were examined with ELISA. Cell adhesion assays evaluated the adhesion of endothelial cells. Co-immunoprecipitation assay was used to test the relationship between NEDD4 and APEX1. The data revealed that NEDD4 expression rapidly declined in oxidized low density lipoprotein (ox-LDL)-induced human umbilical vein endothelial cells (HUVECs). Following NEDD4 overexpression, the active damage, inflammatory release and endothelial cell dysfunction in ox-LDL-induced HUVECs were attenuated. After co-transfection of APEX1 interference plasmids and NEDD4 overexpression plasmids, cell damage, inflammatory release and endothelial cell dysfunction in ox-LDL-induced HUVECs were improved again. Taken together, NEDD4 attenuated ox-LDL-induced inflammation and endothelial dysfunction by regulating APEX1 expression.

Effects of Aerobic Training Progression on Blood Pressure in Individuals With Hypertension: A Systematic Review With Meta-Analysis and Meta-Regression

INTRODUCTION

Aerobic training of moderate intensity is the primary modality recommended in the management of hypertension. The manipulation of training variables can be an important strategy for the continuity of health benefits; however, little is known about the effects of the progression of aerobic training variables in the adaptations of blood pressure in hypertensive adults.

OBJECTIVE

To analyze, through a systematic review with meta-analysis, the effects of aerobic training with and without progression on systolic blood pressure (SBP) and diastolic blood pressure (DBP) in hypertensive adults.

METHOD

The search for the studies was carried out in the PubMed, Cochrane Central, SPORTDiscus and LILACS databases. Clinical trials that analyzed the effect of aerobic training, lasting at least six weeks, on blood pressure in hypertensive individuals comparing with a control group without intervention were selected. The selection of studies and data extraction were carried out independently by two pairs of researchers. The results are presented as mean difference and 95% confidence interval. Statistical significance was considered with p < 0.05.

RESULTS

Of the 13,028 studies found, 24 were selected and included in this review, 12 with progression of training variables and 12 without progression, with a total of 1,207 participants analyzed. There was a reduction in SBP after aerobic training with progression (-10.67 mmHg; 95% CI -15.421, -5.926; p < 0.001) and without progression (-10.17 mmHg; CI -12.213, -8.120; p < 0.001). DBP also decreased after aerobic training with progression (-5.49 mmHg; 95% CI -8.663, -2.310; p < 0.001) and without progression (-6.51 mmHg; 95% CI -9.147, -3.868; p < 0.001). According to the results of the meta-regression analyses, only age showed an association with the reduction of SBP (β: -0.323; CI -0.339, -0.307; p < 0.001).

CONCLUSION

Aerobic training promotes a reduction in the SBP and DBP levels of adults with hypertension, regardless of whether or not the training variables progression.

Possible roles of exercise and apelin against pregnancy complications

The prevalence of maternal obesity during pregnancy is associated with the risk of gestational diabetes, preeclampsia, and cardiomyopathy. Environmental factors such as active lifestyles and apelin may lead to beneficial changes. In rats, apelin and exercise (45 to 65% VO_2max for 6 to 9 weeks) during pregnancy increase brown adipose tissue (BAT) proteins such as Cidea, Elovl3, UCP1, PRDM16, and PGC-1α in males and females fetuses, while white adipose tissue (WAT) is reduced. In humans and animals, apelin and exercise stimulate the expression of the glucose transporters (GLUT1/2/4) in the muscle and adipose tissue through the PI3K/Akt and AMPK pathways. Hence, exercise and apelin may are known as regulators of energy metabolism and be anti-obesity and anti-diabetic properties. In mice, exercise also creates a short-term hypoxic environment in the pregnant mother, activating HIF-1, VEGF, and VEGFR, and increasing angiogenesis. Exercise and apelin also increase vasodilation, angiogenesis, and suppression of inflammation through the L-arginine/eNOS/NO pathway in humans. Exercise can stimulate the ACE2-Ang-(1-7)-Mas axis in parallel with inhibiting the ACE-Ang II-AT1 pathway. Exercise and apelin seem to prevent preeclampsia through these processes. In rats, moderate-intensity exercise (60 to 70% VO_2max for 8 weeks) and apelin/APJ also may prevent pathological hypertrophy in pregnancy by activating the PI3K/Akt/mTOR/p70S6K pathway, PI3k-Akt-ERK1/2-p70S6K pathway, and the anti-inflammatory cytokine IL-10. Since pre-clinical studies have been more on animal models, future research with scientific guidelines should pay more attention to human specimens. In future research, time factors such as the first, second, and third trimesters of pregnancy and the intensity and duration of exercise are important variables that should be considered to determine the optimal intensity and duration of exercise.

Long-term aerobic exercise training in type two diabetic patients alters the expression of miRNA-223 and its corresponding target, the P2RY12 receptor, attenuating platelet function

BACKGROUND

Type two diabetes mellitus (T2DM) patients are prone to develop atherothrombotic events due to platelet hyper-reactivity stemming from platelet miRNA-223 down-regulation and over-expression of its corresponding target, P2RY12.

OBJECTIVE

The study sought to determine the effects of long-term aerobic training on the expression levels of miRNA-223 and P2RY12 mRNA, and platelet function in T2DM patients.

METHODS

Twenty-four patients with T2DM (age, 60.0±2.8 yrs.) were selected and randomly divided into two groups: aerobic exercise training (AET, n = 12) and control (CON, n = 12). The AET protocol was performed with moderate intensity for 12 weeks, while patients in the CON group followed their usual routine. Weight, body mass index (BMI), peak oxygen consumption (VO2peak), lipid profile, fasting blood glucose (FBG), glycated hemoglobin (HbA1c), insulin resistance index (HOMA-IR), platelet miRNA-223 and P2RY12 expression were measured before and after the period.

RESULTS

There was a significant improvement in body weight, BMI, VO2peak, FBG, HbA1c, and HOMA-IR, after 12 weeks of AET (P <  0.01). Platelet aggregation decreased significantly after 12 weeks in the AET group compared with the CON (P <  0.001) group. Platelets' miRNA-223 and P2RY12 were significantly up- and down-regulated after AET in comparison with the CON group (P <  0.05), respectively. Moreover, the relative expression of miRNA-223 and P2RY12 significantly correlated with FBG changes following the intervention.

CONCLUSIONS

It can be concluded that long-term moderate-intensity aerobic training might be effective for reducing the occurrence of atherothrombotic events leading to premature death in T2DM patients through the modulation of miRNA-223, P2RY12 receptor expression, and platelet function.

Associations of long-term exposure to air pollutants, physical activity and platelet traits of cardiovascular risk in a rural Chinese population

BACKGROUND

Long-term exposure to air pollutants relate to increase risk of cardiovascular diseases that may be partially attributable to platelet dysfunction. Physical activity (PA) may attenuate inflammation to modulate platelet function. Thus, this study aimed to evaluate associations of air pollutants and PA with platelet traits of cardiovascular risk.

METHODS

A total of 31,282 participants were obtained from the Henan Rural Cohort (n = 39,259). The concentrations of particulate matter (PM) (PM with an aerodynamic diameter ≤1.0 μm (PM₁), ≤2.5 μm (PM_2.5), or ≤10 μm (PM₁₀)) and nitrogen dioxide (NO₂) were evaluated by using a spatiotemporal model incorporated into satellites data. Independent and combined effects of air pollutants and PA on platelet traits were analyzed by linear mixed models.

RESULTS

Positive associations of PM₁, PM_2.5, PM₁₀ and NO₂ with platelet indices (mean platelet volume (MPV), platelet distribution width (PDW) and platelet large cell ratio (P-LCR), the MPV to platelet counts (PLT) ratio (MPVP)) were observed, whereas negative associations of PM₁₀ and NO₂ with PLT or plateletcrit (PCT) were observed; negative interaction effects of PM_2.5 PM₁₀ and NO₂ and PA on MPV, PDW or P-LCR were found; negative interaction effects of PM₁, PM_2.5 and PM₁₀ and PA on PCT were observed.

CONCLUSIONS

Long-term exposure to air pollutants were related to increase platelet size and these associations were attenuated by increased PA, implying that PA is a costless and affordable method to decrease adverse effects on platelet traits in relation to air pollutants.

Aerobic training improves platelet function in type 2 diabetic patients: role of microRNA-130a and GPIIb

AIMS

MicroRNAs (miRs) that are mediators of gene expression have been implicated in type 2 diabetes mellitus (T2DM). Platelet hyper-reactivity is one of the most important disorders in T2DM patients. In this study, we explored the effects of aerobic training (AT) on platelet aggregation and Glycoprotein IIb (GPIIb) receptor and miR-130a expression.

METHODS

In a quasi-experimental controlled trial, 24 sedentary, eligible female participants with T2DM were selected (age 61.92 ± 3.63) and divided into AT and control (CON) groups based on their peak oxygen consumption (VO_2peak). AT protocol was performed three times per week in non-consecutive days on a treadmill with mean intensity (60-75% VO_2peak) for 8 weeks, while the control group refrained from any type of exercise training. Two blood samples were taken before and after this period. Real-time PCR was used to determine the expression of platelet GPIIb and miR-130a. Moreover, platelet indices (PLT, MPV, PDW, and PCT), collagen-induced platelet aggregation and glycemic variables were measured.

RESULTS

Analyses of data showed that anthropometric variables, VO_2peak and glycemic control improved significantly (P < 0.01) after AT. Furthermore, MPV, PDW (P < 0.01), and platelet aggregation (P < 0.001) decreased significantly following AT compared with control group. Platelet GPIIb expression down-regulated significantly (P < 0.05) in AT group but up-regulation of miR-130a expression was not significant between two groups (P > 0.05).

CONCLUSIONS

Platelet hyper-reactivity in T2DM females might be decreased not only by glycemic control and amelioration of anthropometric and platelet indices, but also the down-regulation of GPIIb following AT. However, more research is needed to determine the effects of exercise training on platelet miR-130a.

Reducing effect of aerobic exercise on blood pressure of essential hypertensive patients: A meta-analysis

BACKGROUND

The comprehensive meta-analysis aimed to explore the reductive effect of aerobic exercise on blood pressure of hypertensive patients.

METHODS

The related researches were selected from PubMed and Embase databases up to June 2016. Based on specific inclusive criteria, the eligible studies were selected, and the heterogeneities in their results were estimated by χ-based Q-test and I statistics. Quantitative meta-analysis was assessed by R 3.12 software, and results were presented by standardized mean difference (SMD) and their 95% confidence intervals (CIs). Outcome indicators were systolic blood pressure (SBP) and diastolic blood pressure (DBP). The publication biases were estimated by Egger test. Besides, the "leave one out" method was used for sensitivity evaluations.

RESULTS

As a result, a total of 13 papers with 802 samples were included. Based on the meta-analysis results, there were no significant differences in SBP and DBP between aerobic and control groups before exercise (SMD = 0.15, 95%CI: -0.16-0.46; SMD = 0.16, 95% CI: -0.23-0.55). However, significant reductions were obviously in aerobic group after aerobics, compared with control (SMD = -0.79, 95% CI: -1.29 to -0.28; SMD = -0.63, 95% CI: -1.14 to -0.12). A significant publication bias was detected in SBP (t = -2.2314, P = 0.04549) but not in DBP (t = -1.4962, P = 0.1604). Additionally, the DBP result would be altered after the exclusion of 2 individual papers.

CONCLUSION

Aerobic exercise may be a potential nonpharmacological treatment for blood pressure improvement in essential hypertensive patients.

Effects of Physical (In)activity on Platelet Function

As platelet activation is closely related to the liberation of growth factors and inflammatory mediators, platelets play a central role in the development of CVD. Virtually all cardiovascular risk factors favor platelet hyperreactivity and, accordingly, also physical (in)activity affects platelet function. Within this paper, we will summarize and discuss the current knowledge on the impact of acute and habitual exercise on platelet function. Although there are apparent discrepancies regarding the reported effects of acute, strenuous exercise on platelet activation, a deeper analysis of the available literature reveals that the applied exercise intensity and the subjects' cardiorespiratory fitness represent critical determinants for the observed effects. Consideration of these factors leads to the summary that (i) acute, strenuous exercise can lead to platelet activation, (ii) regular physical activity and/or physical fitness diminish or prevent platelet activation in response to acute exercise, and (iii) habitual physical activity and/or physical fitness also favorably modulate platelet function at physical rest. Notably, these effects of exercise on platelet function show obvious similarities to the well-recognized relation between exercise and the risk for cardiovascular events where vigorous exercise transiently increases the risk for myocardial infarction and a physically active lifestyle dramatically reduces cardiovascular mortality.

Impact of physical activity interventions on blood pressure in Brazilian populations

Background

High blood pressure is associated with cardiovascular disease, which is the leading cause of mortality in the Brazilian population. Lifestyle changes, including physical activity, are important for lowering blood pressure levels and decreasing the costs associated with outcomes.

Objective

Assess the impact of physical activity interventions on blood pressure in Brazilian individuals.

Methods

Meta-analysis and systematic review of studies published until May 2014, retrieved from several health sciences databases. Seven studies with 493 participants were included. The analysis included parallel studies of physical activity interventions in adult populations in Brazil with a description of blood pressure (mmHg) before and after the intervention in the control and intervention groups.

Results

Of 390 retrieved studies, eight matched the proposed inclusion criteria for the systematic review and seven randomized clinical trials were included in the meta-analysis. Physical activity interventions included aerobic and resistance exercises. There was a reduction of -10.09 (95% CI: -18.76 to -1.43 mmHg) in the systolic and -7.47 (95% CI: -11.30 to -3.63 mmHg) in the diastolic blood pressure.

Conclusions

Available evidence on the effects of physical activity on blood pressure in the Brazilian population shows a homogeneous and significant effect at both systolic and diastolic blood pressures. However, the strength of the included studies was low and the methodological quality was also low and/or regular. Larger studies with more rigorous methodology are necessary to build robust evidence.

Exercise-induced changes in inflammatory processes: Implications for thrombogenesis in cardiovascular disease

Sedentary lifestyle is a risk factor and a strong predictor for chronic disease and premature death. Low-grade inflammation has been proved a key player in the pathogenesis of cardiovascular disease. Inflammatory processes have been also involved in maintaining the balance between coagulation and fibrinolysis. In addition, an inverse linear dose-response relation between physical activity and mortality risks has also been reported. However, the favorable effects of structured exercise programs and the independent contribution of physical activity to cardiovascular risk are still under investigation. In response to heavy exercise, interleukin-6 (IL-6) is secreted by contracting skeletal muscles, followed by an acute reactant release of C-reactive protein (CRP). Both CRP and IL-6 can stimulate monocyte tissue factor production, provoke platelet hyperreactivity, promote fibrinogen biosynthesis, and enhance microparticle formation and erythrocyte aggregability, thus triggering prothrombotic state. By contrast, regular exercise and physical activity are protective against all-cause mortality through suppressing pro-inflammatory cytokine production, enhancing anti-inflammatory mediators and antioxidant development, and promoting fibrinolytic activity. Low-load resistance exercise also plays an advantageous role in thrombogenesis by reducing inflammatory processes and potentiating fibrinolytic features. In the present review article, we provide an overview of the impact of different modes and intensities of physical activity on vascular inflammation and thrombogenesis.

L-arginine-nitric oxide pathway and oxidative stress in plasma and platelets of patients with pre-eclampsia

Pre-eclampsia (PE), a syndrome of pregnancy-induced hypertension, continues to be a leading cause of maternal and fetal morbidity and mortality. The aim of this study was to investigate whether changes in oxidative status are correlated with alterations in the L-arginine-nitric oxide pathway and platelet aggregation in PE. Plasma and platelets from women with PE (n=24) or normotensive pregnancy (NP, n=27) recruited in the third trimester of gestation were used to measure oxidative damage assessed by protein carbonyl content, antioxidant activities of superoxide dismutase (SOD), catalase (CAT) and nitrite levels. Transport of L-[(3)H]-arginine, as well as the activities of the nitric oxide (NO) synthase (eNOS and inducible NO synthase (iNOS)) and platelet aggregation, were also evaluated. Plasma nitrite levels and the activities of SOD and CAT were reduced in PE (5.2±2.7, 3.4±0.8, 0.3±0.4, respectively, P<0.05) compared with NP (8.7±2.3, 6.7±3.1, 1.0±0.5, respectively), whereas protein carbonyl content and L-arginine levels were not significantly different between PE and NP groups. In platelets, L-arginine transport was reduced in PE (19.2±10.5, P<0.05) compared with NP (62.0±31.1), whereas the NOS activity, eNOS and iNOS expression, nitrite levels and platelet aggregation were unaffected. Protein carbonyl content was increased, and CAT activity was reduced in platelets from PE (0.03±0.02, 0.55±0.30, respectively, P<0.05), compared with NP (0.005±0.005, 1.01±0.36, respectively). The data suggest that a systemic impairment of antioxidant defense mechanisms is associated with decreased plasma nitrite levels, which may contribute to hypertension in PE. Oxidative stress may contribute to the reduced influx of L-arginine in platelets. Compensatory mechanisms may contribute to the maintenance of NO production and its modulatory role on platelet function.

Upregulation of platelet L-arginine – nitric oxide pathway after exercise training in hypertension

We investigated whether physical exercise can affect platelet L-arginine – nitric oxide pathway in spontaneously hypertensive rats (SHR). Sixteen male SHR and 16 Wistar Kyoto rats (WKY) were divided among exercise (EX) and sedentary (SED) groups. After 20 weeks of treadmill training, systolic blood pressure (mm Hg) was significantly lower in exercised spontaneously hypertensive rats (SHR/EX; 138 ± 8) than in sedentary spontaneously hypertensive rats (SHR/SED; 214 ± 9). Exercise significantly increased platelet L-arginine transport (pmol L-arginine·(109 cells)–1·min–1), assessed by incubation with L-[3H]-arginine, in both WKY (SED, 0.196 ± 0.054 compared with EX, 0.531 ± 0.052) and SHR (SED, 0.346 ± 0.076 compared with EX, 0.600 ± 0.049). Nitric oxide synthase (NOS) activity (pmol L-citrulline·(108 cells)–1), measured by the conversion of L-[3H]-arginine to L-[3H]-citrulline, was significantly increased in SHR/EX (0.072 ± 0.007) compared with SHR/SED (0.038 ± 0.007), but no changes were observed in WKY. The iNOS and eNOS protein levels assessed by Western blot were not affected by exercise. This upregulation of the platelet L-arginine–NO pathway may attenuate the risk of thromboembolic events, supporting the role of exercise in hypertension management.

Platelet activation, oxidative stress and overexpression of inducible nitric oxide synthase in moderate heart failure

1. Chronic heart failure (CHF) is a common disabling disorder associated with thromboembolic events, the genesis of which is not yet fully understood. Nitric oxide (NO), derived from the vascular endothelium and platelets, has an important role in the physiological regulation of blood flow. It is generated from the amino acid L-arginine via NO synthase (NOS). 2. The main objective of the present study was to investigate NO production and its relationship with platelet aggregation, oxidative stress, inflammation and related amino acids in patients with moderate CHF. The expression and activity of NOS isoforms were analysed by western blotting and conversion of L-[(3)H]-arginine to L-[(3)H]-citrulline, respectively, in CHF patients (n = 12) and healthy controls (n = 15). Collagen- and ADP-induced platelet aggregation, oxidative stress (thiobarbituric acid-reactive substances (TBARS) formation and superoxide dismutase (SOD) activity) and plasma levels of amino acids and inflammatory markers (fibrinogen and C-reactive protein (CRP)) were also determined. 3. Both collagen- and ADP-induced platelet aggregation were increased in CHF patients compared with controls. Platelets from CHF patients did not show any changes in NOS activity in the presence of overexpression of inducible NOS. Systemic and intraplatelet TBARS production was elevated, whereas SOD activity was decreased in CHF patients. l-arginine plasma concentrations were lower in CHF patients than in controls. Systemic levels of CRP and fibrinogen were increased in CHF patients. 4. The results show that, in patients with moderate CHF, there is platelet activation and reduced intraplatelet NO bioavailability due to oxidative stress, which suggests a role for platelets in the prothrombotic state.

Thrombosis, physical activity, and acute coronary syndromes

Acute coronary syndromes (ACS) are common, life-threatening cardiac disorders that typically are triggered by rupture or erosion of an atherosclerotic plaque. Platelet deposition and activation of the blood coagulation cascade in response to plaque disruption lead to the formation of a platelet-fibrin thrombus, which can grow rapidly, obstruct coronary blood flow, and cause myocardial ischemia and/or infarction. Several clinical studies have examined the relationship between physical activity and ACS, and numerous preclinical and clinical studies have examined specific effects of sustained physical training and acute physical activity on atherosclerotic plaque rupture, platelet function, and formation and clearance of intravascular fibrin. This article reviews the available literature regarding the role of physical activity in determining the incidence of atherosclerotic plaque rupture and the pace and extent of thrombus formation after plaque rupture.

Hemodynamic changes quantified in abdominal aortic aneurysms with increasing exercise intensity using mr exercise imaging and image-based computational fluid dynamics

Abdominal aortic aneurysm (AAA) is a vascular disease resulting in a permanent, localized enlargement of the abdominal aorta. We previously hypothesized that the progression of AAA may be slowed by altering the hemodynamics in the abdominal aorta through exercise [Dalman, R. L., M. M. Tedesco, J. Myers, and C. A. Taylor. Ann. N.Y. Acad. Sci. 1085:92-109, 2006]. To quantify the effect of exercise intensity on hemodynamic conditions in 10 AAA subjects at rest and during mild and moderate intensities of lower-limb exercise (defined as 33 ± 10% and 63 ± 18% increase above resting heart rate, respectively), we used magnetic resonance imaging and computational fluid dynamics techniques. Subject-specific models were constructed from magnetic resonance angiography data and physiologic boundary conditions were derived from measurements made during dynamic exercise. We measured the abdominal aortic blood flow at rest and during exercise, and quantified mean wall shear stress (MWSS), oscillatory shear index (OSI), and particle residence time (PRT). We observed that an increase in the level of activity correlated with an increase of MWSS and a decrease of OSI at three locations in the abdominal aorta, and these changes were most significant below the renal arteries. As the level of activity increased, PRT in the aneurysm was significantly decreased: 50% of particles were cleared out of AAAs within 1.36 ± 0.43, 0.34 ± 0.10, and 0.22 ± 0.06 s at rest, mild exercise, and moderate exercise levels, respectively. Most of the reduction of PRT occurred from rest to the mild exercise level, suggesting that mild exercise may be sufficient to reduce flow stasis in AAAs.

Characterization of the L-arginine-NO-cGMP pathway in spontaneously hypertensive rat platelets: the effects of pregnancy

Nitric oxide (NO) is a short-lived intercellular messenger that provides an efficient vascular regulatory mechanism to support homeostasis and prevent thrombosis. Endothelial dysfunction and reduced NO bioavailability have a central role in hypertension associated with pregnancy. The purpose of this study was to investigate the impact of pregnancy on the L-arginine-NO-cGMP pathway in platelets and its correlation to platelet function and blood pressure in normotensive rats and spontaneously hypertensive rats (SHRs). Platelets were obtained from blood on the 20th day of pregnancy from female SHRs (SHR-P) and normotensive controls (P) or age-matched nonpregnant rats (SHR-NP and NP). Intraplatelet NO synthase (NOS) activity was reduced in P compared to NP, despite unchanged L-arginine influx. The expression levels of endothelial NOS (eNOS) and inducible NOS (iNOS) were diminished during pregnancy in normotensive rats. Paradoxically, cyclic guanosine monophosphate (cGMP) levels were similar between NP and P, as were phosphodiesterase type 5 (PDE5) expression and platelet aggregation induced by adenosine diphosphate. In SHRs, L-arginine influx was reduced in SHR-P compared to SHR-NP. SHR-P exhibited impaired NOS activity and reduced iNOS expression compared with SHR-NP. Soluble guanylyl cyclase and PDE5 expression in platelets were lower in SHR-P than in SHR-NP, whereas no differences were noted between groups with respect to cGMP levels. However, increased levels of cGMP were observed in SHR-P compared to normotensive groups and platelet aggregability remained unaltered. In conclusion, these observations prompted the hypothesis that normal platelet aggregation in pregnant SHRs may be related to a reduction in PDE5 expression and consequently the maintenance of cGMP levels, independently of reduced platelet NO bioavailability.

Quantifying in vivo hemodynamic response to exercise in patients with intermittent claudication and abdominal aortic aneurysms using cine phase-contrast MRI

PURPOSE

To evaluate rest and exercise hemodynamics in patients with abdominal aortic aneurysms (AAA) and peripheral occlusive disease (claudicants) using phase-contrast MRI.

MATERIALS AND METHODS

Blood velocities were acquired by means of cardiac-gated cine phase-contrast in a 0.5 Tesla (T) open MRI. Volumetric flow was calculated at the supraceliac (SC), infrarenal (IR), and mid-aneurysm (MA) levels during rest and upright cycling exercise using an MR-compatible exercise cycle.

RESULTS

Mean blood flow increased during exercise (AAA: 130%, Claudicants: 136% of resting heart rate) at the SC and IR levels for AAA participants (2.6 +/- 0.6 versus 5.8 +/- 1.6 L/min, P < 0.001 and 0.8 +/- 0.4 versus 5.1 +/- 1.7 L/min, P < 0.001) and claudicants (2.3 +/- 0.5 versus 4.5 +/- 0.9 L/min, P < 0.005 and 0.8 +/- 0.2 versus 3.3 +/- 0.9 L/min, P < 0.005). AAA participants had a significant decrease in renal and digestive blood flow from rest to exercise (1.8 +/- 0.7 to 0.7 +/- 0.6 L/min, P < 0.01). The decrease in renal and digestive blood flow during exercise correlated with daily activity level for claudicants (R = 0.81).

CONCLUSION

Abdominal aortic hemodynamic changes due to lower extremity exercise can be quantified in patients with AAA and claudication using PC-MRI. The redistribution of blood flow during exercise was significant and different between the two disease states.

Oxidative stress, l-arginine-nitric oxide and arginase pathways in platelets from adolescents with anorexia nervosa

Anorexia nervosa (AN) is associated with high cardiovascular mortality. Nitric oxide (NO) inhibits platelet function and regulates the cardiovascular homeostasis. The aim of this study was to investigate the l-arginine-NO-GMPc and arginase pathways and oxidative stress in platelets from patients with AN. Intraplatelet l-arginine transport, NOS expression and activity, cGMP levels, platelet aggregation, arginase expression and oxidative stress were measured in adolescent patients with AN (n=11) and healthy controls (n=12). Plasma l-arginine levels were significantly reduced in AN. l-arginine transport, NOS activity and cGMP basal levels were reduced in platelets associated with unchanged platelet aggregability. The expression of NOS isoforms was not affected. TBARS production was diminished, while the activity of superoxide dismutase was elevated in AN patients. There was an overexpression of arginase II in AN. Alterations of l-arginine-NO-GMPc and arginase pathways in platelets can be early predictors of the incidence of cardiovascular disease into adult life in AN.