Pharmacological modulation of platelet function in hypertension

Renal Medulla in Hypertension

Studies have found that blood flow to the renal medulla is an important determinant of pressure-natriuresis and the long-term regulation of arterial pressure. First, a brief review of methods developed enabling the study of the medullary circulation is presented. Second, studies performed in rats are presented showing medullary blood flow plays a vital role in the pressure-natriuresis relationship and thereby in hypertension. Third, it is shown that chronic reduction of medullary blood flow results in hypertension and that enhancement of medullary blood flow reduces hypertension hereditary models of both salt-sensitive rats and salt-resistant forms of hypertension. The key role that medullary nitric oxide production plays in protecting this region from ischemic injury associated with circulating vasoconstrictor agents and reactive oxygen species is presented. The studies cited are largely the work of my students, research fellows, and colleagues with whom I have performed these studies dating from the late 1980s to more recent years.

Functional Foods in Preventing Human Blood Platelet Hyperactivity-Mediated Diseases-An Updated Review

Backgrounds/Objectives: Abnormal platelet functions are associated with human morbidity and mortality. Platelets have emerged as critical regulators of numerous physiological and pathological processes beyond their established roles in hemostasis and thrombosis. Maintaining physiological platelet function is essential to hemostasis and preventing platelet-associated diseases such as cardiovascular disease, cancer metastasis, immune disorders, hypertension, diabetes, sickle cell disease, inflammatory bowel disease, sepsis, rheumatoid arthritis, myeloproliferative disease, and Alzheimer's disease. Platelets become hyperactive in obesity, diabetes, a sedentary lifestyle, hypertension, pollution, and smokers. Platelets, upon activation, can trawl leukocytes and progenitor cells to the vascular sites. Platelets release various proinflammatory, anti-inflammatory, and angiogenic factors and shed microparticles in the circulation, thus promoting pathological reactions. These platelet-released factors also maintain sustained activation, further impacting these disease processes. Although the mechanisms are unknown, multiple stimuli induce platelet hyperreactivity but involve the early pathways of platelet activation. The exact mechanisms of how hyperactive platelets contribute to these diseases are still unclear, and antiplatelet strategies are inevitable for preventing these diseases. Reducing platelet function during the early stages could significantly impact these diseases. However, while this is potentially a worthwhile intervention, using antiplatelet drugs to limit platelet function in apparently healthy individuals without cardiovascular disease is not recommended due to the increased risk of internal bleeding, resistance, and other side effects. The challenge for therapeutic intervention in these diseases is identifying factors that preferentially block specific targets involved in platelets' complex contribution to these diseases while leaving their hemostatic function at least partially intact. Since antiplatelet drugs such as aspirin are not recommended as primary preventives, it is essential to use alternative safe platelet inhibitors without side effects.

METHODS

A systematic search of the PUBMED database from 2000 to 2023 was conducted using the selected keywords: "functional foods", "polyphenols", "fatty acids", "herbs", fruits and vegetables", "cardioprotective agents", "plant", "platelet aggregation", "platelet activation", "clinical and non-clinical trial", "randomized", and "controlled".

RESULTS

Potent natural antiplatelet factors have been described, including omega-3 fatty acids, polyphenols, and other phytochemicals. Antiplatelet bioactive compounds in food that can prevent platelet hyperactivity and thus may prevent several platelet-mediated diseases, including cardiovascular disease.

CONCLUSIONS

This narrative review describes the work during 2000-2023 in developing functional foods from natural sources with antiplatelet effects.

Obesity, thrombosis, venous disease, lymphatic disease, and lipedema: An obesity medicine association (OMA) clinical practice statement (CPS) 2023

Background

This Obesity Medicine Association (OMA) Clinical Practice Statement (CPS) is intended to provide clinicians with an overview on obesity, thrombosis, venous disease, lymphatic disease, and lipedema.

Methods

The scientific support for this CPS is based upon published citations, clinical perspectives of OMA authors, and peer review by the Obesity Medicine Association leadership.

Results

Topics in this CPS include obesity, thrombosis, venous disease, lymphatic disease, and lipedema. Obesity increases the risk of thrombosis and cardiovascular disease via fat mass and adiposopathic mechanisms. Treatment of thrombosis or thrombotic risk includes healthful nutrition, physical activity, and the requisite knowledge of how body weight affects anti-thrombotic medications. In addition to obesity-related thrombotic considerations of acute coronary syndrome and ischemic non-hemorrhagic stroke, this Clinical Practice Statement briefly reviews the diagnosis and management of clinically relevant presentations of deep vein thromboses, pulmonary embolism, chronic venous stasis, varicose veins, superficial thrombophlebitis, lipodermatosclerosis, corona phlebectatica, chronic thromboembolic pulmonary hypertension, iliofemoral venous obstruction, pelvic venous disorder, post-thrombotic syndrome, as well as lymphedema and lipedema - which should be included in the differential diagnosis of other edematous or enlargement disorders of the lower extremities.

Conclusions

This Obesity Medicine Association (OMA) Clinical Practice Statement (CPS) on obesity, thrombosis, and venous/lymphatic disease is one of a series of OMA CPSs designed to assist clinicians in the care of patients with the disease of obesity.

Platelet indices and blood pressure: a multivariable mendelian randomization study

BACKGROUND

Platelet indices are blood-based parameters reflecting the activation of platelets. Previous studies have identified an association between platelet indices and blood pressure (BP). However, causal inferences are prone to bias by confounding effects and reverse causation. We performed a Mendelian randomization (MR) study to compare the causal roles between genetically determined platelet indices and BP levels.

METHODS

Single-nucleotide polymorphisms (SNPs) associated with platelet count (PLT), plateletcrit (PCT), mean platelet volume (MPV), platelet distribution width (PDW), and BP at the level of genome-wide significance (p < 5 × 10^- 8) in the UK Biobank were used as instrumental variables. In bidirectional univariable MR analyses, inverse variance-weighted (IVW), MR‒Egger, and weighted median methods were used to obtain estimates for individual causal power. In addition, heterogeneity and sensitivity analyses were performed to examine the pleiotropy of effect estimates. Finally, multivariable MR analyses were undertaken to disentangle the comparative effects of four platelet indices on BP.

RESULTS

In the univariable MR analyses, increased levels of PLT and PCT were associated with higher BP, and PDW was associated with higher DBP alone. In the reverse direction, SBP had a minor influence on PLT and PCT. In multivariable MR analysis, PDW and PLT revealed an independent effect, whereas the association for PCT and MPV was insignificant after colinear correction.

CONCLUSION

These findings suggest that platelets and BP may affect each other. PDW and PLT are independent platelet indices influencing BP. Increased platelet activation and aggregation may be involved in the pathogenesis of hypertension, which may provide insights into evaluating thromboembolic events in people with high BP. The necessity of initiating antiplatelet therapy among hypertension groups needs further investigation.

Cav 3.2 T-type calcium channel regulates mouse platelet activation and arterial thrombosis

BACKGROUND

Cav 3.2 is a T-type calcium channel that causes low-threshold exocytosis. T-type calcium channel blockers reduce platelet granule exocytosis and aggregation. However, studies of the T-type calcium channel in platelets are lacking.

OBJECTIVE

To examine the expression and role of Cav 3.2 in platelet function.

METHODS

Global Cav 3.2-/- and platelet-specific Cav 3.2-/- mice and littermate controls were used for this study. Western blot analysis was used to detect the presence of Cav 3.2 and activation of the calcium-responsive protein extracellular signal-regulated kinase (ERK). Fura-2 dye was used to assess platelet calcium. Flow cytometry and light transmission aggregometry were used to evaluate platelet activation markers and aggregation, respectively. FeCl3 -induced thrombosis and a microfluidic flow device were used to assess in vivo and ex vivo thrombosis, respectively.

RESULTS

Cav 3.2 was expressed in mouse platelets. As compared with wild-type controls, Cav 3.2-/- mouse platelets showed reduced calcium influx. Similarly, treatment with the T-type calcium channel inhibitor Ni2+ decreased the calcium influx in wild-type platelets. As compared with controls, both Cav 3.2-/- and Ni2+ -treated wild-type platelets showed reduced activation of ERK. ATP release, P-selectin exposure, and αIIb β3 activation were reduced in Cav 3.2-/- and Ni2+ -treated wild-type platelets, as was platelet aggregation. On in vivo and ex vivo thrombosis assay, Cav3.2 deletion caused delayed thrombus formation. However, tail bleeding assay showed intact hemostasis.

CONCLUSION

These results suggest that Cav 3.2 is required for the optimal activation of platelets.

Circulating Extracellular Vesicles Are Strongly Associated With Cardiovascular Risk Markers

Background

Extracellular vesicles (EVs) are submicron membrane-bound vesicles released from various cells, which are emerging as a potential novel biomarker in cardiovascular diseases (CVDs) due to their procoagulatory and prothrombotic properties. However, there is little information about the relationships between circulating EVs and conventional and thrombogenic risk markers of CVDs.

Objective

To investigate the relationships between circulating EVs, conventional cardiovascular risk markers and thrombogenic markers in subjects with moderate risk of CVDs.

Design

Subjects (n = 40) aged 40-70 years with moderate risk of CVDs were recruited and assessed for body mass index, blood pressure and plasma lipid profile, as well as platelet aggregation, clot formation, thrombin generation and fibrinolysis. Numbers of circulating EVs were assessed by Nanoparticle Tracking Analysis and flow cytometry. A range of assays were used to assess the procoagulatory activity of plasma and circulating EVs.

Results

Circulating EV numbers were positively associated with body mass index, blood pressure, plasma triacylglycerol concentration and overall CVD risk. Higher circulating EV numbers were also associated with increased thrombin generation and enhanced clot formation, and EVs isolated from subjects with moderate CVD risk promoted thrombin generation ex vivo. Higher numbers of endothelial-derived EVs were associated with a greater tendency for clot lysis. Plasma triacylglycerol concentration and diastolic blood pressure independently predicted circulating EV numbers, and EV numbers independently predicted aspects of thrombin generation and clot formation and 10-year CVD risk.

Conclusion

Circulating EVs were strongly associated with both conventional and thrombogenic risk markers of CVDs, and also with overall CVD risk, highlighting a potentially important role for EVs in CVDs.

A pilot clinical study to Evaluate Liraglutide-mediated Anti-platelet activity in patients with type-2 Diabetes (ELAID study)

BACKGROUND

Liraglutide is an effective treatment for the management of type 2 diabetes mellitus (T2DM). In addition to glycemic control and potential cardioprotective effects, recent studies suggest a possible role for liraglutide in the inhibition of platelet reactivity, further attenuating atherothrombotic risk in patients with T2DM. We evaluated the in-vivo antiplatelet effect of liraglutide in T2DM patients without macrovascular disease or concurrent anti-platelet therapy.

METHODS

A double-blind, placebo-controlled pilot study of 16 T2DM patients, 51-69 y/o, (mean age 60.4 y/o, 63.0% male) randomised to receive liraglutide (1.8 mg/day) or placebo (saline) for 6 months was conducted. Platelet aggregation studies at baseline and after initiation of the study intervention: days 1, 7, and 14 and months 1, 3 and 6 were performed.

RESULTS

Liraglutide (n = 7) and placebo (n = 9) treated patients demonstrated normal platelet aggregation responses although transient and significant attenuation in maximum slope of platelet aggregation in response to collagen (p ≤ 0.05), arachidonic acid (p ≤ 0.05) and ADP (p ≤ 0.02) was observed in liraglutide compared to placebo treated patients in the first week.

CONCLUSIONS

In this pilot study of patients with T2DM liraglutide treatment was associated with a significant, early and transient decrease in maximum slope of platelet aggregation. The clinical significance of this effect is currently unknown and may warrant further investigation.

CLINICAL TRIAL REGISTRATION NUMBER

UTN 1111-1181-9567.

Elucidation of a Causal Relationship Between Platelet Count and Hypertension: A Bi-Directional Mendelian Randomization Study

Hypertension has been reported as a major risk factor for diseases such as cardiovascular disease, and associations between platelet activation and risk for hypertension are well-established. However, the exact nature of causality between them remains unclear. In this study, a bi-directional Mendelian randomization (MR) analysis was conducted on 15,996 healthy Taiwanese individuals aged between 30 and 70 years from the Taiwan Biobank, recorded between 2008 and 2015. The inverse variance weighted (IVW) method was applied to determine the causal relationship between platelet count and hypertension with single nucleotide polymorphisms as instrumental variables (IVs). Furthermore, to check for pleiotropy and validity of the IVs, sensitivity analyses were performed using the MR-Egger, weighted median and simple median methods. This study provided evidence in support of a positive causal effect of platelet count on the risk of hypertension (odds ratio: 1.149, 95% confidence interval: 1.131-1.578, P < 0.05), using the weighted median method. A significant causal effect of platelet count on hypertension was observed using the IVW method. No pleiotropy was observed. The causal effect of hypertension on platelet count was found to be non-significant. Therefore, the findings from this study provide evidence that higher platelet count may have a significant causal effect on the elevated risk of hypertension for the general population of Taiwan.

Identification of lncRNA-mRNA regulatory network associated with isolated systolic hypertension and atherosclerotic cerebral infarction

Background

Increasingly, evidence has shown that long non-coding RNAs (lncRNAs) play an important role in isolated systolic hypertension (ISH). However, a systematic lncRNA-messenger RNA (mRNA) regulatory network is still absent in isolated systolic hypertension and atherosclerotic cerebral infarction patients (ISH & ACI). This research aimed to establish a lncRNA-mRNA co-expression network in patients with ISH & ACI, to probe into the potential functions of lncRNA in such patients.

Methods

Expression profiles of lncRNA and mRNAs were collected and compared, from 8 patients with ISH and 8 patients with ISH & ACI by RNA-seq data. Differentially expressed lncRNAs and mRNAs were screened out via high-throughput sequencing in the plasma of ISH/ACI patients and control ISH patients. Then, a lncRNA-mRNA interaction network was built using the Pearson correlation coefficient by Cytoscape software. The expression levels of the hub genes and lncRNAs were verified by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in another 10 ISH/ACI patients and 10 control patients. This study was approved by the responsible institutional review board (IRB) and informed consent was provided by participants.

Results

A total of 2,768 differentially expressed lncRNAs and 747 differentially expressed mRNAs were identified. We identified two hub genes (CD226 and PARVB) and 11 lncRNAs in the lncRNA-mRNA interaction network. The results of qRT-PCR and cell assay verified that lncRNAs ENST00000590604 and CD226 are highly expressed in patients of ISH & ACI. Further, CD226 was associated with vascular endothelial cells growth and stability through the platelet activation and focal adhesion pathway.

Conclusions

We established a novel mRNA-lncRNA interaction network. The lncRNAs ENST00000590604 and CD226 might be the potential biomarkers of ISH & ACI.

Association between central non-dipping pattern and platelet morphology in adults with type 1 diabetes without cardiovascular disease: a cross-sectional study

The non-dipping pattern is nighttime systolic blood pressure (SBP) fall of less than 10%. Several studies showed that the non-dipping pattern, increased mean platelet volume (MPV), and platelet distribution width (PDW) are associated with elevated cardiovascular risk. Hypertensives with the non-dipping pattern have higher MPV than the dippers but this relationship was never investigated among people with type 1 diabetes mellitus (T1DM). This study aimed to investigate the association between the central dipping pattern and platelet morphology in T1DM subjects. We measured the central and brachial blood pressure with a validated non-invasive brachial oscillometric device—Arteriograph 24—during twenty-four-hour analysis in T1DM subjects without diagnosed hypertension. The group was divided based on the central dipping pattern for the dippers and the non-dippers. From a total of 62 subjects (32 males) aged 30.1 (25.7–37) years with T1DM duration 15.0 (9.0–20) years, 36 were non-dippers. The non-dipper group had significantly higher MPV (MPV (10.8 [10.3–11.5] vs 10.4 [10.0–10.7] fl; p = 0.041) and PDW (13.2 [11.7–14.9] vs 12.3 [11.7–12.8] fl; p = 0.029) than dipper group. Multivariable logistic regression revealed that MPV (OR 3.74; 95% CI 1.48–9.45; p = 0.005) and PDW (OR 1.91; 95% CI 1.22–3.00; p = 0.005) were positively associated with central non-dipping pattern adjusting for age, sex, smoking status, daily insulin intake, and height. MPV and PDW are positively associated with the central non-dipping pattern among people with T1DM.

Differentially expressed proteins in platelets derived from patients with hypertension

Hypertension (HTN) causes end-organ damage and is a major cause of morbidity and mortality globally. Recent studies suggested blood cells participate in the maintenance of HTN. Platelets—anucleated cell fragments derived from megakaryocytes—exert diverse functions, including their well-characterized role in the formation of hemostatic clots. However, platelets from patients with HTN exhibit altered membrane lipid and protein compositions that impact platelet function and lead to formation of aggregates and vascular obstructions. Here, for the first time, we have identified, by proteomic analyses, the most relevant 11 proteins that show the greatest difference in their expression in platelets derived from patients with HTN, in comparison with those from normotensive individuals. These proteins are involved in cytoskeletal organization and the coagulation cascade that contributes to platelet activation, release of granule contents, and aggregation, which culminate in thrombus formation. These results have important implications in our understanding of the molecular mechanisms associated with the development of HTN, and in consequence, the development of new strategies to counteract the cardiovascular disorders associated with constitutive activation of platelets in HTN.

The Impact of the Renin-Angiotensin-Aldosterone System on Inflammation, Coagulation, and Atherothrombotic Complications, and to Aggravated COVID-19

Atherosclerosis is considered a disease caused by a chronic inflammation, associated with endothelial dysfunction, and several mediators of inflammation are up-regulated in subjects with atherosclerotic disease. Healthy, intact endothelium exhibits an antithrombotic, protective surface between the vascular lumen and vascular smooth muscle cells in the vessel wall. Oxidative stress is an imbalance between anti- and prooxidants, with a subsequent increase of reactive oxygen species, leading to tissue damage. The renin-angiotensin-aldosterone system is of vital importance in the pathobiology of vascular disease. Convincing data indicate that angiotensin II accelerates hypertension and augments the production of reactive oxygen species. This leads to the generation of a proinflammatory phenotype in human endothelial and vascular smooth muscle cells by the up-regulation of adhesion molecules, chemokines and cytokines. In addition, angiotensin II also seems to increase thrombin generation, possibly via a direct impact on tissue factor. However, the mechanism of cross-talk between inflammation and haemostasis can also contribute to prothrombotic states in inflammatory environments. Thus, blocking of the renin-angiotensin-aldosterone system might be an approach to reduce both inflammatory and thrombotic complications in high-risk patients. During COVID-19, the renin-angiotensin-aldosterone system may be activated. The levels of angiotensin II could contribute to the ongoing inflammation, which might result in a cytokine storm, a complication that significantly impairs prognosis. At the outbreak of COVID-19 concerns were raised about the use of angiotensin converting enzyme inhibitors and angiotensin receptor blocker drugs in patients with COVID-19 and hypertension or other cardiovascular comorbidities. However, the present evidence is in favor of continuing to use of these drugs. Based on experimental evidence, blocking the renin-angiotensin-aldosterone system might even exert a potentially protective influence in the setting of COVID-19.

Prevalence and Risk Factors of Childhood Hypertension in Urban-Rural Areas of China: A Cross-Sectional Study

OBJECTIVE

The increased blood pressure level in children and adolescents is recognized as an essential predictor of adulthood cardiovascular disease. This study aimed to ascertain the prevalence and the urban-rural disparity of childhood hypertension in the southwest of China.

METHODS

Using stratified cluster sampling in urban and rural areas, a total of 13597 primary school children aged 6∼12 years living in the Southwest of China were included. The prevalence of hypertension was analyzed. The risk factors were collected by questionnaires, and the risk factors of childhood hypertension were analyzed by the logistic regression model.

RESULTS

The prevalence of hypertension was 13.75%, 9.02%, and 17.47% in total, urban, and rural children, respectively, and the urban-rural difference was 8.44% (95%CI: 7.32%, 9.56%). Children with obesity, maternal gestational hypertension, >10 months of breastfeeding, or low family income had a significantly increased prevalence of hypertension (29.4%, 20.00%, 16.31%, and 16.25%, respectively). Rural residence, intake of more pickle (in rural), maternal gestational hypertension (in urban), low birth weight (in rural), obesity, increased heart rate, and red blood cell counts were the risk factors of childhood hypertension. The adjusted R ² values were 13.61%, 23.25%, 10.88%, 11.12%, 12.23%, and 25.04% in the full models excluding and including serum indexes for total, urban, and rural children, respectively.

CONCLUSIONS

The prevalence of childhood hypertension is significant in the Southwest of China and alarming in rural areas, which requires community intervention. Children living in rural areas combined with obesity, low social economic status, dietary imbalance, and abnormal lipid metabolism were associated with an increased risk of hypertension, and routine care programs should be conducted to prevent childhood hypertension.

Association Between Hypertension, Platelet Reactivity, and the Risk of Adverse Events After Percutaneous Coronary Intervention (From the ADAPT-DES Study)

Hypertension is associated with vascular and endothelial dysfunction that may result in a greater propensity for reactive platelets to cause thrombosis. We sought to assess whether the risk of major adverse cardiac events (MACE) after percutaneous coronary intervention (PCI) in patients with on-clopidogrel residual high platelet reactivity (HPR) varies in patients with versus without hypertension. Assessment of dual antiplatelet therapy with drug eluting stents (ADAPT-DES) was a prospective, multicenter registry of patients successfully treated with coronary drug-eluting stents (DES). HPR was defined as P2Y12 reaction units (PRU) >208, as assessed by the VerifyNow point-of-care assay. Multivariable Cox proportional hazards regression was used to assess whether the adjusted association between HPR and 2-year risk of MACE (cardiac death, myocardial infarction [MI], or stent thrombosis) was different in patients with versus without hypertension. A total of 6833 of 8582 patients (79.6%) had a history of hypertension. Patients with compared with those without hypertension were older, more likely to have other cardiovascular risk factors, and had higher PRU (190.1 ± 97.3 vs 179.5 ± 94.3; p <0.0001). Patients with hypertension had significantly higher 2-year rates of MACE (7.0% vs 4.4%, p <0.001), all-cause death (4.2% vs 2.5%, p = 0.001), and MI (5.2% vs 3.2%, p <0.001), and had nominally higher rates of stent thrombosis (1.0% vs 0.5%, p = 0.059). A significant interaction was present between hypertension and HPR regarding 2-year MACE risk (adjusted hazard ratio for HPR vs no HPR 1.38, 95% confidence interval 1.14 to 1.68 for patients with hypertension vs 0.81, 95% confidence interval 0.50 to 1.33 for patients without hypertension, p = 0.046). In conclusion, following successful PCI with DES, 2-year MACE rates are increased in patients with both hypertension and residual HPR on clopidogrel. HPR had a greater effect on the risk of adverse events among patients with versus without hypertension.

The association between mean platelet volume and inflammation in geriatric patients with emergency hypertension

Objectives

We aimed to investigate the role of inflammation parameters and platelet activation in geriatric patients with hypertension. Therefore, we compared the levels of those parameters in patients with hypertensive urgency and emergency. We also investigated the potential relationship between those parameters.

Methods

Ninety-six hypertensive (HT) patients (aged > 60) were included in the study in two groups: HT emergency (N = 48, group 1) and HT urgency (N = 48, group 2). Mean platelet volume (MPV), neutrophil-to-lymphocyte ratio (NLR) and high-sensitive C reactive protein (hs-CRP) were compared between those groups. Optimum cut-off levels of each parameter were determined by the use of Receiver operating characteristic (ROC) curve analysis. Pearson correlation test was used to examine the relationship between variables.

Results

The mean MPV and hs-CRP levels were significantly higher in patients with HT emergencies (both P < 0.001). Mean NLR was also significantly different between the two groups (P = 0.011). Pearson correlation analysis revealed a positive but weak correlation between the MPV and NLR (r = 0.245, P = 0.016), the hs-CRP level (r = 0.394, P < 0.001), and the WBC count (r = 0.362, P < 0.001).

Conclusion

Increased platelet activity and inflammation are associated with the end organ failure. Levels of MPV and other inflammatory parameters may be useful in the management of geriatric patients with HT.

Chemical composition, vasorelaxant, antioxidant and antiplatelet effects of essential oil of Artemisia campestris L. from Oriental Morocco

BACKGROUND

Artemisia campestris L. (Asteraceae) is a medicinal herb traditionally used to treat hypertension and many other diseases. Hence, this study is aimed to analyze the essential oil of A. campestris L (AcEO) and to investigate the antiplatelet, antioxidant effects and the mechanisms of its vasorelaxant effect.

METHODS

The chemical composition of AcEO was elucidated using GC/MS analysis. Then, the antioxidant effect was tested on DPPH radical scavenging and on the prevention of β-carotene bleaching. The antiplatelet effect was performed on the presence of the platelet agonists: thrombin and ADP. The mechanism of action of the vasorelaxant effect was studied by using the cellular blockers specified to explore the involvement of NO/GC pathway and in the presence of calcium channels blockers and potassium channels blockers.

RESULTS

AcEO is predominated by the volatiles: spathulenol, ß-eudesmol and p-cymene. The maximal antioxidant effect was obtained with the dose 2 mg/ml of AcEO. The dose 1 mg/ml of AcEO showed a maximum antiplatelet effect of, respectively 49.73% ±9.54 and 48.20% ±8.49 on thrombin and ADP. The vasorelaxation seems not to be mediated via NOS/GC pathway neither via the potassium channels. However, pretreatment with calcium channels blockers attenuated this effect, suggesting that the vasorelaxation is mediated via inhibition of L-type Ca²⁺ channels and the activation of SERCA pumps of reticulum plasma.

CONCLUSION

This study confirms the antioxidant, antiplatelet and vasorelaxant effects of A.campestris L essential oil. However, the antihypertensive use of this oil should be further confirmed by the chemical fractionation and subsequent bio-guided assays.

Chemical composition, vasorelaxant, antioxidant and antiplatelet effects of essential oil of Artemisia campestris L. from Oriental Morocco

BACKGROUND

Artemisia campestris L. (Asteraceae) is a medicinal herb traditionally used to treat hypertension and many other diseases. Hence, this study is aimed to analyze the essential oil of A. campestris L (AcEO) and to investigate the antiplatelet, antioxidant effects and the mechanisms of its vasorelaxant effect.

METHODS

The chemical composition of AcEO was elucidated using GC/MS analysis. Then, the antioxidant effect was tested on DPPH radical scavenging and on the prevention of β-carotene bleaching. The antiplatelet effect was performed on the presence of the platelet agonists: thrombin and ADP. The mechanism of action of the vasorelaxant effect was studied by using the cellular blockers specified to explore the involvement of NO/GC pathway and in the presence of calcium channels blockers and potassium channels blockers.

RESULTS

AcEO is predominated by the volatiles: spathulenol, ß-eudesmol and p-cymene. The maximal antioxidant effect was obtained with the dose 2 mg/ml of AcEO. The dose 1 mg/ml of AcEO showed a maximum antiplatelet effect of, respectively 49.73% ±9.54 and 48.20% ±8.49 on thrombin and ADP. The vasorelaxation seems not to be mediated via NOS/GC pathway neither via the potassium channels. However, pretreatment with calcium channels blockers attenuated this effect, suggesting that the vasorelaxation is mediated via inhibition of L-type Ca2+ channels and the activation of SERCA pumps of reticulum plasma.

CONCLUSION

This study confirms the antioxidant, antiplatelet and vasorelaxant effects of A.campestris L essential oil. However, the antihypertensive use of this oil should be further confirmed by the chemical fractionation and subsequent bio-guided assays.

Association between high platelet indices and proteinuria in patients with hypertension

Background

We aimed to determine the association between platelet indices including plateletcrit (PCT), mean platelet volume (MPV), platelet distribution width (PDW), and proteinuria associated with hypertension (HT) as well as the relative power of each to predict proteinuria.

Methods

The study included 223 patients (68 men and 155 women) with primary HT. PCT, MPV, PDW, and proteinuria levels were measured. The patients were divided into two groups according to proteinuria status based on 24-hr urinary protein excretion: proteinuria (+) group (15 men and 40 women) and proteinuria (-) group (53 men and 115 women).

Results

The mean and SD of platelet count, PDW, PCT, and MPV were 278.8±49.6×10⁹/L, 13.5±1.8%, 0.31±0.07%, and 11.3±2.6 fL, respectively. The mean platelet count, PCT, MPV, and PDW were significantly higher in the proteinuria (+) group than in the proteinuria (-) group (P<0.05); there were no significant differences in the other blood parameters between the two groups. The platelet count, PCT, MPV, and PDW were independent risk factors predictive of proteinuria according to a stepwise regression analysis of PDW, PCT, and MPV. PCT was the strongest independent predictor of proteinuria.

Conclusions

The platelet indices PCT, PDW, and MPV were significantly higher in patients with proteinuria than in those without it. Among these three indices, PCT was the strongest predictor of proteinuria.

Diagnostic validity of hematologic parameters in evaluation of massive pulmonary embolism

BACKGROUND

The aim of this study was to determine the hematologic parameter with the highest diagnostic differentiation in the identification of massive acute pulmonary embolism (APE).

METHODS

A retrospective study was performed on patients diagnosing with APE between June 2014 and June 2016. All radiological and laboratory parameters of patients were scanned through the electronic information management system of the hospital. PLR was obtained from the ratio of platelet count to lymphocyte count, NLR was obtained from the ratio of neutrophil count to lymphocyte count, WMR was obtained from white blood cell in mean platelet volume ratio, MPR was obtained from the ratio of mean platelet volume to platelet count, and RPR was obtained from the ratio of red distribution width to platelet count.

RESULTS

Six hundred and thirty-nine patients consisting of 292 males (45.7%) and 347 females (54.3%) were included in the research. Independent predictors of massive risk as compared to sub-massive group were; pulmonary arterial systolic pressure (PASP) (OR=1.40; P=.001), PLR (OR=1.59; P<.001), NLR (OR=2.22; P<.001), WMR (OR=1.22; P<.001), MPR (OR=0.33; P<.001), and RPR (OR=0.68; P<.001). Upon evaluation of the diagnostic differentiation of these risk factors for massive APE by employing receiver operating characteristic curve analysis, it was determined that PLR (AUC±SE=0.877±0.015; P<.001), and NLR (AUC±SE=0.893±0.013; P<.001) have similar diagnostic differentiation in diagnosing massive APE and these two parameters are superior over PASP, MPR, WMR, and RPR.

CONCLUSION

We determined that the levels of NLR and PLR are superior to other parameters in the determination of clinical severity in APE cases.

Effect of Antihypertensive Therapy on Blood Rheology in Patients with Essential Hypertension

Hypertension is an important risk factor for cardiovascular disease, and antihypertensive drugs can decrease the occurrence of such events in hypertensive patients. This study compared the rheological properties of blood in 22 untreated hypertensive patients, 42 patients taking antihypertensive drugs and 74 normotensive subjects. Using a microchannel method, the whole blood passage time was measured and blood movement was observed with a microscope connected to an image display unit. The blood passage time in untreated hypertensive patients was significantly higher than in treated hypertensive patients or normotensive subjects, but was similar in the latter two groups. Microscopic observations showed that platelet aggregation and leucocyte adhesion were increased in untreated hypertensive patients, resulting in poor flow, while blood samples from treated hypertensive patients and normotensive subjects passed smoothly through the microchannels. These rheological differences could contribute to the decrease in cardiovascular disease seen when hypertensive patients are treated effectively.

Pharmacological interventions into the renin-angiotensin system with ACE inhibitors and angiotensin II receptor antagonists: effects beyond blood pressure lowering

Hypertension is recognized as an important risk factor for cardiovascular morbidity and mortality. Lowering of blood pressure has been shown to minimize the risk of cardiovascular events, with the majority of antihypertensives demonstrating a similar ability to reduce coronary events and stroke for a given reduction in blood pressure. Agents that modify the activity of the renin-angiotensin system (RAS) have been proposed to exhibit additional effects that might go beyond simple blood pressure lowering. The RAS is a crucial system that regulates extracellular fluid volume and blood pressure. Proposed potential benefits of RAS blockade that go beyond blood pressure lowering include a reduction in platelet aggregation and thrombosis, blunting of cardiac and vascular remodeling, favorable metabolic effects and reno- and cerebro-protection. However, factors such as treatment adherence, duration of action of antihypertensive agents and differences in effects on central versus brachial blood pressure may also result in apparent differences in efficacy of different antihypertensives. The aim of this review article is to examine the available data from clinical studies of antihypertensive drugs for evidence of effects that might legitimately be claimed to go beyond simple blood pressure lowering.

Effect of β-blockers on platelet aggregation: a systematic review and meta-analysis

AIMS

Platelets play an important role in cardiovascular disease, and β-blockers are often prescribed for cardiovascular disease prevention. β-Blockers may directly affect platelet aggregation, because β-adrenergic receptors are present on platelets. There is uncertainty about the existence and magnitude of an effect of β-blockers on platelet aggregation. The aim of this study was to perform a systematic review and meta-analysis of the effect of β-blockers on platelet aggregation.

METHODS

MEDLINE and EMBASE were searched until April 2014. Two reviewers independently performed data extraction and risk of bias assessment. Type of β-blocker, population, treatment duration and platelet aggregation were extracted. Standardized mean differences were calculated for each study and pooled in a random-effects meta-analysis.

RESULTS

We retrieved 31 studies (28 clinical trials and three observational studies). β-Blockers decreased platelet aggregation (standardized mean difference -0.54, 95% confidence interval -0.85 to -0.24, P < 0.0001). This corresponds to a reduction of 13% (95% confidence interval 8-17%). Nonselective lipophilic β-blockers decreased platelet aggregation more than selective nonlipophilic β-blockers.

CONCLUSIONS

Clinically used β-blockers significantly reduce platelet aggregation. Nonselective lipophilic β-blockers seem to reduce platelet aggregation more effectively than selective nonlipophilic β-blockers. These findings may help to explain why some β-blockers are more effective than others in preventing cardiovascular disease.

Assessment of Mean Platelet Volume in Patients with Resistant Hypertension, Controlled Hypertension and Normotensives

OBJECTIVE

Patients with resistant hypertension are at increased risk for cardiovascular events. Mean platelet volume (MPV) is an accepted biomarker of platelet activation and considered as a risk factor for cardiovascular disease. The aim of this study was to determine whether MPV levels are higher in resistant hypertensive (RHTN) patients than in controlled hypertensive (CHTN) patients and healthy normotensive controls.

MATERIALS AND METHODS

279 consecutive patients were included in this study. Patients were divided into three groups: Resistant hypertension patient group [n=78; mean age 56.8±9.8; 42 males (53.8%)]; controlled hypertension patient group [n=121; mean age 54.1±9.6; 49 males (40.5%)]; and normotensive control group [n=80; mean age 49.8±8.5; 34 males (42.5%)]. Physical examination, laboratory work-up, and 24-hour ambulatory blood pressure measurement (ABPM) were performed in all participants.

RESULTS

The mean platelet volume levels were significantly higher in RHTN group than in the CHTN and normotensive groups (p<0.001). In correlation analysis office systolic and diastolic blood pressure was positively correlated with MPV.

CONCLUSION

Our study demonstrated that MPV, as an important indicator of platelet activation, was statistically higher in RHTN patients than in CHTN and in normotensive subjects. Elevated MPV levels may help to determine a high risk group for atherosclerosis in RHTN patients.

Assessment of mean platelet volume and soluble CD40 ligand levels in patients with non-dipper hypertension, dippers and normotensives

Abstract Objective: Patients with a lack of nocturnal decline in blood pressure (BP) are at an increased risk for cardiovascular events. Mean platelet volume (MPV) and soluble CD40 ligand (sCD40L) are accepted biomarkers of platelet activation and considered as a risk factor for cardiovascular disease. The aim of this study was to determine whether MPV and sCD40L levels are higher in non-dipper hypertensive (NDHT) patients than in dipper hypertensive (DHT) patients and healthy controls.

METHODS

124 consecutive patients were included to this study. Patients were divided into three groups: NDHT patient group [n = 43; mean age 51.8 ± 6.6; 31 males (72.1%)]; DHT patient group [n = 41; mean age 50.2 ± 7.3; 22 males (53.7%)]; and normotensive group [n = 40; mean age 49.9 ± 6.7; 22 males (55%)]. Physical examination, laboratory work-up and 24-h ABPM were performed for all participants.

RESULTS

The sCD40L and MPV levels were significantly higher in the NDHT group than in the DHT and normotensive groups (p < 0.05). In correlation analysis, MPV, 24-h systolic blood pressure (SBP), 24-h diastolic blood pressure (DBP), night-time SBP and night-time DBP were positively correlated with sCD40L.

CONCLUSION

Our study demonstrated that MPV and sCD40L levels were significantly higher in NDHT patients compared to DHT and normotensive patients. sCD40L levels were positively correlated with MPV, 24-h SBP, 24-h DBP, night-time SBP and night-time DBP.

New marker of platelet activation, SCUBE1, is elevated in hypertensive patients

BACKGROUND

Hypertension is associated with an increase in platelet activation and endothelial dysfunction and leads to a tendency to cardiovascular events (CVEs). Signal peptide-CUB-EGF domain-containing protein 1 (SCUBE1) is a novel platelet activation marker. There are currently no studies showing the level of SCUBE1 in hypertensive patients. The purpose of this study was to determine the level of SCUBE1 in this patient group and to investigate the parameters affecting that level.

METHODS

Forty-five newly diagnosed, untreated, stage 1 hypertensive patients and 21 healthy individuals were included. Blood specimens were collected to determine SCUBE1, soluble CD40 ligand, prothrombin time, partial thromboplastin time, fibrinogen, D dimer, hemogram, lipid parameters, blood urea nitrogen, creatinine, and uric acid levels. The relation between SCUBE1 level and demographic data and biochemical parameters was then investigated.

RESULTS

SCUBE1 and sCD40L levels obtained from plasma specimens from the hypertensive group were significantly higher than those of the control group (P < 0.001; P < 0.05, respectively). Hypertensive group blood pressure (BP) values and uric acid, low-density lipoprotein, total cholesterol, and triglyceride levels were also statistically higher than those of the control group. Parameters affecting SCUBE1 levels were systolic and diastolic BP, sCD40L, lipid parameters, and uric acid levels.

CONCLUSIONS

We show elevated levels of SCUBE1, a novel platelet activation marker, in primary hypertensive patients. We think that, when supported by further clinical studies, this newly described marker may be useful in the monitoring of CVEs in this patient group, in which platelet activation is known to be associated with such events.

Vascular and platelet responses to aspirin in patients with coronary artery disease

BACKGROUND

Variability in the response to aspirin (sometimes known as aspirin resistance) in modulating platelet activity is a potentially important clinical issue in coronary artery disease (CAD), but may be also be important in other areas of pathophysiology.

MATERIALS AND METHODS

Testing the hypothesis of a relationship between aspirin resistance and vascular function, inflammation and coagulation, we recruited 175 stable CAD outpatients taking 75 mg aspirin daily. Indices were compared to 58 controls not taking aspirin. Platelet activity was assessed by light transmission aggregometry (LTA) to 0·5 mg/mL arachidonic acid (AA), plasma markers soluble P selectin and thromboxane (ELISA), and resting and AA stimulated membrane P selectin and PAC-1 expression (flow cytometry). Vascular function was assessed by arterial stiffness (Sphygmocor system), von Willebrand factor and soluble E selectin (ELISA), inflammation by high sensitivity CRP and interleukin-6, and coagulation by tissue factor and fibrin d-dimers levels (all immunoassay).

RESULTS

The 5-min LTA response AA was superior to flow cytometry in discriminating the response of platelets to aspirin. Using the cut-off of 20% LTA response to AA, 32·6% of patients were aspirin resistant. The latter had higher soluble P selectin (P = 0·03), CRP (P = 0·029) and fibrin d-dimers (P = 0·01) compared to those who were aspirin sensitive. There was no relationship between aspirin response status and any vascular index.

CONCLUSION

We conclude that LTA is a more sensitive marker of aspirin resistance than is flow cytometry for P-selectin and PCA-1, and that aspirin response has no influence on vascular function.

The mean platelet volume and atherogenic index of plasma in nondipper normotensive individuals compared to dippers

Mean platelet volume (MPV) is a determinant of platelet activation. Atherogenic index of plasma (AIP), which is defined as the logarithm of the ratio of plasma level of triglycerides to the level of high-density lipoprotein (HDL)-cholesterol (log[ TG/HDL-C]), has recently been used as a marker of atherogenicity. This study included 104 normotensive individuals. Mean platelet volume and AIP were measured in all patients. Nondipper individuals (8.6 ± 0.9 fL, 0.3 ± 0.2) demonstrated higher values of MPV and AIP compared with dippers (7.9 ± 1.1 fL, 0.1 ± 0.2) (P < .001 and < .001, respectively). Mean platelet volume and AIP have a positive correlation with insufficient decline in nocturnal blood pressure.

Potential pharmacodynamic drug-drug interaction between concomitantly administered lisinopril and diclofenac sodium: a call for appropriate management in hypertensive osteoarthritic patients

BACKGROUND

The present study was designed as an open label, multiple-dose, randomized, parallel trial to evaluate the pharmacodynamic drug-drug interaction of lisinopril and concomitantly administered diclofenac sodium in non-diabetic and diabetic, mild to moderate hypertensive, osteoarthritic patients.

METHODS

Post-screening and on inclusion, patients were put on a 2-week washout period and then randomly assigned to either only lisinopril 10 mg or combination of lisinopril 10 mg and diclofenac sodium 100 mg treatments for 8-12 weeks in diseased states of hypertension and osteoarthritis with or without type 2 diabetes mellitus.

RESULTS

The blood pressure (BP) control with lisinopril was reduced by concomitantly administered diclofenac sodium in non-diabetic (SBP: p=0.00002; DBP: p=0.000008) and diabetic (SBP: p=0.002; DBP: p=0.001) patients when compared with the patients receiving lisinopril alone. Insulin sensitivity was improved (p=0.00002) and urinary albumin excretion rate was better controlled (p=0.0096) in lisinopril-treated patients when compared with the combination treatment in diabetic pool. Serum creatinine levels increased significantly in non-diabetic patients (p=0.00004) receiving combination treatment. In addition, creatinine clearance (CLCR) and blood urea nitrogen (BUN) were significantly higher in diabetic (CLCR: p<0.00001; BUN: p=0.0098) as well as in non-diabetic (CLCR: p<0.00001; BUN: p=0.03) patients treated with combination treatment. The alterations in serum electrolytes, reduction in % platelet aggregation activity and improvement in lipid profile was more profound with combination treatment in comparison to lisinopril alone.

CONCLUSIONS

The antihypertensive efficacy and insulin sensitivity improving property of lisinopril along with the renal function might get worse in hypertensive osteoarthritic patients receiving concomitant treatment of oral diclofenac sodium with lisinopril. In addition to this, close monitoring of serum electrolytes is also suggested to rule out any long-term detrimental effect.

Endothelin attenuates endothelium-dependent platelet inhibition in man

AIM

The vascular endothelium produces several substances, including nitric oxide (NO) and endothelin-1 (ET-1), which participate in the regulation of vascular tone in humans. Both these substances may exert other actions of importance for cardiovascular disease, e.g. effects on vascular smooth muscle cell proliferation and inflammation, and NO inhibits platelet function. Experiments were designed to investigate the effect of ET-1 on endothelium-dependent vasodilatation and attenuation of platelet activation.

METHODS

In 25 healthy male subjects (25 +/- 1 years), forearm blood flow was measured by venous occlusion plethysmography, and platelet activity was assessed by whole blood flow cytometry (platelet fibrinogen binding and P-selectin expression) in unstimulated and adenosine diphosphate (ADP)-stimulated samples during administration of ET-1, the endothelium-dependent vasodilator acetylcholine and the NO synthase inhibitor l-NMMA.

RESULTS

Acetylcholine increased forearm blood flow and significantly inhibited platelet activation in both unstimulated and ADP-stimulated samples. In samples stimulated with 0.3 microm ADP, fibrinogen binding decreased from 41 +/- 4% to 31 +/- 3% (P < 0.01, n = 11) after acetylcholine administration. The vasodilator response to acetylcholine was significantly impaired during infusions of ET-1 and l-NMMA. ET-1 did not affect platelet activity per se, whereas l-NMMA increased platelet P-selectin expression. Both ET-1 and l-NMMA attenuated the acetylcholine-induced inhibition of platelet activity.

CONCLUSIONS

Our study indicates that, further to inhibiting endothelium-dependent vasodilatation, ET-1 may also attenuate endothelium-dependent inhibition of platelet activation induced by acetylcholine. An enhanced ET-1 activity, as suggested in endothelial dysfunction, may affect endothelium-dependent platelet modulation and thereby have pathophysiological implications.

Platelet activation in essential hypertension: implications for antiplatelet treatment

Essential hypertension is associated with increased risk of arterial thrombotic disease. Among other factors, enhanced platelet activity contributes significantly to this phenomenon. An increased level of circulating monocyte-platelet aggregates (MPAs) represents one of the most robust markers of platelet activation; furthermore, these aggregates are also believed to contribute to the pathophysiology of atherothrombotic disease. Putative mechanisms that contribute to platelet activation in essential hypertension include endothelial dysfunction, neurohumoral (sympathetic and renin-angiotensin systems) overactivity, decreased platelet nitric oxide (NO) biosynthesis, and platelet degranulation secondary to increased shear. Current recommendations are that hypertensive patients receive aspirin therapy only if their calculated cardiovascular risk is high and their blood pressure (BP) is adequately controlled. By contrast, the use of antiplatelet treatment in low-risk hypertensive patients is not established and merits further investigation. Moreover, the place of alternative antiplatelet agents other than aspirin, such as clopidogrel, is unclear at present. Some experimental evidence suggests that clopidogrel may confer an additive protective effect over and above aspirin in hypertensive patients, by virtue of effects on the evolution of the atherosclerotic process. This now needs to be investigated in long-term clinical outcome studies.

The interaction of vasoactive substances during exercise modulates platelet aggregation in hypertension and coronary artery disease

Background

Acute vigorous exercise, associated with increased release of plasma catecholamines, transiently increases the risk of primary cardiac arrest. We tested the effect of acute submaximal exercise on vasoactive substances and their combined result on platelet function.

Methods

Healthy volunteers, hypertensive patients and patients with coronary artery disease (CAD) performed a modified treadmill exercise test. We determined plasma catecholamines, thromboxane A₂, prostacyclin, endothelin-1 and platelet aggregation induced by adenosine diphosphate (ADP) and collagen at rest and during exercise.

Results

Our results during exercise showed a) platelet activation (increased thromboxane B₂, TXB₂), b) increased prostacyclin release from endothelium and c) decreased platelet aggregation in all groups, significantly more in healthy volunteers than in patients with CAD (with hypertensives lying in between these two groups).

Conclusion

Despite the pronounced activation of Sympathetic Nervous System (SNS) and increased TXB₂ levels during acute exercise platelet aggregation decreases, possibly to counterbalance the prothrombotic state. Since this effect seems to be mediated by the normal endothelium (through prostacyclin and nitric oxide), in conditions characterized by endothelial dysfunction (hypertension, CAD) reduced platelet aggregation is attenuated, thus posing such patients in increased risk for thrombotic complications.

Vascular endothelial functions, carotid intima-media thickness, and soluble CD40 ligand levels in dipper and nondipper essential hypertensive patients

OBJECTIVE

The lack of nocturnal decline in blood pressure (BP) is associated with an increase in cardiovascular events. Soluble CD40 ligand (sCD40L) is involved in the pathogenesis of risk factor-related vascular damage. The purpose of this study was to examine the relationship between vascular endothelial functions, carotid intima-media thickness (cIMT), plasma sCD40L levels and circadian BP profile in patients with essential hypertension.

MATERIAL AND METHODS

The study population consisted of 81 essential hypertensive out-patients. BP dipping was defined as a night-to-day systolic and diastolic decrease >or=10%. Forty-seven dipper and 34 nondipper patients were compared. High sensitivity C-reactive protein (hs-CRP), sCD40L and urinary albumin were measured. Brachial artery flow-mediated dilatation (FMD) and cIMT was compared between the groups.

RESULTS

sCD40L level (3.28 +/- 2.08 and 2.30 +/- 1.99 ng/ml, respectively, P = 0.036) and urinary albumin concentration (36.7 +/- 20.1 and 23 +/- 29.7 mg/l, respectively, P < 0.0001) were higher in nondippers than in dippers. Serum hs-CRP levels were not significantly different. FMD was found higher in dippers than nondippers (11.8 +/- 3.9% and 6.6 +/- 2.2%, respectively, P < 0.0001). The average cIMT was significantly higher in nondippers than dippers (0.928 +/- 0.060 Vs. 0.734 +/- 0.134 mm; P < 0.0001).

CONCLUSIONS

Nondipper patern has an additional negative effect on endothelial functions in hypertensive patients. Nondippers have enhanced sCD40L levels, which may contribute to their increased susceptibility to develop vascular damage.

Association of low-grade inflammation and platelet activation in patients with hypertension with microalbuminuria

Increased levels of sCD40L (soluble CD40 ligand) have been associated with enhanced in vivo platelet activation, and may represent a molecular link between inflammation and a prothrombotic state. The aim of the present study was to analyse the relationship between platelet activation, endothelial dysfunction, low-grade inflammation and sCD40L in patients with hypertension with or without MA (microalbuminuria). A cross-sectional comparison of sCD40L levels was performed in 25 patients with MH (essential hypertension with MA) pair-matched for gender and age with 25 patients with EH (essential hypertension) and 25 HS (healthy subjects with normotension). Circulating levels of CRP (C-reactive protein), a marker of inflammation, sP-selectin (soluble P-selectin), a marker of in vivo platelet activation, and ADMA (asymmetric dimethylarginine) and vWF (von Willebrand factor), markers of endothelial dysfunction, were analysed in each subject. sCD40L levels were increased in patients with MH compared with either patients with EH (P<0.001) or HS (P<0.0001). A highly significant correlation between plasma sCD40L and sP-selectin (P<0.0001), vWF (P<0.001) or CRP levels (P<0.05) was observed in patients with MH. Multivariate regression analysis showed that sP-selectin was the strongest independent predictor of sCD40L levels (P<0.0001) in patients with MH. Patients with hypertension with both vWF and CRP levels above the median had the highest sCD40L levels (P<0.0001). Factorial ANOVA of all of the patients with hypertension confirmed that only patients with MH with low-grade inflammation had elevated levels of sCD40L. In conclusion, sCD40L levels appear to discriminate a subset of patients characterized by MA and low-grade inflammation, suggesting that inhibition of the CD40/CD40L system may represent a potential therapeutic target in subjects with hypertension at a high risk of cardiovascular events.

Plasma serotonin levels and the platelet serotonin transporter

Serotonin (5HT) is a platelet-stored vasoconstrictor. Altered concentrations of circulating 5HT are implicated in several pathologic conditions, including hypertension. The actions of 5HT are mediated by different types of receptors and terminated by a single 5HT transporter (SERT). Therefore, SERT is a major mechanism that regulates plasma 5HT levels to prevent vasoconstriction and thereby secure a stable blood flow. In this study, the response of platelet SERT to the plasma 5HT levels was examined within two models: (i) in subjects with chronic hypertension or normotension; (ii) on platelets isolated from normotensive subjects and pretreated with 5HT at various concentrations. The platelet 5HT uptake rates were lower during hypertension due to a decrease in Vmax with a similar Km; also, the decrease in Vmax was primarily due to a decrease in the density of SERT on the platelet membrane, with no change in whole cell expression. Additionally, while the platelet 5HT content decreased 33%, the plasma 5HT content increased 33%. Furthermore, exogenous 5HT altered the 5HT uptake rates by changing the density of SERT molecules on the plasma membrane in a biphasic manner. Therefore, we hypothesize that in a hypertensive state, the elevated plasma 5HT levels induces a loss in 5HT uptake function in platelets via a decrease in the density of SERT molecules on the plasma membrane. Through the feedback effect of this proposed mechanism, plasma 5HT controls its own concentration levels by modulating the uptake properties of platelet SERT.

The effects of angiotensin II and genetic hypertension upon extracellular nucleotide hydrolysis by rat platelet ectoenzymes

The extracellular nucleotides, ATP and ADP, as well as adenosine have been implicated in a great number of physiological functions. ADP is one of the major platelet recruiting factors, whereas ATP is considered to be a competitive inhibitor of ADP-induced platelet aggregation and adenosine is able to induce vasodilatation and to inhibit platelet aggregation. The di- and triphosphate nucleosides can be hydrolyzed by members of several families of ectonucleotidases, including ecto-nucleoside triphosphate diphosphohydrolases (E-NTPDases) and ecto-nucleotide pyrophosphatase/phosphodiesterases (E-NPPs) that, together with an ecto-5'-nucleotidase, catalyze adenosine formation. The renin-angiotensin system is the most important regulator of renal and cardiovascular functions and angiotensin II induces, physiologically, platelet activation. The aim of this study was to clarify the effects of ANGII and genetic hypertension upon extracellular nucleotide hydrolysis by rat platelet ectoenzymes. ANGII, in all tested doses (5, 50, 500 and 5000 pmol), was able to increase ATP (21, 31, 44 and 27%, respectively), ADP (22, 28, 78 and 37%, respectively) and AMP (40, 64, 60 and 64%, respectively) hydrolysis by rat platelets. Furthermore, losartan, a specific antagonist of the AT1 angiotensin-receptor, prevented the nucleotide hydrolysis effects. Additionally, an increase in AMP (about 144%) hydrolysis and a decrease in p-Nph-5'TMP (about 27%) hydrolysis were observed in platelets from spontaneously hypertensive rats (SHR) when compared to Wistar normotensive rats. We, herein, present data to demonstrate interactions between rat platelet angiotensinergic and adenosinergic systems that could contribute to the understanding and treatment of cardiovascular diseases such as hypertension, thrombosis and arteriosclerosis.

Effects of nebivolol on platelet activation in hypertensive patients: A comparative study with metoprolol

OBJECTIVES

We evaluated the effects of nebivolol on platelet activation in hypertensive patients by measuring mean platelet volume (MPV) and plasma soluble P-selectin (sP-sel) levels and compared with those of the patients taking metoprolol.

MATERIALS AND METHODS

Eighty newly diagnosed hypertensive patients in grade 1 hypertension were enrolled in this prospective, blinded randomized study. Seventy two patients completed the study. After baseline assessment, each patient was randomly allocated to 5 mg daily dose of nebivolol (n=37, 20 male) or 100 mg daily dose of metoprolol (n=35, 18 male) and treated for 6 months. Blood pressure, heart rate, lipid profile, plasma glucose, sP-selectin levels, platelet counts and MPV were measured before and after treatment.

RESULTS

At the end of 6 months, nebivolol significantly decreased MPV and plasma sP-selectin levels (7.59+/-0.78 fl vs. 7.42+/-0.74 fl, p<0.001; 1.29+/-0.46 ng/ml vs. 1.21+/-0.36 ng/ml, p=0.002, respectively) compared to those of pretreatment. Although pretreatment sP-selectin levels of the two groups were similar, posttreatment plasma sP-selectin levels were significantly reduced with nebivolol compared with those of metoprolol group (1.21+/-0.36 ng/ml vs. 1.46+/-0.30 ng/ml, p=0.008). In contrast, metoprolol treatment did not cause any significant change in platelet activation parameters after treatment.

CONCLUSION

Beneficial effects of nebivolol on platelet activation were more potent than those of metoprolol. We consider that decreased platelet activation with nebivolol might play a role to reduce thrombotic risk in hypertensive patients.

Elevated platelet P-selectin expression and platelet activation in high risk patients with uncontrolled severe hypertension

BACKGROUND

Uncontrolled severe hypertension is associated with alarming rates of cardiovascular events but the mechanisms of vascular injury are not well understood. Recent investigative interest has focused on platelet activation and platelet P-selectin (CD62P) as direct mediators of vascular inflammation and injury. We investigated the association of extreme blood pressure (BP) elevation with platelet P-selectin and fibrinolytic markers in high risk patients with severe hypertension.

METHODS

Cross-sectional comparison of platelet CD62, tissue plasminogen activator antigen (tPA), and plasminogen activator inhibitor-1 activity (PAI-1) among 3 BP groups: untreated severely hypertensive patients (SHT; n=18), untreated mildly hypertensive patients (MHT; n=19), and normotensive controls (NT; n=16).

RESULTS

Platelet CD62 was greatest in SHT (p=0.00008) and showed a strong correlation with both systolic (p=0.0002, r=0.52) and diastolic (p=0.0003, r=0.52) BP. tPA was greater in SHT than MHT or NT (ANOVA; p=0.02) and correlated with diastolic BP but not SBP. PAI-1 did not correlate with either SBP or DBP but was related to body mass index, diabetes, and dyslipidemia.

CONCLUSIONS

Platelet CD62 demonstrated a strong and graded association with both systolic and diastolic BP that persisted in the presence of multiple concomitant risk factors. The association of BP with CD62P was stronger than with either PAI-1 or tPA-Ag. Platelet activation and platelet CD62 increase in a BP-dependent manner and this relationship persists at extreme levels of BP. Platelet activation and platelet CD62 may participate in the accelerated target organ injury observed in high risk patients with severe hypertension.

Effect of doxazosin gastrointestinal therapeutic system on platelet degranulation and platelet-leukocyte microaggregate formation induced by physiologic shear stress in hypertension

INTRODUCTION

In this prospective, ex vivo, single-blind study, the effect of doxazosin on platelet function was studied in patients with hypertension.

MATERIALS AND METHODS

Platelet activation by shear stress was measured in whole blood samples of 22 hypertensive patients and 22 normotensive controls, using flow cytometry. Sheared samples were evaluated for CD62 expression, microaggregate formation, and Ca2+ mobilization. Results were collected at baseline and after 1 and 2 months of single-dose (4 mg/d) extended-release doxazosin gastrointestinal therapeutic system therapy.

RESULTS

Doxazosin normalized blood pressure in hypertensive patients after 1 and 2 months of treatment. Hypertensive patients had a higher baseline percentage (mean+/-SD) of degranulated platelets (CD62+) than the normotensive control group (4.14+/-1.05 vs. 2.47+/-0.68, P<0.01). After 2 months of doxazosin gastrointestinal therapeutic system treatment, the percentage of CD62+ in the experimental group significantly decreased (P<0.05). At baseline, the number of platelet-leukocyte aggregates in vivo was greater in hypertensive patients (P<0.01); doxazosin did not normalize this measurement. Following shearing, platelet expression of CD62 increased significantly in the hypertensive group (P<0.001 vs. control). Shear stress-induced platelet activation and microaggregate formation were also greater in hypertensive patients. Intraplatelet-free calcium concentration was higher in hypertensive patients at baseline than in the normotensive group (P<0.001). At 2 months, doxazosin significantly reduced thrombin-stimulated Ca2+ mobilization in hypertensive patients (P<0.01 vs. baseline).

CONCLUSIONS

Platelets from hypertensive patients are more readily activated by shear stress and demonstrate significant alterations in cytoplasmic-free calcium mobilization. Doxazosin treatment reduced blood pressure and normalized alterations in platelet function.