Superoxide dismutase and catalase anti-oxidant activity in leucocyte lysates from hypertensive patients: effects of eprosartan treatment.

INTRODUCTION: In an earlier study, our group reported that circulating leucocytes in hypertensive (HT) patients show a significant increase in oxidative stress compared to the control group, and this normalised after two months of treatment with eprosartan.(1) It can be speculated that these facts may be attributable to a possible reduction in anti-oxidative activity in untreated HT patients, which would be corrected by eprosartan. MATERIALS AND METHODS: In this observational pilot study, superoxide dismutase and catalase activities were evaluated in leucocyte lysates in a group of 21 HT patients at baseline and after two months of treatment with eprosartan (600 mg/ day). For the control group, 25 normotensive volunteers were recruited with comparable characteristics to the patients. RESULTS: The results obtained indicate, paradoxically, that the untreated HT patients present greater anti-oxidant enzyme activity than the control group. CONCLUSION: This result could be interpreted as a cell defence mechanism against the greater oxidative stress that exists in these patients.This hypothesis is consistent with the facts reported previously by our group in which a reduction in oxidative stress was found after two months of treatment with eprosartan.( 1) Upon reducing this stress, less anti-oxidative activity would be necessary, just as was observed in the present study after two months of treatment with eprosartan.

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.

Effect of atorvastatin upon platelet activation in hypercholesterolemia, evaluated by flow cytometry.

Hyperlipidemia is a well established risk factor for cardiovascular disease and atherothrombotic events, in which platelet activation also plays a significant role. However, very few studies have addressed platelet activation in hypercholesterolemia, the potential effect of lipid lowering drugs upon platelet hyperfunction, and the question of whether changes in the latter are correlated to normalization of plasma lipids. This study used whole blood flow cytometry to assess in vivo and in vitro platelet activation in a group of 33 patients with hypercholesterolemia, and also the ex vivo effect of atorvastatin (20 mg/day) upon such activation. A control group of 40 normolipidemic volunteers matched in terms of age, sex and added risk factors to the patient group was used. The results showed that hypercholesterolemic patients had in vivo a significantly greater percentage of GPIIb/IIIa- and phosphatidylserine-positive platelets compared with the control group (4.62+/-3.51% and 2.58+/-1.19% versus 2.73+/-1.08% and 1.54+/-0.68%, respectively). In vitro response of CD62 expression to thrombin was also greater in the patients than in the controls (92.51+/-6.00% versus 89.63+/-10.72%, p<0.05). Atorvastatin therapy normalized platelet hyperfunction in the patients studied and reduced GPIIb/IIIa response to ADP (from 82.65+/-6.43% to 75.84+/-4.89%, p<0.01). A significant correlation can be seen between such normalization and the decrease in plasma levels of total and LDL cholesterol.

Effect of eprosartan on cytoplasmic free calcium mobilization, platelet activation, and microparticle formation in hypertension.

BACKGROUND: Hypertensive patients show greater platelet activation than do normotensive individuals. Platelet activation is characterized by increased phosphatidylserine (PS) exposure in the external hemilayer of the membrane, a larger number of platelet microparticles (PMP), and changes in intraplatelet-free calcium kinetics. This study evaluated whether eprosartan can protect against undesirable platelet activation. METHODS: A total of 30 hypertensive patients (systolic blood pressure [SBP] 140 to 189 mm Hg; diastolic blood pressure [DBP] 90 to 109 mm Hg) without renal, liver, or cardiac organic lesions and with a mean age of 47.6 +/- 9.4 years and mean body mass index (BMI) of 27.9 +/- 3.9 kg/m2 received eprosartan (600 mg/day). They were compared with 31 normotensive individuals with a mean age of 43.3 +/- 6.7 years and a mean BMI of 26.8 +/- 3.9 kg/m2. Blood pressure measurements and platelet function changes were assessed at baseline (control and hypertensive patients) and after 1 and 2 months of eprosartan monotherapy (hypertensive patients only). RESULTS: Significant baseline to endpoint (month 2) changes in SBP and DBP were noted in the eprosartan group (SBP: baseline 152.2 +/- 16.8 mm Hg, endpoint 142.2 +/- 16.9 mm Hg, P <.01; DBP: baseline 93.5 +/- 9.9 mm Hg, endpoint 85.8 +/- 11.9 mm Hg, P <.001). Native circulating activated platelets increased in both groups after shear stress or Ca2+ ionophore activation, and were reduced by eprosartan (after shear exposure from 104% at month 1 to 76% after 2 months of therapy). Eprosartan therapy normalized the number of microparticles after blood shear exposure (P <.01) and after exposure to Ca2+ ionophore activation (P <.05) and significantly reduced the trend for platelets to be more readily activated in hypertensive compared with normotensive subjects (baseline to endpoint change P <.001; increase/shear versus baseline P <.001). Eprosartan partially normalizes cytoplasmic-free calcium mobilization in platelets. CONCLUSIONS: Eprosartan significantly reduces blood pressure and normalizes undesirable changes in platelet function.

Flow cytometric analysis of platelet activation in hypertensive patients. Effect of doxazosin.

The percentage of spontaneously activated platelets and the platelet response to several agonists were studied in 26 hypertensive patients. The percentage of platelets expressing glycoprotein (GP) IIb/IIIa in its active conformation (GPIIb/IIIa*), P-selectin and phosphatidylserine (PS) was measured by flow cytometry at baseline and 1 and 2 months after treatment with doxazosin (4 mg/day). The response to ADP and Ca2+ ionophore was also evaluated. The results were compared with those of a control group of 71 normotensive volunteers. Spontaneous platelet activation was higher in patients than in controls (P-selectin-positive results in 4.4+/-2.0% patients vs. 2.7+/-1.7 controls, p<0.05; phosphatidylserine-positive results in 0.7+/-0.4% vs. 0.5+/-0.3%, respectively, p<0.05), and higher in response to ionophore action (phosphatidylserine-positive results 51.8+/-11.1% vs. 43.4+/-11.7%, p<0.01). Platelet activation in patients decreased after 2 months of doxazosin administration compared to baseline (P-selectin-positive results 2.7+/-1.4% vs. 4.4+/-2.0%, p<0.05; phosphatidylserine-positive results 0.3+/-0.2% vs. 0.7+/-0.4%, p<0.05). No significant differences were noted in GPIIb/IIIa*. The clinical significance of normalization of platelet activity by doxazosin remains to be established.

Cytoplasmic free calcium mobilization in platelets, expression of P-selectin, phosphatidylserine, and microparticle formation, measured by whole blood flow cytometry, in hypertensive patients. Effect of doxazosin GITS.

The effects of doxazosin on expression of CD62 (P-selectin) and phosphatidylserine on platelet membrane and platelet calcium flux were studied in 50 uncomplicated essential hypertensive patients (World Health Organization stages 1-2) and 80 normotensive control subjects, matched for age, sex, and cardiovascular risk factors. Hypertensive patients showed greater in vivo platelet activation at baseline than control patients (percentage of CD62-positive platelets, 4.1+/-2.2% versus 2.4+/-1.5%, p<0.001; percentage of phosphatidylserine-positive platelets, 0.8+/-0.5% versus 0.5+/-0.3%, p<0.001). Increased platelet activation was associated with significant changes in the mobilization of free intraplatelet calcium, evaluated by a whole blood flow cytometric kinetic method. With this method, an arbitrary Ca(2+) mobilization index was defined as the ratio of cytoplasmic free calcium before activation with thrombin to the slope of the calcium removal rate following the action of the agonist. This index was significantly higher in untreated hypertensive patients than in normotensive controls (0.12+/-0.06 versus 0.05+/-0.08, p<0.001). Treatment of hypertensive patients with doxazosin gastrointestinal therapeutic system (4 mg/day as a single dose) for 2 months normalized both platelet activation and Ca(2+) mobilization. Changes in the expression of CD62 and phosphatidylserine in the platelet membrane after treatment with doxazosin gastrointestinal therapeutic system may be related to normalization of the kinetics of cytoplasmic free Ca(2+). Normalization of platelet activation may represent an additional beneficial effect to the known antihypertensive action of doxazosin gastrointestinal therapeutic system.

Efecto del telmisartán en el estrés oxidativo y actividad antioxidante en leucocitos de sangre periférica de pacientes hipertensos / Effects of telmisartan on oxidative stress and antioxidant activities in peripheral leukocytes from hypertensive patients

Introducción: Se han determinado el estrés oxidativo y la actividad enzimática antioxidante en leucocitos de pacientes hipertensos inmediatamente antes de iniciar el tratamiento con80 mg/día de telmisartán y después de 2 meses de instaurada la medicación. Adicionalmente se ha valorado en paralelo un grupo control. Material y métodos: Como marcador de estrés oxidativo, se ha determinado el potencial de membrana mitocondrial ( ) en leucocitos. La actividad antioxidante se ha determinado midiendo la actividad superóxido dismutasa y catalasa en lisados leucocitarios. Resultados: Nuestros resultados muestran mayor estrés oxidativo y mayor actividad antioxidante en los pacientes en situación basal que en los controles. Estos resultados sugieren que la hipertensión se asocia con una situación de estrés oxidativo, con adaptaciones de mecanismos antioxidantes, con el fin de contrarrestar los efectos negativos de la oxidación. Probablemente el sistema antioxidante celular defensivo posee capacidad de adaptación al efecto del estrés oxidativo que acompaña a la hipertensión. Así pues, en esta patología observamos un aumento de estrés oxidativo, que no puede ser atribuido a un defecto del sistema antioxidante. Conclusiones: Puede especularse que cuando el estrés oxidativo es mayor, la célula generauna mayor actividad antioxidante. Después de dos meses de tratamiento con telmisartán, las cifras tensionales disminuyen junto al estrés oxidativo de los leucocitos. En paralelo, se observa una disminución del sistema de antioxidante. Dicho descenso parece indicar que la célula no necesita tanta actividad antioxidante cuando la hipertensión se normaliza (AU)

Introduction: Oxidative stress and antioxidant activity were determined in leukocytes from 30hypertensive patients prior to telmisartan treatment and at two months. A control group was evaluated in parallel. Material and methods: Mitochondrial membrane potential ( ) in leucocytes was evaluated as a marker of oxidative stress. The antioxidant activity was determined by measuring superoxide dismutase (SOD) and catalase (CAT) activity in leukocyte lysates. Results: Our results demonstrate enhanced oxidative stress in hypertension as indicated by their increased mitochondrial membrane potential. Activities of leukocyte antioxidant enzymes were also higher in patients at baseline. These results indicate that hypertension leads to oxidative stress with antioxidant enzyme adaptations in order to avoid the negative effect of the oxidation. It is likely that the cellular antioxidant defense systems are capable of adapting to the chronic oxidative stress associated to hypertension. Our observations indicate that there is an increase in oxidative stress that cannot be attributed to a defect in the antioxidant system. Conclusions: It can be speculated that when oxidative stress is greater, the cell generates higher antioxidant activity as a defense mechanism. After two month of treatment with telmisartan, hypertension and leukocyte oxidative stress were decreased. Parallelly, a decrease was observed in the antioxidant defense system. This decline suggests that the cells do not need as much antioxidant activity when blood pressure is normalized (AU)