Polymorphonuclear integrins, membrane fluidity, and cytosolic Ca(2+) content after activation in essential hypertension

Calcium channel blockers suppress cytokine-induced activation of human neutrophils

BACKGROUND

Neutrophils, in concert with proinflammatory cytokines, play an important role in the progression of atherosclerosis. Calcium channel blockers are commonly used in the treatment of hypertension, and their pleiotropic effects, other than the lowering of blood pressure, have been recently recognized.

METHODS

We studied the effects of various calcium channel blockers (amlodipine, nicardipine, cilnidipine, benidipine, efonidipine, nifedipine, azelnidipine, verapamil, and diltiazem; each being used at 5 and 10 micromol/l) on superoxide (O(2)(-)) release, migration, and signaling pathways in human neutrophils stimulated by granulocyte-macrophage colony-stimulating factor (GM-CSF) or tumor necrosis factor-alpha (TNF-alpha).

RESULTS

GM-CSF-induced O(2)(-) release was suppressed by amlodipine, nicardipine, and cilnidipine, whereas TNF-alpha-induced O(2)(-) release was suppressed by amlodipine, nicardipine, cilnidipine, benidipine, efonidipine, nifedipine, and azelnidipine. TNF-alpha-induced phosphorylation of extracellular signal-regulated kinase (ERK) and Akt, but not p38 mitogen-activated protein kinase (MAPK), was attenuated by nicardipine, cilnidipine, benidipine, efonidipine, and azelnidipine. By contrast, GM-CSF-induced phosphorylation of ERK, p38, and Akt was affected by none of the blockers. GM-CSF-induced neutrophil migration was also suppressed by amlodipine and nicardipine, but not by azelnidipine, when these blockers were assessed for their effect on neutrophil migration.

CONCLUSIONS

These findings suggest that (i) some calcium channel blockers can suppress cytokine-induced neutrophil activation, leading to possible prevention of the progression of atherosclerosis; and (ii) that activation of the ERK and phosphatidylinositol 3-kinase (PI3K)/Akt pathways, induced by TNF-alpha but not by GM-CSF, is selectively affected by some blockers.

Mechanisms of disease: oxidative stress and inflammation in the pathogenesis of hypertension

Animal studies have shown that oxidative stress and renal tubulointerstitial inflammation are associated with, and have major roles in, the pathogenesis of hypertension. This view is supported by the observations that alleviation of oxidative stress and renal tubulointerstitial inflammation reduce arterial pressure in animal models. Conversely, hypertension has been shown to cause oxidative stress and inflammation in renal and cardiovascular tissues in experimental animals. Taken together, these observations indicate that oxidative stress, inflammation and arterial hypertension participate in a self-perpetuating cycle which, if not interrupted, can lead to progressive cardiovascular disease and renal complications. These events usually occur in an insidious and asymptomatic manner over an extended period following the onset of hypertension. Severe target organ injury can, however, occasionally occur precipitously in the course of malignant or accelerated hypertension. Given the high degree of heterogeneity of hypertensive disorders, the factor(s) initiating the vicious cycle described vary considerably in different forms of hypertension. For instance, oxidative stress in the kidney and vascular tissue is the primary mediator in the pathogenesis of angiotensin-induced, and perhaps lead-induced, hypertension. By contrast, increased arterial pressure is probably the initiating trigger in salt-sensitive hypertension. Although the initiating factor might vary between hypertensive disorders, according to the proposed model, the three components of the cycle eventually coalesce in all forms of hypertension.

Is there an association between angiotensin-converting enzyme gene polymorphism and functional activation of monocytes and macrophage in young patients with essential hypertension?

BACKGROUND

This study was undertaken to determine whether the phenotype of monocytes and monocyte-derived macrophages is more proatherogenic in young persons with arterial hypertension and whether this phenotype is affected by smoking or polymorphism of the angiotensin-converting enzyme (ACE) gene.

METHODS

We enrolled 40 young patients (24.1 +/- 4.7 years) with previously untreated arterial hypertension and 40 age-matched healthy controls. There were 20 smokers and 20 non-smokers in each group.

RESULTS

In the hypertensive group, we found enhanced monocyte expression of CD11a (P < 0.001), reduced expression of CD49d (P < 0.001) and CD62L (P < 0.005), greater oxidative stress in resting and phorbol-12-mistrate-13-acetate-stimulated monocytes (P < 0.001), enhanced adhesion of monocytes to endothelial cells (P < 0.001), greater expression of CD36 on monocyte-derived macrophages (P < 0.001), and enhanced production of reactive oxygen species by resting and phorbol-12-mistrate-13-acetate-stimulated macrophages (P < 0.001). Cigarette smoking by hypertensive patients was associated with enhanced (P < 0.002) CD11a expression. There were no associations of ACE gene polymorphism with cellular expression or reactive oxygen species production studied among hypertensive patients. Only CD62L expression in DD homozygote participants was higher (P < 0.039) than in II homozygote participants.

CONCLUSIONS

It is concluded that arterial hypertension affects the function of monocytes/macrophages in young persons. Polymorphism of the ACE gene is without effect on the functional activation of monocytes and macrophages.

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.

Hypertension promotes integrin expression and reactive oxygen species generation by circulating leukocytes

BACKGROUND

Compelling evidence has emerged pointing to the role of oxidative stress in the pathogenesis of hypertension (HTN) in experimental animals. Excess production of reactive oxygen species (ROS) in the renal and vascular tissues has been shown to raise arterial pressure via inactivation of nitric oxide and generation of isoprostanes. Accumulation of inflammatory cells in the renal interstitium has been shown to increase ROS generation in the kidneys of hypertensive animals. In addition, considerable evidence has emerged pointing to spontaneous activation of circulating leukocytes in animals and humans with hereditary HTN. This study was designed to explore whether induction of HTN in genetically normal animals can lead to spontaneous activation and ROS production in circulating leukocytes.

METHODS

Integrin expression, superoxide, and hydrogen peroxide production were assessed by flow cytometry in the circulating and splenic leukocytes of Sprague-Dawley rats rendered hypertensive by abdominal aorta banding above the renal arteries, and in sham-operated control rats.

RESULTS

The hypertensive animals studied 4 weeks after abdominal aorta banding exhibited a significant increase in superoxide and H(2)O(2) production in the circulating granulocyte, and a marked increase in H(2)O(2) production in the blood and splenic helper and cytotoxic T-lymphocytes. This was coupled with a significant up-regulation of CD18 and CD11a in splenic helper T-cells and cytotoxic T cells, and of CD18 in the circulating helper T cells.

CONCLUSION

Induction of HTN in genetically normotensive rats causes a spontaneous increase in ROS generation in the circulating and splenic leukocytes. This phenomenon can contribute to systemic oxidative stress, inflammation, cardiovascular and renal complications in hypertensive animals.

Immune cell CD62L and CD11a expression in response to a psychological stressor in human hypertension

This study examined the effects of hypertension and an acute psychological stressor on white blood cells and their expression of CD62L and CD11a. Seventeen mild hypertensive and 23 normotensive volunteers were studied prior to and following a standardized laboratory public speech. In response to the speech, all subjects increased the number of circulating leukocyte populations (p's<.01). Patients with hypertension increased the number of circulating white blood cells more than normotensives (p<.01). Hypertensives also showed a greater increase in the number of circulating CD3(+)CD8(+) T cells (p<.02) in response to the speech. Only hypertensives increased the number of circulating CD8(+)CD62L(high) T cells (p=.001). The density of CD11a on lymphocytes was increased in all subjects following the speech (p<.001). Hypertensives showed a greater mean density of CD11a on lymphocytes (p<.01). Coupled with observations of increased expression of the endothelial CD11a ligand ICAM-1 in hypertension, these findings are consistent with the notion that patients with hypertension exhibit a circulatory environment conducive to increased leukocyte adhesion. Exposure to repeated psychological stressors may further augment this potentially adverse circulatory environment.