Polymorphonuclear Integrins, Membrane Fluidity, and Cytosolic Ca ²⁺ Content After Activation in Essential Hypertension

Abstract

Abstract-The purpose of this research was to obtain further information about the role of polymorphonuclear leukocytes in essential hypertension. These cells could be involved in the pathogenesis of organ injury. Thirty subjects (14 men and 16 women) with essential hypertension were enrolled. In these subjects we determined, at baseline and after in vitro activation with 4-phorbol 12-myristate 13-acetate and N-formyl-methionyl-leucyl-phenylalanine, the polymorphonuclear leukocyte membrane fluidity, obtained by labeling the cells with 1-[4-(trimethylamino)phenyl]-6-phenyl-1,3,5-hexatriene, cytosolic Ca 2ϩ concentration, obtained by marking the cells with Fura 2-AM, and integrin pattern (CD11a, CD11b, CD11c, and CD18), by using the indirect immunofluorescence with a flow cytometer. At baseline there was no difference in membrane fluidity between normal subjects and hypertensives, whereas hypertensives showed an increase in cytosolic Ca 2ϩ content and an increase of the phenotypical expression of CD11a, CD11b, and CD18. In normal subjects and in hypertensives, after activation, no variation was found in membrane fluidity and cytosolic Ca 2ϩ content. In normal subjects, after activation, we observed a significant increase of the expression of all adhesion molecules, whereas in hypertensives we found an increase of the expression of CD11b, CD11c, and CD18 but also a decrease of CD11a. The behavior of the polymorphonuclear leukocyte integrin profile may have several explanations, and in particular, the trend of CD11a after chemotactic activation may be related to its cleavage or to an altered integrin phosphorylation/dephosphorylation balance hypothetically present in this clinical condition. Key Words: hypertension, essential Ⅲ neutrophils Ⅲ integrins Ⅲ membranes Ⅲ calcium I n recent years, the knowledge about hypertensive disease was enriched by much evidence regarding the role of circulating leukocytes. In fact, from observations of an altered leukocyte count in experimental and clinical hypertension, 1-5 some authors hypothesized that leukocytes could be activated and that this condition, strengthened by nitrobule tetrazolium (NBT) reduction test, could contribute to explaining organ injury. 6 -11 In our previous works, 12,13 we evaluated, in essential hypertension, the leukocyte rheology, expressed as flow properties, polymorphonuclear leukocyte (PMN) membrane fluidity and PMN cytosolic Ca 2ϩ content at baseline and after chemotactic activation.Subsequently, our aim was to examine, in hypertensives, the PMN adhesion molecule profile. Our interest in this topic, for which there is little information in the literature, is derived from the fact that some experimental data underline how in this clinical condition an abnormality of the leukocyte adhesion is present. 9 -11,14 As we know, adhesion is particularly mediated by integrins; among these, ␤ 2 integrins (CD11a, CD11b, CD11c, CD18) are very important.Integrins 15,16 are usually in a low-affinity state that makes them unable to interact with their corresponding...

Fluidity and cytosolic Ca2+ concentration of circulating polymorphonuclear leukocytes at baseline in some chronic and acute clinical conditions: review of our survey

“…In addition, it has to be emphasized, while in normal controls and in VAD subjects without DM we found a significant positive correlation between PMN membrane fluidity and PMN cytosolic Ca 2+ concentration, this finding was not observed in the group of VAD subjects with type 2 DM [18]. The same results have been noted in hypertensive [20,21,22] and in CKD patients [23,24,25,26]. At baseline, in subjects with essential hypertension we found an increase in PMN cytosolic calcium content only.…”

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

“…In addition, Dorffel et al [36] have provided evidence for preactivation and enhanced susceptibility of peripheral blood monocytes to angiotensin-II-mediated cytokine generation in humans with essential HTN. Likewise, Caimi et al [37] have demonstrated a significant increase in integrin expression and cytosolic Ca 2+ concentration, as well as enhanced susceptibility to phorbol ester and fMLP-mediated activation in polymorphonuclear leukocytes from humans with essential HTN. Taken together, published studies in animals and humans with genetic HTN have provided compelling evidence for spontaneous activation of circulating leukocytes.…”

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“…Cellularactivation is generallyreflected in altered intracellularcalcium concentration and membrane fluidity.Calcium acts as asecondmessenger, initiating anumber of pathwaysinvolved in cell migration, adhesion, survivala nd coagulation in cells (20)(21)(22),and free cytosolic calcium providesameasureofcellularactivation. Cellularplasma membrane fluidity (the reciprocal of membrane microviscosity) defines the moleculardynamics of associated receptor proteins that arei nvolved in cell adhesion, migration and coagulation (23)(24)(25).Changesinmembrane fluidity can reflect or parallelaltered calcium homeostasis and cellularcytoskeleton organization. Altered cell activation and potentialc hangesi nc ella dhesion, migration and invasion are expected to change the fluidityinthe coreand surfaceofthe cell membrane (24).…”