Leukotriene D4 activates {beta}2-integrin adhesion in human polymorphonuclear leukocytes.

We examined the functional role and mechanisms by which activation of cysteinyl leukotriene-1 receptor (cysLT(1)R) regulates beta(2)-integrin adhesion to intercellular adhesion molecule (ICAM)-1 in human polymorphonuclear leukocytes (PMNs) in vitro. Human peripheral blood PMNs and eosinophils were isolated separately from the same mildly atopic donors. Surface expression of cysLT(1)R was identified both in PMNs and in eosinophils by immunofluorescence analysis. Total cysLT(1)R protein was substantially greater in eosinophils than in PMNs as determined by Western blot analysis. However, leukotriene D(4) (LTD(4)) upregulated beta(2)-integrin adhesion of PMNs to ICAM-1 with high efficacy in a time- and concentration-dependent manner. Upregulated beta(2)-integrin adhesion of PMNs was related temporally and quantitatively to phosphorylation of 85-kDa cytosolic group IVa phospholipase A2 (gIVaPLA2). Augmented LTD(4)-induced adhesion was blocked significantly by montelukast, a cysLT(1)R antagonist. Trifluoromethylketone (a gIVaPLA2 inhibitor) blocked beta(2)-integrin adhesion caused by LTD(4) activation, as did anti-CD18 monoclonal antibody directed against beta(2)-integrin on the PMN surface. Our data demonstrate that LTD(4) causes phosphorylation of gIVaPLA2 and upregulation of beta(2)-integrin adhesion to ICAM-1 or ICAM-1 surrogate through cysLT(1)R activation. Activation of gIVaPLA2 is a critical step through which beta(2)-integrin adhesion is upregulated by the cysLT(1)R expressed on the surface membrane of human PMN.

Phosphodiesterase 4 inhibition of beta2-integrin adhesion caused by leukotriene B4 and TNF-alpha in human neutrophils.

Phosphodiesterase (PDE)4 inhibition attenuates neutrophilic inflammation in chronic obstructive pulmonary disease. The objective of the present study was to examine the efficacy and mechanism by which PDE4 inhibition blocks adhesion of beta(2)-integrin to an endothelial counterligand. Neutrophils (polymorphonuclear leukocytes (PMNs)) were isolated from humans receiving no medication. Adhesion was analysed by myeloperoxidase activity. The effects of cilomilast+/-salmeterol on the following were determined: 1) surface CD11b expression; 2) adhesion; 3) intracellular cyclic adenosine monophosphate (cAMP) concentration; and 4) extracellular signal-regulated kinase (ERK)-1/2-mediated group IVA-phospholipase A(2) (gIVA-PLA(2)) phosphorylation caused by leukotriene (LT)B(4) or tumour necrosis factor (TNF)-alpha activation. Either cilomilast or rolipram+/-salmeterol caused concentration-related blockade of LTB(4)-induced adhesion to counterligand, but had no effect on TNF-alpha-activated PMNs. A comparable increase in intracellular cAMP concentration for PMNs activated with LTB(4) and TNF-alpha was caused by 1 muM cilomilast and 0.1 microM salmeterol. Upregulation of surface CD11b expression and ERK-1/2 phosphorylation were blocked by cilomilast or rolipram+/-salmeterol for PMNs activated by LTB(4), but not for cells stimulated by TNF-alpha. Cilomilast+/-salmeterol also blocked gIVA-PLA(2) phosphorylation caused by LTB(4) but not TNF-alpha. In conclusion, the current study demonstrates that both leukotriene B(4) and tumour necrosis factor-alpha upregulate cyclic adenosine monophosphate. However, cyclic adenosine monophosphate does not block beta(2)-integrin adhesion caused by tumour necrosis factor-alpha. It was concluded that tumour necrosis factor-alpha prevents inhibition of extracellular signal-regulated kinase-1/2-mediated group IVA-phospholipase A(2) activation, which is essential for beta(2)-integrin adhesion in polymorphonuclear leukocytes.

Additive blockade of beta 2-integrin adhesion of eosinophils by salmeterol and fluticasone propionate.

Migration of human eosinophils is regulated by integrin expression, conformational change, and activation of cytosolic phospholipase A2 (cPLA2). Corticosteroids have been shown to inhibit cPLA2 hydrolysis in human eosinophils. The objective of this study was to determine the mechanisms of fluticasone propionate (FP) alone or in combination with salmeterol (SM) in blocking adhesion mediated by beta 2-integrin in human eosinophils. Human eosinophils were isolated by negative magnetic selection. beta 2-integrin-mediated eosinophil adhesion was measured by residual eosinophil peroxidase activity. Eosinophils were pretreated for 12 h to 24 h with FP and with or without SM for 30 min. Both SM alone and FP alone inhibited eosinophil adhesion in concentration- and time-dependent manner. SM alone modestly (approximately 30%) inhibited interleukin (IL)-5-induced eosinophil adhesion. Blockade of IL-5-induced eosinophil adhesion caused by 10(-7) M FP at 24 h was augmented by 10(-7) M SM from 41.5% to 72.5%. Similar blockade was also observed for eotaxin-induced eosinophil adhesion. Neither SM, FP, nor FP + SM blocked either: 1) upregulation of CD11b surface expression; or 2) phosphorylation of cPLA2. Blockade of beta 2-integrin-mediated eosinophil adhesion by fluticasone propionate is augmented by salmeterol. Decreased adhesion results from augmented blockade of nuclear translocation of cytosolic phospholipase A2 caused by addition of salmeterol to fluticasone.