Leukocytes synthesize a variety of inflammatory mediators that are packaged and stored in the cytoplasm within membrane-bound granules. Upon stimulation, the cells secrete the granule contents via an exocytotic process whereby the granules translocate to the cell periphery, the granule membranes fuse with the plasma membrane, and the granule contents are released extracellularly. We have reported previously that another exocytotic process, release of mucin by secretory cells of the airway epithelium, is regulated by the myristoylated alanine-rich C kinase substrate ( Keywords: MARCKS protein; leukocytes; degranulationLeukocytes synthesize a number of inflammatory mediators that are packaged and stored in cytoplasmic membrane-bound granules. These mediators include myeloperoxidase (MPO) in neutrophils (1), eosinophil peroxidase (EPO) and major basic pro- (2), lysozyme in monocytes/macrophages (3, 4), and granzyme in natural killer (NK) cells and cytotoxic lymphocytes (5-8). These mediators are released at sites of injury and contribute to inflammation and repair in the lung and elsewhere. Leukocytes release these granules via an exocytotic mechanism (9, 10), but the regulatory molecules and specific pathways involved in the exocytotic process have not been fully described.Several exogenous stimuli can provoke degranulation of leukocytes via a pathway that involves activation of protein kinase C (PKC) and subsequent phosphorylation events (9-13). MARCKS (myristoylated alanine-rich C kinase substrate), a ubiquitous phosphorylation target of PKC, is highly expressed in leukocytes (14-16). We have previously demonstrated that MARCKS protein is involved in exocytotic secretion of mucin by goblet cells that line the respiratory airways (17, 18). In airway epithelial cells, the N-terminus of MARCKS seems to be integral to the secretory process. The mechanism seems to involve the binding of MARCKS to membranes of intracellular mucin granules because a peptide against the N-terminus of MARCKS blocked mucin secretion and binding of MARCKS to mucin granule membranes in these cells (18). Because MARCKS is a prominent protein in leukocytes, we investigated whether or not MARCKS, and specifically its N-terminus, could play a role in leukocyte degranulation.In these studies, we used four different leukocyte types or models that secrete specific granule contents in response to phorbol ester-induced activation of PKC. First, neutrophils were isolated from human blood, and the in vitro release of MPO by these cells was assessed. Due to difficulties in isolating sufficient amounts of other leukocyte types from blood, we investigated the release of membrane-bound inflammatory mediators from commercially available human leukocyte cell lines. The human promyelocytic cell line HL-60 clone 15 was used to assess secretion of , the monocytic leukemia cell line U937 was used to assess secretion of lysozyme (3,4,23), and the lymphocyte NK cell line NK-92 was used to assess the release of granzyme (6-8). In all cases, the cells were preinc...

There are few reports regarding the measurement of cytokines and surface analysis of eosinophils in Churg-Strauss syndrome (CSS). To examine the pathophysiology of CSS, concentrations of cytokines in serum and bronchoalveolar lavage fluid (BALF), and surface antigens on peripheral blood eosinophils were analyzed in five patients with CSS. Concentrations of cytokines (interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), interleukin-3 (IL-3), interleukin-5 (IL-5) and granulocyte/macrophage colony stimulating factor (GM-CSF) were measured using ELISA. Surface antigens on eosinophils in peripheral blood were analyzed using flow cytometry. A concentration of interleukin-5 (IL-5) and TNF-alpha in serum was detected in five cases; however IL-1 beta, GM-CSF, and IL-3 were detected in 3 of 5, 2 of 5, and 1 of 5 patients, respectively. In BALF, TNF-alpha and IL-5 were detected in 2 of 3 and 1 of 3 patients, respectively; however, neither IL-1 beta, GM-CSF, nor IL-3 was detected in any. Newly expressed surface antigens such as CD25, CD4, and CD69 were observed on peripheral blood eosinophils in five cases. CD54 and HLA-DR were expressed in 4 of 5 and 3 of 5 patients, respectively. Eosinophils in peripheral blood are activated to various degrees, possibly depending on cytokine stimulation. This eosinophil activation may be related to the clinical stage of CSS.

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Background: Acute eosinophilic pneumonia (AEP) is a rare disease with unknown etiology. To examine pathophysiology of AEP we measured the cell number of eosinophils and eosinophil active cytokines in the peripheral blood and bronchoalveolar lavage fluid (BALF) of AEP patients and compared the levels with those measured in chronic eosinophilic pneumonia (CEP) patients. Methods: Cell number of eosinophils in peripheral blood and BALF from patients with AEP (n = 3) and CEP (n = 3) were measured. Eosinophil active cytokines in serum and BALF from the patients were measured using ELISA. Results: Eosinophil cell number in peripheral blood was 274–1,377/mm³ in AEP and 526–2,500/mm³ in CEP. The percentages of BALF eosinophils were high in AEP and CEP. Eosinophilia disappeared after methylprednisolone pulse therapy (1 g for 3 days) in AEP, however the cell number of eosinophils gradually increased after methylprednisolone pulse therapy and then spontaneously decreased to within normal range without any further medication. The concentrations of IL-5 in AEP were very high in serum and in BALF, however the concentrations in CEP were low in serum and BALF. Conclusion: AEP is a disease in which eosinophil active cytokine IL-5 is predominantly involved; CEP is not. The factors involving eosinophil infiltration to inflammatory loci differ between AEP and CEP.

We have reported that CD54 on eosinophils is involved in eosinophil degranulation. However, the role of CD54 in eosinophil and neutrophil superoxide production is still uncertain. We assessed the effect of CD54 on eosinophils and neutrophils in recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF)- or phorbol myristate acetate (PMA)-induced superoxide production through CD18. Anti-CD54 monoclonal antibody attenuated leukocyte aggregation and superoxide production of rGM-CSF- or PMA-stimulated neutrophils and PMA-stimulated eosinophils. Anti-CD18 monoclonal antibody or theophylline attenuated superoxide production of eosinophils and neutrophils stimulated by either stimuli. Flow cytometric analysis demonstrated CD54 expression on freshly isolated neutrophils but not on freshly isolated eosinophils. CD54 newly expressed on eosinophils reached its peak expression 30 min after PMA stimulation. The increase in CD18 and CD54 expression on neutrophils caused by rGM-CSF stimulation was partially inhibited by theophylline. These data demonstrated that CD54 and CD18 interaction of eosinophils or neutrophils is involved in superoxide production and that the inhibition of superoxide production by theophylline may be at least partly due to the inhibition of CD54 and CD18.