Citations

Abstract Eosinophils play a key role in the pathogenesis of asthma and other allergic inflammatory diseases. We have previously shown that treatment of eosinophils with lidocaine preferentially inhibits IL-5-induced survival. This inhibition cannot be overcome by increasing concentrations of IL-5 and is not due to the blocking of Na+ channels by lidocaine. Here we report that one class of K+ channel blockers, the sulfonylureas, inhibits eosinophil survival in a manner similar to lidocaine. The sulfonylurea glyburide inhibits eosinophil survival even at high concentrations of IL-5. In contrast, increasing concentrations of IL-3 or granulocyte-macrophage CSF overcome glyburide inhibition. Glyburide also blocks cytokine-induced eosinophil superoxide production. Similar results were seen with the sulfonylureas tolbutamide and glipizide. Interestingly, the effects of glyburide are not antagonized by the ATP-sensitive K+ channel openers cromakalim, pinacidil, or diazoxide. Although Scatchard analysis of [3H]glyburide binding to eosinophil membranes indicated that the high affinity sulfonylurea receptor (SUR1) is not present on eosinophils, human eosinophils do express mRNA homologous to the sulfonylurea receptor family, in keeping with the presence of a sulfonylurea receptor. Finally, coculture of eosinophils with combinations of glyburide, lidocaine, and dexamethasone resulted in synergistic inhibition of cytokine-mediated eosinophil survival and superoxide production. These results have intriguing clinical implications for the treatment of eosinophil-associated diseases.

Abstract Eosinophils and cytokines active on eosinophils, especially IL-5, are believed to be critically involved in chronic allergic diseases. IL-5 activates eosinophils and enhances their survival in vitro by delaying apoptosis. In this study, we found that lidocaine and six analogues blunt responses of eosinophils to IL-5. Lidocaine and its derivatives inhibit IL-5-mediated eosinophil survival in a concentration-dependent manner (IC50 = 110 μM for 30 pg/ml IL-5). At suboptimal lidocaine concentrations, the eosinophil survival response to IL-5 shifts and more IL-5 is required to maintain survival. The inhibitory effect requires at least 24-h exposure of eosinophils to lidocaine, and the protein kinase C activator, PMA, completely reverses the inhibition. A multiparameter flow-cytometric analysis shows that lidocaine hastens the apoptosis of eosinophils normally delayed by IL-5. Lidocaine does not affect IL-5R expression or IL-5-induced protein tyrosine phosphorylation. Lidocaine also inhibits eosinophil survival mediated by IL-3 or granulocyte-macrophage CSF, although less potently than that mediated by IL-5. Furthermore, lidocaine inhibits eosinophil superoxide production stimulated by IL-5, granulocyte-macrophage CSF, or IL-3, but not that stimulated by platelet-activating factor, immobilized IgG, or PMA. Lidocaine and its derivatives show novel immunomodulatory properties and are able to blunt eosinophil responses to cytokines in addition to their local anesthetic or antiarrhythmic properties. Thus, lidocaine and its derivatives may represent a new class of therapeutic agents to treat patients with allergic diseases.

Abstract Migration of eosinophils through the basement membrane barrier is an important step for their infiltration into tissues. To investigate the mechanism of transmigration, we used a chamber fitted with a Matrigel membrane as a model of the basement membrane. In this model, eosinophils treated with cytokines or chemotactic factors alone did not transmigrate from the upper to the lower chamber. However, platelet-activating factor (PAF) strongly induced transmigration of eosinophils stimulated by interleukin (IL)-5, indicating that both a cytokine and a chemotactic factor are required for eosinophil migration through Matrigel. Granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-3 also stimulated eosinophil transmigration in the presence of PAF. Of seven eosinophil chemotactic factors tested, leukotriene B4, C5a, RANTES, macrophage inflammatory protein-1α, and IL-8 did not induce significant eosinophil transmigration. Only PAF and eotaxin induced transmigration of eosinophils through Matrigel in the presence of IL-5; PAF was more potent than eotaxin at the optimal concentration. In contrast, PAF, eotaxin, and RANTES all potently induced migration of eosinophils through bare membrane in the absence of IL-5. Finally, eosinophil migration through Matrigel was markedly reduced by a combination of anti-CD18 and anti-CD29 monoclonal antibodies, suggesting that it is mediated by β1- and β2-integrin adhesion molecules. Our findings demonstrate that eosinophil transmigration through a basement membrane model requires both a specific chemoattractant, such as PAF, and an eosinophil-activating cytokine, such as IL-5. This synergistic effect is likely important in the tissue accumulation of activated eosinophils in allergic and other eosinophil-associated diseases.

Abstract In general, inflammatory cells cross basement membranes by producing proteinases. To investigate the role of proteinases in eosinophil basement membrane migration, we studied peripheral blood eosinophils in Matrigel®-coated chemotaxis chambers. Electron microscopy showed degradation of the Matrigel® layer when eosinophils, added to the upper chamber, transmigrated the membrane in the presence of both platelet-activating factor (PAF) in the lower chamber and interleukin (IL)-5 in both chambers. In the absence of either or both PAF and IL-5, no changes occurred in the Matrigel® layer. Matrigel® transmigration of eosinophils induced by PAF and IL-5 was inhibited by 1,10-phenanthroline, batimastat, 3,4-dichloroisocoumarin, chymostatin, and a neutralizing antibody for the matrix metalloproteinase (MMP)-9, indicating that serine proteinase(s) and MMP, specifically MMP-9, were involved in the transmigration of eosinophils through Matrigel®. In contrast, eosinophil migration through a bare membrane was not affected by batimastat. Using gelatin zymography and immunoblotting, MMP-9 was detected in the migration upper chamber supernatant of the eosinophil transmigration assay and in the conditioned medium of eosinophils. Release of MMP-9 by eosinophils was increased by IL-5, PAF, or both, but the substrate-degrading activity of MMP-9 was increased only in the presence of both IL-5 and PAF, indicating that the releasing and activating mechanisms of MMP-9 are involved in eosinophil basement membrane migration. This study implicates MMP-9 in basement membrane migration of eosinophils and suggests its involvement in inflammatory diseases where tissue eosinophilia plays a role.

Abstract Evidence suggests that cellular adhesion is critical for eosinophil effector functions. Here, we tested the hypothesis that an adhesion molecule, specifically β2 integrin, participates in intracellular signaling events of eosinophils. Eosinophils stimulated with interleukin (IL)-5 and adherent to protein-coated tissue culture plates via β2 integrin (CD18) showed tyrosine phosphorylation of a number of proteins. Among these proteins, tyrosine phosphorylation of the 105 kD and 115 kD proteins and the product of the c-cbl protooncogene, Cbl, was specifically inhibited using soluble anti-CD18 monoclonal antibody (mAb) to block eosinophil cell adhesion. Furthermore, phosphoinositide turnover of IL-5-stimulated adherent eosinophils was also inhibited by anti-CD18 mAb, suggesting that cellular adhesion plays important roles in eosinophil signal transduction. αMβ2 (Mac-1, CD11b/18) was one of the β2 integrins involved in eosinophil adhesion to protein-coated plates. We found that direct ligation of eosinophil αMβ2 with anti-CD11b mAb coupled to polystyrene microbeads induced tyrosine phosphorylation of a 115 kD protein and Cbl. Furthermore, anti-CD11b mAb microbeads induced increases in both phosphoinositide hydrolysis and the eosinophil degranulation response. Control antibodies, such as mouse myeloma IgG1 and anti-HLA class I antigen mAb, did not induce these cellular responses. These results suggest that engagement of β2 integrin either by cell adhesion or by anti-CD11b mAb triggers activation of an intracellular signaling cascade, including protein tyrosine phosphorylation and phosphoinositide turnover, and subsequent cellular degranulation in human eosinophils. Tyrosine phosphorylation of a 115 kD protein and Cbl may play important roles in adhesion-dependent cellular functions of eosinophils.

SUMMARY Eosinophils and eosinophil granule proteins may play an important role in the pathogenesis of asthma. BALF from 40 patients with symptomatic asthma were analysed for cytokine activity by the eosinophil survival assay. BALF from 15 patients showed increased survival activity. Survival activities in BALF from four of these patients were almost completely blocked by anti-IL-5 MoAb, and the remaining activities were blocked by anti-granulocyte-macrophage colony-stimulating factor (GM-CSF), anti-IL-3 antibody, or both. Surprisingly, BALF samples from the other 25 patients decreased eosinophil viabilities below the levels of medium control. The inhibitory factor in these BALF was of low molecular weight, was heat-stable, was largely overcome by excess exogenously added cytokines, and was positively correlated with the concentrations of lidocaine in the BALF. Lidocaine itself inhibited eosinophil survival at concentrations less than those present in the BALF. These findings indicate that lidocaine is an inhibitor of cytokines in the eosinophil survival assay, and they suggest the need for caution in analyses of BALF containing lidocaine or other local anaesthetics.