Human eotaxin represents a potent activator of the respiratory burst of human eosinophils

Abstract

Increased numbers of eosinophils are found in parasitic infections, autoimmune diseases and allergic diseases such as allergic asthma. They are activated by distinct cytokines and chemokines leading to the immigration in the inflamed tissue and mediate tissue damage by releasing reactive oxygen species. Here, the effect of the recently cloned CC chemokine human eotaxin was investigated for its ability to affect different eosinophil effector functions and compared to the CC chemokines MCP-3 and RANTES. Human eotaxin induced chemotaxis of human eosinophils in a dose-dependent manner. The range of efficacy of the CC chemokines compared to the well-known chemotaxin C5a was eotaxin = RANTES > MCP-3 = C5a. In addition, eotaxin induced rapid and transient actin polymerization, a prerequisite for cell migration, in eosinophils in the same range of efficacy as observed for chemotaxis. To investigate whether eotaxin was able to activate the respiratory burst of eosinophils, release of reactive oxygen species was measured by lucigenin-dependent chemiluminescence. Eotaxin induced production of significantly high amounts of reactive oxygen species at a concentration between 10 ng/ml and 500 ng/ml. Surprisingly, the effect of eotaxin was comparable to the well-known eosinophil activator C5a. The range of efficacy of the CC chemokines compared to C5a in the activation of the respiratory burst was eotaxin = C5a > MCP-3 > RANTES. Production of reactive oxygen species was inhibited by pertussis toxin, staurosporin, genestein and wortmannin. Furthermore, eotaxin induced transient increases in intracellular calcium concentration ([Ca2+]i) in human eosinophils. Therefore, pertussis toxin-sensitive Gi-proteins, protein kinase C, tyrosine kinase, phosphatidylinositol-3-kinase and transient increases in [Ca2+]i are involved in the signal transduction of eosinophils following stimulation with eotaxin. In summary, this study reveals the importance of the CC chemokine eotaxin as a potent activator of the respiratory burst, actin polymerization and chemotaxis. Eotaxin, therefore, plays an important role not only by attracting eosinophils to the site of inflammation but also by damaging tissue by its capacity to induce the release of reactive oxygen species.

Eotaxin/CCL11 Suppresses IL-8/CXCL8 Secretion from Human Dermal Microvascular Endothelial Cells

“…6B), indicating a dependence on G i proteins and phosphatidylinositol 3-kinase (PI3K). This is consistent with previous reports demonstrating these mediators are important in CCR3 signaling in eosinophils (33).…”

“…In addition, treatment with pertussis toxin and wortmannin also blocked the suppressive effect of eotaxin/CCL11, indicating the involvement of G i proteins and PI3K. Previous reports have indicated the activity of these mediators in CCR3-mediated chemotaxis and respiratory burst in eosinophils (33). This study now demonstrates that a novel link exists between a G i -, PI3K-dependent pathway and chemokine production in HDMEC.…”

Δ12-Prostaglandin J2, a Plasma Metabolite of Prostaglandin D2, Causes Eosinophil Mobilization from the Bone Marrow and Primes Eosinophils for Chemotaxis

“…Eotaxin-induced eosinophil responses have been shown to involve signaling pathways dependent upon p38 MAPK and PI-3 kinase (18,22,31), which can couple to pathways regulating actin polymerization (32), integrin-dependent eosinophil adhesion (33), and chemokinesis (25,28). In addition, eosinophil adhesion in response to IL-5 and platelet-activating factor has been shown to involve MEK (33).…”

Receptor reserve analysis of the human CCR3 receptor in eosinophils and CCR3-transfected cells

“…Several chemokines have been described to bind to CCR3 on human eosinophils [7,8,12] and induce chemotaxis in vitro [12,15,16,19,20]. Other measurements of receptor-activated intracellular events such as increases in intracellular calcium levels [7,12,15,16,[20][21][22][23], production of reactive oxygen [15,[21][22][23][24], histamine release [15], and actin polymerization [22][23][24] have also been used to characterize CCR3 ligands.…”