Different functions for the interleukin 8 receptors (IL-8R) of human neutrophil leukocytes: NADPH oxidase and phospholipase D are activated through IL-8R1 but not IL-8R2.

Abstract

Two monoclonal antibodies, anti-IL8Rl and anti-IL8R2, raised against both interleukin 8 receptors (IL-8R) of human neutrophils, IL-8R1 and IL-8R2, were used to study individual receptor functions after stimulation with IL-8, GROa, or NAP-2. Efficacy and selectivity of the antibodies were tested in Jurkat cells transfected with cDNA coding for one or the other receptor. The binding of 1251-labeled IL-8 and IL-8-induced changes of the cytosolic free Ca2+ concentration were inhibited by anti-IL8Rl in cells expressing IL-8R1 and by anti-IL8R2 in cells expressing IL-8R2. In human neutrophils, release of elastase was observed after stimulation with IL-8 or GROa. The response to IL-8 was inhibited slightly by anti-IL8R1 and more substantially when both monoclonal antibodies were present, while the response to GROa was inhibited by anti-IL8R2 but was not affected by anti-IL8Rl. These results indicate that both IL-8 receptors can signal independently for granule enzyme release. Superoxide production, a measure of the respiratory burst, was obtained with increasing concentrations of IL-8 with maximum effects at 25 to 50 nM, but no response was observed upon challenge with GROca or NAP-2 up to 1000 nM. The superoxide production induced by IL-8 was inhibited by anti-IL8Rl, but was not affected by anti-IL8R2. Stimulation of neutrophils with IL-8, in contrast to GROa or NAP-2, also elicited phospholipase D activity. The effect of IL-8 was again inhibited by anti-IL8Rl but not by anti-IL8R2, indicating that this response, like the respiratory burst, was mediated by IL-8R1. Taken together, our results show that IL-8R1 and IL-8R2 are functionally different. Responses, such as cytosolic free Ca2+ changes and the release of granule enzymes, are mediated through both receptors, whereas the respiratory burst and the activation of phospholipase D depend exclusively on stimulation through IL-SRi.Chemokines constitute a large family of structurally related proteins which activate and attract leukocytes. Interleukin 8 (IL-8) and its analogs, GROa, GRO,3, GROT, NAP-2, and ENA-78, act predominantly on neutrophils and are called CXC chemokines because their first two conserved cysteines are separated by one amino acid (1). CXC chemokines share two distinct receptors, IL-8 receptors 1 (IL-8R1) and IL-8 receptor 2 (IL-8R2), which are both expressed in high numbers on neutrophils (1). IL-8 binds with high affinity (Kd values between 0.5 to 3 nM) to both receptors, whereas all the other CXC chemokines have high affinity for IL-8R2 only (2, 3). The two receptors have considerable amino acid sequence identity within the seven transmembrane domains and connecting loops, but differ almost totally in their NH2-and COOHterminal regions. This suggests that they not only possess distinct ligand-binding properties but also signal differently. Because the receptors are expressed together on neutrophils, their individual properties were studied in Jurkat cells after transfection of the respective cDNA. IL-8R1 and IL-8R2 were found to function ind...

Respiratory burst of neutrophils is not required for stem cell mobilization in mice

“…Both receptors are phosphorylated upon stimulation (Richardson et al, 1998) but have been shown to have diverging signal transduction pathways (L'Heureux et al, 1995). CXCR1 is probably responsible for phospholipase D activation and respiratory burst, whereas CXCR2 was found to be mainly responsible for intracellular Ca mobilization, chemotaxis and granule exocytosis (Jones et al, 1996;Wolf et al, 1998). However, elastase release in response to IL-8 was found after activation of either receptor (Jones et al, 1996).…”

“…CXCR1 is probably responsible for phospholipase D activation and respiratory burst, whereas CXCR2 was found to be mainly responsible for intracellular Ca mobilization, chemotaxis and granule exocytosis (Jones et al, 1996;Wolf et al, 1998). However, elastase release in response to IL-8 was found after activation of either receptor (Jones et al, 1996). In mice, only the homologue of the CXCR2 receptor has been identified (Lee et al, 1995), and it remains uncertain whether IL-8 stimulation of mouse neutrophils can activate a respiratory burst-dependent signal transduction pathway.…”

Functional Distinction between CXC Chemokines, Interleukin-8 (IL-8), and Growth Related Oncogene (GRO)α in Neutrophil Infiltration

“…The importance of CXCR1 in chemokine-mediated elastase release from neutrophils has also been reported (Jones et al, 1996). Thus, it is possible that IL-8, but not GRO␣, activates serine proteases, leading to an inactivation of TNF␣.…”

A Role for Interleukin 8 in Direct Regulation of T Cell Functional Activity

“…В нашей работе мы показа-ли разнонаправленное влияние IL-8 на экспрес-сию CD181, выявляемую на разных Т-клеточных субпопуляциях. Возможно, это связано с ин-тернализацией рецептора после его связывания с IL-8 [18,20].…”