ELR-CXC Chemokine Receptor Antagonism Targets Inflammatory Responses at Multiple Levels

Abstract

The ELR-CXC chemokines play important roles in neutrophilic inflammation. We report in this study that a fully human ELR-CXC chemokine antagonist that we have generated, CXCL8(3–72)K11R/G31P (G31P), has potent anti-inflammatory effects that arise through its actions at multiple levels. G31P inhibited CXCL8-induced chemotactic responses and intracellular Ca2+ flux in CXCR1-transfected HEK cells and neutrophils, and responses of neutrophils to CXCR2-exclusive ligands. G31P desensitized heterologous G protein-coupled receptors on neutrophils, 52–86% reducing their Ca2+ flux and chemotactic responses to leukotriene B4, C5a, and the bacterial tripeptide fMLP. G31P also 60–90% blocked neutrophil chemotactic responses to mediators present in 10 of 12 sputum samples from cystic fibrosis or bronchiectasis subjects with bacterial pneumonia. Moreover, whereas A549 bronchial epithelial cells (which expressed CXCR1) secreted ≈29,000 pg/ml CXCL8 in response to in vitro endotoxin challenge, G31P reduced this response by up to 98%, presumably by interrupting an autocrine inflammatory loop. The anti-inflammatory effects of G31P extended also to reversing the antiapoptotic influence of ELR-CXC chemokines on neutrophils. That these effects were relevant in vivo was confirmed in a guinea pig model of airway endotoxemia, wherein the human form of G31P >95% blocked neutrophil infiltration into and activation within the airways, as determined by airway levels of the neutrophil primary, secondary, and tertiary granule markers myeloperoxidase, lactoferrin, and matrix metalloproteinase-9, respectively, and the epithelial cell marker matrix metalloproteinase-2. These data suggest that the beneficial effects of ELR-CXC chemokine antagonism arise through effects that occur at multiple levels, including epithelial cells, neutrophils, and alternate G protein-coupled receptors.