Tumor necrosis factor α regulates CXC chemokine receptor expression and function

The α chemokine family is central to the participation of neutrophils in the acute inflammatory response. These substances interact with neutrophils through two cell surface receptors, CXCR-1 and CXCR-2 (formally known as IL-8R-1 and IL-8R-2). We investigated the possible regulatory effects of tumor necrosis factor α (TNFα) pretreatment on CXCR-1 and CXCR-2. To this end, we examined these receptors with flow cytometry, radioligand binding, Northern blot analyzes, calcium mobilization, and chemotaxis experiments on human neutrophils. In flow cytometry experiments, TNFα pretreatment substantially decreased cell surface CXCR-2 receptor levels but showed partial recovery at 120 min. On the other hand, CXCR-1 receptor levels had a sharp decline at 15 min and maintained that level to 120 min. Northern blot analyzes showed that mRNA levels of both IL-8 receptors were essentially unchanged after 45 min of TNFα pretreatment, but declined markedly following 2 h of pretreatment. Chemotaxis experiments on cells treated with TNFα for 5-120 min showed a substantial down-regulation of chemotaxis to IL-8 and GROα. This was noted to be much greater than the decline in cell surface receptors. Calcium mobilization experiments revealed minimal inhibition of the IL-8-induced increase in calcium after pretreatment with TNFα, but the response to NAP-2 was substantially inhibited. The data demonstrate differential regulation of the IL-8 receptor.