Tumor necrosis factor alpha regulates CXC chemokine receptor expression and function

The alpha chemokine family is central to the participation of neutrophils i n the acute inflammatory response. These substances interact with neutrophi ls 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 t umor necrosis factor alpha(TNF alpha) pretreatment on CXCR-1 and CXCR-2. To this end, we examined these receptors with flow cytometry, radioligand bin ding, Northern blot analyzes, calcium mobilization, and chemotaxis experime nts on human neutrophils. In flow cytometry experiments, TNF alpha pretreat ment 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 b lot analyzes showed that mRNA levels of both IL-8 receptors were essentiall y unchanged after 45 min of TNF alpha pretreatment, but declined markedly f ollowing 2 h of pretreatment. Chemotaxis experiments on cells treated with TNF alpha for 5-120 min showed a substantial down-regulation of chemotaxis to IL-8 and GRO alpha. This was noted to be much greater than the decline i n cell surface receptors. Calcium mobilization experiments revealed minimal inhibition of the IL-8-induced increase in calcium after pretreatment with TNF alpha, but the response to NAP-2 was substantially inhibited. The data demonstrate differential regulation of the IL-8 receptor.