Crucial pathophysiological role of CXCR2 in experimental ulcerative colitis in mice.

Polymorphonuclear leukocyte infiltration and activation into colonic mucosa are believed to play a pivotal role in mediating tissue damage in human ulcerative colitis (UC). Ligands of human CXC chemokine receptor 1 and 2 (CXCR1/R2) are chemoattractants of PMN, and high levels were found in the mucosa of UC patients. To investigate the pathophysiological role played by CXCR2 in experimental UC, we induced chronic experimental colitis in WT and CXCR2(-/-) mice by two consecutive cycles of 4% dextran sulfate sodium administration in drinking water. In wild-type (WT) mice, the chronic relapsing of DSS-induced colitis was characterized by clinical signs and histopathological findings that closely resemble human disease. CXCR2(-/-) mice failed to show PMN infiltration into the mucosa and, consistently with a key role of PMN in mediating tissue damage in UC, showed limited signs of mucosal damage and reduced clinical symptoms. Our data demonstrate that CXCR2 plays a key pathophysiological role in experimental UC, suggesting that CXCR2 activation may represent a relevant pharmacological target for the design of novel pharmacological treatments in human UC.

The role of CXCR2 activity in the contact hypersensitivity response in mice.

The recruitment of polymorphonuclear neutrophil leukocytes (PMN) into a challenge site, and their subsequent activation, are thought to play a role in the elicitation of the contact hypersensitivity (CHS) response. The present study investigated the role played by CXCR2 activity in tissue PMN infiltration and subsequent triggering of CHS. Our results show that the cutaneous infiltration by PMN, induced by hapten challenge was dramatically inhibited in sensitized, CXCR2-deficient (CXCR2(-/-)) mice. Inhibition of PMN recruitment into the hapten-challenged ears of CXCR2(-/-) mice was associated with a consistent reduction of the CHS response (ear swelling) in CXCR2(-/-) mice as compared with that observed in neutropenic, wild-type (CXCR2(+/+)) mice. Prevention of skin PMN infiltration and the ear swelling response by the absence of functional CXCR2 was observed regardless of the hapten used. These data clearly suggest that CXCR2 activity plays an essential role in mediating cutaneous recruitment and activation of PMN, and thus indirectly regulates recruitment of hapten-primed T cells into challenge sites, with the subsequent elicitation of the CHS response. The role played by CXCR2 activity in the CHS response provides the rationale for testing CXCR2 inhibitors as a new therapeutic approach to skin diseases.