Objectives: Polymorphonuclear leukocytes (PMN) feature prominently in the mucosa, including in crypt abscesses, of patients with inflammatory bowel disease, yet the mediators that are responsible for this migration are unknown. We discovered that CXCR2 chemokines (reportedly elevated in the mucosa) have reduced potency recruiting PMN across epithelial cell monolayers versus acellular filters, so the objective was to determine what molecules modify transepithelial PMN migration to CXCR2 chemokines.
Methods: Transwells with T84 colon carcinoma monolayers or no epithelium were used with adolescent patient peripheral blood PMN and CXCL8 (interleukin-8 [IL-8], binds CXCR1 and CXCR2), CXCL5 (epithelial-derived neutrophil chemoattractant-78 [ENA-78]), or CXCL1 (Gro-α, both bind CXCR2) as chemoattractants.
Results: IL-8 was equally potent at recruiting PMN across filters and T84 monolayers growing on the filters. In contrast, ENA-78 and Gro-α were significantly less potent at recruiting PMN across monolayers than across bare filters. Blocking CXCR1 reduced PMN migration across monolayers to IL-8. We ruled out superoxide radicals possibly enhancing migration to IL-8 by using PMN from a patient with chronic granulomatous disease. PMN constitutively produce adenosine, so we added adenosine deaminase to the transwell assays and observed increased migration to ENA-78 across T84 monolayers. The level of migration was further enhanced by pretreating PMN with adenosine before adding the cells to the assay in the presence of the deaminase.
Conclusions: PMN migration mediated by CXCR2 through the epithelium is regulated by adenosine. Adenosine appears to reduce transepithelial migration by influencing β2 integrin use on the PMN.