Eosinophil adhesion to nasal polyp endothelium is P-selectin-dependent.

Abstract

SummaryTissue eosinophilia is a characteristic feature of a number of inflammatory diseases including asthma and nasal polyposis. Eosinophil migration into tissues is controlled in part by interactions between eosinophil adhesion receptors and counter-structures on the vascular endothelium. To determine the receptors used by eosinophils to adhere to vascular endothelium in allergic inflammation we have adapted the Stamper-Woodruff frozen section assay (FSA) to study eosinophil adhesion to nasal polyp endothelium. Immunohistology indicated that intercellular adhesion molecule I (ICAM-1), E-selectin and P-selectin were well expressed by nasal polyp endothelium, whereas expression of vascular cell adhesion molecule 1 (VCAM-1) was weak or absent. Unstimulated human peripheral blood eosinophils adhered specifically to nasal polyp endothelium. Adherence was temperature and divalent cation-dependent and saturable at cell densities >5 x 106 cells/ml. Eosinophil adhesion was almost completely inhibited by a monoclonal antibody (mAb) against P-selectin and by a chimeric molecule consisting of the Fc portion of human IgG and the lectin binding domain of P-selectin, which binds to the P-selectin ligand on leucocytes. Anti-Mac-1 mAb partially inhibited eosinophil adhesion whereas mAb against E-selectin, L-selectin, ICAM-1, VCAM-1, very late activation antigen 4, and lymphocyte function-associated antigen 1 had no effect. P-selectin is stored in intracellular granules within the endothelial cell and in vitro is only transiently expressed. To determine if P-selectin was expressed on the membrane of the nasal polyp endothelium we compared P-selectin expression in normal skin and nasal polyps after acetone fixation, which permeabilizes cells, and paraformaldehyde, which only allows staining of membrane expressed receptors. In the skin, good expression was seen with acetone fixation but no expression was seen after paraformaldehyde treatment, whereas in nasal polyps, similar expression was observed with both fixatives. In addition immunoftuorescence with confocal microscopy demonstrated lumenal staining of nasal polyp endothelium indicating that P-selectin was located on the surface of endothelial cells while in skin only an intracellular granular distribution was apparent. Lastly, whereas eosinophils bound consistently to nasal polyp endothelium, no binding was observed to blood vessels in normal skin further supporting the idea that eosinophils were binding to membrane expressed and not intracellular P-selectin. The importance of P-selectin in eosinophil adhesion to nasal polyp endothelium suggests that P-selectin antagonists may be effective at inhibiting eosinophil accumulation at sites of allergic inflammation.

Characterisation of adhesion receptors mediating lymphocyte adhesion to bronchial endothelium provides evidence for a distinct lung homing pathway

“…28 We have found that the tethering step is mediated primarily by PSGL-1 binding to P-selectin with a contribution from L-selectin, and that the arrest step is mediated by LFA-1 binding to ICAM-1 and ICAM-2.…”

Interleukin 4 or oncostatin M induces a prolonged increase in P-selectin mRNA and protein in human endothelial cells.

“…Endothelial cells stimulated with secretagogues normally limit the time that P-selectin can function by clearing it from the surface by endocytosis (37,38). However, P-selectin has also been observed on the luminal surface of endothelial cells in tissues with chronic or allergic inflammation (43)(44)(45). In these conditions, there must be mechanisms that prolong the surface expression of P-selectin.…”

“…Persistent expression of P-selectin on the endothelial cell surfa.ce has also been observed in tissues with chronic or allergic inflammation such as rheumatoid synovium (43), atherosclerotic plaque (44), and nasal polyp (45). In vitro, TNF-a or LPS induces a two-to fourfold increase in the steady-state levels of P-selectin transcripts in murine and bovine endothelial cells (46)(47)(48).…”

Stat6 Activation Is Essential for Interleukin-4 Induction of P-Selectin Transcription in Human Umbilical Vein Endothelial Cells

“…5 The importance of P-selectin in inflammation is aptly demonstrated by the decrease in numbers of rolling leukocytes in P-selectin-deficient mice, resulting in delayed and decreased leukocyte extravasation during acute inflammation. 6 Increased expression of P-selectin in the blood vessels at sites of inflammation has been observed in a number of chronic inflammatory diseases such as rheumatoid arthritis, 7 Graves disease, 8 nasal polyps, 9 and atherogenic plaques. 10 In a recent study of P-selectin-null mice crossed with low density lipoprotein receptor-null mice (an established model of familial hypercholesterolemia 11 ), the resulting double-knockout mice showed significantly smaller and fewer fatty streaks with delayed onset compared with their low density lipoprotein receptor-null parents.…”