Ca2+ response in neutrophils after exposure to bacterial N-formyl-methionyl-leucyl-phenylalanine: delayed response in ulcerative colitis.
OBJECTIVE
In acute stages of ulcerative colitis (UC), neutrophils migrate from the circulation into inflamed colonic tissue, initiated by yet unknown stimuli. The bacterial peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP) is a component of the surface membrane of colonic bacteria such as Escherichia coli and stimulates Ca2+ influx into neutrophils, reflecting the fact that ionized calcium is an important secondary messenger for several neutrophil functions, including locomotion, phagocytosis and free oxygen radical production. Recent studies have revealed that Ca2+ dependent ICAM-1/beta 2-integrin mediated neutrophil migration is impaired in UC patients. The aim of the present work was to study the influx of Ca2+ into peripheral blood neutrophils of UC patients after exposure to FMLP and after binding of either beta 2-integrins or intercellular adhesion molecule-1 (ICAM-1).


METHODS
The relative intracellular Ca2+ levels ([Ca2+]i ) were measured spectrofluorometrically in neutrophils isolated from eight UC patients and eight controls. The cells were exposed to 1 nm FMLP, 5 pm free ICAM-1, or antibodies binding ICAM-1 or the beta 2-integrins CD11a, CD11b, CD11c and CD18.


RESULTS
A pronounced increase in [Ca2+]i was observed by exposure of cells to FMLP, and neutrophils from UC patients showed a consistent and significant delayed response as compared to cells from control subjects (P < 0.01). Antibody mediated cross-linking of CD18 triggered a small but detectable increase in [Ca2+]i, which did not differ between patients and controls.


CONCLUSIONS
A delayed response to bacterial peptides appears to be a phenotypic trait for neutrophils of UC patients. A connection between FMLP stimulated Ca2+ influx and CD11/CD18 upregulation is discussed.
Vainer
Ben
B
Department of Pathology, Rigshospitalet, Copenhagen, Denmark. vainer@rh.dk
Lamberth
Kasper
K
Brimnes
Jens
J
Nielsen
Ole H
OH
Claësson
Mogens H
MH
D000328:Adult; D000368:Aged; D018845:CD11 Antigens / Q000097:blood; D002118:Calcium / Q000097:blood*; D015815:Cell Adhesion Molecules / Q000097:blood; D002465:Cell Movement; D002478:Cells, Cultured; D003093:Colitis, Ulcerative / Q000097:blood*; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects
D018845:CD11 Antigens; D015815:Cell Adhesion Molecules; D009240:N-Formylmethionine Leucyl-Phenylalanine; D002118:Calcium