C5a-induced migration of human monocytes is primed by dexamethasone.

Abstract

Allergic inflammation in the lung is characteristic of allergic asthma. This inflammatory process is inhibited by treatment with glucocorticoids. One of the cell types involved in the inflammatory process, the monocyte, is found in enhanced numbers in mucosal lung biopsies of asthmatic patients. Little is known about the mechanisms that lead to increased numbers of monocytes in lung tissue. We studied one of the processes involved, chemotaxis, in a modified Boyden Chamber assay. The effect of the antiinflammatory drug dexamethasone was tested on monocyte chemotactic responses to complement fragment C5a. Human monocytes from peripheral blood of normal human volunteers were purified by centrifugal elutriation. The monocytes showed a reproducible chemotactic response toward C5a with an optimum at a concentration of 10(-9) M. After culture of the monocytes overnight, the monocyte responses were clearly impaired. It is interesting that upon culture, dexamethasone increased monocyte chemotaxis in a dose-dependent manner. Analysis of the filters with an image analyzer showed that the effect was not through modulation of a subpopulation of monocytes. This steroid effect was specific and modulated via steroid receptors, because the introduction of RU 38486, a steroid receptor antagonist, completely inhibited the effect of dexamethasone. These findings are a further illustration of the complex mechanisms involved in the orchestration of the inflammatory response in asthma.

P-selectin and MAC-1 mediate monocyte rolling and adhesion to ECM-bound platelets under flow conditions

“…Tissue culture supplies (media, antibiotics, and trypsin) were purchased from GIBCO Biocult (Paisley, UK). Experiments were carried out in HEPES buffer [20 …”

Complement Receptors in Inflammation

“…C5aR is a powerful chemoattractant receptor for monocytes (Pieters et al, 1995), neutrophils (Webster et al, 1980), eosinophils (DiScipio et al, 1999), basophils (Lett-Brown and Leonard, 1977), mast cells (Hartmann et al, 1997), B cells (Kupp et al, 1991) and T cells (Nataf et al, 1999). It also stimulates mast cell degranulation , mast cell chemotaxis in specific mast cell subtypes (Hartmann et al, 1997, McCloskey et al, 1999, oxidative burst in granulocytes and the production of reactive oxygen species (ROS) in neutrophils , secretion of lysosomal enzymes from macrophages (McCarthy and Henson, 1979) and polymorphonuclear (PMN) cells as well as the secretion of proinflammatory mediators from monocytes, eosinophils (Takafuji et al, 1994) and mast cells (Hartmann et al, 1997).…”

The Complement System

“…Antibody cross-linking of CD59 on human neutrophils was shown rapidly to trigger calcium flux and an oxidase response via activation of tyrosine kinases (102,140). In lymphocytes, it is apparent that CD59 within lipid rafts interacts with adaptor proteins that link through to intracellular kinases (99,100). The requirement for association in lipid rafts was vividly demonstrated by incorporating purified GPI-anchored CD59 into a CD59-negative cell line (141).…”