Sabine Krüger-Krasagakes

Pharmacological modulation of IL‐6 and IL‐8 secretion by the H1‐antagonist decarboethoxy‐loratadine and dexamethasone by human mast and basophilic cell lines

Abstract Mast cells and basophils are central effector cells of allergic reactions and are involved in inflammatory diseases. These cell types produce an array of mediators including a broad spectrum of cytokines. In order to examine whether antiallergic drugs modulate the release of these mediators, we have investigated the influence of dexamethasone and decarboethoxy‐loratadine (DEL), the active metabolite of the H1‐blocking agent loratadine, on the release of IL‐6 and IL‐8 by the human mast cell line HMC‐1 and the human basophilic cell line KU812 by ELISA. Dexamethasone (10−6‐10−11 M) or Del (10−5‐10−14 M) were added to the cells either 1 h prior to or simultaneously with PMA and Ca‐ionophore A23187. When preincubated with the cells, DEL dose‐dependently suppressed IL‐6 release by up to 40% and IL‐8 release by up to 50%. Dexamethasone potently suppressed secretion of both cytokines if simultaneously added to the cells with the stimuli by up to 60% and after preincubalion by up to 80%. Since both antihistamines and glucocorticoids are used for treatment of allergic diseases, the findings reported here indicate that these drugs may modulate allergic reactions via inhibition of cytokine release from mast cells and basophils.

Adhesion of human mast cells to extracellular matrix provides a co-stimulatory signal for cytokine production

Engagement of integrin receptors during cell adhesion leads to changes in the morphology and the state of activation of cells. We therefore examined whether mast cell adhesion to extracellular matrix proteins affects the synthesis and release of various proinflammatory cytokines. Cells of the human mast cell line HMC‐1 were added to fibronectin (FN)‐, vitronectin (VN)‐ or, as a control, bovine serum albumin (BSA)‐coated wells and were stimulated with phorbol 12‐myristate 13‐acetate (PMA) and/or calcium ionophore A23187 (ionophore). Cytokine production was evaluated using semiquantitative reverse transcription–polymerase chain reaction (RT–PCR) analysis of cell extracts and enzyme‐linked immunosorbent assay (ELISA) analysis of cell supernatants. After a 4‐hr incubation, mRNA expression of interleukin (IL)‐8 (and weakly of IL‐6) was up‐regulated in matrix‐adherent cells, with further increase in the presence of PMA and/or ionophore, compared with unstimulated cells. High‐level de novo expression of IL‐3 and of granulocyte–macrophage colony‐stimulating factor (GM‐CSF) was observed mainly in matrix‐adherent cells. These changes were paralleled by the secretory pattern of HMC‐1 cells after a 24‐hr stimulation. Unstimulated cells adherent to FN or VN had already released small amounts of IL‐8, and both VN‐ and FN‐adherent cells produced, almost invariably, a higher level of cytokines than BSA‐exposed cells after additional stimulation. These results show that mast cell adhesion to matrix proteins by itself has only selected and minor effects, but additional activation of mast cells by secretory stimuli causes significantly enhanced cytokine gene expression and secretion, suggesting that mast cells are far more active in their natural tissue environment than hitherto suggested from data in suspension cultures.

Glucocorticoid-induced modulation of cytokine secretion from normal and leukemic human myelomonocytic cells.

Since glucocorticoid effects on inflammatory processes may be mediated via modulation of cytokine release, different types of myelomonocytic cells were stimulated in vitro with lipopolysaccharide (50 ng/ml) or phorbol myristate acetate (25 ng/ml) plus the ionophore A23187, 2 x 10(-7) M, and release of interleukin (IL)-1 beta, IL-8 and tumor necrosis factor (TNF)-alpha was measured after 24 h by ELISA. Peripheral blood mononuclear cells from two allergic and two normal human donors released similarly large quantities of IL-8 and lower amounts of IL-1 beta and TNF-alpha. This also held for myelomonocytic cell lines, with THP-1 cells being most active, followed by U-937 and HL-60 cells. All potent glucocorticoids studied caused a dose-dependent inhibition of cytokine release from donor cells, being most marked for IL-1 beta and lowest for IL-8. Inhibition of cytokine release was also noted with U-937 cells, with clear differences in potency between the glucocorticoids, whereas release was enhanced in all experiments with THP-1 cells. These results were confirmed with Northern blot analysis. Modulating effects of glucocorticoids on cytokine release are thus complex, and are particularly dependent on the cell type studied.

Mast cells in the cytokine network: the what, where from and what for

Abstract The basic understanding of mast cell ontogeny and function has been fundamentally changed in recent years with observations that the cells produce and respond to a broad range of cytokines. These rapidly accruing data and their potential significance were discussed at the recent symposium “Mast Cells in the Cytokine Network”, and the overview lectures of most speakers are summarized in this special journal issue. In the present introductory manuscript, the organizers of the meeting discuss data fundamental to an understanding of the topic and highlight aspects of special interest. They consider mast cells to be defined most reliably by their unique ultrastructure since the cells are highly heterogeneous in dependence of the species studied, their tissue location, their stage of development and probably also in relation to cytokines. Most other characteristics of mast cells are shared with diverse other cell types. Murine mast cell development is induced by several cytokines. These factors are mostly ineffective in human cells except for stem cell factor which causes mast cell development from CD34+/c‐kit+ progenitors. There is however recent evidence thai fibroblasts and keratinocytes produce additional growth factors for human mast cells. Regarding cytokine secretion, most molecules known so far are produced by both murine and human mast cells. The cells furthermore bear receptors for several cytokines, enabling them to respond in an autocrine and paracrine fashion. Mast cells may thus function within a complex cytokine network, affecting physiological as well as immunological and inflammatory processes.

Cytokine secretion by human mast cells

Abstract Mast cells have been traditionally viewed as effector cells of immediate‐type hypersensitivity reactions. Besides this, mast cell activation and degranulation have been associated with various biologically and clinically important functions. Results of the past few years suggest that mast cells are involved in the development of late‐phase reactions and influence other chronic inflammatory responses through the generation and secretion of various multipotcnlial cylokines.

Modulation of in vitro Cytokine Release from Human Leukemic Mast Cells (HMC-1) by Glucocorticoids

Mast cells are well known effector cells not only in allergic but also in diverse acute and chronic inflammatory diseases. We have shown previously that these cells produce a broad spectrum of cytokines which might contribute to mast cell-dependent pathology. In the present study, we have investigated the influence of four potent glucocorticoids, methylprednisolone-aceponate, methylprednisolone-17-propionate, prednicarbate, and betametasone valerate (10(-5) M-10(-9) M), on the IL-1 beta, IL-3, IL-8, and tumor necrosis factor alpha secretion of the HMC-1 mast cell line as measured by ELISA. All four glucocorticoids caused a comparable dose- and time-dependent inhibition of cytokine release from HMC-1 cells stimulated for 24 h with phorbol 12-myristate 13-acetate 25 ng/ml and calcium ionophore 2 x 10(-7) M. These results shed further light on the mechanisms involved in antiinflammatory effects of glucocorticoids in allergic inflammation.