Release of prostaglandin D2 by murine mast cells: importance of metabolite formation for antiproliferative activity.

Prostaglandin (PG) D2, PGJ2 and delta12-PGJ2 are antiproliferative eicosanoids. We investigated the production of PGD2 by murine bone marrow-derived mast cells (BMMC) taking into consideration metabolism of PGD2 to PGD2 and delta12-PGJ2. PG-metabolites were quantified by high performance liquid chromatography (HPLC) combined with radioimmunoassay (RIA). Stimulated with calcium ionophore A23187 BMMC released eight-fold more PGJ2 and delta12-PGJ2 than PGD2. Conversion of endogenously produced PGD2 to PGJ2 and delta12-PGJ2 proceeded rapidly in contrast to metabolism of exogenously added PGD2. The antiproliferative potency of these prostaglandins is demonstrated in vitro. We conclude that determination of PGD2 production by mast cells must take into consideration rapid conversion to active derivatives, which may play a significant role in growth regulation

Mast Cells Control Neutrophil Recruitment during T Cell–Mediated Delayed-Type Hypersensitivity Reactions through Tumor Necrosis Factor and Macrophage Inflammatory Protein 2

Polymorphonuclear leukocytes (PMNs) characterize the pathology of T cell–mediated autoimmune diseases and delayed-type hypersensitivity reactions (DTHRs) in the skin, joints, and gut, but are absent in T cell–mediated autoimmune diseases of the brain or pancreas. All of these reactions are mediated by interferon γ–producing type 1 T cells and produce a similar pattern of cytokines. Thus, the cells and mediators responsible for the PMN recruitment into skin, joints, or gut during DTHRs remain unknown. Analyzing hapten-induced DTHRs of the skin, we found that mast cells determine the T cell–dependent PMN recruitment through two mediators, tumor necrosis factor (TNF) and the CXC chemokine macrophage inflammatory protein 2 (MIP-2), the functional analogue of human interleukin 8. Extractable MIP-2 protein was abundant during DTHRs in and around mast cells of wild-type (WT) mice but absent in mast cell–deficient WBB6F1-KitW/KitW-v (KitW/KitW-v) mice. T cell–dependent PMN recruitment was reduced >60% by anti–MIP-2 antibodies and >80% in mast cell–deficient KitW/KitW-v mice. Mast cells from WT mice efficiently restored DTHRs and MIP-2–dependent PMN recruitment in KitW/KitW-v mice, whereas mast cells from TNF−/− mice did not. Thus, mast cell–derived TNF and MIP-2 ultimately determine the pattern of infiltrating cells during T cell–mediated DTHRs

IL-9 Induces VEGF Secretion from Human Mast Cells and IL-9/IL-9 Receptor Genes Are Overexpressed in Atopic Dermatitis

Interleukin 9 (IL-9) has been implicated in mast cell-related inflammatory diseases, such as asthma, where vascular endothelial growth factor (VEGF) is involved. Here we report that IL-9 (10–20 ng/ml) induces gene expression and secretion of VEGF from human LAD2. IL-9 does not induce mast cell degranulation or the release of other mediators (IL-1, IL-8, or TNF). VEGF production in response to IL-9 involves STAT-3 activation. The effect is inhibited (about 80%) by the STAT-3 inhibitor, Stattic. Gene-expression of IL-9 and IL-9 receptor is significantly increased in lesional skin areas of atopic dermatitis (AD) patients as compared to normal control skin, while serum IL-9 is not different from controls. These results imply that functional interactions between IL-9 and mast cells leading to VEGF release contribute to the initiation/propagation of the pathogenesis of AD, a skin inflammatory disease

Tetrahydro-6-biopterin is associated with tetrahydro-7-biopterin in primary murine mast cells.

Murine bone marrow-derived mast cells proliferate in response to interleukin 3. In addition to 6-biopterin, 7-biopterin was identified in these cells by HPLC analysis of iodine oxidized extracts and by alkaline permanganate oxidation to the 6- and 7-carboxylic acids. 7-Biopterin comprised 31.9 (±7.7)% of the total biopterin. It was absent in cells which were grown with of L-p-chlorophenylalanine, an inhibitor of tryptophan 5-monooxygenase. Both 6- and 7-biopterin were present in the cell as their tetrahydro forms. From these data we conclude that 7-biopterin, in contrast to e.g. brain tissue, regularly occurs as a normal metabolite in primary mast cells and that it is generated during hydroxylation of tryptophan

Mast cell growth-enhancing activity (MEA) stimulates interleukin 6 production in a mouse bone marrow-derived mast cell line and a malignant subline.

A novel mast cell growth-enhancing activity (MEA/P40/interleukin 9 [IL-9]) purified from the conditioned medium of a murine interleukin 2 (IL-2)-dependent Mlsa-specific T-cell line (MLS4.2) was tested for its capacity to induce interleukin 6 (IL-6) production in a mouse bone marrow-derived factor-dependent mast cell line (L138.8A). This interleukin 3 (IL-3)/interleukin 4 (IL-4)/MEA-responsive cell line was demonstrated recently to express IL-6 mRNA and to secrete IL-6 when cultured with IL-3/IL-4. Now we were able to show that conditioned medium from L138.8A mast cells stimulated with MEA alone contained growth factor activity for the IL-6-dependent mouse hybridoma cell line 7TD1 that was completely blocked by the monoclonal anti-IL-6 antibody 6B4. A dose-response study including IL-3, IL-4, and MEA tested either alone or in different combinations revealed that among these growth factors MEA was the most potent inducer of IL-6 in L138.8A cells. Moreover, IL-4 but not IL-3 had a strong synergistic effect on MEA-induced IL-6 production. The autonomous malignant mast cell subline L138Cauto also showed enhanced IL-6 production when stimulated with MEA. Our findings indicate that MEA (IL-9) not only provides a proliferation signal, but also leads to a marked functional activation of responsive mast cells