Masahiro Kimata

Effects of luteolin, quercetin and baicalein on immunoglobulin E-mediated mediator release from human cultured mast cells.

Flavonoids have a variety of activities including anti‐allergic activities, and are known to inhibit histamine release from human basophils and murine mast cells.

Roles of mitogen-activated protein kinase pathways for mediator release from human cultured mast cells

Human cultured mast cells (HCMC) secrete histamine, sulfidoleukotrienes (LTs), and prostaglandin D(2) (PGD(2)), and produce a variety of cytokines after aggregation of high-affinity receptors for IgE (FcepsilonRI). With respect to the mitogen-activated protein kinase (MAPK) family, extracellular signal-regulated kinases (ERKs), c-Jun NH(2)-terminal kinases (JNKs), and p38 mitogen-activated protein kinase (p38 MAPK) are known. To investigate the roles of these kinase pathways for mediator release from human mast cells, we examined the participation of the activation of these kinases in mediator release, using 1,4-diamino-2, 3-dicyano-1,4-bis(2-aminophenylthio)butadiene (U0126), an ERK pathway inhibitor, and 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imid azo le (SB203580), a p38 MAPK pathway inhibitor. U0126 inhibited ERK activation, LT and PGD(2) release, and granulocyte macrophage-colony stimulating factor (GM-CSF) production after stimulation of HCMC. SB203580, on the other hand, potentiated JNK activation and GM-CSF production. The findings of the present study demonstrated that: (i) the release of arachidonic acid metabolites is mediated by the ERK pathway; (ii) GM-CSF production may be driven by both the ERK and JNK pathways; and (iii) the p38 MAPK pathway negatively regulates the JNK pathway. This suggests that MAPK pathways play important roles in mediator release from human mast cells.

Pharmacological Modulation of LPS-Induced MIP-1α Production by Peripheral Blood Mononuclear Cells

In the present study, we investigated the effects of some anti-asthmatic drugs on the production of the CC chemokine, macrophage inflammatory protein-1α (MIP-1α), in response to lipopolysaccharide (LPS) by peripheral blood mononuclear cells (PBMC). MIP-1α production was induced by LPS in a concentration-dependent fashion and reached the maximum at 10 µg/ml LPS (27.5±2.3 ng MIP-1α/106 PBMC). At a submaximal concentration of LPS (1 µg/ml), the release of MIP-1α increased with time and reached the maximum 24 h after LPS stimulation. Actinomycin D and cycloheximide inhibited MIP-1α production completely, but glucocorticoids did not completely inhibit MIP-1α production, with a maximum inhibition of 70%. We examined the effect of β-stimulants and phosphodiesterase inhibitors, which upregulate intracellular cyclic AMP levels, on MIP-1α production. When PBMC were treated with β-stimulants alone, β-stimulants showed a slightly inhibitory effect on MIP-1α production. However, the coadministration of roliplam significantly potentiated the inhibitory effect of β-stimulants on MIP-1α production. Moreover, db-cAMP suppressed MIP-1α production dose-dependently. The above data indicate that the production of MIP-1α is regulated by cyclic AMP and that cyclic AMP could provide a useful target for therapeutic treatment in asthmatic diseases and other diseases where MIP-1α is involved in their etiology.

Prednisolone Inhibits an IgE-Mediated Late-Phase Allergic Cutaneous Reactionby Interfering w ith the Activation of Mast Cells in Mice

Epicutaneous antigen challenge in passively sensitized mice with IgE produces a biphasic cutaneous response which peaks 1 h (immediate-phase reaction) and 24 h (late-phase reaction; LPR) after the antigen challenge. In this model, anaphylactic degranulation and interleukin 6 (IL-6) expression between 4 and 8 h are observed in resident mast cells as the preceding stage of LPR. Prednisolone at a dose of 3 mg kg–1 clearly inhibited the LPR when administered 2 h before and 4 h after antigen challenge. Slight or no inhibition of LPR was observed by prednisolone administered 6–12 h after challenge. Histologically, prednisolone treatment 2 h before antigen challenge completely inhibited edema and inflammatory cell infiltration, while treatment at 6 h did not at all. In order to investigate the relationship between inhibition of LPR by prednisolone and mast cell activation, the effects of prednisolone on degranulation of mast cells and IL-6 expression in mast cells were investigated. 8 h after antigen challenge, prednisolone clearly inhibited the increase in the number of anaphylactic degranulated and IL-6-positive mast cells by administration 2 h before challenge, but did not affect it by administration 6 h after challenge. These data indicate that the inhibitory mechanism of prednisolone on LPR, at least, involves the inhibition of mast cell activation before LPR.

Selective potentiation of IgE-dependent histamine release from rat peritoneal mast cells by stem cell factor

Effect of stem cell factor on histamine release from rat peritoneal mast cells was studied. Although stem cell factor did not evoke histamine release by itself, it clearly potentiated histamine release from sensitized mast cells caused by antigen, anti-IgE and concanavalin A. However, stem cell factor did not affect histamine release caused by compound 48/80, calcium ionophore A23187 and substance P. Although maximum potentiation of antigen-induced histamine release by stem cell factor was accomplished after 1-10 minute-preincubation, potentiation was decline after a longer incubation period. Potentiation of histamine release by phosphatidylserine and non-mast cells in the rat peritoneal cavity was incubation time-dependent. Potentiation by stem cell factor was additive to that by phosphatidylserine or non-mast cells. These results indicate that stem cell factor selectively potentiates IgE-dependent histamine release from rat peritoneal mast cells, and suggest that the mechanism involved is distinct from that of phosphatidylserine or non-mast cells in the rat peritoneal cavity.

The Roles of Mitogen-Activated Protein Kinase Pathways for Human Cultured Mast Cells

Background: Human cultured mast cells release histamine, sulfidoleukotrienes and prostaglandin D2, and produce some cytokines after an allergic reaction. As concerns the mitogen-activated protein kinase family, extracellular signal-regulated kinases, c-Jun NH2-terminal kinases and p38 mitogen-activated protein kinase are known. The present study has been conducted to investigate the role of mitogen-activated protein kinase in the mediator release from human cultured mast cells. Material and Methods: To investigate the role of these kinase pathways, we examined the participation of this kinase activation for mediator release by making use of U0126, a signal transduction, extracellular signal-regulated kinase pathway inhibitor, and SB203580, a p38 mitogen-activated protein kinase pathway inhibitor. Results: Histamine release is not related to mitogen-activated protein kinase pathways. Sulfidoleukotrienes and prostaglandin D2 release are mediated by signal transduction, extracellular signal-regulated kinase pathway. Granulocyte macrophage-colony-stimulating factor production may be induced by both signal transduction, extracellular signal-regulated kinase and c-Jun NH2-terminal kinase pathways. Conclusion: Mitogen-activated protein kinase pathways play an important role in mediator release from human mast cells.