Sensitized mast cells migrate toward the antigen: a response regulated by p38 mitogen-activated protein kinase and Rho-associated coiled-coil-forming protein kinase.

Although mast cells accumulate within the mucosal epithelial layer of patients with allergic rhinitis and bronchial asthma, the responsible chemotactic factors are undefined. We investigated whether mast cells sensitized with Ag-specific IgE migrate toward the Ag. MC/9 mast cells sensitized with anti-DNP IgE migrated toward DNP-conjugated human serum albumin. This migration was directional, and the degree was stronger than that induced by stem cell factor. IL-3 and stem cell factor-dependent cultured mast cells derived from mouse bone marrow also migrated toward the Ag. Subsequent migration mediated by the Fc(epsilon)RI was significantly inhibited by incubating the cells with Y-27632, a Rho-associated coiled-coil-forming protein kinase inhibitor, or with SB203580, a p38 mitogen-activated protein kinase (MAPK) inhibitor. Both p38 MAPK and MAPK-activated protein kinase (MAPKAPK)2 were activated following Fc(epsilon)RI aggregation, and activation of MAPKAPK2 was almost completely inhibited by 10 microM SB203580. Wortmannin or a low concentration of SB203580 partially inhibited MAPKAPK2, but did not block mast cell migration. In contrast, Y-27632 did not affect the activation of MAPKAPK2. These results indicate that Ag works not only as a stimulant for allergic mediators from IgE-sensitized mast cells, but also as a chemotactic factor for mast cells. Both p38 MAPK activation and Rho-dependent activation of Rho-associated coiled-coil-forming protein kinase may be required for Fc(epsilon)RI-mediated cell migration.

Sphingosine 1-phosphate may be a major component of plasma lipoproteins responsible for the cytoprotective actions in human umbilical vein endothelial cells.

Sphingosine 1-phosphate (S1P), a novel lipid mediator, is concentrated in the fraction of lipoproteins that include high density lipoprotein (HDL) and low density lipoprotein (LDL) in human plasma. Here, we show that oxidation of LDL resulted in a marked reduction in the S1P level in association with a marked accumulation of lysophosphatidylcholine (LPC). We therefore investigated the role of the lipoprotein-associated lipids especially S1P in the lipoprotein-induced cytoprotective or cytotoxic actions in human umbilical vein endothelial cells. The viability of the cells gradually decreased in the absence of serum or growth factors in the culture medium. The addition of oxidized LDL (ox-LDL) accelerated the decrease in the cell viability. LPC and 7-ketocholesterol mimicked ox-LDL actions. On the other hand, HDL and LDL almost completely reversed the serum deprivation- or ox-LDL-induced cytotoxicity. Exogenous S1P mimicked cytoprotective actions. Moreover, the S1P-rich fraction and chromatographically purified S1P from HDL exerted cytoprotective actions, but the rest of the fractions did not. The cytoprotective actions of HDL and S1P were associated with extracellular signal-regulated kinase (ERK) activation and were almost completely inhibited by pertussis toxin and PD98059, an ERK kinase inhibitor. The HDL-induced action was specifically desensitized in the S1P-pretreated cells. Taken together, these results indicate that the lipoprotein-associated S1P and the lipid receptor-mediated signal pathways may be responsible for the lipoprotein-induced cytoprotective actions. Furthermore, the decrease in the S1P content, in addition to the accumulation of cytotoxic substances such as LPC, may be important for the acquisition of the cytotoxic property to ox-LDL.

Inhibitory effect of a novel quinolinone derivative, TA-270, on asthmatic inflammatory responses in sensitized guinea pigs.

TA-270 (4-hydroxy-1-methyl-3-octyloxy-7-sinapinoylamino-2(1H)- quinolinone), a novel quinolinone derivative, was designed as an antioxidant to scavenge reactive oxygen species. Here, we investigated the effects of TA-270, in comparison with several antiasthmatic drugs, on asthmatic responses as induced by ovalbumin in sensitized guinea pigs. When orally administered 1 h before and 3 h after the antigen challenge, TA-270 at 10 mg/kg and higher doses significantly inhibited both immediate and late responses in airway resistance induced by the antigen. The inhibitory effects were comparable to or superior, at least under the present experimental conditions, to those of several clinically used antiasthmatic drugs. Furthermore, TA-270, in a dose-dependent manner, reduced accumulation of pulmonary inflammatory cells, especially eosinophils, and significantly reversed the airway hyperresponsiveness to acetylcholine 24 h after the antigen challenge. These results suggest that TA-270 may be of therapeutic use for bronchial asthma.