Abstract
Tricin, a flavone present in rice bran, is confirmed as the major efficacious compound present in the enzyme-treated Zizania latifolia extract (ETZL), which protects against UVB-induced skin-aging. However, the suppressive mechanism of tricin on allergic responses remains unknown. The present study, therefore, aimed to determine the mechanisms of tricin and ETZL on mast cell degranulation in IgE-activated rat basophilic leukemia cell line (RBL-2H3) cells. We investigated the regulatory effects of tricin and ETZL on degranulation, production of cytokines and lipid mediators, and signaling proteins involved in the IgE-bound high-affinity IgE receptor activation, mitogen-activated protein kinase, arachidonic acid and Syk. The production of β–hexosaminidase, tumor necrosis factor-α, interleukin-4, leukotrienes (LT) B4, LTC4 and prostaglandin E2 in IgE-stimulated RBL-2H3 cells were significantly inhibited by exposure to tricin or ETZL. Moreover, tricin and ETZL inhibit the phosphorylation of cytosolic phospholipase A2, 5-lipoxygenase and cyclooxygenase-2. Furthermore, the phosphorylation of Akt, ERK, p38, JNK, protein kinase Cδ and phospholipase Cγ1 were effectively suppressed by both samples. Exposure to tricin or ETZL also significantly decreases the phosphorylation of Lyn and Syk, but has minimal effect on Fyn. Taken together, our data indicate that tricin and ETZL are potential anti-allergic materials that could be applied for the prevention of allergy-related diseases.
Highlights
Zizania latifolia (Gramineae) is the only member of the wild rice genus Zizania native to Asia, including China, Korea and Japan
The same derivatives were identified for the ethanol extract of Z. latifolia
Our previous quantitative study identifying the tricin derivatives in extract of Z. latifolia (ETZL) confirmed the simultaneous increase of four derivatives along with tricin levels, as compared to the contents obtained in NEZL
Summary
Zizania latifolia (Gramineae) is the only member of the wild rice genus Zizania native to Asia, including China, Korea and Japan. The methanol extract of the aerial portion suppresses allergic responses in rat basophilic leukemia cell line (RBL-2H3) through inhibition of compound 48/80-induced degranulation, antigen-induced β-hexosaminidase release and phorbol 12-myristate 13-acetate plus A23187-induced tumor necrosis factor (TNF)-α production [8]. (Figure in the methanol extractrelease prepared using the aerial portion of Z. latifolia. The tricin derivatives were1)determined to prevent of β-hexosaminidase in RBL-2H3 cells [8]. The tricin derivatives were determined to prevent releaseEof β-hexosaminidase in RBL-2H3 cells sensitized with anti-dinitrophenyl (DNP) immunoglobulin (IgE). Tricin was found to be theprostaglandin quantitativelyEmajor component obtained in cells and murine plasma [9]. With an enzyme mixture significantly increased the tricin content in a hydrolyzed ethanol extract [7]
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