Modulatory effects of phytoglycoprotein (75 kDa) on allergic inflammatory cytokines in Di(2-ethylhexyl) phthalate (DEHP)-stimulated RBL-2H3 cells.

This study investigated the inhibitory effect of a glycoprotein isolated from Cudrania tricuspidata Bureau (CTB glycoprotein) on di(2-ethylhexyl) phthalate (DEHP)-induced mast cell degranulation and related signaling cascade in RBL-2H3 cells. This experiment evaluated the intracellular Ca(2+) level, and the activities of protein kinase C (PKC), mitogen-activated protein kinase (MAPK), transcription factor, and the cytokines in DEHP-treated RBL-2H3 cells. Our results revealed that the CTB glycoprotein in the presence of DEHP inhibits the release of histamine and expression of interleukin (IL)-4, IL-6, and TNF-alpha in RBL-2H3 cells. We also found that the CTB glycoprotein inhibits the intracellular Ca(2+) level, translocation of PKC from cytosol to membrane and the phosphorylation of ERK1/2 in cells. Moreover, the CTB glycoprotein (100 microg/ml) has suppressive effects on transcriptional activation of nuclear factor (NF)-kappaB in DEHP-treated RBL-2H3 cells. The activation of NF-kappaB was collectively blocked by treatment with PKC inhibitor (staurosporine) as well as ERK1/2 inhibitor (PD98059), respectively. The results from these experiments indicated that the CTB glycoprotein inhibits release of histamine and expressions of IL-4, IL-6, and TNF-alpha via down regulations of PKC/MAPK and NF-kappaB on the stage of mast cell degranulation induced by DEHP. Moreover, oral administration of CTB glycoprotein (10-20 mg/kg) inhibited compound 48/80-mediated systemic reaction in mice. In conclusion, we speculated that the CTB glycoprotein might be one component for preparation of health supplements for prevention of allergic immune disorders.