Studies on the Phytoestrogens-induced Cyclooxygenase-2 Expression in Macrophages and Glomerular Mesangial Cells

• Main Authors: Chuan-Ju Chou, 周娟如
• Other Authors: 劉興華
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/12648101824502801807

碩士 === 國立臺灣大學 === 毒理學研究所 === 90 === Phytoestrogens are natural constituents of the human diet. The possible estrogenic effects of phytoestrogens have been investigated using a combination of in vitro and in vivo assays. Cyclooxygenase (COX) is the key enzyme required for the conversion of arachidonic acid to prostaglandins. There are two isoforms of cyclooxygenase, COX-1 and COX-2. COX-1 expression is consistent throughout the cell cycle and is relatively unaffected by treatment of cells with mitogenic or inflammatory compounds. COX-2, on the other hand, is highly inducible; its expression is elevated by variety of stimuli, including mitogens, tumor promoters and cytokines. Few, if any, studies have been made on the impact of these compounds on the immune system and renal function. Prostaglandins are important mediators of activated macrophage functions and their inducible synthesis is mediated by cycloxygenase-2 (COX-2). We sought to determine the activities of various phytoestrogens on the modulation of the COX-2 gene and protein expression in macrophage cell line RAW264.7 and mesangial cell line SV40 MES13. 17β- estradiol (E2) was capable of inducing the COX-2 gene and protein expression, and could be partially antagonized by antiestrogen ICI182780. Similar to the E2 response, phytoestrogens, β-sitosterol (β-SIT), resveratrol (RES), genistein (GEN), adlay seed extract (AE) and yam extract (YE) could also induce the COX-2 expression, and was partially antagonized by ICI182870. These phytoestrogens trigger the phosphorylation of ERK1/2 and p38 MAPK in cells. MAP kinase kinase (MEK) inhibitor PD98059 and p38 MAP kinase inhibitor SB203586 were capable of inhibiting the COX-2 expression induced by these phytoestrogens. PI3-kinase inhibitor wortmanin and LY294002 were also capable of inhibiting the COX-2 expression induced by these phytoestrogens. Moreover, phytoestrogens could induce reactive oxygen species (ROS) production in RAW264.7 and SV40 MES13, and the antioxidant NAC could inhibit COX-2 induction by phytoestrogens. Then, we found phytoestrogens also could activate NF-κB, and transfection of cells with dominant negative mutants of IKKα and IKKβ partially inhibited phytoestrogens-induced expression of COX-2. These phytoestrogens was capable of triggering the production of PGE2 in cells. On the cell proliferation, β-SIT, RES and GEN inhibited cell growth, while AE and YE promote cell growth. COX-2 selective inhibitor NS-398 inhibited cell proliferation by AE and YE, but unaffected cell growth inhibition by β-SIT, RES and GEN. These results indicate that the MAPK pathway and PI3-kinase pathway were involved in phytoestrogens-induced COX-2 expression in macrophages and glomerular mesangial cells, and NF-κB is an important mediator in the process.