SIGNAL-TRANSDUCING MECHANISM OF OXLDL-INDUCED LOX-1 GENE EXPRESSION IN CEREBRAL ENDOTHELIAL CELLS

• Main Authors: Lu,Yi-Ling, 陸怡伶
• Other Authors: Chen, Ruei-Ming
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/07388557106024189705

碩士 === 臺北醫學大學 === 醫學研究所 === 94 === Low density lipoprotein (LDL) can be oxidized to oxidized LDL (oxLDL). OxLDL can damage a variety of tissues and cells. Lectin-like oxLDL receptor-1 (LOX-1) is a membrane protein specifically mediating endocytosis of oxLDL and its toxicity to cells. Cerebral endothelial cells (CECs) are important components in blood brain barrier (BBB). LOX-1 is inducible in CECs, but its regulatory mechanism is still unknown. This study is aimed to evaluate the signal-tranducing mechanism of oxLDL-induced LOX-1 gene expression using mouse CECs as the experimental model. Previous studies in our lab revealed that oxLDL could cause apoptosis in CECs. Thus, one of the specific aims in this study was to determine if LOX-1 receptor had a critical role in oxLDL-induced apoptosis of CECs. Administration of CECs with oxLDL increased LOX-1 mRNA production in concentration- and time-dependent manners. In the LOX-1 siRNA experiment, we detect the distribution of apoptotic cells using microscope and flow cytometry. The data show that LOX-1 siRNA effectively inhibited oxLDL-induced apoptosis. Thus, the other aim of this study was to evaluate the signal-tranducing mechanism of oxLDL on LOX-1 gene expression. Previous studies in our lab revealed that oxLDL could increase reactive oxygen species (ROS) in CECs. NF-κB is a redox sensitive transcription factor. In parallel with LOX-1 mRNA induction, oxLDL activated transcription factor NF-κB and promoted its translocation from cytoplasm into nuclei. Administration of Bay 11-7085, an NF-κB inhibitor, then consequently inhibited LOX-1 mRNA production. NF-κB activated by upstream protein kinases. IKK, an upstream kinase for NF-κB activation, was activated after exposure to oxLDL for 30 min. ERK1/2, an upstream kinase for IKK activation, was activated after exposure to oxLDL for 15 min. When exposed to oxLDL for 5 min, MEK1/2, a kinase for ERK1/2 activation, was activated. Besides , Raf, a kinase for MEK 1/2 activation, was activated by oxLDL. Ras, a kinase for Raf, was also activated by oxLDL. We also observed that oxLDL-induced LOX-1 gene expression, NF-κB translocation and Raf phosphorylation were inhibited in the LOX-1 siRNA experiment. This study has shown that LOX-1 mediated oxLDL-induced apoptosis of CECs, and oxLDL induced LOX-1 gene expression via a Ras/Raf/MEK/ERK-dependent activation of NF-κB.