Fehrenbach H, Weiskirchen R, Kasper M, Gressner A M
Institute of Pathology, University Clinics Carl Gustav Carus, Dresden, Germany.
Hepatology. 2001 Nov;34(5):943-52. doi: 10.1053/jhep.2001.28788.
Receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily of cell-surface molecules. Blockade of RAGE has been reported to considerably improve liver function and accelerate regeneration after hepatectomy. The aim of this study was to investigate the cell type-specific expression of RAGE, and to examine whether transdifferentiation of hepatic stellate cells (HSC) into myofibroblasts (MFB) is associated with changes in RAGE expression. Northern blot analysis revealed that RAGE mRNA was exclusively expressed by HSC isolated from rat liver, while no transcripts were seen in hepatocytes, Kupffer cells, or sinusoidal endothelial cells. Expression of RAGE mRNA was up-regulated during transdifferentiation of HSC into MFB. Concomitantly, expression of RAGE protein was increased as confirmed by Western blotting and immunohistochemistry. As assessed by radioactive labeling, transforming growth factor beta(1) (TGF-beta(1)) induced a time-dependent 2- to 15-fold increase in the de novo synthesis of RAGE protein, which was completely abolished using PD098059, a specific inhibitor of the mitogen-activated protein kinase (MAPK) kinase. As shown by double-immunofluorescence staining, RAGE colocalized with alpha-smooth muscle actin, and immunoelectron microscopy demonstrated the most prominent labeling for RAGE at filopodial membranes of MFB. In conclusion, this study demonstrates that expression of RAGE is restricted to rat HSC, and that expression is up-regulated during activation of HSC and transition to MFB. The preferential immunogold labeling of RAGE to focal membrane areas of filopodia of MFB is suggestive of a role of RAGE in the spreading and migration of activated HSC/MFB, major players in liver fibrogenesis.
晚期糖基化终末产物受体（RAGE）是细胞表面分子免疫球蛋白超家族的成员。据报道，阻断RAGE可显著改善肝功能并加速肝切除术后的再生。本研究的目的是调查RAGE的细胞类型特异性表达，并检查肝星状细胞（HSC）向肌成纤维细胞（MFB）的转分化是否与RAGE表达的变化相关。Northern印迹分析显示，RAGE mRNA仅由从大鼠肝脏分离的HSC表达，而在肝细胞、库普弗细胞或窦状内皮细胞中未检测到转录本。在HSC向MFB的转分化过程中，RAGE mRNA的表达上调。同时，蛋白质印迹和免疫组织化学证实RAGE蛋白的表达增加。通过放射性标记评估，转化生长因子β(1)（TGF-β(1)）诱导RAGE蛋白的从头合成呈时间依赖性增加2至15倍，使用丝裂原活化蛋白激酶（MAPK）激酶的特异性抑制剂PD098059可完全消除这种增加。如双免疫荧光染色所示，RAGE与α-平滑肌肌动蛋白共定位，免疫电子显微镜显示在MFB的丝状伪足膜上RAGE的标记最为突出。总之，本研究表明RAGE的表达仅限于大鼠HSC，并且在HSC激活和向MFB转变过程中表达上调。RAGE在MFB丝状伪足的局灶膜区域的优先免疫金标记提示RAGE在肝纤维化形成的主要参与者活化HSC/MFB的扩散和迁移中起作用。
