Cubilin在白蛋白刺激肾小管上皮细胞表达MCP-1、RANTES中的作用

The role of Cubilin in albumin induced MCP-1, RANTES expression by renal tubular epithelial cells

目的 探讨白蛋白刺激肾小管上皮细胞表达细胞趋化因子的分子机制。方法 免疫组织化学方法检测 10例肾病综合征患者和 8例单纯血尿患者肾组织白蛋白沉积和MCP 1、RANTES的表达 ,常规染色观察肾组织病理改变。以DOTAP分别将空载体、正义或反义Cubilin核酸转染至HK2细胞 ,荧光显微镜观察HK2细胞对白蛋白的摄取情况 ,Westernblot检测HK2细胞Cubilin、MCP 1和RANTES的表达变化。结果 对照组肾组织中肾小管上皮细胞胞浆可见少量白蛋白沉积 ,MCP 1、RANTES有微弱表达 ;肾病综合征组肾小管上皮细胞胞浆可见大量白蛋白颗粒 ,MCP 1和RANTES表达明显增强 ,并可见肾间质单个核细胞浸润等组织学改变。体外实验 ,与正义Cubilin组、空载体组和DOTAP组比较 ,反义Cubilin组Cubilin表达显著下调 ,HK2细胞的白蛋白吞饮以及MCP 1、RANTES的表达减少。结论 肾小管上皮细胞对白蛋白的重吸收增加可能与其趋化因子表达上调有密切关系 ,其中Cubilin可能具有重要作用。

Objective To study the molecular mechanism of albumin induced MCP 1 and RANTES expression by renal tubular epithelial cells (RTECs). Methods Ten nephrotic syndrome patients and eight hematuric patients were collected into this study. In vivo, albumin deposition,MCP 1 and RANTES expression in kidney tissues from these patients were examined by immunochemstry. In vitro, expression vector harboring sense or antisense cubilin gene fragment was transfected into HK2 cells with lipofectin DOTAP. Endocytosis of FITC labeled human serum albumin (FITC HSA) by RTECs was detected by fluorescent microscope. MCP 1 and RANTES expression were determined by Western blot analysis. Results Under the light microscope, normal histological configuration was observed in the hematuric patients; obvious tubulointerstitial lesions such as inflammatory cell infiltration, tubular cell atrophy and tubulointerstitial fibrosis were shown in the nephrotic syndrome patients. By immunohistochemistry study, only a small quantity of albumin were found within the RTECs in the hematuric patients; but a large amount of albumin were seen within the RTECs and interstitium in the nephrotic syndrome patients. MCP 1 and RANTES were weakly expressed in the hematuric patients; but very strongly expressed in the nephrotic syndrome patients. In vitro, cubilin expression by HK2 cells was obviously inhibited by antisense cubilin (pCDNA ACUB). HSA FITC uptake was lower in HK2 cells transfected with pCDNA ACUB than in the cells harboring sense cubilin (pCDNA CUB) or Vector (pCDNA3.1(+)). Both MCP 1 and RANTES expression were significantly suppressed in HK2 cells transtected with pCDNA ACUB when compared with the cells harboring pCDNA CUB or pCDNA3.1(+), respectively. Conclusion Excessive albumin reabsorption may have close relationship with over expression of MCP 1 and RANTES by RTECs, which might be responsible for the tubulointersitial injury associated with proteinuria. Cubilin may play a key role in regulation of this process.