炎症状态下NF-κB-mTOR通路及转录因子RUNX1调控肾小管上皮细胞DC-SIGN表达研究

NF-κB-mTOR and RUNX1 regulate the expression of DC-SIGN in renal tubular epithelial cells during inflammation

探讨炎症状态下NF-κB通路、mTOR通路以及转录因子RUNX1对肾小管上皮细胞DC-SIGN表达调控。体外培养肾小管上皮细胞株(HK-2)并经TNF-α刺激,分别给予NF-κB抑制剂(BAY 11-7082)和mTOR抑制剂(Rapamycin)干预。采用免疫印迹试验和实时定量PCR法检测HK-2细胞DC-SIGN表达;免疫印迹试验检测mTOR的磷酸化水平。用上述经TNF-α刺激的HK-2以及建立的肾炎损伤小鼠模型,以实时定量PCR法检测HK-2细胞以及分离的模型鼠肾小管上皮细胞中RUNX1表达。进一步利用HK-2构建过表达RUNX1稳定转染细胞株并经TNF-α刺激,实时定量PCR法检测RUNX1和DC-SIGN表达。结果显示,HK-2经TNF-α刺激模拟炎症状态下,可促进mTOR磷酸化并诱导DC-SIGN表达;NF-κB抑制剂和mTOR抑制剂均能抑制HK-2细胞的DC-SIGN表达,NF-κB抑制剂亦可抑制mTOR的磷酸化。还发现炎症因素刺激下,人和小鼠肾小管上皮细胞体内体外均明显表达RUNX1,且过表达RUNX1的HK-2细胞稳转株显著表达DCSIGN,并在TNF-α刺激下可进一步上调DC-SIGN表达。本研究表明,肾脏微炎症状态下,NF-κB-mTOR通路以及转录因子RUNX1均参与了肾小管上皮细胞DC-SIGN的表达调控。提示此过程中,NF-κB通路作为mTOR上游通路,通过激活后者参与DC-SIGN表达,而转录因子RUNX1可能是启动DC-SIGN表达的关键调控因素。

We investigated the regulatory roles of NF-κB, mTOR and transcription factor RUNX1 in the expression of DC- SIGN in renal epithelial cells when the cells were in the environment of inflammation. The human cell line HK-2 cells were stimulated with TNF-α in the presence of NF-κB inhibitor BAY 11-7082 and mTOR inhibitor Rapamycin. And then the expres- sion of DC-SIGN and phosphorylation of mTOR were examined by Western blotting or quantitative RT-PCR. The mRNA lev els of RUNX1 in HK-2 cells and the isolated mice renal tubular epithelial cells from LPS-induced acute inflammatory kidney in jury were assessed by quantitative RT-PCR. Finally, the mRNA levels of RUNX1 and DC-SIGN in HK-2 cells that overex- pressed RUNX1 owing to TNF-α stimulation were determined by quantitative RT-PCR. The results showed that TNF-α, a ma- jor trigger of inflammation, could promote the phosphorylation of roTOR and the expression of DC SIGN, and both BAY 11 7082 and Rapamycin could inhibit TNF-α induced expression of DC-SIGN in HK-2 cells. On the other hand, BAY 11 7082 could block phosphorylation of mTOR. In addition, in vivo or in vitro inflammatory stimulation promoted RUNX1 expression in renal tubular epithelial cells. We further found that RUNX1 overexpression promoted the expression of DC-SIGN in HK-2 cells with or without TNF-α stimulation. This study suggests that all of NF-κB, roTOR and transcription factor RUNX1 par- ticipate in regulating the expression of DC-SIGN in renal tubular epithelial cells during inflammation. It further reveals that NF- κB which is located at upstream of mTOR could participate in regulating DC SIGN expression and RUNX1 may have a vital role in activating DC-SIGN expression.