Kooistra T, Lansink M, Arts J, Sitter T, Toet K
Gaubius Laboratory, TNO-PG, Leiden, The Netherlands.
Eur J Biochem. 1995 Sep 1;232(2):425-32.
Retinoids stimulate tissue-type plasminogen-activator (t-PA) gene expression in human endothelial cells, and are likely to do so by binding to one or more nuclear retinoid receptors. The present study was initiated to identify the retinoid receptor(s) involved in this process. Expression and regulation of retinoic acid receptors (RARs) and retinoid X receptors (RXRs) were analyzed by Northern-blot analysis of total or poly(A)-rich RNA prepared from cultured human umbilical vein endothelial cells (HUVEC). Prior to any exposure to retinoids, HUVEC express two transcripts for RAR-alpha (3.6 kb and 2.8 kb), and low levels of transcripts for RAR-beta (3.4 kb and 3.2 kb) and RAR-gamma (3.3 kb and 3.1 kb). Two RXR subtypes were identified, RXR-alpha (4.8 kb) and, at a much lower concentration, RXR-beta (2.4 kb); no evidence for the presence of RXR-gamma was found. Furthermore, HUVEC express cellular retinol-binding protein I (CRBP-I) and cellular retinoic-acid-binding protein I (CRABP-I) mRNA. Exposure of HUVEC to 1 microM retinoic acid or the retinobenzoic acid, Ch55, led to the induction of the two RAR-beta mRNAs, RXR-alpha mRNA and CRBP-I mRNA, whereas the expression of the other receptor and CRABP-I transcripts did not change appreciably. Using retinoid analogues that bind preferentially to one of the RAR or RXR subtypes, we found evidence that RAR-alpha is involved in the retinoid-induced t-PA expression in HUVEC. This conclusion was strengthened by experiments in which blocking of RAR-alpha with a specific RAR-alpha antagonist, Ro 41-5253, was demonstrated to suppress the induction of t-PA by retinoids.
维甲酸可刺激人内皮细胞中组织型纤溶酶原激活剂（t-PA）基因的表达，并且可能是通过与一种或多种核维甲酸受体结合来实现的。本研究旨在鉴定参与这一过程的维甲酸受体。通过对从培养的人脐静脉内皮细胞（HUVEC）中制备的总RNA或富含多聚腺苷酸（poly(A)）的RNA进行Northern印迹分析，来分析维甲酸受体（RARs）和维甲酸X受体（RXRs）的表达及调控情况。在未接触任何维甲酸之前，HUVEC表达两种RAR-α转录本（3.6 kb和2.8 kb），以及低水平的RAR-β转录本（3.4 kb和3.2 kb）和RAR-γ转录本（3.3 kb和3.1 kb）。鉴定出两种RXR亚型，即RXR-α（4.8 kb）和浓度低得多的RXR-β（2.4 kb）；未发现存在RXR-γ的证据。此外，HUVEC表达细胞视黄醇结合蛋白I（CRBP-I）和细胞视黄酸结合蛋白I（CRABP-I）的mRNA。将HUVEC暴露于1 μM维甲酸或视黄酸苯甲酸酯Ch5A，可导致两种RAR-β mRNA以及RXR-α mRNA和CRBP-I mRNA的诱导表达，而其他受体和CRABP-I转录本的表达没有明显变化。使用优先结合RAR或RXR亚型之一的维甲酸类似物，我们发现有证据表明RAR-α参与了维甲酸诱导的HUVEC中t-PA的表达。用特异性RAR-α拮抗剂Ro 41-5253阻断RAR-α的实验表明，该拮抗剂可抑制维甲酸对t-PA的诱导，从而强化了这一结论。
