Cagliero E, Roth T, Taylor A W, Lorenzi M
Schepens Eye Research Institute, Boston, Massachusetts, USA.
Lab Invest. 1995 Nov;73(5):667-73.
Because accumulation of extracellular matrix is a prominent characteristic of the microangiopathy that complicates long-term diabetes, a pathogenetic role for transforming growth factor beta (TGF-beta) is being considered. Having observed that glucose levels mimicking diabetic hyperglycemia induce in vitro endothelial cell overexpression of extracellular matrix molecules, decreased replication, and increased levels of TGF-beta mRNA, we have examined whether the effects of high glucose are mediated by autocrine TGF-beta.
TGF-beta levels were measured by bioassay in the media conditioned by human umbilical vein endothelial cells cultured in the presence of high (30 mM) or normal (5 mM) glucose concentrations. The effect of high glucose was tested on the proliferation of two epithelial cell lines, one (Mv1Lu) exquisitely sensitive to TGF-beta and the other (DR mutants) insensitive to the cytokine. To examine whether high glucose and TGF-beta affect cellular programs in a similar manner, the effects of high glucose and exogenous TGF-beta were compared on proliferation and gene expression of endothelial cells.
Media conditioned by endothelial cells cultured in high or normal glucose contained similar amounts of TGF-beta (4.9 +/- 3.5 and 3.7 +/- 2.5 ng/10(6) cells, respectively (mean +/- SD)), all in the latent form. The replication of parental Mv1Lu cells and their DR mutants was decreased by high glucose to the same extent. Whereas the inhibitory effect of high glucose on endothelial cell replication was reversible, that of TGF-beta was not. Both perturbations induced up-regulation of fibronectin expression, but the effects were additive. Only TGF-beta induced overexpression of Type IV collagenase.
These combined observations indicate that (a) endothelial cells exposed to high glucose do not secrete TGF-beta in excess of control cells, (b) there are growth-inhibitory effects of high glucose that are independent of TGF-beta, and (c) high glucose and TGF-beta exert their effects through distinct pathways and at different loci.
由于细胞外基质的积累是长期糖尿病所并发微血管病变的一个显著特征，因此正在考虑转化生长因子β（TGF-β）在发病机制中的作用。我们观察到模拟糖尿病高血糖水平的葡萄糖可在体外诱导内皮细胞过度表达细胞外基质分子、降低复制能力并增加TGF-β mRNA水平，于是我们研究了高糖的这些作用是否由自分泌的TGF-β介导。
通过生物测定法测量在高（30 mM）或正常（5 mM）葡萄糖浓度下培养的人脐静脉内皮细胞所分泌培养基中的TGF-β水平。检测了高糖对两种上皮细胞系增殖的影响，其中一种（Mv1Lu）对TGF-β极为敏感，另一种（DR突变体）对该细胞因子不敏感。为了研究高糖和TGF-β是否以相似的方式影响细胞程序，比较了高糖和外源性TGF-β对内皮细胞增殖和基因表达的影响。
在高糖或正常葡萄糖条件下培养的内皮细胞所分泌的培养基中，TGF-β含量相似（分别为4.9±3.5和3.7±2.5 ng/10(6) 个细胞，均值±标准差），均为潜伏形式。高糖使亲本Mv1Lu细胞及其DR突变体的复制能力下降程度相同。高糖对内皮细胞复制的抑制作用是可逆的，而TGF-β的抑制作用则不可逆。两种干扰均诱导纤连蛋白表达上调，但作用是相加的。只有TGF-β诱导IV型胶原酶过度表达。
这些综合观察结果表明：（a）暴露于高糖环境的内皮细胞分泌的TGF-β并不比对照细胞多；（b）高糖具有独立于TGF-β的生长抑制作用；（c）高糖和TGF-β通过不同途径和在不同位点发挥作用。
