Kim H J, Kim T-Y
Department of Pharmacology, College of Medicine, Gyeongsang National University, 92 Chilan-dong, Jinju, South Korea.
Br J Dermatol. 2005 Mar;152(3):418-25. doi: 10.1111/j.1365-2133.2004.06397.x.
Vascular endothelial growth factor (VEGF) is overexpressed in hyperproliferative diseases such as psoriasis and cancer, which are characterized by an increased angiogenesis. It was reported that insulin-like growth factor (IGF)-II is highly expressed during hepatocarcinogenesis and is increased in psoriatic lesions. The increase in IGF-II is believed to be associated with the pathogenesis of these diseases by increasing angiogenesis.
In order to investigate the relationship between IGF-II and angiogenesis-related VEGF, VEGF expression in the IGF-II-treated human keratinocytes was monitored and the IGF-II signalling pathways were examined with respect to VEGF expression.
Northern blot analysis for the VEGF mRNA levels and an enzyme-linked immunosorbent assay for the VEGF protein were performed to determine if IGF-II (100 ng mL(-1)) can increase the VEGF expression levels with or without a pretreatment with protein inhibitors in primary normal human keratinocytes and HaCaT cells.
The mRNA and protein levels of VEGF by IGF-II were increased in a time-dependent manner and reached the maximum level 2 h and 8 h after the IGF-II treatment, respectively. However, this increase was abrogated by pretreatment with an extracellular signal-regulated kinase (ERK) inhibitor but not by a p38 inhibitor. The IGF-II-mediated VEGF induction was also effectively inhibited by a pretreatment with the tyrosine kinase inhibitor and Src inhibitor. The PI3-kinase inhibitor also inhibited the expression of VEGF by IGF-II. However, the phospholipase C (PLC) and protein kinase C (PKC) inhibitors did not block the increases of VEGF mRNA level and its protein level by IGF-II, and the PKC inhibitor instead increased VEGF expression by IGF-II.
These results suggest that the tyrosine kinase-Src-ERK1/2 pathway and the PI3-kinase pathway are involved in IGF-II-mediated VEGF expression, but PKC is negatively associated in the IGF-II-mediated VEGF expression.
血管内皮生长因子（VEGF）在银屑病和癌症等以血管生成增加为特征的过度增殖性疾病中过度表达。据报道，胰岛素样生长因子（IGF）-II在肝癌发生过程中高度表达，且在银屑病皮损中增加。IGF-II的增加被认为通过增加血管生成与这些疾病的发病机制相关。
为了研究IGF-II与血管生成相关的VEGF之间的关系，监测了IGF-II处理的人角质形成细胞中VEGF的表达，并就VEGF表达检查了IGF-II信号通路。
进行Northern印迹分析以检测VEGF mRNA水平，并进行酶联免疫吸附测定以检测VEGF蛋白，以确定IGF-II（100 ng mL(-1)）在原代正常人角质形成细胞和HaCaT细胞中，无论有无用蛋白抑制剂预处理，是否能增加VEGF表达水平。
IGF-II诱导的VEGF的mRNA和蛋白水平呈时间依赖性增加，分别在IGF-II处理后2小时和8小时达到最高水平。然而，用细胞外信号调节激酶（ERK）抑制剂预处理可消除这种增加，而p38抑制剂则不能。用酪氨酸激酶抑制剂和Src抑制剂预处理也有效抑制了IGF-II介导的VEGF诱导。PI3激酶抑制剂也抑制了IGF-II诱导的VEGF表达。然而，磷脂酶C（PLC）和蛋白激酶C（PKC）抑制剂并未阻断IGF-II诱导的VEGF mRNA水平及其蛋白水平的增加，相反，PKC抑制剂增加了IGF-II诱导的VEGF表达。
这些结果表明，酪氨酸激酶-Src-ERK1/2途径和PI3激酶途径参与了IGF-II介导的VEGF表达，但PKC与IGF-II介导的VEGF表达呈负相关。
