Baumann Marc U, Zamudio Stacy, Illsley Nicholas P
Dept. of Obstetrics, Gynecology, and Women's Health, New Jersey Medical School, 185 S. Orange Ave., MSB E506, Newark, NJ 07103, USA.
Am J Physiol Cell Physiol. 2007 Jul;293(1):C477-85. doi: 10.1152/ajpcell.00075.2007. Epub 2007 Apr 18.
Placental hypoxia has been implicated in pregnancy pathologies, including fetal growth restriction and preeclampsia; however, the mechanism by which the trophoblast cell responds to hypoxia has not been adequately explored. Glucose transport, a process crucial to fetoplacental growth, is upregulated by hypoxia in a number of cell types. We investigated the effects of hypoxia on the regulation of trophoblast glucose transporter (GLUT) expression and activity in BeWo choriocarcinoma cells, a trophoblast cell model, and human placental villous tissue explants. GLUT1 expression in BeWo cells was upregulated by the hypoxia-inducing chemical agents desferroxamine and cobalt chloride. Reductions in oxygen tension resulted in dose-dependent increases in GLUT1 and GLUT3 expression. Exposure of cells to hypoxic conditions also resulted in an increase in transepithelial glucose transport. A role for hypoxia-inducible factor (HIF)-1 was suggested by the increase in HIF-1alpha as a result of hypoxia and by the increase in GLUT1 expression following treatment of BeWo with MG-132, a proteasomal inhibitor that increases HIF-1 levels. The function of HIF-1 was confirmed in experiments where the hypoxic upregulation of GLUT1 and GLUT3 was inhibited by antisense HIF-1alpha. In contrast to BeWo cells, hypoxia produced minimal increases in GLUT1 expression in explants; however, treatment with MG-132 did upregulate syncytial basal membrane GLUT1. Our results show that GLUTs are upregulated by hypoxia via a HIF-1-mediated pathway in trophoblast cells and suggest that the GLUT response to hypoxia in vivo will be determined not only by low oxygen tension but also by other factors that modulate HIF-1 levels.
胎盘缺氧与包括胎儿生长受限和先兆子痫在内的妊娠病理有关;然而,滋养层细胞对缺氧的反应机制尚未得到充分研究。葡萄糖转运是胎儿胎盘生长的关键过程,在许多细胞类型中,缺氧会使其上调。我们研究了缺氧对滋养层细胞模型BeWo绒毛膜癌细胞和人胎盘绒毛组织外植体中滋养层葡萄糖转运蛋白(GLUT)表达和活性调节的影响。缺氧诱导化学试剂去铁胺和氯化钴可上调BeWo细胞中GLUT1的表达。氧张力降低导致GLUT1和GLUT3表达呈剂量依赖性增加。将细胞暴露于缺氧条件下也会导致跨上皮葡萄糖转运增加。缺氧诱导因子(HIF)-1的作用通过缺氧导致HIF-1α增加以及用蛋白酶体抑制剂MG-132处理BeWo后GLUT1表达增加而得到提示,MG-132可增加HIF-1水平。在反义HIF-1α抑制GLUT1和GLUT3缺氧上调的实验中证实了HIF-1的功能。与BeWo细胞相反,缺氧在外植体中使GLUT1表达的增加最小;然而,用MG-132处理确实上调了合体滋养层基底膜GLUT1。我们的结果表明,在滋养层细胞中,GLUT通过HIF-1介导的途径被缺氧上调,并表明体内GLUT对缺氧的反应不仅将由低氧张力决定,还将由调节HIF-1水平的其他因素决定。