Increased Immortalization-Upregulated Protein 2 (IMUP-2) by Hypoxia Induces Apoptosis of the Trophoblast and Pre-eclampsia

In regulation of the developmental process, the balance between cellular proliferation and cell death is critical. Placental development tightly controls this mechanism, and increased apoptosis of placental trophoblasts can cause a variety of gynecological diseases. Members of the immortalization-upregulated protein (IMUP) family are nuclear proteins implicated in SV40-mediated immortalization and cellular proliferation; however, the mechanisms by which their expression is regulated in placental development are still unknown. We compared IMUP-2 expression in normal and pre-eclamptic placental tissues and evaluated the function of IMUP-2 in HTR-8/SVneo trophoblast cells under hypoxic conditions. IMUP-2 was expressed in syncytiotrophoblasts and syncytial knots of the placental villi. IMUP-2 expression was significantly higher in preterm pre-eclampsia patients than in patients who went to term (P<0.001); however, we observed no differences in IMUP-2 expression between normal term patients with and without pre-eclampsia. Hypoxic conditions increased apoptosis of HTR8/SVneo trophoblast cells and induced IMUP-2 expression. Also, apoptosis of HTR-8/SVneo trophoblast cells was increased after IMUP-2 gene transfection. These results suggest that IMUP-2 expression is specifically elevated in preterm pre-eclampsia and under hypoxic conditions, and that IMUP-2 induces apoptosis of the trophoblast. Therefore, IMUP-2 might have functional involvement in placental development and gynecological diseases such as pre-eclampsia. J. Cell. Biochem. 110: 522-530, 2010. (C) 2010 Wiley-Liss, Inc.