title: Ascorbic acid uptaken by sodium-dependent vitamin C transporter 2 induces βhCG expression through Sp1 and TFAP2A transcription factors in human choriocarcinoma cells.
abstract: BACKGROUND
  Vitamin C [ascorbic acid (AA)] is transported by sodium-dependent vitamin C transporters (SVCT) 1 and 2, and our previous studies show AA induces a dramatic production of steroid hormones in human choriocarcinoma cells. However, whether AA induces the production of placental polypeptide hormones remains unknown. Here we investigated the mechanisms governing AA-induced β-human chorionic gonadotropin (hCG) expression.
  
  
  METHODS
  Frozen sections from human term placentas were used for immunostaining of SVCT, and βhCG mRNA expression and its production in primary human placental cytotrophoblasts and JEG-3 cells were examined by quantitative RT-PCR and ELISA, respectively. Knockdown of SVCT2, transcription factor activating enhancer-binding protein 2α (TFAP2A), or specificity protein-1 (Sp1) expression was achieved by retrovirus-mediated short hairpin RNA, and the transcriptional factors responsible for AA-induced βhCG expression was identified by reporter constructs.
  
  
  RESULTS
  Both SVCT1 and SVCT2 are expressed in human term placentas. SVCT2 is predominantly localized in the syncytial layer, whereas SVCT1 is predominantly distributed in the villous core. AA dramatically induces βhCG mRNA expression and its production in JEG-3 cells and primary human cytotrophoblasts, and knockdown of SVCT2 expression in JEG-3 cells significantly decreases AA-induced βhCG expression. Data from βhCG5 construct and its deletion mutants further indicate that AA induces βhCG5 transactivation through Sp1 and TFAP2A transcriptional factors, and silence of Sp1 and/or TFAP2A expression significantly decreased AA-induced βhCG5 reporter activity and βhCG expression as well.
  
  
  CONCLUSIONS
  The present study revealed the novel effects of AA on polypeptide hormone, βhCG, production and the potential mechanisms governing AA-induced βhCG expression, suggesting the potentially indispensable roles of AA in placental endocrine and pregnant maintenance.
authors: Department of Pharmacology, School of Medicine, Zhejiang University, No. 866, Yuhangtang Road, Hangzhou 310058, People's Republic of China.
authors: Lihua
authors: L
authors: Chen
authors: Haibin
authors: H
authors: Zhu
authors: Yibin
authors: Y
authors: Pan
authors: Chao
authors: C
authors: Tang
authors: Mai
authors: M
authors: Watanabe
authors: Hongfeng
authors: H
authors: Ruan
authors: Yongjie
authors: Y
authors: Wang
authors: Jirong
authors: J
authors: Wang
authors: Hong-Yi
authors: HY
authors: Yao
authors: Takuma
authors: T
authors: Iguchi
authors: Ximei
authors: X
authors: Wu
mesh_terms: D000328:Adult; D001205:Ascorbic Acid / Q000378:metabolism* / Q000494:pharmacology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002822:Choriocarcinoma / Q000378:metabolism*; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000096:biosynthesis*; D000242:Cyclic AMP / Q000032:analysis / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005455:Fluorescent Antibody Technique; D005822:Genetic Vectors; D006801:Humans; D010920:Placenta / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis; D034741:RNA, Small Interfering / Q000096:biosynthesis / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012190:Retroviridae / Q000235:genetics; D060347:Sodium-Coupled Vitamin C Transporters / Q000378:metabolism*; D016329:Sp1 Transcription Factor / Q000235:genetics*; D050656:Transcription Factor AP-2 / Q000235:genetics*
chemical_list: D018997:Chorionic Gonadotropin, beta Subunit, Human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C555163:SLC23A2 protein, human; D060347:Sodium-Coupled Vitamin C Transporters; D016329:Sp1 Transcription Factor; C493673:TFAP2A protein, human; D050656:Transcription Factor AP-2; D000242:Cyclic AMP; D001205:Ascorbic Acid