Ascorbic acid transported by sodium-dependent vitamin C transporter 2 stimulates steroidogenesis in human choriocarcinoma cells.
Reduced vitamin C [ascorbic acid (AA)], which is taken up into cells by sodium-dependent vitamin C transporter (SVCT) 1 and 2, is believed to be important for hormone synthesis, but its role in generating placental steroids needed to maintain pregnancy and fetal development is not clear. To determine the steroidogenic effect of AA and the role of SVCT2 in AA-induced steroidogenesis, we tested the effects of AA treatment and SVCT2 knockdown on steroidogenesis in human choriocarcinoma cell lines. AA treatment of JEG-3, BeWo, and JAR cells for 48-h dose dependently increased progesterone and estradiol levels. In JEG-3 cells, AA increased the mRNA expression of P450 cholesterol side-chain cleavage enzyme, 3beta-hydroxysteroid dehydrogenase type 1, and aromatase, key enzymes for steroidogenesis. Stable knockdown of SVCT2 in JEG-3 cells by retrovirally mediated RNA interference decreased the maximal velocity of AA uptake by approximately 50%, but apparent affinity values were not affected. SVCT2 knockdown in JEG-3 cells significantly suppressed the AA-induced mRNA expression of placental P450 cholesterol side-chain cleavage enzyme, 3beta-hydroxysteroid dehydrogenase type 1, and aromatase. This suppression of the AA-induced mRNA expression of steroidogenic enzymes subsequently decreased progesterone and estradiol production. In addition, inhibition of MAPK kinase-ERK signaling, which is a major pathway for AA-regulated gene expression, failed to affect AA-induced steroidogenesis. Our observations indicate that SVCT2-mediated AA uptake into cells is necessary for AA-induced steroidogenesis in human choriocarcinoma cell, but MAPK kinase-ERK signaling is not involved in AA-induced steroidogenesis.
Wu
Ximei
X
Department of Toxicology, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan.
Iguchi
Takuma
T
Itoh
Norio
N
Okamoto
Kousuke
K
Takagi
Tatsuya
T
Tanaka
Keiichi
K
Nakanishi
Tsuyoshi
T
D015096:3-Hydroxysteroid Dehydrogenases / Q000235:genetics / Q000378:metabolism; D001141:Aromatase / Q000235:genetics / Q000378:metabolism; D001205:Ascorbic Acid / Q000378:metabolism* / Q000494:pharmacology*; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000235:genetics / Q000378:metabolism; D002822:Choriocarcinoma / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D004958:Estradiol / Q000096:biosynthesis; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism / Q000502:physiology; D008954:Models, Biological; D029363:Organic Anion Transporters, Sodium-Dependent / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011247:Pregnancy; D011374:Progesterone / Q000096:biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D060347:Sodium-Coupled Vitamin C Transporters; D013256:Steroids / Q000096:biosynthesis*; D027981:Symporters / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014594:Uterine Neoplasms / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*
D029363:Organic Anion Transporters, Sodium-Dependent; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C555163:SLC23A2 protein, human; D060347:Sodium-Coupled Vitamin C Transporters; D013256:Steroids; D027981:Symporters; D011374:Progesterone; D004958:Estradiol; D015096:3-Hydroxysteroid Dehydrogenases; D001141:Aromatase; D002786:Cholesterol Side-Chain Cleavage Enzyme; D020929:Mitogen-Activated Protein Kinase Kinases; D001205:Ascorbic Acid