Monobutyl phthalate inhibits steroidogenesis by downregulating steroidogenic acute regulatory protein expression in mouse Leydig tumor cells (MLTC-1).
Di-n-butyl phthalate (DBP) and its active metabolite, monobutyl phthalate (MBP), display no binding affinity for the androgen receptor, yet exert antiandrogenic effects by altering steroid biosynthesis. However, the mechanisms underlying this observed effect are not known. The purpose of this study was to determine the site of MBP action on steroidogenesis in vitro using mouse Leydig tumor cells (MLTC-1). Various concentrations of MBP (0, 50, 100, 200, 400, or 800 micromol/L) were added to the medium for 24 h followed by stimulation with some compounds such as human chorionic gonadotrophin (hCG), cholera toxin (CT), cAMP analog 8-Br-cAMP, 22(R)-hydroxycholesterol (22R-HC), and pregnenolone. Data showed that MBP inhibited the increases in progesterone production induced by hCG and CT. In contrast, the levels of intracellular cAMP remained unaltered. In addition, 8-Br-cAMP-stimulated progesterone production was also suppressed by MBP. These results suggested that the site in the steroid biosynthesis pathway affected by MBP occurs downstream of PKA activation in MLTC-1 cells. Moreover, incubation with 22R-HC and pregnenolone as progesterone precursors for P-450 side-chain cleavage enzyme (P450scc) and 3beta-hydroxysteroid dehydrogenase (3betaHSD) respectively resulted in no marked change in progesterone production, indicating that MBP did not influence P450scc and 3betaHSD but did exert an effect on cholesterol transportation into mitochondria, the rate-limiting step. These results were supported by the downregulated StAR expression seen with MBP administration, as StAR is a key factor in this process. Data indicate that MBP interfered with steroid hormone production by affecting StAR expression in MLTC-1 cells.
Wang
Yu-Bang
YB
Key Laboratory of Reproductive Medicine of Jiangsu Province, Institute of Toxicology, Nanjing Medical University, Nanjing, People's Republic of China.
Song
Ling
L
Cui
Lun-Biao
LB
Hong
Xia
X
Zhang
Zheng-Dong
ZD
Wang
Xin-Ru
XR
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002772:Cholera Toxin / Q000494:pharmacology; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004261:DNA Replication / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D004338:Drug Combinations; D052244:Endocrine Disruptors / Q000633:toxicity*; D006801:Humans; D006888:Hydroxycholesterols / Q000494:pharmacology; D007984:Leydig Cell Tumor / Q000188:drug therapy* / Q000378:metabolism; D008297:Male; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010795:Phthalic Acids / Q000633:toxicity*; D011284:Pregnenolone / Q000494:pharmacology; D011374:Progesterone / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D013736:Testicular Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D000098682:Steroidogenic Acute Regulatory Protein
D006063:Chorionic Gonadotropin; D004338:Drug Combinations; D052244:Endocrine Disruptors; D006888:Hydroxycholesterols; D010750:Phosphoproteins; D010795:Phthalic Acids; D012333:RNA, Messenger; D000098682:Steroidogenic Acute Regulatory Protein; C003585:22-hydroxycholesterol; D015124:8-Bromo Cyclic Adenosine Monophosphate; D011374:Progesterone; D011284:Pregnenolone; D002772:Cholera Toxin; D000242:Cyclic AMP; C028577:monobutyl phthalate