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Polyamines control human chorionic gonadotropin production in the JEG-3 choriocarcinoma cell
J J Moore1, D W Lundgren, R M Moore
1Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio 44109.
Abstract:
The effect of inhibition of ornithine decarboxylase with difluoromethylornithine (DFMO) and the resultant lowering of polyamine levels upon human chorionic gonadotropin (hCG) production in JEG-3 choriocarcinoma cells was investigated. DFMO (10 mM) totally inhibited ornithine decarboxylase activity. In DFMO-treated cells, cellular spermidine concentrations fell to nondetectable levels (less than 1% of control values) within 24 h and spermine concentrations were reduced to 41.9% of controls over 6 days. DFMO caused a 70-80% inhibition of hCG production. Levels of mRNA for both the alpha and beta subunits of hCG were also inhibited relative to mRNA for tubulin. Exogenous putrescine normalized hCG production in a dose-dependent manner. Other diamines, including cadaverine, 1,3-diaminopropane, 1,6-diaminohexane, and 1,7-diaminoheptane, were ineffective in reestablishing hCG production in DFMO-treated cells. Dibutyryl cAMP (1 mM) stimulated hCG production and increased levels of mRNA for the alpha and beta subunit 5-40-fold in both DFMO-treated and control cells. Polyamines appear to have a fundamental role in hCG production in JEG-3 choriocarcinoma cells. However, dibutyryl cAMP can partially overcome or circumvent the requirement for polyamines in hCG biosynthesis.
Insights
Difluoromethylornithine (DFMO) significantly reduced polyamine levels and inhibited human chorionic gonadotropin (hCG) production in choriocarcinoma cells. Exogenous putrescine restored hCG production, indicating polyamines are crucial for hCG biosynthesis.
Area of Science:
- Biochemistry
- Cell Biology
- Reproductive Endocrinology
Background:
- Human chorionic gonadotropin (hCG) is a critical hormone produced by placental cells.
- Polyamines are essential for cell growth and proliferation.
- The role of polyamines in hCG production by choriocarcinoma cells is not fully understood.
Purpose of the Study:
- To investigate the effect of ornithine decarboxylase inhibition by difluoromethylornithine (DFMO) on hCG production in JEG-3 choriocarcinoma cells.
- To determine the impact of altered polyamine levels on hCG subunit mRNA expression.
- To explore the potential of exogenous polyamines and cAMP to modulate hCG production.
Main Methods:
- JEG-3 choriocarcinoma cells were treated with DFMO to inhibit ornithine decarboxylase and reduce polyamine levels.
- Cellular concentrations of spermidine and spermine were measured.
- hCG production and mRNA levels for hCG subunits (alpha and beta) were quantified.
- The effects of exogenous putrescine and dibutyryl cAMP were assessed.
Main Results:
- DFMO completely inhibited ornithine decarboxylase activity, leading to undetectable spermidine and significantly reduced spermine levels.
- hCG production was inhibited by 70-80% in DFMO-treated cells.
- mRNA levels for both hCG alpha and beta subunits were decreased.
- Exogenous putrescine dose-dependently restored hCG production, while other diamines were ineffective.
- Dibutyryl cAMP stimulated hCG production and mRNA levels in both control and DFMO-treated cells.
Conclusions:
- Polyamines play a fundamental role in regulating hCG production in JEG-3 choriocarcinoma cells.
- Inhibition of polyamine synthesis significantly impairs hCG biosynthesis.
- Dibutyryl cAMP can partially overcome the requirement for polyamines in hCG production, suggesting alternative regulatory pathways.