The use of rat Leydig tumor (R2C) and human hepatoma (HEPG2) cells to evaluate potential inhibitors of rat and human steroid aromatase

Disruption of steroidogenesis: Cell models for mechanistic investigations and as screening tools

In the modern world, humans are exposed during their whole life to a large number of synthetic chemicals. Some of these chemicals have the potential to disrupt endocrine functions and contribute to the development and/or progression of major diseases. Every year approximately 1000 novel chemicals, used in industrial production, agriculture, consumer products or as pharmaceuticals, are reaching the market, often with limited safety assessment regarding potential endocrine activities. Steroids are essential endocrine hormones, and the importance of the steroidogenesis pathway as a target for endocrine disrupting chemicals (EDCs) has been recognized by leading scientists and authorities. Cell lines have a prominent role in the initial stages of toxicity assessment, i.e. for mechanistic investigations and for the medium to high throughput analysis of chemicals for potential steroidogenesis disrupting activities. Nevertheless, the users have to be aware of the limitations of the existing cell models in order to apply them properly, and there is a great demand for improved cell-based testing systems and protocols. This review intends to provide an overview of the available cell lines for studying effects of chemicals on gonadal and adrenal steroidogenesis, their use and limitations, as well as the need for future improvements of cell-based testing systems and protocols.

Regulation of cytochrome P450 1B1 expression by luteinizing hormone in mouse MA-10 and rat R2C Leydig cells: role of protein kinase A

In the present study, we investigated the signaling pathway involved in luteinizing hormone (LH)-mediated regulation of testicular CYP1B1 in mouse MA-10 and rat R2C Leydig cells. CYP1B1 mRNA and protein levels were measured in MA-10 and R2C cells treated with LH and protein kinase activators or inhibitors. Treatment with LH or 8-bromo-cAMP, a protein kinase A (PRKA) activator, increased CYP1B1 expression and PRKA activity in a concentration-dependent manner in both cell lines, albeit to different extents. Treatment with 8-(4-chlorophenylthio)adenosine-3',5'-cyclic monophosphorothioate, Rp-isomer, a PRKA inhibitor, decreased basal CYP1B1 expression and attenuated LH-elicited increases in CYP1B1 mRNA and protein levels and PRKA activity. In contrast, treatment with a protein kinase G activator or an inhibitor of protein kinase C had no effect on basal or LH-induced CYP1B1 expression in MA-10 or R2C cells. Collectively, the results identify PRKA as the major signaling pathway involved in the LH-mediated regulation of testicular CYP1B1 expression in Leydig tumor cells.

Genome-wide biological response fingerprinting (BioReF) of the Chinese botanical formulation ISF-1 enables the selection of multiple marker genes as a potential metric for quality control

Quality control plays a critical role in the process of translating the traditional/alternative medicines into modern evidence-based therapies. High performance liquid chromatography (HPLC) is widely applied to assess the chemical composition of botanical drug products. The chromatographic fingerprints or chemical profiles are currently used as the de facto quality control metric. As a complement to chemical profiles, a biological quality control assessment offers distinct advantages. This study describes a genome-wide biological response fingerprinting (BioReF) approach to define a set of marker genes that define a signature pattern for a specific botanical formulation. These marker genes are chosen on the basis of the levels of the regulated expression and the involvement in the cellular signaling pathways. Subsequently, qRT-PCR technique is used to simultaneously monitor the gene expression of multiple marker genes in an efficient and quantitative manner. This set of marker genes represents the biological responses of human cells to the chemical composition of the botanical drug that could serve as potential quality control of botanical drugs in terms of the consistency of biological activities. We demonstrate the BioReF approach with a well-documented Chinese Medicine formula, designated as ISF-1, traditionally used for the management of post-stroke disorders. A set of nine marker genes were selected to assess the batch-to-batch consistency of the biological effects of ISF-1. This approach provides a potential comprehensive and cost-effective quality control metric of the biological activities of botanical drugs.

Screening of selected pesticides for inhibition of CYP19 aromatase activity in vitro

Many pesticides are able to block or activate the steroid hormone receptors and/or to affect the levels of sex hormones, thereby potentially affecting the development or expression of the male and female reproductive system or both. This emphasizes the relevance of screening pesticides for a wide range of hormone-mimicking effects. Twenty-two pesticides were tested for their ability to affect CYP19 aromatase activity in human placental microsomes using the classical [(3)H](2)O method. Prochloraz, imazalil, propioconazole, fenarimol, triadimenol, triadimefon (all fungicides), and dicofol (an acaricide) gave rise to a statistically significant inhibition of aromatase activity. The IC(50)s of prochloraz, imazalil, propioconazole fenarimol, triadimenol, and triadimefon were calculated from dose-response curves to be 0.04, 0.34, 6.5, 10, 21 and 32 microM, respectively. The IC(50) of dicofol was greater than 50 microM. The positive control 4-hydroxyandrostendione (1 microM) caused an inhibition of aromatase activity by 74%. The compounds, which did not affect the aromatase activity, were bromopropylate, chlorfenvinphos, chlorobenzilate, chlorpyrifos, diuron, heptachlor, iprodion, linuron, pentachlorphenol, procymidon, propyzamide, quintozen, tetrachlorvinphos and tetradifon. With the purpose of comparing the results for fenarimol obtained with the microsomal system with data from an intact cell system, an aromatase assay based on JEG-3 cells was established. 4-Hydroxyandrostendione (1 microM) inhibited the aromatase activity in JEG-3 cells by 94%. The IC(50) for fenarimol in this system was 2 microM, slightly lower than that observed in the microsomal system. For the first time, fenarimol has been demonstrated to inhibit aromatase activity in human tissues and, furthermore, propioconazole, triadimefon, and triadimenol were identified as weak aromatase inhibitors. In conclusion, seven out of 22 tested pesticides turned out to be weak to moderate aromatase inhibitors in vitro, indicating the relevance of elucidating the endocrine effects in vivo of these- compounds.