Wenping Li

In Utero Exposure to Di-(2-ethylhexyl) Phthalate Exerts Both Short-Term and Long-Lasting Suppressive Effects on Testosterone Production in the Rat

We examined the effects of fetal exposure to a wide range of di-(2-ethylhexyl) phthalate (DEHP) doses on fetal, neonatal, and adult testosterone production. Pregnant rats were administered DEHP from Gestational Day (GD) 14 to the day of parturition (Postnatal Day 0). Exposure to between 234 and 1250 mg/kg/day of DEHP resulted in increases in the absolute volumes of Leydig cells per adult testis. Despite this, adult serum testosterone levels were reduced significantly compared to those of controls at all DEHP doses. Organ cultures of testes from GD20 rats exposed in utero to DEHP showed dose-dependent reductions in basal testosterone production. Surprisingly, however, no significant effect of DEHP was found on hCG-induced testosterone production by GD20 testes, suggesting that the inhibition of basal steroidogenesis resulted from the alteration of molecular events upstream of the steroidogenic enzymes. Reduced fetal and adult testosterone production in response to in utero DEHP exposure appeared to be unrelated to changes in testosterone metabolism. In view of the DEHP-induced reductions in adult testosterone levels, a decrease in the expression of steroidogenesis-related genes was anticipated. Surprisingly, however, significant increases were seen in the expression of Cyp11a1, Cy17a1, Star, and Tspo transcripts, suggesting that decreased testosterone production after birth could not be explained by decreases in steroidogenic enzymes as seen at GD20. These changes may reflect an increased number of Leydig cells in adult testes exposed in utero to DEHP rather than increased gene expression in individual Leydig cells, but this remains uncertain. Taken together, these results demonstrate that in utero DEHP exposure exerts both short-term and long-lasting effects on testicular steroidogenesis that might involve distinct molecular targets in fetal and adult Leydig cells.

Expression of Peripheral Benzodiazepine Receptor (PBR) in Human Tumors: Relationship to Breast, Colorectal, and Prostate Tumor Progression

Abstract High levels of peripheral‐type benzodiazepine receptor (PBR), the alternative‐binding site for diazepam, are part of the aggressive human breast cancer cell phenotype in vitro. We examined PBR levels and distribution in normal tissue and tumors from multiple cancer types by immunohistochemistry. Among normal breast tissues, fibroadenomas, primary and metastatic adenocarcinomas, there is a progressive increase in PBR levels parallel to the invasive and metastatic ability of the tumor (p < 0.0001). In colorectal and prostate carcinomas, PBR levels were also higher in tumor than in the corresponding non‐tumoral tissues and benign lesions (p < 0.0001). In contrast, PBR was highly concentrated in normal adrenal cortical cells and hepatocytes, whereas in adrenocortical tumors and hepatomas PBR levels were decreased. Moreover, malignant skin tumors showed decreased PBR expression compared with normal skin. These results indicate that elevated PBR expression is not a common feature of aggressive tumors, but rather may be limited to certain cancers, such as those of breast, colon‐rectum and prostate tissues, where elevated PBR expression is associated with tumor progression. Thus, we propose that PBR overexpression could serve as a novel prognostic indicator of an aggressive phenotype in breast, colorectal and prostate cancers.

Molecular mechanisms mediating the effect of mono-(2-ethylhexyl) phthalate on hormone-stimulated steroidogenesis in MA-10 mouse tumor Leydig cells.

Di-(2-ethylhexyl) phthalate, a widely used plasticizer, and its active metabolite, mono-(2-ethylhexyl) phthalate (MEHP), have been shown to exert adverse effects on the reproductive tract in developing and adult animals. As yet, however, the molecular mechanisms by which they act are uncertain. In the present study, we address the molecular and cellular mechanisms underlying the effects of MEHP on basal and human chorionic gonadotropin (hCG)-stimulated steroid production by MA-10 Leydig cells, using a systems biology approach. MEHP induced dose-dependent decreases in hCG-stimulated steroid formation. Changes in mRNA and protein expression in cells treated with increasing concentrations of MEHP in the presence or absence of hCG were measured by gene microarray and protein high-throughput immunoblotting analyses, respectively. Expression profiling indicated that low concentrations of MEHP induced the expression of a number of genes that also were expressed after hCG stimulation. Cross-comparisons between the hCG and MEHP treatments revealed two genes, Anxa1 and AR1. We suggest that these genes may be involved in a new self-regulatory mechanism of steroidogenesis. The MEHP-induced decreases in hCG-stimulated steroid formation were paralleled by increases in reactive oxygen species generation, with the latter mediated by the Cyp1a1 gene and its network. A model for the mechanism of MEHP action on MA-10 Leydig cell steroidogenesis is proposed.

Prenatal exposure of rats to Ginkgo biloba extract (EGb 761) increases neuronal survival/growth and alters gene expression in the developing fetal hippocampus

Hippocampal neuron survival/growth and gene expression have been examined after prenatal (in utero) exposure of rats to EGb 761, a leaf extract of Ginkgo biloba. Oral administration of EGb 761 (100 or 300 mg/kg/day) to pregnant dams for 5 days increased the number of hippocampal neurons (maintained in culture) of their fetuses, indicating a neurotrophic effect of the extract. Using large-scale oligonucleotide microarrays containing over 8000 combined rat genes and expressed sequence tag clusters, it was shown that treatment of pregnant dams with EGb 761 (25, 50 or 100 mg/kg/day for 5 days) altered the expression of 187 genes in the hippocampi of male fetuses and 160 genes in those of female fetuses. Using gene-cluster analysis, these genes were grouped into 18 distinct clusters for males and 17 distinct clusters for females. Among these clusters, 35 genes shared a common expression pattern in male and female hippocampal development. Of these genes, the changes observed in insulin growth factor II, insulin growth factor binding protein 2, testosterone repressed prostate message-2, glutathione-dependent dehydroascorbate reductase, lipoprotein lipase, guanylate cyclase and DNA binding protein Brn-2 were confirmed by real-time quantitative polymerase chain reaction. These findings, which have provided the first genetic profile of the effects of EGb 761 on the developing rat hippocampus, increase our understanding of the molecular and genetic programs that are activated by the extract. These effects of EGb 761 may underlie its neuroprotective properties.