Jin-Yong Chung

Bisphenol A exposure during adulthood causes augmentation of follicular atresia and luteal regression by decreasing 17β-estradiol synthesis via downregulation of aromatase in rat ovary.

Background: Bisphenol A (BPA) has been detected in human body fluids, such as serum and ovarian follicular fluids. Several reports indicated that BPA exposure is associated with the occurrence of several female reproductive diseases resulting from the disruption of steroid hormone biosynthesis in the adult ovary. Objective: We hypothesized that long-term exposure to low concentrations of BPA disrupts 17β-estradiol (E2) production in granulosa cells via an alteration of steroidogenic proteins in ovarian cells. Methods: Adult female rats received BPA for 90 days by daily gavage at doses of 0, 0.001, or 0.1 mg/kg body weight. We determined serum levels of E2, testosterone (T), follicle-stimulating hormone (FSH), and luteinizing hormone (LH). We also analyzed the expressions of steroidogenic acute regulatory protein (StAR), P450 side-chain cleavage (P450scc), 3β-hydroxysteroid dehydrogenase isomerase (3β-HSD), and aromatase cytochrome P450 (P450arom) in the ovary. Results: Exposure to BPA significantly decreased E2 serum concentration, which was accompanied by augmented follicular atresia and luteal regression via increase of caspase-3–associated apoptosis in ovarian cells. After BPA exposure, P450arom and StAR protein levels were significantly decreased in granulosa cells and theca-interstitial (T-I) cells, respectively. However, P450scc and 3β-HSD protein levels remained unchanged. The increase in LH levels appeared to be associated with the decreased synthesis of T in T-I cells after BPA exposure via homeostatic positive feedback regulation. Conclusions: BPA exposure during adulthood can disturb the maintenance of normal ovarian functions by reducing E2. The steroidogenic proteins StAR and P450arom appear to be targeted by BPA.

Benzo[a]pyrene reduces testosterone production in rat Leydig cells via a direct disturbance of testicular steroidogenic machinery.

Background: Benzo[a]pyrene (B[a]P), a polycyclic aromatic hydrocarbon (PAH), is a ubiquitous environmental pollutant that is currently suspected of being an endocrine disruptor. The testis is an important target for PAHs, yet insufficient attention has been paid to their effects on steroidogenesis in Leydig cells. Objective: We hypothesized that long-term exposure to low concentrations of B[a]P might disrupt testosterone production in Leydig cells via an alteration of steroidogenic proteins. Results: Oral exposure to B[a]P reduced serum and intratesticular fluid testosterone levels in rats. However, we did not observe serious testicular atrophy or azoospermia, although spermatogonial apoptosis was significantly increased. Compared with control cells, Leydig cells primed with B[a]P in vivo produced less testosterone in response to human chorionic gonadotropin (hCG) or dibutyl cyclic adenosine monophosphate in vitro. Of note, the reduction of testosterone levels was accompanied by decreased expression of steroidogenic acute regulatory protein (StAR) and 3β-hydroxysteroid dehydrogenase (3β-HSD), as well as increased levels of cytochrome P450 side chain cleavage (P450scc), in Leydig cells. The up-regulation of P450scc expression after exposure to B[a]P appears to be associated with a compensatory mechanism for producing the maximum amount of pregnenolone with the minimum amount of transported cholesterol by StAR; the down-regulation of 3β-HSD may occur because B[a]P can negatively target 3β-HSD, which is required for testosterone production. Conclusions: B[a]P exposure can decrease epididymal sperm quality, possibly by disturbing testosterone levels, and StAR may be a major steroidogenic protein that is targeted by B[a]P or other PAHs.

Ellipticine induces apoptosis in human endometrial cancer cells: The potential involvement of reactive oxygen species and mitogen-activated protein kinases

Ellipticine, an alkaloid isolated from Apocyanaceae plants, has been shown to exhibit antitumor activity in several human malignant tissues including breast, thyroid, and ovarian cancers. The antitumor activity of ellipticine is thought to be primarily mediated by the induction of DNA damage through the inhibition of topoisomerase II and formation of DNA adducts. The human endometrium is known to express topoisomerase II. However, the apoptogenic activity of ellipticine and the mechanisms underlying its action have not been investigated in endometrial cancer cells. In the present study, exposure to ellipticine (1-10μM) was shown to induce apoptosis in RL95-2 human endometrial cancer cells. Ellipticine-induced cell death was associated with the accumulation of cells in the G2/M phase of the cell cycle and was accompanied by depolarization of the mitochondrial membrane potential, release of cytochrome c and apoptosis-inducing factor (AIF) from the mitochondrial membrane, and caspase activation. The production of intracellular reactive oxygen species (ROS) was increased and sustained at high levels during ellipticine treatment. Subsequent to ROS accumulation, extracellular-signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) were activated in ellipticine-treated cells. Release of AIF from the mitochondria appeared to be affected by caspases, ROS, and ERK. The present data show that the treatment of RL95-2 cells with ellipticine induces apoptosis, ellipticine-induced apoptosis is mediated by ROS and the activation of MAPKs, and release of AIF is involved in a caspase-independent pathway. These results demonstrate the potential of ellipticine as a therapeutic strategy for the treatment of human endometrial cancers.

Arsenic trioxide-induced apoptosis in TM4 Sertoli cells: The potential involvement of p21 expression and p53 phosphorylation

Arsenic is a toxic metalloid that exists ubiquitously in the environment, and exhibits carcinogenicity. Conversely, arsenic trioxide (AsTO) has successfully been employed in the treatment of acute promyelocytic leukemia (APL). It has been shown that AsTO efficiently induces apoptosis in the malignant cells of APL in vitro. Although the mechanisms underlying AsTO-induced apoptosis in certain types of cancer cells, such as APL cells, have been delineated, the mechanism underlying AsTO-induced cell death in non-cancer cells remains unknown. In the present study, we examined AsTO-provoked cytotoxicity and cell death mechanism(s) in TM4 Sertoli cells. Exposure of these cells to AsTO generates reactive oxygen species and alters mitochondrial apoptosis, inducing cell death via both caspase-dependent and caspase-independent pathways. AsTO-induced apoptosis was concomitant with the downregulation of p53, phosphorylation of p53 at serine residues, and G2/M cell cycle arrest. Particularly, the interaction of p21 with caspase-3 proteins during AsTO treatment suggested an antiapoptotic role of p21 against genotoxic stresses in TM4 Sertoli cells. However, clinically relevant concentrations of AsTO failed to induce cell death in TM4 Sertoli cells, indicating that these cells could be resistant to cancer treatment. The results presented herein may not represent the actual effect of AsTO on Sertoli cells in vivo. Thus, further studies on the exposure effects of AsTO on the morphology and function of Sertoli cells in animal experiments will provide a more precise knowledge of AsTO cytotoxicity on male reproduction.

Bisphenol-A Concentrations from Leiomyoma Patients by LC/MS

The aim of this study is to investigate how many leiomyoma patients are exposed to bisphenol-A (BPA) , an endocrine disruptor, and whether the serum concentration of BPA is related to leiomyoma growth. Initially, 128 patients were divided into one control and three leiomyoma groups (mild, moderate and severe) according to the size of the leiomyomas. Serum BPA concentrations were measured by liquid chromatography and mass spectrometry (LC/MS) . Nearly two-thirds of leiomyoma patients were exposed to BPA and the range of BPA was from non-detection to 2.603 ng/ml. The mean BPA concentrations in the groups were 1.015 ± 0.775 ng/ml (control) , 0.774 ± 0.834 ng/ml (mild) , 1.261 ± 0.797 ng/ml (moderate) and 1.244 ± 0.860 ng/ml (severe) (p = 0.158) . After recombination into two group, Group 1 (control plus mild) vs. Group 2 (moderate plus severe) , higher level was found in Group 2 even with no statistical significance (p = 0.06) . In conclusion, about two-thirds of leiomyoma patients were exposed to BPA, but it may not have growth promoting effect on leiomyoma.

p53 interferes with microtubule-stabilizing agent-induced apoptosis in prostate and colorectal cancer cells

Taxanes are microtubule-stabilizing agents that have anticancer activity against several types of human solid tumors. Although the primary mechanism of action of these drugs is well understood, the signaling pathways that confer resistance to these agents in certain types of cancer remain poorly understood. In particular, the association of p53 with the mechanism(s) of taxane-mediated cell death is still controversial. In this study, we showed that p53 has a profound inhibitory effect on docetaxel (Doc)-induced apoptosis in prostate and colorectal cancer cells and that caspases play a critical role in this process. Doc induced prostate cancer cell apoptosis at high levels in p53-null PC3 cells, at intermediate levels in p53-mutant DU145 cells and at low levels in p53 wild-type LNCaP cells. While transient overexpression of p53 in PC3 cells suppressed Doc-induced apoptosis, knockdown of p53 in LNCaP cells increased apoptosis. This finding was further confirmed using an isogenic pair of colorectal cancer cell lines, HCT-116 p53-/- and p53+/+, indicating that p53 inhibits induction of apoptosis by Doc. To our knowledge, this is the first report describing that chemical or genetic knockout of p53 enhances the susceptibility of both prostate and colorectal cancer cells to Doc-induced apoptosis. These results may suggest an approach to stratify patients for regimens involving Doc.

Evaluation of Cell Death and the Reduction of ERK Phosphorylation in Non-Small Cell Lung Cancer Cells after Exposure to Sodium Butyrate

Histone deacetylase inhibitor (HDACI) is a new promising candidate as an antineoplastic agent for the treatment of solid and hematologic malignancies. In order to evaluate cell death and to elucidate the related mechanism(s) in NSCLC cells after HDACI, sodium butyrate (SB), a representative HDACI, was used to treat H460 cells for 48 hrs. SB exposure resulted in a significant reduction of cell viability at concentrations below 7.5 mM, and about 50% of cell death occurred at 20 mM. The types of cell death induced by SB were both apoptosis and necrosis, evaluated by Annexin-V staining combined with propidium iodide. SB treatment significantly evoked G2/M cell cycle arrest and subsequently induced cell death with caspase-dependent manner. While ERK protein content was not altered after SB, phosphorylated forms of ERK were markedly reduced. Taken together, SB is significantly able to induce cell death in NSCLC cell line H460, and it is suggested that the reduction of ERK phosphorylation might be closely involved in the cancer cell death mechanism initiated by HDACI.