Ki Soo Yoo

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.

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.

The novel resveratrol analog HS-1793-induced polyploid LNCaP prostate cancer cells are vulnerable to downregulation of Bcl-xL

Since resveratrol is not a potent cytotoxic compound when compared with other chemotherapeutic agents, several previous studies have been performed to obtain synthetic analogs of resveratrol with potent activity. Our previous study demonstrated that the resveratrol analog HS-1793 showed stronger antitumor activity than resveratrol in various cancer cells. We examined the antitumor activity exerted by HS-1793 in prostate cancer cells, and we observed that HS-1793 acts as a polyploidy inducer. Noticeably, multinucleation and polyploidization were induced in most LNCaP cells treated with HS-1793 at the dose causing a slight decline in cell viability. However, the induction of multinucleation and polyploidization was much lower in PC-3 prostate cancer cells treated with the same dose of HS-1793. Western blot and RT-PCR analyses showed that the expression of Aurora B was almost undetectable in LNCaP cells, but it was highly expressed in PC-3 cells. Further, silencing of Aurora B sensitized PC-3 cells to HS-1793-induced multi-nucleation. These results indicate that expression of Aurora B determines multinucleation in prostate cancer cells treated with HS-1793. Additional assays using multiple cancer cell lines show that the population of multinucleated cells induced by HS-1793 treatment is inversely proportional to Aurora B expression. We further elicited that the HS-1793-induced polyploid LNCaP cells are vulnerable to downregulation of Bcl-xL. Since the polyploidization in LNCaP induced by HS-1793 does not appear to cause definite commitment to apoptosis, the termination of polyploid cells by inhibition of Bcl-xL could provide an advantageous means to improve chemotherapeutic efficacy of HS-1793.

Magnoliae Flos Induces Apoptosis of RBL-2H3 Cells via Mitochondria and Caspase

Background: Magnoliae flores (MF), the buds of Magnolia denudata Desrousseaux, have been successfully used for the management of allergic diseases in Korea. The purpose of the present study was to determine their causal role in inducing apoptosis of mast cells and to verify the underlying mechanism. Methods: The viability of mast cells was assessed by the trypan blue exclusion test. Induction of apoptosis was confirmed by DNA fragmentation, nuclear staining and DNA hypoploidy. Western blotting and immunofluorescent staining were performed to study the alterations in expression level and translocation of apoptosis-related proteins. Mitochondrial membrane potential (MMP) change and cytochrome C release were assayed. Results: We present several lines of evidence indicating that MF induce apoptosis. Changes in cell morphology, generation of DNA fragmentation, cell cycle arrest, activation of caspase-3, and PARP and DFF degradations were demonstrated. The reduction of MMP and the release of cytochrome C to cytosol were also shown. Either PTP blockers, bongkrekic acid and cyclosporin A, or pancaspase inhibitors, Boc.D-fmk and zVAD-fmk, did not prevent the release of cytochrome C. Bax protein content was increased, and Bax was translocated from cytosol into mitochondria at early time points after MF treatment. Conclusions: We have demonstrated that MF induce mitochondria- and caspase-dependent mast cell apoptosis. Our observations contribute new insights to the role of MF and support the view that the clinical effect of MF may depend on their pharmacological efficacy in regulating mast cell apoptosis.

Genistein-induced apoptosis of p815 mastocytoma cells is mediated by Bax and augmented by a proteasome inhibitor, lactacystin

Although genistein has been demonstrated to induce apoptosis of various cells, there is no report of its effect on mast cell proliferation. Here we show that genistein reduced the viability of mast cell tumor cell lines, p815 and RBL-2H, but not of a human mast cell line, HMC-1. Further investigation on its growth-inhibitory mechanism was undertaken on p815 mastocytoma cells. Genistein induced G2/M arrest and subsequent apoptotic death. p815 cells undergoing apoptosis showed many apoptotic manifestations, such as reduction of mitochondrial membrane potential, release of cytochrome c to cytosol, translocation of apoptosis-inducing factor to nucleus, activation of caspase-3, nuclear condensation, and generation of DNA fragmentation. Genistein treatment resulted in the increase of Bax expression and its translocation into mitochondria, whereas expression levels of Bcl-2 remained unchanged. Proteasome activity decreased at the early time points after genistein treatment, but thereafter it fluctuated at increased levels. A proteasome inhibitor, lactacystin, potentiated the induction of apoptosis. Taken together, genistein-induced apoptosis of p815 mastocytoma cells is at least in part mediated by proteasome, Bax, apoptosis-inducing factor, and caspase and augmented by cotreatment with a proteasome inhibitor, lactacystin.

Synthetic bile acid derivatives induce nonapoptotic death of human retinal pigment epithelial cells

Purpose. To study whether the synthetic ursodeoxycholic acid (UDCA) and chenodeoxycholic acid (CDCA) derivatives, which we have synthesized and have reported their apoptosis-inducing effect, have the effect on the proliferation of retinal pigment epithelial cells. Methods. UDCA, CDCA, and their synthetic derivatives were administered in culture to the human retinal pigment cell line, ARPE-19. The effect on cell viability and growth was assessed by trypan blue dye exclusion. In order to evaluate the type of cell death, mitochondrial membrane potential assay, DNA electrophoresis, TUNEL assay, nuclear staining and Western blotting for caspase-3 and poly(ADP-ribose) polymerase (PARP) activities were conducted. Results. Unlike UDCA and CDCA, which did not exhibit a significant effect on viability, their synthetic derivatives decreased the viability of ARPE-19 cells in a concentration-dependent manner. The cells treated with the synthetic derivatives did not demonstrate the characteristic findings of apoptosis, such as DNA ladder, DNA fragmentation, nuclear condensation or fragmentation, and caspase-3 and PARP activation. The reduction of mitochondrial membrane potential was shown. In electron microscopical study nuclear condensation was not shown. Conclusions. The synthetic UDCA and CDCA derivatives induced nonapoptotic death of ARPE-19 cells.

Szygium aromaticum (L.) Merr. Et Perry (Myrtaceae) flower bud induces apoptosis of p815 mastocytoma cell line

This study was conducted to investigate SAFB-induced apoptosis of mast cells as it pertains to both its basic drug mechanism and the potential therapeutics of the pathologic conditions accompanying mast cell proliferation. SAFB induced many apoptotic manifestations as evidenced by changes in cell morphology, generation of DNA fragmentation, activation of caspase 3, and DNA hypoploidy. The reduction of mitochondrial membrane potential and the release of cytochrome c to cytosol were also demonstrated. However, reduction of mitochondrial membrane potential and cytochrome c release were not prevented by caspase inhibitor zVAD-fmk or PTP blockers such as bongkrekic acid and cyclosporin A. Expression levels of Bcl-2 and Fas remained unchanged following SAFB treatment. This results suggest that the clinical effect of SAFB may depend on the pharmacological mechanism regulating the demise of mast cells.

Momilactone B, an allelochemical of rice hulls, induces apoptosis on human lymphoma cells (Jurkat) in a micromolar concentration.

Although momilactone B has been studied as an allelochemical of rice (Oryza sativa L.), to date we have no report showing the effect of momilactone B on mammalian cells. This study was undertaken to examine whether this allelochemical has anticancer activity on cancer cells. We show here that momilactone B at micromolar doses has antitumor efficacy by inducing apoptosis in several blood cancer cells including human leukemic T cells. In addition, our study elucidated that anticancer activity of momilactone B on human leukemic T cells resulted from the induction of apoptosis via caspase and mitochondria. From these results, momilactone B can be considered as a novel therapeutic strategy for human leukemic T cells from its direct apoptosis-inducing activity.

Fatty acid synthase inhibitor cerulenin inhibits topoisomerase I catalytic activity and augments SN-38-induced apoptosis

Fatty acid synthase (FASN) is overexpressed in a wide variety of human cancers, making it an attractive target for anticancer therapy. One of the most widely used inhibitors of FASN, cerulenin, is a natural product of Cephalosporium caerulens. Cerulenin is selectively toxic to human cancer cells in vitro. However, the mechanism by which FASN inhibition causes apoptosis in tumor cells remains unclear. Because of the widespread clinical interest in combining cerulenin with other chemotherapeutic agents, we performed this study to gain insight into the downstream effects of FASN inhibition that lead to apoptosis. Here, we observed the increased antitumor effect of cerulenin when combined with the topoisomerase inhibitor SN-38. We identified topoisomerase I as a potential mediator of cerulenin-induced apoptosis, possibly by upregulating intracellular polyunsaturation. Finally, we show that suppressing topoisomerase I catalytic activity results in synergistic effects between cerulenin and LY294002. Our results suggest that topoisomerase I could participate in cerulenin-induced apoptosis by upregulating intracellular polyunsaturation. These results will help determine the molecular basis of the cerulenin and SN-38 drug combination. Further investigation of this pathway will provide new insight into cancer cell metabolism and may aid in the design of additional cancer chemotherapeutic agents.