Effect of microRNA-409 on the pathogenesis of polycystic ovary syndrome.

OBJECTIVE: To explore the expression level of microRNA-409 in PCOS (polycystic ovary syndrome) rats, as well as its potential effects on fertility of PCOS rats and phenotypes of offspring rats. MATERIALS AND METHODS: PCOS model in rats was established by Letasazole administration. Follicular development of rats was evaluated by the percentages of the cystic follicle (FC) and corpus luteum (CL) of all follicles. The enzyme-linked immunosorbent assay (ELISA) was conducted to detect serum levels of hormones in rats, including LH, LH/FSH, T, INS, FSH, and E2. Subsequently, PCOS rats received a subcapsular injection of microRNA-409 mimics. The expression level of microRNA-409 in ovary was determined by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). Serum levels of LH, LH/FSH, T, INS, FSH, and E2 in PCOS rats with microRNA-409 overexpression were accessed by enzyme-linked immunosorbent assay (ELISA) as well. PCOS rats were mated with male rats for recording pregnancy rate. At 6-week-old of offspring, they were sacrificed for detecting microRNA-409 level, percentages of FC and CL, as well as serum levels of hormones. RESULTS: PCOS rats showed irregular estrous cycle and they were mainly in the anestrum. Rats in the control group were in a regular estrous cycle. A higher percentage of FC and a lower percentage of CL were seen in PCOS rats compared with those of controls. ELISA data revealed higher serum levels of LH, LH/FSH, and T in PCOS rats compared with those of controls. However, levels of FSH and E2 were lower in PCOS rats. Although INS level increased in PCOS rats, we did not observe a significant difference in INS level between PCOS rats and control rats. MicroRNA-409 was lowly expressed in ovaries of PCOS rats than those of controls. After injection of microRNA-409 mimics into rat ovary, microRNA-409 expression remarkably upregulated than those PCOS rats without injection. Rats in PCOS+microRNA-409 mimics group showed the largest body weight compared with those in the PCOS group and control group. PCOS rats showed a lower pregnancy rate than those of controls, which was markedly increased after administration of microRNA-409 mimics. Rats in PCOS+microRNA-409 mimics group presented lower levels of LH, LH/FSH, T, and INS, but higher levels of FSH and E2 than those in PCOS group. CONCLUSIONS: MicroRNA-409 is lowly expressed in the ovary of PCOS rats. Overexpression of microRNA-409 could improve hormone levels and pregnancy rate in PCOS rats, as well as affect clinical phenotypes of their offspring.

Dose-response transition from cell cycle arrest to apoptosis with selective degradation of Mdm2 and p21WAF1/CIP1 in response to the novel anticancer agent, aminoflavone (NSC 686,288).

Aminoflavone (AF, NSC 686,288) is beginning clinical trials. It induces replication-mediated histone H2AX phosphorylation, DNA-protein crosslinks and activates p53. Here, we studied p21(CIP1/WAF1) and Mdm2 responses to AF. Although p53 stabilization and phosphorylation at serine 15 increased with dose and time of exposure, Mdm2 and p21(CIP1/WAF1) protein levels displayed a biphasic response, as they accumulated at submicromolar doses and then decreased with increasing AF. As both Mdm2 and p21(CIP1/WAF1) mRNA levels increased with AF concentration without reduction at higher concentrations, we measured the half-lives of Mdm2 and p21(CIP1/WAF1) proteins. Mdm2 and p21(CIP1/WAF1) half-lives were shortened with increasing AF concentrations. Proteasomal degradation appears responsible for the decrease of both Mdm2 and p21(CIP1/WAF1), as MG-132 prevented their degradation and revealed AF-induced Mdm2 polyubiquitylation. AF also induced protein kinase B (Akt) activation, which was reduced with increasing AF concentrations. Suppression of Akt by small interfering RNA was associated with downregulation of Mdm2 and p21(CIP1/WAF1) and with enhanced apoptosis. These results suggest that the cellular responses to AF are determined at least in part by Mdm2 and p21(CIP1/WAF1) protein levels, as well as by Akt activity, leading either to cell cycle arrest when Mdm2 and p21(CIP1/WAF1) are elevated, or to apoptosis when Mdm2 and p21(CIP1/WAF1) are degraded by the proteasome and Akt insufficiently activated to protect against apoptosis.

p21CDKN1A allows the repair of replication-mediated DNA double-strand breaks induced by topoisomerase I and is inactivated by the checkpoint kinase inhibitor 7-hydroxystaurosporine.

This study provides evidence for the importance of p21(CDKN1A) for the repair of replication-mediated DNA double-strand breaks (DSBs) induced by topoisomerase I. We report that defects of p21(CDKN1A) and p53 enhance camptothecin-induced histone H2AX phosphorylation (gammaH2AX), a marker for DNA DSBs. In human colon carcinoma HCT116 cells with wild-type (wt) p53, gammaH2AX reverses after camptothecin removal. By contrast, gammaH2AX increases after camptothecin removal in HCT116 cells deficient for p53 (p53-/-) or p21(CDKN1A) (p21-/-) as the cells reach the late-S and G2 phases. Since p21-/- cells exhibit similar S-phase arrest as wt cells in response to camptothecin and aphidicolin does not abrogate the enhanced gammaH2AX formation in p21-/- cells, we conclude that enhanced gammaH2AX formation in p21-/- cells is not due to re-replication. The cell cycle checkpoint abrogator and Chk1/Chk2 inhibitor 7-hydroxystaurosporine (UCN-01) also increases camptothecin-induced gammaH2AX formation and inhibits camptothecin-induced p21(CDKN1A) upregulation in HCT116 wt cells. TUNEL (terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling) assays demonstrate that gammaH2AX formation in late S and G2 cells following CPT treatment corresponds to DNA breaks. However, these breaks are not related to apoptotic DNA fragmentation. We propose that p21(CDKN1A) prevents the collapse of replication forks damaged by stabilized topoisomerase I cleavage complexes.

DNA topoisomerase II as the primary cellular target for salvicine in Saccharomyces cerevisiae.

AIM: To identify whether DNA topoisomerase II (Topo II) is the primary cellular target of salvicine in Saccharomyces cerevisiae (S cerevisiae) and the action mode of salvicine. METHODS: The catalytic activity of Topo II was determined by Topo II mediated supercoiled pBR322 relaxation. The effects of salvicine on the growth of four strains of S cerevisiae were assessed by clone forming assay. RESULTS: Salvicine inhibited Topo II mediated supercoiled pBR322 relaxation in cell-free system. Cytotoxicities of salvicine to parent (JN394) and TOP1 deleted (JN394top1-) yeast cells were at the same level, suggesting Topo I might not be the cellular target of salvicine. Salvicine displayed high activity against JN394t2-1 cells at 25 degrees C, while no growth inhibition was observed at 30 degrees C in the concentration range of interest. Furthermore, JN394t2-5 cells which expressed top2-5 mutant allele were highly resistant to salvicine and etoposide (VP16). CONCLUSION: Topo II was the primary cellular target of salvicine in vivo and salvicine killed yeast cells mainly by trapping the DNA-Topo II cleavage complex. Salvicine and VP16 might share some similar action locus on Topo II.

Salvicine, a novel DNA topoisomerase II inhibitor, exerting its effects by trapping enzyme-DNA cleavage complexes.

Salvicine, a structurally modified diterpenoid quinone derived from Salvia prionitis, is a novel anticancer drug candidate. The compound has significant in vitro and in vivo activity against malignant tumor cells and xenografts, especially some human solid tumor models. This anticancer activity of salvicine is associated with its ability to induce tumor cell apoptosis. Salvicine was also found to have a profound cytotoxic effect on multidrug-resistant (MDR) cell lines by down-regulating the expression of MDR-1 mRNA of MDR cells. Salvicine acted as a topoisomerase II (Topo II) poison through its marked enhancement effect on Topo II-mediated DNA double-strand breaks as observed in the DNA cleavage assay. Strong inhibitory activity of salvicine against Topo II was observed in a kDNA decatenation assay, with an approximate IC(50) value of 3 microM. A similar result was obtained by a Topo II-mediated supercoiled DNA relaxation assay. In contrast, no inhibitory activity was observed against the catalytic activity of Topo I. When the effects of salvicine on individual steps of the catalytic cycle of Topo II were dissected, it was found that the mechanism by which salvicine inactivates Topo II is different from that by other anti-Topo II agents. Salvicine greatly promoted Topo II-DNA binding and inhibited pre- and post-strand Topo II-mediated DNA religation without interference with the forward cleavage steps. In addition, salvicine was not a DNA intercalative agent, as demonstrated by DNA unwinding assays. The results of this study indicate that the inhibitory activity of salvicine against Topo II was derived from its ability to stabilize DNA strand breaks through interactions with the enzyme alone or with the DNA-enzyme complex. It is therefore postulated that salvicine acts on Topo by trapping the DNA-Topo II complex, which in turn produces anticancer effects.

Cytotoxic oxoisoaporphine alkaloids from Menispermum dauricum.

Four new oxoisoaporphine alkaloids, daurioxoisoporphines A-D (1-4), were isolated from the rhizomes of Menispermum dauricum. The structures of these alkaloids were established by spectroscopic methods. The cytotoxic evaluation of 1 and 2 is reported against four cancer cell lines.

Synthesis of ethyl alkylidene alpha cyanoacetates under ultrasound irradiation.

Condensation of ketones with ethyl cyanoacetate catalysed by ammonium acetate-acetic acid results in ethyl alkylidene alpha cyanoacetate in 31-89% yield under ultrasound irradiation.