雌、孕激素联合应用对豚鼠心室乳头肌细胞动作电位及收缩力的影响

目的:观察不同浓度17β雌二醇(E2)与孕酮(P)联合运用时豚鼠心室乳头肌细胞动作电位及心肌收缩力的影响.方法:采用常规玻璃微电极技术记录豚鼠心室乳头肌细胞动作电位,生理二道记录仪与示波器连接记录收缩力.结果:①E2与P单独作用可使动作电位时程(APD90、APD)延长,APD20缩短,心肌收缩力降低,APA、Vmax降低.②不同浓度E2与P联合应用,P可加强E2的效应.结论:E2与P可能抑制Ca2 通道、K 通道、Na 通道,不同浓度E2与P联合应用,P可加强E2的效应,这种作用可能呈现浓度依赖性,提示在临床应用中加用孕激素应以低浓度为益.     

Ovarian cycle of the captive formosan gem‐faced civets (Paguma larvata taivana)

Formosan gem‐faced civets are classified to be endemic sub‐species of Paguma larvata in Taiwan. Little about their reproductive physiology has been reported. This study was designed to characterize the ovarian activity throughout the year and define ovarian cycle length and the lengths of its component phases. Serum samples were collected for enzyme immunoassay (progesterone and estradiol) from seven captive civets twice weekly for 1 year. Meanwhile, periodic changes in external genitalia (vulva swelling) and vaginal cytology were examined and recorded. Results showed estrous cycles exhibited two types: 18‐day (18.5±1.1, n=64) and 28‐day (27.6±1.0, n=28) as shown by progesterone and estradiol fluctuations and corresponding changes in vulva morphology and vaginal cytology. Both types showed a similar 7‐day follicular phase, peaking progesterone at Day 7. The 18‐day cycle type prevails in the spring and summer whereas the 28‐day cycle type is significant in the autumn. In summary, female gem‐faced civets are polyestrous (approximately 13 cycles/year), and non‐typical seasonal breeders, with follicular phase and two distinct durations of luteal phases (diestrus) cycling throughout the year, but the frequency of ovarian cycles was remarkably gradually decreased from September to February of next year. Zoo Biol 0:1–11, 2007. © 2007 Wiley‐Liss, Inc.     

A kinetic study on the lactoperoxidase catalyzed oxidation of estrogens

Lactoperoxidase, which is produced in mammary glands, is proposed to be involved in carcinogenesis, because of its ability to react with estrogenic molecules, oxidizing them to free radicals. In the present study the reactivity towards six species (estradiol, ethynylestradiol, estriol, estrone, pregnenolone and mestranol) was investigated by means of a NADH-coupled system. The enzyme activity towards estradiol, ethynylestradiol, estriol and estrone did not vary much, suggesting that the different substituents in the D-ring of the steroid had little effect on the reaction. A somewhat higher K _m-value was obtained with estriol; possibly because of a more effective splitting of the enzyme–substrate complex into products. Pregnenolone, without resonance in the A-ring, and a methyl group in 19-position, did not react with the enzyme, in spite of having the proposed essential hydroxyl group in 3-position. Mestranol, with a methoxy group in 3-position, did not react with the enzyme either, supporting the suggestion that lactoperoxidase reacts with the 3-hydroxyl group of the estrogens.     

17β-estradiol inhibits the production of infectious particles of hepatitis C virus

Persistent infection with hepatitis C virus causes serious liver diseases, such as chronic hepatitis, hepatic cirrhosis and hepatocellular carcinoma. The male gender is one of the critical factors in progression of hepatic fibrosis due to chronic HCV infection; thus female hormones may play a role in delaying the progression of hepatic fibrosis. It has also been reported that women are more likely than men to clear HCV in the acute phase of infection. These observations lead the present authors to the question: do female hormones inhibit HCV infection? In this study using HCV J6/JFH1 and Huh‐7.5 cells, the possible inhibitory effect(s) of female hormones such as 17β‐estradiol (the most potent physiological estrogen) and progesterone on HCV RNA replication, HCV protein synthesis and production of HCV infectious particles (virions) were analyzed. It was found that E₂, but not P₄, significantly inhibited production of the HCV virion without inhibiting HCV RNA replication or HCV protein synthesis. E₂–mediated inhibition of HCV virion production was abolished by a nuclear estrogen receptor (ER) antagonist ICI182780. Moreover, treatment with the ERα‐selective agonist 4, 4′, 4″‐ (4‐propyl‐[1H]‐pyrazole‐1, 3, 5‐triyl)trisphenol (PPT), but not with the ERβ‐selective agonist 2, 3‐bis (4‐hydroxyphenyl)‐propionitrile (DPN) or the G protein‐coupled receptor 30 (GPR30)‐selective agonist 1‐(4‐[6‐bromobenzo 1, 3 dioxol‐5‐yl]‐3a, 4, 5, 9b‐tetrahydro‐3H‐cyclopenta [c] quinolin‐8‐yl)‐ethanone (G‐1), significantly inhibited HCV virion production. Taken together, the present results suggest that the most potent physiological estrogen, E₂, inhibits the production of HCV infectious particles in an ERα–dependent manner.     

Conversion of Tubercidin to Toyocamycin: Some Properties of Tubercidin Derivatives (Nucleosides and Nucleotides. 47)1

Abstract

A facile method of conversion of tubercidin to the 5-methyl derivative and toyocamycin is described. The NMR and CD spectra of 5- and 6-substituted tubercidins are presented. These data show that the 6-substituted tubercidins are in the syn-conformations in solution.     

Reprogramming of non-genomic estrogen signaling by the stemness factor SOX2 enhances the tumor-initiating capacity of breast cancer cells

The restoration of pluripotency circuits by the reactivation of endogenous stemness factors, such as SOX2, may provide a new paradigm in cancer development. The tumoral stem cell reprogramming hypothesis, i.e., the ability of stemness factors to redirect normal and differentiated tumor cells toward a less-differentiated and stem-like state, adds new layers of complexity to cancer biology, because the effects of such reprogramming may remain dormant until engaged later in response to (epi)genetic and/or (micro)environmental events. To test this hypothesis, we utilized an in vitro model of a SOX2-overexpressing cancer stem cell (CSC)-like cellular state that was recently developed in our laboratory by employing Yamanaka’s nuclear reprogramming technology in the estrogen receptor α (ERα)-positive MCF-7 breast cancer cell line. Despite the acquisition of distinct molecular features that were compatible with a breast CSC-like cellular state, such as strong aldehyde dehydrogenase activity, as detected by ALDEFLUOR, and overexpression of the SSEA-4 and CD44 breast CSC markers, the tumor growth-initiating ability of SOX2-overexpressing CSC-like MCF-7 cells solely occurred in female nude mice supplemented with estradiol when compared with MCF-7 parental cells. Ser118 phosphorylation of estrogen receptor α (ERα), which is a pivotal integrator of the genomic and nongenomic E₂/ERα signaling pathways, drastically accumulated in nuclear speckles in the interphase nuclei of SOX2-driven CSC-like cell populations. Moreover, SOX2-positive CSC-like cells accumulated significantly higher numbers of actively dividing cells, and the highest levels of phospho-Ser118-ERα occurred when chromosomes lined up on a metaphase plate. The previously unrecognized link between E₂/ERα signaling and SOX2-driven stem cell circuitry may significantly impact our current understanding of breast cancer initiation and progression, i.e., SOX2 can promote non-genomic E₂ signaling that leads to nuclear phospho-Ser118-ERα, which ultimately exacerbates genomic ER signaling in response to E₂. Because E₂ stimulation has been recently shown to enhance breast tumor-initiating cell survival by downregulating miR-140, which targets SOX2, the establishment of a bidirectional cross-talk interaction between the stem cell self-renewal regulator, SOX2, and the local and systemic ability of E₂ to increase breast CSC activity may have profound implications for the development of new CSC-directed strategies for breast cancer prevention and therapy.     

Conventional protein kinase C isoforms mediate neuroprotection induced by phorbol ester and estrogen

Rapid signal transduction pathways play a prominent role in mediating neuroprotective actions of estrogen in the CNS. We have previously shown that estrogen-induced neuroprotection of primary cerebrocortical neurons from beta-amyloid peptide (Abeta) toxicity depends on activation of protein kinase C (PKC). PKC activation with phorbol-12-myristate-13-acetate (PMA) also provides neuroprotection in this paradigm. Because the PKC family includes several isoforms that have opposing roles in regulating cell survival, we sought to identify which PKC isoforms contribute to neuroprotection induced by PMA and estrogen. We detected protein expression of multiple PKC isoforms in primary neuron cultures, including conventional (alpha, betaI, betaII), novel (delta, epsilon, theta) and atypical (zeta, iota/lambda) PKC. Using a panel of isoform-specific peptide inhibitors and activators, we find that novel and atypical PKC isoforms do not participate in the mechanism of either PMA or estrogen neuroprotection. In contrast, a selective peptide activator of conventional PKC isoforms provides dose-dependent neuroprotection against Abeta toxicity. In addition, peptide inhibitors of conventional, betaI, or betaII PKC isoforms significantly reduce protection afforded by PMA or 17beta-estradiol. Taken together, these data provide evidence that conventional PKC isoforms mediate phorbol ester and estrogen neuroprotection of cultured neurons challenged by Abeta toxicity.