Antioxidant effect of a phytoestrogen equol on cultured muscle cells of embryonic broilers.

Previous studies have shown that the in ovo injection of equol can markedly improve the water-holding capacity of muscles of broilers chickens at 7 wk of age through promotion of the antioxidant status. We aimed to investigate directly the antioxidant effects of equol on muscle cells in broilers. Muscle cells were separated from leg muscle of embryos on the 11th day of incubation and treated with equol and H(2)O(2), either alone or together. Cells were pretreated with medium containing 1, 10, or 100 µM equol for 1 h prior to the addition of 1 mM H(2)O(2) for a further 1 h. Photomicrographs of cells were obtained. Cell viability, malondialdehyde (MDA) content, and L-lactate dehydrogenase (LDH) activity in the cell supernatant, as well as intracellular total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) activities were determined. Treatment with 1 mM H(2)O(2) caused serious damage to cells, indicated by comets with no clear head region but a very apparent tail of DNA fragments. Pretreatment with low (1 µM) but not high concentrations of equol (10 µM) inhibited cell damage, while 100 µM equol caused more serious damage than H(2)O(2) alone. Pretreatment with 1 µM equol had no effect on cell viability, while pretreatment with 10 and 100 µM equol significantly decreased cell viability in a dose-dependent manner. Compared with H(2)O(2) alone, pretreatment with low-dosage equol markedly decreased LDH activity and MDA production in the supernatant, significantly increased intracellular T-SOD activity (P < 0.05) and tended to increase intracellular GSH-Px activity (0.05 < P < 0.1). Pretreatment with high-dosage equol (10 and 100 µM) significantly enhanced LDH activity, but had no effect on MDA content, T-SOD or GSH-Px activity induced by H(2)O(2,) except for an obvious increase in GSH-Px activity caused by 10 µM equol. These results indicate that equol at low dosage can prevent skeletal muscle cell damage induced by H(2)O(2), while pretreatment with high-dosage equol shows a synergistic effect with H(2)O(2) in inducing cell damage.

Effect of glucocorticoids pretreatment on steroidogenic capacity of adrenocortical cells isolated from Meishan piglets.

The present in vitro experiment was designed to test whether 48 h of pretreatment with glucocorticoids, cortisol, or dexamethasone (DEX), would affect basal and corticotrophin (ACTH) stimulated (24 h) cortisol secretion from primary cultures of pig adrenocortical cells. Cells were divided into six groups: control pretreatment with or without ACTH challenge, cortisol pretreatment with or without ACTH challenge, and DEX pretreatment with or without ACTH. The culture medium and cells were collected at the end of treatment. Cortisol concentration in medium was measured by radioimmunoassay, and protein content of glucocorticoid receptor (GR) and key regulatory factors for steroidogenesis, including melanocortin type 2 receptor (MC2R), steroidogenic acute regulatory protein (StAR) and cholesterol side-chain cleavage cytochrome P450 (P450scc), were detected by Western blot analysis. The results showed that glucocorticoid pretreatment did not affect cortisol secretion under basal condition without ACTH challenge, but significantly enhanced ACTH-stimulated cortisol secretion. Furthermore, the protein content of GR, MC2R, StAR, and P450scc was all increased in groups pretreated with glucocorticoids. These results indicate that adrenocortical cells pretreated with glucocorticoids display higher steroidogenic capacity under ACTH challenge, through the upregulation of GR and other steroidogenic regulatory factors.

Dual effects of daidzein on chicken hepatic vitellogenin II expression and estrogen receptor-mediated transactivation in vitro.

Two in vitro systems were employed to delineate the estrogenic activity of daidzein (Da), alone or in combination with high or low concentrations of estrogen in two cell types possessing different estrogen-receptor (ER) isoforms, ERalpha and/or ERbeta: (1) vitellogenin II (VTG), the egg yolk precursor protein and the endpoint biomarker for estrogenicity, in chicken primary hepatocytes, and (2) CHO-K1 cells transiently co-transfected with ERalpha or ERbeta and estrogen-response elements (ERE) linked to a luciferase reporter gene. Da (100 microM) alone induced VTG mRNA expression in chicken hepatocytes, albeit with much less potency compared to estradiol (E(2)). Da exhibited different effects in the presence of 1 microM and 10 microM E(2). At a concentration of 100 microM, Da enhanced 1 microM E(2)-induced VTG transcription by 2.4-fold, but significantly inhibited 10 microM E(2)-induced VTG mRNA expression in a dose-dependent fashion from 1 to 100 microM. Tamoxifen completely blocked the estrogenic effect of daidzein, alone or in combination with 1 microM of E(2), but did not influence its anti-estrogenic effect on 10 microM E(2)-induced VTG mRNA expression. Furthermore, neither E(2) nor daidzein, alone or in combination, affected ERalpha mRNA expression, yet all the treatments significantly up-regulated ERbeta mRNA expression in chicken hepatocytes. E(2) effectively triggered estrogen-response elements (ERE)-driven reporter gene transactivation in CHO-K1 cells expressing ERalpha or ERbeta and showed much greater potency with ERalpha than with ERbeta. In contrast, daidzein was 1000 times more powerful in stimulating ERbeta- over ERalpha-mediated transactivation. Daidzein, in concentrations ranging from 5 nM to 50 microM, did not affect ERbeta-mediated transactivation induced by 1 nM E(2), but it significantly inhibited ERbeta-mediated transactivation induced by 10 nM E(2) at 500 nM. Despite the tremendous difference in sensitivity between the two in vitro systems, daidzein exhibited greater potency as an estrogen-antagonist for ERbeta-mediated activity.

[Isolation and expression of novel expressed sequence tags (ESTs) from ovarian follicles of Shaoxing ducks].

Three expressed sequence tags ( ESTs), SXDF0201 (271 bp), SXDF0202 (200 bp) and SXDF0203 (173 bp), were isolated from ovarian follicles of Shaoxing ducks by using silver staining mRNA differential display. GenBank/BLAST analysis revealed that SXDF0201 was not homologous to any of the published sequences from all species, indicating that it was a novel EST and was then registered in GenBank (GenBank Accession No.: CB072629), while SXDF0202 and SXDF0203 were found to be highly homologous to seven known chicken ESTs and chicken mRNA for gizzard smooth muscle myosin heavy chain. 5'-RACE was employed to extend the SXDF0201 to 544 bp which was confirmed as novel in BLAST search. The temporal and spatial expression of SXDF0201 and SXDF0202 were also investigated with semi-quantitative RT-PCR. The result showed that: both SXDF0201 and SXDF0202 were found to be expressed in hypothalamus, pituitary, muscle, liver, and fat tissues of Shaoxing ducks; SXDF0201 was expressed significantly higher in ovaries of 30-day-old Shaoxing ducks compared with that of 60-day-old (P < 0.05) and 90-day-old (P = 0.015), but the expression of SXDF0202 showed no difference throughout the ovarian development; granulose layers expressed higher SXDF0201 than theca layers in almost all hierarchical follicles, the expression of SXDF0202 in granulose layers increased along with follicular maturation (P < 0.01) from Fw to F3 follicles, but decreased dramatically to the lowest in F1 follicles (P < 0.01). In theca layers, the highest expression of SXDF0202 was found in Fw follicles (P < 0.01).

[Expression of mRNAs for GHR, IGF-IR, FSHR and LHR in granulosa and theca layers of ovarian follicles of Shaoxing ducks].

Expression of genes encoding growth hormone receptor (GHR), type I insulin-like growth factor receptor (IGF-IR), follicle-stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHR) was measured in granulosa and theca layers of the largest (F1), third largest (F3), fifth largest (F5) preovulatory follicles and large white follicles (LWF) in the ovary of Shaoxing ducks, with relative quantitative reverse transcription-polymerase chain reaction (RT-PCR) using beta-actin as an internal standard. The results showed that GHR mRNA was more abundant in theca layer than in granulosa layer in all the follicles investigated, in theca layer, the LWF follicle expressed highest the level of GHR mRNA, while no differences in granulosa layer were observed among follicles at different stages of development. In contrast, the expression of IGF-IR mRNA in theca layer was evidently lower than that in granulosa layer, but no significant changes were found among different stages of follicles in either layers, except that LWF trended to express higher IGF-IR mRNA in the theca layer compared to other preovulatory follicles. Similar to IGF-IR mRNA, FSHR mRNA was more abundant in granulosa layer and no significant differences were found among different stages of follicles in either layers. In contrast, the expression of LHR mRNA followed a different pattern. In the theca layer, the expression level maintained consistent, while in the granulosa layer, a significant stepwise increase was observed as the follicles matured, resulting in higher mRNA level of LHR in the granulosa layer of largest follicles (F1), but lower mRNA level of LHR in the granulosa layer of smaller follicles (F5 and LWF). These results suggest that GH and IGF-I regulate ovary function by respective dominant sites in the follicles, and they cooperate with LH and FSH to regulate the follicle development via their respective receptors. The high expression of LHR mRNA in granulosa layer of large follicles might be related to the establishment of the follicle hierarchy and ovulation.