The transcription factor-E2-related factor 2 (Nrf2) is an important regulator against the process of oxidative stress. It can effectively scavenge oxygen-free radicals within cells to maintain homeostasis. In this study, we cultured primary myocardial cells, established the hypoxia/reoxygenation (H/R) model to simulate myocardial ischemia/reperfusion injury, and examined effects of 17β-estradiol (E2) on the quantitative changes of Nrf2 in cytosolic and nuclear extracts, the mRNA expression of heme oxygenase 1 (HO-1), superoxide dismutase (Cu/Zn-SOD), glutathione S transferase (GST), and glutamate cysteine ligase amide (GCL) of each model group by Western blot assays and reverse transcription polymerase chain reaction, to investigate the effects of E2 against H/R/ injury in cultured myocardial cells. The present study shows that E2 can upregulate Nrf2 in nuclear extracts and increase the expression of HO-1, Cu/Zn-SOD, GST, and GCL significantly during H/R injury. Hence, our present findings suggest that E2 exhibits its antioxidant role by upregulating Nrf2 in nuclear extracts.

Song control nuclei have distinct sexual differences and thus are an ideal model to address how brain areas are sexually differentiated. Through a combination of histological analysis and electrical lesions, we first identified the ventricle site for HVC progenitor cells. We then found that there were significant sex differences in the cellular proliferation activity in the ventricular zone of the HVC, the number of migrating cells along the radial cells (positive immunoreactions to vimentin) and differentiation towards neurons. Through co-culturing of male and female slices containing the developing HVC in the same well, we found that the male slices could produce diffusible substances to masculinize the female HVC. By adding estrogen, an estrogen antagonist, brain-derived neurotrophic factor (BDNF) or its antibody into the culture medium, separately or in combination, we found that these diffusible substances may include estrogen and BDNF. Finally, we found that 1) estrogen-induced BDNF upregulation could be detected 48 hr after estrogen treatment and could not be blocked by a vascular endothelial growth factor (VEGF) receptor inhibitor and 2) the amount of VEGF mRNA expressed in the developing HVC and its adjacent area did not display any significant sex differences, as did the distribution of VEGF and laminin-expressing endothelial cells in the developing HVC. Because these findings are largely different from previous reports on the adult female HVC, it is suggested that our estrogen-induced BDNF up-regulation and the resultant sexual differentiation might not be mediated by VEGF and endothelial cells, but instead, may result from the direct effects of estrogen on BDNF.

Song control nuclei have distinct sexual differences in songbirds. However, the mechanism that underlies the sexual differentiation of song nuclei is still not well understood. Using a combination of anatomical, pharmacological, genetic, and behavioral approaches, the present study investigated the role of erbb2 (a homolog of the avian erythroblastic leukemia viral oncogene homolog 2) and the erbb2-interacting gene, erbin, in the sexual differentiation of the song nucleus HVC in the Bengalese finch. We first found that both erbin and erbb2 were expressed in the developing HVC at posthatch day (PHD) 15 in a male-biased fashion using qRT-PCR and in situ hybridization. Following the addition of a pharmaceutical inhibitor of the ErbB2 signaling pathway to the culture medium, cell proliferation in the cultured ventricle zone (VZ) that overlies the developing HVC decreased significantly. After the injection of erbin-or erbb2-interfering lentiviruses into the HVC and its overlying VZ at PHD 15, the cell proliferation in the VZ at PHD 24, the number of the differentiated neurons (Hu 1 /BrdU 1 or NeuN 1 /BrdU 1 ) in the HVC at PHD 31 or PHD 130, and the number of RAprojecting cells at PHD 130 all decreased significantly. Additionally, the adult songs displayed serious abnormalities. Finally, 173 male-biased genes were expressed in the developing HVC at PHD 15 using cDNA microarrays, of which 27.2% were Z-linked genes and approximately 20 genes were involved in the Erbin-or ErbB2-related signaling pathways. Our results provide some specific genetic factors that contribute to neurogenesis and sex differentiation in a song nucleus of songbirds.