Prenatal sevoflurane exposure causes abnormal development of the entorhinal cortex in rat offspring.

As a gamma-aminobutyric acid type A receptor agonist sevoflurane is a common general anesthetic used in anesthesia and affects the neural development in offspring. We hypothesized that sevoflurane could regulate interneurons via the neuregulin-1-epidermal growth factor receptor-4 (NRG1-ErbB4) pathway in the entorhinal cortex (ECT) of the middle pregnancy. Six female rats in middle pregnancy (14.5 days of pregnancy) were randomly and equally divided into sevoflurane (SeV) and control groups. The rats in the SeV group were exposed to 4% sevoflurane for 3 hours. The expression levels of NRG1 and ErbB4, parvalbumin (PV) and glutamic acid decarboxylase (GAD67), and N-methyl-D-aspartate receptor subunit 2A (NR2A) and subunit 2B (NR2B) in offspring were examined through immunohistochemistry. The pyramidal neurons in the ECT were examined via Golgi staining. The levels of NRG1 and ErbB4 were significantly decreased (P < 0.01) and the levels of PV and GAD67 (interneurons) were found to be decreased in the SeV group (P < 0.01). The level of NR2B was found to be increased while the level of NR2A being decreased in the SeV group (P < 0.01). The development of pyramidal neurons was abnormal in the SeV group (P < 0.05). Conclusively, prenatal sevoflurane exposure could lead to the disturbance of the interneurons by activating the NRG1-ErbB4 pathway and subsequently result in abnormal development of pyramidal neurons in middle pregnancy. Prenatal sevoflurane exposure in middle pregnancy could be potentially harmful to the neural development of rat offspring. This study may reveal a novel pathway in the influence mechanism of sevoflurane on rat offspring.

Shi-Zhen-An-Shen Decoction, a Herbal Medicine That Reverses Cuprizone-Induced Demyelination and Behavioral Deficits in Mice Independent of the Neuregulin-1 Pathway.

Shi-Zhen-An-Shen decoction (SZASD), a Chinese herbal medicine that is a liquor extracted from plants by boiling, has been reported to be effective in treating schizophrenia. However, the mechanism is unclear. Abnormal demyelination has been implicated in schizophrenia. The aim of this study was to investigate the effect of SZASD on myelin in demyelinated mice exhibiting schizophrenia-like behaviors. Sixty male C57BL/6 mice were randomly divided into six groups (n = 10 per group): (1) control group, (2) cuprizone (CPZ, a copper chelator that induced demyelination, 0.2% w/w)+saline, (3) CPZ+low-dose SZASD (8.65 g·kg-1·d-1), (4) CPZ+medium-dose SZASD (17.29 g·kg-1·d-1), (5) CPZ+high-dose SZASD (25.94 g·kg-1·d-1), and (6) CPZ+quetiapine (QTP, an atypical antipsychotic that served as a positive treatment control, 10 mg·kg-1·d-1). Mice in groups 2-6 were treated with CPZ added to rodent chow for six weeks to induce demyelination. During the last two weeks, these mice were given an oral gavage of sterile saline, SZASD, or quetiapine. Behavioral tests and brain analyses were conducted after the last treatment. The brain expression of myelin basic protein (MBP) and neuregulin-1 (NRG-1) was assessed using immunohistochemistry and Western blots. CPZ induced significant schizophrenia-like behaviors in the mice, including reduced nest-building activity and sensory gating deficits. Hyperlocomotor activity was accompanied by significant reductions in MBP expression in the corpus callosum, hippocampus, and cerebral cortex. However, both QTP and SZASD significantly reversed the schizophrenia-like behaviors and demyelination in CPZ-fed mice. The QTP and medium-dose SZASD resulted in better therapeutic effects compared to the low and high SZASD doses. Reduced NRG-1 expression was observed in CPZ-fed mice compared with controls, but neither QTP nor SZASD showed significant influence on NRG-1 expression in the hippocampus. Together, SZASD showed a therapeutic effect on demyelinated mice, and the improvement of demyelination might not be through the NRG-1 pathway.

Differential expression of neuregulin 1 (NRG1) and candidate miRNA regulating NRG1 transcription in the chicken oviduct in response to hormonal changes.

Neuregulin 1 (NRG1), a signaling protein that binds to members of the erythroblastoma (ErbB) family, is known to play essential biological roles in mediating cell-cell interactions and orchestrating vital cell functions in the heart and nervous system. NRG1 is closely associated with developmental processes in various organs and expression of several NRG1 isoforms are regulated by estrogen. However, expression and its hormonal regulation during development of the female reproductive tract remain unknown. The reproductive system of chickens undergoes dynamic morphological and functional changes in response to estrogen and the molting process. Therefore, in the current study, we found differential expression of and candidate microRNA regulating chicken transcription in response to estrogen stimulation and/or the molting process. The results revealed that relative expression of mRNA increased in the oviducts of chicks treated with diesthylstilbestrol (DES; a synthetic non-steroidal estrogen). Additionally, abundant NRG1 mRNA expression was primarily in the glandular (GE) and luminal (LE) epithelia of the magnum in the developing chick oviduct in response to exogenous estrogen. Also, expression decreased during regression of the oviduct following induced molting by feeding high levels of zinc in the diet, and then gradually resurged as the oviduct underwent remodeling and recrudescence in laying hens. In addition, the present results revealed changes in relative expression of candidate chicken microRNA (, and ) targeting transcription in chicken oviducts in response to exogenous estrogen. In conclusion, these results provide the first evidence that is a novel estrogen-responsive gene closely correlated with the estrogen-dependent development of the oviduct of chicks and regeneration of the oviduct after molting. Further, regulation of expression involving at least 3 chicken miRNA is likely a prerequisite for those estrogen regulated developmental events.

Gonadotropin-Dependent Neuregulin-1 Signaling Regulates Female Rat Ovarian Granulosa Cell Survival.

Mammalian ovarian follicular development and maturation of an oocyte competent to be fertilized and develop into an embryo depends on tightly regulated, spatiotemporally orchestrated crosstalk among cell death, survival, and differentiation signals through extra- and intraovarian signals, as well as on a permissive ovarian follicular microenvironment. Neuregulin-1 (NRG1) is a member of the epidermal growth factor-like factor family that mediates its effects by binding to a member of the erythroblastoma (ErbB) family. Our experimental results suggest gonadotropins promote differential expression of NRG1 and erbB receptors in granulosa cells (GCs), and NRG1 in theca cells during follicular development, and promote NRG1 secretions in the follicular fluid (FF) of rat ovaries. During the estrous cycle of rat, NRG1 and erbB receptors are differentially expressed in GCs and correlate positively with serum gonadotropins and steroid hormones. Moreover, in vitro experimental studies suggest that the protein kinase C inhibitor staurosporine (STS) causes the physical destruction of GCs by the activation of caspase-3. Exogenous NRG1 treatment of GCs delayed onset of STS-induced apoptosis and inhibited cleaved caspase-3 expressions. Moreover, exogenous NRG1 treatment of GCs alters STS-induced death by maintaining the expression of ErbB2, ErbB3, pAkt, Bcl2, and BclxL proteins. Taken together, these studies demonstrate that NRG1 is gonadotropin dependent, differentially regulated in GCs and theca cells, and secreted in ovarian FF as an intracellular survival factor that may govern follicular maturation.

Chronic administration of calcitriol enhanced neuregulin-1/ErbB signaling in rat myocardium.

Although emerging evidence suggests that vitamin D has beneficial effects in the cardiovascular health, the underlying mechanisms are far from fully elucidated. Given the indispensable role of neuregulin-1 (NRG1)/ErbB signaling in the cardiovascular system, the present study investigated the influences of prolonged administration of calcitriol, the active form of vitamin D, on the NRG1/ErbB system. We examined the protein expression of NRG1, ErbB receptors (ErbB2 and ErbB4) and their phosphorylated forms in the myocardium of rats following 6-week administration of calcitriol (50 ng/kg/day or 100 ng/kg/day). We further assessed the myocardial vitamin D receptor (VDR) to confirm the effect of calcitriol treatment. Additionally, serum neuregulin-1 level was also analyzed. Generally, calcitriol enhanced myocardial VDR expression and NRG1/ErbB signaling. Calcitriol increased NRG1 protein level at the higher dose, while both doses promoted ErbB2 and phosphorylated ErbB2 expression. Although calcitriol has no significant influence on ErbB4 expression, phosphorylated ErbB4 receptors were enhanced at the higher dose. Furthermore, the serum neuregulin-1 concentration was increased at both doses. Overall, our data firstly showed that chronic calcitriol administration enhanced NRG1/ErbB signaling in the heart, indicating a novel mechanism underlying the cardiac effects of vitamin D.

Disruption of hippocampal neuregulin 1-ErbB4 signaling contributes to the hippocampus-dependent cognitive impairment induced by isoflurane in aged mice.

BACKGROUND: A prolonged isoflurane exposure may lead to cognitive decline in rodents. Neuregulin 1 (NRG1)-ErbB4 signaling plays a key role in the modulation of hippocampal synaptic plasticity through regulating the neurotransmission. The authors hypothesized that hippocampal NRG1-ErbB4 signaling is involved in isoflurane-induced cognitive impairments in aged mice. METHODS: Fourteen-month-old C57BL/6 mice were randomized to receive 100% O2 exposure, vehicle injection after 100% O2 exposure, vehicle injection after exposure to isoflurane carried by 100% O2, NRG1-ß1 injection after exposure to isoflurane carried by 100% O2, and NRG1-ß1 and an ErbB4 inhibitor AG1478 injection after exposure to isoflurane carried by 100% O2. Fear conditioning test was used to assess the cognitive function of mice 48-h postexposure. The brain tissues were harvested 48-h postexposure to determine the levels of NRG1, ErbB4, p-ErbB4, parvalbumin, and glutamic acid decarboxylase 67 in the hippocampus using Western blotting, enzyme-linked immunosorbent assay, and immunofluorescence. RESULTS: The percentage of freezing time to context was decreased from 50.28 ± 11.53% to 30.82 ± 10.00%, and the hippocampal levels of NRG1, p-ErbB4/ErbB4, parvalbumin, and glutamic acid decarboxylase 67 were decreased from 172.79 ± 20.85 ng/g, 69.15 ± 12.20%, 101.68 ± 11.21%, and 104.71 ± 6.85% to 112.92 ± 16.65 ng/g, 42.26 ± 9.71%, 75.89 ± 10.26%, and 73.87 ± 16.89%, respectively, after isoflurane exposure. NRG1-ß1 attenuated the isoflurane-induced hippocampus-dependent cognitive impairment and the declines in the hippocampal NRG1, p-ErbB4/ErbB4, parvalbumin, and glutamic acid decarboxylase 67. AG1478 inhibited the rescuing effects of NRG1-ß1. CONCLUSION: Disruption of NRG1-ErbB4 signaling in the parvalbumin-positive interneurons might, at least partially, contribute to the isoflurane-induced hippocampus-dependent cognitive impairment after exposure to isoflurane carried by 100% O2 in aged mice.

2,4-Dinitrophenol blocks neurodegeneration and preserves sciatic nerve function after trauma.

Preventing the harm caused by nerve degeneration is a major challenge in neurodegenerative diseases and in various forms of trauma to the nervous system. The aim of the current work was to investigate the effects of systemic administration of 2,4-dinitrophenol (DNP), a compound with newly recognized neuroprotective properties, on sciatic-nerve degeneration following a crush injury. Sciatic-nerve injury was induced by unilateral application of an aneurysm clip. Four groups of mice were used: uninjured, injured treated with vehicle (PBS), injured treated with two intraperitoneal doses of DNP (0.06 mg DNP/kg every 24 h), and injured treated with four doses of DNP (every 12 h). Animals were sacrificed 48 h post injury and both injured and uninjured (contralateral) sciatic nerves were processed for light and electron microscopy. Morphometric, ultrastructural, and immunohistochemical analysis of injured nerves established that DNP prevented axonal degeneration, blocked cytoskeletal disintegration, and preserved the immunoreactivity of amyloid precursor protein (APP) and Neuregulin 1 (Nrg1), proteins implicated in neuronal survival and myelination. Functional tests revealed preservation of limb function following injury in DNP-treated animals. Results indicate that DNP prevents nerve degeneration and suggest that it may be a useful small-molecule adjuvant in the development of novel therapeutic approaches in nerve injury.