Rapid Elevation of Calcium Concentration in Cultured Dorsal Spinal Cord Astrocytes by Corticosterone

High-Throughput Metabolomics Discovers Metabolic Biomarkers and Pathways to Evaluating the Efficacy and Exploring Potential Mechanisms of Osthole Against Osteoporosis Based on UPLC/Q-TOF-MS Coupled With Multivariate Data Analysis

Postmenopausal osteoporosis (PMOP) is the most common metabolic bone illness among the elderly especially in postmenopausal women resulting from a reduction in bone mineral density, but there is no effective drug at present. The study was aimed at evaluating efficacy of osthole against osteoporosis using high-throughput metabolomics method. The blood samples for illustrating the pathological mechanism of PMOP and exploring the efficacy of osthole treatment (ST) were collected to perform metabolites and metabolic profiles and pathways analysis using ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) and pattern recognition methods. In addition, backbone weight, the bone density, and some vital biochemical indexes were also detected. A total of 28 metabolites were identified as biomarkers for ovariectomized-osteoporosis model, and ST could significantly regulate 19 of them including lysine, linoleic acid, 3-hydroxybutyric acid, prostaglandin F2a, taurocholic acid, LysoPC(15:0), l-carnitine, glucose, arginine, citric acid, corticosterone, ornithine, tryptophan, arachidonic acid, Cer(d18:0/18:0), glutamine, uric acid, 8-HETE, estriol, which mainly related with 13 metabolic pathways, such as linoleic acid metabolism, starch, and sucrose metabolism, arachidonic acid metabolism, alanine, aspartate and glutamate metabolism, arginine and proline metabolism, citrate cycle (TCA cycle), and arginine biosynthesis. The ovariectomized model (OVX) rats display a significant decrease bone density, TGF-β1, NO, and NOS level, and a significant increase bone weight, IL-6, TNF-α, and Ca 2+ level. These parameters in the ST rats were evidently improved as compared to the OVX group. ST effectively mitigated ovariectomy-induced osteoporosis in rats by affecting endogenous metabolite-related metabolic mechanism and showed the natural alternative with potential for the treatment of PMOP.

Astrocytes in neuroendocrine systems: An overview

A class of glial cell, astrocytes, is highly abundant in the central nervous system (CNS). In addition to maintaining tissue homeostasis, astrocytes regulate neuronal communication and synaptic plasticity. There is an ever-increasing appreciation that astrocytes are involved in the regulation of physiology and behaviour in normal and pathological states, including within neuroendocrine systems. Indeed, astrocytes are direct targets of hormone action in the CNS, via receptors expressed on their surface, and are also a source of regulatory neuropeptides, neurotransmitters and gliotransmitters. Furthermore, as part of the neurovascular unit, astrocytes can regulate hormone entry into the CNS. This review is intended to provide an overview of how astrocytes are impacted by and contribute to the regulation of a diverse range of neuroendocrine systems: energy homeostasis and metabolism, reproduction, fluid homeostasis, the stress response and circadian rhythms.

Nongenomic glucocorticoid effects and their mechanisms of action in vertebrates

Glucocorticoids (GC) act on multiple organ systems to regulate a variety of physiological processes in vertebrates. Due to their immunosuppressive and anti-inflammatory actions, glucocorticoids are an attractive target for pharmaceutical development. Accordingly, they are one of the most widely prescribed classes of therapeutics. Through the classical mechanism of steroid action, glucocorticoids are thought to mainly affect gene transcription, both in a stimulatory and suppressive fashion, regulating de novo protein synthesis that subsequently leads to the physiological response. However, over the past three decades multiple lines of evidence demonstrate that glucocorticoids may work through rapid, nonclassical mechanisms that do not require alterations in gene transcription or translation. This review assimilates evidence across the vertebrate taxa on the diversity of nongenomic actions of glucocorticoids and the membrane-associated cellular mechanisms that may underlie rapid glucocorticoid responses to include potential binding sites characterized to date.

Glucocorticoids, genes and brain function

The identification of key genes in transcriptomic data constitutes a huge challenge. Our review of microarray reports revealed 88 genes whose transcription is consistently regulated by glucocorticoids (GCs), such as cortisol, corticosterone and dexamethasone, in the brain. Replicable transcriptomic data were combined with biochemical and physiological data to create an integrated view of the effects induced by GCs. The most frequently reported genes were Errfi1 and Ddit4. Their up-regulation was associated with the altered transcription of genes regulating growth factor and mTORC1 signaling (Gab1, Tsc22d3, Dusp1, Ndrg2, Ppp5c and Sesn1) and progression of the cell cycle (Ccnd1, Cdkn1a and Cables1). The GC-induced reprogramming of cell function involves changes in the mRNA level of genes responsible for the regulation of transcription (Klf9, Bcl6, Klf15, Tle3, Cxxc5, Litaf, Tle4, Jun, Sox4, Sox2, Sox9, Irf1, Sall2, Nfkbia and Id1) and the selective degradation of mRNA (Tob2). Other genes are involved in the regulation of metabolism (Gpd1, Aldoc and Pdk4), actin cytoskeleton (Myh2, Nedd9, Mical2, Rhou, Arl4d, Osbpl3, Arhgef3, Sdc4, Rdx, Wipf3, Chst1 and Hepacam), autophagy (Eva1a and Plekhf1), vesicular transport (Rhob, Ehd3, Vps37b and Scamp2), gap junctions (Gjb6), immune response (Tiparp, Mertk, Lyve1 and Il6r), signaling mediated by thyroid hormones (Thra and Sult1a1), calcium (Calm2), adrenaline/noradrenaline (Adcy9 and Adra1d), neuropeptide Y (Npy1r) and histamine (Hdc). GCs also affected genes involved in the synthesis of polyamines (Azin1) and taurine (Cdo1). The actions of GCs are restrained by feedback mechanisms depending on the transcription of Sgk1, Fkbp5 and Nr3c1. A side effect induced by GCs is increased production of reactive oxygen species. Available data show that the brain's response to GCs is part of an emergency mode characterized by inactivation of non-core activities, restrained inflammation, restriction of investments (growth), improved efficiency of energy production and the removal of unnecessary or malfunctioning cellular components to conserve energy and maintain nutrient supply during the stress response.

Apelin-13 Protects PC12 Cells from Corticosterone-Induced Apoptosis Through PI3K and ERKs Activation

It is widely accepted that environmental stress is a risk factor for mental disorders. Glucocorticoid hormones play a vital role in the regulation of physiological response to stress. High concentrations of corticosterone can induce cellular damage in PC12 cells, which possess typical neuronal features. Apelin and its receptor APJ are widely distributed in the central nervous system including limbic structures involved in stress responses. Previous studies have suggested that apelin has a neuroprotective function. However, the effect of apelin on corticosterone-induced neuronal damage remains to be elucidated. In the present study, we explored the potential protective activity of apelin-13 in PC12 cells treated with corticosterone and its underling mechanisms. The viability of the cells, the apoptosis of the cells, the level of phosphorylation of Akt (p-Akt) and extracellular signal-regulated kinases (p-ERKs) and cleaved caspase-3 expression were detected by MTT, Hoechst staining and flow cytometer assays and Western blotting. Results showed that corticosterone induced cells viability loss, cell apoptosis, down-regulation of p-Akt and p-ERKs and up-regulation of cleaved caspase-3. The effects induced by corticosterone were attenuated by apelin-13 pretreatment. Furthermore, apelin-13-mediated anti-viability loss, antiapoptosis and caspase-3 suppression activities were blocked by specific inhibitors of phosphatidylinositol 3-kinase (PI3K) (LY294002) and ERKs (PD98059). The data suggest that apelin-13 protects PC12 cells from corticosterone-induced apoptosis through activating PI3K/Akt and ERKs signaling pathways.

Dihydromyricetin ameliorates the oxidative stress response induced by methylglyoxal via the AMPK/GLUT4 signaling pathway in PC12 cells

Dihydromyricetin (DMY), the major bioactive flavonoid ingredient extracted from the leaves of Ampelopsis grossedentata (Hand.-Mazz) W.T. Wang, displays multiple pharmacological activities, including oxidation resistance, antitumor properties and free radical scavenging capacities. However, the role of DMY in methylglyoxal (MG)-induced diabetes-associated cognitive decline and its underlying molecular mechanisms are unclear. The aim of the present study was to evaluate the effects of DMY on oxidative stress and glucose transport activity in a MG-induced PC12 cell line and to explore the related mechanisms. The effects of DMY on cell survival and apoptosis were examined, and the dysregulation of intracellular Ca(2+) was determined. Oxidative stress was evaluated by monitoring ROS production and the glutathione to glutathione disulfide ratio. The effects of DMY on glucose metabolism were investigated using a fluorescently labeled deoxyglucose analog and by measuring ATP and lactate production. Western blot analysis was performed to examine the protein levels of glyoxalase I (Glo-1), glucose transporter 4 (GLUT4), AMP-activated protein kinase (AMPKα) and phosphorylated AMPKα (p-AMPKα). The results revealed that DMY suppressed cellular oxidative stress in PC12 cells and balanced glucose metabolism. Additionally, DMY reduced GLUT4 translocation dysfunction and increased Glo-1 and p-AMPKα expression. We found that DMY protected PC12 cells against MG-induced apoptosis and glycometabolic disorders, at least in part by restraining the hyperactivation of p-AMPK activity and normalizing the translocation of GLUT4 from the intracellular compartment, resulting in a balance in glucose uptake. This result indicates that DMY may serve as a novel and effective candidate agent to treat diabetic encephalopathy by reducing the toxicity of MG.