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MED20 is a non-essential subunit of the transcriptional coactivator Mediator complex, but its physiological function remains largely unknown. Here, we identify MED20 as a substrate of the anti-obesity CRL4-WDTC1 E3 ubiquitin ligase complex through affinity purification and candidate screening. Overexpression of WDTC1 leads to degradation of MED20, whereas depletion of WDTC1 or CUL4A/B causes accumulation of MED20. Depleting MED20 inhibits adipogenesis, and a non-degradable MED20 mutant restores adipogenesis in WDTC1-overexpressing cells. Furthermore, knockout of Med20 in preadipocytes abolishes development of brown adipose tissues. Removing one allele of Med20 in preadipocytes protects mice from diet-induced obesity and reverses weight gain in Cul4a- or Cul4b-depleted mice. Chromatin immunoprecipitation sequencing (ChIP-seq) analysis reveals that MED20 organizes the early adipogenic complex by bridging C/EBPβ and RNA polymerase II to promote transcription of the central adipogenic factor, PPARγ. Our findings have thus uncovered a critical role of MED20 in promoting adipogenesis, development of adipose tissue and diet-induced obesity.

The aim of this study was to evaluate the immune responses in turbot, Scophthalmus maximus, treated with 1 × 107 cfu/ml attenuated Edwardsiella tarda (0.1 ml/fish) under low density (LD; ∼5.25-5.13 kg/m2, initial to final density), medium density (MD; ∼10.41-13.95 kg/m2), and high density (HD; ∼20.53-30.77 kg/m2) conditions for 8 weeks. The results showed that there was a peak value in the percentage of sIg+ (surface immunoglobulin-positive) cells in blood leucocytes (BL), spleen leucocytes (SL), and pronephros leucocytes (PL) during the sixth week in the HD, which was delayed by week compared with the other groups. The specific immunoglobulin M (IgM) antibody levels increased from the first week in all groups and reached a peak in the fifth week in the LD and MD groups, but in the sixth week in the HD group. The serum cortisol levels were greater in the HD group compared with the other groups in the last 3 or 4 weeks. These results show that stocking turbot at a LD obtained the most effective immunization, and thus we conclude that crowding stress may reduce the ability to deal with immune challenge.

Nitrite (NO2(-)) is commonly present as contaminant in aquatic environment and toxic to aquatic organisms. In the present study, we investigated the effects of nitrite exposure on haematological parameters, oxidative stress and apoptosis in juvenile turbot (Scophthalmus maximus). Fish were exposed to various concentrations of nitrite (0, 0.02, 0.08, 0.4 and 0.8mM) for 96 h. Fish blood and gills were collected to assay haematological parameters, oxidative stress and expression of genes after 0, 24, 48 and 96 h of exposure. In blood, the data showed that the levels of methemoglobin (MetHb), triglyceride (TG), potassium (K(+)), cortisol, heat shock protein 70 (HSP70) and glucose significantly increased in treatments with higher concentrations of nitrite (0.4 and/or 0.8mM) after 48 and 96 h, while the levels of haemoglobin (Hb) and sodium (Na(+)) significantly decreased in these treatments. In gills, nitrite (0.4 and/or 0.8mM) apparently reduced the levels of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione (GSH), increased the formation of malondialdehyde (MDA), up-regulated the mRNA levels of c-jun amino-terminal kinase (JUK1), p53, caspase-3, caspase-7 and caspase-9 after 48 and 96 h of exposure. The results suggested caspase-dependent and JUK signaling pathways played important roles in nitrite-induced apoptosis in fish. Further, this study provides new insights into how nitrite affects the physiological responses and apoptosis in a marine fish.

Summary: Neocortical neurons with similar functional properties assemble into spatially coherent circuits, but it remains unclear how inhibitory interneurons are organized. We applied in vivo two-photon functional Ca2+ imaging and whole-cell recording of synaptic currents to record visual responses of cortical neurons and analyzed their spatial arrangements. GABAergic interneurons were clustered in the 3D space of the mouse visual cortex, and excitatory neurons located within the clusters (insiders) had a lower amplitude and sharper orientation tuning of visual responses than outsiders. Inhibitory synaptic currents recorded from the insiders were larger than those of the outsiders. Single, isolated interneurons did not show such a location-tuning/amplitude relationship. The two principal subtypes of interneurons, parvalbumin- and somatostatin-expressing neurons, also formed clusters with only slightly overlapping each other and exhibited a different location-tuning relationship. These findings suggest that GABAergic interneurons and their subgroups form clusters to make their inhibitory function more effective than isolated interneurons. : Ebina et al. find 3D clustering of GABAergic neurons and their principal subtypes, parvalbumin- and somatostatin-expressing neurons. They demonstrate that inhibitory actions on excitatory neurons inside these clusters are stronger than outside, suggesting that GABAergic neurons form clusters in order to make their inhibitory function more effective than in isolated neurons.

With the increasing applications of titanium dioxide nanoparticles (TiO(2) NPs) in industry and daily life, an increasing number of studies showed that TiO(2) NPs may have negative effects on the respiratory or metabolic circle systems of organisms, while very few studies focused on the brain central nervous system (CNS). Synaptic plasticity in hippocampus is believed to be associated with certain high functions of CNS, such as learning and memory. Thus, in this study, we investigated the effects of developmental exposure to TiO(2) NPs on synaptic plasticity in rats' hippocampal dentate gyrus (DG) area using in vivo electrophysiological recordings. The input/output (I/O) functions, paired-pulse reaction (PPR), field excitatory postsynaptic potential, and population spike amplitude were measured. The results showed that the I/O functions, PPR, and long-term potentiation were all attenuated in lactation TiO(2) NPs-exposed offspring rats compared with those in the control group. However, in the pregnancy TiO(2) NPs exposure group, only PPR was attenuated significantly. These findings suggest that developmental exposure to TiO(2) NPs could affect synaptic plasticity in offspring's hippocampal DG area in vivo, which indicates that developmental brains, especially in lactation, are susceptible to TiO(2) NPs exposure. This study reveals the potential toxicity of TiO(2) NPs in CNS. It may give some hints on the security of TiO(2) NPs production and application and shed light on its future toxicological studies.

Epigallocatechin-3-gallate (EGCG), a catechin polyphenols component, is the main ingredient of green tea extract. It has been reported that EGCG is a potent antioxidant and beneficial in oxidative stress-related diseases, but others and our previous study showed that EGCG has pro-oxidant effects at high concentration. Thus, in this study, we tried to examine the possible pathway of EGCG-induced cell death in cultures of rat hippocampal neurons. Our results showed that EGCG caused a rapid elevation of intracellular free calcium levels ([Ca2+]i) in a dose-dependent way. Exposure to EGCG dose- and time-dependently increased the production of reactive oxygen species (ROS) and reduced mitochondrial membrane potential (Δψ m) as well as the Bcl-2/Bax expression ratio. Importantly, acetoxymethyl ester of 5,5′-dimethyl-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid, ethylene glycol-bis-(2-aminoethyl)-N,N,N′,N′-tetraacetic acid, and vitamin E could attenuate EGCG-induced apoptotic responses, including ROS generation, mitochondrial dysfunction, and finally partially prevented EGCG-induced cell death. Furthermore, treatment of hippocampal neurons with EGCG resulted in an elevation of caspase-3 and caspase-9 activities with no significant accompaniment of lactate dehydrogenase release, which provided further evidence that apoptosis was the dominant mode of EGCG-induced cell death in cultures of hippocampal neurons. Taken together, these findings indicated that EGCG induced hippocampal neuron death through the mitochondrion-dependent pathway.

(−)-Epigallocatechin-3-gallate (EGCG), the main active component of green tea, is commonly known for its beneficial properties at low doses. On the other hand, little is known about the adverse effects of EGCG. Voltage-gated sodium channel (VGSC) is responsible for both initiation and propagation of action potentials of the neurons in the hippocampus and throughout the central nervous system (CNS). In this study, the effects of EGCG on voltage-gated sodium channel currents ( I Na ) were investigated in rat primary cultures of hippocampal CA1 neurons via the conventional whole-cell patch-clamp technique. We found that I Na was not affected by EGCG at the concentration of 0.1 μM, but was completely blocked by EGCG at the concentration of 400 μM and higher, and EGCG reduced the amplitudes of I Na in a concentration-dependent manner in the range of 0.1–400 μM. Furthermore, our results also showed that at the concentration of 100 μM, EGCG was known to have the following performances: (1) it decreased the activation threshold and the voltage at which the maximum I Na current was evoked, caused negative shifts of I Na steady-state activation curve. (2) It enlarged I Na tail-currents. (3) It induced a left shift of the steady-state inactivation. (4) It reduced fraction of available sodium channels. (5) It delayed the activation of I Na in a voltage-dependent manner. (6) It prolonged the time course of the fast inactivation of sodium channels. (7) It accelerated the activity-dependent attenuation of I Na . On the basis of these findings, we propose that EGCG could impair certain physiological functions of VGSCs, which may contribute, directly or indirectly, to EGCG's effects in CNS.

Quantum dots (QDs) are colloidal nanocrystalline semiconductors with unique optical and electrical properties (Bruchez et al. 1998). As a new class of inorganic fluorophore, which has the advantages of broad absorption spectra, narrow emission spectra, stable photostability, and long fluorescent lifetime, QDs are gaining widespread recognition and are rapidly applied to fluorescent labeling of cellular proteins (Kaul et al. 2003; Mansson et al. 2004; Sukhanova et al. 2004), cell tracking (Dubertret et al. 2002; Jaiswal et al. 2003), and even imaging in vivo (Akerman et al. 2002; Chen et al. 2004; Gao et al. 2004; Lim et al. 2003; Morgan et al. 2005). Although some reports have evaluated the cytotoxicity of various QDs in different cell lines under different circumstances (Chan et al. 2006; Kirchner et al. 2005; Lovric et al. 2005; Zhang et al. 2006), little is known about QD toxicity both in vivo and in vitro. Santra et al. successfully labeled brain tissue with TAT-conjugated CdSratioMn/ZnS QDs that were intraarterially delivered to the rat brain (Santra et al. 2005), but this method of brain tissue labeling raised subsequent worries about QD toxicity on the toxin-susceptible brain. In fact, many QDs may seem harmless, but they can be destabilized because of their sequestration in tissues and long-term exposure to the bioenvironment. Cell structures and functions can be impaired when cells are exposed to unstable, poorly capped, or coated QDs (Choi et al. 2007, 2008; Hardman 2006; Lovric et al. 2005). In other words, even if the QDs are well modified, the potential risks are still present in subsequent biologic and clinical applications of QDs. In the central nervous system (CNS), voltage-gated sodium channels (VGSCs) are responsible for both initiation and propagation of action potentials of the neurons. Therefore, potential modulation of the functional properties of VGSCs by QDs would be expected to alter the activity and functions of CNS neurons. Meanwhile, there is hardly a biological reaction in the CNS that is not regulated, directly or indirectly, by calcium ions. Transient rises of calcium ions in the cytoplasmic levels are believed to serve as second messenger signals that control numerous neuronal functions, whereas sustained elevation of cytoplasmic calcium levels is obviously deleterious to various neuronal functions. Of even greater concern is that the sustained increase of intra-cellular calcium may result in cell apoptosis/ death (Fox et al. 1999; McConkey and Orrenius 1996; Nicotera et al. 1994). Some reports have shown that QDs could impair cell functions and even induce cell apoptosis or death in certain cell lines (Chan et al. 2006; Choi et al. 2007, 2008; Medintz et al. 2005), but these studies mostly focused on the free Cd2+ (QD core degradation), free radical formation, and interaction of QDs with intracellular components, and little attention has been paid to the potential toxicity exerted by QDs through intracellular calcium steady-state and functional properties of neuronal ion channels. Using confocal laser scanning and standard whole-cell patch clamp techniques, the present study explored the potential for the neurotoxicity of unmodified cadmium selenium (CdSe) QDs in a rat primary hippocampal culture model, focusing on cytoplasmic calcium levels and VGSC functions.

Among the developmental changes identified in rats exposed to lead are impairments in long-term potentiation (LTP) in the hippocampus and changes in the levels of reactive oxygen species (ROS) in cells and some soft tissues. alpha-Lipoic acid (LA) has been reported to be highly effective in improving the thiol capacity of the cells and in reducing lead-induced oxidative stress. To explore the effects of LA on LTP in chronically lead-exposed rats and the relationship between ROS and LTP in both control and lead-exposed rats, we have compared LTP and oxidative stress parameters in groups of lead-exposed and control rats with or without LA treatment (10, 25, 50, and 100 mg/kg through intraperitoneal injection). The capacity of LA to decrease hippocampal lead levels in lead-exposed rats was examined. We found that LA had no effects in decreasing the level of lead in the hippocampus, but it did appear to have both antioxidant properties and a reparatory effect on LTP amplitude in rats developmentally exposed to lead for 2 weeks following birth. Interestingly, bell-shaped dose-response curves emerged. In the lower LA dosage groups (10, 25 mg/kg LA), there was an increasing LTP amplitude. The strongest protective effect in terms of the induction and amplitude of LTP in the lead-exposed group with at 25 mg/kg LA; when higher dosages were applied (50, 100 mg/kg LA), the LTP amplitude decreased as compared to the 25 mg/kg LA treatment group. The administration of LA to control animals resulted in a significant impairment of LTP amplitude, with the 100 mg/kg LA treatment having harmful effects on the oxidative parameters. These differential effects of LA on LTP in control and lead-exposed rats may be due to the different redox status of the control and lead-exposed rats.

Studies reported that quantum dots (QDs), as a novel probe, demonstrated a promising future for in vivo imaging, but also showed potential toxicity. This study is mainly to investigate in vivo response in the central nervous system (CNS) after exposure to QDs in a rat model of synaptic plasticity and spatial memory. Adult rats were exposed to streptavidin-conjugated CdSe/ZnS QDs (Qdots 525, purchased from Molecular Probes Inc.) by intraperitoneal injection for 7 days, followed by behavioral, electrophysiological, and biochemical examinations. The electrophysiological results show that input/output (I/O) functions were increased, while the peak of paired-pulse reaction and long-term potentiation were decreased after QDs insult, indicating synaptic transmission was enhanced and synaptic plasticity in the hippocampus was impaired. Meanwhile, behavioral experiments provide the evidence that QDs could impair rats’ spatial memory process. All the results present evidences of interference of synaptic transmission and plasticity in rat hippocampal dentate gyrus area by QDs insult and suggest potential adverse issues which should be considered in QDs applications.

Increasing evidence suggests that lead (Pb) produces impairments partly through oxidative stress. Though many researchers have investigated protective effect of some antioxidant nutrients against Pb toxicity, little information is available about the effect of antioxidants on Pb-induced impairment of synaptic plasticity. Quercetin, a strong antioxidant and radical scavenger, is the representative natural flavonoid molecule abundant in fruits and vegetables. Previous studies have found that quercetin was neuroprotective in many cases. This study was designed to evaluate the effect of quercetin on chronic Pb exposure-induced impairment of synaptic plasticity in adult rat dentate gyrus (DG) area in vivo. The input/output (I/O) functions, paired-pulse reactions (PPR), excitatory postsynaptic potential (EPSP), and population spike (PS) amplitude were measured in the DG area of different groups of rats in response to stimulation applied to the lateral perforant path. The results showed that the depressed I/O, PPR, and long-term potentiation (LTP) of Pb-exposed group were significantly increased by quercetin treatment. In addition, hippocampal Pb concentration was partially reduced after quercetin treatment. These findings suggest that quercetin treatment could relieve chronic Pb exposure-induced impairment of synaptic plasticity and might be a potential therapeutic intervention to cure cognitive deficits induced by Pb.