99 research outputs found
Gelsolin : a regulator of postsynaptic actin assembly and AMPA receptor expression
No full textDendritic spines are the postsynaptic contact sites for the majority of excitatory
synapses in the brain. Synaptic activity influences the number, shape and
motility of dendritic spines and these effects are likely mediated by dynamic
actin filaments, which are highly concentrated in spine heads. Drugs that inhibit
actin dynamics block spine motility and interfere with the development of longterm
potentiation (LTP), a long-lasting increase in synaptic strength considered
to be closely related to learning and memory. This suggests that actin may
serve as a link between activity-induced modulation of synaptic transmission
and long-term changes in synaptic morphology. Despite this evidence for the
importance of actin dynamics in synaptic plasticity, very little is known about its
regulation at the synapse. In particular the mechanisms linking synaptic activity
to the actin cytoskeleton in dendritic spines are not well understood.
The experiments described in this thesis were focused on gelsolin as a
promising candidate for mediating synaptic activity to actin cytoskeleton in
dendritic spines. It is shown here that exposure of cultured hippocampal
neurons to glutamate results in the accumulation of gelsolin in dendritic spines.
This effect is the consequence of activation of NMDA receptors and influx of
Ca2+. It is also shown that the F-actin binding domain of gelsolin is necessary
for its enrichment at postsynaptic sites. Further experiments showed that actin
filaments are more vulnerable to disruption by glutamate stimulation in gelsolin
over-expressing neurons. The disruption of actin filaments in these neurons is
also dependent on NMDA receptor activation and Ca2+ influx. LTD-related
electric field stimulation likewise increased the loss of filamentous actin in
gelsolin expressing cells compared with untransfected cells. The disruption of
actin filaments required the severing function of gelsolin, which is associated
with the specific filament-severing domain (domain 1) of the gelsolin molecule. Severing of F-actin by active gelsolin reduces the amount of AMPA receptors
(GluR1) associated with dendritic spines.
These results indicate that gelsolin plays an important role in linking synaptic
activity to the postsynaptic actin cytoskeleton. Our results are also consistent
with evidence that activation of NMDA receptors and influx of calcium ions play
a crucial role in regulating the actin cytoskeleton in dendritic spines and hence
are involved in the regulation of postsynaptic glutamate receptor plasticity at
excitatory synapses via a feedback mechanism. This could occur in both the
developing and mature brain under both normal and pathologic conditions.
Taken together, our data support a model in which activity-dependent targeting
of proteins into dendritic spines is a major mechanism for regulating synaptic
plasticity at excitatory synapses
Comprehensive characterization and identification of chemical constituents of Pingwei Powder by ultra high performance liquid chromatography tandem quadrupole-time-of-flight tandem mass spectrometry
No full textPingwei Powder, a basic traditional Chinese medicine (TCM) prescription, was used for treating the chronic colitis, liver cirrhosis, and acute gastritis, etc. However, its systematic chemical characteristics has not been reported, which hinders the interpretation of its therapeutic mechanism, and quality control.To develop a powerful ultra high performance liquid chromatography tandem quadrupole-time-of-flight tandem mass spectrometry (UHPLC-Q-TOF-MS)-based method for the systematic chemical characterisation of Pingwei Powder, providing a basis for further research on pharmacological substance basis, and quality control of Pingwei Powder. UHPLC-Q-TOF-MS was used to detect a wide range of chemical substances in Pingwei Powder, and the obtained spectral data were imported into PeakView 1.2 software for data processing. Subsequently, the chemical substances in Pingwei Powder were identified by comparison with reference standards, literatures, and the built-in database of SCIEX OS 2.2 software. Finally, the chemical profile of Pingwei Powder was acquired, and 329 chemical components in Pingwei Powder were identified for the first time, mainly including flavonoids, terpenoids, organic acids, alkaloids, phenylpropanoids. Of note, 48 were from Atractylodis Rhizoma, 37 were from Magnoliae Officinalis Cortex, 72 were from Citri Reticulatae Pericarpium, 80 were from Glycyrrhizae Radix et Rhizoma, 32 were from Ginger, 60 were from Ziziphus jujuba. A scientifically efficient and credible method for obtaining the comprehensive chemical profile of Pingwei Powder based on UHPLC-Q-TOF-MS was developed for the first time, providing a basis for further research on pharmacological substance basis, and quality control of Pingwei Powder
Novel analogs of PSNCBAM-1 as allosteric modulators of cannabinoid CB1 receptor
No full textIn this work, we explored the molecular framework of the known CB1R allosteric modulator PSNCBAM-1 with the aim to generate new bioactive analogs and to deepen the structure-activity relationships of this type of compounds. In particular, the introduction of a NH group between the pyridine ring and the phenyl nucleus generated the amino-phenyl-urea derivative SN15b that behaved as a positive allosteric modulator (PAM), increasing the CB1R binding affinity of the orthosteric ligand CP55,940. The functional activity was evaluated using serum response element (SRE) assay, which assesses the CB1R-dependent activation of the MAPK/ERK signaling pathway. SN15b and the biphenyl-urea analog SC4a significantly inhibited the response produced by CP55,940 in the low ÂμM range, thus behaving as negative allosteric modulators (NAMs). The new derivatives presented here provide further insights about the modulation of CB1R binding and functional activity by allosteric ligands
Pingwei San Ameliorates Spleen Deficiency-Induced Diarrhea through Intestinal Barrier Protection and Gut Microbiota Modulation
No full textPingwei San (PWS) has been used for more than a thousand years as a traditional Chinese medicine prescription for treating spleen-deficiency diarrhea (SDD). Nevertheless, the exact mechanism by which it exerts its antidiarrheal effects remains unclear. The objective of this investigation was to explore the antidiarrheal efficacy of PWS and its mechanism of action in SDD induced by Rhubarb. To this end, UHPLC-MS/MS was used to identify the chemical composition of PWS, while the body weight, fecal moisture content, and colon pathological alterations were used to evaluate the effects of PWS on the Rhubarb-induced rat model of SDD. Additionally, quantitative polymerase chain reaction (qPCR) and immunohistochemistry were employed to assess the expression of inflammatory factors, aquaporins (AQPs), and tight junction markers in the colon tissues. Furthermore, 16S rRNA was utilized to determine the impact of PWS on the intestinal flora of SDD rats. The findings revealed that PWS increased body weight, reduced fecal water content, and decreased inflammatory cell infiltration in the colon. It also promoted the expression of AQPs and tight junction markers and prevented the loss of colonic cup cells in SDD rats. In addition, PWS significantly increased the abundance of Prevotellaceae, Eubacterium_ruminantium_group, and Tuzzerella, while decreasing the abundance of Ruminococcus and Frisingicoccus in the feces of SDD rats. The LEfSe analysis revealed that Prevotella, Eubacterium_ruminantium_group, and Pantoea were relatively enriched in the PWS group. Overall, the findings of this study indicate that PWS exerted a therapeutic effect on Rhubarb-induced SDD in rats by both protecting the intestinal barrier and modulating the imbalanced intestinal microbiota
Structural and Functional Studies of the Receptor-binding and Glycosaminogly-canbinding Mechanisms of a Viral Chemokine Analog vMIP-II and Rational Design of Chemokine-based Highly Potent HIV-1 Entry Inhibitors
No full textChemokines are small immune system proteins mediating leukocyte migration and activation, and are important in many aspects of health and diseases. Some chemokines also have the ability to block HIV-1 infection by binding to the HIV-1 co-receptors CCR5 (CC chemokine receptor 5) and CXCR4 (CXC chemokine receptor 4). The first part of this work is to determine the mechanism of action of a human herpesvirus-8 encoded viral chemokine analog vMIP-II (viral macrophage inflammatory protein-II) by characterizing its interactions with endothelial surface glycosaminoglycans (GAGs) and cell surface receptors. Nuclear magnetic resonance (NMR), mutagenesis and molecular-docking were conducted and results show that vMIP-II tightly binds glycosaminoglycans using residues distributed along one face of the protein, such as R18, R46 and R48, and that there is a shift in the GAG binding site between the monomer and dimer form of vMIP-II where the N-terminus is involved in GAG binding for the dimer. This study, for the first time, provides a model that explains the mechanism of how quaternary structure affects chemokine-GAG binding. Mutagenesis and competition binding assays were conducted to study the receptor-binding mechanism of vMIP-II. Preliminary results suggest that vMIP-II uses the same positively charged binding surface comprising R18, K45, R46 and R48 to interact with the negatively charged N-termini of CCR5 and CXCR4. NMR studies on how vMIP-II interacts with N-terminal peptides of CCR5 and CXCR4 is on-going.
The second part of this work was to rationally design HIV-1 entry inhibitors based on our knowledge of the mechanisms of chemokine-receptor binding and HIV-1 cell entry. We successfully designed two chimeric HIV entry inhibitors composed of CCR5-targeting RANTES variants (5P12-RANTES and 5P14-RANTES) linked to a gp41 targeting C-peptide, C37. In in vitro assays, chimeric inhibitors 5P12-linker-C37 and 5P14-linker-C37 showed the highest anti-viral potency yet published with IC50 values as low as 0.001 nM against certain virus strains. On human peripheral blood mononuclear cells, the chimeric inhibitors also exhibited very strong inhibition against R5-tropic and X4-tropic viruses, with IC50 values as low as 0.015 nM and 0.44 nM, respectively. A clear delivery mechanism was observed and characterized. These fully recombinant inhibitors can be easily produced at low cost and are excellent candidates for HIV microbicides
Characteristics of Speciation of Heavy Metals in Municipal Sewage Sludge of Guangzhou as Fertilizer
No full textAbstractApplication of municipal sewage sludge to agricultural land especially in shallow soils, demands to validate the maximum amount of heavy metal, monitoring its effects on soil and on plants. The use of sewage sludge as a fertilizer and soil amendment has resulted in high concentrations of heavy metals in the soil and food limiting its use. Controlling the pollution of heavy metals is the key factor to realize the safe utilization of sewage sludge. In the present study, the heavy metal stabilizers were added to sludge contained in used plastic containers, through artificially watering or naturally rain falling, the nutrient components flowed out with leaching water and fertilized plants but the heavy metals retained in the sludge within container. The potential toxic risks from heavy metals of sludge depend on their chemical speciation. The contents of heavy metals in different treatments were analyzed and their speciation was determined. The pot experiments with plants (Zea mays and Laetuca satiuali) showed that the positive effects of the mixture of the sludge and K2SO4 on plant production and reduction of heavy metal contents in plants were significant. The BCR sequential extraction procedure was applied for measurement of heavy metals in the experimental sludge. The results showed that the concentrations of Zn were predominant in acid exchangeable and reducible fractions, and Cu was principally distributed in oxidizable fractions. Metals-bound sludge could be collected easily after treatment to prevent the secondary pollution, provided the heavy metals were fixed within the container and reduced obviously the leaching of heavy metals to soil
Elevated Levels of Cerebrospinal Fluid and Plasma Interleukin-37 in Patients with Guillain-Barré Syndrome
No full textAims. Interleukin-37 (IL-37) is an anti-inflammatory cytokine. This study aims to investigate the concentrations of plasma and cerebrospinal fluid (CSF) IL-37 in patients with Guillain-Barré Syndrome (GBS). Methods. The levels of plasma and CSF IL-37, IL-17A, IFN-γ, and TNF-α in 25 GBS patients and 20 healthy controls (HC) were determined by enzyme-linked immunoabsorbent assay and flow cytometric bead array assay, respectively. The values of clinical parameters in the patients were also measured. Results. The concentrations of plasma IL-37, IL-17A, IFN-γ, and TNF-α and CSF IL-37 and IL-17A in patients at the acute phase of GBS were significantly higher than those in the HC. The levels of plasma IL-37, IL-17A, IFN-γ, and TNF-α were positively correlated in those patients, and the levels of CSF IL-37 and IL-17A as well as the levels of plasma TNF-α were correlated positively with the GBS disability scale scores (GDSs) in those patients. Treatment with intravenous immunoglobulin significantly reduced the levels of plasma IL-37, IL-17A, IFN-γ, and TNF-α in the drug-responding patients. Conclusions. Our findings indicate higher levels of plasma and CSF IL-37 and IL-17A and other proinflammatory cytokines in patients with GBS
Effects of entecavir on peripheral blood lymphocyte profiles in chronic hepatitis B patients with suboptimal responses to adefovir
No full textNarrow bandwidth metamaterial sensor based on periodic grating structure for temperature sensing
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