Biomedical subjects

Hong Xue

Publications and source records attributed to Hong Xue.

At least 37 records · Page 2Linked to original sources

PubMed2005

Novel dimeric acetylcholinesterase inhibitor bis7-tacrine, but not donepezil, prevents glutamate-induced neuronal apoptosis by blocking N-methyl-D-aspartate receptors.

The neuroprotective properties of bis(7)-tacrine, a novel dimeric acetylcholinesterase (AChE) inhibitor, on glutamate-induced excitotoxicity were investigated in primary cultured cerebellar granule neurons (CGNs). Exposure of CGNs to 75 mum glutamate resulted in neuronal apoptosis as demonstrated by Hoechst staining, TUNEL, and DNA fragmentation assays. The bis(7)-tacrine treatment (0.01-1 mum) on CGNs markedly reduced glutamate-induced apoptosis in dose- and time-dependent manners. However, donepezil and other AChE inhibitors, even at concentrations of inhibiting AChE to the similar extents as 1 mum bis(7)-tacrine, failed to prevent glutamate-induced excitotoxicity in CGNs; moreover, both atropine and dihydro-beta-erythroidine, the cholinoreceptor antagonists, did not affect the anti-apoptotic properties of bis(7)-tacrine, suggesting that the neuroprotection of bis(7)-tacrine appears to be independent of inhibiting AChE and cholinergic transmission. In addition, ERK1/2 and p38 pathways, downstream signals of N-methyl-d-aspartate (NMDA) receptors, were rapidly activated after the exposure of glutamate to CGNs. Bis(7)-tacrine inhibited the apoptosis and the activation of these two signals with the same efficacy as the coapplication of PD98059 and SB203580. Furthermore, using fluorescence Ca(2+) imaging, patch clamp, and receptor-ligand binding techniques, bis(7)-tacrine was found effectively to buffer the intracellular Ca(2+) increase triggered by glutamate, to reduce NMDA-activated currents and to compete with [(3)H]MK-801 with an IC(50) value of 0.763 mum in rat cerebellar cortex membranes. These findings strongly suggest that bis(7)-tacrine prevents glutamate-induced neuronal apoptosis through directly blocking NMDA receptors at the MK-801-binding site, which offers a new and clinically significant modality as to how the agent exerts neuroprotective effects.

Animals↗

PubMed2005

Topology characterization of a benzodiazepine-binding beta-rich domain of the GABAA receptor alpha1 subunit.

Structural investigation of GABAA receptors has been limited by difficulties imposed by its trans-membrane-complex nature. In the present study, the topology of a membrane-proximal beta-rich (MPB) domain in the C139-L269 segment of the receptor alpha1 subunit was probed by mapping the benzodiazepine (BZ)-binding and epitopic sites, as well as fluorescence resonance energy transfer (FRET) analysis. Ala-scanning and semiconservative substitutions within this segment revealed the contribution of the phenyl rings of Y160 and Y210, the hydroxy group of S186 and the positive charge on R187 to BZ-binding. FRET with the bound BZ ligand indicated the proximity of Y160, S186, R187, and S206 to the BZ-binding site. On the other hand, epitope-mapping using the monoclonal antibodies (mAbs) against the MPB domain established a clustering of T172, R173, E174, Q196, and T197. Based on the lack of FRET between Trp substitutionally placed at R173 or V198 and bound BZ, this epitope-mapped cluster is located on a separate end of the folded protein from the BZ-binding site. Mutations of the five conserved Cys and Trp residues in the MPB domain gave rise to synergistic and rescuing effects on protein secondary structures and unfolding stability that point to a CCWCW-pentad, reminiscent to the CWC-triad "pin" of immunoglobulin (Ig)-like domains, important for the structural maintenance. These findings, together with secondary structure and fold predictions suggest an anti-parallel beta-strand topology with resemblance to Ig-like fold, having the BZ-binding and the epitopic residues being clustered at two different ends of the fold.

Amino Acids↗

PubMed2005

Therapeutic potential of wogonin: a naturally occurring flavonoid.

The search for flavonoids with novel therapeutic effects has been intense. Wogonin, as a naturally existing monoflavonoid, has been shown to have therapeutic potential in vitro and in vivo. Methods for its extraction from herbs and its chemical synthesis have been developed. Pharmacokinetic studies have shown a rapid tissue distribution and prolonged plasma elimination phase of wogonin. It has been shown experimentally that wogonin exerts anti-oxidant activity, which may, in part, underlie its antiinflammatory, anti-cancer, antiviral and neuroprotective actions. The recent discovery of its anxiolytic activity suggests a new mechanism of action, involving interaction with the benzodiazepine (BZD) binding site of the GABA(A) receptor and modulation of this receptor activity. Although the safety record of wogonin is remarkable and voluminous literature about its pharmacological effects is available, it has not been used in Western medicine in the form of a pure chemical. In this article we review its therapeutic effects, its sources and pharmacokinetic profile to highlight its therapeutic potential.

Animals↗

PubMed2005

Similar effects on rat renal mesangial cells by expressing different fragments of adrenomedullin gene in vitro.

AIM: To construct pEGFP-N3 recombinant vectors carrying adrenomedullin (AM) or fragments of the AM gene, and to express AM or fragments of AM from the pEGFP-N3 recombinant vectors (pEGFP-N3-AM1-2 and pEGFP-N3-AM1-3) and study their biological properties on cultured rat renal mesangial cells (RMC). METHODS: Total RNA of rat kidney was obtained using TriZol reagent. The cDNA was synthesized by reverse transcriptase using oligo-deoxythymidine as primer. The fragments of AM gene were then amplified by polymerase chain reaction (PCR) with specific upstream and downstream oligonucleotides. The PCR products were digested with EcoRI and BamHI and subcloned into the plasmid pEGFP-N3. Facilitated by cationic liposomes, RMC were transfected with pEGFP-N3-AM1-2 or pEGFP-N3-AM1-3. After 24 h, green fluorescent protein (GFP) fluorescent images were examined with a fluorescence microscope. After 48 h, the proliferation of RMC was detected using the MTT assay, and the mRNA expression of transforming growth factor-beta1 (TGF-beta1) was measured by semiquantitative PCR. RESULTS: DNA sequence reports verified that pEGFP-N3-AM1-2, which carried the full length AM gene translation fragment (preproadrenomedullin preproAM1-185), and pEGFP-N3-AM1-3, which carried the translation fragment of preproAM [without adrenotensin (ADT, preproAM150-185)], were constructed successfully. After 24 h, green fluorescence was observed in RMC into which either pEGFP-N3-AM1-2 or pEGFP-N3-AM1-3 was transfected, while in the control cells no fluorescence was observed. Either pEGFP-N3-AM1-2 or pEGFP-N3-AM1-3 delivery inhibited the proliferation of RMC (P<0.01) and decreased the mRNA transcription level of TGF-beta1 in RMC (P<0.05). However, no significant difference was observed between the effects of pEGFP-N3-AM1-2 and pEGFP-N3-AM1-3. CONCLUSION: pEGFP-N3-AM1-2 and pEGFP-N3-AM1-3 were constructed successfully and were functionally expressed in RMC. Expressing the fragment of AM without ADT has similar inhibitory biological effects on RMS proliferation and TGF-beta1 transcription with full length preproAM.

Adrenomedullin↗

PubMed2005

Neuroactive flavonoids interacting with GABAA receptor complex.

Classical benzodiazepines (BZs) are the most widely prescribed drugs acting on the central nervous system (CNS). They exert their therapeutic effects via binding to the BZ-site of GABAA receptors, and allosterically modulating the chloride flux through the ion channel complex. Given the multiple actions of classical BZs, the serious limitations to their usefulness have directed much research into development of novel ligands for the BZ-site with retained therapeutic effectiveness and minimal side effects. From the studies of CNS-active chemical constituents of medicinal herbs, some members of the family of flavonoids were demonstrated to have moderate binding affinities for the BZ-site. In vivo studies revealed that these compounds were mostly partial agonists of GABAA receptors, and only a few flavonoids were shown to possess antagonistic activities. At effective anxiolytic doses, the actions of partial agonistic flavonoids were often not accompanied by sedative and myorelaxant side effects. Based on structure-activity relationship (SAR) studies, incorporation of electronegative groups to the C6 and C3' on the flavone backbone was found to yield significant increases in the binding affinities for the BZ-site. It was also shown that 2'-hydroxyl was a critical moiety on flavonoids with regard to BZ-site binding. These have guided the identification of several synthetic flavonoids with high BZ-site binding affinity and in vivo activity, and further quantitative SAR studies resulted in the development of several pharmacophore models. This review attempts to summarize these findings, which has led to the establishment of flavonoids as potential therapeutics for GABAA receptor-mediated disorders.

Analysis of Variance↗

PubMed2005

[Polymorphisms in the apolipoprotein A5 gene and apolipoprotein C3 gene in patients with coronary artery disease].

OBJECTIVE: To investigate the association between the -1131T/C and 56C/G polymorphism in the APOA5 gene as well as the -482C/T in the APOC3 gene and susceptibility to coronary artery disease (CAD) in a Chinese Han population. METHODS: Using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and polyacrylamide gel electrophoresis (PAGE) methods, we analyzed the genotypes in 312 CAD patients diagnosed by angiography and 317 healthy controls. The levels of serum lipid profiles were also studied by biochemical methods. RESULTS: The frequency of the APOA5 -1131 C allele in CAD patients was significantly higher than that of the control group (39.9% vs. 33.3%, P = 0.02). Compared with the wild type TT, CC homozygotes had a significantly increased CAD risk (OR = 1.93 and OR = 1.80 using unadjusted and adjusted logistic regression models, respectively). This association still existed after adjustment for the APOC3-482 variant. The APOA5-1131C allele also showed a correlation with increasing plasma TG levels (P < 0.01). CONCLUSIONS: The APOA5-1131T/C polymorphism but not APOC3-482C/T might contribute to an increased risk of CAD among Chinese accompanied by an elevation of serum TG levels; this effect was found to be independent of the APOC3-482C/T variant.

Adult↗

PubMed2004

Energetic salts from N-aminoazoles.

New energetic salts (2, 3, 5, 6, 13, 14, 21, 22) were synthesized via the quaternization of derivatives of N-aminoazoles with nitric or perchloric acid or with iodomethane followed by metathesis reaction with silver nitrate or silver perchlorate. The structure of 2-amino-4,5-dimethyltetrazolium nitrate (21) was confirmed by single-crystal X-ray analysis. Most of the salts exhibit good thermal stabilities and low melting points. By using experimentally determined constant volume combustion energies, the standard molar enthalpies of formation were derived on the basis of designed Hess thermochemical cycles.

Journal Article↗

PubMed2004

The first 1-alkyl-3-perfluoroalkyl-4,5- dimethyl-1,2,4-triazolium salts.

Syntheses of quaternary 1-alkyl-3-perfluoroalkyl-4,5-dimethyl-1,2,4-triazolium iodides have led to a variety of new quaternary salts via metathesis reactions. 1,4,5-Trimethyl-3-trifluoro-methyl-1,2,4-triazolium iodide (6) with LiN(SO(2)CF(3))(2), KSO(3)CF(3), AgClO(4), AgBF(4); 1-(3-fluoropropyl)-3-trifluoromethyl-4,5-dimethyl-1,2,4-triazolium iodide (7) with LiN(SO(2)CF(3))(2); and 1,4,5-trimethyl-3-perfluorooctyl-1,2,4-triazolium iodide (8) with LiN(SO(2)CF(3))(2), AgClO(4), AgBF(4) gave excellent yields of new thermally stable and relatively low melting quaternary salts. The structure of 1,4,5-trimethyl-3-perfluorooctyl-1,2,4-triazolium tetrafluoroborate (11c) was confirmed by single-crystal X-ray analysis. Although the molecular weight of 11c (cation) is 3-fold greater than that of the 3-trifluoromethyl derivative 9d, its melting point is 32 degrees C lower.

Journal Article↗

PubMed2004

Low melting N-4-functionalized-1-alkyl or polyfluoroalkyl-1,2,4-triazolium salts.

Butane sulfobetaines 2a,b, zwitterionic oxo perfluorocarboxylates 3a,b, and functionalized triazolium bromides 4b,c and 5a-c have been synthesized and subsequently reacted to give a series of hydrophilic and hydrophobic fluorinated and nonfluorinated N-1-alkyl-N-4-functionalized-triazolium compounds (6a-11b). With the exception of 11b (mp 41 degrees C), all are liquids at room temperature. Metathesis of the fluorinated quaternary triazolium halides with other anions led to the formation of a new class of compounds, namely, [(R)(R(funct))-Taz](+)Y(-), Y = PF(6), (CF(3)SO(2))( 2)N, and CF(3)SO(3), in good isolated yields. All of the new compounds were characterized by (1)H, (19)F, and (13)C NMR, and MS spectral and elemental analyses. Thermal analyses indicate that high temperatures are attainable prior to decomposition. DSC studies show glass transitions for several samples, and all functionalized compounds, 5-11, have T(g)s or T(m)s <100 degrees C. Densities range between 1.4 and 1.61 g cm(-)(3). 1-Heptyl-4-(butyl-4-sulfonic acid) triazolium trifluoromethanesulfonate, 6b, in its role as a Brønsted acid, is an effective solvent/catalyst for high yield esterification and hetero-Michael addition reactions and may be recycled for repetitive use.

Journal Article↗

PubMed2003

Naturally occurring 2'-hydroxyl-substituted flavonoids as high-affinity benzodiazepine site ligands.

Screening of traditional medicines has proven invaluable to drug development and discovery. Utilizing activity-guided purification, we previously reported the isolation of a list of flavonoids from the medicinal herb Scutellaria baicalensis Georgi, one of which manifested an affinity for the benzodiazepine receptor (BDZR) comparable to that of the synthetic anxiolytic diazepam (K(i)=6.4 nM). In the present study, this high-affinity, naturally occurring flavonoid derivative, 5,7,2'-trihydroxy-6,8-dimethoxyflavone (K36), was chosen for further functional and behavioral characterization. K36 inhibited [3H]flunitrazepam binding to native BDZR with a K(i) value of 6.05 nM. In electrophysiological experiments K36 potentiated currents mediated by rat recombinant alpha(1)beta(2)gamma(2) GABA(A) receptors expressed in Xenopus oocytes. This potentiation was characterized by a threshold (1 nM) and half-maximal stimulation (24 nM) similar to diazepam. This enhancement was demonstrated to act via the BDZR, since co-application of 1 microM of the BDZR antagonist Ro15-1788 reversed the potentiation. Oral administration of K36 produced significant BDZR-mediated anxiolysis in the mice elevated plus-maze, which was abolished upon co-administration of Ro15-1788. Sedation, myorelaxation and motor incoordination were not observed in the chosen dosage regimen. Structure-activity relationships utilizing synthetic flavonoids with different 2' substituents on the flavone backbone supported that 2'-hydroxyl-substitution is a critical moiety on flavonoids with regard to BDZR affinities. These results further underlined the potential of flavonoids as therapeutics for the treatment of BDZR-associated syndromes.

Allosteric Regulation↗

PubMed2003

Two conformations of archaeal Ssh10b. The origin of its temperature-dependent interaction with DNA.

The DNA-binding protein Ssh10b from the hyperthermophilic archaeon Sulfolobus shibatae is a member of the Sac10b family, which has been speculated to be involved in the organization of the chromosomal DNA in Archaea. Ssh10b affects the DNA topology in a temperature dependent fashion that has not been reported for any other DNA-binding proteins. Heteronuclear NMR and site-directed mutagenesis were used to analyze the structural basis of the temperature-dependent Ssh10b-DNA interaction. The data analysis indicates that two forms of Ssh10b homodimers co-exist in solution, and the slow cis-trans isomerization of the Leu61-Pro62 peptide bond is the key factor responsible for the conformational heterogeneity of the Ssh10b homodimer. The T-form dimer, with the Leu61-Pro62 bond in the trans conformation, dominates at higher temperature, whereas population of the C-form dimer, with the bond in the cis conformation, increases on decreasing the temperature. The two forms of the Ssh10b dimer show the same DNA binding site but have different conformational features that are responsible for the temperature-dependent nature of the Ssh10b-DNA interaction.

Archaeal Proteins↗

PubMed2003

Association of APOE gene with schizophrenia in Chinese: a possible risk factor in times of malnutrition.

Five hundred and seventy nine Chinese patients with schizophrenia who met DSMIV criteria for the disorder were genotyped for alleles epsilon 2,3,4 of apolipoprotein E (APOE) gene. All were recruited from inpatients and outpatients attending a large mental health centre in Shanghai. Results were compared to APOE data on 1528 controls drawn from the same area. Major differences in APOE genotype ratios and allele frequencies were observed between the patients and controls. The patients with schizophrenia had highly significantly (p<0.0001) increased epsilon 4/-genotypes and allele frequencies, and decreased epsilon 3/3 genotypes and epsilon 3 allele frequencies compared to controls. The effect was independent of sex and/or age of onset of illness, but strongly influenced by date of birth. Significant differences were restricted to individuals with schizophrenia born either before 1949 or during the period 1958-1967. Both were times of severe food shortages and malnutrition. We suggest that APOE may operate as an additional risk factor for schizophrenia in individuals subjected to fetal and/or early postnatal malnutrition.

Adult↗

PubMed2003

5,7-Dihydroxy-6-methoxyflavone, a benzodiazepine site ligand isolated from Scutellaria baicalensis Georgi, with selective antagonistic properties.

As part of an effort to identify naturally occurring GABA(A) receptor benzodiazepine binding site (BDS) ligands from traditional medicinal herbs, we previously reported that flavonoid derivatives isolated from Scutellaria baicalensis (S. baicalensis) Georgi exhibited significant affinities for the BDS. The present study describes the characterization of 5,7-dihydroxy-6-methoxyflavone (oroxylin A), one of the major components of the herbal extract. Oroxylin A inhibited [3H]flunitrazepam binding to rat cerebral cortical membrane with a IC(50) value of 1.09+/-0.07 microM. A GABA ratio of 1.09+/-0.04 suggests that oroxylin A interacts as an antagonist at the recognition site. In neuropharmacological studies, oral administration of oroxylin A (3.75-60 mg kg(-1)) did not result in significant changes in animal models routinely employed for benzodiazepine (BD) evaluation. However, oroxylin A selectively abolished the anxiolytic, myorelaxant and motor incoordination, but not the sedative and anticonvulsant effects elicited by diazepam, a BDS agonist. These results add oroxylin A to the list of CNS active flavonoids, and as the first naturally occurring member endowed with selective antagonistic actions via the BDS.

Animals↗

PubMed2003

Transfer RNA paralogs: evidence for genetic code-amino acid biosynthesis coevolution and an archaeal root of life.

A search has been performed on 2878 tRNA sequences from 60 different genomes in order to detect the existence of closely related 'alloacceptor' tRNAs accepting dissimilar amino acids that could be paralogs generated by gene duplications. This has led to the identification of extremely conserved tRNA(Phe)-tRNA(Tyr) pairs displaying as high as 94% identity between them, and also other potentially paralogous tRNA pairs in archaeal species. These paralogous pairs are enriched for amino acid pairs belonging to the same amino acid biosynthetic family, thus providing evidence for the coevolution of genetic code and amino acid biosynthesis. Overall, the genetic distances between alloacceptor tRNAs yield estimates of how closely clustered in sequence space are the tRNAs in a genome. Among 34 Bacteria, 18 Archaea and 8 Eukarya, Methanopyrus kandleri and Aeropyrum pernix have yielded the lowest alloacceptor distances and largest number of paralogous pairs. Based on a cluster-dispersion model of tRNA evolution, such tight alloacceptor clustering is a measure of primitiveness of tRNA genotypes, and places last universal common ancestor (LUCA) between the branches leading to these two archaea in the tRNA phylogenetic tree.

Amino Acids↗

PubMed2003

Topological structure analysis of the protein-protein interaction network in budding yeast.

Interaction detection methods have led to the discovery of thousands of interactions between proteins, and discerning relevance within large-scale data sets is important to present-day biology. Here, a spectral method derived from graph theory was introduced to uncover hidden topological structures (i.e. quasi-cliques and quasi-bipartites) of complicated protein-protein interaction networks. Our analyses suggest that these hidden topological structures consist of biologically relevant functional groups. This result motivates a new method to predict the function of uncharacterized proteins based on the classification of known proteins within topological structures. Using this spectral analysis method, 48 quasi-cliques and six quasi-bipartites were isolated from a network involving 11,855 interactions among 2617 proteins in budding yeast, and 76 uncharacterized proteins were assigned functions.

Algorithms↗

PubMed2003

Anxiolytic-like action of orally administered dl-tetrahydropalmatine in elevated plus-maze.

dl-Tetrahydropalmatine (dl-THP), a naturally occurring alkaloid, has been intensively studied for its sedative and hypnotic effects. Putative explanation for its mechanism and target of action involves the dopaminergic neurotransmission system. In view of the close interactions between the dopaminergic and the GABAergic neurons in the amygdala, pharmacological effects of dl-THP were tested for activity at the GABAA receptor benzodiazepine site (BDS). Effects of dl-THP were examined in mice employing the elevated plus-maze, the holeboard and the horizontal-wire tests. In the elevated plus-maze, mice treated with low doses of dl-THP (0.5-10 mg/kg) exhibited significant increase in the percentage of entries and time spent in open arms without altering the number of closed-arm entries when compared to the control group, indicative of its selective anxiolytic effect. In the holeboard and horizontal wire tests, where exploratory behavior and potential muscle relaxant effect were assessed, respectively, only mice treated with as much as 50 mg/kg dl-THP manifested sedation and myorelaxation, as observed in the significant decrease in the number of head dips and the decrease in the percentage of mice grasping wire in comparison to control. Notably, coadministration of the BDS antagonist flumazenil abolished the dl-THP-induced anxiolysis as seen in the reversal of the increase of both the number of entries and time spent in open arms back to basal levels in the elevated plus-maze test. The results suggest that dl-THP at defined low dosages acts as anxiolytics in mice, and the BDS mediates, at least in part, such anxiolytic effect of dl-THP.

Administration, Oral↗

PubMed2003

Ssh10b, a conserved thermophilic archaeal protein, binds RNA in vivo.

Proteins of the Sac10b family, which is highly conserved among hyperthermophilic archaea, have been regarded as DNA-binding proteins. Based on their in vitro DNA-binding properties, these proteins are thought to be involved in chromosomal organization or DNA repair/recombination. We show that Ssh10b, a member of the Sac10b family from Sulfolobus shibatae, bound with similar affinities to double-stranded DNA, single-stranded DNA and RNA in vitro. However, the protein was exclusively bound to RNA in S. shibatae cells, as revealed by in vivo UV cross-linking and co-immunoprecipitation. Ribosomal RNAs were among the RNA species co-immunoprecipitated with Ssh10b. Consistent with this observation, Ssh10b was co-purified with ribosomes under low salt conditions. Furthermore, we demonstrate by UV-cross-linking hybridization that, when the cells were irradiated with UV, Ssh10b became cross-linked to 16S, 23S rRNAs and mRNAs. Our data indicate that RNA is the physiological binding target of the Sac10b family.

Archaeal Proteins↗

PubMed2003

Recombinant extracellular domain of the three major subunits of GABAA receptor show comparable secondary structure and benzodiazepine binding properties.

The three most widely expressed subunits of the GABAA receptor are alpha(1), beta(2), and gamma(2) subunits, and the major isoform in the human brain is a pentameric receptor composed of 2alpha(1)2beta(2)1gamma(2). Previously, we overexpressed the extracellular domain Q28-R248 of GABAA receptor alpha(1) subunit. In the present study, the homologous extracellular domains Q25-G243 of GABAA receptor beta(2) subunit and Q40-G273 of gamma(2) subunit were also obtained through overexpression in Escherichia coli. Successful production of recombinant beta(2) and gamma(2) subunit receptor protein domains facilitates the comparison of structural and functional properties of the three subunits. To this end, the secondary structures of the three fragments were measured using CD spectroscopy and the beta-strand contents calculated to be >30%, indicating a beta-rich structure for all three fragments. In addition, the benzodiazepine (BZ)-binding affinity of the recombinant fragments were measured using fluorescence polarization to be 2.16 microM, 3.63 microM, and 1.34 microM for the alpha(1), beta(2), and gamma(2) subunit fragments, respectively, indicating that all three homomeric assemblies, including that of the beta(2) subunit, generally not associated with BZ binding, can bind BZ in the micromolar range. The finding that the BZ binding affinity of these recombinant domains was highest for the gamma(2) subunit and lowest for the beta(2) subunit is consistent with results from previous binding studies using hetero-oligomeric receptors. The present results exemplify the effective approach to characterize and compare the three major subunits of the GABAA receptor, for two of which the overexpression in E. coli is reported for the first time.

Amino Acid Sequence↗