Biomedical subjects

Jun Peng

Publications and source records attributed to Jun Peng.

At least 19 recordsLinked to original sources

PubMed2006

A missense mutation (G604S) in the S5/pore region of HERG causes long QT syndrome in a Chinese family with a high incidence of sudden unexpected death.

Long QT syndrome (LQTS) is characterized by abnormalities in cardiac repolarization that lead to prolongation of the electrocardiographic (ECG) QT interval. Mutations in the human ether-a-go-go-related gene (HERG, KCNH2) cause the chromosome 7-linked LQT2 form of congenital LQTS, which is characterized by a prolonged QT interval and a bifid T-wave with an increased susceptibility to life-threatening cardiac arrhythmias, especially in children. We describe the genotypic and phenotypic pedigree of a large Chinese family (n = 36) in which 11 members were diagnosed with LQTS on the basis of typical ECG patterns for LQT2. Symptomatic syncopal episodes appeared in seven members of this family at a young age; an additional four members had died suddenly at ages of 18, 19, 24 and 70 years, respectively. Screening for SCN5A and HERG candidate genes identified a heterozygous missense mutation 1810G-->A in exon 7 of HERG that leads to the substitution of the amino acid glycine by serine (G604S); this mutation was located in the S5/pore region of the HERG protein and was associated with a malignant phenotype. Ten of the family members carrying the mutation showed a prolongation of the corrected QT interval (QTc), and seven of these had experienced multiple syncopal episodes. The retrospective examination of documented ECG records revealed that one family member who had died suddenly also had a prolonged QT interval. This study is the first to demonstrate a close correlation between clinical phenotype and genotype with a 100% penetrance based on the pedigree of a Chinese family with LQT2.

Adolescent↗

PubMed2006

Nigrostriatal dopaminergic neurodegeneration in the weaver mouse is mediated via neuroinflammation and alleviated by minocycline administration.

The murine mutant weaver (gene symbol, wv) mouse, which carries a mutation in the gene encoding the G-protein inwardly rectifying potassium channel Girk2, exhibits a diverse range of defects as a result of postnatal cell death in several different brain neuron subtypes. Loss of dopaminergic nigrostriatal neurons in the weaver, unlike cerebellar granule neuronal loss, is via a noncaspase-mediated mechanism. Here, we present data demonstrating that degeneration of midbrain dopaminergic neurons in weaver is mediated via neuroinflammation. Furthermore, in vivo administration of the anti-inflammatory agent minocycline attenuates nigrostriatal dopaminergic neurodegeneration. This has novel implications for the use of the weaver mouse as a model for Parkinson's disease, which has been associated with increased neuroinflammation.

Analysis of Variance↗

PubMed2006

Keggin POM microtubes: a coincident product of crystal growth and species transformation.

Microtubes of alpha-K4SiW12O40 with the length around 1 cm and inner diameter and wall thickness in the ranges of 7-55 mum and 3-15 mum, respectively, were copiously fabricated by a one-step, template-free aqueous synthesis. The formation mechanism is discussed. The discovered tubular structure of the polyoxometalate is believed to be promising for use in templates, as a precursor of tungsten oxide ceramic microtubes, and for other uses associated with tubular structures.

Journal Article↗

PubMed2006

Hypothyroidism leads to increased collagen-based stiffness and re-expression of large cardiac titin isoforms with high compliance.

Because long-term hypothyroidism results in diastolic dysfunction, we investigated myocardial passive stiffness in hypothyroidism and focused on the possible role of titin, an important determinant of diastolic stiffness. A rat model of hypothyroidism was used, obtained by administering propylthiouracil (PTU) for times that varied from 1 month (short-term) to 4 months (long-term). Titin expression was determined by transcript analysis, gel electrophoresis and immunoelectron microscopy. Diastolic function was measured at the isolated heart, skinned muscle, and cardiac myocyte levels. We found that hypothyroidism resulted in expression of a large titin isoform, the abundance of which gradually increased with time to become the most dominant isoform in long-term hypothyroid rats. This isoform co-migrates on high-resolution gels with fetal cardiac titin. Transcript analysis on myocardium of long-term PTU rats, provided evidence for expression of additional PEVK and Ig domain exons, similar to what has been described in fetal myocardium. Consistent with the expression of a large titin isoform, titin-based restoring and passive forces were significantly reduced in single cardiac myocytes and muscle strips of long-term hypothyroid rats. Overall muscle stiffness and LV diastolic wall stiffness were increased, however, due to increased collagen-based stiffness. We conclude that long term hypothyroidism triggers expression of a large cardiac titin isoform and that the ensuing reduction in titin-based passive stiffness functions as a compensatory mechanism to reduce LV wall stiffness.

Animals↗

PubMed2006

tBid elicits a conformational alteration in membrane-bound Bcl-2 such that it inhibits Bax pore formation.

During initiation of apoptosis, Bcl-2 family proteins regulate the permeability of mitochondrial outer membrane. BH3-only protein, tBid, activates pro-apoptotic Bax to release cytochrome c from mitochondria. tBid also activates anti-apoptotic Bcl-2 in the mitochondrial outer membrane, changing it from a single-spanning to a multispanning conformation that binds the active Bax and inhibits cytochrome c release. However, it is not known whether other mitochondrial proteins are required to elicit the tBid-induced Bcl-2 conformational alteration. To define the minimal components that are required for the functionally important Bcl-2 conformational alteration, we reconstituted the reaction using purified proteins and liposomes. We found that purified tBid was sufficient to induce a conformational alteration in the liposome-tethered, but not cytosolic Bcl-2, resulting in a multispanning form that is similar to the one found in the mitochondrial outer membrane of drug-treated cells. Mutations that abolished tBid/Bcl-2 interaction also abolished the conformational alteration, demonstrating that a direct tBid/Bcl-2 interaction at the membrane is both required and sufficient to elicit the conformational alteration. Furthermore, active Bax also elicited the Bcl-2 conformational alteration. Bcl-2 mutants that displayed increased or decreased activity in the conformational alteration assay showed corresponding activities in inhibiting pore formation by Bax in vitro and in preventing apoptosis in vivo. Thus, there is a strong correlation between the direct interaction of membrane-bound Bcl-2 and tBid with activation of Bcl-2 in vitro and in vivo.

Animals↗

PubMed2006

Effect of diastolic pressure on MLC2v phosphorylation in the rat left ventricle.

The effect of passive muscle stretch on the extent of MLC2v phosphorylation was investigated. We used an isolated rat heart preparation and controlled the passive pressure of the left ventricle (LV) at 0 or 15 mmHg. The hearts were flash frozen and the LV free wall was split into epicardial and the endocardial halves. The samples were solubilized using a novel method that minimizes changes in the phosphate content of MLC2v under non-denaturing conditions. The proteins were separated by urea glycerol PAGE and identified by mass spectrometry and Western blots. At 0 mmHg passive pressure, the extent of MLC2v phosphorylation of the epicardium (34.1+/-1.7%) was the same as that of the endocardium (35.3+/-3.4%). At 15 mmHg passive pressure, we found a significant increase in MLC2v phosphorylation in the epicardium (to 41.5+/-2.0%) and a significant reduction in the endocardium (to 24.2+/-1.2%), giving rise to a gradient in the extent of MLC2v phosphorylation from epicardium (high) to endocardium (low). These changes in MLC2v phosphorylation that take place in response to increased diastolic pressure are likely to impact on the calcium sensitivity of actomyosin interaction (with an increased sensitivity towards the epicardium) and may play a role in the Frank-Starling mechanism of the heart.

Animals↗

PubMed2006

Increased murine neonatal iron intake results in Parkinson-like neurodegeneration with age.

Iron elevation is well-documented in the Parkinsonian midbrain but its cause and contribution to subsequent neurodegeneration remain unknown. Mice administered iron at doses equivalent to those found in iron-fortified human infant formula during a developmental period equivalent to the first human year of life display progressive midbrain neurodegeneration and enhanced vulnerability to toxic injury. This may have major implications for the impact of neonatal iron intake as a potential risk factor for later development of Parkinson's disease (PD).

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed2006

Quantum-dot-labeled DNA probes for fluorescence in situ hybridization (FISH) in the microorganism Escherichia coli.

Semiconductor quantum dots (QDs) as a kind of nonisotopic biological labeling material have many unique fluorescent properties relative to conventional organic dyes and fluorescent proteins, such as composition- and size-dependent absorption and emission, a broad absorption spectrum, photostability, and single-dot sensitivity. These properties make them a promising stable and sensitive label, which can be used for long-term fluorescent tracking and subcellular location of genes and proteins. Here, a simple approach for the construction of QD-labeled DNA probes was developed by attaching thiol-ssDNA to QDs via a metal-thiol bond. The as-prepared QD-labeled DNA probes had high dispersivity, bioactivity, and specificity for hybridization. Based on such a kind of probe with a sequence complementary to multiple clone sites in plasmid pUC18, fluorescence in situ hybridization of the tiny bacterium Escherichia coli has been realized for the first time.

DNA Probes↗

PubMed2006

Auto-activation of the apoptosis protein Bax increases mitochondrial membrane permeability and is inhibited by Bcl-2.

Interactions among Bcl-2 family proteins mediated by Bcl-2 homology (BH) regions transform apoptosis signals into actions. The interactions between BH3 region-only proteins and multi-BH region proteins such as Bax and Bcl-2 have been proposed to be the dominant interactions required for initiating apoptosis. Experimental evidence also suggests that both homo- and hetero-interactions are mediated primarily by the BH3 regions in all Bcl-2 family proteins and contribute to commitment to or inhibition of apoptosis. We found that a peptide containing the BH3 helix of Bax was not sufficient to activate recombinant Bax to permeabilize mitochondria. However, an extended peptide containing the BH3 helix and additional downstream sequences activated Bax to permeabilize mitochondria and liposomes. Bcl-2 inhibited the membrane-permeabilizing activity of peptide-activated Bax. This activity of Bcl-2 was inhibited by the extended but not the BH3-only peptide despite both peptides binding to Bcl-2 with similar affinity. Further, membrane-bound Bax activation intermediates directly activated soluble Bax further permeabilizing the membrane. Bcl-2 inhibited Bax auto-activation. We therefore propose that Bax auto-activation amplifies the initial death signal produced by BH3-only proteins and that Bcl-2 functions as an inhibitor of Bax auto-activation.

Animals↗

PubMed2006

Cell-mediated lysis of autologous platelets in chronic idiopathic thrombocytopenic purpura.

OBJECTIVES: Investigate the contribution and mechanism of cell-mediated cytotoxicity to the pathogenesis of idiopathic thrombocytopenic purpura (ITP). METHODS: We observed the cytotoxic effect of cytotoxic T-lymphocyte (CTL) (CD8+) and natural killer cells (CD3- CD16+ CD56+) toward chronic ITP patient's autologous platelets, and investigated the expression of Fas ligand (FasL), tumor necrosis factor (TNF)-alpha and TNF-related apoptosis inducing ligand, as well as perforin and granzyme B mRNA in CD8+ cells using flow cytometry and reverse transcriptase-polymerase chain reaction. RESULTS: We found that platelet lysis was seen only using purified CD8+ T cells as effector cells; expression of FasL and TNF-alpha in CD8+ T cells in ITP group was elevated. Moreover, the mRNA levels of granzyme B and perforin in CD8+ cells of ITP patients were increased. CONCLUSIONS: Our findings suggest that CTLs are activated in chronic ITP and might be involved in the pathogenesis of this disorder. Apoptosis and perforin/granzyme-mediated cytotoxicity constitute an important pathway through which CTLs destruct autologous platelets. CTLs might be a reasonable target for a therapeutic strategy.

Adolescent↗

PubMed2006

Antiproliferation effects of oridonin on HPB-ALL cells and its mechanisms of action.

Oridonin, an ent-kaurane diterpenoid derived from the herbal Rabdosia rubescens, has been recently reported to have antitumor effects on a large variety of cancer cells. The present study was undertaken to investigate the in vitro antiproliferation and apoptosis inducing effects of oridonin on HPB-ALL cell lines and its mechanisms of action. HPB-ALL cells in culture medium in vitro were treated with different concentrations of oridonin (16-56 micromol/L). MTT assay was used to detect the cell growth inhibitory rate, and the cell viability was assessed by the trypan blue dye-exclusion method. Cell apoptosis and the mitochondrial membrane potential (delta psi m) were investigated by flow cytometry (FCM), Hoechst 33258 staining, and DNA fragmentation analysis. The expression of caspase-3 and different apoptosis modulators, including Fas and Bcl-2 family members, was analyzed by Western blotting. The results revealed that oridonin could significantly inhibit the growth of HPB-ALL cells and cause apoptosis, and the suppression was both time- and dose-dependent. After treatment with oridonin for 48 hr, the percentage of disruption of delta psi m gradually increased in a dose-dependent manner along with marked changes of cell apoptosis, and necrotic cells increased remarkably after the cells were treated with oridonin for 72 hr; Western blotting showed cleavage of the caspase-3 zymogen protein (32 kDa) with the appearance of its 20-kDa subunit when apoptosis occurred; expression of Bcl-2 and Bcl-XL was downregulated remarkably while expression of Bax and Bid was upregulated concurrently after the cells were treated with oridonin for 24 hr. Of note, the expressions of Fas and other Bcl-2 family members including Bak and Bad remained constant before and after apoptosis occurred. We therefore conclude that oridonin has significant antiproliferation effects on HPB-ALL cells by induction of apoptosis as well as directly causing cell necrosis and that oridonin-induced apoptosis on HPB-ALL cells is mainly related to the disruption of delta psi m and activation of caspase-3 as well as downregulation of anti-apoptotic protein Bcl-2, Bcl-XL, and upregulation of pro-apoptotic proteins Bax and Bid. The results indicate that oridonin may serve as a potential antileukemia reagent.

Antineoplastic Agents↗

PubMed2006

Ponicidin, an ent-kaurane diterpenoid derived from a constituent of the herbal supplement PC-SPES, Rabdosia rubescens, induces apoptosis by activation of caspase-3 and mitochondrial events in lung cancer cells in vitro.

Ponicidin, an ent-kaurane diterpenoid derived from a constituent of the herbal supplement PC-SPES, Rabdosia rubescens, is recently reported to have anti-tumor effects on a large variety of cancers. In this study, we demonstrate that ponicidin exhibits cytotoxicity, induces apoptosis, disrupts the mitochondrial membrane potential, and triggers the activation of caspase-3, -8 and -9 in lung cancer A549 and GLC-82 cells. Ponicidin treatment of lung cancer cells caused downregulation of anti-apoptotic protein Bcl-2 and survivin as well as upregulaton of pro-apoptotic protein Bax in a time dependent manner when apoptosis ocurred. Ponicidin induced activation of caspase-3 can be blocked by a caspase-3-specific inhibitor z-DEVD-FMK Furthermore, the caspase-8-specific inhibitor z-IETD-FMK could block the ponicidin-induced activation of caspase-3, PARP cleavage, and prevented the release of cytochrome c from mitochondria into the cytoplasm. This indicate that activated caspase-8 initiates the release of cytochrome c during ponicidin-induced apoptosis. We therefore conclude that ponicidin has significant apoptosis-inducing effects by activation of caspase-3 -8, and -9 as well as downregulation of anti-apoptotic protein Bcl-2, survivin and upregulation of pro-apoptotic protein Bax, with caspase-8 acting as an upstream activator. The data offer a potential mechanism for ponicidin-induced apoptosis in lung cancer cells, suggesting that ponicidin may severve as an effective reagent for the treatment of lung cancer, and that in vivo anti-cancer effects as well as its potential clinical effectiveness need further investigation.

Animals↗

PubMed2006

Identification of human platelet glycoprotein VI-specific IgG autoantibody and its fragments.

Glycoprotein VI (GPVI), as a major receptor for collagen on the platelet surface, mediates the initial platelet contact with collagen, and causes platelet aggregation and thrombosis. Agents of anti-GPVI can inhibit the adhesion, activation and aggregation function of platelets, which can be used for preventing thrombotic diseases. To make humanized monoclonal antibodies by phage surface display technology, we studied plasmas from 44 patients with chronic idiopathic thrombocytopenic purpura using modified monoclonal antibody immobilization of platelet antigen assays. GPVI-specific antibodies were found in six (13.6%) patients. Among these, only one showed significant inhibition of platelet aggregation induced by collagen. The IgG antibody and F(ab')2 fragments of this patient's plasma were further purified and their immunoreactivities and effects on platelet aggregation were reanalyzed. It was found that purified IgG and its F(ab')2 fragments from the patient not only retained the ability to bind to platelet GPVI, but also inhibited collagen-induced platelet aggregation. In this study, therefore, the specific anti-platelet GPVI autoantibody that inhibits collagen-induced platelet aggregation has been successfully screened out, which can be used to develop completely humanized anti-GPVI phage antibody.

Abciximab↗

PubMed2006

Characterization of the N-terminal domain of classical swine fever virus RNA-dependent RNA polymerase.

To investigate RNA-dependent RNA polymerase (RdRp) further, mutational analysis of the N-terminal domain of the NS5B protein of Classical swine fever virus was performed. Results show that the N-terminal domain (positions 1-300) of the protein might be divided artificially into four different regions, N1-N4. The N1 region (positions 1-61) contained neither conserved lysine nor conserved arginine residues. NS5B protein with deletion of the N1 region has the capacity for elongative RNA synthesis, but not for de novo RNA synthesis on natural templates. All substitutions of the conserved lysines and arginines in the N2 region (positions 63-216) destroyed RdRp activity completely. Substitutions of the conserved arginines in the N3 region (positions 217-280) seriously reduced RdRp activity. However, all substitutions of the conserved lysines in this region enhanced RNA synthesis and made the mutants synthesize RNA on any template. Substitutions of the conserved arginines in the N4 region (positions 281-300) reduced elongative synthesis and destroyed de novo RNA synthesis. In contrast, substitutions of lysines in this region did not affect RdRp activity significantly. These data indicate that the N3 region might be related to the enzymic specificity for templates, and the conserved lysines and arginines in different regions have different effects on RdRp activity. In combination with the published crystal structure of bovine viral diarrhea virus NS5B, these results define the important role of the N-terminal domain of NS5B for template recognition and de novo RNA synthesis.

Amino Acid Sequence↗

PubMed2006

Effects of IgG and its F(ab')2 fragments of some patients with idiopathic thrombocytopenic purpura on platelet aggregation.

OBJECTIVES: To make humanized monoclonal antibodies by phage surface display technology, we screened out the specific anti-platelet glycoproteins (GPs) IgG antibody from patients with chronic idiopathic thrombocytopenic purpura (ITP), which can inhibit platelet aggregation. METHODS: We studied plasmas from 68 patients with ITP for the presence of IgG antibodies specific for GPIIb/IIIa and/or GPIb/IX using modified monoclonal antibody immobilization of platelet antigen assays. The IgG antibody and its F(ab')(2) fragments of the positive plasmas which could inhibit platelet aggregation function were prepared and purified. Their immunoreactivity to platelet GPs and effects on platelet function were further analyzed. RESULTS: GPIIb/IIIa- and GPIb/IX-specific antibodies were found in 21 and 19 patients, respectively. Six of them had antibodies against both GP complexes. Among the 34 positive plasmas, four with positive anti-GPIIb/IIIa autoantibody showed significant inhibition of platelet aggregation induced by adenosine diphosphate (ADP), whereas one with GPIb/IX-specific antibody inhibited ristocetin-induced platelet aggregation. The purified IgG and its F(ab')(2) fragments from two patients not only retained the ability to bind to platelet GPs but also impaired the in vitro ADP-induced platelet aggregation. CONCLUSIONS: F(ab')(2) portion of the IgG is a functional fragment, which is responsible for the autoantibody interaction with platelet GPs in ITP, and some of them also affect platelet function, which can be used to develop completely humanized anti-GPIIb/IIIa small molecular phage antibody.

Adolescent↗

PubMed2006

[The immunoreactivity of IgG and its fragments from ITP patients and their effects on platelet aggregation function].

OBJECTIVE: To prepare ITP plasma IgG and its F(ab')2 fragments and investigate their immunoreactivity to platelet GPIIb/IIIa and/or GPIb/IX and their effects on platelet aggregation function. METHODS: The ITP patients having inhibitory autoantibody to the platelet aggregation were selected by modified MAIPA and platelet aggregation test with turbidimetry. Plasma IgG and its F(ab')2 fragments were prepared by streptococcal protein A affinity column and pepsin digestion. The immunoreactivity and the effects on platelet aggregation function of the whole antibody and its fragments were detected by modified MAIPA and platelet aggregation test, respectively. RESULTS: (1) Anti-platelet GPIIb/IIIa and/or GPIb/IX autoantibodies were detected in 34 of 68 (53.6%) ITP patients' plasmas and that from 5 patients significantly inhibited the platelet aggregation induced by ADP or ristocetin. (2) By using protein A column combined with protease digestion, pure IgG and its F(ab')2 fragments were successfully obtained. (3) The purified IgG and its F(ab')2 fragments retained the ability to bind to their respective glycoproteins and inhibited the platelet aggregation function, whereas the IgG depleted plasma lost the ability of binding to the platelet GPs. CONCLUSIONS: F(ab')2 fragment of the IgG antibody is a functional fragment, which not only has the binding ability to the platelet GPs but also inhibits the platelet aggregation function in a dose-dependent manner.

Adolescent↗

PubMed2006

[Diallyl trisulfide induces apoptosis of human gastric cancer cell line MGC803 through caspase-3 pathway].

BACKGROUND & OBJECTIVE: Garlic and the organosulfer compound from garlic have antitumor effects, but the mechanisms still remain unclear. This study was to investigate the changes and significance of caspase-3 activity in diallyl trisulfide (DATS)-induced apoptosis of human gastric cancer cell line MGC803. METHODS: Effects of DATS on the apoptosis of MGC803 cells and the change of activated caspase-3 were observed under a fluorescent and an electron microscopy, and detected by flow cytometry and Western blot. RESULTS: After incubation with DATS, MGC803 cells showed typical apoptotic morphologic changes, and the apoptosis rate increased significantly. DATS activated caspase-3 in a time-dependent manner: the positive rates of activated caspase-3 were 1.9%, 3.0%, 7.3%, 14.4%, and 27.6% respectively in MGC-803 cells treated with 12 mg/L DATS for 0, 4, 8, 12 and 24 h. When treated with 12 mg/L DATS for 24 h, the apoptosis rate was significantly lower in the cells with pretreatment of Ac-DEVD-CHO (a caspase-3 inhibitor) than in the cells without pretreatment (5.1% vs. 23.0%, P<0.01), indicating that Ac-DEVD-CHO efficiently attenuated DATS-induced apoptosis of MGC803 cells. Moreover, pro-caspase-3 was hydrolyzed and activated in DATS-treated MGC803 cells. CONCLUSION: DATS induces apoptosis in MGC803 cells which may be through the activation of caspase-3 pathway.

Adenocarcinoma, Mucinous↗

PubMed2006

[Role of costimulatory signals in idiopathic thrombocytopenia purpura: review].

Idiopathic thrombocytopenia purpura (ITP) is an autoimmune disease which is characterized by destruction of platelets by macrophages in the reticuloendothelial system. Recent studies suggest that ITP is related to the abnormal activation and apoptosis of T/B cells which lead to failure of immune tolerance. Now it is becoming clear that costimulatory signals are required for full T/B cell activation and assumed to modulate T/B cells responses as well as other aspects of the immune system. This review focuses on the role and state-of-the-art advancements of costimulatory signals in ITP.

Antigens, CD↗