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Biomedical subjects

Qian Chen

Publications and source records attributed to Qian Chen.

At least 37 records · Page 2Linked to original sources
PubMed2006

Cytohesin binder and regulator augments T cell receptor-induced nuclear factor of activated T Cells.AP-1 activation through regulation of the JNK pathway.

Cytohesin binder and regulator (Cybr; also known as CYTIP, CASP, and PSCDBP) is a cytokine-induced gene preferentially expressed in hematopoietic tissues and in T helper 1 cells. Cybr protein associates with members of the cytohesin family, which are known ADP-ribosylation factors-GDP/GTP exchange factors, and its functions appear to regulate lymphocyte adhesion and cell-cell contact. Here we show that Cybr mRNA and protein levels are increased upon T cell receptor engagement. Cybr expression then influences T cell receptor-dependent signaling events, such as nuclear factor of activated T cells and AP-1 transcriptional activity. In addition, expression of Cybr results in increased T cell receptor-mediated activation of the Rho/Rac exchange factor Vav and of the JNK-p38 MAPK signaling pathway. The effects of Cybr on nuclear factor of activated T cells and AP-1 are dependent on MAPK activation, and enhanced activation of this cascade results in cooperation between the two transcription factors in the regulation of gene expression. These findings provide the first evidence that the adaptor protein Cybr not only regulates lymphocyte adhesion and cell-cell interaction but also contributes to the regulation of the signaling cascade and of the genetic program downstream of the T cell receptor.

Cell Adhesion↗
PubMed2006

Effect of M(CO)3 (M = Cr, Mn+) on aromatic C-Cl BDE in (eta6-ArCl)M(CO)3 complexes.

The coordination of Cr(CO)3 to chlorobenzenes significantly reduces the C-Cl bond dissociation energy. Treatment of chloroarene-Cr(CO)3 complexes with SmI2/HMPA at room temperature led to complete dechlorination. Reaction of o-allyloxychlorobenzene-Cr(CO)3 complexes with SmI2 at room temperature resulted in the corresponding dechlorinative cyclization products in good to excellent yields. Competition experiments indicated the following relative reactivities of dehalogenation by SmI2: PhI/PhCl-Cr(CO)3/PhBr/PhCl = 50:1:0.3:<0.001. On the other hand, the coordination of Mn(CO)3(+) to chlorobenzene showed a much smaller activation effect. Density functional theory calculations revealed that the spin delocalization effect of the metal center plays an important role in the C-Cl bond activation.

Journal Article↗
PubMed2006

Recombinant AAV-mediated HSVtk gene transfer with direct intratumoral injections and Tet-On regulation for implanted human breast cancer.

BACKGROUND: HSVtk/ganciclovir (GCV) gene therapy has been extensively studied in tumors and relies largely on the gene expression of HSVtk. Most studies, however, have failed to demonstrate any significant benefit of a controlled gene expression strategy in cancer treatment. The Tet-On system is commonly used to regulate gene expression following Dox induction. We have evaluated the antitumor effect of HSVtk/ganciclovir gene therapy under Tet-On regulation by means of adeno-associated virus-2 (AAV-2)-mediated HSVtk gene transfer with direct intratumoral injections in mice bearing breast cancer tumors. METHODS: Recombinant adeno-associated virus-2 (rAAV) was constructed and transduced into MCF-7 cell line. GCV treatment to the rAAV infected MCF-7 cells was performed by MTT assay under the doxycycline (Dox) induction or without Dox induction at a vp (viral particle) number of > or =10(4)/cell. The virus was administered intratumorally to nude mice that had also received GCV intraperitoneally. The antitumor effects were evaluated by measuring tumor regression and histological analysis. RESULTS: We have demonstrated that GCV treatment to the infected MCF-7 cells under the Dox induction was of more inhibited effects than those without Dox induction at > or =10(4) vp/cell. In ex vivo experiments, tumor growth of BALB/C nude mice breast cancer was retarded after rAAV-2/HSVtk/Tet-On was injected into the tumors under the Dox induction. Infiltrating cells were also observed in tumors after Dox induction followed by GCV treatment and cells were profoundly damaged. The expression of HSVtk gene in MCF-7 cells and BALB/C nude mice tumors was up-regulated by Tet-On under Dox induction with reverse transcription-PCR (RT-PCR) analysis. CONCLUSION: The antitumor effect of rAAV-mediated HSVtk/GCV gene therapy under the Dox induction with direct intratumoral injections may be a useful treatment for breast cancer and other solid tumors.

Adenocarcinoma↗
PubMed2006

Adenosine A2a receptors induce heterologous desensitization of chemokine receptors.

Adenosine, released by cells in an injurious or hypoxic environment, possesses potent anti-inflammatory effects by inhibiting the production of proinflammatory cytokines and superoxide anions (O2-). We hypothesized that adenosine compounds also induced heterologous desensitization of chemokine receptors, which played a critical role in leukocyte trafficking. Our studies using adenosine receptor subtype-specific agonists revealed that pretreatment with adenosine compounds suppressed RANTES-induced chemotaxis and Ca2+ flux through activation of A2a adenosine receptor. Adenosine compounds also desensitized IL-8- and MCP-1-induced chemotaxis, but not that induced by fMLP. Activation of protein kinase A (PKA), a component of the signaling pathway induced by the A2a receptor, was sufficient to desensitize RANTES-induced chemotaxis. Inhibition of PKA reversed the desensitization effects of adenosine compounds, suggesting that PKA was necessary for A2a receptor-mediated heterologous desensitization. In a mouse model, prior activation of A2a receptors blocked RANTES-induced recruitment of leukocytes in an air pouch. Moreover, the A2a receptor-induced cross-desensitization also reduced the susceptibility of monocytes to infection by an R5 strain of HIV-1. Our results suggest that activation of A2a adenosine receptors suppresses chemokine receptor function, and such receptor cross-talk was based on the simple mechanism of PKA-mediated heterologous desensitization, thus contributing to the antiinflammatory activity of adenosine.

Adenosine↗
PubMed2006

Molecular mechanism of mutagenesis induced by olaquindox using a shuttle vector pSP189/mammalian cell system.

Olaquindox, a quinoxaline 1,4-dioxide derivative from quindoxin, is widely used as an animal growth promoter in China. We tested olaquindox as a mutagen in a SV40-based shuttle vector pSP189 and African green kidney cell (Vero E6 cell line) system to define the safety of olaquindox as a food-additive for animals. When applied at 6.6 microg/ml, olaquindox caused 12 times higher mutation frequency in comparison to untreated controls. More than 70% of base substitutions happened at G:C base pairs featuring G:C to T:A or G:C to A:T conversions. Frequency of point mutations for in vitro modified plasmids was also dramatically increased from the spontaneous background level. Olaquindox-induced mutations did not occur randomly along the supF shuttle vector, but instead, had a hot spot at base pair #155 which accounts for 37% of total mutations. Olaquindox-induced mutations also showed sequence-specificity in which most point mutations occurred at site N in a 5'-NNTTNN-3' sequence while most tandem bases deletion and rearrangement were seen at the 5'-ANGGCCNAAA-3' sequence. We conclude that olaquindox induces DNA mutation, therefore, should not be used as an additive to promote animal growth.

Animals↗
PubMed2006

Elevated cholecystokininergic tone constitutes an important molecular/neuronal mechanism for the expression of anxiety in the mouse.

Cholecystokinin (CCK), one of the most abundant neuropeptides in the brain, plays an important role in anxiogenesis through the activation of CCK receptor-2 (CCKR-2). Accumulating evidence, however, has suggested this role depends on endogenous CCKergic "tone," which is largely determined by the expression level of the CCKR-2. Using the tTA/tetO-inducible transgenic (tg) approach, we show here that overexpression of the CCKR-2 in neurons of the forebrain significantly increases CCKR-2 binding capacity in tg mice compared with their littermate controls. Interestingly, these tg mice consistently exhibit increased fear responses, which are generally interpreted as anxiety-like behaviors in the rodent, in a battery of behavioral tests, which represented conflict situations or delivered stress to the subjects. The inhibition of transgene expression with doxycycline treatment completely diminished both increased receptor-binding activity and all behavioral phenotypes. Furthermore, treatment of tg mice with diazepam significantly attenuated these anxiety-like behaviors. Our results directly demonstrate that the elevated CCKergic tone via overexpression of the CCKR-2 in the brain may constitute an underlying molecular/neuronal mechanism for the expression of anxiety. In addition, our study has validated a robust genetic anxiety model in the mouse in terms of their face, constructive, and predictive validity.

Animals↗
PubMed2006

Gene expression in the LNCaP human prostate cancer progression model: progression associated expression in vitro corresponds to expression changes associated with prostate cancer progression in vivo.

Identification of the genes involved in prostate cancer (PCa) progression to a virulent and androgen-independent (AI) form is a major focus in the field. cDNA microarray was used to compare the gene expression profile of the indolent, androgen sensitive (AS) LNCaP PCa cell line to the aggressively metastatic, AI C4-2. Thirty-eight unique sequences from a 6388 cDNA array were found differentially expressed (> or =2-fold, 95% CI). The expression of 14 genes was lower in C4-2 than in LNCaP cells, while the reverse was true for 24 genes. Twelve genes were validated using Q-PCR, Western blotting and immunohistochemistry (IHC) of LNCaP and C4-2 xenograft. Q-PCR showed that 10 of 12 (83.3%) genes had similar patterns of expression to the array (LNCaP>C4-2: TMEFF2, ATP1B1, IL-8, BTG1, BChE, NKX3.1; LNCaP<C4-2: BNIP3, TM4SF1, AMACR, UCH-L1). By Western blot, 4/5 genes examined: TMEFF2, NKX3.1, AMACR, and UCH-L1, not IL-8, were consistent with RNA profiling. Protein expression levels were confirmed in human tumor xenografts using IHC. A large proportion of the markers found in this expression profile is consistent with those recently identified in human PCa tissues along with several novel genes that remain to be examined. These data further demonstrate the utility of the LNCaP human PCa progression model as a tool to investigate the phenotypic changes required for the progression to AI and metastasis.

Blotting, Western↗
PubMed2006

Celecoxib inhibits interleukin-12 alphabeta and beta2 folding and secretion by a novel COX2-independent mechanism involving chaperones of the endoplasmic reticulum.

Celecoxib (CE) is a nonsteroidal anti-inflammatory drug (NSAID) that is a specific inhibitor of cyclooxygenase 2 (COX2). It is indicated for a variety of chronic inflammatory conditions, including rheumatoid arthritis. Over the last few years, adverse cardiovascular effects and increased risk for heart attacks have been associated with this drug. In addition, evidence is emerging for COX2-independent molecular targets. CE has been shown to induce apoptosis in various cancer cells lines through a COX2-independent mechanism that seems to involve inactivation of protein kinase Akt and inhibition of endoplasmic reticulum (ER) Ca2+ ATPase. In this study, we show that both CE and an analog devoid of COX2 inhibitory activity [1-(4-sulfamoyl phenyl)-3-trifluoromethyl-5-(4-trifluoromethylphenyl)pyrazole, CEA] inhibit the secretion of the dimeric interleukin-12 (IL-12) alphabeta and beta2 forms with identical IC50 values of 20 and 30 microM, respectively, whereas no such effect was seen with rofecoxib. Reverse transcription-polymerase chain reaction analysis showed that this inhibition was not due to a blockage of transcription of the alpha- and beta-chain expression cassettes. Secretion of the beta monomer form was less strongly inhibited, suggestive for a mechanism primarily targeting dimer assembly in the ER. Analysis of intracellular fractions revealed that both CE and CEA increased the association of IL-12 with calreticulin, an endoplasmic reticulum-resident chaperone involved in the retention of misfolded cargo proteins while blocking interaction with ERp44. Our findings reveal a previously undescribed effect of celecoxib on oligomer protein folding and assembly in the endoplasmic reticulum and ensuing secretion and suggest that celecoxib-driven alteration of the secretome may be involved in some of its clinical side effects.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2006

CD95-induced osteoarthritic chondrocyte apoptosis and necrosis: dependency on p38 mitogen-activated protein kinase.

One of the hallmarks of osteoarthritic cartilage is the loss of chondrocyte cellularity due to cell death. However, considerable controversy has recently arisen surrounding the extent of apoptotic cell death involved in development of osteoarthritis (OA). To shed light on this issue, we characterized cell death in primary OA chondrocytes mediated by the CD95 (Fas) pathway. Treatment of chondrocytes with anti-CD95 not only increased the rate of cell death but also increased the production of CD95 ligand by chondrocytes. This reveals a novel autocrine regulatory loop whereby activated chondrocytes may amplify CD95 signals by inducing synthesis of CD95 ligand. Multiple morphologic detection analyses indicated that apoptosis accounted for only a portion of chondrocyte death, whereas the other chondrocytes died by necrosis. Both chondrocyte apoptosis and necrosis depended on the activity of p38 mitogen-activated protein kinase (MAPK) within chondrocytes. Treatment of chondrocytes with the p38 MAPK inhibitor SB203580 abolished anti-CD95 induced cell death by inhibiting the activities of activating transcription factor-2 and caspase-3. In addition, inhibition of p38 MAPK activity in chondrocytes stimulated chondrocyte proliferation, as indicated by 5-bromo-2-deoxyuridine (BrdU) index. Thus, p38 MAPK is a potential therapeutic target, inhibition of which may maintain the cellularity of articular chondrocytes by inhibiting cell death and its amplification signal and by increasing cell proliferation.

Apoptosis↗
PubMed2006

Identification of clock as a mechanosensitive gene by large-scale DNA microarray analysis: downregulation in osteoarthritic cartilage.

The chondrocytes of cartilage have so far been reported to include three mechanoresponsive genes: cartilage matrix protein (CMP, matrilin-1), type X collagen, and Indian hedgehog (Ihh). In fact, all of the genes identified in these chondrocytes are associated solely with mechanical stress. In this study we examined the how mechanical stress influenced the patterns of gene expression of chondrocytes in three-dimensional (3D) sponges in order to better understand the mechanisms that control the chondrocyte phenotype during the development of osteoarthritis. We cultured mouse chondrocytes in 3D sponge as a model of mechanical stress and isolated total RNA for a large-scale DNA microarray analysis covering 12,000 genes. We analyzed the pattern of gene expression in relation to gene localization in cellular components such as the cytoplasm, cytoskeleton, and nucleus. Immunoblotting of osteoarthritis cartilage were performed using polyclonal anti-clock antibody. The biological rhythm of mRNA of clock and clock-related genes was analyzed by real-time polymerase chain reaction (PCR). Clock gene was confirmed by real-time PCR to validate the microarray data. Other clock-related genes such as Per1 and Per2 were also expressed in chondrocytes, exhibiting biological rhythm after serum shock. The large-scale DNA microarray indicated that clock and other genes functionally associated with mechanical stress play an essential role in regulating the biological rhythm of chondrocyte metabolism in osteoarthritis cartilage.

Animals↗
PubMed2006

Induction of dendritic cell maturation by pertussis toxin and its B subunit differentially initiate Toll-like receptor 4-dependent signal transduction pathways.

OBJECTIVE: Pertussis toxin (PT) has the capacity to activate dendritic cells (DCs) for the augmentation of cell-mediated immune responses. To investigate the mechanism(s) by which PT activates DCs, we investigated the effects of PT and its B-oligomer (PTB) on the maturation of human and mouse DCs and determined whether PT could act as a pathogen-associated molecular pattern to activate one of the Toll-like receptors (TLRs). METHODS: The effects of PT and PTB on the maturation of human and mouse DCs were analyzed in terms of surface marker expression, cytokine production, antigen-presenting capacity, and intracellular signaling. The participation of TLR4 in PT-induced signaling was determined by comparing the effect of PT on DCs derived from TLR4-deficient and wild-type mice, as well as by measuring PT-induced NF-kappaB activation in HEK293 cells transiently transfected to express various TLRs. RESULTS: Although both promoted phenotypic and functional maturation DCs, however, unlike PT that induced DC production of interleukin (IL)-6, tumor necrosis factor-alpha, IL-12, and interferon-inducible protein, PTB was capable of stimulating the production of interferon-inducible protein. Bone marrow-derived DCs from C3H/HeJ mice with defective TLR-4 alleles were unresponsive to PT and PTB, whereas DCs from C3H/HeN mice responded. In addition, PT induced NF-kappaB activation and IL-8 production in HEK293 cells transfected with a combination of TLR4 and MD2 but not in nontransfected or TLR2-transfected HEK293 cells. Comparison of the patterns of cytokine induction and intracellular signaling events in DCs treated by PT and PTB revealed that although PT, like lipopolysaccharide, triggered both MyD88-dependent and -independent pathways, PTB preferentially triggered MyD88-independent pathways. Interestingly, mouse splenocyte proliferation in response to PT and PTB was only partially dependent on TLR4. CONCLUSION: The data identify PT as another pathogen-associated molecular pattern that induces DC maturation in a TLR4-dependent manner. Unlike PT, which triggers both MyD88-dependent and -independent pathways, PTB only triggers the MyD88-independent pathway in DCs.

Animals↗
PubMed2006

Dynamics of assembly and reorganization of extracellular matrix proteins.

This chapter will review advances in our understanding of the dynamics of assembly and reorganization of extracellular matrix (ECM) proteins and will highlight the role of fibronectin as a key orchestrator for the assembly of multiple ECM proteins. The dynamic rather than static nature of the ECM will be emphasized by reviewing time-lapse imaging studies in living cell and embryo systems, with a particular focus on fibronectin and members of the fibrillin superfamily. These studies have provided new insights into the assembly and reorganization of ECM fibrillar networks, suggesting that fibril assembly is a hierarchical process, with increasingly larger fibrillar structures formed by the progressive aggregation of smaller units. These studies have also revealed that motile cells appear to be actively involved in the assembly and reorganization of ECM fibrillar networks by shunting fibrillar material from one location to another, adding fibrillar material to the ends of growing fibrils, and exchanging material between fibrils. A common theme emerging from these studies is that cell- and tissue-generated mechanical forces are critical in the assembly and remodeling of the ECM.

Animals↗
PubMed2006

The newest interleukins: recent additions to the ever-growing cytokine family.

Cytokines play a critical role in the control of the innate and adaptive immune responses. The most recent additions to the ever-growing family of cytokines include interleukin (IL)-27, IL-28A, IL-28B, IL-29, IL-31, IL-32, and IL-33. Many of the newly identified cytokines and/or their specific receptors have been identified using bioinformatics. The coming of age of this discipline has coincided with completion of the sequencing of the human genome thus enabling the identification of new uncharacterized proteins. The latest additions to the interleukin family have shed new light on the intricacies of immune system regulation. These novel cytokines have pleiotrophic actions ranging from antiviral immunity to the regulation of Th2 immune responses. For example, the discovery of IL-27 has greatly improved our understanding of the factors regulating the polarization of the T helper cell responses and IL-31 appears to be an important regulator of Th2 responses. On the other hand, IL-28 and IL-29 are considered to be critical for mounting an efficient antiviral response and IL-32 and IL-33, which are yet to be fully characterized, are emerging as important components of the inflammatory response in allergy and autoimmunity. These new cytokine/receptor combinations may therefore serve as novel targets for the treatment and control of allergy, autoimmune diseases, and some cancers.

Animals↗
PubMed2006

Functional knockout of the matrilin-3 gene causes premature chondrocyte maturation to hypertrophy and increases bone mineral density and osteoarthritis.

Mutations in the gene encoding matrilin-3 (MATN3), a noncollagenous extracellular matrix protein, have been reported in a variety of skeletal diseases, including multiple epiphyseal dysplasia, which is characterized by irregular ossification of the epiphyses and early-onset osteoarthritis, spondylo-epimetaphyseal dysplasia, and idiopathic hand osteoarthritis. To assess the role of matrilin-3 in the pathogenesis of these diseases, we generated Matn3 functional knockout mice using embryonic stem cell technology. In the embryonic growth plate of the developing long bones, Matn3 null chondrocytes prematurely became prehypertrophic and hypertrophic, forming an expanded zone of hypertrophy. This expansion was attenuated during the perinatal period, and Matn3 homozygous null mice were viable and showed no gross skeletal malformations at birth. However, by 18 weeks of age, Matn3 null mice had a significantly higher total body bone mineral density than Matn1 null mice or wild-type littermates. Aged Matn3 null mice were much more predisposed to develop severe osteoarthritis than their wild-type littermates. Here, we show that matrilin-3 plays a role in modulating chondrocyte differentiation during embryonic development, in controlling bone mineral density in adulthood, and in preventing osteoarthritis during aging. The lack of Matn3 does not lead to postnatal chondrodysplasia but accounts for higher incidence of osteoarthritis.

Aging↗
PubMed2006

[Diagnosis and treatment of laryngeal web in infants].

OBJECTIVE: To summarize the clinical manifestation, operative method and therapeutic effect of various type of laryngeal web in infants. METHODS: The clinical data of 12 cases were analyzed, 5 cases of which were congenital laryngeal web (4 cases, glottic type; 1 case, subglottic type), 7 cases of which were secondary laryngeal web (1 case, tuberculous laryngeal web; 6 cases, traumatic laryngeal web). Diagnosis was mainly depended on history and clinical manifestation. Final diagnosis was depended on fibrolaryngoscope and pathological report. Microlaryngoscopic surgery was the main operative method. However, specific infection should be cured before operation. RESULTS: During 3-18 months follow-up, 4 glottic laryngeal webs were cured. One subglottic laryngeal web case well recovered and secondary surgery is not needed at least recently. One tuberculous laryngeal web was followed up for 6 months, no vocal adhesion was observed. During 3-6 months follow-up, 1 traumatic laryngeal web was cred, while the other 6 cases need secondary surgery. CONCLUSIONS: Final diagnosis of congenital laryngeal web is mainly depended on fibrolaryngoscope. And prognosis of it is well. Laryngeal web induced by specific infection should be cured specific infection before operation. The prevention is the key for traumatic laryngeal web because the surgery outcome is not satisfactory.

Child↗
PubMed2006

[ABR evaluation of children with cheilopalatognathus].

OBJECTIVE: To study the characteristics of hearing loss in children with cheilopalatognathus. METHOD: Sixty-eight children (136 ears) with cleft palate and 70 children (140 ears) with cleft lip were tested with ABR. They were divided into three groups according to the age (<6 months, 6-12 months, 13-24 months). Other 80 age-matched healthy children were enrolled in the control group. The ABR results were compared between the three groups and the control group. RESULT: Hearing loss was found in 91.9% of children with cleft palate and in 89.3% with cheilopalatognathus, the majority of which was moderate or severe. When comparing to the control group, the latency values of waves I, III and V were prolonged and the threshold of wave V was elevated. No significant difference of the transmission time between wave I and wave V was found between the children under one year old with cleft palate or cheilopalatognathus and the children in the control group With aging, the inducing rate of threshold in children with cleft palate and the inducing rate of waves I, III and V in children with cheilopalatognathus were elevated. CONCLUSION: The majority of children with cheilopalatognathus has hearing loss. Because the central nervous system of infants is at the developing stage, a continuously evaluation of hearing is needed.

Case-Control Studies↗
PubMed2006

[Assessment of myocardial performance in fetuses by using Tei index].

OBJECTIVE: To define the value of Tei index of normal fetuses and to estimate the influence of gestational week and heart rate on the index. METHODS: Fetal echocardiograms were performed on 225 normal single fetuses, which were divided into three groups (18 approximately 27(+6), 28 approximately 36(+6), 37 approximately 42 gestational weeks). The Tei indexes of both left and right ventricles (LV and RV) were measured by color Doppler ultrasonography. t test was used to compare the Tei index between LV and RV. The correlation between Tei index, gestational week and fetal heart rate were analyzed. RESULTS: The Tei indexes in three different gestational week groups (18 approximately 27(+6), 28 approximately 36(+6), 37 approximately 42 gestational weeks) were 0.37 +/- 0.08, 0.27 +/- 0.05, 0.22 +/- 0.05 of LV and 0.39 +/- 0.04, 0.30 +/- 0.05, 0.24 +/- 0.04 of RV respectively. There was significant difference of Tei index of RV and LV during 28 approximately 36(+6) gestational weeks (P < 0.05). The Tei index of LV and RV decreased linearly with advancing gestational week during 18 - 42 weeks (LV: r = -0.755, PP < 0.05; RV: r = -0.721, P < 0.05) in normal single fetuses. None of the fetal Tei indexes of LV and RV was related to fetal heart rate (LV: r = 0.133, P > 0.05; RV: r = 0.100, P > 0.05). CONCLUSION: Tei index may be useful, convenient and reliable in fetal cardiac function assessment.

Adult↗