Biomedical subjects

Xiaobo Wang

Publications and source records attributed to Xiaobo Wang.

At least 37 records · Page 2Linked to original sources

PubMed2005

RelB/p52 NF-kappaB complexes rescue an early delay in mammary gland development in transgenic mice with targeted superrepressor IkappaB-alpha expression and promote carcinogenesis of the mammary gland.

Classical NF-kappaB (p65/p50) transcription factors display dynamic induction in the mammary gland during pregnancy. To further elucidate the role of NF-kappaB factors in breast development, we generated a transgenic mouse expressing the IkappaB-alpha S32/36A superrepressor (SR) protein under control of the mouse mammary tumor virus (MMTV) long terminal repeat promoter. A transient delay in mammary ductal branching was observed in MMTV-SR-IkappaB-alpha mice early during pregnancy at day 5.5 (d5.5) and d7.5; however, development recovered by mid- to late pregnancy (d14.5). Recovery correlated with induction of nuclear cyclin D1 and RelB/p52 NF-kappaB complexes. RelB/p52 complexes induced cyclin D1 and c-myc promoter activities and failed in electrophoretic mobility shift assay to interact with IkappaB-alpha-glutathione S-transferase, indicating that their weak interaction with IkappaB-alpha can account for the observed recovery of mammary gland development. Activation of IKKalpha and NF-kappaB-inducing kinase was detected by d5.5, implicating the alternative NF-kappaB signaling pathway in RelB/p52 induction. Constitutively active IKKalpha induced p52, RelB, and cyclin D1 in untransformed mammary epithelial cells. Moreover, mouse mammary tumors induced by 7,12-dimethylbenz(a)anthracene treatment displayed increased RelB/p52 activity. Inhibition of RelB in breast cancer cells repressed cyclin D1 and c-Myc levels and growth in soft agar. These results implicate RelB/p52 complexes in mammary gland development and carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed2004

B-Myb represses elastin gene expression in aortic smooth muscle cells.

B-Myb represses collagen gene transcription in vascular smooth muscle cells (SMCs) in vitro and in vivo. Here we sought to determine whether elastin is similarly repressed by B-Myb. Levels of tropoelastin mRNA and protein were lower in aortas and isolated SMCs of adult transgenic mice expressing the human B-myb gene, driven by the basal cytomegalovirus promoter, compared with age-matched wild type (WT) animals. However, the vessel wall architecture and levels of insoluble elastin revealed no differences. Since elastin deposition occurs early in development, microarray analysis was performed using nontransgenic mice. Aortic levels of tropoelastin mRNA were low during embryonal growth and increased substantially in neonates, whereas B-myb levels varied inversely. Tropoelastin mRNA expression in aortas of 6-day-old neonatal transgenic and WT animals was comparable. Recently, we demonstrated that cyclin A-Cdk2 prevents B-Myb-mediated repression of collagen promoter activity. Cyclin A2 levels were higher in neonatal versus adult WT or transgenic mouse aortas. Ectopic cyclin A expression reversed the ability of B-Myb to repress elastin gene promoter activity in adult SMCs. These results demonstrate for the first time that B-Myb represses SMC elastin gene expression and that cyclin A plays a role in the developmental regulation of elastin gene expression in the aorta. Furthermore, the findings provide additional insight into the mechanism of B-myb-mediated resistance to femoral artery injury.

Animals↗

PubMed2004

Mechanism of action of transmembrane activator and calcium modulator ligand interactor-Ig in murine systemic lupus erythematosus.

B cell-activating factor belonging to the TNF family (BAFF) blockade prevents the onset of disease in systemic lupus erythematosus (SLE)-prone NZB/NZW F(1) mice. To determine the mechanism of this effect, we administered a short course of TACI-Ig with and without six doses of CTLA4-Ig to 18- to 20-wk-old NZB/NZW F(1) mice and evaluated the effect on B and T cell subsets and on anti-dsDNA Ab-producing B cells. Even a brief exposure to TACI-Ig had a beneficial effect on murine SLE; CTLA4-Ig potentiated this effect. The combination of TACI-Ig and CTLA4-Ig resulted in a temporary decrease in serum IgG levels. However, after cessation of treatment, high titers of IgG anti-dsDNA Abs appeared in the serum and IgG Abs deposited in the kidneys. Despite the appearance of pathogenic autoantibodies, the onset of proteinuria was markedly delayed; this was associated with prolonged depletion of B cells past the T1 stage, a decrease in the size of the spleen and lymph nodes, and a decrease in the absolute number of activated and memory CD4(+) T cells. TACI-Ig treatment normalized serum levels of IgM that are markedly elevated in NZB/W F(1) mice; this appeared to be due to a prolonged effect on the ability of the splenic microenvironment to support short-lived IgM plasma cells. Finally, a short course of combination TACI-Ig and CTLA4-Ig prolonged life and even reversed proteinuria in aged NZB/W F(1) mice, suggesting that BAFF blockade may be an effective therapeutic strategy for active SLE.

Abatacept↗

PubMed2004

Label-free, real-time monitoring of IgE-mediated mast cell activation on microelectronic cell sensor arrays.

Immunoglobulin E (IgE)-mediated mast cell activation is involved in the immediate phase of allergic reactions and plays a central role in the onslaught and persistence of allergic diseases. IgE-mediated mast cell activation includes two important events: cell sensitization resulting from IgE binding to Fc (FcepsilonRI) receptor and cell activation triggered by allergen-mediated oligomerization of membrane-bound IgE. Real-time monitoring of these events is needed to dissect the molecular mechanisms underlying IgE-mediated mast cell activation. Existing technologies are limited to label-based end-point assay formats, which detect either early signaling or final phase of mast cell activation. We describe a microelectronic cell sensor-based technology allowing dynamic monitoring of IgE-mediated mast cell sensitization and activation in real-time without any labeling steps. RBL-2H3 mast cells were cultured onto the surface of microelectronic cell sensor arrays integrated into the bottom of microtiter plates, which record electric properties, such as impedance between cell membrane and sensor surface. In the presence of the allergen, dinitrophenyl (DNP)-bovine serum albumin (BSA), anti-DNP IgE-sensitized cells were activated within 5 min and the entire activation process was quantitatively and continuously recorded. Impedance measurements correlate with morphological dynamics and mediator release as measured by beta-hexosaminidase activity, and can be blocked by pharmacological agents, inhibiting IgE-mediated signaling. The assay on microelectronic cell sensor arrays can be scaled up for high-throughput screening of pharmacological inhibitors of IgE-mediated mast cell activation and other cell-based receptor-ligand assays.

Cell Degranulation↗

PubMed2004

Tumor-specific expression detected with the use of an expression vector driven by human telomerase reverse transcriptase gene promoter.

To construct the tumor-specific expression vector driven by human telomerase reserve transcriptase gene promoter, we amplified a fragment of the enhanced green fluorescent protein (EGFP) gene from the pEGFP-N1 plasmid and cloned it into the multiple cloning site of the pLNCX vector, then named the recombinant as pLNCX-EGFP. The fragment of human telomerase reverse transcriptase gene promoter (hTERT) was amplified from the human genome with the use of human telomerase reserve transcriptase gene-specific primers and cloned into the pLNCX-EGFP vector, from which the cytomegalovirus promoter had previously been removed through the use of restriction enzymes, in sense orientation relative to the green fluorescent protein coding sequence. Then the expression vector pLNT-EGFP--under the control of the human telomerase reserve transcriptase gene promoter, which contains green fluorescent protein reporter gene-was successfully constructed. To detect the transcriptional activity of the human telomerase reserve transcriptase gene promoter, we conducted transient transfection of this specific expression vector into human lung fibroblast (HLF) cell lines with high telomerase activity and normal human fetal lung fibroblast (WI38) cell lines without telomerase activity. The results of transient transfection showed that the pLNT-EGFP vector strongly expressed the green fluorescent protein reporter gene in telomerase-positive cells but not in telomerase-negative cells.

Base Sequence↗

PubMed2004

Application of real-time cell electronic sensing (RT-CES) technology to cell-based assays.

Label-free detection emerges as a new approach in the development of technologies for cell-based screening assays. Unlike the classic detection methods that use fluorescence, radioisotope, luminescence, or light absorption, label-free detection directly measures the cell function without using a labeled molecule. The advantages of label-free detection include a simple homogeneous assay format, noninvasive measurement, less interference with normal cell function, kinetic measurement, and reduced time for assay development. Here, we have applied the electrical impedance detection method in a real-time cell electronic sensing (RT-CES trade mark ) system for cell-based assays. The cell growth rate measured by this RT-CES system was comparable to actual cell number counted manually. In addition, cell proliferation, cytotoxicity, cytoprotection, cell growth inhibition, and apoptosis data generated by this RT-CES system correlated with those determined by the classic methods. The conclusion is that the RT-CES system is a useful tool for label-free detection of certain cell-based parameters.

Cell Line, Tumor↗

PubMed2003

A natural allele of Nxf1 suppresses retrovirus insertional mutations.

Endogenous retroviruses have shaped the evolution of mammalian genomes. Host genes that control the effects of retrovirus insertions are therefore of great interest. The modifier-of-vibrator-1 locus (Mvb1) controls levels of correctly processed mRNA from genes mutated by endogenous retrovirus insertions into introns, including the Pitpn(vb) tremor mutation and the Eya1(BOR) model of human branchiootorenal syndrome. Positional complementation cloning identifies Mvb1 as the nuclear export factor Nxf1, providing an unexpected link between the mRNA export receptor and pre-mRNA processing. Population structure of the suppressive allele in wild Mus musculus castaneus suggests selective advantage. A congenic Mvb1(CAST) allele is a useful tool for modifying gene expression from existing mutations and could be used to manipulate engineered mutations containing retroviral elements.

Alleles↗

PubMed2003

Short term administration of costimulatory blockade and cyclophosphamide induces remission of systemic lupus erythematosus nephritis in NZB/W F1 mice by a mechanism downstream of renal immune complex deposition.

NZB/W F(1) mice with established nephritis were treated with a single dose of cyclophosphamide with or without a 2-wk course of murine CTLA4Ig, either alone or in combination with anti-CD154. Sixty to 80% of treated mice entered remission, and remission could be reinduced following relapse. A decrease in the frequency of anti-DNA-producing B cells and activated T cells was observed in treated mice, but this effect lasted only 3-6 wk, while remissions were sustained for up to 20 wk. Light microscopy of the kidneys of mice in remission revealed less glomerular inflammation, less tubular damage, and less infiltration of inflammatory cells. By immunofluorescence, however, IgG and C3 staining of glomeruli was no different in treated mice vs controls. Since chemokines and their receptors play an important role in inflammatory cell infiltration of affected organs in autoimmune diseases, we examined chemokine expression in the kidneys. Decreases in the expression of inflammatory cytokines and chemokines were evident in mice in the early stages of remission, but these differences were no longer present in late remission. Increased expression of CXCL13 was detected in the inflammatory infiltrates of the control NZB/NZW mice. Strikingly, we could not detect any CXCL13 in the kidneys of the treated group even in late remission. These findings suggest that costimulatory blockade together with cyclophosphamide influence the activation state of renal CD11c-positive cells and therefore lead to less B and T cell infiltration and nephritis.

Abatacept↗

PubMed2003

Effects of anti-CD154 treatment on B cells in murine systemic lupus erythematosus.

OBJECTIVE: To determine the immunologic effects of anti-CD154 (CD40L) therapy in the (NZB x NZW)F(1) mouse model of systemic lupus erythematosus. METHODS: Twenty-week-old and 26-week-old (NZB x NZW)F(1) mice were treated with continuous anti-CD154 therapy. Mice were followed up clinically, and their spleens were studied at intervals for B and T cell numbers and subsets and frequency of anti-double-stranded DNA (anti-dsDNA)-producing B cells. T cell-dependent immunity was assessed by studying the humoral response to the hapten oxazolone. RESULTS: IgG anti-dsDNA antibodies decreased during therapy and disease onset was delayed, but immune tolerance did not occur. During treatment, there was marked depletion of CD19+ cells in the spleen; however, autoreactive IgM-producing B cells could still be detected by enzyme-linked immunospot assay. In contrast, few IgG- and IgG anti-dsDNA-secreting B cells were detected. Eight weeks after treatment cessation, the frequency of B cells producing IgG anti-dsDNA antibodies was still decreased in 50% of the mice, and activation and transition of T cells from the naive to the memory compartment were blocked. Anti-CD154 treatment blocked both class switching and somatic mutation and induced a variable period of relative unresponsiveness of IgG anti-dsDNA-producing B cells, as shown by decreased expression of the CD69 marker and failure to generate spontaneous IgG anti-dsDNA-producing hybridomas. Treated mice mounted an attenuated IgM response to the hapten oxazolone and produced no IgG antioxazolone antibodies. CONCLUSION: Anti-CD154 is a B cell-depleting therapy that affects multiple B cell subsets. Activation of both B and T cells is prevented during therapy. After treatment cessation, autoreactive B cells progress through a series of activation steps before they become fully competent antibody-producing cells. The general immunosuppression induced during treatment will need to be taken into account when using B cell-depleting regimens in humans.

Amino Acid Sequence↗

PubMed2003

A benchmark study with sealchip planar patch-clamp technology.

Although conventional patch-clamp methods provide high information content, they are labor-intensive and suffer from low throughput and high overall cost. Several approaches for achieving high throughput electrophysiology are under development, among which microchip-based patch-clamp systems uniquely achieve a higher degree of miniaturization, faster perfusion and mixing, and lower reagent cost without losing information content. The goal of this study was to establish a benchmark for our biochip technology with 52 chips tested sequentially. We demonstrate that our microfabrication and processing technology is sufficiently mature to produce a consistent hole size. We further demonstrate high-quality planar whole-cell patch clamping with >75% overall success rate at achieving gigaohm seals, followed by stable whole-cell access lasting at least 15 min with access resistance (Ra) below 15 MOmega and membrane resistance (Rm) above 200 MOmega. These biochips are ideally suited for high throughput compound screening for ion channel targets.

Animals↗

PubMed2003

Automated electrophysiology: high throughput of art.

Electrophysiological measurements, in particular, patch clamping, have long been regarded as the "gold standard" for assaying ion channels. Despite its high information content, the technique suffers from laborious, manual processing by highly skilled workers and extremely low throughput. Recently, a number of researchers have started to automate patch clamping by either automating conventional micropipette-based patch clamping or developing planar microelectrode arrays. This article reviews the brief history of these emerging technologies and discusses the technical details, advantages, and disadvantages of each approach and technique. As will be evident from the discussion, two types of automated patch-clamping technologies are emerging. The first places emphasis on data quality, comparable to conventional patch clamping, and the second has much higher throughput. Future developments will include sophisticated patch-clamping devices with both high-quality data and high throughput capabilities and further integration of patch clamping with other cell-based assays.

Animals↗

PubMed2003

Blockage of immune-mediated inner ear damage by etanercept.

HYPOTHESIS: Etanercept will be able to reduce the inflammation and hearing loss associated with experimentally induced labyrinthitis. BACKGROUND: Inner ear immune responses cause hearing loss that may be reversible with pharmacologic treatment. Etanercept, tumor necrosis factor receptor blocker, was investigated in a guinea pig model of immune-mediated hearing loss. Sterile labyrinthitis was created by injection of keyhole limpet hemocyanin into the inner ear after systemic sensitization to keyhole limpet hemocyanin with adjuvant. Labyrinthitis involves infiltration of inflammatory cells and hearing loss detectable 3 to 5 days after challenge with keyhole limpet hemocyanin. METHODS: Etanercept was administered either systemically (2.5 mg) 30 minutes before intracochlear challenge with keyhole limpet hemocyanin, with a second intraperitoneal dose (2.5 mg) 3 days later or locally by long-term infusion into the scala tympani with an osmotic pump (5.0 microg/h for 7 days). Auditory evoked brainstem response thresholds were measured before and after treatment to determine hearing loss. Cochleas were evaluated for the amount of inflammation. RESULTS: Hearing loss in the untreated systemic group averaged 71 +/- 21 dB versus 37 +/- 32 dB in the etanercept-treated animals (t test, P < 0.001). There was also less inflammation in the cochleas from etanercept-treated animals (t test, P < 0.01). Hearing loss with local administration of etanercept was 59 +/- 31 dB in the nontreated ears and 18 +/- 8 dB in the treated ears (t test, P < 0.02). Inflammation was also less (t test, P < 0.01). Etanercept was not ototoxic. CONCLUSION: Prompt intervention with the anti-inflammatory drug etanercept significantly reduces inflammation sufficient for substantive hearing preservation.

Animals↗

PubMed2003

Co-stimulatory blockade in the treatment of murine systemic lupus erythematosus (SLE).

Although the life span of patients with systemic lupus erythematosus (SLE) has improved considerably over the last several decades, the toxicities of chronic immunosuppressive therapy are major causes of morbidity and mortality. Safer and more effective therapies for SLE are clearly needed. SLE is characterized by excessive activation of both B and T lymphocytes. Activation of these cells requires both antigen engagement and co-stimulatory signals from interacting lymphocytes (Carreno, B.M. M. Collins, 2002, Annu. Rev. Immunol. 20: 29-53; Grewal, I.S. R.A. Flavell, 1998, Annu. Rev. Immunol. 16: 111-135). Thus, blockade of co-stimulatory signals offers a new therapeutic approach to SLE. Our short-term goal has been to understand the effect of co-stimulatory blocking reagents on the development, selection, and activation of pathogenic anti-dsDNA antibody producing B cells in mice genetically pre-determined to develop SLE and showing signs of either early or advanced disease activity. Our long-term goal is to use the knowledge we gain to design therapeutic regimens for humans that avoid the complications of long-term immunosuppression. As new co-stimulatory molecules are discovered, studying their mechanism of action in animal models and their clinical utility in human autoimmune disease should lead both to a new understanding of disease pathogenesis and also to safer and more effective therapies.

Abatacept↗

PubMed2002

Mechanism of action of combined short-term CTLA4Ig and anti-CD40 ligand in murine systemic lupus erythematosus.

Short-term combination therapy with the costimulatory antagonists CTLA4Ig and anti-CD40 ligand induces prolonged suppression of disease onset in New Zealand Black/New Zealand White F(1) systemic lupus erythematosus-prone mice. To determine the mechanism for this effect, 20- to 22-wk-old New Zealand Black/New Zealand White F(1) mice were treated with six doses each of CTLA4Ig and anti-CD40 ligand Ab over 2 wk. Combination-treated mice, but not mice treated with either agent alone, had prolonged survival and the production of pathogenic IgG anti-dsDNA Ab was suppressed. Twenty weeks after completion of treatment the frequency of activated B cells producing anti-dsDNA Ab was decreased, and the abnormal transition of T cells from the naive to the memory compartment was blocked. Combination treatment partially suppressed class switching and decreased the frequency of somatic mutations in the V(H)BW-16 gene, which is expressed by pathogenic anti-DNA Abs. Treated mice were still able to respond to the hapten oxazolone when it was given 8 wk after treatment initiation, and they mounted a somatically mutated IgG anti-oxazolone response that was noncross-reactive with dsDNA. Fifty to 60% of previously treated mice, but only 14% of previously untreated mice, responded within 2-3 wk to a second course of therapy given at the onset of fixed proteinuria and remained well for a further 3-4 mo. Although this treatment had no immediate effect on serum anti-dsDNA Abs or on the abnormal T cell activation observed in sick mice, 25% of treated mice lived for >18 mo compared with 5% of untreated controls. These results suggest that the effect of costimulatory blockade in remission induction must be mediated by a different mechanism than is demonstrated in the disease prevention studies.

Abatacept↗

PubMed2002

Simulation of bone adaptive remodeling using a stochastic process as loading history.

In this simulation study for bone adaptive remodeling, loading conditions are described as stochastic processes to catch the unpredictable characteristics of daily physical activities, which are observed to be closely related with bone adaptive remodeling. This will not only eliminate the necessity of arbitrary choices for loading conditions, but also generate greater flexibility for simulations of bone adaptive remodeling. The sensitivity of simulation outcomes to the parameters in the simulation algorithm was examined by applying stochastic loading conditions on finite element models of simplified spine structures. In this way, the limitations induced by simplifying loading conditions into constant or cyclic loads can be avoided and, potentially, more clinical observations could be accommodated when more comprehensive finite element models are available.

Algorithms↗

PubMed2002

A phase II study of etoposide, doxorubicin, and carboplatin in the treatment of advanced gastric cancer.

Many phase II studies have reported improved response rates with severe toxicity of etoposide, doxorubicin (Adriamycin), and cisplatin in advanced gastric cancer. In an attempt to obtain a better regimen with high efficacy and less toxicity, a combination regimen of etoposide, doxorubicin, and carboplatin (EAC) had been developed and evaluated in this phase II study. Forty-six patients with advanced gastric cancer were enrolled in the study. The treatment consisted of doxorubicin 20 mg/m2 given intravenously on days 1 and 7, etoposide 70 mg/m2 intravenously on days 4, 5, and 6, and carboplatin 200 mg/m2 intravenously on days 2 and 8. Therapy was repeated every 4 weeks. Patients who had stable disease or who responded, received an additional two to six cycles of therapy. Among 45 patients evaluable for response and toxicity, there was a 49% objective response rate, including 7% complete remission and 42% partial response. There was 11% stable disease and 27% progressive disease. Among 11 patients with lymph node metastasis only after a curative gastrectomy, there was an 82% objective response rates with 27% having complete remission and 55% having partial response. The median follow-up was 16 months. The median survival duration of all 45 patients was 11 months. The median time to progression was 5 months. The main toxicity was myelosuppression, with a high incidence of 82% leukopenia but only 9% of grades III to IV. Gastrointestinal toxicity was mild, with a low incidence of 42% nausea and vomiting and only 2% of grades III to IV. There were no chemotherapy-related deaths. With mild and tolerable toxicity, the EAC regimen in our study has active antitumor activity in advanced gastric cancer, which may have a positive influence on long-term survival time. It has a high efficacy, especially in patients with lymph node metastasis only after a curative gastrectomy. This regimen deserves further clinical studies for testing activity and toxicity in advanced gastric cancer.

Adult↗

PubMed2002

[Preoperative high-dose chemotherapy with peripheral blood stem cell support in breast cancer: report of 3 cases].

OBJECTIVE: To investigate the possibility and short-term effect of high dose chemotherapy with peripheral blood stem cell support in the preoperative therapy of breast cancer, and-its influence on the following operation and would healing. METHODS: Three patients with T(3)N(1)M(0) (III(a)), T(4)N(1)M(0) (III(b)), T(4)N(1)M(1) (IV) of breast cancer were diagnosed histopathologically. After receiving HDC/APBSCT, the 3 patients were operated on. HDC/APBSCT process included 2 cycles of FEC induction chemotherapy; PBSC mobilization, APBSC collection and cryopreservation and PBSC infusion; and high-dose chemotherapy, APBSC infusion and supportive therapy. The therapy consisted of CTX2.5 g/m(2), VP-16 600 mg/m(2), and cerboplatin 600 mg/m(2) delivered on day 1, APBSC infusion 48 h later, rhG-CSF (150 microg, BID) was administered 4 h after infusion of APBSC until WBC was higher than 10 x 10(9)/L. During HDC/APBSCT, the patients were protected in the air laminar flow room with supportive therapy of antibiotics, anti-virus and anti-fungus drugs. They left the air laminar flow room after their WBC was greater than 2 x 10(9)/L. Case 1 was treated by radical mastectomy, Case 2 by improved radical mastectomy, Case 3 by improved radical mastectomy and transplantation of skin for the large area. RESULTS: Rapid recovery of bone marrow function was observed in all 3 patients. Operation was performed 4 weeks after HDC/PBSCT in Cases 1, 2 and 33 days in Case 3. No influence was seen on operative procedure and would healing, especially in Case 3 with a large area of skin transplantation. Two patients with stage III(a) and III(b) have been alive since the treatment for 30 months and the other with stage IV died of brain metastasis 16 months later. CONCLUSIONS: HDC/APBSCT as a preoperative therapy for breast cancer has no influence on the coming surgery and would healing, even on skin transplantation for a large area. It has a practical response in stage III(a) and III(b), but it is still controversial in stage IV. This method as a salvage therapy for patients with breast cancer of intemuediate or stage.

Adult↗

PubMed2001

Ion-channel assay technologies: quo vadis?

Although many existing methods are used to study the functions of ion channels and to screen lead compounds for important ion-channel targets, new technologies are being developed for improved performance. It is important to identify the advantages and disadvantages of each technology. In this review, we segment the ion-channel assay market according to distinguishable applications, and compare the needs of each market segment with the capabilities of different technologies in terms of multiple assay attributes. We further discuss the future directions in the development of ion-channel assays.

Journal Article↗