Biomedical subjects

Y Chen

Publications and source records attributed to Y Chen.

At least 397 records · Page 22Linked to original sources

PubMed2001

Nonphlogistic clearance of late apoptotic neutrophils by macrophages: efficient phagocytosis independent of beta 2 integrins.

Neutrophils undergo constitutive death by apoptosis, leading to safe nonphlogistic phagocytosis and clearance by macrophages. Recent work has shown that before secondary necrosis, neutrophils exhibiting classical features of apoptosis can progress to a morphologically defined late apoptotic state. However, whether such neutrophils could be safely cleared was unknown. We now report that human late apoptotic neutrophils could be purified from cultured neutrophil populations undergoing constitutive death and were subsequently ingested by human monocyte-derived macrophages by serum-independent mechanisms that did not trigger the release of IL-8 or TNF-alpha. Such ingestion was specifically inhibited by Abs to thrombospondin-1 and the alpha(v)beta(3) vitronectin receptor. Murine bone marrow-derived macrophage phagocytosis of late and early apoptotic neutrophils occurred by similar mechanisms, proceeding with the same efficiency as that observed for wild-type controls when macrophages from [alpha(m)](-/-) or [beta(2)](-/-) mice were used. We conclude that specific nonphlogistic, beta(2) integrin-independent mechanisms involving thrombospondin-1 and alpha(v)beta(3) allow macrophages to ingest late apoptotic neutrophils without eliciting inflammatory cytokine secretion.

Animals↗

PubMed2001

Pharmacokinetic behavior of cyclosporin A in rabbits by oral administration of lecithin vesicle and Sandimmun Neoral.

The present study was undertaken to investigate the incorporation of lipophilic polypeptide, cyclosporin A (CsA) into lecithin vesicular system and to compare its pharmacokinetics behavior with Sandimmun Neoral (CsA-NEO). Lecithin vesicles of cyclosporin A (CsA-VES) were prepared by the rotary evaporation method, treated further with sonication. Studies were carried out to characterize the vesicles on physical properties, content, entrapment efficiency, particle size, polydispersity and Zeta potential. Pharmacokinetic behaviors were studied in rabbits at dose of 30 mg/kg. Results showed CyA vesicles were spherical particles, with content of 3.137+/-0.060% mg/ml, entrapment efficiency of 98.91+/-0.80%, particle size of 63.89+/-4.75 nm, polydispersity of 43.2+/-6.1% and Zeta potential of -13 mV. The best model fitting experimental data was a two-compartment open model with first-order kinetics. The relative bioavailability of CsA-VES versus CsA-NEO was 105+/-21% (n=6) and statistical analysis demonstrated both preparations were bioequivalent. In conclusion, lecithin vesicles are promising carriers in the oral delivery of CsA, considering their absorption enhancement effect and low-toxic property.

Administration, Oral↗

PubMed2001

Synthesis of 2-substituted (+/-)-(2r,3r,5r)-tetrahydrofuran-3,5-dicarboxylic acid derivatives.

An efficient synthesis of 2-substituted (+/-)-(2R,3R,5R)-tetrahydrofuran-3,5-dicarboxylic acid derivatives has been developed. Starting from 5-norborne-2-ol, the key intermediate (+/-)-methyl 5,6-exo,exo-(isopropylidenedioxy)-2-oxabicyclo[2.2.1]heptane-3-exo-carboxylate (15) was synthesized in an efficient six-step sequence. The key transformation is the base-catalyzed methanolysis-rearrangement of (+/-)-6,7-exo,exo-(isopropylidenedioxy)-4-exo-iodo-2-oxabicyclo[3.2.1]octan-3-one (14). Further manipulation of the 3-substituent of (+/-)-methyl 5,6-exo,exo-(isopropylidenedioxy)-2-oxabicyclo[2.2.1]heptane-3-exo-carboxylate (15) followed by deprotection of the diol moiety and ring opening catalyzed by RuCl(3)/NaIO(4) gave the title compounds in good yield.

Dicarboxylic Acids↗

PubMed2001

Corticosterone-induced rapid phosphorylation of p38 and JNK mitogen-activated protein kinases in PC12 cells.

The present study showed that corticosterone (B) could induce a rapid activation of p38 and c-Jun NH(2)-terminal protein kinase (JNK) in PC12 cells. The dose-response and time-response curves were bell-shaped with maximal activation at 10(-9) M and at 15 min. RU38486 had no effect, and bovine serum albumin-coupled B could induce the activation. Genistein failed to block the phosphorylation, suggesting the pathway was not involved in tyrosine kinase activity. Phorbol 12-myristate 13-acetate could mimic, while Gö6976 could abolish the actions. These results demonstrated that B might act via a putative membrane receptor to activate p38 and JNK rapidly through a protein kinase C-dependent pathway.

Animals↗

PubMed2001

Astrocytes overexpressing Cu,Zn superoxide dismutase have increased resistance to oxidative injury.

Overexpression of Cu,Zn SOD (SOD1) can increase survival of neurons under some pathological conditions. Prior studies have shown, however, that SOD1 overexpression can reduce neuronal survival during exposure to superoxide generators by a mechanism involving excess H(2)O(2) accumulation. Since astrocytes exhibit greater H(2)O(2) catabolism capacity than do neurons, the present study examined the effects of SOD1 overexpression on astrocyte survival under these conditions. Cultures were prepared from transgenic mice that overexpress human SOD1 and from nontransgenic littermate controls. Exposure to xanthine oxidase/hypoxanthine (XO/HPX) or menadione caused dose-dependent astrocyte death. In contrast to prior observations with neurons, astrocytes that overexpress SOD1 showed increased resistance to superoxide toxicity. Surprisingly, increased survival in SOD1 overexpressing cultures remained evident even when H(2)O(2) catabolism was inhibited by preincubation with aminotriazole (to block catalase) and buthionine sulfoximine (to deplete glutathione). These findings suggest differences in superoxide metabolism between neurons and astrocytes, and that the greater resistance of astrocytes to oxidative stress is due at least partly to factors other than greater glutathione peroxidase and catalase activity in astrocytes. GLIA 33:343-347, 2001. Published 2001 Wiley-Liss, Inc.

Animals↗

PubMed2001

A novel series of highly potent benzimidazole-based microsomal triglyceride transfer protein inhibitors.

A series of benzimidazole-based analogues of the potent MTP inhibitor BMS-201038 were discovered. Incorporation of an unsubstituted benzimidazole moiety in place of a piperidine group afforded potent inhibitors of MTP in vitro which were weakly active in vivo. Appropriate substitution on the benzimidazole ring, especially with small alkyl groups, led to dramatic increases in potency, both in a cellular assay of apoB secretion and especially in animal models of cholesterol lowering. The most potent in this series, 3g (BMS-212122), was significantly more potent than BMS-201038 in reducing plasma lipids (cholesterol, VLDL/LDL, TG) in both hamsters and cynomolgus monkeys.

Administration, Oral↗

PubMed2001

Redirection of T cell effector function in vivo and enhanced collagen-induced arthritis mediated by an IL-2R beta/IL-4R alpha chimeric cytokine receptor transgene.

Chronic inflammatory autoimmune diseases such as diabetes, experimental autoimmune encephalomyelitis, and collagen-induced arthritis (CIA) are associated with type 1 (Th1, Tc1) T cell-dependent responses against autoantigens. Immune deviation toward type 2 (Th2, Tc2) response has been proposed as a potential means of gene therapy or immunomodulation to treat autoimmune diseases based on evidence that type 2 cytokines can prevent or alleviate these conditions. In this report we assessed the effects of elevated type 2 responses on CIA using transgenic mice expressing an IL-2R beta/IL-4R alpha chimeric cytokine receptor transgene specifically in T cells. In response to IL-2 binding, this chimeric receptor transduces IL-4-specific signals and dramatically enhances type 2 responses. In contrast to published reports of Th2-mediated protection, CIA was exacerbated in IL-2R beta/IL-4R alpha chimeric receptor transgenic mice, with increased disease incidence, severity, and earlier disease onset. The aggravated disease in transgenic mice was associated with an increase in type 2 cytokines (IL-4, IL-5, IL-10) and an increase in collagen-specific IgG1 levels. However, IFN-gamma production is not affected significantly in the induction phase of the disease. There is also an extensive eosinophilic infiltration in the arthritic joints of the transgenic animal, suggesting a direct contribution of type 2 response to joint inflammation. Taken together, our findings provide novel evidence that enhancement of a polyclonal type 2 response in immunocompetent hosts may exacerbate an autoimmune disease such as CIA, rather than serving a protective role. This finding raises significant caution with regard to the potential use of therapeutic approaches based on immune deviation toward type 2 responses.

Amino Acid Sequence↗

PubMed2001

RGD-Tachyplesin inhibits tumor growth.

Tachyplesin is an antimicrobial peptide present in leukocytes of the horseshoe crab (Tachypleus tridentatus). In this study, a synthetic tachyplesin conjugated to the integrin homing domain RGD was tested for antitumor activity. The in vitro results showed that RGD-tachyplesin inhibited the proliferation of both cultured tumor and endothelial cells and reduced the colony formation of TSU prostate cancer cells. Staining with fluorescent probes of FITC-annexin V, JC-1, YO-PRO-1, and FITC-dextran indicated that RGD-tachyplesin could induce apoptosis in both tumor and endothelial cells. Western blotting showed that treatment of cells with RGD-tachyplesin could activate caspase 9, caspase 8, and caspase 3 and increase the expression of the Fas ligand, Fas-associated death domain, caspase 7, and caspase 6, suggesting that apoptotic molecules related to both mitochondrial and Fas-dependent pathways are involved in the induction of apoptosis. The in vivo studies indicated that the RGD-tachyplesin could inhibit the growth of tumors on the chorioallantoic membranes of chicken embryos and in syngenic mice.

3T3 Cells↗

PubMed2001

[In vitro study of the biological activities and immunogenicity of recombinant adhesin of Heliobacter pylori rHpaA].

OBJECTIVE: To evaluate the biological activities and immunogenicity of recombinant adhesin of Helicobacter pylori rHpaA in vitro and the feasibility of its application in development of Helicobacter pylori vaccine. METHODS: The effect of rHpaA and its antibody on the adhesion of H. pylori to human gastric epithelial cell lines was investigated by flow cytometry and light microscopy. ELISA was used to measure the HpaA-specific antibodies in sera of H. pylori-infected patients. The proliferation of peripheral blood lymphocytes (PBL) in response to rHpaA was examined by (3)H-TDR incorporation test. Flow cytometry was adopted to detect the selective proliferation effect of rHpaA on different phenotypes of T helper cells in PBLs. RESULTS: Both rHpaA and anti-HpaA serum partially inhibited the adhesion of Heliobacter pylori to gastric epithelial cell lines. Anti-HpaA antibodies (coated with rHpaA) were detected in sera from H. Pylori-infected patients with a detection rate similar to that of anti-HpaA antibodies coated with HpSON (50% Vs 53.75%, P > 0.05). The rHpaA was capable of stimulating the proliferation of PBL (P < 0.05), no matter IL-2 was added into the culture medium or not. Both Hp positive and negative PBLs, after incubation with rHpaA, could significantly raise the proportion of IL-4 positive T cell (Th2 cell) (P < 0.05). CONCLUSION: HpaA is an immunogenic surface protein of H. pylori and can selectively increase the proportion of Th2 cells in vitro and is a hopeful new antigen in the development of H. pylori vaccine.

Adhesins, Bacterial↗

PubMed2001

Two point mutations in mitochondrial DNA of cytochrome c oxidase coexist with normal mtDNA in a patient with Alzheimer's disease.

The mitochondrial cytochrome c oxidase (CO) gene sequence was determined on a patient with Alzheimer's disease (AD). Compared to the standard Cambridge sequence to identify base changes,two missense mutations were found in the patient with AD. The mutations were a G to T transition at np 8206 and an A to T transition at np 8224. The np 8206 mutation changed a Met to an Ile and np 8224 mutation changed a Leu to a Phe. The normal bases and the mutations of mitochondrial DNA (mtDNA) coexist in the patient. Further studies will be required to demonstrate the role of the point mutations of mitochondrial DNA in the pathogenesis of Alzheimer's disease.

Aged↗

PubMed2001

Circulating IL-6 as a predictor of radiation pneumonitis.

PURPOSE: We report results from a clinical research protocol investigating circulating pro-inflammatory cytokines (interleukin-6 [IL-6] and tumor necrosis factor alpha [TNFalpha]) in relation to radiation pulmonary injury. METHODS AND MATERIALS: In a protocol for cytokine measurement, 25 patients had clinical follow-up longer than 12 months, and 24 had serial cytokine data. Serial plasma specimens before, during, and after thoracic radiotherapy were analyzed for IL-6 and TNFalpha using enzyme-linked immunosorbent assay (ELISA). Radiation pulmonary injury was defined using National Cancer Institute Common Toxicity Criteria. RESULTS: Of the 24 patients, 6 had Grade 1 pneumonitis, and 13 had Grade 2 pneumonitis. There was no Grade 3/4 pneumonitis. Median time of radiation pneumonitis was between 8 and 12 weeks post-therapy. IL-6 levels before, during, and after thoracic radiation therapy were significantly higher in those who developed pneumonitis. In contrast, we did not detect a significant correlation between plasma TNFalpha and radiation pneumonitis. CONCLUSIONS: High pretreatment plasma levels of IL-6 predisposed patients to the risk of radiation pneumonitis. Pretreatment IL-6 level may serve as a predictor for radiation pneumonitis. Serial plasma IL-6 was consistently higher for the pneumonitis group. The role of IL-6 in the cytokine cascades that promote radiation pulmonary injury deserves further investigation.

Adult↗

PubMed2001

The human estrogen receptor alpha dimer binds a single SRC-1 coactivator molecule with an affinity dictated by agonist structure.

Nuclear receptors act as ligand-inducible transcription factors. Agonist binding leads to interaction with coactivator proteins, and to the assembly of the general transcription machinery. In addition to structural information, a thorough understanding of transcriptional activation by the nuclear receptors requires the characterization of the thermodynamic parameters governing these protein/protein interactions. In this study we have quantitatively characterized the interactions of full-length baculovirus expressed human estrogen receptor alpha (ERalpha), as well as ERalpha hormone binding domain (ERHBD) with a fragment of the coactivator protein SRC-1 (amino acid residues 570 to 780). Fluorescence anisotropy and fluorescence correlation spectroscopy of fluorescently labeled SRC-1(570-780) demonstrate unambiguously that the stoichiometry of the SRC-1/ERalpha/estradiol complex is one coactivator molecule per ERalpha dimer. The affinity of the estradiol or estriol bound ERalpha/SRC-1 complexes was found to be significantly higher than that observed in the presence of estrone. No binding was observed in the absence of ligand or in the presence of antagonists. Distinct anisotropy values for the ERalpha-SRC-1 complexes with different agonists suggest distinct conformations of the complexes depending upon agonist structure.

Anisotropy↗

PubMed2001

Gene-expression profiles in hereditary breast cancer.

BACKGROUND: Many cases of hereditary breast cancer are due to mutations in either the BRCA1 or the BRCA2 gene. The histopathological changes in these cancers are often characteristic of the mutant gene. We hypothesized that the genes expressed by these two types of tumors are also distinctive, perhaps allowing us to identify cases of hereditary breast cancer on the basis of gene-expression profiles. METHODS: RNA from samples of primary tumor from seven carriers of the BRCA1 mutation, seven carriers of the BRCA2 mutation, and seven patients with sporadic cases of breast cancer was compared with a microarray of 6512 complementary DNA clones of 5361 genes. Statistical analyses were used to identify a set of genes that could distinguish the BRCA1 genotype from the BRCA2 genotype. RESULTS: Permutation analysis of multivariate classification functions established that the gene-expression profiles of tumors with BRCA1 mutations, tumors with BRCA2 mutations, and sporadic tumors differed significantly from each other. An analysis of variance between the levels of gene expression and the genotype of the samples identified 176 genes that were differentially expressed in tumors with BRCA1 mutations and tumors with BRCA2 mutations. Given the known properties of some of the genes in this panel, our findings indicate that there are functional differences between breast tumors with BRCA1 mutations and those with BRCA2 mutations. CONCLUSIONS: Significantly different groups of genes are expressed by breast cancers with BRCA1 mutations and breast cancers with BRCA2 mutations. Our results suggest that a heritable mutation influences the gene-expression profile of the cancer.

Algorithms↗

PubMed2001

Eosinophil peroxidase catalyzes bromination of free nucleosides and double-stranded DNA.

Chronic parasitic infections are a major risk factor for cancer development in many underdeveloped countries. Oxidative damage of DNA may provide a mechanism linking these processes. Eosinophil recruitment is a hallmark of parasitic infections and many forms of cancer, and eosinophil peroxidase (EPO), a secreted hemoprotein, plays a central role in oxidant production by these cells. However, mechanisms through which EPO may facilitate DNA oxidation have not been fully characterized. Here, we show that EPO effectively uses plasma levels of bromide as a cosubstrate to brominate bases in nucleotides and double-stranded DNA, forming several stable novel brominated adducts. Products were characterized by HPLC with on-line UV spectroscopy and electrospray ionization tandem mass spectrometry (LC/ESI/MS/MS). Ring assignments for brominated purine bases as their 8-bromo adducts were identified by NMR spectroscopy. Using stable isotope dilution LC/ESI/MS/MS, we show that while guanine is the preferred purine targeted for bromination as a free nucleobase, 8-bromoadenine is the major purine oxidation product generated following exposure of double-stranded DNA to either HOBr or the EPO/H(2)O(2)/Br(-) system. Bromination of nucleobases was inhibited by scavengers of hypohalous acids such as the thioether methionine, but not by a large molar excess of primary amines. Subsequently, N-monobromoamines were demonstrated to be effective brominating agents for both free nucleobases and adenine within intact DNA. A rationale for selective modification of adenine, but not guanine, in double-stranded DNA based upon stereochemical criteria is presented. Collectively, these results suggest that specific brominated DNA bases may serve as novel markers for monitoring oxidative damage of DNA and the nucleotide pool by brominating oxidants.

Adenine↗

PubMed2001

Field-induced three- and two-dimensional freezing in a quantum spin liquid.

Field-induced commensurate transverse magnetic ordering is observed in the Haldane-gap compound Ni(C(5)D(14)N(2))2N(3)(PF(6)) by means of neutron diffraction. Depending on the direction of applied field, the high-field phase is shown to be either a three-dimensional ordered Néel state or a short-range ordered state with dominant two-dimensional spin correlations. The structure of the high-field phase is determined, and properties of the observed quantum phase transition are discussed.

Journal Article↗

PubMed2001

Flux closure structures in cobalt rings.

Measurements are reported on the magnetization reversal in submicron magnetic rings fabricated by high-resolution electron beam lithography and lift-off from cobalt thin films. For all dimensions investigated, with diameters of 300-800 nm and a thickness of 10-50 nm, the flux closure state is the stable magnetization configuration. However, with increasing diameter and decreasing film thickness a metastable near single domain state can be obtained during the reversal process in an in-plane applied field.

Journal Article↗

PubMed2001

Role of mitochondrial dysfunction in S-(1,2-dichlorovinyl)-l-cysteine-induced apoptosis.

The nephrotoxicity of trichloroethylene and dichloroacetylene has previously been linked to mitochondrial dysfunction induced by the metabolite S-(1,2-dichlorovinyl)-l-cysteine (DCVC). In this study, we examined whether key biochemical steps associated with mitochondria occur in DCVC-induced apoptosis in cultured porcine proximal tubular LLC-PK1 cells. DCVC caused a decrease in mitochondrial membrane potential (mt Delta Psi) beginning at 4 h and a release of cytochrome c into the cytoplasm at 6 h. Caspase-3-like activity was detected at 6 h and extensive DNA fragmentation was observed at 8 h. Decreases in cellular ATP were not evident until 8 h and later, even though electron microscopy showed that the mitochondria were extensively swollen. Aminooxyacetic acid (AOAA), an inhibitor of cysteine-conjugate beta-lyase, protected against mitochondrial changes and apoptosis. Overexpression of the antiapoptotic Bcl-2 protein desensitized LLC-PK1 cells to DCVC-induced apoptosis. These results support the interpretation that mitochondrial release of cyt c and cyt c-dependent activation of caspase-3 could have a central role in nephrotoxicity due to haloalkene-derived cysteine S-conjugates.

Aminooxyacetic Acid↗

PubMed2001

Pilot trial of interleukin-2 with granulocyte colony-stimulating factor for the mobilization of progenitor cells in advanced breast cancer patients undergoing high-dose chemotherapy: expansion of immune effectors within the stem-cell graft and post-stem-cell infusion.

PURPOSE: To evaluate whether administration of interleukin-2 (IL-2) with granulocyte colony-stimulating factor (G-CSF) improves mobilization of immune effector cells into the stem-cell graft of patients undergoing high-dose chemotherapy and autografting. PATIENTS AND METHODS: We performed a trial of stem-cell mobilization with IL-2 and G-CSF in advanced breast cancer patients receiving high-dose chemotherapy with cyclophosphamide, thiotepa, and carboplatin and stem cells followed by IL-2. The trial defined immune, hematologic, and clinical effects of IL-2 in this setting. RESULTS: Of 32 patients enrolled, nine received G-CSF alone for mobilization. Twenty-one of 23 patients mobilized with IL-2 plus G-CSF had stem cells collected with more mononuclear cells than those receiving G-CSF (19.3 v 10.4 x 10(8)/kg; P =.006), but fewer CD34(+) progenitor cells (6.9 v 22.0 x 10(6)/kg; P =.049). The IL-2 plus G-CSF-mobilized patients had greater numbers of activated T (CD3(+)/CD25(+)) cells (P =.009), natural killer (NK; CD56(+)) cells (P =.007), and activated NK (CD56 bright(+)) cells (P: =.039) than those patients mobilized with G-CSF. NK (P =.042) and lymphokine-activated killer (LAK) (P =.016) activity was increased in those mobilized with IL-2 + G-CSF, whereas G-CSF-mobilized patients had a decline in cytolytic activity. In the third week posttransplantation, immune reconstitution was superior in those mobilized with IL-2 plus G-CSF based on greater numbers of activated T cells (P =.003), activated NK cells (P =.04), and greater LAK activity (P =.003). The 16 of 21 IL-2 + G-CSF-mobilized patients with adequate numbers of stem cells (> 1.5 x 10(6) CD34(+) cells/kg) collected engrafted rapidly posttransplantation. CONCLUSION: The results demonstrate that G-CSF + IL-2 can enhance the number and function of antitumor effector cells in a mobilized autograft without impairing the hematologic engraftment, provided that CD34 cell counts are more than 1.5 x 10(6) cells/kg. Mobilization of CD34(+) stem cells does seem to be adversely affected. In those mobilized with IL-2 and G-CSF, post-stem-cell immune reconstitution of antitumor immune effector cells was enhanced.

Adult↗