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Biomedical subjects

B Wang

Publications and source records attributed to B Wang.

At least 109 records · Page 6Linked to original sources
PubMed2001

CD1-restricted NK T cells protect nonobese diabetic mice from developing diabetes.

NK T cells are a unique subset of T cells that recognize lipid antigens presented by CD1d. After activation, NK T cells promptly produce large amounts of cytokines, which may modulate the upcoming immune responses. Previous studies have documented an association between decreased numbers of NK T cells and the progression of some autoimmune diseases, suggesting that NK T cells may control the development of autoimmune diseases. To investigate the role of NK T cells in autoimmune diabetes, we crossed CD1 knockout (CD1KO) mutation onto the nonobese diabetic (NOD) genetic background. We found that male CD1KO NOD mice exhibited significantly higher incidence and earlier onset of diabetes compared with the heterozygous controls. The diabetic frequencies in female mice showed a similar pattern; however, the differences were less profound between female CD1KO and control mice. Early treatment of NOD mice with alpha-galactosylceramide, a potent NK T cell activator, reduced the severity of autoimmune diabetes in a CD1-dependent manner. Our results not only suggest a protective role of CD1-restricted NK T cells in autoimmune diabetes but also reveal a causative link between the deficiency of NK T cells and the induction of insulin-dependent diabetes mellitus.

Animals↗
PubMed2001

Synthesis of 6- and 7- hydroxy-8-azabicyclo[3.2.1]octanes and their binding affinity for the dopamine and serotonin transporters.

Cocaine is a potent stimulant of the central nervous system. Its reinforcing and stimulant effects are related to its ability to inhibit the membrane bound dopamine transporter (DAT). Inhibition of the DAT causes an increase of dopamine in the synapse with a resultant activation of postsynaptic receptors. The rapid onset and short duration of action of cocaine contribute to its high addictive potential. Consequently, the design of tropane analogues of cocaine that display longer onset times on the DAT and extended duration of action is driven by the need to develop cocaine medication. This study extends the exploration of bridge hydroxylated azabicyclo[3.2.1]octanes (tropanes). A series of 6- and 7-hydroxylated tropanes was prepared and evaluated biologically. Structure activity relationships lead to the following conclusions. Bridge hydroxylated tropanes retain biological enantioselectivity but display higher DAT versus SERT selectivity, particularly for the 3 alpha-aryl compounds as compared with the 3beta-aryl compounds, than the bridge unsubstituted analogues. The 7-hydroxyl compounds are more potent at the DAT than their 6-hydroxyl counterparts. The general SAR of the tropanes is maintained and the rank order of potencies based on substitution at the C3 position remains 3,4-dichloro > 2-naphthyl > 4-fluoro > phenyl.

Animals↗
PubMed2001

Multiple paths for activation of naive CD8+ T cells: CD4-independent help.

CD8(+) CTLs play a pivotal role in immune responses against many viruses and tumors. Two models have been proposed. The "three-cell" model focuses on the role of CD4(+) T cells, proposing that help is only provided to CTLs by CD4(+) T cells that recognize Ag on the same APC. The sequential "two-cell" model proposes that CD4(+) T cells can first interact with APCs, which in turn activate naive CTLs. Although these models provide a general framework for the role of CD4(+) T cells in mediating help for CTLs, a number of issues are unresolved. We have investigated the induction of CTL responses using dendritic cells (DCs) to immunize mice against defined peptide Ags. We find that help is required for activation of naive CTLs when DCs are used as APCs, regardless of the origin or MHC class I restriction of the peptides we studied in this system. However, CD8(+) T cells can provide self-help if they are present at a sufficiently high precursor frequency. The important variable is the total number of T cells responding, because class II-knockout DCs pulsed with two noncompeting peptides are effective in priming.

Animals↗
PubMed2001

Activation of NF-kappa B by nontypeable Hemophilus influenzae is mediated by toll-like receptor 2-TAK1-dependent NIK-IKK alpha /beta-I kappa B alpha and MKK3/6-p38 MAP kinase signaling pathways in epithelial cells.

Nontypeable Hemophilus influenzae (NTHi) is an important human pathogen in both children and adults. In children, it causes otitis media, the most common childhood infection and the leading cause of conductive hearing loss in the United States. In adults, it causes lower respiratory tract infections in the setting of chronic obstructive pulmonary disease, the fourth leading cause of death in the United States. The molecular mechanisms underlying the pathogenesis of NTHi-induced infections remain undefined, but they may involve activation of NF-kappa B, a transcriptional activator of multiple host defense genes involved in immune and inflammatory responses. Here, we show that NTHi strongly activates NF-kappa B in human epithelial cells via two distinct signaling pathways, NF-kappa B translocation-dependent and -independent pathways. The NF-kappa B translocation-dependent pathway involves activation of NF-kappa B inducing kinase (NIK)--IKK alpha/beta complex leading to I kappa B alpha phosphorylation and degradation, whereas the NF-kappa B translocation-independent pathway involves activation of MKK3/6--p38 mitogen-activated protein (MAP) kinase pathway. Bifurcation of NTHi-induced NIK-IKK alpha/beta-I kappa B alpha and MKK3/6--p38 MAP kinase pathways may occur at transforming growth factor-beta activated kinase 1 (TAK1). Furthermore, we show that toll-like receptor 2 (TLR2) is required for NTHi-induced NF-kappa B activation. In addition, several key inflammatory mediators including IL-1 beta, IL-8, and tumor necrosis factor-alpha are up-regulated by NTHi. Finally, P6, a 16-kDa lipoprotein highly conserved in the outer membrane of all NTHi and H. influenzae type b strains, appears to also activate NF-kappa B via similar signaling pathways. Taken together, our results demonstrate that NTHi activates NF-kappa B via TLR2-TAK1-dependent NIK--IKK alpha/beta-I kappa B alpha and MKK3/6--p38 MAP kinase signaling pathways. These studies may bring new insights into molecular pathogenesis of NTHi-induced infections and open up new therapeutic targets for these diseases.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed2001

Regulation of vascular endothelial growth factor expression by acidosis in human cancer cells.

The influence of acidosis on the expression of the vascular endothelial growth factor (VEGF) gene was determined. FG human pancreatic adenocarcinoma cells were incubated for various time periods in media at a physiologically relevant pH level (6.7-7.4). The expression of VEGF mRNA and protein secretion was inversely correlated with pH in a pH- and time-dependent manner. Transient acidosis also activated the VEGF promoter/enhancer luciferase reporter, which was consistent with an increased VEGF gene transcription rate and VEGF mRNA half-life. These data indicated that acidosis transcriptionally and posttranscriptionally regulates VEGF expression, suggesting that an acidic tumor microenvironment contributes to tumor angiogenesis and progression.

3' Untranslated Regions↗
PubMed2001

Three conformational polymorphs of di-mu-chlorotetrakis(1-methylboratabenzene)diyttrium: synthesis, x-ray structures, quantum chemical calculations, and lattice energy minimizations.

The reaction of yttrium trichloride with lithium 1-methylboratabenzene (1/2) in toluene (110 degrees C, 3 days) afforded the donor-free dinuclear sandwich complex [(C(5)H(5)BMe)(2)Y(mu-Cl)](2) (1) in 85% yield as pale-yellow crystals. By means of single crystal and powder diffraction methods, three conformational polymorphs, alpha-1 [P2(1)/n (No. 14), monoclinic, a = 6.6124(8) A, b = 14.352(9) A, c = 14.120(1) A, beta = 95.57(1) degrees, V = 1333.7(9) A(3), Z = 2], beta-1 [P2(1)/a (No. 14), monoclinic, a = 8.542(2) A, b = 13.712(6) A, c = 11.76(1) A, beta = 102.60(4) degrees, V = 1344.5(13) A(3), Z = 2], and gamma-1 [Pbca (No. 61), orthorhombic, a = 20.091(5) A, b = 13.527(3) A, c = 9.976(2) A, V = 2711.2(11) A(3), Z = 4], were characterized in the solid state of 1. The molecules in the three phases vary remarkably in the rotational position of boratabenzene ligands with differences of 91.1, 133.1, and 24.9 degrees between each pair. DFT calculations at the B3LYP/LanL2DZ level reveal that the three molecular structures observed in the solid state correspond closely to three minima on the gas-phase potential energy surface. The beta conformation is 2.8 and 7.2 kJ/mol more stable than the alpha and gamma conformations, respectively. Lattice energy minimizations predict that the alpha-1 phase is about 5.5 and 18.7 kJ mol(-)(1) more stable than the beta-1 and gamma-1 modifications, in agreement with the packing coefficients and the molecular volumes of the three crystal structures. While the alpha-1 and beta-1 modifications have comparable total energies, the gamma-1 form is less stable. The total energy differences among the polymorphs are greater than generally expected.

Journal Article↗
PubMed2001

Nonclassical behavior in the capacitance of a nanojunction.

The capacitance of a nanojunction formed by a scanning tunneling microscope (STM) tip and a two-dimensional gold cluster was measured through the single electron tunneling spectroscopy of a double-barrier tunnel junction. By decreasing the STM tip-cluster separation, it was observed that the capacitance first increases and then decreases at short separation. This characteristic clearly deviates from the classical behavior and provides evidence for potential quantum effects on the capacitance.

Journal Article↗
PubMed2001

A glutamic acid decarboxylase 65-specific Th2 cell clone immunoregulates autoimmune diabetes in nonobese diabetic mice.

Several studies have provided indirect evidence in support of a role for beta cell-specific Th2 cells in regulating insulin-dependent diabetes (IDDM). Whether a homogeneous population of Th2 cells having a defined beta cell Ag specificity can prevent or suppress autoimmune diabetes is still unclear. In fact, recent studies have demonstrated that beta cell-specific Th2 cell clones can induce IDDM. In this study we have established Th cell clones specific for glutamic acid decarboxylase 65 (GAD65), a known beta cell autoantigen, from young unimmunized nonobese diabetic (NOD) mice. Adoptive transfer of a GAD65-specific Th2 cell clone (characterized by the secretion of IL-4, IL-5, and IL-10, but not IFN-gamma or TGF-beta) into 2- or 12-wk-old NOD female recipients prevented the progression of insulitis and subsequent development of overt IDDM. This prevention was marked by the establishment of a Th2-like cytokine profile in response to a panel of beta cell autoantigens in cultures established from the spleen and pancreatic lymph nodes of recipient mice. The immunoregulatory function of a given Th cell clone was dependent on the relative levels of IFN-gamma vs IL-4 and IL-10 secreted. These results provide direct evidence that beta cell-specific Th2 cells can indeed prevent and suppress autoimmune diabetes in NOD mice.

Adoptive Transfer↗
PubMed2001

Induction of M3-restricted cytotoxic T lymphocyte responses by N-formylated peptides derived from Mycobacterium tuberculosis.

Major histocompatibility complex (MHC) class I-restricted CD8(+) T cells play a critical role in the protective immunity against Mycobacterium tuberculosis (Mtb). However, only a few Mtb peptides recognized by MHC class Ia-restricted CD8(+) T cells have been identified. Information on epitopes recognized by class Ib-restricted T cells is even more limited. M3 is an MHC class Ib molecule that preferentially presents N-formylated peptides to CD8(+) T cells. Because bacteria initiate protein synthesis with N-formyl methionine, the unique binding specificity of M3 makes it especially suitable for presenting these particular bacterial epitopes. We have scanned the full sequence of the Mtb genome for NH2-terminal peptides that share features with other M3-binding peptides. Synthetic peptides corresponding to these sequences were tested for their ability to bind to M3 in an immunofluorescence-based peptide-binding assay. Four of the N-formylated Mtb peptides were able to elicit cytotoxic T lymphocytes (CTLs) from mice immunized with peptide-coated splenocytes. The Mtb peptide-specific, M3-restricted CTLs lysed the Mtb-infected macrophages effectively, suggesting that these N-formylated Mtb peptides are presented as the naturally processed epitopes by Mtb-infected cells. Furthermore, T cells from Mtb-infected lungs, spleen, and lymph nodes responded to N-formylated Mtb peptides in an M3-restricted manner. Taken together, our data suggest that M3-restricted T cells may participate in the immune response to Mtb.

Animals↗
PubMed2001

Constitutive Sp1 activity is essential for differential constitutive expression of vascular endothelial growth factor in human pancreatic adenocarcinoma.

Vascular endothelial growth factor (VEGF) is a key angiogenic molecule that plays an important role in the growth and metastasis of many types of human cancer, including pancreatic adenocarcinoma. In this study, we explored the regulation of VEGF in human pancreatic cancer cells. Over 70% of the human pancreatic cancer cell lines studied in vitro secreted constitutively high levels of VEGF. High VEGF-secreting cells also generally expressed an elevated steady-state level of VEGF mRNA. Kinetic analysis revealed that the elevated steady-state level of VEGF mRNA was due to enhanced VEGF gene transcription and increased constitutive VEGF promoter activity. Deletive mutation analyses of the VEGF promoter revealed that the region from -109 to -38 bp was essential for constitutive VEGF promoter activity. Further deletion and point mutation analyses indicated that mutation of individual or all of the putative Sp1 binding sites reduced or eliminated the constitutive VEGF promoter activity and abrogated the differential activity of the promoter in high and low VEGF-expressing cells. Consistent with the constitutive VEGF transcription activation, a high level of constitutive Sp1 expression and activity was detected in pancreatic cancer cell lines and pancreatic cancer tissue specimens overexpressing VEGF. Collectively, our data demonstrated that constitutive Sp1 activation is essential for the differential overexpression of VEGF, which in turn plays an important role in the angiogenesis and progression of human pancreatic cancer.

Adenocarcinoma↗
PubMed2001

Changing epidemiology of HIV type 1 infections in India: evidence of subtype B introduction in Bombay from a common source.

India has experienced multiple introductions of diverse HIV-1 subtypes A, B, C, and E, along with subtype B of HIV-2 between the 1980s and early 1990s. In this study, we have carried out a molecular investigation of 21 heterosexually and vertically acquired HIV-infected individuals from the New Bombay area, who tested positive for HIV-1 by commercial enzyme-linked immunosorbent assay (ELISA) and Western blot assay. We have sequenced the proviral DNA segments from the uncultured PBMCs in the hypervariable env V(3) region (286 bp) and a full-length vpr gene (291 bp). Overall, phylogenetic clustering of all Indian strains and also their clustering with subtype B strains were evident from both V(3)- and vpr gene-based trees, strongly supporting their recent introduction from a common source. This is the first report on subtype B introduction in Bombay, a region where subtype C predominates. Overall, these subtype B strains from Bombay shared genetic closeness with subtype B strains from Europe, the United States, and Asia.

Adult↗
PubMed2001

Azepanone-based inhibitors of human and rat cathepsin K.

The synthesis, in vitro activities, and pharmacokinetics of a series of azepanone-based inhibitors of the cysteine protease cathepsin K (EC 3.4.22.38) are described. These compounds show improved configurational stability of the C-4 diastereomeric center relative to the previously published five- and six-membered ring ketone-based inhibitor series. Studies in this series have led to the identification of 20, a potent, selective inhibitor of human cathepsin K (K(i) = 0.16 nM) as well as 24, a potent inhibitor of both human (K(i) = 0.0048 nM) and rat (K(i,app) = 4.8 nM) cathepsin K. Small-molecule X-ray crystallographic analysis of 20 established the C-4 S stereochemistry as being critical for potent inhibition and that unbound 20 adopted the expected equatorial conformation for the C-4 substituent. Molecular modeling studies predicted the higher energy axial orientation at C-4 of 20 when bound within the active site of cathepsin K, a feature subsequently confirmed by X-ray crystallography. Pharmacokinetic studies in the rat show 20 to be 42% orally bioavailable. Comparison of the transport of the cyclic and acyclic analogues through CaCo-2 cells suggests that oral bioavailability of the acyclic derivatives is limited by a P-glycoprotein-mediated efflux mechanism. It is concluded that the introduction of a conformational constraint has served the dual purpose of increasing inhibitor potency by locking in a bioactive conformation as well as locking out available conformations which may serve as substrates for enzyme systems that limit oral bioavailability.

Administration, Oral↗
PubMed2001

Drosophila Rho-associated kinase (Drok) links Frizzled-mediated planar cell polarity signaling to the actin cytoskeleton.

Frizzled (Fz) and Dishevelled (Dsh) are components of an evolutionarily conserved signaling pathway that regulates planar cell polarity. How this signaling pathway directs asymmetric cytoskeletal reorganization and polarized cell morphology remains unknown. Here, we show that Drosophila Rho-associated kinase (Drok) works downstream of Fz/Dsh to mediate a branch of the planar polarity pathway involved in ommatidial rotation in the eye and in restricting actin bundle formation to a single site in developing wing cells. The primary output of Drok signaling is regulating the phosphorylation of nonmuscle myosin regulatory light chain, and hence the activity of myosin II. Drosophila myosin VIIA, the homolog of the human Usher Syndrome 1B gene, also functions in conjunction with this newly defined portion of the Fz/Dsh signaling pathway to regulate the actin cytoskeleton.

Actins↗
PubMed2001

[Dyslipidemia-related risk factors for myocardial infarction and polymorphism of ApoE gene among myocardial infarction patients and their siblings].

OBJECTIVE: To assess the risk factors of myocardial infarction (MI) and the polymorphism of the gene Apoliprotein (ApoE) genotype among MI patients and their siblings. METHODS: Questionnaire survey and clinical examination were conducted to 65 male MI patients, 141 "healthy" male siblings of the MI patients, and 47 healthy persons matched in age and sex. RESULTS: (1) The medians of TC, TG, LDL-C, TC/HDL-C in MI group and sibling group were higher than those in the control group with statistical significance. (2) BMI > 25 kg/m(2), cigarette > 10/d, TC > 5.2 mmol/L, TG > 2.26 mmol/L, LDL-C > 3.4 mmol/L, TC/HDL-C > 5.0, and FBG > 5.6 mmol/L were risk factors for MI; and HDL-C > 0.9 mmol/L was a protective factor for MI. (3) Among the three genotypes of ApoE, E3/3 was the commonest one. However, no significant difference was found in the distribution frequencies of these 3 genotypes, levels of serum lipid and lipoprotein, and TC/HDL-C. (4) Among the MI patients the number of allele E4 carrier was nearly twice the number of the non-allele E4 carrier. CONCLUSION: Dyslipidemia is an important risk factor for MI, and polymorphism of ApoE may be an indirect risk factor of coronary heart disease genetically.

Adult↗
PubMed2001

Human CD1d functions as a transplantation antigen and a restriction element in mice.

To study the potential functions of human CD1d (hCD1d), we developed transgenic (Tg) mice that ectopically express hCD1d under the control of H-2K(b) promoter. High levels of hCD1d expression were detected in all Tg tissues tested. Skin grafts from the K(b)/hCD1d Tg mice were rapidly rejected by MHC-matched non-Tg recipient mice, suggesting that hCD1d can act as transplantation Ags. Furthermore, we were able to elicit hCD1d-restricted CD8(+) CTLs from mice immunized with K(b)/hCD1d Tg splenocytes. These CTLs express TCR rearrangements that are distinct from invariant TCR of NK T cells, and secrete significant amounts of IFN-gamma upon Ag stimulation. Analysis with various hCD1d-expressing targets and use of Ag presentation inhibitors indicated the recognition of hCD1d by CTLs did not involve species or tissue-specific ligands nor require the processing pathways of endosomes or proteasomes. Additionally, the reactivity of hCD1d-specific CTLs was not affected by acid stripping followed by brefeldin A treatment, suggesting that CTLs may recognize a ligand/hCD1d complex that is resistant to acid denaturation, or empty hCD1d molecules. Our results show that hCD1d can function as an alloantigen for CD8(+) CTLs. The hCD1d Tg mice provide a versatile model for the study of hCD1d-restricted cytolytic responses to microbial Ags.

Animals↗