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  • Beta2-glycoprotein I can exist in 2 conformations: implications for our understanding of the antiphospholipid syndrome. 20462962

    The antiphospholipid syndrome is defined by the presence of antiphospholipid antibodies in blood of patients with thrombosis or fetal loss. There is ample evidence that beta(2)-glycoprotein I (beta(2)GPI) is the major antigen for antiphospholipid antibodies. The autoantibodies recognize beta(2)GPI when bound to anionic surfaces and not in solution. We showed that beta(2)GPI can exist in at least 2 different conformations: a circular plasma conformation and an "activated" open conformation. We also showed that the closed, circular conformation is maintained by interaction between the first and fifth domain of beta(2)GPI. By changing pH and salt concentration, we were able to convert the conformation of beta(2)GPI from the closed to the open conformation and back. In the activated open conformation, a cryptic epitope in the first domain becomes exposed that enables patient antibodies to bind and form an antibody-beta(2)GPI complex. We also demonstrate that the open conformation of beta(2)GPI prolonged the activated partial thromboplastin time when added to normal plasma, whereas the activated partial thromboplastin time is further prolonged by addition of anti-beta(2)GPI antibodies. The conformational change of beta(2)GPI, and the influence of the autoantibodies may have important consequences for our understanding of the antiphospholipid syndrome.
    Document Type:
    Reference
    Product Catalog Number:
    UFC30GV0S
    Product Catalog Name:
    Ultrafree-MC Centrifugal Filter

  • Phosphorylation and desensitization of human endothelin A and B receptors. Evidence for G protein-coupled receptor kinase specificity. 9211925

    Although endothelin-1 can elicit prolonged physiologic responses, accumulating evidence suggests that rapid desensitization affects the primary G protein-coupled receptors mediating these responses, the endothelin A and B receptors (ETA-R and ETB-R). The mechanisms by which this desensitization proceeds remain obscure, however. Because some intracellular domain sequences of the ETA-R and ETB-R differ substantially, we tested the possibility that these receptor subtypes might be differentially regulated by G protein-coupled receptor kinases (GRKs). Homologous, or receptor-specific, desensitization occurred within 4 min both in the ETA-R-expressing A10 cells and in 293 cells transfected with either the human ETA-R or ETB-R. In 293 cells, this desensitization corresponded temporally with agonist-induced phosphorylation of each receptor, assessed by receptor immunoprecipitation from 32Pi-labeled cells. Agonist-induced receptor phosphorylation was not substantially affected by PKC inhibition but was reduced 40% (p < 0.03) by GRK inhibition, effected by a dominant negative GRK2 mutant. Inhibition of agonist-induced phosphorylation abrogated agonist-induced ETA-R desensitization. Overexpression of GRK2, -5, or -6 in 293 cells augmented agonist-induced ET-R phosphorylation approximately 2-fold (p < 0.02), but each kinase reduced receptor-promoted phosphoinositide hydrolysis differently. While GRK5 inhibited ET-R signaling by only approximately 25%, GRK2 inhibited ET-R signaling by 80% (p < 0.01). Congruent with its superior efficacy in suppressing ET-R signaling, GRK2, but not GRK5, co-immunoprecipitated with the ET-Rs in an agonist-dependent manner. We conclude that both the ETA-R and ETB-R can be regulated indistinguishably by GRK-initiated desensitization. We propose that because of its affinity for ET-Rs demonstrated by co-immunoprecipitation, GRK2 is the most likely of the GRKs to initiate ET-R desensitization.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • Connexin43 gene expression in the rabbit arterial wall: effects of hypercholesterolemia, balloon injury and their combination. 9075822

    The specialized functions of endothelium require intercellular communication between endothelial cells within the monolayer, and between endothelium and other cells present in the vessel wall. This is accomplished by a combination of paracrine soluble mediators and direct gap-junctional intercellular communication (GJIC) mediated by a family of connexin proteins. A prominent connexin expressed by vascular cells in vivo and in vitro is connexin 43 (Cx43). We have investigated the in vivo gene regulation of Cx43 in the context of vascular pathology, as a result of mechanical injury, hypercholesterolemia or both. The aortoiliac bifurcation in the rabbit was examined following three types of insult: (1) diet-induced hypercholesterolemia resulting in macrophage-rich fatty streak lesions, (2) mechanical, stretch-denudation injury resulting in intimal smooth muscle cell (SMC) proliferation and (3) mechanical injury superimposed on hypercholesterolemia resulting in a complex vascular lesion having characteristics of both interventions. The normal rabbit iliac artery expressed approximately equal levels of Cx43 mRNA in the medial SMC layers and in the endothelium. In hypercholesterolemia-induced atherosclerosis, Cx43 expression was most prominent in macrophage foam cells even though normocholesterolemic precursor monocytes did not express Cx43 mRNA. Antibodies directed specifically to Cx43 protein confirmed the expression of macrophage gap junction protein in these cells. Medial SMC in hypercholesterolemia exhibited less Cx43 than their normal counterparts in control animals. Mechanical injury in the absence of hypercholesterolemia resulted in intimal thickening in which Cx43 expression in the intimal SMC was equivalent to that in the subjacent medial SMC, both being approximately equivalent to normal uninjured rabbit medial SMC expression. Cell-specific expression of Cx43 in combined mechanical injury/hypercholesterolemia was similar to that observed in hypercholesterolemia alone: Cx43 upregulation in macrophages, while medial SMC were downregulated. Normo- and hypercholesterolemic alveolar macrophages of the lung and Kupffer cells of the liver did not exhibit induction of Cx43 mRNA, nor did macrophages isolated from peritoneal or bronchial lavage fluid of the same animals. This work extends our previous finding of Cx43 upregulation in human atherectomy tissue and demonstrates that atherosclerotic lesions in situ, in a controlled animal model of atherosclerosis, exhibit cell-specific changes in Cx43 gene expression. Changes in medial SMC migration, proliferation and phenotype, as well as enhanced interactions between adherent/infiltrating monocytes and endothelium may be related to modified GJIC pathways in the vessel wall.
    Document Type:
    Reference
    Product Catalog Number:
    MAB3068

  • Dermatophagoides-farinae-induced pulmonary eosinophilic inflammation in mice. 8980467

    Dermatophagoides farinae (Der f) is one of the most common species of dust mites that induce asthma and allergic rhinitis. We have reported that Der f challenge on sensitized mice elicited a distinct type of hypersensitivity, called early-type hypersensitivity (ETH), in subcutaneous tissues and in airways. The airway ETH was accompanied by a series of inflammatory and immunological events including cytokine production, adhesion molecule expression, inflammatory cell infiltration, eosinophilia, and airway hyperreactivity. In the present study, we further defined the course of the Der-f-induced eosinophilia and examined the local cytokine gene expression and the roles of cytokines, mast-cell-derived vasoactive amines, and corticosteroids in the development of pulmonary eosinophilia. BALB/c mice were sensitized with crude extract of Der f in complete Freund's adjuvant and were intranasally challenged with Der f on day 14 after sensitization. The number of blood eosinophils, total and differential leukocyte counts in bronchoalveolar lavage (BAL) fluids, and the expression of cytokine genes in BAL cells were assessed at various time points after challenge for up to 12 days. The total number of leukocytes in the BAL fluids was increased 6 h after challenge (AC) and peaked at 72 h. The early cellular response in the BAL fluids was dominated by neutrophils which were subsequently replaced by a marked infiltration of eosinophils. The number of eosinophils in BAL fluids increased at 24 h and peaked at 72 h, making up 43% of all cells recovered by BAL. BAL eosinophils declined gradually to normal background levels around day 12. Concurrently, there was a significant reduction in the number of eosinophils in blood 24 h AC. The number of blood eosinophils increased thereafter, reached a peak at 72 h, and remained above baseline level for up to 10 days. Saline challenge did not induce eosinophilia in BAL fluids and blood of sensitized mice. Histopathological examination revealed a mixed granulocytic, monocytic pulmonary inflammation with a large number of eosinophils accumulating within the submucosa of the airways and blood vessels of sensitized mice after challenge. Der f challenge induced a sequential expression pattern of eight cytokine genes in BAL cells. The mRNA of interleukin (IL)-1 beta and tumor necrosis factor (TNF)-alpha strongly expressed throughout the course of the experiment. The IL-6 mRNA expression peaked at 0.5-72 h, IL-10 at 1-6 and 48-72 h, IL-4 at 6-72 h, IL-2 at 6-96 h, IL-5 at 24-72 h, and interferon-gamma at 24-96 h. Intraperitoneal injection of sensitized mice with monoclonal antibody (mAb) to murine IL-5 (TRFK5, 300 micrograms/mouse) 1 h before challenge caused 62% suppression of eosinophils in the BAL fluids. The concomitant accumulation of neutrophils and mononuclear cells, however, was not affected by this treatment. On the other hand, intranasal administration of mAb to murine TNF-alpha (MP6-XT3, 20 micrograms/ mouse), but not IL-5, 1 h before challenge and 24 h AC significantly reduced the numbers of eosinophils, neutrophils, and lymphocytes in the BAL fluids. The intraperitoneal injection of dexamethasone (50 mg/kg) for a total of four times resulted in total inhibition of the Der-f-induced cellular responses, whereas vasoactive amine antagonists (diphenhydramine, ketanserin and cyprohepatidine) did not show any effect.
    Document Type:
    Reference
    Product Catalog Number:
    05-168
    Product Catalog Name:
    Anti-TNFα Antibody, clone MPG-XT3

  • Ethnicity modifies the effect of obesity on insulin resistance in pregnancy: a comparison of Asian, South Asian, and Caucasian women. 16249285

    CONTEXT: Women of Asian and South Asian descent are at increased risk of developing gestational diabetes mellitus compared with Caucasians, despite lower body mass index (BMI). Nevertheless, there has been limited study of insulin action during pregnancy in these ethnic groups. OBJECTIVE: The objective of the study was to compare insulin sensitivity in pregnancy in Asian, South Asian, and Caucasian subjects and to determine whether the impact of obesity on insulin action is modified by ethnicity. DESIGN AND PARTICIPANTS: A cross-sectional study was performed in outpatients undergoing oral glucose tolerance testing in late pregnancy. Participants were stratified into three groups: 1) Caucasian (n = 116); 2) South Asian (n = 31); and 3) Asian (n = 28). MAIN OUTCOME MEASURE: Insulin sensitivity was measured using the oral glucose tolerance test (IS(OGTT)) index of M. Matsuda and R. DeFronzo, previously validated in pregnancy. Results: There were no significant ethnic differences in insulin sensitivity despite variation in prepregnancy BMI (Caucasians, 25.2 kg/m(2); South Asians, 23.3 kg/m(2); Asians, 21.4 kg/m(2); overall P = 0.0001). On multiple linear regression analysis, the strongest independent determinants of IS(OGTT) were gestational diabetes mellitus (t = -5.71; P 0.0001) and BMI (t = -5.43; P 0.0001). Importantly, both Asian (t = -2.87; P = 0.0047) and South Asian (t = -2.46; P = 0.015) ethnicity also emerged as negative, independent determinants of IS(OGTT). Furthermore, Asian ethnicity significantly modified the association of prepregnancy BMI with IS(OGTT) (interaction term, t = -2.29; P = 0.0231). CONCLUSIONS: Asian and South Asian ethnicity are both independently associated with increased insulin resistance in late pregnancy. Prepregnancy BMI has a much greater effect on insulin resistance in pregnancy in Asian women than in Caucasians. Ethnicity thus emerges as a factor that modulates the effect of obesity on insulin resistance in pregnancy.
    Document Type:
    Reference
    Product Catalog Number:
    HPI-15K
    Product Catalog Name:
    Human Proinsulin RIA

  • Kaempferol stimulates bone sialoprotein gene transcription and new bone formation. 20564228

    Kaempferol is a typical flavonol-type flavonoid that is present in a variety of vegetables and fruits, and has a protective effect on postmenopausal bone loss. Bone sialoprotein (BSP) is thought to function in the initial mineralization of bone and could be crucial for osteoblast differentiation, bone matrix mineralization and tumor metastasis. In the present study we investigated the regulation of BSP transcription by kaempferol in rat osteoblast-like UMR106 cells, and the effect of kaempferol on new bone formation. Kaempferol (5 microM) increased BSP and Osterix mRNA levels at 12 h and up-regulated Runx2 mRNA expression at 6 h. Kaempferol increased luciferase activity of the construct pLUC3, which including the promoter sequence between nucleotides -116 to +60. Transcriptional stimulation by kaempferol abrogated in constructs included 2 bp mutations in the inverted CCAAT, CRE, and FRE elements. Gel shift analyses showed that kaempferol increased nuclear protein binding to CRE and FRE elements, whereas the CCAAT-protein complex did not change after kaempferol stimulation. Twelve daily injections of 5 microM kaempferol directly into the periosteum of parietal bones of newborn rats increased new bone formation. These data suggest that kaempferol increased BSP gene transcription mediated through inverted CCAAT, CRE, and FRE elements in the rat BSP gene promoter, and could induce osteoblast activities in the early stage of bone formation.
    Document Type:
    Reference
    Product Catalog Number:
    AB5728

  • Lead exposure during synaptogenesis alters vesicular proteins and impairs vesicular release: potential role of NMDA receptor-dependent BDNF signaling. 20375082

    Lead (Pb(2+)) exposure is known to affect presynaptic neurotransmitter release in both in vivo and cell culture models. However, the precise mechanism by which Pb(2+) impairs neurotransmitter release remains unknown. In the current study, we show that Pb(2+) exposure during synaptogenesis in cultured hippocampal neurons produces the loss of synaptophysin (Syn) and synaptobrevin (Syb), two proteins involved in vesicular release. Pb(2+) exposure also increased the number of presynaptic contact sites. However, many of these putative presynaptic contact sites lack Soluble NSF attachment protein receptor complex proteins involved in vesicular exocytosis. Analysis of vesicular release using FM 1-43 dye confirmed that Pb(2+) exposure impaired vesicular release and reduced the number of fast-releasing sites. Because Pb(2+) is a potent N-methyl-D-aspartate receptor (NMDAR) antagonist, we tested the hypothesis that NMDAR inhibition may be producing the presynaptic effects. We show that NMDAR inhibition by aminophosphonovaleric acid mimics the presynaptic effects of Pb(2+) exposure. NMDAR activity has been linked to the signaling of the transsynaptic neurotrophin brain-derived neurotrophic factor (BDNF), and we observed that both the cellular expression of proBDNF and release of BDNF were decreased during the same period of Pb(2+) exposure. Furthermore, exogenous addition of BDNF rescued the presynaptic effects of Pb(2+). We suggest that the presynaptic deficits resulting from Pb(2+) exposure during synaptogenesis are mediated by disruption of NMDAR-dependent BDNF signaling.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple