Synthesis of novel 2,4-diaminopyrrolo-[2,3-d]pyrimidines with antioxidant, neuroprotective, and antiasthma activity.
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Animals↗
Biomedical subjects
J E Chin
Publications and source records attributed to J E Chin.
Phenotypic characterization of T lymphocytes emigrating into lung tissue and the airway lumen after antigen inhalation in sensitized mice.
Cytokines released from CD4+ T lymphocytes contribute to the pathogenesis of asthma by influencing the differentiation and function of eosinophils, the primary effector cells that cause airway epithelial damage. Using a model of ovalbumin (OA)-induced, eosinophil-rich chronic lung inflammation in sensitized mice, we have defined the role of T lymphocytes further by using three-color flow cytometry to characterize the adhesion and activation antigens that may be associated with the migration of these cells into the lung and airway lumen. OA inhalation in OA-sensitized C57BL/6 mice resulted in an early (6 to 24 h) influx of neutrophils into the bronchial lumen as enumerated by bronchoalveolar lavage (BAL), which was followed by a marked accumulation of lymphocytes and eosinophils between 24 to 72 h. Phenotypic analysis of BAL or lung tissue T cells showed that most Thy-1 CD3+ T cells were CD4+ (CD4: CD8 ratio of 3 to 4:1). The majority (90%) of the T cells in lung or BAL fluid expressed alpha beta T-cell receptors (TCR). Only 3 to 7% of the T cells were gamma delta TCR+ even though almost 25% of the T cells were CD4- CD8-. There were very few natural killer (NK) or B cells in BAL fluid compared with 15% B cells in dissagregated lung tissue. In contrast to T cells in spleen, almost all the lung and BAL T cells were of the memory phenotype, as ascertained by the expression of high levels of CD44 and by the absence of L-selectin and CD45RB on the cell surface. Fifty to ninety percent of lung and BAL T cells from vehicle-sensitized or OA-sensitized and challenged mice expressed the adhesion molecules CD11a (LFA-1), CD54 (ICAM-1), and CD49d (VLA-4). The early T-cell activation marker CD69 was upregulated on 30% of the lung and BAL T cells in OA-sensitized mice after antigen inhalation. When BAL fluid T cells from OA-sensitized and challenged mice were analyzed for their coexpression of adhesion and/or activation molecules, 75% of the cells that expressed one of three adhesion molecules, CD54, CD49d, or CD11a, also expressed at least one of the other two antigens. At least 15% of BAL T cells had all three of these molecules on their cell surfaces. The OA-dependent, temporally regulated emigration of T cells into the bronchial lumen after exposure to aerosolized antigen may be correlated with the accumulation of cells that express the memory phenotype with enhanced expression of adhesion molecules.
Administration, Intranasal↗
Biochemical mechanisms of insulin resistance.
The insulin receptor tyrosine kinase is required for insulin to elicit subsequent biological signalling. Recent studies have identified several endogenous substrates of the insulin receptor kinase, including one called insulin receptor substrate 1 (IRS-1). Tyrosine phosphorylation of this substrate results in its being bound by various proteins containing src homology 2 (SH2) sites, including a phosphatidylinositol 3-kinase and a ras activator complex containing GRB2 and son of sevenless (SOS) 1. Decreases in the insulin receptor tyrosine kinase activity have been observed in various insulin-resistant states, such as non-insulin-dependent diabetes mellitus. A model of insulin resistance has recently been described in which the insulin receptor is expressed in Chinese hamster ovary cells along with the phospholipid- and calcium-activated serine/threonine kinase called protein kinase C. In this model system, activation of protein kinase C is shown to interfere with insulin receptor signalling by inhibiting tyrosine phosphorylation of IRS-1 and its subsequent binding by phosphatidylinositol 3-kinase. Such a model system may be further utilized to determine the detailed biochemical basis for insulin resistance.
Animals↗
Activation of protein kinase C alpha inhibits insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1.
Chinese hamster ovary (CHO) cells were transfected with a cDNA encoding protein kinase C alpha (PKC) and a cell line (CHO-PKC alpha) expressing approximately 7-fold greater amounts of PKC as the parental cells were isolated. Activation of PKC by 12-O-tetradecanoylphorbol-13-acetate in the CHO-PKC alpha cells inhibited by approximately 75% the: 1) insulin-stimulated increase in antiphosphotyrosine precipitable phosphatidylinositol 3-kinase activity in these cells; 2) insulin-stimulated increase in PI 3-kinase activity associated with insulin receptor substrate-1; and 3) tyrosine phosphorylation of the endogenous substrate, insulin receptor substrate-1. In contrast, 12-O-tetradecanoylphorbol-13-acetate treatment did not inhibit any of these responses in the parental CHO cells. These results indicate that excessive PKC activity can interfere in a very early step in insulin receptor signaling and are consistent with the hypothesis that excessive PKC activity may contribute to some states of insulin resistance.
Animals↗
Attenuation of oxidant-induced lung injury by 21-aminosteroids (lazaroids): correlation with the mRNA expression for E-selectin, P-selectin, ICAM-1, and VCAM-1.
We compared the effects of treatment with methylprednisolone or the 21-aminosteroids, U-74389 and U-74006F (Tirilizad mesylate), on hyperoxic lung injury and the associated expression of mRNA for several adhesion molecules in rats. Inhalation of > 95% oxygen for up to 72 hr in Sprague-Dawley rats produced a marked increase in lung weight and an accumulation of fluid in the thorax when compared with air-breathing controls. Hyperoxia also induced a marked neutrophil-rich influx of inflammatory cells into the bronchial lumen as measured by bronchoalveolar lavage. Neutrophil numbers in bronchoalveolar lavage fluid peaked after 60 hr of exposure to s 95% oxygen; this was associated with a marked upregulation of mRNA for the adhesion molecules P-selectin and E-selectin but not VCAM-1. mRNA for ICAM-1 was constitutively expressed at high levels in both air-breathing controls and in the lungs of rats exposed to high concentrations of oxygen. Pretreatment with the 21-aminosteroids reduced hyperoxic lung damage and improved survival times in animals exposed to > 95% oxygen. However, treatment with methylprednisolone significantly decreased survival times. Treatment with U-74389 did not significantly (p > 0.05) inhibit the BAL neutrophilia and did not significantly (p > 0.05) reduce hyperoxia-induced increases in mRNA expression for P-selectin and E-selectin. The inhibition of hyperoxic lung damage coupled with improved survival seen in treated animals suggests that 21-aminosteroids may provide valuable treatments for pulmonary disorders in which oxidant damage has been implicated.
Animals↗
A comparison of the monocyte monolayer assay with 51chromium red cell recovery for determining the clinical significance of red cell alloantibodies.
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Journal Article↗
Overexpression of protein kinase C isoenzymes alpha, beta I, gamma, and epsilon in cells overexpressing the insulin receptor. Effects on receptor phosphorylation and signaling.
Chinese hamster ovary cells overexpressing the human insulin receptor were transfected with cDNAs encoding protein kinase C isoenzymes alpha, beta I, gamma, and epsilon as well as an inactive alpha. Overexpression of these protein kinase Cs did not affect expression of the insulin receptor or insulin-stimulated tyrosine phosphorylation of the receptor. However, in response to phorbol esters, cells overexpressing isoenzymes alpha, beta I, and gamma, but not epsilon or inactive alpha, exhibited 3-4-fold higher levels of insulin receptor phosphorylation. This increased phosphorylation occurred exclusively on serines and threonine. Tryptic peptide maps indicated that this phosphorylation was primarily on serines 1305/1306 and threonine 1348 as well as several other unidentified sites. This phorbol ester-stimulated phosphorylation did not inhibit activation of the insulin receptor kinase when the receptor was activated in situ but assayed in vitro. However, in cells overexpressing protein kinase C alpha, it did inhibit an in vivo monitor of the activation of the insulin receptor kinase, the insulin-stimulated increase in anti-phosphotyrosine-precipitable phosphatidylinositol 3-kinase activity. These results indicate that increased protein kinase C alpha activity can inhibit insulin-stimulated responses and support the hypothesis that excessive protein kinase C is involved in the insulin resistance observed in non-insulin-dependent diabetics.
Animals↗
Characterization of insulin-stimulated protein serine/threonine kinases in CHO cells expressing human insulin receptors with point and deletion mutations.
The activation of insulin-stimulated protein-serine/threonine kinases has been investigated in CHO cell lines transfected with cDNAs encoding either wild-type or mutant human insulin receptors. (1) Insulin treatment of CHO cells over-expressing wild-type insulin receptors resulted in the rapid and substantial (5-10-fold) activation of cytosolic protein kinases which phosphorylated myelin basic protein, Kemptide and two peptide substrates based on sites phosphorylated on ribosomal protein S6 in vivo. (2) Further fractionation of cytosolic extracts by MonoQ chromatography revealed two peaks of insulin-stimulated myelin basic protein kinase activity which were highly related to the previously described mitogen-activated protein (MAP) kinases ERK1 and ERK2. In addition, at least two major peaks of S6 kinase activity were resolved, which exhibited properties similar to the 70 kDa and 90 kDa S6 kinases described by others; the predominant effect of insulin was on the activity of the 90 kDa enzyme and was in excess of 10-fold. (3) MonoQ fractionation of extracts from parental CHO cells, or cells expressing kinase-deficient receptors, showed all insulin-stimulated peaks of activity to be almost completely absent. (4) Further studies demonstrated that substitution of tyrosine residues 1162 and 1163 (or 1162 alone) with phenylalanine led to a substantial reduction in the ability of insulin to stimulate these protein kinase activities when assayed in cytosolic extracts. In contrast, deletion of 69 amino acids from the C-terminus of the insulin receptor beta-subunit caused a leftward shift in the insulin dose-response curve of the MAP kinase activity, but apparently not in that of the 90 kDa S6 kinase activity.
Amino Acid Sequence↗
Substrates and signalling complexes: the tortured path to insulin action.
In the last few years several potential substrates of the insulin receptor tyrosine kinase have been identified, purified, and their cDNAs isolated. These putative substrates include: 1) pp15, a fatty acid-binding protein; 2) pp120, a plasma membrane ecto-ATPase; 3) pp42, a MAP serine/threonine kinase; 4) pp85, a subunit of the Type 1 phosphatidylinositol kinase; and 5) pp185, a phosphatidylinositol kinase binding protein. Although the tyrosine phosphorylation of several of these substrates correlates with the signalling capabilities of various mutant receptors, the role of these substrates in mediating any one of insulin's many biological responses is still unknown. In addition, recent data indicate that the tyrosine phosphorylation of pp42 may in fact be due to autophosphorylation, thereby removing it from the list of putative substrates of the insulin receptor kinase. Finally, the present review discusses the question of whether signalling occurs as a result of the tyrosine phosphorylation of substrates or via the formation of signalling complexes.
1-Phosphatidylinositol 4-Kinase↗
Evidence for hybrid rodent and human insulin receptors in transfected cells.
Chinese hamster ovary cells and NIH 3T3 cells overexpressing mutant human insulin receptors were examined for the presence of hybrid receptors composed of human and rodent insulin receptors. In the present studies, most of the endogenous rodent receptors were found to be immunoprecipitated from the transfected cells but not the parental cells with a monoclonal antibody specific for human receptor. These data indicate that in these transfected cells, most of the endogenous rodent receptors are in a hybrid complex with the overexpressed human receptor. These results together with the in vitro studies of Treadway et al. (Treadway, J.L., Morrison, B.D., Soos, M.A., Siddle, K., Olefsky, J., Ullrich, A., McClain, D.A., and Pessin, J.E. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 214-218) showing that hybrid receptors exhibit transdominant inhibition explain the prior finding indicating that overexpression of defective insulin receptors interferes with the normal signaling of endogenous receptors.
Animals↗
Biologic effects of an interleukin-1 receptor antagonist protein on interleukin-1-stimulated cartilage erosion and chondrocyte responsiveness.
Recombinant human interleukin-1 alpha (IL-1 alpha) and recombinant human IL-1 beta stimulate matrix proteoglycan degradation and inhibit glycosaminoglycan synthesis in bovine nasal cartilage explants. A 17-kd human recombinant IL-1 receptor antagonist protein (IRAP) caused a concentration-dependent (0.2-200 ng/ml) suppression of the effects of IL-1 alpha and IL-1 beta in cartilage organ cultures. IRAP inhibited the binding of radiolabeled IL-1 alpha to rabbit articular chondrocytes. Matrix metalloproteinase (collagenase, gelatinase, and stromelysin) and prostanoid production by IL-1-activated rabbit articular chondrocytes was also suppressed by IRAP. These results could have potential significance in the development of a new antiarthritis therapy based on an IRAP.
Animals↗
Interactions between interleukin-1 and basic fibroblast growth factor on articular chondrocytes. Effects on cell growth, prostanoid production, and receptor modulation.
The interactions of interleukin-1 beta (IL-1 beta) and basic fibroblast growth factor (bFGF) with monolayer cultures of rabbit articular chondrocytes were examined. Both agonists resulted in a synergistic increase in prostanoid production, to levels higher than the maximal level for either protein alone. The synergy was time- and dose-dependent, was augmented in serum-free medium, and was blocked by indomethacin or a polyclonal antibody to IL-1 beta. The proteins had opposite effects on cell growth, and IL-1 beta completely blocked the mitogenic effect of bFGF. Pretreatment of cells with IL-1 beta induced a down-regulation in the number of the bFGF high-affinity receptors. Pretreatment of cells with bFGF increased the number of IL-1 receptors, which was dependent on messenger RNA synthesis.
6-Ketoprostaglandin F1 alpha↗
Platelet-derived growth factor potentiates cellular responses of articular chondrocytes to interleukin-1.
Recombinant human interleukin-1 alpha (IL-1 alpha) induced a time-dependent (0-72 hours) and concentration-dependent (0.01-10 ng/ml) production of metalloproteinases (collagenase, gelatinase, stromelysin) and prostaglandin E2 (PGE2) in rabbit articular chondrocytes (RAC). Exposure of RAC to recombinant human platelet-derived growth factor homodimer BB (PDGF-BB; 2-200 ng/ml) in the presence of stimulatory and substimulatory concentrations of IL-1 alpha resulted in a marked augmentation of metalloproteinase and PGE2 production. PDGF-BB exerted no agonist effects on RAC responsiveness. PDGF-BB up-regulated the number of IL-1 receptors per chondrocyte but had no effect on receptor affinity. Cycloheximide and actinomycin D caused a concentration-dependent suppression of the PDGF-BB-mediated potentiation of radiolabeled IL-1 alpha binding to RAC and cell responsiveness to IL-1 alpha. Similarly, IL-1 increased the number of PDGF receptors on RAC without changing receptor affinity. These data are discussed within the context of cytokine-growth factor interactions as components of the pathogenesis of arthritic diseases.
Animals↗
T lymphocyte adhesion to human synovial fibroblasts. Role of cytokines and the interaction between intercellular adhesion molecule 1 and CD11a/CD18.
We studied the adhesion of human peripheral blood T lymphocytes to human synovial fibroblasts stimulated with interferon-gamma (IFN gamma), tumor necrosis factor alpha (TNF alpha), interleukin-1 beta (IL-1 beta), or combinations of these cytokines. T lymphocytes bound poorly to untreated human synovial fibroblasts. IFN gamma treatment resulted in the largest increase in adhesion, followed by TNF alpha and IL-1 beta. Combinations of IFN gamma + TNF alpha and IFN gamma + IL-1 beta had a synergistic effect on intercellular adhesion molecule 1 (ICAM-1) expression and adhesion. The increase in cellular adhesion induced by cytokines correlated with the up-regulation of the number of cells expressing ICAM-1 and the density of antigen/cell. There was no synergistic effect on leukocyte function-associated antigen 3 (LFA-3) or on HLA class I or class II antigen expression. Adhesion was only partially inhibited by anti-ICAM-1, anti-LFA-1, or anti-CD18. These findings suggest the existence of ICAM-1--independent and CD11/CD18-independent adhesion mechanisms. Anti-LFA-3 was completely ineffective as an inhibitor of adhesion. There was no additive or synergistic advantage of using combinations of antibodies to increase the level of inhibition, i.e., anti--ICAM-1 + anti-LFA-3, anti-ICAM-1 + anti-CD18, or anti-ICAM-1 + anti-LFA-1 (CD11a). Our data indicate that proinflammatory cytokines may play a prominent role in the formation and exacerbation of synovial hyperplasia, by regulating the recruitment and retention of T lymphocytes via the up-regulation of adhesion molecules on synovial fibroblasts.
Antibodies↗
Role of cytokines in inflammatory synovitis. The coordinate regulation of intercellular adhesion molecule 1 and HLA class I and class II antigens in rheumatoid synovial fibroblasts.
This study was undertaken in an effort to understand the role of cytokines in T lymphocyte trafficking into inflamed synovium and in the potential enhancement of antigen presentation by human synovial fibroblasts. We found that interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha (TNF alpha), and interferon-gamma (IFN gamma) each increased the cell surface expression of intercellular adhesion molecule 1 (ICAM-1) on human synovial fibroblasts in a dose- and time-dependent manner. Maximal ICAM-1 expression occurred within 8 hours of induction, with the following order of efficacy: IFN gamma greater than TNF alpha greater than IL-1 beta. The number of cells bearing the ICAM-1 antigen also increased, from a basal level of approximately 30% to more than 83% after cytokine induction (for all 3 cytokines). ICAM-1 expression rapidly decreased following cytokine removal. The expression of lymphocyte function-associated antigen 3 was also examined, but it was not changed by any of the 3 cytokines. Class I major histocompatibility complex antigen expression was increased modestly by all 3 cytokines, and expression was maximal by 24 hours after treatment. Only IFN gamma induced HLA class II antigen expression, and this expression persisted for up to 6 days following removal of the lymphokine. IL-6 and granulocyte-macrophage colony-stimulating factor had no effect on any of the parameters examined. Our data support an interactive role for inflammatory cytokines and the expression of adhesion ligands and HLA antigens by human synovial fibroblasts in the pathogenesis of synovial inflammation in rheumatoid arthritis.
Antigens, Surface↗
Quantitative analysis of MDR1 (multidrug resistance) gene expression in human tumors by polymerase chain reaction.
The resistance of tumor cells to chemotherapeutic drugs is a major obstacle to successful cancer chemotherapy. In human cells, expression of the MDR1 gene, encoding a transmembrane efflux pump (P-glycoprotein), leads to decreased intracellular accumulation and resistance to a variety of lipophilic drugs (multidrug resistance; MDR). The levels of MDR in cell lines selected in vitro have been shown to correlate with the steady-state levels of MDR1 mRNA and P-glycoprotein. In cells with a severalfold increase in cellular drug resistance, MDR1 expression levels are close to the limits of detection by conventional assays. MDR1 expression has been frequently observed in human tumors after chemotherapy and in some but not all types of clinically refractory tumors untreated with chemotherapeutic drugs. We have devised a highly sensitive, specific, and quantitative protocol for measuring the levels of MDR1 mRNA in clinical samples, based on the polymerase chain reaction. We have used this assay to measure MDR1 gene expression in MDR cell lines and greater than 300 normal tissues, tumor-derived cell lines, and clinical specimens of untreated tumors of the types in which MDR1 expression was rarely observed by standard assays. Low levels of MDR1 expression were found by polymerase chain reaction in most solid tumors and leukemias tested. The frequency of samples without detectable MDR1 expression varied among different types of tumors; MDR1-negative samples were most common among tumor types known to be relatively responsive to chemotherapy.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
Interleukin 1 receptors on rabbit articular chondrocytes: relationship between biological activity and receptor binding kinetics.
This study gives an account of the biologic and kinetic binding properties of interleukin 1 alpha (IL 1 alpha), interleukin 1 beta (IL 1 beta), and Glu-4 (an NH2-terminal mutant of IL 1 beta) to interleukin 1 (IL 1) receptors in rabbit articular chondrocytes. All three IL 1's demonstrated full agonist properties in their ability to stimulate prostaglandin E2 (PGE2) synthesis. IL 1 alpha was 23-fold more biologically active than IL 1 beta, which was around 110-fold more active than Glu-4 based on the concentration of IL 1 required for half-maximal stimulation of PGE2. The binding of all three ligands was concentration-dependent and saturable at 4 degrees C. Scatchard analysis of receptor binding data showed that the dissociation constant (KD) of IL 1 alpha was 46 +/- 12 pM, and the receptor density was 3120 sites/cell. The association of IL 1 alpha at 4 degrees C did not attain equilibrium until after 10 h at 100 pM of 125I-labeled IL 1 alpha. The dissociation of bound IL 1 alpha was very slow, t1/2 of 21 h, although only one class of high-affinity receptors was detected. The KD of IL 1 beta binding was 72 +/- 3 pM with a receptor density of 800 +/- 40 sites/cell. Dissociation of bound 125I-labeled IL 1 beta at 4 degrees C appeared to indicate the presence of two receptor subsets, a fast and a slower component with a t1/2 of 2 min and 5 h, respectively. The receptor binding affinity of Glu-4 was 324 +/- 3 pM, in line with its reduced biologic activity. Both IL 1 alpha and IL 1 beta are rapidly internalized in chondrocytes in a time- and temperature-dependent manner.
Animals↗
Substrates of the insulin receptor kinase.
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1-Phosphatidylinositol 4-Kinase↗