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Ban-Hock Toh

Publications and source records attributed to Ban-Hock Toh.

At least 19 recordsLinked to original sources
PubMed2006

GM-CSF deficiency reduces macrophage PPAR-gamma expression and aggravates atherosclerosis in ApoE-deficient mice.

OBJECTIVE: Granulocyte-macrophage colony-stimulating factor (GM-CSF) is expressed in atherosclerotic lesions but its significance for lesion development is unknown. Consequently, we investigated the significance of GM-CSF expression for development of atherosclerotic lesions in apolipoprotein E-deficient (apoE(-/-)) mice. METHODS AND RESULTS: We generated apoE(-/-) mice deficient in GM-CSF (apoE(-/-).GM-CSF(-/-) mice), fed them a high-fat diet, and compared lesion development with apoE(-/-) mice. We measured lesion size, macrophage, smooth muscle cell, and collagen accumulation at the aortic sinus, and expression of genes that regulate cholesterol transport and inflammation. No differences in serum cholesterol were found between the 2 groups. Lesion size in hyperlipidemic apoE(-/-).GM-CSF(-/-) increased by 30% (P<0.05), macrophage accumulation doubled, and collagen content reduced by 15% (P<0.05); smooth muscle cell accumulation and vascularity were unaffected. Analysis of PPAR-gamma, ABCA1, and CD36 in lesions showed reduced expression (50%, 65%, and 55%, respectively), whereas SR-A doubled. In peritoneal macrophages, PPAR-gamma and ABCA1 expression was also reduced by 50% and 70%, respectively, as was cholesterol efflux, by 50%. In lesions, pro-inflammatory MCP-1 and tumor necrosis factor (TNF)-alpha expression increased 2- and 3.5-fold, respectively, vascular cell adhesion molecule (VCAM)-1 expression enhanced and interleukin (IL)-1 receptor antagonist reduced by 50%. CONCLUSIONS: GM-CSF deficiency increases atherosclerosis under hypercholesterolemic conditions, indicating antiatherogenic role for GM-CSF. We suggest this protective role is mediated by PPAR-gamma and ABCA1, molecules that affect cholesterol homeostasis and inflammation.

ATP Binding Cassette Transporter 1↗
PubMed2006

Transplantation of bone marrow genetically engineered to express proinsulin II protects against autoimmune insulitis in NOD mice.

BACKGROUND: Type 1 diabetes (T1D) is a T-cell-dependent autoimmune disease resulting from destructive inflammation (insulitis) of the insulin-producing pancreatic beta-cells. Transgenic expression of proinsulin II by a MHC class II promoter or transfer of bone marrow from these transgenic mice protects NOD mice from insulitis and diabetes. We assessed the feasibility of gene therapy in the NOD mouse as an approach to treat T1D by ex vivo genetic manipulation of normal hematopoietic stem cells (HSCs) with proinsulin II followed by transfer to recipient mice. METHODS: HSCs were isolated from 6-8-week-old NOD female mice and transduced in vitro with retrovirus encoding enhanced green fluorescent protein (EGFP) and either proinsulin II or control autoantigen. Additional control groups included mice transferred with non-manipulated bone marrow and mice which did not receive bone marrow transfer. EGFP-sorted or non-sorted HSCs were transferred into pre-conditioned 3-4-week-old female NOD mice and insulitis was assessed 8 weeks post-transfer. RESULTS: Chimerism was established in all major lymphoid tissues, ranging from 5-15% in non-sorted bone marrow transplants to 20-45% in EGFP-sorted bone marrow transplants. The incidence and degree of insulitis was significantly reduced in mice receiving proinsulin II bone marrow compared to controls. However, the incidence of sialitis in mice receiving proinsulin II bone marrow and control mice was not altered, indicating protection from insulitis was antigen specific. CONCLUSIONS: We show for the first time that ex vivo genetic manipulation of HSCs to express proinsulin II followed by transplantation to NOD mice can establish molecular chimerism and protect from destructive insulitis in an antigen-specific manner.

Animals↗
PubMed2006

TGF-beta and cancer: is Smad3 a repressor of hTERT gene?

Transforming growth factor beta (TGF-beta) carries out tumor suppressor activity in epithelial and lymphoid cells, whereas telomerase is required for most cancers. Although the molecular mechanisms by which TGF-beta acts as a tumor suppressor are yet to be fully established, a link between TGFb and its tumor suppressor activity by telomerase has been suggested. Recently, we have noted a novel mode of action for TGF-beta through which human telomerase reverse transcriptase (hTERT) gene is repressed in immortal and neoplastic cells, confirming that one of the mechanisms underlying TGF-beta suppression of tumor growth may be through inhibiting hTERT gene transcription. Moreover, the inhibition of hTERT gene by TGF-beta suggests a cis action of the TGF-beta signaling molecule Smad3 on hTERT promoter directly. This article examines our current understanding and investigation of TGF-beta regulation of telomerase activity, and presents a model in which Smad3 participates in regulating hTERT gene transcription by acting as a repressor directly. Engineering the interface between Smad3 and hTERT gene may lead to a new strategy to inhibit telomerase activity in cancer.

Gene Expression Regulation, Enzymologic↗
PubMed2006

Gene therapy strategies towards immune tolerance to treat the autoimmune diseases.

Autoimmune diseases such as type 1 diabetes and multiple sclerosis pose a significant health burden on our society. As a whole, autoimmune diseases affect approximately 6% of the population and are the third largest disease burden after heart disease and cancer. Such pathologic manifestations arise by way of damaging reactions of B-cell derived antibodies and/or T-cells to self-antigens and are triggered by genetic and environmental factors. Currently there is no known cure, with treatment restricted to toxic, long-term immunosuppressive regimes, replacement therapy and in intractable cases, transplantation of autologous or allogeneic haematopoietic stem cells. In experimental models of autoimmunity, gene therapeutic approaches have demonstrated promise in treating the autoimmune diseases. These include delivery of anti-inflammatory cytokines and exploitation of regulatory T cells. However, none of these approaches provide lasting, long-term benefit. We hypothesise that therapeutically transduced haematopoietic stem cells followed by transplantation is an alternative strategy to establish permanent immune tolerance that can not only prevent autoimmunity but also cure these diseases. Our approach is focused on directing autoimmune disease-specific autoantigen expression in the thymus by genetic manipulation of haematopoietic stem cells to establish molecular chimeras. Our hypothesis originates from experimental studies with a mouse model of experimental autoimmune gastritis (EAG) and more recently with the non-obese diabetic (NOD) mouse model for type 1 diabetes (T1D).

Animals↗
PubMed2005

Histone H3 serine 10 phosphorylation by Aurora B causes HP1 dissociation from heterochromatin.

Histones are subject to numerous post-translational modifications. Some of these 'epigenetic' marks recruit proteins that modulate chromatin structure. For example, heterochromatin protein 1 (HP1) binds to histone H3 when its lysine 9 residue has been tri-methylated by the methyltransferase Suv39h (refs 2-6). During mitosis, H3 is also phosphorylated by the kinase Aurora B. Although H3 phosphorylation is a hallmark of mitosis, its function remains mysterious. It has been proposed that histone phosphorylation controls the binding of proteins to chromatin, but any such mechanisms are unknown. Here we show that antibodies against mitotic chromosomal antigens that are associated with human autoimmune diseases specifically recognize H3 molecules that are modified by both tri-methylation of lysine 9 and phosphorylation of serine 10 (H3K9me3S10ph). The generation of H3K9me3S10ph depends on Suv39h and Aurora B, and occurs at pericentric heterochromatin during mitosis in different eukaryotes. Most HP1 typically dissociates from chromosomes during mitosis, but if phosphorylation of H3 serine 10 is inhibited, HP1 remains chromosome-bound throughout mitosis. H3 phosphorylation by Aurora B is therefore part of a 'methyl/phos switch' mechanism that displaces HP1 and perhaps other proteins from mitotic heterochromatin.

Amino Acid Sequence↗
PubMed2005

Major immunoreactive domains of human ribosomal P proteins lie N-terminal to a homologous C-22 sequence: application to a novel ELISA for systemic lupus erythematosus.

The aim of this study was to identify immunoreactive domains on human ribosomal P0, P1 and P2 proteins, other than the C-22 peptide, to develop a novel ELISA using a combination of these proteins and to compare this ELISA with one using the C-22 peptide. Human recombinant P0, P1, P2 and mutant P0 lacking the homologous C-22 peptide (N-P0) were produced in bacteria and tested by ELISA and immunoblotting using sera from 48 patients with systemic lupus erythematosus (SLE), 48 with an unrelated inflammatory disorder (Crohn's disease) and 47 healthy controls. ELISA with P0, P1 and P2, premixed at equimolar concentrations, gave higher OD readings than each protein tested individually. Eighteen SLE sera tested positive by ELISA with premixed P0, P1, P2 but only 3 tested positive with the C-22 peptide. Twenty-two SLE sera reacted positively, as determined by immunoblotting, with 5 different P protein combinations: P1P2, P0P1P2, P1, P0P1, P0 and P1. Only sera reactive with all three P proteins reacted with the C-22 peptide, with absent or minimal reactivity with N-P0. Native antigens yielded sensitivity (6/48, 13%) similar to the C-22 peptide assay. An ELISA with premixed P1 and P2 gave higher OD values than the arithmetic means with P1 or P2. Fifteen SLE patients had antibodies to double stranded (ds)-DNA, of which 6 also had antibodies to P0P1P2 by ELISA but 12 reactive with P0P1P2 did not have discernable ds-DNA antibodies. Ribosomal P autoantibodies react mainly with epitopes N-terminal to a homologous C-22 peptide. An ELISA with premixed P0, P1 and P2 has 5-fold greater sensitivity (38%) for SLE than an assay with the conventional C-22 peptide (7%). The combined sensitivity for SLE for antibodies to P0P1P2 and ds-DNA is 56%, higher than C-22 and ds-DNA, 38%. Only one of the SLE patients had neuropsychiatric lupus.

Amino Acid Sequence↗
PubMed2005

Telomerase down-regulation does not mediate PC12 pheochromocytoma cell differentiation induced by NGF, but requires MAP kinase signalling.

Telomerase is a ribonucleoprotein complex that maintains chromosomal telomere homeostasis and underlies continuous renewal of stem cells and immortalization of neoplastic cells. Telomerase is down-regulated during cell differentiation, but the mechanisms of down-regulation are largely unknown. Here, we examined roles of mitogen-activated protein (MAP) kinase and phosphatidylinositol-3 (PI3) kinase signalling pathways in telomerase down-regulation triggered by nerve growth factor (NGF), and the role of telomerase down-regulation in NGF-induced neural differentiation in PC12 cells. We report that NGF-induced telomerase down-regulation requires MAP kinase signalling. While mutations of all putative Akt phosphorylation sites in telomerase reverse transcriptase (TERT) has no effect on telomerase activity, inhibition of MAP kinase signalling by PD98059 or U0126 abolishes NGF-induced telomerase down-regulation in a concentration-dependent manner. Reversal of NGF-induced telomerase down-regulation by TERT overexpression does not prevent NGF-induced neural differentiation. Down-regulation of telomerase by silencing TERT gene expression does not trigger cell differentiation in the absence of NGF, nor enhances NGF-induced differentiation. Thus, telomerase, withdraws by a mechanism at TERT gene transcription level involving MAP kinase signalling while cells cease proliferation and undergo differentiation. The withdrawal of telomerase is not required to mediate NGF-induced PC12 cell differentiation and re-establishment of telomerase activity at significant levels does not inhibit differentiation.

Animals↗
PubMed2004

Interaction between p230 and MACF1 is associated with transport of a glycosyl phosphatidyl inositol-anchored protein from the Golgi to the cell periphery.

The molecular basis by which proteins are transported along cytoskeletal tracts from the trans-Golgi network (TGN) to the cell periphery remains poorly understood. Previously, using human autoimmune sera, we identified and characterized a TGN protein, p230/Golgin-245, an extensively coiled-coil protein with flexible amino- and carboxyl-terminal ends, that is anchored to TGN membranes and TGN-derived vesicles by its carboxyl-terminal GRIP domain. To identify molecules that interact with the flexible amino-terminal end of p230, we used this domain as bait to screen a human brain cDNA library in a yeast two-hybrid assay. We found that this domain interacts with the carboxyl-terminal domain of MACF1, a protein that cross-links microtubules to the actin cytoskeleton. The interaction was confirmed by co-immunoprecipitation, an in vitro binding assay, double immunofluorescence images demonstrating overlapped localization in HeLa cells, and co-localization of FLAG-tagged constructs containing the interacting domains of these two proteins with their endogenous partners. Expression in HeLa cells of FLAG-tagged constructs containing the interacting domains of p230 and MACF1 disrupted transport of the glycosyl phosphatidyl inositol-anchored marker protein conjugated with yellow fluorescent protein (YFP-SP-GPI), while trafficking of the transmembrane marker protein, vesicular stomatitis virus glycoprotein conjugated with YFP (VSVG3-GL-YFP), was unaffected. Our results suggest that p230, through its interaction with MACF1, provides the molecular link for transport of GPI-anchored proteins along the microtubule and actin cytoskeleton from the TGN to the cell periphery.

Amino Acid Sequence↗
PubMed2004

Tumor necrosis factor alpha is not implicated in the genesis of experimental autoimmune gastritis.

Experimental autoimmune gastritis (EAG) characterised by mononuclear cell infiltrate, parietal and zymogenic cell destruction and circulating autoantibodies to gastric H(+)/K(+)ATPase is an animal model for human autoimmune gastritis, that leads to pernicious anaemia. We have previously shown that Fas has a role in initiating damage to target cells in EAG. Here we used three strategies to examine the role of TNFalpha in this disease. We administered neutralising anti-TNFalpha antibody either as a single injection or as twice weekly injections for 8 weeks to mice subjected to neonatal thymectomy-induced EAG. To address the role of apoptotic signals through TNFR1, TNFR1 deficient mice were either neonatally thymectomised or crossed to PC-GMCSF transgenic mice that spontaneously develop EAG. Neonatally thymectomised mice treated with anti-TNFalpha antibody developed destructive gastritis and autoantibodies to gastric H(+)/K(+)ATPase similar to control mice. Following either neonatal thymectomy or crossing to PC-GMCSF transgenic mice, TNFR1 deficient mice developed autoantibody-positive destructive gastritis at similar frequency compared with wild type and heterozygous littermates. Our observations that neutralisation of TNFalpha and absence of TNFR1 has no discernible effect on development of EAG suggest that TNFalpha is not required for mucosal cell damage or development of autoimmune gastritis. While blocking TNFalpha activity has therapeutic benefit in certain autoimmune diseases, this is not the case for EAG.

Animals↗
PubMed2004

Pernicious anaemia.

Explore the source record for details and available documents.

Anemia, Pernicious↗
PubMed2004

Induction of tolerance to self-antigens using genetically modified bone marrow cells.

The challenge of finding a lasting cure for autoimmune disease(s) has not been met. Although the use of systemic anti-inflammatory agents still dominates the treatment of these diseases, there is a push towards developing novel and more specific strategies. In addressing autoimmunity, there is the intrinsic need to understand the mechanisms that lead to the development and maintenance of immunological tolerance to self-antigens. Experimental evidence has shown that directed antigen expression in the thymus can induce immunological tolerance to that antigen. This forms the cornerstone of one strategy directed towards the cure of autoimmunity. In this strategy, individuals with autoimmune disease are transplanted with bone marrow stem cells that have been genetically modified and in this way allow expression of the self-antigen in the thymus.

Animals↗
PubMed2003

Stem cells engineered to express self-antigen to treat autoimmunity.

Autoimmune diseases are incurable. We propose a combination curative strategy using haematopoietic stem cells and gene therapy. The strategy should establish molecular chimerism with culprit antigen expressed by donor antigen-presenting cells in the thymus, resulting in immunological tolerance. Our strategy is based on the intrathymic tolerance and disease resistance established by transgenic expression of antigen in the thymus under control of an MHC class II promoter. We propose that transplantation with genetically engineered stem cells provides an advance over current autologous bone marrow transplantation, in that it should remove the significant risk of disease relapse.

Animals↗
PubMed2003

Tolerance established in autoimmune disease by mating or bone marrow transplantation that target autoantigen to thymus.

Autoimmune diseases are a significant cause of death and morbidity, affecting up to 5% of the population. At present, there is no cure. Autologous bone marrow transplantation has been promoted as a treatment for achieving disease reversal and long-term remission. However, clinical trials in progress in Europe and North America report a significant risk of relapse. Here, we have addressed whether we can establish tolerance in an active autoimmune disease model by thymic expression of autoantigen. We show that tolerance and disease resistance can indeed be established in transgenic mice that spontaneously develop granulocyte macrophage colony stimulating factor-induced autoimmune gastritis, by mating them with disease-resistant transgenic mice that target autoantigen to the thymus. T cells from these double-transgenic mice are non-responsive to gastric antigen in vitro and fail to initiate disease following transfer to naive recipients. Further, we show that transplantation with bone marrow from disease-resistant transgenic mice renders recipient mice with gastritis tolerant to autoantigen as shown by a dramatic fall in autoantibody levels and T cell non-responsiveness to antigen in vitro. We suggest that genetically modified bone marrow targeting autoantigen to the thymus may be used to establish tolerance and prevent relapse of autoimmune disease following autologous bone marrow transplantation.

Animals↗
PubMed2002

Fas/CD95 is required for gastric mucosal damage in autoimmune gastritis.

BACKGROUND & AIMS: Experimental autoimmune gastritis (EAG), characterized by a gastric mononuclear cell infiltrate, mucosal cell damage, and autoantibodies to parietal cell-associated H(+)/K(+) adenosine triphosphatase, is a model for human autoimmune gastritis that leads to pernicious anemia. Previous in vitro studies have implicated Fas/CD95 in initiating damage to gastric mucosal cells in humans and an animal model of autoimmune gastritis. Here we used 2 in vivo animal models to examine the role of Fas in the development of mucosal cell damage in autoimmune gastritis. METHODS: We initiated EAG in BALB/cCrSlc mice by neonatal thymectomy and examined for Fas expression in the gastric mucosa by immunohistochemistry. To address the in vivo relevance of Fas in mucosal injury, we examined the stomachs and sera of BALB/cCrSlc lpr/lpr mice subjected to neonatal thymectomy and BALB/cCrSlc nu/nu lpr/lpr mice transferred with lymphocytes from gastritic BALB/cCrSlc mice. RESULTS: Fas expression was up-reguiated in parietal cells of mice with EAG. Neonatally thymectomized lpr/lpr mice were resistant to developing destructive gastritis compared with heterozygous and wild-type littermates. Nu/nu Fas-sufficient mice transferred with lymphocytes from thymectomized lpr/lpr mice developed destructive gastritis. Nu/nu lpr/lpr mice transferred with lymphocytes from gastritic mice developed a nondestructive gastritis. CONCLUSIONS: The observations that Fas is up-regulated in gastric parietal cells of mice with EAG and that Fas-deficient mice are resistant to development of destructive gastritis provide compelling evidence that Fas is required in vivo for development of gastric mucosal cell damage in autoimmune gastritis.

Animals↗
PubMed2002

Organ-specific autoimmunity in granulocyte macrophage-colony stimulating factor (GM-CSF) deficient mice.

Granulocyte macrophage-colony stimulating factor (GM-CSF) is a pleiotrophic proinflammatory cytokine that augments adaptive immunity by linking it to innate immunity. Experimental autoimmune gastritis is an animal model of human autoimmune gastritis and pernicious anaemia. We have previously shown that GM-CSF is expressed in the gastric mucosa of mice with gastritis initiated by neonatal thymectomy (Gastroenterology 110 (1996) 1791) and that transgenic expression of GM-CSF in the stomach induces autoimmune gastritis in mice (J. Immunol. 166 (2001) 2090). Here we have examined the development of autoimmune gastritis initiated by immunisation or by neonatal thymectomy in GM-CSF deficient mice. We found that gastritis develops in GM-CSF deficient mice initiated by neonatal thymectomy but not by immunisation with gastric antigen. These observations suggest that GM-CSF is not absolutely required for the initiation of autoimmunity and highlights the different conclusions that can be drawn using different disease models.

Animals↗
PubMed2002

Autoantibodies in neuropsychiatric lupus.

The American College of Rheumatology presented a consensus document in 1999 proposing the classification of 19 different syndromes defined by neurological and psychiatric manifestations of systemic lupus erythematosus (SLE). The detection of autoantibodies in patient's serum or cerebrospinal fluid has not been used as diagnostic markers for the proposed neuropsychiatric lupus classifications as their disease associations remain highly contentious. Autoantibodies detected in the serum and/or cerebrospinal fluid, that have been reported to segregate with patients presenting with neuropsychiatric lupus include: (1) anti-neuronal antibodies, (2) brain-lymphocyte cross-reactive antibodies, (3) anti-ribosomal P antibodies, (4) anti-phospholipid antibodies and (5) anti-ganglioside antibodies. Tests for anti-neuronal, anti-brain-lymphocyte cross-reactive and anti-ganglioside antibodies remain highly specialized whereas tests for ribosomal P antibodies and for antiphospholipid antibodies are currently routinely available in most diagnostic laboratories. Anti-ribosomal antibodies segregate with SLE. Antiphospholipid P antibodies are markers for the antiphospholipid syndrome. This syndrome may be associated with another disease, commonly SLE. In this setting, neuropsychiatric manifestations in SLE may arise as a consequence of thrombotic episodes involving the cerebral vasculature. There is a pressing need for antibodies to ribosomal P and to phospholipids to be standardized for routine diagnostic application. We conclude that the search for specific antibody marker(s) that can be applied for the routine laboratory diagnosis for neuropsychiatric lupus remains elusive.

Antibodies, Antiphospholipid↗
PubMedDate not supplied

Reversing the autoimmune condition: experience with experimental autoimmune gastritis.

Autoimmune diseases remain a significant health problem in our society, despite the best efforts to understand and treat these conditions. Current clinical treatments are aimed at alleviating the consequences of these diseases, with limited prospects for cure. Our studies with the experimental model of autoimmune gastritis have led us to explore potential curative strategies that can reverse the autoimmune condition. Using mouse models, we have shown that expression of the known gastric autoantigen in the thymus results in immunological tolerance and resistance to the induction of autoimmune gastritis. Also, induced tolerance in donor mice can be transferred to syngeneic recipient mice by bone marrow cells. Strategies based on these observations could lead to reversal of established disease. Transfer of ensuing knowledge to the cure of serious human autoimmune diseases is our ultimate goal.

Animals↗