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Biomedical subjects

G Schmitz

Publications and source records attributed to G Schmitz.

At least 55 records · Page 3Linked to original sources
PubMed2001

The zinc finger protein 202 (ZNF202) is a transcriptional repressor of ATP binding cassette transporter A1 (ABCA1) and ABCG1 gene expression and a modulator of cellular lipid efflux.

The zinc finger gene 202 (ZNF202) located within a hypoalphalipoproteinemia susceptibility locus on chromosome 11q23 is a transcriptional repressor of various genes involved in lipid metabolism. To provide further evidence for a functional linkage between ZNF202 and hypoalphalipoproteinemia, we investigated the effect of ZNF202 expression on ATP binding cassette transporter A1 (ABCA1) and ABCG1. ABCA1 is a key regulator of the plasma high density lipoprotein pool size, whereas ABCG1 is another mediator of cellular cholesterol and phospholipid efflux in human macrophage. We demonstrate here that the full-length ZNF202m1 isoform binds to GnT repeats within the promotors of ABCA1 (-229/-210) and ABCG1 (-572/-552). ZNF202m1 expression in HepG2 cells dose-dependently repressed the promotor activities of ABCA1 and ABCG1. This transcriptional effect required the presence of the SCAN domain in ZNF202 and the functional integrity of a TATA box at position -24 of ABCA1, whereas the presence of GnT binding motifs was nonessential. The state of ZNF202 SCAN domain oligomerization affected the ability of the adjacent ZNF202 Krüppel-associated box domain to recruit the transcriptional corepressor KAP1. Overexpression of ZNF202m1 in RAW264.7 macrophages prevented the induction of ABCA1 gene expression by 20(S)OH-cholesterol and 9-cis-retinoic acid, further substantiating the interference of ZNF202 in critical elements of transcriptional activation. Finally, HDL and apoAImediated lipid efflux was significantly reduced in RAW264.7 cells stably expressing ZNF202m1. In conclusion, we have identified ABCA1 and ABCG1 as target genes for ZNF202-mediated repression and thus, provide evidence for a functional linkage between ZNF202 and hypoalphalipoproteinemia.

ATP Binding Cassette Transporter 1↗
PubMed2001

Two novel mutant alleles of the gene encoding neurotrophic tyrosine kinase receptor type 1 (NTRK1) in a patient with congenital insensitivity to pain with anhidrosis: a splice junction mutation in intron 5 and cluster of four mutations in exon 15.

Congenital insensitivity to pain with anhidrosis (CIPA), also called hereditary sensory and autonomic neuropathy type IV (HSAN IV), is caused by mutations of the NTRK1 gene coding for the neurotrophic tyrosine kinase receptor type 1. We report the results of the NTRK1 sequence analysis in a CIPA family from Poland. We found that the patient was in a state of compound heterozygosity. He had one mutant allele with a novel G>A substitution in the conserved splice junction donor site affecting the first base pair of intron 5 (IVS5+1G>A). In the other allele he had a cluster of four single nucleotide substitutions in exon 15: an 1876C>T change (relative to the transcription start site) and three G>T changes (1904G>T, 1909G>T and 1915G>T). All of these mutations change the sense of the codons: H598Y, G607V, E609X and V611L, respectively. Mutations E609X and V611L are novel and unique to the patient family and at least one of them, which creates a premature stop codon in position 609, should have a deleterious effect on the gene function. The other two substitutions H598Y and G607V are most likely rare polymorphisms, which are in linkage disequilibrium. They occur together with an estimated allele frequency of about 6%. Our report increases the spectrum of NTRK1 mutations in CIPA patients and describes an unusual case of a cluster of four mutations located close to each other in one exon.

Alleles↗
PubMed2001

Interaction of CD163 with the regulatory subunit of casein kinase II (CKII) and dependence of CD163 signaling on CKII and protein kinase C.

CD163 is a recently identified member of the scavenger receptor cysteine-rich superfamily, which is expressed on peripheral blood monocytes and most tissue macrophages and is thought to play an important role in the regulation of the inflammatory response of these cells. Cross-linking of CD163 on glucocorticoid-stimulated macrophages results in the secretion of several proinflammatory cytokines, but the precise mechanism of CD163 mediated signal transduction is not understood. The existence of several CD163 isoforms, which differ in the structure of their cytoplasmic domains and putative phosphorylation sites, suggests that these isoforms also differ in their signaling mechanism. Using the Yeast Two-Hybrid system and further in vitro and in vivo studies, we identified the regulatory beta-subunit of casein kinase II (CKII), which specifically binds to the cytoplasmic domain of CD163 and its isoforms. We also found, that in vitro the CD163 isoforms differ in their association with the CKII holoenzyme and in the phosphorylation by CKII. Furthermore, we demonstrated that the cytoplasmic domains of CD163 variants are phosphorylated by PKC-alpha in vitro. Inhibition studies using specific kinase inhibitors reveal that both CKII and PKC are involved in the CD163 signaling mechanism resulting in the secretion of proinflammatory cytokines.

2,3-Diphosphoglycerate↗
PubMed2001

Lipopolysaccharide and ceramide docking to CD14 provokes ligand-specific receptor clustering in rafts.

The glycosylphosphatidylinositol-anchored receptor CD14 plays a major role in the inflammatory response of monocytes to lipopolysaccharide. Here, we describe that ceramide, a constituent of atherogenic lipoproteins, binds to CD14 and induces clustering of CD14 to co-receptors in rafts. In resting cells, CD14 was associated with CD55, the Fcgamma-receptors CD32 and CD64 and the pentaspan CD47. Ceramide further recruited the complement receptor 3 (CD11b/CD18) and CD36 into proximity of CD14. Lipopolysaccharide, in addition, induced co-clustering with Toll-like receptor 4, Fcgamma-RIIIa (CD16a) and the tetraspanin CD81 while CD47 was dissociated. The different receptor complexes may be linked to ligand-specific cellular responses initiated by CD14.

Antigens, CD↗
PubMed2001

Increased histidine decarboxylase expression during in vitro monocyte maturation; a possible role of endogenously synthesised histamine in monocyte/macrophage differentiation.

OBJECTIVE: In this study the expression of histidine decarboxylase (HDC), the pivotal enzyme in histamine formation and the effect of endogenously produced histamine on differentiation antigens was examined during in vitro differentiation of human monocytes. MATERIAL AND TREATMENT: Human elutriated monocytes from healthy volunteers were incubated with macrophage colony stimulating factor (M-CSF) and the expression of HDC was followed at both mRNA and protein levels. To study the possible function of histamine we followed the expression of some cell surface markers (CD14, CD16, CD91, CD49d and CD11c) relevant for phagocytic differentiation upon incubation in the presence of different histamine inhibitors, an HDC inhibitor: S(+)-alpha-fluoromethyl-histidine HCl, (alphaFMH), a compound that disturbs the interaction of histamine with intracellular cyp450 moieties: N,N-diethyl-2-[4-(phenylmethyl) phenoxy]-ethanamine HCI, (DPPE); and H1 and H2 receptor antagonists, Triprolidine and Cimetidine. RESULTS: During in vitro culture of elutriated human monocytes, in the presence of M-CSF, the gene expression and biosynthesis of HDC was considerably increased. The various antihistamine agents decreased the expression of the cell surface markers examined in this study. CONCLUSIONS: These data support the elevation of HDC expression during human monocytic differentiation and the possibility that monocyte-derived histamine is partially involved in regulation of M-CSF induced in vitro human monocyte/macrophage phagocytic differentiation.

Antigens, CD↗
PubMed2001

Pharmacogenomics: implications for laboratory medicine.

Pharmacogenomics deals with the interactions of individual genetic constitution with drug therapy. It has potentially far reaching consequences for drug development and future treatment strategies, but also for clinical in vitro diagnostics. With increasing knowledge about interactions between genes and drug treatment, there will be an equally increasing demand for rapid and reliable diagnostic tests prior to the institution of therapy. In fact, it is very likely that pharmacogenetic tests will make up a significant proportion of total molecular biology testing in the coming years. Therefore, this review focuses on the implications of pharmacogenomics on the clinical laboratory.

Clinical Laboratory Techniques↗
PubMed2001

Apolipoprotein AI and HDL(3) inhibit spreading of primary human monocytes through a mechanism that involves cholesterol depletion and regulation of CDC42.

The objective of the current study was to characterize the influence of high density lipoproteins (HDL) on processes related to the vascular recruitment of human monocytes, which may contribute to the anti-atherogenic properties of these lipoproteins. We show that HDL(3) and apo AI inhibit the following processes in primary human monocytes: (1) M-CSF induced cell spreading; (2) M-CSF stimulated expression of surface molecules involved in adhesion, migration, and scavenging; (3) fMLP induced chemotaxis. These processes are obviously modulated by the regulation of cellular cholesterol pools as indicated by the following findings. In Tangier monocytes with defective apo AI induced cholesterol efflux, apo AI had no influence on the spreading response. In control cells, stimulation of cholesterol efflux by p-cyclodextrin mimicked the effect of apo AI and HDL(3) on spreading and chemotaxis, whereas cholesterol loading with enzymatically modified LDL (E-LDL) showed the opposite effect. Finally, a similar inverse regulation by E-LDL and apo AI/HDL(3) was also observed in regard to the surface expression of beta(1)- and beta(2)-integrins as well as the hemoglobin/haptoglobin scavenger receptor CD163 and the Fcgamma-IIIaR CD16. CDC42 was identified as a potential downstream target linking changes in cellular cholesterol content to monocyte spreading and chemotaxis. Thus, CDC42 antisense markedly reduced spreading and, in parallel with their influence on monocyte spreading, HDL(3), apo AI and p-cyclodextrin down-regulated CDC42 expression while E-LDL had the inverse effect. The apo AI induced decrease of CDC42 protein expression was paralleled by the reduction of active GTP-bound CDC42. In summary, we provide evidence that HDL(3) and apo AI are able to inhibit processes in primary human monocytes, which are related to the recruitment of monocytes into the vessel wall and probably involve regulation of cellular cholesterol pools and CDC42 function.

Apolipoprotein A-I↗
PubMed2001

Rapid improvement of nitric oxide bioavailability after lipid-lowering therapy with cerivastatin within two weeks.

OBJECTIVES: We investigated whether improvement of endothelial dysfunction in hypercholesterolemia can be achieved with short-term lipid-lowering therapy. BACKGROUND: Impaired endothelium-dependent vasodilation plays a pivotal role in the pathogenesis of atherosclerosis and acute coronary syndromes. METHODS: In a randomized, double-blind, placebo-controlled trial, we studied 37 patients (52 +/- 11 yrs) with low density lipoprotein cholesterol > or = 160 mg/dl (196 +/- 44 mg/dl) randomly assigned to either cerivastatin (0.4 mg/d) or placebo. Endothelium-dependent vasodilation of the forearm vasculature was measured by plethysmography and intra-arterial infusion of acetylcholine (ACh 12, 48 microg/min) and endothelium-independent vasodilation by intra-arterial infusion of nitroprusside (3.2, 12.8 microg/min). RESULTS: Low density lipoprotein cholesterol decreased after two weeks of treatment (cerivastatin -33 +/- 4% vs. placebo + 2 +/- 4%, x +/- SEM, p < 0.001). Endothelium-dependent vasodilation improved after two weeks of therapy with cerivastatin compared with baseline (ACh 12 microg/min: + 22.3 +/- 5.2 vs. + 11.2 +/- 1.9 ml/min/100 ml, p < 0.01; ACh 48 microg/min: +31.2 +/- 6.3 vs. +19.1 +/- 3.1 ml/min/100 ml, p < 0.05). In contrast, changes in forearm blood flow to ACh were similar before and after therapy in the placebo group (ACh 12 microg/min: + 12.9 +/- 3.6 vs. + 9.0 +/- 1.9 ml/min/100 ml, NS; ACh 48 microg/min: +20.7 +/- 3.7 vs. 19.4 +/- 2.9 ml/min/100 ml, NS). Endothelium-dependent vasodilation improved in comparison with placebo (ACh 48 microg/min: +203 +/- 85% [cerivastatin] vs. -26 +/- 71% [placebo], p < 0.05). This improvement in endothelium-dependent vasodilation was no longer observed when the nitric oxide-synthase inhibitor N(G)-monomethyl-L-arginine was coinfused (ACh 48 microg/min + N(G)-monomethyl-L-arginine 4 micromol/min -48 +/- 85% [cerivastatin]). CONCLUSIONS: Short-term lipid-lowering therapy with cerivastatin can improve endothelial function and NO bioavailability after two weeks in patients with hypercholesterolemia.

Adult↗
PubMed2001

A novel transposon tagging element for obtaining gain-of-function mutants based on a self-stabilizing Ac derivative.

A novel tagging system AcREH, designed for obtaining gain-of-function mutations, was prepared on the basis of a self-stabilizing Ac transposon derivative. The transposable element, DsAT, was constructed in a way that it can activate transcription of neighboring genes by two 35S promoters and/or by four tandem repeats of the enhancer fragment of this promoter. DsAT revealed somatic excision in the first generation of the tobacco transformants. The element exhibited germinal excision to the next generation, as demonstrated by PCR and Southern hybridization analysis. In spite of the structure of the element, which may inhibit the expression of the transposase gene, the frequency of germinal excision was comparable to or higher than those so far reported, suggesting the applicability of the element for gene tagging.

Base Sequence↗
PubMed2001

Intracellular cholesterol and phospholipid trafficking: comparable mechanisms in macrophages and neuronal cells.

During the past ten years considerable evidences have accumulated that in addition to monocytes/macrophages, that are implicated in innate immunity and atherogenesis, neuronal cells also exhibit an extensive cellular metabolism. The present study focuses on the major protein players that establish cellular distribution of cholesterol and phospholipids. Evidences are provided that neuronal cells and monocytes/macrophages are equipped with comparable intracellular lipid trafficking mechanisms. Selected examples are presented that trafficking dysfunctions lead to disease development, such as Tangier disease and Niemann-Pick disease type C, or contribute to the pathogenesis of diseases such as Alzheimer disease and atherosclerosis.

Animals↗
PubMed2001

A new endotoxin adsorber: first clinical application.

In an open, uncontrolled pilot study, 5 men and 1 woman with suspected gram-negative sepsis were treated with a new whole-blood endotoxin adsorption system. Lipopolysaccharide (LPS) adsorption was carried out by hemoperfusion over high-affinity polymethacrylate-bound albumin (Fresenius Endotoxin Adsorber EN 500). All patients suffered from endotoxemia (>20 pg/ml LAL) and met at least two systemic inflammatory response syndrome (SIRS) criteria. Four patients suffered from pneumonia due to mechanical ventilation, one from peritonitis, and one from pneumonia and peritonitis. Endotoxin adsorption was very well tolerated, and efficient LPS removal was shown in all patients. Apache II score immediately before immunoadsorption was 23.5 and was 22.3 after the last treatment. All 6 critically ill patients improved substantially and were discharged from the intensive care unit. LPS whole blood immunoadsorption is a promising new method. No side effects have been observed thus far. A large controlled study to prove clinical efficacy in patients with severe sepsis is under way.

APACHE↗
PubMed2001

ATP-binding cassette transporter A1 (ABCA1) affects total body sterol metabolism.

BACKGROUND AND AIMS: Members of the family of ABC transporters are involved in different processes of sterol metabolism, and ABCA1 was recently identified as a key regulator of high-density lipoprotein (HDL) metabolism. Our aim was to further analyze the role of ABCA1 in cholesterol metabolism. METHODS: ABCA1-deficient mice (ABCA1-/-) and wild-type mice were compared for different aspects of sterol metabolism. Intestinal cholesterol absorption was determined by a dual stable isotope technique, and analysis of fecal, plasma, and tissue sterols was performed by gas chromatography/mass spectrometry. Key regulators of sterol metabolism were investigated by Northern and Western blot analyses or enzyme activity assays. RESULTS: ABCA1-disrupted sv129/C57BL/6 hybrid mice showed a significant reduction in intestinal cholesterol absorption. The decrease in cholesterol absorption was followed by an enhanced fecal loss of neutral sterols, whereas fecal bile acid excretion was not affected. Total body cholesterol synthesis was significantly increased, with enhanced 3-hydroxy-3-methyglutaryl-coenzyme A (HMG-CoA) reductase observed in adrenals and spleen. In addition, ABCA1-/- mice showed markedly increased concentrations of cholesterol precursors in the plasma, lung, intestine, and feces. Reduced HMG-CoA reductase messenger RNA and enzyme activity in the liver suggest that enhanced cholesterol synthesis in ABCA1-/- mice occurs in peripheral tissues rather than the liver. CONCLUSIONS: The metabolism of cholesterol and cholesterol precursors is markedly affected by a lack of ABCA1 function.

ATP Binding Cassette Transporter 1↗
PubMed2001

The influence of the duration of cardiopulmonary bypass on coagulation, fibrinolysis and platelet function.

BACKGROUND: The duration of cardiopulmonary bypass (CPB) might influence blood coagulation. This appears particularly relevant in the light of new, less invasive techniques that propose smaller incisions at the expense of a possible prolongation of time on CPB. METHODS: The time-dependent effects on coagulation, fibrinolysis and platelet function were investigated in 94 patients scheduled for elective coronary artery bypass grafting. Tests on coagulation, fibrinolysis, and platelet function (flow cytometric assay of expression densities of glycoprotein IIb/IIIa and P-selection were performed the day before surgery and after completion of surgery. RESULTS: A significant correlation was found between the duration of CPB and parameters of increased coagulation, decrease of platelet counts during CPB and platelet function. Longer duration of CPB led to an increased need for transfusion of red blood cells. CONCLUSIONS: The duration of CPB affects thrombin formation as well as platelet count and function, but not the fibrinolytic system. This may prove to be a disadvantage when employing minimally invasive techniques that prolong the duration of CPB.

Aged↗
PubMed2001

Gly15Gly polymorphism within the human adipocyte-specific apM-1gene but not Tyr111His polymorphism is associated with higher levels of cholesterol and LDL-cholesterol in caucasian patients with type 2 diabetes.

UNLABELLED: The recently described mutations within the human adipocyte-specific apM-1 gene might play a role in the pathogenesis of obesity, type 2 diabetes and related metabolic disorders. DESIGN: Frequency of apM-1 gene polymorphisms and their association with metabolic parameters was evaluated in a population-based sample of 556 type 2 (316 males / 240 females) diabetic patients. PCR-based RFLP analysis was performed in blood samples. The T --> G transition at nucleotide +45 within exon-2 [Gly15Gly] was detected with an allelic frequency of 0.91 for the wildtype allele and 0.09 for the mutated allele. The missense point mutation (TAC --> CAC) at nucleotide +331 within exon 3 [Tyr111His] was detected with an allelic frequency of 0.97 and 0.03, respectively. These frequencies did not differ from a non-diabetic cohort examined earlier. Concerning the Gly15Gly polymorphism, the TT-genotype was found in 457 (82.2%) and the TG-genotype in 99 (17.8%), concerning the Tyr111His polymorphism, TT-genotype was found in 525 (94.4) and TC-genotype in 31 (5.6%) of type 2 diabetic patients. In TG-genotype as compared to TT-genotype significantly more patients had LDL-serum levels in high LDL-classes (<150 mg/dl: 24.4% (TG) vs. 41.4% (TT), 150mg/dl to 190mg/dl: 40.0% (TG) vs. 33.9% (TT), >190 mg/l: 35.6% (TG) vs. 25.0% (TT); p = 0.010). No differences in serum levels of lipids were found in genotype-subgroups of the Tyr111His polymorphism. Thus, Gly15Gly polymorphism of apM-1 gene might play a role in dyslipidaemia in type 2 diabetic patients.

Adipocytes↗
PubMed2001

Gene variants of the bactericidal/permeability increasing protein and lipopolysaccharide binding protein in sepsis patients: gender-specific genetic predisposition to sepsis.

OBJECTIVES: To determine whether the genotype frequencies of the five bi-allelic polymorphisms in the bactericidal/permeability increasing protein (BPI) (Lys216 --> Glu; PstI polymorphism in intron 5; silent mutation G545 --> C) and the lipopolysaccharide binding protein (LBP) (Cys98 --> Gly; Pro436 --> Leu) are associated with the incidence and lethality of sepsis. DESIGN: Case control study of patients with sepsis. SETTING: Intensive care units within university hospitals. PATIENTS: A total of 204 patients diagnosed with sepsis and 250 healthy blood donors. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Short DNA fragments containing the polymorphic sites of the LBP and BPI locus were amplified by the polymerase chain reaction or mismatched polymerase chain reaction. The individual polymorphisms were determined with the appropriate restriction enzyme digestions and subsequent agarose gel electrophoresis. The presence of LBP genotypes with the less frequent Gly98 allele was found to be associated with sepsis (p < .02) in male patients, but not in females. Patients which were homozygote for either of the rare Gly98 (n = 6) and/or Leu436 (n = 5) LBP alleles, furthermore, exclusively were nonsurvivors of sepsis. The genotype frequencies in the BPI gene did not differ between patients and control individuals. CONCLUSIONS: Our findings suggest that common polymorphisms in the gene for LBP in combination with male gender are associated with an increased risk for the development of sepsis and, furthermore, may be linked to an unfavorable outcome. These data support the important immunomodulatory role of LBP in Gram-negative sepsis and suggest that genetic testing may be helpful for the identification of patients with an unfavorable response to Gram-negative infection.

Acute-Phase Proteins↗
PubMed2001

Structure, function and regulation of the ABC1 gene product.

The role of the ATP-binding cassette transporter 1 (ABCA1) in cellular lipid efflux and high density lipoprotein metabolism has been recently documented by mutations in genetic HDL deficiency syndromes such as classical Tangier disease. Analysis of ABCA1 knockout mice and overexpression studies have established the importance of ABCA1 as a major determinant of HDL cholesterol in plasma. These studies also indicate that ABCA1 is critically involved in cellular trafficking of cholesterol and choline-phospholipids and in total body lipid homeostasis, such as intestinal cholesterol and fat-soluble vitamin absorption and in the modulation of steroidogenesis. First insights into the upregulation of ABCA1 gene expression by cellular cholesterol and cAMP have identified critical ABCA1 promoter elements, which bind the transcription factors liver X receptor, retinoid X receptor, Sp1 and E-box proteins. The finding that a lipid sensitive subgroup of ABC transporters is able to translocate cholesterol and phospholipids supports the concept that in ABCA1 deficiency, compensatory mechanisms possibly involving MDR1, MDR3 and MRP-family members could be active. This suggests that a network of ABC transporters involved in cellular lipid transport exists, which is under the tight control of energy pathways directly linked to high density lipoprotein metabolism and atherogenesis.

ATP Binding Cassette Transporter 1↗