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R R Schumann

Publications and source records attributed to R R Schumann.

At least 19 recordsLinked to original sources
PubMed2006

Escherichia coli strain Nissle 1917 ameliorates experimental colitis via toll-like receptor 2- and toll-like receptor 4-dependent pathways.

Toll-like receptors (TLRs) are key components of the innate immune system that trigger antimicrobial host defense responses. The aim of the present study was to analyze the effects of probiotic Escherichia coli Nissle strain 1917 in experimental colitis induced in TLR-2 and TLR-4 knockout mice. Colitis was induced in wild-type (wt), TLR-2 knockout, and TLR-4 knockout mice via administration of 5% dextran sodium sulfate (DSS). Mice were treated with either 0.9% NaCl or 10(7) E. coli Nissle 1917 twice daily, followed by the determination of disease activity, mucosal damage, and cytokine secretion. wt and TLR-2 knockout mice exposed to DSS developed acute colitis, whereas TLR-4 knockout mice developed significantly less inflammation. In wt mice, but not TLR-2 or TLR-4 knockout mice, E. coli Nissle 1917 ameliorated colitis and decreased proinflammatory cytokine secretion. In TLR-2 knockout mice a selective reduction of gamma interferon secretion was observed after E. coli Nissle 1917 treatment. In TLR-4 knockout mice, cytokine secretion was almost undetectable and not modulated by E. coli Nissle 1917, indicating that TLR-4 knockout mice do not develop colitis similar to the wt mice. Coculture of E. coli Nissle 1917 and human T cells increased TLR-2 and TLR-4 protein expression in T cells and increased NF-kappaB activity via TLR-2 and TLR-4. In conclusion, our data provide evidence that E. coli Nissle 1917 ameliorates experimental induced colitis in mice via TLR-2- and TLR-4-dependent pathways.

Animals↗
PubMed2005

Chronic periodontal disease is associated with single-nucleotide polymorphisms of the human TLR-4 gene.

Periodontitis is an inflammatory disease affecting the connective tissue surrounding the teeth leading to tooth loss. Pathogens associated with periodontitis interact with Toll-like receptors (TLRs) to induce cytokines causing and aggravating disease. We screened 197 individuals suffering from generalized periodontitis for the presence of Asp299Gly and Thr399Ile of TLR-4 as well as Arg753Gln of TLR-2 in comparison to matched controls. Single-nucleotide polymorphisms (SNPs) of TLR-4 were elevated among patients (odd's ratio 3.650, 95% CI 1.573-8.467, P < or = 0.0001), while no difference was observed for TLR-2. TLR-4 SNPs were correlated with chronic periodontitis (odd's ratio 5.562, 95% CI 2.199-14.04, P < or = 0.0001), but not with aggressive periodontitis. This observation was confirmed employing a group of periodontally healthy probands over 60 years of age. These data demonstrate that genetic variants of TLR-4 may act as risk factors for the development of generalized chronic periodontitis in humans.

Adult↗
PubMed2004

A coding mutation within the first exon of the human MD-2 gene results in decreased lipopolysaccharide-induced signaling.

MD-2 is an accessory protein of the Toll-like receptor (TLR)-4, necessary for assembling a receptor complex to sense low quantities of lipopolysaccharide in order to subsequently trigger innate immune responses. MD-2 and TLR-4 are expressed on a variety of immunocompetent cells. Mutations within the TLR-4 gene have been shown to attenuate immune responses against lipopolysaccharide in mice. In humans, a TLR-4 polymorphism has been associated with a higher risk for developing severe Gram-negative sepsis and with a lower risk for atherosclerosis. Since MD-2 is an essential part of the lipopolysaccharide receptor complex, we screened 20 patients that underwent surgical cancer therapy for novel MD-2 mutations by a single-strand conformation polymorphism technique. In one patient we found an A --> G substitution at position 103, resulting in an amino-acid exchange from Thr 35 to Ala. Reporter gene assays revealed that this mutation resulted in a reduced lipopolysaccharide-induced signaling. The patient displayed an uneventful postoperative course, with the exception of slightly decreased TNF-alpha levels after in vitro stimulation with LPS as compared to wt patients. Genotyping of a further 41 patients by a newly developed Lightcycler/FRET method failed to detect any additional polymorphism carriers, indicating that this is a rare mutation.

Alanine↗
PubMed2004

Toll-like receptor 2 and Toll-like receptor 4 expression in human adrenals.

Toll-like receptors (TLRs) are key elements in the innate immune response, functioning as pattern-recognition receptors for the detection and response to endotoxins and other microbial ligands. Inflammatory cytokines play an important role in the activation of the hypothalamic-pituitary-adrenal HPA axis during inflammation and sepsis. The newly recognized major role of TLR2 and TLR4 and the adrenal stress response during critical illnesses such as inflammation and sepsis demand comprehensive analysis of their interactions. Therefore, we analyzed TLR2 and TLR4 expression in human adrenal glands. Western blot analysis demonstrated the expression of TLR2 and TLR4 in the human adrenocortical cell line NCI-H295. Immunohistochemical analysis of normal human adrenal glands revealed TLR2 and TLR4 expression in the adrenal cortex, but not in the adrenal medulla. Considering the crucial role of the HPA axis and the innate immune response during acute sepsis or septic shock, elucidating the functional interaction of these systems should be of great clinical relevance.

Adrenal Cortex↗
PubMed2004

Computer-assisted learning in human and dental medicine.

This article describes the development and application of new didactic methods for use in computer-assisted teaching and learning systems for training doctors and dentists. Taking the Meducase project as an example, didactic models and their technological implementation are explained, together with the limitations of imparting knowledge with the "new media". In addition, legal concepts for a progressive, pragmatic, and innovative distribution of knowledge to undergraduate students are presented. In conclusion, potential and visions for the wide use of electronic learning in the German and European universities in the future are discussed. Self-directed learning (SDL) is a key component in both undergraduate education and lifelong learning for medical practitioners. E-learning can already be used to promote SDL at undergraduate level. The Meducase project uses self-directed, constructive, case- and problem-oriented learning within a learning platform for medical and dental students. In the long run, e-learning programs can only be successful in education if there is consistent analysis and implementation of value-added factors and the development and use of media-didactic concepts matched to electronic learning. The use of innovative forms of licensing - open source licenses for software and similar licenses for content - facilitates continuous, free access to these programs for all students and teachers. These legal concepts offer the possibility of innovative knowledge distribution, quality assurance and standardization across specializations, university departments, and possibly even national borders.

Computer-Assisted Instruction↗
PubMed2002

TLR2: cellular sensor for microbial and endogenous molecular patterns.

Toll-like receptor (TLR) 2 is a member of the vertebrate protein family of TLRs that has been studied in substantial detail over the last years. The extracellular domain of the type I receptor molecule TLR2 contains 18 to 20 leucine rich repeat (LRR) and LRR like motives. The intracellular domain of TLR2 contains a Toll/IL-1 receptor/resistance protein typical TIR domain. After the first implication of TLR4 in immunity thereinafter followed by the discovery of the lipopolysaccharide signal transducer function of TLR4, TLR2 was the first of ten mammalian TLRs proven to be directly involved in recognition of pathogen associated molecular patterns (PAMPs). Among the TLR2 specific agonists are microbial products representing broad groups of species such as Gram-positive and Gram-negative bacteria, as well as mycobacteria, spirochetes, and mycoplasm. PAMP induced phagosomal localization of TLR2 and TLR2 dependent apoptosis have been shown. Complex formation with other molecules involved in pattern recognition such as CD14, MD2, TLR1, and TLR6 has been implicated for TLR2. Surprisingly even proteinaceous host material such as heat shock protein (HSP) 60 has been demonstrated to activate cells through TLR2. Thus, TLR2 may be a sensor and inductor of specific defense processes, including oxidative stress and cellular necrosis initially spurred by microbial compounds. Here we summarize the current knowledge on the structure and function of TLR2, which is far from being complete. Detailed understanding of the biology of TLR2 will probably contribute to the characterization of a number of infectious diseases and potentially help in the development of novel intervention strategies.

Amino Acid Sequence↗
PubMed2001

High concentrations of lipopolysaccharide-binding protein in serum of patients with severe sepsis or septic shock inhibit the lipopolysaccharide response in human monocytes.

Lipopolysaccharide-binding protein (LBP), an acute-phase protein recognizing lipopolysaccharide (LPS), catalyzes in low concentrations its transfer to the cellular LPS receptor consisting of CD14 and Toll-like receptor-4. It has recently been shown that high concentrations of recombinant LBP can protect mice in a peritonitis model from the lethal effects of LPS. To determine whether in humans the acute-phase rise of LBP concentrations can inhibit LPS binding to monocytes and induction of proinflammatory cytokines, LBP concentrations were analyzed in 63 patients meeting the American College of Chest Physicians/Society of Critical Care Medicine criteria of severe sepsis or septic shock and the ability of these sera to modulate LPS effects in vitro was assessed employing different assays. Transfer of fluorescein isothiocyanate-labeled LPS to human monocytes was assessed by a fluorescence-activated cell sorter-based method, and activation of monocytes was investigated by measuring LPS-induced tumor necrosis factor-alpha secretion in the presence of the sera. Anti-LBP antibodies and recombinant human LBP were instrumental for depletion and reconstitution of acute-phase sera and subsequent assessment of their modulating effects on LPS activity. Sera of patients with severe sepsis/septic shock exhibited a diminished LPS transfer activity and LPS-induced tumor necrosis factor-alpha secretion as compared with sera from healthy controls. LBP depletion of sepsis sera and addition of rhLBP resulting in concentrations found in severe sepsis confirmed that LBP was the major serum component responsible for the observed effects. In summary, the inhibition of LPS effects by high concentrations of LBP in acute-phase serum, as described here, may represent a novel defense mechanism of the host in severe sepsis and during bacterial infections.

Acute-Phase Proteins↗
PubMed2001

The role of toll-like receptors (TLRs) in bacteria-induced maturation of murine dendritic cells (DCS). Peptidoglycan and lipoteichoic acid are inducers of DC maturation and require TLR2.

Toll-like receptors (TLRs) have been found to be key elements in pathogen recognition by the host immune system. Dendritic cells (DCs) are crucial for both innate immune responses and initiation of acquired immunity. Here we focus on the potential involvement of TLR ligand interaction in DC maturation. TLR2 knockout mice and mice carrying a TLR4 mutation (C3H/HeJ) were investigated for DC maturation induced by peptidoglycan (PGN), lipopolysaccharide (LPS), or lipoteichoic acids (LTAs). All stimuli induced maturation of murine bone marrow-derived DCs in control mice. TLR2(-)/- mice lacked maturation upon stimulation with PGN, as assessed by expression of major histocompatibility complex class II, CD86, cytokine, and chemokine production, fluorescein isothiocyanate-dextran uptake, and mixed lymphocyte reactions, while being completely responsive to LPS. A similar lack of maturation was observed in C3H/HeJ mice upon stimulation with LPS. DC maturation induced by LTAs from two different types of bacteria was severely impaired in TLR2(-)/-, whereas C3H/HeJ mice responded to LTAs in a manner similar to wild-type mice. We demonstrate that DC maturation is induced by stimuli from Gram-positive microorganisms, such as PGN and LTA, with similar efficiency as by LPS. Finally, we provide evidence that TLR2 and TLR4 interaction with the appropriate ligand is essential for bacteria-induced maturation of DCs.

Animals↗
PubMed2001

Induction of cross-tolerance by lipopolysaccharide and highly purified lipoteichoic acid via different Toll-like receptors independent of paracrine mediators.

Exposure of macrophages to LPS induces a state of hyporesponsiveness to subsequent stimulation with LPS termed LPS desensitization or tolerance. To date, it is not known whether similar mechanisms of macrophage refractoriness are induced on contact with components of Gram-positive bacteria. In the present study, we demonstrate that pretreatment with highly purified lipoteichoic acid (LTA) results in suppression of cytokine release on restimulation with LTA in vitro and in vivo in both C3H/HeN and C3H/HeJ mice, but not in macrophages from Toll-like receptor (TLR)-2-deficient mice. Furthermore, desensitization in response to LPS or LTA exposure also inhibits responses to the other stimulus ("cross-tolerance"), suggesting that signaling pathways shared by TLR2 and TLR4 are impaired during tolerance. Finally, we show that LPS- or LTA-induced cross-tolerance is not transferred to hyporesponsive cells cocultured with LPS/LTA-responsive macrophages, showing that soluble mediators do not suffice for tolerance induction in neighboring cells.

Animals↗
PubMed2001

Toll-like receptor-2 mediates Treponema glycolipid and lipoteichoic acid-induced NF-kappaB translocation.

Recently Toll-like receptors (TLRs) have been found to be involved in cellular activation by microbial products, including lipopolysaccharide, lipoproteins, and peptidoglycan. Although for these ligands the specific transmembrane signal transducers TLR-4, TLR-2, or TLR-2 and -6 have now been identified, the molecular basis of recognition of lipoteichoic acids (LTAs) and related glycolipids has not been completely understood. In order to determine the role of TLRs in immune cell activation by these stimuli, experiments involving TLR-2-negative cell lines, TLR-expression plasmids, macrophages from TLR-4-deficient C3H/HeJ-mice, and inhibitory TLR-4/MD-2 antibodies were performed. Glycolipids from Treponema maltophilum and Treponema brennaborense, as well as highly purified LTAs from Staphylococcus aureus and Bacillus subtilis exhibited TLR-2 dependence in nuclear factor kappaB activation and cytokine induction; however, T. brennaborense additionally appeared to signal via TLR-4. Fractionation of the T. brennaborense glycolipids by hydrophobic interaction chromatography and subsequent cell stimulation experiments revealed two peaks of activity, one exhibiting TLR-2-, and a second TLR-4-dependence. Furthermore, we show involvement of the signaling molecules MyD88 and NIK in cell stimulation by LTAs and glycolipids by dominant negative overexpression experiments. In summary, the results presented here indicate that TLR-2 is the main receptor for Treponema glycolipid and LTA-mediated inflammatory response.

Animals↗
PubMed2000

Activation of mitogen-activated protein kinases p42/44, p38, and stress-activated protein kinases in myelo-monocytic cells by Treponema lipoteichoic acid.

We have shown previously that phenol/water extracts derived from two novel Treponema species, Treponema maltophilum, and Treponema brennaborense, resembling lipoteichoic acid (LTA), induce cytokines in mononuclear cells. This response was lipopolysaccharide binding-protein (LBP)-dependent and involved Toll-like receptors (TLRs). Here we show that secretion of tumor necrosis factor-alpha induced by Treponema culture supernatants and extracted LTA was paralleled by an LBP-dependent phosphorylation of mitogen-activated protein kinases (MAPKs) p42 and p44, and p38, as well as the stress-activated protein kinases c-Jun N-terminal kinases 1 and 2. Phosphorylation of p42/44 correlated with an increase of activity, and tumor necrosis factor-alpha levels were significantly reduced by addition of inhibitors of p42/44 and p38, PD 98059 and SB 203580, respectively. Treponeme LTA differed from bacterial lipopolysaccharide regarding time course of p42/44 phosphorylation, exhibiting a prolonged activation of MAPKs. Furthermore, MAPK activation and cytokine induction failed to be strictly correlated. Involvement of TLR-4 for phosphorylation of p42/44 was shown employing the neutralizing anti-murine TLR-4 antibody MTS 510. In TLR-2-negative U373 cells, the compounds studied differed regarding MAPK activation with T. maltophilum leading to a stronger activation. In summary, the data presented here show that treponeme LTA are able to activate the MAPK and stress-activated protein kinase pathway involving LBP and TLR-4.

Animals↗
PubMed2000

Involvement of lipopolysaccharide binding protein, CD14, and Toll-like receptors in the initiation of innate immune responses by Treponema glycolipids.

Culture supernatants from Treponema maltophilum associated with periodontitis in humans and Treponema brennaborense found in a bovine cattle disease accompanied with cachexia caused a dose-dependent TNF-alpha synthesis in human monocytes increasing with culture time. This activity could be reduced significantly by blocking the CD14-part of the LPS receptor using the My 4 mAb and by polymyxin B. In the murine macrophage cell line RAW 264.7, Treponema culture supernatants induced TNF-alpha secretion in a LPS binding protein (LBP)-dependent fashion. To enrich for active compounds, supernatants were extracted with butanol, while whole cells were extracted using a phenol/water method resulting in recovery of material exhibiting a similar activity profile. An LPS-LBP binding competition assay revealed an interaction of the treponeme phenol/water extracts with LBP, while precipitation studies implied an affinity to polymyxin B and endotoxin neutralizing protein. Macrophages obtained from C3H/HeJ mice carrying a Toll-like receptor (TLR)-4 mutation were stimulated with treponeme extracts for NO release to assess the role of TLRs in cell activation. Furthermore, NF-kappaB translocation in TLR-2-negative Chinese hamster ovary (CHO) cells was studied. We found that phenol/water-extracts of the two strains use TLRs differently with T. brennaborense-stimulating cells in a TLR-4-dependent fashion, while T. maltophilum-mediated activation apparently involved TLR-2. These results indicate the presence of a novel class of glycolipids in Treponema initiating inflammatory responses involving LBP, CD14, and TLRs.

Acute-Phase Proteins↗
PubMed2000

Binding of lipopolysaccharide (LPS) to CHO cells does not correlate with LPS-induced NF-kappaB activation.

Activation of myeloid cells by lipopolysaccharide (LPS) is a key event in the development of gram-negative sepsis. One crucial step within this process is the binding of LPS to CD14. CD14 is a glycosylphosphatidylinositol (GPI)-anchored membrane protein requiring at least one additional membrane-spanning molecule for signal transduction. It is not clear whether the function of CD14 is to merely catalyze LPS binding, followed by the interaction of LPS with the signal transducer, or whether CD14 has a more specific function and may be a part of the signaling complex. To address this question we generated Chinese hamster ovary (CHO) cells expressing a human GPI-anchored form of LPS-binding protein (mLBP) to substitute for CD14 as LPS acceptor molecule. By comparison of CHO / mLBP with CHO / vector and CHO / CD14 cells we found that expression of GPI-linked LBP results in an enhanced binding of LPS but not in an increase in cell activation as determined by translocation of NF-kappaB. Furthermore, excess of recombinant soluble LBP resulted also in increased LPS binding without affecting NF-kappaB translocation. These data show that LPS binding alone is not sufficient to induce signaling. We conclude that CD14 is more than a catalyst for LPS binding: it seems to be directly involved in LPS signaling and thus appears to be an essential part of the signaling complex.

Acute-Phase Proteins↗
PubMed2000

Detection of two variants of complement component C3 in C3-deficient guinea pigs distinguished by the absence and presence of a thiolester.

The complement system is an essential part of the innate defense, and C3 is an integral part of this powerful system. In previously identified complement C3 deficient guinea pigs only approx. 5% of the normal serum C3 level is detectable. No differences were found between in vitro C3 protein synthesis and C3 mRNA levels of cells from C3-deficient and wild-type animals and the amino acid sequences of both C3 proteins are identical as deduced from cDNA sequencing. Previously, the principal inability to form a C3 thiolester was discussed as a possible reason for this C3-deficiency. Here we report the isolation of two functionally different C3 species from the C3-deficient animals. Only one of these C3 proteins exhibits normal hemolytic activity and contains a thiolester group. The second C3 species is exclusively present in C3-deficient animals and lacks a thiolester, explaining its failure to express hemolytic activity. The presence of a second C3 species lacking a thiolester structure only in C3-deficient animals indicates that the stability of the thiolester may play a role in C3 deficiency. However further analysis of the in vitro stability of the thiolesters of C3 from normal and C3-deficient guinea pigs revealed no differences. A decreased in vivo thiolester stability might lead to the presence of C3 with and without a thiolester or alternatively the expression of two isoforms of C3 in these animals. Considering the central role of C3 in host defense, the mechanisms of C3 thiolester formation require further analysis.

Animals↗
PubMed2000

Lipopolysaccharide binding protein in acute pancreatitis.

OBJECTIVE: To assess the expression of plasma lipopolysaccharide binding protein (LBP) concentrations and its relationship to markers of the systemic inflammatory response syndrome during acute pancreatitis. DESIGN: A prospective study. SETTING: General surgical units of university teaching hospitals in the Belfast area. PATIENTS: The study included 18 patients admitted with established diagnosis of acute pancreatitis on the basis of elevated serum amylase or by contrast radiology. Patients were retrospectively stratified using the Modified Glasgow Criteria into severe (n = 7) and mild (n = 11) disease. INTERVENTIONS AND MEASUREMENTS: Blood samples were obtained at admission (day 1) and for a further 3 days for the measurement of LBP, C-reactive protein (CRP), tumor necrosis factor, and interleukin (IL)-6. Acute Physiology and Chronic Health Evaluation (APACHE) II scores were calculated on day 1 and day 2. MAIN RESULTS: LBP and CRP concentrations were significantly increased from healthy control values in acute pancreatitis patients at presentation. In the mild group LBP, CRP and IL-6 concentrations remained relatively constant throughout the study period. By comparison, severe acute pancreatitis was associated with significantly higher LBP concentrations and a marked systemic inflammatory response as evidenced by increased CRP, IL-6, and APACHE II scores. The rise in LBP occurred after the observed increase of these markers. Significant correlations were found among CRP and LBP, IL-6 and LBP, and IL-6 and APACHE II scores. There were no fatalities in the mild group, whereas four of the seven patients with severe disease died. CONCLUSIONS: LBP was significantly raised in patients with severe acute pancreatitis but would seem to be of limited use in predicting disease severity. This acute phase protein may have a role in the progression of systemic complications associated with acute pancreatitis.

APACHE↗
PubMed2000

Induced hypothermia in experimental pneumococcal meningitis.

Pneumococcal meningitis resulting from Streptococcus pneumoniae has a death rate of 28% in adults. In severe head injury and stroke, inflammatory changes and intracranial hypertension are improved by induced hypothermia, which also is neuroprotective. We hypothesized that moderate hypothermia ameliorates inflammatory changes in experimental pneumococcal meningitis. Wistar rats were cooled systemically, and meningitis was induced by pneumococcal cell wall components. The increase of regional cerebral blood flow in the meningitis animals was blocked by hypothermia at 6 hours. The reduction of intracranial pressure correlated with temperature. The influx of leukocytes into the cerebrospinal fluid and levels of tumor necrosis factor alpha in the cerebrospinal fluid were decreased. Cooling the animals 2 hours after meningitis induction to 30.5 degrees C was also protective. We conclude that hypothermia is a new adjuvant approach to reduce meningitis-induced changes, in particular intracranial pressure, in the early phase of the disease.

Animals↗
PubMed1999

Cerebral endothelial cells release TNF-alpha after stimulation with cell walls of Streptococcus pneumoniae and regulate inducible nitric oxide synthase and ICAM-1 expression via autocrine loops.

TNF-alpha, inducible NO synthase (iNOS), and ICAM-1 are considered to be key proteins in the inflammatory response of most tissues. We tested the hypothesis that cell walls of Streptococcus pneumoniae (PCW), the most common cause of adult bacterial meningitis, induce TNF-alpha, iNOS, and ICAM-1 expression in rat primary brain microvascular endothelial cell cultures. We detected TNF-alpha mRNA by RT-PCR already 1 h after stimulation with PCW, while TNF-alpha protein peaked at 4 h (9.4 +/- 3.6 vs 0.1 +/- 0.1 pg/microgram protein). PCW induced iNOS mRNA 2 h after stimulation, followed by an increase of the NO degradation product nitrite (18.1 +/- 4 vs 5.8 +/- 1.8 at 12 h; 18.1 +/- 4 vs 5.8 +/- 1.8 pmol/microgram protein at 72 h). The addition of TNF-alpha Ab significantly reduced nitrite production to 62.2 +/- 14.4% compared with PCW-stimulated brain microvascular endothelial cells (100%). PCW induced the expression of ICAM-1 (measured by FACS), which was completely blocked by TNF-alpha Ab (142 +/- 18.6 vs 97.5 +/- 12.4%; 100% unstimulated brain microvascular endothelial cells). Cerebral endothelial cells express TNF-alpha mRNA as well as iNOS mRNA and release the bioactive proteins in response to PCW. PCW-induced NO production is mediated in part by an autocrine pathway involving TNF-alpha, whereas ICAM-1 expression is completely mediated by this autocrine loop. By these mechanisms, cerebral endothelial cells may regulate critical steps in inflammatory blood-brain-barrier disruption of bacterial meningitis.

Animals↗