No abstract

The lipopolysaccharide (LPS)-binding protein (LBP) has a concentration-dependent dual role in the pathogenesis of gram-negative sepsis: low concentrations of LBP enhance the LPS-induced activation of mononuclear cells (MNC), whereas the acute-phase rise in LBP concentrations inhibits LPS-induced cellular stimulation. In stimulation experiments, we have found that LBP mediates the LPS-induced cytokine release from MNC even under serum-free conditions. In biophysical experiments we demonstrated that LBP binds and intercalates into lipid membranes, amplified by negative charges of the latter, and that intercalated LBP can mediate the CD14-independent intercalation of LPS into membranes in a lipid-specific and temperaturedependent manner. In contrast, prior complexation of LBP and LPS inhibited binding of these complexes to membranes due to different binding of LBP to LPS or phospholipids. This results in a neutralization of LPS and, therefore, to a reduced production of tumor necrosis factor by MNC. We propose that LBP is not only present as a soluble protein in the serum but may also be incorporated as a transmembrane protein in the cytoplasmic membrane of MNC and that the interaction of LPS with membrane-associated LBP may be an important step in LBP-mediated activation of MNC, whereas LBP-LPS complexation in the serum leads to a neutralization of LPS.Human lipopolysaccharide (LPS)-binding protein (LBP) is a serum glycoprotein belonging to a family of lipid-binding proteins which includes bactericidal/permeability-increasing protein (BPI), phospholipid ester transfer protein, and cholesterol ester transfer protein (1,18,36). It consists of 456 amino acid residues preceded by a hydrophobic signal sequence of 25 residues (31). LBP is synthesized by hepatocytes (26) and intestinal epithelial cells (42) and is present in normal serum at concentrations of 5 to 10 g/ml, rising up to 200 g/ml 24 h after induction of an acute-phase response (35). This rise in LBP levels is caused by transcriptional activation of the LBP gene mediated by interleukin-1 (IL-1) and . LBP has a concentration-dependent dual role: low concentrations of LBP enhance the LPS-induced activation of mononuclear cells (MNC), whereas the acute-phase rise in LBP concentrations inhibits LPS-induced cellular stimulation (20). LBP binds a variety of LPS (endotoxin) chemotypes from rough and smooth strains of gram-negative bacteria and even lipid A, the lipid moiety of LPS (37, 38). The LPS molecules, components of the outer membrane of gram-negative bacteria, are important mediators in the pathogenesis of gram-negative sepsis and septic shock (25). Because the lipid A moiety has been shown to be responsible for the biological activity of LPS in most in vivo and in vitro test systems, it has been termed the endotoxic principle of LPS (27).LPSs activate monocytes and macrophages to secrete inflammatory cytokines (tumor necrosis factor alpha [TNF-␣] and IL-1, etc.) and other potent mediators (32) by an intracellular signal amplification pathway. These mediato...

The tripeptide glutathione is a major antioxidant and redox buffer with multiple roles in plant metabolism. Glutathione biosynthesis is restricted to the cytosol and the plastids and the product is distributed to the various organelles by unknown mechanisms. In the present study immunogold cytochemistry based on anti-glutathione antisera and transmission electron microscopy was used to determine the relative concentration of glutathione in different organelles of Arabidopsis thaliana leaf and root cells. Glutathione-specific labelling was detected in all cellular compartments except the apoplast and the vacuole. The highest glutathione content was surprisingly not found in plastids, which have been described before as a major site of glutathione accumulation, but in mitochondria which lack the capacity for glutathione biosynthesis. Mitochondria of both leaf and root cells contained 7-fold and 4-fold, respectively, higher glutathione levels than plastids while the density of glutathione labelling in the cytosol, nuclei, and peroxisomes was intermediate. The accuracy of the glutathione labelling is supported by two observations. First, pre-adsorption of the anti-glutathione antisera with glutathione reduced the density of the gold particles in all organelles to background levels. Second, the overall glutathione-labelling density was reduced by about 90% in leaves of the glutathione-deficient Arabidopsis mutant pad2-1 and increased in transgenic plants with enhanced glutathione accumulation. Hence, there was a strong correlation between immunocytochemical and biochemical data of glutathione accumulation. Interestingly, the glutathione labelling of mitochondria in pad2-1 remained very similar to wild-type plants thus suggesting that the high mitochondrial glutathione content is maintained in a situation of permanent glutathione-deficiency at the expense of other glutathione pools. High and constant levels of glutathione in mitochondria appear to be particularly important in cell survival strategies and it is predicted that mitochondria must have highly competitive mitochondrial glutathione uptake systems. The present results underline the suggestion that subcellular glutathione concentrations are not controlled by a global mechanism but are controlled on an individual basis and it is therefore not possible to conclude from global biochemical glutathione analysis on the status of the various organellar pools.

LPS (endotoxins) activate cells of the human immune system, among which are monocytes and macrophages, to produce endogenous mediators. These regulate the immune response, but may also cause severe harm leading to septic shock. The activation of monocytes/macrophages by LPS is mediated by a membrane-bound LPS receptor, mCD14. As mCD14 lacks a transmembrane domain, a further protein is required for the signal transducing step to the cell interior. Here we show, using excised outside-out membrane patches, that activation of a high-conductance Ca2+- and voltage-dependent potassium channel is an early step in the transmembrane signal transduction in macrophages. The channel is activated by endotoxically active LPS in a dose-dependent manner. Channel activation can be completely inhibited by LPS antagonists and by anti-CD14 Abs. Activation of the channel is essential for LPS-induced cytokine production as shown by its inhibition by selective K+ channel blockers.

This study deals with the effect of altitudinal variation on the content of phenolic compounds in three traditional herbal plants, which are also consumed as food in Central Europe. Herbs of Calluna vulgaris (L.) HULL, flowers and fruits of Sambucus nigra L., and berries of Vaccinium myrtillus L. collected in the Naturpark Solktaler (Austria) were extracted using accelerated solvent extraction (ASE). Identification and quantification of the constituents in the polar extracts (methanol 80%, v/v) were achieved by means of RP-HPLC-PDA and/or LC-PDA-MS analysis with external standards. 3,5- O-Dicaffeoylquinic acid was identified in flowers of S. nigra for the first time. Rising concentrations of flavonoids and especially flavonol-3- O-glycosides with adjacent hydroxyl groups in ring B in C. vulgaris and S. nigra with increasing altitude were observed. Anthocyanins from the berries of both S. nigra and V. myrtillus occurred in decreasing amounts with rising altitude. C. vulgaris showed the best radical scavenging capacity based on the DPPH assay.