Binding of LPS and LPS--LDL complexes to rat hepatocytes

Lipopolysaccharide enters the rat brain by a lipoprotein-mediated transport mechanism in physiological conditions

Physiologically, lipopolysaccharide (LPS) is present in the bloodstream and can be bound to several proteins for its transport (i.e.) LPS binding protein (LBP) and plasma lipoproteins). LPS receptors CD14 and TLR-4 are constitutively expressed in the Central Nervous System (CNS). To our knowledge, LPS infiltration in CNS has not been clearly demonstrated. A naturalistic experiment with healthy rats was performed to investigate whether LPS is present with its receptors in brain. Immunofluorescences showed that lipid A and core LPS were present in circumventricular organs, choroid plexus, meningeal cells, astrocytes, tanycytes and endothelial cells. Co-localization of LPS regions with CD14/TLR-4 was found. The role of lipoprotein receptors (SR-BI, ApoER2 and LDLr) in the brain as targets for a LPS transport mechanism by plasma apolipoproteins (i.e. ApoAI) was studied. Co-localization of LPS regions with these lipoproteins markers was observed. Our results suggest that LPS infiltrates in the brain in physiological conditions, possibly, through a lipoprotein transport mechanism, and it is bound to its receptors in blood-brain interfaces.

Tumor necrosis factor alpha increases intestinal permeability in mice with fulminant hepatic failure

AIM: To determine the effect of tumor necrosis factor alpha (TNF-α) on intestinal permeability (IP) in mice with fulminant hepatic failure (FHF), and the expression of tight junction proteins.

METHODS: We selected D-lactate as an index of IP, induced FHF using D-galactosamine/lipopolysaccharide and D-galactosamine/TNF-α, assessed the results using an enzymatic-spectrophotometric method, transmission electron microscopy, immunohistochemistry, Western blotting and real-time quantitative polymerase chain reaction. The effect of the administration of anti-TNF-α immunoglobulin G (IgG) antibody, before the administration of D-galactosamine/lipopolysaccharide, on TNF-α was also assessed.

RESULTS: IP was significantly increased in the mouse model of FHF 6 h after injection (13.57 ± 1.70 mg/L, 13.02 ± 1.97 mg/L vs 3.76 ± 0.67 mg/L, P = 0.001). Electron microscopic analysis revealed tight junction (TJ) disruptions, epithelial cell swelling, and atrophy of intestinal villi. Expression of occludin and claudin-1 mRNA was significantly decreased in both FHF models (occludin: 0.57 ± 0.159 fold vs baseline, P = 0.000; claudin-1: 0.3067 ± 0.1291 fold vs baseline, P = 0.003), as were the distribution density of proteins in the intestinal mucosa and the levels of occludin and claudin-1 protein (occludin: 0.61 ± 0.0473 fold vs baseline, P = 0.000; claudin-1: 0.6633 ± 0.0328 fold vs baseline, P = 0.000). Prophylactic treatment with anti-TNF-α IgG antibody prevented changes in IP (4.50 ± 0.97 mg/L vs 3.76 ± 0.67 mg/L, P = 0.791), intestinal tissue ultrastructure, and the mRNA levels of occludin and claudin-1 expression (occludin: 0.8865 ± 0.0274 fold vs baseline, P = 0.505; claudin-1: 0.85 ± 0.1437 fold vs baseline, P = 0.1), and in the protein levels (occludin: 0.9467 ± 0.0285 fold vs baseline, P > 0.05; claudin-1: 0.9533 ± 0.0186 fold vs baseline, P = 0.148).

CONCLUSION: Increased in IP stemmed from the downregulation of the TJ proteins occludin and claudin-1, and destruction of the TJ in the colon, which were induced by TNF-α in FHF mice.

Effects of ethanol and lipopolysaccharide on the sphingomyelin cycle in rat hepatocytes

Lipopolysaccharide toxin added to primary hepatocyte culture slightly modified the basal concentrations of (3)H-serine-labeled sphingomyelin, sphingosine, and ceramide. Ethanol reduced the levels of sphingomyelin and sphingosine by 20-25 and 15-20%, respectively, but increased ceramide content by 7-17%. Tumor necrosis factor reduced the concentrations of sphingomyelin and sphingosine, but did not modify the content of ceramide. Combined treatment with lipopolysaccharide toxin and ethanol potentiated the effect of alcohol.

Polyethylene glycol-conjugated immunoliposomes specific for olfactory ensheathing glial cells

A novel immunoliposome delivery system was developed for directed transport into cultured olfactory epithelium cells. Monoclonal antibodies against glial fibrillary acidic protein (GFAP) served as a vector. Fluorescence microscopy showed that the target cells are specifically stained with Dil dye incorporated into liposomal membranes. This transport system holds promise for the delivery of bioactive substances to olfactory epithelial cells and modulation of their capacity to stimulate axonal regeneration.