The Formation of Non-Specific Immunological Memory Phenotype in Human Monocyte-Like THP-1 and U-937 Cell Lines.

We studied the formation of the phenotype of non-specific immunological memory (trained immunity) in human monocyte-like THP-1 and U-937 cell lines. The absence of the lag phase after primary contact with the pathogen (Mycobacterium bovis, BCG vaccine) does not contribute to the formation of the trained immunity phenotype in the cells. The presence of the lag phase promotes the development of the trained immunity phenotype, especially in THP-1 cells. The second stimulation (bacterial LPS) did not increase the production of lactate, nitric oxide, and glucose consumption by cells, which can be a consequence of the Warburg phenomenon in these monocyte-like human cell lines.

Functional phenotypes of macrophages and the M1-M2 polarization concept. Part I. Proinflammatory phenotype.

Current concepts concerning the main functional phenotypes of mononuclear phagocytes are systematized, molecular mechanisms of their formation are considered, and the functional polarization concept of macrophages is critically analyzed. Mechanisms of macrophage priming activation mediated by pattern recognition receptors TLR, NLR, RLR, and CLR are described, and the features of each phenotype acquired via various pattern recognition receptors are emphasized. It is concluded that there is a huge variety of proinflammatory phenotypes from highly to poorly polarized ones. Thus the widespread notion of "classical activation" of macrophage concerns just a particular case of proinflammatory phenotype formation.

In vitro accumulation of complexes of endotoxin and low-density lipoproteins by macrophages and arterial wall.

Binding and uptake of complexes of endotoxin and low-density lipoproteins (LPS-LDL) in the arterial wall and mononuclear phagocytes were studied under in vitro conditions. Incubation of aortic explants from Wistar rats with complexes of (125)I-LDL and S. minnesota R595 LPS or (125)I-LDL was accompanied by a 6-fold increase in binding (0 degrees C) and 2-fold increase in the uptake (37 degrees C) of LDL-LPS complexes as compared to free LDL. Binding and degradation of (125)I-LDL-LPS complexes in the culture of peritoneal macrophages were higher compared to the corresponding parameters for free (125)I-LDL. Our results suggest that the formation of LDL-LPS complexes is followed by the increased binding and accumulation of LDL in the arterial wall and macrophages. These changes probably induce the cascade of major atherogenic events in the vascular wall.

Cholesterol-induced stimulation of postinflammatory liver fibrosis.

We studied the effect of high-cholesterol diet and factors inhibiting 3-hydroxy-3-methylglutaryl coenzyme A reductase on the development of liver fibrosis in C57Bl/6 mice with CCl4- or zymosan-induced hepatitis. Feeding a high-cholesterol diet led to a sharp increase in collagen content in the liver tissue of animals with CCl4-induced or zymosan-induced hepatitis. Atorvastatin and calcitriol produced less pronounced fibrogenic effects. Mevalonate partially prevented the development of cholesterol-induced fibrogenesis. High-cholesterol diet led to accumulation of oxysterols, cholesterol esters, and triglycerides and increased the expression of transforming growth factor-beta1 mRNA in liver tissue. Cholesterol-induced potentiation of the fibrogenic response is probably associated with transforming growth factor-beta1 induction due to accumulation of lipids and oxysterols in the liver.

Endotoxin-lipoprotein complex formation as a factor in atherogenesis: associations with hyperlipidemia and with lecithin:cholesterol acyltransferase activity.

A potential role of endotoxin-lipoprotein (bacterial lipopolysaccharide-lipoprotein, LPS-LP) complex formation as a pathogenic factor for atherosclerosis has not been studied yet. The aim of this study was to test the hypothesis that in endotoxinemia in humans hyperlipidemia associated with atherosclerosis development can favor an excessive LPS-LP complex formation, and endotoxin presented in blood can inhibit lecithin:cholesterol acyltransferase (LCAT), one of the key enzymes of reverse cholesterol transport. Endotoxin-binding capacity of lipoproteins (LP) in patients with normolipidemia and hyperlipidemia types IIa and IV was estimated from label incorporation into different LP fractions isolated by means of sequential ultracentrifugation following serum preincubation with Salmonella minnesota R595 125I-labeled LPS. The effect of varied concentrations of S. minnesota R595 LPS on LCAT activity was evaluated from the overall esterifying activity of serum using [1,2-3H2]cholesterol-labeled substrate. The elevation of low density LP (LDL) and very low density LP (VLDL) contents in blood serum in hyperlipidemia types IIa and IV, respectively, resulted in significant elevation of LPS binding to these fractions. LPS added to the blood serum leads to the dose-dependent decrease in LCAT activity. The revealed phenomena of elevated LPS binding to atherogenic LP fractions in hypercholesterolemia and endotoxin-induced LCAT inhibition suggest the pathogenic role of LPS-LP complexes in atherogenesis.

Carboxymethylated beta-1,3-glucan inhibits the binding and degradation of acetylated low density lipoproteins in macrophages in vitro and modulates their plasma clearance in vivo.

In atherosclerotic lesions, macrophages are transformed into foam cells accumulating modified low density lipoproteins (LDL) via the scavenger receptor pathway. We have investigated the effects of carboxymethylated beta-1,3-glucan (CMG) on acetylated LDL (AcLDL) metabolism in murine peritoneal macrophages in vitro and upon the clearance of AcLDL by rat liver in vivo. In cultured murine peritoneal macrophages, CMG reduced substantially the AcLDL-induced synthesis of cholesteryl esters, decreased the binding and degradation of [125I]-AcLDL in a dose-dependent manner with complete inhibition at 20-30 nM, but had no effect on the binding and degradation of native [125I]-LDL. In contrast, other polysaccharides studied, namely zymosan lipopolysaccharide, non-modified glucan and mannan Rhodexman, had a slight effect at concentrations significantly exceeding the concentrations of CMG. [125I]-AcLDL injected intravenously into rats was cleared from the blood with a half-life of 3.7 min. About 56 per cent of the label of injected [125I]-AcLDL was recovered in the liver 15 min after administration. Co-injection of the labelled AcLDL with CMG (25 mg kg-1 b.w.) decreased the rate of AcLDL clearance so that the half-life increased to 6.0 min. Injections of CMG (25 mg kg-1 b.w.) 48 and 24 h before the determination increased the rate of [125I]-AcLDL clearance (with a half-life of about 2.3 min) and increased the uptake of AcLDL by the liver. We suggest that CMG competed with AcLDL for scavenger receptors in vitro and in vivo and repeated CMG injections before the measurements of AcLDL resulted in the induction of scavenger receptor function.