[Influence of cholesterol on macrophage foam cells formation at zymosan-induced inflammation of mice].

It has been shown recently that significant number (to 40% from total population) of macrophage foam cells (MFC) is formed during early time (24 h) of zymosan-induced peritonitis resolution and agonists of peroxisome proliferation activated receptors-α, -γ (PPAR-α, -γ) exert anti-inflammatory action, protecting their formation (Dushkin et al., 2007). The work is devoted to investigate of the influence of cholesterol-containing liposomes (CHL) on dinamic of zimozan-induced peritonitis in C57Bl/6 mice. The accumulation of cholesterol, the change of cytokine production, PPAR-γ activity and cholesterol efflux in macrophages of C57Bl/6 mice has been investigated. The infiltration of neutrophils, amounts of mononuclear cells and MFC formation were significantly increased in peritonel cavity of zymosan-induced mice that led to in expansion of the period of inflammatory resolution and of the period of MFC resolution. If macrophages obtained after zymosan injection mainly accumulated triglycerides (TG) and at high speed incorporated [1-14C]oleate into TG, the injection of CHL after zymosan-indused inflammation lead to dramatic promotion MFC containing primarily free cholesterol and Ch ethers and been aggravation of [1-14C]oleate incorporation into cholesterol ethers in macrophages (mainly for 2 days). It has to shown that CHL against a background of inflammation promoted reduction of fluorescent NBD-cholesterol efflux from macrophages throughout the studied period (5 days) whereas zymosan inhibited cholesterol efflux at the early stages of inflammation (1 and 2 days), then, on 3ed day, the cholesterol efflux was recovered and increased on day 5. At the same time CHL stimulated the production of TNFα and TGFß and inhibited the production of IL-10 and DNA-binding activity of PPAR-γ macrophages obtained at early as well as late stages of zymosan-induced peritonitis (compared with injection zymosan only). Thus, accumulation of cholesterol in inflammatory macrophages and promotion of MFC formation prolog timely resoluti- on of acute inflammation inducing alteration of pro- and anti-inflammatory cytokine balance and evoking the repression of macrophage DNA-binding activity of PPAR-γ and cholesterol efflux.

Effect of melatonin on cellular composition of the spleen and parameters of lipid metabolism in rats with alimentary obesity.

We studied the effects of melatonin on the status of immune organs and parameters of lipid metabolism in rats with alimentary obesity and parameters of lipid metabolism and immune status in Wistar rats kept on high-fat diet and receiving melatonin solution per os. Melatonin leveled the changes in blood and liver parameters of lipid metabolism, which was paralleled by normalization of cellular composition of immune organs. We conclude that melatonin can be a promising agent for the treatment of lipid metabolism and immune status disorders in alimentary obesity.

Rats of hypertensive ISIAH strain are resistant to the development of metabolic syndrome induced by high-fat diet.

We studied the influence of high-fat diet on the development of metabolic syndrome in rats of hypertensive ISIAH strain and normotensive WAG strain. In contrast to ISIAH rats, high-fat diet in WAG rats led visceral obesity, glucose tolerance, and dyslipidemia. DNA-binding activity of the peroxisome proliferator-activated receptor α (PPARα) decreased in the liver of WAG rats and increased in ISIAH rats. Blood levels of TNF-α, IL-6, and corticosterone increased more significantly in WAG rats. Corticosterone content in the adrenal glands was more markedly reduced in WAG rats. High-fat diet had no effect on BP in ISIAH and WAG rats. It was concluded that ISIAH rats can be used as a genetic model in studies of the mechanism of resistance to the metabolic syndrome.

Effect of toll-like receptor agonists on the formation of macrophage/foam cells upon acute peritonitis in mice.

We studied effects of zymosan, double-stranded RNA, LPS of E. coli and bacterial CpG DNA, agonists of toll-like receptor TLR2, TLR3, TLR4 and TLR9, respectively, on the formation of macrophage/foam cells 24 h after induction of acute peritonitis. Administration of agonists led to transformation of peritoneal macrophages into foam cells and significant activation of cell biosynthesis and increased the content of triglycerides and cholesterol esters in the absence of LDL and irrespective of the capacity of TLR agonists to stimulate neutrophil infiltration and TNF-α production in the peritoneal cavity.

Effects of experimental desynchronosis on the organs of immune system in WAG and ISIAH rats.

We studied the influence of abnormal illumination regimen on cell composition of the central and peripheral organs of the immune system in ISIAH rats and control WAG rats. In ISIAH rats, 24-h illumination for 14 days led to more pronounced inhibition of cell proliferation and differentiation in the thymus and more pronounced decrease in splenocyte proliferation and T and B cell counts in the spleen in comparison with WAG rats; however, the level of antigen-presenting cells in the spleen of ISIAH increased. We concluded that ISIAH rats are more sensitive to abnormal illumination regimen than WAG rats. Twenty-four-hour illumination was associated with impairments of central differentiation of T cells and activation of systemic inflammation followed by impairment of differentiation regulation, which can aggravate metabolic dysfunctions in these animals.

Bezafibrate causes depression of the immune response and increases the sensitivity to endotoxin in association with low level of HDL and PPARα activity in hypertensive ISIAH rats.

We studied the effect of bezafibrate on hepatic PPARα activity and immune parameters in hypertensive ISIAH rats in comparison with normotensive WAG rats under conditions of LPS treatment. Bezafibrate increased activity of PPARα in WAG rats, but not in ISIAH rats. As differentiated from WAG rats, bezafibrate produced a potent effect on the content of T cell subpopulations in the thymus and spleen of ISIAH rats. Administration of LPS after injection of bezafibrate caused death of 50% ISIAH animals (but not WAG rats), which was associated with low level of HDL cholesterol and increased triglyceride content. Our results suggest that the hypolipidemic treatment (e.g., bezafibrate) can increase the severity of complications in patients with infectious and inflammatory diseases in association with low level of HDL.

Reactivity of the immune system and activities of PPARα and PPARγ in the liver under conditions of LPS-induced acute inflammatory response in hypertensive ISIAH rats.

The effects of LPS from E. coli on DNA-binding activities of PPARα and PPARγ in the liver and immune system parameters of were studied in hypertensive ISIAH rats and normotensive WAG rats. In ISIAH rats characterized by low basal level of PPARα, PPARγ, and HDL, the response of the peripheral immune system compartment to LPS was more pronounced and was not associated with decrease in DNA-binding activities of PPARα observed in WAG. Proinflammatory stimulus did not induce proliferative changes in the thymus of ISIAH rats, which can reflect impaired relationships between the central and peripheral organs of the immune system. The character of regulatory interactions between PPARα and immune cells can differ in various rat strains and depend on initial PPARα activity, HDL level, specific features of immune status, resistance to stress, and hormonal and metabolic background.

Macrophage/foam cell is an attribute of inflammation: mechanisms of formation and functional role.

Transformation of macrophages into foam cells is traditionally considered in the context of atherogenesis, because lipid accumulation is believed to be a consequence of uptake of oxidized low density lipoproteins (oxLDL) through scavenger receptors (SR) of macrophages. However, an excessive uptake of oxLDL is recently shown to trigger compensatory mechanisms of cholesterol elimination from macrophages. Maintaining the lipid homeostasis in macrophages is mediated by regulation of a system of lipid sensors, which is reprogrammed under conditions of inflammation leading to formation of foam cell phenotype without involvement of SR. The increase in the inflammatory potential on macrophage polarization into the M1 phenotype is associated with suppression of LXR and PPAR, their target genes, induction of expression of genes responsible for fatty acid and cholesterol metabolism controlled by SREBP1c and SREBP2, proteins associated with lipid inclusions, macropinocytosis activation, secretion of LXR and PPAR endogenous ligands, and development of apoptosis. In this review the role of foam cells in development and resolution of acute inflammation, mechanisms of their formation from macrophages infected by some bacterial and virus pathogens causing chronic inflammation, and the significance of LXR and PPAR as therapeutic targets in chronic infectious and inflammatory diseases are also discussed.

[The role of peroxisome proliferator activated receptors in metabolic balance disturbances under stress].

Some aspects of peroxisome proliferator activated receptors (PPAR) involvement in regulation of stress-dependent biological processes leading to insulin resistance, lipid imbalance, hypertension and inflammation are reviewed. Analysis of literature data clearly shows the main role of PPAR in stress signal transduction following to metabolic disbalance development under prolonged stress conditions. The interplay of three PPAR isoforms functional activity with metabolic process disturbances during stress is under special emphasis. Taking into account experimental data described in literature we suggest that PPAR activation under acute stress is an adaptive response while stable PPAR hyperexpression under prolonged stress can cause insulin resistance, hypertension, and visceral obesity. The strategy of PPAR using as pharmacological targets in metabolic syndrome correction is under consideration.

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.

The content of PPAR, LXR, and RXR and the PPAR DNA-binding activity in macrophages over the course of inflammation in mice.

The content of peroxisome proliferation activating proteins PPAR-alpha and PPAR-gamma, liver X receptors (LXR), and retinoid X receptors (RXR) and activity of PPAR-alpha, PPAR-gamma, and PPAR-delta binding to DNA response elements in C57Bl/6 mouse macrophages were studied during different phases of aseptic inflammation, induced by intraperitoneal injection of 50 mg/kg zymosan A. The DNA-binding activities of PPAR-alpha and PPAR-gamma and the levels of PPAR-alpha, PPAR-gamma, LXR, and RXR in peritoneal macrophages dropped on days 1 and 3 after zymosan injection. On days 7 and 14 the DNA-binding activity of PPAR-gamma and content of PPAR-gamma and LXR-beta protein increased in comparison with the control, while the DNA-binding activity and content of PPAR-alpha in the cells remained low. Recovery of RXR protein content in macrophages was observed only on day 14 after zymosan injection.

Effects of cholesterol and nuclear hormone receptor agonists on the production of transforming growth factor-beta in macrophages.

We studied the effects of cholesterol, its oxidized derivatives mevalonate, and nuclear receptor agonists LXR, RXR, and FXR on the production of transforming growth factor-beta1 (TGF- beta1) by macrophages. After recruiting of macrophage monocytes into the focus of inflammation, the production of TGF-beta1 increased by 3.5 times in comparison with control macrophages. Cholesterol diet stimulated the production of TGF-beta1 by 2.5 times. Cholesterol directly stimulated macrophage production of TGF-beta1 in vitro, while addition of mevalonate to the incubation medium effectively reduced this induced production. Agonists of nuclear receptor sharply reduced the production of TGF-beta1 in recruited macrophages. Under conditions of inflammation, hypercholesterolemia can be a factor of fibrogenesis due to TGF-beta1 induction in macrophages, which depends on the products of mevalonate biochemical chain.

Ketoconazole inhibits oxidative modification of low density lipoprotein.

Known cytochrome P450-dependent oxygenase inhibitor ketoconazole (5-50 microM) blocked the murine macrophage-mediated modification of human low density lipoprotein (LDL) as measured by production of thiobarbituric acid-reactive substance, stimulation of [125I]LDL degradation in a fresh set of macrophages and LDL electrophoretic mobility, in a dose-dependent manner with complete inhibition at 30-40 microM. When resident macrophages were incubated with LDL in the presence of metyrapone, methoxsalen and alpha-naphthaflavone at concentrations that have been shown to inhibit the cytochrome P450-dependent oxygenases, there was no change in LDL modification. Induction of benzo[alpha]pyrene hydroxylase activity in macrophages by 24 h incubation with benzo[alpha]pyrene was accompanied by a 1.5-fold increase of LDL modification which has been leveled down by ketoconazole as well as methoxsalen and alpha-naphthaflavone. Furthermore, ketoconazole effectively diminished cell-free LDL oxidation induced by iron, but not copper ions, and reduced the spontaneous and zymosan-stimulated lucigenin-amplified chemiluminescence of macrophages. The data allow us to suggest that ketoconazole inhibits LDL oxidation by acting as an iron chelator and/or inhibitor of prooxidant forms of iron-containing enzymes.

Effect of verapamil and nifedipine on cholesteryl ester metabolism and low-density lipoprotein oxidation in macrophages.

Using mouse macrophage cultures, the effects of verapamil and nifedipine on cholesteryl ester and low-density lipoprotein (LDL) metabolism were studied with special reference to the following parameters: (a) incorporation of [14C]oleate into cholesteryl esters (ChE), (b) contents of total and free cholesterol (FCh), (c) liberation of [14C]oleate from ChE and incorporation of [3H]FCh into ChE, (d) excretion of [3H]Ch from the cells, and (e) LDL oxidation. Verapamil and nifedipine (10-100 microM) were shown to decrease in a dose-dependent manner the incorporation of [14C]oleate into ChE and to increase the concentration of FCh but had no appreciable effect on the concentration of total cholesterol in macrophages cultured in the presence of acetylated LDL. The drugs stimulated the liberation of [14C]oleate from cellular ChE. The pharmacological concentrations (25-75 microM) of verapamil and nifedipine increased the excretion of [3H]FCh from ChE of macrophages in the presence of serum and high-density lipoproteins. The same concentrations of the drugs inhibited both LDL-derived malonyldialdehyde-like products and nitroblue tetrazolium dye reduction in a dose-dependent fashion. The results obtained suggest that verapamil and nifedipine exert their macrophage-mediated antiatherosclerotic effect via reduction of LDL oxidative modification, reduction of intracellular ChE synthesis, stimulation of ChE hydrolysis and cholesterol excretion from the cells.

Soluble glucan protects against endotoxin shock in the rat: the role of the scavenger receptor.

Soluble carboxymethyl-b-1,3-glucan (CMG), a possible ligand for scavenger receptors, has macrophage-activating action but lacks the granulomatose inflammatory side effect: it is a promising immunomodulator that may mitigate the severity of sepsis. This motivated us to study in rats the effect of CMG (25 mg/kg), injected into the tail vein at 48 and 24 h prior to the administration of 5 mg/kg Escherichia coli 0127.B8 endotoxin on survival, hemodynamic condition, and, in vitro, on the chemiluminescence of PMNs and macrophages, and on macrophagal tumor necrosis factor (TNF) production. Acetylated low density lipoprotein (AcLDL) clearance in vivo and in vitro binding to macrophages was used to study scavenger receptor function. In the nonpretreated group 9 of 10 rats died during the first 24 h after endotoxin, but all CMG-pretreated rats survived. CMG-pretreatment prevented severe decreases in cardiac output and blood pressure after endotoxin. Chemiluminescence of macrophages and PMNs from CMG-pretreated rats was about two times less (p < .05) than that from nonpretreated ones; the endotoxin induced TNF production by macrophages also decreased. Pretreatment with CMG increased, but coinjection of CMG and AcLDL decreased the AcLDL clearance, while coinjection of endotoxin and AcLDL decreased the survival rate. In vitro AcLDL uptake by macrophages decreased after coinjection with CMG. Our results thus showed that CMG was protective in rat endotoxin shock, which seemed partly connected with enhancement of endotoxin clearance through scavenger receptors and to decreased TNF production.

[Influence of the activation of the immune system cells on the parameters of lipid metabolism in macrophages]. / Vliianie aktivatsii kletok immunnoi sistemy na parametry lipidnogo obmena v makrofagakh.

The influence of tumor necrosis factor a (TNF-alpha) and media, conditioned by activated macrophages and lymphocytes and containing a complex of biologically active compounds (including cytokines), on the parameters of lipid metabolism in macrophages was studied. The addition of recombinant TNF-alpha and immunocompetent cell-conditioned media to mouse peritoneal macrophages culture stimulated labelled oleate incorporation into cholesterol esters and triglycerides, as well as labelled glycerine incorporation into cholesterol esters, but inhibited labelled cholesterol incorporation into cholesterol esters. One of the mechanisms of the influence of activated immunocompetent cells on cholesterol metabolism in macrophages was, supposedly, the stimulation of sphigmomyelinase activity by a complex of anti-inflammatory cytokines produced by these cells on their activation.

[Effect of modified low density lipoproteins on humoral immune response and functional activity of macrophages in mice]. / Vliianie modifitsirovannykh lipoproteinov nizkoi plotnosti na gumoral'nyi immunyi otvet i funktsional'nuiu aktivnost' makrofagov myshi.

Intravenous injection of acetylated low density lipoproteins (acLDL) in mice in a dose of 0.5 mg per mouse decreased the intensity of humoral immune response to sheep red blood cells (SRBC) by 35%. The addition of acLDL to mouse peritoneal macrophages in vitro resulted in inhibition of Fc-dependent phagocytosis of SRBC and fourfold increased secretion of prostaglandins E2 by macrophages. Fc-dependent phagocytosis of SRBC was also found to be inhibited by oxysterols (25-hydroxycholesterol and 7-ketocholesterol), added to the incubation medium of macrophages in vitro in doses of 0.5-5 mg/ml. The conclusion was made that oxidative metabolism of cholesterol and arachidonic acid, contained in LDL, may mediate the immunomodulating effects of modified LDL.

[Effect of ketoconazole on the activity of key enzymes of biosynthesis of cholesterol and its esters in the liver of rats maintained on a cholesterol-enriched diet]. / Vliianie ketokonazola na aktivnost' kliuchevykh fermentov biosinteza kholesterina i ego éfirov v pecheni krys, soderzhavshikhsia na obogashchennoi kholesterinom diete.

Ketoconazole in vivo has been studied for its effect on the activity of key enzymes of the cholesterol and its esters' biosynthesis in the liver and on the cholesterol concentration in certain fractions of blood lipoproteins in normal and cholesterol-fed rats. It is established that ketoconazole decreases cholesterol concentration in low-density lipoproteins and in very low-density lipoproteins as well as decrease the acyl-CoA-cholesterol acyl-transferase activity and increases the 3-hydroxy-3-methyl-glutaryl-CoA-reductase activity in the liver microsomes of intact and test animals. It is supposed that the possible cause of the observed changes can be a disturbance in regulation of basic links of cholesterol metabolism in the liver.

[The effect of ketoconazole on the cholesterol content of the blood serum lipoproteins and bile in experimental hypercholesterolemia]. / Vliianie ketokonazola na soderzhanie kholesterina v lipoproteidakh syvorotki krovi i v zhelchi pri éksperimental'noi giperkholesteronemii.

Inclusion of ketonazole (in a daily dose of 400 mg/kg for 8 days) into the diet of intact and cholesterol-fed (5% dietary cholesterol) rats produced a respective 20- and 30-percent lowering of cholesterol content in blood serum. In all the animals, the hypocholesterolemic effect of ketoconazole was realized via a decrease of the concentration of very low and low density lipoproteins. Ketoconazole also gave rise to a reduction of the concentration of cholesterol and bile acids in bile of the intact rats and of cholesterol in bile of the cholesterol-fed animals.

[The effect of verapamil and nifedipine on cholesterol esterification and accumulation in macrophages]. / Vliianie verapamila i nifedipina na ésterifikatsiiu i nakoplenie kholesterina v makrofagakh.

Administration of verapamil and nifedipine in doses of 10-75 microM into the culture of mouse peritoneal macrophages incubated in a non-lipid medium with acetylated low density lipoproteins (50 g protein/ml) decreased the incorporation of 14C oleate into cholesterol esters by 50-90%, increased the content of intracellular free cholesterol by 19-79% and did not influence the content of total cholesterol in macrophages. Administration of verapamil and nifedipine in doses of 25 and 50 microM in the culture of macrophages previously enriched with cholesterol reduced the rate of cholesterol esterification by 22-62%. After combined administration of verapamil and nifedipine in doses of 25 microM into the medium the rate of cholesterol esterification in macrophages fell by 72.4%.