Early-stage atherosclerosis in poloxamer 407-induced hyperlipidemic mice: pathological features and changes in the lipid composition of serum lipoprotein fractions and subfractions.

BACKGROUND: The aims of this study were to evaluate the effect of poloxamer 407 administration on atherogenic serum lipoprotein fractions and subfractions associated with cholesterol, triglycerides and phospholipids, as well as the onset of early atherosclerosis, in mice. METHODS: Mice were administered either sterile saline or poloxamer 407 (to induce a dose-controlled hyperlipidemia) for 1 month and then sacrificed at 1, 4 and 10 days after the last dose of poloxamer 407. Systolic and diastolic blood pressure, the activity of a cysteine protease (cathepsin B) in cardiac and liver tissue, and histological/morphological examination of heart and liver specimens was performed for each group of mice at each time point. Lastly, small angle X-ray scattering was utilized to analyze the lipoprotein fractions and subfractions associated with cholesterol, triglycerides and phospholipids for both groups of mice at each time point. Statistical analysis was performed using one-way, analysis-of-variance with post hoc analysis to determine significantly different mean values, while correlation analysis employed the Spearman test. RESULTS: Poloxamer 407-treated mice revealed significant hyperlipidemia, moderately elevated blood pressure, general lipidosis in liver cells, increased cysteine protease activity in heart tissue, and contractile-type changes in cardiomyocytes. Similar to humans, the onset of atherosclerosis in poloxamer 407-treated mice was characterized by a steady increase in serum low-density, intermediate-density and very-low-density lipoprotein fractions, as well as very-low-density lipoprotein subfractions. CONCLUSIONS: We would propose that the sustained elevation of serum atherogenic lipoprotein fractions and subfractions induced by the administration of poloxamer 407 to mice resulted in the morphological changes we observed in both heart and liver cells, which are suggested to precede atherosclerosis, since this is a well-established mouse model of atherosclerosis. Since most of the cellular, biochemical and physiological changes documented in the present study using poloxamer 407-treated mice are related to the symptoms of early atherosclerosis in humans, it is suggested that the poloxamer 407-induced mouse model of hyperlipidemia and atherosclerosis might prove beneficial as an experimental animal model with which to evaluate the pathological features observed in early-stage atherosclerosis.

The influence of repeated administration of poloxamer 407 on serum lipoproteins and protease activity in mouse liver and heart.

The effects of repeated administration of poloxamer 407 (P-407) on lipoprotein-cholesterol (LP-C) and lipoprotein-triglyceride (LP-TG) fractions and subfractions, as well as the effect on liver and heart proteases, were studied. Repeated administration of P-407 to male CBA mice resulted in a model of atherosclerosis with increased diastolic blood pressure; there was a drastic increase in total serum cholesterol and especially TG. A novel small-angle X-ray scattering method for the determination of the fractional and subfractional composition of LP-C and LP-TG was used. In chronically P-407-treated mice, P-407 significantly increased atherogenic low-density lipoprotein C (LDL-C) fractions, as well as intermediate-density lipoprotein C (IDL-C), and LDL1₋3-C subfractions, and very-low-density lipoprotein-C (VLDL-C) fractions, as well as VLDL1₋2-C and VLDL3₋5-C subfractions), to a lesser extent, the total anti-atherogenic high-density lipoprotein C (HDL-C) fraction, as well as HDL2-C and HDL3-C subfractions. Additionally, we demonstrated an increase in the serum chitotriosidase activity, without significant changes in serum matrix metalloprotease (MMP) activity. Morphological changes observed in P-407-treated mice included atherosclerosis in the heart and storage syndrome in the liver macrophages. P-407 significantly increased the activity of cysteine, aspartate proteases, and MMPs in the heart, and only the activity of cathepsin B and MMPs in the liver of mice. Thus, repeated administration of P-407 to mice induced atherosclerosis secondary to sustained dyslipidemia and formation of foamy macrophages in liver, and also modulated the activity of heart and liver proteases.

Influence of atorvastatin and carboxymethylated glucan on the serum lipoprotein profile and MMP activity of mice with lipemia induced by poloxamer 407.

The effects of atorvastatin and carboxymethylated ß-glucan (CMG) on the lipoprotein-cholesterol (LP-C) and lipoprotein-triglyceride (LP-TG) fractions and subfractions at the early stage of murine hyperlipidemia, and its pleiotropic anti-inflammatory effects, were studied. Atorvastatin and CMG were administered in ICR male mice with acute lipemia induced with a single injection of poloxamer 407 (P-407). A novel small-angle X-ray scattering method for the determination of fractional and subfractional composition of LP-C and LP-TG was used. In P-407-treated animals, there was a drastic increase of total cholesterol and especially TG. Atorvastatin decreased both the total cholesterol and TG, but not to control levels. CMG primarily decreased TG and was not as potent as atorvastatin. P-407 increased atherogenic LDL-C (IDL-C and LDL(1-3)-C subfractions) and very low-density lipoprotein-C (VLDL-C) (VLDL(1-2)-C and VLDL(3-5)-C subfractions) fractions, with an increase of the total anti-atherogenic HDL-C fraction (HDL(2)-C subfraction). Atorvastatin treatment of lipemia was followed by a decrease in the total LP-C, total LDL-C (LDL(1-3)-C subfraction), and the LDL(1-3)-TG subfraction. Additionally, atorvastatin treatment resulted in an increase in the serum matrix metalloproteases activity both in control and P-407-treated mice. In general, high-dose atorvastatin therapy exerts its lipid-lowering and pleiotropic effects in the early stages of acute lipemia induced in mice by treatment with P-407.

Influence of atorvastatin on fractional and subfractional composition of serum lipoproteins and MMP activity in mice with Triton WR 1339-induced lipaemia.

OBJECTIVES: The effects of atorvastatin on the atherogenic and anti-atherogenic lipoprotein-cholesterol (C-LP) and lipoprotein-triglyceride (TG-LP) fractions and subfractions at the early stage of murine acute hyperlipidaemia, and its pleiotropic anti-inflammatory effects via the activity of matrix metalloproteinases (MMPs) were studied. METHODS: Atorvastatin (75 mg/kg) was administered to ICR mice with acute lipaemia induced by a single injection of Triton WR 1339 (500 mg/kg). A novel small-angle X-ray scattering (SAXS) method was used for the determination of the fractional and subfractional composition of C-LP and TG-LP. KEY FINDING: In Triton WR 1339-treated mice, there was a drastic increase in the atherogenic low-density C-LP (C-LDL) fraction, intermediate density lipoprotein-cholesterol (C-IDL) subfraction, and very low-density C-LP (C-VLDL) fractions (C-VLDL(3-5) subfraction). Additionally, there was an increase in the C-HDL(3) subfraction. Treatment of lipaemia with atorvastatin resulted in the normalization of the atherogenic C-LDL fraction and the C-IDL subfraction. A decrease in C-VLDL (C-VLDL(3-5) subfraction), total cholesterol and, especially, triglyceride (TG) concentrations was also demonstrated. Similar results were obtained with the TG-LP fractions and subfractions. Additionally, atorvastatin treatment resulted in an increase in the serum and liver MMP activity. CONCLUSION: High-dose atorvastatin therapy exerts its rapid lipid-lowering and pleiotropic effect(s) in the early stages of acute lipaemia induced with Triton WR-1339.

Small-angle X-ray characterization of the nucleoprotein complexes resulting from DNA-induced oligomerization of HIV-1 integrase.

HIV-1 integrase (IN) catalyses integration of a DNA copy of the viral genome into the host genome. Specific interactions between retroviral IN and long terminal repeats (LTR) are required for this insertion. To characterize quantitatively the influence of the determinants of DNA substrate specificity on the oligomerization status of IN, we used the small-angle X-ray scattering (SAXS) technique. Under certain conditions in the absence of ODNs IN existed only as monomers. IN preincubation with specific ODNs led mainly to formation of dimers, the relative amount of which correlated well with the increase in the enzyme activity in the 3'-processing reaction. Under these conditions, tetramers were scarce. Non-specific ODNs stimulated formation of catalytically inactive dimers and tetramers. Complexes of monomeric, dimeric and tetrameric forms of IN with specific and non-specific ODNs had varying radii of gyration (R(g)), suggesting that the specific sequence-dependent formation of IN tetramers can probably occur by dimerization of two dimers of different structure. From our data we can conclude that the DNA-induced oligomerization of HIV-1 IN is probably of importance to provide substrate specificity and to increase the enzyme activity.