Lipid and protein oxidation in erythrocyte membranes of hypercholesterolemic subjects

The role of oxidative stress in alterations of hematological parameters and inflammatory markers induced by early hypercholesterolemia

AIMS

The investigation of the effects of a high cholesterol diet (HD) for a short-time period on hematological parameters and the potential role of oxidative stress and inflammation markers.

MAIN METHODS

Rabbits were fed either a control diet or a diet containing 1% cholesterol (HD) for 5-6 weeks. The plasma lipid levels, C reactive protein (CRP), total red blood cells (RBC), total white blood cells (WBC), platelet count, packed cell volume (PCV) and leukocyte formula were determined. Oxidative stress was evaluated by the thiobarbituric acid reactive substances (TBARS), total glutathione and GSH serum level measurements. The osmotic fragility and the membrane fluidity of erythrocytes were determined. The levels of total cholesterol and TBARS were also measured in the erythrocyte membrane suspension.

KEY FINDINGS

A decrease in the RBC and PCV was observed in rabbits fed on HD. The membrane rigidity and osmotic fragility were increased, and the morphological changes caused by the HD and TBARS levels in the erythrocyte membrane may account for this phenomenon. The inflammatory markers as the CRP levels, the platelet count, the WBC and the neutrophils were increased. The TBARS and GSH levels in the serum were increased and decreased, respectively.

SIGNIFICANCE

This study shows that feeding rabbits an HD for a short time induces hematological alterations, disturbances in the oxidant-antioxidant balance and an increase of inflammatory markers. These findings support the importance of the early correction or prevention of high cholesterol levels to disrupt the process leading to the development of cardiovascular diseases.

Effects of nutritional and excessive levels of selenium on red blood cells of rats fed a high cholesterol diet

In this study, we investigated the effects of selenium (Se) on the properties of erythrocytes and atherogenic index in the presence and absence of high cholesterol diet (HCD). The effect of selected two different doses (1 μg and 50 μg Se/kg/body weight) on HCD-induced oxidative stress was investigated. The hemolysis of the erythrocytes of the HCD rats as well as by high levels of selenium or their combination was markedly increased. Likewise, atherogenic index and plasma glutathione peroxidase (GPx) activity were significantly increased in the same groups of rats compared to control ones. In contrast, paraoxonase activity, glutathione levels and protein thiol levels, catalase, GPx, and superoxide dismutase activities were significantly decreased in rats that received the HCD, high selenium dose, or their combination. Malondialdehyde and protein carbonyl levels in the plasma and red blood cells were significantly increased by HCD and high selenium dose administration. Co-administration of selenium at low dose with or without an HCD restored all of the investigated parameters to near-normal values. The results of this study suggest that excess selenium administration with HCD worsens the atherogenic index and enhances formation of oxidized red blood cells. At dosage levels in the nutritional range such as 1 μg Se/kg body weight, selenium ameliorates the atherogenic index and preserves the antioxidant capacity of the erythrocytes.

Bivariate and multivariate analyses of the influence of blood variables of patients submitted to Roux-en-Y gastric bypass on the stability of erythrocyte membrane against the chaotropic action of ethanol

The stability of the erythrocyte membrane, which is essential for the maintenance of cell functions, occurs in a critical region of fluidity, which depends largely on its composition and the composition and characteristics of the medium. As the composition of the erythrocyte membrane is influenced by several blood variables, the stability of the erythrocyte membrane must have relations with them. The present study aimed to evaluate, by bivariate and multivariate statistical analyses, the correlations and causal relationships between hematologic and biochemical variables and the stability of the erythrocyte membrane against the chaotropic action of ethanol. The validity of this type of analysis depends on the homogeneity of the population and on the variability of the studied parameters, conditions that can be filled by patients who undergo bariatric surgery by the technique of Roux-en-Y gastric bypass since they will suffer feeding restrictions that have great impact on their blood composition. Pathway analysis revealed that an increase in hemoglobin leads to decreased stability of the cell, probably through a process mediated by an increase in mean corpuscular volume. Furthermore, an increase in the mean corpuscular hemoglobin (MCH) leads to an increase in erythrocyte membrane stability, probably because higher values of MCH are associated with smaller quantities of red blood cells and a larger contact area between the cell membrane and ethanol present in the medium.

Pravastatin provides antioxidant activity and protection of erythrocytes loaded Primaquine

Loading erythrocytes with Primaquine (PQ) is advantageous. However, PQ produces damage to erythrocytes through free radicals production. Statins have antioxidant action and are involved in protective effect against situation of oxidative stress. Thus the protective effect of pravastatin (PS) against PQ induced oxidative damage to human erythrocytes was investigated in the current studies upon loading to erythrocytes.The erythrocytes were classified into; control erythrocytes, erythrocytes incubated with either 2 mM of PS or 2 mM of PQ, and erythrocytes incubated with combination of PS plus PQ. After incubation for 30 min, the effect of the drugs on erythrocytes hemolysis as well as some biomarkers of oxidative stress (none protein thiols, protein carbonyl, thiobarbituric acid reactive substance) were investigated.Our results revealed that PS maintains these biomarkers at values similar to that of control ones. On the other hand, PQ cause significant increases of protein carbonyl by 115% and thiobarbituric acid reactive substance by 225% while non-protein thiols were significantly decreased by 112 % compared with control erythrocytes. PS pre-incubation before PQ exerts marked reduction of these markers in comparison with PQ alone. Moreover, at NaCl concentrations between 0.4% and 0.8%, PQ causes significant increase of Red Blood Cells (RBCs) hemolysis in comparison with the other groups (P<0. 001). Scanning electron micrograph indicates spherocytes formation by PQ incubation, but in the other groups the discocyte shape of erythrocytes was preserved.The reduction of protein oxidation and lipids peroxidation by PS is related to antioxidants effect of this statin. Preservation of erythrocytes fragility and morphology by PS are related to its free radicals scavenging effect. It is concluded that pravastatin has protective effect against erythrocytes dysfunction related any situations associated with increased oxidative stress, especially when loaded with PQ.

Artichoke leaf extract reduces oxidative stress and lipoprotein dyshomeostasis in rats fed on high cholesterol diet

Hypercholesterolemia and lipid peroxidation play complementary role in atherosclerosis. Artichoke leaf extract (ALE) is rich in natural antioxidants and has a cholesterol-reducing effect. However, there is no study investigating the effect of ALE on lipid levels and lipid peroxidation in experimental hypercholesterolemic conditions. Rats were fed on 4% (w/w) cholesterol and 1% (w/w) cholic acid supplemented diet for 1 month. ALE (1.5 g/kg/day) was given by gavage during the last 2 weeks. Serum lipid composition, malondialdehyde (MDA) and diene conjugate (DC) levels and plasma antioxidant activity (AOA) were measured. In addition, endogenous DC and copper-induced MDA levels were determined in apo B-containing lipoproteins (LDL+VLDL fraction). Serum cholesterol and triglyceride levels and the ratio of cholesterol to HDL-cholesterol decreased due to ALE treatment in rats fed on HC diet. Significant decreases in serum MDA and DC levels and increases in plasma AOA were detected in serum in ALE-treated hypercholesterolemic rats. Endogenous DC and copper-induced MDA levels were also lower in LDL+VLDL fraction due to ALE-treatment in hypercholesterolemic rats. Our results indicate that ALE may be useful for the prevention of hypercholesterolemia-induced pro-oxidant state in LDL+VLDL fraction and the reduction of increased serum cholesterol and triglyceride levels.

Effect of artichoke leaf extract on hepatic and cardiac oxidative stress in rats fed on high cholesterol diet

Hypercholesterolemia and lipid peroxidation play complementary roles in atherosclerosis. Artichoke (Cynara scolymus L., Asteraceae) leaf extract (ALE), rich in antioxidants, has cholesterol-reducing effect. We investigated the effect of ALE on serum and hepatic lipid levels and pro-oxidant-antioxidant balance in the liver and heart of hypercholesterolemic rats. Rats were fed on 4% (w/w) cholesterol and 1% cholic acid (w/w) supplemented diet for 1 month. ALE (1.5 g/kg/day) was given by gavage during the last 2 weeks. High cholesterol (HC) diet caused significant increases in serum and liver cholesterol and triglyceride levels. It increased malondialdehyde (MDA) and diene conjugate (DC) levels in both tissues. Hepatic vitamin E levels and hepatic and cardiac glutathione peroxidase (GSH-Px) activities decreased, but superoxide dismutase and glutathione transferase activities, glutathione, and vitamin C levels remained unchanged due to HC diet. Serum cholesterol and triglyceride levels and ratio of cholesterol to high-density lipoprotein (HDL)-cholesterol decreased in ALE plus HC-treated rats, but liver cholesterol and triglyceride levels remained unchanged. Significant decreases in hepatic and cardiac MDA and DC levels and increases in hepatic vitamin E and GSH-Px activities were observed in ALE-treated hypercholesterolemic rats. Our results indicate that ALE decreases serum lipids and hypercholesterolemia-induced pro-oxidant state in both tissues.

eNOS T-786C polymorphism affects atorvastatin-induced changes in erythrocyte membrane fluidity

PURPOSE

Statins have pleiotropic effects, including endothelial nitric oxide synthase (eNOS) upregulation and increased nitric oxide formation, which can be modulated by a genetic polymorphism in the promoter region of the eNOS gene (T-786C). Here, we report our investigation of whether this polymorphism modulates the effects of atorvastatin on the fluidity of erythrocyte membranes.

METHODS

We genotyped 200 healthy subjects (males, 18-60 years of age) and then randomly selected 15 of these with the TT genotype and 15 with the CC genotype to receive placebo or atorvastatin (10 mg/day oral administration) for 14 days. Cell membrane fluidity was evaluated by electron paramagnetic resonance (EPR) and spin-labeling method. The EPR spectra were registered on a VARIAN-E4 spectrometer. Thiobarbituric acid-reactive species (TBA-RS) and plasma membrane cholesterol were determined in the erythrocytes.

RESULTS

Atorvastatin reduced membrane fluidity in CC subjects (P < 0.05) but not in those with the TT genotype (P > 0.05). While no significant differences were found in plasma membrane cholesterol concentrations, higher TBA-RS concentrations were found in the CC subjects than in the TT subjects (P < 0.05).

CONCLUSIONS

These findings suggest that a short treatment with atorvastatin is disadvantageous to subjects with the CC genotype for the T-786C polymorphism compared to those with TT genotype, at least in terms of the hemorheological properties of erythrocytes.

Anti-inflammatory and hypolipemic effects in vitro of simvastatin comparing to epicatechin in patients with type-2 hypercholesterolemia

OBJECTIVE

The study involved 25 patients with type-2 hypercholesterolemia (mean age 49.3+/-11.3). The control group consisted of 28 healthy individuals (mean age 50.7+/-7.2).

METHODS

The cholesterol concentrations in plasma membranes of erythrocytes were measured by means of Liebermann-Burchard reagent. The membrane lipid peroxidation in whole erythrocytes was determined. The membrane fluidity was estimated by spin labelled method.

RESULTS

The in vitro study shows that the cholesterol concentration in membranes incubated with simvastatin and epicatechin decreases; in healthy donors there are no changes. Simvastatin does not lead to changes in the lipid peroxidation in the in vitro data. Epicatechin decreases the level of membrane lipid peroxidation in patients with hypercholesterolemia and in healthy donors. Simvastatin and epicatechin cause an increase in the fluidity of plasma membranes of erythrocytes.

CONCLUSIONS

Simvastatin causes the decrease in cholesterol concentration in erythrocytes membranes not only in the in vivo but also the in vitro experiments. Flavonoids have antioxidant properties in vitro. Simvastatin influences the lipid peroxidation only in vivo, not in vitro systems. This observation is an additional contribution to the statins' pleiotropic effect.

Structural and oxidative modifications of erythrocyte ghosts in patients with primary biliary cirrhosis: relation with the disease stage and effect of bile acid treatment

BACKGROUND

Erythrocyte membrane modifications in patients with cholestasis are supposed to reflect those of hepatocytes.

METHODS

Erythrocyte membrane composition (cholesterol, phospholipids, fatty acids, protein sulphydrils and carbonyls) was assessed and related to the stage of liver disease in patients with primary biliary cirrhosis before and after 1 year of ursodeoxycholate treatment.

RESULTS

Compared with controls, patients showed lower levels of protein sulphydrils (28.9 +/- 7.1 vs. 65.6 +/- 1.8 nmol mg(-1) prot) and accumulation of carbonyls (4.7 +/- 1.7 vs. 1.4 +/- 0.1 nmol mg(-1) prot). Phosphatidylethanolamine level was lower in stage III-IV cirrhosis while phosphatidylcholine and cholesterol levels were higher; as a consequence the phosphatidylcholine/sphingomyelin ratio was higher than in controls (4.25 +/- 0.55 in the I-II stage and 2.89 +/- 0.44 in the stage III-IV vs. 1.61 +/- 0.30). These changes were particularly evident in patients with more advanced stages of liver disease. Protein sulphydrils and carbonyls, phosphatidylethanolamine and cholesterol levels correlated (P<0.05) with the histological stage of the liver disease, serum and membrane cholesterol levels were significantly related (r=0.66, P<0.05). One year of ursodeoxycholate administration was accompanied by major changes of the membrane lipid composition, partial reversal of protein oxidation, and improvement of serum parameters.

CONCLUSIONS

This study indicates that major alterations in protein status and lipid composition occur in erythrocyte membrane of patients with primary biliary cirrhosis. These changes were more pronounced in patients with advanced liver disease. Ursodeoxycholate was able to revert in part serum and erythrocyte alterations, especially in patients with early stages of liver disease.

Influence on hazelnut oil administration on peroxidation status of erythrocytes and apolipoprotein B 100-containing lipoproteins in rabbits fed on a high cholesterol diet

Hazelnut oil (HO) is rich in monounsaturated fatty acids (MUFA). The effect of a high cholesterol (HC) diet with and without HO on lipids and lipid peroxide levels in plasma, apolipoprotein B 100-containing lipoproteins (VLDL + LDL), and erythrocytes as well as hematological data was investigated in rabbits. A HC diet caused significant increases in lipid peroxide levels in plasma and apo B-containing lipoproteins together with histopathological atherosclerotic findings in aorta. In addition, this diet resulted in hemolytic anemia associated with increased endogenous diene conjugate (DC) levels, but H(2)O(2)-induced malondialdehyde (MDA) levels remained unchanged in erythrocytes. HO supplementation reduced lipid peroxide levels in plasma and apolipoprotein B 100-containing lipoproteins as well as aortic atherosclerotic lesions in rabbits fed an HC diet without any decreasing effect on lipid levels. In addition, HO was found to reduce hemolytic anemia together with significant decreases in DC and H(2)O(2)-induced MDA levels.