Influence of hypercholesterolemia on morphological and rheological characteristics of erythrocytes

The red blood cell as a mediator of endothelial dysfunction in patients with familial hypercholesterolemia and dyslipidemia

BACKGROUND

Patients with familial hypercholesterolemia (FH) display high levels of low-density lipoprotein cholesterol (LDL-c), endothelial dysfunction, and increased risk of premature atherosclerosis. We have previously shown that red blood cells (RBCs) from patients with type 2 diabetes induce endothelial dysfunction through increased arginase 1 and reactive oxygen species (ROS).

OBJECTIVE

To test the hypothesis that RBCs from patients with FH (FH-RBCs) and elevated LDL-c induce endothelial dysfunction.

METHODS AND RESULTS

FH-RBCs and LDL-c >5.0 mM induced endothelial dysfunction following 18-h incubation with isolated aortic rings from healthy rats compared to FH-RBCs and LDL-c <2.5 mM or RBCs from healthy subjects (H-RBCs). Inhibition of vascular but not RBC arginase attenuated the degree of endothelial dysfunction induced by FH-RBCs and LDL-c >5.0 mM. Furthermore, arginase 1 but not arginase 2 was elevated in the vasculature of aortic segments after incubation with FH-RBCs and LDL-c >5.0 mM. A superoxide scavenger, present throughout the 18-h incubation, attenuated the degree of endothelial dysfunction induced by FH-RBCs and LDL-c >5.0 mM. ROS production was elevated in these RBCs in comparison with H-RBCs. Scavenging of vascular ROS through various antioxidants also attenuated the degree of endothelial dysfunction induced by FH-RBCs and LDL-c >5.0 mM. This was corroborated by an increase in the lipid peroxidation product 4-hydroxynonenal. Lipidomic analysis of RBC lysates did not reveal any significant changes across the groups.

CONCLUSION

FH-RBCs induce endothelial dysfunction dependent on LDL-c levels via arginase 1 and ROS-dependent mechanisms.

Red Blood Cell Membrane Cholesterol May Be a Key Regulator of Sickle Cell Disease Microvascular Complications

Cell membrane lipid composition, especially cholesterol, affects many functions of embedded enzymes, transporters and receptors in red blood cells (RBC). High membrane cholesterol content affects the RBCs' main vital function, O₂ and CO₂ transport and delivery, with consequences on peripheral tissue physiology and pathology. A high degree of deformability of RBCs is required to accommodate the size of micro-vessels with diameters significantly lower than RBCs. The potential therapeutic role of high-density lipoproteins (HDL) in the removal of cholesterol and its activity regarding maintenance of an optimal concentration of RBC membrane cholesterol have not been well investigated. On the contrary, the focus for HDL research has mainly been on the clearance of cholesterol accumulated in atherosclerotic macrophages and plaques. Since all interventions aiming at decreasing cardiovascular diseases by increasing the plasma level of HDL cholesterol have failed so far in large outcome studies, we reviewed the potential role of HDL to remove excess membrane cholesterol from RBC, especially in sickle cell disease (SCD). Indeed, abundant literature supports a consistent decrease in cholesterol transported by all plasma lipoproteins in SCD, in addition to HDL, low- (LDL) and very low-density lipoproteins (VLDL). Unexpectedly, these decreases in plasma were associated with an increase in RBC membrane cholesterol. The concentration and activity of the main enzyme involved in the removal of cholesterol and generation of large HDL particles-lecithin cholesterol ester transferase (LCAT)-are also significantly decreased in SCD. These observations might partially explain the decrease in RBC deformability, diminished gas exchange and tendency of RBCs to aggregate in SCD. We showed that incubation of RBC from SCD patients with human HDL or the HDL-mimetic peptide Fx5A improves the impaired RBC deformability and decreases intracellular reactive oxygen species levels. We propose that the main physiological role of HDL is to regulate the cholesterol/phospholipid ratio (C/PL), which is fundamental to the transport of oxygen and its delivery to peripheral tissues.

Sex-Specific Differences of Adenosine Triphosphate Levels in Red Blood Cells Isolated From ApoE/LDLR Double-Deficient Mice

In this study for the first time, we investigated the correlation between sex-specific differences in adenosine triphosphate (ATP) levels in red blood cells (RBCs) and their mechanical, biochemical, and morphological alterations during the progression of atherosclerosis in ApoE/LDLR double-deficient (ApoE/LDLR^−/−) mice. Our results indicate that both sex and age affect alterations in RBCs of both ApoE/LDLR^−/− and C57BL/6J mice. When compared with male RBCs, female RBCs were characterized by lower basal ATP and mean corpuscular hemoglobin concentration (MCHC), higher hemoglobin concentration (HGB), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), deformability, and phosphatidylserine (PS) exposure levels, regardless of age in both, ApoE/LDLR^−/− and C57BL/6J mice. ApoE/LDLR^−/− mice compared with age-matched controls showed lower basal ATP levels regardless of age and sex. Intracellular ATP level of RBCs was decreased solely in senescent female C57BL/6J mice, while it was elevated in males. Basal extracellular ATP levels were 400 times lower than corresponding intracellular level. In conclusion, basal ATP levels, RBC morphology, deformability, PS exposure levels alterations are sex-dependent in mice. Changes in basal ATP levels were correlated with PS exposure and trends of changes in MCV. Trends of changes of the most RBC parameters were similar in both sexes of ApoE/LDLR^−/− mice compared with age-matched controls; however, their kinetics and levels vary greatly between different stages of disease progression.

Antioxidant Effects of Baoyuan Decoction on Dysfunctional Erythrocytes in High-Fat Diet-Induced Hyperlipidemic ApoE-/- Mice

Baoyuan decoction (BYD), a traditional representative formula, has a long usage history in the treatment of cardiovascular diseases. Since the hyperlipidemia-induced dysfunction of erythrocyte is one of the most important causes of cardiovascular diseases, the improving effects of BYD against high-fat diet (HFD) induced the physiological and physical function of the erythrocytic injury and the potential mechanisms were deeply researched in this study. After 6 weeks of drug treatment, all doses of BYD had significantly decreased the lipid peroxidation in plasma of HFD-induced ApoE^−/− mice, even if it had not improved the lipid levels. Then, the erythrocyte-related experimental results showed that BYD had reduced erythrocyte osmotic fragility, stabilized erythrocyte membrane skeleton protein 4.2, and reformed the erythrocyte morphological changes by decreasing erythrocyte membrane lipid peroxidation levels. This study demonstrated that BYD may ameliorate the physiological and physical function of erythrocyte in hyperlipidemic mice through the antioxidant effect on erythrocyte membranes.

Effect of 405 nm low intensity irradiation on the absorption spectrum of in-vitro hyperlipidemia blood

BACKGROUND:

Laser therapy is reported to be clinically effective for improving microcirculation, rheological properties and blood lipid profiles despite the lack of certainty on the mechanism.

OBJECTIVE:

This study intends to provide methods to drop blood lipid level of hyperlipidemia samples by low-intensity laser irradiation therapy and provide reasoning of mechanism.

METHODS:

Twenty whole blood samples of high level of lipids profile are irradiated by 405 nm low-intensity laser at 12 J/cm2 twice a day for 3 days and compared with normal lipids profile group. Then whole blood sample are centrifuged to obtain result of erythrocyte for further interpretation. Multi-scan spectrum microplate reader is used to measure absorption spectrum and data is analyzed by software SPSS 14.0.

RESULTS:

Results show that after 405 nm low-intensity laser irradiation, whole blood samples of high lipid level statistically have higher absorbance peak value than normal samples while erythrocyte samples have lower absorbance peak value.

CONCLUSIONS:

From the divergence of absorption peak value change after low-intensity laser irradiation for whole blood sample and erythrocyte, we suspect that low level laser irradiation affects the enzymes activity of lipid metabolism, improves the cholesterol balance of plasma and cytoplasm in erythrocyte, and decreases aggregation of the erythrocyte.

Antioxidative and Cholesterol-Lowering Effects of Lemon Essential Oil in Hypercholesterolemia-Induced Rabbits

The cholesterol-lowering and anti-atherogenic effects of lemon essential oil (LEO) were investigated and compared with the effects of limonene. Owing to their volatility, both LEO and limonene were microencapsulated before preparation of the diet (20%, w/w). Hypercholesterolemia-induced rabbits were divided into 3 groups based on plasma total cholesterol (TC) levels and fed coating matrix (control group), LEO (LEO group), or limonene (Limonene group) for 8 weeks. LEO dose-dependently inhibited low-density lipoprotein oxidation in vitro. Plasma TC levels were the lowest in the LEO group (P<0.05). Erythrocytes in the LEO group had a normal disc shape, whereas the erythrocytes in the limonene and control groups were aggregated and star-shaped, respectively. The aortic intima thickness was thinnest in the LEO group followed by the control and limonene groups. Plasma TC lowering and anti-atherogenic effects of LEO were greater than limonene, suggesting that other bioactive compounds besides limonene in LEO might contribute to these effects. The bioactive compounds in LEO were limonene (67.57%), β-pinene (10.00%), and γ-terpinene (9.95%). In addition, sabinene, α-pinene, myrcene, and geranial were also present but the amount was in the range of 1~2%. Several bioactive compounds were also detected. In conclusion, LEO had beneficial effects on hypercholesterolemia due to its antioxidative and cholesterol lowering effects.

Chitosan treatment abrogates hypercholesterolemia-induced erythrocyte's arginase activation

This study aimed to evaluate the protective effect of chitosan (CS) against hypercholesterolemia (HC) induced arginase activation and disruption of nitric oxide (NO) biosynthesis using erythrocytes as cellular model. Human erythrocytes were isolated and classified into eight groups. Next, cells were treated with l-arginine (l-ARG), N^ω-nitro-l-arginine methyl ester (l-NAME), CS or CS + l-ARG in the presence of normal plasma or cholesterol enriches plasma. Then, erythrocytes were incubated at 37 °C for 24 h. The present results revealed that, HC induced significant increase of cholesterol inclusion into erythrocytes membrane compared to control. Moreover, HC caused significant decrease in nitric oxide synthase (NOS) activity similar to l-NAME; however, arginase activity and arginase/NOS ratio significantly increased compared to control. On contrast, treatment of HC with, l-arginine, CS or CS plus l-arginine prevents HC induced cholesterol loading into erythrocytes membrane, NOS inhibition and arginase activation. This study suggested that CS could be protective agent against HC induced disruption of erythrocyte’s oxidative status and arginase activation.

Longxuetongluo Capsule Improves Erythrocyte Function against Lipid Peroxidation and Abnormal Hemorheological Parameters in High Fat Diet-Induced ApoE-/- Mice

Chinese dragon's blood, the red resin of Dracaena cochinchinensis, one of the renowned traditional medicines, has been used to facilitate blood circulation and disperse blood stasis for thousands of years. Phenolic compounds are considered to be responsible for its main biological activities. In this study, total phenolic compounds of Chinese dragon's blood were made into capsule (Longxuetongluo Capsule, LTC) and their effects on the abnormal hemorheological properties were examined by high fat diet (HFD) induced ApoE−/− mice. Compared to the model group, LTC recovered the abnormal hemorheological parameters in HFD-induced ApoE−/− mice by reducing whole blood viscosity (WBV) at high rate and improving erythrocyte function. In conclusion, LTC could ameliorate erythrocyte deformability and osmotic fragility through the reduction of lipid peroxidation on plasma and erythrocyte membranes in HFD-induced ApoE−/− mice, which supported the traditional uses of Chinese dragon's blood as an effective agent for improving blood microcirculation in hypercholesterolemia.

Ezetimibe reduces plant sterol accumulation and favorably increases platelet count in sitosterolemia

OBJECTIVE

To assess if ezetimibe (EZE), a sterol-absorption inhibitor, improves platelet (PLT) count and size relative to its effect on plasma plant sterol (PS) in patients with sitosterolemia (STSL).

STUDY DESIGN

Patients with STSL (5 males, 3 females, 16-56 years of age) receiving EZE intervention as part of their routine care participated in this study. EZE was discontinued for 14 weeks (off) and then resumed for another 14 weeks (on). Hematology variables along with plasma and red blood cells (RBC) PS and total cholesterol (TC) levels were measured at the end of each phase.

RESULTS

EZE increased PLT count (23% ± 9%) and decreased mean PLT volume (MPV; 10% ± 3%, all P < .05). In patients off EZE, PLT counts inversely correlated (r = -0.96 and r = -0.91, all P < .01) with plasma and RBC PS to TC ratio (PS/TC), and MPV positively correlated (r = 0.91, P = .03 and r = 0.93, P = .02) with plasma and RBC PS/TC. EZE reduced plasma and RBC sitosterol (-35% ± 4% and -28% ± 3%), total PS (-37% ± 4% and -28% ± 3%, all P < .0001) levels, and PS/TC (-27% ± 4% and -28% ± 4%, P < .01).

CONCLUSIONS

EZE reduces plasma and RBC PS levels, while increasing PLT count and decreasing MPV, and thereby may reduce the risk for bleeding in STSL. Plasma PS levels and ABCG5/ABCG8 genes should be analyzed in patients with unexplained hematologic abnormalities.

Poikilocytosis in rabbits: prevalence, type, and association with disease

Rabbits (Oryctolagus cuniculus) are a popular companion animal, food animal, and animal model of human disease. Abnormal red cell shapes (poikilocytes) have been observed in rabbits, but their significance is unknown. The objective of this study was to investigate the prevalence and type of poikilocytosis in pet rabbits and its association with physiologic factors, clinical disease, and laboratory abnormalities. We retrospectively analyzed blood smears from 482 rabbits presented to the University of California-Davis Veterinary Medical Teaching Hospital from 1990 to 2010. Number and type of poikilocytes per 2000 red blood cells (RBCs) were counted and expressed as a percentage. Acanthocytes (>3% of RBCs) were found in 150/482 (31%) rabbits and echinocytes (>3% of RBCs) were found in 127/482 (27%) of rabbits, both healthy and diseased. Thirty-three of 482 (7%) rabbits had >30% acanthocytes and echinocytes combined. Mild to moderate (>0.5% of RBCs) fragmented red cells (schistocytes, microcytes, keratocytes, spherocytes) were found in 25/403 (6%) diseased and 0/79 (0%) healthy rabbits (P = 0.0240). Fragmentation and acanthocytosis were more severe in rabbits with inflammatory disease and malignant neoplasia compared with healthy rabbits (P<0.01). The % fragmented cells correlated with % polychromasia, RDW, and heterophil, monocyte, globulins, and fibrinogen concentrations (P<0.05). Echinocytosis was significantly associated with renal failure, azotemia, and acid-base/electrolyte abnormalities (P<0.05). Serum cholesterol concentration correlated significantly with % acanthocytes (P<0.0001), % echinocytes (P = 0.0069), and % fragmented cells (P = 0.0109), but correlations were weak (Spearman ρ <0.02). These findings provide important insights into underlying pathophysiologic mechanisms that appear to affect the prevalence and type of naturally-occurring poikilocytosis in rabbits. Our findings support the need to carefully document poikilocytes in research investigations and in clinical diagnosis and to determine their diagnostic and prognostic value.

Hypolipidemic and antioxidant effects of hydroxycinnamic acids, quercetin, and cyanidin 3-glucoside in hypercholesterolemic erythrocytes (in vitro study)

OBJECTIVE

Four polyphenols: ferulic acid and p-coumaric acid (hydroxycinnamic acids), quercetin (flavonol) and cyanidin 3-glucoside (anthocyanin) were selected, and their antioxidant properties and their influence on cholesterol concentration in hypercholesterolemic and normal erythrocytes were investigated.

METHODS

To determine the effect of phenolic compounds, we prospectively studied cholesterol concentration, lipid peroxidation and membranes fluidity. Whole-blood and isolated erythrocytes (2% hematocrit) were incubated for 24 h with selected compounds at concentration 1, 10 and 100 μmol/L. All investigated compounds decreased lipid peroxidation in whole blood. Cyanidin 3-glucoside and quercetin showed higher antioxidant properties than hydroxycinnamic acids (ferulic acid and p-coumaric acid).

RESULTS

Incubation of whole blood of hypercholesterolemic patients with quercetin and cyanidin 3-glucoside resulted in statistically significant reduction of cholesterol concentration in erythrocytes down to 75% (at 10 μmol/L of polyphenols) and 69% (at 100 μmol/L of polyphenols) of initial values. The effect of both compounds on isolated erythrocytes was even more pronounced, reduction down to 70% (at 10 μmol/L of polyphenols) and 58% (at 100 μmol/L of polyphenols) of initial values. After incubation of isolated erythrocytes of hypercholesterolemic patients with quercetin and cyanidin 3-glucoside, increase of membrane fluidity was noticed. After incubation of isolated erythrocytes of healthy donors with investigated compounds, no changes in membrane fluidity were observed.

CONCLUSION

Our results indicate that flavonols and anthocyanins have higher antioxidant properties and higher influence on cholesterol concentration in erythrocytes membranes than simple hydroxycinnamic acids.

Blood rheology and the low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio in dyslipidaemic and normolipidaemic subjects

The association between blood rheology and the ratio of low-density lipoprotein cholesterol (LDL-C) to high-density lipoprotein cholesterol (HDL-C) was investigated in 142 dyslipidaemic and 253 normolipidaemic subjects. Blood rheology was examined by the microchannel method and fasting serum concentrations of LDL-C, triglyceride and HDL-C were measured. Passage time of whole blood correlated positively with LDL-C concentration, triglyceride concentration and LDL-C/HDL-C ratio, and negatively with HDL-C concentration. Passage time of whole blood was significantly higher in dyslipidaemic and normolipidaemic subjects with LDL-C/HDL-C ratio > 2.0 than in those with ratio < 1.5. Thus, dyslipidaemic subjects had impaired blood rheology, elevated LDL-C and triglyceride concentrations and elevated LDL-C/HDL-C ratio, and reduced HDL-C concentrations. Dyslipidaemic and normolipidaemic subjects with a more elevated LDL-C/HDL-C ratio had greater blood rheology impairment than those with a less elevated ratio. These data suggest that an elevated LDL-C/HDL-C ratio may be helpful in predicting impaired blood rheology.

Impaired blood rheology and elevated remnant-like lipoprotein particle cholesterol in hypercholesterolaemic subjects

Blood rheology, fasting serum concentrations of remnant-like lipoprotein particle cholesterol (RLP-C) and concentrations of other lipids were compared in 23 hypercholesterolaemic and 69 normocholesterolaemic subjects, and the relationship between red blood cell (RBC) deformability and RLP-C concentrations were studied in a different set of six hypercholesterolaemic and six normocholesterolaemic subjects. Passage time of whole blood and concentrations of total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and RLP-C were significantly higher in hypercholesterolaemic than in normocholesterolaemic subjects. Passage time of whole blood correlated positively with TC, TG, LDL-C and RLP-C and negatively with high-density lipoprotein cholesterol. Furthermore, the passage time of 10% haematocrit-adjusted RBCs in phosphate-buffered saline, which reflects RBC deformability, correlated positively with the passage time of whole blood and RLP-C. Thus, hypercholesterolaemic subjects had impaired blood rheology and elevated RLP-C concentrations, which may be associated with the pathophysiology of atherosclerosis in hypercholesterolaemic subjects. Impaired RBC deformability may contribute to impaired blood rheology associated with elevated RLP-C in hypercholesterolaemic subjects.

Nitric oxide pathway activation and impaired red blood cell deformability with hypercholesterolemia

The pathophysiological effects of the activation or inhibition of the nitric oxide (NO)-mediated pathway on the deformability of red blood cells (RBC) were evaluated in the presence of hypercholesterolemia induced in rabbits fed a cholesterol-rich diet. RBC deformability was assessed using a microchannel array flow analyzer system. The maximum passage time (MPT) by flowing a suspension of RBC through the microchannels was used as an index of RBC deformability. During cholesterol feeding for 12 weeks, MPT gradually increased with no significant elevation in the serum asymmetric dimethylarginine (ADMA) and arginine/ADMA ratio. The reduction in RBC deformability associated with hypercholesterolemia was significantly improved during incubation with each of three different NO pathway activators: a NO donor, 8-bromo-cyclic GMP, and arginine; however, no additional reduction was observed with ADMA administration. The inhibition of NO synthase due to ADMA caused a significant reduction in the deformability of normal RBC, which was reversed with NO pathway activation. These results suggest that impaired RBC deformability may be associated with a dysfunction in the NO pathway that is partially dependent upon the accumulation of ADMA in RBC, and exogenous NO pathway activators may improve the microcirculation by restoring RBC deformability in the presence of hypercholesterolemia.

The beneficial effects of lipid-lowering drugs beyond lipid-lowering effects: a comparative study with pravastatin, atorvastatin, and fenofibrate in patients with type IIa and type IIb hyperlipidemia

Hyperlipidemia is an important risk factor for atherosclerosis. Hemorheological factors contribute to morbidity and mortality in patients with dyslipidemia. We evaluated the effects of 3 antihyperlipidemic drugs (pravastatin, atorvastatin, and fenofibrate), which have different mechanisms of action and different patterns of action on lipid profiles, on erythrocyte deformability and fibrinogen levels in patients with type IIa and type IIb hyperlipidemia. Twenty-one patients ( 4 men and 17 women) with type IIa and IIb hyperlipidemia were randomized to 3 drugs (pravastatin 20 mg/d, atorvastatin 10 mg/d, fenofibrate 250 mg/d) for 8 weeks. Plasma glucose, total cholesterol, triglyceride, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) analysis were performed on a BM-Hitachi 747-200 autoanalyzer (Hitachi-Roche, Tokyo, Japan). Fibrinogen analysis was performed according to Clauss method. Erythrocyte deformability was assessed with cell transit analysis device. There was no significant difference in body mass index, lipid profile, fibrinogen level, and erythrocyte deformability index values among the groups before treatment ( P > .05). In all groups, there were statistically significant reductions in total LDL-C levels ( P < .05). The triglyceride levels were significantly reduced in the atorvastatin and fenofibrate groups ( P < .05), but not in the pravastatin group ( P > .05). There was no significant change in HDL-C levels during the treatment with statins ( P > .05), but there was a significant increase in the fenofibrate group ( P < .05). Mean erythrocyte deformability index was improved in all the groups ( P < .05). There was no significant change in fibrinogen levels during the treatment of pravastatin and atorvastatin ( P > .05), but in fenofibrate group, fibrinogen levels were significantly decreased ( P < .05). The 3 groups of antihyperlipidemic drugs have beneficial effects on the erythrocyte deformability index. Only fenofibrate has significant beneficial effects on the fibrinogen levels.

Rheological properties of erythrocytes from male hypercholesterolemia

Diet and general health status has close relation to the flow behavior of blood, which influences the circulation of the blood in the body. In this study, we have compared the rheological properties of erythrocyte, plasma and whole blood from high-cholesterol male subjects with healthy male subjects. Intravenous blood was taken from healthy males (n=10) and males with high cholesterol (n=14). Basic health profile, BMI, hematological count and lipid profile (total cholesterol, LDL, HDL and triglyceride) of the blood were determined. Viscosity and shear rate dependent flow behavior of the subjects blood were measured by cone and plate rheometer, and permeability of erythrocytes by pulsed field gradient NMR. Using the microchannel flow analyzer (MC-FAN), the microcirculation of erythrocyte and plasma were investigated. Our data showed a difference in viscosity and consistency index of the whole blood, and permeability (P<0.05) of erythrocytes between the two groups. Also, the time taken for the flow of erythrocyte and plasma through the MC-FAN was slower for the high-cholesterol group. Correlation study showed that consistency index of the blood is closely related to the level of LDL (P<0.05), and total cholesterol, HDL and LDL (P<0.01) highly correlated with the microcirculation of erythrocyte and plasma. A negative correlation (P<0.05) was found between total cholesterol, HDL and LDL, and permeability of erythrocytes. It is concluded that high level of cholesterol, LDL and HDL in vivo alter the morphology and flow behavior of blood cells that can subsequently increase the risk of impairing physical function and microcirculation.

Ultrastructural study of echinocytes induced by poly (ethylene glycol)-cholesterol

Poly (ethylene glycol)-cholesterol (PEG-Chol) consists of a hydrophilic PEG and hydrophobic cholesterol moiety. When PEG-Chol was applied to erythrocytes, the reagent quantitatively induced protrusions by exclusively distributing in the outer monolayer of the membrane. This kind of response has been regarded as a general response that reduces the stress of expansion of the outer monolayer. However, the relationship between the membrane architecture and the distribution of such molecules is unknown. In this study, we examined the distribution of tagged PEG-Chol along the shape change pathway. The echinocytic shape was initiated by the initial formation of bumps on the rim of the discoid, which subsequently elongated as protrusions. These protrusions contained aggregates of granular structures, which appeared to accommodate the increase in the outer monolayer area. At higher concentrations, PEG-Chol further induced sphero-echinocytosis that resulted in numerous branched protrusion processes. We found that PEG-Chol was exclusively distributed in these protrusions and, in particular, accumulated at the tips. These results suggested that externally intercalated PEG-Chol was sequestrated from erythrocytes as membrane protrusions through an as-yet-unknown mechanism.

Damage to the structure of erythrocyte plasma membranes in patients with type-2 hypercholesterolemia

BACKGROUND

Hypercholesterolemia may decrease the deformability of red blood cells which impairs their hemorheological behavior and promotes atherosclerosis. The study involved 60 hypercholesterolemic patients and 30 healthy individuals as the control group.

METHODS

The membrane fluidity of erythrocytes was estimated by a spin-label method (5-doxylstearic acid (5-DSA)). The ratio of weakly to strongly (W/S) immobilized residues of erythrocyte membrane-bond maleimide-tempo spin label was studied in oxidative damage to membrane protein. Damage to erythrocyte proteins was also indicated by means of Na(+) K(+) ATPase activity.

RESULTS

The membranes of hyperlipidemia (hlp) patients contain larger concentrations of cholesterol 2.16+/-0.24 than do those of the normolipemic individuals 0.31+/-0.24 (P<0.001). The level of Na(+) K(+) ATPase in the erythrocyte membrane from the control group was higher 103.4+/-1.3 (nmolPi/(mgproteinsh)) than in the patient group 93.6+/-3.2 (nmolPi/(mgproteinsh)) (P<0.001). The order parameter S 5-DSA in the control group was 0.745+/-0.009 and in hlp patients was 0.755+/-0.009 (P<0.001). The W/S ratio in the control group amounted to 2.00+/-0.09 and in the hlp patient group was 2.50+/-0.11 (P<0.001).

CONCLUSION

Type-2 hypercholesterolemia causes changes in the structure and fluidity of erythrocyte plasma membranes since the excess of cholesterol affects the normal rheology of blood through its interaction with erythrocytes. It also impairs the function and structure of plasma membrane proteins.

Red cell and plasma plant sterols are related during consumption of plant stanol and sterol ester spreads in children with hypercholesterolemia

OBJECTIVE

To show whether the ratios of squalene and cholesterol precursor sterols to cholesterol and cholestanol and plant sterols to cholesterol change differently in plasma and especially in the red cells of hypercholesterolemic children during consumption of plant stanol and sterol ester spreads.

STUDY DESIGN

In a randomized, double-blind, crossover study, hypercholesterolemic children (n = 23) consumed low-fat plant stanol and sterol ester spreads for 5-week periods separated by a 5-week washout period. Plasma and red cell lipids, squalene, and noncholesterol sterols were measured before and at the end of each period.

RESULTS

The plant stanol and sterol ester spreads lowered plasma total (-9% and -6%, respectively) and low-density lipoprotein (-12% and -9%) cholesterol but had no effect on red cell cholesterol, high-density lipoprotein cholesterol, or plasma triglycerides. The ratios of plasma and red cell sitosterol and campesterol to cholesterol decreased by 32% to 36% (P <.001) with the plant stanol ester and increased by 40% to 52% (P <.001) with the sterol ester spread.

CONCLUSIONS

Consumption of plant sterols increases and consumption of plant stanols decreases the ratios of plant sterols to cholesterol in red cells of hypercholesterolemic children proportionately to the respective changes in plasma.

Short-term control of capsaicin on blood and oxidative stress of rats in vivo

Capsaicin (8-methyl-n-vanillyl-6-nonenamide), a pungent component found in red pepper can induce body heat and possibly enhance blood flow as well as increase energy expenditure, and prevent oxidative stress. Male Wistar rats were divided into vehicle, 1 mg/kg body weight capsaicin and 3 mg/kg body weight capsaicin groups. Samples were taken from the animals on day 1 of i.p. treatment with capsaicin and on 3 consecutive days of i.p. treatment with capsaicin. Our investigation demonstrated that blood flow measurements in rats was negatively correlated with LDL after treatment with capsaicin. Although capsaicin did not show a noticeable effect on the serum total cholesterol level, LDL decreased while HDL and triglyceride increased in rats treated with 3 mg/kg capsaicin for 3 days. The antioxidant effect of capsaicin was not shown when the rats were treated with 1 mg/kg body weight capsaicin. However, rats treated with 3 mg/kg body weight capsaicin for 3 days showed a reduction of oxidative stress measured as malondialdehyde in the liver, lung, kidney and muscle. Liver glycogen was found to decrease after 3 days treatment with 3 mg/kg body weight capsaicin. From this study, it is hypothesized that capsaicin can be a potent antioxidant and aid in lowering LDL even when consumed for a short period.

Effects of the antiplatelet agent TA-993 and its metabolite MB3 on the hemorheological properties of rat and human erythrocytes

In the present study, we investigated the effects of the antiplatelet agent TA-993 and its metabolite MB3 on the hemorheological properties of rat and human erythrocytes in comparison with ticlopidine and aspirin. TA-993 and MB3 concentration-dependently lowered the viscosity of rat erythrocyte suspensions. TA-993 and MB3 inhibited both the hypotonic hemolysis of human erythrocytes and the mechanical hemolysis of rat erythrocytes induced by turbulent flow. Treatment of rats with TA-993 (10 mg/kg/day po) for 10 days significantly increased blood filterability, but ticlopidine and aspirin did not show this effect. TA-993 and MB3 enhanced the interaction of 1-anilino-8-naphthalene sulfonate (ANS), a hydrophobic probe, with human erythrocyte ghosts and reduced the fluorescence polarization in 1,6-diphenyl 1,3,5-hexatriene (DPH, a fluidity probe)-labeled human erythrocyte ghosts. TA-993 and MB3 induced aggregation of liposome suspensions prepared from acidic phospholipids. These findings suggest that TA-993 and MB3 may affect the erythrocyte membrane by interacting with acidic phospholipids and thus improve the hemorheological properties.

Vegetable oils high in phytosterols make erythrocytes less deformable and shorten the life span of stroke-prone spontaneously hypertensive rats

Previous studies have shown that canola oil (CA), compared with soybean oil (SO), shortens the life span of stroke-prone spontaneously hypertensive (SHRSP) rats, a widely used model for hemorrhagic stroke. SHRSP rats are highly sensitive to dietary cholesterol manipulations because a deficiency of membrane cholesterol makes their cell membranes weak and fragile. Phytosterols, abundant in CA but not in SO, can inhibit the absorption of cholesterol and also replace a part of cholesterol in cell membranes. This study was performed to determine whether the high concentration of phytosterols in CA might account for its life-shortening effect on SHRSP rats. Male, 35-d-old SHRSP rats (n = 28/group) were fed semipurified diets containing CA, SO, CA fortified with phytosterols (canola oil + phytosterols, CA + P), SO fortified with phytosterols (soybean oil + phytosterols, SO + P), corn oil (CO), olive oil (OO) or a fat blend that mimicked the fat composition of a representative Canadian diet (Canadian fat mimic, CFM; 10 g/100 g diet). These fats provided 97, 36, 207, 201, 114, 27 and 27 mg phytosterols/100 g diet, respectively. Ten rats from each group were killed after 30-32 d for blood and tissue analyses. The remaining rats (18/group) were used for determination of life span. The life span of SHRSP rats fed the high phytosterol oils (CA, CA + P, SO + P and CO) was significantly (P<0.05) shorter than that of CFM- and SO-fed rats. At 30-32 d, the groups fed the high phytosterol oils had greater levels of phytosterols and significantly (P<0.05) higher ratios of phytosterols/cholesterol in plasma, RBC, liver and kidney, and a significantly (P<0.05) lower RBC membrane deformabilty index than the groups fed oils low in phytosterols (SO, OO and CFM). The mean survival times were correlated with RBC deformability index (r(2) = 0.91, P = 0.0033) and cholesterol concentration (r(2) = 0.94, P = 0.0016), and inversely correlated with RBC phytosterol concentration (r(2) = 0.58, P = 0.0798) and phytosterols/cholesterol (r(2) = 0.65, P = 0.0579), except in the OO group. This study suggests that the high concentration of phytosterols in CA and the addition of phytosterols to other fats make the cell membrane more rigid, which might be a factor contributing to the shortened life span of SHRSP rats.

Clinical utility of LDL-apheresis in the treatment of sudden hearing loss: a prospective, randomized study

Although the pathogenesis of sudden hearing loss (SHL) is not as yet known, the clinical picture and the frequent association with vascular risk factors make an ischaemic event likely. This study aimed to assess the effect of an extracorporeal procedure (H.E.L.P.) in removing LDL-cholesterol, fibrinogen and lipoprotein (a) from the plasma, on the recovery of hearing SHL. This procedure using the HELP-system was compared with the usual standard treatment with prednisolone, dextranes and pentoxifyllin. We undertook a single centre, prospective, randomized study in which 18 patients were assigned to H.E.L.P.-apheresis and 9 patients were assigned to standard treatment (2:1 randomization). Audiometric and laboratory testing was performed at baseline, 24 h and 6 weeks after start of treatment. Primary endpoint was the improvement of the average pure-tone threshold between 0.125 and 8 kHz after 24 h. Twenty-four hours after H.E.L.P. treatment average pure-tone threshold recovered by 10.4 dB and by 26.4 dB after 6 weeks. The recovery of hearing of the standard treated patients was 5.8 dB and 16.8 dB after 24 h and 6 weeks respectively. LDL-cholesterol, fibrinogen and lipoprotein (a) were significantly reduced in the HELP treated patients compared with standard therapy, resulting in a significant improve in plasma viscosity, erythrocyte aggregation and resistance to oxidative stress of LDL particles. Our results suggest that the clinical outcome of SHL after a single extracorporeal LDL-apheresis is superior or at least equal to the more expensive standard treatment with prednisolone, dextranes and pentoxifyllin. Re-establishment of vascular endothelial function and improved blood rheology may be the underlying cause. These results must be confirmed in larger-scale trials.

Improvement of erythrocyte deformability by cholesterol-lowering therapy with pravastatin in hypercholesterolemic patients

Erythrocyte deformation is an important regulatory factor of the microcirculation. The present study was designed to examine whether erythrocyte deformability is altered in hypercholesterolemic patients and, if so, whether cholesterol-lowering therapy affects this parameter in these patients. The erythrocyte deformability of 37 hypercholesterolemic patients was evaluated before and after 1 year of therapy with pravastatin, an inhibitor of hepatic hydroxymethyl glutaryl coenzyme A reductase, under various shear stresses (4.7, 9.5, 23.6, 47.3, 118.1, and 236.2 dyne/cm2) using laser diffractometry. At study entry, erythrocyte deformability under 4.7 and 9.5 dyne/cm2 shear stress, which is actually observed in human vessels, was reduced compared with that in 20 age-matched normocholesterolemic subjects and was inversely correlated with serum cholesterol and low-density lipoprotein (LDL) cholesterol. Pravastatin therapy for 1 year, which reduced serum cholesterol from 288 +/- 28 to 223 +/- 20 mg/dL, significantly improved erythrocyte deformability by approximately 20%. There was a significant relation between the improvement of erythrocyte deformability and the reduction of serum cholesterol or LDL cholesterol. The results suggest that erythrocyte deformability is reduced in hypercholesterolemic patients, and that long-term cholesterol-lowering therapy can improve reduced erythrocyte deformability, which may contribute to the improvement of organ perfusion.

Correction of erythrocyte shape abnormalities in familial hypercholesterolemia after LDL-apheresis: does it influence cerebral hemodynamics?

It is well known that red blood cells incubated in low-density lipoprotein (LDL)-rich medium show shape abnormalities that revert to normal after reincubation in normal plasma. Patients with homozygous familial hypercholesterolemia (HFH) have an increased percentage of abnormally-shaped erythrocytes (mostly stomatocytes, knisocytes, and crenated cells) compared to normocholesterolemic controls: 7.73+/-0.96 versus 3.52+/-0.52 (mean+/-SEM; P = 0.001). To confirm the role of high LDL concentration in inducing red cell shape abnormalities we determined the percentage of abnormally shaped erythrocytes in seven HFH patients 1 day after the procedure of LDL-apheresis with a 40% cholesterol decrease. A reduction in kniscocytes, stomatocytes, and crenated cells was observed in the patients treated by LDL-apheresis (P < 0.01). To investigate the possible benefit of a reduction in erythrocyte shape abnormality on cerebral hemodynamics, cerebral flow velocity, as evaluated by transcranial Doppler, was evaluated concomitantly and found to be remarkably increased after apheresis (P < 0.01). No significant change in hematocrit, plasma viscosity, blood viscosity, mean pressure, or cardiac output was detected, 1 day after apheresis. An inverse correlation was demonstrated (r = 0.55; P = 0.04) between changes in the percentage of knisocytes+stomatocytes +crenated cells and percent changes in middle cerebral artery peak systolic velocity. The correction of erythrocyte shape abnormalities after LDL-apheresis might be related to dramatic changes in plasma phospholipid concentration and proportion occurring after this procedure in HFH patients. The reduction of erythrocyte shape abnormalities could contribute, together with other hemorheological factors, to the improvement of cerebral hemodynamics after LDL-apheresis.

Nuclear cholesterol content and nucleoside triphosphatase activity are altered in the JCR:LA-cp corpulent rat

A nuclear pore complex-associated nucleoside triphosphatase (NTPase) activity is believed to provide energy for nuclear export of poly(A)+ mRNA. This study was initiated to determine if nuclear membrane lipid composition is altered during chronic hyperlipidemia, and what effect this has on NTPase activity. The JCR:LA-cp corpulent rat model is characterized by severe hypertriglyceridemia and moderate hypercholesterolemia, and thus represents an ideal animal model in which to study nuclear cholesterol and NTPase activity. NTPase activity was markedly increased in purified hepatic nuclei from corpulent female JCR:LA-cp rats in comparison to lean control rats as a function of assay time, [GTP], [ATP], and [Mg2+]. Nuclear membrane cholesterol and phospholipid content were significantly elevated in the corpulent animals. Nuclei of corpulent animals were less resistant to salt-induced lysis than nuclei of lean animals, suggesting a change in relative membrane integrity. Together, these results indicate that altered lipid metabolism in a genetic corpulent animal model can lead to changes in nuclear membrane lipid composition, which in turn may alter nuclear membrane NTPase activity and integrity.

Erythrocyte membrane cholesterol/phospholipid changes and hemorheological modifications in familial hypercholesterolemia treated with lovastatin

Fourteen patients with familial hypercholesterolemia treated with lovastatin (40 mg/day) for three months were studied to find out whether the expected changes in plasma lipids are accompanied by modifications in the lipid composition of the erythrocyte membrane and whether these in turn induce changes in the rheological behavior of the red blood cell. Our results demonstrate the efficacy of lovastatin in reducing the plasma concentration of cholesterol and LDL cholesterol. The changes observed in the plasma lipids correlate with a significant decrease in the cholesterol/phospholipid ratio of the red blood cell membrane, from 1.19 +/- 0.19 in a basal situation to 0.92 +/- 0.23 (p < 0.01) at the end of treatment. These changes in the lipid composition of the cell are statistically related to a decrease in erythrocyte aggregability and an improvement in blood filterability, which means beneficial change in the patients' hemorheological situation.

Effect of beraprost, a stable prostacyclin analogue, on red blood cell deformability impairment in the presence of hypercholesterolemia in rabbits

We evaluated the effects of orally administered beraprost, a stable prostacyclin analogue, on the rheological behavior of red blood cells (RBC) in the presence of hypercholesterolemia. Rabbits fed a cholesterolrich diet were administered various doses of beraprost or pravastatin. We evaluated rheological behavior of RBC by assessing RBC deformability, using a positive-pressure filtration method. The maximum pressure generated by passing a suspension of RBC through a membrane filter was used as an index of RBC deformability. After animals were fed cholesterol for 16 weeks, the maximum pressure increased significantly from 172 +/- 15 mm Hg at baseline to 261 +/- 18 mm Hg (p < 0.01, n = 24). The reduction in RBC deformability associated with hypercholesterolemia improved dose dependently during 1-h incubation with various doses of beraprost. In ex vivo study, beraprost markedly restored RBC deformability 3 h after its oral administration to 218 +/- 17 mm Hg (n = 9) at a low dose and to 215 +/- 20 mm Hg (n = 9) at a high dose. The effect persisted for at least 2 h. Pravastatin failed to reduce the increased maximum pressure. Findings suggest that beraprost treatment may improve the microcirculation by restoring RBC deformability in the presence of hypercholesterolemia.

Non-ischemic hypoxia of the arterial wall is a primary cause of atherosclerosis

The response-to-injury hypothesis has been the dominant model of atherosclerosis for 20 years. However, it does not explain the experimental role of oxygen in atherogenesis, does not explain many of the clinical features of atherosclerosis, and has failed to provide useful countermeasures. I propose that arterial wall hypoxia results from risk factors for atherosclerosis. The primary mechanism is decreased oxygen delivery by a microcirculatory derangement resulting from impaired erythrocyte deformability. As in a healing wound, hypoxia causes growth factor release within the arterial media. Diffusion of these factors causes intimal proliferation and atheroma formation. This hypothesis implies that simple inexpensive oxygenation regimens might prevent the morbidity and mortality of atherosclerosis. Despite demonstrated effectiveness in experimental models, such treatments have not been extensively studied in clinical atherosclerosis because they conflict with the dominant model. This dogma needs to be re-examined.

Does cholesterol depletion have adverse effects on blood rheology?

Blood viscosity (eta B) at shear rates 10 and 100s-1, plasma viscosity (eta P), hematocrit (Hct), and whole blood cholesterol (Chol) were measured in 50 patients with a history of myocardial infarction or unstable angina pectoris. Erythrocyte morphology was also studied by scanning electron microscopy to determine the proportion of nondiscocytic erythrocytes (NDE). There was a significant positive correlation between Chol and eta P (r = 0.41, P < 0.004) and a highly significant negative correlation (r = -0.69, P < 0.001) between Chol and Tk, a viscometric index of erythrocyte rigidity based on relative blood viscosity at high shear (eta B/eta P) corrected for Hct. This latter result indicates Chol reduction in this population may increase erythrocyte rigidity. Twenty-five patients with Chol values in the range 4.0-8.0 mmol/L were commenced on a standard lipid-lowering diet and after eight weeks half were also given pravastatin (40 mg daily). After thirty-two weeks Chol had fallen significantly more in the pravastatin group (28%) than in the diet only group (11%, P = 0.005). There was no change in eta P for either group but a significant increase in Tk for the pravastatin group only (P = 0.011). The change in total cholesterol (delta Chol) for each patient over thirty-two weeks was negatively correlated with both the change in the index of erythrocyte rigidity (delta Tk) (r = -0.40, P = 0.044) and the change in the proportion of nondiscocytic erythrocytes (delta NDE) (r = -0.47, P = 0.026). These data suggest that cholesterol reduction within the normolipemic range may be associated with unfavorable changes in blood rheology.

Cerebral blood flow velocity and systemic vascular resistance after acute reduction of low-density lipoprotein in familial hypercholesterolemia

BACKGROUND AND PURPOSE

Low-density lipoprotein apheresis is currently used for the treatment of familial hypercholesterolemia, an inherited disorder of metabolism associated with premature development of cardiovascular disease. We wanted to evaluate cerebral blood flow velocity, cardiac output, and systemic vascular resistance in patients with familial hypercholesterolemia before and after low-density lipoprotein apheresis.

METHODS

Ten patients (age range, 14 to 46 years; 4 males, 6 females) with familial hypercholesterolemia (8 homozygotes, 2 heterozygotes) and 10 healthy control subjects of comparable age and sex distribution participated in the study. Low-density lipoprotein apheresis by dextran sulfate was performed in 8 patients (7 homozygotes, 1 heterozygote). Six patients (4 homozygotes, 2 heterozygotes) underwent a procedure of extracorporeal erythrocyte filtration with the same extracorporeal volume as for low-density lipoprotein apheresis, but with the exclusion of the passage of plasma through the dextran sulfate column. Cerebral blood flow velocity (transcranial Doppler), cardiac output, and systemic vascular resistance (electric bioimpedance cardiography) were determined by noninvasive techniques before and 1 day and 7 days after low-density lipoprotein apheresis or extracorporeal erythrocyte filtration. Plasma and blood viscosities were measured at the same time.

RESULTS

Before apheresis, mean and diastolic cerebral flow velocities were abnormally low in hypercholesterolemic patients (P < .01 and P < .02 vs healthy control subjects, respectively). After apheresis, low-density lipoprotein cholesterol was lowered by 40% to 60% from baseline, and cerebral blood flow velocities (mean, systolic, and diastolic velocities) were increased (P < .01). Cardiac output, systemic vascular resistance, and viscosity values were not significantly modified. Extracorporeal erythrocyte filtration (without passage of plasma through the dextran sulfate column) did not modify serum lipids, hemodynamic parameters, or viscosity values.

CONCLUSIONS

Low-density lipoprotein apheresis produces potentially useful hemodynamic effects. They are not adequately explained by changes in blood viscosity alone and might reflect a restoration of endothelium-mediated vasodilation, which is inhibited by high concentrations of low-density lipoprotein.

Platelet deposition at high shear rates is enhanced by high plasma cholesterol levels. In vivo study in the rabbit model

We have studied the effects of high plasma cholesterol levels on platelet-vessel wall interactions under high shear rate conditions typical of the apex of stenotic arteries (2,600 sec-1). Hypercholesterolemia was induced by feeding rabbits a 0.5% cholesterol-rich diet for 60 days. Platelet deposition was studied by use of an annular perfusion chamber and de-endothelialized abdominal rabbit aortas as substrates. After ingestion of the atherogenic diet, the experimental group of animals developed severe hypercholesterolemia, platelets became more fluid as determined by steady-state fluorescence anisotropy (p less than 0.05), and red blood cell deformability was decreased (p less than 0.001) when compared with normal controls. The fatty acid composition of platelet membranes showed an increase in the percentage of the long-chain saturated fatty acids (palmitic, C16:0, and stearic, C18:0) that may account for the lower polyunsaturated/saturated fatty acid ratio observed in the hyperlipemic animals. Total platelet deposition was significantly increased (p less than 0.05) in the hyperlipemic group as compared with the control group at 5 minutes' perfusion time, becoming less evident at 20 minutes' perfusion time. Our results suggest that the presence of hyperlipidemia may contribute to acute thrombosis by enhancing platelet-vessel wall interaction.

Hemorheologic and coagulative pattern in hypercholesterolemic subjects treated with lipid-lowering drugs

The effects on the coagulative and rheologic pattern of two lipid-lowering drugs, bezafibrate and simvastatin, were studied in 36 hypercholesterolemic subjects. Patients were randomly divided into two groups (18 subjects each) and received bezafibrate R 400 mg/day or simvatatin 10-40 mg/day over a twelve week period. Besides a decrease in plasma fibrinogen and fibrinopeptide A (p less than 0.001 both), bezafibrate induced a reduction of factor VIIc and VIIIc activity (p less than 0.001 both), while antithrombin 3 activity was increased (p less than 0.001) and the hemorheologic pattern was greatly improved (p less than 0.001). Simvastatin caused a slight decrease in factor VIIIc activity and a moderate reduction of beta-thromboglobulin. The efficacy of bezafibrate in reducing the activation of the coagulative cascade and improving the hemorheologic pattern has been confirmed; the peculiar triglycerides- and fibrinogen-lowering effect of the drug, not observed with simvastatin, could be responsible for these modifications.

Abnormalities of blood rheology in familial hypercholesterolaemia: effects of treatment

Whole blood and plasma viscosity, red cell aggregability and deformability, and plasma fibrinogen have been compared between 20 patients with heterozygous familial hypercholesterolaemia (FH), without clinical arterial disease, and 20 age- and sex-matched controls. Plasma fibrinogen was elevated in FH, associated with increased whole blood viscosity at low shear rate, plasma viscosity and red cell aggregation. At high shear rate blood viscosity was not elevated, and red cell deformability was normal. The effect of 12 weeks double blind treatment with cholestyramine 16-24 g/day, pravastatin 20 mg b.i.d. or placebo on blood rheology was studied in 17 FH patients. Mean plasma cholesterol fell significantly by 24.7% with pravastatin and 21.5% with cholestyramine, the latter also causing a significant 42% rise in triglyceride. Pravastatin, but not cholestyramine, caused a significant fall in plasma viscosity and fibrinogen, but no change was seen in whole blood rheology. This suggests that the rheological abnormalities in FH are at least partly related to the plasma lipid levels and hence reversible with treatment.