Red cell cholesterol enrichment and spur cell anemia in dogs fed a cholesterol-enriched atherogenic diet

Identifying Erythrocyte Injury in Toxicology Studies

The hematological impacts of a drug can affect erythropoiesis at the level of the bone marrow, or decrease the life span of the RBC (red blood cell). The most common and recognizable clinical manifestation of either type of drug-induced erythropoietic injury is a decrease in RBC mass, or what is clinically referred to as an anemia. A decrease in RBC production can generally be separated from increased destruction (hemolysis) by evaluation of the hemogram for evidence of regeneration. In most healthy mammalian species, hemolysis will result in a regenerative response characterized by an increase in circulating reticulocytes. Hemorrhage as an alternative cause of a regenerative anemia can generally be excluded by careful clinical evaluation of the animal. Subsequently, the investigation of a drug-induced regenerative anemia should involve a very thorough evaluation of RBC morphology for evidence of immune-mediated destruction, RBC oxidative injury, and fragmentation that can help to identify the underlying pathological mechanism(s) involved.

Influence of Erythrocyte Membrane Stability in Atherosclerosis

PURPOSE OF REVIEW

The purpose of this study is to show how an excess of cholesterol in the erythrocyte membrane contributes stochastically to the progression of atherosclerosis, leading to damage in blood rheology and O₂ transport, deposition of cholesterol (from trapped erythrocytes) in an area of intraplaque hemorrhage, and local exacerbation of oxidative stress.

RECENT FINDINGS

Cholesterol contained in the membrane of erythrocytes trapped in an intraplaque hemorrhage contributes to the growth of the necrotic nucleus. There is even a relationship between the amount of cholesterol in the erythrocyte membrane and the severity of atherosclerosis. In addition, the volume variability among erythrocytes, measured by RDW, is predictive of a worsening of this disease. Erythrocytes contribute to the development of atherosclerosis in several ways, especially when trapped in intraplate hemorrhage. These erythrocytes are oxidized and phagocytosed by macrophages. The cholesterol present in the membrane of these erythrocytes subsequently contributes to the growth of the atheroma plaque. In addition, when they rupture, erythrocytes release hemoglobin, which leads to the generation of free radicals. Finally, increased RDW may predict the worsening of atherosclerosis, due to the effects of inflammation and oxidative stress on erythropoiesis and erythrocyte volume. A better understanding of erythrocyte participation in atherosclerosis may contribute to the improvement of the prevention and treatment strategies of this disease.

Oxidation of human red blood cells by a free radical initiator: effects on rheological properties

The main aim of this study was the investigation of the rheological properties of Red Blood Cells (RBCs) obtained from subjects admitted to blood donors, associated with the lipid profile of High-Density Lipoprotein Cholesterol (HDL-C), Low-Density Lipoprotein Cholesterol (LDL-C), Triglyceride (TG) and Total Cholesterol (TOT-C). The deformability index of RBCs was determined by using a Dynamic Stress Rheometer (DSR-500) under oxidative injury induced by 2.2'-azo-bis (2-amidinopropane) dihydrochloride (AAPH). An increased rigidity of RBCs in subjects with borderline level of hyperlipidemia was found, compared with the control group. In order to explain the reason for the reduced deformability, a borderline group was studied for the evaluation of anionic permeability on membrane, haemolysis and morphological changes induced by AAPH, as well as ThioBarbituric Acid Reactive Substances (TBARs) generation. Haemolysis by AAPH indicated a decrease of globular resistance in the borderline group, furthermore, the elevated values of TBARs suggested lipid peroxidative damage to the RBCs membrane associated with morphological changes and anion permeability alterations. Our study shows the correlation between biochemical and morphological parameters of RBCs and their rheological behavior during oxidative injury. Rheological studies might be useful as a clinical and diagnostic monitoring technique and provide support for further research.

Increased erythrocytic osmotic fragility in anemic domestic shorthair and purebred cats

OBJECTIVES

Increased erythrocytic osmotic fragility and splenomegaly have been reported in anemic Abyssinian and Somali cats. Here we report on this condition in anemic domestic shorthair cats and two other breeds, and describe common features of the clinicopathological profiles, management and outcomes.

METHODS

Anemic cats, other than Abyssinians and Somalis, were included. The erythrocytic osmotic fragility test was performed, known causes of anemia were excluded, the illness was followed and medical records were reviewed.

RESULTS

Twelve neutered cats were first found to be anemic between 0.5 and 9.0 years of age. Pallor, lethargy, inappetence, pica, weight loss and splenomegaly were commonly observed. A moderate-to-severe macrocytic and hypochromic anemia with variable regeneration was noted. Infectious disease screening, direct Coombs' and pyruvate kinase DNA mutation test results were negative. Freshly drawn blood did not appear hemolysed but became progressively lysed during storage at 4°C. The sigmoid osmotic fragility curves were moderately to severely right shifted, indicating erythrocytic fragility at 20°C. Cross-correction studies indicated an intrinsic red cell effect rather than plasma effect. Most cats were treated with immunosuppressive doses of prednisolone and doxycycline, with variable responses. Five cats with recurrent or persistent anemia responded well to splenectomy. However, two had occasional recurrence of severe anemia: one was found to be Bartonella vinsonii-positive during one episode and responded to azithromycin and prednisolone, while the other cat had two episodes of severe anemia of unknown cause. Finally, six cats were euthanized within 1 month and 7 years after initial presentation. Histopathology of six spleens revealed mainly congestion and extramedullary hematopoiesis.

CONCLUSIONS AND RELEVANCE

Similarly to Abyssinian and Somali cats, domestic shorthair and cats of other breeds can also develop severe erythrocytic osmotic fragility with anemia and splenomegaly, which should be considered as a differential diagnosis in anemic cats.

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.

Increases in beta-lipoproteins in hyperlipidemic and dyslipidemic dogs are associated with increased erythrocyte osmotic fragility

BACKGROUND

The capacity of RBCs to traverse endothelium and deliver oxygen to tissues is dependent on a mechanically stable yet flexible plasma membrane. The lipid composition of the RBC membrane is crucial in maintaining its structure and fluidity. Lacking a nucleus and having minimal synthetic capacity, RBCs are exquisitely sensitive to changes in plasma lipids.

OBJECTIVE

The objective of this study was to investigate the effects of plasma lipids on RBC fragility in hyperlipidemic and dyslipidemic dogs.

METHODS

Osmotic fragility of RBCs, plasma lipoprotein fractions, and cholesterol and phospholipid content of RBC membranes were measured in hyperlipidemic, dyslipidemic, and healthy control dogs. Osmotic fragility of normal canine RBCs incubated in phosphate-buffered saline and in both intact and lipid-depleted plasma from diabetic dogs was also measured.

RESULTS

RBCs from hyperlipidemic and dyslipidemic dogs with diabetes mellitus and dogs treated with glucocorticoids were significantly more fragile than RBCs from healthy control dogs. RBCs from hyperlipidemic dogs with cholestatic disease tended to be more stable relative to RBCs from controls. RBC osmotic fragility was positively correlated with beta-lipoprotein levels, but was only weakly correlated with serum cholesterol concentration. Incubation in plasma from hyperlipidemic diabetic dogs rendered RBCs from healthy dogs osmotically fragile, whereas lipid-depleted plasma from the same diabetic dogs had no effect.

CONCLUSIONS

RBCs from hyperlipidemic and dyslipidemic dogs are osmotically fragile, and fragility is highly correlated with increases in beta-lipoproteins. Future studies are planned to address the consequences of lipid-induced fragility and subclinical hemolysis on endothelial cells, platelets, and coagulation.

The effects of L-carnitine on some hematological parameters in rats fed a cholesterol-rich diet

We evaluated the effects of L-carnitine on the hematological characteristics of rats fed a cholesterol-rich diet. Healthy male Wistar Albino rats were assigned to four equal groups. During the 40 day experiment, group 1 was fed standard rat pellets, group 2 was fed standard rat pellets containing 7.5 % cholesterol powder, group 3 was fed standard rat pellets and water that contained 75 mg/l L-carnitine, and group 4 was fed standard rat pellets that contained 7.5% cholesterol and water that contained 75 mg/l L-carnitine. Blood samples were analyzed for red (RBC) and white (WBC) blood cells, hemoglobin, hematocrit, granulocytes, lymphocytes, monocytes, mean cell volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC) using an automated cell counter. The RBC count in the group that received the 7.5% cholesterol diet was decreased significantly compared to the other groups. The hematocrit of the cholesterol group was lower than for the L-carnitine + cholesterol and L-carnitine groups. The MCV in the cholesterol group was significantly higher than the control group. The MCH in the cholesterol group was higher than for the other groups. There was no significant difference among the groups with regard to hemoglobin, MCHC, WBCs and leukocyte types. L-carnitine appears to have beneficial effects on erythrocyte stability, erythropoiesis and hyperlipidemia.

The use of the rapid osmotic fragility test as an additional test to diagnose canine immune-mediated haemolytic anaemia

Background

Diagnosing canine immune-mediated haemolytic anaemia (IMHA) is often challenging because all currently available tests have their limitations. Dogs with IMHA often have an increased erythrocyte osmotic fragility (OF), a characteristic that is sometimes used in the diagnosis of IMHA. Since the classic osmotic fragility test (COFT) is time-consuming and requires specialized equipment, an easy and less labour-intensive rapid osmotic fragility test (ROFT) has been used in some countries, but its diagnostic value has not yet been investigated.

This study aimed to evaluate erythrocyte osmotic fragility in dogs with and without IMHA, to compare results of the classic (COFT) and rapid (ROFT) test and to assess the value of the ROFT as diagnostic test for canine IMHA.

Nineteen dogs with IMHA (group 1a), 21 anaemic dogs without IMHA (group 1b), 8 dogs with microcytosis (group 2), 13 hyperlipemic dogs (group 3), 10 dogs with lymphoma (group 4), 8 dogs with an infection (group 5) and 13 healthy dogs (group 6) were included.

In all dogs, blood smear examination, in-saline auto-agglutination test, Coombs’ test, COFT and ROFT were performed. In the COFT, OF5, OF50 and OF90 were defined as the NaCl concentrations at which respectively 5, 50 and 90% of erythrocytes were haemolysed.

Results

Compared with healthy dogs, OF5 and OF50 were significantly higher in group 1a (P < 0.001) and OF5 was significantly higher in group 3 (P = 0.0266). The ROFT was positive in 17 dogs with IMHA, 10 hyperlipemic dogs, one anaemic dog without IMHA and one healthy dog.

Conclusions

Osmotic fragility was increased in the majority of dogs with IMHA and in dogs with hyperlipidemia, but not in dogs with microcytosis, lymphoma or an infection. Although more detailed information was obtained about the osmotic fragility by using the COFT, the COFT and ROFT gave similar results. The ROFT does not require specialized equipment, is rapid and easy to perform and can be used easily in daily practice. Although, the ROFT cannot replace other diagnostic tests, it may be a valuable additional tool to diagnose canine IMHA.

Relationship between serum cholesterol and indices of erythrocytes and platelets in the US population

Whereas dyslipidemia has been associated with leukocytosis, the relationship between serum cholesterol and other hematopoietic lineages is poorly defined. Erythrocytes and platelets, anucleate cells relegated to nonspecific diffusional exchange of cholesterol with serum, have been proposed to have a distinct relationship to cholesterol from leukocytes. We examined the relationship between serum cholesterol and circulating erythrocyte/platelet indices in 4,469 adult participants of the National Health and Nutrition Examination Survey (NHANES) 2005-2006. In linear regression analyses, serum non-high density lipoprotein-cholesterol (non-HDL-C) was positively associated with mean erythrocyte number, hematocrit, hemoglobin concentration, platelet count, and platelet crit independently of age, gender, race/ethnicity, smoking, body mass index, serum folate, and C-reactive protein. The magnitude of the relationship was most marked for platelets, with lowest versus highest non-HDL-C quartile subjects having geometric mean platelet counts of 258,000/μl versus 281,000/μl, respectively (adjusted model, P < 0.001 for trend). These associations persisted in a sensitivity analysis excluding several conditions that affect erythrocyte/platelet and/or serum cholesterol levels, and were also noted in an independent analysis of 5,318 participants from NHANES 2007-2008. As non-HDL-C, erythrocytes, and platelets all impact cardiovascular disease risk, there is a need for advancing understanding of the underlying interactions that govern levels of these three blood components.

Hypolipidemic effect of ginger in 1,2-dimethyl hydrazine-induced experimental colon carcinogenesis

Colorectal cancer is increasingly common nowadays in Asian countries and still remains the second leading cause of cancer death in the United States. In our laboratory, we studied the chemopreventive and hypolipidemic effect of ginger, a dietary spice, in 1,2-dimethylhydrazine (DMH)-induced colon cancer. Rats were given a weekly subcutaneous injection of DMH (20 mg/kg body weight), a known colon carcinogen, in the groin for 15 weeks. Ginger (50 mg/kg body weight P.O.) was given at the initiation and also at the postinitiation stages of carcinogenesis. The animals were sacrificed at the end of the experimental period of 30 weeks. The fecal bile acids, neutral sterols, and tissue lipid profile were evaluated using various biochemical estimations. The levels of fecal bile acids, neutral sterols, cholesterol, HMG CoA reductase, free fatty acids, triglycerides, phospholipase A, and phospholipase C were significantly increased, whereas the levels of tissue phospholipids was decreased in DMH-treated rats as compared to control rats. On administering ginger at the initiation and also at the postinitiation stages of colon carcinogenesis, the levels of fecal bile acids, neutral sterols, tissue cholesterol, HMG CoA reductase, free fatty acids, triglycerides, phospholipase A, and phospholipase C were significantly decreased, whereas the levels of phospholipids were increased as compared to unsupplemented DMH treated rats. Thus, ginger supplementation was found to reduce the risk of colon cancer markedly by virtue of its hypolipidemic and antioxidative effects.

Membrane cholesterol modulates the fluid shear stress response of polymorphonuclear leukocytes via its effects on membrane fluidity

Continuous exposure of polymorphonuclear leukocytes (PMNLs) to circulatory hemodynamics points to fluid flow as a biophysical regulator of their activity. Specifically, fluid flow-derived shear stresses deactivate leukocytes via actions on the conformational activities of proteins on the cell surface. Because membrane properties affect activities of membrane-bound proteins, we hypothesized that changes in the physical properties of cell membranes influence PMNL sensitivity to fluid shear stress. For this purpose, we modified PMNL membranes and showed that the cellular mechanosensitivity to shear was impaired whether we increased, reduced, or disrupted the organization of cholesterol within the lipid bilayer. Notably, PMNLs with enriched membrane cholesterol exhibited attenuated pseudopod retraction responses to shear that were recovered by select concentrations of benzyl alcohol (a membrane fluidizer). In fact, PMNL responses to shear positively correlated (R(2) = 0.96; P < 0.0001) with cholesterol-related membrane fluidity. Moreover, in low-density lipoprotein receptor-deficient (LDLr(-/-)) mice fed a high-fat diet (a hypercholesterolemia model), PMNL shear-responses correlated (R(2) = 0.5; P < 0.01) with blood concentrations of unesterified (i.e., free) cholesterol. In this regard, the shear-responses of PMNLs gradually diminished and eventually reversed as free cholesterol levels in blood increased during 8 wk of the high-fat diet. Collectively, our results provided evidence that cholesterol is an important component of the PMNL mechanotransducing capacity and elevated membrane cholesterol impairs PMNL shear-responses at least partially through its impact on membrane fluidity. This cholesterol-linked perturbation may contribute to dysregulated PMNL activity (e.g., chronic inflammation) related to hypercholesterolemia and causal for cardiovascular pathologies (e.g., atherosclerosis).

Drug-induced Hemolytic Anemia and Thrombocytopenia Associated with Alterations of Cell Membrane Lipids and Acanthocyte Formation

CXCR3 is a chemokine receptor, upregulated upon activation of T cells and expressed on nearly 100% of T cells in sites of inflammation. SCH 900875 is a selective CXCR3 receptor antagonist. Thrombocytopenia and severe hemolytic anemia with acanthocytosis occurred in rats at doses of 75, 100, and 150 mg/kg/day. Massively enlarged spleens corresponded histologically to extramedullary hematopoiesis, macrophages, and hemosiderin pigment and sinus congestion. Phagocytosed erythrocytes and platelets were within splenic macrophages. IgG and/or IgM were not detected on erythrocyte and platelet membranes. Ex vivo increased osmotic fragility of RBCs was observed. Lipid analysis of the RBC membrane revealed modifications in phosphatidylcholine, overall cholesterol, and/or sphingomyelin. Platelets exhibited slender filiform processes on their plasma membranes, analogous to those of acanthocytes. The presence of similar morphological abnormalities in acanthocytes and platelets suggests that possibly similar alterations in the lipid composition of the plasma membrane have taken place in both cell types. This phenotype correlated with alterations in plasma lipids (hypercholesterolemia and low triglycerides) that occurred after SCH 900875 administration, although other factors cannot be excluded. The increased cell destruction was considered triggered by alterations in the lipid profile of the plasma membranes of erythrocytes and platelets, as reflected morphologically.

Inhibitory effect of morin on DMH-induced biochemical changes and aberrant crypt foci formation in experimental colon carcinogenesis

Morin is a flavonoid present in fruits and Chinese herbs, exhibits various beneficial biological activities. There are numerous evidence suggesting that total dietary fat intake is generally associated with early promotion of colon cancer, the alterations in the lipid profile is important for malignant transformation and tumor development and carbohydrate moieties of glycoproteins reflect the stage of cancer. Aberrant crypt foci (ACF) consisting of morphologically irregular crypts, are thought to be precancerous lesions for colon cancer. Our aim was to study the inhibitory effect morin on aberrant crypt foci and alterations in the levels of lipids, and glycoconjugates in experimental rat colon cancer. Group 1 served as control, groups 2 and 4 received 50mg/kg b.w. morin orally everyday for 30 weeks. Groups 3 and 4 were given subcutaneous injection of 1,2-dimethylhydrazine (DMH) 20mg/kg b.w. for the first 15 weeks. Administration of morin at the dose of 50mg/kg b.w., significantly suppressed the formation of ACF its multiplicity and lowered levels of serum and tissue lipids, cholesterol-phospholipid ratio, glycoconjugate and also increased the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG CoA reductase). These results indicate that morin has a protective effect against DMH-induced colon carcinogenesis.

Effects of a synbiotic containing Lactobacillus acidophilus ATCC 4962 on plasma lipid profiles and morphology of erythrocytes in hypercholesterolaemic pigs on high- and low-fat diets

The aim of this study was to evaluate the effect of a synbiotic containing Lactobacillus acidophilus ATCC 4962, fructooligosaccharide, inulin and mannitol on plasma lipid profiles and erythrocyte membrane properties in hypercholesterolaemic pigs on high- and low-fat diets. Twenty-four white male Landrace pigs were randomly allocated to four treatment groups for 8 weeks (n 6). Treatment factors were the supplementation of synbiotic (with and without) and dietary fat (5 and 15 %). The supplementation of synbiotic reduced plasma total cholesterol (P = 0.001), TAG (P = 0.002) and LDL-cholesterol (P = 0.045) for both dietary fats. A higher concentration of esterified-cholesterol in HDL of pigs supplemented with synbiotic than the control regardless of dietary fat (P = 0.036) indicated that cholesterol was reduced in the form of cholesteryl esters. Reduced concentration of cholesteryl esters (P < 0.001) and increased concentration of TAG (P = 0.042) in LDL of pigs on synbiotic suggested that LDL-cholesterol was reduced via the hydrolysis of smaller and denser LDL particles. The erythrocytes of pigs without any synbiotic showed more prevalence of spur cells than those given the synbiotic, as supported by the higher cholesterol: phospholipid ratio in erythrocytes (P = 0.001). Also, membrane fluidity and rigidity were improved as supported by the decreased fluorescence anisotropies in the Hb-free erythrocyte membrane of pigs given synbiotic (P < 0.001). The administration of the synbiotic reduced plasma TAG, total cholesterol and LDL-cholesterol in hypercholesterolaemic pigs, possibly in the form of cholesteryl esters, via the interrelated pathways of lipid transporters (VLDL, LDL and HDL). The synbiotic also reduced deformation of erythrocytes via improved membrane fluidity and permeability.

Enhanced erythro-phagocytosis in polycythemic mice overexpressing erythropoietin

Adaptive mechanisms to hematocrit levels of 0.9 in our erythropoietin-overexpressing mice (tg6) include increased plasma nitric oxide levels and erythrocyte flexibility. Doubled reticulocyte counts in tg6 suggest an increased erythrocyte turnover. Here we show that compared with wild-type (wt) animals, erythrocyte lifespan in tg6 is 70% lower in tg6 mice. Transgenic mice have a younger erythrocyte population as indicated by higher intercellular water and potassium content, higher flexibility, decreased density, increased surface to volume ratio, and decreased osmotic fragility. Interestingly, despite being younger, the tg6 erythrocyte population also harbors characteristics of accelerated aging such as an increased band 4.1a to 4.1b ratio, signs of oxidative stress, or decreased surface CD47 and sialic acids. In tg6, in vivo tracking of PKH26-labeled erythrocytes revealed dramatically increased erythrocyte incorporation by their liver macrophages. In vitro experiments showed that tg6 macrophages are more active than wt macrophages and that tg6 erythrocytes are more attractive for macrophages than wt ones. In conclusion, in tg6 mice erythrocyte aging is accelerated, which results, together with an increased number and activity of their macrophages, in enhanced erythrocyte clearance. Our data points toward a new mechanism down-regulating red cell mass in excessive erythrocytosis in mice.

Effect of spices on lipid metabolism in 1,2-dimethylhydrazine-induced rat colon carcinogenesis

Colon cancer is the second most common cancer among men and women worldwide. We investigated the effect of red chilli (Capsicum annum L.), cumin (Cuminum cyminum L.), and black pepper (Piper nigrum L.) on colon cancer induced in rats by a colon-specific carcinogen, 1,2-dimethylhydrazine (DMH). Colon cancer was induced by subcutaneous injection of DMH at a dosage of 20 mg/kg of body weight (15 doses, at 1-week intervals). The rats were continued with the standard pellet diet and supplemented red chilli [C. annum L., 0.015% (wt/wt) mixed with the diet], cumin seeds [C. cyminum L., 1.25% (wt/wt) mixed with the diet], and black pepper (P. nigrum L., 0.5% (wt/wt) mixed with the diet] throughout the experimental period. After the total experimental period of 32 weeks (including 2 weeks of acclimatization) the incidence and number of tumors in the colon were observed to be significantly higher in the rats administered DMH and/or red chillis, as compared with the cumin + DMH and black pepper + DMH groups. No tumors were observed in the control, cumin + DMH, or black pepper + DMH groups. The levels of fecal bile acids and neutral sterols in 24-hour fecal samples were significantly decreased in DMH + chilli-administered rats, while the excretion of fecal bile acids and neutral sterols was significantly increased in cumin + DMH- and black pepper + DMH-administered rats. In DMH-, chilli-, and chilli + DMH-administered rats the levels of cholesterol, cholesterol/phospholipid ratio, and 3-hydroxy-3-methylglutaryl-CoA reductase activity were decreased in cumin + DMH- and black pepper + DMH-treated rats. The phospholipid levels were reduced in the DMH, chilli, and chilli + DMH groups as compared with the cumin + DMH and black pepper + DMH groups. Our results show that chilli supplementation promotes colon carcinogenesis, whereas cumin or black pepper suppresses colon carcinogensis in the presence of the procarcinogen DMH.

HDL cholesterol levels are an important factor for determining the lifespan of erythrocytes

OBJECTIVE

Scavenger receptor class B, type I (SR-BI) is a multifunctional receptor that promotes the selective uptake of cholesteryl esters from high-density lipoprotein (HDL). Disruption of SR-BI in mice results in a dramatic increase in HDL cholesterol. Interestingly, mice lacking SR-BI also develop anemia, as evidenced by accumulation of reticulocytes in the circulation. The objective of the current study was to delineate the mechanism underlying development of anemia in the absence of SR-BI.

METHODS

Expression of important mediators of erythropoiesis, as well as key enzymes in the degradation of erythrocytes, were analyzed using real-time polymerase chain reaction in SR-BI wild-type and SR-BI knockout mice. In addition, in vivo studies were performed using biotinylated erythrocytes to determine erythrocyte survival.

RESULTS

mRNA expression of TAL-1, GATA-1, FOG-1, erythropoietin receptor, and ferrochelatase, important mediators of erythropoiesis, was increased in spleens of SR-BI-deficient mice. In addition, the relative amount of early Ter119(high)CD71(high) -expressing erythroblasts was increased in SR-BI-deficient spleens. Interestingly, also expression of hemeoxygenase 1 and biliverdin reductase, enzymes involved in the degradation of erythrocytes, was increased. Furthermore, an elevated amount of conjugated bilirubin, the breakdown product of hemoglobin, was found in bile. Using biotinylated erythrocytes, we show that survival of erythrocytes was decreased in SR-BI-deficient mice. Thus, the observed increased erythropoiesis in the SR-BI-deficient mice is most likely a direct response to the reduced erythrocyte lifespan. Finally, we show that increased HDL cholesterol levels due to SR-BI deficiency induce erythrocyte cholesterol:phospholipid ratios, resulting in decreased deformability and increased osmotic fragility, thereby providing an explanation for the observed reduced lifespan.

CONCLUSIONS

SR-BI is not only essential for HDL cholesterol homeostasis and atherosclerosis susceptibility, but also for maintaining normal erythrocyte lifespan.

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.

Postprandial chylomicrons

We examined whether postprandial (PP) chylomicrons (CMs) can serve as vehicles for transporting cholesterol from endogenous cholesterol-rich lipoprotein (LDL+HDL) fractions and cell membranes to the liver via lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) activities. During incubation of fresh fasting and PP plasma containing [(3)H]cholesteryl ester (CE)-labeled LDL+HDL, both CMs and VLDL served as acceptors of [(3)H]CE or cholesterol from LDL+HDL. The presence of CMs in PP plasma suppressed the ability of VLDL to accept [(3)H]CE from LDL+HDL. In reconstituted plasma containing an equivalent amount of triglycerides from isolated VLDL or CMs, a CM particle was about 40 times more potent than a VLDL particle in accepting [(3)H]CE or cholesterol from LDL+HDLs. When incubated with red blood cells (RBCs) as a source for cell membrane cholesterol, the cholesterol content of CMs, VLDL, LDL, and HDL in PP plasma increased by 485%, 74%, 13%, and 30%, respectively, via LCAT and CETP activities. The presence of CMs in plasma suppressed the ability of endogenous lipoproteins to accept cholesterol from RBCs. Our data suggest that PP CMs may play an important role in promoting reverse cholesterol transport in vivo by serving as the preferred ultimate vehicle for transporting cholesterol released from cell membranes to the liver via LCAT and CETP.

Measurement of erythrocyte lipids, lipid peroxidation, antioxidants and osmotic fragility in cervical cancer patients

BACKGROUND

Our aim was to examine the structural integrity of red blood cells in cervical cancer patients by measuring the concentrations of thiobarbituric acid reactive substances (TBARS), antioxidant status, cholesterol/phospholipid (C/P) molar ratio, enzyme activity and osmotic fragility of erythrocytes.

METHODS

This study has been conducted on 32 adult female cervical cancer patients and an equal number of age- and sex-matched normal subjects. Erythrocyte concentrations of lipids, TBARS, vitamin E, reduced glutathione and enzymic activities of catalase and Na(+)K(+)-ATPase were measured as well as plasma concentrations of sodium and potassium. The present study also examined the changes in erythrocyte osmotic fragility in cervical cancer patients and normal subjects. The red cell fluidity and permeability were determined by estimating the C/P ratio and Na(+)K(+)-ATPase activity, respectively.

RESULTS

The release of thiobarbituric acid reactive substances was significantly higher in cervical cancer patients as compared to normal subjects. The increased lipid peroxidation with concomitant decrease in antioxidants was notable in cervical cancer patients. Red blood cells of cervical cancer patients were more fragile than those from normal subjects. Increase in red cell membrane C/P ratio and Na(+)K(+)-ATPase activity was noticed in cervical cancer patients as compared to normal subjects.

CONCLUSIONS

Increased lipid peroxidation, insufficient antioxidant potential and changes in C/P molar ratio as well as activity of Na(+)K(+)-ATPase cause structural and functional abnormalities in the erythrocytes of cervical cancer patients.

Potencies of lipoproteins in fasting and postprandial plasma to accept additional cholesterol molecules released from cell membranes

To investigate the role of various lipoproteins in plasma to promote cholesterol efflux from cell membranes, potencies of lipoproteins in normolipidemic fasting and postprandial (PP) plasmas to accept additional cholesterol molecules from cell membranes were determined. We used red blood cells (RBCs) and lipoproteins in fresh blood as donors and acceptors of cell membrane cholesterol, respectively. When fresh fasting plasma (n=24) containing active lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer proteins (CETP) was incubated with a 3-fold excess of autologous RBCs at 37 degrees C for 18 hours, plasma cholesterol levels increased by 19.6% (38.5+/-14.2 mg/dL) owing to an exclusive increase in the CE level. Very low density lipoprotein (VLDL), low density lipoprotein (LDL), and high density lipoprotein (HDL) fractions retained 48.1%, 26.3%, and 25.6% of the net cholesterol mass increase in fasting plasma, resulting in 91%, 8%, and 21% increases in their cholesterol contents, respectively. The PP plasma was 1.3-fold more potent than fasting plasma in promoting cholesterol efflux from RBCs by associating excess cholesterol with chylomicrons, resulting in a 356% increase in the cholesterol content of chylomicrons. These increases in lipoprotein cholesterol content indicate that chylomicrons were about 3.9x, 44x, and 17x more potent than fasting VLDL, LDL, and HDL, respectively, in accepting additional cholesterol molecules released from RBCs. The capacity of PP plasma to promote cholesterol efflux from RBCs was significantly correlated with plasma cholesterol levels (r=0.60, P<0.005), triglycerides (r=0.68, P<0.001), chylomicrons (r=0.90, P<0.001), VLDL (r=0.65, P<0.001), and LDL (r=0.47, P<0.025) but not with the levels of HDL (r= -0.34, P<0.20). In fasting plasma containing a low level of VLDL and HDL, isolated chylomicrons supplemented to the plasma were approximately 9x more potent than HDL in boosting the capacity of plasma to promote cholesterol efflux from RBCs. This study indicates that chylomicrons in PP plasma are the most potent ultimate acceptors of cholesterol released from cell membranes and that a low HDL level is not a factor that limits the ability of PP plasma to promote cholesterol efflux from cell membranes. Our data obtained from an in-vitro system suggest that PP chylomicrons may play a major role in promoting reverse cholesterol transport in vivo, since the transfer of cholesterol from cell membranes to chylomicrons will lead to the rapid removal of this cholesterol by the liver. HDL in vivo may promote reverse cholesterol transport by enhancing the rapid removal of chylomicrons from the circulation, since the rate of clearance of chylomicrons is positively correlated with the HDL level in plasma.

Influence of hypercholesterolemia on morphological and rheological characteristics of erythrocytes

The changes in shape and rheological parameters of erythrocytes in cholesterol-fed rabbits (fed with normal diet plus 0.5% cholesterol for a duration of 1 year) and in vitro cholesterol enrichment of erythrocytes in cholesterol enriched plasma were studied. This process affects the shape of erythrocytes. In rabbits the actual shape change begins after 6 weeks of cholesterol feeding. The shape changes in rabbits and in vitro cholesterol-enrichment are similar. The extent of shape changes depends on the amount of cholesterol incorporated into the membrane. The rheological parameters such as blood viscosity, osmotic fragility and deformability are measured. The whole blood viscosity is increased and deformability decreased. The cells become osmotically more fragile in cholesterol-fed rabbits but are resistant to osmotic lysis in in vitro cholesterol enrichment. The altered lipid composition may be responsible for the observed changes in these parameters.

Heartworm infection

Dirofilaria immitis is an epizootic filarial parasite that most often infects domestic dogs. This article provides information about the life cycle of Dirofilaria immitis as well as the epidemiology, diagnosis, clinical signs, and treatment of heartworm infection.

Accumulation of cholesteryl ester and lipid droplets in macrophages after uptake of cholesterol-rich necrotic products

The prevalence of degenerated cells in the thickened intima of cholesterol-fed animals suggested that necrotic regions might become a focus for lesion development by attracting histiocytes or monocytes. We propose that cholesterol-rich necrotic products scavenged by macrophages incite the accumulation of cholesteryl ester and the formation of cholesteryl ester droplets. The feasibility of this hypothesis was tested with readily available materials, namely, lung macrophages and plasma membrane vesicles (PMV) released from dying cholesterol-rich and normal hepatocytes. PMV from cholesterol-rich hepatocytes contained 30-fold more cholesteryl ester than PMV from normal hepatocytes. Degradation of 125I-PMV to trichloroacetic acid-soluble products by macrophages was fourfold higher than that of 125I-acetylated low density lipoprotein (acetyl-LDL) at 100 micrograms/ml of ligand in the incubation medium. Within this concentration range, degradation of PMV increased almost linearly with increasing concentrations of PMV, while the degradation of acetyl-LDL followed a saturation curve. Cholesterol-rich PMV increased the cholesteryl ester content of macrophages fourfold and augmented the incorporation of oleate threefold relative to normal PMV. These studies were extended to aortic smooth muscle cells. As with hepatocyte-PMV, smooth muscle cell-PMV was internalized and degraded by macrophages. The results suggested that cholesterol-rich necrotic materials could play a significant role in atherogenesis.

Simultaneous occurrence of hypercholesterolemia and hemolytic anemia in rats fed cholesterol diet

Cholesterol diet-induced hemolytic anemia in rats was described. When rats were fed a cholesterol diet for 11 weeks, serum cholesterol rapidly increased within the first week, and was maintained in 5-10 times higher levels throughout the study as compared to those of control rats. Erythrocyte count, hematocrit and hemoglobin concentration decreased from about 2 weeks of feeding. The spleen showed an increase of hemosiderin deposition from 6 weeks of feeding. The half life of erythrocytes labelled with 51Cr was shortened significantly at 6 weeks of feeding. These findings indicate that cholesterol diet can induce hemolytic anemia. Serum cholesterol and phospholipid were markedly increased, but in erythrocyte membrane, free cholesterol content was not persistently increased and phospholipid content was decreased. In hemorrheological studies, erythrocyte deformability and mechanical hemolysis tended to reduce. In conclusion, it was considered that as a result of reduced phospholipid content the erythrocytes of cholesterol-fed rats were decreased in its deformability and were captured more easily by the spleen. The profile of hemolytic anemia in cholesterol-fed rats was quite different from those reported in cholesterol-fed guinea pigs, rabbits and dogs.

Influence of serum lipoproteins and carbohydrate metabolism on erythrocyte membrane composition in children: Bogalusa Heart Study

The influence of serum lipoprotein profile and measures of carbohydrate metabolism on erythrocyte membrane composition were examined in four groups of children (n = 356, ages 6 to 18 years) from a total biracial population whose earlier very low density (VLDL-C) or low density lipoprotein cholesterol (LDL-C) levels (or both) were in the extreme quintiles or quartiles. Erythrocyte membranes of white children contained significantly increased levels of protein (+2.0%) and phospholipid (+2.7%) and decreased levels of neutral sugars (-4.6%) when compared to black children. Membrane neutral sugars were markedly higher (+4.7%) in girls than in boys. Membrane protein was lowest in children characterized by high LDL-C and low VLDL-C. The phospholipid/protein ratio was consistently higher (+1.9%) in the low VLDL-C strata. The relationships between membrane constituents and plasma/serum variables were explored after controlling for race, sex, and age effects and after combining the four selection groups. Less membrane cholesterol was present in the lowest (v highest) quintile of serum LDL-C/high density lipoprotein cholesterol (HDL-C) ratio (P less than 0.01). Membrane phospholipid levels were lower in the highest (v lowest) quintiles of the apoB/apoA-I ratio (P less than 0.01). With respect to measures of carbohydrate tolerance, membrane hexosamine showed low values in the highest (v lowest) quintile of hemoglobin A1c, while the trend was opposite for plasma insulin response (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo modulation of brain cholesterol level and learning performance by a novel plant lipid: indications for interactions between hippocampal-cortical cholesterol and learning

In this account we report in vivo effects of a plant lipid preparation (MMPL) on brain cholesterol and the activity and learning performance of aging male rats. Three-month-old rats were fed for 3 months with a diet that was enriched with 3% MMPL. Another group of 18 month-old rats was fed for 6 months with a 3% MMPL-enriched diet. This food regime lowered markedly the cholesterol level in the hippocampal and cortical regions and increased their lipid membrane fluidity. The animals of both age groups also responded to MMPL with a higher activity and their learning performances, compared to normal diet-fed animals, improved notably. This improvement continued at least 4 months after terminating the supply of MMPL. Significant inverse correlationships were obtained between the length of the training period required to attain proper criteria and cholesterol levels of the hippocampal and cortical brain fractions.

The effect of hypercholesterolemia on guinea pig platelets, erythrocytes and megakaryocytes

This study has examined the effect of diet-induced hypercholesterolemia on guinea pig platelets, erythrocytes, megakaryocytes and plasma. The cholesterol/phospholipid ratios of plasma and erythrocytes began to increase after one day on the diet and increased steadily for two weeks and more slowly thereafter until 30 days. In contrast, the cholesterol/phospholipid ratio of platelets remained constant for 4-5 days, then increased until reaching a maximum of about 0.85 in two weeks. Thus, the time-course for increase of the cholesterol/phospholipid ratio is different for platelets than for erythrocytes and plasma. The increase in the cholesterol/phospholipid ratio of megakaryocytes was small and not dependent on the degree of increase in the plasma cholesterol/phospholipid ratio. The cholesterol esters of both platelets and megakaryocytes increased with time for two weeks. The increase in megakaryocyte cholesterol esters appeared to precede that of platelets. The protein content of platelets and megakaryocytes and average megakaryocyte size were increased. Normal platelets incubated in plasma from hypercholesterolemic guinea pigs did not accumulate excess cholesterol, but erythrocyte cholesterol increased 45% in 6 h under the same conditions. Cholesterol synthesis in megakaryocytes was depressed 50-80% by cholesterol feeding and by in vitro incubation of the cells in hypercholesterolemic plasma. The data suggest that the platelets and erythrocytes may accumulate excess cholesterol by different mechanisms. The effects of cholesterol feeding on megakaryocytes and the lag in accumulation of cholesterol in platelets relative to erythrocytes and plasma suggest that a defect in the megakaryocyte may be a primary determinant of accumulation of cholesterol in platelets.

Increased leukocyte aggregation in patients with hypercholesterolaemia

Leukocyte aggregation induced by N-formylmethionyl-leucyl-phenylalanine (FMLP) has been measured in a group of patients with hypercholesterolaemia (n = 22) and in a group of control subjects (n = 26), age- and sex-matched. When hypercholesterolaemic patients were divided into two groups, with a discriminatory level of 7.7 mmol/l of plasma cholesterol, FMLP-induced leukocyte aggregation of patients with greater than 7.7 mmol/l of plasma cholesterol was significantly higher compared both with control subjects and patients with plasma cholesterol levels less than 7.7 mmol/l. A positive significant correlation was found between leukocyte aggregation and plasma cholesterol, whereas no correlation was observed between leukocyte aggregation and plasma triglycerides or APO-B levels. These findings provide further support for the hypothesis that elevated plasma cholesterol levels may induce a cellular membrane abnormality responsible for the increased leukocyte aggregation and, subsequently, endothelial damage.

Cholesterol blocks the disordering effects of ethanol in biomembranes

To assess the relation between the physical order of a membrane and its sensitivity to ethanol, we enriched biomembranes with cholesterol, both in vivo and in vitro. Japanese quail of the SEA line (selectively bred for susceptibility to experimental atherosclerosis) were treated for 9 to 16 weeks with a diet that contained 2% cholesterol. This regimen increased the cholesterol content of serum and erythrocytes. The cholesterol content of brain synaptosomal plasma membranes (SPM) was unaffected by the high cholesterol diet. In other experiments, isolated mouse synaptosomal plasma membranes were incubated with cholesterol/phospholipid (C/P) vesicles; different amounts of cholesterol were transferred according to the sterol content of the donor vesicles. Membrane order was determined in both types of membranes by a sensitive electron paramagnetic resonance (EPR) technique. The order parameter with 5- and 12-doxylstearic acid increased along with the cholesterol content. As expected, ethanol disordered membranes (decreased the order parameter) in a concentration-related manner. The slope of the concentration response curve was less steep in high cholesterol than low cholesterol membranes, indicating that cholesterol enrichment partially blocks the membrane action of ethanol in both types of membranes.

Increased leucocyte oxidative metabolism in hyperlipoproteinaemia

Polymorphonuclear leucocytes (PMN) from a group of subjects with hyperlipoproteinaemia (HLP) had higher oxidative metabolism with greater release of superoxide anion (O2-) than PMN from age-matched controls. Release of O2- was significantly correlated with serum cholesterol and light-density-lipoprotein-cholesterol levels, PMN from HLP subjects also has higher hexose monophosphate shunt activity and chemiluminescence than controls. A causal relation was suggested by the finding that oxidative metabolism was normal in a group of HLP subjects whose lipid levels were lowered by treatment with cholestyramine.

Effects of diabetes and high fat-high cholesterol diet on plasma lipid levels and on erythrocyte membrane composition

Erythrocyte membrane composition was studied in rats subjected to experimental hyperlipidemia and/or hyperglycemia by means of 6 weeks of high fat (40% w/w)-high cholesterol (5% w/w)diet with and without 8 weeks of streptozotocin-induced diabetes. High fat-high cholesterol diet lowered plasma glucose levels in control and in diabetic animals. While the atherogenic diet produced only hypercholesterolemia, the same diet fed to diabetic animals produced both hypercholesterolemia and hypertriglyceridemia. The membrane protein content was lower in diabetic rats than in controls, while the cholesterol and phospholipids were higher in diabetic rat erythrocyte membranes. Feeding the atherogenic diet increased membrane lipid levels in only nondiabetic animals. The total carbohydrate content of the membranes was greater in diabetic animals than controls. Difference in relative proportion of individual sugars, e.g., galactose, mannose, glucose, and fucose of the membranes was observed between diabetic and control groups. These observations suggest that rat erythrocyte membrane composition is altered both in hyperglycemic and hyperlipidemic conditions, and may provide a useful model for evaluating lipid carbohydrate abnormalities of membrane structures in diabetes mellitus.