Scavenger receptors and oxidized low density lipoproteins

RFX1 regulates foam cell formation and atherosclerosis by mediating CD36 expression

BACKGROUND AND AIMS

Atherosclerosis (AS) is a continuously low-grade inflammatory disease, and monocyte-derived macrophages play a vital role in AS pathogenesis. Regulatory factor X1 (RFX1) has been reported to participate in differentiation of various cells. Our previous report showed that RFX1 expression in CD14+ monocytes from AS patients was decreased and closely related to AS development. Macrophages mostly derive from monocytes and play an important role in AS plaque formation and stability. However, the functions of RFX1 in the formation of macrophage-derived foam cells and consequent AS development are unclear.

METHODS

We explored the effects of RFX1 on oxidation low lipoprotein (ox-LDL)-stimulated foam cell formation and CD36 expression by increasing or silencing Rfx1 expression in mouse peritoneal macrophages (PMAs). The ApoE-/-Rfx1f/f or ApoE-/-Rfx1f/f Lyz2-Cre mice fed a high-fat diet for 24 weeks were used to further examine the effect of RFX1 on AS pathogenesis. We then performed dual luciferase reporter assays to study the regulation of RFX1 for CD36 transcription.

RESULTS

Our results demonstrate that RFX1 expression was significantly reduced in ox-LDL induced foam cells and negatively correlated with lipid uptake in macrophages. Besides, Rfx1 deficiency in myeloid cells aggravated atherosclerotic lesions in ApoE-/- mice. Mechanistically, RFX1 inhibited CD36 expression by directly regulating CD36 transcription in macrophages.

CONCLUSIONS

The reduction of RFX1 expression in macrophages is a vital determinant for foam cell formation and the initiation of AS, proving a potential novel approach for the treatment of AS disease.

Pathogenesis of Common Ocular Diseases: Emerging Trends in Extracellular Matrix Remodeling

The prevalence of visual impairments in human societies is worrying due to retinopathy complications of several chronic diseases such as diabetes, cardiovascular diseases, and many more that are on the rise worldwide. Since the proper function of this organ plays a pivotal role in people's quality of life, identifying factors affecting the development/exacerbation of ocular diseases is of particular interest among ophthalmology researchers. The extracellular matrix (ECM) is a reticular, three-dimensional (3D) structure that determines the shape and dimensions of tissues in the body. The ECM remodeling/hemostasis is a critical process in both physiological and pathological conditions. It consists of ECM deposition, degradation, and decrease/increase in the ECM components. However, disregulation of this process and an imbalance between the synthesis and degradation of ECM components are associated with many pathological situations, including ocular disorders. Despite the impact of ECM alterations on the development of ocular diseases, there is not much research conducted in this regard. Therefore, a better understanding in this regard, can pave the way toward discovering plausible strategies to either prevent or treat eye disorders. In this review, we will discuss the importance of ECM changes as a sentimental factor in various ocular diseases based on the research done up to now.

Triacylglycerol uptake and handling by macrophages: From fatty acids to lipoproteins

Macrophages are essential innate immune cells and form our first line of immune defense. Also known as professional phagocytes, macrophages interact and take up various particles, including lipids. Defective lipid handling can drive excessive lipid accumulation leading to foam cell formation, a key feature of various cardiometabolic conditions such as atherosclerosis, non-alcoholic fatty liver disease, and obesity. At the same time, intracellular lipid storage and foam cell formation can also be viewed as a protective and anti-lipotoxic mechanism against a lipid-rich environment and associated elevated lipid uptake. Traditionally, foam cell formation has primarily been linked to cholesterol uptake via native and modified low-density lipoproteins. However, other lipids, including non-esterified fatty acids and triacylglycerol (TAG)-rich lipoproteins (very low-density lipoproteins and chylomicrons), can also interact with macrophages. Recent studies have identified multiple pathways mediating TAG uptake and processing by macrophages, including endocytosis and receptor/transporter-mediated internalization and transport. This review will present the current knowledge of how macrophages take up different lipids and lipoprotein particles and address how TAG-rich lipoproteins are processed intracellularly. Understanding how macrophages take up and process different lipid species such as TAG is necessary to design future therapeutic interventions to correct excessive lipid accumulation and associated co-morbidities.

Macrophages take up VLDL-sized emulsion particles through caveolae-mediated endocytosis and excrete part of the internalized triglycerides as fatty acids

Triglycerides are carried in the bloodstream as part of very low-density lipoproteins (VLDLs) and chylomicrons, which represent the triglyceride-rich lipoproteins. Triglyceride-rich lipoproteins and their remnants contribute to atherosclerosis, possibly by carrying remnant cholesterol and/or by exerting a proinflammatory effect on macrophages. Nevertheless, little is known about how macrophages process triglyceride-rich lipoproteins. Here, using VLDL-sized triglyceride-rich emulsion particles, we aimed to study the mechanism by which VLDL triglycerides are taken up, processed, and stored in macrophages. Our results show that macrophage uptake of VLDL-sized emulsion particles is dependent on lipoprotein lipase (LPL) and requires the lipoprotein-binding C-terminal domain but not the catalytic N-terminal domain of LPL. Subsequent internalization of VLDL-sized emulsion particles by macrophages is carried out by caveolae-mediated endocytosis, followed by triglyceride hydrolysis catalyzed by lysosomal acid lipase. It is shown that STARD3 is required for the transfer of lysosomal fatty acids to the ER for subsequent storage as triglycerides, while NPC1 likely is involved in promoting the extracellular efflux of fatty acids from lysosomes. Our data provide novel insights into how macrophages process VLDL triglycerides and suggest that macrophages have the remarkable capacity to excrete part of the internalized triglycerides as fatty acids.

How do macrophages take up and process very low density lipoprotein (VLDL) particles? This study reveals that endocytic uptake of VLDLs depends on lipoprotein lipase and caveolae; internalized VLDLs are then processed by lysosomes, and the lipids are hydrolyzed and translocated to the ER for storage as triglycerides.

HDL Receptor in Schistosoma japonicum Mediating Egg Embryonation: Potential Molecular Basis for High Prevalence of Cholesteryl Ester Transfer Protein Deficiency in East Asia

Schistosomiasis is a life-threatening parasitic disease caused by blood flukes, Schistosomes. In its intestinal type, the parasites reside in visceral/portal veins of the human hosts and lay eggs to excrete in feces via intestinal tracts, and some of the aberrant eggs plug into the liver via the portal blood flow. Ectopic growth of these eggs causes fatal granulomatosis and cirrhosis of the liver. The parasites ingest nutrients from the host blood plasma by using nonspecific and specific transport via their body surface and alimentary tracts. It is especially important for the female adults to obtain lipid molecules because they synthesize neither fatty acids nor sterols and yet produce egg yolk. Low-density lipoprotein receptors have been identified in the body of the Schistosomes but their functions in the parasite life cycle have not clearly been characterized. On the other hand, CD36-related protein was identified in the body and the eggs of Asian blood fluke, Schistosoma japonicum, and characterized as a molecule that mediates selective uptake of cholesteryl ester from the host plasma high-density lipoproteins (HDLs). This reaction was shown crucial for their eggs to grow to miracidia. Interestingly, abnormal large HDL generated in lack of cholesteryl ester transfer protein (CETP) is a poor substrate for this reaction, and, therefore, CETP deficiency resists pathogenic ectopic growth of the aberrant parasite eggs in the liver. This genetic mutation is exclusively found in East Asia, overlapping with the current and historic regions of Schistosoma japonicum epidemic, so that this infection could be related to high prevalence of CETP deficiency in East Asia.

The Potential Health Benefits of the Ketogenic Diet: A Narrative Review

Considering the lack of a comprehensive, multi-faceted overview of the ketogenic diet (KD) in relation to health issues, we compiled the evidence related to the use of the ketogenic diet in relation to its impact on the microbiome, the epigenome, diabetes, weight loss, cardiovascular health, and cancer. The KD diet could potentially increase genetic diversity of the microbiome and increase the ratio of Bacteroidetes to Firmicutes. The epigenome might be positively affected by the KD since it creates a signaling molecule known as β-hydroxybutyrate (BHB). KD has helped patients with diabetes reduce their HbA1c and reduce the need for insulin. There is evidence to suggest that a KD can help with weight loss, visceral adiposity, and appetite control. The evidence also suggests that eating a high-fat diet improves lipid profiles by lowering low-density lipoprotein (LDL), increasing high-density lipoprotein (HDL), and lowering triglycerides (TG). Due to the Warburg effect, the KD is used as an adjuvant treatment to starve cancer cells, making them more vulnerable to chemotherapy and radiation. The potential positive impacts of a KD on each of these areas warrant further analysis, improved studies, and well-designed randomized controlled trials to further illuminate the therapeutic possibilities provided by this dietary intervention.

Efficacy and Safety of a Ketogenic Diet in Children and Adolescents with Refractory Epilepsy-A Review

Epilepsy in the pediatric and adolescent populations is a devastating condition where individuals are prone to recurrent epileptic seizures or changes in behavior or movement that is the direct result of a primary change in the electrical activity in the brain. Although many children with epilepsy will have seizures controlled with antiseizure medications (ASMs), a large percentage of patients are refractory to drug therapy and may consider initiating a ketogenic diet. The term Ketogenic Diet or Ketogenic Diet Therapy (KDT) refers to any diet therapy in which dietary composition results in a ketogenic state of human metabolism. Currently, there are 4 major Ketogenic diet therapies—the classic ketogenic diet (cKD), the modified Atkins diet (MAD), the medium chain triglyceride ketogenic diet (MCTKD) and the low glycemic index treatment (LGIT). The compositions of the 4 main KDTs differ and limited evidence to distinguish the efficacy among different diets currently exists. Although it is apparent that more randomized controlled trials (RCTs) and long-term studies are needed to evaluate efficacy, side effects and individual response to the diet, it is imperative to study and understand the metabolic profiles of patients with epilepsy in order to isolate which dietary restrictions are necessary to maximize clinical benefit.

The effects of exercise training on lipid metabolism and coronary heart disease

Blood lipoproteins are formed by various amounts of cholesterol (C), triglycerides (TGs), phospholipids, and apolipoproteins (Apos). ApoA1 is the major structural protein of high-density lipoprotein (HDL), accounting for ~70% of HDL protein, and mediates many of the antiatherogenic functions of HDL. Conversely, ApoB is the predominant low-density lipoprotein (LDL) Apo and is an indicator of circulating LDL, associated with higher coronary heart disease (CHD) risk. Thus, the ratio of ApoB to ApoA1 (ApoB/ApoA1) is used as a surrogate marker of the risk of CHD related to lipoproteins. Elevated or abnormal levels of lipids and/or lipoproteins in the blood are a significant CHD risk factor, and several studies support the idea that aerobic exercise decreases CHD risk by partially lowering serum TG and LDL-cholesterol (LDL-C) levels and increasing HDL-C levels. Exercise also exerts an effect on HDL-C maturation and composition and on reverse C transport from peripheral cells to the liver to favor its catabolism and excretion. This process prevents atherosclerosis, and several studies showed that exercise training increases heart lipid metabolism and protects against cardiovascular disease. In these and other ways, it more and more appears that regular exercise, nutrition, and strategies to modulate lipid profile should be viewed as an integrated whole. The purpose of this review is to assess the effects of endurance training on the nontraditional lipid biomarkers, including ApoB, ApoA1, and ApoB/ApoA1, in CHD risk.

A Standard Lipid Panel Is Insufficient for the Care of a Patient on a High-Fat, Low-Carbohydrate Ketogenic Diet

High-fat, low-carbohydrate ketogenic diets have recently become popular for weight loss and the treatment of numerous chronic diseases; however, the general medical community still expresses concern regarding the impact of high-fat diets on serum lipids and cardiovascular risk. Herein, we report on a young man who adopted a ketogenic diet to treat his inflammatory bowel disease. Incidentally, changes in his serum lipids that would be considered adverse by current standards were noted. A more critical analysis of his lipid profile suggests that the changes he experienced may not be dangerous and may, at least with regard to several parameters, represent improvements. This case study demonstrates how the manner in which lipid panels are often reported and reviewed can lead to misleading conclusions and highlights that, at least in the care of those on a ketogenic diet, more nuanced analyses of lipid subfractionations should be conducted in order for physicians to provide optimal care and clinical recommendations.

Cellular Uptake and Clearance of Oxidatively-modified Apolipoprotein E3 by Cerebral Cortex Endothelial Cells

Apolipoprotein E3 (apoE3) plays a critical role in the metabolism of lipoproteins and lowers plasma lipid levels by serving as a ligand for the low-density lipoprotein receptor (LDLr) family of proteins and by promoting macrophage cholesterol efflux. The current study examines the effect of acrolein (an endogenously generated metabolite and an environmental pollutant) modification on the structure and function of apoE3. Acrolein modification was confirmed in Western blots by reactivity with acrolein–lysine-specific antibody and by the presence of oligomeric species due to cross-linking. LC-MS/MS analysis revealed modification of 10 out of 12 lysines in apoE3, with N^ε-(3-methylpyridinium)-lysine being the predominant form of modification, and Lys75 being a ‘hot spot’ in terms of susceptibility to oxidation. Circular dichroism spectroscopy showed no major change in overall secondary structure compared to unmodified apoE3. Reconstituted high density lipoprotein (HDL) bearing acrolein modified apoE3 showed loss of binding to soluble LDLr; however, incubation with mouse endothelioma bEnd.3 cells showed that it was internalized. Incubation with excess LDL did not abolish cellular uptake of acrolein modified apoE3, suggesting alternative mechanism(s) not involving LDLr. Incubation with anti-CD36 antibody did not show a decrease in internalization while incubation with anti- lectin-like oxidized LDL receptor 1 (LOX1) showed partial internalization. However, incubation with anti-scavenger receptor class B type I (SRB1) antibody abolished internalization of acrolein modified apoE3. Taken together, our studies suggest that acrolein modification of apoE3 at lysine residues leads to increase in net negative charge, and as a consequence, results in clearance by LOX1 and SRB1 on endothelial cells. Overall, oxidative modification of apoE3 likely impairs its role in regulating plasma cholesterol homeostasis, eventually leading to lipid disorders.

The association of matrix metalloproteinases polymorphisms and interleukins in advanced age-related macular degeneration

PURPOSE

To assess the impact of matrix metalloproteinase (MMP)1-1607 1G/2G (rs1799750), MMP7-181 A/G (rs11568818) single-nucleotide polymorphism and systemic cytokins interleukin-1 beta (IL-1β), IL-6 levels on the development of exudative age-related macular degeneration (eAMD) Methodology: The study group comprised 282 patients with eAMD, and the control group enrolled 379 randomly selected persons. The genotyping of MMP1-1607 (rs1799750) and MMP7-181 (rs11568818) was performed by using the polymerase chain reaction-based restriction fragment length polymorphism method. To determine IL-1β and IL-6 serum levels, the immunoenzymatic method with monoclonal antibodies coated plates was performed.

RESULTS

MMP1 rs1799750 1G/2G genotype was more frequently found in the development of eAMD. It was associated with a 4.3-fold increased risk for eAMD under the codominant model and a 4.9-fold increased risk for eAMD under the overdominant model. The effect was more pronounced at the age of less than 65 years. IL-1β concentration was significantly higher for MMP1 rs1799750 1G/1G genotype and MMP7 rs11568818 A/G genotype in eAMD patients compared with control group subjects.

CONCLUSIONS

MMP1 rs1799750 1G/2G genotype was found to play a significant role in the development of eAMD at the age of less than 65 years. IL-1β concentration was significantly higher in eAMD patients for MMP1 rs1799750 1G/1G genotype and MMP7 rs11568818 A/G genotype compared with control group subjects.

Oxidized Low-Density Lipoprotein-Deteriorated Psoriasis Is Associated with the Upregulation of Lox-1 Receptor and Il-23 Expression In Vivo and In Vitro

Psoriasis is a chronic inflammatory skin disease. Even though scientists predict that abnormalities in lipid metabolism play an important role in the pathogenesis of psoriasis, the actual underlying mechanisms are still unclear. Therefore, understanding the possible relationship between mechanisms of the occurrence of psoriasis and dyslipidemia is an important issue that may lead to the development of effective therapies. Under this principle, we investigated the influences of hyperlipidemia in imiquimod (IMQ)-induced psoriasis-like B6.129S2-Apoe^tm1Unc/J mice and oxidized low-density lipoprotein (oxLDL) in tumor necrosis factor (TNF)-α-stimulated Hacat cells. In our study, we showed that a high-cholesterol diet aggravated psoriasis-like phenomena in IMQ-treated B6.129S2-Apoe^tm1Unc/J mice. In vitro analysis showed that oxLDL increased keratinocyte migration and lectin-type oxLDL receptor 1 (LOX-1) expression. Evidence suggested that interleukin (IL)-23 was a main cytokine in the pathogenesis of psoriasis. High-cholesterol diet aggravated IL-23 expression in IMQ-treated B6.129S2-Apoe^tm1Unc/J mice, and oxLDL induced IL-23 expression mediated by LOX-1 in TNF-α-stimulated Hacat cells. Therefore, it will be interesting to investigate the factors for the oxLDL induction of LOX-1 in psoriasis. LOX-1 receptor expression may be another novel treatment option for psoriasis and might represent the most promising strategy.

Neurodevelopmental Genetic Diseases Associated With Microdeletions and Microduplications of Chromosome 17p13.3

Chromosome 17p13.3 is a region of genomic instability that is linked to different rare neurodevelopmental genetic diseases, depending on whether a deletion or duplication of the region has occurred. Chromosome microdeletions within 17p13.3 can result in either isolated lissencephaly sequence (ILS) or Miller-Dieker syndrome (MDS). Both conditions are associated with a smooth cerebral cortex, or lissencephaly, which leads to developmental delay, intellectual disability, and seizures. However, patients with MDS have larger deletions than patients with ILS, resulting in additional symptoms such as poor muscle tone, congenital anomalies, abnormal spasticity, and craniofacial dysmorphisms. In contrast to microdeletions in 17p13.3, recent studies have attracted considerable attention to a condition known as a 17p13.3 microduplication syndrome. Depending on the genes involved in their microduplication, patients with 17p13.3 microduplication syndrome may be categorized into either class I or class II. Individuals in class I have microduplications of the YWHAE gene encoding 14-3-3ε, as well as other genes in the region. However, the PAFAH1B1 gene encoding LIS1 is never duplicated in these patients. Class I microduplications generally result in learning disabilities, autism, and developmental delays, among other disorders. Individuals in class II always have microduplications of the PAFAH1B1 gene, which may include YWHAE and other genetic microduplications. Class II microduplications generally result in smaller body size, developmental delays, microcephaly, and other brain malformations. Here, we review the phenotypes associated with copy number variations (CNVs) of chromosome 17p13.3 and detail their developmental connection to particular microdeletions or microduplications. We also focus on existing single and double knockout mouse models that have been used to study human phenotypes, since the highly limited number of patients makes a study of these conditions difficult in humans. These models are also crucial for the study of brain development at a mechanistic level since this cannot be accomplished in humans. Finally, we emphasize the usefulness of the CRISPR/Cas9 system and next generation sequencing in the study of neurodevelopmental diseases.

Dual signaling evoked by oxidized LDLs in vascular cells

The oxidative theory of atherosclerosis relies on the modification of low density lipoproteins (LDLs) in the vascular wall by reactive oxygen species. Modified LDLs, such as oxidized LDLs, are thought to participate in the formation of early atherosclerotic lesions (accumulation of foam cells and fatty streaks), whereas their role in advanced lesions and atherothrombotic events is more debated, because antioxidant supplementation failed to prevent coronary disease events and mortality in intervention randomized trials. As oxidized LDLs and oxidized lipids are present in atherosclerotic lesions and are able to trigger cell signaling on cultured vascular cells and macrophages, it has been proposed that they could play a role in atherogenesis and atherosclerotic vascular remodeling. Oxidized LDLs exhibit dual biological effects, which are dependent on extent of lipid peroxidation, nature of oxidized lipids (oxidized phospholipids, oxysterols, malondialdehyde, α,β-unsaturated hydroxyalkenals), concentration of oxidized LDLs and uptake by scavenger receptors (e.g. CD36, LOX-1, SRA) that signal through different transduction pathways. Moderate concentrations of mildly oxidized LDLs are proinflammatory and trigger cell migration and proliferation, whereas higher concentrations induce cell growth arrest and apoptosis. The balance between survival and apoptotic responses evoked by oxidized LDLs depends on cellular systems that regulate the cell fate, such as ceramide/sphingosine-1-phosphate rheostat, endoplasmic reticulum stress, autophagy and expression of pro/antiapoptotic proteins. In vivo, the intimal concentration of oxidized LDLs depends on the influx (hypercholesterolemia, endothelial permeability), residence time and lipid composition of LDLs, oxidative stress intensity, induction of defense mechanisms (antioxidant systems, heat shock proteins). As a consequence, the local cellular responses to oxidized LDLs may stimulate inflammatory or anti-inflammatory pathways, angiogenic or antiangiogenic responses, survival or apoptosis, thereby contributing to plaque growth, instability, complication (intraplaque hemorrhage, proteolysis, calcification, apoptosis) and rupture. Finally, these dual properties suggest that oxLDLs could be implicated at each step of atherosclerosis development, from early fatty streaks to advanced lesions, depending on the nature and concentration of their oxidized lipid content.

So Much Cholesterol: the unrecognized importance of smooth muscle cells in atherosclerotic foam cell formation

PURPOSE OF REVIEW

Smooth muscle cells (SMCs) form the thickened intimal layer in atherosclerosis-prone arteries in early life, and provide the initial site for retention and uptake of atherogenic lipoproteins. Here we review current knowledge regarding the importance of SMCs in the deposition of cholesterol in atherosclerotic plaque.

RECENT FINDINGS

SMCs were found to comprise at least 50% of total foam cells in human coronary artery atherosclerosis, and exhibit a selective loss of expression of the cholesterol efflux promoter ATP-binding cassette transporter A1. Cholesterol loading induced a loss of SMC gene expression and an increase in macrophage and proinflammatory marker expression by cultured mouse and human arterial SMCs, with reversal of these effects upon removal of the excess cholesterol. Mice engineered to track all cells of SMC lineage indicated that, at most, SMCs make up about one-third of total cells in atherosclerotic plaque in these animals.

SUMMARY

SMCs appear to be the origin of the majority of foam cells in human atherosclerotic plaque. Recent studies suggest a renaissance of research on the role of SMCs in atherosclerosis is needed to make the next leap forward in the prevention and treatment of this disease.

Icariin inhibits foam cell formation by down-regulating the expression of CD36 and up-regulating the expression of SR-BI

Icariin is an important pharmacologically active flavonol diglycoside that can inhibit inflammation in lipopolysaccharide (LPS)-stimulated macrophages. However, little is known about the molecular mechanisms underlying the inhibitory effect of Icariin in the formation of foam cells. In this study, macrophages were cultured with LPS and oxidized low-density lipoprotein (oxLDL) in the presence or absence of Icariin. RT-PCR and western blot were used to detect the levels of mRNA and protein expression of CD36, scavenger receptor class B type I (SR-BI) and the phosphorylation of p38MAPK. It was demonstrated that 4 µM or 20 µM Icariin treatment significantly inhibited the cholesterol ester (CE)/total cholesterol (TC) and oxLDL-mediated foam cell formation (P < 0.05). The binding of oxLDL to LPS-activated macrophages was also significantly hindered by Icariin (P < 0.05). Furthermore, Icariin down-regulated the expression of CD36 in LPS-activated macrophages in a dose-dependent manner and CD36 over-expression restored the inhibitory effect of Icariin on foam cell formation. The phosphorylation of p38MAPK was reduced by Icariin, indicating that Icariin reduced the expression of CD36 through the p38MAPK pathway. In addition, Icariin up-regulated SR-BI protein expression in a dose-dependent manner, and SR-BI gene silencing restored the inhibitory effect of Icariin on foam cell formation. These data demonstrate that Icariin inhibited foam cell formation by down-regulating the expression of CD36 and up-regulating the expression of SR-BI. Therefore, our findings provide a new explanation as to why Icariin could inhibit atherosclerosis.

A novel assay uncovers an unexpected role for SR-BI in LDL transcytosis

AIMS

Retention of low-density lipoprotein (LDL) cholesterol beneath the arterial endothelium initiates an inflammatory response culminating in atherosclerosis. Since the overlying endothelium is healthy and intact early on, it is likely that LDL passes through endothelial cells by transcytosis. However, technical challenges have made confirming this notion and elucidating the mechanisms of transcytosis difficult. We developed a novel assay for measuring LDL transcytosis in real time across coronary endothelial cell monolayers; we used this approach to identify the receptor involved.

METHODS AND RESULTS

Murine aortas were perfused ex vivo with LDL and dextran of a smaller molecular radius. LDL (but not dextran) accumulated under the endothelium, indicating that LDL transcytosis occurs in intact vessels. We then confirmed that LDL transcytosis occurs in vitro using human coronary artery endothelial cells. An assay was developed to quantify transcytosis of DiI-LDL in real time using total internal reflection fluorescence microscopy. DiI-LDL transcytosis was inhibited by excess unlabelled LDL, while degradation of the LDL receptor by PCSK9 had no effect. Instead, LDL colocalized partially with the scavenger receptor SR-BI and overexpression of SR-BI increased LDL transcytosis; knockdown by siRNA significantly reduced it. Excess HDL, the canonical SR-BI ligand, significantly decreased LDL transcytosis. Aortas from SR-BI-deficient mice were perfused ex vivo with LDL and accumulated significantly less sub-endothelial LDL compared with wild-type littermates.

CONCLUSION

We developed an assay to quantify LDL transcytosis across endothelial cells and discovered an unexpected role for SR-BI. Elucidating the mechanisms of LDL transcytosis may identify novel targets for the prevention or therapy of atherosclerosis.

Postprandial phase time influences the uptake of TAG from postprandial TAG-rich lipoproteins by THP-1 macrophages

Postprandial TAG-rich lipoproteins (TRL) can be taken up by macrophages, leading to the formation of foam cells, probably via receptor-mediated pathways. The present study was conducted to investigate whether the postprandial time point at which TRL are collected modulates this process. A meal containing refined olive oil was given to nine healthy young men and TRL were isolated from their serum at 2, 4 and 6 h postprandially. The lipid class and apoB compositions of TRL were determined by HPLC and SDS–PAGE, respectively. The accumulation of lipids in macrophages was determined after the incubation of THP-1 macrophages with TRL. The gene expression of candidate receptors was measured by real-time PCR. The highest concentrations of TAG, apoB48 and apoB100 in TRL were observed at 2 h after the consumption of the test meal. However, excessive intracellular TAG accumulation in THP-1 macrophages was observed in response to incubation with TRL isolated at 4 h, when their particle size (estimated as the TAG:apoB ratio) was intermediate. The abundance of mRNA transcripts in macrophages in response to incubation with TRL was down-regulated for LDL receptor (LDLR), slightly up-regulated for VLDL receptor and remained unaltered for LDLR-related protein, but no effect of the postprandial time point was observed. In contrast, the mRNA expression of scavenger receptors SRB1, SRA2 and CD36 was higher when cells were incubated with TRL isolated at 4 h after the consumption of the test meal. In conclusion, TRL led to excessive intracellular TAG accumulation in THP-1 macrophages, which was greater when cells were incubated with intermediate-sized postprandial TRL isolated at 4 h and was associated with a significant increase in the mRNA expression of scavenger receptors.

Age-related macular degeneration and changes in the extracellular matrix

Age-related macular degeneration (AMD) is the leading cause of permanent, irreversible, central blindness (scotoma in the central visual field that makes reading and writing impossible, stereoscopic vision, recognition of colors and details) in patients over the age of 50 years in European and North America countries, and an important role is attributed to disorders in the regulation of the extracellular matrix (ECM). The main aim of this article is to present the crucial processes that occur on the level of Bruch’s membrane, with special consideration of the metalloproteinase substrates, metalloproteinase, and tissue inhibitor of metalloproteinase (TIMP).

A comprehensive review of the literature was performed through MEDLINE and PubMed searches, covering the years 2005–2012, using the following keywords: AMD, extracellular matrix, metalloproteinases, tissue inhibitors of metalloproteinases, Bruch’s membrane, collagen, elastin.

In the pathogenesis of AMD, a significant role is played by collagen type I and type IV; elastin; fibulin-3, -5, and -6; matrix metalloproteinase (MMP)-2, MMP-9, MMP-14, and MMP-1; and TIMP-3. Other important mechanisms include: ARMS2 and HTR1 proteins, the complement system, the urokinase plasminogen activator system, and pro-renin receptor activation.

Continuous rebuilding of the extracellular matrix occurs in both early and advanced AMD, simultaneously with the dysfunction of retinal pigment epithelium (RPE) cells and endothelial cells. The pathological degradation or accumulation of ECM structural components are caused by impairment or hyperactivity of specific MMPs/TIMPs complexes, and is also endangered by the influence of other mechanisms connected with both genetic and environmental factors.

Development of targeted 1,2-diacyl-sn-glycero-3-phospho-l-serine-coated gelatin nanoparticles loaded with amphotericin B for improved in vitro and in vivo effect in leishmaniasis

OBJECTIVE

The principle objective of this study was to develop 1,2-diacyl-sn-glycero-3-phospho-l-serine (PS)-coated gelatin nanoparticles (GNPs) bearing amphotericin B (AmB) for specific targeting to the macrophages involved in visceral leishmaniasis (VL).

METHOD

The two-step desolvation method has been used for the preparation of GNPs with AmB, which was further coated with PS (PS-AmB-GNPs). The targeting potential of it was compared with uncoated AmB-loaded GNPs (AmB-GNPs) for in vitro and in vivo macrophage uptake.

RESULTS

The results of flow cytometric data revealed enhanced uptake of PS-AmB-GNPs in J774A.1 macrophage cell lines compared with AmB-GNPs. In vivo organ distribution studies in Wistar rats demonstrated a significantly higher extent of accumulation of PS-AmB-GNPs compared with AmB-GNPs in macrophage-rich organs, particularly in liver and spleen. The in vivo anti-leishmanial activity of plain AmB, AmB-GNPs and PS-AmB-GNPs was tested against VL in Leishmania donovani-infected hamsters. Highly significant anti-leishmanial activity (p < 0.05 compared with AmB-GNPs) was observed with PS-AmB-GNPs, causing 85.3 ± 7.89% inhibition of splenic parasitic burden. AmB-GNPs and plain AmB caused only 71.0 ± 3.87 and 50.5 ± 5.12% parasite inhibitions, respectively, in Leishmania-infected hamsters (p < 0.05 for PS-AmB-GNPs versus plain AmB and AmB-GNPs versus plain AmB).

CONCLUSION

The objective of the preparation was achieved and high accumulation of AmB in liver and spleen has been found, which resulted in enhanced anti-leishmanial activity.

Specific Kv1.3 blockade modulates key cholesterol-metabolism-associated molecules in human macrophages exposed to ox-LDL

Cholesterol-metabolism-associated molecules, including scavenger receptor class A (SR-A), lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), CD36, ACAT1, ABCA1, ABCG1, and scavenger receptor class B type I, can modulate cholesterol metabolism in the transformation from macrophages to foam cells. Voltage-gated potassium channel Kv1.3 has increasingly been demonstrated to play an important role in the modulation of macrophage function. Here, we investigate the role of Kv1.3 in modulating cholesterol-metabolism-associated molecules in human acute monocytic leukemia cell-derived macrophages (THP-1 macrophages) and human monocyte-derived macrophages exposed to oxidized LDL (ox-LDL). Human Kv1.3 and Kv1.5 channels (hKv1.3 and hKv1.5) are expressed in macrophages and form a heteromultimeric channel. The hKv1.3-E314 antibody that we had generated as a specific hKv1.3 blocker inhibited outward delayed rectifier potassium currents, whereas the hKv1.5-E313 antibody that we had generated as a specific hKv1.5 blocker failed. Accordingly, the hKv1.3-E314 antibody reduced percentage of cholesterol ester and enhanced apoA-I-mediated cholesterol efflux in THP-1 macrophages and human monocyte-derived macrophages exposed to ox-LDL. The hKv1.3-E314 antibody downregulated SR-A, LOX-1, and ACAT1 expression and upregulated ABCA1 expression in THP-1 macrophages and human monocyte-derived macrophages. Our results reveal that specific Kv1.3 blockade represents a novel strategy modulating cholesterol metabolism in macrophages, which benefits the treatment of atherosclerotic lesions.

Regulation of foam cells by adenosine

Macrophages rely on reverse cholesterol transport mechanisms to rid themselves of excess cholesterol. By reducing accumulation of cholesterol in the artery wall, reverse cholesterol transport slows or prevents development of atherosclerosis. In stable macrophages, efflux mechanisms balance influx mechanisms, and accumulating lipids do not overwhelm the cell. Under atherogenic conditions, inflow of cholesterol exceeds outflow, and the cell is ultimately transformed into a foam cell, the prototypical cell in the atherosclerotic plaque. Adenosine is an endogenous purine nucleoside released from metabolically active cells by facilitated diffusion and generated extracellularly from adenine nucleotides. Under stress conditions, such as hypoxia, a depressed cellular energy state leads to an acute increase in the extracellular concentration of adenosine. Extracellular adenosine interacts with 1 or more of a family of G protein-coupled receptors (A(1), A(2A), A(2B), and A(3)) to modulate the function of nearly all cells and tissues. Modulation of adenosine signaling participates in regulation of reverse cholesterol transport. Of particular note for the development of atherosclerosis, activation of A(2A) receptors dramatically inhibits inflammation and protects against tissue injury. Potent antiatherosclerotic effects of A(2A) receptor stimulation include inhibition of macrophage foam cell transformation and upregulation of the reverse cholesterol transport proteins cholesterol 27-hydroxylase and ATP binding cassette transporter A1. Thus, A(2A) receptor agonists may correct or prevent the adverse effects of inflammatory processes on cellular cholesterol homeostasis. This review focuses on the importance of extracellular adenosine acting at specific receptors as a regulatory mechanism to control the formation of foam cells under conditions of lipid loading.

Iron as a target of chemoprevention for longevity in humans

Iron is universally abundant and no life can exist without it. However, iron levels should be maintained within a narrow range. Iron deficiency causes anaemia, whereas excessive iron increases cancer risk, presumably by free radical generation. Several pathological conditions such as genetic haemochromatosis, chronic viral hepatitis B and C, conditions related to asbestos fibre exposure and ovarian endometriosis have been recognized as iron overload-associated conditions that also increase human cancer risks. Iron's carcinogenicity has been documented in animal experiments. Surprisingly, these studies have revealed that the homozygous deletion of CDKN2A/2B is a major hallmark of iron-induced carcinogenesis. Recently, the hormonal regulation of iron metabolism has been elucidated. A commonly hypothesized mechanism may be the lack of any iron disposal pathway other than for bleeding and a mechanism of iron re-uptake as catechol chelate has been discovered. Iron overload in neurons via the ferroportin block may play a role in Alzheimer's disease. Furthermore, a recent epidemiological study reported that iron reduction by phlebotomy was associated with decreased cancer risks in a general population. Given that the required amounts of iron decrease during ageing, the fine control of body iron stores would be a wise strategy for chemoprevention of several diseases.

Wine and Health: A Paradigm for Alcohol and Antioxidants

Moderate alcohol consumption has been shown in many epidemiological investigations to prolong overall life expectancy by reducing the risk of certain diseases. Those that account most for this reduction are coronary heart disease and ischemic stroke, both of which are caused by atherosclerotic vascular disease. It has been claimed that these effects are beverage-specific, with red wine being the most potent. This review examines the relative contributions of ethanol and the polyphenolic antioxidants of red wine by considering their potential to inhibit atherogenesis and the mechanisms involved. There is good evidence, bothin vitroandin vivo, that ethanol increases production and circulating levels of HDL-Cholesterol, and reduces clot formation by blocking thrombin activity as well as by inhibition of fibrinolysis. It also prevents migration of smooth-muscle cells to the intimal layer of arteries and reduces the incidence of Type II Diabetes Mellitus, a major risk factor for atherosclerotic disease. Red wine, in addition to ethanol, contains many polyphenolic antioxidants that are also present in fruit and vegetables (such as catechin and quercetin), as well as resveratrol that is almost restricted to grapes and red wine. These polyphenols, especially the last-named, have been shown byin vitroexperiments to exhibit many potent properties conducive to preventing atherosclerosis. In addition to lowering clot formation, they diminish inflammatory reactions by down-regulating production of eicosanoids and cytokines, they prevent oxidation of LDL, reduce expression of cell-adhesion molecules, and increase NO production. However, investigations in whole animals and human subjects have yielded conflicting results. The above paradox can be explained by studies demonstrating that these polyphenols, when taken orally, are rapidly conjugated with glucuronide and sulfate by the small-intestinal mucosa prior to absorption, following which the deactivated water-soluble conjugates are quickly excreted by the kidney. The free biologically-active parent compounds appear in the circulation in very low concentrations and with a very rapid halflife. Uptake by relevant tissues could not be demonstrated. In line with this evidence, red and white wines have comparable effects when administered to humans that are essentially attributable to their alcohol content alone. These findings suggest that dietary antioxidants may be less effective than previously thought.

Ox-LDL-induced LOX-1 expression in vascular smooth muscle cells: role of reactive oxygen species

Oxidized low density lipoprotein (ox-LDL) and lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) have been implicated in the development of atherosclerosis. This study was designed to investigate the expression regulation of LOX-1 by ox-LDL and the potential underlying mechanisms in cultured rat vascular smooth muscle cells (VSMCs). VSMCs were treated with ox-LDL, and the expressions of LOX-1 mRNA and proteins were determined by RT-PCR and western blotting, respectively. The intracellular reactive oxygen species (ROS) production was monitored by flow cytometry with fluorescence probe, DCFH(2) -DA. The effect of several inhibitors including aspirin, NDGA, allopurinol, apocynin, and rotenone on ox-LDL-induced ROS formation and LOX-1 expression was also investigated. The roles of NF-κB p65 and JNK were explored. Ox-LDL significantly induced LOX-1 expression at both mRNA and protein levels in a dose-dependent and time-dependent manner. Aspirin, NDGA, and preconditioned apocynin suppressed ox-LDL-induced intracellular ROS production and LOX-1 expression, while allopurinol and rotenone failed to do so. Vitamin C and N-acetyl-l-cysteine demonstrated similar effect. Furthermore, both NF-κB p65 expression and phosphorylated JNK (p-JNK) to JNK expression ratio were elevated after ox-LDL treatment. In addition, the NF-κB inhibitor PDTC and JNK inhibitor SP600125 pretreatment partly abolished ox-LDL-induced LOX-1 expression. These findings suggested that ROS mediated ox-LDL-induced LOX-1 expression in VSMCs through NF-κB and JNK signaling pathways.

Oligo-guanosine nucleotide induces neuropilin-1 internalization in endothelial cells and inhibits angiogenesis

Ligand interaction with cognate cell-surface receptor often promotes receptor internalization, protecting cells from prolonged or excessive signaling from extracellular ligands. Compounds that induce internalization of surface receptors prevent ligand binding to cognate cell-surface receptors serving as inhibitors. Here, we show that synthetic polyriboguanosine (poly G) and oligo-deoxyriboguanosine (oligo G) reduce endothelial levels of surface neuropilin-1 (NRP1), a receptor shared by semaphorin 3A and vascular endothelial growth factor (VEGF), which plays critical roles in angiogenesis. Oligo G also reduces levels of cell-surface scavenger receptor expressed by endothelial cells I (SREC-I), but not levels of NRP2, gp130, CD31, VEGFR-1, or VEGFR-2. Poly or oligo A, T, and C do not promote NRP1 or SREC-I internalization. We find that oligo G binds to NRP1 with high affinity (Kd:1.3 ± 0.16 nM), bridges the extracellular domain of NRP1 to that of SREC-I, and induces coordinate internalization of NRP1 and SREC-I. In vitro, oligo G blocks the binding and function of VEGF(165) in endothelial cells. In vivo, intravitreal administration of oligo G reduces choroidal neovascularization in mice. These results demonstrate that synthetic oligo G is an inhibitor of pathologic angiogenesis that reduces cell-surface levels and function of NRP1 acting as an internalization inducer.

Fluorescent high-content imaging allows the discrimination and quantitation of E-LDL-induced lipid droplets and Ox-LDL-generated phospholipidosis in human macrophages

Macrophage foam cells formed during uptake of atherogenic lipoproteins are a hallmark of atherosclerotic lesion development. In this study, human macrophages were incubated with two prototypic atherogenic LDL modifications enzymatically degraded LDL (E-LDL) and oxidized LDL (Ox-LDL) prepared from the same donor LDL. To detect differences in macrophage lipid storage, fluorescent high-content imaging was used. Lipid droplets were stained using Bodipy 493/503, and the fluorescent phospholipid probe NBD-PE was used to detect endolysosomal phospholipidosis in high-content imaging assays. The phospholipidosis assay was validated using phospholipidosis-inducing cationic amphiphilic drugs. In addition, neutral lipids and phospholipidosis were determined using LipidTOX. Images of 96-well cell culture microtiter plates were captured with multichannel laser-based high-content confocal microscopy, and subsequently cell- and well-based data were analyzed. E-LDL-loaded macrophages show increased intensity of Bodipy 493/503 and LipidTOX-Green neutral lipid droplet staining and a greater mean area and number of lipid droplets per cell compared to Ox-LDL-loaded and M-CSF-differentiated control macrophages. In contrast, Ox-LDL-loaded macrophages show increased intensity of NBD-PE and LipidTOX-Red detectable phospholipidosis in the endolysosomal compartment compared to E-LDL-loaded and M-CSF-differentiated macrophages. Treatment with the peroxisome proliferator-activated receptor-gamma agonist pioglitazone leads to lipid droplet induction depending on the lipid loading state of the macrophages. These results indicate that E-LDL preferentially induces lipid droplets, while Ox-LDL provokes endolysosomal phospholipidosis in human macrophages representing two different lipid storage principles. Therefore, fluorescent high-content imaging is a useful tool to discriminate between and quantify lipid storage compartments in macrophages also in response to drugs affecting cellular lipid metabolism.

Curcumin eliminates oxidized LDL roles in activating hepatic stellate cells by suppressing gene expression of lectin-like oxidized LDL receptor-1

Type II diabetes mellitus (T2DM) is often accompanied by non-alcoholic steatohepatitis (NASH) and associated with hypercholesterolemia, that is, increased levels of plasma low-density lipoprotein (LDL) and oxidized LDL (ox-LDL). Approximately one-third of NASH develops hepatic fibrosis. The role of hypercholesterolemia in T2DM and NASH-associated hepatic fibrogenesis remains obscure. We previously reported that the phytochemical curcumin inhibited the activation of hepatic stellate cells (HSCs), the major effector cells during hepatic fibrogenesis, and protected the liver from fibrogenesis in vitro and in vivo. The aims of this study are to evaluate the role of ox-LDL in activation of HSCs, to assess curcumin effects on eliminating the role of ox-LDL, and to further explore the underlying mechanisms. In this report, we observe that ox-LDL alters the expression of genes closely relevant to HSC activation, which is eliminated by curcumin. Curcumin suppresses gene expression of lectin-like oxidized LDL receptor-1 (LOX-1), leading to the blockade of the transport of extracellular ox-LDL into cells. This suppressive effect of curcumin results from the interruption of Wnt signaling and the activation of peroxisome proliferator-activated receptor-gamma (PPARgamma). In conclusion, these results support our initial hypothesis and demonstrate that ox-LDL stimulates HSC activation, which is eliminated by curcumin by suppressing lox-1 expression by interrupting Wnt signaling and stimulating PPARgamma activity. These results provide novel insights into the role of ox-LDL in T2DM and NASH-associated hepatic fibrogenesis and mechanisms by which curcumin suppresses ox-LDL-induced HSC activation, as well as the implication of curcumin in the treatment of T2DM and NASH-associated hepatic fibrosis.

Transmembrane signaling pathway mediates oxidized low-density lipoprotein-induced expression of plasminogen activator inhibitor-1 in vascular endothelial cells

Atherosclerotic cardiovascular disease is the number one cause of death for adults in Western society. Plasminogen activator inhibitor-1 (PAI-1), the major physiological inhibitor of plasminogen activators, has been implicated in both thrombogenesis and atherogenesis. Previous studies demonstrated that copper-oxidized low-density lipoprotein (C-oLDL) stimulated production of PAI-1 in vascular endothelial cells (EC). The present study examined the involvement of lectin-like oxidized LDL receptor-1 (LOX-1) and Ras/Raf-1/ERK1/2 pathway in the upregulation of PAI-1 in cultured EC induced by oxidized LDLs. The results demonstrated that C-oLDL or FeSO(4)-oxidized LDL (F-oLDL) increased the expression of PAI-1 or LOX-1 in human umbilical vein EC (HUVEC) or coronary artery EC (HCAEC). Treatment with C-oLDL significantly increased the levels of H-Ras mRNA, protein, and the translocation of H-Ras to membrane fraction in EC. LOX-1 blocking antibody, Ras farnesylation inhibitor (FTI-277), or small interference RNA against H-Ras significantly reduced C-oLDL or LDL-induced expression of H-Ras and PAI-1 in EC. Incubation with C-oLDL or F-oLDL increased the phosphorylation of Raf-1 and ERK1/2 in EC compared with LDL or vehicle. Treatment with Raf-1 inhibitor blocked Raf-1 phosphorylation and the elevation of PAI-1 mRNA level in EC induced by C-oLDL or LDL. Treatment with PD-98059, an ERK1/2 inhibitor, blocked C-oLDL or LDL-induced ERK1/2 phosphorylation or PAI-1 expression in EC. The results suggest that LOX-1, H-Ras, and Raf-1/ERK1/2 are implicated in PAI-1 expression induced by oxidized LDLs or LDL in cultured EC.

Sulfated polysaccharides identified as inducers of neuropilin-1 internalization and functional inhibition of VEGF165 and semaphorin3A

Neuropilin-1 (NRP1) and NRP2 are cell surface receptors shared by class 3 semaphorins and vascular endothelial growth factor (VEGF). Ligand interaction with NRPs selects the specific signal transducer, plexins for semaphorins or VEGF receptors for VEGF, and promotes NRP internalization, which effectively shuts down receptor-mediated signaling by a second ligand. Here, we show that the sulfated polysaccharides dextran sulfate and fucoidan, but not others, reduce endothelial cell-surface levels of NRP1, NRP2, and to a lesser extent VEGFR-1 and VEGFR-2, and block the binding and in vitro function of semaphorin3A and VEGF(165). Administration of fucoidan to mice reduces VEGF(165)-induced angiogenesis and tumor neovascularization in vivo. We find that dextran sulfate and fucoidan can bridge the extracellular domain of NRP1 to that of the scavenger receptor expressed by endothelial cells I (SREC-I), and induce NRP1 and SREC-I coordinate internalization and trafficking to the lysosomes. Overexpression of SREC-I in SREC-I-negative cells specifically reduces cell-surface levels of NRP1, indicating that SREC-I mediates NRP1 internalization. These results demonstrate that engineered receptor internalization is an effective strategy for reducing levels and function of cell-surface receptors, and identify certain sulfated polysaccharides as "internalization inducers."

In search of antioxidants and anti-atherosclerotic agents from herbal medicines

Many recent studies have suggested that low-density lipoprotein (LDL) oxidation, endothelial dysfunction, and inflammation are involved in the pathogenesis of atherosclerosis. Herbal regimens in the treatment of blood stasis, a counterpart of atherosclerosis, commonly use medicinal plants of leguminosae and labiatae. We have developed disease-oriented screening methods to search for bioactive components, particularly isoflavones in leguminosae and polyphenols in labiatae from Chinese herbal medicines. Many bioactive components and active fractions capable of inhibiting a. Cu(II)-induced LDL oxidation, b. oxidized LDL-induced endothelial damage, c. uptake of oxidized LDL by macrophages (J774A.1), and d. expression of cell adhesion molecules (CAMs) have been identified. A polyphenol, namely salvianolic acid B from Salvia miltiorrhiza was identified to be a potent antioxidant, endothelial-protecting agent, and an inhibitor to suppress the expression of ICAM and VCAM. This review also briefly describes the strategy for developing herbal medicines as anti-atherosclerotic agents.

Native and oxidized low-density lipoproteins modulate the vasoactive actions of soluble β-amyloid peptides in rat aorta

Cerebrovascular accumulation of Aβ (β-amyloid) occurs in aging and AD (Alzheimer's disease). Hypercholesterolaemia, which is associated with raised plasma LDL (low-density lipoprotein), may predispose to AD. Soluble Aβ is found in the circulation and enhances vasoconstriction. Under conditions that may favour the formation of short Aβ oligomers, as opposed to more severe polymerization leading to Aβ fibrillogenesis, we investigated the influence of LDLs on the vasoactive actions of soluble Aβ. Thus the actions of Aβ40 and Aβ42 in combination with native or oxidized LDL on vasoconstriction to NA (noradrenaline) and vasodilatation to ACh (acetylcholine) were examined in rat aortic rings. LDL, particularly when oxidized, potentiated NA-induced constriction when combined with soluble Aβ40 and, especially, Aβ42. Soluble Aβ40 reduced relaxation induced by ACh, but Aβ42 was ineffective. Native and oxidized LDL also attenuated relaxation. Synergism occurred between oxidized LDL and Aβ with respect to ACh-induced relaxation, but not between native LDL and Aβ. We have shown for the first time that, under conditions that may result in Aβ oligomer formation, LDL, particularly when oxidized, modulates the vascular actions of soluble Aβ to extents greater than those reported previously for fibrillar Aβ preparations. Mechanisms whereby a treatable condition, namely hypercholesterolaemia, might contribute to the development of the cerebrovascular component of AD are indicated.

Immunological response in alcoholic liver disease

The development of alcoholic liver disease (ALD) can be attributed to many factors that cause damage to the liver and alter its functions. Data collected over the last 30 years strongly suggests that an immune component may be involved in the onset of this disease. This is best evidenced by the detection of circulating autoantibodies, infiltration of immune cells in the liver, and the detection of hepatic aldehyde modified proteins in patients with ALD. Experimentally, there are numerous immune responses that occur when proteins are modified with the metabolites of ethanol. These products are formed in response to the high oxidative state of the liver during ethanol metabolism, causing the release of many inflammatory processes and potential of necrosis or apoptosis of liver cells. Should cellular proteins become modified with these reactive alcohol metabolites and be recognized by the immune system, then immune responses may be initiated. Therefore, it was the purpose of this article to shed some insight into how the immune system is involved in the development and/or progression of ALD.

Oxidized LDL specifically promotes the initiation of monocyte invasion during transendothelial migration with upregulated PECAM-1 and downregulated VE-cadherin on endothelial junctions

It is poorly understood how oxidized LDL (oxLDL) promotes monocyte dynamics in transendothelial migration (TEM) in atherogenesis. We developed an in vitro 3D-live-single cell TEM assay system with subendothelial oxLDL embedded in ultra-thin collagen gels, mimicking subendothelial oxLDL accumulation in vivo. With dividing monocyte dynamics into three stages (1: adhesion on endothelium, 2: invasion and 3: complete transmigration below endothelium), we analyzed the stage transition dynamics of individual living human monocytes. OxLDL did not enhance initial monocyte adhesion to endothelium (stage 1), but it specifically primed adherent monocytes to start invasion (stage 1-->2). Once invasion started, it had no effect thereafter on monocyte stage transition (stage 2-->3). OxLDL upregulated PECAM-1 and downregulated VE-cadherin on endothelial junctions without monocyte addition, both of which could promote monocyte entry by enhanced homophilic binding to monocyte PECAM-1, and by disrupted junctional barrier, respectively. Meanwhile, monocyte speed at neither locomotion on endothelium (stage 1) nor subendothelial migration (stage 3) was altered by oxLDL. These data indicate that before monocyte adhesion, endothelial junctions changed their conformation to more monocyte-acceptable state in response to oxLDL, resulting the stage-specific promotion of monocyte TEM (stage 1-->2; initiation of invasion) with no enhancement of its initial adhesion or migration speed.

Lectin-like oxidized low-density lipoprotein receptor-1, a new promising target for the therapy of atherosclerosis?

Endothelial activation and dysfunction induced by oxidized modified low-density lipoprotein (ox-LDL) is one of the key steps in the initiation of atherosclerosis. Recent studies have shown that a new lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) mediates the recognition and internalization of ox-LDL. LOX-1 is the main receptor for ox-LDL and may play an important role in the pathogenesis of hypertension, diabetes, and, especially, of atherosclerosis. The potential role of LOX-1 in the pathogenesis of atherosclerosis includes: endocytosis of ox-LDL, expression co-location with atherosclerosis enhanced by atherosclerosis-related risk factors, elevated LOX-1 protein in cardiovascular disease, effects related to atherosclerosis and eliminated by antiatherosclerotic drugs. Identification and regulation of LOX-1 and understanding its signal transduction pathways might improve our insight toward the pathogenesis of atherosclerosis and provide a selective treatment approach. LOX-1 might be a potential and promising target for the development of novel antiatherosclerotic drugs. However, due to limited knowledge about LOX-1, there are still many questions to be answered.

Genetic evidence of a functional monocyte dichotomy

Human peripheral blood monocytes are found as two distinct populations based upon differential expression of chemokine receptors, adhesion molecules, Fc receptors, and cytokines. cDNA microarray analysis now reveals additional differences between these subsets that suggest dramatically diverse functions. One monocyte subset (CD14++CD16-) appears to be closely paired with neutrophils, and may have as its primary function the removal and recycling of apoptotic neutrophils at sites of inflammation. The other monocyte subset (CD14+CD16+) expresses numerous genes encoding proteins with antimicrobial activity and thus may be more directly involved in peripheral host defense. The production of monocytes capable of efficiently removing dying neutrophils may be necessary to prevent host tissue damage and autoimmune response induction. Therefore, species like humans that produce relatively high levels of circulating neutrophils must also produce relatively high numbers of the recycling monocytes. Conversely, species such as mice and rats that maintain relatively lower levels of circulating neutrophils require fewer recycling monocytes.

Increased gene expression of scavenger receptors and proinflammatory markers in peripheral blood mononuclear cells of hyperlipidemic males

Interactions between peripheral blood mononuclear cells (PBMCs) and those within plaques are suggested to be pathophysiologically relevant to lipid-induced arteriosclerosis. In this study, gene expressions of scavenger receptors (CD36, CD68), LPS receptor (CD14), proinflammatory (tumor necrosis factor alpha [TNFalpha], CD40, interleukin-1 beta [IL-1beta]) and oxidative stress-related (manganese superoxide dismutase [MnSOD]) markers were analyzed in PBMCs of clinically asymptomatic males with classical proatherogenic risk factors such as smoking and/or hyperlipidemia. PBMCs were isolated from venous blood of normolipidemic non-smokers (n = 10) and smokers (n = 8), and hyperlipidemic non-smokers (n = 9) and smokers (n = 8). RNA from PBMCs was used for PCR analyses. Plasma concentrations of oxidized low-density lipoproteins (oxLDL) were measured by ELISA. The gene expressions of CD36, CD68, CD40, TNFalpha, and MnSOD were significantly higher in PBMCs of hyperlipidemics than in normolipidemics, irrespective of whether they were smoking or not. The individual expression of these genes showed significant positive correlations with each other but also with serum cholesterol or plasma oxLDL concentrations. The higher expressions of scavenger receptors, proinflammatory and oxidative stress-related genes of PBMCs are suggested to result mainly from hyperlipidemia and the accompanied increase of oxLDL concentrations.

Photosensitizer delivery to vulnerable atherosclerotic plaque: comparison of macrophage-targeted conjugate versus free chlorin(e6)

We have previously shown that a conjugate (MA-ce6) between maleylated serum albumin and the photosensitizer chlorin(e6) (ce6) is targeted in vitro to macrophages via class A scavenger receptors. We now report on the ability of this conjugate to localize in macrophage-rich atherosclerotic plaques in vivo. Both the conjugate and the free photosensitizer ce6 are studied after injection into New Zealand White rabbits that are rendered atherosclerotic by a combination of aortic endothelial injury and cholesterol feeding into normal rabbits. Rabbits are sacrificed at 6 and 24 h after injection and intravascular fluorescence spectroscopy is carried out by fiber-based fluorimetry in intact blood-filled arteries. Surface spectrofluorimetry of numbered excised aortic segments together with injured and normal iliac arteries is carried out, and quantified ce6 content by subsequent extraction and quantitative fluorescence determination of the arterial segments and also of nontarget organs. There is good agreement between the various techniques for quantifying ce6 localization, and high contrast between arteries from atherosclerotic and normal rabbits is obtained. Fluorescence correlates with the highest burden of plaque in the aorta and the injured iliac artery. The highest accumulation in plaques is obtained using MA-ce6 at 24 h. Free ce6 gives better accumulation at 6 h compared to 24 h. The liver, spleen, lung, and gall bladder have the highest uptake in nontarget organs. Macrophage-targeted photosensitizer conjugates may have applications in both detecting and treating inflamed vulnerable plaque.

Homocysteine from endothelial cells promotes LDL nitration and scavenger receptor uptake

We recently reported that methionine-loaded human umbilical vein endothelial cells (HUVECs) exported homocysteine (Hcy) and were associated with hydroxyl radical generation and oxidation of lipids in LDL. Herein we have analysed the Hcy-induced posttranslational modifications (PTMs) of LDL protein. PTMs have been characterised using electrophoretic mobility shift, protein carbonyl ELISA, HPLC with electrochemical detection and Western blotting of 3-nitrotyrosine, and LDL uptake by scavenger receptors on monocyte/macrophages. We have also analysed PTMs in LDL isolated from rheumatoid (RA) and osteo-(OA) arthritis patients with cardiovascular disease (CVD). While reagent Hcy (< 50 microM) promoted copper-catalysed LDL protein oxidation, Hcy released from methionine-loaded HUVECs promoted LDL protein nitration. In addition, LDL nitration was associated with enhanced monocyte/macrophage uptake when compared with LDL oxidation. LDL protein nitration and uptake by monocytes, but not carbonyl formation, was elevated in both RA and OA patients with CVD compared with disease-matched patients that had no evidence of CVD. Moreover, a direct correlation between plasma total Hcy (tHcy) and LDL uptake was observed. The present studies suggest that elevated plasma tHcy may promote LDL nitration and increased scavenger receptor uptake, providing a molecular mechanism that may contribute to the clinical link between CVD and elevated plasma tHcy.