Thematic Review Series: The Immune System and Atherogenesis. Molecular mechanisms regulating monocyte recruitment in atherosclerosis

Bioactive TNIIIA2 Sequence in Tenascin-C Is Responsible for Macrophage Foam Cell Transformation; Potential of FNIII14 Peptide Derived from Fibronectin in Suppression of Atherosclerotic Plaque Formation

One of the extracellular matrix proteins, tenascin-C (TN-C), is known to be upregulated in age-related inflammatory diseases such as cancer and cardiovascular diseases. Expression of this molecule is frequently detected, especially in the macrophage-rich areas of atherosclerotic lesions; however, the role of TN-C in mechanisms underlying the progression of atherosclerosis remains obscure. Previously, we found a hidden bioactive sequence termed TNIIIA2 in the TN-C molecule and reported that the exposure of this sequence would be carried out through limited digestion of TN-C by inflammatory proteases. Thus, we hypothesized that some pro-atherosclerotic phenotypes might be elicited from macrophages when they were stimulated by TNIIIA2. In this study, TNIIIA2 showed the ability to accelerate intracellular lipid accumulation in macrophages. In this experimental condition, an elevation of phagocytic activity was observed, accompanied by a decrease in the expression of transporters responsible for lipid efflux. All these observations were mediated through the induction of excessive β1-integrin activation, which is a characteristic property of the TNIIIA2 sequence. Finally, we demonstrated that the injection of a drug that targets TNIIIA2's bioactivity could rescue mice from atherosclerotic plaque expansion. From these observations, it was shown that TN-C works as a pro-atherosclerotic molecule through an internal TNIIIA2 sequence. The possible advantages of clinical strategies targeting TNIIIA2 are also indicated.

Extracellular vesicles and atherosclerotic peripheral arterial disease

Atherogenesis involves a complex multifactorial process including chronic inflammation that requires the participation of several cell types and molecules. In addition to their role in vascular homeostasis, extracellular vesicles also appear to play an important role in atherogenesis, including monocyte transmigration and foam cell formation, SMC proliferation and migration, leukocyte transmigration, and thrombosis. Peripheral arterial disease, a major form of peripheral vascular disease, is characterized by structural or functional impairment of peripheral arterial supply, often secondary to atherosclerosis. Elevated levels of extracellular vesicles have been demonstrated in patients with peripheral arterial disease and implicated in the development of atherosclerosis within peripheral vascular beds. However, extracellular vesicles also appear capable of delivering cargo with atheroprotective effects. This capability has been exploited in vesicles engineered to carry content capable of neovascularization, suggesting potential for therapeutic angiogenesis. This dual capacity holds substantial promise for diagnosis and therapy, including possibly limb- and life-saving options for peripheral arterial disease management.

Sphingolipids and Atherosclerosis: The Dual Role of Ceramide and Sphingosine-1-Phosphate

Sphingolipids are bioactive molecules that play either pro- and anti-atherogenic roles in the formation and maturation of atherosclerotic plaques. Among SLs, ceramide and sphingosine-1-phosphate showed antithetic properties in regulating various molecular mechanisms and have emerged as novel potential targets for regulating the development of atherosclerosis. In particular, maintaining the balance of the so-called ceramide/S1P rheostat is important to prevent the occurrence of endothelial dysfunction, which is the trigger for the entire atherosclerotic process and is strongly associated with increased oxidative stress. In addition, these two sphingolipids, together with many other sphingolipid mediators, are directly involved in the progression of atherogenesis and the formation of atherosclerotic plaques by promoting the oxidation of low-density lipoproteins (LDL) and influencing the vascular smooth muscle cell phenotype. The modulation of ceramide and S1P levels may therefore allow the development of new antioxidant therapies that can prevent or at least impair the onset of atherogenesis, which would ultimately improve the quality of life of patients with coronary artery disease and significantly reduce their mortality.

Stem cell therapy targets the neointimal smooth muscle cells in experimentally induced atherosclerosis: involvement of intracellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM)

Smooth muscle cells (SMCs) are currently considered a central pivotal player in pathogenesis and development of atherosclerotic lesions. As consequence of vascular injury, SMCs migrate from the tunica media into the tunica intima layers where they contribute to neointimal formation by converting into foam cells and producing pro-inflammatory and oxidative stress markers. We targeted the replacement of neointimal SMCs by using the mesenchymal stem cells (MSCs) therapy in experimentally induced atherosclerosis in an attempt to improve the atherosclerotic lesion and its concomitant complications. Rats were divided into 4 groups (n=20). Control group: rats kept on a standard chow diet; atherosclerotic group: rats received the atherogenic diet; stem cells-treated group: rats were injected with CD34+ stem cells (6×106 cells in 0.5 mL PBS in rat tail vein) and maintained on the atherogenic diet; and resveratrol-treated group: rats were supplemented orally with resveratrol at a dose level 3 mg/kg per day and the atherogenic diet. After 12 weeks, rats were euthanized, blood samples were collected for separation of serum, and abdominal aortas were excised for further biochemical, molecular, and histopathological investigations. We used resveratrol, the well-established anti-atherosclerotic drug, as a benchmark to assess the efficacy of stem cell therapy. MSCs treatment revealed significant amelioration in both histopathological and biochemical patterns as evidenced by decreased foam cells formation, ICAM-1, VCAM, M-CSF, iNOS, COX-2, and TNF-α. We concluded that MSCs therapy significantly replaced the neointimal SMCs and decreased adhesion molecules as well as the oxidative and inflammatory markers in atherosclerosis.

Daily White kwao krua dietary supplement alleviates LDL oxidative susceptibility, plasma LDL level and improves vasculature in a hypercholesterolemia rabbit model

BACKGROUND AND AIM

White kwao krua is an edible plant that grows in Southeast Asia. It is very rich in natural phytoestrogens. Previous clinical studies revealed that the use of White kwao krua as a hormone replacement therapy has beneficial effects on the lipid profile of menopause women. In this present study, we utilized the hypercholesterolemia rabbit model to demonstrate the effect of White kwao krua on the daily intake of high-fat diet.

EXPERIMENTAL PROCEDURE

We induced hypercholesterolemia in rabbits by feeding with high-fat diet (1% cholesterol-containing diet). The animals were maintained 12 weeks for the experimentation. The White kwao krua supplement was administered 100 mg/kg/day, and the effects were monitored comparing with Statins and turmeric. Blood was collected periodically to monitor the plasma cholesterol level and the oxidative susceptibility of isolated LDL-cholesterol. At the end of the experiment, the aorta was collected from the animal and performed endothelial-dependent relaxation and endothelial-independent relaxation assays. The relative ratio of intima to media layer was microscopically evaluated from hematoxylin/eosin-stained tissues.

RESULTS AND CONCLUSION

We showed that the White kwao krua supplement reduced LDL-cholesterol about 40% compared with high-fat diet consumption alone. Administration of White kwao krua had significantly prolonged the susceptibility of LDL-cholesterol to oxidation. Besides, it led to the improvement of vascular function by recovering endothelium-dependent relaxation and alleviating vascular structure impairment induced by high-fat dietary intake. Together, we suggest that White kwao krua should be used as a dietary supplement to reduce the atherogenesis in high-fat dietary consumption.

SECTION

Dietary therapy/nutrients supplements.

TAXONOMY

Inflammation, Disease.

The association between local arteriosclerosis of the prostatic arteries and chronic inflammation in human benign prostatic enlargement

BACKGROUND

To elucidate the pathogenesis of benign prostatic enlargement (BPE) in humans due to chronic inflammation caused by arteriosclerosis, the relationships between prostate size and the degree of chronic inflammation induced by local arteriosclerosis were investigated.

METHODS

The present cohort included 50 subjects who underwent robot-assisted radical prostatectomy (RARP) in a prospective study. The presence or absence of local arteriosclerosis in the prostatic arteries removed during RARP was evaluated by microscopic assessment. Chronic inflammation in the prostate was judged according to both the density and the extent of inflammatory cells. The expression of lectin-like oxidized-low density lipoprotein receptor-1 (LOX-1) and the infiltration of macrophages in the prostate, which are high in arteriosclerosis, were investigated by immunohistochemistry.

RESULTS

Local arteriosclerosis was observed in 28% (14/50). Prostate size and the inflammation score were significantly increased in the presence of arteriosclerosis (P = 0.006, P < 0.001, respectively). There was also a significant increase of LOX-1 in the epithelial and stromal cells of the prostate in the presence of arteriosclerosis (all, P < 0.001). Concerning the presence of macrophages, subjects with arteriosclerosis had significantly more positive expression of ionized calcium-binding adapter molecule-1 (IBA-1), a marker of macrophages, than subjects without arteriosclerosis (P < 0.001).

CONCLUSIONS

In human surgical specimens, chronic inflammation owing to local arteriosclerosis of the prostatic arteries was significantly related to prostatic enlargement. Given the immunohistochemical analyses, the putative pathogenesis for this relationship is that LOX-1 induces macrophage infiltration, leading to BPE.

Piper sarmentosum attenuates TNF-α-induced VCAM-1 and ICAM-1 expression in human umbilical vein endothelial cells

Objectives

Inflammation plays a key role in the pathogenesis of atherosclerosis. Piper sarmentosum is an herb with antioxidant and anti-atherosclerotic activities. The aim of this study was to evaluate the anti-inflammatory properties of an aqueous extract of P. sarmentosum (AEPS) in human umbilical vein endothelial cells (HUVECs).

Methods

HUVECs were divided into six groups: control, treatment with 10 ng/ml TNF-α, and co-treatment of 10 ng/ml TNF-α with four different concentrations of AEPS (100, 150, 250, and 300 μg/ml) for 24 h. Subsequently, vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) protein expression, U937 monocyte cells adhesion, and nuclear factor-kappaB (NF-κB) p65 expression in HUVECs were measured.

Results

Treatment of TNF-α-stimulated HUVECs with AEPS at different concentrations resulted in decreased VCAM-1 and ICAM-1 protein expression in a dose-dependent manner. Furthermore, AEPS also inhibited TNF-α-stimulated U937 monocyte cells adhesion to HUVECs. In addition, AEPS reduced TNF-α-induced NF-κB p65 expression in a dose-dependent manner.

Conclusions

The results indicated that AEPS suppressed TNF-α-induced VCAM-1 and ICAM-1 expression NF-κB signaling.

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Piper sarmentosum attenuates VCAM-1 and ICAM-1 expression in TNF-α-induced HUVEC.

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P. sarmentosum inhibits TNF-α-stimulated monocytes adhesion to HUVEC.

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P. sarmentosum reduces TNF-α-induced NF-κB p65 expression in HUVEC.

Novel role of the nutraceutical bioactive compound berberine in lectin-like OxLDL receptor 1-mediated endothelial dysfunction in comparison to lovastatin

BACKGROUND AND AIMS

Oxidized LDL (oxLDL) or pro-inflammatory stimuli lead to increased oxidative stress linked to endothelial dysfunction and atherosclerosis. The oxLDL receptor-1 (LOX1) is elevated within atheromas and cholesterol-lowering statins inhibit LOX1 expression. Berberine (BBR), an alkaloid extracted from plants of gender Berberis, has lipid-lowering and anti-inflammatory activity. However, its role in regulating LOX1-mediated signaling is still unknown. The aim of this study was to investigate the effect of BBR on oxLDL- and TNFα-induced endothelial dysfunction in human umbilical vein endothelial cells (HUVECs) and to compare it with that of lovastatin (LOVA).

METHODS AND RESULTS

Cytotoxicity was determined by lactate dehydrogenase assay. Antioxidant capacity was measured with chemiluminescent and fluorescent method and intracellular ROS levels through a fluorescent dye. Gene and protein expression levels were assayed by qRT-PCR and western blot, respectively. HUVECs exposure to oxLDL (30 μg/ml) or TNFα (10 ng/ml) for 24 h led to a significant increase in LOX1 expression, effect abrogated by BBR (5 μM) and LOVA (5 μM). BBR but not LOVA treatment abolished the TNFα-induced cytotoxicity and restored the activation of Akt signaling. In spite of a low direct antioxidant capacity, both compounds reduced intracellular ROS levels generated by treatment of TNFα but only BBR inhibited NOX2 expression, MAPK/Erk1/2 signaling and subsequent NF-κB target genes VCAM and ICAM expression, induced by TNFα.

CONCLUSIONS

These findings demonstrated for the first time that BBR could prevent the oxLDL and TNFα - induced LOX1 expression and oxidative stress, key events that lead to NOX, MAPK/Erk1/2 and NF-κB activation linked to endothelial dysfunction.

CHEMICAL COMPOUNDS STUDIED IN THIS ARTICLE

Berberine (PubChem CID: 2353); Lovastatin (PubChem CID: 53232).

On the Roles of the Transient Receptor Potential Canonical 3 (TRPC3) Channel in Endothelium and Macrophages: Implications in Atherosclerosis

In the cardiovascular and hematopoietic systems the Transient Receptor Potential Canonical 3 (TRPC3) channel has a well-recognized role in a number of signaling mechanisms that impact the function of diverse cells and tissues in physiology and disease. The latter includes, but is not limited to, molecular and cellular mechanisms associated to the pathogenesis of cardiac hypertrophy, hypertension and endothelial dysfunction. Despite several of these functions being closely related to atherorelevant mechanisms, the potential roles of TRPC3 in atherosclerosis, the major cause of coronary artery disease, have remained largely unexplored. Over recent years, a series of studies from the authors' laboratory revealed novel functions of TRPC3 in mechanisms related to endothelial inflammation, monocyte adhesion to endothelium and survival and apoptosis of macrophages. The relevance of these new TRPC3 functions to atherogenesis has recently began to receive validation through studies in mouse models of atherosclerosis with conditional gain or loss of TRPC3 function. This chapter summarizes these novel findings and provides a discussion of their impact in the context of atherosclerosis, in an attempt to delineate a framework for further exploration of this terra incognita in the TRPC field.

High fat challenges with different fatty acids affect distinct atherogenic gene expression pathways in immune cells from lean and obese subjects

SCOPE

Early perturbations in vascular health can be detected by imposing subjects to a high fat (HF) challenge and measure response capacity. Subtle responses can be determined by assessment of whole-genome transcriptional changes. We aimed to magnify differences in health by comparing gene-expression changes in peripheral blood mononuclear cells toward a high MUFA or saturated fatty acids (SFA) challenge between subjects with different cardiovascular disease risk profiles and to identify fatty acid specific gene-expression pathways.

METHODS AND RESULTS

In a cross-over study, 17 lean and 15 obese men (50-70 years) received two 95 g fat shakes, high in SFAs or MUFAs. Peripheral blood mononuclear cell gene-expression profiles were assessed fasted and 4-h postprandially. Comparisons were made between groups and shakes. During fasting, 294 genes were significantly differently expressed between lean and obese. The challenge increased differences to 607 genes after SFA and 2516 genes after MUFA. In both groups, SFA decreased expression of cholesterol biosynthesis and uptake genes and increased cholesterol efflux genes. MUFA increased inflammatory genes and PPAR-α targets involved in β-oxidation.

CONCLUSION

Based upon gene-expression changes, we conclude that an HF challenge magnifies differences in health, especially after MUFA. Our findings also demonstrate how SFAs and MUFAs exert distinct effects on lipid handling pathways in immune cells.

Role of lectin-like oxidized low density lipoprotein-1 in fetoplacental vascular dysfunction in preeclampsia

The bioavailability of nitric oxide (NO) represents a key marker in vascular health. A decrease in NO induces a pathological condition denominated endothelial dysfunction, syndrome observed in different pathologies, such as obesity, diabetes, kidney disease, cardiovascular disease, and preeclampsia (PE). PE is one of the major risks for maternal death and fetal loss. Recent studies suggest that the placenta of pregnant women with PE express high levels of lectin-like oxidized LDL receptor-1 (LOX-1), which induces endothelial dysfunction by increasing reactive oxygen species (ROS) and decreasing intracellular NO. Besides LOX-1 activation induces changes in migration and apoptosis of syncytiotrophoblast cells. However, the role of this receptor in placental tissue is still unknown. In this review we will describes the physiological roles of LOX-1 in normal placenta development and the potential involvement of this receptor in the pathophysiology of PE.

HIV protein Nef causes dyslipidemia and formation of foam cells in mouse models of atherosclerosis

Patients with HIV are at an increased risk of cardiovascular disease. In this study we investigated the effect of Nef, a secreted HIV protein responsible for the impairment of cholesterol efflux, on the development of atherosclerosis in two animal models. ApoE(-/-) mice fed a high-fat diet and C57BL/6 mice fed a high-fat, high-cholesterol diet were injected with recombinant Nef (40 ng/injection) or vehicle, and the effects of Nef on development of atherosclerosis, inflammation, and dyslipidemia were assessed. In apoE(-/-) mice, Nef significantly increased the size of atherosclerotic lesions and caused vessel remodeling. Nef caused elevation of total cholesterol and triglyceride levels in the plasma while reducing high-density lipoprotein cholesterol levels. These changes were accompanied by a reduction of ABCA1 abundance in the liver, but not in the vessels. In C57BL/6 mice, Nef caused a significant number of lipid-laden macrophages presented in adventitia of the vessels; these cells were absent from the vessels of control mice. Nef caused sharp elevations of plasma triglyceride levels and body weight. Taken together, our findings suggest that Nef causes dyslipidemia and accumulation of cholesterol in macrophages within the vessel wall, supporting the role of Nef in pathogenesis of atherosclerosis in HIV-infected patients.-Cui, H. L., Ditiatkovski, M., Kesani, R., Bobryshev, Y. V., Liu, Y., Geyer, M., Mukhamedova, N., Bukrinsky, M., Sviridov, D. HIV protein Nef causes dyslipidemia and formation of foam cells in mouse models of atherosclerosis.

Resveratrol and its metabolites modulate cytokine-mediated induction of eotaxin-1 in human pulmonary artery endothelial cells

Coronary heart disease (CHD) is a leading cause of death in many developed countries. Evidence has long implicated endothelial injury and inflammation as apical events in the pathogenesis of atherosclerosis, the primary cause of CHD. Numerous risk factors contribute to a damaged, inflamed endothelium. Conversely, cardioprotective agents targeting the dysfunctional endothelium have also been identified, notably from dietary sources. We have used cultured human pulmonary artery endothelial cells (HPAECs) to test the diet-mediated cardioprotective hypothesis. In this review, we summarize our recent findings on control of transcription and expression of inflammation biomarker eotaxin-1 in HPAECs exposed to single or combined proinflammatory cytokines interleukin-13 (IL-13) and tumor necrosis factor-α (TNF-α), and attenuation of the observed eotaxin-1 responses by prior or simultaneous treatment with resveratrol and its metabolites. Control of eotaxin-1 gene regulation may be considered an in vitro model to evaluate agents linking cardioprotection with endothelial cell damage and inflammation.

Oxidation-specific epitopes and immunological responses: Translational biotheranostic implications for atherosclerosis

Oxidation-specific epitopes (OSE), present on oxidized LDL (OxLDL), apoptotic cells, cell debris and modified proteins in the vessel wall, accumulate in response to hypercholesterolemia, and generate potent pro-inflammatory, disease-specific antigens. They represent an important class of 'danger associated molecular patterns' (DAMPs), against which a concerted innate immune response is directed. OSE are recognized by innate 'pattern recognition receptors', such as scavenger receptors present on dendritic cells and monocyte/macrophages, as well as by innate proteins, such as IgM natural antibodies and soluble proteins, such as C-reactive protein and complement factor H. These innate immune responses provide a first line of defense against atherosclerosis-specific DAMPs, and engage adaptive immune responses, provided by T and B-2 cells, which provide a more specific and definitive response. Such immune responses are ordinarily directed to remove foreign pathogens, such as those found on microbial pathogens, but when persistent or maladaptive, lead to host damage. In this context, atherosclerosis can be considered as a systemic chronic inflammatory disease initiated by the accumulation of OSE type DAMPs and perpetuated by maladaptive response of the innate and adaptive immune system. Understanding this paradigm leads to new approaches to defining cardiovascular risk and suggests new modes of therapy. Therefore, OSE have become potential targets of diagnostic and therapeutic agents. Human and murine OSE-targeting antibodies have been developed and are now being used as biomarkers in human studies and experimentally in translational applications of non-invasive molecular imaging of oxidation-rich plaques and immunotherapeutics.

Decreased blood pressure with a corresponding decrease in adhesive molecules in diabetic rats caused by vitamin E administration

BACKGROUND

Hypertension is one of the important clinical problems of diabetic cardiovascular disease. The aim of this study was to determine the effect of vitamin E on blood pressure parameters and adhesive molecule amounts in diabetic rats.

METHODS

Twenty-four male Wistar rats were divided into three groups (each of n = 8): the controls (C), non-treated diabetic (NTD), and vitamin E treated diabetic (VETD) groups. A single intraperitoneal injection of buffered streptozotocin (60 mg/kg) in cold sodium citrate (pH 4.5) was used to induce diabetes. The VETD group received 300 mg of vitamin E daily intragastrically for 6 weeks. Systolic and diastolic blood pressure, mean arterial pressure, as well as the dicrotic pressure, crest time, systolic and diastolic periods, and plasma levels of intercellular adhesion molecule-1 and E-selectin were measured after 6 weeks.

RESULTS

The results revealed that there was a significant increase in systolic and diastolic blood pressures, mean arterial pressure, crest time, systolic duration, and the amount of sICAM-1 and E-selectin in diabetic rats. There was no significant difference in the heart rate or cardiac cyclic duration among the different groups. Significant improvement of blood pressure parameters as well as attenuation of the elevated ICAM-1 and E-selectin amounts was found in the vitamin E treated group.

CONCLUSIONS

These findings indicate that vitamin E significantly improved blood pressure elevation in diabetic rats and that these effects could be associated with reducing adhesive molecule and antioxidant properties of vitamin E.

Redox regulation of MAPK phosphatase 1 controls monocyte migration and macrophage recruitment

Monocytic adhesion and chemotaxis are regulated by MAPK pathways, which in turn are controlled by redox-sensitive MAPK phosphatases (MKPs). We recently reported that metabolic disorders prime monocytes for enhanced recruitment into vascular lesions by increasing monocytes' responsiveness to chemoattractants. However, the molecular details of this proatherogenic mechanism were not known. Here we show that monocyte priming results in the S-glutathionylation and subsequent inactivation and degradation of MKP-1. Chronic exposure of human THP-1 monocytes to diabetic conditions resulted in the loss of MKP-1 protein levels, the hyperactivation of ERK and p38 in response to monocyte chemoattractant protein-1 (MCP-1), and increased monocyte adhesion and chemotaxis. Knockdown of MKP-1 mimicked the priming effects of metabolic stress, whereas MKP-1 overexpression blunted both MAPK activation and monocyte adhesion and migration induced by MCP-1. Metabolic stress promoted the S-glutathionylation of MKP-1, targeting MKP-1 for proteasomal degradation. Preventing MKP-1 S-glutathionylation in metabolically stressed monocytes by overexpressing glutaredoxin 1 protected MKP-1 from degradation and normalized monocyte adhesion and chemotaxis in response to MCP-1. Blood monocytes isolated from diabetic mice showed a 55% reduction in MKP-1 activity compared with nondiabetic mice. Hematopoietic MKP-1 deficiency in atherosclerosis-prone mice mimicked monocyte priming and dysfunction associated with metabolic disorders, increased monocyte chemotaxis in vivo, and accelerated atherosclerotic lesion formation. In conclusion, we identified MKP-1 as a central redox-sensitive regulator of monocyte adhesion and migration and showed that the loss of MKP-1 activity is a critical step in monocyte priming and the metabolic stress-induced conversion of blood monocytes into a proatherogenic phenotype.

Palmitate promotes monocyte atherogenicity via de novo ceramide synthesis

Elevated plasma free fatty acids (FAs) are associated with increased risk of cardiovascular disease. This study investigates the effects of the saturated FA palmitate and unsaturated FA oleate on monocyte phenotype and function. Incubation of human U937 and THP-1 monocytes with palmitate for 24h increased cell surface expression of integrin CD11b and scavenger receptor CD36 in a concentration-dependent manner with some decrease in mitochondrial reducing capacity at high concentration (300 μM). Monocytes incubated with palmitate, but not oleate, showed increased uptake of oxidized LDL and increased adhesion to rat aortic endothelium, particularly at bifurcations. The palmitate-induced increase in CD11b and CD36 expression was associated with increased cellular C16 ceramide and sphingomyelin, loss of reduced glutathione, and increased reactive oxygen species (ROS). Increased monocyte surface CD11b and CD36 was inhibited by fumonisin B1, an inhibitor of de novo ceramide synthesis, but not by the superoxide dismutase mimetic MnTBap. In contrast, MnTBap prevented the mitochondrial ROS increase and metabolic inhibition due to 300μM palmitate. This study demonstrates that in viable monocytes, palmitate but not oleate increases expression of surface CD11b and CD36. Palmitate increases monocyte adhesion to the aortic wall and promotes uptake of oxidized LDL and this involves de novo ceramide synthesis.

Clerodendron glandulosum.Coleb leaf extract attenuates in vitro macrophage differentiation and expression of VCAM-1 and P-selectin in thoracic aorta of atherogenic diet fed rats

Present inventory evaluates the anti-atherogenic potential of C. glandulosum.Coleb leaf extract (CG) using in vivo and in vitro experimental models. Serum markers of low density lipoprotein (LDL-C) oxidation, cholesterol, triglycerides, lipoproteins, auto-antibody titer, ex vivo LDL-C oxidation, LDL-C aggregation, aortic lipids, histopathological evaluations and immunolocalization of macrophage surface marker (F4/80), vascular cell adhesion molecule-1 (VCAM-1) and P-selectin were performed in CON [rats treated with single dose of saline (i.p.) and fed with laboratory chow], ATH [rats treated with single dose of vitamin D3 (600,000 IU, i.p) and fed with atherogenic diet] and ATH+CG [rats treated with single dose of vitamin D3 (600,000 IU, i.p.) and fed with atherogenic diet and simultaneously treated with 200 mg/kg CG extract, p.o.] for 8 weeks. CG extract supplementation to atherogenic diet fed rats significantly prevented increment in serum cholesterol, triglycerides, and lipoproteins, markers of LDL-C oxidation, auto-antibody titer and aortic lipids. Also, LDL-C isolated from ATH+CG rats recorded mimimal aggregation and susceptibility to undergo ex vivo LDL-C oxidation. Microscopic evaluation of thoracic aorta of ATH+CG rats reveled prevention of atheromatous plaque formation, accumulation of lipid laden macrophages, calcium deposition, distortion/defragmentation of elastin, accumulation of macrophages and, down regulation of cell adhesion molecules (VCAM-1 and P-selectin) expression. Further, in vitro monocyte to macrophage differentiation was significantly attenuated in presence of CG extract (200 µg/mL). It can be concluded from the present study that, CG extract is capable of controlling induction of experimental atherosclerosis and warrants further scrutiny at the clinical level as a possible therapeutic agent.

OxLDL-mediated survival of macrophages does not require LDL internalization or signalling by major pattern recognition receptors

Macrophages play a key role in the pathogenesis of atherosclerosis, in part by destabilizing plaques. We and others have shown that low concentrations of oxidized LDL (oxLDL) inhibit macrophage apoptosis. As oxLDL is present in lesions, this may be a mechanism by which macrophage populations in the intima are expanded. We have previously shown that oxLDL activates prosurvival signalling pathways such as the phosphoinositide 3-kinase (PI3K) pathway in bone marrow derived macrophages (BMDMs). However, little is known about more upstream signalling events especially at the receptor level. The endocytic pattern recognition receptors (PRRs), scavenger receptor A (SR-A) and CD36, are the main receptors on macrophages for uptake of oxLDL and are therefore important in foam cell formation. The signalling PRRs such as toll-like receptor (TLR) 2 and 4 also bind some types of oxLDL. This study was done to determine if any of the known PRRs are required for the anti-apoptotic effects of oxLDL in BMDMs. To do this, we tested the effect of oxLDL on viability of BMDMs lacking both SR-A and CD36 or lacking TLR2, TLR4, CD14, FcγRIIb, or RAGE. Our results indicate that none of these receptors are essential for activating the oxLDL prosurvival pathway. Furthermore, we show that the anti-apoptotic effect is not dependent on the uptake of oxLDL.

The oxidized low-density lipoprotein receptor mediates vascular effects of inhaled vehicle emissions

RATIONALE

To determine vascular signaling pathways involved in inhaled air pollution (vehicular engine emission) exposure-induced exacerbation of atherosclerosis that are associated with onset of clinical cardiovascular events.

OBJECTIVES

To elucidate the role of oxidized low-density lipoprotein (oxLDL) and its primary receptor on endothelial cells, the lectin-like oxLDL receptor (LOX-1), in regulation of endothelin-1 expression and matrix metalloproteinase activity associated with inhalational exposure to vehicular engine emissions.

METHODS

Atherosclerotic apolipoprotein E knockout mice were exposed by inhalation to filtered air or mixed whole engine emissions (250 μg particulate matter [PM]/m(3) diesel + 50 μg PM/m(3) gasoline exhausts) 6 h/d for 7 days. Concurrently, mice were treated with either mouse IgG or neutralizing antibodies to LOX-1 every other day. Vascular and plasma markers of oxidative stress and expression proatherogenic factors were assessed. In a parallel study, healthy human subjects were exposed to either 100 μg PM/m(3) diesel whole exhaust or high-efficiency particulate air and charcoal-filtered "clean" air (control subjects) for 2 hours, on separate occasions.

MEASUREMENTS AND MAIN RESULTS

Mixed emissions exposure increased oxLDL and vascular reactive oxygen species, as well as LOX-1, matrix metalloproteinase-9, and endothelin-1 mRNA expression and also monocyte/macrophage infiltration, each of which was attenuated with LOX-1 antibody treatment. In a parallel study, diesel exhaust exposure in volunteer human subjects induced significant increases in plasma-soluble LOX-1.

CONCLUSIONS

These findings demonstrate that acute exposure to vehicular source pollutants results in up-regulation of vascular factors associated with progression of atherosclerosis, endothelin-1, and matrix metalloproteinase-9, mediated through oxLDL-LOX-1 receptor signaling, which may serve as a novel target for future therapy.

Superoxide dismutase type 1 in monocytes of chronic kidney disease patients

We analyzed proteomic profiles in monocytes of chronic kidney disease (CKD) patients and healthy control subjects. Two-dimensional electrophoresis (2-DE) and silver staining indicated differences in protein pattern. Among the analyzed proteins, superoxide dismutase type 1 (SOD1), which was identified both by MS/MS mass-spectrometry and immunoblotting, was reduced in kidney disease. We characterized SOD1 protein amount, using quantitative in-cell Western assay and immunostaining of 2-DE gel blots, and SOD1 gene expression, using quantitative real-time polymerase chain reaction (PCR), in 98 chronic hemodialysis (HD) and 211 CKD patients, and 34 control subjects. Furthermore, we showed that different SOD1 protein species exist in human monocytes. SOD1 protein amount was significantly lower in HD (normalized SOD1 protein, 27.2 ± 2.8) compared to CKD patients (34.3 ± 2.8), or control subjects (48.0 ± 8.6; mean ± SEM; P < 0.05). Analysis of SOD1 immunostaining showed significantly more SOD1 protein in control subjects compared to patients with CKD or HD (P < 0.0001, analysis of main immunoreactive protein spot). SOD1 gene expression was significantly higher in HD (normalized SOD1 gene expression, 17.8 ± 2.3) compared to CKD patients (9.0 ± 0.7), or control subjects (5.5 ± 1.0; P < 0.0001). An increased SOD1 gene expression may indicate increased protein degradation in patients with CKD and compensatory increase of SOD1 gene expression. Taken together, we show reduced SOD1 protein amount in monocytes of CKD, most pronounced in HD patients, accompanied by increased SOD1 gene expression.

Oxidized LDL in human carotid plaques is related to symptomatic carotid disease and lesion instability

BACKGROUND

Oxidative stress is an important determinant in atherosclerosis development. Various markers of oxidative stress, such as oxidation of low-density lipoprotein (LDL), nitrosative stress, lipid peroxidation, and protein oxidation, have been implicated in the initiation and/or progression of atherosclerosis, but their association with plaque erosion and symptomatic carotid disease has not been fully defined. In addition, certain oxidative markers have been shown in various models to promote plaque remodeling through matrix metalloproteinase (MMP) activation.

OBJECTIVE

To perform a global investigation of various oxidative stress markers and assess for potential relationships with destabilization and symptomatic development in human carotid plaques.

METHODS

Thirty-six patients undergoing endarterectomy were evaluated and compared with 20 control specimens obtained at the time of autopsy. Differences between stable and unstable plaques, symptomatic and asymptomatic patients, and >or=90% and <90% stenosis were evaluated. Oxidized LDL (ox-LDL), nitrotyrosine (NT), malondialdehyde (MDA), and protein carbonyls (PCs) levels were determined in atheromatic plaques homogenates by corresponding biochemical assays. Immunohistochemical (IHC) analysis was also employed to determine the percentage and topological distribution of cells expressing NT and metalloproteinase-9 (MMP-9) in serial sections from corresponding atheromatic plaques. MMP-9 expression was further verified using Western blot analysis.

RESULTS

Ox-LDL was increased in symptomatic patients (P < .05). Also, ox-LDL and NT levels were significantly higher in unstable versus stable carotid plaques (P < .05, respectively). Furthermore, IHC serial section analysis, corroborated by statistical analysis, showed a topological and expressional correlation between NT and MMP-9 (P < .05). MDA and PCs levels, although increased in carotid plaques, did not distinguish stable from unstable carotid plaques as well as symptomatic from asymptomatic patients with various degrees of stenosis.

CONCLUSION

All types of investigated oxidative stress markers were significantly increased in human carotid plaques, but only ox-LDL levels were associated with clinical symptoms, while peroxynitrite products and MMP-9 were specifically related to plaque instability.

Application of magnetic force-based cell patterning for controlling cell-cell interactions in angiogenesis

To investigate the effects of cell-cell interactions on cellular function, the microenvironment surrounding cells should be precisely controlled. Here, we describe a cell patterning technique, which utilizes magnetic force and magnetite nanoparticles. This method was used to develop cell culture arrays for investigation of cell behaviors in angiogenesis. Pin holder devices that contain more than 6,000 pillars on the surface are used for fabricating the cell culture arrays by setting it on a magnet. The magnetically labeled cells were arranged by magnetic distribution. When the human umbilical vein endothelial cells are arranged at 250 microm intervals (5.9 cells/spot), the cells spread toward other cell cluster on adjacent spots in 4.5 h, and formed cord-like structures in 8.5 h. It was shown that cell-cell interactions were successfully investigated using magnetic cell arrangement.

AM-251 and SR144528 are acyl CoA:cholesterol acyltransferase inhibitors

Oxysterol-induced macrophage apoptosis may have a role in atherosclerosis. Macrophages lacking the type 2 cannabinoid receptor (CB2) are partially resistant to apoptosis induced by 7-ketocholesterol (7KC). AM-251 and SR144528 are selective antagonists of CB1 and CB2 receptors, respectively. We observed that both compounds reduce 7KC-induced apoptosis in Raw 264.7 macrophages. As oxysterol-induced macrophage apoptosis requires acyl-coenzymeA:cholesterol acyltransferase (ACAT) activity, we tested their affects on ACAT activity. AM-251 and SR144528 both reduced cholesteryl ester synthesis in unstimulated and acetylated LDL-stimulated Raw 264.7 macrophages, CB2(+/+) and CB2(-/-) peritoneal macrophages, as well as in vitro, in mouse liver microsomes. Consistent with inhibition of ACAT, the development of foam cell characteristics in macrophages by treatment with acetylated LDL was reduced by both compounds. This work is the first evidence that AM-251 and SR144528 are inhibitors of ACAT and as a result, might have anti-atherosclerotic activities independent of their affect on cannabinoid signaling.

The lectin-like oxidized low-density-lipoprotein receptor: a pro-inflammatory factor in vascular disease

Scavenger receptors are membrane glycoproteins that bind diverse ligands including lipid particles, phospholipids, apoptotic cells and pathogens. LOX-1 (lectin-like oxidized low-density lipoprotein receptor-1) is increasingly linked to atherosclerotic plaque formation. Transgenic mouse models for LOX-1 overexpression or gene knockout suggests that LOX-1 contributes to atherosclerotic plaque formation and progression. LOX-1 activation by oxidized LDL (low-density lipoprotein) binding stimulates intracellular signalling, gene expression and production of superoxide radicals. A key question is the role of leucocyte LOX-1 in pro-atherogenic lipid particle trafficking, accumulation and signalling leading to differentiation into foam cells, necrosis and plaque development. LOX-1 expression is elevated within vascular lesions and a serum soluble LOX-1 fragment appears diagnostic of patients with acute coronary syndromes. LOX-1 is increasingly viewed as a vascular disease biomarker and a potential therapeutic target in heart attack and stroke prevention.

Role of cell adhesion molecules and immune-cell migration in the initiation, onset and development of atherosclerosis

Atherosclerosis is currently the leading factor of death in developed countries. It is now recognized as a chronic immune-inflammatory disease, whose initial stages involve the interaction of leukocytes with the endothelial monolayer. The initial stage of atherosclerosis requires the interplay of various cell adhesion molecules and immune cells to trigger leukocyte and lymphocyte migration from the circulating blood into the arterial intima. Studies have unveiled the role of inflammatory mediators in the initiation, onset and progression of the disease. During the last few years we have gained a greater understanding of the mechanism that modulates monocyte, macrophage and T cell infiltration, the role these cells play in the atherosclerotic lesion, in the formation of the fibrous plaque formation with the consequent narrowing of the arteries, and the mechanisms that lead to plaque rupture and the formation of thrombi and emboli. This review talks about the leukocyte recruitment in early atherosclerosis, the formation of the plaque, and the mechanisms that lead to thrombosis in advanced atherosclerosis. Finally, we discuss the potential for novel therapies to treat this disease.

Extracellular survivin up-regulates adhesion molecules on the surface of leukocytes changing their reactivity pattern

Rheumatoid arthritis (RA) is an autoimmune disease with joints as a principal target of inflammation. We have shown recently that the extracellular expression of the antiapoptotic protein survivin is associated with a destructive course of RA. Here, we address the potential impact of extracellular survivin on peripheral blood leukocytes (PBL). The binding of survivin to the surface of human PBL as well as the expression of adhesion molecules were assessed by FACS. The expression of adhesion molecules on leukocytes as a function of circulating survivin was analyzed in blood of 24 patients with RA and compared with eight healthy individuals. We show that extracellular survivin expresses immunomodulatory properties. It binds to the surface of the majority of granulocytes and a significant part of lymphocytes and monocytes inducing the activation of alpha-chains of beta-integrins and their ligand ICAM-1. Survivin-induced expression of alpha-chains of beta 2-integrins is regulated by p38 MAPK and PI-3K but not by the NF-kappaB signaling pathway. Clinical relevance of our findings is supported by the in vivo association of high circulating survivin levels with an increased expression of CD11c on monocytes and granulocytes in RA patients. The results of our study demonstrate that extracellular survivin affects the phenotype of leukocytes having a possible impact on homing of inflammatory cells during arthritis.

Do glucose and lipids exert independent effects on atherosclerotic lesion initiation or progression to advanced plaques?

It is becoming increasingly clear that suboptimal blood glucose control results in adverse effects on large blood vessels, thereby accelerating atherosclerosis and cardiovascular disease, manifested as myocardial infarction, stroke, and peripheral vascular disease. Cardiovascular disease is accelerated by both type 1 and type 2 diabetes. In type 1 diabetes, hyperglycemia generally occurs in the absence of elevated blood lipid levels, whereas type 2 diabetes is frequently associated with dyslipidemia. In this review article, we discuss hyperglycemia versus hyperlipidemia as culprits in diabetes-accelerated atherosclerosis and cardiovascular disease, with emphasis on studies in mouse models and isolated vascular cells. Recent studies on LDL receptor-deficient mice that are hyperglycemic, but exhibit no marked dyslipidemia compared with nondiabetic controls, show that diabetes in the absence of diabetes-induced hyperlipidemia is associated with an accelerated formation of atherosclerotic lesions, similar to what is seen in fat-fed nondiabetic mice. These effects of diabetes are masked in severely dyslipidemic mice, suggesting that the effects of glucose and lipids on lesion initiation might be mediated by similar mechanisms. Recent evidence from isolated endothelial cells demonstrates that glucose and lipids can induce endothelial dysfunction through similar intracellular mechanisms. Analogous effects of glucose and lipids are also seen in macrophages. Furthermore, glucose exerts many of its cellular effects through lipid mediators. We propose that diabetes without associated dyslipidemia accelerates atherosclerosis by mechanisms that can also be activated by hyperlipidemia.

Cell patterning chip for controlling the stem cell microenvironment

Cell-cell signaling is an important component of the stem cell microenvironment, affecting both differentiation and self-renewal. However, traditional cell-culture techniques do not provide precise control over cell-cell interactions, while existing cell-patterning technologies are limited when used with proliferating or motile cells. To address these limitations, we created the Bio Flip Chip (BFC), a microfabricated polymer chip containing thousands of microwells, each sized to trap down to a single stem cell. We have demonstrated the functionality of the BFC by patterning a 50 x 50 grid of murine embryonic stem cells (mESCs), with patterning efficiencies >75%, onto a variety of substrates--a cell-culture dish patterned with gelatin, a 3-D substrate, and even another layer of cells. We also used the BFC to pattern small groups of cells, with and without cell-cell contact, allowing incremental and independent control of contact-mediated signaling. We present quantitative evidence that cell-cell contact plays an important role in depressing mESC colony formation, and show that E-cadherin is involved in this negative regulatory pathway. Thus, by allowing exquisite control of the cellular microenvironment, we provide a technology that enables new applications in tissue engineering and regenerative medicine.

Enhanced Expression of the Homeostatic Chemokines CCL19 and CCL21 in Clinical and Experimental Atherosclerosis

Objective— Based on their role in T-cell homing into nonlymphoid tissue, we examined the role of the homeostatic chemokines CCL19 and CCL21 and their common receptor CCR7 in coronary artery disease (CAD).

Methods and Results— We performed studies in patients with stable (n=40) and unstable (n=40) angina and healthy controls (n=20), in vitro studies in T-cells and macrophages, and studies in apolipoprotein-E–deficient (ApoE −/− ) mice and human atherosclerotic carotid plaques. We found increased levels of CCL19 and CCL21 within the atherosclerotic lesions of the ApoE −/− mice, in human atherosclerotic carotid plaques, and in plasma of CAD patients. Whereas strong CCR7 expression was seen in T-cells from murine and human atherosclerotic plaques, circulating T-cells from angina patients showed decreased CCR7 expression. CCL19 and CCL21 promoted an inflammatory phenotype in T-cells and macrophages and increased matrix metalloproteinase (MMP) and tissue factor levels in the latter cell type. Although aggressive statin therapy increased CCR7 and decreased CCL19/CCL21 levels in peripheral blood from CAD patients, conventional therapy did not.

Conclusions— The abnormal regulation of CCL19 and CCL21 and their common receptor in atherosclerosis could contribute to disease progression by recruiting T-cells and macrophages to the atherosclerotic lesions and by promoting inflammatory responses in these cells.

Metabolism of 5-hydroxy-6,8,11,14-eicosatetraenoic acid by human endothelial cells

There is increasing evidence that proinflammatory products of the 5-lipoxygenase pathway play an important role in cardiovascular disease. In the present study, we found that human endothelial cells rapidly oxidize the 5-lipoxygenase product 5S-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) to 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE), a potent chemoattractant for myeloid cells. 5-Oxo-ETE synthesis is strongly stimulated by oxidative stress. This effect is enhanced following inhibition of the pentose phosphate pathway with dehydroepiandrosterone and is mimicked by diamide, which oxidizes intracellular GSH to GSSG. Conversely, it is blocked by depletion of intracellular GSH/GSSG. The kinetics of H2O2-induced 5-oxo-ETE synthesis by endothelial cells correlate well with changes in the intracellular levels of GSSG and NADP+. These results suggest that exposure of the endothelium to oxidative stress and inflammation could result in the synthesis of 5-oxo-ETE, which could then induce the infiltration of inflammatory cells into the tissue.

GM-CSF Deficiency Reduces Macrophage PPAR-γ Expression and Aggravates Atherosclerosis in ApoE-Deficient Mice

Objective— Granulocyte-macrophage colony-stimulating factor (GM-CSF) is expressed in atherosclerotic lesions but its significance for lesion development is unknown. Consequently, we investigated the significance of GM-CSF expression for development of atherosclerotic lesions in apolipoprotein E-deficient (apoE −/− ) mice.

Methods and Results— We generated apoE −/− mice deficient in GM-CSF (apoE −/− .GM-CSF −/− mice), fed them a high-fat diet, and compared lesion development with apoE −/− mice. We measured lesion size, macrophage, smooth muscle cell, and collagen accumulation at the aortic sinus, and expression of genes that regulate cholesterol transport and inflammation. No differences in serum cholesterol were found between the 2 groups. Lesion size in hyperlipidemic apoE −/− .GM-CSF −/− increased by 30% ( P <0.05), macrophage accumulation doubled, and collagen content reduced by 15% ( P <0.05); smooth muscle cell accumulation and vascularity were unaffected. Analysis of PPAR-γ, ABCA1, and CD36 in lesions showed reduced expression (50%, 65%, and 55%, respectively), whereas SR-A doubled. In peritoneal macrophages, PPAR-γ and ABCA1 expression was also reduced by 50% and 70%, respectively, as was cholesterol efflux, by 50%. In lesions, pro-inflammatory MCP-1 and tumor necrosis factor (TNF)-α expression increased 2- and 3.5-fold, respectively, vascular cell adhesion molecule (VCAM)-1 expression enhanced and interleukin (IL)-1 receptor antagonist reduced by 50%.

Conclusions— GM-CSF deficiency increases atherosclerosis under hypercholesterolemic conditions, indicating antiatherogenic role for GM-CSF. We suggest this protective role is mediated by PPAR-γ and ABCA1, molecules that affect cholesterol homeostasis and inflammation.

CRP promotes monocyte-endothelial cell adhesion via Fcγ receptors in human aortic endothelial cells under static and shear flow conditions

Monocyte-endothelial cell adhesion is a key early event in atherogenesis. C-reactive protein (CRP), a cardiovascular risk marker, is known to stimulate ICAM and VCAM in human aortic endothelial cells (HAEC) and induces monocyte-endothelial cell adhesion. In this study, we examined the mechanisms by which native CRP promotes monocyte-endothelial cell adhesion under static conditions and tested the effect of CRP on adhesion under shear flow. Incubation of HAEC with CRP (>25 μg/ml) upregulated NF-κB activity, and this resulted in a significant increase in ICAM (54% increase, P < 0.001), VCAM (41% increase, P < 0.01), and monocyte-endothelial cell adhesion (44% increase, P < 0.02) compared with those of control. Preincubation with antibodies to CD32 and CD64 but not CD16 effectively inhibited this activation. Blocking NF-κB activity with inhibitors or a dominant negative inhibitory κB significantly decreased ICAM, VCAM upregulation, and subsequent monocyte-endothelial cell adhesion. Preincubation with antibodies to CD32 and CD64 or transient transfection with small interference RNA to CD32 attenuated CRP-induced NF-κB activity, ICAM, VCAM, and monocyte-endothelial cell adhesion under static conditions. Also, the Syk kinase inhibitor piceatannol and MG-132, a proteasome degradation inhibitor, produced similar attenuation in NF-κB activity, ICAM, VCAM, and adhesion. Furthermore, CRP-activated endothelial cells supported monocyte rolling, arrest, and transmigration in shear flow (2 dyn/cm2), and this was also inhibited by preincubation with antibodies to CD32 and CD64. Thus, in HAEC, CRP upregulates monocyte-endothelial adhesion by activation of NF-κB through engaging the Fcγ receptors CD32 and CD64.

Analysis of inflammation

In the past, inflammation has been associated with infections and with the immune system. But more recent evidence suggests that a much broader range of diseases have telltale markers for inflammation. Inflammation is the basic mechanism available for repair of tissue after an injury and consists of a cascade of cellular and microvascular reactions that serve to remove damaged and generate new tissue. The cascade includes elevated permeability in microvessels, attachment of circulating cells to the vessels in the vicinity of the injury site, migration of several cell types, cell apoptosis, and growth of new tissue and blood vessels. This review provides a summary of the major microvascular, cellular, and molecular mechanisms that regulate elements of the inflammatory cascade. The analysis is largely focused on the identification of the major participants, notably signaling and adhesion molecules, and their mode of action in the inflammatory cascade. We present a new hypothesis for the generation of inflammatory mediators in plasma that are derived from the digestive pancreatic enzymes responsible for digestion. The inflammatory cascade offers a large number of opportunities for development of quantitative models that describe various aspects of human diseases.

Inflammation and Atherosclerosis

PURPOSE

The aim of this article is to discuss the role of inflammation in atherosclerosis.

SUMMARY

An initial chemical, mechanical or immunological insult induces endothelial dysfunction. This triggers a cascade of inflammatory reactions, in which monocytes, macrophages, T lymphocytes and vascular smooth muscle cells participate. Leukocyte adhesion molecules, cytokines, growth factors and metalloproteinases participate in all stages of atherogenesis. Almost all of the traditional risk factors for atherosclerosis are associated with and participate in the inflammatory process. Many infectious agents, mainly Chlamydia pneumoniae, have been proposed as potential triggers of the cascade. The immune system has been implicated in plaque formation, through the activation of cellular and humoral immunity against innate or microbial heat shock protein 60. Methods of detection of systemic or local plaque inflammation have been developed and research is being conducted on the potential use of anti-inflammatory and antibiotic drugs in atherosclerosis.

Monocyte recruitment and foam cell formation in atherosclerosis

Atherosclerosis is a chronic immune-inflammatory disease in which the interactions of monocytes with activated endothelium are crucial events leading to atherosclerotic alteration of the arterial intima. In early atherosclerosis, monocytes migrate into the subendothelial layer of the intima where they differentiate into macrophages or dendritic cells. In the subendothelial space enriched with atherogenic lipoproteins, most macrophages transform into foam cells. Foam cells aggregate to form the atheromatous core and as this process progresses, the atheromatous centres of plaques become necrotic, consisting of lipids, cholesterol crystals and cell debris. This review highlights some aspects of monocyte recruitment and foam cell formation in atherosclerosis.