The molecular basis of vulnerable plaque: potential therapeutic role for immunomodulation:

The Role of Angiotensin Antagonism in Coronary Plaque Regression: Insights from the Glagovian Model

The benefit of antagonizing the effect of the renin angiotensin aldosterone system (RAAS), notably by the use of angiotensin-converting enzyme inhibitor (ACEi) and angiotensin II type 1 receptor blocker (ARB) for coronary artery disease (CAD), has been demonstrated in multiple studies, which may be attributed to their ability to inhibit the deleterious effect of RAAS to the cardiovascular system. It is well known that angiotensin II (Ang II) plays a vital role in atheromatous plaque formation and progression through multiple pathways, including inflammatory and arterial remodeling aspects. Significant coronary atheromatous plaque regression has been previously demonstrated in various studies using statin agents. Similar results have been reported in different studies using angiotensin inhibitor agents, notably ARB agents. Analysis from various trials utilizing ARB showed a significant plaque regression using olmesartan and telmisartan as evaluated by IVUS studies. In contrary, the use of ACEi did not demonstrated significant plaque regression, which may be attributed to the heavy plaque calcification in respective studies. On this review, we aim to present the basic mechanism on the role of RAAS in plaque modulation and its arterial remodeling aspect, which is then integrated with the clinical evidence based on the available intravascular ultrasonography (IVUS) studies on coronary arteries.

The cholesterol-lowering effect of unripe Rubus coreanus is associated with decreased oxidized LDL and apolipoprotein B levels in subjects with borderline-high cholesterol levels: a randomized controlled trial

BACKGROUND

Rubus coreanus (R. coreanus) possesses properties that may decrease cholesterol levels.

METHODS

The effects of unripe R. coreanus (uRC) consumption on low-density lipoprotein (LDL) and total cholesterol levels related to decreased circulating apolipoprotein (Apo) B and oxidized LDL levels were evaluated. This randomized, double-blind, placebo-controlled study included subjects with borderline-high cholesterol levels (between 200 and 239 mg/dL) who consumed one capsule daily containing 600 mg of freeze-dried uRC extract (n = 39) or the placebo (n = 38).

RESULTS

After 12 weeks, the uRC group showed reductions of 21.23 ± 4.36 mg/dL in total cholesterol levels (P = 0.007) and 15.61 ± 4.16 mg/dL in LDL cholesterol levels (P = 0.032). In addition, significantly greater reductions in Apo B levels were observed in the uRC group (- 3.48 ± 3.40 mg/dL), but Apo B levels were increased in the placebo group (6.21 ± 2.84 mg/dL; P = 0.032). Furthermore, a remarkably lower oxidized LDL level was detected in the uRC group (57.76 ± 2.07 U/L) than in the placebo group (66.09 ± 3.47 U/L) after 12 weeks of consumption (P = 0.044).

CONCLUSIONS

Because of its cholesterol-lowering effect, uRC shows great promise as a therapeutic agent for subjects with borderline-high total blood cholesterol levels.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03649620 (8/28/2018, retrospectively registered).

Effect of cardiac rehabilitation on inflammation: A systematic review and meta-analysis of controlled clinical trials

BACKGROUND

This systematic review and meta-analysis aimed to assess the effect of cardiac rehabilitation (CR) on serum C-reactive protein (CRP) as an indicator of the inflammatory state and predictor of recurrent cardiovascular events.

METHODS

PubMed, SCOPUS, Cochrane library, and Google Scholar databases were searched up to January 2014 for original articles which investigated the effect of CR on CRP among adult patients with previous cardiovascular events. The random effects model was used to assess the overall effect of CR on the variation in serum CRP levels.

RESULTS

In the present systematic review and meta-analysis, 15 studies were included. The analysis showed that CR might significantly reduce high-sensitivity CRP (hs-CRP) levels [Difference in means (DM) = -1.81 mg/l, 95% confidence interval (CI): -2.65, -0.98; P = 0.004). However, the heterogeneity between studies was significant (Cochran's Q test, P < 0.001, I-squared = 84.9%). To find the source of variation, the studies were categorized based on study design (quality) and duration. The negative effect was higher among studies which followed their participants for 3 weeks or less (DM = -2.75 mg/l, 95% CI: -3.86, -1.64; P < 0.001) compared to studies which investigated the effect of CR for 3-8 weeks (DM = -0.89 mg/l, 95% CI: -1.35, -0.44; P < 0.001) and those which lasted more than 8 weeks (DM = -1.71 mg/l, 95% CI: -2.53, -0.89; P < 0.001). There was no evidence of heterogeneity when the categorization was based on the follow-up period.

CONCLUSION

Both short- and long-term CR have resulted in improvement in serum hs-CRP levels. CR can be perceived as a beneficial tool to reduce inflammatory markers among patients with previous cardiac events.

A Comparative Study of Lipid Profile and Cardiovascular Risk Biomarkers Among Chronic Haemodialysis Patients and Healthy Individuals

INTRODUCTION

Lipid abnormalities and increase in inflammatory markers are common among patients with End Stage Renal Disease (ESRD) and it tends to persist/worsen even after initiating Intermittent Haemodialysis (IHD). The cardiovascular mortality and morbidity remains significantly high in this population.

AIM

The present study was carried out to assess the pattern of lipid abnormality in our population and to find its association with inflammatory markers.

MATERIALS AND METHODS

It was a cross-sectional, observational study on ESRD patients undergoing Haemodialysis (HD) in comparison with age and sex matched healthy individuals in a tertiary care hospital. About 40 adult male and female patients aged >18 years, undergoing chronic HD for more than 6 months were enrolled in Group A. Patients who were alcoholics, tobacco consumers and those on steroids and hypolipidemic drugs were excluded. Group B consisted of healthy, age and sex matched controls. Serum lipid profile, lipoprotein A, apolipoprotein A1, apolipoprotein B and apo B/A1 ratio, serum uric acid, homocysteine, hs-CRP and testosterone levels were estimated among patients undergoing intermittent HD and healthy individuals. Chi-square/Fisher's-exact test was used for comparing ratios. A p-value of <0.05 was considered statistically significant.

RESULTS

The mean Total Cholesterol (TC), Low Density Lipoprotein (LDL) and Non-HDL High Density Lipoprotein cholesterol was significantly lower in HD patients as compared to control group with all the three parameters attaining statistical significance (p<0.005). The mean lipoprotein A level was significantly higher (p=0.037), while Apo A1 was found to be significantly lower (p=0.001) in patients receiving HD. Inflammatory markers like uric acid was high (p<0.005) and serum testotsterone level in male HD patient was significantly low (p<0.005).

CONCLUSION

The mean values of traditional serum lipid profile remained lower in HD patients than the control group. The abnormalities in lipoprotein A and apolipoproteins were more pronounced in patients undergoing HD. The mean level of testosterone also was found to be lower in male patients receiving HD. Hence, estimation of lipoprotein A, apolipoproteins and inflammatory markers may serve as a potential tool in cardiovascular risk stratification.

Cardiovascular protective effect of glabridin: Implications in LDL oxidation and inflammation

Atherosclerosis is one of the most common causes of death in Western countries and now considered as a chronic inflammatory disease in broad outline. Glaridin, a flavonoid isolated from licorice root, has been shown to exert a variety of biological activities, including antimicrobial, antioxidant, anti-inflammatory and cardiovascular protective effects. Among these, the most extensive research area in the past two decades was a cardiovascular protection-related activity of glabridin. The protective effect of glabridin on LDL oxidation, which is one of the important processes involved in the development of atherosclerosis, was demonstrated in vitro and in vivo and the mechanisms involved in this process were established well. Structure-activity relationship of glabridin derivatives on LDL oxidation was also reported. In addition, the inhibitory effects of glabridin on early inflammatory processes, including the expression of adhesion molecules on endothelial cells and the activation of macrophages and dendritic cells, were also demonstrated previously. In this review, we summarized the cardiovascular protection-related activities of glabridin and the mechanism of action involved in these activities. Collectively, it is hoped that glabridin or glabridin derivatives might be used as a therapeutic agent for the treatment of cardiovascular diseases in the future.

Elevated high-density lipoprotein cholesterol and cardiovascular mortality in maintenance hemodialysis patients

BACKGROUND

High-density lipoprotein (HDL) confers protection against atherosclerosis by several different mechanisms. Although in the general population, increasing levels of HDL are associated with reduced cardiovascular (CV) mortality, this association is not well known in patients with chronic disease states such as end-stage renal disease. We hypothesize that the association of serum HDL concentration and its ratio to total cholesterol with all-cause and CV mortality in hemodialysis patients is different from the general population.

METHODS

A 3-year (July 2004 to June 2007) cohort of 33 109 chronic hemodialysis patients was studied in the USA in the dialysis clinics where lipid profile was measured in at least 50% of all outpatients of the clinic during a given calendar quarter. Cox proportional hazard models were adjusted for demographics and case-mix variables and cubic splines were plotted.

RESULTS

Higher HDL concentrations up to 50 mg/dL were associated with better overall survival, while HDL at 60 mg/dL and above was associated with a rise in all-cause and CV mortality. All-cause and CV mortality hazard ratio was 1.28 (1.20-1.38) and 1.08 (1.01-1.16) for HDL <30 mg/dL and 1.05 (1.00-1.10) and 1.08 (1.00-1.16) for HDL ≥ 60 mg/dL, respectively (reference: HDL: 30-<60 mg/dL).

CONCLUSIONS

In contrast to the general population, low total cholesterol to HDL ratio was associated with higher mortality in hemodialysis patients. A U-shaped association between HDL cholesterol level and all-cause and CV mortality exists in hemodialysis patients with HDL between 50 and <60 mg/dL exhibiting the best survival. The underlying mechanisms responsible for these seemingly paradoxical associations await further investigation.

Therapeutic approaches to drug targets in atherosclerosis

Non-communicable diseases such as cancer, atherosclerosis and diabetes are responsible for major social and health burden as millions of people are dying every year. Out of which, atherosclerosis is the leading cause of deaths worldwide. The lipid abnormality is one of the major modifiable risk factors for atherosclerosis. Both genetic and environmental components are associated with the development of atherosclerotic plaques. Immune and inflammatory mediators have a complex role in the initiation and progression of atherosclerosis. Understanding of all these processes will help to invent a range of new biomarkers and novel treatment modalities targeting various cellular events in acute and chronic inflammation that are accountable for atherosclerosis. Several biochemical pathways, receptors and enzymes are involved in the development of atherosclerosis that would be possible targets for improving strategies for disease diagnosis and management. Earlier anti-inflammatory or lipid-lowering treatments could be useful for alleviating morbidity and mortality of atherosclerotic cardiovascular diseases. However, novel drug targets like endoglin receptor, PPARα, squalene synthase, thyroid hormone analogues, scavenger receptor and thyroid hormone analogues are more powerful to control the process of atherosclerosis. Therefore, the review briefly focuses on different novel targets that act at the starting stage of the plaque form to the thrombus formation in the atherosclerosis.

Salutary effects of hemodialysis on low-density lipoprotein proinflammatory and high-density lipoprotein anti-inflammatory properties in patient with end-stage renal disease

End-stage renal disease (ESRD) causes oxidative stress, inflammation, low-density lipoprotein (LDL) oxidation, high-density lipoprotein (HDL) deficiency and accelerated atherosclerosis. Uptake of oxidized LDL by macrophages results in foam cell and plaque formation. HDL mitigates atherosclerosis via reverse cholesterol transport and inhibition of LDL oxidation. ESRD heightens LDL inflammatory activity and suppresses HDL anti-inflammatory activity. The effect of hemodialysis on the LDL and HDL inflammatory properties is unknown. By removing the potential pro-oxidant/proinflammatory uremic toxins, dialysis may attenuate LDL inflammatory and HDL anti-inflammatory properties. Conversely, exposure to dialyzer membrane and tubing and influx of impurities from dialysate can intensify LDL and HDL inflammatory activities. This study examined the effect of hemodialysis on LDL and HDL inflammatory activities. Plasma samples were obtained from 12 normal control and 26 ESRD patients before and after hemodialysis with (16 patients) or without (10 patients) heparinization. HDL and LDL were isolated and tested for monocyte chemotactic activity in cultured endothelial cells. ESRD patients had increased LDL chemotactic activity, reduced HDL anti-inflammatory activity, paraoxonase and glutathione peroxidase levels, and elevated plasma IL-6 before dialysis. Hemodialysis partially improved LDL inflammatory and HDL anti-inflammatory activities and enhanced patients' HDL ability to suppress their LDL inflammatory activity. The salutary effect on LDL inflammatory activity was significantly greater in patients dialyzed with than those without heparin. ESRD heightens LDL inflammatory and impairs HDL anti-inflammatory activities. Hemodialysis partially improves LDL and HDL inflammatory activities. The salutary effects of hemodialysis are in part mediated by heparin, which is known to possess lipolytic and antioxidant properties.

Lipotoxicity and impaired high density lipoprotein-mediated reverse cholesterol transport in chronic kidney disease

Chronic kidney disease (CKD) is associated with a high risk of death from cardiovascular disease. Inflammation, oxidative stress, and dyslipidemia, which are common consequences of CKD, contribute to the pathogenesis of atherosclerosis and cardiovascular disease in this population. Dyslipidemia of CKD is characterized by diminished plasma high density lipoprotein (HDL) concentration, impaired HDL anti-oxidant and anti-inflammatory activities, and elevated plasma triglyceride, very low density lipoprotein (VLDL), intermediate density lipoprotein, chylomicron remnants, and oxidized lipids and lipoproteins. The constellation of inflammation, HDL deficiency, and oxidative modification of lipoproteins can cause atherosclerosis and progression of renal disease. We have recently found lipid accumulation in the remnant kidney and the wall of aorta in rats with CKD induced by 5/6 nephrectomy. This was mediated by up-regulation of scavenger receptors involved in the influx of oxidized lipids or lipoproteins, tubular reabsorption of lipid binding proteins through megalin-cubilin complexes, upregulation of fatty acid synthesis, and downregulation of fatty acid oxidation pathways. The combination of increased lipid influx, elevated production and reduced catabolism of lipids, and impaired HDL-mediated reverse cholesterol transport can promote atherosclerosis, glomerulosclerosis, and tubulointerstitial damage. Although statins can be effective in slowing CKD progression in patients with mild-to-moderate CKD, they have consistently failed to mitigate oxidative stress, inflammation, HDL deficiency, or cardiovascular mortality in the end-stage renal disease populations. Similarly, high doses of antioxidant vitamins have failed to either ameliorate oxidative stress, inflammation, or improve overall mortality in end-stage renal disease. This article is intended to provide a brief review of the effects of CKD on HDL structure and function and pathways of lipid influx, efflux, synthesis, and catabolism in the artery wall and the diseased kidney.

Lp-PLA₂- a novel risk factor for high-risk coronary and carotid artery disease

Lipoprotein-associated phospholipase A2 (Lp-PLA₂) is at the crossroads of lipid metabolism and the inflammatory response. It is produced by inflammatory cells, bound to LDL and other lipoproteins, and once in the arterial wall facilitates hydrolysis of phospholipids. Elevated serum levels of Lp-PLA₂ have been associated with increased cardiovascular risk in healthy populations and in patients with known vascular disease. Here, we review the role of Lp-PLA₂ in the development of atherosclerosis and progression to unstable disease, the utility of Lp-PLA₂ as a risk predictor for coronary and carotid events and the potential clinical benefit of pharmacologic inhibition of Lp-PLA₂.

Anti-inflammatory activity of natural dietary flavonoids

Over the past few decades, inflammation has been recognized as a major risk factor for various human diseases. Acute inflammation is short-term, self-limiting and it's easy for host defenses to return the body to homeostasis. Chronic inflammatory responses are predispose to a pathological progression of chronic illnesses characterized by infiltration of inflammatory cells, excessive production of cytokines, dysregulation of cellular signaling and loss of barrier function. Targeting reduction of chronic inflammation is a beneficial strategy to combat several human diseases. Flavonoids are widely present in the average diet in such foods as fruits and vegetables, and have been demonstrated to exhibit a broad spectrum of biological activities for human health including an anti-inflammatory property. Numerous studies have proposed that flavonoids act through a variety mechanisms to prevent and attenuate inflammatory responses and serve as possible cardioprotective, neuroprotective and chemopreventive agents. In this review, we summarize current knowledge and underlying mechanisms on anti-inflammatory activities of flavonoids and their implicated effects in the development of various chronic inflammatory diseases.

Akt pathway is hypoactivated by synergistic actions of diabetes mellitus and hypercholesterolemia resulting in advanced coronary artery disease

Atherosclerosis is an inflammatory process leading to enhanced cellular proliferation, apoptosis, and vasa vasorum (VV) neovascularization. While both diabetes mellitus (DM) and hypercholesterolemia (HC) predispose to atherosclerosis, the precise interaction of these risk factors is unclear. Akt is a central node in signaling pathways important for inflammation, and we hypothesized that DM/HC would lead to aberrant Akt signaling and advanced, complex atherosclerosis. DM was induced in pigs by streptozotocin and HC by a high-fat diet. Animals were randomized to control (non-DM, non-HC), DM only, HC only, and DM/HC groups. Coronary artery homogenates were analyzed by immunoblotting for proteins involved in the Akt pathway, including phosphorylated (p)-Akt (Ser473), p-GSK-3beta (Ser9), activated NF-kappaB p65, and VEGF. Immunohistochemical staining for Ki67 (cell proliferation), terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) (apoptosis), and von Willebrand factor (vWF) (neovascularization) was performed. Neovascularization was visualized with micro-computerized tomography (CT). Only DM/HC animals developed advanced atherosclerosis and showed decreased p-Akt (Ser473) and p-GSK-3beta (Ser9) levels (P < 0.01 and P < 0.05, respectively). DM/HC arteries demonstrated increased cellular proliferation (P < 0.001), apoptosis (P < 0.01), and activation of NF-kappaB p65 (P < 0.05). Induction of DM/HC also resulted in significant VV neovascularization by enhanced VEGF expression (P < 0.05), increased vWF staining (P < 0.01), and increased density by micro-CT. In conclusion, DM and HC synergistically resulted in complex atherosclerosis associated with attenuated p-Akt (Ser473) levels. Aberrant Akt signaling correlated with increased inflammation, cellular proliferation, apoptosis, and VV neovascularization. Our results revealed a synergistic effect of DM and HC in triggering abnormal Akt signaling, resulting in advanced atherosclerosis.

HDL metabolism and activity in chronic kidney disease

Chronic kidney disease (CKD) is associated with development of atherosclerosis and premature death from cardiovascular disease. The predisposition of patients with CKD to atherosclerosis is driven by inflammation, oxidative stress and dyslipidemia, all of which are common features of this condition. Markers of dyslipidemia in patients with advanced CKD are impaired clearance and heightened oxidation of apolipoprotein-B-containing lipoproteins and their atherogenic remnants, and a reduction of the plasma concentration, antioxidant, and anti-inflammatory properties of high-density lipoprotein (HDL). Studies in animal models of CKD indicate that the disease promotes lipid accumulation in the artery wall and kidney, leading to atherosclerosis, glomerulosclerosis and tubulointerstitial injury. These effects seem to be mediated by an increased cellular influx of lipids, elevated cellular production and reduced cellular catabolism of fatty acids, and impaired antioxidant, anti-inflammatory and reverse lipid transport properties of HDL. Available pharmacological therapies have been largely ineffective in ameliorating oxidative stress, inflammation, HDL deficiency and/or dysfunction, and the associated atherosclerosis and cardiovascular disease in patients with end-stage renal disease. This Review aims to provide an overview of the mechanisms and consequences of CKD-induced HDL deficiency and dysfunction.

Darapladib

IMPORTANCE OF THE FIELD

Atherosclerosis is an inflammatory-immune mediated disease process. Plaque rupture is responsible for the clinical events of ischemic death, myocardial infarction, acute coronary syndromes and ischemic strokes. Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) seems to play a major role in the development of such high-risk lesions, in both the coronary and carotid arteries. Darapladib is a selective inhibitor of Lp-PLA(2).

AREAS COVERED IN THIS REVIEW

An overview of darapladib by reviewing the studies (1990 - 2009) that have provided the rationale for the development of darapladib; and a discussion of its potential merit as a new therapeutic drug to target high-risk atherosclerosis.

WHAT THE READER WILL GAIN

The reader should gain an understanding of the importance of inflammation during atherogenesis as well as of the biology of Lp-PLA(2) and its proatherogenic role. Additional insights will be gained into the role of selective inhibitors of Lp-PLA(2) as new therapeutic agents.

TAKE HOME MESSAGE

Darapladib is a selective inhibitor of Lp-PLA(2) and represents a new class of therapeutic agents that target inflammation to treat high-risk atherosclerosis.

A physiological function of inflammation-associated SerpinB2 is regulation of adaptive immunity

SerpinB2 (plasminogen activator inhibitor-2) is widely described as an inhibitor of urokinase plasminogen activator; however, SerpinB2(-/-) mice show no detectable increase in urokinase plasminogen activator activity. In this study, we describe an unexpected immune phenotype in SerpinB2(-/-) mice. After immunization with OVA in CFA, SerpinB2(-/-) mice made approximately 6-fold more IgG2c and generated approximately 2.5-fold more OVA-specific IFN-gamma-secreting T cells than SerpinB2(+/+) littermate controls. In SerpinB2(+/+) mice, high inducible SerpinB2 expression was seen at the injection site and in macrophages low levels in draining lymph nodes and conventional dendritic cells, and no expression was seen in plasmacytoid dendritic, B, T, or NK cells. SerpinB2(-/-) macrophages promoted greater IFN-gamma secretion from wild-type T cells in vivo and in vitro and, when stimulated with anti-CD40/IFN-gamma or cultured with wild-type T cells in vitro, secreted more Th1-promoting cytokines than macrophages from littermate controls. Draining lymph node SerpinB2(-/-) myeloid APCs similarly secreted more Th1-promoting cytokines when cocultured with wild-type T cells. Regulation of Th1 responses thus appears to be a physiological function of inflammation-associated SerpinB2; an observation that may shed light on human inflammatory diseases like pre-eclampsia, lupus, asthma, scleroderma, and periodontitis, which are associated with SerpinB2 polymorphisms or dysregulated SerpinB2 expression.

In vitro stimulation of HDL anti-inflammatory activity and inhibition of LDL pro-inflammatory activity in the plasma of patients with end-stage renal disease by an apoA-1 mimetic peptide

Features of end-stage renal disease such as oxidative stress, inflammation, hypertension, and dyslipidemia are associated with accelerated atherosclerosis and increased risk of death from cardiovascular disease. By inhibiting the formation and increasing the disposal of oxidized lipids, HDL exerts potent antioxidant and anti-inflammatory actions. Given that apolipoproteinA-1 can limit atherosclerosis, we hypothesized that an apolipoproteinA-1 mimetic peptide, 4F, may reduce the proinflammatory properties of LDL and enhance the anti-inflammatory properties of HDL in uremic plasma. To test this, plasma from each of 12 stable hemodialysis patients and age-matched control subjects was incubated with 4F or vehicle. The isolated HDL and LDL fractions were added to cultured human aortic endothelial cells to quantify monocyte chemotactic activity, thus measuring their pro- or anti-inflammatory index. The LDL from the hemodialysis patients was more pro-inflammatory and their HDL was less anti-inflammatory than those of the control subjects. Pre-incubation of the plasma from the hemodialysis patients with 4F decreased LDL pro-inflammatory activity and enhanced HDL anti-inflammatory activity. Whether 4F or other apolipoproteinA-1 mimetic peptides will have any therapeutic benefit in end-stage renal disease will have to be examined directly in clinical studies.

Cardiometabolic risk in psoriasis: differential effects of biologic agents

Psoriasis is associated to an increased risk of cardiovascular (CV) complications. Overall, the pathogenic mechanisms involved in premature CV complications in psoriasis appear to be complex and multifactorial, with traditional and nontraditional risk factors possibly contributing to the increased risk. Based on what is known about the pathogenesis of psoriasis and extrapolating the current knowledge on CV complications in other inflammatory diseases, studies are needed to investigate if appropriate control of the inflammatory, immunologic and metabolic disturbances present in psoriasis can prevent the development of this potentially lethal complication. It is clear that there is a great need for heightened awareness of the increased risk for vascular damage in patients with psoriasis. It is also crucial to closely monitor patients with psoriasis for CV risk factors including obesity, hypertension, diabetes, and hyperlipidemia. Whether treatment regimens that effectively manage systemic inflammation will lead to prevention of CV complications in psoriasis needs to be investigated. Clearly, studies should focus on establishing the exact mechanisms that determine CV risk in psoriasis so that appropriate preventive strategies and treatment guidelines can be established.

Impaired antioxidant activity of high-density lipoprotein in chronic kidney disease

Chronic kidney disease (CKD) is associated with accelerated atherosclerosis and increased mortality from cardiovascular disease. CKD results in oxidative stress, inflammation, and high-density lipoprotein (HDL) deficiency, which work in concert to promote atherosclerosis. Normal HDL confers protection against atherosclerosis by inhibiting the oxidation of lipids and lipoproteins and by retrieving surplus cholesterol and phospholipids from lipid-laden cells in the artery wall for disposal in the liver (reverse cholesterol transport). The plasma level of oxidized low-density lipoprotein (LDL) is increased, plasma HDL-cholesterol is reduced, and HDL maturation is impaired in CKD. This study was designed to examine the antioxidant properties of HDL in patients with CKD. In all, 32 stable hemodialysis-dependent patients and 13 age-matched controls were studied. HDL was isolated and used for determination of in vitro antioxidant activity. In addition, the plasma level of key components of HDL, namely paraoxonase (PON), glutathione peroxidase (GPX), platelet activating factor acetylhydrolase (PAF-AH), lecithin cholesterol acyltransferase (LCAT), and apolipoprotein A-I (ApoA-I), were measured. The end-stage renal disease (ESRD) patients exhibited significant reductions of HDL-cholesterol, ApoA-I (-41%), GPX (-50%), and LCAT (-60%) concentrations, and a decrease in PON (-30%) and GPX (-50%) activities. These results were accompanied by a marked reduction of antioxidant activity of HDL (-127%), which was unaffected by the hemodialysis procedure. Thus, in addition to diminished plasma HDL concentration, the composition and antioxidant activity of HDL are altered in CKD; these events can contribute to a heightened risk of atherosclerosis.

Matrix vesicles in the fibrous cap of atherosclerotic plaque: possible contribution to plaque rupture

Plaque rupture is the most common type of plaque complication and leads to acute ischaemic events such as myocardial infarction and stroke. Calcification has been suggested as a possible indicator of plaque instability. Although the role of matrix vesicles in the initial stages of arterial calcification has been recognized, no studies have yet been carried out to examine a possible role of matrix vesicles in plaque destabilization. Tissue specimens selected for the present study represented carotid specimens obtained from patients undergoing carotid endarterectomy. Serial frozen cross-sections of the tissue specimens were cut and mounted on glass slides. The thickness of the fibrous cap (FCT) in each advanced atherosclerotic lesion, containing a well developed lipid/necrotic core, was measured at its narrowest sites in sets of serial sections. According to established criteria, atherosclerotic plaque specimens were histologically subdivided into two groups: vulnerable plaques with thin fibrous caps (FCT <100 μm) and presumably stable plaques, in which fibrous caps were thicker than 100 μm. Twenty-four carotid plaques (12 vulnerable and 12 presumably stable plaques) were collected for the present analysis of matrix vesicles in fibrous caps. In order to provide a sufficient number of representative areas from each plaque, laser capture microdissection (LCM) was carried out. The quantification of matrix vesicles in ultrathin sections of vulnerable and stable plaques revealed that the numbers of matrix vesicles were significantly higher in fibrous caps of vulnerable plaques than those in stable plaques (8.908±0.544 versus 6.208±0.467 matrix vesicles per 1.92 μm² standard area; P= 0.0002). Electron microscopy combined with X-ray elemental microanalysis showed that some matrix vesicles in atherosclerotic plaques were undergoing calcification and were characterized by a high content of calcium and phosphorus. The percentage of calcified matrix vesicles/microcalcifications was significantly higher in fibrous caps in vulnerable plaques compared with that in stable plaques (6.705±0.436 versus 5.322±0A94; P= 0.0474). The findings reinforce a view that the texture of the extracellular matrix in the thinning fibrous cap of atherosclerotic plaque is altered and this might contribute to plaque destabilization.