Human paraoxonase-1 overexpression inhibits atherosclerosis in a mouse model of metabolic syndrome

Dantrolene is an HDL-associated paraoxonase-1 activator with immunosuppressive and atheroprotective properties

Human paraoxonase 1 (PON1), an enzyme bound to high-density lipoprotein (HDL), hydrolyzes oxidized lipids and contributes to HDL atheroprotective functions. Decreased serum paraoxonase and arylesterase activities of PON1 have been reported in patients at increased atherosclerosis risk, such as rheumatoid arthritis patients, and associated with arthritis severity and cardiovascular risk. Agents that can modulate PON1 activity and HDL-mediated effects have not been discovered. Aiming to discover chemical tools that enhance PON1 activity, we screened a library of marketed drugs (956 compounds) to identify small molecules that can increase HDL-associated PON1 activity. Screening was performed by a kinetic absorbance assay using human HDL as a source of PON1, and paraoxon and phenyl acetate as substrates to measure paraoxonase and arylesterase activities, respectively. Screening identified the drug dantrolene as a potential PON1 activator, which was confirmed by enzymatic kinetic assays using recombinant wild-type PON1, as well as the PON1[L55M] variant displaying decreased enzyme activity in humans. Furthermore, we used the collagen-induced arthritis (CIA) mouse model to examine the effect of dantrolene on HDL properties and arthritis in vivo. Administration of dantrolene in CIA mice increased paraoxonase and arylesterase activities of PON1, as well as the antioxidant capacity of HDL, and reduced arthritis severity by inhibition of naïve CD4+ T cell differentiation to effector memory cells and generation of Th1 cells. Collectively, our in vitro and in vivo findings indicate using small molecules to enhance HDL-associated PON1 activity is a tractable approach that could lead to novel therapeutics targeting immune responses and atherosclerosis.

Modulation of the antioxidant enzyme paraoxonase-1 for protection against cardiovascular diseases

AIM

The enzyme paraoxonase 1 (PON1) bound to high-density lipoprotein has received special attention for its protective role against stress-mediated damage and use as a potential regulatory target in atherosclerosis and related vascular diseases.

DATA SYNTHESIS

We present an overview of the literature on PON1 activity and mRNA levels by investigating its modulation for clinical translations. Specifically, the expression of PON1 and its regulated activity can be modified in different ways with natural substances, drugs, and lifestyle factors thar affect the development of atherosclerosis.

CONCLUSIONS

The endothelial contribution of PON1 to overcome differences considering an individual's disease development risk is supported by polymorphism interaction data and the susceptibility to modify PON1 responses in chronic events composed by biological and environmental factors.

Unraveling metabolic stress response in dairy cows: Genetic control of plasma biomarkers throughout lactation and the transition period

Breeding animals able to effectively respond to stress could be a long-term, sustainable, and affordable strategy to improve resilience and welfare in livestock systems. In the present study, the concentrations of 29 plasma biomarkers were used as candidate endophenotypes for metabolic stress response in single-SNP, gene- and haplotype-based GWAS using 739 healthy lactating Italian Holstein cows and 88,271 variants. Significant genetic associations were found in all the 3 GWAS approaches for plasma γ-glutamyl transferase concentration on BTA17, for paraoxonase on BTA4, and for alkaline phosphatase and zinc on BTA2. On these chromosomes, single-SNP and gene-based chromosome-wide association studies were performed, confirming GWAS findings. The signals identified for paraoxonase, γ-glutamyl transferase, and alkaline phosphatase were in proximity to the genes coding for them. The heritability of these 4 biomarkers ranged from moderate to high (from 0.39 to 0.54). Plasma biomarkers are known to undergo large changes in concentration during metabolic stress in the transition period, with an interindividual variability in the rate of change and recovery time. Genetics may account in part for these differences. To assess this, we studied a subset of 139 periparturient cows homozygous at 3 SNPs known to be respectively associated with concentration of plasma ceruloplasmin, paraoxonase, and γ-glutamyl transferase. We compared the immune-metabolic profile measured in plasma at -7, +5, and +30 d relative to calving between groups of opposite homozygotes. A significant effect of the genotype was found on paraoxonase and γ-glutamyl transferase plasma concentration at all the 3 time points. No evidence for genotype effect was detected for ceruloplasmin. Understanding the genetic control underlying metabolic stress response may suggest new approaches to foster resilience in dairy cows.

The Molecular Bases of Anti-Oxidative and Anti-Inflammatory Properties of Paraoxonase 1

The anti-oxidative and anti-inflammatory properties of high-density lipoprotein (HDL) are thought to be mediated by paraoxonase 1 (PON1), a calcium-dependent hydrolytic enzyme carried on a subfraction of HDL that also carries other anti-oxidative and anti-inflammatory proteins. In humans and mice, low PON1 activity is associated with elevated oxidized lipids and homocysteine (Hcy)-thiolactone, as well as proteins that are modified by these metabolites, which can cause oxidative stress and inflammation. PON1-dependent metabolic changes can lead to atherothrombotic cardiovascular disease, Alzheimer's disease, and cancer. The molecular bases underlying these associations are not fully understood. Biochemical, proteomic, and metabolic studies have significantly expanded our understanding of the mechanisms by which low PON1 leads to disease and high PON1 is protective. The studies discussed in this review highlight the changes in gene expression affecting proteostasis as a cause of the pro-oxidative and pro-inflammatory phenotypes associated with attenuated PON1 activity. Accumulating evidence supports the conclusion that PON1 regulates the expression of anti-oxidative and anti-inflammatory proteins, and that the disruption of these processes leads to disease.

Paraoxonase 1: evolution of the enzyme and of its role in protecting against atherosclerosis

PURPOSE OF REVIEW

To review the discoveries which led to the concept that serum paraoxonase 1 (PON1) is inversely related to atherosclerotic cardiovascular disease (ASCVD) incidence, how this association came to be regarded as causal and how such a role might have evolved.

RECENT FINDINGS

Animal models suggest a causal link between PON1 present on HDL and atherosclerosis. Serum PON1 activity predicts ASCVD with a similar reliability to HDL cholesterol, but at the extremes of high and low HDL cholesterol, there is discordance with PON1 being potentially more accurate. The paraoxonase gene family has its origins in the earliest life forms. Its greatest hydrolytic activity is towards lactones and organophosphates, both of which can be generated in the natural environment. It is active towards a wide range of substrates and thus its conservation may have resulted from improved survival of species facing a variety of evolutionary challenges.

SUMMARY

Protection against ASCVD is likely to be the consequence of some promiscuous activity of PON1, but nonetheless has the potential for exploitation to improve risk prediction and prevention of ASCVD.

HDL Function and Atherosclerosis: Reactive Dicarbonyls as Promising Targets of Therapy

Epidemiologic studies detected an inverse relationship between HDL (high-density lipoprotein) cholesterol (HDL-C) levels and atherosclerotic cardiovascular disease (ASCVD), identifying HDL-C as a major risk factor for ASCVD and suggesting atheroprotective functions of HDL. However, the role of HDL-C as a mediator of risk for ASCVD has been called into question by the failure of HDL-C-raising drugs to reduce cardiovascular events in clinical trials. Progress in understanding the heterogeneous nature of HDL particles in terms of their protein, lipid, and small RNA composition has contributed to the realization that HDL-C levels do not necessarily reflect HDL function. The most examined atheroprotective function of HDL is reverse cholesterol transport, whereby HDL removes cholesterol from plaque macrophage foam cells and delivers it to the liver for processing and excretion into bile. Indeed, in several studies, HDL has shown inverse associations between HDL cholesterol efflux capacity and ASCVD in humans. Inflammation plays a key role in the pathogenesis of atherosclerosis and vulnerable plaque formation, and a fundamental function of HDL is suppression of inflammatory signaling in macrophages and other cells. Oxidation is also a critical process to ASCVD in promoting atherogenic oxidative modifications of LDL (low-density lipoprotein) and cellular inflammation. HDL and its proteins including apoAI (apolipoprotein AI) and PON1 (paraoxonase 1) prevent cellular oxidative stress and LDL modifications. Importantly, HDL in humans with ASCVD is oxidatively modified rendering HDL dysfunctional and proinflammatory. Modification of HDL with reactive carbonyl species, such as malondialdehyde and isolevuglandins, dramatically impairs the antiatherogenic functions of HDL. Importantly, treatment of murine models of atherosclerosis with scavengers of reactive dicarbonyls improves HDL function and reduces systemic inflammation, atherosclerosis development, and features of plaque instability. Here, we discuss the HDL antiatherogenic functions in relation to oxidative modifications and the potential of reactive dicarbonyl scavengers as a therapeutic approach for ASCVD.

Proteomic Exploration of Paraoxonase 1 Function in Health and Disease

High-density lipoprotein (HDL) exhibits cardio- and neuro-protective properties, which are thought to be promoted by paraoxonase 1 (PON1), a hydrolytic enzyme associated with an HDL subfraction also enriched with an anticoagulant protein (PROS1) and amyloid beta-transport protein clusterin (CLU, APOJ). Reduced levels of PON1 activity, characterized biochemically by elevated levels of homocysteine (Hcy)-thiolactone, oxidized lipids, and proteins modified by these metabolites in humans and mice, are associated with pathological abnormalities affecting the cardiovascular system (atherothrombosis) and the central nervous system (cognitive impairment, Alzheimer's disease). The molecular bases of these abnormalities have been largely unknown. Proteomic and metabolic studies over the past decade have significantly contributed to our understanding of PON1 function and the mechanisms by which PON1 deficiency can lead to disease. Recent studies discussed in this review highlight the involvement of dysregulated proteostasis in the pro-oxidative, pro-atherothrombotic, and pro-amyloidogenic phenotypes associated with low PON1 activity.

A green-inspired method to prepare non-split high-density lipoprotein (HDL) carrier with anti-dysfunctional activities superior to reconstituted HDL

Numerous studies have demonstrated that dysfunctional high-density lipoprotein (HDL), especially oxidized HDL (OxHDL), could generate multifaceted in vivo proatherogenic effects that run counter to the antiatherogenic activities of HDL. It thereby reminded us that the in vitro reconstituted HDL (rHDL) might encountered with oxidation-induced dysfunction. Accordingly, a green-inspired method was employed to recycle non-split HDL from human plasma fraction IV. Then it was compared with rHDL formulated by an ethanol-injection method in terms of physicochemical properties and anti-dysfunctional activities. Results exhibited that rHDL oxidation extent exceeded that of non-split HDL evidenced by higher malondialdehy content, weaker inhibition on low-density lipoprotein (LDL) oxidation and more superoxide anion. The reserved paraoxonase-1 activity on non-split HDL could partially explain for above experimental results. In the targeted transport mechanism experiment, upon SR-BI receptor inhibition and/or CD36 receptor blockage, the almost unchanged non-split HDL uptake in lipid-laden macrophage indicated its negligible oxidation modification profile with regard to rHDL again. Furthermore, compared to rHDL, better macrophage biofunctions were observed for non-split HDL as illustrated by accelerated cholesterol efflux, inhibited oxidized LDL uptake and lessened cellular lipid accumulation. Along with decreased ROS secretion, obviously weakened oxidative stress damage was also detected under treatment with non-split HDL. More importantly, foam cells with non-split HDL-intervention inspired an enhanced inflammation repression and apoptosis inhibition effect. Collectively, the anti-dysfunctional activities of non-split HDL make it suitable as a potential nanocarrier platform for cardiovascular drug payload and delivery.

Paraoxonase 1 and atherosclerosis

Paraoxonase 1 (PON1), residing almost exclusively on HDL, was discovered because of its hydrolytic activity towards organophosphates. Subsequently, it was also found to hydrolyse a wide range of substrates, including lactones and lipid hydroperoxides. PON1 is critical for the capacity of HDL to protect LDL and outer cell membranes against harmful oxidative modification, but this activity depends on its location within the hydrophobic lipid domains of HDL. It does not prevent conjugated diene formation, but directs lipid peroxidation products derived from these to become harmless carboxylic acids rather than aldehydes which might adduct to apolipoprotein B. Serum PON1 is inversely related to the incidence of new atherosclerotic cardiovascular disease (ASCVD) events, particularly in diabetes and established ASCVD. Its serum activity is frequently discordant with that of HDL cholesterol. PON1 activity is diminished in dyslipidaemia, diabetes, and inflammatory disease. Polymorphisms, most notably Q192R, can affect activity towards some substrates, but not towards phenyl acetate. Gene ablation or over-expression of human PON1 in rodent models is associated with increased and decreased atherosclerosis susceptibility respectively. PON1 antioxidant activity is enhanced by apolipoprotein AI and lecithin:cholesterol acyl transferase and diminished by apolipoprotein AII, serum amyloid A, and myeloperoxidase. PON1 loses this activity when separated from its lipid environment. Information about its structure has been obtained from water soluble mutants created by directed evolution. Such recombinant PON1 may, however, lose the capacity to hydrolyse non-polar substrates. Whilst nutrition and pre-existing lipid modifying drugs can influence PON1 activity there is a cogent need for more specific PON1-raising medication to be developed.

Role of Oxidative Stress in the Pathogenesis of Atherothrombotic Diseases

Oxidative stress is generated by the imbalance between reactive oxygen species (ROS) formation and antioxidant scavenger system’s activity. Increased ROS, such as superoxide anion, hydrogen peroxide, hydroxyl radical and peroxynitrite, likely contribute to the development and complications of atherosclerotic cardiovascular diseases (ASCVD). In genetically modified mouse models of atherosclerosis, the overexpression of ROS-generating enzymes and uncontrolled ROS formation appear to be associated with accelerated atherosclerosis. Conversely, the overexpression of ROS scavenger systems reduces or stabilizes atherosclerotic lesions, depending on the genetic background of the mouse model. In humans, higher levels of circulating biomarkers derived from the oxidation of lipids (8-epi-prostaglandin F_2α, and malondialdehyde), as well as proteins (oxidized low-density lipoprotein, nitrotyrosine, protein carbonyls, advanced glycation end-products), are increased in conditions of high cardiovascular risk or overt ASCVD, and some oxidation biomarkers have been reported as independent predictors of ASCVD in large observational cohorts. In animal models, antioxidant supplementation with melatonin, resveratrol, Vitamin E, stevioside, acacetin and n-polyunsaturated fatty acids reduced ROS and attenuated atherosclerotic lesions. However, in humans, evidence from large, placebo-controlled, randomized trials or prospective studies failed to show any athero-protective effect of antioxidant supplementation with different compounds in different CV settings. However, the chronic consumption of diets known to be rich in antioxidant compounds (e.g., Mediterranean and high-fish diet), has shown to reduce ASCVD over decades. Future studies are needed to fill the gap between the data and targets derived from studies in animals and their pathogenetic and therapeutic significance in human ASCVD.

Effect of Carotenoids on Paraoxonase-1 Activity and Gene Expression

Paraoxonase 1 (PON1) is an antioxidant enzyme attached to HDL with an anti-atherogenic potential. It protects LDL and HDL from lipid peroxidation. The enzyme is sensitive to various modulating factors, such as genetic polymorphisms as well as pharmacological, dietary (including carotenoids), and lifestyle interventions. Carotenoids are nutritional pigments with antioxidant activity. The aim of this review was to gather evidence on their effect on the modulation of PON1 activity and gene expression. Carotenoids administered as naturally occurring nutritional mixtures may present a synergistic beneficial effect on PON1 status. The effect of carotenoids on the enzyme depends on age, ethnicity, gender, diet, and PON1 genetic variation. Carotenoids, especially astaxanthin, β-carotene, and lycopene, increase PON1 activity. This effect may be explained by their ability to quench singlet oxygen and scavenge free radicals. β-carotene and lycopene were additionally shown to upregulate PON1 gene expression. The putative mechanisms of such regulation involve PON1 CpG-rich region methylation, Ca(2+)/calmodulin-dependent kinase II (CaMKKII) pathway induction, and upregulation via steroid regulatory element-binding protein-2 (SREBP-2). More detailed and extensive research on the mechanisms of PON1 modulation by carotenoids may lead to the development of new targeted therapies for cardiovascular diseases.

S-Nitrosylation of Paraxonase 1 (PON1) Elevates Its Hydrolytic and Antioxidant Activities

Covalent binding between nitric oxide (NO) and a protein’s free thiol group (SH) is termed protein S-nitrosylation. Protein S-nitrosylation is involved in cellular regulation mechanisms that underlie a wide range of critical functions, such as apoptosis, alteration of enzyme activities, and transcription-factor stability. Impaired protein S-nitrosylation is associated with a growing list of pathophysiological conditions, such as cardiovascular disease, multiple sclerosis, pulmonary hypertension, and sickle cell disease. The enzyme paraoxonase 1 (PON1) binds to high-density lipoprotein to provide many of its antiatherogenic properties. The enzyme has a strong antioxidant capacity, which protects fats, lipids, and lipoproteins from oxidation, in addition to breaking down oxidized fats. We investigated the effect of S-S transnitrosylation on PON1 activities. Incubation of recombinant PON1 (rePON1) with nitrosylated human serum albumin (HSA-NO) resulted in S-nitrosylation of about 70% of the rePON1, as measured by Q-TOF LC/MS. S-nitrosylation significantly increased rePON1 hydrolytic activities. It also increased rePON1’s ability to inhibit low-density lipoprotein oxidation induced by Cu²⁺. Finally, it increased the enzyme’s penetration into macrophage cells by 31%. Our findings suggest that S-nitrosylation of rePON1 improves its biological functions which may positively affect atherosclerosis disease progression.

Hepatic paraoxonase 1 ameliorates dysfunctional high-density lipoprotein and atherosclerosis in scavenger receptor class B type I deficient mice

Background

High-density lipoprotein (HDL) plays an antiatherogenic role by mediating reverse cholesterol transport (RCT), antioxidation, anti-inflammation, and endothelial cell protection. Recently, series of evidence have shown that HDL can also convert to proatherogenic HDL under certain circumstances. Plasma paraoxonase 1 (PON1) as an HDL-bound esterase, is responsible for most of the antioxidant properties of HDL. However, whether PON1 can serve as a therapeutic target of dysfunctional HDL-related atherosclerosis remains unclear.

Methods

In this study, scavenger receptor class B type I deficient (Scarb1^−/−) mice were used as the animal model with dysfunctional HDL and increased atherosclerotic susceptibility. Hepatic PON1 overexpression and secretion into circulation were achieved by lentivirus injection through the tail vein. We monitored plasma lipids levels and lipoprotein profiles in Scarb1^−/− mice, and measured the levels and activities of proteins associated with HDL function. Meanwhile, lipid deposition in the liver and atherosclerotic lesions was quantified. Hepatic genes relevant to HDL metabolism and inflammation were analyzed.

Results

The results showed the relative levels of PON1 in liver and plasma were increased by 1.1-fold and 1.6-fold, respectively, and mean plasma PON1 activity was increased by 63%. High-level PON1 increased the antioxidative and anti-inflammatory properties, promoted HDL maturation and macrophage cholesterol efflux through increasing HDL functional proteins components apolipoprotein A1 (APOA1), apolipoprotein E (APOE), and lecithin-cholesterol acyltransferase (LCAT), while decreased inflammatory protein markers, such as serum amyloid A (SAA), apolipoprotein A4 (APOA4) and alpha 1 antitrypsin (A1AT). Furthermore, hepatic PON1 overexpression linked the effects of antioxidation and anti-inflammation with HDL metabolism regulation mainly through up-regulating liver X receptor alpha (LXRα) and its downstream genes. The pleiotropic effects involved promoting HDL biogenesis by raising the level of APOA1, increasing cholesterol uptake by the liver through the APOE-low density lipoprotein receptor (LDLR) pathway, and increasing cholesterol excretion into the bile, thereby reducing hepatic steatosis and aorta atherosclerosis in Western diet-fed mice.

Conclusions

Our study reveals that high-level PON1 improved dysfunctional HDL and alleviated the development of atherosclerosis in Scarb1^−/− mice. It is suggested that PON1 represents a promising target of HDL-based therapeutic strategy for HDL-related atherosclerotic cardiovascular disease.

Myeloperoxidase-induced modification of HDL by isolevuglandins inhibits paraoxonase-1 activity

Reduced activity of paraoxonase 1 (PON1), a high-density lipoprotein (HDL)-associated enzyme, has been implicated in the development of atherosclerosis. Post-translational modifications of PON1 may represent important mechanisms leading to reduced PON1 activity. Under atherosclerotic conditions, myeloperoxidase (MPO) is known to associate with HDL. MPO generates the oxidants hypochlorous acid and nitrogen dioxide, which can lead to post-translational modification of PON1, including tyrosine modifications that inhibit PON1 activity. Nitrogen dioxide also drives lipid peroxidation, leading to the formation of reactive lipid dicarbonyls such as malondialdehyde and isolevuglandins, which modify HDL and could inhibit PON1 activity. Because isolevuglandins are more reactive than malondialdehyde, we used in vitro models containing HDL, PON1, and MPO to test the hypothesis that IsoLG formation by MPO and its subsequent modification of HDL contributes to MPO-mediated reductions in PON1 activity. Incubation of MPO with HDL led to modification of HDL proteins, including PON1, by IsoLG. Incubation of HDL with IsoLG reduced PON1 lactonase and antiperoxidation activities. IsoLG modification of recombinant PON1 markedly inhibited its activity, while irreversible IsoLG modification of HDL before adding recombinant PON1 only slightly inhibited the ability of HDL to enhance the catalytic activity of recombinant PON1. Together, these studies support the notion that association of MPO with HDL leads to lower PON1 activity in part via IsoLG-mediated modification of PON1, so that IsoLG modification of PON1 could contribute to increased risk for atherosclerosis, and blocking this modification might prove beneficial to reduce atherosclerosis.

Current Understanding of the Immunomodulatory Activities of High-Density Lipoproteins

Lipoproteins interact with immune cells, macrophages and endothelial cells - key players of the innate and adaptive immune system. High-density lipoprotein (HDL) particles seem to have evolved as part of the innate immune system since certain HDL subspecies contain combinations of apolipoproteins with immune regulatory functions. HDL is enriched in anti-inflammatory lipids, such as sphingosine-1-phosphate and certain saturated lysophospholipids. HDL reduces inflammation and protects against infection by modulating immune cell function, vasodilation and endothelial barrier function. HDL suppresses immune cell activation at least in part by modulating the cholesterol content in cholesterol/sphingolipid-rich membrane domains (lipid rafts), which play a critical role in the compartmentalization of signaling pathways. Acute infections, inflammation or autoimmune diseases lower HDL cholesterol levels and significantly alter HDL metabolism, composition and function. Such alterations could have a major impact on disease progression and may affect the risk for infections and cardiovascular disease. This review article aims to provide a comprehensive overview of the immune cell modulatory activities of HDL. We focus on newly discovered activities of HDL-associated apolipoproteins, enzymes, lipids, and HDL mimetic peptides.

Complex Coronary Instent Chronic Total Occlusion Lesions: Oxidative Stress, Inflammation, and Coronary Stent Lengths

The oxidative stress and inflammation played the key roles in the development of atherosclerotic coronary plaques. However, the relationships between pro/antioxidant, pro/anti-inflammatory status, and complex coronary instent chronic total occlusion lesions were not clear in the elderly patients with very long stent implantations. We tried to evaluate the roles of pro/antioxidant and pro/anti-inflammatory biomarkers in the diagnosis of complex reocclusion lesions in elderly patients after coronary stenting. We evaluated the expression levels of acrolein (ACR), malondialdehyde (MDA), high sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-α (TNF-α), superoxide dismutase 3 (SOD3), paraoxonase-1 (PON-1), endothelial nitric oxide synthase (eNOS), and stromal cell-derived factor-1α (SDF-1α) in the elderly patients with very long stent implantations and complex reocclusion lesions. Levels of ACR, MDA, hs-CRP, and TNF-α were remarkably increased (P < 0.001), and levels of SOD3, PON-1, eNOS, and SDF-1α were decreased significantly (P < 0.001) in the elderly patients with very long stents and complex reocclusion lesions. The prooxidant and proinflammatory biomarkers were remarkably increased, as well as antioxidant and anti-inflammatory biomarkers were decreased significantly in the elderly patients with very long stent implantations and complex reocclusion lesions after coronary stenting. In conclusion, these findings indicated that the imbalance between prooxidant/proinflammatory and antioxidant/anti-inflammatory status was associated with complex reocclusion lesions, suggesting that oxidative stress and inflammation played the key roles in progression of complex reocclusion lesions in the elderly patients with very long stent implantations.

Flavonoids-Macromolecules Interactions in Human Diseases with Focus on Alzheimer, Atherosclerosis and Cancer

Flavonoids, a class of polyphenols, consumed daily in our diet, are associated with a reduced risk for oxidative stress (OS)-related chronic diseases, such as cardiovascular disease, neurodegenerative diseases, cancer, and inflammation. The involvement of flavonoids with OS-related chronic diseases have been traditionally attributed to their antioxidant activity. However, evidence from recent studies indicate that flavonoids' beneficial impact may be assigned to their interaction with cellular macromolecules, rather than exerting a direct antioxidant effect. This review provides an overview of the recent evolving research on interactions between the flavonoids and lipoproteins, proteins, chromatin, DNA, and cell-signaling molecules that are involved in the OS-related chronic diseases; it focuses on the mechanisms by which flavonoids attenuate the development of the aforementioned chronic diseases via direct and indirect effects on gene expression and cellular functions. The current review summarizes data from the literature and from our recent research and then compares specific flavonoids' interactions with their targets, focusing on flavonoid structure-activity relationships. In addition, the various methods of evaluating flavonoid-protein and flavonoid-DNA interactions are presented. Our aim is to shed light on flavonoids action in the body, beyond their well-established, direct antioxidant activity, and to provide insights into the mechanisms by which these small molecules, consumed daily, influence cellular functions.

Endothelial Lipase Modulates Paraoxonase 1 Content and Arylesterase Activity of HDL

Endothelial lipase (EL) is a strong modulator of the high-density lipoprotein (HDL) structure, composition, and function. Here, we examined the impact of EL on HDL paraoxonase 1 (PON1) content and arylesterase (AE) activity in vitro and in vivo. The incubation of HDL with EL-overexpressing HepG2 cells decreased HDL size, PON1 content, and AE activity. The EL modification of HDL did not diminish the capacity of HDL to associate with PON1 when EL-modified HDL was incubated with PON1-overexpressing cells. The overexpression of EL in mice significantly decreased HDL serum levels but unexpectedly increased HDL PON1 content and HDL AE activity. Enzymatically inactive EL had no effect on the PON1 content of HDL in mice. In healthy subjects, EL serum levels were not significantly correlated with HDL levels. However, HDL PON1 content was positively associated with EL serum levels. The EL-induced changes in the HDL-lipid composition were not linked to the HDL PON1 content. We conclude that primarily, the interaction of enzymatically active EL with HDL, rather than EL-induced alterations in HDL size and composition, causes PON1 displacement from HDL in vitro. In vivo, the EL-mediated reduction of HDL serum levels and the consequently increased PON1-to-HDL ratio in serum increase HDL PON1 content and AE activity in mice. In humans, additional mechanisms appear to underlie the association of EL serum levels and HDL PON1 content.

Current Understanding of the Relationship of HDL Composition, Structure and Function to Their Cardioprotective Properties in Chronic Kidney Disease

In the general population, the ability of high-density lipoproteins (HDLs) to promote cholesterol efflux is a predictor of cardiovascular events, independently of HDL cholesterol levels. Although patients with chronic kidney disease (CKD) have a high burden of cardiovascular morbidity and mortality, neither serum levels of HDL cholesterol, nor cholesterol efflux capacity associate with cardiovascular events. Important for the following discussion on the role of HDL in CKD is the notion that traditional atherosclerotic cardiovascular risk factors only partially account for this increased incidence of cardiovascular disease in CKD. As a potential explanation, across the spectrum of cardiovascular disease, the relative contribution of atherosclerotic cardiovascular disease becomes less important with advanced CKD. Impaired renal function directly affects the metabolism, composition and functionality of HDL particles. HDLs themselves are a heterogeneous population of particles with distinct sizes and protein composition, all of them affecting the functionality of HDL. Therefore, a more specific approach investigating the functional and compositional features of HDL subclasses might be a valuable strategy to decipher the potential link between HDL, cardiovascular disease and CKD. This review summarizes the current understanding of the relationship of HDL composition, metabolism and function to their cardio-protective properties in CKD, with a focus on CKD-induced changes in the HDL proteome and reverse cholesterol transport capacity. We also will highlight the gaps in the current knowledge regarding important aspects of HDL biology.

Plasma paraoxonase1 activity in rats treated with monocrotophos: a study of the effect of duration of exposure

We have earlier demonstrated the potential of monocrotophos (MCP), a highly toxic organophosphorus insecticide (OPI), to elicit insulin resistance in rats after chronic exposure. Given the understanding of role of paraoxonase1 (PON1) in OPI toxicity and diabetes pathology, this study was envisaged to understand the effect of duration of exposure to MCP on plasma PON1 activity in rats. Rats were administered MCP per os at 1/20 and 1/10^th LD₅₀ as daily doses for 180 days. Interim blood samples were collected at 15, 30, 45, 90 and 180 d for analysis of plasma parameters. Exposure to MCP for 45 resulted in persistent trend of hyperinsulinemia, while significant increase in fasting glucose levels was observed after 180 days. MCP caused suppression of plasma cholinesterase activity though the study period, albeit extent of inhibition was more severe during the early phase of the study. Exposure to MCP for 180 d resulted in hypertriglyceridemia and marginal decrease in HDL-C levels. MCP failed to modulate PON1 activity in plasma during the early phase of the study (up to 45 d). However, prolonged exposure resulted in significant increase in the plasma PON1 activity. This suggests that manifestation of insulin resistance in rats subjected to chronic exposure to MCP is associated with increase in PON1 activity. Our work provides rationale for studying whether the increase in PON1 activity observed in the present study serves to counter the deleterious effect of long term exposure to organophosphorus insecticides on metabolic homeostasis.

Study on molecular mechanisms of nattokinase in pharmacological action based on label-free liquid chromatography-tandem mass spectrometry

Cardiovascular diseases (CVDs) are the leading causes of premature death and disability in people around the world. Therefore, the prevention and treatment of CVDs has become an important subject. In this study, we verified the thrombolytic activities of a nattokinase-like protease named NK-01 in vivo. Label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS) technique was used in our study. NK-01 could inhibit the activity of coagulation factors though the up-regulation of proteinase C inhibitors and protein S. NK-01 also could inhibit the angiotensinogen conversion to AngII and promote the degradation of kininogen to reduce the blood pressure. In addition, NK-01 could increase the content of paraoxonase 1, which could prevent atherosclerosis. In our study, we found that NK-01 cloud effect some key proteins which participant in CVDs associated metabolic processes such as coagulation system, blood pressure, and atherosclerosis. Taken together, the underlying molecular mechanisms for the biological beneficial of NK-01 were investigated. Our proteomic study will provide further theoretical basis for application of NK in prevention or adjuvant treatment in biomedicine areas.

Expression levels of paraoxonase-1 in aortic valve tissue are associated with the progression of calcific aortic valve stenosis

Background

Paraoxonase-1 (PON1) participates in several vital steps of lipid metabolism, which is associated with calcific aortic valve stenosis (CAVS). Although a few studies have suggested that PON1 in blood could inhibit aortic valve calcification, they did not provide detailed descriptions. In this study, we hypothesized that PON1 is expressed in the aortic valve and that the PON1 level is related to the severity of CAVS.

Methods

A total of 118 consecutive patients with CAVS were enrolled in the study; 35 individuals without aortic valve calcification were included in the control group. Aortic valve tissue was obtained from postoperative pathologic specimens. PON1 was detected qualitatively using immunohistochemistry and quantitatively using an enzyme-linked immunosorbent assay. The severity of aortic stenosis was evaluated using echocardiography.

Results

We detected PON1 in the aortic valve and noticed that the PON1 level was significantly lower in the case group than in the control group (P<0.001). Furthermore, we found no significant difference between the mild and moderate stenosis groups (P=0.395). However, the PON1 levels were obviously higher in both the mild and moderate stenosis groups than in the severe stenosis group (both P<0.001). We also detected a significant negative correlation between PON1 level and the maximum aortic valve gradient in the case group.

Conclusions

We detected PON1 in the aortic valve for the first time, and our results suggest that the PON1 level in aortic valve tissue decreases with increasing severity of aortic valve stenosis.

Circulating Oxidative Stress Biomarkers in Clinical Studies on Type 2 Diabetes and Its Complications

Type 2 diabetes (T2DM) and its complications constitute a major worldwide public health problem, with high rates of morbidity and mortality. Biomarkers for predicting the occurrence and development of the disease may therefore offer benefits in terms of early diagnosis and intervention. This review provides an overview of human studies on circulating biomarkers of oxidative stress and antioxidant defence systems and discusses their usefulness from a clinical perspective. Most case-control studies documented an increase in biomarkers of oxidative lipid, protein, and nucleic acid damage in patients with prediabetes and in those with a diagnosis of T2DM compared to controls, and similar findings were reported in T2DM with micro- and macrovascular complications compared to those without. The inconsistence of the results regarding antioxidant defence systems renders difficulty to draw a general conclusion. The clinical relevance of biomarkers of oxidative lipid and protein damage for T2DM progression is uncertain, but prospective studies suggest that markers of oxidative nucleic acid damage such as 8-hydroxy-2'-deoxyguanosine and 8-hydroxyguanosine are promising for predicting macrovascular complications of T2DM. Emerging evidence also points out the relationship between serum PON1 and serum HO1 in T2DM and its complications. Overall, enhanced oxidative damage represents an underlying mechanism of glucose toxicity in T2DM and its related micro- and macrovascular complications suggesting that it may be considered as a potential additional target for pharmacotherapy. Therefore, further studies are needed to understand whether targeting oxidative stress may yield clinical benefits. In this view, the measurement of oxidative stress biomarkers in clinical trials deserves to be considered as an additional tool to currently used parameters to facilitate a more individualized treatment of T2DM in terms of drug choice and patient selection.

Paraoxonases Activities and Polymorphisms in Elderly and Old-Age Diseases: An Overview

Aging is defined as the accumulation of progressive organ dysfunction. There is much evidence linking the involvement of oxidative stress in the pathogenesis of aging. With increasing age, susceptibility to the development of diseases related to lipid peroxidation and tissue injury increases, due to chronic inflammatory processes, and production of reactive oxygen species (ROS) and free radicals. The paraoxonase (PON) gene family is composed of three members (PON1, PON2, PON3) that share considerable structural homology and are located adjacently on chromosome 7 in humans. The most studied member product is PON1, a protein associated with high-density lipoprotein with paraoxonase/esterase activity. Nevertheless, all the three proteins prevent oxidative stress. The major aim of this review is to highlight the importance of the role of PON enzymes in the aging process, and in the development of the main diseases present in the elderly: cardiovascular disease, diabetes mellitus, neurodegenerative diseases, and cancer.

Serum paraoxonase 1 activity is paradoxically maintained in nonalcoholic fatty liver disease despite low HDL cholesterol

Nonalcoholic fatty liver disease (NAFLD) is characterized by low HDL cholesterol, but the activity of the HDL-associated antioxidative enzyme paraoxonase-1 (PON-1) remains unclear. To determine the association of PON-1 with suspected NAFLD, we measured serum enzyme activity in 7,622 participants of the Prevention of Renal and Vascular End-Stage Disease cohort. A fatty liver index (FLI) ≥60, a proxy of NAFLD, was present in 2,083 participants (27.3%) and coincided with increased prevalence of T2D, metabolic syndrome (MetS), (central) obesity, elevated triglycerides, and low HDL cholesterol (all P < 0.001). In men and women combined, serum PON-1 activity did not vary according to elevated FLI (P = 0.98), whereas in men with elevated FLI PON-1 activity was increased (P = 0.016). In multivariable linear regression analyses (adjusted for age, sex, T2D, MetS, alcohol use, and smoking), PON-1 activity was unexpectedly associated with elevated FLI (β = 0.083; P < 0.001). In a sensitivity analysis (n = 5,126) that excluded subjects with positive cardiovascular history, impaired estimated glomerular filtration rate, elevated urinary albumin excretion, and drug use, PON-1 activity was also independently associated with elevated FLI (β = 0.045; P = 0.017). These results indicate that PON-1 is paradoxically maintained and may even be increased in NAFLD despite inverse associations with metabolic disorders and low HDL cholesterol.

Exogenous (Pomegranate Juice) or Endogenous (Paraoxonase1) Antioxidants Decrease Triacylglycerol Accumulation in Mouse Cardiovascular Disease-Related Tissues

The polyphenol-rich pomegranate juice (PJ) and the high-density lipoprotein (HDL)-associated paraoxonase1 (PON1) are known as potent atheroprotective antioxidants, but their effects on other tissues related to cardiovascular disease (CVD) remain unknown. The current study aimed to investigate the effects of treating mice with PJ or recombinant PON1 (rePON1) on the oxidation and lipid status of CVD-related tissues: serum, aorta, heart, liver, kidney, visceral, and subcutaneous adipose tissues (VAT and SAT). Both PJ consumption and rePON1 injection decreased the serum levels of thiobarbituric acid-reactive substances (16% and 19%) and triacylglycerols (TAG, 24% and 27%), while only rePON1 increased the levels of thiol groups (35%) and decreased serum cholesterol (15%). Both PJ and rePON1 significantly decreased aortic cholesterol (38% and 32%) and TAG (62% and 58%) contents in association with downregulation of the key TAG biosynthetic enzyme diacylglycerol O-acyltransferase 1 (DGAT1, 71% and 65%), while only PJ decreased aortic lipid peroxides (47%). Substantial TAG-lowering effects of both PJ and rePON1 were observed also in the heart (31% and 42%), liver (34% and 42%), and kidney (42% and 57%). In both VAT and SAT, rePON1 decreased the levels of lipid peroxides (28% and 25%), while PJ decreased the TAG content (22% and 18%). Ex vivo incubation of SAT with serum derived from mice that consumed PJ or injected with rePON1 decreased SAT lipid peroxides (35% or 28%) and TAG mass (12% or 10%). These novel findings highlight potent TAG-lowering properties of exogenous (PJ) and endogenous (PON1) antioxidants in tissues associated with CVD.

Serum paraoxonase-1 activity is associated with light to moderate alcohol consumption: the PREVEND cohort study

Background

Paraoxonase-1 (PON-1) is a high-density lipoprotein (HDL)-associated enzyme with antioxidative properties, which may protect against the development of cardiovascular disease. Alcohol consumption increases HDL cholesterol, but the extent to which alcohol consumption gives rise to higher serum PON-1 activity is uncertain.

Objective

In a population-based study, we determined the relation of serum PON-1 activity with alcohol consumption when taking account of HDL cholesterol and apolipoprotein A-I (apoA-I), its major apolipoprotein.

Design

A cross-sectional study was performed in 8224 participants of the Prevention of Renal and Vascular End-Stage Disease (PREVEND) cohort. Alcohol consumption was categorized as 1) no/rarely (25.3%); 2) 0.1-10 g/d (49.3%); 3) 10-30 g/d (20.1%); and 4) >30 g/d (5.2%) with 1 drink equivalent to 10 g alcohol. Serum PON-1 activity was measured as its arylesterase activity (phenyl acetate as substrate).

Results

Median serum PON-1 activity was 50.8, 53.1, 54.4, and 55.7 U/L in the 4 categories of alcohol consumption, respectively (P < 0.001). Its increase paralleled the increments in HDL cholesterol and apoA-I. Notably, there was no further increase in PON-1 activity, HDL cholesterol, and apoA-I when alcohol consumption was increased from 10-30 g/d to >30 g/d. Multivariable linear regression analysis demonstrated that PON-1 activity was related to alcohol consumption independently from clinical covariates, high sensitivity C-reactive protein, and lipid concentrations, including HDL cholesterol (P < 0.001 for each category of alcohol consumption with no alcohol consumption as the reference category). Notably, as inferred from standardized β-coefficients, there was no difference in PON-1 activity between 10-30 g alcohol/d and >30 g alcohol/d.

Conclusions

Alcohol consumption is associated with an increase in serum PON-1 activity, but its effect seems to reach a plateau with alcohol consumption of 10-30 g/d.

Feasibility of a plasma bioassay to assess oxidative protection of low-density lipoproteins by high-density lipoproteins

BACKGROUND

Traditionally, the impact of lipoproteins on vascular disease has been evaluated in light of their quantity, that is, cholesterol content, in plasma. However, recent studies of high-density lipoproteins (HDLs) have focused on functionality with regard to atheroprotection. For example, bioassays have emerged to assess the ability of HDL, in its near native plasma environment, to promote cholesterol removal (efflux) from cells. As a result, attention has focused on developing plasma-based assays for other putative HDL protective functions including protecting low-density lipoproteins (LDLs) from oxidative damage.

OBJECTIVE

To determine the feasibility of such an assay in a complex sample such as plasma, we evaluated the contribution of HDL vs other plasma factors in preventing LDL oxidation.

METHODS

We separated normolipidemic human plasma by gel filtration chromatography and assessed each fraction for its ability to prevent LDL modification by water soluble radical and copper-initiated oxidation mechanisms.

RESULTS

Using proteomics and selective precipitation methods, we identified major antioxidative contributions for fibrinogen, immunoglobulin G, albumin, and small soluble molecules like uric acid and ascorbate, with albumin being especially dominant in copper-initiated mechanisms. HDL particles were minor contributors (∼1%-2%) to the antioxidant capacity of plasma, irrespective of oxidation mechanism.

CONCLUSIONS

Given the overwhelming background of antioxidant capacity inherent to highly abundant plasma proteins, specific bioassays of HDL antioxidative function will likely require its complete separation from plasma.

High density lipoprotein proteome is associated with cardiovascular risk factors and atherosclerosis burden as evaluated by coronary CT angiography

BACKGROUND AND AIMS

High density lipoprotein cholesterol (HDL-C) is associated with risk of cardiovascular disease (CVD); however, therapeutic manipulations of HDL-C have failed to reduce CVD events. This suggests that HDL-C and the atheroprotective capacity of HDL are not directly linked. The goal of this study was to evaluate the relationships between HDL-bound proteins and measures of atherosclerosis burden and HDL function.

METHODS

The HDL proteome was analyzed using mass spectrometry in 126 human subjects, who had undergone coronary computed tomography angiography (CCTA) to quantify calcified (CB) and non-calcified (NCB) atherosclerosis burden. Partial least squares regression analysis was used to evaluate associations between HDL-bound proteins and CB, NCB, or cholesterol efflux capacity (CEC).

RESULTS

Significant overlap was found among proteins associated with NCB and CEC. Proteins that were associated with NCB displayed an inverse relationship with CEC, supporting a link between this protective function of HDL and clinical plaque burden. CB was associated with a set of proteins mostly distinct from NCB and CEC. When CVD risk factors were evaluated, BMI had a stronger influence on important HDL proteins than gender, age, or HDL-C. Most HDL proteins associated with function or atherosclerosis burden were not significantly correlated with HDL-C.

CONCLUSIONS

These findings indicate that the HDL proteome contains information not captured by HDL- C and, therefore, has potential for future development as a biomarker for CVD risk. Additionally, the proteome effects detected in this study may provide HDL compositional goals for evaluating new and existing HDL-modification therapies.

Mahdy E, R. Youness E, Shafee N, S.S. Mowafy M, M. Mabrouk M. Effect of Co Enzyme Q10 Alone or in Combination with Vitamin C on Lipopolysaccharide-Induced Brain Injury in Rats

Our was to determine the impact of CoenzymeQ10 (Co Q10) and vitamin C alone or in combination on oxidative stress in brain tissue of rats during endotoxemia induced by single intraperitoneal dose of Lipopolysaccharide (LPS), 500µg/kg. Both CoQ10&vitamin C were given orally to rats with doses (200&100 mg/kg) respectively for 7successive days prior induction of endotoxemia .LPS injected, with Co Q10 with doses (100 &200 mg/kg) &vit. C (50&100 mg/kg).In addition CoQ10 and vitamin C together in doses (100&50 mg/kg) & (200&100 mg/kg) respectively were added to LPS-treated rats. Then euthanized 4 hours later. Histopathological assessment of brain tissue was done. Results: LPS injection induced oxidative stress in brain tissue, resulting in marked increase in malondiadehyde (MDA), nitrite (NO) and Amyloid beta (Aβ), while decreasing reduced glutathione (GSH), paraoxonase-1 (PON1) and brain derived neurotrophic factor (BDNF).CoQ10 and vit.C administration with doses(200&100 mg/ kg) before endotoxemia result in reduction of brain MDA, NO and Aβ, while increasing levels of GSH, PON1 and BDNF compared to controls. The addition of both Co Q10 &vit.C to LPS- treated rats lead to decrease of brain NO, MDA and Aβ, also increase of GSH, PON1 and BDNF. This effect was more obviouswith high doses, this due to the ameliorating effect of both CoQ10 and vit.C on oxidative stress of brain tissue during endotoxemia.This consisted with the histopathological results. Conclusion: this work focuses on the possible role of CoQ10 &vit.C as antioxidants in protecting brain tissue.

Genome-wide mapping of plasma protein QTLs identifies putatively causal genes and pathways for cardiovascular disease

Identifying genetic variants associated with circulating protein concentrations (protein quantitative trait loci; pQTLs) and integrating them with variants from genome-wide association studies (GWAS) may illuminate the proteome's causal role in disease and bridge a knowledge gap regarding SNP-disease associations. We provide the results of GWAS of 71 high-value cardiovascular disease proteins in 6861 Framingham Heart Study participants and independent external replication. We report the mapping of over 16,000 pQTL variants and their functional relevance. We provide an integrated plasma protein-QTL database. Thirteen proteins harbor pQTL variants that match coronary disease-risk variants from GWAS or test causal for coronary disease by Mendelian randomization. Eight of these proteins predict new-onset cardiovascular disease events in Framingham participants. We demonstrate that identifying pQTLs, integrating them with GWAS results, employing Mendelian randomization, and prospectively testing protein-trait associations holds potential for elucidating causal genes, proteins, and pathways for cardiovascular disease and may identify targets for its prevention and treatment.

Punicalagin Decreases Serum Glucose Levels and Increases PON1 Activity and HDL Anti-Inflammatory Values in Balb/c Mice Fed a High-Fat Diet

Polyphenols are consumed daily in the human diet and are associated with reduced risk of a number of chronic diseases, including cancer, cardiovascular disease, and diabetes. Traditionally, the health benefits of polyphenols have been attributed to their antioxidant activity, but many studies might be hampered by oral administration and insignificant bioavailability. Rather than exerting a direct antioxidant effect, the mechanisms by which polyphenols express their beneficial effect seem to involve their interaction with proteins. The present study is aimed at broadening and confirming our recently published in vitro results showing that polyphenols may reduce atherosclerosis risk via interaction with proteins and lipoproteins related to atherosclerosis. The biological functions of punicalagin and quercetin in relation to glucose and lipid levels, paraoxonase 1 (PON1) activity, and inflammation were examined in vivo. Mice were fed a high-fat diet (HFD) for 12 weeks, and during the last 4 weeks, they received subcutaneous treatments via implanted minipumps, which released physiological concentrations of punicalagin, quercetin, or atorvastatin (as a positive control) daily into the serum. The HFD reduced serum PON1 activity, whereas punicalagin administration restored PON1 activity to the level of mice fed a normal diet. In addition, punicalagin significantly reduced glucose levels in HFD mice and improved HDL anti-inflammatory properties. In conclusion, beyond antioxidant activity, the mechanisms by which polyphenols exert their beneficial properties appear to involve their interaction with serum proteins that mediate HDL function and lipid-glucose state in the circulation.

Paraoxonase-1 is a better indicator than HDL of Atherosclerosis - A pilot study in North Indian population

OBJECTIVES

The present study aims to evaluate the levels of HDL and Paraoxonase-1 (PON1) and their correlation in atherosclerotic patients with and without diabetic mellitus (DM) as well as in control subjects in Northern Indian population.

MATERIALS AND METHODS

We analyzed lipid profiles and Serum PON1 levels by automated analyzer and ELISA, respectively. Study subjects (N = 150) were divided in three groups; Group I: Atherosclerotic patients without DM (N = 50), Group II: Atherosclerotic patients with DM (N = 50); Group III: Controls (N = 50).

RESULTS

We found a significantly (p < 0.0001) low levels of HDL-C in Group I (32.2 ± 7.3) and Group II (36.9 ± 11.5) as compared to Group III (41.0 ± 7.1). PON-1 levels were also significantly lower in Group I (60.1 ± 10.5) and Group II (50.0 ± 13.9) when compared to Group III (95.0 ± 12.0). We observed a significant correlation (r = 0.59, p < 0.001) between the levels of PON1 and HDL-C in study subjects.

CONCLUSIONS

The reduced levels of HDL and PON-1 and their significant correlation in CAD patients may be associated with the pathogenesis of this disease. Considering HDL as a dependent variable, Paraoxonase-1 is the most important parameter contributing to the total variation in HDL in CAD.

Dysfunctional HDL in diabetes mellitus and its role in the pathogenesis of cardiovascular disease

Coronary artery disease, the leading cause of death in the developed and developing countries, is prevalent in diabetes mellitus with 68% cardiovascular disease (CVD)-related mortality. Epidemiological studies suggested inverse correlation between HDL and CVD occurrence. Therefore, low HDL concentration observed in diabetic patients compared to non-diabetic individuals was thought to be one of the primary causes of increased risks of CVD. Efforts to raise HDL level via CETP inhibitors, Torcetrapib and Dalcetrapib, turned out to be disappointing in outcome studies despite substantial increases in HDL-C, suggesting that factors beyond HDL concentration may be responsible for the increased risks of CVD. Therefore, recent studies have focused more on HDL function than on HDL levels. The metabolic environment in diabetes mellitus condition such as hyperglycemia-induced advanced glycation end products, oxidative stress, and inflammation promote HDL dysfunction leading to greater risks of CVD. This review discusses dysfunctional HDL as one of the mechanisms of increased CVD risks in diabetes mellitus through adversely affecting components that support HDL function in cholesterol efflux and LDL oxidation. The dampening of reverse cholesterol transport, a key process that removes cholesterol from lipid-laden macrophages in the arterial wall, leads to increased risks of CVD in diabetic patients. Therapeutic approaches to keep diabetes under control may benefit patients from developing CVD.

Cardiovascular risk in patients with rheumatoid arthritis

Substantial epidemiologic data have shown an increased risk of cardiovascular (CV) disease in rheumatoid arthritis (RA) patients. Traditional CV risk factors may partly contribute to CV disease in RA; however, current evidence underlines the important role of inflammation in the pathogenesis of atherosclerosis and amplification of CV risk. Interplays between inflammation and lipid metabolism in the development of atherosclerosis have been established by recent scientific advances. Atherosclerosis is currently viewed as an inflammatory disease, and modifications of lipoproteins during inflammation accelerate atherogenesis. The role of inflammation in the increased CV risk in RA has been further demonstrated by the CV protective effect of methotrexate and TNF antagonists, particularly in patients responding to these treatments. The management of CV risk in RA should include the use of effective disease-modifying anti-rheumatic drugs to control disease activity and the treatment of traditional CV risk factors.

Dynamic changes of paraoxonase 1 activity towards paroxon and phenyl acetate during coronary artery surgery

BACKGROUND

Serum paraoxonase 1 (PON1), an enzyme associated with high - density lipoproteins (HDL) particles, inhibits the oxidation of serum lipoproteins and cell membranes. PON1 activity is lower in patients with atherosclerosis and in inflammatory diseases. The systemic inflammatory response provoked during cardiopulmonary bypass grafting may contribute to the development of postoperative complications. The aim of the present study was to estimate the dynamic changes in paraoxonase 1 (PON1) activity towards paraoxon and phenyl acetate during and after coronary artery surgery.

METHODS

Twenty six patients with coronary heart disease undergoing coronary artery bypass grafting (CABG) were enrolled into the study. Venous blood samples were obtained preoperatively, after aortic clumping, after the end of operation, at 6, 18, 30 and 48 h after operation. Paraoxonase activity was measured spectrophotometrically in 50 mM glycine/NaOH buffer (pH 10.5) containing 1.0 mM paraoxon, and 1.0 mM CaCl₂. Arylesterase activity was measured in 20 mM TrisCl buffer (pH 8.0) containing 1 mM phenyl acetate and 1 mM CaCl₂.

RESULTS

PON1 activity toward paraoxon and phenyl acetate significantly decreased after aorta cross clumping and increased directly after operation. PON1 activity towards paraoxon in preoperative period and PON1 activity towards phenyl acetate in seventh stage of experiment tended to inversely correlate with the occurrence of postoperative complications.

CONCLUSION

The paraoxonase 1 plasma activity is markedly reduced during CABG surgery.

Ion-Current-Based Temporal Proteomic Profiling of Influenza-A-Virus-Infected Mouse Lungs Revealed Underlying Mechanisms of Altered Integrity of the Lung Microvascular Barrier

Investigation of influenza-A-virus (IAV)-infected lung proteomes will greatly promote our understanding on the virus-host crosstalk. Using a detergent-cocktail extraction and digestion procedure and a reproducible ion-current-based method, we performed the first comprehensive temporal analysis of mouse IAV infection. Mouse lung tissues at three time points post-inoculation were compared with controls (n = 4/group), and >1600 proteins were quantified without missing value in any animal. Significantly changed proteins were identified at 4 days (n = 144), 7 days (n = 695), and 10 days (n = 396) after infection, with low false altered protein rates (1.73-8.39%). Functional annotation revealed several key biological processes involved in the systemic host responses. Intriguingly, decreased levels of several cell junction proteins as well as increased levels of tissue metalloproteinase MMP9 were observed, reflecting the IAV-induced structural breakdown of lung epithelial barrier. Supporting evidence of MMP9 activation came from immunoassays examining the abundance and phosphorylation states of all MAPKs and several relevant molecules. Importantly, IAV-induced MMP gelatinase expression was suggested to be specific to MMP9, and p38 MAPK may contribute predominantly to MMP9 elevation. These findings help to resolve the long-lasting debate regarding the signaling pathways of IAV-induced MMP9 expression and shed light on the molecular mechanisms underlying pulmonary capillary-alveolar leak syndrome that can occur during influenza infection.

Anti-atherogenic properties of high-density lipoproteins in psychiatric patients before and after two months of atypical anti-psychotic therapy

Some of the medications used for the management of schizophrenia are associated with clinically significant increases in weight and adverse alterations in serum lipid levels. The aim of the study was to investigate the effect of short-term (two months) treatment with atypical anti-psychotics on coronary heart disease risk factors, including the functional properties of high-density lipoprotein (HDL), in psychiatric patients. Nineteen patients diagnosed with schizophrenia, schizoaffective, and bipolar disorder and ten healthy volunteers were enrolled in the study. In the present study blood was drawn at baseline and after two months of atypical anti-psychotic treatment. Wilcoxon non-parametric-test was used to examine differences in the psychotic group before and two months after treatment.Waist circumference and oxidative stress in psychiatric patients were higher compared with the control group. Serum-mediated cholesterol efflux capacity was lower in psychotic patients compared to controls. Two months of anti-psychotic therapy was associated with increased abdominal obesity, decreased paraoxonase lactonase activity, but with no further change in serum-mediated cholesterol efflux from macrophages. Psychotic patients have low serum-mediated cholesterol efflux from macrophages as a parameter of HDL functionality. Atypical anti-psychotic treatment for two months increased metabolic derangements in these patients but without further decrement in serum-mediated cholesterol efflux.

A Cluster of Proteins Implicated in Kidney Disease Is Increased in High-Density Lipoprotein Isolated from Hemodialysis Subjects

Cardiovascular disease is the leading cause of death in end-stage renal disease (ESRD) patients treated with hemodialysis. An important contributor might be a decline in the cardioprotective effects of high-density lipoprotein (HDL). One important factor affecting HDL's cardioprotective properties may involve the alterations of protein composition in HDL. In the current study, we used complementary proteomics approaches to detect and quantify relative levels of proteins in HDL isolated from control and ESRD subjects. Shotgun proteomics analysis of HDL isolated from 20 control and 40 ESRD subjects identified 63 proteins in HDL. Targeted quantitative proteomics by isotope-dilution selective reaction monitoring revealed that 22 proteins were significantly enriched and 6 proteins were significantly decreased in ESRD patients. Strikingly, six proteins implicated in renal disease, including B2M, CST3, and PTGDS, were markedly increased in HDL of uremic subjects. Moreover, several of these proteins (SAA1, apoC-III, PON1, etc.) have been associated with atherosclerosis. Our observations indicate that the HDL proteome is extensively remodeled in uremic subjects. Alterations of the protein cargo of HDL might impact HDL's proposed cardioprotective properties. Quantifying proteins in HDL may be useful in the assessment of cardiovascular risk in patients with ESRD and in assessing response to therapeutic interventions.

Human paraoxonase-1 (PON1): Gene structure and expression, promiscuous activities and multiple physiological roles

Human PON1 is a HDL-associated lipolactonase capable of preventing LDL and cell membrane oxidation and is therefore considered to be atheroprotective. PON1 contributes to the antioxidative function of HDL and reductions in HDL-PON1 activity, prevalent in a wide variety of diseases with an inflammatory component, are believed to lead to dysfunctional HDL which can promote inflammation and atherosclerosis. However, PON1 is multifunctional and may contribute to other HDL functions such as in innate immunity, preventing infection by quorum sensing gram negative bacteria by destroying acyl lactone mediators of quorum sensing, and putative new roles in cancer development and the promotion of healthy ageing. In this review we explore the physiological roles of PON1 in disease development, as well as PON1 gene and protein structure, promiscuous activities and the roles of SNPs and ethnicity in determining PON1 activity.

Anticipatory role of high density lipoprotein and endothelial dysfunction: an overview

High Density Lipoprotein (HDL) has been witnessed to possess a range of different functions that contribute to its atheroprotective effects. These functions are: the promotion of macrophage cholesterol efflux, reverse cholesterol transport, anti-inflammatory, anti-thrombotic, anti-apoptotic, pro-fibrinolytic and anti-oxidative functions. Paraoxonase 1 (PON1) is an HDL associated enzyme esterase/homocysteinethiolactonase that contributes to the anti-oxidant and anti-atherosclerotic capabilities of HDL. PON1 is directly involved in the etiopathogenesis of atherosclerosis through the modulation of nitric oxide (NO) bioavailability. The aim of this review is to summarize the role of HDL on endothelial homeostasis, and also to describe the recently characterized molecular pathways involved.

Low paraoxonase 1 arylesterase activity and high von Willebrand factor levels are associated with severe coronary atherosclerosis in patients with non-diabetic stable coronary artery disease

Background

Paraoxonase 1 (PON1) activity and von Willebrand factor (VWF) release are associated with lesion initiation in atherosclerosis. Diabetes can complicate coronary artery disease (CAD) due to the production of advanced glycation end products. This study evaluated PON1 activity and VWF levels in non-post-acute coronary syndrome, stable CAD (SCAD) patients without diabetes.

Material/Methods

Non-diabetic SCAD patients and patients experiencing acute stress periods were selected (n=130). Forty-seven cases with normal coronary angiography and 50 healthy individuals served as controls. The non-diabetic SCAD group was then stratified into single-vessel lesions, multiple-vessel lesions, and mild or severe luminal stenosis according to the number and the degree of luminal stenoses. Serum PON1 paraoxonase and arylesterase activities, and plasma VWF levels were measured, as well as serum total cholesterol, total triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and apolipoprotein A1. PON1 arylesterase activity was detected with an ordinary chemistry system using a novel phenylacetate derivative.

Results

Both PON1 paraoxonase and arylesterase were lower in the non-diabetic SCAD group, but VWF levels were higher (versus controls, all P<0.001). PON1 paraoxonase activity (OR=0.991), PON1 arylesterase activity (OR=0.981), and VWF (OR 2.854) influenced SCAD in multiple logistic regression. Decreased PON1 arylesterase activity and increased VWF levels were associated with severe atherosclerosis in non-diabetic SCAD patients. We also observed a slight negative correlation between VWF and PON1 paraoxonase/arylesterase.

Conclusions

PON1 and VWF are detectable markers that may predict the severity of stenoses, ideally facilitating a non-diabetic SCAD diagnosis before the sudden onset of life-threatening symptoms.

Human carotid plaque phosphatidylcholine specifically interacts with paraoxonase 1, increases its activity, and enhances its uptake by macrophage at the expense of its binding to HDL

Human carotid atherosclerotic plaque is in direct contact with circulatory blood components. Thus, plaque and blood components may affect each other. The current study presents the effects of plaque chloroform:methanol (C:M) extract on the HDL-associated enzyme paraoxnase 1 (PON1). This study is part of our investigation on the mutual effects of the interactions between atherosclerotic lesions and blood components. Recombinant PON1 (rePON1) was incubated with the human carotid plaques C:M extract and PON1 activities were analyzed. Lactonase and paraoxonase activities were elevated due to C:M treatment, by 140 and by 69%, respectively. Analytical chemistry analyses revealed specific phosphatidylcholines (PCs) as the plaque active components. Tryptophan fluorescence quenching assay, together with molecular docking, shows that PON1 activity is enhanced in correlation with the level of PC affinity to PON1. Molecular docking revealed that PCs interact specifically with H2-PON1 α-helix, which together with H1 enzyme α-helix links the protein to the HDL surface. These findings are supported by additional results from the PON1 ∆20 mutant that lack its H1-α-helix. Incubation of this mutant with the plaque C:M extract increased PON1 activity by only 20%, much less than the wild-type PON1 that elevated PON1 activity at the same concentration by as much as 95%. Furthermore, as much as the affinity of the enzyme to the PC was augmented, the ability of PON1 to bind to the HDL particle decreased. Finally, PON1 interaction with PC enhance its uptake into the macrophage cytoplasm. In conclusions, Specific lesion phosphatidylcholines (PCs) present in the human carotid plaque significantly enhance PON1 catalytic activities due to their interaction with the enzyme. Such a lesion׳s PC-PON1 interaction, in turn, competes with HDL PCs and enhances PON1 uptake by macrophage at the expense of PON1 binding to the HDL.