Paraoxonase active site required for protection against LDL oxidation involves its free sulfhydryl group and is different from that required for its arylesterase/paraoxonase activities: selective action of human paraoxonase allozymes Q and R

PON1 has palmitoyl-protein thioesterase (PPT) activity, and can affect the presence of SR-B1 on the endothelial cell membrane

The high-density lipoprotein (HDL)-associated enzyme paraoxonase 1 (PON1) is expressed almost exclusively in the liver and is then transported by HDL to the peripheral tissues. The lipophilic nature of PON1 enables its easy exchange between the lipoprotein and cell membranes in a process that is dependent on the HDL receptor scavenger receptor class B, type 1 (SR-B1). In endothelial cells, PON1 binding to the cell membrane leads to its internalization by endocytosis and subsequent lysosomal degradation. PON1 is a "promiscuous" enzyme with unusually broad substrate specificity in vitro, but its actual function and substrate are still unknown. The enzyme requires a lipid environment and becomes completely inactive upon delipidation. However, when PON1 binds HDL, its active site faces the lipoprotein's core and is inaccessible to external substrates. Hence, the HDL-bound PON1 is inactive toward substrates outside the particle's lipid core and is rapidly degraded and becomes inactive upon internalization. Consequently, the enzyme is only active in the cell membrane during its transit from HDL to the cytoplasm. To assign a function to PON1, we investigated whether it is a palmitoyl-protein thioesterase (PPT) that can hydrolyze the palmitoyl moieties of membrane proteins involved in HDL and cholesterol transport, such as SR-B1, ABCA1, or their neighboring caveola proteins to facilitate the release of HDL or trigger its endocytosis. This study shows that PON1 can hydrolyze palmitoyl-cysteine thioester bonds in vitro, has direct or indirect PPT activity in vivo, and can significantly decrease the presence of SR-B1 in the endothelial membrane.

Genetic polymorphisms in the angiotensin converting enzyme, actinin 3 and paraoxonase 1 genes in women with diabetes and hypertension

Objective

To study associations between polymorphisms in the angiotensin converting enzyme (ACE I/D), actinin 3 (ACTN3 R577X) and paraoxonase 1 (PON1 T(-107)C) genes and chronic diseases (diabetes and hypertension) in women.

Materials and methods

Genomic DNA was extracted from saliva samples of 78 women between 18 and 59 years old used for genetic polymorphism screening. Biochemical data were collected from the medical records in Basic Health Units from Southern Brazil. Questionnaires about food consumption, physical activity level and socioeconomic status were applied.

Results

The XX genotype of ACTN3 was associated with low HDL levels and high triglycerides, total cholesterol and glucose levels. Additionally, high triglycerides and LDL levels were observed in carriers of the TT genotype of PON1, and lower total cholesterol levels were associated to the CC genotype. As expected, women with diabetes/hypertense had increased body weight, BMI (p = 0.02), waist circumference (p = 0.01), body fat percentage, blood pressure (p = 0.02), cholesterol, triglycerides (p = 0.02), and blood glucose (p = 0.01), when compared to the control group.

Conclusion

Both ACTN3 R577X and PON1 T(-107)C polymorphisms are associated with nutritional status and blood glucose and lipid levels in women with diabetes/hypertense. These results contribute to genetic knowledge about predisposition to obesity-related diseases.

Effect of Exercise Repetitions on Arylesterase Activity of PON1 in Plasma of Average-Trained Men-The Dissociation between Activity and Concentration

Exercise may increase the antioxidant capacity of plasma by stimulating antioxidant enzymes. The study aimed to measure the effect of three repetitions of acute exercise on arylesterase (ARE) activity of the paraoxonase 1 (PON1) enzyme. Eleven average-trained men (age 34.0 ± 5.2 years) completed three treadmill runs. ARE activity in plasma was evaluated spectrophotometrically and compared with PON1 concentration (PON1c), paraoxonase (PON) activity, and high-density lipoprotein cholesterol (HDL-C) at rest and after exercise. In all repetitions of the exercise, ARE activity remained stable, and ARE activity standardized for PON1c (ARE/PON1c) was lower post- than pre-exercise. The ARE/PON1c ratio changes returned to baseline levels during rest after each exercise session. Pre-exercise ARE activity correlated negatively with post-exercise C-reactive protein (CRP) (ρ = -0.35, p = 0.049), white blood cell count (WBC) (ρ = -0.35, p = 0.048), polymorphonuclear leukocytes (PMN) (ρ = -0.37, p = 0.037), and creatine kinase (CK) (ρ = -0.37, p = 0.036). ARE activity may be depleted under conditions of oxidative stress, as increases in PON1c during acute exercise did not result in parallel increases in ARE activity. No adaptation of the response of ARE activity to exercise was detected in subsequent exercise sessions. Individuals with lower pre-exercise ARE activity may develop a higher inflammatory response to strenuous exercise.

Paraoxonase-1: How a xenobiotic detoxifying enzyme has become an actor in the pathophysiology of infectious diseases and cancer

Both infectious and non-infectious diseases can share common molecular mechanisms, including oxidative stress and inflammation. External factors, such as bacterial or viral infections, excessive calorie intake, inadequate nutrients, or environmental factors, can cause metabolic disorders, resulting in an imbalance between free radical production and natural antioxidant systems. These factors may lead to the production of free radicals that can oxidize lipids, proteins, and nucleic acids, causing metabolic alterations that influence the pathogenesis of the disease. The relationship between oxidation and inflammation is crucial, as they both contribute to the development of cellular pathology. Paraoxonase 1 (PON1) is a vital enzyme in regulating these processes. PON1 is an enzyme that is bound to high-density lipoproteins and protects the organism against oxidative stress and toxic substances. It breaks down lipid peroxides in lipoproteins and cells, enhances the protection of high-density lipoproteins against different infectious agents, and is a critical component of the innate immune system. Impaired PON1 function can affect cellular homeostasis pathways and cause metabolically driven chronic inflammatory states. Therefore, understanding these relationships can help to improve treatments and identify new therapeutic targets. This review also examines the advantages and disadvantages of measuring serum PON1 levels in clinical settings, providing insight into the potential clinical use of this enzyme.

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.

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.

Cardioprotective Role for Paraoxonase-1 in Chronic Kidney Disease

Paraoxonase-1 (PON-1) is a hydrolytic enzyme associated with HDL, contributing to its anti-inflammatory, antioxidant, and anti-atherogenic properties. Deficiencies in PON-1 activity result in oxidative stress and detrimental clinical outcomes in the context of chronic kidney disease (CKD). However, it is unclear if a decrease in PON-1 activity is mechanistically linked to adverse cardiovascular events in CKD. We investigated the hypothesis that PON-1 is cardioprotective in a Dahl salt-sensitive model of hypertensive renal disease. Experiments were performed on control Dahl salt-sensitive rats (SSMcwi, hereafter designated SS-WT rats) and mutant PON-1 rats (SS-Pon1em1Mcwi, hereafter designated SS-PON-1 KO rats) generated using CRISPR gene editing technology. Age-matched 10-week-old SS and SS-PON-1 KO male rats were maintained on high-salt diets (8% NaCl) for five weeks to induce hypertensive renal disease. Echocardiography showed that SS-PON-1 KO rats but not SS-WT rats developed compensated left ventricular hypertrophy after only 4 weeks on the high-salt diet. RT-PCR analysis demonstrated a significant increase in the expression of genes linked to cardiac hypertrophy, inflammation, and fibrosis, as well as a significant decrease in genes essential to left ventricular function in SS-PON-1 KO rats compared to SS-WT rats. A histological examination also revealed a significant increase in cardiac fibrosis and immune cell infiltration in SS-PON-1 KO rats, consistent with their cardiac hypertrophy phenotype. Our data suggest that a loss of PON-1 in the salt-sensitive hypertensive model of CKD leads to increased cardiac inflammation and fibrosis as well as a molecular and functional cardiac phenotype consistent with compensated left ventricular hypertrophy.

Associação do Genótipo e Fenótipo da Paraoxonase-1 com Angiografia Positiva para Doença Arterial Coronariana

Fundamento

Tem sido demonstrado que um aumento dos níveis séricos de PON1 é protetor contra vários distúrbios. Foi relatado que vários polimorfismos de nucleotídeo único (SNPs, single nucleotide polymorphisms ) do gene PON1 estão associados a níveis e atividade de proteínas enzimáticas séricas.

Objetivos

Investigar a associação de SNPs do PON1 e atividade da paraoxonase sérica com a doença arterial coronariana (DAC).

Métodos

Foram estudados 601 pacientes não relacionados submetidos à angiografia coronária, incluindo aqueles com estenose >50% (N=266) e aqueles com estenose <30% (N=335). Os SNPs rs662 e rs840560 do gene da paraoxonase foram determinados utilizando o método ARMS-PCR e o SNP rs705379 foi genotipado utilizando análise de PCR-RFLP. A atividade da paraoxonase sérica foi medida utilizando paraoxon como substrato. O valor de p<0,05 foi considerado significante.

Resultados

A atividade da paraoxonase sérica não foi significativamente diferente entre os grupos de estudo. Após ajuste para idade, sexo, hipertensão, diabetes mellitus e dislipidemia, o genótipo GG e o modelo codominante de rs662 foram positivamente associados a uma angiografia positiva (respectivamente, OR = 2,424, IC 95% [1,123-5,233], p <0,05, OR = 1,663, IC 95% [1,086-2,547]). A atividade da paraoxonase sérica foi significativamente maior no alelo G e variante GG do polimorfismo rs662, alelo A e variante AA de rs854560 e alelo C e variante CC de rs705379. A análise de haplótipos mostrou que o haplótipo ATC foi significativamente mais prevalente no grupo com angiografia negativa. A análise entre os grupos indicou que o alelo A de rs662 foi significativamente associado à menor atividade da paraoxonase no grupo com angiografia positiva (p=0,019).

Conclusões

A presença do alelo G do polimorfismo de nucleotídeo único rs662 está independentemente associada ao aumento do risco de DAC.

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.

The Relationship between Cancer and Paraoxonase 1

Extensive research has been carried out to understand and elucidate the mechanisms of paraoxonase 1 (PON1) in the development of diseases including cancer, cardiovascular diseases, neurological diseases, and inflammatory diseases. This review focuses on the relationship between PON1 and cancer. The data suggest that PON1, oxidative stress, chronic inflammation, and cancer are closely linked. Certainly, the gene expression of PON1 will remain challenging to study. Therefore, targeting PON1, redox-sensitive pathways, and transcription factors promise prevention and therapy in the development of several diseases, including cancer.

The effect of Paraoxonase gene polymorphisms and paraoxonase enzyme activity on Non-Hodgkin lymphoma

Non-Hodgkin Lymphoma (NHL) is a malignant lymphoproliferative disease. Antioxidant paraoxonase enzyme (PON1) has a vital role in the elimination of potential carcinogenic organophosphate molecules. The polymorphisms in the PON1 gene, especially Q192R and L55M, may affect negatively the activity and synthesis of PON1 enzyme. The aim of this study was to evaluate the effect of these polymorphisms together with PON1 enzyme activity on NHL. We surveyed these polymorphisms together with PON1 enzyme activity in 93 patients with NHL and in 93 healthy individuals by real-time polymerase chain reaction (RT-PCR) and spectrophotometer. Although carrying the M and R alleles of L55M and Q192R polymorphisms increases the risk of NHL, they were not significant. Furthermore, the NHL patients carrying 192 R allele had significantly lower enzyme activity than controls having same allele (P = 0.025). This research is the first study worldwide investigating the effect of Q192R and L55M polymorphisms on PON1 enzyme activity in NHL disease. The risk of developing NHL may be further increased in individuals with low enzyme activity having R risk allele of the Q192R polymorphism. The present study suggests that these polymorphisms in NHL disease should be analyzed together with PON1 enzyme activity in larger populations.Supplemental data for this article is available online at https://doi.org/10.1080/15257770.2022.2052315 .

The Effects of Acute and Chronic Exercise on Paraoxonase-1 (PON1): A Systematic Review With Meta-Analysis

Purpose: To determine the acute and chronic effects of exercise on Paraoxonase-1 (PON1) concentration and activity. Methods: A literature search was performed using 16 electronic databases. Effect sizes (ES) were computed and two-tailed α values < .05 and non-overlapping 95% confidence intervals (95%CI) were considered statistically significant. Heterogeneity, inconsistency (I²), and small-study effects using the LFK index were examined. Results: Eighteen studies (n = 377 participants) met the criteria for inclusion. The acute effects of exercise on PON1 concentration were trivial and non-significant (ES = -.03, 95%CI = -.39 to .34, p > .05), heterogeneous (p = .05), moderately inconsistent (I² = 48%), with minor asymmetry (LFK index = 1.34). The chronic effects of exercise on PON1 concentration were also trivial and non-significant (ES = -.04, 95%CI = -.53 to.45, p > .05), homogenous (p = .65), displayed low inconsistency (I² = 0%), and minor asymmetry (LFK index = -1.14). The acute effects of exercise on PON1 activity were trivial and non-significant (ES = .11, 95%CI = -.02 to.24, p > .05), homogenous (p = .85), showed low inconsistency (I² = 0%), and no asymmetry (LFK index = .82). The chronic effects of exercise on PON1 activity were trivial and non-significant (ES = .31, 95%CI = -.03 to.65, p > .05), homogenous (p = .17), moderately inconsistent (I² = 36%), with no asymmetry (LFK index = .60). Conclusion: Acute and chronic exercise training, overall, exerted a trivial effect on PON1 concentration and activity.

Symmetry of Post-Translational Modifications in a Human Enzyme

Paraoxonase 2 (PON2) is a member of a small family of human lactonases. Recently, post-translational modifications (PTMs) of PON2 were highlighted, one of which involved the modulation of the enzyme activity. Furthermore, two important single nucleotide polymorphisms (SNPs) involved in type 2 diabetes and its consequences, were found to modulate the enzyme activity as well. The position on the PON2 structural model of both residues corresponding to SNPs and PTMs suggested a symmetry of the molecule. By sequence and structure superposition we were able to confirm this finding. The result will be discussed in light of the evolution of symmetry in biological molecules and their function.

Parsing the Role of PPARs in Macrophage Processes

Cells are richly equipped with nuclear receptors, which act as ligand-regulated transcription factors. Peroxisome proliferator activated receptors (PPARs), members of the nuclear receptor family, have been extensively studied for their roles in development, differentiation, and homeostatic processes. In the recent past, there has been substantial interest in understanding and defining the functions of PPARs and their agonists in regulating innate and adaptive immune responses as well as their pharmacologic potential in combating acute and chronic inflammatory disease. In this review, we focus on emerging evidence of the potential roles of the PPAR subtypes in macrophage biology. We also discuss the roles of dual and pan PPAR agonists as modulators of immune cell function, microbial infection, and inflammatory diseases.

Repetitions of Strenuous Exercise Consistently Increase Paraoxonase 1 Concentration and Activity in Plasma of Average-Trained Men

Objectives

Oxidative stress, induced by physical activity, may stimulate the expression, release, and activity of certain antioxidant enzymes. We investigated the effect of three repeated bouts of strenuous exercise on paraoxonase 1 concentration (PON1c) and paraoxonase activity (PON).

Methods

Eleven average-trained healthy men (age 34.0 ± 5.2 years) performed three strenuous exercise tests on a treadmill separated by 72 hours periods of resting. PON1c, PON, ferric-reducing activity of plasma (FRAP), lipid profile, C-reactive protein concentration (CRP), and lactate concentration were determined in plasma.

Results

Each exercise bout resulted in similar PON1c, PON, FRAP, and high-density lipoprotein concentration (HDL-C) increments, while PON/HDL-C ratio remained stable in all repetitions. Percentage increments at the bout of each exercise were higher for PON1c (by 64.82% at the first, by 92.9% at the second, and by 77.02% at the third exercise) than for PON (by 6.49% at the first, 10.06% at the second, and by 12.32% at the third exercise). Association was found between preexercise PON and PON1c (r = 0.56, p = 0.029), pre- (r = 0.87, p = 0.00003) and postexercise HDL-C (r = 0.6, p = 0.0002), preexercise PON and cardiovascular fitness level of participants measured as VO₂max (r = 0.39, p = 0.026), and postexercise PON and lactate concentration (r = 0.44, p = 0.01).

Conclusions

PON1c and PON increase during strenuous exercise, yet the effect of exercise on PON1 concentration is more pronounced. PON1 does not show tolerance to physical activity. The enzyme may provide short-term protection from oxidative stress in each exercise bout. PON may depend on exercise load. Cardiovascular fitness levels may be associated with PON1 activity.

Dietary Strategies to Improve Cardiovascular Health: Focus on Increasing High-Density Lipoprotein Functionality

Cardiovascular disease is one of the leading causes of morbidity and mortality worldwide, with increasing incidence. A cornerstone of cardiovascular disease prevention is lifestyle modification through dietary changes to influence various risk factors such as obesity, hypertension and diabetes. The effects of diet on cardiovascular health are complex. Some dietary components and metabolites directly affect the composition and structure of high-density lipoproteins (HDL) and increase anti-inflammatory and vasoprotective properties. HDLs are composed of distinct subpopulations of particles of varying size and composition that have several dynamic and context-dependent functions. The identification of potential dietary components that improve HDL functionality is currently an important research goal. One of the best-studied diets for cardiovascular health is the Mediterranean diet, consisting of fish, olive oil, fruits, vegetables, whole grains, legumes/nuts, and moderate consumption of alcohol, most commonly red wine. The Mediterranean diet, especially when supplemented with extra virgin olive oil rich in phenolic compounds, has been shown to markedly improve metrics of HDL functionality and reduce the burden, or even prevent the development of cardiovascular disease. Particularly, the phenolic compounds of extra virgin olive oil seem to exert the significant positive effects on HDL function. Moreover, supplementation of anthocyanins as well as antioxidants such as lycopene or the omega-3 fatty acid eicosapentaenoic acid improve parameters of HDL function. In this review, we aim to highlight recent discoveries on beneficial dietary patterns as well as nutritional components and their effects on cardiovascular health, focusing on HDL function.

Human carboxylesterase 1A plays a predominant role in the hydrolytic activation of remdesivir in humans

Remdesivir, an intravenous nucleotide prodrug, has been approved for treating COVID-19 in hospitalized adults and pediatric patients. Upon administration, remdesivir can be readily hydrolyzed to form its active form GS-441524, while the cleavage of the carboxylic ester into GS-704277 is the first step for remdesivir activation. This study aims to assign the key enzymes responsible for remdesivir hydrolysis in humans, as well as to investigate the kinetics of remdesivir hydrolysis in various enzyme sources. The results showed that remdesivir could be hydrolyzed to form GS-704277 in human plasma and the microsomes from human liver (HLMs), lung (HLuMs) and kidney (HKMs), while the hydrolytic rate of remdesivir in HLMs was the fastest. Chemical inhibition and reaction phenotyping assays suggested that human carboxylesterase 1 (hCES1A) played a predominant role in remdesivir hydrolysis, while cathepsin A (CTSA), acetylcholinesterase (AchE) and butyrylcholinesterase (BchE) contributed to a lesser extent. Enzymatic kinetic analyses demonstrated that remdesivir hydrolysis in hCES1A (SHUTCM) and HLMs showed similar kinetic plots and much closed K_m values to each other. Meanwhile, GS-704277 formation rates were strongly correlated with the CES1A activities in HLM samples from different individual donors. Further investigation revealed that simvastatin (a therapeutic agent for adjuvant treating COVID-19) strongly inhibited remdesivir hydrolysis in both recombinant hCES1A and HLMs. Collectively, our findings reveal that hCES1A plays a predominant role in remdesivir hydrolysis in humans, which are very helpful for predicting inter-individual variability in response to remdesivir and for guiding the rational use of this anti-COVID-19 agent in clinical settings.

l-Glutamine supplementation enhances glutathione peroxidase and paraoxonase-1 activities in HDL of exercising older individuals

BACKGROUND

Oxidative stress is an important factor in the formation of atherosclerotic plaques. High-density lipoprotein (HDL) harbors paraoxonase-1 (PON-1) and glutathione peroxidase (GPx), key enzymes in the protection against the harmful effects of oxidative stress. Although exercise training can increase both HDL-c content and its antioxidant action, and glutamine (Gln) intake also promotes GPx-based defenses, the association between exercise training and Gln in the regulation of PON-1 activity was not explored. Therefore, the objective of this study was to investigate the effects of Gln supplementation on the redox balance and on the total HDL antioxidant capacity by evaluation of the activity of PON-1 and GPx enzymes in physically exercised elderly individuals compared to non-exercised ones.

METHODS

Fifty-one practitioners of a combined exercise training program (CET, age: 71.9 ± 5.7 years) and 32 non-practitioners (NP, age: 73 ± 6.3 years) participated in the study. CET and NP groups were separated into 2 subgroups according to the supplementation: Gln, 0.3 g/kg/day + 10 g maltodextrin (CET-Gln, n = 26; and NP-Gln, n = 16) or placebo, 10 g maltodextrin (CET-PL, n = 25; and NP-PL, n = 16). Blood samples were drawn at baseline and after 30 days after commencement of the supplementation for biochemical and enzyme activity analyses.

RESULTS

Increased HDL-c, total peroxidase (PRx), and GPx activities were found in both CET-Gln and NP-Gln after the supplementation period, compared to baseline, in opposition to CET-PL and NP-PL groups. PON-1 activity increased only in CET-Gln. In both CET-Gln and NP-Gln groups, there was a reduction of the total peroxides/PRx, iron/PRx, and total peroxides/GPX ratios after supplementation. In CET-Gln, thiobarbituric acid-reactive substances (TBARS)/PRx and TBARS/GPx ratios were also lower after supplementation. CET-Gln and CET-PL subgroups had lower glycemia than NP-Gln and NP-PL, either at baseline or after the supplementation periods. The other parameters were unchanged after supplementation [total cholesterol, LDL-c, triglycerides, non-HDL cholesterol, total peroxides, TBARS, iron serum, Trolox-equivalent antioxidant capacity (TEAC), and uric acid].

CONCLUSIONS

Gln supplementation can increase glutathione peroxidase activity regardless the individuals were physically active or sedentary, but the PON-1 activity only increased in physically active individuals. These results show the potential of Gln supplementation in the maintenance of the vascular redox balance, with potential implications for atherogenesis protection.

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.

Fetal High-Density Lipoproteins: Current Knowledge on Particle Metabolism, Composition and Function in Health and Disease

Cholesterol and other lipids carried by lipoproteins play an indispensable role in fetal development. Recent evidence suggests that maternally derived high-density lipoprotein (HDL) differs from fetal HDL with respect to its proteome, size, and function. Compared to the HDL of adults, fetal HDL is the major carrier of cholesterol and has a unique composition that implies other physiological functions. Fetal HDL is enriched in apolipoprotein E, which binds with high affinity to the low-density lipoprotein receptor. Thus, it appears that a primary function of fetal HDL is the transport of cholesterol to tissues as is accomplished by low-density lipoproteins in adults. The fetal HDL-associated bioactive sphingolipid sphingosine-1-phosphate shows strong vasoprotective effects at the fetoplacental vasculature. Moreover, lipoprotein-associated phospholipase A2 carried by fetal-HDL exerts anti-oxidative and athero-protective functions on the fetoplacental endothelium. Notably, the mass and activity of HDL-associated paraoxonase 1 are about 5-fold lower in the fetus, accompanied by an attenuation of anti-oxidative activity of fetal HDL. Cholesteryl ester transfer protein activity is reduced in fetal circulation despite similar amounts of the enzyme in maternal and fetal serum. This review summarizes the current knowledge on fetal HDL as a potential vasoprotective lipoprotein during fetal development. We also provide an overview of whether and how the protective functionalities of HDL are impaired in pregnancy-related syndromes such as pre-eclampsia or gestational diabetes mellitus.

The Relevance of Noncoding DNA Variations of Paraoxonase Gene Cluster in Atherosclerosis-Related Diseases

The human paraoxonase (PON) gene cluster is comprised of three contiguous genes (PON1, PON2 and PON3) of presumably common origin coding three lactonases of highly similar structure and substrate specificity. The catalytic activity of PON proteins is directed toward artificial organophosphates and in physiological conditions toward thiolactones and oxidized phospholipids. Consequently, PON enzymes are regarded as an effective defense against oxidative stress and, as a result, against atherosclerosis development. Additionally, both PON's serum activity and its concentration are influenced by several polymorphic variations in coding and noncoding DNA regions of the PON gene cluster remaining in linkage disequilibrium. Hence, the genetic polymorphism of the PON gene cluster may contribute to atherosclerotic process progression or deceleration. In this review the authors analyzed the relevance of noncoding DNA polymorphic variations of PON genes in atherosclerosis-related diseases involving coronary and peripheral artery disease, stroke, diabetes mellitus, dementia and renal disease and concluded that the effect of PON gene cluster' polymorphism has a considerable impact on the course and outcome in these conditions. The following PON genetic variations may serve as additional predictors of the risk of atherosclerosis in selected populations and individuals.

Human Paraoxonase-2 (PON2): Protein Functions and Modulation

PON1, PON2, and PON3 belong to a family of lactone hydrolyzing enzymes endowed with various substrate specificities. Among PONs, PON2 shows the highest hydrolytic activity toward many acyl-homoserine lactones (acyl-HL) involved in bacterial quorum-sensing signaling. Accordingly, defense against pathogens, such as Brevundimonas aeruginosa (B. aeruginosa), was postulated to be the principal function of PON2. However, recent findings have highlighted the importance of PON2 in oxidative stress control, inhibition of apoptosis, and the progression of various types of malignancies. This review focuses on all of these aspects of PON2.

Role of Paraoxonase1 in the Regulation of High-Density Lipoprotein Functionality and in Cardiovascular Protection

Significance: Human paraoxonase (PON) is a member of the gene family that includes paraoxonase 1 (PON1), PON2, and PON3. PON is known for its capacity to hydrolyze a wide range of substrates, including organophosphorus compounds, nerve gases, and aromatic carboxylic acid esters. Recent Advances: Several studies have highlighted the involvement of PON, particularly PON1, in the modulation of the capacity of high-density lipoprotein (HDL) to protect against the atherosclerosis process and its clinical manifestations. PON1 exhibits antioxidant and anti-inflammatory activities and may be involved in the regulation of the principal antiatherogenic activity of HDL, that is, the regulation of the reverse cholesterol transport process. Critical Issues: Although epidemiological studies have shown that there is an inverse relationship between HDL levels and cardiovascular risk, several studies have emphasized the importance of HDL functionality in protecting against cardiovascular diseases (CVD). Given that PON1 is involved in several atheroprotective functions of HDL, the aim of this article is to review the existing literature on PON1 and to discuss the principal mechanisms by which PON1 may exert its different activities. Future Directions: The elucidation of the mechanisms by which PON1 modulates the functionality of HDL as well as the identification of the interventions that stimulate PON1 activity and/or increase its plasma concentration would make it possible to propose new strategies to prevent CVD. Antioxid. Redox Signal. 34, 191-200.

The Structure and Function of Paraoxonase-1 and Its Comparison to Paraoxonase-2 and -3

Serum paraoxonase-1 (PON1) is the most studied member of the group of paraoxonases (PONs). This enzyme possesses three enzymatic activities: lactonase, arylesterase, and paraoxonase activity. PON1 and its isoforms play an important role in drug metabolism as well as in the prevention of cardiovascular and neurodegenerative diseases. Although all three members of the PON family have the same origin and very similar amino acid sequences, they have different functions and are found in different locations. PONs exhibit substrate promiscuity, and their true physiological substrates are still not known. However, possible substrates include homocysteine thiolactone, an analogue of natural quorum-sensing molecules, and the recently discovered derivatives of arachidonic acid—bioactive δ-lactones. Directed evolution, site-directed mutagenesis, and kinetic studies provide comprehensive insights into the active site and catalytic mechanism of PON1. However, there is still a whole world of mystery waiting to be discovered, which would elucidate the substrate promiscuity of a group of enzymes that are so similar in their evolution and sequence yet so distinct in their function.

Obesity-Related Changes in High-Density Lipoprotein Metabolism and Function

In obese individuals, atherogenic dyslipidemia is a very common and important factor in the increased risk of cardiovascular disease. Adiposity-associated dyslipidemia is characterized by low high-density lipoprotein cholesterol (HDL-C) levels and an increase in triglyceride-rich lipoproteins. Several factors and mechanisms are involved in lowering HDL-C levels in the obese state and HDL quantity and quality is closely related to adiponectin levels and the bioactive lipid sphingosine-1-phosphate. Recent studies have shown that obesity profoundly alters HDL metabolism, resulting in altered HDL subclass distribution, composition, and function. Importantly, weight loss through gastric bypass surgery and Mediterranean diet, especially when enriched with virgin olive oil, is associated with increased HDL-C levels and significantly improved metrics of HDL function. A thorough understanding of the underlying mechanisms is crucial for a better understanding of the impact of obesity on lipoprotein metabolism and for the development of appropriate therapeutic approaches. The objective of this review article was to summarize the newly identified changes in the metabolism, composition, and function of HDL in obesity and to discuss possible pathophysiological consequences.

PON1 lactonase activity and its association with cardiovascular disease

BACKGROUND

Paraoxonase 1 (PON1) is important in the development of atherosclerosis, and it has become the subject of intensive research. Our aim was to evaluate the association of serum PON1 activity and polymorphisms with cardiovascular disease (CVD) using four different substrates.

MATERIALS AND METHODS

Activity of PON1-related to arylesterase (AREase and 4-CMPAse), paraoxonase (PONase), and lactonase (LACase), and polymorphisms (A-162G, T-108C, L55M, and Q192R) were evaluated in subjects with CVD, cardiovascular risk factor (CFR), and controls. An ordered logistic-regression analysis of PON1 phenotypes was performed in the CVD group with respect to the control group.

RESULTS AND CONCLUSIONS

Logistic-regression analysis showed that CC-108 genotype was associated with CRF and CVD. The CVD group had the lowest activities of PON1. The LACase might be a better biomarker for CVD (OR, 0.52; 95% CI, 0.44-0.61) followed by CMPAse (OR, 0.82; 95% CI, 0.77-0.86), AREase (OR, 0.98; 95% CI, 0.97-0.99) and PONase (OR, 0.99, 95% CI, 0.99-0.99). Logistic regression of PON1 phenotypes by haplotypes showed that LACase activity was not influenced by the polymorphisms and that it could be a new potential biomarker in the development of CVD. Larger scale longitudinal studies are required.

Paraoxonase 1: The Lectin-Like Oxidized LDL Receptor Type I and Oxidative Stress in the Blood of Men with Type II Obesity

Objectives

Obesity has serious consequences such as the onset of metabolic syndrome, type 2 diabetes, atherosclerosis, or cardiovascular complications. The aim of this study was to evaluate the levels of paraoxonase 1 (PON1), lectin-like oxidized LDL receptor-1 (LOX-1), antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)), and lipid peroxidation processes in the course of obesity.

Methods

28 men took part in the experiment. Fourteen of them were obese; the control group consisted of 14 physically active men without obesity features. The concentrations of malondialdehyde (MDA), PON1, LOX-1, and tumor necrosis factor α (TNFα) as well as the activities of erythrocytic SOD, CAT, and GPx were determined in the study.

Results

Statistically significant higher MDA, LOX-1, and TNFα levels were observed in obese subjects. Conversely, lower concentrations of PON1 in obese men were found.

Conclusions

An imbalance in oxidation-reduction processes accompanies obesity. Moreover, inflammatory cytokines and atherosclerotic complications are involved in the obesity process. The obtained results suggest that the studied parameters may be independent prognostic markers preceding the development of cardiovascular and metabolic complications in people afflicted with type II obesity.

Paraoxonase-1 as a Regulator of Glucose and Lipid Homeostasis: Impact on the Onset and Progression of Metabolic Disorders

Metabolic disorders are characterized by an overall state of inflammation and oxidative stress, which highlight the importance of a functional antioxidant system and normal activity of some endogenous enzymes, namely paraoxonase-1 (PON1). PON1 is an antioxidant and anti-inflammatory glycoprotein from the paraoxonases family. It is mainly expressed in the liver and secreted to the bloodstream, where it binds to HDL. Although it was first discovered due to its ability to hydrolyze paraoxon, it is now known to have an antiatherogenic role. Recent studies have shown that PON1 plays a protective role in other diseases that are associated with inflammation and oxidative stress, such as Type 1 and Type 2 Diabetes Mellitus and Non-Alcoholic Fatty Liver Disease. The aim of this review is to elucidate the physiological role of PON1, as well as the impact of altered PON1 levels in metabolic disorders.

The epigenetic regulation of paraoxonase 1 (PON1) as an important enzyme in HDL function: The missing link between environmental and genetic regulation

BACKGROUND

Paraoxonase 1 (PON1) is an important antiatherogenic and antioxidant enzyme in the circulation that has been associated with adverse health outcomes particularly cardiovascular disease (CVD) and other metabolic disorders. PON1 is a highly promiscuous enzyme and can hydrolyse a large variety of substrates, however, detailed structure/function studies have concluded that the natural substrates for PON1 are lipophilic lactones. The interindividual variability in PON1 activity has been mainly attributed to genetic determinants; however, it appears that the contribution of epigenetics has been ignored as a result of the lack of adequate research.

CONTENT

Epigenetic processes, including the histone modifications in the PON1 gene, the methylation of CpG sites in the promoter region of the PON1 gene and the microRNA modulation of PON1 expression can be responsible for the under researched gap between the environmental and genetic regulation of PON1. Environmental factors, including diet, pollution and lifestyle-related factors widely differ between individuals and populations and can cause large differences in the distribution of PON1 and it is important to note that their effects may be exerted through the epigenetic processes. This review discusses and emphasizes the importance of the epigenetic regulation of PON1 as a less-studied subject to highlight future research landscapes.

SUMMARY

Epigenetic regulation is known as an important contributor to the pathogenesis of human diseases, particularly multifactorial diseases such as CVD, which is life-threatening. Due to the importance of PON1 in the functionality of high-density lipoprotein (HDL) and its association with CVD, further explorations of its epigenetic regulation using advanced methods such as Methyl-Seq may lead to the identification of new epigenetic contributors that in turn may lead to targeted therapies.

How Monocytes Contribute to Increased Risk of Atherosclerosis in Virologically-Suppressed HIV-Positive Individuals Receiving Combination Antiretroviral Therapy

Combination antiretroviral therapy (ART) is effective at suppressing HIV viremia to achieve persistently undetectable levels in peripheral blood in the majority of individuals with access and ability to maintain adherence to treatment. However, evidence suggests that ART is less effective at eliminating HIV-associated inflammation and innate immune activation. To the extent that residual inflammation and immune activation persist, virologically suppressed people living with HIV (PLWH) may have increased risk of inflammatory co-morbidities, and adjunctive therapies may need to be considered to reduce HIV-related inflammation and fully restore the health of virologically suppressed HIV+ individuals. Cardiovascular disease (CVD) is the single leading cause of death in the developed world and is becoming more important in PLWH with access to ART. Arterial disease due to atherosclerosis, leading to acute myocardial infarction (AMI) and stroke, is a major component of CVD. Atherosclerosis is an inflammatory disease, and epidemiological comparisons of atherosclerosis and AMI show a higher prevalence and suggest a greater risk in PLWH compared to the general population. The reasons for greater prevalence of CVD in PLWH can be broadly grouped into four categories: (a) the higher prevalence of traditional risk factors e.g., smoking and hypertension (b) dyslipidemia (also a traditional risk factor) caused by off-target effects of ART drugs (c) HIV-related inflammation and immune activation and (d) other undefined HIV-related factors. Management strategies aimed at reducing the impact of traditional risk factors in PLWH are similar to those for the general population and their effectiveness is currently being evaluated. Together with improvements in ART regimens and guidelines for treatment, and a greater awareness of its impact on CVD, the HIV-related risk of AMI and stroke is decreasing but remains elevated compared to the general community. Monocytes are key effector cells which initiate the formation of atherosclerotic plaques by migrating into the intima of coronary arteries and accumulating as foam cells full of lipid droplets. This review considers the specific role of monocytes as effector cells in atherosclerosis which progresses to AMI and stroke, and explores mechanisms by which HIV may promote an atherogenic phenotype and function independent of traditional risk factors. Altered monocyte function may represent a distinct HIV-related factor which increases risk of CVD in PLWH.

Lowered PON1 activities are strongly associated with depression and bipolar disorder, recurrence of (hypo)mania and depression, increased disability and lowered quality of life

Objectives: Mood disorders (MDs) frequently co-exist with cardiovascular disease (CVD) and immune-inflammatory and oxidative stress are important shared pathophysiological pathways. Even though there has been an extensive investigation of the enzyme paraoxonase 1 (PON1) as a biomarker of susceptibility for CVD, there are few reports studying PON1 in MDs. The aim of this study was to determine the association between PON1 activities as well as functional genotypes and MD diagnosis, clinical characteristics and outcomes. Methods: PON1 activities and functional genotypes were assayed in 58 bipolar disorder (BD) and 32 major depressed patients (MDD) and compared with 59 controls. Results: Our findings show significantly lower PON1 total and CMPAase activities in MDs, which are partly related to the number of previous depressive and manic episodes. Lowered CMPAase activity is associated with a worse outcome of MDs as indicated by lowered quality of life (WHOQoL-BREF scale) and increased disability in the Sheeham scale. Conclusions: We hypothesise that lowered PON1 total and CMPAase activities may play a role in the pathophysiology of MDs by lowering antioxidant defences thereby increasing the risk of lipid peroxidation and inflammation; lowered inhibition of quorum-sensing lactones thereby increasing bacterial proliferation; and attenuated homocysteine thiolactone catabolism which may trigger immune-inflammatory response and/or induce neurotoxicity.

Paraoxonase 1 Activity, Polymorphism and Atherosclerosis Risk Factors in Patients Undergoing Coronary Artery Surgery

Background: Paraoxonase1 (PON1), an enzyme connected to high density lipoproteins (HDL) particles, plays an important role in protecting arteries against atherosclerosis. The serum activity and concentration of PON1 depends on several genetic polymorphisms as well as environmental factors. Materials and methods: Investigated population consisted of 71 patients aged 43–76 years with confirmed coronary heart disease (CHD). Established risk factors of CHD such as hypertension, elevated total cholesterol and LDL cholesterol (LDL-C), low HDL cholesterol (HDL-C), diabetes mellitus, obesity, smoking and premature CHD in family history were assessed. PON1 genotype for −108C/T promotor region was determined by polymerase chain reaction-restriction fragments length polymorphism (PCR–RFLP) method. Paraoxonase activity towards paraoxon and arylesterase activity towards phenyl acetate were measured spectrophotometrically. Results: Significant correlations between diabetes mellitus and paraoxonase activity (R = −0.264, p = 0.026) and between the premature coronary heart disease in family history and PON1 activity (R = −0.293, p = 0.013) were found. In multivariate analysis, PON1 paraoxonase activity was independently of confounding factors associated with diabetes (OR = 0.985; p = 0.024) and premature CHD in family history (OR = 0.983; p = 0.027). PON1 activity towards aryl acetate positively correlated with HDL-C level (R = 0.255, p = 0.032). In patients treated with statins, PON1 paraoxonase activity was significantly (p = 0.033) higher than in patients without treatment. Conclusions: In diabetic patients with CHD, paraoxonase activity is lower than in normoglycemic patients despite similar lipid profiles. Diabetes and positive family history in patients with overt CHD are associated with the serum PON1 activity, which might be an additional factor helpful in evaluating cardiovascular risk in this group of patients.

Association of paraoxonase-1 L55M and Q192R polymorphisms with PCOS risk and potential risk factors for atherosclerosis

Aim: To examine the PON1-L55M and -Q192R polymorphisms for polycystic ovary syndrome (PCOS) risk in relation with atherosclerosis risk markers. Methods: Blood samples were collected from 203 women (PCOS [n = 151], control [n = 52]). Genomic DNA was extracted and RFLP method was performed following the amplifications of the target regions. Results: Individuals with 192QR/192RR genotypes had a 2.5-fold increased risk of representing PCOS compared with the individuals with 192QQ genotype. Q192R was more strongly associated with PCOS than previously suggested atherosclerosis risk markers. Q192R status and body mass index values in combination were established to be a significant predictor of PCOS (AUC: 0.655, p = 0.001). Conclusion: This is one of the first studies suggesting the use of combination biomarkers to better predict the risk of developing PCOS.

Evaluation of antioxidant and antiproliferative activities of 1,2-bis (p-amino-phenoxy) ethane derivative Schiff bases and metal complexes

In this study, the effects of the two Schiff base derivatives and their metal complexes were tested for MDA concentration, which is an indicator of lipid peroxidation, antioxidant vitamin A, vitamin E, and vitamin C levels in cell culture. A comparison was performed among the groups and it was observed that MDA, vitamin A, vitamin E, and vitamin C concentrations were statistically changed. According to the results, all compounds caused a significant oxidative stress without Zn complexes. Moreover, Mn(II), Cu(II), Zn(II), and Ni(II) complexes of Schiff bases derived from a condensation of 1,2-bis (p-aminophenoxy) ethane with naphthaldehydes and 4-methoxy benzaldehyde were examined in terms of antitumor activity against MCF-7 human breast cancer and L1210 murine leukemia cells. Furthermore, the derivatives were tested for antioxidative and prooxidative effects on MCF-7 breast cancer cells. The compounds which were tested revealed that there was an antitumor activity for MCF-7 and L 1210 cancer cells. Also, some of the compounds induced oxidative harmful.

Genotype and phenotype of salt-stimulated paraoxonase 1 (PON1) is associated with atherogenic indices in type 2 diabetes

Background

Paraoxonase 1 (PON1) and lipid abnormalities contribute to the development of cardiovascular disease, which is the principal cause of mortality in patients with type 2 diabetes (T2D). Data are not available on the potential association between salt-stimulated activity of PON1 (PON1-salt) and the atherogenic indices in T2D, therefore, we focused on these associations and evaluated whether the functional variants PON1-Q192R and PON1-L55M influence the associations.

Methods

Paraoxonase activity (PON1-para), arylesterase activity (PON1-aryl) and salt-stimulated activity (PON1-salt) were measured by spectrophotometric assays. The atherogenic index of plasma (AIP) was calculated from the log (TG/HDL-C). The genetic analyses were made by the restricted fragment length polymorphism after PCR amplification.

Results

We observed that PON1-salt was negatively correlated with total cholesterol (TC)/HDL-C (r = −0.441,p = 0.006), LDL-C/HDL-C (r = −0.415, p = 0.011), and AIP (r = −0.422, p = 0.009). Correlations between PON1-salt and all three atherogenic indices were significantly affected by PON1-L55M and PON1-Q192R. Linear regression showed that AIP (p = 0.002), LDL-C/HDL-C (p = 0.005), and TC/HDL-C (p = 0.002) were independently associated with PON1-salt. Based on Ridge regression, the standardized coefficients −0.358, −0.297, and − 0.044 were obtained for AIP, LDL-C/HDL-C, and TC/HDL-C, respectively, and this shows that AIP could have more negative effect on PON1-salt than the others.

Conclusions

The decreased PON1-salt may be considered as a risk factor for atherosclerosis in T2D, therefore, understanding the associations between PON1-salt as an important although neglected property and atherogenic indices may be valuable in T2D. Accordingly, detection of PON1-salt status (phenotype and genotype) together with the atherogenic indices particularly AIP could be beneficial in identifying the increased atherogenicity in T2D.

Effect of continuous renal-replacement therapy on paraoxonase-1-related variables in patients with acute renal failure caused by septic shock

BACKGROUND

Acute renal failure in patients with sepsis is associated with high mortality. Studies have highlighted alterations in serum paraoxonase-1 in severe infections. However, the published literature has no insight into the clinical evolution of these parameters in patients with sepsis and acute renal failure treated with extra-renal depuration techniques.

METHODS

We studied 25 patients with sepsis and acute renal failure who were treated with continuous renal-replacement therapy. Blood for laboratory analyses was collected at days 0, 1, 2, 5, 7, and 10. We measured serum paraoxonase-1 activity and concentration, lipid profile, aminotransferase activities, pH, and lactate, urea, creatinine and C-reactive protein concentrations. Values were compared with those of 50 healthy individuals.

RESULTS

Patients with sepsis and acute renal failure had lower serum paraoxonase-1 activity, lower high-density lipoprotein cholesterol concentrations, and higher serum paraoxonase-1 concentrations than the control group. We found a significant inverse correlation between serum paraoxonase-1 concentrations and the Acute Physiology And Chronic Health Evaluation II score in survivors as well as non-survivors, and a significant inverse correlation between serum paraoxonase-1 concentrations and the Sequential Organ Failure Assessment score only in survivors. Extra-renal depuration techniques produced a further increase in this enzyme related to the duration of treatment, and to serum urea concentration.

CONCLUSION

Our results show an inverse relationship between the concentration of paraoxonase-1 and the disease severity of patients with renal failure caused by septic shock. These results highlight relationships between paraoxonase-1 and infectious diseases and sepsis, with insights into potential clinical evolution of treatment.

Primary prevention of atherosclerosis by pretreatment of low-density lipoprotein receptor knockout mice with sesame oil and its aqueous components

Pharmacological intervention using statins and PCSK9 inhibitors have become first-line therapy in the prevention of hypercholesterolemia and atherosclerosis. Currently, no agent is available for the primary prevention of atherosclerosis. However, there is an emerging hypothesis that atherosclerosis could be driven by inflammation. In this study, we tested whether pretreatment with an aqueous extract from sesame oil (SOAE), which showed potent anti-inflammatory properties without hypocholesterolemic actions, would prevent subsequent atherosclerosis development in a mouse model. RAW 264.7 macrophages and female low-density lipoprotein receptor knockout (LDLR^−/−) mice were used for in vitro and in vivo studies, respectively. Plasma lipids, cytokines and atherosclerotic lesions were quantified at the end of the study. RNA was extracted from the liver and aortic tissues and used for gene analysis. Pre-treatment of SOAE prevented Ox-LDL uptake by RAW macrophages and further inflammation in vitro. SOAE pre-treatment significantly reduced atherosclerotic lesions and pro-inflammatory gene expressions in LDLR^−/− mice as compared to control mice. No significant change in plasma cholesterol levels was observed. A significant reduction in plasma levels of TNF-α, IL-6, MCP-1 and VCAM1 was observed in the SOAE pre-treated animals. This is the first study that demonstrates that pre-treatment with anti-inflammatory agents, could delay/decrease atherosclerosis.

Synthesis and characterization of four novel palladium(II) and platinum(II) complexes with 1-(2-aminoethyl)pyrrolidine, diclofenac and mefenamic acid: In vitro effect of these complexes on human serum paraoxanase1 activity

In this study, the effects of four novel mononuclear palladium(II) and platinum(II) complexes on the activity of human serum paraoxanase1 were examined. First, four novel mononuclear palladium(II) and platinum(II) complexes were synthesized with a nitrogen donor ligand 1-(2-aminoethyl)pyrrolidine and nonsteroidal anti-inflammatory drugs diclofenac, mefenamic acid. These complexes were characterized by spectroscopic, thermal, and elemental analyses. The crystal structures of complex [Pd(2-amepyr)₂ ](dicl)₂ 1 and [Pd(2-amepyr)₂ ](mef)₂ 3 were determined by X-ray crystallography. Then, paraoxonase1 enzyme was purified from human serum. The effects of these complexes on enzyme were evaluated in vitro. The complexes consist of the cationic unit and the counterions. The diclofenac and mefenamic acid acted as a counterion in the complexes. It was observed that all the complexes were stable up to high temperatures. These complexes, even at low doses, inhibited the activity of the enzyme with different inhibition mechanisms.

Cholesterol reduction and macrophage function: role of paraoxonases

PURPOSE OF REVIEW

Unregulated uptake of oxidized LDL by macrophages to form foam cells is the hallmark for atherosclerosis. The paraoxonase (PON) family of enzymes plays a critical role in attenuating atherosclerotic lesion formation by hydrolyzing lipid peroxides (LOOHs) and preventing the oxidation of LDL particles and by enhancing HDL-mediated cholesterol efflux. Findings in recent years suggest novel mechanisms by which PON isoforms interact with macrophages to regulate cholesterol metabolism and cellular function.

RECENT FINDINGS

The association of PON with HDL particles facilitates binding of the particle to macrophages and ABCA1-dependent cholesterol efflux. The hydrolysis of membrane phospholipids by PON generates lysophosphatidylcholine which is shown to regulate expression of cholesterol transport proteins. The PON family also regulates multiple aspects of macrophage function. PON attenuates inflammation and prevents induction of apoptosis via activation of a scavenger receptor class B type-1-dependent signaling mechanism. PON limits macrophage-dependent oxidant formation by preventing the activation of the membrane-associated NADPH oxidase and by stabilizing mitochondria. PON also promotes the differentiation of macrophages to an anti-inflammatory phenotype. This function appears to be independent of PON enzymatic activity and, rather, is dependent on the ability of endogenous sulfhydryls to neutralize pro-inflammatory peroxides.

SUMMARY

In recent years, the therapeutic efficacy of HDL-based therapies has been subject to dispute. Pharmacological approaches that target an increase in the expression and/or activity of PON may facilitate macrophage cholesterol metabolism and attenuate inflammatory injury.

The role of paraoxonase 1 in regulating high-density lipoprotein functionality during aging

Pharmacological interventions to increase the concentration of high-density lipoprotein (HDL) have led to disappointing results and have contributed to the emergence of the concept of HDL functionality. The anti-atherogenic activity of HDLs can be explained by their functionality or quality. The capacity of HDLs to maintain cellular cholesterol homeostasis and to transport cholesterol from peripheral cells to the liver for elimination is one of their principal anti-atherogenic activities. However, HDLs possess several other attributes that contribute to their protective effect against cardiovascular diseases. HDL functionality is regulated by various proteins and lipids making up HDL particles. However, several studies investigated the role of paraoxonase 1 (PON1) and suggest a significant role of this protein in the regulation of the functionality of HDLs. Moreover, research on PON1 attracted much interest following several studies indicating that it is involved in cardiovascular protection. However, the mechanisms by which PON1 exerts these effects remain to be elucidated.

Relationship between rs854560 PON1 Gene Polymorphism and Tobacco Smoking with Coronary Artery Disease

Paraoxonase-1 (PON1) is the antioxidant marker of high-density lipoproteins protecting against atherosclerosis and coronary artery disease (CAD) phenotype. The purpose of the present study was to determine whether the PON1 gene rs854560 polymorphism (163T>A) is associated with CAD in Polish population. rs854560 was genotyped in 494 subjects: 248 patients with premature CAD and 246 blood donors as a control. We found that the risk of CAD was significantly higher in TT homozygotes than in A allele carriers (OR = 1.87, p = 0.041). The synergistic effect between the TT genotype and cigarette smoking was observed (SIM = 9.81; SI = 14.70). The relative increase in risk from interaction between factors was over 37 (RERI = 36.13). The PON1 polymorphism did not modulate the risk of CAD in response to exposure to other traditional risk factors. In conclusion, the rs854560 polymorphism may modulate the risk of CAD in response to cigarette smoking in Polish population. Carriers of TT genotype seem to be particularly at risk of CAD, when exposed to cigarette smoking.

Alzheimer's Disease and Paraoxonase 1 (PON1) Gene Polymorphisms

BACKGROUND

Some studies have indicated that human paraoxonase 1 (PON1) activity shows a polymorphic distribution. The aim of this study was to determine the distribution of PON1 polymorphism in patients with Alzheimer's disease in Gorgan and compare it with a healthy control group.

METHOD

The study included 100 healthy individuals and 50 patients. Enzyme activity and genetic polymorphism of PON1 were determined.

RESULT

There were significant differences in distribution of genotypes and alleles among patients and control group. The most common genotype was CT in patients and control group, while the most frequent alleles were T and C in patients and controls, respectively. There was a statistically significant variation between serum PON1 activity and -108C> T polymorphism. The highest PON1 enzyme activities in the patients and controls were found in CC, while lower enzyme activities were seen in CT and TT genotypes in both genders and age groups.

CONCLUSION

Onset of Alzheimer's disease may depend on different polymorphisms of the PON1 enzyme. Late or early-onset of Alzheimer's disease may also depend on age and gender distribution, especially for arylesterase enzyme. Further studies on polymorphism of the enzyme are necessary for interpretation of possible polymorphic effects of enzyme on PON1 activity in humans.

Association of the serum myeloperoxidase/high-density lipoprotein particle ratio and incident cardiovascular events in a multi-ethnic population: Observations from the Dallas Heart Study

BACKGROUND AND AIMS

Myeloperoxidase (MPO), a product of systemic inflammation, promotes oxidation of lipoproteins; whereas, high-density lipoprotein (HDL) exerts anti-oxidative effects in part via paraoxonase-1 (PON1). MPO induces dysfunctional HDL particles; however, the interaction of circulating levels of these measures in cardiovascular disease (CVD) has not been studied in humans. We tested whether serum levels of MPO indexed to HDL particle concentration (MPO/HDLp) are associated with increased CVD risk in a large multiethnic population sample, free of CVD at baseline.

METHODS

Levels of MPO, HDL-C, and HDL particle concentration (HDLp) by NMR were measured at baseline in 2924 adults free of CVD. The associations of MPO/HDLp with incident ASCVD (first non-fatal myocardial infarction, non-fatal stroke, coronary revascularization, or CVD death) and total CVD were assessed in Cox proportional-hazards models adjusted for traditional risk factors. The median follow-up period was 9.4 years.

RESULTS

Adjusted for sex and race/ethnicity, MPO/HDLp was associated directly with body mass index, smoking status, high-sensitivity C-reactive protein, and interleukin 18, and inversely with age, HDL-C levels, HDL size, and PON1 arylesterase activity, but not with cholesterol efflux. In fully adjusted models, the highest versus lowest quartile of MPO/HDLp was associated with a 74% increase in incident ASCVD (aHR, 1.74, 95% CI 1.12-2.70) and a 91% increase in total incident CVD (aHR, 1.91, 95% CI 1.27-2.85).

CONCLUSIONS

Increased MPO indexed to HDL particle concentration (MPO/HDLp) at baseline is associated with increased risk of incident CVD events in a population initially free of CVD over the 9.4 year period.

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.

Transcriptional regulation of human Paraoxonase 1 by nuclear receptors

Paraoxonase 1 (PON1) is a calcium-dependent lactonase synthesized primarily in the liver and secreted into the plasma, where it is associates with high density lipoproteins (HDL). PON1 acts as antioxidant preventing low-density lipoprotein (LDL) oxidation, a process considered critical in the initiation and progression of atherosclerosis. Additionally, PON1 hydrolyzes and detoxifies some toxic metabolites of organophosphorus compounds (OPs). Thus, PON1 activity and expression levels are important for determining susceptibility to OPs intoxication and risk of developing diseases related to inflammation and oxidative stress. Increasing evidence has demonstrated the modulation of PON1 expression by many factors is due to interaction with nuclear receptors (NRs). Here, we briefly review the studies in this area and discuss the role of nuclear receptors in the regulation of PON1 expression, as well as how understanding these mechanisms may allow us to manipulate PON1 levels to improve drug efficacy and treat disease.