Human Plasma Paraoxonase 1 (PON1) Arylesterase Activity During Aging: Correlation with Susceptibility of LDL Oxidation

Hesperidin Supplementation Improves Altered PON -1, LDL Oxidation, Inflammatory Response and Hepatic Function in an Experimental Rat Model of Hyperlipidemia

In this study, we have examined the effect of hesperidin on rats fed on an experimental high-fat diet. Male Wistar rats were given a high-fat diet orally for one month for developing an HFD (High fat- diet) model. Rats were also supplemented with hesperidin (100 mg/kg body weight) for one month. We determined serum LDL (Low-density lipoprotein) oxidation, Paraoxonase-1 (PON-1) activity, and histopathological profile of the liver. Inflammatory cytokines levels were also measured in serum. HFD induced significant changes in LDL oxidation and PON-1 activity. Liver tissue histopathology and gene expression of inflammatory markers (Il-6(Interleukin-6), TNF- alpha (Tumor necrosis factor alpha), NF-KB (Nuclear factor kappa B) show that significant changes occur in the hyperlipidemic model of rats. We also show that hesperidin can effectively improve plasma antioxidant, LDL oxidation, and inflammatory cytokine expression in rats already subjected to hyperlipidemic stress. We conclude that hesperidin may protect the liver from oxidative stress by improving hepatic function.

Vitamin C Improves Inflammatory-related Redox Status in Hyperlipidemic Rats

Excessive dietary fat is mainly responsible for metabolic diseases including atherosclerosis and cardiovascular disease. We have evaluated the role of Vitamin C in an experimental hyperlipidemic model of rats (male Wistar rat 12-16 months). The hyperlipidemic model of the rat was created by treatment with an atherogenic suspension: cholesterol, cholic acid, and coconut oil, for 30 days once daily, and supplemented with Vitamin C (Ascorbic acid) doses of 0.5 g/kg body weight (orally) for the 30 days once daily. Bodyweight, fasting glucose, triglyceride, cholesterol, ROS (Reactive oxygen species), MDA (Malondialdehyde), FRAP (Ferric reducing the ability of plasma), GSH (Reduced glutathione), PCO (Protein carbonyl), PON-1(Paraoxonase-1), AGE (Advanced glycation end product), PMRS (Plasma membrane reduced system), and inflammatory cytokines (TNF-α and IL-6) were estimated in blood and plasma. Our result shows that oxidative stress, and inflammatory markers, were increased in the HFD-treated group of rats. Vitamin C supplementation protected against lipidemic and, oxidative stress. We conclude that Vitamin C may be useful in maintaining cellular redox balance and protecting against lipidemic stress.

Modulatory Effect of Lifestyle-Related, Environmental and Genetic Factors on Paraoxonase-1 Activity: A Review

Paraoxonase-1 (PON1) is a calcium-dependent, HDL-bound serum hydrolase active toward a wide variety of substrates. PON1 displays three types of activities, among which lactonase, paraoxonase, arylesterase and phosphotriesterase can be distinguished. Not only is this enzyme a major organophosphate compound detoxifier, but it is also an important constituent of the cellular antioxidant system and has anti-inflammatory and antiatherogenic functions. The concentration and activity of PON1 is highly variable among individuals, and these differences can be both of genetic origin and be a subject of epigenetic regulation. Owing to the fact that, in recent decades, the exposure of humans to an increasing number of different xenobiotics has been continuously rising, the issues concerning the role and activity of PON1 shall be reconsidered with particular attention to growing pharmaceuticals intake, dietary habits and environmental awareness. In the following manuscript, the current state of knowledge concerning the influence of certain modifiable and unmodifiable factors, including smoking, alcohol intake, gender, age and genotype variation on PON1 activity, along with pathways through which these could interfere with the enzyme's protective functions, is presented and discussed. Since exposure to certain xenobiotics plays a key role in PON1 activity, the influence of organophosphates, heavy metals and several pharmaceutical agents is also specified.

Baicalein maintains redox balance in experimental hyperlipidemic rats

Context: An altered lipid profile may lead to the development of CVD.Objective: We evaluated the protective role of baicalein (BAC) against lipidemic and oxidative stress in hyperlipidemic challenged Wistar rats.Materials and methods: Male Wistar rats were given a high-fat diet (HFD) (suspension (w/v) of 0.5% cholesterol, 3% coconut oil and 0.25% cholic acid for 30 days) to create a hyperlipidemic model. BAC was supplemented to experimental rats (80 mg/kg body weight). Biomarkers of oxidative stress including ROS, FRAP, GSH, PMRS, AGE, MDA, PCO, AOPP, and other parameters (Paraoxonase-1, SGOT, SGPT) including TNF-α and IL-6, were estimated in blood.Results: Oxidative stress and inflammatory markers were significantly increased in the HFD treated group. BAC treatment protected rats from HFD mediated alterations.Discussion & conclusion: Our results indicate that baicalein provides protection against hyperlipidemic stress and redox imbalance induced by HFD in rats.

Abnormal Paraoxonase-1 (PON1) enzyme activity in idiopathic inflammatory myopathies

OBJECTIVES

Patients with idiopathic inflammatory myopathies (IIM) have severe vascular involvement, which contributes to disease morbidity and mortality. Paraoxonase-1 (PON1) is a high-density lipoprotein (HDL) associated protein, which protects the vascular endothelium from oxidative injury and damage. The current work assessed the functional and genetic determinants of PON1 activity in IIM patients.

METHODS

184 IIM patients and 112 healthy controls (HC) were included. PON1 enzyme activity was assessed by paraoxonase, arylesterase and lactonase assays, and the Q192R PON1 single nucleotide polymorphism (SNP) was analyzed. Multivariate regression models examined associations of PON1 activity with IIM diagnosis and myositis disease outcomes.

RESULTS

The arylesterase and lactonase activities of PON1 were significantly lower in IIM patients compared with HC. Higher myositis disease activity, the presence of severe IIM associated interstitial lung disease (ILD), and the presence of MDA5 or anti-synthetase antibodies were significantly associated with lower PON1 activity. The PON1 Q192R polymorphism was strongly linked to the paraoxonase activity of PON1 in IIM, and patients with the PON1 QQ genotype had better IIM disease outcomes compared with patients with the QR or RR genotypes.

CONCLUSIONS

The arylesterase and lactonase activities of PON1 are significantly impaired in IIM patients compared with HC, and inversely associate with IIM disease activity and the presence of severe ILD. The PON1 QQ genotype associates with more favorable disease outcomes in IIM patients. Large prospective studies are needed to further evaluate the role of PON1 and PON1 genetic polymorphisms in the development and propagation of IIM and IIM-ILD.

Protective effect of hesperidin in Poloxamer-407 induced hyperlipidemic experimental rats

Hyperlipidemia is one of the leading causes of, atherosclerosis, and cardiovascular disease. In this study, we evaluated the protective role of hesperidin (HES) against lipidemic stress in a hyperlipidemic model of rats. We developed a hyperlipidemic model of the rat through an i.p dose of poloxamer-407, 0.5 g/kg body weight for 3 alternative days in a week for 30 days and rats were supplemented with HES orally (100 mg/kg body weight) once daily. Bodyweight, fasting glucose, insulin, HOMA-IR index, triglyceride, cholesterol, ROS, FRAP, GSH, PMRS, AGE, MDA, PCO, AOPP, PON-1, TNF-α and IL-6, SGPT and SGOT were estimated in blood and plasma, and histopathology was done in liver tissue. Our data show that oxidative stress, inflammatory markers were increased in the P-407 treated group. Liver tissue histology also changes in the hyperlipidemic groups of rats.HES supplementation protects against P-407 induced alterations and maintains the redox homeostasis. Our results provide evidence that HES protects against lipidemic stress and redox imbalance induced by P-407 in rats.

The role of high-density lipoprotein cholesterol, apolipoprotein A and paraoxonase-1 in the pathophysiology of neuroprogressive disorders

Lowered high-density lipoprotein (HDL) cholesterol has been reported in major depressive disorder, bipolar disorder, first episode of psychosis, and schizophrenia. HDL, its major apolipoprotein component, ApoA1, and the antioxidant enzyme paraoxonase (PON)1 (which is normally bound to ApoA1) all have anti-atherogenic, antioxidant, anti-inflammatory, and immunomodulatory roles, which are discussed in this paper. The paper details the pathways mediating the anti-inflammatory effects of HDL, ApoA1 and PON1 and describes the mechanisms leading to compromised HDL and PON1 levels and function in an environment of chronic inflammation. The molecular mechanisms by which changes in HDL, ApoA1 and PON1 might contribute to the pathophysiology of the neuroprogressive disorders are explained. Moreover, the anti-inflammatory actions of ApoM-mediated sphingosine 1-phosphate (S1P) signalling are reviewed as well as the deleterious effects of chronic inflammation and oxidative stress on ApoM/S1P signalling. Finally, therapeutic interventions specifically aimed at improving the levels and function of HDL and PON1 while reducing levels of inflammation and oxidative stress are considered. These include the so-called Mediterranean diet, extra virgin olive oil, polyphenols, flavonoids, isoflavones, pomegranate juice, melatonin and the Mediterranean diet combined with the ketogenic diet.

Interdependence of Anti-Inflammatory and Antioxidant Properties of Squalene-Implication for Cardiovascular Health

Cardiovascular diseases (CVD) have been recognized as the leading cause of mortality worldwide, accounting for 31% of global mortality. Among the risk factors of CVD, hyperlipidemia has been established as the most potent risk factor. Statins, a class of drug that reduces lower-density lipoprotein cholesterol (LDL-C), are the preferred medical treatment. However, due to the development of statin-associated muscle symptoms, statins are associated with patients' discontinuation and nonadherence. Other statin-induced side effects, such as hepatotoxicity and gastrointestinal upset, all contribute to patients choosing alternative medicines. Squalene (SQ), an unsaturated hydrocarbon naturally synthesized in plants and animals, could become the alternative treatment or supplementary agent for cardiovascular health. SQ has been shown to exert cardioprotective effect via its antioxidant activity. Oxidative stress and inflammatory responses are closely related to each other, which proposes an interdependence relation between antioxidant and anti-inflammatory. Therefore, this review explores the interdependence between the antioxidant and anti-inflammatory effects of SQ implicated on cardiovascular health.

Elevated serum OxLDL is associated with progression of type 2 Diabetes Mellitus to diabetic retinopathy

Hyperlipidemia is associated with the progression of diabetic retinopathy (DR). Paraoxonase 1 (PON1), an esterase is known to prevent systemic LDL oxidation. This study assessed if serum oxLDL is associated with the progression of Type 2 DM to DR. This study is part of a three-year hospital based prospective study where 87 subjects were recruited. This included T2DM without DR (n = 22); Non-Proliferative (NPDR) (n = 21) and Proliferative DR (PDR) (n = 22) along with age/sex matched controls (n = 22). Serum oxLDL-Ab was estimated by ELISA. Serum PON esterase activity and plasma Malondialdehyde (MDA) level were estimated by spectrophotometry and the serum Advanced Glycation End products (AGE) level by spectroflourimetry. The systemic levels of oxLDL, AGE and MDA were increased with the progression of T2DM without DR to DR as seen by ANOVA (P < 0.05). Serum oxLDL-Ab levels showed a positive correlation to total cholesterol (P = 0.04) as evaluated in the DR group. Statin intake was found to lower PON esterase activity (P < 0.05). Based on this pilot study, it is proposed that elevated serum oxLDL should be validated in larger cohort studies to ensure it could be potential risk factor for the progression of T2DM to DR.

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.

Decreases in Paraoxonase-1 Activities Promote a Pro-inflammatory Effect of Lipids Peroxidation Products in Non-smoking and Smoking Patients with Acute Pancreatitis

Aim: The study investigated the extent to which tobacco smoke exposure causes changes in lipids biochemistry through measurement blood concentrations of: paraoxonase-1 (PON-1) activities as lipid-bound enzyme into cell membrane, concentration of malonyldialdehyde (MDA), protein adducts of 4-hydroxynonenal (HNE-adducts), oxidized low density lipoproteins (oxLDL), total cholesterol (CH) and high-density lipoprotein cholesterol (HDL). Additionally, the activity of P isoform of glutathione S-transferase (GST-π) was measured. Methods: Investigations were performed in the blood of patients with acute pancreatitis (AP) on the 1st, 3rd and 7th day of hospitalization and in healthy volunteers. The activities of PON-1 forms, GST-π were determined spectrophotometrically. Concentrations of PON-1, MDA, HNE-adducts, oxLDL, HDL, CH were measured using commercial tests. Results: Near 2-fold higher concentrations of MDA, HNE-adducts, oxLDL, correlating with inflammatory markers in AP patients compared to healthy subjects were demonstrated, which were accompanied by gradually increasing CH/HDL ratio during hospitalization. During hospital treatment, decreased activities of all PON-1 subtypes were observed in AP patients compared to healthy subjects, more pronounced in tobacco smokers. A decreased PON-1 phosphotriesterase activity in non-AP control group smokers compared to non-smokers was noted. In non-smoking AP patients GST-π activity normalized during hospitalization in contrast to smokers. Conclusions: GST-π and PON-1 phosphotriesterase activities seem to be a sensitive marker of pro/antioxidative imbalance in smokers. Lipids peroxidation products generated during AP can intensify preexisting inflammation. Increasing stay in the hospital was associated with worsening of lipids peroxidation markers and the parameters of lipid profile, in both non-smoking and smoking AP patients, what can indicate that the oxidative-inflammatory process are not extinguished.

Lipid-lowering and antiatherogenic effects of Vitex megapotamica (Spreng.) Moldenke in a mice experimental model

ETHNOPHARMACOLOGICAL RELEVANCE

Vitex megapotamica (Spreng.) Moldenke is a deciduous tree, native of South America. Its leaves are traditionally used to treat cardiovascular diseases. This activity is related to the presence of flavonoids, the major compounds of the crude extract.

AIM OF THE STUDY

This study investigated the effects of the oral administration of crude extract and standardized fractions from V. megapotamica leaves on lipid profile and on the formation of atherosclerotic plaque in C57BL/6 LDLr-KO mice treated with high-fat diet (HFD).

MATERIALS AND METHODS

Male C57BL/6 LDLr-KO mice were fed with HFD (cholesterol, 1.25%) for 30 days. They were treated with hydroethanolic extract (500 or 1000mg/kg/day) or fractions (125 or 250mg/kg/day). After 30 days of treatment, it was evaluated the serum lipid profile, atherogenic index, and atherosclerotic plaque.

RESULTS

All doses of the hydroethanolic extract reduced significantly the levels of total cholesterol, triglycerides, LDL-c and the atherogenic index. The n-butanolic fraction also reduced significantly the levels of total cholesterol, triglycerides, LDL-c and the atherogenic index, at all doses, with exception for the triglycerides, which only the lower dose was effective. The residual fraction reduced significantly the levels of total cholesterol, LDL-c and the atherogenic index, at all doses, with exception for the atherogenic index, which only the higher dose was effective. The atherosclerotic plaque formation was impaired only by the lower dose of the hydroethanolic extract.

CONCLUSIONS

Overall, our data suggest that V. megapotamica has potential for the treatment of dyslipidemias.

Ocular distribution of antioxidant enzyme paraoxonase & its alteration in cataractous lens & diabetic retina

Background & objectives:

The enzyme paraoxonase (PON), an antioxidant enzyme that has both arylesterase and thiolactonase activity, is well studied in cardiovascular diseases. Although a few studies have shown altered PON activity in ocular diseases such as age-related macular degeneration and diabetic retinopathy, but the tissue-wise expression of PON in its three gene forms has not been studied. This study was conducted to see the ocular distribution of PON for any altered expression in ocular pathologies such as in cataract and diabetes mellitus.

Methods:

Immunohistochemistry (IHC) of the ocular tissues was done for localizing all three forms of the PON in the human donor eyeballs. The PON arylesterase (PON-AREase) and thiolactonase (PON-HCTLase) activities were determined by spectrophotometry in kinetic mode, and the mRNA expression of the PON genes (PON1-3) was determined by reverse transcription-polymerase chain reaction.

Results:

IHC showed the presence of both PON1 and 2 in all the ocular tissues and PON3 was seen only in retina. The mRNA expression analysis showed that PON2 and PON3 were present in all the tissues, whereas PON1 was seen only in ciliary and retina. Both the PON-AREase and PON-HCTLase activities were detected in all ocular tissues and was in the order of lens>retina>choroid>ciliary body>iris. The expression and activity were studied in cataractous lens and in diabetic retina of the donor eyes. A significant decrease in PON-AREase activity was seen in cataractous lens (P<0.05) but not in diabetic retina, and there was an increase in PON- HCTLase activity (P<0.05) only in diabetic retina. Bioinformatic studies and in vitro experiments indicated that advanced glycation end products (AGE) such as carboxymethyl -lysine might decrease the PON- AREase activity of the PON.

Interpretation & conclusions:

Distribution of PON enzyme and its activity in ocular tissues is reported here. The study revealed maximal PON activity in lens and retina, which are prone to higher oxidative stress. Differential activities of PON were observed in the lens and retinal tissues from cataractous and diabetic patients, respectively.

Bovine lactoferrin ameliorates antioxidant esterase activity and 8-isoprostane levels in high-cholesterol-diet fed rats

Abstract. The main aim of the present study was to show the effect of bovineLactoferrin (bLF), an 80 kD iron-binding glycoprotein, its application on antioxidant esterase activities and 8-isoprostane changes in high-cholesterol-diet fed (HCD-Fed) rats. The 44 adult Sprague-Dawley male rats were randomly assigned into four experimental groups. They were randomly assigned into four equivalent groups (n = 11). The groups included the control group which was fed with normal diet, bLF group, the third group which were made hypercholesterolemia by being fed with high cholesterol diet, and the last group which consisted of hypercholesterolemia rats treated with bLF (HCD + bLF) for 4 weeks (200 mg.kg−1 per day wt. dissolved in 0.9% normal saline).After 4 weeks, the serum Paraoxonase1 (PON1), Arylesterase (ARE) activity and 8-isoprostane with lipid profile were measured. Upon treatment with the bLF, the decrease in LDL-Cholesterol (LDL-C), Glucoses, Triglyceride (TG) and Total-Cholesterol (TC) levels and an increase in HDL-Cholesterol (HDL-C) level were observed. The co-administration of bLf for 4 weeks had decreased the 8-isoprostane levels significantly (P < 0.001) (86.36 ± 7.1 vs 117.18 ± 8.62) when compared to hypercholesterolemia-induced rats. Also, the Atherogenic Index (AI) in HCD + bLF group showed a significant decrease as compared to the HCD group (P < 0.001) (0.37 ± 0.07 vs 0.57 ± 0.09). The results indicated that bLF was effective against oxidative stress by its ability to increase PON1 activity and reduce the lipid peroxidation in high-cholesterol-fed rats.

Lipid associated antioxidants: arylesterase and paraoxonase-1 in benign prostatic hyperplasia treatment-naïve patients

Background

Oxidative stress and antioxidants have been implicated in many diseases including prostate cancer and benign prostatic hyperplasia (BPH). Lipid peroxidation contributes to oxidative stress. However, new and emerging antioxidants such as paraoxonase 1 (PON1) and arylesterase (ARE) associated with lipoprotein peroxidation have not been examined in BPH patients. PON1 and ARE, a high-density lipoprotein (HDL) cholesterol-bound enzyme system of antioxidants, protect low-density lipoprotein (LDL) cholesterol and HDL from oxidation by hydrolysis. The study primarily determined paraoxonase (PON1) and ARE activities in BPH treatment-naïve patients.

Materials and methods

Sixty newly diagnosed patients (treatment-naïve) alongside 30 apparently healthy controls were recruited. Blood examinations included lipid profile (total cholesterol, triglycerides, LDL, HDL), glutathione peroxidase, PON1, ARE, and prostate specific antigen (PSA).

Prostate volume and International Prostate Symptoms Score (IPSS) were determined.

Results

PSA was significantly different between patient and control groups (P < 0.0001). Total cholesterol, triglycerides, and LDL were significantly higher in the patient group (P = 0.002, P < 0.001, P = 0.003, respectively). Glutathione peroxidase was very low in the patient group compared to the control group (5.65 ± 2.30 ng/mL and 17.43 ± 10.98 ng/mL, respectively). Although PON1 was higher in the patient group (50.22 ± 19.68/61.30 ± 29.55 ng/mL; P > 0.05), ARE was significantly lower in the patient group (61.31 ± 21.76/49.30 ± 19.82 ng/mL; P = 0.0098). No correlation was established between antioxidants and the lipid profile except for the LDL and PON1 patient group (r = 0.1486, P = 0.0374). Similarly, a weak correlation was also established between PSA and LDL in the patient group (r = –0.275, P = 0.033). PON1/HDL ratio was not significantly different. However, the ARE/HDL ratio was significantly lower in the patient group (P < 0.0001).

Conclusion

These results signify the presence of a higher lipoprotein peroxidation activity and lower lipid-associated antioxidant activity in the patient group. The ARE/HDL ratio is a better indicator of the HDL associated antioxidant than the PON1/HDL ratio or the individual antioxidants (PON1 and ARE) as reported by others.

Paraoxonase (PON1) polymorphisms Q192R and L55M are not associated with human longevity: A meta-analysis

BACKGROUND

Genetic mutations in the paraoxonase 1 (PON1) encoding gene have been considered to affect mortality and of these the functional promoter region polymorphisms Q192R and L55M are among the most widely studied.

OBJECTIVE

The aim of this study was to determine whether the Q192R and L55M polymorphisms of PON1 can increase susceptibility to longevity. A meta-analysis was performed to obtain a comprehensive estimation of the association between Q192R and L55M and longevity in long-lived individuals (LLIs) aged 80 years or more.

MATERIAL AND METHODS

A search was carried out in the PubMed database (from January 2001 to May 2014) to obtain data on the role of PON1 polymorphisms in longevity and a pooled odds ratio (OR) with a 95% confidence interval (CI) was used to assess the associations.

RESULTS

The meta-analysis was based on 9 studies of PON1 Q192R and 5 studies of PON1 L55M that covered a total of 5086 LLIs and 4494 controls. Overall, significantly increased risks were not observed for either Q192R or L55M. The results of the statistical calculations were as follows: R vs. Q (additive model): OR = 1.080, 95% CI = 0.989-1.179, p = 0.088 and RR + RQ vs. QQ (dominant model): OR = 1.099, 95% CI = 0.975-1.240, p = 0.124; M vs. L (additive model): OR = 0.946, 95% CI = 0.862-1.039, p = 0.245 and MM + ML vs. LL (dominant model): OR = 0.951, 95% CI = 0.836-1.081, p = 0.442 for Q192R and L55M, respectively. The results did not change with an age cut-off among the LLIs of ≥ 93 years.

CONCLUSION

No evidence that the Q192R and L55M polymorphisms of PON1 impacted on the probability of reaching extreme ages was found although this cannot be completely ruled out; however, the possibility of population-specific effects due to the influence of and interaction between different genes or environmental factors could not be ruled out.

[Is PON1 a factor of cardiovascular risk in type 2 diabetes?]

OBJECTIVE

We evaluate the association between the decrease of serum paraxonase 1 activity and the risk of cardiovascular disease in type 2 diabetes.

METHODS

One hundred and fourteen patients with type 2 diabetes were included in the present study. Seventy-one of them have significant coronary disease. The control group consisted of 53 healthy adults.

RESULTS

PON1 activity was significantly reduced in diabetic patients compared to controls (P=0.021), especially in those with significant coronary disease (P=0.013). No significant variation in PON1 activity according to age was observed both in controls and in patients. When HDLc≥1.03mmol/L, the PON1 activity was significantly higher in patients without significant coronary disease compared to those with significant coronary disease (0.030). In case of significant coronary disease, a decrease of 12.23% in PON1 activity was observed in smokers compared with non-smokers, but without statistical significance. The PON1 activity did not very significantly according to the presence or absence of hypertension in patients with significant coronary disease.

CONCLUSION

The implication of diabetes in the decrease of PON1 activity seems highly probable but PON1 activity seems not to be in itself a marker of cardiovascular disease.

New chemiluminescent substrates of paraoxonase 1 with improved specificity: synthesis and properties

Paraoxonase 1 (PON1) is an important hydrolase, and the enzyme activity decreases in patients with liver disease, diabetes, coronary heart disease, etc. Phenyl acetate and organophosphates are usually employed as substrates for serum PON1 activity assay. However, phenyl acetate for arylesterase activity assay exhibits disadvantage of high background. According to properties of PON1, four new chemiluminescent acridinium esters were designed, prepared through three steps, and characterized with (1)H NMR and mass spectrometry (MS) data, and their properties as PON1 substrates were investigated. The hydrolyses of the four compounds catalyzed by recombinant human PON1 (rhPON1) (or serum) followed first-order kinetics within 22 min. The PON1 activator (NaCl, 0.10 mol L(-1)) could boost the rhPON1-mediated and serum-mediated hydrolyses of the acridinium esters to 2.01 ~ 2.26 folds, but 1.0 mol L(-1) NaCl decreased the serum arylesterase activity. RhPON1 showed selectivity over other serum esterases such as lipase, acetylcholinesterase, and esterase D more than 300 folds. By using ethylene diamine tetraacetic acid (EDTA) inhibitor, the specificities of the four substrates toward serum PON1 were determined as 78.3 ~ 92.9%, which is improved than that of the model compound 9-(4-chloro-phenoxycarbonyl)-10-methylacridinium ester triflate. Due to low toxicity, high specificity, and sensitivity of the substrates, they are useful for serum PON1 activity assay.

Paraoxonase 1 activity and level of antibodies directed against oxidized low density lipoproteins in a group of an elderly population in Poland - PolSenior study

The aim of this study was to assess two factors influencing the amount of oxidized LDL-paraoxonase 1 (PON1) activity and the level of anti-oxidized LDL antibodies (anti-ox LDL) in a large group of elderly individuals in Poland. The effects of cognitive status, hypertension and metabolic syndrome and of selected serum lipids and inflammation indicators on PON1 activity and anti-ox LDL level were also examined. The investigated population consisted of 3154 individuals aged 65 and more - participants of the population-based PolSenior project. PON1 arylesterase activity was determined spectrophotometrically, anti-ox-LDL antibodies using ELISA method. PON1 activity significantly decreased with advancing age, was lower in males than in females and decreased in persons with impaired cognition. Individuals with hypertension and high lipid levels showed higher PON1 activity. Lower PON1 activity was related to higher level of inflammation indicators - hsCRP and IL-6. The significant association of PON1 activity with age, HDL-C, LDL-C, sex and IL-6 was confirmed in multivariate analysis. Anti-ox LDL antibodies level was significantly higher in the two oldest subgroups of males. It was significantly lower in males than in females. It was decreased in persons with higher serum triglycerides. No relationship of anti-ox LDL level with cognition, hypertension, metabolic syndrome, inflammation indicators and serum lipid levels was observed. In some persons very high levels of anti-ox LDL were stated, most frequently in the oldest persons, particularly in men.

CONCLUSION

Both investigated antioxidant factors - PON1 activity and anti-ox LDL level, could play an important role in aging.

Onion extract (Allium cepa L.), quercetin and catechin up-regulate paraoxonase 1 activity with concomitant protection against low-density lipoprotein oxidation in male Wistar rats subjected to oxidative stress

BACKGROUND

Paraoxonase 1 (PON1) protects the oxidative modification of low-density lipoprotein (LDL) and is a major anti-atherosclerotic protein component of high-density lipoprotein. We explored the effect of onion extract and flavonoids (quercetin and catechin) in the regulation of PON1 expression and correlating with oxidised LDL levels in male Wistar rats subjected to mercuric chloride (HgCl₂) induced oxidative insult. Rats were divided into eight groups: Control, Experimental (HgCl₂), Experimental + onion/catechin/quercetin, Positive control (Normal + onion/catechin/quercetin). Treatment continued for 4 weeks.

RESULTS

PON1 activity and radical scavenging activity decreased in the Experimental group (P < 0.001) with increased susceptibility of LDL for oxidation and plasma malondialdehyde levels (P < 0.001). Onion extract significantly attenuated the adverse effects of HgCl₂ by up-regulating PON1 activity (P < 0.05), radical scavenging activity (P < 0.01), and protected against LDL oxidation (P < 0.001) and lipid peroxidation (P < 0.01). Similar effects were observed with quercetin and to a lesser extent with catechin.

CONCLUSIONS

The findings may explain the anti-atherosclerotic effect of onion and also foods containing quercetin and catechins.

Paraoxonase 1 polymorphisms within a Mississippi USA population as possible biomarkers of enzyme activities associated with disease susceptibility

Paraoxonase (PON1) hydrolyzes paraoxon (PO) and diazoxon (DZO), active metabolites of insecticides parathion and diazinon. The PON1 gene has single nucleotide polymorphisms (SNPs) including a codon 192 arginine (R) to glutamine (Q) and methionine (M) to leucine (L) at codon 55. Hydrolysis of PO (POase), DZO (DZOase), dihydrocoumarin (lactonase), and phenyl acetate (arylesterase) were evaluated for associations with race, gender, age, and PON1 55/192 SNP genotypes. Variables were analyzed both individually and in combination. QQ individuals had higher lactonase (p < 0.001) than RR individuals. This might partially explain why predominantly RR African Americans have higher rates of coronary disease than predominantly QQ Caucasians. Significant (p < 0.001) differences in arylesterase were seen among genotypes with QQ and MM lowest whereas RR and LL were highest. This opposes the prevailing belief that arylesterase is unaffected by genotype and suggests that this activity cannot be used to quantify PON1 protein.

Plasma paraoxonase 1 arylesterase activity in D-galactose-induced aged rat model: correlation with LDL oxidation and redox status

OBJECTIVE

There is much evidence linking the involvement of oxidative stress in the pathogenesis of aging. Paraoxonase 1 (PON1) is an HDL-associated antioxidant enzyme that inhibits the oxidative modification of low-density lipoproteins (LDL). We have investigated the changes in plasma PON1 activity, LDL oxidation, radical scavenging activity and lipid peroxidation in D-galactose-induced aging rat model and also compared the results with 24-month naturally aged rats.

METHOD

Arylesterase activity of PON1, susceptibility of LDL for oxidation, plasma radical scavenging activity and plasma thiobarbituric acid reactive substances (TBARS) were measured in normal control rats (4-months-old control rats subjected to D-galactose-induced experimental aging, and 24-month-old naturally aged rats).

RESULTS

There was a significant decrease in plasma PON1 arylesterase activity in both subcutaneous D-galactose-treated groups and 24-month-old aged rats (P < 0.05, for each). TBARS, an oxidative stress marker, was seen to increase in the experimental groups (P < 0.01). In both subcutaneous galactose-treated and naturally aged rats, there was a significant rise in plasma LDL oxidation (P < 0.05, for each). However, radical scavenging activity was decreased significantly (P < 0.01) in both groups, as compared to control.

CONCLUSIONS

The D-galactose-induced rat model of aging mimics the naturally aged rat with reference to PON1 arylesterase activity and susceptibility to LDL oxidation. The results emphasize the importance of PON1 with respect to aging and its association with redox balance of the body.

Age-dependent paraoxonase 1 (PON1) activity and LDL oxidation in Wistar rats during their entire lifespan

Paraoxonase 1 (PON1) is an HDL bound enzyme which plays a key role in the protection of LDL and HDL from oxidation by hydrolyzing activated phospholipids and lipid peroxide products. Oxidative stress plays a crucial role in the development of atherosclerosis by oxidation of LDL. This study was conducted to determine age-dependent changes in plasma PON1 arylesterase activity and LDL oxidation in rats during their entire lifespan. 48 Wistar strain rats were grouped in six different age groups (1, 4, 8, 12, 18, and 24 months). We observe a significant (P < 0.001) age-dependent decrease in plasma PON1 arylesterase activity correlating with increase in susceptibility of LDL oxidation and increase in plasma MDA level concomitantly with a significant (P < 0.001) decrease in plasma radical scavenging activity after 8 months. The reduction of PON1 and free radical scavenging activity with age could have a considerable impact on the increased incidence of atherosclerosis with age. Our observation of a significant decline in PON1 activity which correlates with increased LDL oxidation after 8 months of age is an interesting observation and needs further investigation.

Extra-virgin olive oil consumption reduces the age-related decrease in HDL and paraoxonase 1 anti-inflammatory activities

Paraoxonase 1 (PON1) is associated with HDL and modulates the antioxidant and anti-inflammatory role of HDL. The goals of the present study were to investigate the effect of ageing and the role of PON1 on the anti-inflammatory activity of HDL, and to determine whether extra-virgin olive oil (EVOO) consumption could improve the atheroprotective activity of HDL. HDL and PON1 were isolated from the plasma of ten young (Y-HDL and Y-PON1) and ten elderly (E-HDL and E-PON1) healthy volunteers before and after 12 weeks of EVOO consumption. Inflammation was assessed by measuring intracellular adhesion molecule 1 (ICAM-1) expression. THP-1 (human acute monocytic leukaemia cell line) monocyte chemotaxis was measured using a Boyden chamber. Oxidative damage to HDL was assessed by measuring conjugated diene formation and changes in electrophoretic migration. Y-HDL had more anti-inflammatory activity than E-HDL. The conjugated diene content and the electrophoretic mobility of E-HDL were higher than those of Y-HDL. Y-PON1 had significant anti-inflammatory activity, reducing ICAM-1 expression by 32·64 (SD 2·63)%, while E-PON1 had no significant effect. THP-1 chemotaxis measurements confirmed the ICAM-1 expression results. The 12 weeks of EVOO consumption significantly increased the anti-inflammatory activities of both HDL and PON1. The anti-inflammatory activity of HDL was modulated by PON1 and was lower in the elderly volunteers. EVOO consumption increased the anti-inflammatory effect of HDL and reduced the age-related decrease in anti-atherogenic activity.

N,N-Dimethyl-p-phenylenediamine dihydrochloride-based method for the measurement of plasma oxidative capacity during human aging

N,N-Dimethyl-p-phenylenediamine dihydrochloride (DMPD) is a compound that is normally used to measure the antioxidant potential. In the presence of Fe(3+), it gets converted to DMPD(∙+) radical, which is scavenged by antioxidant molecules present in test samples. In plasma, due to the presence of iron, this method cannot be applied for the measurement of antioxidant potential. The modified DMPD method proposed by us measures with great accuracy the oxidant potential of plasma using the oxidizing effect of plasma to oxidize DMPD into producing a stable pink color. The method is fast and reproducible. We show that plasma oxidative capacity increases significantly during human aging.