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.

In vivo/in silico insight into the effect of titanium dioxide nanoparticle on serum paraoxonase 1 activity in rat

Serum paraoxonase1 (PON1) has special function in human body organism including the antioxidant and anti-atherogenic properties. In the present study, the effect of TiO₂ nanoparticles on the activity and structure of the PON1 has been evaluated through in vivo and in silico methods. After treatments of the rats with different doses of TiO₂ NPs, blood samples were collected and serum PON1 activity was measured by phenylacetate and paraoxon as substrate. In addition, the effects of TiO₂ NP on enzyme structure were analyzed through Molecular dynamic (MD) simulation via Gromacs software package to obtain RMSD, RMSF, Rg, SASA, and secondary structures values. A significant reduction (p < 0.05) in arylesterase & paraoxonase activities of serum PON1 were monitored in Spectrometric assays when rats were treated with 150 and 200 mg/kg doses of TiO₂ NPs. RMSD, RG, RMSF, and SASA values in the presence of TiO₂ have been increased while RMSF values of the L1 and L2 loops (gate of the catalytic site) have been reduced. Moreover, Hydrogen bonds and secondary structure values of the enzyme decreased in the presence of TiO₂ NP. All of these MD simulation results could indicate the instability of the PON1 structure bounded to TiO₂ NP. TiO₂ NP could cause a disturbance in the enzyme structure and function of PON1 based on the results. PON1 prevents oxidation of LDL and can delay atherosclerosis progression while in the presence of TiO₂ NP these protective effects could be endangered.Communicated by Ramaswamy H. Sarma.

Comparison of early cardiovascular risk among Brazilian and African university students

Cardiovascular diseases are among the main causes of mortality worldwide, and dyslipidemia is a principal factor risk. Hence the study of biochemical markers is necessary for early diagnosis.

OBJECTIVES

Evaluate biomarkers to diagnose the risks of cardiovascular diseases in healthy Brazilian and African young adults.

DESIGN & METHODS

Weight, height, waist circumference, percentage of body fat and systemic blood pressure were measured; and fasting blood samples were taken for biochemical analysis. Triglycerides, total cholesterol, HDL-c, and apolipoproteins A-I and B were measured on automated equipment using commercially available kits, in addition to the tests of antioxidant capacity of HDL and the enzymatic activity of Paraoxonase 1.

RESULTS

After statistical analysis, it was found that BMI, WC, fat (%), triglycerides, ApoB/ApoA-I ratio and Vmax were higher in Brazilians, while HDL-c, ApoA-I, Lag Time, Vmax and PON1 activity were higher in Africans. In Brazilians, the ApoB/ApoA-I ratio was related to obesity factors and lipid profile, but in Africans it was related only to lipids. The antioxidant capacity of HDL and PON1 activity was better in Africans. Through independence testing, we observed an association with moderate risk of myocardial infarction with gender in Africans. In the binary logistic regression analysis, it was found that men in general - and particularly African men - have higher risk of myocardial infarction than women; Odds Ratio 2144 (CI_95%: 1343-3424) and 2281 (CI_95%: 1082-4811), respectively.

CONCLUSIONS

The anthropometric and biochemical parameters of Brazilians, especially men, predispose them to greater risks of cardiovascular diseases.

Assessment of PON1 activity and circulating TF levels in relation to BMI, testosterone, HOMA-IR, HDL-C, LDL-C, CHO, SOD activity and TAC in women with PCOS: An observational study

BACKGROUND

Polycystic Ovary Syndrome (PCOS) is the most common female endocrinopathy among premenopausal women associated with hyperandrogenism, obesity, dyslipidemia, insulin resistance and inflammation. Oxidative stress is an important component of cardio-metabolic risk seen in PCOS.

MATERIAL AND METHODS

A total of 95 women with PCOS and 95 healthy controls were included in this observational study. Serum PON1 activity and stress markers were measured by spectrophotometric methods. Circulating TF level was measured by ELISA.

RESULTS

We found decreased PON1 activity and increased TF levels in women with PCOS compared to healthy controls. Fasting insulin, HOMA-IR, testosterone, LDL-C, MDA, PC and SOD activity were significantly increased whereas FGIR, QUICKI, HDLC, CAT and TAC were significantly decreased in PCOS women than controls. We observed a positive association of PON1 activity with FGIR, QUICKI, HDL-C and TAC, and its negative association was observed with LH, testosterone, fasting insulin and HOMA-IR in PCOS women. We further observed a positive association of TF with waist, waist to hip ratio, BMI, glucose 1hr, cholesterol, LDL-C, SGPT, uric acid and SOD activity in PCOS women.

CONCLUSIONS

Decreased PON1 activity and raised circulating TF levels are respective indicators of pro-inflammatory and procoagulant status in PCOS women. The imbalanced oxidant/antioxidant status further supports the evidences that PCOS is an oxidant state. Further, the association of PON1 activity and TF levels with the clinical, laboratory findings and stress marker levels suggest that these factors taken together are involved in aggravating the pro-inflammatory status in PCOS women.

Functional implications of single nucleotide polymorphisms rs662 and rs854860 on the antioxidative activity of paraoxonase1 (PON1) in patients with rheumatoid arthritis

BACKGROUND

Atherosclerosis leading to cardiovascular disease (CVD) is the main cause of mortality and morbidity in patients with rheumatoid arthritis (RA). Paraoxonase1 (PON1) is the best understood member of plasma paraoxonases with anti-atherogenic properties.

PATIENTS AND METHODS

Spanish RA (n = 549) consecutively recruited from 1 single center and 477 ethnically matched healthy controls were included in a case-control study. The concentration of PON1 was evaluated by means of an enzyme-linked immunosorbent sssay (ELISA). An arylesterase/paraoxonase assay kit was used to evaluate PON1 activity. Sample genotyping was performed by using TaqMan assays-on-demand. All results were expressed as medians ± interquartile range. One-way ANOVA comparisons were done using a nonparametric Kruskall-Wallis test. P values under 0.05 were considered to be significant.

RESULTS

The concentration of PON1 in the RA group was higher than in control group (p = 0.0003), although the differences were not significant when PON1 activities were compared between both groups. No significant differences were found related to distributions of rs662 genotypes in RA patients compared to healthy controls. Among rs854860 polymorphisms, overall genotype was widely distributed between RA patients and controls. Overall PON1 concentration in plasma was not significantly different between individuals carrying any of rs662 (p = 0.8501) or rs854860 (p = 0.2741) polymorphisms. Although PON1 levels were not associated with any of the SNPs in the study, differences appear when enzyme activities are compared for each SNP separately. CVD in RA patients correlate with increased PON1 levels and lower PON1 activity.

CONCLUSIONS

Although protective role of PON1 against oxidative damage in vivo could be related to other activities, in our study arylesterase activity was useful to identify phenotypic differences with emphasis placed on two SNPs coding for nonconservative amino acid changes in the functional protein.

Daily supplementation with fresh pomegranate juice increases paraoxonase 1 expression and activity in mice fed a high-fat diet

PURPOSE

Studies have found that pomegranate juice (PJ) consumption increases the binding of high-density lipoproteins (HDL) to paraoxonase 1 (PON1), thus increasing the catalytic activity of this enzyme. PON1 is an antioxidant arylesterase synthesized in the liver and transported in plasma in association with HDL. Decreased levels of PON1 are associated with higher levels of cholesterol. We determined the effects of PJ on body weight, cholesterol, and triacylglycerols through 5 months of supplementation. In addition, the effect of PJ on pon1 gene expression in the liver was also measured by RT-qPCR as well as the activity in serum by a semiautomated method using paraoxon as a substrate.

METHODS

CD-1 mice were either fed a control diet or were fed a high-fat diet 1.25% (wt/wt) cholesterol, 0.5% (wt/wt) sodium cholate, and 15% (wt/wt) saturated fat. 300 μL of PJ containing 0.35 mmol total polyphenols was administered by oral gavage to half of the high fat mice daily. The rest of the high fat mice and the control mice were administered with 300 μL of water.

RESULTS

PJ-supplemented animals had significantly higher levels of expression of pon1 compared to the unsupplemented group. PJ-supplemented animals had twice the PON1 activity of the unsupplemented group. In addition, PJ-supplemented animals had the lowest body weight and significantly reduced cholesterol and triacylglycerol levels, although the tricylglycerol levels were not consistently decreased.

CONCLUSIONS

These results suggest that PJ protects against the effects of a high-fat diet in body weight, and cholesterol levels.

The role of 'paraoxonase-1 activity' as an antioxidant in coronary artery diseases

BACKGROUND AND OBJECTIVES

A majority of the Coronary Artery Diseases (CAD) result from complications of atherosclerosis. There is a growing body of evidence which has revealed that the reduced activity of the HDL-associated enzyme, paraoxonase1 (PON1), is predictive of vascular disease in humans, which include the results from prospective studies. The mechanisms by which PON1 activity influences risk of vascular disease continue to be evaluated. It is generally thought that PON1 contributes to the antioxidant, and thus, to the antiatherogenic properties of High Density Lipoproteins (HDL). Depleted antioxidant levels could be a risk factor for coronary artery disease. Hence, this study was done to evaluate PON1, as antioxidant, in CAD patients.

METHODS

This study was done to determine serum levels of PON1 activity in 50 controls and in 60 clinically and ECG proven CAD cases and to compare PON1 activity with total cholesterol and triglycerides.

RESULTS

Serum levels of PON1 activity (p<0.001) were significantly lower in CAD cases than in controls. Serum total cholesterol (p< 0.001) and triglyceride (p< 0.001) levels were significantly higher in CAD cases than in controls. There was a negative correlation between PON 1 activity and total cholesterol and triglycerides. The negative correlation between PON1 activity and total cholesterol was significant (p<0.05).

INTERPRETATION AND CONCLUSION

From our present study, we can conclude that PON1 can exert a protective effect on HDL by preventing its oxidative damage. Further, a decreased PON 1 activity may be a risk factor for CAD, which is likely to be explained by derangement of PON 1 activity towards lipid peroxidation. This study suggested that serum antioxidant activity of PON1 was an important factor which provided protection from oxidative stress and lipid peroxidation in CAD. Thus, evaluating the effects of PON 1 for CAD patients may be promising in the treatment and prognosis of CAD.

Effect of Resveratrol and Nicotine on PON1 Gene Expression: In Vitro Study

Dietary and lifestyle factors have been shown to have a profound effect on paraoxonase-1 (PON1) activity. Cigarette smoke has been shown to inhibit its mass and activity where as resveratrol has been shown to enhance it. We exposed hepatoma derived cell line (HepG2) to resveratrol and nicotine in varying doses and measured PON1 enzymatic activity and PON1 gene expression. In addition, total protein content of HepG2 cells was also measured. Resveratrol in a dose of 15 μmol/l or above significantly increased the PON1 enzyme activity (p > 0.001) where as nicotine in a dose of 1 μmol/l or higher significantly reduced it (p < 0.05). The resveratrol in this dose also enhanced the PON1 gene expression whereas nicotine decreased it as compared to controls. However, the protein conent of cells was not changed suggesting that they were not cytotoxic in the doses used. Till date the antioxidant vitamins have shown disappointing results against LDL oxidation and cardiovascular protection. However, the effect of resveratrol on PON1 gene expression and activity was significant, suggesting increase in PON1 activity and enhanced gene expression may be its alternative mechanism for offering protection against cardiovascular disease and may be an potential pharmacological agent which can be used for this.