Serum paraoxonase activity and the extent of lipid peroxidation are not affected by increased levels of human apolipoprotein A-I: studies in transgenic mice

Multi-Pathway Microenvironment Regulation for Atherosclerosis Therapy Based on Beta-Cyclodextrin/L-Arginine/Au Nanomotors with Dual-Mode Propulsion

Most of the current non-pharmacological treatment strategies for atherosclerosis (AS) suffer from poor penetration into the plaque and only aim at a certain factor in its formation process, resulting in limited therapeutic effect. Herein, a kind of nanomotor with dual-mode propulsion is constructed, which is sensitive to higher reactive oxygen species (ROS) at the AS site and near-infrared (NIR) laser by the covalent binding and self-assembly of β-cyclodextrin (β-CD) and L-arginine (LA) with immobilization of Au nanoparticles. NIR laser irradiation can be used as a driving force and to ablate inflammatory macrophages through the photothermal effect. The nitric oxide (NO) released by the nanomotors can be used as another driving force and a therapeutic agent to promote endothelial repair in the plaque site. LA can eliminate ROS in the inflammatory site, and β-CD can promote the removal of cholesterol from foam cells. In particular, the two driving modes of nanomotors synergistically promote their aggregation and penetration in the plaque. This kind of nanomotor can regulate the microenvironment of AS in multiple ways, including combination therapy for endothelial repair, lipid clearance, and reducing ROS, which is expected to become a potential non-pharmacological strategy in the treatment of AS.

Paraoxonase-1 enzyme activity assay for clinical samples: validation and correlation studies

BACKGROUND

Paraoxonase-1 (PON1) enzyme is reported in various types of tissues and linked to numerous pathophysiological disorders. It is a potential biomarker in many pathological conditions such as cardiovascular diseases.

MATERIAL AND METHODS

We conducted several small-scale studies to evaluate PON1 performance as affected by sample types, storage, and interferences. We also carried out short-term studies to compare the performance of the widely used PON1 assay to the similar commercially available PON1 kit assay method; sample size for the method comparison was N=40, and the number varied for other validation experiments.

RESULTS

Our studies using various types of anticoagulants show that samples collected in tubes with NaF, citrate, EDTA, clot activator, and sodium heparin have increased PON1 levels that are 49%, 24.5%, 19.8%, 11.4%, and 8%, respectively, higher compared to serum samples collected in plain tubes. However, samples collected in lithium heparin tubes demonstrated 10.4% lower PON1 levels compared to serum collected in plain tubes. Biological interference such as hemolysis has little effect on PON1 levels; however, samples spiked with lipids have shown 13% lower PON 1 levels. Our studies comparing the PON1 method commonly available for PON1 assay and a similar non-ELISA commercially available PON1 kit method showed a weak Spearman correlation coefficient of R2=0.40 for the range of 104.9-245.6 U/L.

CONCLUSIONS

The current study provides new validation data on enzyme PON1 performance. While no appreciable change was seen with storage, samples type affects the enzyme performance. Our results should encourage additional clinical studies to investigate other aspects of factors known to affect PON1 enzyme function and performance.

Serum homocysteine levels and paraoxonase 1 activity in preschool aged children in Greece

BACKGROUND

Over the past decade, it has been well established that elevated total serum homocysteine (tHcy) in adults is associated with increased risk of cardiovascular and thromboembolic diseases. Since risk factors for such diseases are established at a young age, the aim of the present study was to measure serum tHcy levels in 134 (71 boys, 63 girls) randomly selected healthy preschool children aged 4-6 years (mean 5.1), and to investigate possible correlation with paraoxonase 1 (PON1) activity, an antioxidant enzyme that contributes to the antiatherogenic properties of high-density lipoprotein (HDL).

METHODS

tHcy was determined using an IMX tHcy assay (FPIA). PON1 was measured by a spectrophotometric method at 412 nm.

RESULTS

Mean serum tHcy was 7.71+/-2.35 mumol/L. A relatively significant percentage (15.6%) of boys and girls had elevated serum tHcy levels (>10 mumol/L). tHcy levels were slightly higher in girls compared to boys (8.20+/-2.80 vs. 7.29+/-1.79 mumol/L, respectively; p<0.11). There was no significant interaction between age and tHcy levels. Mean PON1 activity was 124.86+/-66.62 U/L. No statistical difference in enzyme activity was observed between boys and girls (126.81+/-69.99 vs. 121.74+/-64.78 U/L) was observed. On the contrary, a weak negative relationship between tHcy concentration and PON1 activity was detected, with Pearson's correlation coefficient of r=-0.27.

CONCLUSIONS

The significant percentage of elevated tHcy levels observed in healthy preschool cases and the negative tHcy correlation with PON1 activity are reported for the first time. Since children with a family history of cardiovascular disease have higher levels of serum Hcy, tHcy screening in children, even of this age, in relation to other parameters, such the protective PON1, might prove a useful prevention procedure for the genetic risk of premature atherosclerosis.

Effects of intranasal estradiol treatment on serum paraoxonase and lipids in healthy, postmenopausal women

BACKGROUND/AIMS

Serum lipid concentrations worsen after the menopause because of estrogen deficiency, leading to an increased atherogenic pattern. It is known that serum paraoxonase (PON1) activity prevents the development of atherosclerosis. The aim of this cross-sectional study was to observe the effects of intranasal 17beta-estradiol (300 microg/day) on serum PON1 and lipid levels in healthy postmenopausal women.

METHODS

48 healthy, postmenopausal women were enrolled into this cross-sectional study. 28 subjects without an intact uterus and ovaries were using single-dose (300 microg/day) intranasal 17beta-estradiol and 20 subjects with spontaneous natural menopause were not on any hormone therapy. Body mass index (BMI), blood pressure, serum follicle-stimulating hormone, estradiol, fasting glucose, insulin, lipid fractions and PON1 levels were measured. Homeostasis model assessment (HOMA-R) was used to estimate insulin resistance.

RESULTS

The higher estradiol, high-density lipoprotein and salt-stimulated paraoxonase (SSP) levels were observed in intranasal 17beta-estradiol users in comparison with non-users. There were no statistically significant differences in BMI, blood pressures, other lipid fractions, basal paraoxonase, arylesterase, fasting glucose and insulin levels, HOMA-R between the groups. SSP was inversely associated with fasting insulin levels and HOMA-R.

CONCLUSION

These observations may suggest that intranasal 17beta-estradiol does not have harmful effects on the PON1 activity and lipid metabolism.

Correlation Studies of Plasma Paraoxonase Activity and Uric Acid Concentration with AAPH-Induced Erythrocyte Hemolysis in Hemodialysis Patients

Uric acid possesses antioxidant properties and is an important determinant of total plasma antioxidant capacity. Uric acid concentrations tend to be elevated in patients with renal failure requiring maintenance hemodialysis but are abruptly reduced by the dialysis procedure itself. Paraoxonase (PON1), an enzyme which circulates in association with high density lipoprotein (HDL), confers protection against free radicals by limiting the oxidation of phospholipids. The relationship between pre- and postdialysis uric acid concentration, PON1 activity, and high density lipoprotein cholesterol (HDL-C) level and the resistance of erythrocytes from hemodialysis patients to hemolysis induced by the free radical generator 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) was studied. Red cells were washed free of plasma prior to the assay, and no plasma was added to the hemolysis assay tubes. Postdialysis erythrocytes were found to be more susceptible to hemolysis compared to blood samples obtained at the initiation of the session (784 +/- 713 vs. 256 +/- 256 micro mol/L hemoglobin released after 60 min incubation and 1530 +/- 696 vs. 1354 +/- 757 micro mol/L at 90 min). Hemolysis correlated negatively with the concentration of uric acid and positively with PON1 arylesterase activity but not with HDL-C level in the corresponding plasma samples. There was a strong negative correlation between uric acid and PON1 in predialysis blood samples (r2 = 0.4, P < 0.001). The conclusion is that the reciprocal relationship between uric acid and PON1 may reflect a mechanism that protects erythrocytes from subsequent oxidative stress.