In vivo effects of oral contraceptives on paraoxonase, catalase and carbonic anhydrase enzyme activities on mouse

In vitro effects of thirty-eight cardiac drugs on human serum paraoxonase

In this study, the effects of 38 commonly used cardiac drugs on the human paraoxonase (PON1) were investigated. PON1 was purified from human serum blood by ammonium sulfate precipitation (60%-80%) and hydrophobic interaction chromatography (Sepharose-4B~L-tyrosine~1-napthylamine gel). All of the cardiac drugs inhibited PON1 at the micro molar level. IC₅₀ and K_i values were determined for each drug. The tested drugs displayed potent PON1 inhibitory activity. It was found that the weakest PON1 inhibitors are Irbesartan (K_i : 421.73 µM), Glyceryl Trinitrate (K_i : 351.48 µM), and Apixaban (K_i : 333.27 µM). Bisoprolol hemifumarate (K_i : 269.31 µM) is also other weak PON1 inhibitor. Therefore, these drugs, having weak PON1 inhibitory activity, may be preferred primarily in patients with atheroclerotic heart disease compared to other drugs due to the protective effect of PON1 on atherosclerosis. Conversely, the most potent inhibitors against PON1 were propafenone (K_i : 0.35 µM), Lacidipine (K_i : 0.78 µM), Lidocaine HCl (K_i : 1.78 µM), and Propranolol (K_i : 1.86 µM). Molecular docking was also applied to confirm the activity of some cardiac drugs on PON1.

Mutual Influences between Nitric Oxide and Paraoxonase 1

One of the best consolidated paradigms in vascular pharmacology is that an uncontrolled excess of oxidizing chemical species causes tissue damage and loss of function in the endothelial and subendothelial layers. The fact that high-density lipoproteins play an important role in preventing such an imbalance is integrated into that concept, for which the expression and activity of paraoxonases is certainly crucial. The term paraoxonase (aryldialkyl phosphatase, EC 3.1.8.1) encompasses at least three distinct isoforms, with a wide variation in substrate affinity, cell and fluid localization, and biased expression of polymorphism. The purpose of this review is to determine the interactions that paraoxonase 1 has with nitric oxide synthase, its reaction product, nitric oxide (nitrogen monoxide, NO), and its derived reactive species generated in an oxidative medium, with a special focus on its pathological implications.

Sex difference: an important issue to consider in epidemiological and clinical studies dealing with serum paraoxonase-1

The aim of this study was to evaluate the influence of sex on serum paraoxonase-1 (PON1) activities and on its relationship with cardiovascular disease risk factors such as overall and central obesity. Arylesterase and lactonase activities of PON1 were assessed in 374 women and 92 men. Both arylesterase and lactonase activities were significantly higher in women compared to men (p<0.001), irrespectively of confounders such as high density lipoprotein-cholesterol, age, smoking and body mass index or waist circumference. Sex also strongly influenced the interplay between PON1 and both fat measures, with only the arylesterase showing a significant and independent inverse correlation with the former parameter (r = -0.248, p<0.001) and the risk of overall obesity (odds ratio: 0.559, 95% confidence interval: 0.340-0.919) in women, but not in men; conversely, neither of the two activities remained associated with waist circumference in men or women after full adjustment. Noteworthy, the association between arylesterase and BMI in the female subsample was significant among women younger than forty-five years (r = -0.453, p<0.001, R ² = 0.207). In conclusion, our study suggests that sex might chiefly influence PON1 activity and its contribution to cardiovascular disease risk. Further studies are needed to confirm and clarify our preliminary findings.

Sex difference: an important issue to consider in epidemiological and clinical studies dealing with serum paraoxonase-1

The aim of this study was to evaluate the influence of sex on serum paraoxonase-1 (PON1) activities and on its relationship with cardiovascular disease risk factors such as overall and central obesity. Arylesterase and lactonase activities of PON1 were assessed in 374 women and 92 men. Both arylesterase and lactonase activities were significantly higher in women compared to men (p<0.001), irrespectively of confounders such as high density lipoprotein-cholesterol, age, smoking and body mass index or waist circumference. Sex also strongly influenced the interplay between PON1 and both fat measures, with only the arylesterase showing a significant and independent inverse correlation with the former parameter (r = −0.248, p<0.001) and the risk of overall obesity (odds ratio: 0.559, 95% confidence interval: 0.340–0.919) in women, but not in men; conversely, neither of the two activities remained associated with waist circumference in men or women after full adjustment. Noteworthy, the association between arylesterase and BMI in the female subsample was significant among women younger than forty-five years (r = −0.453, p<0.001, R² = 0.207). In conclusion, our study suggests that sex might chiefly influence PON1 activity and its contribution to cardiovascular disease risk. Further studies are needed to confirm and clarify our preliminary findings.

Paraoxonases: metabolic role and pharmacological projection

Atherosclerosis is one of the leading causes of death in Western countries, with high-density lipoproteins (HDL) playing an important protective role due to their ability to inhibit oxidation of low-density lipoproteins (LDL), thus relieving vascular subendothelial damage. One of the proteins constituting HDL particles is paraoxonase-1 (PON1), an enzyme able to hydrolyze aryl esters, lactones, and organophosphates. Other closely related paraoxonases are designated as PON2, which is a protein localized inside many different kinds of cells, and PON3, not only present in HDL but also in mitochondria and endoplasmic reticulum, as well. Given that the amount and the activity of PON1 in human serum are significantly lower in people suffering from cardiovascular diseases, enhancing both parameters might contribute to their treatment and prevention. One of the physiologically interesting substrates for the abovementioned hydrolytic cleavage is homocysteine thiolactone (HTL), an atherothrombotic active form of homocysteine. Although it was therefore postulated that PON1 would participate in preventing the HTL-mediated lipid peroxidation, some attention is recently paid to other enzymes, like biphenyl hydrolase-like protein, that seem to more selectively involved in lowering this risk factor. The aim of this paper is to elucidate the role of paraoxonases, especially PON1, by reviewing the latest studies in order to understand both its physiological role and modulation by drugs, nutrients, and plant extracts.

Influence of oral contraceptives on lipid profile and paraoxonase and commonly hepatic enzymes activities

BACKGROUND

The aim of the study was to verify the influence of oral contraceptives (OCs) on lipid profile and the arylesterase, lactonase and phosphotriesterase activities of paraoxonase 1 (PON1). Also commonly hepatic enzymes: aspartate aminotransferase (AST), alanine aminotransferase (ALT) and γ-glutamyltranspherase (GGT) were measured.

METHODS

Lipid profile and hepatic enzymes were determined using commercial available reagents. Paraoxonase activities were estimated using earlier published procedures. Blood samples were collected from 120 women of similar age (22.6±1.0 years) with similar BMI (20.71±2.20 kg/m2 ). Participations were divided into two groups: 74 females do not take (group A) and 46 women taking OCs (group B).

RESULTS

Higher triglycerides and lower low-density lipoproteins levels were observed in group B than in group A) (56.9±19.7 mg/dL. Castelli risk index I was significantly higher in group B when compared to group A (P<.0001), whereas we did not observe any statistically significant differences in Castelli risk index II value between studied groups. In group B, increase in ALT, AST and GGT activities were found, while the de Ritis ratio was lower in group B than in group A. In group B, lower phosphotriesterase activity and higher arylesterase and lactonase activities were found when compared to group A.

CONCLUSION

Higher ALT, AST and GGT activities in serum as well as changes in lipid profile and PON activities can indicate that OCs usage can cause disorder in these parameters in the serum of women taking OCs.

An alternative purification method for human serum paraoxonase 1 and its interaction with methidathion

In this study, an alternative purification method for human Paraoxonase 1 (hPON1) enzyme was developed using two-step procedures, namely ammonium sulphate precipitation and Sepharose-4B-L-tyrosine-1-aminoanthracene hydrophobic interaction chromatography. SDS-polyacrylamide gel electrophoresis of the enzyme indicates a single band with an apparent MW of 43 kDa. The enzyme was purified 674-fold with a yield of 16%. Furthermore, we examined the in vitro effect of methidathion on the enzyme activity to understand the better inhibitory properties of the compound. Methidathion is a highly toxic insecticide used to control a broad spectrum of agricultural insect and mite pests. IC₅₀ value was found to be 0.130 mM for the pesticide. Methidathion showed a competitive inhibition with Ki of 0.119 mM for paraoxon.

An alternative purification method for human serum paraoxonase 1 and its interactions with anabolic compounds

In this study, an alternative purification method for human paraoxonase 1 (hPON1) enzyme was developed using two-step procedures, namely, ammonium sulfate precipitation and Sepharose-4B-L-tyrosine-3-aminophenantrene hydrophobic interaction chromatography. SDS-polyacrylamide gel electrophoresis of the enzyme indicates a single band with an apparent M(W) of 43 kDa. The enzyme was purified 219-fold with a final specific activity of 4,408,400 U/mg and a yield of 10%. Furthermore, we examined the in vitro effects of some anabolic compounds, such as zeranol, 17 β-estradiol, diethylstilbestrol, oxytocin, and trenbolone on the enzyme activity to understand the better inhibitory properties of these molecules. The five anabolic compounds dose dependently decreased the activity of hPON1 with inhibition constants in the millimolar-micromolar range. The results show that these compounds exhibit inhibitory effects on hPON1 at low concentrations with IC50 values ranging from 0.064 to 16.900 µM.

Species differences in paraoxonase mediated hydrolysis of several organophosphorus insecticide metabolites

Paraoxonase (PON1) is a calcium dependent enzyme that is capable of hydrolyzing organophosphate anticholinesterases. PON1 activity is present in most mammals and previous research established that PON1 activity differs depending on the species. These studies mainly used the organophosphate substrate paraoxon, the active metabolite of the insecticide parathion. Using serum PON1 from different mammalian species, we compared the hydrolysis of paraoxon with the hydrolysis of the active metabolites (oxons) of two additional organophosphorus insecticides, methyl parathion and chlorpyrifos. Paraoxon hydrolysis was greater than that of methyl paraoxon, but the level of activity between species displayed a similar pattern. Regardless of the species tested, the hydrolysis of chlorpyrifos-oxon was significantly greater than that of paraoxon or methyl paraoxon. These data indicate that chlorpyrifos-oxon is a better substrate for PON1 regardless of the species. The pattern of species differences in PON1 activity varied with the change in substrate to chlorpyrifos-oxon from paraoxon or methyl paraoxon. For example, the sex difference observed here and reported elsewhere in the literature for rat PON1 hydrolysis of paraoxon was not present when chlorpyrifos-oxon was the substrate.

The human paraoxonase gene cluster as a target in the treatment of atherosclerosis

The paraoxonase (PON) gene cluster contains three adjacent gene members, PON1, PON2, and PON3. Originating from the same fungus lactonase precursor, all of the three PON genes share high sequence identity and a similar β propeller protein structure. PON1 and PON3 are primarily expressed in the liver and secreted into the serum upon expression, whereas PON2 is ubiquitously expressed and remains inside the cell. Each PON member has high catalytic activity toward corresponding artificial organophosphate, and all exhibit activities to lactones. Therefore, all three members of the family are regarded as lactonases. Under physiological conditions, they act to degrade metabolites of polyunsaturated fatty acids and homocysteine (Hcy) thiolactone, among other compounds. By detoxifying both oxidized low-density lipoprotein and Hcy thiolactone, PONs protect against atherosclerosis and coronary artery diseases, as has been illustrated by many types of in vitro and in vivo experimental evidence. Clinical observations focusing on gene polymorphisms also indicate that PON1, PON2, and PON3 are protective against coronary artery disease. Many other conditions, such as diabetes, metabolic syndrome, and aging, have been shown to relate to PONs. The abundance and/or activity of PONs can be regulated by lipoproteins and their metabolites, biological macromolecules, pharmacological treatments, dietary factors, and lifestyle. In conclusion, both previous results and ongoing studies provide evidence, making the PON cluster a prospective target for the treatment of atherosclerosis.

Pharmacological and dietary modulators of paraoxonase 1 (PON1) activity and expression: the hunt goes on

Paraoxonase 1 (PON1) is a high density lipoprotein (HDL)-associated enzyme displaying esterase and lactonase activity. PON1 hydrolyzes several organophosphorus (OP) insecticides and nerve agents, a number of exogenous and endogenous lactones, and metabolizes toxic oxidized lipids of low density lipoproteins (LDL) and HDL. As such, PON1 plays a relevant role in determining susceptibility to OP toxicity, cardiovascular diseases and several other diseases. Serum PON1 activity in a given population can vary by at least 40-fold. Most of this variation can be accounted for by genetic polymorphisms in the coding region (Q192R, L55M) and in the promoter region (T-108C). However, exogenous factors may also modulate PON1 activity and/or level of expression. This paper examines various factors that have been found to positively modulate PON1. Certain drugs (e.g. hypolipemic and anti-diabetic compounds), dietary factors (antioxidants, polyphenols), and life-style factors (moderate alcohol consumption) appear to increase PON1 activity. Given the relevance of PON1 in protecting from certain environmental exposure and from cardiovascular and other diseases, there is a need for further mechanistic, animal, and clinical research in this area, and for consideration of possible alternative strategies for increasing the levels and activity of PON1.

Estradiol enhances cell-associated paraoxonase 1 (PON1) activity in vitro without altering PON1 expression

PON1 is a high density lipoprotein-associated enzyme that plays an important role in organophosphate detoxification and prevention of atherosclerosis. In vivo animal and human studies have indicated that estradiol (E2) supplementation enhances serum PON1 activity. In this study, we sought to determine if E2 directly up-regulates cell-associated PON1 activity in vitro and to characterize the mechanism of regulation. In vitro E2 treatment of both the human hepatoma cell line Huh7 and normal rat hepatocytes resulted in a 2- to 3-fold increase in cell-associated PON1 catalytic activity. E2 potently induced PON1 activity with average EC(50) values of 15nM for normal hepatocytes and 68nM for Huh7. The enhancement of PON1 activity by E2 was blocked by the estrogen receptor (ER) antagonist ICI 182,780 indicating that E2 was acting through the ER. The up-regulation of PON1 activity by E2 did not involve enhancement of PON1 mRNA or protein levels and did not promote secretion of PON1. Thus, E2 can enhance cell-associated PON1 activity in vitro without altering PON1 gene expression or protein level. Our data suggest that E2 may regulate the specific activity and/or stability of cell surface PON1.