Increase In PON1 Activity Research Articles

Effects of thymoquinone and the curcumin analog EF-24 on the activity of the enzyme paraoxonase-1 in human glioblastoma cells U87MG

The spices and aromatic herbs were used not only in cooking to add flavour and smell to dishes but also for medicinal use. Nigella sativa, also called black cumin, is one of the species that contains an important bioactive component, thymoquinone (TQ), which has antioxidant, anti-inflammatory, antimicrobial, and antidiabetic effects. Curcuma longa, which also includes curcumin, has numerous anti-cancer properties. However, the bioavailability of curcumin is lower than that of its analogs. An analog of curcumin (EF-24), which has better bioavailability than curcumin, is capable of exerting a high anti-cancer effect. In our study, we determined the effects of PON1 enzyme activity on the proliferation and aggressiveness of glioblastoma cancer treated with TQ and EF-24 from lysates of the glioblastoma cell line U87MG. The results were determined as increased PON1 activity after treatment with TQ and EF-24 in the U87MG cell line (p < 0.0001).

Role of paraoxonase 1 activity and PON1 gene polymorphisms in sickle cell disease

Sickle cell disease (SCD) patients often exhibit a dyslipidemic sub-phenotype. Paraoxonase 1 (PON 1) is a serum glycoprotein associated with the high-density lipoproteins cholesterol (HDL-C), and variability in PON1 activity depends on the PON1 genotypes. We investigated the influence of PON1c.192Q > R and PON1c.55L > M polymorphisms on PON1 activity and laboratory parameters and the association between PON1 activity and clinical manifestations in SCD patients. We recruited 350 individuals, including 154 SCD patients and 196 healthy volunteers, which comprised the control group. Laboratory parameters and molecular analyses were investigated from the participants' blood samples. We have found increased PON1 activity in SCD individuals compared to the control group. In addition, carriers of the variant genotype of each polymorphism presented lower PON1 activity. SCD individuals carrying the variant genotype of PON1c.55L > M polymorphism had lower platelet and reticulocyte counts, C-reactive protein, and aspartate aminotransferase levels; in addition to higher creatinine levels. SCD individuals carrying the variant genotype of PON1c.192Q > R polymorphism had lower triglyceride, VLDL-c, and indirect bilirubin levels. Furthermore, we observed an association between PON1 activity history of stroke and splenectomy. The present study confirmed the association between PON1c.192Q > R and PON1c.55L > M polymorphisms and PON1 activity, in addition to demonstrate their effects on markers of dislipidemia, hemolysis and inflammation, in SCD individuals. Moreover, data suggest PON1 activity as a potential biomarker related to stroke and splenectomy.

Clove (Syzygium aromaticum) ameliorates oxidative stress-induced inflammation and improves reverse cholesterol transport and paraoxonase 1 activity in diabetic rats

Diabetes is a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both. The chronic hyperglycemia of diabetes is associated with long-term damage, dysfunction, and failure of various organs. Accordingly, in the current study we have investigated the effect of clove on lipid metabolism, and on oxidative stress-induced inflammation response in diabetic rats. Diabetes was induced intraperitonially by a single injection of streptozotocin (STZ). The treated group received daily orally clove extract, for 4 weeks. Daily treatment by clove lowered significantly blood glucose, HbA1c levels and ameliorates the lipid profiles and showed increased PON1 activity. The study of lipid peroxidation showed that, the treatment with clove decreased TBARS levels in LDL fraction and in pancreas. Furthermore, in pancreas TNF-alpha and IL-1β levels were decreased in treated group. These results were confirmed by the histopathological assessments which clove treatment showed marked improvement of the destructive effect on pancreas islet cells induced by STZ. The present findings clearly demonstrated that clove could prevent many diabetic complications by reducing inflammation and oxidative damage. Thus, the effectiveness of clove in treating diabetes potentially may possibly due to presence of bioactive compounds.

NEUROCHEMICAL AND HISTOLOGICAL BRAIN ALTERATIONS AFTER TRAMADOL ADMINISTRATION TO ROTENONE- INDUCED PARKINSON'S DISEASE IN RATS

Objective: Tramadol is favorably used for relief of moderate and severe pain. Over 30% of Parkinson’s disease (PD) patients experience persistent pain that has a negative impact on their quality of life. However, its physiological effect in such disorder has not been studied. The current study aimed at investigating the neurochemical and histopathological changes resulting from tramadol administration to experimental PD- induced by rotenone in rats. Methodology: Forty adult male Sprague-Dawley rats were allocated into 5 equal groups; Group 1(control) received saline p.o and DMSO, s.c., Group 2(Rotenone) received rotenone (1.5 mg/kg, s.c., every other day for 12 days), Group 3 (Tramadol) received tramadol HCl given p.o., daily at doses of 20 mg/kg, Group 4 (Rot-Trama 10) PD-induced with rotenone and treated with tramadol HCl, 10 mg/kg, p.o., daily, Group 5(Rot-Trama 20) PD-induced with rotenone and treated with tramadol HCl, 20 mg/kg, p.o., daily. Results : PD-induced rats exhibited significantly reduced dopamine (DA) content (- 33.0%), increased serotonin ( 5-HT) content (+ 11.5%), but no change in 5-hydroxyindole acetic acid (5-HIAA) compared to vehicle-treated counterparts. Rotenone also inhibited both brain paraoxonase 1 (PON1) and acetylcholinesterase (AChE) activities and increased brain oxidative stress causing reduced glutathione depletion by 32% and increasing thiobarbituric acid reactive substances (TBARS), nitric oxide (NO) by 43% and 81%, respectively. Rotenone caused the appearance of apoptotic neurons with cytoplasmic vacoulations. On the other hand, tramadol -treated control rats showed increased DA (74%), 5-HT (23%), 5-HIAA (50%) contents and decreased serotonin turnover (18.0%) without causing oxidative stress. In rotenone-intoxicated rats, tramadol (10 or 20 mg/kg) increased brain dopamine and at 20 mg/kg increased 5-HT and 5-HIAA. The drug increased PON-1 activity, restored AChE activity and alleviated the changes in lipid peroxidation and reduced glutathione, increased tumour necrosis factor-alpha (TNF-α) without changing the histopathological changes caused by rotenone. Conclusion: These results indicate that short-term use of tramadol in an experimentally-induced PD has dual effects that should be carefully weighed. Tramadol decreased oxidative stress and restored normal DA content and AChE activity that can help in PD. However, the drug resulted in increased proinflammatory cytokine TNF-α and 5-HT level.

Capsicum Protects Against Rotenone-Induced Toxicity in Mice Brain Via Reduced Oxidative Stress and 5-Lipoxygenase Activation

Objective: Is to investigate the effect of Capsicum annuum L extract for its ability to prevent neuronal degeneration in rotenone intoxicated mice. Methods: Rotenone 1.5 mg/kg was subcutaneously given three times per week for two consecutive weeks. Starting from the first day of rotenone treatment, mice also received intraperitoneal injections of Capsicum extract (56 or 224 mg/kg). The brain and liver content of the lipid peroxidation product malondialdehyde (MDA), nitric oxide, reduced glutathione (GSH), paraoxonase 1 activity as well as brain cholinesterase and 5-lipoxygenase activities were determined. Histopathology and glial fibrillary acidic protein (GFAP) immunostaining in brain were also performed. Results: Rotenone treatment caused significantly raised brain and liver MDA by 64.4% and 93.3% and nitric oxide by 77.8% and 40.3%, respectively. Reduced glutathione decreased by 45.4% and 24.3% and PON1 activity fell by 39.4% and 28.7% in both the brain and liver, respectively. Cholinesterase activity in brain was inhibited by 60.6% while 5-lipoxygenase increased by 38.9%. In brain tissue, Capsicum prevented the increase in MDA and nitric oxide levels. Capsicum also restored GSH, PON-1 activity and alleviated the increase in 5-lipoxygenase activity. Cholinesterase activity was almost restored to control value by the higher dose of Capsicum. In the liver tissue, Capsicum caused a significant decrease in MDA, and nitric oxide levels, and increased GSH. It also increased PON-1 activity. The neurotoxicity of rotenone was prevented by the administration of Capsicum extract which prevented the neuronal degeneration and restored GFAP positive cells. Conclusions: Capsicum exerts a neuroprotective effect in rotenone intoxicated mice and this is likely to involve reduced oxidative stress and 5-lipoxygenase activation.

Oxidative stress in drug naïve first episode psychosis and antioxidant effects of risperidone

BackgrooundSchizophrenia is accompanied by increased lipid peroxidation and nitric oxide (NO) levels and by lowered antioxidant levels. However, the effect of antipsychotic agents on these processes remains unclear. The objective of this study is to determine the oxidative stress (OS) status in drug naïve first-episode psychotic patients (FEP) compared to healthy controls and to delineate the effects of risperidone on these biomarkers. Methods51 drug naive FEP patients and 61 healthy controls were enrolled; FEP patients were reassessed 11 weeks after risperidone treatment. Three OS biomarkers, i.e. lipid hydroperoxides – LOOH, NO metabolites – NOx, and advanced oxidation protein products – AOPP, and two antioxidant biomarkers, i.e. total radical-trapping antioxidant parameter – TRAP, and paraoxonase 1 – PON1, were measured. The Positive and Negative Syndrome Scale (PANSS) and the Calgary Depression Scale for Schizophrenia (CDSS) were used to measure symptoms severity. ResultsSignificantly lower PON1 activity and increased TRAP values were found in FEP patients. There were no significant associations between any of the OS/antioxidant biomarkers and clinical data. Risperidone treatment significantly increased PON1 activity and decreased LOOH levels. These effects of risperidone were not significantly associated with the clinical response and risperidone dosage. DiscussionChanges in antioxidant profile, but not in lipid or protein oxidation or increased NO production, were found in drug-naive FEP. Risperidone may have antioxidant effects by lowering lipid peroxidation and increasing the antioxidant defenses against lipid peroxidation related to PON1. None of the biomarkers predicted treatment outcome.

Role of Curcumin in Modulating Plasma PON1 Arylesterase Activity and Susceptibility to LDL Oxidation in Oxidatively Challenged Wistar Rats

Curcumin (β-diketones diferuloylmethane), a biphenolic compound of Curcuma longa is reported to elicit a plethora of health protective effects. The present study was carried out to investigate the in vivo protective effect of curcumin (340 mg/kg b.w., oral) against HgCl2 induced oxidative stress in wistar rats. PON1 arylesterase activity, -SH value, and LDL oxidation susceptibility were determined in plasma of control, control+ curcumin, control+ HgCl2, HgCl2+ curcumin treated rats. Oxidative stress down-regulated PON1 activity, decreased -SH value and increased LDL oxidation susceptibility in plasma. Curcumin treatment significantly (p<0.05) increased PON1 activity, -SH value and reduced LDL oxidation susceptibility in healthy and HgCl2 treated rats. We show that curcumin protects PON1 activity, -SH value and LDL oxidation, and hypothesize that its supplementation may lower the incidence of those diseases where reduced PON1 activity and higher LDL oxidation is reported. Keywords: Curcumin, LDL oxidation, oxidative stress, plasma, PON1, thiol (-SH).

P.3.b.006 NGF and BDNF as markers of long-term functionality in first-episode psychosis patients with/without cannabis consumption

Schizophrenia is accompanied by increased lipid peroxidation and nitric oxide (NO) levels and by lowered antioxidant levels. However, the effect of antipsychotic agents on these processes remains unclear. The objective of this study is to determine the oxidative stress (OS) status in drug naïve first-episode psychotic patients (FEP) compared to healthy controls and to delineate the effects of risperidone on these biomarkers.51 drug naive FEP patients and 61 healthy controls were enrolled; FEP patients were reassessed 11 weeks after risperidone treatment. Three OS biomarkers, i.e. lipid hydroperoxides – LOOH, NO metabolites – NOx, and advanced oxidation protein products – AOPP, and two antioxidant biomarkers, i.e. total radical-trapping antioxidant parameter – TRAP, and paraoxonase 1 – PON1, were measured. The Positive and Negative Syndrome Scale (PANSS) and the Calgary Depression Scale for Schizophrenia (CDSS) were used to measure symptoms severity.Significantly lower PON1 activity and increased TRAP values were found in FEP patients. There were no significant associations between any of the OS/antioxidant biomarkers and clinical data. Risperidone treatment significantly increased PON1 activity and decreased LOOH levels. These effects of risperidone were not significantly associated with the clinical response and risperidone dosage.Changes in antioxidant profile, but not in lipid or protein oxidation or increased NO production, were found in drug-naive FEP. Risperidone may have antioxidant effects by lowering lipid peroxidation and increasing the antioxidant defenses against lipid peroxidation related to PON1. None of the biomarkers predicted treatment outcome.

Clinical Study on the Effect of Simvastatin on Paraoxonase Activity

Human paraoxonase (PON1) is a serum high-density lipoprotein-associated phosphotriesterase. High-density lipoprotein (HDL) plays the role of a carrier and the site of action of this enzyme. According to a majority of authors, PON1 acts as an antioxidant, preventing low-density lipoprotein (LDL) peroxidation. However, due to the fact that in vivo serum PON1 is predominantly associated with HDL, its major physiological role might be to protect HDL, rather than LDL, from oxidation. Nevertheless, the physiological substrate of PON1 still remains to be discovered. The objective of this study was to determine changes in PON1 activity during treatment with simvastatin (CAS 79902-63-9, Lipex) in patients with type IIa and/or IIb hyperlipoproteinemia. PON1 activity was assessed in 32 patients with hyperlipoproteinemia type IIa or IIb with an LDL cholesterol concentration higher than 4.2 mmol/l. Patients received simvastatin in a daily dose of 20 mg. The lipid status and PON1 activity were assessed at baseline, as well as 3 and 6 months after the beginning of treatment. The study demonstrated a statistically significant lipid lowering effect of simvastatin on total and LDL cholesterol, and an increase in PON1 activity in patients with both types of hyperlipoproteinemia. No statistically significant correlation was observed either between changes in PON1 activity and HDL, HDL2, HDL3 and LDL cholesterol and triglyceride levels, or between their first differences in patients with both type IIa and IIb hyperlipoproteinemia. The obtained results suggest that the antioxidant properties of simvastatin might be caused by a mechanism independent of apoAI-containing lipoprotein concentration. The antioxidant properties of simvastatin, which play an important role in HDL protection from oxidation, could be the mechanism inducing the increase in PON1 activity.

Modulating effect of atorvastatin on paraoxonase 1 activity in type 2 diabetic Egyptian patients with or without nephropathy

The aim of this study was to investigate the modulating effect of atorvastatin on serum paraoxonase 1 enzyme (PON1) activity in type 2 diabetic Egyptian patients with or without nephropathy. The present study was carried out on the following groups: control group, which consisted of 30 healthy persons; Group I, which consisted of 20 type 2 diabetic patients without nephropathy; and Group II, which consisted of 20 type 2 diabetic patients with nephropathy. All the patients selected were under an antidiabetic regimen of insulin, and patients receiving antihypertensive agents were excluded from the follow-up study to avoid drug interaction fallacies. Twenty-two patients (15 without nephropathy and seven with nephropathy) received atorvastatin in individually adjusted oral dosage (range 10–20 mg) once per day for 12 weeks. All cases were subjected to thorough clinical examination and history taking and measurement of serum levels of PON1 activity, malondialdehyde (MDA), glutathione reductase activity, fasting glucose, total cholesterol, triglycerides, high-density lipoprotein (HDL), low-density lipoprotein (LDL), urea, and creatinine. Urine samples were collected for determination of proteinuria. The obtained results showed that PON1 activity and HDL significantly decreased and fasting glucose significantly increased in Group I and Group II when compared to the control group, with significant difference in their levels between Group II and Group I. MDA, total cholesterol, and LDL levels significantly increased and glutathione reductase activity significantly decreased in Group I and Group II when compared to the control group. Urea, creatinine, and proteinuria levels showed significant increase in Group II when compared to the control group and Group I, with nonsignificant difference between control group and Group I. Atorvastatin therapy caused a significant increase in PON1 activity, and serum levels of MDA and glutathione reductase activity were significantly decreased and increased, respectively. Also, total cholesterol, triglyceride and LDL-cholesterol levels were significantly reduced with a significant increase in HDL-cholesterol levels. There was a significant modest reduction in serum urea and creatinine levels as well as in proteinuria level. Fasting glucose level was significantly reduced under the antidiabetic regimen of insulin through the follow-up period. PON1 activity showed a significant negative correlation with glucose and LDL, and a significant positive correlation with HDL in all the studied groups. It could be concluded that atorvastatin with its pleiotropic effects could provide optimal therapeutic intervention to control not only dyslipidemia, but also oxidative stress status with consequent improvement in the course of type 2 diabetes and diabetic nephropathy. More specifically, restoration of PON1 activity by atorvastatin opens a window to investigate other drugs that could provide a new adjuvant therapeutic line for better control of diabetes and diabetic nephropathy. Further research is also recommended to study the distribution of PON1 genetic polymorphism among the Egyptian population to explain the variability in its activity and its relationship with other factors that associate diabetes and its complications.

Paraoxonase-1 55/192 genotypes in schizophrenic patients and their relatives in Turkish population

Oxidative stress and free radical-induced toxicity have been implicated in the pathophysiology of schizophrenia. In this study, we examined paraoxonase (PON1)-55/192 polymorphisms and PON1 activity in patients with schizophrenia, first-degree relatives of schizophrenic patients, and healthy controls. This study consisted of 292 healthy participants, 267 unrelated patients with schizophrenia and 311 first-degree relatives of schizophrenic patients. PON1 55 (rs 854560) and PON1 192 (rs 662) polymorphisms were performed by restriction fragment length polymorphism. The frequencies of the QQ and LL genotypes were significantly overpresented in controls compared with those of schizophrenic patients and their relatives. In contrast, the RR genotype was more prevalent in patients than their relatives and healthy controls. The frequencies of the LM and QR genotypes in relatives were higher than controls. Serum PON1 activities of controls were significantly higher when compared with both schizophrenic patients and their relatives. The RR and LL genotypes were associated with a significantly increased PON1 activity as compared with QR or QQ and MM or LM genotypes, respectively, in all groups. This is the first study that shows the association between PON1-55/192 polymorphisms and schizophrenia. Our data suggest that the subjects carrying R allele or RR genotype might be susceptible to schizophrenia and subjects with QQ or LL might be protected against schizophrenia. First-degree relatives of schizophrenic patients have higher heterozygote genotypes, suggesting that this group can shift either to patient or control group depending on their allele types and environmental factors. PON1 genetic variations are also associated with PON1 activities. Reduced PON1 activity in patients and their relatives might result from the combined effects of more than one polymorphic variant in PON1 or other genes and/or increased oxidative stress, supporting the hypothesis that reactive oxygen species-mediated cellular damage might contribute to the neuropathology of schizophrenia.

Effect of N-acetylcysteine on the Murine Model of Colitis Induced by Dextran Sodium Sulfate Through Up-Regulating PON1 Activity

Reactive oxygen species (ROS) are increased in inflammatory bowel disease (IBD) and have been implicated as mediators of intestinal inflammation. We investigated the hypothesis that N-acetylcysteine (NAC) as a glutathione (GSH) precursor attenuates disease progression in a murine dextran sodium sulfate (DSS)-induced colitis model. A colitis model was induced by adding 5% DSS into the drinking water for 7 days. BALB/c mice were injiciatur enema with saline, 5-ASA, N-acetylcysteine, respectively, and free drinking water as control group. DSS-treated mice developed severe colitis as shown by bloody diarrhea, weight loss, and pathologic involvement. Colon lengths were significantly decreased in DSS-treated mice with decreased GSH activity too (P < 0.01). ROS in the colon, the level of interleukin 1 beta (IL-1 beta) in colonic mucosa, serum tumor necrosis factor a (TNF-alpha), MPO, and MDA were significantly increased in DSS-treated animals (P < 0.01), with decreased PON1 activity (P < 0.01). However, NAC significantly decreased colonic MPO activity, ROS, TNF-alpha and IL-1 beta levels and increased PON1 activity and GSH concentration. Moreover, NAC attenuated the macroscopic colonic damage and the histopathologic changes-induced by DSS while similar to 5-ASA group. These results suggest that NAC may be effective in the treatment of colitis through its up-regulating PON1 and scavenging oxygen-derived free radicals.

Increased glutathione levels and activity of PON1 (phenyl acetate esterase) in the liver of rats after a single dose of cyclophosphamide: A defense mechanism?

The clinical utility of cyclophosphamide (CYP) as an anticancer drug is limited by its urotoxicity and nephrotoxicity and to a lesser extent by its hepatotoxicity. The present study was undertaken in order to find out the reason why liver is least susceptible of the three organs to CYP-induced damage although it is the major site for drug activation and metabolism. Adult female Wistar rats weighing 200–250 g were administered single intraperitoneal injection of CYP at the dose of 150 mg/kg body weight and sacrificed at various time intervals 6, 16 or 24 h after the dose of CYP. The control rats were administered saline alone. Hepatotoxicity was assessed by measuring plasma alanine aminotransferase (ALT) activity and histopathology of the liver. Liver was used for the assay of reduced glutathione; activity of paraoxonase (PON1) malondialdehyde – marker of lipid peroxidation. Serum was used for the assay of ALT activity and PON1 activity. The level of reduced glutathione in the liver CYP treated rat was increased by 22% and 57% at 16 and 24 h, respectively. Interestingly, a marked increase in the activity of PON1 (122%) was observed in the livers of CYP treated rats 24 h after treatment. This was accompanied by significant increase in PON1 activity (23%) in the serum. No significant alteration in hepatic malondialdehyde level was observed at any time period after treatment. Serum ALT activity was increased slightly 24 h after treatment with CYP. Mild liver damage was observed histologically only 24 h after treatment with the drug. The present investigation shows for the first time that an increase in antioxidant levels in the liver may be a defense mechanism to prevent/minimize CYP-induced liver damage.

Enhanced PON1 activity in the kidneys of cyclophosphamide treated rats may play a protective role as an antioxidant against cyclophosphamide induced oxidative stress

Recent studies have shown that paraoxanase (PON1) has protective effect against oxidative stress and hence can act as an antioxidant. A time course study was carried out in order to find out alterations in PON1 activity in cyclophosphamide (CYP) induced renal injury. Eight to ten weeks old female rats were administered CYP at the dose of 150 mg/kg body wt. (i.p.) and sacrificed at 6, 16, or 24 h after treatment. Saline treated rats served as control. CYP exposure for 6 h caused a dramatic increase in PON1 activity (83%), which escalated to 160% at 16 h. The renal PON1 activity reached control values 24 h after treatment with CYP. The renal malondialdehyde level was unaltered 6 h after treatment with CYP and an increase by 35% was observed 16 h after treatment with CYP. The present investigation shows for the first time that an increase in renal PON1 activity is an early biochemical event in cyclophosphamide induced renal damage. It is suggested that this enzyme may have a role within the antioxidant systems of the kidney.

ROSIGLITAZONE MODULATES FASTING AND POST‐PRANDIAL PARAOXONASE 1 ACTIVITY IN TYPE 2 DIABETIC PATIENTS

1. In the present study, we have explored the effect of rosiglitazone on post-prandial paraoxonase (PON)-1, an enzyme with potent anti-oxidant properties that may protect against atherosclerosis because increased post-prandial lipaemia, although sometimes understated, is part of the diabetic dyslipidaemia. 2. A randomized, cross-over, placebo-controlled, double-blind clinical trial was performed. Participants (19 type 2 diabetic patients on oral antihyperglycaemic agents) were randomly assigned to receive either placebo or rosiglitazone 4 mg twice daily for 8 weeks. After a 6 week wash-out, the alternative treatment was implemented. Standardized 6 h oral fat-loading tests were performed after each treatment period. 3. Patients assigned to rosiglitazone had increased fasting PON-1 activity (from 331 +/- 29 to 362 +/- 32 U/L before treatment vs after treatment, respectively; P = 0.015), although the PON-1 mass did not change (68.8 +/- 21.1 vs 64.2 +/- 25.4 mg/L before treatment vs after treatment, respectively). In addition, rosiglitazone significantly decreased fasting plasma peroxides compared with placebo (162 +/- 25 vs 214 +/- 28 mmol/L, respectively; P = 0.019). The post-prandial fall in PON-1 activity, expressed as area under the curve, was attenuated by rosiglitazone (-97 +/- 14 vs-161 +/- 24 Uh/L for rosiglitazone vs placebo, respectively; P = 0.02) and the increase in PON-1 activity caused by rosiglitazone correlated with reductions in fasting plasma glucose (r = -0.42; P < 0.05), homeostatic model assessment index (r = -0.59; P < 0.01) and peroxides (r = -0.40; P = 0.07). 4. The present data indicate that rosiglitazone may convey increased protection against the oxidative modification that represents increased post-prandial lipaemia.

Paraoxonase-1 concentrations in end-stage renal disease patients increase after hemodialysis: Correlation with low molecular AGE adduct clearance

BackgroundHemorrhagic stroke and ischemic heart disease continue to be key problems in patients with end stage renal failure. Reduced serum paraoxonase (PON-1) activity has been described in these patients, which could contribute to the accelerated development of atherosclerosis. We hypothesized that retention of uremic toxins and or “middle molecules” including advanced glycation (AGE) free adducts and peptides could play a mechanistic role in decreasing PON-1 activity. MethodsWe enrolled 22 ESRD patients undergoing hemodialysis in whom paired pre- and post-dialysis samples were studied along with 30 age-matched control subjects. ResultsESRD patients showed a 76% decrease in PON-1 activity. As expected, ESRD patients had an increase in lipoperoxides and advanced oxidation protein products (AOPP). Our patients had a 3-fold increase in serum AGEs and a striking 10-fold increase in low molecular weight (<10 kDa) AGEs. Post-dialysis samples in all patients displayed an increase in PON-1 activity, which ranged from 4 to 40% of the predialysis value. HDL-cholesterol, apoAI, free cholesterol (as a LCAT surrogate), HDL-subclasses and TG did not change significantly after dialysis. Changes in PON-1 activity display a good correlation (r=0.66, p<0.001) with rates in which creatinine and urea are cleared. Clearance of low molecular weight AGEs after hemodialysis explains 79% of the changes in PON-1 activity and are hence a much better predictor than creatinine changes (r=0.89, p<0.00). In vitro incubation of paraoxonase with serum ultrafiltrates show a time and concentration dependent inhibition of PON-1 by the ultrafiltrates, an inhibition that is up to 3 times higher (from 8 to 24%) when chronic renal failure patients are the source of the ultrafiltrate. ConclusionWe showed that HD results in a significant, consistent increase in the activity of the antioxidant enzyme PON-1. The effect, correlates with the effectiveness of dialysis to clear creatinine and urea, and with the clearance of AGE adducts of low molecular weight. This effect was replicated in vitro, showing time and dose dependency. Our results suggest that another cause for the observed lower PON-1 concentrations in CRF are the retention of low-middle molecules and demonstrate a positive effect of hemodialysis in the delicate oxidant–antioxidant state of these patients, that should be weighted against other pro-oxidant effects that have also been shown to occur previously. If the hypothesis that AGEs are the main culprits is proved in further research, this opens a putative therapeutic avenue for AGE blockers in ESRD.

Antioxidant effect of atorvastatin is independent of PON1 gene T(–107)C, Q192R and L55M polymorphisms in hypercholesterolaemic patients

ABSTRACTBackground: Serum paraoxonase (PON1), a high density lipoprotein (HDL)-bound antioxidant enzyme, plays a role in atherosclerosis. An increase in PON1 activity has been reported following statin treatment.Objective: In the present study the following factors were evaluated: the influence of PON1 gene Q192R, L55M and T(–107)C polymorphisms on the response of LDL oxidisability and PON1 activity to atorvastatin treatment.Research design and methods: 205 Sicilian subjects with primary hypercholesterolaemia (HCh) and 69 healthy subjects as controls were concurrently enrolled. Hypercholesterolaemic patients were randomly divided into two groups: an atorvastatin group (10 mg/day atorvastatin) and a placebo group. Lipid profile, markers of LDL resistance to in vitro oxidation (lag-phase, oxidation rate and thiobarbituric acid-reactive substances), vitamin E content in LDL, PON1 activity and genotypes in both HCh and control subjects were determined at baseline. The same parameters were measured again after 3 weeks of treatment in both the atorvastatin and placebo groups.Results: HCh subjects showed significantly lower LDL resistance to oxidation, vitamin E content and PON1 activity levels than controls. A strong association was found among PON1 T(–107)C genotypes, LDL susceptibility to oxidation, vitamin E content and PON1 activity. After treatment, the atorvastatin group displayed a significant decrease in total cholesterol, LDL-cholesterol levels, and LDL susceptibility to oxidation, and an increase in vitamin E content and PON1 activity, compared with baseline values. Unlike PON1 activity levels, no difference among PON1 gene polymorphisms and reduction in markers of LDL oxidisability was observed.Conclusions: These results show, for the first time, that atorvastatin is able to improve the resistance to LDL oxidation independently of PON1 gene polymorphism.

High-density lipoprotein composition and paraoxonase activity in Type I diabetes

Type I diabetes is associated with a high incidence of coronary heart disease (CHD), despite a normal or even increased concentration of high-density lipoprotein (HDL) cholesterol. This paradox may be explained by changes in the antioxidant capacity of HDL, related to paraoxonase (PON1) activity. HDL compositional changes in subjects with Type I diabetes may result in changes in PON1 activity that are associated with a higher incidence of CHD. Single-vertical-spin density-gradient ultracentrifugation was used to isolate seven HDL fractions from serum according to density. PON1 activity was measured in serum and in the HDL fractions using phenyl acetate as substrate. The mean recovery of PON1 activity in the HDL fractions was 87% (S.D. 12%). CHD risk was assessed using B-mode ultrasound to measure carotid artery intima-media thickness (IMT). Groups of 35 subjects with Type I diabetes [duration of diabetes 18 years (12-32 years) [median (interquartile range)]; glycated haemoglobin 7.67% (1.17%)] and 24 non-diabetic control subjects were studied. Carotid IMT was greater in the diabetic subjects [0.60 (0.55-0.70) compared with 0.55 (0.45-0.64) mm; P=0.042] and HDL cholesterol concentration was higher [1.53 (0.36) compared with 1.32 (0.34) mmol/l; P=0.031]. There were qualitative differences in HDL in subjects with Type I diabetes: HDL particles were triacylglycerol-deplete, and there were greater numbers of the larger, more buoyant HDL particles. These properties were not those found to determine PON1 activity. PON1 activity increased as HDL particle density increased and particle size decreased; the increase in PON1 activity was associated with an increase in the ratio of the two HDL surface lipid components, phospholipid and unesterified cholesterol, as particle density increased. PON1 activity was similar in diabetic and non-diabetic subjects [121 (28) and 120 (36) micromol x min(-1) x ml(-1) respectively; P=0.887]. PON1 activity was not associated with carotid IMT in either group. Our results suggest that the PON1 activities of HDL particles relate to the density, size and composition of the particles. However, PON1 activity does not appear to contribute to the greater risk of CHD in subjects with Type I diabetes.

Effect of Simvastatin Therapy on Paraoxonase Activity and Related Lipoproteins in Familial Hypercholesterolemic Patients

Human paraoxonase (PON1) is a calcium-dependent esterase closely associated with high density lipoprotein (HDL)-containing apolipoprotein AI (apoAI), which has been shown to confer antioxidant properties to HDL. PON1 has been recently implicated in the pathogenesis of atherosclerosis. Low PON1 activities have been found in familial hypercholesterolemia (FH) and diabetes mellitus. We have undertaken a study of the effect of the lipid-lowering drug simvastatin on serum PON1 activity (in relation to paraoxon and arylesterase activity), on apoAI-containing and apolipoprotein B (apoB)-containing lipoproteins, and on lipid peroxide concentrations in 64 (39 women and 25 men) unrelated FH patients. We have also analyzed the influence of the PON1-192 and PON1-55 genetic polymorphisms on the response of PON1 activity to simvastatin therapy. A venous blood sample for a baseline analysis and another after 4 months of simvastatin therapy at a dosage of 20 mg per day were taken. The major effect of simvastatin on lipid traits was to decrease serum cholesterol, low density lipoprotein (LDL) cholesterol, and lipid peroxide concentrations by 19.9%, 26.3%, and 37.3%, respectively. There was also a significant decrease in serum apoB, LDL apoB, and triglyceride concentrations (20.5%, 21.1%, and 15.6%, respectively). Conversely, simvastatin had no significant influence on very low density lipoprotein-lipid content, HDL cholesterol, apoAI concentrations, and lipoprotein AI and AI:AII particles. Remarkably, serum PON1 activity toward paraoxon significantly increased during treatment with simvastatin (168. 7+/-100.3 U/L before therapy versus 189.5+/-116.5 U/L after therapy, P:=0.005). Arylesterase activity displayed only a nonsignificant trend to increase after therapy. Whereas PON1 activity levels were significantly lower in FH patients before simvastatin therapy compared with those of 124 normolipidemic subjects (168.7+/-100.3 versus 207.6+/-125.2 U/L, respectively; P:<0.05), this difference disappeared after simvastatin therapy. After simvastatin therapy, a significantly negative correlation between PON1 activity and lipid peroxide concentration was observed (r=-0.35, P:=0.028). The latter also strongly correlated with LDL cholesterol concentration (r=0.64, P:<0.001). Serum PON1 activity levels were significantly lower in the low-activity PON1-192 QQ and PON1-55 M carriers than in R carriers and in LL carriers, respectively. No significant differences were found in the therapeutic response of PON1 activity between genotype groups (8.5% and 11.1% increase for QQ homozygous and R-carrier FH patients, respectively, and 12.7% and 9.5% increase for LL homozygotes and M carriers, respectively). We conclude that simvastatin may have important antioxidant properties through increasing serum PON1 activity, perhaps as a consequence of reducing oxidative stress, by a mechanism independent of apoAI-containing lipoprotein concentration and without the influence of PON1-192 and PON1-55 genetic polymorphisms. Further studies are clearly warranted to clarify the precise mechanism by which simvastatin therapy is associated with increased PON1 activity.