Paraoxonase-1 Gene Expression Research Articles

Investigation of the effects of Terminalia chebula seed hydroalcoholic extract on Paraoxonase1 enzyme activity in rats

Background and aims: Paraoxonase 1 (PON1) is related to high-density lipoprotein (HDL) in serum and protects against low-density lipoprotein (LDL) oxidation. This study aimed to investigate the effects of Terminalia chebula on PON1 in hyperlipidemic rats and the molecular docking effects of some compounds of this medical plant on PON1 activity. Methods: Overall, 40 male rats (200–250 gr) were randomly divided into four groups, including the control group, the hyperlipid group, the hyperlipid group receiving 400 mg/kg of the hydroalcoholic extract of T. chebula seeds, and the hyperlipid group receiving 800 mg/kg of the hydroalcoholic extract of T. chebula seeds. The PON1 arylesterase activity in serum and the PON1 gene expression in the liver tissue underwent investigation. Then, the molecular docking effects of its compounds were studied on PON1 through in-silico studies using the AutoDock software (version 4.2.0). Results: T. chebula decreased (P<0.001) the serum triglycerides from 105.88±10.15 mg/dL in the hyperlipidemic group to 66.88±14.90 and 74.25±9.51 mg/dL in hyperlipidemic groups receiving 400 and 800 mg/kg of the hydroalcoholic extract of T. chebula seeds, respectively. In addition, the PON1 serum aryl esterase activity increased from 202.12±6058 in hyperlipidemic rats to 224.34±58.74 (P=0.83) and 235.80±37.05 (P=0.6) in hyperlipidemic groups receiving 400 mg/kg and 800 mg/kg of the hydroalcoholic extract of T. chebula seeds, respectively. It also demonstrated a significant effect on PON1 gene expression (P<0.001). In addition, the in-silico and docking results revealed that the main antioxidant compounds of T. chebula, such as catechin, kaempferol, and quercetin, could bind to the PON1 enzyme directly and influence the enzyme activity. Conclusion: T. chebula increased PON1 activity and PON1 gene expression. However, among the plant’s compounds, catechin, kaempferol, and quercetin played the most substantial role in the PON1 activity. It seems that these compounds can be useful as co-treatments in hyperlipidemia therapies.

Methylprednisolone Does Not Enhance Paraoxonase 1 Activity During Cardiopulmonary Bypass Surgery—A Randomized, Controlled Clinical Trial

ObjectivesCardiopulmonary bypass (CPB) is linked to systemic inflammatory responses and oxidative stress. Paraoxonase 1 (PON1) is an antioxidant enzyme with a cardioprotective role, whose activity is decreased in systemic inflammation, and in patients with acute myocardial and global ischemia. Glucocorticoids counteract the effect of oxidative stress by up-regulating PON1 gene expression. We aimed to determine the effect of methylprednisolone on PON1 activity during cardiac surgery on CPB. DesignProspective, randomized, controlled clinical trial. SettingThe study was conducted at the University Medical Centre Ljubljana, Slovenia. Participants40 adult patients, who underwent complex cardiac surgery on CPB between February 2016 and December 2017, were randomized into methylprednisolone and control group (n=20 each). InterventionsPatients in the methylprednisolone group received 1g of methylprednisolone in the CPB priming solution, while patients in the control group were not given methylprednisolone during CPB. Measurements and Main ResultsWe compared the effect of methylprednisolone from CPB priming solution with standard care during CPB on PON1 activity until the 5. postoperative day. Correlations of PON1 activity with lipid status, mediators of inflammation, and hemodynamics were analyzed as well. No significant differences existed between study groups for PON1 activity, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) in any of the measurement intervals (p>0.016). Methylprednisolone group had significantly lower TNF-a (p<0.001), IL-6 (p<0.001), as well as CRP and procalcitonin (p<0.016) after surgery. No significant difference was found between groups for hemodynamic parameters. A positive correlation existed between PON1 and lipid status, whereas a negative correlation was found between PON1 activity and TNF-a, IL-6, as well as CPB duration. ConclusionsMethylprednisolone doesn't influence PON1 activity during cardiac surgery on CPB.

Effect of Carotenoids on Paraoxonase-1 Activity and Gene Expression.

Paraoxonase 1 (PON1) is an antioxidant enzyme attached to HDL with an anti-atherogenic potential. It protects LDL and HDL from lipid peroxidation. The enzyme is sensitive to various modulating factors, such as genetic polymorphisms as well as pharmacological, dietary (including carotenoids), and lifestyle interventions. Carotenoids are nutritional pigments with antioxidant activity. The aim of this review was to gather evidence on their effect on the modulation of PON1 activity and gene expression. Carotenoids administered as naturally occurring nutritional mixtures may present a synergistic beneficial effect on PON1 status. The effect of carotenoids on the enzyme depends on age, ethnicity, gender, diet, and PON1 genetic variation. Carotenoids, especially astaxanthin, β-carotene, and lycopene, increase PON1 activity. This effect may be explained by their ability to quench singlet oxygen and scavenge free radicals. β-carotene and lycopene were additionally shown to upregulate PON1 gene expression. The putative mechanisms of such regulation involve PON1 CpG-rich region methylation, Ca(2+)/calmodulin-dependent kinase II (CaMKKII) pathway induction, and upregulation via steroid regulatory element-binding protein-2 (SREBP-2). More detailed and extensive research on the mechanisms of PON1 modulation by carotenoids may lead to the development of new targeted therapies for cardiovascular diseases.

Changes in serum PON1 activity, gene expression and their association with lipid profile parameters in healthy Darehshori neonatal foals: a preliminary study

Paraoxonase 1 (PON1) contributes to the antioxidant mechanisms that prevent lipoprotein oxidation and act as a negative acute-phase protein. This study aimed to evaluate changes in serum PON1 activity, the leukocyte PON1 gene expression, as well as lipid profile tests (LDL, HDL, triglyceride, and cholesterol) in 16 healthy Darehshori newborn foals up to 60 days of life. Blood samples were collected at 1, 7, 15, 30, and 60 days used for detecting biochemical parameters, PON1 activity, and, and its gene expression, using realtime RT-PCR. Low levels of PON1 activity were observed at birth, which increased significantly with increasing age at days 7, 15, 30, and 60. In addition, HDL levels were significantly increased at 15, 30, and 60 days in male foals, and in contrast, LDL and cholesterol levels were significantly reduced on days 15, 30, and 60 compared to the first day of life in newborn foals. For the first time, PON1 mRNA was detected in foal leukocytes and its gene expression showed a significant decrease compared to the birthday. The positive correlations between PON1 expression/HDL, LDL, and cholesterol in the first week of life and between PON1 enzyme activity/ HDL, LDL, and cholesterol in different samples and sexes may indicate an adaptive increase in antioxidant defenses in response to oxidative stress. The authors suggest that PON1 expression in leukocytes may be related to the enzyme?s ability to reduce intracellular oxidant levels.

Modulation of Paraoxonase-1 and Apoptotic Gene Expression Involves in the Cardioprotective Role of Flaxseed Following Gestational Exposure to Diesel Exhaust Particles and/or Fenitrothion Insecticide.

The developmental exposure to a single chemical may elicit apoptosis in the different fetal organs, while the combined effects are restricted. We have examined the protective role of flaxseed (FS) against diesel exhaust particles (DEPs)- and/or fenitrothion (FNT)-induced fetal cardiac oxidative stress and apoptosis. A total of 48 timed pregnant rats were divided into eight groups (n = 6). The first group was saved as the control and the second fed on 20% FS diet. Animals in the third, fourth, and fifth groups were administered with DEPs (2.0mg/kg), FNT (3.76mg/kg), and their combination, respectively, while the sixth, seventh, and eighth groups were supplemented with 20% FS through intoxication with DEPs, FNT, and their combination, respectively. Our results revealed that DEPs and/or FNT significantly elevated the level of protein carbonyl and superoxide dismutase activity in the fetal cardiac tissues. However, the catalase activity and total thiol level were decreased; besides the histopathological alterations were remarked. Moreover, DEPs and/or FNT exhibited significant down-regulation in the anti-apoptotic (Bcl-2) and paraoxonase-1 gene expression, and up-regulation in the apoptotic (Bax and caspase-3) gene expression along with DNA fragmentation. Remarkably, FS supplementation significantly ameliorated the fetal cardiac oxidative injury, down-regulated the expression of the apoptotic genes, up-regulated the anti-apoptotic and paraoxonase-1 gene expression, reduced DNA fragmentation, and alleviated the myocardial cell architectures. These findings revealed that FS attenuates DEPs- and/or FNT-induced apoptotic cell death by repairing the disturbance in the anti-apoptotic/pro-apoptotic gene balance toward cell survival in the fetal myocardial cells.

The effect of curcumin and exercise rehabilitation on liver paraoxonase-1 and NF-kβ gene expression in the rat induced by forced drinking of ethanol.

Aim of the studyBinge ethanol drinking causes liver damage and decreased paraoxonase-1 (PON-1) gene expression. On the other hand, regular physical activity and curcumin consumption as non-invasive interventions can have liver protective effects through enhancing antioxidant defense, and improving PON-1 and NF-kβ (nuclear factor kappa B) gene expression. The aim of this study was to investigate the interactive effect of exercise rehabilitation and curcumin consumption on hepatocyte damage as well as NF-kβ and PON-1 gene expression in rats.Material and methodsFifty-six male Wistar rats were randomly selected and equally divided into seven groups: dextrose-control (Dext-Con), ethanol-control (Eth-Con), ethanol-saline (Eth-sal), ethanol-DMSO (Eth-DMSO), ethanol-curcumin (Eth-Cur), ethanol-swimming training (Eth-SWT) and ethanol-SWT + curcumin (Eth-SWT + Cur). After four days of the binge drinking protocol followed by six days of quitting, the interventions of SWT and curcumin (50 mg/kg) were employed for 14 days. Afterwards, the rats’ liver tissues were collected and sent to the laboratory for biochemical assays.ResultsThe interaction of SWT and curcumin caused an increase in PON-1 gene expression (p = 0.02). In addition, curcumin consumption (p = 0.003) and its interaction with SWT (p = 0.004) resulted in a reduction in NF-kβ gene expression. Also, liver tissue damage was observed in the Eth-Con group compared to other groups.ConclusionsThe combination of curcumin and SWT may be used to reduce the side effects of binge ethanol drinking and improve recovery in the quitting period.

The Effects of Anthocyanins and Their Microbial Metabolites on the Expression and Enzyme Activities of Paraoxonase 1, an Important Marker of HDL Function

High circulating HDL concentrations and measures of various HDL functions are inversely associated with cardiovascular disease (CVD) risk. Paraoxonase 1 (PON1) contributes to many of the athero-protective functions of HDL, such as promoting the reverse cholesterol transport process and reducing the levels of oxidized LDL. PON1 activities are influenced by several factors, the most important being diet and genetic polymorphisms. Reported data from randomized controlled trials have shown that anthocyanin consumption increased PON1 activity. However, the underlying molecular mechanisms by which anthocyanins increase PON1 activity are not understood. Therefore, the aim of this research was to investigate the ability of anthocyanins and their metabolites to increase PON1 gene expression and/or enzyme activities as potential mechanisms. The effect of the two predominant dietary anthocyanins and 18 of their recently identified microbial metabolites including their phase-II conjugates on PON1 gene expression was studied using a PON1-Huh7 stably-transfected cell line and reporter gene assay. The effects of these compounds on PON1 arylesterase and lactonase activities were investigated using two isoforms of the PON1 enzyme that are the phenotypes of the 192Q/R polymorphism. None of the compounds caused even modest changes in PON1 promoter activity (p ≥ 0.05). Further, none of the compounds at physiological concentrations caused any significant changes in the arylesterase or lactonase activity of either of the iso-enzymes. Cyanidin reduced the lactonase activity of the PON1-R192R enzyme at high concentrations (−22%, p < 0.001), but not at physiologically achievable concentrations. In conclusion, none of the data reported here support the notion that anthocyanins or their metabolites affect PON1 transactivation or enzyme activities.

Identification of Prognostic Value of Rs3735590 Polymorphism in 3’-Untranslated Region (3’-UTR) of Paraoxonase 1 (PON-1) in Chronic Obstructive Pulmonary Disease Patients who Received Coronary Artery Bypass Grafting (CABG)

Background/Aims: In the treatment of serious and symptomatic coronary heart disease (CHD), coronary artery bypass grafting (CABG) is a frequently utilized intervention. In addition, the risk of CHD is strongly associated with the low activity of paraoxonase-1 (PON1), whose 3’-UTR harbors an rs3735590 polymorphism. The aim of this study was to investigate whether the rs3735590 polymorphism could be used as a prognosis marker in chronic obstructive pulmonary disease (COPD) patients undergoing CABG. In addition, the hypothesis, i.e., the rs3735590 polymorphism may be involved in the regulation of PON1 gene expression via modulating its interaction with miRNAs, was tested in this study. Methods: 292 patients diagnosed with COPD and treated with CABG were recruited for this study. Genomic DNA was extracted from clinical samples, and real-time quantitative PCR and Western-blot were used to measure the expression of miR-616 and PON1 in liver cells of different genotypes. Results: 292 COPD patients were divided into three groups according to their genotypes, i.e., rs3735590: CC (212), TC (75), and TT (5), respectively (TC and TT were merged in one group of T carriers for statistical analyses). Patients with the CC genotype were associated with a shorter event-free survival time as compared to patients with the T genotypes. In addition, PON1 was confirmed as a direct target gene of miR-616, while experiments with primary cells of different genotypes showed that miR-616 inhibited the expression of PON1 in CC cells. On the contrary, rs3735590 impaired such inhibitory effect of miR-616 in TT cells. Conclusion: The rs3735590 polymorphism of PON1 acts as a prognostic biomarker in COPD patients treated by CABG.

Paraoxonases and psoriasis: negative imbalance of antioxidant endogenous mechanisms.

Numerous reports have shown that psoriasis patients are more exposed to lipoprotein peroxidation and to a decrease in the activity of paraoxonase (PON)1, an antioxidant and anti-inflammatory enzyme. Thus, it has been suggested that malfunction of the antioxidant system and an increased production of reactive oxygen species drive immune inflammatory events, that result in progressive skin cell damage in patients with psoriasis. The PON protein family, including PON1, PON2 and PON3, is one of the most important endogenous defense mechanisms against oxidative stress. In the present study, we investigated PON gene expression in psoriasis and in cutaneous oxidative stress. The study population included 10 patients affected by moderate-to-severe plaque psoriasis and 15 healthy donors who have undergone to plastic surgery, were used as control. Skin punch biopsies of lesional and non lesional psoriatic skin were performed for analysis of PON2 and PON3 gene expression. In addition, oxidation assays in ex vivo full-thickness healthy skin organ cultures were performed. No significant differences were observed between PON2 and PON3 gene expression in psoriatic lesional and non lesional skin compared with healthy controls. H2O2 treatment induced a significant decrease of PON2 and PON3 expression in ex vivo full-thickness healthy skin organ cultures; conversely the pretreatment of samples with the antioxidant reagent N-acetyl-L-cysteine (NAC) induced a significant increase. Interestingly, no significant alterations were reported for PON2 and PON3 expression in ex vivo full-thickness healthy skin organ cultures stimulated with IL-17. Taken together our findings have revealed that a strong pro-oxidative activity is not effectively countered by antioxidant endogenous mechanisms both in psoriatic skin and in ex vivo experimental model.

The Q192R polymorphism of the paraoxonase-1 (PON1) gene is associated with susceptibility to gestational diabetes mellitus in the Greek population

A key factor protecting from oxidative stress in gestational diabetes mellitus (GDM) and in type 2 diabetes (T2D) is paraoxonase-1 (PON1). Inconclusive and limited data exist regarding the effect of a coding polymorphism (Q192R) of the PON1 gene in conferring susceptibility to both states. In the present study, we investigated the association between the PON1 gene and the risk for GDM in the Greek population and assessed for the first time its transcriptional efficiency. We studied 185 women with GDM and 104 non-diabetic controls for the PON1 polymorphism. For PON1 mRNA expression, peripheral leucocytes were harvested from 20 GDM and 20 control women, harboring different genotypes for the polymorphism, using real-time quantitative PCR. The RR genotype and the R allele of the PON1 Q192R polymorphism were significantly associated with an increased risk for GDM (p = 0.012 and p < 0.0001, respectively). Furthermore, there was no statistical correlation between the individual metabolic parameters tested and the three genotypes. Finally, the expression levels of PON1 mRNA in GDM patients did not exhibit any statistical difference compared with normal controls (p = 0.138). These data independently document that the Q192R polymorphism is closely associated with GDM susceptibility, while the PON1 gene expression is not impaired in GDM.

Serum Paraoxonase activity in relation to lipid profile in Age-related Macular Degeneration patients

Age-related Macular Degeneration (AMD) is a multifactorial disease causing visual impairment in old age. Oxidative stress is one of the main contributors for the disease progression. Paraoxonase (PON), a HDL-resident antioxidant enzyme which removes oxidized low density lipoprotein (oxLDL), which is not studied much in AMD. This study assesses the PON activities in relation to the lipid status and genetic variants in AMD patients. In this prospective case-control study, a total of 48 AMD patients and 30 unrelated healthy controls were recruited. The serum oxLDL and Plasma Homocysteine (Hcy) levels were estimated by ELISA. Plasma Homocysteine thiolactone (HCTL) was estimated by HPLC. Serum PON activities were estimated by spectrophotometry. PON gene expression was assessed by qPCR and protein expression by western blot, immunofluorescence and FACS analysis. Two known single nucleotide polymorphisms (SNPs) in the coding region of PON1, Q192R and L55M variants were checked in the AMD patients and controls and their association with PON activity and lipid levels were determined. Serum paraoxonase (PONase) and thiolactonase (PON-HCTLase) activities were significantly elevated in AMD patients than in controls apart from elevated serum levels of total cholesterol (TC), triglycerides (TG), oxLDL. While serum LDL levels in AMD patients correlate positively with PON HCTLase activity, the serum high density lipoprotein (HDL) correlates with both PONase and PON-HCTLase activities. However, multiple regression analysis showed that, amongst the parameters, only serum TG was a significant risk factor for AMD, after adjusting for demographic parameters as well as cataract. PON2 was significantly increased at the level of gene expression (p = 0.03) as seen in circulating peripheral blood mononuclear cells (PBMC) of AMD patients possibly mediated by the transcription factor SP1, that showed 2-fold increase. PON1 and 2 protein expressions also showed significant increase in the PBMC of AMD patients. At serum level, PON1 protein was significantly increased in AMD patients. Cholesterol transporters such as CD36, SR-B1 and ABCA1 gene expressions were also found to be higher (1.5, 1.9 and 2.4-fold respectively) in AMD, though not statistically significant. While the wet AMD (CNV) was found to be associated with increase in oxLDL and serum PONase activity, the dry AMD was associated with increased HDL and serum PON-HCTLase activity. The genotype and allele frequencies of Q192R & L55M were not significantly different between AMD patients and controls. However, altered lipid status and PON activities were associated with the genotype in AMD patients. A higher enzyme activity was observed for the RR genotype of Q192R in the cohort, irrespective of case and control. Thus the PON genotype and phenotype seem to play a role in the pathogenesis of AMD.

Downregulation of human paraoxonase 1 (PON1) by organophosphate pesticides in HepG2 cells.

Paraoxonase 1 (PON1) is a calcium-dependent esterase synthesized primarily in the liver and secreted into the plasma where it is associated with high-density lipoproteins (HDL). PON1 hydrolyzes and detoxifies some toxic metabolites of organophosphorus compounds (OPs) such as methyl parathion and chlorpyrifos. Thus, PON1 activity and expression levels are important for determining susceptibility against OPs poisoning. Some studies have demonstrated that OPs can modulate gene expression through interactions with nuclear receptors. In this study, we evaluated the effects of methyl parathion and chlorpyrifos on the modulation of PON1 in Human Hepatocellular Carcinoma (HepG2) cells by real-time PCR, PON1 activity assay, and western blot. The results showed that the treatments with methyl parathion and chlorpyrifos decreased PON1 mRNA and immunoreactive protein and increased inflammatory cytokines in HepG2 cells. The effects of methyl parathion and chlorpyrifos on the downregulation of PON1 gene expression in HepG2 cells may provide evidence of OPs cytotoxicity related to oxidative stress and an inflammatory response. A decrease in the expression of the PON1 gene may increase the susceptibility to OPs intoxication and the risk of diseases related to inflammation and oxidative stress. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 490-500, 2017.

Paraoxonase Gene Expression in Pediatric Inflammatory Bowel Disease

Background: Oxidative stress plays a role in the pathogenesis of inflammatory bowel disease (IBD). The Paraoxonase (PON) genes, expressed in the human intestine, are thought to prevent oxidative stress and modulate inflammation. We investigated the effect of IBD and steroids on PON gene. We hypothesized that PON gene expression is decreased in IBD patients and that steroid treatment would return it to normal.Methods: Pediatric patients diagnosed with IBD, were enrolled and matched to control subjects. For in vitro studies, human epithelial colorectal adenocarcinoma (Caco-2) cells were treated with hydrogen peroxide (H2O2) and dexamethasone. PON genes expression was evaluated by quantitative real-time PCR for both the biopsies and the Caco-2 cells.Results: PON gene expression was decreased in intestinal biopsies from medication naive IBD patients when compared to controls (p<0.05). Biopsies from IBD patients on steroids exhibited up regulation of PON gene expression (p<0.05). Caco-2 cells treated with H2O2 had decreased PON gene expression compared to controls (p<0.05). Dexamethasone increased PON gene expression in Caco-2 cells (p<0.05).Conclusion: Our data suggests that decreased PON expression in IBD patients is a consequence of oxidative stress which plays a role in the pathogenesis of IBD. Further, steroids counteract the effect of oxidative stress by up regulating PON gene expression. PON genes may be targets for the management of intestinal diseases like IBD.

Interleukin-6 upregulates paraoxonase 1 gene expression via an AKT/NF-κB-dependent pathway

The aim of this study is to investigate the relationship between paraoxonase 1 (PON1) and atherosclerosis-related inflammation. In this study, human hepatoma HepG2 cell line was used as a hepatocyte model to examine the effects of the pro-inflammatory cytokines on PON1 expression. The results showed that IL-6, but not TNF-α and IL-1β, significantly increased both the function and protein level of PON1; data from real-time RT-PCR analysis revealed that the IL-6-induced PON1 expression occurred at the transcriptional level. Increase of IκB kinase activity and IκB phosphorylation, and reduction of IκB protein level were also observed in IL-6-treated HepG2 cells compared with untreated culture. This event was accompanied by increase of NF-κB-p50 and -p65 nuclear translocation. Moreover, treatment with IL-6 augmented the DNA binding activity of NF-κB. Furthermore, pharmacological inhibition of NF-κB activation by PDTC and BAY 11-7082, markedly suppressed the IL-6-mediated PON1 expression. In addition, IL-6 increased the levels of phosphorylated protein kinase B (PKB, AKT). An AKT inhibitor LY294002 effectively suppressed IKK/IκB/NF-κB signaling and PON1 gene expression induced by IL-6. Our findings demonstrate that IL-6 upregulates PON1 gene expression through an AKT/NF-κB signaling axis in human hepatocyte-derived HepG2 cell line.

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 15μmol/l or above significantly increased the PON1 enzyme activity (p>0.001) where as nicotine in a dose of 1μmol/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.

Regulation of FMO and PON Detoxication Systems in ALS Human Tissues

Amyotrophic lateral sclerosis (ALS) is an adult-onset, progressive, and fatal neurodegenerative disease with unknown etiology. Recent evidence suggests an association between the exposure to toxic environmental factors and sporadic ALS. The flavin-containing monooxygenases (FMOs) and paraoxonase (PONs) genes encode enzymes involved in xenobiotic detoxication and are associated with ALS. FMO and PON gene expression has been examined in the human central nervous system including human brain subregions defined as the spinal cord, medulla, and cerebral cortex and in the peripheral tissues (lymphocytes, fibroblasts) in ALS patients and normal control subjects. FMO expression was generally higher in tissues from ALS subjects than in control tissues, with the largest increases in FMO expression detected in the spinal cord. In peripheral tissues, the FMO mRNA level was found to be lower compared with FMO expression in brain tissue, and no differences were detected between ALS patients and the control tissue. FMO and PON gene expression was low in peripheral tissues. In contrast to FMO5 expression, the PON2 gene was down-regulated in ALS patients compared to the controls. Because FMO and PON are involved in the detoxication processes and their functional activity to bioactivate chemicals to toxins has been documented, the data herein suggest that environmental toxin exposure may play a role in a subset of individuals who contract ALS by altering FMO and PON gene expression. Although the precise pathogenic link is presently unknown, these findings suggest a role at FMO and PON genes in the development of ALS.

Biomarkers of oxidative stress, antioxidant defence and inflammation are altered in the senescence-accelerated mouse prone 8

In this study we compared biomarkers of oxidative stress, stress response, antioxidant defence and inflammation between mice (n = 10 per group, female, 7 months old) with an accelerated (SAMP8) and a normal ageing phenotype (SAMR1). As compared to SAMR1 mice, SAMP8 mice exhibited higher levels of lipid peroxides and protein carbonyls as well as a lower activity of the proteasomal subunit β-5. Furthermore, heme oxygenase-1 and paraoxonase-1 (PON-1) status was lower in SAMP8 mice indicating impaired stress response. Biomarkers of inflammation such as C-reactive protein and serum amyloid P were elevated in SAMP8 mice. Interestingly, impaired stress response and increased inflammation in SAMP8 mice were associated with elevated concentrations of ascorbic acid and α-tocopherol in the liver. An age-dependent increase in hepatic vitamin E and a decline in PON-1 gene expression were also observed in aged compared to young C57BL/6 mice.

Regulation of paraoxonase 1 (PON1) in PCB 126-exposed male Sprague Dawley rats

3,3′,4,4′,5-Pentachlorobiphenyl (PCB 126), an aryl hydrocarbon receptor (AhR) agonist and most potent dioxin-like PCB congener, significantly alters gene expression, lipid metabolism, and oxidative stress in the liver. PON1, an antioxidant and anti-atherogenic enzyme, is produced in the liver and secreted into the blood where it is incorporated into high density lipoprotein (HDL) and protects LDL and cellular membranes against lipid peroxidation. To explore the regulation of PON1, male Sprague-Dawley rats were treated with ip injections of corn oil or 1μmol/kg or 5μmol/kg PCB 126 and euthanized up to two weeks afterwards. Serum total and HDL-cholesterol were increased by low dose and decreased by high dose exposure, while LDL-cholesterol was unchanged. PCB 126 significantly increased hepatic PON1 gene expression and liver and serum PON1 activities. Liver and serum thiobarbituric acid reactive substances levels were not elevated except for high dose and long exposure times. Serum antioxidant capacity was unchanged across all exposure doses and time points. This study, the first describing the regulation of gene expression of PON1 by a PCB congener, raises interesting questions whether elevated PON1 is able to ameliorate PCB 126-induced lipid peroxidation and whether serum PON1 levels may serve as a new biomarker of exposure to dioxin-like compounds.

Ethanol Extract ofGraptopetalum paraguayenseUpregulates Paraoxonase 1 Gene Expression via an AKT/NF-κB-Dependent Pathway

Human serum paraoxonase 1 (PON1), a calcium-dependent ester hydrolase, protects against the oxidative modification of low-density lipoprotein (LDL) and is a major anti-atherosclerotic component of high-density lipoprotein (HDL). Graptopetalum paraguayense, a folk herbal medicine commonly used in Taiwan, has antioxidative, anti-inflammatory, anti-hypertensive, and anti-atherogenic properties. The effects of G. paraguayense on the activity and/or expression of PON1 were examined using various extracts of the plant; extracts were made in water (GPWE), 50% ethanol (GP50E), and 95% ethanol (GP95E). Of these extracts, GP50E was found to be the most effective at increasing the function and expression of PON1 in a human hepatoma HepG2 cell line. Data from electrophoretic mobility shift assays and promoter-reporter luciferase analyses demonstrated that the DNA binding activity and transactivation ability of NF-κB were enhanced by GP50E. Treatment with NF-κB inhibitors, pyrrolidine dithiocarbamate, and BAY 11-7082 significantly attenuated GP50E-induced PON1 production and NF-κB transactivation activity. In addition, GP50E increased the levels of phosphorylated protein kinase B (PKB/AKT). Pharmacological inhibition of AKT by LY294002 effectively suppressed NF-κB activation and PON1 gene expression, suggesting that AKT was an upstream regulator of GP50E-mediated biological events. Overall, the results show that GP50E up-regulated PON1 gene expression via an AKT/NF-κB-dependent signaling pathway in human hepatoma HepG2 cells. This observation led to the conclusion that the anti-atherogenic characteristics of G. paraguayense are modulated, at least in part, via the up-regulation of hepatocyte PON1 gene expression.

Regulation of Hepatic Paraoxonase-1 Expression

Serum paraoxonase-1 (PON1) is a member of the paraoxonases family (PON1, PON2, and PON3). PON1 is synthesized and secreted by the liver, and in circulation it is associated with HDL. PON1 has antioxidative properties, which are associated with the enzyme's capability to decrease oxidative stress in atherosclerotic lesions and to attenuate atherosclerosis development. Epidemiological evidence demonstrates that low PON1 activity is associated with increased risk of cardiovascular events and cardiovascular disease and is an independent risk factor for coronary artery disease. Therefore, pharmacological modulation of PON1 activity or PON1 gene expression could constitute a useful approach for preventing atherosclerosis. A primary determinant of serum PON1 levels is the availability of the enzyme for release by the liver, the principal site of PON1 production. Together with the enzyme secretion rate, enzymatic turnover, and protein stability, the level of PON1 gene expression is a major determinant of PON1 status. This paper summarizes recent progress in understanding the regulation of PON1 expression in hepatocytes.