Preferable stimulation of PON1 arylesterase activity by phosphatidylcholines with unsaturated acyl chains or oxidized acyl chains at sn-2 position

Redox Pathogenesis in Rheumatic Diseases

Despite being some of the most anecdotally well-known roads to pathogenesis, the mechanisms governing autoimmune rheumatic diseases are not yet fully understood. The overactivation of the cellular immune system and the characteristic development of autoantibodies have been linked to oxidative stress. Typical clinical manifestations, such as joint swelling and deformities and inflammation of the skin and internal organs, have also been connected directly or indirectly to redox mechanisms. The differences in generation and restraint of oxidative stress provide compelling evidence for the broad variety in pathology among rheumatic diseases and explain some of the common triggers and discordant manifestations in these diseases. Growing evidence of redox mechanisms in pathogenesis has provided a broad array of new potential therapeutic targets. Here, we explore the mechanisms by which oxidative stress is generated, explore its roles in autoimmunity and end-organ damage, and discuss how individual rheumatic diseases exhibit unique features that offer targets for therapeutic interventions.

Evaluation of the Protective and Regenerative Properties of Commercially Available Artichoke Leaf Powder Extract on Plasma and Liver Oxidative Stress Parameters

Hepatocellular damage by the harmful effects of xenobiotics, which increase the production of free radicals, is a widespread phenomenon. The extract from the leaves of Cynara scolymus L. available as an artichoke preparation (natural source) of antioxidants may serve as a potential hepatoprotective factor. This study aimed to evaluate the impact of the protective and regenerative properties of artichoke preparation on the liver in three extract doses: 0.5; 1.0; and 1.5 g/kg bw/day. The evaluation was conducted by measuring the levels of oxidative stress parameters, including glutathione (GSH), glutathione S-transferases (GST), nitric oxide (NO), superoxide dismutase (SOD), catalase (CAT), Trolox equivalent antioxidant capacity (TEAC), thiobarbituric acid reactive substances (TBARS), glutathione peroxidase (GPx), paraoxonase 1 (PON1), SH- group, nitrosylated protein (RSNO), as well as such liver enzymes as alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) in the plasma and liver homogenate of rats with liver damage induced by CCl4 (1 mL/kg bw). Measurements were taken in plasma and liver homogenate. The results have demonstrated that the artichoke preparation, owing to its high antioxidative potential, exhibits protective and regenerative effects on the liver. This is supported by the observation of higher GSH levels in the plasma of rats treated with artichoke extract for two weeks before CCl4 exposure. Furthermore, the artichoke extract has shown regenerative properties, as evidenced by lower ALT, AST, and SOD activity in the group treated with artichoke extract after CCl4 exposure. These findings suggest that the in vivo administration of artichoke preparation may be beneficial for the protection and regeneration of the liver.

Unraveling the Complexity of HDL Remodeling: On the Hunt to Restore HDL Quality

Increasing evidence has cast doubt over the HDL-cholesterol hypothesis. The complexity of the HDL particle and its proven susceptibility to remodel has paved the way for intense molecular investigation. This state-of-the-art review discusses the molecular changes in HDL particles that help to explain the failure of large clinical trials intending to interfere with HDL metabolism, and details the chemical modifications and compositional changes in HDL-forming components, as well as miRNA cargo, that render HDL particles ineffective. Finally, the paper discusses the challenges that need to be overcome to shed a light of hope on HDL-targeted approaches.

The Early Effect of Carotid Artery Stenting on Antioxidant Capacity and Oxidative Stress in Patients with Carotid Artery Stenosis

The treatment of carotid artery stenosis is associated with the risk of complications, which may include stroke after carotid artery stenting (CAS) and myocardial infarction after carotid endarterectomy (CEA). The imbalance between prooxidative mechanisms and antioxidant capacity creates a milieu of factors, which may increase the risk of complications after endovascular procedures. We have examined 43 consecutive patients with carotid artery stenosis. Sera were analyzed for the activity of paraoxonase (PON) and arylesterase (ARE), sulfhydryl groups (SG), malondialdehyde (MDA), and conjugated dienes (CD) concentrations by means of spectrophotometric methods before and next day after CAS. We have found lowered PON (P = 0.0032), increase in ARE activity (P = 0.0058), and decrease in sulfhydryl groups concentration (P = 0.0267). No effect on absolute MDA and CD concentrations was observed. The degree of carotid artery stenosis correlated negatively with PON/ARE ratio after CAS (r_S = -0.507, P = 0.0268). To conclude, CAS influences both enzymatic (differently, PON and ARE activity) and nonenzymatic antioxidant defense. Females are more susceptible to lipid peroxidation after CAS. PON/ARE ratio after CAS correlated with the degree of carotid artery stenosis. The changes (deltas) in ARE activity, SG, and MDA concentrations correlated with the severity of neurological deficit and disability.

Proteomic and lipidomic analyses of paraoxonase defined high density lipoprotein particles: Association of paraoxonase with the anti-coagulant, protein S

PURPOSE

Characterizing high density lipoprotein (HDL) particles and their relevance to HDL function is a major research objective. One aim is to identify functionally distinct particles. To try to limit both functional and compositional heterogeneity the present study focused on paraoxonase-1 (PON1) as a target for isolation of a minor HDL subfraction.

EXPERIMENTAL DESIGN

Immunoaffinity techniques were applied to isolate PON1-containing HDL (P-HDL) and total HDL (T-HDL), which were subsequently characterized and compared.

RESULTS

Analyses of the lipidomes showed significant differences between the fractions in the relative concentrations of individual lipid subspecies, notably reduced levels of unsaturated lysophosphatidylcholine (p < 0.05) in P-HDL (reflected in a significantly reduced total lysophosphatidylcholine polyunsaturated fatty acid content, p < 0.004). Significant differences were also observed for the proteomes. P-HDL was highly enriched in the anti-coagulant, vitamin K activated protein S (prot S) (p < 0.0001), and alpha2 macroglobulin (p < 0.01), compared to T-HDL. Conversely, procoagulant proteins kininogen 1 and histidine-rich glycoprotein were largely excluded from P-HDL. Immunoabsorption of PON1 from plasma significantly reduced prot S anti-coagulant activity.

CONCLUSIONS AND CLINICAL RELEVANCE

The P-HDL lipidome and proteome showed significant differences from T-HDL. Enrichment in anti-coagulation proteins indicates complementary functionalities within P-HDL particles and underlines their anti-atherosclerotic potential.

Therapeutic applications of reconstituted HDL: When structure meets function

Reconstituted forms of HDL (rHDL) are under development for infusion as a therapeutic approach to attenuate atherosclerotic vascular disease and to reduce cardiovascular risk following acute coronary syndrome and ischemic stroke. Currently available rHDL formulations developed for clinical use contain apolipoprotein A-I (apoA-I) and one of the major lipid components of HDL, either phosphatidylcholine or sphingomyelin. Recent data have established that quantitatively minor molecular constituents of HDL particles can strongly influence their anti-atherogenic functionality. Novel rHDL formulations displaying enhanced biological activities, including cellular cholesterol efflux, may therefore offer promising prospects for the development of HDL-based, anti-atherosclerotic therapies. Indeed, recent structural and functional data identify phosphatidylserine as a bioactive component of HDL; the content of phosphatidylserine in HDL particles displays positive correlations with all metrics of their functionality. This review summarizes current knowledge of structure-function relationships in rHDL formulations, with a focus on phosphatidylserine and other negatively-charged phospholipids. Mechanisms potentially underlying the atheroprotective role of these lipids are discussed and their potential for the development of HDL-based therapies highlighted.

Arylesterase phenotype-specific positive association between arylesterase activity and cholinesterase specific activity in human serum

Context: Cholinesterase (ChE) specific activity is the ratio of ChE activity to ChE mass and, as a biomarker of exposure to cholinesterase inhibitors, has a potential advantage over simple ChE activity. Objective: To examine the association of several potential correlates (serum arylesterase/paraoxonase activity, serum albumin, sex, age, month of blood collection, and smoking) with plasma ChE specific activity. Methods: We analyzed data from 195 cancer-free controls from a nested case-control study, accounting for potential confounding. Results: Arylesterase activity had an independent, statistically significant positive association with ChE specific activity, and its magnitude was the greatest for the arylesterase phenotype corresponding to the QQ PON1₁₉₂ genotype followed by phenotypes corresponding to QR and RR genotypes. Serum albumin was positively associated with ChE specific activity. Conclusions: Plasma arylesterase activity was positively associated with plasma ChE specific activity. This observation is consistent with protection conferred by a metabolic phenotype resulting in reduced internal dose.

Monocyte-macrophage membrane possesses free radicals scavenging activity: stimulation by polyphenols or by paraoxonase 1 (PON1)

In the current study, we analysed free radicals scavenging activity of monocytes-macrophages in the absence or presence of antioxidants such as polyphenols or paraoxonase 1 (PON1). THP-1 human monocytic cell line, murine J774A.1 macrophages, as well as human primary monocytes have the capability to scavenge free radicals, as measured by the 1-diphenyl-2-picryl-hydrazyl (DPPH) assay. This effect (which could be attributed to the cell's membrane) was cell number and incubation time dependent. Upon incubation of J774A.1 macrophages with acetylated LDL (Ac-LDL), with VLDL, or with the radical generator, AAPH, the cells' lipid peroxides content, and paraoxonase 2 (PON2) activity were significantly increased. While non-treated cells decreased DPPH absorbance by 65%, the Ac-LDL-, VLDL- or AAPH-treated cells, decreased it by only 33%, 30%, or 45%, respectively. We next analysed the effect of J774A.1 macrophage enrichment with antioxidants, such as polyphenols or PON1 on the cells' free radicals scavenging activity. Non-treated cells decreased DPPH absorbance by 50%, whereas vitamin E-, punicalagin- or PJ-treated cells significantly further decreased it, by 75%. Similarly, in PON1-treated cells DPPH absorbance was further decreased by 63%, in association with 23% increment in PON1 catalytic activity. In cells under oxidative stress [treated with AAPH-, or with oxidized LDL], PON1 activity was decreased by 31% or 40%, as compared to the activity observed in PON1 incubated with non-treated cells. We conclude that monocytes-macrophages possess free radicals scavenging activity, which is decreased under atherogenic conditions, and increased upon cell enrichment with potent antioxidants such as nutritional polyphenols, or PON1.

Olive oil supplemented with Coenzyme Q(10): effect on plasma and lipoprotein oxidative status

Olive oil consumption is associated with protective cardiovascular properties, including some beneficial modifications in lipoprotein profile and composition. Coenzyme Q(10) (CoQ(10)) exerts a protective effect on plasma lipoproteins. Aim of the study was to investigate whether extra virgin (EV) olive oil enriched with CoQ(10) affects CoQ(10) levels and oxidative status in plasma and in isolated lipoproteins. Twelve subjects were administered 20 mL olive oil per day for 2 weeks, followed by 2 weeks of olive oil enriched with 20 mg and 2 more weeks with 40 mg of CoQ(10). Plasma and isolated lipoproteins were collected in each phase of the study and subsequently analyzed to assess lipid profile, CoQ10 levels, ORAC assay, resistance of lipoproteins to peroxidation and paroxonase 1 activity. Plasma CoQ(10) levels significantly increased with the 20 mg (+73%) and 40 mg dose (+170%), while the percentage of oxidized CoQ(10) decreased. A significant inverse correlation was found in plasma between percentage of oxidized CoQ(10) and total antioxidant capacity. A lower susceptibility of LDL to peroxidation was also found. Finally, a positive correlation was observed between concentration of CoQ(10) in HDL and paraoxonase-1 activity. EV olive oil enriched with both doses of CoQ(10) significantly affects its bioavailability and plasma redox status. These changes are associated with a decreased susceptibility of plasma lipoproteins to peroxidation associated with a chain-breaking antioxidant activity of the formulation.

Autoimmune-mediated reduction of high-density lipoprotein-cholesterol and paraoxonase 1 activity in systemic lupus erythematosus-prone gld mice

OBJECTIVE

To characterize modifications of high-density lipoprotein (HDL) in autoimmune gld mice that may be relevant to premature atherosclerosis in systemic lupus erythematosus, and to assess their relationship to specific aspects of autoimmune disease.

METHODS

HDL cholesterol (HDL-C), apolipoprotein A-I (Apo A-I), paraoxonase 1 (PON1) activity, hepatic gene expression, and HDL biogenesis were measured in aging female gld and wild-type congenic mice. Autoantibodies, lymphoid organs, and cytokines were analyzed by enzyme-linked immunosorbent assay, flow cytometry, and multiplex assay, respectively.

RESULTS

Plasma HDL-C, HDL Apo A-I, and HDL-associated PON1 activity were reduced in aging gld mice in association with the development of autoimmunity, independent of changes in hepatic Apo A-I and PON1 expression or HDL biogenesis. Hepatic induction of the acute-phase reactant serum amyloid A1 resulted in its incorporation into HDL in gld mice. Deletion of the lipid-sensitive receptor G2A in gld mice (G2A-/- gld) attenuated reductions in HDL-C and PON1 activity without altering hepatic Apo A-I and PON1 expression, HDL biogenesis, or levels of acute-phase proinflammatory cytokines. Plasma anti-Apo A-I autoantibodies were elevated in aging gld mice commensurate with detectable increases in Apo A-I immune complexes. Autoantibody levels were lower in aging G2A-/- gld mice compared with gld mice, and anti-Apo A-I autoantibody levels were significantly related to HDL-C concentrations (r=-0.645, P<0.00004) and PON1 activity (r=-0.555, P<0.0007) among autoimmune gld and G2A-/- gld mice.

CONCLUSION

Autoantibodies against Apo A-I contribute to reducing HDL-C and PON1 activity in autoimmune gld mice independently of hepatic HDL biogenesis, suggesting that functional impairment and premature clearance of HDL immune complexes may be principal mechanisms involved.

Paraoxonase 1 interactions with HDL, antioxidants and macrophages regulate atherogenesis - a protective role for HDL phospholipids

Macrophage cholesterol accumulation and foam cell formation is the hallmark of early atherogenesis. In addition to macrophages, at least three more major players regulate atherosclerosis development; paraoxonase 1 (PON1), antioxidants, and HDL. PON1 is an HDL-associated lactonase which posses antioxidant and anti-atherogenic properties. PON1 protects against macrophage-mediated LDL oxidation, and increases HDL binding to macrophages which, in turn, stimulates HDL's ability to promote cholesterol efflux. These two major anti-atherogenic properties of HDL (and of PON1) require, at least in part, macrophage binding sites for HDL-associated PON1. Indeed, PON1, as well as HDL-associated PON1, specifically binds to macrophages, leading to anti-atherogenic effects. Macrophage PON1 binding sites may thus be a target for future cardioprotection therapy. Studying the interactions among PON1, antioxidants, and macrophages can thus assist in achieving appropriate treatment and prevention of atherosclerosis.

A high throughput serum paraoxonase assay for discovery of small molecule modulators of PON1 activity

PON1 has been demonstrated to be the serum enzyme responsible for detoxifying organophosphate chemical weapons and plays a protective role against atherosclerosis. In order to identify small molecules that modulate PON1 activity in serum, we developed a high throughput kinetic absorbance assay using mouse serum and the organophosphate paraoxon. The IC(50) value obtained for the known PON1 inhibitor, 2-hydroxyquinoline, matched the value reported for purified PON1. A compound library was screened resulting in no confirmed activators, but 12 confirmed inhibitors. Seven of these hits also inhibited purified human PON1. One compound was only two-fold less potent than 2-hydroxyquinoline in the serum assay, but 10-fold more potent against purified PON1. This compound (IC(50) = 420 nM) may be useful towards a chemical probe for PON1. Therefore, this assay has utility as a high throughput assay for discovery of small molecule modulators of PON1 activity that maintain activity in serum.

Oxygenation of arachidonoyl lysophospholipids by lipoxygenases from soybean, porcine leukocyte, or rabbit reticulocyte

Oxygenation of arachidonoyl lysophosphatidylcholine (lysoPC) or arachidonoyl lysophosphatidic acid (lysoPA) by lipoxygenase (LOX) was examined. The oxidized products were identified by HPLC/UV spectrophotometry/mass spectrometry analyses. Straight-phase and chiral-phase HPLC analyses indicated that soybean LOX-1 and rabbit reticulocyte LOX oxygenated arachidonoyl lysophospholipids mainly at C-15 with the S form as major enantiomer, whereas porcine leukocyte LOX oxygenated at C-12 with the S form. Next, the sequential exposure of arachidonoyl-lysoPC to soybean LOX-1 and porcine leukocyte LOX afforded two major isomers of dihydroxy derivatives with conjugated triene structure, suggesting that 15(S)-hydroperoxyeicosatetraenoyl derivatives were converted to 8,15(S)-dihydroxyeicosatetraenoyl derivatives. Separately, arachidonoyl-lysoPA, but not arachidonoyl-lysoPC, was found to be susceptible to double oxygenation by soybean LOX-1 to generate a dihydroperoxyeicosatetraenoyl derivative. Overall, arachidonoyl lysophospholipids were more efficient than arachidonic acid as LOX substrate. Moreover, the catalytic efficiency of arachidonoyl-lysoPC as substrate of three lipoxygenases was much greater than that of arachidonoyl-lysoPA or arachidonic acid. Taken together, it is proposed that arachidonoyl-lysoPC or arachidonoyl-lysoPA is efficiently oxygenated by plant or animal lipoxygenases, C12- or C15-specific, to generate oxidized products with conjugated diene or triene structure.