Modification Of Lipoprotein Research Articles

Low-Density Lipoprotein (LDL) Antioxidants and Antiplatelet Compounds from Selected Malaysian Plants as Leads for the Development of Cardiovascular Protective Agents

Oxidative modification of low-density lipoprotein (LDL) plays a significant role in the onset and acceleration of atherosclerotic process and the development of cardiovascular diseases. The chronic antioxidant, hypolipidemic, antithrombotic and antiplatelet activities of many phytochemicals have important roles in prevention of lipoprotein oxidation and atherosclerotic lesion development. Phytochemicals of diverse chemical structures, including phenolic compounds, xanthones, prenylflavonoids, benzophenones, alkaloids and triterpenoids isolated from Malaysian plants were investigated for their ability to inhibit arachidonic acid (AA), collagen and adenosine diphosphate (ADP) induced platelet aggregation in human whole blood using an electrical impedance method. The compounds were also investigated for their ability to inhibit human LDL oxidation using thiobarbituric acid reactive substances (TBARS) assay. Among the compounds tested, 2-(3-methylbut-2-enyl)1,3,5,-trihydroxyxanthone, 2-(3-methylbut-2-enyl)-1,3,5,6-tetrahydroxyxanthone, rubraxanthone and 3,5,3′,5′-tetrahydroxy-4methoxybenzophenone isolated from Guttiferae species showed strong inhibition on platelet aggregation. Curcumin, cardamonin, pinocembrine, 5,6-dehydrokawain and 3-deacetylcrotepoxide were the strong antiplatelet compounds identified from Zingiberaceae species. Of the alkaloids tested, (-)-N-acetylnornuciferine, (-)-N-acetylanonaine and 1-(N-acetyl-Nmethylamino)ethyl-3,4,6-trimethoxy-7-hydroxyphenanthrene from Armodendron elegans showed strong inhibition on platelet aggregation caused by all three inducers. 3,5,3′,5′-Tetrahydroxy-4-methoxybenzophenone and 1, 7-dihydroxyxanthone showed strong inhibitory activity on LDL oxidation. Curcumin, demethoxycurcumin and bisdemethoxycurcumin exhibited stronger activity than the reference, probucol, as LDL antioxidants. Xanthorrhizol, zerumbone and ar-turmerone from the oils of Curcuma species showed relatively strong antioxidant activity. 3,5,3′,5′-Tetrahydroxy-4-methoxybenzophenone and 1, 7dihydroxyxanthone also showed strong inhibitory activity on LDL oxidation. Of the triterpenoids tested, garcihombronane B from Garcinia cantleyana showed moderate activity against LDL oxidation. The compounds are new classes of natural products that can be used as leads for development of new cardiovascular protective agents.

NMR Spectroscopy of Macrophages Loaded with Native, Oxidized or Enzymatically Degraded Lipoproteins

Oxidized and enzymatically modified low-density lipoproteins (oxLDL and eLDL) play a key role in early stages of atherogenesis. Their uptake by recruited macrophages leads to endolysosomal phospholipidosis or foam cell formation, respectively, each of which is preceded by highly differential lipid restructuring processes. We applied 1H-NMR spectroscopy (NMRS) to elucidate these structural rearrangements both in consequence of lipoprotein modifications and following phagocytosis. Being specifically sensitive to the mobile lipid subset, NMRS of oxLDL and eLDL revealed a partial and total immobilization of lipids, respectively. NMRS of intact macrophages showed a sixfold increase in mobile lipids in case of loading with eLDL but no significant changes for oxLDL or native LDL. This finding reflected the disparate lipid storage in lipid droplets and in multilamellar endolysosomal clusters when loaded with either eLDL or oxLDL, respectively. Moreover, a significant shift of the degree of saturation towards mainly polyunsaturated fatty acid chains was found for the mobile lipid pool in eLDL-loaded macrophages. Additional analyses of lipid extracts by NMRS and mass spectrometry (MS) reflected these changes in lipid content and in fatty acid composition only partially. In summary, in-cell NMRS represents a unique lipidomics tool to investigate structural changes within the mobile lipid pool following atherogenic triggers that can be not detected by the analysis of lipid extracts by MS or NMRS.

Relationship between free fatty acids, insulin resistance markers, and oxidized lipoproteins in myocardial infarction and acute left ventricular failure

BackgroundThe most common cause of myocardial infarction (MI) is stenotic atherosclerotic lesions in subepicardial coronary arteries. Artery disease progression induces clinical signs and symptoms, among which MI is the leader in mortality and morbidity. Recent studies have been trying to find new biochemical markers that could predict the evolution of clinical complications; among those markers, free fatty acids (FFA) and oxidative modification of low-density lipoproteins (oxidized LDL) have a special place.Materials and methodsSeventy-nine ST-elevation MI patients were enrolled. The first group included MI patients without the signs of acute heart failure (Killip class I) while MI patients with Killip classes II–IV made up the second group. Thirty-three individuals with no cardiovascular disease were the controls. The lipid profile, serum oxidized LDL, and their antibodies, C-peptide and insulin were measured at days 1 and 12. The level of insulin resistance was assessed with the quantitative insulin sensitivity check index (QUICKI).ResultsMI patients had atherogenic dyslipidemia; however, the Killip II–IV group had the most pronounced and prolonged increase in FFA, oxidized LDL, and their antibodies. Additionally, positive correlations between FFA levels and creatine kinase activity (12 days, R = 0.301; P = 0.001) and negative correlations between the QUICKI index and FFA levels (R = −0.46; P = 0.0013 and R = −0.5; P = 0.01) were observed in the both groups.ConclusionThe development of MI complications is accompanied by a significant increase in FFA levels, which not only demonstrate myocardial injury, but also take part in development of insulin resistance. Measuring FFA levels can have a great prognostic potential for risk stratification of both acute and recurrent coronary events and choice of treatment strategy.

Evaluation of the effects of weak and moderate static magnetic fields on the characteristics of human low density lipoprotein in vitro

It has been suggested that exposure to electromagnetic fields may be a risk factor for cardiovascular disease in humans. Low density lipoprotein (LDL) modifications such as peroxidation and aggregation have been implicated in the pathogenesis of atherosclerosis. The present study investigated the effects of weak (0.125-0.5 mT) and moderate (1-4 mT) static magnetic fields (SMFs) on LDL oxidation, aggregation and zeta potential in vitro. Our results demonstrated that magnetic flux densities of 0.25 and 0.5 mT decreased, and magnetic flux densities of 3 and 4 mT increased the zeta potential and LDL oxidation in comparison with the control samples. All doses of SMFs increased the LDL aggregation in a time- and dose-dependent manner. It is concluded that SMFs can alter the susceptibility of LDL to oxidation and this alteration is dependent on the applied magnetic flux density. The SMF, in addition to its role in the production and stabilization of free radicals and promotion of lipid peroxidation, may influence the metabolism of lipoproteins and their interaction with other molecules such as apolipoproteins, enzymes and receptors through the alteration of the LDL zeta potential and its particles tendency to aggregation.

Association between paraoxonase gene and stroke in the Han Chinese population.

BackgroundThe human paraoxonase (PON) gene family has three isoforms: PON1, PON2 and PON3. These genes are implicated as potential risk factors of cerebrovascular disease and can prevent oxidative modification of low-density lipoproteins and atherosclerosis. This study evaluated the association between the genetic variants of all three PON genes and the risks of total stroke, ischemic stroke and hemorrhagic stroke in the Han Chinese population.MethodsA total of 1016 subjects were recruited, including 508 healthy controls and 498 patients (328 with ischemic stroke and 170 with hemorrhagic stroke). A total of 11 single nucleotide polymorphisms (SNPs) covering the PON genes were genotyped for statistical analysis. Two of the 11 SNPs (rs662 and rs854560) were contextualized in a meta-analysis of ischemic stroke.ResultsThe presence of rs705381 (−162) in the promoter region of PON1 was significantly associated with total stroke (Padjusted = 0.0007, OR = 0.57 [95% CI = 0.41-0.79]) and ischemic stroke (Padjusted = 0.0017, OR = 0.54 [95% CI = 0.37-0.79]) when analyzed using a dominant model, but was not associated with hemorrhagic stroke. There was also a nominal association between rs854571 (−824) and total stroke. Meta-analysis demonstrated a significant nominal association between rs662 and ischemic stroke, but there was no evidence of an association between rs662 and ischemic stroke risk in a single site association study.ConclusionsThese findings indicate that polymorphisms of PON1 gene may be a risk factor of stroke.

Disubstituted diaryl diselenides as potential atheroprotective compounds: Involvement of TrxR and GPx-like systems

Oxidative modifications of low-density lipoproteins (LDLs) have a determinant role in atherogenesis and the study of agents that can modulate LDL oxidation is of pharmacological and therapeutic significance. Therefore, the aim of this study was to evaluate the antioxidant effect of the disubstituted diaryl diselenides, p-methoxyl-diphenyl diselenide (p-CH3O–C6H4Se)2 (DM) and p-chloro-diphenyl diselenide (p-Cl–C6H4Se)2 (DC), on Cu2+-induced LDL oxidation. Both compounds caused a dose-dependent inhibition of human serum and isolated LDL oxidation evidenced by the increasing of the lag phase of lipid peroxidation and decreased the lipid oxidation rate (Vmax). The protein moieties from isolated LDL were also protected from Cu2+-induced oxidation. Moreover, the disubstituted diaryl diselenides efficiently decreased the oxidized LDL (ox-LDL) induced foam cell formation in J774A.1 macrophage cells. Mechanistically, we have demonstrated that the antioxidant and antiatherogenic effects of DM and DC are related to formation of their selenol intermediates (RSeH) either by a direct reaction with endogenous thiols (GPx-like activity) or via their reduction by TrxR (using NADPH as electron donor). Considering the powerful effect of DM and DC against LDL-induced toxicity, they could be considered for developing of new therapeutic approaches to preventing and treating atherosclerosis and cardiovascular diseases.

Antioxidant effects of vitamins C and e on the low-density lipoprotein oxidation mediated by myeloperoxidase.

Oxidative modification of low-density lipoprotein (LDL) appears to be an early step in the pathogenesis of atherosclerosis. Meanwhile, myeloperoxidase (MPO)-catalyzed reaction is one of the potent pathway for LDL oxidation in vivo. The aim of this study was to evaluate in vitro antioxidant effects of vitamins C and E on LDL oxidation mediated by MPO. MPO was isolated from fresh plasma by sequential centrifugation using density ultracentrifugation. It was incubated with LDL and the LDL oxidation level was determined spectrophotometrically by measuring conjugated diene absorbance at 234 nm. Furthermore, vitamin C (50-200 mM) and vitamin E (10-40 mM) were added and the LDL oxidation level was determined. The purity index of MPO and its enzymatic activity were 0.69 and 1127 U/mg protein, respectively. It was demonstrated that vitamin C in vitro inhibited LDL oxidation mediated by MPO; however, vitamin E was unable to act in the same way. The protection by vitamin C was concentration dependent and maximum protective effect of vitamin C was observed at 150 mM, where about 64% of the LDL oxidation was inhibited. Vitamin C increased lag time of LDL oxidation mediated by MPO up to 2.4 times. It can be concluded from our results that vitamin C is able to improve LDL resistance to oxidative modification in vitro. In addition, vitamin C might be effective in LDL oxidation mediated by MPO in vivo, resulting in reduction of atherosclerosis process rate.

АSSOCIATION BETWEEN OXIDATIVE-ANTIOXIDANT MODIFICATIONS OF LOW-DENSITY LIPOPROTEINS AND CORONARY HEART DISEASE IN A MALE POPULATION OF NOVOSIBIRSK

Aim. To investigate the association between potentially atherogenic oxidativeantioxidant modifications of low-density lipoproteins (LDL) and coronary heart disease (CHD) in a male population. Material and methods. A population-based survey included 1024 male residents ofNovosibirskCity, aged 47–73 years. The participants underwent a questionnaire survey, a standard cardiologic survey, anthropometry, blood pressure measurement, and electrocardiography. “Definite CHD” (Functional Class II–IV stable effort angina) was registered in 223 men (21,8%), according to validated epidemiologic, clinical, and functional criteria. Blood biochemistry analyses focused on the levels of total cholesterol (TCH), triglycerides (TG), high-density lipoprotein cholesterol (HDL–CH), high-sensitivity C-reactive protein (hsCRP), glucose, baseline levels of lipid peroxidation (LPO) products and fat-soluble antioxidants (alpha-tocopherol, retinol, beta-carotene, and xanthines) in LDL, LDL oxidation resistance in vitro, and an concentration of autoantibodies to oxidised LDL (oxLDL). Results. There were positive correlations and independent associations between the oxidative LDL modifications, in particular between reduced LDL oxidation resistance and CHD. On the other hand, there were negative correlations between the antioxidant LDL modifications (such as reduced alpha-tocopherol levels in LDL) and CHD. The prevalence of CHD was higher in participants with baseline levels of LPO products in LDL >0,8 nM MDA/mg LDL protein and with reduced LDL oxidation resistance (baseline levels >5,4 nM MDA/mg LDL protein vs. levels >13,2 nM MDA/mg LDL protein at later stages of LDL oxidation). However, the prevalence of CHD was lower in individuals with LDL levels of alpha-tocopherol >1,06 mg/mg LDL protein. Conclusion. These findings agree with the previously obtained data on the key role of oxidative LDL modifications in the pathogenesis of atherosclerosis and CHD.

Assessment of immunoglobulin G antibodies against oxidized low-density lipoproteins in patients with acute coronary syndrome

Background Oxidative modification of low-density lipoproteins (LDLs) induces formation of immunogenic epitopes in the LDL molecule, which leads to the formation of antibodies against oxidized low-density lipoprotein (OxLDL) that can be detected in serum. Aim of the study The objective of this study was to evaluate the association between autoantibodies against OxLDL and acute coronary syndrome (ACS). Patients and methods A total of 50 patients diagnosed as having ACS (37 male patients and 13 female patients), age ranging between 19 and 82 years and admitted to the critical care department, Cairo University, and 19 matched healthy controls were enrolled in our study. All patients were subjected to detailed medical history-taking and physical examination, serial 12-lead ECGs, serial cardiac biomarkers on admission and 24 h later, echocardiography, coronary angiography and assessement of severity using the Gensini score, and IgG anti-OxLDL antibodies measurement. Results We found significant difference in the level of antibody between patients with ACS and matched healthy controls ( P r = 0.709) as well as between the echocardiographic findings as assessed by the wall motion score index ( r = 0.589). During hospitalization, there was significant correlation of the antibody level with mechanical complications ( P = 0.047) and needed immediate intervention ( P P value (0.219) was insignificant because of high SD, and there was no correlation with ischemic complications ( P = 0.798). Conclusion With respect to the correlation of anti-OxLDL antibodies and ACS, the patients with ACS had higher anti-OxLDL antibodies level. In addition, anti-OxLDL antibodies level was correlated with the Gensini score, wall motion score index, and major adverse cardiovascular events during hospitalization.

Mobilization of ectopic yolk in Gallus domesticus: a novel reverse lipid transport process

In many oviparous animals, bursting type atresia of ovarian follicles occurs during the reproductive cycle, resulting in the escape of yolk into the extracellular compartment. In birds, this ectopic yolk is rapidly cleared by an unknown process that involves the appearance of yolk-engorged macrophage-like cells. To study this unique type of lipid transport, we injected young male chickens intra-abdominally with egg yolk. Absorption of egg yolk from the body cavity markedly increased the triacylglyceride-rich fraction (TRL) of plasma lipoproteins and was coincident with increased levels of plasma triacylglycerides (TAGs) but not non-esterified fatty acids (NEFAs). Thus, the transport of yolk lipids from the abdominal cavity appears to occur in lipoproteins and be more similar to the transport of hepatic TAGs to the periphery via lipoproteins than to transport of adipose TAGs to the periphery via NEFAs released by the action of lipases. When macrophages were exposed to yolk in vitro, they quickly phagocytized yolk; however, it is unclear whether this level of phagocytosis contributes significantly to total yolk clearance. Instead, the chicken macrophage may function more as a facilitator of yolk clearance through the modification of yolk lipoproteins and the regulation of the local and systemic immune response to ectopic yolk. Yolk appears to be anti-inflammatory in nature. Yolk did not increase levels of the inflammatory cytokines IL-1, IL-6 and IFNγ either in vivo or in vitro; in fact, yolk dampened many inflammatory changes caused by lipopolysaccharide (LPS). Conversely, LPS-induced inflammation retarded yolk clearance from the abdominal cavity and plasma TAG levels.

Association of Paraoxonase1 Gene Q192R Polymorphism and Apolipoprotein B in Asian Indian Women with Coronary Artery Disease Risk

Human serum paraoxonase1 (PON1), a high-density lipoprotein-associated enzyme, prevents oxidative modification of low-density lipoprotein and, thus, arrests the development of atheroma formation, whose major consequence is the development of coronary artery disease (CAD). A single-nucleotide polymorphism (SNP) Q192R in the coding region at pon1 locus is a determinant of PON1 activity. The relationship between PON1 activity and vascular disease may be influenced by the relationship of PON1 activity or PON1 SNP genotype to lipid and apolipoprotein (Apo) levels. The aim of the study is to ascertain the prevalence of PON1 Q192R polymorphism in male and female subjects with and without CAD along with its influence on ApoA-I and ApoB levels in Asian Indians. Determination of genotypes was carried out in 249 diagnosed CAD cases and in 243 age-, gender-matched asymptomatic controls by polymerase chain reaction-restriction fragment length polymorphism. Fasting plasma Apo-levels were estimated by immunoturbidimetric assay. The genotype frequencies did not differ markedly between the overall CAD and control groups and in male and female subjects, suggesting a lack of any genotype-CAD correlation. ApoB levels were found to be higher in female patients carrying RR when compared with QQ genotypes (p=0.03) with no effect on controls. This may be attributed to the postmenopausal state of the women. PON1 Q192R can be used as the DNA marker test to evaluate the risk of CAD in postmenopausal Indian women with high ApoB.

Abstract 19334: Exposure to Diesel Exhaust Emissions Markedly Induce Systemic Lipid Peroxidation and the Development of Dysfunctional Prooxidative and Proinflammatory HDL

Rationale: Exposure to ambient particulate matter is associated with increased cardiovascular ischemic events and enhanced atherosclerosis, likely due in part to the promotion of systemic pro-oxidant and pro-inflammatory effects. Objective: The purpose of this study was to test our hypothesis that air pollutants may induce oxidative modifications of plasma lipoproteins resulting in alteration of the anti-oxidant and anti-inflammatory properties of high-density lipoproteins (HDL). Methods and Results: We exposed ApoE-/- and C57BL/6 wild-type male mice to diesel exhaust (DE) emissions at 200-300 µg PM2.5/m3 for two weeks, filtered air (FA) for two weeks or DE for two weeks, followed by FA for one week (DE+FA). HDL anti-oxidant capacity was assessed by a DCF-based cell fluorescence assay that evaluate the ability of HDL to inhibit LDL oxidation, determined by the level of fluorescence intensity. In the ApoE-/- background, DE and DE+FA mice significantly impaired the HDL anti-oxidant capacity in comparison with FA mice (p<0.001), as judged by almost a doubling in the level of DCF fluorescence and by a promotion rather than inhibition of oxidation. Decreased HDL anti-oxidant properties was accompanied by reduced anti-inflammatory capacity, as determined by a monocyte chemotaxis assay. The HDL anti-oxidant dysfunction correlated with decreased paraoxonase enzymatic activity, increased levels of plasma 8-isoprostanes, 12-HETE, and 13-HODE as well as liver malondialdehyde and 5-HETE levels (p< 0.05), with subsequent up-regulation of hepatic anti-oxidant genes, activation of unfolded protein response and the 5-lipoxygenase pathway. Moreover, while DE led to enhanced lipid peroxidation in the bronchoalveolar lavage fluid of both ApoE-/- and C57BL/6J mice, there were no effects of DE exposure on systemic lipid peroxidation or HDL functionality in the latter. Conclusions: DE emissions induced systemic pro-oxidant effects that led to the development of dysfunctional HDL in hyperlipidemic ApoE-/- mice, which might be one of the mechanisms how air pollution contributes to enhanced atherosclerosis.

Induction of Anti-Anti-Idiotype Antibodies Against Sulfated Glycosaminoglycans Reduces Atherosclerosis in Apolipoprotein E–Deficient Mice

The pathogenesis of atherosclerosis is associated with the early retention of low-density lipoproteins that are trapped in the extracellular matrix of the arterial intima by interaction with glycosaminoglycan side chains of proteoglycans. Mutant mouse/human chimeric antibodies of the murine monoclonal antibody P3, which react with N-glycolyl-containing gangliosides and sulfated glycosaminoglycans, were tested for their potentially antiatherogenic properties through the induction of an idiotypic antibody network that may specifically interfere with the binding of low-density lipoproteins to proteoglycan side chains, low-density lipoprotein modification, and foam cell formation. Apolipoprotein E-deficient mice fed a high-fat, high-cholesterol diet received 5 to 6 doses of chP3R99 or chP3S98 mutant antibodies, showing high and low reactivity, respectively, against their respective antigens. Both chimeric antibodies elicited an immunodominant anti-idiotypic response in the absence of adjuvant. A striking (40%-43%) reduction (P<0.01) in total lesion areas was observed in 18-week-old mice immunized with chP3R99, but not chP3S98, compared with PBS-treated mice. The antiatherosclerotic effect was associated with increased mice sera reactivity against heparin and sulfated glycosaminoglycans, including chondroitin and dermatan sulfate. In addition, purified IgG from chP3R99-immunized mice blocked the retention of apolipoprotein B-containing lipoproteins within the arterial wall of apolipoprotein E(-/-) mice. The present study supports use of active immunization and the mounting of an idiotypic antibody network response against glycosaminoglycans as a novel approach to target atherosclerosis.

Circulating Very-Low-Density Lipoprotein from Subjects with Impaired Glucose Tolerance Accelerates Adrenocortical Cortisol and Aldosterone Synthesis

Apart from their role in cardiovascular homeostasis and immunomodulation, aldosterone and cortisol are also implicated in the pathogenesis of insulin resistance and type 2 diabetes mellitus (T2DM). Furthermore, glycoxidative modifications of lipoproteins are increasingly recognized as an etiological factor for increased cardiovascular morbidity and mortality in prediabetic individuals. The causative relationship between in vivo lipoprotein modifications and steroidogenesis in subjects with impaired glucose tolerance (IGT), however, is not well defined. Therefore, we aimed to investigate the impact of in vivo modified lipoproteins on aldosterone and cortisol release from human adrenocortical H295R cells. Following an oral glucose tolerance test, 20 individuals with normal glucose tolerance (NGT) and 20 IGT subjects were randomly selected from the ongoing PRAEDIAS prevention study in our department. Cells were incubated for 24 h with lipoproteins isolated from NGT and IGT individuals and aldosterone and cortisol release was measured in the supernatants. VLDL induced a greater stimulating effect on adrenocortical aldosterone and cortisol release compared to HDL and LDL. Moreover, IGT-VLDL evoked a significantly higher effect (p<0.05) on hormone release than NGT-VLDL. Incubation of cells with in vitro modified lipoproteins and specific pharmacological inhibitors suggests that VLDL presumably recruits ERK1/2 as one of the downstream effectors of Jak-2. In summary, in vivo modified VLDL are able to promote prediabetic hormonal dysregulation by modulating adrenocortical steroidogenesis via Jak-2-ERK dependent pathway.

Role of lipoprotein modification by the myeloperoxidase-derived oxidant HOSCN in the formation of foam cells in atherosclerosis

Role of lipoprotein modification by the myeloperoxidase-derived oxidant HOSCN in the formation of foam cells in atherosclerosis

Immune response to lipoproteins in atherosclerosis.

Atherosclerosis, the underlying cause of cardiovascular disease, is characterized by chronic inflammation and altered immune response. Cholesterol is a well-known risk factor associated with the development of cardiovascular diseases. Elevated serum cholesterol is unique because it can lead to development of atherosclerosis in animals and humans even in the absence of other risk factors. Modifications of low-density lipoproteins mediated by oxidation, enzymatic degradation, and aggregation result in changes in their function and activate both innate and adaptive immune system. Oxidized low-density lipoprotein (LDL) has been identified as one of the most important autoantigens in atherosclerosis. This escape from self-tolerance is dependent on the formation of oxidized phospholipids. The emerging understanding of the importance of immune responses against oxidized LDL in atherosclerosis has focused attention on the possibility of development of novel therapy for atherosclerosis. This review provides an overview of immune response to lipoproteins and the fascinating possibility of developing an immunomodulatory therapy for atherosclerosis.

Modified lipoproteins provide lipids that modulate dendritic cell immune function

Both physiological and pathological situations can result in biochemical changes of low-density lipoproteins (LDL). Because they can deliver signals to dendritic cells (DC), these modified lipoproteins now appear as regulators of the immune response. Among these modified lipoproteins, oxidized LDL (oxLDL) that accumulate during inflammatory conditions have been extensively studied. Numerous studies have shown that oxLDL induce the maturation of DC, enhancing their ability to activate IFNγ secretion by T cells. LDL treated by secreted phospholipase A(2) also promote DC maturation. Among the bioactive lipids generated by oxidation or phospholipase treatment of LDL, lysophosphatidylcholine (LPC) and some saturated fatty acids induce DC maturation whereas some unsaturated fatty acids or oxidized derivatives have opposite effects. Among other factors, the nuclear receptor peroxisome-proliferator activated receptor γ (PPARγ) plays a crucial role in this regulation. Non-modified lipoproteins also contribute to the regulation of DC function, suggesting that the balance between native and modified lipoproteins, as well as the biochemical nature of the LDL modifications, can regulate the activation threshold of DC. Here we discuss two pathological situations in which the impact of LDL modifications on inflammation and immunity could play an important role. During atherosclerosis, modified LDL accumulating in the arterial intima may interfere with DC maturation and function, promoting a Th1 immune response and a local inflammation favoring the development of the pathology. In patients chronically infected, the hepatitis C virus (HCV) interferes with lipoprotein metabolism resulting in the production of infectious modified lipoproteins. These lipo-viral-particles (LVP) are modified low-density lipoproteins containing viral material that can alter DC maturation and affect specific toll-like receptor signaling. In conclusion, lipoprotein modifications play an important role in the regulation of immunity by delivering signals of danger to DC and modulating their function.

Expression of sialic acids and other nonulosonic acids in Leptospira

BackgroundSialic acids are negatively charged nine carbon backbone sugars expressed on mammalian cell surfaces. Sialic acids are part of a larger family of nonulosonic acid (NulO) molecules that includes pseudaminic and legionaminic acids. Microbial expression of sialic acids and other nonulosonic acids has been shown to contribute to host-microbe interactions in a variety of contexts, including participation in colonization, immune subversion, and behaviors such as biofilm formation, autoagglutination and motility. Previous research has suggested that some spirochetes may also express these molecules.ResultsHere we use a combination of molecular tools to investigate the presence of NulO biosynthetic gene clusters among clinical and saprophytic isolates of the genus Leptospira. Polymerase chain reaction and Southern blotting suggested that a variety of leptospires encoded NulO biosynthetic pathways. High performance liquid chromatography and mass spectrometry analyses provided biochemical evidence that di-N-acetylated NulO molecules are expressed at relatively high levels by L. interrogans serovar Lai strain 55601, and at lower levels by L. alexanderi serovar Manhao and L. fainei serovar Hurstbridge. Endogenous expression of N-acetylneuraminic acid (Neu5Ac, the most common sialic acid) was documented in L. interrogans serovar Copenhageni strain L1-130. Neu5Ac biosynthesis is also supported by a unique gene fusion event resulting in an enzyme with an N-terminal N-acetylneuraminic acid synthase domain and a C-terminal phosphatase domain. This gene fusion suggests that L. interrogans uses a Neu5Ac biosynthetic pathway more similar to animals than to other bacteria. Analysis of the composition and phylogeny of putative NulO biosynthetic gene clusters in L. interrogans serovar Lai and serovar Copenhageni revealed that both strains have complete biosynthetic pathways for legionamimic acid synthesis, a molecule with the same stereochemistry as sialic acid. Lectin-based affinity purification of NulO-modified molecules, followed by mass spectrometric identification suggests post-translational modification of surface lipoproteins, including Loa22.ConclusionsLeptospira species encode NulO biosynthetic pathways and synthesize multiple NulO molecules including sialic acid. Additional studies are needed to clarify the exact context and functional significance of NulO expression. These findings have implications for immune evasion during systemic leptospirosis.

Cholesteryl ester acyl oxidation and remodeling in murine macrophages: formation of oxidized phosphatidylcholine

Cholesterol is an essential component of eukaryotic cell membranes, regulating fluidity and permeability of the bilayer. Outside the membrane, cholesterol is esterified to fatty acids forming cholesterol esters (CEs). Metabolism of CEs is characterized by recurrent hydrolysis and esterification as part of the CE cycle; however, since recombinant 15-lipoxygenase (15-LO) was shown to oxidize cholesteryl linoleate of LDL, there has been interest in CE oxidation, particularly in the context atherogenesis. Studies of oxidized CE (oxCE) metabolism have focused on hydrolysis and subsequent reverse cholesterol transport with little emphasis on the fate the newly released oxidized fatty acyl component. Here, using mass spectrometry to analyze lipid oxidation products, CE metabolism in murine peritoneal macrophages was investigated. Ex vivo macrophage incubations revealed that cellular 15-LO directly oxidized multiple CE substrates from intracellular stores and from extracellular sources. Freshly harvested murine macrophages also contained 15-LO-specific oxCEs, suggesting the enzyme may act as a CE-oxidase in vivo. The metabolic fate of oxCEs, particularly the hydrolysis and remodeling of oxidized fatty acyl chains, was also examined in the macrophage. Metabolism of deuterated CE resulted in the genesis of deuterated, oxidized phosphatidylcholine (oxPC). Further experiments revealed these oxPC species were formed chiefly from the hydrolysis of oxidized CE and subsequent reacylation of the oxidized acyl components into PC.

Inhibitory effect of some local medicinal plants on in-vitro oxidative modification of low-density lipoprotein

Background Oxidative modification of low-density lipoprotein (LDL) has been implicated in atherogenesis. Antioxidants that prevent LDL oxidation may reduce atherosclerosis. Methods The antioxidant activity of 45 extracts from 15 locally used medicinal plants were studied in-vitro employing using three different systems; the DPPH (1,1-diphenyle-2-picryl-hydrazyl) radical scavenging assay, superoxide anion generated in Xanthine–Xanthine oxidase (X-XOD) system and the LDL oxidation induced by cupper ions. Results It was observed that the leaf extracts of olive, Jew's mallow, celery, the seed extract of celery and safflower, and ginger extracts had the highest antioxidant activity in the three assays. Conclusion It could be concluded that these plant extracts could play an important role in the inhibition of lipid peroxidation in biological systems through their antioxidant, metal chelating, and free radical scavenging activities.