Auto-Antibody Production During Experimental Atherosclerosis in ApoE-/- Mice

Current models stipulate that B cells and antibodies function during atherosclerosis in two distinct ways based on antibody isotype, where IgM is protective and IgG is inflammatory. To examine this model, we generated ApoE-/- Aid-/- mice, which are unable to produce IgG antibodies due to the absence of activation-induced deaminase (AID) but maintain high plasma cholesterol due to the absence of apolipoprotein E (APOE). We saw a dramatic decrease in plaque formation in ApoE-/- Aid-/- mice compared to ApoE-/- mice. Rigorous analysis of serum antibodies revealed both ApoE-/- and ApoE-/- Aid-/- mice had substantially elevated titers of IgM antibodies compared to C57BL/6J controls, suggesting a more complex dynamic than previously described. Analysis of antigen specificity demonstrated that ApoE-/- Aid-/- mice had elevated titers of antibodies specific to malondialdehyde-oxidized low density lipoprotein (MDA-oxLDL), which has been shown to block macrophage recruitment into plaques. Conversely, ApoE-/- mice showed low levels of MDA-oxLDL specificity, but had antibodies specific to numerous self-proteins. We provide evidence for a hierarchical order of antibody specificity, where elevated levels of MDA-oxLDL specific IgM antibodies inhibit plaque formation. If the level of MDA-oxLDL specific IgM is insufficient, self-reactive IgM and IgG antibodies are generated against debris within the arterial plaque, resulting in increased inflammation and further plaque expansion.

Evaluation of Enhanced Lipid Oxidation and Compensatory Suppression using Natriuretic Peptide in Patients with Cardiovascular Diseases

Malondialdehyde-modified low-density lipoprotein (MDA-LDL) is recognized as a surrogate marker of lipid oxidation and is associated with arteriosclerosis. However, there are limited reports on the relationship between heart failure and MDA-LDL. Therefore, we aimed to determine whether MDA-LDL is activated in patients with left ventricular (LV) dysfunction and examine our hypothesis that the B-type natriuretic peptide (BNP) masks the enhancement of MDA-LDL in patients with LV dysfunction by its strong antioxidative action. The study population comprised 2,976 patients with various cardiovascular diseases. Patients were divided into four groups depending on the LV ejection fraction (LVEF) or plasma BNP level. A nonparametric analysis with the Kruskal-Wallis test was used to perform an interquartile comparison. In addition, structural equation modeling and Bayesian estimation were used to compare the effects of LVEF and BNP on MDA-LDL. MDA-LDL levels did not significantly change (P > 0.05) with respect to the degree of LVEF among the four groups. In contrast, MDA-LDL levels were significantly decreased (P < 0.001) with respect to the degree of BNP among the four groups. A path model based on structural equation modeling clearly showed a significant effect of LVEF (standardized regression coefficient; β: -0.107, P < 0.001) and BNP (β: -0.114, P < 0.001) on MDA-LDL, with a significant inverse association between LVEF and BNP (correlation coefficient -0.436, P < 0.001). MDA-LDL should be activated in patients with LV dysfunction; however, BNP is thought to exert a strong compensatory suppression on lipid oxidation, masking the relationship between heart failure and lipid oxidation.

Evaluation of Malondialdehyde Low-Density Lipoprotein Stratified by Low-Density Lipoprotein Cholesterol

BACKGROUND

Malondialdehyde low-density lipoprotein (MDA-LDL) is a major form of oxidized LDL and considered to be more atherogenic than LDL. Information on major determinants of MDA-LDL and their association in subjects who are not under treatment for diabetes mellitus and dyslipidemia is limited.

METHODS

This study included 778 Japanese subjects who were not taking medication for diabetes mellitus and dyslipidemia. All subjects underwent an annual health examination that included MDA-LDL analysis. Study subjects were divided into four groups according to mean values of LDL-C and MDA-LDL, and the metabolic profile was compared.

RESULTS

LDL cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) were mainly associated with MDA-LDL. When subjects were stratified based on LDL-C levels, small dense LDL-C and MDA-LDL levels increased as LDL-C levels increased. Comparison of the characteristics of study subjects in the same LDL-C level group revealed that subjects with high MDA-LDL showed high metabolic risk in all LDL-C groups, particularly notable in the group with LDL-C levels < 120 mg/dL.

CONCLUSIONS

Our data indicated that high LDL-C and low HDL-C levels were independently associated with high MDA-LDL. To prevent high MDA-LDL, it is important to lower LDL-C level as well as to increase HDL-C even in subjects with low LDL-C level by lifestyle modification.

Relationship of Autoantibodies to MDA-LDL and ApoB-Immune Complexes to Sex, Ethnicity, Subclinical Atherosclerosis, and Cardiovascular Events

OBJECTIVE

Modifications of lipid constituents within atherosclerotic lesions generate neoepitopes that activate innate and adaptive immune responses. We aimed to define the prevalence, distribution, and relationship of autoantibody titers of oxidized lipoproteins to subclinical atherosclerosis and major adverse cardiovascular events (MACE) in different ethnic groups.

APPROACH AND RESULTS

IgG and IgM autoantibodies to malondialdehyde-modified low-density lipoprotein (MDA-LDL) and apolipoprotein B-100-immune complexes were measured in 3509 individuals (1814 blacks, 1031 whites, 589 Hispanics, and 85 no race identifier) from the Dallas Heart Study with median 10.5-year follow-up. Coronary artery calcium score, abdominal aortic plaque by magnetic resonance imaging, and MACE were quantified. IgG MDA-LDL and IgG and IgM apolipoprotein B-100-immune complexes were significantly different between groups, with blacks having the highest levels of IgG MDA-LDL and IgG apolipoprotein B-100-immune complexes and Hispanics having the highest levels of IgM apolipoprotein B-100-immune complexes (P<0.001 for all). IgGs tended to be higher and IgMs lower with age for all markers. In multivariable-adjusted binary logistic regression analysis, a doubling of IgG MDA-LDL levels was associated with prevalent coronary artery calcium score >10 Agatston units (odds ratio [95% confidence interval], 1.21 [1.07-1.36]; P=0.002). Multivariable-adjusted Cox regression analysis revealed that IgG MDA-LDL was independently associated with time to incident MACE in the entire group (hazard ratio [95% confidence interval], 1.76 [1.16-2.72]; P=0.009 for fourth versus first quartile). This effect was particularly prominent in black subjects (hazard ratio [95% confidence interval], 2.52 [1.39-4.57]; P=0.002).

CONCLUSIONS

Autoantibodies to oxidized lipoproteins and immune complexes with apoB-100 lipoproteins vary significantly by sex, age, and ethnicity. Higher baseline IgG MDA-LDL titers independently associate with new MACE. These findings may contribute to the understanding of differences in ethnic-specific MACE events.

Malondialdehyde-Modified LDL IgG Antibody Levels and Indices of Cardiac Function in Valvular Heart and Coronary Artery Disease Patients

OBJECTIVE

To compare the changes in anti-malondialdehyde-modified low-density lipoprotein (MDA-LDL) IgG levels among patients undergoing off-pump and on-pump coronary artery bypass grafting (CABG) or valvuloplasty.

SUBJECTS AND METHODS

A total of 38, 39 and 34 patients who underwent off-pump CABG, on-pump CABG and valvuloplasty, respectively, were enrolled in this study. Serum anti-MDA-LDL IgG values were measured 24 h before and after the operative procedures and at discharge. Echocardiography was also done before surgery and before discharge. The results were compared with values from 50 healthy controls.

RESULTS

In all patients, a reduction in antibody titers was observed post-operatively. However, the decrease was significant only in the off-pump CABG - before surgery: 42.33 (25.83-58.51), after surgery: 30.86 (16.36-51.33) and at discharge: 10.96 (6.82-23.57; p = 0.027). There was a significant positive association between anti-MDA-LDL IgG levels and ejection fraction (r = 0.248, p = 0.036) and a negative association with E/E', a marker of pulmonary capillary wedge pressure, in the coronary patients (r = -0.345, p = 0.012), but no significant associations were found in patients with valvular heart disease.

CONCLUSIONS

Serum anti-MDA-LDL IgG levels were associated with cardiac function indices in coronary patients undergoing CABG.

Pedometer step counts and oxidized low-density lipoprotein levels among asymptomatic subjects

While daily step counts are considered to be a useful measure of cardiovascular health, the biochemical predictors of step counts have not been fully characterized. This study investigated the correlation between pedometer-determined daily step counts and cardiometabolic variables, including the serum level of malondialdehyde-modified low-density lipoprotein (MDA-LDL), among asymptomatic subjects (n = 50, mean age 63 years). Simple and stepwise multiple linear correlation tests revealed that there was a significant inverse correlation between the step counts and MDA-LDL levels (r = -0.41, P < 0.01; β = -0.38, P < 0.01). The data suggest that daily steps may be beneficially associated with atherosclerosis in correlation with reduced oxidized low-density lipoprotein, and in addition that the MDA-LDL level may be used as a measure reflective of the daily steps.

Electron-topological, energetic and π-electron delocalization analysis of ketoenamine-enolimine tautomeric equilibrium

The ketoenamine-enolimine tautometic equilibrium has been studied by the analysis of aromaticity and electron-topological parameters. The influence of substituents on the energy of the transition state and of the tautomeric forms has been investigated for different positions of chelate chain. The quantum theory of atoms in molecules method (QTAIM) has been applied to study changes in the electron-topological parameters of the molecule with respect to the tautomeric equilibrium in intramolecular hydrogen bond. Dependencies of the HOMA aromaticity index and electron density at the critical points defining aromaticity and electronic state of the chelate chain on the transition state (TS), OH and HN tautomeric forms have been obtained.

Determination of urinary malondialdehyde by isotope dilution LC-MS/MS with automated solid-phase extraction: a cautionary note on derivatization optimization

A highly sensitive quantitative LC-MS/MS method was developed for measuring urinary malondialdehyde (MDA). With the use of an isotope internal standard and online solid-phase extraction, urine samples can be directly analyzed within 10 min after 2,4-dinitrophenylhydrazine (DNPH) derivatization. The detection limit was estimated as 0.08 pmol. This method was further applied to assess the optimal addition of DNPH for derivatization and to measure urinary MDA in 80 coke oven emission (COE)-exposed and 67 nonexposed workers. Derivatization optimization revealed that to achieve complete derivatization reaction, an excess of DNPH is required (DNPH/MDA molar ratio: 893-8929) for urine samples that is about 100 times higher than that of MDA standard solutions (molar ratio: 10-80). Meanwhile, the mean urinary concentrations of MDA in COE-exposed workers were significantly higher than those in nonexposed workers (0.23±0.17 vs 0.14±0.05 μmol/mmol creatinine, P<0.005). Urinary MDA concentrations were also significantly associated with the COE (P<0.005) and smoking exposure (P<0.05). Taken together, this method is capable of routine high-throughput analysis and accurate quantification of MDA and would be useful for assessing the whole-body burden of oxidative stress. Our findings, however, raise the issue that derivatization optimization should be performed before it is put into routine biological analysis.

Reduced levels of anti-MDA LDL antibodies in patients with carbohydrate metabolism disorders

BACKGROUND

Diabetic patients undergoing percutaneous coronary intervention (PCI) have a worse prognosis than non-diabetic patients. The anti-oxidized LDL antibodies (anti-LDLox ab) have recently been suggested to be protective against the development of diabetes. The aim of this study was to compare the levels of IgG and IgM anti-oxidized LDL antibodies with reference to the new diagnostic criteria for carbohydrate metabolism disorders after an oral glucose tolerance test (OGTT) in hospitalized patients scheduled to undergo percutaneous coronary intervention.

METHODS

We undertook a cross-sectional study of 110 patients undergoing PCI. The patients were classified as being normal (oral glucose test tolerance normal, OGTT-N), or having impaired glucose tolerance (IGT) or type 2 diabetes mellitus (T2DM) according to their glucose levels at baseline and after an OGTT.

RESULTS

An inverse slope was found in the levels of IgG anti-oxidized LDL antibodies between the OGTT-N patients (optical density (OD) = 0.109) and the patients with IGT (OD = 0.099) or T2DM (OD = 0.084) (p = 0.019). An inverse correlation was also detected between the levels of IgG anti-oxidized LDL antibodies and baseline glycemia (r = -0.23, p = 0.018).

CONCLUSIONS

Patients with coronary disease and carbohydrate metabolism disorders have much lower levels of IgG anti-oxidized LDL antibodies than normoglycemic patients.

[Endogenous intoxication syndrome in children with mixed enteric parasitoses]

The degree of endogenous intoxication and the activation of lipid peroxidation products (LPO) were studied in patients with enteric parasitoses. The findings suggest that the expression of medium-molecular-weight peptides in relation with the values of LPO is of importance in the pathogenesis of parasitoses.

Microsomal triglyceride transfer protein gene polymorphism strongly influences circulating malondialdehyde-modified low-density lipoprotein

Microsomal triglyceride transfer protein (MTP) plays a critical role in the assembly of lipoproteins. Therefore, we studied whether MTP gene polymorphisms are associated with atherosclerosis-promoting parameters, especially metabolic profiles and endothelial function, in healthy young men. One hundred one healthy men (mean age, 30.3 years) were studied. We analyzed the 2 promoter polymorphisms (-493G/T and -400A/T) of the MTP gene. Linkage disequilibrium analysis revealed a significant but incomplete linkage disequilibrium between the 2 polymorphisms (D' = 0.74). The -493T allele carriers (n = 26) showed marked increases in their levels of malondialdehyde-modified low-density lipoprotein (mean value, 135 vs 99 U/L in the G/G carriers; P = .003) and triglycerides (2.15 vs 1.16 mmol/L, P = .014), and reduced low-density lipoprotein particle size (259.2 vs 264.3 nm, P = .023), whereas there was no difference in apolipoproteins, insulin, adiponectin, homocysteine, folate, and endothelial function assessed using ultrasound measurement of brachial artery flow-mediated vasodilation. In contrast, the -400T allele carriers (n = 61) showed a reduced endothelial function (P = .044), accompanied by elevated apolipoprotein B levels in subjects with higher triglyceride levels. These results indicate that both promoter polymorphisms may be associated with the development of atherosclerosis and cardiovascular diseases, but that the mechanism responsible may be different.

Impact of the high-molecular-weight form of adiponectin on endothelial function in healthy young men

OBJECTIVE

Adiponectin is an adipocyte-derived, antiatherogenic protein that is present in plasma as a large multimeric structure of high molecular weight (HMW) and in a trimer or hexamer form (non-HMW). The biological activities of these isoforms have not yet been elucidated. We therefore examined the effect of these isoforms on endothelial function in healthy young men.

DESIGN

One hundred apparently healthy young men without overt cardiovascular disease (mean age 30 years) were recruited in this cross-sectional study based on voluntary enrollment.

MEASUREMENTS

We evaluated endothelial function estimated by flow-mediated dilatation (FMD) of the brachial artery during reactive hyperaemia, and measured total and HMW adiponectin levels.

RESULTS

Both HMW and non-HMW adiponectin levels showed a significant, inverse correlation with body mass index (BMI). FMD was significantly correlated with fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), malondialdehyde-modified low density lipoprotein (MDA-LDL), LDL particle size, and HMW adiponectin (r = 0.320, P = 0.001), but not non-HMW adiponectin (r = 0.125, P = 0.22). In multivariate analysis, HMW adiponectin and MDA-LDL were selected as independent factors capable of influencing FMD. No variables determined nitroglycerin-induced dilatation.

CONCLUSIONS

These results suggest that even in young men, plasma adiponectin levels can predict endothelial dysfunction before any overt vascular disease has occurred. HMW adiponectin may be more useful as a marker of endothelial dysfunction than total adiponectin.

Bulge migration of the malondialdehyde OPdG DNA adduct when placed opposite a two-base deletion in the (CpG)3 frameshift hotspot of the Salmonella typhimurium hisD3052 gene

The OPdG adduct N (2)-(3-oxo-1-propenyl)dG, formed in DNA exposed to malondialdehyde, was introduced into 5'-d(ATCGC XCGGCATG)-3'.5'-d(CATGCCGCGAT)-3' at pH 7 (X = OPdG). The OPdG adduct is the base-catalyzed rearrangement product of the M 1dG adduct, 3-(beta- d-ribofuranosyl)pyrimido[1,2- a]purin-10(3 H)-one. This duplex, named the OPdG-2BD oligodeoxynucleotide, was derived from a frameshift hotspot of the Salmonella typhimuium hisD3052 gene and contained a two-base deletion in the complementary strand. NMR spectroscopy revealed that the OPdG-2BD oligodeoxynucleotide underwent rapid bulge migration. This hindered its conversion to the M 1dG-2BD duplex, in which the bulge was localized and consisted of the M 1dG adduct and the 3'-neighbor dC [ Schnetz-Boutaud, N. C. , Saleh, S. , Marnett, L. J. , and Stone, M. P. ( 2001) Biochemistry 40, 15638- 15649 ]. The spectroscopic data suggested that bulge migration transiently positioned OPdG opposite dC in the complementary strand, hindering formation of the M 1dG-2BD duplex, or alternatively, reverting rapidly formed intermediates in the OPdG to M 1dG reaction pathway when dC was placed opposite from OPdG. The approach of initially formed M 1dG-2BD or OPdG-2BD duplexes to an equilibrium mixture of the M 1dG-2BD and OPdG-2BD duplexes was monitored as a function of time, using NMR spectroscopy. Both samples attained equilibrium in approximately 140 days at pH 7 and 25 degrees C.

CONCENTRATION OF MALONDIALDEHYDE-MODIFIED LOW-DENSITY LIPOPROTEIN IN THE JUGULAR BULB DURING CAROTID ENDARTERECTOMY CORRELATES WITH DEVELOPMENT OF POSTOPERATIVE COGNITIVE IMPAIRMENT

OBJECTIVE

Approximately 20 to 30% of patients undergoing carotid endarterectomy (CEA) subsequently develop cognitive impairment. The purpose of the present study is to determine whether or not malondialdehyde (MDA)-modified low-density lipoprotein (LDL), a biochemical marker of oxidative damage, concentrations in the jugular bulb during CEA correlates with development of postoperative cognitive impairment.

METHODS

Fifty-five patients undergoing CEA were assessed with a battery of neuropsychological tests before and 1 month after surgery. Serum samples for measurement of MDA-LDL concentration were obtained from a venous catheter inserted into the ipsilateral jugular bulb at the following time points: immediately before clamping of the internal carotid artery (ICA), 10 minutes after clamping of the ICA, and 5 and 20 minutes after declamping of the ICA.

RESULTS

The MDA-LDL concentrations at 5 and 20 minutes after ICA declamping were both significantly higher than concentrations before ICA clamping (P < 0.0001). At the postoperative neuropsychological assessment, six (11%) out of 55 patients showed postoperative cognitive impairment. Logistic regression analysis demonstrated that higher values of MDA-LDL increase (calculated as a percentage of the preclamp values) at either 5 or 20 minutes after ICA declamping were significantly associated with the development of postoperative cognitive impairment (95% confidence interval, 0.787-0.981; P = 0.0209) among the variables tested.

CONCLUSION

MDA-LDL concentration in the jugular bulb during CEA correlates with development of postoperative cognitive impairment.

PON1, a new biomarker of cardiovascular disease, is low in patients with systemic vasculitis

OBJECTIVES

Because systemic vasculitis (SV) predisposes to atherosclerosis, and high-density lipoprotein (HDL) prevents atherosclerosis by "reverse cholesterol transport" and by inhibiting low-density lipoprotein (LDL) oxidation thanks to apolipoprotein A-I (Apo-AI) and paraoxonase 1 (PON1), we assessed whether LDL oxidation was increased in SV and associated with less PON1 activity.

METHODS

The sera of 33 patients with active SV (ASV), 32 in full remission of SV (RSV) and 20 healthy subjects (HS) were analyzed for C-reactive protein (CRP), high-sensitivity-CRP, lipids, lipoproteins, apolipoproteins, PON1 activity, LDL-immune complexes (LDL-IC), and auto-antibodies to oxidized-LDL (ox-LDL), and anticardiolipin antibodies.

RESULTS

CRP was higher in ASV than RSV and HS, and negatively correlated with HDL-cholesterol and Apo-AI. Autoantibodies to ox-LDL and highly oxidized malondialdehyde-LDL were higher in RSV than ASV and HS (P<0.05). LDL-IC titers were higher in ASV than RSV and HS (P<0.05). PON1 activity was lower in ASV and RSV than HS (P=0.02). A trend toward a negative correlation between basal PON1 activity and anti-MDA-LDL antibodies (P=0.06) was observed.

CONCLUSION

Inflammatory markers in SV were associated with a modified lipoprotein profile, which could lower PON1 activity and contribute to increased ox-LDL titers and accelerated atherosclerosis development.

Beneficial effects of grape seed extract on malondialdehyde-modified LDL

Following consecutive 12-wk administration of tablets containing 0, 200 or 400 mg grape seed extract (calculated as proanthocyanidin) to 61 healthy subjects with LDL cholesterol (LDL-C) levels of 100 to 180 mg/dL, effects of such treatment compared to administration of placebo tablets on malondialdehyde-modified LDL (MDA-LDL), representing one oxidized type of LDL, were investigated by a single blind method. MDA-LDL level in the 200 mg (calculated as proanthocyanidin) group was significantly (p = 0.008) reduced compared to the basal level, 12 wk after the start of administration. In the 400 mg (calculated as proanthocyanidin) group, a significant decrease in MDA-LDL level compared to the basal level was found 6 and 12 wk after the start of administration (6 wk: p = 0.015, 12 wk: p = 0.009). Subjects with high levels of MDA-LDL/ApoB (MDA-LDL/ApoB > or = 100 mU/mL) in the 200 mg group showed significantly (p = 0.011) reduced MDA-LDL levels at 12 wk after the start of administration. In the 400 mg group, significant decreases in MDA-LDL level compared to the basal level were seen 6 and 12 wk after the start of administration (6 wk: p = 0.001, 12 wk: p < 0.001); and at week 6, significantly (p = 0.048) lower values were observed compared to those in patients who took placebo tablets (0 mg proanthocyanidin). In subjects demonstrating the least body weight changes during the test period (less than +/- 1.0 kg) in the 400 mg group, there was an increasing trend (p = 0.088) in adiponectin levels 12 wk after the start of treatment. These results suggested that tablets containing grape seed extract exerted reducing effects on oxidized LDL, and might be useful in preventing lifestyle-related diseases such as arteriosclerosis.

C-H...O hydrogen bond in chloroform-triformylmethane complex: blue-shifted or red-shifted?

B3LYP/6-311+G** level of theory is used to investigate the C-H...O hydrogen bond formed by chloroform and two conformers of triformylmethane (TFM), i.e. cis-TFM (concerned with C1 configuration) and trans-TFM (concerned with C2 and C3 configurations). Polarized continuum model (PCM) is used to study the solvent (chloroform) effect on this hydrogen bond. The C3 configuration is more stable than the C1 configuration whether the absolute energy or the stabilization energy is concerned. For the C1 and C2 configurations this hydrogen bond is of blue-shifted type both in gas phase and in chloroform solution. For the C3 configuration this hydrogen bond is of red-shifted type in gas phase but turns into blue-shifted type in chloroform solution instead. It's inappropriate to simply designate this hydrogen bond as blue-shifted type or red-shifted type.

Real-time observation of intramolecular proton transfer in the electronic ground state of chloromalonaldehyde: Anab initiostudy of time-resolved photoelectron spectra

The authors report on studies of time-resolved photoelectron spectra of intramolecular proton transfer in the ground state of chloromalonaldehyde, employing ab initio photoionization matrix elements and effective potential surfaces of reduced dimensionality, wherein the couplings of proton motion to the other molecular vibrational modes are embedded by averaging over classical trajectories. In the simulations, population is transferred from the vibrational ground state to vibrationally hot wave packets by pumping to an excited electronic state and dumping with a time-delayed pulse. These pump-dump-probe simulations demonstrate that the time-resolved photoelectron spectra track proton transfer in the electronic ground state well and, furthermore, that the geometry dependence of the matrix elements enhances the tracking compared with signals obtained with the Condon approximation. Photoelectron kinetic energy distributions arising from wave packets localized in different basins are also distinguishable and could be understood, as expected, on the basis of the strength of the optical couplings in different regions of the ground state potential surface and the Franck-Condon overlaps of the ground state wave packets with the vibrational eigenstates of the ion potential surface.

Characterization of human monoclonal autoantibody Fab fragments against oxidized LDL

Oxidized low-density lipoprotein (oxLDL) is a key autoantigen in atherosclerosis. The genetic structures and pathogenic roles of autoantibodies against this protein remain to be established. In this study, we cloned several monoclonal IgG autoantibody Fab fragments specific for oxLDL from peripheral blood lymphocytes of atherosclerosis patients, using phage display technology. The sequences of their variable regions were determined at the cDNA level. The closest germline counterparts for the heavy chains belonged to the V(H)3 or V(H)1 family. The sequences and lengths of complementarity-determining regions (CDR)3-V(H) were diverse, and frequent mutations of positively charged amino acids (particularly arginine) over entire V(H) and V(L) sequences were observed. It is proposed that anti-oxLDL autoantibody formation is driven by antigens. Among the Fabs, P2-8 and P3-175 bound to both MDA-LDL and Cu-oxLDL, and inhibited the uptake of oxLDL by macrophages, suggesting the epitope(s) recognized by the Fabs is a part of ligands on oxLDL that is involved in uptake by macrophage scavenger receptor. These human autoantibody Fabs require detailed investigation to ascertain their potential as agents for clinical applications.

Induction of oral tolerance to oxidized low-density lipoprotein ameliorates atherosclerosis

BACKGROUND

Oxidation of low-density lipoprotein (LDL) and the subsequent processing of oxidized LDL (oxLDL) by macrophages results in activation of specific T cells, which contributes to the development of atherosclerosis. Oral tolerance induction and the subsequent activation of regulatory T cells may be an adequate therapy for the treatment of atherosclerosis.

METHODS AND RESULTS

Tolerance to oxLDL and malondialdehyde-treated LDL (MDA-LDL) was induced in LDL receptor-/- mice fed a Western-type diet by oral administration of oxLDL or MDA-LDL before the induction of atherogenesis. Oral tolerance to oxLDL resulted in a significant attenuation of the initiation (30% to 71%; P<0.05) and progression (45%; P<0.05) of atherogenesis. Tolerance to oxLDL induced a significant increase in CD4+ CD25+ Foxp3+ cells in spleen and mesenteric lymph nodes, and these cells specifically responded to oxLDL with increased transforming growth factor-beta production. Tolerance to oxLDL also increased the mRNA expression of Foxp3, CTLA-4, and CD25 in the plaque. In contrast, tolerance to MDA-LDL did not affect atherogenesis.

CONCLUSIONS

OxLDL-specific T cells, present in LDL receptor-/- mice and important contributors in the immune response leading to atherosclerotic plaque, can be counteracted by oxLDL-specific CD4+ CD25+ Foxp3+ regulatory T cells activated via oral tolerance induction to oxLDL. We conclude that the induction of oral tolerance to oxLDL may be a promising strategy to modulate the immune response during atherogenesis and a new way to treat atherosclerosis.

Eplerenone Inhibits Atherosclerosis in Nonhuman Primates

Aldosterone may be involved in the pathogenesis of atherosclerosis. We investigated the effect of eplerenone, a selective mineralocorticoid receptor blocker, on atherosclerosis in monkeys fed a high-cholesterol diet. Monkeys fed a high-cholesterol diet for 9 months were divided into 3 groups: those treated with a low dose of eplerenone (30 mg/kg per day); those treated with a high dose of eplerenone (60 mg/kg per day); and the placebo-treated group. The normal group consisted of monkeys fed a normal diet. There were no significant differences in blood pressure and cholesterol levels between the placebo- and eplerenone-treated groups. On the other hand, monocyte chemoattractant protein-1 and malondialdehyde-modified LDL were significantly higher in the placebo-treated group than in the normal group, whereas they were suppressed in the eplerenone-treated groups. The ratio of intimal volume to total volume by intravascular ultrasound analysis imaging of the aortas was dose-dependently lower in the eplerenone-treated groups than in the placebo-treated group. Acetylcholine-induced vasorelaxation was significantly weaker in the placebo-treated group than in the normal group, but the vasorelaxation was strengthened in the eplerenone-treated groups. A significant upregulation of angiotensin-converting enzyme activity was observed in the placebo-treated group, but the activity was suppressed in the eplerenone-treated groups. In conclusion, eplerenone may strengthen the endothelium-dependent relaxation and suppress angiotensin-converting enzyme activity in the vasculature, thus preventing the development of atherosclerosis in nonhuman primates.

Effect of pravastatin on malondialdehyde-modified low-density lipoprotein levels and coronary plaque regression as determined by three-dimensional intravascular ultrasound

We hypothesized that a reduction in atherogenic malondialdehyde-modified low-density lipoprotein (MDA-LDL) levels, which may antagonize the action of atheroprotective high-density lipoprotein cholesterol, leads to coronary plaque regression. This study investigated the effects of pravastatin on the serum levels of MDA-LDL and coronary atherosclerosis. In a 6-month prospective study, 75 patients with stable coronary artery disease were randomly assigned to a pravastatin-treatment group (n = 52) or a control group (n = 23). Volumetric analyses were performed in matched coronary artery segments by 3-dimensional intravascular ultrasound. Pravastatin therapy for 6 months resulted in a decrease in coronary plaque volume (14.4%, p <0.0001) and a corresponding reduction in serum MDA-LDL levels (12.7%, p = 0.0001). In the pravastatin treatment group, the percentage of change in plaque volume correlated with changes in the MDA-LDL and high-density lipoprotein cholesterol levels (r = 0.52 and -0.55, respectively, p <0.0001) but not with the changes in any other lipid levels. Multivariate regression analysis revealed that a reduced MDA-LDL level is an independent predictor of plaque regression, as was an increase in high-density lipoprotein cholesterol. In conclusion, these results suggest that the reduction in the MDA-LDL levels induced by pravastatin may serve as a novel marker of coronary atherosclerosis regression.

Lesion Development and Response to Immunization Reveal a Complex Role for CD4 in Atherosclerosis

Atherosclerosis is a complex disease, bearing many of the characteristics of a chronic inflammatory process. Both cellular and humoral immune responses may be involved in the disease development. Oxidized low-density lipoprotein (oxLDL) is suggested to be an autoantigen in atherosclerosis. A protective effect against atherosclerosis has been demonstrated in animals immunized with oxLDL. Such a protection is associated with elevation of T cell–dependent IgG antibodies against oxLDL. In addition, it has been shown that immunization with Freund adjuvant alone also confers protection against development of atherosclerosis. We therefore hypothesized that CD4+ T cells are critical in the development of atherosclerosis and that they are involved in protective immune reactions after immunization. The development of atherosclerosis was studied in apolipoprotein E knockout (apoE KO) mice and CD4/apoE double knockout (dKO) mice that were immunized with either oxLDL in Freund adjuvant or adjuvant alone, or left untreated. Our results show that (1) the absence of CD4+ cells in apoE KO mice leads to reduced atherosclerosis, indicating that CD4+ cells constitute a major proatherogenic cell population, and (2) the atheroprotective effect of LDL immunization does not depend on CD4+ cells, whereas (3) the atheroprotective effect of adjuvant injection is CD4-dependent. These findings demonstrate complex roles of immune cell-cell interactions in the regulation of the atherosclerotic process and point to several possible targets in the treatment and prevention of atherosclerosis.

Methyl malondialdehyde is not suitable as an internal standard for malondialdehyde detection in urine after derivatisation with 2,4-dinitrophenylhydrazine

A previously described method of measurement of malondialdehyde (MDA) in human urine after derivatisation with 2,4-dinitrophenylhydrazine (DNPH) was tested for a possibility of using methyl malondialdehyde (MeMDA) as an internal standard. Despite structural similarity, those compounds were found to produce different yields of derivatisation under the same conditions depending on urine matrix. We conclude, that MeMDA is not suitable as an internal standard for the measurement of MDA in urine under previously reported conditions when DNPH is used as a deriviatising agent.

Effect of monotherapy and combination therapy with richlocaine on tissue hypoxia and activity of keratinocyte detoxifying systems in ischemic skin flap

Treatment with richlocaine alone and, especially, in combination with antihypoxant energostim decreased the total content of hydroxyproline in the ischemic skin flap on day 3 after excision. Combination therapy with richlocaine and energostim normalized the redox potential in the energy supply system, improved antioxidant protection, and promoted the recovery of a balance between various components in the antioxidant system. These changes were not accompanied enhanced production of malonic dialdehyde. Our results suggest that combination therapy with richlocaine and energostim maintains the adaptive reserves of detoxifying systems in keratinocytes and prevents endotoxemia. Richlocaine primarily stimulates glycolytic synthesis of ATP, activates nonmitochondrial antioxidant enzymes, and increases RNase activity in lysosomes.

Reactions of 9-substituted guanines with bromomalondialdehyde in aqueous solution predominantly yield glyoxal-derived adducts

Reactions of 9-ethylguanine, 2'-deoxyguanosine and guanosine with bromomalondialdehyde in aqueous buffers over a wide pH-range were studied. The main products were isolated and characterized by (1)H and (13)C NMR and mass spectroscopy. The final products formed under acidic and basic conditions were different, but they shared the common feature of being derived from glyoxal. Among the 1 : 1 adducts, 1,N(2)-(trans-1,2-dihydroxyethano)guanine adduct (6) predominated at pH < 6 and N(2)-carboxymethylguanine adduct (10a,b) at pH > 7. In addition to these, an N(2)-(4,5-dihydroxy-1,3-dioxolan-2-yl)methylene adduct (11a,b) and an N(2)-carboxymethyl-1,N(2)-(trans-1,2-dihydroxyethano)guanine adduct (12) were obtained at pH 10. The results of kinetic experiments suggest that bromomalondialdehyde is significantly decomposed to formic acid and glycolaldehyde under the conditions required to obtain guanine adducts. Glycolaldehyde is oxidized to glyoxal, which then modifies the guanine base more readily than bromomalondialdehyde. Besides the glyoxal-derived adducts, 1,N(2)-ethenoguanine (5a-c) and N(2),3-ethenoguanine adducts (4a-c) were formed as minor products, and a transient accumulation of two unstable intermediates, tentatively identified as 1,N(2)-(1,2,2,3-tetrahydroxypropano)(8) and 1,N(2)-(2-formyl-1,2,3-trihydroxypropano)(9) adducts, was observed.

Fourier transforms infrared spectra and structure of triformylmethane. A density functional theoretical study

Molecular structure and vibrational frequencies of triformylmethane have been investigated by means of density functional theory (DFT) calculations. The geometrical parameters and vibrational frequencies obtained in the B3LYP, B3PW91, BLYP, BPW91, G96LYP and G96PW91 levels of DFT and compared with the corresponding parameters of malonaldehyde (MA). Fourier transform infrared spectra of triformylmethane and its deuterated analogue were clearly assigned. Theoretical calculations show that the hydrogen bond strength of triformylmethane is stronger than that of MA, which is in agreement with spectroscopic results.

Improved method for plasma malondialdehyde measurement by high-performance liquid chromatography using methyl malondialdehyde as an internal standard

Measurement of malondialdehyde (MDA) is an important contribution to the assessment of oxidative stress. We report a sensitive and reproducible high-performance liquid chromatography (HPLC) method for measurement of plasma MDA in the assessment of lipid peroxidation. Using methyl malondialdehyde (Me-MDA) as an internal standard with reversed-phase HPLC and UV detection and derivatisation with 2,4 dinitrophenylhydrazine (DNPH), we obtained maximum MDA values with 60-min incubation of 10% plasma with 1 M NaOH at 60 degrees C. The dilution of the plasma and a longer incubation time in the alkaline hydrolysis step greatly improved recovery of MDA from its bound form. Ratios of peak height of MDA/Me-MDA were linear over a range of 0-100 microM with correlation coefficients >0.99. The recovery was 88.5%. Within and between run variations were <4 and <7%, respectively. The mean MDA value measured in 20 healthy volunteers was 13.8 microM (+/-1.32).

Structural and functional characterization of pronyl-lysine, a novel protein modification in bread crust melanoidins showing in vitro antioxidative and phase I/II enzyme modulating activity

Application of an in vitro antioxidant assay to solvent fractions isolated from bread crust, bread crumb, and flour, respectively, revealed the highest antioxidative potential for the dark brown, ethanol solubles of the crust, whereas corresponding crumb and flour fractions showed only minor activities. To investigate whether these browning products may also act as antioxidants in biological systems, their modulating activity on detoxification enzymes was investigated as a functional parameter in intestinal Caco-2 cells. The bread crust and, in particular, the intensely brown, ethanolic crust fraction induced a significantly elevated glutathione S-transferase (GST) activity and a decreased phase I NADPH-cytochrome c reductase (CCR) activity compared to crumb-exposed cells. Antioxidant screening of Maillard-type model mixtures, followed by structure determination, revealed the pyrrolinone reductones 1 and 2 as the key antioxidants formed from the hexose-derived acetylformoin and N(alpha)-acetyl-L-lysine methyl ester or glycine methyl ester, chosen as model substances to mimic nonenzymatic browning reactions with the lysine side chain or the N terminus of proteins, respectively. Quantitation of protein-bound pyrrolinone reductonyl-lysine, abbreviated pronyl-lysine, revealed high amounts in the bread crust (62.2 mg/kg), low amounts in the crumb (8.0 mg/kg), and the absence of this compound in untreated flour. Exposing Caco-2 cells for 48 h to either synthetically pronylated albumin or purified pronyl-glycine (3) significantly increased phase II GST activity by 12 or 34%, respectively, thus demonstrating for the first time that "pronylated" proteins as part of bread crust melanoidins act as monofunctional inducers of GST, serving as a functional parameter of an antioxidant, chemopreventive activity in vitro.

Validation of methyl malondialdehyde as internal standard for malondialdehyde detection by capillary electrophoresis

The aim of this study was to validate, by capillary electrophoresis, the use of synthesized methyl malondialdehyde as the internal standard for the direct quantification of free and total (free+bound) malondialdehyde in biological samples. All analyses were performed in 20 cm x 50 microm uncoated capillaries at 20 degrees C, using 25 mmol/L borax (pH 9.3) and 5 mmol/L tetradecyltrimethylammonium bromide as running buffer. The applied voltage was -4kV (about 8 microA), the detector being set at 260 nm for a total run time of 8 min per sample. Free malondialdehyde was evaluated after acetonitrile extraction, while the samples evaluated for total malondialdehyde were, before extraction, hydrolyzed for 1h at 60 degrees C in the presence of 1 mol/L NaOH. The detection threshold was 0.2 micromol/L in microsomes and 0.4 micromol/L in plasma. As an application of the method, three pools of rat liver microsomes were quantified before (0.35+/-0.1 and 1.1+/-0.5 nmol/mg protein, free and total malondialdehyde, respectively, mean+/-SD) and after lipoperoxidation induction using systems able to generate oxygen free radicals (18.4+/-3.2 and 19.7+/-2.0 nmol/mg protein). The results were confirmed by isotopic dilution gas chromatography-mass spectrometry, used as the reference method. The feasibility of capillary electrophoresis for malondialdehyde determination in normal and pathological human plasma was also investigated.

Malonyl-coenzyme A reductase from Chloroflexus aurantiacus, a key enzyme of the 3-hydroxypropionate cycle for autotrophic CO(2) fixation

The 3-hydroxypropionate cycle is a new autotrophic CO(2) fixation pathway in Chloroflexus aurantiacus and some archaebacteria. The initial step is acetyl-coenzyme A (CoA) carboxylation to malonyl-CoA by acetyl-CoA carboxylase, followed by NADPH-dependent reduction of malonyl-CoA to 3-hydroxypropionate. This reduction step was studied in Chloroflexus aurantiacus. A new enzyme was purified, malonyl-CoA reductase, which catalyzed the two-step reduction malonyl-CoA + NADPH + H(+) --> malonate semialdehyde + NADP(+) + CoA and malonate semialdehyde + NADPH + H(+) --> 3-hydroxypropionate + NADP(+). The bifunctional enzyme (aldehyde dehydrogenase and alcohol dehydrogenase) had a native molecular mass of 300 kDa and consisted of a single large subunit of 145 kDa, suggesting an alpha(2) composition. The N-terminal amino acid sequence was determined, and the incomplete gene was identified in the genome database. Obviously, the enzyme consists of an N-terminal short-chain alcohol dehydrogenase domain and a C-terminal aldehyde dehydrogenase domain. No indication of the presence of a prosthetic group was obtained; Mg(2+) and Fe(2+) stimulated and EDTA inhibited activity. The enzyme was highly specific for its substrates, with apparent K(m) values of 30 microM malonyl-CoA and 25 microM NADPH and a turnover number of 25 s(-1) subunit(-1). The specific activity in autotrophically grown cells was 0.08 micromol of malonyl-CoA reduced min(-1) (mg of protein)(-1), compared to 0.03 micromol min(-1) (mg of protein)(-1) in heterotrophically grown cells, indicating downregulation under heterotrophic conditions. Malonyl-CoA reductase is not required in any other known pathway and therefore can be taken as a characteristic enzyme of the 3-hydroxypropionate cycle. Furthermore, the enzyme may be useful for production of 3-hydroxypropionate and for a coupled spectrophotometric assay for activity screening of acetyl-CoA carboxylase, a target enzyme of potent herbicides.

Identification of conjugate adducts formed in the reactions of malonaldehyde-acetaldehyde and malonaldehyde-formaldehyde with cytidine

Malonaldehyde was reacted with cytidine in buffered aqueous solutions in the presence of acetaldehyde or formaldehyde. The reaction mixtures were analyzed by HPLC, and the products were isolated by preparative C18 chromatography and structurally characterized by UV absorbance, fluorescence emission, (1)H and (13)C NMR spectroscopy, and mass spectrometry. The major adducts formed in the reaction of malonaldehyde and acetaldehyde were identified as 7-(beta-D-ribofuranosyl)-4-methyl-6-oxo-6,7-dihydro-4H-pyrimido[1,6-a]pyrimidine-3-carbaldehyde (M(1)AA-Cyd) and 1-(beta-D-ribofuranosyl)-4-(3,5-diformyl-4-methyl-1,4-dihydro-1-pyridyl)pyrimidine (M(2)AA-Cyd). In the reaction of malonaldehyde and formaldehyde, the major product was identified as 7-(beta-D-ribofuranosyl)-6-oxo-6,7-dihydro-4H-pyrimido[1,6-a]pyrimidine-3-carbaldehyde (M(1)FA-Cyd). The highest yields of M(1)AA-Cyd and M(2)AA-Cyd, 3.2 and 0.5 mol %, respectively, were obtained in the reaction performed at pH 4.6 and 37 degrees C for 8 days, while M(1)FA-Cyd was produced at a yield of 0.3 mol % after 3 days of reaction at pH 4.0 and 37 degrees C. The products consist of units derived from malonaldehyde and acetaldehyde (M(1)AA-Cyd and M(2)AA-Cyd) or from malonaldehyde and formaldehyde (M(1)FA-Cyd), and are thus further examples of nucleoside modifications containing structural elements derived from aldehyde condensation reactions. Trace amounts of the adducts may be formed at physiological conditions and may be involved in the mutagenicity of the studied aldehydes.

Mutagenicity of the malondialdehyde oligomerization products 2-(3'-oxo-1'-propenyl)-malondialdehyde and 2,4-dihydroxymethylene-3-(2,2-dimethoxyethyl)glutaraldehyde in Salmonella

Malondialdehyde (MDA), a byproduct of non-enzymatic lipid peroxidation and prostaglandin biosynthesis, has been shown to be a weak frameshift mutagen in Salmonella mutagenicity assays. Because it is a dialdehyde, MDA can undergo self condensation to form polymeric products. It is possible that these condensation products are highly mutagenic and have contributed to previously reported estimates of MDA mutagenicity. We synthesized two major MDA polymerization products, (1) 2-(3'-oxo-1'-propenyl)-malondialdehyde [(MDA)2] and (2) 2,4-dihydroxymethylene-3-(2,2-dimethoxyethyl)glutaraldehyde [(MDA)3Me2] and tested their mutagenicity in the Salmonella frameshift tester strains hisD3052 and TA94 (hisD3052/pKM101). Analysis of the reversion rates revealed both (MDA)2 and (MDA)3Me2 to be weak mutagens, approximately equipotent to MDA. Although both (MDA)2 and (MDA)3Me2 are mutagenic, the fact that their formation is thermodynamically unfavorable under physiological conditions suggests they do not contribute significantly to the mutagenicity of MDA solutions.

Condensation of triformylmethane with guanosine

Guanosine has been reacted with triformylmethane (TFM) in refluxing pyridine. Four different products, 4-7, were isolated by preparative RP-HPLC, and characterized by 1H and 13C NMR and UV spectroscopy and mass spectrometry. One of the products. the cyclic 1:1 adduct 4, is a stable cyclic carbinolamine formed probably by cyclization of the expected aminomethylene derivative 3. Compound 4 then undergoes reversible dehydration to the fully conjugated adduct 5. The appearance of the additional adducts, 6 and 7, suggests that TFM is prone to transformations resulting in the formation of methylenemalonaldehyde (9) and 1,1,3,3-tetraformylpropane (11).

Evidence that malondialdehyde-derived aminoenimine is not a fluorescent age pigment

It has been suggested that protein modifications by malondialdehyde (MDA), a major product of lipid peroxidation, contribute to the fluorescence formation of lipofuscin. Although early studies proposed an aminoenimine structure (RNHCH=CHCH=NR) formed from MDA and the epsilon-amino groups of the lysine residues for the fluorophores, there has been considerable doubt as to whether the aminoenimine is fluorescent. To date, however, there is no conclusive evidence that the aminoenimine is nonfluorescent. This is because that it has not yet been isolated. In this study, we succeeded in isolating an aminoenimine, N,N'-bis[5-(tert-butoxycarboxamido)-5-carboxypentyl]-1-amino-3-iminopropene [(Boc-Lys)(2)MDA], formed from the reaction of MDA with a lysine derivative, N(alpha)-tert-butoxycarbonyl-L-lysine (Boc-Lys), at neutral pH, and confirmed that the purified (Boc-Lys)(2)MDA exhibited no fluorescence. This result demonstrates that aminoenimines formed from MDA and lysine residues do not contribute to the fluorescence formation of lipofuscin.

Methyl malondialdehyde as an internal standard for the determination of malondialdehyde

Methyl malondialdehyde (Me-MDA) is suggested as an internal standard for the determination of the lipid peroxidation product, malondialdehyde (MDA). A procedure for synthesising the Me-MDA sodium salt is described in detail. The purity and identity of the synthesised Me-MDA have been confirmed using nuclear magnetic resonance and UV spectroscopy, and by micellar electrokinetic chromatography. The applicability of Me-MDA as an internal standard has been demonstrated for rat brain homogenate samples. These samples were purified solely through ultrafiltration. The preferred analytical technique was capillary zone electrophoresis (CZE) with UV detection at 267 nm. The limits of detection (3 S/N) for the CZE separations of Me-MDA and MDA were 0.5 and 0.2 microM, respectively, and the total analysis time was approximately 10 min. Details of separations are also presented using high-performance liquid chromatography (HPLC) with UV detection at 245 nm, and gas chromatography, together with either electron capture or mass spectrometric detection. The GC separations require derivatisation of MDA and Me-MDA with pentafluorophenylhydrazine while the CZE and HPLC separations can be performed on the native molecules.

Melatonin reduces phenylhydrazine-induced oxidative damage to cellular membranes: evidence for the involvement of iron

Phenylhydrazine and iron overload result in augmented oxidative damage and an increased likelihood of cancer. Melatonin is a well known antioxidant and free radical scavenger. The aim of this study was to determine whether melatonin would protect against phenylhydrazine-induced oxidative damage to cellular membranes and to evaluate the possible role of iron in this process. Changes in lipid peroxidation and microsomal membrane fluidity were estimated after the treatment of rats with phenylhydrazine (15 mg/kg body weight, daily, 7 days) alone and melatonin or ascorbic acid (15 mg/kg body weight, two times daily, 8 days), or their combination. Additionally, lipid peroxidation was measured in liver homogenates from untreated and melatonin or ascorbic acid-treated rats in vivo and exposed to iron in vitro. Melatonin, but not ascorbic acid, reduced phenylhydrazine-induced lipid peroxidation in vivo in spleen (3.16+/-0.06 vs. 3.83+/-0.12 nmol/mg protein, P<0.05) and plasma (7. 73+/-0.52 vs. 9.96+/-0.71 nmol/ml, P<0.05) and attenuated the decrease in hepatic microsomal membrane fluidity (1/polarization, 3. 068+/-0.007 vs. 3.027+/-0.008, P<0.05). In vitro exposure to iron significantly enhanced the lipid peroxidation in liver homogenates from untreated (3.34+/-0.75 vs. 1.25+/-0.28, P<0.05) or ascorbic acid-treated rats (2.72+/-0.39 vs. 0.88+/-0.06, P<0.05) but not from melatonin-treated rats (1.49+/-0.55 vs. 0.68+/-0.20, NS). It is concluded that free radical mechanisms are involved in the toxicity of phenylhydrazine and that the antioxidant melatonin, but not ascorbic acid, reduces the toxic affects of phenylhydrazine in vivo and of iron in vitro in cell membranes. Therefore, melatonin co-treatment in conditions of iron overload may prove beneficial.

Autoxidation products of both carbohydrates and lipids are increased in uremic plasma: is there oxidative stress in uremia?

BACKGROUND

Advanced glycation end products (AGEs), formed by non-enzymatic glycation and oxidation (glycoxidation) reactions, have been implicated in the pathogenesis of several diseases, including normoglycemic uremia. AGE research in uremia has focused on the accumulation of carbohydrate-derived adducts generated by the Maillard reaction. Recent studies, however, have demonstrated that one AGE, the glycoxidation product carboxymethyllysine (CML), could be derived not only from carbohydrates but also from oxidation of polyunsaturated fatty acids in vitro, raising the possibility that both carbohydrate and lipid autoxidation might be increased in uremia.

METHODS

To address this hypothesis, we applied gas chromatography-mass spectrometry and high performance liquid chromatography to measure protein adducts formed in uremic plasma by reactions between carbonyl compounds and protein amino groups: pentosidine derived from carbohydrate-derived carbonyls, malondialdehyde (MDA)-lysine derived from lipid-derived carbonyls, and CML originating possibly from both sources.

RESULTS

All three adducts were elevated in uremic plasma. Plasma CML levels were mainly (>95%) albumin bound. Their levels were not correlated with fructoselysine levels and were similar in diabetic and non-diabetic patients on hemodialysis, indicating that their increase was not driven by glucose. Pentosidine and MDA-lysine were also increased in plasma to the same extent in diabetic and non-diabetic hemodialysis patients. Statistical analysis indicated that plasma levels of CML correlated weakly (P < 0.05) with those of pentosidine and MDA-lysine, but that pentosidine and MDA-lysine varied independently (P > 0.5).

CONCLUSIONS

These data suggest that the increased levels of AGEs in blood, and probably in tissues, reported in uremia implicate a broad derangement in non-enzymatic biochemistry involving alterations in autoxidation of both carbohydrates and lipids.

Anti-low-density lipoprotein antibodies in alcoholics without and with liver disease and in social drinkers

Antibodies directed to native and to in-vitro acetaldehyde-modified (ethylated) low-density lipoproteins (LDL) were determined in 28 alcoholic subjects divided into two groups: one with no clinical nor laboratory evidence of liver involvement and the second with histologically proven alcohol-related liver disease. The control group consisted of 18 individuals who drank alcohol socially. In the individuals with alcoholic liver disease IgG reactivity against both native and ethylated LDL was significantly higher than in alcoholic individuals without liver injury. High levels of IgG reactivity in individuals with alcoholic liver disease were also observed against malondialdehyde-modified, methylated, acetylated and carbamylated LDL. A selective high anti-ethylated LDL IgG reactivity was observed in 11% of control subjects.

A simplified and efficient synthesis of 5,10-dideaza-5,6,7,8-tetrahydrofolic acid (DDATHF)

A new and extremely efficient synthesis of DDATHF from 4-vinylbenzoic acid and bromomalondialdehyde as precursors has been developed which proceeds in 48% overall yield.

Mutational spectra of Salmonella typhimurium revertants induced by chlorohydroxyfuranones, byproducts of chlorine disinfection of drinking water

The base substitution specificities of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), 3-chloro-4-(chloromethyl)-5-hydroxy-2(5H)-furanone (CMCF), 3,4-dichloro-5-hydroxy-2(5H)-furanone (MCA), and chloromalonaldehyde (CMA), a putative breakdown product of MCA, were examined in the hisG46 gene and in the hisG428 gene of Salmonella typhimurium using allele specific oligonucleotide hybridization. Although the compounds are structurally closely related, they induced substantially different mutation spectra: MCA and CMA caused primarily GC-->AT transitions in the hisG46 allele (target sequence CCC), in particular, at the second position of the codon in strain TA100. In TA100 the mutation spectrum of MCA was similar to that of CMA. The mutational specificity of MCA can be explained as a consequence of misincorporation opposite to cyclic etheno adducts identical to those formed by the carcinogen vinyl chloride. The spectra induced by MX and CMCF in TA100 were almost identical but distinctively different from the spectra of MCA and CMA. Both compounds induced primarily GC-->TA transversions, in particular, at the second position of the codon, and to a lesser extent in the first position of the codon. An identical site bias is induced by carcinogens such as polycyclic aromatic hydrocarbons and heterocyclic amines as a consequence of formation of (noncyclic) guanosine adducts. In hisG428 (target sequence TAA) MX induced again primarily GC-->TA transversions in Tyr tRNA genes (supC/M) and, to a lesser extent, intragenic AT-->TA transversions (TAA-->AAA). The possible involvement of guanosine and adenosine adducts in the mutational specificity of MX is addressed.

Enzymatic elimination of fluoride from alpha-fluoro-beta-alanine

Rat liver homogenates catalyzed the elimination of fluoride from (R,S)-alpha-fluoro-beta-alanine. The substrate specificity and physical properties of the defluorinating enzyme were similar to those of mitochondrial L-alanine-glyoxylate aminotransferase II (EC 2.6.1.44, AlaAT-II). Furthermore, AlaAT-II activity, measured with L-alanine and glyoxylate as substrates, copurified with the alpha-fluoro-beta-alanine-defluorinating enzyme. The NH2-terminal sequence (18 residues) of the enzyme did not show significant sequence similarity with any of the proteins currently listed in GenBank. The purified enzyme catalyzed the transamination of L-alanine (Ala) and glyoxylate (glyx) at pH 8.5 by a ping-pong mechanism with kinetic parameters of kcat = 17 sec-1, KL-Ala = 3.2 mM, and Kglyx = 0.3 mM, respectively. The kinetic parameters for the defluorination of (R)-alpha-fluoro-beta-alanine and (S)-alpha-fluoro-beta-alanine were kcat = 6.2 and 2.6 min-1, respectively, and Km = 2.7 and 0.88 mM, respectively. L-Alanine potently inhibited the defluorination reaction with an apparent Ki of 0.024 mM. (R,S)-alpha-Fluoro-beta-alanine converted the optical spectrum of the enzyme-bound cofactor from the pyridoxal form to the pyridoxamino form, which indicated that this cofactor may participate in the defluorination reaction. The product of the enzymatic reaction, malonic semialdehyde, reacted nonenzymatically with (R,S)-alpha-fluoro-beta-alanine to form an adduct that was detected spectrally. AlaAT-II was not inactivated during dehalogenation of (R,S)-alpha-fluoro-beta-alanine but was inactivated completely during dehalogenation of beta-chloro-L-alanine.

Synthesis of fluorescent derivatives of 7-methylguanine through reaction with 2-aryl-substituted malondialdehydes: analysis by HPLC with fluorescence detection

Fluorescent derivatives of 7-methylguanine were prepared through reaction with 2-aryl-substituted-malondialdehydes and analysed by reversed-phase HPLC with fluorescence detection. Reaction of carbons 1 and 3 of the malondialdehyde molecule at the N1 and N2 positions of 7-methylguanine yielded fluorescent tricyclic structures. Two novel fluorescent derivatives of 7-MeG were obtained, namely, 7-(3,4-dimethoxyphenyl)-10-oxo-1-methyl-9,10-dihydropyrimido[1,2- alpha]purine (yield 15-34%) and 7-(1-naphthyl)-10-oxo-1-methyl-9,10- dihydropyrimido[1,2-alpha]purine (yield 56-70%) after reaction with 3,4-dimethoxyphenylmalondialdehyde and 1-naphthylmalondialdehyde, respectively which were characterized by IR, NMR, MS and UV and fluorescence spectroscopy. The fluorescence intensity of the derivatives was found to be 10-20-fold higher than the intrinsic fluorescence of 7-methylguanine. Concentration versus fluorescence intensity curves exhibit linearity in the picomole to nanomole range. The 2-aryl-substituted malondialdehydes were used to analyse the concentration of 7-methylguanine in neutral hydrolysates obtained from calf thymus DNA samples alkylated with dimethyl sulfate. The results obtained indicate their potential as reagents for the analysis of alkylated guanines in biological samples. Molecular modeling calculations were carried out to generate lowest energy spatial configurations. The results obtained indicated that the aryl-substituents on the malondialdehyde moiety do not lie in the same plane as the tricyclic moiety of the fluorescent derivatives with implications for their fluorescence properties.

Formation of ethenocarbaldehyde derivatives of adenosine and cytidine in reactions with mucochloric acid

Mucochloric acid, a genotoxic compound formed during chlorine disinfection of drinking water, was reacted with adenosine and cytidine at pH 4.0, 90 degrees C. HPLC analyses with UV detection at 325 nm showed that one previously unidentified product peak was formed in each reaction. The products were separated and isolated by HPLC and characterized by UV absorbance, 1H and 13C NMR spectroscopy, and mass spectrometry. The products were identified as 3-(beta-D-ribofuranosyl)-7-formylimidazo[2,1-i]purine (I) and 6-(beta-D-ribofuranosyl)-3-formylimidazo[1,2-c]pyrimidin-5(6H)-one (II) (ethenocarbaldehyde derivatives of adenosine and cytidine, respectively). The ethenocarbaldehyde derivative of adenosine was also produced in reactions carried out at pH 7.4 and 37 degrees C. The formation of the ethanocarbaldehyde derivatives and the previously identified etheno derivatives from mucochloric acid is explained by an initial conversion of mucochloric acid, through hydrolysis and decarboxylation, to chloromalonaldehyde. Chloromalonaldehyde reacts with the nucleosides and forms an intermediate adduct which either undergoes ring closure by intramolecular displacement of the chlorine atom or breaks down to form chloroacetaldehyde which subsequently produces the etheno derivatives.