Aldehyde-modified proteins as mediators of early inflammation in atherosclerotic disease

Malondialdehyde Mediated Alpha-Synuclein Aggregation: A Plausible Etiology of Parkinson's Disease in Oxidative Stress

Malondialdehyde (MDA), a major reactive byproduct of lipid peroxidation, has been implicated in numerous pathological conditions as a result of altering the structure and function of crucial proteins. One such protein is α-synuclein (α-Syn), which plays a vital role in the pathogenesis of Parkinson's disease (PD). This study investigates the hypothesis that MDA causes structural alterations in α-Syn, promoting its aggregation and exacerbating its toxicological effects. In vivo experiments were conducted where MDA and MDA-modified α-Syn were injected to the brain of mice. Behavioral assessments were performed to evaluate motor function changes, while immunohistochemistry was employed to examine the extent of α-Syn aggregation in brain tissues. An extraction protocol was also developed exquisitely, enabling quantification of modified α-Syn from brain tissue. Moreover, 15Nitrogen-labeled α-Syn was employed to establish an absolute quantification method on nLC-HRMS/MS. Our findings demonstrate that MDA-induced modifications in α-Syn alter its structural properties and also significantly enhance its aggregation propensity, potentially contributing to the neurodegenerative processes observed in PD. The developed model displayed a nonreversible decline in motor function, neurodegeneration, and aggregation of proteins in the brain mimicking the PD conditions. This research provides valuable insights into the molecular mechanisms of PD, emphasizing the role of MDA-modified proteins in the etiology of PD.

Advance in aldehydes derived from lipid oxidation: A review of the formation mechanism, attributable food thermal processing technology, analytical method and toxicological effect

The aldehydes derived from lipid oxidation are highly active electrophilic compounds including saturated aldehydes, dialdehydes, olefin aldehydes and hydroxyl aldehydes. The active groups like carbonyls, C=C bond, and hydroxyl groups make them prone to participate in chemical reactions with protein, phospholipids, which can further affect food properties. In addition, aldehydes can attack the nucleic acids and thiol group of endogenous antioxidants, result in oxidative stress and biological damage of cells, which usually serve as the direct trigger of various diseases. However, their structure-activity relationship has not received enough attention. Therefore, to provide a comprehensive understanding of reactive aldehydes on food safety and human health, the formation mechanism of aldehydes, attributable fundamental thermal processing, analytical methods, and toxicological effects based on the structure-activity relationship, have been reviewed and discussed. It was indicated that aldehydes generation exerted significant specificity of fatty acids substrate. Significant structure-activity relationships for the toxicological effects of aldehydes could be observed. Effective, accurate and eco-friendly detection techniques should be established based on the inherent advantages and limitations for food quality preservation and safety assurance.

Identification of plasma proteins binding oxidized phospholipids using pull-down proteomics and OxLDL masking assay

Oxidized phospholipids (OxPLs) are increasingly recognized as toxic and proinflammatory mediators, which raises interest in the mechanisms of their detoxification. Circulating OxPLs are bound and neutralized by plasma proteins, including both antibodies and non-immunoglobulin proteins. The latter group of proteins is essentially not investigated because only three OxPC-binding plasma proteins are currently known. The goal of this work was to characterize a broad spectrum of plasma proteins selectively binding OxPLs. Using pull-down-proteomic analysis, we found about 150 non-immunoglobulin proteins preferentially binding oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-phosphatidylcholine (OxPAPC) as compared to non-oxidized PAPC. To test if candidate proteins indeed can form a barrier isolating OxPLs from recognition by other proteins, we applied an immune masking assay. Oxidized LDL (OxLDL) immobilized in multiwell plates was used as a carrier of OxPLs, while mAbs recognizing OxPC or OxPE were used as "detectors" showing if OxPLs on the surface of OxLDL are physically accessible to external binding partners. Using an orthogonal combination of pull-down and masking assays we confirmed that previously described OxPL-binding proteins (non-fractionated IgM, CFH, and Apo-M) indeed can bind to and mask OxPC and OxPE on liposomes and OxLDL. Furthermore, we identified additional plasma proteins selectively binding and masking OxPC including Apo-D, Apo-H, pulmonary surfactant-associated protein B, and antithrombin-III. We hypothesize that in addition to circulating antibodies, multiple non-immunoglobulin plasma proteins can also bind OxPLs and modulate their recognition by innate and adaptive immunity.

Dual effects of endogenous formaldehyde on the organism and drugs for its removal

Endogenous formaldehyde (FA) is produced in the human body via various mechanisms to preserve healthy energy metabolism and safeguard the organism. However, endogenous FA can have several negative effects on the body through epigenetic alterations, including cancer growth promotion; neuronal, hippocampal and endothelial damages; atherosclerosis acceleration; haemopoietic stem cell destruction and haemopoietic cell production reduction. Certain medications with antioxidant effects, such as glutathione, vitamin E, resveratrol, alpha lipoic acid and polyphenols, lessen the detrimental effects of endogenous FA by reducing oxidative stress, directly scavenging endogenous FA or promoting its degradation. This study offers fresh perspectives for managing illnesses associated with endogenous FA exposure.

Small Animal Multisubject PET/CT Workflow

Positron emission tomography (PET) is a highly sensitive molecular imaging technique that uses radioactive tracers to map molecular and metabolic processes in living animals. PET can be performed as a stand-alone modality but is often combined with CT to provide for objective anatomical localization of PET signals in a multimodality approach. In order to outline the general approach to evaluating four mice simultaneously by dynamic PET imaging, the use of the aldehyde-targeted radiotracer [18F]NA3BF3 in mouse models of hepatotoxicity will be described. Indeed the production of aldehydes is upregulated in a wide range of disease and injury, making them a suitable biomarker for PET imaging of numerous pathologies.

Autoreactive B cells against malondialdehyde-induced protein cross-links are present in the joint, lung, and bone marrow of rheumatoid arthritis patients

Autoantibodies to malondialdehyde (MDA) proteins constitute a subset of anti-modified protein autoantibodies in rheumatoid arthritis (RA), which is distinct from citrulline reactivity. Serum anti-MDA IgG levels are commonly elevated in RA and correlate with disease activity, CRP, IL6, and TNF-α. MDA is an oxidation-associated reactive aldehyde that together with acetaldehyde mediates formation of various immunogenic amino acid adducts including linear MDA-lysine, fluorescent malondialdehyde acetaldehyde (MAA)-lysine, and intramolecular cross-linking. We used single-cell cloning, generation of recombinant antibodies (n = 356 from 25 donors), and antigen-screening to investigate the presence of class-switched MDA/MAA+ B cells in RA synovium, bone marrow, and bronchoalveolar lavage. Anti-MDA/MAA+ B cells were found in bone marrow plasma cells of late disease and in the lung of both early disease and risk-individuals and in different B cell subsets (memory, double negative B cells). These were compared with previously identified anti-MDA/MAA from synovial memory and plasma cells. Seven out of eight clones carried somatic hypermutations and all bound MDA/MAA-lysine independently of protein backbone. However, clones with somatic hypermutations targeted MAA cross-linked structures rather than MDA- or MAA-hapten, while the germline-encoded synovial clone instead bound linear MDA-lysine in proteins and peptides. Binding patterns were maintained in germline converted clones. Affinity purification of polyclonal anti-MDA/MAA from patient serum revealed higher proportion of anti-MAA versus anti-MDA compared to healthy controls. In conclusion, IgG anti-MDA/MAA show distinct targeting of different molecular structures. Anti-MAA IgG has been shown to promote bone loss and osteoclastogenesis in vivo and may contribute to RA pathogenesis.

Liver enzymes mediate the association between aldehydes co-exposure and hypertriglyceridemia

Aldehydes are recognized environmental toxicants that may affect lipid metabolism. For instance, acrolein has been found to increase serum triglyceride (TG) levels exclusively. However, it remains unclear whether other aldehydes are also associated with hypertriglyceridemia (HTG), and what mechanisms may be involved. This cross-sectional study analyzed data from the National Health and Nutrition Examination Survey (NHANES, 2013-2014) to identify associations between serum aldehydes, liver enzymes, and HTG. Serum aldehydes included crotonaldehyde (CRAL), propanaldehyde (3AL), butyraldehyde (4AL), pentanaldehyde (5AL), isopentanaldehyde (I5AL), and heptanaldehyde (7AL). Liver enzymes included alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and gamma-glutamyltransferase (GGT). HTG was defined as fasting TG levels ≥ 1.7 mmol/L. Aldehyde co-exposure was quantified using weighted quantile sum (WQS) regression and Bayesian kernel machine regression (BKMR), while mediation analysis was performed to investigate the role of liver enzymes. Among 1474 participants (mean age 38.6 years, male 50.0%), 426 were diagnosed with HTG. 4AL, 5AL, I5AL, and 7AL were shown to be positively associated with HTG (all P values <0.05). Aldehydes co-exposure was also positively associated with HTG (OR 1.706, 95%CI 1.299-2.240), with 5AL contributing the highest weight (35.3%). Furthermore, aldehydes co-exposure showed positive associations with ALT, AST, and GGT (all P values <0.05), and all four liver enzymes were positively associated with HTG (all P values <0.05). Mediation analysis revealed that liver enzymes (ALT, AST, and GGT) may mediate the associations of 5AL and 7AL with HTG (all P values <0.05). This study identified a positive association between aldehyde co-exposure and HTG, which may be partially mediated by liver enzymes.

Malondialdehyde-Induced Post-translational Modifications in Hemoglobin of Smokers by NanoLC-NSI/MS/MS Analysis

Malondialdehyde (MDA) is the most abundant α,β-unsaturated aldehyde generated from endogenous peroxidation of polyunsaturated fatty acids and is present in cigarette smoke. Post-translational modifications of blood hemoglobin can serve as biomarkers for exposure to chemicals. In this study, two types of MDA-induced modifications, the N-propenal and the dihydropyridine (DHP), were identified at multiple sites in human hemoglobin digest by the high-resolution mass spectrometry. The N-propenal and the DHP types of modification led to the increase of 54.0106 and 134.0368 amu, respectively, at the N-terminal and lysine residues. Among the 21 MDA-modified peptides, 14 with dose-response to MDA concentrations were simultaneously quantified in study subjects by the nanoflow liquid chromatography nanoelectrospray ionization tandem mass spectrometry under selected reaction monitoring (nanoLC-NSI-MS/MS-SRM) without prior enrichment. The results showed that the modifications of the N-propenal-type at α-Lys-11, α-Lys-16, α-Lys-61, β-Lys-8, and β-Lys-17, as well as the DHP-type at the α-N-terminal valine, are significantly higher in hemoglobin isolated from the blood of smokers than in nonsmoking individuals. This is the first report to identify and quantify multiple sites of MDA-induced modifications in human hemoglobin from peripheral blood. Our results suggest that the MDA-derived modifications on hemoglobin might represent valuable biomarkers for MDA-induced protein damage.

Identification of Immunoglobulin G Autoantibody Against Malondialdehyde-Acetaldehyde Adducts as a Novel Serological Biomarker for Ulcerative Colitis

INTRODUCTION

Inflammatory bowel disease (IBD) is associated with immune responses with oxidative stress wherein high levels of malondialdehyde result in the formation of a highly stable and immunogenic malondialdehyde-acetaldehyde adduct (MAA). Thus, this study evaluated the status of MAA and anti-MAA antibody isotypes in IBD and their potential as novel serological biomarkers for differentiating ulcerative colitis (UC) from Crohn's disease (CD).

METHODS

Levels of MAA and anti-MAA antibodies were examined in patients with IBD (171), non-IBD gastrointestinal diseases (77), and controls (83) from 2 independent cohorts using immunohistochemistry and enzyme-linked immunosorbent assay. Receiver operating characteristic curves and Youden cutoff index from logistic regression were used to determine the sensitivity and specificity.

RESULTS

The MAA and blood immunoglobulin G (IgG) anti-MAA antibody levels were significantly elevated in IBD compared with non-IBD patients (P = 0.0008) or controls (P = 0.02). Interestingly, patients with UC showed higher levels of IgG anti-MAA (P < 0.0001) than patients with CD including those with colonic CD (P = 0.0067). The odds ratio by logistic regression analysis predicted stronger association of IgG anti-MAA antibody with UC than CD. Subsequent analysis showed that IgG anti-MAA antibody levels could accurately identify (P = 0.0004) UC in the adult cohort with a sensitivity of 75.3% and a specificity of 71.4% and an area under the curve of 0.8072 (0.7121-0.9024). The pediatric cohort also showed an area under the curve of 0.8801 (0.7988-0.9614) and precisely distinguished (P < 0.0001) UC with sensitivity (95.8%) and specificity (72.3%).

DISCUSSION

Circulating IgG anti-MAA antibody levels can serve as a novel, noninvasive, and highly sensitive test to identify patients with UC and possibly differentiate them from patients with CD.

Association Between Serum Aldehydes and Hypertension in Adults: A Cross-Sectional Analysis of the National Health and Nutrition Examination Survey

Background

Exposure to ambient pollutants and chemicals were found to be associated with increased risk of hypertension. However, the relationship between the increased aldehyde exposure and hypertension are still unclear. This study aimed to investigate the potential associations of serum aldehydes levels with prevalent hypertension.

Methods

A total of 1,733 U.S. adults with data on hypertension outcome and serum aldehydes measurement from the National Health and Nutrition Examination Survey 2013–2014 were included. The serum levels of aldehydes were measured via an automated analytical method using solid phase microextraction gas chromatography and high-resolution mass spectrometry. Multivariate logistic regression models were adopted to assess the associations between six selected aldehydes exposure (benzaldehyde, butyraldehyde, heptanaldehyde, hexanaldehyde, isopentanaldehyde, and propanaldehyde) and prevalence of hypertension.

Results

The mean age was 48.0 ± 16.7 years and an approximately equivalent of sex distribution was observed (female 49.9%). There seems to be a numerically higher level of hexanaldehyde in participants with hypertension when compared to participants without hypertension (2.6 ± 3.9 ng/mL vs. 2.3 ± 1.1 ng/mL). After adjusting for potential confounders, the odds ratio (OR) for hypertension was 2.15 [95% confidence interval (CI): 1.33–3.51] in participants from the highest quartile of serum hexanaldehyde concentration in comparison to those from the lowest quartile. Subgroup analyses and sensitivity analyses showed generally similar results.

Conclusion

In summary, current evidence suggested that increased serum hexanaldehyde level was positively associated with prevalent hypertension in U.S. adults.

Biochemical Mechanisms Associating Alcohol Use Disorders with Cancers

Simple Summary

Of all yearly deaths attributable to alcohol consumption globally, approximately 12% are due to cancers, representing approximately 0.4 million deceased individuals. Ethanol metabolism disturbs cell biochemistry by targeting the structure and function of essential biomolecules (proteins, nucleic acids, and lipids) and by provoking alterations in cell programming that lead to cancer development and cancer malignancy. A better understanding of the metabolic and cell signaling realm affected by ethanol is paramount to designing effective treatments and preventive actions tailored to specific neoplasias.

Abstract

The World Health Organization identifies alcohol as a cause of several neoplasias of the oropharynx cavity, esophagus, gastrointestinal tract, larynx, liver, or female breast. We review ethanol’s nonoxidative and oxidative metabolism and one-carbon metabolism that encompasses both redox and transfer reactions that influence crucial cell proliferation machinery. Ethanol favors the uncontrolled production and action of free radicals, which interfere with the maintenance of essential cellular functions. We focus on the generation of protein, DNA, and lipid adducts that interfere with the cellular processes related to growth and differentiation. Ethanol’s effects on stem cells, which are responsible for building and repairing tissues, are reviewed. Cancer stem cells (CSCs) of different origins suffer disturbances related to the expression of cell surface markers, enzymes, and transcription factors after ethanol exposure with the consequent dysregulation of mechanisms related to cancer metastasis or resistance to treatments. Our analysis aims to underline and discuss potential targets that show more sensitivity to ethanol’s action and identify specific metabolic routes and metabolic realms that may be corrected to recover metabolic homeostasis after pharmacological intervention. Specifically, research should pay attention to re-establishing metabolic fluxes by fine-tuning the functioning of specific pathways related to one-carbon metabolism and antioxidant processes.

Existence of natural mouse IgG mAbs recognising epitopes shared by malondialdehyde acetaldehyde adducts and Porphyromonas gingivalis

Natural Abs are produced by B lymphocytes in the absence of external Ag stimulation. They recognise self, altered self and foreign Ags, comprising an important first-line defence against invading pathogens and serving as innate recognition receptors for tissue homeostasis. Natural IgG Abs have been found in newborns and uninfected individuals. Yet, their physiological role remains unclear. Previously, no natural IgG Abs to oxidation-specific epitopes have been reported. Here, we show the cloning and characterisation of mouse IgG mAbs against malondialdehyde acetaldehyde (MAA)-modified low-density lipoprotein. Sequence analysis reveals high homology with germline genes, suggesting that they are natural. Further investigation shows that the MAA-specific natural IgG Abs cross-react with the major periodontal pathogen Porphyromonas gingivalis and recognise its principle virulence factors gingipain Kgp and long fimbriae. The study provides evidence that natural IgGs may play an important role in innate immune defence and in regulation of tissue homeostasis by recognising and removing invading pathogens and/or modified self-Ags, thus being involved in the development of periodontitis and atherosclerosis.

Increased serum levels of aldehydes are associated with cardiovascular disease and cardiovascular risk factors in adults

Previous studies have identified several genetic and environmental risk factors for cardiovascular disease (CVD), but little is known about the associations between serum aldehydes and CVD risk. Herein, we examined associations between serum levels of aldehydes and the risk of CVD and CVD subtypes among 1947 U.S. adults participating in the National Health and Nutrition Examination Survey (NHANES) 2013-2014. Bayesian kernel machine regression (BKMR) was used to analyze the combined effect of serum aldehydes on the overall risk of CVD. We found that isopentanaldehyde concentrations were positively associated with the odds of CVD (adjusted odds ratio (aOR): 2.17; 95 % confidence interval (95 % CI): 1.36, 3.46). The result of BKMR also indicated a positive association of mixed aldehydes with CVD risk. Isopentanaldehyde had the highest posterior inclusion probabilities (PIP = 0.90). Each one-unit (ng/mL) increase in the isopentanaldehyde concentration was associated with a 25.0 mg/dL increase in triglycerides and a 0.9 × 10⁹/L increase in white blood cell (WBC) count in the fully adjusted model. Current evidence suggests that isopentanaldehyde may increase the risk of CVD by elevating triglycerides and WBC count.

Modified hyaluronic acid hydrogels with chemical groups that facilitate adhesion to host tissues enhance cartilage regeneration

Stable integration of hydrogel implants with host tissues is of critical importance to cartilage tissue engineering. Designing and fabricating hydrogels with high adhesive strength, stability and regeneration potential are major challenges to be overcome. This study fabricated injectable adhesive hyaluronic acid (HA) hydrogel modified by aldehyde groups and methacrylate (AHAMA) on the polysaccharide backbone with multiple anchoring mechanisms (amide bond through the dynamic Schiff base reaction, hydrogen bond and physical interpenetration). AHAMA hydrogel exhibited significantly improved durability and stability within a humid environment (at least 7 days), together with higher adhesive strength (43 KPa to skin and 52 KPa to glass), as compared to commercial fibrin glue (nearly 10 KPa) and HAMA hydrogel (nearly 20 KPa). The results showed that AHAMA hydrogel was biocompatible and could be easily and rapidly prepared in situ. In vitro cell culture experiments showed that AHAMA hydrogel could enhance proliferation (1.2-folds after 3 days) and migration (1.5-folds after 12 h) of bone marrow stem cells (BMSCs), as compared to cells cultured in a culture dish. Furthermore, in a rat osteochondral defect model, implanted AHAMA hydrogel significantly promoted integration between neo-cartilage and host tissues, and significantly improved cartilage regeneration (modified O'Driscoll histological scores of 16.0 ± 4.1 and 18.3 ± 4.6 after 4 and 12-weeks of post-implantation in AHAMA groups respectively, 12.0 ± 2.7 and 12.2 ± 2.8 respectively in HAMA groups, 9.8 ± 2.4 and 11.5 ± 2.1 respectively in untreated groups). Hence, AHAMA hydrogel is a promising adhesive biomaterial for clinical cartilage regeneration and other biomedical applications.

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Adhesive hydrogel composed of single natural polymer component.

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The single component enhance stable and easy to use in surgical operation of hydrogel.

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Adhesive hydrogel exhibited strong adhesive strength through multiple anchoring mechanisms.

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Adhesive hydrogel promoted integration between neo-cartilage and host tissues, drastically improved cartilage regeneration.

Retinoic Acid-Loaded Poly(lactic-co-glycolic acid) Nanoparticle Formulation of ApoB-100-Derived Peptide 210 Attenuates Atherosclerosis

We developed a vaccine formulation containing ApoB derived P210 peptides as autoantigens, retinoic acid (RA) as an immune enhancer, both of which were delivered using PLGA nanoparticles. The formula was used to induce an immune response in 12-week-old male Apoe^-/- mice with pre-existing atherosclerotic lesions. The nanotechnology platform PRINT^® was used to fabricate PLGA nanoparticles that encapsulated RA inside and adsorbed the P210 onto the particle surface. In this study, we demonstrated that immunization of Apoe^-/- mice with the formulation was able to considerably attenuate atherosclerotic lesions, accompanied by increased P210 specific IgM and another oxidized lipid derived autoantigen, M2AA, specific IgG autoantibodies, and decreased the inflammatory response, as compared to the P210 group with Freund's adjuvant. Our formulation represents an exciting technology to enhance the efficacy of the P210 vaccine.

Antibodies to malondialdehyde-acetaldehyde modified low-density lipoprotein in patients with newly diagnosed inflammatory joint disease

Objective:To assess antibodies to malondialdehyde-acetaldehyde-modified low-density lipoprotein (MAA-LDL) in patients with newly diagnosed inflammatory joint disease.Method: Patients with rheumatoid arthritis (RA), spondyloarthritis (SpA), and undifferentiated arthritis (UA), participating in the Northern Savo 2010 Study, were evaluated for metabolic syndrome (MetS), metabolic and inflammatory markers, antibodies to MAA-LDL, Aggregatibacter actinomycetemcomitans, and Porphyromonas gingivalis.Results: Among 135 newly diagnosed untreated patients, of whom 53 (39%) were diagnosed to have RA, 44 (33%) SpA, and 38 (28%) UA, 49%, 30%, and 47%, respectively, had MetS. After adjusting for age and gender, anti-MAA-LDL immunoglobulin (Ig)A (p = 0.009), IgG (p = 0.031), and IgM (p = 0.001) levels differed between the diagnostic categories, but not in patients with MetS present or absent. All antibody classes to MAA-LDL correlated with erythrocyte sedimentation rate (ESR), and IgA and IgG antibodies with high-sensitivity C-reactive protein (hs-CRP). IgA antibodies to MAA-LDL correlated with rheumatoid factor (RF), anti-citrullinated protein antibodies (ACPAs), fasting plasma glucose, IgA antibodies to A. actinomycetemcomitans, and in IgA and IgG antibodies to P. gingivalis.Conclusion: Among various arthritis groups, antibodies to MAA-LDL were most common in RA. Antibodies to modified lipoproteins were associated with inflammation measured by ESR and hs-CRP. IgA antibodies to MAA-LDL correlated with age, antibodies to periodontal bacteria, RF, ACPA, and fasting glucose. Associations between antibodies to MAA-LDL and antibodies to periodontal bacteria, RA-associated antibodies, inflammatory parameters, and plasma glucose already reflect cardiovascular burden in inflammatory joint diseases at diagnosis.

Humoral immune response to heat shock protein 60 of Aggregatibacter actinomycetemcomitans and cross-reactivity with malondialdehyde acetaldehyde-modified LDL

Atherosclerosis is a chronic inflammatory disease and major cause of mortality worldwide. One of the crucial steps for atherosclerotic plaque development is oxidation of low-density lipoprotein (LDL). Through the oxidation, highly immunogenic epitopes are created and the immune system is activated. Association between atherosclerosis and periodontal diseases is well documented, and one of the main oral pathogens common in periodontitis is Aggregatibacter actinomycetemcomitans (Aa). Heat shock protein 60 (HSP60) is an important virulence factor for Aa bacteria and a strong activator of the immune system. Cross-reactivity of HSP60 and oxidized LDL (OxLDL) antibodies could be a potential mechanism in the progression of atherosclerosis and one possible link between atherosclerosis and periodontitis. Human plasma samples from neonates and mothers were analyzed to determine if antibody titer to Aa-HSP60 protein is already present in newborns. Further objectives were to characterize antibody response in Aa-HSP60 immunized mice and to determine possible antibody cross-reaction with oxidized LDL. We demonstrated that newborns already have IgM antibody levels to Aa-HSP60. We also showed that in mice, Aa-HSP60 immunization provoked IgG and IgM antibody response not only to Aa-HSP60 but also to malondialdehyde acetaldehyde-modified LDL (MAA-LDL). Competition assay revealed that the antibodies were specific to Aa-HSP60 and cross-reacted with MAA-LDL. Our results suggest a possibility of molecular mimicry between Aa-HSP60 and MAA-LDL, making it intriguing to speculate on the role of HSP60 protein in atherosclerosis that manifests at young age.

Expression of Salivary and Serum Malondialdehyde and Lipid Profile of Patients with Periodontitis and Coronary Heart Disease

Malondialdehyde (MAA) within a lipid pathway has been demonstrated to possess an important role in endothelial function that undergoes periodontitis and coronary heart disease (CHD) development. This study evaluated the impact of periodontitis, CHD, or a combination of both diseases (periodontitis + CHD) on salivary and serum MAA levels. The periodontal and clinical characteristics, serum, and saliva samples were collected from 32 healthy subjects, 34 patients with periodontitis, 33 patients with CHD, and 34 patients with periodontitis and CHD. Lipid profile and levels of MDA and C-reactive protein (CRP) were assessed. Patients in the periodontitis group (serum: 3.92 (3.7-4.4) µmol/L; salivary 1.81 (1-2.1) µmol/g protein, p < 0.01) and in the periodontitis + CHD (serum: 4.34 (3.7-4.8) µmol/L; salivary 1.96 (1.7-2.3) µmol/g protein, p < 0.001) group presented higher median concentrations of salivary and serum MAA compared to patients in the CHD (serum: 3.72 (3.5-4.1) µmol/L; salivary 1.59 (0.9-1.8) µmol/g protein, p < 0.01) and control group (serum: 3.14 (2.8-3.7) µmol/L; salivary 1.41 (0.8-1.6) µmol/g protein, p < 0.01). In univariate models, periodontitis (p = 0.034), CHD (p < 0.001), and CRP (p < 0.001) were significantly associated with MAA. In the multivariate model, only CRP remained a significant predictor of serum and salivary MAA (p < 0.001) MAA levels. Patients with periodontitis and with periodontitis + CHD presented higher levels of salivary and serum MAA compared to healthy subjects and CHD patients. CRP has been found to be a significant predictor of increased salivary and serum MAA levels.

Relevance of the antioxidant properties of methotrexate and doxycycline to their treatment of cardiovascular disease

Many medications exhibit clinical benefits that are unrelated to their primary therapeutic uses. In many cases, the mechanisms underpinning these pleotropic effects are unknown. Two commonly prescribed medications that exhibit pleotropic benefits in cardiovascular disease and other diseases associated with chronic inflammation are methotrexate (MTX) and doxycycline (DOX). The vast majority of cardiovascular disease is associated with atherosclerosis. Because atherosclerosis is a chronic inflammatory disease, possible mechanisms by which MTX and DOX reduce inflammation have been investigated. Interestingly, the primary structure of both of these medications contain aromatic phenolic rings, which resemble polyphenols that are known to possess antioxidant activity. Inflammation and oxidative stress are intimately related. Inflammation promotes oxidative stress, which in turn leads to further inflammation; in this way, oxidative stress and inflammation can establish a self-perpetuating cycle. It has been shown that MTX and DOX act as antioxidants and are capable of scavenging free radicals and the reactive oxygen species (ROS) superoxide (O₂^-). Furthermore, both MTX and DOX inhibit the formation of malondialdehyde acetaldehyde (MAA) adducts, products of oxidative stress and lipid peroxidation. Importantly, MAA-adducts are highly immunogenic and initiate inflammatory responses; thereby, fueling the cycle of inflammation and oxidative stress that results in chronic inflammation. Thus, reducing the formation of MAA-adducts may ameliorate inflammation that leads to ROS production and in this way, break the self-sustaining cycle of oxidative stress and inflammation. It is possible that the under-recognized antioxidant properties of these medications may be a mechanism by which they and other medications provide pleotropic benefit in the treatment of chronic inflammatory disease.

The Role of ALDH2 in Sepsis and the To-Be-Discovered Mechanisms

Sepsis, defined as life-threatening tissue damage and organ dysfunction caused by a dysregulated host response to infection, is a critical disease which imposes global health burden. Sepsis-induced organ dysfunction, including circulatory and cardiac dysfunction, hepatic dysfunction, renal dysfunction, etc., contributes to high mortality and long-term disability of sepsis patients. Altered inflammatory response, ROS and reactive aldehyde stress, mitochondrial dysfunction, and programmed cell death pathways (necrosis, apoptosis, and autophagy) have been demonstrated to play crucial roles in septic organ dysfunction. Unfortunately, except for infection control and supportive therapies, no specific therapy exists for sepsis. New specific therapeutic targets are highly warranted. Emerging studies suggested a role of potential therapeutic target of ALDH2, a tetrameric enzyme located in mitochondria to detoxify aldehydes, in septic organ dysfunction. In this article, we will review the presentations and pathophysiology of septic organ dysfunction, as well as summarize and discuss the recent insights regarding ALDH2 in sepsis.

Mass Spectrometry-Based Methodologies for Targeted and Untargeted Identification of Protein Covalent Adducts (Adductomics): Current Status and Challenges

Protein covalent adducts formed upon exposure to reactive (mainly electrophilic) chemicals may lead to the development of a wide range of deleterious health outcomes. Therefore, the identification of protein covalent adducts constitutes a huge opportunity for a better understanding of events underlying diseases and for the development of biomarkers which may constitute effective tools for disease diagnosis/prognosis, for the application of personalized medicine approaches and for accurately assessing human exposure to chemical toxicants. The currently available mass spectrometry (MS)-based methodologies, are clearly the most suitable for the analysis of protein covalent modifications, providing accuracy, sensitivity, unbiased identification of the modified residue and conjugates along with quantitative information. However, despite the huge technological advances in MS instrumentation and bioinformatics tools, the identification of low abundant protein covalent adducts is still challenging. This review is aimed at summarizing the MS-based methodologies currently used for the identification of protein covalent adducts and the strategies developed to overcome the analytical challenges, involving not only sample pre-treatment procedures but also distinct MS and data analysis approaches.

Mapping aldehydic load in vivo by positron emission tomography with [18F]NA3BF3

A new radiotracer, [¹⁸F]NA₃BF₃, capable of rapid, stable, and catalyst-free complexation of aldehydes in vivo is reported. [¹⁸F]NA₃BF₃ was shown to bind aldehydes in live subjects using locally administered aldehyde-presenting microparticles, and was then applied to mapping aldehydic load in a mouse model of sepsis. [¹⁸F]NA₃BF₃ may enable the direct investigation of the chemical biology of aldehydes in living subjects, and may open avenues for the adoption of endogenous aldehydic load as an imaging biomarker of inflammatory pathology.

Salivary IgA to MAA-LDL and Oral Pathogens Are Linked to Coronary Disease

A large body of literature has established the link between periodontal disease and cardiovascular disease. Oxidized low-density lipoproteins (OxLDLs) have a crucial role in atherosclerosis progression through initiation of immunological response. Monoclonal IgM antibodies to malondialdehyde-modified low-density lipoprotein (MDA-LDL) and to malondialdehyde acetaldehyde-modified low-density lipoprotein (MAA-LDL) have been shown to cross-react with the key virulence factors of periodontal pathogens Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans. We have previously shown that salivary IgA antibodies to MAA-LDL cross-react with P. gingivalis in healthy humans. In this study, we aim to assess whether oral mucosal immune response represented by salivary IgA to MAA-LDL and oral pathogens is associated with coronary artery disease (CAD). Also, the molecular mimicry through antibody cross-reaction between salivary IgA to MAA-LDL and oral pathogens was evaluated. The study subjects consisted of 451 patients who underwent a coronary angiography with no CAD ( n = 133), stable CAD ( n = 169), and acute coronary syndrome (ACS, n = 149). Elevated salivary IgA antibody levels to MAA-LDL, Rgp44 (gingipain A hemagglutinin domain of P. gingivalis), and Aa-HSP60 (heat shock protein 60 of A. actinomycetemcomitans) were discovered in stable-CAD and ACS patients when compared to no-CAD patients. In a multinomial regression model adjusted for known cardiovascular risk factors, stable CAD and ACS were associated with IgA to MAA-LDL ( P = 0.016, P = 0.043), Rgp44 ( P = 0.012, P = 0.004), Aa-HSP60 ( P = 0.032, P = 0.030), Tannerella forsythia ( P = 0.002, P = 0.004), Porphyromonas endodontalis ( P = 0.016, P = 0.020), Prevotella intermedia ( P = 0.038, P = 0.005), and with total IgA antibody concentration ( P = 0.002, P = 0.016). Salivary IgA to MAA-LDL showed cross-reactivity with the oral pathogens tested in the study patients. The study highlights an association between salivary IgA to MAA-LDL and atherosclerosis. However, whether salivary IgA to MAA-LDL and the related oral humoral responses play a causal role in the development in the CAD should be elucidated in the future.

Methyl 5-MeO-N-aminoanthranilate, a minimalist fluorogenic probe for sensing cellular aldehydic load

A minimalist fluorogenic probe is presented capable of the mapping of aldehydic load through live cell microscopy.

The Interplay of Inflammatory Processes and Cognition in Alcohol Use Disorders-A Systematic Review

Rationale: Of late, evidence emerges that the pathophysiology of psychiatric diseases and their affiliated symptomatologies are at least partly contributable to inflammatory processes. Also in alcohol use disorders (AUD), this interaction is strongly apparent, with severely immunogenic liver cirrhosis being one of the most critical sequelae of chronic abusive drinking. This somatic immune system activation negatively impacts brain functioning, and additionally, alcohol abuse appears to have a direct detrimental effect on the brain by actively stimulating its immune cells and responses. As cognitive decline majorly contributes to AUD's debility, it is important to know to what extent impairment of cognitive functioning is due to these (neuro-)inflammatory aberrations. Method: We hereby summarize the current existing literature on the interplay between AUD, inflammation, and cognition in a systematic review according to the PRISMA-P guidelines for the systematic review. Main findings: Although literature on the role of inflammation in alcohol use-related cognitive deficiency remains scarce, current findings indicate that pro-inflammatory processes indeed result in exacerbation of several domains of cognitive deterioration. Interestingly, microglia, the immune cells of the brain, appear to exert initial compensatory neuroprotective functionalities upon acute ethanol exposure while chronic alcohol intake seems to attenuate these responses and overall microglial activity. Conclusion: As these results indicate inflammation to be of importance in cognitive impairment following alcohol consumption and might as such provide alternate therapeutic avenues, a considerable increase in research efforts in this domain is urgently required.

Novel Antioxidant Properties of Doxycycline

Doxycycline (DOX), a derivative of tetracycline, is a broad-spectrum antibiotic that exhibits a number of therapeutic activities in addition to its antibacterial properties. For example, DOX has been used in the management of a number of diseases characterized by chronic inflammation. One potential mechanism by which DOX inhibits the progression of these diseases is by reducing oxidative stress, thereby inhibiting subsequent lipid peroxidation and inflammatory responses. Herein, we tested the hypothesis that DOX directly scavenges reactive oxygen species (ROS) and inhibits the formation of redox-mediated malondialdehyde-acetaldehyde (MAA) protein adducts. Using a cell-free system, we demonstrated that DOX scavenged reactive oxygen species (ROS) produced during the formation of MAA-adducts and inhibits the formation of MAA-protein adducts. To determine whether DOX scavenges specific ROS, we examined the ability of DOX to directly scavenge superoxide and hydrogen peroxide. Using electron paramagnetic resonance (EPR) spectroscopy, we found that DOX directly scavenged superoxide, but not hydrogen peroxide. Additionally, we found that DOX inhibits MAA-induced activation of Nrf2, a redox-sensitive transcription factor. Together, these findings demonstrate the under-recognized direct antioxidant property of DOX that may help to explain its therapeutic potential in the treatment of conditions characterized by chronic inflammation and increased oxidative stress.

Fingerprinting Biogenic Aldehydes through Pattern Recognition Analyses of Excitation-Emission Matrices

Biogenic carbonyls, especially aldehydes, have previously demonstrated their potential to serve as early diagnostic biomarkers for disease and injury that have not been fully realized owing, in part, to the lack of a rapid and simple point-of-care method for aldehyde identification. The ability to determine which carbonyl compound is elevated and not just the total aldehydic load may provide more disease- or injury-specific diagnostic information. Toward this end, a novel fluorophore is presented that is able to form a complex with biogenic carbonyls under catalyst-free conditions so as to give a fluorescent fingerprint of the resulting hydrazone. The successful identification of bound carbonyls was accomplished with a newly described algorithm that applied principal curvature analysis of excitation-emission matrices to reduce surface features to ellipse representations, followed by a pattern-matching routine. With this algorithm, carbonyls were identified over a range of concentrations, and mixture components were successfully parsed. Overall, the results presented lay the groundwork for novel implementations of chemometrics to low-cost, rapid, and simple-to-implement point-of-care diagnostics.

Recent advances in understanding hematopoiesis in Fanconi Anemia

Fanconi anemia is an inherited disease characterized by genomic instability, hypersensitivity to DNA cross-linking agents, bone marrow failure, short stature, skeletal abnormalities, and a high relative risk of myeloid leukemia and epithelial malignancies. The 21 Fanconi anemia genes encode proteins involved in multiple nuclear biochemical pathways that effect DNA interstrand crosslink repair. In the past, bone marrow failure was attributed solely to the failure of stem cells to repair DNA. Recently, non-canonical functions of many of the Fanconi anemia proteins have been described, including modulating responses to oxidative stress, viral infection, and inflammation as well as facilitating mitophagic responses and enhancing signals that promote stem cell function and survival. Some of these functions take place in non-nuclear sites and do not depend on the DNA damage response functions of the proteins. Dysfunctions of the canonical and non-canonical pathways that drive stem cell exhaustion and neoplastic clonal selection are reviewed, and the potential therapeutic importance of fully investigating the scope and interdependences of the canonical and non-canonical pathways is emphasized.

Immunization with gingipain A hemagglutinin domain of Porphyromonas gingivalis induces IgM antibodies binding to malondialdehyde-acetaldehyde modified low-density lipoprotein

Treatment of periodontitis has beneficial effects on systemic inflammation markers that relate to progression of atherosclerosis. We aimed to investigate whether immunization with A hemagglutinin domain (Rgp44) of Porphyromonas gingivalis (Pg), a major etiologic agent of periodontitis, would lead to an antibody response cross-reacting with oxidized low-density lipoprotein (OxLDL) and how it would affect the progression of atherosclerosis in low-density lipoprotein receptor-deficient (LDLR^-/-) mice. The data revealed a prominent IgM but not IgG response to malondialdehyde-acetaldehyde modified LDL (MAA-LDL) after Rgp44 and Pg immunizations, implying that Rgp44/Pg and MAA adducts may share cross-reactive epitopes that prompt IgM antibody production and consequently confer atheroprotection. A significant negative association was observed between atherosclerotic lesion and plasma IgA to Rgp44 in Rgp44 immunized mice, supporting further the anti-atherogenic effect of Rgp44 immunization. Plasma IgA levels to Rgp44 and to Pg in both Rgp44- and Pg-immunized mice were significantly higher than those in saline control, suggesting that IgA to Rgp44 could be a surrogate marker of immunization in Pg-immunized mice. Distinct antibody responses in plasma IgA levels to MAA-LDL, to Pg lipopolysaccharides (Pg-LPS), and to phosphocholine (PCho) were observed after Rgp44 and Pg immunizations, indicating that different immunogenic components between Rpg44 and Pg may behave differently in regard of their roles in the development of atherosclerosis. Immunization with Rgp44 also displayed atheroprotective features in modulation of plaque size through association with plasma levels of IL-1α whereas whole Pg bacteria achieved through regulation of anti-inflammatory cytokine levels of IL-5 and IL-10. The present study may contribute to refining therapeutic approaches aiming to modulate immune responses and inflammatory/anti-inflammatory processes in atherosclerosis.

Malondialdehyde-Acetaldehyde (MAA) Protein Adducts Are Found Exclusively in the Lungs of Smokers with Alcohol Use Disorders and Are Associated with Systemic Anti-MAA Antibodies

BACKGROUND

Malondialdehyde (MDA) and acetaldehyde (AA) exist following ethanol metabolism and tobacco pyrolysis. As such, lungs of individuals with alcohol use disorders (AUDs) are a target for the effects of combined alcohol and cigarette smoke metabolites. MDA and AA form a stable protein adduct, malondialdehyde-acetaldehyde (MAA) adduct, known to be immunogenic, profibrotic, and proinflammatory. MAA adduct is the dominant epitope in anti-MAA antibody formation. We hypothesized that MAA-adducted protein forms in lungs of those who both abuse alcohol and smoke cigarettes, and that this would be associated with systemically elevated anti-MAA antibodies.

METHODS

Four groups were established: AUD subjects who smoked cigarettes (+AUD/+smoke), smokers without AUD (-AUD/+smoke), AUD without smoke (+AUD/-smoke), and non-AUD/nonsmokers (-AUD/-smoke).

RESULTS

We observed a significant increase in MAA adducts in lung cells of +AUD/+smoke versus -AUD/-smoke. No significant increase in MAA adducts was observed in -AUD/+smoke or in +AUD/-smoke compared to -AUD/-smoke. Serum from +AUD/+smoke had significantly increased levels of circulating anti-MAA IgA antibodies. After 1 week of alcohol that MAA-adducted protein is formed in the lungs of those who smoke cigarettes and abuse alcohol, leading to a subsequent increase in serum IgA antibodies.

CONCLUSIONS

MAA-adducted proteins could play a role in pneumonia and other diseases of the lung in the setting of AUD and smoking.

Evidence that endogenous formaldehyde produces immunogenic and atherogenic adduct epitopes

Endogenous formaldehyde is abundantly present in our bodies, at around 100 µM under normal conditions. While such high steady state levels of formaldehyde may be derived by enzymatic reactions including oxidative demethylation/deamination and myeloperoxidation, it is unclear whether endogenous formaldehyde can initiate and/or promote diseases in humans. Here, we show that fluorescent malondialdehyde-formaldehyde (M2FA)-lysine adducts are immunogenic without adjuvants in mice. Natural antibody titers against M2FA are elevated in atherosclerosis-prone mice. Staining with an antibody against M2FA demonstrated that M2FA is present in plaque found on the aortic valve of ApoE^−/− mice. To mimic inflammation during atherogenesis, human myeloperoxidase was incubated with glycine, H₂O₂, malondialdehyde, and a lysine analog in PBS at a physiological temperature, which resulted in M2FA generation. These results strongly suggest that the 1,4-dihydropyridine-type of lysine adducts observed in atherosclerosis lesions are likely produced by endogenous formaldehyde and malondialdehyde with lysine. These highly fluorescent M2FA adducts may play important roles in human inflammatory and degenerative diseases.

Scavenger Receptor A Mediates the Clearance and Immunological Screening of MDA-Modified Antigen by M2-Type Macrophages

In this study, we investigated the uptake of malondialdehyde (MDA)-modified myelin oligodendrocyte glycoprotein (MOG) in the context of lipid peroxidation and its implications in CNS autoimmunity. The use of custom-produced fluorescently labeled versions of MOG or MDA-modified MOG enabled us to study and quantify the uptake by different macrophage populations and to identify the responsible receptor, namely SRA. The SRA-mediated uptake of MDA-modified MOG is roughly tenfold more efficient compared to that of the native form. Notably, this uptake is most strongly associated with anti-inflammatory M2-type macrophages. MDA-modified MOG was demonstrated to be resistant to degradation by lysine-dependent proteases in vitro, but the overall digestion fragments appeared to be similar in cell lysates, although their relative abundance appeared to be altered as a result of faster uptake. Accordingly, MDA-modified MOG is processed for presentation by APCs, allowing maximized recall proliferation of MOG_35-55-specific 2D2 T cells in vitro due to higher uptake. However, MDA modification of MOG did not enhance immune priming or disease course in the in vivo MOG-EAE model, but did induce antibody responses to both MOG and MDA adducts. Taken together our results indicate that MDA adducts primarily constitute clearance signals for phagocytes and promote rapid removal of antigen, which is subjected to immunological screening by previously licensed T cells.

Direct antioxidant properties of methotrexate: Inhibition of malondialdehyde-acetaldehyde-protein adduct formation and superoxide scavenging

Methotrexate (MTX) is an immunosuppressant commonly used for the treatment of autoimmune diseases. Recent observations have shown that patients treated with MTX also exhibit a reduced risk for the development of cardiovascular disease (CVD). Although MTX reduces systemic inflammation and tissue damage, the mechanisms by which MTX exerts these beneficial effects are not entirely known. We have previously demonstrated that protein adducts formed by the interaction of malondialdehyde (MDA) and acetaldehyde (AA), known as MAA-protein adducts, are present in diseased tissues of individuals with rheumatoid arthritis (RA) or CVD. In previously reported studies, MAA-adducts were shown to be highly immunogenic, supporting the concept that MAA-adducts not only serve as markers of oxidative stress but may have a direct role in the pathogenesis of inflammatory diseases. Because MAA-adducts are commonly detected in diseased tissues and are proposed to mitigate disease progression in both RA and CVD, we tested the hypothesis that MTX inhibits the generation of MAA-protein adducts by scavenging reactive oxygen species. Using a cell free system, we found that MTX reduces MAA-adduct formation by approximately 6-fold, and scavenges free radicals produced during MAA-adduct formation. Further investigation revealed that MTX directly scavenges superoxide, but not hydrogen peroxide. Additionally, using the Nrf2/ARE luciferase reporter cell line, which responds to intracellular redox changes, we observed that MTX inhibits the activation of Nrf2 in cells treated with MDA and AA. These studies define previously unrecognized mechanisms by which MTX can reduce inflammation and subsequent tissue damage, namely, scavenging free radicals, reducing oxidative stress, and inhibiting MAA-adduct formation.

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MTX is commonly used to treat RA and is being tested in CVD patients.

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MDA and AA are produced during lipidperoxidation and can interact to form MAA-adducts.

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MAA-adducts are found in atheromas and in diseased synovial tissue of RA patients.

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MTX scavenges the free radical O_2⁻ and prevents the formation of MAA-adducts.

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Scavenging O_2⁻ may be a mechanism by which MTX reduces inflammation and disease.

Autoreactivity to malondialdehyde-modifications in rheumatoid arthritis is linked to disease activity and synovial pathogenesis

Oxidation-associated malondialdehyde (MDA) modification of proteins can generate immunogenic neo-epitopes that are recognized by autoantibodies. In health, IgM antibodies to MDA-adducts are part of the natural antibody pool, while elevated levels of IgG anti-MDA antibodies are associated with inflammatory and autoimmune conditions. Yet, in human autoimmune disease IgG anti-MDA responses have not been well characterized and their potential contribution to disease pathogenesis is not known. Here, we investigate MDA-modifications and anti-MDA-modified protein autoreactivity in rheumatoid arthritis (RA). While RA is primarily associated with autoreactivity to citrullinated antigens, we also observed increases in serum IgG anti-MDA in RA patients compared to controls. IgG anti-MDA levels significantly correlated with disease activity by DAS28-ESR and serum TNF-alpha, IL-6, and CRP. Mass spectrometry analysis of RA synovial tissue identified MDA-modified proteins and revealed shared peptides between MDA-modified and citrullinated actin and vimentin. Furthermore, anti-MDA autoreactivity among synovial B cells was discovered when investigating recombinant monoclonal antibodies (mAbs) cloned from single B cells, and 3.5% of memory B cells and 2.3% of plasma cells were found to be anti-MDA positive. Several clones were highly specific for MDA-modification with no cross-reactivity to other antigen modifications such as citrullination, carbamylation or 4-HNE-carbonylation. The mAbs recognized MDA-adducts in a variety of proteins including albumin, histone 2B, fibrinogen and vimentin. Interestingly, the most reactive clone, originated from an IgG1-bearing memory B cell, was encoded by near germline variable genes, and showed similarity to previously reported natural IgM. Other anti-MDA clones display somatic hypermutations and lower reactivity. Importantly, these anti-MDA antibodies had significant in vitro functional properties and induced enhanced osteoclastogenesis, while the natural antibody related high-reactivity clone did not. We postulate that these may represent distinctly different facets of anti-MDA autoreactive responses.

Beyond citrullination: other post-translational protein modifications in rheumatoid arthritis

The presence of autoantibodies is one of the hallmarks of rheumatoid arthritis (RA). In the past few decades, rheumatoid factors (autoantibodies that recognize the Fc-tail of immunoglobulins) as well as anti-citrullinated protein antibodies (ACPAs) have been studied intensively. ACPAs recognize post-translationally modified proteins in which the amino acid arginine has been converted into a citrulline. More recently, other autoantibody systems recognizing post-translationally modified proteins have also gained attention, including autoantibodies recognizing fragmented immunoglobulin (anti-hinge antibodies), autoantibodies recognizing acetylated proteins and autoantibodies recognizing proteins that are modified by adducts formed under oxidative stress. In particular, detailed insights have been obtained on the presence and properties of autoantibodies recognizing carbamylated proteins, commonly called anti-carbamylated protein (anti-CarP) antibodies. In this Review, we summarize the current knowledge relating to these emerging autoantibodies that recognize post-translationally modified proteins identified in RA, with an emphasis on anti-CarP antibodies.

A purified MAA-based ELISA is a useful tool for determining anti-MAA antibody titer with high sensitivity

Atherosclerosis is widely accepted to be a chronic inflammatory disease, and the immunological response to the accumulation of LDL is believed to play a critical role in the development of this disease. 1,4-Dihydropyridine-type MAA-adducted LDL has been implicated in atherosclerosis. Here, we have demonstrated that pure MAA-modified residues can be chemically conjugated to large proteins without by-product contamination. Using this pure antigen, we established a purified MAA-ELISA, with which a marked increase in anti-MAA antibody titer was determined at a very early stage of atherosclerosis in 3-month ApoE-/- mice fed with a normal diet. Our methods of Nε-MAA-L-lysine purification and purified antigen-based ELISA will be easily applicable for biomarker-based detection of early stage atherosclerosis in patients, as well as for the development of an adduct-specific Liquid Chromatography/Mass Spectrometry-based quantification of physiological and pathological levels of MAA.

Aldehyde dehydrogenase 2 in aplastic anemia, Fanconi anemia and hematopoietic stem cells

Maintenance of the hematopoietic stem cell (HSC) compartment depends on the ability to metabolize exogenously and endogenously generated toxins, and to repair cellular damage caused by such toxins. Reactive aldehydes have been demonstrated to cause specific genotoxic injury, namely DNA interstrand cross-links. Aldehyde dehydrogenase 2 (ALDH2) is a member of a 19 isoenzyme ALDH family with different substrate specificities, subcellular localization, and patterns of expression. ALDH2 is localized in mitochondria and is essential for the metabolism of acetaldehyde, thereby placing it directly downstream of ethanol metabolism. Deficiency in ALDH2 expression and function are caused by a single nucleotide substitution and resulting amino acid change, called ALDH2*2. This genetic polymorphism affects 35-45% of East Asians (about ~560 million people), and causes the well-known Asian flushing syndrome, which results in disulfiram-like reactions after ethanol consumption. Recently, the ALDH2*2 genotype has been found to be associated with marrow failure, with both an increased risk of sporadic aplastic anemia and more rapid progression of Fanconi anemia. This review discusses the unexpected interrelationship between aldehydes, ALDH2 and hematopoietic stem cell biology, and in particular its relationship to Fanconi anemia.