Histone Carbonylation Is a Redox-Regulated Epigenomic Mark That Accumulates with Obesity and Aging

Covalent adduct formation of histone with organophosphorus pesticides in vitro

It is established that organophosphorus pesticide (OPP) toxicity results from modification of amino acids in active sites of target proteins. OPPs can also modify unrelated target proteins such as histones and such covalent histone modifications can alter DNA-binding properties and lead to aberrant gene expression. In the present study, we report on non-enzymatic covalent modifications of calf thymus histones adducted to selected OPPs and organophosphate flame retardants (OPFRs) in vitro using a bottom-up proteomics method approach. Histones were not found to form detectable adducts with the two tested OPFRs but were avidly modified by a few of the seven OPPs that were tested in vitro. Dimethyl phosphate (or diethyl phosphate) adducts were identified on Tyr, Lys and Ser residues. Most of the dialkyl phosphate adducts were identified on Tyr residues. Methyl and ethyl modified histones were also detected. Eleven amino residues in histones showed non-enzymatic covalent methylation by exposure of dichlorvos and malathion. Our bottom-up proteomics approach showing histone-OPP adduct formation warrants future studies on the underlying mechanism of chronic illness from exposure to OPPs.

Oxidative stress and metabolism meet epigenetic modulation in physical exercise

Physical exercise is established as an important factor of health and generally is recommended for its positive effects on several tissues, organs, and systems. These positive effects come from metabolic adaptations that also include oxidative eustress, in which physical activity increases ROS production and antioxidant mechanisms, although this depends on the intensity of the exercise. Muscle metabolism through mechanisms such as aerobic and anaerobic glycolysis, tricarboxylic acid cycle, and oxidative lipid metabolism can produce metabolites and co-factors which directly impact the epigenetic machinery. In this review, we clearly reinforce the evidence that exercise regulates several epigenetic mechanisms and explain how these mechanisms can be regulated by metabolic products and co-factors produced during exercise. In fact, recent evidence has demonstrated the importance of epigenetics in the gene expression changes implicated in metabolic adaptation after exercise. Importantly, intermediates of the metabolism generated by continuous, acute, moderate, or strenuous exercise control the activity of epigenetic enzymes, therefore turning on or turning off the gene expression of specific programs which can lead to physiological adaptations after exercise.

The 4-Hydroxynonenal–Protein Adducts and Their Biological Relevance: Are Some Proteins Preferred Targets?

It is well known that oxidative stress and lipid peroxidation (LPO) play a role in physiology and pathology. The most studied LPO product with pleiotropic capabilities is 4-hydroxynonenal (4-HNE). It is considered as an important mediator of cellular signaling processes and a second messenger of reactive oxygen species. The effects of 4-HNE are mainly attributed to its adduction with proteins. Whereas the Michael adducts thus formed are preferred in an order of potency of cysteine > histidine > lysine over Schiff base formation, it is not known which proteins are the preferred targets for 4-HNE under what physiological or pathological conditions. In this review, we briefly discuss the methods used to identify 4-HNE–protein adducts, the progress of mass spectrometry in deciphering the specific protein targets, and their biological relevance, focusing on the role of 4-HNE protein adducts in the adaptive response through modulation of the NRF2/KEAP1 pathway and ferroptosis.

Bottom-up proteomics analysis for adduction of the broad-spectrum herbicide atrazine to histone

Histones are the major proteinaceous components of chromatin in eukaryotic cells and an important part of the epigenome. The broad-spectrum herbicide atrazine (2-chloro-4-[ethylamino]-6-[isopropylamino]-1, 3, 5-triazine) and its metabolites are known to form protein adducts, but the formation of atrazine-histone adducts has not been studied. In this study, a bottom-up proteomics analysis method was optimized and applied to identify histone adduction by atrazine in vitro. Whole histones of calf thymus or human histone H3.3 were incubated with atrazine. After solvent-based protein precipitation, the protein was digested by trypsin/Glu-C and the resulting peptides were analyzed by high-resolution mass spectrometry using an ultra-high-performance liquid chromatograph interfaced with a quadrupole Exactive-Orbitrap mass spectrometer. The resulting tryptic/Glu-C peptide of DTNLCAIHAK from calf thymus histone H3.1 or human histone H3.3 was identified with an accurate mass shift of  +179.117 Da in atrazine incubated samples. It is deduced that a chemical group with an elemental composition of C8H13N5 (179.1171 Da) from atrazine adducted with calf thymus histone H3.1 or human histone H3.3. It was confirmed by MS/MS analysis that the adduction position was at its cysteine 110 residue. Time- and concentration-dependent assays also confirmed the non-enzymatic covalent modification of histone H3.3 by atrazine in vitro. Thus, the potential exists that atrazine adduction may lead to the alteration of histones that subsequently disturbs their normal function.

Relationship between 4-Hydroxynonenal (4-HNE) as Systemic Biomarker of Lipid Peroxidation and Metabolomic Profiling of Patients with Prostate Cancer

An oxidative degradation product of the polyunsaturated fatty acids, 4-hydroxynonenal (4-HNE), is of particular interest in cancer research due to its concentration-dependent pleiotropic activities affecting cellular antioxidants, metabolism, and growth control. Although an increase in oxidative stress and lipid peroxidation was already associated with prostate cancer progression a few decades ago, the knowledge of the involvement of 4-HNE in prostate cancer tumorigenesis is limited. This study investigated the appearance of 4-HNE-protein adducts in prostate cancer tissue by immunohistochemistry using a genuine 4-HNE monoclonal antibody. Plasma samples of the same patients and samples of the healthy controls were also analyzed for the presence of 4-HNE-protein adducts, followed by metabolic profiling using LC-ESI-QTOF-MS and GC-EI-Q-MS. Finally, the analysis of the metabolic pathways affected by 4-HNE was performed. The obtained results revealed the absence of 4-HNE-protein adducts in prostate carcinoma tissue but increased 4-HNE-protein levels in the plasma of these patients. Metabolomics revealed a positive association of different long-chain and medium-chain fatty acids with the presence of prostate cancer. Furthermore, while linoleic acid positively correlated with the levels of 4-HNE-protein adducts in the blood of healthy men, no correlation was obtained for cancer patients indicating altered lipid metabolism in this case. The metabolic pathway of unsaturated fatty acids biosynthesis emerged as significantly affected by 4-HNE. Overall, this is the first study linking 4-HNE adduction to plasma proteins with specific alterations in the plasma metabolome of prostate cancer patients. This study revealed that increased 4-HNE plasma protein adducts could modulate the unsaturated fatty acids biosynthesis pathway. It is yet to be determined if this is a direct result of 4-HNE or whether they are produced by the same underlying mechanisms. Further mechanistic studies are needed to grasp the biological significance of the observed changes in prostate cancer tumorigenesis.

CBR1 decreases protein carbonyl levels via the ROS/Akt/CREB pathway to extend lifespan in the cotton bollworm, Helicoverpa armigera

Reactive oxygen species (ROS) are considered a major cause of ageing and ageing-related diseases through protein carbonylation. Little is known about the molecular mechanisms that confer protection against ROS. Here, we observed that, compared with nondiapause-destined pupae, high protein carbonyl levels are present in the brains of diapause-destined pupae, which is a 'non-ageing' phase in the moth Helicoverpa armigera. Protein carbonyl levels respond to ROS and decrease metabolic activity to induce diapause in order to extend lifespan. However, protein carbonylation in the brains of diapause-destined pupae still occurs at a physiological level compared to young adult brains. We find that ROS activate Akt, and Akt then phosphorylates the transcription factor CREB to facilitate its nuclear import. CREB binds to the promoter of carbonyl reductase 1 (CBR1) and regulates its expression. High CBR1 levels reduce protein carbonyl levels to maintain physiological levels. This is the first report showing that the moth brain can naturally control protein carbonyl levels through a distinct ROS-Akt-CREB-CBR1 pathway to extend lifespan.

Recent progress in epigenetics of obesity

Nowadays, obesity is one of the largest public health problems worldwide. In the last few decades, there has been a marked increase in the obesity epidemic and its related comorbidities. Worldwide, more than 2.2 billion people (33%) are affected by overweight or obesity (712 million, 10%) and its associated metabolic complications. Although a high heritability of obesity has been estimated, the genetic variants conducted from genetic association studies only partially explain the variation of body mass index. This has led to a growing interest in understanding the potential role of epigenetics as a key regulator of gene-environment interactions on the development of obesity and its associated complications. Rapid advances in epigenetic research methods and reduced costs of epigenome-wide association studies have led to a great expansion of population-based studies. The field of epigenetics and metabolic diseases such as obesity has advanced rapidly in a short period of time. The main epigenetic mechanisms include DNA methylation, histone modifications, microRNA (miRNA)-mediated regulation and so on. DNA methylation is the most investigated epigenetic mechanism. Preliminary evidence from animal and human studies supports the effect of epigenetics on obesity. Studies of epigenome-wide association studies and genome-wide histone modifications from different biological specimens such as blood samples (newborn, children, adolescent, youth, woman, man, twin, race, and meta-analysis), adipose tissues, skeletal muscle cells, placenta, and saliva have reported the differential expression status of multiple genes before and after obesity interventions and have identified multiple candidate genes and biological markers. These findings may improve the understanding of the complex etiology of obesity and its related comorbidities, and help to predict an individual's risk of obesity at a young age and open possibilities for introducing targeted prevention and treatment strategies.

Lipid Peroxidation in Obesity: Can Bariatric Surgery Help?

Obesity and chronic oxidative stress, often being associated with each other in a vicious circle, are important factors of chronic diseases. Although it was usually considered to accompany aging and wealth, global trends show the increase in obesity among children even in Third World countries. Being manifested by an imbalance between energy consumption and food intake, obesity is characterized by an excessive or abnormal fat accumulation, impaired redox homeostasis and metabolic changes often associated with the self-catalyzed lipid peroxidation generating 4-hydroxynonenal, pluripotent bioactive peroxidation product of polyunsaturated fatty acids. Conservative methods targeting obesity produced only modest and transient results in the treatment of morbid obesity. Therefore, in recent years, surgery, primarily bariatric, became an attractive treatment for morbid obesity. Since adipose tissue is well known as a stress organ with pronounced endocrine functions, surgery results in redox balance and metabolic improvement of the entire organism. The source of bioactive lipids and lipid-soluble antioxidants, and the complex pathophysiology of lipid peroxidation should thus be considered from the aspects of personalized and integrative biomedicine to treat obesity in an appropriate way.

Oxidative Stress and 4-hydroxy-2-nonenal (4-HNE): Implications in the Pathogenesis and Treatment of Aging-related Diseases

Oxidative stress plays an important role in the development of aging-related diseases by accelerating the lipid peroxidation of polyunsaturated fatty acids in the cell membrane, resulting in the production of aldehydes, such as malondialdehyde and 4-hydroxy-2-nonenal (4-HNE) and other toxic substances. The compound 4-HNE forms adducts with DNA or proteins, disrupting many cell signaling pathways including the regulation of apoptosis signal transduction pathways. The binding of proteins to 4-HNE (4-HNE-protein) acts as an important marker of lipid peroxidation, and its increasing concentration in brain tissues and fluids because of aging, ultimately gives rise to some hallmark disorders, such as neurodegenerative diseases (Alzheimer's and Parkinson's diseases), ophthalmic diseases (dry eye, macular degeneration), hearing loss, and cancer. This review aims to describe the physiological origin of 4-HNE, elucidate its toxicity in aging-related diseases, and discuss the detoxifying effect of aldehyde dehydrogenase and glutathione in 4-HNE-driven aging-related diseases.

A Comprehensive Proteome and Acetyl-Proteome Atlas Reveals Molecular Mechanisms Adapting to the Physiological Changes From Pre-laying to Peak-Laying Stage in Liver of Hens (Gallus gallus)

Along with sexual maturity, the liver undergoes numerous metabolic processes to adapt the physiological changes associated with egg-laying in hens. However, mechanisms regulating the processes were unclear. In this study, comparative hepatic proteome and acetyl-proteome between pre- and peak-laying hens were performed. The results showed that the upregulated proteins were mainly related to lipid and protein biosynthesis, while the downregulated proteins were mainly involved in pyruvate metabolism and were capable of inhibiting gluconeogenesis and lactate synthesis in peak-laying hens compared with that in pre-laying hens. With unchanged expression level, the significant acetylated proteins were largely functioned on activation of polyunsaturated fatty acid oxidation in peroxisome, while the significant deacetylated proteins were principally used to elevate medium and short fatty acid oxidation in mitochondria and oxidative phosphorylation. Most of the proteins which involved in gluconeogenesis, lipid transport, and detoxification were influenced by both protein expression and acetylation. Taken overall, a novel mechanism wherein an alternate source of acetyl coenzyme A was produced by activation of FA oxidation and pyruvate metabolism to meet the increased energy demand and lipid synthesis in liver of laying hens was uncovered. This study provides new insights into molecular mechanism of adaptation to physiological changes in liver of laying hens.

DNA methylation and histone variants in aging and cancer

Aging-related diseases such as cancer can be traced to the accumulation of molecular disorder including increased DNA mutations and epigenetic drift. We provide a comprehensive review of recent results in mice and humans on modifications of DNA methylation and histone variants during aging and in cancer. Accumulated errors in DNA methylation maintenance lead to global decreases in DNA methylation with relaxed repression of repeated DNA and focal hypermethylation blocking the expression of tumor suppressor genes. Epigenetic clocks based on quantifying levels of DNA methylation at specific genomic sites is proving to be a valuable metric for estimating the biological age of individuals. Histone variants have specialized functions in transcriptional regulation and genome stability. Their concentration tends to increase in aged post-mitotic chromatin, but their effects in cancer are mainly determined by their specialized functions. Our increased understanding of epigenetic regulation and their modifications during aging has motivated interventions to delay or reverse epigenetic modifications using the epigenetic clocks as a rapid readout for efficacity. Similarly, the knowledge of epigenetic modifications in cancer is suggesting new approaches to target these modifications for cancer therapy.

The Interplay Between Adipose Tissue and Vasculature: Role of Oxidative Stress in Obesity

Cardiovascular diseases (CVDs) rank the leading cause of morbidity and mortality globally. Obesity and its related metabolic syndrome are well-established risk factors for CVDs. Therefore, understanding the pathophysiological role of adipose tissues is of great importance in maintaining cardiovascular health. Oxidative stress, characterized by excessive formation of reactive oxygen species, is a common cellular stress shared by obesity and CVDs. While plenty of literatures have illustrated the vascular oxidative stress, very few have discussed the impact of oxidative stress in adipose tissues. Adipose tissues can communicate with vascular systems, in an endocrine and paracrine manner, through secreting several adipocytokines, which is largely dysregulated in obesity. The aim of this review is to summarize current understanding of the relationship between oxidative stress in obesity and vascular endothelial dysfunction. In this review, we briefly describe the possible causes of oxidative stress in obesity, and the impact of obesity-induced oxidative stress on adipose tissue function. We also summarize the crosstalk between adipose tissue and vasculature mediated by adipocytokines in vascular oxidative stress. In addition, we highlight the potential target mediating adipose tissue oxidative stress.