Recent Advances in Histone Glycation: Emerging role in Diabetes and Cancer

Glycoxidation of mammalian whole histone generates highly immunogenic aggregates: Sera of SLE patients contain autoantibodies against aggregates

Non-enzymatic glycation and oxidation of self-proteins, causing formation and accumulation of advanced glycation end products (AGEs), have been reported in an array of pathologies, including systemic lupus erythematosus (SLE). Such modifications may generate neo-epitopes, break immunological tolerance, and induce antibody response. In this study, we have first analysed the structural modifications of whole histone in the presence of deoxyribose followed by oxidation with hydroxyl radicals. Changes in the secondary and tertiary structure of the whole histone were determined by spectroscopic techniques and biochemical assays. Fluorescence spectroscopy and UPLC-MS showed the generation of AGEs such as carboxymethyl lysine and pentosidine, while DLS and TEM indicated the presence of amorphous AGE-aggregates. Moreover, rabbits immunized with these histone-AGEs exhibited enhanced immunogenicity and ELISA and western immunoblot of IgG antibodies from SLE patients' sera showed a significantly higher specificity towards modified histone-AGEs than the native histone.

Macrophage plasticity: signaling pathways, tissue repair, and regeneration

Macrophages are versatile immune cells with remarkable plasticity, enabling them to adapt to diverse tissue microenvironments and perform various functions. Traditionally categorized into classically activated (M1) and alternatively activated (M2) phenotypes, recent advances have revealed a spectrum of macrophage activation states that extend beyond this dichotomy. The complex interplay of signaling pathways, transcriptional regulators, and epigenetic modifications orchestrates macrophage polarization, allowing them to respond to various stimuli dynamically. Here, we provide a comprehensive overview of the signaling cascades governing macrophage plasticity, focusing on the roles of Toll-like receptors, signal transducer and activator of transcription proteins, nuclear receptors, and microRNAs. We also discuss the emerging concepts of macrophage metabolic reprogramming and trained immunity, contributing to their functional adaptability. Macrophage plasticity plays a pivotal role in tissue repair and regeneration, with macrophages coordinating inflammation, angiogenesis, and matrix remodeling to restore tissue homeostasis. By harnessing the potential of macrophage plasticity, novel therapeutic strategies targeting macrophage polarization could be developed for various diseases, including chronic wounds, fibrotic disorders, and inflammatory conditions. Ultimately, a deeper understanding of the molecular mechanisms underpinning macrophage plasticity will pave the way for innovative regenerative medicine and tissue engineering approaches.

Epigenetic contributions to cancer: Exploring the role of glycation reactions

Advanced Glycation End-products (AGEs), with their prolonged half-life in the human body, are emerging as potent diagnostic indicators. Early intervention studies, focusing on AGE cross-link breakers, have shown encouraging results in heart failure patients, paving the way for disease progression monitoring and therapy effectiveness evaluation. AGEs are the byproducts of a non-enzymatic reaction where sugars interact with proteins, lipids, and nucleic acids. These compounds possess the power to alter numerous biological processes, ranging from disrupting molecular conformation and promoting cross-linking to modifying enzyme activity, reducing clearance, and impairing receptor recognition. The damage inflicted by AGEs through the stimulation of intracellular signaling pathways is associated with the onset of chronic diseases across various organ systems. This review consolidates the characteristics of AGEs and the challenges posed by their expression in diverse physiological and pathological states. Furthermore, it highlights the clinical relevance of AGEs and the latest research breakthroughs aimed at reducing AGE accumulation.

Crotonaldehyde induced structural alterations in Low-Density Lipoprotein: Immunogenicity of the modified protein in experimental animals and auto-antibodies generation in various cancers

Crotonaldehyde (CA), a prominent component of cigarette smoke (CS) is a pervasive environmental pollutant that is a highly toxic, unsaturated aldehyde. Exposure to CA-rich pollutants has been linked to the emergence of many malignancies in humans. To better understand the role of CA in biomolecule modification, this study investigated the detailed structural alterations in low-density lipoprotein (LDL) modified by CA, as well as the immunogenicity of the modified protein in experimental animals and the search for autoantibodies in various cancers patients.In vitro, results indicated alterations in secondary and tertiary structures; examined using UV-visible, fluorescence, far-UV circular dichroism, and Fourier transform infrared spectroscopy techniques. Changes in the oxidation status of LDL were studied by carbonyl content assay and NBT assay. ThT binding assay, scanning, and transmission electron microscopy were used to study aggregate formation. The findings revealed significant structural damage in LDL modified by CA. The modification resulted in the unmasking of hydrophobic clusters, the loss of the protein α-helix, and the formation of β-pleated sheet structure. The amyloid aggregate formation was confirmed through ThT microscopy and electron spectroscopy. Rabbits immunized with crotonaldehyde; lead to structural changes in the LDL; that acted as extra antigenic determinants, eliciting strong antibody response. Immunoglobulin response is highly specific for modified LDL as demonstrated by the ELISA. The presence of antibodies against CA-modified LDL was confirmed by the immunoglobulin content of blood sera from human subjects with lung cancer, and competitive ELISA demonstrated the specificity of these antibodies. This study offers insights into the CA-mediated LDL modification and immunogenicity in lung cancer that will have diagnostic importance.

Protein Advanced Glycation End Products and Their Implications in Pancreatic Cancer

Protein advanced glycation end products (AGE) formed by nonenzymatic glycation can disrupt the normal structure and function of proteins, and stimulate the receptor for AGEs (RAGE), triggering intricate mechanisms that are etiologically related to various chronic diseases, including pancreatic cancer. Many common risk factors of pancreatic cancer are the major sources for the formation of protein AGEs and glycative stress in the human body. Abnormal accumulation of protein AGEs can impair the cellular proteome and promote AGE-RAGE driven pro-inflammatory signaling cascades, leading to increased oxidative stress, protease resistance, protein dysregulation, transcription activity of STAT, NF-κB, and AP-1, aberrant status in ubiquitin-proteasome system and autophagy, as well as other molecular events that are susceptible for the carcinogenic transformation towards the development of neoplasms. Here, we review studies to highlight our understanding in the orchestrated molecular events in bridging the impaired proteome, dysregulated functional networks, and cancer hallmarks initiated upon protein AGE formation and accumulation in pancreatic cancer.

Post-translational modifications of histone and non-histone proteins in epigenetic regulation and translational applications in alcohol-associated liver disease: Challenges and research opportunities

Epigenetic regulation is a process that takes place through adaptive cellular pathways influenced by environmental factors and metabolic changes to modulate gene activity with heritable phenotypic variations without altering the DNA sequences of many target genes. Epigenetic regulation can be facilitated by diverse mechanisms: many different types of post-translational modifications (PTMs) of histone and non-histone nuclear proteins, DNA methylation, altered levels of noncoding RNAs, incorporation of histone variants, nucleosomal positioning, chromatin remodeling, etc. These factors modulate chromatin structure and stability with or without the involvement of metabolic products, depending on the cellular context of target cells or environmental stimuli, such as intake of alcohol (ethanol) or Western-style high-fat diets. Alterations of epigenetics have been actively studied, since they are frequently associated with multiple disease states. Consequently, explorations of epigenetic regulation have recently shed light on the pathogenesis and progression of alcohol-associated disorders. In this review, we highlight the roles of various types of PTMs, including less-characterized modifications of nuclear histone and non-histone proteins, in the epigenetic regulation of alcohol-associated liver disease (ALD) and other disorders. We also describe challenges in characterizing specific PTMs and suggest future opportunities for basic and translational research to prevent or treat ALD and many other disease states.

AGEs and RAGE: metabolic and molecular signatures of the glycation-inflammation axis in malignant or metastatic cancers

From attributing mutations to cancers with the advent of cutting-edge genetic technology in recent decades, to re-searching the age-old theory of intrinsic metabolic shift of cancers (Warburg's glycolysis), the quest for a precise panacea for mainly the metastatic cancers, remains incessant. This review delineates the advanced glycation end product (AGE)-receptor for AGE (RAGE) pathway driven intricate oncogenic cues, budding from the metabolic (glycolytic) reliance of tumour cells, branching into metastatic emergence of malignancies. Strong AGE-RAGE concomitance in metastasis, chemo-resistance and cancer resurgence adversely incite disease progression and patient mortality. At the conjunction of metabolic and metastatic shift of cancers, are the "glycolytically" generated AGEs and AGE-activated RAGE, instigating aberrant molecular pathways, culminating in aggressive malignancies. AGEs as by-products of metabolic insurgence, modify the metabolome, epigenome and microbiome, besides coercing the inter-, intra- and extra-cellular micro-milieu conducive for oncogenic events like epithelial-mesenchymal transition (EMT). AGE-RAGE synergistically elicit ATP surge for surplus energy, autophagy for apoptotic evasion and chemo-resistance, insulin-like growth factor 1 (IGF-1) for meta-inflammation and angiogenesis, high mobility group box-1 (HMGB1) for immune tolerance, S100 proteins for metastasis, and p53 protein attenuation for tumour suppression. AGEs are pronouncedly reported in invasive forms of breast, prostate, colon and pancreatic cancers, higher in patients with cancer than healthy counterparts, and higher in advanced stage than localized phase. Hence, the investigation of person-specific presence of AGEs, soluble RAGE and AGE-activated RAGE can be advocated as impending bio-markers for diagnostic, prognostic and therapeutic purposes, to predict cancer risk in patients with diabetes, obesity, metabolic syndrome as well as general population, to monitor prognosis and metastasis in patients with cancer, and to reckon complications in cancer survivors. Furthermore, clinical reports of exogenous (dietary) and endogenous (internally formed) AGEs in cancer patients, and contemporary clinical trials involving AGE-RAGE axis in cancer are underlined with theranostic implications.

Flaxseed Reduces Cancer Risk by Altering Bioenergetic Pathways in Liver: Connecting SAM Biosynthesis to Cellular Energy

This article illustrates how dietary flaxseed can be used to reduce cancer risk, specifically by attenuating obesity, type 2 diabetes, and non-alcoholic fatty liver disease (NAFLD). We utilize a targeted metabolomics dataset in combination with a reanalysis of past work to investigate the "metabo-bioenergetic" adaptations that occur in White Leghorn laying hens while consuming dietary flaxseed. Recently, we revealed how the anti-vitamin B6 effects of flaxseed augment one-carbon metabolism in a manner that accelerates S-adenosylmethionine (SAM) biosynthesis. Researchers recently showed that accelerated SAM biosynthesis activates the cell's master energy sensor, AMP-activated protein kinase (AMPK). Our paper provides evidence that flaxseed upregulates mitochondrial fatty acid oxidation and glycolysis in liver, concomitant with the attenuation of lipogenesis and polyamine biosynthesis. Defatted flaxseed likely functions as a metformin homologue by upregulating hepatic glucose uptake and pyruvate flux through the pyruvate dehydrogenase complex (PDC) in laying hens. In contrast, whole flaxseed appears to attenuate liver steatosis and body mass by modifying mitochondrial fatty acid oxidation and lipogenesis. Several acylcarnitine moieties indicate Randle cycle adaptations that protect mitochondria from metabolic overload when hens consume flaxseed. We also discuss a paradoxical finding whereby flaxseed induces the highest glycated hemoglobin percentage (HbA1c%) ever recorded in birds, and we suspect that hyperglycemia is not the cause. In conclusion, flaxseed modifies bioenergetic pathways to attenuate the risk of obesity, type 2 diabetes, and NAFLD, possibly downstream of SAM biosynthesis. These findings, if reproducible in humans, can be used to lower cancer risk within the general population.

Endogenous Biological Drivers in Diabetic Lower Limb Wounds Recurrence: Hypothetical Reflections

An impaired healing response underlies diabetic foot wound chronicity, frequently translating to amputation, disability, and mortality. Diabetics suffer from underappreciated episodes of post-epithelization ulcer recurrence. Recurrence epidemiological data are alarmingly high, so the ulcer is considered in "remission" and not healed from the time it remains epithelialized. Recurrence may result from the combined effects of behavioral and endogenous biological factors. Although the damaging role of behavioral, clinical predisposing factors is undebatable, it still remains elusive in the identification of endogenous biological culprits that may prime the residual scar tissue for recurrence. Furthermore, the event of ulcer recurrence still waits for the identification of a molecular predictor. We propose that ulcer recurrence is deeply impinged by chronic hyperglycemia and its downstream biological effectors, which originate epigenetic drivers that enforce abnormal pathologic phenotypes to dermal fibroblasts and keratinocytes as memory cells. Hyperglycemia-derived cytotoxic reactants accumulate and modify dermal proteins, reduce scar tissue mechanical tolerance, and disrupt fibroblast-secretory activity. Accordingly, the combination of epigenetic and local and systemic cytotoxic signalers induce the onset of "at-risk phenotypes" such as premature skin cell aging, dysmetabolism, inflammatory, pro-degradative, and oxidative programs that may ultimately converge to scar cell demise. Post-epithelialization recurrence rate data are missing in clinical studies of reputed ulcer healing therapies during follow-up periods. Intra-ulcer infiltration of epidermal growth factor exhibits the most consistent remission data with the lowest recurrences during 12-month follow-up. Recurrence data should be regarded as a valuable clinical endpoint during the investigational period for each emergent healing candidate.

Leveraging histone glycation for cancer diagnostics and therapeutics

Cancer cells undergo metabolic reprogramming to rely mostly on aerobic glycolysis (the Warburg effect). The increased glycolytic intake enhances the intracellular levels of reactive sugars and sugar metabolites. These reactive species can covalently modify macromolecules in a process termed glycation. Histones are particularly susceptible to glycation, resulting in substantial alterations to chromatin structure, function, and transcriptional output. Growing evidence suggests a link between dysregulated metabolism of tumors and cancer proliferation through epigenetic changes. This review discusses recent advances in the understanding of histone glycation, its impact on the epigenetic landscape and cellular fate, and its role in cancer. In addition, we investigate the possibility of using histone glycation as biomarkers and targets for anticancer therapeutics.

Protein glycation in diabetes mellitus

Diabetes mellitus is the ninth leading cause of mortality worldwide. It is a complex disease that manifests as chronic hyperglycemia. Glucose exposure causes biochemical changes at the proteome level as reflected in accumulation of glycated proteins. A prominent example is hemoglobin A1c (HbA1c), a glycated protein widely accepted as a diabetic indicator. Another emerging biomarker is glycated albumin which has demonstrated utility in situations where HbA1c cannot be used. Other proteins undergo glycation as well thus impacting cellular function, transport and immune response. Accordingly, these glycated counterparts may serve as predictors for diabetic complications and thus warrant further inquiry. Fortunately, modern proteomics has provided unique analytic capability to enable improved and more comprehensive exploration of glycating agents and glycated proteins. This review broadly covers topics from epidemiology of diabetes to modern analytical tools such as mass spectrometry to facilitate a better understanding of diabetes pathophysiology. This serves as an attempt to connect clinically relevant questions with findings of recent proteomic studies to suggest future avenues of diabetes research.

Metabolic substrates, histone modifications, and heart failure

Histone epigenetic modifications are chemical modification changes to histone amino acid residues that modulate gene expression without altering the DNA sequence. As both the phenotypic and causal factors, cardiac metabolism disorder exacerbates mitochondrial ATP generation deficiency, thus promoting pathological cardiac hypertrophy. Moreover, several concomitant metabolic substrates also promote the expression of hypertrophy-responsive genes via regulating histone modifications as substrates or enzyme-modifiers, indicating their dual roles as metabolic and epigenetic regulators. This review focuses on the cardiac acetyl-CoA-dependent histone acetylation, NAD⁺-dependent SIRT-mediated deacetylation, FAD⁺-dependent LSD-mediated, and α-KG-dependent JMJD-mediated demethylation after briefly addressing the pathological and physiological cardiac energy metabolism. Besides using an "iceberg model" to explain the dual role of metabolic substrates as both metabolic and epigenetic regulators, we also put forward that the therapeutic supplementation of metabolic substrates is promising to blunt HF via re-establishing histone modifications.

Association between diabetes and cancer. Current mechanistic insights into the association and future challenges

Compelling pieces of epidemiological, clinical, and experimental research have demonstrated that Diabetes mellitus (DM) is a major risk factor associated with increased cancer incidence and mortality in many human neoplasms. In the pathophysiology context of DM, many of the main classical actors are relevant elements that can fuel the different steps of the carcinogenesis process. Hyperglycemia, hyperinsulinemia, metabolic inflammation, and dyslipidemia are among the classic contributors to this association. Furthermore, new emerging actors have received particular attention in the last few years, and compelling data support that the microbiome, the epigenetic changes, the reticulum endoplasmic stress, and the increased glycolytic influx also play important roles in promoting the development of many cancer types. The arsenal of glucose-lowering therapeutic agents used for treating diabetes is wide and diverse, and a growing body of data raised during the last two decades has tried to clarify the contribution of therapeutic agents to this association. However, this research area remains controversial, because some anti-diabetic drugs are now considered as either promotors or protecting elements. In the present review, we intend to highlight the compelling epidemiological shreds of evidence that support this association, as well as the mechanistic contributions of many of these potential pathological mechanisms, some controversial points as well as future challenges.

Investigating pathological epigenetic aberrations by epi-proteomics

Epigenetics includes a complex set of processes that alter gene activity without modifying the DNA sequence, which ultimately determines how the genetic information common to all the cells of an organism is used to generate different cell types. Dysregulation in the deposition and maintenance of epigenetic features, which include histone posttranslational modifications (PTMs) and histone variants, can result in the inappropriate expression or silencing of genes, often leading to diseased states, including cancer. The investigation of histone PTMs and variants in the context of clinical samples has highlighted their importance as biomarkers for patient stratification and as key players in aberrant epigenetic mechanisms potentially targetable for therapy. Mass spectrometry (MS) has emerged as the most powerful and versatile tool for the comprehensive, unbiased and quantitative analysis of histone proteoforms. In recent years, these approaches-which we refer to as "epi-proteomics"-have demonstrated their usefulness for the investigation of epigenetic mechanisms in pathological conditions, offering a number of advantages compared with the antibody-based methods traditionally used to profile clinical samples. In this review article, we will provide a critical overview of the MS-based approaches that can be employed to study histone PTMs and variants in clinical samples, with a strong focus on the latest advances in this area, such as the analysis of uncommon modifications and the integration of epi-proteomics data into multi-OMICs approaches, as well as the challenges to be addressed to fully exploit the potential of this novel field of research.

Role of Diet in Stem and Cancer Stem Cells

Diet and lifestyle factors greatly affect health and susceptibility to diseases, including cancer. Stem cells’ functions, including their ability to divide asymmetrically, set the rules for tissue homeostasis, contribute to health maintenance, and represent the entry point of cancer occurrence. Stem cell properties result from the complex integration of intrinsic, extrinsic, and systemic factors. In this context, diet-induced metabolic changes can have a profound impact on stem cell fate determination, lineage specification and differentiation. The purpose of this review is to provide a comprehensive description of the multiple “non-metabolic” effects of diet on stem cell functions, including little-known effects such as those on liquid-liquid phase separation and on non-random chromosome segregation (asymmetric division). A deep understanding of the specific dietetic requirements of normal and cancer stem cells may pave the way for the development of nutrition-based targeted therapeutic approaches to improve regenerative and anticancer therapies.

Biophysical characterization of structural and conformational changes in methylmethane sulfonate modified DNA leading to the frizzled backbone structure and strand breaks in DNA

Methyl methanesulfonate (MMS) is a highly toxic DNA-alkylating agent that has a potential to damage the structural integrity of DNA. This work employed multiple biophysical and computational methods to report the MMS mediated structural alterations in the DNA (MMS-DNA). Spectroscopic techniques and gel electrophoresis studies revealed MMS induced exposure of chromophoric groups of DNA; methylation mediated anti→syn conformational change, DNA fragmentation and reduced nucleic acid stability. MMS induced single-stranded regions in the DNA were observed in nuclease S1 assay. FT-IR results indicated MMS mediated loss of the assigned peaks for DNA, partial loss of C-O ribose, loss of deoxyribose region, C-O stretching and bending of the C-OH groups of hexose sugar, a progressive shift in the assigned guanine and adenine peaks, loss of thymine peak, base stacking and presence of C-O-H vibrations of glucose and fructose, indicating direct strand breaks in DNA due to backbone loss. Isothermal titration calorimetry showed MMS-DNA interaction as exothermic with moderate affinity. Dynamic light scattering studies pointed towards methylation followed by the generation of single-stranded regions. Electron microscopy pictured the loss of alignment in parallel base pairs and showed the formation of fibrous aggregates in MMS-DNA. Molecular docking found MMS in close contact with the ribose sugar of DNA backbone having non-bonded interactions. Molecular dynamic simulations confirmed that MMS is capable of interacting with DNA at two levels, one at the level of nitrogenous bases and another at the DNA backbone. The study offers insights into the molecular interaction of MMS and DNA.Communicated by Ramaswamy H. Sarma.