Advanced glycation end products impair NLRP3 inflammasome-mediated innate immune responses in macrophages

Molecular Assessment of Methylglyoxal-Induced Toxicity and Therapeutic Approaches in Various Diseases: Exploring the Interplay with the Glyoxalase System

This comprehensive exploration delves into the intricate interplay of methylglyoxal (MG) and glyoxalase 1 (GLO I) in various physiological and pathological contexts. The linchpin of the narrative revolves around the role of these small molecules in age-related issues, diabetes, obesity, cardiovascular diseases, and neurodegenerative disorders. Methylglyoxal, a reactive dicarbonyl metabolite, takes center stage, becoming a principal player in the development of AGEs and contributing to cell and tissue dysfunction. The dual facets of GLO I-activation and inhibition-unfold as potential therapeutic avenues. Activators, spanning synthetic drugs like candesartan to natural compounds like polyphenols and isothiocyanates, aim to restore GLO I function. These molecular enhancers showcase promising outcomes in conditions such as diabetic retinopathy, kidney disease, and beyond. On the contrary, GLO I inhibitors emerge as crucial players in cancer treatment, offering new possibilities in diseases associated with inflammation and multidrug resistance. The symphony of small molecules, from GLO I activators to inhibitors, presents a nuanced understanding of MG regulation. From natural compounds to synthetic drugs, each element contributes to a molecular orchestra, promising novel interventions and personalized approaches in the pursuit of health and wellbeing. The abstract concludes with an emphasis on the necessity of rigorous clinical trials to validate these findings and acknowledges the importance of individual variability in the complex landscape of health.

Advanced glycation end products of dietary origin and their association with inflammation in diabetes - A minireview

Advanced glycation end products (AGEs) are a diverse group of compounds that are formed as a result of the non-enzymatic reaction between a reducing sugar such as glucose and the free NH2 groups of an amino acid in a protein or other biomolecule. The chemical reaction, by which these products are generated, is known as the Maillard reaction and occurs as a part of the body's normal metabolism. Such a reaction is enhanced during diabetes due to hyperglycemia, but it can also occur during the preparation, processing, and preservation of certain foods. Therefore, AGEs can also be obtained from the diet (d-AGE) and contribute to an increase of the total serum pool of these compounds. They have been implicated in a wide variety of pathological processes, mainly because of their ability to induce inflammatory responses and oxidative stress increase. They are extensively accumulated as a part of the normal aging, especially in tissues rich in long half-life proteins, which can compromise the physiology of these tissues. d-AGEs are abundant in diets rich in processed fats and sugars. This review is addressed to the current knowledge on these products and their impact on the immunomodulation of various mechanisms that may contribute to exacerbation of the diabetes pathophysiology.

Ultra-High Temperature Treatment of Liquid Infant Formula, Systemic Immunity, and Kidney Development in Preterm Neonates

SCOPE

Ready-to-feed liquid infant formulas (IFs) are increasingly being used for newborn preterm infants when human milk is unavailable. However, sterilization of liquid IFs by ultra-high temperature (UHT) introduces Maillard reaction products (MRPs) that may negatively affect systemic immune and kidney development.

METHODS AND RESULTS

UHT-treated IF without and with prolonged storage (SUHT) are tested against pasteurized IF (PAST) in newborn preterm pigs as a model for preterm infants. After 5 days, blood leukocytes, markers of systemic immunity and inflammation, kidney structure and function are evaluated. No consistent differences between UHT and PAST pigs are observed. However, SUHT increases plasma TNFα and IL-6 and reduces neutrophils and in vitro response to LPS. In SUHT pigs, the immature kidneys show minor upregulation of gene expressions related to inflammation (RAGE, MPO, MMP9) and oxidative stress (CAT, GLO1), together with glomerular mesangial expansion and cell injury. The increased inflammatory status in SUHT pigs appears unrelated to systemic levels of MRPs.

CONCLUSION

SUHT feeding may impair systemic immunity and affect kidney development in preterm newborns. The systemic effects may be induced by local gut inflammatory effects of MRPs. Optimal processing and length of storage are critical for UHT-treated liquid IFs for preterm infants.

Treatment With Small Molecule Inhibitors of Advanced Glycation End-Products Formation and Advanced Glycation End-Products-Mediated Collagen Cross-Linking Promotes Experimental Aortic Aneurysm Progression in Diabetic Mice

Background Although diabetes attenuates abdominal aortic aneurysms (AAAs), the mechanisms by which diabetes suppresses AAAs remain incompletely understood. Accumulation of advanced glycation end- (AGEs) reduces extracellular matrix (ECM) degradation in diabetes. Because ECM degradation is critical for AAA pathogenesis, we investigated whether AGEs mediate experimental AAA suppression in diabetes by blocking AGE formation or disrupting AGE-ECM cross-linking using small molecule inhibitors. Methods and Results Male C57BL/6J mice were treated with streptozotocin and intra-aortic elastase infusion to induce diabetes and experimental AAAs, respectively. Aminoguanidine (AGE formation inhibitor, 200 mg/kg), alagebrium (AGE-ECM cross-linking disrupter, 20 mg/kg), or vehicle was administered daily to mice from the last day following streptozotocin injection. AAAs were assessed via serial aortic diameter measurements, histopathology, and in vitro medial elastolysis assays. Treatment with aminoguanidine, not alagebrium, diminished AGEs in diabetic AAAs. Treatment with both inhibitors enhanced aortic enlargement in diabetic mice as compared with vehicle treatment. Neither enhanced AAA enlargement in nondiabetic mice. AAA enhancement in diabetic mice by aminoguanidine or alagebrium treatment promoted elastin degradation, smooth muscle cell depletion, mural macrophage accumulation, and neoangiogenesis without affecting matrix metalloproteinases, C-C motif chemokine ligand 2, or serum glucose concentration. Additionally, treatment with both inhibitors reversed suppression of diabetic aortic medial elastolysis by porcine pancreatic elastase in vitro. Conclusions Inhibiting AGE formation or AGE-ECM cross-linking enhances experimental AAAs in diabetes. These findings support the hypothesis that AGEs attenuate experimental AAAs in diabetes. These findings underscore the potential translational value of enhanced ECM cross-linking as an inhibitory strategy for early AAA disease.

Blood and Tissue Advanced Glycation End Products as Determinants of Cardiometabolic Disorders Focusing on Human Studies

Cardiometabolic disorders are characterised by a cluster of interactive risk determinants such as increases in blood glucose, lipids and body weight, as well as elevated inflammation and oxidative stress and gut microbiome changes. These disorders are associated with onset of type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). T2DM is strongly associated with CVD. Dietary advanced glycation end products (dAGEs) attributable from modern diets high in sugar and/or fat, highly processed foods and high heat-treated foods can contribute to metabolic etiologies of cardiometabolic disorders. This mini review aims to determine whether blood dAGEs levels and tissue dAGEs levels are determinants of the prevalence of cardiometabolic disorders through recent human studies. ELISA (enzyme-linked immunosorbent assay), high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) for blood dAGEs measurement and skin auto fluorescence (SAF) for skin AGEs measurement can be used. Recent human studies support that a diet high in AGEs can negatively influence glucose control, body weight, blood lipid levels and vascular health through the elevated oxidative stress, inflammation, blood pressure and endothelial dysfunction compared with a diet low in AGEs. Limited human studies suggested a diet high in AGEs could negatively alter gut microbiota. SAF could be considered as one of the predictors affecting risks for cardiometabolic disorders. More intervention studies are needed to determine how dAGEs are associated with the prevalence of cardiometabolic disorders through gut microbiota changes. Further human studies are conducted to find the association between CVD events, CVD mortality and total mortality through SAF measurement, and a consensus on whether tissue dAGEs act as a predictor of CVD is required.

RIPK3 promoter hypermethylation in hepatocytes protects from bile acid-induced inflammation and necroptosis

Necroptosis facilitates cell death in a controlled manner and is employed by many cell types following injury. It plays a significant role in various liver diseases, albeit the cell-type-specific regulation of necroptosis in the liver and especially hepatocytes, has not yet been conceptualized. We demonstrate that DNA methylation suppresses RIPK3 expression in human hepatocytes and HepG2 cells. In diseases leading to cholestasis, the RIPK3 expression is induced in mice and humans in a cell-type-specific manner. Overexpression of RIPK3 in HepG2 cells leads to RIPK3 activation by phosphorylation and cell death, further modulated by different bile acids. Additionally, bile acids and RIPK3 activation further facilitate JNK phosphorylation, IL-8 expression, and its release. This suggests that hepatocytes suppress RIPK3 expression to protect themselves from necroptosis and cytokine release induced by bile acid and RIPK3. In chronic liver diseases associated with cholestasis, induction of RIPK3 expression may be an early event signaling danger and repair through releasing IL-8.

Methylglyoxal - an advanced glycation end products (AGEs) precursor - Inhibits differentiation of human MSC-derived osteoblasts in vitro independently of receptor for AGEs (RAGE)

A major precursor of advanced glycation end-products (AGEs) - methylglyoxal (MG) - is a reactive carbonyl metabolite that originates from glycolytic pathways. MG formation and accumulation has been implicated in the pathogenesis of diabetes and age-related chronic musculoskeletal disorders. Human bone marrow-derived stromal cells (BMSCs) are multipotent cells that have the potential to differentiate into cells of mesenchymal origin including osteoblasts, but the role of MG on their differentiation is unclear. We therefore evaluated the effect of MG on proliferation and differentiation of BMSC-derived osteoblasts. Cells were treated with different concentrations of MG (600, 800 and 1000 μM). Cell viability was assessed using a Cell Counting Kit-8 assay. Alkaline phosphatase (ALP) activity and calcium deposition assays were performed to evaluate osteoblast differentiation and mineralization. Gene expression was measured using qRT-PCR, whereas AGE specific receptor (RAGE) and collagen 1 were examined by immunocytochemistry and Western blotting. RAGE knockdown was performed by transducing RAGE specific short hairpin RNAs (shRNAs) using lentivirus. During osteogenic differentiation, MG treatment resulted in reduction of cell viability (27.7 %), ALP activity (45.5 %) and mineralization (82.3 %) compared to untreated cells. MG significantly decreased expression of genes involved in osteogenic differentiation - RUNX2 (2.8 fold), ALPL (3.2 fold), MG detoxification through glyoxalase - GLO1 (3 fold) and collagen metabolism - COL1A1 (4.9 fold), COL1A2 (6.8 fold), LOX (5.4 fold) and PLOD1 (1.7 fold). MG significantly reduced expression of collagen 1 (53.3 %) and RAGE (43.1 %) at protein levels. Co-treatment with a MG scavenger - aminoguanidine - prevented all negative effects of MG. RAGE-specific knockdown during MG treatment did not reverse the effects on cell viability, osteogenic differentiation or collagen metabolism. In conclusion, MG treatment can negatively influence the collagen metabolism and differentiation of BMSCs-derived osteoblasts through a RAGE independent mechanism.

Methylglyoxal and Its Adducts: Induction, Repair, and Association with Disease

Metabolism is an essential part of life that provides energy for cell growth. During metabolic flux, reactive electrophiles are produced that covalently modify macromolecules, leading to detrimental cellular effects. Methylglyoxal (MG) is an abundant electrophile formed from lipid, protein, and glucose metabolism at intracellular levels of 1-4 μM. MG covalently modifies DNA, RNA, and protein, forming advanced glycation end products (MG-AGEs). MG and MG-AGEs are associated with the onset and progression of many pathologies including diabetes, cancer, and liver and kidney disease. Regulating MG and MG-AGEs is a potential strategy to prevent disease, and they may also have utility as biomarkers to predict disease risk, onset, and progression. Here, we review recent advances and knowledge surrounding MG, including its production and elimination, mechanisms of MG-AGEs formation, the physiological impact of MG and MG-AGEs in disease onset and progression, and the latter in the context of its receptor RAGE. We also discuss methods for measuring MG and MG-AGEs and their clinical application as prognostic biomarkers to allow for early detection and intervention prior to disease onset. Finally, we consider relevant clinical applications and current therapeutic strategies aimed at targeting MG, MG-AGEs, and RAGE to ultimately improve patient outcomes.

HMGB1 Upregulates RAGE to Trigger the Expression of Inflammatory Factors in the Lung Tissue in a Hypoxic Pulmonary Hypertension Rat Model

Hypoxic pulmonary hypertension (HPH), a form of pulmonary hypertension (PH) caused by hypoxia, could cause serious complications and has a high mortality rate, and no clinically effective treatments are currently available. In this study, we established an HPH preclinical model in rats by simulating clinicopathological indicators of the disease. Our results showed that high mobility group box-1 protein (HMGB1) aggravated the clinical symptoms of HPH. We aimed at establishing protocols and ideas for the clinical treatment of HPH by identifying downstream HMGB1 binding receptors. Our investigation showed that continuous hypoxia could cause significant lung injury in rats. ELISA and western blotting experiments revealed that HPH induces inflammation in the lung tissue and increases the expression of a hypoxia-inducible factor. Testing of lung tissue proteins in vivo and in human pulmonary artery endothelial cells in vitro revealed that the HMGB1-mediated increase in the receptor for advanced glycation end products (RAGE) expression promoted inflammation. In summary, we successfully established an HPH rat model providing a new model for preclinical HPH research and elucidated the role of HMGB1 in HPH. Furthermore, we describe that HMGB1 induced inflammation in the HPH model via RAGE, causing severe lung dysfunction. This study could potentially provide novel ideas and methods for the clinical treatment of HPH.

Inhibition of HDAC6 With CAY10603 Ameliorates Diabetic Kidney Disease by Suppressing NLRP3 Inflammasome

Background: Diabetic nephropathy (DN) is one of the leading causes of chronic kidney disease (CKD) worldwide, tubular injury is the driving force during the pathogenesis and progression of DN. Thus, we aim to utilize the connectivity map (CMap) with renal tubulointerstitial transcriptomic profiles of biopsy-proven DN to identify novel drugs for treating DN.

Methods: We interrogated the CMap profile with tubulointerstitial transcriptomic data from renal biopsy-proven early- and late-stage DN patients to screen potential drugs for DN. Therapeutic effects of candidate drug were assessed in Murine model of diabetic kidney disease (STZ-induced CD-1 mice), and HK-2 cells and immortalized bone marrow-derived macrophages (iBMDMs).

Results: We identified CAY10603, a specific inhibitor of histone deacetylase 6 (HDAC6), as a potential drug that could significantly reverse the altered genes in the tubulointerstitial component. In DN patients and mice, upregulation of HDAC6 was mainly observed in renal tubular cells and infiltrated macrophages surrounding the diluted tubules. In both early- and late-onset diabetic mice, daily CAY10603 administration effectively alleviated renal dysfunction and reduced macrophage infiltration, tubular injury and tubulointerstitial fibrosis. Mechanistically, CAY10603 suppressed NLRP3 activation in both HK-2 cells and iBMDMs.

Conclusion: CAY10603 exhibited therapeutic potential for DN by suppressing NLRP3 inflammasome activation in both tubular cells and macrophages.

Notch/NICD/RBP-J signaling axis regulates M1 polarization of macrophages mediated by advanced glycation end products

Advanced glycation end products (AGEs) aggregation and macrophages polarization are identified as the main factors contributing to bone diseases caused by aging or diabetes, such as senile or diabetic osteoporosis. Here, we aimed to elucidate the involvement and potential mechanism of AGEs in macrophages polarization and osteoclastogenesis. Firstly, AGEs-treated RAW264.7 macrophages were observed to up-regulate the release of nitric oxide (NO), the expression of M1-associated genes and the surface antigen marker CD86. The detection of osteoclast-related markers and TRAP staining revealed that the osteoclastogenic ability of M1 macrophages was markedly enhanced by AGEs. Further, AGEs were found to effectively activate the transduction of Notch signaling pathway and promote the nuclear translocation of NICD1. In addition, with the signals transduction of Notch pathway blocked by γ-secretase inhibitor DAPT and siRNA targeting silencing RBP-J, AGEs-induced M1 polarization was significantly mitigated. Collectively, we defined a critical role for AGEs in inducing M1 polarization and osteoclastogenesis of macrophages, and further identified Notch/NICD/RBP-J signaling axis as an essential mechanism regulating AGEs-mediated M1 polarization.

Advanced Glycation End-Products (AGEs): Formation, Chemistry, Classification, Receptors, and Diseases Related to AGEs

Advanced glycation end-products (AGEs) constitute a non-homogenous, chemically diverse group of compounds formed either exogeneously or endogeneously on the course of various pathways in the human body. In general, they are formed non-enzymatically by condensation between carbonyl groups of reducing sugars and free amine groups of nucleic acids, proteins, or lipids, followed by further rearrangements yielding stable, irreversible end-products. In the last decades, AGEs have aroused the interest of the scientific community due to the increasing evidence of their involvement in many pathophysiological processes and diseases, such as diabetes, cancer, cardiovascular, neurodegenerative diseases, and even infection with the SARS-CoV-2 virus. They are recognized by several cellular receptors and trigger many signaling pathways related to inflammation and oxidative stress. Despite many experimental research outcomes published recently, the complexity of their engagement in human physiology and pathophysiological states requires further elucidation. This review focuses on the receptors of AGEs, especially on the structural aspects of receptor-ligand interaction, and the diseases in which AGEs are involved. It also aims to present AGE classification in subgroups and to describe the basic processes leading to both exogeneous and endogeneous AGE formation.

Advanced glycation end products promote melanogenesis via activating NLRP3 inflammasome in human dermal fibroblasts

Advanced glycation end products (AGEs) accumulation is significantly increased in the dermis of photoaged skin and plays crucial roles in photoaging. Although AGEs have been found to contribute to the yellowish discoloration of photoaged skin, their roles in photoaging-associated hyperpigmentation disorders have not been extensively studied. In this study, we observed that AGEs, NLRP3 and IL-18 were increased in the dermis of sun-exposed skin and lesions of melasma and solar lentigo and that dermal deposition of AGEs was positively correlated with epidermal melanin levels. Additionally, we found AGEs-BSA potently activated NLRP3 inflammasome and promoted IL-18 production and secretion in cultured fibroblasts, which was mediated by RAGE/NF-κB pathway. Moreover, AGEs-BSA significantly promoted melanogenesis through increasing tyrosinase activity and expression of microphthalmia-associated transcription factor and tyrosinase, which was dependent on NLRP3 inflammasome activation and IL-18 secretion in fibroblasts. Notably, AGEs-collagen could activate NLRP3 inflammasome in fibroblasts and enhance melanogenesis. Further, we found IL-18 enhanced melanogenesis through binding to its receptor and activating p38 MAPK and ERK1/2 signaling pathways in melanocytes. Importantly, the pro-melanogenesis of AGEs-BSA was verified in ex vivo cultured skin and mice models. These findings suggest that dermal AGEs stimulate melanogenesis and contribute to the development of photoaging-associated hyperpigmentation disorders.

Novel insights into NOD-like receptors in renal diseases

Nucleotide-binding oligomerization domain-like receptors (NLRs), including NLRAs, NLRBs (also known as NAIPs), NLRCs, and NLRPs, are a major subfamily of pattern recognition receptors (PRRs). Owing to a recent surge in research, NLRs have gained considerable attention due to their involvement in mediating the innate immune response and perpetuating inflammatory pathways, which is a central phenomenon in the pathogenesis of multiple diseases, including renal diseases. NLRs are expressed in different renal tissues during pathological conditions, which suggest that these receptors play roles in acute kidney injury, obstructive nephropathy, diabetic nephropathy, IgA nephropathy, lupus nephritis, crystal nephropathy, uric acid nephropathy, and renal cell carcinoma, among others. This review summarises recent progress on the functions of NLRs and their mechanisms in the pathophysiological processes of different types of renal diseases to help us better understand the role of NLRs in the kidney and provide a theoretical basis for NLR-targeted therapy for renal diseases.

Crosstalk Between Senescent Bone Cells and the Bone Tissue Microenvironment Influences Bone Fragility During Chronological Age and in Diabetes

Bone is a complex organ serving roles in skeletal support and movement, and is a source of blood cells including adaptive and innate immune cells. Structural and functional integrity is maintained through a balance between bone synthesis and bone degradation, dependent in part on mechanical loading but also on signaling and influences of the tissue microenvironment. Bone structure and the extracellular bone milieu change with age, predisposing to osteoporosis and increased fracture risk, and this is exacerbated in patients with diabetes. Such changes can include loss of bone mineral density, deterioration in micro-architecture, as well as decreased bone flexibility, through alteration of proteinaceous bone support structures, and accumulation of senescent cells. Senescence is a state of proliferation arrest accompanied by marked morphological and metabolic changes. It is driven by cellular stress and serves an important acute tumor suppressive mechanism when followed by immune-mediated senescent cell clearance. However, aging and pathological conditions including diabetes are associated with accumulation of senescent cells that generate a pro-inflammatory and tissue-destructive secretome (the SASP). The SASP impinges on the tissue microenvironment with detrimental local and systemic consequences; senescent cells are thought to contribute to the multimorbidity associated with advanced chronological age. Here, we assess factors that promote bone fragility, in the context both of chronological aging and accelerated aging in progeroid syndromes and in diabetes, including senescence-dependent alterations in the bone tissue microenvironment, and glycation changes to the tissue microenvironment that stimulate RAGE signaling, a process that is accelerated in diabetic patients. Finally, we discuss therapeutic interventions targeting RAGE signaling and cell senescence that show promise in improving bone health in older people and those living with diabetes.

Modulatory Properties of Food and Nutraceutical Components Targeting NLRP3 Inflammasome Activation

Inflammasomes are key intracellular multimeric proteins able to initiate the cellular inflammatory signaling pathway. NLRP3 inflammasome represents one of the main protein complexes involved in the development of inflammatory events, and its activity has been largely demonstrated to be connected with inflammatory or autoinflammatory disorders, including diabetes, gouty arthritis, liver fibrosis, Alzheimer’s disease, respiratory syndromes, atherosclerosis, and cancer initiation. In recent years, it has been demonstrated how dietary intake and nutritional status represent important environmental elements that can modulate metabolic inflammation, since food matrices are an important source of several bioactive compounds. In this review, an updated status of knowledge regarding food bioactive compounds as NLRP3 inflammasome modulators is discussed. Several chemical classes, namely polyphenols, organosulfurs, terpenes, fatty acids, proteins, amino acids, saponins, sterols, polysaccharides, carotenoids, vitamins, and probiotics, have been shown to possess NLRP3 inflammasome-modulating activity through in vitro and in vivo assays, mainly demonstrating an anti-NLRP3 inflammasome activity. Plant foods are particularly rich in important bioactive compounds, each of them can have different effects on the pathway of inflammatory response, confirming the importance of the nutritional pattern (food model) as a whole rather than any single nutrient or functional compound.

Contributing factors common to COVID‑19 and gastrointestinal cancer

The devastating complications of coronavirus disease 2019 (COVID-19) result from the dysfunctional immune response of an individual following the initial severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Multiple toxic stressors and behaviors contribute to underlying immune system dysfunction. SARS-CoV-2 exploits the dysfunctional immune system to trigger a chain of events, ultimately leading to COVID-19. The authors have previously identified a number of contributing factors (CFs) common to myriad chronic diseases. Based on these observations, it was hypothesized that there may be a significant overlap between CFs associated with COVID-19 and gastrointestinal cancer (GIC). Thus, in the present study, a streamlined dot-product approach was used initially to identify potential CFs that affect COVID-19 and GIC directly (i.e., the simultaneous occurrence of CFs and disease in the same article). The nascent character of the COVID-19 core literature (~1-year-old) did not allow sufficient time for the direct effects of numerous CFs on COVID-19 to emerge from laboratory experiments and epidemiological studies. Therefore, a literature-related discovery approach was used to augment the COVID-19 core literature-based ‘direct impact’ CFs with discovery-based ‘indirect impact’ CFs [CFs were identified in the non-COVID-19 biomedical literature that had the same biomarker impact pattern (e.g., hyperinflammation, hypercoagulation, hypoxia, etc.) as was shown in the COVID-19 literature]. Approximately 2,250 candidate direct impact CFs in common between GIC and COVID-19 were identified, albeit some being variants of the same concept. As commonality proof of concept, 75 potential CFs that appeared promising were selected, and 63 overlapping COVID-19/GIC potential/candidate CFs were validated with biological plausibility. In total, 42 of the 63 were overlapping direct impact COVID-19/GIC CFs, and the remaining 21 were candidate GIC CFs that overlapped with indirect impact COVID-19 CFs. On the whole, the present study demonstrates that COVID-19 and GIC share a number of common risk/CFs, including behaviors and toxic exposures, that impair immune function. A key component of immune system health is the removal of those factors that contribute to immune system dysfunction in the first place. This requires a paradigm shift from traditional Western medicine, which often focuses on treatment, rather than prevention.

Two types of immune infiltrating cells and six hub genes can predict the occurrence of myasthenia gravis in patients with thymoma

Thymoma is the most common primary mass in anterior mediastinum. Although associated with low malignancy, it is often accompanied by myasthenia gravis resulting in poor prognosis. Due to the dual factors of tumor immune tolerance and autoimmune reaction, it is urgent to understand the immune status of MG with thymoma. In this study, RNA sequencing data were obtained from the TCGA and GEO cohorts to identify differentially expressed messenger RNAs and infiltrated immune cells. A total of 121 samples in TCGA and 43 samples in GEO were screened out. The infiltrated immune cells were identified by CIBERSORT, in which Tfh cells and activated DC cells were abnormal in thymoma patients. The differently expressed genes were performed by package LIMMA. The functional characteristics of differently expression genes were analyzed by GO and KEGG; one GO and seven KEGG pathways were both found in both TCGA and GEO cohorts. Meanwhile, 27 common differently expressed genes were obtained and were displayed by a Venn diagram. The TRRUST was used to screen the hub genes for the common 27 different genes and 6 genes were found. Then, PPI networks were constructed. Subsequently, the relationship between SCNAs of common genes and related immune cells tested by TIMER. Kaplan–Meier plots, ROC curve and Cox’s expression model for immune infiltration and hub genes were also tested. In conclusion, we found that two types of immune infiltrated cells and six hub genes can predict the occurrence of myasthenia gravis in thymoma patients.

Common contributing factors to COVID-19 and inflammatory bowel disease

The devastating complications of coronavirus disease 2019 (COVID-19) result from an individual's dysfunctional immune response following the initial severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Multiple toxic stressors and behaviors contribute to underlying immune system dysfunction. SARS-CoV-2 exploits the dysfunctional immune system to trigger a chain of events ultimately leading to COVID-19. We have previously identified many contributing factors (CFs) (representing toxic exposure, lifestyle factors and psychosocial stressors) common to myriad chronic diseases. We hypothesized significant overlap between CFs associated with COVID-19 and inflammatory bowel disease (IBD), because of the strong role immune dysfunction plays in each disease. A streamlined dot-product approach was used to identify potential CFs to COVID-19 and IBD. Of the fifty CFs to COVID-19 that were validated for demonstration purposes, approximately half had direct impact on COVID-19 (the CF and COVID-19 were mentioned in the same record; i.e., CF---→COVID-19), and the other half had indirect impact. The nascent character of the COVID-19 core literature (∼ one year old) did not allow sufficient time for the direct impacts of many CFs on COVID-19 to be identified. Therefore, an immune system dysfunction (ID) literature directly related to the COVID-19 core literature was used to augment the COVID-19 core literature and provide the remaining CFs that impacted COVID-19 indirectly (i.e., CF---→immune system dysfunction---→COVID-19). Approximately 13000 potential CFs for myriad diseases (obtained from government and university toxic substance lists) served as the starting point for the dot-product identification process. These phrases were intersected (dot-product) with phrases extracted from a PubMed-derived IBD core literature, a nascent COVID-19 core literature, and the COVID-19-related immune system dysfunction (ID) core literature to identify common ID/COVID-19 and IBD CFs. Approximately 3000 potential CFs common to both ID and IBD, almost 2300 potential CFs common to ID and COVID-19, and over 1900 potential CFs common to IBD and COVID-19 were identified. As proof of concept, we validated fifty of these ∼3000 overlapping ID/IBD candidate CFs with biologic plausibility. We further validated 24 of the fifty as common CFs in the IBD and nascent COVID-19 core literatures. This significant finding demonstrated that the CFs indirectly related to COVID-19 -- identified with use of the immune system dysfunction literature -- are strong candidates to emerge eventually as CFs directly related to COVID-19. As discussed in the main text, many more CFs common to all these core literatures could be identified and validated. ID and IBD share many common risk/contributing factors, including behaviors and toxic exposures that impair immune function. A key component to immune system health is removal of those factors that contribute to immune system dysfunction in the first place. This requires a paradigm shift from traditional Western medicine, which often focuses on treatment, rather than prevention.

Dietary AGEs as Exogenous Boosters of Inflammation

Most chronic modern non-transmissible diseases seem to begin as the result of low-grade inflammation extending over prolonged periods of time. The importance of diet as a source of many pro-inflammatory compounds that could create and sustain such a low-grade inflammatory state cannot be ignored, particularly since we are constantly exposed to them during the day. The focus of this review is on specific components of the diet associated with inflammation, specifically advanced glycation end products (AGEs) that form during thermal processing of food. AGEs are also generated in the body in normal physiology and are widely recognized as increased in diabetes, but many people are unaware of the potential importance of exogenous AGEs ingested in food. We review experimental models, epidemiologic data, and small clinical trials that suggest an important association between dietary intake of these compounds and development of an inflammatory and pro-oxidative state that is conducive to chronic diseases. We compare dietary intake of AGEs with other widely known dietary patterns, such as the Mediterranean and the Dietary Approaches to Stop Hypertension (DASH) diets, as well as the Dietary Inflammation Index (DII). Finally, we delineate in detail the pathophysiological mechanisms induced by dietary AGEs, both direct (i.e., non-receptor-mediated) and indirect (receptor-mediated).

Dietary advanced glycation end-products elicit toxicological effects by disrupting gut microbiome and immune homeostasis

The aging immune system is characterized by a low-grade chronic systemic inflammatory state ("inflammaging") marked by elevated serum levels of inflammatory molecules such as interleukin (IL)-6 and C-reactive protein (CRP). These inflammatory markers were also reported to be strong predictors for the development/severity of Type 2 diabetes, obesity, and COVID-19. The levels of these markers have been positively associated with those of advanced glycation end-products (AGEs) generated via non-enzymatic glycation and oxidation of proteins and lipids during normal aging and metabolism. Based on the above observations, it is clinically important to elucidate how dietary AGEs modulate inflammation and might thus increase the risk for aging-exacerbated diseases. The present narrative review discusses the potential pro-inflammatory properties of dietary AGEs with a focus on the inflammatory mediators CRP, IL-6 and ferritin, and their relations to aging in general and Type 2 diabetes in particular. In addition, underlying mechanisms - including those related to gut microbiota and the receptors for AGEs, and the roles AGEs might play in affecting physiologies of the healthy elderly, obese individuals, and diabetics are discussed in regard to any greater susceptibility to COVID-19.

Towards Goals to Refine Prophylactic and Therapeutic Strategies Against COVID-19 Linked to Aging and Metabolic Syndrome

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) gave rise to the coronavirus disease 2019 (COVID-19) pandemic. A strong correlation has been demonstrated between worse COVID-19 outcomes, aging, and metabolic syndrome (MetS), which is primarily derived from obesity-induced systemic chronic low-grade inflammation with numerous complications, including type 2 diabetes mellitus (T2DM). The majority of COVID-19 deaths occurs in people over the age of 65. Individuals with MetS are inclined to manifest adverse disease consequences and mortality from COVID-19. In this review, we examine the prevalence and molecular mechanisms underlying enhanced risk of COVID-19 in elderly people and individuals with MetS. Subsequently, we discuss current progresses in treating COVID-19, including the development of new COVID-19 vaccines and antivirals, towards goals to elaborate prophylactic and therapeutic treatment options in this vulnerable population.

Autoantibodies Against Methylglyoxal-Modified Apolipoprotein B100 and ApoB100 Peptide Are Associated With Less Coronary Artery Atherosclerosis and Retinopathy in Long-Term Type 1 Diabetes

OBJECTIVE

Methylglyoxal (MGO), a reactive aldehyde forming advanced glycation end products (AGEs), is increased in diabetes and recognized by the immune system, resulting in anti-AGE-specific autoantibodies. The association of these immune responses with macro- and microvascular complications in type 1 diabetes remains unclarified. We investigated associations between MGO-modified apolipoprotein B100 (apoB100) and apoB100 peptide 5 (MGO-p5) autoantibodies and coronary atherosclerosis and retinopathy in type 1 diabetes.

RESEARCH DESIGN AND METHODS

IgM and IgG against MGO-apoB100 and MGO-p5 were measured by ELISA in plasma from 103 subjects with type 1 diabetes and 63 control subjects (Dialong study) and in a replication cohort of 27 subjects with type 1 diabetes (Oslo study). Coronary atherosclerosis was assessed by computed tomography coronary angiography or intravascular ultrasound. Retinopathy was classified by retinal photos.

RESULTS

MGO-apoB100 IgM and MGO-p5 IgM levels were higher in subjects with diabetes with no coronary artery stenosis compared with subjects with significant stenosis (median [interquartile range]: 96.2 arbitrary units [AU] [71-126.8] vs. 54 AU [36.1-85.4], P = 0.003 for MGO-apoB100; and 77.4 AU [58-106] vs. 36.9 AU [28.9-57.4], P = 0.005 for MGO-p5). MGO-apoB100 IgM and MGO-p5 IgM were associated with less severe coronary stenosis after adjusting for confounders (odds ratio 0.2 [95% CI 0.05-0.6], P = 0.01; and 0.22 [0.06-0.75], P = 0.02). The inverse association of MGO-p5 IgM and coronary stenosis was confirmed in the replication cohort. Subjects with proliferative retinopathy had significantly lower MGO-apoB100 IgM and MGO-p5 IgM than those with background retinopathy.

CONCLUSIONS

Autoantibodies against AGE-modified apoB100 are inversely associated with coronary atherosclerosis and proliferative retinopathy, suggesting vascular protective effects of these autoantibodies in type 1 diabetes.

Pleiotropic consequences of metabolic stress for the major histocompatibility complex class II molecule antigen processing and presentation machinery

Hyperglycemia and hyperlipidemia are often observed in individuals with type II diabetes (T2D) and related mouse models. One dysmetabolic biochemical consequence is the non-enzymatic reaction between sugars, lipids, and proteins, favoring protein glycation, glycoxidation, and lipoxidation. Here, we identified oxidative alterations in key components of the major histocompatibility complex (MHC) class II molecule antigen processing and presentation machinery in vivo under conditions of hyperglycemia-induced metabolic stress. These modifications were linked to epitope-specific changes in endosomal processing efficiency, MHC class II-peptide binding, and DM editing activity. Moreover, we observed some quantitative and qualitative changes in the MHC class II immunopeptidome of Ob/Ob mice on a high-fat diet compared with controls, including changes in the presentation of an apolipoprotein B100 peptide associated previously with T2D and metabolic syndrome-related clinical complications. These findings highlight a link between glycation reactions and altered MHC class II antigen presentation that may contribute to T2D complications.

Classically activated mouse macrophages produce methylglyoxal that induces a TLR4- and RAGE-independent proinflammatory response

The highly reactive compound methylglyoxal (MG) can cause direct damage to cells and tissues by reacting with cellular macromolecules. MG has been identified as a biomarker associated with increased sepsis-induced mortality. Patients undergoing septic shock have significantly elevated circulating MG levels compared to postoperative patients and healthy controls. Furthermore, MG has been implicated in the development of type II diabetes mellitus and Alzheimer's disease. Because MG is generated during glycolysis, we hypothesized that MG may be produced by classically activated (M1) macrophages, possibly contributing to the inflammatory response. LPS and IFN-γ-treated macrophages acquired an M1 phenotype (as evidenced by M1 markers and enhanced glycolysis) and formed MG adducts, MG-H1, MG-H2, and MG-H3, which were detected using antibodies specific for MG-modified proteins (methylglyoxal 5-hydro-5-methylimidazolones). MG adducts were also increased in the lungs of LPS-treated mice. Macrophages treated with LPS and IFN-γ also exhibited decreased expression of glyoxalase 1 (Glo1), an enzyme that metabolizes MG. Concentrations of exogenous, purified MG > 0.5 mM were toxic to macrophages; however, a nontoxic dose of 0.3 mM induced TNF-α and IL-1β, albeit to a lesser extent than LPS stimulation. Despite prior evidence that MG adducts may signal through "receptor for advanced glycation endproducts" (RAGE), MG-mediated cell death and cytokine induction by exogenous MG was RAGE-independent in primary macrophages. Finally, RAGE-deficient mice did not exhibit a significant survival advantage following lethal LPS injection. Overall, our evidence suggests that MG may be produced by M1 macrophages during sepsis, following IFN-γ-dependent down-regulation of Glo1, contributing to over-exuberant inflammation.

AGER1 downregulation associates with fibrosis in nonalcoholic steatohepatitis and type 2 diabetes

Type 2 diabetes is clinically associated with progressive necroinflammation and fibrosis in nonalcoholic steatohepatitis (NASH). Advanced glycation end-products (AGEs) accumulate during prolonged hyperglycemia, but the mechanistic pathways that lead to accelerated liver fibrosis have not been well defined. In this study, we show that the AGEs clearance receptor AGER1 was downregulated in patients with NASH and diabetes and in our NASH models, whereas the proinflammatory receptor RAGE was induced. These findings were associated with necroinflammatory, fibrogenic, and pro-oxidant activity via the NADPH oxidase 4. Inhibition of AGEs or RAGE deletion in hepatocytes in vivo reversed these effects. We demonstrate that dysregulation of NRF2 by neddylation of cullin 3 was linked to AGER1 downregulation and that induction of NRF2 using an adeno-associated virus-mediated approach in hepatocytes in vivo reversed AGER1 downregulation, lowered the level of AGEs, and improved proinflammatory and fibrogenic responses in mice on a high AGEs diet. In patients with NASH and diabetes or insulin resistance, low AGER1 levels were associated with hepatocyte ballooning degeneration and ductular reaction. Collectively, prolonged exposure to AGEs in the liver promotes an AGER1/RAGE imbalance and consequent redox, inflammatory, and fibrogenic activity in NASH.

From mitochondria to sarcopenia: Role of inflammaging and RAGE-ligand axis implication

Sarcopenia is characterized by a loss of muscle mass and function that reduces mobility, diminishes quality of life, and can lead to fall-related injuries. At the intracellular level, mitochondrial population alterations are considered as key contributors to the complex etiology of sarcopenia. Mitochondrial dysfunctions lead to reactive oxygen species production, altered cellular proteostasis, and promotes inflammation. Interestingly, the receptor for advanced glycation end-products (RAGE) is a pro-inflammatory receptor involved in inflammaging. In this review, after a brief description of sarcopenia, we will describe how mitochondria and the pathways controlling mitochondrial population quality could participate to age-induced muscle mass and force loss. Finally, we will discuss the RAGE-ligand axis during aging and its possible connection with mitochondria to control inflammaging and sarcopenia.

The role of RAGE in host pathology and crosstalk between RAGE and TLR4 in innate immune signal transduction pathways

Although the innate immune receptor protein, Receptor for Advanced Glycation End products (RAGE), has been extensively studied, there has been renewed interest in RAGE for its potential role in sepsis, along with a host of other inflammatory diseases of chronic, noninfectious origin. In contrast to other innate immune receptors, for example, Toll-like receptors (TLRs), that recognize ligands derived from pathogenic organisms that are collectively known as "pathogen-associated molecular patterns" (PAMPs) or host-derived "damage-associated molecular patterns" (DAMPs), RAGE has been shown to recognize a broad collection of DAMPs exclusively. Historically, these DAMPs have been shown to be pro-inflammatory in nature. Early studies indicated that the adaptor molecule, MyD88, might be important for this change. More recent studies have explored further the mechanisms underlying this inflammatory change. Overall, the newer results have shown that there is extensive crosstalk between RAGE and TLRs. The three canonical RAGE ligands, Advanced Glycation End products (AGEs), HMGB1, and S100 proteins, have all been shown to activate both TLRs and RAGE to varying degrees in order to induce inflammation in in vitro models. As with any field that delves deeply into innate signaling, obstacles of reagent purity may be a cause of some of the discrepancies in the literature, and we have found that commercial antibodies that have been widely used exhibit a high degree of nonspecificity. Nonetheless, the weight of published evidence has led us to speculate that RAGE may be physically interacting with TLRs on the cell surface to elicit inflammation via MyD88-dependent signaling.

Dietary Advanced Glycation Endproducts and the Gastrointestinal Tract

The prevalence of inflammatory bowel diseases (IBD) is increasing in the world. The introduction of the Western diet has been suggested as a potential explanation of increased prevalence. The Western diet includes highly processed food products, and often include thermal treatment. During thermal treatment, the Maillard reaction can occur, leading to the formation of dietary advanced glycation endproducts (dAGEs). In this review, different biological effects of dAGEs are discussed, including their digestion, absorption, formation, and degradation in the gastrointestinal tract, with an emphasis on their pro-inflammatory effects. In addition, potential mechanisms in the inflammatory effects of dAGEs are discussed. This review also specifically elaborates on the involvement of the effects of dAGEs in IBD and focuses on evidence regarding the involvement of dAGEs in the symptoms of IBD. Finally, knowledge gaps that still need to be filled are identified.

Stochastic non-enzymatic modification of long-lived macromolecules - A missing hallmark of aging

Damage accumulation in long-living macromolecules (especially extracellular matrix (ECM) proteins, nuclear pore complex (NPC) proteins, and histones) is a missing hallmark of aging. Stochastic non-enzymatic modifications of ECM trigger cellular senescence as well as many other hallmarks of aging affect organ barriers integrity and drive tissue fibrosis. The importance of it for aging makes it a key target for interventions. The most promising of them can be AGE inhibitors (chelators, O-acetyl group or transglycating activity compounds, amadorins and amadoriases), glucosepane breakers, stimulators of elastogenesis, and RAGE antagonists.

The Inflammasome in Chronic Complications of Diabetes and Related Metabolic Disorders

Diabetes mellitus (DM) ranks seventh as a cause of death worldwide. Chronic complications, including cardiovascular, renal, and eye disease, as well as DM-associated non-alcoholic fatty liver disease (NAFLD) account for most of the morbidity and premature mortality in DM. Despite continuous improvements in the management of late complications of DM, significant gaps remain. Therefore, searching for additional strategies to prevent these serious DM-related conditions is of the utmost importance. DM is characterized by a state of low-grade chronic inflammation, which is critical in the progression of complications. Recent clinical trials indicate that targeting the prototypic pro-inflammatory cytokine interleukin-1β (IL-1 β) improves the outcomes of cardiovascular disease, which is the first cause of death in DM patients. Together with IL-18, IL-1β is processed and secreted by the inflammasomes, a class of multiprotein complexes that coordinate inflammatory responses. Several DM-related metabolic factors, including reactive oxygen species, glyco/lipoxidation end products, and cholesterol crystals, have been involved in the pathogenesis of diabetic kidney disease, and diabetic retinopathy, and in the promoting effect of DM on the onset and progression of atherosclerosis and NAFLD. These metabolic factors are also well-established danger signals capable of regulating inflammasome activity. In addition to presenting the current state of knowledge, this review discusses how the mechanistic understanding of inflammasome regulation by metabolic danger signals may hopefully lead to novel therapeutic strategies targeting inflammation for a more effective treatment of diabetic complications.

Loratadine Alleviates Advanced Glycation End Product-Induced Activation of NLRP3 Inflammasome in Human Chondrocytes

Background

Chondrocytes in joint tissue are responsible for the synthesis and degradation of the cartilage matrix. Chondrocytes have been closely linked to the pathogenesis of osteoarthritis and cartilage damage. Targeted drug intervention directed at chondrocyte function is a promising strategy for the treatment of osteoarthritis. The effects of histamine receptor H1 (H1R) and its antagonist loratadine in osteoarthritic chondrocytes are less known.

Materials and Methods

The inhibitory effects of loratadine on NLRP3 inflammasome and the NADPH oxidase subunit NOX4 were assessed in advanced glycation end products (AGEs)-treated SW1353 chondrocytes by real-time PCR, ELISA, and Western blot experiments. The mitochondrial ROS level was measured using the specific probe MitoSOX Red. The dependent effect of loratadine on the transcriptional factor nuclear factor erythroid 2-related factor 2 (NRF2) was evaluated through an oligo-based siRNA knockdown approach and Western blot analysis.

Results

The expression of H1R was dose-responsively induced by AGEs in chondrocytes. Treatment with loratadine mitigated AGEs-induced oxidative stress, as revealed by suppressed production of mitochondrial ROS and the NADPH oxidase subunit NOX4. Loratadine treatment inhibited the expression of TxNIP and several components of the NLRP3 inflammasome complex, including NLRP3, ASC, and cleaved caspase 1 (P10). Moreover, loratadine suppressed the expression of NRF2, and the silencing of NRF2 abolished the suppressive effect of loratadine on NLRP3 inflammasome activation.

Conclusion

Our study demonstrates that loratadine protects chondrocytes from AGEs-induced TxNIP/NLRP3 inflammasome activation by modulating the expression of the transcriptional factor NRF2. This finding implies that loratadine has therapeutic potential in the treatment of osteoarthritis and cartilage injury.

Soluble Receptor for Glycation End-products Concentration Increases Following the Treatment of Severe Diabetic Ketoacidosis

OBJECTIVE

To determine the time relationships of soluble receptor for glycation end-products (sRAGE), [a decoy of the advanced glycation end-products (AGE)-RAGE axis] and D-lactate, (a metabolite of methylglyoxal) in the inflammatory response to diabetic ketoacidosis (DKA).

METHODS

Sixteen children and adolescents with type 1 diabetes (T1D) had blood samples obtained, 6-12 hours into treatment, at three weeks and three months post start of treatment. sRAGE and D-lactate concentrations at three months were considered baseline. Expression of RAGE was investigated in the myocardium of a newly diagnosed and untreated young person with fatal T1D/DKA.

RESULTS

sRAGE 6-12 hours after the start of treatment was 39% lower than the values at two weeks (p=0.0036) and at three months (p=0.0023) post treatment. D-lactate was higher during treatment than at three weeks (p=0.04) and at three months (p=0.035).

CONCLUSION

sRAGE concentration was decreased during treatment, compared to concentrations at two weeks and three months after treatment. The increased D-lactate during treatment was in keeping with the known increase in dicarbonyls at this time. The finding of RAGE expression in a young myocardium prior to DKA treatment suggested cardiovascular inflammation pre-treatment and at a young age.

Why does COVID-19 disproportionately affect older people?

The severity and outcome of coronavirus disease 2019 (COVID-19) largely depends on a patient's age. Adults over 65 years of age represent 80% of hospitalizations and have a 23-fold greater risk of death than those under 65. In the clinic, COVID-19 patients most commonly present with fever, cough and dyspnea, and from there the disease can progress to acute respiratory distress syndrome, lung consolidation, cytokine release syndrome, endotheliitis, coagulopathy, multiple organ failure and death. Comorbidities such as cardiovascular disease, diabetes and obesity increase the chances of fatal disease, but they alone do not explain why age is an independent risk factor. Here, we present the molecular differences between young, middle-aged and older people that may explain why COVID-19 is a mild illness in some but life-threatening in others. We also discuss several biological age clocks that could be used in conjunction with genetic tests to identify both the mechanisms of the disease and individuals most at risk. Finally, based on these mechanisms, we discuss treatments that could increase the survival of older people, not simply by inhibiting the virus, but by restoring patients' ability to clear the infection and effectively regulate immune responses.

Polyphenols and AGEs/RAGE axis. Trends and challenges

The formation of advanced glycation end-products (AGEs) is a key pathophysiological event linked not only to the onset and progression of diabetic complications, but also to neurodegeneration, cardiovascular diseases, cancer, and others important human diseases. AGEs contributions to pathophysiology are mainly through the formation of cross-links and by engaging the receptor for advanced glycation end-products (RAGE). Polyphenols are secondary metabolites found largely in fruits, vegetables, cereals, and beverages, and during many years, important efforts have been made to elucidate their beneficial effects on human health, mainly ascribed to their antioxidant activities. In the present review, we highlighted the beneficial actions of polyphenols aimed to diminish the harmful consequences of advanced glycation, mainly by the inhibition of ROS formation during glycation, the inhibition of Schiff base, Amadori products, and subsequent dicarbonyls group formation, the activation of the glyoxalase system, as well as by blocking either AGEs-RAGE interaction or cell signaling.

Acetate Downregulates the Activation of NLRP3 Inflammasomes and Attenuates Lung Injury in Neonatal Mice With Bronchopulmonary Dysplasia

Background: Bronchopulmonary dysplasia (BPD) is a common pulmonary complication in preterm infants. Acetate is a metabolite produced by the gut microbiota, and its anti-inflammatory function is well known. The role of acetate in BPD has not been studied. Here, we investigate the effects of acetate on lung inflammation and damage in mice model of BPD. Objective: To investigate the role of acetate in the development of BPD. Methods: C57BL/6 mice were randomly divided into three groups on the 3rd day after birth: room air group, hyperoxia group, and hyperoxia + acetate (250 mM, 0.02 ml/g) group. The expression of inflammatory factors was determined by ELISA and RT-PCR, and NLRP3 and caspase-1 were detected by Western blot. High-throughput sequencing was used to detect bacterial communities in the mice intestines. Results: After acetate treatment, the expression levels of TNF-α, IL-1β, IL-18, NLRP3, and caspase-1 were significantly reduced, while the expression of GPR43 was increased. In the BPD mice treated with acetate, the proportion of Escherichia-Shigella was lower than in placebo-treated BPD mice, while the abundance of Ruminococcus was increased. Conclusions: These results indicate that acetate may regulate intestinal flora and reduce inflammatory reactions and lung injury in BPD. Therefore, acetate may be an effective drug to protect against neonatal BPD.

Clinical/Translational Aspects of Advanced Glycation End-Products

Advanced glycation end-products (AGEs) have been implicated in chronic hyperglycemia and age-related diseases. Endogenous AGEs produced by humans generate oxidative stress and activation of inflammatory signaling pathways via AGE-specific receptors. The present review summarizes current knowledge on the pathogenic role of AGEs in chronic noncommunicable diseases. Although correlations exist between glycation and the pathogenesis of these diseases, uncertainties remain in light of recurrent intervention failures of apparently promising animal models to be translated into clinically useful anti-AGE strategies. Future intervention of AGEs or their receptors should embrace more carefully executed clinical trials. Nevertheless, suppressing symptoms via lifetime drug application is unlikely to eliminate the burden of chronic diseases unless deep-rooted lifestyle issues that cause these diseases are simultaneously addressed.

Wnt Glycation Inhibits Canonical Signaling

Glycation occurs as a non-enzymatic reaction between amino and thiol groups of proteins, lipids, and nucleotides with reducing sugars or α-dicarbonyl metabolites. The chemical reaction underlying is the Maillard reaction leading to the formation of a heterogeneous group of compounds named advanced glycation end products (AGEs). Deleterious effects have been observed to accompany glycation such as alterations of protein structure and function resulting in crosslinking and accumulation of insoluble protein aggregates. A substantial body of evidence associates glycation with aging. Wnt signaling plays a fundamental role in stem cell biology as well as in regeneration and repair mechanisms. Emerging evidence implicates that changes in Wnt/β-catenin pathway activity contribute to the aging process. Here, we investigated the effect of glycation of Wnt3a on its signaling activity. Methods: Glycation was induced by treatment of Wnt3a-conditioned medium (CM) with glyoxal (GO). Effects on Wnt3a signaling activity were analyzed by Topflash/Fopflash reporter gene assay, co-immunoprecipitation, and quantitative RT-PCR. Results: Our data show that GO-treatment results in glycation of Wnt3a. Glycated Wnt3a suppresses β-catenin transcriptional activity in reporter gene assays, reduced binding of β-catenin to T-cell factor 4 (TCF-4) and extenuated transcription of Wnt/β-catenin target genes. Conclusions: GO-induced glycation impairs Wnt3a signaling function.

Macrophage NLRP3 inflammasome activated by CVB3 capsid proteins contributes to the development of viral myocarditis

Viral myocarditis, mainly caused by enteroviruses specially coxsackievirus B3 (CVB3) infection, is a common clinical cardiovascular disease and characterized by cardiac massive inflammation. Our previous study showed that CVB3-induced myocardial NLRP3 contributed to the development of viral myocarditis. In this study, we found that beside of being up-regulated in myocardiocytes, NLPR3 was also obviously increased in the cardiac infiltrating macrophages. While whether this accumulated NLRP3 influences, macrophage inflammatory responses remains unknown. By adoptive transfer assays, we found that mice receiving NLRP3 up-regulated macrophages showed much more abundant cardiac IL-1β production and more severe myocardial inflammation, while those receiving NLRP3 down-regulated macrophages showed much less IL-1β production and milder myocarditis, indicating that NLRP3 up-regulated macrophages played a pathological role in CVB3-induced myocarditis. In addition, we further found that it was CVB3 capsid proteins VP1 (predominant) and VP2, but not viral RNAs, robustly triggered macrophage NLRP3 up-regulation and activation. Our study demonstrated macrophage NLRP3 inflammasome could be efficiently be activated by CVB3 capsid proteins, and contributed to the pathogenesis of viral myocarditis. It might provide some clues to the development of new therapeutic strategies based on macrophage NLRP3 modulation.

The effect of NLRP inflammasome on the regulation of AGEs-induced inflammatory response in human periodontal ligament cells

BACKGROUND AND OBJECTIVE

Diabetes influences the frequency and development of periodontitis. Inflammation of human periodontal ligament cells (HPDLCs) participates in this pathologic process. Hence, this study aims to explore whether advanced glycation end products (AGEs), by-products of diabetes, could exaggerate inflammation induced by muramyl dipeptide (MDP) in HPDLCs, and whether nucleotide-binding oligomerization domain-like receptors (NLRs) signaling pathway was involved.

MATERIAL AND METHODS

Human periodontal ligament cells were pre-treated with 100 μg/mL AGEs for 24 hours and stimulated with 10 μg/mL MDP for 24 hours. IL-6, IL-1β, and RAGE were detected, and the activation of NF-κB signaling pathway was observed. The expression of NLRs was evaluated with or without silencing RAGE or blocking NF-κB pathway under AGEs stimulation. Statistical analyses were performed by using independent sample t test.

RESULTS

Advanced glycation end products induced significant increase of inflammatory cytokines in HPDLCs (P < 0.05). Results of western blot (WB) showed that after 45 minutes stimulation of AGEs, p-p65/p65 ratio peaked; AGEs promoted the expression of NLRP1, NLRP3, and apoptosis-associated speck-like protein containing a CARD (ASC). After silencing RAGE or blocking NF-κB pathway, the up-regulation of NLRs protein caused by AGEs was attenuated. Additionally, AGEs pre-treatment could enhance the inflammatory response of MDP and the expression of NLRs, which were demonstrated by more expression of IL-6, IL-1β, NOD2, NLRP1, NLRP3, and ASC.

CONCLUSION

Advanced glycation end products induced inflammatory response in HPDLCs via NLRP1-inflammasome and NLRP3-inflammasome activation in which NF-κB signal pathway was involved. Besides, AGEs promoted the inflammatory response of MDP via NOD2, NLRP1-inflammasome, and NLRP3-inflammasome.

[Change in the expression of the NLRP3 inflammasome signaling pathway in peripheral blood and its significance in children with Mycoplasma pneumoniae pneumonia]

OBJECTIVE

To investigate the expression of the NLRP3 inflammasome signaling pathway in peripheral blood and its significance in children with Mycoplasma pneumoniae pneumonia (MPP).

METHODS

According to the severity, 147 children with MPP were divided into mild group with 83 children and severe group with 64 children. According to the stage of disease, the children were divided into acute group with 77 children and recovery stage with 70 children. A total of 50 healthy children were enrolled as the control group. Quantitative real-time PCR was used to measure the mRNA expression of NLRP3, ASC, and caspase-1. ELISA was used to measure the serum levels of interleukin-1β (IL-1β) and interleukin-18 (IL-18).

RESULTS

Compared with the control group, the children with MMP had significantly higher relative mRNA expression levels of NLRP3, ASC, and caspase-1 in peripheral blood and serum levels of IL-1β and IL-18 (P<0.05). Compared with the control group, both mild and severe groups had significantly higher relative mRNA expression levels of NLRP3, ASC, and caspase-1 in peripheral blood and serum levels of IL-1β and IL-18 (P<0.05). The severe group had significantly higher levels of above mentioned parameters than the mild group (P<0.05). Both acute group and recovery group had significantly higher relative mRNA expression levels of NLRP3, ASC, and caspase-1 in peripheral blood and serum levels of IL-1β and IL-18 than the control group (P<0.05). The acute group had significantly higher levels of above mentioned parameters than the recovery group (P<0.05). The relative expression level of NLRP3 was positively correlated with the relative mRNA expression levels of ASC and caspase-1 and the serum levels of IL-1β and IL-18 (r=0.701, 0.717, 0.676, and 0.645 respectively; P<0.05).

CONCLUSIONS

The NLRP3 inflammasome signaling pathway might be involved in the pathogenesis of MPP in children and is closely associated with the severity and course of the disease.

Glycans and glycosaminoglycans in neurobiology: key regulators of neuronal cell function and fate

The aim of the present study was to examine the roles of l-fucose and the glycosaminoglycans (GAGs) keratan sulfate (KS) and chondroitin sulfate/dermatan sulfate (CS/DS) with selected functional molecules in neural tissues. Cell surface glycans and GAGs have evolved over millions of years to become cellular mediators which regulate fundamental aspects of cellular survival. The glycocalyx, which surrounds all cells, actuates responses to growth factors, cytokines and morphogens at the cellular boundary, silencing or activating downstream signaling pathways and gene expression. In this review, we have focused on interactions mediated by l-fucose, KS and CS/DS in the central and peripheral nervous systems. Fucose makes critical contributions in the area of molecular recognition and information transfer in the blood group substances, cytotoxic immunoglobulins, cell fate-mediated Notch-1 interactions, regulation of selectin-mediated neutrophil extravasation in innate immunity and CD-34-mediated new blood vessel development, and the targeting of neuroprogenitor cells to damaged neural tissue. Fucosylated glycoproteins regulate delivery of synaptic neurotransmitters and neural function. Neural KS proteoglycans (PGs) were examined in terms of cellular regulation and their interactive properties with neuroregulatory molecules. The paradoxical properties of CS/DS isomers decorating matrix and transmembrane PGs and the positive and negative regulatory cues they provide to neurons are also discussed.

Healthy brain aging: Interplay between reactive species, inflammation and energy supply

Brains' high energy expenditure with preferable utilization of glucose and ketone bodies, defines the specific features of its energy homeostasis. The extensive oxidative metabolism is accompanied by a concomitant generation of high amounts of reactive oxygen, nitrogen, and carbonyl species, which will be here collectively referred to as RONCS. Such metabolism in combination with high content of polyunsaturated fatty acids creates specific problems in maintaining brains' redox homeostasis. While the levels of products of interaction between RONCS and cellular components increase slowly during the first two trimesters of individuals' life, their increase is substantially accelerated towards the end of life. Here we review the main mechanisms controlling the redox homeostasis of the mammalian brain, their age-dependencies as well as their adaptive potential, which might turn out to be much higher than initially assumed. According to recent data, the organism seems to respond to the enhancement of aging-related toxicity by forming a new homeostatic set point. Therefore, further research will focus on understanding the properties of the new set point(s), the general nature of this phenomenon and will explore the limits of brains' adaptivity.