The advanced glycation end product Nϵ -carboxymethyllysine and its precursor glyoxal increase serotonin release from Caco-2 cells

How dietary advanced glycation end products could facilitate the occurrence of food allergy

BACKGROUND

Food allergy (FA) is one of the most common chronic conditions in children with an increasing prevalence facilitated by the exposure to environmental factors in predisposed individuals. It has been hypothesized that the increased consumption of ultra-processed foods, containing high levels of dietary advanced glycation end products (AGEs), could facilitate the occurrence of FA.

OBJECTIVE

We sought to provide preclinical and clinical evidence on the potential role of AGEs in facilitating the occurrence of FA.

METHODS

Human enterocytes, human small intestine organ culture, and PBMCs from children at risk for allergy were used to investigate the direct effect of AGEs on gut barrier, inflammation, TH2 cytokine response, and mitochondrial function. Intake of the 3 most common glycation products in Western diet foods, Nε-(carboxymethyl) lysine, Nε-(1-carboxyethyl) lysin, and Nδ-(5-hydro-5- methyl-4-imidazolone-2-yl)-ornithine (MG-H1), and the accumulation of AGEs in the skin were comparatively investigated in children with FA and in age-matched healthy controls.

RESULTS

Human enterocytes exposed to AGEs showed alteration in gut barrier, AGE receptor expression, reactive oxygen species production, and autophagy, with increased transepithelial passage of food antigens. Small intestine organ cultures exposed to AGEs showed an increase of CD25+ cells and proliferating crypt enterocytes. PBMCs exposed to AGEs showed alteration in proliferation rate, AGE receptor activation, release of inflammatory and TH2 cytokines, and mitochondrial metabolism. Significant higher dietary AGE intake and skin accumulation were observed children with FA (n = 42) compared with age-matched healthy controls (n = 66).

CONCLUSIONS

These data, supporting a potential role for dietary AGEs in facilitating the occurrence of FA, suggest the importance of limiting exposure to AGEs children as a potential preventive strategy against this common condition.

Role of the dietary components in food allergy: A comprehensive review

Currently, the increasing incidence of food allergy is considered a major public health and food safety concern. Importantly, food-induced anaphylaxis is an acute, life-threatening, systemic reaction with varied clinical presentations and severity that results from the release of mediators from mast cells and basophils. Many factors are blamed for the increasing incidence of food allergy, including hygiene, microbiota (composition and diversity), inopportune complementary foods (a high-fat diet), and increasing processed food consumption. Studies have shown that different food components, including lipids, sugars, polyphenols, and vitamins, can modify the immunostimulating properties of allergenic proteins and change their bioavailability. Understanding the role of the food components in allergy might improve diagnosis, treatment, and prevention of food allergy. This review considers the role of the dietary components, including lipids, sugars, polyphenols, and vitamins, in the development of food allergy as well as results of mechanistic investigations in in vivo and in vitro models.

Glyoxal damages human aortic endothelial cells by perturbing the glutathione, mitochondrial membrane potential, and mitogen-activated protein kinase pathways

Background

Exposure to glyoxal, the smallest dialdehyde, is associated with several diseases; humans are routinely exposed to glyoxal because of its ubiquitous presence in foods and the environment. The aim of this study was to examine the damage caused by glyoxal in human aortic endothelial cells.

Methods

Cell survival assays and quantitative fluorescence assays were performed to measure DNA damage; oxidative stress was detected by colorimetric assays and quantitative fluorescence, and the mitogen-activated protein kinase pathways were assessed using western blotting.

Results

Exposure to glyoxal was found to be linked to abnormal glutathione activity, the collapse of mitochondrial membrane potential, and the activation of mitogen-activated protein kinase pathways. However, DNA damage and thioredoxin oxidation were not induced by dialdehydes.

Conclusions

Intracellular glutathione, members of the mitogen-activated protein kinase pathways, and the mitochondrial membrane potential are all critical targets of glyoxal. These findings provide novel insights into the molecular mechanisms perturbed by glyoxal, and may facilitate the development of new therapeutics and diagnostic markers for cardiovascular diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02418-3.

Glyoxal-Lysine Dimer, an Advanced Glycation End Product, Induces Oxidative Damage and Inflammatory Response by Interacting with RAGE

The glyoxal-lysine dimer (GOLD), which is a glyoxal (GO)-derived advanced glycation end product (AGE), is produced by the glycation reaction. In this study, we evaluated the effect of GOLD on the oxidative damage and inflammatory response in SV40 MES 13 mesangial cells. GOLD significantly increased the linkage with the V-type immunoglobulin domain of RAGE, a specific receptor of AGE. We found that GOLD treatment increased RAGE expression and reactive oxygen species (ROS) production in mesangial cells. GOLD remarkably regulated the protein and mRNA expression of nuclear factor erythroid 2-related factor 2 (NRF2) and glyoxalase 1 (GLO1). In addition, mitochondrial deterioration and inflammation occurred via GOLD-induced oxidative stress in mesangial cells. GOLD regulated the mitogen-activated protein kinase (MAPK) and the release of proinflammatory cytokines associated with the inflammatory mechanism of mesangial cells. Furthermore, oxidative stress and inflammatory responses triggered by GOLD were suppressed through RAGE inhibition using RAGE siRNA. These results demonstrate that the interaction of GOLD and RAGE plays an important role in the function of mesangial cells.

Food Contaminants Effects on an In Vitro Model of Human Intestinal Epithelium

Pesticide residues represent an important category of food contaminants. Furthermore, during food processing, some advanced glycation end-products resulting from the Maillard reaction can be formed. They may have adverse health effects, in particular on the digestive tract function, alone and combined. We sought to validate an in vitro model of the human intestinal barrier to mimic the effects of these food contaminants on the epithelium. A co-culture of Caco-2/TC7 cells and HT29-MTX was stimulated for 6 h with chlorpyrifos (300 μM), acrylamide (5 mM), N^ε-Carboxymethyllysine (300 μM) alone or in cocktail with a mix of pro-inflammatory cytokines. The effects of those contaminants on the integrity of the gut barrier and the inflammatory response were analyzed. Since the co-culture responded to inflammatory stimulation, we investigated whether this model could be used to evaluate the effects of food contaminants on the human intestinal epithelium. CPF alone affected tight junctions’ gene expression, without inducing any inflammation or alteration of intestinal permeability. CML and acrylamide decreased mucins gene expression in the intestinal mucosa, but did not affect paracellular intestinal permeability. CML exposure activated the gene expression of MAPK pathways. The co-culture response was stable over time. This cocktail of food contaminants may thus alter the gut barrier function.

Nε -carboxymethyllysine and Nε -carboxyethyllysine kinetics and water loss analysis during chicken braising

BACKGROUND

Braised chicken is one of the well-known traditional processed meat products in China. However, reports are scarce with respect to the formation of N^ɛ -carboxymethyllysine (CML) and N^ɛ -carboxyethyllysine (CEL) during chicken braising. Furthermore, braising for a long time and using high-temperature process will result in water loss. However, the relationship between water loss and advanced glycation end products (AGEs) kinetics is limited. The present study aimed to investigate the relationship between water loss and kinetics of free and protein-bound CML and CEL in braised chicken under different braising conditions (60-100 °C for 5-60 min).

RESULTS

Levels of free and protein-bound CML and CEL were found to increase with heating time and temperature. The correlation coefficient (r² ) was largest at zero-order reaction (free CML: r² = 0.908-0.954, protein-bound CML: r² = 0.901-0.958, free CEL: r² = 0.952-0.973, protein-bound CEL: r² = 0.959-0.965). The activation energy was 44.158 ± 3.638 kJ mol^-1 for free CML, 40.041 ± 3.438 kJ mol^-1 for protein-bound CML, 40.971 ± 0.334 kJ mol^-1 for free CEL and 40.247 ± 0.553 kJ mol^-1 for protein-bound CEL. Furthermore, with the increase of braising time and temperature, the drip loss and cooking loss also became aggravated. A significant positive correlation between water loss and AGEs levels during braising was observed by Pearson's correlation analysis (P < 0.05).

CONCLUSION

We conclude that the levels of free and protein-bound CML and CEL during braising were different, although they all met zero-order reaction kinetics. Water loss was probably one of the main reasons for the formation of AGEs during chicken braising. © 2020 Society of Chemical Industry.

High-Efficiency Reverse (5'→3') Synthesis of Complex DNA Microarrays

DNA microarrays are important analytical tools in genetics and have recently found multiple new biotechnological roles in applications requiring free 3' terminal hydroxyl groups, particularly as a starting point for enzymatic extension via DNA or RNA polymerases. Here we demonstrate the highly efficient reverse synthesis of complex DNA arrays using a photolithographic approach. The method is analogous to conventional solid phase synthesis but makes use of phosphoramidites with the benzoyl-2-(2-nitrophenyl)-propoxycarbonyl (BzNPPOC) photolabile protecting group on the 3'-hydroxyl group. The use of BzNPPOC, with more than twice the photolytic efficiency of the 2-(2-nitrophenyl)-propoxycarbonyl (NPPOC) previously used for 5'→3' synthesis, combined with additional optimizations to the coupling and oxidation reactions results in an approximately 3-fold improvement in the reverse synthesis efficiency of complex arrays of DNA oligonucleotides. The coupling efficiencies of the reverse phosphoramidites are as good as those of regular phosphoramidites, resulting in comparable yields. Microarrays of DNA surface tethered on the 5' end and with free 3' hydroxyl termini can be synthesized quickly and with similarly high stepwise coupling efficiency as microarrays using conventional 3'→5' synthesis.

Impact of free Nε-carboxymethyllysine, its precursor glyoxal and AGE-modified BSA on serotonin release from human parietal cells in culture

Advanced glycation end products (AGEs) are frequently encountered in a western diet, in addition to their formation in vivo. N-Epsilon-carboxymethyllysine (CML), one of the chemically diverse compounds formed in the reaction between reducing carbohydrates and amines, is often used as a marker of advanced glycation, and has been shown to stimulate serotonin release from cells representing the central (SH-SY5Y cells) and the peripheral (Caco-2 cells) serotonin system in vitro. Here, we investigated the effect of glyoxal, free CML, and protein-linked AGE-BSA on serotonin release from human gastric tumour cells, which originate from an adenocarcinoma of the stomach and have recently been shown to be capable of serotonin synthesis and release. Microarray experiments showed both CML and glyoxal to alter genes associated with serotonin receptors. Furthermore, treatment with glyoxal resulted in a small change in RAGE expression while CML did not alter its expression. On a functional level, treatment with 500 μM CML increased extracellular serotonin content by 341 ± 241%, while treatment with 1 mg mL-1 AGE-BSA led to a reduction by 49 ± 11% compared to non-treated cells. The CML-induced serotonin release was reduced by the HTR3 antagonist granisetron. Incubation with the RAGE antagonist FPS-ZM1 abolished the effect of AGE-BSA on serotonin release, while no impact on CML-induced serotonin release was observed. Furthermore, treatment with 5 mM CML stimulated proton secretion as a functional outcome measure, assessed using a pH sensitive dye. Taken together, these results indicate a likely HTR3-mediated, RAGE-independent effect of free CML on serotonin release and a RAGE-dependent mechanism for the protein linked AGE-BSA.