Methylglyoxal-bovine serum albumin stimulates tumor necrosis factor alpha secretion in RAW 264.7 cells through activation of mitogen-activating protein kinase, nuclear factor kappaB and intracellular reactive oxygen species formation

Intracellular methylglyoxal accumulation in classically activated mouse macrophages is mediated by HIF-1α

Approximately one million cases of sepsis in the United States occur annually. The early phase of sepsis features dramatic changes in host metabolism and inflammation. While examining the effects of metabolic pathways on inflammation, we discovered that the highly reactive glycolytic metabolite, methylglyoxal (MG), accumulates intracellularly during classical activation of macrophages. Herein, we explored the role of glycolysis and the master regulator of glycolysis, Hypoxia-Inducing Factor-1α (HIF-1α), in inflammation and MG accumulation in mouse and human macrophages. To determine how HIF-1α regulates the inflammatory response of macrophages, we correlated HIF-1α stabilization with proinflammatory gene expression and MG-adduct accumulation in WT vs HIF1a-deficient macrophages treated with LPS or LPS + IFN-γ. A nearly complete loss of HIF-1α protein expression in response to the hypoxia mimetic, cobalt chloride, confirmed the phenotype of the HIF1a-deficient macrophages. Moreover, absence of HIF-1α was also associated with decreased MG accumulation. Increasing the glucose concentration in cultured macrophages was sufficient to cause accumulation of endogenous MG-adducts which correlated with increased Tnf and Il1b expression during classical activation. The use of the MG antagonist, aminoguanidine, led to a significant decrease in Tnf and Il1b expression in both mouse macrophages and the THP-1 human macrophage cell line. Although off-target effects cannot be ruled out, these results are consistent with the possibility that MG regulates cytokine expression in classically activated macrophages. Collectively, this work suggests that HIF-1α stabilization is upstream of MG accumulation and that targeting the activity of HIF-1α in macrophages may be therapeutic during sepsis by limiting endogenous MG accumulation.

Diabetic Glycation of Human Serum Albumin Affects Its Immunogenicity

Advanced glycation end-products (AGEs) are products of a non-enzymatic reaction between amino acids and reducing sugars. Glycated human serum albumin (HSA) increases in diabetics as a consequence of elevated blood glucose levels and glycating metabolites like methylglyoxal (MGO). The impact of different types of glycation on the immunomodulatory properties of HSA is poorly understood and is studied here. HSA was glycated with D-glucose, MGO, or glyoxylic acid (CML). Glycation-related biochemical changes were characterized using various biochemical methods. The binding of differentially glycated HSA to AGE receptors was determined with inhibition ELISAs, and the impact on inflammatory markers in macrophage cell line THP-1 and adherent monocytes isolated from human peripheral blood mononuclear cells (PBMCs) was studied. All glycation methods led to unique AGE profiles and had a distinct impact on protein structure. Glycation resulted in increased binding of HSA to the AGE receptors, with MGO modification showing the highest binding, followed by glucose and, lastly, CML. Additionally, modification of HSA with MGO led to the increased expression of pro-inflammatory markers in THP-1 macrophages and enhanced phosphorylation of NF-κB p65. The same pattern, although less prominent, was observed for HSA glycated with glucose and CML, respectively. An increase in pro-inflammatory markers was also observed in PBMC-derived monocytes exposed to all glycated forms of HSA, although HSA-CML led to a significantly higher inflammatory response. In conclusion, the type of HSA glycation impacts immune functional readouts with potential relevance for diabetes.

A quasi-experimental study assessing the effectiveness of a community-based egg intervention in the nutritional and health status of young children from rural Honduras

OBJECTIVE

This community-public-private-academic coalition project implemented and evaluated the effectiveness of a rural, community-based egg intervention that aimed to support the nutrition and health of children living in rural, poor communities from Intibucá, Honduras, during the COVID-19 pandemic.

DESIGN

This investigator-blind, non-randomized, controlled study was informed by a community health improvement process and participatory research. Women from 13 communities were given a microloan to start an egg farm that supplied 1 egg daily to 201 children ages 6-24 months for 1 year (intervention group). Control communities (n = 14) were selected from neighboring municipalities with similar sociodemographic backgrounds based on size. Sociodemographic-, anthropometric-, and morbidity data were collected biannually between January 2021 to January 2022. Outcome changes were compared with linear-, generalized- or Poisson- mixed models adjusted by sex, age, maternal education, breastfeeding status, assets, adults living at home, baseline outcomes, and community-cluster.

RESULTS

Baseline to 6- and 12-month weekly frequency of egg intake significantly increased in the intervention vs. the control group: 6-month change = 1.86; 95%CI (1.61, 2.14); 12-month change = 1.63; 95%CI (1.42, 1.87 p<0.001), respectively. Baseline to 12-month changes in the intervention group were not significant for length/height-for-age-z-scores = 0.12, p = 0.187; weight-for-length/height-z-scores = -0.02, p = 0.78; and diarrhea prevalence, AOR = 1.69; 95%CI (0.53, 5.42), p = 0.378. Lower odds of respiratory infections were observed for the intervention vs. the control group at 6- and 12-month post: AOR = 0.28; 95%CI (0.12, 0.63), p = 0.002; AOR = 0.30; 95%CI (0.12, 0.75), p = 0.010, respectively.

CONCLUSIONS AND RELEVANCE

Children in the intervention group reported consuming eggs more days per week relative to the control group. Lower odds of respiratory infections were observed in the intervention group throughout the study. Ongoing follow-up will offer more insights on the intervention's effectiveness in linear growth, dietary diversity, food security, and other nutritional outcomes.

Nanomaterials-Involved Tumor-Associated Macrophages' Reprogramming for Antitumor Therapy

Tumor-associated macrophages (TAMs) play pivotal roles in tumor development. As primary contents of tumor environment (TME), TAMs secrete inflammation-related substances to regulate tumoral occurrence and development. There are two kinds of TAMs: the tumoricidal M1-like TAMs and protumoral M2-like TAMs. Reprogramming TAMs from immunosuppressive M2 to immunocompetent M1 phenotype is considered a feasible way to improve immunotherapeutic efficiency. Notably, nanomaterials show great potential for biomedical fields due to their controllable structures and properties. There are many types of nanomaterials that exhibit great regulatory activities for TAMs' reprogramming. In this review, the recent progress of nanomaterials-involved TAMs' reprogramming is comprehensively discussed. The various nanomaterials for TAMs' reprogramming and the reprogramming strategies are summarized and introduced. Additionally, the challenges and perspectives of TAMs' reprogramming for efficient therapy are discussed, aiming to provide inspiration for TAMs' regulator design and promote the development of TAMs-mediated immunotherapy.

Methylglyoxal in Cardiometabolic Disorders: Routes Leading to Pathology Counterbalanced by Treatment Strategies

Methylglyoxal (MGO) is the major compound belonging to reactive carbonyl species (RCS) responsible for the generation of advanced glycation end products (AGEs). Its upregulation, followed by deleterious effects at the cellular and systemic levels, is associated with metabolic disturbances (hyperglycemia/hyperinsulinemia/insulin resistance/hyperlipidemia/inflammatory processes/carbonyl stress/oxidative stress/hypoxia). Therefore, it is implicated in a variety of disorders, including metabolic syndrome, diabetes mellitus, and cardiovascular diseases. In this review, an interplay between pathways leading to MGO generation and scavenging is addressed in regard to this system's impairment in pathology. The issues associated with mechanistic MGO involvement in pathological processes, as well as the discussion on its possible causative role in cardiometabolic diseases, are enclosed. Finally, the main strategies aimed at MGO and its AGEs downregulation with respect to cardiometabolic disorders treatment are addressed. Potential glycation inhibitors and MGO scavengers are discussed, as well as the mechanisms of their action.

Porous Silicon Nanocarriers Boost the Immunomodulation of Mitochondria-Targeted Bovine Serum Albumins on Macrophage Polarization

The development of nanosystems with intrinsic immunomodulatory effects on macrophage polarization is important for the macrophage-targeted immunotherapy. Here, mitochondria-targeted bovine serum albumins (BSAs) via the conjugation of fluorescent, lipophilic, and cationic rhodamine 110 molecules can efficiently enhance the gene expression of the proinflammatory phenotype of macrophages and correspondingly inhibit the gene expression of their anti-inflammatory phenotype. On this basis, porous silicon nanocarriers can further boost the immunomodulation of these mitochondria-targeted BSAs in vitro or in vivo, accompanied by the secretion of proinflammatory mediators including tumor necrosis factor α, nitric oxide, and reactive oxygen species (ROS). Meanwhile, BSA coatings can also improve the biocompatibility of porous silicon nanoparticulate cores on macrophages. Finally, the mechanism investigations demonstrate that porous silicon nanocarriers can efficiently deliver mitochondria-targeted BSA into macrophages to generate mitochondrial ROS via the interference with mitochondrial respiratory chains, which can further trigger the downstream signaling transduction pathways for the proinflammatory transition. Considering the good biosafety and versatile loading capability, this developed porous silicon@BSA nanosystem with a strong proinflmmatory regulatory effect has important potential on the combinatorial chemoimmunotherapy against cancer or viral/bacterial-related infectious diseases.

Anti-Alzheimer's disease potential of traditional chinese medicinal herbs as inhibitors of BACE1 and AChE enzymes

Alzheimer's disease (AD) is a common neurodegenerative disease that often occurs in the elderly population. At present, most drugs for AD on the market are single-target drugs, which have achieved certain success in the treatment of AD. However, the efficacy and safety of single-target drugs have not achieved the expected results because AD is a multifactorial disease. Multi-targeted drugs act on multiple factors of the disease network to improve efficacy and reduce adverse reactions. Therefore, the search for effective dual-target or even multi-target drugs has become a new research trend. Many of results found that the dual-target inhibitors of the beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) and acetylcholinesterase (AChE) found from traditional Chinese medicine have a good inhibitory effect on AD with fewer side effects. This article reviews sixty-six compounds extracted from Chinese medicinal herbs, which have inhibitory activity on BACE1 and AChE. This provides a theoretical basis for the further development of these compounds as dual-target inhibitors for the treatment of AD.

Diet and Obesity-Induced Methylglyoxal Production and Links to Metabolic Disease

The obesity rate in the United States is 42.4% and has become a national epidemic. Obesity is a complex condition that is influenced by socioeconomic status, ethnicity, genetics, age, and diet. Increased consumption of a Western diet, one that is high in processed foods, red meat, and sugar content, is associated with elevated obesity rates. Factors that increase obesity risk, such as socioeconomic status, also increase consumption of a Western diet because of a limited access to healthier options and greater affordability of processed foods. Obesity is a public health threat because it increases the risk of several pathologies, including atherosclerosis, diabetes, and cancer. The molecular mechanisms linking obesity to disease onset and progression are not well understood, but a proposed mechanism is physiological changes caused by altered lipid peroxidation, glycolysis, and protein metabolism. These metabolic pathways give rise to reactive molecules such as the abundant electrophile methylglyoxal (MG), which covalently modifies nucleic acids and proteins. MG-adducts are associated with obesity-linked pathologies and may have potential for biomonitoring to determine the risk of disease onset and progression. MG-adducts may also play a role in disease progression because they are mutagenic and directly impact protein stability and function. In this review, we discuss how obesity drives metabolic alterations, how these alterations lead to MG production, the association of MG-adducts with disease, and the potential impact of MG-adducts on cellular function.

Dairy-Derived and Egg White Proteins in Enhancing Immune System Against COVID-19

Coronavirus disease (COVID-19) is a global health challenge, caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) triggers a plethora of respiratory disturbances and even multiple organs failure that can be fatal. Nutritional intervention is one of the key components toward to a proper management of COVID-19 patients, especially in those requiring medication, and should thus be considered the first-line treatment. Immuno-modulation and -stimulation are currently being explored in COVID-19 management and are gaining interest by food and pharmaceutical industries. Various dietary combinations, bioactive components, nutrients and fortified foods have been reported to modulate inflammation during disease progression. Dietary combinations of dairy-derived products and eggs are gaining an increasing attention given the huge immunomodulatory and anti-inflammatory properties attributed to some of their chemical constituents. Eggs are complex dietary components containing many essential nutrients and bioactive compounds as well as a high-quality proteins. Similarly, yogurts can replenish beneficial bacteria and contains macronutrients capable of stimulating immunity by enhancing cell immunity, reducing oxidative stress, neutralizing inflammation and regulating the intestinal barriers and gut microbiome. Thus, this review highlights the impact of nutritional intervention on COVID-19 management, focusing on the immunomodulatory and inflammatory effects of immune-enhancing nutrients.

Methylglyoxal Drives a Distinct, Nonclassical Macrophage Activation Status

Metabolic complications in diabetic patients are driven by a combination of increased levels of nutrients and the presence of a proinflammatory environment. Methylglyoxal (MG) is a toxic byproduct of catabolism and has been strongly associated with the development of such complications. Macrophages are key mediators of inflammatory processes and their contribution to the development of metabolic complications has been demonstrated. However, a direct link between reactive metabolites and macrophage activation has not been demonstrated yet. Here, we show that acute MG treatment activated components of the p38 MAPK pathway and enhanced glycolysis in primary murine macrophages. MG induced a distinct gene expression profile sharing similarities with classically activated proinflammatory macrophages as well as metabolically activated macrophages usually found in obese patients. Transcriptomic analysis revealed a set of 15 surface markers specifically upregulated in MG-treated macrophages, thereby establishing a new set of targets for diagnostic or therapeutic purposes under high MG conditions, including diabetes. Overall, our study defines a new polarization state of macrophages that may specifically link aberrant macrophage activation to reactive metabolites in diabetes.

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.

Albumin Reduces Oxidative Stress and Neuronal Apoptosis via the ERK/Nrf2/HO-1 Pathway after Intracerebral Hemorrhage in Rats

BACKGROUND

Albumin has been regarded as a potent antioxidant with free radical scavenging activities. Oxidative stress and neuronal apoptosis are responsible for its highly damaging effects on brain injury after intracerebral hemorrhage (ICH). Here, the present study investigated the neuroprotective effect of albumin against early brain injury after ICH and the potential underlying mechanisms.

METHODS

Adult male Sprague-Dawley rats were subjected to intrastriatal injection of autologous blood to induce ICH. Human serum albumin was given by intravenous injection 1 h after ICH. U0126, an inhibitor of extracellular signal-regulated kinase (ERK1/2), and ML385, an inhibitor of nuclear factor-E2-related factor 2 (Nrf2), were intraperitoneally administered 1 h before ICH induction. Short- and long-term neurobehavioral tests, western blotting, immunofluorescence staining, oxidative stress evaluations, and apoptosis measurements were performed.

RESULTS

Endogenous expression of albumin (peaked at 5 days) and heme oxygenase 1 (HO-1, peaked at 24 h) was increased after ICH compared with the sham group. Albumin and HO-1 were colocalized with neurons. Compared with vehicle, albumin treatment significantly improved short- and long-term neurobehavioral deficits and reduced oxidative stress and neuronal death at 72 h after ICH. Moreover, albumin treatment significantly promoted the phosphorylation of ERK1/2; increased the expression of Nrf2, HO-1, and Bcl-2; and downregulated the expression of Romo1 and Bax. U0126 and ML385 abolished the treatment effects of albumin on behavior and protein levels after ICH.

CONCLUSIONS

Albumin attenuated oxidative stress-related neuronal death may in part via the ERK/Nrf2/HO-1 signaling pathway after ICH in rats. Our study suggests that albumin may be a novel therapeutic method to ameliorate brain injury after ICH.

Anticancer and immunomodulatory activity of egg proteins and peptides: a review

Eggs are widely recognized as a highly nutritious food source that offer specific health benefits for humans. Eggs contain all of the proteins, lipids, vitamins, minerals, and growth factors necessary for embryonic development. In particular, egg white and yolk proteins are considered functional food substances because they possess biological activities such as antimicrobial, antioxidant, metal-chelating, antihypertensive, anticancer, and immunomodulatory activities. Peptides produced via processes such as enzymatic hydrolysis, fermentation by microorganisms, and some chemical and physical treatments of egg proteins have been shown to enhance the functional properties and solubility of these peptides. Peptide activity is strongly related to amino acid sequence, composition, and length. At present, cancer remains among the leading causes of mortality worldwide, and therefore research aimed at developing new treatments for cancer immunotherapy is of great interest. The present review focuses primarily on the anticancer and immunomodulatory activities of egg proteins and their peptides and provides some insight into their underlying mechanisms of action. A number of egg proteins and peptides have been reported to induce apoptosis in cancer cells, protect against DNA damage, decrease the invasion ability of cancer cells, and exhibit cytotoxic and antimutagenic activity in various cancer cell lines. Furthermore, egg proteins and peptides can stimulate or suppress pro- or anti-inflammatory cytokines, as well as affect the production of inflammatory mediators in a variety of cell lines. In addition, the composition of eggs and the processes of egg proteins and peptides production will be discussed.

Identification of ovalbumin-derived peptides as multi-target inhibitors of AChE, BChE, and BACE1

BACKGROUND

Alzheimer's disease (AD) is a kind of progressive neurodegenerative disease that affects the elderly. There is no ideal treatment for AD. Thus, the purpose of this study is to identify anti-AD peptides from ovalbumin.

RESULTS

The potential tripeptides IEK, LYR, and CIK were selected for molecular docking. The '-CDOCKER_Energy' values of the best docking positions of the tripeptide IEK, LYR, and CIK interacting with acetylcholinesterase (AChE) were 93.8119, 86.9556 and 73.6370 kcal mol^-1 , respectively. The '-CDOCKER_Energy' values for interaction with butyrylcholinesterase (BChE) were 96.6386, 80.8392, and 87.4341 kcal mol^-1 , respectively. Most importantly, the '-CDOCKER_Energy' values for interaction with β-site amyloid precursor protein cleavage enzyme1 (BACE1) were 85.5903, 71.3342, and 68.4290 kcal mol^-1 , respectively. Overall, in vitro assay results demonstrated that the peptide CIK exhibited impressive inhibitory activities against AChE, BChE, and BACE1, with half maximal inhibitory concentration (IC₅₀ ) values of 6.76, 7.72, and 34.48 μmol L^-1 , respectively. In particular, CIK can be joined with some peripheral anion sites (PAS) and catalytic sites on AChE, BChE, and BACE1.

CONCLUSION

Tripeptide CIK can effectively inhibit the activities of AChE, BChE, and BACE1. Tripeptide CIK therefore has the potential to treat AD effectively. © 2020 Society of Chemical Industry.

Methylglyoxal, a Highly Reactive Dicarbonyl Compound, in Diabetes, Its Vascular Complications, and Other Age-Related Diseases

The formation and accumulation of methylglyoxal (MGO), a highly reactive dicarbonyl compound, has been implicated in the pathogenesis of type 2 diabetes, vascular complications of diabetes, and several other age-related chronic inflammatory diseases such as cardiovascular disease, cancer, and disorders of the central nervous system. MGO is mainly formed as a byproduct of glycolysis and, under physiological circumstances, detoxified by the glyoxalase system. MGO is the major precursor of nonenzymatic glycation of proteins and DNA, subsequently leading to the formation of advanced glycation end products (AGEs). MGO and MGO-derived AGEs can impact on organs and tissues affecting their functions and structure. In this review we summarize the formation of MGO, the detoxification of MGO by the glyoxalase system, and the biochemical pathways through which MGO is linked to the development of diabetes, vascular complications of diabetes, and other age-related diseases. Although interventions to treat MGO-associated complications are not yet available in the clinical setting, several strategies to lower MGO have been developed over the years. We will summarize several new directions to target MGO stress including glyoxalase inducers and MGO scavengers. Targeting MGO burden may provide new therapeutic applications to mitigate diseases in which MGO plays a crucial role.

Bioactive Egg Proteins

The nutritional excellence of chicken egg is derived from its task as a life-giving medium, supplying the necessary nutrients to the hen's embryo while protecting it from external threats. Additionally, egg proteins possess unique biological activities above and beyond their known functional and nutritional roles. In the last few decades, extensive research has been done to evaluate the various biological activities of egg proteins and protein-derived peptides. Egg proteins and protein-derived peptides have been attributed to diverse biological activities, the most well-known being their antimicrobial properties. However, egg proteins and peptides have been shown to have other biological activities, such as antihypertensive, antioxidant, anticancer, immunomodulatory, and protease inhibitory activity. Egg-derived bioactive proteins have had a relevant scientific impact and exhibit promising applicability as an ingredient for the development of functional foods and nutraceuticals. However, it is critical to understand the effects of these proteins in signaling pathways to delineate their molecular mechanisms of action. Further studies are required to fill the current knowledge gaps. Therefore, the purpose of the chapter is to illustrate the present knowledge of the bioactivity of different egg proteins and their physiological effects.

Inflammatory Mechanisms as New Biomarkers and Therapeutic Targets for Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of CKD and end-stage kidney disease (ESKD) worldwide. Approximately 30-40% of people with diabetes develop this microvascular complication, placing them at high risk of losing kidney function as well as of cardiovascular events, infections, and death. Current therapies are ineffective for arresting kidney disease progression and mitigating risks of comorbidities and death among patients with DKD. As the global count of people with diabetes will soon exceed 400 million, the need for effective and safe treatment options for complications such as DKD becomes ever more urgent. Recently, the understanding of DKD pathogenesis has evolved to recognize inflammation as a major underlying mechanism of kidney damage. In turn, inflammatory mediators have emerged as potential biomarkers and therapeutic targets for DKD. Phase 2 clinical trials testing inhibitors of monocyte-chemotactic protein-1 chemokine C-C motif-ligand 2 and the Janus kinase/signal transducer and activator of transcription pathway, in particular, have produced promising results.

Peptides: Production, bioactivity, functionality, and applications

Production of peptides with various effects from proteins of different sources continues to receive academic attention. Researchers of different disciplines are putting increasing efforts to produce bioactive and functional peptides from different sources such as plants, animals, and food industry by-products. The aim of this review is to introduce production methods of hydrolysates and peptides and provide a comprehensive overview of their bioactivity in terms of their effects on immune, cardiovascular, nervous, and gastrointestinal systems. Moreover, functional and antioxidant properties of hydrolysates and isolated peptides are reviewed. Finally, industrial and commercial applications of bioactive peptides including their use in nutrition and production of pharmaceuticals and nutraceuticals are discussed.

The structural damages of lens crystallins induced by peroxynitrite and methylglyoxal, two causative players in diabetic complications and preventive role of lens antioxidant components

Peroxynitrite (PON) and methylglyoxal (MGO), two diabetes-associated compounds, are believed to be important causative players in development of diabetic cataracts. In the current study, different spectroscopic methods, gel electrophoresis, lens culture and microscopic assessments were applied to examine the impact of individual, subsequent or simultaneous modification of lens crystallins with MGO and PON on their structure, oligomerization and aggregation. The protein modifications were confirmed with detection of the significantly increased quantity of carbonyl groups and decreased levels of sulfhydryl, tyrosine and tryptophan. Also, lens proteins modification with these chemical agents was accompanied with important structural alteration, oligomerization, disulfide/chromophore mediated protein crosslinking and important proteolytic instability. All these structural damages were more pronounced when the lens proteins were modified in the presence of both mentioned chemical agents, either in sequential or simultaneous manner. Ascorbic acid and glutathione, as the main components of lens antioxidant defense mechanism, were also capable to markedly prevent the damaging effects of PON and MGO on lens crystallins, as indicated by gel electrophoresis. The results of this study may highlight the importance of lens antioxidant defense system in protection of crystallins against the structural insults induced by PON and MGO during chronic hyperglycemia in the diabetic patients.

An overview of in vitro and in vivo glycation of albumin: a potential disease marker in diabetes mellitus

Non-enzymatic glycation of macromolecules, especially proteins leading to their oxidation is increased in diabetes mellitus due to hyperglycaemia and play an important role in associated complications of the disease. Protein glycation mostly occurs in intra chain lysine residues resulting in the formation of early stage Amadori products which are finally converted to advance glycation end products (AGEs). This review deals with the structural studies of in vitro and in vivo glycated human serum albumin (HSA). The aim of this review is to explain the disturbance in secondary and tertiary structure of albumin upon glucosylation and the immunogenic potential of modified albumin. Amadori-albumin may have enough potential to provoke the immunoregulatry cells and generate autoantibodies in diabetic patients. Role of Amadori-albumin in the induction of autoantibodies in type2 diabetes especially in chronic kidney disease (CKD) patients has been discussed. This review also considers various studies that investigate the effects of glycation on the structural and immunological properties of HSA. The use of glycated albumin (GA) as a short to intermediate term marker for glycaemic control in diabetes is also focused.

Food-derived immunomodulatory peptides

Food proteins contain specific amino acid sequences within their structures that may positively impact bodily functions and have multiple immunomodulatory effects. The functional properties of these specific sequences, also referred to as bioactive peptides, are revealed only after the degradation of native proteins during digestion processes. Currently, milk proteins have been the most explored source of bioactive peptides, which presents an interesting opportunity for the dairy industry. However, plant- and animal-derived proteins have also been shown to be important sources of bioactive peptides. This review summarizes the in vitro and in vivo evidence of the role of various food proteins as sources of immunomodulatory peptides and discusses the possible pathways involving these properties. © 2016 Society of Chemical Industry.

Methylglyoxal-Induced Endothelial Cell Loss and Inflammation Contribute to the Development of Diabetic Cardiomyopathy

The mechanisms for the development of diabetic cardiomyopathy remain largely unknown. Methylglyoxal (MG) can accumulate and promote inflammation and vascular damage in diabetes. We examined if overexpression of the MG-metabolizing enzyme glyoxalase 1 (GLO1) in macrophages and the vasculature could reduce MG-induced inflammation and prevent ventricular dysfunction in diabetes. Hyperglycemia increased circulating inflammatory markers in wild-type (WT) but not in GLO1-overexpressing mice. Endothelial cell number was reduced in WT-diabetic hearts compared with nondiabetic controls, whereas GLO1 overexpression preserved capillary density. Neuregulin production, endothelial nitric oxide synthase dimerization, and Bcl-2 expression in endothelial cells was maintained in the hearts of GLO1-diabetic mice and corresponded to less myocardial cell death compared with the WT-diabetic group. Lower receptor for advanced glycation end products and tumor necrosis factor-α (TNF-α) levels were also observed in GLO1-diabetic versus WT-diabetic mice. Over a period of 8 weeks of hyperglycemia, GLO1 overexpression delayed and limited the loss of cardiac function. In vitro, MG and TNF-α were shown to synergize in promoting endothelial cell death, which was associated with increased angiopoietin 2 expression and reduced Bcl-2 expression. These results suggest that MG in diabetes increases inflammation, leading to endothelial cell loss. This contributes to the development of diabetic cardiomyopathy and identifies MG-induced endothelial inflammation as a target for therapy.

Impact of glycation on structural and antioxidant function of human serum albumin: Relevance in diabetic complications

AIM

Non-enzymatic glycation impairs the structural and functional characterstics of human serum albumin (HSA) native conformation. Prolonged hyperglycemia causes cross links formation in proteins that may contribute to progression of diabetic complications.

METHODS

HSA (20μM) was incubated with different concentration of d-glucose100, 200, 300 and 400mg/dl for a period of 40 days in phosphate buffer saline (20mM pH=7.4) under sterile conditions. Incubated samples were extensively dialyzed and structural changes were analyzed by far and near UV circular dichroism spectra measurement. Fructosamine assay with nitroblue tetrazolonium was performed to confer isomerisation between glucose and protein. Aggregations of the glycated product (AGEs) formed during reduction of nitrobluetetrazolium dye were evaluated by transmission electron microscopy. Crosslinks aggregates were investigated by in-situ Congo red binding assay. Red blood cells hemolysis test was performed to decipher the antioxidant activity of albumin samples.

RESULTS

Fructosamine content in glycated albumin demonstrates the non-enzymatic addition of glucose to HSA and confers the formation of monoformazone (marker of glycation). Significant changes were found in the glycated samples of HSA compared to native (unmodified) in far and near UV circular dichroism. Transmission electron microscopy, Congo red staining, showed the formation of crosslink's aggregated mass in glycated HSA. Glycation of albumin reduces the antioxidant capacity of native albumin confirmed by red blood cells hemolysis test.

CONCLUSION

The finding of present study brings new evidences on the detrimental alterations of on albumin vital functions after non-enzymatic glycation with glucose. These results may emphasize the albumin associated diabetic complications under glycemic range of diabetes mellitus.

Effects of ROS-relative NF-κB signaling on high glucose-induced TLR4 and MCP-1 expression in podocyte injury

High glucose (HG) induced inflammation is central to progression in diabetic nephropathy (DN). Recent studies have suggested that nuclear factor-kappa B (NF-κB) signaling activation is associated with DN, and podocyte damage may be involved in orchestrating these effects. Therefore, the aim of this study was to investigate the effects of NF-κB signaling on podocytes under HG conditions. The effects of HG and NF-κB signaling on podocytes were assessed by CCK-8 assay, cellular NF-κB translocation assay, measurement of reactive oxygen species (ROS) and Western blot analysis. We found that HG reduced cell viability, activated NF-κB signaling and up-regulated toll-like receptor 4 (TLR4) and monocyte chemoattractant protein-1 (MCP-1). In these cells, NF-κB inhibition with ammonium pyrrolidinethiocarbamate (PDTC) resulted in effectively constraining TLR4 and MCP-1 up-regulation, indicating that protective effects associated with the inhibition of NF-κB were linked to TLR4 and MCP-1 down-regulation in podocytes. Furthermore, HG significantly increased the production of intracellular ROS. Pretreatment with N-acetyl-l-cysteine (NAC) significantly inhibited intracellular ROS generation and increased cell viability, accompanied by a significant NF-κB inhibition and suppression of TLR4 and inflammatory cytokine MCP-1 expression. Collectively, our novel data suggest that HG induces the over-experssion of TLR-4 and MCP-1 through a NF-κB-dependent signaling. NF-κB-mediated increased inflammation is possibly via ROS and contributes to the cell injury. These results may provide potential therapeutic target for diabetic nephropathy in the future.

The role of methylglyoxal and the glyoxalase system in diabetes and other age-related diseases

The formation and accumulation of advanced glycation endproducts (AGEs) are related to diabetes and other age-related diseases. Methylglyoxal (MGO), a highly reactive dicarbonyl compound, is the major precursor in the formation of AGEs. MGO is mainly formed as a byproduct of glycolysis. Under physiological circumstances, MGO is detoxified by the glyoxalase system into D-lactate, with glyoxalase I (GLO1) as the key enzyme in the anti-glycation defence. New insights indicate that increased levels of MGO and the major MGO-derived AGE, methylglyoxal-derived hydroimidazolone 1 (MG-H1), and dysfunctioning of the glyoxalase system are linked to several age-related health problems, such as diabetes, cardiovascular disease, cancer and disorders of the central nervous system. The present review summarizes the mechanisms through which MGO is formed, its detoxification by the glyoxalase system and its effect on biochemical pathways in relation to the development of age-related diseases. Although several scavengers of MGO have been developed over the years, therapies to treat MGO-associated complications are not yet available for application in clinical practice. Small bioactive inducers of GLO1 can potentially form the basis for new treatment strategies for age-related disorders in which MGO plays a pivotal role.

Bioactive peptides from egg: a review

Purpose

– The aim of the article was to focus on various peptides identified in the egg and their probable application as novel ingredients in the development of functional food products. Bioactive peptides of egg origin have attracted increasing interest as one of the prominent candidates for development of various health-promoting functional and designer foods.

Design/methodology/approach

– Traditionally known as a source of highly valuable proteins in human nutrition, eggs are nowadays also considered as an important source of many bioactive peptides which may find wide application in medicine and food production. These specific protein fragments from egg proteins which, above and beyond their nutritional capabilities, have a positive impact on the body’s function or condition by affecting the digestive, endocrine, cardiovascular, immune and nervous systems, and may ultimately influence health.

Findings

– Several peptides that are released in vitro or in vivo from egg proteins have been attributed to different health effects, including antihypertensive effects, antimicrobial properties, antioxidant activities, anticancer activity, immunomodulating activity, antiadhesive properties and enhancement of nutrient absorption and/or bioavailability. Extensive research has been undertaken to identify and characterize these biologically active peptides of egg origin which has changed the image of egg as a new source of biologically active ingredients for the development of functional foods with specific benefits for human health and treatment and prevention of diseases.

Originality/value

– The paper mainly describes the above-stated properties of bioactive peptides derived from egg proteins.

Glycated Serum Albumin and AGE Receptors

In vivo modification of proteins by molecules with reactive carbonyl groups leads to intermediate and advanced glycation end products (AGE). Glucose is a significant glycation reagent due to its high physiological concentration and poorly controlled diabetics show increased albumin glycation. Increased levels of glycated and AGE-modified albumin have been linked to diabetic complications, neurodegeneration, and vascular disease. This review discusses glycated albumin formation, structural consequences of albumin glycation on drug binding, removal of circulating AGE by several scavenger receptors, as well as AGE-induced proinflammatory signaling through activation of the receptor for AGE. Analytical methods for quantitative detection of protein glycation and AGE formation are compared. Finally, the use of glycated albumin as a novel clinical marker to monitor glycemic control is discussed and compared to glycated hemoglobin (HbA1c) as long-term indicator of glycemic status.

Dicarbonyl stress in the absence of hyperglycemia increases endothelial inflammation and atherogenesis similar to that observed in diabetes

The deleterious effects of high glucose levels and enhanced metabolic flux on the vasculature are thought to be mediated by the generation of toxic metabolites, including reactive dicarbonyls like methylglyoxal (MG). In this article, we demonstrate that increasing plasma MG to levels observed in diabetic mice either using an exogenous source (1% in drinking water) or generated following inhibition, its primary clearance enzyme, glyoxalase-1 (with 50 mg/kg IP bromobenzyl-glutathione cyclopentyl diester every second day), was able to increase vascular adhesion and augment atherogenesis in euglycemic apolipoprotein E knockout mice to a similar magnitude as that observed in hyperglycemic mice with diabetes. The effects of MG appear partly mediated by activation of the receptor for advanced glycation end products (RAGE), as deletion of RAGE was able to reduce inflammation and atherogenesis associated with MG exposure. However, RAGE deletion did not completely prevent inflammation or vascular damage, possibly because the induction of mitochondrial oxidative stress by dicarbonyls also contributes to inflammation and atherogenesis. Such data would suggest that a synergistic combination of RAGE antagonism and antioxidants may offer the greatest utility for the prevention and management of diabetic vascular complications.

Glycated serum albumin: a potential disease marker and an intermediate index of diabetes control

Glycation is a non-enzymatic spontaneous process in proteins which has remarkable impact on its physical and functional aspect. This alteration with addition of carbohydrate residue to human serum albumin leads to several pathological events such as diabetic nephropathy, neuropathy, retinopathy and cardiovascular complications. Human serum albumin is the major protein and is most susceptible to non-enzymatic glycation. Structural and biological properties of functional albumin alter due to the addition of reducing carbohydrate to free amino terminal residues vivo. These irreversible changes in functional albumin are stable which makes this modified albumin as new gold standard future diagnostic marker in diabetes associated complications. Glycated albumin can be used to determine the glycemic control due to short half life than erythrocytes which makes it an alternate reliable disease marker in diabetes. In this review, Human serum albumin glycation has been overviewed, stating concept of glycation and sites that are prone to this modifications. Impact of non-enzymatic addition of carbohydrate to albumin's structural and biological properties has also been elaborated. Accurate measurements of glycated albumin with implications of new highly sensitive techniques have also been described briefly. Interestingly human serum albumin imposed glycation can serve as future tool not for diagnosing diabetes but also its potential in assessment of diabetes associated complications.

Relationship of Advanced Glycation End Products With Cardiovascular Disease in Menopausal Women

Cardiovascular disease (CVD) represents the most significant cause of death in postmenopausal women. Advanced glycation end products (AGEs) are formed by nonenzymatic modification of proteins, lipids, and nucleic acids by glucose. This review focuses on the contribution of AGEs and their receptors to the development of CVD in menopause. Advanced glycation end products circulate and activate the proinflammatory endothelial cell surface receptor called RAGE, bind to the extracellular matrix of the cardiovascular system, or bind to the circulating anti-inflammatory soluble form of RAGE (sRAGE). Data emerging from human and animal studies suggest that AGEs and both receptors (RAGE and sRAGE) are implicated in the pathophysiology of CVD. Particular emphasis has been given to the role of AGE-RAGE axis in oxidative stress, inflammation, endothelial cell toxicity, and progression of atherosclerosis in menopause. Data accruing from human and animal studies suggest that RAGE expression level and circulating sRAGE level are associated with estradiol and are correlated with CVD risk factors, such as adiposity, dyslipidemia, insulin resistance, diabetes, and metabolic syndrome. By recognizing the impact of AGEs on atherosclerosis, pharmacological strategies targeting the AGE-RAGE pathway hold therapeutic potential for CVD in menopausal women.

Inhibitory effect of apocynin on methylglyoxal-mediated glycation in osteoblastic MC3T3-E1 cells

Methylglyoxal (MG), a highly reactive metabolite of hyperglycemia, can enhance protein glycation, oxidative stress or inflammation. The present study investigated the effects of apocynin on the mechanisms associated with MG toxicity in osteoblastic MC3T3-E1 cells. Pretreatment of MC3T3-E1 cells with apocynin prevented the MG-induced protein glycation and formation of intracellular reactive oxygen species and mitochondrial superoxide in MC3T3-E1 cells. In addition, apocynin increased glutathione levels and restored the activity of glyoxalase I inhibited by MG. These findings suggest that apocynin provide a protective action against MG-induced cell damage by reducing oxidative stress and by increasing the MG detoxification system. Apocynin treatment decreased the levels of proinflammatory cytokines such as tumor necrosis factor-α and interleukin-6 induced by MG. Additionally, the nitric oxide level reduced by MG was significantly increased by apocynin. These findings indicate that apocynin might exert its therapeutic effects via upregulation of glyoxalase system and antioxidant activity. Taken together, apocynin may prove to be an effective treatment for diabetic osteopathy.

Role of methylglyoxal in Alzheimer's disease

Alzheimer's disease is the most common and lethal neurodegenerative disorder. The major hallmarks of Alzheimer's disease are extracellular aggregation of amyloid β peptides and, the presence of intracellular neurofibrillary tangles formed by precipitation/aggregation of hyperphosphorylated tau protein. The etiology of Alzheimer's disease is multifactorial and a full understanding of its pathogenesis remains elusive. Some years ago, it has been suggested that glycation may contribute to both extensive protein cross-linking and oxidative stress in Alzheimer's disease. Glycation is an endogenous process that leads to the production of a class of compounds known as advanced glycation end products (AGEs). Interestingly, increased levels of AGEs have been observed in brains of Alzheimer's disease patients. Methylglyoxal, a reactive intermediate of cellular metabolism, is the most potent precursor of AGEs and is strictly correlated with an increase of oxidative stress in Alzheimer's disease. Many studies are showing that methylglyoxal and methylglyoxal-derived AGEs play a key role in the etiopathogenesis of Alzheimer's disease.

Methylglyoxal-induced cytotoxicity in neonatal rat brain: a role for oxidative stress and MAP kinases

Carbonyl compounds such as methylglyoxal (MGO) seem to play an important role in complications resulting from diabetes mellitus, in aging and neurodegenerative disorders. In this study, we are showing, that MGO is able to suppress cell viability and induce apoptosis in the cerebral cortex and hippocampus of neonatal rats ex-vivo. These effects are partially related with ROS production, evaluated by DCFH-DA assay. Coincubation of MGO and reduced glutathione (GSH) or Trolox (vitamin E) totally prevented ROS production but only partially prevented the MGO-induced decreased cell viability in the two brain structures, as evaluated by the MTT assay. Otherwise, L-NAME, a nitric oxide (NO) inhibitor, partially prevented ROS production in the two structures but partially prevented cytotoxicity in the hippocampus. Pharmacological inhibition of Erk, has totally attenuated MGO-induced ROS production and cytotoxicity, suggesting that MEK/Erk pathway could be upstream of ROS generation and cell survival. Otherwise, p38MAPK and JNK failed to prevent ROS generation but induced decreased cell survival consistent with ROS-independent mechanisms. We can propose that Erk, p38MAPK and JNK are involved in the cytotoxicity induced by MGO through different signaling pathways. While Erk could be an upstream effector of ROS generation, p38MAPK and JNK seem to be associated with ROS-independent cytotoxicity in neonatal rat brain. The cytotoxic damage progressed to apoptotic cell death at MGO concentration higher than those described for adult brain, suggesting that the neonatal brain is resistant to MGO-induced cell death. The consequences of MGO-induced brain damage early in life, remains to be clarified. However, it is feasible that high MGO levels during cortical and hippocampal development could be, at least in part, responsible for the impairment of cognitive functions in adulthood.

Quercetin protects against diabetes-induced exaggerated vasoconstriction in rats: effect on low grade inflammation

Vascular complications are the leading cause of morbidity and mortality in patients with diabetes. Quercetin is an important flavonoid with antioxidant and anti-inflammatory activity. Here, the effect of quercetin on diabetes-induced exaggerated vasoconstriction in insulin deficient and insulin resistant rat models was investigated. Insulin deficiency was induced by streptozotocin while, insulin resistance by fructose. Rats were left 8 weeks or 12 weeks after STZ or fructose administration respectively. Quercetin was daily administered in the last 6 weeks. Then, tail blood pressure (BP) was recorded in conscious animals; concentration-response curves for phenylephrine (PE) and KCl were studied in thoracic aorta rings. Non-fasting blood glucose level, serum insulin level, insulin resistance index, serum tumour necrosis factor-α (TNF-α) and serum C-reactive protein (CRP) were determined. Nuclear transcription factor-κB (NF-κB) was assessed by immunofluorescence technique. Histopathological examination was also performed. The results showed that quercetin protected against diabetes-induced exaggerated vasoconstriction and reduced the elevated blood pressure. In addition, quercetin inhibited diabetes associated adventitial leukocyte infiltration, endothelial pyknosis and increased collagen deposition. These effects were accompanied with reduction in serum level of both TNF-α and CRP and inhibition of aortic NF-κB by quercetin in both models of diabetes. On the other hand, quercetin did not affect glucose level in any of the used diabetic models. This suggests that the protective effect of quercetin is mediated by its anti-inflammatory effect rather than its metabolic effects. In summary, quercetin is potential candidate to prevent diabetic vascular complications in both insulin deficiency and resistance via its inhibitory effect on inflammatory pathways especially NF-κB signaling.

Exploring post-translational arginine modification using chemically synthesized methylglyoxal hydroimidazolones

The methylglyoxal-derived hydroimidazolones (MG-Hs) comprise the most prevalent class of non-enzymatic, post-translational modifications of protein arginine residues found in nature. These adducts form spontaneously in the human body, and are also present at high levels in the human diet. Despite numerous lines of evidence suggesting that MG-H-arginine adducts play critical roles in both healthy and disease physiology in humans, detailed studies of these molecules have been hindered by a lack of general synthetic strategies for their preparation in chemically homogeneous form, and on scales sufficient to enable detailed biochemical and cellular investigations. To address this limitation, we have developed efficient, multigram-scale syntheses of all MG-H-amino acid building blocks, suitably protected for solid-phase peptide synthesis, in 2-3 steps starting from inexpensive, readily available starting materials. Thus, MG-H derivatives were readily incorporated into oligopeptides site-specifically using standard solid-phase peptide synthesis. Access to synthetic MG-H-peptide adducts has enabled detailed investigations, which have revealed a series of novel and unexpected findings. First, one of the three MG-H isomers, MG-H3, was found to possess potent, pH-dependent antioxidant properties in biochemical and cellular assays intended to replicate redox processes that occur in vivo. Computational and mechanistic studies suggest that MG-H3-containing constructs are capable of participating in mechanistically distinct H-atom-transfer and single-electron-transfer oxidation processes. Notably, the product of MG-H3 oxidation was unexpectedly observed to disassemble into the fully unmodified arginine residue and pyruvate in aqueous solution. We believe these observations provide insight into the role(s) of MG-H-protein adducts in human physiology, and expect the synthetic reagents reported herein to enable investigations into non-enzymatic protein regulation at an unprecedented level of detail.

V, Patócs A, Lichthammer A, Veresné Bálint M, Rácz K, Reismann P. The role of methylglyoxal metabolism in type-2 diabetes and its complications

Transient or chronic hyperglycaemia increases the formation of intracellular reactive oxygen species and aldehydes. The accumulation of reactive aldehydes is implicated in the development of diabetic complications. Methylglyoxal, a glucose dependent α-dicarbonyl might be the most important reactive aldehyde in diabetes and its complications. Diabetes was the first disease in which evidence emerged for the increased formation of methylglyoxal in the cells and in the serum. Methylglyoxal has a toxic effect on insulin secretion from pancreatic beta-cells, and on modifications of proteins and nucleic acids. Moreover, methylglyoxal is one of the major precursors of advanced glycation end-products. The glyoxalase enzyme system that exists in all mammalian cells is catalyzing the detoxification of methylglyoxal. This review summarizes the methylglyoxal metabolism in normoglycaemic and hyperglycamic conditions and the role of methylglyoxal in the development of late diabetic microvascular complications. Orv. Hetil., 2012, 153, 574–585.

NF-κB-inducing kinase increases renal tubule epithelial inflammation associated with diabetes

The impact of increased NF-κB-inducing kinase (NIK), a key component of the NF-κB activation pathways, on diabetes-induced renal inflammation remains unknown. We overexpressed NIK wild type (NIKwt) or kinase-dead dominant negative mutants (NIKdn) in HK-2 cells and demonstrated that RelB and p52, but not RelA, abundance and DNA binding increased in nuclei of NIKwt but not NIKdn overexpressed cells, and this corresponded with increases in multiple proinflammatory cytokines. Since TRAF3 negatively regulates NIK expression, we silenced TRAF3 by >50%; this increased nuclear levels of p52 and RelB, and transcript levels of proinflammatory cytokines and transcription factors. In HK-2 cells and mouse primary proximal tubule epithelial cells treated with methylglyoxal-modified albumin, multiple proinflammatory cytokines and NIK were increased in association with increased nuclear RelB and p52. These observations indicate that NIK regulates proinflammatory responses of renal proximal tubular epithelial cells via mechanisms involving TRAF3 and suggest a role for NF-κB noncanonical pathway activation in modulating diabetes-induced inflammation in renal tubular epithelium.

Carbonyl compounds methylglyoxal and glyoxal affect interleukin-8 secretion in intestinal cells by superoxide anion generation and activation of MAPK p38

The carbonyl compounds methylglyoxal (MG) and glyoxal (GL) are reactive intermediates of glucose degradation pathways and capable of inducing cellular damage. Although immune-stimulating activity has been investigated in endothelial cells, little is known about the signaling pathways of cytokine induction of these compounds in the intestine. Hence, we investigated the impact of mitogen-activated protein kinases (MAPK) and nuclear factor kappa B (NF-κB) on IL-8 production by human intestinal cells (Caco-2 and HT-29) after stimulation by MG and GL. Both compounds induced a dose-dependent enhancement of IL-8 secretion in human intestinal cells. MAPK p38 and extracellular signal-regulated kinase (ERK) were phosphorylated in these cells after having been stimulated by MG and GL. Furthermore, inhibitors of MAPK p38 (SB 203580 and 239063), ERK1/2 (PD 98059) and NF-κB activation (SM-7368 and SC-514) reduced IL-8 secretion. The most important mechanism by which MG and GL induced IL-8 secretion was the generation of superoxide anions which was confirmed by the inhibition of the cytosolic NADPH oxidase with diphenyl iodonium (DPI) or by application of superoxide dismutase (SOD). Our data suggest that multiple pathways were simultaneously activated; however, superoxide dependent MAPK p38 activation seems to be the most dominant pathway for IL-8 secretion in intestinal cells.

The glycation of albumin: structural and functional impacts

Oxidative stress and protein modifications are frequently observed in numerous disease states. Glucose constitutes a vital nutrient necessary to cellular oxygen metabolism. However, hyperglycemia-associated damage is an important factor in diabetes disorders. Albumin, the major circulating protein in blood, can undergo increased glycation in diabetes. From recent studies, it has become evident that protein glycation has important implications for protein activity, unfolding, and degradation, as well as for cell functioning. After giving a brief overview of the key role of albumin in overall antioxidant defense, this review examines its role as a target of glycation reactions. A synthesis of state of the art methods for measuring and characterizing albumin glycation is detailed. In light of recent data, we then report the impact of glycation on the structure of albumin and its various activities, especially its antioxidant and binding capacities. The biological impact of glycated albumin on cell physiology is also discussed, specifically the role of the protein as a biological marker of diabetes.

Methylglyoxal induced activation of murine peritoneal macrophages and surface markers of T lymphocytes in sarcoma-180 bearing mice: involvement of MAP kinase, NF-kappa beta signal transduction pathway

Methylglyoxal profoundly stimulates host's immune response against tumor cell by producing reactive oxygen intermediates (ROI's) and reactive nitrogen intermediates (RNI's) [Bhattacharyya, N., Pal, A., Patra, S., Haldar, A.K., Roy, S., Ray, M., 2008. Activation of macrophages and lymphocytes by methylglyoxal against tumor cells in the host. Int. Immunophar. 8 (11), 1503-1512]. Present study indicated that methylglyoxal stimulates iNOS activation by p38 MAPK-NF-kappa beta dependent pathway and ROS production by ERK and JNK activation in sarcoma-180 tumor bearing mice. Proinflammatory cytokines, for macrophage activation, IL-6 and IL-1 beta were also increased. Production of TLR 4 and TLR 9, which acts through the same signaling pathway, were also upregulated. Hence, concluded that methylglyoxal augmented the IL-6 and IL-1 beta, expression of TLR 4 and TLR 9 and produced MAPKs, important regulators of ROIs and RNIs. Methylglyoxal treatment also increased M-CSF, an upregulator of macrophage production. CD8 and CD4 molecules, associated with T(C) and T(H) cells respectively, were also increased. Overall methylglyoxal treatment is important for enhancement of macrophages and lymphocyte activation or immunomodulation against sarcoma-180 tumor.

Cytotoxicity of advanced glycation endproducts in human micro- and astroglial cell lines depends on the degree of protein glycation

Advanced glycation endproducts (AGEs) arise from the reaction of sugars with side chains and the N-terminus of proteins and are thought to be involved in the pathogenesis of several diseases by inducing oxidative stress, inflammation and cell death presumably mediated through activation of the receptor of AGE (RAGE). To address the question whether the cell damaging effect of AGE depends on the degree of its protein glycation, differential modified AGEs derived from incubating human serum albumin with increasing concentrations of methyl glyoxal were tested on cell viability, reactive oxygen species (ROS) formation, intracellular ATP levels, and activation of caspases 3/7 in two human glial cell lines, which were used as a model for human glia cells. All AGEs tested, regardless of their degree of modification, were found to induce ROS formation in both microglial (CHME-5) and astroglial cells (U373 MG), while only highly modified AGEs were able to decrease the cell viability and to induce apoptosis. This indicates that apoptotic events may be involved in the change of physiological parameters.

Free radical generation by methylglyoxal in tissues

Methylglyoxal (MG) is a reactive dicarbonyl intermediate of the glycolytic pathway. Increased oxidative stress is associated with conditions of increased MG, such as diabetes mellitus. Increased oxidative stress is due to an increase in highly reactive by-products of metabolic pathways, the so-called reactive oxygen species, such as superoxide anion, hydroxyl radical, hydrogen peroxide, nitric oxide and peroxynitrite. These reactive species react with a variety of proteins, enzymes, lipids, DNA and other molecules and disrupt their normal function. Oxidative stress causes many pathological changes that lead to vascular complications of diabetes mellitus, hypertension, neurodegenerative diseases and aging. In this review we summarize the correlation of elevated MG and various reactive oxygen species, and the enzymes that produce them or take part in their disposal, such as antioxidant enzymes and cofactors. The findings reported in various studies reviewed have started filling in gaps in our knowledge that will ultimately provide us with a clear picture of how the whole process that causes cellular dysfunction is initiated.

Advanced glycation end products enhance the proliferation and activation of hepatic stellate cells

BACKGROUND

Advanced glycation end products (AGEs), final reaction products of protein with sugars, are known to contribute to diabetes-related complications. We have recently demonstrated high levels of serum AGEs in patients with nonalcoholic steatohepatitis (NASH). However, direct evidence for the participation of AGEs in hepatic inflammation and fibrosis has not been shown. To explore the pathogenesis of NASH, we examined the biological infl uence of AGEs on hepatic stellate cells (HSCs) in vitro.

METHODS

An established human HSC line, LI90, was exposed to a glyceraldehyde-derived-AGE (glycer-AGE), and the phenotypical changes of the LI90 cells were investigated. Intracellular formation of reactive oxygen species (ROS) was measured using a fl uorescent probe. Cell proliferation was examined by MTS assay. Fibrogenic marker gene expression was analyzed by quantitative real-time polymerase chain reaction. The production of monocyte chemoattractant protein 1 (MCP-1) was assessed by enzyme-linked immunosorbent assay.

RESULTS

The expression of AGE receptor was confirmed in LI90 cells at the mRNA and protein levels. In addition to increasing intracellular ROS generation, glycer-AGE upregulated fibrogenic genes such as those encoding for alpha-smooth muscle actin, transforming growth factor-beta1, and collagen type Ialpha2. The expression of MCP-1 mRNA in LI90 cells as well as its secretion into the culture medium was significantly increased in response to AGEs. These changes were attenuated by treatment with the antioxidant N-acetylcysteine.

CONCLUSIONS

These data indicate that AGEs induce ROS generation and intensify the proliferation and activation of HSCs, supporting the possibility that antioxidants may represent a promising treatment for prevention of the development of hepatic fibrosis in NASH.

Activation of macrophages and lymphocytes by methylglyoxal against tumor cells in the host

Methylglyoxal is a normal metabolite and has the potential to affect a wide variety of cellular processes. In particular, it can act selectively against malignant cells. The study described herein was to investigate whether methylglyoxal can enhance the non-specific immunity of the host against tumor cells. Methylglyoxal increased the number of macrophages in the peritoneal cavity of both normal and tumor-bearing mice. It also elevated the phagocytic capacity of macrophages in both these groups of animals. This activation of macrophages was brought about by increased production of Reactive Oxygen Intermediates (ROIs) and Reactive Nitrogen Intermediates (RNIs). The possible mechanism for the production of ROIs and RNIs can be attributed to stimulation of the respiratory burst enzyme NADPH oxidase and iNOS, respectively. IFN-gamma, which is a regulatory molecule of iNOS pathway also showed an elevated level by methylglyoxal. TNF-alpha, which is an important cytokine for oxygen independent killing by macrophage also increased by methylglyoxal in both tumor-bearing and non tumor-bearing animals. Methylglyoxal also played a role in the proliferation and cytotoxicity of splenic lymphocytes. In short, it can be concluded that methylglyoxal profoundly stimulates the immune system against tumor cells.