A brief critical overview of the biological effects of methylglyoxal and further evaluation of a methylglyoxal-based anticancer formulation in treating cancer patients

Layer-by-Layer Coatings of Collagen-Hyaluronic acid Loaded with an Antibacterial Manuka Honey Bioactive Compound to Fight Metallic Implant Infections

Implant-associated severe infections can result in catastrophic implant failures; thus, advanced antibacterial coatings are needed to combat infections. This study focuses on harnessing nature-inspired self-assembly of extracellular matrix (ECM)-like coatings on Ti alloy with a combination of jellyfish-derived collagen (J-COLL) and hyaluronic acid (HA) using our customized automated hybrid layer-by-layer apparatus. To improve the anti-infection efficacy of coatings, we have incorporated a natural antibacterial agent methylglyoxal (MGO, a Manuka honey compound) in optimized multilayer coatings. The obtainment of MGO-loaded multilayer coatings was successfully assessed by profilometry, contact angle, attenuated total reflectance (ATR)-Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. In vitro degradation confirmed the controlled release activity of MGO with a range of concentrations from 0.90 to 2.38 mM up to 21 days. A bacterial cell culture study using Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis) confirmed that the MGO incorporated within layers 7 and 9 had a favorable effect on preventing bacterial growth and colonization on their surfaces. An in vitro cytocompatibility study confirmed that MGO agents included in the layers did not affect or reduce the cellular functionalities of L929 fibroblasts. In addition, MGO-loaded layers with Immortalized Mesenchymal Stem Cells (Y201 TERT-hMSCs) were found to favor the growth and differentiation of Y201 cells and promote calcium nodule formation. Overall, these surface coatings are promising candidates for delivering antimicrobial activity with bone-inducing functions for future bone tissue engineering applications.

The Dual-Role of Methylglyoxal in Tumor Progression - Novel Therapeutic Approaches

One of the hallmarks of cancer cells is their metabolic reprogramming, which includes the preference for the use of anaerobic glycolysis to produce energy, even in presence of normal oxygen levels. This phenomenon, known as “Warburg effect”, leads to the increased production of reactive intermediates. Among these Methylglyoxal (MGO), a reactive dicarbonyl known as the major precursor of the advanced glycated end products (AGEs), is attracting great attention. It has been well established that endogenous MGO levels are increased in several types of cancer, however the MGO contribution in tumor progression is still debated. Although an anti-cancer role was initially attributed to MGO due to its cytotoxicity, emerging evidence has highlighted its pro-tumorigenic role in several types of cancer. These apparently conflicting results are explained by the hormetic potential of MGO, in which lower doses of MGO are able to establish an adaptive response in cancer cells while higher doses cause cellular apoptosis. Therefore, the extent of MGO accumulation and the tumor context are crucial to establish MGO contribution to cancer progression. Several therapeutic approaches have been proposed and are currently under investigation to inhibit the pro-tumorigenic action of MGO. In this review, we provide an overview of the early and latest evidence regarding the role of MGO in cancer, in order to define its contribution in tumor progression, and the therapeutic strategies aimed to counteract the tumor growth.

Coadministration of liposomal methylglyoxal increases the activity of amphotericin B against Candida albicans in leukopoenic mice

In this study, we investigated the therapeutic efficacy of a combination of liposomal amphotericin B (Lip-Amp B) and Methylglyoxal (Lip-MG) against Candida albicans in the leukopoenic mice. The antifungal efficacy of Lip-Amp B or Lip-MG or a combination of Lip-Amp B and Lip-MG was evaluated by the analysis of the survival rate and the fungal load in the treated mice. The immune-stimulatory effect of Lip-MG on macrophages was evaluated by analysing the secretion of proinflammatory cytokines. C. albicans infected mice treated at the doses of 1 and 2 mg/kg of Lip-Amp B showed 20% and 50% survival rates, respectively. Whereas the mice treated with free Amp B at the same doses died within 40 days of treatment. Interestingly, C. albicans infected mice treated with a combination of Lip-Amp B and Lip-MG had 70% survival rate on day 40 postinfection. Moreover, treatment of macrophages with Lip-MG increased their fungicidal activity and the secretion of proinflammatory cytokines, including TNF-α and IL-1β. These findings suggested that co-treatment with Lip-Amp B and Lip-MG had a synergistic effect and could be effective against C. albicans in immunocompromised subjects.

Potential of Methylglyoxal-Conjugated Chitosan Nanoparticles in Treatment of Fluconazole-Resistant Candida albicans Infection in a Murine Model

Background

Fungal infections are becoming more prevalent and threatening because of the continuous emergence of azole-resistant fungal infections. The present study was aimed to assess the activity of free Methylglyoxal (MG) or MG-conjugated chitosan nanoparticles (MGCN) against fluconazole-resistant Candida albicans.

Materials and Methods

A novel formulation of MGCN was prepared and characterized to determine their size, shape and polydispersity index. Moreover, the efficacy of fluconazole or MG or MGCN was determined against intracellular C. albicans in macrophages and the systematic candidiasis in a murine model. The safety of MG or MGCN was tested in mice by analyzing the levels of hepatic and renal toxicity parameters.

Results

Candida albicans did not respond to fluconazole, even at the highest dose of 20 mg/kg, whereas MG and MGCN effectively eliminated C. albicans from the macrophages and infected mice. Mice in the group treated with MGCN at a dose of 10 mg/kg exhibited a 90% survival rate and showed the lowest fungal load in the kidney, whereas the mice treated with free MG at the same dose exhibited 50% survival rate. Moreover, the administration of MG or MGCN did not induce any liver and kidney toxicity in the treated mice.

Conclusion

The findings of the present work suggest that MGCN may be proved a promising therapeutic formulation to treat azole-resistant C. albicans infections.

Circulating free methylglyoxal as a metabolic tumor biomarker in a rat colon adenocarcinoma model

Since the 1956 hypothesis of Otto Warburg, aerobic glycolysis has been recognized as a metabolic hallmark of cancer. Because methylglyoxal (MG) is a naturally occurring waste metabolite of glycolysis, we measured blood levels of this molecule in colon cancer-bearing rats. To compare the blood levels of free MG in cancerous and healthy animals,the present study used a dedicated tumor graft model consisting of the subcutaneous administration in syngenic BD-IX rats of a tumorigenic cell clone (PROb) and another non-tumorigenic clone (REGb) derived from the same tumor. Rats grafted with the PROb growing tumor cell clone exhibited a statistically significant increase in free MG blood levels (P=0.003), whereas rats transplanted with the REGb non-growing tumor cell clone exhibited normal MG values. The present study (first of three parts) suggests that cancer cells can produce and release free MG at higher levels than normal cells, making MG a putative novel metabolic biomarker of cancer.

Methylglyoxal at metronomic doses sensitizes breast cancer cells to doxorubicin and cisplatin causing synergistic induction of programmed cell death and inhibition of stemness

Potent anticancer activity coupled with absence of toxicity at therapeutic dose established the glycolytic metabolite, methylglyoxal, as a promising candidate against malignant neoplasia. In this preclinical study we illustrate the applicability of methylglyoxal in formulating an optimally designed combination regimen with chemotherapeutic drugs against breast cancer. Results demonstrated a synergistic augmentation in doxorubicin and cisplatin mediated cytotoxicity in human breast cancer cell lines MDA MB 231 & MCF 7 with methylglyoxal co-treatment at metronomic concentrations. The cell death due to combination treatment was significantly prevented by N-Acetylcysteine and the synergistic effects were attenuated in presence of inhibitors for apoptosis and necroptosis, in MDA MB 231 and MCF 7 cells, respectively. Additionally, acridine orange staining and immunoblotting with LC3B antibody indicated the suppression of doxorubicin induced autophagy flux with methylglyoxal co-treatment. This report documents for the first time the preferential targeting of breast cancer stem cells by methylglyoxal. Combination treatment with doxorubicin or cisplatin hindered mammosphere forming efficiency and inclusively eliminated both cancer stem as well as non-stem cancer cells. The synergistic effect was validated in Ehrlich mammary carcinoma cell induced murine ascites model and the combination advantage in vivo was achieved without any additional deleterious effect to liver and kidney. Our present study evidences the implications of methylglyoxal inclusion in adjuvant multimodal chemotherapeutics against breast cancer and offers noteworthy insights into the possible outcome.

Randomised masked trial of the clinical safety and tolerability of MGO Manuka Honey eye cream for the management of blepharitis

Objective

To assess the clinical safety and tolerability of a novel MGO Manuka Honey microemulsion (MHME) eye cream for the management of blepharitis in human subjects.

Methods and analysis

Twenty-five healthy subjects were enrolled in a prospective, randomised, paired-eye, investigator-masked trial. The MHME eye cream (Manuka Health New Zealand) was applied to the closed eyelids of one eye (randomised) overnight for 2 weeks. LogMAR visual acuity, eyelid irritation symptoms, ocular surface characteristics and tear film parameters were assessed at baseline, day 7 and day 14. Expression of markers of ocular surface inflammation (matrix metalloproteinase-9 and interleukin-6) and goblet cell function (MUC5AC) were quantified using impression cytology at baseline and day 14.

Results

There were no significant changes in visual acuity, eyelid irritation symptoms, ocular surface characteristics, tear film parameters and inflammatory marker expression during the 2-week treatment period in treated and control eyes (all p>0.05), and measurements did not differ significantly between eyes (all p>0.05). No major adverse events were reported. Two subjects experienced transient ocular stinging, presumably due to migration of the product into the eye, which resolved following aqueous irrigation.

Conclusion

The MHME eye cream application was found to be well tolerated in healthy human subjects and was not associated with changes in visual acuity, ocular surface characteristics, tear film parameters, expression of markers of inflammation or goblet cell function. The findings support future clinical efficacy trials in patients with blepharitis.

Trial registration number

ACTRN12616000540415.

Antioxidant-rich leaf extract of Barringtonia racemosa significantly alters the in vitro expression of genes encoding enzymes that are involved in methylglyoxal degradation III

Background

Barringtonia racemosa is a medicinal plant belonging to the Lecythidaceae family. The water extract of B. racemosa leaf (BLE) has been shown to be rich in polyphenols. Despite the diverse medicinal properties of B. racemosa, information on its major biological effects and the underlying molecular mechanisms are still lacking.

Methods

In this study, the effect of the antioxidant-rich BLE on gene expression in HepG2 cells was investigated using microarray analysis in order to shed more light on the molecular mechanism associated with the medicinal properties of the plant.

Results

Microarray analysis showed that a total of 138 genes were significantly altered in response to BLE treatment (p < 0.05) with a fold change difference of at least 1.5. SERPINE1 was the most significantly up-regulated gene at 2.8-fold while HAMP was the most significantly down-regulated gene at 6.5-fold. Ingenuity Pathways Analysis (IPA) revealed that “Cancer, cell death and survival, cellular movement” was the top network affected by the BLE with a score of 44. The top five canonical pathways associated with BLE were Methylglyoxal Degradation III followed by VDR/RXR activation, TR/RXR activation, PXR/RXR activation and gluconeogenesis. The expression of genes that encode for enzymes involved in methylglyoxal degradation (ADH4, AKR1B10 and AKR1C2) and glycolytic process (ENO3, ALDOC and SLC2A1) was significantly regulated. Owing to the Warburg effect, aerobic glycolysis in cancer cells may increase the level of methylglyoxal, a cytotoxic compound.

Conclusions

BLE has the potential to be developed into a novel chemopreventive agent provided that the cytotoxic effects related to methylglyoxal accumulation are minimized in normal cells that rely on aerobic glycolysis for energy supply.

Biological activity of dendrimer–methylglyoxal complexes for improved therapeutic efficacy against malignant cells

A facile strategy to synthesize polymer based conjugation of methylglyoxal which demonstrated inhibition against malignant cells with desired selectivity can revolutionize the cancer treatment via minimizing the human health risks.

Nanofabrication of methylglyoxal with chitosan biopolymer: a potential tool for enhancement of its anticancer effect

Purpose

The normal metabolite methylglyoxal (MG) specifically kills cancer cells by inhibiting glycolysis and mitochondrial respiration without much adverse effect upon normal cells. Though the anticancer property of MG is well documented, its gradual enzymatic degradation in vivo has prompted interest in developing a nanoparticulate drug delivery system to protect it and also to enhance its efficacy.

Materials and methods

MG-conjugated chitosan nanoparticles (Nano-MG) were prepared by conjugating the carbonyl group of MG with the amino group of chitosan polymer (Schiff’s base formation). Nano-MG were characterized in detail using the dynamic light scattering method, zeta potential measurement, Fourier transform infrared spectroscopy, and transmission electron microscopic analysis. Amount of MG anchored to Nano-MG, stability of Nano-MG, and in vitro release of MG from Nano-MG were estimated spectrophotometrically. Ehrlich ascites carcinoma (EAC) cells, human breast cancer cell line HBL-100, and lung epithelial adenocarcinoma cell line A549 were used as test systems to compare Nano-MG with bare MG in vitro. Cytotoxicity to EAC cells was evaluated by the trypan blue dye exclusion test, and cell viability of HBL-100 and A549 cells were studied using 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis of HBL-100 cells was assessed by flow cytometry and confocal microscopy. In vivo studies were performed on both EAC cells inoculated and also in sarcoma-180-induced solid tumor-bearing Swiss albino mice to assess the anticancer activity of Nano-MG in comparison to bare MG with varying doses, times, and administrative routes.

Results

Fourier transform infrared spectroscopy revealed the presence of imine groups in Nano-MG due to conjugation of the amino group of chitosan and carbonyl group of MG with diameters of nanoparticles ranging from 50–100 nm. The zeta potential of Nano-MG was +21 mV and they contained approximately 100 μg of MG in 1 mL of solution. In vitro studies with Nano-MG showed higher cytotoxicity and enhanced rate of apoptosis in the HBL-100 cell line in comparison with bare MG, but no detrimental effect on normal mouse myoblast cell line C2C12 at the concerned doses. Studies with EAC cells also showed increased cell death of nearly 1.5 times. Nano-MG had similar cytotoxic effects on A549 cells. In vivo studies further demonstrated the efficacy of Nano-MG over bare MG and found them to be about 400 times more potent in EAC-bearing mice and nearly 80 times more effective in sarcoma-180-bearing mice. Administration of ascorbic acid and creatine during in vivo treatments augmented the anticancer effect of Nano-MG.

Conclusion

The results clearly indicate that Nano-MG may constitute a promising tool in anticancer therapeutics in the near future.

Regulation of methylglyoxal-elicited leukocyte recruitment by endothelial SGK1/GSK3 signaling

Excessive levels of the glycolysis metabolite methylglyoxal (MG) elicit enhanced expression of adhesion molecules which foster leukocyte-endothelial cell interactions. The signaling mechanisms involved remain elusive. To address this, we investigated the signal transduction of leukocyte- and endothelial-expressed phosphoinositide 3-kinase (PI3K) effector kinases glycogen synthase kinase 3 (GSK3) and serum- and glucocorticoid-inducible kinase 1 (SGK1) in the regulation of MG-elicited leukocyte recruitment. Using intravital microscopy of mouse cremasteric microvasculature, we demonstrate that GSK3 inhibitors lithium and SB216763 mitigate MG-elicited leukocyte recruitment and microvascular hyperpermeability. In SVEC4-10EE2 endothelial cells, but not in neutrophils, MG transiently activates GSK3 by reducing inhibitory phospho-GSK3α/β (Ser21/9) which parallels decrease of phospho-Akt at early time points (<30min). At later time points (≥1h), MG induces GSK3 deactivation which is dissipated by siRNA silencing of SGK. MG treatment potentiates endothelial SGK1 mRNA, total SGK1, phospho-SGK1 and phospho-NDRG1. The SGK1 inhibitor GSK650394 attenuates MG-elicited leukocyte recruitment. Pharmacological inhibition or silencing endothelial GSK3 or SGK attenuates MG-triggered nuclear factor (NF)-κB activity. Furthermore, silencing SGK blunts MG-triggered redox-sensitive phosphorylation of endothelial transcription factor CREB. Inhibition of SGK1 or GSK3 mitigates the expression of endothelial adhesion molecules P- and E-selectins and ICAM-1. Moreover, SGK1-dependent CREB activation participates in MG-elicited ICAM-1 upregulation. We conclude that temporal activation of endothelial SGK1 and GSK3 is decisive in MG-elicited upregulation of transcription factors, adhesion molecule expression, and leukocyte-vascular endothelium interactions. This novel signaling pathway may link excessive MG levels in vivo to inflammation, thus, unraveling potential therapeutic targets.

Reactive carbonyl species in vivo: generation and dual biological effects

Reactive carbonyls are widespread species in living organisms and mainly known for their damaging effects. The most abundant reactive carbonyl species (RCS) are derived from oxidation of carbohydrates, lipids, and amino acids. Chemical modification of proteins, nucleic acids, and aminophospholipids by RCS results in cytotoxicity and mutagenicity. In addition to their direct toxicity, modification of biomolecules by RCS gives rise to a multitude of adducts and cross links that are increasingly implicated in aging and pathology of a wide range of human diseases. Understanding of the relationship between metabolism of RCS and the development of pathological disorders and diseases may help to develop effective approaches to prevent a number of disorders and diseases. On the other hand, constant persistence of RCS in cells suggests that they perform some useful role in living organisms. The most beneficial effects of RCS are their establishment as regulators of cell signal transduction and gene expression. Since RCS can modulate different biological processes, new tools are required to decipher the precise mechanisms underlying dual effects of RCS.

Polymer based nanoformulation of methylglyoxal as an antimicrobial agent: efficacy against resistant bacteria

Functionalized polymer conjugated nanoformulations of methylglyoxal demonstrated broad-spectrum antimicrobial activity, leading to new generation antimicrobial agents and minimizing the environment risks.

Inhibition of tumour cell growth by carnosine: some possible mechanisms

The naturally occurring dipeptide carnosine (β-alanyl-L-histidine) has been shown to inhibit, selectively, growth of transformed cells mediated, at least in part, by depleting glycolytic ATP levels. The mechanism(s) responsible has/have yet to be determined. Here, we discuss a number of probable and/or possible processes which could, theoretically, suppress glycolytic activity which would decrease ATP supply and generation of metabolic intermediates required for continued cell reproduction. Possibilities include effects on (i) glycolytic enzymes, (ii) metabolic regulatory activities, (iii) redox biology, (iv) protein glycation, (v) glyoxalase activity, (vi) apoptosis, (vii) gene expression and (viii) metastasis. It is possible, by acting at various sites that this pluripotent dipeptide may be an example of an endogenous "smart drug".

Two α-dicarbonyls downregulate migration, invasion, and adhesion of liver cancer cells in a p53-dependent manner

BACKGROUND

Hepatocellular carcinoma accounts for more than 600,000 deaths per year due to it being a highly invasive tumor. The α-dicarbonyl, methylglyoxal demonstrates efficacy at reducing tumor burden, however the anti-cancerous activities of 3-deoxyglucosone, have never been studied.

AIMS

To determine the anti-cancerous potential of methylglyoxal and 3-deoxyglucosone on liver tumor cells.

METHODS

The in vitro effects of methylglyoxal and 3-deoxyglucosone were studied by investigating migration, invasion, and adhesion of Huh-7, HepG2, and Hep3B cells.

RESULTS

3-Deoxyglucosone inhibited migration of Huh-7 and HepG2 cells. Methylglyoxal decreased migration of HepG2 cells. Additionally, 3-deoxyglucosone and methylglyoxal impaired invasion, and adhesion of Huh-7 and HepG2 cells. In Hep3B cells, a p53 null cell line, 3-deoxyglucosone and methylglyoxal had no effect on migration, invasion, or adhesion. However, both compounds inhibited invasion of wild-type p53 transfected Hep3B cells. Silencing of p53 in Huh-7 and HepG2 cells abrogated the effects of the α-dicarbonyls on cell invasion. 3DG and MG did not alter p53 total protein but promoted nuclear translocation of p53.

CONCLUSIONS

These studies suggest that 3-deoxyglucosone and methylglyoxal impair invasion, migration, and adhesion of hepatocellular carcinoma. The effects of both compounds on cell invasion are dependent on p53 and imply that α-dicarbonyls could be efficacious in the treatment of p53-expressing invasive liver tumors.

Critical evaluation of toxic versus beneficial effects of methylglyoxal

In various organisms, an array of enzymes is involved in the synthesis and breakdown of methylglyoxal. Through these enzymes, it is intimately linked to several other physiologically important metabolites, suggesting that methylglyoxal has some important role to play in the host organism. Several in vitro and in vivo studies showed that methylglyoxal acts specifically against different types of malignant cells. These studies culminated in a recent investigation to evaluate a methylglyoxal-based formulation in treating a small group of cancer patients, and the results were promising. Methylglyoxal acts against a number of pathogenic microorganisms. However, recent literature abounds with the toxic effects of methylglyoxal, which are supposed to be mediated through methylglyoxal-derived advanced glycation end products (AGE). Many diseases such as diabetes, cataract formation, hypertension, and uremia are proposed to be intimately linked with methylglyoxal-derived AGE. However methylglyoxal-derived AGE formation and subsequent pathogenesis might be a very minor event because AGE are nonspecific reaction products that are derived through the reactions of carbonyl groups of reducing sugars with amino groups present in the side chains of lysine and arginine and in terminal amino groups of proteins. Moreover, the results of some in vitro experiments with methylglyoxal under non-physiological conditions were extrapolated to the in vivo situation. Some experiments even showed contradictory results and were differently interpreted. For this reason conclusions about the potential beneficial effects of methylglyoxal have often been neglected, thus hindering the advancement of medical science and causing some confusion in fundamental understanding. Overall, the potential beneficial effects of methylglyoxal far outweigh its possible toxic role in vivo, and it should be utilized for the benefit of suffering humanity.

Methylglyoxal and glucose metabolism: a historical perspective and future avenues for research

Methylglyoxal, an alpha-oxoaldehyde discovered in the 1880s, has had a hectic scientific career, at times being considered of fundamental importance and at other times viewed as playing a very subordinate role. Much has been learned about methylglyoxal, but the function of its production in the metabolic machinery is still unknown. This paper gives an overview of the changing role of methylglyoxal from a historical aspect and arrives at the conclusion that methylglyoxal is tightly bound to glycolysis from an evolutionary perspective, its production therefore being inevitable. It is not situated in the main stream of the glycolytic sequence, but a role can be assigned to its production in the phosphate supply of operating glycolysis in some prokaryotes and yeast under conditions of phosphate deficiency. This function is presumed to be performed by the enzyme methylglyoxal synthase, which is specialized for the conversion of dihydroxyacetone-phosphate to methylglyoxal. However, it is still unknown whether this enzyme and this kind of regulation also exist in animals.