Transduced Tat-glyoxalase protein attenuates streptozotocin-induced diabetes in a mouse model

Potential of oligonucleotide- and protein/peptide-based therapeutics in the management of toxicant/stressor-induced diseases

Exposure to toxicants/stressors has been linked to the development of many human diseases. They could affect various cellular components, such as DNA, proteins, lipids, and non-coding RNAs (ncRNA), thereby triggering various cellular pathways, particularly oxidative stress, inflammatory responses, and apoptosis, which can contribute to pathophysiological states. Accordingly, modulation of these pathways has been the focus of numerous investigations for managing related diseases. The involvement of various ncRNAs, such as small interfering RNA (siRNA), microRNAs (miRNA), and long non-coding RNAs (lncRNA), as well as various proteins and peptides in mediating these pathways, provides many target sites for pharmaceutical intervention. In this regard, various oligonucleotide- and protein/peptide-based therapies have been developed to treat toxicity-induced diseases, which have shown promising results in vitro and in vivo. This comprehensive review provides information about various aspects of toxicity-related diseases including their causing factors, main underlying mechanisms and intermediates, and their roles in pathophysiological states. Particularly, it highlights the principles and mechanisms of oligonucleotide- and protein/peptide-based therapies in the treatment of toxicity-related diseases. Furthermore, various issues of oligonucleotides and proteins/peptides for clinical usage and potential solutions are discussed.

Cell-penetrating peptide-mediated delivery of therapeutic peptides/proteins to manage the diseases involving oxidative stress, inflammatory response and apoptosis

OBJECTIVES

Peptides and proteins represent great potential for modulating various cellular processes including oxidative stress, inflammatory response, apoptosis and consequently the treatment of related diseases. However, their therapeutic effects are limited by their inability to cross cellular barriers. Cell-penetrating peptides (CPPs), which can transport cargoes into the cell, could resolve this issue, as would be discussed in this review.

KEY FINDINGS

CPPs have been successfully exploited in vitro and in vivo for peptide/protein delivery to treat a wide range of diseases involving oxidative stress, inflammatory processes and apoptosis. Their in vivo applications are still limited due to some fundamental issues of CPPs, including nonspecificity, proteolytic instability, potential toxicity and immunogenicity.

SUMMARY

Totally, CPPs could potentially help to manage the diseases involving oxidative stress, inflammatory response and apoptosis by delivering peptides/proteins that could selectively reach proper intracellular targets. More studies to overcome related CPP limitations and confirm the efficacy and safety of this strategy are needed before their clinical usage.

Increased synthesis of hyaluronic acid by enhanced penetration of CTP-EGF recombinant in human keratinocytes

BACKGROUND

Epidermal growth factor (EGF) plays an important role in regeneration and proliferation of skin cells. It synthesizes fibrous proteins, such as collagen, and induces the proliferation of keratinocytes and fibroblasts. It can also induce hyaluronic acid synthesis, which subsequently leads to improved skin elasticity, wrinkle improvement, and moisturizing effects. Thus, the EGF is an attractive cosmetic additive for skin care.

OBJECTIVES

We tested the use of cytoplasmic transduction peptide (CTP) as a delivery peptide for EGF into skin cells. Additionally, we characterized the skin permeability of CTP-EGF for its potential use in skin antiaging and antiwrinkle cosmetics.

METHODS

Skin penetration by recombinant CTP-EGF protein was confirmed using fluorescent imaging techniques. The ability to synthesize hyaluronic acid was confirmed by immunoblotting and ELISA.

RESULTS

CTP-EGF displayed cell membrane permeability and could penetrate skin cells. Treatment with CTP-EGF increased collagen protein formation, which is a major regulator of skin elasticity. Further, CTP-EGF treatment led to increased expression of HAS3 enzyme and subsequently boosted hyaluronic acid synthesis. The CTP-EGF also performed better than natural EGF in wound healing assays.

CONCLUSIONS

CTP-EGF has a superior ability, compared with natural EGF, to permeate skin and induce hyaluronic acid synthesis and collagen formation. Thus, it has great potential to be used in cosmetics and therapeutic agents to improve wrinkles and health of the skin.

Protective effects of Tat-DJ-1 protein against streptozotocin-induced diabetes in a mice model

A major feature of type 1 diabetes mellitus (T1DM) is hyperglycemia and dysfunction of pancreatic β-cells. In a previous study, we have shown that Tat-DJ-1 protein inhibits pancreatic RINm5F β-cell death caused by oxidative stress. In this study, we examined effects of Tat-DJ-1 protein on streptozotocin (STZ)-induced diabetic mice. Wild type (WT) Tat-DJ-1 protein transduced into pancreas where it markedly inhibited pancreatic β-cell destruction and regulated levels of serum parameters including insulin, alkaline phosphatase (ALP), and free fatty acid (FFA) secretion. In addition, transduced WT Tat-DJ-1 protein significantly inhibited the activation of NF-κB and MAPK (ERK and p38) expression as well as expression of COX-2 and iNOS in STZ exposed pancreas. In contrast, treatment with C106A mutant Tat-DJ-1 protein showed no protective effects. Collectively, our results indicate that WT Tat-DJ-1 protein can significantly ameliorate pancreatic tissues in STZ-induced diabetes in mice. [BMB Reports 2018; 51(7): 362-367].

Glyoxalase 1 copy number variation in patients with well differentiated gastro-entero-pancreatic neuroendocrine tumours (GEP-NET)

Background

The glyoxalase-1 gene (GLO1) is a hotspot for copy-number variation (CNV) in human genomes. Increased GLO1 copy-number is associated with multidrug resistance in tumour chemotherapy, but prevalence of GLO1 CNV in gastro-entero-pancreatic neuroendocrine tumours (GEP-NET) is unknown.

Methods

GLO1 copy-number variation was measured in 39 patients with GEP-NET (midgut NET, n = 25; pancreatic NET, n = 14) after curative or debulking surgical treatment. Primary tumour tissue, surrounding healthy tissue and, where applicable, additional metastatic tumour tissue were analysed, using real time qPCR. Progression and survival following surgical treatment were monitored over 4.2 ± 0.5 years.

Results

In the pooled GEP-NET cohort, GLO1 copy-number in healthy tissue was 2.0 in all samples but significantly increased in primary tumour tissue in 43% of patients with pancreatic NET and in 72% of patients with midgut NET, mainly driven by significantly higher GLO1 copy-number in midgut NET. In tissue from additional metastases resection (18 midgut NET and one pancreatic NET), GLO1 copy number was also increased, compared with healthy tissue; but was not significantly different compared with primary tumour tissue. During mean 3 - 5 years follow-up, 8 patients died and 16 patients showed radiological progression. In midgut NET, a high GLO1 copy-number was associated with earlier progression. In NETs with increased GLO1 copy number, there was increased Glo1 protein expression compared to non-malignant tissue.

Conclusions

GLO1 copy-number was increased in a large percentage of patients with GEP-NET and correlated positively with increased Glo1 protein in tumour tissue. Analysis of GLO1 copy-number variation particularly in patients with midgut NET could be a novel prognostic marker for tumour progression.

Methylglyoxal-induced dicarbonyl stress in aging and disease: first steps towards glyoxalase 1-based treatments

Dicarbonyl stress is the abnormal accumulation of dicarbonyl metabolites leading to increased protein and DNA modification contributing to cell and tissue dysfunction in aging and disease. It is produced by increased formation and/or decreased metabolism of dicarbonyl metabolites. MG (methylglyoxal) is a dicarbonyl metabolite of relatively high flux of formation and precursor of the most quantitatively and functionally important spontaneous modifications of protein and DNA clinically. Major MG-derived adducts are arginine-derived hydroimidazolones of protein and deoxyguanosine-derived imidazopurinones of DNA. These are formed non-oxidatively. The glyoxalase system provides an efficient and essential basal and stress-response-inducible enzymatic defence against dicarbonyl stress by the reduced glutathione-dependent metabolism of methylglyoxal by glyoxalase 1. The GLO1 gene encoding glyoxalase 1 has low prevalence duplication and high prevalence amplification in some tumours. Dicarbonyl stress contributes to aging, disease and activity of cytotoxic chemotherapeutic agents. It is found at a low, moderate and severe level in obesity, diabetes and renal failure respectively, where it contributes to the development of metabolic and vascular complications. Increased glyoxalase 1 expression confers multidrug resistance to cancer chemotherapy and has relatively high prevalence in liver, lung and breast cancers. Studies of dicarbonyl stress are providing improved understanding of aging and disease and the basis for rational design of novel pharmaceuticals: glyoxalase 1 inducers for obesity, diabetes and cardiovascular disease and glyoxalase 1 inhibitors for multidrug-resistant tumours. The first clinical trial of a glyoxalase 1 inducer in overweight and obese subjects showed improved glycaemic control, insulin resistance and vascular function.

Multiple roles of glyoxalase 1-mediated suppression of methylglyoxal glycation in cancer biology-Involvement in tumour suppression, tumour growth, multidrug resistance and target for chemotherapy

Glyoxalase 1 (Glo1) is part of the glyoxalase system in the cytoplasm of all human cells. It catalyses the glutathione-dependent removal of the endogenous reactive dicarbonyl metabolite, methylglyoxal (MG). MG is formed mainly as a side product of anaerobic glycolysis. It modifies protein and DNA to form mainly hydroimidazolone MG-H1 and imidazopurinone MGdG adducts, respectively. Abnormal accumulation of MG, dicarbonyl stress, increases adduct levels which may induce apoptosis and replication catastrophe. In the non-malignant state, Glo1 is a tumour suppressor protein and small molecule inducers of Glo1 expression may find use in cancer prevention. Increased Glo1 expression is permissive for growth of tumours with high glycolytic activity and is thereby a biomarker of tumour growth. High Glo1 expression is a cause of multi-drug resistance. It is produced by over-activation of the Nrf2 pathway and GLO1 amplification. Glo1 inhibitors are antitumour agents, inducing apoptosis and necrosis, and anoikis. Tumour stem cells and tumours with high flux of MG formation and Glo1 expression are sensitive to Glo1 inhibitor therapy. It is likely that MG-induced cell death contributes to the mechanism of action of current antitumour agents. Common refractory tumours have high prevalence of Glo1 overexpression for which Glo1 inhibitors may improve therapy.

Tat-DJ-1 inhibits oxidative stress-mediated RINm5F cell death through suppression of NF-κB and MAPK activation

Oxidative stress is highly involved in the development of diabetes mellitus by destruction of pancreatic β-cells. DJ-1 is an antioxidant protein and DJ-1 expression levels are known to be reduced in diabetes mellitus. Thus, we examined the effects of DJ-1 protein against oxidative stress-induced pancreatic β-cell (RINm5F) death using cell permeable wild-type and mutant-type (C106A) Tat-DJ-1 proteins, which both efficiently transduced into RINm5F cells. Intracellular stability of wild-type Tat-DJ-1 persisted two times longer than C106A Tat-DJ-1. Wild-type Tat-DJ-1 protein markedly protected cells from hydrogen peroxide-induced toxicities such as cell death, reactive oxygen species generation, and DNA fragmentation. Further, wild-type Tat-DJ-1 protein significantly inhibited hydrogen peroxide-induced activation of mitogen-activated protein kinases and NF-κB signaling. On the other hand, C106A Tat-DJ-1 protein did not show the same protective effects. These results indicate that wild-type Tat-DJ-1 inhibits oxidative stress-induced cellular toxicity and activation of mitogen-activated protein kinases and NF-κB signals in RINm5F cells. These results suggest that wild-type Tat-DJ-1 protein may be a potential therapeutic agent against diabetes mellitus or toward the prevention of pancreatic β-cell destruction.

Dicarbonyls and glyoxalase in disease mechanisms and clinical therapeutics

The reactive dicarbonyl metabolite methylglyoxal (MG) is the precursor of the major quantitative advanced glycation endproducts (AGEs) in physiological systems - arginine-derived hydroimidazolones and deoxyguanosine-derived imidazopurinones. The glyoxalase system in the cytoplasm of cells provides the primary defence against dicarbonyl glycation by catalysing the metabolism of MG and related reactive dicarbonyls. Dicarbonyl stress is the abnormal accumulation of dicarbonyl metabolites leading to increased protein and DNA modification contributing to cell and tissue dysfunction in ageing and disease. It is produced endogenously by increased formation and/or decreased metabolism of dicarbonyl metabolites. Dicarbonyl stress contributes to ageing, disease and activity of cytotoxic chemotherapeutic agents. It contributes to ageing through age-related decline in glyoxalase 1 (Glo-1) activity. Glo-1 has a dual role in cancer as a tumour suppressor protein prior to tumour development and mediator of multi-drug resistance in cancer treatment, implicating dicarbonyl glycation of DNA in carcinogenesis and dicarbonyl-driven cytotoxicity in mechanism of action of anticancer drugs. Glo-1 is a driver of cardiovascular disease, likely through dicarbonyl stress-driven dyslipidemia and vascular cell dysfunction. Dicarbonyl stress is also a contributing mediator of obesity and vascular complications of diabetes. There are also emerging roles in neurological disorders. Glo-1 responds to dicarbonyl stress to enhance cytoprotection at the transcriptional level through stress-responsive increase of Glo-1 expression. Small molecule Glo-1 inducers are in clinical development for improved metabolic, vascular and renal health and Glo-1 inhibitors in preclinical development for multidrug resistant cancer chemotherapy.

Tat-ATOX1 inhibits streptozotocin-induced cell death in pancreatic RINm5F cells and attenuates diabetes in a mouse model

Antioxidant 1 (ATOX1) functions as an antioxidant against hydrogen peroxide and superoxide, and therefore may play a significant role in many human diseases, including diabetes mellitus (DM). In the present study, we examined the protective effects of Tat-ATOX1 protein on streptozotocin (STZ)-exposed pancreatic insulinoma cells (RINm5F) and in a mouse model of STZ-induced diabetes using western blot analysis, immunofluorescence staining and MTT assay, as well as histological and biochemical analysis. Purified Tat-ATOX1 protein was efficiently transduced into RINm5F cells in a dose- and time-dependent manner. Additionally, Tat-ATOX1 protein markedly inhibited reactive oxygen species (ROS) production, DNA damage and the activation of Akt and mitogen activated protein kinases (MAPKs) in STZ-exposed RINm5F cells. In addition, Tat-ATOX1 protein transduced into mice pancreatic tissues and significantly decreased blood glucose and hemoglobin A1c (HbA1c) levels as well as the body weight changes in a model of STZ-induced diabetes. These results indicate that transduced Tat-ATOX1 protein protects pancreatic β-cells by inhibiting STZ-induced cellular toxicity in vitro and in vivo. Based on these findings, we suggest that Tat-ATOX1 protein has potential applications as a therapeutic agent for oxidative stress-induced diseases including DM.

Blockade of monocyte-endothelial trafficking by transduced Tat-superoxide dismutase protein

It has previously been suggested that reactive oxygen species (ROS) are involved in the pathogenesis of chronic inflammatory diseases, which entails the initial activation of pro-inflammatory cytokines to facilitate leukocyte transmigration. The present study investigated whether intracellular superoxide dismutase (SOD) suppressed monocyte endothelial trafficking and transmigration. Human umbilical vein endothelial cells (HUVECs) and THP-1 monocytes were activated by the cytokine tumor necrosis factor-α (TNF-α) in the absence and presence of cell-permeable transactivator of transcription (Tat)-SOD protein. External stimulation with SOD was conducted using endothelial cells and monocytes. Purified cell-permeable Tat-SOD, but not non-targeted SOD, at 1-3 µM was transduced into endothelial cells in a time‑ and dose-dependent manner. Non-toxic Tat-SOD at ≤0.5 µM, but not 1 µM SOD, blocked the monocyte-endothelium interactions by inhibiting the TNF-α-induced stimulation of vascular cell adhesion molecule-1 (VCAM-1) in HUVECs and integrin β1 in THP-1 cells. Endothelial VCAM-1 induction by TNF-α was responsible for superoxide anion production being quenched by N-acetyl-cysteine and Tat-SOD. SOD treatment markedly inhibited superoxide anion production induced by TNF-α, but no inhibition of endothelial transmigration was noted. Tat-SOD prevented transendothelial monocyte migration by firmly localizing occludin-1, platelet/endothelial cell adhesion molecule‑1 (PECAM-1) and vascular endothelial‑cadherin present in paracellular junctions and inhibiting endothelial induction and activation of matrix-degrading membrane type-1 (MT-1) matrix metalloproteinase (MMP), MMP-2 and MMP-9. By contrast, treatment with 1 µM SOD did not have such effects. Furthermore, transduced Tat-SOD hindered nuclear transactivation of nuclear factor-κB (NF-κB), modulating the induction of paracellular junction proteins and matrix‑degrading MMP in TNF-α‑stimulated HUVECs. Transduced Tat-SOD, but not external SOD, impeded cytokine-induced endothelial adhesion and the transmigration of monocytes. Thus, we suggest that transduced Tat-SOD qualifies as an atheroprotective agent against oxidation-driven and inflammation-associated atherosclerosis.

Methylglyoxal, the foe and friend of glyoxalase and Trx/TrxR systems in HT22 nerve cells

Methylglyoxal (MGO) is a major glycating agent that reacts with basic residues of proteins and promotes the formation of advanced glycation end products (AGEs) which are believed to play key roles in a number of pathologies, such as diabetes, Alzheimer's disease, and inflammation. Here, we examined the effects of MGO on immortalized mouse hippocampal HT22 nerve cells. The endpoints analyzed were MGO and thiol status, the glyoxalase system, comprising glyoxalase 1 and 2 (GLO1/2), and the cytosolic and mitochondrial Trx/TrxR systems, as well as nuclear Nrf2 and its target genes. We found that nuclear Nrf2 is induced by MGO treatment in HT22 cells, as corroborated by induction of the Nrf2-controlled target genes and proteins glutamate cysteine ligase and heme oxygenase 1. Nrf2 knockdown prevented MGO-dependent induction of glutamate cysteine ligase and heme oxygenase 1. The cystine/glutamate antiporter, system xc(-), which is also controlled by Nrf2, was also induced. The increased cystine import (system xc(-)) activity and GCL expression promoted GSH synthesis, leading to increased levels of GSH. The data indicate that MGO can act as both a foe and a friend of the glyoxalase and the Trx/TrxR systems. At low concentrations of MGO (0.3mM), GLO2 is strongly induced, but at high MGO (0.75 mM) concentrations, GLO1 is inhibited and GLO2 is downregulated. The cytosolic Trx/TrxR system is impaired by MGO, where Trx is downregulated yet TrxR is induced, but strong MGO-dependent glycation may explain the loss in TrxR activity. We propose that Nrf2 can be the unifying element to explain the observed upregulation of GSH, GCL, HO1, TrxR1, Trx2, TrxR2, and system xc(-) system activity.

Activity, regulation, copy number and function in the glyoxalase system

Molecular, catalytic and structural properties of glyoxalase pathway enzymes of many species are now known. Current research has focused on the regulation of activity and expression of Glo1 (glyoxalase I) and Glo2 (glyoxalase II) and their role in health and disease. Human GLO1 has MRE (metal-response element), IRE (insulin-response element), E2F4 (early gene 2 factor isoform 4), AP-2α (activating enhancer-binding protein 2α) and ARE (antioxidant response-element) regulatory elements and is a hotspot for copy number variation. The human Glo2 gene, HAGH (hydroxyacylglutathione hydrolase), has a regulatory p53-response element. Glo1 is linked to healthy aging, obesity, diabetes and diabetic complications, chronic renal disease, cardiovascular disease, other disorders and multidrug resistance in cancer chemotherapy. Mathematical modelling of the glyoxalase pathway predicts that pharmacological levels of increased Glo1 activity markedly decrease cellular methylglyoxal and related glycation, and pharmacological Glo1 inhibition markedly increases cellular methylglyoxal and related glycation. Glo1 inducers are in development to sustain healthy aging and for treatment of vascular complications of diabetes and other disorders, and cell-permeant Glo1 inhibitors are in development for treatment of multidrug-resistant tumours, malaria and potentially pathogenic bacteria and fungi.

Dicarbonyl proteome and genome damage in metabolic and vascular disease

Methylglyoxal is a potent protein-glycating agent. It is an arginine-directed glycating agent and often modifies functionally important sites in proteins. Glycation forms mainly MG-H1 [Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)ornithine] residues. MG-H1 content of proteins is quantified by stable isotopic dilution analysis-MS/MS and also by immunoblotting with specific monoclonal antibodies. Methylglyoxal-modified proteins undergo cellular proteolysis and release MG-H1 free adduct for excretion. MG-H1 residues have been found in proteins of animals, plants, bacteria, fungi and protoctista. MG-H1 is often the major advanced glycation end-product in proteins of tissues and body fluids, increasing in diabetes and associated vascular complications, renal failure, cirrhosis, Alzheimer's disease, arthritis, Parkinson's disease and aging. Proteins susceptible to methylglyoxal modification with related functional impairment are called the DCP (dicarbonyl proteome). The DCP includes albumin, haemoglobin, transcription factors, mitochondrial proteins, extracellular matrix proteins, lens crystallins and others. DCP component proteins are linked to mitochondrial dysfunction in diabetes and aging, oxidative stress, dyslipidaemia, cell detachment and anoikis and apoptosis. Methylglyoxal also modifies DNA where deoxyguanosine residues are modified to imidazopurinone MGdG {3-(2'-deoxyribosyl)-6,7-dihydro-6,7-dihydroxy-6/7-methylimidazo-[2,3-b]purine-9(8)one} isomers. MGdG was the major quantitative adduct detected in vivo. It was linked to frequency of DNA strand breaks and increased markedly during apoptosis induced by a cell-permeant glyoxalase I inhibitor. Glyoxalase I metabolizes >99% methylglyoxal and thereby protects the proteome and genome. Gene deletion of GLO1 is embryonically lethal and GLO1 silencing increases methylglyoxal concentration, MG-H1 and MGdG, premature aging and disease. Studies of methylglyoxal glycation have importance for human health, longevity and treatment of disease.

Tat-CBR1 inhibits inflammatory responses through the suppressions of NF-κB and MAPK activation in macrophages and TPA-induced ear edema in mice

Human carbonyl reductase 1 (CBR1) plays a crucial role in cell survival and protects against oxidative stress response. However, its anti-inflammatory effects are not yet clearly understood. In this study, we examined whether CBR1 protects against inflammatory responses in macrophages and mice using a Tat-CBR1 protein which is able to penetrate into cells. The results revealed that purified Tat-CBR1 protein efficiently transduced into Raw 264.7 cells and inhibited lipopolysaccharide (LPS)-induced cyclooxygenase-2 (COX-2), nitric oxide (NO) and prostaglandin E2 (PGE2) expression levels. In addition, Tat-CBR1 protein leads to decreased pro-inflammatory cytokine expression through suppression of nuclear transcription factor-kappaB (NF-κB) and mitogen activated protein kinase (MAPK) activation. Furthermore, Tat-CBR1 protein inhibited inflammatory responses in 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced skin inflammation when applied topically. These findings indicate that Tat-CBR1 protein has anti-inflammatory properties in vitro and in vivo through inhibition of NF-κB and MAPK activation, suggesting that Tat-CBR1 protein may have potential as a therapeutic agent against inflammatory diseases.

Tat-glyoxalase protein inhibits against ischemic neuronal cell damage and ameliorates ischemic injury

Methylglyoxal (MG), a metabolite of glucose, is the major precursor of protein glycation and induces apoptosis. MG is associated with neurodegeneration, including oxidative stress and impaired glucose metabolism, and is efficiently metabolized to S-D-lactoylglutathione by glyoxalase (GLO). Although GLO has been implicated as being crucial in various diseases including ischemia, its detailed functions remain unclear. Therefore, we investigated the protective effect of GLO (GLO1 and GLO2) in neuronal cells and an animal ischemia model using Tat-GLO proteins. Purified Tat-GLO protein efficiently transduced into HT-22 neuronal cells and protected cells against MG- and H2O2-induced cell death, DNA fragmentation, and activation of caspase-3 and mitogen-activated protein kinase. In addition, transduced Tat-GLO protein increased D-lactate in MG- and H2O2-treated cells whereas glycation end products (AGE) and MG levels were significantly reduced in the same cells. Gerbils treated with Tat-GLO proteins displayed delayed neuronal cell death in the CA1 region of the hippocampus compared with a control. Furthermore, the combined neuroprotective effects of Tat-GLO1 and Tat-GLO2 proteins against ischemic damage were significantly higher than those of each individual protein. Those results demonstrate that transduced Tat-GLO protein protects neuronal cells by inhibiting MG- and H2O2-mediated cytotoxicity in vitro and in vivo. Therefore, we suggest that Tat-GLO proteins could be useful as a therapeutic agent for various human diseases related to oxidative stress including brain diseases.