Glutaredoxin-1 up-regulation induces soluble vascular endothelial growth factor receptor 1, attenuating post-ischemia limb revascularization

The significance of glutaredoxins for diabetes mellitus and its complications

Diabetes mellitus is a non-communicable metabolic disease hallmarked by chronic hyperglycemia caused by beta-cell failure. Diabetic complications affect the vasculature and result in macro- and microangiopathies, which account for a significantly increased morbidity and mortality. The rising incidence and prevalence of diabetes is a major global health burden. There are no feasible strategies for beta-cell preservation available in daily clinical practice. Therefore, patients rely on antidiabetic drugs or the application of exogenous insulin. Glutaredoxins (Grxs) are ubiquitously expressed and highly conserved members of the thioredoxin family of proteins. They have specific functions in redox-mediated signal transduction, iron homeostasis and biosynthesis of iron-sulfur (FeS) proteins, and the regulation of cell proliferation, survival, and function. The involvement of Grxs in chronic diseases has been a topic of research for several decades, suggesting them as therapeutic targets. Little is known about their role in diabetes and its complications. Therefore, this review summarizes the available literature on the significance of Grxs in diabetes and its complications. In conclusion, Grxs are differentially expressed in the endocrine pancreas and in tissues affected by diabetic complications, such as the heart, the kidneys, the eye, and the vasculature. They are involved in several pathways essential for insulin signaling, metabolic inflammation, glucose and fatty acid uptake and processing, cell survival, and iron and mitochondrial metabolism. Most studies describe significant changes in glutaredoxin expression and/or activity in response to the diabetic metabolism. In general, mitigated levels of Grxs are associated with oxidative distress, cell damage, and even cell death. The induced overexpression is considered a potential part of the cellular stress-response, counteracting oxidative distress and exerting beneficial impact on cell function such as insulin secretion, cytokine expression, and enzyme activity.

In vivo laser speckle contrast imaging of microvascular blood perfusion using a chip-on-tip camera

Laser speckle contrast imaging (LSCI) is an important non-invasive capability for real-time imaging for tissue-perfusion assessment. Yet, the size and weight of current clinical standard LSCI instrumentation restricts usage to mainly peripheral skin perfusion. Miniaturization of LSCI could enable hand-held instrumentation to image internal organ/tissue to produce accurate speckle-perfusion maps. We characterized a 1mm2 chip-on-tip camera for LSCI of blood perfusion in vivo and with a flow model. A dedicated optical setup was built to compare chip-on-tip camera to a high specification reference camera (GS3) for LSCI. We compared LSCI performance using a calibration standard and a flow phantom. Subsequently the camera assessed placenta perfusion in a small animal model. Lastly, a human study was conducted on the perfusion in fingertips of 13-volunteers. We demonstrate that the chip-on-tip camera can perform wide-field, in vivo, LSCI of tissue perfusion with the ability to measure physiological blood flow changes comparable with a standard reference camera.

Glutaredoxin-1 modulates the NF-κB signaling pathway to activate inducible nitric oxide synthase in experimental necrotizing enterocolitis

Inducible nitric oxide synthase (iNOS), regulated by nuclear factor kappa B (NF-κB), is crucial for intestinal inflammation and barrier injury in the progression of necrotizing enterocolitis (NEC). The NF-κB pathway is inhibited by S-glutathionylation of inhibitory κB kinase β (IKKβ), which can be restored by glutaredoxin-1 (Grx1). Thus, we aim to explore the role of Grx1 in experimental NEC. Wild-type (WT) and Grx1-knockout (Grx1-/-) mice were treated with an NEC-inducing regimen. Primary intestinal epithelial cells (IECs) were subjected to LPS treatment. The production of iNOS, NO, and inflammation injuries were assessed. NF-κB and involved signaling pathways were also explored. The severity of NEC was attenuated in Grx1-/- mice. Grx1 ablation promoted IKKβ glutathionylation, NF-κB inactivation, and decreased iNOS, NO, and O2·- production in NEC mice. Furthermore, Grx1 ablation restrained proinflammatory cytokines and cell apoptosis, ameliorated intestinal barrier damage, and promoted proliferation in NEC mice. Grx1 ablation protected NEC through iNOS and NO inhibition, which related to S-glutathionylation of IKKβ to inhibit NF-κB signaling. Grx1-related signaling pathways provide a new therapeutic target for NEC.

Ergothioneine improves myocardial remodeling and heart function after acute myocardial infarction via S-glutathionylation through the NF-ĸB dependent Wnt5a-sFlt-1 pathway

Myocardial infarction (MI) remains the leading cause of cardiovascular death worldwide. Studies have shown that soluble fms-like tyrosine kinase-1 (sFlt-1) has a harmful effect on the heart after MI. However, ergothioneine (ERG) has been shown to have protective effects in rats with preeclampsia by reducing circulating levels of sFlt-1. In this study, we aimed to investigate the mechanism by which ERG protects the heart after MI in rats. Our results indicate that treatment with 10 mg/kg ERG for 7 days can improve cardiac function as determined by echocardiography. Additionally, ERG can reduce the size of the damaged area, prevent heart remodeling, fibrosis, and reduce cardiomyocyte death after MI. To explain the mechanism behind the cardioprotective effects of ERG, we conducted several experiments. We observed a significant reduction in the expression of monocyte chemoattractant protein-1 (MCP-1), p65, and p-p65 proteins in heart tissues of ERG-treated rats compared to the control group. ELISA results also showed that ERG significantly reduced plasma levels of sFlt-1. Using Glutaredoxin-1 (GLRX) and CD31 immunofluorescence, we found that GLRX was expressed in clusters in the myocardial tissue surrounding the coronary artery, and ERG can reduce the expression of GLRX caused by MI. In vitro experiments using a human coronary artery endothelial cell (HCAEC) hypoxia model confirmed that ERG can reduce the expression of sFlt-1, GLRX, and Wnt5a. These findings suggest that ERG protects the heart from MI damage by reducing s-glutathionylation through the NF-ĸB-dependent Wnt5a-sFlt-1 pathway.

Involvement of HIF1 stabilization and VEGF signaling modulated by Grx-1 in murine model of bronchopulmonary dysplasia

Hypoxia inducible factor (HIF)-1α could be stabilized by Grx1 deletion, which is implicated critical in the pathogenesis of bronchopulmonary dysplasia (BPD). Until now, the stabilization of HIF-1α by glutathionylation to regulate the pulmonary microcirculation in BPD is not well addressed. In this study, we investigated whether the HIF-1α stabilization modulated by Grx1 ablation could ameliorate the pathological changes in the mouse model of BPD, including angiogenesis and alveolar formation. We found that depletion of Grx1 increased levels of GSH-protein adducts, which was associated with the improvement in the numbers of alveoli, the capillary density in the pulmonary microcirculation and the survival rate in the littermates with hyperoxic exposure. Grx1 ablation could promote HIF-1α glutathionylation by increasing GSH adducts to stabilize HIF-1α and to induce VEGF-A production in the lung tissue. The above phenotype of capillary density and VEGF-A production was removed by the pharmacological administration of YC-1, the HIF-1α inhibitor, suggesting the HIF-1α dependent manner for pulmonary microcirculatory perfusion. These data indicate that HIF-1α stabilization plays an critical role in modification pulmonary microcirculatory perfusion, which is associated with the pathological damage under hyperoxic conditions, suggesting that targeting with HIF-1α stabilization should be a potential clinical and therapeutic strategy for BPD treatment.

S-Glutathionylation-Controlled Apoptosis of Lung Epithelial Cells; Potential Implications for Lung Fibrosis

Glutathione (GSH), a major antioxidant in mammalian cells, regulates several vital cellular processes, such as nutrient metabolism, protein synthesis, and immune responses. In addition to its role in antioxidant defense, GSH controls biological processes through its conjugation to reactive protein cysteines in a post-translational modification known as protein S-glutathionylation (PSSG). PSSG has recently been implicated in the pathogenesis of multiple diseases including idiopathic pulmonary fibrosis (IPF). Hallmarks of IPF include repeated injury to the alveolar epithelium with aberrant tissue repair, epithelial cell apoptosis and fibroblast resistance to apoptosis, and the accumulation of extracellular matrix and distortion of normal lung architecture. Several studies have linked oxidative stress and PSSG to the development and progression of IPF. Additionally, it has been suggested that the loss of epithelial cell homeostasis and increased apoptosis, accompanied by the release of various metabolites, creates a vicious cycle that aggravates disease progression. In this short review, we highlight some recent studies that link PSSG to epithelial cell apoptosis and highlight the potential implication of metabolites secreted by apoptotic cells.

Hypoxia-Inducible Factor 1α Stability Modified by Glutaredoxin-1 in Necrotizing Enterocolitis

INTRODUCTION

Hypoxia-inducible factor (HIF) 1α is essential for the pathogenesis of necrotizing enterocolitis (NEC). HIF-1α is stabilized by glutaredoxin-1 (Grx1) deletion. The precise role of HIF-1α in the intestinal microcirculation in NEC is not well defined. We aimed to determine the role of HIF-1α in the regulation of the intestinal microcirculation during the development of NEC.

METHODS

Experimental NEC was induced in full-term C57BL/6 mice and Grx1^-/- pups through the formula gavage and hypoxia technique. HIF-1α signaling was blocked using the HIF-1α inhibitor, YC-1 [3-(5-hydroxymethyl-2-furyl)-1-benzyl indazole]. Intestinal tissues were collected at predetermined time points for the assessment of the intestinal microcirculation and HIF-1α activity and signaling.

RESULTS

We found that NEC induction impaired the intestinal microcirculation, but the impairment of the intestinal blood flow and capillary density was ameliorated in Grx1^-/- mice. This amelioration was associated with tripeptide glutathione-protein adducts in the intestinal tissue. Grx1 ablation also promoted vascular endothelial growth factor A production in the intestinal tissue. This intestinal microvascular improvement was not found in HIF-1α-inhibited mice, suggesting that HIF-1α was involved in the intestinal microcirculatory perfusion.

CONCLUSIONS

The current data demonstrated that HIF-1α signaling is involved in the intestinal microvascular modification during the pathogenesis of NEC, suggesting that targeting HIF-1α might be a promising strategy for NEC treatment.

Administration of Glutaredoxin-1 Attenuates Liver Fibrosis Caused by Aging and Non-Alcoholic Steatohepatitis

Liver fibrosis is a sign of non-alcoholic fatty liver disease progression towards steatohepatitis (NASH) and cirrhosis and is accelerated by aging. Glutaredoxin-1 (Glrx) controls redox signaling by reversing protein S-glutathionylation, induced by oxidative stress, and its deletion causes fatty liver in mice. Although Glrx regulates various pathways, including metabolism and apoptosis, the impact of Glrx on liver fibrosis has not been studied. Therefore, we evaluated the role of Glrx in liver fibrosis induced by aging or by a high-fat, high-fructose diet. We found that: (1) upregulation of Glrx expression level inhibits age-induced hepatic apoptosis and liver fibrosis. In vitro studies indicate that Glrx regulates Fas-induced apoptosis in hepatocytes; (2) diet-induced NASH leads to reduced expression of Glrx and higher levels of S-glutathionylated proteins in the liver. In the NASH model, hepatocyte-specific adeno-associated virus-mediated Glrx overexpression (AAV-Hep-Glrx) suppresses fibrosis and apoptosis and improves liver function; (3) AAV-Hep-Glrx significantly inhibits transcription of Zbtb16 and negatively regulates immune pathways in the NASH liver. In conclusion, the upregulation of Glrx is a potential therapeutic for the reversal of NASH progression by attenuating inflammatory and fibrotic processes.

Oxidative Post-Translational Modifications: A Focus on Cysteine S-Sulfhydration and the Regulation of Endothelial Fitness

Significance: Changes in the oxidative balance can affect cellular physiology and adaptation through redox signaling. The endothelial cells that line blood vessels are particularly sensitive to reactive oxygen species, which can alter cell function by a number of mechanisms, including the oxidative post-translational modification (oxPTM) of proteins on critical cysteine thiols. Such modifications can act as redox-switches to alter the function of targeted proteins. Recent Advances: Mapping the cysteine oxPTM proteome and characterizing the effects of individual oxPTMs to gain insight into consequences for cellular responses has proven challenging. A recent addition to the list of reversible oxPTMs that contributes to cellular redox homeostasis is persulfidation or S-sulfhydration. Critical Issues: It has been estimated that up to 25% of proteins are S-sulfhydrated, making this modification almost as abundant as phosphorylation. In the endothelium, persulfides are generated by the trans-sulfuration pathway that catabolizes cysteine and cystathionine to generate hydrogen sulfide (H₂S) and H₂S-related sulfane sulfur compounds (H₂S_n). This pathway is of particular importance for the vascular system, as the enzyme cystathionine γ lyase (CSE) in endothelial cells accounts for a significant portion of total vascular H₂S/H₂S_n production. Future Directions: Impaired CSE activity in endothelial dysfunction has been linked with marked changes in the endothelial cell S-sulfhydrome and can contribute to the development of atherosclerosis and hypertension. It will be interesting to determine how changes in the S-sulfhydration of specific networks of proteins contribute to endothelial cell physiology and pathophysiology. Antioxid. Redox Signal. 35, 1494-1514.

Glutaredoxin-1 levels in plasma can predict future events in patients with cardiovascular diseases

Reactive oxygen species that increase during cardiovascular disease (CVD) react with protein cysteine residues to form a glutathione adduct by S-glutathionylation, which is selectively removed by glutaredoxin-1 (Glrx). We previously showed that S-glutathionylation and Glrx play important roles in mouse models of CVD, such as heart failure and peripheral artery disease models. However, there are few clinical studies on Glrx in CVD. Although Glrx is a cytosolic protein expressed in various organs, it is detectable in human plasma. Studies have reported that Glrx in plasma is a potential disease maker, such as CVD and chronic kidney disease and diabetes, however, it remains unclear whether Glrx is related to the prognosis of patients with CVD. The purpose of this study was to elucidate whether Glrx levels in plasma are associated with future events in patients with CVD. Plasma levels of Glrx were measured in 555 patients with CVD who underwent cardiac catheterization using enzyme-linked immunosorbent assay. All patients were followed prospectively for ≤36 months or until occurrence of adverse events, including all-cause death, non-fatal myocardial infarction, and worsening heart failure. During a mean follow-up period of 33 months, 54 adverse events occurred. Kaplan-Meier analysis showed that higher levels of Glrx (>0.622 ng/mL, determined by receiver-operating characteristic curve) resulted in a higher probability for adverse events compared with lower levels of Glrx (≤0.622 ng/mL) (P < 0.01, log-rank test). Multivariate Cox proportional hazards analysis showed that Glrx was a significant predictor of adverse events after adjustment for known risk factors. In conclusion, levels of plasma Glrx >0.662 ng/mL can predict future events in patients with CVD.

Oxidized GAPDH transfers S-glutathionylation to a nuclear protein Sirtuin-1 leading to apoptosis

AIMS

S-glutathionylation is a reversible oxidative modification of protein cysteines that plays a critical role in redox signaling. Glutaredoxin-1 (Glrx), a glutathione-specific thioltransferase, removes protein S-glutathionylation. Glrx, though a cytosolic protein, can activate a nuclear protein Sirtuin-1 (SirT1) by removing its S-glutathionylation. Glrx ablation causes metabolic abnormalities and promotes controlled cell death and fibrosis in mice. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a key enzyme of glycolysis, is sensitive to oxidative modifications and involved in apoptotic signaling via the SirT1/p53 pathway in the nucleus. We aimed to elucidate the extent to which S-glutathionylation of GAPDH and glutaredoxin-1 contribute to GAPDH/SirT1/p53 apoptosis pathway.

RESULTS

Exposure of HEK 293T cells to hydrogen peroxide (H₂O₂) caused rapid S-glutathionylation and nuclear translocation of GAPDH. Nuclear GAPDH peaked 10-15 min after the addition of H₂O₂. Overexpression of Glrx or redox dead mutant GAPDH inhibited S-glutathionylation and nuclear translocation. Nuclear GAPDH formed a protein complex with SirT1 and exchanged S-glutathionylation to SirT1 and inhibited its deacetylase activity. Inactivated SirT1 remained stably bound to acetylated-p53 and initiated apoptotic signaling resulting in cleavage of caspase-3. We observed similar effects in human primary aortic endothelial cells suggesting the GAPDH/SirT1/p53 pathway as a common apoptotic mechanism.

CONCLUSIONS

Abundant GAPDH with its highly reactive-cysteine thiolate may function as a cytoplasmic rheostat to sense oxidative stress. S-glutathionylation of GAPDH may relay the signal to the nucleus where GAPDH trans-glutathionylates nuclear proteins such as SirT1 to initiate apoptosis. Glrx reverses GAPDH S-glutathionylation and prevents its nuclear translocation and cytoplasmic-nuclear redox signaling leading to apoptosis. Our data suggest that trans-glutathionylation is a critical step in apoptotic signaling and a potential mechanism that cytosolic Glrx controls nuclear transcription factors.

Thiol-based redox-active proteins as cardioprotective therapeutic agents in cardiovascular diseases

Thiol-based redox compounds, namely thioredoxins (Trxs), glutaredoxins (Grxs) and peroxiredoxins (Prxs), stand as a pivotal group of proteins involved in antioxidant processes and redox signaling. Glutaredoxins (Grxs) are considered as one of the major families of proteins involved in redox regulation by removal of S-glutathionylation and thereby reactivation of other enzymes with thiol-dependent activity. Grxs are also coupled to Trxs and Prxs recycling and thereby indirectly contribute to reactive oxygen species (ROS) detoxification. Peroxiredoxins (Prxs) are a ubiquitous family of peroxidases, which play an essential role in the detoxification of hydrogen peroxide, aliphatic and aromatic hydroperoxides, and peroxynitrite. The Trxs, Grxs and Prxs systems, which reversibly induce thiol modifications, regulate redox signaling involved in various biological events in the cardiovascular system. This review focuses on the current knowledge of the role of Trxs, Grxs and Prxs on cardiovascular pathologies and especially in cardiac hypertrophy, ischemia/reperfusion (I/R) injury and heart failure as well as in the presence of cardiovascular risk factors, such as hypertension, hyperlipidemia, hyperglycemia and metabolic syndrome. Further studies on the roles of thiol-dependent redox systems in the cardiovascular system will support the development of novel protective and therapeutic strategies against cardiovascular diseases.

The complex role of Wnt ligands in type 2 diabetes mellitus and related complications

Type 2 diabetes mellitus (T2DM) is one of the major chronic diseases, whose prevalence is increasing dramatically worldwide and can lead to a range of serious complications. Wnt ligands (Wnts) and their activating Wnt signalling pathways are closely involved in the regulation of various processes that are important for the occurrence and progression of T2DM and related complications. However, our understanding of their roles in these diseases is quite rudimentary due to the numerous family members of Wnts and conflicting effects via activating the canonical and/or non-canonical Wnt signalling pathways. In this review, we summarize the current findings on the expression pattern and exact role of each human Wnt in T2DM and related complications, including Wnt1, Wnt2, Wnt2b, Wnt3, Wnt3a, Wnt4, Wnt5a, Wnt5b, Wnt6, Wnt7a, Wnt7b, Wnt8a, Wnt8b, Wnt9a, Wnt9b, Wnt10a, Wnt10b, Wnt11 and Wnt16. Moreover, the role of main antagonists (sFRPs and WIF-1) and coreceptor (LRP6) of Wnts in T2DM and related complications and main challenges in designing Wnt-based therapeutic approaches for these diseases are discussed. We hope a deep understanding of the mechanistic links between Wnt signalling pathways and diabetic-related diseases will ultimately result in a better management of these diseases.

Glutaredoxin: Discovery, redox defense and much more

Glutaredoxin, Grx, is a small protein containing an active site cysteine pair and was discovered in 1976 by Arne Holmgren. The Grx system, comprised of Grx, glutathione, glutathione reductase, and NADPH, was first described as an electron donor for Ribonucleotide Reductase but, from the first discovery in E.coli, the Grx family has impressively grown, particularly in the last two decades. Several isoforms have been described in different organisms (from bacteria to humans) and with different functions.

The unique characteristic of Grxs is their ability to catalyse glutathione-dependent redox regulation via glutathionylation, the conjugation of glutathione to a substrate, and its reverse reaction, deglutathionylation. Grxs have also recently been enrolled in iron sulphur cluster formation. These functions have been implied in various physiological and pathological conditions, from immune defense to neurodegeneration and cancer development thus making Grx a possible drug target.

This review aims to give an overview on Grxs, starting by a phylogenetic analysis of vertebrate Grxs, followed by an analysis of the mechanisms of action, the specific characteristics of the different human isoforms and a discussion on aspects related to human physiology and diseases.

Strategies to Overcome the Barrier of Ischemic Microenvironment in Cell Therapy of Cardiovascular Disease

The transplantation of various immune cell types are promising approaches for the treatment of ischemic cardiovascular disease including myocardial infarction (MI) and peripheral arterial disease (PAD). Major limitation of these so-called Advanced Therapy Medicinal Products (ATMPs) is the ischemic microenvironment affecting cell homeostasis and limiting the demanded effect of the transplanted cell products. Accordingly, different clinical and experimental strategies have been evolved to overcome these obstacles. Here, we give a short review of the different experimental and clinical strategies to solve these issues due to ischemic cardiovascular disease.

S-glutathionylation, friend or foe in cardiovascular health and disease

Glutathione is a low molecular weight thiol that is present at high levels in the cell. The high levels of glutathione in the cell make it one of the most abundant antioxidants contributing to cellular redox homeostasis. As a general rule, throughout cardiovascular disease and progression there is an imbalance in redox homeostasis characterized by reactive oxygen species overproduction and glutathione underproduction. As research into these imbalances continues, glutathione concentrations are increasingly being observed to drive various physiological and pathological signaling responses. Interestingly in addition to acting directly as an antioxidant, glutathione is capable of post translational modifications (S-glutathionylation) of proteins through both chemical interactions and enzyme mediated events. This review will discuss both the chemical and enzyme-based S-glutathionylation of proteins involved in cardiovascular pathologies and angiogenesis.

Role of Glutaredoxin-1 and Glutathionylation in Cardiovascular Diseases

Cardiovascular diseases are the leading cause of death worldwide, and as rates continue to increase, discovering mechanisms and therapeutic targets become increasingly important. An underlying cause of most cardiovascular diseases is believed to be excess reactive oxygen or nitrogen species. Glutathione, the most abundant cellular antioxidant, plays an important role in the body’s reaction to oxidative stress by forming reversible disulfide bridges with a variety of proteins, termed glutathionylation (GSylation). GSylation can alter the activity, function, and structure of proteins, making it a major regulator of cellular processes. Glutathione-protein mixed disulfide bonds are regulated by glutaredoxins (Glrxs), thioltransferase members of the thioredoxin family. Glrxs reduce GSylated proteins and make them available for another redox signaling cycle. Glrxs and GSylation play an important role in cardiovascular diseases, such as myocardial ischemia and reperfusion, cardiac hypertrophy, peripheral arterial disease, and atherosclerosis. This review primarily concerns the role of GSylation and Glrxs, particularly glutaredoxin-1 (Glrx), in cardiovascular diseases and the potential of Glrx as therapeutic agents.

Redox Regulation via Glutaredoxin-1 and Protein S-Glutathionylation

Significance: Over the past several years, oxidative post-translational modifications of protein cysteines have been recognized for their critical roles in physiology and pathophysiology. Cells have harnessed thiol modifications involving both oxidative and reductive steps for signaling and protein processing. One of these stages requires oxidation of cysteine to sulfenic acid, followed by two reduction reactions. First, glutathione (reduced glutathione [GSH]) forms a S-glutathionylated protein, and second, enzymatic or chemical reduction removes the modification. Under physiological conditions, these steps confer redox signaling and protect cysteines from irreversible oxidation. However, oxidative stress can overwhelm protein S-glutathionylation and irreversibly modify cysteine residues, disrupting redox signaling. Critical Issues: Glutaredoxins mainly catalyze the removal of protein-bound GSH and help maintain protein thiols in a highly reduced state without exerting direct antioxidant properties. Conversely, glutathione S-transferase (GST), peroxiredoxins, and occasionally glutaredoxins can also catalyze protein S-glutathionylation, thus promoting a dynamic redox environment. Recent Advances: The latest studies of glutaredoxin-1 (Glrx) transgenic or knockout mice demonstrate important distinct roles of Glrx in a variety of pathologies. Endogenous Glrx is essential to maintain normal hepatic lipid homeostasis and prevent fatty liver disease. Further, in vivo deletion of Glrx protects lungs from inflammation and bacterial pneumonia-induced damage, attenuates angiotensin II-induced cardiovascular hypertrophy, and improves ischemic limb vascularization. Meanwhile, exogenous Glrx administration can reverse pathological lung fibrosis. Future Directions: Although S-glutathionylation modifies many proteins, these studies suggest that S-glutathionylation and Glrx regulate specific pathways in vivo, and they implicate Glrx as a potential novel therapeutic target to treat diverse disease conditions. Antioxid. Redox Signal. 32, 677-700.

Endothelial cell-specific redox gene modulation inhibits angiogenesis but promotes B16F0 tumor growth in mice

Glutaredoxin-1 (Glrx) is a small cytosolic enzyme that removes S-glutathionylation, glutathione adducts of protein cysteine residues, thus modulating redox signaling and gene transcription. Although Glrx up-regulation prevented endothelial cell (EC) migration and global Glrx transgenic mice had impaired ischemic vascularization, the effects of cell-specific Glrx overexpression remained unknown. Here, we examined the role of EC-specific Glrx up-regulation in distinct models of angiogenesis; namely, hind limb ischemia and tumor angiogenesis. EC-specific Glrx transgenic (EC-Glrx TG) overexpression in mice significantly impaired EC migration in Matrigel implants and hind limb revascularization after femoral artery ligation. Additionally, ECs migrated less into subcutaneously implanted B16F0 melanoma tumors as assessed by decreased staining of EC markers. Despite reduced angiogenesis, EC-Glrx TG mice unexpectedly developed larger tumors compared with control mice. EC-Glrx TG mice showed higher levels of VEGF-A in the tumors, indicating hypoxia, which may stimulate tumor cells to form vascular channels without EC, referred to as vasculogenic mimicry. These data suggest that impaired ischemic vascularization does not necessarily associate with suppression of tumor growth, and that antiangiogenic therapies may be ineffective for melanoma tumors because of their ability to implement vasculogenic mimicry during hypoxia.-Yura, Y., Chong, B. S. H., Johnson, R. D., Watanabe, Y., Tsukahara, Y., Ferran, B., Murdoch, C. E., Behring, J. B., McComb, M. E., Costello, C. E., Janssen-Heininger, Y. M. W., Cohen, R. A., Bachschmid, M. M., Matsui, R. Endothelial cell-specific redox gene modulation inhibits angiogenesis but promotes B16F0 tumor growth in mice.

Construction of a vascularized bladder with autologous adipose-derived stromal vascular fraction cells combined with bladder acellular matrix via tissue engineering

The formation of an effective vascular network can promote peripheral angiogenesis, ensuring an effective supply of blood, oxygen, and nutrients to an engineered bladder, which is important for bladder tissue engineering. Stromal vascular fraction cells (SVFs) promote vascularization and improve the function of injured tissues. In this study, adipose tissue-derived SVFs were introduced as an angiogenic cell source and seeded into the bladder acellular matrix (BAM) to generate a SVF-BAM complex for bladder reconstruction. The morphological regeneration and functional restoration of the engineered bladder were evaluated. In addition, we also explored the role of the Wnt5a/sFlt-1 noncanonical Wnt signaling pathway in regulating the angiogenesis of SVFs, and in maintaining the rational capability of SVFs to differentiate into vasculature in regenerated tissues. Histological assessment indicated that the SVF-BAM complex was more effective in promoting smooth muscle, vascular, and nerve regeneration than BAM alone and subsequently led to the restoration of bladder volume and bladder compliance. Moreover, exogenous Wnt5a was able to enhance angiogenesis by increasing the activity of MMP2, MMP9, and VEGFR2. Simultaneously, the expression of sFlt-1 was also increased, which enhanced the stability of the SVFs angiogenic capability. SVFs may be a potential cell source for tissue-engineered bladders. The Wnt5a/sFlt-1 pathway is involved in the regulation of autologous vascular formation by SVFs. The rational regulation of this pathway can promote neo-microvascularization in tissue-engineered bladders.

Differential gene expression during substrate probing in larvae of the Caribbean coral Porites astreoides

The transition from larva to adult is a critical step in the life history strategy of most marine animals. However, the genetic basis of this life history change remains poorly understood in many taxa, including most coral species. Recent evidence suggests that coral planula larvae undergo significant changes at the physiological and molecular levels throughout the development. To investigate this, we characterized differential gene expression (DGE) during the transition from planula to adult polyp in the abundant Caribbean reef-building coral Porites astreoides, that is from nonprobing to actively substrate-probing larva, a stage required for colony initiation. This period is crucial for the coral, because it demonstrates preparedness to locate appropriate substrata for settlement based on vital environmental cues. Through RNA-Seq, we identified 860 differentially expressed holobiont genes between probing and nonprobing larvae (p ≤ .01), the majority of which were upregulated in probing larvae. Surprisingly, differentially expressed genes of endosymbiotic dinoflagellate origin greatly outnumbered coral genes, compared with a nearly 1:1 ratio of coral-to-dinoflagellate gene representation in the holobiont transcriptome. This unanticipated result suggests that dinoflagellate endosymbionts may play a significant role in the transition from nonprobing to probing behaviour in dinoflagellate-rich larvae. Putative holobiont genes were largely involved in protein and nucleotide binding, metabolism and transport. Genes were also linked to environmental sensing and response and integral signalling pathways. Our results thus provide detailed insight into molecular changes prior to larval settlement and highlight the complex physiological and biochemical changes that occur in early transition stages from pelagic to benthic stages in corals, and perhaps more importantly, in their endosymbionts.

Cysteine Glutathionylation Acts as a Redox Switch in Endothelial Cells

Oxidative post-translational modifications (oxPTM) of receptors, enzymes, ion channels and transcription factors play an important role in cell signaling. oxPTMs are a key way in which oxidative stress can influence cell behavior during diverse pathological settings such as cardiovascular diseases (CVD), cancer, neurodegeneration and inflammatory response. In addition, changes in oxPTM are likely to be ways in which low level reactive oxygen and nitrogen species (RONS) may contribute to redox signaling, exerting changes in physiological responses including angiogenesis, cardiac remodeling and embryogenesis. Among oxPTM, S-glutathionylation of reactive cysteines emerges as an important regulator of vascular homeostasis by modulating endothelial cell (EC) responses to their local redox environment. This review summarizes the latest findings of S-glutathionylated proteins in major EC pathways, and the functional consequences on vascular pathophysiology. This review highlights the diversity of molecules affected by S-glutathionylation, and the complex consequences on EC function, thereby demonstrating an intricate dual role of RONS-induced S-glutathionylation in maintaining vascular homeostasis and participating in various pathological processes.

Wnt5a-Mediated Neutrophil Recruitment Has an Obligatory Role in Pressure Overload-Induced Cardiac Dysfunction

BACKGROUND

Although the complex roles of macrophages in myocardial injury are widely appreciated, the function of neutrophils in nonischemic cardiac pathology has received relatively little attention.

METHODS

To examine the regulation and function of neutrophils in pressure overload-induced cardiac hypertrophy, mice underwent treatment with Ly6G antibody to deplete neutrophils and then were subjected to transverse aortic constriction.

RESULTS

Neutrophil depletion diminished transverse aortic constriction-induced hypertrophy and inflammation and preserved cardiac function. Myeloid deficiency of Wnt5a, a noncanonical Wnt, suppressed neutrophil infiltration to the hearts of transverse aortic constriction-treated mice and produced a phenotype that was similar to the neutropenic conditions. Conversely, mice overexpressing Wnt5a in myeloid cells displayed greater hypertrophic growth, inflammation, and cardiac dysfunction. Neutrophil depletion reversed the Wnt5a overexpression-induced cardiac pathology and eliminated differences in cardiac parameters between wild-type and myeloid-specific Wnt5a transgenic mice.

CONCLUSIONS

These findings reveal that Wnt5a-regulated neutrophil infiltration has a critical role in pressure overload-induced heart failure.

Oxidative stress and antioxidant treatment in patients with peripheral artery disease

Peripheral artery disease is an atherosclerotic disease of arterial vessels that mostly affects arteries of lower extremities. Effort induced cycles of ischemia and reperfusion lead to increased reactive oxygen species production by mitochondria. Therefore, the pathophysiology of peripheral artery disease is a consequence of metabolic myopathy, and oxidative stress is the putative major operating mechanism behind the structural and metabolic changes that occur in muscle. In this review, we discuss the evidence for oxidative damage in peripheral artery disease and discuss management strategies related to antioxidant supplementation. We also highlight the major pathways governing oxidative stress in the disease and discuss their implications in disease progression. Potential therapeutic targets and diagnostic methods related to these mechanisms are explored, with an emphasis on the Nrf2 pathway.

Critical Roles of Glutaredoxin in Brain Cells-Implications for Parkinson's Disease

SIGNIFICANCE

Glutaredoxin (Grx)1, an evolutionarily conserved and ubiquitous enzyme, regulates redox signal transduction and protein redox homeostasis by catalyzing reversible S-glutathionylation. Grx1 plays different roles in different cell types. In Parkinson's disease (PD), Grx1 regulates apoptosis signaling in dopaminergic neurons, so that loss of Grx1 leads to increased cell death; in microglial cells, Grx1 regulates proinflammatory signaling, so that upregulation of Grx1 promotes cytokine production. Here we examine the regulatory roles of Grx1 in PD with a view toward therapeutic innovation. Recent Advances: In postmortem midbrain PD samples, Grx1 was decreased relative to controls, specifically within dopaminergic neurons. In Caenorhabditis elegans models of PD, loss of the Grx1 homologue led to exacerbation of the neurodegenerative phenotype. This effect was partially relieved by overexpression of neuroprotective DJ-1, consistent with regulation of DJ-1 content by Grx1. Increased GLRX copy number in PD patients was associated with earlier PD onset; and Grx1 levels correlated with levels of proinflammatory tumor necrosis factor-α in mouse and human brain samples. In vitro studies showed Grx1 to be upregulated on proinflammatory activation of microglia. Direct overexpression of Grx1 increased microglial activation; silencing Grx1 diminished activation. Grx1 upregulation in microglia corresponded to increased neuronal cell death in coculture. Overall, these studies identify competing roles of Grx1 in PD etiology.

CRITICAL ISSUES

The dilemma regarding Grx1 as a PD therapeutic target is whether to stimulate its upregulation for neuroprotection or inhibit its proinflammatory activity.

FUTURE DIRECTIONS

Further investigation is needed to understand the preponderant role of Grx1 regarding dopaminergic neuronal survival.

Detecting post-translational modification signatures as potential biomarkers in clinical mass spectrometry

INTRODUCTION

Numerous diseases are caused by changes in post-translational modifications (PTMs). Therefore, the number of clinical proteomics studies that include the analysis of PTMs is increasing. Combining complementary information-for example changes in protein abundance, PTM levels, with the genome and transcriptome (proteogenomics)-holds great promise for discovering important drivers and markers of disease, as variations in copy number, expression levels, or mutations without spatial/functional/isoform information is often insufficient or even misleading. Areas covered: We discuss general considerations, requirements, pitfalls, and future perspectives in applying PTM-centric proteomics to clinical samples. This includes samples obtained from a human subject, for instance (i) bodily fluids such as plasma, urine, or cerebrospinal fluid, (ii) primary cells such as reproductive cells, blood cells, and (iii) tissue samples/biopsies. Expert commentary: PTM-centric discovery proteomics can substantially contribute to the understanding of disease mechanisms by identifying signatures with potential diagnostic or even therapeutic relevance but may require coordinated efforts of interdisciplinary and eventually multi-national consortia, such as initiated in the cancer moonshot program. Additionally, robust and standardized mass spectrometry (MS) assays-particularly targeted MS, MALDI imaging, and immuno-MALDI-may be transferred to the clinic to improve patient stratification for precision medicine, and guide therapies.

Redox Control of Angiogenesis

SIGNIFICANCE

Angiogenesis is the formation of new vessels that sprout from existing vessels. This process is highly complex and requires a coordinated shift of the endothelial phenotype from a quiescent cell in the vessel wall into a migrating or proliferating cell. Such change in the life of the endothelial cell is induced by a variety of factors such as hypoxia, metabolic changes, or cytokines. Recent Advances: Within the last years, it became clear that the cellular redox state and oxidation of signaling molecules or phosphatases are critical modulators in angiogenesis.

CRITICAL ISSUES

According to the wide variety of stimuli that induce angiogenesis, a complex signaling network is needed to support a coordinated response of the endothelial cell. Reactive oxygen species (ROS) now are second messengers that either directly oxidize a target molecule or initiate a cascade of redox sensitive steps that transmit the signal. Further Directions: For the understanding of redox signaling, it is essential to recognize and accept that ROS do not represent master regulators of angiogenetic processes. They rather modulate existing signal cascades. This review summarizes some current findings on redox signaling in angiogenesis.

Important roles of endothelial caveolin-1 in endothelium-dependent hyperpolarization and ischemic angiogenesis in mice

Although increased levels of reactive oxygen species (ROS) are involved in the pathogenesis of cardiovascular diseases, the importance of physiological ROS has also been emerging. We have previously demonstrated that endothelium-derived H₂O₂ is an endothelium-dependent hyperpolarization (EDH) factor and that loss of endothelial caveolin-1 reduces EDH/H₂O₂ in the microcirculation. Caveolin-1 (Cav-1) is a scaffolding/regulatory protein that interacts with diverse signaling pathways, including angiogenesis. However, it remains unclear whether endothelial Cav-1 plays a role in ischemic angiogenesis by modulating EDH/H₂O₂. In the present study, we thus addressed this issue in a mouse model of hindlimb ischemia using male endothelium-specific Cav-1 (eCav-1) knockout (KO) mice. In isometric tension experiments with femoral arteries from eCav-1-KO mice, reduced EDH-mediated relaxations to acetylcholine and desensitization of sodium nitroprusside-mediated endothelium-independent relaxations were noted ( n = 4~6). An ex vivo aortic ring assay also showed that the extent of microvessel sprouting was significantly reduced in eCav-1-KO mice compared with wild-type (WT) littermates ( n = 12 each). Blood flow recovery at 4 wk assessed with a laser speckle flowmeter after femoral artery ligation was significantly impaired in eCav-1-KO mice compared with WT littermates ( n = 10 each) and was associated with reduced capillary density and muscle fibrosis in the legs ( n = 6 each). Importantly, posttranslational protein modifications by reactive nitrogen species and ROS, as evaluated by thiol glutathione adducts and nitrotyrosine, respectively, were both increased in eCav-1-KO mice ( n = 6~7 each). These results indicate that endothelial Cav-1 plays an important role in EDH-mediated vasodilatation and ischemic angiogenesis through posttranslational protein modifications by nitrooxidative stress in mice in vivo. NEW & NOTEWORTHY Although increased levels of reactive oxygen species (ROS) are involved in the pathogenesis of cardiovascular diseases, the importance of physiological ROS has also been emerging. The present study provides a line of novel evidence that endothelial caveolin-1 plays important roles in endothelium-dependent hyperpolarization and ischemic angiogenesis in hindlimb ischemia in mice through posttranslational protein modifications by reactive nitrogen species and ROS in mice in vivo.

IL-33 induction and signaling are controlled by glutaredoxin-1 in mouse macrophages

Interleukin (IL)-33 is an interleukin-1 like cytokine that enhances Th2 responses and mediates mucosal immunity and allergic inflammation but the mechanism regulating endogenous IL-33 production are still under investigation. In macrophages, lipopolysaccharide (LPS) administration resulted in marked induction of IL-33 mRNA that was blunted in macrophages from glutaredoxin-1 (Glrx) knockout mice and in RAW264.7 macrophages with Glrx knockdown by siRNA. Glutaredoxin-1 is a small cytosolic thioltransferase that controls a reversible protein thiol modification, S-glutationylation (protein-GSH adducts), thereby regulating redox signaling. In this study, we examined the mechanism of Glrx regulation of endogenous IL-33 induction in macrophages. Glrx knockdown resulted in impaired de-glutathionylation of TRAF6, which is required for TRAF6 activation, and inhibited downstream IKKβ and NF-κB activation. Inhibitors of NF-κB suppressed IL-33 induction and chromatin IP sequencing data analysis confirmed that IL-33 is an NF-κB-responsive gene. Since TRAF6-NF-κB activation is also essential for IL-33 signaling through its receptor, ST2L, we next tested the involvement of Glrx in exogenous IL-33 responses in RAW264.7 cells. Recombinant IL-33 (rIL-33) administration induced IL-33 mRNA expression in RAW264.7 macrophages, and this was inhibited by Glrx knockdown. Interestingly, rIL-33-induced IL-33 protein was identified as the 20 kDa cleaved form whereas LPS-induced IL-33 protein was identified as full-length IL-33, which may be less active than the cleaved form. In a clinically-relevant mouse model of asthma, intra-tracheal cockroach antigen treatment induced Glrx protein in wild type mouse lungs but Glrx induction was attenuated in IL-33 knockout mouse lungs, suggesting that IL-33 may regulate Glrx induction in vivo in response to allergen challenge. In summary, our data reveal a novel mechanism by which Glrx controls both LPS- and IL-33-mediated NF-κB activation leading to IL-33 production, and paracrine IL-33 can induce Glrx to further regulate inflammatory reactions.

Vascular endothelial growth factor signaling requires glycine to promote angiogenesis

Peripheral vascular occlusive disease (PVOD) is a common manifestation of atherosclerosis, and it has a high rate of morbidity. Therapeutic angiogenesis would re-establish blood perfusion and rescue ischemic tissue. Vascular endothelial growth factor (VEGF) induces angiogenesis and can potentially be used to treat ischemic diseases, yet in clinical trials VEGF has not fulfilled its full potential with side effects. Whether amino acids promote angiogenesis and the molecular mechanisms are largely unknown. Here we showed that (1) Glycine significantly promoted angiogenesis both in vitro and in vivo and effectively protected mitochondrial function. (2) Activation of glycine transporter 1(GlyT1) induced by VEGF led to an increase in intracellular glycine. (3) Glycine directly bounded to voltage dependent anion channel 1 (VDAC1) on the mitochondrial outer membrane and inhibited its opening. These original results highlight glycine as a necessary mediator in VEGF signalling via the GlyT1-glycine-mTOR-VDAC1 axis pathway. Therefore, the findings in this study are of significance providing new mechanistic insights into angiogenesis and providing better understanding of glycine function in angiogenesis, which may provide valuable information for development of novel therapeutic targets for the treatment of angiogenic vascular disorders.

European contribution to the study of ROS: A summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS)

The European Cooperation in Science and Technology (COST) provides an ideal framework to establish multi-disciplinary research networks. COST Action BM1203 (EU-ROS) represents a consortium of researchers from different disciplines who are dedicated to providing new insights and tools for better understanding redox biology and medicine and, in the long run, to finding new therapeutic strategies to target dysregulated redox processes in various diseases. This report highlights the major achievements of EU-ROS as well as research updates and new perspectives arising from its members. The EU-ROS consortium comprised more than 140 active members who worked together for four years on the topics briefly described below. The formation of reactive oxygen and nitrogen species (RONS) is an established hallmark of our aerobic environment and metabolism but RONS also act as messengers via redox regulation of essential cellular processes. The fact that many diseases have been found to be associated with oxidative stress established the theory of oxidative stress as a trigger of diseases that can be corrected by antioxidant therapy. However, while experimental studies support this thesis, clinical studies still generate controversial results, due to complex pathophysiology of oxidative stress in humans. For future improvement of antioxidant therapy and better understanding of redox-associated disease progression detailed knowledge on the sources and targets of RONS formation and discrimination of their detrimental or beneficial roles is required. In order to advance this important area of biology and medicine, highly synergistic approaches combining a variety of diverse and contrasting disciplines are needed.

Endothelial Cell Redox Regulation of Ischemic Angiogenesis

The endothelium produces and responds to reactive oxygen and nitrogen species (RONS), providing important redox regulation to the cardiovascular system in physiology and disease. In no other situation are RONS more critical than in the response to tissue ischemia. Here, tissue healing requires growth factor-mediated angiogenesis that is in part dependent on low levels of RONS, which paradoxically must overcome the damaging effects of high levels of RONS generated as a result of ischemia. Although the generation of endothelial cell RONS in hypoxia/reoxygenation is acknowledged, the mechanism for their role in angiogenesis is still poorly understood. During ischemia, the major low molecular weight thiol glutathione (GSH) reacts with RONS and protein cysteines, producing GSH-protein adducts. Recent data indicate that GSH adducts on certain proteins are essential to growth factor responses in endothelial cells. Genetic deletion of the enzyme glutaredoxin-1, which selectively removes GSH protein adducts, improves, whereas its overexpression impairs revascularization of the ischemic hindlimb of mice. Ischemia-induced GSH adducts on specific cysteine residues of several proteins, including p65 NF-kB and the sarcoplasmic reticulum calcium ATPase 2, evidently promote ischemic angiogenesis. Identifying the specific proteins in the redox response to ischemia has provided therapeutic opportunities to improve clinical outcomes of ischemia.

Glutaredoxin-1 Deficiency Causes Fatty Liver and Dyslipidemia by Inhibiting Sirtuin-1

AIMS

Nonalcoholic fatty liver (NAFL) is a common liver disease associated with metabolic syndrome, obesity, and diabetes that is rising in prevalence worldwide. Various molecular perturbations of key regulators and enzymes in hepatic lipid metabolism cause NAFL. However, redox regulation through glutathione (GSH) adducts in NAFL remains largely elusive. Glutaredoxin-1 (Glrx) is a small thioltransferase that removes protein GSH adducts without having direct antioxidant properties. The liver contains abundant Glrx but its metabolic function is unknown.

RESULTS

Here we report that normal diet-fed Glrx-deficient mice (Glrx^-/-) spontaneously develop obesity, hyperlipidemia, and hepatic steatosis by 8 months of age. Adenoviral Glrx repletion in the liver of Glrx^-/- mice corrected lipid metabolism. Glrx^-/- mice exhibited decreased sirtuin-1 (SirT1) activity that leads to hyperacetylation and activation of SREBP-1 and upregulation of key hepatic enzymes involved in lipid synthesis. We found that GSH adducts inhibited SirT1 activity in Glrx^-/- mice. Hepatic expression of nonoxidizable cysteine mutant SirT1 corrected hepatic lipids in Glrx^-/- mice. Wild-type mice fed high-fat diet develop metabolic syndrome, diabetes, and NAFL within several months. Glrx deficiency accelerated high-fat-induced NAFL and progression to steatohepatitis, manifested by hepatic damage and inflammation.

INNOVATION

These data suggest an essential role of hepatic Glrx in regulating SirT1, which controls protein glutathione adducts in the pathogenesis of hepatic steatosis.

CONCLUSION

We provide a novel redox-dependent mechanism for regulation of hepatic lipid metabolism, and propose that upregulation of hepatic Glrx may be a beneficial strategy for NAFL. Antioxid. Redox Signal. 27, 313-327.

Peripheral artery disease, redox signaling, oxidative stress - Basic and clinical aspects

Reactive oxygen and nitrogen species (ROS and RNS, e.g. H2O2, nitric oxide) confer redox regulation of essential cellular signaling pathways such as cell differentiation, proliferation, migration and apoptosis. At higher concentrations, ROS and RNS lead to oxidative stress and oxidative damage of biomolecules (e.g. via formation of peroxynitrite, fenton chemistry). Peripheral artery disease (PAD) is characterized by severe ischemic conditions in the periphery leading to intermittent claudication and critical limb ischemia (end stage). It is well known that redox biology and oxidative stress play an important role in this setting. We here discuss the major pathways of oxidative stress and redox signaling underlying the disease progression with special emphasis on the contribution of inflammatory processes. We also highlight therapeutic strategies comprising pharmacological (e.g. statins, angiotensin-converting enzyme inhibitors, phosphodiesterase inhibition) and non-pharmacological (e.g. exercise) interventions. Both of these strategies induce potent indirect antioxidant and anti-inflammatory mechanisms that may contribute to an improvement of PAD associated complications and disease progression by removing excess formation of ROS and RNS (e.g. by ameliorating primary complications such as hyperlipidemia and hypertension) as well as the normalization of the inflammatory phenotype suppressing the progression of atherosclerosis.

The Impact of Environmental Factors in Influencing Epigenetics Related to Oxidative States in the Cardiovascular System

Oxidative states exert a significant influence on a wide range of biological and molecular processes and functions. When their balance is shifted towards enhanced amounts of free radicals, pathological phenomena can occur, as the generation of reactive oxygen species (ROS) in tissue microenvironment or in the systemic circulation can be detrimental. Epidemic chronic diseases of western societies, such as cardiovascular disease, obesity, and diabetes correlate with the imbalance of redox homeostasis. Current advances in our understanding of epigenetics have revealed a parallel scenario showing the influence of oxidative stress as a major regulator of epigenetic gene regulation via modification of DNA methylation, histones, and microRNAs. This has provided both the biological link and a potential molecular explanation between oxidative stress and cardiovascular/metabolic phenomena. Accordingly, in this review, we will provide current insights on the physiological and pathological impact of changes in oxidative states on cardiovascular disorders, by specifically focusing on the influence of epigenetic regulation. A special emphasis will highlight the effect on epigenetic regulation of human's current life habits, external and environmental factors, including food intake, tobacco, air pollution, and antioxidant-based approaches. Additionally, the strategy to quantify oxidative states in humans in order to determine which biological marker could best match a subject's profile will be discussed.

Redox regulation of ischemic limb neovascularization - What we have learned from animal studies

Mouse hindlimb ischemia has been widely used as a model to study peripheral artery disease. Genetic modulation of the enzymatic source of oxidants or components of the antioxidant system reveal that physiological levels of oxidants are essential to promote the process of arteriogenesis and angiogenesis after femoral artery occlusion, although mice with diabetes or atherosclerosis may have higher deleterious levels of oxidants. Therefore, fine control of oxidants is required to stimulate vascularization in the limb muscle. Oxidants transduce cellular signaling through oxidative modifications of redox sensitive cysteine thiols. Of particular importance, the reversible modification with abundant glutathione, called S-glutathionylation (or GSH adducts), is relatively stable and alters protein function including signaling, transcription, and cytoskeletal arrangement. Glutaredoxin-1 (Glrx) is an enzyme which catalyzes reversal of GSH adducts, and does not scavenge oxidants itself. Glrx may control redox signaling under fluctuation of oxidants levels. In ischemic muscle increased GSH adducts through Glrx deletion improves in vivo limb revascularization, indicating endogenous Glrx has anti-angiogenic roles. In accordance, Glrx overexpression attenuates VEGF signaling in vitro and ischemic vascularization in vivo. There are several Glrx targets including HIF-1α which may contribute to inhibition of vascularization by reducing GSH adducts. These animal studies provide a caution that excess antioxidants may be counter-productive for treatment of ischemic limbs, and highlights Glrx as a potential therapeutic target to improve ischemic limb vascularization.

Mechanistic Insights into the Anti-angiogenic Activity of Trypanosoma cruzi Protein 21 and its Potential Impact on the Onset of Chagasic Cardiomyopathy

Chronic chagasic cardiomyopathy (CCC) is arguably the most important form of the Chagas Disease, caused by the intracellular protozoan Trypanosoma cruzi; it is estimated that 10-30% of chronic patients develop this clinical manifestation. The most common and severe form of CCC can be related to ventricular abnormalities, such as heart failure, arrhythmias, heart blocks, thromboembolic events and sudden death. Therefore, in this study, we proposed to evaluate the anti-angiogenic activity of a recombinant protein from T. cruzi named P21 (rP21) and the potential impact of the native protein on CCC. Our data suggest that the anti-angiogenic activity of rP21 depends on the protein's direct interaction with the CXCR4 receptor. This capacity is likely related to the modulation of the expression of actin and angiogenesis-associated genes. Thus, our results indicate that T. cruzi P21 is an attractive target for the development of innovative therapeutic agents against CCC.

Upregulation of Glutaredoxin-1 Activates Microglia and Promotes Neurodegeneration: Implications for Parkinson's Disease

AIMS

Neuroinflammation and redox dysfunction are recognized factors in Parkinson's disease (PD) pathogenesis, and diabetes is implicated as a potentially predisposing condition. Remarkably, upregulation of glutaredoxin-1 (Grx1) is implicated in regulation of inflammatory responses in various disease contexts, including diabetes. In this study, we investigated the potential impact of Grx1 upregulation in the central nervous system on dopaminergic (DA) viability.

RESULTS

Increased GLRX copy number in PD patients was associated with earlier PD onset, and Grx1 levels correlated with levels of proinflammatory tumor necrosis factor-alpha (TNF-α) in mouse and human brain samples, prompting mechanistic in vitro studies. Grx1 content/activity in microglia was upregulated by lipopolysaccharide (LPS), or TNF-α, treatment. Adenoviral overexpression of Grx1, matching the extent of induction by LPS, increased microglial activation; Grx1 silencing diminished activation. Selective inhibitors/probes of nuclear factor κB (NF-κB) activation revealed glrx1 induction to be mediated by the Nurr1/NF-κB axis. Upregulation of Grx1 in microglia corresponded to increased death of neuronal cells in coculture. With a mouse diabetes model of diet-induced insulin resistance, we found upregulation of Grx1 in brain was associated with DA loss (decreased tyrosine hydroxylase [TH]; diminished TH-positive striatal axonal terminals); these effects were not seen with Grx1-knockout mice.

INNOVATION

Our results indicate that Grx1 upregulation promotes neuroinflammation and consequent neuronal cell death in vitro, and synergizes with proinflammatory insults to promote DA loss in vivo. Our findings also suggest a genetic link between elevated Grx1 and PD development.

CONCLUSION

In vitro and in vivo data suggest Grx1 upregulation promotes neurotoxic neuroinflammation, potentially contributing to PD. Antioxid. Redox Signal. 25, 967-982.

The redox mechanism for vascular barrier dysfunction associated with metabolic disorders: Glutathionylation of Rac1 in endothelial cells

BACKGROUND

Oxidative stress is implicated in increased vascular permeability associated with metabolic disorders, but the underlying redox mechanism is poorly defined. S-glutathionylation, a stable adduct of glutathione with protein sulfhydryl, is a reversible oxidative modification of protein and is emerging as an important redox signaling paradigm in cardiovascular physiopathology. The present study determines the role of protein S-glutathionylation in metabolic stress-induced endothelial cell permeability.

METHODS AND RESULTS

In endothelial cells isolated from patients with type-2 diabetes mellitus, protein S-glutathionylation level was increased. This change was also observed in aortic endothelium in ApoE deficient (ApoE-/-) mice fed on Western diet. Metabolic stress-induced protein S-glutathionylation in human aortic endothelial cells (HAEC) was positively correlated with elevated endothelial cell permeability, as reflected by disassembly of cell-cell adherens junctions and cortical actin structures. These impairments were reversed by adenoviral overexpression of a specific de-glutathionylation enzyme, glutaredoxin-1 in cultured HAECs. Consistently, transgenic overexpression of human Glrx-1 in ApoE-/- mice fed the Western diet attenuated endothelial protein S-glutathionylation, actin cytoskeletal disorganization, and vascular permeability in the aorta. Mechanistically, glutathionylation and inactivation of Rac1, a small RhoGPase, were associated with endothelial hyperpermeability caused by metabolic stress. Glutathionylation of Rac1 on cysteine 81 and 157 located adjacent to guanine nucleotide binding site was required for the metabolic stress to inhibit Rac1 activity and promote endothelial hyperpermeability.

CONCLUSIONS

Glutathionylation and inactivation of Rac1 in endothelial cells represent a novel redox mechanism of vascular barrier dysfunction associated with metabolic disorders.

Regulation of DJ-1 by Glutaredoxin 1 in Vivo: Implications for Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide, caused by the degeneration of the dopaminergic neurons in the substantia nigra. Mutations in PARK7 (DJ-1) result in early onset autosomal recessive PD, and oxidative modification of DJ-1 has been reported to regulate the protective activity of DJ-1 in vitro. Glutathionylation is a prevalent redox modification of proteins resulting from the disulfide adduction of the glutathione moiety to a reactive cysteine-SH, and glutathionylation of specific proteins has been implicated in regulation of cell viability. Glutaredoxin 1 (Grx1) is the principal deglutathionylating enzyme within cells, and it has been reported to mediate protection of dopaminergic neurons in Caenorhabditis elegans; however many of the functional downstream targets of Grx1 in vivo remain unknown. Previously, DJ-1 protein content was shown to decrease concomitantly with diminution of Grx1 protein content in cell culture of model neurons (SH-SY5Y and Neuro-2A lines). In the current study we aimed to investigate the regulation of DJ-1 by Grx1 in vivo and characterize its glutathionylation in vitro. Here, with Grx(-/-) mice we provide show that Grx1 regulates protein levels of DJ-1 in vivo. Furthermore, with model neuronal cells (SH-SY5Y) we observed decreased DJ-1 protein content in response to treatment with known glutathionylating agents, and with isolated DJ-1 we identified two distinct sites of glutathionylation. Finally, we found that overexpression of DJ-1 in the dopaminergic neurons partly compensates for the loss of the Grx1 homologue in a C. elegans in vivo model of PD. Therefore, our results reveal a novel redox modification of DJ-1 and suggest a novel regulatory mechanism for DJ-1 content in vivo.

Glutathione adducts induced by ischemia and deletion of glutaredoxin-1 stabilize HIF-1α and improve limb revascularization

Reactive oxygen species (ROS) are increased in ischemic tissues and necessary for revascularization; however, the mechanism remains unclear. Exposure of cysteine residues to ROS in the presence of glutathione (GSH) generates GSH-protein adducts that are specifically reversed by the cytosolic thioltransferase, glutaredoxin-1 (Glrx). Here, we show that a key angiogenic transcriptional factor hypoxia-inducible factor (HIF)-1α is stabilized by GSH adducts, and the genetic deletion of Glrx improves ischemic revascularization. In mouse muscle C2C12 cells, HIF-1α protein levels are increased by increasing GSH adducts with cell-permeable oxidized GSH (GSSG-ethyl ester) or 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanyl thiocarbonylamino) phenylthiocarbamoylsulfanyl] propionic acid (2-AAPA), an inhibitor of glutathione reductase. A biotin switch assay shows that GSSG-ester-induced HIF-1α contains reversibly modified thiols, and MS confirms GSH adducts on Cys(520) (mouse Cys(533)). In addition, an HIF-1α Cys(520) serine mutant is resistant to 2-AAPA-induced HIF-1α stabilization. Furthermore, Glrx overexpression prevents HIF-1α stabilization, whereas Glrx ablation by siRNA increases HIF-1α protein and expression of downstream angiogenic genes. Blood flow recovery after femoral artery ligation is significantly improved in Glrx KO mice, associated with increased levels of GSH-protein adducts, capillary density, vascular endothelial growth factor (VEGF)-A, and HIF-1α in the ischemic muscles. Therefore, Glrx ablation stabilizes HIF-1α by increasing GSH adducts on Cys(520) promoting in vivo HIF-1α stabilization, VEGF-A production, and revascularization in the ischemic muscles.

Redox Regulation of Ischemic Angiogenesis - Another Aspect of Reactive Oxygen Species

Antioxidants are expected to improve cardiovascular disease (CVD) by eliminating oxidative stress, but clinical trials have not shown promising results in chronic CVD. Animal studies have revealed that reactive oxygen species (ROS) exacerbate acute CVDs in which high levels of ROS are observed. However, ROS are also necessary for angiogenesis after ischemia, because ROS not only damage cells but also stimulate the cell signaling required for angiogenesis. ROS affect signaling by protein modifications, especially of cysteine amino acid thiols. Although there are several cysteine modifications, S-glutathionylation (GSH adducts; -SSG), a reversible cysteine modification by glutathione (GSH), plays an important role in angiogenic signal transduction by ROS. Glutaredoxin-1 (Glrx) is an enzyme that specifically removes GSH adducts in vivo. Overexpression of Glrx inhibits, whereas deletion of Glrx improves revascularization after mouse hindlimb ischemia. These studies indicate that increased levels of GSH adducts in ischemic muscle are beneficial in promoting angiogenesis. The underlying mechanism can be explained by multiple targets of S-gluathionylation, which mediate the angiogenic effects in ischemia. Increments in the master angiogenic transcriptional factor, HIF-1α, reduction of the anti-angiogenic factor sFlt1, activation of the endoplasmic reticulum Ca(2+)pump, SERCA, and inhibition of phosphatases may occur as a consequence of enhanced S-glutathionylation in ischemic tissue. In summary, inducing S-glutathionylation by inhibiting Glrx may be a therapeutic strategy to improve ischemic angiogenesis in CVD. (Circ J 2016; 80: 1278-1284).

Paradoxical Roles of Antioxidant Enzymes: Basic Mechanisms and Health Implications

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate "paradoxical" outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of "antioxidant" nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that "paradoxical" roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways.

Endothelial Dysfunction in Human Diabetes Is Mediated by Wnt5a-JNK Signaling

OBJECTIVE

Endothelial dysfunction is linked to insulin resistance, inflammatory activation, and increased cardiovascular risk in diabetes mellitus; however, the mechanisms remain incompletely understood. Recent studies have identified proinflammatory signaling of wingless-type family member (Wnt) 5a through c-jun N-terminal kinase (JNK) as a regulator of metabolic dysfunction with potential relevance to vascular function. We sought to gain evidence that increased activation of Wnt5a-JNK signaling contributes to impaired endothelial function in patients with diabetes mellitus.

APPROACH AND RESULTS

We measured flow-mediated dilation of the brachial artery and characterized freshly isolated endothelial cells by protein expression, eNOS activation, and nitric oxide production in 85 subjects with type 2 diabetes mellitus (n=42) and age- and sex-matched nondiabetic controls (n=43) and in human aortic endothelial cells treated with Wnt5a. Endothelial cells from patients with diabetes mellitus displayed 1.3-fold higher Wnt5a levels (P=0.01) along with 1.4-fold higher JNK activation (P<0.01) without a difference in total JNK levels. Higher JNK activation was associated with lower flow-mediated dilation, consistent with endothelial dysfunction (r=0.53, P=0.02). Inhibition of Wnt5a and JNK signaling restored insulin and A23187-mediated eNOS activation and improved nitric oxide production in endothelial cells from patients with diabetes mellitus. In endothelial cells from nondiabetic controls, rWnt5a treatment inhibited eNOS activation replicating the diabetic endothelial phenotype. In human aortic endothelial cells, Wnt5a-induced impairment of eNOS activation and nitric oxide production was reversed by Wnt5a and JNK inhibition.

CONCLUSIONS

Our findings demonstrate that noncanonical Wnt5a signaling and JNK activity contribute to vascular insulin resistance and endothelial dysfunction and may represent a novel therapeutic opportunity to protect the vasculature in patients with diabetes mellitus.

The role of oxidative stress in skeletal muscle injury and regeneration: focus on antioxidant enzymes

Reactive oxygen species (ROS) are generated in skeletal muscle both during the rest and contractile activity. Myogenic cells are equipped with antioxidant enzymes, like superoxide dismutase, catalase, glutathione peroxidase, γ-glutamylcysteine synthetase and heme oxygenase-1. These enzymes not only neutralise excessive ROS, but also affect myogenic regeneration at several stages: influence post-injury inflammatory reaction, enhance viability and proliferation of muscle satellite cells and myoblasts and affect their differentiation. Finally, antioxidant enzymes regulate also processes accompanying muscle regeneration-induce angiogenesis and reduce fibrosis. Elevated ROS production was also observed in Duchenne muscular dystrophy (DMD), a disease characterised by degeneration of muscle tissue and therefore-increased rate of myogenic regeneration. Antioxidant enzymes are consequently considered as target for therapies counteracting dystrophic symptoms. In this review we present current knowledge regarding the role of oxidative stress and systems of enzymatic antioxidant defence in muscular regeneration after both acute injury and persistent muscular degeneration.

ROS signaling and redox biology in endothelial cells

The purpose of this review is to provide an overview of redox mechanisms, sources and antioxidants that control signaling events in ECs. In particular, we describe which molecules are involved in redox signaling and how they influence the relationship between ECs and other vascular component with regard to angiogenesis. Recent and new tools to investigate physiological ROS signaling will be also discussed. Such findings are providing an overview of the ROS biology relevant for endothelial cells in the context of normal and pathological angiogenic conditions.

Regulation of neovascularization by S-glutathionylation via the Wnt5a/sFlt-1 pathway

S-glutathionylation occurs when reactive oxygen or nitrogen species react with protein-cysteine thiols. Glutaredoxin-1 (Glrx) is a cytosolic enzyme which enzymatically catalyses the reduction in S-glutathionylation, conferring reversible signalling function to proteins with redox-sensitive thiols. Glrx can regulate vascular hypertrophy and inflammation by regulating the activity of nuclear factor κB (NF-κB) and actin polymerization. Vascular endothelial growth factor (VEGF)-induced endothelial cell (EC) migration is inhibited by Glrx overexpression. In mice overexpressing Glrx, blood flow recovery, exercise function and capillary density were significantly attenuated after hindlimb ischaemia (HLI). Wnt5a and soluble Fms-like tyrosine kinase-1 (sFlt-1) were enhanced in the ischaemic-limb muscle and plasma respectively from Glrx transgenic (TG) mice. A Wnt5a/sFlt-1 pathway had been described in myeloid cells controlling retinal blood vessel development. Interestingly, a Wnt5a/sFlt-1 pathway was found also to play a role in EC to inhibit network formation. S-glutathionylation of NF-κB components inhibits its activation. Up-regulated Glrx stimulated the Wnt5a/sFlt-1 pathway through enhancing NF-κB signalling. These studies show a novel role for Glrx in post-ischaemic neovascularization, which could define a potential target for therapy of impaired angiogenesis in pathological conditions including diabetes.

The Role of Vascular Endothelial Growth Factor Receptor-1 Signaling in the Recovery from Ischemia

Vascular endothelial growth factor (VEGF) is one of the most potent angiogenesis stimulators. VEGF binds to VEGF receptor 1 (VEGFR1), inducing angiogenesis through the receptor's tyrosine kinase domain (TK), but the mechanism is not well understood. We investigated the role of VEGFR1 tyrosine kinase signaling in angiogenesis using the ischemic hind limb model. Relative to control mice, blood flow recovery was significantly impaired in mice treated with VEGFA-neutralizing antibody. VEGFR1 tyrosine kinase knockout mice (TK-/-) had delayed blood flow recovery from ischemia and impaired angiogenesis, and this phenotype was unaffected by treatment with a VEGFR2 inhibitor. Compared to wild type mice (WT), TK-/- mice had no change in the plasma level of VEGF, but the plasma levels of stromal-derived cell factor 1 (SDF-1) and stem cell factor, as well as the bone marrow (BM) level of pro-matrix metalloproteinase-9 (pro-MMP-9), were significantly reduced. The recruitment of cells expressing VEGFR1 and C-X-C chemokine receptor type 4 (CXCR4) into peripheral blood and ischemic muscles was also suppressed. Furthermore, WT transplanted with TK-/- BM significantly impaired blood flow recovery more than WT transplanted with WT BM. These results suggest that VEGFR1-TK signaling facilitates angiogenesis by recruiting CXCR4+VEGFR1+ cells from BM.

Glutaredoxin mediated redox effects of coenzyme Q10 treatment in type 1 and type 2 diabetes patients

The possible beneficial effects of coenzyme Q10 (CoQ10) supplementation on disease progression and oxidant status in diabetes remains debated. In the present study, patients with type 1 and type 2 diabetes were treated with oral CoQ10, 100 mg twice daily for 12 weeks. We assessed total antioxidant capacity, intra- and extracellular levels of the redox regulating protein glutaredoxin 1 (Grx1), CoQ10, oxidized LDL-cholesterol, lipid profile and HbA1c. We have previously shown that extracellular Grx1 is increased in patients with type 2 diabetes compared to healthy subjects. In the present study, CoQ10 treatment significantly decreased serum Grx1 activity as well as total antioxidant capacity independent of type of diabetes, indicating an improvement to a less oxidized extracellular environment. The effect on serum Grx1 activity was more prominent in patients not on statin treatment. Conversely, intracellular Grx1 activity as well as mRNA levels increased independent of statin treatment. There was a significant improvement in oxidized LDL-cholesterol and lipid profile, with a tendency to improved metabolic control (HbA1c). Additionally, we describe for the first time that CoQ10 is a direct substrate for glutathione, and that Grx1 catalyzes this reaction, thus presenting a novel mechanism for CoQ10 reduction which could explain our findings of an increased intracellular Grx1. In conclusion, 12 weeks CoQ10 treatment significantly improved the extracellular redox balance and lipid profile, indicating that prolonged treatment may have beneficial effects also on clinical outcome in diabetes.