The biphasic redox sensing of SENP3 accounts for the HIF-1 transcriptional activity shift by oxidative stress

Bioinspired artificial antioxidases for efficient redox homeostasis and maxillofacial bone regeneration

Reconstructing large, inflammatory maxillofacial defects using stem cell-based therapy faces challenges from adverse microenvironments, including high levels of reactive oxygen species (ROS), inadequate oxygen, and intensive inflammation. Here, inspired by the reaction mechanisms of intracellular antioxidant defense systems, we propose the de novo design of an artificial antioxidase using Ru-doped layered double hydroxide (Ru-hydroxide) for efficient redox homeostasis and maxillofacial bone regeneration. Our studies demonstrate that Ru-hydroxide consists hydroxyls-synergistic monoatomic Ru centers, which efficiently react with oxygen species and collaborate with hydroxyls for rapid proton and electron transfer, thus exhibiting efficient, broad-spectrum, and robust ROS scavenging performance. Moreover, Ru-hydroxide can effectively sustain stem cell viability and osteogenic differentiation in elevated ROS environments, modulating the inflammatory microenvironment during bone tissue regeneration in male mice. We believe this Ru-hydroxide development offers a promising avenue for designing antioxidase-like materials to treat various inflammation-associated disorders, including arthritis, diabetic wounds, enteritis, and bone fractures.

SENP3-regulated Nodal signaling plays a potential role in cardiac left-right asymmetry development

Congenital heart disease (CHD) is a type of major defect that occurs during embryonic development. Although significant advances have been made in the treatment of CHD, its etiology and molecular mechanism remain unclear. To identify the critical role of SUMOylation in cardiac development, we generated SENP3 knockout mice and showed that SENP3 knockout mice die on embryonic day 8.5 with an open neural tube and reversed left-right cardiac asymmetry. Moreover, SENP3 knockout promoted apoptosis and senescence of H9C2 cells. Further studies showed that Nodal, a critical gene that forms left-right asymmetry, is regulated by SENP3 and that SENP3 regulates cell apoptosis and senescence in a Nodal-dependent manner. Furthermore, Nodal was hyper-SUMOylated after SENP3 knockout, and SUMOylation of Nodal inhibited its ubiquitination and ubiquitin-proteasome degradation pathway. Nodal overexpression enhanced cell apoptosis and senescence; however, the mutation at the SUMOylation site of Nodal reversed its effect on the apoptosis and senescence of H9C2 cells. More importantly, the SENP3-Nodal axis regulates cell senescence by inducing cell autophagy. These results suggest that the SENP3-Nodal signaling axis regulates cardiac senescence-autophagy homeostasis, which in turn affects cardiac development and results in the occurrence of CHD.

SENP3 attenuates foam cell formation by deSUMOylating NLRP3 in macrophages stimulated with ox-LDL

SUMO-specific protease 3 (SENP3) participates in the removal of SUMOylation and maintains the balance of the SUMO system, which ensures normal functioning of substrates and cellular activities. In the present study, we found that SENP3 expression was significantly reduced in ox-LDL-stimulated macrophages. SENP3 overexpression suppressed and SENP3 knockdown promoted macrophage foam cell formation. Moreover, SENP3 inhibited cholesterol uptake, CD36 expression, and NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) inflammasome activation in ox-LDL-stimulated macrophages. Ox-LDL-stimulated NLRP3 SUMOylation was reduced by SENP3. Blocking NLRP3 SUMOylation inhibited foam cell formation and NLRP3 inflammasome activation. Thus, this study revealed that SENP3 inhibits macrophage foam cell formation by deSUMOylating NLRP3 and regulating NLRP3 inflammasome activation, which may provide a potentially innovative approach to treatment of atherosclerosis.

Myeloid SENP3 deficiency protects mice from diet and age-induced obesity via regulation of YAP1 SUMOylation

Obesity is characterized by chronic low-grade inflammation, which is driven by macrophage infiltration in adipose tissue and leads to elevated cytokines such as interleukin-1β (IL-1β) in the circulation and tissues. Previous studies demonstrate that SENP3, a redox-sensitive SUMO2/3-specific protease, is strongly implicated in the development and progression of cancer and cardiovascular diseases. However, the role of SENP3 in obesity-associated inflammation remains largely unknown. To better understand the effects of SENP3 on adipose tissue macrophage (ATM) activation and function within the context of obesity, we generated mice with myeloid-specific deletion of SENP3 (Senp3flox/flox;Lyz2-Cre mice). We found that the expression of SENP3 is dramatically increased in ATMs during high-fat diet (HFD)-induced obesity in mice. Senp3flox/flox;Lyz2-Cre mice show lower body weight gain and reduced adiposity and adipocyte size after challenged with HFD and during aging. Myeloid-specific SENP3 deletion attenuates macrophage infiltration in adipose tissue and reduces serum levels of inflammatory factors during diet and age-induced obesity. Furthermore, we found that SENP3 knockout markedly inhibits cytokine release from macrophage after lipopolysaccharide and palmitic acid treatment in vitro. Mechanistically, in cultured peritoneal macrophages, SENP3 protein level is enhanced by IL-1β, in parallel with the upregulation of Yes-associated protein 1 (YAP1). Moreover, we demonstrated that SENP3 modulates de-SUMO modification of YAP1 and SENP3 deletion abolishes the upregulation of YAP1 induced by IL-1β. Most importantly, SENP3 deficiency reduces YAP1 protein level in adipose tissue during obesity. Our results highlight the important role of SENP3 in ATM inflammation and diet and age-induced obesity.

Overexpression of SENP3 promotes PPAR-γ transcription through the increase of HIF-1α stability via SUMO2/3 and participates in molecular mechanisms of osteoporosis

Patients with type II diabetes are exposed to a high risk of osteoporosis. The present study sought to exploit the detailed mechanisms of the SENP3/HIF-1α/PPAR-γ axis in osteoporosis. A rat model of type II diabetic osteoporosis was established, followed by the isolation of bone marrow mononuclear macrophages (BMMs). Gain- and loss-of-function assays were conducted in rat models and BMMs from rat models, followed by the evaluation of SENP3, HIF-1α, and PPAR-γ expression and detection of osteoclast differentiation-related indexes. Next, the SUMOylated modification of HIF-1α and the regulation of SENP3 on SUMOylated modification level of HIF-1α were assessed using immunoprecipitation, and the binding of HIF-1α to the PPARγ promoter was identified with ChIP and dual-luciferase reporter assays. SENP3 and HIF-1α expression was down-regulated in tissues of type II diabetes-induced osteoporotic rats and BMMs, with high SUMOylated modification levels of HIF-1α. Mechanically, HIF-1α was modified by SUMO2/3. SENP3 suppressed SUMOylated modification of HIF-1α and enhanced HIF-1α stability. HIF-1α bound to the PPAR-γ promoter and facilitated PPAR-γ transcription. SENP3 overexpression restrained osteoblast differentiation in type II diabetes-induced osteoporotic rats and BMMs from rat models. SENP3 knockdown facilitated osteoclast differentiation in type II diabetes-induced osteoporotic rats and BMMs from rat models, which was neutralized by further HIF-1α overexpression. To sum up, SENP3 overexpression restrained osteoclast differentiation in type II diabetic osteoporosis by increasing HIF-1α stability and expression and thus promoting PPAR-γ expression via de-SUMOylation, which might expand the understanding of the mechanisms of type II diabetes combined with osteoporosis.

Mitochondrial Dysfunction in Pulmonary Hypertension

Pulmonary hypertension (PH) is a multi-etiological condition with a similar hemodynamic clinical sign and end result of right heart failure. Although its causes vary, a similar link across all the classifications is the presence of mitochondrial dysfunction. Mitochondria, as the powerhouse of the cells, hold a number of vital roles in maintaining normal cellular homeostasis, including the pulmonary vascular cells. As such, any disturbance in the normal functions of mitochondria could lead to major pathological consequences. The Warburg effect has been established as a major finding in PH conditions, but other mitochondria-related metabolic and oxidative stress factors have also been reported, making important contributions to the progression of pulmonary vascular remodeling that is commonly found in PH pathophysiology. In this review, we will discuss the role of the mitochondria in maintaining a normal vasculature, how it could be altered during pulmonary vascular remodeling, and the therapeutic options available that can treat its dysfunction.

Chemical and biochemical responses to sub-lethal doses of mercury and cadmium in gilthead seabream (Sparus aurata)

Specimens of Sparus aurata were exposed to sub-lethal concentrations of Hg and Cd for 25 days and the levels of both metals were investigated in organs and tissues. Bioaccumulation of Hg decreased as follow: gills > kidney > liver > skin > muscle, while the order of Cd bioaccumulation was: liver > kidney > gills > skin > muscle. Immediately after exposure, both metals showed the highest bioaccumulation in gills and skin indicating that these organs are reliable targets for biomonitoring studies after short term exposure. Metals introduction caused a significant time-dependent concentrations increase in kidney and liver, while in the muscle a significant increase of Hg was recorded only at the end of the experimentation. The effects of exposure were also investigated, at biochemical level, in the liver, which represents the main target of xenobiotics biotransformation and metabolism in fish. Exposed fishes exhibited a reduction of total lipid level, a decrease of polyunsaturated fatty acids (PUFA), together with a MDA increase. This suggests a direct effect of contaminants on oxidative stress induction that, through the MDA increase, altered the membrane fatty acids composition decreasing the PUFA content. As it regards molecular markers related to oxidative stress and lipid metanolism, a significant increase of Nrf2, Hif-1α and Ampk and a decrease of Fas were observed after exposure to both metals, while an Nf-kB increase was recorded in specimens exposed to Hg, docuemnting a correlation with oxidative stress and consequent metabolism adaptation. Finally, these results suggest the possibility to adopt these biomarkers to explore fish metabolic responses to environmental pollution.

Cancer-Associated Dysregulation of Sumo Regulators: Proteases and Ligases

SUMOylation is a post-translational modification that has emerged in recent decades as a mechanism involved in controlling diverse physiological processes and that is essential in vertebrates. The SUMO pathway is regulated by several enzymes, proteases and ligases being the main actors involved in the control of sumoylation of specific targets. Dysregulation of the expression, localization and function of these enzymes produces physiological changes that can lead to the appearance of different types of cancer, depending on the enzymes and target proteins involved. Among the most studied proteases and ligases, those of the SENP and PIAS families stand out, respectively. While the proteases involved in this pathway have specific SUMO activity, the ligases may have additional functions unrelated to sumoylation, which makes it more difficult to study their SUMO-associated role in cancer process. In this review we update the knowledge and advances in relation to the impact of dysregulation of SUMO proteases and ligases in cancer initiation and progression.

Metabolic Adaptation-Mediated Cancer Survival and Progression in Oxidative Stress

Undue elevation of ROS levels commonly occurs during cancer evolution as a result of various antitumor therapeutics and/or endogenous immune response. Overwhelming ROS levels induced cancer cell death through the dysregulation of ROS-sensitive glycolytic enzymes, leading to the catastrophic depression of glycolysis and oxidative phosphorylation (OXPHOS), which are critical for cancer survival and progression. However, cancer cells also adapt to such catastrophic oxidative and metabolic stresses by metabolic reprograming, resulting in cancer residuality, progression, and relapse. This adaptation is highly dependent on NADPH and GSH syntheses for ROS scavenging and the upregulation of lipolysis and glutaminolysis, which fuel tricarboxylic acid cycle-coupled OXPHOS and biosynthesis. The underlying mechanism remains poorly understood, thus presenting a promising field with opportunities to manipulate metabolic adaptations for cancer prevention and therapy. In this review, we provide a summary of the mechanisms of metabolic regulation in the adaptation of cancer cells to oxidative stress and the current understanding of its regulatory role in cancer survival and progression.

Maternal nicotine exposure induces congenital heart defects in the offspring of mice

Maternal cigarette smoking is a risk factor for congenital heart defects (CHDs). Nicotine replacement therapies are often offered to pregnant women following failed attempts of smoking cessation. However, the impact of nicotine on embryonic heart development is not well understood. In the present study, the effects of maternal nicotine exposure (MNE) during pregnancy on foetal heart morphogenesis were studied. Adult female mice were treated with nicotine using subcutaneous osmotic pumps at 0.75 or 1.5 mg/kg/day and subsequently bred with male mice. Our results show that MNE dose-dependently increased CHDs in foetal mice. CHDs included atrial and ventricular septal defects, double outlet right ventricle, unguarded tricuspid orifice, hypoplastic left ventricle, thickened aortic and pulmonary valves, and ventricular hypertrophy. MNE also significantly reduced coronary artery size and vessel abundance in foetal hearts. Moreover, MNE resulted in higher levels of oxidative stress and altered the expression of key cardiogenic regulators in the developing heart. Nicotine exposure reduced epicardial-to-mesenchymal transition in foetal hearts. In conclusion, MNE induces CHDs and coronary artery malformation in mice. These findings provide insight into the adverse outcomes of foetuses by MNE during pregnancy.

The Role of m6A Ribonucleic Acid Modification in the Occurrence of Atherosclerosis

The N6-methyladenosine (m6A) modification is the most abundant epitranscriptomic modification in eukaryotic messenger RNA (mRNA). The m6A modification process is jointly regulated by various enzymes and proteins, such as methyltransferases, demethylases and related m6A-binding proteins. The process is dynamic and reversible, and it plays an essential role in mRNA metabolism and various biological activities. Recently, an increasing number of researchers have confirmed that the onset and development of many diseases are closely associated with the molecular biological mechanism of m6A RNA methylation. This study focuses on the relationship between m6A RNA modification and atherosclerosis (AS). It thoroughly summarizes the mechanisms and processes of m6A RNA modification in AS-related cells and the relationships between m6A RNA modification and AS risk factors, and it provides a reference for exploring new targets for the early diagnosis and treatment of AS.

The Function of SUMOylation and Its Critical Roles in Cardiovascular Diseases and Potential Clinical Implications

Cardiovascular disease (CVD) is a common disease caused by many factors, including atherosclerosis, congenital heart disease, heart failure, and ischemic cardiomyopathy. CVD has been regarded as one of the most common diseases and has a severe impact on the life quality of patients. The main features of CVD include high morbidity and mortality, which seriously threaten human health. SUMO proteins covalently conjugate lysine residues with a large number of substrate proteins, and SUMOylation regulates the function of target proteins and participates in cellular activities. Under certain pathological conditions, SUMOylation of proteins related to cardiovascular development and function are greatly changed. Numerous studies have suggested that SUMOylation of substrates plays critical roles in normal cardiovascular development and function. We reviewed the research progress of SUMOylation in cardiovascular development and function, and the regulation of protein SUMOylation may be applied as a potential therapeutic strategy for CVD treatment.

Post-translational modification of RNA m6A demethylase ALKBH5 regulates ROS-induced DNA damage response

Faithful genome integrity maintenance plays an essential role in cell survival. Here, we identify the RNA demethylase ALKBH5 as a key regulator that protects cells from DNA damage and apoptosis during reactive oxygen species (ROS)-induced stress. We find that ROS significantly induces global mRNA N6-methyladenosine (m6A) levels by modulating ALKBH5 post-translational modifications (PTMs), leading to the rapid and efficient induction of thousands of genes involved in a variety of biological processes including DNA damage repair. Mechanistically, ROS promotes ALKBH5 SUMOylation through activating ERK/JNK signaling, leading to inhibition of ALKBH5 m6A demethylase activity by blocking substrate accessibility. Moreover, ERK/JNK/ALKBH5-PTMs/m6A axis is activated by ROS in hematopoietic stem/progenitor cells (HSPCs) in vivo in mice, suggesting a physiological role of this molecular pathway in the maintenance of genome stability in HSPCs. Together, our study uncovers a molecular mechanism involving ALKBH5 PTMs and increased mRNA m6A levels that protect genomic integrity of cells in response to ROS.

Redox-sensitive enzyme SENP3 mediates vascular remodeling via de-SUMOylation of β-catenin and regulation of its stability

Background

Oxidative stress plays critical pathophysiological roles in vascular remodeling-related cardiovascular diseases, including hypertension, atherosclerosis, and restenosis. Previous studies demonstrate that SENP3, a redox-sensitive SUMO2/3-specific protease, is strongly implicated in cancer development and progression. However, the role of SENP3 in vascular remodeling remains unknown.

Methods

We generated three mouse models of vascular remodeling due to low shear stress, hypertension, and atherosclerosis. The expression of SENP3 was determined by western blotting and/or immunofluorescence staining in cultured vascular smooth muscle cells (VSMCs), animal models, and human samples. The biological function of SENP3 in proliferation and migration of VSMC and vascular remodeling was further investigated in vitro and in vivo models.

Findings

SENP3 was highly expressed in VSMCs of remodeled arteries, accompanied by elevated reactive oxygen species (ROS) levels. In cultured VSMCs, SENP3 protein levels were enhanced by oxidized low-density lipoprotein and Angiotensin II in a ROS-dependent manner. SENP3 overexpression significantly promoted and sh-RNA-mediated knockdown markedly inhibited VSMCs proliferation and migration. Immunofluorescence staining showed that SENP3 expression was correlated with intimal area in remodeled arteries. Furthermore, we demonstrated that SENP3 interacted with β-catenin and inhibited its proteasome-dependent degradation via de-SUMOylation of β-catenin. Most importantly, SENP3^+/− mice exhibited alleviated vascular remodeling.

Interpretation

Our results highlight the important function of SENP3 as a redox sensor and mediator in vascular remodeling.

SENP Proteases as Potential Targets for Cancer Therapy

Simple Summary

Post-translational modification—the biochemical addition of functional groups or proteins—occurs following protein biosynthesis and contributes to an increase in the functional diversity of the proteome. Post-translational modifications include SUMOylation—the covalent attachment of small ubiquitin-related modifier (SUMO) proteins to substrate proteins. SUMOylation is a reversible modification, which is erased by SUMO-specific proteases (SENPs). Deregulation of SENPs leads to cellular dysfunction and is associated with various diseases, including cancer. The role of SENPs in cancer pathogenesis is expected, and thus these proteins are considered promising targets for drug design and development. In this review, we will discuss the role of SENPs, focusing on DNA repair and the cell cycle—cellular pathways malfunctioning in most cancer cells—and provide an update on advances in the development of SENP-oriented inhibitors.

Abstract

SUMOylation is a reversible post-translational modification (PTM) involving a covalent attachment of small ubiquitin-related modifier (SUMO) proteins to substrate proteins. SUMO-specific proteases (SENPs) are cysteine proteases with isopeptidase activity facilitating the de-conjugation of SUMO proteins and thus participating in maintaining the balance between the pools of SUMOylated and unSUMOylated proteins and in SUMO recycling. Several studies have reported that SENPs’ aberrant expression is associated with the development and progression of cancer. In this review, we will discuss the role of SENPs in the pathogenesis of cancer, focusing on DNA repair and the cell cycle—cellular pathways malfunctioning in most cancer cells. The plausible role of SENPs in carcinogenesis resulted in the design and development of their inhibitors, including synthetic protein-based, peptide-based, and small molecular weight inhibitors, as well as naturally occurring compounds. Computational methods including virtual screening have been implemented to identify a number of lead structures in recent years. Some inhibitors suppressed the proliferation of prostate cancer cells in vitro and in vivo, confirming that SENPs are suitable targets for anti-cancer treatment. Further advances in the development of SENP-oriented inhibitors are anticipated toward SENP isoform-specific molecules with therapeutic potential.

The Critical Roles of the SUMO-Specific Protease SENP3 in Human Diseases and Clinical Implications

Post-translational modification by SUMO (small ubiquitin-like modifier) proteins has been shown to regulate a variety of functions of proteins, including protein stability, chromatin organization, transcription, DNA repair, subcellular localization, protein–protein interactions, and protein homeostasis. SENP (sentrin/SUMO-specific protease) regulates precursor processing and deconjugation of SUMO to control cellular mechanisms. SENP3, which is one of the SENP family members, deconjugates target proteins to alter protein modification. The effect of modification via SUMO and SENP3 is crucial to maintain the balance of SUMOylation and guarantee normal protein function and cellular activities. SENP3 acts as an oxidative stress-responsive molecule under physiological conditions. Under pathological conditions, if the SUMOylation process of proteins is affected by variations in SENP3 levels, it will cause a cellular reaction and ultimately lead to abnormal cellular activities and the occurrence and development of human diseases, including cardiovascular diseases, neurological diseases, and various cancers. In this review, we summarized the most recent advances concerning the critical roles of SENP3 in normal physiological and pathological conditions as well as the potential clinical implications in various diseases. Targeting SENP3 alone or in combination with current therapies might provide powerful targeted therapeutic strategies for the treatment of these diseases.

Autophagy and Redox Homeostasis in Parkinson's: A Crucial Balancing Act

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated primarily from endogenous biochemical reactions in mitochondria, endoplasmic reticulum (ER), and peroxisomes. Typically, ROS/RNS correlate with oxidative damage and cell death; however, free radicals are also crucial for normal cellular functions, including supporting neuronal homeostasis. ROS/RNS levels influence and are influenced by antioxidant systems, including the catabolic autophagy pathways. Autophagy is an intracellular lysosomal degradation process by which invasive, damaged, or redundant cytoplasmic components, including microorganisms and defunct organelles, are removed to maintain cellular homeostasis. This process is particularly important in neurons that are required to cope with prolonged and sustained operational stress. Consequently, autophagy is a primary line of protection against neurodegenerative diseases. Parkinson's is caused by the loss of midbrain dopaminergic neurons (mDANs), resulting in progressive disruption of the nigrostriatal pathway, leading to motor, behavioural, and cognitive impairments. Mitochondrial dysfunction, with associated increases in oxidative stress, and declining proteostasis control, are key contributors during mDAN demise in Parkinson's. In this review, we analyse the crosstalk between autophagy and redoxtasis, including the molecular mechanisms involved and the detrimental effect of an imbalance in the pathogenesis of Parkinson's.

High SENP3 Expression Promotes Cell Migration, Invasion, and Proliferation by Modulating DNA Methylation of E-Cadherin in Osteosarcoma

SENP3, a sentrin/SUMO2/3-specific protease, is recognized as a transcriptional factor that accumulates under cellular oxidative stress and plays a significant role in the removal of SUMO2/3 modification. In our study, we examined a TCGA dataset and found that the transcripts per million (TPM) value of SENP3 is high in sarcoma, including osteosarcoma (OS). We found that SENP3 was highly expressed in OS cancer tissues when compared with osteofibrous dysplasia tissues. The survival data of SENP3 in TCGA showed that the sarcoma patients with higher SENP3 expression levels showed poor prognosis. In vitro, SENP3 knockdown in OS cancer cells inhibited cell proliferation, migration, and invasion and induced apoptosis. In contrast, SENP3 overexpression reversed these effects. Next, we found that SENP3 inhibited the expression of E-cadherin (E-Cad) by increasing methylation of the E-Cad promoter. Finally, E-Cad expression was increased in the OS cell line MG63 following methylation, and the cell proliferation, migration, and invasion capacity were decreased. In summary, SENP3 played a significant role in OS carcinogenesis and may act as a potential biomarker in the diagnosis and treatment of OS.

Sub-lethal doses of polybrominated diphenyl ethers affect some biomarkers involved in energy balance and cell cycle, via oxidative stress in the marine fish cell line SAF-1

Polybrominated diphenyl ethers (PBDEs) are a class of persistent contaminants which are found all over the world in the marine environment. Sparus aurata fibroblast cell line (SAF-1) was exposed to increasing concentrations of PBDEs 47 and 99, until 72 h to evaluate the cytotoxicity, reactive oxygen species (ROS) production and the expression of some selected molecular markers related to cell cycle, cell signaling, energetic balance and oxidative stress (p53, erk-1, hif-1α and nrf-2), by real-time PCR. Furthermore, SAF-1 cells were exposed for 7 and 15 days to sub-lethal concentrations, in order to evaluate the response of some biomarkers by immunoblotting (p53, ERK-1, AMPK, HIF-1α and NRF-2). After 48 and 72 h, the cells showed a significant decrease of cell vitality as well as an increase of intracellular ROS production. Gene expression analysis showed that sub-lethal concentrations of BDE-99 and 47, after 72 h, up-regulated cell cycle and oxidative stress biomarkers, although exposure to 100 μmol L^-1 down-regulated the selected markers related to cell cycle, cell signaling, energetic balance. After 7 and 15 days of sub-lethal doses exposure, all the analyzed markers resulted affected by the contaminants. Our results suggest that PBDEs influence the cells homeostasis first of all via oxidative stress, reducing the cell response and defense capacity and affecting its energetic levels. This situation of stress and energy imbalance could represents a condition that, modifying some of the analyzed biochemical pathways, would predispose to cellular transformation.

Reactive Oxygen Species Drive Epigenetic Changes in Radiation-Induced Fibrosis

Radiation-induced fibrosis (RIF) develops months to years after initial radiation exposure. RIF occurs when normal fibroblasts differentiate into myofibroblasts and lay down aberrant amounts of extracellular matrix proteins. One of the main drivers for developing RIF is reactive oxygen species (ROS) generated immediately after radiation exposure. Generation of ROS is known to induce epigenetic changes and cause differentiation of fibroblasts to myofibroblasts. Several antioxidant compounds have been shown to prevent radiation-induced epigenetic changes and the development of RIF. Therefore, reviewing the ROS-linked epigenetic changes in irradiated fibroblast cells is essential to understand the development and prevention of RIF.

Oxidative Stress, Induced by Sub-Lethal Doses of BDE 209, Promotes Energy Management and Cell Cycle Modulation in the Marine Fish Cell Line SAF-1

The effects of sub-lethal doses of polybrominated diphenyl ether (PBDE)-209 in terms of toxicity, oxidative stress, and biomarkers were evaluated in the Sparus aurata fibroblast cell line (SAF-1). Vitality and oxidative stress status were studied after incubation with PBDE for 72 h. Concomitantly, the quantification of proteins related to cell cycle and DNA repair (p53), cell proliferation (extracellular signal–regulated kinase 1 (ERK1)), energetic restriction (hypoxia-inducible factor 1 (HIF1)), and redox status (Nuclear factor erythroid 2–related factor 2 (NRF2)) was also determined after prolonged exposure (7–15 days) by immunoblotting. Our results demonstrated that rising concentrations of PBDEs exposure-induced oxidative stress, and that this event modulates different cell pathways related to cell cycle, cell signaling, and energetic balance in the long term, indicating the negative impact of sub-lethal dose exposure to cell homeostasis.

SENP3-mediated host defense response contains HBV replication and restores protein synthesis

Certain organs are capable of containing the replication of various types of viruses. In the liver, infection of Hepatitis B virus (HBV), the etiological factor of Hepatitis B and hepatocellular carcinoma (HCC), often remains asymptomatic and leads to a chronic carrier state. Here we investigated how hepatocytes contain HBV replication and promote their own survival by orchestrating a translational defense mechanism via the stress-sensitive SUMO-2/3-specific peptidase SENP3. We found that SENP3 expression level decreased in HBV-infected hepatocytes in various models including HepG2-NTCP cell lines and a humanized mouse model. Downregulation of SENP3 reduced HBV replication and boosted host protein translation. We also discovered that IQGAP2, a Ras GTPase-activating-like protein, is a key substrate for SENP3-mediated de-SUMOylation. Downregulation of SENP3 in HBV infected cells facilitated IQGAP2 SUMOylation and degradation, which leads to suppression of HBV gene expression and restoration of global translation of host genes via modulation of AKT phosphorylation. Thus, The SENP3-IQGAP2 de-SUMOylation axis is a host defense mechanism of hepatocytes that restores host protein translation and suppresses HBV gene expression.

Concepts and Methodologies to Study Protein SUMOylation: An Overview

Protein modification by the small ubiquitin-related modifier (SUMO) was simultaneously discovered by several groups at the middle of the 1990s. Although distinct names were proposed including Sentrin, GMP1, PIC1, or SMT3, SUMO became the most popular. Early studies on the functions of SUMOylation focused on activities in the nucleus, including transcription activation, chromatin structure, and DNA repair. However, it is now recognized that SUMOylation affects a large diversity of cellular processes both in the nucleus and the cytoplasm and functions of SUMOylation appear to have undefined limits. SUMO-conjugating enzymes and specific proteases actively regulate the modification status of target proteins. The recent discoveries of ubiquitin-SUMO hybrid chains, multiple SUMO-interacting motifs, and macromolecular complexes regulated by SUMOylation underscore the high complexity of this dynamic reversible system. New conceptual frameworks suggested by these findings have motivated the development of new methodologies to study pre- and post-SUMOylation events in vitro and in vivo, using distinct model organisms. Here we summarize some of the new developments and methodologies in the field, particularly those that will be further elaborated on in the chapters integrating this book.

Monoamine oxidase B levels are highly expressed in human gliomas and are correlated with the expression of HiF-1α and with transcription factors Sp1 and Sp3

Monoamine oxidases A and B (MAOA and MAOB) are highly expressed in many cancers. Here we investigated the level of MAOB in gliomas and confirmed its high expression. We found that MAOB levels correlated with tumor grade and hypoxia-inducible factor 1-alpha (HiF-1α) expression. HiF-1α was localized to the nuclei in high-grade gliomas, but it was primarily cytosolic in low-grade gliomas and normal human astrocytes. Expression of both glial fibrillary acidic protein (GFAP) and MAOB are correlated to HiF-1α expression levels. Levels of MAOB are correlated by the levels of transcription factor Sp3 in the majority of GBM examined, but this control of MAOB expression by Sp3 in low grade astrocytic gliomas is significantly different from control in the in the majority of glioblastomas. The current findings support previous suggestions that MAOB can be exploited for the killing of cancer cells. Selective cell toxicity can be achieved by designing non-toxic prodrugs that require MAOB for their catalytic conversion into mature cytotoxic chemotherapeutics.

SUMO-specific protease 3 is a key regulator for hepatic lipid metabolism in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive lipid accumulation in hepatocytes. The role of SENP3 in lipid metabolism, particularly NAFLD, is unclear. Our results showed that hepatic SENP3 was up-regulated in NAFLD patients and an animal model in vivo and after loading hepatocytes with free fatty acids (FFA) in vitro. Intracellular lipid accumulation was determined in SENP3 silenced or overexpressed hepatocytes with/without FFA in vitro. Confirming a role for SENP3, gene silencing was associated in vitro with amelioration of lipid accumulation and overexpression with enhancement of lipid accumulation. SENP3 related genes in NAFLD were determined in vitro using RNA-Seq. Eleven unique genes closely associated with lipid metabolism were generated using bioinformatics. Three selected genes (apoe, a2m and tnfrsf11b) were verified in vitro, showing apoe, a2m and tnfrsf11b were regulated by SENP3 with FFA stimulation. Intrahepatic and circulating APOE, A2M and TNFRSF11B were elevated in NAFLD compared with controls. These data demonstrate the important role of SENP3 in lipid metabolism during the development of NAFLD via downstream genes, which may be useful information in the development of NAFLD. The precise role of SENP3 in NAFLD will be investigated using liver-specific conditional knockout mice in future studies.

The Ubiquitin-Like SUMO System and Heart Function: From Development to Disease

SUMOylation is a ubiquitin-related transient posttranslational modification pathway catalyzing the conjugation of small ubiquitin-like modifier (SUMO) proteins (SUMO1, SUMO2, and SUMO3) to lysine residues of proteins. SUMOylation targets a wide variety of cellular regulators and thereby affects a multitude of different cellular processes. SUMO/sentrin-specific proteases are able to remove SUMOs from targets, contributing to a tight control of SUMOylated proteins. Genetic and cell biological experiments indicate a critical role of balanced SUMOylation/deSUMOylation for proper cardiac development, metabolism, and stress adaptation. Here, we review the current knowledge about SUMOylation/deSUMOylation in the heart and provide an integrated picture of cardiac functions of the SUMO system under physiologic or pathologic conditions. We also describe potential therapeutic approaches targeting the SUMO machinery to combat heart disease.

Hydrogen peroxide - production, fate and role in redox signaling of tumor cells

Hydrogen peroxide (H₂O₂) is involved in various signal transduction pathways and cell fate decisions. The mechanism of the so called “redox signaling” includes the H₂O₂-mediated reversible oxidation of redox sensitive cysteine residues in enzymes and transcription factors thereby altering their activities. Depending on its intracellular concentration and localization, H₂O₂ exhibits either pro- or anti-apoptotic activities. In comparison to normal cells, cancer cells are characterized by an increased H₂O₂ production rate and an impaired redox balance thereby affecting the microenvironment as well as the anti-tumoral immune response. This article reviews the current knowledge about the intracellular production of H₂O₂ along with redox signaling pathways mediating either the growth or apoptosis of tumor cells. In addition it will be discussed how the targeting of H₂O₂-linked sources and/or signaling components involved in tumor progression and survival might lead to novel therapeutic targets.

DeSUMOylation: An Important Therapeutic Target and Protein Regulatory Event

The discovery of the process of small ubiquitin-like modifier (SUMO)-mediated post-translational modification of targets (SUMOylation) in early 1990s proved to be a significant step ahead in understanding mechanistic regulation of proteins and their functions in diverse life processes at the cellular level. The critical step in reversing the SUMOylation pathway is its ability to be dynamically deSUMOylated by SUMO/sentrin-specific protease (SENP). This review is intended to give a brief introduction about the process of SUMOylation, different mammalian deSUMOylating enzymes with special emphasis on their regulation of ribosome biogenesis at the molecular level, and its emerging roles in mitochondrial dynamics that might reveal usefulness of SENPs for therapeutic applications.

Redox signalling and mitochondrial stress responses; lessons from inborn errors of metabolism

Mitochondria play a key role in overall cell physiology and health by integrating cellular metabolism with cellular defense and repair mechanisms in response to physiological or environmental changes or stresses. In fact, dysregulation of mitochondrial stress responses and its consequences in the form of oxidative stress, has been linked to a wide variety of diseases including inborn errors of metabolism. In this review we will summarize how the functional state of mitochondria -- and especially the concentration of reactive oxygen species (ROS), produced in connection with the respiratory chain -- regulates cellular stress responses by redox regulation of nuclear gene networks involved in repair systems to maintain cellular homeostasis and health. Based on our own and other's studies we re-introduce the ROS triangle model and discuss how inborn errors of mitochondrial metabolism, by production of pathological amounts of ROS, may cause disturbed redox signalling and induce chronic cell stress with non-resolving or compromised cell repair responses and increased susceptibility to cell stress induced cell death. We suggest that this model may have important implications for those inborn errors of metabolism, where mitochondrial dysfunction plays a major role, as it allows the explanation of oxidative stress, metabolic reprogramming and altered signalling growth pathways that have been reported in many of the diseases. It is our hope that the model may facilitate novel ideas and directions that can be tested experimentally and used in the design of future new approaches for pre-symptomatic diagnosis and prognosis and perhaps more effective treatments of inborn errors of metabolism.

Sentrin/small ubiquitin-like modifier-specific protease 5 protects oral cancer cells from oxidative stress-induced apoptosis

The aim of the present study was to investigate the role of sentrin/small ubiquitin-like modifier (SUMO)-specific protease 5 (SENP5) in oral squamous cell carcinoma (OSCC), as the overexpression of SENP5 has been observed in 31 OSCC tissue specimens. CAL-27 OSCC cells were used for in vitro measurements. The distribution of SENP5 was visualized using immunohistochemistry and H2O2-induced oxidative stress, and the effects of SENP-small interfering RNA on SENP5 were analyzed via western blotting. The apoptotic rates of the CAL-27 cells during oxidative stress and SENP5 silencing were estimated using flow-cytometry, and the mitochondrial structures were analyzed using a mitochondria tracker. The SENP5 protein was localized in the nuclei and cytosols of the CAL-27 cells, and incubation with 100 µm H2O2 for >1 h led to its stabilization. Incubation with H2O2 alone had no effect on the CAL-27 cells, however, a combination of H2O2 and SENP5 silencing led to enhanced apoptotic rates (P<0.001). Analysis of the mitochondrial structures revealed that H2O2 alone enhanced mitochondrial network formation, whereas the combination of H2O2 and SENP5 silencing led to mitochondrial fragmentation in the CAL-27 cells. The overexpression of SENP5 partly localized in the cytosol of the OSCC cells. Mild oxidative stress stabilized the SENP5 protein in the CAL-27 cells, and only the combination of SENP5 silencing and H2O2 application led to mitochondria fragmentation and a significant increase in cell apoptosis. Therefore, SENP5 protected the OSCC cells from oxidative stress-induced apoptosis.

Pregestational diabetes induces fetal coronary artery malformation via reactive oxygen species signaling

Hypoplastic coronary artery disease is a congenital coronary artery malformation associated with a high risk of sudden cardiac death. However, the etiology and pathogenesis of hypoplastic coronary artery disease remain undefined. Pregestational diabetes increases reactive oxygen species (ROS) levels and the risk of congenital heart defects. We show that pregestational diabetes in mice induced by streptozotocin significantly increased 4-hydroxynonenal production and decreased coronary artery volume in fetal hearts. Pregestational diabetes also impaired epicardial epithelial-to-mesenchymal transition (EMT) as shown by analyses of the epicardium, epicardial-derived cells, and fate mapping. Additionally, the expression of hypoxia-inducible factor 1α (Hif-1α), Snail1, Slug, basic fibroblast growth factor (bFgf), and retinaldehyde dehydrogenase (Aldh1a2) was decreased and E-cadherin expression was increased in the hearts of fetuses of diabetic mothers. Of note, these abnormalities were all rescued by treatment with N-acetylcysteine (NAC) in diabetic females during gestation. Ex vivo analysis showed that high glucose levels inhibited epicardial EMT, which was reversed by NAC treatment. We conclude that pregestational diabetes in mice can cause coronary artery malformation through ROS signaling. This study may provide a rationale for further clinical studies to investigate whether pregestational diabetes could cause hypoplastic coronary artery disease in humans.

mTOR signaling regulates nucleolar targeting of the SUMO-specific isopeptidase SENP3

Ribosome biogenesis is a multistep cellular pathway that involves more than 200 regulatory components to ultimately generate translation-competent 80S ribosomes. The initial steps of this process, particularly rRNA processing, take place in the nucleolus, while later stages occur in the nucleoplasm and cytoplasm. One critical factor of 28S rRNA maturation is the SUMO-isopeptidase SENP3. SENP3 tightly interacts with the nucleolar scaffold protein NPM1 and is associated with nucleolar 60S preribosomes. A central question is how changes in energy supply feed into the regulation of ribosome maturation. Here, we show that the nutrient-sensing mTOR kinase pathway controls the nucleolar targeting of SENP3 by regulating its interaction with NPM1. We define an N-terminal domain in SENP3 as the critical NPM1 binding region and provide evidence that mTOR-mediated phosphorylation of serine/threonine residues within this region fosters the interaction of SENP3 with NPM1. The inhibition of mTOR triggers the nucleolar release of SENP3, thereby likely compromising its activity in rRNA processing. Since mTOR activity is tightly coupled to nutrient availability, we propose that this pathway contributes to the adaptation of ribosome maturation in response to the cellular energy status.

P300-dependent STAT3 acetylation is necessary for angiotensin II-induced pro-fibrotic responses in renal tubular epithelial cells

AIM

To explore the signal transducer and activator of transcription 3 (STAT3) signaling pathway, especially STAT3 acetylation, in angiotensin II (Ang II)-induced pro-fibrotic responses in renal tubular epithelial cells.

METHODS

Rat renal tubular epithelial cell line (NRK-52E) was used. STAT3 acetylation and phosphorylation, as well as the expression of fibronectin, collagen IV and transforming growth factor-β1 (TGF-β1) were examined using Western blotting. The level and localization of STAT3 phosphorylation on Tyr705 were detected with fluorescence immunocytochemistry. The cells were transfected with a plasmid vector carrying p300 gene or siRNA targeting p300 to regulate p300 expression.

RESULTS

Overexpression of p300 significantly increased STAT3 acetylation on Lys685, STAT3 phosphorylation on Tyr705, and the expression of TGF-β1, collagen IV and fibronectin in the cells. Treatment of the cells with Ang II (1 μmol/L) significantly increased STAT3 phosphorylation on Tyr705 through JAK2 activation, and dose-dependently increased the expression of fibronectin, collagen IV and TGF-β1. Pretreatment with curcumin, an inhibitor of JAK2 and p300, blocked Ang II-induced effects. Knockdown of p300 significantly decreased STAT3 acetylation on Lys685, and abolished Ang II-stimulated STAT3 phosphorylation on Tyr705, whereas pretreatment of the cells with C646, a selective inhibitor of p300, inhibited Ang II-induced STAT3 nuclear translocation and the expression of TGF-β1, collagen IV and fibronectin. Pretreatment of the cells with AG490, a JAK2 inhibitor, markedly inhibited Ang II-induced STAT3 phosphorylation on Tyr705 and fibronectin expression.

CONCLUSION

p300-dependent STAT3 acetylation is necessary for Ang II-induced STAT3 phosphorylation and the consequent pro-fibrotic responses in renal tubular epithelial cells in vitro.

SUMO-specific proteases/isopeptidases: SENPs and beyond

We summarize the evolutionary relationship, structure and subcellular distribution of SUMO proteases (or SUMO isopeptidases). We also discuss their functions and allude to their involvement in human disease.

Genetic and cellular modifiers of oxidative stress: what can we learn from fatty acid oxidation defects?

During the last two decades the realization has emerged that the phenotype of the majority of inherited genetic diseases, including inborn errors of metabolism, cannot be predicted by the genotype identified in patients. This is true for PKU and in the majority of fatty acid oxidation (FAO) defects, where the genotypes identified in patients may be allocated into two groups. One comprising big deletions and small out-of-frame deletions/insertions as well as severe splice and stop codon changes, generally giving rise to no or very little protein product, and the other group, comprising small in-frame deletions/insertions and missense variations, resulting in misfolding proteins with varying stability. In all cases of FAO defects the pathophysiology may be due to energy insufficiency as well as toxic effects from accumulated enzyme substrates. In patients carrying missense variations, it may in addition be caused by the presence of misfolding proteins. A common effect of accumulated substrates and misfolding proteins is chronic oxidative stress, the severeness of which may depend on a complex interplay of modifying factors, including genetic, cellular, environmental and dietary. In this review we will discuss the hypothesis that especially the amounts of reactive oxygen species (ROS) and reactive nitrogen species (RNS), created in connection with the electron transport chain (ETC), are the driving forces in the balance between cell survival and death. In young and healthy cells small amounts of ROS function as signaling molecules, activating cell protection systems, such as protein quality networks, antioxidant enzymes and metabolic shift from ATP production by the ETC to glycolysis. In the sick and old cell, containing misfolding and damaged proteins, the dynamic range of these protecting systems are narrowed, and cells develop a state of chronic stress, which easier than young and healthy cells may initiate cell death programs like apoptosis and necrosis. We will discuss a wealth of literature that support this hypothesis, which - if supported by studies - is important for new treatment strategies. We conclude that crude antioxidant treatment may not be beneficial, since it may inhibit the survival stress responses. We discuss the ongoing studies to enhance the residual activity of mild misfolding enzyme proteins by cofactor or chemical chaperones or by inducing the transcription of FAO enzyme proteins by bezafibrate with respect to misfolding/distorted conformational proteins ability to create ROS, and the need to know the exact pathophysiological mechanisms in order to suggest new treatment regimes.