Gsta4 Null Mouse Embryonic Fibroblasts Exhibit Enhanced Sensitivity to Oxidants: Role of 4-Hydroxynonenal in Oxidant Toxicity

Regorafenib activates oxidative stress by inhibiting SELENOS and potentiates oxaliplatin-induced cell death in colon cancer cells

Colorectal cancer (CRC) is the third most common cancer, and is one of the leading causes of cancer-related death worldwide. At the time of diagnosis, about 20% of patients with CRC present metastatic disease. Regorafenib, an oral multi-kinase inhibitor, has been demonstrated the efficacy and tolerability in patients with metastatic CRC. Oxaliplatin is a frontline treatment regimen for CRC, and combination treatments with oxaliplatin and other chemotherapeutic agents exert superior therapeutic effects. However, side effects and drug resistance limited their further clinical application. Here, we found that combined treatment with regorafenib and oxaliplatin synergistically enhanced anti-tumor activities in CRC by activating reactive oxygen species (ROS) mediated endoplasmic reticulum (ER) stress, C-Jun-amino-terminal kinase (JNK) and p38 signaling pathways. Regorafenib promoted ROS production by suppressing the expression of selenoprotein S (SELENOS). Knocking down SELENOS sensitized ROS-mediated anti-tumor effects of regorafenib in CRC cells. Furthermore, mouse xenograft models demonstrated that synergistic anti-tumor effects of combined treatment with regorafenib and oxaliplatin. This study provided solid experimental evidences for the combined treatment with regorafenib and oxaliplatin in CRC.

Cross-Regulation Between Redox and Epigenetic Systems in Tumorigenesis: Molecular Mechanisms and Clinical Applications

Significance: Redox and epigenetics are two important regulatory processes of cell physiological functions. The cross-regulation between these processes has critical effects on the occurrence and development of various types of tumors. Recent Advances: The core factor that influences redox balance is reactive oxygen species (ROS) generation. The ROS functions as a double-edged sword in tumors: Low levels of ROS promote tumors, whereas excessive ROS induces various forms of tumor cell death, including apoptosis and ferroptosis as well as necroptosis and pyroptosis. Many studies have shown that the redox balance is influenced by epigenetic mechanisms such as DNA methylation, histone modification, chromatin remodeling, non-coding RNAs (microRNA, long non-coding RNA, and circular RNA), and RNA N6-methyladenosine modification. Several oxidizing or reducing substances also affect the epigenetic state. Critical Issues: In this review, we summarize research on the cross-regulation between redox and epigenetics in cancer and discuss the relevant molecular mechanisms. We also discuss the current research on the clinical applications. Future Directions: Future research can use high-throughput methods to analyze the molecular mechanisms of the cross-regulation between redox and epigenetics using both in vitro and in vivo models in more detail, elucidate regulatory mechanisms, and provide guidance for clinical treatment. Antioxid. Redox Signal. 39, 445-471.

Involvement of redox signalling in tumour cell dormancy and metastasis

Decades of research on oncogene-driven carcinogenesis and gene-expression regulatory networks only started to unveil the complexity of tumour cellular and molecular biology. This knowledge has been successfully implemented in the clinical practice to treat primary tumours. In contrast, much less progress has been made in the development of new therapies against metastasis, which are the main cause of cancer-related deaths. More recently, the role of epigenetic and microenviromental factors has been shown to play a key role in tumour progression. Free radicals are known to communicate the intracellular and extracellular compartments, acting as second messengers and exerting a decisive modulatory effect on tumour cell signalling. Depending on the cellular and molecular context, as well as the intracellular concentration of free radicals and the activation status of the antioxidant system of the cell, the signalling equilibrium can be tilted either towards tumour cell survival and progression or cell death. In this regard, recent advances in tumour cell biology and metastasis indicate that redox signalling is at the base of many cell-intrinsic and microenvironmental mechanisms that control disseminated tumour cell fate and metastasis. In this manuscript, we will review the current knowledge about redox signalling along the different phases of the metastatic cascade, including tumour cell dormancy, making emphasis on metabolism and the establishment of supportive microenvironmental connections, from a redox perspective.

Role of Oxidative Stress in Liver Disorders

Oxygen is vital for life as it is required for many different enzymatic reactions involved in intermediate metabolism and xenobiotic biotransformation. Moreover, oxygen consumption in the electron transport chain of mitochondria is used to drive the synthesis of ATP to meet the energetic demands of cells. However, toxic free radicals are generated as byproducts of molecular oxygen consumption. Oxidative stress ensues not only when the production of reactive oxygen species (ROS) exceeds the endogenous antioxidant defense mechanism of cells, but it can also occur as a consequence of an unbalance between antioxidant strategies. Given the important role of hepatocytes in the biotransformation and metabolism of xenobiotics, ROS production represents a critical event in liver physiology, and increasing evidence suggests that oxidative stress contributes to the development of many liver diseases. The present review, which is part of the special issue “Oxidant stress in Liver Diseases”, aims to provide an overview of the sources and targets of ROS in different liver diseases and highlights the pivotal role of oxidative stress in cell death. In addition, current antioxidant therapies as treatment options for such disorders and their limitations for future trial design are discussed.

MPO/HOCl Facilitates Apoptosis and Ferroptosis in the SOD1G93A Motor Neuron of Amyotrophic Lateral Sclerosis

Background. Oxidative stress and reactive oxygen species (ROS) are important in the pathogenesis of amyotrophic lateral sclerosis (ALS). Hypochlorous acid (HOCl) is a powerful oxidant of the reactive oxygen species (ROS) family. HOCl’s role in the progress of ALS remains unclear due to the lack of an effective HOCl detection method. Cumulative evidence supports oxidative damage incurred by mutant hSOD1 contributing to motor neuron death; however, whether HOCl as well as its catalytic enzyme myeloperoxidase (MPO) function in the cell death of SOD1G93A ALS remains elusive. Methods. The hSOD1WT and hSOD1G93A NSC-34 cell and SOD1G93A ALS mouse models were employed. With a novel fluorescent HOCl probe, HKOCl-3, we detected the expressions of HOCl and its catalytic enzyme, MPO, in the above models in vitro and in vivo. The regulation of MPO/HOCl by hSOD1G93A mutation and cell deaths by MPO/HOCl were also assayed, including apoptosis, ferroptosis, and autophagy. Results. Our results showed that hSOD1G93A mutation promoted the activation of the MPO/HOCl pathway in SOD1G93A ALS cell models. The activation of MPO/HOCl pathways facilitated apoptosis and ferroptosis through increasing the Bax/Bcl-2 ratio and expression of caspase-3 or inhibiting the expressions of GPX4 and NQO1 and thus leading to irreversible lipid peroxidation. Overexpressed FSP1, a glutathione-independent suppressor, could ameliorate ferroptosis. In vivo, we demonstrated that the activation of the MPO/HOCl pathway occurred differently in motor neurons of the motor cortices, brain stems, and spinal cords in male and female SOD1G93A transgenic mice. In addition, inhibiting MPO improved the motor performance of SOD1G93A transgenic mice, as demonstrated by the rotarod test. Conclusions. We concluded that aggregation of mutant hSOD1 proteins contributed to activation of the MPO/HOCl pathway, triggering apoptosis and ferroptosis in motor neuronal deaths and exerting impaired motor performance.

Anticancer Activity of Ω-6 Fatty Acids through Increased 4-HNE in Breast Cancer Cells

Simple Summary

Epidemiological evidence suggests that breast cancer risk is lowered by Ω-3 and increased by Ω-6 polyunsaturated fatty acids (PUFAs). Paradoxically, the Ω-6 PUFA metabolite 4-hydroxynonenal (4-HNE) inhibits cancer cell growth. This duality prompted us to study whether arachidonic acid (AA) would enhance doxorubicin (dox) cytotoxicity towards breast cancer cells. We found that supplementing AA or inhibiting 4-HNE metabolism potentiated doxorubicin (dox) toxicity toward Her2-dependent breast cancer but spared myocardial cells. Our results suggest that Ω-6 PUFAs could improve outcomes of dox chemotherapy in Her2-overexpressing breast cancer.

Abstract

Her2-amplified breast cancers resistant to available Her2-targeted therapeutics continue to be a challenge in breast cancer therapy. Dox is the mainstay of chemotherapy of all types of breast cancer, but its usefulness is limited by cumulative cardiotoxicity. Because oxidative stress caused by dox generates the pro-apoptotic Ω-6 PUFA metabolite 4-hydroxynonenal (4-HNE), we surmised that Ω-6 PUFAs would increase the effectiveness of dox chemotherapy. Since the mercapturic acid pathway enzyme RALBP1 (also known as RLIP76 or Rlip) that limits cellular accumulation of 4-HNE also mediates dox resistance, the combination of Ω-6 PUFAs and Rlip depletion could synergistically improve the efficacy of dox. Thus, we studied the effects of the Ω-6 PUFA arachidonic acid (AA) and Rlip knockdown on the antineoplastic activity of dox towards Her2-amplified breast cancer cell lines SK-BR-3, which is sensitive to Her2 inhibitors, and AU565, which is resistant. AA increased lipid peroxidation, 4-HNE generation, apoptosis, cellular dox concentration and dox cytotoxicity in both cell lines while sparing cultured immortalized cardiomyocyte cells. The known functions of Rlip including clathrin-dependent endocytosis and dox efflux were inhibited by AA. Our results support a model in which 4-HNE generated by AA overwhelms the capacity of Rlip to defend against apoptosis caused by dox or 4-HNE. We propose that Ω-6 PUFA supplementation could improve the efficacy of dox or Rlip inhibitors for treating Her2-amplified breast cancer.

IRGM/Irgm1 facilitates macrophage apoptosis through ROS generation and MAPK signal transduction: Irgm1 +/- mice display increases atherosclerotic plaque stability

Rationale: Atherosclerosis plaque rupture (PR) is the pathological basis and chief culprit of most acute cardiovascular events and death. Given the complex and important role of macrophage apoptosis and autophagy in affecting plaque stability, an important unanswered question include is whether, and how, immunity-related GTPase family M protein (IRGM) and its mouse orthologue IRGM1 affect macrophage survival and atherosclerotic plaque stability.

Methods: To investigate whether serum IRGM of ST-segment elevation myocardial infarction (STEMI) patients is related to plaque morphology, we divided 85 STEMI patients into those with and without plaque rupture (PR and non-PR, respectively) based on OCT image analysis, and quantified the patients' serum IRGM levels. Next, we engineered Irgm1 deficient mice (Irgm1^+/-) and chimera mice with Irgm1 deficiency in the bone marrow on an ApoE^-/- background, which were then fed a high-fat diet for 16 weeks. Pathological staining was used to detect necrotic plaque cores, ratios of neutral lipids and cholesterol crystal, as well as collagen fiber contents in these mice to characterize plaque stability. In addition, immunofluorescence, immunohistochemical staining and western blot were used to detect the apoptosis of macrophages in the plaques. In vitro, THP-1 and RAW264.7 cells were stimulated with ox-LDL to mimic the in vivo environment, and IRGM/IRGM1 expression were modified by specific siRNA (knockdown) or IRGM plasmid (knocked-in). The effect of IRGM/Irgm1 on autophagy and apoptosis of macrophages induced by ox-LDL was then evaluated. In addition, we introduced inhibitors of the JNK/p38/ERK signaling pathway to verify the specific mechanism by which Irgm1 regulates RAW264.7 cell apoptosis.

Results: The serum IRGM levels of PR patients is significantly higher than that of non-PR patients and healthy volunteers, which may be an effective predictor of PR. On a high-fat diet, Irgm1-deficient mice exhibit reduced necrotic plaque cores, as well as neutral lipid and cholesterol crystal ratios, with increased collagen fiber content. Additionally, macrophage apoptosis is inhibited in the plaques of Irgm1-deficient mice. In vitro, IRGM/Irgm1 deficiency rapidly inhibits ox-LDL-induced macrophage autophagy while inhibiting ox-LDL-induced macrophage apoptosis in late stages. Additionally, IRGM/Irgm1 deficiency suppresses reactive oxygen species (ROS) production in macrophages, while removal of ROS effectively inhibits macrophage apoptosis induced by IRGM overexpression. We further show that Irgm1 can affect macrophage apoptosis by regulating JNK/p38/ERK phosphorylation in the MAPK signaling pathway.

Conclusions: Serum IRGM may be related to the process of PR in STEMI patients, and IRGM/Irgm1 deficiency increases plaque stability. In addition, IRGM/Irgm1 deficiency suppresses macrophage apoptosis by inhibiting ROS generation and MAPK signaling transduction. Cumulatively, these results suggest that targeting IRGM may represent a new treatment strategy for the prevention and treatment of acute cardiovascular deaths caused by PR.

Cox4i2 Triggers an Increase in Reactive Oxygen Species, Leading to Ferroptosis and Apoptosis in HHV7 Infected Schwann Cells

Emerging evidence suggests that reactive oxygen species (ROS) play a significant role in the pathogenesis of peripheral nerve damage. Our previous study indicated that human herpesvirus 7 (HHV7) induces Bell’s palsy. However, the specific mechanism underlying the effects of ROS in HHV7 infection-induced facial nerve damage is unknown. In this study, we established a rat FN model by inoculating an HHV7 virus solution. The facial grading score and LuxolFastBlue (LFB) staining were used to assess the success of the model. Using mRNA-sequencing analysis, we found that the expression of Complex IV Subunit 4 Isoform 2 (Cox4i2) increased in infected Schwann cells (SCs). Cox4i2 was suggested to increase COX activity, thereby promoting ROS production. The changes in the endogenous oxidant and antioxidant system were assessed, and the results showed that oxidative stress increased after HHV7 infection in vivo and in vitro. However, we found that oxidative injury was relieved after the transfection of shCox4i2 in HHV7-treated SCs by evaluating cell death, cell proliferation, and the ROS level as well as the levels of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH). Furthermore, we hypothesised that Cox4i2 loss would attenuate HHV7-induced ferroptosis and apoptosis, which are closely related to ROS in SCs. Our research illustrated that the knockdown of Cox4i2 suppresses HHV7-induced RSC96 cell ferroptosis as well as apoptosis via the ERK signalling pathway. Overall, several in vitro and in vivo methods were adopted in this study to reveal the new mechanism of ROS-induced and Cox4i2-mediated apoptosis and ferroptosis in HHV7 infected SCs.

The Multifaceted Regulation of Mitochondria in Ferroptosis

Ferroptosis is characterized as a novel form of regulated cell death, which is initiated by the lethal accumulation of lipid peroxidation catalyzed by cellular labile free iron. This iron driven cell death sharply differs from other well characterized forms of regulated cell death at morphological, genetic and biochemical levels. Increasing research has elaborated a high relevance between dysregulated ferroptosis and the pathogenesis of degenerative diseases and organs injury in human patients. Additionally, targeted induction of ferroptosis is considered as a potentially therapeutic design for the clinical intervention of other therapy-resistant cancers. It is well understood that mitochondria, the cellular powerhouse, determine several types of regulated cell death. Recently, compromised mitochondrial morphology and functionalities have been primarily formulated in ferroptosis. Several mitochondria associated proteins and metabolic processes have been elaborated to fine-tune ferroptotic program. Herein, we critically review the recent advances in this booming field, with focus on summarizing the multifaceted mitochondrial regulation of ferroptosis and providing a perspective on the potential biochemical basis. Finally, we are attempting to shed light on an integrative view on the possibility of mitochondria- and ferroptosis-targeting therapeutics as novel treatment designs for the intervention of ferroptosis related diseases.

Reactive Oxygen Species-Induced Lipid Peroxidation in Apoptosis, Autophagy, and Ferroptosis

Reactive oxygen species- (ROS-) induced lipid peroxidation plays a critical role in cell death including apoptosis, autophagy, and ferroptosis. This fundamental and conserved mechanism is based on an excess of ROS which attacks biomembranes, propagates lipid peroxidation chain reactions, and subsequently induces different types of cell death. A highly evolved sophisticated antioxidant system exists that acts to protect the cells from oxidative damage. In this review, we discussed how ROS propagate lipid peroxidation chain reactions and how the products of lipid peroxidation initiate apoptosis and autophagy in current models. We also discussed the mechanism of lipid peroxidation during ferroptosis, and we summarized lipid peroxidation in pathological conditions of critical illness. We aim to bring a more global and integrative sight to know how different ROS-induced lipid peroxidation occurs among apoptosis, autophagy, and ferroptosis.

Lipoxidation and cancer immunity

Lipoxidation is a well-known reaction between electrophilic carbonyl species, formed during oxidation of lipids, and specific proteins that, in most cases, causes an alteration in proteins function. This can occur under physiological conditions but, in many cases, it has been associated to pathological process, including cancer. Lipoxidation may have an effect in cancer development through their effects in tumour cells, as well as through the alteration of immune components and the consequent modulation of the immune response. The formation of protein adducts affects different proteins in cancer, triggering different mechanism, such as proliferation, cell differentiation and apoptosis, among others, altering cancer progression. The divergent results obtained documented that the formation of lipoxidation adducts can have either anti-carcinogenic or pro-carcinogenic effects, depending on the cell type affected and the specific adduct formed. Moreover, lipoxidation adducts may alter the immune response, consequently causing either positive or negative alterations in cancer progression. Therefore, in this review, we summarize the effects of lipoxidation adducts in cancer cells and immune components and their consequences in the evolution of different types of cancer.

Redox Signaling by Reactive Electrophiles and Oxidants

The concept of cell signaling in the context of nonenzyme-assisted protein modifications by reactive electrophilic and oxidative species, broadly known as redox signaling, is a uniquely complex topic that has been approached from numerous different and multidisciplinary angles. Our Review reflects on five aspects critical for understanding how nature harnesses these noncanonical post-translational modifications to coordinate distinct cellular activities: (1) specific players and their generation, (2) physicochemical properties, (3) mechanisms of action, (4) methods of interrogation, and (5) functional roles in health and disease. Emphasis is primarily placed on the latest progress in the field, but several aspects of classical work likely forgotten/lost are also recollected. For researchers with interests in getting into the field, our Review is anticipated to function as a primer. For the expert, we aim to stimulate thought and discussion about fundamentals of redox signaling mechanisms and nuances of specificity/selectivity and timing in this sophisticated yet fascinating arena at the crossroads of chemistry and biology.

Sulforaphane potentiates anticancer effects of doxorubicin and attenuates its cardiotoxicity in a breast cancer model

Breast cancer is the most common malignancy in women of the Western world. Doxorubicin (DOX) continues to be used extensively to treat early-stage or node-positive breast cancer, human epidermal growth factor receptor-2 (HER2)-positive breast cancer, and metastatic disease. We have previously demonstrated in a mouse model that sulforaphane (SFN), an isothiocyanate isolated from cruciferous vegetables, protects the heart from DOX-induced toxicity and damage. However, the effects of SFN on the chemotherapeutic efficacy of DOX in breast cancer are not known. Present studies were designed to investigate whether SFN alters the effects of DOX on breast cancer regression while also acting as a cardioprotective agent. Studies on rat neonatal cardiomyocytes and multiple rat and human breast cancer cell lines revealed that SFN protects cardiac cells but not cancer cells from DOX toxicity. Results of studies in a rat orthotopic breast cancer model indicated that SFN enhanced the efficacy of DOX in regression of tumor growth, and that the DOX dosage required to treat the tumor could be reduced when SFN was administered concomitantly. Additionally, SFN enhanced mitochondrial respiration in the hearts of DOX-treated rats and reduced cardiac oxidative stress caused by DOX, as evidenced by the inhibition of lipid peroxidation, the activation of NF-E2-related factor 2 (Nrf2) and associated antioxidant enzymes. These studies indicate that SFN not only acts synergistically with DOX in cancer regression, but also protects the heart from DOX toxicity through Nrf2 activation and protection of mitochondrial integrity and functions.

Regulatory roles of glutathione-S-transferases and 4-hydroxynonenal in stress-mediated signaling and toxicity

Glutathione-S-Transferases (GSTs) have primarily been thought to be xenobiotic metabolizing enzymes that protect cells from toxic drugs and environmental electrophiles. However, in last three decades, these enzymes have emerged as the regulators of oxidative stress-induced signaling and toxicity. 4-Hydroxy-trans 2-nonenal (HNE) an end-product of lipid peroxidation, has been shown to be a major determinant of oxidative stress-induced signaling and toxicity. HNE is involved in signaling pathways, including apoptosis, proliferation, modulation of gene expression, activation of transcription factors/repressors, cell cycle arrest, and differentiation. In this article, available evidence for a major role of GSTs in the regulation of HNE-mediated cell signaling processes through modulation of the intracellular levels of HNE is discussed.

Antioxidants and HNE in redox homeostasis

Under physiological conditions, cells are in a stable state known as redox homeostasis, which is maintained by the balance between continuous ROS/RNS generation and several mechanisms involved in antioxidant activity. ROS overproduction results in alterations in the redox homeostasis that promote oxidative damage to major components of the cell, including the biomembrane phospholipids. Lipid peroxidation subsequently generates a diverse set of products, including α,β-unsaturated aldehydes. Of these products, 4-hydroxy-2-nonenal (HNE) is the most studied aldehyde on the basis of its involvement in cellular physiology and pathology. This review summarizes the current knowledge in the field of HNE generation, metabolism, and detoxification, as well as its interactions with various cellular macromolecules (protein, phospholipid, and nucleic acid). The formation of HNE-protein adducts enables HNE to participate in multi-step regulation of cellular metabolic pathways that include signaling and transcription of antioxidant enzymes, pro-inflammatory factors, and anti-apoptotic proteins. The most widely described roles for HNE in the signaling pathways are associated with its activation of kinases, as well as transcription factors that are responsible for redox homeostasis (Ref-1, Nrf2, p53, NFκB, and Hsf1). Depending on its level, HNE exerts harmful or protective effects associated with the induction of antioxidant defense mechanisms. These effects make HNE a key player in maintaining redox homeostasis, as well as producing imbalances in this system that participate in aging and the development of pathological conditions.

Genotoxicity of lipid oxidation compounds

Lipid peroxidation, the oxidative degradation of membrane lipids by reactive oxygen species generates a large variety of breakdown products such as alkanes, aldehydes, ketones, alcohols, furans and others. Due to their reactivity aldehydes (alkanals, 2-alkenals, 2,4-alkadienals, 4-hydroxyalkenals) received a lot of attention, in particular because they can diffuse from the site of formation and interact with proteins and nucleic acids thus acting as second toxic messengers. The major aldehydic peroxidation product of membrane lipids is 4-hydroxynonenal (HNE). Since HNE and other 4-hydroxyalkenals are strong alkylating agents they have therefore been considered to be the biologically most important peroxidation products. Although initially research focused on the toxicological potential of these compounds it is now well known that they play also a crucial role in cell signaling under physiological and pathophysiological conditions. Thus, it is obvious that the biological effects will be determined by the intracellular concentrations which can trigger adaptation, DNA damage and cell death. This review will not cover all these aspects but will concentrate on the genotoxic properties of selected lipid oxidation products important in the context of pathophysiological developments together with a chapter on epigenetic modifications.

Astrocytic Expression of GSTA4 Is Associated to Dopaminergic Neuroprotection in a Rat 6-OHDA Model of Parkinson's Disease

Idiopathic Parkinson’s disease (PD) is a complex disease caused by multiple, mainly unknown, genetic and environmental factors. The Ventral root avulsion 1 (Vra1) locus on rat chromosome 8 includes the Glutathione S-transferase alpha 4 (Gsta4) gene and has been identified in crosses between Dark Agouti (DA) and Piebald Virol Glaxo (PVG) rat strains as being associated to neurodegeneration after nerve and brain injury. The Gsta4 protein clears lipid peroxidation by-products, a process suggested to being implicated in PD. We therefore investigated whether PVG alleles in Vra1 are neuroprotective in a toxin-induced model of PD and if this effect is coupled to Gsta4. We performed unilateral 6-hydroxydopamine (6-OHDA) partial lesions in the striatum and compared the extent of neurodegeration in parental (DA) and congenic (DA.VRA1) rats. At 8 weeks after 6-OHDA lesion, DA.VRA1 rats displayed a higher density of remaining dopaminergic fibers in the dorsolateral striatum compared to DA rats (44% vs. 23%, p < 0.01), indicating that Vra1 alleles derived from the PVG strain protect dopaminergic neurons from 6-OHDA toxicity. Gsta4 gene expression levels in the striatum and midbrain were higher in DA.VRA1 congenic rats compared to DA at 2 days post-lesion (p < 0.05). The GSTA4 protein co-localized with astrocytic marker GFAP, but not with neuronal marker NeuN or microglial marker IBA1, suggesting astrocyte-specific expression. This is the first report on Vra1 protective effects on dopaminergic neurodegeneration and encourages further studies on Gsta4 in relation to PD susceptibility.

Redox Imbalance and Viral Infections in Neurodegenerative Diseases

Reactive oxygen species (ROS) are essential molecules for many physiological functions and act as second messengers in a large variety of tissues. An imbalance in the production and elimination of ROS is associated with human diseases including neurodegenerative disorders. In the last years the notion that neurodegenerative diseases are accompanied by chronic viral infections, which may result in an increase of neurodegenerative diseases progression, emerged. It is known in literature that enhanced viral infection risk, observed during neurodegeneration, is partly due to the increase of ROS accumulation in brain cells. However, the molecular mechanisms of viral infection, occurring during the progression of neurodegeneration, remain unclear. In this review, we discuss the recent knowledge regarding the role of influenza, herpes simplex virus type-1, and retroviruses infection in ROS/RNS-mediated Parkinson's disease (PD), Alzheimer's disease (AD), and amyotrophic lateral sclerosis (ALS).

Hormetic and regulatory effects of lipid peroxidation mediators in pancreatic beta cells

Nutrient sensing mechanisms of carbohydrates, amino acids and lipids operate distinct pathways that are essential for the adaptation to varying metabolic conditions. The role of nutrient-induced biosynthesis of hormones is paramount for attaining metabolic homeostasis in the organism. Nutrient overload attenuate key metabolic cellular functions and interfere with hormonal-regulated inter- and intra-organ communication, which may ultimately lead to metabolic derangements. Hyperglycemia and high levels of saturated free fatty acids induce excessive production of oxygen free radicals in tissues and cells. This phenomenon, which is accentuated in both type-1 and type-2 diabetic patients, has been associated with the development of impaired glucose tolerance and the etiology of peripheral complications. However, low levels of the same free radicals also induce hormetic responses that protect cells against deleterious effects of the same radicals. Of interest is the role of hydroxyl radicals in initiating peroxidation of polyunsaturated fatty acids (PUFA) and generation of α,β-unsaturated reactive 4-hydroxyalkenals that avidly form covalent adducts with nucleophilic moieties in proteins, phospholipids and nucleic acids. Numerous studies have linked the lipid peroxidation product 4-hydroxy-2E-nonenal (4-HNE) to different pathological and cytotoxic processes. Similarly, two other members of the family, 4-hydroxyl-2E-hexenal (4-HHE) and 4-hydroxy-2E,6Z-dodecadienal (4-HDDE), have also been identified as potential cytotoxic agents. It has been suggested that 4-HNE-induced modifications in macromolecules in cells may alter their cellular functions and modify signaling properties. Yet, it has also been acknowledged that these bioactive aldehydes also function as signaling molecules that directly modify cell functions in a hormetic fashion to enable cells adapt to various stressful stimuli. Recent studies have shown that 4-HNE and 4-HDDE, which activate peroxisome proliferator-activated receptor δ (PPARδ) in vascular endothelial cells and insulin secreting beta cells, promote such adaptive responses to ameliorate detrimental effects of high glucose and diabetes-like conditions. In addition, due to the electrophilic nature of these reactive aldehydes they form covalent adducts with electronegative moieties in proteins, phosphatidylethanolamine and nucleotides. Normally these non-enzymatic modifications are maintained below the cytotoxic range due to efficient cellular neutralization processes of 4-hydroxyalkenals. The major neutralizing enzymes include fatty aldehyde dehydrogenase (FALDH), aldose reductase (AR) and alcohol dehydrogenase (ADH), which transform the aldehyde to the corresponding carboxylic acid or alcohols, respectively, or by biding to the thiol group in glutathione (GSH) by the action of glutathione-S-transferase (GST). This review describes the hormetic and cytotoxic roles of oxygen free radicals and 4-hydroxyalkenals in beta cells exposed to nutritional challenges and the cellular mechanisms they employ to maintain their level at functional range below the cytotoxic threshold.

Lipids and Oxidative Stress Associated with Ethanol-Induced Neurological Damage

The excessive intake of alcohol is a serious public health problem, especially given the severe damage provoked by chronic or prenatal exposure to alcohol that affects many physiological processes, such as memory, motor function, and cognitive abilities. This damage is related to the ethanol oxidation in the brain. The metabolism of ethanol to acetaldehyde and then to acetate is associated with the production of reactive oxygen species that accentuate the oxidative state of cells. This metabolism of ethanol can induce the oxidation of the fatty acids in phospholipids, and the bioactive aldehydes produced are known to be associated with neurotoxicity and neurodegeneration. As such, here we will review the role of lipids in the neuronal damage induced by ethanol-related oxidative stress and the role that lipids play in the related compensatory or defense mechanisms.

Sympathetic Nervous System Control of Carbon Tetrachloride-Induced Oxidative Stress in Liver through α-Adrenergic Signaling

In addition to being the primary organ involved in redox cycling, the liver is one of the most highly innervated tissues in mammals. The interaction between hepatocytes and sympathetic, parasympathetic, and peptidergic nerve fibers through a variety of neurotransmitters and signaling pathways is recognized as being important in the regulation of hepatocyte function, liver regeneration, and hepatic fibrosis. However, less is known regarding the role of the sympathetic nervous system (SNS) in modulating the hepatic response to oxidative stress. Our aim was to investigate the role of the SNS in healthy and oxidatively stressed liver parenchyma. Mice treated with 6-hydroxydopamine hydrobromide were used to realize chemical sympathectomy. Carbon tetrachloride (CCl₄) injection was used to induce oxidative liver injury. Sympathectomized animals were protected from CCl₄ induced hepatic lipid peroxidation-mediated cytotoxicity and genotoxicity as assessed by 4-hydroxy-2-nonenal levels, morphological features of cell damage, and DNA oxidative damage. Furthermore, sympathectomy modulated hepatic inflammatory response induced by CCl₄-mediated lipid peroxidation. CCl₄ induced lipid peroxidation and hepatotoxicity were suppressed by administration of an α-adrenergic antagonist. We conclude that the SNS provides a permissive microenvironment for hepatic oxidative stress indicating the possibility that targeting the hepatic α-adrenergic signaling could be a viable strategy for improving outcomes in patients with acute hepatic injury.

Increased Expression of Aldehyde Dehydrogenase 2 Reduces Renal Cell Apoptosis During Ischemia/Reperfusion Injury After Hypothermic Machine Perfusion

Hypothermic machine perfusion (MP) can reduce graft's injury after kidney transplantation; however, the mechanism has not been elucidated. In the past decade, many studies showed that aldehyde dehydrogenase 2 (ALDH2) is a protease which can inhibit cell apoptosis. Therefore, this study aims to explore whether ALDH2 takes part in reducing organ damage after MP. Eighteen healthy male New Zealand rabbits (12 weeks old, weight 3.0 ± 0.3 kg) were randomly divided into three groups: normal group, MP group, and cold storage (CS) group (n = 6). The left kidney of rabbits underwent warm ischemia for 35 min through clamping the left renal pedicle and then reperfusion for 1 h. Left kidneys were preserved by MP or CS (4°C for 4 h) in vivo followed by the right nephrectomy and 24-h reperfusion, and then the specimens and blood were collected. Finally, concentration of urine creatinine (Cr), blood urea nitrogen (BUN), and 4-HNE were tested. Renal apoptosis was detected by TUNEL staining, and the expression of ALDH2, cleaved-caspase 3, bcl-2/ bax, MAPK in renal tissue was detected by immunohistochemistry or Western blot; 24 h after surgery, the concentration of Cr in MP group was 355 ± 71μmol/L, in CS group was 511 ± 44 μmol/L (P < 0.05), while the BUN was 15.02 ± 2.34 mmol/L in MP group, 22.64 ± 3.58 mmol/L in CS group (P < 0.05). The rate of apoptosis and expression of cleaved caspase-3, p-P38, p-ERK, and p-JNK in MP group was significantly lower than that in CS group (P < 0.05), while expression of ALDH2 and bcl-2/bax in MP group was significantly higher than that in CS group (P < 0.05); expression of cleaved caspase-3 in both MP and CS group significantly increased as compared with that in normal group (P < 0.05). In conclusion, increased expression of ALDH2 can reduce the renal cell apoptosis through inhibiting MAPK pathway during ischemia/reperfusion injury (IRI) after hypothermic MP.

Resveratrol alleviates diabetes-induced testicular dysfunction by inhibiting oxidative stress and c-Jun N-terminal kinase signaling in rats

Diabetes adversely affects reproductive functions in humans and animals. The present study investigated the effects of Resveratrol on diabetes-induced alterations in oxidative stress, c-Jun N-terminal kinase (JNK) signaling and apoptosis in the testis. Adult male Wistar rats (13-15 weeks; n=6/group) were segregated into 1) normal control, 2) Resveratrol-treated (5mg/kg; ip; given during last 3 weeks), 3) Streptozotocin-induced diabetic and, 4) Resveratrol-treated diabetic groups, and euthanized on day 42 after the confirmation of diabetes. Resveratrol did not normalize blood glucose levels in diabetic rats. Resveratrol supplementation recovered diabetes-induced decreases in reproductive organ weights, sperm count and motility, intra-testicular levels of superoxide dismutase, catalase, and glutathione peroxidase and an increase in 4-hydroxynonenal activities (P<0.05). Resveratrol also recovered diabetes-induced increases in JNK signaling pathway proteins, namely, ASK1 (apoptosis signal-regulating kinase 1), JNKs (46 and 54 kDa isoforms) and p-JNK to normal control levels (P<0.05). Interestingly, the expression of a down-stream target of ASK1, MKK4 (mitogen-activated protein kinase kinase 4) and its phosphorylated form (p-MKK4) did not change in experimental groups. Resveratrol inhibited diabetes-induced increases in AP-1 (activator protein-1) components, c-Jun and ATF2 (activating transcription factor 2), but not their phosphorylated forms, to normal control levels (P<0.05). Further, Resveratrol inhibited diabetes-induced increase in cleaved-caspase-3 to normal control levels. In conclusion, Resveratrol alleviates diabetes-induced apoptosis in testis by modulating oxidative stress, JNK signaling pathway and caspase-3 activities, but not by inhibiting hyperglycemia, in rats. These results suggest that Resveratrol supplementation may be a useful strategy to treat diabetes-induced testicular dysfunction.

Sulforaphane protects the heart from doxorubicin-induced toxicity

Cardiotoxicity is one of the major side effects encountered during cancer chemotherapy with doxorubicin (DOX) and other anthracyclines. Previous studies have shown that oxidative stress caused by DOX is one of the primary mechanisms for its toxic effects on the heart. Since the redox-sensitive transcription factor, Nrf2, plays a major role in protecting cells from the toxic metabolites generated during oxidative stress, we examined the effects of the phytochemical sulforaphane (SFN), a potent Nrf2-activating agent, on DOX-induced cardiotoxicity. These studies were carried out both in vitro and in vivo using rat H9c2 cardiomyoblast cells and wild type 129/sv mice, and involved SFN pretreatment followed by SFN administration during DOX exposure. SFN treatment protected H9c2 cells from DOX cytotoxicity and also resulted in restored cardiac function and a significant reduction in DOX-induced cardiomyopathy and mortality in mice. Specificity of SFN induction of Nrf2 and protection of H9c2 cells was demonstrated in Nrf2 knockdown experiments. Cardiac accumulation of 4-hydroxynonenal (4-HNE) protein adducts, due to lipid peroxidation following DOX-induced oxidative stress, was significantly attenuated by SFN treatment. The respiratory function of cardiac mitochondria isolated from mice exposed to DOX alone was repressed, while SFN treatment with DOX significantly elevated mitochondrial respiratory complex activities. Co-administration of SFN reversed the DOX-associated reduction in nuclear Nrf2 binding activity and restored cardiac expression of Nrf2-regulated genes at both the RNA and protein levels. Together, our results demonstrate for the first time that the Nrf2 inducer, SFN, has the potential to provide protection against DOX-mediated cardiotoxicity.

Effects of Local Heart Irradiation in a Glutathione S-Transferase Alpha 4-Null Mouse Model

Glutathione S-transferase alpha 4 (GSTA4-4) is one of the enzymes responsible for the removal of 4-hydroxynonenal (4-HNE), an electrophilic product of lipid peroxidation in cellular membranes during oxidative stress. 4-HNE is a direct activator of nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a transcription factor with many target genes encoding antioxidant and anti-electrophile enzymes. We have previously shown that Gsta4-null mice on a 129/Sv background exhibited increased activity of Nrf2 in the heart. Here we examined the sensitivity of this Gsta4-null mouse model towards cardiac function and structure loss due to local heart irradiation. Male Gsta4-null and wild-type mice were exposed to a single X-ray dose of 18 Gy to the heart. Six months after irradiation, immunohistochemical staining for respiratory complexes 2 and 5 indicated that radiation exposure had caused most pronounced alterations in mitochondrial morphology in Gsta4-null mice. On the other hand, wild-type mice showed a decline in cardiac function and an increase in plasma levels of troponin-I, while no such changes were observed in Gsta4-null mice. Radiation-induced Nrf2-target gene expression only in Gsta4-null mice. In conclusion, although loss of GSTA4-4 led to enhanced susceptibility of cardiac mitochondria to radiation-induced loss of morphology, cardiac function was preserved in Gsta4-null mice. We propose that this protection against cardiac function loss may occur, at least in part, by upregulation of the Nrf2 pathway.

Overview on major lipid peroxidation bioactive factor 4-hydroxynonenal as pluripotent growth-regulating factor

The reactive aldehyde 4-hydroxynonenal (HNE) is major bioactive marker of lipid peroxidation generated under oxidative stress from polyunsaturated fatty acids. Biomedical significance of HNE was first revealed in pathogenesis of various degenerative and malignant diseases. Thus, HNE was considered for decades only as cytotoxic molecule, "second toxic messenger of free radicals" responsible for numerous undesirable consequences of oxidative stress. However, the increase of knowledge on physiology of redox signaling revealed also desirable, physiological roles of HNE, especially in the field of cellular signaling pathways regulating proliferation, differentiation, and apoptosis. These pluripotent effects of HNE can be explained by its concentration-dependent interactions with the cytokine networks and complex cellular antioxidant systems also showing cell and tissue specificities. Therefore, this paper gives a comprehensive, yet short overview on HNE as pluripotent growth-regulating factor.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

ATP-binding cassette transporter Abcg2 lineage contributes to the cardiac vasculature after oxidative stress

Due to their specialized location, stem and progenitor cells are often exposed to oxidative stress. Although ATP-binding cassette transporter subfamily G member 2 (Abcg2)-expressing cells have been implicated in cardiac protective mechanisms involving oxidative stress, there remains a lack of understanding regarding the behavior of cardiac Abcg2-expressing cells when exposed to ROS. The aim of the present study was to characterize the response of the cardiac Abcg2 lineage to oxidative stress. In vitro analysis demonstrated that the antioxidant program regulated by Abcg2 is dependent on a functional transporter. Delivery of paraquat dichloride (PQ), a systemic oxidative stress-inducing agent, to mice confirmed that Abcg2 provides a survival benefit. When exposed to PQ, reporter mice showed an increase in the Abcg2 lineage. Transcriptional and immunohistochemical analysis of Abcg2 lineage-positive cells revealed an enhanced vascular commitment after stress. Finally, preconditioning with PQ demonstrated a reduction in scar size and an increase in angiogenesis after permanent left coronary artery ligation. In conclusion, the data suggest that Abcg2 plays a cytoprotective role in response to in vivo oxidative stress. The contribution of the Abcg2 lineage to the vasculature in the heart is increased after PQ delivery.