1,721,018 research outputs found
Oxidative Stress, Antioxidant Defenses, and the Liver
No full textOxidative stress is an unavoidable consequence of life in an oxygenrich
atmosphere. Reactive oxygen species (ROS) and reactive
nitrogen species (RNS) are generated as by-products of aerobic
metabolism and are critical intermediates in the normal physiology
and pathophysiology of hepatocytes. To cope with ROS and RNS,
cells have developed antioxidant defenses in order to maintain the
balance between production and detoxification processes. ROS are
important in the creation of oxidative stimuli required for normal
physiologic homeostasis of hepatocytes, but when the equilibrium
between ROS generation and the antioxidant defense of the cell is
disrupted, the consequence is the generation of an oxidative stress
condition. In this chapter we will describe the main cellular source
of free radicals, the damages generated by ROS accumulation, and
all the principal enzymatic and non-enzymatic antioxidant defenses
Oxidative Stress, Antioxidant Defenses, and the Liver.
No full textProvides a comprehensive look at all aspects of oxidative stress in the liver from basic science principles to cell damage and response
Beyond the critical basic science and pathophysiology of liver disorders, most of the chapters focus on specific diseases and cancer, making this unique and essential reading for both research and clinical hepatologists
Examines the current state of free radicals’ impact on hepatic disorder
Blockade of Base Excision Repair: Inhibition of Small Lesions Results in Big Consequences to Cancer Cells
No full textTranscription, Processing, and Decay of Mitochondrial RNA in Health and Disease
Full text linkAlthough the large majority of mitochondrial proteins are nuclear encoded, for their correct functioning mitochondria require the expression of 13 proteins, two rRNA, and 22 tRNA codified by mitochondrial DNA (mtDNA). Once transcribed, mitochondrial RNA (mtRNA) is processed, mito-ribosomes are assembled, and mtDNA-encoded proteins belonging to the respiratory chain are synthesized. These processes require the coordinated spatio-temporal action of several enzymes, and many different factors are involved in the regulation and control of protein synthesis and in the stability and turnover of mitochondrial RNA. In this review, we describe the essential steps of mitochondrial RNA synthesis, maturation, and degradation, the factors controlling these processes, and how the alteration of these processes is associated with human pathologies
The importance of redox state in liver damage.
No full textOxidative stress is a major pathogenetic event occurring in several liver disorders ranging from metabolic to proliferative ones, and is a major cause of liver damage due to Ischemia/Reperfusion (I/R) during liver transplantation. The main sources of ROS are represented by mitochondria and cytocrome P450 enzymes in the hepatocyte, by Kupffer cells and by neutrophils. Cells are provided with efficient molecular strategies to strictly control the intracellular ROS level and to maintain the balance between oxidant and antioxidant molecules. A cellular oxidative stress condition is determined by an imbalance between the generation of ROS and the antioxidant defense capacity of the cell and can affect major cellular components including lipids, proteins and DNA. Proteins are very important signposts of cellular redox status and through their structure/function modulation, ROS can also influence gene expression profile by affecting intracellular signal transduction pathways. While several enzymatic (such as superoxide dismutase, catalase, glutathione peroxidase) and non enzymatic (such as 4-hydroxynonenal, decrease of glutathione, vitamin E, vitamin C, malondialdehyde) markers of chronic oxidative stress in liver are well known, early protein targets of oxidative injury are yet not well defined. Identification of these markers will enable early detection of liver diseases and will allow monitoring the degree of liver damage, the response to pharmacological therapies and the development of new therapeutic approaches. In the new era of molecular medicine, new proteomics methodologies promise to establish a relationship between pathological hallmarks of disease and protein structural and functional abnormalities in liver disease, thus allowing a better understanding and a more rational therapy on these disorders
DNA Base Excision Repair Therapeutics:Summary of Targets with a focus on APE1
No full textThis chapter focuses on the components of the base excision repair (BER) pathway, the types of lesions that BER repairs, and the proteins involved in the repair process. Because BER repairs the damage caused by many anticancer agents and many BER proteins are expressed abnormally in cancers, compensatory upregulation of certain BER proteins have been implicated in contributing to chemo- and radio-resistance. It is well known that abnormal DNA damage signaling, deficiencies in DNA repair, and compensatory upregulation of DNA repair proteins are early events in tumorigenesis. Targeting key repair proteins that a tumor relies on can abolish one of the tumor’s survival advantages. Four inhibitors of BER proteins are in various stages of preclinical and clinical development: inhibitors of AP endonuclease 1 (APE1), flap endonuclease (FEN1), polymerase β, and PARP (poly-ADP ribose polymerase). A number of PARP inhibitors are already in clinical trials, and their success supports the value of pursuing other BER inhibitors as anticancer treatments
Combining RNAi and in vivo confocal microscopy analysis of the photoconvertible fluorescent protein Dendra2 to study a DNA repair protein
No full textClinical approaches for tumor treatment often rely on combination therapy where a DNA damaging agent is used in combination with a DNA repair protein inhibitor. For this reason, great efforts have been made during the last decade to identify inhibitors of DNA repair proteins or, alternatively, small molecules that specifically alter protein stability or trafficking. Unfortunately, when studying these drug candidates, classical biochemical approaches are prone to artifacts. The apurinic/apyrimidinic endonuclease (APE1) protein is an essential component of the base excision repair (BER) pathway that is responsible for repairing DNA damage caused by oxidative and alkylating agents. In this work, we combined conditional gene expression knockdown of APE1 protein by RNA interference (RNAi) technology with re-expression of an ectopic recombinant form of APE1 fused with the photoconvertible fluorescent protein (PCFP) Dendra2. Dendra2 did not alter the subcellular localization or endonuclease activity of APE1. We calculated APE1 half-life and compared these results with the classical biochemical approach, which is based on cycloheximide (CHX) treatment. In conclusion, we combined RNAi and in vivo confocal microscopy to study a DNA repair protein demonstrating the feasibility and the advantage of this approach for the study of the cellular dynamic of a DNA repair protein
Mitochondrial translocation of APE1 relies on the MIA pathway
Full text linkAPE1 is a multifunctional protein with a fundamental role in repairing nuclear and mitochondrial DNA lesions caused by oxidative and alkylating agents. Unfortunately, comprehensions of the mechanisms regulating APE1 intracellular trafficking are still fragmentary and contrasting. Recent data demonstrate that APE1 interacts with the mitochondrial import and assembly protein Mia40 suggesting the involvement of a redox-assisted mechanism, dependent on the disulfide transfer system, to be responsible of APE1 trafficking into the mitochondria. The MIA pathway is an import machinery that uses a redox system for cysteine enriched proteins to drive them in this compartment. It is composed by two main proteins: Mia40 is the oxidoreductase that catalyzes the formation of the disulfide bonds in the substrate, while ALR reoxidizes Mia40 after the import. In this study, we demonstrated that: (i) APE1 and Mia40 interact through disulfide bond formation; and (ii) Mia40 expression levels directly affect APE1's mitochondrial translocation and, consequently, play a role in the maintenance of mitochondrial DNA integrity. In summary, our data strongly support the hypothesis of a redox-assisted mechanism, dependent on Mia40, in controlling APE1 translocation into the mitochondrial inner membrane space and thus highlight the role of this protein transport pathway in the maintenance of mitochondrial DNA stability and cell survival
Alterations in the redox state and liver damage: Hints from the EASL Basic School of Hepatology
No full textSummary
The importance of a correct balance between oxidative and reductive events has been shown to have a paramount effect on cell function for quite a long time. However, in spite of this body of rapidly growing evidence, the implication of the alteration of the redox state in human disease has been so far much less appreciated. Liver diseases make no exception. Although not fully comprehensive, this article reports what discussed during an EASL Basic School held in 2012 in Trieste, Italy, where the effect of the alteration of the redox state was addressed in different experimental and human models. This translational approach resulted in further stressing the concept that this topic should be expanded in the future not only to better understand how oxidative stress may be linked to a liver damage but also, perhaps more important, how this may be the target for better, more focused treatments. In parallel, understanding how alteration of the redox balance may be associated with liver damage may help define sensitive and ideally early biomarkers of the disorder.
Abbreviations: ROS, reactive oxygen species, RNS, reactive nitrogen species, SOD, superoxide dismutase, ALI, acute liver injuries, CLD, chronic liver diseases, HCC, hepatocarcinoma, HBV, hepatitis B virus, HCV, hepatitis C virus, NAFLD, non-alcoholic fatty liver disease, MDA, malondialdehyde, 4-HNE, 4-hydroxynonenal, APE1/Ref-1, apurinic apyrimidinic endonuclease/redox effector factor 1, TNF, tumor necrosis factor, NOS2, nitric oxide synthase 2, ETC, electron transport chain, I/R, ischemia/reperfusion, FA, fatty acids, NASH, non-alcoholic steatohepatitis, ASH, alcoholic steatohepatitis, 8OHdG, 8-hydrossyguanosine, HIF-1 α, hypoxia-inducible factor 1α, PHD, prolyl-hydroxylases, NF-κB, nuclear factor-κB, GSH, reduced glutathione, GSSG, oxidized glutathione, CVD, cardiovascular disease, ER, endoplasmic reticulum, ERS, endoplasmic reticulum stress, HH, hereditary hemochromatosis, MPO, myeloperoxidase, HLPP, Human Liver Proteome Project, 2-DE, two-dimensional electrophoresis, MS, mass spectrometry, LC, liquid chromatography
Keywords: Liver disease, Oxidative stress, Redox proteomics, Inflammatio
Isolation of mitochondria is necessary for precise quantification of mitochondrial DNA damage in human carcinoma samples.
Full text linkAddress correspondence to Carlo Vascotto, Department of Medical and Biological Sciences, University of Udine, Udine, 33100, Italy. E-mail: [email protected]
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