Featured Article: Accelerated decline of physical strength in peroxiredoxin-3 knockout mice

Mapping Novel Frataxin Mitochondrial Networks Through Protein- Protein Interactions

Friedreich's Ataxia (FRDA) is a neuromuscular degenerative disorder caused by trinucleotide expansions in the first intron of the frataxin (FXN) gene, resulting in insufficient levels of functional FNX protein. Deficits in FXN involve mitochondrial disruptions including iron-sulfur cluster synthesis and impaired energetics. These studies were to identify unique protein-protein interactions with FXN to better understand its function and design therapeutics. Two complementary approaches were employed, BioID and Co-IP, to identify protein interactions with FXN at the direct binding, indirect binding, and non-proximal levels. Forty-one novel protein interactions were identified by BioID and IP techniques. The FXN protein landscape was further analyzed incorporating both interaction type and functional pathways using a maximum path of 6 proteins with a potential direct interaction between FXN and NFS1. Probing the intersection between FXN-protein landscape and biological pathways associated with FRDA, we identified 41 proteins of interest. Peroxiredoxin 3 (Prdx3) was chosen for further analysis because of its role in mitochondrial oxidative injury. Our data has demonstrated the strengths of employing complementary methods to identify a unique interactome for FXN. Our data provides new insights into FXN function and regulation, a potential direct interaction between FXN and NFS1, and pathway interactions between FXN and Prdx3.

Developmental expression of peroxiredoxin gene family in early embryonic development of Xenopus tropicalis

Peroxidase genes (Prdx) encode a family of antioxidant proteins, which can protect cells from oxidative damage by reducing various cellular peroxides. This study investigated the spatiotemporal expression patterns of gene members in this family during the early development of Xenopus tropicalis. Real-time quantitative PCR showed that all members of this gene family have a distinct temporal expression pattern during the early development of X. tropicalis embryos. Additionally, whole mount in situ hybridization revealed that individual prdx genes display differential expression patterns, with overlapping expression in lymphatic vessels, pronephros, proximal tubule, and branchial arches. This study provides a basis for further study of the function of the prdx gene family.

From workout to molecular switches: How does skeletal muscle produce, sense, and transduce subcellular redox signals?

Skeletal muscle is crucial for maintaining human health and overall quality of life. Acute exercise introduces a multifaceted intracellular stress, with numerous post-translational modifications believed to underpin the health benefits of sustained exercise training. Reactive oxygen species (ROS) are posited to serve as second messengers, triggering cytoprotective adaptations such as the upregulation of enzymatic scavenger systems. However, a significant knowledge gap exists between the generation of oxidants in muscle and the exact mechanisms driving muscle adaptations. This review delves into the current research on subcellular redox biochemistry and its role in the physiological adaptations to exercise. We propose that the subcellular regulation of specific redox modifications is key to ensuring specificity in the intracellular response.

Regulation of peroxiredoxin-3 gene expression under basal and hyperglycemic conditions: Key roles for transcription factors Sp1, CREB and NF-κB

Peroxiredoxin-3 (Prx-3), a thioredoxin-dependent peroxidase located exclusively in the mitochondrial matrix, catalyses peroxides/peroxinitrites. Altered levels of Prx-3 is associated with diabetic cardiomyopathy (DCM). However, molecular mechanisms of Prx-3 gene regulation remain partially understood. We undertook a systemic analysis of the Prx-3 gene to identify the key motifs and transcriptional regulatory molecules. Transfection of promoter-reporter constructs in the cultured cells identified -191/+20 bp domain as the core promoter region. Stringent in silico analysis of this core promoter revealed putative binding sites for specificity protein 1 (Sp1), cAMP response element-binding protein (CREB) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Interestingly, while co-transfection of the -191/+20 bp construct with Sp1/CREB plasmid diminished Prx3 promoter-reporter activity, mRNA and protein levels, co-transfection with NF-κB expression plasmid augmented the same. Consistently, inhibition of Sp1/CREB/NF-κB expression reversed the promoter-reporter activity, mRNA and protein levels of Prx-3, thereby confirming their regulatory effects. ChIP assays provided evidence for interactions of Sp1/CREB/NF-κB with the Prx-3 promoter. H9c2 cells treated with high glucose as well as streptozotocin (STZ)-treated diabetic rats showed time-dependent reduction in promoter activity, endogenous transcript and protein levels of Prx-3. Augmentation of Sp1/CREB protein levels and their strong binding with Prx-3 promoter are responsible for diminished Prx-3 levels under hyperglycemia. The activation/increase in the NF-κB expression under hyperglycemia was not sufficient to restore the reduction of endogenous Prx-3 levels owing to its weak binding affinity. Taken together, this study elucidates the previously unknown roles of Sp1/CREB/NF-κB in regulating Prx-3 gene expression under hyperglycemic condition.

A novel biallelic variant further delineates PRDX3-related autosomal recessive cerebellar ataxia

Cerebellar ataxias (CAs) comprise a rare group of neurological disorders characterized by extensive phenotypic and genetic heterogeneity. In the last several years, our understanding of the CA etiology has increased significantly and resulted in the discoveries of numerous ataxia-associated genes. Herein, we describe a single affected individual from a consanguineous family segregating a recessive neurodevelopmental disorder. The proband showed features such as global developmental delay, cerebellar atrophy, hypotonia, speech issues, dystonia, and profound hearing impairment. Whole-exome sequencing and Sanger sequencing revealed a biallelic nonsense variant (c.496A > T; p.Lys166*) in the exon 5 of the PRDX3 gene that segregated perfectly within the family. This is the third report that associates the PRDX3 gene variant with cerebellar ataxia. In addition, associated hearing impairment further delineates the PRDX3 associated gene phenotypes.

Scavenging mitochondrial hydrogen peroxide by peroxiredoxin 3 overexpression attenuates contractile dysfunction and muscle atrophy in a murine model of accelerated sarcopenia

Age-related muscle atrophy and weakness, or sarcopenia, are significant contributors to compromised health and quality of life in the elderly. While the mechanisms driving this pathology are not fully defined, reactive oxygen species, neuromuscular junction (NMJ) disruption, and loss of innervation are important risk factors. The goal of this study is to determine the impact of mitochondrial hydrogen peroxide on neurogenic atrophy and contractile dysfunction. Mice with muscle-specific overexpression of the mitochondrial H₂ O₂  scavenger peroxiredoxin3 (mPRDX3) were crossed to Sod1KO mice, an established mouse model of sarcopenia, to determine whether reduced mitochondrial H₂ O₂ can prevent or delay the redox-dependent sarcopenia. Basal rates of H₂ O₂  generation were elevated in isolated muscle mitochondria from Sod1KO, but normalized by mPRDX3 overexpression. The mPRDX3 overexpression prevented the declines in maximum mitochondrial oxygen consumption rate and calcium retention capacity in Sod1KO. Muscle atrophy in Sod1KO was mitigated by ~20% by mPRDX3 overexpression, which was associated with an increase in myofiber cross-sectional area. With direct muscle stimulation, maximum isometric specific force was reduced by ~20% in Sod1KO mice, and mPRDX3 overexpression preserved specific force at wild-type levels. The force deficit with nerve stimulation was exacerbated in Sod1KO compared to direct muscle stimulation, suggesting NMJ disruption in Sod1KO. Notably, this defect was not resolved by overexpression of mPRDX3. Our findings demonstrate that muscle-specific PRDX3 overexpression reduces mitochondrial H₂ O₂  generation, improves mitochondrial function, and mitigates loss of muscle quantity and quality, despite persisting NMJ impairment in a murine model of redox-dependent sarcopenia.

Overexpression of Peroxiredoxin 3 in Cartilage Reduces the Severity of Age‐Related Osteoarthritis But Not Surgically Induced Osteoarthritis in Mice

Objective

The study objective was to determine whether overexpression of the mitochondrial antioxidant peroxidase, peroxiredoxin 3 (Prx3), reduces the severity of osteoarthritis (OA) in mice.

Methods

Age‐related OA (age 18 and 24 months) and OA induced by destabilization of the medial meniscus (DMM at age 6 months) were assessed in male mice that overexpress a human Prdx3 transgene encoding the Prx3 protein. Lox‐stop‐lox‐Prdx3 (iPrdx3) mice were crossed with aggrecan‐Cre^ERT2 mice to produce iPrdx3AgCre^ERT2 or with Col2Cre to produce iPrdx3Col2Cre mice. Germline transgenics (Prdx3Tg) were also evaluated. Prx3 protein level was assessed by immunoblotting and functionally after induction of elevated mitochondrial hydrogen peroxide (H₂O₂) using menadione. Histological sections of stifle joints were scored for cartilage damage (Articular Cartilage Structure score [ACS]), osteophytes, and synovial hyperplasia and were evaluated by histomorphometry.

Results

Overexpression of Prx3 maintained mitochondrial membrane integrity and inhibited p38 phosphorylation in the presence of elevated H₂O₂. ACS scores of 18‐month‐old iPrdx3AgCre^ERT2 mice (mean ± SD, 4.88 ± 5.05) were significantly lower than age‐matched iPrdx3 controls (11.75 ± 6.34, P = 0.002) and trended lower in the 18‐month Prdx3Tg group (P = 0.14), whereas no significant differences between experimental and control groups at 24 months of age or in OA induced by DMM surgery were noted. Osteophyte scores trended lower in the 18‐month‐old Prdx3Tg group (P = 0.09) and at 24 months in the iPrdx3Col2Cre mice (P = 0.05). There were no significant group differences in synovial hyperplasia or histomorphometric measures.

Conclusion

Overexpression of the mitochondrial peroxidase Prx3 reduced the severity of age‐related OA, but not at advanced ages and not in DMM‐induced OA in younger mice.

Cellular senescence or stemness: hypoxia flips the coin

Cellular senescence is a complex physiological state whose main feature is proliferative arrest. Cellular senescence can be considered the reverse of cell immortalization and continuous tumor growth. However, cellular senescence has many physiological functions beyond being a putative tumor suppressive trait. It remains unknown whether low levels of oxygen or hypoxia, which is a feature of every tissue in the organism, modulate cellular senescence, altering its capacity to suppress the limitation of proliferation. It has been observed that the lifespan of mammalian primary cells is increased under low oxygen conditions. Additionally, hypoxia promotes self-renewal and pluripotency maintenance in adult and embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs) and cancer stem cells (CSCs). In this study, we discuss the role of hypoxia facilitating senescence bypass during malignant transformation and acquisition of stemness properties, which all contribute to tumor development and cancer disease aggressiveness.

Specificity of Human Sulfiredoxin for Reductant and Peroxiredoxin Oligomeric State

Human peroxiredoxins (Prx) are a family of antioxidant enzymes involved in a myriad of cellular functions and diseases. During the reaction with peroxides (e.g., H₂O₂), the typical 2-Cys Prxs change oligomeric structure between higher order (do)decamers and disulfide-linked dimers, with the hyperoxidized inactive state (-SO₂H) favoring the multimeric structure of the reduced enzyme. Here, we present a study on the structural requirements for the repair of hyperoxidized 2-Cys Prxs by human sulfiredoxin (Srx) and the relative efficacy of physiological reductants hydrogen sulfide (H₂S) and glutathione (GSH) in this reaction. The crystal structure of the toroidal Prx1-Srx complex shows an extended active site interface. The loss of this interface within engineered Prx2 and Prx3 dimers yielded variants more resistant to hyperoxidation and repair by Srx. Finally, we reveal for the first time Prx isoform-dependent use of and potential cooperation between GSH and H₂S in supporting Srx activity.

NOX4 links metabolic regulation in pancreatic cancer to endoplasmic reticulum redox vulnerability and dependence on PRDX4

There is an urgent need to identify vulnerabilities in pancreatic ductal adenocarcinoma (PDAC). PDAC cells acquire metabolic changes that augment NADPH production and cytosolic redox homeostasis. Here, we show that high NADPH levels drive activity of NADPH oxidase 4 (NOX4) expressed in the endoplasmic reticulum (ER) membrane. NOX4 produces H₂O₂ metabolized by peroxiredoxin 4 (PRDX4) in the ER lumen. Using functional genomics and subsequent in vitro and in vivo validations, we find that PDAC cell lines with high NADPH levels are dependent on PRDX4 for their growth and survival. PRDX4 addiction is associated with increased reactive oxygen species, a DNA-PKcs-governed DNA damage response and radiosensitivity, which can be rescued by depletion of NOX4 or NADPH. Hence, this study has identified NOX4 as a protein that paradoxically converts the reducing power of the cytosol to an ER-specific oxidative stress vulnerability in PDAC that may be therapeutically exploited by targeting PRDX4.

Biallelic loss-of-function variations in PRDX3 cause cerebellar ataxia

Peroxiredoxin 3 (PRDX3) belongs to a superfamily of peroxidases that function as protective antioxidant enzymes. Among the six isoforms (PRDX1-PRDX6), PRDX3 is the only protein exclusively localized to the mitochondria, which are the main source of reactive oxygen species. Excessive levels of reactive oxygen species are harmful to cells, inducing mitochondrial dysfunction, DNA damage, lipid and protein oxidation and ultimately apoptosis. Neuronal cell damage induced by oxidative stress has been associated with numerous neurodegenerative disorders including Alzheimer's and Parkinson's diseases. Leveraging the large aggregation of genomic ataxia datasets from the PREPARE (Preparing for Therapies in Autosomal Recessive Ataxias) network, we identified recessive mutations in PRDX3 as the genetic cause of cerebellar ataxia in five unrelated families, providing further evidence for oxidative stress in the pathogenesis of neurodegeneration. The clinical presentation of individuals with PRDX3 mutations consists of mild-to-moderate progressive cerebellar ataxia with concomitant hyper- and hypokinetic movement disorders, severe early-onset cerebellar atrophy, and in part olivary and brainstem degeneration. Patient fibroblasts showed a lack of PRDX3 protein, resulting in decreased glutathione peroxidase activity and decreased mitochondrial maximal respiratory capacity. Moreover, PRDX3 knockdown in cerebellar medulloblastoma cells resulted in significantly decreased cell viability, increased H2O2 levels and increased susceptibility to apoptosis triggered by reactive oxygen species. Pan-neuronal and pan-glial in vivo models of Drosophila revealed aberrant locomotor phenotypes and reduced survival times upon exposure to oxidative stress. Our findings reveal a central role for mitochondria and the implication of oxidative stress in PRDX3 disease pathogenesis and cerebellar vulnerability and suggest targets for future therapeutic approaches.

Dietary proanthocyanidins alleviated ovarian fibrosis in letrozole-induced polycystic ovary syndrome in rats

This study investigated the effects of proanthocyanidins (PCs) on ovarian fibrosis in letrozole-induced polycystic ovary syndrome (PCOS) in rats. The administration of PCs effectively reduced the body weight (BW) and relative ovarian weight in PCOS rats. ELISA results revealed that PCs significantly reduced the level of serum T, LH, LH/FSH in the PCOS group. In addition, qRT-PCR results revealed that treatment with PCs significantly increased the main antioxidant enzymes (Cat, Sod2, Gpx3, Mgst1, Gsta4, Sod1 and Prdx3) in PCOS rats. Also, the expression analysis of proteins by Western blotting revealed that PCs significantly decreased the level of TGF-βR1, p-Smad3, p-Smad2 and Smad4 and reversed the downregulation of Smad7 in PCOS rats. The study suggested that PCs improved ovarian fibrosis in PCOS rats by regulating the serum hormone level, inhibiting oxidative stress and suppressing the activation of the TGF-β1/Smads signaling pathway. PRACTICAL APPLICATIONS: Currently, plant extracts are being widely used to treat female reproductive and metabolic disorders. Particularly, proanthocyanidins (PCs), the well-known natural polyphenolic compounds, which are a significant source of antioxidants present in many colored fruits, are consumed as fruits as well as a dietary supplement to prevent many disorders. Recent pharmacological studies have reported that PCs have many health beneficial properties, such as antioxidant activity, improving cholesterol homeostasis, blood lipid regulatory properties, microcirculation improvement effect, antitumor activity and anti-aging activity. Despite these properties of PCs, the antifibrosis effect of PCs has not been studied to date. The main purpose of this study was to research the role and the mechanisms of PCs in ovarian fibrosis in PCOS rats.

Physical Activity and Redox Balance in the Elderly: Signal Transduction Mechanisms

Reactive Oxygen Species (ROS) are molecules naturally produced by cells. If their levels are too high, the cellular antioxidant machinery intervenes to bring back their quantity to physiological conditions. Since aging often induces malfunctioning in this machinery, ROS are considered an effective cause of age-associated diseases. Exercise stimulates ROS production on one side, and the antioxidant systems on the other side. The effects of exercise on oxidative stress markers have been shown in blood, vascular tissue, brain, cardiac and skeletal muscle, both in young and aged people. However, the intensity and volume of exercise and the individual subject characteristics are important to envisage future strategies to adequately personalize the balance of the oxidant/antioxidant environment. Here, we reviewed the literature that deals with the effects of physical activity on redox balance in young and aged people, with insights into the molecular mechanisms involved. Although many molecular pathways are involved, we are still far from a comprehensive view of the mechanisms that stand behind the effects of physical activity during aging. Although we believe that future precision medicine will be able to transform exercise administration from wellness to targeted prevention, as yet we admit that the topic is still in its infancy.

MicroRNA-383 promotes reactive oxygen species-induced autophagy via downregulating peroxiredoxin 3 in human glioma U87 cells

Peroxiredoxin 3 (PRDX3) is an abundant and effective enzyme, which aids in the removal of H₂O₂ in the mitochondria, thereby inhibiting cell autophagy. PRDX3 is a target protein of microRNA (miRNA/miR)-383, the overexpression of which has been found to inhibit the growth of glioma cells. We hypothesized that miR-383 serves an antitumor role by inhibiting oxidative stress during tumor growth. In the current study, human glioma U87 cells were transfected with pre-/short hairpin (sh)-PRDX3 vectors and miR-383 mimics/inhibitors. Apoptosis and reactive oxygen species (ROS) production were detected using flow cytometry. Autophagy was examined using acridine orange staining, and the expression of cytoplasmic autophagy-related proteins [autophagy-related protein 9 (ATG9), Ras-related protein Rab-1A (Rab1) and p62] was determined using western blot analysis. The interaction between miR-383 and PRDX3 was assessed using a dual-luciferase assay. The results indicated that both sh-PRDX3 and miR-383 mimics promoted apoptosis and increased the level of mitochondrial ROS, whilst acridine orange staining revealed that sh-PRDX3 promoted autophagy in U87 cells compared with that in the control cells. The detection of autophagic proteins indicated that sh-PRDX3 and miR-383 mimics increased the protein expression level of ATG9 and RAB1, and inhibited that of p62. On the contrary, the effect of miR-383 mimics was opposite to that of pre-PRDX3 in U87 cells. Reverse transcription-quantitative PCR and western blot assays revealed that miR-383 was negatively associated with PRDX3 in U87 cells. miR-383 was indicated to interact with PRDX3, as demonstrated using a dual-luciferase assay. In conclusion, the present study demonstrated that miR-383 induced cell apoptosis and mitochondrial ROS production by downregulating PRDX3 in U87 cells, thereby promoting oxidative stress-induced autophagy.

Riding the tiger - physiological and pathological effects of superoxide and hydrogen peroxide generated in the mitochondrial matrix

Elevated mitochondrial matrix superoxide and/or hydrogen peroxide concentrations drive a wide range of physiological responses and pathologies. Concentrations of superoxide and hydrogen peroxide in the mitochondrial matrix are set mainly by rates of production, the activities of superoxide dismutase-2 (SOD2) and peroxiredoxin-3 (PRDX3), and by diffusion of hydrogen peroxide to the cytosol. These considerations can be used to generate criteria for assessing whether changes in matrix superoxide or hydrogen peroxide are both necessary and sufficient to drive redox signaling and pathology: is a phenotype affected by suppressing superoxide and hydrogen peroxide production; by manipulating the levels of SOD2, PRDX3 or mitochondria-targeted catalase; and by adding mitochondria-targeted SOD/catalase mimetics or mitochondria-targeted antioxidants? Is the pathology associated with variants in SOD2 and PRDX3 genes? Filtering the large literature on mitochondrial redox signaling using these criteria highlights considerable evidence that mitochondrial superoxide and hydrogen peroxide drive physiological responses involved in cellular stress management, including apoptosis, autophagy, propagation of endoplasmic reticulum stress, cellular senescence, HIF1α signaling, and immune responses. They also affect cell proliferation, migration, differentiation, and the cell cycle. Filtering the huge literature on pathologies highlights strong experimental evidence that 30-40 pathologies may be driven by mitochondrial matrix superoxide or hydrogen peroxide. These can be grouped into overlapping and interacting categories: metabolic, cardiovascular, inflammatory, and neurological diseases; cancer; ischemia/reperfusion injury; aging and its diseases; external insults, and genetic diseases. Understanding the involvement of mitochondrial matrix superoxide and hydrogen peroxide concentrations in these diseases can facilitate the rational development of appropriate therapies.

Knockout Mouse Models for Peroxiredoxins

Peroxiredoxins (PRDXs) are members of a highly conserved peroxidase family and maintain intracellular reactive oxygen species (ROS) homeostasis. The family members are expressed in most organisms and involved in various biological processes, such as cellular protection against ROS, inflammation, carcinogenesis, atherosclerosis, heart diseases, and metabolism. In mammals, six PRDX members have been identified and are subdivided into three subfamilies: typical 2-Cys (PRDX1, PRDX2, PRDX3, and PRDX4), atypical 2-Cys (PRDX5), and 1-Cys (PRDX6) subfamilies. Knockout mouse models of PRDXs have been developed to investigate their in vivo roles. This review presents an overview of the knockout mouse models of PRDXs with emphases on the biological and physiological changes of these model mice.

Peroxiredoxin2 Deficiency Aggravates Aging-Induced Insulin Resistance and Declines Muscle Strength

This study examined the role of peroxiredoxin2 (Prx2) in aging-induced insulin resistance and reduction in skeletal muscle function in young (2-month-old) and old (24-month-old) Prx2 knockout (KO) and wild-type mice. Plasma insulin levels increased with aging in Prx2 KO mice but not in wild-type mice. Insulin sensitivity in the whole-body and skeletal muscle as assessed with the hyperinsulinemic-euglycemic clamp was lower in Prx2 KO mice than in wild-type mice in the old group but was not significantly different between the two genotypes in the young group. Insulin-induced activation of intracellular signaling molecules was also suppressed in old Prx2 KO mice compared to their wild-type littermates. Oxidative stress, inflammation, and p53 expression levels in skeletal muscle were higher in Prx2 KO mice than in wild-type mice in the old group but were not different between the two genotypes in the young group. p53 expression was negatively correlated with skeletal muscle insulin sensitivity in old mice. Skeletal muscle mass was similar between the two genotypes but grip strength was reduced in old Prx2 KO mice compared to old wild-type mice. These results suggest that Prx2 plays a protective role in aging-induced insulin resistance and declines in muscle strength by suppressing oxidative stress.

Catalytic and Signaling Role of Peroxiredoxins in Carcinogenesis

Cancer cells experience strong oxidative stress caused by disorders in cell metabolism and action of external factors. For survival, cancer cells have developed a highly efficient system of antioxidant defense, some of the most important elements of which are peroxiredoxins (Prxs). Prxs are an evolutionarily ancient family of selenium-independent peroxidases that reduce a wide range of organic and inorganic hydroperoxides in the cell and the extracellular space. In addition, some Prxs exhibit chaperone and phospholipase activities. Prxs play an important role in the maintenance of the cell redox homeostasis; they prevent oxidation and aggregation of regulatory proteins, thereby affecting many cell signaling pathways. Prxs are involved in the regulation of cell growth, differentiation, and apoptosis. Due to their versatility and wide representation in all tissues and organs, Prxs participate in the development/suppression of many pathological conditions, among which cancer occupies a special place. This review focuses on the role of Prxs in the development of various forms of cancer. Understanding molecular mechanisms of Prx involvement in these processes will allow to develop new approaches to the prevention and treatment of cancer.

Radioprotective Role of Peroxiredoxin 6

Peroxiredoxin 6 (Prdx6) is a member of an evolutionary ancient family of peroxidase enzymes with diverse functions in the cell. Prdx6 is an important enzymatic antioxidant. It reduces a wide range of peroxide substrates in the cell, thus playing a leading role in the maintenance of the redox homeostasis in mammalian cells. Beside peroxidase activity, Prdx6 has been shown to possess an activity of phospholipase A2, an enzyme playing an important role in membrane phospholipid metabolism. Moreover, Prdx6 takes part in intercellular and intracellular signal transduction due to its peroxidase and phospholipase activity, thus facilitating the initiation of regenerative processes in the cell, suppression of apoptosis, and activation of cell proliferation. Being an effective and important antioxidant enzyme, Prdx6 plays an essential role in neutralizing oxidative stress caused by various factors, including action of ionizing radiation. Endogenous Prdx6 has been shown to possess a significant radioprotective potential in cellular and animal models. Moreover, intravenous infusion of recombinant Prdx6 to animals before irradiation at lethal or sublethal doses has shown its high radioprotective effect. Exogenous Prdx6 effectively alleviates the severeness of radiation lesions, providing normalization of the functional state of radiosensitive organs and tissues, and leads to a significant elevation of the survival rate of animals. Prdx6 can be considered as a potent and promising radioprotective agent for reducing the pathological effect of ionizing radiation on mammalian organisms. The radioprotective properties and mechanisms of radioprotective action of Prdx6 are discussed in the current review.

The Multifaceted Impact of Peroxiredoxins on Aging and Disease

SIGNIFICANCE

Peroxiredoxins (Prxs), a family of thiol-associated peroxidases, are purported to play a major role in sensing and managing hydrogen peroxide concentrations and transducing peroxide-derived signals. Recent Advances: Prxs can act as detoxifying factors and impart effects to cells that can be either sparing or suicidal. Advances have been made to address the qualitative changes in Prx function in response to quantitative changes in the signal level and to understand how Prx activity could be affected by their own substrates. Here we rationalize the basis for both positive and negative effects on signaling pathways and cell physiology, summarizing data from model organisms, including invertebrates.

CRITICAL ISSUES

Resolving the relationship between the promiscuous behavior of reactive oxygen species and the specificity of Prxs toward different targets in redox-sensitive signaling pathways is a key area of research. Attempts to understand Prx function and underlying mechanisms were conducted in vitro or in vivo under nonphysiological conditions, leaving the physiological relevance yet to be defined. Other issues: Why despite the high degree of homology and similarities in subcellular and tissue distribution between Prxs do they display differential effects on signaling? How is the specificity of post-translational protein modifications determined? Other than chaperone-like activity, how do hyperoxidized Prxs function?

FUTURE DIRECTIONS

Genetic models with mutated catalytic and resolving cysteines should be further exploited to dissect the functional significance of individual Prxs in their different states together with their alternative reducing partners. Such an analysis may then be extended to help identify Prx-specific targets.

Happily (n)ever after: Aging in the context of oxidative stress, proteostasis loss and cellular senescence

Aging is a complex phenomenon and its impact is becoming more relevant due to the rising life expectancy and because aging itself is the basis for the development of age-related diseases such as cancer, neurodegenerative diseases and type 2 diabetes. Recent years of scientific research have brought up different theories that attempt to explain the aging process. So far, there is no single theory that fully explains all facets of aging. The damage accumulation theory is one of the most accepted theories due to the large body of evidence found over the years. Damage accumulation is thought to be driven, among others, by oxidative stress. This condition results in an excess attack of oxidants on biomolecules, which lead to damage accumulation over time and contribute to the functional involution of cells, tissues and organisms. If oxidative stress persists, cellular senescence is a likely outcome and an important hallmark of aging. Therefore, it becomes crucial to understand how senescent cells function and how they contribute to the aging process. This review will cover cellular senescence features related to the protein pool such as morphological and molecular hallmarks, how oxidative stress promotes protein modifications, how senescent cells cope with them by proteostasis mechanisms, including antioxidant enzymes and proteolytic systems. We will also highlight the nutritional status of senescent cells and aged organisms (including human clinical studies) by exploring trace elements and micronutrients and on their importance to develop strategies that might increase both, life and health span and postpone aging onset.

The Relevance of Mammalian Peroxiredoxins to the Gametogenesis, Embryogenesis, and Pregnancy Outcomes

Peroxiredoxin (PRX) defines a family that provides antioxidant defense in different cell types by removing reactive oxygen species (ROS) through conserved active cysteines, with the support of other types of antioxidants such as thioredoxin, glutaredoxin, and glutathione peroxidase. By regulation of intracellular ROS levels, the mammalian PRXs influence a variety of reproductive processes including gamete maturation, fertilization, and embryo development. Experimental mice lacking PRXs developed normally, but some showed accelerated decrease in fertility with aging, suggesting that deficiency of PRXs did not have lethal consequences for reproduction. The aim of this review is to summarize the role of mammalian PRXs in the reproductive performance.