Reduction in glutathione peroxidase 4 increases life span through increased sensitivity to apoptosis

Involvement of ferroptosis in eribulin-induced cytotoxicity in ovarian clear cell carcinoma

Ovarian clear cell carcinoma (OCCC) is a unique clinicopathological subtype of epithelial ovarian cancer that is resistant to standard chemotherapy. Eribulin, a microtubule dynamics inhibitor of halichondrin class, has unique effects in the cancer microenvironment such as induction of epithelization and reduction in metastatic potential in breast cancer cells; however, nothing is known about the effect of eribulin and the detailed mechanisms in OCCC. This study aimed to investigate the involvement of ferroptosis and its mechanism in the antitumor activity of eribulin in OCCC cells and a mouse xenograft model. We found that eribulin-induced cell death was reduced by ferroptosis inhibitors; deferoxamine, an iron chelator and ferrostatin-1, a lipid peroxidation inhibitor. Eribulin increased the levels of intracellular iron, reactive oxygen species (ROS), and lipid peroxides, and increased the mitochondrial membrane potential. Eribulin downregulated the expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), the mitochondrial enzyme dihydroorotate dehydrogenase (DHODH), and superoxide dismutase (SOD) activity. The combination of eribulin and ML210, a glutathione peroxidase 4-inhibiting ferroptosis inducer, had a synergistic effect on ferroptosis. Taken together, our findings show firstly that eribulin triggers ferroptosis in OCCC and this effect occurs via the suppression of the Nrf2-HO-1 signaling pathway, SOD activity and the promotion of lipid peroxidation. These findings suggest that eribulin-induced ferroptosis is associated with its anti-tumor effect and also could be a potential therapeutic target in OCCC.

Astaxanthin Added during Post-Warm Recovery Mitigated Oxidative Stress in Bovine Vitrified Oocytes and Improved Quality of Resulting Blastocysts

Various antioxidants are tested to improve the viability and development of cryopreserved oocytes, due to their known positive health effects. The aim of this study was to find whether astaxanthin (AX), a xanthophyll carotenoid, could mitigate deteriorations that occurred during the vitrification/warming process in bovine oocytes. Astaxanthin (2.5 µM) was added to the maturation medium during the post-warm recovery period of vitrified oocytes for 3 h. Afterward, the oocytes were fertilized in vitro using frozen bull semen and presumptive zygotes were cultured in the B2 Menezo medium in a co-culture with BRL-1 cells at 38.5 °C and 5% CO2 until the blastocyst stage. AX addition significantly reduced ROS formation, lipid peroxidation, and lysosomal activity, while increasing mitochondrial activity in vitrified oocytes. Although the effect of AX on embryo development was not observed, it stimulated cell proliferation in the blastocysts derived from vitrified oocytes and improved their quality by upregulation or downregulation of some genes related to apoptosis (BCL2, CAS9), oxidative stress (GPX4, CDX2), and development (GJB5) compared to the vitrified group without AX. Therefore, the antioxidant properties of astaxanthin even during short exposure to bovine vitrified/warmed oocytes resulted in improved blastocyst quality comparable to those from fresh oocytes.

MANIPULATING MITOCHONDRIAL REACTIVE OXYGEN SPECIES ALTERS SURVIVAL IN UNEXPECTED WAYS IN A DROSOPHILA MODEL OF NEURODEGENERATION

Reactive oxygen species (ROS) are associated with aging and neurodegeneration, but the significance of this association remains obscure. Here, using a Drosophila model of age-related neurodegeneration, we probe this relationship in the pathologically relevant tissue, the brain, by quantifying three specific mitochondrial ROS and manipulating these redox species pharmacologically. Our goal is to ask whether pathology-associated changes in redox state are detrimental for survival, whether they may be beneficial responses, or whether they are simply covariates of pathology that do not alter viability. We find, surprisingly, that increasing mitochondrial H2O2 correlates with improved survival. We also find evidence that drugs that alter the mitochondrial glutathione redox potential modulate survival primarily through the compensatory effects they induce rather than through their direct effects on the final mitochondrial glutathione redox potential per se. We also find that the response to treatment with a redox-altering drug varies dramatically depending on the age at which the drug is administered, the duration of the treatment, and the genotype of the individual receiving the drug. These data have important implications for the design and interpretation of studies investigating the effect of redox state on health and disease as well as on efforts to modify the redox state to achieve therapeutic goals.

Tumor-specific GPX4 degradation enhances ferroptosis-initiated antitumor immune response in mouse models of pancreatic cancer

Lipid peroxidation-dependent ferroptosis has become an emerging strategy for tumor therapy. However, current strategies not only selectively induce ferroptosis in malignant cells but also trigger ferroptosis in immune cells simultaneously, which can compromise anti-tumor immunity. Here, we used In-Cell Western assays combined with an unbiased drug screening to identify the compound N6F11 as a ferroptosis inducer that triggered the degradation of glutathione peroxidase 4 (GPX4), a key ferroptosis repressor, specifically in cancer cells. N6F11 did not cause the degradation of GPX4 in immune cells, including dendritic, T, natural killer, and neutrophil cells. Mechanistically, N6F11 bound to the RING domain of E3 ubiquitin ligase tripartite motif containing 25 (TRIM25) in cancer cells to trigger TRIM25-mediated K48-linked ubiquitination of GPX4, resulting in its proteasomal degradation. Functionally, N6F11 treatment caused ferroptotic cancer cell death that initiated HMGB1-dependent antitumor immunity mediated by CD8+ T cells. N6F11 also sensitized immune checkpoint blockade that targeted CD274/PD-L1 in advanced cancer models, including genetically engineered mouse models of pancreatic cancer driven by KRAS and TP53 mutations. These findings may establish a safe and efficient strategy to boost ferroptosis-driven antitumor immunity.

GPX4 in cell death, autophagy, and disease

Selenoprotein GPX4 (glutathione peroxidase 4), originally known as PHGPX (phospholipid hydroperoxide glutathione peroxidase), is the main oxidoreductase in the use of glutathione as a reducing agent in scavenging lipid peroxidation products. There are three GPX4 isoforms: cytosolic (cGPX4), mitochondrial (mGPX4), and nuclear (nGPX4), with distinct spatiotemporal expression patterns during embryonic development and adult life. In addition to inducing the main phenotype of ferroptosis, the loss of GPX4 can in some cells trigger apoptosis, necroptosis, pyroptosis, or parthanatos, which mediates or accelerates developmental defects, tissue damage, and sterile inflammation. The interaction of GPX4 with the autophagic degradation pathway further modulates cell fate in response to oxidative stress. Impaired GPX4 function is implicated in tumorigenesis, neurodegeneration, infertility, inflammation, immune disorders, and ischemia-reperfusion injury. Additionally, the R152H mutation in GPX4 can promote the development of Sedaghatian-type spinal metaphyseal dysplasia, a rare and fatal disease in newborns. Here, we discuss the roles of classical GPX4 functions as well as emerging GPX4-regulated processes in cell death, autophagy, and disease.Abbreviations: AA: arachidonic acid; cGPX4: cytosolic GPX4; CMA: chaperone-mediated autophagy; DAMPs: danger/damage-associated molecular patterns; mGPX4: mitochondrial GPX4; nGPX4: nuclear GPX4; GSDMD-N: N-terminal fragment of GSDMD; I/R: ischemia-reperfusion; PLOOH: phospholipid hydroperoxide; PUFAs: polyunsaturated fatty acids; RCD: regulated cell death; ROS: reactive oxygen species; Se: selenium; SSMD: Sedaghatian-type spondylometaphyseal dysplasia; UPS: ubiquitin-proteasome system.

Targeting GPX4 in human cancer: Implications of ferroptosis induction for tackling cancer resilience

Cancer metabolic alterations have been emphasized to protect cancer cells from cell death. The metabolic reprogramming toward a mesenchymal state makes cancer cells resistant to therapy but vulnerable to ferroptosis induction. Ferroptosis is a new form of regulated cell death based on the iron-dependent accumulation of excessive lipid peroxidation. Glutathione peroxidase 4 (GPX4) is the core regulator of ferroptosis by detoxifying cellular lipid peroxidation using glutathione as a cofactor. GPX4 synthesis requires selenium incorporation into the selenoprotein through isopentenylation and selenocysteine tRNA maturation. GPX4 synthesis and expression can be regulated by multiple levels of its transcription, translation, posttranslational modifications, and epigenetic modifications. Targeting GPX4 in cancer may be a promising strategy for effectively inducing ferroptosis and killing therapy-resistant cancer. Several pharmacological therapeutics targeting GPX4 have been developed constantly to activate ferroptosis induction in cancer. The potential therapeutic index of GPX4 inhibitors remains to be tested with thorough examinations of their safety and adverse effects in vivo and clinical trials. Many papers have been published continuously in recent years, requiring state-of-the-art updates in targeting GPX4 in cancer. Herein, we summarize targeting the GPX4 pathway in human cancer, which leads to implications of ferroptosis induction for tackling cancer resilience.

Haemato-biochemical, mutagenic, and histopathological changes in Oreochromis niloticus exposed to BTX

The study of the DNA damage response in erythrocytes after exposure to volatile organic compounds (VOCs) can present evidence for its potential effect as genotoxic- biomarkers for environmental pollution. Although VOCs are dangerous pollutants, still little is known about hemotoxic, cytotoxic, and genotoxic effects of such pollutants on fish. We optimized an assay method for apoptosis and DNA damage in erythrocytes of adult tilapia fish after 15 days exposure to benzene (0.762 ng/L), toluene (26.614 ng/L), and xylene (89.403 ng/L). The highest level of apoptosis and DNA damage were recorded in benzene-exposed fish, as was the highest level of histopathological alterations in gills, liver, and kidney. The imbalance of the antioxidants profile explained the stress-case reported in exposed fish. These results suggest that hemotoxic, cytotoxic, genotoxic, and tissue damage were recorded after exposure to BTX in Oreochromis niloticus.

The analyse of the antioxidant effect of natural peloidotherapy in aging process

Medical research has developed remarkably in recent years, including the involvement of the glutathione peroxidase (GPx) family of enzymes in the course of human aging, with numerous clinical studies published in the literature reporting this particular fact. Thus, mud therapy and its effect on biological aging have been represented in papers that have been published to date. Papers published in the literature analyzing GPx vari-ation during sapropelic mud therapy suggest the beneficial effect of this family of en-zymes in diseases with an important inflammatory component, mainly monitored in patients with osteoarthritis. This study investigated the effects of sapropelic mud treat-ment on GPx values in patients receiving treatment with sapropelic mud at the Balneal and Rehabilitation Sanatorium of Techirghiol, Romania. We included 52 patients, split into two groups, who received treatment with cold mud baths and warm mud baths. Values close to statistical significance were found in patients who received treatment with cold mud baths in terms of mean GPx values at the four-time points studied. Fur-ther studies evaluating GPx in patients receiving sapropelic mud treatment are needed.

The Potential Role of Regulated Cell Death in Dry Eye Diseases and Ocular Surface Dysfunction

The research on new treatments for dry eye diseases (DED) has exponentially grown over the past decades. The increased prevalence of dry eye conditions, particularly in the younger population, has received much attention. Therefore, it is of utmost importance to identify novel therapeutical targets. Regulated cell death (RCD) is an essential process to control the biological homeostasis of tissues and organisms. The identification of different mechanisms of RCD stimulated the research on their involvement in different human pathologies. Whereas apoptosis has been widely studied in DED and included in the DED vicious cycle, the role of RCD still needs to be completely elucidated. In this review, we will explore the potential roles of different types of RCD in DED and ocular surface dysfunction. Starting from the evidence of oxidative stress and inflammation in dry eye pathology, we will analyse the potential therapeutic applications of the following principal RCD mechanisms: ferroptosis, necroptosis, and pyroptosis.

New perspectives on ferroptosis and its role in hepatocellular carcinoma

ABSTRACT

For a long time, the morbidity and mortality rates of hepatocellular carcinoma (HCC) have remained high. Since the concept of ferroptosis was introduced in 2012, researchers' perspectives have shifted toward finding novel ferroptosis-related treatment strategies, especially for tumors that are resistant to apoptosis. In recent years, there have been an increasing number of studies on ferroptosis, and these studies have found that ferroptosis has great potential and promise for cancer treatment. Ferroptosis is a kind of regulated cell death (RCD); unlike apoptosis, ferroptosis is an iron-dependent type of RCD driven by lipid peroxidation. The whole process of ferroptosis mainly revolves around three pathways (system xc-/ glutathione peroxidase 4 [GPX4]), lipid peroxidation, and iron metabolism), which are also regulated by various metabolic factors. This review will attempt to analyze the relationship between the system xc-/GPX4 pathway, lipid peroxidation, iron metabolism, and ferroptosis from three aspects (triggering, execution, and regulation), and the regulatory factors for ferroptosis will be summarized. In this review, we will also illustrate the relationship between ferroptosis and tumors as well as its application in tumors from the perspective of HCC. Finally, we will summarize the current limitations and needs and provide perspectives related to the focus of development in the future.

Ferroptosis: A Novel Therapeutic Direction of Spinal Cord Injury

An injury to the spinal cord results in a crucial central nervous system event that further causes irreversible impairment or loss of motor, autonomic, and sensory functions. A progressive pathophysiological cascade following spinal cord injury (SCI) includes ischemia/reperfusion injury, oxidative stress, proapoptotic signaling, peripheral inflammatory cell infiltration, and glutamate-mediated excitotoxicity, and regulated cell death. These complex pathological and physiological changes continue to cause cell injury over the long-term and severely limit the efficacy of clinical treatment strategies in restoring the injured nervous system. Ferroptosis is a nonapoptotic, iron-regulated kind of cell death that has recently been discovered. It is distinguished by iron overload-induced toxic lipid peroxidation associated with mitochondrial morphological changes during the cell death process. For example, after SCI, iron overload activates the reactive oxygen species generation, dysregulation of glutathione/glutathione peroxidase 4 (GSH/GPX4) metabolism, and accumulation of lipid peroxides, which cause lipid membrane deterioration and ferroptosis. Conversely, knockout or differential expression of key genes and application of lipid peroxidation inhibitors and iron chelators (e.g., deferoxamine) (e.g., SRS-16-86) can block ferroptosis and promote neuronal repair for functional recovery after SCI. Although the findings of numerous investigations have been confirmed the importance of ferroptosis in several human neurologic sicknesses and its potential in SCI, the mechanism of ferroptosis and its application in SCI has not been elucidated. This review highlights current ferroptosis research and its impact on SCI, as well as the key molecular mechanism of ferroptosis in promoting the recovery from SCI. Understanding ferroptosis' process and function in SCI could provide useful insight into the treatment and avoidance of such a destructive injury.

Heat Shock Proteins and Ferroptosis

Ferroptosis is a new form of regulatory cell death named by Dixon in 2012, which is characterized by the accumulation of lipid peroxides and iron ions. Molecular chaperones are a class of evolutionarily conserved proteins in the cytoplasm. They recognize and bind incompletely folded or assembled proteins to help them fold, transport or prevent their aggregation, but they themselves do not participate in the formation of final products. As the largest number of molecular chaperones, heat shock proteins can be divided into five families: HSP110 (HSPH), HSP90 (HSPC), HSP70 (HSPA), HSP40 (DNAJ) and small heat shock proteins (HSPB). Different heat shock proteins play different roles in promoting or inhibiting ferroptosis in different diseases. It is known that ferroptosis is participated in tumors, nervous system diseases, renal injury and ischemia-reperfusion injury. However, there are few reviews about the relationship of heat shock proteins and ferroptosis. In this study, we systematically summarize the roles of heat shock proteins in the occurrence of ferroptosis, and predict the possible mechanisms of different families of heat shock proteins in the development of ferroptosis.

Cyclophosphamide-induced GPX4 degradation triggers parthanatos by activating AIFM1

Cyclophosphamide is an alkylating agent used to treat a variety of cancers, including leukemia. Here, we show a previously unrecognized role of cyclophosphamide in triggering the protein degradation of glutathione peroxidase 4 (GPX4), a phospholipid hydroperoxidase that protects cells from oxidative damage. Mechanistically, we found that the ubiquitin-proteasome system, but not autophagy, mediates cyclophosphamide-induced degradation of GPX4 in human leukemia cell lines. Surprisingly, cyclophosphamide-induced degradation of GPX4 leads to caspase-independent parthanatos, but not lipid peroxidation-mediated ferroptosis, through the nuclear translocation of apoptosis-inducing factor mitochondria-associated 1 (AIFM1). Consequently, the overexpression of GPX4 or the knockdown of AIFM1 limits the anticancer activity of cyclophosphamide in vitro and in xenograft tumor models. These findings establish a new framework for understanding the central role of GPX4 in blocking oxidative cell death.

The Role of Ferric Nitrilotriacetate in Renal Carcinogenesis and Cell Death: From Animal Models to Clinical Implications

Iron is essential for cellular growth, and various ferroproteins and heme-containing proteins are involved in a myriad of cellular functions, such as DNA synthesis, oxygen transport, and catalytic reactions. As a consequence, iron deficiency causes pleiotropic effects, such as hypochromic microcytic anemia and growth disturbance, while iron overload is also deleterious by oxidative injury. To prevent the generation of iron-mediated reactive oxygen species (ROS), ferritin is synthesized to store excess iron in cells that are consistent with the clinical utility of the serum ferritin concentration to monitor the therapeutic effect of iron-chelation. Among the animal models exploring iron-induced oxidative stress, ferric nitrilotriacetate (Fe-NTA) was shown to initiate hepatic and renal lipid peroxidation and the development of renal cell carcinoma (RCC) after repeated intraperitoneal injections of Fe-NTA. Here, current understanding of Fe-NTA-induced oxidative stress mediated by glutathione-cycle-dependent iron reduction and the molecular mechanisms of renal carcinogenesis are summarized in combination with a summary of the relationship between the pathogenesis of human RCC and iron metabolism. In addition to iron-mediated carcinogenesis, the ferroptosis that is triggered by the iron-dependent accumulation of lipid peroxidation and is implicated in the carcinogenesis is discussed.

Emerging Mechanisms and Disease Implications of Ferroptosis: Potential Applications of Natural Products

Ferroptosis, a newly discovered form of regulatory cell death (RCD), has been demonstrated to be distinct from other types of RCD, such as apoptosis, necroptosis, and autophagy. Ferroptosis is characterized by iron-dependent lipid peroxidation and oxidative perturbation, and is inhibited by iron chelators and lipophilic antioxidants. This process is regulated by specific pathways and is implicated in diverse biological contexts, mainly including iron homeostasis, lipid metabolism, and glutathione metabolism. A large body of evidence suggests that ferroptosis is interrelated with various physiological and pathological processes, including tumor progression (neuro)degenerative diseases, and hepatic and renal failure. There is an urgent need for the discovery of novel effective ferroptosis-modulating compounds, even though some experimental reagents and approved clinical drugs have been well documented to have anti- or pro-ferroptotic properties. This review outlines recent advances in molecular mechanisms of the ferroptotic death process and discusses its multiple roles in diverse pathophysiological contexts. Furthermore, we summarize chemical compounds and natural products, that act as inducers or inhibitors of ferroptosis in the prevention and treatment of various diseases. Herein, it is particularly highlighted that natural products show promising prospects in ferroptosis-associated (adjuvant) therapy with unique advantages of having multiple components, multiple biotargets and slight side effects.

Impact of Selenium on Biomarkers and Clinical Aspects Related to Ageing. A Review

Selenium (Se) is an essential dietary trace element that plays an important role in the prevention of inflammation, cardiovascular diseases, infections, and cancer. Selenoproteins contain selenocysteine in the active center and include, i.a., the enzymes thioredoxin reductases (TXNRD1–3), glutathione peroxidases (GPX1–4 and GPX6) and methionine sulfoxide reductase, involved in immune functions, metabolic homeostasis, and antioxidant defense. Ageing is an inevitable process, which, i.a., involves an imbalance between antioxidative defense and reactive oxygen species (ROS), changes in protein and mitochondrial renewal, telomere attrition, cellular senescence, epigenetic alterations, and stem cell exhaustion. These conditions are associated with mild to moderate inflammation, which always accompanies the process of ageing and age-related diseases. In older individuals, Se, by being a component in protective enzymes, operates by decreasing ROS-mediated inflammation, removing misfolded proteins, decreasing DNA damage, and promoting telomere length. Se-dependent GPX1–4 and TXNRD1–3 directly suppress oxidative stress. Selenoprotein H in the cell nucleus protects DNA, and selenoproteins residing in the endoplasmic reticulum (ER) assist in the removal of misfolded proteins and protection against ER stress. In this review, we highlight the role of adequate Se status for human ageing and prevention of age-related diseases, and further its proposed role in preservation of telomere length in middle-aged and elderly individuals.

Role of Ferroptosis in Lung Diseases

Ferroptosis is a new type of programmed cell death characterized by intracellular iron accumulation and lipid peroxidation that leads to oxidative stress and cell death. The metabolism of iron, lipids, and amino acids and multiple signalling pathways precisely regulate the process of ferroptosis. Emerging evidence has demonstrated that ferroptosis participates in the occurrence and progression of various pathological conditions and diseases, such as infections, neurodegeneration, tissue ischaemia-reperfusion injury and immune diseases. Recent studies have also indicated that ferroptosis plays a critical role in the pathogenesis of acute lung injury, chronic obstructive pulmonary disease, pulmonary fibrosis, pulmonary infection and asthma. Herein, we summarize the latest knowledge on the regulatory mechanism of ferroptosis and its association with iron, lipid and amino acid metabolism as well as several signalling pathways. Furthermore, we review the contribution of ferroptosis to the pathogenesis of lung diseases and discuss ferroptosis as a novel therapeutic target for various lung diseases.

Ferroptosis, radiotherapy, and combination therapeutic strategies

Ferroptosis, an iron-dependent form of regulated cell death driven by peroxidative damages of polyunsaturated-fatty-acid-containing phospholipids in cellular membranes, has recently been revealed to play an important role in radiotherapy-induced cell death and tumor suppression, and to mediate the synergy between radiotherapy and immunotherapy. In this review, we summarize known as well as putative mechanisms underlying the crosstalk between radiotherapy and ferroptosis, discuss the interactions between ferroptosis and other forms of regulated cell death induced by radiotherapy, and explore combination therapeutic strategies targeting ferroptosis in radiotherapy and immunotherapy. This review will provide important frameworks for future investigations of ferroptosis in cancer therapy.

The Role of Non-Coding RNAs in the Neuroprotective Effects of Glutathione

The establishment of antioxidative defense systems might have been mandatory for most living beings with aerobic metabolisms, because oxygen consumption produces adverse byproducts known as reactive oxygen species (ROS). The brain is especially vulnerable to the effect of ROS, since the brain has large amounts of unsaturated fatty acids, which are a target of lipid oxidation, as well as comparably high-energy consumption compared to other organs that results in ROS release from mitochondria. Thus, dysregulation of the synthesis and/or metabolism of antioxidants-particularly glutathione (GSH), which is one of the most important antioxidants in the human body-caused oxidative stress states that resulted in critical diseases, including neurodegenerative diseases in the brain. GSH plays crucial roles not only as an antioxidant but also as an enzyme cofactor, cysteine storage form, the major redox buffer, and a neuromodulator in the central nervous system. The levels of GSH are precisely regulated by uptake systems for GSH precursors as well as GSH biosynthesis and metabolism. The rapid advance of RNA sequencing technologies has contributed to the discovery of numerous non-coding RNAs with a wide range of functions. Recent lines of evidence show that several types of non-coding RNAs, including microRNA, long non-coding RNA and circular RNA, are abundantly expressed in the brain, and their activation or inhibition could contribute to neuroprotection through the regulation of GSH synthesis and/or metabolism. Interestingly, these non-coding RNAs play key roles in gene regulation and growing evidence indicates that non-coding RNAs interact with each other and are co-regulated. In this review, we focus on how the non-coding RNAs modulate the level of GSH and modify the oxidative stress states in the brain.

Beneficial and Detrimental Effects of Reactive Oxygen Species on Lifespan: A Comprehensive Review of Comparative and Experimental Studies

Aging is the greatest risk factor for a multitude of diseases including cardiovascular disease, neurodegeneration and cancer. Despite decades of research dedicated to understanding aging, the mechanisms underlying the aging process remain incompletely understood. The widely-accepted free radical theory of aging (FRTA) proposes that the accumulation of oxidative damage caused by reactive oxygen species (ROS) is one of the primary causes of aging. To define the relationship between ROS and aging, there have been two main approaches: comparative studies that measure outcomes related to ROS across species with different lifespans, and experimental studies that modulate ROS levels within a single species using either a genetic or pharmacologic approach. Comparative studies have shown that levels of ROS and oxidative damage are inversely correlated with lifespan. While these studies in general support the FRTA, this type of experiment can only demonstrate correlation, not causation. Experimental studies involving the manipulation of ROS levels in model organisms have generally shown that interventions that increase ROS tend to decrease lifespan, while interventions that decrease ROS tend to increase lifespan. However, there are also multiple examples in which the opposite is observed: increasing ROS levels results in extended longevity, and decreasing ROS levels results in shortened lifespan. While these studies contradict the predictions of the FRTA, these experiments have been performed in a very limited number of species, all of which have a relatively short lifespan. Overall, the data suggest that the relationship between ROS and lifespan is complex, and that ROS can have both beneficial or detrimental effects on longevity depending on the species and conditions. Accordingly, the relationship between ROS and aging is difficult to generalize across the tree of life.

Broadening horizons: the role of ferroptosis in cancer

The discovery of regulated cell death processes has enabled advances in cancer treatment. In the past decade, ferroptosis, an iron-dependent form of regulated cell death driven by excessive lipid peroxidation, has been implicated in the development and therapeutic responses of various types of tumours. Experimental reagents (such as erastin and RSL3), approved drugs (for example, sorafenib, sulfasalazine, statins and artemisinin), ionizing radiation and cytokines (such as IFNγ and TGFβ1) can induce ferroptosis and suppress tumour growth. However, ferroptotic damage can trigger inflammation-associated immunosuppression in the tumour microenvironment, thus favouring tumour growth. The extent to which ferroptosis affects tumour biology is unclear, although several studies have found important correlations between mutations in cancer-relevant genes (for example, RAS and TP53), in genes encoding proteins involved in stress response pathways (such as NFE2L2 signalling, autophagy and hypoxia) and the epithelial-to-mesenchymal transition, and responses to treatments that activate ferroptosis. Herein, we present the key molecular mechanisms of ferroptosis, describe the crosstalk between ferroptosis and tumour-associated signalling pathways, and discuss the potential applications of ferroptosis in the context of systemic therapy, radiotherapy and immunotherapy.

Healthful aging mediated by inhibition of oxidative stress

The progressive increase in lifespan over the past century carries with it some adversity related to the accompanying burden of debilitating diseases prevalent in the older population. This review focuses on oxidative stress as a major mechanism limiting longevity in general, and healthful aging, in particular. Accordingly, the first goal of this review is to discuss the role of oxidative stress in limiting longevity, and compare healthful aging and its mechanisms in different longevity models. Secondly, we discuss common signaling pathways involved in protection against oxidative stress in aging and in the associated diseases of aging, e.g., neurological, cardiovascular and metabolic diseases, and cancer. Much of the literature has focused on murine models of longevity, which will be discussed first, followed by a comparison with human models of longevity and their relationship to oxidative stress protection. Finally, we discuss the extent to which the different longevity models exhibit the healthful aging features through physiological protective mechanisms related to exercise tolerance and increased β-adrenergic signaling and also protection against diabetes and other metabolic diseases, obesity, cancer, neurological diseases, aging-induced cardiomyopathy, cardiac stress and osteoporosis.

Mitochondrial pathways in human health and aging

Mitochondria are eukaryotic organelles known best for their roles in energy production and metabolism. While often thought of as simply the 'powerhouse of the cell,' these organelles participate in a variety of critical cellular processes including reactive oxygen species (ROS) production, regulation of programmed cell death, modulation of inter- and intracellular nutrient signaling pathways, and maintenance of cellular proteostasis. Disrupted mitochondrial function is a hallmark of eukaryotic aging, and mitochondrial dysfunction has been reported to play a role in many aging-related diseases. While mitochondria are major players in human diseases, significant questions remain regarding their precise mechanistic role. In this review, we detail mechanisms by which mitochondrial dysfunction participate in disease and aging based on findings from model organisms and human genetics studies.

Molecular Mechanisms of Ferroptosis and Its Role in Pulmonary Disease

Ferroptosis is a new mode of cell death that is characterized by the excessive accumulation of iron and lipid peroxides. It has unique morphological changes and disparate biochemical features and plays an intricate role in many pathophysiological processes. A great deal of researches confirms that ferroptosis can be regulated by numerous molecules through different mechanisms, supporting great potentials for novel pharmacological therapeutics. Recently, several studies reveal that ferroptosis is also closely associated with the initiation and development of respiratory disease. Understanding the specific mechanism, the molecular trait of ferroptosis and their relationship with pulmonary disease could provide significant references regarding effective treatment of these obstinate disease.

Progress in Understanding Ferroptosis and Challenges in Its Targeting for Therapeutic Benefit

Ferroptosis is an iron-dependent cell-death modality driven by oxidative phospholipid damage. In contrast to apoptosis, which enables organisms to eliminate targeted cells purposefully at specific times, ferroptosis appears to be a vulnerability of cells that otherwise use high levels of polyunsaturated lipids to their advantage. Cells in this high polyunsaturated lipid state generally have safeguards that mitigate ferroptotic risk. Since its recognition, ferroptosis has been implicated in degenerative diseases in tissues including kidney and brain, and is a targetable vulnerability in multiple cancers-each likely characterized by the high polyunsaturated lipid state with insufficient or overwhelmed ferroptotic safeguards. In this Perspective, we present progress toward defining the essential roles and key mediators of lipid peroxidation and ferroptosis in disease contexts. Moreover, we discuss gaps in our understanding of ferroptosis and list key challenges that have thus far limited the full potential of targeting ferroptosis for improving human health.

Thioredoxin and aging: What have we learned from the survival studies?

Our laboratory has conducted the first systematic survival studies to examine the biological effects of the antioxidant protein thioredoxin (Trx) on aging and age-related pathology. Our studies with C57BL/6 mice overexpressing Trx1 [Tg(act-TRX1)^+/0 and Tg(TXN)^+/0) demonstrated a slight extension in early lifespan compared to wild-type (WT) mice; however, no significant effects were observed in the later part of life. Overexpression of Trx2 in male C57BL/6 mice [Tg(TXN2)^+/0] demonstrated a slightly extended lifespan compared to WT mice. The pathology results from two lines of Trx1 transgenic mice showed a slightly higher incidence of age-related neoplastic diseases compared to WT mice, and a slight increase in the severity of lymphoma, a major neoplastic disease, was observed in Trx2 transgenic mice. Together these studies indicate that Trx overexpression in one compartment of the cell (cytosol or mitochondria alone) has marginal beneficial effects on lifespan. On the other hand, down-regulation of Trx in either the cytosol (Trx1KO) or mitochondria (Trx2KO) showed no significant changes in lifespan compared to WT mice, despite several changes in pathophysiology of these knockout mice. When we examined the synergetic effects of overexpressing Trx1 and Trx2, TXNTg x TXN2Tg mice showed a significantly shorter lifespan with accelerated cancer development compared to WT mice. These results suggest that synergetic effects of Trx overexpression in both the cytosol and mitochondria on aging are deleterious and the development of age-related cancer is accelerated. On the other hand, we have recently found that down-regulation of Trx in both the cytosol and mitochondria in Trx1KO x Trx2KO mice has beneficial effects on aging. The results generated from our lab along with our ongoing study using Trx1KO x Trx2KO mice could elucidate the key pathways (i.e., apoptosis and autophagy) that prevent accumulation of damaged cells and genomic instability leading to reduced cancer formation.

Mouse Models to Disentangle the Hallmarks of Human Aging

Model organisms have provided fundamental evidence that aging can be delayed and longevity extended. These findings gave rise to a new era in aging research aimed at elucidating the pathways and networks controlling this complex biological process. The identification of 9 hallmarks of aging has established a framework to evaluate the relative contribution of each hallmark and the interconnections among them. In this review, we revisit these hallmarks with the information obtained exclusively through the generation of genetically modified mouse models that have a significant impact on the aging process. We discuss within each hallmark those interventions that accelerate aging or that have been successful at increasing lifespan, with the final goal of identifying the most promising antiaging avenues based on the current knowledge provided by in vivo models.

Selenium Deficiency Aggravates Aflatoxin B1-Induced Immunotoxicity in Chick Spleen by Regulating 6 Selenoprotein Genes and Redox/Inflammation/Apoptotic Signaling

BACKGROUND

Selenium (Se) plays a protective role in aflatoxin B1 (AFB1)-induced splenic immunotoxicity in chicks.

OBJECTIVE

This study was designed to reveal the underlying mechanism of Se-mediated protection against AFB1-induced splenic injury in broilers.

METHODS

Four groups of 1-d-old Cobb male broilers (n = 5 cages/diet, 6 chicks/cage) were arranged in a 3-wk 2 × 2 factorial design trial whereby they were fed an Se-deficient, corn- and soy-based diet [base diet (BD), 36 μg Se/kg], BD plus 1.0 mg AFB1/kg, BD plus 0.3 mg Se/kg, or BD plus 1.0 mg AFB1/kg and 0.3 mg Se/kg (as 2-hydroxy-4-methylselenobutanoic acid). Serum and spleen were collected at week 3 to assay for cytokines, histology, redox status, selected inflammation- and apoptosis-related genes and proteins, and the selenogenome.

RESULTS

Dietary AFB1 induced growth retardation and spleen injury, decreasing (P < 0.05) body weight gain, feed intake, feed conversion efficiency, and serum interleukin-1β by 17.8-98.1% and increasing (P < 0.05) the spleen index and serum interleukin-6 by 37.6-113%. It also reduced the splenic lymphocyte number, the white pulp region, and histiocyte proliferation in Se-adequate groups. However, Se deficiency aggravated (P < 0.05) these AFB1-induced alterations by 16.2-103%. Moreover, Se deficiency decreased (P < 0.05) splenic glutathione peroxidase (GPX) activity and glutathione-S transferase and glutathione concentrations by 35.6-89.4% in AFB1-exposed groups. Furthermore, Se deficiency upregulated (P < 0.05) the apoptotic (Caspase 3 and Caspase 9) and antimicrobial (β defensin 1 and 2) genes, but downregulated (P < 0.05) antiapoptotic (B-cell lymphoma 2) and inflammatory (E3 ubiquitin-protein ligase CBL-B) genes at the mRNA and/or protein level in AFB1 supplementation groups. Additionally, Se deficiency downregulated (P < 0.05) GPX3, thioredoxin reductase 1 (TXNRD 1), GPX4, and selenoprotein (SELENO) S, and upregulated (P < 0.05) SELENOT and SELENOU in spleen in AFB1 administered groups.

CONCLUSIONS

Dietary Se deficiency exacerbated AFB1-induced spleen injury in chicks, partially through the regulation of oxidative stress, inflammatory and apoptotic signaling, and 6 selenoproteins.

Selenium Deficiency Is Associated with Pro-longevity Mechanisms

Selenium (Se) is an essential trace element because of its presence in selenoproteins in the form of selenocysteine residue. Both Se deficiency, which compromises selenoprotein functions, and excess Se, which is toxic, have been associated with altered redox homeostasis and adverse health conditions. Surprisingly, we found that, although Se deficiency led to a drastic decline in selenoprotein expression, mice subjected to this dietary regimen for their entire life had normal lifespans. To understand the molecular mechanisms involved, we performed systemic analyses at the level of metabolome, transcriptome, and microRNA profiling. These analyses revealed that Se deficiency reduced amino acid levels, elevated mononucleotides, altered metabolism, and activated signaling pathways linked to longevity-related nutrient sensing. The data show that the metabolic control associated with nutrient sensing coordinately responds to suppressed selenoprotein functions, resulting in normal lifespan under Se deficiency.

The tumor suppressor protein p53 and the ferroptosis network

Ferroptosis is a form of lipid peroxidation-induced cell death that can be regulated in many ways, from altering the activity of antioxidant enzymes to the level of transcription factors. The p53 tumor suppressor is 'the guardian of the genome' that participates in the control of cell survival and division under various stresses. Beyond its effects on apoptosis, autophagy, and cell cycle, p53 also regulates ferroptosis either through a transcriptional or posttranslational mechanism. On one hand, p53 can enhance ferroptosis by inhibiting the expression of SLC7A11 (solute carrier family 7 member 11) or by enhancing that of SAT1 (spermidine/spermine N1-acetyltransferase 1) and GLS2 (glutaminase 2). On the other hand, p53 suppresses ferroptosis through the direct inhibition of DPP4 (dipeptidyl peptidase 4) activity or by the induction of CDKN1A/p21 (cyclin dependent kinase inhibitor 1 A) expression. Here, we review recent discoveries and emerging trends in the study of the ferroptosis network and highlight the context-dependent impact of p53 on ferroptosis and oxidative stress.

The development of the concept of ferroptosis

The term ferroptosis was coined in 2012 to describe an iron-dependent regulated form of cell death caused by the accumulation of lipid-based reactive oxygen species; this type of cell death was found to have molecular characteristics distinct from other forms of regulated cell death. Features of ferroptosis have been observed periodically over the last several decades, but these molecular features were not recognized as evidence of a distinct form of cell death until recently. Here, we describe the history of observations consistent with the current definition of ferroptosis, as well as the advances that contributed to the emergence of the concept of ferroptosis. We also discuss recent implications and applications of manipulations of the ferroptotic death pathway.

Cytoplasmic and Mitochondrial NADPH-Coupled Redox Systems in the Regulation of Aging

The reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) protects against redox stress by providing reducing equivalents to antioxidants such as glutathione and thioredoxin. NADPH levels decline with aging in several tissues, but whether this is a major driving force for the aging process has not been well established. Global or neural overexpression of several cytoplasmic enzymes that synthesize NADPH have been shown to extend lifespan in model organisms such as Drosophila suggesting a positive relationship between cytoplasmic NADPH levels and longevity. Mitochondrial NADPH plays an important role in the protection against redox stress and cell death and mitochondrial NADPH-utilizing thioredoxin reductase 2 levels correlate with species longevity in cells from rodents and primates. Mitochondrial NADPH shuttles allow for some NADPH flux between the cytoplasm and mitochondria. Since a decline of nicotinamide adenine dinucleotide (NAD⁺) is linked with aging and because NADP⁺ is exclusively synthesized from NAD⁺ by cytoplasmic and mitochondrial NAD⁺ kinases, a decline in the cytoplasmic or mitochondrial NADPH pool may also contribute to the aging process. Therefore pro-longevity therapies should aim to maintain the levels of both NAD⁺ and NADPH in aging tissues.

Cause or casualty: The role of mitochondrial DNA in aging and age-associated disease

The mitochondrial genome (mtDNA) represents a tiny fraction of the whole genome, comprising just 16.6 kilobases encoding 37 genes involved in oxidative phosphorylation and the mitochondrial translation machinery. Despite its small size, much interest has developed in recent years regarding the role of mtDNA as a determinant of both aging and age-associated diseases. A number of studies have presented compelling evidence for key roles of mtDNA in age-related pathology, although many are correlative rather than demonstrating cause. In this review we will evaluate the evidence supporting and opposing a role for mtDNA in age-associated functional declines and diseases. We provide an overview of mtDNA biology, damage and repair as well as the influence of mitochondrial haplogroups, epigenetics and maternal inheritance in aging and longevity.

Beneficial and paradoxical roles of selenium at nutritional levels of intake in healthspan and longevity

Accumulation of genome and macromolecule damage is a hallmark of aging, age-associated degeneration, and genome instability syndromes. Although processes of aging are irreversible, they can be modulated by genome maintenance pathways and environmental factors such as diet. Selenium (Se) confers its physiological functions mainly through selenoproteins, but Se compounds and other proteins that incorporate Se nonspecifically also impact optimal health. Bruce Ames proposed that the aging process could be mitigated by a subset of low-hierarchy selenoproteins whose levels are preferentially reduced in response to Se deficiency. Consistent with this notion, results from two selenotranscriptomic studies collectively implicate three low-hierarchy selenoproteins in age or senescence. Experimental evidence generally supports beneficial roles of selenoproteins in the protection against damage accumulation and redox imbalance, but some selenoproteins have also been reported to unexpectedly display harmful functions under sporadic conditions. While longevity and healthspan are usually thought to be projected in parallel, emerging evidence suggests a trade-off between longevity promotion and healthspan deterioration with damage accumulation. We propose that longevity promotion under conditions of Se deficiency may be attributed to 1) stress-response hormesis, an advantageous event of resistance to toxic chemicals at low doses; 2) reduced expression of selenoproteins with paradoxical functions to a lesser extent. In particular, selenoprotein H is an evolutionally conserved nuclear selenoprotein postulated to confer Se functions in redox regulation, genome maintenance, and senescence. This review highlights the need to pinpoint roles of specific selenoproteins and Se compounds in healthspan and lifespan for a better understanding of Se contribution at nutritional levels of intake to healthy aging.

Adaptive homeostasis and the free radical theory of ageing

The Free Radical Theory of Ageing, was first proposed by Denham Harman in the mid-1950's, based largely on work conducted by Rebeca Gerschman and Daniel Gilbert. At its core, the Free Radical Theory of Ageing posits that free radical and related oxidants, from the environment and internal metabolism, cause damage to cellular constituents that, over time, result in an accumulation of structural and functional problems. Several variations on the original concept have been advanced over the past six decades, including the suggestion of a central role for mitochondria-derived reactive species, and the proposal of an age-related decline in the effectiveness of protein, lipid, and DNA repair systems. Such innovations have helped the Free Radical Theory of Aging to achieve widespread popularity. Nevertheless, an ever-growing number of apparent 'exceptions' to the Theory have seriously undermined its acceptance. In part, we suggest, this has resulted from a rather simplistic experimental approach of knocking-out, knocking-down, knocking-in, or overexpressing antioxidant-related genes to determine effects on lifespan. In some cases such experiments have yielded results that appear to support the Free Radical Theory of Aging, but there are just as many published papers that appear to contradict the Theory. We suggest that free radicals and related oxidants are but one subset of stressors with which all life forms must cope over their lifespans. Adaptive Homeostasis is the mechanism by which organisms dynamically expand or contract the homeostatic range of stress defense and repair systems, employing a veritable armory of signal transduction pathways (such as the Keap1-Nrf2 system) to generate a complex profile of inducible and enzymatic protection that best fits the particular need. Viewed as a component of Adaptive Homeostasis, the Free Radical Theory of Aging appears both viable and robust.

Mitochondria and Calcium Regulation as Basis of Neurodegeneration Associated With Aging

Age is the main risk factor for the onset of neurodegenerative diseases. A decline of mitochondrial function has been observed in several age-dependent neurodegenerative diseases and may be a major contributing factor in their progression. Recent findings have shown that mitochondrial fitness is tightly regulated by Ca²⁺ signals, which are altered long before the onset of measurable histopathology hallmarks or cognitive deficits in several neurodegenerative diseases including Alzheimer’s disease (AD), the most frequent cause of dementia. The transfer of Ca²⁺ from the endoplasmic reticulum (ER) to the mitochondria, facilitated by the presence of mitochondria-associated membranes (MAMs), is essential for several physiological mitochondrial functions such as respiration. Ca²⁺ transfer to mitochondria must be finely regulated because excess Ca²⁺ will disturb oxidative phosphorylation (OXPHOS), thereby increasing the generation of reactive oxygen species (ROS) that leads to cellular damage observed in both aging and neurodegenerative diseases. In addition, excess Ca²⁺ and ROS trigger the opening of the mitochondrial transition pore mPTP, leading to loss of mitochondrial function and cell death. mPTP opening probably increases with age and its activity has been associated with several neurodegenerative diseases. As Ca²⁺ seems to be the initiator of the mitochondrial failure that contributes to the synaptic deficit observed during aging and neurodegeneration, in this review, we aim to look at current evidence for mitochondrial dysfunction caused by Ca²⁺ miscommunication in neuronal models of neurodegenerative disorders related to aging, with special emphasis on AD.

GPx4, Lipid Peroxidation, and Cell Death: Discoveries, Rediscoveries, and Open Issues

SIGNIFICANCE

Iron-dependent lipid peroxidation is a complex oxidative process where phospholipid hydroperoxides (PLOOH) are produced in membranes and finally transformed into a series of decomposition products, some of which are endowed with biological activity. It is specifically prevented by glutathione peroxidase 4 (GPx4), the selenoenzyme that reduces PLOOH by glutathione (GSH). PLOOH is both a product and the major initiator of peroxidative chain reactions, as well as an activator of lipoxygenases. α-Tocopherol both specifically breaks peroxidative chain propagation and inhibits lipoxygenases. Thus, GPx4, GSH, and α-tocopherol are integrated in a concerted anti-peroxidant mechanism. Recent Advances: Ferroptosis has been recently identified as a cell death subroutine that is specifically activated by missing GPx4 activity and inhibited by iron chelation or α-tocopherol supplementation. Ferroptosis induction may underlie spontaneous human diseases, such as major neurodegeneration and neuroinflammation, causing an excessive cell death. The basic mechanism of ferroptosis, therefore, fits the features of activation of lipid peroxidation.

CRITICAL ISSUES

Still lacking are convincing proofs that lipoxygenases are involved in ferroptosis. Also, unknown are the molecules eventually killing cells and the mechanisms underlying the drop of the cellular anti-peroxidant capacity.

FUTURE DIRECTIONS

Molecular events and mechanisms of ferroptosis to be unraveled and validated on animal models are GPx4 inactivation, role of GSH concentration, increased iron availability, and membrane structure and composition. This is expected to drive drug discovery that is aimed at halting cell death in degenerative diseases or boosting it in cancer cells. Antioxid. Redox Signal. 29, 61-74.

Hepatoprotective effects of capping protein gelsolin against hyperoxia-induced hepatotoxicity, oxidative stress and DNA damage in neonatal rats

Tissues and organs get exposed to high oxygen (O₂) supply in hyperoxia conditions. The goal of this research was to investigate the protective effect of actin binding protein gelsolin on hyperoxia-induced hepatotoxicity through histopathology and measurement of oxidative stress parameters and DNA damage in a neonatal Wistar albino rats. The pups were randomly separated to four equal groups such as: normoxia control group (NC), normoxia plus gelsolin group (NG, 10 ng/kg bw/day gelsolin), hyperoxia (≥85% O₂) group (HC), hyperoxia plus gelsolin group (HG, ≥85% O₂; 10 ng/kg bw/day gelsolin). Histopathological changes of pups in hyperoxia condition were revealed in the form of severe leukocyte infiltration, vascular congestion, necrosis, vacuolar degeneration, binucleated hepatocytes and hemorrhage in the liver tissue. SOD, CAT, GPx and GST activities decreased and MDA level increased in the hyperoxia-induced group in liver tissue (P < 0.05). Tail DNA%, tail length and moment indicating DNA damage statistically increased in hyperoxia treatment groups when compared to controls. Treatment of rats with hyperoxia plus gelsolin prevented hyperoxia-induced changes in tissue structure, antioxidant enzyme activities and MDA level, mean tail DNA% and length. Based on these findings, gelsolin restored these changing to near normal levels but it does not protect completely in the hyperoxia conditions.

A Reassessment of Genes Modulating Aging in Mice Using Demographic Measurements of the Rate of Aging

Many studies have reported genetic interventions that have an effect on mouse life span; however, it is crucial to discriminate between manipulations of aging and aging-independent causes of life extension. Here, we used the Gompertz equation to determine whether previously reported aging-related mouse genes statistically affect the demographic rate of aging. Of 30 genetic manipulations previously reported to extend life span, for only two we found evidence of retarding demographic aging: Cisd2 and hMTH1. Of 24 genetic manipulations reported to shorten life span and induce premature aging features, we found evidence of five accelerating demographic aging: Casp2, Fn1, IKK-β, JunD, and Stub1. Overall, our reassessment found that only 15% of the genetic manipulations analyzed significantly affected the demographic rate of aging as predicted, suggesting that a relatively small proportion of interventions affecting longevity do so by regulating the rate of aging. By contrast, genetic manipulations affecting longevity tend to impact on aging-independent mortality. Our meta-analysis of multiple mouse longevity studies also reveals substantial variation in the controls used across experiments, suggesting that a short life span of controls is a potential source of bias. Overall, the present work leads to a reassessment of genes affecting the aging process in mice, with broad implications for our understanding of the genetics of mammalian aging and which genes may be more promising targets for drug discovery.

Role/s of 'Antioxidant' Enzymes in Ageing

Reactive oxygen species (ROS), generated externally and during aerobic metabolism, are a potent cause of cell damage. Oxidative damage is a feature of many diseases and ageing, including age-associated diseases, such as diabetes, cancer, cardiovascular and neurodegenerative diseases. Indeed, this association helped lead to the widely expounded 'Free Radical Theory of Aging', proposing that the accumulation of ROS-induced damage is the underlying cause of ageing. In the last decade, it has become apparent that ROS play more complex roles in ageing than simply causing damage. This includes the induction of signalling pathways that protect against/repair cell damage. Cells encode a variety of enzymes that metabolise ROS, some of which reduce them to less reactive species. In this chapter, we review the evidence that manipulating the levels of these enzymes has any effect/s on ageing. We will also highlight a few examples illustrating why it is an over-simplification to describe the activities of some of these enzymes as 'antioxidants'. We discuss how these studies have helped refine our view of how ROS and ROS-metabolising enzymes contribute to the ageing process.

Sperm RNA elements as markers of health

Idiopathic infertility, an etiology not identified as part of standard clinical assessment, represents approximately 20% of all infertility cases. Current male infertility diagnosis focuses on the concentration, motility, and morphology of spermatozoa. This is of limited value when predicting birth success and of limited utility when selecting the optimum treatment. At fertilization, spermatozoa provide their genomic contribution, as well as a set of RNAs and proteins that have distinct roles in development. The potential of spermatozoal RNAs to be used as a prognostic of live birth has been shown [Jodar et al. (2015) Science Translational Medicine 7(295):295re6]. This relied on a set of 648 sperm RNA elements derived from 285 genes that are perhaps indicative of future health status. To address this tenet, the present study correlated the levels of each transcript among all samples to assess linkage between transcript absence, birth success, and possible disease association. Correlations between transcript levels of the 285 genes were analyzed amongst themselves, and within the context of the entire transcript population for these samples. The transcripts ACE, GIGYF2, and ODF2 had many negative correlations and form the majority of correlations, suggesting an important function for these transcripts. Eleven of the 285 queried genes had disease-associated variants within a sperm RNA element. Three genes, GPX4, NDRG1, and RPS24 had SREs were absent in at least one individual from the test cohort. GPX4 and RPS24 are associated with developmental defects and/or neonatal lethality. This leaves the intriguing possibility that, while sperm RNAs delivered to the oocyte inform the success of live birth, they may also be predictors of human health.

ABBREVIATIONS

GO: Gene Ontology; ART: assisted reproductive technology; IVF: in vitro fertilization; ICSI: intra-cytoplasmic sperm injection; RNA-seq: RNA-sequencing; TIC: timed intercourse; IUI: intrauterine insemination; SRE: sperm RNA elements; HPA: Human Protein Atlas; SMDS: sedaghatian-type spondylometaphyseal dysplasia; DBA: Diamond-Blackfan anemia; RPKM: reads per kilobase per million; TPM: transcripts per million; IPA: Ingenuity Pathway Analysis; OMIM: Online Mendelian Inheritance in Man.

Redox homeostasis and age-related deficits in neuromuscular integrity and function

Skeletal muscle is a major site of metabolic activity and is the most abundant tissue in the human body. Age-related muscle atrophy (sarcopenia) and weakness, characterized by progressive loss of lean muscle mass and function, is a major contributor to morbidity and has a profound effect on the quality of life of older people. With a continuously growing older population (estimated 2 billion of people aged >60 by 2050), demand for medical and social care due to functional deficits, associated with neuromuscular ageing, will inevitably increase. Despite the importance of this 'epidemic' problem, the primary biochemical and molecular mechanisms underlying age-related deficits in neuromuscular integrity and function have not been fully determined. Skeletal muscle generates reactive oxygen and nitrogen species (RONS) from a variety of subcellular sources, and age-associated oxidative damage has been suggested to be a major factor contributing to the initiation and progression of muscle atrophy inherent with ageing. RONS can modulate a variety of intracellular signal transduction processes, and disruption of these events over time due to altered redox control has been proposed as an underlying mechanism of ageing. The role of oxidants in ageing has been extensively examined in different model organisms that have undergone genetic manipulations with inconsistent findings. Transgenic and knockout rodent studies have provided insight into the function of RONS regulatory systems in neuromuscular ageing. This review summarizes almost 30 years of research in the field of redox homeostasis and muscle ageing, providing a detailed discussion of the experimental approaches that have been undertaken in murine models to examine the role of redox regulation in age-related muscle atrophy and weakness.

Mitochondrial protein Fus1/Tusc2 in premature aging and age-related pathologies: critical roles of calcium and energy homeostasis

Decreased energy production and increased oxidative stress are considered to be major contributors to aging and aging-associated pathologies. The role of mitochondrial calcium homeostasis has also been highlighted as an important factor affecting different pathological conditions. Here, we present evidence that loss of a small mitochondrial protein Fus1 that maintains mitochondrial homeostasis results in premature aging, aging-associated pathologies, and decreased survival. We showed that Fus1KO mice develop multiple early aging signs including lordokyphosis, lack of vigor, inability to accumulate fat, reduced ability to tolerate stress, and premature death. Other prominent pathological changes included low sperm counts, compromised ability of adult stem cells to repopulate tissues, and chronic inflammation. At the molecular level, we demonstrated that mitochondria of Fus1 KO cells have low reserve respiratory capacity (the ability to produce extra energy during sudden energy demanding situations), and show significantly altered dynamics of cellular calcium response.

Our recent studies on early hearing and memory loss in Fus1 KO mice combined with the new data presented here suggest that calcium and energy homeostasis controlled by Fus1 may be at the core of its aging-regulating activities. Thus, Fus1 protein and Fus1-dependent pathways and processes may represent new tools and targets for anti-aging strategies.

Slow aging in mammals-Lessons from African mole-rats and bats

Traditionally, the main mammalian models used in aging research have been mice and rats, i.e. short-lived species that obviously lack effective maintenance mechanisms to keep their soma in a functional state for prolonged periods of time. It is doubtful that life-extending mechanisms identified only in such short-lived species adequately reflect the diversity of longevity pathways that have naturally evolved in mammals, or that they have much relevance for long-lived species such as humans. Therefore, some complementary, long-lived mammalian models have been introduced to aging research in the past 15-20 years, particularly naked mole-rats (and to a lesser extent also other mole-rats) and bats. Here, I summarize and compare the most important results regarding various aspects of aging - oxidative stress, molecular homeostasis and repair, and endocrinology - that have been obtained from studies using these new mammalian models of high longevity. I argue that the inclusion of these models was an important step forward, because it drew researchers' attention to certain oversimplifications of existing aging theories and to several features that appear to be universal components of enhanced longevity in mammals. However, even among mammals with high longevity, considerable variation exists with respect to other candidate mechanisms that also must be taken into account if inadequate generalizations are to be avoided.

Signaling Networks Determining Life Span

The health of an organism is orchestrated by a multitude of molecular and biochemical networks responsible for ensuring homeostasis within cells and tissues. However, upon aging, a progressive failure in the maintenance of this homeostatic balance occurs in response to a variety of endogenous and environmental stresses, allowing the accumulation of damage, the physiological decline of individual tissues, and susceptibility to diseases. What are the molecular and cellular signaling events that control the aging process and how can this knowledge help design therapeutic strategies to combat age-associated diseases? Here we provide a comprehensive overview of the evolutionarily conserved biological processes that alter the rate of aging and discuss their link to disease prevention and the extension of healthy life span.

Opposing impacts on healthspan and longevity by limiting dietary selenium in telomere dysfunctional mice

Selenium (Se) is a trace metalloid essential for life, but its nutritional and physiological roles during the aging process remain elusive. While telomere attrition contributes to replicative senescence mainly through persistent DNA damage response, such an aging process is mitigated in mice with inherently long telomeres. Here, weanling third generation telomerase RNA component knockout mice carrying short telomeres were fed a Se‐deficient basal diet or the diet supplemented with 0.15 ppm Se as sodium selenate to be nutritionally sufficient throughout their life. Dietary Se deprivation delayed wound healing and accelerated incidence of osteoporosis, gray hair, alopecia, and cataract, but surprisingly promoted longevity. Plasma microRNA profiling revealed a circulating signature of Se deprivation, and subsequent ontological analyses predicted dominant changes in metabolism. Consistent with this observation, dietary Se deprivation accelerated age‐dependent declines in glucose tolerance, insulin sensitivity, and glucose‐stimulated insulin production in the mice. Moreover, DNA damage and senescence responses were enhanced and Pdx1 and MafA mRNA expression were reduced in pancreas of the Se‐deficient mice. Altogether, these results suggest a novel model of aging with conceptual advances, whereby Se at low levels may be considered a hormetic chemical and decouple healthspan and longevity.

Different Mechanisms of Longevity in Long-Lived Mouse and Caenorhabditis elegans Mutants Revealed by Statistical Analysis of Mortality Rates

Mouse and Caenorhabditis elegans mutants with altered life spans are being used to investigate the aging process and how genes determine life span. The survival of a population can be modeled by the Gompertz function, which comprises two parameters. One of these parameters ("G") describes the rate at which mortality accelerates with age and is often described as the "rate of aging." The other parameter ("A") may correspond to the organism's baseline vulnerability to deleterious effects of disease and the environment. We show that, in mice, life-span-extending mutations systematically fail to affect the age-dependent acceleration of mortality (G), but instead affect only baseline vulnerability (A). This remains true even when comparing strains maintained under identical environmental conditions. In contrast, life-span-extending mutations in C. elegans were associated with decreases in G These observations on mortality rate kinetics suggest that the mechanisms of aging in mammals might fundamentally differ from those in nematodes.