S-nitrosylation drives cell senescence and aging in mammals by controlling mitochondrial dynamics and mitophagy

The effects of nitric oxide in Alzheimer's disease

Alzheimer's disease (AD), the most prevalent cause of dementia, is a progressive neurodegenerative condition that commences subtly and inexorably worsens over time. Despite considerable research, a specific drug that can fully cure or effectively halt the progression of AD remains elusive. Nitric oxide (NO), a crucial signaling molecule in the nervous system, is intimately associated with hallmark pathological changes in AD, such as amyloid-beta deposition and tau phosphorylation. Several therapeutic strategies for AD operate through the nitric oxide synthase/NO system. However, the potential neurotoxicity of NO introduces an element of controversy regarding its therapeutic utility in AD. This review focuses on research findings concerning NO's role in experimental AD and its underlying mechanisms. Furthermore, we have proposed directions for future research based on our current comprehension of this critical area.

Nitric Oxide Signaling and Sensing in Age-Related Diseases

Nitric oxide (NO) is a key signaling molecule involved in numerous physiological and pathological processes within the human body. This review specifically examines the involvement of NO in age-related diseases, focusing on the cardiovascular, nervous, and immune systems. The discussion delves into the mechanisms of NO signaling in these diseases, emphasizing the post-translational modifications of involved proteins, such as S-nitrosation and nitration. The review also covers the dual nature of NO, highlighting both its protective and harmful effects, determined by concentration, location, and timing. Additionally, potential therapies that modulate NO signaling, including the use of NO donors and nitric oxide synthases (NOSs) inhibitors in the treatment of cardiovascular, neurodegenerative, and oncological diseases, are analyzed. Particular attention is paid to the methods for the determination of NO and its derivatives in the context of illness diagnosis and monitoring. The review underscores the complexity and dual role of NO in maintaining cellular balance and suggests areas for future research in developing new therapeutic strategies.

Small Molecular Inhibitors That Target ATM for Drug Discovery: Current Research and Potential Prospective

The protein kinase ataxia telangiectasia mutated (ATM) is a constituent of the phosphatidylinositol 3-kinase-related kinase (PIKK) family, exerting a pivotal influence on diverse cellular processes, notably the signaling of double-strand DNA breaks (DSB) and stress response. The dysregulation of ATM is implicated in the pathogenesis of cancer and other diseases such as neurodegeneration. Hence, ATM is deemed a promising candidate for potential therapeutic interventions across a spectrum of diseases. Presently, while ATM small molecule inhibitors are not commercially available, various selective inhibitors have progressed to the clinical research phase. Specifically, AZD1390, WSD0628, SYH2051, and ZN-B-2262 are under investigation in clinical studies pertaining to glioblastoma multiforme and advanced solid tumors, respectively. In this Perspective, we encapsulate the structure, biological functions, and disease relevance of ATM. Subsequently, we concentrate on the design concepts and structure-activity relationships (SAR) of ATM inhibitors, delineating potential avenues for the development of more efficacious ATM-targeted inhibitors.

Young small extracellular vesicles rejuvenate replicative senescence by remodeling Drp1 translocation-mediated mitochondrial dynamics

BACKGROUND

Human mesenchymal stem cells have attracted interest in regenerative medicine and are being tested in many clinical trials. In vitro expansion is necessary to provide clinical-grade quantities of mesenchymal stem cells; however, it has been reported to cause replicative senescence and undefined dysfunction in mesenchymal stem cells. Quality control assessments of in vitro expansion have rarely been addressed in ongoing trials. Young small extracellular vesicles from the remnant pulp of human exfoliated deciduous teeth stem cells have demonstrated therapeutic potential for diverse diseases. However, it is still unclear whether young small extracellular vesicles can reverse senescence-related declines.

RESULTS

We demonstrated that mitochondrial structural disruption precedes cellular dysfunction during bone marrow-derived mesenchymal stem cell replication, indicating mitochondrial parameters as quality assessment indicators of mesenchymal stem cells. Dynamin-related protein 1-mediated mitochondrial dynamism is an upstream regulator of replicative senescence-induced dysfunction in bone marrow-derived mesenchymal stem cells. We observed that the application of young small extracellular vesicles could rescue the pluripotency dissolution, immunoregulatory capacities, and therapeutic effects of replicative senescent bone marrow-derived mesenchymal stem cells. Mechanistically, young small extracellular vesicles could promote Dynamin-related protein 1 translocation from the cytoplasm to the mitochondria and remodel mitochondrial disruption during replication history.

CONCLUSIONS

Our findings show that Dynamin-related protein 1-mediated mitochondrial disruption is associated with the replication history of bone marrow-derived mesenchymal stem cells. Young small extracellular vesicles from human exfoliated deciduous teeth stem cells alleviate replicative senescence by promoting Dynamin-related protein 1 translocation onto the mitochondria, providing evidence for a potential rejuvenation strategy.

Role of dynamin-related protein 1-dependent mitochondrial fission in drug-induced toxicity

Dynamin-related protein 1 (DRP1) is an essential controller of mitochondrial fission whose activity is tightly controlled to ensure balanced mitochondrial dynamics and maintain internal cellular homeostasis. Growing evidence suggests that DRP1-dependent mitochondrial fission plays a role in drug-induced toxicity (DIT). Therefore, understanding the molecular mechanisms underlying DIT and the precise regulation of DRP1 function will inform the development of potential therapeutic treatments for DIT. This review comprehensively summarizes the diverse DITs and their potential mechanism associated with DRP1-dependent mitochondrial fission and discusses in vivo and in vitro model studies of toxicity protection targeting DRP1.

Protein modification in neurodegenerative diseases

Posttranslational modifications play a crucial role in governing cellular functions and protein behavior. Researchers have implicated dysregulated posttranslational modifications in protein misfolding, which results in cytotoxicity, particularly in neurodegenerative diseases such as Alzheimer disease, Parkinson disease, and Huntington disease. These aberrant posttranslational modifications cause proteins to gather in certain parts of the brain that are linked to the development of the diseases. This leads to neuronal dysfunction and the start of neurodegenerative disease symptoms. Cognitive decline and neurological impairments commonly manifest in neurodegenerative disease patients, underscoring the urgency of comprehending the posttranslational modifications' impact on protein function for targeted therapeutic interventions. This review elucidates the critical link between neurodegenerative diseases and specific posttranslational modifications, focusing on Tau, APP, α-synuclein, Huntingtin protein, Parkin, DJ-1, and Drp1. By delineating the prominent aberrant posttranslational modifications within Alzheimer disease, Parkinson disease, and Huntington disease, the review underscores the significance of understanding the interplay among these modifications. Emphasizing 10 key abnormal posttranslational modifications, this study aims to provide a comprehensive framework for investigating neurodegenerative diseases holistically. The insights presented herein shed light on potential therapeutic avenues aimed at modulating posttranslational modifications to mitigate protein aggregation and retard neurodegenerative disease progression.

The role of redox-active small molecules and oxidative protein post-translational modifications in seed aging

Seed vigor is a crucial indicator of seed quality. Variations in seed vigor are closely associated with seed properties and storage conditions. The vigor of mature seeds progressively declines during storage, which is called seed deterioration or aging. Seed aging induces a cascade of cellular damage, including impaired subcellular structures and macromolecules, such as lipids, proteins, and DNA. Reactive oxygen species (ROS) act as signaling molecules during seed aging causing oxidative damage and triggering programmed cell death (PCD). Mitochondria are the main site of ROS production and change morphology and function before other organelles during aging. The roles of other small redox-active molecules in regulating cell and seed vigor, such as nitric oxide (NO) and hydrogen sulfide (H2S), were identified later. ROS, NO, and H2S typically regulate protein function through post-translational modifications (PTMs), including carbonylation, S-glutathionylation, S-nitrosylation, and S-sulfhydration. These signaling molecules as well as the PTMs they induce interact to regulate cell fate and seed vigor. This review was conducted to describe the physiological changes and underlying molecular mechanisms that in seed aging and provides a comprehensive view of how ROS, NO, and H2S affect cell death and seed vigor.

GSNOR overexpression enhances CAR-T cell stemness and anti-tumor function by enforcing mitochondrial fitness

Chimeric antigen receptor-T (CAR-T) cell has been developed as a promising agent for patients with refractory or relapsed lymphoma and leukemia, but not all the recipients could achieve a long-lasting remission. The limited capacity of in vivo expansion and memory differentiation post activation is one of the major reasons for suboptimal CAR-T therapeutic efficiency. Nitric oxide (NO) plays multifaceted roles in mitochondrial dynamics and T cell activation, but its function on CAR-T cell persistence and anti-tumor efficacy remains unknown. Herein, we found the continuous signaling from CAR not only promotes excessive NO production, but also suppressed S-nitrosoglutathione reductase (GSNOR) expression in T cells, which collectively led to increased protein S-nitrosylation, resulting in impaired mitochondrial fitness and deficiency of T cell stemness. Intriguingly, enforced expression of GSNOR promoted memory differentiation of CAR-T cell after immune activation, rendered CAR-T better resistance to mitochondrial dysfunction, further enhanced CAR-T cell expansion and anti-tumor capacity in vitro and in a mouse tumor model. Thus, we revealed a critical role of NO in restricting CAR-T cell persistence and functionality, and defined that GSNOR overexpression may provide a solution to combat NO stress and render patients with more durable protection from CAR-T therapy.

GSNOR negatively regulates the NLRP3 inflammasome via S-nitrosation of MAPK14

Hyperactivation of the NLRP3 inflammasome has been implicated in the pathogenesis of numerous diseases. However, the precise molecular mechanisms that modulate the transcriptional regulation of NLRP3 remain largely unknown. In this study, we demonstrated that S-nitrosoglutathione reductase (GSNOR) deficiency in macrophages leads to significant increases in the Nlrp3 and Il-1β expression levels and interleukin-1β (IL-1β) secretion in response to NLRP3 inflammasome stimulation. Furthermore, in vivo experiments utilizing Gsnor-/- mice revealed increased disease severity in both lipopolysaccharide (LPS)-induced septic shock and dextran sodium sulfate (DSS)-induced colitis models. Additionally, we showed that both LPS-induced septic shock and DSS-induced colitis were ameliorated in Gsnor-/- Nlrp3-/- double-knockout (DKO) mice. Mechanistically, GSNOR deficiency increases the S-nitrosation of mitogen-activated protein kinase 14 (MAPK14) at the Cys211 residue and augments MAPK14 kinase activity, thereby promoting Nlrp3 and Il-1β transcription and stimulating NLRP3 inflammasome activity. Our findings suggested that GSNOR is a regulator of the NLRP3 inflammasome and that reducing the level of S-nitrosylated MAPK14 may constitute an effective strategy for alleviating diseases associated with NLRP3-mediated inflammation.

Key genes and convergent pathogenic mechanisms in Parkinson disease

Parkinson disease (PD) is a neurodegenerative disorder marked by the preferential dysfunction and death of dopaminergic neurons in the substantia nigra. The onset and progression of PD is influenced by a diversity of genetic variants, many of which lack functional characterization. To identify the most high-yield targets for therapeutic intervention, it is important to consider the core cellular compartments and functional pathways upon which the varied forms of pathogenic dysfunction may converge. Here, we review several key PD-linked proteins and pathways, focusing on the mechanisms of their potential convergence in disease pathogenesis. These dysfunctions primarily localize to a subset of subcellular compartments, including mitochondria, lysosomes and synapses. We discuss how these pathogenic mechanisms that originate in different cellular compartments may coordinately lead to cellular dysfunction and neurodegeneration in PD.

Mitochondria, Autophagy and Inflammation: Interconnected in Aging

In this manuscript, I discuss the direct link between abnormalities in inflammatory responses, mitochondrial metabolism and autophagy during the process of aging. It is focused on the cytosolic receptors nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) and cyclic GMP-AMP synthase (cGAS); myeloid-derived suppressor cells (MDSCs) expansion and their associated immunosuppressive metabolite, methyl-glyoxal, all of them negatively regulated by mitochondrial autophagy, biogenesis, metabolic pathways and its distinct metabolites.

The Role of Protein S-Nitrosylation in Mitochondrial Quality Control in Central Nervous System Diseases

S-Nitrosylation is a reversible covalent post-translational modification. Under physiological conditions, S-nitrosylation plays a dynamic role in a wide range of biological processes by regulating the function of substrate proteins. Like other post-translational modifications, S-nitrosylation can affect protein conformation, activity, localization, aggregation, and protein interactions. Aberrant S-nitrosylation can lead to protein misfolding, mitochondrial fragmentation, synaptic damage, and autophagy. Mitochondria are essential organelles in energy production, metabolite biosynthesis, cell death, and immune responses, among other processes. Mitochondrial dysfunction can result in cell death and has been implicated in the development of many human diseases. Recent evidence suggests that S-nitrosylation and mitochondrial dysfunction are important modulators of the progression of several diseases. In this review, we highlight recent findings regarding the aberrant S- nitrosylation of mitochondrial proteins that regulate mitochondrial biosynthesis, fission and fusion, and autophagy. Specifically, we discuss the mechanisms by which S-nitrosylated mitochondrial proteins exercise mitochondrial quality control under pathological conditions, thereby influencing disease. A better understanding of these pathological events may provide novel therapeutic targets to mitigate the development of neurological diseases.

PPSNO: A Feature-Rich SNO Sites Predictor by Stacking Ensemble Strategy from Protein Sequence-Derived Information

The protein S-nitrosylation (SNO) is a significant post-translational modification that affects the stability, activity, cellular localization, and function of proteins. Therefore, highly accurate prediction of SNO sites aids in grasping biological function mechanisms. In this document, we have constructed a predictor, named PPSNO, forecasting protein SNO sites using stacked integrated learning. PPSNO integrates multiple machine learning techniques into an ensemble model, enhancing its predictive accuracy. First, we established benchmark datasets by collecting SNO sites from various sources, including literature, databases, and other predictors. Second, various techniques for feature extraction are applied to derive characteristics from protein sequences, which are subsequently amalgamated into the PPSNO predictor for training. Five-fold cross-validation experiments show that PPSNO outperformed existing predictors, such as PSNO, PreSNO, pCysMod, DeepNitro, RecSNO, and Mul-SNO. The PPSNO predictor achieved an impressive accuracy of 92.8%, an area under the curve (AUC) of 96.1%, a Matthews correlation coefficient (MCC) of 81.3%, an F1-score of 85.6%, an SN of 79.3%, an SP of 97.7%, and an average precision (AP) of 92.2%. We also employed ROC curves, PR curves, and radar plots to show the superior performance of PPSNO. Our study shows that fused protein sequence features and two-layer stacked ensemble models can improve the accuracy of predicting SNO sites, which can aid in comprehending cellular processes and disease mechanisms. The codes and data are available at https://github.com/serendipity-wly/PPSNO .

S-nitrosothiol homeostasis maintained by ADH5 facilitates STING-dependent host defense against pathogens

Oxidative (or respiratory) burst confers host defense against pathogens by generating reactive species, including reactive nitrogen species (RNS). The microbial infection-induced excessive RNS damages many biological molecules via S-nitrosothiol (SNO) accumulation. However, the mechanism by which the host enables innate immunity activation during oxidative burst remains largely unknown. Here, we demonstrate that S-nitrosoglutathione (GSNO), the main endogenous SNO, attenuates innate immune responses against herpes simplex virus-1 (HSV-1) and Listeria monocytogenes infections. Mechanistically, GSNO induces the S-nitrosylation of stimulator of interferon genes (STING) at Cys257, inhibiting its binding to the second messenger cyclic guanosine monophosphate-adenosine monophosphate (cGAMP). Alcohol dehydrogenase 5 (ADH5), the key enzyme that metabolizes GSNO to decrease cellular SNOs, facilitates STING activation by inhibiting S-nitrosylation. Concordantly, Adh5 deficiency show defective STING-dependent immune responses upon microbial challenge and facilitates viral replication. Thus, cellular oxidative burst-induced RNS attenuates the STING-mediated innate immune responses to microbial infection, while ADH5 licenses STING activation by maintaining cellular SNO homeostasis.

A metabolic perspective on nitric oxide function in melanoma

Nitric oxide (NO) generated from nitric oxide synthase (NOS) exerts a dichotomous effect in melanoma, suppressing or promoting tumor progression. This dichotomy is thought to depend on the intracellular NO concentration and the cell type in which it is generated. Due to its central role in the metabolism of multiple critical constituents involved in signaling and stress, it is crucial to explore NO's contribution to the metabolic dysfunction of melanoma. This review will discuss many known metabolites linked to NO production in melanoma. We discuss the synthesis of these metabolites, their role in biochemical pathways, and how they alter the biological processes observed in the melanoma tumor microenvironment. The metabolic pathways altered by NO and the corresponding metabolites reinforce its dual role in melanoma and support investigating this effect for potential avenues of therapeutic intervention.

Formaldehyde regulates S-adenosylmethionine biosynthesis and one-carbon metabolism

One-carbon metabolism is an essential branch of cellular metabolism that intersects with epigenetic regulation. In this work, we show how formaldehyde (FA), a one-carbon unit derived from both endogenous sources and environmental exposure, regulates one-carbon metabolism by inhibiting the biosynthesis of S-adenosylmethionine (SAM), the major methyl donor in cells. FA reacts with privileged, hyperreactive cysteine sites in the proteome, including Cys120 in S-adenosylmethionine synthase isoform type-1 (MAT1A). FA exposure inhibited MAT1A activity and decreased SAM production with MAT-isoform specificity. A genetic mouse model of chronic FA overload showed a decrease n SAM and in methylation on selected histones and genes. Epigenetic and transcriptional regulation of Mat1a and related genes function as compensatory mechanisms for FA-dependent SAM depletion, revealing a biochemical feedback cycle between FA and SAM one-carbon units.

S-Nitrosylation at the intersection of metabolism and autophagy: Implications for cancer

Metabolic plasticity, which determines tumour growth and metastasis, is now understood to be a flexible and context-specific process in cancer metabolism. One of the major pathways contributing to metabolic adaptations in eucaryotic cells is autophagy, a cellular degradation and recycling process that is activated during periods of starvation or stress to maintain metabolite and biosynthetic intermediate levels. Consequently, there is a close association between the metabolic adaptive capacity of tumour cells and autophagy-related pathways in cancer. Additionally, nitric oxide regulates protein function and signalling through S-nitrosylation, a post-translational modification that can also impact metabolism and autophagy. The primary objective of this review is to provide an up-to-date overview of the role of S-nitrosylation at the intersection of metabolism and autophagy in cancer. First, we will outline the involvement of S-nitrosylation in the metabolic adaptations that occur in tumours. Then, we will discuss the multifaceted role of autophagy in cancer, the interplay between metabolism and autophagy during tumour progression, and the contribution of S-nitrosylation to autophagic dysregulation in cancer. Finally, we will present insights into relevant therapeutic aspects and discuss prospects for the future.

Cross-talk between DNA damage response and the central carbon metabolic network underlies selective vulnerability of Purkinje neurons in ataxia-telangiectasia

Cerebellar ataxia is often the first and irreversible outcome in the disease of ataxia-telangiectasia (A-T), as a consequence of selective cerebellar Purkinje neuronal degeneration. A-T is an autosomal recessive disorder resulting from the loss-of-function mutations of the ataxia-telangiectasia-mutated ATM gene. Over years of research, it now becomes clear that functional ATM-a serine/threonine kinase protein product of the ATM gene-plays critical roles in regulating both cellular DNA damage response and central carbon metabolic network in multiple subcellular locations. The key question arises is how cerebellar Purkinje neurons become selectively vulnerable when all other cell types in the brain are suffering from the very same defects in ATM function. This review intended to comprehensively elaborate the unexpected linkages between these two seemingly independent cellular functions and the regulatory roles of ATM involved, their integrated impacts on both physical and functional properties, hence the introduction of selective vulnerability to Purkinje neurons in the disease will be addressed.

Mitochondrial GSNOR Alleviates Cardiac Dysfunction via ANT1 Denitrosylation

BACKGROUND

The cardiac-protective role of GSNOR (S-nitrosoglutathione reductase) in the cytoplasm, as a denitrosylase enzyme of S-nitrosylation, has been reported in cardiac remodeling, but whether GSNOR is localized in other organelles and exerts novel effects remains unknown. We aimed to elucidate the effects of mitochondrial GSNOR, a novel subcellular localization of GSNOR, on cardiac remodeling and heart failure (HF).

METHODS

GSNOR subcellular localization was observed by cellular fractionation assay, immunofluorescent staining, and colloidal gold particle staining. Overexpression of GSNOR in mitochondria was achieved by mitochondria-targeting sequence-directed adeno-associated virus 9. Cardiac-specific knockout of GSNOR mice was used to examine the role of GSNOR in HF. S-nitrosylation sites of ANT1 (adenine nucleotide translocase 1) were identified using biotin-switch and liquid chromatography-tandem mass spectrometry.

RESULTS

GSNOR expression was suppressed in cardiac tissues of patients with HF. Consistently, cardiac-specific knockout mice showed aggravated pathological remodeling induced by transverse aortic constriction. We found that GSNOR is also localized in mitochondria. In the angiotensin II-induced hypertrophic cardiomyocytes, mitochondrial GSNOR levels significantly decreased along with mitochondrial functional impairment. Restoration of mitochondrial GSNOR levels in cardiac-specific knockout mice significantly improved mitochondrial function and cardiac performance in transverse aortic constriction-induced HF mice. Mechanistically, we identified ANT1 as a direct target of GSNOR. A decrease in mitochondrial GSNOR under HF leads to an elevation of S-nitrosylation ANT1 at cysteine 160 (C160). In accordance with these findings, overexpression of either mitochondrial GSNOR or ANT1 C160A, non-nitrosylated mutant, significantly improved mitochondrial function, maintained the mitochondrial membrane potential, and upregulated mitophagy.

CONCLUSIONS

We identified a novel species of GSNOR localized in mitochondria and found mitochondrial GSNOR plays an essential role in maintaining mitochondrial homeostasis through ANT1 denitrosylation, which provides a potential novel therapeutic target for HF.

Autophagy, Oxidative Stress, and Alcoholic Liver Disease: A Systematic Review and Potential Clinical Applications

Ethanol consumption triggers oxidative stress by generating reactive oxygen species (ROS) through its metabolites. This process leads to steatosis and liver inflammation, which are critical for the development of alcoholic liver disease (ALD). Autophagy is a regulated dynamic process that sequesters damaged and excess cytoplasmic organelles for lysosomal degradation and may counteract the harmful effects of ROS-induced oxidative stress. These effects include hepatotoxicity, mitochondrial damage, steatosis, endoplasmic reticulum stress, inflammation, and iron overload. In liver diseases, particularly ALD, macroautophagy has been implicated as a protective mechanism in hepatocytes, although it does not appear to play the same role in stellate cells. Beyond the liver, autophagy may also mitigate the harmful effects of alcohol on other organs, thereby providing an additional layer of protection against ALD. This protective potential is further supported by studies showing that drugs that interact with autophagy, such as rapamycin, can prevent ALD development in animal models. This systematic review presents a comprehensive analysis of the literature, focusing on the role of autophagy in oxidative stress regulation, its involvement in organ-organ crosstalk relevant to ALD, and the potential of autophagy-targeting therapeutic strategies.

Importance of DJ-1 in autophagy regulation and disease

Autophagy is a highly conserved biological process that has evolved across evolution. It can be activated by various external stimuli including oxidative stress, amino acid starvation, infection, and hypoxia. Autophagy is the primary mechanism for preserving cellular homeostasis and is implicated in the regulation of metabolism, cell differentiation, tolerance to starvation conditions, and resistance to aging. As a multifunctional protein, DJ-1 is commonly expressed in vivo and is associated with a variety of biological processes. Its most widely studied role is its function as an oxidative stress sensor that inhibits the production of excessive reactive oxygen species (ROS) in the mitochondria and subsequently the cellular damage caused by oxidative stress. In recent years, many studies have identified DJ-1 as another important factor regulating autophagy; it regulates autophagy in various ways, most commonly by regulating the oxidative stress response. In particular, DJ-1-regulated autophagy is involved in cancer progression and plays a key role in alleviating neurodegenerative diseases(NDS) and defective reperfusion diseases. It could serve as a potential target for the regulation of autophagy and participate in disease treatment as a meaningful modality. Therefore, exploring DJ-1-regulated autophagy could provide new avenues for future disease treatment.

S-nitroso-glutathione (GSNO) inhibits hydrogen peroxide production by alpha-ketoglutarate dehydrogenase: An investigation into sex and diet effects

Pyruvate dehydrogenase (PDH) and α-ketoglutarate dehydrogenase (KGDH) are vital sources of hydrogen peroxide (H₂O₂) and key sites for redox regulation. Here, we report KGDH is more sensitive to inhibition by S-nitroso-glutathione (GSNO) when compared to PDH and deactivation of both enzymes by nitro modification is affected by sex and diet. Liver mitochondria from male C57BL/6N mice displayed a robust inhibition of H₂O₂ production after exposure to 500-2000 μM GSNO. H₂O₂ genesis by PDH was not significantly affected by GSNO. Purified KGDH of porcine heart origin displayed a ∼82% decrease in H₂O₂ generating activity at 500 μM GSNO, which was mirrored by a decrease in NADH production. By contrast, H₂O₂- and NADH-producing activity of purified PDH was only minimally affected by an incubation in 500 μM GSNO. Incubations in GSNO had no significant effect on the H₂O₂-generating activity of KGDH and PDH in female liver mitochondria when compared to samples collected from males, which was attributed to higher GSNO reductase (GSNOR) activity. High fat feeding augmented the GSNO-mediated inhibition of KGDH in liver mitochondria from male mice. Exposure of male mice to a HFD also resulted in a significant decrease in the GSNO-mediated inhibition of H₂O₂ genesis by PDH, an effect not observed in mice fed a control-matched diet (CD). Female mice displayed higher resistance to the GSNO-induced inhibition of H₂O₂ production, regardless of being fed a CD or HFD. However, exposure to a HFD did result in a small but significant decrease in H₂O₂ production by KGDH and PDH when female liver mitochondria were treated with GSNO. Although, the effect was less when compared to their male counterparts. Collectively, we show for the first time GSNO deactivates H₂O₂ production by α-keto acid dehydrogenases and we demonstrate that sex and diet are determinants for the nitro-inhibition of both KGDH and PDH.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

From Diabetes to Diabetic Complications: Role of Autophagy

Diabetes and its complications reduce quality of life and are life-limiting. At present, diabetes treatment consists of hypoglycemic agents to control blood glucose and the use of insulin-sensitizing drugs to overcome insulin resistance. In diabetes, autophagy is impaired and thus there is poor intracellular environment homeostasis. Pancreatic β-cells and insulin target tissues are protected by enhancing autophagy. Autophagy decreases β-cell apoptosis, promotes β-cell proliferation, and alleviates insulin resistance. Autophagy in diabetes is regulated by the mammalian target of rapamycin (mTOR)/adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) pathway and others. Autophagy enhancers can likely be used as a treatment for diabetes and its complications. This review examines the evidence linking autophagy to diabetes.

Melatonin ameliorates glyphosate- and hard water-induced renal tubular epithelial cell senescence via PINK1-Parkin-dependent mitophagy

The combination of glyphosate (Gly) and hard water (Hwt) is a suspected risk factor for chronic interstitial nephritis in agricultural communities (CINAC). Accumulated mitochondrial damage and proximal tubular epithelial (PTE) cell senescence have been implicated in CINAC pathogenesis. Melatonin (Mel) has potential mitochondrial function and renoprotective properties, but its role and mechanism in CINAC are unknown. Here, we detected PTE cell senescence and PTEN-induced putative protein kinase 1 (PINK1)-parkin RBR E3 ubiquitin protein ligase (Parkin)-dependent mitophagy in mice orally administered with different doses of Gly combined with Hwt (Gly: 100 mg/kg·bw and 0.7 mg/L; Hwt: 2,500 mg/L CaCO₃ and 250 mg/L Ca²⁺) for different durations (12 and 36 w) using histological examination, transmission electron microscopy (TEM), immunofluorescence (IF) analysis, and immunohistochemistry (IHC), immunoblotting, ELISA and biochemical assays with kits. The same assays were performed after combination treatment with Mdivi-1 (an inhibitor of mitophagy, i.p. 10 mg/kg·bw, twice a week for 12 w) or Mel (i.p. 10 mg/kg·bw, once a day for 12 w) under high-level exposure. Gly combined with Hwt (Gly-Hwt) significantly increased P16-P21-dependent PTE cell senescence, mitochondrial fission and oxidative stress, and activated PINK1-Parkin-mediated mitophagy, accompanied by defective autophagic flux at high doses but unaltered autophagic flux at low doses. Improved senescence occurred after Mdivi-1 administration, suggesting that mitophagy is involved in cellular senescence. Mel significantly decreased senescence induced by Gly-Hwt. Furthermore, PINK1-Parkin-dependent mitophagy and autophagic flux were markedly enhanced, and mitochondrial function was improved, as evidenced by reductions in mitochondrial fission and subsequent oxidative damage. Thus, Gly and Hwt synergistically promote PTE cell senescence through PINK1-Parkin-mediated mitophagy, and Mel exerts renoprotective effects by modulating mitophagy, suggesting therapeutic applications in ageing-related CINAC.

Chemical inhibition of mitochondrial fission via targeting the DRP1-receptor interaction

Mitochondrial fission is critical for mitochondrial dynamics and homeostasis. The dynamin superfamily GTPase DRP1 is recruited by three functionally redundant receptors, MFF, MiD49, and MiD51, to mitochondria to drive fission. Here, we exploit high-content live-cell imaging to screen for mitochondrial fission inhibitors and have developed a covalent compound, mitochondrial division inhibitor (MIDI). MIDI treatment potently blocks mitochondrial fragmentation induced by mitochondrial toxins and restores mitochondrial morphology in fusion-defective cells carrying pathogenic mitofusin and OPA1 mutations. Mechanistically, MIDI does not affect DRP1 tetramerization nor DRP1 GTPase activity but does block DRP1 recruitment to mitochondria. Subsequent biochemical and cellular characterizations reveal an unexpected mechanism that MIDI targets DRP1 interaction with multiple receptors via covalent interaction with DRP1-C367. Taken together, beyond developing a potent mitochondrial fission inhibitor that profoundly impacts mitochondrial morphogenesis, our study establishes proof of concept for developing protein-protein interaction inhibitors targeting DRP1.

GSNOR deficiency promotes tumor growth via FAK1 S-nitrosylation

Nitric oxide (NO) production in the tumor microenvironment is a common element in cancer. S-nitrosylation, the post-translational modification of cysteines by NO, is emerging as a key transduction mechanism sustaining tumorigenesis. However, most oncoproteins that are regulated by S-nitrosylation are still unknown. Here we show that S-nitrosoglutathione reductase (GSNOR), the enzyme that deactivates S-nitrosylation, is hypo-expressed in several human malignancies. Using multiple tumor models, we demonstrate that GSNOR deficiency induces S-nitrosylation of focal adhesion kinase 1 (FAK1) at C658. This event enhances FAK1 autophosphorylation and sustains tumorigenicity by providing cancer cells with the ability to survive in suspension (evade anoikis). In line with these results, GSNOR-deficient tumor models are highly susceptible to treatment with FAK1 inhibitors. Altogether, our findings advance our understanding of the oncogenic role of S-nitrosylation, define GSNOR as a tumor suppressor, and point to GSNOR hypo-expression as a therapeutically exploitable vulnerability in cancer.

Rescue of Mitochondrial Function in Hutchinson-Gilford Progeria Syndrome by the Pharmacological Modulation of Exportin CRM1

Hutchinson-Gilford progeria syndrome (HGPS) is a rare premature aging disorder caused by the expression of progerin, a mutant variant of Lamin A. Recently, HGPS studies have gained relevance because unraveling its underlying mechanism would help to understand physiological aging. We previously reported that the CRM1-mediated nuclear protein export pathway is exacerbated in HGPS cells, provoking the mislocalization of numerous protein targets of CRM1. We showed that normalization of this mechanism by pharmacologically inhibiting CRM1 with LMB (specific CRM1 inhibitor), mitigates the senescent phenotype of HGPS cells. Since mitochondrial dysfunction is a hallmark of HGPS, in this study we analyze the effect of LMB on mitochondrial function. Remarkably, LMB treatment induced the recovery of mitochondrial function in HGPS cells, as shown by the improvement in mitochondrial morphology, mitochondrial membrane potential, and ATP levels, which consequently impeded the accumulation of ROS but not mitochondrial superoxide. We provide evidence that the beneficial effect of LMB is mechanistically based on a combinatory effect on mitochondrial biogenesis via upregulation of PGC-1α expression (master transcription cofactor of mitochondrial genes), and mitophagy through the recovery of lysosomal content. The use of exportin CRM1 inhibitors constitutes a promising strategy to treat HGPS and other diseases characterized by mitochondrial impairment.

Cellular mitophagy: Mechanism, roles in diseases and small molecule pharmacological regulation

Cellular mitophagy means that cells selectively wrap and degrade damaged mitochondria through an autophagy mechanism, thus maintaining mitochondria and intracellular homeostasis. In recent years, mitophagy has received increasing attention as a research hotspot related to the pathogenesis of clinical diseases, such as neurodegenerative diseases, cardiovascular diseases, cancer, metabolic diseases, and so on. It has been found that the regulation of mitophagy may become a new direction for the treatment of some diseases. In addition, numerous small molecule modulators of mitophagy have also been reported, which provides new opportunities to comprehend the procedure and potential of therapeutic development. Taken together, in this review, we summarize current understanding of the mechanism of mitophagy, discuss the roles of mitophagy and its relationship with diseases, introduce the existing small-molecule pharmacological modulators of mitophagy and further highlight the significance of their development.

Unraveling Parkinson's Disease Neurodegeneration: Does Aging Hold the Clues?

Aging is the greatest risk factor for Parkinson's disease (PD), suggesting that mechanisms driving the aging process promote PD neurodegeneration. Several lines of evidence support a role for aging in PD. First, hallmarks of brain aging such as mitochondrial dysfunction and oxidative stress, loss of protein homeostasis, and neuroinflammation are centrally implicated in PD development. Second, mutations that cause monogenic PD are present from conception, yet typically only cause disease following a period of aging. Third, lifespan-extending genetic, dietary, or pharmacological interventions frequently attenuate PD-related neurodegeneration. These observations support a central role for aging in disease development and suggest that new discoveries in the biology of aging could be leveraged to elucidate novel mechanisms of PD pathophysiology. A recent rapid growth in our understanding of conserved molecular pathways that govern model organism lifespan and healthspan has highlighted a key role for metabolism and nutrient sensing pathways. Uncovering how metabolic pathways involving NAD+ consumption, insulin, and mTOR signaling link to the development of PD is underway and implicates metabolism in disease etiology. Here, we assess areas of convergence between nervous system aging and PD, evaluate the link between metabolism, aging, and PD and address the potential of metabolic interventions to slow or halt the onset of PD-related neurodegeneration drawing on evidence from cellular and animal models.

S-Glutathionylation and S-Nitrosylation in Mitochondria: Focus on Homeostasis and Neurodegenerative Diseases

Redox post-translational modifications are derived from fluctuations in the redox potential and modulate protein function, localization, activity and structure. Amongst the oxidative reversible modifications, the S-glutathionylation of proteins was the first to be characterized as a post-translational modification, which primarily protects proteins from irreversible oxidation. However, a growing body of evidence suggests that S-glutathionylation plays a key role in core cell processes, particularly in mitochondria, which are the main source of reactive oxygen species. S-nitrosylation, another post-translational modification, was identified >150 years ago, but it was re-introduced as a prototype cell-signaling mechanism only recently, one that tightly regulates core processes within the cell’s sub-compartments, especially in mitochondria. S-glutathionylation and S-nitrosylation are modulated by fluctuations in reactive oxygen and nitrogen species and, in turn, orchestrate mitochondrial bioenergetics machinery, morphology, nutrients metabolism and apoptosis. In many neurodegenerative disorders, mitochondria dysfunction and oxidative/nitrosative stresses trigger or exacerbate their pathologies. Despite the substantial amount of research for most of these disorders, there are no successful treatments, while antioxidant supplementation failed in the majority of clinical trials. Herein, we discuss how S-glutathionylation and S-nitrosylation interfere in mitochondrial homeostasis and how the deregulation of these modifications is associated with Alzheimer’s, Parkinson’s, amyotrophic lateral sclerosis and Friedreich’s ataxia.

A postpartum enriched environment rescues impaired cognition and oxidative markers in aged mice with gestational inflammation

INTRODUCTION

Previous studies have shown that gestational inflammation can accelerate age-associated cognitive decline (AACD) in maternal mice; enriched environments (EEs) have been reported to protect normally aging mice from AACD and improve mitochondrial function. However, it is unclear whether the nitrosative stress-related proteins tet methylcytosine dioxygenase 1 (TET1) and S-nitrosoglutathione reductase (GSNOR) are involved in the accelerated aging process of gestational inflammation and whether EEs can slow this process.

METHODS

In this study, CD-1 female mice on the 15th day of pregnancy were injected with bacterial lipopolysaccharide (50 μg/kg; LPS group) or an equivalent amount of normal saline (CON group) from the abdominal cavity for 4 consecutive days. Twenty-one days after delivery, half of the LPS-treated mice were randomly selected for EE until the end of the behavioral experiment (LPS-E group). When the female rats were raised to 6 months and 18 months of age, the Morris water maze (MWM) was used to detect spatial learning and memory ability; RT-PCR and Western blots were used to measure the mRNA and protein levels of hippocampal TET1 and GSNOR.

RESULTS

As for the control group, compared with 6-month-old mice, the spatial learning and memory ability of 18-month-old mice decreased, and the hippocampal TET1 and GSNOR mRNA and protein levels were decreased. Gestational inflammation exacerbated these age-related changes, but an EE alleviated the effects. Pearson's correlation analysis indicated that performance during the learning and memory periods in the MWM correlated with the levels of hippocampal TET1 and GSNOR.

CONCLUSIONS

Our findings suggest that gestational inflammation accelerates age-related learning and memory impairments and that postpartum EE exposure could alleviate these changes. These effects may be related to hippocampal TET1 and GSNOR expression.

The role of mitochondrial fission in cardiovascular health and disease

Mitochondria are organelles involved in the regulation of various important cellular processes, ranging from ATP generation to immune activation. A healthy mitochondrial network is essential for cardiovascular function and adaptation to pathological stressors. Mitochondria undergo fission or fusion in response to various environmental cues, and these dynamic changes are vital for mitochondrial function and health. In particular, mitochondrial fission is closely coordinated with the cell cycle and is linked to changes in mitochondrial respiration and membrane permeability. Another key function of fission is the segregation of damaged mitochondrial components for degradation by mitochondrial autophagy (mitophagy). Mitochondrial fission is induced by the large GTPase dynamin-related protein 1 (DRP1) and is subject to sophisticated regulation. Activation requires various post-translational modifications of DRP1, actin polymerization and the involvement of other organelles such as the endoplasmic reticulum, Golgi apparatus and lysosomes. A decrease in mitochondrial fusion can also shift the balance towards mitochondrial fission. Although mitochondrial fission is necessary for cellular homeostasis, this process is often aberrantly activated in cardiovascular disease. Indeed, strong evidence exists that abnormal mitochondrial fission directly contributes to disease development. In this Review, we compare the physiological and pathophysiological roles of mitochondrial fission and discuss the therapeutic potential of preventing excessive mitochondrial fission in the heart and vasculature.

S-Denitrosylation: A Crosstalk between Glutathione and Redoxin Systems

S-nitrosylation of proteins occurs as a consequence of the derivatization of cysteine thiols with nitric oxide (NO) and is often associated with diseases and protein malfunction. Aberrant S-nitrosylation, in addition to other genetic and epigenetic factors, has gained rapid importance as a prime cause of various metabolic, respiratory, and cardiac disorders, with a major emphasis on cancer and neurodegeneration. The S-nitrosoproteome, a term used to collectively refer to the diverse and dynamic repertoire of S-nitrosylated proteins, is relatively less explored in the field of redox biochemistry, in contrast to other covalently modified versions of the same set of proteins. Advancing research is gradually unveiling the enormous clinical importance of S-nitrosylation in the etiology of diseases and is opening up new avenues of prompt diagnosis that harness this phenomenon. Ever since the discovery of the two robust and highly conserved S-nitrosoglutathione reductase and thioredoxin systems as candidate denitrosylases, years of rampant speculation centered around the identification of specific substrates and other candidate denitrosylases, subcellular localization of both substrates and denitrosylases, the position of susceptible thiols, mechanisms of S-denitrosylation under basal and stimulus-dependent conditions, impact on protein conformation and function, and extrapolating these findings towards the understanding of diseases, aging and the development of novel therapeutic strategies. However, newer insights in the ever-expanding field of redox biology reveal distinct gaps in exploring the crucial crosstalk between the redoxins/major denitrosylase systems. Clarifying the importance of the functional overlap of the glutaredoxin, glutathione, and thioredoxin systems and examining their complementary functions as denitrosylases and antioxidant enzymatic defense systems are essential prerequisites for devising a rationale that could aid in predicting the extent of cell survival under high oxidative/nitrosative stress while taking into account the existence of the alternative and compensatory regulatory mechanisms. This review thus attempts to highlight major gaps in our understanding of the robust cellular redox regulation system, which is upheld by the concerted efforts of various denitrosylases and antioxidants.

Posttranslational S-nitrosylation modification regulates HMGB1 secretion and promotes its proinflammatory and neurodegenerative effects

Nuclear protein high-mobility group box 1 (HMGB1) can be actively secreted by activated immune cells and functions as a proinflammatory cytokine. Regulation of HMGB1 secretion is critical for treatment of HMGB1-mediated inflammation and related diseases. This study demonstrates that S-nitrosylation (SNO; the covalent binding of nitric oxide [NO] to cysteine thiols) by inducible nitric oxide synthase (iNOS)-derived NO at Cys106 is essential and sufficient for inflammation-elicited HMGB1 secretion. iNOS deletion or inhibition or Cys106Ser mutation prevents lipopolysaccharide (LPS)- and/or poly(I:C)-elicited HMGB1 secretion. NO donors induce SNO of HMGB1 and reproduce inflammogen-triggered HMGB1 secretion. SNO of HMGB1 promotes its proinflammatory and neurodegenerative effects. Intranigral HMGB1 injection induces chronic microglial activation, dopaminergic neurodegeneration, and locomotor deficits, the key features of Parkinson’s disease (PD), in wild-type, but not Mac1 (CD11b/CD18)-deficient, mice. This study indicates pivotal roles for SNO modification in HMGB1 secretion and HMGB1-Mac1 interaction for inflammatory neurodegeneration, identifying a mechanistic basis for PD development.

Regulation of HMGB1 secretion is critical for the treatment of HMGB1-mediated inflammation and related diseases. Yang et al. demonstrate that posttranslational S-nitrosylation modification (the covalent binding of nitric oxide to protein cysteine thiols) regulates HMGB1 secretion and promotes its proinflammatory and neurodegenerative effects, thereby contributing to Parkinson’s disease pathogenesis.

The RING finger protein family in health and disease

Ubiquitination is a highly conserved and fundamental posttranslational modification (PTM) in all eukaryotes regulating thousands of proteins. The RING (really interesting new gene) finger (RNF) protein, containing the RING domain, exerts E3 ubiquitin ligase that mediates the covalent attachment of ubiquitin (Ub) to target proteins. Multiple reviews have summarized the critical roles of the tripartite-motif (TRIM) protein family, a subgroup of RNF proteins, in various diseases, including cancer, inflammatory, infectious, and neuropsychiatric disorders. Except for TRIMs, since numerous studies over the past decades have delineated that other RNF proteins also exert widespread involvement in several diseases, their importance should not be underestimated. This review summarizes the potential contribution of dysregulated RNF proteins, except for TRIMs, to the pathogenesis of some diseases, including cancer, autoimmune diseases, and neurodegenerative disorder. Since viral infection is broadly involved in the induction and development of those diseases, this manuscript also highlights the regulatory roles of RNF proteins, excluding TRIMs, in the antiviral immune responses. In addition, we further discuss the potential intervention strategies targeting other RNF proteins for the prevention and therapeutics of those human diseases.

NO news: S-(de)nitrosylation of cathepsins and their relationship with cancer

Tumor formation and progression have been much of a study over the last two centuries. Recent studies have seen different developments for the early diagnosis and treatment of the disease; some of which even promise survival of the patient. Cysteine proteases, mainly cathepsins have been unequivocally identified as putative worthy players of redox imbalance that contribute to the premonition and further progression of cancer by interfering in the normal extracellular and intracellular proteolysis and initiating a proteolytic cascade. The present review article focuses on the study of cancer so far, while establishing facts on how future studies focused on the cellular interrelation between nitric oxide (NO) and cancer, can direct their focus on cathepsins. For a tumor cell to thrive and synergize a cancerous environment, different mutations in the proteolytic and signaling pathways and the proto-oncogenes, oncogenes, and the tumor suppressor genes are made possible through cellular biochemistry and some cancer-stimulating environmental factors. The accumulated findings show that S-nitrosylation of cathepsins under the influence of NO-donors can prevent the invasion of cancer and cause cancer cell death by blocking the activity of cathepsins as well as the major denitrosylase systems using a multi-way approach. Faced with a conundrum of how to fill the gap between the dodging of established cancer hallmarks with cathepsin activity and gaining appropriate research/clinical accreditation using our hypothesis, the scope of this review also explores the interplay and crosstalk between S-nitrosylation and S-(de)nitrosylation of this protease and highlights the utility of charging thioredoxin (Trx) reductase inhibitors, low-molecular-weight dithiols, and Trx mimetics using efficient drug delivery system to prevent the denitrosylation or regaining of cathepsin activity in vivo. In foresight, this raises the prospect that drugs or novel compounds that target cathepsins taking all these factors into consideration could be deployed as alternative or even better treatments for cancer, though further research is needed to ascertain the safety, efficiency and effectiveness of this approach.

GSNOR deficiency attenuates MPTP-induced neurotoxicity and autophagy by facilitating CDK5 S-nitrosation in a mouse model of Parkinson's disease

The S-nitrosoglutathione reductase (GSNOR) is a key denitrosating enzyme that regulates protein S-nitrosation, a process which has been found to be involved in the pathogenesis of Parkinson's disease (PD). However, the physiological function of GSNOR in PD remains unknown. In a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model, we found that GSNOR expression was significantly increased and accompanied by autophagy mediated by MPTP-induced cyclin dependent kinase 5 (CDK5), behavioral dyskinesias and dopaminergic neuron loss. Whereas, knockout of GSNOR, or treatment with the GSNOR inhibitor N6022, alleviated MPTP-induced PD-like pathology and neurotoxicity. Mechanistically, deficiency of GSNOR inhibited MPTP-induced CDK5 kinase activity and CDK5-mediated autophagy by increasing S-nitrosation of CDK5 at Cys83. Our study indicated that GSNOR is a key regulator of CDK5 S-nitrosation and is actively involved in CDK5-mediated autophagy induced by MPTP.

Effects of Aldo-Keto Reductase Family 1 Member A on Osteoblast Differentiation Associated with Lactate Production in MC3T3-E1 Preosteoblastic Cells

Aldo-keto reductase family 1 member A (AKR1A) is an NADPH-dependent aldehyde reductase widely expressed in mammalian tissues. In this study, induced differentiation of MC3T3-E1 preosteoblasts was found to increase AKR1A gene expression concomitantly increased NOx- (nitrite+nitrate), increased glucose uptake, increased [NAD(P)+]/[NAD(P)H] and lactate production but decreased reactive oxygen species (ROS) without changes in eNOS (endothelial nitric oxide synthase) expression in differentiated osteoblasts (OBs). A study using gain- and loss-of-function MC3T3-E1 cells indicated that AKR1A is essential for modulating OB differentiation and gene expression of collagen1 A1, receptor activator of nuclear factor kappa-Β ligand, and osteoprotegerin in OBs. Immunofluorescence microscopy also revealed that changes in AKR1A expression altered extracellular collagen formation in differentiated OBs. Consistently, analyses of alkaline phosphatase activity and calcium deposits of matrix mineralization by Alizarin Red S staining verified that AKR1A is involved in the regulation of OB differentiation and bone matrix formation. In addition, AKR1A gene alterations affected the levels of NOx-, eNOS expression, glucose uptake, [NAD(P)+]/[NAD(P)H] dinucleotide redox couples, lactate production and ROS in differentiated OBs. Herein, we report that AKR1A-mediated denitrosylation may play a role in the regulation of lactate metabolism as well as redox homeostasis in cells, providing an efficient way to quickly gain energy and to significantly reduce oxidative stress for OB differentiation.

Reactive Species in Progeroid Syndromes and Aging-Related Processes

Significance: Reactive species have been classically considered causative of age-related degenerative processes, but the scenario appears considerably more complex and to some extent counterintuitive than originally anticipated. The impact of reactive species in precocious aging syndromes is revealing new clues to understand and perhaps challenge the resulting degenerative processes. Recent Advances: Our understanding of reactive species has considerably evolved, including their hormetic effect (beneficial at a certain level, harmful beyond this level), the occurrence of diverse hormetic peaks in different cell types and organisms, and the extended type of reactive species that are relevant in biological processes. Our understanding of the impact of reactive species has also expanded from the dichotomic damaging/signaling role to modulation of gene expression. Critical Issues: These new concepts are affecting the study of aging and diseases where aging is greatly accelerated. We discuss how notions arising from the study of the underlying mechanisms of a progeroid disease, Cockayne syndrome, represent a paradigm shift that may shed a new light in understanding the role of reactive species in age-related degenerative processes. Future Issues: Future investigations urge to explore established and emerging notions to elucidate the multiple contributions of reactive species in degenerative processes linked to pathophysiological aging and their possible amelioration. Antioxid. Redox Signal. 37, 208-228.

Mitochondrial dysfunction in cell senescence and aging

Mitochondrial dysfunction and cell senescence are hallmarks of aging and are closely interconnected. Mitochondrial dysfunction, operationally defined as a decreased respiratory capacity per mitochondrion together with a decreased mitochondrial membrane potential, typically accompanied by increased production of oxygen free radicals, is a cause and a consequence of cellular senescence and figures prominently in multiple feedback loops that induce and maintain the senescent phenotype. Here, we summarize pathways that cause mitochondrial dysfunction in senescence and aging and discuss the major consequences of mitochondrial dysfunction and how these consequences contribute to senescence and aging. We also highlight the potential of senescence-associated mitochondrial dysfunction as an antiaging and antisenescence intervention target, proposing the combination of multiple interventions converging onto mitochondrial dysfunction as novel, potent senolytics.

The multifaceted regulation of mitophagy by endogenous metabolites

Owing to the dominant functions of mitochondria in multiple cellular metabolisms and distinct types of regulated cell death, maintaining a functional mitochondrial network is fundamental for the cellular homeostasis and body fitness in response to physiological adaptations and stressed conditions. The process of mitophagy, in which the dysfunctional or superfluous mitochondria are selectively engulfed by autophagosome and subsequently degraded in lysosome, has been well formulated as one of the major mechanisms for mitochondrial quality control. To date, the PINK1-PRKN-dependent and receptors (including proteins and lipids)-dependent pathways have been characterized to determine the mitophagy in mammalian cells. The mitophagy is highly responsive to the dynamics of endogenous metabolites, including iron-, calcium-, glycolysis-TCA-, NAD+-, amino acids-, fatty acids-, and cAMP-associated metabolites. Herein, we summarize the recent advances toward the molecular details of mitophagy regulation in mammalian cells. We also highlight the key regulations of mammalian mitophagy by endogenous metabolites, shed new light on the bidirectional interplay between mitophagy and cellular metabolisms, with attempting to provide a perspective insight into the nutritional intervention of metabolic disorders with mitophagy deficit.Abbreviations: acetyl-CoA: acetyl-coenzyme A; ACO1: aconitase 1; ADCYs: adenylate cyclases; AMPK: AMP-activated protein kinase; ATM: ATM serine/threonine kinase; BCL2L1: BCL2 like 1; BCL2L13: BCL2 like 13; BNIP3: BCL2 interacting protein 3; BNIP3L: BCL2 interacting protein 3 like; Ca2+: calcium ion; CALCOCO2: calcium binding and coiled-coil domain 2; CANX: calnexin; CO: carbon monoxide; CYCS: cytochrome c, somatic; DFP: deferiprone; DNM1L: dynamin 1 like; ER: endoplasmic reticulum; FKBP8: FKBP prolyl isomerase 8; FOXO3: forkhead box O3; FTMT: ferritin mitochondrial; FUNDC1: FUN14 domain containing 1; GABA: γ-aminobutyric acid; GSH: glutathione; HIF1A: hypoxia inducible factor 1 subunit alpha; IMMT: inner membrane mitochondrial protein; IRP1: iron regulatory protein 1; ISC: iron-sulfur cluster; ITPR2: inositol 1,4,5-trisphosphate type 2 receptor; KMO: kynurenine 3-monooxygenase; LIR: LC3 interacting region; MAM: mitochondria-associated membrane; MAP1LC3: microtubule associated protein 1 light chain 3; MFNs: mitofusins; mitophagy: mitochondrial autophagy; mPTP: mitochondrial permeability transition pore; MTOR: mechanistic target of rapamycin kinase; NAD+: nicotinamide adenine dinucleotide; NAM: nicotinamide; NMN: nicotinamide mononucleotide; NO: nitric oxide; NPA: Niemann-Pick type A; NR: nicotinamide riboside; NR4A1: nuclear receptor subfamily 4 group A member 1; NRF1: nuclear respiratory factor 1; OPA1: OPA1 mitochondrial dynamin like GTPase; OPTN: optineurin; PARL: presenilin associated rhomboid like; PARPs: poly(ADP-ribose) polymerases; PC: phosphatidylcholine; PHB2: prohibitin 2; PINK1: PTEN induced kinase 1; PPARG: peroxisome proliferator activated receptor gamma; PPARGC1A: PPARG coactivator 1 alpha; PRKA: protein kinase AMP-activated; PRKDC: protein kinase, DNA-activated, catalytic subunit; PRKN: parkin RBR E3 ubiquitin protein ligase; RHOT: ras homolog family member T; ROS: reactive oxygen species; SIRTs: sirtuins; STK11: serine/threonine kinase 11; TCA: tricarboxylic acid; TP53: tumor protein p53; ULK1: unc-51 like autophagy activating kinase 1; VDAC1: voltage dependent anion channel 1.

Protein S-Nitrosation: Biochemistry, Identification, Molecular Mechanisms, and Therapeutic Applications

Protein S-nitrosation (SNO), a posttranslational modification (PTM) of cysteine (Cys) residues elicited by nitric oxide (NO), regulates a wide range of protein functions. As a crucial form of redox-based signaling by NO, SNO contributes significantly to the modulation of physiological functions, and SNO imbalance is closely linked to pathophysiological processes. Site-specific identification of the SNO protein is critical for understanding the underlying molecular mechanisms of protein function regulation. Although careful verification is needed, SNO modification data containing numerous functional proteins are a potential research direction for druggable target identification and drug discovery. Undoubtedly, SNO-related research is meaningful not only for the development of NO donor drugs but also for classic target-based drug design. Herein, we provide a comprehensive summary of SNO, including its origin and transport, identification, function, and potential contribution to drug discovery. Importantly, we propose new views to develop novel therapies based on potential protein SNO-sourced targets.

Enhancing S-nitrosoglutathione reductase decreases S-nitrosylation of Drp1 and reduces neuronal apoptosis in experimental subarachnoid hemorrhage both in vivo and in vitro

Subarachnoid hemorrhage (SAH) is a hemorrhagic stroke with a high mortality and disability rate. Nitric oxide (NO) can promote blood supply through vasodilation, leading to protein S-nitrosylation. However, the function of S-nitrosylation in neurons after SAH remains unclear. Excessive NO in the pathological state is converted into S-nitrosoglutathione (GSNO) and stored in cells, which leads to high S-nitrosylation of intracellular proteins and causes nitrosative stress. S-nitrosoglutathione reductase (GSNOR) promotes GSNO degradation and protects cells from excessive S-nitrosylation. We conducted an in vivo rat carotid puncture model and an in vitro neuron hemoglobin intervention. The results showed that SAH induction increased NO, GSNO, neuron protein S-nitrosylation, and neuronal apoptosis, while decreasing the level and activity of GSNOR. GSNOR overexpression by lentivirus decreased GSNO but had little effect on NO. GSNOR overexpression also improved short- and long-term neurobehavioral outcomes in rats and alleviated nitrosative stress. Furthermore, GSNOR reduced neuronal apoptosis and played a neuroprotective role by alleviating Drp1 S-nitrosylation, reducing mitochondrial division. Thus, the regulation of GSNOR in early brain injury and neuronal denitrosylation may play an important role in neuroprotection.

MicroRNAs, Long Non-Coding RNAs, and Circular RNAs in the Redox Control of Cell Senescence

Cell senescence is critical in diverse aspects of organism life. It is involved in tissue development and homeostasis, as well as in tumor suppression. Consequently, it is tightly integrated with basic physiological processes during life. On the other hand, senescence is gradually being considered as a major contributor of organismal aging and age-related diseases. Increased oxidative stress is one of the main risk factors for cellular damages, and thus a driver of senescence. In fact, there is an intimate link between cell senescence and response to different types of cellular stress. Oxidative stress occurs when the production of reactive oxygen species/reactive nitrogen species (ROS/RNS) is not adequately detoxified by the antioxidant defense systems. Non-coding RNAs are endogenous transcripts that govern gene regulatory networks, thus impacting both physiological and pathological events. Among these molecules, microRNAs, long non-coding RNAs, and more recently circular RNAs are considered crucial mediators of almost all cellular processes, including those implicated in oxidative stress responses. Here, we will describe recent data on the link between ROS/RNS-induced senescence and the current knowledge on the role of non-coding RNAs in the senescence program.

Novel Insight into the Serum Sphingolipid Fingerprint Characterizing Longevity

Sphingolipids (SLs) are structural components of the lipid bilayer regulating cell functions. In biological fluids, their distribution is sex-specific and is at variance in aging and many disorders. The aim of this study is to identify SL species associated with the decelerated aging of centenarians. SLs, extracted from serum of adults (Ad, 35–37 years old), aged (Ag, 75–77 years old) and centenarian (C, 105–107 years old) women were analyzed by LC-MS/MS in combination with mRNA levels in peripheral blood mononuclear cells (PBMCs) of SL biosynthetic enzymes. Results indicated in Ag and C vs. Ad a comparable ceramides (Cers) increase, whereas dihydroceramide (dhCer) decreased in C vs. Ad. Hexosylceramides (HexCer) species, specifically HexCer 16:0, 22:0 and 24:1 acyl chains, increased in C vs. Ag representing a specific trait of C. Sphingosine (Sph), dihydrosphingosine (dhSph), sphingosine-1-phosphate (S1P) and dihydrosphingosine-1-phosphate (dhS1P), increased both in Ag and C vs. Ad, with higher levels in Ag, indicating a SL fine-tuning associated with a reduced physiological decline in C. mRNA levels of enzymes involved in ceramide de novo biosynthesis increased in Ag whereas enzymes involved in sphingomyelin (SM) degradation increased in C. Collectively, results suggest that Ag produce Cers by de novo synthesis whereas C activate a protective mechanism degrading SMs to Cers converting it into glycosphingolipids.

Looking at denitrosylation to understand the myogenesis gone awry theory of rhabdomyosarcoma

S-nitrosylation of proteins is a nitric oxide (NO)-based post-translational modification of cysteine residues. By removing the NO moiety from S-nitrosothiol adducts, denitrosylases restore sulfhydryl protein pool and act as downstream tuners of S-nitrosylation signaling. Alterations in the S-nitrosylation/denitrosylation dynamics are implicated in many pathological states, including cancer ontogenesis and progression, skeletal muscle myogenesis and function. Here, we aim to provide and link different lines of evidence, and elaborate on the possible role of S-nitrosylation/denitrosylation signaling in rhabdomyosarcoma, one of the most common pediatric mesenchymal malignancy.

GSNOR regulates ganoderic acid content in Ganoderma lucidum under heat stress through S-nitrosylation of catalase

As a master regulator of the balance between NO signaling and protein S-nitrosylation, S-nitrosoglutathione (GSNO) reductase (GSNOR) is involved in various developmental processes and stress responses. However, the proteins and specific sites that can be S-nitrosylated, especially in microorganisms, and the physiological functions of S-nitrosylated proteins remain unclear. Herein, we show that the ganoderic acid (GA) content in GSNOR-silenced (GSNORi) strains is significantly lower (by 25%) than in wild type (WT) under heat stress (HS). Additionally, silencing GSNOR results in an 80% increase in catalase (CAT) activity, which consequently decreases GA accumulation via inhibition of ROS signaling. The mechanism of GSNOR-mediated control of CAT activity may be via protein S-nitrosylation. In support of this possibility, we show that CAT is S-nitrosylated (as shown via recombinant protein in vitro and via GSNORi strains in vivo). Additionally, Cys (cysteine) 401, Cys642 and Cys653 in CAT are S-nitrosylation sites (assayed via mass spectrometry analysis), and Cys401 may play a pivotal role in CAT activity. These findings indicate a mechanism by which GSNOR responds to stress and regulates secondary metabolite content through protein S-nitrosylation. Our results also define a new S-nitrosylation site and the function of an S-nitrosylated protein regulated by GSNOR in microorganisms.

Liu et al. identify catalase as a target of S-nitrosylation by GSNOR and the specific sites of S-nitrosylation critical for its role in regulating secondary metabolite production in Ganoderma lucidum under heat stress. This study suggests that GSNOR regulates other metabolic pathways in microorganisms through S-nitrosylation of target proteins in response to environmental changes.