Glutathione S-Transferase Regulates Mitochondrial Populations in Axons through Increased Glutathione Oxidation

Mechanisms underlying targeted mitochondrial therapy for programmed cardiac cell death

Heart diseases are common clinical diseases, such as cardiac fibrosis, heart failure, hypertension and arrhythmia. Globally, the incidence rate and mortality of heart diseases are increasing by years. The main mechanism of heart disease is related to the cellular state. Mitochondrion is the organ of cellular energy supply, participating in various signal transduction pathways and playing a vital role in the occurrence and development of heart disease. This review summarizes the cell death patterns and molecular mechanisms associated with heart disease and mitochondrial dysfunction.

Toxicity mechanism of metal-organic framework HKUST-1 and its carbonized product to Tetradesmus obliquus: Physiological and transcriptomic analysis

Metal-organic frameworks (MOFs) are emerging materials with unique structures and properties, which have been widely used in many fields due to their various advantages. However, compared with its popular application research, the ecological safety of MOFs has rarely been reported. In this paper, a biological model, the common freshwater green algae Tetradesmus obliquus (T. obliquus) was used to study the effects of the copper-based MOF HKUST-1 and its carbonation product DHKUST-1 on the physiology and transcription level of the algae. A suite of advanced material characterization techniques has been utilized to multidimensionally reveal the physicochemical properties of HKUST-1 and its carbonation product. Notably, DHKUST-1 exhibit higher stability than HKUST-1 in aqueous environments, with lower ion release. During a 96-h exposure experiment, relevant indicators such as algae density, chlorophyll-a content and antioxidant enzyme activities were measured. Additionally, an intriguing IBR model was employed to comprehensively assess the toxicity of HKUST-1 and DHKUST-1 on the antioxidant system of T. obliquus. Furthermore, an in-depth analysis was conducted on the differential gene expression changes in T. obliquus under 10 mg/L HKUST-1 stress, exploring the impact on various pathways within algal cells. Briefly, the toxicity mechanism of HKUST-1 on T. obliquus is multi-involved. The findings of this study are expected to provide important basic data and references for the evaluation of the ecological safety of MOFs.

New insights into the functions of ACBD4/5-like proteins using a combined phylogenetic and experimental approach across model organisms

Acyl-CoA binding domain-containing proteins (ACBDs) perform diverse but often uncharacterised functions linked to cellular lipid metabolism. Human ACBD4 and ACBD5 are closely related peroxisomal membrane proteins, involved in tethering of peroxisomes to the ER and capturing fatty acids for peroxisomal β-oxidation. ACBD5 deficiency causes neurological abnormalities including ataxia and white matter disease. Peroxisome-ER contacts depend on an ACBD4/5-FFAT motif, which interacts with ER-resident VAP proteins. As ACBD4/5-like proteins are present in most fungi and all animals, we combined phylogenetic analyses with experimental approaches to improve understanding of their evolution and functions. Notably, all vertebrates exhibit gene sequences for both ACBD4 and ACBD5, while invertebrates and fungi possess only a single ACBD4/5-like protein. Our analyses revealed alterations in domain structure and FFAT sequences, which help understanding functional diversification of ACBD4/5-like proteins. We show that the Drosophila melanogaster ACBD4/5-like protein possesses a functional FFAT motif to tether peroxisomes to the ER via Dm_Vap33. Depletion of Dm_Acbd4/5 caused peroxisome redistribution in wing neurons and reduced life expectancy. In contrast, the ACBD4/5-like protein of the filamentous fungus Ustilago maydis lacks a FFAT motif and does not interact with Um_Vap33. Loss of Um_Acbd4/5 resulted in an accumulation of peroxisomes and early endosomes at the hyphal tip. Moreover, lipid droplet numbers increased, and mitochondrial membrane potential declined, implying altered lipid homeostasis. Our findings reveal differences between tethering and metabolic functions of ACBD4/5-like proteins across evolution, improving our understanding of ACBD4/5 function in health and disease. The need for a unifying nomenclature for ACBD proteins is discussed.

Interaction between acid-tolerant alga Graesiella sp. MA1 and schwertmannite under long-term acidic condition

Schwertmannite (Sch), a typical Fe(III)-oxyhydroxysulphate mineral, is the precipitation reservoir of toxic elements in acid mine drainage (AMD). Acid-tolerant microbes in AMD can participate in the microbe-mediated transformation of Sch, while Sch affects the physiological characteristics of these acid-tolerant microbes. Based on our discovery of algae and Sch enrichment in a contaminated acid mine pit lake, we predicted the interaction between algae and Sch when incubated together. The acid-tolerant alga Graesiella sp. MA1 was isolated from the pit-lake surface water of an acidic mine and incubated with different contents of Sch. Sch was detected as the main product at the end of 81 d; however, there was a weak transformation. The presence of dissolved Fe(II) could be largely attributed to the photoreduction dissolution of Sch, which was promoted by Graesiella sp. MA1. The adaptation and growth phases of Graesiella sp. MA1 differed under Sch stress. The photosynthetic and metabolic activities increased and decreased at the adaptation and growth phases, respectively. The MDA contents and antioxidant activity of SOD, APX, and GSH in algal cells gradually enhanced as the Sch treatment content increased, indicating a defense strategy of Graesiella sp. MA1. Metabolomic analysis revealed that Sch affected the expression of significant differential metabolites in Graesiella sp. MA1. Organic carboxylic acid substances were essentially up-regulated in response to Sch stress. They were abundant in the medium-Sch system with the highest Fe(III) reduction, capable of complexing Fe(III), and underwent photochemical reactions via photo-induced charge transfer. The significant up-regulation of reducing sugars revealed the high energy requirement of Graesiella sp. MA1 under Sch stress. And first enriched KEGG pathway demonstrated the importance of sugar metabolism in Graesiella sp. MA1. Data acquired in this study provide novel insights into extreme acid stress adaptation of acid-tolerant algae and Sch, contributing to furthering understanding of AMD environments.

Adenosine diphosphate released from stressed cells triggers mitochondrial transfer to achieve tissue homeostasis

Cell-to-cell mitochondrial transfer has recently been shown to play a role in maintaining physiological functions of cell. We previously illustrated that mitochondrial transfer within osteocyte dendritic network regulates bone tissue homeostasis. However, the mechanism of triggering this process has not been explored. Here, we showed that stressed osteocytes in mice release adenosine diphosphate (ADP), resulting in triggering mitochondrial transfer from healthy osteocytes to restore the oxygen consumption rate (OCR) and to alleviate reactive oxygen species accumulation. Furthermore, we identified that P2Y2 and P2Y6 transduced the ADP signal to regulate osteocyte mitochondrial transfer. We showed that mitochondrial metabolism is impaired in aged osteocytes, and there were more extracellular nucleotides release into the matrix in aged cortical bone due to compromised membrane integrity. Conditioned medium from aged osteocytes triggered mitochondrial transfer between osteocytes to enhance the energy metabolism. Together, using osteocyte as an example, this study showed new insights into how extracellular ADP triggers healthy cells to rescue energy metabolism crisis in stressed cells via mitochondrial transfer in tissue homeostasis.

A neuron-glia lipid metabolic cycle couples daily sleep to mitochondrial homeostasis

Sleep is thought to be restorative to brain energy homeostasis, but it is not clear how this is achieved. We show here that Drosophila glia exhibit a daily cycle of glial mitochondrial oxidation and lipid accumulation that is dependent on prior wake and requires the Drosophila APOE orthologs NLaz and GLaz, which mediate neuron-glia lipid transfer. In turn, a full night of sleep is required for glial lipid clearance, mitochondrial oxidative recovery and maximal neuronal mitophagy. Knockdown of neuronal NLaz causes oxidative stress to accumulate in neurons, and the neuronal mitochondrial integrity protein, Drp1, is required for daily glial lipid accumulation. These data suggest that neurons avoid accumulation of oxidative mitochondrial damage during wake by using mitophagy and passing damage to glia in the form of lipids. We propose that a mitochondrial lipid metabolic cycle between neurons and glia reflects a fundamental function of sleep relevant for brain energy homeostasis.

Discovery of benzopyridone cyanoacetates as new type of potential broad-spectrum antibacterial candidates

Unique benzopyridone cyanoacetates (BCs) as new type of promising broad-spectrum antibacterial candidates were discovered with large potential to combat the lethal multidrug-resistant bacterial infections. Many prepared BCs showed broad antibacterial spectrum with low MIC values against the tested strains. Some highly active BCs exhibited rapid sterilization capacity, low resistant trend and good predictive pharmacokinetic properties. Furthermore, the highly active sodium BCs (NaBCs) displayed low hemolysis and cytotoxicity, and especially octyl NaBC 5g also showed in vivo potent anti-infective potential and appreciable pharmacokinetic profiles. A series of preliminary mechanistic explorations indicated that these active BCs could effectively eliminate bacterial biofilm and destroy membrane integrity, thus resulting in the leakage of bacterial cytoplasm. Moreover, their unique structures might further bind to intracellular DNA, DNA gyrase and topoisomerase IV through various direct noncovalent interactions to hinder bacterial reproduction. Meanwhile, the active BCs also induced bacterial oxidative stress and metabolic disturbance, thereby accelerating bacterial apoptosis. These results provided a bright hope for benzopyridone cyanoacetates as potential novel multitargeting broad-spectrum antibacterial candidates to conquer drug resistance.

Oxidase enzyme genes are differentially expressed during Acanthamoeba castellanii encystment

Acanthamoeba castellanii, a ubiquitous protozoan, is responsible for significant diseases such as Acanthamoeba keratitis and granulomatous amoebic encephalitis. A crucial survival strategy of A. castellanii involves the formation of highly resistant cysts during adverse conditions. This study delves into the cellular processes underpinning encystment, focusing on gene expression changes related to reactive oxygen species (ROS) balance, with a particular emphasis on mitochondrial processes. Our findings reveal a dynamic response within the mitochondria during encystment, with the downregulation of key enzymes involved in oxidative phosphorylation (COX, AOX, and NADHalt) during the initial 48 h, followed by their overexpression at 72 h. This orchestrated response likely creates a pro-oxidative environment, facilitating encystment. Analysis of other ROS processing enzymes across the cell reveals differential expression patterns. Notably, antioxidant enzymes, such as catalases, glutaredoxins, glutathione S-transferases, peroxiredoxins, and thioredoxins, mirror the mitochondrial trend of downregulation followed by upregulation. Additionally, glycolysis and gluconeogenesis are downregulated during the early stages in order to potentially balance the metabolic requirement of the cyst. Our study underscores the importance of ROS regulation in Acanthamoeba encystment. Understanding these mechanisms offers insights into infection control and identifies potential therapeutic targets. This work contributes to unraveling the complex biology of A. castellanii and may aid in combatting Acanthamoeba-related infections. Further research into ROS and oxidase enzymes is warranted, given the organism's remarkable respiratory versatility.

Mitophagy in Alzheimer's Disease: A Bibliometric Analysis from 2007 to 2022

Background

The investigation of mitophagy in Alzheimer's disease (AD) remains relatively underexplored in bibliometric analysis.

Objective

To delve into the progress of mitophagy, offering a comprehensive overview of research trends and frontiers for researchers.

Methods

Basic bibliometric information, targets, and target-drug-clinical trial-disease extracted from publications identified in the Web of Science Core Collection from 2007 to 2022 were assessed using bibliometric software.

Results

The study encompassed 5,146 publications, displaying a consistent 16-year upward trajectory. The United States emerged as the foremost contributor in publications, with the Journal of Alzheimer's Disease being the most prolific journal. P. Hemachandra Reddy, George Perry, and Xiongwei Zhu are the top 3 most prolific authors. PINK1 and Parkin exhibited an upward trend in the last 6 years. Keywords (e.g., insulin, aging, epilepsy, tauopathy, and mitochondrial quality control) have recently emerged as focal points of interest within the past 3 years. "Mitochondrial dysfunction" is among the top terms in disease clustering. The top 10 drugs/molecules (e.g., curcumin, insulin, and melatonin) were summarized, accompanied by their clinical trials and related targets.

Conclusions

This study presents a comprehensive overview of the mitophagy research landscape in AD over the past 16 years, underscoring mitophagy as an emerging molecular mechanism and a crucial focal point for potential drug in AD. This study pioneers the inclusion of targets and their correlations with drugs, clinical trials, and diseases in bibliometric analysis, providing valuable insights and inspiration for scholars and readers of JADR interested in understanding the potential mechanisms and clinical trials in AD.

Facile synthesis of NS-doped carbon dots as sensitive "ON-OFF-ON" fluorescent sensor for Cu2+ and GSH detection

In this paper, a novel nitrogen and sulfur co-doped carbon quantum dots (NS-CQDs) were successfully prepared by a dehydration exothermic carbonization method. The NS-CQDs exhibited uniform size distribution, splendid photostability, and bright fluorescence emission with a fluorescence quantum yield of 24.1 %. It was found that Cu2+ could quench the fluorescence at 467 nm based on the static quenching effect when Cu2+ was added to the NS-CQDs. At this time, the fluorescence sensor changed from the "ON" state to the "OFF" state. When glutathione (GSH) was further introduced into the NS-CQDs/Cu2+ system, the fluorescence intensity of NS-CQDs was amazingly restored through the coordination reaction between GSH and Cu2+. The fluorescence sensor changed from the "OFF" state to the "ON" state. Therefore, NS-CQDs as an "ON-OFF-ON" fluorescence sensor was designed for sequential detection of Cu2+ and GSH. Furthermore, this study successfully demonstrated the sensor's ability to selectively detect Cu2+ and GSH within a wide concentration range. Specifically, the detection range for Cu2+ was 0.1 μM-200.0 μM with a detection limit of 0.07 μM, while the range for GSH was 0.6 μM-180.0 μM with a detection limit of 0.1 μM. Most importantly, the NS-CQDs nanosensor could reliably monitor Cu2+ and GSH levels in human serum samples, with significant potential for practical applications.

A Switch-On Affinity-Based Iridium(III) Conjugate Probe for Imaging Mitochondrial Glutathione S-Transferase in Breast Cancer Cells

Glutathione S-transferase is heterogeneously expressed in breast cancer cells and is therefore emerging as a potential diagnostic biomarker for studying the heterogeneity of breast cancers. However, available fluorescent probes for GSTs depend heavily on GSTs-catalyzed glutathione (GSH) nucleophilic substitution reactions, making them susceptible to interference by the high concentration of nucleophilic species in the cellular environment. Moreover, the functions of subcellular GSTs are generally overlooked due to the lack of suitable luminescence probes. Herein, we report a highly selective affinity-based luminescence probe 1 for GST in breast cancer cells through tethering a GST inhibitor, ethacrynic acid, to an iridium(III) complex. Compared to activity-based probes which require the use of GSH, this probe could image GST-pi in the mitochondria by directly adducting to GST-pi (or potentially GST-pi/GS) in living cells. Probe 1 possesses desirable photophysical properties including a lifetime of 911 ns, a Stokes shift of 343 nm, and high photostability. The "turn on" luminescence mode of the probe enables highly selective detection of the GST with a limit of detection of 1.01 μM, while its long emission lifetime allows sensitive detection in organic dye-spiked autofluorescence samples by a time-resolved mode. The probe was further applied to specifically and quantitatively visualize MDA-MB-231 cells via specific binding to mitochondrial GST, and could differentiate breast cell lines based on their expression levels of GST. To the best of our knowledge, this probe is the first affinity-based iridium(III) imaging probe for the subcellular GST. Our work provides a valuable tool for unmasking the diverse roles of a subcellular GST in living systems, as well as for studying the heterogeneity of breast cancers.

Cdk12 maintains the integrity of adult axons by suppressing actin remodeling

The role of cyclin-dependent kinases (CDKs) that are ubiquitously expressed in the adult nervous system remains unclear. Cdk12 is enriched in terminally differentiated neurons where its conical role in the cell cycle progression is redundant. We find that in adult neurons Cdk12 acts a negative regulator of actin formation, mitochondrial dynamics and neuronal physiology. Cdk12 maintains the size of the axon at sites proximal to the cell body through the transcription of homeostatic enzymes in the 1-carbon by folate pathway which utilize the amino acid homocysteine. Loss of Cdk12 leads to elevated homocysteine and in turn leads to uncontrolled F-actin formation and axonal swelling. Actin remodeling further induces Drp1-dependent fission of mitochondria and the breakdown of axon-soma filtration barrier allowing soma restricted cargos to enter the axon. We demonstrate that Cdk12 is also an essential gene for long-term neuronal survival and loss of this gene causes age-dependent neurodegeneration. Hyperhomocysteinemia, actin changes, and mitochondrial fragmentation are associated with several neurodegenerative conditions such as Alzheimer's disease and we provide a candidate molecular pathway to link together such pathological events.

Metabolomic and physiological changes of acid-tolerant Graesiella sp. MA1 during long-term acid stress

Algae plays a significant role for the primary production in the oligotrophic ecosystems such as the acid mine pit lakes. Graesiella sp. MA1 was a new acid-tolerant photosynthetic protist isolated from an acid mine pit lake. To understand the acid responses of Graesiella sp. MA1, its physiological changes and metabolomics were studied during long-term acid stress. Photosynthetic pigments, soluble proteins, and antioxidant systems of Graesiella sp. MA1 cells displayed two phases, the adaptation phase and the growth phase. During the adaptation phase, both photosynthetic pigments and soluble proteins were inhibited, while antioxidant activity of SOD, APX, and GSH were promoted to response to the organism's damage. Metabolomics results revealed lipids and organic acids were abundant components in Graesiella sp. MA1 cells. In response to acid stress, the levels of acid-dependent resistant amino acids, including glutamate, aspartate, arginine, proline, lysine, and histidine, accumulated continuously to maintain orderly intracellular metabolic processes. In addition, fatty acids were mainly unsaturated, which could improve the fluidity of the cell membranes under acid stress. Metabolomic and physiological changes showed that Graesiella sp. MA1 had tolerance during long-term acid stress and the potential to be used as a bioremediation strain for the acidic wastewater.

COPI-regulated mitochondria-ER contact site formation maintains axonal integrity

Coat protein complex I (COPI) is best known for its role in Golgi-endoplasmic reticulum (ER) trafficking, responsible for the retrograde transport of ER-resident proteins. The ER is crucial to neuronal function, regulating Ca2+ homeostasis and the distribution and function of other organelles such as endosomes, peroxisomes, and mitochondria via functional contact sites. Here we demonstrate that disruption of COPI results in mitochondrial dysfunction in Drosophila axons and human cells. The ER network is also disrupted, and the neurons undergo rapid degeneration. We demonstrate that mitochondria-ER contact sites (MERCS) are decreased in COPI-deficient axons, leading to Ca2+ dysregulation, heightened mitophagy, and a decrease in respiratory capacity. Reintroducing MERCS is sufficient to rescue not only mitochondrial distribution and Ca2+ uptake but also ER morphology, dramatically delaying neurodegeneration. This work demonstrates an important role for COPI-mediated trafficking in MERC formation, which is an essential process for maintaining axonal integrity.

How neurons maintain their axons long-term: an integrated view of axon biology and pathology

Axons are processes of neurons, up to a metre long, that form the essential biological cables wiring nervous systems. They must survive, often far away from their cell bodies and up to a century in humans. This requires self-sufficient cell biology including structural proteins, organelles, and membrane trafficking, metabolic, signalling, translational, chaperone, and degradation machinery-all maintaining the homeostasis of energy, lipids, proteins, and signalling networks including reactive oxygen species and calcium. Axon maintenance also involves specialised cytoskeleton including the cortical actin-spectrin corset, and bundles of microtubules that provide the highways for motor-driven transport of components and organelles for virtually all the above-mentioned processes. Here, we aim to provide a conceptual overview of key aspects of axon biology and physiology, and the homeostatic networks they form. This homeostasis can be derailed, causing axonopathies through processes of ageing, trauma, poisoning, inflammation or genetic mutations. To illustrate which malfunctions of organelles or cell biological processes can lead to axonopathies, we focus on axonopathy-linked subcellular defects caused by genetic mutations. Based on these descriptions and backed up by our comprehensive data mining of genes linked to neural disorders, we describe the 'dependency cycle of local axon homeostasis' as an integrative model to explain why very different causes can trigger very similar axonopathies, providing new ideas that can drive the quest for strategies able to battle these devastating diseases.

Schizophrenia Synaptic Pathology and Antipsychotic Treatment in the Framework of Oxidative and Mitochondrial Dysfunction: Translational Highlights for the Clinics and Treatment

Schizophrenia is a worldwide mental illness characterized by alterations at dopaminergic and glutamatergic synapses resulting in global dysconnectivity within and between brain networks. Impairments in inflammatory processes, mitochondrial functions, energy expenditure, and oxidative stress have been extensively associated with schizophrenia pathophysiology. Antipsychotics, the mainstay of schizophrenia pharmacological treatment and all sharing the common feature of dopamine D2 receptor occupancy, may affect antioxidant pathways as well as mitochondrial protein levels and gene expression. Here, we systematically reviewed the available evidence on antioxidants' mechanisms in antipsychotic action and the impact of first- and second-generation compounds on mitochondrial functions and oxidative stress. We further focused on clinical trials addressing the efficacy and tolerability of antioxidants as an augmentation strategy of antipsychotic treatment. EMBASE, Scopus, and Medline/PubMed databases were interrogated. The selection process was conducted in respect of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. Several mitochondrial proteins involved in cell viability, energy metabolism, and regulation of oxidative systems were reported to be significantly modified by antipsychotic treatment with differences between first- and second-generation drugs. Finally, antioxidants may affect cognitive and psychotic symptoms in patients with schizophrenia, and although the evidence is only preliminary, the results indicate that further studies are warranted.

Insights from Drosophila on Aβ- and tau-induced mitochondrial dysfunction: mechanisms and tools

Alzheimer's disease (AD) is the most prevalent neurodegenerative dementia in older adults worldwide. Sadly, there are no disease-modifying therapies available for treatment due to the multifactorial complexity of the disease. AD is pathologically characterized by extracellular deposition of amyloid beta (Aβ) and intracellular neurofibrillary tangles composed of hyperphosphorylated tau. Increasing evidence suggest that Aβ also accumulates intracellularly, which may contribute to the pathological mitochondrial dysfunction observed in AD. According with the mitochondrial cascade hypothesis, mitochondrial dysfunction precedes clinical decline and thus targeting mitochondria may result in new therapeutic strategies. Unfortunately, the precise mechanisms connecting mitochondrial dysfunction with AD are largely unknown. In this review, we will discuss how the fruit fly Drosophila melanogaster is contributing to answer mechanistic questions in the field, from mitochondrial oxidative stress and calcium dysregulation to mitophagy and mitochondrial fusion and fission. In particular, we will highlight specific mitochondrial insults caused by Aβ and tau in transgenic flies and will also discuss a variety of genetic tools and sensors available to study mitochondrial biology in this flexible organism. Areas of opportunity and future directions will be also considered.

mRNA Sequencing Reveals Upregulation of Glutathione S-Transferase Genes during Acanthamoeba Encystation

Some members of the genus Acanthamoeba are facultative pathogens typically with a biphasic lifestyle: trophozoites and cysts. Acanthamoeba is capable of infecting the cornea, resulting in Acanthamoeba keratitis. The cyst is one of the key components for the persistence of infection. Gene expression during Acanthamoeba encystation showed an upregulation of glutathione S-transferase (GST) genes and other closely related proteins. mRNA sequencing showed GST, and five genes with similar sequences were upregulated after 24 h of inducing encystation. GST overexpression was verified with qPCR using the HPRT and the cyst-specific protein 21 genes as controls. The GST inhibitor ethacrynic acid was found to decrease cell viability by 70%. These results indicate a role of GST in successful encystation, possibly by maintaining redox balance. GST and associated processes could be targets for potential treatments alongside regular therapies to reduce relapses of Acanthamoeba infection.

GSH-specific fluorescent probe for sensing, bioimaging, rapid screening of natural inhibitor Celastrol and ccRCC theranostics

High level of intracellular glutathione (GSH) has been identified as a major barrier for cancer therapy. Therefore, effective regulation of GSH can be regarded as a novel approach for cancer therapy. In this study, an off-on fluorescent probe (NBD-P) is developed for selective and sensitive sensing GSH. NBD-P has a good cell membrane permeability that can be applied in bioimaging endogenous GSH in living cells. Moreover, the NBD-P probe is used to visualize GSH in animal models. In addition, a rapid drug screening method is successfully established using the fluorescent probe NBD-P. A potent natural inhibitor of GSH is identified as Celastrol from Tripterygium wilfordii Hook F, which effectively triggers mitochondrial apoptosis in clear cell renal cell carcinoma (ccRCC). More importantly, NBD-P can selectively respond to GSH fluctuations to distinguish cancer tissues from normal tissues. Thus, the present study provides insights into fluorescence probes for the screening GSH inhibitors and cancer diagnosis, as well as in-depth exploration of the anti-cancer effects of Traditional Chinese Medicine (TCM).

An ultrasensitive GSH-specific fluorescent probe unveils celastrol-induced ccRCC ferroptosis

Glutathione (GSH) is closely related to the occurrence and development of tumors. The intracellular GSH levels are abnormally altered when tumor cells undergo programmed cell death. Therefore, real-time monitoring of the dynamic changes of intracellular GSH levels can better enable the early diagnosis of diseases and evaluate the effects of cell death-inducing drugs. In this study, a stable and highly selective fluorescent probe AR has been designed and synthesized for the fluorescence imaging and rapid detection of GSH in vitro and in vivo, as well as patient-derived tumor tissue. More importantly, the AR probe can be used to track changes in GSH levels and fluorescence imaging during the treatment of clear cell renal cell carcinoma (ccRCC) with celastrol (CeT) via inducing ferroptosis. These findings demonstrate that the developed fluorescent probe AR exhibits high selectivity and sensitivity, as well as good biocompatibility and long-term stability, which can be used to image endogenous GSH in living tumors and cells. Also, a significant decrease in GSH levels was observed by the fluorescent probe AR during the treatment of ccRCC with CeT-induced ferroptosis in vitro and in vivo. Overall, these findings will provide a novel strategy for celastrol targeting ferroptosis in the treatment of ccRCC and the application of fluorescent probes to help reveal the underlying mechanism of CeT in the treatment of ccRCC.

MORN4 protects cardiomyocytes against ischemic injury via MFN2-mediated mitochondrial dynamics and mitophagy

The imbalance of mitochondrial fission and fusion dynamics causes ischemic cardiomyocyte apoptosis and heart injury by affecting mitophagy. Regulation of mitochondrial dynamics is an important therapeutic strategy for ischemic heart diseases. Considering the important roles of MORN motifs in heart diseases and chloroplast fission, we aimed to investigate the possible role of MORN repeat-containing protein 4 (MORN4) in the progression of myocardial infarction (MI), ischemic cardiomyocyte apoptosis, mitochondrial dynamics, and mitophagy. We found that in the MI mouse, MORN4 knockdown remarkably accelerated cardiac injury and fibrosis with deteriorating cardiac dysfunction. Sphingosylphosphorylcholine (SPC) alleviated ischemic cardiomyocyte apoptosis and heart injury through increased level of MORN4, indicating a vital function of MORN4 in heart with SPC used to clarify the molecular mechanisms underlying the functions of MORN4. Mechanistically, we found that MORN4 directly binds to MFN2 and promotes the phosphorylation of MFN2 S442 through Rho-associated protein kinase 2 (ROCK2), which mediates beneficial mitophagy induced by mitochondrial dynamics, while SPC promoted the binding of MORN4 and MFN2 and the process. Taken together, our data reveal a new perspective role of MORN4 in ischemic heart injury, and report that SPC could regulate myocardial mitochondrial homeostasis by activating the MORN4-MFN2 axis during the ischemic situation, this finding provides novel targets for improving myocardial ischemia tolerance and rescue of acute myocardial infarction.

Analysis of Mitochondrial Dynamics in Adult Drosophila Axons

Neuronal survival depends on the generation of ATP from an ever-changing mitochondrial network. This requires a fine balance between the constant degradation of damaged mitochondria, biogenesis of new mitochondria, movement along microtubules, dynamic processes, and adequate functional capacity to meet firing demands. The distribution of mitochondria needs to be tightly controlled throughout the entire neuron, including its projections. Axons in particular can be enormous structures compared to the size of the cell soma, and how mitochondria are maintained in these compartments is poorly defined. Mitochondrial dysfunction in neurons is associated with aging and neurodegenerative diseases, with the axon being preferentially vulnerable to destruction. Drosophila offer a unique way to study these organelles in fully differentiated adult neurons in vivo. Here, we briefly review the regulation of neuronal mitochondria in health, aging, and disease and introduce two methodological approaches to study mitochondrial dynamics and transport in axons using the Drosophila wing system.

Clonal Imaging of Mitochondria in the Dissected Fly Wing

Mitochondria are essential for long-term neuronal function and survival. They are maintained in neurons, including long axonal stretches, through dynamic processes such as fission, fusion, biogenesis, and mitophagy. Here, we describe a protocol for the in-depth morphological analysis of individual mitochondria in axons in vivo. Most mitochondrial analysis of axons is currently performed in vitro with neurons in a developmental state. Therefore, an understanding of the axonal mitochondrial network during aging in fully differentiated neurons and the long-term consequence of gene knockout is often not developed. By using a clonal system paired with fluorescent genetically encoded markers in the Drosophila wing, we can visualize individual neurons (out of the whole bundle), including their long axons and the mitochondria that they contain, using confocal imaging. The clonal system also allows visualization of neurons with genetic perturbations that would otherwise be lethal if present in the whole organism, allowing investigators to bypass lethality. This protocol can further be adapted to measure the physiological and biochemical state of the mitochondria. Mitochondrial morphology and health in axons are tightly linked to aging, axon injury, and neurodegeneration; therefore, this method can be used to investigate mitochondrial dysfunction associated with novel genes or those linked to neurodegenerative disease and axonopathy.

Minimal adaptation of the molecular regulators of mitochondrial dynamics in response to unilateral limb immobilisation and retraining in middle-aged men

PURPOSE

Mitochondrial dynamics are regulated by the differing molecular pathways variously governing biogenesis, fission, fusion, and mitophagy. Adaptations in mitochondrial morphology are central in driving the improvements in mitochondrial bioenergetics following exercise training. However, there is a limited understanding of mitochondrial dynamics in response to inactivity.

METHODS

Skeletal muscle biopsies were obtained from middle-aged males (n = 24, 49.4 ± 3.2 years) who underwent sequential 14-day interventions of unilateral leg immobilisation, ambulatory recovery, and resistance training. We quantified vastus lateralis gene and protein expression of key proteins involved in mitochondrial biogenesis, fusion, fission, and turnover in at baseline and following each intervention.

RESULTS

PGC1α mRNA decreased 40% following the immobilisation period, and was accompanied by a 56% reduction in MTFP1 mRNA, a factor involved in mitochondrial fission. Subtle mRNA decreases were also observed in TFAM (17%), DRP1 (15%), with contrasting increases in BNIP3L and PRKN following immobilisation. These changes in gene expression were not accompanied by changes in respective protein expression. Instead, we observed subtle decreases in NRF1 and MFN1 protein expression. Ambulatory recovery restored mRNA and protein expression to pre-intervention levels of all altered components, except for BNIP3L. Resistance training restored BNIP3L mRNA to pre-intervention levels, and further increased mRNA expression of OPA-1, MFN2, MTFP1, and PINK1 past baseline levels.

CONCLUSION

In healthy middle-aged males, 2 weeks of immobilisation did not induce dramatic differences in markers of mitochondria fission and autophagy. Restoration of ambulatory physical activity following the immobilisation period restored altered gene expression patterns to pre-intervention levels, with little evidence of further adaptation to resistance exercise training.

Glutathione S-transferases Control astrocyte activation and neuronal health during neuroinflammation

Glutathione S-transferases (GST) are phase II detoxification enzymes of xenobiotic metabolism and readily expressed in the brain. Nevertheless, the current knowledge about their roles in the brain is limited. We have recently discovered that GSTM1 promotes the production of pro-inflammatory mediators by astrocytes and enhances microglial activation during acute brain inflammation. Here we report that GSTM1 significantly affects TNF-α-dependent transcriptional program in astrocytes and modulates neuronal activities and stress during brain inflammation. We have found that a reduced expression of GSTM1 in astrocytes downregulates the expression of pro-inflammatory genes while upregulating the expression of genes involved in interferon responses and fatty acid metabolism. Our data also revealed that GSTM1 reduction in astrocytes increased neuronal stress levels, attenuating neuronal activities during LPS-induced brain inflammation. Furthermore, we found that GSTM1 expression increased in the frontal cortex and hippocampus of aging mice. Thus, this study has further advanced our understanding of the role of Glutathione S-transferases in astrocytes during brain inflammation and paved the way for future studies to determine the critical role of GSTM1 in reactive astrocyte responses in inflammation and aging.

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.

Oral Administration of Glutathione Trisulfide Increases Reactive Sulfur Levels in Dorsal Root Ganglion and Ameliorates Paclitaxel-Induced Peripheral Neuropathy in Mice

Peripheral neuropathy is a dose-limiting side effect of chemotherapy with paclitaxel. Paclitaxel-induced peripheral neuropathy (PIPN) is typically characterized by a predominantly sensory neuropathy presenting with allodynia, hyperalgesia and spontaneous pain. Oxidative mitochondrial damage in peripheral sensory neurons is implicated in the pathogenesis of PIPN. Reactive sulfur species, including persulfides (RSSH) and polysulfides (RSnH), are strong nucleophilic and electrophilic compounds that exert antioxidant effects and protect mitochondria. Here, we examined the potential neuroprotective effects of glutathione trisulfide (GSSSG) in a mouse model of PIPN. Intraperitoneal administration of paclitaxel at 4 mg/kg/day for 4 days induced mechanical allodynia and thermal hyperalgesia in mice. Oral administration of GSSSG at 50 mg/kg/day for 28 days ameliorated mechanical allodynia, but not thermal hyperalgesia. Two hours after oral administration, 34S-labeled GSSSG was detected in lumber dorsal root ganglia (DRG) and in the lumber spinal cord. In mice treated with paclitaxel, GSSSG upregulated expression of genes encoding antioxidant proteins in lumber DRG, prevented loss of unmyelinated axons and inhibited degeneration of mitochondria in the sciatic nerve. In cultured primary neurons from cortex and DRG, GSSSG mitigated paclitaxel-induced superoxide production, loss of axonal mitochondria, and axonal degeneration. These results indicate that oral administration of GSSSG mitigates PIPN by preventing axonal degeneration and mitochondria damage in peripheral sensory nerves. The findings suggest that administration of GSSSG may be an approach to the treatment or prevention of PIPN and other peripheral neuropathies.

Discovery of novel phenylhydrazone-based oxindole-thiolazoles as potent antibacterial agents toward Pseudomonas aeruginosa

With the soaring of bacterial infection and drug resistance, it is imperative to exploit new efficient antibacterial agents. This work constructed a series of unique phenylhydrazone-based oxindole-thiolazoles to combat monstrous bacterial resistance. Some target molecules showed potent antibacterial activity, among which oxindole-thiolimidazole derived carboxyphenylhydrazone 4e exhibited an 8-fold stronger inhibitory ability than norfloxacin on the growth of P. aeruginosa, with MIC value of 1 μg/mL. Compound 4e with imperceptible hemolysis could hamper bacterial biofilm formation and significantly impede the development of bacterial resistance. Subsequent mechanism studies demonstrated that 4e could destruct bacterial cytoplasmic membrane, causing the leakage of cellular contents (protein and nucleic acid). Moreover, metabolic stagnation and intracellular oxidative stress caused by 4e expedited the death of bacteria. Furthermore, molecule 4e existed supramolecular interactions with DNA to block DNA proliferation. These research results provided a promising light for phenylhydrazone-based oxindole-thiolazoles as novel potential antibacterial agents.

Recent insights into the role of glia and oxidative stress in Alzheimer's disease gained from Drosophila

Here, we discuss findings made using Drosophila on Alzheimer's disease (AD) risk and progression. Recent studies have investigated the mechanisms underlying glia-mediated neuroprotection in AD. First, we discuss a novel mechanism of glial lipid droplet formation that occurs in response to elevated reactive oxygen species in neurons. The data suggest that disruptions to this process contribute to AD risk. We further discuss novel mechanistic insights into glia-mediated Aβ42-clearance made using the fly. Finally, we highlight work that provides evidence that the aberrant accumulation of reactive oxygen species in AD may not just be a consequence of disease but contribute to disease progression as well. Cumulatively, the discussed studies highlight recent, relevant discoveries in AD made using Drosophila.

Detailed Imaging of Mitochondrial Transport and Precise Manipulation of Mitochondrial Function with Genetically Encoded Photosensitizers in Adult Drosophila Neurons

Precise distribution of mitochondria is essential for maintaining neuronal homeostasis. Although detailed mechanisms governing the transport of mitochondria have emerged, it is still poorly understood how the regulation of transport is coordinated in space and time within the physiological context of an organism. How alteration in mitochondrial functionality may trigger changes in organellar dynamics also remains unclear in this context. Therefore, the use of genetically encoded tools to perturb mitochondrial functionality in real time would be desirable. Here we describe methods to interfere with mitochondrial function with high spatiotemporal precision with the use of photosensitizers in vivo in the intact wing nerve of adult Drosophila. We also provide details on how to visualize the transport of mitochondria and to improve the quality of the imaging to attain super-resolution in this tissue.

Dopaminergic Ric GTPase activity impacts amphetamine sensitivity and sleep quality in a dopamine transporter-dependent manner in Drosophila melanogaster

Dopamine (DA) is required for movement, sleep, and reward, and DA signaling is tightly controlled by the presynaptic DA transporter (DAT). Therapeutic and addictive psychostimulants, including methylphenidate (Ritalin; MPH), cocaine, and amphetamine (AMPH), markedly elevate extracellular DA via their actions as competitive DAT inhibitors (MPH, cocaine) and substrates (AMPH). DAT silencing in mice and invertebrates results in hyperactivity, reduced sleep, and blunted psychostimulant responses, highlighting DAT's essential role in DA-dependent behaviors. DAT surface expression is not static; rather it is dynamically regulated by endocytic trafficking. PKC-stimulated DAT endocytosis requires the neuronal GTPase, Rit2, and Rit2 silencing in mouse DA neurons impacts psychostimulant sensitivity. However, it is unknown whether or not Rit2-mediated changes in psychostimulant sensitivity are DAT-dependent. Here, we leveraged Drosophila melanogaster to test whether the Drosophila Rit2 ortholog, Ric, impacts dDAT function, trafficking, and DA-dependent behaviors. Orthologous to hDAT and Rit2, dDAT and Ric directly interact, and the constitutively active Ric mutant Q117L increased dDAT surface levels and function in cell lines and ex vivo Drosophila brains. Moreover, DAergic RicQ117L expression caused sleep fragmentation in a DAT-dependent manner but had no effect on total sleep and daily locomotor activity. Importantly, we found that Rit2 is required for AMPH-stimulated DAT internalization in mouse striatum, and that DAergic RicQ117L expression significantly increased Drosophila AMPH sensitivity in a DAT-dependent manner, suggesting a conserved impact of Ric-dependent DAT trafficking on AMPH sensitivity. These studies support that the DAT/Rit2 interaction impacts both baseline behaviors and AMPH sensitivity, potentially by regulating DAT trafficking.

Is There a Glutathione Centered Redox Dysregulation Subtype of Schizophrenia?

Schizophrenia continues to be an illness with poor outcome. Most mechanistic changes occur many years before the first episode of schizophrenia; these are not reversible after the illness onset. A developmental mechanism that is still modifiable in adult life may center on intracortical glutathione (GSH). A large body of pre-clinical data has suggested the possibility of notable GSH-deficit in a subgroup of patients with schizophrenia. Nevertheless, studies of intracortical GSH are not conclusive in this regard. In this review, we highlight the recent ultra-high field magnetic resonance spectroscopic studies linking GSH to critical outcome measures across various stages of schizophrenia. We discuss the methodological steps required to conclusively establish or refute the persistence of GSH-deficit subtype and clarify the role of the central antioxidant system in disrupting the brain structure and connectivity in the early stages of schizophrenia. We propose in-vivo GSH quantification for patient selection in forthcoming antioxidant trials in psychosis. This review offers directions for a promising non-dopaminergic early intervention approach in schizophrenia.

Redox as a bioprocess parameter: analytical redox quantification in biological therapeutic production

Engineered Chinese hamster ovary (CHO) cells are the most widely utilized cell line for protein-based therapeutics production at industrial scales. Process development strategies which improve production capacity and quality are often implemented without an understanding of underlying intracellular changes. Intracellular redox conditions drive reactions in pathways critical to biologics production, including bioenergetic and biosynthetic pathways, necessitating methods to quantify redox-related changes. Advances in methods for analytical redox quantification presented here, including bioreactor probes, redox-targeted proteomics, genetically encoded redox-sensitive fluorescent proteins, and biochemical assays, are creating new opportunities to characterize the effects of redox in biologics production. Implementing these methods will lead to enhanced media formulations, improved bioprocess strategies, and new cell line engineering targets and ultimately develop redox into an optimizable bioprocess parameter to improve the yield and quality of these lifesaving medicines.

Molecular design and preparation of 2-aminothiazole sulfanilamide oximes as membrane active antibacterial agents for drug resistant Acinetobacter baumannii

A series of 2-aminothiazole sulfanilamide oximes were developed as new membrane active antibacterial agents to conquer the microbial infection. Benzoyl derivative 10c was preponderant for the treatment of drug-resistant A. baumannii infection in contrast to norfloxacin and exerted excellent biocompatibility against mammalian cells including erythrocyte and LO2 cell line. Meanwhile, it had ability to eradicate established biofilm to alleviate the resistance burden. Mechanism investigation elucidated that compound 10c was able to disturb the membrane effectively and inhibit lactic dehydrogenase, which led to cytoplasmic content leakage. The cellular redox homeostasis was interfered via the production of reactive oxygen and nitrogen species (RONS), which further contributed to respiratory pathway inactivation and reduction of GSH activity. This work indicated that 2-aminothiazole sulfanilamide oximes could be a promising start for the exploitation of novel antibacterial agents against pathogens.

TSG101 negatively regulates mitochondrial biogenesis in axons

There is a tight association between mitochondrial dysfunction and neurodegenerative diseases and axons that are particularly vulnerable to degeneration, but how mitochondria are maintained in axons to support their physiology remains poorly defined. In an in vivo forward genetic screen for mutants altering axonal mitochondria, we identified tsg101 Neurons mutant for tsg101 exhibited an increase in mitochondrial number and decrease in mitochondrial size. TSG101 is best known as a component of the endosomal sorting complexes required for transport (ESCRT) complexes; however, loss of most other ESCRT components did not affect mitochondrial numbers or size, suggesting TSG101 regulates mitochondrial biology in a noncanonical, ESCRT-independent manner. The TSG101-mutant phenotype was not caused by lack of mitophagy, and we found that autophagy blockade was detrimental only to the mitochondria in the cell bodies, arguing mitophagy and autophagy are dispensable for the regulation of mitochondria number in axons. Interestingly, TSG101 mitochondrial phenotypes were instead caused by activation of PGC-1ɑ/Nrf2-dependent mitochondrial biogenesis, which was mTOR independent and TFEB dependent and required the mitochondrial fission-fusion machinery. Our work identifies a role for TSG101 in inhibiting mitochondrial biogenesis, which is essential for the maintenance of mitochondrial numbers and sizes, in the axonal compartment.

A Perspective on Accelerated Aging Caused by the Genetic Deficiency of the Metabolic Protein, OPA1

Autosomal Dominant Optic Atrophy (ADOA) is an ophthalmological condition associated primarily with mutations in the OPA1 gene. It has variable onset, sometimes juvenile, but in other patients, the disease does not manifest until adult middle age despite the presence of a pathological mutation. Thus, individuals carrying mutations are considered healthy before the onset of clinical symptoms. Our research, nonetheless, indicates that on the cellular level pathology is evident from birth and mutant cells are different from controls. We argue that the adaptation and early recruitment of cytoprotective responses allows normal development and functioning but leads to an exhaustion of cellular reserves, leading to premature cellular aging, especially in neurons and skeletal muscle cells. The appearance of clinical symptoms, thus, indicates the overwhelming of natural cellular defenses and break-down of native protective mechanisms.

Mitochondrial hyperfusion: a friend or a foe

The cellular mitochondrial population undergoes repeated cycles of fission and fusion to maintain its integrity, as well as overall cellular homeostasis. While equilibrium usually exists between the fission-fusion dynamics, their rates are influenced by organellar and cellular metabolic and pathogenic conditions. Under conditions of cellular stress, there is a disruption of this fission and fusion balance and mitochondria undergo either increased fusion, forming a hyperfused meshwork or excessive fission to counteract stress and remove damaged mitochondria via mitophagy. While some previous reports suggest that hyperfusion is initiated to ameliorate cellular stress, recent studies show its negative impact on cellular health in disease conditions. The exact mechanism of mitochondrial hyperfusion and its role in maintaining cellular health and homeostasis, however, remain unclear. In this review, we aim to highlight the different aspects of mitochondrial hyperfusion in either promoting or mitigating stress and also its role in immunity and diseases.

Mitochondria-lysosome membrane contacts are defective in GDAP1-related Charcot-Marie-Tooth disease

Mutations in the GDAP1 gene cause Charcot-Marie-Tooth (CMT) neuropathy. GDAP1 is an atypical glutathione S-transferase (GST) of the outer mitochondrial membrane and the mitochondrial membrane contacts with the endoplasmic reticulum (MAMs). Here, we investigate the role of this GST in the autophagic flux and the membrane contact sites (MCSs) between mitochondria and lysosomes in the cellular pathophysiology of GDAP1 deficiency. We demonstrate that GDAP1 participates in basal autophagy and that its depletion affects LC3 and PI3P biology in autophagosome biogenesis and membrane trafficking from MAMs. GDAP1 also contributes to the maturation of lysosome by interacting with PYKfyve kinase, a pH-dependent master lysosomal regulator. GDAP1 deficiency causes giant lysosomes with hydrolytic activity, a delay in the autophagic lysosome reformation, and TFEB activation. Notably, we found that GDAP1 interacts with LAMP-1, which supports that GDAP1-LAMP-1 is a new tethering pair of mitochondria and lysosome membrane contacts. We observed mitochondria-lysosome MCSs in soma and axons of cultured mouse embryonic motor neurons and human neuroblastoma cells. GDAP1 deficiency reduces the MCSs between these organelles, causes mitochondrial network abnormalities, and decreases levels of cellular glutathione (GSH). The supply of GSH-MEE suffices to rescue the lysosome membranes and the defects of the mitochondrial network, but not the interorganelle MCSs nor early autophagic events. Overall, we show that GDAP1 enables the proper function of mitochondrial MCSs in both degradative and nondegradative pathways, which could explain primary insults in GDAP1-related CMT pathophysiology, and highlights new redox-sensitive targets in axonopathies where mitochondria and lysosomes are involved.

The redox language in neurodegenerative diseases: oxidative post-translational modifications by hydrogen peroxide

Neurodegenerative diseases, a subset of age-driven diseases, have been known to exhibit increased oxidative stress. The resultant increase in reactive oxygen species (ROS) has long been viewed as a detrimental byproduct of many cellular processes. Despite this, therapeutic approaches using antioxidants were deemed unsuccessful in circumventing neurodegenerative diseases. In recent times, it is widely accepted that these toxic by-products could act as secondary messengers, such as hydrogen peroxide (H₂O₂), to drive important signaling pathways. Notably, mitochondria are considered one of the major producers of ROS, especially in the production of mitochondrial H₂O₂. As a secondary messenger, cellular H₂O₂ can initiate redox signaling through oxidative post-translational modifications (oxPTMs) on the thiol group of the amino acid cysteine. With the current consensus that cellular ROS could drive important biological signaling pathways through redox signaling, researchers have started to investigate the role of cellular ROS in the pathogenesis of neurodegenerative diseases. Moreover, mitochondrial dysfunction has been linked to various neurodegenerative diseases, and recent studies have started to focus on the implications of mitochondrial ROS from dysfunctional mitochondria on the dysregulation of redox signaling. Henceforth, in this review, we will focus our attention on the redox signaling of mitochondrial ROS, particularly on mitochondrial H₂O₂, and its potential implications with neurodegenerative diseases.

Mitochondrial Glutathione: Recent Insights and Role in Disease

Mitochondria are the main source of reactive oxygen species (ROS), most of them deriving from the mitochondrial respiratory chain. Among the numerous enzymatic and non-enzymatic antioxidant systems present in mitochondria, mitochondrial glutathione (mGSH) emerges as the main line of defense for maintaining the appropriate mitochondrial redox environment. mGSH’s ability to act directly or as a co-factor in reactions catalyzed by other mitochondrial enzymes makes its presence essential to avoid or to repair oxidative modifications that can lead to mitochondrial dysfunction and subsequently to cell death. Since mitochondrial redox disorders play a central part in many diseases, harboring optimal levels of mGSH is vitally important. In this review, we will highlight the participation of mGSH as a contributor to disease progression in pathologies as diverse as Alzheimer’s disease, alcoholic and non-alcoholic steatohepatitis, or diabetic nephropathy. Furthermore, the involvement of mitochondrial ROS in the signaling of new prescribed drugs and in other pathologies (or in other unmet medical needs, such as gender differences or coronavirus disease of 2019 (COVID-19) treatment) is still being revealed; guaranteeing that research on mGSH will be an interesting topic for years to come.

Aging shifts mitochondrial dynamics toward fission to promote germline stem cell loss

Changes in mitochondrial dynamics (fusion and fission) are known to occur during stem cell differentiation; however, the role of this phenomenon in tissue aging remains unclear. Here, we report that mitochondrial dynamics are shifted toward fission during aging of Drosophila ovarian germline stem cells (GSCs), and this shift contributes to aging-related GSC loss. We found that as GSCs age, mitochondrial fragmentation and expression of the mitochondrial fission regulator, Dynamin-related protein (Drp1), are both increased, while mitochondrial membrane potential is reduced. Moreover, preventing mitochondrial fusion in GSCs results in highly fragmented depolarized mitochondria, decreased BMP stemness signaling, impaired fatty acid metabolism, and GSC loss. Conversely, forcing mitochondrial elongation promotes GSC attachment to the niche. Importantly, maintenance of aging GSCs can be enhanced by suppressing Drp1 expression to prevent mitochondrial fission or treating with rapamycin, which is known to promote autophagy via TOR inhibition. Overall, our results show that mitochondrial dynamics are altered during physiological aging, affecting stem cell homeostasis via coordinated changes in stemness signaling, niche contact, and cellular metabolism. Such effects may also be highly relevant to other stem cell types and aging-induced tissue degeneration.

Temporal Control of Axonal Transport: The Extreme Case of Organismal Ageing

A fundamental question in cell biology is how cellular components are delivered to their destination with spatial and temporal precision within the crowded cytoplasmic environment. The long processes of neurons represent a significant spatial challenge and make these cells particularly dependent on mechanisms for long-range cytoskeletal transport of proteins, RNA and organelles. Although many studies have substantiated a role for defective transport of axonal cargoes in the pathogenesis of neurodevelopmental and neurodegenerative diseases, remarkably little is known about how transport is regulated throughout ageing. The scale of the challenge posed by ageing is considerable because, in this case, the temporal regulation of transport is ultimately dictated by the length of organismal lifespan, which can extend to days, years or decades. Recent methodological advances to study live axonal transport during ageing in situ have provided new tools to scratch beneath the surface of this complex problem and revealed that age-dependent decline in the transport of mitochondria is a common feature across different neuronal populations of several model organisms. In certain instances, the molecular pathways that affect transport in ageing animals have begun to emerge. However, the functional implications of these observations are still not fully understood. Whether transport decline is a significant determinant of neuronal ageing or a mere consequence of decreased cellular fitness remains an open question. In this review, we discuss the latest developments in axonal trafficking in the ageing nervous system, along with the early studies that inaugurated this new area of research. We explore the possibility that the interplay between mitochondrial function and motility represents a crucial driver of ageing in neurons and put forward the hypothesis that declining axonal transport may be legitimately considered a hallmark of neuronal ageing.

The Glucosinolates: A Sulphur Glucoside Family of Mustard Anti-Tumour and Antimicrobial Phytochemicals of Potential Therapeutic Application

This study reviewed aspects of the biology of two members of the glucosinolate family, namely sinigrin and glucoraphanin and their anti-tumour and antimicrobial properties. Sinigrin and glucoraphanin are converted by the β-sulphoglucosidase myrosinase or the gut microbiota into their bioactive forms, allyl isothiocyanate (AITC) and sulphoraphanin (SFN) which constitute part of a sophisticated defence system plants developed over several hundred million years of evolution to protect them from parasitic attack from aphids, ticks, bacteria or nematodes. Delivery of these components from consumption of cruciferous vegetables rich in the glucosinolates also delivers many other members of the glucosinolate family so the dietary AITCs and SFN do not act in isolation. In vitro experiments with purified AITC and SFN have demonstrated their therapeutic utility as antimicrobials against a range of clinically important bacteria and fungi. AITC and SFN are as potent as Vancomycin in the treatment of bacteria listed by the World Health Organisation as antibiotic-resistant “priority pathogens” and also act as anti-cancer agents through the induction of phase II antioxidant enzymes which inactivate potential carcinogens. Glucosinolates may be useful in the treatment of biofilms formed on medical implants and catheters by problematic pathogenic bacteria such as Pseudomonas aeruginosa and Staphylococcus aureus and are potent antimicrobials against a range of clinically important bacteria and fungi. The glucosinolates have also been applied in the prevention of bacterial and fungal spoilage of food products in advanced atmospheric packaging technology which improves the shelf-life of these products.