The cell biology of mitochondrial membrane dynamics

Recent development of mitochondrial metabolism and dysfunction in osteoarthritis

Osteoarthritis is a degenerative joint disorder characterized by cartilage degradation, synovial inflammation, and altered subchondral bone structure. Recent insights have identified mitochondrial dysfunction as a pivotal factor in OA pathogenesis, contributing to chondrocyte apoptosis, oxidative stress, and extracellular matrix degradation. Disruptions in mitochondrial dynamics, including impaired biogenesis, mitophagy, and metabolic shifts from oxidative phosphorylation to glycolysis, exacerbate cartilage damage by promoting the production of reactive oxygen species and matrix-degrading enzymes such as ADAMTS and MMPs. This review explores the molecular mechanisms underlying mitochondrial dysfunction in OA, emphasizing its role in cartilage homeostasis and inflammation. Furthermore, it highlights emerging therapeutic strategies targeting mitochondrial pathways, including antioxidants, mitophagy enhancers, and metabolic modulators, as potential interventions to mitigate disease progression, which offer promising avenues for advancing personalized and disease-modifying treatments in OA.

Pharmacologic activation of integrated stress response kinases inhibits pathologic mitochondrial fragmentation

Excessive mitochondrial fragmentation is associated with the pathologic mitochondrial dysfunction implicated in the pathogenesis of etiologically diverse diseases, including many neurodegenerative disorders. The integrated stress response (ISR) - comprising the four eIF2α kinases PERK, GCN2, PKR, and HRI - is a prominent stress-responsive signaling pathway that regulates mitochondrial morphology and function in response to diverse types of pathologic insult. This suggests that pharmacologic activation of the ISR represents a potential strategy to mitigate pathologic mitochondrial fragmentation associated with human disease. Here, we show that pharmacologic activation of the ISR kinases HRI or GCN2 promotes adaptive mitochondrial elongation and prevents mitochondrial fragmentation induced by the calcium ionophore ionomycin. Further, we show that pharmacologic activation of the ISR reduces mitochondrial fragmentation and restores basal mitochondrial morphology in patient fibroblasts expressing the pathogenic D414V variant of the pro-fusion mitochondrial GTPase MFN2 associated with neurological dysfunctions, including ataxia, optic atrophy, and sensorineural hearing loss. These results identify pharmacologic activation of ISR kinases as a potential strategy to prevent pathologic mitochondrial fragmentation induced by disease-relevant chemical and genetic insults, further motivating the pursuit of highly selective ISR kinase-activating compounds as a therapeutic strategy to mitigate mitochondrial dysfunction implicated in diverse human diseases.

Near-Native Imaging of Metal Ion-Initiated Cell State Transition

Metal ions are indispensable to life, as they can serve as essential enzyme cofactors to drive fundamental biochemical reactions, yet paradoxically, excess is highly toxic. Higher-order cells have evolved functionally distinct organelles that separate and coordinate sophisticated biochemical processes to maintain cellular homeostasis upon metal ion stimuli. Here, we uncover the remodeling of subcellular architecture and organellar interactome in yeast initiated by several metal ion stimulations, relying on near-native three-dimensional imaging, cryo-soft X-ray tomography. The three-dimensional architecture of intact yeast directly shows that iron or manganese triggers a hormesis-like effect that promotes cell proliferation. This process leads to the reorganization of organelles in the preparation for division, characterized by the polar distribution of mitochondria, an increased number of lipid droplets (LDs), volume shrinkage, and the formation of a hollow structure. Additionally, vesicle-like structures that detach from the vacuole are observed. Oppositely, cadmium or mercury causes stress-associated phenotypes, including mitochondrial fragmentation, LD swelling, and autophagosome formation. Notably, the organellar interactome, encompassing the interactions between mitochondria and LDs and those between the nuclear envelope and LDs, is quantified and exhibits alteration with multifaceted features in response to different metal ions. More importantly, the dynamics of organellar architecture render them more sensitive biomarkers than traditional approaches for assessing the cell state. Strikingly, yeast has a powerful depuration capacity to isolate and transform the overaccumulated cadmium in the vacuole, mitochondria, and cytoplasm as a high-value product, quantum dots. This work presents the possibility of discovering fundamental links between organellar morphological characteristics and the cell state.

Unraveling the role of Nrf2 in dopaminergic neurons: a review of oxidative stress and mitochondrial dysfunction in Parkinson's disease

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an essential transcriptional factor, involved in the regulation of countenance of various anti-oxidant enzymes and cytoprotective genes that respond to mitochondrial dysfunctions, oxidative stress, and neuroinflammation, thus potentially contributing to several neurodegenerative diseases (NDDs), including Parkison's disease (PD). PD is the second most prevalent progressive NDD, characterized by gradual neuronal death in substantia nigra pars compacta (SNpc), depletion of dopamine level, and a wide range of motor symptoms, including bradykinesia, tremor, tingling, and muscle fatigue. The etiopathology of PD is caused by multifactorial intertwined with the onset and progression of the disease. In this context, Nrf2 exhibits neuroprotective action by preserving dopaminergic neurons in the striatum and retarding the disease progression; thus, Nrf2 activation plays a crucial role in PD. Additionally, Nrf2 binds with the antioxidant response element, which is located in the promoter region of most of the genes that are responsible for coding antioxidant enzymes. Moreover, protein kinase C (PKC) mitogen-activated protein kinase (MAPK), and phosphatidylinositol 3-kinase (PI3K) are also involved in the regulation of Keap1 pathway-mediated Nrf2 activation. As Nrf2 revealed its defensive and protective role in the central nervous system (CNS), it is gaining enough interest in treating PD. The treatments that are currently available are intended to alleviate the symptoms of PD; however, they are unable to halt the progression and severity of the disease. Therefore, in this review we delve deeper into various molecular mechanisms associated with oxidative stress, mitochondrial dysfunction, and neuroinflammation in PD. Additionally, we elaborated on the substantial role that NRF2 plays in mitigating these adverse effects and its potential as a therapeutic target.

Harnessing an MMP-Independent NIR Probe Unveiling the Different Mitochondrial Cristae Changes during Mitophagy and Ferroptosis under STED Microscopy

Mitochondrial cristae remain dynamic structures in order to adapt various physiopathologic processes (e.g., mitophagy and ferroptosis); thus, visualizing and tracking different changes of cristae are crucial for a deeper understanding of these processes. Fluorescent probes that can realize long-term visualization of mitochondrial cristae under stimulated emission depletion (STED) microscopy are powerful tools for their in-depth research. However, there are few reports on such probes, and their constructions remain challenging. Here, we reported a robust squaraine probe (CSN) for visualizing and tracking the changes of mitochondrial cristae in various physiological and pathological processes using STED microscopy. The lipophilic unit of CSN enabled it to firmly immobilize in mitochondria via a hydrophobic interaction, which let the labeling ability of CSN independent of mitochondrial membrane potential (MMP). Using CSN, the mitochondrial cristae were clearly observed at a resolution of 52 nm under STED microscopy. Furthermore, CSN was successfully applied to track the destruction processes of mitochondrial cristae during autophagy and ferroptosis. Interestingly, we found that during mitophagy, mitochondria first underwent swelling and cristae rupture, and then partial vacuolization, and finally complete vacuolization, whereas during ferroptosis, mitochondria first underwent a gradual reduction in the number of cristae, and then partial fracture, and finally vacuolization. This work revealed the difference in mitochondrial cristae changes during mitophagy and ferroptosis, which provided insights into the two physiological and pathological processes. We believed that CSN could serve as a desirable tool to track cristae changes of intracellular activity processes.

How the Topology of the Mitochondrial Inner Membrane Modulates ATP Production

Cells in heart muscle need to generate ATP at or near peak capacity to meet their energy demands. Over 90% of this ATP comes from mitochondria, strategically located near myofibrils and densely packed with cristae to concentrate ATP generation per unit volume. However, a consequence of dense inner membrane (IM) packing is that restricted metabolite diffusion inside mitochondria may limit ATP production. Under physiological conditions, the flux of ATP synthase is set by ADP levels in the matrix, which in turn depends on diffusion-dependent concentration of ADP inside cristae. Computer simulations show how ADP diffusion and consequently rates of ATP synthesis are modulated by IM topology, in particular (i) number, size, and positioning of crista junctions that connect cristae to the IM boundary region, and (ii) branching of cristae. Predictions are compared with the actual IM topology of a cardiomyocyte mitochondrion in which cristae vary systematically in length and morphology. The analysis indicates that this IM topology decreases but does not eliminate the "diffusion penalty" on ATP output. It is proposed that IM topology normally attenuates mitochondrial ATP output under conditions of low workload and can be regulated by the cell to better match ATP supply to demand.

Mitofusin 2 displays fusion-independent roles in proteostasis surveillance

Mitochondria are essential organelles and their functional state dictates cellular proteostasis. However, little is known about the molecular gatekeepers involved, especially in absence of external stress. Here we identify a role of MFN2 in quality control independent of its function in organellar shape remodeling. MFN2 ablation alters the cellular proteome, marked for example by decreased levels of the import machinery and accumulation of the kinase PINK1. Moreover, MFN2 interacts with the proteasome and cytosolic chaperones, thereby preventing aggregation of newly translated proteins. Similarly to MFN2-KO cells, patient fibroblasts with MFN2-disease variants recapitulate excessive protein aggregation defects. Restoring MFN2 levels re-establishes proteostasis in MFN2-KO cells and rescues fusion defects of MFN1-KO cells. In contrast, MFN1 loss or mitochondrial shape alterations do not alter protein aggregation, consistent with a fusion-independent role of MFN2 in cellular homeostasis. In sum, our findings open new possibilities for therapeutic strategies by modulation of MFN2 levels.

Betaine enhances SCAPs chondrogenic differentiation and promotes cartilage repair in TMJOA through WDR81

BACKGROUND

The cartilage tissue regeneration mediated with mesenchymal stem cells (MSCs) is considered as a viable strategy for temporomandibular joint osteoarthritis (TMJOA). Betaine has been confirmed to modulate the multidirectional differentiation of MSCs, while its effect on chondrogenic differentiation of Stem Cells from the Apical Papilla (SCAPs) is unknown. Here, we explored the effects and underlying mechanisms of betaine on chondrogenic differentiation of SCAPs.

METHODS

Betaine was added for SCAPs chondrogenic induction. The chondrogenic differentiation potential was assessed using Alcian Blue staining, Sirius Red staining and the main chondrogenic markers. In vivo cartilage regeneration effects were evaluated by the rat TMJOA model. RNA-sequencing and biological analyses were performed to select target genes and biological processes involved. The mechanism betaine acts on chondrogenic differentiation of SCAPs was further explored.

RESULTS

Betain-treated SCAPs demonstrated stronger cartilage regeneration in vitro and promoted cartilage repair of TMJOA in vivo. Betaine enhanced the expression of WDR81 in SCAPs during chondrogenesis. WDR81 overexpression promoted chondrogenic differentiation of SCAPs, while WDR81 depletion inhibited chondrogenic differentiation. In addition, both betaine treatment and WDR81 overexpression reduced intracellular reactive oxygen species levels and increased mitochondrial membrane potential in SCAPs.

CONCLUSION

Betaine promotes SCAPs chondrogenic differentiation and provided an effective candidate for TMJOA treatment. WDR81 may serve as the potential drug target through mitophagy.

Mitochondrial Alterations, Oxidative Stress, and Therapeutic Implications in Alzheimer's Disease: A Narrative Review

The relationship between aging, mitochondrial dysfunction, neurodegeneration, and the onset of Alzheimer's disease (AD) is a complex area of study. Aging is the primary risk factor for AD, and it is associated with a decline in mitochondrial function. This mitochondrial dysfunction is believed to contribute to the neurodegenerative processes observed in AD. Neurodegeneration in AD is characterized by the progressive loss of synapses and neurons, particularly in regions of the brain involved in memory and cognition. It is hypothesized that mitochondrial dysfunction plays a pivotal role by disrupting cellular energy metabolism and increasing the production of reactive oxygen species (ROS), which can damage cellular components and exacerbate neuronal loss. Despite extensive research, the precise molecular pathways linking mitochondrial dysfunction to AD pathology are not fully understood. Various hypotheses have been proposed, including the mitochondrial cascade hypothesis, which suggests that mitochondrial dysfunction is an early event in AD pathogenesis that triggers a cascade of cellular events leading to neurodegeneration. With this narrative review, we aim to summarize some specific issues in the literature on mitochondria and their involvement in AD onset, with a focus on the development of therapeutical strategies targeting the mitochondria environment and their potential application for the treatment of AD itself.

Tissue-Specific Diversity of Nuclear-Encoded Mitochondrial Genes Related to Lipid and Carbohydrate Metabolism in Buffalo

Buffaloes play a crucial role in Asian agriculture, enhancing food security and rural development. Their distinct metabolic needs drive tissue-specific mitochondrial adaptations, regulated by both mitochondrial and nuclear genomes. This study explores how nuclear-encoded mitochondrial genes involved in lipid and carbohydrate metabolism vary across tissues-an area with significant implications for buffalo health, productivity, and human health. We hypothesize that tissue-specific variations in metabolic pathways are reflected in the expression of nuclear-encoded mitochondrial genes, which are tailored to the metabolic needs of each tissue. We utilized high-throughput RNA sequencing (RNA-seq) data to assess the expression of nuclear-encoded mitochondrial genes related to lipid and carbohydrate metabolism across various tissues in healthy female buffaloes aged 3-5 years, including the kidney, heart, brain, and ovary. Differential expression analysis was performed using DESeq2, with significance set at p < 0.05 for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. A total of 164 genes exhibited tissue-specific regulation, with the heart and brain, which have higher energy demands, expressing more genes than the kidney and ovary. Notably, the comparison between the kidney and ovary showed the highest number of differentially expressed genes. Interestingly, the kidney up-regulates gluconeogenesis-related genes (e.g., PCK2, PCCA, LDHD), promoting glucose production, while these genes are down-regulated in the ovary. In contrast, the brain up-regulates pyruvate metabolism genes (e.g., PCCA, PDHA1, LDHD), underscoring its reliance on glucose as a primary energy source, while these genes are down-regulated in the ovary. The higher abundance of EHHADH in the brain compared to the ovary further emphasizes the critical role of fatty acid metabolism in brain function, aligned with the brain's high energy demands. Additionally, down-regulation of the StAR gene in both the kidney versus ovary and brain versus ovary comparisons suggests tissue-specific differences in steroid hormone regulation. These findings highlight tissue-specific variations in nuclear-encoded mitochondrial genes related to lipid and carbohydrate metabolism, reflecting adaptations to each tissue's unique metabolic needs. This study lays a foundation for advancing mitochondrial metabolism research in livestock, with significant implications for human health. Insights could inform dietary or therapeutic strategies for metabolic disorders, such as cardiovascular diseases and metabolic syndrome, while also enhancing livestock productivity.

Aerobic exercise timing affects mitochondrial dynamics and insulin resistance by regulating the circadian clock protein expression and NAD+-SIRT1-PPARα-MFN2 pathway in the skeletal muscle of high-fat-diet-induced diabetes mice

The circadian clock regulates mitochondrial function and affects time-dependent metabolic responses to exercise. The present study aimed to determine the effects of aerobic exercise timing at the light-dark phase on the proteins expression of the circadian clock, mitochondrial dynamics, and, NAD+-SIRT1-PPARα axis in skeletal muscle of high-fat diet-induced diabetic mice. In this experimental study, thirty male mice were randomly assigned into two groups based on time: the early light phase, ZT3, and the early dark phase, ZT15, and three groups at each time: (1) Healthy Control (HC), (2) Diabetic Control (DC), and (3) Diabetic + Exercise (DE). Diabetes was induced by 5 weeks of feeding with a high-fat diet and Streptozotocin injection. Following confirmation of diabetes, animals underwent treadmill running at ZT3 and ZT15 for eight-weeks (5 days, 60-80 min, 50-60%Vmax). The expression of proteins of muscle aryl-hydrocarbon receptor nuclear translocator-like-1 (BMAL1), period-2 (PER2), mitofusin-2 (MFN2), dynamin-related proteins-1 (DRP-1), glucose transporter (GLUT4), sirtuin-1 (SIRT1), peroxisome proliferator-activated receptor-alpha (PPARα), and nicotinamide adenine dinucleotide (NAD+) level were analyzed in gastrocnemius muscle at both exercise times. The results showed that aerobic exercise at both times reversed the dysregulation of the diabetes-induced skeletal muscle clock by increasing the BMAL1 and PER2 protein levels. Aerobic exercise, especially at ZT15 compared to ZT3, increased GLUT4-mediated glucose uptake, and improved the diabetes-induced imbalance of mitochondrial fusion-fission by a significant increase in MFN2 protein level. Moreover, time-dependent aerobic exercise only at ZT15 increased the SIRT1 and PPARα protein levels and reduced diabetes-induced hyperglycemia. However, the aerobic exercise timing could not restore the attenuation of diabetes-induced NAD+ levels and DRP-1 protein. Our findings demonstrated that the synchronization of aerobic exercise with the circadian rhythm of NAD+-SIRT1 may boost MFN2-mediated mitochondrial fusion by activating the BMAL1-PER2-SIRT1-PPARα axis in the skeletal muscle of diabetic mice and be more effective in facilitating glycemic control and insulin resistance.

Enzymatic tools for mitochondrial genome manipulation

Mutations in mitochondrial DNA (mtDNA) can manifest phenotypically as a wide range of neuromuscular and neurodegenerative pathologies that are currently only managed symptomatically without addressing the root cause. A promising approach is the development of molecular tools aimed at mtDNA cutting or editing. Unlike nuclear DNA, a cell can have hundreds or even thousands of mitochondrial genomes, and mutations can be present either in all of them or only in a subset. Consequently, the developed tools are aimed at reducing the number of copies of mutant mtDNA or editing mutant nucleotides. Despite some progress in the field of mitochondrial genome editing in human cells, working with model animals is still limited due to the complexity of their creation. Furthermore, not all existing editing systems can be easily adapted to function within mitochondria. In this review, we evaluate the mtDNA editing tools available today, with a particular focus on specific mtDNA mutations linked to hereditary mitochondrial diseases, aiming to provide an in-depth understanding of both the opportunities and hurdles to the development of mitochondrial genome editing technologies.

The dual role of PGAM5 in inflammation

In recent years, the focus on human inflammation in research has increased, with aging-related inflammation widely recognized as a defining characteristic of aging. Inflammation is strongly correlated with mitochondrial dysfunction. Phosphoglycerate mutase family member 5 (PGAM5) is a novel modulator of mitochondrial homeostasis in response to mechanical stimulation. Here we review the structure and sublocalization of PGAM5, introduce its importance in programmed cell death and summarize its crucial roles in the development and progression of inflammatory diseases such as pneumonia, hepatitis, neuroinflammation and aging. Notably, PGAM5 has dual effects on controlling inflammation: distinct PGAM5-mediated mitochondrial functions exhibit cellular heterogeneity, leading to its dual functions in inflammation control. We therefore highlight the double-edged sword nature of PGAM5 as a potential critical regulator and innovative therapeutic target in inflammation. Finally, the challenges and future directions of the use of PGAM5, which has dual properties, as a target molecule in the clinic are discussed. This review provides crucial insights to guide the development of intelligent therapeutic strategies targeting PGAM5-specific regulation to treat intractable inflammatory conditions, as well as the potential extension of its broader application to other diseases to achieve more precise and effective treatment outcomes.

Molecular mechanisms of mitochondrial dynamics

Mitochondria not only synthesize energy required for cellular functions but are also involved in numerous cellular pathways including apoptosis, calcium homoeostasis, inflammation and immunity. Mitochondria are dynamic organelles that undergo cycles of fission and fusion, and these transitions between fragmented and hyperfused networks ensure mitochondrial function, enabling adaptations to metabolic changes or cellular stress. Defects in mitochondrial morphology have been associated with numerous diseases, highlighting the importance of elucidating the molecular mechanisms regulating mitochondrial morphology. Here, we discuss recent structural insights into the assembly and mechanism of action of the core mitochondrial dynamics proteins, such as the dynamin-related protein 1 (DRP1) that controls division, and the mitofusins (MFN1 and MFN2) and optic atrophy 1 (OPA1) driving membrane fusion. Furthermore, we provide an updated view of the complex interplay between different proteins, lipids and organelles during the processes of mitochondrial membrane fusion and fission. Overall, we aim to present a valuable framework reflecting current perspectives on how mitochondrial membrane remodelling is regulated.

How crosstalk between mitochondria, lysosomes, and other organelles can prevent or promote dry age-related macular degeneration

Organelles such as mitochondria, lysosomes, peroxisomes, and the endoplasmic reticulum form highly dynamic cellular networks and exchange information through sites of physical contact. While each organelle performs unique functions, this inter-organelle crosstalk helps maintain cell homeostasis. Age-related macular degeneration (AMD) is a devastating blinding disease strongly associated with mitochondrial dysfunction, oxidative stress, and decreased clearance of cellular debris in the retinal pigment epithelium (RPE). However, how these occur, and how they relate to organelle function both with the RPE and potentially the photoreceptors are fundamental, unresolved questions in AMD biology. Here, we report the discussions of the "Mitochondria, Lysosomes, and other Organelle Interactions" task group of the 2024 Ryan Initiative for Macular Research (RIMR). Our group focused on understanding the interplay between cellular organelles in maintaining homeostasis in the RPE and photoreceptors, how this could be derailed to promote AMD, and identifying where these pathways could potentially be targeted therapeutically.

Ginsenoside Rd-Loaded Antioxidant Polymersomes to Regulate Mitochondrial Homeostasis for Bone Defect Healing in Periodontitis

Periodontitis is the leading cause of tooth loss in adults. Initially triggered by bacterial infection, it is characterized by subsequent dysregulation of mitochondrial homeostasis, leading to ongoing loss of periodontal tissue. Mitophagic flux, a critical physiological mechanism for maintaining mitochondrial homeostasis, is compromised in periodontitis. Additionally, increased release of reactive oxygen species (ROS) exacerbates mitochondrial damage. In this study, a ginsenoside Rd (Rd)-loaded antioxidative polymersome (RdAP) is designed, which is self-assembled from a mitochondrial-protective and ROS-scavenging block copolymer, poly(ethylene oxide)-block-poly(phenylboronic acid pinacol ester-conjugated polylysine) (PEO113-b-P(Lys-PAPE)60). The phenylboronic acid pinacol ester (PAPE) segment exhibits excellent ROS-responsive properties, enabling effective ROS scavenging through antioxidant production. Rd significantly enhances mitophagic flux by 2.5-fold in periodontal ligament stem cells (PDLSCs) under oxidative stress. Together with the antioxidative polymersome, RdAPs restore mitochondrial homeostasis and enhance the osteogenic capacity of PDLSCs, bringing it closer to that of healthy controls. In a mouse model of periodontitis, the bone mass in the RdAP-treated group is 1.37 times greater than that in the untreated periodontitis group. Overall, the findings propose a novel strategy for addressing refractory periodontitis, which may also be applicable to other diseases characterized by mitochondrial homeostasis imbalance.

Role of calcium overload-mediated disruption of mitochondrial dynamics in offspring neurotoxicity due to methylmercury exposure during pregnancy and lactation

Methylmercury (MeHg) is a potent neurotoxicant with neurodevelopmental toxicity that is widely ingested into the body through drinking water and food. MeHg crosses the placental barrier and accumulates in the brain of the fetus, affecting the growth and development of the central nervous system. Although it has been demonstrated that MeHg induces neuronal calcium overload in the rat cerebral cortex, the role of calcium overload in MeHg-induced neurodevelopmental toxicity remains unclear. Here, we used ICR-pregnant mice and their resulting offspring and administered the BAPTA-AM calcium antagonist to investigate the molecular mechanisms by which MeHg exposure during gestation and lactation affects neurodevelopment. We found that exposure to MeHg during gestation and lactation resulted in developmental arrest and neurobehavioral dysfunction in the offspring, with calcium overload, disturbed mitochondrial dynamics, and apoptosis. However, the calcium overload inhibitor BAPTA-AM rescued MeHg-induced neurodevelopmental damage, attenuated the onset of calcium overload, reduced mitochondrial kinetic disturbances and apoptosis. Meanwhile, the activation of the CaM/CaMKII/DRP1 signaling pathway induced by calcium overload was inhibited, and the interaction between DRP1 and BAX was attenuated, which alleviated apoptosis to a certain extent. In summary, our study suggests that MeHg-induced calcium overload may induce disturbed mitochondrial dynamics through activation of the CaM/CaMKII/DRP1 signaling pathway, resulting in neuronal apoptosis.

The Potential Mechanism of D-Amino Acids - Mitochondria Axis in the Progression of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a major complication of diabetes mellitus (DM) and stands out as the leading cause of end-stage renal disease worldwide. There is increasing evidence that mitochondrial dysfunction, including impaired mitochondrial biogenesis, dynamics, and oxidative stress, contributes to the development and progression of DKD. D-amino acids (D-AAs), which are enantiomers of L-AAs, have recently been detected in various living organisms and are acknowledged to play important roles in numerous physiological processes in the human body. Accumulating evidence demonstrates that D-AA levels in blood or urine could serve as useful biomarkers for reflecting renal function. The physiological roles of D-AAs are implicated in the regulation of cellular proliferation, oxidative stress, generation of reactive oxygen species (ROS), and innate immunity. This article reviews current evidence relating to D-AAs and mitochondrial dysfunction and proposes a potential interaction and contribution of the D-AAs-mitochondria axis in DKD pathophysiology and progression. This insight could provide novel therapeutic approaches for preventing or ameliorating DKD based on this biological axis.

Cellular takeover: How new world alphaviruses impact host organelle function

Alphavirus replication is dependent on host cell organelles to facilitate multiple steps of the viral life cycle. New world alphaviruses (NWA) consisting of eastern, western and Venezuelan equine encephalitis viruses are a subgroup of alphaviruses associated with central nervous system disease. Despite differing morbidity and mortality amongst these viruses, all are important human pathogens due to their transmission through viral aerosolization and mosquito transmission. In this review, we summarize the utilization of host organelles for NWA replication and the subversion of the host innate immune responses. The impact of viral proteins and replication processes on organelle function is also discussed. Literature involving old world alphaviruses (OWA), such as chikungunya virus and Sindbis virus, is included to compare and contrast between OWA and NWA and highlight gaps in knowledge for NWA. Finally, potential targets for therapeutics or vaccine candidates are highlighted with a focus on host-directed therapeutics.

Electrical homeostasis of the inner mitochondrial membrane potential

The electric potential across the inner mitochondrial membrane must be maintained within certain bounds for the proper functioning of the cell. A feedback control mechanism for the homeostasis of this membrane potential is proposed whereby an increase in the electric field decreases the rate-limiting steps of the electron transport chain (ETC). An increase in trans-membrane electric field limits the rate of proton pumping to the inter-membrane gap by slowing the ETC reactions and by intrinsically induced electroporation that depolarizes the inner membrane. The proposed feedback mechanism is akin to a Le Chatelier's-type principle of trans-membrane potential feedback control.

Rg1 improves Alzheimer's disease by regulating mitochondrial dynamics mediated by the AMPK/Drp1 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Alzheimer's disease (AD) is the most prevalent form of dementia, characterized by a complex pathogenesis that includes Aβ deposition, abnormal phosphorylation of tau protein, chronic neuroinflammation, and mitochondrial dysfunction. In traditional medicine, ginseng is revered as the 'king of herbs'. Ginseng has the effects of greatly tonifying vital energy, strengthening the spleen and benefiting the lungs, generating fluids and nourishing the blood, and calming the mind while enhancing intelligence. Ginsenoside Rg1 (Rg1) is a well-defined major active component found in ginseng, known for its relatively high content. It has been demonstrated to exhibit neuroprotective effects in both in vivo and in vitro models, capable of ameliorating Aβ and tau pathology, regulating synaptic function, and reducing inflammation, oxidative stress, and apoptosis. However, the potential of Rg1 to improve AD pathology through the regulation of mitochondrial dynamics is still uncertain.

AIM OF THE STUDY

Despite the active research efforts on drugs for AD, the currently available anti-AD medications can only slow disease progression and manage symptoms, yet unable to provide a cure for AD. Furthermore, some anti-AD drugs failed phase III and IV clinical trials due to significant side effects. Therefore, there is an urgent need to further investigate the pathogenesis of AD, to identify new therapeutic targets, and to explore more effective therapies. The aim of this study is to evaluate the potential therapeutic effects of Rg1 on APP/PS1 double transgenic mice and Aβ42-induced HT22 cell models, and to investigate the potential mechanisms through which it provides neuroprotective effects.

MATERIALS AND METHODS

This study investigates the effects of Rg1 in treating AD on APP/PS1 double transgenic mice and Aβ42-induced HT22 cells. In the in vivo experiments, APP/PS1 mice were divided into a model group, Rg1-L group, Rg1-H group, and donepezil group, with C57BL/6 mice serving as the control group (n = 12 per group). The Rg1-L and Rg1-H groups were administered Rg1 at doses of 5 mg/kg/d and 10 mg/kg/d, respectively, while the donepezil group received donepezil at a dose of 1.3 mg/kg/d. Both the control and model groups received an equal volume of physiological saline daily for 28 days. Learning and spatial memory were assessed by the Morris water maze (MWM) and novel object recognition (NOR) tests, and neuronal damage by Nissl staining. Aβ deposition was analyzed through immunohistochemistry and Western blot, while the expression levels of synaptic proteins PSD95 and SYN were evaluated via immunofluorescence staining and Western blot. The dendritic spines of neurons was observed by Golgi staining.The ultrastructure of neuronal mitochondria and synapses was examined by transmission electron microscopy (TEM). Mitochondrial function was assessed through measurements of Reactive oxygen species (ROS), Superoxide Dismutase (SOD), and Adenosine Triphosphate (ATP), and Western blot analysis was performed to detect the expression levels of AMPK, p-AMPK, Drp1, p-Drp1, OPA1, Mfn1, and Mfn2, thereby investigating the protective effects of Rg1 on mitochondrial dysfunction and cognitive impairment in APP/PS1 double transgenic mice. In vitro experiments, HT22 cells were treated with Aβ42 of 10 μM for 24 h to verify the therapeutic effects of Rg1. Flow cytometry was used to detect ROS and JC-1, biochemical methods were employed to measure SOD and ATP, immunofluorescence staining was used to detect the expression levels of PSD95 and SYN, and Western blot analysis was conducted to elucidate its potential mechanisms of action.

RESULTS

The findings suggest that after 28 days of Rg1 treatment, cognitive dysfunction in APP/PS1 mice was improved. Pathological and immunohistochemical analyses demonstrated that Rg1 treatment significantly reduced Aβ deposition and neuronal loss. Rg1 can improve synaptic dysfunction and mitochondrial function in APP/PS1 mice. Rg1 activated AMPK, enhanced p-AMPK expression, inhibited Drp1, and reduced p-Drp1 levels, which led to increased expression of OPA1, Mfn1, and Mfn2, thereby inhibiting mitochondrial fission and facilitating mitochondrial fusion. Additionally, Rg1 effectively reversed the decrease in mitochondrial membrane potential (MMP) and the increase in ROS production induced by Aβ42 in HT22 cells, restoring SOD and ATP levels. Furthermore, Rg1 regulated mitochondrial fission mediated by the AMPK/Drp1 signaling pathway, promoting mitochondrial fusion and improving synaptic dysfunction.

CONCLUSION

Our research provides evidence for the neuroprotective mechanisms of Rg1 in AD models. Rg1 modulates mitochondrial dynamics through the AMPK/Drp1 signaling pathway, thereby reducing synaptic and mitochondrial dysfunction in APP/PS1 mice and AD cell models.

In vitro stretch modulates mitochondrial dynamics and energy metabolism to induce smooth muscle differentiation in mesenchymal stem cells

The smooth muscle cells (SMCs) located in the vascular media layer are continuously subjected to cyclic stretching perpendicular to the vessel wall and play a crucial role in vascular wall remodeling and blood pressure regulation. Mesenchymal stem cells (MSCs) are promising tools to differentiate into SMCs. Mechanical stretch loading offers an opportunity to guide the MSC-SMC differentiation and mechanical adaption for function regeneration of blood vessels. This study shows that cyclic stretch induces the expression of SMC markers α-SMA and SM22 in MSCs. These cells exhibit contractile ability in vitro and facilitate angiogenesis in the Matrigel plug assay in vivo. The contraction of SMCs requires remodeling of their energy metabolism. However, the underlying mechanism in the differentiation of MSCs into SMCs remains to be revealed. Cyclic stretch training promotes glycolysis, oxidative phosphorylation, and mitochondrial fusion and modulates mitochondrial dynamics-related proteins (MFN1, MFN2, DRP1) expression, thereby contributing to MSCs differentiation. Yes-associated protein (YAP) affects mitochondrial dynamics, oxidative phosphorylation, and glycolysis to regulate stretch-mediated differentiation into SMCs. Additionally, Piezo-type mechanosensitive ion channel component 1 (Piezo1) impacts energy metabolism and MSCs differentiation by regulating intracellular Ca2+ levels and YAP nuclear localization. It indicates that YAP can integrate stretch force and energy metabolism signals to regulate the differentiation of MSCs into SMCs.

Epstein-Barr virus-driven cardiolipin synthesis sustains metabolic remodeling during B cell transformation

The Epstein-Barr virus (EBV) infects nearly 90% of adults globally and is linked to over 200,000 annual cancer cases. Immunocompromised individuals from conditions such as primary immune disorders, HIV, or posttransplant immunosuppressive therapies are particularly vulnerable because of EBV's transformative capability. EBV remodels B cell metabolism to support energy, biosynthetic precursors, and redox equivalents necessary for transformation. Most EBV-driven metabolic pathways center on mitochondria. However, how EBV regulates B cell mitochondrial function and metabolic fluxes remains unclear. Here, we show that EBV boosts cardiolipin (CL) biosynthesis, essential for mitochondrial cristae biogenesis, via EBV nuclear antigen 2/MYC-induced CL enzyme transactivation. Pharmacological and CRISPR genetic analyses underscore the essentiality of CL biosynthesis in EBV-transformed B cells. Metabolomic and isotopic tracing highlight CL's role in sustaining respiration, one-carbon metabolism, and aspartate synthesis. Disrupting CL biosynthesis destabilizes mitochondrial matrix enzymes pivotal to these pathways. We demonstrate EBV-induced CL metabolism as a therapeutic target, offering synthetic lethal strategies against EBV-associated B cell malignancies.

SLC29A1 and SLC29A2 are human nicotinamide cell membrane transporters

Nicotinamide (NAM), a main precursor of NAD+, is essential for cellular fuel respiration, energy production, and other cellular processes. Transporters for other precursors of NAD+ such as nicotinic acid and nicotinamide mononucleotide (NMN) have been identified, but the cellular transporter of nicotinamide has not been elucidated. Here, we demonstrate that equilibrative nucleoside transporter 1 and 2 (ENT1 and 2, encoded by SLC29A1 and 2) drive cellular nicotinamide uptake and establish nicotinamide metabolism homeostasis. In addition, ENT1/2 exhibits a strong capacity to change the cellular metabolite composition and the transcript, especially those related to nicotinamide. We further observe that ENT1/2 regulates cellular respiration and senescence, contributing by altering the NAD+ pool level and mitochondrial status. Changes to cellular respiration, mitochondrial status and senescence by ENT1/2 knockdown are reversed by NMN supplementation. Together, ENT1 and ENT2 act as both cellular nicotinamide-level keepers and nicotinamide biological regulators through their NAM transport functions.

From micro to macro, nanotechnology demystifies acute pancreatitis: a new generation of treatment options emerges

Acute pancreatitis (AP) is a disease characterized by an acute inflammatory response in the pancreas. This is caused by the abnormal activation of pancreatic enzymes by a variety of etiologic factors, which results in a localized inflammatory response. The symptoms of this disease include abdominal pain, nausea and vomiting and fever. These symptoms are induced by a hyperinflammatory response and oxidative stress. In recent years, research has focused on developing anti-inflammatory and antioxidative therapies for the treatment of acute pancreatitis (AP). However, there are still limitations to this approach, including poor drug stability, low bioavailability and a short half-life. The advent of nanotechnology has opened up a novel avenue for the management of acute pancreatitis (AP). Nanomaterials can serve as an efficacious vehicle for conventional pharmaceuticals, enhancing their targeting ability, improving bioavailability and prolonging their half-life. Moreover, they can also exert a direct therapeutic effect. This review begins by introducing the general situation of acute pancreatitis (AP). It then discusses the pathogenesis of acute pancreatitis (AP) and the current status of treatment. Finally, it considers the literature related to the treatment of acute pancreatitis (AP) by nanomaterials. The objective of this study is to provide a comprehensive review of the existing literature on the use of nanomaterials in the treatment of acute pancreatitis (AP). In particular, the changes in inflammatory markers and therapeutic outcomes following the administration of nanomaterials are examined. This is done with the intention of offering insights that can inform subsequent research and facilitate the clinical application of nanomaterials in the management of acute pancreatitis (AP).

Leptin drives glucose metabolism to promote cardiac protection via OPA1-mediated HDAC5 translocation and Glut4 transcription

Metabolic reprogramming, the shifting from fatty acid oxidation to glucose utilization, improves cardiac function as heart failure (HF) progresses. Leptin plays an essential role in regulating glucose metabolism. However, the crosstalk between leptin and metabolic reprogramming is poorly understood. We tested the hypothesis that leptin improves cardiac function after myocardial infarction via enhancing glucose metabolism. In the isoproterenol (ISO)-induced heart failure model in vitro, H9c2 cell apoptosis was assessed by the TUNEL and Annexin V/PI staining assay. Leptin-mediated mitochondrial fusion was performed via TEM, and glucose oxidation was explored, as well as the ECAR, OCR, and protein expression of the vital metabolic enzymes. By blocking OPA1 expression or HDAC5 inhibition, the mitochondrial dynamic and glucose metabolic were detected to evaluate the role of OPA1 and HDAC5 in leptin-stimulated glucose metabolism. In the mouse model of HF in vivo, intraperitoneal leptin administration appreciably increased glucose oxidation and preserved cardiac function 56 days after coronary artery ligation. In vitro, we identified the OPA1-dependent HDAC5 nucleus export as a crucial process in boosting glucose utilization by activating MEF2 to upregulate Glut4 expression using the RNA interference technique in H9c2 cells. In vivo, leptin promotes glucose utilization and confers heart functional and survival benefits in chronic ischemic HF. The current study provided a novel insight into the role of leptin in metabolic reprogramming and revealed potential therapeutic targets for chronic HF.

Ferroptosis triggers mitochondrial fragmentation via Drp1 activation

Constitutive mitochondrial dynamics ensure quality control and metabolic fitness of cells, and their dysregulation has been implicated in various human diseases. The large GTPase Dynamin-related protein 1 (Drp1) is intimately involved in mediating constitutive mitochondrial fission and has been implicated in mitochondrial cell death pathways. During ferroptosis, a recently identified type of regulated necrosis driven by excessive lipid peroxidation, mitochondrial fragmentation has been observed. Yet, how this is regulated and whether it is involved in ferroptotic cell death has remained unexplored. Here, we provide evidence that Drp1 is activated upon experimental induction of ferroptosis and promotes cell death execution and mitochondrial fragmentation. Using time-lapse microscopy, we found that ferroptosis induced mitochondrial fragmentation and loss of mitochondrial membrane potential, but not mitochondrial outer membrane permeabilization. Importantly, Drp1 accelerated ferroptotic cell death kinetics. Notably, this function was mediated by the regulation of mitochondrial dynamics, as overexpression of Mitofusin 2 phenocopied the effect of Drp1 deficiency in delaying ferroptosis cell death kinetics. Mechanistically, we found that Drp1 is phosphorylated and activated after induction of ferroptosis and that it translocates to mitochondria. Further activation at mitochondria through the phosphatase PGAM5 promoted ferroptotic cell death. Remarkably, Drp1 depletion delayed mitochondrial and plasma membrane lipid peroxidation. These data provide evidence for a functional role of Drp1 activation and mitochondrial fragmentation in the acceleration of ferroptotic cell death, with important implications for targeting mitochondrial dynamics in diseases associated with ferroptosis.

Metal Ion Signaling in Biomedicine

Complex multicellular organisms are composed of distinct tissues involving specialized cells that can perform specific functions, making such life forms possible. Species are defined by their genomes, and differences between individuals within a given species directly result from variations in their genetic codes. While genetic alterations can give rise to disease-causing acquisitions of distinct cell identities, it is now well-established that biochemical imbalances within a cell can also lead to cellular dysfunction and diseases. Specifically, nongenetic chemical events orchestrate cell metabolism and transcriptional programs that govern functional cell identity. Thus, imbalances in cell signaling, which broadly defines the conversion of extracellular signals into intracellular biochemical changes, can also contribute to the acquisition of diseased cell states. Metal ions exhibit unique chemical properties that can be exploited by the cell. For instance, metal ions maintain the ionic balance within the cell, coordinate amino acid residues or nucleobases altering folding and function of biomolecules, or directly catalyze specific chemical reactions. Thus, metals are essential cell signaling effectors in normal physiology and disease. Deciphering metal ion signaling is a challenging endeavor that can illuminate pathways to be targeted for therapeutic intervention. Here, we review key cellular processes where metal ions play essential roles and describe how targeting metal ion signaling pathways has been instrumental to dissecting the biochemistry of the cell and how this has led to the development of effective therapeutic strategies.

Living Cell-Mediated Self-Assembly: From Monomer Design and Morphology Regulation to Biomedical Applications

The self-assembly of molecules into highly ordered architectures is a ubiquitous and natural process, wherein molecules spontaneously organize into large structures to perform diverse functions. Drawing inspiration from the formation of natural nanostructures, cell-mediated self-assembly has been developed to create functional assemblies both inside and outside living cells. These techniques have been employed to regulate the cellular world by leveraging the dynamic intracellular and extracellular microenvironment. This review highlights the recent advances and future trends in living cell-mediated self-assembly, ranging from their cytocompatible monomer designs, synthetic strategies, and morphological control to functional applications. The assembly behaviors are also discussed based on the dimensionality of the self-assembled morphologies from zero to three dimensions. Finally, this review explores its promising potential for biomedical applications, clarifying the relationship between initial morphological regulation and the therapeutic effects of subsequent artificial assemblies. Through rationally designing molecular structures and precisely controlling assembly morphologies, living cell mediated self-assembly would provide an innovative platform for executing biological functions.

Tea Polyphenol-Derived Carbon Dots Alleviate Abdominal Aortic Aneurysm Progression by Mitigating Oxidative Stress and Ferroptosis

Abdominal aortic aneurysm (AAA) is a cardiovascular disease with potentially fatal consequences, yet effective therapies to prevent its progression remain unavailable. Oxidative stress is associated with AAA development. Carbon dots have reactive oxygen species-scavenging activity, while green tea extract exhibits robust antioxidant properties. However, the potential of green tea derived carbon dots in mitigating AAA progression has not been fully elucidated. In this study, tea polyphenol carbon dots (TP-CDs) were synthesized via hydrothermal methods and characterized for their antioxidant properties. The antioxidant effects of TP-CDs were evaluated, and TP-CDs' impact on phenotypic transformation, oxidative stress, apoptosis and ferroptosis was investigated comprehensively in an Ang II-induced AAA model, employing techniques such as Western blotting, flow cytometry, and immunohistochemistry. The results revealed that TP-CDs effectively alleviated oxidative stress induced by Ang II stimulation, thereby inhibiting phenotypic transformation, apoptosis, and ferroptosis in vivo. Furthermore, treatment with TP-CDs significantly attenuated AAA progression in a mouse AAA model. Overall, these findings demonstrate that TP-CDs reduced reactive oxygen species levels in the microenvironment and alleviated the progression of AAA, offering a promising therapeutic strategy for this condition.

Mitochondrial segmentation and function prediction in live-cell images with deep learning

Mitochondrial morphology and function are intrinsically linked, indicating the opportunity to predict functions by analyzing morphological features in live-cell imaging. Herein, we introduce MoDL, a deep learning algorithm for mitochondrial image segmentation and function prediction. Trained on a dataset of 20,000 manually labeled mitochondria from super-resolution (SR) images, MoDL achieves superior segmentation accuracy, enabling comprehensive morphological analysis. Furthermore, MoDL predicts mitochondrial functions by employing an ensemble learning strategy, powered by an extended training dataset of over 100,000 SR images, each annotated with functional data from biochemical assays. By leveraging this large dataset alongside data fine-tuning and retraining, MoDL demonstrates the ability to precisely predict functions of heterogeneous mitochondria from unseen cell types through small sample size training. Our results highlight the MoDL's potential to significantly impact mitochondrial research and drug discovery, illustrating its utility in exploring the complex relationship between mitochondrial form and function within a wide range of biological contexts.

Novel strategies targeting mitochondria-lysosome contact sites for the treatment of neurological diseases

Mitochondria and lysosomes are critical for neuronal homeostasis, as highlighted by their dysfunction in various neurological diseases. Recent studies have identified dynamic membrane contact sites between mitochondria and lysosomes, independent of mitophagy and the lysosomal degradation of mitochondrial-derived vesicles (MDVs), allowing bidirectional crosstalk between these cell compartments, the dynamic regulation of organelle networks, and substance exchanges. Emerging evidence suggests that abnormalities in mitochondria-lysosome contact sites (MLCSs) contribute to neurological diseases, including Parkinson's disease, Charcot-Marie-Tooth (CMT) disease, lysosomal storage diseases, and epilepsy. This article reviews recent research advances regarding the tethering processes, regulation, and function of MLCSs and their role in neurological diseases.

The roles of KRAS in cancer metabolism, tumor microenvironment and clinical therapy

KRAS is one of the most mutated genes, driving alternations in metabolic pathways that include enhanced nutrient uptaking, increased glycolysis, elevated glutaminolysis, and heightened synthesis of fatty acids and nucleotides. However, the beyond mechanisms of KRAS-modulated cancer metabolisms remain incompletely understood. In this review, we aim to summarize current knowledge on KRAS-related metabolic alterations in cancer cells and explore the prevalence and significance of KRAS mutation in shaping the tumor microenvironment and influencing epigenetic modification via various molecular activities. Given that cancer cells rely on these metabolic changes to sustain cell growth and survival, targeting these processes may represent a promising therapeutic strategy for KRAS-driven cancers.

The interconnective role of the UPS and autophagy in the quality control of cancer mitochondria

Uncontrollable cancer cell growth is characterized by the maintenance of cellular homeostasis through the continuous accumulation of misfolded proteins and damaged organelles. This review delineates the roles of two complementary and synergistic degradation systems, the ubiquitin-proteasome system (UPS) and the autophagy-lysosome system, in the degradation of misfolded proteins and damaged organelles for intracellular recycling. We emphasize the interconnected decision-making processes of degradation systems in maintaining cellular homeostasis, such as the biophysical state of substrates, receptor oligomerization potentials (e.g., p62), and compartmentalization capacities (e.g., membrane structures). Mitochondria, the cellular hubs for respiration and metabolism, are implicated in tumorigenesis. In the subsequent sections, we thoroughly examine the mechanisms of mitochondrial quality control (MQC) in preserving mitochondrial homeostasis in human cells. Notably, we explored the relationships between mitochondrial dynamics (fusion and fission) and various MQC processes-including the UPS, mitochondrial proteases, and mitophagy-in the context of mitochondrial repair and degradation pathways. Finally, we assessed the potential of targeting MQC (including UPS, mitochondrial molecular chaperones, mitochondrial proteases, mitochondrial dynamics, mitophagy and mitochondrial biogenesis) as cancer therapeutic strategies. Understanding the mechanisms underlying mitochondrial homeostasis may offer novel insights for future cancer therapies.

Mitochondrial Dysfunction in Diabetic Periodontitis: Mechanisms and Therapeutic Potential

Diabetic periodontitis is a common oral complication of diabetes characterized by progressive destruction of periodontal tissues. Recent evidence suggests that mitochondrial dysfunction plays a crucial role in the pathogenesis and progression of this condition. This review aims to systematically summarize the role and potential mechanisms of mitochondrial dysfunction in diabetic periodontitis. We first explore the relationship between diabetes and mitochondrial dysfunction, then analyze the specific manifestations of mitochondrial dysfunction in diabetic periodontitis, including morphological changes, energy metabolism disorders, increased oxidative stress, and enhanced apoptosis. We further delve into the connections between mitochondrial dysfunction and the pathogenic mechanisms of diabetic periodontitis, such as exacerbated inflammatory responses, decreased tissue repair capacity, and autophagy dysregulation. Finally, we discuss potential therapeutic targets based on mitochondrial function, including antioxidant strategies, mitochondria-targeted drugs, and autophagy regulators. We also propose future research directions, emphasizing the need for in-depth exploration of molecular mechanisms, development of new diagnostic markers and therapeutic strategies, and personalized treatment approaches. This review provides new insights into understanding the pathogenic mechanisms of diabetic periodontitis and offers a theoretical basis for developing targeted prevention and treatment strategies to improve oral health in diabetic patients.

Long-term mitochondrial and metabolic impairment in lymphocytes of subjects who recovered after severe COVID-19

The underlying mechanisms explaining the differential course of SARS-CoV-2 infection and the potential clinical consequences after COVID-19 resolution have not been fully elucidated. As a dysregulated mitochondrial activity could impair the immune response, we explored long-lasting changes in mitochondrial functionality, circulating cytokine levels, and metabolomic profiles of infected individuals after symptoms resolution, to evaluate whether a complete recovery could be achieved. Results of this pilot study evidenced that different parameters of aerobic respiration in lymphocytes of individuals recuperated from a severe course lagged behind those shown upon mild COVID-19 recovery, in basal conditions and after simulated reinfection, and they also showed altered glycolytic capacity. The severe groups showed trends to enhanced superoxide production in parallel to lower OPA1-S levels. Unbalance of pivotal mitochondrial fusion (MFN2, OPA1) and fission (DRP1, FIS1) proteins was detected, suggesting a disruption in mitochondrial dynamics, as well as a lack of structural integrity in the electron transport chain. In serum, altered cytokine levels of IL-1β, IFN-α2, and IL-27 persisted long after clinical recovery, and growing amounts of the latter after severe infection correlated with lower basal and maximal respiration, ATP production, and glycolytic capacity. Finally, a trend for higher circulating levels of 3-hydroxybutyrate was found in individuals recovered after severe compared to mild course. In summary, long after acute infection, mitochondrial and metabolic changes seem to differ in a situation of full recovery after mild infection versus the one evolving from severe infection.

CDK4 inactivation inhibits apoptosis via mitochondria-ER contact remodeling in triple-negative breast cancer

The energetic demands of proliferating cells during tumorigenesis require close coordination between the cell cycle and metabolism. While CDK4 is known for its role in cell proliferation, its metabolic function in cancer, particularly in triple-negative breast cancer (TNBC), remains unclear. Our study, using genetic and pharmacological approaches, reveals that CDK4 inactivation only modestly impacts TNBC cell proliferation and tumor formation. Notably, CDK4 depletion or long-term CDK4/6 inhibition confers resistance to apoptosis in TNBC cells. Mechanistically, CDK4 enhances mitochondria-endoplasmic reticulum contact (MERCs) formation, promoting mitochondrial fission and ER-mitochondrial calcium signaling, which are crucial for TNBC metabolic flexibility. Phosphoproteomic analysis identified CDK4's role in regulating PKA activity at MERCs. In this work, we highlight CDK4's role in mitochondrial apoptosis inhibition and suggest that targeting MERCs-associated metabolic shifts could enhance TNBC therapy.

Mitochondrial quality control: a pathophysiological mechanism and potential therapeutic target for chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a prevalent chronic respiratory disease worldwide. Mitochondrial quality control mechanisms encompass processes such as mitochondrial biogenesis, fusion, fission, and autophagy, which collectively maintain the quantity, morphology, and function of mitochondria, ensuring cellular energy supply and the progression of normal physiological activities. However, in COPD, due to the persistent stimulation of harmful factors such as smoking and air pollution, mitochondrial quality control mechanisms often become deregulated, leading to mitochondrial dysfunction. Mitochondrial dysfunction plays a pivotal role in the pathogenesis of COPD, contributing toinflammatory response, oxidative stress, cellular senescence. However, therapeutic strategies targeting mitochondria remain underexplored. This review highlights recent advances in mitochondrial dysfunction in COPD, focusing on the role of mitochondrial quality control mechanisms and their dysregulation in disease progression. We emphasize the significance of mitochondria in the pathophysiological processes of COPD and explore potential strategies to regulate mitochondrial quality and improve mitochondrial function through mitochondrial interventions, aiming to treat COPD effectively. Additionally, we analyze the limitations and challenges of existing therapeutic strategies, aiming to provide new insights and methods for COPD treatment.

ZNF143 is a transcriptional regulator of nuclear-encoded mitochondrial genes that acts independently of looping and CTCF

Gene expression is orchestrated by transcription factors, which function within the context of a three-dimensional genome. Zinc-finger protein 143 (ZNF143/ZFP143) is a transcription factor that has been implicated in both gene activation and chromatin looping. To study the direct consequences of ZNF143/ZFP143 loss, we generated a ZNF143/ZFP143 depletion system in mouse embryonic stem cells. Our results show that ZNF143/ZFP143 degradation has no effect on chromatin looping. Systematic analysis of ZNF143/ZFP143 occupancy data revealed that a commonly used antibody cross-reacts with CTCF, leading to its incorrect association with chromatin loops. Nevertheless, ZNF143/ZFP143 specifically activates nuclear-encoded mitochondrial genes, and its loss leads to severe mitochondrial dysfunction. Using an in vitro embryo model, we find that ZNF143/ZFP143 is an essential regulator of organismal development. Our results establish ZNF143/ZFP143 as a conserved transcriptional regulator of cell proliferation and differentiation by safeguarding mitochondrial activity.

Prohibitin 1 tethers lipid membranes and regulates OPA1-mediated membrane fusion

Prohibitins (PHBs) are ubiquitously expressed proteins in the mitochondrial inner membrane (MIM) that provide membrane scaffolds for both mitochondrial proteins and phospholipids. Eukaryotic PHB complexes contain two highly homologous PHB subunits, PHB1 and PHB2, which are involved in various cellular processes, including metabolic control through the regulation of mitochondrial dynamics and integrity. Their mechanistic actions at the molecular level, however, particularly those of PHB1, remain poorly understood. To gain insight into the mechanistic actions of PHB1, we established an overexpression system for the full-length recombinant protein using silkworm larvae and characterized its biophysical properties in vitro. Using recombinant PHB1 proteoliposomes reconstituted into MIM-mimicking phospholipids, we found that PHB1 forms an oligomer via its carboxy-terminal coiled-coil region. A proline substitution into the PHB1 coiled-coil collapsed its well-ordered oligomeric state, and its destabilization correlated with mitochondrial morphologic defects. Negative-staining electron microscopy revealed that homotypic PHB1-PHB1 interactions via the coiled-coil also induced liposome tethering with remodeling of the lipid membrane structure. We clarified that PHB1 promotes membrane fusion mediated by optic atrophy 1 (OPA1), a key regulator of MIM fusion. Additionally, the presence of PHB1 reduces the dependency of lipids and OPA1 for completing the fusion process. Our in vitro study provides structural insight into how the mitochondrial scaffold plays a crucial role in regulating mitochondrial dynamics. Modulating the structure and/or function of PHB1 may offer new therapeutic potential, not only for mitochondrial dysfunction but also for other cell-related disorders.

Beyond ATP: Metabolite Networks as Regulators of Physiological and Pathological Erythroid Differentiation

Hematopoietic stem cells (HSCs) possess the capacity for self-renewal and the sustained production of all mature blood cell lineages. It has been well established that a metabolic rewiring controls the switch of HSCs from a self-renewal state to a more differentiated state, but it is only recently that we have appreciated the importance of metabolic pathways in regulating the commitment of progenitors to distinct hematopoietic lineages. In the context of erythroid differentiation, an extensive network of metabolites, including amino acids, sugars, nucleotides, fatty acids, vitamins, and iron, is required for red blood cell (RBC) maturation. In this review, we highlight the multifaceted roles via which metabolites regulate physiological erythropoiesis as well as the effects of metabolic perturbations on erythroid lineage commitment and differentiation. Of note, the erythroid differentiation process is associated with an exceptional breadth of solute carrier (SLC) metabolite transporter upregulation. Finally, we discuss how recent research, revealing the critical impact of metabolic reprogramming in diseases of disordered and ineffective erythropoiesis, has created opportunities for the development of novel metabolic-centered therapeutic strategies.

Osteosarcoma stem cells resist chemotherapy by maintaining mitochondrial dynamic stability via DRP1

Osteosarcoma malignancy exhibits significant heterogeneity, comprising both osteosarcoma stem cells (OSCs) and non‑OSCs. OSCs demonstrate increased resistance to chemotherapy due to their distinctive cellular and molecular characteristics. Alterations in mitochondrial morphology and homeostasis may enhance chemoresistance by modulating metabolic and regulatory processes. However, the relationship between mitochondrial homeostasis and chemoresistance in OSCs remains to be elucidated. The present study employed high‑resolution microscopy to perform multi‑layered image reconstructions for a quantitative analysis of mitochondrial morphology. The results indicated that OSCs exhibited larger mitochondria in comparison with non‑OSCs. Furthermore, treatment of OSCs with cisplatin (CIS) or doxorubicin (DOX) resulted in preserved mitochondrial morphological stability, which was not observed in non‑OSCs. This finding suggested a potential association between mitochondrial homeostasis and chemoresistance. Further analysis indicated that dynamin‑related protein 1 (DRP1) might play a pivotal role in maintaining the stability of mitochondrial homeostasis in OSCs. Depletion of DRP1 resulted in the disruption of mitochondrial stability when OSCs were treated with CIS or DOX. Additionally, knocking out DRP1 in OSCs led to a reduction in chemoresistance. These findings unveil a novel mechanism underlying chemoresistance in osteosarcoma and suggest that targeting DRP1 could be a promising therapeutic strategy to overcome chemoresistance in OSCs. This provided valuable insights for enhancing treatment outcomes among patients with osteosarcoma.

Real-Time Measurement of Mitochondrial Function and Glycolysis in Lymphoblastoid Cell Lines

Cells require energy in the form of ATP to function. The two main ways in which cells generate energy in mammalian cells is through glycolysis and oxidative phosphorylation (OXPHOS). Glycolysis takes place in the cytosol and involves the breakdown of glucose molecules, generating ATP and pyruvate, while OXPHOS takes place in the mitochondria and is responsible for producing the majority of ATP for the cell. A dysregulation of these cellular processes has been reported in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). In order to understand the mechanisms of the disease, it is imperative to understand how the bioenergetic pathways are altered in ME/CFS. Here we describe a method for measuring mitochondrial function and glycolytic function using the Agilent Seahorse Extracellular Flux Analyzer. We have optimized these assays for use in actively proliferating lymphoblastoid cell lines that are generated from blood cells. This assay measures oxygen consumption rate and extracellular acidification rates providing an overview of mitochondrial function and efficiency and glycolytic rate and capacity, respectively. These assays are performed on live, intact cells, and enable us to view different components and measurements of energy metabolism through the injection of different compounds that stimulate or inhibit various sections of these pathways. The below method details an optimized glycolysis and mitochondrial assay for 96-well plates with modifications noted for use in 24-well plates.

Electron Microscopy to Visualize and Quantify Mitochondrial Structure and Organellar Interactions in Cultured Cells During Senescence

Mitochondria are multifunctional organelles that play a crucial role in numerous cellular processes, including oncogene-induced senescence. Recent studies have demonstrated that mitochondria undergo notable morphological and functional changes during senescence, with mitochondria dysregulation being a critical factor contributing to the induction of this state. To elucidate the intricate and dynamic structure of these organelles, high-resolution visualization techniques are imperative. Electron microscopy offers nanometer-scale resolution images, enabling the comprehensive study of organelles' architecture. This chapter provides a detailed guide for preparing fixed samples from cultured cells for electron microscopy imaging. It also describes various quantification methods to accurately assess organellar parameters, including morphometric measurements of mitochondrial shape, cristae structure, and mitochondria-endoplasmic reticulum contact sites. These analyses yield valuable insights into the status of subcellular organelles, advancing our understanding of their involvement in cellular senescence and disease.

Revealing mitochondrial microenvironmental changes triggered by ferroptosis regulation

Ferroptosis is a unique form of iron-dependent cell death characterized by dramatic ultrastructural changes in mitochondria. Since mitochondria are intracellular energy factories and binding sites for producing reactive oxygen species, there is increasing evidence that mitochondria are closely related to ferroptosis and play a crucial role in the regulation and execution of ferroptosis. The pH of the mitochondrial microenvironment is an important parameter for cellular physiological activities. Its abnormal fluctuations are commonly thought to be associated with cancers and other diseases. Herein, a surface-enhanced Raman scattering (SERS)-based pH nanosensor with high sensitivity and targeting function was utilized to quantify and monitor mitochondrial pH value. This nanosensor was constructed by gold nanorods (AuNRs) functionalized with pH-responsive molecules (4-mercaptopyridine, MPy) and mitochondrion-targeting peptides (AMMT) that can precisely deliver AuNRs to mitochondria. Super-resolution fluorescence imaging was employed to evidence the mitochondrial targeting feature of this nanosensor. Ferroptosis regulation induces intracellular accumulation of lipid peroxide (LPO) and reactive oxygen species (ROS), which cause changes in the mitochondrial pH. This method reveals that ferroptosis leads to the gradual acidification of the mitochondrial internal environment. The conclusion deduced by this study will be helpful for the evaluation and diagnosis of diseases according to intracellular abnormal microenvironments.

Poration of mitochondrial membranes by amyloidogenic peptides and other biological toxins

Mitochondria are essential organelles known to serve broad functions, including in cellular metabolism, calcium buffering, signaling pathways and the regulation of apoptotic cell death. Maintaining the integrity of the outer (OMM) and inner mitochondrial membranes (IMM) is vital for mitochondrial health. Cardiolipin (CL), a unique dimeric glycerophospholipid, is the signature lipid of energy-converting membranes. It plays a significant role in maintaining mitochondrial architecture and function, stabilizing protein complexes and facilitating efficient oxidative phosphorylation (OXPHOS) whilst regulating cytochrome c release from mitochondria. CL is especially enriched in the IMM and at sites of contact between the OMM and IMM. Disorders of protein misfolding, such as Alzheimer's and Parkinson's diseases, involve amyloidogenic peptides like amyloid-β, tau and α-synuclein, which form metastable toxic oligomeric species that interact with biological membranes. Electrophysiological studies have shown that these oligomers form ion-conducting nanopores in membranes mimicking the IMM's phospholipid composition. Poration of mitochondrial membranes disrupts the ionic balance, causing osmotic swelling, loss of the voltage potential across the IMM, release of pro-apoptogenic factors, and leads to cell death. The interaction between CL and amyloid oligomers appears to favour their membrane insertion and pore formation, directly implicating CL in amyloid toxicity. Additionally, pore formation in mitochondrial membranes is not limited to amyloid proteins and peptides; other biological peptides, as diverse as the pro-apoptotic Bcl-2 family members, gasdermin proteins, cobra venom cardiotoxins and bacterial pathogenic toxins, have all been described to punch holes in mitochondria, contributing to cell death processes. Collectively, these findings underscore the vulnerability of mitochondria and the involvement of CL in various pathogenic mechanisms, emphasizing the need for further research on targeting CL-amyloid interactions to mitigate mitochondrial dysfunction.

Inhibition of the mitochondrial permeability transition pore as a promising target for protecting auditory function in cisplatin-induced hearing loss

mPTP is a multi-protein complex that opens in mitochondria during cell death. Cisplatin-induced hearing loss is also known to be caused by mPTP opening. Thus, our study evaluated the protective effect of a novel mPTP inhibitor named DBP-iPT against cisplatin-induced hearing loss. The cell viability result showed that DBP-iPT provided a 40 % protective effect compared to the group treated with cisplatin. In addition, the DBP-iPT treated group exhibited a reduction in intracellular ROS levels, counteracting the excessive ROS accumulation induced by cisplatin at the whole cell level. Intriguingly, mitochondrial ROS levels in the DBP-iPT group were elevated three-fold compared to the cisplatin-treated group. Despite this increase in mitochondrial ROS, the mitochondrial membrane potential in the DBP-iPT group was three times higher than that of the control. These findings present intriguing contradictions to prior studies. Therefore, we investigated whether the mitochondria were damaged or not and found that DBP-iPT treatment maintained an increased portion of elongated mitochondria, suggesting autophagy-mediated removal of damaged mitochondria. This process leads to improved mitochondrial dynamics. Finally, in vivo studies confirmed that the ABR test using a mouse model showed the same pattern of protection against cisplatin-induced hearing loss in the DBP-iPT treatment group. We have identified a new target that has a protective effect against cisplatin-induced hearing loss. Therefore, this study is expected to provide valuable insights as it focuses on targeting mPTP opening to protect against ototoxicity caused by cisplatin. This discovery will serve as a significant foundation for future research.

Calcium-mediated mitochondrial fission and mitophagy drive glycolysis to facilitate arterivirus proliferation

Mitochondria, recognized as the "powerhouse" of cells, play a vital role in generating cellular energy through dynamic processes such as fission and fusion. Viruses have evolved mechanisms to hijack mitochondrial function for their survival and proliferation. Here, we report that infection with the swine arterivirus porcine reproductive and respiratory syndrome virus (PRRSV), manipulates mitochondria calcium ions (Ca2+) to induce mitochondrial fission and mitophagy, thereby reprogramming cellular energy metabolism to facilitate its own replication. Mechanistically, PRRSV-induced mitochondrial fission is caused by elevated levels of mitochondria Ca2+, derived from the endoplasmic reticulum (ER) through inositol 1,4,5-triphosphate receptor (IP3R)-voltage-dependent anion channel 1 (VDAC1)-mitochondrial calcium uniporter (MCU) channels. This process is associated with increased mitochondria-associated membranes (MAMs), mediated by the upregulated expression of sigma non-opioid intracellular receptor 1 (SIGMAR1). Elevated mitochondria Ca2+ further activates the Ca2+/CaM-dependent protein kinase kinase β (CaMKKβ)-AMP-activated protein kinase (AMPK)-dynamin-related protein 1 (DRP1) signaling pathway, which interacts with mitochondrial fission protein 1 (FIS1) and mitochondrial dynamics proteins of 49 kDa (MiD49) to promote mitochondrial fission. PRRSV infection, alongside mitochondrial fission, triggers mitophagy via the PTEN-induced putative kinase 1 (PINK1)-Parkin RBR E3 ubiquitin (Parkin) pathway, promoting cellular glycolysis and excessive lactate production to facilitate its own replication. This study reveals the mechanism by which mitochondrial Ca2+ regulates mitochondrial function during PRRSV infection, providing new insights into the interplay between the virus and host cell metabolism.

Targeting mitochondrial transfer: a new horizon in cardiovascular disease treatment

Cardiovascular diseases (CVDs) are the leading cause of mortality among individuals with noncommunicable diseases worldwide. Obesity is associated with an increased risk of developing cardiovascular disease (CVD). Mitochondria are integral to the cardiovascular system, and it has been reported that mitochondrial transfer is associated with the pathogenesis of multiple CVDs and obesity. This review offers a comprehensive examination of the relevance of mitochondrial transfer to cardiovascular health and disease, emphasizing the critical functions of mitochondria in energy metabolism and signal transduction within the cardiovascular system. This highlights how disruptions in mitochondrial transfer contribute to various CVDs, such as myocardial infarction, cardiomyopathies, and hypertension. Additionally, we provide an overview of the molecular mechanisms governing mitochondrial transfer and its potential implications for CVD treatment. This finding underscores the therapeutic potential of mitochondrial transfer and addresses the various mechanisms and challenges in its implementation. By delving into mitochondrial transfer and its targeted modulation, this review aims to advance our understanding of cardiovascular disease treatment, presenting new insights and potential therapeutic strategies in this evolving field.

Mitochondrial Structural Abnormalities and Cardiac Reverse Remodeling in Patients With Systolic Dysfunction

BACKGROUND

Mitochondrial dysfunction in the heart is associated with the development of heart failure (HF). However, the clinical consequences of mitochondrial structural abnormalities in patients with HF remain unexplored.

METHODS AND RESULTS

Ninety-one patients with left ventricular (LV) systolic dysfunction who underwent endomyocardial biopsy (EMB) were enrolled in the study. Myocardial specimens were obtained from the right ventricular septum. Specimens were characterized using electron microscopy to assess mitochondrial size, outer membrane disruption, and cristae disorganization. The primary endpoint was a composite of cardiovascular death and unplanned hospitalization for HF. Patients were classified into LV reverse remodeling (LVRR)-positive (n=52; 57.1%) and LVRR-negative (n=39; 42.9%) groups. Cristae disorganization was observed in 21 (23.1%) patients: 6 (11.5%) in the LVRR-positive group and 15 (38.5%) in the LVRR-negative group (P=0.005). During the 1-year post-EMB observation period, 16 patients (17.6%) met the primary endpoint, with 2 (2.2%) cardiovascular deaths and 14 (15.4%) HF hospitalizations. Cristae disorganization (P=0.002) was significantly associated with the endpoints, independent of age (P=0.115), systolic blood pressure (P=0.004), B-type natriuretic peptide level (P=0.042), and mitral regurgitation (P=0.003).

CONCLUSIONS

We classified mitochondrial structural abnormalities and showed that cristae disorganization was associated with LVRR and worse prognosis. These findings may affect the management of patients with HF and systolic dysfunction who undergo EMB.