Determinants and outcomes of mitochondrial dynamics

Harmine derivative H-2-168 induces the death of Echinococcus granulosus by regulating mitochondrial fusion and fission

CONTEXT

H-2-168 has pharmacological effects similar to those of harmine, with less toxicity. The health of cells and organisms depends on a delicate balance between mitochondrial fusion and fission.

OBJECTIVE

This study investigated the roles of H-2-168 and mitochondrial fusion and fission in Echinococcus granulosus.

MATERIALS AND METHODS

Notably, E. granulosus were isolated from fresh sheep livers, and then treated with H-2-168 (25 μg/mL), mitochondrial division inhibitor 1 (Mdivi-1, 25 μg/mL) or the combination of H-2-168:Mdivi-1 (25 μg/mL:12.5 μg/mL). After 24 h of culture, the indices related to E. granulosus were measured. Additionally, Drp1 was knocked down to explore its effects on E. granulosus growth.

RESULTS

The EC50 values of H-2-168, Mdivi-1 and H-2-168:Mdivi-1 against E. granulosus were 44.171, 117.882 and 32.924 μg/mL, respectively. Compared with H-2-168 or Mdivi-1, the combination of H-2-168 and Mdivi-1 showed better inhibitory effects on E. granulosus viability, as well as increased levels of ROS and LDH, decreased ATP levels, inhibited mitochondrial activity and reduced mitochondrial membrane potential (p < 0.05), with the upregulation of Caspase-3, Cyt-c, Drp1, Fis1 and downregulation of Bcl-2, Mfn2 and OPA1. Additionally, Drp1 knockdown was successfully performed in E. granulosus, which significantly inhibited E. granulosus viability (p < 0.05) and further downregulated Mfn2 expression induced by H-2-168.

DISCUSSION AND CONCLUSION

Drp1 is closely associated with mitochondrial fusion and fission, and H-2-168 may promote E. granulosus death through disrupting the balance between mitochondrial fusion and fission.

Mitophagy in acute central nervous system injuries: regulatory mechanisms and therapeutic potentials

Acute central nervous system injuries, including ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage, traumatic brain injury, and spinal cord injury, are a major global health challenge. Identifying optimal therapies and improving the long-term neurological functions of patients with acute central nervous system injuries are urgent priorities. Mitochondria are susceptible to damage after acute central nervous system injury, and this leads to the release of toxic levels of reactive oxygen species, which induce cell death. Mitophagy, a selective form of autophagy, is crucial in eliminating redundant or damaged mitochondria during these events. Recent evidence has highlighted the significant role of mitophagy in acute central nervous system injuries. In this review, we provide a comprehensive overview of the process, classification, and related mechanisms of mitophagy. We also highlight the recent developments in research into the role of mitophagy in various acute central nervous system injuries and drug therapies that regulate mitophagy. In the final section of this review, we emphasize the potential for treating these disorders by focusing on mitophagy and suggest future research paths in this area.

Acetaldehyde dehydrogenase 2 attenuates lipopolysaccharide -induced endothelial barrier damage by inhibiting mitochondrial fission in sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is a common neurological complication of sepsis, and acetaldehyde dehydrogenase 2 (ALDH2) has been identified as a protective factor for endothelial cells against oxidative stress. In this study, we aimed to investigate the therapeutic potential of ALDH2 and its impact on mitochondrial dynamics using both mouse and brain microvascular endothelial cells (BMECs) injury models induced by lipopolysaccharide (LPS). Our findings demonstrated that ALDH2 attenuated LPS-induced brain endothelial barrier damage, as evidenced by reduced brain water content and Evans blue dye in mice, decreased transepithelial electrical resistance (TEER), and increased fluorescein isothiocyanate-dextran (FITC-Dextran) leakage in bEnd.3 cells. Furthermore, ALDH2 reduced the levels of reactive oxygen species (ROS) and malondialdehyde (MDA), while enhancing the activities of superoxide dismutase (SOD) and catalase (CAT). ALDH2 also decreased 4-HNE content and restored mitochondrial membrane potential and ATP production, promoting a balanced mitochondrial fission and fusion. Notably, our use of the mitochondrial fission inhibitor Mdivi-1 confirmed that ALDH2 alleviated mitochondrial damage by inhibiting dynamin-related protein 1 (Drp1). Consequently, our findings suggest that the effects of ALDH2 on LPS-induced blood-brain barrier (BBB) damage and oxidative stress may alleviate SAE by inhibiting Drp1 to maintain mitochondrial homeostasis.

PFOS causes lysosomes-regulated mitochondrial fission through TRPML1-VDAC1 and oligomerization of MCU/ATP5J2

Perfluorooctane sulfonate (PFOS), a listed persistent organic pollutant, poses risks to human health and is closely linked to chronic metabolic diseases. Although the role of mitochondrial fission in these diseases has garnered attention, whether and how PFOS induces mitochondrial fission remains obscure. Here, we found that PFOS induced mitochondrial fission, as demonstrated by the fragmentation of mitochondria and the upregulation of dynamin-related protein 1 (DRP1), phospho-DRP1 and mitochondrial fission protein 1 (FIS1) in human hepatocytes MIHA and mice liver. Blocking the calcium transfer from lysosomes to mitochondria that was executed by transient receptor potential mucolipin 1 (TRPML1) of lysosomes and voltage-dependent anion channel 1 (VDAC1) of mitochondria, did not affect PFOS-induced mitochondrial fission. In contrast, knockdown of TRPML1 or VDAC1 reversed this process. Knockdown of mitochondrial calcium uniporter (MCU), rather than inhibiting its activity, effectively alleviated PFOS-induced mitochondrial fission. Additionally, PFOS increased MCU oligomers without affecting MCU monomer. Inhibiting autophagy reversed the MCU oligomerization. Further investigation unveiled the interactions of MCU with VDAC1, TRPML1, mitochondrial Fo complex subunit F2 (ATP5J2) and DRP1 in PFOS-exposed mice liver and MIHA cells. We also discovered that knockdown of ATP5J2 alleviated PFOS-induced mitochondrial fission. Ulteriorly, PFOS upregulated ATP5J2 that underwent oligomerization. Knockdown of MCU reversed the increase in ATP5J2. Our study uncovers the presence and molecular basics of lysosomes-regulated mitochondrial fission under PFOS exposure, explains the regulatory pathways on MCU and ATP5J2 oligomerization and their pivotal roles in mitochondrial fission, highlighting the involvement of mitochondrial fission in PFOS-related health risks.

Mitochondria: An overview of their origin, genome, architecture, and dynamics

Mitochondria are traditionally viewed as the powerhouses of eukaryotic cells, i.e., the main providers of the metabolic energy required to maintain their viability and function. However, the role of these ubiquitous intracellular organelles far extends energy generation, encompassing a large suite of functions, which they can adjust to changing physiological conditions. These functions rely on a sophisticated membrane system and complex molecular machineries, most of which imported from the cytosol through intricate transport systems. In turn, mitochondrial plasticity is rooted on mitochondrial biogenesis, mitophagy, fusion, fission, and movement. Dealing with all these aspects and terminology can be daunting for newcomers to the field of mitochondria, even for those with a background in biological sciences. The aim of the present educational article, which is part of a special issue entitled "Mitochondria in aging, cancer and cell death", is to present these organelles in a simple and concise way. Complex molecular mechanisms are deliberately omitted, as their inclusion would defeat the stated purpose of the article. Also, considering the wide scope of the article, coverage of each topic is necessarily limited, with the reader directed to excellent reviews, in which the different topics are discussed in greater depth than is possible here. In addition, the multiple cell type-specific genotypic and phenotypic differences between mitochondria are largely ignored, focusing instead on the characteristics shared by most of them, with an emphasis on mitochondria from higher eukaryotes. Also ignored are highly degenerate mitochondrion-related organelles, found in various anaerobic microbial eukaryotes lacking canonical mitochondria.

Agent-based modeling of neuronal mitochondrial dynamics using intrinsic variables of individual mitochondria

Mitochondrial networks undergo remodeling to regulate form and function. The dynamic nature of mitochondria is maintained by the dueling processes of mitochondrial fission and fusion. Dysfunctional mitochondrial dynamics have been linked to debilitating diseases and injuries, suggesting mitochondrial dynamics as a promising therapeutic target. Increasing our understanding of the factors influencing mitochondrial dynamics will help inform therapeutic development. Utilizing live imaging of primary neurons, we analyzed how intrinsic properties of individual mitochondria influence their behavior. We found that size, shape, mitochondrial membrane potential, and protein oxidation predict mitochondrial fission and fusion. We constructed an agent-based model of mitochondrial dynamics, the mitochondrial dynamics simulation (MiDyS). In silico experiments of neuronal ischemia/reperfusion injury and antioxidant treatment illustrate the utility of MiDyS for testing hypothesized mechanisms of injury progression and evaluating therapeutic strategies. We present MiDyS as a framework for leveraging in silico experimentation to inform and improve the design of therapeutic trials.

Single-cell mitochondrial morphomics reveals cellular heterogeneity and predicts complex I, III, and ATP synthase Inhibition responses

Mitochondrial heterogeneity drives diverse cellular responses in neurodegenerative diseases, complicating the evaluation of mitochondrial dysfunction. In this study, we describe a high-throughput imaging and analysis approach to investigate cell-to-cell mitochondrial variability. We applied known mitochondrial function inhibitors - rotenone, antimycin, and oligomycin to inhibit complexes I, III, and V (ATP synthase) function in human induced pluripotent stem cell-derived cortical neurons, a model commonly used in neurodegenerative disease research. We captured a large number of cell images and extracted a diverse range of mitochondrial morphological features related to shape, size, texture, and spatial distribution, for an unbiased and comprehensive analysis of mitochondrial morphology. Group-level cell analysis, which examines the collective responses of cells exposed to the same mitochondrial inhibitor, showed that cells treated with rotenone, antimycin, or oligomycin clustered together based on their shared morphological changes. Rotenone and antimycin, both targeting different complexes of the electron transport chain, formed sub-clusters within a larger cluster. In contrast, oligomycin, which inhibits ATP synthase, resulted in a distinct cluster likely due to its differing effect on ATP production. Single-cell analysis using dimensionality reduction techniques revealed distinct subpopulations of cells with varying degrees of sensitivity to each mitochondrial inhibitor, identifying the most affected cells. Mitochondrial feature differential expression analysis showed that neurite-related mitochondrial features, such as intensity and size, were more severely impacted than cell body-related mitochondrial features, particularly with rotenone and antimycin, which target the electron transport chain. In contrast, oligomycin which affects ATP synthesis by directly inhibiting ATP synthase showed relatively less severe alterations in neurite-related mitochondrial features, highlighting a distinct effect of the mode of action between inhibitors. By incorporating the most affected cells into machine learning models, we significantly improved the prediction accuracy of mitochondrial dysfunction outcomes - 81.97% for antimycin, 75.12% for rotenone, and 94.42% for oligomycin. This enhancement underscores the value of targeting highly responsive cell subpopulations, offering a more precise method for evaluating mitochondrial modulators and therapeutic interventions in neurodegenerative diseases.

MG53 deficiency mediated skeletal muscle dysfunction in chronic obstructive pulmonary disease via impairing mitochondrial fission

BACKGROUND

Myokine dysregulation and mitochondrial dysfunction are implicated in the pathogenesis of sarcopenia in chronic obstructive pulmonary disease. The objective of this study is to explore the role of myokines and mitochondrial dysfunction in sarcopenia in chronic obstructive pulmonary disease.

METHODS

We identified mitsugumin 53 and its clinical correlation through an enzyme-linked immunosorbent assay using the plasma samples of patients with chronic obstructive pulmonary disease. The role of mitsugumin 53 was confirmed in mitsugumin 53-knockout mice. The underlying mechanisms were investigated using multi-omics sequencing, live-cell imaging, and histological and molecular experiments. The effectiveness and safety of recombinant mitsugumin 53 in treating cigarette smoke-induced muscle dysfunction were evaluated in vitro and in vivo.

RESULTS

Plasma mitsugumin 53 levels were decreased in patients with chronic obstructive pulmonary disease and were associated with skeletal muscle dysfunction. Mitsugumin 53 deficiency exacerbated cigarette smoking-induced skeletal muscle atrophy. In muscle cells, mitsugumin 53 co-localized with the mitochondria and regulated mitochondrial fission. As a lipid transporter, mitsugumin 53 directly bound to the mitochondria-specific lipid cardiolipin and participated in maintaining mitochondrial homeostasis and membrane integrity. As an E3-ligase, mitsugumin 53 deletion triggered BCL2L13-mediated mitochondrial fission upon cigarette smoking stimulation. Supplementation with recombinant mitsugumin 53 significantly alleviated cigarette smoking-induced muscle atrophy and rescued mitochondrial dysfunction in vitro and in vivo.

CONCLUSIONS

Mitsugumin 53 is a vital regulator of sarcopenia in patients with chronic obstructive pulmonary disease. Thus, mitsugumin 53 and mitochondrial fission may be promising therapeutic targets for muscle dysfunction in chronic obstructive pulmonary disease.

Zinc Mitigates the Combined Neurotoxicity of Binary Metal Mixtures via Mitophagy and Mitochondrial Fusion

Environmental metal mixtures can cause combined neurotoxicity, but the underlying mechanism remains unclear. Mitochondria are crucial for energy metabolism in the nervous system, and their dysfunction leads to neurodegeneration. Zinc (Zn) is a coenzyme of many mitochondrial enzymes that controls mitochondrial function. This study investigated the role of Zn in the neurotoxicity induced by Mn + Pb and Pb + As mixtures. Zn supplementation improved the survival rate and learning ability of Caenorhabditis elegans following their exposure to mixtures of Mn + Pb and Pb + As by enhancing their mitochondrial morphology, membrane potential, and respiratory chain. Similarly, in HT22 cells, Zn mitigated the decrease in cellular activity and increase in apoptosis induced by the Mn + Pb and Pb + As mixtures by improving mitochondrial morphology and function. Mechanistically, Zn activated the PINK1 and MFN-2/OPA-1 pathways, promoting mitophagy and mitochondrial fusion. However, inhibition of mitophagy reversed the protective effect of Zn, indicating its reliance on mitophagy for neuroprotection. Our study demonstrated that Zn alleviates the combined neurotoxicity of Mn + Pb and Pb + As mixtures by enhancing mitophagy and mitochondrial fusion, suggesting that Zn supplementation is a potential treatment for metal-induced neurotoxicity.

Mitochondrial Quality Control in Ovarian Function: From Mechanisms to Therapeutic Strategies

Mitochondrial quality control plays a critical role in cytogenetic development by regulating various cell-death pathways and modulating the release of reactive oxygen species (ROS). Dysregulated mitochondrial quality control can lead to a broad spectrum of diseases, including reproductive disorders, particularly female infertility. Ovarian insufficiency is a significant contributor to female infertility, given its high prevalence, complex pathogenesis, and profound impact on women's health. Understanding the pathogenesis of ovarian insufficiency and devising treatment strategies based on this understanding are crucial. Oocytes and granulosa cells (GCs) are the primary ovarian cell types, with GCs regulated by oocytes, fulfilling their specific energy requirements prior to ovulation. Dysregulation of mitochondrial quality control through gene knockout or external stimuli can precipitate apoptosis, inflammatory responses, or ferroptosis in both oocytes and GCs, exacerbating ovarian insufficiency. This review aimed to delineate the regulatory mechanisms of mitochondrial quality control in GCs and oocytes during ovarian development. This study highlights the adverse consequences of dysregulated mitochondrial quality control on GCs and oocyte development and proposes therapeutic interventions for ovarian insufficiency based on mitochondrial quality control. These insights provide a foundation for future clinical approaches for treating ovarian insufficiency.

A lipid in transit - the journey of cholesterol into the heart of mitochondrial research

Mitochondrial cholesterol biology in non-steroidogenic tissues remains understudied in cell science. Although detecting cholesterol in mitochondria is challenging due to isolation difficulties, studies using mitoplasts (mitochondria stripped of their outer membrane) and imaging approaches confirm its presence in the inner mitochondrial membrane. Through analysis of published evidence and first-principles reasoning, we advance a model of cholesterol trafficking into and out of mitochondria via phospholipids at mitochondria-associated membranes (MAMs), challenging the traditional view of protein-driven transport. In this model, cholesterol enters mitochondria alongside phosphatidylserine and exits with phosphatidylethanolamine - either unchanged or in a hydroxylated form after modification by the enzyme CYP27A1. Strong cholesterol-phospholipid binding energies, ∼17 kcal/mol (71.128 kJ/mol), support this lipid-mediated mechanism, suggesting it complements protein-based pathways. Future research should explore how these mechanisms collaborate to regulate mitochondrial cholesterol trafficking. By rethinking cholesterol dynamics, we raise the possibility that cholesterol plays a larger role in mitochondrial biology, influencing membrane-dependent functions like cristae structure, respiratory efficiency and inter-organelle communication. This Perspective also highlights the potential of mitochondria to regulate both dietary and endogenous cholesterol flux and homeostasis across the cell.

The Role of N6-Methyladenosine in Mitochondrial Dysfunction and Pathology

Mitochondria are indispensable in cells and play crucial roles in maintaining cellular homeostasis, energy production, and regulating cell death. Mitochondrial dysfunction has various manifestations, causing different diseases by affecting the diverse functions of mitochondria in the body. Previous studies have mainly focused on mitochondrial-related diseases caused by nuclear gene mutations or mitochondrial gene mutations, or mitochondrial dysfunction resulting from epigenetic regulation, such as DNA and histone modification. In recent years, as a popular research area, m6A has been involved in a variety of important processes under physiological and pathological conditions. However, there are few summaries on how RNA methylation, especially m6A RNA methylation, affects mitochondrial function. Additionally, the role of m6A in pathology through influencing mitochondrial function may provide us with a new perspective on disease treatment. In this review, we summarize several manifestations of mitochondrial dysfunction and compile examples from recent years of how m6A affects mitochondrial function and its role in some diseases.

BDH1 reduces apoptosis and alleviates mitochondrial damage of cardiomyocytes under high glucose condition as a downstream target of miR-125b

Diabetes is a chronic metabolic disease, characterized prominently by a persistent elevation of blood glucose level beyond the normal range. Prolonged hyperglycemia exerts deleterious effects on systems and organs of the body, leading to complications like diabetic cardiomyopathy (DCM). Our study commenced by screening the gene 3-hydroxybutyrate dehydrogenase 1 (BDH1) with low expression in DCM via Gene Expression Omnibus (GEO) analysis (GSE123975). Subsequently, we cultivated AC16 human cardiomyocytes in high glucose (HG) conditions and observed a reduction in BDH1 expression. To further investigate, we constructed plasmids for BDH1 knockdown (sh-BDH1) and overexpression (OE-BDH1). When BDH1 was overexpressed in HG-treated AC16 cells, apoptosis decreased, with reduced Bax/Bcl2 and Cleaved Caspase3/Caspase3 ratios. Additionally, mitochondrial ROS decreased, while expression of mitochondrial fusion protein mitofusin 2 (MFN2) and mitochondrial repair protein folliculin interacting protein 1 (FNIP1) increased. Notably, microRNA-125 b was upregulated in AC16 cells with hyperglycemia, and dual-luciferase reporter assays confirmed its targeting and inhibition of BDH1 mRNA. Inhibition of miR-125 b in HG-treated AC16 cells reversed apoptosis and mitochondrial ROS increase, yet simultaneous inhibition of both miR-125 b and BDH1 abolished this effect. In addition, we overexpressed BDH1 in diabetic mice by tail vein injection, and proved that overexpression of BDH1 could reduce cardiomyocyte apoptosis in vivo. In conclusion, our findings suggested that the miR-125-BDH1 axis could inhibit the production of mitochondrial ROS, promote mitochondrial fusion and repair, and reduce the apoptosis and mitochondrial damage of cardiomyocytes in HG condition.

Novel Insights into Microcystin-LR Uptake, Accumulation, and Toxicity Mechanisms in Lettuce (Lactuca sativa L.) Using a Protoplast Model

Prevalent microcystin-LR (MC-LR), a cyanotoxin, in agricultural fields compromises produce safety and threatens human health. However, little is known about its uptake and accumulation in plant cells and its resultant toxicity mechanisms. This study revealed that the MC-LR uptake into protoplasts was controlled by an active transmembrane transport process mediated by the protein carrier. MC-LR in the plant cells can enlarge the specific mitochondrial permeability transition pores and probably bind with the electron transport chain complex I (especially, NADH oxidoreductase 1, -30.59 kcal/mol of binding energy) and complex III (especially, cytochrome b, -36.98 kcal/mol of binding energy) via hydrophobic force and hydrogen bond. The interactions between MC-LR and the mitochondrial complex proteins block the electron transfer, causing high levels of reactive oxygen species (ROS), especially for H2O2. The MC-LR-induced ROS destroys the mitochondrial inner membrane structure and decreases the cell viability by 13.6-30.6% in a significant dose-dependent manner at 1-5 mg/L MC-LR stress. The findings provided direct evidence of MC-LR entry into the cells via active plasma membrane transport for the first time and clarified the associations between MC accumulation and its toxicity at cellular and molecular levels, thereby providing crucial insights for ensuring food safety and safeguarding human health.

Restoring Vascular Smooth Muscle Cell Mitochondrial Function Attenuates Abdominal Aortic Aneurysm in Mice

BACKGROUND

Abdominal aortic aneurysm (AAA) is a complex vascular pathology without pharmaceutical interventions. This study aimed to evaluate whether restoring vascular smooth muscle cell (VSMC) mitochondrial function could prevent AAA development.

METHODS

Ang II (angiotensin II)-induced AAA was established in Ldlr-deficient mice, and the gene expression profiles in abdominal aortic tissues exhibiting varying degrees of severity were analyzed. Synthetic high-density lipoprotein (sHDL) formulated with Apoa1 mimetic peptide and phospholipids was evaluated for the protective effects on VSMC mitochondria. The therapeutic efficacy of sHDL was further investigated in Ang II-infusion and PPE (porcine pancreatic elastase)-induced AAA models.

RESULTS

VSMC mitochondrial damage intensified gradually during AAA development, which was confirmed in distinct AAA animal models and human tissues. sHDL accumulated in the aneurysmatic lesions and restored mitochondrial DNA levels and the expression of genes related to oxidative phosphorylation following Ang II infusion. In mouse primary VSMCs, sHDL maintained mitochondrial homeostasis by suppressing the upregulation of DRP1 (dynamin-related protein 1), a protein involved in mitochondrial fission, reducing the generation of reactive oxygen species, preventing the loss of mitochondrial membrane potential, and preserving mitochondrial respiratory capacity. Administration of sHDL decreased Ang II-induced AAA incidence (control versus treatment, 76% versus 40%; P<0.05) and maximum aortic diameters. The protective effects of sHDL were further validated in the PPE model, with reductions observed in maximum aortic diameters and aortic mitochondrial DNA loss. Post-Ang II infusion, administration of sHDL improved VSMC mitochondrial function and suppressed aneurysm growth in Apoe-deficient mice. Human AAA is characterized by mitochondrial dysfunction, and liver-derived HDL (high-density lipoprotein) components play a pivotal role in regulating gene expression in aortic tissues.

CONCLUSIONS

VSMC mitochondrial damage is a pivotal factor in the development of AAA. The utilization of sHDL nanoparticles represents a promising novel therapeutic approach for AAA, aimed at restoring VSMC mitochondrial function.

Circadian clockwork controls the balance between mitochondrial turnover and dynamics: What is life … without time marking?

Circadian rhythms driven by biological clocks regulate physiological processes in all living organisms by anticipating daily geophysical changes, thus enhancing environmental adaptation. Time-resolved serial multi-omic analyses in vivo, ex vivo, and in synchronized cell cultures have revealed rhythmic changes in the transcriptome, proteome, and metabolome, involving up to 50 % of the mammalian genome. Mitochondrial oxidative metabolism is central to cellular bioenergetics, and many nuclear genes encoding mitochondrial proteins exhibit both circadian and ultradian oscillatory expression. However, studies on mitochondrial DNA (mtDNA) gene expression remain incomplete. Using a well-established in vitro synchronization protocol, we investigated the time-resolved expression of mtDNA genes coding for respiratory chain complex subunits, revealing a rhythmic profile dependent on BMAL1, the master circadian clock transcription factor. Additionally, the expression of genes coding for key mitochondrial biogenesis transcription factors, PGC1a, NRF1, and TFAM, showed BMAL1-dependent circadian oscillations. Notably, LC3-II, involved in mitophagy, displayed a similar in-phase circadian expression, thereby maintaining stable respiratory chain complex levels. Moreover, we found that simultaneous mitochondrial biogenesis and degradation occur in a coordinated manner with cycles in organelle dynamics, leading to rhythmic changes in mitochondrial fission and fusion. This study provides new insights into circadian clock regulation of mitochondrial turnover, emphasizing the importance of temporal regulation in cellular metabolism. Understanding these mechanisms opens potential therapeutic avenues for targeting mitochondrial dysfunctions and related metabolic disorders.

Hydrogen sulfide sustains mitochondria functions via targeting mitochondria fission regulator 1 like protein to restore human cytotrophoblast invasion and migration

Hydrogen sulfide (H2S) is bioactive in mammals. Reduced H2S was observe in pregnancy complications, pre-eclampsia (PE). Our previous data demonstrated that low dose of H2S enhanced cytotrophoblast (CTB) invasion and migration via mitochondria dynamics without knowing the mechanisms. This study was designed to explore the functional regulation of CTB by mitochondrial fission regulator 1 like (MTFR1L) and the mechanisms. By studying human placenta samples and HTR-8/SVneo cell line, MTFR1L was found expressed in CTB. While MTFR1L expression was lower in PE placenta and CTB comparing with Normal pregnancy. Knockdown of MTFR1L decreased CTB invasion and migration, as well as the ATP production, while increased the mitochondria fragmentation, ROS production and mitochondria membrane potential indicating MTFR1L was key regulator of mitochondria. The posttranslational modulation analysis showed enhanced persulfidation of MTFR1L on cystine 222 and 230 by H2S. Mutations of MTFR1LC222/C230 suppressed ATP production, CTB invasion, migration, and increased mitochondria fragmentation, ROS production and mitochondria membrane potential. The present study showed the functional MTFR1L received endogenous CBS/H2S regulation. MTFR1LC222/230 persulfidation by H2S maintained mitochondria morphology and functions thus restored CTB invasion and migration. These findings established a new regulatory pathway for CTB invasion and migration, and provided new targets for PE treatment.

Mitochondrial Involvement in the Pathogenesis of Endometriosis and its Potential as Therapeutic Targets

Endometriosis is an estrogen-dependent benign disease characterized by the development of endometrial tissue outside the uterus. This intricate ailment markedly affects a patient's well-being and lacks a definitive cure. Endometriotic cells enhance their viability by modulating genetic and epigenetic characteristics, with mitochondria being important organelles in determining cellular metabolic pathways. Mitochondrial malfunction is associated with various human disorders, and the disruption of mitochondrial adaptation mechanisms may help develop new therapies for endometriosis. This article examines the significance of mitochondrial balance in the etiology and advancement of endometriosis and introduces several potential drugs targeting mitochondria for its treatment.

Inhibition of PGAM5 hyperactivation reduces neuronal apoptosis in PC12 cells and experimental vascular dementia rats

PURPOSE

The incidence of vascular dementia (VaD), as one of the main types of dementia in old age, has been increasing year by year, and exploring its pathogenesis and seeking practical and effective treatment methods are undoubtedly the key to solving this problem. Phosphoglycerate translocase 5 (PGAM5), as a crossroads of multiple signaling pathways, can lead to mitochondrial fission, which in turn triggers the onset and development of necroptosis, and thus PGAM5 may be a novel target for the prevention and treatment of vascular dementia.

METHODS

Animal model of vascular dementia was established by Two-vessel occlusion (2-VO) method, and cellular model of vascular dementia was established by oxygen glucose deprivation (OGD) method. Neuronal damage was detected in vivo and in vitro in different groups using different concentrations of the PGAM5-specific inhibitor LFHP-1c, and necroptosis and mitochondrial dynamics-related factors were determined.

RESULTS

In vivo experiments, 10 mg/kg-1 and 20 mg/kg-1 LFHP-1c improved cognitive deficits, reduced neuronal edema and vacuoles, increased the number of nissl bodies, and it could modulate the expression of Caspase family and Bcl-2 family related proteins and mRNAs and ameliorate neuronal damage. Simultaneously, in vitro experiments, 5 μM, 10 μM and 20 μM LFHP-1c increased the activity and migration number of model cells, reduced the number of apoptotic cells, ameliorated the excessive accumulation of intracellular reactive oxygen species, inhibited the over-activation of caspase-family and Bcl-2-family related proteins and mRNAs, and improved the mitochondrial dynamics of the fission and fusion states. Moreover, in vivo and in vitro experiments have shown that LFHP-1c can also upregulate the expression level of BDNF, inhibit the expression content of TNF-α and ROS, regulate the expression of proteins and mRNAs related to the RIPK1/RIPK3/MLKL pathway and mitochondrial dynamics, and reduce neuronal apoptosis.

CONCLUSIONS

Inhibition of PGAM5 expression level can reduce neuronal damage caused by chronic cerebral ischemia and hypoxia, which mainly prevents necroptosis by targeting the RIPK1/RIPK3/MLKL signaling pathway and regulates the downstream mitochondrial dynamics homeostasis system to prevent excessive mitochondrial fission, thus improving cognition and exerting cerebroprotective effects.

Copper doped bioactive glass promotes matrix vesicles-mediated biomineralization via osteoblast mitophagy and mitochondrial dynamics during bone regeneration

Bone defect repair remains a great challenge in the field of orthopedics. Human body essential trace element such as copper is essential for bone regeneration, but how to use it in bone defects and the underlying its mechanisms of promoting bone formation need to be further explored. In this study, by doping copper into mesoporous bioactive glass nanoparticles (Cu-MBGNs), we unveil a previously unidentified role of copper in facilitating osteoblast mitophagy and mitochondrial dynamics, which enhance amorphous calcium phosphate (ACP) release and subsequent biomineralization, ultimately accelerating the process of bone regeneration. Specifically, by constructing conditional knockout mice lacking the autophagy gene Atg5 in osteogenic lineage cells, we first confirmed the role of Cu-MBGNs-promoted bone formation via mediating osteoblast autophagy pathway. Then, the in vitro studies revealed that Cu-MBGNs strengthened mitophagy by inducing ROS production and recruiting PINK1/Parkin, thereby facilitating the efficient release of ACP from mitochondria into matrix vesicles for biomineralization during bone regeneration. Moreover, we found that Cu-MBGNs promoted mitochondrion fission via activating dynamin related protein 1 (Drp1) to reinforce mitophagy pathway. Together, this study highlights the potential of Cu-MBGNs-mediated mitophagy and biomineralization for augmenting bone regeneration, offering a promising avenue for the development of advanced bioactive materials in orthopedic applications.

Icarisid Ⅱ modulates mitochondrial dynamics for anti-HBV activity

Introduction

To investigate the potential anti-hepatitis B virus (HBV) activity of Icariside Ⅱ (ICS Ⅱ), and elucidate its underlying mitochondrial dynamics mechanisms.

Methods

The study employed in vivo and in vitro assays to evaluate anti-HBV effects of ICS Ⅱ. An HBV replicating mouse model was established through hydrodynamic injection of pAAV/HBV1.2, the impact of ICS Ⅱ on HBV replication and liver toxicity was assessed. In vitro cell-based assays used HBV-positive HepG2.2.15 cells. Cytotoxicity was determined with CCK-8 assay, while ELISA and qPCR were employed to measure HBsAg, HBeAg, and HBV DNA levels. The livers of ICS II-treated HBV-infected mice were taken for transcriptome sequencing to screen for different genes, and the results were verified by Western Blot. Mitochondrial morphology and dynamics were visualized using confocal imaging and transmission electron microscopy. Key protein expressions related to mitochondrial fission and fusion were analyzed via WB. Intracellular ROS generation was assessed using fluorescence staining.

Results

The study found that ICS Ⅱ exhibited significant anti-HBV effects both in vivo and in vitro. The results of RNA-Seq indicated that ICS Ⅱ modulated the mRNA levels of Fisl, a protein associated with mitochondrial dynamics, during the anti-HBV response. It induced mitochondrial fragmentation and enhanced mitochondrial motility in HBV-positive cells. Notably, key proteins associated with mitochondrial fission and fusion demonstrated alterations favoring fission. Furthermore, ICS Ⅱ effectively reduced ROS production in HBV-positive cells.

Conclusion

ICS Ⅱ exhibits significant anti-HBV potential through its regulation of mitochondrial dynamics and ROS production.

Compositionally unique mitochondria in filopodia support cellular migration

Local metabolic demand within cells varies widely, and the extent to which individual mitochondria can be specialized to meet these functional needs is unclear. We examined the subcellular distribution of the mitochondrial contact site and cristae organizing system (MICOS) complex, a spatial and functional organizer of mitochondria, and discovered that it dynamically enriches at the tip of a minor population of mitochondria in the cell periphery. Based on their appearance, we term these mitochondria "METEORs". METEORs have a unique composition, and MICOS enrichment sites are depleted of mtDNA and matrix proteins and contain high levels of the Ca2+ uniporter MCU, suggesting a functional specialization. METEORs are also enriched for the myosin MYO19, which promotes their trafficking to a small subset of filopodia. We identify a positive correlation between the length of filopodia and the presence of METEORs and show that elimination of mitochondria from filopodia impairs cellular motility. Our data reveal a novel type of mitochondrial heterogeneity and suggest compositionally specialized mitochondria support cell migration.

Inhibition of Mitochondrial Dynamics by Mitochondrial Division Inhibitor-1 Suppresses Cell Migration and Metastatic Markers in Colorectal Cancer HCT116 Cells

Introduction

The mitochondria are highly dynamic organelles. The mitochondrial morphology and spatial distribution within the cell is determined by fusion and fission processes of mitochondria. Several studies have used mitochondrial division inhibitor-1 (Mdivi.1) to explore the roles of mitochondrial dynamics in various pathological conditions, including diabetic cardiomyopathy, myocardial infarction, cardiac hypertrophy, Alzheimer's disease, Huntington's disease and cancers.

Purpose

The objective of the study was to investigate the role of mitochondrial dynamics in the invasiveness of HCT116 colorectal cancer cells.

Material and Methods

MTT assay was used to determine the Mdivi.1-induced toxicity in HCT116 cells. Wound healing, cell migration and colony forming assays were adopted to measure the migration and invasion activity of HCT116 cells. Furthermore, flow cytometry was used to determine the Mdivi.1-induced mitochondrial mass quantification, mitochondrial membrane potential and reactive oxygen species generation in HCT116 cells. Additionally, Western Blot analysis was used to determine the expression level of Drp1, p-Drp1, Mnf2, AMPK-α, p-AMPK-α, Cox-2, iNos and MMP9 in HCT116 cells.

Results

We found that Mdivi.1 induced toxicity and altered the morphology of HCT116 cells in concentration- and time-dependent manners. Mdivi.1 significantly increased mitochondrial mass and dissipated the mitochondrial membrane potential. Furthermore, Mdivi.1 induced reactive oxygen species (ROS) generation and mitochondrial superoxide production, leading to AMPK activation. Moreover, Mdivi.1 decreased dynamin-related protein-1 (Drp1) and phosphorylated-Drp1 expression and increased mitofusin-2 (Mfn2) expression in a concentration-dependent manner at 48 and 72 h post-treatment. Notably, Mdivi.1 induced inhibition of translocation of Drp1 from the cytosol to the outer mitochondrial membrane. Mdivi.1 significantly suppressed the invasion and migration of HCT116 cells and inhibited the formation of HCT116 cell colonies. In addition, Mdivi.1 significantly decreased the expression of metastatic markers including Cox-2, iNos, and MMP-9 in HCT116 cells.

Conclusion

Collectively, this study revealed that Mdivi.1 downregulates Drp1, upregulates Mfn2, and increases mitochondrial mass with attenuated oxidative metabolism, leading to the inhibition of cell invasion and metastasis in colorectal cancer HCT116 cells. Mitochondrial dynamics are regarded as possible drug targets for interrupting colorectal cancer cell migration and metastasis.

Regular exercise alleviates metabolic dysfunction-associated steatohepatitis through rescuing mitochondrial oxidative stress and dysfunction in liver

Metabolic dysfunction-associated steatohepatitis (MASH) is characterized by severe mitochondrial dysfunction, associated with the production of mitochondrial reactive oxygen species (mROS). The substantial generation of mROS in the MASH liver, resulting from lipid surplus and electron transport chain (ETC) overload, impairs mitochondrial structure and functionality, thereby contributing to the development of severe hepatic steatosis and inflammation. Regular exercise represents an effective strategy for the treatment of MASH. Understanding the effects of exercise on oxidative stress and mitochondrial function is essential for effective treatment of MASH. This article reviews the pathological alterations in mitochondrial β-oxidation, ETC efficiency and mROS production within MASH liver. Additionally, it discusses how exercise influences the redox state and mitochondrial quality control mechanisms-such as biogenesis, mitophagy, fusion, and fission-within the MASH liver. The article emphasizes the importance of in-depth studies on exercise-induced MASH mitigation through the enhancement of mitochondrial redox balance, quality control, and function. Exploring the relationship between exercise and hepatic mitochondria could provide valuable insights into identifying potential therapeutic targets for MASH.

Melatonin refines ovarian mitochondrial dysfunction in PCOS by regulating the circadian rhythm gene Clock

Mitochondrial dysfunction is present in the ovaries of patients with polycystic ovary syndrome (PCOS). Melatonin (MT) has shown promise in treating PCOS by improving mitochondrial dysfunction, though the underlying mechanisms remain unclear. In this study, we first assessed the levels of proteins associated with mitochondrial autophagy and dynamics in ovary granulosa cells (GCs) of PCOS patients and in the ovaries of DHEA-induced PCOS mice. We found abnormal expression of these proteins, indicating the presence of mitochondrial dysfunction in PCOS ovaries. Notably, the expression of the circadian gene Clock and melatonin synthetic enzymes were also decreased in the ovaries of PCOS patients. Studies have suggested a potential role of circadian rhythm genes in the pathogenesis and progression of PCOS. We subsequently observed that pretreatment with MT could ameliorate the abnormal levels of mitochondrial-related proteins, reverse the low expression of CLOCK, and reduce pyroptosis in PCOS ovaries. Given the potential interaction between MT and Clock, we focused on whether exogenous MT improves mitochondrial dysfunction in PCOS ovaries by regulating the expression of the circadian gene Clock. Through in vitro culture of the human ovarian granulosa cell line KGN, we further found that when CLOCK levels were inhibited, the beneficial effects of MT on abnormal mitochondrial autophagy, disturbed mitochondrial dynamics, and mitochondrial dysfunction in PCOS ovaries were not significant, and there was no notable improvement in ovary GCs pyroptosis. Our study suggests that MT may improve ovary mitochondrial dysfunction by regulating circadian gene Clock while also reducing GCs pyroptosis in PCOS.

Functionally conserved inner mitochondrial membrane proteins CCDC51 and Mdm33 demarcate a subset of fission events

While extensive work has examined the mechanisms of mitochondrial fission, it remains unclear whether internal mitochondrial proteins in metazoans play a direct role in the process. Previously, the yeast inner membrane protein Mdm33 was shown to be required for normal mitochondrial morphology and has been hypothesized to be involved in mitochondrial fission. However, it is unknown whether Mdm33 plays a direct role, and it is not thought to have a mammalian homolog. Here, we use a bioinformatic approach to identify a structural ortholog of Mdm33 in humans, CCDC51 (also called MITOK), whose depletion phenocopies loss of Mdm33. We find that knockdown of CCDC51 also leads to reduced rates of mitochondrial fission. Further, we spatially and temporally resolve Mdm33 and CCDC51 to a subset of mitochondrial fission events. Finally, we show that CCDC51 overexpression promotes its spatial association with Drp1 and induces mitochondrial fragmentation, suggesting it is a positive effector of mitochondrial fission. Together, our data reveal that Mdm33 and CCDC51 are functionally conserved and suggest that internal mitochondrial proteins are directly involved in at least a subset of mitochondrial fission events in human cells.

Fatty acid desaturase 2 (FADS2) affects the pluripotency of hESCs by regulating energy metabolism

Human embryonic stem cells (hESCs) possess the ability to differentiate into various cell types, which is intricately linked to fatty acid synthesis and metabolism. Fatty acid desaturase 2 (FADS2) plays important role in fatty acid metabolism. In this study, we elucidate that the inhibition of FADS2 by SC-26196 enhances hESC pluripotency by upregulating key pluripotency genes such as POU5F1, NANOG, and KLF5. Moreover, SC-26196 treatment alters the fatty acid metabolic profile of hESCs, decreasing the synthesis of saturated fatty acids (SFAs) while increasing the content of monounsaturated fatty acids (MUFAs). Meanwhile, transcriptomic and proteomic analyses revealed that under FADS2 inhibition, hESCs maintain pluripotency primarily through enhanced oxidative phosphorylation and modified fatty acid metabolism. Knockdown and overexpression experiments confirm that FADS2 is a crucial regulator of these metabolic processes, and is essential for sustaining hESCs pluripotency. Collectively, this study unveils the pivotal role of FADS2 in the metabolic regulation of hESCs and provide new insights into the mechanisms governing pluripotency.

Therapeutic Potential of STE20-Type Kinase STK25 Inhibition for the Prevention and Treatment of Metabolically Induced Hepatocellular Carcinoma

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is a rapidly growing malignancy with high mortality. Recently, metabolic dysfunction-associated steatohepatitis (MASH) has emerged as a major HCC catalyst; however, signals driving transition of MASH to HCC remain elusive and treatment options are limited. Herein, we investigated the role of STE20-type kinase STK25, a critical regulator of hepatocellular lipotoxic milieu and MASH susceptibility, in the initiation and progression of MASH-related HCC.

METHODS

The clinical relevance of STK25 in HCC was assessed in publicly available datasets and by RT-qPCR and proximity ligation assay in a validation cohort. The functional significance of STK25 silencing in human hepatoma cells was evaluated in vitro and in a subcutaneous xenograft mouse model. The therapeutic potential of STK25 antagonism was examined in a mouse model of MASH-driven HCC, induced by a single diethylnitrosamine injection combined with a high-fat diet.

RESULTS

Analysis of public databases and in-house cohorts revealed that STK25 expression in human liver biopsies positively correlated with HCC incidence and severity. The in vitro silencing of STK25 in human hepatoma cells suppressed proliferation, migration, and invasion with efficacy comparable to that achieved by anti-HCC drugs sorafenib or regorafenib. STK25 knockout in human hepatoma cells also blocked tumor formation and growth in a subcutaneous xenograft mouse model. Furthermore, pharmacologic inhibition of STK25 with antisense oligonucleotides-administered systemically or hepatocyte-specifically-efficiently mitigated the development and exacerbation of hepatocarcinogenesis in a mouse model of MASH-driven HCC.

CONCLUSION

This study underscores STK25 antagonism as a promising therapeutic strategy for the prevention and treatment of HCC in the context of MASH.

Multienzyme-Activity Sulfur Quantum Dot Nanozyme-Mediated Cascade Reactions in Whole-Stage Symptomatic Therapy of Infected Bone Defects

Integrating the therapeutic efficacy of early bacterial clearance, midstage inflammatory remission, and late-stage effective tissue healing is considered a pivotal challenge in symptomatic treatment of infected bone defects (IBDs). Herein, a microenvironment-adaptive nanoplatform based on a sulfur quantum dot (SQD) nanozyme was proposed for whole-stage symptomatic therapy of IBDs by mediating the sequence of enzyme cascade reactions. The SQD nanozyme prepared by a size-engineering modification strategy exhibits enhanced multienzyme activity compared to conventional micrometer- and nanometer-sized sulfur particles. In the early stages of bacterial infection, the SQD nanozyme self-activates superoxide dismutase-peroxidase activity, resulting in the production of reactive oxygen species (ROS) that effectively eliminate bacteria. After disinfection, the SQD nanozyme self-switched to superoxide dismutase-catalase mimetic behavior and eliminated excess ROS, efficiently promoting macrophage polarization to an anti-inflammatory phenotype in the midinflammatory microenvironment. Importantly, SQD nanozyme-mediated M2 macrophage polarization significantly improved the damaged bone immune microenvironment, accelerating bone repair at late-stage tissue healing. Therefore, this strategy offers a promising and viable approach for the treatment of infectious tissue healing by developing multienzyme-activity nanozymes that respond intelligently to the microenvironment at different stages, effectively fighting bacteria, reducing inflammation, and promoting tissue regeneration for whole-stage symptomatic therapy.

Mitochondrial DAMPs: Key mediators in neuroinflammation and neurodegenerative disease pathogenesis

Neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS) are increasingly linked to mitochondrial dysfunction and neuroinflammation. Central to this link are mitochondrial damage-associated molecular patterns (mtDAMPs), including mitochondrial DNA, ATP, and reactive oxygen species, released during mitochondrial stress or damage. These mtDAMPs activate inflammatory pathways, such as the NLRP3 inflammasome and cGAS-STING, contributing to the progression of neurodegenerative diseases. This review delves into the mechanisms by which mtDAMPs drive neuroinflammation and discusses potential therapeutic strategies targeting these pathways to mitigate neurodegeneration. Additionally, it explores the cross-talk between mitochondria and the immune system, highlighting the complex interplay that exacerbates neuronal damage. Understanding the role of mtDAMPs could pave the way for novel treatments aimed at modulating neuroinflammation and slowing disease progression, ultimately improving patient outcome.

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.

Mitochondrial DNA leakage: underlying mechanisms and therapeutic implications in neurological disorders

Mitochondrial dysfunction is a pivotal instigator of neuroinflammation, with mitochondrial DNA (mtDNA) leakage as a critical intermediary. This review delineates the intricate pathways leading to mtDNA release, which include membrane permeabilization, vesicular trafficking, disruption of homeostatic regulation, and abnormalities in mitochondrial dynamics. The escaped mtDNA activates cytosolic DNA sensors, especially cyclic gmp-amp synthase (cGAS) signalling and inflammasome, initiating neuroinflammatory cascades via pathways, exacerbating a spectrum of neurological pathologies. The therapeutic promise of targeting mtDNA leakage is discussed in detail, underscoring the necessity for a multifaceted strategy that encompasses the preservation of mtDNA homeostasis, prevention of membrane leakage, reestablishment of mitochondrial dynamics, and inhibition the activation of cytosolic DNA sensors. Advancing our understanding of the complex interplay between mtDNA leakage and neuroinflammation is imperative for developing precision therapeutic interventions for neurological disorders.

Biallelic PTPMT1 variants disrupt cardiolipin metabolism and lead to a neurodevelopmental syndrome

Primary mitochondrial diseases (PMDs) are among the most common inherited neurological disorders. They are caused by pathogenic variants in mitochondrial or nuclear DNA that disrupt mitochondrial structure and/or function, leading to impaired oxidative phosphorylation (OXPHOS). One emerging subcategory of PMDs involves defective phospholipid metabolism. Cardiolipin, the signature phospholipid of mitochondria, resides primarily in the inner mitochondrial membrane, where it is biosynthesized and remodelled via multiple enzymes and is fundamental to several aspects of mitochondrial biology. Genes that contribute to cardiolipin biosynthesis have recently been linked with PMD. However, the pathophysiological mechanisms that underpin human cardiolipin-related PMDs are not fully characterized. Here, we report six individuals, from three independent families, harbouring biallelic variants in PTPMT1, a mitochondrial tyrosine phosphatase required for de novo cardiolipin biosynthesis. All patients presented with a complex, neonatal/infantile onset neurological and neurodevelopmental syndrome comprising developmental delay, microcephaly, facial dysmorphism, epilepsy, spasticity, cerebellar ataxia and nystagmus, sensorineural hearing loss, optic atrophy and bulbar dysfunction. Brain MRI revealed a variable combination of corpus callosum thinning, cerebellar atrophy and white matter changes. Using patient-derived fibroblasts and skeletal muscle tissue, combined with cellular rescue experiments, we characterized the molecular defects associated with mutant PTPMT1 and confirmed the downstream pathogenic effects that loss of PTPMT1 has on mitochondrial structure and function. To further characterize the functional role of PTPMT1 in cardiolipin homeostasis, we created a ptpmt1 knockout zebrafish. This model had abnormalities in body size, developmental alterations, decreased total cardiolipin levels and OXPHOS deficiency. Together, these data indicate that loss of PTPMT1 function is associated with a new autosomal recessive PMD caused by impaired cardiolipin metabolism, highlighting the contribution of aberrant cardiolipin metabolism towards human disease and emphasizing the importance of normal cardiolipin homeostasis during neurodevelopment.

Depleting chemoresponsive mitochondrial fission mediator DRP1 does not mitigate sarcoma resistance

Specific patterns of mitochondrial dynamics have been repeatedly reported to promote drug resistance in cancer. However, whether targeting mitochondrial fission- and fusion-related proteins could be leveraged to combat multidrug-resistant pediatric sarcomas is poorly understood. Here, we demonstrated that the expression and activation of the mitochondrial fission mediator DRP1 are affected by chemotherapy exposure in common pediatric sarcomas, namely, rhabdomyosarcoma and osteosarcoma. Unexpectedly, decreasing DRP1 activity through stable DRP1 knockdown neither attenuated sarcoma drug resistance nor affected growth rate or mitochondrial network morphology. The minimal impact on sarcoma cell physiology, along with the up-regulation of fission adaptor proteins (MFF and FIS1) detected in rhabdomyosarcoma cells, suggests an alternative DRP1-independent mitochondrial fission mechanism that may efficiently compensate for the lack of DRP1 activity. By exploring the upstream mitophagy and mitochondrial fission regulator, AMPKα1, we found that markedly reduced AMPKα1 levels are sufficient to maintain AMPK signaling capacity without affecting chemosensitivity. Collectively, our findings challenge the direct involvement of DRP1 in pediatric sarcoma drug resistance and highlight the complexity of yet-to-be-characterized noncanonical regulators of mitochondrial dynamics.

The role of mitochondrial remodeling in neurodegenerative diseases

Neurodegenerative diseases are a group of diseases that pose a serious threat to human health, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD) and Amyotrophic Lateral Sclerosis (ALS). In recent years, it has been found that mitochondrial remodeling plays an important role in the onset and progression of neurodegenerative diseases. Mitochondrial remodeling refers to the dynamic regulatory process of mitochondrial morphology, number and function, which can affect neuronal cell function and survival by regulating mechanisms such as mitochondrial fusion, division, clearance and biosynthesis. Mitochondrial dysfunction is an important intrinsic cause of the pathogenesis of neurodegenerative diseases. Mitochondrial remodeling abnormalities are involved in energy metabolism in neurodegenerative diseases. Pathological changes in mitochondrial function and morphology, as well as interactions with other organelles, can affect the energy metabolism of dopaminergic neurons and participate in the development of neurodegenerative diseases. Since the number of patients with PD and AD has been increasing year by year in recent years, it is extremely important to take effective interventions to significantly reduce the number of morbidities and to improve people's quality of life. More and more researchers have suggested that mitochondrial remodeling and related dynamics may positively affect neurodegenerative diseases in terms of neuronal and self-adaptation to the surrounding environment. Mitochondrial remodeling mainly involves its own fission and fusion, energy metabolism, changes in channels, mitophagy, and interactions with other cellular organelles. This review will provide a systematic summary of the role of mitochondrial remodeling in neurodegenerative diseases, with the aim of providing new ideas and strategies for further research on the treatment of neurodegenerative diseases.

Skeletal Muscle Mitochondrial and Autophagic Dysregulation Are Modifiable in Spinal Muscular Atrophy

BACKGROUND

Spinal muscular atrophy (SMA) is a health- and life-limiting neuromuscular disorder. Although varying degrees of mitochondrial abnormalities have been documented in SMA skeletal muscle, the influence of disease progression on pathways that govern organelle turnover and dynamics are poorly understood. Thus, the purpose of this study was to investigate skeletal muscle mitochondria during SMA disease progression and determine the effects of therapeutic modalities on organelle biology.

METHODS

Smn2B/+ and Smn2B/- severe SMA-like mice were used to investigate mitochondrial turnover and dynamics signalling. Muscles were analysed at postnatal day 9 (P9), P13 or P21 to address pre-symptomatic, early symptomatic and late symptomatic periods of the disorder. Additionally, we utilized an acute dose of exercise and urolithin A (UA) to stimulate organelle remodelling in skeletal muscle of SMA mice in vivo and in SMA patient-derived myotubes in vitro, respectively.

RESULTS

Smn2B/+ and Smn2B/- mice demonstrated similar levels of muscle mitochondrial oxidative phosphorylation (OxPhos) proteins throughout disease progression. In contrast, at P21 the mRNA levels of upstream factors important for the transcription of mitochondrial genes encoded by the nuclear and mitochondrial DNA, including nuclear respiratory factor 2, sirtuin 1, mitochondrial transcription factor A and tumour protein 53, were upregulated (+31%-195%, p < 0.05) in Smn2B/- mice relative to Smn2B/+. Early and late symptomatic skeletal muscle from SMA-like mice showed greater autophagosome formation as denoted by more phosphorylated autophagy related 16-like 1 (p-ATG16L1Ser278) puncta (+60%-80%, p < 0.05), along with a build-up of molecules indicative of damaged mitochondria such as BCL2 interacting protein 3, Parkin and PTEN-induced kinase 1 (+100%-195%, p < 0.05). Furthermore, we observed a fragmented mitochondrial phenotype at P21 that was concomitant with abnormal splicing of Optic atrophy 1 transcripts (-53%, p < 0.05). A single dose of exercise augmented the expression of citrate synthase (+43%, p < 0.05) and corrected the over-assembly of autophagosomes (-64%, p < 0.05). In patient muscle cells, UA treatment stimulated autophagic flux, increased the expression of OxPhos proteins (+15%-47%, p < 0.05) and improved maximal oxygen consumption (+84%, p < 0.05).

CONCLUSIONS

Abnormal skeletal muscle mitochondrial turnover and dynamics are associated with disease progression in Smn2B/- mice despite compensatory elevations in upstream factors important for organelle synthesis and recycling. Exercise and UA enhance mitochondrial health in skeletal muscle, which indicates that lifestyle-based and pharmacological interventions may be effective countermeasures targeting the organelle for therapeutic remodelling in SMA.

The tRF-33/IGF1 axis dysregulates mitochondrial homeostasis in HER2-negative breast cancer

Transfer RNA-derived small RNAs (tsRNAs), a recently identified noncoding RNA subset, are mainly classified into transfer RNA (tRNA)-derived small RNA fragments (tRFs) and tRNA-derived stress-induced RNAs (tiRNAs). tsRNAs dysregulation is frequently observed in numerous cancer types, suggesting involvement in tumorigenesis. However, their functions in breast cancer (BC) remain to be fully understood. Here, it was discovered that tRF-33-MEF91SS2PMFI0Q (tRF-33), derived from mature tRNA-LysTTT, was markedly upregulated in human epidermal receptor 2 (HER2)-negative BC cells and tissue samples. tRF-33 stimulated the proliferation, migration, and invasiveness of BC cells in vitro and facilitated tumor progression in vivo. Mechanistically, tRF-33 was found for the first time to bind directly to the 3'-UTR of IGF1, resulting in downregulation of both its mRNA and protein and thus affecting mitochondrial homeostasis and progression of BC. These results demonstrate a novel tsRNA modulatory mechanism and a potential direction for treating HER2-negative BC.NEW & NOTEWORTHY In this study, we identified differential expression of tRNA fragments in HER2-negative BC tissues compared with adjacent normal tissues, observing significant upregulation of an i-tRF type tRF-33-MEF91SS2PMFI0Q (tRF-33) in the tumor tissue. We also found that tRF-33 promoted tumorigenesis in BC cells. We demonstrated for the first time that IGF1 was a target gene of tRF-33 and also showed that the tRF-33/IGF1 axis impaired mitochondrial dynamics, thus affecting mitochondrial homeostasis and promoting HER2-negative BC progression.

Early Synapse-Specific Alterations of Photoreceptor Mitochondria in the EAE Mouse Model of Multiple Sclerosis

Multiple sclerosis (MS) is an inflammatory autoimmune disease of the central nervous system (CNS) linked to many neurological disabilities. The visual system is frequently impaired in MS. In previous studies, we observed early malfunctions of rod photoreceptor ribbon synapses in the EAE mouse model of MS that included alterations in synaptic vesicle cycling and disturbances of presynaptic Ca2+ homeostasis. Since these presynaptic events are highly energy-demanding, we analyzed whether synaptic mitochondria, which play a major role in synaptic energy metabolism, might be involved at that early stage. Rod photoreceptor presynaptic terminals contain a single large mitochondrion next to the synaptic ribbon. In the present study, we analyzed the expression of functionally relevant mitochondrial proteins (MIC60, ATP5B, COX1, PINK1, DRP1) by high-resolution qualitative and quantitative immunofluorescence microscopy, immunogold electron microscopy and quantitative Western blot experiments. We observed a decreased expression of many functionally relevant proteins in the synaptic mitochondria of EAE photoreceptors at an early stage, suggesting that early mitochondrial dysfunctions play an important role in the early synapse pathology. Interestingly, mitochondria in presynaptic photoreceptor terminals were strongly compromised in early EAE, whereas extra-synaptic mitochondria in photoreceptor inner segments remained unchanged, demonstrating a functional heterogeneity of photoreceptor mitochondria.

Ultrastructure analysis of mitochondria, lipid droplet and sarcoplasmic reticulum apposition in human heart failure

Background

Cardiomyocyte structural remodeling is reported as a causal contributor to heart failure (HF) development and progression. Growing evidence highlights the role of organelle apposition in cardiomyocyte function and homeostasis. Disruptions in organelle crosstalk, such as that between the sarcoplasmic reticulum (SR) and mitochondria, are thought to impact numerous cellular processes such as calcium handling and cellular bioenergetics; two processes that are disrupted and implicated in cardiac pathophysiology. While the physical distance between organelles is thought to be essential for homeostatic cardiomyocyte function, whether the interactions and coupling of organelles are altered in human heart failure remains unclear.

Methods

Here, we utilized transmission electron microscopy and careful quantification of ultrastructure to characterize the changes in organelle apposition in cardiomyocytes isolated from the hearts of patients diagnosed with various types of HF. Subsequently we employed molecular approaches to examine the expression of proposed organelle tethers.

Results

We demonstrate that cardiomyocytes isolated from dilated cardiomyopathy, hypertrophic cardiomyopathy and ischemic cardiomyopathy hearts display smaller, more rounded mitochondria, as compared to nonfailing controls. Failing cardiomyocytes also exhibited disrupted SR-mitochondria juxtaposition and changes in the expression of proposed molecular tethers. Further analysis revealed alterations in lipid droplet dynamics including decreased lipid droplet content and less lipid droplets in association with mitochondria in failing cardiomyocytes.

Conclusion

Here we observed changes in organelle dynamics in cardiomyocytes isolated from heart failure patients diagnosed with differing etiologies. Our results suggest that organelle structure and apposition may be a ubiquitous contributor to human HF progression.

Epithelial OPA1 links mitochondrial fusion to inflammatory bowel disease

Dysregulation at the intestinal epithelial barrier is a driver of inflammatory bowel disease (IBD). However, the molecular mechanisms of barrier failure are not well understood. Here, we demonstrate dysregulated mitochondrial fusion in intestinal epithelial cells (IECs) of patients with IBD and show that impaired fusion is sufficient to drive chronic intestinal inflammation. We found reduced expression of mitochondrial fusion-related genes, such as the dynamin-related guanosine triphosphatase (GTPase) optic atrophy 1 (OPA1), and fragmented mitochondrial networks in crypt IECs of patients with IBD. Mice with Opa1 deficiency in the gut epithelium (Opa1i∆IEC) spontaneously developed chronic intestinal inflammation with mucosal ulcerations and immune cell infiltration. Intestinal inflammation in Opa1i∆IEC mice was driven by microbial translocation and associated with epithelial progenitor cell death and gut barrier dysfunction. Opa1-deficient epithelial cells and human organoids exposed to a pharmacological OPA1 inhibitor showed disruption of the mitochondrial network with mitochondrial fragmentation and changes in mitochondrial size, ultrastructure, and function, resembling changes observed in patient samples. Pharmacological inhibition of the GTPase dynamin-1-like protein in organoids derived from Opa1i∆IEC mice partially reverted this phenotype. Together, our data demonstrate a role for epithelial OPA1 in regulating intestinal immune homeostasis and epithelial barrier function. Our data provide a mechanistic explanation for the observed mitochondrial dysfunction in IBD and identify mitochondrial fusion as a potential therapeutic target in this disease.

Oxidative phosphorylation decline and mitochondrial dynamics disequilibrium are involved in chicken large white follicle atresia

In domestic hens, the atresia of large white follicles (LWFs) directly affects the number of follicles that enter the hierarchical development and ovulation. Figuring out factors responsible for LWFs atresia is helpful to improve egg production of hens. At the LWF stage, yellow yolk begins to be deposited into the follicles via receptor mediated endocytosis, which requires large amounts of ATP. Mitochondrial oxidative phosphorylation (OXPHOS) is the primary source of ATP for follicular development. However, it is not clear whether the OXPHOS is changed along LWFs atresia. In this study, firstly, differences in morphological appearance, histology, cell proliferation, apoptosis, OXPHOS and mitochondrial dynamics between LWFs and atretic large white follicles (ALWFs) in hens at the peak laying stage (35W) were determined to elucidate whether OXPHOS changes in ALWFs. Then, these differences of LWFs between the peak laying hens (35W-LWFs) and the late laying hens (70W-LWFs) were detected to confirm whether OXPHOS changes during LWFs atresia. The results showed that ALWFs exhibited a wrinkled surface with several hemorrhage spots, and numerous intercellular vacuoles, as well as severe nuclear pyknosis. Compared to LWFs, a higher cell apoptosis rate and a lower proliferation rate were observed in ALWFs. In ALWFs, OXPHOS declined as manifested by reductions in ATP levels, ATP synthetase abundance, NAD+, NADH and NAD+/NADH ratio, and mRNA levels of genes associated with OXPHOS complexes I-V. Meanwhile, mitochondrial dynamics disequilibrium was detected in ALWFs as the expression levels of proteins and genes related to mitochondrial fusion (MFN1, MFN2, and OPA1) decreased, while the expression levels of proteins and genes related to mitochondrial fission (DRP1 and FIS1) increased. Further, compared to 35W-LWFs, 70W-LWFs showed a histology resembling to ALWFs, manifested as a slightly loosen structure of granulosa layers, and a lower cell proliferation rate. Moreover, both lower OXPHOS and impaired mitochondrial dynamics were detected in 70W-LWFs. In conclusion, our results indicated that OXPHOS decline and mitochondrial dynamics disequilibrium are involved in LWFs atresia in laying hens.

Mitochondrial diseases: from molecular mechanisms to therapeutic advances

Mitochondria are essential for cellular function and viability, serving as central hubs of metabolism and signaling. They possess various metabolic and quality control mechanisms crucial for maintaining normal cellular activities. Mitochondrial genetic disorders can arise from a wide range of mutations in either mitochondrial or nuclear DNA, which encode mitochondrial proteins or other contents. These genetic defects can lead to a breakdown of mitochondrial function and metabolism, such as the collapse of oxidative phosphorylation, one of the mitochondria's most critical functions. Mitochondrial diseases, a common group of genetic disorders, are characterized by significant phenotypic and genetic heterogeneity. Clinical symptoms can manifest in various systems and organs throughout the body, with differing degrees and forms of severity. The complexity of the relationship between mitochondria and mitochondrial diseases results in an inadequate understanding of the genotype-phenotype correlation of these diseases, historically making diagnosis and treatment challenging and often leading to unsatisfactory clinical outcomes. However, recent advancements in research and technology have significantly improved our understanding and management of these conditions. Clinical translations of mitochondria-related therapies are actively progressing. This review focuses on the physiological mechanisms of mitochondria, the pathogenesis of mitochondrial diseases, and potential diagnostic and therapeutic applications. Additionally, this review discusses future perspectives on mitochondrial genetic diseases.

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.

Idebenone Protects Photoreceptors Impaired by Oxidative Phosphorylation Disorder in Retinal Detachment

Purpose

Oxidative phosphorylation (OXPHOS) is an aerobic metabolic mechanism, and its dysfunction plays an important role in the pathological changes of ischemic diseases. However, systematic studies on the occurrence of retinal detachment (RD) are lacking.

Methods

Single-cell RNA sequencing (scRNA-seq) of the human retina was performed to detect the metabolic changes of various retinal cells after RD. In this study, animal experiments were conducted to explore the OXPHOS activity after RD. In addition, idebenone, a coenzyme Q10 (CoQ10) analog currently used to treat Leber hereditary optic neuropathy (LHON), was used to improve the OXPHOS disorder in experimental RD model.

Results

ScRNA-seq revealed abnormal energy metabolism and OXPHOS pathways in retinal cells after RD. Adenosine triphosphate (ATP) and reactive oxygen species (ROS) are the main products of OXPHOS, the mouse RD model indicated that the rise in ROS levels may have a greater impact on photoreceptors in the early stage, whereas decreased ATP synthesis was observed in the later stage; these changes threaten the function and morphology of the retina. Idebenone was administered to model mice intragastrically, leading to reduced ROS levels in the early stage post-RD and improved ATP synthesis in the later stage, which was closely related to the maintenance of mitochondrial morphology.

Conclusions

OXPHOS disorder leads to photoreceptor degeneration after RD, which can be alleviated by improving OXPHOS function.

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.

SENP1 prevents high fat diet-induced non-alcoholic fatty liver diseases by regulating mitochondrial dynamics

Mitochondrial dynamics plays a crucial role in the occurrence and development of non-alcoholic fatty liver diseases (NAFLD). SENP1, a SUMO-specific protease, catalyzes protein de-SUMOylation and involves in various physiological and pathological processes. However, the exact role of SENP1 in NAFLD remains unclear. Therefore, we investigated the regulatory role of SENP1 in mitochondrial dynamics during the progression of NAFLD. In the study, the NAFLD in vivo model induced by high fat diet (HFD) and in vitro model induced by free fatty acids (FFA) were established to investigate the role and underlying mechanism of SENP1 through detecting mitochondrial morphology and dynamics. Our results showed that the down-regulation of SENP1 expression and the mitochondrial dynamics dysregulation occurred in the NAFLD, evidenced as mitochondrial fragmentation, up-regulation of p-Drp1 ser616 and down-regulation of MFN2, OPA1. However, over-expression of SENP1 significantly alleviated the NAFLD, rectified the mitochondrial dynamics disorder, reduced Cyt-c release and ROS levels induced by FFA or HFD; moreover, the over-expression of SENP1 also reduced the SUMOylation levels of Drp1 and prevented the Drp1 translocation to mitochondria. Our findings suggest that the possible mechanisms of SENP1 were through rectifying the mitochondrial dynamics disorder, reducing Cyt-c release and ROS-mediated oxidative stress. The findings would provide a novel target for the prevention and treatment of NALFD.

Understanding Mitochondrial and Lysosomal Dynamics by Fluorescent Microscopy

Live cell imaging is a robust method to visualize dynamic cellular structures, especially organelles with network-like structures such as mitochondria. In this regard, mitochondrial dynamics, namely mitochondrial fission and fusion, are highly dynamic processes that regulate mitochondrial size and morphology depending on a plethora of cellular cues. Likewise, lysosome size and distribution may hint at their function and state.Here, we describe how to perform live cell confocal imaging using commercially available organelle dyes (MitoTracker, LysoTracker), followed by either 2D or 3D analyses of mitochondrial morphology/network connectivity and lysosomal morphology using the freely available Mitochondria Analyzer plugin for ImageJ/Fiji.

Construction of AMPK-related circRNA network in mouse myocardial ischemia-reperfusion injury model

OBJECTIVE

To screen Myocardial ischemia-reperfusion Injury in mice. adenosine monophate-activatedprotein kinase (AMPK) -related differentially expressed circularRNA (circRNA) in MIRI model, Ampk-related circRNA network was drawn to provide possible ideas for the prevention and treatment of MIRI.

METHODS

The mouse MIRI model was constructed by ligation of the left anterior descending artery. After the model was successfully established, the related indicators of cardiac function were detected, and high-throughput sequencing was performed on the myocardial tissue of the mice.

RESULTS

MIRI model was successfully constructed, and two AMPK related differentially expressed loops (novel_circ_043550 and novel_circ_035243) were screened out. A circRNA-miRNA-mRNA network consisting of 2 circRNA, 28 microRNA(miRNA) and 229 messengerRNA (mRNA) was constructed.

CONCLUSIONS

This study reveals the differential expression of several AMPK-related circRNAs in MIRI in mice, and the AMPK-related circRNA regulatory network is constructed, suggesting that AMPK-related circRNA may have potential clinical application prospects as a potential molecular marker and therapeutic target for MIRI.

Important Role of Mitochondrial Dysfunction in Immune Triggering and Inflammatory Response in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease, primarily characterized by chronic symmetric synovial inflammation and erosive bone destruction.Mitochondria, the primary site of cellular energy production, play a crucial role in energy metabolism and possess homeostatic regulation capabilities. Mitochondrial function influences the differentiation, activation, and survival of both immune and non-immune cells involved in RA pathogenesis. If the organism experiences hypoxia, genetic predisposition, and oxidative stress, it leads to mitochondrial dysfunction, which further affects immune cell energy metabolism, synovial cell proliferation, apoptosis, and inflammatory signaling, causing the onset and progression of RA; and, mitochondrial regulation is becoming increasingly important in the treatment of RA.In this review, we examine the structure and function of mitochondria, analyze the potential causes of mitochondrial dysfunction in RA, and focus on the mechanisms by which mitochondrial dysfunction triggers chronic inflammation and immune disorders in RA. We also explore the effects of mitochondrial dysfunction on RA immune cells and osteoblasts, emphasizing its key role in the immune response and inflammatory processes in RA. Furthermore, we discuss potential biological processes that regulate mitochondrial homeostasis, which are of great importance for the prevention and treatment of RA.

ATAD1 Regulates Neuronal Development and Synapse Formation Through Tuning Mitochondrial Function

Mitochondrial function is essential for synaptic function. ATAD1, an AAA+ protease involved in mitochondrial quality control, governs fission-fusion dynamics within the organelle. However, the distribution and functional role of ATAD1 in neurons remain poorly understood. In this study, we demonstrate that ATAD1 is primarily localized to mitochondria in dendrites and, to a lesser extent, in spines in cultured hippocampal neurons. We found that ATAD1 deficiency disrupts the mitochondrial fission-fusion balance, resulting in mitochondrial fragmentation. This deficiency also impairs dendritic branching, hinders dendritic spine maturation, and reduces glutamatergic synaptic transmission in hippocampal neuron. To further investigate the underlying mechanism, we employed an ATP hydrolysis-deficient mutant of ATAD1 to rescue the neuronal deficits associated with ATAD1 loss. We discovered that the synaptic deficits are independent of the mitochondrial morphology changes but rely on its ATP hydrolysis. Furthermore, we show that ATAD1 loss leads to impaired mitochondrial function, including decreased ATP production, impaired membrane potential, and elevated oxidative stress. In conclusion, our results provide evidence that ATAD1 is crucial for maintaining mitochondrial function and regulating neurodevelopment and synaptic function.