Mitochondrial cristae shape determines respiratory chain supercomplexes assembly and respiratory efficiency

Update on the correlation between mitochondrial function and osteonecrosis of the femoral head osteocytes

Mitochondrial health is maintained in a steady state through mitochondrial dynamics and autophagy processes. Recent studies have identified healthy mitochondria as crucial regulators of cellular function and survival. This process involves adenosine triphosphate (ATP) synthesis by mitochondrial oxidative phosphorylation (OXPHOS), regulation of calcium metabolism and inflammatory responses, and intracellular oxidative stress management. In the skeletal system, they participate in the regulation of cellular behaviors and the responses of osteoblasts, osteoclasts, chondrocytes, and osteocytes to external stimuli. Indeed, mitochondrial damage or dysfunction occurs in the development of a few bone diseases. For example, mitochondrial damage may lead to an imbalance in osteoblasts and osteoclasts, resulting in osteoporosis, osteomalacia, or poor bone production, and chondrocyte death and inflammatory infiltration in osteoarthritis are the main causes of cartilage degeneration due to mitochondrial damage. However, the opposite exists for osteosarcoma, where overactive mitochondrial metabolism is able to accelerate the proliferation and migration of osteosarcoma cells, which is a major disease feature. Bone is a dynamic organ and osteocytes play a fundamental role in all regions of bone tissue and are involved in regulating bone integrity. This review examines the impact of mitochondrial physiological function on osteocyte health and summarizes the microscopic molecular mechanisms underlying its effects. It highlights that targeted therapies focusing on osteocyte mitochondria may be beneficial for osteocyte survival, providing a new insight for the diagnosis, prevention, and treatment of diseases associated with osteocyte death.

Prognostic signature based on mitochondria- and angiogenesis-related genes associated with immune microenvironment of multiple myeloma

INTRODUCTION

Mitochondria and angiogenesis play key roles in multiple myeloma (MM) development, but their interrelated genes affecting MM prognosis are under-studied.

METHODS

We analyzed TCGA_MMRF and GSE4581 datasets to identify four genes - CCNB1, CDC25C, HSP90AA1, and PARP1 - that significantly correlate with MM prognosis, with high expression indicating poor outcomes.

RESULTS

A prognostic signature based on these genes stratified patients into high- and low-risk groups, with the latter showing better survival. The signature was validated as an independent prognostic factor. Biological function analysis revealed differences in cell cycle processes between risk groups, and immune microenvironment analysis showed distinct immune cell infiltration patterns.

CONCLUSION

This mitochondria- and angiogenesis-related prognostic signature could enhance MM prognosis assessment and offer new therapeutic insights.

Mitigation of the toxic effects of nitrite: Role and mechanism of isoleucine in mitigating mitochondrial DNA leakage-induced inflammation in grass carp (Ctenopharyngodon idella) under nitrite exposure

The physiological and growth processes of fish are closely associated with their surrounding environment. This study investigated the role and underlying mechanisms of isoleucine (Ile) in alleviating mitochondrial DNA (mtDNA) leakage-induced inflammation in grass carp under nitrite exposure. Grass carp were fed six experimental diets containing different Ile levels (0.00, 3.00, 6.00, 9.00, 12.00 and 15.00 g/kg) for 9 weeks, followed by a 96-hour nitrite exposure trial. Ile supplementation mitigated the deterioration of blood parameters including glutamic oxaloacetic transaminase (GOT), glutamic alanine transaminase (GPT), glucose, cortisol and lactate dehydrogenase (LDH) induced by nitrite exposure. Additionally, Ile enhanced its transport to the liver and mitochondria, as well as increased metabolism of Ile in mitochondria. Histological analyses revealed that Ile mitigated nitrite exposure-induced liver damage and mitochondrial cristae disruption. Furthermore, Ile preserved the mitochondrial cristae homeostasis by upregulating key proteins involved in mitochondrial structure maintenance, while inhibiting mtDNA leakage. Mechanistically, Ile attenuated mtDNA leakage-induced inflammation under nitrite exposure associated with the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-Stimulator of Interferon Genes (STING) and NOD-like receptor thermal protein domain associated protein 3 (NLRP3) pathways. These findings highlight the protective role of Ile in reducing inflammation triggered by environmental nitrite exposure, offering new insights into aquatic toxicology, and determined that Ile concentration of 11.13 g/kg diet could be optimal for mitigating nitrite-induced stress in grass carp, providing a theoretical basis for formulating anti- nitrite stress diets in aquaculture.

Role of Mitochondrial Dysfunctions in Neurodegenerative Disorders: Advances in Mitochondrial Biology

Mitochondria, essential organelles responsible for cellular energy production, emerge as a key factor in the pathogenesis of neurodegenerative disorders. This review explores advancements in mitochondrial biology studies that highlight the pivotal connection between mitochondrial dysfunctions and neurological conditions such as Alzheimer's, Parkinson's, Huntington's, ischemic stroke, and vascular dementia. Mitochondrial DNA mutations, impaired dynamics, and disruptions in the ETC contribute to compromised energy production and heightened oxidative stress. These factors, in turn, lead to neuronal damage and cell death. Recent research has unveiled potential therapeutic strategies targeting mitochondrial dysfunction, including mitochondria targeted therapies and antioxidants. Furthermore, the identification of reliable biomarkers for assessing mitochondrial dysfunction opens new avenues for early diagnosis and monitoring of disease progression. By delving into these advancements, this review underscores the significance of understanding mitochondrial biology in unraveling the mechanisms underlying neurodegenerative disorders. It lays the groundwork for developing targeted treatments to combat these devastating neurological conditions.

Arginase 1 drives mitochondrial cristae remodeling and PANoptosis in ischemia/hypoxia-induced vascular dysfunction

Ischemic/hypoxic injury significantly damages vascular function, detrimentally impacting patient outcomes. Changes in mitochondrial structure and function are closely associated with ischemia/hypoxia-induced vascular dysfunction. The mechanism of this process remains elusive. Using rat models of ischemia and hypoxic vascular smooth muscle cells (VSMCs), we combined transmission electron microscopy, super-resolution microscopy, and metabolic analysis to analyze the structure and function change of mitochondrial cristae. Multi-omics approaches revealed arginase 1 (Arg1) upregulation in ischemic VSMCs, confirmed by in vivo and in vitro knockout models showing Arg1's protective effects on mitochondrial cristae, mitochondrial and vascular function, and limited the release of mtDNA. Mechanistically, Arg1 interacting with Mic10 led to mitochondrial cristae remodeling, together with hypoxia-induced VDAC1 lactylation resulting in the opening of MPTP and release of mtDNA of VSMCs. The released mtDNA led to PANoptosis of VSMCs via activation of the cGAS-STING pathway. ChIP-qPCR results demonstrated that lactate-mediated Arg1 up-regulation was due to H3K18la upregulation. VSMCs targeted nano-material PLGA-PEI-siRNA@PM-α-SMA (NP-siArg1) significantly improved vascular dysfunction. This study uncovers a new mechanism of vascular dysfunction following ischemic/hypoxic injury: a damaging positive feedback loop mediated by lactate-regulated Arg1 expression between the nucleus and mitochondria, leading to mitochondria cristae disorder and mtDNA release, culminating in VSMCs PANoptosis. Targeting VSMCs Arg1 inhibition offers a potential therapeutic strategy to alleviate ischemia/hypoxia-induced vascular impairments.

Copper Chelation Induces Morphology Change in Mitochondria of Triple-Negative Breast Cancer

Recent studies implicate mitochondria playing a key role in the cellular response to copper depletion therapy; however, evidence has been indirect and downstream, and the initial target of chelation remains to be defined. Here, we show, using super-resolution voltage and structure imaging microscopy, that copper chelation directly affects mitochondria morphology (causing fragmentation of the filamentous network) and ultrastructure (causing internal cristae remodeling). When triple-negative breast cancer cells are treated with a mitochondria-targeting copper chelator, mitochondria undergo an irreversible change in morphology from tubular to spherical. This process can be prevented by the addition of exogenous copper during the treatment. We find that a tailor-designed chelating agent with positive charges to target mitochondrial electrostatics localizes inside the mitochondrial cristae in a voltage-dependent manner. On pharmacological induction of membrane potential collapse, the chelator is dispersed while the mitochondrial cristae structure is preserved. These results indicate that voltage-dependent localization/targeting of the copper chelator in mitochondrial cristae plays a key role in its cytotoxicity.

Powering immunity: mitochondrial dynamics in natural killer cells

Natural killer (NK) cells are innate lymphocytes that are crucial for eliminating malignant and infected cells, and have significant therapeutic potential against cancer and viral infections. However, their functionality is often impaired under pathological conditions. Emerging evidence identifies mitochondria as key regulators of NK cell metabolism, fitness, and fate. This review examines how mitochondrial dysfunction impacts on NK cell activity in cancer, viral infections, and inflammatory disorders. We discuss strategies to target mitochondrial architecture, dynamics, and function as potential therapies to restore NK cell fitness. Finally, we highlight unanswered questions and future directions to better understand mitochondrial regulation in NK cells and its implications for therapeutic development.

Molecular machineries shaping the mitochondrial inner membrane

Mitochondria display intricately shaped deep invaginations of the mitochondrial inner membrane (MIM) termed cristae. This peculiar membrane architecture is essential for diverse mitochondrial functions, such as oxidative phosphorylation or the biosynthesis of cellular building blocks. Conserved protein nano-machineries such as F1Fo-ATP synthase oligomers and the mitochondrial contact site and cristae organizing system (MICOS) act as adaptable protein-lipid scaffolds controlling MIM biogenesis and its dynamic remodelling. Signal-dependent rearrangements of cristae architecture and MIM fusion events are governed by the dynamin-like GTPase optic atrophy 1 (OPA1). Recent groundbreaking structural insights into these nano-machineries have considerably advanced our understanding of the functional architecture of mitochondria. In this Review, we discuss how the MIM-shaping machineries cooperate to control cristae and crista junction dynamics, including MIM fusion, in response to cellular signalling pathways. We also explore how mutations affecting MIM-shaping machineries compromise mitochondrial functions.

Mitochondrial Maintenance in Skeletal Muscle

Skeletal muscle is one of the tissues with the highest range of variability in metabolic rate, which, to a large extent, is critically dependent on tightly controlled and fine-tuned mitochondrial activity. Besides energy production, other mitochondrial processes, including calcium buffering, generation of heat, redox and reactive oxygen species homeostasis, intermediate metabolism, substrate biosynthesis, and anaplerosis, are essential for proper muscle contractility and performance. It is thus not surprising that adequate mitochondrial function is ensured by a plethora of mechanisms, aimed at balancing mitochondrial biogenesis, proteostasis, dynamics, and degradation. The fine-tuning of such maintenance mechanisms ranges from proper folding or degradation of individual proteins to the elimination of whole organelles, and in extremis, apoptosis of cells. In this review, the present knowledge on these processes in the context of skeletal muscle biology is summarized. Moreover, existing gaps in knowledge are highlighted, alluding to potential future studies and therapeutic implications.

LRRC4 Deficiency Drives Premature Ovarian Insufficiency by Disrupting Metabolic Homeostasis in Granulosa Cells

Premature ovarian insufficiency (POI), defined by early loss of ovarian activity before the age of 40 years, is the leading cause of infertility and systematic aging in women, posing a public health challenge worldwide. However, its molecular etiology and therapeutic options are still lacking. Here, leucine-rich repeat containing 4 (LRRC4) is identified as a critical regulator of folliculogenesis expressed in granulosa cells (GCs), which contributes to ovarian reserve maintenance. LRRC4 deficiency triggers defective oocyte maturation and excessive follicular atresia through inhibition of GC differentiation and ultimately leads to POI. Mechanistically, LRRC4 balances mitochondrial fission and fusion to inhibit excessive mitophagy by promoting the K48-linked ubiquitination degradation of Yes-associated protein (YAP), thereby maintaining the metabolic homeostasis of mitochondrial aerobic respiration and glycolysis. Importantly, targeting LRRC4 normalized follicular development and ovarian function in POI model mice. In conclusion, these data reveal the novel pathogenesis of POI and suggest that LRRC4 is a potential target for the diagnosis and treatment of POI.

Angiotensin-Converting Enzyme-Dependent Intrarenal Angiotensin II Contributes to CTP: Phosphoethanolamine Cytidylyltransferase Downregulation, Mitochondrial Membranous Disruption, and Reactive Oxygen Species Overgeneration in Diabetic Tubulopathy

Aims: The limited therapeutic options for diabetic tubulopathy (DT) in early diabetic kidney disease (DKD) reflect the difficulty of targeting renal tubular compartment. While renin-angiotensin-aldosterone system (RAS) inhibitors are commonly utilized in the management of DKD, how intrarenal RAS contributes to diabetic tubular injury is not fully understood. Mitochondrial disruption and reactive oxygen species (ROS) overgeneration have been involved in diabetic tubular injury. Herein, we aim to test the hypothesis that angiotensin-converting enzyme (ACE)-dependent intrarenal angiotensin II (AngII) disrupts tubular mitochondrial membranous homeostasis and causes excessive ROS generation in DT. Results: Mice suffered from renal tubular mitochondrial disruption and ROS overgeneration following high-fat diet/streptozocin-type 2 diabetic induction. Intrarenal AngII generation is ACE-dependent in DT. Local AngII accumulation in renal tissues was achieved by intrarenal artery injection. ACE-dependent intrarenal AngII-treated mice exhibit markedly elevated levels of makers of tubular injury. CTP: Phosphoethanolamine cytidylyltransferase (PCYT2), the primary regulatory enzyme for the biosynthesis of phosphatidylethanolamine, was enriched in renal tubules according to single-cell RNA sequencing. ACE-dependent intrarenal AngII-induced tubular membranous disruption, ROS overgeneration, and PCYT2 downregulation. The diabetic ambiance deteriorated the detrimental effect of ACE-dependent intrarenal AngII on renal tubules. Captopril, the ACE inhibitor (ACEI), showed efficiency in partially ameliorating ACE-dependent intrarenal AngII-induced tubular deterioration pre- and post-diabetic induction. Innovation and Conclusion: This study uncovers a critical role of ACE-dependent intrarenal AngII in mitochondrial membranous disruption, ROS overgeneration, and PCYT2 deficiency in diabetic renal tubules, providing novel insight into DT pathogenesis and ACEI-combined therapeutic targets. Antioxid. Redox Signal. 42, 767-786.

H2S remodels mitochondrial ultrastructure and destabilizes respiratory supercomplexes

Mitochondrial form and function are intimately interconnected, responding to cellular stresses and changes in energy demand. Hydrogen sulfide, a product of amino acid metabolism, has dual roles as an electron transport chain substrate and complex IV (CIV) inhibitor, leading to a reductive shift, which has pleiotropic metabolic consequences. Luminal sulfide concentration in the colon is high due to microbial activity, and in this study, we demonstrate that chronic sulfide exposure of colonocyte-derived cells leads to lower Mic60 and Mic19 expression that is correlated with a profound loss of cristae and lower mitochondrial networking. Sulfide-induced depolarization of the inner mitochondrial membrane activates Oma1-dependent cleavage of Opa1 and is associated with a profound loss of CI and CIV activities associated with respirasomes. Our study reveals a potential role for sulfide as an endogenous modulator of mitochondrial dynamics and suggests that this regulation is corrupted in hereditary or acquired diseases associated with elevated sulfide.

Targeting the Galectin-7/TRPM2/Zn2+/DRP-1 Signaling Pathway: A Potential Therapeutic Intervention in the Pathogenesis of SJS/TEN

BACKGROUND

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) represent a spectrum of severe drug-induced cutaneous reactions. These conditions are characterized by widespread and confluent keratinocyte apoptosis, which differentiates them from erythema multiforme (EM). Mounting evidence has implicated the mitochondrial-dependent apoptosis pathway in the pathogenesis of SJS/TEN, but the potential roles and specific mechanisms of these pathways in SJS/TEN remain largely unexplored.

METHODS

Proteomic analyses were conducted to investigate differential protein expression in blister fluid (BF)-derived exosomes from suction surgery in healthy individuals (Con Exo) or patients with EM (EM Exo) or SJS/TEN (TEN Exo). Further analysis involved glutathione S-transferase (GST) pull-down assay, liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis, and validation of MS results through proximity ligation assay (PLA) and coimmunoprecipitation (co-IP). Phenotypic and mechanistic analyses were performed using immunohistochemistry (IHC) staining, enzyme-linked immunosorbent assay (ELISA), western blotting, reverse transcription-polymerase chain reaction (RT-PCR), co-IP, CCK-8 assay, adenosine triphosphate (ATP) level measurements, and flow cytometry.

RESULTS

Galectin-7 was markedly upregulated in BF-derived exosomes from SJS/TEN patients and showed a correlation with disease severity. Further analysis confirmed the interaction between galectin-7 and transient receptor potential (melastatin) 2 (TRPM2). BF-derived exosomes from SJS/TEN patients induced an imbalance in mitochondrial dynamics via galectin-7/TRPM2 upregulation. Activation of TRPM2 led to an elevation in mitochondrial Zn2+, which facilitated the recruitment of the fission factor dynamin-related protein-1 (DRP-1) to mitochondria to trigger mitochondrial fission in the keratinocyte. In addition, the recruitment of DRP-1-dependent mitochondrial fission via the voltage-dependent anion channel 1 (VDAC1)/hexokinase 2 (HK2)-mediated opening of the mitochondrial permeability transition pore (mPTP)-triggered cytochrome c release. These effects ultimately induce activation of the intrinsic mitochondrial apoptotic pathway and contribute to the pathogenesis of SJS/TEN.

CONCLUSIONS

Targeting the galectin-7/TRPM2/Zn2+/DRP-1 signaling pathway in keratinocytes presents a prospective therapeutic strategy for mitigating SJS/TEN in the future.

The association of mitochondrial morphology and supercomplex redistribution with skeletal muscle oxidative capacity in older adults

Skeletal muscle maximal oxidative capacity (ATPmax) is a key component of age-related sarcopenia and muscle health. The contribution of mitochondrial morphology and electron transport chain supercomplex (SC) assemblies to ATPmax has yet to be determined in human muscle. ATPmax measured in vivo by 31phosphorus magnetic resonance spectroscopy in the quadriceps femoris of nine volunteers (65.5 ± 3.3 years old) was correlated with muscle biopsy outcomes before and after 4 months of supervised exercise. Mitochondrial morphology was assessed in electron micrographs, and SCs were measured by blue native gel electrophoresis. In the sedentary conditions, ATPmax was positively associated with complex (C) I and CIII in SC I+III2+IVn and negatively associated with CI and CIII in SC I+III2. Regarding mitochondrial morphology, ATPmax was positively associated with markers of mitochondrial elongation. Exercise training-induced increases in ATPmax were accompanied by mitochondrial elongation and by the redistribution of free complex III. Indicators of mitochondrial elongation were associated with the redistribution of specific complexes to SC I+III2+IVn. Higher skeletal muscle oxidative capacity in older adults is associated with mitochondrial elongation and the redistribution of electron transport chain complexes into higher rank SCs in the same muscle. Further, we provide evidence that mitochondrial elongation favors mitochondrial SC assembly.

Mitochondria-targeting materials and therapies for regenerative engineering

The hemostatic, inflammatory, proliferative, and remodeling phases of healing require precise spatiotemporal coordination and orchestration of numerous biological processes. As the primary energy generators in the cell, mitochondria play multifunctional roles in regulating metabolism, stress reactions, immunity, and cell density during the process of tissue regeneration. Mitochondrial dynamics involves numerous crucial processes, fusion, fission, autophagy, and translocation, which are all necessary for preserving mitochondrial function, distributing energy throughout cells, and facilitating cellular signaling. Tissue regeneration is specifically associated with mitochondrial dynamics due to perturbations of Ca2+, H2O2 and ROS levels, which can result in mitochondrial malfunction. Increasing evidence from multiple models suggests that clinical interventions or medicinal drugs targeting mitochondrial dynamics could be a promising approach. This review highlights significant advances in the understanding of mitochondrial dynamics in tissue regeneration, with specific attention on mitochondria-targeting biomaterials that accelerate multiple tissues' regeneration by regulating mitochondrial metabolism. The innovations in nanomaterials and nanosystems enhance mitochondrial-targeting therapies are critically examined with the prospects of modulating mitochondrial dynamics for new therapies in regenerative engineering.

Crosstalk between calcium and reactive oxygen species signaling in cancer revisited

The homeostasis of cellular reactive oxygen species (ROS) and calcium (Ca2+) are intricately linked. ROS signaling and Ca2+ signaling are reciprocally regulated within cellular microdomains and are crucial for transcription, metabolism and cell function. Tumor cells often highjack ROS and Ca2+ signaling mechanisms to ensure optimal cell survival and tumor progression. Expression and regulation of Ca2+ channels and transporters at the plasma membrane, endoplasmic reticulum, mitochondria and other endomembranes are often altered in tumor cells, and this includes their regulation by ROS and reactive nitrogen species (RNS). Likewise, alterations in cellular Ca2+ levels influence the generation and scavenging of oxidants and thus can alter the redox homeostasis of the cell. This interplay can be either beneficial or detrimental to the cell depending on the localization, duration and levels of ROS and Ca2+ signals. At one end of the spectrum, Ca2+ and ROS/RNS can function as signaling modules while at the other end, lethal surges in these species are associated with cell death. Here, we highlight the interplay between Ca2+ and ROS in cancer progression, emphasize the impact of redox regulation on Ca2+ transport mechanisms, and describe how Ca2+ signaling pathways, in turn, can regulate the cellular redox environment.

OPA1 mutations in dominant optic atrophy: domain-specific defects in mitochondrial fusion and apoptotic regulation

BACKGROUND

Autosomal dominant optic atrophy (ADOA), a leading common inherited optic neuropathy, arises from progressive retinal ganglion cell degeneration, often linked to OPA1 mutations. OPA1, a mitochondrial GTPase, regulates mitochondrial fusion, crista structure, and apoptosis. While GTPase-related dysfunction is well-studied, the role of other OPA1 domains in ADOA pathology remains unclear.

METHODS

To investigate ADOA-linked OPA1 mutations, we assessed mitochondrial morphology, membrane potential, cytochrome c release, and cell viability in primary cortical neurons and N2a cells expressing OPA1 wild-type or mutant constructs. RNA sequencing and structural predictions (SWISS-MODEL) provided insights into molecular pathways and structural impacts.

RESULTS

Two ADOA-associated mutations were characterized: V465F (GTPase β-fold) and V560F (BSE α-helix). Both mutations impaired mitochondrial fusion and cell survival under apoptotic stimuli. Notably, the BSE-located V560F mutation caused greater deficits in membrane potential maintenance, earlier apoptosis, and distinct molecular pathway changes compared to V465F.

CONCLUSIONS

This study highlights the domain-specific impacts of OPA1 mutations on mitochondrial function and ADOA pathology, revealing unique roles of the BSE domain in apoptosis regulation and mitochondrial integrity. These findings provide insights into ADOA mechanisms and potential therapeutic targets.

Impact of mitochondrial metabolism on T-cell dysfunction in chronic lymphocytic leukemia

T cells play a central role in anti-tumor immunity, yet their function is often compromised within the immunosuppressive tumor microenvironment, leading to cancer progression and resistance to immunotherapies. T-cell activation and differentiation require dynamic metabolic shifts, with mitochondrial metabolism playing a crucial role in sustaining their function. Research in cancer immunometabolism has revealed key mitochondrial abnormalities in tumor-infiltrating lymphocytes, including reduced mitochondrial capacity, depolarization, structural defects, and elevated reactive oxygen species. While these mitochondrial disruptions are well-characterized in solid tumors and linked to T-cell exhaustion, their impact on T-cell immunity in lymphoproliferative disorders remains underexplored. Chronic lymphocytic leukemia (CLL), the most prevalent chronic adult leukemia, is marked by profound T-cell dysfunction that limits the success of adoptive cell therapies. Emerging studies are shedding light on the role of mitochondrial disturbances in CLL-related T-cell dysfunction, but significant knowledge gaps remain. This review explores mitochondrial metabolism in T-cell exhaustion, emphasizing recent findings in CLL. We also discuss therapeutic strategies to restore T-cell mitochondrial function and identify key research gaps.

Novel in vivo models of autosomal optic atrophy reveal conserved pathological changes in neuronal mitochondrial structure and function

Autosomal optic atrophy (AOA) is a form of hereditary optic neuropathy characterized by the irreversible and progressive degermation of the retinal ganglion cells. Most cases of AOA are associated with a single dominant mutation in OPA1, which encodes a protein required for fusion of the inner mitochondrial membrane. It is unclear how loss of OPA1 leads to neuronal death, and despite ubiquitous expression appears to disproportionately affect the RGCs. This study introduces two novel in vivo models of OPA1-mediated AOA, including the first developmentally viable vertebrate Opa1 knockout (KO). These models allow for the study of Opa1 loss in neurons, specifically RGCs. Though survival is significantly reduced in Opa1 deficient zebrafish and Drosophila, both models permit the study of viable larvae. Moreover, zebrafish Opa1 KO larvae show impaired visual function but unchanged locomotor function, indicating that retinal neurons are particularly sensitive to Opa1 loss. Proteomic profiling of both models reveals marked disruption in protein expression associated with mitochondrial function, consistent with an observed decrease in mitochondrial respiratory function. Similarly, mitochondrial fragmentation and disordered cristae organization were observed in neuronal axons in both models highlighting Opa1's highly conserved role in regulating mitochondrial morphology and function in neuronal axons. Importantly, in Opa1 deficient zebrafish, mitochondrial disruption and visual impairment precede degeneration of RGCs. These novel models mimic key features of AOA and provide valuable tools for therapeutic screening. Our findings suggest that therapies enhancing mitochondrial function may offer a potential treatment strategy for AOA.

Metabolic reprogramming in T cell senescence: a novel strategy for cancer immunotherapy

The complex interplay between cancer progression and immune senescence is critically influenced by metabolic reprogramming in T cells. As T cells age, especially within the tumor microenvironment, they undergo significant metabolic shifts that may hinder their proliferation and functionality. This manuscript reviews how metabolic alterations contribute to T cell senescence in cancer and discusses potential therapeutic strategies aimed at reversing these metabolic changes. We explore interventions such as mitochondrial enhancement, glycolytic inhibition, and lipid metabolism adjustments that could rejuvenate senescent T cells, potentially restoring their efficacy in tumor suppression. This review also focuses on the significance of metabolic interventions in T cells with aging and further explores the future direction of the metabolism-based cancer immunotherapy in senescent T cells.

Tetrahydrobenzimidazole TMQ0153 targets OPA1 and restores drug sensitivity in AML via ROS-induced mitochondrial metabolic reprogramming

BACKGROUND

Acute myeloid leukemia (AML) is a highly aggressive cancer with a 5-year survival rate of less than 35%. It is characterized by significant drug resistance and abnormal energy metabolism. Mitochondrial dynamics and metabolism are crucial for AML cell survival. Mitochondrial fusion protein optic atrophy (OPA)1 is upregulated in AML patients with adverse mutations and correlates with poor prognosis.

METHOD

This study investigated targeting OPA1 with TMQ0153, a tetrahydrobenzimidazole derivative, to disrupt mitochondrial metabolism and dynamics as a novel therapeutic approach to overcome treatment resistance. Effects of TMQ0153 treatment on OPA1 and mitofusin (MFN)2 protein levels, mitochondrial morphology, and function in AML cells. In this study, we examined reactive oxygen species (ROS) production, oxidative phosphorylation (OXPHOS) inhibition, mitochondrial membrane potential (MMP) depolarization, and apoptosis. Additionally, metabolic profiling was conducted to analyze changes in metabolic pathways.

RESULTS

TMQ0153 treatment significantly reduced OPA1 and mitofusin (MFN)2 protein levels and disrupted the mitochondrial morphology and function in AML cells. This increases ROS production and inhibits OXPHOS, MMP depolarization, and caspase-dependent apoptosis. Metabolic reprogramming was observed, shifting from mitochondrial respiration to glycolysis and impaired respiratory chain activity. Profiling revealed reduced overall metabolism along with changes in the glutathione (GSH)/oxidized glutathione (GSSG) and NAD⁺/NADH redox ratios. TMQ0153 treatment reduces tumor volume and weight in MV4-11 xenografts in vivo. Combination therapies with TMQ0153 and other AML drugs significantly reduced the leukemic burden and prolonged survival in NOD scid gamma (NSG) mice xenografted with U937-luc and MOLM-14-luc cells.

CONCLUSION

TMQ0153 targets mitochondrial dynamics by inhibiting OPA1, inducing metabolic reprogramming, and triggering apoptosis in AML cells. It enhances the efficacy of existing AML therapies and provides a promising combination treatment approach that exploits mitochondrial vulnerability and metabolic reprogramming to improve treatment outcomes in AML.

MARIGOLD and MitoCIAO, two searchable compendia to visualize and functionalize protein complexes during mitochondrial remodeling

Mitochondrial proteins assemble dynamically in high molecular weight complexes essential for their functions. We generated and validated two searchable compendia of these mitochondrial complexes. Following identification by mass spectrometry of proteins in complexes separated using blue-native gel electrophoresis from unperturbed, cristae-remodeled, and outer membrane-permeabilized mitochondria, we created MARIGOLD, a mitochondrial apoptotic remodeling complexome database of 627 proteins. MARIGOLD elucidates how dynamically proteins distribute in complexes upon mitochondrial membrane remodeling. From MARIGOLD, we developed MitoCIAO, a mitochondrial complexes interactome tool that, by statistical correlation, calculates the likelihood of protein cooccurrence in complexes. MitoCIAO correctly predicted biologically validated interactions among components of the mitochondrial cristae organization system (MICOS) and optic atrophy 1 (OPA1) complexes. We used MitoCIAO to functionalize two ATPase family AAA domain-containing 3A (ATAD3A) complexes: one with OPA1 that regulates mitochondrial ultrastructure and the second containing ribosomal proteins that is essential for mitoribosome stability. These compendia reveal the dynamic nature of mitochondrial complexes and enable their functionalization.

Bringing together but staying apart: decisive differences in animal and fungal mitochondrial inner membrane fusion

Mitochondria are dynamic and plastic, undergoing continuous fission and fusion and rearrangement of their bioenergetic sub-compartments called cristae. These fascinating processes are best understood in animal and fungal models, which are taxonomically grouped together in the expansive Opisthokonta supergroup. In opisthokonts, crista remodelling and inner membrane fusion are linked by dynamin-related proteins (DRPs). Animal Opa1 (optical atrophy 1) and fungal Mgm1 (mitochondrial genome maintenance 1) are tacitly considered orthologs because their similar mitochondria-shaping roles are mediated by seemingly shared biochemical properties, and due to their presence in the two major opisthokontan subdivisions, Holozoa and Holomycota, respectively. However, molecular phylogenetics challenges this notion, suggesting that Opa1 and Mgm1 likely had separate, albeit convergent, evolutionary paths. Herein, we illuminate disparities in proteolytic processing, structure, and interaction network that may have bestowed on Opa1 and Mgm1 distinct mechanisms of membrane remodelling. A key disparity is that, unlike Mgm1, Opa1 directly recruits the mitochondrial phospholipid cardiolipin to remodel membranes. The differences outlined herein between the two DRPs could have broader impacts on mitochondrial morphogenesis. Outer and inner membrane fusion are autonomous in animals, which may have freed Opa1 to repurpose its intrinsic activity to remodel cristae, thereby regulating the formation of respiratory chain supercomplexes. More significantly, Opa1-mediated crista remodelling has emerged as an integral part of cytochrome c-regulated apoptosis in vertebrates, and perhaps in the cenancestor of animals. By contrast, outer and inner membrane fusion are coupled in budding yeast. Consequently, Mgm1 membrane-fusion activity is inextricable from its role in the biogenesis of fungal lamellar cristae. These disparate mitochondrial DRPs ultimately may have contributed to the different modes of multicellularity that have evolved within Opisthokonta.

Bcl-xL overexpression in T cells preserves muscle mitochondrial structure and function and prevents frailty in old mice

Our previous transcriptomic analysis revealed an up-regulation of the antiapoptotic protein B cell lymphoma-extra large (Bcl-xL) in centenarians relative to octogenarians or younger cohorts. In this study, we used Bcl-xL-overexpressing mice to assess its impact on successful aging. Our findings indicate that Bcl-xL overexpression modifies T cell subsets and improves their metabolism, apoptosis resistance, macroautophagy, and cytokine production during aging. This more resilient immune system reduces inflammation and preserves mitochondrial integrity and function in muscle tissue, thereby retarding the onset of frailty. These results underscore the important contribution of Bcl-xL to healthy aging, a phenomenon that is conserved across mammalian species.

CD4+ anti-TGF-β CAR T cells and CD8+ conventional CAR T cells exhibit synergistic antitumor effects

Transforming growth factor (TGF)-β1 restricts the expansion, survival, and function of CD4+ T cells. Here, we demonstrate that CD4+ but not CD8+ anti-TGF-β CAR T cells (T28zT2 T cells) can suppress tumor growth partly through secreting Granzyme B and interferon (IFN)-γ. TGF-β1-treated CD4+ T28zT2 T cells persist well in peripheral blood and tumors, maintain their mitochondrial form and function, and do not cause in vivo toxicity. They also improve the expansion and persistence of untransduced CD8+ T cells in vivo. Tumor-infiltrating CD4+ T28zT2 T cells are enriched with TCF-1+IL7R+ memory-like T cells, express NKG2D, and downregulate T cell exhaustion markers, including PD-1 and LAG3. Importantly, a combination of CD4+ T28zT2 T cells and CD8+ anti-glypican-3 (GPC3) or anti-mesothelin (MSLN) CAR T cells exhibits augmented antitumor effects in xenografts. These findings suggest that rewiring TGF-β signaling with T28zT2 in CD4+ T cells is a promising strategy for eradicating solid tumors.

The Balance of MFN2 and OPA1 in Mitochondrial Dynamics, Cellular Homeostasis, and Disease

Mitochondrial dynamics, governed by fusion and fission, are crucial for maintaining cellular homeostasis, energy production, and stress adaptation. MFN2 and OPA1, key regulators of mitochondrial fusion, play essential roles beyond their structural functions, influencing bioenergetics, intracellular signaling, and quality control mechanisms such as mitophagy. Disruptions in these processes, often caused by MFN2 or OPA1 mutations, are linked to neurodegenerative diseases like Charcot-Marie-Tooth disease type 2A (CMT2A) and autosomal dominant optic atrophy (ADOA). This review explores the molecular mechanisms underlying mitochondrial fusion, the impact of MFN2 and OPA1 dysfunction on oxidative phosphorylation and autophagy, and their role in disease progression. Additionally, we discuss the divergent cellular responses to MFN2 and OPA1 mutations, particularly in terms of proliferation, senescence, and metabolic signaling. Finally, we highlight emerging therapeutic strategies to restore mitochondrial integrity, including mTOR modulation and autophagy-targeted approaches, with potential implications for neurodegenerative disorders.

Mitochondrial dynamics and quality control regulate proteostasis in neuronal ischemia-reperfusion

Mitochondrial damage and dysfunction are hallmarks of neuronal injury during cerebral ischemia-reperfusion (I/R). Critical mitochondrial functions including energy production and cell signaling are perturbed during I/R, often exacerbating damage and contributing to secondary injury. The integrity of the mitochondrial proteome is essential for efficient function. Mitochondrial proteostasis is mediated by the cooperative forces of mitophagy and intramitochondrial proteolysis. The aim of this study was to elucidate the patterns of mitochondrial protein dynamics and their key regulators during an in vitro model of neuronal I/R injury. Utilizing the MitoTimer reporter, we quantified mitochondrial protein oxidation and turnover during I/R injury, highlighting a key point at 2 h reoxygenation for aged/oxidized protein turnover. This turnover was found to be mediated by both LONP1-dependent proteolysis and PRKN/parkin-dependent mitophagy. Additionally, the proteostatic response of neuronal mitochondria is influenced by both mitochondrial fusion and fission machinery. Our findings highlight the involvement of both mitophagy and intramitochondrial proteolysis in the response to I/R injury.Abbreviations: cKO: conditional knockout; CLPP: caseinolytic mitochondrial matrix peptidase proteolytic subunit; DIV: days in vitro; DNM1L/DRP1: dynamin 1 like; ETC: electron transport chain; hR: hours after reoxygenation; I/R: ischemia-reperfusion; LONP1: lon peptidase 1, mitochondrial; mtUPR: mitochondrial unfolded protein response; OGD: oxygen glucose deprivation; OGD/R: oxygen glucose deprivation and reoxygenation; OPA1: OPA1 mitochondrial dynamin like GTPase; PINK1: PTEN induced kinase 1; PRKN: parkin RBR E3 ubiquitin protein ligase; ROI: region of interest; WT: wild-type.

OPA1 deficiency induces mitophagy through PINK1/Parkin pathway during bovine oocytes maturation

In vitro embryo production (IVP) technology has been increasingly applied to beef cattle breeding. In vitro maturation (IVM) technology is the basis of IVP. However, the quality of in vitro-generated mature oocytes is still poor. Mitochondria are the energy factories of oocytes, so they are crucial for oocyte quality. OPA1 is a protein located on the mitochondrial inner membrane, and its main function is to mediate mitochondrial inner membrane fusion. This work demonstrated that OPA1 is expressed at different stages of meiosis in bovine oocytes. The inhibition of OPA1 activity resulted in a reduced rate of first polar body excretion from bovine oocytes and disruption of the spindle structure. OPA1 deficiency impacted mitochondria by leading to mitochondrial dysfunction, promoting mitochondrial fission, and inducing mitophagy through the PINK1/Parkin pathway. Taken together, our findings suggest that OPA1 is essential for bovine oocyte maturation and that OPA1 deficiency leads to mitochondrial dysfunction and promotes mitochondrial fission as well as mitophagy.

Platelet-derived mitochondria attenuate muscle atrophy following rotator cuff tears in a rat model

BACKGROUND

Rotator cuff tears (RCTs) often result in muscle atrophy, compromising surgical outcomes and recovery. Mitochondrial dysfunction is implicated in this process, suggesting potential for mitochondria-based therapies. This study aimed to investigate the effects of platelet-derived mitochondria (Plt-Mito) administration into the supraspinatus muscle (SSP) following RCTs.

METHODS

Seventy-two male Sprague-Dawley rats were allocated into 3 distinct groups: (1) a sham surgery group, (2) a group with RCTs treated with Plt-Mito, and (3) a group with RCTs treated with phosphate-buffered saline. Treatments were administered every 2 weeks. After 12 weeks, the SSPs were analyzed for wet muscle weight ratio, muscle fiber cross-sectional area, fibrosis, antioxidant activity, mitochondrial markers, capillary density, and mitochondrial structure.

RESULTS

Plt-Mito successfully incorporated into SSP, maintaining functional integrity. Compared to the phosphate-buffered saline group, Plt-Mito treatment significantly preserved wet muscle weight, increased mean muscle fiber cross-sectional area, promoted muscle regeneration, reduced fibrosis, enhanced antioxidant activity (increased superoxide dismutase activity and decreased malondialdehyde activity), improved muscle vascularity (increased platelet endothelial cell adhesion molecule-1 and α-smooth muscle actin), increased expression of mitochondrial markers (C oxidase subunit IV and uncoupling protein 1) and maintained mitochondrial density and structure.

CONCLUSIONS

Our findings demonstrated Plt-Mito administration effectively halted muscle atrophy and fibrosis, while attenuating mitochondrial damage and dysfunction following RCTs.

Type 3 diabetes and metabolic reprogramming of brain neurons: causes and therapeutic strategies

Abnormal glucose metabolism inevitably disrupts normal neuronal function, a phenomenon widely observed in Alzheimer's disease (AD). Investigating the mechanisms of metabolic adaptation during disease progression has become a central focus of research. Considering that impaired glucose metabolism is closely related to decreased insulin signaling and insulin resistance, a new concept "type 3 diabetes mellitus (T3DM)" has been coined. T3DM specifically refers to the brain's neurons becoming unresponsive to insulin, underscoring the strong link between diabetes and AD. Recent studies reveal that during brain insulin resistance, neurons exhibit mitochondrial dysfunction, reduced glucose metabolism, and elevated lactate levels. These findings suggest that impaired insulin signaling caused by T3DM may lead to a compensatory metabolic shift in neurons toward glycolysis. Consequently, this review aims to explore the underlying causes of T3DM and elucidate how insulin resistance drives metabolic reprogramming in neurons during AD progression. Additionally, it highlights therapeutic strategies targeting insulin sensitivity and mitochondrial function as promising avenues for the successful development of AD treatments.

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.

Mitochondrial Localization and Function of Adenosine Receptors

G-protein coupled receptors (GPCRs) are typically expressed on the cell surface where they mediate extracellular signals from hormones, neurotransmitters and growth factors, among others. However, growing evidence support the intracellular localization of GPCRs, including mitochondria. In the present work, we assessed the presence and functionality of adenosine receptors in mitochondria by combining techniques such as western blotting, radioligand binding, electron microscopy, enzymatic activities determination, oxygen consumption measurement and 3D morphological analysis of mitochondrial networks. Our results demonstrate the mitochondrial localization of adenosine A1 and A2 receptors in pure mitochondria fractions isolated from mouse brain and liver, human brain, HeLa and SH-SY5Y cells. Adenylyl cyclase activity assays revealed that these receptors are functional in the mitochondria. Moreover, exposure of isolated mitochondria to selective A1, A2A and A2B receptors agonists revealed these receptors as potential modulators of mitochondrial energy metabolism, since ATP production and coupling efficiency increased in the presence of BAY 60-6583 (A2B agonist) whereas proton leak and acute response were higher with CGS 21680 (A2A agonist). Also, proton leak, ATP production, acute response and acute respiration were increased in the presence of CPA (A1 agonist). Interestingly, different mitochondrial morphological changes were detected in HeLa cells exposed to these receptors' agonists.

Role of ferroptosis in atrial fibrillation: a review

Cardiovascular disease remains the leading cause of mortality, with atrial fibrillation emerging as one of the most common conditions encountered in clinical practice. However, its underlying mechanisms remain poorly understood, prompting ongoing research. Ferroptosis, a recently discovered form of regulated cell death characterized by lipid peroxidation and disrupted cellular redox balance leading to cell death due to iron overload, has attracted significant attention. Since its identification, ferroptosis has been extensively studied in various contexts, including cancer, stroke, myocardial ischemia/reperfusion injury, and heart failure. Growing evidence suggests that ferroptosis may also play a critical role in the onset and progression of atrial fibrillation, though research in this area is still limited. This article provides a concise overview of the potential mechanisms by which ferroptosis may contribute to the pathogenesis of atrial fibrillation.

Mitochondrial complex-1 as a therapeutic target for cardiac diseases

Mitochondrial dysfunction is critical for the development and progression of cardiovascular diseases (CVDs). Complex-1 (CI) is an essential component of the mitochondrial electron transport chain that participates in oxidative phosphorylation and energy production. CI is the largest multisubunit complex (~ 1 Mda) and comprises 45 protein subunits encoded by seven mt-DNA genes and 38 nuclear genes. These subunits function as the enzyme nicotinamide adenine dinucleotide  hydrogen (NADH): ubiquinone oxidoreductase. CI dysregulation has been implicated in various CVDs, including heart failure, ischemic heart disease, pressure overload, hypertrophy, and cardiomyopathy. Several studies demonstrated that impaired CI function contributes to increased oxidative stress, altered calcium homeostasis, and mitochondrial DNA damage in cardiac cells, leading to cardiomyocyte dysfunction and apoptosis. CI dysfunction has been associated with endothelial dysfunction, inflammation, and vascular remodeling, critical processes in developing atherosclerosis and hypertension. Although CI is crucial in physiological and pathological conditions, no potential therapeutics targeting CI are available to treat CVDs. We believe that a lack of understanding of CI's precise mechanisms and contributions to CVDs limits the development of therapeutic strategies. In this review, we comprehensively analyze the role of CI in cardiovascular health and disease to shed light on its potential therapeutic target role in CVDs.

The acute and chronic influence of exercise on mitochondrial dynamics in skeletal muscle

Exercise and nutritional modulation are potent stimuli for eliciting increases in mitochondrial mass and function. Collectively, these beneficial adaptations are increasingly recognized to coincide with improvements in skeletal muscle health. Mitochondrial dynamics of fission and fusion are increasingly implicated as having a central role in mediating aspects of key organelle adaptations that are seen with exercise. Exercise-induced mitochondrial adaptation dynamics that have been implicated are 1) increases to mitochondrial turnover, resulting from elevated rates of mitochondrial synthesis (biogenesis) and degradative (mitophagy) processes and 2) morphological changes to the three-dimensional (3-D) tubular network, known as the mitochondrial reticulum, that mitochondria form in skeletal muscle. Notably, mitochondrial fission has also been implicated in coordinating increases in mitophagy, following acute exercise. Furthermore, increased fusion following exercise training promotes increased connectivity of the mitochondrial reticulum and is associated with improved metabolism and mitochondrial function. However, the molecular basis and fashion in which exercise infers beneficial mitochondrial adaptations through mitochondrial dynamics remains to be fully elucidated. This review attempts to highlight recent developments investigating the effects of exercise on mitochondrial dynamics, while attempting to offer a perspective of the methodological refinements and potential variables, such as substrate/glycogen availability, which should be considered going forward.

Liver Mitochondrial Morphology and Gene Expression as Markers of Liver Reserve: Prognostic Implications for Native Liver Survival in Biliary Atresia

PURPOSE

Hepatocyte mitochondrial morphology and gene expression were compared between biliary atresia (BA), infantile cholestasis (IC), and normal liver (NL) as prognostic indicators.

METHODS

Specimens of liver at portoenterostomy (PE) for BA, from intrahepatic bile duct paucity patients for IC, and from choledochal cyst or hepatoblastoma patients for NL were collected prospectively (P) beginning in 2021 (P-BA = 11, P-IC = 9, P-NL = 7) and retrospectively (R) from paraffin-embedded tissue going back to 1981 (R-BA = 25, R-IC = 9, R-NL = 4). The P-cohort had transmission electron microscopy (TEM) to image mitochondria, immunoblotting for heat shock protein 60 (HSP60), and quantitative PCR (qPCR) for HSP60 and mitochondrial functional genes. Both cohorts had immunofluorescence for HSP60 quantified as a ratio to albumin-positive hepatocytes (ALB) with HSP60/ALB<1.0 as a cutoff limit using ImageJ.

RESULTS

HSP60 was significantly lower in BA/IC than NL on qPCR (BA: p < 0.01, IC: p < 0.05) and lower in BA than IC/NL on immunoblotting (p < 0.05). HSP60/ALB was significantly lower in BA than NL/IC (p < 0.001). Despite BA subjects being matched for types of BA and ages at PE, HSP60/ALB did not correlate with jaundice clearance (JC; T-Bil<1.2 mg/dL) but was significantly higher in native liver survivors (NLS) after PE compared with liver transplant (LTx) cases (p < 0.05) and significantly lower in LTx cases achieving JC than NLS achieving JC (p < 0.05). TEM showed BA had significantly more mitochondrial inclusion bodies (p < 0.05) and significantly larger cristae (p < 0.01) than IC/NL. qPCR in BA showed significant repression of mitochondrial functional genes for mRNA stabilization and energy facilitation.

CONCLUSION

HSP60/ALB correlates with NLS after PE for BA.

LEVEL OF EVIDENCE

II.

Global cellular proteo-lipidomic profiling of diverse lysosomal storage disease mutants using nMOST

Lysosomal storage diseases (LSDs) comprise ~50 monogenic disorders marked by the buildup of cellular material in lysosomes, yet systematic global molecular phenotyping of proteins and lipids is lacking. We present a nanoflow-based multiomic single-shot technology (nMOST) workflow that quantifies HeLa cell proteomes and lipidomes from over two dozen LSD mutants. Global cross-correlation analysis between lipids and proteins identified autophagy defects, notably the accumulation of ferritinophagy substrates and receptors, especially in NPC1-/- and NPC2-/- mutants, where lysosomes accumulate cholesterol. Autophagic and endocytic cargo delivery failures correlated with elevated lysophosphatidylcholine species and multilamellar structures visualized by cryo-electron tomography. Loss of mitochondrial cristae, MICOS complex components, and OXPHOS components rich in iron-sulfur cluster proteins in NPC2-/- cells was largely alleviated when iron was provided through the transferrin system. This study reveals how lysosomal dysfunction affects mitochondrial homeostasis and underscores nMOST as a valuable discovery tool for identifying molecular phenotypes across LSDs.

Mitochondria as a Therapeutic Target: Focusing on Traumatic Brain Injury

Mitochondria are organelles of eukaryotic cells delimited by two membranes and cristae that consume oxygen to produce adenosine triphosphate (ATP), and are involved in the synthesis of vital metabolites, calcium homeostasis, and cell death mechanisms. Strikingly, normal mitochondria function as an integration center between multiple conditions that determine neural cell homeostasis, whereas lesions that lead to mitochondrial dysfunction can desynchronize cellular functions, thus contributing to the pathophysiology of traumatic brain injury (TBI). In addition, TBI leads to impaired coupling of the mitochondrial electron transport system with oxidative phosphorylation that provides most of the energy needed to maintain vital functions, ionic homeostasis, and membrane potentials. Furthermore, mitochondrial metabolism produces signaling molecules such as reactive oxygen species (ROS), regulating calcium levels and controlling the expression profile of intrinsic pro-apoptotic effectors influenced by TBI. Hence, the set of these functions is widely referred to as 'mitochondrial function', although the complexity of the relationship between such components limits such a definition. In this review, we present mitochondria as a therapeutic target, focus on TBI, and discuss aspects of mitochondrial structure and function.

Coordination of cytochrome bc1 complex assembly at MICOS

The boundary and cristae domains of the mitochondrial inner membrane are connected by crista junctions. Most cristae membrane proteins are nuclear-encoded and inserted by the mitochondrial protein import machinery into the inner boundary membrane. Thus, they must overcome the diffusion barrier imposed by crista junctions to reach their final location. Here, we show that respiratory chain complexes and assembly intermediates are physically connected to the mitochondrial contact site and cristae organizing system (MICOS) that is essential for the formation and stability of crista junctions. We identify the inner membrane protein Mar26 (Fmp10) as a determinant in the biogenesis of the cytochrome bc1 complex (complex III). Mar26 couples a Rieske Fe/S protein-containing assembly intermediate to MICOS. Our data indicate that Mar26 maintains an assembly-competent Rip1 pool at crista junctions where complex III maturation likely occurs. MICOS facilitates efficient Rip1 assembly by recruiting complex III assembly intermediates to crista junctions. We propose that MICOS, via interaction with assembly factors such as Mar26, contributes to the spatial and temporal coordination of respiratory chain biogenesis.

Nicotinamide riboside targets mitochondrial unfolded protein response to reduce alcohol-induced damage in Kupffer cells

The pathogenesis of alcohol-related liver disease (ALD) is closely linked to mitochondrial dysfunction and impaired cellular energy metabolism. In this study, we explored how ethanol triggers inflammation, oxidative stress, and mitochondrial dysfunction in Kupffer cells, i.e.hepatic resident macrophages, primarily focusing on the mitochondrial unfolded protein response (UPRmt) using immortalized mouse Kupffer cells (ImKCs) and mouse primary KCs. The UPRmt is a cellular defense mechanism activated in response to the perturbation of mitochondrial proteostasis to maintain mitochondrial integrity and function by upregulating the expression of mitochondrial chaperones and proteases. We also determined whether nicotinamide riboside (NR), a NAD+ precursor, could mitigate ethanol-triggered cellular damage. When ImKCs were exposed to 80 mm ethanol for 72 h, they displayed inflammation, oxidative stress, and impaired mitochondrial function with decreased mitochondrial content and deformed mitochondrial crista structure. NR, however, counteracted the effects of ethanol. Furthermore, ethanol increased mRNA and protein levels of UPRmt genes, such as mitochondrial chaperones and proteases, which were attenuated by NR. Notably, the ethanol-induced shift in the entry of activating transcription factor 5 (ATF5), a putative transcriptional regulator of UPRmt, to the nucleus from the mitochondria was abolished by NR. The induction of UPRmt genes by ethanol was significantly repressed when Atf5 was knocked down, indicating the role of ATF5 in the induction of UPRmt genes in ImKCs exposed to ethanol. We also confirmed the induction of UPRmt gene expression in mouse and human livers exposed to alcohol. Our findings demonstrate the ability of NR to alleviate ethanol-induced oxidative stress, inflammation, and mitochondrial dysfunction, partly by modulating the ATF5-dependent UPRmt pathway in ImKCs, suggesting its potential for ALD therapy. © 2024 The Pathological Society of Great Britain and Ireland.

Revealing mitochondrial architecture and functions with single molecule localization microscopy

Understanding the spatiotemporal organization of components within living systems requires the highest resolution possible. Microscopy approaches that allow for a resolution below 250 nm include electron and super-resolution microscopy (SRM). The latter combines advanced imaging techniques and the optimization of image processing methods. Over the last two decades, various SRM-related approaches have been introduced, especially those relying on single molecule localization microscopy (SMLM). To develop and apply SMLM approaches, mitochondria are an ideal cellular compartment due to their size, which is below the standard diffraction limit. Furthermore, mitochondria are a dynamic yet narrow compartment, and a resolution below 250 nm is required to study their composition and multifaceted functions. To this end, several SMLM technologies have been used to reveal mitochondrial composition. However, there is still room for improvement in existing techniques to study protein-protein interactions and protein dynamics within this compartment. This review aims to offer an updated overview of the existing SMLM techniques and probes associated with mitochondria to enhance their resolution at the nanoscale. Last, it paves the way for future SMLM improvements to better resolve mitochondrial dynamics and functions.

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.

Metabolic Profiling of Tumor and Immune Cells Integrating Seahorse and Flow Cytometry

Studying metabolism in the different cellular compartments of the tumor microenvironment (TME) is crucial to identify the specific metabolic signatures that contribute to tumor progression. Additionally, TME-driven metabolic changes can disrupt the essential metabolic processes involved in immune cell function, hindering immunotherapy success. Extracellular flux analysis (Seahorse) is a well-established approach used to characterize cellular metabolism. When combined with flow cytometry-based measurements, it offers a comprehensive view of the metabolic signatures within the different cellular compartments of the TME. Here we provide a detailed description on the procedures of Seahorse analysis and complementary flow cytometry-based metabolic readouts on tumor cells and T cells in the context of cancer, which can also be applied to other physiological and pathological situations.

New insights into mitochondrial quality control in anthracycline-induced cardiotoxicity: molecular mechanisms, therapeutic targets, and natural products

Anthracyclines (ANTs) are widely used in cancer therapy, particularly for lymphoma, sarcoma, breast cancer, and childhood leukemia, and have become the cornerstone of chemotherapy for various malignancies. However, it is associated with fatal and dose-dependent cardiovascular complications, especially cardiotoxicity. Mitochondrial quality control mechanisms, encompassing mitophagy, mitochondrial dynamics, and mitochondrial biogenesis, maintain mitochondrial homeostasis in the cardiovascular system. Recent studies have highlighted that mitochondrial quality control mechanisms play considerable roles in ANTs-induced cardiotoxicity (AIC). In addition, natural products targeting mitochondrial quality control mechanisms have emerged as potential therapeutic strategies to alleviate AIC. This review summarizes the types, incidence, prevention, treatment, and pathomechanism of AIC, delves into the molecular mechanisms of mitochondrial quality control in the pathogenesis of AIC, and explores natural products that target these mechanisms, so as to provide potential targets and therapeutic drugs for address the clinical challenges in AIC prevention and treatment, where no effective medicines are available.

Protocol to monitor live-cell, real-time, mitochondrial respiration in mouse muscle cells using the Resipher platform

Mitochondrial function is typically assessed by measuring oxygen consumption at a given time point. However, this approach cannot monitor respiratory changes that occur over time. Here, we present a protocol to measure mitochondrial respiration in freshly isolated muscle stem cells, primary skeletal muscle, and immortalized C2C12 myoblasts in real time using the Resipher platform. We describe steps for preparing and plating cells, performing media changes, setting up the software and device, and analyzing data. This method can be adapted to other cell types. For complete details on the use and execution of this protocol, please refer to Triolo et al.1.

An Overview of the Biological Complexity of Vitiligo

Vitiligo is a skin disease that affects all ethnicities and genders and is characterized by the loss of pigment essentially due to the selective loss of melanocytes. Although it is generally considered a systemic disease associated with polymorphisms in genes involved in the immune response, vitiligo is also considered an oxidative imbalance-associated disease. It represents a multifactorial pathology in which some genetic predisposition and epigenetic factors coupled with some critical biochemical and molecular pathways could play a pivotal role. The aim of this work was thus to review some of the fine cellular mechanisms involved in the etiopathogenesis of vitiligo, mainly focusing on the nonimmunological ones, extensively highlighted elsewhere. We took into consideration, in addition to oxidative stress, both the cause and the hallmark of the pathology, some less investigated aspects such as the role of epigenetic factors, e.g., microRNAs, of receptors of catecholamines, and the more recently recognized role of the mitochondria. Sex differences associated with vitiligo have also been investigated starting from sex hormones and the receptors through which they exert their influence. From literature analysis, a picture seems to emerge in which vitiligo can be considered not just a melanocyte-affecting disease but a systemic pathology that compromises the homeostasis of a complex tissue such as the skin, in which different cell types reside playing multifaceted physiological roles for the entire organism. The exact sequence of cellular and subcellular events associated with vitiligo is still a matter of debate. However, the knowledge of the individual biological factors implicated in vitiligo could help physicians to highlight useful innovative markers of progression and provide, in the long run, new targets for more tailored treatments based on individual manifestations of the disease.

Mitochondrial dynamics govern whole-body regeneration through stem cell pluripotency and mitonuclear balance

Tissue regeneration is a complex process involving large changes in cell proliferation, fate determination, and differentiation. Mitochondrial dynamics and metabolism play a crucial role in development and wound repair, but their function in large-scale regeneration remains poorly understood. Planarians offer an excellent model to investigate this process due to their remarkable regenerative abilities. In this study, we examine mitochondrial dynamics during planarian regeneration. We find that knockdown of the mitochondrial fusion gene, opa1, impairs both tissue regeneration and stem cell pluripotency. Interestingly, the regeneration defects caused by opa1 knockdown are rescued by simultaneous knockdown of the mitochondrial fission gene, drp1, which partially restores mitochondrial dynamics. Furthermore, we discover that Mitolow stem cells exhibit an enrichment of pluripotency due to their fate choices at earlier stages. Transcriptomic analysis reveals the delicate mitonuclear balance in metabolism and mitochondrial proteins in regeneration, controlled by mitochondrial dynamics. These findings highlight the importance of maintaining mitochondrial dynamics in large-scale tissue regeneration and suggest the potential for manipulating these dynamics to enhance stem cell functionality and regenerative processes.

Stimulated Emission Depletion Imaging Reveals Mitochondrial Phenotypic Heterogeneity under Apoptosis Stimuli across Living Glioma Models

The mitochondrial phenotypes contribute to the understanding of disease mechanisms and treatments, which are typically characterized through the omics methods. However, the high dynamics and phenotypic heterogeneity of mitochondria require high-resolution characterization within individual living cells. Therefore, we introduce a fluorescence analysis method, based on two-color and fluorescence lifetime stimulated emission depletion (STED) super-resolution imaging, to explore mitochondrial phenotypic heterogeneity in human (U87) and mouse (GL261) glioma models. Furthermore, we used rotenone and etoposide to simulate the effects of antitumor drugs, inducing apoptosis through mitochondrial dysfunction, respectively. The two-color labeling introduces intracellular parameters to qualitatively visualize changes in mitochondrial morphology, while fluorescence lifetime reflects the status of mitochondria and their microenvironment from the perspective of probe characteristics. This method reveals mitochondria phenotypic heterogeneity induced by the apoptotic stimuli in human and mouse glioma models from a morphological perspective.

The potential mechanism of mitochondrial homeostasis in postoperative neurocognitive disorders: an in-depth review

Postoperative neurocognitive disorders (PND) are the most common neurological disorders following surgery and anaesthesia before and within 12 months after surgery, with a high prevalence in the geriatric population. PND can severely deteriorate the quality of life of patients, especially among the elderly, mainly manifested as memory loss, attention, decline and language comprehension disorders, mostly in elderly patients, with an incidence as high as 31%. Previous studies have also raised the possibility of accelerated cognitive decline and underlying neuropathological processes associated with diseases that affect cognitive performance (e.g. Alzheimer's dementia) for reasons related to anaesthesia and surgery. Currently, most research on PND has focused on various molecular pathways, especially in the geriatric population. The various hypotheses that have been proposed regarding the mechanisms imply peripheral neuroinflammation, oxidative stress, mitochondrial homeostasis, synaptic function, autophagy disorder, blood-brain barrier dysfunction, the microbiota-gut-brain axis and lack of neurotrophic support. However, the underlying pathogenesis and molecular mechanisms of PND have not yet been uncovered. Recent research has focused on mitochondrial homeostasis. In this paper, we present a review of various studies to better understand and characterize the mechanisms of associated cognitive dysfunction. As the biochemical basis of PND becomes more clearly defined, future treatments based on mitochondrial homeostasis modulation can prove to be very promising.

The Role and Applied Value of Mitochondria in Glioma-Related Research

Mitochondria, known as the "energy factory" of cells, are essential organelles with a double membrane structure and genetic material found in most eukaryotic cells. They play a crucial role in tumorigenesis and development, with alterations in mitochondrial structure and function in tumor cells leading to characteristics such as rapid proliferation, invasion, and drug resistance. Glioma, the most common brain tumor with a high recurrence rate and limited treatment options, has been linked to changes in mitochondrial structure and function. This review focuses on the bioenergetics, dynamics, metastasis, and autophagy of mitochondria in relation to glioma proliferation, as well as the potential use of mitochondria-targeting drugs in glioma treatment.