Search Results (136)

Charcot-Marie-Tooth (CMT) disease type 2A is a rare heritable disorder caused by pathogenic variants of mitofusin (MFN) 2 that suppress mitochondrial fusion and motility in peripheral nerves, culminating in denervation myoatrophy. The rarity of this condition and the limited choice of animal models preclude pre-clinical evaluation of many tests that could be translated to human trials. Here, we introduced the CMT2A pathogenic variant MFN2 T105M into the rat genome for phenotype characterization and evaluation of disease response to a third-generation mitofusin activator, 8015-P2. CMT2A rats exhibited peripheral motor and sensory neuron dysfunction. Functional, histological, neuroelectrophysiological and magnetic resonance imaging testing readily distinguished between wild-type (WT) and mutant rats via axonopathy and myoatrophy. Compound 8015-P2 reversed CMT2A-linked neuromuscular degeneration in a dose- and time-dependent manner; at 10 mg/kg/d, normalization occurred at 4 weeks. The minimal effective 8015-P2 dose was 2 mg/kg/day. Rapidity of phenotype reversal and primary muscle abnormalities are consistent with extra-neuronal effects of the causal MFN2 DNA variant. These data demonstrate unprecedented utility of the Mfn2 T105M rat as a model of CMT2A, expand the menu of clinically applicable tests that may have use in future human trials, and establish a strong foundation for exploration of extra-neuronal consequences of pathogenic mitofusin variants in non-mouse models. Full article

Mitofusin-2 (MFN2) variants are a well-established cause of Charcot–Marie–Tooth disease type 2A, although central nervous system involvement has increasingly been recognized in a subset of affected patients. We report a 51-year-old woman carrying a likely pathogenic MFN2 variant (c.2119C>T, p.Arg707Trp) who developed rapidly progressive spastic paraplegia and became wheelchair-dependent within several months. Neurological examination demonstrated severe pyramidal tract signs with preserved sensory function. Nerve conduction studies were suggestive of distal motor axonal involvement, while transcranial magnetic stimulation and somatosensory evoked potentials indicated corticospinal and central sensory pathway dysfunction in the lower extremities. Brain magnetic resonance imaging revealed extensive bilateral confluent periventricular and deep white matter hyperintensities. Comprehensive investigations excluded inflammatory, vascular, metabolic, infectious, neoplastic, and common genetic causes of hereditary spastic paraplegia. Targeted next-generation sequencing identified a heterozygous likely pathogenic MFN2 p.Arg707Trp variant. Although central nervous system manifestations have previously been described in MFN2-related disease, this phenotype is unusual because of the combination of late-onset rapidly progressive spastic paraplegia, and extensive cerebral white matter abnormalities associated with the p.Arg707Trp variant. This case further expands the recognized phenotypic spectrum of MFN2-related disease and highlights that MFN2 variants should be considered in the differential diagnosis of selected patients with late-onset progressive spastic paraplegia accompanied by cerebral white matter abnormalities and distal motor axonal neuropathy. Full article

Hyperbaric oxygen (HBO) shows neuroprotective potential in cerebral ischemia–reperfusion (CIR) injury, but its variable efficacy suggests that the underlying cellular mechanisms remain incompletely defined. We previously showed that HBO suppresses microglial NLRP3 inflammasome activation after CIR injury in a reactive oxygen species (ROS)-dependent manner; yet, how ROS couples to this effect remains unclear. Since mitochondria regulate ROS and inflammasome signaling, we investigated whether HBO modulates microglial mitochondrial dynamics in CIR injury. In adult male ICR mice (n = 71, 8–12 weeks) subjected to 60 min middle cerebral artery occlusion followed by 24 h reperfusion, HBO improved neurological function, reduced infarct area, and decreased ASC-positive microglia/macrophages. In lipopolysaccharide/nigericin-stimulated primary microglia, HBO suppressed IL-1β release, reduced mitochondrial fragmentation, preserved mitochondrial membrane potential, maintained mitofusin 2 (MFN2) protein level, and reduced DRP1 Ser616 phosphorylation without altering total DRP1 or FIS1 expression. MitoTEMPOL abolished HBO-mediated protection against mitochondrial fragmentation, MFN2 reduction, and DRP1 Ser616 phosphorylation in vitro. Edaravone, when combined with HBO, attenuated HBO-mediated neuroprotection and counteracted HBO-induced regulation of MFN2 and DRP1 Ser616 phosphorylation in vivo. These findings support ROS-dependent remodeling of microglial mitochondrial dynamics as a mechanism contributing to HBO-mediated suppression of inflammasome-associated inflammation after CIR injury. Full article

Fatty liver disease represents a major metabolic disorder affecting domestic animals worldwide, with significant implications for animal health, welfare, and agricultural productivity. Disrupted communication between mitochondria and other organelles—particularly the endoplasmic reticulum, lipid droplets, and lysosomes—plays a critical role in disease pathogenesis. This review synthesizes knowledge on inter-organellar communication across domestic animals, with emphasis on species-specific adaptations. We address the “Dairy Cow Paradox”—periparturient dairy cows develop severe hepatic steatosis (>30% liver fat), yet under sterile conditions, they have a higher threshold for progressing to sterile steatohepatitis compared to rodents and humans. However, it is critical to note that severe fatty liver in dairy cows is indeed associated with impaired autophagy, inflammation, and liver damage, particularly when accompanied by ketosis or concurrent infections, and 39% of transition cows exhibit moderate to severe lymphocytic hepatitis. We propose that the tolerance to severe steatosis in dairy cows arises from three adaptations: (1) attenuated innate immune sensing via the cGAS-STING pathway; (2) enhanced lipid buffering from perilipin 5 (PLIN5) with a hypothesized ruminant-specific Val152 substitution that may stabilize lipid droplet–mitochondria contacts; and (3) dampened calcium signaling due to ER–mitochondria membrane lipid raft rigidity, elevated inositol 1,4,5-trisphosphate receptor 2 (IP₃R2) expression, and reduced mitochondrial calcium uniporter (MCU) conductance. We contrast this with the inflammatory steatohepatitis common in rodent models driven by calcium overload and mitochondrial DNA (mtDNA) release, and glucocorticoid-mediated mitofusin 1 (MFN1) suppression, causing mitochondrial fragmentation in poultry. We identify critical knowledge gaps, including the need to define bovine and avian mitochondria-associated endoplasmic reticulum membrane (MAM) proteomes and spatially resolve hepatic zonal communication patterns. Targeting organellar communication hubs with nutraceuticals or pharmacological agents offers promising therapeutic strategies. Full article

Chemotherapy-induced metabolic reprogramming of glioblastoma multiforme (GBM) cells increases intracellular levels of reductive and energetic carriers, thereby fueling drug-relocation and retention systems and enhancing GBM drug-resistance. We have previously shown the role of this process in the adaptation of poly(morpho)nuclear “giant” cells (PGCs) in T98G populations to doxorubicin (DOX)-induced stress. Here, we addressed the role of a “resistance triad”, which coordinates metabolic T98G reprogramming with the activation of the drug-relocation and drug-retention axis, in the recovery of GBM populations from chemotherapeutic stress. A combination of proteomic analyses with metabolic and phenotypic profiling of pulse DOX-treated T98G cells revealed the significance of mitochondrial dynamics for the efficiency of the T98G “resistance triad”. DOX-induced mobilization of ATP-generating systems and ATP-dependent anabolic pathways was accompanied by the formation of DOX-negative, “mosaic” mitochondrial networks and the upregulation of mitofusin-2 (MFN2) in T98G PGCs. Transient MFN2 down-regulation correlated with the respiratory capacity of T98G cells, while impairing cell welfare in the absence and presence of DOX. However, minute fractions of PGCs, which withstood combined MFN2 down-regulation and pulse DOX treatment, retained mitochondrial networks and displayed efficient ABC transporter-/V-type channel-dependent lysosomal DOX retention. Collectively, a “triad” of mitochondrial activation, ABC transporter-dependent perinuclear redistribution and V-type channel-mediated lysosomal DOX compartmentalization determines DOX resistance of T98G cells. Whereas MFN2-dependent mitochondrial rearrangements may contribute to these processes, complementary adaptative mechanisms can compensate MFN2 dysfunction, limiting its potential as a therapeutic target. Full article

Pneumoconiosis, characterized by progressive pulmonary fibrosis, remains a predominant occupational disease in China, with coal workers’ pneumoconiosis (CWP) and silicosis being the primary subtypes. Despite extensive research, its underlying pathogenic mechanisms are not yet fully understood. Mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) are crucial subcellular microdomains that govern Ca²⁺ transport, sustain cellular bioenergetics, and maintain systemic homeostasis. Emerging evidence has linked the structural and functional dysregulation of MAMs to the pathogenesis of various fibrotic disorders. Apoptosis, a highly regulated cell death process, is a key driver in pneumoconiosis progression, in which Ca²⁺ imbalance serves as a critical signaling cascade. Mitofusin 2 (MFN2), a core regulator of MAMs’ structural integrity, mediates mitochondrial fusion and directly bridges the ER with the outer mitochondrial membrane, thereby stabilizing ER–mitochondrial coupling. However, whether MFN2 mitigates fibrosis by preserving MAMs’ integrity and subsequently suppressing Ca²⁺-dependent apoptosis remains elusive. In this study, we established SD rat and A549 cell models of CWP. Our results demonstrated that MFN2 expression was downregulated after coal dust exposure, accompanied by MAMs impairment, Ca²⁺ imbalance, and increased apoptosis, which ultimately drove the pathological progression of pulmonary fibrosis. Notably, MFN2 overexpression restored MAMs’ structure and Ca²⁺ homeostasis, alleviated abnormal apoptosis, and subsequently inhibited fibrosis. This study highlights the importance of the MFN2–MAMs–Ca²⁺–apoptosis axis and identifies MFN2 as a potential therapeutic target for pneumoconiosis. Full article

Mitochondria are crucial carriers of maternal effects, and their function is closely related to energy metabolism and disease occurrence. Previous studies have shown that chickens with different mitochondrial haplogroups exhibit differences in production performance, but the underlying mechanism remains unclear. This study investigates the differences in mitochondrial structure and function-related indices between the A and E mitochondrial haplogroups (referred to as A-group and E-group) in recessive white-feathered chickens. It was achieved using in vivo fasting/refeeding models and an in vitro model of treating hepatocytes with nutritional factors (glucose and fatty acids). In vivo study indicated that compared to A-group chicken hepatocytes, E-group hepatocytes had shorter perimeters of mitochondria and shorter lengths of mitochondria associated with the endoplasmic reticulum membrane during refeeding (p < 0.05); mitochondria were more abundant (p = 0.05) but displayed compromised structural integrity during fasting; mitochondrial swelling was more severe during both refeeding and fasting (p < 0.01, p < 0.05); the protein level of mitofusin 2 (MFN2) was lower during fasting (p < 0.05); and there were more vacuoles and lipid accumulation in liver sections during refeeding (p < 0.05). In cultured hepatocytes, compared to A-group cells, E-group cells had higher reactive oxygen species (ROS) level after oleic acid treatments (p < 0.001); the protein level of microtubule-associated protein 1A/1B-light chain 3 beta (LC3) was lower after glucose treatment (p < 0.01), and the protein levels of MFN2 and LC3 were lower after oleic acid treatment (p < 0.01, p < 0.05). These findings suggest that mitochondrial haplogroups are associated with mitochondrial structure and function, oxidative stress, autophagy, and lipid metabolism of chicken hepatocytes in response to energy stimulation. The findings may explain how mitochondrial haplogroups affect chicken production performance. Full article

Background: Myocardial ischemia–reperfusion (IR) injury is associated with dysregulated Ca²⁺ handling and oxidative stress, particularly in the middle-aged heart. Sarcoplasmic reticulum (SR)–mitochondria communication via mitochondria-associated membranes (MAMs) is essential for coordinating Ca²⁺ transfer and redox signaling; however, its role in IR injury in the middle-aged myocardium remains incompletely understood. This study investigated changes in cardiac MAM protein composition and associated functional and oxidative parameters during ischemia and IR. Methods: Middle-aged rat hearts were subjected to global ischemia or IR using the Langendorff perfusion model. Mitochondrial, MAM, and homogenate fractions were analyzed using biochemical, proteomic, and functional assays to assess Ca²⁺-handling proteins, redox enzymes, lipid peroxidation markers, and mitochondrial antioxidant defenses. Results: Myocardial ischemia and IR disrupted SR–mitochondria communication in middle-aged hearts, leading to impaired Ca²⁺ handling, redox imbalance, and reduced contractile recovery. Ischemia induced significant MAM remodeling, characterized by reduced mitofusin 2 levels and increased enrichment of voltage-dependent anion channel 1. These changes were associated with disturbed mitochondrial Ca²⁺ signaling, impaired SR Ca²⁺ sequestration. Although mitochondrial antioxidant defenses, including MnSOD, were largely preserved, IR was associated with compartment-specific redox alterations within MAMs, as inferred from altered redox enzyme activity and enhanced lipid peroxidation. Conclusions: Disruption of SR–mitochondria coupling and MAM-associated redox regulation represents a key mechanism underlying increased vulnerability to IR injury in the middle-aged heart. Targeting MAM integrity and modulating Ca²⁺-redox cross-talk may improve cardiac resilience in elderly populations. Full article

Airborne particulate matter with a diameter of <10 μm (PM₁₀) can damage the corneal epithelium by inducing oxidative stress, disrupting the NRF2 antioxidant pathway, and triggering epithelial barrier dysfunction and inflammation. However, the role of mitochondria in mediating PM₁₀-induced damage remains unexplored. This study investigated the impact of PM₁₀ on mitochondrial homeostasis in both immortalized human corneal epithelial cells (HCE-2) and the mouse corneal epithelium, as well as the protective effects of SKQ1. For in vivo assessment, female C57BL/6 mice were exposed to either control air or PM₁₀ (±SKQ1) in a whole-body exposure chamber for 2 weeks (3 h/day, 5 days/week, with weekends off). In vitro, HCE-2 cells were exposed to 100 μg/mL PM₁₀ (±SKQ1) for 24 h, and mitochondrial function and morphology were evaluated. In vitro, PM₁₀ significantly impaired mitochondrial function by reducing basal, maximal, and ATP-linked respiration; reserve capacity; and coupling efficiency compared to the control and SKQ1 groups. PM₁₀ also downregulated mitofusin1 (MFN1) and optic atrophy1 (OPA1) and upregulated dynamin-related protein1 (DRP1) and mitochondrial fission protein1 (FIS1) in HCE-2 cells. In addition, PM₁₀ exposure significantly decreased the mitochondrial membrane potential; mitochondrial DNA copy number; and cytochrome c oxidase subunit 4 isoform 1 (COX4i1), mitochondrial transcription factor A (TFAM), and peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) levels. SKQ1 pre-treatment significantly attenuated these effects. In vivo, PM₁₀ exposure significantly decreased the levels of MFN1, TFAM, COX4i1, and superoxide dismutase (SOD2), whereas SKQ1 treatment significantly reversed these effects. Overall, these findings demonstrate that PM₁₀ exposure induces mitochondrial fragmentation, disrupts mitochondrial biogenesis and quality control, and reduces mitochondrial respiration, resulting in mitochondrial dysfunction. SKQ1 effectively reversed these changes, suggesting its potential as a therapeutic strategy to protect corneal epithelial cells from PM₁₀-induced mitochondrial damage. Full article

Mitochondria–endoplasmic reticulum contacts (MERCs) are physical structures formed between mitochondria and the endoplasmic reticulum (ER) through various tethering proteins, playing crucial roles in multiple physiological processes, including Ca²⁺ and lipid exchange between the ER and mitochondria, regulation of mitochondrial morphology and dynamics (fusion and fission), as well as the induction of autophagy and apoptosis. Mitofusin 2 (MFN2), a key mitochondrial fusion protein, has been identified as an essential structural component of MERCs. Our research demonstrates that 16:8 circadian intermittent fasting (CIF) leads to enhanced mitochondrial fusion. The upregulation of MFN2 reinforces MERC stability, thereby facilitating efficient Ca²⁺ transfer between the ER and mitochondria. This process sustains the activity of mitochondrial oxidative phosphorylation (OXPHOS) enzymes, elevates mitochondrial oxygen utilization efficiency, and ultimately augments ATP production. Consequently, these adaptations enhance cardiomyocyte tolerance to hypoxic conditions. This study elucidates a novel mechanism by which MERCs regulate cellular hypoxia resistance and proposes a potential therapeutic strategy for improving acute hypoxia tolerance through the modulation of Ca²⁺ transport at MERCs. Full article

ADCY9, a crucial member of the adenylate cyclase family, exerts neuroprotective and analgesic effects in the nervous system by modulating the activity of the cAMP/AMPK signaling pathway. However, the role of the ADCY9 gene in neural regeneration remains unreported. In this study, we utilized Dugesia japonica, a highly regenerative planarian species, as a model to systematically examine the spatiotemporal expression pattern of the ADCY9 gene during planarian brain regeneration and investigate its regulatory function in this process. The results demonstrated that the downregulation of ADCY9 resulted in abnormal brain regeneration in planarians, characterized by partial loss of the nerve cord, reduced numbers of collateral branches, and significant inhibition of the regeneration and differentiation of multiple neuron types. RNA sequencing revealed that the downregulation of ADCY9 led to 499 differentially expressed genes, with KEGG enrichment pathway analysis indicating significant associations with neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease. Double RNAi experiments demonstrated that simultaneous knockdown of ADCY9 and Mitofusin-1 significantly restored neural regeneration. Collectively, ADCY9 might promote the comprehensive reconstruction of neural structure by hierarchically regulating the regeneration intensity through negative regulation of the downstream inhibitory factor Mitofusin-1. This study discloses the function of ADCY9 in planarian neural regeneration, providing a theoretical foundation for its application in investigating neural regeneration mechanisms and neurodegenerative disease pathogenesis in higher vertebrates. Full article

Mutations in the Mitofusin 2 (MFN2) gene cause Charcot–Marie–Tooth type 2A (CMT2A). Neurotrophin 3 (NT-3) is an autocrine factor that supports Schwann cell survival and differentiation, axon regeneration and myelination, neuromuscular junction (NMJ) integrity, and mitochondrial function. In this study, we assessed the efficacy of NT-3 gene therapy using the AAVrh74 serotype in the Mfn2^+/− mouse model for CMT2A. Although haploinsufficiency is not reported in CMT2A patients, our model shows some features of CMT2A, including axonal atrophy, muscle atrophy, length-dependent axon loss, and abnormal mitochondria, in muscle in the enzyme histochemistry. Eight-month-old Mfn2^+/− mice received a 3 × 10¹¹ vector genome dose of AAVrh74.tMCK.NT-3 intramuscularly, and functional, electrophysiological, and histological outcomes were assessed six months post-treatment. NT-3 gene therapy in Mfn2^+/− mice significantly improved grip strength and rotarod performance, and ameliorated electrophysiological abnormalities and NMJ denervation in lumbrical muscles. Additionally, our therapeutic approach improved muscle histopathology with reductions in mitochondrial abnormalities and oxidative stress. NT-3 further remodeled carbohydrate metabolism in muscle. Our study indicated that AAV.NT-3 gene therapy has a disease-modifying effect in the Mfn2^+/− model of CMT2A, providing further support for the translational potential of this surrogate gene therapy approach to CMT2A patients. Full article

Ischemic stroke initiates a complex cascade of pathophysiological events—including energy failure, excitotoxicity, oxidative stress, inflammation, apoptosis, and mitochondrial dysfunction—that together lead to extensive neuronal damage. Effectively targeting these interconnected mechanisms is crucial for achieving neuroprotection. Alpinetin, known for its antioxidant, anti-inflammatory, and cytoprotective properties, has shown promise as a potential therapeutic agent for cerebral ischemia in preliminary studies. However, the exact molecular mechanisms underlying its neuroprotective effects remain unclear. Therefore, this study aimed to investigate the multifaceted actions of alpinetin in a preclinically relevant right middle cerebral artery occlusion (Rt.MCAO) rat model, focusing on its impact on neuronal survival, inflammation, oxidative stress, apoptosis, and mitochondrial function. Forty male Wistar rats were randomly assigned to four groups: sham operation, Rt.MCAO + vehicle, Rt.MCAO + piracetam (250 mg/kg BW), and Rt.MCAO + alpinetin (100 mg/kg BW). We examined glial cell morphology, protein kinase B (Akt) expression, mitochondrial superoxide dismutase (MnSOD), myeloperoxidase (MPO), anti-apoptotic proteins, mitogen-activated protein kinase (p38 MAPK) and mitofusin-2 (Mfn2). Treatment with alpinetin for 3 days exerted robust neuroprotective effects by significantly reducing astrocytic and microglial activation through the downregulation of glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule 1 (Iba-1), restoring Akt expression, decreasing MPO activity, and enhancing MnSOD activity. Additionally, alpinetin modulated apoptotic signaling by lowering pro-apoptotic markers Bcl-2 Associated X-protein (Bax) and caspase-3 while increasing the expression of the anti-apoptotic protein B-cell lymphoma-extra large (Bcl-XL). It also attenuated p38 MAPK activation and preserved mitochondrial integrity by mitigating the decline in Mfn2 levels. Overall, these findings highlight the therapeutic potential of alpinetin in targeting multiple pathological processes involved in ischemic brain injury, supporting its promise as an effective treatment for stroke. Full article

Background: Hypoxia-induced oxidative stress compromises the survival and function of transplanted islets, contributing to high rates of islet transplantation failure. Methods: This study investigated the small-molecule mitochondrial fusion agonist S89, which specifically activates mitofusin 1 (MFN1). We assessed its protective effects against hypoxia-induced oxidative stress and apoptosis in pancreatic β-cells. Results: In mouse insulinoma cells (Min6), S89 enhanced cell viability by promoting mitochondrial fusion to inhibit mitochondrial reactive oxygen species (mtROS) overaccumulation (S89 reduced mtROS by approximately 30%) and attenuated mitochondrial lipid peroxidation; furthermore, it suppressed hypoxia-induced apoptosis via downregulation of the BAX/BCL-2 ratio, thus protecting the cells from hypoxia-induced oxidative damage. Notably, S89 significantly potentiated glucose-stimulated insulin secretion (GSIS) in both the Min6 β-cell line and primary mouse islets. Critically, S89 pretreatment enhanced hypoxia resistance in islets and significantly increased graft survival upon transplantation into streptozotocin (STZ)-induced type 1 diabetic (T1D) mice, maintaining prolonged blood glucose homeostasis. Conclusions: These findings demonstrate that S89 protects β-cells from hypoxic injury, indicating its efficacy as a therapeutic approach for improving islet transplantation outcomes. Full article

Mono(2-ethylhexyl) phthalate (MEHP), a bioactive metabolite of di(2-ethylhexyl) phthalate (DEHP), has been detected in the placenta and urine of pregnant women and is linked to adverse pregnancy outcomes. However, its effects on mitochondrial homeostasis in trophoblast cells remain incompletely understood. This study examined the impact of MEHP (0.5–200 µM) on mitochondrial function, dynamics, and biogenesis in human HTR-8/SVneo trophoblast cells. MEHP (≥5 µM) reduced MTT conversion without compromising membrane integrity, suggesting early metabolic or redox imbalance. A dose-dependent loss of mitochondrial membrane potential was observed, with increased reactive oxygen species (ROS) generation only at 200 µM. MEHP modulated the expression of mitochondrial dynamics genes, with a more pronounced mitofusin 1 (MFN1) induction at low doses and increased mitochondrial DNA content, suggesting a compensatory response to mild stress. Conversely, high doses more strongly induced fission and mitochondrial 1 (FIS1) expression, suggesting mitochondrial fragmentation. Both concentrations induced the expression of the mitochondrial biogenesis regulators peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) and nuclear factor erythroid 2–related factor 2 (Nrf2), while sirtuin 1 (SIRT1) expression and activity declined progressively with dose. These results demonstrate that MEHP disrupts mitochondrial homeostasis in trophoblast cells at concentrations spanning the estimated human exposure range. The dose-dependent effects, from adaptive responses to overt dysfunction, may help explain the associations between MEHP exposure and placental pathology observed in epidemiological studies. Full article