Search Results (14)

Background/Objectives: In 4-octylphenol (4-OP), a toxic environmental pollutant with endocrine disruptive effect, the use of 4-OP causes pollution in the freshwater environment and poses risks to aquatic organisms. Common carps (Cyprinus carpio L.) live in freshwater and are experimental animals for studying the toxic effects of environmental pollutants on fish. Its heart is susceptible to toxicants. However, whether 4-OP has a toxic effect on common carp heart remains unknown. Methods: Here, we conducted a common carp 4-OP exposure experiment (carp treated with 17 μg/L 4-OP for 45 days), aiming to investigate whether 4-OP has a toxic effect on common carp hearts. We observed the microstructure and ultrastructure of carp heart and detected autophagy genes, mitochondrial fission genes, mitochondrial fusion genes, glycolytic enzymes, AMPK, ATPase, and oxidative stress factors, to investigate the molecular mechanism of 4-OP induced damage in common carp hearts. Results: Our results showed that 4-OP exposure caused mitochondrial damage, autophagy, and damage in common carp hearts. 4-OP exposure increased the levels of miR-144, and eight autophagy factors (Beclin1, RB1CC1, ULK1, LC3-I, LC3-II, ATG5, ATG12, and ATG13), and decreased the levels of four autophagy factors (PI3K, AKT, mTOR, and SQSTM1). Furthermore, 4-OP exposure induced the imbalance between mitochondrial fission and fusion and mitochondrial dynamics imbalance, as demonstrated by the increase in three mitochondrial fission factors (Mff, Drp1, and Fis1) and the decrease in three mitochondrial fusion factors (Mfn1, Mfn2, and Opa1). Moreover, excess 4-OP treatment caused energy metabolism disorder, as demonstrated by the reduction in four ATPase (Na⁺K⁺-ATPase, Ca²⁺Mg²⁺-ATPase, Ca²⁺-ATPase, and Mg²⁺-ATPase), elevation in four glycolysis genes (HK1, HK2, LDHA, and PGK1), reduction in glycolysis gen (PGAM2), and the elevation in energy-sensing AMPK. Finally, 4-OP treatment induced the imbalance between antioxidant and oxidant and oxidative stress, as demonstrated by the increase in oxidant H₂O₂, and the decreases in five antioxidant factors (CAT, SOD, T-AOC, Nrf2, and HO-1). Conclusions: miR-144 mediated autophagy by targeting PI3K, mTOR, and SQSTM1, and the miR-144/PI3K-AKT-mTOR/ULK1 pathway was involved in 4-OP-induced autophagy. Mff-Drp1 axis took part in 4-OP-caused mitochondrial dynamics imbalance, and mitochondrial dynamics imbalance mediated autophagy via Mfn2-SQSTM1, Mfn2/Beclin1, and Mff-LC3-II axes. Energy metabolism disorder mediated mitochondrial dynamics imbalance through the AMPK-Mff-Drp1 pathway. Oxidative stress mediated energy metabolism disorder via the H₂O₂-AMPK axis. Taken together, oxidative stress triggered energy metabolism disorder, induced mitochondrial dynamics imbalance, and caused autophagy via the H₂O₂-AMPK-Mff-LC3-II pathway. Our study provided references for the toxic effects of endocrine disruptor on common carp hearts, and provided a basis for assessing environmental pollutant-induced damage in common carp heart. We only studied the toxic effects of 4-OP on common carp, and the toxic effects of 4-OP on other fish species need to be further studied. Full article

Microgravity can induce alterations in liver morphology, structure, and function, with mitochondria playing an important role in these changes. Tail suspension (TS) is a well-established model for simulating the effects of microgravity on muscles and bones, but its impact on liver function remains unclear. In the current study, we explored the regulatory mechanisms of apoptosis, autophagy, fission, and fusion in maintaining liver mitochondrial homeostasis in mice subjected to TS for 2 or 4 weeks (TS2 and TS4). The results showed the following: (1) No significant differences were observed in nuclear ultrastructure or DNA fragmentation between the control and TS-treated groups. (2) No significant differences were detected in the mitochondrial area ratio among the three groups. (3) Cysteine aspartic acid-specific protease 3 (Caspase3) activity and the Bcl-2-associated X protein (bax)/B-cell lymphoma-2 (bcl2) ratio were not higher in the TS2 and TS4 groups compared to the control group. (4) dynamin-related protein 1 (DRP1) protein expression was increased, while mitochondrial fission factor (MFF) protein levels were decreased in the TS2 and TS4 groups compared to the control, suggesting stable mitochondrial fission. (5) No significant differences were observed in the optic atrophy 1 (OPA1), mitofusin 1 and 2 (MFN1 and MFN2) protein expression levels across the three groups. (6) Mitochondrial autophagy vesicles were present in the TS2 and TS4 groups, with a significant increase in Parkin phosphorylation corresponding to the duration of the TS treatment. (7) ATP synthase and citrate synthase activities were significantly elevated in the TS2 group compared to the control group but were significantly reduced in the TS4 group compared to the TS2 group. In summary, the coordinated regulation of apoptosis, mitochondrial fission and fusion, and particularly mitochondrial autophagy preserved mitochondrial morphology and contributed to the restoration of the activities of these two key mitochondrial enzymes, thereby maintaining liver mitochondrial homeostasis in mice under TS conditions. Full article

Mitochondrial dynamics, including fission and fusion processes, are essential for heart health. Mitochondria, the powerhouses of cells, maintain their integrity through continuous cycles of biogenesis, fission, fusion, and degradation. Mitochondria are relatively immobile in the adult heart, but their morphological changes due to mitochondrial morphology factors are critical for cellular functions such as energy production, organelle integrity, and stress response. Mitochondrial fusion proteins, particularly Mfn1/2 and Opa1, play multiple roles beyond their pro-fusion effects, such as endoplasmic reticulum tethering, mitophagy, cristae remodeling, and apoptosis regulation. On the other hand, the fission process, regulated by proteins such as Drp1, Fis1, Mff and MiD49/51, is essential to eliminate damaged mitochondria via mitophagy and to ensure proper cell division. In the cardiac system, dysregulation of mitochondrial dynamics has been shown to cause cardiac hypertrophy, heart failure, ischemia/reperfusion injury, and various cardiac diseases, including metabolic and inherited cardiomyopathies. In addition, mitochondrial dysfunction associated with oxidative stress has been implicated in atherosclerosis, hypertension and pulmonary hypertension. Therefore, understanding and regulating mitochondrial dynamics is a promising therapeutic tool in cardiac diseases. This review summarizes the role of mitochondrial morphology in heart diseases for each mitochondrial morphology regulatory gene, and their potential as therapeutic targets to heart diseases. Full article

Mitochondria, which generate ATP through aerobic respiration, also have important noncanonical functions. Mitochondria are dynamic organelles, that engage in fission (division), fusion (joining) and translocation. They also regulate intracellular calcium homeostasis, serve as oxygen-sensors, regulate inflammation, participate in cellular and organellar quality control and regulate the cell cycle. Mitochondrial fission is mediated by the large GTPase, dynamin-related protein 1 (Drp1) which, when activated, translocates to the outer mitochondrial membrane (OMM) where it interacts with binding proteins (Fis1, MFF, MiD49 and MiD51). At a site demarcated by the endoplasmic reticulum, fission proteins create a macromolecular ring that divides the organelle. The functional consequence of fission is contextual. Physiological fission in healthy, nonproliferating cells mediates organellar quality control, eliminating dysfunctional portions of the mitochondria via mitophagy. Pathological fission in somatic cells generates reactive oxygen species and triggers cell death. In dividing cells, Drp1-mediated mitotic fission is critical to cell cycle progression, ensuring that daughter cells receive equitable distribution of mitochondria. Mitochondrial fusion is regulated by the large GTPases mitofusin-1 (Mfn1) and mitofusin-2 (Mfn2), which fuse the OMM, and optic atrophy 1 (OPA-1), which fuses the inner mitochondrial membrane. Mitochondrial fusion mediates complementation, an important mitochondrial quality control mechanism. Fusion also favors oxidative metabolism, intracellular calcium homeostasis and inhibits cell proliferation. Mitochondrial lipids, cardiolipin and phosphatidic acid, also regulate fission and fusion, respectively. Here we review the role of mitochondrial dynamics in health and disease and discuss emerging concepts in the field, such as the role of central versus peripheral fission and the potential role of dynamin 2 (DNM2) as a fission mediator. In hyperproliferative diseases, such as pulmonary arterial hypertension and cancer, Drp1 and its binding partners are upregulated and activated, positing mitochondrial fission as an emerging therapeutic target. Full article

Mitochondria, the membrane-bound cell organelles that supply most of the energy needed for cell function, are highly regulated, dynamic organelles bearing the ability to alter both form and functionality rapidly to maintain normal physiological events and challenge stress to the cell. This amazingly vibrant movement and distribution of mitochondria within cells is controlled by the highly coordinated interplay between mitochondrial dynamic processes and fission and fusion events, as well as mitochondrial quality-control processes, mainly mitochondrial autophagy (also known as mitophagy). Fusion connects and unites neighboring depolarized mitochondria to derive a healthy and distinct mitochondrion. In contrast, fission segregates damaged mitochondria from intact and healthy counterparts and is followed by selective clearance of the damaged mitochondria via mitochondrial specific autophagy, i.e., mitophagy. Hence, the mitochondrial processes encompass all coordinated events of fusion, fission, mitophagy, and biogenesis for sustaining mitochondrial homeostasis. Accumulated evidence strongly suggests that mitochondrial impairment has already emerged as a core player in the pathogenesis, progression, and development of various human diseases, including cardiovascular ailments, the leading causes of death globally, which take an estimated 17.9 million lives each year. The crucial factor governing the fission process is the recruitment of dynamin-related protein 1 (Drp1), a GTPase that regulates mitochondrial fission, from the cytosol to the outer mitochondrial membrane in a guanosine triphosphate (GTP)-dependent manner, where it is oligomerized and self-assembles into spiral structures. In this review, we first aim to describe the structural elements, functionality, and regulatory mechanisms of the key mitochondrial fission protein, Drp1, and other mitochondrial fission adaptor proteins, including mitochondrial fission 1 (Fis1), mitochondrial fission factor (Mff), mitochondrial dynamics 49 (Mid49), and mitochondrial dynamics 51 (Mid51). The core area of the review focuses on the recent advances in understanding the role of the Drp1-mediated mitochondrial fission adaptor protein interactome to unravel the missing links of mitochondrial fission events. Lastly, we discuss the promising mitochondria-targeted therapeutic approaches that involve fission, as well as current evidence on Drp1-mediated fission protein interactions and their critical roles in the pathogeneses of cardiovascular diseases (CVDs). Full article

Mitochondria have many forms and can change their shape through fusion and fission of the outer and inner membranes, called “mitochondrial dynamics”. Mitochondrial outer membrane proteins, such as mitochondrial fission protein 1 (FIS1), mitochondrial fission factor (MFF), mitochondrial 98 dynamics proteins of 49 kDa (MiD49), and mitochondrial dynamics proteins of 51 kDa (MiD51), can aggregate at the outer mitochondrial membrane and thus attract Dynamin-related protein 1 (DRP1) from the cytoplasm to the outer mitochondrial membrane, where DRP1 can perform a scissor-like function to cut a complete mitochondrion into two separate mitochondria. Other organelles can promote mitochondrial fission alongside mitochondria. FIS1 plays an important role in mitochondrial–lysosomal contacts, differentiating itself from other mitochondrial-fission-associated proteins. The contact between the two can also induce asymmetric mitochondrial fission. The kidney is a mitochondria-rich organ, requiring large amounts of mitochondria to produce energy for blood circulation and waste elimination. Pathological increases in mitochondrial fission can lead to kidney damage that can be ameliorated by suppressing their excessive fission. This article reviews the current knowledge on the key role of mitochondrial-fission-associated proteins in the pathogenesis of kidney injury and the role of their various post-translational modifications in activation or degradation of fission-associated proteins and targeted drug therapy. Full article

Sjögren’s syndrome (SS) is a chronic autoimmune multifactorial disease characterized by inflammation and lymphocytic infiltration of the exocrine glands. Several studies have highlighted the involvement of oxidative stress in this pathology, suggesting that it could induce mitochondrial dysfunctions. Mitochondria could have a role in inflammatory and immune processes. Since the mitochondrial DNA (mtDNA) copy number could change in response to physiological or environmental stimuli, this study aimed to evaluate possible alterations in the mtDNA copy number in SS. We have analyzed the amount of mtDNA in the peripheral blood of 74 SS patients and 61 healthy controls by qPCR. Then, since mitochondrial fusion and fission play a crucial role in maintaining the number of mitochondria, we investigated the expression variability of the genes most commonly involved in mitochondrial dynamics in a subgroup of SS patients and healthy controls. Interestingly, we observed a highly significant decrease in mtDNA copies in the SS patients compared to healthy controls (p = 1.44 × 10⁻¹²). Expression levels of mitochondrial fission factor (MFF), mitofusin-1 (MFN1), and mitochondrial transcription factor A (TFAM) genes were analyzed, showing a statistically significant increase in the expression of MFF (p = 0.003) and TFAM (p = 0.022) in the SS patients compared to healthy controls. These results give further insight into the possible involvement of mitochondrial dysfunctions in SS disease. Full article

The activity and quantity of mitochondrial proteins and the mitochondrial volume density (Mito_VD) are higher in trained muscles; however, the underlying mechanisms remain unclear. Our goal was to determine if 20 weeks’ endurance training simultaneously increases running performance, the amount and activity of mitochondrial proteins, and Mito_VD in the gastrocnemius muscle in humans. Eight healthy, untrained young men completed a 20-week moderate-intensity running training program. The training increased the mean speed of a 1500 m run by 14.0% (p = 0.008) and the running speed at 85% of maximal heart rate by 9.6% (p = 0.008). In the gastrocnemius muscle, training significantly increased mitochondrial dynamics markers, i.e., peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) by 23%, mitochondrial transcription factor A (TFAM) by 29%, optic artrophy-1 (OPA1) by 31% and mitochondrial fission factor (MFF) by 44%, and voltage-dependent anion channel 1 (VDAC1) by 30%. Furthermore, training increased the amount and maximal activity of citrate synthase (CS) by 10% and 65%, respectively, and the amount and maximal activity of cytochrome c oxidase (COX) by 57% and 42%, respectively, but had no effect on the total Mito_VD in the gastrocnemius muscle. We concluded that not Mito_VD per se, but mitochondrial COX activity (reflecting oxidative phosphorylation activity), should be regarded as a biomarker of muscle adaptation to endurance training in beginner runners. Full article

Mitochondrial fission factor (MFF) is an adapter that targets dynamin-related protein 1 from the cytosol to the mitochondria for fission. Loss-of-function MFF mutations cause encephalopathy due to defective mitochondrial and peroxisomal fission 2 (EMPF2). To elucidate the molecular mechanisms that were involved, we analyzed the functional effects of MFF depletion in deciduous teeth-derived dental pulp stem cells differentiating into dopaminergic neurons (DNs). When treated with MFF-targeting small interfering RNA, DNs showed impaired neurite outgrowth and reduced mitochondrial signals in neurites harboring elongated mitochondria. MFF silencing also caused mitochondrial Ca²⁺ accumulation through accelerated Ca²⁺ influx from the endoplasmic reticulum (ER) via the inositol 1,4,5-trisphosphate receptor. Mitochondrial Ca²⁺ overload led DNs to produce excessive reactive oxygen species (ROS), and downregulated peroxisome proliferator-activated receptor-gamma co-activator-1 alpha (PGC-1α). MFF was co-immunoprecipitated with voltage-dependent anion channel 1, an essential component of the ER-mitochondrial Ca²⁺ transport system. Folic acid supplementation normalized ROS levels, PGC-1α mediated mitochondrial biogenesis, and neurite outgrowth in MFF depleted DNs, without affecting their mitochondrial morphology or Ca²⁺ levels. We propose that MFF negatively regulates the mitochondrial Ca²⁺ influx from the ER. MFF-insufficiency recapitulated the EMPF2 neuropathology with increased oxidative stress and suppressed mitochondrial biogenesis. ROS and mitochondrial biogenesis might be potential therapeutic targets for EMPF2. Full article

Peroxisomes, in concert with mitochondria, have been established as platforms for the establishment of a rapid and stable antiviral immune response, due to the presence of the mitochondrial antiviral signaling protein (MAVS) at their membranes. Upon intracellular recognition of viral RNA, retinoic acid inducible gene-I (RIG-I)-like proteins interact with MAVS, inducing its oligomerization and the establishment of a signaling cascade that culminates with the production of direct antiviral effectors, preventing important steps in viral propagation. We and others have demonstrated that different viruses have developed specific mechanisms to counteract peroxisome-dependent antiviral signaling. We have shown that the human cytomegalovirus (HCMV) protein vMIA hijacks the peroxisome transport machinery to travel to the organelle, interact with MAVS, and inhibit the immune response. Here, we further unravel the mechanisms by which HCMV is able to evade peroxisome-dependent antiviral signaling. We demonstrate that vMIA localizes at the peroxisomes in a complex with MAVS and the stimulator of interferon genes (STING) protein. Furthermore, vMia interacts with mitochondrial fission factor (MFF) at the peroxisomal membrane, which we show to be essential for vMia-dependent inhibition of the antiviral immune response. Importantly, we demonstrate that vMIA’s interaction with MAVS impedes its oligomerization and the consequent activation of the downstream signaling cascade. Interestingly, our results underline important differences between vMIA’s mechanisms of action at the peroxisomes and the mitochondria. Our results unravel novel mechanisms involving the interplay between the HCMV and peroxisomes that may ultimately contribute to the discovery of novel targets for antiviral combat. Full article

(1) Background: There are no successive treatments for heart failure with preserved ejection fraction (HFpEF) because of complex interactions between environmental, histological, and genetic risk factors. The objective of the study is to investigate changes in cardiomyocytes and molecular networks associated with HFpEF. (2) Methods: Dahl salt-sensitive (DSS) rats developed HFpEF when fed with a high-salt (HS) diet for 7 weeks, which was confirmed by in vivo and ex vivo measurements. Shotgun proteomics, microarray, Western blot, and quantitative RT-PCR analyses were further carried out to investigate cellular and molecular mechanisms. (3) Results: Rats with HFpEF showed diastolic dysfunction, impaired systolic function, and prolonged repolarization of myocytes, owing to an increase in cell size and apoptosis of myocytes. Heatmap of multi-omics further showed significant differences between rats with HFpEF and controls. Gene Set Enrichment Analysis (GSEA) of multi-omics revealed genetic risk factors involved in cardiac muscle contraction, proteasome, B cell receptor signaling, and p53 signaling pathway. Gene Ontology (GO) analysis of multi-omics showed the inflammatory response and mitochondrial fission as top biological processes that may deteriorate myocyte stiffening. GO analysis of protein-to-protein network indicated cytoskeleton protein, cell fraction, enzyme binding, and ATP binding as the top enriched molecular functions. Western blot validated upregulated Mff and Itga9 and downregulated Map1lc3a in the HS group, which likely contributed to accumulation of aberrant mitochondria to increase ROS and elevation of myocyte stiffness, and subsequent contractile dysfunction and myocardial apoptosis. (4) Conclusions: Multi-omics analysis revealed multiple pathways associated with HFpEF. This study shows insight into molecular mechanisms for the development of HFpEF and may provide potential targets for the treatment of HFpEF. Full article

Autism spectrum disorder (ASD) is a highly prevalent neurodevelopmental disorder that exhibits a common set of behavioral and cognitive impairments. Although the etiology of ASD remains unclear, mitochondrial dysfunction has recently emerged as a possible causative factor underlying ASD. The ketogenic diet (KD) is a high-fat, low-carbohydrate diet that augments mitochondrial function, and has been shown to reduce autistic behaviors in both humans and in rodent models of ASD. The aim of the current study was to examine mitochondrial bioenergetics in the BTBR mouse model of ASD and to determine whether the KD improves mitochondrial function. We also investigated changes in mitochondrial morphology, which can directly influence mitochondrial function. We found that BTBR mice had altered mitochondrial function and exhibited smaller more fragmented mitochondria compared to C57BL/6J controls, and that supplementation with the KD improved both mitochondrial function and morphology. We also identified activating phosphorylation of two fission proteins, pDRP1^S616 and pMFF^S146, in BTBR mice, consistent with the increased mitochondrial fragmentation that we observed. Intriguingly, we found that the KD decreased pDRP1^S616 levels in BTBR mice, likely contributing to the restoration of mitochondrial morphology. Overall, these data suggest that impaired mitochondrial bioenergetics and mitochondrial fragmentation may contribute to the etiology of ASD and that these alterations can be reversed with KD treatment. Full article

The increasing demand for more animal products put pressure on improving livestock production efficiency and sustainability. In this context, advanced animal nutrition studies appear indispensable. Here, the effect of grape pomace (GP), the polyphenol-rich agricultural by-product, was evaluated on Holstein-Friesian cows’ whole-blood transcriptome, milk production and composition. Two experimental groups were set up. The first one received a basal diet and served as a control, while the second one received a 7.5% GP-supplemented diet for a total of 60 days. Milk production and composition were not different between the group; however, the transcriptome analysis revealed a total of 40 genes significantly affected by GP supplementation. Among the most interesting down-regulated genes, we found the DnaJ heat-shock protein family member A1 (DNAJA1), the mitochondrial fission factor (MFF), and the impact RWD domain protein (IMPACT) genes. The gene set enrichment analysis evidenced the positive enrichment of ‘interferon alpha (IFN-α) and IFN-γ response’, ‘IL6-JAK-STAT3 signaling’ and ‘complement’ genes. Moreover, the functional analysis denoted positive enrichment of the ‘response to protozoan’ and ‘negative regulation of viral genome replication’ biological processes. Our data provide an overall view of the blood transcriptomic signature after a 60-day GP supplementation in dairy cows which mainly reflects a GP-induced immunomodulatory effect. Full article

Mitochondrial fusion and fission tailors the mitochondrial shape to changes in cellular homeostasis. Players of this process are the mitofusins, which regulate fusion of the outer mitochondrial membrane, and the fission protein DRP1. Upon specific stimuli, DRP1 translocates to the mitochondria, where it interacts with its receptors FIS1, MFF, and MID49/51. Another fission factor of clinical relevance is GDAP1. Here, we identify and discuss cysteine residues of these proteins that are conserved in phylogenetically distant organisms and which represent potential sites of posttranslational redox modifications. We reveal that worms and flies possess only a single mitofusin, which in vertebrates diverged into MFN1 and MFN2. All mitofusins contain four conserved cysteines in addition to cysteine 684 in MFN2, a site involved in mitochondrial hyperfusion. DRP1 and FIS1 are also evolutionarily conserved but only DRP1 contains four conserved cysteine residues besides cysteine 644, a specific site of nitrosylation. MFF and MID49/51 are only present in the vertebrate lineage. GDAP1 is missing in the nematode genome and contains no conserved cysteine residues. Our analysis suggests that the function of the evolutionarily oldest proteins of the mitochondrial fusion and fission machinery, the mitofusins and DRP1 but not FIS1, might be altered by redox modifications. Full article