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Biomolecules Jul 2021Mitochondria play key roles in ATP supply, calcium homeostasis, redox balance control and apoptosis, which in neurons are fundamental for neurotransmission and to allow... (Review)
Review
Mitochondria play key roles in ATP supply, calcium homeostasis, redox balance control and apoptosis, which in neurons are fundamental for neurotransmission and to allow synaptic plasticity. Their functional integrity is maintained by mitostasis, a process that involves mitochondrial transport, anchoring, fusion and fission processes regulated by different signaling pathways but mainly by the peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α). PGC-1α also favors Ca homeostasis, reduces oxidative stress, modulates inflammatory processes and mobilizes mitochondria to where they are needed. To achieve their functions, mitochondria are tightly connected to the endoplasmic reticulum (ER) through specialized structures of the ER termed mitochondria-associated membranes (MAMs), which facilitate the communication between these two organelles mainly to aim Ca buffering. Alterations in mitochondrial activity enhance reactive oxygen species (ROS) production, disturbing the physiological metabolism and causing cell damage. Furthermore, cytosolic Ca overload results in an increase in mitochondrial Ca, resulting in mitochondrial dysfunction and the induction of mitochondrial permeability transition pore (mPTP) opening, leading to mitochondrial swelling and cell death through apoptosis as demonstrated in several neuropathologies. In summary, mitochondrial homeostasis is critical to maintain neuronal function; in fact, their regulation aims to improve neuronal viability and to protect against aging and neurodegenerative diseases.
Topics: Aging; Animals; Calcium; Homeostasis; Humans; Inflammation; Insulin Resistance; Mitochondria; Neurodegenerative Diseases; Neurons; Reactive Oxygen Species
PubMed: 34356637
DOI: 10.3390/biom11071012 -
Chemico-biological Interactions Nov 2020A cellular model of cardiomyocytes (H9c2 cell line) and mitochondria isolated from mouse liver were used to understand the drug action of BPDZ490 and BPDZ711, two...
A cellular model of cardiomyocytes (H9c2 cell line) and mitochondria isolated from mouse liver were used to understand the drug action of BPDZ490 and BPDZ711, two benzopyran analogues of the reference potassium channel opener cromakalim, on mitochondrial respiratory parameters and swelling, by comparing their effects with those of the parent compound cromakalim. For these three compounds, the oxygen consumption rate (OCR) was determined by high-resolution respirometry (HRR) and their impact on adenosine triphosphate (ATP) production and calcium-induced mitochondrial swelling was investigated. Cromakalim did not modify neither the OCR of H9c2 cells and the ATP production nor the Ca-induced swelling. By contrast, the cromakalim analogue BPDZ490 (1) induced a strong increase of OCR, while the other benzopyran analogue BPDZ711 (2) caused a marked slowdown. For both compounds, 1 displayed a biphasic behavior while 2 still showed an inhibitory effect. Both compounds 1 and 2 were also found to decrease the ATP synthesis, with pronounced effect for 2, while cromakalim remained without effect. Overall, these results indicate that cromakalim, as parent molecule, does not induce per se any direct effect on mitochondrial respiratory function neither on whole cells nor on isolated mitochondria whereas both benzopyran analogues 1 and 2 display totally opposite behavior profiles, suggesting that compound 1, by increasing the maximal respiration capacity, might behave as a mild uncoupling agent and compound 2 is taken as an inhibitor of the mitochondrial electron-transfer chain.
Topics: Adenosine Triphosphate; Animals; Calcium; Cell Line; Cromakalim; Male; Mice; Mice, Inbred C57BL; Mitochondria; Oxygen Consumption; Potassium Channels; Respiratory Rate
PubMed: 33010220
DOI: 10.1016/j.cbi.2020.109272 -
Circulation Research May 2024During myocardial ischemia/reperfusion (I/R) injury, high levels of matrix Ca and reactive oxygen species (ROS) induce the opening of the mitochondrial permeability...
BACKGROUND
During myocardial ischemia/reperfusion (I/R) injury, high levels of matrix Ca and reactive oxygen species (ROS) induce the opening of the mitochondrial permeability transition pore (mPTP), which causes mitochondrial dysfunction and ultimately necrotic death. However, the mechanisms of how these triggers individually or cooperatively open the pore have yet to be determined.
METHODS
Here, we use a combination of isolated mitochondrial assays and in vivo I/R surgery in mice. We challenged isolated liver and heart mitochondria with Ca, ROS, and Fe to induce mitochondrial swelling. Using inhibitors of the mPTP (cyclosporine A or ADP) lipid peroxidation (ferrostatin-1, MitoQ), we determined how the triggers elicit mitochondrial damage. Additionally, we used the combination of inhibitors during I/R injury in mice to determine if dual inhibition of these pathways is additivity protective.
RESULTS
In the absence of Ca, we determined that ROS fails to trigger mPTP opening. Instead, high levels of ROS induce mitochondrial dysfunction and rupture independently of the mPTP through lipid peroxidation. As expected, Ca in the absence of ROS induces mPTP-dependent mitochondrial swelling. Subtoxic levels of ROS and Ca synergize to induce mPTP opening. Furthermore, this synergistic form of Ca- and ROS-induced mPTP opening persists in the absence of CypD (cyclophilin D), suggesting the existence of a CypD-independent mechanism for ROS sensitization of the mPTP. These ex vivo findings suggest that mitochondrial dysfunction may be achieved by multiple means during I/R injury. We determined that dual inhibition of the mPTP and lipid peroxidation is significantly more protective against I/R injury than individually targeting either pathway alone.
CONCLUSIONS
In the present study, we have investigated the relationship between Ca and ROS, and how they individually or synergistically induce mitochondrial swelling. Our findings suggest that Ca mediates mitochondrial damage through the opening of the mPTP, although ROS mediates its damaging effects through lipid peroxidation. However, subtoxic levels both Ca and ROS can induce mPTP-mediated mitochondrial damage. Targeting both of these triggers to preserve mitochondria viability unveils a highly effective therapeutic approach for mitigating I/R injury.
Topics: Animals; Lipid Peroxidation; Mitochondrial Permeability Transition Pore; Reactive Oxygen Species; Mice; Mitochondria, Heart; Male; Myocardial Reperfusion Injury; Mice, Inbred C57BL; Mitochondrial Membrane Transport Proteins; Mitochondria, Liver; Calcium; Mitochondrial Swelling
PubMed: 38618716
DOI: 10.1161/CIRCRESAHA.123.323882 -
Bio Systems Dec 2021An extended biophysical model was obtained by upgrading the previously reported one (Khmelinskii and Makarov, 2021). The upgraded model accommodates variations of solute...
An extended biophysical model was obtained by upgrading the previously reported one (Khmelinskii and Makarov, 2021). The upgraded model accommodates variations of solute transport rates through the inner mitochondrial membrane (IMM) within the mitochondrial population, described by a Gaussian distribution. However, the model may be used for any functional form of the distribution. The dynamics of system parameters as predicted by the current model differed from that predicted by the previous model in the same initial conditions (Khmelinskii and Makarov, 2021). The amount of change varied from one parameter to the other, remaining in the 1-38% range. The upgraded model fitted the available experimental data with a better accuracy (R = 0.993) compared to the previous model (R = 0.978) using the same experimental data (Khmelinskii and Makarov, 2021). The fitting procedure also estimated the Gaussian distribution parameters. The new model requires much larger computational resources, but given its higher accuracy, it may be used for better analysis of experimental data and for better prediction of MS dynamics in different initial conditions. Note that activities of individual mitochondria in mitochondrial populations should vary within biological tissues. Thus, the currently upgraded model is a better tool for biological and bio-medical applications. We believe that this model is much better adapted to the analysis of MS dynamics in vivo.
Topics: Animals; Biophysical Phenomena; Humans; Mitochondria; Mitochondrial Membranes; Mitochondrial Swelling; Models, Biological
PubMed: 34627969
DOI: 10.1016/j.biosystems.2021.104559 -
American Journal of Physiology. Heart... Apr 2023Mitochondrial DNA (mtDNA) haplotype regulates mitochondrial structure/function and reactive oxygen species in aortocaval fistula (ACF) in mice. Here, we unravel the...
Mitochondrial DNA (mtDNA) haplotype regulates mitochondrial structure/function and reactive oxygen species in aortocaval fistula (ACF) in mice. Here, we unravel the mitochondrial haplotype effects on cardiomyocyte mitochondrial ultrastructure and transcriptome response to ACF in vivo. Phenotypic responses and quantitative transmission electron microscopy (TEM) and RNA sequence at 3 days were determined after sham surgery or ACF in vivo in cardiomyocytes from wild-type (WT) C57BL/6J (C57:C57) and C3H/HeN (C3H:C3H) and mitochondrial nuclear exchange mice (C57:C3H or C3H:C57). Quantitative TEM of cardiomyocyte mitochondria C3HWT hearts have more electron-dense compact mitochondrial cristae compared with C57WT. In response to ACF, mitochondrial area and cristae integrity are normal in C3HWT; however, there is mitochondrial swelling, cristae lysis, and disorganization in both C57WT and MNX hearts. Tissue analysis shows that C3HWT hearts have increased autophagy, antioxidant, and glucose fatty acid oxidation-related genes compared with C57WT. Comparative transcriptomic analysis of cardiomyocytes from ACF was dependent upon mtDNA haplotype. C57mtDNA haplotype was associated with increased inflammatory/protein synthesis pathways and downregulation of bioenergetic pathways, whereas C3HmtDNA showed upregulation of autophagy genes. In conclusion, ACF in vivo shows a protective response of C3Hmt haplotype that is in large part driven by mitochondrial nuclear genome interaction. The results of this study support the effects of mtDNA haplotype on nuclear gene expression in cardiomyocytes. Currently, there is no acceptable therapy for volume overload due to mitral regurgitation. The findings of this study could suggest that mtDNA haplotype activates different pathways after ACF warrants further investigations on human population of heart disease from different ancestry backgrounds.
Topics: Mice; Animals; Humans; Myocytes, Cardiac; Haplotypes; Mice, Inbred C3H; Mice, Inbred C57BL; Mitochondria; Heart Failure; DNA, Mitochondrial
PubMed: 36800507
DOI: 10.1152/ajpheart.00371.2022 -
Advances in Experimental Medicine and... 2023The mitochondrial permeability transition (mPT) is a process that permits rapid exchange of small molecules across the inner mitochondrial membrane (IMM) and thus plays... (Review)
Review
The mitochondrial permeability transition (mPT) is a process that permits rapid exchange of small molecules across the inner mitochondrial membrane (IMM) and thus plays a vital role in mitochondrial function and cellular signaling. Formation of the pore that mediates this flux is well-documented in injury and disease but its regulation has also emerged as critical to the fate of stem cells during embryonic development. The precise molecular composition of the mPTP has been enigmatic, with far more genetic studies eliminating molecular candidates than confirming them. Rigorous studies in the recent decade have implicated central involvement of the FF ATP synthase, or complex V of the electron transport chain, and continue to confirm a regulatory role for Cyclophilin D (CypD), encoded by Ppif, in modulating the sensitivity of the pore to opening. A host of endogenous molecules have been shown to trigger flux characteristic of mPT, including positive regulators such as calcium ions, reactive oxygen species, inorganic phosphate, and fatty acids. Conductance of the pore has been described as low or high, and reversibility of pore opening appears to correspond with the relative abundance of negative regulators of mPT such as adenine nucleotides, hydrogen ion, and divalent cations that compete for calcium-binding sites in the mPTP. Current models suggest that distinct pores could be responsible for differing reversibility and conductance depending upon cellular context. Indeed, irreversible propagation of mPT inevitably leads to collapse of transmembrane potential, arrest of ATP synthesis, mitochondrial swelling, and cell death. Future studies should clarify ambiguities in mPTP structure and reveal new roles for mPT in dictating specialized cellular functions beyond cell survival that are tied to mitochondrial fitness including stem cell self-renewal and fate. The focus of this review is to describe contemporary models of the mPTP and highlight how pore activity impacts stem cells and development.
Topics: Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; Calcium; Mitochondrial Transmembrane Permeability-Driven Necrosis; Adenosine Triphosphate; Stem Cells; Permeability
PubMed: 35739412
DOI: 10.1007/5584_2022_720 -
Mitochondrion Jul 2023As the cell's energy factory and metabolic hub, mitochondria are critical for ATP synthesis to maintain cellular function. Mitochondria are highly dynamic organelles... (Review)
Review
As the cell's energy factory and metabolic hub, mitochondria are critical for ATP synthesis to maintain cellular function. Mitochondria are highly dynamic organelles that continuously undergo fusion and fission to alter their size, shape, and position, with mitochondrial fusion and fission being interdependent to maintain the balance of mitochondrial morphological changes. However, in response to metabolic and functional damage, mitochondria can grow in size, resulting in a form of abnormal mitochondrial morphology known as megamitochondria. Megamitochondria are characterized by their considerably larger size, pale matrix, and marginal cristae structure and have been observed in various human diseases. In energy-intensive cells like hepatocytes or cardiomyocytes, the pathological process can lead to the growth of megamitochondria, which can further cause metabolic disorders, cell damage and aggravates the progression of the disease. Nonetheless, megamitochondria can also form in response to short-term environmental stimulation as a compensatory mechanism to support cell survival. However, extended stimulation can reverse the benefits of megamitochondria leading to adverse effects. In this review, we will focus on the findings of the different roles of megamitochondria, and their link to disease development to identify promising clinical therapeutic targets.
Topics: Humans; Mitochondrial Swelling; Mitochondria; Metabolic Diseases; Hepatocytes; Mitochondrial Membranes; Mitochondrial Dynamics
PubMed: 37276954
DOI: 10.1016/j.mito.2023.06.001 -
Investigative Ophthalmology & Visual... Nov 2023Endoplasmic reticulum (ER) and mitochondrial stress are independently associated with corneal endothelial cell (CEnC) loss in many corneal diseases, including Fuchs'...
PURPOSE
Endoplasmic reticulum (ER) and mitochondrial stress are independently associated with corneal endothelial cell (CEnC) loss in many corneal diseases, including Fuchs' endothelial corneal dystrophy (FECD). However, the role of ER stress in mitochondrial dysfunction contributing to CEnC apoptosis is unknown. The purpose of this study is to explore the crosstalk between ER and mitochondrial stress in CEnC.
METHODS
Human corneal endothelial cell line (HCEnC-21T) and human corneal endothelial tissues were treated with ER stressor tunicamycin. ER stress-reducing chemical 4-phenyl butyric acid (4-PBA) was used in HCEnC-21T after tunicamycin. Fuchs' corneal endothelial cell line (F35T) was used to determine differential activation of ER stress with respect to HCEnC-21T at the baseline. ER stress, mitochondrial-mediated intrinsic apoptotic, mitochondrial fission, and fusion proteins were determined using immunoblotting and immunohistochemistry. Mitochondrial bioenergetics were assessed by mitochondrial membrane potential (MMP) loss and ATP production at 48 hours after tunicamycin. Mitochondria dynamics (shape, area, perimeter) were also analyzed at 24 hours using transmission electron microscopy.
RESULTS
Treatment of HCEnC-21T cell line with tunicamycin activated three ER stress pathways (PERK-eIF2α-CHOP, IRE1α-XBP1, and ATF6), reduced cell viability, upregulated mitochondrial-mediated intrinsic apoptotic molecules (cleaved caspase 9, caspase 3, PARP, Bax, cytochrome C), downregulated anti-apoptotic Bcl-2 protein, initiated mitochondrial dysfunction by loss of MMP and lowering of ATP production, and caused mitochondrial swelling and fragmentation with increased expression of mitochondrial fission proteins (Fis1 and p-Drp1). Fuchs' CEnC (F35T) cell line also showed activation of the ER stress-related proteins (p-eIF2α, GRP78, CHOP, XBP1) compared to HCEnC-21T at the baseline. The 4-PBA ameliorated cell loss and reduced cleaved caspase 3 and 9, thereby rescuing tunicamycin-induced cell death but not mitochondrial bioenergetics in HCEnC-21T cell line.
CONCLUSIONS
Tunicamycin-induced ER stress disrupts mitochondrial bioenegetics, dynamics and contributes to the loss of CEnC viability. This novel study highlights the importance of ER-mitochondria crosstalk and its contribution to CEnCs apoptosis, seen in many corneal diseases, including FECD.
Topics: Humans; Caspase 3; Endoribonucleases; Tunicamycin; Protein Serine-Threonine Kinases; Apoptosis; Endoplasmic Reticulum Stress; Corneal Diseases; Fuchs' Endothelial Dystrophy; Butyric Acid; Energy Metabolism; Endothelial Cells; Adenosine Triphosphate
PubMed: 37962528
DOI: 10.1167/iovs.64.14.18 -
Clinical Immunology (Orlando, Fla.) Nov 2023In our previous study, we found for the first time that temozolomide (TMZ), the first-line chemotherapeutic agent for glioblastoma (GBM), can generate a large amount of...
BACKGROUND
In our previous study, we found for the first time that temozolomide (TMZ), the first-line chemotherapeutic agent for glioblastoma (GBM), can generate a large amount of reactive oxygen species (ROS) under ultrasound irradiation. Sonodynamic therapy (SDT) using TMZ as the sonosensitizer produced more potent antitumor effects than TMZ alone. Here, we further evaluate the effects of TMZ-based SDT on subcellular structures and investigate the immunogenic cell death (ICD)-inducing capability of TMZ-based SDT.
METHODS
The sonotoxic effects of TMZ were explored in LN229 and GL261 glioma cells. The morphology of endoplasmic reticulum and mitochondria was observed by transmission electron microscopy. The nuclear DNA damage was represented by γ-H2AX staining. Bone marrow-derived dendritic cells (BMDCs) were employed to assess ICD-inducing capability of TMZ-based SDT. A cyclic arginine-glycine-aspartic (c(RGDyC))-modified nanoliposome drug delivery platform was used to improve the tumor targeting of SDT.
RESULTS
TMZ-based SDT had a greater inhibitory effect on glioma cells than TMZ alone. Transmission electron microscopy revealed that TMZ-based SDT caused endoplasmic reticulum dilation and mitochondrial swelling. In addition, endoplasmic reticulum stress response (ERSR), nuclear DNA damage and mitochondrial permeability transition pore (mPTP) opening were promoted in TMZ-based SDT group. Most importantly, we found that TMZ-based SDT could promote the "danger signals" produced by glioma cells and induce the maturation and activation of BMDCs, which was associated with the mitochondrial DNA released into the cytoplasm in glioma cells. In vivo experiments showed that TMZ-based SDT could remodel glioma immune microenvironment and provoke durable and powerful anti-tumor immune responses. What's more, the engineered nanoliposome vector of TMZ conferred SDT tumor targeting, providing an option for safer clinical application of TMZ in combination with SDT in the future.
CONCLUSIONS
TMZ-based SDT was capable of triggering ICD in glioma. The discovery of TMZ as a sonosensitizer have shown great promise in the treatment of GBM.
Topics: Humans; Temozolomide; Immunogenic Cell Death; Apoptosis; Glioma; Glioblastoma; Cell Line, Tumor; Brain Neoplasms; Tumor Microenvironment
PubMed: 37716612
DOI: 10.1016/j.clim.2023.109772 -
Basic Research in Cardiology Sep 2023Giant mitochondria are frequently observed in different disease models within the brain, kidney, and liver. In cardiac muscle, these enlarged organelles are present... (Review)
Review
Giant mitochondria are frequently observed in different disease models within the brain, kidney, and liver. In cardiac muscle, these enlarged organelles are present across diverse physiological and pathophysiological conditions including in ageing and exercise, and clinically in alcohol-induced heart disease and various cardiomyopathies. This mitochondrial aberration is widely considered an early structural hallmark of disease leading to adverse organ function. In this thematic paper, we discuss the current state-of-knowledge on the presence, structure and functional implications of giant mitochondria in heart muscle. Despite its demonstrated reoccurrence in different heart diseases, the literature on this pathophysiological phenomenon remains relatively sparse since its initial observations in the early 60s. We review historical and contemporary investigations from cultured cardiomyocytes to human tissue samples to address the role of giant mitochondria in cardiac health and disease. Finally, we discuss their significance for the future development of novel mitochondria-targeted therapies to improve cardiac metabolism and functionality.
Topics: Humans; Myocytes, Cardiac; Mitochondrial Swelling; Mitochondria; Cardiomyopathies; Myocardium; Mitochondria, Heart
PubMed: 37775647
DOI: 10.1007/s00395-023-01011-3