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Hepatology (Baltimore, Md.) Jan 2023Increased megamitochondria formation and impaired mitophagy in hepatocytes have been linked to the pathogenesis of alcohol-associated liver disease (ALD). This study...
BACKGROUND AND AIMS
Increased megamitochondria formation and impaired mitophagy in hepatocytes have been linked to the pathogenesis of alcohol-associated liver disease (ALD). This study aims to determine the mechanisms by which alcohol consumption increases megamitochondria formation in the pathogenesis of ALD.
APPROACH AND RESULTS
Human alcoholic hepatitis (AH) liver samples were used for electron microscopy, histology, and biochemical analysis. Liver-specific dynamin-related protein 1 (DRP1; gene name DNM1L, an essential gene regulating mitochondria fission ) knockout (L-DRP1 KO) mice and wild-type mice were subjected to chronic plus binge alcohol feeding. Both human AH and alcohol-fed mice had decreased hepatic DRP1 with increased accumulation of hepatic megamitochondria. Mechanistic studies revealed that alcohol feeding decreased DRP1 by impairing transcription factor EB-mediated induction of DNM1L . L-DRP1 KO mice had increased megamitochondria and decreased mitophagy with increased liver injury and inflammation, which were further exacerbated by alcohol feeding. Seahorse flux and unbiased metabolomics analysis showed alcohol intake increased mitochondria oxygen consumption and hepatic nicotinamide adenine dinucleotide (NAD + ), acylcarnitine, and ketone levels, which were attenuated in L-DRP1 KO mice, suggesting that loss of hepatic DRP1 leads to maladaptation to alcohol-induced metabolic stress. RNA-sequencing and real-time quantitative PCR analysis revealed increased gene expression of the cGAS-stimulator of interferon genes (STING)-interferon pathway in L-DRP1 KO mice regardless of alcohol feeding. Alcohol-fed L-DRP1 KO mice had increased cytosolic mtDNA and mitochondrial dysfunction leading to increased activation of cGAS-STING-interferon signaling pathways and liver injury.
CONCLUSION
Alcohol consumption decreases hepatic DRP1 resulting in increased megamitochondria and mitochondrial maladaptation that promotes AH by mitochondria-mediated inflammation and cell injury.
Topics: Mice; Humans; Animals; Hepatitis, Alcoholic; Mitochondrial Swelling; Liver Diseases, Alcoholic; Mitochondria; Ethanol; Nucleotidyltransferases; Inflammation; Interferons; Mitochondrial Dynamics
PubMed: 35698731
DOI: 10.1002/hep.32604 -
Cell Biology and Toxicology Apr 2023Mitochondrial metabolism and function are modulated by changes in matrix Ca. Small increases in the matrix Ca stimulate mitochondrial bioenergetics, whereas excessive Ca...
Mitochondrial metabolism and function are modulated by changes in matrix Ca. Small increases in the matrix Ca stimulate mitochondrial bioenergetics, whereas excessive Ca leads to cell death by causing massive matrix swelling and impairing the structural and functional integrity of mitochondria. Sustained opening of the non-selective mitochondrial permeability transition pores (PTP) is the main mechanism responsible for mitochondrial Ca overload that leads to mitochondrial dysfunction and cell death. Recent studies suggest the existence of two or more types of PTP, and adenine nucleotide translocator (ANT) and FF-ATP synthase were proposed to form the PTP independent of each other. Here, we elucidated the role of ANT in PTP opening by applying both experimental and computational approaches. We first developed and corroborated a detailed model of the ANT transport mechanism including the matrix (ANT), cytosolic (ANT), and pore (ANT) states of the transporter. Then, the ANT model was incorporated into a simple, yet effective, empirical model of mitochondrial bioenergetics to ascertain the point when Ca overload initiates PTP opening via an ANT switch-like mechanism activated by matrix Ca and is inhibited by extra-mitochondrial ADP. We found that encoding a heterogeneous Ca response of at least three types of PTPs, weakly, moderately, and strongly sensitive to Ca, enabled the model to simulate Ca release dynamics observed after large boluses were administered to a population of energized cardiac mitochondria. Thus, this study demonstrates the potential role of ANT in PTP gating and proposes a novel mechanism governing the cryptic nature of the PTP phenomenon.
Topics: Mitochondrial Membrane Transport Proteins; Adenine Nucleotides; Mitochondrial Swelling; Mitochondria; Mitochondrial Permeability Transition Pore; Calcium
PubMed: 35606662
DOI: 10.1007/s10565-022-09724-2 -
Methods in Molecular Biology (Clifton,... 2022The loss of mitochondrial cristae integrity and mitochondrial swelling are hallmarks of multiple forms of necrotic cell death. One of the most well-studied and relevant...
The loss of mitochondrial cristae integrity and mitochondrial swelling are hallmarks of multiple forms of necrotic cell death. One of the most well-studied and relevant inducers of mitochondrial swelling is matrix calcium (Ca). Respiring mitochondria will intake available Ca into their matrix until a threshold is reached which triggers the opening of the mitochondrial permeability transition pore (MPTP). Upon opening of the pore, mitochondrial membrane potential dissipates and the mitochondria begin to swell, rendering them dysfunctional. The total amount of Ca taken up by a mitochondrion prior to the engagement of the MPTP is referred to as mitochondrial Ca retention capacity (CRC). The CRC/swelling assay is a useful tool for observing the dose-dependent event of mitochondrial dysfunction in real-time. In this technique, isolated mitochondria are treated with specific boluses of Ca until they reach CRC and undergo swelling. A fluorometer is utilized to detect an increase in transmitted light passing through the sample as the mitochondria lose cristae density, and simultaneously measures calcium uptake by way of a Ca-specific membrane impermeable fluorescent dye. Here we provide a detailed protocol describing the mitochondrial CRC/swelling assay and we discuss how varying amounts of mitochondria and Ca added to the system affect the dose-dependency of the assay. We also report how to validate the assay by using MPTP and calcium uptake inhibitors and troubleshooting common mistakes that occur with this approach.
Topics: Calcium; Mitochondria; Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; Mitochondrial Swelling; Permeability
PubMed: 35771440
DOI: 10.1007/978-1-0716-2309-1_9 -
Mitochondrion Jan 2018Mitochondria are critical players involved in both cell life and death through multiple pathways. Structural integrity, metabolism and function of mitochondria are... (Review)
Review
Mitochondria are critical players involved in both cell life and death through multiple pathways. Structural integrity, metabolism and function of mitochondria are regulated by matrix volume due to physiological changes of ion homeostasis in cellular cytoplasm and mitochondria. Ca and K presumably play a critical role in physiological and pathological swelling of mitochondria when increased uptake (influx)/decreased release (efflux) of these ions enhances osmotic pressure accompanied by high water accumulation in the matrix. Changes in the matrix volume in the physiological range have a stimulatory effect on electron transfer chain and oxidative phosphorylation to satisfy metabolic requirements of the cell. However, excessive matrix swelling associated with the sustained opening of mitochondrial permeability transition pores (PTP) and other PTP-independent mechanisms compromises mitochondrial function and integrity leading to cell death. The mechanisms of transition from reversible (physiological) to irreversible (pathological) swelling of mitochondria remain unknown. Mitochondrial swelling is involved in the pathogenesis of many human diseases such as neurodegenerative and cardiovascular diseases. Therefore, modeling analysis of the swelling process is important for understanding the mechanisms of cell dysfunction. This review attempts to describe the role of mitochondrial swelling in cell life and death and the main mechanisms involved in the maintenance of ion homeostasis and swelling. The review also summarizes and discusses different kinetic models and approaches that can be useful for the development of new models for better simulation and prediction of in vivo mitochondrial swelling.
Topics: Cardiovascular Diseases; Electron Transport; Humans; Mitochondria; Mitochondrial Membranes; Mitochondrial Swelling; Models, Biological; Neurodegenerative Diseases; Osmotic Pressure; Oxidative Phosphorylation; Permeability
PubMed: 28802667
DOI: 10.1016/j.mito.2017.08.004 -
Journal of Visualized Experiments : JoVE May 2018The production of ATP by oxidative phosphorylation is the primary function of mitochondria. Mitochondria in higher eukaryotes also participate in cytosolic Ca buffering,...
The production of ATP by oxidative phosphorylation is the primary function of mitochondria. Mitochondria in higher eukaryotes also participate in cytosolic Ca buffering, and the ATP production in mitochondrial can be mediated by intramitochondrial free Ca concentration. Ca retention capacity can be regarded as the capability of mitochondria to retain calcium in the mitochondrial matrix. Accumulated intracellular Ca leads to the permeability of the inner mitochondrial membrane, termed the opening of mitochondrial permeability transition pore (mPTP), which leads to the leakage of molecules with a molecular weight less than 1.5 kDa. Ca-triggered mitochondria swelling is used to indicate the mPTP opening. Here, we describe two assays to examine the Ca retention capacity and Ca-triggered mitochondrial swelling in isolated mitochondria. After certain amounts of Ca are added, all steps can be completed in one day and recorded by a microplate reader. Thus, these two simple and effective assays can be adopted to assess the Ca-related mitochondrial functions.
Topics: Biological Assay; Calcium; Humans; Mitochondrial Swelling; Protein Biosynthesis
PubMed: 29781984
DOI: 10.3791/56236 -
Cells Feb 2019Thirty-five years ago, we described fragmentation of the mitochondrial population in a living cell into small vesicles (mitochondrial fission). Subsequently, this... (Review)
Review
Thirty-five years ago, we described fragmentation of the mitochondrial population in a living cell into small vesicles (mitochondrial fission). Subsequently, this phenomenon has become an object of general interest due to its involvement in the process of oxidative stress-related cell death and having high relevance to the incidence of a pathological phenotype. Tentatively, the key component of mitochondrial fission process is segregation and further asymmetric separation of a mitochondrial body yielding healthy (normally functioning) and impaired (incapable to function in a normal way) organelles with subsequent decomposition and removal of impaired elements through autophagy (mitophagy). We speculate that mitochondria contain cytoskeletal elements, which maintain the mitochondrial shape, and also are involved in the process of intramitochondrial segregation of waste products. We suggest that perturbation of the mitochondrial fission/fusion machinery and slowdown of the removal process of nonfunctional mitochondrial structures led to the increase of the proportion of impaired mitochondrial elements. When the concentration of malfunctioning mitochondria reaches a certain threshold, this can lead to various pathologies, including aging. Overall, we suggest a process of mitochondrial fission to be an essential component of a complex system controlling a healthy cell phenotype. The role of reactive oxygen species in mitochondrial fission is discussed.
Topics: Animals; Humans; Membrane Potential, Mitochondrial; Mitochondria; Mitochondrial Dynamics; Mitochondrial Swelling; Models, Biological; Reactive Oxygen Species
PubMed: 30791381
DOI: 10.3390/cells8020175 -
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 -
American Journal of Physiology. Cell... Jan 2007Mitochondrial volume homeostasis is a housekeeping cellular function essential for maintaining the structural integrity of the organelle. Changes in mitochondrial volume... (Review)
Review
Mitochondrial volume homeostasis is a housekeeping cellular function essential for maintaining the structural integrity of the organelle. Changes in mitochondrial volume have been associated with a wide range of important biological functions and pathologies. Mitochondrial matrix volume is controlled by osmotic balance between cytosol and mitochondria. Any dysbalance in the fluxes of the main intracellular ion, potassium, will thus affect the osmotic balance between cytosol and the matrix and promote the water movement between these two compartments. It has been hypothesized that activity of potassium efflux pathways exceeds the potassium influx in functioning mitochondria and that potassium concentration in matrix could be actually lower than in cytoplasm. This hypothesis provides a clear-cut explanation for the mitochondrial swelling observed after mitochondrial depolarization, mitochondrial calcium overload, or opening of permeability transition pore. It should also be noted that the rate of water flux into or out of the mitochondrion is determined not only by the osmotic gradient that acts as the driving force for water transport but also by the water permeability of the inner membrane. Recent data suggest that the mitochondrial inner membrane has also specific water channels, aquaporins, which facilitate water movement between cytoplasm and matrix. This review discusses different phases of mitochondrial swelling and summarizes the potential effects of mitochondrial swelling on cell function.
Topics: Animals; Aquaporins; Calcium; Cell Physiological Phenomena; Homeostasis; Humans; Membrane Potentials; Mitochondria; Mitochondrial Swelling; Potassium
PubMed: 16870828
DOI: 10.1152/ajpcell.00272.2006 -
Physiological Reports Apr 2018Kidney proximal tubules (PTs) contain a high density of mitochondria, which are required to generate ATP to power solute transport. Mitochondrial dysfunction is...
Kidney proximal tubules (PTs) contain a high density of mitochondria, which are required to generate ATP to power solute transport. Mitochondrial dysfunction is implicated in the pathogenesis of numerous kidney diseases. Damaged mitochondria are thought to produce excess reactive oxygen species (ROS), which can lead to oxidative stress and activation of cell death pathways. MitoQ is a mitochondrial targeted anti-oxidant that has shown promise in preclinical models of renal diseases. However, recent studies in nonkidney cells have suggested that MitoQ might also have adverse effects. Here, using a live imaging approach, and both in vitro and ex vivo models, we show that MitoQ induces rapid swelling and depolarization of mitochondria in PT cells, but these effects were not observed with SS-31, another targeted anti-oxidant. MitoQ consists of a lipophilic cation (Tetraphenylphosphonium [TPP]) joined to an anti-oxidant component (quinone) by a 10-carbon alkyl chain, which is thought to insert into the inner mitochondrial membrane (IMM). We found that mitochondrial swelling and depolarization was also induced by dodecyltriphenylphosphomium (DTPP), which consists of TPP and the alkyl chain, but not by TPP alone. Surprisingly, MitoQ-induced mitochondrial swelling occurred in the absence of a decrease in oxygen consumption rate. We also found that DTPP directly increased the permeability of artificial liposomes with a cardiolipin content similar to that of the IMM. In summary, MitoQ causes mitochondrial swelling and depolarization in PT cells by a mechanism unrelated to anti-oxidant activity, most likely because of increased IMM permeability due to insertion of the alkyl chain.
Topics: Animals; Antioxidants; Cells, Cultured; Kidney Tubules, Proximal; Mice; Mitochondria; Mitochondrial Swelling; Opossums; Organophosphorus Compounds; Ubiquinone
PubMed: 29611340
DOI: 10.14814/phy2.13667 -
Biochimica Et Biophysica Acta 2006Mitochondria are crucial organelles for life and death of the cell. They are prominent players in energy conversion and integrated signaling pathways including... (Review)
Review
Mitochondria are crucial organelles for life and death of the cell. They are prominent players in energy conversion and integrated signaling pathways including regulation of Ca2+ signals and apoptosis. Their functional versatility is matched by their morphological plasticity and by their high mobility, allowing their transport at specialized cellular sites. This transport occurs by interactions with a variety of cytoskeletal proteins that also have the ability to influence shape and function of the organelle. A growing body of evidence suggests that mitochondria use cytoskeletal proteins as tracks for their movement; in turn, mitochondrial morphology and function is regulated via mostly uncharacterized pathways, by the cytoskeleton.
Topics: Actin Cytoskeleton; Actins; Animals; Cytoskeleton; Humans; Microtubules; Mitochondria; Mitochondrial Swelling; Yeasts
PubMed: 16729962
DOI: 10.1016/j.bbabio.2006.04.013