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Mitochondrial dynamics and motility inside living vascular endothelial cells: role of bioenergetics.

ABSTRACT: The mitochondrial network is dynamic with conformations that vary between a tubular continuum and a fragmented state. The equilibrium between mitochondrial fusion/fission, as well as the organelle motility, determine network morphology and ultimately mitochondrial/cell function. Network morphology has been linked with the energy state in different cell types. In this study, we examined how bioenergetic factors affect mitochondrial dynamics/motility in cultured vascular endothelial cells (ECs). ECs were transduced with mitochondria-targeted green fluorescent protein (mito-GFP) and exposed to inhibitors of oxidative phosphorylation (OXPHOS) or ATP synthesis. Time-lapse fluorescence videos were acquired and a mathematical program that calculates size and speed of each mitochondrial object at each time frame was developed. Our data showed that inner mitochondrial membrane potential (??(m)), ATP produced by glycolysis, and, to a lesser degree, ATP produced by mitochondria are critical for maintaining the mitochondrial network, and different metabolic stresses induce distinct morphological patterns (e.g., mitochondrial depolarization is necessary for "donut" formation). Mitochondrial movement, characterized by Brownian diffusion with occasional bursts in displacement magnitude, was inhibited under the same conditions that resulted in increased fission. Hence, imaging/mathematical analysis shed light on the relationship between bioenergetics and mitochondrial network morphology; the latter may determine EC survival under metabolic stress.

SUBMITTER: Giedt RJ

PROVIDER: S-EPMC3416955 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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Mitochondrial dynamics and motility inside living vascular endothelial cells: role of bioenergetics.

Giedt Randy J RJ Pfeiffer Douglas R DR Matzavinos Anastasios A Kao Chiu-Yen CY Alevriadou B Rita BR

Annals of biomedical engineering 20120417 9

The mitochondrial network is dynamic with conformations that vary between a tubular continuum and a fragmented state. The equilibrium between mitochondrial fusion/fission, as well as the organelle motility, determine network morphology and ultimately mitochondrial/cell function. Network morphology has been linked with the energy state in different cell types. In this study, we examined how bioenergetic factors affect mitochondrial dynamics/motility in cultured vascular endothelial cells (ECs). E ...[more]

PMID: 22527011

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Project description:PurposeEndoplasmic 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.MethodsHuman 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.ResultsTreatment 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.ConclusionsTunicamycin-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.

Project description:Mitochondria are widely described as being highly dynamic and adaptable organelles, and their movement is thought to be vital for cell function. Yet, in various native cells, including those of heart and smooth muscle, mitochondria are stationary and rigidly structured. The significance of the differences in mitochondrial behavior to the physiological function of cells is unclear and was studied in single myocytes and intact resistance-sized cerebral arteries. We hypothesized that mitochondrial dynamics is controlled by the proliferative status of the cells.High-speed fluorescence imaging of mitochondria in live vascular smooth muscle cells shows that the organelle undergoes significant reorganization as cells become proliferative. In nonproliferative cells, mitochondria are individual (? 2 ?m by 0.5 ?m), stationary, randomly dispersed, fixed structures. However, on entering the proliferative state, mitochondria take on a more diverse architecture and become small spheres, short rod-shaped structures, long filamentous entities, and networks. When cells proliferate, mitochondria also continuously move and change shape. In the intact pressurized resistance artery, mitochondria are largely immobile structures, except in a small number of cells in which motility occurred. When proliferation of smooth muscle was encouraged in the intact resistance artery, in organ culture, the majority of mitochondria became motile and the majority of smooth muscle cells contained moving mitochondria. Significantly, restriction of mitochondrial motility using the fission blocker mitochondrial division inhibitor prevented vascular smooth muscle proliferation in both single cells and the intact resistance artery.These results show that mitochondria are adaptable and exist in intact tissue as both stationary and highly dynamic entities. This mitochondrial plasticity is an essential mechanism for the development of smooth muscle proliferation and therefore presents a novel therapeutic target against vascular disease.

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Mitochondrial dynamics and motility inside living vascular endothelial cells: role of bioenergetics.

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Mitochondrial dynamics and motility inside living vascular endothelial cells: role of bioenergetics.

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