Name: mitochondrial ca2+ retention capacity assay and ca2+-triggered mitochondrial swelling assay
Uploaded: 2018-05-01T12:30:00
Description: Watch this Scientific Journal Video about Mitochondrial Ca2+ Retention Capacity Assay and Ca2+-triggered Mitochondrial Swelling Assay at JoVE.com

This study was supported by grants from grant of the Outstanding Scientist of Shandong (JQ201421) and grant from NSFC (81371226).

1. Isolation of Mitochondria
NOTE: All solutions and equipment should be precooled to 0 - 4 &#176;C and kept on ice.
<ol>
	<li>Seed about 3 x 106 SH-SY5Y cells per 10 cm cell culture dish. Culture cells in high-glucose Dulbecco&#39;s modified Eagle medium with 10% fetal bovine serum, penicillin (100 U/mL)-streptomycin (100 &#181;g/mL). Maintain at 37 &#176;C in an incubator containing 5% CO2 overnight. 
	NOTE: At least 1 - 2 x 107 SH-SY5Y cells are neede...

<ol>
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L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cyclosporin+A+increases+mitochondrial+calcium+uptake+capacity+in+cortical+astrocytes+but+not+cerebellar+granule+neurons.">Cyclosporin A increases mitochondrial calcium uptake capacity in cortical astrocytes but not cerebellar granule neurons.</a> J Bioenerg Biomembr. 38 (1), 43-47 (2006).</li><li>Zhao, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell-permeable+peptide+antioxidants+targeted+to+inner+mitochondrial+membrane+inhibit+mitochondrial+swelling,+oxidative+cell+death,+and+reperfusion+injury.">Cell-permeable peptide antioxidants targeted to inner mitochondrial membrane inhibit mitochondrial swelling, oxidative cell death, and reperfusion injury.</a> J Biol Chem. 279 (33), 34682-34690 (2004).</li><li>Muriel, M. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+free+calcium+levels+(Rhod-2+fluorescence)+and+ultrastructural+alterations+in+neuronally+differentiated+PC12+cells+during+ceramide-dependent+cell+death.">Mitochondrial free calcium levels (Rhod-2 fluorescence) and ultrastructural alterations in neuronally differentiated PC12 cells during ceramide-dependent cell death.</a> J Comp Neurol. 426 (2), 297-315 (2000).</li><li>Allman, R., Hann, A. C., Phillips, A. P., Martin, K. L., Lloyd, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+of+Azotobacter+vinelandii+with+correlation+of+Coulter+cell+size,+flow+cytometric+parameters,+and+ultrastructure.">Growth of Azotobacter vinelandii with correlation of Coulter cell size, flow cytometric parameters, and ultrastructure.</a> Cytometry. 11 (7), 822-831 (1990).</li><li>Wiechelman, K. J., Braun, R. D., Fitzpatrick, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigation+of+the+bicinchoninic+acid+protein+assay:+identification+of+the+groups+responsible+for+color+formation.">Investigation of the bicinchoninic acid protein assay: identification of the groups responsible for color formation.</a> Anal Biochem. 175 (1), 231-237 (1988).</li><li>Petronilli, V., Nicolli, A., Costantini, P., Colonna, R., Bernardi, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+the+permeability+transition+pore,+a+voltage-dependent+mitochondrial+channel+inhibited+by+cyclosporin+A.">Regulation of the permeability transition pore, a voltage-dependent mitochondrial channel inhibited by cyclosporin A.</a> Biochim Biophys Acta. 1187 (2), 255-259 (1994).</li><li>Pastorino, J. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+consequences+of+the+sustained+or+transient+activation+by+Bax+of+the+mitochondrial+permeability+transition+pore.">Functional consequences of the sustained or transient activation by Bax of the mitochondrial permeability transition pore.</a> J Biol Chem. 274 (44), 31734-31739 (1999).</li><li>Gunter, T. E., Sheu, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristics+and+possible+functions+of+mitochondrial+Ca(2+)+transport+mechanisms.">Characteristics and possible functions of mitochondrial Ca(2+) transport mechanisms.</a> Biochim Biophys Acta. 1787 (11), 1291-1308 (2009).</li></ol>

Here, we described a simple and effective protocol for the mitochondrial Ca2+ retention capacity assay and Ca2+-triggered mitochondrial swelling assay.
For the mitochondrial isolation, make sure that all the materials and tubes are on ice, especially when homogenizing the cells. 0.25% trypsin-EDTA can also be used to detach cells from the dish for 5 min at 37 &#176;C. After 15 - 25 strokes, it is necessary to observe the intact cell membrane under the microscope and avoid...

Mitochondria are the main cellular organs to produce nearly 95% of the ATP used in the mammalian cells by oxidative phosphorylation. It is reported that the sequestered micromolar concentration of Ca2+ by mitochondria, the presence of ADP, and inorganic phosphate can be used to phosphorylate ADP to synthesis ATP1. When the concentration of cytosolic Ca2+ goes above a threshold, mitochondria can uptake Ca2+ rapidly and efflux it slowly. Thus, the functioning mitochondria can influx the increased cytosolic Ca2+. Irrelevant to the participation in the oxidative phosphorylation, the mitochondrial Ca2+ also take part in the cytosolic calcium signals and activate the mitochondrial apoptotic mechanism by inducing the opening of the mPTP in the inner mitochondrial membrane2. It has been widely recognized that abnormal elevation of intracellular Ca2+ can induce mitochondrial massive swelling by opening the mPTP3. Thus, this protocol aims to assess the mitochondrial function by quantifying the mitochondrial Ca2+ retention capacity and Ca2+-trigged mitochondrial swelling.
Ca2+ retention capacity is the measurement of the ability of mitochondria to uptake cytosolic calcium. Mitochondria can buffer the cytosolic free calcium and regulate calcium-dependent cellular processes by calcium uptake in the form of inactive precipitates. Impaired Ca2+ retention capacity occurs in stress phenomena associated with energy limitation and even neurodegenerative diseases4,5. Isolated mitochondria or digitonin-permeabilized cells can be used to identify the Ca2+ retention capacity, and the elevated ability to accumulate Ca2+ by isolated mitochondria with the additonal glutamate and malate is not effected by the mitochondrial isolation procedure6. A titrated amount of digitonin should be used to permeabilize the plasma membranes of different cell types. The hexapotassium salt of Ca2+-binding green fluorescent dye, a Ca2+-sensitive cell-impermeant visible light-excitable indicator, has been widely used7. Ca2+-binding green fluorescent dye is a low-affinity indicator and used to show that intracellular free Ca2+ concentrations continue to rise during prolonged (5 min) stimulations8. This method was less sensitive than the radioactive filter technique but was greatly simplified. The additional Ca2+ elevates calcium green fluorescence and the Ca2+ uptake by mitochondria returns the fluorescence to baseline. Sequential additions of Ca2+ were made until the mitochondria failed to uptake extramitochondrial Ca2+ 9. A fluorescence microplate reader can be used to continuously report the calcium green fluorescence.
After Ca2+ accumulation, mitochondria depolarized, released Ca2+ into the medium, and began to swell. Ca2+-triggered mitochondria swelling is used to indicate the mPTP opening. Electron microscopy and the decrease in light absorbance at 540 nm can be used to measure the Ca2+-triggered mitochondrial swelling10,11. Mitochondria volume can be directly determined by forward angle light scattering12, where decreases in the absorbance reflect passive swelling of the mitochondrial matrix.
Here, we illustrate the methodology to examine the mitochondrial Ca2+ retention capacity and Ca2+-triggered mitochondrial swelling in isolated mitochondria from SH-SY5Y cells.

<table>
	<tbody>
		<tr>
			<td>SH-SY5Y cell line</td>
			<td>ATCC (The Global Bioresource Center)</td>
			<td>ATCC Number: CRL-2266</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcium green-5N</td>
			<td>Life Technologies</td>
			<td>c-3737</td>
			<td>Ca2+-binding green fluorescent dye</td>
		</tr>
		<tr>
			<td>complete protease inhibitors</td>
			<td>Roche Molecular Biochemicals</td>
			<td>4693116001</td>
			<td></td>
		</tr>
		<tr>
			<td>glass homogenizer</td>
			<td>Kimble Chase</td>
			<td>9885303002</td>
			<td></td>
		</tr>
		<tr>
			<td>glutamate</td>
			<td>Sigma-Aldrich</td>
			<td>RES5063G-A7</td>
			<td></td>
		</tr>
		<tr>
			<td>malate</td>
			<td>Sigma-Aldrich</td>
			<td>46940-U</td>
			<td></td>
		</tr>
		<tr>
			<td>rotenone</td>
			<td>Sigma-Aldrich</td>
			<td>R8875</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma-Aldrich</td>
			<td>H3375</td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2</td>
			<td>Sigma-Aldrich</td>
			<td>00457</td>
			<td></td>
		</tr>
		<tr>
			<td>K2HPO4</td>
			<td>Sigma-Aldrich</td>
			<td>V900050</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma-Aldrich</td>
			<td>P9541</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2</td>
			<td>Sigma-Aldrich</td>
			<td>V900266</td>
			<td></td>
		</tr>
		<tr>
			<td>Varioskan flash instruments</td>
			<td>Thermo Scientific</td>
			<td>IC100E</td>
			<td></td>
		</tr>
		<tr>
			<td>Bongkrekate</td>
			<td>Biovision</td>
			<td>1820-100</td>
			<td></td>
		</tr>
		<tr>
			<td>atractyloside</td>
			<td>Sigma-Aldrich</td>
			<td>C4992</td>
			<td></td>
		</tr>
		<tr>
			<td>high-glucose Dulbecco&#8217;s modified Eagle medium</td>
			<td>Hyclone</td>
			<td>SH30022</td>
			<td>4.5 g/L glucose, L-glutamine, without sodium pyruvate</td>
		</tr>
		<tr>
			<td>fetal bovine serum</td>
			<td>Hyclone</td>
			<td>SV30087</td>
			<td></td>
		</tr>
		<tr>
			<td>penicillin</td>
			<td>Sigma-Aldrich</td>
			<td>P3032</td>
			<td></td>
		</tr>
		<tr>
			<td>streptomycin</td>
			<td>Invitrogen</td>
			<td>11860-038</td>
			<td></td>
		</tr>
		<tr>
			<td>BCA assay kit</td>
			<td>Thermo Scientific</td>
			<td>NCI3225CH</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Hyclone</td>
			<td>SH30256.01</td>
			<td></td>
		</tr>
		<tr>
			<td>10 cm cell culture dish</td>
			<td>NEST</td>
			<td>704001</td>
			<td></td>
		</tr>
	</tbody>
</table>

mitochondrial ca2+ retention capacity assay and ca2+-triggered mitochondrial swelling assay

The production of ATP by oxidative phosphorylation is the primary function of mitochondria. Mitochondria in higher eukaryotes also participate in cytosolic Ca2+ buffering, and the ATP production in mitochondrial can be mediated by intramitochondrial free Ca2+ concentration. Ca2+ retention capacity can be regarded as the capability of mitochondria to retain calcium in the mitochondrial matrix. Accumulated intracellular Ca2+ 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. Ca2+-triggered mitochondria swelling is used to indicate the mPTP opening. Here, we describe two assays to examine the Ca2+ retention capacity and Ca2+-triggered mitochondrial swelling in isolated mitochondria. After certain amounts of Ca2+ 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 Ca2+-related mitochondrial functions.

Representative Results of Ca2+ Retention Capacity: 
Results were expressed as fluorescence values. With the additional pulses of Ca2+ (200 nmols/mg mitochondrial protein), the fluorescence increased by double above baseline with the mPTP opening. 5 &#956;M Bongkrekate (BKA), an inhibitor of Ca2+-induced mPTP opening, or 1 &#956;M atractyloside (ATR), an activator of Ca2+-induced mPTP opening, were added in isolated mitochondria. Th...

Watch this Scientific Journal Video about Mitochondrial Ca2+ Retention Capacity Assay and Ca2+-triggered Mitochondrial Swelling Assay at JoVE.com

Mitochondrial Ca2+ Retention Capacity Assay and Ca2+-triggered Mitochondrial Swelling Assay

This protocol aims to describe a method to examine the Ca2+ retention capacity and Ca2+- triggered mitochondrial swelling of isolated mitochondria of SH-SY5Y cells step-by-step.

Mitochondrial Ca2+ Retention Capacity Assay and Ca2+-triggered Mitochondrial Swelling Assay

The production of ATP by oxidative phosphorylation is the primary function of mitochondria. Mitochondria in higher eukaryotes also participate in ...

The overall goal of this experiment is to determine mitochondrial calcium retention capacity in calcium induced mitochondrial swelling. This method can help answer key questions in the study of mitochondrial dysfunction, such as abnormal energy metabolism. The main advantage of this technique is that it's very simple and effective.To begin, seed about three million SH-SY5Y cells per 10 centimeter cell culture dish. Remove the medium and wash the cells with about one milliliter of ice cold PBS in a 10 centimeter cell culture dish three times. Add one milliliter of ice cold PBS into the 10 centimeter cell culture dish and scrape the adherent cells into a new 1.5 milliliter tube.Centrifuge at 800 times G for 10 minutes at four degrees Celsius. During the centrifugation, prepare five milliliters of mitochondrial isolation buffer, supplemented with 50 microliters of protease inhibitor stock solution. Remove the supernatant and re-suspend the pellet with one milliliter of mitochondrial isolation buffer.Incubate the 1.5 milliliter tube on ice for 30 minutes. Then, lyse the suspended cells with a glass homogenizer, up and down manually on ice. Transfer the homogenate into a 1.5 milliliter tube.Then, centrifuge at 1, 000 times G for five minutes at four degrees Celsius to remove the debris. Following centrifugation, transfer the supernatant into a new 1.5 milliliter tube before centrifuging again as before. After transferring the supernatant to a new tube, centrifuge at 14, 000 times G for 15 minutes at four degrees Celsius.Remove the supernatant and re-suspend the pellet containing mitochondria with one milliliter of mitochondrial isolation buffer. Then centrifuge the solution for 15 minutes at 14, 000 times G and four degrees Celsius to precipitate the mitochondria. The resulting mitochondria pellet must be kept on ice and re-suspended in 50 to 100 microliters of potassium chloride media, according to the pellet volume before any assay.Finally, use five microliters of mitochondrial solution to measure the mitochondrial protein concentration by standard BCA assay, measuring OD562 using a plate reader. Prepare the potassium chloride media and add the calcium binding green fluorescent dye to a final concentration of 0.5 micromolar before the experiment. To determine mitochondrial calcium retention capacity, first transfer one milliliter of isolated mitochondria in potassium chloride media containing 0.5 micromolar calcium binding green fluorescent dye to each well of a six well plate.Incubate the mitochondria and the calcium binding green fluorescent dye in the six well plate at room temperature, protected from ambient light for one minute. Following incubation, add four microliter aliquots at the 20 millimolar calcium chloride solution to each well of the six well plate using the automatic dispense setting to introduce 200 nanomoles of calcium per milligram of mitochondrial protein. Use the fluorescent spectrometer to monitor the fluorescence changes every three seconds for two minutes with an excitation wavelength of 506 nanometers and an emission wavelength of 531 nanometers.The plate is equipped with shaking at 600 rpm for three seconds between readings, controlled by software. Add an additional four microliter aliquot of 20 millimolar calcium chloride solution to each well, then monitor the fluorescence changes every three seconds for two minutes. To determine calcium induced mitochondrial swelling, transfer one milliliter of isolated mitochondria in potassium chloride media to each well of a six well plate.Then, add 10 microliters of 20 millimolar calcium chloride aqueous solution to the mitochondrial protein to trigger mitochondrial swelling. Using a microplate reader controlled by software, record the decrease in absorbance every three seconds for 10 minutes at 540 nanometers. Representative results of mitochondrial calcium retention capacity of bongkrekic, an inhibitor of the calcium induced mitochondrial permeability transition pore, or MPTP, opening atractyloside, an activator of the calcium induced MPTP opening and a blank control, are shown here.The capacity on in the bongkrekic treatment is much higher than the atractyloside group, as expected. Representative results of calcium induced mitochondrial swelling of bongkrekic, atractyloside, and the no treatment control are shown here. The decreased absorbance monitored at 540 nanometers indicates the mitochondrial swellings.The results suggest that BKA can inhibit the MPTP opening, while ATR can facilitate the MPTP opening. Once mastered, this technique can be done in five hours if it is performed properly. While attempting this procedure, it's important to remember to keep all the solutions on ice.

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Research

JoVE Journal

Neuroscience

Visualization of Mitochondrial DNA Replication in Individual Cells by EdU Signal Amplification

Mitochondria are key regulators of cellular energy and mitochondrial biogenesis is an essential component of regulating mitochondria numbers in healthy cells1-3. One approach for monitoring mitochondrial biogenesis is to measure the rate of mitochondrial DNA (mtDNA) replication4. We developed a sensitive technique to label newly synthesized mtDNA in individual cells in order to study mtDNA biogenesis. The technique combines the incorporation of 5-ethynyl-2'-deoxyuridine (EdU)5-7 with a tyramide signal amplification (TSA)8 protocol to visualize mtDNA replication within subcellular compartments of neurons. EdU is superior to other thymidine analogs, such as 5-bromo-2-deoxyuridine (BrdU), because the initial click reaction to label EdU5-7 does not require the harsh acid treatments or enzyme digests that are required for exposing the BrdU epitope. The milder labeling of EdU allows for direct comparison of its incorporation with other cellular markers9-10. The ability to visualize and quantify mtDNA biogenesis provides an essential tool for investigating the mechanisms used to regulate mitochondrial biogenesis and would provide insight into the pathogenesis associated with drug toxicity, aging, cancer and neurodegenerative diseases. Our technique is applicable to sensory neurons as well as other cell types. The use of this technique to measure mtDNA biogenesis has significant implications in furthering the understanding of both normal cellular physiology as well as impaired disease states.

We developed a sensitive technique to label newly synthesized mitochondrial DNA (mtDNA) in individual cells in order to study mtDNA biogenesis. The technique combines the incorporation of EdU together with a tyramide signal amplification (TSA) protocol to visualize mtDNA replication within subcellular compartments of neurons.

Mitochondria are key regulators of cellular energy and mitochondrial biogenesis is an essential component of regulating mitochondria numbers in healthy ...

Neuromodulation and Mitochondrial Transport: Live Imaging in Hippocampal Neurons over Long Durations

To understand the relationship between mitochondrial transport and neuronal function, it is critical to observe mitochondrial behavior in live cultured neurons for extended durations1-3. This is now possible through the use of vital dyes and fluorescent proteins with which cytoskeletal components, organelles, and other structures in living cells can be labeled and then visualized via dynamic fluorescence microscopy. For example, in embryonic chicken sympathetic neurons, mitochondrial movement was characterized using the vital dye rhodamine 1234. In another study, mitochondria were visualized in rat forebrain neurons by transfection of mitochondrially targeted eYFP5. However, imaging of primary neurons over minutes, hours, or even days presents a number of issues. Foremost among these are: 1) maintenance of culture conditions such as temperature, humidity, and pH during long imaging sessions; 2) a strong, stable fluorescent signal to assure both the quality of acquired images and accurate measurement of signal intensity during image analysis; and 3) limiting exposure times during image acquisition to minimize photobleaching and avoid phototoxicity.
Here, we describe a protocol that permits the observation, visualization, and analysis of mitochondrial movement in cultured hippocampal neurons with high temporal resolution and under optimal life support conditions. We have constructed an affordable stage-top incubator that provides good temperature regulation and atmospheric gas flow, and also limits the degree of media evaporation, assuring stable pH and osmolarity. This incubator is connected, via inlet and outlet hoses, to a standard tissue culture incubator, which provides constant humidity levels and an atmosphere of 5-10% CO2/air. This design offers a cost-effective alternative to significantly more expensive microscope incubators that don't necessarily assure the viability of cells over many hours or even days. To visualize mitochondria, we infect cells with a lentivirus encoding a red fluorescent protein that is targeted to the mitochondrion. This assures a strong and persistent signal, which, in conjunction with the use of a stable xenon light source, allows us to limit exposure times during image acquisition and all but precludes photobleaching and phototoxicity. Two injection ports on the top of the stage-top incubator allow the acute administration of neurotransmitters and other reagents intended to modulate mitochondrial movement. In sum, lentivirus-mediated expression of an organelle-targeted red fluorescent protein and the combination of our stage-top incubator, a conventional inverted fluorescence microscope, CCD camera, and xenon light source allow us to acquire time-lapse images of mitochondrial transport in living neurons over longer durations than those possible in studies deploying conventional vital dyes and off-the-shelf life support systems.

We describe a protocol that allows imaging of mitochondria in living neurons via fluorescence microscopy over long durations. Imaging over extended periods is accomplished through lentivirus-mediated expression of a mitochondrially targeted fluorescent protein and use of an inexpensive stage-top incubator that was designed and built in our laboratory.

To understand the relationship between mitochondrial transport and neuronal function, it is critical to observe mitochondrial behavior in live cultured ...

Determination of Mitochondrial Membrane Potential and Reactive Oxygen Species in Live Rat Cortical Neurons

Mitochondrial membrane potential (&Delta;&Psi;m) is critical for maintaining the physiological function of the respiratory chain to generate ATP. A significant loss of &Delta;&Psi;m renders cells depleted of energy with subsequent death. Reactive oxygen species (ROS) are important signaling molecules, but their accumulation in pathological conditions leads to oxidative stress. The two major sources of ROS in cells are environmental toxins and the process of oxidative phosphorylation. Mitochondrial dysfunction and oxidative stress have been implicated in the pathophysiology of many diseases; therefore, the ability to determine &Delta;&Psi;m and ROS can provide important clues about the physiological status of the cell and the function of the mitochondria. 
Several fluorescent probes (Rhodamine 123, TMRM, TMRE, JC-1) can be used to determine &Delta;&psi;m in a variety of cell types, and many fluorescence indicators (Dihydroethidium, Dihydrorhodamine 123, H2DCF-DA) can be used to determine ROS. Nearly all of the available fluorescence probes used to assess &Delta;&Psi;m or ROS are single-wavelength indicators, which increase or decrease their fluorescence intensity proportional to a stimulus that increases or decreases the levels of &Delta;&Psi;m or ROS. Thus, it is imperative to measure the fluorescence intensity of these probes at the baseline level and after the application of a specific stimulus. This allows one to determine the percentage of change in fluorescence intensity between the baseline level and a stimulus. This change in fluorescence intensity reflects the change in relative levels of &Delta;&Psi;m or ROS. In this video, we demonstrate how to apply the fluorescence indicator, TMRM, in rat cortical neurons to determine the percentage change in TMRM fluorescence intensity between the baseline level and after applying FCCP, a mitochondrial uncoupler. The lower levels of TMRM fluorescence resulting from FCCP treatment reflect the depolarization of mitochondrial membrane potential. We also show how to apply the fluorescence probe H2DCF-DA to assess the level of ROS in cortical neurons, first at baseline and then after application of H2O2. This protocol (with minor modifications) can be also used to determine changes in &#x2206;&#x03A8;m and ROS in different cell types and in neurons isolated from other brain regions.

We demonstrate application of the fluorescence indicator, TMRM, in cortical neurons to determine the relative changes in TMRM fluorescence intensity before and after application of a specific stimulus. We also show application of the fluorescence probe H2DCF-DA to assess the relative level of reactive oxygen species in cortical neurons.

Mitochondrial membrane potential (&Delta;&Psi;m) is critical for maintaining the physiological function of the respiratory chain to generate ATP.  A ...

Evaluation of Bioenergetic Function in Cerebral Vascular Endothelial Cells

The integrity of the blood-brain-barrier (BBB) is critical to prevent brain injury. Cerebral vascular endothelial (CVE) cells are one of the cell types that comprise the BBB; these cells have a very high-energy demand, which requires optimal mitochondrial function. In the case of disease or injury, the mitochondrial function in these cells can be altered, resulting in disease or&#160;the opening of the BBB. In this manuscript, we introduce a method to measure mitochondrial function in CVE cells by using whole, intact cells and a bioanalyzer. A mito-stress assay is used to challenge the cells that have been perturbed, either physically or chemically, and evaluate their bioenergetic function. Additionally, this method also provides a useful way to screen new therapeutics that have direct effects on mitochondrial function. We have optimized the cell density necessary to yield oxygen consumption rates that allow for the calculation of a variety of mitochondrial parameters, including ATP production, maximal respiration, and spare capacity. We also show the sensitivity of the assay by demonstrating that the introduction of the&#160;microRNA, miR-34a, leads to a pronounced and detectable decrease in mitochondrial activity. While the data shown in this paper is optimized for the bEnd.3 cell line, we have also optimized the protocol for primary CVE cells, further suggesting the utility in preclinical and clinical models.

Endothelial cell mitochondria are critical to maintain blood-brain-barrier integrity. We introduce a protocol to measure bioenergetic function in cerebral vascular endothelial cells.

The integrity of the blood-brain-barrier (BBB) is critical to prevent brain injury. Cerebral vascular endothelial (CVE) cells are one of the cell types ...

Assay Development for High Content Quantification of Sod1 Mutant Protein Aggregate Formation in Living Cells

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that can be caused by inherited mutations in the gene encoding copper-zinc superoxide dismutase 1 (SOD1). The structural instability of SOD1 and the detection of SOD1-positive inclusions in familial-ALS patients supports a potential causal role for misfolded and/or aggregated SOD1 in ALS pathology. In this study, we describe the development of a cell-based assay designed to quantify the dynamics of SOD1 aggregation in living cells by high content screening approaches. Using lentiviral vectors, we generated stable cell lines expressing wild-type and mutant A4V SOD1 tagged with yellow fluorescent protein and found that both proteins were expressed in the cytosol without any sign of aggregation. Interestingly, only SOD1 A4V stably expressed in HEK-293, but not in U2OS or SH-SY5Y cell lines, formed aggregates upon proteasome inhibitor treatment. We show that it is possible to quantify aggregation based on dose-response analysis of various proteasome inhibitors, and to track aggregate-formation kinetics by time-lapse microscopy. Our approach introduces the possibility of quantifying the effect of ALS mutations on the role of SOD1 in aggregate formation as well as screening for small molecules that prevent SOD1 A4V aggregation.

We describe a method to quantify the aggregation of misfolded proteins. Our protocol details lentiviral induced stable cell line generation, automated confocal imaging, and image analysis of protein aggregates. As an illustrative application, we studied the effect of small molecules in promoting SOD1 aggregation in a time- and dose-dependent manner.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that can be caused by inherited mutations in the gene encoding copper-zinc ...

Analyzing Mitochondrial Transport and Morphology in Human Induced Pluripotent Stem Cell-Derived Neurons in Hereditary Spastic Paraplegia

Neurons have intense demands for high energy in order to support their functions. Impaired mitochondrial transport along axons has been observed in human neurons, which may contribute to neurodegeneration in various disease states. Although it is challenging to examine mitochondrial dynamics in live human nerves, such paradigms are critical for studying the role of mitochondria in neurodegeneration. Described here is a protocol for analyzing mitochondrial transport and mitochondrial morphology in forebrain neuron axons derived from human induced pluripotent stem cells (iPSCs). The iPSCs are differentiated into telencephalic glutamatergic neurons using well-established methods. Mitochondria of the neurons are stained with MitoTracker CMXRos, and mitochondrial movement within the axons are captured using a live-cell imaging microscope equipped with an incubator for cell culture. Time-lapse images are analyzed using software with &#34;MultiKymograph&#34;, &#34;Bioformat importer&#34;, and &#34;Macros&#34; plugins. Kymographs of mitochondrial transport are generated, and average mitochondrial velocity in the anterograde and retrograde directions is read from the kymograph. Regarding mitochondrial morphology analysis, mitochondrial length, area, and aspect ratio are obtained using the ImageJ. In summary, this protocol allows characterization of mitochondrial trafficking along axons and analysis of their morphology to facilitate studies of neurodegenerative diseases.

Impaired mitochondrial transport and morphology are involved in various neurodegenerative diseases. The presented protocol uses induced pluripotent stem cell-derived forebrain neurons to assess mitochondrial transport and morphology in hereditary spastic paraplegia. This protocol allows characterization of mitochondrial trafficking along axons and analysis of their morphology, which will facilitate the study of neurodegenerative disease.

Neurons have intense demands for high energy in order to support their functions. Impaired mitochondrial transport along axons has been observed in human ...

Generation of Human Brain Organoids for Mitochondrial Disease Modeling

Mitochondrial diseases represent the largest class of inborn errors of metabolism and are currently incurable. These diseases cause neurodevelopmental defects whose underlying mechanisms remain to be elucidated. A major roadblock is the lack of effective models recapitulating the early-onset neuronal impairment seen in the patients. Advances in the technology of induced pluripotent stem cells (iPSCs) enable the generation of three-dimensional (3D) brain organoids that can be used to investigate the impact of diseases on the development and organization of the nervous system. Researchers, including these authors, have recently introduced human brain organoids to model mitochondrial disorders. This paper reports a detailed protocol for the robust generation of human iPSC-derived brain organoids and their use in mitochondrial bioenergetic profiling and imaging analyses. These experiments will allow the use of brain organoids to investigate metabolic and developmental dysfunctions and may provide crucial information to dissect the neuronal pathology of mitochondrial diseases.

We describe a detailed protocol for the generation of human induced pluripotent stem cell-derived brain organoids and their use in modeling mitochondrial diseases.

Mitochondrial diseases represent the largest class of inborn errors of metabolism and are currently incurable. These diseases cause neurodevelopmental ...

Determination of Mitochondrial Respiration and Glycolysis in Ex Vivo Retinal Tissue Samples

Mitochondrial respiration is a critical energy-generating pathway in all cells, especially retinal photoreceptors that possess a highly active metabolism. In addition, photoreceptors also exhibit high aerobic glycolysis like cancer cells. Precise measurements of these metabolic activities can provide valuable insights into cellular homeostasis under physiological conditions and in disease states. High throughput microplate-based assays have been developed to measure mitochondrial respiration and various metabolic activities in live cells. However, a vast majority of these are developed for cultured cells and have not been optimized for intact tissue samples and for application ex vivo. Described here is a detailed step-by-step protocol, using microplate-based fluorescence technology, to directly measure oxygen consumption rate (OCR) as an indicator of mitochondrial respiration, as well as extracellular acidification rate (ECAR) as an indicator of glycolysis, in intact ex vivo retinal tissue. This method has been used to successfully assess metabolic activities in adult mouse retina and demonstrate its application in investigating cellular mechanisms of aging and disease.

Determination of Mitochondrial Respiration and Glycolysis in Ex Vivo Retinal Tissue Samples

Described here is a detailed protocol for performing mitochondrial stress assay and glycolytic rate assay in ex vivo retinal tissue samples using a commercial bioanalyzer.

Mitochondrial respiration is a critical energy-generating pathway in all cells, especially retinal photoreceptors that possess a highly active metabolism. ...

Imaging Mitochondrial Ca2+ Uptake in Astrocytes and Neurons using Genetically Encoded Ca2+ Indicators (GECIs)

Mitochondrial Ca2+ plays a critical role in controlling cytosolic Ca2+ buffering, energy metabolism, and cellular signal transduction. Overloading of mitochondrial Ca2+ contributes to various pathological conditions, including neurodegeneration and apoptotic cell death in neurological diseases. Here we present a cell-type specific and mitochondria targeting molecular approach for mitochondrial Ca2+ imaging in astrocytes and neurons in vitro and in vivo. We constructed DNA plasmids encoding mitochondria-targeting genetically encoded Ca2+ indicators (GECIs) GCaMP5G or GCaMP6s (GCaMP5G/6s) with astrocyte- and neuron-specific promoters gfaABC1D and CaMKII and mitochondria-targeting sequence (mito-). For in vitro mitochondrial Ca2+ imaging, the plasmids were transfected in cultured astrocytes and neurons to express GCaMP5G/6s. For in vivo mitochondrial Ca2+ imaging, adeno-associated viral vectors (AAVs) were prepared and injected into the mouse brains to express GCaMP5G/6s in mitochondria in astrocytes and neurons. Our approach provides a useful means to image mitochondrial Ca2+ dynamics in astrocytes and neurons to study the relationship between cytosolic and mitochondrial Ca2+ signaling, as well as astrocyte-neuron interactions.

Imaging Mitochondrial Ca2+ Uptake in Astrocytes and Neurons using Genetically Encoded Ca2+ Indicators GECIs

This proctocol aims to provide a method for in vitro and in vivo mitochondrial Ca2+ imaging in astrocytes and neurons.

Mitochondrial Ca2+ plays a critical role in controlling cytosolic Ca2+ buffering, energy metabolism, and cellular signal transduction. Overloading of ...

Live-imaging of Mitochondrial System in Cultured Astrocytes

While much attention has been given to mitochondrial alterations at the neuronal level, recent evidence demonstrates that mitochondrial dynamics and function in astrocytes are implicated in cognition. This article describes the method for time-lapse imaging of astrocyte cultures equipped with a mitochondrial biosensor: MitoTimer. MitoTimer is a powerful and unique tool to assess mitochondrial dynamics, mobility, morphology, biogenesis, and redox state. Here, the different procedures for culture, image acquisitions, and subsequent mitochondrial analysis are presented.

This article describes the method for mitochondrial time-lapse imaging of astrocyte cultures equipped with MitoTimer biosensor and the resulting multiparametric analysis of mitochondrial dynamics, mobility, morphology, biogenesis, redox state, and turnover.

While much attention has been given to mitochondrial alterations at the neuronal level, recent evidence demonstrates that mitochondrial dynamics and ...