Name: assessing mitochondrial function in sciatic nerve by high-resolution respirometry
Uploaded: 2022-05-05T14:00:00
Description: Watch this Scientific Journal Video about Assessing Mitochondrial Function in Sciatic Nerve by High-Resolution Respirometry at JoVE.com

This study was financed by Instituto Serrapilheira, Funda&#231;&#227;o de Amparo &#224; Pesquisa do Estado do Rio de Janeiro (FAPERJ), Conselho Nacional de Desenvolvimento Cient&#237;fico e Tecnol&#243;gico (CNPq) and Coordena&#231;&#227;o de Aperfei&#231;oamento de Pessoal de N&#237;vel Superior-Brasil (CAPES). We are grateful to Dr. Antonio Galina Filho, Dr. Monica Montero Lomeli and Dr. Claudio Masuda for the support with laboratory facilities, and Dr. Martha Sorenson for kind and valuable comments in improving the article.

The present protocol is approved by the Ethics Committee on the Use of Animals in Research, CCS/UFRJ (CEUA-101/19), and National Institutes of Health guidelines for the care and use of experimental animals. The sciatic nerve is isolated from four-month-old male C57BL/6 mice, euthanized by cervical dislocation as per the institutional guidelines. The protocol steps are optimized to avoid mitochondrial deterioration. Therefore, in this protocol, calibration of polarographic oxygen sensors was performed prior to mouse sciat...

Several diseases or conditions accompanying neuropathies have mitochondrial dysfunction as a risk factor. The evaluation of mitochondrial function in peripheral nerves is essential to elucidate how the mitochondria act in these neurodegenerative conditions. The assessment of mitochondrial function is laborious due to the difficulty of the isolation method and the scarcity of material. Thus, the development of tissue permeabilization techniques that do not require the isolation of mitochondria is essential.
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Mitochondria are essential for maintaining cell viability and perform numerous cell functions such as energy metabolism (glucose, amino acid, lipid, and nucleotide metabolism pathways). As the primary site of reactive oxygen species (ROS) production, mitochondria are central in several cell signaling processes such as apoptosis and participate in the synthesis of iron-sulfur (Fe-S) clusters, mitochondrial protein import and maturation, and maintenance of their genome and ribosomes1,2,3. The mitochondrial membrane dynamics network is controlled by fusion and fission processes, and they also have machinery for quality control and mitophagy4,5,6.
Mitochondrial dysfunction is associated with the appearance of several pathological conditions such as cancer, diabetes, and obesity7. Disturbances in mitochondrial function are detected in neurodegenerative disorders that affect the central nervous system, as in Alzheimer&#39;s disease8,9, Parkinson&#39;s disease10,11, amyotrophic lateral sclerosis12,13, and Huntington&#39;s disease14,15. In the peripheral nervous system, loss of mitochondrial function in axons is observed in immune neuropathies, such as Guillain-Barr&#233; syndrome16,17, and in association with high mitochondrial ROS production in axons, these events lead to MAP Kinase activation in Schwann cells18. This demonstrates that mitochondrial physiology may be essential not only for a site-specific cell, but for an entire tissue. In HIV-associated distal sensory polyneuropathy (HIV-DSP), mitochondria have a role in the mechanism by which the trans-activator of transcription (HIV-TAT) protein allows HIV to replicate efficiently, as well as several other roles in HIV infection pathogenesis19,20.
Evaluation of sciatic nerve mitochondrial physiology has emerged as an essential target for investigating neuropathy7,21,22. In diabetic neuropathy, proteomic and metabolomic analyses suggest that most molecular alterations in diabetes affect sciatic nerve mitochondrial oxidative phosphorylation and lipid metabolism7. These alterations also seem to be early signs of obesity-induced diabetes21. In a mouse model of chemotherapy-induced painful neuropathy, mitochondrial impairment in the sciatic nerve is detected as a decrease in oxidative phosphorylation22, and a reduction of mitochondrial complexes activities, membrane potential, and ATP content23. However, although several groups have cited mitochondrial dysfunction in neuropathies, these studies are limited to the measurements of activity in mitochondrial complexes with no preservation of the mitochondrial membranes, lacking evaluation of mitochondrial integrity or measurements of ATP content as a parameter for mitochondrial ATP production. In general, a proper assessment of mitochondrial oxygen consumption and ROS production requires the isolation of mitochondria by differential centrifugation in a percoll/sucrose gradient. Isolation of mitochondria can also be a limiting factor for sciatic nerve tissue because of the large amount of tissue needed and mitochondria loss and disruption.
The present study aims to provide a protocol to measure mitochondrial physiology as mitochondrial oxygen consumption and ROS production in the sciatic nerve, preserving mitochondrial membranes and without the need for isolating mitochondria. This protocol is adapted from oxygen consumption measurements in permeabilized muscle fibers24 by high-resolution respirometry (HRR). The advantages of this procedure are the possibility of evaluating mitochondria in small amounts of tissue such as the sciatic nerve and evaluating mitochondrial parameters in situ, thereby preserving the mitochondrial environment, structure, and bioenergetic profile, to obtain a physiologically trustworthy result. The mitochondrial respiratory states were determined with substrates and inhibitors after sciatic nerve permeabilization to properly assess mitochondrial bioenergetics and cytochrome c coefficient for mitochondrial membrane integrity, providing a guide for steps of the mitochondrial electron transport system (ETS) evaluation and calculation of essential parameters. This study can provide tools for answering questions in pathophysiological mechanisms in which sciatic nerve metabolism is implicated, such as peripheral neuropathies.

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			<td>Adenosine 5&#39; triphosphate dissodium salt hydrate</td>
			<td>Sigma-Aldrich</td>
			<td>A26209</td>
			<td></td>
		</tr>
		<tr>
			<td>Adenosine 5&#8242;-diphosphate sodium salt</td>
			<td>Sigma-Aldrich</td>
			<td>A2754</td>
			<td></td>
		</tr>
		<tr>
			<td>Amplex Red Reagent</td>
			<td>Thermo Fisher scientific</td>
			<td>A12222</td>
			<td>Amplex Red is prepared in DMSO accordindly with product datasheet</td>
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		<tr>
			<td>Antimycin A (from Streptomyces sp.)</td>
			<td>Sigma-Aldrich</td>
			<td>A8674</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin</td>
			<td>Sigma-Aldrich</td>
			<td>A7030</td>
			<td>heat shock fraction, protease free, fatty acid free, essentially globulin free, pH 7, &#8805;98%</td>
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		<tr>
			<td>Calcium carbonate</td>
			<td>Sigma-Aldrich</td>
			<td>C6763</td>
			<td></td>
		</tr>
		<tr>
			<td>Carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP)</td>
			<td>Sigma-Aldrich</td>
			<td>C2920</td>
			<td></td>
		</tr>
		<tr>
			<td>Cytochrome c</td>
			<td>Sigma-Aldrich</td>
			<td>C7752</td>
			<td>(from equine heart; small hemeprotein)</td>
		</tr>
		<tr>
			<td>DataLab version 5.1.1.91</td>
			<td>OROBOROS INSTRUMENTS, Austria</td>
			<td></td>
			<td>Copyright (c) 2002 - 13 by Dr. Erich Gnaiger</td>
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		<tr>
			<td>Digital orbital microplate shaker 120V</td>
			<td>Thermo Fisher scientific</td>
			<td>88882005</td>
			<td></td>
		</tr>
		<tr>
			<td>DL-Dithiothreitol</td>
			<td>Sigma-Aldrich</td>
			<td>43819</td>
			<td></td>
		</tr>
		<tr>
			<td>EGTA sodium salt</td>
			<td>Sigma-Aldrich</td>
			<td>E8145</td>
			<td></td>
		</tr>
		<tr>
			<td>Hamilton syringe</td>
			<td>Sigma-Aldrich</td>
			<td>HAM80075</td>
			<td>10 uL, 25 uL and 50 uL</td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma-Aldrich</td>
			<td>H3375</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrogen peroxide solution 30% W/W</td>
			<td>Merck</td>
			<td>H1009</td>
			<td></td>
		</tr>
		<tr>
			<td>Imidazole</td>
			<td>Sigma-Aldrich</td>
			<td>I2399</td>
			<td></td>
		</tr>
		<tr>
			<td>L-(&#8722;)-Malic acid</td>
			<td>Sigma-Aldrich</td>
			<td>M7397</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium chloride hexahydrate</td>
			<td>Sigma-Aldrich</td>
			<td>M2393</td>
			<td></td>
		</tr>
		<tr>
			<td>MES sodium salt</td>
			<td>Sigma-Aldrich</td>
			<td>M3885</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro-dissecting forceps, curved</td>
			<td>Sigma-Aldrich</td>
			<td>F4142</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro-dissecting forceps, straight</td>
			<td>Sigma-Aldrich</td>
			<td>F4017</td>
			<td></td>
		</tr>
		<tr>
			<td>O2K - Filter set Amplex Red</td>
			<td>OROBOROS INSTRUMENTS, Austria</td>
			<td>44321-01</td>
			<td>Fasching M, Sumbalova Z, Gnaiger E (2013) O2k-Fluorometry: HRR and H2O2 production in mouse brain mitochondria. Mitochondr Physiol Network 17.17.</td>
		</tr>
		<tr>
			<td>O2K - Fluorescence LED2 - module component Fluorscence-Sensor Green</td>
			<td>OROBOROS INSTRUMENTS, Austria</td>
			<td>44210-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Oligomycin</td>
			<td>Sigma-Aldrich</td>
			<td>O4876</td>
			<td>(from Streptomyces diastatochromogenes; mixture of oligomycins A, B, and C</td>
		</tr>
		<tr>
			<td>OROBOROS Oxygraph-2k</td>
			<td>OROBOROS INSTRUMENTS, Austria</td>
			<td>http://www.oroboros.at</td>
			<td></td>
		</tr>
		<tr>
			<td>Palmitoylcarnitine (Palmitoyl-DL-carnitine-HCl)</td>
			<td>Sigma-Aldrich</td>
			<td>P4509</td>
			<td></td>
		</tr>
		<tr>
			<td>Peroxidase from horseradish</td>
			<td>Sigma-Aldrich</td>
			<td>P8375</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dishes, polystyrene</td>
			<td>MERCK</td>
			<td>P5606</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphocreatine disodium salt hydrate</td>
			<td>Sigma-Aldrich</td>
			<td>P7936</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium dihydrogen phosphate monobasic</td>
			<td>Sigma-Aldrich</td>
			<td>PHR1330</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium hydroxide</td>
			<td>Sigma-Aldrich</td>
			<td>221473</td>
			<td></td>
		</tr>
		<tr>
			<td>Rotenone</td>
			<td>Sigma-Aldrich</td>
			<td>R8875</td>
			<td></td>
		</tr>
		<tr>
			<td>Saponin</td>
			<td>Sigma-Aldrich</td>
			<td>SAE0073</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium pyruvate</td>
			<td>Sigma-Aldrich</td>
			<td>P5280</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium succinate dibasic hexahydrate</td>
			<td>Sigma-Aldrich</td>
			<td>S2378</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Sigma-Aldrich</td>
			<td>S9378</td>
			<td></td>
		</tr>
		<tr>
			<td>Taurine</td>
			<td>Sigma-Aldrich</td>
			<td>T0625</td>
			<td></td>
		</tr>
	</tbody>
</table>

assessing mitochondrial function in sciatic nerve by high-resolution respirometry

Mitochondrial dysfunction in peripheral nerves accompanies several diseases associated with peripheral neuropathy, which can be triggered by multiple causes, including autoimmune diseases, diabetes, infections, inherited disorders, and tumors. Assessing mitochondrial function in mouse peripheral nerves can be challenging due to the small sample size, a limited number of mitochondria present in the tissue, and the presence of a myelin sheath. The technique described in this work minimizes these challenges by using a unique permeabilization protocol adapted from one used for muscle fibers, to assess sciatic nerve mitochondrial function instead of isolating the mitochondria from the tissue. By measuring fluorimetric reactive species production with Amplex Red/Peroxidase and comparing different mitochondrial substrates and inhibitors in saponin-permeabilized nerves, it was possible to detect mitochondrial respiratory states, reactive oxygen species (ROS), and the activity of mitochondrial complexes simultaneously. Therefore, the method presented here offers advantages compared to the assessment of mitochondrial function by other techniques.

The mitochondrial oxygen consumption by the permeabilized sciatic nerve is represented in Figure 2. The red trace represents the O2 flux per unit mass in pmol/s.mg. After recording a basal oxygen consumption with endogenous substrates (routine respiration), succinate (SUCC) is injected to record complex II (succinate dehydrogenase)-driven respiration, resulting in an increase in the oxygen consumption rate. In sequence, a saturating concentration of ADP is added, activating ATP sy...

Watch this Scientific Journal Video about Assessing Mitochondrial Function in Sciatic Nerve by High-Resolution Respirometry at JoVE.com

Assessing Mitochondrial Function in Sciatic Nerve by High-Resolution Respirometry

High-resolution respirometry coupled to fluorescence sensors determines mitochondrial oxygen consumption and reactive oxygen species (ROS) generation. The present protocol describes a technique to assess mitochondrial respiratory rates and ROS production in the permeabilized sciatic nerve.

Mitochondrial dysfunction in peripheral nerves accompanies several diseases associated with peripheral neuropathy, which can be triggered by multiple ...

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