After calibrating polarographic oxygen sensors, remove the stoppers and open the chambers. Wash the stoppers and chambers with 100%ethanol, 70%ethanol, and distilled water. Transfer the flies into a microcentrifuge tube.
Add 200 microliters of chilled MiR05 buffer into the tube and homogenize the flies by applying gentle pressure with four to six strokes of the pestle. Using a micropipette, transfer the homogenized fly suspension into the chamber. Cover the chamber with a stopper without introducing air bubbles.
Next, click on the layout menu and select Option 5, Flow by Corrected Volume. Another new window will open. Here, in the space, experimental code, name the experiment.
In the sample field, name each sample in its respective chamber A and B.Then set the unit field to Unit and in the concentration field, define the chamber volume as one per milliliter. To start the high-resolution respirometry, ensure that the oxygen flux signal is steady on the positive value. Add digitonin to permeabilize the mitochondrial membrane.
Then add pyruvate, malate, and proline substrates until the oxygen flux increases and stabilizes. Press the F4 key on the keyboard and enter the name of the reagent to mark the event. Add ADP to couple the mitochondrial respiratory chain, and wait for the increase and stabilization of the oxygen flux.
Then add succinate and measure the oxygen flux. TO inhibit ATP synthase, add oligomycin and examine for a decrease in oxygen flux. After the red line stabilizes, uncouple the mitochondrial electron transfer using 0.25-micromolar FCCP until maximum oxygen consumption is reached, demonstrated by the rise of the red line.
Next, add rotenone complex I inhibitor and wait for the decrease and stabilization of the oxygen flux. Then add malonate complex II inhibitor and measure the oxygen flux. Finally, add antimycin complex III inhibitor and wait for the decrease, followed by the increase and stabilization of the oxygen flux.
Click on the GraphPad Prism software to extract the oxygen flux values from the graphs. OXPHOS CI refers to the value of oxygen flux after adding ADP. Then use the given formula to calculate OXHPOS CII.
Using the following equation, calculate the ETS CI and CII oxygen values for the uncouples and inhibitors. Then calculate the ATP synthesis as the difference between the OXPHOS and LEAK. Finally, calculate the OXPHOS by LEAK ratio to determine the respiratory control ratio.
The oxygen flux in both OXHPOS CI and OXPHOS CI and CII states was significantly reduced in PINK1 B9 null flies. compared to control flies. Additionally, the oxygen flux in ETS CI, ETS CII, and ETS CI and CII state were lower in PINK1 B9 null flies, indicating an impaired electron transfer system compared to the control flies.
The disruption in the flux of electrons affects the OXPHOS process, leading to reduced ATP synthesis in the PINK1 B9 null flies. The reduction in the respiratory control ratio of null flies suggests mitochondrial uncoupling, indicating that the mitochondria were less efficient at utilizing oxygen and producing ATP.
