Fig. 7.

Propofol reduced the mitochondrial membrane potential and induced an earlier opening of the mitochondrial permeability transition pore (mPTP) in human embryonic stem cell (hESC)-derived neurons and mPTP opening was delayed by blockade of mitochondrial fission. hESC-derived neurons were exposed for 6 hours to 20 μg/mL propofol or control with or without mdivi-1 pretreatment and loaded for 20 minutes with 50 nM tetramethylrhodamine ethyl ester (TMRE), a red dye taken up by the mitochondria. Rapid laser scanning (imaging the cells every 3.5 seconds for 55 frames) using the 561 nm laser of the confocal microscope was used to generate oxidative stress and induce opening of the mPTP. (A) The mitochondria appeared severely fragmented in the “propofol no treatment” and “propofol mdivi-1 control” groups. (B) Opening of the mPTP was observed as a rapid loss of TMRE fluorescence which was traced by plotting the fluorescence intensity recorded at each of the 55 frames obtained during the photoexcitiation. Arbitrary mPTP opening time was assessed by determining the time at which TMRE fluorescence had decreased by half between the initial and residual TMRE fluorescence. Propofol exposure induced a significantly earlier opening of the mPTP which was rescued to control levels by pretreatment for 1 hour with 25 μM mdivi-1. (C) The mitochondrial membrane potential was also assessed in the cells following exposure to the vehicle control or propofol by loading the cells with TMRE and imaging on the confocal microscope. Propofol exposure reduced the mitochondrial membrane potential in the cells when compared to control-treated cells further indicating mitochondrial damage following propofol exposure. (**P < 0.01 vs. all control groups and propofol mdivi-1 pretreatment group, *P < 0.05 vs. control, n = 5 coverslips/group). DMSO = dimethyl sulfoxide (the vehicle control).