Mitochondrial cholesterol content and membrane properties in porcine myocardial ischemia

Abstract

Regional myocardial ischemia was produced in anesthetized pigs by occluding the left anterior descending coronary artery. Mitochondria were prepared from both normally perfused and ischemic myocardium after 2 h of occlusion. Mitochondria from the ischemic area exhibited an 89% increase in cholesterol content from 32.7 +/- 1.9 (control) to 62.0 +/- 0.47 (ischemic) nmol/mg protein with no change in either total phospholipid content or in membrane fatty acid composition. This increase in mitochondrial membrane cholesterol was accompanied by an increase in membrane microviscosity as indicated by increased fluorescence polarization using the fluorescent membrane probe, 1,6-diphenyl-1,3,5-hexatriene. In these same experiments the Arrhenius plot discontinuity temperature of oligomycin-sensitive adenosinetriphosphatase (ATPase) activity fell from 20.0 to 14.2 degrees C. Our results suggest that, during the myocardial ischemic process in pigs, there is an intracellular redistribution of free cholesterol that produces a marked increase in mitochondrial membrane cholesterol content. This appears to produce an altered mitochondrial membrane lipid bilayer packing, resulting in increased membrane microviscosity and, possibly, altered inner membrane ATPase function. Intracellular cholesterol redistribution may thus contribute to the cell membrane damage that occurs during the myocardial ischemic process.

Cardioprotection by the TSPO ligand 4′-chlorodiazepam is associated with inhibition of mitochondrial accumulation of cholesterol at reperfusion

“…In mitochondria isolated from control hearts, the concentration of cholesterol was 39.9 + 3.51 nmol/mg protein (Figure 1), a similar level to that previously obtained in rat and pig heart mitochondria. 25,26 There was no difference between free and total cholesterol showing the absence of esterified cholesterol and that cholesterol was essentially in the free form confirming previous observations by other investigators. 25,26 We also evaluated the concentration of cholesterol in isolated mitochondria subfractionated into membranes (inner plus outer) and matrix plus intermembrane space (called matrix).…”

“…25,26 There was no difference between free and total cholesterol showing the absence of esterified cholesterol and that cholesterol was essentially in the free form confirming previous observations by other investigators. 25,26 We also evaluated the concentration of cholesterol in isolated mitochondria subfractionated into membranes (inner plus outer) and matrix plus intermembrane space (called matrix). Figure 2 shows that the subfractionation method allowed us to obtain enriched fractions in mitochondrial membranes and matrix as demonstrated by the measure of the activity of specific enzymatic markers and Figure 1 Ischaemia induced a decrease in mitochondrial cholesterol, which is observed in both the membrane and the matrix fractions (Figure 1).…”

Cholesterol Impairs the Adenine Nucleotide Translocator-mediated Mitochondrial Permeability Transition through Altered Membrane Fluidity

“…ATR range of change in fluorescence anisotropy using DPH was similar to our present findings. For instance mitochondria from ischemic pig hearts exhibited higher mitochondrial cholesterol content (2-fold) and increased DPH fluorescence polarization (16% increase) (47). Moreover, membranes from HEK-OTR and HEK-CCKR cells loaded with cholesterol showed increased (13-16%) fluorescence anisotropy values for DPH (49).…”

Cholesterol Effects on BAX Pore Activation

“…Adding cholesterol (≈20 mol%) to liposomes and the OMM significantly inhibits BAX(ΔC19) pore formation. This is more cholesterol than the concentrations reported to be present in the OMM and less than the cholesterol content of the plasma membranes [31,23,66,67]. There-fore, we conclude that the sterol concentrations of defined liposome membranes can play a role in regulating the pore formation by BAX.…”