This study examined whether alpha lipoic acid (ALA), an antioxidant with anti-apoptotic properties, synthesized in mitochondria of endothelial cells, would inhibit intrinsic apoptotic signaling and microvascular endothelial cell hyperpermeability.

Rat lung microvascular endothelial cells were transfected with BAK (BH3) peptide (5 μg/mL) or active caspase-3 (5 μg/mL) and were pretreated with ALA (10 and 100 μmol/L). Hyperpermeability was determined using fluorescein isothiocyanate albumin-flux across the cells grown as monolayer. Reactive oxygen species (ROS) formation was determined using 123 dihydrorhodamine and mitochondrial membrane potential using JC-1. Cytochrome c levels and caspase-3 activity were determined using an enzyme-linked immunosorbent assay and a fluorometric assay, respectively.

ALA (100 μmol/L) pretreatment attenuated BAK (BH3)-induced hyperpermeability and ROS formation. ALA restored BAK (BH3)-induced collapse in mitochondrial membrane potential and decreased BAK (BH3)-induced cytochrome c release and caspase-3 activity.

These findings suggest that ALA attenuates BAK-induced monolayer hyperpermeability through the inhibition of ROS formation and intrinsic apoptotic signaling.