α-LIPOIC ACID ATTENUATES HEMORRHAGIC SHOCK-INDUCED APOPTOTIC SIGNALING AND VASCULAR HYPERPERMEABILITY

Hemorrhagic shock (HS) is associated with the disruption of endothelial cell barrier leading to vascular hyperpermeability. Previous studies from our laboratory implicate reactive oxygen species (ROS) and the intrinsic apoptotic signaling cascades as mediators of vascular hyperpermeability after HS. Here we report the protective effects of a-lipoic acid, a natural antioxidant with antiapoptotic properties, against vascular hyperpermeability after HS. Hemorrhagic shock was induced in Sprague-Dawley rats by withdrawing blood to reduce the MAP to 40 mmHg for 60 min followed by resuscitation for 60 min. The rats were given fluorescein isothiocyanate-albumin (50 mg/kg) i.v., and the mesenteric postcapillary venules were examined for change in hyperpermeability using intravital microscopy. Mitochondrial ROS formation and change in mitochondrial transmembrane potential were measured using dihydrorhodamine 123 and the cationic dye JC-1, respectively. The mitochondrial release of cytochrome c and activation of caspase 3 were measured using enzyme-linked immunosorbent assay and fluorometric assay, respectively. Hemorrhagic shock resulted in vascular hyperpermeability and mitochondrial ROS formation. The activation of mitochondrial intrinsic apoptotic signaling pathway was evidenced from mitochondrial depolarization, an increase in cytochrome c release, and activation of caspase 3. alpha-Lipoic acid (100 mg/kg) given before the shock period attenuated vascular hyperpermeability, mitochondrial ROS formation, mitochondrial depolarization, cytochrome c release, and activation of caspase 3 (P < 0.05). Together, these results demonstrate that alpha-lipoic acid provides protection against vascular hyperpermeability by modulating the mitochondrial "intrinsic" apoptotic signaling.