Remote and local ischemic postconditioning further impaired skeletal muscle mitochondrial function after...

Muscular injuries contribute to perioperative and long-term morbidity after vascular surgery in humans. We determined whether local and remote ischemic postconditioning might similarly decrease muscle mitochondrial dysfunction through reduced oxidative stress.

Eighteen male Black-6 mice were divided in three groups: (1) sham mice had no ischemia (sham), (2) ischemia-reperfusion (IR) mice underwent 2-hour tourniquet-induced ischemia on both hind limbs, followed by 2-hour reperfusion, and (3) postconditioning (PoC) mice underwent four bouts of 30-second reperfusion and 30-second ischemia at the onset of reperfusion on the right limb; thus, the right limb underwent local PoC and left limb underwent remote PoC (rPoC). Maximal oxidative capacity (V(max)) of the gastrocnemius muscle mitochondrial respiratory chain was measured. Oxidative stress was evaluated by dihydroethidium staining. Expressions of genes involved in antioxidant defense (superoxide dismutase [SOD1], SOD2, glutathione peroxidase [GPx]), apoptosis (Bax, BclII), and inflammation (interleukin-6) were determined by quantitative real-time polymerase chain reaction. Muscle inflammation was determined using immunohistochemistry.

IR reduced V(max) (8.5 ± 2.2 vs 10.2 ± 1.8 μmol O(2)/min/g dry weight; P = .034), and increased dihydroethidium staining (134.8%; P = .039). IR decreased GPx expression (-47.9%; P = .048) and increased the proapoptotic marker Bax (255.5%; P = .020). Local PoC and rPoC further increased these deleterious effects. PoC decreased V(max) to 4.4 ± 1.4 μmol O(2)/min/g dry weight (sham vs PoC, -56.9% [P < .001]; IR vs PoC, -48.2% [P < .001]). rPoC similarly reduced V(max) to 5.1 ± 1.9 μmol O(2)/min/g dry weight (sham vs PoC, -50.0% [P < .001]; IR vs PoC, -40.0% [P = .001]). Dihydroethidium staining was further increased by PoC (207.2%; P = .002) and rPoC (305.4%; P < .001) compared with sham and was associated with macrophage infiltration. Local PoC increased SOD1, SOD2, and the antiapoptotic Bcl-2, and rPoC increased Bax (391.6%; P < .001) and the Bax/BclII ratio (621.7%; P < .001).

Local and remote ischemic postconditioning further increased injury by enhancing mitochondrial dysfunction, oxidative stress production, and inflammation. Caution should be applied when considering ischemic postconditioning in vascular surgery.