Effect of the Phosphodiesterase 5 Inhibitor Sildenafil on Ischemia-Reperfusion-Induced Muscle Mitochondrial Dysfunction and Oxidative Stress.

Lower-limb ischemia-reperfusion (IR) is frequent and associated with significant morbidity and mortality. Phosphodiesterase 5 inhibitors demonstrated antioxidant and beneficial effects in several organs submitted to IR, but their effects on muscle mitochondrial functions after lower-limb IR are unknown. Unilateral hindlimb IR (2 h tourniquet followed by 2 h reperfusion) without or with sildenafil (1mg/kg ip 30 minutes before ischemia) was performed in 18 mice. Maximal oxidative capacity (V), relative contribution of the mitochondrial respiratory chain complexes, calcium retention capacity (CRC)-a marker of apoptosis-and reactive oxygen species (ROS) production were determined using high-resolution respirometry, spectrofluorometry, and electron paramagnetic resonance in gastrocnemius muscles from both hindlimbs. IR significantly reduced mitochondrial V (from 11.79 ± 1.74 to 4.65 ± 1.11 pmol/s*mg wet weight (ww), < 0.05, -50.2 ± 16.3%) and CRC (from 2.33 ± 0.41 to 0.84 ± 0.18 µmol/mg dry weight (dw), < 0.05; -61.1 ± 6.8%). ROS tended to increase in the ischemic limb (+64.3 ± 31.9%, = 0.08). Although tending to reduce IR-related ROS production (-42.4%), sildenafil failed to reduce muscle mitochondrial dysfunctions (-63.3 ± 9.2%, < 0.001 and -55.2 ± 7.6% < 0.01 for V and CRC, respectively). In conclusion, lower limb IR impaired skeletal muscle mitochondrial function, but, despite tending to reduce ROS production, pharmacological preconditioning with sildenafil did not show protective effects.