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

Abstract

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 (VMax), 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 VMax (from 11.79 ± 1.74 to 4.65 ± 1.11 pmol/s*mg wet weight (ww), p < 0.05, −50.2 ± 16.3%) and CRC (from 2.33 ± 0.41 to 0.84 ± 0.18 µmol/mg dry weight (dw), p < 0.05; −61.1 ± 6.8%). ROS tended to increase in the ischemic limb (+64.3 ± 31.9%, p = 0.08). Although tending to reduce IR-related ROS production (−42.4%), sildenafil failed to reduce muscle mitochondrial dysfunctions (−63.3 ± 9.2%, p < 0.001 and −55.2 ± 7.6% p < 0.01 for VMax, 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.

Aging Exacerbates Ischemia-Reperfusion-Induced Mitochondrial Respiration Impairment in Skeletal Muscle

“…Two other young and aged groups were submitted to 2 h ischemia with a tourniquet placed around the right hindlimb, at the level of the groin, followed by 2 h reperfusion (Y-IR ( n = 7), A-IR ( n = 7), respectively). Ischemia was ascertained by visual observation of cyanosis of the limb and mice were sacrificed at the end of the experiment [13].…”

“…PAD pathophysiology clearly demonstrated a major role for skeletal muscle mitochondrial dysfunction and oxidative stress, which promote cell damage and death. Thus, oxidative phosphorylation capacity is reduced, hampering adenosine triphosphate (ATP) generation [7,8,9,10,11,12,13]. Interestingly, further underlining the importance of mitochondria, mitochondrial content in skeletal muscle demonstrated to be a good predictor of the mortality rate during PAD in humans [14].…”

Therapeutic Approaches to Treat Mitochondrial Diseases: “One-Size-Fits-All” and “Precision Medicine” Strategies

“…However, the NO pathway was not evaluated in this study; instead, a possible link with the activation of Ca 2+ -activated potassium channels mediated by cGMP was speculated [ 176 ]. Nevertheless, the beneficial effects of PDE5i to treat PMD are still poorly understood, since preclinical studies [ 177 , 178 ] and case reports [ 179 ] gave controversial results; further investigations on the mechanisms need to be implemented.…”

The Rise of Mitochondria in Peripheral Arterial Disease Physiopathology: Experimental and Clinical Data

“…Rodent models of PAD displayed elevated protein expression of the apoptotic factors cleaved-caspase 3, cleaved-poly (ADP-robose) polymerase (PARD) and mitochondrial and cytosolic Bcl2-associated X (Bax), and reduced protein expression of the anti-apoptotic factor Bcl-2, compared with controls [21,54,55]. Furthermore, a decrease in mitochondrial calcium retention capacity was observed in ischemic limbs compared with contralateral ones (Table 5) [25,44,47,56,57]. IR increased Bax (63.4%, p = 0.020) and Bax/Bcl-2 ratio (+84.6%, p = 0.029).…”