Asymmetric superoxide release inside and outside the mitochondria in skeletal muscle under conditions of aging and disuse

Abstract

Superoxide released from mitochondria forms reactive oxygen species that can cause severe oxidative damage and have been associated with aging- and disuse-induced muscle dysfunction. Superoxide is released to both the exterior and the matrix of mitochondria, where oxidative damage is not necessarily the same. This complicates determining the role of mitochondrial superoxide in eliciting oxidative stress in skeletal muscle. A newly developed capillary electrophoretic method analyzes hydroxytriphenylphosphonium ethidium, a superoxide-specific product of triphenylphosphonium hydroethidine, released to outside the mitochondria (supernatant) and retained in the matrix (pellet). In this study, we investigated the mitochondrial superoxide production of soleus (type I) and semimembranosus (type II) muscles of Fischer 344 rats affected by aging (13 vs. 26 mo) and disuse (hindlimb unloading). In agreement with previous studies, overall superoxide production increased with aging and disuse. On the other hand, the new experimental method revealed that superoxide production outside the mitochondria of the soleus does not show a significant age-related increase. Another observation was that the superoxide production increase in the matrix occurs earlier (7 days of disuse) compared with the outside mitochondria (14 days of disuse) in both muscle types. These findings indicate that superoxide release is complex as it occurs asymmetrically at both sides of the mitochondrial inner membrane, and that such release has muscle type and temporal specificity. These findings are important to refine current concepts on oxidative stress associated with muscle aging and disuse.

The calcineurin antagonist RCAN1-4 is induced by exhaustive exercise in rat skeletal muscle

“…Soleus in which large number of fibers are of the slow twitch variety, works longer than other muscles in endurance exercise [55], which may mean that it experiences more oxidative stress than the other muscle groups. Slow twitch fibers have typically more robust antioxidant defenses [28,29], and produces more superoxide and hydrogen peroxide than the other muscles via leakage of electrons from mitochondrial oxidative phosphorylation [49,56,57]. The increase in catalase and CuZnSOD is a possible mechanism to explain why no increase in protein carbonyl was observed post exercise in soleus.…”

Mitochondrial signaling contributes to disuse muscle atrophy

“…Since those initial reports, numerous studies have confirmed that muscle inactivity is associated with mitochondrial changes that, in theory, could contribute to disuse muscle atrophy (3,8,26,42,63,72). Nonetheless, most published reports have been descriptive and do not provide direct evidence that mitochondrial signaling contributes to muscle fiber atrophy.…”

Antioxidative Effect of Far-Infrared Radiation in Human

“…No significant difference among testing groups was observed from the distribution of demographic characteristics analyzed by chi-squared or one-way ANOVA. The concentration of superoxide anions in blood was previously indicated being influenced by age [26,[33][34][35]. Therefore, the subjects over 30 years old were excluded from the test to avoid the effect of age.…”