Oxidative stress after muscle damage from immobilization and remobilization occurs locally and systemically

Long-term locked knee ankle foot orthosis use: A perspective overview of iatrogenic biomechanical and physiological perils

A knee ankle foot orthosis (KAFO) may be prescribed to the person with severe neuromusculoskeletal impairment of the lower limb to promote walking stability. The locked knee ankle foot orthosis (L-KAFO) is among the KAFO's routinely prescribed; however, long-term use of the L-KAFO is associated with musculoskeletal (arthrogenic and myogenic) and integumentary changes, and gait asymmetry with increased energy expenditure. Consequently, the risk of developing low back pain, osteoarthritis of the lower limbs and spinal joints, skin dermatitis, and ulceration increases, all of which impact quality of life. This article synthesizes the iatrogenic biomechanical and physiological perils of long-term L-KAFO use. It promotes using recent advances in rehabilitation engineering to improve daily activities and independence for proper patient groups.

Hemin, heme oxygenase-1 inducer, attenuates immobilization-induced skeletal muscle atrophy in mice

AIMS

The present study examined the effect of the heme oxygenase (HO)-1 inducer hemin on skeletal muscle atrophy induced by single limb immobilization in mice.

MAIN METHODS

Immobilization was conducted in the left hindlimb of C57BL/6 mice for 1 week and the right hindlimb was used as a control. Hemin (30 mg/kg) was administered intraperitoneally once a day during the immobilization period. Gastrocnemius muscles were used for analysis. Muscle weight was measured to quantify degree of atrophy, and exhaustion treadmill test was performed to assess muscle function.

KEY FINDINGS

Immobilization increased HO-1 protein levels in skeletal muscle, which was further increased by hemin treatment. Immobilization induced weight loss and a functional reduction in skeletal muscle, which were attenuated by hemin treatment. Gene expression and protein levels of MuRF1 and atrogin-1 were increased by immobilization and hemin treatment attenuated the increment. The phosphorylation of mTOR and p70S6k was decreased by immobilization in skeletal muscle and hemin had no effect on mTOR and p70S6k phosphorylation. Gene expression of the antioxidants superoxide dismutase and glutathione peroxidase 1 in skeletal muscle was reduced by immobilization and hemin treatment recovered the reduction. Immobilization increased levels of carbonylated protein and nitrotyrosine in skeletal muscle, which was reversed by hemin treatment. Gene expression of inflammatory cytokines was increased by immobilization and was normalized as a result of hemin treatment.

SIGNIFICANCE

These results suggest that hemin attenuates immobilization-induced skeletal muscle atrophy through the suppression of protein degradation via its anti-oxidant and anti-inflammatory properties.

Effect of Celastrus paniculatus seed oil (Jyothismati oil) on acute and chronic immobilization stress induced in swiss albino mice

Stress alters the homeostasis and is produced by several factors. Immobilization stress induced due to reduced floor area provided for the mobility results in the imbalance of oxidant and antioxidant status. The modern computer savvy world decreases human mobility in the working environment, leading to the formation of oxygen free radicals and if left untreated might result in severe health problems like hypertension, cardiovascular disease, premature aging and brain dysfunction. Hence, modern medicines rely upon the medicinal plants for some drugs with zero side effects. In this context, Jyothismati oil (JO), extracted from Celastrus paniculatus seeds, was used to treat acute and chronic immobilization induced experimentally. C. paniculatus plant is considered to be rich in antioxidant content and so the seed oil extract's efficacy was tested against immobilization stress in albino mice. The animals were kept in a restrainer for short and long durations, grouped separately and fed with the drug. Animals were sacrificed and the samples were analyzed. The antioxidant enzyme levels of the animals regained and markedly increased in the acute and chronic immobilized groups, respectively. The results suggested that the extract of C. paniculatus seed was highly efficacious in reducing the stress induced by least mobility for hours.

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

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.

Mitochondrial death effectors: relevance to sarcopenia and disuse muscle atrophy

Accelerated apoptosis in skeletal muscle is increasingly recognized as a potential mechanism contributing to the development of sarcopenia of aging and disuse muscle atrophy. Given their central role in the regulation of apoptosis, mitochondria are regarded as key players in the pathogenesis of myocyte loss during aging and other atrophying conditions. Oxidative damage to mitochondrial constituents, impaired respiration and altered mitochondrial turnover have been proposed as potential triggering events for mitochondrial apoptotic signaling. In addition, iron accumulation within mitochondria may enhance the susceptibility to apoptosis during the development of sarcopenia and possibly acute muscle atrophy, likely through exacerbation of oxidative stress. Mitochondria can induce myocyte apoptosis via both caspase-dependent and independent pathways, although the apoptogenic mediators involved may be different depending on age, muscle type and specific atrophying conditions. Despite the considerable advances made, additional research is necessary to establish a definite causal link between apoptotic signaling and the development of sarcopenia and acute atrophy. Furthermore, a translational effort is required to determine the role played by apoptosis in the pathogenesis of sarcopenia and disuse-induced muscle loss in human subjects.

Carbonic anhydrase III and four-and-a-half LIM protein 1 are preferentially oxidized with muscle unloading

The identities of proteins that show disuse-related changes in the content of oxidative modification are unknown. Furthermore, it is unknown whether the global accumulation of oxidized proteins is greater in aged animals with muscle disuse. The purposes of this study are 1) to identify the exact proteins that show disuse-related changes in oxidation levels and 2) to test the hypothesis that the global accumulation of oxidized proteins with muscle disuse would be greater in aged animals. Adult and old rats were randomized into four groups: weight bearing and 3, 7, or 14 days of hindlimb unloading. Soleus muscles were harvested to investigate the protein oxidation with unloading. Slot blot, SDS-PAGE, and Western blot analyses were used to detect the accumulation of 4-hydroxy-2-nonenol (HNE)- and nitrotyrosine (NT)-modified proteins. Matrix-assisted laser desorption ionization-time of flight and tandem mass spectroscopy were used to identify modified proteins. We found that global HNE- and NT-modified proteins accumulated significantly with aging but not with muscle unloading. Two HNE and NT target proteins, four-and-a-half LIM protein 1 (FHL1) and carbonic anhydrase III (CAIII), showed changes in the oxidation levels with muscle unloading. The changes in the oxidation levels happened to adult rats but not old rats. However, old rats had higher baseline levels of HNE-modified FHL1. In summary, the data suggest that the muscle unloading-related changes of protein oxidation are more significant in specific proteins and that the changes are age related.

Muscle disuse: adaptation of antioxidant systems is age dependent

This study investigated the age effect on antioxidant adaptation to muscle disuse. Adult and old rats were randomized into 4 groups: weight bearing (control), 3 days of hind-limb unloading (HU), 7 days of HU, and 14 days of HU. Activities of Cu-Zn superoxide dismutase (SOD), catalase, and glutathione (GSH), as well as GSH peroxidase levels were measured in the soleus. Neither disuse nor aging changed the activity of Cu-Zn SOD. The old rats had greater GSH peroxidase activity, whereas the activity of catalase had a compensatory increase with disuse, independent of age. Reduced GSH level and total glutathione (tGSH) level had age-related change with disuse. In old rats, the GSH and tGSH levels were lower with disuse, whereas the levels remained stable with disuse in adult rats. The depletion of intracellular GSH and tGSH levels of muscles from aged animals with disuse may make aged muscles more susceptible to oxidative damage.

Exercise running and tetracycline as means to enhance skeletal muscle stem cell performance after external fixation

Prolonged limb immobilization, which is often the outcome of injury and illness, results in the atrophy of skeletal muscles. The basis of muscle atrophy needs to be better understood in order to allow development of effective countermeasures. The present study focused on determining whether skeletal muscle stem cells, satellite cells, are directly affected by long-term immobilization as well as on investigating the potential of pharmacological and physiological avenues to counterbalance atrophy-induced muscle deterioration. We used external fixation (EF), as a clinically relevant model, to gain insights into the relationships between muscle degenerative and regenerative conditions to the myogenic properties and abundance of bona fide satellite cells. Rats were treated with tetracycline (Tet) through the EF period, or exercise trained on a treadmill for 2 weeks after the cessation of the atrophic stimulus. EF induced muscle mass loss; declined expression of the muscle specific regulatory factors (MRFs) Myf5, MyoD, myogenin, and also of satellite cell numbers and myogenic differentiation aptitude. Tet enhanced the expression of MRFs, but did not prevent the decline of the satellite cell pool. After exercise running, however, muscle mass, satellite cell numbers (enumerated through the entire length of myofibers), and myogenic differentiation aptitude (determined by the lineal identity of clonal cultures of satellite cells) were re-gained to levels prior to EF. Together, our results point to Tet and exercise running as promising and relevant approaches for enhancing muscle recovery after atrophy.