TNF-α is involved in activating DNA fragmentation in skeletal muscle

Intraperitoneal administration of 100 μg kg−1 (body weight) of tumour necrosis factor-α to rats for 8 consecutive days resulted in a significant decrease in protein content, which was concomitant with a reduction in DNA content. Interestingly, the protein/DNA ratio was unchanged in the skeletal muscle of the tumour necrosis factor-α-treated animals as compared with the non-treated controls. Analysis of muscle DNA fragmentation clearly showed enhanced laddering in the skeletal muscle of tumour necrosis factor-α-treated animals, suggesting an apoptotic phenomenon. In a different set of experiments, mice bearing a cachexia-inducing tumour (the Lewis lung carcinoma) showed an increase in muscle DNA fragmentation (9.8-fold) as compared with their non-tumour-bearing control counterparts as previously described. When gene-deficient mice for tumour necrosis factor-α receptor protein I were inoculated with Lewis lung carcinoma, they were also affected by DNA fragmentation; however the increase was only 2.1-fold. These results suggest that tumour necrosis factor-α partly mediates DNA fragmentation during experimental cancer-associated cachexia

T Regulatory Cells Are Markers of Disease Activity in Multiple Sclerosis Patients

FoxP3+ Treg cells are believed to play a role in the occurrence of autoimmunity and in the determination of clinical recurrences. Contradictory reports are, however, available describing frequency and function of Treg cells during autoimmune diseases. We examined, by both polychromatic flow cytometry, and real-time RT-PCR, several Treg markers in peripheral blood mononuclear cells from patients with multiple sclerosis (MS), an autoimmune disease affecting the central nervous system. We found that Tregs, as defined by CD25, CD39, FoxP3, CTLA4, and GITR expression, were significantly decreased in stable MS patients as compared to healthy donors, but, surprisingly, restored to normal levels during an acute clinical attack. We conclude that Treg cells are not involved in causing clinical relapses, but rather react to inflammation in the attempt to restore homeostasis

Skeletal muscle fibers synthesis in heart failure: role of PGC-1 alpha, calcineurin and GH

Background: Patients with congestive heart failure (CHF) have decreased exercise capacity because of muscle fatigability. Symptoms are due to a specific myopathy with increased expression of fast type 11 fibres, fast MHCs and muscle atrophy. PGC-1 alpha, a potent transcriptional coactivator for nuclear receptors, induces mitochondrial myogenesis and the preferential synthesis of slow fibres. IGF1-Calcineurin stimulation can lead to increased expression of PGC-1 alpha. Methods: We investigated the levels of PGC-1 alpha during progression and regression of skeletal myopathy in the soleus muscle of rats with right heart failure secondary to monocrotaline-induced pulmonary hypertension. We used GH to stimulate the IGF1-calcineurin-PGC-1 alpha axis. Results: The slow MHC1 decreased from 90.6 +/- 0.5 to 71.7 +/- 2.2 in the CHF rats (p<0.00001) and increased to 82.1 +/- 1.8 after GH (p<0.00002). Western blot analysis showed that PGC-1 alpha is significantly decreased in CHF, while it came back to control values after GH. Cytochrome c was decreased in CHF and returned to control values with GH. Troponin I was expressed solely as slow isoform in the control soleus, while the fast isoform appeared in CHF. Its expression returned to control values after GH. Conclusions: We conclude that PGC-1 alpha plays an important role in regulating slow fibres expression. PGC1-1 alpha is in turn regulated by the IGF1-calcineurin axis. GH by increasing the circulating levels of IGF1, enhanced the expression of slow MHC1, TnI and the synthesis of mitochondria. (c) 2005 Elsevier Ireland Ltd. All rights reserved

ATROPHY, PROTEIN OXIDATION AND CELLULAR STRESS RESPONSE OF DISUSED HUMAN SKELETAL MUSCLE. THE OSMA BED-REST STUDY - VALDOLTRA 2007.

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Skeletal muscle myofibrillar protein oxidation in heart failure and the protective effect of Carvedilol

Heart failure is characterized by limited exercise tolerance and by a skeletal muscle myopathy with atrophy and shift toward fast fibres. An inflammatory status with elevated pro-inflammatory cytokines and exaggerated free radicals production, can worsen muscle damage. In a well established model of heart failure, the monocrotaline treated rat, we show that CHF is accompanied by oxidation of the skeletal muscle actin, tropomyosin and myosin, which further depresses muscle function and exercise capacity. We have also tested the efficacy of Carvedilol, a non-selective beta(1)-beta(2)-blocker, which has been widely used in clinical trials to improve exercise tolerance and reduce mortality in moderate and severe CHF, in preventing contractile protein oxidation in CHF rats. As comparison we used Bisoprolol a beta(1) selective agent, without known anti-oxidative properties. Carvedilol at the dose of 2 mg/kg per day was able to prevent the myofibrillar protein oxidation, while Bisoprolol (0.1 mg/kg) did it only partially, as demonstrated by the oxyblot analysis. While Carvedilol improved force production on isolated muscles, Bisoprolol did not. After the COMET trial, the anti-oxidative capacity of Carvedilol has been invoked as one of the mechanism that makes this drug superior to other selective beta-blockers in the treatment of CHF. One of the reason of Carvedilol superiority could be the effect on skeletal muscle with reduction of contractile protein peroxidation, amelioration of muscle function and improvement of exercise tolerance. Inhibition of reactive oxygen species (ROS) production, and of pro-inflammatory cytokines may also lead to a decreased muscle wastage, another factor contributing to worsening of exercise tolerance

A transient antioxidant stress response accompanies the onset of disuse atrophy in human skeletal muscle

It is presently unknown whether oxidative stress increases in disused skeletal muscle in humans. Markers of oxidative stress were investigated in biopsies from the vastus lateralis muscle, collected from healthy subjects before [time 0 (T0)], after 1 wk (T8), and after 5 wk (T35) of bed rest. An 18% decrease in fiber cross-sectional area was detected in T35 biopsies (P<0.05). Carbonylation of muscle proteins significantly increased about twofold at T35 (P<0.02) and correlated positively with the decrease in fiber cross-sectional area (P=0.04). Conversely, T8 biopsies showed a significant increase in protein levels of heme oxygenase-1 and glucose-regulated protein-75 (Grp75)/mitochondrial heat shock protein-70, two stress proteins involved in the antioxidant defense (P<0.05). Heme oxygenase-1 increase, which involved a larger proportion of slow fibers compared with T0, appeared blunted in T35 biopsies. Grp75 protein level increased threefold in T8 biopsies and localized especially in slow fibers (P<0.025), to decrease significantly in T35 biopsies (P<0.05). Percent change in Grp75 levels positively correlated with fiber cross-sectional area (P=0.01). Parallel investigations on rat soleus muscles, performed after 1-15 days of hindlimb suspension, showed that Grp75 protein levels significantly increased after 24 h of unloading (P = 0.02), i.e., before statistically significant evidence of muscle atrophy, to decrease thereafter in relation to the degree of muscle atrophy (P=0.03). Therefore, in humans as in rodents, disuse muscle atrophy is characterized by increased protein carbonylation and by the blunting of the antioxidant stress response evoked by disuse

A transient antioxidant stress response accompanies the onset of disuse atrophy in human skeletal muscle

It is presently unknown whether oxidative stress increases in disused skeletal muscle in humans. Markers of oxidative stress were investigated in biopsies from the vastus lateralis muscle, collected from healthy subjects before [time 0 (T0)], after 1 wk (T8), and after 5 wk (T35) of bed rest. An 18% decrease in fiber cross-sectional area was detected in T35 biopsies (P < 0.05). Carbonylation of muscle proteins significantly increased about twofold at T35 (P < 0.02) and correlated positively with the decrease in fiber cross-sectional area (P = 0.04). Conversely, T8 biopsies showed a significant increase in protein levels of heme oxygenase-1 and glucose-regulated protein-75 (Grp75)/mitochondrial heat shock protein-70, two stress proteins involved in the antioxidant defense (P < 0.05). Heme oxygenase-1 increase, which involved a larger proportion of slow fibers compared with T0, appeared blunted in T35 biopsies. Grp75 protein level increased threefold in T8 biopsies and localized especially in slow fibers (P < 0.025), to decrease significantly in T35 biopsies (P < 0.05). Percent change in Grp75 levels positively correlated with fiber cross-sectional area (P = 0.01). Parallel investigations on rat soleus muscles, performed after 1-15 days of hindlimb suspension, showed that Grp75 protein levels significantly increased after 24 h of unloading (P = 0.02), i.e., before statistically significant evidence of muscle atrophy, to decrease thereafter in relation to the degree of muscle atrophy (P = 0.03). Therefore, in humans as in rodents, disuse muscle atrophy is characterized by increased protein carbonylation and by the blunting of the antioxidant stress response evoked by disuse