Carbonylation of α-actin (A) and CK (B), depicted as ratio of carbonylated protein to total protein, are inversely correlated to peak tetanic force development.

<p>Sedentary+NaCl n = 7, Sedentary+TNF- α n = 8, Exercise+NaCl n = 8, Exercise+TNF- α n = 7.</p

Working model for the TNF-α induced loss of contractile force in the diaphragm occurring after 24 hours and its prevention by exercise training.

<p>Thin lines indicate that these pathways are probably not involved in the TNF-α induced loss in diaphragmatic force as far as supported by our data.</p

2-D gel electrophoresis (A) revealed 2.6-fold increase in carbonylated α-actin and carbonylated CK, depicted as a ratio of carbonylated α-actin to total α-actin or carbonylated CK to total CK, respectively.

<p>Exercise training diminished the carbonylation of α-actin and CK (B and C). In D and E the results of the MALDI TOF analyses are depicted confirming that the spots are α-actin and CK. KO = sedentary mice, ET = exercised mice. Sedentary+NaCl n = 7, Sedentary+TNF- α n = 8, Exercise+NaCl n = 8, Exercise+TNF- α n = 7.</p

Force development is impaired in sedentary animals treated with TNF-α as shown by the force-frequency-relation (A).

<p>Specific peak tetanic force development (B) is reduced by ∼42% due to a single intraperitoneal TNF-α administration. This loss of force can be almost prevented by extensive exercise training four weeks prior to TNF-α administration. Power of the diaphragm is also reduced in sedentary mice by TNF-α, but this can be essentially prevented by exercise training (C and D). *p<0.01 vs. sedentary+NaCl and exercise+TNF-α; n = 10 per group.</p

Trypsin-like (A) and peptidylglutamyl-hydrolizing activity of the proteasome (B) is enhanced by TNF-α in sedentary mice whereas no increase is detectable in exercise trained animals.

<p>Chemotryptic activity is not affected by both exercise and TNF-α (C). Neither TNF-α nor exercise training changed the activity of Calpain significantly (D). *p<0.05 vs. sedentary+NaCl and exercise+TNF-α, n = 10 per group.</p

Possible sources of ROS: Activity of NAD(P)H oxidase (A) is induced by TNF-α in both sedentary and exercise trained animals.

<p>In contrast, activity of xanthine oxidase (B) and mitochondrial derived ROS, indirectly measured as the ratio of aconitase to fumarase activity (C), were only altered in sedentary mice treated with TNF-α whereas exercise training prevented an increase in xanthine oxidase activity or an inhibition of aconitase/fumarase activity via mitochondrial ROS by TNF-α. *p<0.05 vs. sedentary+NaCl, §p<0.05 vs. exercise+NaCl, $p<0.05 vs. sedentary+NaCl and exercise+TNF-α, n = 10 per group.</p

Exercise Training Prevents TNF-α Induced Loss of Force in the Diaphragm of Mice

<div><h3>Rationale</h3><p>Inflammatory cytokines like tumor necrosis factor alpha (TNF-α) are elevated in congestive heart failure and are known to induce the production of reactive oxygen species as well as to deteriorate respiratory muscle function.</p> <h3>Objectives</h3><p>Given the antioxidative effects of exercise training, the aim of the present study was to investigate if exercise training is capable of preventing a TNF-α induced loss of diaphragmatic force in mice and, if so, to elucidate the potential underlying mechanisms.</p> <h3>Methods</h3><p>Prior to intraperitoneal injection of TNF-α or saline, C57Bl6 mice were assigned to four weeks of exercise training or sedentary behavior. Diaphragmatic force and power generation were determined in vitro. Expression/activity of radical scavenger enzymes, enzymes producing reactive oxygen species and marker of oxidative stress were measured in the diaphragm.</p> <h3>Main Results</h3><p>In sedentary animals, TNF-α reduced specific force development by 42% concomitant with a 2.6-fold increase in the amount of carbonylated α-actin and creatine kinase. Furthermore, TNF-α led to an increased NAD(P)H oxidase activity in both sedentary and exercised mice whereas xanthine oxidase activity and intramitochondrial ROS production was only enhanced in sedentary animals by TNF-α. Exercise training prevented the TNF-α induced force reduction and led to an enhanced mRNA expression and activity of glutathione peroxidase. Carbonylation of proteins, in particular of α-actin and creatine kinase, was diminished by exercise training.</p> <h3>Conclusion</h3><p>TNF-α reduces the force development in the diaphragm of mice. This effect is almost abolished by exercise training. This may be a result of reduced carbonylation of proteins due to the antioxidative properties of exercise training.</p> </div

The mRNA and protein expression of MurF1 (A and B) and MafBx (C and D) is not affected by TNF-α or exercise training.

<p>The mRNA and protein expression of MurF1 (A and B) and MafBx (C and D) is not affected by TNF-α or exercise training.</p

Total CK activity (A) in the diaphragm is reduced in sedentary animals treated with TNF-α compared to sham treated sedentary animals and TNF-α treated exercise trained animals.

<p>Activity of CK is correlated to peak tetanic force development (B). *p<0.05 vs. sedentary+NaCl and exercise+TNF-α; n = 10 per group.</p

mRNA expression (A) and activity (B) of glutathione peroxidase (GPX) is induced by exercise training but not by TNF-α.

<p>Expression and activity of catalase is not influenced by exercise training or TNF-α administration (C; D). The activity of total superoxide dismutase (SOD) and manganese superoxide dismutase (Mn-SOD) is not affected by exercise training or TNF-α administration (E, F). *p<0.01 vs. sedentary+NaCl, §p<0.05 vs. sedentary+TNF-α, n = 10 per group.</p