BACKGROUND: Tumor necrosis factor alpha (TNF-α) has been implicated in loss of muscle mass in chronic obstructive pulmonary disease and other consumptive processes. TNF-α production would be related to inflammation arising from pulmonary disease itself or, alternatively, from smoking, and would be carried to the muscle through the blood stream. However, it has also been suggested that TNF-α may be expressed directly in muscle tissue. Regardless the site of production of TNF-α, its relation to subsequent muscle damage is unclear. OBJECTIVE: We studied the expression of TNF-α and an interleukin inhibitor of its production (IL-10) in the main respiratory muscles and a peripheral muscle in the dog. METHOD: Nine young, male Beagle dogs were included. From all animals we obtained a biopsy of the diaphragm (Dph) and external intercostal (ExtI) muscles and a leg muscle (internal vastus of the quadriceps, IntV). TNF-α and IL-10 gene expressions were measured through the analysis of messenger RNA levels, using reverse transcription and polymerase chain reaction. We also assessed sarcolemmal damage using intracellular fibronectin detection (immunohistochemistry). RESULTS: The expression of both cytokines showed wide interindividual variability. On the one hand, TNF-α (was very low in Dph and ExtI (0.02 ± 0.03 and 0.05 ± 0.06 a.u., respectively), but relatively high in the IntV (0.14 ± 0.08 a.u.). IL-10 expression, on the other hand was low in the Dph (0.06 ± 0.05 a.u.) and slightly higher in the ExtI (2.7 ± 1.9 a.u., p < 0.01) and IntV (1.6 ± 1.7 a.u.). Sarcolemmal damage was minimal in all three muscles and was related to TNF-α expression in the peripheral muscle (r = 0.682, p < 0.05). CONCLUSIONS: 1) TNF-α and IL-10 appear to be constitutively expressed within the skeletal muscle in dogs. 2) Basal TNF-α expression is lower in respiratory muscles than in peripheral muscles. 3) The expression in the latter is related to membrane damage.
|Journal||Archivos de Bronconeumologia|
|Publication status||Published - 1 Jan 2002|
- Peripheral muscles
- Respiratory muscles