TITLE:
A new feature of importance for the TNF-alpha system in inflammation—Bilateral myositis that develops early in response to unilateral overuse shows a marked involvement of TNF-alpha not only in the exercised side but also contralaterally
AUTHORS:
Lina Renström, Per Stål, Sture Forsgren
KEYWORDS:
TNF-Alpha; Muscle Overuse; Myositis; Soleus Muscle; Contralateral
JOURNAL NAME:
Modern Research in Inflammation,
Vol.2 No.4,
November
26,
2013
ABSTRACT: Using a rabbit model
leading to myositis in response to
exercise-induced muscle overuse, we have previously observed that
TNF-alpha is involved in the exercised muscle in early developing myositis as
well as both ipsiand contralaterally in the myositis which develops in response to a lengthened period of overuse.
It is unknown if TNF-alpha can also be engaged contralaterally in early stages
of myositis. The hypothesis was that this is the case. It was therefore
evaluated whether the TNF-alpha system is early involved contralaterally. An
experimental model of 1 week of overuse of the soleus muscle on one side
leading to myositis was used, and in situ hybridization and immunohistochemistry were
applied to study the expression patterns of TNF-alpha in the soleus
muscle in the contralateral side. TNF-alpha was expressed in the myositis
process which occurred contralaterally.
There were thus TNF-alpha mRNA reactions in the cells of the
inflammatory infiltrates, in blood vessel walls and in certain of the muscle
fibers. Parts of the latter were necrotic fibers, whereas others were
interpreted to be in a regenerative stage.
TNF-alpha immunoreactions were seen for infiltrating white blood cells. The
observations show that the TNF-alpha system is early involved in the cross-over
effects that occur in response to unilateral muscle overuse leading to myositis bilaterally. TNF-alpha is likely
to have pro-inflammatory and destructive effects but also to have effects in
the muscle regenerative processes. The occurrence of an early involvement of
the TNF-alpha system contralaterally to the injury side shows a new aspect of
importance of this system in inflammation.