Visit our Expo - Redox and Inflammation signaling 2012

Session XVII : Cell signaling in health and disease Poster XVII, 12
Are key factors of signalling intracellular pathways involved in the regulation of
neuromuscular changes after disuse conditions ?
Erwan Dupont, Marie-Hélène Canu, Maurice Falempin, Yvonne Mounier and Laurence
Stevens
Laboratoire de Plasticité Neuromusculaire, EA 1032, IFR 118, Unité de Neurosciences et
Physiologie Adaptatives, Bât SN4, Université des Sciences et Technologies de Lille,
59655 Villeneuve d’Ascq cedex, France
The performance of the neuromuscular system is highly dependent on activity. A situation of
disuse induced by hypodynamia-hypokinesia (HH) in rats induces profound changes in
skeletal muscles like phenotype transformations, and a marked atrophy resulting from a loss
in mass and protein content. HH is also a model of hindpaw sensory deprivation since in these
conditions, the cutaneous receptors located on the foot sole are deactivated. HH produces a
cortical reorganisation of the somatosensory cortex (SmI), indicating the existence of a
neuronal plasticity.
The factors responsible for these impairments are still unknown and the cellular and
molecular processes sustaining this “plasticity” are not well described. The major aims here
were to better understand the mechanisms i) that characterized muscular plasticity,
phenotypical transitions and atrophy, and ii) involved in cortical plasticity (sensory
conduction and/or cortical excitability changes, regulation of neurotransmitter and
neurotrophin expression). Among multiple intracellular signalling pathways, one major is
implied in controlling more specifically muscle and/or nervous plasticity : the MAPKinase
(Mitogen-Activated Protein Kinase) cascade. We induced modulations of transformations
using different periods of disuse (from 7 to 28 days of HH) in rats. Key markers of
MAPKinase cascade were followed : ERK, JNK and p38. Their protein expressions were
evaluated by western blots (using specific antibodies) performed on all the animal groups, as
well at the muscular as at the cortical levels. For the muscles, the expression of all MAPK
markers was increased in a time-dependent manner of disuse, excepted for 14 days of HH, the
increase being lower than for 7 and 28 days. At the cortical level, the increase was less
pronounced and not disuse-dependent.
Taken together, these results may help to develop strategies that aim at attenuating the effects
of pathologies, like long-term immobilizations, on the neuromuscular system.
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