Neuropathic pain may arise following
peripheral nerve injury though the molecular mechanisms associated with this are unclear. We used proteomic profiling to examine changes in
protein expression associated with the formation of hyper-excitable
neuromas derived from rodent saphenous nerves. A two-dimensional difference gel electrophoresis (2D-DIGE) profiling strategy was employed to examine
protein expression changes between developing
neuromas and normal nerves in whole tissue lysates. We found around 200
proteins which displayed a >1.75-fold change in expression between
neuroma and normal nerve and identified 55 of these
proteins using mass spectrometry. We also used immunoblotting to examine the expression of low-abundance
ion channels Nav1.3, Nav1.8 and
calcium channel alpha2delta-1 subunit in this model, since they have previously been implicated in neuronal hyperexcitability associated with
neuropathic pain. Finally, S35methionine in vitro labelling of
neuroma and control samples was used to demonstrate local
protein synthesis of neuron-specific genes. A number of
cytoskeletal proteins,
enzymes and
proteins associated with oxidative stress were up-regulated in
neuromas, whilst overall levels of voltage-gated
ion channel proteins were unaffected. We conclude that altered
mRNA levels reported in the somata of damaged DRG neurons do not necessarily reflect levels of altered
proteins in hyper-excitable damaged nerve endings. An altered repertoire of
protein expression, local
protein synthesis and topological re-arrangements of
ion channels may all play important roles in
neuroma hyper-excitability.