Peripheral nerve injury induces endoneurial expression of IFN-gamma, IL-10and TNF-alpha mRNA

Axotomy of a peripheral nerve leads to interruption of axon continuity with Wallerian degeneration in the distal segment and regenerative events in th e proximal remaining neuron. Local inflammation is a consequence of trauma in general and signal molecules regulating inflammation, such as cytokines, participate in the outcome of nerve trauma. We studied a broad set of pote nt immunoregulatory cytokines after transection of rat sciatic nerve. The e ndoneurium of the transected rat sciatic nerve was taken from both proximal and distal stumps. The pooled endoneurium of 6 rats was studied using reve rse transcription polymerase chain reaction (RT-PCR) after 14 h; 1, 3, 5, 7 days; 2 and 4 weeks after transection. A new observation was that TNF-alph a mRNA showed phasic expression pattern; three distinct peaks were seen, im mediately (14 h), after 5 days and in the distal part also after 2 weeks. T his phenomenon may be related to the breakdown of the blood-nerve barrier a nd to the recruitment of circulating macrophages. We further noticed that I FN-gamma mRNA was expressed between 5 days and 2 weeks. This suggests that T-cells may also take part in the regenerative processes. Furthermore, we o bserved that IL-IO mRNA is expressed continuously during Wallerian degenera tion. The continuous expression of IL-10 mRNA may attenuate the production of inflammatory cytokines by macrophages and other cells. (C) 2000 Elsevier Science B.V. All rights reserved.