Control mechanisms of degeneration and immune cell regulation after injury of peripheral nerves or spinal cord
Zusammenfassung der Projektergebnisse
The purpose of this project was to gain further information on the control of myelin breakdown and phagocytosis after nerve injury, a process essential for nerve regeneration. Earlier studies showed the influence of calcium-independent A2 (iPLA2) and calcium-dependent PLA2 (cPLA2) phospholipases, which stimulate macrophage recruitment and regulate myelin phagocytosis after nerve injury. So far, it is not known what triggers the expression and activation of these PLA2 enzymes. Our hypotheses are, that calcium-independent (iPLA2) could be regulated by injuryinduced cytokines. Since cPLA2 requires calcium for its activation, it is possible that the rapid influx of calcium into the axon immediately after peripheral nerve injury could also increase calcium into the paranodal loops of the myelin sheath via connexin 29 hemichannels that are located in the innermost aspect of the paranodes and juxtaparanodes. The specific aims of this ongoing study are assess the expression and role of proinflammatory cytokines and Cx29 in regulating cPLA2 and iPLA2 expression and activation using in vivo and in vitro models and thereby detect early triggering mechanisms. During the period of sponsorship, proinflammatory cytokines have been investigated on the mRNA expression level after sciatic nerve injury. Several cytokines, including TNFalpha, are upregulated as early as as 1 hour after injury. The effect of these cytokines in regulation of PLA2s on Schwann cell cultures will be investigated. Furthermore, sciatic nerve crush surgery has been performed in various mouse strains, including Cx32-/-, Cx29/-, Cx29/Cx32 double knockout mice and the respective controls. Tissue has been collected for electron microscopic investigations and fluorescence microscopy and will be analyzed shortly.
