Laminin activates NF-kappaB in Schwann cells to enhance neurite outgrowth

Abstract

Extracellular matrix (ECM) molecules and Schwann cells (SCs) are important components of peripheral nerve regeneration. In this study, the role of the transcription factor nuclear factor kappa B (NF-kappaB) in SC activation in response to laminin and the subsequent effect on in vitro neurite outgrowth was investigated. Immunocytochemistry and Western blot analysis showed that compared with poly-d-lysine (PDL), laminin enhanced the phosphorylation of IkappaB and p65 NF-kappaB signalling proteins in SCs. Phospho NF-kappaB-p65 was localised to the nucleus indicating activation of NF-kappaB. To assess the functional effect of NF-kappaB activation, SCs plated on PDL or laminin were pre-treated with NF-kappaB inhibitors, 6-amino-4-(4-phenoxyphenylethylamino)quinazoline (QNZ) or Z-leu-leu-leu-CHO (MG-132) before NG108-15 neuronal cells were seeded on the SC monolayer. After 24h co-culture in the absence of inhibitors, SCs seeded on laminin enhanced the mean number and length of neurites extended by NG108-15 cells (1.87+/-0.13 neurites; 238.74+/-8.53microm) compared with those cultured in the presence of SCs and PDL (1.26+/-0.07 neurites; 157.57+/-9.80microm). At 72h, neurite length had further increased to 321.83+/-6.60microm in the presence of SCs and laminin. Inhibition of NF-kappaB completely abolished the effect of laminin on SC evoked neurite outgrowth at 24h and reduced the enhancement of neurite length by over 60% at 72h. SC proliferation was unaffected by NF-kappaB inhibition suggesting that the NF-kappaB signalling pathway plays a discrete role in the activation of SCs and their neurotrophic potential.