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

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-κB) 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 IκB and p65 NF-κB signalling proteins in SCs. Phospho NF-κB-p65 was localised to the nucleus indicating activation of NF-κB. To assess the functional effect of NF-κB activation, SCs plated on PDL or laminin were pre-treated with NF-κB 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 24 h 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 ± 8.53 μm) compared with those cultured in the presence of SCs and PDL (1.26 ± 0.07 neurites; 157.57 ± 9.80 μm). At 72 h, neurite length had further increased to 321.83 ± 6.60 μm in the presence of SCs and laminin. Inhibition of NF-κB completely abolished the effect of laminin on SC evoked neurite outgrowth at 24 h and reduced the enhancement of neurite length by over 60% at 72 h. SC proliferation was unaffected by NF-κB inhibition suggesting that the NF-κB signalling pathway plays a discrete role in the activation of SCs and their neurotrophic potential.