Figure 11.

sTNFα promotes growth of CGRP⁺ neurites in an NF-κB -dependent manner. Dissociated adult DRGs plated on poly-L-lysine were incubated with just serum-free media or serum-free media containing sTNFα (50 ng/ml), the cell-permeable NF-κB inhibitor SN50 (10 μm), or both sTNFα and SN50 for 48 h. Cultures were stained to visualize CGRP⁺ neurons and their neurites. Compared with the growth seen in the control cultures (a), adding sTNFα to the culture media increases both the total CGRP⁺ growth per neuron (b, e) as well as the length of the longest neurite (f). While the presence of the NF-κB inhibitor SN50 alone did not negatively affect growth compared with control cultures (c, e, f), its presence did nullify the growth-promoting effects of sTNFα (d–f). These data indicate that sTNFα is also capable of directly promoting the growth of CGRP⁺ nociceptive sensory neurons. Data are mean ± SEM. *p < 0.05 (one-way ANOVA and post hoc Fisher's LSD tests). **p < 0.01 (one-way ANOVA and post hoc Fisher's LSD tests). ****p < 0.0001 (one-way ANOVA and post hoc Fisher's LSD tests). n = 30 neurons per condition. Scale bar, 50 μm.