Figure 1. Proinflammatory cytokines stimulate a transient reorganization of the neuronal cytoskeleton.

Serum-starved SH-SY5Y human neuroblastoma cells grown on collagen were incubated with proinflammatory cytokines (200 ng/ml, 10 μl/500 μl medium) or PBS (10 μl/500 μl medium) either for 15 min (A–C) or 30 min (D–F) and immediately thereafter fixed with fixed paraformaldehyde fixation. Actin filaments were labeled with rhodamine phalloidin followed by confocal imaging. (A and D) Under control conditions (PBS), SH-SY5Y cells exhibited an atrophic, condensed morphology with virtually no lamellipodia or membrane ruffles, which persisted over time. (B) In contrast, exposure to 200 ng/ml TNFα for 15 min resulted in lamellipodia formation, membrane ruffling, and cell spreading (arrowheads). (C) Similarly, 200 ng/ml Il-1β for 15 min induced lamellipodia formation and membrane ruffling (arrowheads). (E) However after a 30 min in the presence of 200 ng/ml TNFα, SH-SY5Y cells resumed their atrophic, condensed morphology devoid of lamellipodia and membrane ruffles. The extent of lamellipodia formation and cell spreading was indistinguishable from controls. (F) SH-SY5Y cells also reverted to their original atrophic, condensed morphology after 30 min in the presence of or 200 ng/ml Il-1β. (Scale bar = 10 μm)