Disruption of the actin cytoskeleton results in nuclear factor-kappaB activation and inflammatory mediator production in cultured human intestinal epithelial cells.

The cytoskeleton in eukaryotic cells is composed of two major filament systems, the microtubule system and the actin cytoskeleton. The microtubule system has recently emerged as an important regulator of NF-kappaB function. However, the role that the actin microfilament system plays in controlling NF-kappaB activation is incompletely understood. In this study, we examined the effect of actin cytoskeleton disruption on NF-kappaB activation in human intestinal epithelial cells. Treatment of HT-29 or Caco-2 cells with the prototypic actin disrupting agents cytochalasin D or latrunculin B resulted in increased NF-kappaB DNA binding and NF-kappaB-dependent transcriptional activity. This NF-kappaB activation by cytochalasin D was secondary to an effect on IkappaB, because cytochalasin D-induced IkappaB degradation and the cytochalasin D-induced increase in NF-kappaB-dependent transcriptional activity was prevented by a dominant negative IkappaB mutant. Exposure of the cells to cytochalasins or latrunculin B increased gene expression and release of the NF-kappaB-dependent chemokines IL-8 and GRO-alpha. Cytochalasin D also activated p38 MAP kinase, which pathway contributed to the cytochalasin D-induced increase in IL-8 production. These results demonstrate that the actin cytoskeleton plays an important role in the regulation of NF-kappaB activation and inflammatory events in intestinal epithelial cells.