Individuals exposed to dusts from concentrated animal feeding operations report increased numbers of respiratory tract symptoms and bronchoalveolar lavage samples from such individuals demonstrate elevated lung inflammatory mediators, including interleukin (IL)-8 and IL-6. We previously found that exposure of bronchial epithelial cells to hog barn dusts resulted in a protein kinase C (PKC) -dependent increase in IL-6 and IL-8 release. We hypothesized that cattle feedlot dusts would also generate bronchial epithelial interleukin release in vitro. To test this, we used interleukin ELISAs and direct PKC isoform assays. We found that a dust extract from cattle feedlots (FLDE) augments PKC activity of human bronchial epithelial cells in vitro. A 5-10% dilution of FLDE stimulated a significant release of IL-6 and IL-8 at 6-24 hr in a PKC-dependent manner vs. control medium-treated cells. An increase in PKC alpha activity was observed with 1 hr of FLDE treatment and PKC epsilon activity was elevated at 6 hr FLDE exposure. The PKC alpha inhibitor, Go 6976, did not inhibit FLDE-stimulated IL-8 and IL-6 release. However, the PKC epsilon inhibitor, Ro 31-8220, effectively inhibited FLDE-stimulated IL-8 and IL-6 release. Inhibition of FLDE-stimulated IL-6 and IL-8 was confirmed in a dominant negative PKC epsilon expressing BEAS-2B cell line, but not observed in a PKC alpha dominant negative BEAS-2B cell line. These data support the hypothesis that FLDE exposure stimulates bronchial epithelial IL-8 and IL-6 release via a PKC epsilon-dependent pathway.