Feedlot dust stimulation of interleukin-6 and -8 requires protein kinase C{varepsilon} in human bronchial epithelial cells

1 Pulmonary and Critical Care Medicine Section, Department of Internal Medicine, Omaha; 2 Research Service, Department of Veterans Affairs Medical Center, Omaha; 3 Texas A & M Agricultural Research & Extension Center, Amarillo, Texas; and 4 Department of Ophthalmology and Visual Sciences, Nebraska Medical Center, Omaha, Nebraska Submitted 16 March 2007 ; accepted in final form 21 August 2007 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 [feedlot dust extract (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 h in a PKC-dependent manner vs. control medium-treated cells. An increase in PKC activity was observed with 1 h of FLDE treatment, and PKC activity was elevated at 6 h of FLDE exposure. The PKC inhibitor, Gö-6976, did not inhibit FLDE-stimulated IL-8 and IL-6 release. However, the PKC 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 -expressing BEAS-2B cell line but not observed in a PKC 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 -dependent pathway. feedlot dust extract Address for reprint requests and other correspondence: D. J. Romberger, Research Service, VA Nebraska Western Iowa Health Care System (Omaha Div.), 4101 Woolworth Ave., Omaha, NE 68105 (e-mail: dromberg{at}unmc.edu )