Regulation of airway epithelial cell NF-κB-dependent gene expression by protein kinase Cδ

Airway epithelial cells synthesize proinflammatory molecules such as IL-8, GM-CSF, RANTES, and ICAM-1, the expression of which is increased in the airways of patients with asthma. We investigated the regulation of these NF-kappaB-dependent genes by the novel protein kinase C (PKC) isoform PKCdelta in 16HBE14o- human airway epithelial cells, focusing on IL-8 expression. Transient transfection with the constitutively active catalytic subunit of PKCdelta (PKCdelta-CAT), and treatment with bryostatin 1, an activator of PKCdelta, each increased transcription from the IL-8 promoter, whereas overexpression of PKCepsilon had minor effects. Expression of a dominant negative PKCdelta mutant (PKCdelta-KR) or pretreatment of cells with rottlerin, a chemical PKCdelta inhibitor, attenuated TNF-alpha- and phorbol ester-induced transcription from the IL-8 promoter. Bryostatin 1 treatment increased IL-8 protein abundance in primary airway epithelial cells. Selective activation of PKCS by bryostatin also activated NF-kappaB, as evidenced by p65 RelA and p50 NF-kappaB1 binding to DNA, NF-kappaB trans-activation, and IkappaB degradation. The sufficiency of PKCdelta to induce NF-kappaB nuclear translocation and binding to DNA was confirmed in a 16HBE14o- cell line inducibly expressing PKCS-CAT under the tet-off system. Deletion of the NF-kappaB response element severely attenuated PKCS-induced IL-8 promoter activity. Finally, PKCdelta-CAT induced transcription from the GM-CSF, RANTES, and ICAM-1 promoters. Together these data suggest that PKCdelta plays a key role in the regulation of airway epithelial cell NF-kappaB-dependent gene expression.