Effects of nuclear factor-kappa B on regulation of cytokine expression and apoptosis in bovine monocytes exposed to Mycobacterium avium subsp paratuberculosis

Objective-To evaluate the role of the nuclear factor-kappa B (NF-kappa B) in the response of bovine monocytes to exposure to Mycobacterium avium subsp paratuberculosis (MAP). Sample Population-Monocytes from healthy adult Holstein cows that were known to be negative for MAP infection. Procedures-Monocytes were incubated with MAP organisms with or without a specific inhibitor of the NF-kappa B pathway (pyrrolidine dithiocarbamate), and activation of the NF-kappa B pathway was detected by use of an electrophorectic mobility shift assay. The capacities of monocytes to express tumor necrosis factor (TNF)-alpha, interleukin (IL)-10, and IL-12; to acidify phagosomes; to phagocytize and kill MAP organisms; and to undergo apoptosis were evaluated. Results-Addition of MAP organisms to monocytes activated the NF-kappa B pathway as indicated by increased NF-kappa B-DNA binding. Addition of pyrrolidine dithiocarbamate prevented nuclear translocation of NF-kappa B, decreased expression of TNF-alpha and IL-10, and increased IL-12 expression. Treatment of MAP-exposed monocytes with pyrrolidine dithiocarbamate increased the rate of apoptosis but failed to alter phagosome acidification, organism uptake, or organism killing by those cells. Conclusions and Clinical Relevance-Results indicated that NF-kappa B rapidly translocated to the nucleus after exposure of bovine monocytes to MAP organisms. These data suggest that NF-kappa B is involved in initiation of inflammatory cytokine transcription and inhibition of apoptosis but that it is not directly involved in phagosome acidification or organism killing.