Mycobacterium bovisBacillus Calmette-Guérin Induces CCL5 Secretion via the Toll-Like Receptor 2-NF-κB and -Jun N-Terminal Kinase Signaling Pathways

In response toMycobacterium bovis bacillus Calmette-Guérin (BCG), CC chemokines are secreted from host cells to attract components of the innate and adaptive immune systems to the site of infection. Toll-like receptor 2 (TLR2) has been shown to recognizeM. bovis BCG and to initiate signaling pathways that result in enhanced secretion of CC chemokines. Despite the essential requirement of TLR2 inM. bovis BCG infection, the mechanisms by which it induces secretion of CC chemokines are not well defined. In this study, we report that stimulation of HEK293 cells expressing human TLR2 withM. bovis BCG resulted in increased CCL2 and CCL5 secretion, as determined by an enzyme-linked immunosorbent assay.M. bovis BCG infection resulted in the activation of c-Jun N-terminal kinase (JNK), and the inhibition of JNK activity had a significant effect onM. bovis BCG-dependent CCL5 secretion in TLR2-expressing cells but no effect onM. bovis BCG-dependent CCL2 secretion from infected HEK293 cells expressing human TLR2. TheM. bovis BCG-induced CCL5 release was attenuated by sulfasalazine (a well-described inhibitor of NF-κB activity), BAY 11-7082 (an IκB phosphorylation inhibitor), and ALLN (a well-described inhibitor of NF-κB activation that prevents degradation of IκB and eventually results in a lack of translocated NF-κB in the nucleus). In addition, stimulation of TLR2-expressing cells withM. bovis BCG resulted in translocation of NF-κB subunits from the cytoplasmic to the nuclear fraction, and stimulation of cells withM. bovis BCG activated IκB kinase αβ. These findings indicate thatM. bovis BCG induces CCL5 production through mechanisms that include a TLR2-dependent component that requires JNK and NF-κB activities.