Mycobacterium tuberculosis 38-kDa antigen induces endoplasmic reticulum stress-mediated apoptosis via toll-like receptor 2/4

Abstract

Endoplasmic reticulum (ER) stress responses play critical roles in the pathogenesis of tuberculosis. To investigate the regulatory role of the ER stress response in 38-kDa antigen-induced apoptosis, we examined the relationship between the ER stress response and apoptosis in bone marrow-derived macrophages (BMDMs) stimulated with Mycobacterium tuberculosis antigen (38-kDa Ag). The expression of ER molecular chaperones, including C/EBP homologous protein (CHOP), glucose-regulated protein (Bip) and phosphorylated alpha subunit of eukaryotic initiation factor 2, was induced in BMDMs stimulated with the 38-kDa Ag. Interestingly, 38-kDa Ag-stimulation induced apoptosis via activation of caspase-12, -9 and -3. However, 38-kDa Ag-induced apoptosis was significantly reduced in TLR2- and TLR4-deficient macrophages. Because toll-like receptors (TLRs) initiate the activation of mitogen-activated protein kinase (MAPK) signaling cascades, we evaluated the effect of MAPK activation on ER stress. The 38-kDa Ag activated Jun N-terminal kinase, extracellular signal-regulated kinase and p38 phosphorylation. MAPK signaling induced the secretion of proinflammatory cytokines such as MCP-1, TNF-α and IL-6. The 38-kDa Ag-induced MCP-1 was especially associated with the induction of MCP-1-induced protein (MCPIP), which increased the generation of reactive oxygen species (ROS) and ER stress. To investigate the role of MCPIP in ROS-induced ER stress by 38-kDa Ag stimulation, we transfected MCPIP siRNA into RAW264.7 cells before 38-kDa Ag stimulation, and measured the generation of ROS and expression of ER molecular chaperones. ROS production and CHOP expression were decreased by the silencing of MCPIP induction. Our results demonstrate that the expression of MCPIP by 38-kDa Ag stimulation is increased through a TLR-MAPK-dependent signaling pathway, and leads to ER stress-induced apoptosis. In conclusion, MCPIP is important for host defense mechanisms in mycobacterial pathogenesis.

Controlled Mycobacterium tuberculosis infection in mice under treatment with anti-IL-17A or IL-17F antibodies, in contrast to TNFα neutralization

“…Other modulated gene expression patterns have been noted (e.g. increased expression of Irg1 52, Ltb4r 47, Ctla4 , Pdcd1 (PD-1), Cd274 (PD-L1), Lag3 , Socs3 , Zc3h12a (MCPIP)53; decreased expression of Pparg ) (Fig. 2E,G; Supplementary Fig.…”

“…2D,G; Supplementary Fig. 4A,B) following anti-TNFα treatment, both induced by M. tuberculosis 38-kDa antigen in vitro 53, and indicative of monocyte recruitment and macrophage M2 polarization62, respectively. MCPIP1, recently shown to negatively regulate IL-17-mediated signaling and inflammation63, may be one of several immunoregulatory factors engaged in containing infection and limiting host pathology.…”

“…increased expression of Irg1 , Ltb4r1 , Il10 , Il1rn , Ctla4 , Pdcd1 (PD-1), Cd274 (PD-L1), Lag3 , Socs3 ); decreased expression of Pparg )47525354 (Fig. 2E–G; Supplementary Fig.…”

The Role of Prostate Apoptosis Response-4 (Par-4) in Mycobacterium tuberculosis Infected Macrophages

“…NF-κB activation is not only associated with Par-4 production, but also with infection control1415. Importantly, ROS induce ER stress and lead to NF-κB activation during mycobacterial infection2324. These data suggest that mycobacteria-mediated ROS generation is important for inducing Par-4 mediated apoptosis through ER stress activation.…”

“…Mtb -induced GRP78 raised the possibility that it binds to Par-4, and GRP78/Par-4 complex is localized at plasma membrane of macrophage. Previously, we suggested that ER stress induced by infection or antigen stimulation of mycobacteria is important to regulate apoptotic cell death112324. GRP78 localized to the plasma membrane acts as a receptor for extracellular Par-4 leading to activation of apoptosis via mitochondrial release of cytochrome C and caspase activation25.…”