Abstract
BackgroundNecrosis of alveolar macrophages following Mycobacterium tuberculosis infection has been demonstrated to play a vital role in the pathogenesis of tuberculosis. Our previous study demonstrated that Wnt/β-catenin signaling was able to promote mycobacteria-infected cell apoptosis by a caspase-dependent pathway. However, the functionality of this signaling in the necrosis of macrophage following mycobacterial infection remains largely unknown.MethodsMurine macrophage RAW264.7 cells were infected with Bacillus Calmette-Guerin (BCG) in the presence of Wnt/β-catenin signaling. The necrotic cell death was determined by cytometric assay and electronic microscopy; the productions of reactive oxygen species (ROS) and reduced glutathione (GSH) were measured by a cytometric analysis and an enzyme-linked immunosorbent assay, respectively; and the activity of poly (ADP-ribose) polymerase 1 (PARP-1)/apoptosis inhibition factor (AIF) signaling was examined by an immunoblotting assay.ResultsThe BCG can induce RAW264.7 macrophage cells necrosis in a dose- and time-dependent manner along with an accumulation of reactive oxygen species (ROS). Intriguingly, an enhancement of Wnt/β-catenin signaling shows an ability to reduce the mycobacteria-induced macrophage necrosis. Mechanistically, the activation of Wnt/β-catenin signaling is capable of inhibiting the necrotic cell death in BCG-infected RAW264.7 cells through a mechanism by which the Wnt signaling scavenges intracellular ROS accumulation and increases cellular GSH concentration. In addition, immunoblotting analysis further reveals that Wnt/β-catenin signaling is capable of inhibiting the ROS-mediated cell necrosis in part through a PARP-1/AIF- dependent pathway.ConclusionsAn activation of Wnt/β-catenin signaling can inhibit BCG-induced macrophage necrosis by increasing the production of GSH and scavenging ROS in part through a mechanism of repression of PARP-1/AIF signaling pathway. This finding may thus provide an insight into the underlying mechanism of alveolar macrophage cell death in response to mycobacterial infection.
Highlights
Necrosis of alveolar macrophages following Mycobacterium tuberculosis infection has been demonstrated to play a vital role in the pathogenesis of tuberculosis
Bacillus Calmette-Guerin (BCG) induced-RAW264.7 cell necrosis can be inhibited by an activation of Wingless-type MMTV integration site family (Wnt)/β-catenin signaling In order to evaluate the necrosis of macrophages in response to mycobacterial infection, the murine alveolar RAW264.7 macrophage cells were infected with BCG at different dosages for varied time points
Quantitative analysis demonstrated that the addition of Wnt3a-CM significantly could inhibit the BCG-infected cells to necrotic cell death, in comparison with the control-CM treated cells when the necrotic cell numbers were determined by an EM morphology (p < 0.01) (Figure 2B)
Summary
Necrosis of alveolar macrophages following Mycobacterium tuberculosis infection has been demonstrated to play a vital role in the pathogenesis of tuberculosis. Our previous study demonstrated that Wnt/βcatenin signaling was able to promote mycobacteria-infected cell apoptosis by a caspase-dependent pathway. The functionality of this signaling in the necrosis of macrophage following mycobacterial infection remains largely unknown. Necrotic death has been suggested to play a central role in the pathogenesis of TB, an inhibition of Mtb-infected cell necrosis is vital to the pathogenesis of TB disease. Several lines of recent studies suggested that necrosis could follow a strictly programmed and ordered series of events [3,4], the precise mechanism underlying the necrosis of Mtb-infected host cells remains largely unknown
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
