S100A4 Promotes BCG-Induced Pyroptosis of Macrophages by Activating the NF-κB/NLRP3 Inflammasome Signaling Pathway.

Pyroptosis is a host immune strategy to defend against Mycobacterium tuberculosis (Mtb) infection. S100A4, a calcium-binding protein that plays an important role in promoting cancer progression as well as the pathophysiological development of various non-tumor diseases, has not been explored in Mtb-infected hosts. In this study, transcriptome analysis of the peripheral blood of patients with pulmonary tuberculosis (PTB) revealed that S100A4 and GSDMD were significantly up-regulated in PTB patients' peripheral blood. Furthermore, there was a positive correlation between the expression of GSDMD and S100A4. KEGG pathway enrichment analysis showed that differentially expressed genes between PTB patients and healthy controls were significantly related to inflammation, such as the NOD-like receptor signaling pathway and NF-κB signaling pathway. To investigate the regulatory effects of S100A4 on macrophage pyroptosis, THP-1 macrophages infected with Bacillus Calmette-Guérin (BCG) were pre-treated with exogenous S100A4, S100A4 inhibitor or si-S100A4. This research study has shown that S100A4 promotes the pyroptosis of THP-1 macrophages caused by BCG infection and activates NLRP3 inflammasome and NF-κB signaling pathways, which can be inhibited by knockdown or inhibition of S100A4. In addition, inhibition of NF-κB or NLRP3 blocks the promotion effect of S100A4 on BCG-induced pyroptosis of THP-1 macrophages. In conclusion, S100A4 activates the NF-κB/NLRP3 inflammasome signaling pathway to promote macrophage pyroptosis induced by Mtb infection. These data provide new insights into how S100A4 affects Mtb-induced macrophage pyroptosis.

Correction: Nie et al. Endoplasmic Reticulum Stress Mediated NLRP3 Inflammasome Activation and Pyroptosis in THP-1 Macrophages Infected with Bacillus Calmette-Guérin. Int. J. Mol. Sci. 2023, 24, 11692.

Lei Liu was not included as an author in the original publication [...].

GSK2656157, a PERK Inhibitor, Alleviates Pyroptosis of Macrophages Induced by Mycobacterium Bacillus Calmette-Guerin Infection.

Tuberculosis (TB) is the leading cause of human death worldwide due to Mycobacterium tuberculosis (Mtb) infection. Mtb infection can cause macrophage pyroptosis. PERK, as a signaling pathway protein on the endoplasmic reticulum, plays an important role in infectious diseases. It is not clear whether PERK is involved in the regulation of pyroptosis of macrophages during Mtb infection. In this study, Bacillus Calmette-Guerin (BCG) infection resulted in high expression of pro-caspase-1, caspase-1 p20, GSDMD-N, and p-PERK in the THP-1 macrophage, being downregulated with the pre-treatment of GSK2656157, a PERK inhibitor. In addition, GSK2656157 inhibited the secretion of IL-1ß and IL-18, cell content release, and cell membrane rupture, as well as the decline in cell viability induced by BCG infection. Similarly, GSK2656157 treatment downregulated the expressions of pro-caspase-1, caspase-1 p20, caspase-11, IL-1ß p17, IL-18 p22, GSDMD, GSDMD-N, and p-PERK, as well as reducing fibrous tissue hyperplasia, inflammatory infiltration, and the bacterial load in the lung tissue of C57BL/6J mice infected with BCG. In conclusion, the inhibition of PERK alleviated pyroptosis induced by BCG infection, which has an effect of resisting infection.

Endoplasmic Reticulum Stress Mediated NLRP3 Inflammasome Activation and Pyroptosis in THP-1 Macrophages Infected with Bacillus Calmette-Guérin.

Tuberculosis (TB) is a zoonotic infectious disease caused by Mycobacterium tuberculosis (Mtb). Mtb is a typical intracellular parasite, and macrophages are its main host cells. NLRP3 inflammasome-mediated pyroptosis is a form of programmed cell death implicated in the clearance of pathogenic infections. The bidirectional regulatory effect of endoplasmic reticulum stress (ERS) plays a crucial role in determining cell survival and death. Whether ERS is involved in macrophage pyroptosis with Mtb infection remains unclear. This article aims to explore the regulation of the NLRP3 inflammasome and pyroptosis by ERS in THP-1 macrophages infected with Mycobacterium bovis Bacillus Calmette-Guérin (BCG). The results showed that BCG infection induced THP-1 macrophage ERS, NLRP3 inflammasome activation and pyroptosis, which was inhibited by ERS inhibitor TUDCA. NLRP3 inhibitor MCC950 inhibited THP-1 macrophage NLRP3 inflammasome activation and pyroptosis caused by BCG infection. Compared with specific Caspase-1 inhibitor VX-765, pan-Caspase inhibitor Z-VAD-FMK showed a more significant inhibitory effect on BCG infection-induced pyroptosis of THP-1 macrophages. Taken together, this study demonstrates that ERS mediated NLRP3 inflammasome activation and pyroptosis after BCG infection of THP-1 macrophages, and that BCG infection of THP-1 macrophages induces pyroptosis through canonical and noncanonical pathways.

Ror2-mediated cholesterol accumulation regulates autophagic activity within BCG-infected macrophages.

Ror2 is a primary binding partner for the non-classical Wnt signaling pathway regulator Wnt5a that plays a central role in regulating the metabolic processing of lipids within the cell. Mycobacterium tuberculosis is an intracellular pathogen that utilizes the lipid substrate cholesterol as its primary source of carbon. Cholesterol accumulation can regulate autophagy, which is in turn associated with a variety of pathological conditions. This study was designed to explore the pathways that modulate Ror2-regulated cholesterol accumulation within macrophages infected by the mycobacterium Bacillus Calmette-Guerin (BCG). BCG infection of RAW264.7 cells resulted in increased Ror2 expression, cholesterol accumulation, and autophagic activity in addition to promoting the upregulation of cholesterol synthesis-related proteins and the downregulation of cholesterol transporter proteins. Ror2 knockdown, in contrast, reversed these phenotypic changes. Treatment with T0901317 decreased the aggregation of cholesterol within cells and suppressed BCG-induced autophagy, while OX-LDL had the opposite effect. Knocking down Ror2 further reduced cholesterol levels in the context of T0901317 or OX-LDL pretreatment, alleviating BCG-induced autophagy irrespective of either of these pretreatments. Together, these data indicate that Ror2 can shape the autophagic activity induced within macrophages upon BCG infection by modulating intracellular cholesterol levels.

Wnt5a regulates autophagy in Bacille Calmette-Guérin (BCG)-Infected pulmonary epithelial cells.

Autophagy functions as a critical process that can suppress the proliferation of Mycobacterium tuberculosis (Mtb) within infected host cells. Wnt5a is a secreted protein that plays a range of physiological functions, activating several signaling pathways and thereby controlling cellular responses to particular stimuli. The importance of Wnt5a as a regulator of protection against Mtb infection, however, has yet to be fully characterized. Here, changes in murine pulmonary epithelial-like TC-1 cell morphology, autophagy, the Wnt/Ca2+ signaling pathway, and the mTOR autophagy pathway were analyzed following infection with the Mtb model pathogen Bacille Calmette-Guerin (BCG) in order to understand the regulatory role of Wnt5a in this context. These experiments revealed that Wnt5a was upregulated and autophagy was enhanced in TC-1 cells infected with BCG, and Wnt5a overexpression was found to drive BCG-induced autophagy in these cells upon infection, whereas the inhibition or knockdown of Wnt5a yielded the opposite effect. At the mechanistic level, Wnt5a was found to mediate non-canonical Wnt/Ca2+ signaling and thereby inhibit mTOR-dependent pathway activation, promoting autophagic induction within BCG-infected TC-1 cells. These data offer new insight regarding how Wnt5a influences Mtb-induced autophagy within pulmonary epithelial cells, providing a foundation for further research exploring the immunological control of this infection through the modulation of autophagy.

[Knockdown of Wnt7a inhibits BCG induced autophagy in mouse alveolar epithelial cells].

Objective To investigate the regulatory effect of wingless gene 7a (Wnt7a) on Bacille Calmette Guerin (BCG) induced autophagy in alveolar epithelial cells. Methods The alveolar epithelial cells of TC-1 mice were treated with interfering Wnt7a lentivirus and BCG alone or together in four groups, namely, small interfering RNA control (si-NC) group, si-NC combined with BCG group, Wnt7a small interfering RNA (si-Wnt7a) group, and si-Wnt7a combined with BCG group. The expressions of Wnt7a, microtubule associated protein 1 light chain 3 (LC3), P62, and autophagy related gene 5 (ATG5) were detected by Western blot analysis, and the distribution of LC3 was detected by immunofluorescence cytochemical staining. Results Compared with those in the si-NC group, Wnt7a, ATG5 and LC3 expressions increased and green fluorescent spots of LC3 significantly increased in the BCG infected TC-1 cells; the expressions of Wnt7a, LC3, P62, and ATG5 and green fluorescent spots of LC3 significantly decreased in the si-Wnt7a combined with BCG group comparing with those in the si-NC combined with BCG group. Conclusion Knocking down Wnt7a inhibits BCG induced autophagy in mouse alveolar epithelial cells.

[Knockdown of receptor tyrosine kinase-like orphan receptor 2 (ROR2) inhibits the autophagy of RAW264.7 mouse macrophages induced by BCG vaccine].

Objective To investigate the regulation of Wnt5a/receptor tyrosine kinase-like orphan receptor 2 (ROR2) signaling pathway on macrophage autophagy induced by Bacille Calmette Guerin (BCG) infection. Methods RAW264.7 cells were infected with BCG at 0, 2, 6, 12 and 24 hours, and the expressions of Wnt5a, ROR2 and autophagy-related protein microtubule-associated protein 1 light chain 3II (LC3II ) were detected by Western blot analysis. After RAW264.7 cells were treated with ROR2 small interfering RNA and BCG infection respectively or together, the protein expressions of autophagy-related genes 5 (ATG5), P62, beclin-1, ATG7 and LC3II in RAW264.7 cells were tested by Western blot analysis. Autophagy flux was detected by mRFP-GFP-LC3 double-label adenovirus assay. Results Compared with the control group, Wnt5a, ROR2 and LC3II had the highest expression in RAW264.7 cells 6 hours after BCG infection. Compared with the non-infected control group, the expressions of autophagy-related proteins ATG5, P62, beclin-1, ATG7 and LC3II showed an increase, along with increased number of autophagosomes and autophagolysosomes in RAW264.7 cells infected with BCG. Compared with BCG infected group, the expressions of the above proteins observed a decrease, and the number of autophagosomes and autophagolysosomes both descended in the co-treatment group with knockdown ROR2 and BCG infection. Conclusion Knockdown of ROR2 can inhibit autophagy in macrophages induced by BCG infection.