OBJECTIVE: The cGAS-STING pathway is a critical sensor in the innate immune response to intracellular pathogens, yet its therapeutic potential for augmenting macrophage-mediated control of Mycobacterium tuberculosis (Mtb) remains incompletely understood. This study investigated whether pharmacological activation of the STING pathway could enhance autophagy to promote Mtb clearance in human macrophages.
METHODS: Human THP-1 monocytes were differentiated into macrophages and infected with Mtb. The effects of the STING agonist MIW815 (ADU-S100) on Mtb phagocytosis, intracellular bacterial survival, and autophagic flux were assessed using a combination of molecular and cellular techniques, including qRT-PCR, western blotting, colony-forming unit (CFU) assays, and confocal immunofluorescence microscopy. The dependency on the cGAS-STING pathway was confirmed using siRNA-mediated gene silencing.
RESULTS: Pharmacological activation of STING with ADU-S100 significantly enhanced Mtb phagocytosis and subsequent intracellular clearance. This enhanced bactericidal activity was mechanistically linked to an increase in autophagic flux, as evidenced by elevated LC3-II protein levels and significantly increased colocalization of Mtb with lysosomal compartments. Importantly, treatment with the autophagy inhibitor hydroxychloroquine or silencing of cGAS significantly reversed these phenotypes, confirming the pivotal role of the STING-autophagy axis.
CONCLUSION: Activating the STING pathway with ADU-S100 is a potent host-directed strategy to bolster macrophage autophagy and enhance the elimination of intracellular Mtb. This provides a strong rationale for exploring STING agonists as a novel therapeutic intervention for tuberculosis, addressing a significant and clinically relevant challenge in infectious disease.
