Soybean lectin induces autophagy through P2RX7 dependent activation of NF-κB-ROS pathway to kill intracellular mycobacteria

Background: Host-directed therapy is considered a novel anti-tuberculosis strategy in tackling the tuberculosis burden through autophagy induction by various inducers to curtail the growth of intracellular Mycobacterium tuberculosis. Methods: In this study, we investigated the anti-tubercular role of soybean lectin, a lectin isolated from Glycine max (Soybean). Effect of SBL on intracellular mycobacterial viability through autophagy and the mechanism involved in differentiated THP-1 cells was studied using different experimental approaches. Results: We initially performed a time kinetic experiment with the non-cytotoxic dose of SBL (20 μg/ml) and observed autophagy induction after 24 h of treatment. Abrogation of autophagy in the presence of 3-MA and an increase in LC3 puncta formation upon Baf-A1 addition elucidated the specific effect on autophagy and autophagic flux. SBL treatment also led to autophagy induction in mycobacteria infected macrophages that restricted the intracellular mycobacterial growth, thus emphasizing the host defensive role of SBL induced autophagy. Mechanistic studies revealed an increase in P2RX7 expression, NF-κB activation and reactive oxygen species generation upon SBL treatment. Inhibition of P2RX7 expression suppressed NF-κB dependent ROS level in SBL treated cells. Moreover, SBL induced autophagy was abrogated in the presence of either different inhibitors or P2RX7 siRNA, leading to the reduced killing of intracellular mycobacteria. Conclusion: Taken together, these results conclude that SBL induced autophagy exerts an anti-mycobacterial effect in P2RX7-NF-κB dependent manner through the generation of ROS. General significance: This study has provided a novel anti-mycobacterial role of SBL, which may play an important role in devising new therapeutic interventions.