IL-32 positively regulates the AEBP1-IκBα-NF-κB-TNF-α axis to inhibit Mycobacterium tuberculosis infection in human macrophages.

Mycobacterium tuberculosis (MTB), the causative agent of tuberculosis, survives in host macrophages, the primary effector and antigen-presenting cells involved in the host immune response. We previously showed that Interleukin-32 (IL-32) is significantly increased in the peripheral blood plasma of tuberculosis patients, can act as an anti-MTB agent. However, the underlying molecular mechanism for its effect remains unknown. Here, we showed that inhibiting IL-32 with monoclonal antibody increases MTB loads that was positively correlated with higher antibody concentrations and longer exposure times. RNA-Sequencing result indicated that 3797 genes were shown to be up-regulated in response to IL-32 inhibition, while 1365 genes were down-regulated. GO and KEGG analysis indicated that classical signaling pathways, including TNF, cell cycle, and Wnt were significantly enriched. Consistent expression trends were observed in NF-κB pathway-related antibacterial factors that are functionally capable of inhibiting MTB. Using differentially expressed gene and protein-protein interaction analysis, AEBP1 was the gene with the most significant difference in expression and regulated by IL-32. These findings suggest a dynamic molecular and cellular mechanism by which IL-32 positively regulates the AEBP1-IκBα-NF-κB-TNF-α axis to inhibit MTB infection in human macrophages.