A new target for drug repositioning: CEBPα elicits LL-37 expression in a vitamin D-independent manner promoting Mtb clearance.

Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis (Mtb) and is a growing public health problem worldwide. Within the innate immune response, we highlight the secretion of the antimicrobial peptide LL-37, which is crucial for Mtb elimination in infected cells. Previous reports have shown that CEBPα activation induces LL-37 independently of its main inducer, vitamin D, under endoplasmic reticulum (ER) stress. In this study, we report that infection with Mtb causes ER stress in pulmonary epithelial cells and macrophages. The stress induces the activation of CEBPα, which in turn promotes the LL-37 expression. Furthermore, the participation of CEBPα is necessary for the correct clearance of Mtb in an in vitro infection model. We identify candidate drugs (mycophenolic acid, indapamide, and glibenclamide) capable of activating CEBPα and promoting LL-37 through in silico assays. The effect of the drugs was corroborated by gene and protein expression analysis. Finally, we observed that treatment with these drugs improves bacterial clearance in infected cells. Our results lead us to suggest CEBPα as a potential therapeutic target as an adjuvant in the standard treatment of tuberculosis, seeking a reduction in treatment time, and thus a lower appearance of drug resistance.