Adjunct therapy with all-trans-retinoic acid improves therapeutic efficacy through immunomodulation while treating tuberculosis with antibiotics in a murine model.

Tuberculosis (TB) is the second leading infectious killer after COVID-19. Standard anti-tubercular drugs exhibit various limitations like toxicity, lengthy, and unresponsive to dormant and drug resistant organisms. Here, we report that all-trans-retinoic acid (ATRA) improves M.tb clearance in mice while treating with anti-tubercular drug isoniazid (INH). Interestingly, ATRA promoted activities of lysosomes, mitochondria, and production of various inflammatory mediators in macrophages. Furthermore, ATRA upregulated the expression of genes of lipid metabolic pathways in macrophages. Along this line, we registered that ATRA activated MEK/ERK pathway in macrophages in-vitro and MEK/ERK and p38 MAPK pathways in the mice. Finally, ATRA induced both Th1 and Th17 responses in lungs and spleens of M.tb-infected mice. Taken together, these data indicated that ATRA provides beneficial adjunct therapeutic value by modulating MEK/ERK and p38 MAPK pathways and thus warrants further testing for human use.