De novo synthesized polyunsaturated fatty acids operate as both host immunomodulators and nutrients for Mycobacterium tuberculosis

Successful control of Mycobacterium tuberculosis (Mtb) infection by macrophages relies on immunometabolic reprogramming, where the role of fatty acids (FAs) remains poorly understood. Recent studies unraveled Mtbs capacity to acquire saturated and monounsaturated FAs via the Mce1 importer. However, upon activation macrophages produce polyunsaturated FAs (PUFAs), mammal-specific FAs mediating the generation of key immunomodulatory eicosanoids. Here, we asked whether de novo synthesis of PUFAs is modulated in Mtb-infected macrophages and benefits host or pathogen. Quantitative lipidomics revealed that Mtb infection activates the early PUFA biosynthetic pathway for production of eicosanoids. While PUFA synthesis blockade significantly impaired the inflammatory and antimicrobial responses of infected macrophages, it had no effect on Mtb growth in vivo. Using a click-chemistry approach, we found that Mtb efficiently imports PUFAs of the {omega}6 subset via Mce1 in axenic culture, including the eicosanoid precursor arachidonic acid (AA). Notably, Mtb preferentially internalized AA over all other FAs within infected macrophages, but here Mtbs import of AA was largely Mce1-independent and correlated with elevated AA uptake by host cells. Together, these findings reveal AA as a major FA substrate for intracellular Mtb. They suggest that Mtbs hijacking of host-derived AA may counteract its stimulatory effect on anti-mycobacterial immune responses.