Alox15 restrains glycolysis to support M2 macrophage effector function during helminth immunity.

Macrophage polarization by type-2 cytokines is central to anti-helminth immunity and tissue repair. While some hallmark changes in macrophages are well-characterized and associated with protection against helminths, it is still unclear how macrophages exert their anti-helminth effects. In this context, we investigated arachidonate 15-lipoxygenase (LOX) (Alox15), a LOX well known for its role in macrophage polarization in the context of metabolic diseases, and a hallmark of type-2 macrophage (M2) human polarization. We show that in the absence of Alox15, M2 cannot trap and kill helminths. Surprisingly, expression of M2 markers was normal despite a loss of function. Instead, we found a concomitant increase in pro-inflammatory responses due to an uncontrolled activation of glycolysis. We further show that activation of Peroxisome proliferator-activated receptor-delta (PPAR-δ) by lipids downstream of docosapentaenoic acid (DPA) can restore normal glycolysis control, highlighting a novel role of lipids in the fine-tuning of the metabolic support required for optimal macrophage polarization.