Microbial metabolite Enterobactin impairs mitochondrial respiration and alleviates colitis

Host-microbe interactions critically shape cellular metabolism and immune responses. The bacterial siderophore enterobactin (Ent) is known for pilfering iron from the host, but recent evidence suggests that it may also deliver iron to host mitochondria. Its impact on mitochondrial respiration, however, remains poorly understood. Here, we assess the interplay among Ent, iron, and lipocalin-2 (Lcn2, which sequesters Ent) on mitochondrial function. We also examine the effects of the 2, 3-dihydroxybenzoic acid (2, 3-DHBA), the monomeric derivative of Ent, and the mammalian siderophore 2, 5-DHBA in a murine model of colitis.

Murine bone marrow-derived macrophages (BMDMs) and the human model intestinal epithelial cells (IEC) were treated with Ent, with or without iron or rec-Lcn2, and mitochondrial respiration was assessed via Seahorse XFe96 analyzer. For in vivo study, mice were treated with dextran sulfate sodium (DSS) to induce colitis and administered with 2, 3-DHBA or 2, 5-DHBA.

Iron-free Ent impaired mitochondrial oxidative phosphorylation in BMDMs and IEC, as evidenced by reduced ATP production and elevated reactive oxygen species. These effects of Ent were mitigated by iron saturation or upon co-administered with rec-Lcn2. Intriguingly, administration of 2, 3-DHBA, but not 2, 5-DHBA, to mice with DSS-induced colitis attenuated inflammation, increased expression of tight junction proteins, preserved epithelial architecture, and promoted mucosal repair. 2, 3-DHBA treatment also enhanced mitochondrial biogenesis, dynamics, and redox balance.

Ent in its 2, 3-DHBA form confers mucosal protection, despite its inhibitory effects on mitochondrial respiration. These findings suggest that modulating mitochondrial activity, thus reducing cellular metabolism, may be beneficial during colitis and position 2, 3-DHBA as a promising microbiota-derived metabolite for therapeutic intervention in inflammatory bowel disease.