Itaconate promotes inflammatory responses in tissue-resident alveolar macrophages and exacerbates acute lung injury.

Itaconate is an anti-inflammatory metabolite with therapeutic potential in multiple inflammatory diseases. However, its immunomodulatory function has been mainly based on ex vivo-generated macrophages or cell lines, whereas its role in tissue-resident macrophages is still poorly understood. Here, we report that, in contrast to its effects on bone-marrow-derived macrophages (BMDMs), itaconate promotes the production of proinflammatory cytokines and augments the activation of the NACHT-, leucine-rich-repeat- (LRR), and pyrin domain-containing protein 3 (NLRP3) inflammasome in resident alveolar macrophages (AMs). Unlike native itaconate, the itaconate derivatives dimethyl itaconate (DI) and 4-octyl itaconate (4OI) suppress the inflammatory response in AMs. Notably, the intratracheal transfer of BMDMs reversed their responsiveness to itaconate, indicating an essential role of the alveolar microenvironment in shaping macrophage immunometabolism. We also demonstrate that itaconate promotes AM-mediated inflammatory responses in vivo and aggravates lung injury. Taken together, our study unexpectedly demonstrates a proinflammatory role of itaconate in tissue-resident AMs, suggesting that further investigations are needed before its clinical application.