LAUSR

Monocytes play an important role in the regulation of alloimmune responses after heart transplantation (HTx). Recent studies have highlighted the importance of immunometabolism in the differentiation and function of myeloid cells. While the importance of glucose metabolism in monocyte differentiation and function has been reported, a role for fatty acid β-oxidation (FAO) has not been explored. Heterotopic HTx was performed using hearts from Balb/c donor mice implanted into C57Bl/6 recipient mice and treated with etomoxir (eto), an irreversible inhibitor of carnitine palmitoyltransferase 1 (Cpt1), a rate-limiting step of FAO, or vehicle control. FAO inhibition prolonged HTx survival, reduced early T cell infiltration/ activation and reduced dendritic cell (DC) and macrophage infiltration to heart allografts of eto-treated HTx recipients. ELISPOT demonstrated eto-treated HTx were less reactive to activated donor antigen presenting cells. FAO inhibition reduced monocyte-to-DC and monocyte-to-macrophage differentiation in vitro and in vivo. Further, FAO inhibition did not alter the survival of heart allografts when transplanted into Ccr2-deficient recipients, suggesting the effects of FAO inhibition on reduced immune cell infiltration and increased heart allograft survival were dependent on monocyte mobilization. Finally, we confirmed the importance of FAO on monocyte differentiation in vivo using conditional deletion of Cpt1a. Our findings demonstrate that targeting FAO attenuates alloimmunity after HTx, in part through impairing monocyte differentiation.