Erythropoietin (EPO) is the principal cytokine regulating erythropoiesis through its receptor, EPOR. Interestingly, EPORs are also found on immune cells with incompletely understood functions. Here, we show that EPO inhibits the induction of proinflammatory genes including tumor necrosis factor (TNF)-α and inducible nitric oxide (NO) synthase in activated macrophages, which is mechanistically attributable to blockage of nuclear factor (NF)-κB p65 activation by EPO. Accordingly, in systemic Salmonella infection, treatment of mice with EPO results in reduced survival and impaired pathogen clearance because of diminished formation of anti-microbial effector molecules such as TNF-α and NO. However, neutralization of endogenous EPO or genetic ablation of Epor promotes Salmonella elimination. In contrast, in chemically induced colitis, EPO-EPOR interaction decreases the production of NF-κB-inducible immune mediators, thus limiting tissue damage and ameliorating disease severity. These immune-modulatory effects of EPO may be of therapeutic relevance in infectious and inflammatory diseases.
