Nucleotide-Binding Oligomerization Domain 2 Contributes to Limiting Growth of in the Lung of Mice by Regulating Cytokines and Nitric Oxide Production.

is a prominent cause of pulmonary infection in immunosuppressed patients and those with cystic fibrosis. Nucleotide-binding oligomerization domain (NOD) 2 is a cytosolic receptor which senses a bacterial peptidoglycan component, muramyl dipeptide (MDP). Although nucleotide-binding oligomerization domain 2 (NOD2) contributes to protect host against various microbial infections, it is still unclear whether NOD2 is essential to regulate host immune responses against infection. In this study, we sought to clarify the role of NOD2 and the underlying mechanism in host defense against infection. Mice were infected intranasally with and sacrificed at indicated time points. Bacterial survival, cytokines production, and pathology in the lungs were determined. Bone marrow-derived macrophages were used to clarify cellular mechanism of NOD2-mediated immune response. Bacterial clearance was impaired, and pathology was more severe in the lungs of NOD2-deficient mice compared with the wild-type mice. In macrophages, NOD2-mediated activation of p38 and JNK were required for production of proinflammatory cytokines and nitric oxide (NO) and expression of iNOS in response to . NO was critical for limiting intracellular growth of the pathogen. Intranasal administration of MDP reduced bacterial replication and thus improved lung pathology in -infected mice. This study offers important new insights into the potential roles of the NOD2 in initiating and potentiating innate immune response against pulmonary infection.