The NOD/RIP2 pathway is essential for host defenses against Chlamydophila pneumoniae lung infection.
Here we investigated the role of the Nod/Rip2 pathway in host responses to Chlamydophila pneumoniae-induced pneumonia in mice. Rip2(-/-) mice infected with C. pneumoniae exhibited impaired iNOS expression and NO production, and delayed neutrophil recruitment to the lungs. Levels of IL-6 and IFN-gamma levels as well as KC and MIP-2 levels in bronchoalveolar lavage fluid (BALF) were significantly decreased in Rip2(-/-) mice compared to wild-type (WT) mice at day 3. Rip2(-/-) mice showed significant delay in bacterial clearance from the lungs and developed more severe and chronic lung inflammation that continued even on day 35 and led to increased mortality, whereas WT mice cleared the bacterial load, recovered from acute pneumonia, and survived. Both Nod1(-/-) and Nod2(-/-) mice also showed delayed bacterial clearance, suggesting that C. pneumoniae is recognized by both of these intracellular receptors. Bone marrow chimera experiments demonstrated that Rip2 in BM-derived cells rather than non-hematopoietic stromal cells played a key role in host responses in the lungs and clearance of C. pneumoniae. Furthermore, adoptive transfer of WT macrophages intratracheally was able to rescue the bacterial clearance defect in Rip2(-/-) mice. These results demonstrate that in addition to the TLR/MyD88 pathway, the Nod/Rip2 signaling pathway also plays a significant role in intracellular recognition, innate immune host responses, and ultimately has a decisive impact on clearance of C. pneumoniae from the lungs and survival of the infectious challenge.
Division of Pediatrics, Infectious Diseases, and Immunology, Cedars-Sinai Medical Center, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA.
Kenichi
K
Shimada
Shuang
S
Chen
Paul W
PW
Dempsey
Rosalinda
R
Sorrentino
Randa
R
Alsabeh
Anatoly V
AV
Slepenkin
Ellena
E
Peterson
Terence M
TM
Doherty
David
D
Underhill
Timothy R
TR
Crother
Moshe
M
Arditi
D000818:Animals; D001854:Bone Marrow Cells / Q000276:immunology / Q000378:metabolism; D018925:Chemokines / Q000276:immunology / Q000378:metabolism; D023521:Chlamydophila Infections / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D016993:Chlamydophila pneumoniae / Q000276:immunology / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D007113:Immunity, Innate; D008264:Macrophages / Q000276:immunology; D051379:Mice; D018345:Mice, Knockout; D020556:Neutrophil Infiltration / Q000276:immunology; D009569:Nitric Oxide / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis; D053472:Nod Signaling Adaptor Proteins / Q000276:immunology* / Q000378:metabolism; D018410:Pneumonia, Bacterial / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000032:analysis; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology
D018925:Chemokines; D053472:Nod Signaling Adaptor Proteins; D012333:RNA, Messenger; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C506255:Ripk2 protein, mouse