Hematopoietic but Not Endothelial Cell MyD88 Contributes to Host Defense during Gram-negative Pneumonia Derived Sepsis

Abstract

Klebsiella pneumoniae is an important cause of sepsis. The common Toll-like receptor adapter myeloid differentiation primary response gene (MyD)88 is crucial for host defense against Klebsiella. Here we investigated the role of MyD88 in myeloid and endothelial cells during Klebsiella pneumosepsis. Mice deficient for MyD88 in myeloid (LysM-Myd88−/−) and myeloid plus endothelial (Tie2-Myd88−/−) cells showed enhanced lethality and bacterial growth. Tie2-Myd88−/− mice reconstituted with control bone marrow, representing mice with a selective MyD88 deficiency in endothelial cells, showed an unremarkable antibacterial defense. Myeloid or endothelial cell MyD88 deficiency did not impact on lung pathology or distant organ injury during late stage sepsis, while LysM-Myd88−/− mice demonstrated a strongly attenuated inflammatory response in the airways early after infection. These data suggest that myeloid but not endothelial MyD88 is important for host defense during gram-negative pneumonia derived sepsis.

Granzymes A and B Regulate the Local Inflammatory Response during <b><i>Klebsiella pneumoniae</i></b> Pneumonia

“…The modestly reduced pro-inflammatory mediator levels in the gzm-deficient mice may, at least in part, explain the lower MPO concentrations, indicative of total neutrophil content, in these animals at 6 h after infection. In addition, considering that a brisk inflammatory reaction in the lungs is important for antibacterial defence in this model [17,22,23], the impaired early response could have contributed to the higher bacterial loads in the lungs of gzmA -/- and gzmAxB -/- mice at 16 h after infection. Notably, at this intermediate time point (16 h), when the lung infection had advanced to distant sites but was not yet accompanied by distant organ damage, gzmB and gzmAxB deficiency were associated with enhanced pulmonary inflammation.…”

Stimulation of TLR4 Attenuates Alzheimer’s Disease–Related Symptoms and Pathology in Tau-Transgenic Mice

“…C57BL/6J mice were originally imported from Charles River Laboratories and bred in our animal facilities. To establish mice with modified inflammatory activation specifically in myeloid cells, we cross-bred ikbkb fl/fl (24), MyD88 fl/fl (25), or p38a fl/fl (26) mice with LysM-Cre knock-in mice expressing Cre from the endogenous lysozyme 2 gene locus (27) as we did previously (9) LysM-Cre +/2 mice, respectively, and their effects on inflammatory responses in mice have been previously described (28)(29)(30). To estimate the efficiency of LysMCre-mediated gene recombination of floxed ikbkb, myd88, and p38a-mapk genes in myeloid cells, we cross-bred LysM-Cre mice to ROSA mT/mG Cre reporter mice (The Jackson Laboratory, stock no.…”

TIR-Domain-Containing Adaptor-Inducing Interferon-β (TRIF) Mediates Antibacterial Defense during Gram-Negative Pneumonia by Inducing Interferon-&#947;

“…Animals TRIF mutant mice, generated on a C57Bl/6 genetic background [22] [8,9] . The mice were sacrificed at the indicated time points after infection and their organs were harvested and processed exactly as described [8,25] .…”

“…Splenocytes were obtained, seeded at a density of 500,000 cells per well and cultured exactly as described [9] . Cells were stimulated for 48 h in at least quadruplicate with the indicated concentrations of mitomycin C-treated (0.05 mg/ml) (Sigma-Aldrich) growth-arrested K. pneumoniae diluted in RPMI medium without antibiotics, LPS derived from Klebsiella pneumoniae (100 ng/ml; Sigma) or ultrapure Escherichia coli O111 B4 LPS (100 ng/ml; Invivogen) diluted in RPMI medium with antibiotics in a final volume of 200 μl.…”

“…We previously reported the crucial role of the TLR adaptors MyD88 and TRIF during K. pneumoniae infection and their differential contribution to the host response in different body compartments [8,9] . In these studies, we noted that mice deficient for TRIF were incapable of IFN-γ production at the primary site of infection (unpubl.…”