High-mobility group box 1 and the receptor for advanced glycation end products contribute to lung injury during Staphylococcus aureus pneumonia

Abstract

IntroductionStaphylococcus (S.) aureus has emerged as an important cause of necrotizing pneumonia. Lung injury during S. aureus pneumonia may be enhanced by local release of damage associated molecular patterns such as high-mobility group box 1 (HMGB1). In the current study we sought to determine the functional role of HMGB1 and its receptors, toll-like receptor 4 (TLR4) and the receptor for advanced glycation end products (RAGE), in the injurious host response to S. aureus pneumonia.MethodsPneumonia was induced in wild type (Wt), TLR4 deficient (tlr4−/−) and RAGE deficient (rage−/−) mice by intranasal inoculation of 1 × 107 colony-forming units (CFU) of a USA300 S. aureus. In a separate set of experiments, Wt mice were injected intraperitoneally with a monoclonal anti-HMGB1 antibody or an isotype matched control antibody immediately before and every 24 hours after intranasal infection of S. aureus. Mice were sacrificed at 6, 24, 48 or 72 hours after infection for harvesting of blood and organs.ResultsS. aureus pneumonia was associated with HMGB1 release in the bronchoalveolar compartment peaking after 24 hours. Anti-HMGB1 attenuated lung pathology and protein leak and reduced interleukin-1β release 6 hours after infection, but not at later time points. RAGE deficiency more modestly attenuated lung pathology without influencing protein leak, while TLR4 deficiency did not impact on lung injury.ConclusionThese data suggest that HMGB1 and RAGE, but not TLR4, contribute to lung injury accompanying the early phase of S. aureus pneumonia.

Toll-Like Receptor 9 Enhances Bacterial Clearance and Limits Lung Consolidation in Murine Pneumonia Caused by Methicillin-Resistant Staphylococcus aureus

“…In our pneumonia model, MRSA disseminated to the liver while blood cultures remained sterile. This seeming discrepancy, also observed in our earlier studies (21,22), likely is explained by a more rapid clearance of this MRSA strain from the circulation relative to liver tissue. In accordance with this notion, very low bacterial burdens remain in the circulation upon intravenous administration of this MRSA strain with 100-1,000-fold higher bacterial loads in the liver (38).…”

“…In brief, mice were intranasally inoculated with 10 7 colony-forming units (CFU)/50 μL saline solution (n = 8 per strain at each time point) under isoflurane (Abbot Laboratories) inhalation anesthesia. The infectious dose is sublethal and based on earlier dose-finding studies (21). Mice were killed 6, 24, 48 or 72 h after infection by cardiac puncture under Domitor (Pfizer Animal Health Care, active ingredient medetomidine) and Nimatek (Eurovet Animal Health, active ingredient ketamine) anesthesia.…”

“…About 4 μm sections were stained with hematoxylin and eosin (HE) and analyzed by a pathologist blinded for groups as described (21,22). To score lung inflammation and damage, the entire lung surface was analyzed with respect to the following obtained by exposing the trachea via a midline incision.…”

“…experimental Infection and Tissue Preparation Pneumonia was induced as described (21,22), using the MRSA strain BK11540 (USA300), kindly provided by Timothy J Foster, Department of Microbiology, Trinity College, Dublin, Ireland. Characteristics of this strain are: multilocus sequence type ST8, spa type 1, staphylococcal cassette chromosome mecIV, agr type 1 and Panton-Valentine leukocidin negative (23).…”

Myeloid-related protein-14 deficiency promotes inflammation in staphylococcal pneumonia

“…Foster, Dept of Microbiology, Trinity College, Dublin, Ireland) in a 50 μl saline solution (n=7-8 per strain). This sublethal dose was determined in a previously described pilot study [23]. Mice were sacrificed 6, 24, 48 or 72 h thereafter [23].…”