RESUMO
UNLABELLED: Staphylococcus aureus pneumonia is an important cause of sepsis which causes gut injury, inflammation, and apoptosis. The surfactant proteins surfactant protein A (SP-A) and surfactant protein D (SP-D) bind bacterial pathogens and facilitate clearance of pathogens, apoptotic bodies, and modulate immune responses. SP-A and SP-D are expressed in both lung and gut epithelia. We hypothesize SP-A and SP-D regulate pneumonia severity and gut injury during pneumonia. METHODS: Wild-type (WT) and SP-A and SP-D double knockout (SP-A/D KO) mice were subjected to S. aureus or sham pneumonia. Bronchoalveolar lavage and tissue harvest were performed 24âh later. Pneumonia severity, gut mucosal injury, inflammation, and apoptosis were measured using a combination of histology, immunohistochemistry, cytokine assay, TUNEL assay, quantitative real-time polymerase chain reaction, and Western blot analyses. RESULTS: Pneumonia increased gut inflammation, apoptosis, and mucosal injury in both groups. Pneumonia histology and bacterial growth in bronchoalveolar lavage fluid demonstrate more severe infection in SP-A/D KO mice compared with WT controls. SP-A/D KO mice with pneumonia also demonstrate more severe histologic gut mucosal injury, increased gut apoptosis, elevated caspase-3 levels, and Bax/Bcl-2 mRNA expression compared with WT pneumonia mice. Nuclear factor κB (NF-κB) p65 expression and its nuclear translocation, gut levels of tumor necrosis factor α and interleukin-1ß were all increased in SP-A/D KO mice with pneumonia compared with WT controls. CONCLUSIONS: These data provide evidence SP-A and SP-D attenuate S. aureus pneumonia severity resulting in decreased intestinal mucosal injury, apoptosis, and inflammation. Improved pulmonary clearance of S. aureus decreased caspase-3 and Bax/Bcl-2 expressions and decreased activation of the NF-κB signaling pathway in intestine represent potential mechanisms for the effects of SP-A and SP-D on gut injury during pneumonia.
Assuntos
Pneumonia Estafilocócica/imunologia , Pneumonia Estafilocócica/patologia , Proteína A Associada a Surfactante Pulmonar/metabolismo , Proteína D Associada a Surfactante Pulmonar/metabolismo , Animais , Apoptose/fisiologia , Líquido da Lavagem Broncoalveolar/microbiologia , Caspase 3/genética , Caspase 3/metabolismo , Modelos Animais de Doenças , Feminino , Intestinos/citologia , Intestinos/imunologia , Pulmão/citologia , Pulmão/imunologia , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Pneumonia Estafilocócica/genética , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Proteína A Associada a Surfactante Pulmonar/genética , Proteína D Associada a Surfactante Pulmonar/genética , Transdução de Sinais , Proteína X Associada a bcl-2/genética , Proteína X Associada a bcl-2/metabolismoRESUMO
Both natural and synthetic brominated furanones are known to inhibit biofilm formation by bacteria, but their toxicity to mammalian cells is often not reported. Here, we designed and synthesized a new class of brominated furanones (BBFs) that contained a bicyclic structure having one bromide group with well-defined regiochemistry. This class of molecules exhibited reduction in the toxicity to mammalian cells (human neuroblastoma SK-N-SH) and did not inhibit bacteria (Pseudomonas aeruginosa and Escherichia coli) growth, but retained the inhibitory activity towards biofilm formation of bacteria. In addition, all the BBFs inhibited the production of virulence factor elastase B in P. aeruginosa. To explore the effect of BBFs on quorum sensing, we used a reporter gene assay and found that 6-BBF and 7-BBF exhibited antagonistic activities for LasR protein in the lasI quorum sensing circuit, while 5-BBF showed agonistic activity for the rhlI quorum sensing circuit. This study suggests that structural variation of brominated furanones can be designed for targeted functions to control biofilm formation.
