title: Mechanisms of methicillin-resistant Staphylococcus aureus pneumonia-induced intestinal epithelial apoptosis.
abstract: Methicillin-resistant Staphylococcus aureus (MRSA) pneumonia-induced sepsis is a common cause of morbidity in the intensive care unit. Although pneumonia is initiated in the lungs, extrapulmonary manifestations occur commonly. In light of the key role the intestine plays in the pathophysiology of sepsis, we sought to determine whether MRSA pneumonia induces intestinal injury. FVB/N mice were subjected to MRSA or sham pneumonia and killed 24 h later. Septic animals had a marked increase in intestinal epithelial apoptosis by both hematoxylin-eosin and active caspase 3 staining. Methicillin-resistant S. aureus-induced intestinal apoptosis was associated with an increase in the expression of the proapoptotic proteins Bid and Bax and the antiapoptotic protein Bcl-xL in the mitochondrial pathway. In the receptor-mediated pathway, MRSA pneumonia induced an increase in Fas ligand but decreased protein levels of Fas, FADD, pFADD, TNF-R1, and TRADD. To assess the functional significance of these changes, MRSA pneumonia was induced in mice with genetic manipulations in proteins in either the mitochondrial or receptor-mediated pathways. Both Bid-/- mice and animals with intestine-specific overexpression of Bcl-2 had decreased intestinal apoptosis compared with wild-type animals. In contrast, Fas ligand-/- mice had no alterations in apoptosis. To determine if these findings were organism-specific, similar experiments were performed in mice subjected to Pseudomonas aeruginosa pneumonia. Pseudomonas aeruginosa induced gut apoptosis, but unlike MRSA, this was associated with increased Bcl-2 and TNF-R1 and decreased Fas. Methicillin-resistant S. aureus pneumonia thus induces organism-specific changes in intestinal apoptosis via changes in both the mitochondrial and receptor-mediated pathways, although the former may be more functionally significant.
authors.affiliation: Department of Surgery, Washington University School of Medicine, St Louis, Missouri, USA.
authors.forename: Erin E
authors.initials: EE
authors.lastname: Perrone
authors.forename: Enjae
authors.initials: E
authors.lastname: Jung
authors.forename: Elise
authors.initials: E
authors.lastname: Breed
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Dominguez
authors.forename: Zhe
authors.initials: Z
authors.lastname: Liang
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Clark
authors.forename: W Michael
authors.initials: WM
authors.lastname: Dunne
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Burd
authors.forename: Craig M
authors.initials: CM
authors.lastname: Coopersmith
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000172:deficiency / Q000378:metabolism; D049109:Cell Proliferation; D004847:Epithelial Cells / Q000473:pathology; D053222:Fas Ligand Protein / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism / Q000473:pathology*; D055624:Methicillin-Resistant Staphylococcus aureus; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008928:Mitochondria / Q000502:physiology; D010539:Permeability; D018410:Pneumonia, Bacterial / Q000378:metabolism / Q000473:pathology; D011023:Pneumonia, Staphylococcal / Q000378:metabolism / Q000473:pathology*; D011552:Pseudomonas Infections / Q000378:metabolism / Q000473:pathology; D011550:Pseudomonas aeruginosa; D018805:Sepsis / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; C494827:Bax protein, mouse; C494815:Bid protein, mouse; D053222:Fas Ligand Protein; D051028:bcl-2-Associated X Protein