title: Primary alveolar epithelial cell surface membrane microdomain function is required for Pneumocystis β-glucan-induced inflammatory responses.
abstract: Intense lung inflammation characterizes respiratory failure associated with Pneumocystis pneumonia. Our laboratory has previously demonstrated that alveolar epithelial cells (AECs) elaborate inflammatory cytokines and chemokines in response to the Pneumocystis carinii cell wall constituent β-(1→3)-glucan (PCBG), and that these responses require lactosylceramide, a prominent glycosphingolipid constituent of certain cell membrane microdomains. The relevance of membrane microdomains, also termed plasma membrane lipid rafts, in cell signaling and macromolecule handling has been increasingly recognized in many biologic systems, but their role in P. carinii-induced inflammation is unknown. To investigate the mechanisms of microdomain-dependent P. carinii-induced inflammation, we challenged primary rat AECs with PCBG with or without pre-incubation with inhibitors of microdomain function. Glycosphingolipid and cholesterol rich microdomain inhibition resulted in significant attenuation of P. carinii-induced expression of TNF-α and the rodent C-X-C chemokine MIP-2, as well as their known inflammatory secondary signaling pathways. We have previously shown that protein kinase C (PKC) is activated by PCBG challenge and herein show that PKC localizes to AEC microdomains. We also demonstrate by conventional microscopy, fluorescence microscopy, confocal microscopy and spectrophotofluorimetry that AECs internalize fluorescently-labeled PCBG by microdomain-mediated mechanisms, and that anti-microdomain pretreatments prevent internalization. Taken together, these data suggest an important role for AEC microdomain function in PCBG-induced inflammatory responses. This offers a potential novel target for therapeutics for a condition that continues to exert unacceptable morbidity and mortality among immunocompromised populations.
authors.affiliation: Thoracic Diseases Research Unit and the Division of Pulmonary Critical Care and Internal Medicine, Mayo Clinic and Foundation, MN 55905, USA.
authors.forename: Scott E
authors.initials: SE
authors.lastname: Evans
authors.forename: Theodore J
authors.initials: TJ
authors.lastname: Kottom
authors.forename: Richard E
authors.initials: RE
authors.lastname: Pagano
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Limper
mesh_terms: D056809:Alveolar Epithelial Cells / Q000276:immunology*; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D018836:Inflammation Mediators / Q000378:metabolism; D007790:Lactosylceramides / Q000378:metabolism*; D021962:Membrane Microdomains / Q000276:immunology* / Q000378:metabolism*; D016720:Pneumocystis Infections / Q000276:immunology*; D045363:Pneumocystis carinii; D061251:Primary Cell Culture; D011650:Pulmonary Alveoli / Q000276:immunology*; D051381:Rats; D047071:beta-Glucans / Q000276:immunology / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D016207:Cytokines; D018836:Inflammation Mediators; D007790:Lactosylceramides; D047071:beta-Glucans; C009744:CDw17 antigen