title: Pseudomonas aeruginosa biofilm-associated homoserine lactone C12 rapidly activates apoptosis in airway epithelia.
abstract: Pseudomonas aeruginosa (PA) forms biofilms in lungs of cystic fibrosis (CF) patients, a process regulated by quorum-sensing molecules including N-(3-oxododecanoyl)-l-homoserine lactone (C12). C12 (10-100 µM) rapidly triggered events commonly associated with the intrinsic apoptotic pathway in JME (CF ΔF508CFTR, nasal surface) epithelial cells: depolarization of mitochondrial (mito) membrane potential (Δψ(mito)) and release of cytochrome C (cytoC) from mitos into cytosol and activation of caspases 3/7, 8 and 9. C12 also had novel effects on the endoplasmic reticulum (release of both Ca(2+) and ER-targeted GFP and oxidized contents into the cytosol). Effects began within 5 min and were complete in 1-2 h. C12 caused similar activation of caspases and release of cytoC from mitos in Calu-3 (wtCFTR, bronchial gland) cells, showing that C12-triggered responses occurred similarly in different airway epithelial types. C12 had nearly identical effects on three key aspects of the apoptosis response (caspase 3/7, depolarization of Δψ(mito) and reduction of redox potential in the ER) in JME and CFTR-corrected JME cells (adenoviral expression), showing that CFTR was likely not an important regulator of C12-triggered apoptosis in airway epithelia. Exposure of airway cultures to biofilms from PAO1wt caused depolarization of Δψ(mito) and increases in Ca(cyto) like 10-50 µM C12. In contrast, biofilms from PAO1ΔlasI (C12 deficient) had no effect, suggesting that C12 from P. aeruginosa biofilms may contribute to accumulation of apoptotic cells that cannot be cleared from CF lungs. A model to explain the effects of C12 is proposed.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Schwarzer
authors.forename: Zhu
authors.initials: Z
authors.lastname: Fu
authors.forename: Maria
authors.initials: M
authors.lastname: Patanwala
authors.forename: Lauren
authors.initials: L
authors.lastname: Hum
authors.forename: Mirielle
authors.initials: M
authors.lastname: Lopez-Guzman
authors.forename: Beate
authors.initials: B
authors.lastname: Illek
authors.forename: Weidong
authors.initials: W
authors.lastname: Kong
authors.forename: Susan V
authors.initials: SV
authors.lastname: Lynch
authors.forename: Terry E
authors.initials: TE
authors.lastname: Machen
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000378:metabolism / Q000633:toxicity; D017209:Apoptosis; D018441:Biofilms / Q000254:growth & development*; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects*; D006714:Homoserine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000633:toxicity; D006801:Humans; D051336:Mitochondrial Membranes / Q000187:drug effects; D011550:Pseudomonas aeruginosa / Q000254:growth & development / Q000378:metabolism / Q000472:pathogenicity / Q000502:physiology*; D013997:Time Factors
chemical_list: C109860:N-(3-oxododecanoyl)homoserine lactone; D006714:Homoserine; D015107:4-Butyrolactone