title: NALP-3 inflammasome silencing attenuates ceramide-induced transepithelial permeability.
abstract: The hallmark of acute lung injury (ALI) is the influx of proinflammatory cytokines into lung tissue and alveolar permeability that ultimately leads to pulmonary edema. However, the mechanisms involved in inflammatory cytokine production and alveolar permeability are unclear. Recent studies suggest that excessive production of ceramide has clinical relevance as a mediator of pulmonary edema and ALI. Our earlier studies indicate that the activation of inflammasome promotes the processing and secretion of proinflammatory cytokines and causes alveolar permeability in ALI. However, the role of ceramide in inflammasome activation and the underlying mechanism in relation to alveolar permeability is not known. We hypothesized that ceramide activates the inflammasome and causes inflammatory cytokine production and alveolar epithelial permeability. To test this hypothesis, we analyzed the lung ceramide levels during hyperoxic ALI in mice. The effect of ceramide on activation of inflammasome and production of inflammatory cytokine was assessed in primary mouse alveolar macrophages and THP-1 cells. Alveolar transepithelial permeability was determined in alveolar epithelial type-II cells (AT-II) and THP-1 co-cultures. Our results reveal that ceramide causes inflammasome activation, induction of caspase-1, IL-1β cleavage, and release of proinflammatory cytokines. In addition, ceramide further induces alveolar epithelial permeability. Short-hairpin RNA silencing of inflammasome components abrogated ceramide-induced secretion of proinflammatory cytokines in vitro. Inflammasome silencing abolishes ceramide-induced alveolar epithelial permeability in AT-II. Collectively, our results demonstrate for the first time that ceramide-induced secretion of proinflammatory cytokines and alveolar epithelial permeability occurs though inflammasome activation.
authors.affiliation: Division of Allergy and Immunology, Department of Internal Medicine, College of Medicine, University of South Florida, Tampa, Florida 33612, USA. nkollipu@health.usf.edu
authors.forename: Narasaiah
authors.initials: N
authors.lastname: Kolliputi
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Galam
authors.forename: Prasanna Tamarapu
authors.initials: PT
authors.lastname: Parthasarathy
authors.forename: Srinivas M
authors.initials: SM
authors.lastname: Tipparaju
authors.forename: Richard F
authors.initials: RF
authors.lastname: Lockey
mesh_terms: D055371:Acute Lung Injury / Q000139:chemically induced / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000037:antagonists & inhibitors*; D002478:Cells, Cultured; D002518:Ceramides / Q000008:administration & dosage*; D016207:Cytokines / Q000235:genetics* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D018496:Hyperoxia / Q000139:chemically induced; D007249:Inflammation / Q000235:genetics / Q000378:metabolism*; D016676:Macrophages, Alveolar / Q000187:drug effects* / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D010100:Oxygen / Q000008:administration & dosage; D010539:Permeability / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics; D057705:Transendothelial and Transepithelial Migration / Q000187:drug effects / Q000502:physiology
chemical_list: D002352:Carrier Proteins; D002518:Ceramides; D016207:Cytokines; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; D034741:RNA, Small Interfering; D010100:Oxygen