ATP-dependent activation of an inflammasome in primary gingival epithelial cells infected by Porphyromonas gingivalis.
Production of IL-1beta typically requires two-separate signals. The first signal, from a pathogen-associated molecular pattern, promotes intracellular production of immature cytokine. The second signal, derived from a danger signal such as extracellular ATP, results in assembly of an inflammasome, activation of caspase-1 and secretion of mature cytokine. The inflammasome component, Nalp3, plays a non-redundant role in caspase-1 activation in response to ATP binding to P2X(7) in macrophages. Gingival epithelial cells (GECs) are an important component of the innate-immune response to periodontal bacteria. We had shown that GECs express a functional P2X(7) receptor, but the ability of GECs to secrete IL-1beta during infection remained unknown. We find that GECs express a functional Nalp3 inflammasome. Treatment of GECs with LPS or infection with the periodontal pathogen, Porphyromonas gingivalis, induced expression of the il-1beta gene and intracellular accumulation of IL-1beta protein. However, IL-1beta was not secreted unless LPS-treated or infected cells were subsequently stimulated with ATP. Conversely, caspase-1 is activated in GECs following ATP treatment but not P. gingivalis infection. Furthermore, depletion of Nalp3 by siRNA abrogated the ability of ATP to induce IL-1beta secretion in infected cells. The Nalp3 inflammasome is therefore likely to be an important mediator of the inflammatory response in gingival epithelium.
Yilmaz
Ozlem
O
Department of Periodontology, University of Florida, Gainesville, FL 32610, USA. oyilmaz@ufl.edu
Sater
Ali Abdul
AA
Yao
Luyu
L
Koutouzis
Theofilos
T
Pettengill
Matthew
M
Ojcius
David M
DM
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology; D020170:Caspase 1 / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology*; D005881:Gingiva / Q000166:cytology* / Q000382:microbiology*; D006801:Humans; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D016133:Polymerase Chain Reaction; D016966:Porphyromonas gingivalis / Q000502:physiology*; D034622:RNA Interference; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000187:drug effects
D002352:Carrier Proteins; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; D034741:RNA, Small Interfering; D000255:Adenosine Triphosphate; D020170:Caspase 1