Phosphatidylinositol-3-kinase inhibitor LY 294002 blocks Streptococcus mutans-induced interleukin (IL)-6 and IL-8 gene expression in odontoblast-like cells.
OBJECTIVE
To investigate the involvement of the phosphatidylinositol-3-kinase (PI3K) in interleukin-6 (IL-6) and interleukin-8 (IL-8) gene expression in odontoblast-like cells when exposed to heat-killed Streptococcus mutans.


METHODS
Cultured human odontoblast-like cells (Dulbecco's modified Eagle's medium) were pre-treated with a specific inhibitor for PI3K (LY 294002) and subsequently stimulated with heat-killed S. mutans for 6 and 24 h. After stimulation, RNA was extracted from the cells and cDNA synthesis was performed. Gene expression of IL-6 and IL-8 was analysed by real-time polymerase chain reaction and normalized to the gene expression of beta-actin. Cell survival was determined for stimulation experiments.


RESULTS
The gene expression of IL-6 and IL-8 was significantly increased in response to heat-killed S. mutans (P = 0.002 and P < 0.001, respectively). After 6 h, the mRNA expression of IL-6 and IL-8 was significantly higher than after 24 h of stimulation (P = 0.019 and P < 0.001, respectively). Pre-treatment with the inhibitor LY 294002 blocked the induced gene expression of IL-6 and IL-8 (P = 0.002 and P < 0.001, respectively). No differences in viable cell counts were found after stimulation with heat-killed S. mutans and/or pre-treatment with LY 294002 compared with the unstimulated control.


CONCLUSIONS
Gene expression of IL-6 and IL-8 was induced by heat-killed S. mutans via signalling pathways mediated by PI3K. These findings indicate that odontoblasts respond to cariogenic bacteria with increased gene expression of pro-inflammatory mediators and hence participate in immune processes.
Dommisch
H
H
Department of Periodontology, Operative and Preventive Dentistry, University Hospital Bonn, Bonn, Germany. henrik.dommisch@ukb.uni-bonn.de
Steglich
M
M
Eberhard
J
J
Winter
J
J
Jepsen
S
S
D002470:Cell Survival; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis; D016209:Interleukin-8 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D009025:Morpholines / Q000494:pharmacology*; D009804:Odontoblasts / Q000201:enzymology* / Q000276:immunology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018709:Statistics, Nonparametric; D013295:Streptococcus mutans / Q000737:chemistry; D000093242:Interleukin-6 Inhibitors
D002867:Chromones; D004791:Enzyme Inhibitors; D015850:Interleukin-6; D016209:Interleukin-8; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D012333:RNA, Messenger; D000093242:Interleukin-6 Inhibitors; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one