NFE2L2/NRF2, OGG1, and cytokine responses of human gingival keratinocytes against oxidative insults of various origin
Bacterial or tobacco-related insults induce oxidative stress in gingival keratinocytes. The aim of this study was to investigate anti-oxidative and cytokine responses of human gingival keratinocytes (HMK cells) against Porphyromonas gingivalis lipopolysaccharide (Pg LPS), nicotine, and 4-nitroquinoline N-oxide (4-NQO).
Materials and methods
HMK cells were incubated with Pg LPS (1 µl/ml), nicotine (1.54 mM), and 4-NQO (1 µM) for 24 h. Intracellular and extracellular levels of interleukin (IL)-1β, IL-1 receptor antagonist (IL-1Ra), IL-8, monocyte chemoattractant protein (MCP)-1, and vascular endothelial growth factor (VEGF) were measured with the Luminex® xMAP™ technique, and nuclear factor, erythroid 2 like 2 (NFE2L2/NRF2) and 8-oxoguanine DNA glycosylase (OGG1) with Western blots. Data were statistically analyzed by two-way ANOVA with Bonferroni correction.
All tested oxidative stress inducers increased intracellular OGG1 levels, whereas only nicotine and 4-NQO induced NFE2L2/NRF2 levels. Nicotine, 4-NQO, and their combinational applications with Pg LPS induced the secretions of IL-1β and IL-1Ra, while that of IL-8 was inhibited by the presence of Pg LPS. MCP-1 secretion was suppressed by nicotine, alone and together with Pg LPS, while 4-NQO activated its secretion. Treatment of HMK cells with Pg LPS, nicotine, 4-NQO, or their combinations did not affect VEGF levels.
Pg LPS, nicotine, and 4-NQO induce oxidative stress and regulate anti-oxidative response and cytokine expressions in human gingival keratinocytes differently. These results may indicate that bacterial and tobacco-related insults regulate distinct pathways.
KeywordsReactive oxygen species Anti-oxidative response Porphyromonas gingivalis Lipopolysaccharide Nicotine 4-Nitroquinoline N-oxide
The authors are grateful to Katja Sampalahti and Oona Hällfors from the Institute of Dentistry, University of Turku, Finland, for their excellent technical assistance in cytokine level analyses. This study was supported by the Turku University Foundation (Grant No: 12198, UKG), Finnish Dental Society Apollonia (UKG), and by the Scientific and Technological Research Council of Turkey (Grant No: BIDEB 2219-1059B191600656, GK). FZC is grateful to FINDOS Turku Grant for Completing a Doctoral Degree (University of Turku), University of Turku Joint Research Grant Fund, and Selma and Maja-Lisa Selander's Fund (Minerva Foundation, Helsinki) for supporting this work.
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