Abstract
Background: Toll-like receptors (TLRs) and nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are innate, damage-associated molecular patterns (DAMP) sensors. Their expressions in human periodontal resident cells and reactions toward irritations, such as hypoxia and lipopolysaccharide (LPS), remain not well characterized. This cross-sectional study aimed to investigate and characterize TLRs, NOD1/2 and NLRP1/2 expressions at the dento-gingival junction. Methods: Immunohistochemistry screening was carried out on periodontal tissue biopsies sections, while selected DAMP sensors signal and protein expression under Escherichia coli LPS (2 µg/mL) and/or hypoxia (1% O2), 24 h, by human gingival keratinocytes (HGK) or fibroblasts (HGF) were investigated. Results: Positive TLR1/2/4/5/6, NOD1/2 and NLRP1/2 immunostaining were observed in healthy and periodontitis biopsies with apparently more pocket epithelial cells positive for TLR2, TLR4 and NOD1/2. TLR1-6, NOD1/2 and NLRP1/2 messengers were detected in gingival/periodontal biopsies as well as healthy HGK and HGF explants. LPS and/or hypoxia induced signals and protein upregulation of NOD2 in HGKs or TLR1/6 and NOD2 in HGFs. Conclusion: Transcripts and proteins of TLR1/2/4/5/6, NOD1/2 and NLRP1/2 were expressed in human periodontal tissue in health and disease. Putting all observations together, NOD2, perhaps with TLR1/2/4/6, might be considered key, damage-associated molecular pattern sensors on periodontal resident cells.
Highlights
Periodontitis is a common chronic oral disease caused by mixed, predominantly Gram-negative, anaerobic, pathogenic microorganisms in close proximity to periodontal tissues [1]
Thirteen healthy gingival and seventeen periodontitis biopsies were fixed and sectioned for immunohistopathology analysis; 27 healthy gingival biopsies were processed for human gingival keratinocytes (HGK) and human gingival fibroblast (HGF) culture and conventional Reverse Transcription Polymerase Chain Reaction (RT-PCR); and 16 healthy gingival biopsies contributed to human gingival tissue (HGT) mRNA extraction (Table 1)
The quantity of transcripts expression of damage-associated molecular patterns (DAMP) sensors detectable by RT-qPCR from HGK/HGF explants, i.e., TLR1-6, NOD1, NOD2, NLRP1, or NLRP2 (Figure 2), under 1% or 18% O2, 24 h, or 2 μg/mL E. coli LPS under normoxia at 24 h, was followed (Table 4)
Summary
Periodontitis is a common chronic oral disease caused by mixed, predominantly Gram-negative, anaerobic, pathogenic microorganisms in close proximity to periodontal tissues [1]. Toll-like receptors (TLRs) and nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are innate, damage-associated molecular patterns (DAMP) sensors. Their expressions in human periodontal resident cells and reactions toward irritations, such as hypoxia and lipopolysaccharide (LPS), remain not well characterized. This cross-sectional study aimed to investigate and characterize TLRs, NOD1/2 and NLRP1/2 expressions at the dentogingival junction. Methods: Immunohistochemistry screening was carried out on periodontal tissue biopsies sections, while selected DAMP sensors signal and protein expression under Escherichia coli LPS (2 μg/mL) and/or hypoxia (1% O2), 24 h, by human gingival keratinocytes (HGK) or fibroblasts (HGF) were investigated. NOD2, perhaps with TLR1/2/4/6, might be considered key, damage-associated molecular pattern sensors on periodontal resident cells
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
