Toll-like receptor 2 knockdown modulates interleukin (IL)-6 and IL-8 but not stromal derived factor-1 (SDF-1/CXCL12) in human periodontal ligament and gingival fibroblasts.
BACKGROUND
Fibroblasts are now seen as active components of the immune response because these cells express Toll-like receptors (TLRs), recognize pathogen-associated molecular patterns, and mediate the production of cytokines and chemokines during inflammation. The innate host response to lipopolysaccharide (LPS) from Porphyromonas gingivalis is unusual inasmuch as different studies have reported that it can be an agonist for Toll-like receptor 2 (TLR2) and an antagonist or agonist for Toll-like receptor 4 (TLR4). This study investigates and compares whether signaling through TLR2 or TLR4 could affect the secretion of interleukin (IL)-6, IL-8, and stromal derived factor-1 (SDF-1/CXCL12) in both human gingival fibroblasts (HGF) and human periodontal ligament fibroblasts (HPDLF).


METHODS
After small interfering RNA-mediated silencing of TLR2 and TLR4, HGF and HPDLF from the same donors were stimulated with P. gingivalis LPS or with two synthetic ligands of TLR2, Pam2CSK4 and Pam3CSK4, for 6 hours. IL-6, IL-8, and CXCL12 mRNA expression and protein secretion were evaluated by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.


RESULTS
TLR2 mRNA expression was upregulated in HGF but not in HPDLF by all the stimuli applied. Knockdown of TLR2 decreased IL-6 and IL-8 in response to P. gingivalis LPS, or Pam2CSK4 and Pam3CSK4, in a similar manner in both fibroblasts subpopulations. Conversely, CXCL12 remained unchanged by TLR2 or TLR4 silencing.


CONCLUSIONS
These results suggest that signaling through TLR2 by gingival and periodontal ligament fibroblasts can control the secretion of IL-6 and IL-8, which contribute to periodontal pathogenesis, but do not interfere with CXCL12 levels, an important chemokine in the repair process.
Department of Biological Sciences, Bauru School of Dentistry, University of São Paulo, Bauru, São Paulo, Brazil.
Ana Carolina F
AC
Morandini
Pedro Paulo
PP
Chaves Souza
Erivan Schnaider
ES
Ramos-Junior
Daniel Thomas
DT
Brozoski
Carla Renata
CR
Sipert
Carlos Alberto
CA
Souza Costa
Carlos Ferreira
CF
Santos
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D002478:Cells, Cultured; D054377:Chemokine CXCL12 / Q000096:biosynthesis / Q000235:genetics; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D055785:Gene Knockdown Techniques; D005881:Gingiva / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000235:genetics; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D010513:Periodontal Ligament / Q000166:cytology / Q000378:metabolism*; D034622:RNA Interference; D015398:Signal Transduction; D018709:Statistics, Nonparametric; D051195:Toll-Like Receptor 2 / Q000235:genetics*; D051197:Toll-Like Receptor 4 / Q000235:genetics; D055815:Young Adult
D054377:Chemokine CXCL12; D015850:Interleukin-6; D016209:Interleukin-8; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4