NFkB Signaling in Peridontal Ligament Fibroblasts Isolated from Diseased Sites

Objective: Periodontitis is triggered primarily from activated immuno-inflammatory mechanisms which cause site specific damage including alteration in bone and connective tissue leading to failure of periodontal tissue homeostasis. However, periodontal ligament fibroblasts (PDLF) from diseased sites have significantly higher levels of pro-inflammatory gene expression than PDLF cells from healthy sites.  Since NFkB is a major transcriptional modulator of inflammation, we investigated the levels and cellular localization of NFkB subtypes (p65, p52, p50), and  the inhibitor proteins, IkBa, b, and e over time.

Method: PDLF were isolated from patients diagnosed with chronic or advanced periodontitis. Periodontal ligament fibroblasts established in culture from healthy patient tissues served as the control group.  The cells were exposed to (LPS, 1mg/mL, E. coli) for 0, 0.5, 1, 1.5, 2, 3, 4, 6, or 8h.  Cytoplasmic and nuclear fractions were prepared for Western blot analyses using the Odyssey® imaging system to determine the location and quantity of the NFkB subtypes and IkB isoforms.  All gel data were analyzed using ANOVA and Tukey post-hoc test (a= 0.05). 

Result: Nuclear p65 levels were constitutively higher in PDLF cells from diseased sites than those from healthy sites. Nuclear p50 subtype increased by 0.5h and sustained through 2h. Nuclear p65 was higher by 1h but had a cyclic nuclear translocation through 6h, while p52 nuclear translocation  exhibited a delayed response.  PDLF cells from diseased sites had higher levels of cytosolic IkB isoforms than PDLFs from healthy sites.  IkBa levels decreased at 1h but increased again by 1.5h. IkBb increased at 0.5h, then decreased through 6h.  IkBe was not detected

Conclusion: The variation of the NFkB subtypes and IkB isoforms suggest a possible mechanism for a prolonged inflammatory signal which is consistent with our previous data of increased inflammatory gene expression and protein secretion by PDLFs from diseased sites.