Date of Award

2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Stomatology

College

College of Dental Medicine

First Advisor

Keith L. Kirkwood

Second Advisor

Joe W. Krayer

Third Advisor

Robert Gellin

Abstract

Background: Tristetraprolin (TTP) is an RNA binding protein that tightly regulates target mRNA stability and translation through specific interactions with AU-rich regions of target mRNA 3’ untranslated region (UTR). TTP has been shown to play an important role involving decreased translation of important inflammatory cytokines in periodontal disease including TNF- , IL-6 and other immune mediators. The role of TTP was initially demonstrated in TTP knock- out mice that displayed systemic inflammatory conditions, including rheumatoid arthritis and dermatitis. The p38 MAPK cascade that is activated by bacterial-derived lipopolysaccharide (LPS) has been demonstrated to be part of the deactivation process of TTP. MAPK-activated protein kinase-2 (MK2), the immediate downstream kinase of p38 MAPK, directly deactivates TTP through phosphorylation, which allows increased mRNA stability and translation of target inflammatory mediators. Our goal of this study was to determine the amount of expression of proteins MK2, phosphor-MK2 (pMK2, the active form), and total TTP in human gingival tissues in health and disease. Materials and Methods: Human gingival tissues samples were collected from twenty-five periodontally healthy (control group) and twenty-five periodontal disease subjects (test group) in addition to clinical measurements. In order to test a true representation of periodontal health and disease, samples were removed due to clinical confounding factors and insufficient size tissues. Remaining samples were stained with hematoxylin and eosin (H&E) for histopathological analysis. Additionally, immunohistochemistry (IHC) staining was performed with specific antibodies against MK2, pMK2, and TTP. H&E inflammatory infiltrate scores, IHC intensity for all three proteins of interest, and IHC area scores were assigned to each sample by a blinded pathologist. Statistical analysis with Spearman Rank Correlation and Fisher’s Exact Test were performed to determine the relationship between the expression of the proteins and inflammatory scores and clinical measurements. Clinical measurements were represented by the periodontal inflammatory burden index (PIBI). Results: Mean values for all scores were higher for the test group compared to the control group. MK2 and TTP intensity, area, and composite scores had a statistically significant positive correlation to both H&E scores and PIBI shown from the results of the Spearman Rank Correlation. Intensity and composite scores for pMK2 also showed a positive correlation that was statistically significant. The area scores for pMK2 showed a significant relationship to H&E scores but not to PIBI. Findings from the Fisher Exact test stated that the H&E scores and all IHC values except for the pMK2 area score showed high predictability for periodontal disease status. Conclusion: There is an increased expression of MK2, pMK2, and TTP in periodontally diseased tissues when compared to the healthy samples. All three proteins showed a strong, positive correlation to inflammation and periodontal disease. The current TTP findings contrasted those found in previous studies, which can be explained by indiscriminate binding of the TTP antibody to all forms of TTP. Further investigations are necessary to understand the extent of TTP’s role in periodontitis and its potential as a target in treating periodontal disease.

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