I was honored last month when the Journal of Periodonology published the abstract of my masters thesis, “Differential Gene Expression of Inflammatory Signaling in Localized Aggressive Periodontitis.” I spent three years working on this project with my mentor, Dr Thomas Hart, and our hardworking team of immunologists, geneticists, and statisticians. We are planning to publish our full article in the near future. Since I left Chicago, this research effort has been taken over by Dr Julio Obando, an exceptional post-graduate resident at the University of Illinois at Chicago. If you have any questions regarding this work or further interest please feel free to email me at firstname.lastname@example.org.
Differential Gene Expression of Inflammatory Signaling in Localized Aggressive Periodontitis
Whitney D. Weiner, University of Illinois at Chicago College of Dentistry, Chicago, IL
Background: Aggressive periodontitis (AP) is a disease characterized by severe periodontal destruction. Gene-environment interactions are etiologically important in AP, with microbial factors triggering underlying genetic host susceptibility. The genetic basis of AP is incompletely characterized. This study aimed to determine if expression of early innate immune response genes differ between patients with AP and healthy matched controls.
Methods: A comprehensive literature review of all genes reported to have a role in AP (n = 596 articles) identified 38 candidate genes. Relevant protein-protein interactions were confirmed and visualized using on online database of known and predicted protein interactions, which identified 35 of the 38 genes with common involvement in early innate immunity. Based on functional analyses, 20 candidate genes were selected to test the hypothesis that differential expression of early innate immune response genes to inflammatory stimuli could underlie AP susceptibility. Epithelial cells were targeted because they represent the first site of interaction between oral biofilms and cells with the potential to contribute to inflammation and innate immunity. Gingival biopsies were obtained from non-infected sites in three patients with AP and three healthy controls (African-American females, age 15 to 21 years). Primary gingival keratinocytes were isolated, cultured, and incubated overnight. Cells were treated with human recombinant interleukin (IL)-1β, Porphyromonas gingivalis LPS (PgLPS), Aggregatibacter actinomycetemcomitans (AaLPS), or medium only to evaluate gene expression at 0, 3, and 6 hours. Cells were lysed in a reagent, and RNA was isolated. Differential gene expression was analyzed using a multiplex bead-based assay that is an alternative to quantitative reverse transcription-polymerase chain reaction. At baseline, there were no differences in gene expression in patients versus controls. IL-1β treatment caused increased expression of IL8 (P = 0.02), NFKB1 (P = 0.02), and IL-1β (P = 0.05) . IL-1β elicited increased expression of NLRP3 (P = 0.03) and decreased expression of CCL2 (P = 0.05) in patients with AP. LY96 and NLRP3 expression was higher, while CCL2 expression was lower across all treatment conditions. Stimulation with PgLPS and AaLPS elicited different patterns of gene expression between patients with AP and controls for NLRP3 (P = 0.03 and P = 0.02, respectively), increasing in healthy individuals and decreasing in patients with AP over time. Treatment with IL-1β elicited higher gene expression for CCL2 (P = 0.02) in healthy controls versus patients with AP.
Conclusions: The inflammatory triggers AaLPS, PgLPS, and IL-1β elicited differential expression for several genes involved in the early innate immune response. These findings support previous reports of a relationship between the NLRP3 inflammasome complex and periodontal disease, indicating a role for NLRP3 in AP. The present findings also offer insight into host immune responses involved in the pathogenesis of AP by demonstrating a deregulation of inflammatory signaling following immune challenge in patients with AP.
Acknowledgments: Drs. Joseph V. Califano, East Carolina University, Greenville, NC, and Christopher G. Engeland, Shujuan Guo, and Thomas C. Hart, University of Illinois at Chicago, participated in this research. No financial support was received. Figure 1: STRING analysis (version 9.0) of 12 candidate early innate immune response genes interacting with NF-kβ