In chronic (formerly adult) periodontitis, bacteria destroy the dento-gingival junction, especially its Dentally attached (DAT) cells, keratinocytes that are activated by persistent trauma from mastication and oral hygiene. These rapidly dividing cells form the internal basement lamina of junctional epithelium (JE) and maintain the epithelial attachment. The DAT cell coronal extremity grows on interstitial fluid that transudes through the JE to the base of a gingival sulcus, near the site of infecting bacteria. We posit that lysine decarboxylase (LDC), a bacterial enzyme in the sulcus, depletes the transudate of lysine, starving the DAT cells. A small amount of LDC causes a cascade of events predisposing to loss of Dental attachment and colonization of the sulci by well-known periodontopathogens. Oral hygiene controls this colonization, but some adults are refractory and discriminated by increased Capnocytophaga spp. and other LDC producers. The activity of LDC from the bacteria in gingival sulci may be critical for determining whether chronic periodontitis can be controlled by current (oral hygiene-based) therapy.
The Aims of this study are to: 1) develop new assays for measuring the amount of active LDC in the gingival microbiota (plaque); and 2) use these assays for measuring active enzyme in the sulci from refractory and successfully treated patients. LDC activity will be determined by two methods. The first will determine enzyme activity (cadaverine synthesis) in the presence of a saturating amount of substrate (lysine) in extracts of whole-mouth plaque from refractory and successfully treated patients. The second will use H-a-difluoromethyl DL-lysine (DFML), a suicide inhibitor that forms an adduct at the catalytic center of LDC. DFML is not commercially available and it will be synthesized unlabeled and as a radioactive derivative for this project. Radiolabeled adduct formation should be inhibited by an excess of unlabeled L-DFML or lysine and the amount of radioactivity on blots will indicate the amount of active enzyme after incubation with plaque extracts. The application predicts that there will be more enzyme activity in refractory than in successfully treated patient plaque. The results will indicate the relationship of LDC activity in the gingival sulcular microbiota to therapeutic outcome, and whether LDC inhibitors such as DFML might have utility as a new, alternative pharmacotherapeutic for preventing and controlling chronic periodontitis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21DE014583-02
Application #
6769439
Study Section
Special Emphasis Panel (ZRG1-OBM-1 (01))
Program Officer
Mangan, Dennis F
Project Start
2003-07-01
Project End
2005-05-31
Budget Start
2004-06-01
Budget End
2005-05-31
Support Year
2
Fiscal Year
2004
Total Cost
$145,105
Indirect Cost
Name
University of Oklahoma Health Sciences Center
Department
Biochemistry
Type
Schools of Medicine
DUNS #
878648294
City
Oklahoma City
State
OK
Country
United States
Zip Code
73117
Lohinai, Zsolt; Keremi, Beata; Szöko, Eva et al. (2015) Biofilm Lysine Decarboxylase, a New Therapeutic Target for Periodontal Inflammation. J Periodontol 86:1176-84
Peters, Jennifer L; DeMars, Paul L; Collins, Lindsay M et al. (2012) Effects of immunization with natural and recombinant lysine decarboxylase on canine gingivitis development. Vaccine 30:6706-12
Lohinai, Zsolt; Keremi, Beata; Szoko, Eva et al. (2012) Bacterial lysine decarboxylase influences human dental biofilm lysine content, biofilm accumulation, and subclinical gingival inflammation. J Periodontol 83:1048-56