The Influence of Neuro-hormones on Periodontal Pathogens

Psychosocial stress has been implicated in contributing to acute inflammation of chronic periodontitis and gingivitis. Stress related catecholamines can enhance the growth of several gram-negative bacteria, but it is not known if they modulate the growth and enzyme expression of periodontal pathogens. Objectives: To investigate, in vitro, the influence of neuroendocrine stress hormones on the growth response of oral pathogens and monitor effects on enzyme expression activities associated with H2S production. Methods: Treponema denticola (Td) 35405 cultures were inoculated in serum-free GM-1 medium at 3 ml volumes at a starting concentration of OD₆₆₀ 0.03. Each hormone was added at a final concentration of 50-100 nM. The bacteria were incubated either anaerobically in a Coy anaerobic chamber or aerobically in room atmosphere at 37°C for 24 hours; the growth-rate was determined spectrophotometrically at A_620nm. Enzyme activities of ã-glutamyltransferase and cystalysin were determined by colorimetric assays with GNA and L-cysteine as substrates. Actinobacillus actinomycetemcomitans (Aa) and Porphyromonas gingivalis (pg) were inoculated in relative broth and bacterial growth was determined by colonization. Results: Our results demonstrate that norepinephrine and epinephrine both enhance Td growth at a final concentration of 100nM. The increased rates were approximately 8.6-12% under anaerobic conditions versus 54-360% under aerobic conditions. However, only in an aerobic environment did Td grown in the presence of norepinephrine or epinephrine exhibit significant increases in ã-glutamyltransferase (8.6-18.8%) and cystalysin enzyme activities (13%-20%) compared to control. Both Aa and Pg growth were enhanced 4-16 times by the addition of 50 nM norepinephrine. Conclusions: In vitro, norepinephrine and epinephrine can stimulate growth of the periodontal pathogens and enhance Td γ-glutamyltransferase and cystalysin enzyme activities. These results provide evidence that psychosocial stress may play an important role in the periodontal infections. Supported by NIDCR grant DE13819 and DE14318 CO STAR.