Impact of estradiol on the dipeptidyl peptidase IV enzyme activity of the Prevotella intermedia group bacteria

Objectives: Pregnancy-associated gingivitis has been linked to Prevotella intermedia (sensu lato), which is able to use estradiol as an alternative source of growth instead of vitamin K. The aim was to investigate in vitro the impact of estradiol on the bacterial dipeptidyl peptidase IV (DPPIV) enzyme activity of the P. intermedia group bacteria (P. intermedia, P. nigrescens, P. pallens, and P. aurantiaca) grown in biofilms.
Methods: In all experiments, 2 strains of each species were incubated with the concentrations of 0 (control), and 30, 90, and 120 nmol/L of estradiol, representing equivalent serum estradiol concentrations simulating the first, second, and third trimester of pregnancy, and allowed to build biofilms at an air-solid interface. DPPIV activities were measured kinetically during 20 min using a fluorometric assay. The enzyme activity was related to the amount of protein produced by the same biofilm, reflecting the biofilm mass. The experiments were performed in triplicates.
Results: Estradiol significantly increased DPPIV activities of the Prevotella strains in a strain- and dose-dependent manner. Enzyme activity peak was reached in the estradiol concentration of 90 nmol/L in 6 strains, while for 1 P. nigrescens strain and 1 P. pallens strain the peak was reached in the concentration of 30 nmol/L. Dividing the enzyme activity measurements by the total protein mass of biofilms yielded a significant increase in the DPPIV activity in all Prevotella strains tested. The P. aurantiaca strains had the highest enzyme activities but the lowest biofilm mass.
Conclusions: Elevated estradiol concentrations enhance the relative and quantitative DPPIV proteolytic enzyme activity in strain- and dose-dependent manners. This may lead to differences between species to elicit a virulent state, which contributes to the development of pregnancy-related gingivitis. The role of P. aurantiaca in its pathogenesis deserves attention.