Effect of probiotic lactobacilli on the modulation of inflammassome and alveolar bone loss promoted by experimental periodontitis in healthy mice

Abstract

The medical use of probiotics is widely known, but the mechanisms involved on the control of inflammatory diseases, such as periodontitis, are still poorly explored. Probiotic bacteria can promote the modulation of mucosal and systemic immune response, under health or disease conditions. Previous in vitro studies performed in our laboratory revealed that Lactobacillus probiotics are able to interfere in the formation of the multispecies biofilm formed by Porphyromonas gingivalis and Streptococcus species, besides interfering in the processes of adhesion and invasion in epithelial cells, as well as in the response of these cells to the periodontopathogens. Furthermore, our data suggests differences in the ability of Lactobacillus probiotics to modulate the inflammatory response. Although inflammassomes are considered beneficial, as they promote a response against pathogens and endogenous danger signals, their dysregulation can lead to inflammatory diseases. Gingival tissues of patients with chronic periodontitis present NRLP3-mediated activated inflammassomes. The periodontopathogen P. gingivalis activates inflammassomes in gingival epithelial cells (GECS) and macrophages dependent on the cytoplasmic receptors NRLP3 and AIM2. Our initial data showed that P. gingivalis was able to induce IL-1² production and NLRP3 expression, and this effect was attenuated in cells challenged by P. gingivalis when co-cultivated with the probiotic strain L. acidophilus LA5, but exacerbated by the strain L. rhamnosus LR32. The present study aims to evaluate the ability of two probiotic strains of the genus Lactobacillus (L. acidophilus LA5 and L. rhamnosus LR32) to modulate inflammation induced by the periodontopathogenic microbiota and to control the destruction of periodontal tissues in normoglycemic animal models. The probiotic strains will be tested in an animal model of experimental periodontitis induced by polymicrobial oral infection (P. gingivalis, Prevotella intermedia and S. gordonii) in normoglycemic C57Bl6 mice. After euthanasia, levels of IL-1², IL-18 and IL-17 will be analyzed by ELISA, expression of genes encoding intra and extracellular receptors and cytokines will be analyzed by RT-qPCR, in addition to the analysis of caspase-1 activation, release of active IL-1² in gingival tissues and alveolar bone loss evaluation by microCT. Justificative: Periodontitis is an inflammatory disease induced by a dysbiotic microbiota. Strategies to restore the microbial balance and control inflammation should be considered in the treatment and prevention of this disease. The present study will evaluate the possibility of controlling periodontitis using probiotic strains with distinct properties on the host response, which may not only indicate the strain with the greatest potential for periodontal disease control in humans, but may also help to elucidate the mechanisms associated with the destructive immune response.