MicroRNA and periodontal pathogen interaction in shaping innate immune response

Abstract

Abstract MicroRNA (miR) play a critical role in the pathogenesis of immune-mediated diseases, however, their role in periodontal disease (PD) remain poorly studied. We hypothesize that periopathogens (P. gingivalis [Pg] and A. actinomycemtemcomitans [Aa]) impair host immune response by perturbing miR expression. Naïve CD14+ monocytes were isolated from human PBMC and differentiated to M1 MΦ or M2 MΦ in presence of GM-CSF or M-CSF for 7 days. Cells were challenged with Pg or Aa (both 100 MOI) for 4 h and 24 h. Total RNA was isolated to quantitate expression of pro- and anti-inflammatory miRNAs, cell lysate was prepared for protein expression of NFκB, PU.1 and CEBP/β by western blot and supernatants were collected to analyze cytokine profiles. We observed that expression of pro-inflammatory miRNAs viz., miR-125a and miR-155a are increased in M1-MΦ and M2-MΦ challenged with Pg and Aa. Surprisingly, the expression of anti-inflammatory miR-146a was differentially expressed in both MΦ, but miR-511 expression was reduced. miR-142-3p expression in response to Pg and Aa challenge was decreased suggesting its possible anti-inflammatory function. To examine the impact of miR-142-3p on Pg and Aa-mediated immune responses, we examined PU.1 levels, a known TF regulating miR-142 expression, and noticed a significant decrease in PU.1 and it correlates with mature miR-142-3p levels. miR-142-3p transfected MΦ challenged with Pg or Aa exhibit altered secretion of inflammatory cytokines. In conclusion, periopathogen-mediated activation of NFκB and miR-155 augments inflammatory signaling by suppressing expression of anti-inflammatory miR-142-3p by decreasing PU.1 levels. Perturbation of miR by periodontal bacteria is central to the pathogenesis of PD.