Inflammatory response to chlorhexidine, minocycline HCl and doxycycline HCl in an in vivo mouse model

Aim: To examine the effect of locally delivered antimicrobial drugs on the inflammatory response in an in vivo mouse chamber model. Material and Methods: Two weeks following chamber implantation, 24 BALB/c mice, in the experimental group, were given an intra-chamber challenge of heat-killed Porphyromonas gingivalis, followed immediately by injection of the specific antimicrobial drug: 2000 μg/ml chlorhexidine (CHX); 1500 μg/ml minocycline HCl;and 1500 μg/ml doxycycline HCl (concentrations achieved in the periodontal pocket with commercial controlled-release delivery systems). A second group of 24 animals received only the antimicrobial treatment without P. gingivalis challenge. Intra-chamber exudates were sampled at 2 and 24 h following the challenge, and leucocytes, TNFα, IFNγ and IL-10 were evaluated. Results: At 2 h, minocycline HCl induced high levels of IL-10, TNFα and IFNγ, while CHX reduced the levels of TNFα and IFNγ. By 24 h, these responses were attenuated. Following bacterial challenge, the antibacterial agents attenuated the inflammatory process, each in its own fashion. Conclusions: Antibacterial agents applied locally have the ability to induce an inflammatory response. They also modify the inflammatory response to P. gingivalis independent of their antimicrobial effect. CHX and doxycycline HCl appear to have the most marked anti-inflammatory effect.