Antibiotics Used in Regenerative Endodontics Modify Immune Response of Macrophages to Bacterial Infection

Abstract

Introduction: Ciprofloxacin, amoxicillin and metronidazole are antibiotics used in regenerative endodontic therapy (RET). While their antimicrobial properties are well documented, there is a lack of information on the effects of these antibiotics on immune response by host macrophages, and periapical healing. This study thus has 2 objectives, (i) determine the immune response of macrophages to endodontic pathogens in response to the combination of ciprofloxacin or amoxicillin, and metronidazole, and (ii) using conditioned media produced by these macrophages to simulate the periapical microenvironment, determine the impact on the expression of extracellular matrix (ECM) components by periodontal fibroblasts. Methods: Macrophages were treated with ciprofloxacin and metronidazole, or amoxicillin and metronidazole at 10 to 1000µg/mL. The treated macrophages were exposed to lipopolysaccharide (LPS), and pro- and anti-inflammatory cytokines produced were quantified with ELISA. Periodontal fibroblasts were treated with conditioned media from these treated macrophages, and the expression of ECM genes was determined by qPCR. Results: LPS elicited production of pro-inflammatory cytokines IL-1β and TNF-α by macrophages, but this was suppressed by ciprofloxacin and metronidazole. Moreover, only conditioned media from macrophages treated with ciprofloxacin and metronidazole rescued microbial-induced down-regulation of ECM genes by periodontal fibroblasts. Specifically, ciprofloxacin was the antibiotic responsible for these observations. In contrast, these effects were not observed with amoxicillin and metronidazole. Conclusions: Apart from disinfection of the root canal system, the combination of ciprofloxacin and metronidazole also exerts an immunomodulatory effect, which may aid periapical healing.