Although a range of biological and pharmacological activities of melatonin have been reported, little is known about its potential anti-inflammatory efficacy in periodontal disease. In this study, we investigated the effects of melatonin on the production of inflammatory mediators by murine macrophages stimulated with lipopolysaccharide (LPS) from Prevotella intermedia, a major cause of inflammatory reactions in the periodontium, and sought to determine the underlying mechanisms of action. Melatonin suppressed the production of nitric oxide (NO) and interleukin-6 (IL-6) at both gene transcription and translation levels in P. intermedia LPS-activated RAW264.7 cells. P. intermedia LPS-induced NF-κB-dependent luciferase activity was significantly inhibited by melatonin. Melatonin did not reduce NF-κB transcriptional activity at the level of IκB-α degradation. Melatonin blocked NF-κB signaling through the inhibition of nuclear translocation and DNA-binding activity of NF-κB p50 subunit and suppressed STAT1 signaling. Although further research is required to clarify the detailed mechanism of action, we conclude that melatonin may contribute to blockade of the host-destructive processes mediated by these two proinflammatory mediators and could be a highly efficient modulator of host response in the treatment of inflammatory periodontal disease.

Although additional studies are required to dissect the molecular mechanism of action, our results suggest that daidzein could be a promising agent for treating inflammatory periodontal disease. Further research in animal models of periodontitis is necessary to better evaluate the potential of daidzein as a novel therapeutic agent to treat periodontal disease.

Background: Nitric oxide (NO) could be a potential target for the development of new therapeutic approaches to the treatment of periodontal disease because this molecule plays a significant role in the tissue destruction observed in periodontitis. In this study, the authors investigate the effect of kaempferol on the production of NO by murine macrophage‐like RAW264.7 cells stimulated with lipopolysaccharide (LPS) from Prevotella intermedia, a pathogen implicated in periodontal disease, and try to determine the underlying mechanisms of action.Methods: NO production was assayed by measuring the accumulation of nitrite in culture supernatants. Real‐time polymerase chain reaction was performed to quantify inducible NO synthase (iNOS) and heme oxygenase‐1 (HO‐1) mRNA expression. iNOS and HO‐1 protein expression and phosphorylation of c‐Jun N‐terminal kinase and p38 were characterized via immunoblot analysis. Reactive oxygen species (ROS) production was measured using the redox‐sensitive fluorescent probe 2′,7′‐dichlorodihydrofluorescein diacetate.Results: Kaempferol significantly inhibited NO production and expression of iNOS protein in P. intermedia LPS‐stimulated RAW246.7 cells without affecting iNOS mRNA expression. Kaempferol upregulated HO‐1 expression in LPS‐activated cells. Inhibition of HO‐1 activity by tin protoporphyrin IX (SnPP) abolished the suppressive effect of kaempferol on NO production. In addition, kaempferol significantly attenuated P. intermedia LPS‐induced increase of intracellular ROS, and SnPP blocked this reduction. Treatment with antioxidants downregulated the production of LPS‐induced NO.Conclusions: Kaempferol inhibits NO production and iNOS protein expression in P. intermedia LPS‐stimulated RAW264.7 cells at the translational level via HO‐1‐mediated ROS reduction and could be an efficient modulator of host response in the treatment of periodontal disease.

Although further research is encouraged to clarify the detailed mechanism of action, flavonoid luteolin may contribute to blockade of the host-destructive processes mediated by these two proinflammatory mediators and could have potential use in the treatment of inflammatory periodontal disease.

Several reports have indicated that dietary intake of DHA is associated with lower prevalence of periodontitis. In the present study, we investigated the effect of DHA on the production of proinflammatory mediators in murine macrophage-like RAW264.7 cells stimulated with lipopolysaccharide (LPS) isolated from Prevotella intermedia, a pathogen implicated in inflammatory periodontal disease, and its mechanisms of action. LPS was isolated from lyophilised P. intermedia ATCC 25 611 cells using the standard hot-phenol -water protocol. Culture supernatants were collected and assayed for NO, IL-1b and IL-6. Real-time PCR analysis was carried out to detect the expression of inducible NO synthase (iNOS), IL-1b, IL-6 and haeme oxygenase-1 (HO-1) mRNA. Immunoblot analysis was carried out to quantify the expression of iNOS and HO-1 protein and concentrations of signalling proteins. DNA-binding activities of NF-kB subunits were determined using an ELISA-based assay kit. DHA significantly attenuated the production of NO, IL-1b and IL-6 at both gene transcription and translation levels in P. intermedia LPS-activated RAW264.7 cells. DHA induced the expression of HO-1 in cells treated with P. intermedia LPS. Selective inhibition of HO-1 activity by tin protoporphyrin IX significantly mitigated the inhibitory effects of DHA on LPS-induced NO production. DHA significantly attenuated the phosphorylation of c-Jun N-terminal kinase induced by LPS. In addition, DHA suppressed the transcriptional activity of NF-kB by regulating the nuclear translocation and DNA-binding activity of NF-kB p50 subunit and inhibited the phosphorylation of signal transducer and activator of transcription 1. Further in vivo studies are needed to better evaluate the potential of DHA in humans as a therapeutic agent to treat periodontal disease.