Agomelatine, a MT1/MT2 melatonergic receptor agonist with serotonin 5-HT2C receptor antagonistic properties, suppresses Prevotella intermedia lipopolysaccharide-induced production of proinflammatory mediators in murine macrophages

Objective: This study was performed in an attempt to examine the influence of agomelatine in mitigating the generation of proinflammatory mediators in RAW264.7 murine macrophages exposed to lipopolysaccharide (LPS) obtained from Prevotella intermedia, a gram-negative anaerobic bacterium that is related with various types of periodontal diseases, and the molecular mechanisms behind its effects. Design: LPS from P. intermedia strain ATCC 25611 was prepared employing the conventional phenol-water procedure. Conditioned culture media were analyzed for the levels of nitric oxide (NO), interleukin-1 beta (IL-1 beta) and IL-6. Real-time PCR analysis was carried out to determine the mRNA levels of inducible NO synthase (iNOS), IL-1 beta, IL-6 and SOCS1. Protein expression levels were evaluated by immunoblot test. NF-kappa B-dependent SEAP reporter assay was performed using a reporter cell line. DNA-binding activities of NF-kappa B subunits were analyzed utilizing the ELISA-based kits. Results: Agomelatine was found to down-regulate significantly the generation of iNOS-derived NO, IL-1 beta and IL-6 as well as the expression of their mRNAs in cells activated with P. intermedia LPS. Agomelatine decreased NF-kappa B-dependent SEAP release caused by P. intermedia LPS. Agomelatine did not inhibit NF-kappa B transcription induced by LPS at the level of I kappa B-alpha degradation. Instead, LPS-induced nuclear translocation and DNA binding of NF-kappa B p50 subunit was blocked by agomelatine. P. intermedia LPS-elicited activation of STAT1 and STAT3 was reduced notably by co-treatment with agomelatine. Agomelatine showed a tendency to enhance mRNA level of SOCS1 in LPS-activated cells as well. Conclusions: Agomelatine merits further evaluation to reveal its usefulness on the host modulation of periodontal disease.