Rhamnus alpinus leaf extract suppresses lipopolysaccharide-induced, monocyte-derived macrophage chemokine secretion

Periodontitis is a chronic inflammatory disease of bacterial etiology that affects tooth-supporting tissues. The aim of the present study was to investigate the effect of Rhamnus alpinus extracts on lipopolysaccharide (LPS)-induced chemokine secretion by human macrophage-like cells. Phorbol myristic acid-differentiated macrophages were stimulated with Aggregatibacter actinomycetemcomitans LPS in the absence and presence of various concentrations of the extracts. The secretion of interleukin-8 (IL-8), regulated on activation normal T cell expressed and secreted (RANTES), and monocyte chemotactic protein (MCP)-1 was measured using enzyme-linked immunosorbent assays (ELISA). Activation of NF-kappaB p65 was evaluated with an ELISA-based kit containing immobilized oligonucleotides with an NF-kappaB consensus binding site. A. actinomycetemcomitans LPS (1 microg/ml) induced a marked increase in the secretion of IL-8 and RANTES by monocyte-derived macrophages. At non-cytotoxic concentrations, the R. alpinus leaf extract, which contains polyphenols, inhibited the secretion of RANTES and, to a lesser extent, IL-8 in a dose-dependent manner. The extract also decreased the basal levels of MCP-1 secreted by monocyte-derived macrophages. The extract appeared to exert its anti-inflammatory effect by inhibiting NF-kappaB p65 activation. Our results suggest that the leaf extract of R. alpinus possesses a therapeutic potential through its capacity to limit the infiltration of immune cells into periodontal sites. This may impede the progression and aggravation of inflammation given that the migration of immune cells plays an important role in the outcome of periodontitis.