Inhibitory effect of Rhamnus alpinus and Rhamnus saxatilis extracts on chemokine secretion induced by lipopolysaccharide in monocyte-derived macrophages
Periodontitis is a chronic inflammatory disease of bacterial etiology affecting tooth supporting tissues. Periodontal tissue infiltration by immune cells is triggered by chemokines that attract and activate leukocytes . The aim of this study was to investigate the effect of Rhamnus alpinus and Rhamnus saxatilis extracts on lipopolysaccharide-induced chemokine secretion by human macrophages. Both species were collected on Gran Sasso Mountain (Abruzzo, Italy). Phorbol myristic acid (PMA)-differentiated macrophages were stimulated with Aggregatibacter actinomycetemcomitans in the absence and presence of the Rhamni extracts at different concentrations. Secretion of interleukin-8 (IL-8), regulated on activation normal T cell expressed and secreted (RANTES) and monocyte chemotactic protein (MCP)-1 was measured with enzyme-linked immunosorbent assays (ELISA) . A. actinomycetemcomitans LPS (1µg/ml) induced a marked increase in the secretion of all three chemokines by monocyte-derived macrophages. At non-cytotoxic concentrations, both R. alpinis leaf extract and R. saxatalis bark extract inhibited in a dose-dependent manner the secretion of IL-8 (2µg/mL and 10µg/mL respectively), RANTES (2µg/mL and 50µg/mL respectively) and MCP-1 (<50µg/mL for both plant extracts) by monocyte-derived macrophages. Our results suggest that extracts from R. alpinus and R. saxatilis might prove to be effective in limiting the infiltration of immune cells into periodontal sites. Such an inhibition may impede progression of inflammation, taking into account that immune cell migration has an important role in the outcome of periodontal disease.
Acknowledgements: Financial support from Regione Abruzzo L.R. 35/97 „Tutela della biodiversità“ and Ente Parco Nazionale del Gran Sasso e Monti della Laga is gratefully acknowledged.
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