Anti-inflammatory properties of piperlactam S: modulation of complement 5a-induced chemotaxis and inflammatory cytokines production in macrophages.

Macrophages infiltrate tissues in response to chemoattractants including complement 5a (C5a). Infiltrating macrophages clear microorganisms but also can cause tissue damage. We hypothesized that prevention of macrophages from excessive recruitment into infected sites may underlie the anti-inflammatory effects of piperlactam S, an alkaloid isolated from Piper kadsura (Choisy) Ohwi. To test this hypothesis, chemotactic migration of RAW264.7 macrophages was induced by C5a and the effects of piperlactam S were studied. The results showed that piperlactam S (1-30 microM) concentration-dependently suppressed C5a-induced migration across a fibrinogen-coated barrier with an IC50 of 4.5 +/- 0.3 microM. At 30 microM, piperlactam S inhibited chemotaxis by more than 95 % and also decreased phagocytosis by 25 % without reducing macrophage viability and adherent capacity. Furthermore, piperlactam S treated cells adhered but failed to spread and elongate as in control cells. Finally, piperlactam S inhibited the C5a-stimulated release of tumor necrosis factor-alpha and interleukin-1beta. We conclude that retardation of macrophage recruitment by interfering with the migration process and suppression of cytokines production might underlie the potential usefulness of piperlactam S as an anti-inflammatory agent.

Piperlactam S suppresses macrophage migration by impeding F-actin polymerization and filopodia extension.

This study was designed to evaluate the anti-inflammatory effect of piperlactam S on chemoattractant-induced migration, functions underlying leukocyte recruitment in vitro. Results showed that RAW264.7 macrophages migrate toward complement 5a, a powerful chemoattractant for macrophages. This phenomenon could be suppressed concentration dependently by piperlactam S (0.3-30 microM). Fluorescence staining demonstrated that piperlactam S and cytochalasin B both effectively reversed complement 5a-induced cell polarization, filopodia extension, as well as the increase in the cell content of F-actin. Functional inhibition by antibodies suggested that Mac-1 (CD11b) integrin plays a central role in complement 5a-induced migration. However, piperlactam S failed to modify Mac-1 expression. Furthermore, complement 5a triggered the activation of Cdc42, a Rho-family protein involved in the regulation of filopodia extension, with a time course that paralleled that of filopodia extension and which was inhibited by piperlactam S. In summary, piperlactam S exerts anti-inflammatory effects possibly by interfering with cell migration, impeding F-actin polymerization, filopodia formation, and/or Cdc42 activation. However, the detailed mechanism by which piperlactam S regulates the above processes needs further study.