Extract from Calotropis procera latex activates murine macrophages

Calotropis procera latex has long been used in traditional medicines. Extracts from C. procera latex have been reported to have various pharmacological actions, including protection from myocardial infarction, hepatoprotective action, antitumor activity, antinociceptive, and pro- and anti-inflammatory actions. To evaluate the immunomodulatory functions of the water-soluble C. procera extract (CPE), we investigated its ability to activate macrophages-effector cells in inflammatory and immune responses. Intraperitoneal injection of CPE in mice (2 mg/mouse) induced migration of macrophages to the intraperitoneal cavity, confirming the proinflammatory effects of water-soluble CPE. The direct effects of CPE on macrophages were then assessed by measuring the production of nitric oxide (NO) as an indicator for macrophage activation. Addition of CPE (1-10 μg/ml) to the culture medium of the murine monocyte/macrophage cell line RAW264.7 caused an increase in NO production in a time- and dose-dependent manner. CPE-elicited NO production was blocked by application of an inhibitor of inducible nitric oxide synthase (iNOS). Expression of iNOS mRNA was induced by treatment of cultured macrophages with CPE. Injection of CPE in mice also resulted in an increase in plasma NO level. The results suggest that CPE activates macrophages and facilitates NO production via up-regulation of iNOS gene expression.