Rhazya stricta enhances IL-1 and TNFα production by macrophages in mice

Rhazya stricta (RS) is a widely used medicinal plant in the Arabian Peninsula with alleged benefits in many unrelated clinical conditions (e.g. diabetes mellitus and helminthiasis). Previous investigations showed that the alkaloidal fraction (AF) is the most pharmacologically active constituent of the plant extract. We hypothesized that some of RS claimed therapeutic effects may be due to immunomodulatory capacity of the plant extract. Therefore, we tested AF effects on the ex vivo production of peritoneal macrophage-derived cytokines in mice. BALB/c male mice received normal saline, 0.5 or 1 mg/animal of AF intramuscularly twice weekly for up to 5 weeks. The animals were sacrificed and the peritoneal cavity was thoroughly washed with Hank's balanced salt solution. The adherent peritoneal cells were cultured in a 24-well plate at 1×10⁶ cells per well in the presence of 5 ng/ml LPS. Culture supernatants were collected and assayed for IL-1α and TNFα by ELISA. Compared to the control (87 ± 25 pg/ml), AF (0.5 mg/animal) induced a statistically significant increase in IL-1α production (239 ± 50 pg/ml, p < 0.02) and an increase in TNFα production which did not reach the level of statistical significance (p < 0.065). It is concluded that the biological activities of RS may, at least in part, be mediated by enhanced production of proinflammatory cytokines.