In Vivo and In Vitro Immunomodulatory Potential of Swertiamarin Isolated from Enicostema axillare (Lam.) A. Raynal That Acts as an Anti-inflammatory Agent

Swertiamarin is a secoiridoid glycoside found in Enicostema axillare (Lam) A. Raynal, a medicinal plant used as a depurative in the Indian system of traditional medicine. The present study evaluated the immunomodulatory activity of isolated swertiamarin. In vivo immunomodulatory activity of swertiamarin (2, 5, and 10 mg/kg b.w.) was evaluated in a model of sheep red blood cells (SRBC) by assessing its effect on organ weight, hemagglutinating antibody titer (HA), plaque-forming cells (PFC), quantitative hemolysis of SRBC, and delayed type hypersensitivity (DTH). In vitro immunomodulatory potential was studied on isolated splenocytes, neutrophils, and peritoneal macrophages. In silico immunomodulatory effects were evaluated by docking of swertiamarin on proinflammatory cytokines to confirm its potential. In in vivo studies, the animals treated with swertiamarin showed a significant (P ≤ 0.05) increase in antibody titer, plaque-forming cells, and also in weight of the thymus and spleen. A decreased response to DTH reaction was recorded with the treatment of swertiamarin. In in vitro studies, treatment with swertiamarin modulated the messenger RNA (mRNA) and protein expression of IFN-γ, IL-10, and IL-4 significantly (P ≤ 0.05) and also favored Th2-mediated response on concanavalin A (Con A)-induced splenocytes. The compound inhibited the release of free radicals significantly (P ≤ 0.05) in phytohemagglutinin (PHA)-induced neutrophils and also ameliorated the mRNA and protein expression of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) in lipopolysaccharide (LPS)-induced macrophages. In in silico, the best docked pose of swertiamarin with the target proteins (TNF-α, IL-1β, and IL-6) was confirmed that swertiamarin acted as an anti-inflammatory mediator.