Daturalactones as immunomodulators: activation of immune cells conferring cytotoxicity towards colon and pancreatic cancer cells

Datura stramonium L. is an important Ayurvedic herb of the nightshade family (Solanaceae) used in the treatment of innumerable diseases for centuries. Previously, we reported the isolation of three steroidal lactones (Daturalactone (D1), 12-Deoxywithastramonalide (D23), and Daturilin (D27) from D. stramonium L. The present study was designed to evaluate in vitro immunomodulatory potential of these lactones on human peripheral blood mononuclear cells (PBMC). The data revealed that the lactones from D. stramonium significantly enhanced the proliferation of the human PBMC and increased the IL-2, IFN-γ, and TNF-α secretion. Flow cytometry data showed a significant up-regulation of CD3, CD8, and CD56 expression on PBMC. Enhanced intracellular granulysin expression was also observed in Datura lactones treated PBMC. Granulysin is an immunomarker and enhanced expression of granulysin depict activation of Cytotoxic T Lymphocytes and Natural Killer cells. Further, the micro-cytotoxicity assay was performed by co-culturing lactone-activated lymphocytes and target cells (colon cancer cells; HCT-116 and SW620, and pancreatic cancer cells; Panc-1 cells). The human PBMC activated with the lactones exhibited enhanced cancer cell death as compared to the untreated PBMC. It was found that the D27-treated lymphocytes showed higher cancer-killing potential as compared to D1- or D23-activated immune cells. Additionally, mechanistic studies showed that the stimulated lymphocytes enhanced ROS production and loss of mitochondrial membrane potential in the target cancer cells. The current study showed immuno-potentiating effects of D. stramonium lactones on human PBMC.