Type I Interferon-Enhancing Effect of Cardamom Seed Extract via Intracellular Nucleic Acid Sensor Regulation

The induction of type I interferon (IFN) via intracellular nucleic acid sensors may be useful in preventing viral infections. However, little is known about the effect of natural plant materials on sensor responses. We previously found that cardamom (Elettaria cardamomum (L.) Maton) seed extract (CSWE) enhanced type I IFN expression and prevented influenza virus infection. In this study, we investigated the effect of CSWE on type I IFN responses using intracellular nucleic acid sensor molecules. Human lung epithelial A549 cells were treated with CSWE and transfected with poly(dA:dT) or poly(I:C) using lipofection. CSWE and 1,8-cineole, the major CSWE components, dose-dependently induced type I IFNs and IFN-stimulated genes in both poly(dA:dT)- and poly(I:C)-transfected A549 cells. The type I IFN-enhancing effect of CSWE was dependent on the stimulator of interferon genes (STING), whereas the effect of 1,8-cineole was independent of STING and mediated by the down-regulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-inducible poly-ADP-ribose polymerase expression. Our study suggests that CSWE has the potential to act as a beneficial antiviral agent by enhancing homeostatic type I IFN production.