Platycodin D-Induced Immunotoxicity in RAW 264.7 Macrophages via Oxidative Stress-Mediated Apoptosis

Abstract

Platycodin D (PD) is a naturally occurring, biologically active triterpenoid saponin isolated from a medicinal food homology plant called Platycodon grandiflorus (Jacq.) A. DC. It is involved in the processing of various biological activities. While investigating the anti-inflammatory property of PD using lipopolysaccharide (LPS)-stimulated murine RAW 264.7 macrophage cells, we unexpectedly found that PD exhibited toxicity to RAW 264.7 cells. In this study, the toxic effect of PD on RAW 264.7 cells was systematically evaluated for the first time. The results showed that PD (12.5−200 µM) significantly reduced cell viability and inhibited cell proliferation in a dose-dependent manner. At a concentration of 20 µM, PD significantly increased lactate dehydrogenase activity and the mRNA and protein expression of Bax, p53, Casp3, IL-1β, and TNF-α. Interestingly, PD (0.8−20 µM) inhibited the expression of inflammatory cytokines in LPS-stimulated RAW 264.7 cells. PD (20 µM) also significantly increased reactive oxygen species (ROS) levels and the expression of oxidative stress-related genes and proteins. This study revealed that PD exhibited immunotoxicity to RAW 264.7 cells, with possible mechanisms including oxidative stress-mediated apoptosis resulting in activation of the mitochondrial apoptosis pathway and dysregulated expression of inflammatory cytokines. This study evaluated the impact of PD on immunity and provided guidelines for its future biological application.