1,2-naphthoquinone enhances IFN-γ-induced MHC-I expression in dendritic cells, thereby inducing CD8 T cell activation

Dendritic cells play a crucial role in immune responses by capturing pathogens and presenting antigens to T cells via major histocompatibility complex (MHC) molecules, thus triggering adaptive immune responses. 1,2-naphthoquinone (1,2-NQ), a quinone found in diesel exhaust and cigarette smoke, has various physiological functions. In this study, we investigated the effect of 1,2-NQ on the expression of antigen presentation-related molecules in the dendritic cell line DC2.4. The results revealed that 1,2-NQ enhanced the IFN-γ-induced upregulation of MHC-I expression at the transcriptional level. Moreover, it upregulated the expression of NLRC5, a transcriptional activator of MHC-I. 1,2-NQ is a reactive oxygen species (ROS) producing reagent. The 1,2-NQ-induced upregulation of MHC-I expression and downregulation of MHC-II expression were abolished by the ROS scavenger N-acetylcysteine. Similar effects on MHC expression were also observed with ROS-inducing reagents, such as paraquat and diethyl maleate. In addition, dendritic cells stimulated with 1,2-NQ exhibited enhanced efficacy in CD8 T cell activation, which was accompanied by increased IFN-γ production by T cells. These findings demonstrate that 1,2-NQ enhances the IFN-γ-induced activation of dendritic cells and promotes the activation of CD8 T cells.