Deciphering the Immunotoxicity of Titanium Dioxide Nanoparticles (E171) in Mouse Leukocytes through Single-Cell RNA Sequencing

Abstract

Abstract The cellular and immunological responses in the immune system after exposure to TiO2 NPs/E171 are poorly understood. Therefore, comprehensive single-cell RNA-seq (scRNA-seq) analysis was used to explore the unique heterogeneous response upon TiO2 NPs/E171 treatment in Sprague-Dawley rats. Firstly, granulocyte G1 activated innate immune response through the upregulation of genes involved in pro-inflammatory cytokine mediated cytotoxicity. Whereas NK cells resulted in heterogeneity role depending on the subsets where NK1 significantly inhibited cytotoxicity, whereas NK2 and NK3 subsets activated pro-B cell population & inhibited T cell mediated cytotoxicity respectively. While NKT_1 activated innate inflammatory responses which was confirmed by cytotoxic CD8 + T killer cell suppression. Similarly, NKT_2 cells promote inflammatory response by releasing lytic granules and MHC-I complex inhibition to arrest cytotoxic T killer cell responses. Conversely, NKT_3 suppressed inflammatory response by release of anti-inflammatory cytokines suggesting the functional heterogeneity of NKT subset. The formation of MHC-I or MHC-II complexes with T-cell subsets resulted in neither B and T cell dysfunction nor cytotoxic T killer cell inhibition suppressing adaptive immune response. This study not only masks the drawbacks of utilizing homogeneous immune cell types, but also provides a full understanding of high-dimensional heterogeneous immunological response at the single cell level.