Intratracheal instillation of graphene oxide with different diameters suppressed toll-like receptor 3-mediated lipid droplet biogenesis in lungs and livers of mice

Abstract

Recent advances have established lipid droplets as dynamic innate immune hubs coordinating cellular metabolism and defense mechanisms. While previous studies primarily focused on nanomaterials (NMs) altering lipid metabolism to influence lipid droplet dynamics, this study pioneers the investigation of NM-induced immune modulation via Toll-like receptor (TLR) pathways as a novel regulatory axis for lipid droplets. Building on our prior findings that graphene oxide (GO) impaired TLR3-mediated lipid signaling, we systematically explored the role of GO's diameter in modulating this process. Mice were subjected to daily intratracheal instillation of three GO variants (50-200 nm, <500 nm or > 500 nm) at 1 mg/kg for 7 days. Although no significant change in body weight or organ coefficient was observed, all GO exposure suppressed lipid staining in mouse lungs and livers, correlating with altered co-localization of TLR3 and perilipin 2 (PLIN2), critical regulators of lipid droplet biogenesis. Down-regulation of TLR3 signaling components, namely interferon induced protein with tetratricopeptide repeats 1 (IFIT1), radical S-adenosyl methionine domain containing 2 (RSAD2), and PLIN2, occurred in a diameter-dependent manner, with GO 50-200 nm showing the most pronounced effects, likely attributable to the smallest hydrodynamic size and polydispersity index in suspension. This work provides evidence that NM geometry governs TLR-mediated lipid droplet regulation, bridging the knowledge gap between nanotoxicology and immunometabolic cross-talking, a paradigm distinct from conventional lipid metabolism-focused nanotoxicological studies.

Keywords: Intratracheal instillation; diameter; graphene oxide (GO); lipid droplets; toll-like receptor 3 (TLR3).