Nano titanium dioxide induces HaCaT cell pyroptosis via regulating the NLRP3/caspase-1/GSDMD pathway

Nano-titanium dioxide (Nano-TiO₂) is extensively utilized across various industries and has the capacity to penetrate human tissues through multiple biological barriers. The HaCaT cell line, as one of human immortalized keratinocytes, is usually used as a model for studying skin drug toxicology. The objective was to assess the toxic effects of nano-TiO₂ on HaCaT cells and to trigger pyroptosis. We used MTT method to evaluate the effects of three nano-TiO₂ particle sizes (15 nm, 30 nm and 80 nm) on cell viability at different concentrations. Subsequently, we used LDH, Hoechst 33342 and propidium iodide (PI) double staining, scanning electron microscopy (SEM), Western blotting (WB) and real-time quantitative polymerase chain reaction (RT-qPCR) to evaluate the effects of different particle sizes on cells at the same concentration. Our findings indicated that HaCaT cell viability diminished with increasing nano-TiO₂ concentrations. Moreover, nano-TiO₂ increased LDH level in cellular supernatant. Fluorescence double staining, SEM, WB and RT-qPCR showed that nano-TiO₂ induced cell membrane damage by activating pyroptosis pathway of NLRP3/caspase-1/GSDMD. These results suggest that nano-TiO₂ toxicity in HaCaT cells is influenced by both dose and particle size, and is associated with the induction of pyroptosis. Frequent and large exposures to nano- TiO₂ in daily life may cause serious health hazards.