The stress caused by nitrite with titanium dioxide nanoparticles under UVA irradiation in human keratinocyte cell

► Nitrite increased photo-toxicity of nano-TiO2 on human keratinocyte cells in a dose-dependant manner. ► Morphological study suggested the cell death may be mediated by apoptosis inducing factor. ► Protein nitration was generated in the cells, and the most abundant nitrated protein was identified as cystatin-A. ► Tyr35 was the most likely site to be nitrated in cystatin-A.