Titanium dioxide nanoparticles modulate the toxicological response to cadmium in the gills of Mytilus galloprovincialis

tWe investigated the influence of titanium dioxide nanoparticles (nano-TiO2) on the response to cad-mium in the gills of the marine mussel Mytilus galloprovincialis in terms of accumulation and toxicity.Mussels were in vivo exposed to nano-TiO2, CdCl2, alone and in combination. Several cellular biomarkerswere investigated in gills: ABC transport proteins and metallothioneins at gene/protein (abcb1, abcc-likeand mt-20) and functional level, GST activity, NO production and DNA damage (Comet assay). Accu-mulation of total Cd and titanium in gills as in whole soft tissue was also investigated. Significantresponses to Cd exposure were observed in mussel gills as up-regulation of abcb1 and mt-20 gene tran-scription, increases in total MT content, P-gp efflux and GST activity, DNA damage and NO production.Nano-TiO2alone increased P-gp efflux activity and NO production. When combined with Cd, nano-TiO2 reduced the metal-induced effects by significantly lowering abcb1 gene transcription, GST activity, andDNA damage, whereas, additive effects were observed on NO production. A lower concentration of Cdwas observed in the gills upon co-exposure, whereas, Ti levels were unaffected. A competitive effect inuptake/accumulation of nano-TiO2and Cd seems to occur in gills. A confirmation is given by the observedabsence of adsorption of Cd onto nano-TiO2in sea water media.