Impact of Nano- and Micro-Sized Chromium(III) Particles on Cytotoxicity and Gene Expression Profiles Related to Genomic Stability in Human Keratinocytes and Alveolar Epithelial Cells

Exposure to Cr(VI) compounds has been consistently associated with genotoxicity and carcinogenicity, whereas Cr(III) is far less toxic, due to its poor cellular uptake. However, contradictory results have been published in relation to particulate Cr${}_2$O_3$.TheaimofthepresentstudywastoinvestigatewhetherCr(III)particlesexertedpropertiescomparabletowatersolubleCr(III)ortoCr(VI),includingtwonano-sizedandonemicro-sizedparticles.ThemorphologyandsizedistributionweredeterminedbyTEM,whiletheoxidationstatewasanalyzedbyXPS.ChromiumreleasewasquantifiedviaAAS,andcolorimetricallydifferentiatedbetweenCr(VI)andCr(III).Furthermore,thetoxicologicalfingerprintsoftheCr$_2$O_3$ particles were established using high-throughput RT-qPCR and then compared to water-soluble Cr(VI) and Cr(III) in A549 and HaCaT cells. Regarding the Cr${}_2$O_3$ particles, two out of three exerted only minor or no toxicity, and the gene expression profiles were comparable to Cr(III). However, one particle under investigation released considerable amounts of Cr(VI), and also resembled the toxicity profiles of Cr(VI); this was also evident in the altered gene expression related to DNA damage signaling, oxidative stress response, inflammation, and cell death pathways. ... mehrEven though the highest toxicity was found in the case of the smallest particle, size did not appear to be the decisive parameter, but rather the purity of the Cr(III) particles with respect to Cr(VI) content.