Acute exposure to dihydroxyacetone promotes genotoxicity and chromosomal instability in lung, cardiac, and liver cell models.

Inhalation exposures to dihydroxyacetone (DHA) occur through spray tanning and e-cigarette aerosols. Several studies in skin models have demonstrated that millimolar doses of DHA are cytotoxic, yet the genotoxicity was unclear. We examined the genotoxicity of DHA in cell models relevant to inhalation exposures. Human bronchial epithelial cells BEAS-2B, lung carcinoma cells A549, cardiomyocyte Ac16, and hepatocellular carcinoma HepG3 were exposed to DHA, and low millimolar doses of DHA were cytotoxic. IC90 DHA doses induced cell cycle arrest in all cells except the Ac16. We examined DHA's genotoxicity using strand break markers, DNA adduct detection by Repair Assisted Damage Detection (RADD), metaphase spreads, and a forward mutation assay for mutagenesis. Similar to results for skin, DHA did not induce significant levels of strand breaks. However, RADD revealed DNA adducts were induced 24 h after DHA exposure, with BEAS-2B and Ac16 showing oxidative lesions and A549 and HepG3 showing crosslink-type lesions. Yet, only low levels of reactive oxygen species or advanced glycation end products were detected after DHA exposure. Metaphase spreads revealed significant increases in chromosomal aberrations in the BEAS-2B and HepG3 with corresponding changes in ploidy. Finally, we confirmed the mutagenesis observed using the supF reporter plasmid. DHA increased the mutation frequency, consistent with methylmethane sulfonate, a mutagen and clastogen. These data demonstrate DHA is a clastogen, inducing cell-specific genotoxicity and chromosomal instability. The specific genotoxicity measured in the BEAS-2B in this study suggests that inhalation exposures pose health risks to vapers, requiring further investigation.

Proinflammatory Pathways Are Activated in the Human Q344X Rhodopsin Knock-In Mouse Model of Retinitis Pigmentosa.

Retinitis pigmentosa (RP) is a hereditary disease of the retina that results in complete blindness. Currently, there are very few treatments for the disease and those that exist work only for the recessively inherited forms. To better understand the pathogenesis of RP, multiple mouse models have been generated bearing mutations found in human patients including the human Q344X rhodopsin knock-in mouse. In recent years, the immune system was shown to play an increasingly important role in RP degeneration. By way of electroretinography, optical coherence tomography, funduscopy, fluorescein angiography, and fluorescent immunohistochemistry, we show degenerative and vascular phenotypes, microglial activation, photoreceptor phagocytosis, and upregulation of proinflammatory pathway proteins in the retinas of the human Q344X rhodopsin knock-in mouse. We also show that an FDA-approved pharmacological agent indicated for the treatment of rheumatoid arthritis is able to halt activation of pro-inflammatory signaling in cultured retinal cells, setting the stage for pre-clinical trials using these mice to inhibit proinflammatory signaling in an attempt to preserve vision. We conclude from this work that pro- and autoinflammatory upregulation likely act to enhance the progression of the degenerative phenotype of rhodopsin Q344X-mediated RP and that inhibition of these pathways may lead to longer-lasting vision in not only the Q344X rhodopsin knock-in mice, but humans as well.