Asbestos conceives Fe(II)-dependent mutagenic stromal milieu through ceaseless macrophage ferroptosis and β-catenin induction in mesothelium

Redox Biology 2020 September [Link]

Fumiya Ito, Izumi Yanatori, Yuki Maeda, Kenta Nimura, Satoki Ito, Tasuku Hirayama, Hideko Nagasawa, Norihiko Kohyama, Yasumasa Okazaki, Shinya Akatsuka, Shinya Toyokuni


Asbestos is still a social burden worldwide as a carcinogen causing malignant mesothelioma. Whereas recent studies suggest that local iron reduction is a preventive strategy against carcinogenesis, little is known regarding the cellular and molecular mechanisms surrounding excess iron. Here by differentially using high-risk and low-risk asbestos fibers (crocidolite and anthophyllite, respectively), we identified asbestos-induced mutagenic milieu for mesothelial cells. Rat and cell experiments revealed that phagocytosis of asbestos by macrophages results in their distinctive necrotic death; initially lysosome-dependent cell death and later ferroptosis, which increase intra- and extra-cellular catalytic Fe(II). DNA damage in mesothelial cells, as assessed by 8-hydroxy-2′-deoxyguanosine and γ-H2AX, increased after crocidolite exposure during regeneration accompanied by β-catenin activation. Conversely, β-catenin overexpression in mesothelial cells induced higher intracellular catalytic Fe(II) with increased G2/M cell-cycle fraction, when p16INK4A genomic loci localized more peripherally in the nucleus. Mesothelial cells after challenge of H2O2 under β-catenin overexpression presented low p16INK4A expression with a high incidence of deletion in p16INK4A locus. Thus, crocidolite generated catalytic Fe(II)-rich mutagenic environment for mesothelial cells by necrotizing macrophages with lysosomal cell death and ferroptosis. These results suggest novel molecular strategies to prevent mesothelial carcinogenesis after asbestos exposure.