Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8269245 | Free Radical Biology and Medicine | 2015 | 14 Pages |
Abstract
Glyoxalase I (Glo1) is a cellular defense enzyme involved in the detoxification of methylglyoxal (MG), a cytotoxic by-product of glycolysis, and MG-derived advanced glycation end products (AGEs). Argpyrimidine (AP), one of the major AGEs coming from MG modification of protein arginines, is a proapoptotic agent. Crystalline silica is a well-known occupational health hazard, responsible for a relevant number of pulmonary diseases. Exposure of cells to crystalline silica results in a number of complex biological responses, including apoptosis. The present study was aimed at investigating whether, and through which mechanism, Glo1 was involved in Min-U-Sil 5 crystalline silica-induced apoptosis. Apoptosis, by TdT-mediated dUTP nick-end labeling assay, and transcript and protein levels or enzymatic activity, by quantitative real-time PCR, Western blot, and spectrophotometric methods, respectively, were evaluated in human bronchial BEAS-2B cells exposed or not (control) to crystalline silica and also in experiments with appropriate inhibitors. Reactive oxygen species were evaluated by coumarin-7-boronic acid or Amplex red hydrogen peroxide/peroxidase methods for peroxynitrite (ONOOâ) or hydrogen peroxide (H2O2) measurements, respectively. Our results showed that Min-U-Sil 5 crystalline silica induced a dramatic ONOOâ-mediated inhibition of Glo1, leading to AP-modified Hsp70 protein accumulation that, in a mechanism involving JNK and NF-κB, triggered an apoptotic mitochondrial pathway. Inhibition of Glo1 occurred at both functional and transcriptional levels, the latter occurring via ERK1/2 MAPK and miRNA 101 involvement. Taken together, our data demonstrate that Glo1 is involved in the Min-U-Sil 5 crystalline silica-induced BEAS-2B cell mitochondrial apoptotic pathway via a novel mechanism involving Hsp70, JNK, and NF-κB. Because maintenance of an intact respiratory epithelium is a critically important determinant of normal respiratory function, the knowledge of the mechanisms underlying its disruption may provide insight into the genesis, and possibly the prevention, of a number of pathological conditions commonly occurring in silica dust occupational exposure.
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Authors
Cinzia Antognelli, Angela Gambelunghe, Giacomo Muzi, Vincenzo Nicola Talesa,