Reactive oxygen species induce apoptosis in bronchial epithelial BEAS-2B cells by inhibiting the antiglycation glyoxalase I defence: involvement of superoxide anion, hydrogen peroxide and NF-κB

Abstract

Reactive oxygen species (ROS) are implicated in the regulation of apoptosis through a number of distinct mechanisms depending on cell type and stimulation conditions. Glyoxalase I (GI) metabolizes methylglyoxal (MG) and MG-derived advanced glycation end products (AGEs) known to cause apoptosis. This study examined the possible role of GI among the mechanisms of ROS-driven apoptosis in human bronchial epithelial BEAS-2B cells exposed to wood dust and signaling pathways by which these reactive species regulate GI expression. Our results showed that wood dust generated distinct ROS (superoxide anion, and hydrogen peroxide) by selectively inhibiting the enzymatic activity of superoxide dismutase or glutathione peroxidase and catalase enzymes. These ROS caused a dramatic inhibition of the antiglycation GI enzyme, leading to the intracellular accumulation of the pro-apoptotic AGE, argpyrimidine (AP) and programmed cell death via a mitochondrial pathway. Pre-treatment with N-acetyl-L-cysteine (NAC), a ROS scavenger, prevented these events. Hence, ROS-induced apoptosis in BEAS-2B cells occurred via a novel mechanism relying on GI inhibition and AP accumulation. We interestingly found that superoxide anion and hydrogen peroxide induced a diverse apoptosis level by differently inhibiting GI via NF-κB pathway. Since maintenance of an intact epithelium is a critically important determinant of normal respiratory function, the knowledge of the mechanisms underlying its disruption may provide insight into the genesis of a number of pathological conditions commonly occurring in wood dust occupational exposure. Our findings suggest that the antioxidant NAC may merit investigation as a potential preventive agent in wood dust exposure-induced respiratory diseases.