Chemico-Biological Interactions 182 (2009) 13–21 Contents lists available at ScienceDirect Chemico-Biological Interactions journal homepage: www.elsevier.com/locate/chembioint Crystalline silica Min-U-Sil 5 induces oxidative stress in human bronchial epithelial cells BEAS-2B by reducing the efficiency of antiglycation and antioxidant enzymatic defenses Cinzia Antognelli a,∗ , Angela Gambelunghe b , Chiara Del Buono a , Nicola Murgia b , Vincenzo N. Talesa a , Giacomo Muzi b a Department of Experimental Medicine, University of Perugia, via del Giochetto 06123, Perugia, Italy b Department of Clinical and Experimental Medicine, University of Perugia, Perugia, Italy article info Article history: Received 4 May 2009 Received in revised form 31 July 2009 Accepted 4 August 2009 Available online 11 August 2009 Keywords: Crystalline silica Min-U-Sil 5 Oxidative stress Reactive oxygen species Antiglycation/antioxidant defenses Human BEAS-2B abstract Reactive oxygen species (ROS) play an important role as mediators of pulmonary damage in mineral dust-induced diseases. Studies carried out to date have largely focused on silica-induced production of ROS by lung phagocytes. In this study we investigated the hypothesis that crystalline silica Min-U-Sil 5 can induce elevations in intracellular ROS in human bronchial epithelial cells BEAS-2B, via an indirect mechanism that involves ROS-inducing intracellular factors, through a reduction of antiglycation (glyox- alase enzymes) and antioxidant (paraoxonase 1 and glutathione-S-transferases) enzymatic defenses. The results show that crystalline silica Min-U-Sil 5 causes a significant reduction in the efficiency of antigly- cation and antioxidant enzymatic defenses, paralleled by an early and extensive ROS generation, thus preventing the cells from an efficient scavenging action, and eliciting oxidative damage. These results confirm the importance of ROS in development of crystalline silica-induced oxidative stress and empha- size the pivotal role of antiglycation/antioxidant and detoxifying systems in determining the level of protection from free radicals-induced injury for cells exposed to crystalline silica Min-U-Sil 5. © 2009 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Crystalline silica dust is a well-known occupational health hazard, responsible for a relevant number of silicoses, nodular interstitial lung diseases, and of other lung disorders in workers [1]. Numerous investigations have suggested that reactive oxygen species (ROS) may be important mediators of pulmonary dam- age in mineral dust-induced diseases [2–4]. Previous studies have demonstrated that SiO 2 can induce in vitro ROS production in human alveolar macrophages [5] and in vivo, lipid peroxidation [6], as well as changes in the expression of antioxidant enzymes in different bronchoalveolar lavages [7]. In particular, production of DNA-damaging free radicals and ROS may be involved in silica- induced fibrosis and lung cancer [2]. The detailed mechanism by which ROS are generated is still unclear. However, there is evi- dence that crystalline silica can induce ROS, such as hydroxyl free radical, at the particle surface [2], following interaction with lung phagocytic cells [3]. ∗ Corresponding author. Tel.: +39 075 5857475; fax: +39 075 5857483. E-mail address: cinzia.antognelli@unipg.it (C. Antognelli). The dramatic increase in silica-induced ROS levels can result in significant damage to target cell structures, such as bronchiolar and alveolar epithelial cells, and to extracellular components. In partic- ular, ROS are the direct cause of DNA damage [8], morphological changes in cells [9], and lung injury [10]. Furthermore, ROS can damage cell membranes by inducing lipid peroxidation, can oxi- dize amino acids into proteins and inactivate specific enzymes by oxidation of co-factors. Finally, in addition to any direct detrimen- tal action of ROS per se, the generation of ROS-associated factors, e.g., aldehydes and lipid peroxidation products [11], suggests the possibility that such mediators could contribute to a number of silica-induced effects, including the induction of inflammation, DNA damage and cell hyperplasia [12]. Due to the pathogenic role of ROS as well as of ROS-associated aldehydes and lipid peroxidation products, the efficiency of antigly- cation and antioxidant enzymatic defenses might be crucial to prevent free radical mediated tissue destruction and inhibit some of the early events leading to inflammation and tissue destruction in silica-exposed cells. The glyoxalase system, consisting of glyoxalase I (GLOI) and glyoxalase II (GLOII), is an important enzymatic antiglycation defence also found in the human lung. Such a system is widely effective in scavenging methylglyoxal (MG), a reactive carbonyl 0009-2797/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.cbi.2009.08.002