Toxicology Letters 196 (2010) 74–79 Contents lists available at ScienceDirect Toxicology Letters journal homepage: www.elsevier.com/locate/toxlet Fluoride as a pro-inflammatory factor and inhibitor of ATP bioavailability in differentiated human THP1 monocytic cells I. Gutowska a,∗ , I. Baranowska-Bosiacka a , M. Ba ´ skiewicz b , B. Milo c , A. Siennicka c , M. Marchlewicz d , B. Wiszniewska d , B. Machali ´ nski b , E. Stachowska a a Department of Biochemistry and Human Nutrition, Pomeranian Medical University, ˙ Zolnierska 48 Str., Szczecin, Poland b Department of General Pathology, Pomeranian Medical University, Powsta´ nców Wlkp 72 Str., Szczecin, Poland c Department of Clinical Biochemistry and Laboratory Diagnostics, Pomeranian Medical University, Powsta´ nców Wlkp 72 Str., Szczecin, Poland d Department of Histology and Embriology, Pomeranian Medical University, Powsta´ nców Wlkp 72 Str., Szczecin, Poland article info Article history: Received 13 February 2010 Received in revised form 26 March 2010 Accepted 30 March 2010 Available online 22 April 2010 Keywords: Apoptosis ATP Fluoride Macrophage Reactive oxygen species abstract Chronic exposure of humans to fluorine compounds in the air, water and food may be atherogenic via the activation of oxidative stress and increased ROS production. The most important factor that promotes the formation of ROS seems to be the oxidoreduction of electron carriers in the critical points of the respiratory chain, which depends, among other things, on the cellular demand for ATP. This paper examines the effect of fluorides in concentrations determined in human serum on the intracellular synthesis of ROS, the activity of the respiratory chain enzymes and the synthesis of ATP via oxidative and substrate-level phosphorylation. The incubation of macrophages in fluoride solutions significantly decreased the amount of synthesized cellular ATP and increased formation of ROS and apoptosis in a dose-dependent pattern. The addition of respiratory chain inhibitors resulted in a significant decrease in the synthesized ROS. Sodium fluoride probably promotes oxidative stress in macrophages, which is manifested by a strong increase in ROS synthesis and a decrease in ATP. We suppose that fluoride may destabilize the action of respiratory chain. Our results indicate that the respiratory chain is the main site of ROS synthesis. One cannot exclude the stimulating role of fluorine compounds on the formation of ROS that is independent of the respiratory chain. © 2010 Elsevier Ireland Ltd. All rights reserved. 1. Introduction An increasing number of reports have indicated previously unknown harmful effects of fluorine on living organisms, includ- ing the human body (Bhanuprakash Reddy et al., 2003; Ling-Fei and Jian-Gang, 2006). Fluorides accumulate in the body and lead to numerous metabolic disorders even at a low concentration but with long time exposure (Kalyanalakshmi et al., 2007). Chronic long-term exposure to high levels of fluoride leads to fluorosis, a serious health problem in many parts of the world where drinking water contains more than 1–1.5-ppm of fluoride (World Health Organization, 1984). However, the exposure of humans to fluorine is also connected with its presence in the air and food. The concentration of fluorides in drinks and food depends on their concentration in water used in their production. Certain foods may contain considerable amounts of fluorides, regardless of fluoride concentrations in water (Poureslami et al., 2008). ∗ Corresponding author. Tel.: +48 91 466 15 15; fax: +48 91 466 15 16. E-mail address: gutowska@sci.pam.szczecin.pl (I. Gutowska). A long-term exposure to fluorides also leads to changes in amount and catalytic properties of many enzymes (Park et al., 1999; Vani and Reddy, 2000) and to an increased ROS production that can enhance the inflammatory and proliferation reactions (Vendrov et al., 2007), in which a significant role is played by macrophages, cells participating in the formation of atherosclerotic plaques (Lessner et al., 2002). Macrophages are capable of phagocytosing particles opsonized by antibodies and cooperate with lymphocytes in the process of inducing specific immune responses (Lessner et al., 2002; Takahashi et al., 2002). Inflammatory reactions underlie the pathogenesis of the atherosclerotic process (Barbieri et al., 2003) and oxygen free radicals formed during inflammatory reactions contribute to aggra- vation of atherosclerotic lesions (Montuschi et al., 2004). ROS are produced normally during the respiratory burst of phagocytes as a defense mechanism and regulate multiple cell functions. ROS participate in the regulation of numerous cellular functions, e.g. cellular differentiation, intracellular signaling (Irani, 2000), gene expression regulation, and (through activation of caspases or Fas receptors) in apoptotic stimulation (Geronikaki and Gavalas, 2006). Macrophages are also a source of free radicals other than oxygen species ROSs, e.g. reactive nitrogen species. Free radicals may have 0378-4274/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.toxlet.2010.03.1167