Cell Calcium 43 (2008) 184–195 Endoplasmic reticulum stress and alteration in calcium homeostasis are involved in cadmium-induced apoptosis Marta Biagioli a,∗ , Simone Pifferi a,1 , Matilde Ragghianti a , Stefania Bucci a , Rosario Rizzuto b , Paolo Pinton b a Laboratory of Cellular and Development Biology, Department of Biology, University of Pisa, Italy b Department of Experimental and Diagnostic Medicine, Section of General Pathology and Interdisciplinary Centre for the Study of Inflammation (ICSI), University of Ferrara, Italy Received 14 January 2007; received in revised form 30 April 2007; accepted 8 May 2007 Available online 22 June 2007 Abstract Cadmium, a toxic environmental contaminant, exerts adverse effects on different cellular pathways such as cell proliferation, DNA damage and apoptosis. In particular, the modulation of Ca 2+ homeostasis seems to have an important role during Cd 2+ injury, but the precise assessment of Ca 2+ signalling still remains poorly understood. We used aequorin-based probes specifically directed to intracellular organelles to study Ca 2+ changes during cadmium injury. We observed that cadmium decreased agonist-evoked endoplasmic reticulum (ER) Ca 2+ signals and caused a 40% inhibition of sarcoplasmic–ER calcium ATPases activity. Moreover, time course experiments correlate morphological alterations, processing of xbp-1 mRNA and caspase-12 activation during cadmium administration. Finally, the time response of ER to cadmium injury was compared with that of mitochondria. In conclusion, we highlighted a novel pathway of cadmium-induced cell death triggered by ER stress and involving caspase-12. Mitochondria and ER pathways seemed to share common time courses and a parallel activation of caspase-12 and caspase-9 seemed likely to be involved in acute cadmium toxicity. © 2007 Elsevier Ltd. All rights reserved. Keywords: Cadmium; Aequorin chimeras; Endoplasmic reticulum; Calcium homeostasis; Sarcoplasmic–endoplasmic reticulum calcium ATPases; Apoptosis; Caspases 1. Introduction We analysed the mechanisms of cellular toxicity associ- ated to cadmium exposure. This heavy metal, widely diffused in the ecosystems because of its large use in different kinds of industries and other human activities, is characterized by a very long half life [1,2]. Chronic exposure to cadmium in humans is associated with bone, lung and renal dam- age. Furthermore, evidences of human carcinogenicity are ∗ Corresponding author. Present address: Laboratory of Molecular Neu- robiology, International School for Advanced Studies (ISAS), Area Science Park Basovizza Building Q1, SS 14 Km 163,5, 34012 Trieste, Italy. Tel.: +39 040 3756535; fax: +39 040 3756502. E-mail address: biagioli@sissa.it (M. Biagioli). 1 Present address: Neurobiology Sector, International School for Advanced Studies (ISAS), Trieste, Italy. also available linking long-term occupational exposure to increased occurrence of lung, prostate and renal cancer cases [3,4]. At the cellular level, cadmium has been also associated with different biochemical changes characteristic of pro- grammed cell death (PCD) [5]. Even if several hypotheses have been proposed, the mechanisms for cadmium-induced apoptosis remain poorly understood. Alteration in calcium homeostasis and mitochondrial damage [6,7] have been involved with cadmium-induced apoptosis, but other intracellular targets could not be ruled out. Calcium is a ubiquitous intracellular signal responsible for controlling numerous cellular processes including pro- liferation, differentiation, development and cell death [8,9]. Thus, it is not surprising that changes in Ca 2+ concentration 0143-4160/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.ceca.2007.05.003