Cadmium stress: an oxidative challenge Ann Cuypers • Michelle Plusquin • Tony Remans • Marijke Jozefczak • Els Keunen • Heidi Gielen • Kelly Opdenakker • Ambily Ravindran Nair • Elke Munters • Tom J. Artois • Tim Nawrot • Jaco Vangronsveld • Karen Smeets Received: 5 December 2009 / Accepted: 19 March 2010 Ó Springer Science+Business Media, LLC. 2010 Abstract At the cellular level, cadmium (Cd) induces both damaging and repair processes in which the cellular redox status plays a crucial role. Being not redox- active, Cd is unable to generate reactive oxygen species (ROS) directly, but Cd-induced oxidative stress is a common phenomenon observed in multiple studies. The current review gives an overview on Cd-induced ROS production and anti-oxidative defense in organisms under different Cd regimes. Moreover, the Cd-induced oxidative challenge is discussed with a focus on damage and signaling as downstream responses. Gathering these data, it was clear that oxidative stress related responses are affected during Cd stress, but the apparent discrep- ancies observed in between the different studies points towards the necessity to increase our knowl- edge on the spatial and temporal ROS signature under Cd stress. This information is essential in order to reveal the exact role of Cd-induced oxidative stress in the modulation of downstream responses under a diverse array of conditions. Keywords Cadmium Á Glutathione Á Oxidative stress Á Signaling Á Thiol Á Antioxidative defense Á Reactive oxygen species Introduction Cadmium (Cd) is an earth’s crust natural element and is usually found as a mineral in combination with other elements such as oxygen, chlorine, or sulfur. Over the past two centuries, anthropogenic and industrial activities have led to high emissions of Cd into the environment at concentrations significantly exceeding those originating from natural sources (Nriagu 1988; Vangronsveld et al. 1995). Since Cd can not be degraded, the risk of environmental exposure is constantly increasing because of accumulation via the food chain (ATSDR 2005). At the cellular level, Cd induces oxidative stress in many organisms (Bertin and Averbeck 2006; The ´ve- nod 2009), which might result in physiological dam- age to different organs among which kidneys, liver, lung, pancreas, testes, placenta, and bone (Jarup et al. 1998; Nawrot et al. 2008; Jarup and A ˚ kesson 2009). Cadmium is a bivalent cation and unable to generate free radicals directly, nevertheless the production of reactive oxygen species (ROS) after Cd exposure has been reported in multiple studies (Hassoun and Stohs 1996; Hart et al. 1999; Szuster-Ciesielska et al. 2000; The ´venod et al. 2000; Gala ´n et al. 2001; Wang et al. A. Cuypers (&) Á M. Plusquin Á T. Remans Á M. Jozefczak Á E. Keunen Á H. Gielen Á K. Opdenakker Á A. R. Nair Á E. Munters Á T. J. Artois Á T. Nawrot Á J. Vangronsveld Á K. Smeets Centre for Environmental Sciences, Hasselt University, Agoralaan Building D, 3590 Diepenbeek, Belgium e-mail: ann.cuypers@uhasselt.be 123 Biometals DOI 10.1007/s10534-010-9329-x