, 2007, Baum et al., 2008 and Lao et al., 2006). However, curcumin is a highly hydrophobic molecule, and it could accumulate in some body compartments (such as adipose tissue and brain) after repetitive exposure. Indeed, Begum et al. (2008) demonstrated that micromolar concentrations of curcumin accumulates in rat brain after chronic administration. Increasing curcumin solubility with phosphatidyl choline, olive oil, stearic acid or lipid-rich diet, increases the amount of curcumin in plasma and brain (Begum et al., 2008). In this work, we set out to investigate the short and long-term effect of 0–50 μM curcumin in a human renal and intestinal cell line. Indeed,
kidney cells may be involved in excretion of curcumin and/or its metabolites and intestinal cells may be exposed to relatively high curcumin concentrations RGFP966 after ingestion of a meal containing this spice. Considerable effort has been devoted in the last years in identifying the molecular targets responsible for curcumin related effects. Increasing evidence indicates that cationic channels (selective for calcium or potassium and unselective cation channels (Enyeart et al., 2008, Enyeart et al., 2009, Liu et al., 2006, Shin et al., 2011 and Yeon et al., 2010)) can be blocked by extracellular curcumin. In contrast to cationic channels, chloride channels seem
to be activated by curcumin. This was shown for CFTR and two of its mutants found in patients suffering from cystic fibrosis, i.e. G551D (Yu et al., 2011) and ΔF508-CFTR (Berger et al., 2005, Wang et al., 2005 and Wang AZD2281 et al., 2007). Wang et al. pointed out that the structure of curcumin (two aromatic rings separated by a hydrocarbon much spacer) is similar to that of NPPB-AM, an uncharged NPPB derivative that activates CFTR. It is important to note that the effect of curcumin on CFTR and its mutants is controversial (Egan et al., 2004, Grubb et al., 2006, Lipecka et al., 2006 and Norez
et al., 2006). Besides the possible effect of curcumin on CFTR, little is known about a possible effect of curcumin on other chloride channels. Best et al. (2007) describe an activation of IClswell in rat pancreatic cells by curcumin. Curcumin was shown to have pro-apoptotic activity (Shankar et al., 2007 and Shankar and Srivastava, 2007a), and might therefore be a candidate for cancer treatment (Kelkel et al., 2010). Since the molecular structure of curcumin is reminiscent of a substance that could interact with a chloride channel (Wang et al., 2005), and IClswell is activated during RVD following hypotonic stress and as an early event in apoptosis (in isotonic conditions), we set out to investigate the link between curcumin, IClswell and apoptosis. In contrast to Best et al. (2007), we did not detect a direct stimulatory effect of curcumin on IClswell in isotonic conditions. It is important to note, however, that we used a human kidney cell line as opposed to the Best et al.