Heavy metal chelator TPEN attenuates fura-2 fluorescence changes induced by cadmium

Stimulation with heavy metals is known to induce calcium (Ca2+) mobilization in many cell types. Interference with the measurement of intracellular Ca2+ concentration by the heavy metals in cells loaded with Ca2+ indicator fura-2 is an ongoing problem. In this study, we analyzed the effect of heavy metals on the fura-2 fluorescence ratio in human SH-SY5Y neuroblastoma cells by using TPEN, a specific cell-permeable heavy metal chelator. Manganese chloride (30–300 µM) did not cause significant changes in the fura-2 fluorescence ratio. A high concentration (300 µM) of lead acetate induced a slight elevation in the fura-2 fluorescence ratio. In contrast, stimulation with cadmium chloride, mercury chloride or MeHg (3–30 µM) elicited an apparent elevation of the fura-2 fluorescence ratio in a dose-dependent manner. In cells stimulated with 10 or 30 µM cadmium chloride, the addition of TPEN decreased the elevated fura-2 fluorescence ratio to basal levels. In cells stimulated with mercury or MeHg, the addition of TPEN significantly decreased the elevation of the fura-2 fluorescence ratio induced by lower concentrations (10 µM) of mercury or MeHg, but not by higher concentrations (30 µM). Pretreatment with Ca2+ channel blockers, such as verapamil, 2-APB or lanthanum chloride, resulted in different effects on the fura-2 fluorescence ratio. Our study provides a characterization of the effects of several heavy metals on the mobilization of divalent cations and the toxicity of heavy metals to neuronal cells.To get more news about NBMI, you can visit fandachem.com official website.
The Cd is taken up into the cell via carriers, such as low-affinity cation transporters and Fe-regulated transporters in plants (Lindberg et al., 2004; Takahashi et al., 2011). Among the Fe transporters, IRTs and NRAMPs have been reported to take up Cd as well as Fe (Curie et al., 2000; Nakanishi et al., 2006). IRT1 is essential for root Fe uptake in response to Fe deficiency but it also accepts Cd as a substrate and is involved in the root-to-shoot transport of Cd (Rogers et al., 2000). In a transgenic study, elimination of NRAMP5 transporter reduces Cd uptake in rice (Ishikawa et al., 2012). ). Additionally, the ferric chelate reductase (FRO) gene may perform key functions in Fe acquisition in plants (Ling et al., 2002). Barcelo et al. (1993) reported the inhibition of Fe translocation when bean plants were exposed to chromium (Cr) in nutrient solutions. Also, Cr affects Fe uptake in dicots either by inhibiting the reduction of Fe(III) to Fe(II) or by competing with Fe(II) at the site of absorption (Shanker et al., 2005). In addition, IRT1 is induced in response to Fe-deficiency and is capable of transporting minerals and heavy metals (Vert et al., 2002). Further, organic acids such as citrate and malate are major chelators in both Strategy I and II plants, which bind Fe at the site of uptake and facilitate long-distance transport in plants (Abadia et al., 2002; Kabir et al., 2012). Therefore, regulation of Fe uptake has yet to be characterized in detail under Cd stress in plants.