Comparative proteomics analysis of lanthanum citrate complex-induced apoptosis in HeLa cells

The effect of four lanthanides onto a rat kidney cell line (NRK-52E) is dependent on the composition of the cell culture medium

Lanthanide (Ln) exposure poses a serious health risk to animals and humans. In this study, we investigated the effect of 10^-9-10^-3 M La, Ce, Eu, and Yb exposure onto the viability of rat renal NRK-52E cells in dependence on Ln concentration, exposure time, and composition of the cell culture medium. Especially, the influence of fetal bovine serum (FBS) and citrate onto Ln cytotoxicity, solubility, and speciation was investigated. For this, in vitro cell viability studies using the XTT assay and fluorescence microscopic investigations were combined with solubility and speciation studies using TRLFS and ICP-MS, respectively. The theoretical Ln speciation was predicted using thermodynamic modeling. All Ln exhibit a concentration- and time-dependent effect on NRK-52E cells. FBS is the key parameter influencing both Ln solubility and cytotoxicity. We demonstrate that FBS is able to bind Ln³⁺ ions, thus, promoting solubility and reducing cytotoxicity after Ln exposure for 24 and 48 h. In contrast, citrate addition to the cell culture medium has no significant effect on Ln solubility and speciation nor cytotoxicity after Ln exposure for 24 and 48 h. However, a striking increase of cell viability is observable after Ln exposure for 8 h. Out of the four Ln elements under investigation, Ce is the most effective. Results from TRLFS and solubility measurements correlate well to those from in vitro cell culture experiments. In contrast, results from thermodynamic modeling do not correlate to TRLFS results, hence, demonstrating that big gaps in the database render this method, currently, inapplicable for the prediction of Ln speciation in cell culture media. Finally, this study demonstrates the importance and the synergistic effects of combining chemical and spectroscopic methods with cell culture techniques and biological methods.

Effect of four lanthanides onto the viability of two mammalian kidney cell lines

Exposure to lanthanides (Ln) poses a serious health risk to animals and humans. Since Ln are mainly excreted with urine, we investigated the effect of La, Ce, Eu, and Yb exposure on renal rat NRK-52E and human HEK-293 cells for 8, 24, and 48 h in vitro. Cell viability studies using the XTT assay and microscopic investigations were combined with solubility and speciation studies using ICP-MS and TRLFS. Thermodynamic modeling was applied to predict the speciation of Ln in the cell culture medium. All Ln show a concentration- and time-dependent effect on both cell lines with Ce being the most potent element. In cell culture medium, the Ln are completely soluble and most probably complexed with proteins from fetal bovine serum. The results of this study underline the importance of combining biological, chemical, and spectroscopic methods in studying the effect of Ln on cells in vitro and may contribute to the improvement of the current risk assessment for Ln in the human body. Furthermore, they demonstrate that Ln seem to have no effect on renal cells in vitro at environmental trace concentrations. Nevertheless, especially Ce has the potential for harmful effects at elevated concentrations observed in mining and industrial areas.

Proteomic investigation into betulinic acid-induced apoptosis of human cervical cancer HeLa cells

Betulinic acid is a pentacyclic triterpenoid that exhibits anticancer functions in human cancer cells. This study provides evidence that betulinic acid is highly effective against the human cervical cancer cell line HeLa by inducing dose- and time-dependent apoptosis. The apoptotic process was further investigated using a proteomics approach to reveal protein expression changes in HeLa cells following betulinic acid treatment. Proteomic analysis revealed that there were six up- and thirty down-regulated proteins in betulinic acid-induced HeLa cells, and these proteins were then subjected to functional pathway analysis using multiple analysis software. UDP-glucose 6-dehydrogenase, 6-phosphogluconate dehydrogenase decarboxylating, chain A Horf6-a novel human peroxidase enzyme that involved in redox process, was found to be down-regulated during the apoptosis process of the oxidative stress response pathway. Consistent with our results at the protein level, an increase in intracellular reactive oxygen species was observed in betulinic acid-treated cells. The proteins glucose-regulated protein and cargo-selection protein TIP47, which are involved in the endoplasmic reticulum pathway, were up-regulated by betulinic acid treatment. Meanwhile, 14-3-3 family proteins, including 14-3-3β and 14-3-3ε, were down-regulated in response to betulinic acid treatment, which is consistent with the decrease in expression of the target genes 14-3-3β and 14-3-3ε. Furthermore, it was found that the antiapoptotic bcl-2 gene was down-regulated while the proapoptotic bax gene was up-regulated after betulinic acid treatment in HeLa cells. These results suggest that betulinic acid induces apoptosis of HeLa cells by triggering both the endoplasmic reticulum pathway and the ROS-mediated mitochondrial pathway.

Proteomic study on sodium selenite-induced apoptosis of human cervical cancer HeLa cells

Sodium selenite can induce the apoptosis of cancer cells, however its mechanism has seldom been studied via proteomics. In this paper, human cervical cancer HeLa cells were investigated by MTT assay and morphological observation to get appropriate selenite concentrations for proteomic study. Results showed that selenite at concentrations larger than 10 μmol/L significantly inhibited the viability of HeLa cells. 40 μmol/L selenite was in the appropriate range for proteomic study. After 24 h treatment with 40 μmol/L selenite, total proteins were extracted from the cells and applied to two-dimensional gel electrophoresis (2DE). Those proteins with their expression levels altered at least 2-fold comparing to the control were picked up for protein identification via MALDI-TOF mass spectrometry and further confirmed by Western blot analysis. About 1000 spots were detected by the software in each 2DE gel, among which 13 differentially expressed proteins were identified by mass spectrometry and most of them are relevant to oxidative stress, such as peroxiredoxins, superoxide dismutase, quinolinate phosphoribosyl transferase, and D-dopachrome tautomerase. Meanwhile, reactive oxygen species (ROS) and mitochondrial membrane potential were also detected by flow cytometry and laser confocal scanning microscope. An increase in ROS generation and a decrease in mitochondrial membrane potential were detected in the selenite-treated cells compared with the control, which are consistent with the down-expression of antioxidative proteins in proteomics. Those results indicate that selenite induces the apoptosis of HeLa cells via ROS-mediated mitochondrial pathway. The present study also implies the potentiality of selenium in cervical cancer treatment.

Proteomic analysis of lanthanum citrate-induced apoptosis in human cervical carcinoma SiHa cells

Lanthanides possess diverse biological effect and have been shown to promote cell proliferation and induce apoptosis. Our previous studies showing that lanthanide citrate complex has significant antitumor activity in human cervical cancer HeLa cells. This study aims at determining if [LaCit(2)](3-) have the activity against another type of human cervical cancer cell line SiHa and the changes in protein expression that contribute to the mechanism(s) of [LaCit(2)](3-)-mediated apoptosis in SiHa cells. Cell growth inhibition was measured by MTT method, and apoptosis was detected by means of Hoechst 33258 staining and flow cytometry analysis. After [LaCit(2)](3-)-treatment the results show that the growth of SiHa cells was inhibited, the cells displayed typical apoptosis morphological changes, and increase in the rates of apoptosis. Using proteomics approaches, a variety of differentially expressed proteins were identified in SiHa cells before and after treatment with [LaCit(2)](3-). There were profound changes in 10 proteins relating to mitochondrial function and oxidative stress, suggesting that mitochondrial dysfunction plays a key role in [LaCit(2)](3-)-induced apoptosis. This was confirmed by a decrease in the mitochondrial transmembrane potential (Δψ(m)), and increases in H(2)O(2) generation in [LaCit(2)](3-)-treated cells. Among them the alerted proteins, Prx I, ANXA1 and TRAF5 were validated by western blotting analyses. These results suggest that there is an intrinsic molecular pathway of cell apoptosis in [LaCit(2)](3-)-treated SiHa cells. This observation is in accordance with our previous reports about the effects of [LaCit(2)](3-) and [YbCit(2)](3-) on HeLa cells and it provide a molecular mechanism underlying lanthanide citrate complex-mediated cell apoptosis.