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Our previous study indicated that vanadium compounds can block cell cycle progression at the G1/S phase in human hepatoma HepG2 cells via a highly activated extracellular signal-regulated protein kinase (ERK) signal. To explore their differential action on normal cells, we investigated the response of an immortalized hepatic cell line, L02 cells. The results demonstrated that a higher concentration of vanadium compounds was needed to inhibit L02 proliferation, which was associated with S and G2/M cell cycle arrest. In addition, in contrast to insignificant reactive oxygen species (ROS) generation in HepG2 cells, all of the vanadium compounds resulted significant increases in both O and HO levels in L02 cells. At the same time, ERK and c-Jun N-terminal kinase (JNK) as well as cell division control protein 2 homolog (Cdc2) were found to be highly phosphorylated, which could be counteracted with the antioxidant N-acetylcysteine (NAC). The current study also demonstrated that both the ERK and the JNK pathways contributed to the cell cycle arrest induced by vanadium compounds in L02 cells. More importantly, it was found that although NAC can ameliorate the cytotoxicity of vanadium compounds in L02 cells, it did not decrease their cytotoxicity in HepG2 cells. It thus shed light on the potential therapeutic applications of vanadium compounds with antioxidants as synergistic agents to reduce their toxicities in human normal cells without affecting their antitumor activities in cancer cells. [ABSTRACT FROM AUTHOR]

In the present study, we demonstrated that gadolinium-containing particles formed in cell culture medium acted as a biologically active entity to mediate cell cycle progression in NIH3T3 cells. The particles were observed to accumulate at the cell surface by scanning electron microscopy. Energy-dispersive X-ray analysis was undertaken and confirmed that gadolinium was incorporated in the agglomerated particles. Moreover, the smaller gadolinium particles exhibited a stronger cell-cycle-promoting effect than the larger ones, but they shared the common signaling pathways. Both extracellular signal regulated kinase and phosphatidylinositol 3-kinase signaling pathways were activated by gadolinium-containing particles and may account for their proliferation-promoting effect on NIH3T3 cells. Furthermore, the study showed that the free gadolinium ion released from gadolinium-containing particles may be responsible for the proliferation effect. This study will be helpful to clarify the biological effect of the insoluble species formed from Gd3+ as well as other multivalent metal ions under physiological conditions and will help to improve their medical applications. [ABSTRACT FROM AUTHOR]

Our present study provided new evidence for diterbium transferrin (Tb2Tf) as a potential multi-photon-excited microscopy probe. It indicated that the Tb2Tf complex can be transported into human leukemia K562 cells via a process mediated by transferrin (Tf) receptors as an intact entity and with no obvious cellular toxicity. The supporting evidence includes the following. First, the transport kinetic behavior of Tb was compared with that of the Tf moiety. The Tb was determined by inductively coupled plasma mass spectrometry and Tf was determined by fluorescence activated cell sorting analysis. The kinetic synchronization of internalization of both Tb and Tf into human leukemia K562 cells demonstrated the Tb2Tf complex was transported into cells as a whole. Second, using confocal laser scanning microscopy, we observed the localization of Tb2Tf in the cell. This showed that the internalized Tb2Tf was mostly situated in the same perinuclear region as diferric transferrin (Fe2Tf). In addition, pretreatment with pronase largely abolished the transport process of Tb2Tf. The relative fluorescence intensities representing the uptake of Tf into the cells decreased to about 16% and the cytosolic Tb content decreased to almost the same percentage as for Tf. Furthermore, the addition of Fe2Tf can effectively inhibit transport of Tb2Tf into K562 cells. Third, no significant decrease of cell viability was observed in the presence of Tb2Tf even for 24 or 48 h by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Moreover, prospects for the use of Tb2Tf as a multi-photon-excited microscopy probe in a living system are discussed. [ABSTRACT FROM AUTHOR]

Abstract  The effect of gadolinium chloride (Gd) on the proliferation of HeLa cells was investigated at lower concentration. The results obtained by MTT and cell cycle analysis showed that Gd promoted proliferation by inducing S phase entry in HeLa cells at the concentration less than 100 μM. It was further evidenced by both an increase in the levels of phosphorylation of retinoblastoma protein (pRb) and a remarkable increase in cyclin E expression. Moreover, the survival of cells, exposed to Gd up to 3–5 days, was increased compared with control. The attenuation of the serum deprivation-induced cell loss by Gd was associated with the sustained activation of FAK (PY397) and the delayed activation of JNKs pathway. Besides, it appeared that Gd promoted cell proliferation and survival in HeLa cells was not contributed to the ROS generation. Based on the present results, both positive and negative effects of the lanthanides as potential drugs or diagnostic agents are discussed. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate whether Gd is able to exert the proliferation-promoting effect and to explore its possible underlying mechanism. We showed that Gd promoted cell cycle progression with increased S-phase entry in a concentration- and time-dependent manner in NIH 3T3 cells. The effect was further evidenced by the expressions of key proteins in driving cells through the G1/S transition point of the cell cycle. In the presence of Gd, the protein levels of cyclins D, E, and A were dramatically increased and demonstrated a characteristically temporal pattern of sequential mitotic events. Additionally, the levels of phosphorylated retinoblastoma protein were also significantly increased at certain time periods. To further elucidate the underlying mechanism, extracellular signal-regulated kinase and phosphatidylinositol 3-kinase signaling pathways were assessed. Both pathways were activated by Gd. Moreover, the levels of cyclin D and cyclin A were evaluated after the addition of the pharmacological inhibitors at early and late G1 phases, correspondingly, to reveal the contribution of the two pathways in the Gd-promoted G1/S transition. It showed that both pathways were needed for Gd-promoted cell cycle progression. The results presented here provide novel evidence to advance knowledge leading to further understanding of the mechanisms of both cell growth and death caused by Gd and may be helpful for more rational application of Gd-based compounds in the future. [ABSTRACT FROM AUTHOR]

In recent years the anticancer properties of vanadium compounds have been noticed, but the underlying mechanisms are not well understood. In the present work, we found that vanadyl bisacetylacetonate ([VO(acac)2]) blocked cell cycle progression permanently at G1 phase in a dose- and time-dependent manner in HepG2 cells. This was further evidenced by the growth regulatory signals during the G1 stage. After the treatment with [VO(acac)2], the level of phophorylation of retinoblastoma tumor suppressor protein (pRb) and the expressions of cyclin D1, cyclin E and cyclin A were reduced, while the expression of a cyclin-dependent kinase inhibitor p21 was increased dose-dependently. In the meantime, neither O2 •− nor H2O2 level was observed to increase. Interestingly, the levels of phosphorylated extracellular signal-regulated protein kinase (ERK) and Akt were highly activated. After 1-h pretreatment with a lower concentration of MEK inhibitor U0126, the level of phosphorylated pRb was restored, indicating a release of cell cycle arrest. Taken together, we suggested that [VO(acac)2]-induced proliferation inhibition was caused by G1/S cell cycle arrest, which resulted from the decreased level of phosphorylated pRb in its active hypophosphorylated form via a highly activated ERK signal in HepG2 cells. The results presented here provided new insight into the development of vanadium compounds as potential anticancer agents. [ABSTRACT FROM AUTHOR]

Purpose. The aim of this study was to investigate the mechanism of permeation and cytotoxicity of vanadium compounds, [VO(acac)2], [VO(ma)2], and vanadate.Methods. Absorptive transport were carried out in Caco-2 monolayers grown on transwell inserts. Vanadium was quantified using inductively coupled plasma atomic emission spectrometry (ICP-AES). The change of Caco-2 cells in the microvilli morphology and F-actin structure was visualized by transmission electron microscopy and confocal laser scanning microscopy.Results. The three vanadium compounds were taken up by Caco-2 cells via simple passive diffusion. [VO(acac)2] were mainly transcellularly transported and exhibited the highest apparent permeabilty coefficients (8.2 × 10-6 cm). The cell accumulation of [VO(acac)2] was found to be greater than that of [VO(ma)2], and vanadate caused much less accumulation than the other two compounds. Vanadium compounds induced intracellular reactive oxygen species, reduced the transepithelial electric resistance, caused morphological change in microvilli, and led to different perturbation of F-actin structure.Conclusions. The three compounds exhibited different permeability due to different diffusion process and cellular uptake. The toxicity of vanadium complexes on Caco-2 monolayer involved F-actin-related change of tight junction and impairment of microvilli. The toxicity was also related to elevated intracellular reactive oxygen species (ROS) and their cellular accumulation. [ABSTRACT FROM AUTHOR]