La(3+)-induced extracellular signal-regulated kinase (ERK) signaling via a metal-sensing mechanism linking proliferation and apoptosis in NIH 3T3 cells

Gadolinium chloride promotes proliferation of HEK293 human embryonic kidney cells by activating EGFR/PI3K/Akt and MAPK pathways

Prolonged exposure to gadolinium-based contrast agents has been reported to trigger nephrogenic systemic fibrosis in end stage renal disease patients. However, the exact molecular mechanisms are not fully understood, and no effective therapy is available to date. In the present study, we report that gadolinium chloride (Gd³⁺) concentration- and time-dependently promoted the proliferation of HEK293 human embryonic kidney cells by increasing DNA synthesis. Gd³⁺ treatment increased the protein levels of phosphorylated Akt and MAPKs. Inhibition of Akt and ERK by pharmacological inhibitors abolished the increased proliferation and cell cycle progression. Furthermore, Gd³⁺ activated EGFR signaling possibly by enhancing EGFR clustering on the cell membrane. Inhibition of EGFR by gefitinib blocked Gd³⁺-induced proliferation. Gd³⁺ exposure also upregulated the mRNA levels of TGFβ-1, TGFβR1, TNFα, TIMP-1 and integrin αV, β1 which could also be attenuated by the inhibition of Akt and ERK signaling. Our study provides new clues for the etiological role of Gd³⁺ in the pathogenesis of nephrogenic systemic fibrosis, and suggests the inhibition of EGFR/Akt/ERK signaling as a potential treatment strategy.

Regulation of centrin self-assembly investigated by fluorescence resonance light scattering

Centrin is primarily involved in fiber contraction, which is associated with the cell division cycle and ciliogenesis.

GdCl3 induced Hep G2 cell death through mitochondrial and external death pathways without significant elevation of ROS generation

Gadolinium (Gd) compounds have important applications as MRI contrast and potential anticancer agents. The present study investigated the mechanisms of the proapoptotic effect of gadolinium chloride (GdCl(3)) on hepatoblastoma cell line (Hep G2) tumor cells. The experimental results indicated that GdCl(3) induced apoptosis of Hep G2 at high concentration and with long time incubation; however, unlike the actions on normal cell lines, GdCl(3) did not cause any oxidative stress on tumor cells. Cytochrome c (Cyt c) and apoptosis inducing factor release, Bax translocation, collapse of mitochondria membrane potential, caspase 3 and 8 activation, and Bid cleavage were observed along with a sustained activation of extracellular signal-regulated kinase (ERK) and c-Jun NH2 terminal kinase (JNK). Addition of ERK and JNK inhibitor attenuated the effect of GdCl(3) induced apoptosis and Cyt c release. All the results suggested a novel mechanism that GdCl(3) induced Hep G2 cell death through intrinsic and external death pathways without significant elevation of reactive oxygen species generation. The present work provided new insight to understand the mechanisms of the biological effects of GdCl(3) and implications for the development of anticancer Gd agents.

The interaction between lanthanide (III) and N-terminal domain of Euplotes octocarinatus centrin

Centrin, a member of calcium-binding proteins, is an essential component for microtubule-organizing center (MTOC). Lanthanide (Ln) ions can increase amounts, enhance stability and orderliness of microtubules which is an important component of cytoskeleton. To investigate the structural basis of the effect of Ln ions on orderliness of microtubules, we focused on the interactions between the isolated N-terminal domain of Euplotes centrin (N-EoCen) and Ln by some combined biophysical and biochemical methods. Our results suggest that Ln ions may bind to the canonical calcium binding sites on N-EoCen. Taking advantage of ligand competition, we first determined the metal-binding affinities of Nd(3+), Eu(3+), Gd(3+) and Tm(3+) with N-EoCen. Major changes of N-EoCen in secondary and tertiary structure are noted while Ln ions bind with N-EoCen through CD spectra and 2-p-toluidinylnaphthalene-6-sulfonate (TNS) fluorescence. N-EoCen exists in the form of monomer and dimer in the presence of Ln ions. These results can provide some insights into the structural basis of how Ln ions achieve biological effect in cell through the centrin protein.

Fibroblast response to lanthanoid metal ion stimulation: potential contribution to fibrotic tissue injury

The purpose of this study was to compare each of the 14 naturally occurring lanthanoid metal ions for ability to stimulate pro-fibrotic responses in human dermal fibroblasts. When fibroblasts were exposed to individual lanthanoids over the concentration range of 1-100 μM, increased proliferation was observed with each of the agents as compared with control cells that were already proliferating rapidly in a growth factor-enriched culture medium. Dose-response differences were observed among the individual metal ions. Matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinase-1 levels were also increased in response to lanthanoid exposure but type I procollagen production was not. A dose-response relationship between induction of proliferation and increased MMP-1 was observed. Non-lanthanoid transition metal ions (aluminum, copper, cobalt, iron, magnesium, manganese, nickel, and zinc) were examined in the same assays; there was little stimulation with any of these metals. When epidermal keratinocytes were examined in place of dermal fibroblasts, there was no growth stimulation with any of the lanthanoids. Several of the lanthanoid metals inhibited keratinocyte proliferation at higher concentrations (50-100 μM).

Fibroblast response to gadolinium: role for platelet-derived growth factor receptor

OBJECTIVE

The purpose of this study was to assess the effects of gadolinium (Gd3+), provided as gadolinium chloride, on fibroblast function.

MATERIALS AND METHODS

Human dermal fibroblasts in monolayer culture and intact skin in organ culture were exposed to the lanthanide metal (1-20 μM).

RESULTS

Increased proliferation was observed, in association with upregulation of matrix metalloproteinase-1 and tissue inhibitor of metalloproteinases-1, without an apparent increase in production of type I procollagen. A platelet-derived growth factor (PDGF) receptor-blocking antibody inhibited fibroblast proliferation in response to Gd3+ as did inhibitors of signaling pathways--that is, mitogen-activated protein kinase and phosphatidylinositol-3 kinase pathways--that are activated by PDGF.

CONCLUSION

The responses to gadolinium chloride are similar to responses previously seen with chelated Gd3+ in clinically used magnetic resonance imaging contrast agents. Fibroblast responses appear to reflect Gd3+-induced PDGF receptor activation and downstream signaling. Increased dermal fibroblast proliferation in conjunction with effects on matrix metalloproteinase-1 and tissue inhibitor of metalloproteinases-1 could contribute to the fibroplastic/fibrotic changes seen in the lesional skin of individuals with nephrogenic systemic fibrosis.