Diethylentriaminepenta acetic acid glucose conjugates as a cell permeable iron chelator

Abstract

Objective: To find out whether DTPA-DG complex can enhance clearance of intracellular free iron.

Materials and methods: Diethylenetriaminepentaacetic acid-D-deoxy-glucosamine (DTPA-DG) was synthesized and examined for its activity as a cell-permeable iron chelator in human hepatocellular carcinoma (HEPG2) cell line exposed to high concentration of iron sulfate and compared with deferoxamine (DFO), a prototype iron chelator. The effect of DTPA-DG on cell viability was monitored using the 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide MTT assay as well.

Results: There was a significant increase of iron level after iron overload induction in HEPG2 cell culture. DTPA-DG presented a remarkable capacity to iron burden reducing with estimated 50% inhibitory concentration value of 65.77 nM. In fact, glycosyl moiety was gained access of DTPA to intracellular iron deposits through glucose transporter systems.

Conclusion: DTPA-DG, more potent than DFO to sequester deposits of free iron with no profound toxic effect. The results suggest the potential of DTPA-DG in chelating iron and permitting its excretion from primary organ storage.

Keywords: Cell-permeable; glycosyl moiety; human hepatocellular carcinoma; iron chelation; iron overload.

Figure 1

Structural formula of Puchel, lipophilic derivative of diethylenetriaminepentaacetic acid used for plutonium decorporation

Figure 2

Diethylenetriaminepentaacetic acid-folate structure, conjugated form of DTPA for tumor targeting-delivery

Figure 3

Chemical structure of diethylenetriaminepentaacetic acid-D-deoxy-glucosamine

Figure 4

Cellular iron level in control and iron-overload human hepatocellular carcinoma cell model as measurement by atomic absorption spectrometry. Measurements were performed with sample triplicates (n = 3)

Figure 5

MTT assay of cytotoxicity associated with various concentrations of diethylenetriaminepentaacetic acid-D-deoxy-glucosamine after 48 h. Data are presented as the percentage of cell viability relative to the untreated normal human hepatocellular carcinoma (mean ± standard deviation, n = 3). As a result, a negligible (P > 0.05) decrease of cell viability observed by MTT test

Figure 6

A dose-dependent decrease of free iron content after 24 h incubation of human hepatocellular carcinoma cells at 37°C which treated with 20-100 nM of diethylenetriaminepentaacetic acid-D-deoxy-glucosamine. The decrease was significant (P < 0.05) at concentration equal to or higher than 40 nM of DTPA-DG in comparison with untreated cells (n = 3). Results are the mean ± standard deviation of three separate experiments

Figure 7

The comparison of two chelators diethylenetriaminepentaacetic acid-D-deoxy-glucosamine and deferoxamine efficacy in similar conditions after 24 h indicated statistically (P < 0.05) a higher reducing of cellular iron content with DTPA-DG than with DFO at much lower doses. Results are the mean ± standard deviation of three separate experiments (n = 3)

Figure 8

A significant (P < 0.05, r² = 0.994) correlation with iron chelator dose and its success in reducing cellular iron content is shown in this figure. Diethylenetriaminepentaacetic acid D-deoxy-glucosamine at concentration of 65.77 nM has been able to reduce 50% of iron deposits