THE ERYTHROPOIETIC ACTION OF GERMANIUM DIOXIDE

Interaction of Organogermanium Compounds with Saccharides in Aqueous Solutions: Promotion of Aldose-to-ketose Isomerization and Its Molecular Mechanism

This review discusses sugar isomerization with organogermanium compounds. Organogermanium compounds markedly increase the aldose-ketose (glucose-fructose or lactose-lactulose) isomerization ratio, double the initial reaction rate, and significantly reduce the base-catalyzed degradation of sugars. 1H-nuclear magnetic resonance analysis reveals that the affinity of organogermanium compounds with a 3-(trihydroxygermyl)propanoic acid (THGP) structure toward ketoses is 20-40 times stronger than that toward aldoses; thus, such organogermanium compounds form complexes more readily with ketoses than with aldoses. Stable ketose complexes, which contain multiple cis-diol structures and high fractions of furanose structures, suppress the reverse ketose-aldose reaction, thereby shifting the equilibrium toward the ketose side. These complexes also protect sugar molecules from alkaline degradation owing to the repulsion between anionic charges. The increased rate of the initial reaction in the alkaline isomerization process results from stabilizing the transition state by forming a complex between THGP and a cis-enediol intermediate. The cyclic pentacoordinate or hexacoordinate THGP structures give rise to a conjugated system of germanium orbitals, which is extended through dπ-pπ interactions, thereby improving the stability of the complex. Based on these results, we have developed a bench-scale lactulose syrup manufacturing plant incorporating a system to separate, recover, and reuse organogermanium poly-trans-[(2-carboxyethyl)germasesquioxane]. This manufacturing plant can be used as a model of an alkaline isomerization accelerator for continuous industrial production.

Organogermanium compound, Ge-132, forms complexes with adrenaline, ATP and other physiological cis-diol compounds

BACKGROUND

In mammals, adrenaline and ATP are life-essential vicinal diol and cis-diol functional groups. Here, we show that interactions between a safe organogermanium compound and these cis-diol compounds have the potential to regulate physiological functions. In addition, we represent a possible new druggable target for controlling the action of cis-diol compounds.

RESULTS

We analyzed a single crystal structure of organogermanium 3-(trihydroxygermyl)propanoic acid (THGPA), a hydrolysate of safe Ge-132, in complex with catecholamine (adrenaline and noradrenaline), and evaluated the affinity between several cis-diol compounds and THGPA by NMR. An in vitro study using normal human epidermal keratinocytes was performed to investigate the inhibition of cis-diol compound-stimulated receptors by THGPA. At high concentration, THGPA inhibited the calcium influx caused by adrenaline and ATP.

CONCLUSION

This study demonstrates that THGPA can modify cis-diol-mediated cell-to-cell signaling.

Protective effects of gallium, germanium, and strontium against ovariectomized osteoporosis in rats

The effects of trace elements of gallium (Ga), germanium (Ge), and strontium (Sr) on ovariectomized (OVX) osteopenic rats were studied in this paper. The urine calcium content, serum calcium, and phosphorus contents, bone mineral content, mineral dissolution, and mechanical strength of the osteopenic rats were analyzed respectively. After the rats were fed with Ga, Ge, and Sr diet for 8 weeks, respectively, the urine calcium content decreased (P < 0.01). Plasma calcium and phosphate concentrations decreased in the order of OVX group > Ge group > Sr group > Ga group > Sham group. Mineral content increased in the order of OVX group < Ge group < Sr group < Ga group < Sham group. A dramatic decrease in calcium solubility was found both in the gallium and strontium treated animals (P < 0.05). However, the same result did not occur in germanium treated groups. The data provide an important proof of concept that gallium and strontium might be a new potential therapy for the management of postmenopausal osteoporosis in humans.

THE ERYTHROPOIETIC ACTION OF GERMANIUM DIOXIDE : II. THE SOURCE OF THE ERYTHROCYTHEMIA PRODUCED BY GERMANIUM DIOXIDE IN THE ALBINO RAT

A histological comparison of the liver, spleen, bone marrow, circulating young erythrocytes, and differential count in mature male and female albino rats receiving germanium dioxide with their litter controls not receiving this compound was made. It was found that the livers of the test animals in most cases showed a condition of capillary dilatation and that more erythrocytes were in these capillaries than were in those of the controls. There was no evidence of any red cell formation by the liver. The spleens of the test rats gave the impression of being slightly more congested and of having a slightly more dense concentration of cells in the Malpighian corpuscles than those of the controls. There was no evidence of an increased red cell destruction nor was there any evidence of splenic erythropoiesis. In the bone marrow of the rats which had received the germanium dioxide injections there was evidence of a marked stimulation in formation of nucleated erythrocytes, in that many more of these cells were found here than in the marrow sections of the controls. The circulating blood of the test rats contained more young red cells as demonstrated by the increased number of erythrocytes taking the polychromatic stain than did the blood of the controls. No noteworthy differences in the values for the various types of white cells in the circulation determined by the differential count could be found between the two groups. Using, then, as an acceptable criterion of erythropoiesis an increase in the number of erythrocytes in the circulation which is accompanied by an increase in the number of young red cells, and an increased number of nucleated erythrocytes in the bone marrow, we consider ourselves justified in concluding that germanium dioxide is a potent erythropoietic agent and the source of the erythrocythemia produced by this compound is the increased production of red cell precursors by the bone marrow stimulated to increased activity by the compound used.

Comparison of organic and inorganic germanium compounds in cellular radiosensitivity and preparation of germanium nanoparticles as a radiosensitizer

PURPOSE

The aim of this work is to compare the radiosensitizing effect between organic and inorganic germanium compounds and to investigate whether nanometer-sized germanium particles can act as radiosensitizers.

MATERIALS AND METHODS

Bis (2-carboxyethylgermanium) sesquioxide (Ge-132), germanium oxide (GeO(2)) and germanium nanoparticles were used in this study. Cell viability was determined by clonogenic survival assay. Cellular DNA damage was evaluated by alkaline comet assay, confocal microscopy and the cellular level of phospho-histone H2AX (gamma-H2AX).

RESULTS

Nanometer-sized germanium particles were fabricated. They have a similar radiosensitizing effect as that of GeO(2). Conversely, Ge-132 did not enhance the radiosensitivity of cells. Comet assay was employed to evaluate the level of DNA damage and confirmed that inorganic germanium compounds enhanced cellular radiosensitivity. Notably, the comet assay indicated that the nanoparticle itself caused a higher level of DNA damage. The possibility that germanium nanoparticles per se caused DNA damage was ruled out when the cellular level of gamma-H2AX was examined.

CONCLUSIONS

We demonstrated that inorganic but not organic germanium compounds exerted radiosensitizing effect in cells. Nanometer-sized germanium particles were fabricated and were able to enhance the radiosensitivity of cells. Confounding effect may occur when comet assay is used to estimate the level of DNA damage in the presence of germanium nanoparticles.

Germanium dioxide induces mitochondria-mediated apoptosis in Neuro-2A cells

Germanium (Ge) is commonly used in the semiconductor industry as well as health-promoting and medical field. Biologically, germanium possesses erythropoietic, anti-microbial, anti-tumor, anti-amyloidosis, and immunomodulative effects. However, toxic effects of Ge-containing compounds on kidney, muscle, neuronal cells, and nerves have been reported. Mitochondrial dysfunction was found to be involved in the pathogenesis of GeO(2)-induced nephropathy and myopathy. Since it is well known that mitochondria play a major role in apoptosis triggered by many stimuli, an effort was made to examine whether the Ge-induced neurotoxicity occurs through mitochondria-mediated apoptosis. A mouse neuroblastoma cell line, Neuro-2A, was used in the present study. After incubating with 0.1-800microM of GeO(2) for 0-72h, the cell viability of Neuro-2A cells was inhibited in a dose- and time-dependent manner. Further analysis showed that aside from the changes in the nuclear morphology responsible for apoptosis, the release of cytochrome c, the loss of mitochondrial membrane potential, the translocation of Bax, and the reduction of Bcl-2 expression were also observed in Neuro-2A cells after GeO(2) treatment. These results indicate that the mitochondria-mediated apoptosis is involved in this in vitro model of GeO(2)-induced neurotoxicity.

ORAL SINGLE- AND REPEATED-DOSE TOXICITY STUDIES ON GERANTI BIO-GE YEAST, ORGANIC GERMANIUM FORTIFIED YEASTS, IN DOGS

Single- and 13-week repeated-dose toxicities of Geranti Bio-Ge Yeast, organic germanium fortified yeasts, were investigated in dogs. Both sexes of Beagle dogs were orally administered once at a dose of 2,000 mg/kg in single-dose toxicity or daily for 13 weeks at doses of 500, 1,000 or 2,000 mg/kg in repeated-dose toxicity tests. In single-dose toxicity test, no animal dead, moribund, or showing clinical signs or changes in body weight gain was found. In repeated-dose toxicity study, there were no considerable changes in ophthalmoscopy and urinalysis. Several alterations were observed in electrocardiography, hematology and blood biochemistry, including heart rate, R-R interval, QT correcting, reticulocytes, activated partial thromboplastin time and albumin/globulin ratio in only male dogs, but not in females, administered with Geranti Bio-Ge Yeast in a dose-independent manner. In gross findings, several cases of abnormal findings were observed in both control and treatment groups, showing diffuse dark brown to black discoloration of liver, in a dose-independent manner. In microscopic examination, mild lesions, including cholestasis and inflammatory cell foci in liver, kidneys and prostate, were found sporadically in both control and treatment groups. In spite of some alterations in electrocardiography, hematology, blood biochemistry, gross and microscopic findings, such effects were not considered to include toxicopathological significance, based on the marginal changes within normal ranges and lack of dose-dependency, consistent time-course and gender relationship. Taken together, it is suggested that no observed adverse effect level (NOAEL) of Geranti Bio-Ge Yeast is considered to be 2,000 mg/kg in dogs, and that long-term treatment in clinical trials might not exert adverse effects.

ORAL SINGLE- AND REPEATED-DOSE TOXICITY STUDIES ON GERANTI BIO-GE YEAST, ORGANIC GERMANIUM FORTIFIED YEASTS, IN RATS

Single- and 13-week repeated-dose toxicities of Geranti Bio-Ge Yeast, organic germanium fortified yeasts, were investigated in rats. Both sexes of Sprague-Dawley rats were orally administered once at a dose of 2,000 mg/kg in single-dose toxicity or daily for 13 weeks at doses of 500, 1,000 or 2,000 mg/kg in repeated-dose toxicity tests. In single-dose toxicity test to determine dose levels in repeated-dose toxicity study, the body weight gain was suppressed at 2,000 mg/kg, although no death, clinical signs and pathological findings related to the treatment were observed. In repeated-dose toxicity test, there were no clinical signs in animals administered up to 2,000 mg/kg, except one rat died due to a gavage error. In addition, no significant changes in feed consumption and body weight gain were obtained during the treatment period, in spite of week-to-week fluctuation of water consumption. There were no considerable changes in ophthalmoscopy, urinalysis, hematology and serum biochemistry, except a significant decrease in albumin/globulin ratio in males treated with 1,000 mg/kg. In contrast, a significant increase in relative heart weight was observed in both male and female rats treated with a high dose (2,000 mg/kg) of Geranti Bio-Ge Yeast. In microscopic examination, mild lesions were found sporadically in both control and treatment groups in a dose-independent manner. In spite of some alterations in water consumption, serum biochemistry and organ weights, such effects were not considered to include toxicopathological significance, based on the lack of dose-dependency, consistent time-course and gender relationship. Taken together, it is suggested that no observed adverse effect level (NOAEL) of Geranti Bio-Ge Yeast is considered to be over 2,000 mg/kg in rats, and that long-term oral intake in humans might not exert adverse effects.

Germanium oxide enhances the radiosensitivity of cells

We investigated here the combined effect of GeO(2) and radiation on cell viability. Cells were treated with 0 to 22 mM GeO(2) for 12 h followed by 1 Gy X irradiation. A synergistic cytotoxic effect was observed for the combined treatment with a dose-dependent reduction of cell viability. Complete survival curves showed a 2.3- and 2.75-fold increase in radiosensitivity for 50% cell death in the presence of 5 and 15 mM GeO(2), respectively. The increased radiosensitivity also occurred when GeO(2) was given either 4 h prior to irradiation or immediately after radiation exposure. GeO(2) did not affect the total soluble thiol content or the activities of catalase and glutathione S-transferase. Analysis of the production of reactive oxygen species (ROS) revealed that the combined treatment dramatically increased the synthesis of ROS. Addition of N-acetyl cysteine (NAC, 20 mM) decreased the production of ROS in cells. NAC, however, increased cell viability only slightly after treatment with GeO(2) and radiation. Thus increased production of ROS makes little or no contribution to the observed death. The combination of GeO(2) and X radiation, however, significantly increased the frequency of DNA double-strand breaks (DSBs). Notably, the presence of GeO(2) also reduced the efficiency of DNA repair. We conclude that treatment with GeO(2) followed by X irradiation increases DNA DSBs and cell death.

Effects of germanium oxide and other chemical compounds on phenylmercury acetate-induced genotoxicity in cultured human lymphocytes

Phenylmercury acetate (PMA), which not only causes an elevation of sister chromatid exchanges (SCEs) but also induces high frequency of endoreduplication in human lymphocytes, may be genotoxic to humans. The major aim of our study was to investigate the effects of germanium oxide (GeO2), D-penicillamine (D-PA), dimercaprol (BAL), and diltiazem (DTM) on PMA-induced genotoxicity as quantified by SCEs. All concentrations of the four chemical compounds tested alone did not induce genotoxicity in cultured human lymphocytes. However, GeO2 significantly inhibited PMA-induced genotoxicity in a concentration-dependent manner. Similarly, D-PA at concentrations of 3 microM and 10 microM, and BAL at a concentration of 30 microM produced the antigenotoxic effects. In addition, GeO2 (1.5 microM) significantly reversed an increase of endoreduplication frequency caused by PMA. In a cell cycle kinetic study, GeO2 (0.5-5.0 microM) reversed the inhibition of PMA on the proliferating rate index (PRI) of lymphocytes. On the contrary, both D-PA and DTM at concentrations of 30-300 microM markedly potentiated PMA-induced inhibition of PRI. These findings show that GeO2, D-PA and BAL could antagonize PMA-induced genotoxicity, and GeO2 appears to be the most effective.

Mutagenicity, carcinogenicity and teratogenicity of germanium compounds

The metalloid germanium has found widespread application in electronics, nuclear sciences and in medicine. General toxicity of germanium is low, except for the tetrahydride germane, and few observations on toxicity of germanium in man exist. Germanium is not carcinogenic and even appears to inhibit cancer development and, in the form of the organic germanium compound, spirogermanium, to destroy cancer cells. Germanium compounds have no mutagenic activity and may, under certain conditions, inhibit the mutagenic activity of other substances. High doses of germanium may result in an increased embryonic resorption, but possible malformations have been reported only after administration of dimethyl germanium oxide to pregnant animals. Germanium may thus be considered an element of rather low risk to man.

Germanium intoxication with sensory ataxia

Sensory ataxia in inorganic germanium intoxication is rare. A 63-year-old housewife had taken inorganic germanium preparations at a dosage of 36 mg a day for about 6 years (total dose about 80 g). She subsequently developed difficulty in writing and gait disturbance with peripheral neuropathy and renal involvement. Germanium, which is not usually detected in the non-germanium user, was accumulated in her hair and nails, permitting a diagnosis of inorganic germanium intoxication. The peripheral neuropathy and renal injury were not reversible after discontinuing the preparation. Pneumonia and sepsis then supervened and the patient died. Autopsy findings showed degeneration and loss of the dorsal root ganglion cells and degeneration of the dorsal column of the spinal cord. Two previously reported cases presented with ataxia. These patients took germanium for long periods and/or large quantities like our case. It was supposed that sensory ataxia was induced by chronic and dose dependent toxicity of inorganic germanium.

Chronic tubulointerstitial changes induced by germanium dioxide in comparison with carboxyethylgermanium sesquioxide

Chronic nephrotoxicity was investigated in rats orally administered germanium dioxide (GeO2) and carboxyethylgermanium sesquioxide (Ge-132) for 24 weeks. Increased BUN and serum phosphate as well as decreased creatinine clearance, weight loss, anemia and liver dysfunction were apparent at week 24 only in the GeO2 treated group. Vacuolar degeneration and granular depositions were observed by light microscope in the degenerated renal distal tubules in the rats of this group, with the semiquantitative scores of tubular degeneration being 95 +/- 9% in the GeO2 group, 3 +/- 1% in the Ge-132 group and 1 +/- 1% in the control group, respectively. Electron microscopy revealed electron-dense inclusions in the swollen mitochondrial matrix of the distal tubular epithelium in the GeO2 group. Although systemic toxicities were reduced after GeO2 was discontinued at week 24, renal tubulointerstitial fibrosis became prominent even at week 40 (16 weeks after discontinuation). A Ge.K alpha X-ray spectrum was clearly demonstrated in the mitochondrial matrix of the distal tubular epithelium in the GeO2 group with the help of electron probe X-ray microanalysis. On the other hand, neither toxic effects nor renal histological abnormalities were manifested in either the Ge-132 or the control group. The renal tissue content of germanium was high at weeks 24 and 40 in the GeO2 group. From these results, it is concluded that GeO2 causes characteristic nephropathy while Ge-132 does not. In addition, it appears that residual GeO2 remains for a considerably long time even after the cessation of GeO2 intake.