Renal Metallothionein Synthesis Research Articles

Induction of renal metallothionein expression by nano-zinc in cadmium-treated rats

Induction of metallothioneins synthesis by cadmium and zinc is an adaptive/defensive mechanism against metal toxicity. In this study, the effect of size and dose of nano-zinc particles administered solely or simultaneously with cadmium to induce the synthesis of renal metallothioneins was investigated in male rats. Levels of renal metallothioneins (MTs) mRNA expression was estimated semiquantitatively after an oral exposure to different sizes (15, 20, and 30 nm) and doses (3, 10, and 100 mg/kg body weight (bw)) of nano-Zn and cadmium (2.5–5 mg/kg bw) using reverse transcription polymerase chain reaction. According to our results, renal MTs were induced significantly in response to the simultaneous use of cadmium and different doses of nano-Zn (20 and 30 nm) exposure (P < 0.005). The expression of MT mRNAs was significantly upregulated by nano-Zn 20 nm depending on the dose (P < 0.001). Our findings suggested that larger sizes and intensive doses of Zn nanoparticles can upregulate MT expression. In conclusion, coadministration of cadmium with nano-Zn particles could improve the induction of renal metallothionein synthesis.

Zinc supplementation partially prevents renal pathological changes in diabetic rats

We have demonstrated that Zn supplementation mediated up-regulation of cardiac metallothionein (MT) as a potent antioxidant prevented the development of diabetic cardiomyopathy. The present study was undertaken to test whether induction of renal MT synthesis by Zn supplementation protects the kidney from diabetes-induced damage. Streptozotocin-induced diabetic rats were treated with and without Zn supplementation at 5 mg/kg in drinking water for 3 months. Diabetic renal damage was detected by examining renal pathological alterations and 24-h urinary protein levels. Three-month Zn supplementation immediately after the onset of diabetes, partially but significantly, prevented the kidney from diabetes-induced increases in 24-h urinary proteins and pathological alterations. Diabetes-induced renal oxidative damage, inflammation and up-regulated expression of profibrosis mediator connective tissue growth factor (CTGF) were also markedly attenuated by Zn supplementation, along with significant increases in Zn levels concomitant with MT expression in renal tubular cells. Direct exposure of renal tubular (HK11) cells to high levels of glucose (HG) induced CTGF up-regulation predominantly through ERK (extracellular signal-regulated kinase)1/2-dependent, and partially through p38 mitogen-activated protein kinase (MAPK)-dependent pathways. Pretreatment of HK11 cells with Zn or cadmium induced MT expression and also significantly suppressed HG-induced CTGF expression. These results provide the first evidence for Zn supplementation to attenuate diabetes-induced renal pathological changes, likely through prevention of hyperglycemia-induced CTGF expression by Zn-induced MT in renal tubular cells.

Induction of hepatic and renal metallothionein synthesis by ferric nitrilotriacetate in mice: the role of MT as an antioxidant

Metallothionein (MT) demonstrates strong antioxidant properties, yet the physiological relevance of its antioxidant action is not clear. Injection of mice with ferric nitrilotriacetate (Fe-NTA) caused a dose-dependent increase in hepatic and renal MT. Fe-NTA caused a greater increase in hepatic and renal MT concentration (2.5- and 4-fold) compared with FeCl 3 at the same dose of ferric ion. MT mRNA levels were markedly elevated in both of tissues. Thiobarbituric acid (TBA) values in both tissues reached a maximum after 2–4 h. The MT concentrations were significantly increased after 2–4 h in liver and after 8–16 h in kidneys. Plasma concentrations of cytokines such as IL-6 and TNFα were elevated by 4 h; IL-6 levels were 24 times higher after Fe-NTA than that after injection of FeCl 3. Pretreatment of mice with ZnSO 4 attenuated nephrotoxicity induced by Fe-NTA after 2 h, but was not effective 4 h after injection. After a Fe-NTA injection, a loss of Cd-binding properties of preinduced MT was observed only in kidneys of Zn-pretreated mice but not in liver. Treatment with BSO, glutathione (GSH) depletor, intensified a loss of its Cd-binding properties after a Fe-NTA injection. These results indicate that induction of MT synthesis may result from reactive oxygen species (ROS) generated by Fe-NTA, and MT may act in vivo as a complementary antioxidant.

TREATMENT WITH THE ANTIANDROGEN CYPROTERONE ACETATE MODIFIES CADMIUM ACCUMULATION AND METALLOTHIONEIN INDUCTION IN C57 AND C3H MICE

With the continuing concern over both steroid compounds and metals as potential environmental pollutants, the interactions between these compounds could become an important health issue. In our continuing study of the interactions of cadmium with various steroids we recently found that testosterone pretreatment protects against cadmium-induced toxicity in C57 mice but has no effect in C3H mice. The basis of this strain-specific acquired tolerance to cadmium is still unclear. In this study, we examined the effects of the antiandrogen cyproterone acetate (CA) on the toxicokinetics and toxicity of cadmium and on the ability of cadmium to induce metallothionein (MT) in male C57 and C3H mice. To assess the tissue accumulation of cadmium, the mice were given CA (10 mg/kg, sc, at 48, 24, and 0 h) prior to cadmium (10 mumol/kg, 0 h). The tissue distribution of cadmium was markedly affected by CA pretreatment, as accumulation of cadmium in liver of both strains was reduced 24 h after cadmium administration. Renal cadmium levels were not affected in either strain by CA. CA pretreatment reduced testicular accumulation of cadmium in C57 mice but not in C3H mice. Cadmium alone, CA alone, or CA and cadmium in combination were not toxic at the doses studied as reflected by the absence of changes in serum glutamic-oxaloacetic transaminase (GOT) activity, lactate dehydrogenase (LDH) activity, and blood urea nitrogen (BUN). CA alone increased MT synthesis in the liver of both strains of mice. However, the cadmium-induced MT level in the livers of both strains of mice was markedly decreased by CA pretreatment. In the C57 mice cadmium-induced renal MT levels were also substantially reduced by CA pretreatment but not in the C3H mice. In addition, the levels of cadmium-binding protein within testes were not affected by CA with or without additional cadmium treatment. These results indicate that, despite the fact that CA will itself induce MT in the liver, pretreatment with CA reduces cadmium induction of hepatic and, in some cases, renal MT synthesis. This reduction may be secondary to a reduced accumulation of cadmium in the liver, but this does not hold true for the kidney.

Protective role of metallothionein in renal toxicity of cisplatinum.

To elucidate the protective role of metallothionein (MT) in the prevention of cisplatinum (cis-DDP) toxicity, we investigated the lethal and renal toxicities caused by cis-DDP in MT-null transgenic mice in comparison with wild-type control mice, and examined the effect of pretreatment with bismuth nitrate or zinc sulfate on the cis-DDP nephrotoxicity. The MT-null mice were of mixed 129 Ola and C57BL/6 genetic background. Since no differences in cis-DDP nephrotoxicity were observed between these strains, C57BL/6J mice were used as the wild-type control. The basal MT levels in the kidneys were negligible in the MT-null mice and 2.93 +/- 0.77 micrograms/g tissue in the C57BL/6J mice. In terms of both the lethal and renal toxicities of cis-DDP, MT-null mice were far more sensitive than C57BL/6J mice. Preinduction of renal MT synthesis by administration of bismuth nitrate or zinc sulfate protected C57BL/6J mice from cis-DDP nephrotoxicity. In the case of MT-null mice, however, renal MT could not be induced by pretreatment with these metal compounds, and renal toxicity of cis-DDP was not prevented by this pretreatment. These results suggest that MT is an important factor with the potential to suppress the development of cis-DDP toxicity.

Induction of renal metallothionein synthesis bycis-diamminedichloroplatinum (II) in glutathione-depleted mice

Effects of glutathione (GSH) depletion on nephrotoxicity of cis-diamminedichloroplatinum(II) (cis-DDP) and induction of renal metallothionein (MT) synthesis elicited by cis-DDP treatment has been studied using mice. Pretreatment with L-buthionine-SR-sulfoximine (BSO) reduced the GSH level in the kidneys to 20% of the control level at the time of cis-DDP administration. Administration of 45 μmol/kg cis-DDP did not change the blood urea nitrogen (BUN) level, determined as an indicator of nephrotoxicity, until 96 h after administration, whereas BSO pretreatment raised the BUN level as early as 48 h after cis-DDP (45 μmol/kg) treatment. The level of renal MT was also increased in the GSH-depleted mice and was changed in parallel with the BUN level after cis-DDP treatment. Level of plasma fibrinogen, one of acute phase proteins, increased by cis-DDP in GSH-depleted mice. The increase was reduced by dexamethasone pretreatment, although the renal MT level increased by BSO and cis-DDP was not changed by dexamethasone pretreatment. These results suggest that the induction of renal MT synthesis by cis-DDP in BSO-pretreated mice was not related with the acute phase responses such as cytokines induction. Although the mechanism of the induction of MT synthesis by cis-DDP in GSH-depleted mice is unclear, it is possible that MT is induced as an antidote against oxidative stress, which may be a major cause for nephrotoxicity of cis-DDP enhanced by GSH depletion. © 1995 Wiley-Liss, Inc.

Effect of glutathione depletion on metallothionein synthesis induced by paraquat in mice.

The effect of Glutathione (GSH) depletion on the induction of metallothionein (MT) synthesis by paraquat (PQ) was examined in ICR mice. An increase in hepatic MT level in mice was observed after a single PQ administration. Pretreatment of mice with L-buthionine-SR-sulfoximine (BSO), an inhibitor of GSH synthesis, enhanced the induction of hepatic and renal MT synthesis by PQ depending on the decreased tissue GSH level. A similar result was obtained by pretreatment with diethylmaleate, a GSH depleting agent. The ratio of hepatic MT-I to MT-II induced by PQ was not changed by BSO pretreatment. An increase in the hepatic MT level in GSH depleted mice was observed from 3 hr to 24 hr after PQ administration. An increase in the hepatic MT-I mRNA level after treatment with PQ was observed prior to hepatic MT induction in BSO pretreated mice. Pretreatment with actinomycin D, an inhibitor of mRNA synthesis, inhibits the PQ-induced increase in hepatic MT and MT-I mRNA levels in BSO pretreated mice. Pretreatment with BSO did not affect the induction of MT synthesis by zinc, cadmium or dexamethasone. Pretreatment with dexamethasone, an anti-inflammatory agent, enhanced the hepatic MT induction by PQ treatment in GSH depleted mice, while dexamethasone reduced the MT induction by turpentine oil, which is known to induce inflammation and hepatic MT synthesis. These findings suggest that GSH depletion enhances the induction of MT synthesis by PQ because of an increase in the transcription rate, and this enhancement of MT synthesis is not due to an inflammatory response caused by PQ.

Increased metallothionein content in rat liver and kidney following X-irradiation

Hepatic and renal metallothionein (MT) contents were measured in rats following whole-body X-irradiation. When compared with control rats, the hepatic MT-Zn content increased fivefold and MT protein content increased 15-fold by 18 hr following irradiation (2000 rad). Administration of actinomycin-D inhibited both the mobilization of zinc to the liver and the irradiation-induced increase in metallothionein synthesis. Serum zinc levels did not change after irradiation alone, although serum zinc following actinomycin-D treatment and irradiation was significantly elevated. An increase in renal MT-Zn was also observed. In comparison with control, the increase in renal MT-Zn content after irradiation (2000 rad) did not occur earlier than 12 hr but was increased twofold by 24 hr. In comparison with kidney, the hepatic MT-Zn content following irradiation was already elevated threefold by 6 hr. Dose-response studies (250–3000 rad, 72 hr) indicated that similar dose-response relationships for the appearance of MT in the liver and kidney were observed. Total zinc was decreased in the spleen and thymus, and increased in the liver or kidney 18 hr after irradiation (2000 rad). These data indicate that X-ray treatment produces an in vivo induction of hepatic and renal MT synthesis.

Tolerance to cadmium-induced toxicity depends on presynthesized metallothionein in liver.

Tolerance to Cd-induced toxicity following pretreatment with Cd is well documented, yet the exact mechanism of tolerance and role of metallothionein (MT) remains equivocal. In this study it was determined if the rapid induction of MT following injection of a challenge dose of Cd or the concentration of presynthesized MT induced by Cd pretreatment is more important for development of tolerance by ascertaining (1) whether the rates of synthesis of MT differ following injection of the challenge dose of Cd in control and Cd-pretreated rats and (2) if a relationship exists between presynthesized hepatic or renal MT and tolerance to Cd-induced lethality. Rates of hepatic and renal MT synthesis did not differ following injection of a challenge dose of Cd (2.0 mg Cd/kg, iv) in control and Cd-pretreated (2.0 mg Cd/kg, sc) rats. However, the progressive increase in concentration of MT in liver after Cd pretreatment correlated with the increase in tolerance to a lethal dose of Cd (4.0 mg Cd/kg, iv), as evidenced by a decrease in mortality in pretreated rats. A similar correlation was not observed between kidney MT levels and tolerance. Therefore, it appears that presynthesized MT in liver rather than increased synthesis of MT following injection of a second dose of Cd is responsible for Cd-induced tolerance.

The effects of cadmium and copper on the renal uptake and metallothionein binding of gold in the rat and hamster

Rats and hamsters, (pre)-treated with copper and cadmium, were used to investigate whether species-differences in renal metallothionein synthesis in response to gold were determined by changes in the kidney concentrations of other metals. The effects of both dietary copper limitation and excess on the renal metabolism of gold also were studied in the rat. In this species, all of the pre-treatments affected the renal concentrations of total and metallothionein-bound copper, but none of them altered either the kidney uptake or thionein-binding of gold. Incorporation of zinc into the metallothionein, which accompanied the binding of gold in this fraction of the kidney, however, was influenced slightly by the pretreatments. In hamsters, pretreatment with cadmium, which increased the concentrations of total and thionein-bound zinc in the kidneys, also did not affect the renal uptake of gold, although it increased significantly the binding of gold to the metallothionein fraction of the renal cytosol. This increased binding of gold also was accompanied by further increases in the zinc and copper contents of the metallothionein; the contents of total and thionein-bound cadmium, however, remained essentially unchanged. Concentrations of copper and zinc in the hamster kidney were not affected significantly by subcutaneous administration of copper alone (five daily doses, each of 3.2 mg Cu/kg body wt.), but were increased when gold was given during the copper-treatment. The concentrations of gold, copper and zinc in the renal metallothionein fraction also were increased under these conditions. From these results it seems that kidney metallothionein synthesis in response to gold may be related to the changes in either the concentration or distribution of zinc, rather than copper.

Effect of mercuric chloride and methylmercury chloride exposure on tissue concentrations of six essential minerals

There are few data on the effects of mercury exposure on tissue concentrations of essential minerals. Male Sprague-Dawley rats were exposed to mercuric chloride and methylmercury chloride administered via the drinking water. Subsequently, the kidneys, spleen, liver, and brain were analyzed for mercury, calcium, copper, magnesium, manganese, iron, and zinc by atomic absorption spectrophotometry. Significant differences from controls were found for brain copper, kidney copper, and kidney zinc in the mercuric chloride-exposed animals; and for brain iron, kidney copper, kidney iron, kidney magnesium, spleen magnesium, and liver manganese in the methylmercury chloride-exposed rats. There was a fivefold higher mean kidney copper concentration in the mercuric chloride-exposed group; this may be related to the induction of renal metallothionein synthesis by mercury. Increased kidney copper may be a manifestation of heavy metal-induced renal toxicity. Both inorganic and methylmercury exposure produce significant changes in tissue concentrations of some essential minerals.

Induction of renal metallothionein synthesis by parenteral cadmium-thionein in rats

Cadmium-thionein (Cd-Th) was isolated from livers of rats repeatedly treated with small doses of cadmium chloride. A major portion (55 per cent) of intraperitoneally injected Cd-Th was deposited in the kidney followed by renal damage. Subcellular fractionation of kidney homogenate at 1, 4, 24 and 48 hr after Cd-Th injection revealed that only less than 7 per cent of the cadmium war, accumulated in the lysosomal fraction and more than 50 per cent of cadmium was recovered from the cytosol. Injection of [ 35S]cysteine into rats pre-injected with sublethal doses of Cd-Th resulted in the incorporation of radioactivity into newly synthesized thionein in the kidney between 4 and 24 hr. A major portion of the renal cadmium was bound to metallothionein at all time intervals studied. These studies demonstrated that the Cd-Th complex in the processes of entering the renal cells intact produces cell injury. The thionein moiety of the injected Cd-Th is degraded and resynthesized in the kidney, while nearly all of the metal ( > 90 per cent) is always bound to thionein. The role of the lysosomal system in the renal toxicity of Cd-Th is minimal.

Kinetics of cadmium-induced hepatic and renal metallothionein synthesis in the mouse

Rates of hepatic and renal metallothionein synthesis were estimated by measuring the incorporation of [ 3H]cysteine into metallothionein prepared from mice at various times following a single intraperitioneal injection of cadmium acetate (2 mg of Cd/kg). Tissue metallothionein concentrations were measured indirectly as a function of the total cadmium-binding capacity of the isolated metallothionein. Maximal incorporation of [ 3H]cysteine into hepatic metallothionein occurred 6–12 hr following cadmium exposure, while renal metallothionein synthesis was maximal after 3 hr. Incorporation of [ 3H]cysteine into metallothionein as well as metallothionein concentrations was greater in the liver than in the kidney. It is concluded that the liver is the primary site of cadmium-induced metallothionein synthesis.