Transient induction of hepatic metallothionein following oral ethanol administration

doi:10.1016/0041-008X(84)90147-9

Toxicology and Applied Pharmacology

Volume 74, Issue 2, 30 June 1984, Pages 230-236

https://doi.org/10.1016/0041-008X(84)90147-9 Get rights and content

Abstract

Chronic ethanol ingestion has been associated with alterations of zinc homeostasis. Various treatments that alter zinc disposition induce hepatic metallothionein (MT). Therefore, this study was performed to determine the effect of acute ethanol exposure on hepatic MT levels. Adult male CF-1 mice were administered ethanol intragastrically and their hepatic MT was quantified at various times thereafter by the Cd-radioassay method. Ethanol (5 g/kg, ig) produced significant increases in hepatic MT as early as 4 hr after dosing. Maximal hepatic MT concentrations (19-fold increase) were observed 24 hr after ethanol and returned to control concentrations by 48 hr. Hepatic MT levels were increased 24 hr after 5 or 7 g ethanol/kg but were not altered by 1, 2, or 3 g/kg. Elevations in pancreatic MT, but not in renal or intestinal MT, also occurred 24 hr after ethanol (5 g/kg). Actinomycin D (1.25 mg/kg, ip) prevented the increase in hepatic MT produced by ethanol, whereas inhibition of ethanol oxidation by pyrazole (150 mg/kg, ip) did not prevent the induction of hepatic MT. Gel filtration chromatography and uv spectral analysis confirmed the presence of MT in the livers of ethanol-treated mice. These data show that acute ethanol administration produces a marked elevation of hepatic MT that is transient.

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2008, Aquatic Toxicology
Metallothioneins (MTs) are highly conserved intracellular metal-binding proteins that contribute to the homeostasis of essential metals and the detoxification of non-essential heavy metals. MT gene expression is induced by various heavy metal ions, and Zn²⁺ is able to bind and activate a transcription factor associated with the MT gene that is known as the metal responsive element (MRE) binding transcription factor-1 (MTF-1). Heavy metals other than Zn²⁺, such as Cd²⁺ and Cu²⁺, fail to activate the binding of MTF-1 to MREs despite their ability to induce the transcription of the MT gene. To study how different metal ions regulate MT gene expression, a tilapia (ti)-MT gene promoter was cloned and its responses to activation by various metal ions measured using a Hepa T1 cell culture model. The tiMT gene promoter contains six functional MREs within 2118 bp 5′ of the translational start site. A transient gene expression study showed the tiMT gene promoter fragment to be responsive to Cd²⁺, Cu²⁺, Hg²⁺, Pb²⁺, and Zn²⁺. Deletions from the 5′ end and the site-directed mutagenesis of individual MREs in the tiMT gene promoter confirmed that both proximal and distal clusters of MREs were required for the maximal metal induction of the tiMT gene. The distal cluster of MREs greatly enhanced the induction of tiMT gene expression by several of the heavy metal ions, and especially the non-Zn²⁺ ions. Individual MREs showed a different responsiveness to metal ions, with MREe being the most potent, MREb being responsive to Zn²⁺ but not to other metal ions, and MREa being mainly for the basal expression of the tiMT gene. Electrophoretic mobility shift assay (EMSA) identified a transcription factor that was able to bind most of the MREs, with the exception of MREd, but the binding was only activated by the in vivo administration of Zn²⁺, not the administration of Cd²⁺ or Cu²⁺. In conclusion, the results of this study on a Hepa T1 cell model suggest that the mechanism of MT gene activation by non-Zn²⁺ metal ions is different from that of activation by Zn²⁺, and that different MREs may be involved in the activation of the tiMT gene by different metal ions without enhancing the binding of MTF-1 to MREs.
Possible role of metal redistribution, hepatotoxicity and oxidative stress in chelating agents induced hepatic and renal metallothionein in rats
2001, Food and Chemical Toxicology
A study was planned to investigate possible role of oxidative stress, hepato- and nephrotoxicity and essential metal redistribution following administration of amino and thiol chelating agents on hepatic and renal metallothionein (MT) and the levels of some metalloenzymes in male rats. Animals were administered 50 mg/kg, intraperitoneally, twice daily for 15 consecutive days; a dose of three amino and four thiol chelators and were sacrificed 24 h after the last dose. The results indicate no evidence of oxidative stress in hepatic and renal tissues of rats administered thiol and amino chelators, except for some marginal changes in the animals treated with calcium disodium ethylenediaminetetraacetic acid (EDTA) and d-penicillamine (DPA). Redistribution of essential metal (particularly zinc), hepato- and nephrotoxicity seems to play a significant role in influencing the MT induction by amino chelators. Redistribution of essential metals may also be playing a significant role in a number of metalloenzymes, especially by amino chelators compared to thiol chelators. It can thus be concluded that toxic effects of chelating agents, including metal redistribution and hepatotoxicity, might be playing a crucial role in the metallothionein induction.
Effect of ethanol pretreatment on mercury distribution in organs of fetal guinea pigs following in utero exposure to mercury vapor
1997, Toxicology
Ethanol (Et-OH), which is an inhibitor of catalase, reduces oxidation of mercury vapor (Hg⁰) into ionic mercury (Hg²⁺). Consequently, exposure of pregnant animals to Hg⁰ with pretreatment of Et-OH causes penetration of larger amount of Hg⁰ to the fetus. The fate of Hg⁰ in the fetus of pregnant guinea pigs, thus penetrated, was investigated. Et-OH pretreatment of the dams resulted in the transfer of more mercury to the fetuses and led to a marked increase in mercury in the fetal liver. Furthermore, according to the mercury distribution in the fetal organs, the animals in the Et-OH-pretreated group fell into two subgroups: a group of fetuses (subgroup 1) had higher mercury concentrations in the brain, heart and kidney compared with the group which was exposed to Hg⁰ without Et-OH-pretreatment (Hg⁰ group) and another group (subgroup 2) with similar organ mercury concentrations to that of the Hg⁰ group. Determination of metallothionein (MT) concentrations showed that MT concentration in the fetal liver of subgroup 2 was significantly higher than that of subgroup 1 and the Hg⁰ group. Further, the Sephadex G-75 chromatography of the cytosol of the fetal liver in subgroup 2 revealed that most of mercury, about 66%, was bound to metallothionein-like protein. On the other hand, in the cytosol of fetal liver of subgroup 1, a small amount, about 10% appeared in fractions corresponding to MT. These findings suggest that fetal hepatic MT plays a significant defense role against mercury crossing the placenta and is involved in regulating for the mercury distribution in the fetus.
Ethanol inhibits cadmium accumulation in brains of offspring of pregnant rats that consume cadmium
1995, Toxicology Letters
The present study was designed to test the effect of ethanol on cadmium accumulation in tissues of pregnant rats and their offspring. Starting 10 days before mating and continuing until parturition, ethanol (10% v/v) was present in the drinking water of half the rats. Cadmium chloride (CdCl₂; 50 ppm) was present in the water of half the rats (± ethanol) from the first day after mating until parturition. On the day of parturition cadmium accumulated to a moderate level in bone (7.3 μg/g tissue, wet weight; this and other values, P < 0.05 vs. control), liver (12.9 μg/g) and kidney (13.0 μg/g) of dams, while the brain had only a low level of cadmium (0.45 μg/g). In offspring at 6 weeks cadmium accumulated in high amounts in the brain (34.0 μg/g), bone (15.9 μg), kidney (78.2 μg/g) and particularly the liver (227.3 μg/g). Ethanol, given simultaneously with cadmium, inhibited cadmium accumulation in brain (1.8 μg/g), bone (3.28 μg/g) and kidney (61.3 μg/g), but enhanced cadmium accumulation in liver (408.7 μg/g). At 12 weeks there were only residual levels of cadmium in all tissues of offspring. These findings demonstrate an interaction between 2 known teratogenic agents, with ethanol conferring protection of the brain from cadmium accumulation. The nature of this interaction is not known, but is likely to be related to ethanol induction of metallothionein in the liver and placenta.
Effect of ethanol on paraquat toxicity in F344 rats
1994, Food and Chemical Toxicology
The potential modifying effects of ethanol and paraquat on lesion development in livers and lungs of male F344 rats were studied. Animals were divided into diethylnitrosamine (DEN)-initiated and non-initiated groups, subgroups of each being exposed to 10 ml 20% ethanol/kg body weight, 2.5 or 10 mg paraquat/kg body weight or a combination of 10 ml 20% ethanol/kg body weight and 2.5 or 10 mg paraquat/kg body weight, given by intragastric intubation three times a week. Controls received 10 ml saline/kg body weight. All animals were subjected two-thirds partial hepatectomy at the end of wk 3 and killed at the end of wk 8. All five rats receiving 10 mg paraquat/kg body weight without DEN-pretreatment died before termination of the experiment, but the additional ethanol treatment saved animals: only one of five rats died. Rats administered 2.5 or 10 mg paraquat/kg body weight demonstrated lung toxicity, as evidenced by fibrosis and hyperplasia, but not when simultaneously treated with ethanol in DEN-pretreated groups. In the liver, however, evaluation of glutathione S-transferase placental form (GST-P)-positive foci did not reveal any influence of the treatments on lesion development in DEN-initiated animals. It is concluded that ethanol decreases paraquat toxicity, and that neither agent, alone or in combination, exerts any hepatocarcinogenic modification potential.
Enhancement of metallothionein gene expression in male wistar (WF/NCr) rats by treatment with calmodulin inhibitors: Potential role of calcium regulatory pathways in metallothionein induction
1994, Toxicology and Applied Pharmacology
Recent reports indicate that calmodulin inhibitors (CIs) can modify cadmium toxicity in rodents. For instance, pretreatment with CIs prevents cadmium-induced testicular damage in mice and substantially reduces such damage in rats, the latter effect coinciding with significant alterations in cadmium distribution. Although the basis of these effects is unclear, it is frequently observed that metal-binding proteins such as metallothionein (MT) are involved in acquired tolerance to cadmium and this could be true of tolerance induced by CIs. Thus, we examined the effects of various CIs on MT gene expression. Treatment of WF/NCr rats with known CIs, including trifluoperazine (TPZ), N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W7), calmidazolium (CMZ), chlorpromazine (CPZ), and the calcium ionophore, A23187, increased hepatic MT gene expression, as assessed by mRNA levels, in all cases. Furthermore, hepatic MT protein levels were 40 to 180 μg MT/g wet wt (g ww) in rats treated with CIs or A23187 compared to control levels of 10 μg MT/g ww. Treatment with CPZ and CMZ did not increase renal MT protein after exposure, although increases in renal MT mRNA were observed. However, the CIs TPZ and W7 and the calcium ionophore increased both renal MT protein and MT mRNA levels. In contrast, no increases in testicular MT mRNA or the testicular cadmium binding protein (TCBP) levels were seen with any of the treatments. Treatment with CIs or A23187 produced increases in zinc levels in the liver, but not in the kidneys or testes. These results indicate that CIs, such as TPZ, W7, CMZ, and CPZ, as well as the calcium ionophore A23187, have a marked stimulatory effect on hepatic and renal MT gene expression and that calcium regulatory pathways may play an important role in this induction of MT.

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^☆: Work supported by funds from USPHS Grant ES 01142 and presented in part at the annual meeting of the American Society of Pharmacology and Experimental Therapeutics, August 1983, in Philadelphia, Pa.

²: Present address: National Cancer Institute, Frederick Cancer Research Facility, Frederick, Md.

³: Supported by NIEHS Training Grant ES 07079.

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Transient induction of hepatic metallothionein following oral ethanol administration☆

Abstract

Biochem. Pharmacol.

Toxicol. Appl. Pharmacol.

Trends Biochem. Sci.

Toxicol. Appl. Pharmacol.

Toxicol. Appl. Pharmacol.

Toxicology

Toxicology

Toxicology

J. Biol. Chem.

Biochem. Biophys. Res. Commun.

J. Biol. Chem.

Toxicol. Appl. Pharmacol.

Biochem. Pharmacol.

J. Biol. Chem.

Liver alcohol dehydrogenase

Regulatory aspects of zinc metabolism in liver and intestine

Nutr. Rev.

Ligand substitution reactions of metallothioneins with EDTA and apo-carbonic anhydrase

Low-molecular-weight zinc-binding proteins in liver cytosol of allylisopropylacetamine (AIA) treated rats

Acta Biochim. Pol.