Evolutionary Mode of Metallothioneins Inferred from Cd-MT Genes of Tetrahymena

From Tetrahymena thermophila （strain BF5）, the coding region of Cd-MT gene was cloned and sequenced. and identified as MTT1 isoform. A serial duplicate structure is discovered in its amino acid sequence, which separates the coding region into three parts （Part 1：7-61; Part 2：64-118; Part 3：122-162）. The alignments among them and comparison with the corresponding parts of MT1 isoform suggest that MT1 and MTT1 isoforms both come from the same ancient gene that is homologous to Part 1, and Cd-MTs of Tetrahymena are aroused by such ancient gene duplication. The prediction of secondary structures and the analysis of the disulfide-bonding state of cysteine show that there are a lot of differences between MT1 and MTT1 isoforms, which maybe relate to their function mechanism.

Biochemical and Immunochemical Characterization of Caenorhabditis elegans Metallothioneins I and II Induced by Cadmium

Metallothioneins in Caenorhahditis elegans (CeMT-Ⅰ and Ⅱ) were punned by the combination of gel filtration ion-exchange chromatography.and high-performance liquid chromatography.Amino acid compositions and amino-terminal sequences of CeMT-Ⅰ and Ⅱ were slightly different from those of vertebrate MTs previously reported, although cysteine residue contents were relatively high.Enzyme immunoassay using anti-CeMT-Ⅱ antibody showed the difference of antigenicity to rat MT-Ⅰ and Ⅱ and even to CeMT-Ⅰ. Immunohistochemical staining revealed the existence of CeMT-Ⅱ in the intestine and the eggs, suggesting the role of MT in detoxification and homeostasis of heavv metals. 1990 Academic Press.Inc.

THE INDUCTION AND EXTRACTION OF METALLOTHIONEINS IN ARTEMIA

A small amount of heavy metal binding protein,identified by BioRad Protein Assay,has been iso-lated from the adult brine shrimp,Artemia franciscanus.This protein has an apparent molecular weight be-tween 6000 to 9000 dalton.a UV absorption peak at 260 instead of 280 nm like most proteins;andhas high affinity towards binding with radioactive labeled 109Cd.These characteristics are similarto that of metallothioneins reported for many vertebrate and invertebrate,marine and terrestrialanimals.After the brine shrimp is exposed to a small amount of Cd2+for 24 h,a large amount ofmetallothionein can be isolated,showing the inducibility of this detoxifying protein in the adult Artemiain a short period of time.

Kinetic Studies on Ligand Substitution Reactions of Metallothioneins with DTPA and EDTA

Cd, Zn-thionelns were isolated from the rat liver by improved Winge method and purified further. The composition was determined. The mobilization of Cd ions from the Cd, Zn-metallothioneins was studied with spectrophotometric method. The results show that the reaction of DTP A or EDTA with Cd, Zn-thioneins occurs through three steps. The first step follows pseudo-first order reaction with association mechanism. The formation constants and the dissociation rate constants of the relevant intermediate ternary complexes and apparent rate constants, Kapp were determined. The properties and structure of Cd, Zn-thioneins and ligands with low molecular weights affect the values of Kapp.

Cadmium-induced neurotoxicity: still much ado

Cadmium（Cd） is a highly toxic heavy metal that accumulates in living system and as such is currently one of the most important occupational and environmental pollutants. Cd reaches into the environment by anthropogenic mobilization and it is absorbed from tobacco consumption or ingestion of contaminated substances. Its extremely long biological half-life（approximately 20-30 years in humans） and low rate of excretion from the body cause cadmium storage predominantly in soft tissues（primarily, liver and kidneys） with a diversity of toxic effects such as nephrotoxicity, hepatotoxicity, endocrine and reproductive toxicities. Moreover, a Cd-dependent neurotoxicity has been also related to neurodegenerative diseases such as Alzheimer＇s and Parkinson＇s diseases, amyotrophic lateral sclerosis, and multiple sclerosis. At the cellular level, Cd affects cell proliferation, differentiation, apoptosis and other cellular activities. Among all these mechanisms, the Cd-dependent interference in DNA repair mechanisms as well as the generation of reactive oxygen species, seem to be the most important causes of its cellular toxicity. Nevertheless, there is still much to find out about its mechanisms of action and ways to reduce health risks. This article gives a brief review of the relevant mechanisms that it would be worth investigating in order to deep inside cadmium toxicity.

Effect of Maotai liquor on the liver: an experimental study

BACKGROUND: Epidemiology investigation showed that no worker drunk Maotai liquor for nearly 30 years died of hepatic diseases, and no obvious hepatic fibrosis and cirrho- sis were found in 99 workers who had drunk Maotai liquor for a long period by epidemiology investigation and needle biopsy. The same finding was detected in rats that were drunk by Maotai liquor continued for 56 days. This study was to investigate the effects of Maotai liquor on the liver and its mechanism of preventing hepatic fibrosis. METHODS: After ingestion of Maotai for 56 consecutive days, male SD rats were killed for detecting the levels of metallothionein and malondialdehyde (MDA) in liver tis- sues. Rat hepatic stellate cells (HSCs) and human HSCs were cultured in vitro to observe the effect of Maotai on HSCs proliferation and collagen synthesis. After ingestion of Maotai for 14 consecutive weeks, the livers of male SD rats were harvested for pathohistological examination. RESULTS: The level of metallothionein in the liver of Mao- tai-induced rats increased by 22 folds, whereas the levels of hepatic lipid peroxide and MDA was decreased significantly ( P <0.05) in Maotai-induced animals suffering from CCl4. Maotai demonstrated obvious inhibitory effect on prolifera- tion of HSCs and the inhibition was concentration-depen- dent. Gene expression and protein secretion of collagens could also be inhibited by Maotai. In alcoholic group, typi- cal liver cirrhosis was observed. In Maotai group, however, though fatty degeneration of hepatocytes and mild fibrosis of the interstitium were observed, no obvious hepatic fibro- sis and cirrhosis were found. CONCLUSION: It might be an important mechanism of interfering the progress of hepatic fibrosis that Maotai in- creases the level of metallothionein in the liver and inhibits the activation of HSCs and the synthesis of collagen pro- teins.

Generation and analysis of expressed sequence tags from the salt-tolerant eelgrass species, Zostera marina

Zostera marina, a monocotyledonous angiosperm, is one of the most important seagrass species. To inves- tigate the salt-tolerance mechanism and discover salt-tolerant genes in Z. marina, a cDNA library was con- structed. Single-pass sequencing of the 5＇ ends of 4 081 clones yielded 4 002 high quality expressed sequence tags （ESTs）, which were assembled into 241 contigs and 1 673 singletons, representing 1 914 unigenes. The average length of the ESTs was 582 bp, with sizes ranging from 100-1 500 bp. Basic Local Alignment Search Tool （BLASTX） analysis revealed that 1 664 unigenes had significant homology to known genes in the Na- tional Center for Biotechnology Information （NCBI） non-redundant （nr） database （E-value≤5-10）. Among them, the two most abundant genes encoded metallothionein （157 ESTs） and chlorophyll a/b-binding pro- tein （38 ESTs）, accounting for 7.1% and 1.7% of the total ESTs, respectively. Using Kyoto Encyclopedia of Genes and Genomes （KEGG）, 1 462 unigenes were assigned to 1 161 pathways （E-value≤5-10）. A total of 938 unigenes were assigned Gene Ontology （GO） terms based on the GO hierarchy analysis, and InterProScan searches recognized 1 003 InterPro families. Three genes for metallothionein in Z. marina that belonged to Class II was identified. Results of this study will improve understanding of the molecular mechanisms of saline tolerance in Z. marina.

Insulin Expression in Rats Exposed to Cadmium

To investigate the effects of cadmium exposure on insulin expression in rats. Methods Eighteen adult SD rats were administered cadmium subcutaneously （0.5, 1.0, and 2.0 mg/kg bw）. The effects on endocrine of pancreas were assessed. The levels of cadmium and zinc in pancreas, blood and urine glucose, serum insulin and urine NAG （N-acyetyl-β-glucosaminidase） were determined. The gene expressions of metallothionein （MT） and insulin were also measured, and the oral glucose tolerance tests （OGTT） were carried out. Results The contents of cadmium in pancreas in cadmium-treated rats were higher than that in the control group, which was associated with slight increase of zinc in pancreas. Cadmium-exposed rats （1.0 and 2.0 mg/kg bw） demonstrated a marked glucose intolerance. But the levels of serum insulin did not change significantly after cadmium administration, and the UNAG had no change in Cd-treated group. The gene expression of insulin decreased in 1.0 and 2.0 mg/kg bw cadmium-exposed groups, compared with the control group. The expression of MT-I was higher in the groups exposed to 1.0 and 2.0 mg/kg bw cadmium while the expression of MT-II was higher in the group exposed to 2.0 mg/kg bw cadmium. Conclusions Cadmium may be accumulated in the pancreas, resulting in the change of the expression of insulin, MT-I and MT-Ⅱ genes. Cadmium can influence the biosynthesis of insulin, but does not induce the release of insulin. The dysfunction of pancreas occurs earlier than that of kidney after administration of cadmium.

Effect of Feeding Strategies on Molecular Responses of Biotransformation Genes in Crassostrea gigas Exposed to Cadmium

Heavy metals, including cadmium (Cd), are widespread pollutants of great environmental concern because of their ac- cumulation and toxicity. Environmental conditions can affect the accumulation and elimination of Cd in organisms. The aim of this study is to understand the respective responses of metallothioneins (MTs), P-glycoprotein (P-gp), and heat shock protein 70 (hsp70) genes in the mantle and digestive gland of the oyster Crassostrea gigas exposed to 10 g L 1 Cd for 28 days, followed by a depura- tion period of 35 days under different feeding strategies. The MT expression in the digestive gland was higher than in mantle, and was induced in a fluctuating pattern throughout the time of the whole experiment when the oyster was exposed to Cd. The results indicated an enhanced MT activity is required for Cd detoxification. Expression levels of P-gp in the mantle of Cd-exposed oysters fed with algae increased in the first two weeks of the accumulation phase. Then the induction weakened, but the expression still in- creased significantly compared with the control group fed without algae. The P-gp levels in the digestive gland were under-regulated during both the contamination and decontamination periods except in the group fed with Dicrateria inornata at day 0.083. The in- duction of P-gp is possibly related to the important role of pumping Cd out of the cell, while a major implication of P-gp expression inhibition would be a disruption of the protein synthesis. Hsp70 expression exhibited an overall decreasing trend. The highest relative hsp70 inhibition occurred during day 42 to day 63, with approximately 4-fold and 10-fold lower hsp70 levels as compared to the C.gigas feeding with no algae in the mantle and digestive gland, respectively. The induction of hsp70 may be explained by the re- folding of protein in presence of Cd, followed by the inhibition of hsp70 when the protein synthesis was disrupted.

Alterations of organ histopathology and metallolhionein mRNA expression in silver barb,Puntius gonionotus during subchronic cadmium exposure

Common silver barb, Puntius gonionotus, exposed to the nominal concentration of 0.06 mg/L Cd for 60 d, were assessed for histopathological alterations （gills, liver and kidney）, metal accumulation, and metallothionein （MT） mRNA expression. Fish exhibited pathological symptoms such as hypertrophy and hyperplasia of primary and secondary gill lamellae, vacuolization in hepatocytes, and prominent tubular and glomerular damage in the kidney. In addition, kidney accumulated the highest content of cadmium, more than gills and liver. Expression of MT mRNA was increased in both liver and kidney of treated fish. Hepatic MT levels remained high after fish were removed to Cd-free water. In contrast, MT expression in kidney was peaked after 28 d of treatment and drastically dropped when fish were removed to Cd-free water. The high concentrations of Cd in hepatic tissues indicated an accumulation site or permanent damage on this tissue.

Role of MetallothioneinlH in Cisplatin Resistance of Non-Small Cell Lung Cancer Cells

Objective： Despite platinum-based adjuvant chemotherapy has improved greatly patients＇ outcomes, drug resistance poses a major impediment to the successful use of such an effective agent. Metallothioneins（MTs） are known to play putative roles in cancer cell proliferation, apoptosis, differentiation, drug resistance and prognosis. The present studiy was to investigte the role of metallethioeinlH（MTIH） in cisplatin resistance of human non-small cell lung cancer（NSCLC） cell lines in vitro or its possible molecular mechanisms. Methods： MTIH mRNA expression in A549 and A549/DDP cells was detected by RT-PCR. A recombinant eukaryotic expression plasmid pcDNA3.1（-）-MT1H was constructed and transfected into A549 cells which express no MTIH. MT1H siRNA was transfected into A549/DDP cells which express MTIH highly. MTIH expression was detected by RT-PCR and Immunoblot. The chemosensitivity to cisplatin was assessed by MTT assay. Apoptosis rate was determined by Tunel and FCM. Bcl-2 and Bax were determined by immunohistochemistry. Results： MT1H mRNA was expressed in A549/DDP but not in A549. After transfection of MT1H, MT1H expression was enhanced and the chemosensitivity to cisplatin was decreased in A549 cells. Inversely, after transfection of MT1H siRNA, MT1H expression was decreased and the chemosensitivity to cisplatin was increased in A549/DDP. The apoptosis rate induced by cisplatin was increased and Bcl-2 was down-regulated but Bax showed little change in A549/DDP cells interferred with MT1H siRNA. Conclusion： MT1H overexpression can promote drug resistance in A549 cells . Down-regulation of MTIH interfered with siRNA can effectively reverses the drug resistance in A549/DDP cells by down-regulating the expression of Bcl-2 and increasing cisplatin induced apoptosis. SiRNA targeting MT1H combined with chemotherapy may be a very promising strategy for treatment of lung cancer.

Metallothionein 1 Isoform Gene Expression Induced by Cadmium in Human Peripheral Blood Lymphocytes

Objective To study the gene expression of metallothionein 1 （MT-1） isoforms in human peripheral blood lymphocytes （HPBLs）. Methods The expression of mRNA representing the seven active MT-I genes was determined in HPBLs by quantitative RT-PCR before and after exposure to cadmium. Results Basal expressions of MT-IX, and MT-1A in HPBLs were similar to expression of housekeeping gene. In contrast, the basal gene expressions of MT- 1 H, IF, 1E, and 1G were a little transcripts in human HPBLs. No signal was detected for MT-1B. There was a sex difference （P〈0.05）. in basal gene expression of MT-1E. The levels of gene expression of MT-1A, 1E, IF, 1G, 1H, and 1X increased, but the level of MT-1B did not increase after exposure to cadmium. Conclusions Gene expressions of MT-1 G, MT-1 H, MT-1 F, and MT-1X in HPBLs can be used as a potential biomarker of cadmium exposure.

Effects of Metallothionein on Isolated Rat Heart

To investigate the effects of metallothionein （MT） on isolated rat heart, 16 Wistar rats were randomly divided into 2 groups. In control group （group C）, distilled water was injected intraperitoneally and 24 h later isolated hearts were perfused with Langendorff and stored at 4℃ for 3 h with histidine-tryptophan-ketoglutarate （HTK） solutions, and then isolated hearts were perfused for 2 h by Langendorff. In experimental group （group E）, 3.6% ZnSO4 was injected intraperitoneally, 24 h later isolated hearts were perfused by Langendorff and stored at 4℃ for 3 h with HTK solutions, and then the isolated hearts were perfused for 2 h with Langendorff. MT content, the recovery of hemodynamics, myocardial water content （MWC）, lactate dehydrogenase （LDH） and creatine kinase （CK） leakage, adenosine triphosphate （ATP） and malondialdehyde （MDA） content, superoxide dismutase （SOD） activity, myocardial cell Ca^2＋ content, Ca^2＋-ATPase activity of mitochondria （[Ca^2＋-ATPase]m） and its Ca^2＋ content （[Ca^2＋]m）, synthesizing ATP activity of mitochondria （[ATP]m）, and the ultrastructure of cells were examined. There were a significant increase in group E in hemodynamic recovery, ATP content, SOD activity, [Ca^2＋-ATPase]m activity, [ATP]m activity, and substantial reduction in MWC, LDH and CK leakage, MDA content, myocardial cell Ca^2＋ content, [Ca^2＋]m content, and the ultrastructural injury were obviously milder than that of group C. This study demonstrated that MT has protective effects on isolated rat heart.

CLINICAL SIGNIFICANCES OF THE EXPRESSION OF METALLO- THIONEIN IN FIVE TYPES EPITHELIUM CELL CANCER

Objective： To study the expressions of （CSC）, bladder transitional cell cancer metallothionein and the significances in cervical squamous cell cancer （BTC）, esophageal squamous cell cancer （ESC）, gastral tubular adenocarcinoma （GC） and large intestinal tubular adenocarcinoma （LIC）. Methods： lmmunohistochemical method was used to examine the expression rates of MT in five types of cancer tissue. Results： The expression rates of MT were 75.00% （24/32） in ESC, 52.27% （46/88） in GTC, 59.46% （44/74） in LIC, 64.86% （48/74） in BTC and 58.57% （41/70） in CSC respectively. The positive rates of MT expression were higher in low differentiation and deep muscular group than those in medium or high differentiation and superficial muscular invasion group （P〈0.05）. Conclusion： The expression of MT is related to differentiation degree and invasion degree.

Downregulation of miR-491-5p promotes neovascularization after traumatic brain injury

Micro RNA-491-5 p(miR-491-5 p) plays an important role in regulating cell proliferation and migration;however,the effect of miR-491-5 p on neovascularization after traumatic brain injury remains poorly understood.In this study,a controlled cortical injury model in C57 BL/6 mice and an oxygen-glucose deprivation model in microvascular endothelial cells derived from mouse brain were established to simulate traumatic brain injury in vivo and in vitro,respectively.In the in vivo model,quantitative real-time-polymerase chain reaction results showed that the expression of miR-491-5 p increased or decreased following the intracerebroventricular injection of an miR-491-5 p agomir or antagomir,respectively,and the expression of miR-491-5 p decreased slightly after traumatic brain injury.To detect the neuroprotective effects of miR-491-p,neurological severity scores,Morris water maze test,laser speckle techniques,and immunofluorescence staining were assessed,and the results revealed that miR-491-5 p downregulation alleviated neurological dysfunction,promoted the recovery of regional cerebral blood flow,increased the number of lectin-stained microvessels,and increased the survival of neurons after traumatic brain injury.During the in vitro experiments,the potential mechanism of miR-491-5 p on neovascularization was explored through quantitative real-time-polymerase chain reaction,which showed that miR-491-5 p expression increased or decreased in brain microvascular endothelial cells after transfection with an miR-491-5 p mimic or inhibitor,respectively.Dual-luciferase reporter and western blot assays verified that metallothionein-2 was a target gene for miR-491-5 p.Cell counting kit 8(CCK-8) assay,flow cytometry,and 2′,7′-dichlorofluorescein diacetate(DCFH-DA) assay results confirmed that the downregulation of miR-491-5 p increased brain microvascular endothelial cell viability,reduced cell apoptosis,and alleviated oxidative stress under oxygen-glucose deprivation conditions.Cell scratch assay,Transwell assay,tube formation assay,and western blot assay results demonstrated that miR-491-5 p downregulation promoted the migration,proliferation,and tube formation of brain microvascular endothelial cells through a metallothionein-2-dependent hypoxia-inducible factor-1α/vascular endothelial growth factor pathway.These findings confirmed that miR-491-5 p downregulation promotes neovascularization,restores cerebral blood flow,and improves the recovery of neurological function after traumatic brain injury.The mechanism may be mediated through a metallothionein-2-dependent hypoxia-inducible factor-1α/vascular endothelial growth factor signaling pathway and the alleviation of oxidative stress.All procedures were approved by Ethics Committee of the First Affiliated Hospital of Chongqing Medical University,China(approval No.2020-304) on June 22,2020.

Focusing on the protective effects of metallothionein-Ⅰ/Ⅱ in cerebral ischemia

Ischemic stroke is a leading cause of death and has a remarkable social and economical impact, which rises with the increasing age of the industrial population. Unfortunately, treatment strat- egies for cerebral ischemia still remain very limited. Acute reper- fusion therapies with either systemic thrombolysis using rt-PA （recombinant tissue plasminogen activator） or interventional recanalization procedures were shown to be highly effective. In addition, there is also a long-existing concept to modulate stroke-associated pathophysiological events such as exitotox- icity, peri-infarct depolarizations, apoptosis and inflammation （Dirnagl et al., 1999）.

Metallothionein克隆载体及表达载体的构建及转化矮牵牛的初步研究

Metallothionein基因位于文库克隆载体pTriplEx2上,活化菌液并用限制性内切酶SfiI酶切,同时酶切添加了SfiI酶切位点的环状pMD-18TM,回收目的片段和载体并连接,经过酶切和PCR验证,成功构建克隆载体;再用XbaI和SmaI分别双酶切克隆载体和表达载体pc2301,回收目的片段和表达载体并连接,经酶切和PCR验证,成功构建含有目的基因的表达载体,进而转化植物获得耐重金属的植物株系。初步验证转化后的植株具有抗击重金属的能力。

Metallothionein Genes in the Nematode Caenorhabditis elegans and Metal Inducibility in Mammalian Culture Cells

Genomic DNAs of metallothionein Ⅰ and Ⅱ in Caenorhabditis elegans (CeMT-Ⅰand CeMT-Ⅱ) were isolated by YAC library/polytene filter hybridization followed by subcloning of corresponding cosmid clones. Both genes are mapped at chromosome V. Although the similarities of 5'-flanking regions and coding regions have shown only 55-58%, the introns are split at the same position in both genes, indicating that these two genes are originally from the same gene. While several metal responsive elements are conserved among eukaryotes, only one metal responsive element was found in the promoter region in CeMT-Ⅱ and not in CeMT-Ⅰ. Indced, neither of 5'-flanking regions of CeMT-Ⅰ nor CeMT-Ⅱ connected to chloramphenicol acetyltransferase reporter gene is responsive to heavy metals in mammalian culture cells by transient transfection analysis. These results would suggest that the metal regulatory factors in C.elegans might be different from those conserved in invertebrates and vertebrates, although the MTs in C elegans revealed the similarities to mammalian MTs in several points

LABELLING OF METALLOTHIONEIN WITH ^(99m)Tc

99mTc-labelled metallothionein (99mTc-MT) was prepared through both direct and transcomplexation labelling approaches. Buffer systems and a variety of other parameters in the direct labelling procedure were studied in detail. High radiolabelling yields of 93-96% and the specific radioactivity of 3.7 MB/μg were obtained under optimal conditions by the direct labelling method. The prepared 99mTc-MT was stable in vitro. The chelate-exchange kinetics of MT with 99mTc-glucohepatonate and 99mTc-citrate were also studied. Biodistribution and imaging studies showed that 99mTc-MT was accumulated in the animal kidneys at an exceptionally high level, indicating that 99mTc-MT might be a potential renal imaging agent.