MT1G Regulates c-MYC/P53 Signal to Inhibit Proliferation, Invasion and Migration and Promote Apoptosis in Colon Cancer Cells.

INTRODUCTION: Colon cancer is a common and malignant cancer featuring high morbidity and poor prognosis. AIMS: This study was performed to explore the regulatory role of MT1G in colon cancer as well as its unconcealed molecular mechanism. METHODS: The expressions of MT1G, c-MYC, and p53 were assessed with the application of RT-qPCR and western blot. The impacts of MT1G overexpression on the proliferative ability of HCT116 and LoVo cells were measured by CCK-8 and BrdU incorporation assays. Additionally, transwell wound healing, and flow cytometry assays were employed to evaluate the invasive and migrative capacities as well as the apoptosis level of HCT116 and LoVo cells. Moreover, the activity of the P53 promoter region was assessed with the help of a luciferase reporter assay. RESULTS: It was found that the expressions of MT1G at both mRNA and protein levels were greatly decreased in human colon cancer cell lines, particularly in HCT116 and LoVo cell lines. After transfection, it was discovered that the MT1G overexpression suppressed the proliferation, migration and invasion but promoted the apoptosis of HCT116 and LoVo cells, which were then partially reversed after overexpressing c-MYC. Additionally, MT1G overexpression reduced c-MYC expression but enhanced the p53 expression, revealing that the MT1G overexpression could regulate c-MYC/P53 signal. Elsewhere, it was also shown that c-MYC overexpression suppressed the regulatory effects of MT1G on P53. CONCLUSION: To conclude, MT1G was verified to regulate c-MYC/P53 signal to repress the proliferation, migration and invasion but promote the apoptosis of colon cancer cells, which might offer a novel targeted-therapy for the improvement of colon cancer.

Effects of cadmium acetate contaminated drinking water on vital organs: A histopathological and biochemical study.

Cadmium (Cd) is a heavy metal with various human exposure sources. It accumulates in the liver, forming a complex with metallothionein protein and progresses to other organs. As a heavy metal, cadmium can replace calcium and other divalent ions and disturb their cascades, ultimately affecting the vital organs. Since cadmium acetate (CA) is considered more lethal than other Cd compounds, the current study examines the effect of different concentrations of CA doses in drinking water for different exposure times in murine models (Mus musculus). After the exposure period, the murine models were then examined histopathologically and biochemically. The histopathological examination of the heart, liver, and kidneys of the experimental group showed extensive degenerative effects. Atomic absorption spectroscopy was used to determine the quantity of cadmium in serum, kidney, and hepatic tissues. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of hepatic proteins, especially metallothionein, directly related to Cd administration. The biochemical parameters, including creatine kinase, alanine aminotransferase, aspartate aminotransferase, total proteins, glucose, urea, uric acid, and creatinine, were also analyzed. After thorough histochemical and biochemical analysis, it was concluded that even low dose exposure of CA is hazardous to murine models with damaging effects.

The effects of metallothionein in paraquat-induced Parkinson disease model of zebrafish.

INTRODUCTION: Parkinson's disease (PD) is the second most common neurodegenerative disease caused by selective degeneration of dopaminergic neurons in the substantia nigra. Metallothionein has been shown to act as a neuroprotectant in various brain injury. Thus, this study aims to identify the effects of full-length human metallothionein 2 peptide (hMT2) in paraquat-induced brain injury in the zebrafish. METHODOLOGY: A total of 80 adult zebrafish were divided into 4 groups namely control, paraquat-treated, pre-hMT2-treated, and post-hMT2-treated groups. Fish were treated with paraquat intraperitoneally every 3 days for 15 days. hMT2 were injected intracranially on day 0 (pre-treated group) and day 16 (post-treated group). Fish were sacrificed on day 22 and the brains were collected for qPCR, ELISA and immunohistochemistry analysis. RESULTS: qPCR analysis showed that paraquat treatment down-regulated the expression of genes related to dopamine activity and biosynthesis (dat and th1) and neuroprotective agent (bdnf). Paraquat treatment also up-regulated the expression of the mt2, smtb and proinflammatory genes (il-1α, il-1ß, tnf-α and cox-2). hMT2 treatment was able to reverse the effects of paraquat. Lipid peroxidation decreased in the paraquat and pre-hMT2-treated groups. However, lipid peroxidation increased in the post-hMT2-treated group. Paraquat treatment also led to a reduction of dopaminergic neurons while their numbers showed an increase following hMT2 treatment. CONCLUSION: Paraquat has been identified as one of the pesticides that can cause the death of dopaminergic neurons and affect dopamine biosynthesis. Treatment with exogenous hMT2 could reverse the effects of paraquat in the zebrafish brain.

Central and Enteric Neuroprotective Effects by Eucommia ulmoides Extracts on Neurodegeneration in Rotenone-induced Parkinsonian Mouse.

Parkinson's disease (PD) is a progressive neurodegenerative disease of both the central and peripheral / enteric nervous systems. Oxidative stress and neuroinflammation are associated with the pathogenesis of PD, suggesting that anti-oxidative and anti-inflammatory compounds could be neuroprotective agents for PD. Eucommia ulmoides (EU) is a traditional herbal medicine which exerts neuroprotective effects by anti-inflammatory and anti-oxidative properties. Our previous study showed that treatment with chlorogenic acid, a component of EU, protected against neurodegeneration in the central and enteric nervous systems in a PD model. In this study, we examined the effects of EU extract (EUE) administration on dopaminergic neurodegeneration, glial response and α-synuclein expression in the substantia nigra pars compacta (SNpc), and intestinal enteric neurodegeneration in low-dose rotenone-induced PD model mice. Daily oral administration of EUE ameliorated dopaminergic neurodegeneration and α-synuclein accumulation in the SNpc. EUE treatment inhibited rotenone-induced decreases in the number of total astrocytes and in those expressing the antioxidant molecule metallothionein. EUE also prevented rotenone-induced microglial activation. Furthermore, EUE treatment exerted protective effects against intestinal neuronal loss in the PD model. These results suggest that EU exerts neuroprotective effects in the central and enteric nervous systems of rotenone-induced parkinsonism mice, in part by glial modification.

Natural variation in the transcriptional response of Drosophila melanogaster to oxidative stress.

Broadly distributed species must cope with diverse and changing environmental conditions, including various forms of stress. Cosmopolitan populations of Drosophila melanogaster are more tolerant to oxidative stress than those from the species' ancestral range in sub-Saharan Africa, and the degree of tolerance is associated with an insertion/deletion polymorphism in the 3' untranslated region of the Metallothionein A (MtnA) gene that varies clinally in frequency. We examined oxidative stress tolerance and the transcriptional response to oxidative stress in cosmopolitan and sub-Saharan African populations of D. melanogaster, including paired samples with allelic differences at the MtnA locus. We found that the effect of the MtnA polymorphism on oxidative stress tolerance was dependent on the genomic background, with the deletion allele increasing tolerance only in a northern, temperate population. Genes that were differentially expressed under oxidative stress included MtnA and other metallothioneins, as well as those involved in glutathione metabolism and other genes known to be part of the oxidative stress response or the general stress response. A gene coexpression analysis revealed further genes and pathways that respond to oxidative stress including those involved in additional metabolic processes, autophagy, and apoptosis. There was a significant overlap among the genes induced by oxidative and cold stress, which suggests a shared response pathway to these two stresses. Interestingly, the MtnA deletion was associated with consistent changes in the expression of many genes across all genomic backgrounds, regardless of the expression level of the MtnA gene itself. We hypothesize that this is an indirect effect driven by the loss of microRNA binding sites within the MtnA 3' untranslated region.

Naringenin inhibits pro­inflammatory cytokine production in macrophages through inducing MT1G to suppress the activation of NF­κB.

Naringenin (Nar) is a flavanone that has been suggested to provide human health benefits such as anti-inflammatory, anti-oxidant and anti-cancer properties. However, the mechanisms underlying these benefits are complex and still not fully understood. In this study, we investigated the effect of Nar on the inflammatory response of macrophages and its underlying mechanism. In lipopolysaccharide (LPS)-stimulated human macrophages, Nar inhibited the activation of NF-κB pathway and suppressed the downstream expression of pro-inflammatory factors. In addition, Nar was also able to induce metallothionein 1 G (MT1G) expression, and the inhibitory effects of Nar on the production of pro-inflammatory cytokines was dependent on MT1G. Mechanistically, we found that MT1G-mediated inhibition of pro-inflammatory cytokines responses might be through repressing NF-κB activation via zinc chelation. Overall, this study reveals a novel mechanism of Nar on inflammatory responses, the suppression of NF-κB activation through upregulation of MT1G.

Upregulation of Metallothionein-1G Accelerates G1/S Transition in the Growth Phase of Acute Promyelocytic Leukemia NB4 Cells.

Downregulation of the myeloid master regulator Spi1/PU.1 plays a pivotal role in leukemogenesis, and we previously showed that Spi1/PU.1 directly represses metallothionein (MT)-1G through the epigenetic activity of PU.1. Furthermore, we recently demonstrated that overexpression of MT-1G inhibits retinoic acid-induced differentiation of acute promyelocytic leukemia NB4 cells. As PU.1 is a master regulator of growth and differentiation in myeloid cells, we examined its effects on cell proliferation of MT-1G-overexpressing NB4 (NB4MTOE) cells in the present study. Although there were no significant differences in total viable cell numbers between NB4MTOE cells and control cells during the time course examined, the proportion of S-phase cells was obviously increased in all NB4MTOE cells at 16-24 h after serum stimulation. Consistent with these findings, real-time PCR analyses revealed marked increases in the expression of cyclin E (G1/S-phase cyclin) and cyclin A (S-phase cyclin) in NB4MTOE cells during the same time period. Furthermore, NB4MTOE cells were significantly resistant to cytosine arabinoside (Ara-C), an S-phase-specific chemotherapeutic drug. Collectively, these findings suggest a role for MT-1G in G1/S transition during the growth phase of NB4 cells.

Sexually Dimorphic Growth Stimulation in a Strain of Growth Hormone Transgenic Coho Salmon (Oncorhynchus kisutch).

Growth hormone (GH) transgenic fish often exhibit remarkable transformations in growth rate and other phenotypes relative to wild-type. The 5750A transgenic coho salmon strain exhibits strong sexually dimorphic growth, with females possessing growth stimulation at a level typical of that seen for both sexes in other strains harbouring the same gene construct (e.g. M77), while males display a modest level of growth stimulation. GH mRNA levels were significantly higher in females than in males of the 5750A strain but equivalent in the M77 strain, indicating sex and transgene insertion locus altered transgene expression. We found that acute estradiol treatments did not influence GH expression in either strain (5750A and M77) or the transgene promoter (metallothionein-B), suggesting that estradiol level was not a significant factor influencing transgene activity. The feminization of XX and XY fish of the 5750A and M77 strains generated all-female groups and resulted in equalized growth of the two genetic sexes, suggesting that the presence of the Y chromosome was not directly capable of influencing the GH transgene-mediated growth in a physiological female conditions. These data suggest that the difference in growth rate seen between the sexes in the 5750A strain arises from non-estradiol-mediated sex influences on gene regulation at the transgene locus. This study shows how genetic factors and transgene insertion sites can influence transgene expression with significant consequent effects on phenotype.

Effects of selenium, zinc, insulin and metallothionein on cadmium-induced oxidative stress and metallothionein gene expression levels in diabetic rats.

Background The aim of this study was to investigate the effects of selenium, zinc, insulin, and metallothionein on oxidative damage and metallothionein (MT) gene expression levels in streptozotocin (STZ)-induced type 1 diabetic rats exposed to Cd. Methods Rats were categorized under eight groups (control, STZ, Cd, STZ + Cd, Group 5, Group 6, Group 7, and STZ + Cd + MT [n:8/group]) were used. After diabetes was induced by STZ (55 mg/kg, i.p.), Cd was administered (1 mg/kg CdCl, orally) for 4 weeks. In cadmium-treated groups selenium (Na2SeO3 1.5 mg/kg, i.p.), zinc (ZnSO4 10 mg/kg via oral gavage), insulin (insulin glargine, 2U/day, s.c.), and MT (1mg/kg, every other 10 days, s.c.) were administered. MT gene expression levels, MDA levels, GPx, SOD, and CAT activity levels were determined in liver and kidney tissues. Results MT gene expression and MDA levels increased (p < 0.05) while GPx and SOD activity levels decreased (p < 0.05) in STZ, Cd, and STZ + Cd groups. In Group 5, Group 6, Group 7, and Group 8 groups MT gene expression and MDA levels were decreased while GPx and SOD activity levels were increased (p < 0.05). CAT activity significantly increased (p < 0.05) in STZ + Cd group while there were no significance in other groups (p > 0.05). Compared to the control, Group 5, Group 6, Group 7, and Group 8 groups provided no difference for alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen and creatinine levels (p > 0.05). Conclusions Our results suggest that Se, insulin, Zn and MT may have protective effects against hepatotoxicity and nephrotoxicity caused by Cd exposure in diabetic rats by reducing oxidative stress and MT gene expression levels.

Protective effects of metallothionein and vitamin E in the trunk kidney and blood of cadmium poisoned Ctenopharyngodon idellus.

Cadmium (Cd), a substance with one of the most critical health hazard indices, can cause damage to both the blood and kidneys and accumulates in the body at last. The present work studied the toxicological effects of Cd and the therapeutic effects of metallothionein (MT) and vitamin E (VE) on the trunk kidney and blood of freshwater grass carp (Ctenopharyngodon idellus). Grass carp were divided into three groups: Cd + phosphate-buffered saline (PBS) group, Cd + VE group, and the Cd + MT group. Fish were injected with CdCl2 on the first day and then VE, MT, or PBS was administered 4 days post-injection. Fish not injected with Cd were used as a negative control. The blood and trunk kidney amassed Cd and suffered severe damage in the forms of organ toxicity cytotoxicity, and immunotoxicity. However, the MT reduced the Cd content in the trunk kidney and blood and partially stabilized the damaged organs. Treatment with VE, however, only demonstrated weaker protection against on Cd-induced toxicity. The results indicate that exogenous MT may play an essential role in restoring homeostasis of the Cd-poisoned urinary and circulatory system and that it may help eliminate Cd in aquatic animals.

Metallothioneins enhance chromium detoxification through scavenging ROS and stimulating metal chelation in Oryza sativa.

Metallothioneins (MTs) is a metal ion binding protein to detoxify heavy metal stress in plant cells. This study examines involvement of MTs in metal chelation and ROS scavenging in rice seedling under Cr induction either Cr(VI) or Cr(III) at three different effective concentrations using Agilent 44K rice microarray and real-time PCR technology. Results showed that the concentration of Cr was higher in roots than in shoots in both Cr treatments. Accumulation of both H2O2 and O2- in rice tissues was evident, but the fluctuation of H2O2 was more remarkable than O2-. Both Cr exposures resulted in enhancement of MTs in plant tissues. Results from PCR analysis confirmed that ten specific OsMT genes responsible for regulating ROS removal were expressed differentially in plant tissues as well as in Cr variants, suggesting that their different regulation and responsiveness strategies. Expression patterns of metal chelation-related OsMT genes, after Cr exposure were also inconsistent in rice tissues. Longer exposure periods caused more transcriptional changes in both Cr treatments. We also noticed that OsMT1b might carry more weight during Cr chelation in roots rather than in shoots, while OsMT2c had more important role in eliminating H2O2 accumulation in shoots than roots. These results suggest that different speciation of Cr in rice tissues resulted in inconsistent transcriptional changes of OsMT genes, which functioned in different regulation and responsiveness pathways responsible for metal ions chelating and ROS scavenging during Cr detoxification.

Potential ability for metallothionein and vitamin E protection against cadmium immunotoxicity in head kidney and spleen of grass carp (Ctenopharyngodon idellus).

Cadmium (Cd) pollution is an important issue affecting the food safety of aquatic products. Cd can impair the immune system and cause irreversible damage to fish and other aquatic organisms. The immunoprotection activities of exogenous metallothionein (MT) and vitamin E (VE) were investigated in Cd poisoned grass carp, Ctenopharyngodon idellus, in the present study. C. idellus were divided into three groups: Cd+phosphate-buffered saline (PBS) group; Cd+MT; and Cd+VE. All fish were injected with cadmium chloride (CdCl2) on the first day and then treated with PBS, MT or VE four days post-injection. Fish not injected with Cd were used as a negative control. Cd exposure caused severe head-kidney and splenic injury in C. idellus, mainly expressed as an increase in Cd content, histological damage, percentage of head-kidney and splenic cells apoptosis and decreases in immune-related gene mRNA transcript expression. However, MT and VE treatments protected against Cd-induced immunotoxicity in C. idellus by decreasing Cd contents, lessening histological damage, reducing the percentage of apoptosis and recovering immune-related mRNA transcript expression. Our results demonstrate that MT and VE can alleviate Cd-induced immunotoxicity and that MT has a more powerful effect than VE, indicating that MT could be a potential antidote in cases of Cd poisoning.

Cell-penetrating artificial mitochondria-targeting peptide-conjugated metallothionein 1A alleviates mitochondrial damage in Parkinson's disease models.

An excess of reactive oxygen species (ROS) relative to the antioxidant capacity causes oxidative stress, which plays a role in the development of Parkinson's disease (PD). Because mitochondria are both sites of ROS generation and targets of ROS damage, the delivery of antioxidants to mitochondria might prevent or alleviate PD. To transduce the antioxidant protein human metallothionein 1A (hMT1A) into mitochondria, we computationally designed a cell-penetrating artificial mitochondria-targeting peptide (CAMP). The recombinant CAMP-conjugated hMT1A fusion protein (CAMP-hMT1A) successfully localized to the mitochondria. Treating a cell culture model of PD with CAMP-hMT1A restored tyrosine hydroxylase expression and mitochondrial activity and reduced ROS production. Furthermore, injection of CAMP-hMT1A into the brain of a mouse model of PD rescued movement impairment and dopaminergic neuronal degeneration. CAMP-hMT1A delivery into mitochondria might be therapeutic against PD by alleviating mitochondrial damage, and we predict that CAMP could be used to deliver other cargo proteins to the mitochondria.

The roles of metallothioneins in carcinogenesis.

Metallothioneins (MTs) are small cysteine-rich proteins that play important roles in metal homeostasis and protection against heavy metal toxicity, DNA damage, and oxidative stress. In humans, MTs have four main isoforms (MT1, MT2, MT3, and MT4) that are encoded by genes located on chromosome 16q13. MT1 comprises eight known functional (sub)isoforms (MT1A, MT1B, MT1E, MT1F, MT1G, MT1H, MT1M, and MT1X). Emerging evidence shows that MTs play a pivotal role in tumor formation, progression, and drug resistance. However, the expression of MTs is not universal in all human tumors and may depend on the type and differentiation status of tumors, as well as other environmental stimuli or gene mutations. More importantly, the differential expression of particular MT isoforms can be utilized for tumor diagnosis and therapy. This review summarizes the recent knowledge on the functions and mechanisms of MTs in carcinogenesis and describes the differential expression and regulation of MT isoforms in various malignant tumors. The roles of MTs in tumor growth, differentiation, angiogenesis, metastasis, microenvironment remodeling, immune escape, and drug resistance are also discussed. Finally, this review highlights the potential of MTs as biomarkers for cancer diagnosis and prognosis and introduces some current applications of targeting MT isoforms in cancer therapy. The knowledge on the MTs may provide new insights for treating cancer and bring hope for the elimination of cancer.

Metallothionein-1 suppresses rheumatoid arthritis pathogenesis by shifting the Th17/Treg balance.

It is now well accepted that an imbalance between the Th17 and regulatory T-cell responses is closely associated with the development of rheumatoid arthritis (RA). However, the precise regulatory mechanism for the differentiation of Th17 and Treg in RA is not well characterized. The present study showed that metallothionein-1 (MT-1), which is a low molecular weight protein that is involved in the detoxification of heavy metals and scavenging of free radicals, was upregulated in RA. Furthermore, the synovial inflammation and pathologic symptoms in collagen-induced arthritis and collagen antibody-induced arthritis mice were significantly suppressed when MT-1 was expressed intraarticularly. Further investigation revealed that MT-1 inhibited the differentiation of Th17 cells but enhanced that of Treg cells. Furthermore, it markedly decreased both STAT3 and RAR-related orphan receptor gamma t (RORγt) expression in vitro and in vivo. Collectively, our studies demonstrated that MT-1 might manifest as a protein involved in immunosuppression of RA pathogenesis by shifting Th17/Treg balance and may prove to be a potential therapeutic target for RA autoimmune diseases.

Hepatoprotective Activity of Vitamin E and Metallothionein in Cadmium-Induced Liver Injury in Ctenopharyngodon idellus.

As an environmental and industrial pollutant, cadmium (Cd) can cause a broad spectrum of toxicological effects. Multiple organs, especially the liver, are considerably affected by Cd in both humans and animals. We investigated the protective effects of metallothionein (MT) and vitamin E (VE) supplementation on Cd-induced apoptosis in the grass carp (Ctenopharyngodon idellus) liver. Grass carp were divided into four groups: the control group, Cd + phosphate-buffered saline (PBS) group, Cd + VE group, and Cd + MT group. All fish were injected with CdCl2 on the first day and then VE, MT, and PBS were given 4 days postinjection, respectively. The results showed that Cd administration resulted in liver poisoning in grass carp, which was expressed as an increase in Cd contents, malondialdehyde (MDA) concentration, percentage of hepatocyte apoptosis, and apoptosis-related gene mRNA transcript expression. However, VE and MT treatments protected against Cd-induced hepatotoxicity in grass carp by decreasing Cd contents, lipid peroxidation, and histological damage and reducing the percentage of hepatocyte apoptosis by regulating related mRNA transcript expression. These data demonstrate that oxidative stress and activation of the caspase signaling cascade play a critical role in Cd-induced hepatotoxicity. However, VE and MT alleviate Cd-induced hepatotoxicity through their antioxidative and antiapoptotic effects, and MT has a more powerful effect than VE.

The impact of metallothionein-II on microglial response to tumor necrosis factor-alpha (TNFα) and downstream effects on neuronal regeneration.

BACKGROUND: The extracellular environment plays an important role in supporting the regeneration of axons after injury. Metallothionein-II (MTII) is a metal-binding protein known for its neuroprotective effect by directly stimulating the growth of axons after injury. Previous studies have shown that MTII also modulates the response of astrocytes and microglia after injury. However, a detailed analysis describing how MTII modulates the interaction between microglia and neurons is lacking. METHODS: We introduced fluorescently labelled MTII into the cortex at the time of needlestick injury to investigate the cellular uptake of MTII using immunohistochemistry with antibodies against cell-type-specific markers. The role of MTII in modulating the effect of microglia on axon outgrowth following an inflammatory response is further investigated using a co-culture model involving primary rodent microglia pre-treated with TNFα and primary rodent cortical neurons. The axon lengths were assessed 24 h after the plating of the neurons onto treated microglia. We also utilised siRNA to knockdown the expression of LRP1, which allows us to investigate the role of LRP1 receptors in the MTII-mediated effect of microglia on axon outgrowth. RESULTS: Fluorescently labelled MTII was found to be associated with neurons, astrocytes and microglia following injury in vivo. Microglia-neuron co-culture experiments demonstrated that exogenous MTII altered the response of microglia to TNFα. The neurons plated onto the TNFα-stimulated microglia pre-treated with MTII have shown a significantly longer axonal length compare to the TNFα-stimulated microglia without the MTII treatment. This suggested that MTII reduce cytokine-stimulated activation of microglia, which would ordinarily impair neurite outgrowth. This inhibitory effect of MTII on activated microglia was blocked by siRNA-mediated downregulation of LRP1 receptor expression in microglia, suggesting that MTII acts via the LRP1 receptor on microglia. CONCLUSIONS: This study demonstrates that exogenous MTII acts via the LRP1 receptor to alter the inflammatory response of microglia following TNFα stimulation, providing a more supportive environment for axon growth.

Metallothionein is a Potential Therapeutic Strategy for Amyotrophic Lateral Sclerosis.

Lou Gehrig's disease, a synonym of amyotrophic lateral sclerosis, is an adult-onset lethal neurodegenerative disorder. Irrespective of extensive efforts to elucidate the pathogenesis of the disease and searches for therapies, no favorable pharmacotherapeutic strategies have yet to be proposed. In a popular rodent model of ALS, G93A SOD1 strain of mouse, intracellular copper conditions were geared toward copper accumulation inside cells, resulting in an acceleration of oxidative stress and apoptotic process. Disruption of intracellular copper homeostasis was common to transgenic mice expressing human mutant SOD1s. In this review, the novel hypothesis that disruption of intracellular copper homeostasis could be involved in the development of the disease was introduced. Based upon the hypothesis, therapeutic outcomes of agents that are capable of correcting and/or modifying intracellular copper homeostasis are described. Administration of ammonium tetrathiomolybdate, a selective intracellular copper chelator, delayed onset, slowed progression, and prolonged survival of a rodent model of the disease (G93A SOD1 mice). Metallothionein is a low molecular weight, cysteine-rich, metal-binding cytoplasmic protein that has beneficial properties in detoxification of toxic heavy metals, homeostatic regulation of intracellular essential trace elements, including copper, antioxidant, and antiapoptotic roles. In animal experiments of the G93A SOD1 mice, an increase of metallothionein proteins by means of induction by exercise or dexamethasone, genetic overexpression, or intraperitoneal administration, all resulted in a preferable outcome. The therapeutic effects were not inferior to those of approved drugs for ALS in humans. These observations suggest that metallothionein could be worth investigating the therapeutic potential in clinical use.

The role of metallothionein in oncogenesis and cancer treatment.

Metallothionein is cysteine-rich low molecular mass protein. The involvement of MT in many physiological and pathophysiological processes such as apoptosis, proliferation, angiogenesis, and the detoxification of heavy metals suggested participation of this protein in carcinogenesis and tumor therapy. Depending on the type of tissue and classification of carcinoma various it was observed relation between MT expression and tumor type, stage, grade, poor prognosis and body resistance to radiotherapy and chemotherapy. MT in tumor cell plays important role in defense mechanism against the effect of radiation by inhibiting the processes that lead to the apoptosis. A number of studies have shown an increased expression of MT in various human tumors of larynx, pancreas, kidney, uterus and breast, whereas lower MT expression was detected in liver tumors. Variable MT expression was detected in case of thyroid, prostate, lung, stomach and central nervous system tumors. Also MT plays crucial role in the cytostatics treatment. MT can bind cis-platinum compounds and removes them from the cells, which may lead to multidrug resistance. However, the same functions of MT protect against the negative effects of chemotherapeutic treatment. It is especially important in case of heart cells. Analysis of MT expression in tumor cells may be useful in choosing method of treatment. It is difficult to determine whether increased expression of MT is only a inducing factor of the development of the carcinogenesis, its malignances and multidrug resistance, or it is a factor inhibiting the induction and development of cancer.

Low-density Lipoprotein Receptor-related Proteins in a Novel Mechanism of Axon Guidance and Peripheral Nerve Regeneration.

The low-density lipoprotein receptor-related protein receptors 1 and 2 (LRP1 and LRP2) are emerging as important cell signaling mediators in modulating neuronal growth and repair. We examined whether LRP1 and LRP2 are able to mediate a specific aspect of neuronal growth: axon guidance. We sought to identify LRP1 and LRP2 ligands that could induce axonal chemoattraction, which might have therapeutic potential. Using embryonic sensory neurons (rat dorsal root ganglia) in a growth cone turning assay, we tested a range of LRP1 and LRP2 ligands for the ability to guide growth cone navigation. Three ligands were chemorepulsive: α-2-macroglobulin, tissue plasminogen activator, and metallothionein III. Conversely, only one LRP ligand, metallothionein II, was found to be chemoattractive. Chemoattraction toward a gradient of metallothionein II was calcium-dependent, required the expression of both LRP1 and LRP2, and likely involves further co-receptors such as the tropomyosin-related kinase A (TrkA) receptor. The potential for LRP-mediated chemoattraction to mediate axonal regeneration was examined in vivo in a model of chemical denervation in adult rats. In these in vivo studies, metallothionein II was shown to enhance epidermal nerve fiber regeneration so that it was complete within 7 days compared with 14 days in saline-treated animals. Our data demonstrate that both LRP1 and LRP2 are necessary for metallothionein II-mediated chemotactic signal transduction and that they may form part of a signaling complex. Furthermore, the data suggest that LRP-mediated chemoattraction represents a novel, non-classical signaling system that has therapeutic potential as a disease-modifying agent for the injured peripheral nervous system.