Oxygen free radicals and metallothionein

Protection against diabetic cardiomyopathy is achieved using a combination of sulforaphane and zinc in type 1 diabetic OVE26 mice

Sulforaphane (SFN) can effectively induce nuclear factor E2–related factor 2 (Nrf2), and zinc (Zn) can effectively induce metallothionein (MT), both of which have been shown to protect against diabetic cardiomyopathy (DCM). However, it is unclear whether combined treatment with SFN and Zn offers better cardiac protection than either one alone. Here, we treated 5‐week‐old OVE mice that spontaneously develop type 1 diabetes with SFN and/or Zn for 18 weeks. Cardiac dysfunction, by echocardiography, and pathological alterations and remodelling, shown by cardiac hypertrophy, fibrosis, inflammation and oxidative damage, examined by histopathology, Western blotting and real‐time PCR, were observed in OVE mice. All these dysfunction and pathological abnormalities seen in OVE mice were attenuated in OVE mice with treatment of either SFN, Zn or SFN/Zn, and the combined treatment with SFN/Zn was better than single treatments at ameliorating DCM. In addition, combined SFN and Zn treatment increased Nrf2 function and MT expression in the heart of OVE mice to a greater extent than SFN or Zn alone. This indicates that the dual activation of Nrf2 and MT by combined treatment with SFN and Zn may be more effective than monotherapy at preventing the development of DCM via complementary, additive mechanisms.

Regulatory role of metallothionein-1/2 on development of sex differences in a high-fat diet-induced obesity

AIMS

To evaluate the role of metallothionein (MT) in sex differences of obesity, we examined the effect of MT on regulation of lipid accumulation in female and male wild type (WT) and MT1/MT2-null (MT-KO) mice.

MAIN METHODS

Male and female WT and MT-KO mice fed standard diet (SD) or high-fat diet (HFD) for 35 weeks. Surgical castration in male mice was also performed to examine the effects of androgen on fat accumulation under HFD condition.

KEY FINDINGS

The fat mass and size of adipocytes in white adipose tissue (WAT) was greater in adult MT-KO mice than in WT mice after 35 weeks of SD feeding without gender differences, suggesting a role of MT in limiting WAT development during normal growth in both sexes. In female mice fed HFD, weights of WAT and body were greater in MT-KO mice than in WT mice, indicating that MT had a preventive role against excess fat accumulation. In male mice fed HFD, WAT weight hardly increased in MT-KO mice compared to the increase in WT mice. Surgically castrated WT males fed HFD had lower WAT weight compared with sham-treated mice, although castrated MT-KO males fed HFD had greater increases in WAT weight compared with sham-treated mice and castrated WT males.

SIGNIFICANCE

These data suggest that MT could enhance the preventive action of estrogen against excess fat accumulation, on the contrary, MT augmented the ability of androgen to increase fat accumulation. MT may act to modify the susceptibility to obesity under sex hormones.

Sex-dependent expression of metallothioneins MT1 and MT2 and concentrations of trace elements in rat liver and kidney tissues: Effect of gonadectomy

Metallothioneins (MTs) exhibit binding affinity for several essential and toxic trace elements. Previous studies in rodents indicated sex differences in the hepatic and renal expression of MTs and concentrations of various elements. The mechanism responsible for these differences has not been resolved. Here, in the liver and kidney tissues of sham-operated and gonadectomized male and female rats we determined the expression of MT1 and MT2 (MT1&2) mRNA by RT-PCR, abundance of MT1&2 proteins by Western blotting and immunocytochemistry, concentrations of essential (Fe, Zn, Cu, Co) and toxic (Cd, Hg, Pb) elements by ICP-MS, and oxidative status parameters (SOD, GPx, MDA, GSH) by biochemical methods. In both organs, the expression of MT1&2 mRNA and MT1&2 proteins was female-dominant, upregulated by castration, and downregulated by ovariectomy. Concentrations of Fe in the liver and Co in the kidneys followed the same pattern. Most other elements (Zn, Cu, Cd, Hg) exhibited female- or male-dominant sex differences, affected by gonadectomy in one or both organs. Pb was sex- and gonadectomy-unaffected. GPx and MDA were elevated and associated with the highest concentrations of Fe only in the female liver. We conclude that the sex-dependent expression of MT1&2 mRNA and proteins in the rat liver and kidneys may include different mechanisms. In the liver, the female-dominant tissue concentrations of Fe may generate oxidative stress which is a potent enhancer of MTs production, whereas in kidneys, the female-dominant expression of MTs may be unrelated to Fe-mediated oxidative stress.

Supplementing Genistein for Breeder Hens Alters the Fatty Acid Metabolism and Growth Performance of Offsprings by Epigenetic Modification

The experiment was designed to clarify the effect and molecular mechanism of maternal genistein (GEN) on the lipid metabolism and developmental growth of offspring chicks. Laying broiler breeder (LBB) hens were supplemented with 40 mg/kg genistein (GEN), while the control group was fed with the low-soybean meal diet. The offspring chicks were grouped according to the mother generation with 8 replicates each. Hepatic transcriptome data revealed 3915 differentially expressed genes (DEGs, P adjusted < 0.05, fold change > 1.5 or fold change < 0.67) between chicks in the two groups. Maternal GEN activated the GH-IGF1-PI3K/Akt signaling pathway, which promoted the developmental processes and cellular amino acid metabolic processes, as well as inhibited the apoptotic process. GEN treatment significantly increased the weight gain, breast muscle percentage, and liver index in chicks. PANTHER clustering analysis suggested that maternal GEN enhanced the antioxidant activity of chicks by the upregulation of gene (SOD3, MT1, and MT4) expression. Accordingly, the activities of T-AOC and T-SOD in the liver were increased after GEN treatment. The overrepresentation tests revealed that maternal GEN influenced the glycolysis, unsaturated fatty acid biosynthesis, acyl-coenzyme A metabolism, lipid transport, and cholesterol metabolism in the chick livers. Hepatic cholesterol and long-chain fatty acid were significantly decreased after GEN treatment. However, the level of arachidonic acid was higher in the livers of the GEN-treated group compared with the CON group. Moreover, GEN treatment enhanced fatty acid β-oxidation and upregulated PPARδ expression in the chick liver. ChIP-qPCR analysis indicated that maternal GEN might induce histone H3-K36 trimethylation in the promoter region of PPARδ gene (PPARD) through Iws1, methyltransferases. It also induced histone H4-K12 acetylation at the PPARD promoter through MYST2, which activated the PPAR signaling pathways in the chick livers. In summary, supplementing LBB hens with GEN can alter lipid metabolism in the offspring chicks through epigenetic modification and improve the antioxidative capability as well as growth performance.

Combined effects of DDE and hyperlipidic diet on metallothionein expression and synthesis in rat tissues

Metallothionein is well known for its detoxificant and anti-oxidant properties and has been shown to be effective to prevent hydroxyl radical-generated DNA degradation. The purpose of this investigation was to analyze the combined effect of two factors promoting cellular oxidative-stress, that is, the administration of the pesticide dichloro-diphenyl-dichloroethylene (DDE) and a high fat diet, on metallothionein expression and synthesis in rat liver and kidney. DDE is the main metabolite of dichloro-diphenyl-trichloroethane (DDT), and is commonly found in the food chain and in all tissues of living organisms, carried by the fats. Male Wistar rats were fed with a standard (N) or a high fat (HF) diet and exposed to DDE (10 mg/kg body mass, N + DDE and HF + DDE groups) or vehicle (corn oil, N, and HF groups) via gavage every day for 28 days. Tissues histology was determined by light microscopy analysis; differences in metallothionein gene expression and synthesis by real-time PCR and western blot, respectively. Finally, protein cellular localization was established by immunocytochemistry. The results showed a different involvement of metallothionein in defending tissues from HF- and DDE-induced oxidative stress, suggesting that hepatic and renal cells use different strategies against pro-oxidant species. In both cell types a marked increase in the metallothionein content was observed in the nucleus, with a concomitant drop of the cytoplasmatic protein, either under HF- and DDE-stress conditions; however, no synergistic or additive effects were observed between the action of fats and pesticide. These findings reinforce the role of metallothionein in protecting DNA from oxidative damage.

Colonic epithelial cell diversity in health and inflammatory bowel disease

The colonic epithelium facilitates host-microorganism interactions to control mucosal immunity, coordinate nutrient recycling and form a mucus barrier. Breakdown of the epithelial barrier underpins inflammatory bowel disease (IBD). However, the specific contributions of each epithelial-cell subtype to this process are unknown. Here we profile single colonic epithelial cells from patients with IBD and unaffected controls. We identify previously unknown cellular subtypes, including gradients of progenitor cells, colonocytes and goblet cells within intestinal crypts. At the top of the crypts, we find a previously unknown absorptive cell, expressing the proton channel OTOP2 and the satiety peptide uroguanylin, that senses pH and is dysregulated in inflammation and cancer. In IBD, we observe a positional remodelling of goblet cells that coincides with downregulation of WFDC2-an antiprotease molecule that we find to be expressed by goblet cells and that inhibits bacterial growth. In vivo, WFDC2 preserves the integrity of tight junctions between epithelial cells and prevents invasion by commensal bacteria and mucosal inflammation. We delineate markers and transcriptional states, identify a colonic epithelial cell and uncover fundamental determinants of barrier breakdown in IBD.

Short-term high-fat meal intake alters the expression of circadian clock-, inflammation-, and oxidative stress-related genes in human skeletal muscle

Dietary food, depending on timing, amount and composition can influence gene expression in various tissues. Here, we investigated the effect of high-fat meal diets of different compositions on the gene expression pattern of human skeletal muscle. Gene expression data of skeletal muscle samples from human volunteers prior and 4 h after the consumption of high lipid-containing meal consisting of either saturated-, monounsaturated- or polyunsaturated fatty acids were downloaded from the public repository. List of 843 differently expressed genes (DEGs) was generated. Functional analysis revealed that circadian rhythm-, inflammation- and oxidative stress-related genes are highly overrepresented among the DEGs. The magnitude of gene expression changes significantly increases with the saturation level of the dietary fatty acids and the majority of the DEGs are upregulated. We propose that, by altering circadian clock gene expression and inducing inflammation and oxidative stress, high lipid intake can contribute to muscle function decay in the long run.

Exercise promotes a cardioprotective gene program in resident cardiac fibroblasts

Exercise and heart disease both induce cardiac remodeling, but only disease causes fibrosis and compromises heart function. The cardioprotective benefits of exercise have been attributed to changes in cardiomyocyte physiology, but the impact of exercise on cardiac fibroblasts (CFs) is unknown. Here, RNA-sequencing reveals rapid divergence of CF transcriptional programs during exercise and disease. Among the differentially expressed programs, NRF2-dependent antioxidant genes - including metallothioneins (Mt1 and Mt2) - are induced in CFs during exercise and suppressed by TGF-β/p38 signaling in disease. In vivo, mice lacking Mt1/2 exhibit signs of cardiac dysfunction in exercise, including cardiac fibrosis, vascular rarefaction, and functional decline. Mechanistically, exogenous MTs derived from fibroblasts are taken up by cultured cardiomyocytes, reducing oxidative damage-dependent cell death. Importantly, suppression of MT expression is conserved in human heart failure. Taken together, this study defines the acute transcriptional response of CFs to exercise and disease and reveals a cardioprotective mechanism that is lost in disease.

Reactivity of Cu(ii)–, Zn(ii)– and Fe(ii)–thiosemicarbazone complexes with glutathione and metallothionein: from stability to dissociation to transmetallation

Metallothionein and glutathione are key players of the fate of Cu(ii)–/Zn(ii)–/Fe(ii)–thiosemicarbazone anticancer drugs in the cytosol/nucleus.

Hepatic transcriptional dose-response analysis of male and female Fischer rats exposed to hexabromocyclododecane

Hexabromocyclododecane (HBCD) is a brominated flame retardant found in the environment and human tissues. The toxicological effects of HBCD exposure are not clearly understood. We employed whole-genome RNA-sequencing on liver samples from male and female Fischer rats exposed to 0, 250, 1250, and 5000 mg technical mixture of HBCD/kg diet for 28 days to gain further insight into HBCD toxicity. HBCD altered 428 and 250 gene transcripts in males and females, respectively, which were involved in metabolism of xenobiotics, oxidative stress, immune response, metabolism of glucose and lipids, circadian regulation, cell cycle, fibrotic activity, and hormonal balance. Signature analysis supported that HBCD operates through the constitutive androstane and pregnane X receptors. The median transcriptomic benchmark dose (BMD) for the lowest statistically significant pathway was within 1.5-fold of the BMD for increased liver weight, while the BMD for the lowest pathway with at least three modeled genes (minimum 5% of pathway) was similar to the lowest apical endpoint BMD. The results show how transcriptional analyses can inform mechanisms underlying chemical toxicity and the doses at which potentially adverse effects occur. This experiment is part of a larger study exploring the use of toxicogenomics and high-throughput screening for human health risk assessment.

Metallothionein: An Aggressive Scavenger-The Metabolism of Rhodium(II) Tetraacetate (Rh2(CH3CO2)4)

Anthropogenic sources of xenobiotic metals with no physiological benefit are increasingly prevalent in the environment. The platinum group metals (Pd, Pt, Rh, Ru, Os, and Ir) are found in marine and plant species near urban sources, and are known to bioaccumulate, introducing these metals into the human food chain. Many of these metals are also being used in innovative cancer therapy, which leads to a direct source of exposure for humans. This paper aims to further our understanding of nontraditional metal metabolism via metallothionein, a protein involved in physiologically important metal homeostasis. The aggressive reaction of metallothionein and dirhodium(II) tetraacetate, a common synthetic catalyst known for its cytotoxicity, was studied in detail in vitro. Optical spectroscopic and equilibrium and time-dependent mass spectral data were used to define binding constants for this robust reaction, and molecular dynamics calculations were conducted to explain the observed results.

Genetic biosensors for imaging nitric oxide in single cells

Over the last decades a broad collection of sophisticated fluorescent protein-based probes was engineered with the aim to specifically monitor nitric oxide (NO), one of the most important signaling molecules in biology. Here we report and discuss the characteristics and fields of applications of currently available genetically encoded fluorescent sensors for the detection of NO and its metabolites in different cell types.

LONG ABSTRACT

Because of its radical nature and short half-life, real-time imaging of NO on the level of single cells is challenging. Herein we review state-of-the-art genetically encoded fluorescent sensors for NO and its byproducts such as peroxynitrite, nitrite and nitrate. Such probes enable the real-time visualization of NO signals directly or indirectly on the level of single cells and cellular organelles and, hence, extend our understanding of the spatiotemporal dynamics of NO formation, diffusion and degradation. Here, we discuss the significance of NO detection in individual cells and on subcellular level with genetic biosensors. Currently available genetically encoded fluorescent probes for NO and nitrogen species are critically discussed in order to provide insights in the functionality and applicability of these promising tools. As an outlook we provide ideas for novel approaches for the design and application of improved NO probes and fluorescence imaging protocols.

Pulmonary arterial hypertension and the potential roles of metallothioneins: A focused review

The pathophysiology of pulmonary arterial hypertension (PAH) is underlined by cell proliferation and vasoconstriction of pulmonary arterioles this involves multiple molecular factors or proteins, but it is not clear what the exact roles of these factors/proteins are. In addition, there may be other factors/proteins that have not been identified that contribute to PAH pathophysiology. Therefore, research has focused on investigating novel role players, in order to facilitate a better understanding of how PAH develop. Evidence suggest that mitochondrial regulators are key role players in PAH pathophysiology, but regulators that have not received sufficient attention in PAH are metallothioneins (MTs). In PAH patients, MT expression is elevated compared to healthy individuals, suggesting that MTs may be possible biomarkers. In other disease-models, MTs have been shown to regulate cell proliferation and vasoconstriction, processes that are instrumental in PAH pathophysiology. Due to the involvement of these processes in PAH pathophysiology and the ability of MTs to modulate them, this paper propose that cellular MTs may also play a role in PAH development. This paper suggests that PAH-research should perhaps begin to investigate the involvement of cellular MTs in the development of PAH.

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.

Glutathione has a more important role than metallothionein-I/II against inorganic mercury-induced acute renal toxicity

Inorganic mercury is a harmful heavy metal that causes severe kidney damage. Glutathione (GSH), a tripeptide comprising L-glutamic acid, glycine and L-cysteine, and metallothionein (MT), a cysteine-rich and metal-binding protein, are biologically important protective factors for renal toxicity by inorganic mercury. However, the relationship between GSH and MT for the prevention of renal toxicity by inorganic mercury is unknown. We examined the sensitivity of the mice depleted in GSH by treatment with L-Buthionine-SR-sulfoximine (L-BSO), and MT-I/II null mice genetically deleted for MT-I and MT-II, to inorganic mercury (HgCl₂). Kidney damage was not induced in the wild-type mice treated with HgCl₂ (30 µmol/kg). In the MT-I/II null mice, renal toxicity was induced by HgCl₂ at a dose of 30 µmol/kg but not 1.0 µmol/kg. All GSH-depleted mice of both strains were dead following the injection of HgCl₂ (30 µmol/kg). GSH-depleted wild-type mice treated with HgCl₂ (1.0 µmol/kg) developed kidney damage similar to MT-I/II null mice treated with HgCl₂ (30 µmol/kg). Moreover, renal toxicity induced by HgCl₂ (1.0 µmol/kg) was more severe in GSH-depleted MT-I/II null mice compared with GSH-depleted wild-type mice. The present study found that GSH and MT-I/II play cooperatively an important role in the detoxification of severe kidney damage caused by inorganic mercury. In addition, GSH may act as a primary protective factor against inorganic mercury-induced acute renal toxicity, because GSH-depleted mice were more sensitive to inorganic mercury than MT-I/II null mice.

Early-Life Exposure to Cadmium Triggers Distinct Zn-Dependent Protein Expression Patterns and Impairs Brain Development

The objective of this study was to determine if the brain development impairment induced by early-life exposure to cadmium (Cd) could result from changes in the expression pattern of distinct zinc (Zn)-dependent proteins. For this purpose, adult female rats receiving either tap water, Cd, Zn, or Cd + Zn in their drinking water during gestation and lactation periods were used. After birth, the male offspring were screened for locomotors and sensorial defects. At postnatal day 21 (PND 21), the male pups were sacrificed and their brains, liver, and plasma were taken for chemical, biochemical, and molecular analyses. Our results show that exposure to Cd significantly increased the metal accumulation and decreased Zn concentrations in the brain of male pups from Cd-treated mothers. Besides, Cd exposure reduced significantly the locomotor activity of the offspring in open-field test, the body weight, and the cranio-caudal length at PND21. Insulin-like growth factor-I (IGF-1) levels in the plasma and liver were also decreased in male pups from Cd-treated mothers. Cd-induced brain development disruption was accompanied by a significant increase of the superoxide dismutase (SOD) activity, induction of the metallothionein (MT) synthesis, and, at the molecular level, by an upregulation of Zrt-,Irt-related protein 6 (ZIP6) gene and a significant downregulation of the expression of the Zn transporter 3 (ZnT3) and brain-derived neurotrophic factor (BDNF) genes in the brain. No significant changes on the expression of genes encoding other Zn-dependent proteins and factors such as ZnT1, ZIP12, NF-κB, and Zif268. Interestingly, Zn supplementation provided a total or partial correction of the changes induced by the Cd exposure. These data indicated that changes in expression of ZnT3 and ZIP6 as well as alteration of other transcription factors, such as BDNF, or Zn-dependent proteins, such as SOD and MTs, in response to Cd exposure might be an underlying mechanism of Cd-induced brain development impairment.

Inhibition of di(2-ethylhexyl) phthalate (DEHP)-induced endocrine disruption by co-treatment of vitamins C and E and their mechanism of action

The endocrine disrupting actions of di(2-ethylhexyl) phthalate (DEHP) on testicular functions are postulated to involve excess free radical generation. Thus the aim of this study was to examine the ability of antioxidant vitamins C and E to prevent DEHP-induced testicular disruption in male Sprague-Dawley (SD) rats. SD male rats were administered DEHP alone or DEHP with vitamin C and/or vitamin E for 30 days. DEHP alone increased the levels of testosterone (T) and reduced estradiol (E₂) concentrations. Supplementation with antioxidant vitamins diminished or restored serum T levels noted in DEHP-treated rats to control values. In contrast vitamins C and E increased E₂ levels to control in rats administered DEHP. Antioxidants significantly improved the decreased testicular levels of reduced glutathione and activity of superoxide dismutase compared to DEHP-treatment alone. Co-treatment of vitamins C and E also markedly improved the reduced epididymal sperm head counts and elevated levels of malondialdehyde (MDA) or 8-hydroxydeoxyguanosine (8-OHdG) induced by DEHP treatment. These results support the concept that the adverse actions of DEHP may be related to increased free radical generation while co-treatment with vitamins C and E significantly blocked the actions of DEHP on male testicular functions.

Zinc mitigates renal ischemia-reperfusion injury in rats by modulating oxidative stress, endoplasmic reticulum stress, and autophagy

Oxidative stress is a major factor involved in the pathogenesis of renal ischemia/reperfusion (I/R). Exogenous zinc (Zn) was suggested as a potent antioxidant; however, the mechanism by which it strengthens the organ resistance against the effects of reactive oxygen species (ROS) is not yet investigated. The present study aims to determine whether acute zinc chloride (ZnCl₂ ) administration could attenuate endoplasmic reticulum (ER) stress, autophagy, and inflammation after renal I/R. Rats were subjected to either sham operation (Sham group, n = 6), or 1 hr of bilateral ischemia followed by 2 hr of reperfusion (I/R groups, n = 6), or they received ZnCl₂ orally 24 hr and 30 min before ischemia (ZnCl₂ group, n = 6). Rats were subjected to 1 hr of bilateral renal ischemia followed by 2 hr of reperfusion (I/R group, n = 6). Our results showed that ZnCl₂ enhances renal function and reduces cytolysis (p < 0,05). In addition, it increased significantly the activities of antioxidant enzymes (SOD, CAT, and GPX) and the level of GSH in comparison to I/R (p < 0,05). Interestingly, ZnCl₂ treatment resulted in significant decreased ER stress, as reflected by GRP78, ATF-6,p-eIF-2α, XPB-1, and CHOP downregulaion. Rats undergoing ZnCl₂ treatment demonstrated a low expression of autophagy parameters (Beclin-1 and LAMP-2), which was correlated with low induction of apoptosis (caspase-9, caspase-3, and p-JNK), and reduction of inflammation (IL-1ß, IL-6, and MCP-1) (p < 0,05). In conclusion, we demonstrated the potential effect of Zn supplementation to modulate ER pathway and autophagic process after I/R.

Effects of co-exposure to imidacloprid and gibberellic acid on redox status, kidney variables and histopathology in adult rats

Data on the individual nephrotoxic effects of imidacloprid (IMI) and gibberellic acid (GA₃) are scarce. Moreover, there is a lack of information about their combined effects on the renal tissue. Our study investigated the effects of IMI and GA₃ separately or together on rats kidney. IMI (64 mg/kg bw) was given for 3 weeks by gavage either individually or in combination with GA₃ (200 mg/L) via drinking water. IMI associated or no with GA₃ increased the levels of kidney malondialdehyde, advanced oxidation protein products, protein carbonyls and metallothionein, plasma creatinine, urea, blood urea nitrogen and lactate dehydrogenase activity. A decline of kidney uric acid level and antioxidant status was also observed. All these changes were supported by histopathological observations. Our results highlighted the role of IMI and/or GA₃-induced nephrotoxicity. Co-exposure to IMI and GA₃ exhibited synergism in biochemical kidney variables and histopathology and antagonism in physical and morphological parameters.

Effects of co-exposure to lead and zinc on redox status, kidney variables, and histopathology in adult albino rats

Lead (Pb) is a toxic metal that induces a wide range of biochemical and physiological effects in humans. Oxidative damage has been proposed as a possible mechanism involved in Pb toxicity. The current study was carried out to evaluate the antioxidant activities of zinc (Zn) supplement against lead acetate-induced kidney injury in rats. In this study, adults male rats were treated for 15 days with Pb (0.344 g/kg body weight (bw)) associated or not with Zn (10 mg/kg bw). Our study showed that supplementation with Zn prevented renal dysfunction as indicated by plasma biomarkers (urea, uric acid, creatinine, lactate dehydrogenase, and alkaline phosphatase levels) and oxidative stress-related parameters (thiobarbituric acid reactive substances, protein carbonyl, advanced oxidation protein product, superoxide dismutase, catalase, glutathione peroxidase, and vitamins (A, E)) in kidney tissue. The corrective effect of Zn on Pb-induced kidney nephrotoxicity recovered normal kidney histology. Overall, this study indicates that Zn alleviated the toxic effects of this heavy metal on renal tissue, suggesting its role as a potential antioxidant and nephroprotective agent.

Critical Role of Zinc as Either an Antioxidant or a Prooxidant in Cellular Systems

Zinc is recognized as an essential trace metal required for human health; its deficiency is strongly associated with neuronal and immune system defects. Although zinc is a redox-inert metal, it functions as an antioxidant through the catalytic action of copper/zinc-superoxide dismutase, stabilization of membrane structure, protection of the protein sulfhydryl groups, and upregulation of the expression of metallothionein, which possesses a metal-binding capacity and also exhibits antioxidant functions. In addition, zinc suppresses anti-inflammatory responses that would otherwise augment oxidative stress. The actions of zinc are not straightforward owing to its numerous roles in biological systems. It has been shown that zinc deficiency and zinc excess cause cellular oxidative stress. To gain insights into the dual action of zinc, as either an antioxidant or a prooxidant, and the conditions under which each role is performed, the oxidative stresses that occur in zinc deficiency and zinc overload in conjunction with the intracellular regulation of free zinc are summarized. Additionally, the regulatory role of zinc in mitochondrial homeostasis and its impact on oxidative stress are briefly addressed.

Expression and immunolocalization of metallothioneins MT1, MT2 and MT3 in rat nephron

Rodent kidneys exhibit three isoforms of metallothioneins (MTs), MT1, MT2 and MT3, with poorly characterized localization along the nephron. Here we studied in adult male Wistar rats the renal expression of MTs mRNA by end-point RT-PCR and MT proteins by immunochemical methods The expression pattern of MT1 mRNA was cortex (CO)>outer stripe (OS)=inner stripe (IS)=inner medulla (IM), of MT2 mRNA was IM>CO>IS=OS, and of MT3 mRNA was IM>CO=OS=IM. MT1/2-antibody stained with heterogeneous intensity the cell cytoplasm and nuclei in proximal tubule (PT) and thin ascending limb, whereas MT3-antibody stained weakly the cell cytoplasm in various cortical tubules and strongly the nuclei in all nephron segments. However, the isolated nuclei exhibited an absence of MT1/2 and presence of MT3 protein. In MT1/2-positive PT cells, the intracellular staining appeared diffuse or bipolar, but the isolated brush-border, basolateral and endosomal membranes were devoid of MT1/2 proteins. In the lumen of some PT profiles, the heterogeneously sized MT1/2-rich vesicles were observed, with the limiting membrane positive for NHE3, but negative for V-ATPase, CAIV, and megalin, whereas their interior was positive for CAII and negative for cytoskeleton. They seem to be pinched off from the luminal membrane of MT1/2-rich cells, as also indicated by transmission electron microscopy. We conclude that in male rats, MTs are heterogeneously abundant in the cell cytoplasm and/or nuclei along the nephron. The MT1/2-rich vesicles in the tubule lumen may represent a source of urine MT and membranous material, whereas MT3 in nuclei may handle zink and locally-produced reactive oxygen species.

Copper diethyldithiocarbamate as an inhibitor of tissue plasminogen activator synthesis in cultured human coronary endothelial cells

Recent developments have shown that organic-inorganic hybrid molecules have the potential to provide useful tools for analyzing biological systems. In the case of fibrinolysis, which is the phenomenon whereby fibrin is degraded by plasmin that has been converted from plasminogen via tissue plasminogen activator (t-PA) secreted from vascular endothelial cells, we hypothesized that there may be organic-inorganic hybrid molecules that could be used to analyze the mechanisms by which endothelial fibrinolysis is regulated. In our present study, we found that a copper complex - copper diethyldithiocarbamate (Cu10) - reduces t-PA activity in a conditioned medium of cultured human coronary endothelial cells by inhibiting the t-PA synthesis without changing the synthesis of plasminogen activator inhibitor type 1, which is a t-PA inhibitor. Copper sulfate, the Cu10 ligand, and zinc/iron complexes with the same Cu10 ligand, did not exhibit such biological activity. These results indicate that Cu10 has the potential to provide a useful tool for finding alternative pathways that downregulate endothelial t-PA synthesis.

Sialic acid deficiency is associated with oxidative stress leading to muscle atrophy and weakness in GNE myopathy

Sialic acids are monosaccharides found in terminal sugar chains of cell surfaces and proteins; they have various biological functions and have been implicated in health and disease. Genetic defects of the GNE gene which encodes a critical bifunctional enzyme for sialic acid biosynthesis, lead to GNE myopathy, a disease manifesting with progressive muscle atrophy and weakness. The likely mechanism of disease is a lack of sialic acids. There remains, however, an unexplained link between hyposialylation and the muscle atrophy and weakness. In this study, we found that muscle proteins were highly modified by S-nitrosylation, and that oxidative stress-responsive genes were significantly upregulated, in hyposialylated muscles from human GNE myopathy patients and model mice. In both in vitro and in vivo models, the production of reactive oxygen species (ROS) was elevated with cellular hyposialylation, and increasing overall sialylation by extrinsic sialic acid intake reduced ROS and protein S-nitrosylation. More importantly, the antioxidant, oral N-acetylcysteine led to amelioration of the muscle atrophy and weakness in Gne mutant mice. Our data provide evidence of additional important function of sialic acids as a ROS scavenger in skeletal muscles, expanding our understanding on how sialic acid deficiency contributes to disease pathology, and identify oxidative stress as a therapeutic target in GNE myopathy.

Metal binding functions of metallothioneins in the slugArion vulgarisdiffer from metal-specific isoforms of terrestrial snails

Arion vulgarisis a European slug with a huge potential for accumulating and detoxifying heavy metals.

Reproductive effects of cadmium on sperm function and early embryonic development in vitro

Cadmium is a major environmental toxicant that is released into the atmosphere, water and soil in the form of cadmium oxide, cadmium chloride, or cadmium sulfide via industrial activities, such as the manufacturing of batteries and pigments, metal smelting and refining and municipal waste incineration. In the present study, we investigated the effects of cadmium exposure on sperm quality parameters, fertilization capacity and early embryonic development. Our study showed that in vitro incubation of human or mouse sperms with cadmium for a long time (up to 24 hours) could significantly decreased sperm motility in a concentration- and time-dependent manner. Exposure to cadmium in the environment for a short term (30 min) did not affect sperm motility but significantly reduced in vitro fertilization rate. We also evaluated the effects of cadmium at concentrations of 0.625 μg/ml, and 1.25 μg/ml on early embryonic development in vitro and observed that the blastocyst formation rate dramatically decreased with increasing cadmium concentration. This finding emphasizes the hazardous effects of cadmium on sperm quality as well as on natural embryo development and raises greater concerns regarding cadmium pollution.

Metallothionein prevents doxorubicin cardiac toxicity by indirectly regulating the uncoupling proteins 2

Doxorubicin (Dox) is a broad-spectrum anticancer agent, but its clinical use is restricted due to irreversible cardiac toxicity. Metallothionein (MT) can inhibit Dox-induced cardiac toxicity. Applying a proteomics approach we determined that uncoupling proteins (UCPs) may be implicated in this process. This study was designed to examine the mechanisms of MT against Dox cardiac toxicity and the link between MT and UCP2. In vivo, wild-type (MT^+/+) and MT-I/II null (MT^-/-) mice were given a single dose of Dox (15 mg/kg, i.p.) and sacrificed at 4 days after Dox injection. In vitro, cardiomyocytes were prepared from MT^-/- and MT^+/+ neonatal mice and cardiomyocytes were pretreated with typical antioxidant NAC or the UCP2 inhibitor genipin followed by exposure to Dox. Based on the results, genipin enhanced Dox-induced oxidative injury, particularly in MT^-/- cardiomyocyte. UCP2 levels in MT^-/- mice were significantly lower compared to MT^+/+ mice treated with Dox. Co-immunoprecipitation demonstrated that MT did not directly bind to UCP2. The NAC and Nrf2 activator oltipraz inhibit the decrease of UCP2 expression induced by Dox. Therefore, attenuating free radical damage with UCP2 help MT antagonize the Dox-induced cardiac toxicity, but does not directly bind MT. MT may regulate UCP2 expression by up-regulating Nrf2.

ABC294640, A Novel Sphingosine Kinase 2 Inhibitor, Induces Oncogenic Virus-Infected Cell Autophagic Death and Represses Tumor Growth

Kaposi sarcoma-associated herpes virus (KSHV) is the etiologic agent of several malignancies, including Kaposi sarcoma and primary effusion lymphoma (PEL), which preferentially arise in HIV⁺ patients and lack effective treatment. Sphingosine kinase 2 (SphK2) is a key factor within sphingolipid metabolism, responsible for the conversion of proapoptotic ceramides to antiapoptotic sphingosine-1-phosphate (S1P). We have previously demonstrated that targeting SphK2 using a novel selective inhibitor, ABC294640, leads to the accumulation of intracellular ceramides and induces apoptosis in KSHV-infected primary endothelial cells and PEL tumor cells but not in uninfected cells. In this study, we found that ABC294640 induces autophagic death instead of apoptosis in a KSHV long-term-infected immortalized endothelial cell-line, TIVE-LTC, but not in uninfected TIVE cells, through the upregulation of LC3B protein. Transcriptomic analysis indicates that many genes related to cellular stress responses, cell cycle/proliferation, and cellular metabolic process are altered in TIVE-LTC exposed to ABC294640. One of the candidates, Egr-1, was found to directly regulate LC3B expression and was required for the ABC294640-induced autophagic death. By using a Kaposi sarcoma-like nude mice model with TIVE-LTC, we found that ABC294640 treatment significantly suppressed KSHV-induced tumor growth in vivo, which indicates that targeting sphingolipid metabolism, especially SphK2, may represent a promising therapeutic strategy against KSHV-related malignancies. Mol Cancer Ther; 16(12); 2724-34. ©2017 AACR.

Diabetes Mellitus induces alterations in metallothionein protein expression and metal levels in the testis and liver

Objective

To investigate the effect of diabetes with and without vitamin E treatment on testicular metallothionein (MT) and metal (zinc, copper and iron) changes.

Methods

Diabetes was induced with a single intraperitoneal injection (i.p.) of streptozotocin in rats, and diabetic rats were given Vitamin E by i.p. every other day for 4 weeks. MT protein was measured by the cadmium-haeme assay and metal levels were detected by an atomic absorption spectrophotometer.

Results

Diabetes did not change testicular MT protein, but significantly increased hepatic MT protein. Diabetes significantly decreased testicular copper, but not hepatic copper. Zinc and iron levels were unchanged in both diabetic testis and liver. Vitamin E significantly enhanced both testicular and hepatic MT, and zinc levels in diabetic rats. Vitamin E slightly decreased the copper levels, but did not change the testicular and hepatic iron in diabetic rats.

Conclusions

Testicular MT protein expression was not increased, even though hepatic MT significantly increased independent of metal changes, in diabetic rats. Vitamin E enhanced testicular and hepatic MT, which correlated with increased zinc levels.

Effects of Chronic and Acute Zinc Supplementation on Myocardial Ischemia-Reperfusion Injury in Rats

The present study aims to explore the effects of chronic and acute zinc sulfate supplementation on myocardial ischemia-reperfusion injury in rats. The study registered 50 adult male rats which were divided into five groups in equal numbers as follows: group 1, normal control; group 2, sham; group 3, myocardial ischemia reperfusion (My/IR): the group which was fed on a normal diet and in which myocardial I/R was induced; group 4, myocardial ischemia reperfusion + chronic zinc: (5 mg/kg i.p. zinc sulfate for 15 days); and group 5, myocardial ischemia reperfusion + acute zinc: the group which was administered 15 mg/kg i.p. zinc sulfate an hour before the operation and in which myocardial I/R was induced. The collected blood and cardiac tissue samples were analyzed using spectrophotometric method to determine levels of MDA, as an indicator of tissue injury, and GSH, as an indicator of antioxidant activity. The highest plasma and heart tissue MDA levels were measured in group 3 (p < 0.05). Group 5 had lower MDA values than group 3, while group 4 had significantly lower MDA values than groups 3 and 5 (p < 0.05). The highest erythrocyte GSH values were found in group 4 (p < 0.05). Erythrocyte GSH values in group 5 were higher than those in group 3 (p < 0.05). The highest GSH values in heart tissue were measured in group 4 (p < 0.05). The results of the study reveal that the antioxidant activity inhibited by elevated oxidative stress in heart ischemia reperfusion in rats is restored partially by acute zinc administration and markedly by chronic zinc supplementation.

Identification of ATF-7 and the insulin signaling pathway in the regulation of metallothionein in C. elegans suggests roles in aging and reactive oxygen species

It has been proposed that aging results from the lifelong accumulation of intracellular damage via reactions with reactive oxygen species (ROS). Metallothioneins are conserved cysteine-rich proteins that function as efficient ROS scavengers and may affect longevity. To better understand mechanisms controlling metallothionein expression, the regulatory factors and pathways that controlled cadmium-inducible transcription of the C. elegans metallothionein gene, mtl-1, were identified. The transcription factor ATF-7 was identified in both ethylmethanesulfonate mutagenesis and candidate gene screens. PMK-1 and members of the insulin signaling pathway, PDK-1 and AKT-1/2, were also identified as mtl-1 regulators. Genetic and previous results support a model for the regulation of cadmium-inducible mtl-1 transcription based on the derepression of the constitutively active transcription factor ELT-2. In addition, knockdown of the mammalian homologs of PDK1 and ATF7 in HEK293 cells resulted in changes in metallothionein expression, suggesting that this pathway was evolutionarily conserved. The insulin signaling pathway is known to influence the aging process; however, various factors responsible for affecting the aging phenotype are unknown. Identification of portions of the insulin signaling pathway as regulators of metallothionein expression supports the hypothesis that longevity is affected by the expression of this efficient ROS scavenger.

The effect of ozone on the expression of metallothionein in tissues of rats chronically exposed to cadmium

Our aims were to evaluate the expression of metallothionein (MT) in an experimental rat model which experienced chronic exposure to cadmium (Cd) and to measure its expression after ozone therapy (OT) or oxygen (Ox) in the same model, as compared to the control group, which was exposed to neither cadmium nor ozone. Forty male Wistar rats were divided into 5 groups: control, Cd, Cd and Ox, Cd and Oz, and Oz. During our research, Cd concentration (ASA) and MT concentration (ELISA) were determined in supernatants of the kidneys, liver and pancreas. SDS-PAGE analyses and immunohistochemical localization were used to evaluate the level of MT expression in the tissue. In rats intoxicated with Cd, the highest concentration of both Cd and MT was observed in the kidneys and liver, with a significantly lower concentration measured in the pancreas. Ozone therapy reduces the accumulation of cadmium in the liver and kidneys, resulting in a reduced expression of metallothionein in those tissues.

Effects of acrylamide graded doses on metallothioneins I and II induction and DNA fragmentation: Bochemical and histomorphological changes in the liver of adult rats

The present study investigates the toxic effects of acrylamide (ACR) administered to rats at two doses on (i) oxidative stress and disruption of pro-oxidant/antioxidant balance in hepatic cells and (ii) its correlation with metallothioneins (MTs) genes expression, DNA damage and histomorphological changes. Treated rats with 20 and 40 mg/kg body weight of ACR led to an increase in malondialdehyde, hydrogen peroxide, advanced oxidation protein products, protein carbonyl levels as well as an alteration in the antioxidant status. Total MT content in the liver and MT I and MT II genes induction were increased. Plasma transaminases activities, albumin, total protein and glucose levels were also increased, while alkaline phosphatase activity was decreased. Moreover, total cholesterol (TC), triglyceride, low-density lipoprotein cholesterol (LDL-C) levels, TC/high-density lipoprotein cholesterol (HDL-C) and LDL-C/HDL-C ratios were increased, while HDL-C decreased in a dose-dependent manner. A random DNA degradation was observed only in the liver of ACR-treated rats with the highest dose. These changes were confirmed by histopathological observations.

Metallothioneins regulate the adipogenic differentiation of 3T3-L1 cells via the insulin signaling pathway

Knockout of metallothionein (MT) genes contributes to a heavier body weight in early life and the potential to become obese through the intake of a high fat diet (HFD) in mice. It has thus been suggested that MT genes regulate the formation of adipose tissue, which would become the base for later HFD-induced obesity. We evaluated the fat pads of mice during the lactation stage. The fat mass and adipocyte size of MT1 and MT2 knockout mice were greater than those of wild type mice. Next, we assayed the ability of small interfering RNA (siRNA) to silence MT genes in the 3T3-L1 cell line. The expressions of MT1 and MT2 genes were transiently upregulated during adipocyte differentiation, and the siRNA pretreatment led to the suppression of the expression of both MT mRNAs and proteins. The MT siRNA promoted lipid accumulation in adipocytes and caused proliferation of post-confluent preadipocytes; these effects were suppressed by an inhibitor of phosphatidylinositol 3-kinase (LY294002). In addition, MT siRNA promoted insulin-stimulated phosphorylation of Akt, a downstream kinase of the insulin signaling pathway. Enhanced lipid accumulation in 3T3-L1 cells resulting from MT-gene silencing was inhibited by pretreatment with an antioxidant, N-acetylcysteine, used as a substitute for antioxidant protein MTs. These results suggest that interference in MT expression enhanced the activation of the insulin signaling pathway, resulting in higher lipid accumulation in 3T3-L1 adipocytes.

Carbon Tetrachloride-Induced Nephrotoxicity in Mice Is Prevented by Pretreatment with Zinc Sulfate

Carbon tetrachloride (CCl4) is commonly used as a chemical inducer of experimental liver injury. In addition, many studies showed that CCl4 can induce kidney damage. In the current study, we evaluated the protective effect of zinc (Zn) against CCl4-induced nephrotoxicity. We hypothesized that this protective effect would result from the ability of Zn to serve as an inducer of metallothionein (MT), a known endogenous scavenger of free radicals. We administered Zn (as ZnSO4) 50 mg/kg subcutaneously once daily for 3 successive days prior to a single intraperitoneal administration of CCl4 4 g/kg in male ddY mice. Our results showed that Zn pretreatment significantly decreased creatinine and blood urea nitrogen levels and reduced renal histopathological damage at 6 h post-CCl4 injection, observations consistent with enhanced antioxidative activity in the kidney. Moreover, kidney MT levels in the Zn+CCl4-treated group decreased by greater than 70% compared with levels in the Zn-alone group, implying that MT was consumed by CCl4-induced radicals. These findings suggest that prophylaxis with Zn protects mice from CCl4-induced acute nephrotoxicity, presumably by induction of MT, which in turn scavenges radicals induced by CCl4 exposure.

Origin, Function, and Fate of Metallothionein in Human Blood

Toxic heavy metals, toxic organic compounds, reactive oxygen species (ROS), infections, and temperature are well-known metallothionein (MT) inducers in human blood. The current review aims to summarize synthesis, function, and fate of human blood MT in response to the known MT inducers. Part of the MTs that are synthesized in different organs such as the liver, kidney, and spleen is transported and stored in different blood cells and in plasma. Cells of the circulatory system also synthesize MT. From the circulation, MT returns to the kidney where the metal-bound MTs are degraded to release the metal ion that in turn induces MT expression therein. The blood MTs play important roles in metal detoxification, transportation, and storage. By neutralizing ROS, MTs protect blood cells from oxidative stress-induced cytotoxicity and genotoxicity. Arguably, MTs are also involved in immune suppression. Given the permeating distribution of blood MT throughout the body as well as its diverse role in the protection against harmful environmental factors and in metal homeostasis, MT could be better recognized as a major public health protein.

Telomere damage and redox status alterations in free-living passerines exposed to metals

Telomere length may reflect the expected life span and possibly individual quality. Environmental stressors are known to increase oxidative stress and accelerate telomere attrition: however the interactions between redox status and telomere dynamics are not fully understood. We investigated whether exposure to heavy metal pollution is associated with oxidative stress and telomere damage in two insectivorous passerines, the Great tit (Parus major) and the Pied flycatcher (Ficedula hypoleuca). We were also interested to know whether within-brood competition could influence the nestling redox status or telomere length. Breeding females and nestlings were sampled near the point pollution source and compared to birds in non-polluted control zone. We measured heavy metal concentrations, calcium, metallothioneins, telomere lengths and redox status (oxidative damage, and enzymatic and non-enzymatic antioxidants) in liver samples. Great tit nestlings in the polluted zone had significantly shorter telomeres compared to those in the unpolluted control zone. In addition, those great tit nestlings that were lighter than their average siblings, had shorter telomeres compared to the heavier ones. In pied flycatchers neither pollution nor growth stress were associated with telomere length, but adult females had significantly shorter telomeres compared to the nestlings. All the results related to redox status varied remarkably among the species and the age groups. In both species antioxidants were related to pollution. There were no significant associations between redox status and telomere length. Our results suggest that wild birds at a young age are vulnerable to pollution and growth stress induced telomere damage. Redox status seems to interact with pollution and growth, but more studies are needed to clarify the underlying physiological mechanisms of telomere attrition. Our study highlights that all the observed associations and differences between the sampling zones varied depending on the species, age, and degree of exposure to pollution.

Multi-Biomarker Responses After Exposure to Pollution in the Mediterranean Mussels (Mytilus galloprovincialis L.) in the Aegean Coast of Turkey

In this study, sublethal effects on the Mediterranean mussels (Mytilus galloprovincialis L.) collected from the Aegean coast of Turkey were determined. Enzymes such as glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), and acetylcholinesterase (AChE), metallothionein (MT) mRNA expressions, thiobarbituric acid reactive substances (TBARS) contents, determination of 14 heavy metals and micronucleus frequency were selected as multibiomarkers. Results show that heavy metals and an increase in the level of MT gene expression have been determined in tissues of mussels collected from all stations. The GST, SOD and CAT enzymes were increased in mussels of Aliaga and Old Foca, compared to the mussels of Urla, while it was showed inhibition at AChE levels. Extensive LP is determined on mussels of Aliaga. It was determined that mussels in Aliaga region have exposed more oxidative stress than Old Foca and Urla. These biomarkers were carried out for the first time in these stations to assess environmental quality.

Metallothionein-3 Is a Component of a Multiprotein Complex in the Mouse Brain

Metallothlonein (MT)-3, originally called growth inhibitory factor (GIF), was initially identified through its ability to Inhibit the growth of neuronal cells in the presence of brain extract. MT-3 is the brain specific isoform of the MT family whose specific biological activity associates it with neurological disorders. Indeed, studies report that MT-3 is decreased by ~30% in brains of patients with Alzheimer disease (AD). Furthermore, many lines of evidence suggest that MT-3 engages in specific protein interactions. To address this, we conducted Immunoaffinity chromatography experiments using an immobilized anti-mouse MT-3 antibody. We identified five associated proteins from the pool of sixteen recovered using mass spectrometry and tandem mass spectrometry after in-gel trypsin digestion of bands from the affinity chromatography. The proteins identified were: heat shock protein 84 (HSP84), heat shock protein 70 (HSP70), dihydropyrimidinase-like protein-2 (DRP-2), creatine kinase (CK) and β-actin. Coimmunoprecipitation experiments, also conducted on whole mouse brain extract using the anti-mouse MT-3 antibody along with commercially available antibodies against HSP84 and CK, confirmed that these three proteins were in a single protein complex. Immunohistochemical experiments were then conducted on the perfused mouse brain that confirmed the in situ colocallzation of CK and MT-3 in the hippocampus region. These data provide new Insights into the involvement of MT-3 in a multiprotein complex, which will be used to understand the biological activity of MT-3 and its role in neurological disease.

Metallothioneins: Mercury Species-Specific Induction and Their Potential Role in Attenuating Neurotoxicity

Metallothionein (MT) proteins are widespread in bacteria, fungi, plants, and eukaryotic species. They are of low molecular weight (6–7 kDa) and of the 60+ amino acid residues, 20 are cysteines. Functions attributed to MTs include the sequestration and dispersal of metal ions, primarily in zinc and copper homeostasis; regulation of the biosynthesis and activity of zinc metalloproteins, most notably zinc-dependent transcription factors; and cellular cytoprotection from reactive oxygen species, ionizing radiation, electrophilic anticancer drugs and mutagens, and metals. Observations on the abundance of MTs within the central nervous system (CNS) and the identification of a brain-specific isoform, MT-III, suggest that it might have important neurophysiological and neuromodulatory functions. Reinforced by the potential Involvement of MT-III in a number of neurodegenerative disorders, the role of MTs in the CNS has become an intense focus of scientific pursuit. This manuscript represents a survey on the ability of MTs to modulate mercury neurotoxicity, a neurotoxin that has been implied to play an etiologic role in Minamata disease, erethism, and autism, just to name a few.

Anti-oxidative functions of mt2 and smtB mRNA expression in the gills and brain of zebrafish (Danio rerio) upon cadmium exposure

There were not any past studies about metallothionein isoforms (smtB and mt2) having anti-oxidative functions on zebrafish after Cd²⁺ exposure. On the other hand, the anti-oxidative enzymatic factors such as superoxide dismutase (sod), glutathione peroxidase (gpx1a), and catalase (cat) are used as references to investigate whether the smtB and mt2 have anti-oxidative responses on the gills and brain of zebrafish after 1-6 h of 0 and 1.78 μM Cd²⁺ exposure. The anti-oxidative system such as sod, cat, and gpx1a mRNA expressions demonstrated a cascade response upon Cd²⁺-induced oxidative stress in the present study. Interestingly, the smtB mRNA expression levels increased by 3.2- to 6.1-fold, and mt2 raised by 4.1- to 11.3-fold in gills at 1 and 3 h after exposure to Cd²⁺, respectively. On the other hand, the smtB mRNA levels increased by 10.6- to 58.6-fold, but mt2 mRNA levels increased by 2.3- to 11.1-fold in brain at 1 and 3 h after exposure to Cd²⁺, respectively. In addition, both tissues showed increased apoptosis levels at 3 h, and recovery after 6 h of Cd²⁺ exposure. From the results, we suggest that both mt2 and smtB play a role in anti-oxidation responses within 6 h after exposure to Cd²⁺. In conclusion, the smtB mRNA levels have a higher response than mt2 in the brain, but both mRNA expressions appear to have a similar pattern in the gill. We suggest that smtB plays an important role to defend oxidative stress in the brain of adult zebrafish upon acute Cd²⁺ exposure.

Contributions of Streptococcus mutans Cnm and PA antigens to aggravation of non-alcoholic steatohepatitis in mice

Streptococcus mutans, a major pathogen of dental caries, can cause infective endocarditis after invading the bloodstream. Recently, intravenous administration of specific S. mutans strains was shown to aggravate non-alcoholic steatohepatitis (NASH) in a mouse model fed a high-fat diet. Here, we investigated the mechanism of this aggravation in a NASH mouse model by focusing on the S. mutans cell surface collagen-binding protein (Cnm) and the 190-kDa protein antigen (PA). Mice that were intravenously administered a S. mutans strain with a defect in Cnm (TW871CND) or PA (TW871PD) did not show clinical or histopathological signs of NASH aggravation, in contrast to those administered the parent strain TW871. The immunochemical analyses demonstrated higher levels of interferon-γ and metallothionein expression in the TW871 group than in the TW871CND and TW871PD groups. Analysis of bacterial affinity to cultured hepatic cells in the presence of unsaturated fatty acids revealed that the incorporation rate of TW871 was significantly higher than those of TW871CND and TW871PD. Together, our results suggest that Cnm and PA are important cell surface proteins for the NASH aggravation caused by S. mutans adhesion and affinity for hepatic cells.

Immunomodulation of cell-penetrating tat-metallothionein for successful outcome of xenotransplanted pancreatic islet

Pancreatic islet transplantation is a promising treatment for treatment of type 1 diabetes; however, transplantation outcomes have been disappointing due to early graft loss that is mediated by many immune responses. Immune cells not only directly damaged islet but also produced reactive oxygen species (ROS), which is highly toxic to islet cells. Metallothionein (MT) can provide protection against oxidative stress by scavenging various ranges of ROS including superoxide, hydroxyl radical, hydrogen peroxide and nitric oxide. For scavenging immune response-induced ROS, cell-penetrating Tat peptide-metallothionein (Tat-MT) was delivered into islets. The viability of Tat-MT-treated islets was not damaged during co-culture with macrophages or ROS-generating paraquat. When Tat-MT-treated islets were xenotransplanted, ROS production was significantly attenuated at the islets. Eventually, the survival time of Tat-MT-treated islets was significantly enhanced without any immunosuppressant medicine. Additionally, we confirmed that the survival time of Tat-MT-treated islets in all animals was dramatically improved when accompanied with low dose immunosuppressive agents (tacrolimus and anti-CD154 monoclonal antibody), indicating that Tat-MT delivery could have synergistic effect with immunosuppressants. Collectively, this new combination therapy of Tat-MT delivery with low dose immunosuppressant would be a powerful remedy for successful outcome of islet xenotransplantation.