In vivo manipulation of endogenous metallothionein with a monoclonal antibody enhances a T-dependent humoral immune response

Extracellular metallothionein as a therapeutic target in the early progression of type 1 diabetes

Type 1 diabetes (T1D) is characterized by lymphocyte infiltration into the pancreatic islets of Langerhans, leading to the destruction of insulin-producing beta cells and uncontrolled hyperglycemia. In the nonobese diabetic (NOD) murine model of T1D, the onset of this infiltration starts several weeks before glucose dysregulation and overt diabetes. Recruitment of immune cells to the islets is mediated by several chemotactic cytokines, including CXCL10, while other cytokines, including SDF-1α, can confer protective effects. Global gene expression studies of the pancreas from prediabetic NOD mice and single-cell sequence analysis of human islets from prediabetic, autoantibody-positive patients showed an increased expression of metallothionein (MT), a small molecular weight, cysteine-rich metal-binding stress response protein. We have shown that beta cells can release MT into the extracellular environment, which can subsequently enhance the chemotactic response of Th1 cells to CXCL10 and interfere with the chemotactic response of Th2 cells to SDF-1α. These effects can be blocked in vitro with a monoclonal anti-MT antibody, clone UC1MT. When administered to NOD mice before the onset of diabetes, UC1MT significantly reduces the development of T1D. Manipulation of extracellular MT may be an important approach to preserving beta cell function and preventing the development of T1D.

Metallothionein expression in feline injection site fibrosarcomas

BACKGROUND

Feline injection site fibrosarcoma is an aggressive and infiltrative tumour arising in the background of chronic inflammation. The aim of this study was to evaluate the expression of metallothionein (I-II) in feline injection site fibrosarcomas and to assess its possible relationships with Ki67 index, inflammation score and tumour grade. The study included 40 feline fibrosarcomas, located in the common injection sites (i.e., interscapular area, thigh, flank), constituting archival diagnostic specimens collected between 2019-2020. Tumours were graded histologically according to the newly proposed soft-tissue sarcoma grading system in cats. Immunohistochemistry was performed to evaluate the expression of Ki67 and metallothionein in tumour cells.

RESULTS

The cytoplasmic and sometimes nuclear expression of metallothionein was observed in all tumours grade I, 66.67% of tumours grade II and 55% of tumours grade III. The expression of metallothionein was negatively correlated with tumour grade and inflammation score, while the Ki67 index was positively correlated with tumour grade, inflammation score and necrosis score.

CONCLUSION

The downregulation of MT expression in feline injection site fibrosarcomas seems to be connected with an increase in the inflammatory infiltration, hence tumour progression. This is the first study describing metallothionein expression in feline injection site fibrosarcomas.

Metallothioneins alter macrophage phenotype and represent novel therapeutic targets for acetaminophen-induced liver injury

Acetaminophen (APAP) intoxication is the foremost cause of drug-induced liver failure in developed countries. The only pharmacologic treatment option, N-acetylcysteine (NAC), is not effective for patients who are admitted too late and/or who have excessive liver damage, emphasizing the need for alternative treatment options. APAP intoxication results in hepatocyte death and release of danger signals, which further contribute to liver injury, in part by hepatic monocyte/macrophage infiltration and activation. Metallothionein (MT) 1 and 2 have important danger signaling functions and might represent novel therapeutic targets in APAP overdose. Therefore, we evaluated hepatic MT expression and the effect of anti-MT antibodies on the transcriptional profile of the hepatic macrophage population and liver injury following APAP overdose in mice. Hepatic MT expression was significantly induced in APAP-intoxicated mice and abundantly present in human livers. APAP intoxication in mice resulted in increased serum transaminase levels, extended necrotic regions on liver histology and induced expression of proinflammatory markers, which was significantly less pronounced in mice treated with anti-MT antibodies. Anti-MT antibody therapy attenuated proinflammatory macrophage polarization, as demonstrated by RNA sequencing analyses of isolated liver macrophages and in LPS-stimulated bone marrow-derived macrophages. Importantly, NAC and anti-MT antibodies were equally effective whereas administration of anti-MT antibody in combination with NAC exceeded the efficiency of both monotherapies in APAP-induced liver injury (AILI). We conclude that the neutralization of secreted MTs using a monoclonal antibody is a novel therapeutic strategy as mono- or add-on therapy for AILI. In addition, we provide evidence suggesting that MTs in the extracellular environment are involved in macrophage polarization.

Exosomes from mesenchymal stromal cells reduce murine colonic inflammation via a macrophage-dependent mechanism

Conventional treatments for inflammatory bowel disease (IBD) have multiple potential side effects. Therefore, alternative treatments are desperately needed. This work demonstrated that systemic administration of exosomes from human bone marrow-derived mesenchymal stromal cells (MSC-Exos) substantially mitigated colitis in various models of IBD. MSC-Exos treatment downregulated inflammatory responses, maintained intestinal barrier integrity, and polarized M2b macrophages but did not favor intestinal fibrosis. Mechanistically, infused MSC-Exos acted mainly on colonic macrophages, and macrophages from colitic colons acquired obvious resistance to inflammatory restimulation when prepared from mice treated with MSC-Exos versus untreated mice. The beneficial effect of MSC-Exos was blocked by macrophage depletion. Also, the induction of IL-10 production from macrophages was partially involved in the beneficial effect of MSC-Exos. MSC-Exos were enriched in proteins involved in regulating multiple biological processes associated with the anticolitic benefit of MSC-Exos. Particularly, metallothionein-2 in MSC-Exos was required for the suppression of inflammatory responses. Taken together, MSC-Exos are critical regulators of inflammatory responses and may be promising candidates for IBD treatment.

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.

Detection and Manipulation of the Stress Response Protein Metallothionein

Metallothioneins (MTs) are small molecular weight stress response proteins that play a central role as reservoir of essential divalent heavy metal cations such as zinc and copper, and also can diminish the effects of toxic heavy metals such as mercury and cadmium. Historically, MT has been considered to be an intracellular protein with roles to play in the management of heavy metals, as a regulator of cellular redox potential, and as a buffer of free radicals. Our recent studies have highlighted immunomodulatory role of MT in inflammatory diseases and also in the progression of metastatic cell movement. Hence, manipulation and detection of MT is essential for its possible use as a diagnostic and in therapeutic interventions of chronic inflammation. This review describes procedures used to detect MT using techniques such as western immunoblot, competition ELISA, flow cytometry and immunohistochemistry. Additionally, it also describes the use of a colorimetric cell proliferation assay (CellTiter 96 AQ_ueous One Solution/MTS) to study the proliferative effect of MT. © 2017 by John Wiley & Sons, Inc.

The Physiological Roles of Extracellular Metallothionein

Metallothionein (MT) is a low-molecular-weight protein with a number of roles to play in cellular homeostasis. MT is synthesized as a consequence of a variety of cellular stressors, and has been found in both intracellular compartments and in extracellular spaces. The intracellular pool of this cysteine-rich protein can act as a reservoir of essential heavy metals, as a scavenger of reactive oxygen and nitrogen species, as an antagonist of toxic metals and organic molecules, and as a regulator of transcription factor activity. The presence of MT outside of cells due to the Influence of stressors suggests that this protein may make important contributions as a “danger signal” that influences the management of responses to cellular damage. While conventional wisdom has held that extracellular MT is the result of cell death or leakage from stressed cells, there are numerous examples of selective release of proteins by nontraditional mechanisms, including stress response proteins. This suggests that MT may similarly be selectively released, and that the pool of extracellular MT represents an important regulator of various cellular functions. For example, extracellular MT has effects both on the severity of autoimmune disease, and on the development of adaptive immune functions. Extracellular MT may operate as a chemotactic factor that governs the trafficking of inflammatory cells that move to resolve damaged tissues, as a counter to extracellular oxidant-mediated damage, and as a signal that influences the functional behavior of wounded cells. A thorough understanding of the mechanisms of MT release from cells, the conditions under which MT is released to the extracellular environment, and the ways in which MT Interacts with sensitive cells may both illuminate our understanding of an important control mechanism that operates in stressful conditions, and should indicate new opportunities for therapeutic management via the manipulation of this pool of extracellular MT.

Gene expression analysis of metallothionein and mineral elements uptake in tomato (Solanum lycopersicum) exposed to cadmium

Heavy metals such as Cd are considered to be the most important pollutants in soil contamination. Cd is a non-essential element adversely affecting plant growth and development, and it has caused some physiological and molecular changes. Metallothioneins (MTs) are low molecular weight, cysteine-rich, and metal binding proteins. In this study, we aimed to evaluate the MT gene expression levels and minerals uptake in the tissues of Solanum lycopersicum exposed to Cd. The transcriptional expression of the MT genes was determined by real-time quantitative PCR. The MT genes were regulated by the Cd and the mineral elements uptake changed tissue type and applied doses. The MT1 and MT2 transcript levels increased in the roots, the leaves and the fruits of the tomato. The MT3 and MT4 transcript pattern changed according to the tissue types. The Cd treatment on the growth medium increased the Mg, Ca, and Fe content in both the leaves and fruits of the tomato. However, the Cd affected the mineral levels in the roots depending on the mineral types and doses. Also, the Cd content increased in the roots, the leaves, and the fruits of the tomato, respectively. The results presented in this study show that Cd has synergistic and/or antagonistic effects on minerals depending on the tissue types. These results indicate that the MT1 and MT2 expression pattern increased together with the Mg, Ca, and Fe content in both the leaves and the fruits of the tomato.

Metallothionein differentially affects the host response to Listeria infection both with and without an additional stress from cold-restraint

Acute stress alters anti-bacterial defenses, but the neuroimmunological mechanisms underlying this association are not yet well understood. Metallothionein (MT), a cysteine-rich protein, is a stress response protein that is induced by a variety of chemical, biological, and psychological stressors, and MT has been shown to influence immune activities. We investigated MT's role in the management of anti-bacterial responses that occur during stress, using a C57BL/6 (B6) strain that has targeted disruptions of the Mt1 and Mt2 genes (B6-MTKO), and a B6 strain that has additional copies of Mt (B6-MTTGN). The well-characterized listeriosis model was used to examine immune mechanisms that are altered by a 1-h stress treatment (cold-restraint, CR) administered just prior to bacterial infection. Intriguingly, MT gene doses both greater and lower than that of wild-type (WT) B6 mice were associated with improved host defenses against Listeria monocytogenes (LM). This augmented protection was diminished by CR stress in the MTKO mice, but transgenic mice with additional MT copies had no CR stress-induced increase in their listerial burden. During the transition from innate to adaptive immunity, on day 3 after infection, oxidative burst and apoptosis were assessed by flow cytometric methods, and cytokine transcription was measured by real-time quantitative PCR. MT gene expression and CR-stress affected the expression of IL-6 and TNFα. Additionally, these genetic and environmental modulations altered the generation of ROS responses as well as the number of apoptotic cells in livers and spleens. Although the level of MT altered the listerial response, MT expression was equally elevated by listerial infection with or without CR stress. These results indicate the ability of MT to regulate immune response mechanisms and demonstrate that increased amounts of MT can eliminate the immunosuppression induced by CR.

The influence of biological and environmental factors on metallothionein concentration in the blood

The concentration of metallothionein (MT), a low-molecular-weight protein, is regulated by many factors, primarily metals (zinc, cadmium, copper), cytokines, glucocorticoides and free radicals. These factors are determined by such aspects of human biology as gender, pregnancy and age, as well as by environmental factors including the use of oral contraceptives and cigarette smoking, all which may affect MT levels in the body. The aim of this study was to investigate the influence of these biological and environmental factors on MT concentrations in erythrocyte lysate and in plasma. MT concentrations were determined by a two-step direct enzyme-linked immunosorbent assay. Evaluation of exposure to cigarette smoking was performed by checking cotinine levels in the plasma of subjects. The studies showed higher MT concentrations in both the erythrocyte lysate and plasma of women when compared to men. Furthermore, pregnancy causes an increase of MT concentration in plasma, while oral contraceptives cause an elevated concentration of MT in erythrocyte lysate. Age impacts plasma MT concentrations in men, whereas it does not affect concentrations of MT in erythrocyte lysate.

Metallothionein and stress combine to affect multiple organ systems

Metallothioneins (MTs) are a family of low molecular weight, cysteine-rich, metal-binding proteins that have a wide range of functions in cellular homeostasis and immunity. MTs can be induced by a variety of conditions including metals, glucocorticoids, endotoxin, acute phase cytokines, stress, and irradiation. In addition to their important immunomodulatory functions, MTs can protect essential cellular compartments from toxicants, serve as a reservoir of essential heavy metals, and regulate cellular redox potential. Many of the roles of MTs in the neuroinflammation, intestinal inflammation, and stress response have been investigated and were the subject of a session at the 6th International Congress on Stress Proteins in Biology and Medicine in Sheffield, UK. Like the rest of the cell stress response, there are therapeutic opportunities that arise from an understanding of MTs, and these proteins also provide potential insights into the world of the heat shock protein.

Role of metallothioneins as danger signals in the pathogenesis of colitis

Inflammatory bowel diseases (IBDs) are recurrent intestinal pathologies characterized by a compromised epithelial barrier and an exaggerated immune activation. Mediators of immune cell infiltration may represent new therapeutic opportunities. Metallothioneins (MTs) are stress-responsive proteins with immune-modulating functions. Metallothioneins have been linked to IBDs, but their role in intestinal inflammation is inconclusive. We investigated MT expression in colonic biopsies from IBDs and acute infectious colitis patients and healthy controls and evaluated MT's role in experimental colitis using MT knockout mice and anti-MT antibodies. Antibody potential to target extracellular MT and its mechanism was tested in vitro. Biopsies of patients with active colitis showed infiltration of MT-positive cells in a pattern that correlated with the grade of inflammation. MT knockout mice displayed less severe acute dextran sulphate sodium (DSS)-induced colitis compared to congenic wild-type mice based on survival, weight loss, colon length, histological inflammation and leukocyte infiltration. Chronic DSS-colitis confirmed that Mt1 and Mt2 gene disruption enhances clinical outcome. Blockade of extracellular MT with antibodies reduced F4/80-positive macrophage infiltration in DSS- and trinitrobenzene sulphonic acid-colitis, with a tendency towards a better outcome. Whole-body single-photon emission computer tomography of mice injected with radioactive anti-MT antibodies showed antibody accumulation in the colon during colitis and clearance during recovery. Necrotic and not apoptotic cell death resulted in western blot MT detection in HT29 cell supernatant. In a Boyden chamber migration assay, leukocyte attraction towards the necrotic cell supernatant could be abolished with anti-MT antibody, indicating the chemotactic potential of endogenous released MT. Our results show that human colitis is associated with infiltration of MT-positive inflammatory cells. Since antibody blockade of extracellular MT can reduce colitis in mice, MT may act as a danger signal and may represent a novel target for reducing leukocyte infiltration and inflammation in IBD patients.

The analysis of metallothionein immunoreactivity in stromal fibroblasts and macrophages in cases of uterine cervical carcinoma with respect to both the local and distant spread of the disease

PROBLEM

The tumor microenvironment is made up of tissue that is responsible for the growth and progression of the tumor as well as its ability to initiate metastases. The cancer cells on the front of the tumor together with the macrophages and fibroblasts help to constitute the aggressive phenotype of the tumor. The presence of this aggressive phenotype is indicated by the local infiltration of cancer cells and by the development of lymph node metastases. In cases of uterine cancer, the extent of the local and distant spread of the disease is crucial for determining the type of therapeutic strategy to be applied - surgery alone, surgery followed by radio-chemotherapy, or radio-chemotherapy alone. In the interest of trying to improve the patient's quality of life, different studies supporting the therapeutic model of surgery alone have been conducted. While the cancer cells on the tumor front together with the macrophages and the fibroblasts help to constitute the aggressive phenotype of the tumor, metallothionein (MT) has been shown to have both pro-proliferative and anti-apoptotic activities and to participate in microenvironment remodeling. The aim of the current study was to determine the levels of MT immunoreactivity in the uterine cervical cancer cells as well as in the stromal fibroblasts and macrophages of the tumor microenvironment with respect to the depth of the local invasion and the extent of the distant metastases, so that its potential predictive value as a therapeutic strategy for cervical cancer can be ascertained.

METHODS

We determined the levels of immunoreactivity of MT in a total of 57 carcinoma tissue samples (in the tumor front, in its central part, and in the macrophages and fibroblasts present within the tumor microenvironment). The patients from whom the samples derived were divided into groups with respect to the presence of lymph node metastases (distant spread) and to the depth of invasion (local spread) in relation to the FIGO stage.

RESULTS

Metallothionein immunoreactivity was observed in uterine cervical cancer cells; it was also identified in the fibroblasts and macrophages found within the microenvironments of the tumors of patients suffering from the disease. The MT immunoreactivity level significantly increased within the whole cancer nest in relation to the FIGO stage (intensity of the local spread of the disease). Similarly, the infiltration of MT-positive CAFs and TAMs statistically significantly increased in relation to the FIGO stage.

CONCLUSION

The level of MT immunoreactivity found in the fibroblasts and macrophages within the tumor microenvironment seems to be indicative of the intensity of the remodeled cervical tumor microenvironment, and this in turn may be related to the local advancement of the disease. Moreover, it appears that the intensity of the metallothionein immunoreactivity in the immunoreactivity profile of the cervical tumor may be linked to both the depth of the local invasion and the extent of the distant advancement of the disease.

Analysis of metallothionein and vimentin immunoreactivity in pharyngeal squamous cell carcinoma and its microenvironment

Metallothionein (MT) has been shown to have pro-proliferative anti-apoptotic activity and to be involved in microenvironment remodeling. The aim of this study has been to determine whether the changes in MT and vimentin immunoreactivity observed in cancer and its microenvironment are related to the local spread of the disease. The immunoreactivity levels of both MT and vimentin were evaluated together with CD56 and CD57 antigens in 49 tissue samples taken from patients with squamous cell carcinoma originating from the palatine tonsils and in 20 tissue samples derived from patients with chronic tonsillitis (the reference group). MT immunoreactivity levels were statistically significantly higher in the tissue samples from squamous cell carcinoma than in those of the reference group and also higher in the squamous cell carcinoma samples compared with the stromal samples. Moreover, stromal fibroblasts exhibited high vimentin and MT immunoreactivity levels. Statistically significantly higher MT immunoreactivity levels within the tumor cells were identified in patients with the presence of lymph node metastases in contrast to those patients without such metastases. Vimentin was detected in both the tumor and the stromal tissue samples and presented an interesting pattern of staining strongly expressed within the stroma and the septal architecture of the tumor. The number of CD56- and CD57-positive lymphocytes identified in tissue samples both from squamous cell carcinoma and from the stroma was statistically significantly lower than that in the reference group. MT expression by tumor cells is thus associated with an aggressive phenotype of the tumor and the ability to create metastases.

Strength in numbers: "Omics" studies of C. elegans innate immunity

For more than ten years the nematode Caenorhabditis elegans has proven to be a valuable model for studies of the host response to various bacterial and fungal pathogens. When exposed to a pathogenic organism, a clear response is elicited in the nematode, which is characterized by specific alterations on the transcriptional and translational levels. Early on, researchers took advantage of the possibility to conduct large-scale investigations of the C. elegans immune response. Multiple studies demonstrated that C. elegans does indeed mount a protective response against invading pathogens, thus rendering this small nematode a very useful and simple host model for the study of innate immunity and host-pathogen interactions. Here, we provide an overview of key aspects of innate immunity in C. elegans revealed by recent whole-genome transcriptomics and proteomics studies of the global response of C. elegans to various bacterial and fungal pathogens.

Increased circulating leukocyte numbers and altered macrophage phenotype correlate with the altered immune response to brain injury in metallothionein (MT)-I/II null mutant mice

BACKGROUND

Metallothionein-I and -II (MT-I/II) is produced by reactive astrocytes in the injured brain and has been shown to have neuroprotective effects. The neuroprotective effects of MT-I/II can be replicated in vitro which suggests that MT-I/II may act directly on injured neurons. However, MT-I/II is also known to modulate the immune system and inflammatory processes mediated by the immune system can exacerbate brain injury. The present study tests the hypothesis that MT-I/II may have an indirect neuroprotective action via modulation of the immune system.

METHODS

Wild type and MT-I/II(-/-) mice were administered cryolesion brain injury and the progression of brain injury was compared by immunohistochemistry and quantitative reverse-transcriptase PCR. The levels of circulating leukocytes in the two strains were compared by flow cytometry and plasma cytokines were assayed by immunoassay.

RESULTS

Comparison of MT-I/II(-/-) mice with wild type controls following cryolesion brain injury revealed that the MT-I/II(-/-) mice only showed increased rates of neuron death after 7 days post-injury (DPI). This coincided with increases in numbers of T cells in the injury site, increased IL-2 levels in plasma and increased circulating leukocyte numbers in MT-I/II(-/-) mice which were only significant at 7 DPI relative to wild type mice. Examination of mRNA for the marker of alternatively activated macrophages, Ym1, revealed a decreased expression level in circulating monocytes and brain of MT-I/II(-/-) mice that was independent of brain injury.

CONCLUSIONS

These results contribute to the evidence that MT-I/II(-/-) mice have altered immune system function and provide a new hypothesis that this alteration is partly responsible for the differences observed in MT-I/II(-/-) mice after brain injury relative to wild type mice.

The Potential Role of MT and Vimentin Immunoreactivity in the Remodeling of the Microenvironment of Parotid Adenocarcinoma

A tumor stimulates the remodeling of its microenvironment in order to control and accelerate its own growth and to initiate metastases. To create metastases the tumor cells must first acquire the ability to detach from the main tumor and to adhere to, invade, and degrade the adjacent extracellular matrix. The cells must then be able to enter the lumen of the vessels where they home the distant tissues and organs by forming secondary tumors. The acquisition of this phenotype is related to the phenomenon of epithelial-to-mesenchymal transition. On the molecular level, this process is typified by a change in the expression of epithelial markers and by the enhancement of the expression of mesenchymal markers like vimentin that are responsible for cell migration and invasion. Metallothioneins have been shown to help protect against apoptosis. The expression of MT by tumor cells plays an important and complex role not only because of its pro-proliferative, anti-apoptotic activity, but also because it inhibits the immune response. The aim of the present study was to evaluate the immunoreactivity of vimentin and MT in the salivary gland adenocarcinoma and its stroma in order to observe the phenomenon of stromal remodeling. The tissue samples of salivary gland adenocarcinomas and their stromas and the palatine tonsils which constituted the reference group were obtained during routine surgical procedures. The immunoreactivity of vimentin, metalothionein, CD56, CD57 antigens was evaluated by the immunohistochemistry method in 30 tissue samples of parotid adenocarcinoma. The patient's consent was obtained in each case. A statistically significantly higher level of MT immunoreactivity was observed in the adenocarcinoma tissue slides than in either the stromal slides or the reference slides while no differences in MT immunoreactivity were detected when the stroma and reference tissue slides were compared. A statistically significantly higher vimentin immunoreactivity level was identified in the tumor microenvironment tissue slides than in the tumor tissue slides, and a statistically significantly higher level of vimentin immunoreactivity was identified in the tumor microenvironment slides than in the slides of the reference tissue, while no differences were identified between the adenocarcinoma tissue slides and the reference slides with respect to vimentin immunoreactivity. A statistically significantly higher number of CD56- and CD57-expressing cells were identified in the reference tissue slides than in either the adenocarcinoma or stromal slides. In conclusion, the stroma of salivary gland adenocarcinoma in this study has been characterized by remodeling. The remodeling is represented by the expression of both vimentin and MT and by a deficit of CD57- and CD58-expressing cell infiltration. This situation would seem to be the result of immune tolerance for the tumor developing within the tumor microenvironment. Furthermore, the presence of MT and vimentin immunoreactivity in the fibroblasts of the tumor stroma may constitute a marker of active tissue remodeling.

The two faces of metallothionein in carcinogenesis: photoprotection against UVR-induced cancer and promotion of tumour survival

Metallothionein is a multi-functional protein that protects the host against toxic heavy metals. Under stressful situations it can protect against oxidative damage, contribute to tissue repair, modulate immune responses and limit inflammatory processes. Recently, metallothionein's role in ultraviolet radiation (UVR)-induced injury has been investigated. These studies have shown that when metallothionein is upregulated following exposure to UVR, it can protect against UVR-induced damage and the subsequent development of skin cancer. We propose that this initial protection is achieved through its anti-oxidant role resulting in reduced oxidative stress, reduced apoptosis, reduced NFkappaB activation and enhanced repair of DNA damage. However, once UVR-induced neoplasia has occurred, the cancer cells can hijack metallothionein's protective functions, resulting in increased tumour progression and malignancy. These two discordant sets of attributes are context-dependent, and represent the two faces of metallothionein.

The evaluation of metallothionein expression in nasal polyps with respect to immune cell presence and activity

BACKGROUND

The expression of metallothionein (MT) is involved in acquiring resistance to immune-mediated apoptosis; it is also a negative regulator of the immune response. Nasal polyps are typified by a resistance to immune-mediated apoptosis as well as by excessive immune cell infiltration. RCAS1 (receptor-binding cancer antigen expressed on SiSo cells) is a membrane protein capable of inducing the apoptosis of CTLs and NK cells. The aim of the present study has been to explore the expression of metallothionein with respect to immune cell presence and immune cell activity. In our study, we identified immune cells using CD4 and CD68 antigen expression and evaluated their activity using CD25 antigen expression. We then analyzed metallothionein, RCAS1, CD25, CD4, and CD68 in a sampling of 50 nasal polyps using the immunohistochemistry method. We were able to divide the nasal polyps into three main groups according to their predominant immune cell infiltration: eosinophilic nasal polyps (21 cases), lymphocytic nasal polyps (17 cases), and neutrophilic nasal polyps (12 cases).

RESULTS

In the present study, statistically significant differences between the MT expression in the epithelium and that in the stroma of the nasal polyps along with the accompanying alterations in activation markers on immune cells were found and the number of macrophages in both the eosinophilic and the lymphocytic nasal polyps was assessed. RCAS1-expressing macrophages were found only in the eosinophilic nasal polyps.

CONCLUSION

MT expression seems to favor the survival of nasal polyp epithelial cells in the adjacent area of increasingly cytotoxic immune activity. RCAS1-expressing macrophages seem to participate in creating the immune suppressive microenvironment and so help to sustain local inflammation.

Evidence for a potential role of metallothioneins in inflammatory bowel diseases

Inflammatory bowel diseases (IBDs) are a group of chronic, relapsing, immune-mediated disorders of the intestine, including Crohn's disease and ulcerative colitis. Recent studies underscore the importance of the damaged epithelial barrier and the dysregulated innate immune system in their pathogenesis. Metallothioneins (MTs) are a family of small proteins with a high and conserved cysteine content that are rapidly upregulated in response to an inflammatory stimulus. Herein, we review the current knowledge regarding the expression and potential role of MTs in IBD. MTs exert a central position in zinc homeostasis, modulate the activation of the transcription factor nuclear factor (NF)-kappaB, and serve as antioxidants. In addition, MTs could be involved in IBD through their antiapoptotic effects or through specific immunomodulating extracellular effects. Reports on MT expression in IBD are contradictory but clearly demonstrate a deviant MT expression supporting the idea that these aberrations in IBD require further clarification.

Heavy Metal Ions in Normal Physiology, Toxic Stress, and Cytoprotection

As a group, heavy metals include both those essential for normal biological functioning (e.g., Cu and Zn), and nonessential metals (e.g., Cd, Hg, and Pb). Both essential and nonessential metals can be present at concentrations that disturb normal biological functions, and which evoke cellular stress responses. The cellular targets for metal toxicity include tissues of the kidney, liver, heart, and the immune response and nervous systems. Intriguingly, manipulations of specific metals, their reservoirs, and the cellular stress response can have therapeutic effects on certain diseases. In this minireview, we will consider both the biological responses to stressful levels of heavy metal cations, and experimental and clinical manipulations of these cations as a means to improve human health parameters.

The role of methallothioneins in experimental autoimmune encephalomyelitis and multiple sclerosis

Multiple sclerosis is a chronic inflammatory and demyelinating disease of the central nervous system (CNS) in which oxidative stress plays a pathogenic role. Metallothioneins are antioxidant proteins induced in the CNS under conditions where oxidative stress has taken place, such as tissue injury, stress, and some neurodegenerative diseases, which have been postulated to play a neuroprotective role. In this review we summarize recent progress in understanding the regulation and function of methallothioneins during experimental autoimmune encephalomyelitis and multiple sclerosis.

Metallothioneins are multipurpose neuroprotectants during brain pathology

Metallothioneins (MTs) constitute a family of cysteine-rich metalloproteins involved in cytoprotection during pathology. In mammals there are four isoforms (MT-I - IV), of which MT-I and -II (MT-I + II) are the best characterized MT proteins in the brain. Accumulating studies have demonstrated MT-I + II as multipurpose factors important for host defense responses, immunoregulation, cell survival and brain repair. This review will focus on expression and roles of MT-I + II in the disordered brain. Initially, studies of genetically modified mice with MT-I + II deficiency or endogenous MT-I overexpression demonstrated the importance of MT-I + II for coping with brain pathology. In addition, exogenous MT-I or MT-II injected intraperitoneally is able to promote similar effects as those of endogenous MT-I + II, which indicates that MT-I + II have both extra- and intracellular actions. In injured brain, MT-I + II inhibit macrophages, T lymphocytes and their formation of interleukins, tumor necrosis factor-alpha, matrix metalloproteinases, and reactive oxygen species. In addition, MT-I + II enhance cell cycle progression, mitosis and cell survival, while neuronal apoptosis is inhibited. The precise mechanisms downstream of MT-I + II have not been fully established, but convincing data show that MT-I + II are essential for coping with neuropathology and for brain recovery. As MT-I and/or MT-II compounds are well tolerated, they may provide a potential therapy for a range of brain disorders.

Gene expression influences on metal immunomodulation

Heavy metals in the environment originate from both human activities and natural processes. Exposure to these metals can result in important changes to immune activity. Depending on the metal and dose, these changes can result in enhanced immune function, diminished immune responses, or altered responses that produce autoimmune disease. One of the intriguing aspects of these various phenomena are the multiple points of interaction with cellular machinery at which metals elicit these changes. The individual sections of this review serve to underscore the variety of targets that can be altered by exposure to heavy metals, and provide some comparisons between the effects of specific heavy metals on the immune system. These observations may ultimately lead us to a comprehensive understanding of the mechanisms by which metals alter the immune system, and may enable the development of countermeasures to offset these effects.

A Kampo formula Juzen-taiho-to induces expression of metallothioneins in mice

Juzen-taiho-to (JTX), one of the commonly prescribed traditional Japanese herbal medicines (Kampo), is indicated for adjunctive treatment of cancers and autoimmune diseases. To understand the mechanisms underlying the clinical effects of JTX, the effects of orally administered JTX on the expression of metallothioneins (MTs) were examined in the liver, spleen, small and large intestines of mice. In addition, the expression of MTs in specific pathogen free (SPF) mice was examined to understand the participation of intestinal bacteria in the expression of MTs. JTX enhanced expression of MT-I and -II significantly in the liver of SPF mice. Induction of MT-II expression was observed also in the small intestine. Intestinal bacteria appeared to have no effect on MTs expression. Neither expression of MT-III nor its induction was observed in any tissue. These findings strongly suggest that MTs should mediate at least some effects of JTX in mice.

Metallothionein mediates leukocyte chemotaxis

BACKGROUND

Metallothionein (MT) is a cysteine-rich, metal-binding protein that can be induced by a variety of agents. Modulation of MT levels has also been shown to alter specific immune functions. We have noticed that the MT genes map close to the chemokines Ccl17 and Cx3cl1. Cysteine motifs that characterize these chemokines are also found in the MT sequence suggesting that MT might also act as a chemotactic factor.

RESULTS

In the experiments reported here, we show that immune cells migrate chemotactically in the presence of a gradient of MT. This response can be specifically blocked by two different monoclonal anti-MT antibodies. Exposure of cells to MT also leads to a rapid increase in F-actin content. Incubation of Jurkat T cells with cholera toxin or pertussis toxin completely abrogates the chemotactic response to MT. Thus MT may act via G-protein coupled receptors and through the cyclic AMP signaling pathway to initiate chemotaxis.

CONCLUSION

These results suggest that, under inflammatory conditions, metallothionein in the extracellular environment may support the beneficial movement of leukocytes to the site of inflammation. MT may therefore represent a "danger signal"; modifying the character of the immune response when cells sense cellular stress. Elevated metallothionein produced in the context of exposure to environmental toxicants, or as a result of chronic inflammatory disease, may alter the normal chemotactic responses that regulate leukocyte trafficking. Thus, MT synthesis may represent an important factor in immunomodulation that is associated with autoimmune disease and toxicant exposure.

Screening of hepatocyte proteins binding to complete S protein of hepatitis B virus by yeast-two hybrid system

AIM: To investigate the biological function of complete S protein and to look for proteins interacting with complete S protein in hepatocytes.

METHODS: We constructed bait plasmid expressing complete S protein of HBV by cloning the gene of complete S protein into pGBKT7, then the recombinant plasmid DNA was transformed into yeast AH109 (a type). The transformed yeast AH109 was mated with yeast Y187 (α type) containing liver cDNA library plasmid in 2 ×YPDA medium. Diploid yeast was plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing X-α-gal for selection and screening. After extracting and sequencing of plasmids from positive (blue) colonies, we underwent sequence analysis by bioinformatics.

RESULTS: Nineteen colonies were selected and sequenced. Among them, five colonies were Homo sapiens solute carrier family 25, member 23 (SLC25A23), one was Homo sapiens calreticulin, one was human serum albumin (ALB) gene, one was Homo sapiens metallothionein 2A, two were Homo sapiens betaine-homocysteine methyltransferase, three were Homo sapiens Na⁺ and H⁺ coupled amino acid transport system N, one was Homo sapiens CD81 antigen (target of anti-proliferative antibody 1) (CD81), three were Homo sapiens diazepam binding inhibitor, two colonies were new genes with unknown function.

CONCLUSION: The yeast-two hybrid system is an effective method for identifying hepatocyte proteins interacting with complete S protein of HBV. The complete S protein may bind to different proteins i.e., its multiple functions in vivo.

A role for extracellular metallothioneins in CNS injury and repair

For many years, research focus on metallothioneins, small zinc binding proteins found predominantly within astrocytes in the brain, has centred on their ability to indirectly protect neurons from oxygen free radicals and heavy metal-induced neurotoxicity. However, in recent years it has been demonstrated that these proteins have previously unsuspected roles within the cellular response to brain injury. The aim of this commentary is to provide an overview of the exciting recent experimental evidence from several laboratories including our own suggesting a possible extracellular role for these proteins, and to present a hypothetical model explaining the newly identified function of extracellular metallothioneins in CNS injury and repair.

Metallothionein-I overexpression decreases brain pathology in transgenic mice with astrocyte-targeted expression of interleukin-6

Transgenic expression of interleukin-6 (IL-6) in the CNS under the control of the glial fibrillary acidic protein (GFAP) gene promoter (GFAP-IL6 mice) causes significant damage and alters the expression of many genes, including a dramatic upregulation of metallothionein-I (MT-I). The findings in this report support the idea that the upregulation of MT-I observed in GFAP-IL6 mice is an important mechanism for coping with brain damage. Thus, GFAP-IL6 mice that were crossed with TgMTI transgenic mice (GFAP-IL6xTgMTI) and overexpressed MT-I in the brain showed a decreased upregulation of cytokines such as IL-6 and a diminished recruitment and activation of macrophages and T cells throughout the CNS but mainly in the cerebellum. The GFAP-IL6 mice showed clear evidence of increased oxidative stress, which was significantly decreased by MT-I overexpression. Interestingly, MT-I overexpression increased angiogenesis in GFAP-IL6 mice but not in control littermates. Overall, the results strongly suggest that MT-I+II proteins are valuable factors that protect against cytokine-induced CNS injury.

Metallothionein-1+2 deficiency increases brain pathology in transgenic mice with astrocyte-targeted expression of interleukin 6

Transgenic expression of IL-6 under the control of the GFAP gene promoter (GFAP-IL6 mice) in the CNS causes significant damage and alters the expression of many genes, including the metallothionein (MT) family, especially in the cerebellum. The crossing of GFAP-IL6 mice with MT-1+2 knock out (MTKO) mice provided evidence that the increased MT-1+2 expression normally observed in the GFAP-IL6 mice is an important mechanism for coping with brain damage. Thus, the GFAP-IL6xMTKO mice showed a decreased body weight gain and an impaired performance in the rota-rod test, as well as a higher upregulation of cytokines such as IL-6, IL-1alpha,beta, and TNFalpha and recruitment and activation of macrophages and T cells throughout the CNS but mainly in the cerebellum. Clear symptoms of increased oxidative stress and apoptotic cell death caused by MT-1+2 deficiency were observed in the GFAP-IL6xMTKO mice. Interestingly, MT-1+2 deficiency also altered the expected frequency of the offspring genotypes, suggesting a role of these proteins during development. Overall, the results suggest that the MT-1+2 proteins are valuable factors against cytokine-induced CNS injury.