Distribution of metallothionein in normal and pathological human skin

Spatial expression of metallothionein, matrix metalloproteinase-1 and Ki-67 in human epidermal wounds treated with zinc and determined by quantitative immunohistochemistry: A randomised double-blind trial

Reepithelialisation is fundamental to wound healing, but our current understanding largely relies on cellular and animal studies. The aim of the present randomised double-blind three-arm controlled trial was to correlate genuine epidermal wound healing with key proteins and topical zinc treatment in humans. Sixty wounds were produced using deroofed suction blisters in 30 healthy volunteers and randomised to topical zinc sulphate (n = 20), placebo (n = 20), or control (n = 20) treatment for 4 days. All wounds with perilesional skin were processed for automatic immunostaining of paraffin tissue sections with monoclonal antibodies against Ki-67, metallothionein (MT) and matrix metalloproteinase (MMP)-1. Protein expression was quantified by automated digital image analysis. Epidermal Ki-67 and MT labelling indices were increased in keratinocytes in the neoepidermis (∼1.1 mm) and at the wound edge (0.5 mm) compared to normal skin. Increased MMP-1 immunostaining was restricted to the neoepidermis. MT was robustly upregulated in the upper dermis of the wounds. Zinc treatment enhanced MMP-1 expression beneath the neoepidermis via paracrine mechanisms and MT under the neoepidermis and in the nonepithelialised wound bed via direct actions of zinc as indicated by the induction of MT2A mRNA but not MMP-1 mRNA in cultured normal human dermal fibroblasts by zinc sulphate. The present human study demonstrates that quantitative immunohistochemistry can identify proteins involved in reepithelialisation and actions of external compounds. Increased dermal MT expression may contribute to the anti-inflammatory activities of zinc and increased MMP-1 levels to promote keratinocyte migration.

Zinc in Keratinocytes and Langerhans Cells: Relevance to the Epidermal Homeostasis

In the skin, the epidermis is continuously exposed to various kinds of external substances and stimuli. Therefore, epidermal barriers are crucial for providing protection, safeguarding health, and regulating water balance by maintaining skin homeostasis. Disruption of the epidermal barrier allows external substances and stimuli to invade or stimulate the epidermal cells, leading to the elicitation of skin inflammation. The major components of the epidermal barrier are the stratum corneum (SC) and tight junctions (TJs). The presence of zinc in the epidermis promotes epidermal homeostasis; hence, this study reviewed the role of zinc in the formation and function of the SC and TJs. Langerhans cells (LCs) are one of the antigen-presenting cells found in the epidermis. They form TJs with adjacent keratinocytes (KCs), capture external antigens, and induce antigen-specific immune reactions. Thus, the function of zinc in LCs was examined in this review. We also summarized the general knowledge of zinc and zinc transporters in the epidermis with updated findings.

Differential metallothionein expression in oral lichen planus and amalgam-associated oral lichenoid lesions

Background

Oral lichen planus (OLP) is a chronic inflammatory disease mediated by T cells, which manifests as reticular (white) or erosive (red) lesions, that are eventually painful. Oral lichenoid lesion (OLL) are distinguished from OLP by the presence of precipitating factors. The aim of this study was to evaluate whether the presence of metallothionein, which is involved in anti-apoptotic pathways and the anti-oxidative response, could serve as a differential diagnostic for OLP and OLL.

Material and Methods

We evaluated the expression of metallothionein in 40 cases of OLP and 20 cases of OLL using immunohistochemistry.

Results and Conclusions

White OLP has higher concentrations of metallothionein than red OLP in basal and parabasal layers. Moreover, metallothionein was more frequently observed in the cytoplasm and nuclei of basal cells in OLP patients compared to the same regions of OLL cases. Metallothionein levels are related to OLP severity and may contribute to a differential diagnosis between OLP and OLL.

Key words:Oral lichen planus, oral lichenoid lesions, autoimmune disorders, metallothionein, immunohistochemistry.

Zinc and Skin Disorders

The skin is the third most zinc (Zn)-abundant tissue in the body. The skin consists of the epidermis, dermis, and subcutaneous tissue, and each fraction is composed of various types of cells. Firstly, we review the physiological functions of Zn and Zn transporters in these cells. Several human disorders accompanied with skin manifestations are caused by mutations or dysregulation in Zn transporters; acrodermatitis enteropathica (Zrt-, Irt-like protein (ZIP)4 in the intestinal epithelium and possibly epidermal basal keratinocytes), the spondylocheiro dysplastic form of Ehlers-Danlos syndrome (ZIP13 in the dermal fibroblasts), transient neonatal Zn deficiency (Zn transporter (ZnT)2 in the secretory vesicles of mammary glands), and epidermodysplasia verruciformis (ZnT1 in the epidermal keratinocytes). Additionally, acquired Zn deficiency is deeply involved in the development of some diseases related to nutritional deficiencies (acquired acrodermatitis enteropathica, necrolytic migratory erythema, pellagra, and biotin deficiency), alopecia, and delayed wound healing. Therefore, it is important to associate the existence of mutations or dysregulation in Zn transporters and Zn deficiency with skin manifestations.

Zinc and skin biology

Of all tissues, the skin has the third highest abundance of zinc in the body. In the skin, the zinc concentration is higher in the epidermis than in the dermis, owing to a zinc requirement for the active proliferation and differentiation of epidermal keratinocytes. Here we review the dynamics and functions of zinc in the skin as well as skin disorders associated with zinc deficiency, zinc finger domain-containing proteins, and zinc transporters. Among skin disorders associated with zinc deficiency, acrodermatitis enteropathica is a disorder caused by mutations in the ZIP4 transporter and subsequent zinc deficiency. The triad acrodermatitis enteropathica is characterized by alopecia, diarrhea, and skin lesions in acral, periorificial, and anogenital areas. We highlight the underlying mechanism of the development of acrodermatitis because of zinc deficiency by describing our new findings. We also discuss the accumulating evidence on zinc deficiency in alopecia and necrolytic migratory erythema, which is typically associated with glucagonomas.

Metals and metallothioneins in Morelet's crocodile (Crocodylus moreletii) from a transboundary river between Mexico and Belize

The aim of this study was to determine concentrations of heavy metals (cadmium [Cd] and mercury [Hg]) and metallothioneins (MTs) in blood plasma and caudal scutes of Morelet's crocodile (Crocodylus moreletii) from Rio Hondo, a river and natural border between Mexico and Belize. Three transects of the river (approximately 20 km each) were surveyed in September 2012 and April 2013, and samples were collected from 24 crocodiles from these areas. In blood plasma, Cd (7.6 ± 9.6 ng/ml) was detected in 69 % of samples (n = 9); Hg (12.2 ± 9.2 ng/ml) was detected in 46 % of samples (n = 6); and MTs (10,900 ± 9,400 ng/ml) were detected in 92 % of samples (n = 12). In caudal scutes samples, Cd (31.7 ± 39.4 ng/g) was detected in 84 % of samples (n = 12) and Hg (374.1 ± 429.4 ng/g) in 83 % of samples (n = 20). No MTs were detected in caudal scutes. Hg concentrations in scutes from the Rio Hondo were 2- to 5-fold greater than those previously reported in scutes from other localities in northern Belize. In blood plasma, a significant positive relationship between Hg and body size was observed. Mean concentrations of Cd and MTs in size classes suggest that MTs may be related to Cd exposure. This is the first report of MT presence in crocodile blood.

Metallothionein isoform 3 expression in human skin, related cancers and human skin derived cell cultures

Human skin is a well known target site of inorganic arsenic with effects ranging from hyperkeratosis to dermal malignancies. The current study characterizes the expression of a protein known to bind inorganic, As(3+), metallothionein 3 (MT-3). Expression of this protein was assessed immunohistochemically with a specific MT-3 antibody on human formalin-fixed, paraffin-embedded biopsy specimens in normal skin, squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and melanoma. Assessment in normal skin using nine normal specimens showed moderate to intense MT-3 staining in epidermal karatinocytes with staining extending into the basal cells and moderate to intense staining in melanocytes of nevi. MT-3 immunoexpression was shown to be moderate to intense in 12 of 13 of SCC, low to moderate in 8 of 10 BCC, and moderate to intense in 12 melanoma samples. MT-3 expression in cell culture models (normal human epidermal keratinocytes, normal human melanocytes, and HaCaT cells) showed only trace expression of MT-3, while exposures to the histone deacytalase inhibitor, MS-275, partially restored expression levels. These results indicate that the epidermis of human skin and resulting malignancies express high level of MT-3 and potentially impact on the known association of arsenic exposure and the development of skin disorders and related cancers.

Expression of metallothioneins in cutaneous squamous cell carcinoma and actinic keratosis

Metallothioneins (MT) are low-molecular weight proteins implicated in heavy metal detoxification, zinc and cooper homeostasis and cell protection against free radicals. In variety of cancers MT-overexpression was shown, but there are just a few studies on the role of MT in skin carcinogenesis. Current study was undertaken to evaluate MT and Ki-67 expression in pre-cancerous skin lesions as well as in fully developed skin cancers. 73 squamous cell carcinomas (SCC), 23 actinic keratoses (AK) and 20 normal skin samples were included in the study. In obtained paraffin sections immunohistochemical reactions were performed. MT-expression in SCC (mean 2.89 ± 1.83) was significantly higher than in AK (mean 1.69 ± 1.26)(p = 0.006) and higher than in normal skin (mean 2 ± 0.79) (p = 0.0075). The MT-expression positively correlated with Ki-67 expression (R = 0.28; p = 0.017) in SCC and in AK (R = 0.49; p = 0.018). Various clinico-pathological variables, e.g. morphology, size of lesions and the depth of neoplastic infiltration were not associated to MT-expression in both SCC and AK. The grade of histological differentiation of SCC correlated positively with Ki-67 antigen (p < 0.001) and did not correlate with MT-expression (p = 0.06). Ki-67 expression was higher in SCC and in AK than in healthy skin (p = 0,003). In SCC and in AK expression of Ki-67 antigen correlated positively with MT-expression (respectively p = 0.017 and p = 0.018). MT may serve as a good markers of proliferation in SCC and AK. MT-overexpression in SCC may suggest a potential role of MT in skin carcinogenesis.

Cadmium chloride induces the expression of metallothionein mRNA by endometrial stromal cells and amnion-derived (WISH) cells

BACKGROUND

Metallothionein (MT) is known to bind to metals with high affinity. The potential for MT-1 mRNA expression in endometrial stromal cells (ESC) and amniotic cells in response to cytokines and cadmium chloride (CdCl(2)) was evaluated.

METHODS

Human ESC were cultured and treated with interleukin-1α, 12-O-tetradecanoylphobol 13-acetate (TPA), forskolin, transforming growth factor-β, and CdCl(2). Amnion-derived (WISH) cells were also cultured and treated with the same reagents. The levels of MT mRNA were evaluated by Northern blot analysis in ESC and WISH cells.

RESULTS

In response to treatment with CdCl(2) (0.01-10 μM), the expression of MT mRNA markedly increased in ESC and WISH cells in a dose-dependent manner. On the other hand, the expression of MT mRNA did not increase after treatment with interleukin-1α (1 nM), TPA (10 nM), forskolin (1 μM) or transforming growth factor-β (1 nM) in these cells.

CONCLUSION

These findings indicate that MT expression in ESC and WISH cells is sensitive to the CdCl(2) concentration, which is known to be evaluated in cigarette smokers. The present results suggest that increased levels of MT may affect metal metabolism at the feto-maternal interface.

Comparison of metallothionein-overexpression with sentinel lymph node biopsy as prognostic factors in melanoma

BACKGROUND

Metallothioneins (MT) are ubiquitous, intracellular small proteins with high affinity for heavy metal ions. Immunohistochemical MT overexpression in paraffin-embedded tissues of patients with primary melanoma is associated with poor prognosis. While sentinel lymph node (SLN) biopsy is an established surgical technique for high-risk melanoma patients with predictive value for progression, the benefit of this procedure for the individual patient's overall survival remains unclear.

AIM AND METHODS

We examined the role of MT overexpression in comparison with SLN biopsy in melanoma patients as a prognostic marker for progression and survival. One hundred and fifty-eight (158) patients underwent SLN biopsy due to high-risk melanoma. Primary melanoma specimens were investigated by using a monoclonal antibody against MT on routinely fixed, paraffin-embedded tissues. The patients were followed up (median 37 months); the data of disease free survival and overall survival were calculated with a broad panel of statistical analyses.

RESULTS

Twenty-eight (18%) out of 158 recruited melanoma patients developed metastases, 17 (11%) patients died due to widespread disease. Kaplan-Meier curves gave significant disadvantages for the MT-positive as well as the SLN-positive group for progression and survival. In the Fisher's exact test and Pearson's chi(2)-test MT overexpression was highly significant for progression, whereas SLN biopsy failed significance. In univariate as well as multivariate Cox regression analysis MT overexpression proved an excellent marker for progression (P=0.007 and P=0.009), although the P-values for survival were not significant. In contrast, while in the univariate analysis SLN biopsy did not show significant results for progression it did for survival, and in the multivariate analysis reached a P-value < 0.05 for both measured endpoints.

CONCLUSION

Results corroborate the validity of MT overexpression in primary melanoma as a useful prognostic marker in melanoma patients. Accuracy is comparable and to some degree supplementary to the results of SLN biopsy.

Zinc in wound healing: theoretical, experimental, and clinical aspects

Zinc is an essential trace element in the human body and its importance in health and disease is appreciated. It serves as a cofactor in numerous transcription factors and enzyme systems including zinc-dependent matrix metalloproteinases that augment autodebridement and keratinocyte migration during wound repair. Zinc confers resistance to epithelial apoptosis through cytoprotection against reactive oxygen species and bacterial toxins possibly through antioxidant activity of the cysteine-rich metallothioneins. Zinc deficiency of hereditary or dietary cause can lead to pathological changes and delayed wound healing. Oral zinc supplementation may be beneficial in treating zinc-deficient leg ulcer patients, but its therapeutic place in surgical patients needs further clarification. Topical administration of zinc appears to be superior to oral therapy due to its action in reducing superinfections and necrotic material via enhanced local defense systems and collagenolytic activity, and the sustained release of zinc ions that stimulates epithelialization of wounds in normozincemic individuals. Zinc oxide in paste bandages (Unna boot) protects and soothes inflamed peri-ulcer skin. Zinc is transported through the skin from these formulations, although the systemic effects seem insignificant. We present here the first comprehensive account of zinc in wound management in relation to current concepts of wound bed preparation and the wound-healing cascade. This review article suggests that topical zinc therapy is underappreciated even though clinical evidence emphasizes its importance in autodebridement, anti-infective action, and promotion of epithelialization.

Metallothionein immunostaining in adenoid cystic carcinomas of the salivary glands

Metallothionein (MT) is a protein that has been studied in several tumors as a prognostic factor and as a potential myoepithelial cell marker in breast cancer. The aims of this study were to assess the immunohistochemical staining of MT in adenoid cystic carcinomas of the salivary glands (ACC), and to analyze possible morphological and quantitative variations among the solid, cribriform, and tubular histological subtypes. MT was investigated in 15 cases of ACC using the immunohistochemical technique. All of the cases expressed the MT antigen. This expression was noteworthy in cells depicting myoepithelial differentiation. ACC with predominant tubular pattern presented a significantly lower mean index of MT immunopositivity than did solid or cribriform subtypes, while these two latter groups did not differ in terms of MT expression. Our results suggest that MT may be an important tool for immunolocalization of myoepithelial tumor cells in salivary gland neoplasms.

Isoflavonoid Photoprotection in Mouse and Human Skin Is Dependent on Metallothionein

Previous studies report that selected topical isoflavonoids are immunoprotective in both mice and humans, when applied following UV irradiation. Isoflavonoids have documented antioxidant activity, but their mechanism of immunomodulation remains unclear. This study examines whether photoimmunoprotection by the isoflavonoids might result from their interaction with one cutaneous antioxidant known to modulate UV photodamage, metallothionein (MT). In mice bearing a null mutation for MT-I and -II, we found that immunoprotection by the isoflavonoid 4',7-dihydroxyisoflavane (equol) against solar-simulated UV radiation (SSUV) or exogenous cis-urocanic acid was abrogated. Topical equol did not activate MT expression in normal mouse skin, but markedly enhanced the increase in MT expression in murine epidermis following SSUV irradiation. Normal human skin, unlike murine, expressed MT in the basal epidermis. Following SSUV irradiation, topical application of the related synthetic isoflavonoid NV-07alpha to human skin also markedly enhanced epidermal MT expression. The NV-07alpha has been reported previously to protect humans against the UV suppression of Mantoux reactions. Thus, epidermal MT expression appears to protect against photoimmunosuppression in both human and mouse skin. We speculate that equol and its related derivative NV-07alpha may activate the MT gene synergistically with SSUV, to produce the enhanced immunoprotective effect.

Localization and role of metallothioneins in the olfactory pathway after exposure to mercury vapor

We have investigated the localization and physiological roles of metallothioneins (MTs) in the olfactory pathway after exposure to mercury (Hg0) vapor. Male MT-null and wild-type mice were examined for the distribution of mercury, MT immunoreactivity and MT-III mRNA expression. There were no signs of histological changes in MT-null or wild-type mice. Light and electron microscopy of the samples stained with autometallography demonstrated chronological transfer of exposed mercury granules to the olfactory bulb by way of the olfactory tract. Basal expression of MT-I and -II immunoreactivity was observed in supporting cells, basal cells and acinar cells of the Bowman's gland of the olfactory mucosa in wild-type mice even without mercury exposure. In situ hybridization showed that signals for MT-III mRNA dominated in the olfactory cells of the olfactory mucosa, neurons in the olfactory bulb and those of brain in MT-null and wild-type mice. No difference in these findings was observed between samples taken at any interval after mercury exposure.

Interleukin-6 gene ablation in a transgenic mouse model of malignant skin melanoma

Interleukin (IL)-6 is a pleiotropic cytokine that has been shown to inhibit the growth of early stage and to promote the proliferation of advanced stage melanoma cells in vitro. In patients with metastasizing melanomas, highly increased IL-6 blood levels correlate with a poor response to chemotherapy and a worse overall prognosis, suggesting that IL-6 promotes melanoma progression in vivo. Here, we analyzed the role of IL-6 in melanoma development and progression in a transgenic mouse model. We bred IL-6-deficient mice with MT-ret transgenic animals predisposed for melanomas. While MT-ret transgenic animals develop severe melanosis of the skin and subcutis and subsequent melanomas at an incidence of 80% during their first year of life, MT-ret mice devoid of IL-6 developed preneoplastic melanosis and consecutive melanomas significantly less frequently (47%; P < 0.05). Moreover, the tumors were significantly smaller in the groups of MT-ret mice lacking one (P < 0.05) or both (P < 0.01) copies of the IL-6 gene. Immunoblot analysis revealed that ret transgene expression was not reduced in the skin of mice lacking IL-6, indicating that the observed decrease of melanoma incidence and of tumor sizes was not because of a down-regulation of transgene expression. Taken together, these results indicate that IL-6 enhances both the development of melanoma precursor lesions and the subsequent growth of the resulting tumors in the MT-ret model of melanoma development.

Immunohistochemical localization of metallothionein in chronic pancreatitis

Metallothionein (MT) is a low-molecular weight intracellular protein, rich in sulfhydryl residues, and able to bind bivalent metals. MT, like Zn, is a component of the diversified elements of antioxidant system. Recent studies have shown that reactive oxygen species play a role in the pathogenesis and development of chronic pancreatitis. The aim of the study was to identify immunohistochemically (LSAB2-HRP; DAKOCytomation) the localization of metallothionein and to determine MT expression in 9 patients with chronic pancreatitis. Our studies confirm that MT is present in exocrine and endocrine cells of patients with chronic pancreatitis and chronic pancreatitis with concomitant diabetes. They also indicate increased expression of MT, particularly in acinar cells of the pancreas. This suggests that MT is greatly involved in homeostasis of the pancreas and synthesis of pancreatic hormones.

Zinc-metallothionein genoprotective effect is independent of the glutathione depletion in HaCaT keratinocytes after solar light irradiation

UV radiations are the major environmental factors that induce DNA damage of skin cells either by direct absorption (UVB), or after inducing an oxidative stress (UVA and UVB). Cells maintain a reducing intracellular environment to avoid genomic damage. MTs have been expected not only to control metal homeostasis but also counteract the glutathione (GSH) depletion induced by oxidative stress because of their high thiol content. Induction and redistribution of MTs in cultured human keratinocytes (HaCaT) in response to SSL, is an important cellular defense mechanism against DNA damage. Reduced glutathione (GSH) is another way of cellular protection against UV-induced oxidative stress. This study which extend our previous finding focused on the relation between intracellular GSH and Zn genoprotective effects after solar irradiation. HaCaT cells, depleted or not in GSH by a chemical treatment were used to compare MTs induction by Northern blot, expression by Western blot and localization using immunocytochemistry. Zn genoprotection experiments after SSL irradiation was carried out by the comet assay. We demonstrated that in absence of GSH, Zn-MTs could protect DNA after SSL irradiation and that GSH depletion has no effect on MTs induction and localization. Nuclear Zn-MTs could be responsible for this observed genoprotection in GSH depleted cells. So the GSH/Zn and the MT/Zn systems could be two independent but interacting mechanisms of cellular protection against SSL injury.

Effects of cadmium and zinc on solar-simulated light-irradiated cells: potential role of zinc-metallothionein in zinc-induced genoprotection

Zinc is an essential oligoelement for cell growth and cell survival and has been demonstrated to protect cells from oxidative stress induced by UVA or from genotoxic stress due to UVB. In a recent work we demonstrated that the antioxidant role of zinc could be related to its ability to induce metallothioneins (MTs). In this study we identified the mechanism of zinc protection against solar-simulated light (SSL) injury. Cultured human keratinocytes (HaCaT) were used to examine MTs expression and localization in response to solar-simulated radiation. We found translocation to the nucleus, with overexpression of MTs in irradiated cells, a novel observation. The genoprotective effect of zinc was dependent on time and protein synthesis. DNA damage was significantly decreased after 48 h of ZnCl(2) (100 microM) treatment and is inhibited by actinomycin D. ZnCl(2) treatment (100 microM) led to an intense induction, redistribution, and accumulation of MT in the nucleus of irradiated cells. MT expression correlated with the time period of ZnCl(2) treatment. CdCl(2), a potent MT inducer, did not show any genoprotection, although the MTs were expressed in the nucleus. Overall our findings demonstrate that MTs could be a good candidate for explaining the genoprotection mediated by zinc on irradiated cells.

Metallothionein: early marker in the carcinogenesis of ulcerative colitis-associated colorectal carcinoma

Metallothioneins (MTs) are zinc-binding proteins whose overexpression may lead to sequestration of zinc ions and consequently to functional inactivation of the p53 tumor suppressor gene. The aim of the study was to investigate the potential role of MTs in the carcinogenesis of ulcerative colitis (UC) as well as possible effects on p53 function. The monoclonal antibodies E9 (anti-MT), DO-7, and 1801 (anti-p53) and the polyclonal antibody CM-1 (anti-p53) were used to stain formalin-fixed, paraffin-embedded colon specimens obtained from 14 patients with UC-associated colorectal carcinoma (CAC), 13 with high-grade dysplasia (HGD), 10 with low-grade dysplasia (LGD), and 30 with UC without dysplasia or carcinoma. Statistical significance (p <0.05) was assessed using Fisher's exact test. Positive MT staining (> 20% of tumor, dysplastic, or epithelial cells) was found in most UC and LGD but in only a small percentage of HGD and CAC (p <0.01 for CAC vs. UC and LGD vs. HGD). Positive p53 immunoreactivity was observed predominantly in HGD and CAC but not in LGD and UC (p <0.01 for CAC vs. UC and HGD vs. LGD). In histologically normal tissue neighboring CAC, significant MT expression was found in six of seven specimens with simultaneous lack of p53 expression. MT overexpression may represent an important early step in the development of CAC independent of p53 expression and should be investigated in the long term as an independent cancer risk factor in UC.

Metallothioneins: potential therapeutic aids for wound healing in the skin

Metallothioneins are a family of low molecular weight proteins containing approximately 30 % cysteine. Expression of the metallothionein gene is up-regulated in the skin following topical application of zinc and copper, and in wound margins particularly in regions of high mitotic activity. This induction of metallothionein in the wound margin may reflect its role in promoting cell proliferation and reepithelialiation. The action of metallothioneins in these processes may result from the large number of Zinc-dependent and copper-dependent enzymes required for cell proliferation and matrix remodeling. In addition, selected growth factors may modulate metallothionein gene expression and hence the ability of cells to proliferate. Recent studies suggest that metallothioneins may be an attractive target for development as vulnerary agents.

Proliferation and differentiation of the keratinocytes in hyperplastic epidermis overlying dermatofibroma: immunohistochemical characterization

Epidermal changes overlying dermatofibromas (DFs) have been described as ranging from psoriasiform simple hyperplasia to basaloid hyperplasia sometimes morphologically indistinguishable from superficial basal cell carcinoma (BCC). To characterize epidermal hyperplasia overlying DFs and to determine its association with the disease process, we examined 30 cases of DF showing hyperplastic epidermis. We used nine immunohistochemical markers associated with keratinocyte proliferation or differentiation. In DFs, the dermal metallothionein (MT) expression and immunophenotypic changes with regard to epidermal differentiation varied depending on the stage of lesional evolution of the DFs. Immunostaining for epidermal growth factor receptor (EGFR), MT, and keratin 6 (K6) increased in simple hyperplastic epidermis (SHE) overlying DFs (n = 11), whereas it gradually diminished in basaloid hyperplastic epidermis (BHE) overlying DFs (n = 19). In SHE, there was a significant increase in K14 expression. Among 19 BHE cases, 12 showed premature expression of involucrin and delayed appearance of K1 along with aberrant expression of K14. Conversely, the remaining 7 BHE cases showed a pattern of involucrin and K1 similar to that of normal skin coinciding with decreased or absent dermal MT expression. Loricrin and filaggrin expression in all DFs was the same as that of normal skin. Based on the sparse positivity of Ki-67 in the hyperplastic epidermis overlying DFs, we found that the biologic ability of BHE and SHE was not apparent in the hyperproliferative state observed in psoriasis and BCC. These results suggest that the dermal fibrohistiocytic process may trigger the induction of SHE overlying DFs by an unknown mechanism and then mediate both the abnormal keratinocyte differentiation and the transformation of SHE to BHE through the evolution of the dermal lesions.

Immunohistochemical localization of metallothionein in endometrial lesions

Metallothioneins (MTs) are a group of ubiquitous low-molecular-weight proteins essential for the protection of cells against heavy metal ion toxicity. The immunohistochemical expression of MT was studied by immunohistochemistry using a monoclonal antibody (E9) against a conserved epitope of I and II isoforms in a series of 89 endometrial carcinomas, 34 cases of hyperplasia, and 32 samples of normal endometrium. In secretory phase endometrium, extensive MT expression was detected in most cases (92.4%). In contrast, MT immunoreactivity was confined to small foci in 22.2% of proliferative phase cases. The MT values in normal endometrium were inversely correlated with oestrogen receptor (ER) content (p<0.0001), progesterone receptor (PgR) content and with PCNA (p<0.0001) and MIB1 (p=0.001) scores. In hyperplastic lesions, MT expression was detected only in 3.3% of cases, while in the group of carcinomas it was observed in 23.1%. A statistically significant difference of MT expression was observed between carcinomas and simple hyperplasias (p=0.03). In carcinomas, MT expression was positively correlated with grade (p=0.0065), MIB1 (p=0.022), and p53 (p=0.006) expression, and inversely with PgR (p=0.03). A trend of inverse correlation between MT and ER receptor was also detected (p=0.07). These data suggest that MT expression seems to be under hormonal control in normal endometrium; that it may modify p53 expression; and that it could be used as an additional biological marker indicating aggressive behaviour in endometrial lesions.

Metallothionein in pancreatic endocrine neoplasms

Metallothioneins (MTs) are intracellular proteins that bind to metal ions and are involved in heavy metal homeostasis and detoxification. Pancreatic islets were shown to be positive for zinc-containing matrix metalloproteinase-2 and -9 by immunocytochemical staining. The immunolocalization of matrix metalloproteinases in pancreatic islets prompted us to study further the link between zinc and MT in 34 cases of pancreatic endocrine neoplasms, including insulinomas, glucagonomas, gastrinomas, pancreatic polypeptide-omas, and non-functioning endocrine neoplasms. Four types of islet cells were found to be positive for MT, whereas pancreatic endocrine neoplasms mostly were either weakly positive or negative for MT. The presence of MT in normal islet cells and pancreatic endocrine neoplasms is consistent with the notion that MTs modulate zinc homeostasis and metabolism in pancreatic islet cells and pancreatic endocrine neoplasms as those tissues contain zinc-containing matrix metalloproteinases.

Cutaneous metallothionein induction by ultraviolet B irradiation in interleukin-6 null mice

The mediators of cutaneous metallothionein induction by ultraviolet radiation have not been defined. In this study we sought to identify cytokines that might be involved. We examined the role of interleukin-6, using the IL-6 null (IL-6-/-) mouse, which has been observed to be highly sensitive to ultraviolet radiation damage. Whereas cutaneous metallothionein concentration, measured by radioimmunoassay, began to rise in wild-type (IL-6+/+) mice by 12 h after ultraviolet irradiation, there was a significant delay in the IL-6-/- mice until 48 h after UV irradiation. Immunohistologically, metallothionein appeared in IL-6+/+ mice at 24 h in dermal fibroblasts, and then by 48 h in epidermal basal keratinocytes, with intensity increasing until 72 h, and was coincident with proliferating cell nuclear antigen-positive staining. Corresponding metallothionein expression in IL-6-/- mouse skin was significantly delayed. Serum interleukin-6 was elevated in IL-6+/+ mice following ultraviolet irradiation, with peak concentration at 4 h, but no increase in serum interleukin-1beta was found in either IL-6+/+ or IL-6-/- mice. Interestingly, tumor necrosis factor alpha concentration in serum was elevated at 12 h postirradiation in IL-6+/+ mice, but there was an earlier (at 4 and 8 h) time-dependent increase in tumor necrosis factor alpha in serum of the IL-6-/- mice. Skin zinc and copper concentrations were not altered by ultraviolet irradiation in either IL-6+/+ or IL-6-/- mice. The results suggest that interleukin-6 may be a very early mediator of cutaneous metallothionein induction by ultraviolet radiation, but that this role is possibly assumed by alternative cytokines like tumor necrosis factor alpha when interleukin-6 is deficient.

Signal transduction pathways, and nuclear translocation of zinc and metallothionein during differentiation of myoblasts

The changes in subcellular localization of metallothionein during differentiation were studied in two myoblast cell lines, L6 and H9C2. Addition of insulin like growth factor-I or lowering foetal bovine serum to 1% can induce differentiation of myoblasts to myotubes. Metallothionein and zinc were localized mainly in the cytoplasm in myoblasts but were translocated into the nucleus of newly formed myotubes during early differentiation. In fully differentiated myotubes, metallothionein content was decreased with a cytoplasmic localization. Addition of an inhibitor of mitogen-activated protein kinase, PD 98059, did not affect differentiation but blocked nuclear translocation of metallothionein. LY 294092, an inhibitor of PI3 kinase, and rapamycin, an inhibitor of p70S6 serine/threonine kinase, abolished insulin-like growth factor-I induced differentiation of myoblasts, retained metallothionein in the cytoplasm, and decreased metallothionein content. These results demonstrate that the cytoplasmic-nuclear translocation of metallothionein occurs during the early stage of differentiation of myoblasts to myotubes and can be blocked by inhibition of certain signal transduction pathways. The transient nuclear localization of metallothionein and zinc may be related to a high requirement for zinc for metabolic activities during the early stage of differentiation.

Immunocytochemical localization of metallothionein in human pancreatic islets

Metallothioneins (MTs) are small intracellular proteins that bind to metal ions and are involved in heavy-metal homeostasis and detoxication. Pancreatic islets were previously reported to contain zinc-containing matrix metalloproteinases (MMPs) and inhibitors of metalloproteinases (TIMPs) by immunocytochemical staining. The immunolocalization of MMPs and TIMPs in pancreatic islets prompted us to investigate further the link between zinc and MTs. Both beta and nonbeta islet cells were found to contain MTs by this immunocytochemical staining, suggesting that MTs may be involved in pancreatic hormone synthesis and secretion, in addition to their roles in zinc homeostasis and detoxification.

Thimerosal positivities: patch testing to methylmercury chloride in subjects sensitive to ethylmercury chloride

The aim of this paper was to evaluate whether methylmercury chloride (MeHgCl) aq., when patch tested in a group of thimerosal-positive subjects reacting to ethylmercury chloride (EtHgCl), might be a reliable model for the better understanding of interactions between alkylmercury compounds and the skin. 19 out of 21 consecutive patients who previously had given positive patch-test reactions to both ethylmercury chloride 0.0165% eth.(EtHgCl, 0.615 mM) and MeHgCl 0.031% aq.(1.23 mM), and negative reactions to thiosalicylic acid 0.05% (3.24 mM) aq./eth. 50/50, were repatch tested to 8 microl of MeHgCl 0.031% aq. and to 8 microl of aq. solutions containing MeHgCl mixed with cysteine, glutathione, ZnSO4, MgSO4, MnSO4, ZnCl2, MgCl2 and MnCl2, respectively. The results showed that cysteine, glutathione and Zn(II) salts were able to abolish the positive reactions, demonstrating the rôle played by both thiol groups and Zn(II) itself. Patch tests concomitantly carried out in 16 out of 19 patients to 8 microl of aqueous MeHgCl and to 8 microl of aqueous solutions containing MeHgCl and MeHgCl mixed to fragment 56-61 of metallothionein I (MT I), MT I and MT II-Zn, respectively, revealed that all the MTs tested were able to reduce or to inhibit the reactions, demonstrating the effect of the thiol groups. Due to the close chemical similarities to EtHgCl and to its water solubility, MeHgCl seems to be a suitable model for evaluating the reactivity of alkylmercury compounds in the skin. We speculate that both EtHg- and MeHg-derivatives are xenobiotics with similar reactivity. However, the lack of clinical relevance of the reactions to both alkyl compounds lead us to conclude that, since environmental exposure does not seem to play a pivotal rôle, they probably have mostly to do with compounds included in in the standard series, and are elicited by reduced function of physiological SH chelators.

Annular lichen planus showing a change in metallothionein expression on immunohistochemistry

The immunohistochemical localization of metallothioneins (MTs), low-molecular-weight metal-binding proteins, was investigated in a case of annular lichen planus (LP) that enlarged centrifugally with healing in the centre after a month. The annular lesion was found to exhibit the early, developed and late stages of LP, as judged by the clinical and histopathological findings. Immunostaining for MTs was increased around the lesion, discontinuous around the rim of the erythema and undetectable in the centre of the lesion. MT expression was examined in eight specimens of idiopathic LP. Discontinuous immunostaining for MTs was observed in six specimens and increased staining around the lesion was observed in two specimens. These results suggest that MT expression changes depending on the inflammatory stage of LP. Although the role of MTs in dermatological disease is still unknown, their expression might be related to the pathological process of LP.

Epidermal proliferation of the skin in metallothionein-null mice

Metallothionein (MT) is a low-molecular weight metal-binding protein. Although the physiologic function of MT is not fully known, it is present in various species and various organs including the skin. MT is strongly stained in hyperplastic epidermal tissues in normal skin and in hyperplastic skin lesions, and increased expression of mRNA of the MT gene has been demonstrated in skin stimulated by proliferative agents, suggesting that MT is involved in the proliferation of epidermal keratinocytes. To improve our understanding of the role of MT in epidermal hyperplasia, mice with null mutations in their MT-1 and MT-2 genes were used in this study. We compared the epidermal hyperplasia in MT-null mice and in normal C57BL/6 J mice after treatments with cholera toxin, 12-0-tetradecanoylphorbol-13-acetate, and ultraviolet B irradiation, which stimulate epidermal proliferation. Immunostaining of MT was not detected in the skin of MT-null mice, and these mice developed significantly less epidermal hyperplasia than the normal mice after exposure to each stimulator. We determined the metal contents of skin samples by the proton-induced x-ray emission method. The zinc content of the skin of the MT-null mice was lower than that of the control mice before stimulation. After stimulation of epidermal hyperplasia, MT-null and normal mice showed significantly reduced levels of zinc. These findings indicate that cellular MT is involved in the proliferative process of the epidermis induced by cholera toxin, 12-0-tetradecanoylphorbol-13-acetate, and ultraviolet B light through its regulatory action on the metal metabolism required for cell growth.

Clonal overexpression of metallothionein is induced by somatic mutation in morphologically normal colonic mucosa

Metallothionein (MT) overexpression occurs frequently in human tumours but the underlying mechanism is unknown. Morphologically normal-appearing mucosa from human colorectal carcinoma resection specimens and of the colons of ageing laboratory mice contains scattered single crypts whose cells show uniformly increased MT immunostaining, suggesting that MT overexpression arises directly from random crypt stem cell somatic mutation, followed by colonization of the clonal unit by the mutated progeny. This hypothesis has now been tested by quantifying the frequency of immunocytochemically detectable monocryptal colorectal MT overexpression, 5 and 30 days after injection of 8-week-old mice with a single dose of the mutagen dimethylhydrazine (DMH, 30 mg/kg subcutaneous). Otherwise normal-appearing MT-positive crypts were recorded as either wholly or partially involved by the overexpressing phenotype. Five days after DMH injection, the median frequency of partially involved MT-positive crypts was 11.7 x 10(-4), declining significantly to 1.8 x 10(-4) at 30 days (Mann-Whitney U, P < 0.01). In contrast, the median frequency of wholly involved crypts was 0.2 x 10(-4) at 5 days, increasing significantly (P < 0.005) to 12.9 x 10(-4) at 30 days. The frequency of MT-positive crypts and the time course of evolution of partially involved to wholly involved forms were similar to those described for mutation-induced crypt-restricted loss of glucose-6-phosphate dehydrogenase activity in mice treated with an identical DMH regimen. The findings indicate that cellular MT overexpression can occur as a direct consequence of somatic mutation, either cis-activating mutation(s) of the MT gene itself, or trans-activating mutation(s) of other genes involved in controlling MT expression. This is likely to be an important mechanism underlying MT overexpression in neoplasia. Such mutation-induced aberrant MT expression may be involved in the acquisition of selective cellular growth of survival advantage during tumour progression.

Metallothionein and Fas (CD95) are expressed in squamous cell carcinoma of the tongue

Metallothionein (MT) is a chelator present in myoepithelial cells, whilst the Fas-receptor (APO-1, CD95) has been described primarily in human T Jurkat cells. 20 cases of carcinoma of the tongue were investigated immunocytochemically with regard to MT, Fas and Bcl-2. In normal oral squamous epithelium, MT is located in the basal/parabasal dividing cells only. In well-differentiated nests of carcinomas, MT is observed almost entirely in peripherally located cells. In situ end-labelling indicates apoptosis in the centre of these nests, but not in the peripheral areas. Less-differentiated areas show more general MT-positivity, but little apoptosis. All 24 tumours are Fas-positive, but normal epithelia are mainly negative (P < 0.0001). Bcl-2 protein was sparse in the tumours compared with MT and Fas (P < 0.0001). We thus suggest that MT, possibly due to its chelating properties, may contribute to delaying cells entering apoptosis, both in normal epithelium near the base and in less-differentiated regions of carcinoma. Moreover, Fas may be present in cells of human malignancies, as well as those of established malignant cell lines.

Distribution of metallothionein in cigarette smokers and non-smokers in advanced periodontitis patients

This study evaluated the effect of smoking on periodontal tissue in periodontal patients. Gingival biopsies were taken from the flap during periodontal surgery of 33 male patients with advanced periodontal disease (22 cigarette smokers; 11 non-smokers). Frozen sections were made immediately and used for hematoxylin-eosin and Giemsa staining, and for detection of metallothionein (MT), a free radical scavenger. The expression and distribution of MT in these sections was studied using monoclonal antibody and immunohistochemical staining. The smokers had a large number of infiltrate cells in the gingival epithelium compared with non-smokers. Moreover, samples from the smokers showed high levels of MT in the prickle cell layer of the epithelium. In the non-smokers, basal and prickle cell layers of the gingival epithelium also showed detectable MT. Smokers, however, had a higher metallothionein-positive cell ratio in the prickle cell layer as compared to non-smokers. This increased level of MT in smokers may reflect an attempt to defend against free radicals in the gingiva of smokers. These results suggest that inflammation is much greater in periodontal tissues of cigarette smoking periodontal patients than in non-smoking periodontal patients, and that the defense against free radicals is heightened in smokers' gingiva.

Metallothionein expression in basaloid proliferations overlying dermatofibromas and in basal cell carcinomas

Basaloid proliferations overlying dermatofibromas which morphologically resemble superficial basal cell carcinomas have been interpreted as both reactive/regressive and frankly malignant. Metallothioneins (MTs) are low-molecular-weight proteins with a selective binding affinity for heavy metal ions. MTs has been proposed to represent a biological marker of carcinogenesis and, in a variety of human tumours, a correlation between immunohistochemically overexpression of MT and aggressive clinical behaviour has been shown. In order to clarify the nature of basaloid proliferations overlying dermatofibromas, we examined, immunohistochemically, 10 dermatofibromas with overlying simple hyperplasia, 16 dermatofibromas with overlying basaloid proliferation, and 35 basal cell carcinomas, for expression of MT. In normal epidermis, the basal keratinocytes showed cytoplasmatic MT immunoreactivity. The staining intensity was stronger in the basal cells of the rete ridges, an observation which is in accordance with the high proportion of S-phase cells in this area. Simple hyperplasia showed the same MT expression pattern as normal epidermis. Basaloid proliferations stained like superficial and nodular basal cell carcinomas. Of nodular basal cell carcinomas, 92% (12 of 13) showed decreased/absent MT immunoreactivity, while 86% (six of seven) of infiltrating/morphoea-like basal cell carcinomas showed overexpression of MT (P = 0.001, Fisher's exact test). The results demonstrate that MT overexpression in basal cell carcinomas is correlated with infiltrative growth pattern. The similar expression of MT in basaloid proliferations and 'non-infiltrating' basal cell carcinomas suggests that these lesions share a common change in metabolism and/or differentiation.

Histochemistry of the human hair follicle

Immunohistochemistry of the human hair follicle is of increasing interest in hair research. The data on antigen distribution in the different epithelial and mesenchymal structures of this unique skin appendage are superfluous now. In the present chapter, I will concentrate on selected aspects related to hair follicle differentiation, epithelial-mesenchymal interactions, proliferation and metabolic activity. Hair diseases are common. Not unusually, hair growth and structure reflect systemic disturbances. Basic knowledge of hair anatomy and histochemistry is required for their rational evaluation. Immunohistochemistry is a valuable tool for microanatomy of the hair apparatus. It offers a link between the biochemical data and structural components of hair follicles, which may help to better understand physiology of hair growth and hair diseases.