High positive frequency of antibodies to metallothionein and heat shock protein 70 in sera of patients with metal allergy

Heat Shock Protein 90 (Hsp90) and Hsp70 as Potential Therapeutic Targets in Autoimmune Skin Diseases

Over a hundred different autoimmune diseases have been described to date, which can affect every organ in the body, including the largest one, the skin. In fact, up to one-fifth of the world's population suffers from chronic, noninfectious inflammatory skin diseases, the development of which is significantly influenced by an autoimmune response. One of the hallmarks of autoimmune diseases is the loss of immune tolerance, which leads to the formation of autoreactive lymphocytes or autoantibodies and, consequently, to chronic inflammation and tissue damage. The treatment of autoimmune skin diseases mainly focuses on immunosuppression (using, e.g., corticosteroids) but almost never leads to the development of permanent mechanisms of immune tolerance. In addition, current therapies and their long-term administration may cause serious adverse effects. Hence, safer and more effective therapies that bring sustained balance between pro- and anti-inflammatory responses are still desired. Both intra- and extracellular heat shock proteins (Hsps), specifically well-characterized inducible Hsp90 and Hsp70 chaperones, have been highlighted as therapeutic targets for autoimmune diseases. This review presents preclinical data on the involvement of Hsp90 and Hsp70 in modulating the immune response, specifically in the context of the treatment of selected autoimmune skin diseases with emphasis on autoimmune bullous skin diseases and psoriasis.

Metallothionein and Cadmium Toxicology-Historical Review and Commentary

More than one and a half centuries ago, adverse human health effects were reported after use of a cadmium-containing silver polishing agent. Long-term cadmium exposure gives rise to kidney or bone disease, reproductive toxicity and cancer in animals and humans. At present, high human exposures to cadmium occur in small-scale mining, underlining the need for preventive measures. This is particularly urgent in view of the growing demand for minerals and metals in global climate change mitigation. This review deals with a specific part of cadmium toxicology that is important for understanding when toxic effects appear and, thus, is crucial for risk assessment. The discovery of the low-molecular-weight protein metallothionein (MT) in 1957 was an important milestone because, when this protein binds cadmium, it modifies cellular cadmium toxicity. The present authors contributed evidence in the 1970s concerning cadmium binding to MT and synthesis of the protein in tissues. We showed that binding of cadmium to metallothionein in tissues prevented some toxic effects, but that metallothionein can increase the transport of cadmium to the kidneys. Special studies showed the importance of the Cd/Zn ratio in MT for expression of toxicity in the kidneys. We also developed models of cadmium toxicokinetics based on our MT-related findings. This model combined with estimates of tissue levels giving rise to toxicity, made it possible to calculate expected risks in relation to exposure. Other scientists developed these models further and international organizations have successfully used these amended models in recent publications. Our contributions in recent decades included studies in humans of MT-related biomarkers showing the importance of MT gene expression in lymphocytes and MT autoantibodies for risks of Cd-related adverse effects in cadmium-exposed population groups. In a study of the impact of zinc status on the risk of kidney dysfunction in a cadmium-exposed group, the risks were low when zinc status was good and high when zinc status was poor. The present review summarizes this evidence in a risk assessment context and calls for its application in order to improve preventive measures against adverse effects of cadmium exposures in humans and animals.

Antigenic Targets of Patient and Maternal Autoantibodies in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder whose behavioral symptoms become apparent in early childhood. The underlying pathophysiological mechanisms are only partially understood and the clinical manifestations are heterogeneous in nature, which poses a major challenge for diagnosis, prognosis and intervention. In the last years, an important role of a dysregulated immune system in ASD has emerged, but the mechanisms connecting this to a disruption of brain development are still largely unknown. Although ASD is not considered as a typical autoimmune disease, self-reactive antibodies or autoantibodies against a wide variety of targets have been found in a subset of ASD patients. In addition, autoantibodies reactive to fetal brain proteins have also been described in the prenatal stage of neurodevelopment, where they can be transferred from the mother to the fetus by transplacental transport. In this review, we give an extensive overview of the antibodies described in ASD according to their target antigens, their different origins, and timing of exposure during neurodevelopment.

The Role of Molecular Chaperones (Hspas/Hsp70S) in Oral Health and Oral Inflammatory Diseases: A Review

Heat shock proteins of the 70kDa family (HSPAs/HSP70s) are major molecular chaperones and cytokines of most cells and microbes, extracellular and interstitial fluids, blood, synovial fluids and secretory body fluids like saliva. The induction of human HSPAs plays an important role at cellular level under most stress conditions; whereas microbial HSPAs improve microbial tolerance to environmental changes, and improve virulence and resistance against antimicrobial peptides. Extracellular HSPAs reveal cytoprotective properties and are involved in numerous physiological and pathological events, including modulation of cytokine release and immunity. Accordingly, HSPAs play a role in the maintenance of pulpal health, and the repair of injured dental hard tissues. HSPAs also play a role in stress adaptation of periodontal tissues, and in the maintenance of periodontal and mucosal health including defense against microbes, prevention of mucosal allergic reactions, and facilitation of healing of ulcers and wounds. Despite their advantageous effects maintaining health of several oral tissues, HSPAs are likely to play a role in the disadvantageous amplification of pulpal inflammatory response to bacteria, and in the formation of several periapical inflammatory lesions. HSPAs may also induce gingivitis under certain conditions, and play a role in the progression of periodontal bone defects. HSPAs may also play a role in atopic-type allergic reactions, autoimmune disorders, and haptenation in certain cases. Based on the above data, it can be assumed that HSPAs play an important role in oral defense under healthy conditions; however, their role is somewhat “Janus-faced” under pathological conditions.

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.

The Anisakis Transcriptome Provides a Resource for Fundamental and Applied Studies on Allergy-Causing Parasites

Background

Food-borne nematodes of the genus Anisakis are responsible for a wide range of illnesses (= anisakiasis), from self-limiting gastrointestinal forms to severe systemic allergic reactions, which are often misdiagnosed and under-reported. In order to enhance and refine current diagnostic tools for anisakiasis, knowledge of the whole spectrum of parasite molecules transcribed and expressed by this parasite, including those acting as potential allergens, is necessary.

Methodology/Principal Findings

In this study, we employ high-throughput (Illumina) sequencing and bioinformatics to characterise the transcriptomes of two Anisakis species, A. simplex and A. pegreffii, and utilize this resource to compile lists of potential allergens from these parasites. A total of ~65,000,000 reads were generated from cDNA libraries for each species, and assembled into ~34,000 transcripts (= Unigenes); ~18,000 peptides were predicted from each cDNA library and classified based on homology searches, protein motifs and gene ontology and biological pathway mapping. Using comparative analyses with sequence data available in public databases, 36 (A. simplex) and 29 (A. pegreffii) putative allergens were identified, including sequences encoding ‘novel’ Anisakis allergenic proteins (i.e. cyclophilins and ABA-1 domain containing proteins).

Conclusions/Significance

This study represents a first step towards providing the research community with a curated dataset to use as a molecular resource for future investigations of the biology of Anisakis, including molecules putatively acting as allergens, using functional genomics, proteomics and immunological tools. Ultimately, an improved knowledge of the biological functions of these molecules in the parasite, as well as of their immunogenic properties, will assist the development of comprehensive, reliable and robust diagnostic tools.

Nematodes within the genus Anisakis (i.e. A. simplex and A. pegreffii, also known as herring worms) are the causative agents of the fish-borne gastrointestinal illness known as ‘anisakiasis’, with infections resulting in symptoms ranging from mild gastric forms to severe allergic reactions leading to urticaria, gastrointestinal and/or respiratory signs and/or anaphylaxis (‘allergic anisakiasis’). Despite significant advances in knowledge of the pathobiology of allergic anisakiasis, thus far, the exact number and nature of parasite molecules acting as potential allergens are currently unknown; filling this gap is necessary to the development of robust and reliable diagnostics for allergic anisakiasis which, in turn, underpins the implementation of effective therapeutic strategies. Here, we use RNA-Seq and bioinformatics to sequence and annotate the transcriptomes of A. simplex and A. pegreffii, and, as an example application of these resources, mine this data to identify and characterise putative novel parasite allergens based on comparisons with known allergen sequence data from other parasites and other organisms.

Increased oxidative stress and plasma Hsp70 levels among gasoline filling station attendants

OBJECTIVES

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic derivative of manganese (Mn) and is used as an antiknock agent and octane enhancer in gasoline. In this article, we tested the oxidative stress and heat stress protein (Hsp) 70 levels of gasoline station attendants to explore potential plasma biomarkers. Furthermore, the dose-response relationship was also identified.

METHODS

A total of 144 workers, including 96 petrol fillers and 48 cashiers, participated in the study. Ambient concentrations of benzene, toluene, ethylbenzene, and xylene (BTEX) and Mn were monitored at nine filling stations. During the measuring process, the individual cumulative exposure index was calculated. Plasma oxidative stress and Hsp70 levels were also analysed using enzyme-linked immunosorbent assay.

RESULTS

The BTEX time-weighted average in office areas was significantly lower than in refuelling areas ( p < 0.05). In refuelling areas, the content of Mn ranged from 6.44 μg/m³ to 127.34 μg/m³, which was much higher than that in office areas (3.16-7.22 μg/m³; p < 0.05). Exposed workers had significantly different plasma oxidative stress indicators compared with the control group, respectively: superoxide dismutase (SOD), 39.18 ± 6.05 U/mL versus 52.84 ± 3.87 U/mL; glutathione peroxidase (GSH-Px), 186.07 ± 15.63 U versus 194.38 ± 10.42 U; and malondialdehyde (MDA), 1.68 ± 0.52 nmol/L versus 1.43 ± 0.64 nmol/L (in all comparisons, p < 0.05). Plasma Hsp70 level in the exposed group (2.77 ± 0.64 ng/mL) was significantly higher than in the control group (2.32 ± 0.87 ng/mL; p < 0.05). Furthermore, Hsp70 levels were inversely correlated with the activities of SOD ( r = -0.305) and GSH-Px ( r = -0.302) in the exposed group ( p < 0.05). Moreover, a positive correlation ( r = 0.653) was found between plasma Hsp70 levels and plasma MDA levels ( p < 0.05).

CONCLUSION

Exposure to MMT-containing gasoline may result in increasing reactive oxygen stress among filling station attendants. Plasma Hsp70 levels could be used as a sensitive responsive biomarker for exposed workers.

Significance of serum antibodies against HSP 60 and HSP 70 for the diagnostic of infectious diseases

Heat shock proteins (HSP) represent important antigenic targets for the immune response, playing an important role in the pathology and infectious diseases control. The purpose of this work was to investigate the levels of HSP60 and HSP70 specific antibodies in the bloodstream of patients with different bacterial infections and cancer, in order to evaluate their potential role as diagnosis markers of different infectious diseases. Detection of specific anti-HSP 60 and HSP 70 serum levels was performed by ELISA. Statistical analysis of data by multivariate logistic regression was performed using GraphPadPrism software and statistical tests based on chi-square and Student t-test. High levels of anti-HSP60 were found in patients with localized infections, while the levels of anti- HSP70 were higher in the group with generalized infections. The serum levels of both anti-HSP 60 and anti-HSP70 were significantly increased in patients with Gram-negative bacterial infections, as compared with patients harbouring infections produced by Gram-positive and fungal strains, demonstrating their potential use as additional diagnosis and prognosis markers in infections with this etiology.

Determination of the serum metallothionein (MT)1/2 concentration in patients with Wilson's disease and Menkes disease

We have developed an easy and specific enzyme-linked immunoassay (ELISA) for the simultaneous determination of serum metallothinein-1 (MT-1) and 2 (MT-2) in both humans and experimental animals. A competitive ELISA was established using a specific polyclonal antibody against rat MT-2. The antibody used for this ELISA had exhibited the same cross-reactivity with MT in humans and experimental animals. The NH2 terminal peptide of MT containing acetylated methionine was shown to be the epitope of this antibody. The reactivity of this ELISA system with the liver, kidney and brain in MT1/2 knock-out mice was significantly low, but was normal in an MT-3 knock-out mouse. The lowest detection limit of this ELISA was 0.6ng/ml and the spiked MT-1was fully recovered from the plasma. We investigated the normal range of MT1/2 (25-75%tile) in 200 healthy human serum and found it to be 27-48ng/ml, and this was compared with the serum levels in various liver diseases. The serum MT1/2 levels in chronic hepatitis C (HCV) patients were significantly lower than healthy controls and also other liver diseases. In the chronic hepatitis cases, the MT1/I2 levels increased gradually, followed by the progression of the disease to liver cirrhosis and hepatocellular carcinoma. In particular, we found significantly elevated MT1/2 plasma levels in Wilson's disease patients, levels which were very similar to those in the Long-Evans Cinnamon (LEC) rat (model animal of Wilson's disease). Furthermore, a significantly elevated MT1/2 level was found in patients with Menkes disease, an inborn error of copper metabolism such as Wilson's disease.

Kidney dysfunction and cadmium exposure--factors influencing dose-response relationships

Our early toxicological studies showed that metallothionein (MT) is a protein that carries cadmium (Cd) to the kidney, explaining why Cd exposures during long time periods may give rise to kidney dysfunction. This dysfunction is usually considered to be the critical effect, i.e. the adverse effect that occurs at the lowest exposure level. MT also provides intracellular protection against cadmium toxicity. In studies of population groups in cadmium contaminated areas in China, we investigated factors that affected the relationship between internal dose of Cd, as indicated by blood Cd (BCd) or urinary Cd (UCd), and the prevalence of kidney dysfunction. We found dose-response relationships between UCd and the prevalence of increased levels of biomarkers of renal tubular dysfunction (urinary beta-2-microglobulin, B2M, or N-acetyl-beta-d-glucosaminidase - NAG) or urinary albumin (UAlb), a biomarker of glomerular kidney dysfunction. Two years after Cd intake from contaminated rice was diminished, renal tubular dysfunction appeared unchanged or aggravated among those with higher UCd; Another 8 years later, i.e. 10 years after Cd intake was decreased, the prevalence of renal tubular dysfunction was still increased but UAlb had returned to normal. Factors that influenced the dose-response relationships were: (1) time after maximum exposure. (2) Concomitant exposure to other nephrotoxic agents such as inorganic arsenic. (3) Cd induced metallothionein mRNA levels in peripheral blood lymphocytes, used as a biomarker of the ability of each person, to synthesize MT. (4) The occurrence of increased levels in blood plasma of autoantibodies against MT. The two last points further support a role in humans of MT as a protective protein against tissue damage from cadmium and gives support to previous ideas developed partly in experimental systems.

Anti-metallothionein IgG and levels of metallothionein in autistic children with GI disease

AIM

To assess both serum concentration of metallotionein (MT) and anti-metallothionein (anti-MT) immunoglobulin G (IgG) in autistic children with gastrointestinal (GI) symptoms and controls, and to test the hypothesis that there is an association between the presence of MT, anti-MT IgG, and inflammatory GI disease seen in many children with autistic spectrum disorder (ASD).

SUBJECTS AND METHODS

ELISAs were used to measure serum MT and anti-MT IgG in 41 autistic children with chronic digestive disease (many with ileo-colonic lymphoid nodular hyperplasia [LNH] and inflammation of the colorectum, small bowel, and/or stomach), and 33 controls (17 age-matched autistic children with no GI disease and 16 age-matched children without autism or GI disease).

RESULTS

Ten of 41 autistic children with chronic digestive disease had high serum concentration of MT compared to only one of the 33 controls (p < 0.01). Thirteen of the 41 autistic children with chronic digestive disease had anti-MT IgG compared to only four of 33 controls (p < 0.01). Nine of 10 (90%) of autistic children with GI disease with high MT levels had a regressive onset (compared to the expected 25 of 41, or 61%, in this group) (p < 0.05), whereas only nine of 13 of the autistic children with GI disease and anti-MT IgG had a regressive onset (70%) which was not significantly higher than the expected. We didn't find any correlation between severity of GI disease and MT concentration or anti-MT IgG.

DISCUSSION

These results suggest a relationship between MT, anti-MT IgG and GI disease seen in many ASD individuals.

Expression of substance P, vasoactive intestinal peptide and heat shock protein 70 in nasal mucosal smears of patients with allergic rhinitis: investigation using a liquid-based method

OBJECTIVE

The aim of this study was to investigate expression of the neuropeptides substance P, vasoactive intestinal peptide and heat shock protein 70 in the nasal mucosa cells of patients with seasonal allergic rhinitis, in order to obtain more information on the pathophysiological and immunological role of these markers in allergic rhinitis.

MATERIAL AND METHODS

Nasal epithelium specimens obtained from 42 patients with allergic rhinitis were studied, using Shandon's Papspin liquid-based cytology method. Smears were immunostained with antibodies against substance P, vasoactive intestinal peptide and heat shock protein 70, and the results were correlated with the clinical features of seasonal allergic rhinitis.

RESULTS

A positive reaction for substance P, vasoactive intestinal peptide and heat shock protein 70 was observed in 73.8, 66.7 and 69.0 per cent of the allergic rhinitis mucosal smears, respectively. The Pearson chi-square test showed that 40.5 per cent of the immunostained smears had a positive reaction for one or two of the markers studied (i.e. substance P, vasoactive intestinal peptide or heat shock protein 70), and that 47.6 per cent of the smears had a positive reaction for all the markers (p < 0.0001).

CONCLUSIONS

We found a high level of expression of substance P and vasoactive intestinal peptide in the nasal mucosa smears of patients suffering from allergic rhinitis. This indicates a role for these neuropeptides in the neuroregulation of immunity and hypersensivity in this disease. Furthermore, expression of heat shock protein 70 may contribute to the development of allergic rhinitis.

Plasma metallothionein antibody, urinary cadmium, and renal dysfunction in a Chinese type 2 diabetic population

OBJECTIVE

It has been reported that diabetes may increase the risk of cadmium-induced kidney damage. The presence of metallothionein antibody (MT-Ab) increased the susceptibility for tubular damage among cadmium workers. This study focused on the relationships between levels of MT-Ab, urinary cadmium, and kidney function in a Chinese type 2 diabetic population.

RESEARCH DESIGN AND METHODS

A cross-sectional study was performed on 229 type 2 diabetic patients (92 men and 137 women) who were recruited from two community centers in one district of Shanghai City in China. Information was obtained from interviews, health records, and blood and urine samples.

RESULTS

Levels of the tubular biomarker beta2-microglobulin increased significantly when the levels of MT-Ab and urinary cadmium were elevated in male and female subjects; in contrast, the levels of urinary albumin, a glomerular biomarker, did not display such a pattern. After adjusting for potential confounding covariates, logistic regression showed that the odds ratios (ORs) of tubular dysfunction increased upon 1) increasing the MT-Ab concentration from a low to high level (OR 5.56 [95% CI 2.25-13.73]) and 2) increasing the level of urinary cadmium from <1 to >or=1 microg/g creatinine (3.34 [1.17-9.53]); the OR of patients currently smoking was 3.51 (1.14-10.80) relative to that of those who had never smoked.

CONCLUSIONS

This study proves that the presence of MT-Ab can potentiate tubular dysfunction among diabetic subjects and that patients with high MT-Ab levels are more prone to development of tubular damage.

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.

Assessment of metallothionein and antibodies to metallothionein in normal and autistic children having exposure to vaccine-derived thimerosal

Allergic autoimmune reaction after exposure to heavy metals such as mercury may play a causal role in autism, a developmental disorder of the central nervous system. As metallothionein (MT) is the primary metal-detoxifying protein in the body, we conducted a study of the MT protein and antibodies to metallothionein (anti-MT) in normal and autistic children whose exposure to mercury was only from thimerosal-containing vaccines. Laboratory analysis by immunoassays revealed that the serum level of MT did not significantly differ between normal and autistic children. Furthermore, autistic children harboured normal levels of anti-MT, including antibodies to isoform MT-I (anti-MT-I) and MT-II (anti-MT-II), without any significant difference between normal and autistic children. Our findings indicate that because autistic children have a normal profile of MT and anti-MT, the mercury-induced autoimmunity to MT may not be implicated in the pathogenesis of autism.

Antibodies against heat shock proteins in environmental stresses and diseases: friend or foe?

Heat shock proteins (Hsps) can be found in two forms, intracellular and extracellular. The intracellular Hsps are induced as a result of stress and have been found to be cytoprotective in many instances due to their chaperone functions in protein folding and in protein degradation. The origin and role of extracellular Hsps is less clear. Although they were suspected originally to be released from damaged cells (necrosis), their presence in most normal individuals rather suggests that they have regulatory functions in circulation. As immunodominant molecules, Hsps can stimulate the immune system, leading to the production of autoantibodies recognizing epitopes shared by microbial and human Hsps. Thus, extracellular Hsps can influence the inflammatory response as evidenced by the production of inflammatory cytokines. Antibodies to Hsps have been found under normal conditions but seem to be increased in certain stresses and diseases. Such antibodies could regulate the inflammatory response positively or negatively. Here, we review the literature on the findings of antibodies to Hsps in situations of environmental or occupational stress and in a number of diseases and discuss their possible significance for the diagnosis, prognosis, or pathogenesis of these diseases.

Plasma Metallothionein Antibody and Cadmium-Induced Renal Dysfunction in an Occupational Population in China

It has been reported that anti-metallothionein (a metallothionein antibody) is present in the circulation of healthy subjects and in patients suffering from atopic dermatitis. The aim of this study was to investigate whether cadmium-induced renal dysfunction is related to the presence of the plasma metallothionein antibody (MT-Ab) in workers exposed to cadmium (Cd) occupationally. Plasma metallothionein antibody was determined by enzyme linked immunosorbent assay (ELISA) techniques, and both exposure assessment and risk assessment were conducted in cadmium-exposed workers in China. We demonstrate that there is a significantly increased prevalence of renal dysfunction with respect to the level of urinary cadmium in a dose-dependent manner. We found no significant correlations between the levels of MT-Ab and the external or internal exposure doses of cadmium (p > 0.05), but the levels of MT-Ab did correlate positively with two biomarkers of renal dysfunction-urinary beta2-microglobulin (UB2M; r = 0.218, p < 0.05) and N-acetyl-beta-D-glucosaminidase (UNAG; r = 0.302, p < 0.001)-in the cadmium-exposed workers. Workers who have high levels of MT-Ab display cadmium-induced tubular nephrotoxicity more frequently than those possessing low levels of MT-Ab; odds ratio (OR) 4.2; 95% confidence intervals 1.2-14.5 (p < 0.05). This study suggests that subjects that have higher MT-Ab levels more readily develop cadmium-induced renal dysfunction. Thus, the levels of plasma MT-Ab can be used as a biomarker of susceptibility to renal dysfunction in occupational cadmium exposure.

Subproteomic analysis of metal-interacting proteins in human B cells

Metal-protein interactions are vitally important in all living organisms. Metalloproteins, including structural proteins and metabolic enzymes, participate in energy transfer and redox reactions or act as metallochaperones in metal trafficking. Among metal-associated diseases, T cell mediated allergy to nickel (Ni) represents the most common form of human contact hypersensitivity. With the aim to elucidate disease-underlying mechanisms such as Ni-specific T cell activation, we initiated a proteomic approach to identify Ni-interacting proteins in human B cells. As antigen presenting cells, B cells are capable of presenting MHC-associated Ni-epitopes to T cells, a prerequisite for hapten-specific T cell activation. Using metal-affinity enrichment, 2-DE and MS, 22 Ni-interacting proteins were identified. In addition to known Ni-binding molecules such as tubulin, actin or cullin-2, we unexpectedly discovered that at least nine of these 22 proteins belong to stress-inducible heat shock proteins or chaperonins. Enrichment was particularly effective for the hetero-oligomeric TRiC/CCT complex, which is involved in MHC class I processing. Blue Native/SDS electrophoresis analysis revealed that Ni-NTA-beads specifically retained the complete protein machinery, including the associated chaperonin substrate tubulin. The apparent Ni-affinity of heat shock proteins suggests a new function of these molecules in human Ni allergy, by linking innate and adaptive immune responses.

Metallothionein prevents neurodegeneration and central nervous system cell death after treatment with gliotoxin 6-aminonicotinamide

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) induces significant inflammation and neurodegeneration but also affords neuroprotection against acute traumatic brain injury. This neuroprotection is likely mediated by the IL-6-induced protective factors metallothioneins-I and -II (MT-I+II). Here we evaluate the neuroprotective roles of IL-6 vs. MT-I+II during 6-aminonicotinamide (6-AN)-induced neurotoxicity, by using GFAP-IL6 mice and transgenic mice overexpressing MT-I (TgMT) as well as GFAP-IL6 mice crossed with TgMT mice (GFAP-IL6 x TgMT). 6-AN caused acute damage of brainstem gray matter areas identified by necrosis of astrocytes, followed by inflammatory responses. After 6-AN-induced toxicity, secondary damage was observed, consisting of oxidative stress, neurodegeneration, and apoptotic cell death. We hereby show that the primary injury caused by 6-AN was comparable in wild-type and GFAP-IL6 mice, but MT-I overexpression could significantly protect the brain tissue. As expected, GFAP-IL6 mice showed increased CNS inflammation with more gliosis, macrophages, and lymphocytes, including increased cytokine expression, relative to the other mice. However, GFAP-IL6 mice showed reduced oxidative stress (judged from nitrotyrosine, malondialdehyde, and 8-oxoguanine stainings), neurodegeneration (accumulation of neurofibrillary tangles), and apoptosis (determined from TUNEL and caspase-3). MT-I+II expression was significantly higher in GFAP-IL6 mice than in wild types, which may contribute to the IL-6-induced neuroprotection. In support of this, overexpression of MT-I in GFAP-IL6 x TgMT as well as TgMT mice protected the brainstem tissue significantly from 6-AN-induced toxicity and secondary brain tissue damage. Overall, the results demonstrate that brain MT-I+II proteins are fundamental neuroprotective factors, which in the future may become therapeutic agents.