IL-4 gene expression up-regulated by mercury in rat mast cells: a role of oxidant stress in IL-4 transcription

Supplementation of syringic acid-rich Phrynium pubinerve leaves imparts protection against allergic inflammatory responses by downregulating iNOS, COX-2, and NF-κB expressions

Background

The present study was designed to characterize the role of ethanolic leaf extract of Phrynium pubinerve Blume (EPP) supplement in attenuating allergic inflammation, encouraged by the presence of syringic acid in it, as this phenolic acid is reportedly promising in suppressing serum immunoglobulin E (IgE) and inflammatory cytokine levels.

Materials and methods

HPLC-DAD dereplication analysis was performed to determine the presence of the vital polyphenolic metabolites. The efficacy of EPP against lipopolysaccharide (LPS)-induced inflammation in RAW 264.7 cells was evaluated by measuring its inhibitory effects on NO and ROS/RNS production. The expressions of major inflammation-associated molecules (iNOS, COX-2, NF-κB, IL-6, and TNF-α) in RAW 264.7 cells were assessed through Western blot. Physiological and behavioral changes, BMI, and different biochemical parameters in mice blood serum were investigated in the toxicological assays. Formaldehyde-induced paw edema test in mice was conducted using established animal model. TDI-induced allergic model in mice was carried out to determine different allergy-like symptoms, and differential white blood cell (WBC) counts in blood and bronchoalveolar lavage (BAL) fluid. The intermolecular interaction analysis of the identified major metabolite of EPP with H1R and iNOS was studied by molecular docking.

Results

HPLC-DAD analysis showed the presence of syringic acid (89.19 mg/100 g EPP) and a few other compounds. LPS-induced NO generation was reduced by EPP in a concentration-dependent manner, showing IC₅₀ of 28.20 ± 0.27 μg/mL. EPP exhibited a similar inhibitory effect on ROS/RNS production with IC₅₀ of 29.47 ± 2.19 μg/mL. Western blotting revealed that EPP significantly downregulated the expressions of iNOS, COX-2, NF-κB, IL-6, and TNF-α in RAW 264.7 cells when challenged with LPS. The toxicological assays confirmed the dosage and organ-specific safety of EPP. In the formaldehyde-induced paw edema test, EPP caused a 66.41% reduction in mice paw volume at 500 mg/kg dose. It ameliorated TDI-induced allergy-like symptoms and decreased different inflammatory WBCs in mice's blood and BAL fluid in a dose-dependent manner. Finally, syringic acid demonstrated mentionable intermolecular binding affinity towards H1R (-6.6 Kcal/moL) and iNOS (-6.7 Kcal/moL).

Conclusions

Collectively, considerable scientific reasoning was obtained in favor of the suppressive potential of EPP against allergic inflammatory responses that are proposed to be exerted via the downregulation of iNOS, COX-2, and NF-κB expressions, H1R antagonism and suppression of cytokines, such as IL-6, and TNF-α.

OGG1 in Lung—More than Base Excision Repair

As the organ executing gas exchange and directly facing the external environment, the lungs are challenged continuously by various stimuli, causing the disequilibration of redox homeostasis and leading to pulmonary diseases. The breakdown of oxidants/antioxidants system happens when the overproduction of free radicals results in an excess over the limitation of cleaning capability, which could lead to the oxidative modification of macromolecules including nucleic acids. The most common type of oxidative base, 8-oxoG, is considered the marker of DNA oxidative damage. The appearance of 8-oxoG could lead to base mismatch and its accumulation might end up as tumorigenesis. The base 8-oxoG was corrected by base excision repair initiated by 8-oxoguanine DNA glycosylase-1 (OGG1), which recognizes 8-oxoG from the genome and excises it from the DNA double strand, generating an AP site for further processing. Aside from its function in DNA damage repairment, it has been reported that OGG1 takes part in the regulation of gene expression, derived from its DNA binding characteristic, and showed impacts on inflammation. Researchers believe that OGG1 could be the potential therapy target for relative disease. This review intends to make an overall summary of the mechanism through which OGG1 regulates gene expression and the role of OGG1 in pulmonary diseases.

Effect of ambient air PM2.5-bound heavy metals on blood metal(loid)s and children's asthma and allergy pro-inflammatory (IgE, IL-4 and IL-13) biomarkers

BACKGROUND

We investigated the concentrations of metals in fine particulate matter PM_2.5 in the outdoor air around the home sites of 123 male children from Ahvaz, average age 7.56, along with their blood samples to measure pro-inflammatory responses (Immunoglobulin E and cytokines: IgE, IL-4 and IL-13).

METHODS

We measured 6 metals (As, Cd, Cr, Hg, Ni and Pb) in three Ahvaz's regions including industrial (Padad), vehicle traffic (Golestan) and control (Kianpars).

RESULTS

The higher concentrations of metals in the Padad as the industrial ambient air i.e., arsenic, cadmium, chromium, mercury and nickel coincided with the higher concentrations of those metals in exposed children (P < 0.05) versus the controls. Children in Golestan, the high traffic air pollution area had the highest lead concentrations (p < 0.05). Also a significant association was shown in Padad between blood arsenic and IgE (β = 26.59, P < 0.001), IL-4 (β = 172.1, P < 0.001) and IL-13 (β = 14.84, P < 0.001), blood chromium and IgE (β = 10.38, P < 0.001), IL-4 (β = 75.27, P < 0.001) and IL-13 (β = 5.27, P < 0.001) and blood mercury and IgE (β = 13.11, P < 0.001), IL-4 (β = 108.09, P < 0.001) and IL-13 (β = 7.96, P < 0.001) and blood lead and IgE(β = 0.92, P = 0.025), IL-4(β = 7.16, P < 0.001) and IL-13(β = 0.58, P = 0.003). However, no significant relation was found for Cadmium, Nickel in blood with IgE, IL-4 and IL-13 levels. Moreover, children from industrial areas showed significantly higher concentrations of IgE (mean = 146.44 pg/200landa, P < 0.001), IL-4 (mean = 548.23 pg/200landa, P < 0.001) and IL-13 (mean = 52.93 pg/200landa, P < 0.001) versus Golestan and Kianpars.

CONCLUSION

Children residing in an industrial area with high concentrations of metals in PM_2.5 had high metals in blood and high production of IgE, IL-4 and IL-13, reflecting an immune dysregulation and brisk inflammatory responses.

Oxidative stress markers, trace elements, and endocrine disrupting chemicals in children with Hashimoto's thyroiditis

In this study, we aimed to investigate whether bisphenol A (BPA) and di-(2-ethylhexyl) phthalate (DEHP) exposure have any association with Hashimoto's thyroiditis (HT) and its biomarkers and to determine whether oxidative stress biomarkers and trace element levels showed any alterations in children with HT. We found that superoxide dismutase and glutathione peroxidase activities are lower in HT group from control (24% and 46%, respectively, p < 0.05). Zinc levels were significantly lower in HT group vs. control. In addition, the levels of mono-(2-ethylhexyl) phthalate (MEHP) which is the primary metabolite for DEHP, were markedly higher in HT group compared to control (p < 0.05). A negative correlation was observed between urinary BPA levels and fT4. In children with HT, oxidant/antioxidant balance is changed and these differences may be related by EDC exposure, the importance of which should be elucidated with further studies.

Effect of Cyperus Rotundus on Cytokine Gene Expression in Experimental Inflammatory Bowel Disease

BACKGROUND

The protective effect of the chloroform extract of Cyperus rotundus (CHCR) is attributed to its anti-inflammatory and antioxidant activities. Cytokines, important regulators of inflammation and repair, play a key role in the pathogenesis of inflammatory bowel disease (IBD). Targeting these cytokines can effectively ameliorate the symptoms of IBD. The aim of the present study was to unravel the molecular mechanism through cytokine regulation in rats in experimental IBD.

METHODS

Sprague Dawley rats were randomly allocated to 5 groups (n=6). Group I served as the normal control. Group II served as the vehicle control and received 50% ethanol intracolonically on day 11 of the study. Group III served as the model control. Group IV and Group V were given standard drug 5-aminosalicylic acid (100 mg/kg) and CHCR (800 mg/kg), respectively, for 18 days once a day orally. Colitis was induced with dinitrobenzene sulfonic acid (180 mg/kg in 50% ethanol) intracolonically in groups III-V on day 11 of the study. On day 18, the rats were euthanized and colon tissues were removed for IL-4, IL-6, IL-12, and IFN-gamma gene expression studies using quantitative RT-PCR.

RESULTS

The expression levels of proinflammatory cytokines IL-4, IL-6, IL-12, and IFN-gamma were upregulated in the model control rats. Pretreatment with 5-aminosalicylic acid (100 mg/kg) and CHCR (800 mg/kg) significantly decreased the fold of the expression of the above cytokines.

CONCLUSION

CHCR acts as a molecular brake and downregulates the expression of proinflammatory cytokine genes; this is beneficial for reducing the severity of the experimental IBD. Thus, Cyperus rotundus is a safe, economical, and effective alternative for the treatment of patients with IBD.

Impact of fetal and childhood mercury exposure on immune status in children

BACKGROUND

Mercury exposure have been shown to affect immune status in animals as reflected by cytokine expression. It is unclear whether low levels of exposure during fetal and/or childhood periods could impact on immune status in humans.

OBJECTIVES

To test the hypothesis that fetal and childhood mercury exposure is associated with childhood cytokine profiles and to investigate whether childhood selenium levels interact with any of the associations found.

METHODS

Children were recruited from a previously established birth cohort between the ages of 6-9 years for assessment and measurement of blood mercury, selenium and cytokine profile (interleukin (IL)-4, IL-6, IL-8, IL-10, IL-13 and TNF-alpha). Multivariable linear regression models were used to assess the adjusted association of cord blood mercury concentration and current mercury concentrations with levels of the cytokine levels. We tested whether the association with current mercury level varied by current selenium level and cord blood mercury level.

RESULTS

IL-10 was negatively associated with current blood mercury concentration. The effect was greatest in cases with low cord blood mercury and low current selenium concentrations. None of the other cytokine levels were associated with either cord blood or current blood mercury concentrations, except that cord blood mercury was negatively associated with IL-6.

CONCLUSIONS

Childhood mercury exposure was negatively associated with childhood IL-10 levels. It is postulated that while selenium is protective, low levels of fetal mercury exposure may increase the degree of this negative association during childhood. Further studies into the clinical significance of these findings are required.

Au-ACRAMTU-PEt3 Alters Redox Balance To Inhibit T Cell Proliferation and Function

Although T cells play a critical role in protection from viruses, bacteria, and tumors, they also cause autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis. Unwanted T cell responses during organ transplant, graft-versus-host disease, and allergies are also major clinical problems. Although drugs are available to suppress unwanted immune responses, they have limited efficacy with serious side effects. Thus, new therapeutics limiting T cell activation, proliferation, and function can make an immediate clinical impact. To identify new suppressors of lymphocyte activation, proliferation, and function, we examined the immunosuppressive activity of gold(I) analogs of platinum-acridine antitumor agents. We found that the gold complex Au-ACRAMTU-PEt3 is a potent suppressor of murine and human T cell activation. Preincubation with Au-ACRAMTU-PEt3 suppresses the proliferation of CD4(+) and CD8(+) T cells at a similar concentration as pharmaceutical grade cyclosporine A. Au-ACRAMTU-PEt3 pretreatment decreases the production of IFN-γ, TNF-α, IL-2, and IL-17 by human and murine CD4(+) and CD8(+) T cells. When mice were treated with Au-ACRAMTU-PEt3 during viral infection, the expansion of virus-specific CD8(+) T cells was decreased 10-fold and viral load was elevated. Taken together, these results demonstrate that Au-ACRAMTU-PEt3 has potent immunosuppressive activity that could be used to suppress immune responses during transplantation and autoimmunity.

Lupus-like oral mucosal lesions in mercury-induced autoimmune response in Brown Norway rats

Background

Administration of mercury at nontoxic doses induces systemic autoimmune disease in Brown Norway (BN) rats. The pathogenesis of lupus-like oral mucosal lesion by mercury-induced autoimmunity is still unclear, even though the oral mucosa is observed to be commonly affected in mercury-treated BN rats. In this study, we investigated the immunopathology of lupus-like oral mucosal lesions in a model of mercury-induced systemic autoimmunity.

Methods

Brown Norway male rats were injected subcutaneously with either phosphate-buffered saline (control) or mercury at a dose of 1.0 mg per kilogram of body weight on days 0, 3, 5, and 7. Blood, kidney, and tongue samples were taken at various timepoints for evaluation by immunohistochemistry, RT-PCR, and lupus band test (LBT).

Results

Oral mucosal lesions were classified according to three consecutive temporal phases on the basis of infiltration of immunocompetent cells as follows: (phase I) infiltration of MHC class II⁺ dendritic cells (DC) and macrophages; (phase II) addition of ED1⁺ macrophage infiltrates; and (phase III) focal infiltration of pan T cells following increased infiltration of DC and macrophages. Dense infiltration of DC and macrophages was observed in the basement membrane (BM) zone of the oral epithelium. Tissue expression of IL-4 mRNA was detected in early lesions (phase I), suggesting that locally produced IL-4 may be responsible for Th2-mediated immune response. A linear and continuous smooth pattern of fluorescence was observed in the oral epithelial BM in addition to renal glomeruli, indicating immune complex deposits.

Conclusions

Local autoimmune responses are involved in the pathogenesis of mercury-induced lupus-like lesions of the oral mucosa.

Cytokine dysregulation in autism spectrum disorders (ASD): possible role of the environment

Autism spectrum disorders (ASD) are neurodevelopmental diseases that affect an alarming number of individuals. The etiological basis of ASD is unclear, and evidence suggests it involves both genetic and environmental factors. There are many reports of cytokine imbalances in ASD. These imbalances could have a pathogenic role, or they may be markers of underlying genetic and environmental influences. Cytokines act primarily as mediators of immunological activity but they also have significant interactions with the nervous system. They participate in normal neural development and function, and inappropriate activity can have a variety of neurological implications. It is therefore possible that cytokine dysregulation contributes directly to neural dysfunction in ASD. Further, cytokine profiles change dramatically in the face of infection, disease, and toxic exposures. Imbalances in cytokines may represent an immune response to environmental contributors to ASD. The following review is presented in two main parts. First, we discuss select cytokines implicated in ASD, including IL-1Β, IL-6, IL-4, IFN-γ, and TGF-Β, and focus on their role in the nervous system. Second, we explore several neurotoxic environmental factors that may be involved in the disorders, and focus on their immunological impacts. This review represents an emerging model that recognizes the importance of both genetic and environmental factors in ASD etiology. We propose that the immune system provides critical clues regarding the nature of the gene by environment interactions that underlie ASD pathophysiology.

The Use of In Vitro Systems for Evaluating Immunotoxicity: The Report and Recommendations of an ECVAM Workshop

This is the report of a workshop organised by the European Centre for the Validation of Alternative Methods (ECVAM). ECVAM's main goal, as defined in 1993 by its Scientific Advisory Committee, is to promote the scientific and regulatory acceptance of alternative methods that are of importance to the biosciences and which replace, reduce or refine the use of laboratory animals. One of the first priorities set by ECVAM was the implementation of procedures that would enable it to become well informed about the state-of-the-art of non-animal test development and validation, and the potential for the possible incorporation of alternative tests into regulatory procedures. It was decided that this would be best achieved by the organization of ECVAM workshops on specific topics, at which small groups of invited experts would review the current status of various types of in vitro tests and their potential uses, and make recommendations about the best ways forward (Anonymous, 1994). The workshop on "The use of in vitro systems for evaluating Immunotoxicity" was held at ECVAM (Ispra), Italy, on 24th-26th November 2003. The participants represented academia, national organizations, international regulatory bodies and industry. The aim of the workshop was to review the state-of-the-art in the field of in vitro immunotoxicology, and to develop strategies towards the replacement of in vivo testing. At the end of this report are listed the recommendations that should be considered for prevalidation and validation of relevant and reliable procedures, that could replace the use of animals in chemical and cosmetics toxicity testing.

Evaluation of antiallergic and anti-anaphylactic activity of ethanolic extract of Sanseveiria trifasciata leaves (EEST) in rodents

AIM OF THE STUDY

The leaves and rhizomes of Sansevieria trifasciata are used in folk medicine for treating bronchitis, asthma, cough, snake bite and insect bite etc. The ethanolic extract elicited analgesic, anti-inflammatory and antipyretic activity. Hence, it was decided to study the antiallergic activity of ethanolic extract of S. trifasciata (EEST) on various animal models as well as in vitro conditions, and also to understand possible mechanism of action.

MATERIALS AND METHODS

Ethanolic extract of S. trifasciata leaves (EEST) were prepared by cold maceration followed by concentration and evaporation under reduced pressure on a rotary evaporator to obtain semisolid mass. The various phytoconstituents were analyzed. The acute toxicity study of EEST was carried out in mice. The antiallergic and anaphylactic activities were evaluated using animal models viz. milk induced eosinophilia and leukocytosis, compound 48/80 induced mast cell degranulation, active and passive cutaneous anaphylaxis and histamine induced pedal edema. In addition, EEST effect on Shultz-Dale reaction in sensitized guinea pig ileum in ex vivo and antioxidant activity by free radical scavenging by DPPH method (in vitro) were also studied.

RESULTS

EEST treatment at 100mg/kg and 200mg/kg p.o inhibited (a) milk-induced increased eosinophilia, leukocytosis, monocytes and neutrophils. (b) Prevented passive cutaneous and active anaphylactoid reactions. (c) Prevented compound 48/80 induced degranulation of sensitized mesenteric mast cells. (d) Inhibited histamine induced pedal edema formation significantly. EEST pretreatment inhibited Shultz-Dale reaction in guinea pig ileum and also elicited potent antioxidant activity.

CONCLUSION

Experimental findings demonstrate promising antiallergic and anti-anaphylactic activity of EEST and also elicited potent antioxidant activity. The antiallergic and anti-anphylactic activity might be due to inhibition of release of chemical mediators from mast cells largely by phytoconstituents like steroidal saponins, triterpenoids and flavonoids present in EEST.

8-Oxoguanine-DNA glycosylase 1 deficiency modifies allergic airway inflammation by regulating STAT6 and IL-4 in cells and in mice

8-Oxoguanine-DNA glycosylase (OGG-1) is a base excision DNA repair enzyme; however, its function in modulating allergic diseases remains undefined. Using OGG-1 knockout (KO) mice, we show that this protein affects allergic airway inflammation after sensitization and challenge by ovalbumin(OVA). OGG-1 KO mice exhibited less inflammatory cell infiltration and reduced oxidative stress in the lungs after OVA challenge compared to WT mice. The KO phenotype included decreased IL-4, IL-6, IL-10, and IL-17 in lung tissues. In addition, OGG-1 KO mice showed decreased expression and phosphorylation of STAT6 as well as NF-κB. Down-regulation of OGG-1 by siRNA lowered ROS and IL-4 levels but increased IFN-γ production in cultured epithelial cells after exposure to house dust mite extracts. OGG-1 may affect the levels of oxidative stress and proinflammatory cytokines during asthmatic conditions. OGG-1 deficiency negatively regulates allergen-induced airway inflammatory response.

Mountain cedar pollen induces IgE-independent mast cell degranulation, IL-4 production, and intracellular reactive oxygen species generation

Cedar pollens cause severe allergic disease throughout the world. We have previously characterized allergenic pollen glycoproteins from mountain cedar (Juniperus ashei) that bind to allergen-specific immunoglobulin E (IgE). In the present report, we investigated an alternative pathway of mast cell activation by mountain cedar pollen extract through IgE-independent mechanisms. We show that mountain cedar pollen directly induces mast cell serotonin and IL-4 release and enhances release induced by IgE cross-linking. Concomitant with mediator release, high levels of intracellular reactive oxygen species (ROS) were generated, and both ROS and serotonin release were inhibited by anti-oxidants. These findings suggest that alternative mechanisms exist whereby pollen exposure enhances allergic inflammatory mediator release through mechanisms that involve ROS. These mechanisms have the potential for enhancing the allergenic potency of pollens.

Gold activates mast cells via calcium influx through multiple H2O2-sensitive pathways including L-type calcium channels

Heavy metals, including gold, induce severe contact hypersensitivity and autoimmune disorders, which develop through an initial Th2-independent process followed by a Th2-dependent process. It has been shown that mast cell activation plays a role in the Th2-independent process and that gold stimulates histamine release in vitro. However, the mechanisms of the gold-induced mast cell activation remain largely unclear. Here we report that gold directly activates mast cells in a Ca2+-dependent manner. HAuCl4 [Au(III)] at nontoxic concentrations (≤50 μM) induced substantial degranulation and leukotriene C4 secretion in an extracellular Ca2+-dependent manner. Au(III) induced a robust Ca2+ influx but not Ca2+ mobilization from internal stores. Au(III) also stimulated intracellular production of reactive oxygen species, including H2O2, and blockade of the production abolished the mediator release and Ca2+ influx. Au(III) induced Ca2+ influx through multiple store-independent Ca2+ channels, including Cav1.2 L-type Ca2+ channels (LTCCs) and 2-aminoethoxydiphenyl borate (2-APB)-sensitive Ca2+ channels. The 2-APB-sensitive channel seemed to mediate Au(III)-induced degranulation. Our results indicate that gold stimulates Ca2+ influx and mediator release in mast cells through multiple H2O2-sensitive Ca2+ channels including LTCCs and 2-APB-sensitive Ca2+ channels. These findings provide insight into the roles of these Ca2+ channels in the Th2-independent process of gold-induced immunological disorders.

Peroxiredoxin I is a negative regulator of Th2-dominant allergic asthma

Peroxiredoxin (Prx) I, a ubiquitous antioxidant enzyme, is known to protect against inflammation; however, its role in the allergic inflammation remains unidentified. We determined whether intristic Prx I protects against allergic asthma traits using Prx-I knockout (-/-) mice. Prx I (-/-) and wild-type (WT) mice were immunized with ovalbumin (OVA) plus aluminum potassium sulfate (Alum: Th2 adjuvant) and subsequently challenged with OVA. Twenty-four hours after the last OVA challenge, leukocyte influx including eosinophils into bronchoalveolar lavage fluid was significantly greater in Prx I (-/-) mice compared to that in WT mice. On the other hand, when these mice were immunized with OVA+complete Freund's adjuvant (Th1 adjuvant), opposite phenomenon was observed. In the presence of OVA/Alum, peribronchial inflammatory leukocyte infiltration, cholinergic airway resistance, and the lung expression of interleukin (IL)-2 were significantly greater and that of interferon-gamma was significantly lesser in Prx I (-/-) than in WT mice. In vitro, OVA/Alum-sensitized Prx I (-/-) T cells proliferated more profoundly than WT T cells when they were cocultured with syngeneic bone marrow-generated dendritic cells. These results indicate that endogenous Prx I protects against allergen-related Th2-type airway inflammation and hyperresponsiveness, at least partly, via the suppression of the lung expression of IL-2 and regulation of the Th1/Th2 balance in addition to its antioxidative properties. Furthermore, Prx I can inhibit allergen-specific T-cell proliferation through immunological synapse. Our findings implicate an alternative therapeutic value of Prx I in the treatment of Th2-skewed allergic airway inflammatory diseases such as atopic asthma.

Characterization of cis-regulatory elements conferring mercury-induced interleukin-4 gene expression in rat mast cells: a role for signal transducer and activator of transcription 6 and TATA box binding sites

We have previously shown that oxidative stress is involved in the pathogenesis of a mercuric chloride (HgCl(2))-induced, T helper type 2 (Th2)-driven autoimmune syndrome in Brown Norway (BN) rats. In the context of the syndrome, the oxidative stress-induced mast cell response seems to determine the development of the early phase of vasculitis, while oxidative stress-mediated interleukin (IL)-4 production may contribute to the subsequent Th2-driven autoimmune response. However, the molecular basis of IL-4 gene transcription induced by HgCl(2) in mast cells remains unknown. In the present study, we dissect the critical regulatory mechanisms in the IL-4 gene promoter in the rat mast cell line RBL-2H3. Immunoprecipitation provided evidence that treatment with HgCl(2) increased phosphorylation of signal transducer and activator of transcription 6 (STAT6). Transient transfection reporter analyses with a series of 5' end deletions of the IL-4 promoter produced evidence that STAT6 and TATA box binding sites are important in HgCl(2)-induced IL-4 gene expression. Subsequent elimination of one or both sites by site-directed mutagenesis significantly inhibited IL-4 promoter activity. Our results provide evidence that STAT6 and TATA box regulatory elements play an important role in HgCl(2)-induced IL-4 transcription in rat mast cells.

Immunology of mercury

The heavy metal mercury is ubiquitously distributed in the environment resulting in permanent low-level exposure in human populations. Mercury can be encountered in three main chemical forms (elemental, inorganic, and organic) which can affect the immune system in different ways. In this review, we describe the effects of these various forms of mercury exposure on immune cells in humans and animals. In genetically susceptible mice or rats, subtoxic doses of mercury induce the production of highly specific autoantibodies as well as a generalized activation of the immune system. We review studies performed in this model and discuss their implications for the role of environmental chemicals in human autoimmunity.

(-)-Epigallocatechin-3-gallate induces up-regulation of Th1 and Th2 cytokine genes in Jurkat T cells

In the present study, we found that (-)-epigallocatechin-3-gallate (EGCG) significantly up-regulated the mRNA expression of the Th1/Th2 cytokines including IL-2, IFN-gamma, IL-5 and IL-13 in Jurkat T cells. The EGCG-induced mRNA up-regulation of IL-2 and IL-5 was predominantly affected by the extracellular signal-regulated protein kinase (ERK) signalling, whereas IL-13 gene expression, the most responsive to the EGCG treatment, was dependent on neither ERK nor c-jun NH(2)-terminal kinase (JNK) signalling. IFN-gamma gene expression was partially mitigated by both inhibitors of the ERK and JNK pathways. Furthermore, catalase significantly attenuated the intracellular peroxide production, phosphorylation of ERK and JNK, and all cytokine gene expressions induced by EGCG. In addition, physiologically relevant concentrations of both EGCG and H(2)O(2)-induced up-regulation of IL-5 gene expression. Our findings provide biological evidence that EGCG induces Th1/Th2 cytokine mRNA expression via H(2)O(2) production followed by activation of ERK or JNK in Jurkat T cells.

Low and nontoxic inorganic mercury burdens attenuate BCR-mediated signal transduction

The ubiquitous environmental heavy metal contaminant mercury (Hg) is a potent immunomodulator that has been implicated as a factor contributing to autoimmune disease. However, the mechanism(s) whereby Hg initiates or perpetuates autoimmune responses, especially at the biochemical/molecular level, remain poorly understood. Recent work has established a relationship between impaired B-cell receptor (BCR) signal strength and autoimmune disease. In previous studies, we have shown that in mouse WEHI-231 B cells, noncytotoxic concentrations of inorganic mercury (Hg(+2)) interfered with BCR-mediated growth control, suggesting that BCR signal strength was impaired by Hg(+2). Extracellular signal-regulated kinase (ERK) 1,2 mitogen-activated protein kinase (MAPK) is responsible for the activation of several transcription factors in B cells. Phosphorylation of ERK serves as an essential node of signal integration for the BCR. Thus, the magnitude of ERK activation serves as an operational metric for BCR signal strength. Using Western blotting and phospho-specific flow cytometry, we now show that the kinetics and magnitude of BCR-mediated activation of ERK-MAPK are markedly attenuated in WEHI-231 cells and splenic B cells that have been exposed to low and nontoxic burdens of Hg(+2). However, Hg(+2) does not seem to act directly on ERK-MAPK but rather on an upstream element or elements of the BCR signal transduction pathway, above the level of the key protein tyrosine kinase Syk. Our data suggest that the site of action of Hg(+2) may very well be localized on the plasma membrane. These findings support a connection between Hg(+2) and attenuated BCR signal strength in the etiology of autoimmune disease.

Selective Activation of Fyn/PI3K and p38 MAPK Regulates IL-4 Production in BMMC under Nontoxic Stress Condition

Mast cells have the ability to react to multiple stimuli, implicating these cells in many immune responses. Specific signals from the microenvironment in which mast cells reside can activate different molecular events that govern distinct mast cells responses. We previously demonstrated that hydrogen peroxide (H(2)O(2)) promotes IL-4 and IL-6 mRNA production and potentates FcepsilonRI-induced cytokine release in rat basophilic leukemia RBL-2H3 cells. To further evaluate the effect of an oxidative microenvironment (which is physiologically present in an inflammatory site) on mast cell function and the molecular events responsible for mast cell cytokine production in this environment, we analyzed the effect of H(2)O(2) treatment on IL-4 production in bone marrow-derived, cultured mast cells. Our findings show that nanomolar concentrations of H(2)O(2) induce cytokine secretion and enhance IL-4 production upon FcepsilonRI triggering. Oxidative stimulation activates a distinct signal transduction pathway that induces Fyn/PI3K/Akt activation and the selective phosphorylation of p38 MAP kinase. Moreover, H(2)O(2) induces AP-1 and NFAT complexes that recognize the IL-4 promoter. The absence of Fyn and PI3K or the inhibition of p38 MAPK activity demonstrated that they are essential for H(2)O(2)-driven IL-4 production. These findings show that mast cells can respond to an oxidative microenvironment by initiating specific signals capable of eliciting a selective response. The findings also demonstrate the dominance of the Fyn/p38 MAPK pathway in driving IL-4 production.

Dose and Hg species determine the T-helper cell activation in murine autoimmunity

Inorganic mercury (mercuric chloride--HgCl(2)) induces in mice an autoimmune syndrome (HgIA) with T cell-dependent polyclonal B cell activation and hypergammaglobulinemia, dose- and H-2-dependent production of autoantibodies targeting the 34 kDa nucleolar protein fibrillarin (AFA), and systemic immune-complex deposits. The organic mercury species methylmercury (MeHg) and ethylmercury (EtHg--in the form of thimerosal) induce AFA, while the other manifestations of HgIA seen after treatment with HgCl(2) are present to varying extent. Since these organic Hg species are converted to the autoimmunogen Hg(2+) in the body, their primary autoimmunogen potential is uncertain and the subject of this study. A moderate dose of HgCl(2) (8 mg/L drinking water--internal dose 148 micro gHg/kg body weight [bw]/day) caused the fastest AFA response, while the induction was delayed after higher (25 mg/L) and lower (1.5 and 3 mg/L) doses. The lowest dose of HgCl(2) inducing AFA was 1.5 mg/L drinking water which corresponded to a renal Hg(2+) concentration of 0.53 micro g/g. Using a dose of 8 mg HgCl(2)/L this threshold concentration was reached within 24 h, and a consistent AFA response developed after 8-10 days. The time lag for the immunological part of the reaction leading to a consistent AFA response was therefore 7-9 days. A dose of thimerosal close to the threshold dose for induction of AFA (2 mg/L drinking water--internal dose 118 micro gHg/kg bw per day), caused a renal Hg(2+) concentration of 1.8 micro g/g. The autoimmunogen effect of EtHg might therefore be entirely due to Hg(2+) formed from EtHg in the body. The effect of organic and inorganic Hg species on T-helper type 1 and type 2 cells during induction of AFA was assessed as the presence and titre of AFA of the IgG1 and IgG2a isotype, respectively. EtHg induced a persistent Th1-skewed response irrespectively of the dose and time used. A low daily dose of HgCl(2) (1.5-3 mg/L) caused a Th1-skewed AFA response, while a moderate dose (8 mg/L) after 2 weeks resulted in a balanced or even Th2-skewed response. Higher daily doses of HgCl(2) (25 mg/L) caused a balanced Th2-Th1 response already from onset. In conclusion, while metabolically formed Hg(2+) might be the main AFA-inducing factor also after treatment with EtHg, the quality of the Hg-induced AFA response is modified by the species of Hg as well as the dose.

Thimerosal induces TH2 responses via influencing cytokine secretion by human dendritic cells

Thimerosal is an organic mercury compound that is used as a preservative in vaccines and pharmaceutical products. Recent studies have shown a TH2-skewing effect of mercury, although the underlying mechanisms have not been identified. In this study, we investigated whether thimerosal can exercise a TH2-promoting effect through modulation of functions of dendritic cells (DC). Thimerosal, in a concentration-dependent manner, inhibited the secretion of LPS-induced proinflammatory cytokines TNF-alpha, IL-6, and IL-12p70 from human monocyte-derived DC. However, the secretion of IL-10 from DC was not affected. These thimerosal-exposed DC induced increased TH2 (IL-5 and IL-13) and decreased TH1 (IFN-gamma) cytokine secretion from the T cells in the absence of additional thimerosal added to the coculture. Thimerosal exposure of DC led to the depletion of intracellular glutathione (GSH), and addition of exogenous GSH to DC abolished the TH2-promoting effect of thimerosal-treated DC, restoring secretion of TNF-alpha, IL-6, and IL-12p70 by DC and IFN-gamma secretion by T cells. These data suggest that modulation of TH2 responses by mercury and thimerosal, in particular, is through depletion of GSH in DC.

Silver activates mast cells through reactive oxygen species production and a thiol-sensitive store-independent Ca2+ influx

In genetically susceptible human and/or experimental animals, heavy metals such as mercury, gold, and silver have been shown to highly induce adverse immunological reactions such as allergy and autoimmunity, in which mast cell degranulation is implicated as playing a role. We previously reported that silver activates mast cells and induces Ca2+ influx without stimulating intracellular signaling events required for activation of store-operated Ca2+ channels (SOCs). The purpose of the present study was to elucidate the possible involvement of reactive oxygen species (ROS) in the biological effects of silver. Analysis using oxidant-sensitive fluorescent probes such as dichlorodihydrofluorescein and scopoletin, as well as MCLA-amplified chemiluminescence, showed that silver induced intracellular production and/or extracellular release of ROS. Silver induced mast cell degranulation in a Ca2+ -dependent manner. Unlike IgE antigen, silver-induced Ca2+ influx was not affected by depletion of internal Ca2+ stores. Instead, the metal-induced Ca2+ influx was abolished and reversed by the cell-impermeant thiol-reducing agent dithiothreitol, indicating the regulation by oxidation of vicinal thiols on the cell surface. Consistent with this view, Ca2+ influx was blocked by the glutathione peroxidase mimetic ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) and the superoxide dismutase mimetic manganese(III) tetrakis 4-(benzoic acid)porphyrin, but not by exogenously added catalase or superoxide dismutase. These findings indicate that silver evokes the release of ROS and oxidation of thiols critical for the activation of a Ca2+ channel other than SOC. Such a novel ROS-dependent pathway might play a role in mast cell degranulation in metal-induced allergic and autoimmune reactions.

NK-DC interaction: on the usefulness of auto-aggression

In recent years a number of studies have highlighted the novel concept that the actual role of natural killer (NK) cells is not only confined to the destruction of virus-infected cells or tumors. Indeed NK cells, by interacting with myeloid DCs during the early phases of inflammation, appear to play a crucial role in shaping both innate immune reactions (within inflamed peripheral tissues) and adaptive immune responses (in secondary lymphoid compartments). Interestingly, this novel function assigned to NK cells is essentially mediated through the aggression of normal immature myeloid DCs. Only DCs undergoing optimal maturation become refractory to NK cell killing and will obtain the permission to prime Th1 cells after migration to lymph nodes.

Early liaisons between cells of the innate immune system in inflamed peripheral tissues

The crosstalk between natural killer (NK) cells and myeloid dendritic cells (DCs) results in NK-cell activation and DC maturation. Activated NK cells acquire the ability to kill DCs that have failed to undergo complete maturation ('DC editing'). Recent studies have revealed that this crosstalk can be promoted by pathogen-derived products that activate different innate immune cell types directly and simultaneously through their Toll-like receptors (TLRs). These cells include NK cells and DCs, as well as plasmacytoid DCs (PDCs) and mast cells. This crosstalk can have a great impact on the quality and strength of the subsequent adaptive immune response. Thus, NK cells have an important role in the defense against pathogens, acting as regulatory cells as well as effector cells.

Mast cells and autoimmunity

Mast cells (MCs) are major effector cells in allergic diseases. Recently, it has become evident that the contribution of MCs extends far beyond their accepted role in allergic disease, and that they play a more extensive role in a variety of non-allergic immune processes such as the innate immunity response. These cells have a key role in both the induction and elicitation of several autoimmune conditions. Targeting MC development, maturation or activation may be of value in future prevention and treatment of autoimmune conditions.

Prenatal paracetamol exposure and risk of asthma and elevated immunoglobulin E in childhood

BACKGROUND

We recently found that paracetamol (acetaminophen) use in late pregnancy was associated with an increased risk of early wheezing in the offspring.

OBJECTIVE

To see whether use of paracetamol in late pregnancy is associated with an increased risk of asthma, wheezing and other atopic outcomes in the child at school age.

METHODS

In the population-based Avon Longitudinal Study of Parents and Children, we measured associations of paracetamol and aspirin use in late pregnancy (20-32 weeks) with asthma, hayfever, eczema (n = 8511) and wheezing (8381) in the offspring at 69-81 months, and with atopy (positive skin prick test to Dermatophagoides pteronyssinus, cat or grass, n = 6527) and blood total IgE (n = 5148) at 7 years. We used logistic and linear regression to analyse binary outcomes and log-transformed IgE, respectively, controlling for potential confounders.

RESULTS

Use of paracetamol, but not aspirin, in late pregnancy was positively associated with asthma (odds ratios (ORs), comparing children whose mothers took paracetamol 'sometimes' and 'most days/daily' with those whose mothers never took it, 1.22 (95% confidence interval (CI): 1.06-1.41) and 1.62 (95% CI: 0.86-3.04), respectively; P trend = 0.0037), wheezing (ORs 1.20 (95% CI: 1.02-1.40) and 1.86 (95% CI: 0.98-3.55), respectively; P trend = 0.011), and total IgE (geometric mean ratios 1.14 (95% CI: 1.03-1.26) and 1.52 (95% CI: 0.98-2.38), respectively; P trend = 0.0034), but not hayfever, eczema or skin test positivity. The proportion of asthma attributable to paracetamol use in late pregnancy, assuming a causal relation, was 7%.

CONCLUSION

Paracetamol exposure in late gestation may cause asthma, wheezing and elevated IgE in children of school age.

A central role for the mast cell in early phase vasculitis in the Brown Norway rat model of vasculitis: a histological study

Administration of mercuric chloride (HgCl(2)) to Brown Norway rats causes Th2-dominated autoimmunity with raised immunoglobulin E concentrations and gut vasculitis, both of which are T-cell dependent, peak at 14 days after starting HgCl(2) and then spontaneously resolve. If animals are re-challenged with HgCl(2) 6 weeks after initial exposure, they are resistant to autoimmunity, developing only attenuated disease. Recently, a separate phase of early caecal vasculitis was described beginning 24 h after initiating HgCl(2) and prior to caecal entry of T cells. Previous work suggested this early vasculitis was alpha beta T-cell independent and implied a role for mast cells. We further tested this hypothesis by performing a histological study during the first 93 h following HgCl(2) challenge defining the precise relationship between gut mast cell degranulation and appearing caecal vasculitis. We also studied whether early caecal vasculitis enters a resistant phase upon re-challenge with HgCl(2). We show a direct correlation between mast cell degranulation and early caecal vasculitis following initial HgCl(2) challenge. We demonstrate resistance to re-challenge in this phase of injury, with results at re-challenge also showing a correlation between mast cell degranulation and early caecal injury.

Desferrioxamine modulates chemically induced T helper 2-mediated autoimmunity in the rat

A rise in interleukin (IL) 4-dependent immunoglobulin E (IgE) is a hallmark of the mercuric chloride (HgCl2)-induced Th2-mediated autoimmune syndrome in the Brown Norway (BN) rat, and one of the mediators in allergic asthma in human. Oxidative stress, a potential factor related to the pathogenesis of allergy and asthma, has been shown to up-regulate IL-4 in mast cells and predispose to degranulation in vitro. However, it remains unknown whether oxidative/antioxidative imbalance plays a role in this Th2-driven model of autoimmunity in the rat. Here we show that administration of the non-sulphydryl-containing antioxidant desferrioxamine i.p. and s.c. to BN rats reduces HgCl2-enhanced IL-4 gene expression and inhibits HgCl2-induced Th2-mediated autoimmunity. Desferrioxamine treatment suppresses significantly IgE production and lymphoproliferation, and reduces tissue injury in the form of caecal vasculitis in the HgCl2-induced autoimmune syndrome. These results support a role for oxidative stress in the pathogenesis of the HgCl2-induced Th2-dominated autoimmune syndrome. This finding might have implications for understanding the mechanisms involved in Th2 cell responses as seen in allergy and asthma and thereby aid the development of new therapeutic strategies for these diseases.

The mast cell: an antenna of the microenvironment that directs the immune response

Mast cells (MCs) have long been considered as critical effector cells during immunoglobulin (Ig)E-mediated allergic disease and immune response to parasites. Recent studies, however, suggest that this understanding of MC function is incomplete and does not consider the complex roles that MCs play in adaptive and innate immunity. The added function gives an innovative vision of regulation of immune responses and the development of autoimmune diseases. It had been assumed that the aggregation of Fc epsilon receptor I with IgE and specific antigen is the main stimulus able to induce the MC activation, degranulation, release, and generation of mediators of the allergic reaction. However, MCs exhibit an array of molecules involved in cell-cell and cell-extracellular matrix adhesion, mediating delivery of costimulatory signals that empower those cells with an ability to react to multiple nonspecific and specific stimuli. Their tissue distribution and their capability to release many cytokines after stimulation indicate MCs as potential regulatory linkers between innate and acquired immunity. In this review, we will summarize some findings on the roles of MCs in innate and acquired immunity, on the molecular mechanism and signaling pathways, and on selective signals that induce discrete MC response and its ability to polarize adaptive-immune response.

Methylmercury enhances arachidonic acid release and cytosolic phospholipase A2 expression in primary cultures of neonatal astrocytes

Cytosolic phospholipase A(2) (cPLA(2)) stimulates the hydrolysis of sn-2 ester bond in membrane phospholipids releasing arachidonic acid (AA) and lysophospholipids. The present study examined the effect of methylmercury (MeHg) on cPLA(2) activation and AA release in primary cultures of neonatal rat cerebral astrocytes. Astrocytes were preloaded overnight at 37 degrees C with 3H-AA to metabolically label phospholipids. The effect of MeHg on the activation of cPLA(2) was measured by the release of 3H-AA from astrocytes over 120 min. MeHg (5 microM) caused a significant increase in AA release at 10, 30, 60, and 120 min, whereas 2.5 microM MeHg significantly increased AA release only at 120 min. MeHg-induced increase in 3H-AA release was due to cPLA(2) activation, since arachidonyl trifluoromethyl ketone (AACOCF(3)), a selective inhibitor of cPLA(2), completely abolished MeHg's effect. Consistent with these observations, MeHg (5.0 and 10.0 microM) increased cPLA(2) mRNA (6 h) and cPLA(2) protein expression (5.0 and 10.0 microM; 24 h). The time-course of these effects suggests an immediate direct or indirect effect of MeHg on cPLA(2) activation and 3H-AA release as well as a long-term effect involving the induction of cPLA(2). Thin layer chromatographic analysis of 3H-AA-labeled phospholipids showed that MeHg-stimulated astrocyte 3H-AA release was not due to increased incorporation of 3H-AA into the putative substrates of cPLA(2). These results invoke cPLA(2) as a putative target for MeHg toxicity, and support the notion that cPLA(2)-stimulated hydrolysis and release of AA play a critical role in MeHg-induced neurotoxicity.

Redox-linked cell surface-oriented signaling for T-cell death

T-cell death, which occurs either for ontogenic T-cell selection or for activated T-cell elimination, is normally induced through binding of a specific ligand to cell-surface T-cell receptor for crosslinkage. Heavy metals and carbonyl compounds that bind to protein-reactive groups such as cysteine sulfhydryl groups and lysine epsilon-amino groups may also induce crosslinkage of cell-surface proteins, in part replacing or modifying the ligand-mediated action. This chemical event has been found to accompany clustering of membrane rafts, to which signal-transducing elements such as glycosylphosphatidylinositol-anchored proteins and Src family protein tyrosine kinases (PTKs) are attached, and to trigger the signal transduction for apoptotic T-cell death, inducing mitochondrial membrane potential reduction, caspase activation and DNA fragmentation. As signals potentially upstream of this signaling, activations of PTKs and mitogen-activated protein (MAP) family kinases and production of reactive oxygen species (ROS) were induced following the cell-surface event, and crucial roles of activation of c-Jun amino-terminal kinase and apoptosis signal-regulating kinase 1 by a redox-linked mechanism in the cell-death signaling were demonstrated. Intriguingly, ROS production as well as PTK/MAP family kinase activation occurred in a membrane raft integrity-dependent manner. The redox-linked and cell surface-oriented signal delivery pathway demonstrated here may play an important role in induction of immune disorders by protein reactive group-binding chemicals.

Antioxidants inhibit mercuric chloride-induced early vasculitis

In the Brown Norway (BN) rat, mercuric chloride (HgCl(2)) induces a T(h)2-dominated autoimmune syndrome which includes an early phase of mast cell-dependent vasculitis. We have shown in vitro that oxidative stress up-regulates IL-4 in mast cells and predisposes to degranulation. The aim of this study was to determine whether administration of antioxidants inhibits HgCl(2)-induced early vasculitis in vivo, and, if so, to examine whether modulation of the oxidative/antioxidative balance influences IgE and IL-4 expression by mast cells in situ. Groups of rats were given HgCl(2) + saline, HgCl(2) + N-acetyl-L-cysteine (NAC), saline + saline or saline + NAC respectively and blood was taken and animals killed 48 h later. NAC significantly reduced both HgCl2-induced early vasculitis and HgCl(2)-enhanced IgE expression on mast cells with a trend to a decrease in HgCl(2)-enhanced IL-4 expression in these cells. In addition, there was an increased rat mast cell protease (RMCP) II concentration in the serum after HgCl(2) injection and the elevated levels of RMCP II stimulated by HgCl(2) were totally abolished by the administration NAC in the HgCl(2) + NAC group. However, there was no significant change in serum total IgE concentrations between the HgCl(2) + saline group and the HgCl(2) + NAC group. The non-sulphydryl-containing antioxidants desferrioxamine and pyruvate demonstrated a similar effect in inhibiting HgCl(2)-induced early vasculitis. Our data show that administration of an antioxidant to BN rats reduces HgCl(2)-induced early vasculitis, suggesting that oxidative stress plays a role in the pathogenesis of HgCl(2)-induced early vasculitis. This finding may have implications for the understanding of the initiation in this experimental model of T(h)2 cell-driven autoimmunity and possibly of analogous human diseases.

B7-1 and B7-2 co-stimulatory molecules are required for mercury-induced autoimmunity

B7-1 (CD80) and B7-2 (CD86) molecules on antigen presenting cells play important roles in providing co-stimulatory signals required for activation and expansion of autoreactive T cells. Moreover, some reports have suggested that these molecules may have distinct functions in the differentiation of Th1 and Th2 cells. Mercury-induced autoimmunity in H-2s mice is characterized by lymphoproliferation of T and B cells, serum increases in IgG1 and IgE and production of antinucleolar antibodies (ANoA). The mechanisms responsible for the various manifestations of this syndrome have yet to be elucidated. To examine the contributions of B7 co-stimulatory molecules to this model, susceptible mice were treated with antibodies to B7-1, B7-2, or both during the development of mercury-induced autoimmunity. The combination of anti-B7-1 and anti-B7-2 antibodies prevented Hg-induced disease in H-2s mice. Additionally, single anti-B7-1 antibody treatment was sufficient to prevent Hg-induced ANoA production, but not IgG1 and IgE hypergammaglobulinaemia. Further, single antibody treatment with anti-B7-2 resulted in a partial reduction of ANoA titres but had no significant effect on total serum IgG1 and IgE levels. Taken together, these results indicate that B7-1 and B7-2 molecules are critical for the development of Hg-induced autoimmunity and suggest that the different manifestations of the syndrome are regulated by independent mechanisms.