Exosomes derived from human dermal fibroblasts (HDFn-Ex) alleviate DNCB-induced atopic dermatitis (AD) via PPARα

Atopic dermatitis (AD) is a chronic inflammatory skin disease. Skin barrier dysfunction is the initial step in the development of AD. Recently, exosomes have been considered as potential cell-free medicine for skin defects such as aging, psoriasis and wounds. The aim of this study was to investigate the effects of human dermal fibroblast-neonatal-derived exosome (HDFn-Ex) on AD. HDFn-Ex increased the expression of peroxisome proliferator activated receptor α (PPARα) and alleviated the 1-chloro-2,4-dinitrobenzene (DNCB)-mediated downregulation of filaggrin, involucrin, loricrin, hyaluronic acid synthase 1 (HAS1) and HAS2 in human keratinocyte HaCaT cells. However, these effects were inhibited by the PPARα antagonist GW6471. In the artificial skin model, HDFn-Ex significantly inhibited DNCB-induced epidermal hyperplasia and the decrease in filaggrin and HAS1 levels via a PPARα. In the DNCB-induced AD-like mouse model, HDFn-Ex administration reduced epidermis thickening and mast cell infiltration into the dermis compared to DNCB treatment. Moreover, the decreases in PPARα, filaggrin and HAS1 expression, as well as the increases in IgE and IL4 levels induced by DNCB treatment were reversed by HDFn-Ex. These effects were blocked by pre-treatment with GW6471. Furthermore, HDFn-Ex exhibited an anti-inflammatory effect by inhibiting the DNCB-induced increases in IκBα phosphorylation and TNF-α expression. Collectively, HDFn-Ex exhibited a protective effect on AD. Notably, these effects were regulated by PPARα. Based on our results, we suggest that HDFn-Ex is a potential candidate for treating AD by recovering skin barrier dysfunction and exhibiting anti-inflammatory activity.

Pamoic acid-induced peripheral GPR35 activation improves pruritus and dermatitis

BACKGROUND AND PURPOSE

Pruritic dermatitis is a disease with a considerable unmet need for treatment and appears to present with not only epidermal but also peripheral neuronal complications. Here, we propose a novel pharmacological modulation targeting both peripheral dorsal root ganglion (DRG) sensory neurons and skin keratinocytes. GPR35 is an orphan G-protein-coupled receptor expressed in DRG neurons and has been predicted to downregulate neuronal excitability when activated. Modulator information is currently increasing for GPR35, and pamoic acid (PA), a salt-forming agent for drugs, has been shown to be an activator solely specific for GPR35. Here, we investigated its effects on dermatitic pathology.

EXPERIMENTAL APPROACH

We confirmed GPR35 expression in peripheral neurons and tissues. The effect of PA treatment was pharmacologically evaluated in cultured cells in vitro and in in vivo animal models for acute and chronic pruritus.

KEY RESULTS

Local PA application mitigated acute non-histaminergic itch and, consistently, obstructed DRG neuronal responses. Keratinocyte fragmentation under dermatitic simulation was also dampened following PA incubation. Chronic pruritus in 1-chloro-2,4-dinitrobenzene and psoriasis models were also moderately but significantly reversed by the repeated applications of PA. Dermatitic scores in the 1-chloro-2,4-dinitrobenzene and psoriatic models were also improved by its application, indicating that it is beneficial for mitigating disease pathology.

CONCLUSION AND IMPLICATIONS

Our findings suggest that pamoic acid activation of peripheral GPR35 can contribute to the improvement of pruritus and its associated diseases.

The JAK/STAT/NF-κB signaling pathway can be regulated by rosemary essential oil, thereby providing a potential treatment for DNCB-induced in mice

OBJECTIVE

The purpose of this study was to investigate the mechanism through which rosemary essential oil treats atopic dermatitis.

METHODS

A dinitrochlorobenzene (DNCB)-induced atopic dermatitis mouse model was established and treated with low (1%), medium (2%), and high (4%) doses of Rosmarinus officinalis essential oil (EORO). Serum levels of interleukin (IL)-6 and tumor necrosis factor-alpha (TNF-α) in each group were determined using enzyme-linked immunosorbent assay (ELISA). Skin tissues were stained with hematoxylin-eosin and toluidine blue. We used network pharmacology and molecular docking techniques to verify the biological activity of essential proteins and their corresponding compounds in the pathway. Gas chromatography-mass spectrometry (GC-MS) was used for metabolomics analysis and multivariate statistical analysis of mouse serum to screen differential metabolites and metabolic pathway analysis. Protein expression of p-JAK1, CD4+ cells, and IL-4 in the skin tissue was detected by immunohistochemistry analysis. Protein levels of STAT3, p-STAT3, P65, and p-P65 in damaged skin tissues were detected using western blotting.

RESULT

The skin of mice in the model group showed different degrees of erythema, dryness, scratches, epidermal erosion and shedding, and crusting. After treatment, the serum levels of IL-6 and TNF-α in EORO group were significantly decreased, and the expression of p-JAK1,CD4 + cells, IL-4, p-P65 / P65 and p-STAT3 / STAT3 proteins in skin tissues were decreased.

CONCLUSION

EORO can effectively improve DNCB-induced AD-like skin lesions in mice by regulating the JAK/STAT/NF-κB signaling pathway, thereby reducing the production of downstream arachidonic acid metabolites, inhibiting skin inflammation, and restoring epidermal barrier function.

A human 3D immune competent full-thickness skin model mimicking dermal dendritic cell activation

We have integrated dermal dendritic cell surrogates originally generated from the cell line THP-1 as central mediators of the immune reaction in a human full-thickness skin model. Accordingly, sensitizer treatment of THP-1-derived CD14-, CD11c+ immature dendritic cells (iDCs) resulted in the phosphorylation of p38 MAPK in the presence of 1-chloro-2,4-dinitrobenzene (DNCB) (2.6-fold) as well as in degradation of the inhibitor protein kappa B alpha (IκBα) upon incubation with NiSO4 (1.6-fold). Furthermore, NiSO4 led to an increase in mRNA levels of IL-6 (2.4-fold), TNF-α (2-fold) and of IL-8 (15-fold). These results were confirmed on the protein level, with even stronger effects on cytokine release in the presence of NiSO4: Cytokine secretion was significantly increased for IL-8 (147-fold), IL-6 (11.8-fold) and IL-1β (28.8-fold). Notably, DNCB treatment revealed an increase for IL-8 (28.6-fold) and IL-1β (5.6-fold). Importantly, NiSO4 treatment of isolated iDCs as well as of iDCs integrated as dermal dendritic cell surrogates into our full-thickness skin model (SM) induced the upregulation of the adhesion molecule clusters of differentiation (CD)54 (iDCs: 1.2-fold; SM: 1.3-fold) and the co-stimulatory molecule and DC maturation marker CD86 (iDCs ~1.4-fold; SM:~1.5-fold) surface marker expression. Noteworthy, the expression of CD54 and CD86 could be suppressed by dexamethasone treatment on isolated iDCs (CD54: 1.3-fold; CD86: 2.1-fold) as well as on the tissue-integrated iDCs (CD54: 1.4-fold; CD86: 1.6-fold). In conclusion, we were able to integrate THP-1-derived iDCs as functional dermal dendritic cell surrogates allowing the qualitative identification of potential sensitizers on the one hand, and drug candidates that potentially suppress sensitization on the other hand in a 3D human skin model corresponding to the 3R principles ("replace", "reduce" and "refine").

Heat shock protein 90 (Hsp90) inhibitor STA-9090 (Ganetespib) ameliorates inflammation in a mouse model of atopic dermatitis

Molecular chaperones belonging to the heat shock protein 90 (Hsp90) family are implicated in inflammatory processes and described as potential novel therapeutic targets in autoimmune/inflammatory skin diseases. While the pathological role of circulating Hsp90 has been recently proposed in patients with atopic dermatitis (AD), a chronic inflammatory skin disease characterized by intense itching and recurrent skin lesions, studies aimed at investigating the role of Hsp90 as a potential target of AD therapy have not yet been conducted. Here, the effects of the Hsp90 blocker STA-9090 (Ganetespib) applied systemically or topically were determined in an experimental mouse model of dinitrochlorobenzene (DNCB)-induced AD. Intraperitoneal administration of STA-9090 ameliorated clinical disease severity, histological epidermal thickness, and dermal leukocyte infiltration in AD mice which was associated with reducing the scratching behavior in DNCB-treated animals. Additionally, topically applied STA-9090 led to lowered disease activity in AD mice, reduced serum levels of IgE, and up-regulated filaggrin expression in lesional skin samples. Our observations suggest that Hsp90 may be a promising therapeutic target in atopic dermatitis and potentially other inflammatory or autoimmune dermatoses.

Anti-Atopic Dermatitis Effect of TPS240, a Novel Therapeutic Peptide, via Suppression of NF-κB and STAT3 Activation

Atopic dermatitis (AD) is a relapsing skin disease with persistent inflammation as a causal factor for symptoms and disease progression. Current therapies provide only temporary relief and require long-term usage accompanied by side effects due to persistent relapses. A short peptide, TPS240, has been tested for its potential to subside AD. In this study, we confirmed the anti-atopic effect of TPS240 in vivo and in vitro using a DNCB-induced AD mouse model and TNF-α/IFN-γ-stimulated HaCaT cells. In the AD mouse model, topical treatment with TPS240 diminished AD-like skin lesions and symptoms such as epidermal thickening and mast cell infiltration induced by DNCB, similar to the existing treatment, dexamethasone (Dex). Furthermore, skin atrophy, weight loss, and abnormal organ weight changes observed in the Dex-treated group were not detected in the TPS240-treated group. In TNF-α/IFN-γ-stimulated HaCaT cells, TPS240 reduced the expression of the inflammatory chemokines CCL17 and CCL22 and the pruritic cytokines TSLP and IL-31 by inhibiting NF-κB and STAT3 activation. These results suggest that TPS240 has an anti-atopic effect through immunomodulation of AD-specific cytokines and chemokines and can be used as a candidate drug for the prevention and treatment of AD that can solve the safety problems of existing treatments.

Systemic Type 2 Inflammation-Associated Atopic Dermatitis Exacerbates Periodontitis

INTRODUCTION

Atopic dermatitis (AD) is a prevalent and chronic inflammatory skin disease characterized by Th2 cell-mediated type 2 inflammation. Emerging evidence indicated that AD patients exhibit an increased incidence of oral disorders. In the present study, we sought mechanistic insights into how AD affects periodontitis.

METHODS

Onset of AD was induced by 2,4-dinitrochlorobenzene (DNCB). Furthermore, we induced periodontitis (P) in AD mice. The effect of AD in promoting inflammation and bone resorption in gingiva was evaluated. Hematoxylin and eosin staining, tartrate-resistant acid phosphatase staining, immunofluorescence assay, and flow cytometry were used to investigate histomorphology and cytology analysis, respectively. RNA sequencing of oral mucosa is used tissues to further understand the dynamic transcriptome changes. 16S rRNA microbial analysis is used to profile oral microbial composition.

RESULTS

Compared to control group, mice in AD group showed inflammatory signatures and infiltration of a proallergic Th2 (Th2A)-like subset in oral mucosa but not periodontitis, as identified by not substantial changes in mucosa swelling, alveolar bone loss, and TRAP+ osteoclasts infiltration. Similarly, more Th2A-like cell infiltration and interleukin-4 levels were significantly elevated in the oral mucosa of DNCB-P mice compared to P mice. More importantly, AD exacerbates periodontitis when periodontitis has occurred and the severity of periodontitis increased with aggravation of dermatitis. Transcriptional analysis revealed that aggravated periodontitis was positively correlated with more macrophage infiltration and abundant CCL3 secreted. AD also altered oral microbiota, indicating the re-organization of extracellular matrix.

CONCLUSIONS

These data provide solid evidence about exacerbation of periodontitis caused by type 2 dermatitis, advancing our understanding in cellular and microbial changes during AD-periodontitis progression.

Protective Effects of Topical Administration of Laminarin in Oxazolone-Induced Atopic Dermatitis-like Skin Lesions

Laminarin is a polysaccharide isolated from brown marine algae and has a wide range of bioactivities, including immunoregulatory and anti-inflammatory properties. However, the effects of laminarin on atopic dermatitis have not been demonstrated. This study investigated the potential effects of topical administration of laminarin using a Balb/c mouse model of oxazolone-induced atopic dermatitis-like skin lesions. Our results showed that topical administration of laminarin to the ear of the mice improved the severity of the dermatitis, including swelling. Histological analysis revealed that topical laminarin significantly decreased the thickening of the epidermis and dermis and the infiltration of mast cells in the skin lesion. Serum immunoglobulin E levels were also significantly decreased by topical laminarin. Additionally, topical laminarin significantly suppressed protein levels of oxazolone-induced proinflammatory cytokines, such as interleukin-1β, tumor necrosis factor-α, monocyte chemoattractant protein-1, and macrophage inflammatory protein-1α in the skin lesion. These results indicate that topical administration of laminarin can alleviate oxazolone-induced atopic dermatitis by inhibiting hyperproduction of IgE, mast cell infiltration, and expressions of proinflammatory cytokines. Based on these findings, we propose that laminarin can be a useful candidate for the treatment of atopic dermatitis.

Anti-Allergic and Anti-Inflammatory Effects of Neferine on RBL-2H3 Cells

Mast cells play a very important role in skin allergy and inflammation, including atopic dermatitis and psoriasis. In the past, it was found that neferine has anti-inflammatory and anti-aging effects on the skin, but its effect on mast cells has not yet been studied in detail. In this study, we used mast cells (RBL-2H3 cells) and mouse models to study the anti-allergic and inflammatory effects of neferine. First, we found that neferine inhibits the degranulation of mast cells and the expression of cytokines. In addition, we observed that when mast cells were stimulated by A23187/phorbol 12-myristate-13-acetate (PMA), the elevation of intracellular calcium was inhibited by neferine. The phosphorylation of the MAPK/NF-κB pathway is also reduced by pretreatment of neferine. The results of in vivo studies show that neferine can improve the appearance of dermatitis and mast cell infiltration caused by dinitrochlorobenzene (DNCB). Moreover, the expressions of barrier proteins in the skin are also restored. Finally, it was found that neferine can reduce the scratching behavior caused by compound 48/80. Taken together, our results indicate that neferine is a very good anti-allergic and anti-inflammatory natural product. Its effect on mast cells contributes to its pharmacological mechanism.

Anti-Atopic Effect of Acorn Shell Extract on Atopic Dermatitis-Like Lesions in Mice and Its Active Phytochemicals

To investigate the potential effects of acorn shells on atopic dermatitis (AD), we utilized oxazolone (OX)- or 2,4-dinitrochlorobenzene (DNCB)-induced AD-like lesion mouse models. Our research demonstrates that Acorn shell extract (ASE) improved the progression of AD-like lesions, including swelling, which were induced by oxazolone on Balb/c mouse ears. Additionally, ASE significantly decreased the ear thickness (OX: 0.42 ± 0.01 mm, OX-ASE: 0.32 ± 0.02 mm) and epidermal thickness (OX: 75.3 ± 32.6 µm, OX-ASE: 46.1 ± 13.4 µm). The continuous DNCB-induced AD mouse model in SKH-1 hairless mice demonstrated that ASE improved AD-like symptoms, including the recovery of skin barrier dysfunction, Immunoglobulin E hyperproduction (DNCB: 340.1 ± 66.8 ng/mL, DNCB-ASE: 234.8 ± 32.9 ng/mL) and an increase in epidermal thickness (DNCB: 96.4 ± 21.9 µm, DNCB-ASE: 52.4 ± 16.3 µm). In addition, we found that ASE suppressed the levels of AD-involved cytokines, such as Tumor Necrosis Factor α, IL-1β, IL-25 and IL-33 in both animal models. Furthermore, gallic acid and ellagic acid isolated from ASE suppressed β-hexosaminidase release and IL-4 expression in RBL-2H3 cells. The acorn shell and its active phytochemicals have potential as a new remedy for the improvement of atopic dermatitis and other inflammatory diseases.

Selective Disruption of Mitochondrial Thiol Redox State in Cells and In Vivo

Mitochondrial glutathione (GSH) and thioredoxin (Trx) systems function independently of the rest of the cell. While maintenance of mitochondrial thiol redox state is thought vital for cell survival, this was not testable due to the difficulty of manipulating the organelle's thiol systems independently of those in other cell compartments. To overcome this constraint we modified the glutathione S-transferase substrate and Trx reductase (TrxR) inhibitor, 1-chloro-2,4-dinitrobenzene (CDNB) by conjugation to the mitochondria-targeting triphenylphosphonium cation. The result, MitoCDNB, is taken up by mitochondria where it selectively depletes the mitochondrial GSH pool, catalyzed by glutathione S-transferases, and directly inhibits mitochondrial TrxR2 and peroxiredoxin 3, a peroxidase. Importantly, MitoCDNB inactivates mitochondrial thiol redox homeostasis in isolated cells and in vivo, without affecting that of the cytosol. Consequently, MitoCDNB enables assessment of the biomedical importance of mitochondrial thiol homeostasis in reactive oxygen species production, organelle dynamics, redox signaling, and cell death in cells and in vivo.

Oral warfarin intake affects skin inflammatory cytokine responses in rats

Warfarin is an anticoagulant used in prevention/prophylaxis of thromboembolism. Besides the effects on coagulation, non-hemorrhagic reactions have also been documented. Although cutaneous reactions were reported in some patients, the impact on skin immunity was not explored. In the present paper, the effect of 30-day oral warfarin intake on skin cytokine responses in rats was analyzed. Increased release of inflammatory cytokines (TNF, IL-1β and IL-10) was noted by skin explants from rats which received warfarin, but without effect on IL-6. No impact on epidermal cell cytokine secretion was seen, except a tendency of an increase of IL-6 response to stimulation with microbial product lipopolysaccharide (LPS). Topical application of contact allergen dinitrochlorobenzene (DNCB) resulted in slight (numerical solely) increase of TNF release by skin explants of warfarin-treated animals, while epidermal cells responded by increased secretion of all four cytokines examined. The data presented provide new information on the potential of oral warfarin to modulate skin innate immune activity.

The Natural Course of Atopic Dermatitis and the Association with Asthma

In this paper, we aimed to explore the potential mechanism underlying atopic dermatitis (AD) and its association with asthma. The BALB/c mice were randomly assigned to three groups, including the vehicle control (VD) group, the AD group, and the treatment (TR) group. The AD mice model was successfully constructed in the AD and TR group. The dermatitis severity scores and skin lesions were significantly increased in AD mice after DNCB application. Airway responsiveness in the AD group was significantly higher than in the TR group. The number of inflammatory cells was increased in skin lesions and bronchoalveolar lavage fluid (BALF) of AD mice. The levels of IL-4, IL-5, IFN-γ, and OVA-IgE in BALF supernatants of mice in the AD group were higher than those in the VC group. All the changes in AD mice were decreased by tacrolimus. These results indicate that AD may be a significant risk factor for atopic asthma development.

6-Shogaol, an active compound of ginger, alleviates allergic dermatitis-like skin lesions via cytokine inhibition by activating the Nrf2 pathway

Allergic dermatitis (AD) clinically presents with skin erythematous plaques, eruption, and elevated serum IgE, and T helper cell type 2 and 1 (Th2 and Th1) cytokine levels. 6-Shogaol [1-(4-hydroxy-methoxyphenyl)-4-decen-one], a pungent compound isolated from ginger, has shown anti-inflammatory effects, but its inhibitory effects on AD are unknown. The aim of this study was to examine whether 6-shogaol inhibits AD-like skin lesions and their underlying mechanism in vivo and in vitro. An AD-like response was induced by tumor necrosis factor-α (TNF-α)+IFN-γ in human keratinocytes or by 2,4-dinitrochlorobenzene (DNCB) in mice. In vivo, 6-shogaol inhibited the development of DNCB-induced AD-like skin lesions and scratching behavior, and showed significant reduction in Th2/1-mediated inflammatory cytokines, IgE, TNF-α, IFN-γ, thymus and activation-regulated chemokine, IL-1, 4, 12, and 13, cyclooxygenase-2, and nitric oxide synthase levels. In vitro, 6-shogaol inhibited reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPKs) signaling, and increased the levels of total glutathione, heme oxygenase-1, and quinone 1 via nuclear factor erythroid 2 related factor 2 (Nrf2) activation. 6-Shogaol can alleviate AD-like skin lesions by inhibiting immune mediators via regulating the ROS/MAPKs/Nrf2 signaling pathway, and may be an effective alternative therapy for AD.

Glutathione and its related enzymes in the gonad of Nile Tilapia (Oreochromis niloticus)

Glutathione (GSH) concentration, the activity of its metabolizing enzymes, glutathione transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR), and the antioxidant enzyme catalase (CAT) in O. niloticus ovary and testis were examined. GSH concentration of O. niloticus testis exhibited high concentration (129 ± 21 nmol/g tissue) compared with GSH concentration (49.2 ± 8.3 nmol/g tissue) in the ovary. GST, GPx, GR, and CAT activities of O. niloticus testis exhibited high values compared with their corresponding values in ovary homogenates. However, protein concentration in ovary homogenates exhibited higher values (175 ± 40.6 mg) compared with testis homogenates (27.1 ± 3.7 mg). O. niloticus ovary was less effective in excretion of xenobiotices compared with the testis, where its function is mainly in increasing the protein content of the eggs; however, in O. niloticus testis, the glutathione cycle operated in accelerated way in the direction of reduced GSH production in order to protect the maturation stages in a save way. A simple reproducible procedure for the purification of GST from O. niloticus ovary was established. The enzymes proved to be homogenous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and its molecular weight was calculated to be 25.1 kDa. GST of O. niloticus ovary exhibited maximum activity at pH 7.5. The Michaelis-Menten constant (K(m)) of the purified ovary GST for GSH and CDNB was 0.076 mM and 1.0 mM, respectively. Cibacron blue was the most potent inhibitor of ovary GST activity (IC50 value, concentration of inhibitor that will give 50% inhibition, equal 0.002 μM). The specific activity of GST toward different electrophilic substrates was determined. GST activity toward benzyl isothiocyanate was the highest compared with phenethyl isothiocyanate and allyl isothiocyanate.

TISSUE FIBRINOLYTIC ACTIVITY OF ALLERGIC CONTACT DERMATITIS

One of our co-workers was sensitized with a 1% DNCB solution in acetone. Biopsies were obtained from skin lesions 1, 2, 4, 8, 12, 24, 30, 36 and 48 hours after a challenge with 0.1% DNCB solution. In the upper dermis, a rapid decrease of tissue fibrinolytic activity was found which disappeared after 30 hours. In the lower dermis, biphasic changes were observed. Tissue fibrinolytic activity increased one hour and 12-36 hours after challenge, whereas at 48 hours, when erythema was most intensive, it decreased in comparison to the normal activity. Erythema and histological changes of the epidermis and the dermis appeared after approximately 12 hours. As for lymphocytes, T-cells were seen at first. Furthermore, B-cells were noted after approximately 30 hours when marked infiltration began to appear.

STUDIES ON THE DINITROPHENYLATED LYMPHOCYTES IN GUINEA PIG PAINTED WITH DNCB

The number of DNP group-bearing lymphocytes in the regional lymph node, thoracic duct and peripheral blood was determined at various time intervals after painting normal guinea pigs with DNCB by the immunofluorescent method using anti-DNP antibody. The incidence of such cells in the regional node was maximal at 12 hours whereas in the thoracic duct and peripheral blood the maximum incidence was found at 0.1-2 hours after painting. Unreacted DNCB was demonstrated in both the thoracic lymph duct and the blood at least for 12 or 24 hours respectively following exposure to DNCB. The authors therefore suggest that DNCB reacts directly in vivo with the lymphocyte cell membrane of guinea pig following epicutaneous application of the chemical.

The biological importance of glutathione peroxidase and peroxiredoxin backup systems in bivalves during peroxide exposure

Organic peroxide elimination in eukaryotes essentially depends on glutathione peroxidase (GPx) and peroxiredoxin (Prx) enzymes, which are supported by their respective electron donors, glutathione (GSH) and thioredoxin (Trx). This system depends on the ancillary enzymes glutathione reductase (GR) and thioredoxin reductase (TrxR) to maintain GSH and Trx in their reduced state. This study discusses the biological importance of GR and TrxR in supporting GPx and Prx during cumene hydroperoxide (CHP) exposure in brown mussel Perna perna. ZnCl2 or 1-chloro-2,4-dinitrobenze (CDNB) was used to decrease GR and TrxR activities in gills, as already reported with mammals and bivalves. ZnCl2 exposure lowered GR activity (28%), impaired the in vivo CHP decomposition and decreased the survival rates under CHP exposure. CDNB decreased GR (54%) and TrxR (73%) activities and induced glutathione depletion (99%), promoting diminished peroxide elimination and survival rates at a greater extent than ZnCl2. CDNB also increased the susceptibility of hemocytes to CHP toxicity. Despite being toxic and causing mortality at longer exposures, short (2 h) exposure to CHP promoted an up regulation of GSH (50 and 100 μM CHP) and protein-thiol (100 μM CHP) levels, which was blocked by ZnCl2 or CDNB pre-exposure. Results highlight the biological importance of GSH, GR and TrxR in supporting GPx and Prx activities, contributing to organic peroxides elimination and mussel survival under oxidative challenges. To our knowledge, this is the first work that demonstrates, albeit indirectly, the biological importance of GPx/GR/GSH and Prx/TrxR/Trx systems on in vivo organic peroxide elimination in bivalves.

Thioredoxin-related protein 32 (TRP32) specifically reduces oxidized phosphatase of regenerating liver (PRL)

PRL family constitutes a unique class of phosphatases associated with metastasis. The phosphatase activity of PRL has been reported to be important for promoting metastasis, and it is inactivated by reversible oxidation of its catalytic cysteine. Here, we show that TRP32 specifically reduces PRL. Reduction of oxidized PRL in cells is inhibited by 2,4-dinitro-1-chlorobenzene, an inhibitor of TRX reductase. In vitro assays for the reduction of PRL show that only TRP32 can potently reduce oxidized PRL, whereas other TRX-related proteins linked to TRX reductase show little or no reducing activity. Indeed, TRP32 knockdown significantly prolongs the H2O2-induced oxidation of PRL. Binding analyses reveal that the unique C-terminal domain of TRP32 is required and sufficient for its direct interaction with PRL. These results suggest that TRP32 maintains the reduced state of PRL and thus regulates the biological function of PRL.

Prevention of type 1 diabetes by inducing subclinical dermatitis on a small area

OBJECTIVE

We have previously epidemiologically shown that type 1 diabetes is inversely associated with contact allergy. This finding is intriguing as type 1 diabetes and contact allergy are two completely different diseases, although T cells are involved in both diseases. The objective of this study was therefore to experimentally study the effect of contact allergens on the development of diabetes in non-obese diabetic mice.

METHODS

Non-obese diabetic mice 4 weeks of age were separated into seven groups. One group was exposed to tapped water every 14th day, whereas the remaining six groups were split into sensitizations groups or elicitation groups (exposure every 14th day). These groups were then treated with one of the selected contact allergens (PPD or DNCB) or vehicle (AOO). All groups received the sensitizing treatment regime, and hereafter only the elicitation groups were further treated. If the blood glucose reached 14 mM, the mice were considered diabetic and euthanized. Cardiac heart blood was drawn at euthanization, and a Luminex analysis was done on the serum.

RESULTS

We showed that repeated application of a low dose of PPD reduced the incidence of diabetes compared to application with water (47% versus 93%, p=0.004). The rest of the groups developed diabetes with a cumulative incidence rate above 80%. The Luminex cytokine analysis revealed no differences between the groups, and no elevated cytokine level suggested a systemic response. Dermatitis was not noticeable by visual inspection, a histological examination, however, revealed a slight infiltration in the ears in the elicitation groups exposed to contact allergens.

CONCLUSION

This study showed that repeated topical application on the ears with a contact allergen could prevent the development of diabetes in non-obese diabetic mice. The contact allergens gave a non-visible, subclinical dermatitis on the application site. Activation of NKT cells to the ear lymph nodes seems to be involved.

Transactivation of gene expression by NF-κB is dependent on thioredoxin reductase activity

The redox-sensitive transcription factor NF-κB mediates the expression of genes involved in inflammation and cell survival. Thioredoxin reductase-1 (TR1) and its substrate thioredoxin-1 act together to reduce oxidized cysteine residues within the DNA-binding domain of NF-κB and promote maximal DNA-binding activity in vitro. It is not clear, however, if NF-κB is regulated via this mechanism within living cells. The purpose of this study was to determine the mechanism of NF-κB modulation by TR1 in cells stimulated with the inflammatory cytokine tumor necrosis factor-α (TNF). In both control cells and cells depleted of TR1 activity through chemical inhibition or siRNA knockdown, TNF stimulation resulted in degradation of the cytoplasmic NF-κB inhibitor IκB-α and translocation of NF-κB to the nucleus. Similarly, the DNA-binding activity and redox state of NF-κB were unaffected by TR1 depletion. In contrast, NF-κB-mediated gene expression was markedly inhibited in cells lacking TR1 activity, suggesting that the transactivation potential of NF-κB is sensitive to changes in TR1 activity. Consistent with this concept, phosphorylation of the transactivation domain of NF-κB was inhibited in the presence of curcumin. Surprisingly, another TR1 inhibitor, 1-chloro-2,4-dinitrobenzene, had no effect, and siRNA knockdown of TR1 actually increased phosphorylation at this site. These results demonstrate that TR1 activity controls the transactivation potential of NF-κB and that more than one mechanism may mediate this effect.

DA-9601 suppresses 2, 4-dinitrochlorobenzene and dust mite extract-induced atopic dermatitis-like skin lesions

DA-9601 (Stillen™) is a novel anti-peptic formulation prepared from the ethanol extracts of Artemisia asiatica possessing anti-oxidative, anti-allergic and anti-inflammatory activities. However, their effect on atopic dermatitis (AD) has not been studied yet. In this study, we report that topical application of DA-9601 suppressed house dust mite extract (Dermatophagoides farinae extract, DFE) and 2, 4-dinitrochlorobenzene (DNCB)-induced AD-like skin lesions in BALB/c mice model. We established atopic dermatitis model in BALB/c mice by repeated local exposure of DFE/DNCB to the ears. Repeated alternative treatment of DFE/DNCB caused AD-like lesions. DA-9601 reduced AD-like skin lesions based on ear thickness and histopathological analysis, and serum IgE levels. DA-9601 inhibited mast cell infiltration into the ear and elevation of serum histamine in AD model. In addition, DA-9601 suppressed DFE/DNCB-induced expression of IL-4, IL-13, IL-31, and TNF-α in the ears. Taken together, our results showed that topical application of DA-9601 exerts beneficial effects in animal model of AD, suggesting that DA-9601 might be a candidate for the treatment of AD.

Neuroprotective mechanisms of minocycline against sphingomyelinase/ceramide toxicity: Roles of Bcl-2 and thioredoxin

In this study, we determined whether minocycline may protect rat cortical cultures against neurotoxicity induced by sphingomyelinase/ceramide and explored the underlying mechanisms. We found that minocycline exerted strong neuroprotective effects against toxicity induced by bacterial sphingomyelinase and synthetic C2 ceramide. Minocycline enhanced the production of nitric oxide (NO) with resultant increases in cellular cGMP content. Consistently, minocycline-dependent neuroprotection was abolished by the nitric oxide synthase inhibitor L-N(G)-nitroarginine methyl ester (L-NAME) and the soluble guanylate cyclase (sGC) inhibitor 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ). Western blotting revealed that minocycline restored the expression levels of cGMP-dependent protein kinase (PKG)-1, antioxidative thioredoxin-1, and antiapoptotic Bcl-2 that were down-regulated by bacterial sphingomyelinase. Accordingly, the PKG inhibitor KT5823, the thioredoxin reductase inhibitor 1-chloro-2,4-dinitrobenzene (DNCB), and a Bcl-2 inhibitor significantly abolished the minocycline neuroprotection. The minocycline-dependent restoration of Bcl-2 was abolished by L-NAME, ODQ, and KT5823, but not by DNCB, suggesting the involvement of NO/sGC/PKG but not thioredoxin. Furthermore, minocycline-dependent recovery of thioredoxin-1 was PKG-independent. Taken together, our results indicate that minocycline protects rat cortical neurons against bacterial sphingomyelinase/ceramide toxicity via an NO/cGMP/PKG pathway with induction of Bcl-2 and PKG-independent stimulation of thioredoxin-1.

Reactivity of Langerhans cells after application of different chemicals--an ultrastructural analysis

The goal of this study was to investigate changes in epidermal Langerhans cells after application of different chemicals (acetone, 60% alcohol, 5% nickel sulphate, iodisole, and 0.1% 2,4-dinitrochlorobenzene) on the skin of volunteers. The skin of eight volunteers was treated with acetone, 60% alcohol, iodisol, 5% nickel sulphate, and 0.1% 2,4-dinitrochlorobenzene (DNCB). After application of DNCB, Langerhans cells (LCs) showed increased accumulation of Birbeck granules (Bgs). Alcohol and nickel sulphate caused alternative changes, mainly cytoplasmic vacuolation, in LCs. Nickel sulphate was even responsible for the disappearance of dendrites. Both chemicals have cytotoxic effects on LCs: cytoplasmic organelles and Bgs disappear and subsequently, the antigen-presenting activity of epidermal LCs is inhibited. We did not found any morphological changes in LCs after application of acetone.

High levels of thioredoxin reductase 1 modulate drug-specific cytotoxic efficacy

The selenoprotein thioredoxin reductase 1 (TrxR1) is currently recognized as a plausible anticancer drug target. Here we analyzed the effects of TrxR1 targeting in the human A549 lung carcinoma cell line, having a very high basal TrxR1 expression. We determined the total cellular TrxR activity to be 271.4 +/- 39.5 nmol min(-1) per milligram of total protein, which by far exceeded the total thioredoxin activity (39.2 +/- 3.5 nmol min(-1) per milligram of total protein). Knocking down TrxR1 by approx 90% using siRNA gave only a slight effect on cell growth, irrespective of concurrent glutathione depletion (> or = 98% decrease), and no increase in cell death or distorted cell cycle phase distributions. This apparent lack of phenotype could probably be explained by Trx functions being maintained by the remaining TrxR1 activity. TrxR1 knockdown nonetheless yielded drug-specific modulation of cytotoxic efficacy in response to various chemotherapeutic agents. No changes in response upon exposure to auranofin or juglone were seen after TrxR1 knockdown, whereas sensitivity to 1-chloro-2,4-dinitrobenzene or menadione became markedly increased. In contrast, a virtually complete resistance to cisplatin using concentrations up to 20 microM appeared upon TrxR1 knockdown. The results suggest that high overexpression of TrxR has an impact not necessarily linked to Trx function that nonetheless modulates drug-specific cytotoxic responses.

Effects of four oxidants, menadione, 1-chloro-2,4-dinitrobenzene, hydrogen peroxide and cumene hydroperoxide, on fission yeast Schizosaccharmoyces pombe

Several chemical agents have been used to exert oxidative stress in the study of stress response, but differences in the effects of different reagents have received little attention. To elucidate whether such differences exist, the response of Schizosaccharomyces pombe to menadione (MD), 1-chloro-2,4-dinitrobenzene (CDNB), hydrogen peroxide and cumene hydroperoxide (CHP), which are frequently used to exert oxidative stress, was investigated. Sensitivity to these reagents differed among mutants deficient in genes involved in oxidative stress resistance. N-Acetylcysteine restored resistance to MD, CHP and hydrogen peroxide but did not change sensitivity to CDNB. The induction kinetics of genes induced by oxidative stress differed for each reagent. MD, CDNB and hydrogen peroxide caused a transient induction of genes, but the peak times of induction differed among the reagents. CHP gave quite different kinetics in that the induction continued for up to 2 h. The ctt1(+) gene was not induced by CHP. GSH rapidly decreased in the cells treated with high concentrations of these reagents, but at a low concentration only CDNB decreased GSH. These results indicated that S. pombe responded differently to the oxidative stress exerted by these different reagents.

The Arabidopsis glutathione transferase gene family displays complex stress regulation and co-silencing multiple genes results in altered metabolic sensitivity to oxidative stress

Plant glutathione transferases (GSTs) are induced by diverse biotic and abiotic stimuli, and are important for protecting plants against oxidative damage. We have studied the primary transcriptional stress response of the entire Arabidopsis GST family to seven stresses, including both biotic and abiotic stimuli, with a focus on early changes in gene expression. Our results indicate that individual GST genes are highly specific in their induction patterns. Furthermore, we have been able to link individual GSTs to particular stress stimuli. Using RNAi, we successfully co-silenced a group of four phi GSTs that represent some of the most highly expressed GST genes. Despite a marked reduction in total phi GST protein levels, the transgenic plants showed no reduction in GST activity as measured using the model substrate 1-chloro-2,4-dinitrobenzene (CDNB), and appeared to have surprisingly robust physical phenotypes during stress. However, analysis of metabolite pools showed oxidation of the glutathione pool in the RNAi lines, and we observed alterations in carbon and nitrogen compounds following salicylic acid and hydrogen peroxide stress treatments, indicative of oxidative modification of primary metabolism. Thus, there appears to be a high degree of functional redundancy within the Arabidopsis GST family, with extensive disruption being required to reveal the roles of phi GSTs in protection against oxidative stress.

Impaired glutathione-conjugating capacity by cryopreserved human and rat hepatocytes

The activity of glutathione transferase was measured in sonicates of fresh rat hepatocytes and of cryopreserved rat, human and dog hepatocytes in the presence of added glutathione and by using 1-chloro-2,4-dinitrobenzene (CDNB) as non-selective substrate. The glutathione-conjugating capacity was also investigated in the presence of CDNB alone (without glutathione) with intact fresh rat hepatocytes and cryopreserved rat and human hepatocytes. Finally, the intracellular level of glutathione was measured in these hepatocytes. The specific activity of glutathione transferase in sonicates of fresh rat hepatocytes (in the presence of added GSH and CDNB) was about 415 nmol/min/10(6) cells. The corresponding activities in cryopreserved rat, human and dog hepatocytes were approximately 320, 440 and 540 nmol/min/10(6) cells, respectively. In contrast, glutathione conjugation by the intact cryopreserved human and rat hepatocytes in the presence of CDNB alone was less than 10% of the corresponding conjugation by fresh rat hepatocytes, indicating that glutathione was depleted in these cryopreserved hepatocytes. Glutathione depletion was confirmed after analytical measurement of the glutathione levels in fresh and cryopreserved hepatocytes. In fresh rat hepatocytes the level of glutathione was 44 nmol/10(6) cells, whereas it was 2.5 and 4.4 nmol/10(6) cells in cryopreserved rat and human hepatocytes, respectively. In summary, glutathione transferase was active in these cryopreserved hepatocytes but the cryopreservation procedure likely causes depletion in the intracellular level of glutathione, resulting in an overall reduced glutathione conjugating capacity.

Estimation of lymphocyte subpopulations in the peripheral blood of patients with sarcoidosis

Lymphocyte subpopulations in the peripheral blood of 36 sarcoidosis patients and 36 age- and sex-matched controls were determined, using the sheep erythrocyte rosette (SRBC-R) technique and immunofluorescence staining with whole rabbit anti-human immunoglobulin antisera. In the patient group the total number of lymphocytes, SRBC-R lymphocytes, and IgM-positive lymphocytes was reduced in comparison to in the control group. In the patient group no correlation could be found between any of the lymphocyte subpopulations and disease stage, cutaneous involvement of the disease, or cutaneous reactivity to purified protein derivative and dinitrochlorobenzene.

[In vitro evaluation of cutaneous allergic reaction induced by chemicals using dendritic cells]

OBJECTIVE

To investigate the use of dendritic cells derived from mice bone marrow to evaluate the cutaneous allergic reaction induced by chemical sensitizers.

METHODS

Dendritic cells derived from mice bone marrow were cultured and administrated with 2, 4-dinitrochlorobenzene (DNCB), nickel sulfate (NiSO4), sodium dodecyl sulfate (SDS) and hexyl cinnamic aldehyde (HCA), respectively. Cell membrane molecule CD86 and extracellular IL-1 beta, IL-6 and IL-12 were detected after 0, 1, 6, 12, 24, 36, 48 hour's administration, respectively.

RESULTS

CD86 expression reached the highest level after exposure to DNCB for 48 h, and increased by about 279% compared with the control (P < 0.05), while it was lower than that of control after administrated with NiSO4 and HCA for 1 h and 6 h, and SDS for 36 h, respectively (P < 0.05). Extracellular IL-1 beta increased greatly after exposure to NiSO4 just for 1 h, with the maximum at 48 h (298 pg/ml, P < 0.05), and after exposure to HCA for 6 h, with maximum at 48 h (84 pg/ml, P < 0.05). However, it didn't fluctuate significantly after administrated with DNCB and SDS respectively, compared with the control. Extracellular IL-6 increased significantly after exposure to NiSO4 for 1 h, with the maximum at 24 h (2152 pg/ml, P < 0.05). After exposure to HCA, extracellular IL-6 reached the maximum at 1 h (1403 pg/ml), and then it was decreased quickly, but still higher than the control (P < 0.05), while it didn't change significantly after treatment with DNCB and SDS, compared with the control (P > 0.05). Extracellular IL-12 was not detected out among all the groups.

CONCLUSION

Chemical sensitizer DNCB could induce the high expression of CD86 on DC membrane, and NiSO4 and HCA could induce DC to release IL-1 beta and IL-6. However, the irritant SDS had no such effect.

NF-kappaB plays a major role in the maturation of human dendritic cells induced by NiSO(4) but not by DNCB

Dendritic cell (DC) activation is a critical event for the induction of an immune response to haptens. Although signaling pathways such as mitogen-activated protein kinase (MAPK) family members have been reported to play a role in DC activation by haptens, little is known about the implication of the nuclear factor kappa B (NF-kappaB) pathway. In this work, we showed that NiSO(4) induced the expression of HLA-DR, CD83, CD86, and CD40 and the production of interleukin (IL)-8, IL-6, and IL-12p40 in human DCs, whereas DNCB induced mainly the expression of CD83 and CD86 and the production of IL-8. NiSO(4) but not DNCB was able to activate the degradation of IkappaB-alpha leading to the binding of the p65 subunit of NF-kappaB on specific DNA probes. Inhibition of the NF-kappaB pathway using BAY 11-7085 prevents both CD40 and HLA-DR expression and cytokine production induced by NiSO(4). However, BAY 11-7085 only partially inhibited CD86 and CD83 expression induced by NiSO(4). In addition, p38 MAPK and NF-kappaB were independently activated by NiSO(4) since SB203580 did not inhibit NF-kappaB activation by NiSO(4). Interestingly, we also showed that DNCB inhibited the degradation of IkappaB-alpha induced by tumor necrosis factor-alpha leading to alteration of CD40, HLA-DR, and CD83 expression but not of CD86 and CCR7. Extensive modifications of DC phenotype by NiSO(4) in comparison to DNCB are probably the consequence of NF-kappaB activation by NiSO(4) but not by DNCB.

Microtubule inhibitors as a potential treatment for malaria

The spread of parasitic resistance has necessitated the development of new drugs and drug targets for the treatment of malaria. Microtubules, which have gained outstanding importance as target molecules for the development of anticancer drugs, are likely to be potent antimalarial targets. The clinical implementation of microtubule inhibitors has given rise to a detailed mechanistic understanding of their interaction with tubulin on the molecular level and their effects on the cellular level. By comparison, our knowledge on Plasmodium falciparum, the causative agent of the most severe form of malaria, is rather poor. This article gives an overview on the microtubule inhibitors that have been explored in the parasite, reviews their effects on parasite growth and assesses their potential as novel antimalarials.

Artificial phosphatidylserine liposome mimics apoptotic cells in inhibiting maturation and immunostimulatory function of murine myeloid dendritic cells in response to 1-chloro-2,4-dinitrobenze in vitro

Phosphatidylserine (PS) exposed on the apoptotic cell surface inhibits inflammatory responses, implying that PS may regulate the function of dendritic cells (DCs) after being phagocytosed by the latter. Here we use PS liposomes to investigate the effects of PS on the maturation and immunostimulatory functions of DCs in response to the challenge of 1-chloro-2,4-dinitrobenze (DNCB) in vitro. We demonstrate that after treatment with PS, murine DCs display reduced expression of MHC II, CD80, CD86 and CD40, but increased programmed death ligand-1 (PD-L1 and PD-L2); and increased IL-10 and inhibited IL-12 cytokine production. PS-treated DCs exhibit normal endocytic function, but ability to stimulate allogeneic T cells is reduced, similar to immature dendritic cell (iDCs). Treatment of DCs with PS liposomes also suppressed DNCB induced CD4 + T cell proliferation and IFN-gamma production. Addition of exogenous IL-12p70 during the DC-T cell co-culture restored their IFN-gamma production. Furthermore, PS-treated DCs enhance the ratio of CD4(+) CD25(high)Foxp3(+) T cells to CD4(+) T cells and PD-1 expression on CD4(+) T cells. These data demonstrate that PS liposomes have therapeutic potential in allergic contact dermatitis (ACD).

Ultraviolet spectrophotometric determination of nitrate: detecting nitrification rates and inhibition

Simple methods that rapidly detect nitrification inhibition are needed to enforce pretreatment programs and prevent upsets. The objective of this study was to demonstrate a rapid method for measuring nitrification inhibition by using nitrate generation rates (NGRs) coupled with direct UV detection of nitrate. The NGRs were measured with UV spectrophotometry at wavelengths between 225 and 240 nm, without chemical manipulation, and verified against ion chromatography. The method was shown to quickly and accurately measure nitrate concentrations after correcting for nitrite interference. Cadmium, hypochlorite and 1-chloro-2,4-dintrobenzene (CDNB) were tested for their ability to cause nitrification inhibition using this method. The CDNB was found to cause a correctable interference with the test, while hypochlorite provided an uncorrectable interference. Used as a batch method coupled with biotic and abiotic controls, this approach can be deployed at full-scale treatment plants as a relatively rapid (1.5 hours) means of identifying nitrification-inhibiting wastewaters.

Isolation and characterization of a cold-induced nonculturable suppression mutant of Vibrio vulnificus

The viable but nonculturable (VBNC) suppression mutant formed platable cells at low temperature stress after inoculation in artificial seawater (ASW). Suppression subtractive hybridization was used to identify differentially expressed genes among cDNAs of the VBNC suppression mutant and the wild-type Vibrio vulnificus strain. Glutathione S-transferase was identified as a responsive gene of the VBNC suppression mutant in our assay, and was highly expressed from the VBNC suppression mutant at low temperature stress. Culturability tests revealed that the wild-type cells were sensitive to oxidative stress in the hydrogen peroxide (H(2)O(2)) and to 1-chloro-2,4-dinitrobenzene (CDNB) compared with the VBNC suppression mutant cells. Adding glutathione showed that many wild-type V. vulnificus cells maintained culturability in cold ASW. These results suggest that non-nutritional growth inhibitors, such as peroxide that accumulates at low temperatures, influence VBNC in V. vulnificus cells.

Effects of intermittent hypoxia on oxidative stress-induced myocardial damage in mice

Obstructive sleep apnea is associated with increased risk for cardiovascular diseases. As obstructive sleep apnea is characterized by episodic cycles of hypoxia and normoxia during sleep, we investigated effects of intermittent hypoxia (IH) on ischemia-reperfusion-induced myocardial injury. C57BL/6 mice were subjected to IH (2 min 6% O(2) and 2 min 21% O(2)) for 8 h/day for 1, 2, or 4 wk; isolated hearts were then subjected to ischemia-reperfusion. IH for 1 or 2 wk significantly enhanced ischemia-reperfusion-induced myocardial injury. However, enhanced cardiac damage was not seen in mice treated with 4 wk of IH, suggesting that the heart has adapted to chronic IH. Ischemia-reperfusion-induced lipid peroxidation and protein carbonylation were enhanced with 2 wk of IH, while, with 4 wk, oxidative stress was normalized to levels in animals without IH. H(2)O(2) scavenging activity in adapted hearts was higher after ischemia-reperfusion, suggesting the increased antioxidant capacity. This might be due to the involvement of thioredoxin, as the expression level of this protein was increased, while levels of other antioxidant enzymes were unchanged. In the heart from mice treated with 2 wk of IH, ischemia-reperfusion was found to decrease thioredoxin. Ischemia-reperfusion injury can also be enhanced when thioredoxin reductase was inhibited in control hearts. These results demonstrate that IH changes the susceptibility of the heart to oxidative stress in part via alteration of thioredoxin.

Inhibition of cytosolic glutathione S-transferase activity from rat liver by copper

H(2)O(2) inactivation of particular GST isoforms has been reported, with no information regarding the overall effect of other ROS on cytosolic GST activity. The present work describes the inactivation of total cytosolic GST activity from liver rats by the oxygen radical-generating system Cu(2+)/ascorbate. We have previously shown that this system may change some enzymatic activities of thiol proteins through two mechanisms: ROS-induced oxidation and non-specific Cu(2+) binding to protein thiol groups. In the present study, we show that nanomolar Cu(2+) in the absence of ascorbate did not modify total cytosolic GST activity; the same concentrations of Cu(2+) in the presence of ascorbate, however, inhibited this activity. Micromolar Cu(2+) in either the absence or presence of ascorbate inhibited cytosolic GST activity. Kinetic studies show that GSH but no 1-chloro-2,4-dinitrobenzene prevent the inhibition on cytosolic GST induced by micromolar Cu(2+) either in the absence or presence of ascorbate. On the other hand, NEM and mersalyl acid, both thiol-alkylating agents, inhibited GST activity with differential reactivity in a dose-dependent manner. Taken together, these results suggest that an inhibitory Cu(2+)-binding effect is likely to be negligible on the overall inhibition of cytosolic GST activity observed by the Cu(2+)/ascorbate system. We discuss how modification of GST-thiol groups is related to the inhibition of cytosolic GST activity.

Induction of wheat and maize glutathione S-transferase by some herbicide safeners and their effect on enzyme activity against butachlor and terbuthylazine

The expression of glutathione S-transferase (GST) activity in wheat and maize shoots was investigated in response to treatments with the herbicide safeners benoxacor, cloquintocet-mexyl, fenchlorazole-ethyl, fenclorim, fluxofenim and oxabetrinil. These safeners significantly enhanced the GST activity towards 1-chloro-2,4-dinitrobenzene (CDNB) as a 'standard' substrate, with the exception of oxabetrinil in maize. The enhancements of GST (CDNB) activity were found to be concomitant with increases in V(max) (the reaction rate when the enzyme is fully saturated by the substrate) in wheat following cloquintocet-mexyl and fenchlorazole-ethyl treatments, and in maize following fenchlorazole-ethyl treatment. Otherwise, decreases in V(max) were observed in wheat and maize following fenclorim and fluxofenim treatments. With the exception of oxabetrinil, all the safeners significantly reduced the apparent K(M) (the substrate concentration required for 50% of maximum GST activity) of both wheat and maize GST. The V(max) and K(M) variations following safener treatments are discussed in terms of an increased expression of GST enzymes and an increased affinity for the CDNB substrate. The activity of wheat and maize GST was also assayed towards butachlor and terbuthylazine respectively; the results indicate the ability of cloquintocet-mexyl, fenchlorazole-ethyl and fluxofenim to enhance the enzyme activity in wheat and of benoxacor and fenchlorazole-ethyl to do so in maize.

Investigation of mechanisms underlying the T-cell response to the hapten 2,4-dinitrochlorobenzene

T-cell mediated contact sensitization by small molecular weight xenobiotics results in significant morbidity and absences from work. To be recognized by T-cells, xenobiotics must act as haptens, becoming protein-bound. At present, the requirement for processing and presentation of xenobiotics, the nature of the T-cell responses to them and the mechanisms that confer individual susceptibility in humans are unclear. We have investigated the T-cell response to the hapten 2,4-dinitrochlorobenzene (DNCB) which can sensitize all immunocompetent people. Fourteen healthy adults were sensitized with DNCB; 11 demonstrated positive T-cell responses to the chemical in vitro. Responding cells were of both CD4+ and CD8+ subsets, of Th1 and Tc1 phenotypes, producing high levels of IFN-gamma and low levels of IL-10. DNCB-specific T-cell clones were raised from 2 subjects, which in the presence of fixed and unfixed autologous Epstein-Barr virus transformed B cells as antigen-presenting-cells (APC), demonstrated that the chemical requires metabolic processing by the APC in order to initiate the T-cell response. Intracellular-reduced glutathione is consumed in detoxication of DNCB, leaving residual non-detoxified DNCB free to bind to proteins. The results suggest that DNCB forms multiple haptens with intracellular and extracellular proteins leading to Th1 and Tc1 responses in individuals exposed to this compound.

Isolation and characterization of a novel glutathione S-transferase-activating peptide from the oriental medicinal plant Phellodendron amurense

The aim of this study was to elucidate the characteristics of glutathione S-transferase (GST)-activating compounds from medicinal plants. Among 265 kinds of medicinal plants, Phellodendron amurense showed the highest GST activity at 174.8%. The GST-activating compound of P. amurense was maximally extracted when treated with distilled water at 30 degrees C for 12 h. The compound was purified by ultrafiltration, Sephadex G-10 gel filtration chromatography, and reverse-phase HPLC. The purified GST-activating compound from P. amurense was a novel tetrapeptide with an amino acid sequence of Ala-Pro-Trp-Cys and its molecular weight was estimated to be 476 Da. It also displayed a clear detoxicative effect in 1-chloro-2,4-dinitrobenzene treated mice at a dosage of mg/kg body weight.

Inconsistencies between cytokine profiles, antibody responses, and respiratory hyperresponsiveness following dermal exposure to isocyanates

Cytokine profiling of local lymph node responses has been proposed as a simple test to identify chemicals, such as low molecular weight diisocyanates, that pose a significant risk of occupational asthma. Previously, we reported cytokine messenger RNA (mRNA) profiles for dinitrochlorobenzene (DNCB) and six isocyanates: toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, isophorone diisocyanate, p-tolyl(mono)isocyanate, and meta-tetramethylene xylene diisocyanate. The present study was conducted to test the hypothesis that relative differences in the cytokine profile are predictive of relative differences in total serum immunoglobulin (Ig) E and respiratory responses to methacholine (Mch) following dermal exposure to the chemicals. After a preliminary experiment to determine an exposure regimen sufficient to achieve responses to Mch following dermal diisocyanate exposure, BALB/c mice received nine dermal exposures over a period of 28 days to one of six isocyanates, DNCB, or vehicle. Mice were then challenged with increasing doses of Mch and responsiveness was assessed using whole-body plethysmography. Serum antibody responses and cytokine mRNA profiles in the draining lymph node were also assessed. In separate experiments, cytokine protein assays were performed after five dermal exposures over a 14-day period. The response pattern for interleukin (IL)-4, IL-10, and IL-13 for the different isocyanates was highly reproducible as determined by RNAse protection assay, reverse transcription-PCR, or cytokine protein levels. However, the relative differences in T-helper cytokine profiles were not predictive of relative differences in either total serum IgE or respiratory responses to Mch following dermal exposure. The data suggest that the cytokine profiling approach needs to be further developed and refined before adoption and that other approaches to hazard identification should be pursued as well. Based on the weight of evidence from all the assays performed, it appears that all six isocyanates tested have some potential to cause respiratory hypersensitivity following dermal exposure.

Molecular cloning of AbGst1 encoding a glutathione transferase differentially expressed during exposure of Alternaria brassicicola to isothiocyanates

The AbGst1 gene encoding a glutathione transferase from the necrotrophic pathogen Alternaria brassicicola was cloned from a benzyl isothiocyanate-treated conidial culture using differential display reverse transcription. The deduced amino-acid sequence of AbGst1p showed a significant degree of similarity to glutathione transferase-I from Saccharomyces cerevisiae and glutathione transferase-III from Schizosaccharomyces pombe. The transcription of AbGst1 was significantly enhanced by isothiocyanates, heavy metals and 1-chloro-2,4-dinitrobenzene. However, no significant transcript response was obtained with superoxide-generating menadione and paraquat. Recombinant AbGst1p expressed in Escherichia coli exhibited high transferase activity with allyl and benzyl isothiocyanates as substrate compared with 1-chloro-2,4-dinitrobenzene, but no peroxidase activity was detected. AbGst1 was upregulated in planta during the first day postinfection, suggesting the potential involvement of this enzyme in isothiocyanate detoxification mechanisms during host plant infection.

Increased glutathione conjugate transport: a possible compensatory protection mechanism against oxidative stress in obesity?

OBJECTIVE

To compare glutathione S-conjugate transport in obese and nonobese persons, and how glutathione S-conjugates are involved in the antioxidant status in obesity.

MATERIALS AND METHODS

The efflux of glutathione conjugates and malondialdehyde (MDA) levels were measured in erythrocytes of obese (N = 33) and nonobese (N = 28) persons at every 30 min during a 120 min incubation time in vitro. 2,4-dinitrophenyl-S-glutathione (DNP-SG) represented the glutathione S-conjugate.

RESULTS

The efflux of conjugate in erythrocytes from obese subjects (708 +/- 147 DNP-SG efflux nmol/ml erythrocytes/h) was significantly higher than that of control group (490 +/- 105 DNP-SG efflux nmol/ml erythrocytes/h) (P < 0.05). At all time points measured (30-120 min), there was an increase in DNP-SG efflux in obese group (P < 0.05). This is manifested by a decrease in cellular DNP-SG levels. The susceptibility of erythrocytes to in vitro 1-chloro-2,4-dinitrobenzene (CDNB)-induced oxidative stress were greater for cells of control group (P < 0.05), although hemolysis sensitivity of these cells are not different between both groups (P > 0.05). Following CDNB pretreatment, incubation of erythrocyte with vanadate, a DNP-SG transport inhibitor, resulted in an increase of MDA in both groups. However, in this case, the difference in susceptibility was not related to obesity. On the other hand, while erythrocyte glutathione level was lower in obese subjects (79% of control) than in controls (P < 0.05), the adenosine 5'-triphosphate (ATP) levels, the enzyme activities of glutathione S-transferase (GST) and the conjugation capacities of the erythrocytes were not different between groups (P>0.05).

CONCLUSION

Obesity may increase erythrocyte glutathione conjugate transport independent from ATP and GST activity that may protect against MDA formation in vitro.

The cytokine-dependent MUTZ-3 cell line as an in vitro model for the screening of contact sensitizers

Langerhans cells (LC) are key mediators of contact allergenicity in the skin. However, no in vitro methods exist which are based on the activation process of LC to predict the sensitization potential of chemicals. In this study, we have evaluated the performances of MUTZ-3, a cytokine-dependent human monocytic cell line, in its response to sensitizers. First, we compared undifferentiated MUTZ-3 cells with several standard human cells such as THP-1, KG-1, HL-60, K-562, and U-937 in their response to the strong sensitizer DNCB and the irritant SDS by monitoring the expression levels of HLA-DR, CD54, and CD86 by flow cytometry. Only MUTZ-3 and THP-1 cells show a strong and specific response to sensitizer, while other cell lines showed very variable responses. Then, we tested MUTZ-3 cells against a wider panel of sensitizers and irritants on a broader spectrum of cell surface markers (HLA-DR, CD40, CD54, CD80, CD86, B7-H1, B7-H2, B7-DC). Of these markers, CD86 proved to be the most reliable since it detected all sensitizers, including benzocaine, a classical false negative in local lymph node assay (LLNA) but not irritants. We confirmed the MUTZ-3 response to DNCB by real-time PCR analysis. Taken together, our data suggest that undifferentiated MUTZ-3 cells may represent a valuable in vitro model for the screening of potential sensitizers.

Direct measurement of the rate of glutathione synthesis in 1-chloro-2,4-dinitrobenzene treated human erythrocytes

Cell glutathione scavenges free radicals, degrades peroxides, removes damaging electrophiles and maintains the redox state. The aim of this study was to develop an effective and efficient method to measure the rate of glutathione synthesis from its constituent amino acids in whole erythrocytes (RBCs). RBCs (10% haematocrit) were exposed to 0.3 mM 1-chloro-2,4-dinitrobenzene (CDNB) to lower their total glutathione content by 70% and then incubated with glucose, and N-acetylcysteine as a cysteine source. Over 3 h, glutathione levels increased at a constant rate of 1.2 micromol (L RBC)(-1)min(-1), almost 5 times faster than the rate of glutathione synthesis in RBCs with normal glutathione levels. Glutathione at concentrations normally found in RBCs is known to inhibit glutamate cysteine ligase (the major rate controlling enzyme for glutathione synthesis). The rate of glutathione recovery was substantially reduced in RBCs treated with buthionine sulfoximine, a specific inhibitor of glutamate cysteine ligase. Our results indicate that the measurement of glutathione recovery rate after CDNB treatment can be used to estimate de novo synthesis of glutathione. Application of this direct method for measuring glutathione synthesis will increase understanding of the interactions of effectors that determine glutathione levels in RBCs under various physiological and pathological conditions.

Band 3 tyr-phosphorylation in normal and glucose-6-phospate dehydrogenase-deficient human erythrocytes

Haemolysis is usually episodic in glucose-6-phosphate dehydrogenase (G6PD) deficiency, often triggered by a period of oxidative stress. In the present work, we investigate a possible biochemical mechanism underlying the enhanced susceptibility of G6PD deficient red blood cells (RBC) to oxidative stress. We analysed eight male subjects with Mediterranean glucose-6P-dehydrogenase deficiency (G6PDd), class II, for their ability in phosphorylating erythrocyte membrane band 3 following oxidative and osmotic stress. Our findings show that this sensitivity is connected to an early membrane band 3 Tyr-phosphorylation in the presence of diamide. However, since both Syk, and Lyn kinases, and SHP-2 phosphatase, mostly implicated in the band 3 P-Tyr level regulation, are alike in content and activity in normal and patient erythrocytes, an alteration in the membrane organization is likely the cause of the anomalous response to the oxidant. We report, in fact, that hypertonic-induced morphological change in G6PDd erythrocyte induces a higher membrane band 3 Tyr-phosphorylation, suggesting a pre-existing membrane alteration, likely due to the chronic lowering of the redox systems in patients. We also report that 1-chloro-2,4-dinitrobenzene-pre-treatment of normal red cells can alter the normal protein-protein and protein-membrane interaction under hypertonic rather than oxidative stress, thus partially resembling the response in patients, and that RBC may utilize a wider range of redox defence, under oxidative conditions, including, but not exclusively, NADPH and glutathione. On the whole, these results would encourage a different approach to the evaluation of the effects of pharmacological administration to patients, giving more attention to the possible drug-induced membrane alteration evidenced by the abnormal band 3 Tyr-phosphorylation.

Na-K-ATPase in rat cerebellar granule cells is redox sensitive

Redox-induced regulation of the Na-K-ATPase was studied in dispersed rat cerebellar granule cells. Intracellular thiol redox state was modulated using glutathione (GSH)-conjugating agents and membrane-permeable ethyl ester of GSH (et-GSH) and Na-K-ATPase transport and hydrolytic activity monitored as a function of intracellular reduced thiol concentration. Depletion of cytosolic and mitochondrial GSH pools caused an increase in free radical production in mitochondria and rapid ATP deprivation with a subsequent decrease in transport but not hydrolytic activity of the Na-K-ATPase. Selective conjugation of cytosolic GSH did not affect free radical production and Na-K-ATPase function. Unexpectedly, overloading of cerebellar granule cells with GSH triggered global free radical burst originating most probably from GSH autooxidation. The latter was not followed by ATP depletion but resulted in suppression of active K(+) influx and a modest increase in mortality. Suppression of transport activity of the Na-K-ATPase was observed in granule cells exposed to both permeable et-GSH and impermeable GSH, with inhibitory effects of external and cytosolic GSH being additive. The obtained data indicate that redox state is a potent regulator of the Na-K-ATPase function. Shifts from an "optimal redox potential range" to higher or lower levels cause suppression of the Na-K pump activity.

Time-dependent modulation of thioredoxin reductase activity might contribute to sulforaphane-mediated inhibition of NF-kappaB binding to DNA

The chemopreventive agent sulforaphane (SFN) exerts anti-inflammatory activity by thiol-dependent inhibition of nuclear factor kappaB (NF-kappaB) DNA binding. To further analyze the underlying mechanisms, we focused on the thioredoxin/thioredoxin reductase (TrxR) system as a key redox mechanism regulating NF-kappaB DNA binding. Using cultured Raw 264.7 mouse macrophages as a model, 1-chloro-2,4-dinitrobenzene (CDNB), a known inhibitor of TrxR, was identified as an inhibitor of lipopolysaccharide (LPS)-mediated nitric oxide (NO) production and of NF-kappaB DNA binding. CDNB and SFN acted synergistically with respect to inhibition of LPS-induced NO release, and we consequently identified SFN as a novel inhibitor of TrxR enzymatic activity in vitro. Short-term treatment of Raw macrophages with SFN or CDNB resulted in the inhibition of TrxR activity in vivo with half-maximal inhibitory concentration of 25.0 +/- 3.5 microM and 9.4 +/- 3.7 microM, respectively, whereas after a 24-h treatment with 25 microM SFN, TrxR activity was >1.5-fold elevated. In additional experiments, we could exclude that inhibition of trans-activating activity of NF-kappaB contributed to the reduced expression of pro-inflammatory proteins by SFN, based on transient transfection experiments with a (kappaB)(2)- chloramphenicol acetyltransferase construct and a lack of inhibition of protein kinase A activity. These findings further emphasize the importance of redox modulation or thiol reactivity for the regulation of NF-kappaB-dependent transcription by SFN. Antioxid. Redox Signal. 7, 1601-1611.

Regulation by allergens of chemokine receptor expression on in vitro-generated dendritic cells

Immature dendritic cells (DCs) derived from CD34+ progenitor cells or peripheral monocytes, are used as in vitro sensitization models in many chemical allergen treatment studies. During the sensitization, DCs follow maturation process and gain the capacity to migrate to lymph nodes where they stimulate T cells. Chemokine receptor allows DCs to migrate along chemotactic gradients. In this work, we used immature DCs from peripheral monocytes to evaluate the influence of allergens on chemokine receptor and surface-marker expression. We tested the sensitizers dinitrochlorobenzene, Bandrowski's base, and coumarin, as well as the tolerogen dichloronitrobenzene, the irritant sodium dodecyl sulfate and the solvent dimethyl sulfoxide. All skin sensitizers up-regulated the co-stimulatory molecule CD86 and increased the CD83+ cell population. No expression of the chemokine receptors CCR2, CCR3, CCR6, or CXCR5 was observed on DCs exposed to the tested chemicals. The strong allergen dinitrochlorobenzene slightly increased CCR7 expression on DCs but down-regulated CCR1 surface expression. CCR1 down-regulation was not mediated by a classical maturation pathway, as it was unaffected by the corticosteroid dexamethasone.