Chemical activation of innate and specific immunity in contact dermatitis

Socs1-knockout in skin-resident CD4+ T cells in a protracted contact-allergic reaction results in an autonomous skin inflammation with features of early-stage mycosis fungoides

Recent detailed genomic analysis of mycosis fungoides (MF) identified suppressor of cytokine signaling 1 (SOCS1), an inhibitor of JAK/STAT signaling, as one of the frequently deleted tumor suppressors in MF, and one-copy deletion of SOCS1 was confirmed in early-stage MF lesions. To better understand the functional role of SOCS1 in the genesis of MF, we used a genetically engineered mouse model emulating heterozygous SOCS1 loss in skin resident CD4+ T cells. In these mice an experimentally induced contact-allergic reaction was maintained for 20 weeks. Ten weeks after discontinuing contact-allergic challenges, only the skin with locally one-copy deletion of Socs1 in CD4+ T cells still showed high numbers of CD3+/CD4+ Socs1 k.o. cells in the dermis (p ＜ 0.0001) with prevalent Stat3 activation (p ＜0.001). And in one out of 9 mice, this had progressed to far more dramatic increases, including the thickened epidermis, and with an explosive growth of Socs1 k.o. T cells in circulation; indicative of cutaneous lymphoma. Hence, we show that Socs1 mono-allelic loss in CD4+ T cells locally in protractedly inflamed skin results in autonomous skin inflammation with features of early-stage MF.

C10orf99/GPR15L Regulates Proinflammatory Response of Keratinocytes and Barrier Formation of the Skin

The epidermis, outermost layer of the skin, forms a barrier and is involved in innate and adaptive immunity in an organism. Keratinocytes participate in all these three protective processes. However, a regulator of keratinocyte protective responses against external dangers and stresses remains elusive. We found that upregulation of the orphan gene 2610528A11Rik was a common factor in the skin of mice with several types of inflammation. In the human epidermis, peptide expression of G protein-coupled receptor 15 ligand (GPR15L), encoded by the human ortholog C10orf99, was highly induced in the lesional skin of patients with atopic dermatitis or psoriasis. C10orf99 gene transfection into normal human epidermal keratinocytes (NHEKs) induced the expression of inflammatory mediators and reduced the expression of barrier-related genes. Gene ontology analyses showed its association with translation, mitogen-activated protein kinase (MAPK), mitochondria, and lipid metabolism. Treatment with GPR15L reduced the expression levels of filaggrin and loricrin in human keratinocyte 3D cultures. Instead, their expression levels in mouse primary cultured keratinocytes did not show significant differences between the wild-type and 2610528A11Rik deficient keratinocytes. Lipopolysaccharide-induced expression of Il1b and Il6 was less in 2610528A11Rik deficient mouse keratinocytes than in wild-type, and imiquimod-induced psoriatic dermatitis was blunted in 2610528A11Rik deficient mice. Furthermore, repetitive subcutaneous injection of GPR15L in mouse ears induced skin inflammation in a dose-dependent manner. These results suggest that C10orf99/GPR15L is a primary inducible regulator that reduces the barrier formation and induces the inflammatory response of keratinocytes.

Dynamic Regulation of the Molecular Mechanisms of Regulatory T Cell Migration in Inflamed Skin

The presence of regulatory T cells (Tregs) in skin is important in controlling inflammatory responses in this peripheral tissue. Uninflamed skin contains a population of relatively immotile Tregs often located in clusters around hair follicles. Inflammation induces a significant increase both in the abundance of Tregs within the dermis, and in the proportion of Tregs that are highly migratory. The molecular mechanisms underpinning Treg migration in the dermis are unclear. In this study we used multiphoton intravital microscopy to examine the role of RGD-binding integrins and signalling through phosphoinositide 3-kinase P110δ (PI3K p110δ) in intradermal Treg migration in resting and inflamed skin. We found that inflammation induced Treg migration was dependent on RGD-binding integrins in a context-dependent manner. α_v integrin was important for Treg migration 24 hours after induction of inflammation, but contributed to Treg retention at 48 hours, while β₁ integrin played a role in Treg retention at the later time point but not during the peak of inflammation. In contrast, inhibition of signalling through PI3K p110δ reduced Treg migration throughout the entire inflammatory response, and also in the absence of inflammation. Together these observations demonstrate that the molecular mechanisms controlling intradermal Treg migration vary markedly according to the phase of the inflammatory response.

An isoflavone extract from soybean cake suppresses 2,4-dinitrochlorobenzene-induced contact dermatitis

ETHNOPHARMACOLOGICAL RELEVANCE

Numerous epidemiological and clinical studies have demonstrated the protective role of dietary isoflavones against development of several chronic diseases. ISO-1, one fraction of isoflavone powders derived from soybean cake, is reported to attenuate inflammation and photodamage.

AIM OF THE STUDY

Contact dermatitis is a common inflammatory skin disease, which accounts for most occupational skin disorders. Instead of oral administration, we aimed to explore the effects of topical ISO-1 application on contact dermatitis by using 2,4-dinitrochlorobenzene (DNCB)-stimulated HaCaT keratinocytes and DNCB-induced mouse dermatitis as models.

MATERIALS AND METHODS

In the in vitro study, we first evaluated the biologic effects of DNCB on HaCaT keratinocytes. HaCaT keratinocytes were treated with 2,4-dinitrochlorobenzene (DNCB), and cell viability was measured by MTT assay. Then, we detect the prominent induction of IL-8 mRNA expression after DNCB and ISO-1 treatment by reverse transcription polymerase chain reaction (RT-PCR), and release of IL-8 from HaCaT keratinocytes was measured by ELISA assay. HaCaT keratinocytes were pretreated with ISO-1 and then treated with DNCB, phosphorylation of JNK, p38, ERK and IκBα was analyzed by western blot. In the in vivo study, the hairless mice were used for an induced contact dermatitis model. The surface changes in the dorsal skin after DNCB and ISO-1 treatment were recorded using photography, and TEWL, erythema were measured using an MPA-580 cutometer. Blood was also collected from mice for measurement of white blood cell counts.

RESULTS

Results showed ISO-1 inhibited DNCB-induced IL-8 production and also suppressed DNCB-induced phosphorylation of JNK and p38, and IκBα in HaCaT. In the animal model of DNCB-induced contact dermatitis, topical ISO-1 treatment significantly decreased DNCB-induced erythema and transepidermal water loss (TEWL) in mouse skin. ISO-1 also reduced DNCB-induced skin thickening and increase of white blood cell count.

CONCLUSIONS

ISO-1 is promising for improvement of DNCB-induced inflammation and skin barrier impairment, suggesting the potential application of topical ISO-1 for inflammatory dermatoses.

The preclinical efficacy, selectivity and pharmacologic profile of MK-5932, an insulin-sparing selective glucocorticoid receptor modulator

Glucocorticoids are used widely in the treatment of inflammatory diseases, but use is accompanied by a significant burden of adverse effects. It has been hypothesized that gene- and cell-specific regulation of the glucocorticoid receptor by small molecule ligands could be translated into a therapeutic with an improved risk-benefit profile. MK-5932 is a highly selective glucocorticoid receptor modulator that is anti-inflammatory in vivo with an improved profile on glucose metabolism: Bungard et al. (2011). Bioorg. Med. Chem. 19, 7374-7386. Here we describe the full biological profile of MK-5932. Cytokine production following lipopolysaccharide (LPS) challenge was blocked by MK-5932 in both rat and human whole blood. Oral administration reduced inflammatory cytokine levels in the serum of rats challenged with LPS. MK-5932 was anti-inflammatory in a rat contact dermatitis model, but was differentiated from 6-methylprednisolone by a lack of elevation of fasting insulin or glucose levels after 7 days of dosing, even at high exposure levels. In fact, animals in the vehicle group were consistently hyperglycemic at the end of the study, and MK-5932 normalized glucose levels in a dose-dependent manner. MK-5932 was also anti-inflammatory in the rat collagen-induced arthritis and adjuvant-induced arthritis models. In healthy dogs, oral administration of MK-5932 exerted acute pharmacodynamic effects with potency comparable to prednisone, but with important differences on neutrophil counts, again suggestive of a dissociated profile. Important gaps in our understanding of mechanism of action remain, but MK-5932 will be a useful tool in dissecting the mechanisms of glucose dysregulation by therapeutic glucocortiocids.

Cytokines and chemokines in irritant contact dermatitis

Irritant contact dermatitis is a result of activated innate immune response to various external stimuli and consists of complex interplay which involves skin barrier disruption, cellular changes, and release of proinflammatory mediators. In this review, we will focus on key cytokines and chemokines involved in the pathogenesis of irritant contact dermatitis and also contrast the differences between allergic contact dermatitis and irritant contact dermatitis.

Inflammatory and immune mechanisms in contact hypersensitivity (CHS) in rats

Contact hypersensitivity (CHS) is a T-cell-mediated skin inflammatory reaction to cutaneous exposure to small sensitizing chemicals, haptens. Majority of CHS studies were conducted in mice and there is paucity of data in other experimental animals. In this review, after a brief survey of murine CHS, hitherto known characteristics of CHS in rats were presented including inflammatory and immune mechanisms of both sensitization and elicitation phases. Survey of literature of rat CHS is presented, with our data concerning the importance of genetic background both in the induction and in the expression of reaction to dinitrochlorobenzene. The knowledge of CHS in rats, preferred animal in immunopharmacological studies, might help development of immunomodulatory intervention in contact allergy.

Schizonepeta tenuifolia inhibits the development of atopic dermatitis in mice

Historically, Schizonepeta tenuifolia (ST) has been used for the treatment of skin disorders, such as allergic dermatitis, eczema, and inflammatory diseases. In this study, we examined whether ST inhibited 2,4-dinitrochlorobenzene (DNCB)-induced atopic dermatitis (AD) in BALB/c mice. In histopathological analyses of the epidermis and dermis, skin thickness was significantly increased in DNCB-induced mice as compared with normal group. Treatment with ST inhibited this inflammatory change and markedly suppressed the secretion of immunoglobulin E, tumor necrosis factor α, and interleukin 6 levels in the serum of DNCB-induced mice. In addition, ST treatment significantly restored the upregulation of proinflammatory factors, such as nuclear factor (NF)-κB and mitogen-activated protein kinase expression. Taken together, due to its ability to suppress inflammatory factors and upregulate proinflammatory factors, ST may be useful as a therapeutic treatment for AD. ST extract application decreased both epidermis and dermis thickness in DNCB-induced mice. In serum, ST reduced immunoglobulin E, tumor necrosis factor, and interleukin 6 level. In addition, ST suppressed NF-κB activation as well as the mitogen-activated protein kinase activities.

Systemic immunomodulatory effects of topical dinitrochlorobenzene (DNCB) in rats. Activity of peripheral blood polymorphonuclear cells

Topical application of dinitrochlorobenzene (DNCB) is employed in the immunotherapy of skin diseases. Activation of T-cell mediated immune responses (Th1/type1) is the supposed mechanism of the clinical effect of DNCB, but there are no data concerning innate/inflammatory mechanisms. In this study, the effect of repeated topical DNCB application on peripheral blood polymorphonuclear (PMN) leukocytes has been examined in two rat strains which differ in the propensity to mount Th1/type1 or Th2/type2 responses. The dynamics of changes in PMN numbers and effector activities (respiratory burst, nitric oxide production and myeloperoxidase content), as well as in adhesion and TNF-α production following the rat skin sensitization with low (0.4%) and high (4%) DNCB doses were measured. Both priming and activation of PMNs were observed following skin sensitization with DNCB, with dose-dependent as well as time-dependent differences in some PMN activities. Obtained data might be relevant for understanding the immune mechanisms of topical DNCB therapy.

Severe dermatitis with loss of epidermal Langerhans cells in human and mouse zinc deficiency

Zinc deficiency can be an inherited disorder, in which case it is known as acrodermatitis enteropathica (AE), or an acquired disorder caused by low dietary intake of zinc. Even though zinc deficiency diminishes cellular and humoral immunity, patients develop immunostimulating skin inflammation. Here, we have demonstrated that despite diminished allergic contact dermatitis in mice fed a zinc-deficient (ZD) diet, irritant contact dermatitis (ICD) in these mice was more severe and prolonged than that in controls. Further, histological examination of ICD lesions in ZD mice revealed subcorneal vacuolization and epidermal pallor, histological features of AE. Consistent with the fact that ATP release from chemically injured keratinocytes serves as a causative mediator of ICD, we found that the severe ICD response in ZD mice was attenuated by local injection of soluble nucleoside triphosphate diphosphohydrolase. In addition, skin tissue from ZD mice with ICD showed increased levels of ATP, as did cultured wild-type keratinocytes treated with chemical irritants and the zinc-chelating reagent TPEN. Interestingly, numbers of epidermal Langerhans cells (LCs), which play a protective role against ATP-mediated inflammatory signals, were decreased in ZD mice as well as samples from ZD patients. These findings suggest that upon exposure to irritants, aberrant ATP release from keratinocytes and impaired LC-dependent hydrolysis of nucleotides may be important in the pathogenesis of AE.

Polymorphisms in genes involved in innate immunity and susceptibility to benzene-induced hematotoxicity

Benzene, a recognized hematotoxicant and carcinogen, can damage the human immune system. We studied the association between single nucleotide polymorphisms (SNPs) in genes involved in innate immunity and benzene hematotoxicity in a cross-sectional study of workers exposed to benzene (250 workers and 140 controls). A total of 1,236 tag SNPs in 149 gene regions of six pathways were included in the analysis. Six gene regions were significant for their association with white blood cell (WBC) counts (MBP, VCAM1, ALOX5, MPO, RAC2, and CRP) based on gene-region (P<0.05) and SNP analyses (FDR<0.05). VCAM1 rs3176867, ALOX5 rs7099684, and MPO rs2071409 were the three most significant SNPs. They showed similar effects on WBC subtypes, especially granulocytes, lymphocytes, and monocytes. A 3-SNP block in ALOXE3 (rs7215658, rs9892383, and rs3027208) showed a global association (omnibus P = 0.0008) with WBCs even though the three SNPs were not significant individually. Our study suggests that polymorphisms in innate immunity genes may play a role in benzene-induced hematotoxicity; however, independent replication is necessary.

Percutaneous toxicity of dinitrochlorobenzene (DNCB) in rats

Contact hypersensitivity reaction (CHS) is a T-cell-mediated skin inflammatory reaction to cutaneous exposure to small sensitizing chemicals, haptens. While the significance of local inflammatory skin response to the hapten application in CHS induction and expression is known, there is paucity of data concerning systemic inflammation in CHS. In this study, changes in cellular (peripheral blood granulocytes) and humoral (plasma tumor necrosis factor (TNF)-α levels) components of inflammation during sensitization of rats with two consecutive applications of dinitrochlorobenzene (DNCB) were examined. The impact of sensitization on these parameters was determined by employing low (0.4%) and high (4%) hapten doses and by examining the dynamics (i.e. one and three days following the last application of DNCB) of these changes. Dose-dependent increase in relative numbers and priming (for respiratory burst and adhesion) effect of skin sensitization with DNCB on peripheral blood neutrophils in rats were noted. No changes in circulating TNF-α levels were observed following the sensitization. The increase in lung myeloperoxidase content and histologically evident presence of neutrophils was observed in lungs of the sensitized rats. The changes in granulocyte priming for adhesion might have accounted for the observed increase in lung neutrophil content in the sensitized rats.

Restraint stress fails to modulate cutaneous hypersensitivity responses in mice lacking the adenosine A1 receptor

Psychological stress has long been associated with effects on immune function and disease. In particular, differential effects of acute and chronic stress on skin immunity occur in the rodent restraint stress model, with acute stress enhancing and chronic stress suppressing cutaneous hypersensitivity. Extracellular levels of adenosine are known to modulate diverse biological activities in the CNS and peripheral tissues and serve an important protective function against physiological stressors such as inflammation and ischemia. In this study, we utilized the restraint stress model and the skin sensitizer dinitrofluorobezene to test the hypothesis that perceived stress influences contact hypersensitivity through an adenosine A(1) receptor-mediated mechanism. We subjected hapten-sensitized A(1) receptor knockout (A1 KO) mice and their wild-type (WT) littermates to either acute (2.5 h) or chronic (5 h daily × 4 weeks) restraint stress, followed by hapten re-challenge of the pinna. Daily measurements of the resulting pinna swellings from each group were compared to reactions in non-stressed controls. In WT mice, pinna swelling was augmented in acutely stressed mice and suppressed in the chronically stressed group. In contrast, contact hypersensitivity responses in the A1 KO mice failed to be affected by either acute or chronic stress. Absence of the adenosine A(1) receptor did not affect levels of plasma corticosterone or urine catecholamines under these stressful conditions but did lead to reduced numbers of circulating neutrophil granulocytes compared to stressed WT animals. These results suggest that the adenosine A(1) receptor pathway plays a role in the process by which perceived psychological stress influences the contact hypersensitivity response.

Contact allergic response to dinitrochlorobenzene (DNCB) in rats: insight from sensitization phase

Contact hypersensitivity (CHS) is a T-cell-mediated skin inflammatory reaction to cutaneous exposure to small sensitizing chemicals, haptens. Majority of CHS studies were conducted in mice and there is paucity of data in other experimental animals. In the present study, characteristics of contact hypersensitivity reaction to dinitrochlorobenzene (DNCB) were determined in Th1-prone Dark Agouti (DA) rats by evaluating sensitization phase as a function of time-dependent changes in draining lymph nodes (DLN). Apart from basic indices of DLN activity (cellularity and proliferation), the production of cytokines relevant for CHS induction, interleukin-6 (IL-6), interferon-γ (IFN-γ), interleukin-17 (IL-17) and interleukin-4 (IL-4) was analyzed. Anti-inflammatory cytokine interleukin-10 (IL-10) production by DLN cells was determined as well. Highest production of IL-6, IFN-γ and IL-17 in sensitized animals was observed at day 3 after DNCB application, with a decrease at day 5. Increased messages for IFN-γ and IL-17 were noted at this time point. In contrast to inflammatory cytokines, anti-inflammatory cytokine interleukin-4 (IL-4) was undetectable during the entire sensitization phase. Differential pattern (IL-6 and IFN-γ) and level (IFN-γ and IL-17) of inflammatory cytokine production was noted in sensitized Th2-prone Albino Oxford (AO) rats. Similarly to DA rats, no changes in IL-4 were noted in AO rats. Strain-dependent differences in inflammatory cytokine production seem to be based on anti-inflammatory cytokine interleukin-10 (IL-10). Production of IFN-γ concomitantly with undetectable IL-4 in both strains classify rat CHS to DNCB as Th1/type 1 reaction. Detection of IL-17 in sensitized DLN cells points to the involvement of T(IL-17) cells in rat contact hypersensitivity.

Protective effects of black rice bran against chemically-induced inflammation of mouse skin

We investigated the inhibitory effects of black rice (cv. LK1-3-6-12-1-1) bran against 12-O-tetradecanolylphorbol-13-acetate (TPA)-induced skin edema and 2,4-dinitrofluorobenzene (DNFB)-induced allergic contact dermatitis (ACD) in inflammatory mouse models. We also determined the effects of the bran extract on the following biomarkers: pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), eicosanoids leukotriene B4 (LTB4), and prostaglandin E2 (PGE2). Topical application of TPA to ears of CD-1 mice induced inflammation accompanied with substantial increase in TNF-α, IL-1β, IL-6, LTB4, and PGE2 levels and an elevation in intercellular adhesion molecule-1 (ICAM-1) gene expressions in ear skin tissues. Intraperitoneal injection of black rice bran extract prior to TPA application in mice significantly suppressed TPA-induced inflammation (edema) and induced a marked decrease in the production of TNF-α, IL-1β, IL-6, and LTB4. Feeding mice a standard diet with added 10% black rice bran also significantly suppressed DNFB-induced allergic contact dermatitis on the skin of the mice. By contrast, a nonpigmented brown rice bran extract did not inhibit the TPA-induced edema and failed to significantly suppress production of pro-inflammatory biomarkers (mediators). These in vivo findings further demonstrate the potential value of black rice bran as an anti-inflammatory and antiallergic food ingredient and possibly also as a therapeutic agent for the treatment and prevention of diseases associated with chronic inflammation.

Topical anti-inflammatory potential of Physalin E from Physalis angulata on experimental dermatitis in mice

The anti-inflammatory effect of physalin E, a seco-steroid isolated from Physalis angulata L. was evaluated on acute and chronic models of dermatitis induced by 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and oxazolone, respectively, in mouse ear. The changes in ear edema/thickness, production of pro-inflammatory cytokines (TNF-alpha and IFN-gamma), myeloperoxidase (MPO) activity, and histological and immunohistochemical findings were analysed, as indicators of dermal inflammation. Similar to dexamethasone, topically applied Physalin E (0.125; 0.25 and 0.5 mg/ear) potently inhibited the TPA and oxazolone-induced dermatitis, leading to substantial reductions in ear edema/thickness, pro-inflammatory cytokines, and MPO activity. These effects were reversed by mifepristone, a steroid antagonist and confirmed by immunohistochemical and histopathological analysis. The data suggest that physalin E may be a potent and topically effective anti-inflammatory agent useful to treat the acute and chronic skin inflammatory conditions.

A reconsideration of acute Beryllium disease

CONTEXT

Although chronic beryllium disease (CBD) is clearly an immune-mediated granulomatous reaction to beryllium, acute beryllium disease (ABD) is commonly considered an irritative chemical phenomenon related to high exposures. Given reported new cases of ABD and projected increased demand for beryllium, we aimed to reevaluate the patho physiologic associations between ABD and CBD using two cases identified from a survey of beryllium production facility workers.

CASE PRESENTATION

Within weeks after exposure to beryllium fluoride began, two workers had systemic illness characterized by dermal and respiratory symptoms and precipitous declines in pulmonary function. Symptoms and pulmonary function abnormalities improved with cessation of exposure and, in one worker, recurred with repeat exposure. Bronchoalveolar lavage fluid analyses and blood beryllium lymphocyte proliferation tests revealed lymphocytic alveolitis and cellular immune recognition of beryllium. None of the measured air samples exceeded 100 microg/m(3), and most were < 10 microg/m(3), lower than usually described. In both cases, lung biopsy about 18 months after acute illness revealed noncaseating granulomas. Years after first exposure, the workers left employment because of CBD.

DISCUSSION

Contrary to common understanding, these cases suggest that ABD and CBD represent a continuum of disease, and both involve hypersensitivity reactions to beryllium. Differences in disease presentation and progression are likely influenced by the solubility of the beryllium compound involved.

RELEVANCE TO PRACTICE

ABD may occur after exposures lower than the high concentrations commonly described. Prudence dictates limitation of further beryllium exposure in both ABD and CBD.

The glucocorticoid-induced TNF receptor-related protein (GITR)-GITR ligand pathway acts as a mediator of cutaneous dendritic cell migration and promotes T cell-mediated acquired immunity

Glucocorticoid-induced TNFR-related protein (GITR) has various roles in the activation of T cells and inflammation. In this study, we investigated the roles of the GITR-GITR ligand (GITRL) pathway in contact hypersensitivity (CH). Treatment with anti-GITRL mAb at sensitization inhibited CH responses. Depletion studies using an anti-CD25 or anti-PDCA-1 mAb revealed that regulatory T cells and plasmacytoid dendritic cells (DCs), known to express high levels of GITR and GITRL, respectively, were not apparently involved in GITRL-mediated CH responses. Treatment with/addition of anti-GITRL mAb in the experiments for hapten-specific T cell proliferation and IFN-gamma production showed a minor contribution of the GITRL, which was weakly expressed on DCs in draining lymph nodes (dLNs). Interestingly, anti-GITRL mAb treatment inhibited the migration of cutaneous DCs to the dLNs. Epidermal keratinocytes (KCs) constitutively express GITR, whereas Langerhans cells (LCs) express higher levels of GITRL compared with DCs in dLNs. GITR ligation, by an anti-GITR mAb, in KCs promoted expression of multiple proinflammatory cytokines and blockade of GITRL-inhibited IL-1beta and CCR7 expression in sensitized skin. These results suggest that the GITR-GITRL pathway promotes epidermal inflammatory cytokine production by KCs and LCs, resulting in migration of cutaneous DCs from the skin to the dLNs. This is the first report demonstrating the involvement of the GITR-GTRL pathway in interactions with KCs and LCs and the migration of DCs. Our findings provide important implications for understanding the molecular bases of KC-LC interactions and for developing new therapeutic strategies in skin disease.

Topically applied diterpenoids from Egletes viscosa (Asteraceae) attenuate the dermal inflammation in mouse ear induced by tetradecanoylphorbol 13-acetate- and oxazolone

The diterpene compounds, centipedic acid (CA) and 12-acetoxyhawtriwaic acid lactone (AHAL, tanabalin) isolated from the flower buds of Egletes viscosa LESS. (Asteraceae) were evaluated on acute and chronic models of mouse ear dermatitis. A single topical application of CA (0.125; 0.25 and 0.5 mg/ear) or AHAL (0.125, 0.25, 0.5 mg/ear) immediately before 12-O-tetradecanoylphorbol-13-acetate (TPA, 2.5 mug/ear) caused a dose-related significant inhibition of ear inflammatory edema and influx of polymorphonuclear cells, as evidenced by a decrease in ear thickness and reduced myeloperoxidase (MPO) activity and tumor necrosis factor-alpha (TNF-alpha) in ear tissue homogenates. The maximal obtained inhibition for both ear edema and neutrophil influx were almost similar to that of topically applied dexamethasone (0.05 mg/ear). The extent of inhibitions for the respective treatments of CA (0.5 mg/ear), AHAL (0.5 mg/ear), or dexamethasone (0.05 mg/ear) were in the order of 63%, 61% and 81% for the ear edema, and 90%, 95% and 95% for the neutrophil influx. Also, at similar doses, both diterpenes and dexamethasone effectively inhibited the delayed-type hypersensitivity reaction induced by repeated topical application of 1% oxazolone (OXA, 20 microl/ear), as evidenced by significant decreases in ear thickness and interferon-gamma (INF-gamma) levels in ear tissue. Histopathological analysis revealed a marked decrease in epidermal hyperplasia and neutrophil infiltration in animals pretreated with CA or AHAL, in a manner similar to dexamethasone. These data provide evidence for the anti-dermatitis effect of Egletes viscosa diterpenes, by mechanisms that involve a reduced neutrophil influx and decreased production of inflammatory cytokines, TNF-alpha and IFN-gamma.

Activation of Human Dendritic Cells by p-Phenylenediamine

Exposure to p-phenylenediamine (pPD), a primary intermediate in hair dye formulations, is often associated with the development of allergic contact dermatitis. Such reactions involve activation of the subject's immune system. The aim of these studies was to explore the relationship between pPD oxidation and functional maturation of human monocyte-derived dendritic cells in vitro. Dendritic cells were incubated with pPD and Bandrowski's base (BB) for 16 h, and expression of the costimulatory receptors CD40, CD80, CD83, CD86, and major histocompatibility complex class II intracellular glutathione levels and cell viability were measured. In certain experiments, glutathione (1 mM) was added to culture medium. Liquid chromatography-mass spectrometry (LC-MS) analysis and exhaustive solvent extraction were used to monitor the rate of [(14)C]pPD oxidation and the extent of pPD binding to cellular and serum protein, respectively. Proliferation of allogeneic lymphocytes was determined by incorporation of [(3)H]thymidine. Exposure of dendritic cells to pPD (5-50 microM), but not BB, was associated with an increase in CD40 and MHC class II expression and proliferation of allogeneic lymphocytes. Dendritic cell activation with pPD was not associated with apoptotic or necrotic cell death or depletion of glutathione. Neither pPD nor BB altered dendritic cell expression of CD80, CD83, or CD86. LC-MS analysis revealed pPD was rapidly oxidized in cell culture media to BB. Addition of glutathione inhibited BB formation but did not prevent covalent binding of pPD to dendritic cell protein or dendritic cell activation. Collectively, these studies show that pPD, but not BB, selectively activates human dendritic cells in vitro.

CCL17 transgenic mice show an enhanced Th2-type response to both allergic and non-allergic stimuli

CC chemokine ligand (CCL)17 is implicated in the pathogenesis of atopic dermatitis (AD). To study the effect of CCL17 produced by keratinocytes (KC) during inflammation, we created transgenic (Tg) mice in which CCL17 is overexpressed in KC. Th2-type contact hypersensitivity (CHS) was enhanced and Th1-type CHS was suppressed in these mice. Increased numbers of CC chemokine receptor (CCR)4(+) cells and mast cells infiltrated in Tg mice. Levels of IL-4 mRNA were higher and those of IFN-gamma mRNA were lower in both acute and chronic CHS. Higher levels of serum IgE were observed after CHS. Numbers of CCR4(+) cells among PBMC were increased in Tg mice challenged acutely on the trunk. Chronic irritation with croton oil induced dermatitis and an elevation of serum IgE levels. Tg mice showed enhanced ear swelling after tape stripping. CCL17 was thought to modify the inflammation caused by sensitizing reagents as well as irritant reagents by attracting CCR4(+) cells into the lesional skin and creating a Th2-dominant condition. AD-like conditions such as increased number of mast cells and elevated levels of serum IgE were observed. Thus, CCL17 may participate in the pathogenesis of skin diseases such as AD by regulating both allergic and irritant inflammation.

Dissociated nonsteroidal glucocorticoid receptor modulators; discovery of the agonist trigger in a tetrahydronaphthalene-benzoxazine series

The tetrahydronaphthalene-benzoxazine glucocorticoid receptor (GR) partial agonist 4b was optimized to produce potent full agonists of GR. Aromatic ring substitution of the tetrahydronaphthalene leads to weak GR antagonists. Discovery of an "agonist trigger" substituent on the saturated ring of the tetrahydronaphthalene leads to increased potency and efficacious GR agonism. These compounds are efficacy selective in an NFkB GR agonist assay (representing transrepression effects) over an MMTV GR agonist assay (representing transactivation effects). 52 and 60 have NFkB pIC(50) = 8.92 (105%) and 8.69 (92%) and MMTV pEC(50) = 8.20 (47%) and 7.75 (39%), respectively. The impact of the trigger substituent on agonism is modeled within GR and discussed. 36, 52, and 60 have anti-inflammatory activity in a mouse model of inflammation after topical dosing with 52 and 60, having an effect similar to that of dexamethasone. The original lead was discovered by a manual agreement docking method, and automation of this method is also described.

Skin irritants and contact sensitizers induce Langerhans cell migration and maturation at irritant concentration

Skin irritants and contact allergens reduce the number of Langerhans cells (LCs). It has been assumed that this reduction is due their migration to the draining lymph node (LN) for initiating immune sensitization in a host. Skin irritation, however, as opposed to contact allergy is not considered to be an immunological disease. Nevertheless, skin irritants are also known for their adjuvant-like effects on contact allergy, resulting in skin hypersensitivity reactions like toxic dermatitis. The human organotypic skin explant culture (hOSEC) model is used to study the characteristics of chemical-induced migration of CD1a(+) LCs out of the epidermis in relation to irritancy or toxicity. We analysed cells emigrating out of hOSEC for CD1a(+) LCs, CD83(+) mature dendritic cells (DCs) and CCR7(+) LN homing cells. After exposure to a toxic concentration of a non-immunogenic irritant, an increase of CD1a(+)CD83(+) LCs was found in the culture medium. A non-toxic concentration of an sensitizer induced an increase of CD1a(+) cells. About 50% of skin emigrating CD1a(+) LCs were CD83(-) (immature) but all were CCR7(+). Skin irritation by both non-allergenic and allergenic compounds induces LC migration and maturation. In contrast, only allergenic compounds induced LC migration with partial maturation at subtoxic concentration. This effectively demonstrates that irritation is physiologically needed stimuli for inducing LC maturation.

Anti-inflammatory and anti-itch activity of sertaconazole nitrate

Cutaneous fungal infections are frequently associated with an inflammatory component including irritated skin, itching and stinging/burning. Therapeutic anti-fungal agents that have anti-inflammatory activity have the potential to provide clinical benefit beyond fungus eradication. Recently, certain anti-fungal agents have been shown to have intrinsic anti-inflammatory activity, therefore we sought to determine the extent of the anti-inflammatory activity of these compounds. The anti-inflammatory activities of eight anti-fungal agents (butoconazole, ciclopirox olamine, fluconazole, miconazole nitrate, sertaconazole nitrate, terconazole, tioconazole and ketoconazole) were compared in a number of preclinical models of dermal inflammation and pruritus. While butoconazole, ciclopirox olamine, fluconazole, and miconazole nitrate were all found to have anti-inflammatory activity, only sertaconazole nitrate reduced the release of cytokines from activated lymphocytes and mitigated inflammation in animal models of irritant contact dermatitis and neurogenic inflammation. In addition, sertaconazole nitrate inhibited contact hypersensitivity and scratching responses in a murine model of pruritus. Furthermore, the in vitro and in vivo anti-inflammatory activity of sertaconazole nitrate was found to be greater than other topical anti-fungal agents examined. These studies demonstrate that topical administration of clinically relevant concentrations of sertaconazole nitrate resulted in an efficacious anti-inflammatory activity against a broad spectrum of dermal inflammation models and itch. The anti-inflammatory properties of sertaconazole may contribute to the efficacy of the drug in the treatment of cutaneous fungal conditions and provide greater anti-inflammatory activity compared with other anti-fungal agents.

Subtoxic concentrations of allergenic haptens induce LC migration and maturation in a human organotypic skin explant culture model: a novel method for identifying potential contact allergens

The accelerated migration of Langerhans cells (LCs) out of the epidermis and up-regulation of maturation markers, upon treatment with subtoxic concentrations of chemicals, were used as the criteria to determine the potential of allergenic chemicals capable of inducing a hapten-specific delayed-type hypersensitivity reaction. Here we report the findings of a study in which seven chemicals, coded and tested in a blind fashion, were classified as contact allergens or non-allergens using the human organotypic skin explant culture (hOSEC) model. All chemicals that were identified as a contact sensitizer on decoding induced a definite decrease in the number of CD1a and HLA-DR-positive epidermal LCs in the epidermis of the skin explants, as determined by both semiquantitative immunohistochemistry and quantitative flow cytometric analysis. A significant increase in the number of CD83(+) cells was accompanied by up-regulation of activation molecules in the epidermis of hOSEC exposed specifically to contact allergens. In contrast, there were only minor alterations in epidermal LC numbers, expression of CD83 and other activation markers by LCs when the biopsies were treated with non-toxic concentrations of non-allergenic irritants and vehicles. The data suggest that an increased epidermal LC migration and maturation accompanied by increased expression of activation markers could be used as end-point determinants to screen allergens in a non-animal alternative hOSEC model.

Skin-sensitizing and irritant properties of propylene glycol. Data analysis of a multicentre surveillance network (IVDK*) and review of the literature

In the several publications reviewed in this article, propylene glycol (PG; 1,2-propylene glycol) is described as a very weak contact sensitizer, if at all. However, particular exposures to PG-containing products might be associated with an elevated risk of sensitization. To identify such exposures, we analysed patch test data of 45 138 patients who have been tested with 20% PG in water between 1992 and 2002. Out of these, 1044 patients (2.3%) tested positively, 1083 showed a doubtful, follicular or erythematous reaction (2.4%) and 271 explicit irritant reactions (0.6%). This profile of patch test reactions is indicative of a slightly irritant preparation, and thus, many of the 'weak positive' reactions must probably be interpreted as false positive. No private or occupational exposures associated with an increased risk of PG sensitization were identified, except for lower leg dermatitis. Therefore, according to our patch test data, PG seems to exhibit very low sensitization potential, and the risk for sensitization to PG on uncompromised skin seems to be very low.

Drug hypersensitivity reactions in skin: understanding mechanisms and the development of diagnostic and predictive tests

Cutaneous manifestations of drug hypersensitivity can be serious and potentially life threatening and may prevent effective drug therapy. T cells play an important role in the pathology of drug hypersensitivity reactions. Classical studies suggest that T-cell activation requires drug bioactivation, covalent binding to protein and antigen processing to stimulate an immune response. Recent studies have shown that drugs can also be presented to T cells in the absence of antigen processing and drug metabolism. In this article, sulfamethoxazole is used as a paradigm to describe the chemical mechanisms involved in the initiation and maintenance of an aberrant drug antigen specific T-cell response. Presentation of the same drug to different individuals can cause a variety of skin diseases. Such reactions have been classified according to the phenotype and functionality of the T-cell response. This review summarises the different forms of cutaneous hypersensitivity reactions and describes how T-cell clones generated from hypersensitive patients have been used to study the cellular mechanisms of anticonvulsant hypersensitivity. Potential uses of in vitro cell culture assays for patient diagnosis and drug evaluation are also discussed.

Expression of CS-1 fibronectin precedes monocyte chemoattractant protein-1 production during elicitation of allergic contact dermatitis

BACKGROUND

Leucocyte migration within inflammatory skin compartments in allergic contact dermatitis (ACD) is the result of a sophisticated multi-step event where multiple molecules are involved.

OBJECTIVE

Since non-antigen-specific mechanisms have been described as an early participant in elicitation of ACD, we investigated the kinetics of the expression of monocyte chemoattractant protein-1 (MCP-1/CCL2) and the type of infiltrating cells. We compared the time course production of MCP-1/CCL2 with connecting segment-1 (CS-1) fibronectin and thymus and activation-regulated chemokine (TARC/ CCL17) expression.

METHODS

Biopsies from 10 individuals challenged in their back with the antigen responsible for their contact dermatitis and an irrelevant antigen were taken at different times and histology, immunohistochemistry for CS-1 fibronectin, TARC/CCL17, CD3, CD68, CXCR3, CCR4 and in situ hybridization for MCP-1/CCL2 were performed.

RESULTS

At positive antigen stimulated sites expression of MCP-1/CCL2 by basal keratinocytes and isolated cells in dermis started at 10 h. CS-1 fibronectin and TARC/CCL17 expression by blood endothelial cells was found at 2 and 10 h, respectively. This was followed by dermal accumulation of mononuclear cells with a significant increase of CD3+ and CD68+cells. At 48 h, approximately 58% of infiltrating cells were CXCR3+, and 35% CCR4+.

CONCLUSIONS

We showed evidence of the fact that CS-1 fibronectin expression precedes the production of MCP-1/CCL2 and TARC/CCL17 in the skin of patients with ACD, suggesting that these molecules participate in the early complex process of migrating mononuclear cells during elicitation of ACD.

Differential regulation of sensitizer-induced inflammation and immunity by acute restraint stress in allergic contact dermatitis

Previously, we demonstrated that restraint stress applied before chemical sensitization modulates allergic contact dermatitis (ACD) differently than restraint applied before challenge. In this study, we asked if these dichotomous restraint-induced changes reflect modulation of the cutaneous microenvironment or changes in development of antigen-specific immunity in the lymph node (LN) of BALB/c mice. Our data confirm that restraint suppresses T cell-dependent immunity in ACD when applied prior to sensitization or prior to challenge and demonstrate that the stress-induced increase in ear swelling is due to heightened inflammation associated with ACD and is dependent upon the sensitization status of the mouse.

Covalent binding of the nitroso metabolite of sulfamethoxazole leads to toxicity and major histocompatibility complex-restricted antigen presentation

Treatment with sulfamethoxazole (SMX) can lead to hypersensitivity reactions. T cells from hypersensitive patients recognize either the parent drug and/or the reactive nitroso (SMX-NO) metabolite. In this study, using a novel in vitro rat splenocyte assay, we have investigated the toxicological and immunological consequences of cell surface haptenation by SMX-NO. SMX-NO was found to be unstable in solution; spontaneous transformation yielded appreciable amounts of SMX-hydroxylamine, nitro-SMX, and the previously unknown azoxy and azo dimers within 15 min. Irreversible binding of SMX-NO to cellular protein was demonstrated by flow cytometry, with haptenation being greater on the surface of antigen-presenting cells than on T cells. The consequences of irreversible binding of SMX-NO were examined in two ways. First, haptenation above a threshold level led to a proportionate increase in cell death (both apoptosis and necrosis). Indeed, the cells that became haptenated were the same as those that underwent necrotic cell death. Second, sensitized splenocytes proliferated in the presence of major histocompatibility complex (MHC)-restricted antigen derived from both viable and dead cells haptenated with low and high levels of SMX-NO, respectively. However, direct modification of MHC by SMX-NO was not the mechanism of antigen presentation. The antigenic threshold of SMX-NO for T-cell proliferation and toxicity was estimated to be between 0.5 and 1 microM and 5 to 10 microM, respectively. The potential of SMX-NO to generate a potent antigen and cause cytotoxicity may in combination provide the signals necessary to induce a hypersensitivity reaction to SMX.

Early inflammatory markers in elicitation of allergic contact dermatitis

BACKGROUND

Allergic Contact Dermatitis (ACD) is regarded as a T-cell-mediated delayed-type hypersensitivity reaction. We studied the kinetics of the expression of CS-1 fibronectin, thymus and activation-regulated chemokine (CCL17/ TARC) and different chemokine receptors (CR) in skin biopsies from individuals suffering from back problems, with the antigen responsible of their contact dermatitis and an irrelevant antigen.

METHODS

Samples were taken at 2, 10, and 48 hours for histological and immunohistochemical studies using monoclonal antibodies against human CS-1 fibronectin, CCL17, CD3, CD68, CD49d, CXCR3, CCR5, and CCR3.

RESULTS

At positive antigen stimulated sites there was an early expression of CS-1 fibronectin (2 hours), followed by CCL17 and a later accumulation of alplha4/beta1+ (CD49d), CD3+, CD68+, CXCR3+ and CCR5+ mononuclear cells. At 48 hours, approximately 59 % of infiltrating cells were CXCR3+, 42% CCR5+, and only 14 % CCR3+.

CONCLUSIONS

These results showed for the first time a very early expression of CS-1 fibronectin which preceded production of CCL17 in blood endothelial cells (BCEs) from patients' skin with ACD. The role of these molecules in recruitment of monocytes and effector T cells in ACD is discussed.

Vascular endothelium express CS-1 fibronectin in allergic contact dermatitis

BACKGROUND

Allergic contact dermatitis (ACD) is a common human dermatosis in which not all the mechanisms involved in its pathogenesis have been elucidated.

OBJECTIVE

To study the expression of CS-1 fibronectin, TARC and Th1-associated chemokine receptors in biopsies from allergic patch test reactions.

MATERIAL AND METHODS

Thirteen patients already diagnosed with ACD were challenged on the back with the antigen responsible of the disease and macroscopic responses and biopsies taken after 48 h. Skin biopsies from negative control challenge sites, AD and ICD were also taken. Samples were fixed, embedded in paraffin wax and processed in order to perform histological and immunohistochemical studies.

RESULTS

All subjects with ACD showed a positive clinical response and a perivascular mononuclear cell infiltration at 48 h, which was not seen in the negative controls. The majority of skin-infiltrating cells were CD4+ and CD8+ and up to 54% or 40% of them expressed CXCR3 or CCR5, respectively. We also showed expression of CS-1 fibronectin in inflamed endothelial cells not only in ACD but also in AC and ICD. In contrast TARC was only expressed in ACD and AC.

CONCLUSION

We showed for the first time that CS-1 fibronectin is expressed in dermal vessels from allergic patch tests positive reactions, as well as irritant and atopic skin lesions.

Direct effect of croton oil on intestinal epithelial cells and colonic smooth muscle cells

AIM

To investigate the direct effect of croton oil (CO) on human intestinal epithelial cell (HIEC) and guinea pig colonic smooth muscle cells in vitro.

METHODS

Growth curves of HIEC were drawn by MTT colorimetry. The dynamics of cell proliferation was analyzed with flow cytometry, and morphological changes were observed under light and electron microscopy after long-term (6 weeks) treatment with CO. Expression of cyclooxygenase-2 (COX-2) mRNA was detected by dot blot in HIEC treated with CO. Genes related to CO were screened by DD-PCR, and the direct effect of CO on the contractility of isolated guinea pig colonic smooth muscle cells was observed.

RESULTS

High concentration (20-40 mg x L(-1)) CO inhibited cell growth significantly (1, 3, 5, 7d OD sequence: (20 mg x L(-1)) 0.040+/-0.003, 0.081+/-0.012, 0.147+/-0.022,0.024+/-0.016; (40 mg x L(-1)) 0.033+/-0.044, 0.056+/-0.012, 0.104+/-0.010, 0.189+/-0.006; OD control 0.031+/-0.008, 0.096+/-0.012, 0.173+/-0.009, 0.300+/-0.016, P<0.01), which appeared to be related directly to the dosage. Compared with the control, the fraction number of cells in G1 phase decreased from 0.60 to 0.58, while that in S phase increased from 0.30 to 0.34 and DNA index also increased after 6 weeks of treatment with CO (the dosage was increased gradually from 4 to 40 mg x L(-1)). Light microscopic observation revealed that cells had karyomegaly, less plasma and karyoplasm lopsidedness. Electron microscopy also showed an increase in cell proliferation and in the quantity of abnormal nuclei with pathologic mitosis. Expression of COX-2 mRNA decreased significantly in HIEC treated with CO. Thirteen differential cDNA fragments were cloned from HIEC treated with CO, one of which was 100 percent homologous with human mitochondrial cytochrome C oxidase subunit II. The length of isolated guinea pig colonic smooth muscle cells was significantly shortened after treatment with CO (P<0.05).

CONCLUSION

At a high CO concentration (>20 mg x L(-1)), cell growth and proliferation are inhibited in a dosage-dependent manner. Increase in cell proliferation and in malignant conversion of the cellular phenotype is observed in cells cultured chronically with CO. COX-2 mRNA expression decreases significantly, while human mitochondrial cytochrome C oxidase subunit IImRNA expression increases significantly in HIEC treated with CO. CO also has a direct effect on the contractility of Guinea pig colonic smooth muscle cells.

IL-1 alpha, but not IL-1 beta, is required for contact-allergen-specific T cell activation during the sensitization phase in contact hypersensitivity

Contact hypersensitivity (CHS) is a T cell-mediated cellular immune response caused by epicutaneous exposure to contact allergens. In this reaction, after the first epicutaneous allergen sensitization, Langerhans cells (LC) catch allergens and migrate from the skin to draining lymph nodes (LN) and activate naive T cells. Although IL-1 is suggested to be involved in these processes, the mechanisms have not been elucidated completely. In this report, to elucidate roles of IL-1alpha and IL-1beta in CHS, we analyzed ear swelling in 2,4,6-trinitrochlorobenzene (TNCB)-induced CHS using gene-targeted mice. We found that ear swelling was suppressed in IL-1alpha-deficient (IL-1alpha(-/-)) mice but not in IL-1beta(-/-) mice. LC migration from the skin into LN was delayed in both IL-1alpha(-/-) and IL-1beta(-/-) mice, suggesting that this defect was not the direct cause for the reduced CHS in these mice. However, we found that the proliferative response of trinitrophenyl (TNP)-specific T cells after sensitization with TNCB was specifically reduced in IL-1alpha(-/-) mice. Furthermore, adoptive transfer of TNP-conjugated IL-1-deficient epidermal cells (EC) into wild-type mice indicated that only IL-1alpha, but not IL-1beta, produced by antigen-presenting cells in EC could prime allergen-specific T cells. These observations indicate that IL-1alpha, but not IL-1beta, plays a crucial role in TNCB-induced CHS by sensitizing TNP-specific T cells.

Peripheral blood granulocyte activity following contact sensitization of rats with dinitrochlorobenzene

Contact hypersensitivity (CHS) reaction is a classic example of a cell-mediated reaction. As the afferent phase of the reaction includes inflammation, CHS is a suitable model for investigating non-specific immunity. Some aspects of granulocyte activity in the afferent phase of experimentally induced CHS to dinitrochlorobenzene (DNCB) in two genetically different rat strains, AO and DA were examined in this study. A shift in the ratio of granulocytes to lymphocytes in favour of granulocytes and an increase in granulocyte survival were noted in DA rats. Granulocytes from both strains demonstrated increased levels of NBT reduction and an increase in their adhesion to plastic. Decreased granulocyte adhesion in the presence of monoclonal antibodies to beta2 integrins (anti-CD11b/c and anti-CD18) points to the contribution of these molecules to granulocyte adhesiveness during the sensitization phase of CHS. Stimulation of adhesion in the presence of anti-CD11a antibody, points to a differential modulation of adhesion molecule activity during the afferent phase of CHS. Changes in functional activity of granulocytes demonstrated in this study might contribute to the development of CHS in rats.

Analysis of gene expression induced by irritant and sensitizing chemicals using oligonucleotide arrays

Chemical-induced allergy continues to be an important occupational health problem. Despite decades of investigation, the molecular mechanisms underlying chemical-induced hypersensitivity and irritancy remain unclear because of the complex interplay between properties of different chemicals and the immune system. In this study, gene expression induced by toluene diisocyanate (TDI, a primarily IgE-inducing sensitizer), oxazolone (OXA, a cell-mediated hypersensitivity inducing sensitizer), or nonanoic acid (NA, a non-sensitizing irritant) was investigated using gene arrays. Female BALB/c mice were dermally exposed on the ears once daily for 4 consecutive days. On day 5, the lymph nodes draining the exposure sites were collected and used for RNA extraction and subsequent hybridization to Affymetrix Mu6500 oligonucleotide arrays. Of the 6519 genes on the arrays, there were 44, 13, and 51 genes in the TDI-, OXA-, and NA-exposed samples, respectively, that displayed a minimum of twofold change in expression level relative to the vehicle control. There were 32, 19, and 19 genes that were differentially expressed (with a minimum of twofold change) between TDI and OXA, TDI and NA, OXA and NA, respectively. The differentially expressed genes include immune response-related genes, transcriptional factors, signal transducing molecules, and Expressed Sequence Tags. Based on the gene array results, candidate genes were further evaluated using RT-PCR. There was only about 47% concordance between the gene array and RT-PCR results.