Inhibition of NFAT specifically in T cells prevents allergic pulmonary inflammation

Functional assessment of the right ventricle in patients with bronchial asthma of various severity

INTRODUCTION

Pulmonary artery hypertension and its consequences still constitutes an underestimated clinical problem in asthma patients and its non-invasive early detection may influence proper treatment.

AIM

To non-invasively examine the pulmonary artery flow parameters and right ventricular function in patients with asthma of various severity.

MATERIAL AND METHODS

The analysis of parameters of echocardiography and first-pass and gated radionuclide angiography, and baseline examination in 31 patients with bronchial asthma and 16 healthy controls.

RESULTS

Patients with severe asthma had higher mean pulmonary artery pressure (MPAP) compared to the healthy controls. The subgroup analysis of patients who suffered from asthma in their childhood showed that individuals with severe asthma were characterized by significantly higher MPAP than those with the mild/moderate condition (19.16 ±7.51 mm Hg vs. 5.0 ±1.15 mm Hg, p = 0.025). Gated, but not first-pass, radionuclide angiography revealed that individuals with severe asthma were characterized by a lower right ventricular ejection fraction (RVEF). Further analysis of the subgroup of patients in whom the initial manifestation of dyspnoea occurred no earlier than 6 years prior to the study showed that the RVEF of individuals with severe asthma was significantly lower compared to those with mild/moderate asthma (39.8 ±4.79% vs. 51.4 ±8.65%, p = 0.019).

CONCLUSIONS

The pulmonary artery pressure in patients with severe asthma is significantly higher than in healthy individuals; in contrast, these two groups did not differ significantly in terms of the right ventricular echocardiographic characteristics. Gated radionuclide angiography, but not the first-pass technique, allowed for the detection of subtle right ventricular ejection fraction changes in asthma patients.

Ouabain attenuates ovalbumin-induced airway inflammation

PURPOSE

Ouabain, an Na⁺/K⁺-ATPase inhibitor hormone, presents immunomodulatory actions, including anti-inflammatory effect on acute inflammation models.

METHODS

In the present study, the effect of ouabain in a model of allergic airway inflammation induced by ovalbumin (OVA) was assessed.

RESULTS

Initially, it was observed that ouabain treatment inhibited cellular migration induced by OVA on bronchoalveolar lavage fluid (BALF), mostly granulocytes, without modulating macrophage migration. In addition, it was observed, by flow cytometry, that ouabain reduces CD3^high lymphocytes cells on BALF. Furthermore, treatment with ouabain decreased IL-4 and IL-13 levels on BALF. Ouabain also promoted pulmonary histological alterations, including decreased cell migration into peribronchiolar and perivascular areas, and reduced mucus production in bronchioles regions observed through hematoxylin-eosin (HE) and by periodic acid-Schiff stain, respectively. Allergic airway inflammation is characterized by high OVA-specific IgE serum titer. This parameter was also reduced by the treatment with ouabain.

CONCLUSIONS

Therefore, our data demonstrate that ouabain negatively modulates allergic airway inflammation induced by OVA.

GRIM19 ameliorates acute graft-versus-host disease (GVHD) by modulating Th17 and Treg cell balance through down-regulation of STAT3 and NF-AT activation

BACKGROUND

T helper (Th) 17 cells are a subset of T helper cells that express interleukin (IL)-17 and initiate the inflammatory response in autoimmune diseases. Regulatory T cells (Tregs) are a subpopulation of T cells that produce forkhead box P3 (FOXP3) and inhibit the immune response. Graft versus host disease (GVHD) is a complication of allogeneic tissue transplantation, and Th17 cells and their proinflammatory activity play a central role in the pathogenesis of GVHD. Gene associated with retinoid-interferon-induced mortality (GRIM) 19, originally identified as a nuclear protein, is expressed ubiquitously in various human tissues and regulate signal transducer and activator of transcription (STAT)3 activity.

METHODS

Splenoytes and bone marrow cells were transplanted into mice with GVHD. The alloresponse of T cells and GVHD clinical score was measured. Realtime-polymerase chain reaction (realtime-PCR) was used to examine mRNA level. Flow cytometry and enzyme linked immunosorbent assay (ELISA) was used to evaluate protein expression.

RESULTS

A GRIM19 transgenic cell transplant inhibited Th17 cell differentiation, alloreactive T cell responses, and STAT3 expression in mice with GVHD. On the other hand, the differentiation of Tregs and STAT5 production were enhanced by GRIM19. Overall, the severity of GVHD was decreased in mice that had received GRIM19 transgenic bone marrow and spleen transplants. Transplantation from GRIM19-overexpressing cells downregulated the expression of nuclear factor of activated T cells (NFATc1) but promoted the expression of regulator of calcineurin (RCAN)3 while downregulating NFAT-dependent cytokine gene expression. This complex mechanism underlies the therapeutic effect of GRIM19.

CONCLUSIONS

We observed that GRIM19 can reduce Th17 cell differentiation and alloreactive T cell responses in vitro and in vivo. Additionally, GRIM19 suppressed the severity of GVHD by modulating STAT3 activity and controlling Th17 and Treg cell differentiation. These results suggest that GRIM19 attenuates acute GVHD through the inhibition of the excessive inflammatory response mediated by T cell activation.

Cyclosporine nanomicelle eye drop: a novel medication for corneal graft transplantation treatment

Corneal transplantation has been used to treat severe eye disease for decades, but the therapeutic effect of the operation is highly compromised by immunological allograft rejection. To improve the success rate of corneal transplantation, we studied the protective effects of cyclosporine nanomicelle eye drops (CNED) on immune rejection after high-risk corneal transplantation and its underlying mechanisms. The therapeutic effects against immune rejection of both conventional cyclosporine eye drop (CCED) and CNED in different concentrations were assessed and compared using animal models of corneal transplantation. In addition, the expression of nuclear factor-κ-gene binding (NF-κB) as well as its target intracellular adhesion molecule 1 (ICAM-1) in the corneal samples obtained from recipients treated with either CCED or CNED was also screened. The results showed that the CNED displayed significantly better effects at suppressing the immune response induced by corneal transplantation compared to CCED. CNED also significantly down-regulated the NF-κB and ICAM-1 expressions, indicating NF-κB might play an important role in the initiation of an immune response against the allograft. Our study demonstrates CNED may suppress the NF-κB pathway to attenuate the immune response, which highlights the possible therapeutic applications of cyclosporine nanomicelle eye drops in corneal transplantation.

In Vitro Treatment with 2-APB Inhibits the Inflammation in Nasal Polyps

OBJECTIVE

Glucocorticoids are considered the main treatment option for chronic rhinosinusitis with nasal polyps (CRSwNP), but their effect rate ranges from 60.9% to 80%. Novel therapeutic means should be studied. The purpose of this study was to investigate the expression of Orai1 in nasal polyps (NPs) and the influence of intervention of Orai1 on NPs after in vitro treatment of 2-aminoethoxydiphenyl borate (2-APB).

STUDY DESIGN

Prospective cross-sectional study.

SETTING

University hospital.

SUBJECTS AND METHODS

Nasal biopsy samples were obtained from normal subjects or subjects with CRSwNP. We studied the localization of Orai1 protein in NPs by using immunohistochemistry. Then these tissues in cultures were maintained in the absence or presence of dexamethasone (DEX) or 2-APB. Orai1 was examined by Western blot, enzyme-linked immunosorbent assay (ELISA), and real-time reverse transcription-polymerase chain reaction (RT-PCR). Inflammatory mediators including interleukin (IL)-1β, IL-5, eosinophil cation protein (ECP), leukotriene (LT)C4, interferon (IFN)-γ, and dermatophagoides pteronyssinus (DP)-specific immunoglobulin E (sIgE) as well as mucins (MUCs) including MUC5B and MUC7 in cultures were analyzed with ELISA and real-time RT-PCR.

RESULTS

The expression of Orai1 was localized to cytoplasmic membrane of inflammatory cells and submucosal glandular cells and was upregulated in NPs compared with normal nasal mucosa. Orai1 was decreased in NPs after in vitro treatment of 2-APB but not after DEX intervention. The levels of inflammatory mediators and mucins were reduced more after 2-APB treatment when compared with those after DEX treatment.

CONCLUSION

Orai1 may play crucial roles in NP formation, and the intervention of Orai1 may inhibit NP development.

Interleukin-13-induced MUC5AC expression is regulated by a PI3K-NFAT3 pathway in mouse tracheal epithelial cells

Interleukin-13 (IL-13) plays a critical role in asthma mucus overproduction, while the mechanisms underlying this process are not fully elucidated. Previous studies showed that nuclear factor of activated T cells (NFAT) is involved in the pathogenesis of asthma, but whether it can directly regulate IL-13-induced mucus (particularly MUC5AC) production is still not clear. Here we showed that IL-13 specifically induced NFAT3 activation through promoting its dephosphorylation in air-liquid interface (ALI) cultures of mouse tracheal epithelial cells (mTECs). Furthermore, both Cyclosporin A (CsA, a specific NFAT inhibitor) and LY294002 (a Phosphoinositide 3-kinase (PI3K) inhibitor) significantly blocked IL-13-induced MUC5AC mRNA and protein production through the inhibition of NFAT3 activity. We also confirmed that CsA could not influence the forkhead Box A2 (Foxa2) and mouse calcium dependent chloride channel 3 (mClca3) expression in IL-13-induced MUC5AC production, which both are known to be important in IL-13-stimulated mucus expression. Our study is the first to demonstrate that the PI3K-NFAT3 pathway is positively involved in IL-13-induced mucus production, and provided novel insights into the molecular mechanism of asthma mucus hypersecretion.

Asthma and pulmonary arterial hypertension: do they share a key mechanism of pathogenesis?

Although largely distinct and seemingly unrelated, asthma and pulmonary arterial hypertension (PAH) have important pathological features in common, including inflammation, smooth muscle contraction and remodelling. We hypothesised that these common features could be explained by one shared mechanism of pathogenesis: activation of the transcription factor NFAT (nuclear factor of activated T-cells). If this concept is validated, it could lead to the introduction of novel therapeutic strategies against both lung disorders. In several experimental models, airway remodelling is accompanied by remodelling of smaller pulmonary arteries, validating the hypothesis of their similar pathogenesis. In addition, lungs of vasoactive intestinal peptide (VIP) knockout mice express airway hyperresponsiveness with airway inflammation and PAH with vascular remodelling, with both sets of pathological findings being reversible with VIP treatment. Preliminary data suggest that absence of the VIP gene leads to activation of the calcineurin-NFAT pathway, and that VIP is probably a physiological inhibitor of this pathway. Enough evidence exists to support the views that asthma and PAH share important pathological features, probably related to NFAT activation, and that VIP may be a physiological modulator of this mechanism.

Elevation of IL-6 in the allergic asthmatic airway is independent of inflammation but associates with loss of central airway function

Background

Asthma is a chronic inflammatory disease of the airway that is characterized by a Th2-type of immune response with increasing evidence for involvement of Th17 cells. The role of IL-6 in promoting effector T cell subsets suggest that IL-6 may play a functional role in asthma. Classically IL-6 has been viewed as an inflammatory marker, along with TNFα and IL-1β, rather than as regulatory cytokine.

Objective

To investigate the potential relationship between IL-6 and other proinflammatory cytokines, Th2/Th17 cytokines and lung function in allergic asthma, and thus evaluate the potential role of IL-6 in this disease.

Methods

Cytokine levels in induced sputum and lung function were measured in 16 healthy control and 18 mild-moderate allergic asthmatic subjects.

Results

The levels of the proinflammatory biomarkers TNFα and IL-1β were not different between the control and asthmatic group. In contrast, IL-6 levels were specifically elevated in asthmatic subjects compared with healthy controls (p < 0.01). Hierarchical regression analysis in the total study cohort indicates that the relationship between asthma and lung function could be mediated by IL-6. Among Th2 cytokines only IL-13 (p < 0.05) was also elevated in the asthmatic group, and positively correlated with IL-6 levels (r_S = 0.53, p < 0.05).

Conclusions

In mild-moderate asthma, IL-6 dissociates from other proinflammatory biomarkers, but correlates with IL-13 levels. Furthermore, IL-6 may contribute to impaired lung function in allergic asthma.

SWAP-70-like adapter of T cells: a novel Lck-regulated guanine nucleotide exchange factor coordinating actin cytoskeleton reorganization and Ca2+ signaling in T cells

SWAP-70-like adapter of T cells (SLAT) is a recently identified guanine nucleotide exchange factor (GEF) for Cdc42 and Rac1, which is highly expressed in both thymocytes and peripheral T cells. Here, we present and discuss findings resulting from biochemical and genetic analyses aimed at unveiling the role of SLAT in CD4+ T-cell development, activation, and T-helper (Th) cell differentiation. Slat(-/-) mice display a developmental defect at one of the earliest stages of thymocyte differentiation, the double negative 1 (DN1) stage, leading to decreased peripheral T-cell numbers. Slat(-/-) peripheral CD4+ T cells demonstrate impaired T-cell receptor/CD28-induced proliferation and IL-2 production. Moreover, SLAT positively regulates the development of Th1 and Th2 inflammatory responses by controlling Ca2+/NFAT signaling. SLAT is also a positive regulator of the recently emerging Th subset, i.e., Th17 cells, as evidenced by its critical role in Th17 cell-mediated central nervous system inflammation. Furthermore, TCR engagement induces SLAT translocation to the immunological synapse, a process mediated by its Lck-dependent phosphorylation, which thereafter facilitates the triggering of SLAT GEF activity towards Cdc42 and Rac1, leading to NFAT activation and Th1/Th2 differentiation. Future work will aim to dissect the interacting partners of SLAT and may thus shed light on the poorly understood events that coordinate and link actin cytoskeleton reorganization to Ca2+ signaling and gene transcription in T cells.

IL-6 is required for airway mucus production induced by inhaled fungal allergens

Allergic asthma is caused by inhaled allergens and is characterized by airway eosinophilia, as well as mucus hypersecretion, which can lead to airflow obstruction. Despite the association of increased IL-6 levels with human atopic asthma, the contribution of IL-6 to the development of allergic airway inflammation triggered by inhaled allergens remains unclear. In this study, we examined the role of IL-6 in a mouse model of allergic airway inflammation induced by direct airway exposure to extracts of Aspergillus fumigatus, a common allergen in humans. We show that inhaled A. fumigatus extracts rapidly trigger the production of IL-6 in the airways. IL-6 appears to be dispensable for the recruitment of eosinophils to the lung during the development of allergic airway inflammation. However, IL-6 is essential for mucus hypersecretion by airway epithelial cells triggered in response to inhaled A. fumigatus Ags. Impaired mucus production caused by IL-6 deficiency correlates with a severe reduction in the levels of IL-13, a major inducer of mucin glycoproteins. Thus, IL-6 is a key regulator of specific hallmark features of allergic airway inflammation and it could be a potential target for pulmonary diseases that are associated with goblet cell metaplasia and mucus hypersecretion.

IP3 receptor-mediated Ca2+ release in naive CD4 T cells dictates their cytokine program

IP(3) (inositol 1,4,5-trisphosphate) receptors (IP(3)Rs) regulate the release of Ca(2+) from intracellular stores in response to IP(3). Little is known about regulation of the expression of IP(3)Rs and their role during the activation of CD4 T cells. In this study we show that mouse naive CD4 T cells express IP(3)R1, IP(3)R2, and IP(3)R3, but that gene expression of IP(3)R3 primarily is down-regulated upon activation due to loss of the Ets-1 transcription factor. Down-regulation of IP(3)R expression in activated CD4 T cells is associated with the failure of TCR ligation to trigger Ca(2+) release in these cells. We also show that down-regulation of specific IP(3)Rs in activated CD4 T cells correlates with the requirement of IP(3)R-mediated Ca(2+) release only for the induction of, but not for the maintenance of, IL-2 and IFN-gamma expression. Interestingly, while inhibition of IP(3)R function early during activation blocks IL-2 and IFN-gamma production, it promotes the production of IL-17 by CD4 T cells. Thus, IP(3)Rs play a key role in the activation and differentiation of CD4 T cells. The immunosuppressive effect of pharmacological blockers of these receptors may be complicated by promoting the development of inflammatory CD4 T cells.

NFATc1 identifies a population of proximal tubule cell progenitors

Recovery from acute kidney injury requires regeneration of tubule cells. Because calcineurin induces nuclear transport of NFATc proteins, whose expression pattern correlates with the nephron segments injured by calcineurin inhibitors, we hypothesized that NFATc1 plays a role in modifying epithelial regeneration after injury. To test this, we induced proximal tubular cell (PTC) injury in Balb/c mice and Nfatc1(+/-) mice with mercuric chloride; the PTCs of Nfatc1(+/-) mice demonstrated increased apoptosis, sustained injury, and delayed regeneration. To attenuate NFATc1 activity further, we injected cyclosporin A daily. Cyclosporin A-treated Nfatc1(+/-) mice demonstrated rapid and severe injury after administration of mercuric chloride, with increased serum creatinine, increased apoptosis, decreased PTC proliferation, and increased mortality compared with similarly treated wild-type mice. Using a novel NFATc1 transgenic line that reports activation of an NFATc1 enhancer domain critical for NFATc1 autoamplification, we demonstrated accentuated NFATc1 expression in a PTC subpopulation after mercuric chloride-induced injury. In addition, NFATc1-labeled, apoptosis-resistant PTCs proliferated to repair the damaged proximal tubule segment. These data provide evidence for a resident progenitor PTC population and suggest a role for NFATc1 in the regeneration of injured proximal tubules.

Inhibition of arginase activity enhances inflammation in mice with allergic airway disease, in association with increases in protein S-nitrosylation and tyrosine nitration

Pulmonary inflammation in asthma is orchestrated by the activity of NF-kappaB. NO and NO synthase (NOS) activity are important modulators of inflammation. The availability of the NOS substrate, l-arginine, is one of the mechanisms that controls the activity of NOS. Arginase also uses l-arginine as its substrate, and arginase-1 expression is highly induced in a murine model of asthma. Because we have previously described that arginase affects NOx content and interferes with the activation of NF-kappaB in lung epithelial cells, the goal of this study was to investigate the impact of arginase inhibition on the bioavailability of NO and the implications for NF-kappaB activation and inflammation in a mouse model of allergic airway disease. Administration of the arginase inhibitor BEC (S-(2-boronoethyl)-l-cysteine) decreased arginase activity and caused alterations in NO homeostasis, which were reflected by increases in S-nitrosylated and nitrated proteins in the lungs from inflamed mice. In contrast to our expectations, BEC enhanced perivascular and peribronchiolar lung inflammation, mucus metaplasia, NF-kappaB DNA binding, and mRNA expression of the NF-kappaB-driven chemokine genes CCL20 and KC, and lead to further increases in airways hyperresponsiveness. These results suggest that inhibition of arginase activity enhanced a variety of parameters relevant to allergic airways disease, possibly by altering NO homeostasis.

NFAT1 transcription factor regulates pulmonary allergic inflammation and airway responsiveness

Allergic asthma is a chronic inflammatory disease of the lung whose incidence and morbidity continues to rise in developed nations. Despite being a hallmark of asthma, the molecular mechanisms that determine airway hyperresponsiveness (AHR) are not completely established. Transcription factors of the NFAT family are involved in the regulation of several asthma-related genes. It has been shown that the absence of NFAT1 leads to an increased pleural eosinophilic allergic response accompanied by an increased production of Th2 cytokines, suggesting a role for NFAT1 in the regulation of allergic diseases. Herein, we analyze NFAT1-/- mice to address the role of NFAT1 in a model of allergic airway inflammation and its influence in AHR. NFAT1-/- mice submitted to airway inflammation display a significant exacerbation of several features of the allergic disease, including lung inflammation, eosinophilia, and serum IgE levels, which were concomitant with elevated Th2 cytokine production. However, in spite of the increased allergic phenotype, NFAT1-/- mice failed to express AHR after methacholine aerosol. Refractoriness of NFAT1-/- mice to methacholine was confirmed in naïve mice, suggesting that this refractoriness occurs in an intrinsic way, independent of the lung inflammation. In addition, NFAT1-/- mice exhibit increased AHR in response to serotonin inhalation, suggesting a specific role for NFAT1 in the methacholine pathway of bronchoconstriction. Taken together, these data add support to the interpretation that NFAT1 acts as a counterregulatory mechanism to suppress allergic inflammation. Moreover, our findings suggest a novel role for NFAT1 protein in airway responsiveness mediated by the cholinergic pathway.

Tumor-induced impairment of TCR signaling results in compromised functionality of tumor-infiltrating regulatory T cells

This study demonstrates, for the first time, that murine regulatory T (Treg) cells in the tumor microenvironment display both enhanced proliferation and reduced functionality. This enhanced proliferation, combined with decreased apoptosis, leads to an intratumoral accumulation of Treg cells with a unique phenotype: CD4(+)CD25(+)FoxP3(+)GITR(high)CD27(low)CD62L(-). The loss of functionality is associated with down-regulation of the TCR signaling complex, including IL-2-inducible T cell kinase. It is also demonstrated that tumor-infiltrating Treg cells have impaired TCR-mediated signaling and calcium influx. Based on these findings, this study supports the hypothesis that 1) tumor-infiltrating Treg cells lose functionality due to their diminished ability to become effectively activated and 2) intratumoral accumulation of Treg cells may compensate for the impaired functionality, thus maintaining immune tolerance to the tumor.

SLAT regulates Th1 and Th2 inflammatory responses by controlling Ca2+/NFAT signaling

SWAP-70-like adapter of T cells (SLAT) is a novel guanine nucleotide exchange factor for Rho GTPases that is upregulated in Th2 cells, but whose physiological function is unclear. We show that SLAT(-/-) mice displayed a developmental defect at one of the earliest stages of thymocyte differentiation, the double-negative 1 (DN1) stage, leading to decreased peripheral T cell numbers. SLAT(-/-) peripheral CD4(+) T cells demonstrated impaired TCR/CD28-induced proliferation and IL-2 production, which was rescued by the addition of exogenous IL-2. Importantly, SLAT(-/-) mice were grossly impaired in their ability to mount not only Th2, but also Th1-mediated lung inflammatory responses, as evidenced by reduced airway neutrophilia and eosinophilia, respectively. Levels of Th1 and Th2 cytokine in the lungs were also markedly reduced, paralleling the reduction in pulmonary inflammation. This defect in mounting Th1/Th2 responses, which was also evident in vitro, was traced to a severe reduction in Ca(2+) mobilization from ER stores, which consequently led to defective TCR/CD28-induced translocation of nuclear factor of activated T cells 1/2 (NFATc1/2). Thus, SLAT is required for thymic DN1 cell expansion, T cell activation, and Th1 and Th2 inflammatory responses.

Aspergillus fumigatus generates an enhanced Th2-biased immune response in mice with defective cystic fibrosis transmembrane conductance regulator

Cystic fibrosis (CF) lung disease is characterized by persistent airway inflammation and airway infection that ultimately leads to respiratory failure. Aspergillus sp. are present in the airways of 20-40% of CF patients and are of unclear clinical significance. In this study, we demonstrate that CF transmembrane conductance regulator (CFTR)-deficient (CFTR knockout, Cftr(tm1Unc-)TgN(fatty acid-binding protein)CFTR) and mutant (DeltaF508) mice develop profound lung inflammation in response to Aspergillus fumigatus hyphal Ag exposure. CFTR-deficient mice also develop an enhanced Th2 inflammatory response to A. fumigatus, characterized by elevated IL-4 in the lung and IgE and IgG1 in serum. In contrast, CFTR deficiency does not promote a Th1 immune response. Furthermore, we demonstrate that CD4+ T cells from naive CFTR-deficient mice produce higher levels of IL-4 in response to TCR ligation than wild-type CD4+ T cells. The Th2 bias of CD4+ T cells in the absence of functional CFTR correlates with elevated nuclear levels of NFAT. Thus, CFTR is important to maintain the Th1/Th2 balance in CD4+ T cells.

Caffeic acid phenethyl ester modifies the Th1/Th2 balance in ileal mucosa after γ-irradiation in the rat by modulating the cytokine pattern

AIM: To pharmacologically modulate Th polarization in the ileum exposed to ionizing radiation by using the immuno-modulatory/apoptotic properties of Caffeic Acid Phenethyl Ester (CAPE).

METHODS: Rats received CAPE (30 mg/kg) treatment ip 15 min prior to intestinal 10 Gy γ-irradiation and once a day for a 6 d period after irradiation. Expression of genes implicated in Th differentiation in ileal mucosa (IL-23/IL-12Rβ2), Th cytokine responses (IFN-γ, IL-2, IL-4, IL-13), Th migratory behaviour (CXCR3, CCR5, CCR4), Th signalling suppressors (SOCS1, SOCS3), transcription factor (T-Bet, GATA-3) and apoptosis (FasL/Fas, TNF/TNFR, XIAP, Bax, caspase-3) was analyzed by RT-PCR 6 h and 7 d post-irradiation. CD4⁺ and TUNEL positive cells were visualized by immunostaining.

RESULTS: The expression of Th1-related cytokine/chemokine receptors (IFN-γ, IL-2, CXCR3, CCR5) was repressed at 7 d post-irradiation while Th2 cell cytokine/chemokines (IL-4, IL-13, CCR4) were not repressed or even upregulated. The irradiation-induced Th2 profile was confirmed by the upregulation of both Th2-specific transcription factor GATA-3 and SOCS3. Although an apoptosis event occurred 6 h after 10 Gy of intestinal γ-irradiation, apoptotic mediator analysis showed a tendency to apoptotic resistance 7 d post-irradiation. CAPE amplified apoptotic events at 6h and normalized Bax/ FasL expressions at 7 d.

CONCLUSION: CAPE prevented the ileal Th2 immune response by modulating the irradiation-influenced cytokine environment and apoptosis.

Inflammation, a key event in cancer development

Several recent studies have identified nuclear factor-kappaB as a key modulator in driving inflammation to cancers. Besides this transcription factor, essential in regulating inflammation and cancer development, an inflammatory microenvironment inhabiting various inflammatory cells and a network of signaling molecules are also indispensable for the malignant progression of transformed cells, which is attributed to the mutagenic predisposition of persistent infection-fighting agents at sites of chronic inflammation. As a subverted host response to inflammation-induced tumors, the inflammatory cells and regulators may facilitate angiogenesis and promote the growth, invasion, and metastasis of tumor cells. Thus far, research regarding inflammation-associated cancer development has focused on cytokines and chemokines as well as their downstream targets in linking inflammation and cancer. Moreover, other proteins with extensive roles in inflammation and cancer, such as signal transducers and activators of transcription, Nrf2, and nuclear factor of activated T cells, are also proposed to be promising targets for future studies. The elucidation of their specific effects and interactions will accelerate the development of novel therapeutic interventions against cancer development triggered by inflammation.

IFN-γ Production by CD8+ T Cells Depends on NFAT1 Transcription Factor and Regulates Th Differentiation

CD8+ T lymphocytes are excellent sources of IFN-gamma; however, the molecular mechanisms that dictate IFN-gamma expression upon TCR stimulation in these cells are not completely understood. In this study, we evaluated the involvement of NFAT1 in the regulation of IFN-gamma gene expression in murine CD8+ T cells and its relevance during Th differentiation. We show that CD8+, but not CD4+, T cells, represent the very first source of IFN-gamma upon primary T cell activation, and also that the IFN-gamma produced by naive CD8+ T cells may enhance CD4+ Th1 differentiation in vitro. TCR stimulation rapidly induced IFN-gamma expression in CD8+ T lymphocytes in a cyclosporin A-sensitive manner. Evaluation of CD8+ T cells showed that calcium influx alone was sufficient to activate NFAT1 protein, transactivate IFN-gamma gene promoter, and induce IFN-gamma production. In fact, NFAT1-deficient mice demonstrated highly impaired IFN-gamma production by naive CD8+ T lymphocytes, which were totally rescued after retroviral transduction with NFAT1-encoding vectors. Moreover, NFAT1-dependent IFN-gamma production by the CD8+ T cell compartment was crucial to control a Th2-related response in vivo, such as allergic inflammation. Consistently, CD8alpha- as well as IFN-gamma-deficient mice did not mount a Th1 immune response and also developed in vivo allergic inflammation. Our results clearly indicate that IFN-gamma production by CD8+ T cells is dependent of NFAT1 transcription factor and may be an essential regulator of Th immune responses in vivo.

Signaling pathways in Th2 development

In order for an immune response to be successful, it must be of the appropriate type and magnitude. Intracellular residing pathogens require a cell-mediated immune response, whereas extracellular pathogens evoke a humoral immune response. T-helper (Th) cells orchestrate the immune response and are divided into two subsets, Th1 and Th2 cells. Here, we discuss the mechanisms of Th2 development with a focus on signal transduction pathways that influence Th2 differentiation.