Th2 skewing by activation of Nrf2 in CD4(+) T cells

Advances in Molecular Mechanisms of Wheat Allergenicity in Animal Models: A Comprehensive Review

The prevalence of wheat allergy has reached significant levels in many countries. Therefore, wheat is a major global food safety and public health issue. Animal models serve as critical tools to advance the understanding of the mechanisms of wheat allergenicity to develop preventive and control methods. A comprehensive review on the molecular mechanisms of wheat allergenicity using animal models is unavailable at present. There were two major objectives of this study: To identify the lessons that animal models have taught us regarding the molecular mechanisms of wheat allergenicity and to identify the strengths, challenges, and future prospects of animal models in basic and applied wheat allergy research. Using the PubMed and Google Scholar databases, we retrieved and critically analyzed the relevant articles and excluded celiac disease and non-celiac gluten sensitivity. Our analysis shows that animal models can provide insight into the IgE epitope structure of wheat allergens, effects of detergents and other chemicals on wheat allergenicity, and the role of genetics, microbiome, and food processing in wheat allergy. Although animal models have inherent limitations, they are critical to advance knowledge on the molecular mechanisms of wheat allergenicity. They can also serve as highly useful pre-clinical testing tools to develop safer genetically modified wheat, hypoallergenic wheat products, novel pharmaceuticals, and vaccines.

Nrf2 regulates CD4+ T cell-induced acute graft-versus-host disease in mice

Nuclear factor erythroid-derived 2-like 2 (Nrf2) is a ubiquitously expressed transcription factor that is well known for its role in regulating the cellular redox pathway. Although there is mounting evidence suggesting a critical role for Nrf2 in hematopoietic stem cells and innate leukocytes, little is known about its involvement in T-cell biology. In this study, we identified a novel role for Nrf2 in regulating alloreactive T-cell function during allogeneic hematopoietic cell transplantation (allo-HCT). We observed increased expression and nuclear translocation of Nrf2 upon T-cell activation in vitro, especially in CD4+ donor T cells after allo-HCT. Allo-HCT recipients of Nrf2 -/- donor T cells had significantly less acute graft-versus-host disease (GVHD)-induced mortality, morbidity, and pathology. This reduction in GVHD was associated with the persistence of Helios+ donor regulatory T cells in the allograft, as well as defective upregulation of the gut-homing receptor LPAM-1 on alloreactive CD8+ T cells. Additionally, Nrf2 -/- donor CD8+ T cells demonstrated intact cytotoxicity against allogeneic target cells. Tumor-bearing allo-HCT recipients of Nrf2 -/- donor T cells had overall improved survival as a result of preserved graft-versus-tumor activity and reduced GVHD activity. Our findings characterized a previously unrecognized role for Nrf2 in T-cell function, as well as revealed a novel therapeutic target to improve the outcomes of allo-HCT.

The Nrf2 activator tBHQ inhibits the activation of primary murine natural killer cells

Tert-butylhydroquinone (tBHQ) is a commonly used food preservative with known immunomodulatory activity; however, there is little information regarding its role on natural killer (NK) cell activation and function. tBHQ is a known activator of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), which results in induction of cytoprotective genes. Activation of Nrf2 has been shown to modulate immune responses in a number of different models. In addition, studies in our laboratory have shown that tBHQ inhibits numerous early events following T cell activation. In the current study, we investigated whether activated NK cells are impacted by tBHQ, since many signaling cascades that control NK cell effector function also contribute to T cell function. Splenocytes were isolated from female, wild-type C57Bl/6J mice and treated with 1 μM or 5 μM tBHQ. NK cell function was assessed after activation with phorbol 12-myristate 13-acetate (PMA) and ionomycin for 24 h. Activation of NK cells in the presence of tBHQ decreased total NK cell percentage, production of intracellular interferon gamma (IFNɣ), granzyme B, and perforin, and induction of the cell surface proteins CD25 and CD69, which are markers of NK cell activation. In addition to NK cell effector function, NK cell maturation was also altered in response to tBHQ. Notably, this is the first study to demonstrate that the Nrf2 activator, tBHQ, negatively impacts effector function and maturation of NK cells.

Chemical and genetic control of IFNγ-induced MHCII expression

The cytokine interferon-γ (IFNγ) can induce expression of MHC class II (MHCII) on many different cell types, leading to antigen presentation to CD4⁺ T cells and immune activation. This has also been linked to anti-tumour immunity and graft-versus-host disease. The extent of MHCII upregulation by IFNγ is cell type-dependent and under extensive control of epigenetic regulators and signalling pathways. Here, we identify novel genetic and chemical factors that control this form of MHCII expression. Loss of the oxidative stress sensor Keap1, autophagy adaptor p62/SQSTM1, ubiquitin E3-ligase Cullin-3 and chromatin remodeller BPTF impair IFNγ-mediated MHCII expression. A similar phenotype is observed for arsenite, an oxidative stressor. Effects of the latter can be reversed by the inhibition of HDAC1/2, linking oxidative stress conditions to epigenetic control of MHCII expression. Furthermore, dimethyl fumarate, an antioxidant used for the treatment of several autoimmune diseases, impairs the IFNγ response by manipulating transcriptional control of MHCII We describe novel pathways and drugs related to oxidative conditions in cells impacting on IFNγ-mediated MHCII expression, which provide a molecular basis for the understanding of MHCII-associated diseases.

Comparison of Hepatic NRF2 and Aryl Hydrocarbon Receptor Binding in 2,3,7,8-Tetrachlorodibenzo-p-dioxin-Treated Mice Demonstrates NRF2-Independent PKM2 Induction

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) induces hepatic oxidative stress following activation of the aryl hydrocarbon receptor (AhR). Our recent studies showed TCDD induced pyruvate kinase muscle isoform 2 (Pkm2) as a novel antioxidant response in normal differentiated hepatocytes. To investigate cooperative regulation between nuclear factor, erythroid derived 2, like 2 (Nrf2) and the AhR in the induction of Pkm2, hepatic chromatin immunoprecipitation sequencing (ChIP-seq) analyses were integrated with RNA sequencing (RNA-seq) time-course data from mice treated with TCDD for 2-168 hours. ChIP-seq analysis 2 hours after TCDD treatment identified genome-wide NRF2 enrichment. Approximately 842 NRF2-enriched regions were located in the regulatory region of differentially expressed genes (DEGs), whereas 579 DEGs showed both NRF2 and AhR enrichment. Sequence analysis of regions with overlapping NRF2 and AhR enrichment showed over-representation of either antioxidant or dioxin response elements, although 18 possessed both motifs. NRF2 exhibited negligible enrichment within a closed Pkm chromatin region, whereas the AhR was enriched 29-fold. Furthermore, TCDD induced Pkm2 in primary hepatocytes from wild-type and Nrf2-null mice, indicating NRF2 is not required. Although NRF2 and AhR cooperate to regulate numerous antioxidant gene expression responses, the induction of Pkm2 by TCDD is independent of reactive oxygen species-mediated NRF2 activation.

Aging-dependent DNA hypermethylation and gene expression of GSTM1 involved in T cell differentiation

This study investigated whether aging was associated with epigenetic changes of DNA hypermethylation on immune gene expression and lymphocyte differentiation. We screened CG sites of methylation in blood leukocytes from different age populations, picked up genes with age-related increase of CG methylation content more than 15%, and validated immune related genes with CG hypermethylation involved in lymphocyte differentiation in the aged population. We found that 12 genes (EXHX1、 IL-10、 TSP50、 GSTM1、SLC5A5、SPI1、F2R、LMO2、PTPN6、FGFR2、MMP9、MET) were associated with promoter or exon one DNA hypermethylation in the aged group. Two immune related genes, GSTM1 and LMO2, were chosen to validate its aging-related CG hypermethylation in different leukocytes. We are the first to validate that GSTM1_P266 and LMO2_E128 CG methylation contents in T lymphocytes but not polymorphonuclear cells (PMNs) or mononuclear cells (MNCs) were significantly increased in the aged population. The GSTM1 mRNA expression in T lymphocytes but not PMNs or MNCs was inversely associated with the GSTM1 CG hypermethylation levels in the aged population studied. Further studies showed that lower GSTM1 CG methylation content led to the higher GSTM1 mRNA expression in T cells and knockdown of GSTM1 mRNA expression decreased type 1 T helper cell (Th1) differentiation in Jurkat T cells and normal adult CD4 T cells. The GSTM1_P266 hypermethylation in the aged population associated with lower GSTM1 mRNA expression was involved in Th1 differentiation, highlighting that modulation of aging-associated GSTM1 methylation may be able to enhance T helper cell immunity in the elders.

Nrf2 as a therapeutic target for rheumatic diseases

Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a master regulator of cellular protective processes. Rheumatic diseases are chronic conditions characterized by inflammation, pain, tissue damage and limitations in function. Main examples are rheumatoid arthritis, systemic lupus erythematosus, osteoarthritis and osteoporosis. Their high prevalence constitutes a major health problem with an important social and economic impact. A wide range of evidence indicates that Nrf2 may control different mechanisms involved in the physiopathology of rheumatic conditions. Therefore, the appropriate expression and balance of Nrf2 is necessary for regulation of oxidative stress, inflammation, immune responses, and cartilage and bone metabolism. Numerous studies have demonstrated that Nrf2 deficiency aggravates the disease in experimental models while Nrf2 activation results in immunoregulatory and anti-inflammatory effects. These reports reinforce the increasing interest in the pharmacologic regulation of Nrf2 and its potential applications. Nevertheless, a majority of Nrf2 inducers are electrophilic molecules which may present off-target effects. In recent years, novel strategies have been sought to modulate the Nrf2 pathway which has emerged as a therapeutic target in rheumatic conditions.

Dimethyl fumarate attenuates reactive microglia and long-term memory deficits following systemic immune challenge

Background

Systemic inflammation is associated with increased cognitive decline and risk for Alzheimer’s disease. Microglia (MG) activated during systemic inflammation can cause exaggerated neuroinflammatory responses and trigger progressive neurodegeneration. Dimethyl fumarate (DMF) is a FDA-approved therapy for multiple sclerosis. The immunomodulatory and anti-oxidant properties of DMF prompted us to investigate whether DMF has translational potential for the treatment of cognitive impairment associated with systemic inflammation.

Methods

Primary murine MG cultures were stimulated with lipopolysaccharide (LPS) in the absence or presence of DMF. MG cultured from nuclear factor (erythroid-derived 2)-like 2-deficient (Nrf2^−/−) mice were used to examine mechanisms of DMF actions. Conditioned media generated from LPS-primed MG were used to treat hippocampal neuron cultures. Adult C57BL/6 and Nrf2^−/− mice were subjected to peripheral LPS challenge. Acute neuroinflammation, long-term memory function, and reactive astrogliosis were examined to assess therapeutic effects of DMF.

Results

DMF suppressed inflammatory activation of MG induced by LPS. DMF suppressed NF-κB activity through Nrf2-depedent and Nrf2-independent mechanisms in MG. DMF treatment reduced MG-mediated toxicity towards neurons. DMF suppressed brain-derived inflammatory cytokines in mice following peripheral LPS challenge. The suppressive effect of DMF on neuroinflammation was blunted in Nrf2^−/− mice. Importantly, DMF treatment alleviated long-term memory deficits and sustained reactive astrogliosis induced by peripheral LPS challenge. DMF might mitigate neurotoxic astrocytes associated with neuroinflammation.

Conclusions

DMF treatment might protect neurons against toxic microenvironments produced by reactive MG and astrocytes associated with systemic inflammation.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1125-5) contains supplementary material, which is available to authorized users.

Association of NF-E2 Related Factor 2 (Nrf2) and inflammatory cytokines in recent onset Type 2 Diabetes Mellitus

We investigated the association of redox regulator Nuclear factor erythroid 2-related factor 2 (Nrf2) and inflammatory cytokines as well as clinical remission in patients with recent onset type 2 diabetes (DM). Blood was collected from 180 DM patients (105 males/75 females) and 150 control subjects (86 males/64 females). Blood glucose, HbA1c, lipid profile and Nrf2 levels were determined along with circulatory cytokines in study subjects. The data were adjusted with confounding factors such as age and sex using multiple logistic regression analysis. We found that Th1/Th2 and oxidative stress markers were significantly elevated, whereas Nrf2 and its downstream targets were decreased in peripheral blood mononuclear cells (PBMCs) of DM subjects when compared with control. The circulatory levels of Nrf2 showed a positive correlation with Th2 cytokines and negative correlation to Th1 cytokines. Further, the impaired insulin secretion in pancreatic β-cells observed due to cytokine stress has been restored by activation of Nrf2 as assessed by glucose-stimulated insulin secretion (GSIS). This study identifies Nrf2 plays a central role in skewing Th1 and Th2 dominance in the progression of diabetes.

The putative interplay between DJ-1/NRF2 and Dimethyl Fumarate: A potentially important pharmacological target

Recent research has outlined that Dimethyl Fumarate (DMF) functions as a gene regulator via multiple pathways, critical among which is the NRF2 cytoprotective cascade. PARK7/DJ-1 is a multifunctional protein that acts as a redox sensor and effector of multiple cytoprotective pathways, including NRF2. Specifically, it prevents the association of NRF2 with its inhibitor KEAP1, allowing NRF2 to enter the nucleus and mediate cytoprotective and antioxidant cascades. It is our hypothesis that while the NRF2-KEAP1 inhibitory complex is reported the main pharmacological target for DMF's NRF dependent functions, no study to date has explored the effects of DMF on DJ-1's expression, and vice-versa, the possibility of a regulatory inadequacy in the upstream, oxidant-responsive DJ-1 activator of the NRF2 cascade.

The Role of Reactive Oxygen Species in Regulating T Cell-mediated Immunity and Disease

T lymphocytes rely on several metabolic processes to produce the high amounts of energy and metabolites needed to drive clonal expansion and the development of effector functions. However, many of these pathways result in the production of reactive oxygen species (ROS), which have canonically been thought of as cytotoxic agents due to their ability to damage DNA and other subcellular structures. Interestingly, ROS has recently emerged as a critical second messenger for T cell receptor signaling and T cell activation, but the sensitivity of different T cell subsets to ROS varies. Therefore, the tight regulation of ROS production by cellular antioxidant pathways is critical to maintaining proper signal transduction without compromising the integrity of the cell. This review intends to detail the common metabolic sources of intracellular ROS and the mechanisms by which ROS contributes to the development of T cell-mediated immunity. The regulation of ROS levels by the glutathione pathway and the Nrf2-Keap1-Cul3 trimeric complex will be discussed. Finally, T cell-mediated autoimmune diseases exacerbated by defects in ROS regulation will be further examined in order to identify potential therapeutic interventions for these disorders.

KEAP1 Editing Using CRISPR/Cas9 for Therapeutic NRF2 Activation in Primary Human T Lymphocytes

Oxidant stress modifies T lymphocyte activation and function. Previous work demonstrated that murine T cell-specific kelch like-ECH-associated protein 1 (Keap1) deletion enhances antioxidant capacity and protects from experimental acute kidney injury. In this study, we used CRISPR technology to develop clinically translatable human T cell-specific KEAP1 deletion. Delivery of KEAP1 exon 2 specific Cas9:guide RNA in Jurkat T cells led to significant (∼70%) editing and upregulation of NRF2-regulated antioxidant genes NADPH dehydrogenase quinone 1 (NQO1) (up to 11-fold), heme oxygenase 1 (HO1) (up to 11-fold), and GCLM (up to 2-fold). In primary human T cells, delivery of KEAP1 exon 2 target site 2-specific ATTO 550-labeled Cas9:guide RNA edited KEAP1 in ∼40% cells and significantly (p ≤ 0.04) increased NQO1 (16-fold), HO1 (9-fold), and GCLM (2-fold) expression. To further enrich KEAP1-edited cells, ATTO 550-positive cells were sorted 24 h after electroporation. Assessment of ATTO 550-positive cells showed KEAP1 editing in ∼55% cells. There was no detectable off-target cleavage in the top three predicted genes in the ATTO 550-positive cells. Gene expression analysis found significantly (p ≤ 0.01) higher expression of NQO1 mRNA in ATTO 550-positive cells compared with control cells. Flow cytometric assessment showed increased (p ≤ 0.01) frequency of CD4-, CD25-, and CD69-expressing KEAP1 edited cells whereas frequency of CD8- (p ≤ 0.01) and IL-17- (p ≤ 0.05) expressing cells was reduced compared with control cells. Similar experimental conditions resulted in significant KEAP1 editing, increased antioxidant gene expression, and frequency of CD69 and IL-10 positive cells in highly enriched KEAP1-edited regulatory T cells. KEAP1-edited T cells could potentially be used for treating multiple human diseases.

Differential effects of the Nrf2 activators tBHQ and CDDO-Im on the early events of T cell activation

We previously demonstrated that activation of the transcription factor, nuclear factor erythroid 2-related factor 2 (Nrf2) promotes CD4+ Th2 differentiation. In the current study, we assessed the role of Nrf2 in early events following T cell activation. The Nrf2 activators, tBHQ (tert-butylhydroquinone) and CDDO-Im (the imidazolide derivative of the triterpenoid CDDO), were used in conjunction with splenocytes derived from wild-type and Nrf2-null mice to distinguish between Nrf2-specific and off-target effects. CDDO-Im inhibited early IFNγ production in a largely Nrf2-dependent manner. In contrast, tBHQ and CDDO-Im had little effect on expression of CD25 or CD69. Furthermore, tBHQ inhibited GM-CSF and IL-2 production in both wild-type and Nrf2-null T cells, suggesting this effect is Nrf2-independent. Conversely, CDDO-Im caused a concentration-dependent increase in IL-2 secretion in wild-type, but not Nrf2-null, splenocytes, suggesting that Nrf2 promotes IL-2 production. Interestingly, both compounds inhibit NFκB DNA binding, where the suppression by tBHQ is Nrf2-independent and CDDO-Im is Nrf2-dependent. Surprisingly, as compared to wild-type splenocytes, Nrf2-null splenocytes showed lower nuclear accumulation of c-Jun, a member of the AP-1 family of transcription factors, which have been shown to drive multiple immune genes, including IL-2. Both Nrf2 activators caused a Nrf2-dependent trend toward increased nuclear accumulation of c-Jun. These data suggest that modulation of cytokine secretion by tBHQ likely involves multiple pathways, including AP-1, NFκB, and Nrf2. Overall, the data suggest that Nrf2 activation inhibits secretion of the Th1 cytokine IFNγ, and increases early production of IL-2, which has been shown to promote Th2 differentiation, and may support the later occurrence of Th2 polarization.

Inhibition of early T cell cytokine production by arsenic trioxide occurs independently of Nrf2

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a stress-activated transcription factor that induces a variety of cytoprotective genes. Nrf2 also mediates immunosuppressive effects in multiple inflammatory models. Upon activation, Nrf2 dissociates from its repressor protein, Keap1, and translocates to the nucleus where it induces Nrf2 target genes. The Nrf2-Keap1 interaction is disrupted by the environmental toxicant and chemotherapeutic agent arsenic trioxide (ATO). The purpose of the present study was to determine the effects of ATO on early events of T cell activation and the role of Nrf2 in those effects. The Nrf2 target genes Hmox-1, Nqo-1, and Gclc were all upregulated by ATO (1–2 μM) in splenocytes derived from wild-type, but not Nrf2-null, mice, suggesting that Nrf2 is activated by ATO in splenocytes. ATO also inhibited IFNγ, IL-2, and GM-CSF mRNA and protein production in wild-type splenocytes activated with the T cell activator, anti-CD3/anti-CD28. However, ATO also decreased production of these cytokines in activated splenocytes from Nrf2-null mice, suggesting the inhibition is independent of Nrf2. Interestingly, ATO inhibited TNFα protein secretion, but not mRNA expression, in activated splenocytes suggesting the inhibition is due to post-transcriptional modification. In addition, c-Fos DNA binding was significantly diminished by ATO in wild-type and Nrf2-null splenocytes activated with anti-CD3/anti-CD28, consistent with the observed inhibition of cytokine production by ATO. Collectively, this study suggests that although ATO activates Nrf2 in splenocytes, inhibition of early T cell cytokine production by ATO occurs independently of Nrf2 and may instead be due to impaired AP-1 DNA binding.

Systemic Activation of NRF2 Alleviates Lethal Autoimmune Inflammation in Scurfy Mice

The transcription factor NRF2 (nuclear factor [erythroid-derived 2]-like 2) plays crucial roles in the defense mechanisms against oxidative stress and mediates anti-inflammatory actions under various pathological conditions. Recent studies showed that the dysfunction of regulatory T cells (Tregs) is directly linked to the initiation and progression of various autoimmune diseases. To determine the Treg-independent impact of NRF2 activation on autoimmune inflammation, we examined scurfy (Sf) mice, which are deficient in Tregs and succumb to severe multiorgan inflammation by 4 weeks of age. We found that systemic activation of NRF2 by Keap1 (Kelch-like ECH-associated protein 1) knockdown ameliorated tissue inflammation and lethality in Sf mice. Activated T cells and their cytokine production were accordingly decreased by Keap1 knockdown. In contrast, NRF2 activation through cell lineage-specific Keap1 disruption (i.e., in T cells, myeloid cells, and dendritic cells) achieved only partial or no improvement in the inflammatory status of Sf mice. Our results indicate that systemic activation of NRF2 suppresses effector T cell activities independently of Tregs and that NRF2 activation in multiple cell lineages appears to be required for sufficient anti-inflammatory effects. This study emphasizes the possible therapeutic application of NRF2 inducers in autoimmune diseases that are accompanied by Treg dysfunction.

The Oxidative Stress Response in Caenorhabditis elegans Requires the GATA Transcription Factor ELT-3 and SKN-1/Nrf2

Cellular damage caused by reactive oxygen species is believed to be a major contributor to age-associated diseases. Previously, we characterized the Caenorhabditis elegans Brap2 ortholog (BRAP-2) and found that it is required to prevent larval arrest in response to elevated levels of oxidative stress. Here, we report that C. elegans brap-2 mutants display increased expression of SKN-1-dependent, phase II detoxification enzymes that is dependent on PMK-1 (a p38 MAPK C. elegans ortholog). An RNA-interference screen was conducted using a transcription factor library to identify genes required for increased expression of the SKN-1 target gst-4 in brap-2 mutants. We identified ELT-3, a member of the GATA transcription factor family, as a positive regulator of gst-4p::gfp expression. We found that ELT-3 interacts with SKN-1 to activate gst-4 transcription in vitro and that elt-3 is required for enhanced gst-4 expression in the brap-2(ok1492) mutant in vivo Furthermore, nematodes overexpressing SKN-1 required ELT-3 for life-span extension. Taken together, these results suggest a model where BRAP-2 acts as negative regulator of SKN-1 through inhibition of p38 MAPK activity, and that the GATA transcription factor ELT-3 is required along with SKN-1 for the phase II detoxification response in C. elegans.

Nrf2-Dependent and -Independent Effects of tert-Butylhydroquinone, CDDO-Im, and H2O2 in Human Jurkat T Cells as Determined by CRISPR/Cas9 Gene Editing

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a stress-activated transcription factor activated by stimuli such as electrophilic compounds and other reactive xenobiotics. Previously, we have shown that the commonly used food additive and Nrf2 activator tert-butylhydroquinone (tBHQ) suppresses interleukin-2 (IL-2) production, CD25 expression, and NFκB activity in human Jurkat T cells. The purpose of the current studies was to determine whether these effects were dependent upon Nrf2 by developing a human Nrf2-null T cell model using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 technology. The current studies show that suppression of CD25 expression by tBHQ is partially dependent on Nrf2, whereas inhibition of IL-2 secretion is largely Nrf2-independent. Interestingly, tBHQ inhibited NFκB activation in an Nrf2-independent manner. This was an unexpected finding since Nrf2 inhibits NFκB activation in other models. These results led us to investigate another more potent Nrf2 activator, the synthetic triterpenoid 1[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im). Treatment of wild-type and Nrf2-null Jurkat T cells with CDDO-Im resulted in an Nrf2-dependent suppression of IL-2. Furthermore, susceptibility to reactive oxygen species was significantly enhanced in the Nrf2-null clones as determined by decreased mitochondrial membrane potential and cell viability. Importantly, this study is the first to describe the generation of a human Nrf2-null model, which is likely to have multiple applications in immunology and cancer biology. Collectively, this study demonstrates a role for Nrf2 in the effects of CDDO-Im on CD25 and IL-2 expression, whereas the effect of tBHQ on these parameters is complex and likely involves modulation of multiple stress-activated transcription factors, including NFκB and Nrf2.

Mucosal Interactions between Genetics, Diet, and Microbiome in Inflammatory Bowel Disease

Numerous reviews have discussed gut microbiota composition changes during inflammatory bowel diseases (IBD), particularly Crohn’s disease (CD). However, most studies address the observed effects by focusing on studying the univariate connection between disease and dietary-induced alterations to gut microbiota composition. The possibility that these effects may reflect a number of other interconnected (i.e., pantropic) mechanisms, activated in parallel, particularly concerning various bacterial metabolites, is in the process of being elucidated. Progress seems, however, hampered by various difficult-to-study factors interacting at the mucosal level. Here, we highlight some of such factors that merit consideration, namely: (1) the contribution of host genetics and diet in altering gut microbiome, and in turn, the crosstalk among secondary metabolic pathways; (2) the interdependence between the amount of dietary fat, the fatty acid composition, the effects of timing and route of administration on gut microbiota community, and the impact of microbiota-derived fatty acids; (3) the effect of diet on bile acid composition, and the modulator role of bile acids on the gut microbiota; (4) the impact of endogenous and exogenous intestinal micronutrients and metabolites; and (5) the need to consider food associated toxins and chemicals, which can introduce confounding immune modulating elements (e.g., antioxidant and phytochemicals in oils and proteins). These concepts, which are not mutually exclusive, are herein illustrated paying special emphasis on physiologically inter-related processes.

Dimethyl fumarate treatment induces adaptive and innate immune modulation independent of Nrf2

Dimethyl fumarate (DMF) (BG-12, Tecfidera) is a fumaric acid ester (FAE) that was advanced as a multiple sclerosis (MS) therapy largely for potential neuroprotection as it was recognized that FAEs are capable of activating the antioxidative transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathway. However, DMF treatment in randomized controlled MS trials was associated with marked reductions in relapse rate and development of active brain MRI lesions, measures considered to reflect CNS inflammation. Here, we investigated the antiinflammatory contribution of Nrf2 in DMF treatment of the MS model, experimental autoimmune encephalomyelitis (EAE). C57BL/6 wild-type (WT) and Nrf2-deficient (Nrf2(-/-)) mice were immunized with myelin oligodendrocyte glycoprotein (MOG) peptide 35-55 (p35-55) for EAE induction and treated with oral DMF or vehicle daily. DMF protected WT and Nrf2(-/-) mice equally well from development of clinical and histologic EAE. The beneficial effect of DMF treatment in Nrf2(-/-) and WT mice was accompanied by reduced frequencies of IFN-γ and IL-17-producing CD4(+) cells and induction of antiinflammatory M2 (type II) monocytes. DMF also modulated B-cell MHC II expression and reduced the incidence of clinical disease in a B-cell-dependent model of spontaneous CNS autoimmunity. Our observations that oral DMF treatment promoted immune modulation and provided equal clinical benefit in acute EAE in Nrf2(-/-) and WT mice, suggest that the antiinflammatory activity of DMF in treatment of MS patients may occur through alternative pathways, independent of Nrf2.

Activation of Constitutive Androstane Receptor (CAR) in Mice Results in Maintained Biliary Excretion of Bile Acids Despite a Marked Decrease of Bile Acids in Liver

Activation of Constitutive Androstane Receptor (CAR) protects against bile acid (BA)-induced liver injury. This study was performed to determine the effect of CAR activation on bile flow, BA profile, as well as expression of BA synthesis and transport genes. Synthetic CAR ligand 1,4-bis-[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) was administered to mice for 4 days. BAs were quantified by UPLC-MS/MS (ultraperformance liquid chromatography-tandem mass spectrometry). CAR activation decreases total BAs in livers of male (49%) and female mice (26%), largely attributable to decreases of the 12α-hydroxylated BA taurocholic acid (T-CA) (males (M) 65%, females (F) 45%). Bile flow in both sexes was increased by CAR activation, and the increases were BA-independent. CAR activation did not alter biliary excretion of total BAs, but overall BA composition changed. Excretion of muricholic (6-hydroxylated) BAs was increased in males (101%), and the 12α-OH proportion of biliary BAs was decreased in both males (37%) and females (28%). The decrease of T-CA in livers of males and females correlates with the decreased mRNA of the sterol 12α-hydroxylase Cyp8b1 in males (71%) and females (54%). As a response to restore BAs to physiologic concentrations in liver, mRNA of Cyp7a1 is upregulated following TCPOBOP (males 185%, females 132%). In ilea, mRNA of the negative feedback regulator Fgf15 was unaltered by CAR activation, indicating biliary BA excretion was sufficient to maintain concentrations of total BAs in the small intestine. In summary, the effects of CAR activation on BAs in male and female mice are quite similar, with a marked decrease in the major BA T-CA in the liver.

CD4 memory T cells develop and acquire functional competence by sequential cognate interactions and stepwise gene regulation

Memory CD4(+) T cells promote protective humoral immunity; however, how memory T cells acquire this activity remains unclear. This study demonstrates that CD4(+) T cells develop into antigen-specific memory T cells that can promote the terminal differentiation of memory B cells far more effectively than their naive T-cell counterparts. Memory T cell development requires the transcription factor B-cell lymphoma 6 (Bcl6), which is known to direct T-follicular helper (Tfh) cell differentiation. However, unlike Tfh cells, memory T cell development did not require germinal center B cells. Curiously, memory T cells that develop in the absence of cognate B cells cannot promote memory B-cell recall responses and this defect was accompanied by down-regulation of genes associated with homeostasis and activation and up-regulation of genes inhibitory for T-cell responses. Although memory T cells display phenotypic and genetic signatures distinct from Tfh cells, both had in common the expression of a group of genes associated with metabolic pathways. This gene expression profile was not shared to any great extent with naive T cells and was not influenced by the absence of cognate B cells during memory T cell development. These results suggest that memory T cell development is programmed by stepwise expression of gatekeeper genes through serial interactions with different types of antigen-presenting cells, first licensing the memory lineage pathway and subsequently facilitating the functional development of memory T cells. Finally, we identified Gdpd3 as a candidate genetic marker for memory T cells.

Activation of NRF2 pathway in spleen, thymus as well as peripheral blood mononuclear cells by acute arsenic exposure in mice

Arsenic has already been demonstrated to activate the nuclear factor erythroid 2-related factor 2 (NRF2) in many different organs and cell lines. The present study tried to explore the expression of NRF2 pathway by acute arsenic exposure in immune system in vivo. Our results showed that treatment with arsenic (sodium arsenite, 5, 10 and 20mg/kg, intra-gastrically) increased the expression of NRF2 and its downstream targets heme oxygenase-1 (HO-1), glutathione-S-transferase (GST), glutamate-cysteine ligase (GCL) and glutathione reductase (GR) consistently in spleen, thymus, as well as peripheral blood mononuclear cells (PBMCs), as early as treatment from 6h. Arsenic was also detected to up-regulate the mRNA levels of Hmox1, NAD(P)H: quinine oxidoreductase 1 (Nqo1), Gclc and Gclm in spleen and thymus. Besides, we detected the enhancement of Kelch-like ECH-associated protein (KEAP1) expression in these immune organs and immunocytes. What's more, our results also found the imbalanced oxidative redox status under the circumstances that arsenic activated NRF2 pathway, reflected by the generation of lipid peroxidation, as well as the reduction of antioxidative capacities in both spleen and thymus. Taken together, our results here strongly suggested the expression and activation of NRF2 pathway by acute arsenic exposure in immune system in vivo. Further studies are being investigated to explore the possible roles and functions of NRF2 pathway stimulation in the regulation of immune responses of this metalloid.

Fast food consumption in pregnancy and subsequent asthma symptoms in young children

BACKGROUND

Recent cross-sectional studies suggested children's current fast food consumption to be related to frequency of asthma and allergies. Maternal prenatal diet has been suspected to contribute to children's asthma and atopic disease risks.

OBJECTIVES

We hypothesized that maternal fast food intake during pregnancy increases offspring's risk for asthmatic symptoms.

METHODS

We conducted a population-based study of 1201 mother/child pairs in Los Angeles, California. Detailed information about prenatal fast food intake and other dietary, lifestyle/environmental factors, and pregnancy was collected shortly after birth; further data were retrieved from birth certificates. Using the International Study of Asthma and Allergies in Childhood core questions, asthma and rhinitis symptoms were assessed, and doctor's diagnoses were recorded in offspring 3.5 years after birth. Poisson regression with robust error variance using a log link function was used to estimate relative risks (RRs). Models were adjusted using covariates or propensity scores.

RESULTS

Maternal prenatal fast food consumption related to increased relative risks of their children for severe, and current asthma symptoms (wheeze last 12 months combined with doctor's diagnosis) in a dose-dependent manner: 'once a month': RR: 0.99 (95% CI: 0.36, 2.75), 'once a week': 1.26 (0.47, 3.34); '3-4 days a week': 2.17 (0.77, 6.12); and 'every day' 4.46 (1.36 14.6) compared to 'never', adjusting for potential confounders (p for trend = 0.0025). There was also suggestion of increased risks for rhinitis symptoms.

CONCLUSIONS

These findings suggest that in utero exposure to frequent fast food through maternal diet may be a risk factor for asthmatic symptoms in young children.

T Lymphocyte-Specific Activation of Nrf2 Protects from AKI

T lymphocytes are established mediators of ischemia reperfusion (IR)-induced AKI, but traditional immune principles do not explain their mechanism of early action in the absence of alloantigen. Nrf2 is a transcription factor that is crucial for cytoprotective gene expression and is generally thought to have a key role in dampening IR-induced AKI through protective effects on epithelial cells. We proposed an alternative hypothesis that augmentation of Nrf2 in T cells is essential to mitigate oxidative stress during IR-induced AKI. We therefore generated mice with genetically amplified levels of Nrf2 specifically in T cells and examined the effect on antioxidant gene expression, T cell activation, cytokine production, and IR-induced AKI. T cell-specific augmentation of Nrf2 significantly increased baseline antioxidant gene expression. These mice had a high frequency of intrarenal CD25(+)Foxp3(+) regulatory T cells and decreased frequencies of CD11b(+)CD11c(+) and F4/80(+) cells. Intracellular levels of TNF-α, IFN-γ, and IL-17 were significantly lower in CD4(+) T cells with high Nrf2 expression. Mice with increased T cell expression of Nrf2 were significantly protected from functional and histologic consequences of AKI. Furthermore, adoptive transfer of high-Nrf2 T cells protected wild-type mice from IR injury and significantly improved their survival. These data demonstrate that T cell-specific activation of Nrf2 protects from IR-induced AKI, revealing a novel mechanism of tissue protection during acute injury responses.

Radiation and inflammation

The immune system has the power to modulate the expression of radiation-induced normal and tumor tissue damage. On the one hand, it can contribute to cancer cure, and on the other hand, it can influence acute and late radiation side effects, which in many ways resemble acute and chronic inflammatory disease states. The way radiation-induced inflammation feeds into adaptive antigen-specific immune responses adds another dimension to the tumor-host cross talk during radiation therapy and to possible radiation-driven autoimmune responses. Understanding how radiation affects inflammation and immunity is therefore critical if we are to effectively manipulate these forces for benefit in radiation oncology treatments.

Multi-target drugs to address multiple checkpoints in complex inflammatory pathologies: evolutionary cues for novel "first-in-class" anti-inflammatory drug candidates: a reviewer's perspective

Inflammation is a complex, metabolically expensive process involving multiple signaling pathways and regulatory mechanisms which have evolved over evolutionary timescale. Addressing multiple targets of inflammation holistically, in moderation, is probably a more evolutionarily viable strategy, as compared to current therapy which addresses drug targets in isolation. Polypharmacology, addressing multiple targets, is commonly used in complex ailments, suggesting the superior safety and efficacy profile of multi-target (MT) drugs. Phenotypic drug discovery, which generated successful MT and first-in-class drugs in the past, is now re-emerging. A multi-pronged approach, which modulates the evolutionarily conserved, robust and pervasive cellular mechanisms of tissue repair, with AMPK at the helm, regulating the complex metabolic/immune/redox pathways underlying inflammation, is perhaps a more viable strategy than addressing single targets in isolation. Molecules that modulate multiple molecular mechanisms of inflammation in moderation (modulating TH cells toward the anti-inflammatory phenotype, activating AMPK, stimulating Nrf2 and inhibiting NFκB) might serve as a model for a novel Darwinian "first-in-class" therapeutic category that holistically addresses immune, redox and metabolic processes associated with inflammatory repair. Such a multimodal biological activity is supported by the fact that several non-calorific pleiotropic natural products with anti-inflammatory action have been incorporated into diet (chiefly guided by the adaptive development of olfacto-gustatory preferences over evolutionary timescales) rendering such molecules, endowed with evolutionarily privileged molecular scaffolds, naturally oriented toward multiple targets.

Opportunities and challenges of radiotherapy for treating cancer

The past 20 years have seen dramatic changes in the delivery of radiation therapy, but the impact of radiobiology on the clinic has been far less substantial. A major consideration in the use of radiotherapy has been on how best to exploit differences between the tumour and host tissue characteristics, which in the past has been achieved empirically by radiation-dose fractionation. New advances are uncovering some of the mechanistic processes that underlie this success story. In this Review, we focus on how these processes might be targeted to improve the outcome of radiotherapy at the individual patient level. This approach would seem a more productive avenue of treatment than simply trying to increase the radiation dose delivered to the tumour.

The drosophila T-box transcription factor midline functions within Insulin/Akt and c-Jun-N terminal kinase stress-reactive signaling pathways to regulate interommatial bristle formation and cell survival

We recently reported that the T-box transcription factor midline (mid) functions within the Notch-Delta signaling pathway to specify sensory organ precursor (SOP) cell fates in early-staged pupal eye imaginal discs and to suppress apoptosis (Das et al.). From genetic and allelic modifier screens, we now report that mid interacts with genes downstream of the insulin receptor(InR)/Akt, c-Jun-N-terminal kinase (JNK) and Notch signaling pathways to regulate interommatidial bristle (IOB) formation and cell survival. One of the most significant mid-interacting genes identified from the modifier screen is dFOXO, a transcription factor exhibiting a nucleocytoplasmic subcellular distribution pattern. In common with dFOXO, we show that Mid exhibits a nucleocytoplasmic distribution pattern within WT third-instar larval (3(o)L) tissue homogenates. Because dFOXO is a stress-responsive factor, we assayed the effects of either oxidative or metabolic stress responses on modifying the mid mutant phenotype which is characterized by a 50% loss of IOBs within the adult compound eye. While metabolic starvation stress does not affect the mid mutant phenotype, either 1 mM paraquat or 20% coconut oil, oxidative stress inducers, partially suppresses the mid mutant phenotype resulting in a significant recovery of IOBs. Another significant mid-interacting gene we identified is groucho (gro). Mid and Gro are predicted to act as corepressors of the enhancer-of-split gene complex downstream of Notch. Immunolabeling WT and dFOXO null 3(o)L eye-antennal imaginal discs with anti-Mid and anti-Engrailed (En) antibodies indicate that dFOXO is required to activate Mid and En expression within photoreceptor neurons of the eye disc. Taken together, these studies show that Mid and dFOXO serve as critical effectors of cell fate specification and survival within integrated Notch, InR/dAkt, and JNK signaling pathways during 3(o)L and pupal eye imaginal disc development.

The Nrf2 activator tBHQ inhibits T cell activation of primary human CD4 T cells

The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) regulates a battery of antioxidant, detoxification, and cell stress genes. It is activated by oxidative stress and a number of exogenous compounds, one of which is tert-butylhydroquinone (tBHQ), a widely used food preservative. Nrf2 modulates immune responses in numerous rodent models of inflammation, but its effects on human immune cells are not well characterized. The purpose of these studies was to evaluate the effects of the Nrf2 activator tBHQ on early events of T cell activation in primary human cells. Treatment with tBHQ induced mRNA expression of the Nrf2 target genes HMOX-1, GCLC, and NQO1, and also increased NRF2 mRNA expression, albeit to a lesser extent than the other target genes. tBHQ decreased production of the cytokines IL-2 and IFN-γ at both the protein and mRNA levels after stimulation with anti-CD3/anti-CD28 in human peripheral blood mononuclear cells and to an even greater extent in isolated CD4 T cells. Likewise, tBHQ decreased induction of CD25 and CD69 in peripheral blood mononuclear cells (PBMCs) and this decrease was even more marked in isolated CD4 T cells. In addition, tBHQ inhibited induction of NFκB DNA binding in anti-CD3/anti-CD28-activated PBMCs. Collectively, these data suggest that tBHQ inhibits activation of primary human CD4 T cells, which correlates with activation of Nrf2 and inhibition of NFκB DNA binding. Although these studies suggest the food additive tBHQ negatively impacts T cell activation, further studies will be needed to fully elucidate the effect of tBHQ on human immune responses.

Protective effect of ARE-inducing phenol antioxidant TS-13 in chronic inflammation

The protective effect of partially substituted monophenol TS-13 inducing the Nrf2/Keap1/ARE signaling system was studied on the model of chronic inflammation in vivo. It was found that during simulation of inflammation in an air pouch lined with synovial-like membrane, TS-13 did not affect the exudate volume, protein content, and cell count, but significantly reduced the intensity of oxidative metabolism in leukocytes of the exudate. In rheumatoid polyarthritis induced by heterologous collagen, TS-13 reduced the severity of clinical signs of inflammation only at the early stages, but inhibited H2O2 generation by monocytes and, partially, by blood neutrophils. These results suggest that the phlogolytic effect of the redox sensitive Nrf2/Keap1/ARE signaling system is less pronounced in chronic immune-mediated inflammatory processes than in acute inflammation.

Nrf2 knockout attenuates the anti-inflammatory effects of phenethyl isothiocyanate and curcumin

The role of phytochemicals in preventive and therapeutic medicine is a major area of scientific research. Several studies have illustrated the mechanistic roles of phytochemicals in Nrf2 transcriptional activation. The present study aims to examine the importance of the transcription factor Nrf2 by treating peritoneal macrophages from Nrf2^+/+ and Nrf2^–/– mice ex vivo with phenethyl isothiocyanate (PEITC) and curcumin (CUR). The peritoneal macrophages were pretreated with the drugs and challenged with lipopolysaccharides (LPSs) alone and in combination with PEITC or CUR to assess their anti-inflammatory and antioxidative effects based on gene and protein expression in the treated cells. LPS treatment resulted in an increase in the expression of inflammatory markers such as cycloxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in both Nrf2^+/+ and Nrf2^–/– macrophages, detected by quantitative polymerase chain reaction (qPCR). Nrf2^+/+ macrophages treated with PEITC and CUR exhibited a significant decrease in the expression of these anti-inflammatory genes along with an increase in the expression of hemeoxygenase-1 (HO-1), which is an antioxidative stress gene downstream of the Nrf2 transcription factor battery. Although there was no significant decrease in the expression of the anti-inflammatory genes or an increase in HO-1 expression in Nrf2^–/– macrophages treated with either PEITC or CUR, there was a significant decrease in the protein expression of COX-2 and an increase in the expression of HO-1 in Nrf2^+/+ macrophages treated with PEITC compared to that with CUR treatment. No significant changes were observed in the macrophages from knockout animals. Additionally, there was a significant decrease in LPS-induced IL-6 and TNF-α production following PEITC treatment compared with that following CUR in Nrf2^+/+ macrophages, whereas no change was observed in the macrophages from knockout animals. The results from qPCR, western blot, and ELISA analyses in macrophages from Nrf2^+/+ and Nrf2 ^–/– mice indicate that Nrf2 plays an important role in the anti-inflammatory and antioxidative effects of PEITC and CUR, as observed by their decreased activities in Nrf2^–/– macrophages.

Epigenomic analysis of primary human T cells reveals enhancers associated with TH2 memory cell differentiation and asthma susceptibility

A characteristic feature of asthma is the aberrant accumulation, differentiation or function of memory CD4(+) T cells that produce type 2 cytokines (TH2 cells). By mapping genome-wide histone modification profiles for subsets of T cells isolated from peripheral blood of healthy and asthmatic individuals, we identified enhancers with known and potential roles in the normal differentiation of human TH1 cells and TH2 cells. We discovered disease-specific enhancers in T cells that differ between healthy and asthmatic individuals. Enhancers that gained the histone H3 Lys4 dimethyl (H3K4me2) mark during TH2 cell development showed the highest enrichment for asthma-associated single nucleotide polymorphisms (SNPs), which supported a pathogenic role for TH2 cells in asthma. In silico analysis of cell-specific enhancers revealed transcription factors, microRNAs and genes potentially linked to human TH2 cell differentiation. Our results establish the feasibility and utility of enhancer profiling in well-defined populations of specialized cell types involved in disease pathogenesis.

Targeting the NF-E2-related factor 2 pathway: a novel strategy for glioblastoma (review)

Glioblastoma is the most common and malignant subtype among all brain tumors. Nuclear factor erythroid 2-related factor 2 (Nrf2) is an essential component of cellular defense against a variety of endogenous and exogenous stresses. A marked increase in research over the past few decades focusing on Nrf2 and its role in regulating glioblastoma has revealed the potential value of Nrf2 in the treatment of glioblastoma. In the present review, we discuss a novel framework of Nrf2 in the regulation of glioblastoma and the mechanisms regarding the downregulation of Nrf2 in treating glioblastoma. The candidate mechanisms include direct and indirect means. Direct mechanisms target tumor molecular pathways in order to overcome resistance to chemotherapy and radiotherapy, to inhibit proliferation, to block invasion and migration, to induce apoptosis, to promote differentiation, to enhance autophagy and to target glioblastoma stem cells. Indirect mechanisms target the reaction between glioblastoma cells and the surrounding microenvironment. Overall, the value of the Nrf2 pathway in glioblastoma provides a promising opportunity for new approaches by which to treat glioblastoma.

Water-soluble phenol TS-13 combats acute but not chronic inflammation

OBJECTIVE

This study was conducted to evaluate the effect of the synthetic water-soluble phenolic antioxidant TS-13 (sodium 3-(4'-methoxyphenyl)propyl thiosulfonate), an inducer of the redox-dependent Keap1/Nrf2/ARE signaling system, in experimental models of acute and chronic inflammation.

METHODS

Acute local inflammation was induced by intraplantar carrageenan injection into rat hind paws, and acute systemic inflammation was modeled by intravenous zymosan injection (in rats) or LPS-induced endotoxic shock (in mice). Chronic inflammation was investigated in rat models of air pouch and collagen-induced arthritis. The effects of TS-13 treatment were estimated by changes in the intensity of inflammation (paw edema, liver infiltration, animal survival, exudation, and clinical score of arthritis) and by the effects on reactive oxygen species (ROS) generation by leukocytes from peripheral blood and inflammatory exudates.

RESULTS

We found the significant increase in expression of mRNA, content of protein and activity of a well-characterized Nrf2 target enzyme glutathione S-transferase P1, as well as nuclear extract protein binding to the ARE consensus sequence in liver of mice fed with diet containing TS-13. TS-13 markedly attenuated carrageenan-induced paw edema, reduced blood granulocyte number and volume density of liver infiltrates in the systemic zymosan-induced inflammation model, and increased mice survival after lipopolysaccharide-induced septic shock. However, TS-13 administration did not influence cell and protein exudation into air pouches and suppressed clinical manifestation of collagen-induced polyarthritis only at early stages. Nevertheless, TS-13 inhibited the generation of ROS by leukocytes in all inflammation models.

CONCLUSION

The data suggest that the anti-inflammatory effects of Keap1/Nrf2/ARE system are more prominent against acute innate-mediated inflammation than chronic immune inflammation. This narrows the potential therapeutic efficacy of ARE inducers in inflammation treatment.

Nrf2 expression and activity in human T lymphocytes: stimulation by T cell receptor activation and priming by inorganic arsenic and tert-butylhydroquinone

The transcription factor nuclear factor-erythroid 2-related-2 (Nrf2) controls cellular redox homeostasis and displays immunomodulatory properties. Nrf2 alters cytokine expression in murine T cells, but its effects in human T lymphocytes are unknown. This study investigated the expression and activity of Nrf2 in human activated CD4(+) T helper lymphocytes (Th cells) that mediate the adaptive immune response. Th cells were isolated from peripheral blood mononuclear cells and activated with antibodies against CD3 and CD28, mimicking physiologic Th cell stimulation by dendritic cells. Nrf2 is hardly detectable in unstimulated Th cells. Activation of Th cells rapidly and strongly increases the levels of Nrf2 protein by increasing NRF2 gene transcription. Th cell activation also enhances mRNA and protein levels of Nrf2 target genes encoding antioxidant enzymes. Blocking Nrf2 expression using chemical inhibitors or siRNAs prevents these gene inductions. Pretreatment with inorganic arsenic, a Nrf2 inducer that does not alter NRF2 gene expression, increases protein level and transcriptional activity of Nrf2 induced by Th cell stimulation. Inorganic arsenic enhances nuclear translocation of Nrf2, its interaction with the coactivator protein p300, and its DNA binding activity. Inhibition of Nrf2 expression abrogates the effects of inorganic arsenic on mRNA levels of antioxidant genes, but does not alter the expression of IL-2, TNF-α, interferon-γ, or IL-17 in Th cells activated in the absence or presence of the metalloid. In conclusion, this study demonstrates for the first time that stimulation of human Th cells increases transcription of the NRF2 gene and activity of the Nrf2 protein. However, modulation of Nrf2 levels does not modify the secretion of inflammatory cytokines from these T lymphocytes.

Are reactive oxygen species always detrimental to pathogens?

Reactive oxygen species (ROS) are deadly weapons used by phagocytes and other cell types, such as lung epithelial cells, against pathogens. ROS can kill pathogens directly by causing oxidative damage to biocompounds or indirectly by stimulating pathogen elimination by various nonoxidative mechanisms, including pattern recognition receptors signaling, autophagy, neutrophil extracellular trap formation, and T-lymphocyte responses. Thus, one should expect that the inhibition of ROS production promote infection. Increasing evidences support that in certain particular infections, antioxidants decrease and prooxidants increase pathogen burden. In this study, we review the classic infections that are controlled by ROS and the cases in which ROS appear as promoters of infection, challenging the paradigm. We discuss the possible mechanisms by which ROS could promote particular infections. These mechanisms are still not completely clear but include the metabolic effects of ROS on pathogen physiology, ROS-induced damage to the immune system, and ROS-induced activation of immune defense mechanisms that are subsequently hijacked by particular pathogens to act against more effective microbicidal mechanisms of the immune system. The effective use of antioxidants as therapeutic agents against certain infections is a realistic possibility that is beginning to be applied against viruses.

Sequestosome1/p62: a regulator of redox-sensitive voltage-activated potassium channels, arterial remodeling, inflammation, and neurite outgrowth

Sequestosome1/p62 (SQSTM1) is an oxidative stress-inducible protein regulated by the redox-sensitive transcription factor Nrf2. It is not an antioxidant but known as a multifunctional regulator of cell signaling with an ability to modulate targeted or selective degradation of proteins through autophagy. SQSTM1 implements these functions through physical interactions with different types of proteins including atypical PKCs, nonreceptor-type tyrosine kinase p56(Lck) (Lck), polyubiquitin, and autophagosomal factor LC3. One of the notable physiological functions of SQSTM1 is the regulation of redox-sensitive voltage-gated potassium (Kv) channels which are composed of α and β subunits: (Kvα)4 (Kvβ)4. Previous studies have established that SQSTM1 scaffolds PKCζ, enhancing phosphorylation of Kvβ which induces inhibition of pulmonary arterial Kv1.5 channels under acute hypoxia. Recent studies reveal that Lck indirectly interacts with Kv1.3 α subunits and plays a key role in acute hypoxia-induced Kv1.3 channel inhibition in T lymphocytes. Kv1.3 channels provide a signaling platform to modulate the migration and proliferation of arterial smooth muscle cells and activation of T lymphocytes, and hence have been recognized as a therapeutic target for treatment of restenosis and autoimmune diseases. In this review, we focus on the functional interactions of SQSTM1 with Kv channels through two key partners aPKCs and Lck. Furthermore, we provide molecular insights into the functions of SQSTM1 in suppression of proliferation of arterial smooth muscle cells and neointimal hyperplasia following carotid artery ligation, in T lymphocyte differentiation and activation, and in NGF-induced neurite outgrowth in PC12 cells.

The Nrf2 activator, tBHQ, differentially affects early events following stimulation of Jurkat cells

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that is activated by cellular stresses, such as oxidative compounds. After activation, Nrf2 induces transcription of its target genes, many of which have cytoprotective functions. Previously, we have shown that activation of Nrf2 by tert-butylhydroquinone (tBHQ) skews murine CD4⁺ T-cell differentiation. Although the role of Nrf2 in murine T cells is somewhat characterized, it is largely uncharacterized in human T cells. Therefore, the aim of the current studies was to characterize the effects of the Nrf2 activator, tBHQ, on the early events of human CD4⁺ T-cell activation. Pretreatment of Jurkat T cells with tBHQ, prior to activation with anti-CD3/anti-CD28, diminished the production of interleukin-2 (IL-2) at both the transcript and protein levels. Similarly, the expression of CD25 also diminished, albeit to a lesser degree than IL-2, after pretreatment with tBHQ. The decrease in IL-2 production was not due to decreased nuclear translocation of c-fos or c-jun. Although tBHQ caused both a delay and a decrease in Ca²⁺ influx in activated Jurkat cells, no decrease in nuclear factor of activated T cells (NFAT) DNA binding or transcriptional activity was observed. In contrast to NFAT, tBHQ significantly decreased NFκB transcriptional activity. Collectively, our studies show that the Nrf2 activator, tBHQ, inhibits IL-2 and CD25 expression, which correlates with decreased NFκB transcriptional activity in activated Jurkat cells. Overall, our studies suggest that Nrf2 represents a novel mechanism for the regulation of both human and mouse T cell function.

Oxidative stress induced by HIV-1 reverse transcriptase modulates the enzyme's performance in gene immunization

HIV-1 infection induces chronic oxidative stress. The resultant neurotoxicity has been associated with Tat protein. Here, we for the first time describe the induction of oxidative stress by another HIV-1 protein, reverse transcriptase (RT). Expression of HIV-1 RT in human embryonic kidney cells generated potent production of the reactive oxygen species (ROS), detected by the fluorescence-based probes. Quantitative RT-PCR demonstrated that expression of RT in HEK293 cells induced a 10- to 15-fold increased transcription of the phase II detoxifying enzymes human

NAD(P)H

quinone oxidoreductase (Nqo1) and heme oxygenase 1 (HO-1), indicating the induction of oxidative stress response. The capacity to induce oxidative stress and stress response appeared to be an intrinsic property of a vast variety of RTs: enzymatically active and inactivated, bearing mutations of drug resistance, following different routes of processing and presentation, expressed from viral or synthetic expression-optimized genes. The total ROS production induced by RT genes of the viral origin was found to be lower than that induced by the synthetic/expression-optimized or chimeric RT genes. However, the viral RT genes induced higher levels of ROS production and higher levels of HO-1 mRNA than the synthetic genes per unit of protein in the expressing cell. The capacity of RT genes to induce the oxidative stress and stress response was then correlated with their immunogenic performance. For this, RT genes were administered into BALB/c mice by intradermal injections followed by electroporation. Splenocytes of immunized mice were stimulated with the RT-derived and control antigens and antigen-specific proliferation was assessed by IFN-γ/IL-2 Fluorospot. RT variants generating high total ROS levels induced significantly stronger IFN-γ responses than the variants inducing lower total ROS, while high levels of ROS normalized per unit of protein in expressing cell were associated with a weak IFN-γ response. Poor gene immunogenicity was also associated with a high (per unit of protein) transcription of antioxidant response element (ARE) dependent phase II detoxifying enzyme genes, specifically HO-1. Thus, we have revealed a direct link between the propensity of the microbial proteins to induce oxidative stress and their immunogenicity.

Bach2 maintains T cells in a naive state by suppressing effector memory-related genes

The transcriptional repressor BTB and CNC homology 2 (Bach2) is thought to be mainly expressed in B cells with specific functions such as class switch recombination and somatic hypermutation, but its function in T cells is not known. We found equal Bach2 expression in T cells and analyzed its function using Bach2-deficient (-/-) mice. Although T-cell development was normal, numbers of peripheral naive T cells were decreased, which rapidly produced Th2 cytokines after TCR stimulation. Bach2(-/-) naive T cells highly expressed genes related to effector-memory T cells such as CCR4, ST-2 and Blimp-1. Enhanced expression of these genes induced Bach2(-/-) naive T cells to migrate toward CCR4-ligand and respond to IL33. Forced expression of Bach2 restored the expression of these genes. Using Chromatin Immunoprecipitation (ChIP)-seq analysis, we identified S100 calcium binding protein a, Heme oxigenase 1, and prolyl hydroxylase 3 as Bach2 direct target genes, which are highly expressed in effector-memory T cells. These findings indicate that Bach2 suppresses effector memory-related genes to maintain the naive T-cell state and regulates generation of effector-memory T cells.

Nrf2 protection against liver injury produced by various hepatotoxicants

To investigate the role of Nrf2 as a master defense against the hepatotoxicity produced by various chemicals, Nrf2-null, wild-type, Keap1-knock down (Keap1-Kd) and Keap1-hepatocyte knockout (Keap1-HKO) mice were used as a “graded Nrf2 activation” model. Mice were treated with 14 hepatotoxicants at appropriate doses, and blood and liver samples were collected thereafter (6 h to 7 days depending on the hepatotoxicant). Graded activation of Nrf2 offered a Nrf2-dependent protection against the hepatotoxicity produced by carbon tetrachloride, acetaminophen, microcystin, phalloidin, furosemide, cadmium, and lithocholic acid, as evidenced by serum alanine aminotransferase (ALT) activities and by histopathology. Nrf2 activation also offered moderate protection against liver injury produced by ethanol, arsenic, bromobenzene, and allyl alcohol but had no effects on the hepatotoxicity produced by D-galactosamine/endotoxin and the Fas ligand antibody Jo-2. Graded Nrf2 activation reduced the expression of inflammatory genes (MIP-2, mKC, IL-1β, IL-6, and TNFα), oxidative stress genes (Ho-1, Egr1), ER stress genes (Gadd45 and Gadd153), and genes encoding cell death (Noxa, Bax, Bad, and caspase3). Thus, this study demonstrates that Nrf2 prevents the liver from many, but not all, hepatotoxicants. The Nrf2-mediated protection is accompanied by induction of antioxidant genes, suppression of inflammatory responses, and attenuation of oxidative stress.

Cytokines as molecular targets for aryl hydrocarbon receptor ligands: implications for toxicity and xenobiotic detoxification

INTRODUCTION

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor historically known for regulating expression of several important drug-detoxifying proteins. Besides drug metabolism pathways, cytokines have been recently recognized as targeted by the AhR signaling cascade, which may contribute to toxicity and changes in xenobiotic detoxification caused by AhR agonists.

AREAS COVERED

This article summarizes the nature of the main cytokines regulated by AhR ligands and reviews their involvement in toxic effects of AhR ligands, especially in relation with inflammation. The article also discusses the potential implications for drug detoxification pathways.

EXPERT OPINION

Even if various cytokines, including inflammatory ones, have already been demonstrated to constitute robust targets for AhR, the exact role played by AhR with respect to inflammation remains to be determined. Further studies are also required to better characterize the molecular mechanisms implicated in regulation of cytokines by AhR ligands and to determine the role that may play AhR-targeted cytokines in alteration of xenobiotic detoxification. Finally, changes in cytokine receptor expression triggered by AhR ligands have additionally to be taken into account to better and more extensively comprehend the role played by AhR in the cytokine/inflammation area.