NF-kappaB-dependent regulation of the timing of activation-induced cell death of T lymphocytes

Multiomics approaches disclose very-early molecular and cellular switches during insect-venom allergen-specific immunotherapy: an observational study

Allergen-specific immunotherapy (AIT) induces immune tolerance, showing the highest success rate (>95%) for insect venom while a much lower chance for pollen allergy. However, the molecular switches leading to successful durable tolerance restoration remain elusive. The primary outcome of this observational study is the comprehensive immunological cellular characterization during the AIT initiation phase, whereas the secondary outcomes are the serological and Th2-cell-type-specific transcriptomic analyses. Here we apply a multilayer-omics approach to reveal dynamic peripheral immune landscapes during the AIT-initiation phase in venom allergy patients (VAP) versus pollen-allergic and healthy controls. Already at baseline, VAP exhibit altered abundances of several cell types, including classical monocytes (cMono), CD4+ hybrid type 1-type 17 cells (Th1-Th17 or Th1/17) and CD8+ counterparts (Tc1-Tc17 or Tc1/17). At 8-24 h following AIT launch in VAP, we identify a uniform AIT-elicited pulse of late-transitional/IL-10-producing B cells, IL-6 signaling within Th2 cells and non-inflammatory serum-IL-6 levels. Sequential induction of activation and survival protein markers also immediately occur. A disequilibrium between serum IL-6 and cMono in VAP baseline is restored at day seven following AIT launch. Our longitudinal analysis discovers molecular switches during initiation-phase insect-venom AIT that secure long-term outcomes. Trial number: NCT02931955.

NF-κB: Governing Macrophages in Cancer

Tumor-associated macrophages (TAMs) are the major component of the tumor microenvironment (TME), where they sustain tumor progression and or-tumor immunity. Due to their plasticity, macrophages can exhibit anti- or pro-tumor functions through the expression of different gene sets leading to distinct macrophage phenotypes: M1-like or pro-inflammatory and M2-like or anti-inflammatory. NF-κB transcription factors are central regulators of TAMs in cancers, where they often drive macrophage polarization toward an M2-like phenotype. Therefore, the NF-κB pathway is an attractive therapeutic target for cancer immunotherapy in a wide range of human tumors. Hence, targeting NF-κB pathway in the myeloid compartment is a potential clinical strategy to overcome microenvironment-induced immunosuppression and increase anti-tumor immunity. In this review, we discuss the role of NF-κB as a key driver of macrophage functions in tumors as well as the principal strategies to overcome tumor immunosuppression by targeting the NF-κB pathway.

Activation-induced cell death in CAR-T cell therapy

Engineered T cells expressing chimeric antigen receptors (CARs) with tumor specificity have shown remarkable therapeutic effects on hematologic malignancies. However, CAR-T cells are less effective on solid tumors mainly due to the weak persistence of CAR-T cells, which might be caused by T cell death. Significant activation-induced cell death (AICD) of CAR-T cells was triggered by repeated antigen stimulation. AICD of T cell is characterized by the upregulation of death receptors and low persistence of T cells. Understanding the mechanism of AICD is crucial to improve the anti-tumor effect of CAR-T cells against solid tumors. Many approaches have been applied in CAR-T cell modification to enhance their anti-apoptosis ability. In this review, we summarized the molecular mechanisms of AICD in CAR-T cells and the progresses of anti-AICD in CAR-T cells therapy.

Expression analysis of NF-κB-associated long noncoding RNAs in peripheral blood mononuclear cells from relapsing-remitting multiple sclerosis patients

Long noncoding RNAs (lncRNAs) as potential disease biomarkers might be related to severe course of multiple sclerosis (MS). We evaluated expression levels of NF-κB-associated lncRNAs including HOTAIR, THRIL, H19, NKILA, and ANRIL; as well as expression of IL-6, TNF-α and MMP9, in peripheral blood mononuclear cells (PBMCs) from 60 relapse-remitting MS (RRMS) patients. At relapse phase of RRMS, up-regulation of ANRIL and H19 was positively correlated with the overexpression of IL-6; high levels of THRIL and HOTAIR was positively correlated with increased levels of TNF-α and MMP9, respectively; however, the NKILA expression was negatively correlated with the expression of TNF-α.

Blockade of RANKL/RANK and NF-ĸB signalling pathways as novel therapeutic strategies for allergic asthma: A comparative study in a mouse model of allergic airway inflammation

The main aims of this study were: (1) to investigate whether a blockade of the interaction between the receptor activator of nuclear factor-κB (NF-ĸB) ligand (RANKL) and its receptor RANK may have potential as a novel therapeutic strategy for allergic asthma; (2) to compare the efficacies of the blockade of RANKL/RANK interaction as well as the blockade of NF-κB inhibitor kinase (IKK) and of NF-κB translocation to the nucleus, also in comparison with glucocorticosteroid treatment, in terms of the development of a mouse model of allergic airway inflammation (AAI) and accompanying immune response. The blockade of each of the targets fully prevented the development of AAI. All the tested therapeutic strategies seemed to have a certain advantage over glucocorticosteroids with regard to counteracting the development of AAI. Prevention of the activation and clonal expansion of CD4⁺ effector T (Teff) cells in the mediastinal lymph nodes (MLNs) constitutes a fundamental event underlying the anti-asthmatic effect induced by the blockade of IKK, NF-κB translocation or of RANKL/RANK interaction. The results indicate that attenuation of the CD11b⁺CD103^-CD11c^high dendritic cell response in the MLNs is an initial but not the main mechanism responsible for this effect. In turn, the direct anti-proliferative action on CD4⁺ Teff cells seems to constitute the chief mechanism responsible for the anti-asthmatic effect of all the tested therapeutic strategies. A clinical implication is that local inhibition of RANKL/RANK interaction achieved via inhalatory administration of a RANKL antagonist can be considered as a novel therapeutic strategy in treatment of allergic asthma.

Spirulina maxima extract prevents activation of the NLRP3 inflammasome by inhibiting ERK signaling

The blue-green alga Spirulina maxima is a microscopic filamentous cyanobacterium. Spirulina was recently reported to elicit beneficial effects such as reducing cholesterol and inducing weight loss; however, its effects on inflammation are unknown. To determine the effect of S. maxima extract (SME) on innate immunity, we investigated the NLRP3 inflammasome activation, which is a multiprotein scaffolding complex that plays important roles in innate immune responses to many pathogenic infections in macrophages. SME suppressed lipopolysaccharide (LPS)-induced upregulation of the pro-inflammatory cytokines tumor necrosis factor-α, interleukin (IL)-12, IL-1β, and IL-18 in RAW264.7 cells. In addition, SME attenuated LPS-induced NLRP3 inflammasome activation, and thus pro-IL-1β could not be cleaved to IL-1β by activated caspase-1, which is activated by the NLRP3 inflammasome in RAW264.7 cells. Moreover, SME inhibited LPS-induced phosphorylation of extracellular signal-regulated kinase (ERK) in RAW264.7 cells, and attenuated the generation of ERK1 induced-reactive oxygen species (ROS), resulting in decreased expression of NF-κB. These findings suggest that SME suppresses the effects of the NLRP3 inflammasome via regulation of extracellular signal-regulated kinase (ERK). In summary, we demonstrated that SME prevents activation of the NLRP3 inflammasome by inhibiting ERK signaling.

Uncaria tomentosa (Willd. ex Schult.) DC (Rubiaceae) Sensitizes THP-1 Cells to Radiation-induced Cell Death

Background:

Uncaria tomentosa (Willd. ex Schult.) DC (Rubiaceae), known as Cat's Claw or Uña de gato, is a traditionally used medicinal plant native to Peru. Some studies have shown that U. tomentosa can act as an antiapoptotic agent and enhance DNA repair in chemotherapy-treated cells although others have shown that U. tomentosa enhanced apoptosis.

Objective:

To determine if treatment with U. tomentosa can significantly enhance cell death in THP-1 cells exposed to ionizing radiation.

Materials and Methods:

THP-1 monocyte-like cells were treated with ethanolic extracts of U. tomentosa in the presence or absence of bacterial lipopolysaccharide and then exposed to ionizing radiation. Cell proliferation was assessed by MTT and clonogenic assays and the effects on cell cycle measured by flow cytometry and immunoblotting. Changes in cell signaling were determined by immunoblotting and cytokine ELISA and activation of apoptosis measured by caspase activation and DNA fragmentation analysis.

Results:

Treatment of THP-1 cells with U. tomentosa had a small effect on cell proliferation. However, when the U. tomentosa-pretreated cells were also subjected to 5–9 Gy ionizing radiation, they showed a significant decrease in cell proliferation and increased cellular apoptosis as measured by DNA fragmentation and caspase activation. Treatment with U. tomentosa also decreased the expression of Cyclin E and Cyclin B, key regulators of normal cell cycle progression, and decreased the phosphorylation of various stress-activated, cell survival proteins including p38, ERK, and SAP/JNK kinase.

Conclusions:

These results suggest that U. tomentosa could be useful in enhancing cell death following anticancer therapies including ionizing radiation.

SUMMARY

Treatment of THP-1 cells with Uncaria tomentosa increases their susceptibility to X-rays. The combination of Uncaria tomentosa and X-ray exposure strongly inhibits cell signaling and promotes apoptosis.

Abbreviations Used: LPS: Lipopolysaccharide, TNF: Tumor necrosis factor: IL-1, Interleukin-1: SDS: Sodium dodecylsulphate, TBS: Tris-buffered saline.

IEX-1 deficiency induces browning of white adipose tissue and resists diet-induced obesity

Chronic inflammation plays a crucial role in the pathogenesis of obesity and insulin resistance. However, the primary mediators that affect energy homeostasis remain ill defined. Here, we report an unexpected role for immediate early response gene X-1 (IEX-1), a downstream target of NF-κB, in energy metabolism. We found that IEX-1 expression was highly induced in white adipose tissue (WAT) in both epidydmal and subcutaneous depots but not in interscapular brown adipose tissue (BAT) in mice fed a high fat diet (HFD). Null mutation of IEX-1 protected mice against HFD-induced adipose and hepatic inflammation, hepatic steatosis, and insulin resistance. Unexpectedly, IEX-1 knockout (IEX-1(-/-)) mice gained markedly less weight on HFD for 20 weeks as compared to wild-type (WT) littermates (37 ± 3 versus 48 ± 2 gm) due to increased energy expenditure. Mechanistically, we showed that IEX-1 deficiency induced browning and activated thermogenic genes program in WAT but not in BAT by promoting alternative activation of adipose macrophages. Consequently, IEX-1(-/-) mice exhibited enhanced thermogenesis (24 ± 0.1 versus 22 ± 0.1 kcal/hour/kg in WT mice) explaining increased energy expenditure and lean phenotype in these mice. In conclusion, the present study suggests that IEX-1 is a novel physiological regulator of energy homeostasis via its action in WAT.

Gene expression in the Gitr locus is regulated by NF-κB and Foxp3 through an enhancer

Glucocorticoid-induced TNFR (Gitr) and Ox40, two members of the TNFR superfamily, play important roles in regulating activities of effector and regulatory T cells (Treg). Their gene expression is induced by T cell activation and further upregulated in Foxp3+ Treg. Although the role of Foxp3 as a transcriptional repressor in Treg is well established, the mechanisms underlying Foxp3-mediated transcriptional upregulation remain poorly understood. This transcription factor seems to upregulate expression not only of Gitr and Ox40, but also other genes, including Ctla4, Il35, Cd25, all critical to Treg function. To investigate how Foxp3 achieves such upregulation, we analyzed its activity on Gitr and Ox40 genes located within a 15.1-kb region. We identified an enhancer located downstream of the Gitr gene, and both Gitr and Ox40 promoter activities were shown to be upregulated by the NF-κB-mediated enhancer activity. We also show, using the Gitr promoter, that the enhancer activity was further upregulated in conjunction with Foxp3. Foxp3 appears to stabilize NF-κB p50 binding by anchoring it to the enhancer, thereby enabling local accumulation of transcriptional complexes containing other members of the NF-κB and IκB families. These findings may explain how Foxp3 can activate expression of certain genes while suppressing others.

Nuclear factor-kappaB inducing kinase is required for graft-versus-host disease

BACKGROUND

Donor T lymphocytes are directly responsible for graft-versus-host disease. Molecules important in T-cell function may, therefore, be appropriate targets for graft-versus-host disease therapy and/or prophylaxis. Here we analyzed whether nuclear factor-κ B inducing kinase might have a role in graft-versus-host disease.

DESIGN AND METHODS

We studied the expression of nuclear factor-κ B inducing kinase in human samples from patients with graft-versus-host disease. We also explored the effect of nuclear factor-κ B inducing kinase in a murine model of graft-versus-host disease using donor cells from aly/aly mice (deficient in nuclear factor-κ B inducing kinase) and C57BL/6 mice (control).

RESULTS

We detected expression of nuclear factor-κ B inducing kinase in T-lymphocytes in the pathological lesions of patients with acute graft-versus-host disease. Mice transplanted with aly/aly T lymphocytes did not develop graft-versus-host disease at all, while mice receiving C57BL/6 cells died of a lethal form of the disease. Deficiency of nuclear factor-κ B inducing kinase did not affect the engrafting ability of donor T cells, but severely impaired their expansion capacity early after transplantation, and aly/aly T cells showed a higher proportion of apoptosis than did C57BL/6 T cells. Effector T lymphocytes were the T-cell subset most affected by nuclear factor-κ B inducing kinase deficiency. We also detected lower amounts of inflammatory cytokines in the serum of mice receiving aly/aly T cells than in the serum of mice receiving C57BL/6 T cells.

CONCLUSIONS

Our results show that nuclear factor-κ B inducing kinase has a role in graft-versus-host disease by maintaining the viability of activated alloreactive T lymphocytes.

Role of the immediate early response 3 (IER3) gene in cellular stress response, inflammation and tumorigenesis

The expression of the early response gene immediate early response 3 (IER3), formerly known as IEX-1, is induced by a great variety of stimuli, such as growth factors, cytokines, ionizing radiation, viral infection and other types of cellular stress. Being of a rather unique protein structure not sharing any similarity to other vertebrate proteins, IER3 plays a complex and to some extent contradictory role in cell cycle control and apoptosis. As outlined in this review, these effects of IER3 relate to an interference with certain signalling pathways, in particular NF-κB, MAPK/ERK and PI3K/Akt. In addition to numerous functional data relying on cell culture based studies, transgenic and knock-out mouse models revealed an involvement of IER3 expression in immune functions and in the physiology of the cardiovascular system. Deficiency of IER3 expression in mice results in an aberrant immune regulation and enhanced inflammation, in an alteration of blood pressure control and hypertension or in an impaired genomic stability. A number of patient related studies revealed an involvement of IER3 in tumorigenesis in a cell-type dependent but not yet understood manner. Future studies should establish the potential of IER3 as a new predictive marker and as a molecular target in human diseases such as cancer, inflammatory diseases or hypertension.

ATM-dependent expression of IEX-1 controls nuclear accumulation of Mcl-1 and the DNA damage response

The early-response gene product IEX-1 (also known as IER3) was recently found to interact with the anti-apoptotic Bcl-2 family member, myeloid cell leukemia-1 (Mcl-1). In this study we show that this interaction specifically and timely controls the accumulation of Mcl-1 in the nucleus in response to DNA damage. The IEX-1 protein is rapidly induced by γ-irradiation, genotoxic agents or replication inhibitors, in a way dependent on ataxia telangiectasia mutated (ATM) activity and is necessary for Mcl-1 nuclear translocation. Conversely, IEX-1 protein proteasomal degradation triggers the return of Mcl-1 to the cytosol. IEX-1 and Mcl-1 are integral components of the DNA damage response. Loss of IEX-1 or Mcl-1 leads to genomic instability and increased sensitivity to genotoxic and replicative stresses. The two proteins cooperate to maintain Chk1 activation and G2 checkpoint arrest. Mcl-1 nuclear translocation may foster checkpoint and improve the tumor resistance to DNA damage-based cancer therapies. Deciphering the pathways involved in IEX-1 degradation should lead to the discovery of new therapeutic targets to increase sensitivity of tumor cells to chemotherapy.

A role for the atopy-associated gene PHF11 in T-cell activation and viability

Polymorphisms within plant homeodomain finger protein 11 (PHF11) are associated with total IgE, allergic asthma and eczema. PHF11 is a transcriptional co-activator of the Th1 effector cytokine genes, interleukin-2 (IL2) and interferon-γ (IFNG), co-operating with nuclear factor kappa B (NF-κB). The involvement with NF-κB led us to test whether PHF11 might have a broader function in T-cell activation and viability. We show that PHF11 is abundant in the cytoplasm of T-cells and imported into the nucleus of activated T-cells. Consistent with its presence in the nucleus, PHF11 was recruited to the IFNG promoter and over-expression of PHF11 increased the binding of NF-κB to the IFNG promoter and IFNG gene transcription. Over-expression of PHF11 did not increase IL2 gene transcription, suggesting some specificity in promoter recognition. In contrast, small-interfering RNA knock-down of PHF11 decreased transcription of both IFNG and IL2 and led to decreased CD28 cell-surface expression and reduced NF-κB nuclear import and DNA binding. Knock-down of PHF11 also decreased cell viability and was accompanied by reduced expression of GIMAP4 and 5 genes required for T-cell differentiation, viability and homeostasis. Therefore, in addition to its earlier identified function in regulating Th1 cytokine gene expression, we now show that PHF11 has a broader function in contributing to T-cell activation and viability.

Ablation of gly96/immediate early gene-X1 (gly96/iex-1) aggravates DSS-induced colitis in mice: role for gly96/iex-1 in the regulation of NF-kappaB

BACKGROUND

Inflammatory bowel diseases (IBDs) result from environmental and genetic factors and are characterized by an imbalanced immune response in the gut and deregulated activation of the transcription factor NF-kappaB. Addressing the potential role of gly96/iex-1 in the regulation of NF-kappaB in IBD, we used the dextran sodium sulfate (DSS) colitis model in mice in which the gly96/iex-1 gene had been deleted.

METHODS

C57BL/6 mice of gly96/iex-1(-/-) or gly96/iex-1(+/+) genotype were treated continuously with 4% DSS (5 days) and repeatedly with 2% DSS (28 days) for inducing acute and chronic colitis, respectively. In addition to clinical and histological exploration, colon organ culture and bone marrow-derived cells (BMCs) were analyzed for chemo/cytokine expression and NF-kappaB activation.

RESULTS

Compared to wildtype littermates, gly96/iex-1(-/-) mice exhibited an aggravated phenotype of both acute and chronic colitis, along with a greater loss of body weight and colon length. Colonic endoscopy revealed a higher degree of hyperemia, edema, and bleeding in gly96/iex-1(-/-) mice, and immunohistochemistry detected massive mucosal infiltration of leukocytes and marked histological changes. The expression of proinflammatory chemo- and cytokines was higher in the colon of DSS-treated gly96/iex-1(-/-) mice, and the NF-kappaB activation was enhanced particularly in the distal colon. In cultured BMCs from gly96/iex-1(-/-) mice, Pam(3)Cys(4) treatment induced expression of proinflammatory mediators to a higher degree than in gly96/iex-1(+/+) BMCs, along with greater NF-kappaB activation.

CONCLUSIONS

Based on the observation that genetic ablation of gly96/iex-1 triggers intestinal inflammation in mice, we demonstrate for the first time that gly96/iex-1 exerts strong antiinflammatory activity via its NF-kappaB-counterregulatory effect.

Distinct signaling pathways after higher or lower doses of radiation in three closely related human lymphoblast cell lines

PURPOSE

The tumor suppressor p53 plays an essential role in cellular responses to DNA damage caused by ionizing radiation; therefore, this study aims to further explore the role that p53 plays at different doses of radiation.

MATERIALS AND METHODS

The global cellular responses to higher-dose (10 Gy) and lower dose (iso-survival dose, i.e., the respective D0 levels) radiation were analyzed using microarrays in three human lymphoblast cell lines with different p53 status: TK6 (wild-type p53), NH32 (p53-null), and WTK1 (mutant p53). Total RNAs were extracted from cells harvested at 0, 1, 3, 6, 9, and 24 h after higher and lower dose radiation exposures. Template-based clustering, hierarchical clustering, and principle component analysis were applied to examine the transcriptional profiles.

RESULTS

Differential expression profiles between 10 Gy and iso-survival radiation in cells with different p53 status were observed. Moreover, distinct gene expression patterns were exhibited among these three cells after 10 Gy radiation treatment, but similar transcriptional responses were observed in TK6 and NH32 cells treated with iso-survival radiation.

CONCLUSIONS

After 10 Gy radiation exposure, the p53 signaling pathway played an important role in TK6, whereas the NFkB signaling pathway appeared to replace the role of p53 in WTK1. In contrast, after iso-survival radiation treatment, E2F4 seemed to play a dominant role independent of p53 status. This study dissected the impacts of p53, NFkB and E2F4 in response to higher or lower doses of gamma-irradiation.

Naive CD4 T cells from aged mice show enhanced death upon primary activation

Poor T cell immunity is one of the many defects seen in elderly humans and aged (Ad) mice. We report that naive CD4 T cells from aged mice (ANCD4 cells) showed greater apoptosis upon primary activation than those from young (Yg) mice, with loss of mitochondrial membrane potential, poor activation of Rel family transcription factors and increased DNA damage. Their ability to enhance glycolysis, produce lactate and induce autophagy following activation was also compromised. ANCD4 cells remained susceptible to death beyond first cell division. Activated ANCD4 cells also showed poor transition to a 'central memory' (CM) CD44(high), CD62L(high) phenotype in vitro. This correlated with low proportions of CM cells in Ad mice in vivo. Functionally, too, IFN-gamma responses recalled from T cells of immunized Ad mice, poor to begin with, worsened with time as compared with Yg mice. Thus, ANCD4 cells handle activation-associated stress very poorly due to multiple defects, possibly contributing to poor formation of long-lasting memory.

B cell receptor-mediated sustained c-Rel activation facilitates late transitional B cell survival through control of B cell activating factor receptor and NF-kappaB2

Signaling from the BCR and B cell activating factor receptor (BAFF-R or BR3) differentially regulates apoptosis within early transitional (T1) and late transitional (T2; CD21(int)-T2) B cells during selection processes to generate mature B lymphocytes. However, molecular mechanisms underlying the differential sensitivity of transitional B cells to apoptosis remain unclear. In this study, we demonstrate that BCR signaling induced more long-term c-Rel activation in T2 and mature than in T1 B cells leading to increased expression of anti-apoptotic genes as well as prosurvival BAFF-R and its downstream substrate p100 (NF-kappaB2). Sustained c-Rel activation required de novo c-Rel gene transcription and translation via Btk-dependent mechanisms. Like T1 cells, mature B cells from Btk- and c-Rel-deficient mice also failed to activate these genes. These findings suggest that the gain of survival potential within transitional B cells is dependent on the ability to produce a long-term c-Rel response, which plays a critical role in T2 B cell survival and differentiation in vivo by inducing anti-apoptotic genes, BAFF-R and NF-kappaB2, an essential component for BAFF-R survival signaling. Thus, acquisition of resistance to apoptosis during transitional B cell maturation is achieved by integration of BCR and BAFF-R signals.

MyD88 expression by CNS-resident cells is pivotal for eliciting protective immunity in brain abscesses

MyD88 KO (knockout) mice are exquisitely sensitive to CNS (central nervous system) infection with Staphylococcus aureus, a common aetiological agent of brain abscess, exhibiting global defects in innate immunity and exacerbated tissue damage. However, since brain abscesses are typified by the involvement of both activated CNS-resident and infiltrating immune cells, in our previous studies it has been impossible to determine the relative contribution of MyD88-dependent signalling in the CNS compared with the peripheral immune cell compartments. In the present study we addressed this by examining the course of S. aureus infection in MyD88 bone marrow chimaera mice. Interestingly, chimaeras where MyD88 was present in the CNS, but not bone marrow-derived cells, mounted pro-inflammatory mediator expression profiles and neutrophil recruitment equivalent to or exceeding that detected in WT (wild-type) mice. These results implicate CNS MyD88 as essential in eliciting the initial wave of inflammation during the acute response to parenchymal infection. Microarray analysis of infected MyD88 KO compared with WT mice revealed a preponderance of differentially regulated genes involved in apoptotic pathways, suggesting that the extensive tissue damage characteristic of brain abscesses from MyD88 KO mice could result from dysregulated apoptosis. Collectively, the findings of the present study highlight a novel mechanism for CNS-resident cells in initiating a protective innate immune response in the infected brain and, in the absence of MyD88 in this compartment, immunity is compromised.

Androgen ablation augments prostate cancer vaccine immunogenicity only when applied after immunization

BACKGROUND

Androgen ablation (AA) causes apoptosis of normal and neoplastic prostate cells. It is a standard treatment for advanced prostate cancer. Androgen ablation-mediated immunological effects include bone marrow hyperplasia, thymic regeneration, T and B cell lymphopoeisis and restoration of age-related peripheral T cell dysfunction. Androgens also regulate the transcription of several cytokines. Dendritic cells (DC) are the most potent antigen presenting cells that can activate antigen-specific naïve T cells. Despite myriad clinical trials involving DC-based prostate cancer immunotherapies, the effects of AA on DC function remain largely uncharacterized. Therefore, we investigated the effects of AA on DC and whether it could improve the efficacy of prostate cancer immunotherapy.

METHODS

Cytokine expression changes due to AA were quantified by multiplex ELISA. Flow cytometry was used to assess AA-mediated effects on DC maturation and expression of costimulatory markers. Mixed leukocyte reactions and cell-mediated lysis assays elucidated the role of androgens in DC function. The effect of AA on the efficacy of vaccination against a prostate tumor-associated antigen was tested using Elispot assays.

RESULTS

Androgen ablation increased dendritic cell maturation and costimulatory marker expression, but had no effect on DC costimulatory function. However, DC isolated from castrated mice increased the expression of key cytokines by antigen-experienced T cells while decreasing their expression in naïve cells. Finally, androgen ablation improved immune responses to vaccination only when applied after immunization.

CONCLUSION

Androgen ablation causes differential effects of DC on primary and secondary T cell responses, thus augmenting vaccine immunogenicity only when applied after immunization.

Apigenin, a dietary flavonoid, sensitizes human T cells for activation-induced cell death by inhibiting PKB/Akt and NF-kappaB activation pathway

Resistance of T cells to activation-induced cell death (AICD) is associated with autoimmunity and lymphoproliferation. We found that apigenin (4',5,7-trihydroxyflavone), a non-mutagenic dietary flavonoid, augmented both extrinsic and intrinsic pathways of apoptosis in recurrently activated, but not in primarily stimulated, human blood CD4+ T cells. Apigenin potentiated AICD by inhibiting NF-kappaB activation and suppressing NF-kappaB-regulated anti-apoptotic molecules, cFLIP, Bcl-x(L), Mcl-1, XIAP and IAP, but not Bcl-2. Apigenin suppressed NF-kappaB translocation to nucleus and inhibited IkappaBalpha phosphorylation and degradation in response to TCR stimulation in reactivated peripheral blood CD4 T cells, as well as in leukemic Jurkat T cell lines. Among the pathways that lead to NF-kappaB activation upon TCR stimulation, apigenin selectively inhibited PI3K-PKB/Akt, but not PKC-theta activation in the human T cells, and synergized with a PI3K inhibitor to markedly augment AICD. Apigenin also suppressed expression of anti-apoptotic cyclooxygenase 2 (COX-2) protein in activated human T cells, but it did not affect activation of Erk MAPKinase. Thus, in chronically activated human T cells, relatively non-toxic apigenin can suppress anti-apoptotic pathways involving NF-kappaB activation, and especially cFLIP and COX-2 expression that are important for functioning and maintenance of immune cells in inflammation, autoimmunity and lymphoproliferation.

Role of GADD45 beta in the regulation of synovial fluid T cell apoptosis in rheumatoid arthritis

Rheumatoid arthritis (RA) is characterized by persistent Th1 cell infiltration and production of inflammatory cytokines in the location of joint lesion. It is known that infiltrated Th1 cells in the synovial fluid (SF) of RA patients are resistant to apoptosis. Here we demonstrate that Th1 cells accumulated in patient SF expressed a high level of GADD45 beta (Growth Arrest and DNA Damage-inducible 45 beta) which further inhibited Th1 cell apoptosis. Interestingly, in vitro culture of T cells with SF from RA patients increased GADD45 beta expression in Th1 cells and inhibited their apoptosis. Silencing of GADD45 beta by RNAi abolished the anti-apoptotic effect of RA SF, which was accompanied by down-regulation of Bcl-2 and up-regulation of Bax. Further analysis showed that TNF-alpha and IL-12 in RA SF could stimulate GADD45 beta expression in Th1 cells and inhibit their apoptosis. Taken together, our results suggest a novel mechanism by which specific cytokines in the RA SF elevate GADD45 beta expression in local Th1 cells and subsequently leading to the enhanced T cell survival.

Caspase-cleaved HPK1 induces CD95L-independent activation-induced cell death in T and B lymphocytes

Life and death of peripheral lymphocytes is strictly controlled to maintain physiologic levels of T and B cells. Activation-induced cell death (AICD) is one mechanism to delete superfluous lymphocytes by restimulation of their immunoreceptors and it depends partially on the CD95/CD95L system. Recently, we have shown that hematopoietic progenitor kinase 1 (HPK1) determines T-cell fate. While full-length HPK1 is essential for NF-kappaB activation in T cells, the C-terminal fragment of HPK1, HPK1-C, suppresses NF-kappaB and sensitizes toward AICD by a yet undefined cell death pathway. Here we show that upon IL-2-driven expansion of primary T cells, HPK1 is converted to HPK1-C by a caspase-3 activity below the threshold of apoptosis induction. HPK1-C selectively blocks induction of NF-kappaB-dependent antiapoptotic Bcl-2 family members but not of the proapoptotic Bcl-2 family member Bim. Interestingly, T and B lymphocytes from HPK1-C transgenic mice undergo AICD independently of the CD95/CD95L system but involving caspase-9. Knock down of HPK1/HPK1-C or Bim by small interfering RNA shows that CD95L-dependent and HPK1/HPK1-C-dependent cell death pathways complement each other in AICD of primary T cells. Our results define HPK1-C as a suppressor of antiapoptotic Bcl-2 proteins and provide a molecular basis for our understanding of CD95L-independent AICD of lymphocytes.

Life and death in peripheral T cells

During the course of an immune response, antigen-reactive T cells clonally expand and then are removed by apoptosis to maintain immune homeostasis. Life and death of T cells is determined by multiple factors, such as T-cell receptor triggering, co-stimulation or cytokine signalling, and by molecules, such as caspase-8 (FLICE)-like inhibitory protein (FLIP) and haematopoietic progenitor kinase 1 (HPK1), which regulate the nuclear factor-kappaB (NF-kappaB) pathway. Here, we discuss the concepts of activation-induced cell death (AICD) and activated cell-autonomous death (ACAD) in the regulation of life and death in T cells.

4-1BB Costimulation of Effector T Cells for Adoptive Immunotherapy of Cancer: Involvement of Bcl Gene Family Members

We previously reported that in vitro costimulation of murine MCA 205 tumor-draining lymph node (TDLN) cells through a third signal, 4-1BB (CD137), in addition to CD3 and CD28 engagement significantly increases T-cell yield and amplifies antitumor responses in adoptive therapy. The increased T-cell yield seemed to be related to inhibition of activation-induced cell death. In this study, using real time-polymerase chain reaction and intracellular staining, we tested our hypothesis that antiapoptotic Bcl gene members are modulated in 4-1BB ligated TDLN cells. TDLN cells activated through 4-1BB in conjunction with CD3/CD28 demonstrated elevated Bcl-2 and Bcl-xL gene and protein expression compared with CD3/CD28 activation. Furthermore, Bcl-2 and/or Bcl-xL inhibition abrogated 4-1BB-conferred rescue of activation-induced cell death in TDLN cells, and as a result, 4-1BB-enhanced TDLN cell yield was abolished. Congenic mice were used as donors for TDLN cells labeled with CFSE to evaluate proliferation and persistence of activated cells after intravenous adoptive transfer. The effector function of transferred cells was assessed by determining the incidence of interferon-gamma-producing cells in response to tumor stimulation in serial blood samples drawn from treated mice using intracellular cytokine staining. CD28 and CD28/4-1BB costimulation significantly enhanced in vivo proliferation and survival of the infused cells compared with CD3 activation. 4-1BB coligation augmented the proliferation and effector function of the infused cells compared with both CD3 and CD3/CD28-activated cells. Characterizing the function of signaling molecules involved in T-cell activation pathways may allow optimization of conditions in the generation of effector T cells for cancer immunotherapy.

Control of B lymphocyte apoptosis by the transcription factor NF-kappaB

B cells maintain homeostasis by balancing cell viability and cell death. B lymphocytes are susceptible to mitochondria- and receptor-initiated cell death at various stages of peripheral differentiation and during immune responses. The inducible transcription factor NF-kappaB enhances cell viability by activating genes that counteract both cell-death pathways. This review uses characteristic features of NF-kappaB activation and downregulation to provide insight into the regulation of B cell apoptosis in the periphery. In particular, the temporal patterns of NF-kappaB induction, differences between Rel family members, and the intersection between canonical and noncanonical signaling pathways in keeping B cells alive are discussed.

Current insights into the regulation of programmed cell death by NF-kappaB

The nuclear factor-kappaB (NF-kappaB) transcription factors have emerged as major regulators of programmed cell death (PCD) whether via apoptosis or necrosis. In this context, NF-kappaB's activity has important ramifications for normal tissue development, homoeostasis and the physiological functions of various cell systems including the immune, hepatic, epidermal and nervous systems. However, improper regulation of PCD by NF-kappaB can have severe pathologic consequences, ranging from neurodegeneration to cancer, where its activity often precludes effective therapy. Although NF-kappaB generally protects cells by inducing the expression genes encoding antiapoptotic and antioxidizing proteins, its role in apoptosis and necrosis can vary markedly in different cell contexts, and NF-kappaB can sensitize cells to death-inducing stimuli in some instances. This article describes our current knowledge of the role of NF-kappaB in apoptosis and necrosis, and focuses on the many advances since we last reviewed this rapidly evolving topic in Oncogene 3 years ago. There has been substantial progress in understanding NF-kappaB's mode of action in apoptosis and necrosis and the mechanisms that regulate its anti- vs proapoptotic activities. These recent developments shed new light on the role of NF-kappaB in many disease conditions including tumor development, tumor progression and anticancer treatment.

CD8 T cells require Bcl-3 for maximal gamma interferon production upon secondary exposure to antigen

Adjuvant-induced survival of T cells after antigen activation correlates with increased expression of Bcl-3. Bcl-3 is an NF-kappaB/IkappaB family member and has been implicated in transcriptional regulation in several cell types. We tested the ability of mice deficient in Bcl-3 (Bcl-3 KO) to exhibit T-cell adjuvant-induced survival after challenge with the superantigen staphylococcal enterotoxin B (SEB), using lipopolysaccharide (LPS) as a natural adjuvant. These studies showed that Bcl-3 is required for secondary gamma interferon (IFN-gamma) production by CD8 T cells but not for adjuvant-induced survival effects. Specifically, wild-type and Bcl-3 KO mice exhibited comparable long-term increases in the Vbeta8(+) T-cell populations, indicating no lack of survival in response to adjuvant stimulation in the Bcl-3 KO activated T cells. Ectopic expression of the Bcl-3-related molecules IkappaBalpha, IkappaBbeta, and IkappaBepsilon in SEB-activated T cells increased survival during in vitro culture in the absence of adjuvant, suggesting that these IkappaB molecules could exert a survival function in antigen-activated T cells in place of Bcl-3. However, Vbeta8(+) CD8 T cells from SEB- plus LPS-treated Bcl-3 KO mice produced less IFN-gamma upon in vitro restimulation than Vbeta8(+) CD8 T cells from wild-type mice. Therefore, Bcl-3 plays a unique role in the regulation of IFN-gamma production in this model system.

Immunization with autologous T cells enhances in vivo anti-tumor immune responses accompanied by up-regulation of GADD45β

Immunization with inactivated autoreactive T cells may induce idiotype anti-idiotypic reactions to deplete autoreactive T cells, which are involved in autoimmune diseases. However, it is unknown whether attenuated activated healthy autologous T-cell immunization could increase anti-tumor immune responses. To this end, C57Bl/6 mice were immunized with attenuated activated autologous T cells. The splenocytes from immunized mice showed a higher proliferative ability than that from naive mice. The special phenotype analysis showed that there were more CD8+ T cells and CD62L+ T cells in immunized mice after 24 h of culture with 10% fetal calf serum complete medium in vitro (P<0.01). These results demonstrated that this immunization may activate T cells in vivo. Furthermore, the splenocytes from immunized mice revealed resistance to activation-induced cell death (AICD) in vitro. To further study the relative genes that are responsible for the higher proliferation and resistance to AICD, the expression of Fas/Fas ligand (FasL) and GADD45b was measured by real-time PCR. The results indicated that GADD45beta transcription was higher in the splenocytes from immunized mice than that in the naive mice. In addition, the Fas expression showed a parallel higher, but FasL did not change obviously. To investigate the biologic functions induced by immunization in vivo, a tumor model was established by EL-4 tumor cell inoculation in C57/Bl mice. Mice receiving autologous T-cell immunization had significantly inhibited tumor growth in vivo (P<0.01). This study implicated that immunization with attenuated activated autologous T cells enhances anti-tumor immune responses that participate in tumor growth inhibition.

How T lymphocytes switch between life and death

While insufficient cell death of activated T cells can result in autoimmune disorders, elimination of too many T cells can lead to immunodeficiency. Therefore, T lymphocyte fate is highly regulated and requires that cells can switch from an apoptosis-resistant towards an apoptosis-sensitive state. This switch is tightly controlled by various effector molecules. Basically, two separate pathways control the fate of antigen-activated T cells: activation-induced cell death (AICD) and activated T cell autonomous death (ACAD). Autoreactive T lymphocytes are eliminated by restimulation via their T cell receptor (TCR) and undergo AICD involving death receptors (extrinsic pathway). In contrast, ACAD can lead to T cell deletion without TCR restimulation, and is determined by the ratio between anti- and pro-apoptotic Bcl-2 family members at the mitochondria (intrinsic pathway). While the extrinsic and the intrinsic pathway lead to caspase activation, non-caspase proteases (e.g., cathepsins) can be released by the lysosomes and might contribute to AICD as well as to ACAD. Activated T cells poses cell death escape mechanisms which are needed for survival of (memory) T cells, but are deleterious for autoimmune disorders or progression of T cell lymphomas.

Distinct Domains for Anti- and Pro-apoptotic Activities of IEX-1

IEX-1 (immediate early response gene X-1) is a stress-inducible gene. Its overexpression can suppress or enhance apoptosis dependent on the nature of stress, yet the polypeptide does not possess any of the functional domains that are homologous to those present in well characterized effectors or inhibitors of apoptosis. This study using sequence-targeting mutagenesis reveals a transmembrane-like integrated region of the protein to be critical for both pro-apoptotic and anti-apoptotic functions. Substitution of the key hydrophobic residues with hydrophilic ones within this region impairs the capacity IEX-1 to positively and negatively regulate apoptosis. Mutations at N-linked glycosylation and phosphorylation sites or truncation of the C terminus of IEX-1 also abrogated its potential to promote cell survival. However, distinguished from the transmembrane-like domain, these mutants preserved pro-apoptotic activity of IEX-1 fully. On the contrary, mutation of nuclear localization sequence, despite its importance in apoptosis, did not impede IEX-1-mediated cell survival. Strikingly, all the mutants that lose their anti-apoptotic ability are unable to prevent acute increases in production of intracellular reactive oxygen species (ROS) at the initial onset of apoptosis, whereas those mutants that can sustain anti-death function also control acute ROS production as sufficiently as wild-type IEX-1. These findings suggest a critical role of IEX-1 in regulation of intracellular ROS homeostasis, providing new insight into the mechanism underlying IEX-1-mediated cell survival.