Interleukin-9 Regulates NF-κB Activity Through BCL3 Gene Induction

The emerging role of T helper 9 (Th9) cells in immunopathophysiology: A comprehensive review of their effects and responsiveness in various disease states

Th9 cells, a subset of T-helper cells producing interleukin-9 (IL-9), play a vital role in the adaptive immune response and have diverse effects in different diseases. Regulated by transcription factors like PU.1 and IRF4, and cytokines such as IL-4 and TGF-β, Th9 cells drive tissue inflammation. This review focuses on their emerging role in immunopathophysiology. Th9 cells exhibit immune-mediated cancer cell destruction, showing promise in glioma and cervical cancer treatment. However, their role in breast and lung cancer is intricate, requiring a deeper understanding of pro- and anti-tumor aspects. Th9 cells, along with IL-9, foster T cell and immune cell proliferation, contributing to autoimmune disorders. They are implicated in psoriasis, atopic dermatitis, and infections. In allergic reactions and asthma, Th9 cells fuel pro-inflammatory responses. Targeting Foxo1 may regulate innate and adaptive immune responses, alleviating disease symptoms. This comprehensive review outlines Th9 cells' evolving immunopathophysiological role, emphasizing the necessity for further research to grasp their effects and potential therapeutic applications across diseases.

The interweaved signatures of common-gamma-chain cytokines across immunologic lineages

"γc" cytokines are a family whose receptors share a "common-gamma-chain" signaling moiety, and play central roles in differentiation, homeostasis, and communications of all immunocyte lineages. As a resource to better understand their range and specificity of action, we profiled by RNAseq the immediate-early responses to the main γc cytokines across all immunocyte lineages. The results reveal an unprecedented landscape: broader, with extensive overlap between cytokines (one cytokine doing in one cell what another does elsewhere) and essentially no effects unique to any one cytokine. Responses include a major downregulation component and a broad Myc-controlled resetting of biosynthetic and metabolic pathways. Various mechanisms appear involved: fast transcriptional activation, chromatin remodeling, and mRNA destabilization. Other surprises were uncovered: IL2 effects in mast cells, shifts between follicular and marginal zone B cells, paradoxical and cell-specific cross-talk between interferon and γc signatures, or an NKT-like program induced by IL21 in CD8+ T cells.

The World according to IL-9

Among the cytokines regulating immune cells, IL-9 has gained considerable attention for its ability to act on multiple cell types as a regulator of beneficial and pathologic immune responses. Yet, it is still not clearly defined how IL-9 impacts immune responses. IL-9 demonstrates a remarkable degree of tissue-specific functionality and has cellular sources that vary by tissue site and the context of the inflammatory milieu. Here, we provide perspective to summarize the biological activities of IL-9 and highlight cell type-specific roles in the immune pathogenesis of diseases. This perspective will be important in defining the diseases where targeting IL-9 as a therapeutic strategy would be beneficial and where it has the potential to complicate clinical outcomes.

Elevated GRO-α and IL-18 in serum and brain implicate the NLRP3 inflammasome in frontotemporal dementia

Neuroinflammation is a hallmark of frontotemporal dementia (FTD), a heterogeneous group of proteinopathies characterized by the progressive degeneration of the frontal and temporal lobes. It is marked by microglial activation and subsequent cytokine release. Although cytokine levels in FTD brain and CSF have been examined, the number of cytokines measured in each study is limited and knowledge on cytokine concentrations in FTD serum is scarce. Here, we assessed 48 cytokines in FTD serum and brain. The aim was to determine common cytokine dysregulation pathways in serum and brain in FTD. Blood samples and brain tissue samples from the superior frontal cortex (SFC) were collected from individuals diagnosed with behavioral variant FTD (bvFTD) and healthy controls, and 48 cytokines were measured using a multiplex immunological assay. The data were evaluated by principal component factor analysis to determine the contribution from different components of the variance in the cohort. Levels of a number of cytokines were altered in serum and SFC in bvFTD compared to controls, with increases in GRO-α and IL-18 in both serum and SFC. These changes could be associated with NLRP3 inflammasome activation or the NFκB pathway, which activates NLRP3. The results suggest the possible importance of the NLRP3 inflammasome in FTD. An improved understanding of the role of inflammasomes in FTD could provide valuable insights into the pathogenesis, diagnosis and treatment of FTD.

In silico analysis of expression data during the early priming stage of liver regeneration after partial hepatectomy in rat

The priming stage is the first step of liver regeneration (LR). This stage is characterized by the transition from G0 to cell cycle for 4 hours in rat. In this study, individual gene level and gene set level (GSEA) was performed to identify the candidate genes and significantly changed biological processes at 2 h after partial hepatectomy (PH). The leading edge analysis is performed to identify the key genes and iRegulon was employed for transcription factor (TF) analysis. A total of 53 differentially expressed genes were identified using RMA package based on R language at 2 h after PH, including the transcription factor, enzyme and cytokine. As the most important genes in our analysis, Socs3 was selected with a special analysis so as to find the pathways correlate to the expression of it. The changed significantly pathways in LR involved response to stress, ATP metabolism, and regulation of cell cycle mainly. Several transcription factors were identified including Stat5a, Cnot3 and zfp384. Taken together, at the early priming stage of LR in rat, the liver is experiencing some changes including response to stress, activated ATP metabolism and inhibition of cell cycle. Our analysis provided a detailed and comprehensive map for further research of the early priming stage of LR in rat.

Bcl-3 induced by IL-22 via STAT3 activation acts as a potentiator of psoriasis-related gene expression in epidermal keratinocytes

IL-22 induces STAT3 phosphorylation and mediates psoriasis-related gene expression. However, the signaling mechanism leading from pSTAT3 to the expression of these genes remains unclear. We focused on Bcl-3, which is induced by STAT3 activation and mediates gene expression. In cultured human epidermal keratinocytes, IL-22 increased Bcl-3, which was translocated to the nucleus with p50 via STAT3 activation. The increases in CXCL8, S100As and human β-defensin 2 mRNA expression caused by IL-22 were abolished by siRNA against Bcl-3. Although CCL20 expression was also augmented by IL-22, the knockdown of Bcl-3 increased its level. Moreover, the combination of IL-22 and IL-17A enhanced Bcl-3 production, IL-22-induced gene expression, and the expression of other psoriasis-related genes, including those encoding IL-17C, IL-19, and IL-36γ. The expression of these genes (except for CCL20) was also suppressed by the knockdown of Bcl-3. Bcl-3 overexpression induced CXCL8 and HBD2 expression but not S100As expression. We also compared Bcl-3 expression between psoriatic skin lesions and normal skin. Immunostaining revealed strong signals for Bcl-3 and p50 in the nucleus of epidermal keratinocytes from psoriatic skin. The IL-22-STAT3-Bcl-3 pathway may be important in the pathogenesis of psoriasis.

Transcriptome profile of rat genes in injured spinal cord at different stages by RNA-sequencing

Background

Spinal cord injury (SCI) results in fatal damage and currently has no effective treatment. The pathological mechanisms of SCI remain unclear. In this study, genome-wide transcriptional profiling of spinal cord samples from injured rats at different time points after SCI was performed by RNA-Sequencing (RNA-Seq). The transcriptomes were systematically characterized to identify the critical genes and pathways that are involved in SCI pathology.

Results

RNA-Seq results were obtained from total RNA harvested from the spinal cords of sham control rats and rats in the acute, subacute, and chronic phases of SCI (1 day, 6 days and 28 days after injury, respectively; n = 3 in every group). Compared with the sham-control group, the number of differentially expressed genes was 1797 in the acute phase (1223 upregulated and 574 downregulated), 6590 in the subacute phase (3460 upregulated and 3130 downregulated), and 3499 in the chronic phase (1866 upregulated and 1633 downregulated), with an adjusted P-value <0.05 by DESeq. Gene ontology (GO) enrichment analysis showed that differentially expressed genes were most enriched in immune response, MHC protein complex, antigen processing and presentation, translation-related genes, structural constituent of ribosome, ion gated channel activity, small GTPase mediated signal transduction and cytokine and/or chemokine activity. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the most enriched pathways included ribosome, antigen processing and presentation, retrograde endocannabinoid signaling, axon guidance, dopaminergic synapses, glutamatergic synapses, GABAergic synapses, TNF, HIF-1, Toll-like receptor, NF-kappa B, NOD-like receptor, cAMP, calcium, oxytocin, Rap1, B cell receptor and chemokine signaling pathway.

Conclusions

This study has not only characterized changes in global gene expression through various stages of SCI progression in rats, but has also systematically identified the critical genes and signaling pathways in SCI pathology. These results will expand our understanding of the complex molecular mechanisms involved in SCI and provide a foundation for future studies of spinal cord tissue damage and repair.

The sequence data from this study have been deposited into Sequence Read Archive (http://www.ncbi.nlm.nih.gov/sra; accession number PRJNA318311).

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3532-x) contains supplementary material, which is available to authorized users.

IL-9 Signaling Pathway: An Update

Since the discovery of IL-9 almost three decades back as a growth factor, we have come a long way to understand its pleiotropic functions in the immune system. Despite its many functions, IL-9 still remains as an understudied cytokine. In the last decade, renewed emphasis has been provided to understand the biology of IL-9. Any growth factor or cytokine signals via its cognate receptor to mediate biological functions. In this chapter, we discuss the IL-9 signal transduction in different cell types, which would then exert its distinct functions.

Regulation of inflammatory responses by neuregulin-1 in brain ischemia and microglial cells in vitro involves the NF-kappa B pathway

Background

We previously demonstrated that neuregulin-1 (NRG-1) was neuroprotective in rats following ischemic stroke. Neuroprotection by NRG-1 was associated with the suppression of pro-inflammatory gene expression in brain tissues. Over-activation of brain microglia can induce pro-inflammatory gene expression by activation of transcriptional regulators following stroke. Here, we examined how NRG-1 transcriptionally regulates inflammatory gene expression by computational bioinformatics and in vitro using microglial cells.

Methods

To identify transcriptional regulators involved in ischemia-induced inflammatory gene expression, rats were sacrificed 24 h after middle cerebral artery occlusion (MCAO) and NRG-1 treatment. Gene expression profiles of brain tissues following ischemia and NRG-1 treatment were examined by microarray technology. The Conserved Transcription Factor-Binding Site Finder (CONFAC) bioinformatics software package was used to predict transcription factors associated with inflammatory genes induced following stroke and suppressed by NRG-1 treatment. NF-kappa B (NF-kB) was identified as a potential transcriptional regulator of NRG-1-suppressed genes following ischemia. The involvement of specific NF-kB subunits in NRG-1-mediated inflammatory responses was examined using N9 microglial cells pre-treated with NRG-1 (100 ng/ml) followed by lipopolysaccharide (LPS; 10 μg/ml) stimulation. The effects of NRG-1 on cytokine production were investigated using Luminex technology. The levels of the p65, p52, and RelB subunits of NF-kB and IkB-α were determined by western blot analysis and ELISA. Phosphorylation of IkB-α was investigated by ELISA.

Results

CONFAC identified 12 statistically over-represented transcription factor-binding sites (TFBS) in our dataset, including NF-kBP65. Using N9 microglial cells, we observed that NRG-1 significantly inhibited LPS-induced TNFα and IL-6 release. LPS increased the phosphorylation and degradation of IkB-α which was blocked by NRG-1. NRG-1 also prevented the nuclear translocation of the NF-kB p65 subunit following LPS administration. However, NRG-1 increased production of the neuroprotective cytokine granulocyte colony-stimulating factor (G-CSF) and the nuclear translocation of the NF-kB p52 subunit, which is associated with the induction of anti-apoptotic and suppression of pro-inflammatory gene expression.

Conclusions

Neuroprotective and anti-inflammatory effects of NRG-1 are associated with the differential regulation of NF-kB signaling pathways in microglia. Taken together, these findings suggest that NRG-1 may be a potential therapeutic treatment for treating stroke and other neuroinflammatory disorders.

Dimethyl fumarate restores apoptosis sensitivity and inhibits tumor growth and metastasis in CTCL by targeting NF-κB

Despite intensive efforts in recent years, a curative therapy for cutaneous T-cell lymphoma (CTCL) has not yet been developed. Therefore, the establishment of new therapeutic approaches with higher efficacy rates and milder side effects is strongly desired. A characteristic feature of the malignant T-cell population in CTCL is resistance toward cell death resulting from constitutive NF-κB activation. Therefore, NF-κB-dependent cell death resistance represents an interesting therapeutic target in CTCL because an NF-κB-directed therapy would leave bystander T cells widely unaffected. We investigated the effects of dimethyl fumarate (DMF) on CTCL cells in vitro and in vivo. DMF induced cell death in primary patient-derived CD4(+) cells and CTCL cell lines, but hardly in T cells from healthy donors. DMF-induced cell death was linked specifically to NF-κB inhibition. To study the impact of DMF in vivo, we developed 2 CTCL xenograft mouse models with different cutaneous localizations of the T-cell infiltrate. DMF treatment delayed the growth of CTCL tumors and prevented formation of distant metastases. In addition, DMF induced increased cell death in primary CTCL tumors and in liver metastases. In summary, DMF treatment represents a remarkable therapeutic option in CTCL because it restores CTCL apoptosis in vitro and in preclinical models in vivo and prevents spreading of the disease to distant sites. DMF treatment is of particular promise in CTCL because DMF is already in successful clinical use in the treatment of psoriasis and multiple sclerosis allowing fast translation into clinical studies in CTCL.

Regulation of the Adaptive Immune Response by the IκB Family Protein Bcl-3

Bcl-3 is a member of the IκB family of proteins and an important regulator of Nuclear Factor (NF)-κB activity. The ability of Bcl-3 to bind and regulate specific NF-κB dimers has been studied in great depth, but its physiological roles in vivo are still not fully understood. It is, however, becoming clear that Bcl-3 is essential for the proper development, survival and activity of adaptive immune cells. Bcl-3 dysregulation can be observed in a number of autoimmune pathologies, and Bcl3-deficient animals are more susceptible to bacterial and parasitic infection. This review will describe our current understanding of the roles played by Bcl-3 in the development and regulation of the adaptive immune response, including lymphoid organogenesis, immune tolerance, lymphocyte function and dendritic cell biology.

xHeinz: an algorithm for mining cross-species network modules under a flexible conservation model

MOTIVATION

Integrative network analysis methods provide robust interpretations of differential high-throughput molecular profile measurements. They are often used in a biomedical context-to generate novel hypotheses about the underlying cellular processes or to derive biomarkers for classification and subtyping. The underlying molecular profiles are frequently measured and validated on animal or cellular models. Therefore the results are not immediately transferable to human. In particular, this is also the case in a study of the recently discovered interleukin-17 producing helper T cells (Th17), which are fundamental for anti-microbial immunity but also known to contribute to autoimmune diseases.

RESULTS

We propose a mathematical model for finding active subnetwork modules that are conserved between two species. These are sets of genes, one for each species, which (i) induce a connected subnetwork in a species-specific interaction network, (ii) show overall differential behavior and (iii) contain a large number of orthologous genes. We propose a flexible notion of conservation, which turns out to be crucial for the quality of the resulting modules in terms of biological interpretability. We propose an algorithm that finds provably optimal or near-optimal conserved active modules in our model. We apply our algorithm to understand the mechanisms underlying Th17 T cell differentiation in both mouse and human. As a main biological result, we find that the key regulation of Th17 differentiation is conserved between human and mouse.

AVAILABILITY AND IMPLEMENTATION

xHeinz, an implementation of our algorithm, as well as all input data and results, are available at http://software.cwi.nl/xheinz and as a Galaxy service at http://services.cbib.u-bordeaux2.fr/galaxy in CBiB Tools.

CONTACT

gunnar.klau@cwi.nl

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

IL-9-mediated survival of type 2 innate lymphoid cells promotes damage control in helminth-induced lung inflammation

IL-9 acts as an autocrine amplifier of type 2 innate lymphoid cell function to promote tissue repair in the recovery phase of helminth-induced lung infection.

IL-9 fate reporter mice established type 2 innate lymphoid cells (ILC2s) as major producers of this cytokine in vivo. Here we focus on the role of IL-9 and ILC2s during the lung stage of infection with Nippostrongylus brasiliensis, which results in substantial tissue damage. IL-9 receptor (IL-9R)–deficient mice displayed reduced numbers of ILC2s in the lung after infection, resulting in impaired IL-5, IL-13, and amphiregulin levels, despite undiminished numbers of Th2 cells. As a consequence, the restoration of tissue integrity and lung function was strongly impaired in the absence of IL-9 signaling. ILC2s, in contrast to Th2 cells, expressed high levels of the IL-9R, and IL-9 signaling was crucial for the survival of activated ILC2s in vitro. Furthermore, ILC2s in the lungs of infected mice required the IL-9R to up-regulate the antiapoptotic protein BCL-3 in vivo. This highlights a unique role for IL-9 as an autocrine amplifier of ILC2 function, promoting tissue repair in the recovery phase after helminth-induced lung inflammation.

The tumor promoter and NF-κB modulator Bcl-3 regulates splenic B cell development

Bcl-3 is an atypical member of the family of IκB proteins. Unlike the classic members, Bcl-3 functions as a nuclear transcriptional cofactor that may, depending on context, promote or suppress genes via association with p50/NF-κB1 or p52/NF-κB2 homodimers. Bcl-3 is also an oncogene, because it is a partner in recurrent translocations in B cell tumors, resulting in deregulated expression. Bcl-3 functions, however, remain poorly understood. We have investigated the role of Bcl-3 in B cells and discovered a previously unknown involvement in the splenic development of these cells. Loss of Bcl-3 in B cells resulted in significantly more marginal zone (MZ) and fewer follicular (FO) B cells. Conversely, transgenic expression of Bcl-3 in B cells generated fewer MZ and more FO B cells. Both Bcl-3(-/-) FO and MZ B cells were more responsive to LPS stimulation compared with their wild-type counterparts, including increased proliferation. By contrast, Bcl-3(-/-) FO B cells were more prone to apoptosis upon BCR stimulation, also limiting their expansion. The data reveal Bcl-3 as a regulator of B cell fate determination, restricting the MZ path and favoring the FO pathway, at least in part, via increased signal-specific survival of the latter, a finding of relevance to its tumorigenic activity.

Atypical IκB proteins - nuclear modulators of NF-κB signaling

Nuclear factor κB (NF-κB) controls a multitude of physiological processes such as cell differentiation, cytokine expression, survival and proliferation. Since NF-κB governs embryogenesis, tissue homeostasis and the functions of innate and adaptive immune cells it represents one of the most important and versatile signaling networks known. Its activity is regulated via the inhibitors of NF-κB signaling, the IκB proteins. Classical IκBs, like the prototypical protein IκBα, sequester NF-κB transcription factors in the cytoplasm by masking of their nuclear localization signals (NLS). Thus, binding of NF-κB to the DNA is inhibited. The accessibility of the NLS is controlled via the degradation of IκBα. Phosphorylation of the conserved serine residues 32 and 36 leads to polyubiquitination and subsequent proteasomal degradation. This process marks the central event of canonical NF-κB activation. Once their NLS is accessible, NF-κB transcription factors translocate into the nucleus, bind to the DNA and regulate the transcription of their respective target genes. Several studies described a distinct group of atypical IκB proteins, referred to as the BCL-3 subfamily. Those atypical IκBs show entirely different sub-cellular localizations, activation kinetics and an unexpected functional diversity. First of all, their interaction with NF-κB transcription factors takes place in the nucleus in contrast to classical IκBs, whose binding to NF-κB predominantly occurs in the cytoplasm. Secondly, atypical IκBs are strongly induced after NF-κB activation, for example by LPS and IL-1β stimulation or triggering of B cell and T cell antigen receptors, but are not degraded in the first place like their conventional relatives. Finally, the interaction of atypical IκBs with DNA-associated NF-κB transcription factors can further enhance or diminish their transcriptional activity. Thus, they do not exclusively act as inhibitors of NF-κB activity. The capacity to modulate NF-κB transcription either positively or negatively, represents their most important and unique mechanistic difference to classical IκBs. Several reports revealed the importance of atypical IκB proteins for immune homeostasis and the severe consequences following their loss of function. This review summarizes insights into the physiological processes regulated by this protein class and the relevance of atypical IκB functioning.

Anti-cytokine auto-vaccinations as tools for the analysis of cytokine function in vivo

Braking B cell tolerance to generate antibodies against autologous cytokines or chemokines offers an alternative to gene inactivation for functional analysis of these factors in vivo. It is clearly less potent than the genetic approach but offers the advantage of extreme flexibility. The basic principle is to enable a self-reactive B cell to attract T cell help by presenting foreign peptides, a process we called "deceptive" antigen presentation. We here review the different auto-vaccine procedures that are currently used and provide several examples of functional information acquired by this procedure or by mAbs derived from auto-vaccinated mice.

ALL-associated JAK1 mutations confer hypersensitivity to the antiproliferative effect of type I interferon

Activating mutations in JAK1 have been reported in acute lymphoblastic leukemias (ALLs). In this study, we found a type I interferon (IFN) transcriptional signature in JAK1 mutation-positive human ALL samples. This signature was recapitulated in vitro by the expression of JAK1 mutants in BW5147 and BaF3 hematopoietic cell lines. Binding of JAK1 to the IFN receptor was essential because mutations in the FERM domain abrogated this effect. Beside the constitutive activation of the type I IFN signaling cascade, JAK1 mutations also strongly potentiated the response to IFN in vitro. Typically, the proliferation of cell lines expressing JAK1(A634D) was abrogated by type I IFNs. Interestingly, we found that different JAK1 mutations differentially potentiate responses to type I IFNs or to interleukin-9, another cytokine using JAK1 to mediate its effects. This suggests that the type of mutation influences the specificity of the effect on distinct cytokine receptor signaling. Finally, we also showed in an in vivo leukemia model that cells expressing JAK1(A634D) are hypersensitive to the antiproliferative and antitumorigenic effect of type I IFN, suggesting that type I IFNs should be considered as a potential therapy for ALL with JAK1-activating mutations.

Multifunctional host defense peptides: antimicrobial peptides, the small yet big players in innate and adaptive immunity

The term 'antimicrobial peptides' refers to a large number of peptides first characterized on the basis of their antibiotic and antifungal activities. In addition to their role as endogenous antibiotics, antimicrobial peptides, also called host defense peptides, participate in multiple aspects of immunity (inflammation, wound repair, and regulation of the adaptive immune system) as well as in maintaining homeostasis. The possibility of utilizing these multifunctional molecules to effectively combat the ever-growing group of antibiotic-resistant pathogens has intensified research aimed at improving their antibiotic activity and therapeutic potential, without the burden of an exacerbated inflammatory response, but conserving their immunomodulatory potential. In this minireview, we focus on the contribution of small cationic antimicrobial peptides - particularly human cathelicidins and defensins - to the immune response and disease, highlighting recent advances in our understanding of the roles of these multifunctional molecules.

The caspase-cleaved form of LYN mediates a psoriasis-like inflammatory syndrome in mice

We showed previously that Lyn is a substrate for caspases, a family of cysteine proteases, involved in the regulation of apoptosis and inflammation. Here, we report that expression of the caspase-cleaved form of Lyn (LynDeltaN), in mice, mediates a chronic inflammatory syndrome resembling human psoriasis. Genetic ablation of TNF receptor 1 in a LynDeltaN background rescues a normal phenotype, indicating that LynDeltaN mice phenotype is TNF-alpha-dependent. The predominant role of T cells in the disease occurring in LynDeltaN mice was highlighted by the distinct improvement of LynDeltaN mice phenotype in a Rag1-deficient background. Using pan-genomic profiling, we also established that LynDeltaN mice show an increased expression of STAT-3 and inhibitory members of the NFkappaB pathway. Accordingly, LynDeltaN alters NFkappaB activity underlying a link between inhibition of NFkappaB and LynDeltaN mice phenotype. Finally, analysis of Lyn expression in human skin biopsies of psoriatic patients led to the detection of Lyn cleavage product whose expression correlates with the activation of caspase 1. Our data identify a new role for Lyn as a regulator of psoriasis through its cleavage by caspases.

Bcl-3 acts as an innate immune modulator by controlling antimicrobial responses in keratinocytes

Innate immune responses involve the production of antimicrobial peptides (AMPs), chemokines, and cytokines. We report here the identification of B-cell leukemia (Bcl)-3 as a modulator of innate immune signaling in keratinocytes. In this study, it is shown that Bcl-3 is inducible by the Th2 cytokines IL-4 and IL-13 and is overexpressed in lesional skin of atopic dermatitis (AD) patients. Bcl-3 was shown to be important to cutaneous innate immune responses as silencing of Bcl-3 by small-interfering RNA (siRNA) reversed the downregulatory effect of IL-4 on the HBD3 expression. Bcl-3 silencing enhanced vitamin D3 (1,25D3)-induced gene expression of cathelicidin AMP in keratinocytes, suggesting a negative regulatory function on cathelicidin transcription. Furthermore, 1,25D3 suppressed Bcl-3 expression in vitro and in vivo. This study identified Bcl-3 as an important modulator of cutaneous innate immune responses and its possible therapeutic role in AD.

Bcl-3, a multifaceted modulator of NF-kappaB-mediated gene transcription

The transcription factor, NF-kappaB (nuclear factor-kappaB) and associated regulatory factors make up a multi-component signaling pathway that regulates a wide range of biological processes, including cell survival, proliferation, differentiation, stress response, and death, as well as immunity and inflammation. Aberrant NF-kappaB pathway activity is known to be associated with a host of diseases, including immune deficiencies, inflammatory disorders, and cancer. Recent advances in our understanding of the inner workings of the NF-kappaB pathway have led to the development of new therapeutic strategies for the treatment of these diseases. In this review, we focus on the regulation of the NF-kappaB pathway by Bcl-3 (B cell leukemia-3), a nuclear member of the IkappaB (inhibitor of NF-kappaB) family. Both the regulation and the function of Bcl-3 will be discussed.

IL-6 regulates neutrophil trafficking during acute inflammation via STAT3

The successful resolution of inflammation is dependent upon the coordinated transition from the initial recruitment of neutrophils to a more sustained population of mononuclear cells. IL-6, which signals via the common receptor subunit gp130, represents a crucial checkpoint regulator of neutrophil trafficking during the inflammatory response by orchestrating chemokine production and leukocyte apoptosis. However, the relative contribution of specific IL-6-dependent signaling pathways to these processes remains unresolved. To define the receptor-mediated signaling events responsible for IL-6-driven neutrophil trafficking, we used a series of gp130 knockin mutant mice displaying altered IL-6-signaling capacities in an experimental model of acute peritoneal inflammation. Hyperactivation of STAT1 and STAT3 in gp130(Y757F/Y757F) mice led to a more rapid clearance of neutrophils, and this coincided with a pronounced down-modulation in production of the neutrophil-attracting chemokine CXCL1/KC. By contrast, the proportion of apoptotic neutrophils in the inflammatory infiltrate remained unaffected. In gp130(Y757F/Y757F) mice lacking IL-6, neutrophil trafficking and CXCL1/KC levels were normal, and this corresponded with a reduction in the level of STAT1/3 activity. Furthermore, monoallelic ablation of Stat3 in gp130(Y757F/Y757F) mice specifically reduced STAT3 activity and corrected both the rapid clearance of neutrophils and impaired CXCL1/KC production. Conversely, genetic deletion of Stat1 in gp130(Y757F/Y757F) mice failed to rescue the altered responses observed in gp130(Y757F/Y757F) mice. Collectively, these data genetically define that IL-6-driven signaling via STAT3, but not STAT1, limits the inflammatory recruitment of neutrophils, and therefore represents a critical event for the termination of the innate immune response.

IL-9/IL-9 receptor signaling selectively protects cortical neurons against developmental apoptosis

In mammals, programmed cell death (PCD) is a central event during brain development. Trophic factors have been shown to prevent PCD in postmitotic neurons. Similarly, cytokines have neurotrophic effects involving regulation of neuronal survival. Nevertheless, neuronal PCD is only partially understood and host determinants are incompletely defined. The present study provides evidence that the cytokine interleukin-9 (IL-9) and its receptor specifically control PCD of neurons in the murine newborn neocortex. IL-9 antiapoptotic action appeared to be time-restricted to early postnatal stages as both ligand and receptor transcripts were mostly expressed in neocortex between postnatal days 0 and 10. This period corresponds to the physiological peak of apoptosis for postmitotic neurons in mouse neocortex. In vivo studies showed that IL-9/IL-9 receptor pathway inhibits apoptosis in the newborn neocortex. Furthermore, in vitro studies demonstrated that IL-9 and its receptor are mainly expressed in neurons. IL-9 effects were mediated by the activation of the JAK/STAT (janus kinase/signal transducer and activator of transcription) pathway, whereas nuclear factor-kappaB (NF-kappaB) or Erk pathways were not involved in mediating IL-9-induced inhibition of cell death. Finally, IL-9 reduced the expression of the mitochondrial pro-apoptotic factor Bax whereas Bcl-2 level was not significantly affected. Together, these data suggest that IL-9/IL-9 receptor signaling pathway represents a novel endogenous antiapoptotic mechanism for cortical neurons by controlling JAK/STAT and Bax levels.

The latent membrane protein 1 (LMP1) encoded by Epstein-Barr virus induces expression of the putative oncogene Bcl-3 through activation of the nuclear factor-kappaB

The Epstein-Barr virus (EBV)-encoded oncoprotein latent membrane protein 1 (LMP1) has an essential role in B-lymphocyte transformation by the virus and is expressed in certain EBV-associated tumors and lymphoproliferative disorders. By using the Flp-In/TREx-inducible expression system, we introduced LMP1 into two human cell lines, Jurkat and HEK-293, and found that in both of them the putative cellular oncogene Bcl-3 is rapidly induced following the expression of LMP1. Bcl-3 was also induced in Ramos cells after in vitro EBV infection and after transfection with an LMP1 expression vector. This LMP1-induced Bcl-3 expression is considered to be mediated by the transcription factor NF-kappaB, because (1) deletion of a critical NF-kappaB-binding site in the Bcl-3 promoter abolished its responsiveness to LMP1, (2) an IkappaB mutant that specifically inhibits NF-kappaB activity suppressed the LMP1-induced activation of the Bcl-3 promoter, and (3) an LMP1 mutant lacking its effector domain CTAR2, required for the activation of NF-kappaB, is severely impaired in its ability to induce Bcl-3. Western blot analyses showed that all EBV-infected and LMP1-expressing lymphoid cell lines express Bcl-3. These results suggest the possibility that Bcl-3 is involved in the pathogenesis of certain EBV-associated malignancies and lymphoproliferative disorders.

Thymoquinone attenuates proinflammatory responses in lipopolysaccharide-activated mast cells by modulating NF-kappaB nuclear transactivation

Activated mast cells play an important role in the development and maintenance of chronic inflammation by releasing proinflammatory cytokines such as Tumor necrosis factor alpha (TNFalpha). TNFalpha is a key mediator of immune and inflammatory responses as it controls the expression of inflammatory genes network and its overproduction contributes significantly to the pathological complications observed in many inflammatory diseases. We have previously shown that thymoquinone (TQ), which has broad anti-inflammatory activities, attenuates allergic inflammation in mice. In the present study, we investigated the effect of TQ on LPS-induced TNFalpha production in the rat basophil cell line, RBL-2H3. Stimulation of RBL-2H3 cells with LPS markedly increased TNFalpha production. TQ treatment significantly inhibited LPS-induced TNFalpha mRNA expression and protein production. To understand the mechanism by which TQ inhibited TNFalpha production, we examined its effects on activation of NF-kappaB transcription factor, which has been shown to be involved in regulating TNFalpha responses. LPS activated the NF-kappaB pathway, resulting in accumulation of NF-kappaB p65 and p50 subunits in the nucleus and activation of TNFalpha promoter. TQ administration to LPS-stimulated cells did not noticeably alter NF-kappaB cytosolic activation or nuclear expression as demonstrated by western blot analysis. Instead, TQ significantly increased the amount of the repressive NF-kappaB p50 homodimer, and simultaneously decreased the amount of transactivating NF-kappaB p65:p50 heterodimer, bound to the TNFalpha promoter as revealed by electrophoretic mobility shift and chromatin immunoprecipitation assays. Transient transfection of RBL-2H3 cells with TNFalpha promoter-driven luciferase gene constructs demonstrated that one of the three NF-kappaB binding sites in the TNFalpha promoter, the kappaB3 site, played a major role in the induction of TNFalpha promoter-driven luciferase gene expression by LPS, as well as in mediating the inhibitory effects of TQ on TNFalpha production, as TQ had minimal effect on the TNFalpha promoter-luciferase construct that lacks the kappaB3 site. Together, these results suggest that TQ attenuates the proinflammatory response in LPS-stimulated mast cells by modulating nuclear transactivation of NF-kappaB and TNFalpha production.

BCL3 is induced by IL-6 via Stat3 binding to intronic enhancer HS4 and represses its own transcription

BCL3 is a proto-oncogene affected by chromosomal translocations in some patients with chronic lymphocytic leukemia. It is an IkappaB family protein that is involved in transcriptional regulation of a number of NF-kappaB target genes. In this study, interleukin (IL)-6-induced BCL3 expression and its effect on survival of multiple myeloma (MM) cells were examined. We demonstrate the upregulation of BCL3 by IL-6 in INA-6 and other MM cell lines. Sequence analysis of the BCL3 gene locus revealed four potential signal transducer and activator of transcription (Stat) binding sites within two conserved intronic enhancers regions: one located within enhancer HS3 and three within HS4. Chromatin immunoprecipitation experiments showed increased Stat3 binding to both enhancers upon IL-6 stimulation. Silencing Stat3 expression by small interfering RNA (siRNA) abrogated BCL3 expression by IL-6. Using reporter gene assays, we demonstrate that BCL3 transcription depends on HS4. Mutation of the Stat motifs within HS4 abolished IL-6-dependent BCL3 induction. Furthermore, BCL3 transcription was inhibited by its own gene product. This repressive feedback is mediated by NF-kappaB sites within the promoter and HS3. Finally, we show that overexpression of BCL3 increases apoptosis, whereas BCL3-specific siRNA does not affect the viability of INA-6 cells suggesting that BCL3 is not essential for the survival of these cells.

Respiratory syncytial virus-inducible BCL-3 expression antagonizes the STAT/IRF and NF-kappaB signaling pathways by inducing histone deacetylase 1 recruitment to the interleukin-8 promoter

Respiratory syncytial virus (RSV) is a paramyxovirus that produces airway inflammation, in part by inducing interleukin-8 (IL-8) expression, a CXC-type chemokine, via the NF-kappaB/RelA and STAT/IRF signaling pathways. In RSV-infected A549 cells, IL-8 transcription attenuates after 24 h in spite of ongoing viral replication and persistence of nuclear RelA, suggesting a mechanism for transcriptional attenuation. RSV infection induces B-cell lymphoma protein -3 (Bcl-3) expression 6 to 12 h after viral infection, at times when IL-8 transcription is inhibited. By contrast, 293 cells, deficient in inducible Bcl-3 expression, show no attenuation of IL-8 transcription. We therefore examined Bcl-3's role in terminating virus-inducible IL-8 transcription. Transient expression of Bcl-3 potently inhibited virus-inducible IL-8 transcription by disrupting both the NF-kappaB and STAT/IRF pathways. Although previously Bcl-3 was thought to capture 50-kDa NF-kappaB1 isoforms in the cytoplasm, immunoprecipitation (IP) and electrophoretic mobility shift assays indicate that nuclear Bcl-3 associates with NF-kappaB1 without affecting DNA binding. Additionally, Bcl-3 potently inhibited the STAT/IRF pathway. Nondenaturing co-IP assays indicate that nuclear Bcl-3 associates with STAT-1 and histone deacetylase 1 (HDAC-1), increasing HDAC-1 recruitment to the IL-8 promoter. Treatment with the HDAC inhibitor trichostatin A blocks attenuation of IL-8 transcription. A nuclear targeting-deficient Bcl-3 is unable to enhance HDAC-1-mediated chemokine repression. Finally, small inhibitory RNA-mediated Bcl-3 "knockdown" resulted in enhanced RSV-induced chemokine expression in A549 cells. These data indicate that Bcl-3 is a virus-inducible inhibitor of chemokine transcription by interfering with the NF-kappaB and STAT/IRF signaling pathways by complexing with them and recruiting HDAC-1 to attenuate target promoter activity.

The Genes Induced by Signal Transducer and Activators of Transcription (STAT)3 and STAT5 in Mammary Epithelial Cells Define the Roles of these STATs in Mammary Development

Prolactin and leukemia inhibitory factor (LIF) have different roles in the adult mammary gland, which are mediated in part by the signal transducers and activators of transcription (STAT)5 and STAT3. In vivo studies have shown that STAT5 contributes to prolactin-dependent lobuloalveolar development and lactation whereas STAT3 mediates LIF-dependent epithelial apoptosis during postlactational involution. To understand the molecular basis of these STAT-dependent pathways, we demonstrate the ligand-independent effects of STAT5 and STAT3 in mammary epithelial cells in vitro and also identify the genes regulated by these related transcription factors. Thus, using conditionally active STAT3- or STAT5a-GyraseB fusion proteins, we observed that enforced and specific dimerization of STAT3 induced apoptosis whereas STAT5 induced differentiation of mammary epithelial cells. Furthermore, STAT5 attenuated apoptosis mediated by LIF, the physiological inducer of STAT3. Microarray analysis of STAT3- and STAT5-induced genes using this system demonstrated a marked specificity, which reflected their different physiological effects in vitro and in vivo. STAT5-specific gene targets included the milk protein genes alpha-casein and kallikrein-8 and the survival factors prosaposin and Grb10. STAT3-specific genes included the apoptosis regulators CCAAT enhancer binding protein-delta, phosphatidylinositol 3-kinase-regulatory subunits, purine nucleoside phosphorylase, and c-fos. These data illustrate that specific activation of STAT3 and STAT5 alone is sufficient to induce and suppress apoptosis, respectively, and that these transcription factors elicit their actions by inducing distinct subsets of target genes in mammary epithelial cells.

The IκB Protein Bcl-3 Negatively Regulates Transcription of theIL-10Gene in Macrophages

NF-kappaB/Rel transcription factors, implicated in inflammatory and immune responses against pathogens, are regulated by IkappaB proteins. The physiological and molecular function of the IkappaB family member Bcl-3 is understood only poorly. In this study, the role of Bcl-3 in an innate immune response was examined by gene targeting. We demonstrate that Bcl-3(-/-) mice are highly susceptible to Listeria monocytogenes infection. This correlates with diminished production of IL-12 p70 and IFN-gamma in vivo, which is mainly due to elevated synthesis of IL-10. Isolated peritoneal macrophages from Bcl-3(-/-) mice also produce elevated amounts of IL-10, which inhibit IL-12 p70 synthesis in an autocrine fashion. Thus, these data establish Bcl-3 as an inhibitor of IL-10 expression in macrophages. Furthermore, we show that Bcl-3 is not implicated in IL-10 mRNA stabilization but regulates the initiation of IL-10 transcription. Taken together, our results show that an essential function of Bcl-3 during an innate immune response against bacteria is to inhibit transcription of the IL-10 gene in macrophages.

Elevated NF-kappaB p50 complex formation and Bcl-3 expression in classical Hodgkin, anaplastic large-cell, and other peripheral T-cell lymphomas

Transcription factor nuclear factor kappa B (NF-kappaB) plays a central role in the pathogenesis of classical Hodgkin lymphoma (cHL). In anaplastic large-cell lymphomas (ALCLs), which share molecular lesions with cHL, the NF-kappaB system has not been equivalently investigated. Here we describe constitutive NF-kappaB p50 homodimer [(p50)2] activity in ALCL cells in the absence of constitutive activation of the IkappaB kinase (IKK) complex. Furthermore, (p50)2 contributes to the NF-kappaB activity in Hodgkin/Reed-Sternberg (HRS) cells. Bcl-3, which is an inducer of nuclear (p50)2 and is associated with (p50)2 in ALCL and HRS cell lines, is abundantly expressed in ALCL and HRS cells. Notably, a selective overexpression of Bcl-3 target genes is found in ALCL cells. By immunohistochemical screening of 288 lymphoma cases, a strong Bcl-3 expression in cHL and in peripheral T-cell non-Hodgkin lymphoma (T-NHL) including ALCL was found. In 3 of 6 HRS cell lines and 25% of primary ALCL, a copy number increase of the BCL3 gene locus was identified. Together, these data suggest that elevated Bcl-3 expression has an important function in cHL and peripheral T-NHL, in particular ALCL.

CD28 induces immunostimulatory signals in dendritic cells via CD80 and CD86

Bidirectional signaling along the B7-CTLA-4 coreceptor pathway enables reciprocal conditioning of T cells and dendritic cells. Although T cells can instruct dendritic cells to manifest tolerogenic properties after CTLA-4 engagement of B7, such a B7-mediated signaling is not known to occur in response to CD28. Here we show that mouse dendritic cells were induced by soluble CD28 to express interleukin 6 and interferon-gamma. Production of interleukin 6 required B7-1 (CD80), B7-2 (CD86) and p38 mitogen-activated protein kinase and prevented interferon-gamma-driven expression of immunosuppressive tryptophan catabolism. In vivo, an adjuvant activity of soluble CD28 was demonstrated as enhanced T cell-mediated immunity to tumor and self peptides and protection against microbial and tumor challenge. Thus, different ligands of B7 can signal dendritic cells to express functionally distinct effector responses.

BCL-3 and NF-kappaB p50 attenuate lipopolysaccharide-induced inflammatory responses in macrophages

Lipopolysaccharide (LPS) induces expression of tumor necrosis factor alpha (TNFalpha) and other pro-inflammatory cytokines in macrophages. Following its induction, TNFalpha gene transcription is rapidly attenuated, in part due to the accumulation of NF-kappaB p50 homodimers that bind to three kappaB sites in the TNFalpha promoter. Here we have investigated the inhibitory role of BCL-3, an IkappaB-like protein that interacts exclusively with p50 and p52 homodimers. BCL-3 was induced by LPS with delayed kinetics and was associated with p50 in the nucleus. Forced expression of BCL-3 suppressed LPS-induced transcription from the TNFalpha promoter and inhibited two artificial promoters composed of TNFalphakappaB sites that preferentially bind p50 dimers. BCL-3-mediated repression was reversed by trichostatin A and was enhanced by overexpression of HDAC-1, indicating that transcriptional attenuation involves recruitment of histone deacetylase. Analysis of macrophages from p50 and BCL-3 knock-out mice revealed that both transcription factors negatively regulate TNFalpha expression and that BCL-3 inhibits IL-1alpha and IL-1beta. In contrast, induction of the anti-inflammatory cytokine IL-10 was reduced in BCL-3 null macrophages. BCL-3 was not required for the production of p50 homodimers but BCL-3 expression was severely diminished in p50-deficient cells. Together, these findings indicate that p50 and BCL-3 function as anti-inflammatory regulators in macrophages by attenuating transcription of pro-inflammatory cytokines and activating IL-10 expression.

Bcl-3 and NFκB p50-p50 Homodimers Act as Transcriptional Repressors in Tolerant CD4+ T Cells

The transcriptional events that control T cell tolerance are still poorly understood. To investigate why tolerant T cells fail to produce interleukin (IL)-2, we analyzed the regulation of NFkappaB-mediated transcription in CD4(+) T cells after tolerance induction in vivo. We demonstrate that a predominance of p50-p50 homodimers binding to the IL-2 promoter kappaB site in tolerant T cells correlated with repression of NFkappaB-driven transcription. Impaired translocation of the p65 subunit in tolerant T cells was a result from reduced activation of IkappaB kinase and poor phosphorylation and degradation of cytosolic IkappaBs. Moreover, tolerant T cells expressed high amounts of the p50 protein. However, the increased expression of p50 could not be explained by activation-induced de novo synthesis of the precursor p105, which was constitutively expressed in tolerant T cells. We also demonstrate the exclusive induction of the IkappaB protein B cell lymphoma 3 (Bcl-3) in tolerant T cells as well as its specific binding to the NFkappaB site. These results suggest that the cellular ratio of NFkappaB dimers, and thus the repression of NFkappaB activity and IL-2 production, are regulated at several levels in tolerant CD4(+) T cells in vivo.

Crystal Structure of Human Pirin

Pirin is a newly identified nuclear protein that interacts with the oncoprotein B-cell lymphoma 3-encoded (Bcl-3) and nuclear factor I (NFI). The crystal structure of human Pirin at 2.1-A resolution shows it to be a member of the functionally diverse cupin superfamily. The structure comprises two beta-barrel domains, with an Fe(II) cofactor bound within the cavity of the N-terminal domain. These findings suggest an enzymatic role for Pirin, most likely in biological redox reactions involving oxygen, and provide compelling evidence that Pirin requires the participation of the metal ion for its interaction with Bcl-3 to co-regulate the NF-kappaB transcription pathway and the interaction with NFI in DNA replication. Substitution of iron by heavy metals thus provides a novel pathway for these metals to directly influence gene transcription. The structure suggests an interesting new role of iron in biology and that Pirin may be involved in novel mechanisms of gene regulation.

The MEK/ERK pathway acts upstream of NF kappa B1 (p50) homodimer activity and Bcl-2 expression in a murine B-cell lymphoma cell line. MEK inhibition restores radiation-induced apoptosis

In a previously published report (Kurland, J. F., Kodym, R., Story, M. D., Spurgers, K. B., McDonnell, T. J., and Meyn, R. E. (2001) J. Biol. Chem. 276, 45380-45386), we described the NF kappa B status for two murine B-cell lymphoma cell lines, LY-as (apoptosis-sensitive) and LY-ar (apoptosis-refractory) and provided evidence that NF kappa B1 (p50) homodimers contribute to the expression of Bcl-2 in the LY-ar line. In the present study, we investigated the upstream signals leading to p50 homodimer activation and Bcl-2 expression. We found that in LY-ar cells, ERK1 and ERK2 were constitutively phosphorylated, whereas LY-as cells had no detectable ERK1 or ERK2 phosphorylation. Treatment of LY-ar cells with the MEK inhibitors PD 98059, U0126, and PD 184352 led to a loss of phosphorylated ERK1 and ERK2, a reversal of nuclear p50 homodimer DNA binding, and a decrease in Bcl-2 protein expression. Similarly, activation of the MEK/ERK pathway in LY-as cells by phorbol ester led to Bcl-2 expression that could be blocked by PD 98059. Furthermore, treatment of LY-ar cells with tumor necrosis factor-alpha, an I kappa B kinase activator, did not alter the suppressive effect of PD 98059 on p50 homodimer activity, suggesting an I kappa B kinase-independent pathway for p50 homodimer activation. Lastly, all three MEK inhibitors sensitized LY-ar cells to radiation-induced apoptosis. We conclude that the MEK/ERK pathway acts upstream of p50 homodimer activity and Bcl-2 expression in this B-cell lymphoma cell system and suggest that the use of MEK inhibitors could be useful clinically in combination with ionizing radiation to treat lymphoid malignancies.

Identification and characterization of BCL-3-binding protein: implications for transcription and DNA repair or recombination

A putative oncogene bcl-3 was originally identified and cloned at the breakpoint in the recurring chromosome translocation t(14;19) found in some cases of B cell chronic lymphocytic leukemia. Studies of bcl-3-deficient mice demonstrated a critical role for bcl-3 in the development of a normal immune response and the formation of germinal centers in secondary lymphoid organs. However, the molecular mechanism that underlies B cell leukemogenesis and the knockout mouse phenotype remains unclear. Here we have identified and characterized BCL-3-binding protein (B3BP) as a protein interacting specifically with the bcl-3 gene product (BCL-3) by a yeast two-hybrid screen. We found that B3BP associates with not only BCL-3 but also p300/CBP histone acetyltransferases. The N-terminal region of B3BP that contains the ATP-binding site is important for the interaction with BCL-3 and p300/CBP. Homology searches indicate that the ATP-binding region of B3BP, which contains a typical Walker-type ATP-binding P-loop, most resembles that of 2',3'-cyclic nucleotide 3'-phosphodiesterase of mammals and polynucleotide kinase of T4 bacteriophage. In fact B3BP shows intrinsic ATP binding and hydrolyzing activity. Furthermore, we demonstrated that B3BP is a 5'-polynucleotide kinase. We also found a small MutS-related domain, which is thought to be involved in the DNA repair or recombination reaction, in the C-terminal region of B3BP, and it shows nicking endonuclease activity. These observations might help to gain new insights into the function of BCL-3 and p300/CBP, especially the coupling of transcription with repair or recombination.

Synergy between all-trans retinoic acid and tumor necrosis factor pathways in acute leukemia cells

The nuclear receptor ligand all-trans retinoic acid (ATRA) causes dramatic terminal differentiation of acute promyelocytic leukemia (APL) cells in vitro and in patients, but it is less active in other malignancies. However, downstream mediators of the effects of ATRA are not well understood. We used a cDNA microarray to search for ATRA-regulated genes in the APL cell line NB4 and found that ATRA regulated several members of the tumor necrosis factor (TNF) pathway. Here we show that TNF can synergize with ATRA to induce differentiation, showing monocytic characteristics more typical of differentiation mediated by TNF than by ATRA. ATRA and TNF can also induce differentiation of the non-APL cell line U937. Underlying this response was an increase in TNF-induced nuclear factor-kappaB (NF-kappaB) DNA binding within 2 hours in the presence of ATRA and activation of NF-kappaB DNA binding and transcriptional activity in response to ATRA alone within 48 hours of ATRA treatment. Furthermore, we found a synergistic induction of the NF-kappaB target genes BCL-3, Dif-2, and TNF receptor 2 (TNFR2) in response to the combination of TNF and ATRA. These genes have been previously shown to play a role in TNF signaling, and amplification of such genes may represent a mechanism whereby TNF and ATRA can act synergistically. We propose that ATRA can prime cancer cells for differentiation triggered by TNF and suggest that targeting the TNF pathway in combination with ATRA may represent a novel route to treat leukemias.

Interleukin-9 influences chemokine release in airway smooth muscle: role of ERK

Interleukin (IL)-9 is a pleiotropic cytokine that has been proposed as a candidate gene for asthma. As IL-9 expression is correlated with airway hyperresponsiveness in animals, we examined the effects of IL-9 on cultured human airway smooth muscle (HASM) cells. IL-9 alone had no effect on IL-8 release, but at concentrations of > or =30 ng/ml, IL-9 significantly increased IL-8 release induced by TNF-alpha. IL-9 increased phosphorylation of extracellular signal-regulated protein kinase (ERK, p42 and p44) in a concentration- and time-dependent fashion, and U-0126 (10 micro M), which inhibits ERK phosphorylation, abolished the synergism between TNF-alpha and IL-9 on IL-8 release. IL-9 alone had no effect on eotaxin release into HASM cell supernatants but at concentrations of > or =10 ng/ml caused an approximately 50% increase in release of eotaxin evoked by IL-13 (10 ng/ml). U-0126 blocked the synergism between IL-9 and IL-13 on eotaxin release. IL-9 had no effect on cyclooxygenase-2 (COX-2) expression or PGE(2) release and did not augment the COX-2 expression that was induced by IL-1beta. Our results indicate that airway smooth muscle is a target for IL-9 and that IL-9 amplifies the potential for these cells to recruit eosinophils and neutrophils into the airways by a mechanism involving ERK.

Interleukins in atherosclerosis: molecular pathways and therapeutic potential

Interleukins are considered to be key players in the chronic vascular inflammatory response that is typical of atherosclerosis. Thus, the expression of proinflammatory interleukins and their receptors has been demonstrated in atheromatous tissue, and the serum levels of several of these cytokines have been found to be positively correlated with (coronary) arterial disease and its sequelae. In vitro studies have confirmed the involvement of various interleukins in pro-atherogenic processes, such as the up-regulation of adhesion molecules on endothelial cells, the activation of macrophages, and smooth muscle cell proliferation. Furthermore, studies in mice deficient or transgenic for specific interleukins have demonstrated that, whereas some interleukins are indeed intrinsically pro-atherogenic, others may have anti-atherogenic qualities. As the roles of individual interleukins in atherosclerosis are being uncovered, novel anti-atherogenic therapies, aimed at the modulation of interleukin function, are being explored. Several approaches have produced promising results in this respect, including the transfer of anti-inflammatory interleukins and the administration of decoys and antibodies directed against proinflammatory interleukins. The chronic nature of the disease and the generally pleiotropic effects of interleukins, however, will demand high specificity of action and/or effective targeting to prevent the emergence of adverse side effects with such treatments. This may prove to be the real challenge for the development of interleukin-based anti-atherosclerotic therapies, once the mediators and their targets have been delineated.

Chronic ethanol exposure potentiates lipopolysaccharide liver injury despite inhibiting Jun N-terminal kinase and caspase 3 activation

Although ethanol is known to sensitize hepatocytes to tumor necrosis factor (TNF) lethality, the mechanisms involved remain controversial. Recently, others have shown that adding TNFalpha to cultures of ethanol-pretreated hepatocytes provokes the mitochondrial permeability transition, cytochrome c release, procaspase 3 activation, and apoptosis. Although this demonstrates that ethanol can sensitize hepatocytes to TNF-mediated apoptosis, the hepatic inflammation and ballooning hepatocyte degeneration that typify alcohol-induced liver injury suggest that other mechanisms might predominate in vivo. To evaluate this possibility, acute responses to lipopolysaccharide (LPS), a potent inducer of TNFalpha, were compared in mice that had been fed either an ethanol-containing or control diet for 5 weeks. Despite enhanced induction of cytokines such as interleukin (IL)-10, IL-15, and IL-6 that protect hepatocytes from apoptosis, ethanol-fed mice exhibited a 4-5-fold increase in serum alanine aminotransferase after LPS, confirming increased liver injury. Six h post-LPS histology also differed notably in the two groups, with control livers demonstrating only scattered apoptotic hepatocytes, whereas ethanol-exposed livers had large foci of ballooned hepatocytes, inflammation, and scattered hemorrhage. No caspase 3 activity was noted during the initial 6 h after LPS in ethanol-fed mice, but this tripled by 1.5 h after LPS in controls. Procaspase 8 cleavage and activity of the apoptosis-associated kinase, Jun N-terminal kinase, were also greater in controls. In contrast, ethanol exposure did not inhibit activation of cytoprotective mitogen-activated protein kinases and AKT or attenuate induction of the anti-apoptotic factors NF-kappaB and inducible nitric oxide synthase. Consistent with these responses, neither cytochrome c release, an early apoptotic response, nor hepatic oligonucleosomal DNA fragmentation, the ultimate consequence of apoptosis, was increased by ethanol. Thus, ethanol exacerbates TNF-related hepatotoxicity in vivo without enhancing caspase 3-dependent apoptosis.

Activation of an alternative NF-kappaB pathway in skeletal muscle during disuse atrophy

Although cytokine-induced nuclear factor kappaB (NF-kappaB) pathways are involved in muscle wasting subsequent to disease, their potential role in disuse muscle atrophy has not been characterized. Seven days of hind limb unloading led to a 10-fold activation of an NF-kappaB-dependent reporter in rat soleus muscle but not the atrophy-resistant extensor digitorum longus muscle. Nuclear levels of p50 were markedly up-regulated, c-Rel was moderately up-regulated, Rel B was down-regulated, and p52 and p65 were unchanged in unloaded solei. The nuclear IkappaB protein Bcl-3 was increased. There was increased binding to an NF-kappaB consensus oligonucleotide, and this complex bound antibodies to p50, c-Rel, and Bcl-3 but not other NF-kappaB family members. Tumor necrosis factor alpha (TNF-alpha) and TNF receptor-associated factor 2 protein were moderately down-regulated. There was no difference in p38, c-Jun NH(2)-terminal kinase or Akt activity, nor were activator protein 1 or nuclear factor of activated T cell-dependent reporters activated. Thus, whereas several NF-kappaB family members are up-regulated, the prototypical markers of cytokine-induced activation of NF-kappaB seen with disease-related wasting are not evident during disuse atrophy. Levels of an anti-apoptotic NF-kappaB target, Bcl-2, were increased fourfold whereas proapoptotic proteins Bax and Bak decreased. The evidence presented here suggests that disuse muscle atrophy is associated with activation of an alternative NF-kappaB pathway that involves the activation of p50 but not p65.

The putative oncoprotein Bcl-3 induces cyclin D1 to stimulate G(1) transition

Bcl-3 is a distinctive member of the IkappaB family of NF-kappaB inhibitors because it can function to coactivate transcription. A potential involvement of Bcl-3 in oncogenesis is highlighted by the fact that it was cloned due to its location at a breakpoint junction in some cases of human B-cell chronic lymphocytic leukemia and that it is highly expressed in human breast tumor tissue. To analyze the effects of Bcl-3 dysregulation in breast epithelial cells, we created stable immortalized human breast epithelial cell lines either expressing Bcl-3 or carrying the corresponding vector control plasmid. Analysis of the Bcl-3-expressing cells suggests that these cells have a shortened G(1) phase of the cell cycle as well as a significant increase in hyperphosphorylation of the retinoblastoma protein. Additionally, the cyclin D1 gene was found to be highly expressed in these cells. Upon further analysis, Bcl-3, acting as a coactivator with NF-kappaB p52 homodimers, was demonstrated to directly activate the cyclin D1 promoter through an NF-kappaB binding site. Therefore, our results demonstrate that dysregulated expression of Bcl-3 potentiates the G(1) transition of the cell cycle by stimulating the transcription of the cyclin D1 gene in human breast epithelial cells.

NF-kappaB1 (p50) homodimers contribute to transcription of the bcl-2 oncogene

The bcl-2 proto-oncogene is frequently expressed in human cancer. Although bcl-2 was first cloned as the t(14;18) translocation breakpoint from human follicular B-cell lymphoma, it has become apparent that many cell types express bcl-2 because of transcriptional regulation. As such, several transcription factors have been demonstrated to activate expression of bcl-2, including NF-kappaB. We investigated the role of NF-kappaB1 (p50) homodimers in the expression of Bcl-2 in two murine B-cell lymphoma cell lines: LY-as, an apoptosis-proficient line with low Bcl-2 protein expression and no nuclear NF-kappaB activity, and LY-ar, a nonapoptotic line with constitutive p50 homodimer activity and 30 times more Bcl-2 protein expression than LY-as. We found that nuclear p50 homodimer activity correlated with Bcl-2 expression in these cell types and identified several sites within the bcl-2 5'-flanking region that p50 was capable of binding. In vitro transcription revealed that recombinant p50 enhanced the production of run-off transcripts from the bcl-2 P1 promoter. Additional in vitro transcription experiments suggested the sites by which p50 afforded this effect. We conclude that the p50 homodimer is capable of transcriptional activation of the bcl-2 gene and suggest that its nuclear activity contributes to the expression of bcl-2 in LY-ar cells.

Gene array analysis reveals changes in peripheral nervous system gene expression following stimuli that result in reactivation of latent herpes simplex virus type 1: induction of transcription factor Bcl-3

The earliest events within the peripheral mammalian nervous system that cause herpes simplex virus type 1 (HSV-1) to reactivate from latency are unknown but are highly likely to include altered regulation of cellular transcription factors. Using gene array analysis, we have examined the changes that occur in cellular mRNA levels in mouse trigeminal ganglia following explantation, a stimulus that results in HSV-1 reactivation from latency. We have detected both increased and decreased expression levels of particular cellular transcripts, which include RNAs encoding neuronal factors, transcription factors, and factors involved in the cell cycle. Among the transcription factors that are upregulated is Bcl-3, a coactivator for NFkappaB. We have confirmed these increases in Bcl-3 transcription levels using reverse transcription-PCR and S1 nuclease protection assays. In addition, we have shown Bcl-3 upregulation at the protein level. Importantly, Bcl-3 RNA levels were found to increase specifically in neuronal cells within the trigeminal ganglia. We discuss a potential role for this factor in upregulating ICP0 transcription, which is an important viral event for initiation of HSV-1 reactivation.

NF-kappa B-inducible BCL-3 expression is an autoregulatory loop controlling nuclear p50/NF-kappa B1 residence

NF-kappa B is a transcription factor whose nuclear residence is controlled by I kappa B family members. In the NF-kappa B-I kappa B autoregulatory loop, activated (nuclear) Rel A.NF-kappa B1 induces the resynthesis of I kappa B alpha recapturing nuclear Rel A back into the cytoplasm within 1 h of stimulation. In contrast, NF-kappa B1 subunits redistribute more slowly into the cytoplasm (from 6 to 12 h). Here we examine the role of inducible cytoplasmic BCL-3 expression in terminating nuclear NF-kappa B1. Although BCL-3 is a nuclear protein in B lymphocytes, surprisingly, BCL-3 is primarily a cytoplasmic protein in HepG2 cells. Cytoplasmic BCL-3 abundance is induced 6-12 h after tumor necrosis factor-alpha stimulation where it complexes with NF-kappa B1 homodimers. Moreover, BCL-3 mRNA and protein expression are induced by NF-kappa B-activating agents. Two observations are interpreted to indicate that bcl-3 is transactivated by NF-kappa B/Rel A: 1) expression of a dominant negative NF-kappa B inhibitor blocks tumor necrosis factor-alpha-induced BCL-3 expression and 2) expression of constitutively active Rel A is sufficient to induce BCL-3 expression. In gene transfer studies, we identify two high affinity NF-kappa B-binding sites, kappa B1 (located at -872 to -861 nucleotides) and kappa B2 (-106 to -96 nucleotides), and although both bind with high affinity to Rel A, only kappa B2 is required for NF-kappa B-dependent induction of the native BCL-3 promoter. Down-regulation of BCL-3 induction results in prolonged, enhanced NF-kappa B1 binding and increased NF-kappa B-dependent transcription. Together, these data suggest the presence of an NF-kappa B-BCL-3 autoregulatory loop important in terminating NF-kappa B1 action and that individual NF-kappa B isoforms are actively terminated through coordinate induction of inhibitory I kappa B molecules to restore cellular homeostasis.

Kinases: positive and negative regulators of apoptosis

Cells sense and respond to extracellular factors via receptors on the cell surface that trigger intracellular signaling pathways. The signals received by the receptors on hematopoietic cells often determine if the cell proliferates, survives or undergoes apoptosis. Apoptosis can be induced by almost any cytotoxic stimuli. These stimuli may be an absence of signals arising from cellular receptors, stimulation of specific ligand receptors on the cell surface, chemotherapeutic agents, and ionizing radiation or oxygen radicals, as well as a number of other factors. Cellular kinases and phosphatases participate in signaling cascades that influence this process. We review the ability of the calmodulin-dependent-kinases, I-kappaB kinases, PI3-kinases, Jakkinases, PKC, PKA, and MAP kinase signaling pathways (Erk, Jnk, and p38), to influence the apoptotic process. In addition, we discuss the cross-talk that exists between signaling cascades that are pro-apoptotic and anti-apoptotic.