NF-IL6 and AP-1 cooperatively modulate the activation of the TSG-6 gene by tumor necrosis factor alpha and interleukin-1

Gonadotropin regulation of ankyrin-repeat and SOCS-box protein 9 (ASB9) in ovarian follicles and identification of binding partners

Ankyrin-repeat and SOCS-box protein 9 (ASB9) is a member of the large SOCS-box containing proteins family and acts as the specific substrate recognition component of E3 ubiquitin ligases in the process of ubiquitination and proteasomal degradation. We previously identified ASB9 as a differentially expressed gene in granulosa cells (GC) of bovine ovulatory follicles. This study aimed to further investigate ASB9 mRNA and protein regulation, identify binding partners in GC of bovine ovulatory follicles, and study its function. GC were obtained from small follicles (SF: 2–4 mm), dominant follicles at day 5 of the estrous cycle (DF), and ovulatory follicles, 24 hours following hCG injection (OF). Analyses by RT-PCR showed a 104-fold greater expression of ASB9 in GC of OF than in DF. Steady-state levels of ASB9 in follicular walls (granulosa and theca cells) analyzed at 0, 6, 12, 18 and 24 hours after hCG injection showed a significant induction of ASB9 expression at 12 and 18 hours, reaching a maximum induction of 10.2-fold at 24 hours post-hCG as compared to 0 hour. These results were confirmed in western blot analysis showing strongest ASB9 protein amounts in OF. Yeast two-hybrid screening of OF-cDNAs library resulted in the identification of 10 potential ASB9 binding partners in GC but no interaction was found between ASB9 and creatine kinase B (CKB) in these GC. Functional studies using CRISPR-Cas9 approach revealed that ASB9 inhibition led to increased GC proliferation and modulation of target genes expression. Overall, these results support a physiologically relevant role of ASB9 in the ovulatory follicle by targeting specific proteins likely for degradation, contributing to reduced GC proliferation, and could be involved in the final GC differentiation into luteal cells.

Transcriptional control of K5, K6, K14, and K17 keratin genes by AP-1 and NF-kappaB family members

The expression of keratins K5 and K14 is restricted to the basal layers of the healthy epidermis, whereas the expression of K6 and K17 is induced in response to proliferative and inflammatory signals, respectively. The control of keratin expression occurs primarily at the transcriptional level. We studied the effects of transcription factors of the AP-1 and NF-kappaB families on the expression of those four keratin genes. We chose AP-1 and NF-kappaB proteins because they are activated by many extracellular signals, including those in hyperproliferative and inflammatory processes. DNA constructs expressing the transcription factors were, in various combinations, cotransfected with constructs containing keratin gene promoters and the CAT reporter gene into HeLa cells or keratinocytes. We found that the K5 and K14 promoters, which are coexpressed in vivo, are regulated in parallel by the cotransfected genes. Both were activated by the c-Fos and c-Jun components of AP-1, but not by Fra1. On the other hand, the NF-kappaB proteins, especially p65, suppressed these two promoters. The K17 promoter was specifically activated by c-Jun, whereas the other transcription factors tested had no significant effect. In contrast, the K6 promoter was very strongly activated by all AP-1 proteins, especially by the c-Fos + c-Jun and Fra1 + c-Jun combinations. It was also strongly activated by the p65 NF-kappaB protein. AP-1 and NF-kappaB acted synergistically in activating the K6 promoter, although the AP-1 and the NF-kappaB responsive sites could be separated physically. These results suggest that the interplay of AP-1 and NF-kappaB proteins regulates epidermal gene expression and that the activation of these transcription factors by extracellular signaling molecules brings about the differential expression of keratin genes in epidermal differentiation, cutaneous diseases, and wound healing.

Anti-inflammatory cytokine TSG-6 inhibits hypertrophic scar formation in a rabbit ear model

Hypertrophic scars are characterized by excessive fibrosis and extracellular matrix (ECM) deposition and can be functionally and cosmetically problematic; however, there are few satisfactory treatments for controlling hypertrophic scars. The inflammatory cells and cytokines involved in excessive inflammation during wound healing facilitate fibroblast proliferation and collagen deposition, leading to pathologic scar formation. TSG-6 exhibits anti-inflammatory activity. This study examined the effect of recombinant TSG-6 on inflammation in hypertrophic scars using a rabbit ear model. Six 7-mm, full-thickness, circular wounds were made on the ears of 12 rabbits. TSG-6 and PBS were intradermally injected into the right and left ear wounds, respectively. The methods of TEM and TUNEL were used to detect fibroblast apoptosis. The expressions of inflammatory factors: IL-1β, IL-6 and TNF-α, were detected by immunohistochemistry and real time polymerase chain reaction. Collagen I and III expression detected by immunohistochemistry and Masson׳s trichrome staining and SEI (scar elevation index) was used to evaluate the extent of scarring. TSG-6 injection mitigated the formation of a hypertrophic scar in the rabbit ear. TSG-6-treated wounds exhibited decreased inflammation compared with the control group, as evidenced by the lower levels of IL-1β, IL-6, TNF-α and MPO. The SEI and the synthesis of collagens I and III were significantly decreased in the TSG-6-treated scars compared with control scars. The apoptosis rate was higher in the TSG-6-treated scars. TSG-6 exhibited anti-inflammatory effects during the wound healing process and cicatrization and significantly diminished hypertrophic scar formation in a rabbit ear model.

Hyaluronan fragments as mediators of inflammation in allergic pulmonary disease

Asthma is frequently caused and/or exacerbated by sensitization to allergens, which are ubiquitous in many indoor and outdoor environments. Severe asthma is characterized by airway hyperresponsiveness and bronchial constriction in response to an inhaled allergen, leading to a disease course that is often very difficult to treat with standard asthma therapies. As a result of interactions among inflammatory cells, structural cells, and the intercellular matrix of the allergic lung, patients with sensitization to allergens may experience a greater degree of tissue injury followed by airway wall remodeling and progressive, accumulated pulmonary dysfunction as part of the disease sequela. In addition, turnover of extracellular matrix (ECM) components is a hallmark of tissue injury and repair. This review focuses on the role of the glycosaminoglycan hyaluronan (HA), a component of the ECM, in pulmonary injury and repair with an emphasis on allergic asthma. Both the synthesis and degradation of the ECM are critical contributors to tissue repair and remodeling. Fragmented HA accumulates during tissue injury and functions in ways distinct from the larger native polymer. There is gathering evidence that HA degradation products are active participants in stimulating the expression of inflammatory genes in a variety of immune cells at the injury site. In this review, we will consider recent advances in the understanding of the mechanisms that are associated with HA accumulation and inflammatory cell recruitment in the asthmatic lung.

Differential regulation of the rainbow trout (Oncorhynchus mykiss) MT-A gene by nuclear factor interleukin-6 and activator protein-1

BACKGROUND

Previously we have identified a distal region of the rainbow trout (Oncorhynchus mykiss) metallothionein-A (rtMT-A) enhancer region, being essential for free radical activation of the rtMT-A gene. The distal promoter region included four activator protein 1 (AP1) cis-acting elements and a single nuclear factor interleukin-6 (NF-IL6) element. In the present study we used the rainbow trout hepatoma (RTH-149) cell line to further examine the involvement of NF-IL6 and AP1 in rtMT-A gene expression following exposure to oxidative stress and tumour promotion.

RESULTS

Using enhancer deletion studies we observed strong paraquat (PQ)-induced rtMT-A activation via NF-IL6 while the AP1 cis-elements showed a weak but significant activation. In contrast to mammals the metal responsive elements were not activated by oxidative stress. Electrophoretic mobility shift assay (EMSA) mutation analysis revealed that the two most proximal AP1 elements, AP11,2, exhibited strong binding to the AP1 consensus sequence, while the more distal AP1 elements, AP13,4 were ineffective. Phorbol-12-myristate-13-acetate (PMA), a known tumor promoter, resulted in a robust induction of rtMT-A via the AP1 elements alone. To determine the conservation of regulatory functions we transfected human Hep G2 cells with the rtMT-A enhancer constructs and were able to demonstrate that the cis-elements were functionally conserved. The importance of NF-IL6 in regulation of teleost MT is supported by the conservation of these elements in MT genes from different teleosts. In addition, PMA and PQ injection of rainbow trout resulted in increased hepatic rtMT-A mRNA levels.

CONCLUSIONS

These studies suggest that AP1 primarily is involved in PMA regulation of the rtMT-A gene while NF-IL6 is involved in free radical regulation. Taken together this study demonstrates the functionality of the NF-IL6 and AP-1 elements and suggests an involvement of MT in protection during pathological processes such as inflammation and cancer.

c-Jun binding site identification in K562 cells

Determining the binding sites of the transcription factor is important for understanding of transcriptional regulation. Transcription factor c-Jun plays an important role in cell growth, differentiation and development, but the binding sites and the target genes are not clearly defined in the whole human genome. In this study, we performed a ChIP-Seq experiment to identify c-Jun binding site in the human genome. Forty-eight binding sites were selected to process further evaluation by dsDNA microarray assay. We identified 283 c-Jun binding sites in K562 cells. Data analysis showed that 48.8% binding sites located within 100 kb of the upstream of the annotated genes, 28.6% binding sites comprised consensus TRE/CRE motif (5'-TGAC/GTCA-3', 5'-TGACGTCA-3') and variant sequences. Forty-two out of the selected 48 binding sites were found to bind the c-Jun homodimer in dsDNA microarray analysis. Data analysis also showed that 1569 genes are located in the neighborhood of the 283 binding sites and 191 genes in the neighborhood of the 42 binding sites validated by dsDNA microarray. We consulted 38 c-Jun target genes in previous studies and 16 among these 38 genes were also detected in this study. The identification of c-Jun binding sites and potential target genes in the genome scale may improve our fundamental understanding in the molecular mechanisms underlying the transcription regulation related to c-Jun.

Regulation of bovine tumor necrosis factor-alpha-induced protein 6 in ovarian follicles during the ovulatory process and promoter activation in granulosa cells

To study the regulation of bovine TNFalpha-induced protein 6 (TNFAIP6) prior to ovulation, preovulatory follicles obtained after the treatment with human chorionic gonadotropin (hCG) were used. RT-PCR analyses showed that levels of TNFAIP6 mRNA were low before hCG but significantly increased after hCG treatment in follicles. Further analyses and immunohistochemistry indicated that this increase in transcript and protein levels occurred in theca and granulosa cells. To investigate molecular mechanisms involved in TNFAIP6 transactivation, the activity of bovine TNFAIP6 promoter was studied in granulosa cell cultures. Mutant studies identified the minimal region conferring full-length promoter activity, in which activator protein-1 (AP1) and cAMP response element (CRE) elements were required for promoter activity. Overexpression of dominant-negative AP1 and activating transcription factor/cAMP response element-binding protein (CREB) inhibited forskolin-inducible promoter activity. DNA binding assays demonstrated the importance of AP1 and CRE for activity and identified JunD, FosB, Fra2, CREB1, and CREB2 as being part of the AP1 complex, and FosB, Fra2, and CREB1 for the CRE complex. Chromatin immunoprecipitation assays confirmed binding of these proteins with endogenous TNFAIP6 promoter. Treatment with forskolin, prostaglandin E2, and catalytic subunit protein kinase (cPKA) stimulated, but H89, PKA inhibitor peptide, and indomethacin inhibited, TNFAIP6 promoter activity and gene expression in granulosa cells. Collectively, this study is the first to describe that the ovulatory process in cows is associated with a gonadotropin-dependent induction of TNFAIP6 in ovarian follicles and provide the molecular basis through which AP1 and CRE sites and PKA activation played important roles in the regulation of TNFAIP6 in granulosa cells.

Transcriptional responses of human epidermal keratinocytes to cytokine interleukin-1

Interleukin-1 is a proinflammatory and immunomodulatory cytokine that plays a crucial role in inflammatory diseases of the skin, including bacterial infections, bullous diseases, UV damage, and especially psoriasis. To characterize the molecular effects of IL-1 in epidermis, we defined the transcriptional changes in human epidermal keratinocytes 1, 4, 24, and 48 h after treatment with IL-1alpha. IL-1 significantly regulated 388 genes, including genes associated with proteolysis, adhesion, signal transduction, proliferation, and epidermal differentiation. IL-1 induces many genes that have antimicrobial function. Secreted cytokines, chemokines, growth factors, and their receptors are the prominent targets of IL-1 regulation, including IL-8, IL-19, elafin, C3, and S100A proteins, which implicate IL-1 in the pathogenesis of inflammatory diseases. IL-1 induced not only proliferation-associated genes but also differentiation marker genes such as transglutaminase-1 and involucrin, which suggests that IL-1 plays an important role in the aberrant proliferation and differentiation seen in psoriasis. Correlation of IL-1 regulated genes with the TNFalpha and IFNgamma regulated ones showed more similarities between IL-1 and TNFalpha than IL-1 and IFNgamma, whereas Oncostatin-M (OsM) affected a largely unrelated set of genes. IL-1 regulates many genes previously shown to be specifically over-expressed in psoriasis. In summary, IL-1 regulates a characteristic set of genes that define its specific contribution to inflammation and aberrant differentiation in skin diseases.

Sulfur mustard toxicity following dermal exposure: role of oxidative stress, and antioxidant therapy

OBJECTIVE

Sulfur mustard (bis-2-(chloroethyl) sulfide) is a chemical warfare agent (military code: HD) causing extensive skin injury. The mechanisms underlying HD-induced skin damage are not fully elucidated. This review will critically evaluate the evidence showing that oxidative stress is an important factor in HD skin toxicity. Oxidative stress results when the production of reactive oxygen (ROS) and/or reactive nitrogen oxide species (RNOS) exceeds the capacity of antioxidant defense mechanisms.

METHODS

This review will discuss the role of oxidative stress in the pathophysiology of HD skin toxicity in both in vivo and in vitro model systems with emphasis on the limitations of the various model systems. Evidence supporting the therapeutic potential of antioxidants and antioxidant liposomes will be evaluated. Antioxidant liposomes are effective vehicles for delivering both lipophilic (incorporated into the lipid bilayers) and water-soluble (encapsulated in the aqueous inner-spaces) antioxidants to skin. The molecular mechanisms interconnecting oxidative stress to HD skin toxicity are also detailed.

RESULTS

DNA repair and inflammation, in association with oxidative stress, induce intracellular events leading to apoptosis or to a programmable form of necrosis. The free radical, nitric oxide (NO), is of considerable interest with respect to the mechanisms of HD toxicity. NO signaling pathways are important in modulating inflammation, cell death, and wound healing in skin cells.

CONCLUSIONS

Potential future directions are summarized with emphasis on a systems biology approach to studying sulfur mustard toxicity to skin as well as the newly emerging area of redox proteomics.

Molecular characterization of tumor necrosis α-induced protein 6 and its human chorionic gonadotropin-dependent induction in theca and mural granulosa cells of equine preovulatory follicles

The preovulatory rise in gonadotropins causes an expansion of the cumulus–oocyte complex, a process requiring the induction of several genes. The objectives of this study were to clone the equine tumor necrosis factor α-induced protein 6 (TNFAIP6), and investigate its regulation in equine follicles during human chorionic gonadotropin (hCG)-induced ovulation. The isolation of the equine TNFAIP6 cDNA revealed that it contains an open reading frame of 834 bp (including the stop codon), encoding a predicted 277 amino acid protein that is highly similar (91–93% identity) to known mammalian homologs. The regulation of TNFAIP6 mRNA was studied in equine follicles isolated during estrus between 0 and 39 h post-hCG and in corpora lutea (CL) obtained on day 8 of the estrous cycle. Results from semi-quantitative RT-PCR/Southern blot showed that levels of TNFAIP6 mRNA were low in follicles obtained at 0 h, increased at 12 h, returned to basal levels at 24 h, and increased again at 36 h post-hCG (P<0.05). Levels of TNFAIP6 transcripts were relatively moderate in CL, but low in non-ovarian tissues tested. Analyses performed with isolated preparations of theca and granulosa cells indicated that TNFAIP6 mRNA was regulated in both layers, with a maximal induction obtained 33–36 h post-hCG (P<0.05). Immunohistochemical staining of sections of equine follicles isolated at 0 and 33 h post-hCG confirmed the induction of TNFAIP6 protein in both cell types after hCG treatment. Thus, the present study describes for the first time the gonadotropin-dependent regulation of follicular TNFAIP6 during the ovulation in a monoovulatory species. The biphasic induction of TNFAIP6 in equine theca and granulosa cells differs from the pattern observed in rodents, suggesting a distinct control of gene expression in this monoovulatory species.

Gene expression clustering using self-organizing maps: analysis of the macrophage response to particulate biomaterials

The most common cause of total joint replacement failure is peri-implant bone loss causing pain and prosthesis loosening. This process, known as osteolysis or aseptic loosening, is characterized by macrophage phagocytosis of particulate implant wear debris. In an incompletely defined step, particulate biomaterial debris induces macrophages to release a variety of inflammatory mediators and signaling proteins that lead to bone loss. In an in vitro model of this process, we used microarray technology and data analysis techniques, including the use of self-organizing maps (SOMs), to understand the mRNA gene expression changes occurring in macrophages exposed to clinically relevant particles of ultra-high molecular weight polyethylene and TiAlV alloy. Earlier studies have been limited by technology that only allowed analysis of a few genes at a time, but the microarray techniques used in this paper generate the quantitative analysis of over a thousand genes simultaneously. Our microarray analysis utilized an SOM clustering to elucidate general patterns in the data, lists of top up- and down-regulated genes for each time point and genes with differential expression under different biomaterial exposures. The expression levels of the majority of genes (>95%) did not vary over time or with exposure to different biomaterials, but a few important genes, such as TNF-alpha, IL-1beta, IL-6, and MIP1alpha, proved to be highly regulated in response to biomaterial exposure. We also uncovered a novel set of genes, which not only validates and logically extends the current model of the pathogenesis of osteolysis and aseptic loosening, but also provides new targets for further research and therapeutics.

Cytokine-induced gene expression at the crossroads of innate immunity, inflammation and fertility: TSG-6 and PTX3/TSG-14

Two cytokine-inducible gene products, important in inflammation and infection, also play essential roles in female fertility. One of these is the product of tumor necrosis factor (TNF)-stimulated gene 6 (TSG-6), alternatively termed TNFAIP6 (for TNF-alpha-induced protein 6), originally cloned from diploid human fibroblasts stimulated with TNF. The second is pentraxin 3 (PTX3), also termed TSG-14, originally isolated from TNF-stimulated human fibroblasts and from interleukin-1 (IL-1)-stimulated vascular endothelial cells. TSG-6, which specifically binds to hyaluronan (HA) and to inter-alpha-inhibitor (I alpha I), shows potent anti-inflammatory activity in acute and chronic inflammation, notably in several models of autoimmune arthritis. PTX3 was shown to play an important role in resistance to fungal infection with Aspergillus fumigatus. Both TSG-6 and PTX3 are synthesized in the ovary prior to ovulation, where they become components of an expanding viscoelastic matrix that surrounds the oocyte before its release from the follicle at the ovarian surface. Female mice with a targeted disruption of either the TSG-6 or PTX3 gene show severe defects in fertility.

Specificity in Stress Response: Epidermal Keratinocytes Exhibit Specialized UV-Responsive Signal Transduction Pathways

UV light, a paradigmatic initiator of cell stress, invokes responses that include signal transduction, activation of transcription factors, and changes in gene expression. Consequently, in epidermal keratinocytes, its principal and frequent natural target, UV regulates transcription of a distinctive set of genes. Hypothesizing that UV activates distinctive epidermal signal transduction pathways, we compared the UV-responsive activation of the JNK and NFkappaB pathways in keratinocytes, with the activation of the same pathways by other agents and in other cell types. Using of inhibitors and antisense oligonucleotides, we found that in keratinocytes only UVB/UVC activate JNK, while in other cell types UVA, heat shock, and oxidative stress do as well. Keratinocytes express JNK-1 and JNK-3, which is unexpected because JNK-3 expression is considered brain-specific. In keratinocytes, ERK1, ERK2, and p38 are activated by growth factors, but not by UV. UVB/UVC in keratinocytes activates Elk1 and AP1 exclusively through the JNK pathway. JNKK1 is essential for UVB/UVC activation of JNK in keratinocytes in vitro and in human skin in vivo. In contrast, in HeLa cells, used as a control, crosstalk among signal transduction pathways allows considerable laxity. In parallel, UVB/UVC and TNFalpha activate the NFkappaB pathway via distinct mechanisms, as shown using antisense oligonucleotides targeted against IKKbeta, the active subunit of IKK. This implies a specific UVB/UVC responsive signal transduction pathway independent from other pathways. Our results suggest that in epidermal keratinocytes specific signal transduction pathways respond to UV light. Based on these findings, we propose that the UV light is not a genetic stress response inducer in these cells, but a specific agent to which epidermis developed highly specialized responses.

TSG-6: a multifunctional protein associated with inflammation

TSG-6 expression is upregulated in many cell types in response to a variety of proinflammatory mediators and growth factors. This protein is detected in several inflammatory disease states (e.g. rheumatoid arthritis) and in the context of inflammation-like processes, such as ovulation, and is often associated with extracellular matrix remodelling. TSG-6 has anti-inflammatory and chondroprotective effects in various models of inflammation and arthritis, which suggest that it is a component of a negative feedback loop capable of downregulating the inflammatory response. Growing evidence also indicates that TSG-6 acts as a crucial factor in ovulation by influencing the expansion of the hyaluronan-rich cumulus extracellular matrix in the preovulatory follicle. TSG-6 is a member of the Link module superfamily and binds to hyaluronan (a vital component of extracellular matrix), as well as other glycosaminoglycans, via its Link module. In addition, TSG-6 forms both covalent and non-covalent complexes with inter-alpha-inhibitor (a serine protease inhibitor present at high levels in serum) and potentiates its anti-plasmin activity.

The myeloid master regulator transcription factor PU.1 is inactivated by AML1-ETO in t(8;21) myeloid leukemia

The transcription factor PU.1 plays a pivotal role in normal myeloid differentiation. PU.1(-/-) mice exhibit a complete block in myeloid differentiation. Heterozygous PU.1 mutations were reported in some patients with acute myeloid leukemia (AML), but not in AML with translocation t(8;21), which gives rise to the fusion gene AML1-ETO. Here we report a negative functional impact of AML1-ETO on the transcriptional activity of PU.1. AML1-ETO physically binds to PU.1 in t(8;21)(+) Kasumi-1 cells. AML1-ETO binds to the beta(3)beta(4) region in the DNA-binding domain of PU.1 and displaces the coactivator c-Jun from PU.1, thus down-regulating the transcriptional activity of PU.1. This physical interaction of AML1-ETO and PU.1 did not abolish the DNA-binding capacity of PU.1. AML1-ETO down-regulates the transactivation capacity of PU.1 in myeloid U937 cells, and the expression levels of PU.1 target genes in AML French-American-British (FAB) subtype M2 patients with t(8;21) were lower than in patients without t(8;21). Conditional expression of AML1-ETO causes proliferation in mouse bone marrow cells and inhibits antiproliferative function of PU.1. Overexpression of PU.1, however, differentiates AML1-ETO-expressing Kasumi-1 cells to the monocytic lineage. Thus, the function of PU.1 is down-regulated by AML1-ETO in t(8;21) myeloid leukemia, whereas overexpression of PU.1 restores normal differentiation.

Reduced susceptibility to collagen-induced arthritis in DBA/1J mice expressing the TSG-6 transgene

OBJECTIVE

Expression of TSG-6 (tumor necrosis factor-stimulated gene 6) is induced by proinflammatory cytokines. This study was undertaken to examine the effects of local expression of TSG-6 in arthritic joints of TSG-6 transgenic mice, in the collagen-induced arthritis (CIA) model.

METHODS

We generated transgenic mice that harbored the TSG-6 gene under the control of the T cell-specific lck promoter. Arthritis was induced by immunization with bovine type II collagen (CII), and its progression was monitored based on the incidence of arthritis, the arthritis index, and footpad swelling. Anti-CII antibodies and cytokine production were determined by enzyme-linked immunosorbent assay. Gene expression arrays were used to compare gene expression profiles of transgenic and control mice at various stages of CIA.

RESULTS

TSG-6 was expressed in limbs of transgenic mice after immunization with CII, while its expression in nontransgenic animals was insignificant. The incidence of CIA was reduced in TSG-6 transgenic animals, its onset delayed, and all parameters of clinical arthritis significantly reduced. However, the immune response against CII was not significantly inhibited in TSG-6 transgenic mice.

CONCLUSION

TSG-6 expression has been demonstrated in patients with rheumatoid and other forms of arthritis. Our data show that local expression of TSG-6 at sites of inflammation results in potent inhibition of inflammation and joint destruction in a model of autoimmune arthritis in mice. Therefore, it is likely that TSG-6 plays a similar modulatory role in human rheumatoid arthritis and related diseases and may have potential for the treatment of autoimmune arthritis in humans.

Ovulation: new dimensions and new regulators of the inflammatory-like response

Ovulation is a complex process that is initiated by the lutenizing hormone surge and is controlled by the temporal and spatial expression of specific genes. This review focuses on recent endocrine, biochemical, and genetic information that has been derived largely from the identification of new genes that are expressed in the ovary, and from knowledge gained by the targeted deletion of genes that appear to impact the ovulation process. Two main areas are described in most detail. First, because mutant mouse models indicate that appropriate formation of the cumulus matrix is essential for successful ovulation, genes expressed in the cumulus cells and those that control cumulus expansion are discussed. Second, because mice null for the progesterone receptor fail to ovulate and are ideal models for dissecting the critical events downstream of progesterone receptor, genes expressed in mural granulosa cells that regulate the expression of novel proteases are described.

A novel allelic variant of the human TSG-6 gene encoding an amino acid difference in the CUB module. Chromosomal localization, frequency analysis, modeling, and expression

Tumor necrosis factor-stimulated gene-6 (TSG-6) encodes a 35-kDa protein, which is comprised of contiguous Link and CUB modules. TSG-6 protein has been detected in the articular joints of osteoarthritis (OA) patients, with little or no constitutive expression in normal adult tissues. It interacts with components of cartilage matrix (e.g. hyaluronan and aggrecan) and thus may be involved in extracellular remodeling during joint disease. In addition, TSG-6 has been found to have anti-inflammatory properties in models of acute and chronic inflammation. Here we have mapped the human TSG-6 gene to 2q23.3, a region of chromosome 2 linked with OA. A single nucleotide polymorphism was identified that involves a non-synonymous G --> A transition at nucleotide 431 of the TSG-6 coding sequence, resulting in an Arg to Gln alteration in the CUB module (at residue 144 in the preprotein). Molecular modeling of the CUB domain indicated that this amino acid change might lead to functional differences. Typing of 400 OA cases and 400 controls revealed that the A(431) variant identified here is the major TSG-6 allele in Caucasians (with over 75% being A(431) homozygotes) but that this polymorphism is not a marker for OA susceptibility in the patients we have studied. Expression of the Arg(144) and Gln(144) allotypes in Drosophila Schneider 2 cells, and functional characterization, showed that there were no significant differences in the ability of these full-length proteins to bind hyaluronan or form a stable complex with inter-alpha-inhibitor.

Keratins and the keratinocyte activation cycle

In wound healing and many pathologic conditions, keratinocytes become activated: they turn into migratory, hyperproliferative cells that produce and secrete extracellular matrix components and signaling polypeptides. At the same time, their cytoskeleton is also altered by the production of specific keratin proteins. These changes are orchestrated by growth factors, chemokines, and cytokines produced by keratinocytes and other cutaneous cell types. The responding intracellular signaling pathways activate transcription factors that regulate expression of keratin genes. Analysis of these processes led us to propose the existence of a keratinocyte activation cycle, in which the cells first become activated by the release of IL-1. Subsequently, they maintain the activated state by autocrine production of proinflammatory and proliferative signals. Keratins K6 and K16 are markers of the active state. Signals from the lymphocytes, in the form of Interferon-gamma, induce the expression of K17 and make keratinocytes contractile. This enables the keratinocytes to shrink the provisional fibronectin-rich basement membrane. Signals from the fibroblasts, in the form of TGF-beta, induce the expression of K5 and K14, revert the keratinocytes to the healthy basal phenotype, and thus complete the activation cycle.

Isolation and functional characterisation of the promoter region of the human prion protein gene

The human prion protein gene (PRNP) encodes a 33-35 kDa cell surface protein that is highly expressed in the central nervous system and is vital to the pathogenesis of prion diseases. We have characterised the promoter region of PRNP as a first step towards defining the mechanisms regulating its expression. Sequence analysis of a 2.7 kb genomic DNA fragment containing exon I and the 5'-flanking region of PRNP, revealed a number of putative transcriptional factor binding sites, including Sp1, Ap-1, Ap-2 and a CCAAT box. Transient transfection assays in tissue culture cells with constructs consisting of the wild-type and deletion mutants of the PRNP 2.7 kb genomic fragment driving a luciferase reporter gene, demonstrate an active promoter within a 273 bp region (-148 to +125, relative to the cap site).

The constitutive activation of the CEF-4/9E3 chemokine gene depends on C/EBPbeta in v-src transformed chicken embryo fibroblasts

The CEF-4/9E3 chemokine gene is expressed constitutively in chicken embryo fibroblasts (CEF) transformed by the Rous sarcoma virus (RSV). This aberrant induction is controlled at the transcriptional and post-transcriptional levels. Transcriptional activation depends on multiple elements of the CEF-4 promoter composing a Src-responsive-Unit or SRU. The SRU includes a TPA responsive element, a PRDII/kappaB domain and a CAAT box. In this report, we identify C/EBPbeta as a component of the trans-acting factor interacting with the CAAT box of the CEF-4 promoter. In addition, we show that C/EBPbeta binds to a second element located in proximity of the TRE. A mutation of this distal CAAT box impaired the activation of the CEF-4 promoter by pp60(v-src) indicating that this element is also part of the SRU. Using the RCASBP retroviral vector, we expressed a dominant negative mutant of C/EBPbeta (designated Delta184-C/EBPbeta) in RSV-transformed CEF. Delta184-C/EBPbeta decreased the accumulation of the CEF-4 mRNA and activation of the CEF-4 promoter by pp60(v-src). The induction of the Cox-2 gene (CEF-147) was also reduced by Delta184-C/EBPbeta. The effect of the dominant negative mutant was observed within 1 h of the activation of a thermolabile pp60(v-src) suggesting that C/EBPbeta is an early target of v-src transformation. The dominant negative mutant did not inhibit the transformation of CEF by RSV and in fact accentuated the transformed cell phenotype. Therefore, the activation of C/EBPbeta is important for the expression of v-src regulated genes but is not required for the in vitro transformation of CEF by pp60(v-src).

Interleukin-1 induces transcription of keratin K6 in human epidermal keratinocytes

Keratinocytes respond to injury by releasing the proinflammatory cytokine interleukin-1, which serves as the initial "alarm signal" to surrounding cells. Among the consequences of interleukin-1 release is the production of additional cytokines and their receptors by keratinocytes and other cells in the skin. Here we describe an additional effect of interleukin-1 on keratinocytes, namely the alteration in the keratinocyte cytoskeleton in the form of the induction of keratin 6 expression. Keratin 6 is a marker of hyperproliferative, activated keratinocytes, found in wound healing, psoriasis, and other inflammatory disorders. Skin biopsies in organ culture treated with interleukin-1 express keratin 6 in all suprabasal layers of the epidermis, throughout the tissue. In cultured epidermal keratinocytes, the induction of keratin 6 is time and concentration dependent. Importantly, only confluent keratinocytes respond to interleukin-1, subconfluent cultures do not. In the cells starved of growth factors, epidermal growth factor or tumor necrosis factor-alpha, if added simultaneously with interleukin-1, they synergistically augment the effects of interleukin-1. Using DNA-mediated cell transfection, we analyzed the molecular mechanisms regulating the keratin 6 induction by interleukin-1, and found that the induction occurs at the transcriptional level. We used a series of deletions and point mutations to identify the interleukin-1 responsive DNA element in the keratin 6 promoter, and determined that it contains a complex of C/EBP binding sites. The transcription factor C/EBPbeta binds this element in vitro, and the binding is augmented by pretreatment of the cells with interleukin-1. The interleukin-1 responsive element is clearly distinct from the epidermal growth factor responsive one, which means that the proinflammatory and proliferative signals independently regulate the expression of keratin 6. Thus, interleukin-1 initiates keratinocyte activation not only by triggering additional signaling events, but also by inducing directly the synthesis of keratin 6 in epidermal keratinocytes, and thus changing the composition of their cytoskeleton.

Multiple regulatory elements in the murine stromelysin-3 promoter. Evidence for direct control by CCAAT/enhancer-binding protein beta and thyroid and retinoid receptors

Stromelysin-3 (ST3) belongs to the matrix metalloproteinase (MMPs) family, a protease family involved in tissue remodeling. Although this family of enzymes is regulated by nuclear receptors, few hormone-responsive elements have been demonstrated in MMP promoters. In order to identify regulatory elements and/or factors that control the expression of the mouse st3 gene, we have analyzed genomic sequences encompassing 5 kilobase pairs of the ST3 promoter. Analysis of these sequences revealed several CCAAT/enhancer-binding proteins (C/EBP) and retinoic acid-responsive elements (RAREs), as well as one thyroid-responsive element. However, in contrast to most MMP promoters, no AP-1-binding sites were identified. Specific binding activities were demonstrated for all elements. Consistent with previous reports, retinoid X receptor is required for maximal binding to the ST3 RAREs and the TRE. The ST3-C/EBP element was shown to mediate dose-dependent promoter activation by C/EBPbeta. Among the RAREs, the proximal DR1-RARE was shown to be sufficient for ST3 promoter activation by ligand-bound retinoid receptors, whereas the two distal DR2-RAREs appear to be involved more in the control of base-line promoter activity. Accordingly, ST3 expression was induced by retinoic acid and was reduced in cells where specific retinoic acid receptors had been inactivated. The involvement of these conserved regulatory elements is discussed in the context of physiological or pathological situations associated with st3 expression. Our findings therefore assign to C/EBP, retinoids, and thyroid hormone important roles in the regulation of ST3 gene expression.

Expression of tumor necrosis factor-stimulated gene-6 in the rat ovary in response to an ovulatory dose of gonadotropin

Current evidence supports the hypothesis that the biochemical events of mammalian ovulation are analogous to an acute inflammatory reaction. This study reveals that tumor necrosis factor-stimulated gene-6 (TSG-6), which encodes a member of the superfamily of hyaluronan-binding proteins that is specifically translated in inflammatory reactions, is expressed in ovarian follicles that have been induced to ovulate. Immature Wistar rats were primed with 10 IU equine CG s.c.; and 48 h later, the 12-h ovulatory process was initiated by 10 IU human CG (hCG), s.c.. Ovarian RNA was extracted at 0, 2, 4, 8, 12, and 24 h after the primed animals were injected with hCG. The RNA extracts were used for RT-PCR differential display of amplified complementary DNAs (cDNAs) that represented gene expression in the stimulated ovarian tissue. Northern analysis of one of the differentially amplified cDNAs confirmed that it was part of a gene that was substantially up-regulated at 4-8 h after the ovaries had been stimulated by hCG. Subcloning and sequence analysis revealed that the cDNA matched the gene for TSG-6. In situ hybridization indicated that the TSG-6 messenger RNA was primarily located in the cumulus mass and the antral granulosa cells of large ovarian follicles. In conclusion, the data show that expression of TSG-6 is an integral part of the cascade of inflammatory-like changes that occur in an ovulatory follicle in response to a trophic hormone that couples with luteinizing hormone/hCG receptors.

Tumour necrosis factor-alpha regulation of prostaglandin H synthase-2 transcription is not through nuclear factor-kappaB in amnion-derived AV-3 cells

Tumour necrosis factor (TNF)-alpha-stimulated prostaglandin (PG) E(2)biosynthesis by amnion-derived AV3 cells is accompanied by increased prostaglandin H synthase (PGHS)-2 mRNA expression. PGHS-1 mRNA expression is unchanged. PGHS-2 promoter-reporter constructs (-891/+9 and 5' deletions thereof) were prepared. The regions containing concensus nuclear factor kappaB (NF-kappaB) elements (-447/-438 and -222/-213) did not enhance promoter activity. Elements associated with both basal and TNF-alpha-stimulated expression lie between bases -52 and -203. Site-directed mutagenesis of nuclear factor of interleukin-6 (NF-IL6) and cyclic AMP response elements (CREs) in this region reduced both basal and induced transcriptional activity of the -203/+9 construct by over 95 per cent. Electrophoretic mobility-shift assays using oligonucleotides derived from these sites demonstrated formation of specific DNA-protein complexes. Both NF-IL6 and CRE unlabelled oligonucleotides inhibited complex formation with the NF-IL6 oligonucleotide probe. Unlabelled CRE oligonucleotide also effectively inhibited formation of the complex with the CRE probe, but reduced effectiveness was observed when the NF-IL6 oligonucleotide was the competitor. Finally, unlabelled, consensus NF-kappaB oligonucleotide failed to compete for either probe. TNF-alpha treatment did not increase levels of these complexes. Thus NF-kappaB does not enhance basal or TNF-alpha-responsive PGHS-2 transcription in amnion-derived AV-3 cells. A permissive role for NF-IL6/CRE binding proteins in regulating PGHS-2 expression in these cells is indicated, but requires further clarification.

Inflammatory versus proliferative processes in epidermis. Tumor necrosis factor alpha induces K6b keratin synthesis through a transcriptional complex containing NFkappa B and C/EBPbeta

Epidermal keratinocytes respond to injury by becoming activated, i.e. hyperproliferative, migratory, and proinflammatory. These processes are regulated by growth factors and cytokines. One of the markers of activated keratinocytes is keratin K6. We used a novel organ culture system to show that tumor necrosis factor alpha (TNFalpha) induces the expression of K6 protein and mRNA in human skin. Multiple isoforms of K6 are encoded by distinct genes and have distinct patterns of expression. By having shown previously that proliferative signals, such as epidermal growth factor (EGF), induce expression of the cytoskeletal protein keratin K6b, we here demonstrate that the same isoform, K6b, is also induced by TNFalpha, a proinflammatory cytokine. Specifically, TNFalpha induces the transcription of the K6b gene promoter. By using co-transfection, specific inhibitors, and antisense oligonucleotides, we have identified NFkappaB and C/EBPbeta as the transcription factors that convey the TNFalpha signal. Both transcription factors are necessary for the induction of K6b by TNFalpha and act as a complex, although only C/EBPbeta binds the K6b promoter DNA. By using transfection, site-directed mutagenesis, and footprinting, we have mapped the site that responds to TNFalpha, NFkappaB, and C/EBPbeta. This site is separate from the one responsive to EGF and AP1. Our results show that the proinflammatory (TNFalpha) and the proliferative (EGF) signals in epidermis separately and independently regulate the expression of the same K6b keratin isoform. Thus, the cytoskeletal responses in epidermal cells can be precisely tuned by separate proliferative and inflammatory signals to fit the nature of the injuries that caused them.

Proximal promoter of the surfactant protein D gene: regulatory roles of AP-1, forkhead box, and GT box binding proteins

Surfactant protein D (SP-D) plays roles in pulmonary host defense and surfactant homeostasis and is increased following lung injury. Because AP-1 proteins regulate cellular responses to diverse environmental stimuli, we hypothesized that the conserved AP-1 motif (at -109) and flanking sequences in the human SP-D promoter contribute to the regulation of SP-D expression. The AP-1 sequence specifically bound to fra-1, junD, and junB in H441 lung adenocarcinoma nuclear extracts. Mutagenesis of the AP-1 motif in a chloramphenicol acetyltransferase reporter construct containing 285 base pairs of upstream sequence nearly abolished promoter activity, and co-transfection of junD significantly increased wild type but not mutant promoter activity. The sequence immediately downstream of the AP-1 element contained a binding site for HNF-3 (FOXA), and simultaneous mutation of this site (fox-d) and an upstream FoxA binding site (-277, fox-u) caused a 4-fold reduction in chloramphenicol acetyltransferase activity. Immediately upstream of the AP-1-binding site, we identified a GT box-containing positive regulatory element. Despite finding regions of limited homology to the thyroid transcription factor 1-binding site, SP-D promoter activity did not require thyroid transcription factor 1. Thus, transcriptional regulation of SP-D gene expression involves complex interactions with ubiquitous and lineage-dependent factors consistent with more generalized roles in innate immunity.

Synergistic induction of mouse serum amyloid A3 promoter by the inflammatory mediators IL-1 and IL-6

Serum amyloid A (SAA), one of the major acute-phase proteins, increases several hundredfold in concentration in plasma following acute inflammation, primarily as a result of a 200-fold increase in its transcription rate. We have previously demonstrated that a 350-bp promoter fragment from the mouse SAA3 gene could confer conditioned medium-induced expression in cultured cells. The induction is mediated through a 42-bp distal response element (DRE) consisting of three functional regulatory elements. In this study, we show that interleukin-1 (IL-1) is the major cytokine in the conditioned medium responsible for SAA3 induction, and the induction by IL-1 can be effectively blocked by H-7, a protein kinase C inhibitor. Although IL-6 alone had no effect on SAA3 promoter activity, the addition of IL-6 and IL-1 resulted in dramatic synergistic activation of the reporter gene. We further show that the DRE is both necessary and sufficient to confer synergistic induction by IL-1 and IL-6. Moreover, individual mutation of the three regulatory elements within DRE either abolished or drastically reduced the synergistic induction. Our results indicate that synergistic activation of SAA3 promoter by IL-1 and IL-6 is achieved through integration of signals triggered by these two cytokines onto the DRE and that all three functionally distinct regulatory elements in the DRE are required to effectively and fully activate SAA3 gene transcription.

Regulation of spontaneous and TNF/IFN-induced IL-6 expression in two human ovarian-carcinoma cell lines

Autocrine and paracrine production of interleukin-6 (IL-6) is considered to be involved in the ongoing proliferation of ovarian-cancer cells. In view of the variability in IL-6 expression between various ovarian-cancer cells, we questioned whether differences in IL-6-gene regulation might be observed in ovarian tumor cells with and without IL-6 expression. The CAOV-3 cell line spontaneously secreted IL-6, which was enhanced by tumor necrosis factor-alpha (877 +/- 89 vs. 8,452 +/- 1,762 pg/ml, x +/- sd, p < 0.01). The electrophoretic mobility shift assay (EMSA) demonstrated that basic IL-6 expression was associated with DNA binding of activator protein-1 (AP-1) and nuclear factor IL-6 (NF-IL6). Nuclear factor kappa-B (NF-KB), which consisted mainly of p65-NF-KB was induced in response to TNF-alpha stimulation. A2780 cells did not express IL-6, either spontaneously or after stimulation with TNF-alpha. EMSAs, showed spontaneous AP-1 but no NF-IL6 or NF-KB DNA binding. TNF-alpha stimulation enhanced AP-1 and induced NF-KB but no NF-IL6 DNA binding in these cells. NF-IL6 protein, however, was detected in nuclear extracts of these cells by Western blotting. In contrast, IL-6-promoter transfection studies showed no difference in promoter activation between CAOV-3 and A2780. This study reveals that differential IL-6-gene expression observed in ovarian-cancer cell lines is independent of NF-IL6 activation.

Regulated Expression and Functional Role of the Transcription Factor CHOP (GADD153) in Erythroid Growth and Differentiation

The hematopoietic growth factor erythropoietin (Epo) triggers changes in the expression of genes that encode important regulators of erythroid cell growth and differentiation. We now report that Epo markedly upregulates chop (gadd153) expression and that this transcription factor plays a role in erythropoiesis. Using a differential hybridization assay, we isolated a full-length cDNA ofchop as an Epo upregulated gene in Rauscher murine erythroleukemia cells. RNase protection assays demonstrated that Epo or dimethyl sulfoxide induction increased steady-state mRNA levels 10- to 20-fold after 24 to 48 hours. Western blot analysis confirmed a marked increase in CHOP protein. Among the other c/ebp family members, only c/ebp β was also upregulated during erythroid differentiation. Among normal hematopoietic cells examined, steady-state mRNA levels were highest in erythroid cells, with levels peaking during terminal differentiation. Transient overexpression ofchop in Rauscher cells resulted in a significant increase in Epo- or dimethyl sulfoxide (DMSO)-induced hemoglobinization, further linking chop upregulation to erythroid differentiation. Artificial downregulation of chop in normal murine bone marrow cells with antisense oligodeoxynucleotides inhibited colony-forming unit-erythroid (CFU-E)–derived colony growth in a concentration-dependent manner. Burst-forming unit-erythroid (BFU-E)–derived colony growth was not affected. Using a Far Western type of analysis, we detected several potential CHOP binding partners among the nuclear proteins of Rauscher cells. Importantly, the number and relative abundance of these proteins changed with differentiation. The results strongly suggest that CHOP plays a role in erythropoiesis, possibly through interactions with both C/EBP and non-C/EBP family members.

Phorbol ester-induced transcription of a fibroblast growth factor-binding protein is modulated by a complex interplay of positive and negative regulatory promoter elements

Earlier studies from our laboratory showed that a secreted binding protein for fibroblast growth factors (FGF-BP) is expressed at high levels in squamous cell carcinoma (SCC) cell lines. Overexpression studies or conversely reduced expression of FGF-BP by ribozyme targeting have elucidated a direct role of this protein in angiogenesis during tumor development. We have also observed a significant up-regulation of FGF-BP during TPA (12-O-tetradecanoylphorbol-13-acetate) promotion of skin cancer. Here we investigate the mechanism of TPA induction of FGF-BP gene expression in the human ME-180 SCC cell line. We found that TPA increased FGF-BP mRNA levels in a time- and dose-dependent manner mediated via the protein kinase C signal transduction pathway. Results from actinomycin D and cycloheximide experiments as well as nuclear transcription assays revealed that TPA up-regulated the steady-state levels of FGF-BP mRNA by increasing its rate of gene transcription independently of de novo protein synthesis. We isolated the human FGF-BP promoter and determined by deletion analysis that TPA regulatory elements were all contained in the first 118 base pairs upstream of the transcription start site. Further mutational analysis revealed that full TPA induction required interplay between several regulatory elements with homology to Ets, AP-1, and CAATT/enhancer binding protein C/EBP sites. In addition, deletion or mutation of a 10-base pair region juxtaposed to the AP-1 site dramatically increased TPA induced FGF-BP gene expression. This region represses the extent of the FGF-BP promoter response to TPA and contained sequences recognized by the family of E box helix-loop-helix transcription factors. Gel shift analysis showed specific and TPA-inducible protein binding to the Ets, AP-1, and C/EBP sites. Furthermore, distinct, specific, and TPA-inducible binding to the imperfect E box repressor element was also apparent. Overall, our data indicate that TPA effects on FGF-BP gene transcription are tightly controlled by a complex interplay of positive elements and a novel negative regulatory element.

Epidermal signal transduction and transcription factor activation in activated keratinocytes

In the area of biology, many laboratories around the world are dissecting and characterizing signal transduction mechanisms and transcription factors responsive to various growth factors and cytokines, in various cell types. However, because of the differences in systems used, it is not clear whether these systems coexist, whether they interact meaningfully, and what their relative roles are. Epidermal keratinocytes are the perfect cell type in which to integrate this knowledge, because in these cells these mechanisms are known to be relevant. Keratinocytes both produce and respond to growth factors and cytokines, especially in pathological conditions and during wound healing, when the physiology of keratinocytes is altered in a way specified by the presence of a subset growth factors and cytokines. In fact, growth factors and cytokines cause the major changes in gene expression and keratinocyte behavior in various cutaneous diseases. In some cases, such as in wound healing, these responses are highly beneficial; in others, such as in psoriasis, they are pathological. It is not clear at present which are operating in which conditions, which are important for the healing process and which are harmful. Growth factors and cytokines affect keratinocytes sometimes simultaneously, at other times individually. In this manuscript we describe the signal transduction pathways responsible for the effects of interferons, the EGF/TGF alpha family and the TNF alpha/IL-1 family of signaling molecules. We also describe the important transcription factors known to be functional in epidermis, with particular emphasis on those factors that are activated by growth factors and cytokines. Finally, we describe what is known about transcriptional regulation of keratin genes, especially those specifically expressed in pathological processes in the epidermis. We expect that the enhanced understanding of the pathways regulating gene expression in keratinocytes will identify the pharmacological targets, the signal transducing proteins and the corresponding transcription factors, used by growth factors and cytokines. This research will led to development of compounds precisely aimed at those targets, allowing us to isolate and inhibit the harmful side effects of growth factors and cytokines. Such compounds should lead to highly specific and therefore more effective treatments of the cutaneous disorders in which these pathways play significant roles.

Interleukin-1 beta and dexamethasone regulate gene expression of prostaglandin H synthase-2 via the NF-kB pathway in human amnion derived WISH cells

Interleukin-1beta (IL-1beta) stimulated PGE2 synthesis in human amnion derived WISH cells, whereas dexamethasone blocked IL-1beta-mediated stimulation of PGE2 production. Sequence analysis of the 5'-flanking region of the human prostaglandin H synthase-2 (PGHS-2) gene indicates two putative NF-kB binding sites. Mutation of a single site or both sites resulted in significantly decreased activity of the PGHS-2 promoter. IL-1beta treatment increased significantly the native promoter activity and this increase was attenuated by using the NF-kB-mutant promoter. Dexamethasone treatment also decreased the IL-1beta mediated stimulation of the PGHS-2 native promoter but not the NF-kB mutant promoter. Furthermore, the involvement of the NF-kB was supported by electrophoretic mobility shift assay which revealed an increased nuclear binding of the NF-kB probe upon IL-1beta induction and a decreased nuclear binding of the NF-kB probe upon dexamethasone pre-treatment. These results provide convincing evidence that NF-kB may mediate the IL-1beta stimulation of PGHS-2 gene expression as well as the dexamethasone inhibition of the IL-1beta induction process in WISH cells.

Transcriptional regulation during B cell development

Information is increasingly available concerning the molecular events that occur during primary and antigen-dependent stages of B cell development. In this review the roles of transcription factors and coactivators are discussed with respect to changes in expression patterns of various genes during B cell development. Transcriptional regulation is also discussed in the context of developmentally regulated immunoglobulin gene V(D)J recombination, somatic hypermutation, and isotype switch recombination.

The transcriptional activation pattern of lipopolysaccharide binding protein (LBP) involving transcription factors AP-1 and C/EBP beta

Lipopolysaccharide (LPS) Binding Protein (LBP) is an acute phase protein with the ability to recognize bacterial LPS and transport it to the CD14 molecule or into HDL particles. It is synthesized in hepatocytes and secreted into the blood stream. LBP levels significantly rise during the acute phase response and levels of LBP may be important for an appropriate host reaction to bacterial challenge and for developing the sepsis syndrome. In order to elucidate the mechanisms of LBP regulation we investigated its transcription pattern and performed promoter studies under experimental conditions mimicking an acute phase scenario. In human hepatoma cell lines stimulation with IL-1 beta, IL-6, TNF-alpha and dexamethasone leads to strong transcriptional activation of the LBP gene in a dose- and time-dependent manner. IL-6 alone induces LBP significantly, whereas IL-1 beta mainly increases the IL-6 effect when applied in combination. Our results furthermore show that AP-1 and C/EBP beta are transcription factors involved in the activation of the LBP gene, as revealed by Luciferase reporter gene analysis and electromobility shift assays. Elucidating the mechanism of transcriptional activation of LBP potentially may help in understanding host-pathogen response patterns and mechanisms involved in the acute phase reaction and in the pathophysiology of sepsis.

Cross-talk between transcription factors NF-kappa B and C/EBP in the transcriptional regulation of genes

The study of the acute phase response has attracted substantial interest, not only for its medical implication, but also its provision as an excellent system with which to elucidate the molecular mechanisms involved in the modulation of gene expression. Our previous data suggest that the synergistic induction of the major acute phase reactant serum amyloid A2 (SAA2) expression by interleukin-1 (IL-1) and interleukin-6 (IL-6) is mediated by two families of transcription factors, namely NF-kappa B and C/EBP. To understand the molecular mechanisms of this synergy, we have undertaken a molecular dissection of the factors involved in the formation of the regulatory complex. Electrophoretic mobility shift analysis indicates that NF-kappa B p65 (RelA) and p50, but not p52 or c-Rel, bind specifically to the NF-kappa B site of the SAA2 promoter in response to IL-1 stimulation. In addition, C/EBP beta and C/EBP delta, but not C/EBP alpha, bind specifically to the C/EBP site of SAA2 in response to IL-6 stimulation. Transient co-transfection analysis indicates that co-operative association of NF-kappa B p65 with C/EBP beta and, in particular, with C/EBP delta, results in synergistic transcriptional activation of the SAA2 promoter. When incubated together, NF-kappa B p65 and C/EBP beta form a ternary complex by direct protein/protein interaction. Mutational analysis demonstrates that the C-terminus region of the Rel homology domain (RHD) and the C-terminus of the activation domain of p65 are important for its interaction with C/EBP beta. These results suggest the NF-kappa B and C/EBP may form a new complex of transcription factors that mediates the synergistic induction of SAA2 by IL-1 and IL-6.

Growth factor and cytokine-regulated hyaluronan-binding protein TSG-6 is localized to the injury-induced rat neointima and confers enhanced growth in vascular smooth muscle cells

Hyaluronan (HA) and HA-binding proteins have been implicated in a diverse array of biological processes, including development, tissue repair, and tumor invasion. However, the role of HA and HA-binding proteins in atherosclerosis and restenosis is poorly understood. PS4 (TSG-6) is a HA-binding protein expressed by cultured vascular smooth muscle cells (SMCs) in response to serum and growth factor stimulation. To delineate a possible role for TSG-6 in vascular disease progression, we have characterized its expression in cultured SMCs and in a rat vascular injury model, and we have studied the effect of constitutive overexpression of TSG-6 on SMC behavior. We found that interleukin-1 (IL-1) but not tumor necrosis factor or interleukin-6 was able to stimulate TSG-6 expression in SMCs. The IL-1 pathway could be distinguished from the growth factor pathway by its insensitivity to protein synthesis inhibitors. Furthermore, epidermal growth factor, fibroblast growth factor-1, and transforming growth factor-beta1 were all capable of augmenting maximum IL-1-induced expression of TSG-6. To gain further insight into the function of TSG-6 in SMCs, we examined the effect of constitutive overexpression of TSG-6 on these cells. We found that TSG-6-overexpressing cells grew >50% faster than control cells. Furthermore, this growth advantage became more evident in the absence of serum growth factors, with an average increase in cell number of 118% over control cells after 6 days. Consistent with these in vitro data, we observed intense immunostaining for TSG-6 in proliferating SMCs in the rat neointima after injury, whereas only an occasional cell was positive for TSG-6 in the medial layer and in nonballooned arteries. We conclude that the expression of TSG-6 is tightly controlled by growth factors and cytokines via two distinct pathways in SMCs and that overexpression of TSG-6 confers a growth advantage to these cells.

TSG-6: an IL-1/TNF-inducible protein with anti-inflammatory activity

The pro-inflammatory cytokines IL-1 and TNF-alpha are primary mediators of the acute phase response, the complex reaction of the mammalian organism to infection and injury. Among the genes activated by TNF-alpha and IL-1 in a variety of cells is TNF-stimulated gene 6 (TSG-6). The TSG-6 cDNA encodes a secreted 35 kDa glycoprotein which is abundant in synovial fluids of patients with various forms of arthritis and detectable in serum of patients with different inflammatory or autoimmune disorders. TSG-6 protein consists of two structural domains: a hyaluronan-binding link module, the characteristic domain of the hyaladherin family of proteins, and a C-terminal CUB domain, present in a variety of diverse proteins. TSG-6 forms a stable complex with components of the plasma protein inter-alpha-inhibitor (I[alpha]I), a Kunitz-type serine protease inhibitor. TSG-6 and I(alpha)I synergize to inhibit plasmin, a serine protease involved in the activation of matrix metalloproteinases which are part of the proteolytic cascade associated with inflammation. Recombinant human TSG-6 protein exerts a potent anti-inflammatory effect in a murine model of acute inflammation. Modulation of the proteolytic network associated with inflammatory processes may be a mechanism whereby TSG-6, in cooperation with I(alpha)I, inhibits inflammation. Activation of the TSG-6 gene by pro-inflammatory cytokines, presence of TSG-6 protein in inflammatory lesions and its anti-inflammatory effect suggest a role for TSG-6 in a negative feed-back control of the inflammatory response.

C/EBPbeta is a negative regulator of human papillomavirus type 11 in keratinocytes

We have evaluated the impact of the CCAAT enhancer-binding protein (C/EBP) transcription factors on human papillomavirus type 11 (HPV11). C/EBPbeta is in nuclei of cultured foreskin keratinocytes and binds its consensus sequence in HPV11 DNA. We have used the novel approach of depleting the availability of C/EBPs in vivo using nuclease-resistant oligomers containing C/EBP DNA binding sites. In cultured foreskin keratinocytes containing replicating HPV11 DNA, levels of both HPV11 transcripts and HPV DNA increase after treatment with oligomers; containing the C/EBPbeta DNA binding motif. These results indicate that C/EBPbeta is a repressor for HPV11 in keratinocytes.

Interleukin-1 signal transduction

Interleukin-1 (IL-1) is primarily an inflammatory cytokine, although it is capable of mediating a wide variety of effects on many different cell types. Nearly every known signal transduction pathway has been reported to be activated in response to IL-1. However, the significance of many of these signaling events is unclear, due to the use of different and sometimes unique cell lines in studying IL-1-initiated signal transduction. Complicating matters further is the lack of association in many studies between identified IL-1-induced signals and subsequent biological responses. In this article, we review what is known about IL-1 receptor signaling and, whenever possible, correlate signaling events to biological responses.

Promoter structure and transcriptional activation of the murine TSG-14 gene encoding a tumor necrosis factor/interleukin-1-inducible pentraxin protein

Human TNF-stimulated gene 14 (TSG-14) encodes a secreted 42-kDa glycoprotein that shows significant homology to proteins of the pentraxin family, which includes the acute phase reactants C-reactive protein and serum amyloid P component. Levels of TSG-14 protein (also termed PTX-3) become elevated in the serum of mice and humans after injection with bacterial lipopolysaccharide, but in contrast to conventional acute phase proteins, the bulk of TSG-14 synthesis in the intact organism occurs outside the liver. In the present study we cloned and partially sequenced murine genomic TSG-14 DNA. Analysis of the coding region predicts a high degree of amino acid sequence homology between murine and human TSG-14 (88 and 75% identity in the first and second exons, respectively). The promoter of the TSG-14 gene lacks consensus sequences for either a TATA box or CCAAT box. Primer extension analysis and S1 nuclease protection assay revealed one major transcription start site, situated within a consensus sequence for an initiator element. Sequence analysis of a approximately 1.4-kilobase pair fragment of the 5'-flanking region of the TSG-14 gene revealed the presence of numerous potential enhancer binding elements, including six NF-IL6-like sites, four AP-1, one AP-2, one NF-kB, two Sp1, two interferon-gamma-activated sites (GAS), one Hox-1.3, and five binding sites for Ets family members. Transfection of BALB/c 3T3 cells with promoter DNA fragments linked to the luciferase reporter gene revealed that the 5'-flanking region of the TSG-14 gene comprises elements that can mediate a basal level of transcription and inducibility by TNF.

Identification of a second region upstream of the mouse heme oxygenase-1 gene that functions as a basal level and inducer-dependent transcription enhancer

A 161-base pair fragment (AB1) approximately 10 kilobase pairs upstream of the transcription start site of the mouse heme oxygenase-1 gene functions as a basal level and inducer-dependent enhancer. AB1/chloramphenicol acetyltransferase fusion genes stably transfected into mouse hepatoma (Hepa) cells or L929 fibroblasts were activated 7-8- or 17-22-fold, respectively, after treatment of the cells with either CdCl2 or heme. The AB1 fragment is composed largely of three tandem repeats containing two conserved core elements, A and B. Part of core element A (TCCGGAGCTGTG) resembles the consensus-binding site for transcription factor AP-4, whereas core element B (GCTGAGTCANGG) includes the consensus-binding site (TGAGTCA) for the AP-1 family of transcription factors. Nuclear proteins from Hepa cells did not bind to any of the core A elements, but bound to all three copies of the core B element. AB1 derivatives with one or two mutant AP-1-binding elements exhibited reduced but measurable inducer-dependent enhancer activity, but mutation of all three AP-1-binding sites abolished activation by CdCl2 and heme and also by mercury chloride, zinc chloride, H2O2, sodium arsenate, and 12-O-tetradecanoylphorbol-13-acetate. Pretreatment of stably transfected L929 cells with protein kinase C inhibitors, but not with tyrosine kinase inhibitors or N-acetylcysteine, abrogated 12-O-tetradecanoylphorbol-13-acetate-dependent activation of the AB1/chloramphenicol acetyltransferase fusion gene. Induction by H2O2 was unaffected by the kinase inhibitors, but completely abolished by N-acetylcysteine. Heme-dependent induction was not significantly affected by any of these chemicals.

Activation of the TSG-6 gene by NF-IL6 requires two adjacent NF-IL6 binding sites

Tumor necrosis factor (TNF)-stimulated gene 6 (TSG-6) encodes a protein expressed during inflammation. We have previously shown that transcription factors of the NF-IL6 and AP-1 families cooperatively modulate activation of the TSG-6 gene by TNF or interleukin 1 (IL-1) through a promoter region that contains an NF-IL6 site (-106 to -114) and an AP-1 element (-126 to -119). In this study we report the identification of an additional NF-IL6 site (NF-IL6*) located at positions -92 to -83. Footprinting and electrophoretic mobility shift assay suggested that NF-IL6 binds with higher affinity to the newly identified NF-IL6* site than to the earlier identified promoter-distal NF-IL6 site and that the two sites cooperate in binding NF-IL6. TNF and IL-1 stimulate specific binding of nuclear proteins to the NF-IL6* site more efficiently than to the promoter-distal NF-IL6 site. Moreover, a mutation in the NF-IL6* site abolished transactivation of the TSG-6 promoter by NF-IL6 despite the presence of the intact promoter-distal NF-IL6 site. A mutation in the promoter-distal NF-IL6 site also greatly decreased activation of the TSG-6 promoter by NF-IL6. We conclude that the two NF-IL6 sites are functionally interdependent in the activation of the TSG-6 gene.