Interleukin-6 activates and regulates transcription factors of the interferon regulatory factor family in M1 cells

Cytokines in milk and the role of TGF-beta

Cytokines are required for normal growth and development of the mammary gland and TGF-β prominently represents an established effector of apoptosis, e.g., during involution of the mammary gland. By the control of intracellular signaling pathways, including JAK/STAT, MAPK, PI-3K, and NF-κB, cytokines efficiently regulate cell proliferation and inflammation in the breast. Therefore, cytokines are discussed also in a context of malignant mammary growth. As a group of tissue hormones produced by somatic cells or by cells from the immune system, cytokines are defined by their immunomodulatory potential. Over the past 40 years, multiple cytokines were identified in colostrum and milk. Importantly, cytokines derived from mammary secretions after birth are required for maturation of the immune system in the developing gastrointestinal tract from the suckling. Moreover, recent studies have further assessed the particular interactions between probiotic bacterial strains and cytokines. In light of the increasing prevalence of inflammatory diseases of the gastrointestinal system, the effects of probiotic microorganisms during milk fermentation may have immunotherapeutic potential in the future.

IRF-1 promotes inflammation early after ischemic acute kidney injury

Acute renal ischemia elicits an inflammatory response that may exacerbate acute kidney injury, but the regulation of the initial signals that recruit leukocytes is not well understood. Here, we found that IFN regulatory factor 1 (IRF-1) was a critical, early proinflammatory signal released during ischemic injury in vitro and in vivo. Within 15 min of reperfusion, proximal tubular cells of the S3 segment produced IRF-1, which is a transcription factor that activates proinflammatory genes. Transgenic knockout of IRF-1 ameliorated the impairment of renal function, morphologic injury, and inflammation after acute ischemia. Bone marrow chimera experiments determined that maximal ischemic injury required IRF-1 expression by both leukocytes and radioresistant renal cells, the latter identified as S3 proximal tubule cells in the outer medulla by in situ hybridization and immunohistochemistry. In vitro, reactive oxygen species, generated during ischemia/reperfusion injury, stimulated expression of IRF-1 in an S3 proximal tubular cell line. Taken together, these data suggest that IRF-1 gene activation by reactive oxygen species is an early signal that promotes inflammation after ischemic renal injury.

Posttranscriptional Inhibition of Gene Expression byMycobacterium tuberculosisOffsets Transcriptional Synergism with IFN-γ and Posttranscriptional Up-Regulation by IFN-γ

Host defense against Mycobacterium tuberculosis requires the cytokine IFN-gamma and IFN regulatory factor 1 (IRF-1), a transcription factor that is induced to high levels by IFN-gamma. Therefore, we chose to study regulation of IRF-1 expression as a model for effects of M. tuberculosis on response to IFN-gamma. We found that IRF-1 mRNA abundance increased far more than transcription rate in human monocytic THP-1 cells stimulated by IFN-gamma, but less than transcription rate in cells infected by M. tuberculosis. IFN-gamma stimulation of infected cells caused a synergistic increase in IRF-1 transcription, yet IRF-1 mRNA abundance was similar in uninfected and infected cells stimulated by IFN-gamma, as was the IRF-1 protein level. Comparable infection by Mycobacterium bovis bacillus Calmette-Guérin failed to induce IRF-1 expression and had no effect on the response to IFN-gamma. We also examined the kinetics of transcription, the mRNA t(1/2), and the distribution of IRF-1 transcripts among total nuclear RNA, poly(A) nuclear RNA, and poly(A) cytoplasmic RNA pools in cells that were infected by M. tuberculosis and/or stimulated by IFN-gamma. Our data suggest that infection by M. tuberculosis inhibits RNA export from the nucleus. Moreover, the results indicate that regulated entry of nascent transcripts into the pool of total nuclear RNA affects IRF-1 expression and that this process is stimulated by IFN-gamma and inhibited by M. tuberculosis. The ability of infection by M. tuberculosis to limit the increase in IRF-1 mRNA expression that typically follows transcriptional synergism may contribute to the pathogenicity of M. tuberculosis.

Transactivation of gp130 in myeloma cells

Receptor transactivation, i.e., interaction between unrelated receptor systems, is a growing theme in cytokine and growth factor signaling. In this study we reveal for the first time the ability of IFN-alpha to transactivate gp130 in myeloma cells. An epidermal growth factor receptor/gp130 chimeric receptor previously shown by us to transactivate endogenous gp130, provided a complementary tool to study the underlying mechanisms of receptor cross-talk. Further analysis revealed that transactivation of gp130 by IFN-alpha did not require the extracellular or trans-membrane domain of gp130. Moreover, transactivation of gp130 was critically dependent upon Janus kinase activation by the initiating receptor and correlated with rapid and sustained Janus kinase 1 and tyrosine kinase (Tyk) 2 tyrosine phosphorylation. Finally, transactivation of gp130 may be a common theme in myeloma cells, perhaps providing a mechanism for enhanced or qualitatively distinct cellular responses to specific stimuli.

Cytokine regulation of gingival fibroblast lysyl oxidase, collagen, and elastin

BACKGROUND

Systemic therapy with cyclosporin A, phenytoin, and nifedipine modulates cytokine levels in human gingival tissues. Functional relationships between altered cytokine levels and gingival extracellular matrix production are partially characterized. The present study investigates in cultured human gingival fibroblasts the regulation of lysyl oxidase, alpha-1 type I collagen, and elastin by selected cytokines that are elevated in drug-induced gingival overgrowth tissues.

METHODS

Normal human gingival fibroblasts were cultured and then treated with selected cytokines: interleukin (IL)-1beta, IL-6, platelet-derived growth factor (PDGF)-BB, and basic fibroblast growth factor (bFGF or FGF-2). Cells were harvested at intervals, and changes in lysyl oxidase enzyme activity, and in mRNA levels of lysyl oxidase, alpha-1 type I collagen, and elastin were determined.

RESULTS

bFGF reproducibly and significantly decreased human gingival fibroblast lysyl oxidase and alpha-1 type I collagen mRNA levels in a dose- and time-dependent manner; 1 nM bFGF reduced lysyl oxidase and collagen mRNA levels to 53% and to less than 10% of control after 48 hours of treatment. Interestingly, bFGF downregulated lysyl oxidase enzyme activity by 10% to 20%. IL-1, IL-6, and PDGF-BB did not significantly regulate lysyl oxidase enzyme activity, or alpha-1 type I collagen, elastin, and lysyl oxidase mRNA levels under the conditions tested.

CONCLUSIONS

Previous studies have shown that modulated levels of bFGF occur in gingiva as a result of certain pharmacologic therapies. The present study suggests that modulated levels of bFGF likely influence gingival connective tissue metabolism.

IFN regulatory factor-1-mediated transcriptional activation of mouse STAT-induced STAT inhibitor-1 gene promoter by IFN-gamma

STAT-induced STAT inhibitor-1 (SSI-1), also referred to as suppressor of cytokine signaling-1 and JAK-binding protein, is a member of a new family, the members of which are negative regulators of cytokine signals. SSI-1 is induced by various cytokines; however, the transcriptional mechanism of the SSI-1 gene is not fully understood. Here, we showed that transcription of the mouse SSI-1 gene was initiated from six adjoining sites accompanying three GC boxes and a single GC box-like element near them, but not from the TATA box or an initiator sequence. We also showed that IFN-gamma induced SSI-1 mRNA more strongly than IL-6 in NIH-3T3 fibroblasts and that this IFN-gamma effect was mediated by Stat1. To determine the signal pathway downstream of Stat1, transcriptional activities of several mutant promoters were examined. The region mediating stimulatory effect of IFN-gamma to the gene transcription was localized to the -88/-60 region containing three tandem GAAA units, named variant IFN-gamma-responsive element (VIRE), while four IFN-gamma activation site (GAS)-like elements located far upstream were not related to the IFN-gamma response. Gel-shift assays revealed that IFN-gamma induced IFN regulatory factor-1 (IRF-1) binding to VIRE, but not that of IRF-2 or three components of ISGF3. Furthermore, forced expression of IRF-1 mimicked and that of IRF-2 inhibited the stimulatory effect of IFN-gamma on SSI-1 gene transcription. Finally, mouse embryonal fibroblasts lacking IRF-1 showed impaired SSI-1 mRNA induction by IFN-gamma. These results demonstrated that IRF-1, which is induced by activation of Stat1, mediated transcriptional activation of the SSI-1 gene by IFN-gamma via VIRE.

Interferon in the Treatment of Multiple Myeloma

BACKGROUND: The role of interferon (IFN) in the treatment of multiple myeloma has been investigated for nearly two decades. The mechanisms underlying antitumor activity of IFN may be mediated by antiproliferative and immunomodulatory effects. The benefits of treatment remain controversial, and guidelines for the use of IFN in myeloma are needed. This review evaluates available data on the impact of IFN therapy on multiple myeloma. METHODS: A MEDLINE search of published prospective, randomized trials of IFN in multiple myeloma provided the data included in this review, as well as selected abstracts presented at international meetings. RESULTS: IFN has complex and pleiotropic effects on human myeloma lines and ex vivo myeloma cells. An antiproliferative effect with disruption of the IL-6-mediated growth loop may be crucial, but biologic heterogeneity in myeloma may have important clinical implications for response to IFN. IFN has demonstrable antitumor activity in multiple myeloma but appears to have a modest effect on overall survival when combined with chemotherapy during induction or when used as maintenance therapy. Most studies have shown a prolongation of the plateau phase of disease with IFN of variable duration of between four and 12 months. CONCLUSIONS: A reliable estimate of the benefit of IFN in the overall population of patients with myeloma is difficult to determine with discordant results from different trials. Possible sources of heterogeneity in randomized trials need to be identified, and recognition of subsets of patients who may benefit is important. Cost-benefit analyses with integration of quality-of-life data are essential for developing guidelines for the use of IFN in myeloma.

Human herpesvirus 8 encodes an interferon regulatory factor (IRF) homolog that represses IRF-1-mediated transcription

Human herpesvirus 8 (HHV-8) is the probable viral etiologic agent for Kaposi's sarcoma. The HHV-8 genome encodes viral interferon regulatory factor (vIRF), a gene product that has homology to the IRF family of transcription factors. We demonstrate that vIRF inhibits responses to type I and type II interferons and blocks IRF-1-mediated transcription. vIRF does not compete with IRF-1 for binding to DNA or complex directly with IRF-1. The ability of vIRF to block IRF-1-mediated transcription is independent of the DNA binding domains of both vIRF and IRF-1. These data suggest that vIRF may contribute to viral pathogenesis and cellular transformation by interfering with interferon- and IRF-1-mediated gene expression through a novel mechanism.

Interferon gamma-dependent induction of human intercellular adhesion molecule-1 gene expression involves activation of a distinct STAT protein complex

In response to interferon gamma (IFNgamma), intercellular adhesion molecule-1 (ICAM-1) is expressed on human keratinocytes, a cell type that is critically involved in cutaneous inflammation. An ICAM-1 5' regulatory region palindromic response element, pIgammaRE, has been shown to confer IFNgamma-dependent transcription enhancement. By electrophoretic mobility shift assays (EMSA), pIgammaRE forms a distinct complex with proteins from IFNgamma-treated human keratinocytes, termed gamma response factor (GRF). Binding of GRF is tyrosine phosphorylation-dependent, and mutations of pIgammaRE that disrupt the palindromic sequence or alter its spatial relationship abrogate GRF binding. Supershift EMSAs using antibodies to characterized STAT proteins suggest that GRF contains a Stat1alpha-like protein; however, non-ICAM-1 IFNgamma-responsive elements (REs) known to bind Stat1alpha homodimers fail to compete for GRF binding in EMSA, and pIgammaRE does not cross-compete with these REs that complex with homodimeric stat1alpha. The pIgammaRE x GRF complex also displays a distinctly different electrophoretic mobility compared to that of IFNgammaREs complexed to homodimeric Stat1alpha. These findings indicate that a distinct complex containing a Stat1alpha-like protein mediates IFNgamma-induced ICAM-1 gene transcription and identifies a subset of IFNgamma-responsive genes that appear to be regulated by this complex.

Cytokines in human milk: properties and potential effects upon the mammary gland and the neonate

Epidemiologic and immunologic studies of breastfed and nonbreastfed infants and investigations of certain biologic activities in human milk led to the identification of immunomodulating agents in human milk. Among them were the cytokines interleukin-1 beta (IL-1 beta); IL-6, IL-8, IL-10, granulocyte-colony stimulating factor, macrophage-colony stimulating factor (M-CSF), tumor necrosis factor-alpha, interferon-gamma, epithelial growth factor (EGF), transforming growth factor-alpha (TGF-alpha), and TGF-beta 2. Interferon-gamma may originate from T cells in milk; EGF, TGF-alpha, TGF-beta, M-CSF, IL-6, and IL-8 may be produced by mammary gland epithelium. Based upon their known functions, we hypothesize that cytokines influence the development and immunologic function of the mammary gland and the neonate. Those in vivo functions remain to be defined by future investigations.

Cloning, sequencing and partial functional characterization of the 5' region of the human p75 tumor necrosis factor receptor-encoding gene (TNF-R)

A 1887-bp region at the 5' flank of the human p75 tumor necrosis factor receptor (p75 TNF-R)-encoding gene was found to be active in driving expression of the luc (luciferase-encoding) reporter gene, suggesting that it contains the promoter for the receptor. Rather unexpectedly, a 1827-bp region at the 3' end of the first intron of the p75 TNF-R gene also displayed promoter activity. This activity may be artefactual, reflecting only the presence of an enhancer in this region; yet it also raises the possibility that p75 TNF-R is controlled by more than one promoter and that it encodes various forms of the receptor, or even other proteins. We present here the nucleotide sequences of the 5' flanking and intron regions. Possible implications for the transcriptional regulation of the p75 TNF-R gene are discussed.

The human interferon alpha-receptor protein confers differential responses to human interferon-beta versus interferon-alpha subtypes in mouse and hamster cell transfectants

The human interferon alpha-receptor (IFNAR gene product or IFN alpha R protein) was expressed in hamster CHO cells and in mouse A9 cells. The response of the IFN alpha R cDNA transfectants to human IFNs was studied by measuring induction of (2'-5') A synthetase (2'-5' AS). In the murine cells, the IFN alpha R protein conferred response to the human IFN-alpha-8 (alpha-B) subtype, but not to huIFN-alpha-2 (alpha-A) or to huIFN-beta. In murine huIFN alpha R cDNA transfectants, containing a hygromycin B resistance gene placed under the control of the 2'-5' AS gene Interferon Response Sequence (IRS), survival and growth of the cells in the presence of hygromycin B was induced by huIFN-alpha-8 but not by huIFN-alpha-2, indicating that the effect of huIFN alpha R is transcriptional. In hamster CHO cells, the huIFN alpha R protein conferred a completely different pattern of response to human IFN subtypes. Thus, the CHO-IFN alpha R transfectants responded to huIFN-beta by 2'-5' AS induction as well as by activation of the ISGF3 and IRF-1 transcription factors. In contrast, the CHO-IFN alpha R cells showed no response to huIFN-alpha-8. The differential response conferred by the huIFN alpha R protein in the two types of rodent cells, indicates that IFN subtype recognition is influenced by another component contributed by the rodent host cell. The ability of human cells, and of human-mouse hybrid cells containing human chromosome 21, to respond to all IFN subtypes is likely to depend also on interactions of the IFN alpha R protein with additional receptor components.

Differentiation primary response genes and proto-oncogenes as positive and negative regulators of terminal hematopoietic cell differentiation

By genetically manipulating hematopoietic cells of the myeloid lineage, including both normal cells and differentiation inducible leukemic cell lines, evidence was obtained to indicate that myeloid differentiation primary response (MyD) genes and proto-oncogenes, which are known to control cell growth, function as positive and negative regulators of terminal hematopoietic cell differentiation, which is associated with inhibition of cell growth, and, ultimately programmed cell death (apoptosis). Interferon regulatory factor-1 (IRF-1), an MyD gene induced by Interleukin 6 (IL-6) or Leukemia Inhibitory factor (LIF), plays a role in growth inhibition associated with terminal differentiation. Leucine zipper transcription factors of the fos/jun family, also identified as MyD genes, function as positive regulators of hematopoietic cell differentiation, increasing the propensity of myeloblastic leukemia cells to be induced for differentiation in vitro, and reducing the aggressiveness of their leukemic phenotype in vivo. The zinc finger transcription factor EGR-1, an MyD gene specifically induced upon macrophage differentiation, was shown to be essential for and to restrict differentiation along the macrophage lineage. Finally, evidence has been accumulating to indicate that the novel MyD genes--MyD116, MyD118 and gadd45 (a member in the MyD118 gene family)--play a role in growth arrest and apoptosis of hematopoietic cells, as well as other cell types. The proto-oncogenes c-myc and c-myb, known to regulate cellular growth, were shown to function as negative regulators of terminal differentiation. Both c-myc and c-myb are normally expressed in proliferating myeloblasts and suppressed following induction of differentiation. Deregulated and continuous expression of c-myc was shown to block terminal myeloid differentiation at an intermediate stage in the progression from immature blasts to mature macrophages, whereas deregulated and continuous expression of c-myb blocked the terminal differentiation program at the immature myeloblast stage. By manipulating myc function in conditional (differentiation inducible) mutant myeloblastic leukemia cell lines, expressing a chimeric mycer transgene, it was shown that there is a window during myeloid differentiation, after the addition of the differentiation inducer, when the terminal differentiation program switches from being dependent on c-myc suppression to becoming c-myc suppression independent, and where activation of c-myc has no apparent effect on mature macrophages. These myeloblastic leukemia cell lines provide a powerful tool to increase our understanding of the role of c-myc in normal hematopoiesis and in leukemogenesis, while also providing a strategy to clone myc target genes.(ABSTRACT TRUNCATED AT 250 WORDS)