Genomic characterization of a gamma-interferon-inducible gene (IP-10) and identification of an interferon-inducible hypersensitive site

Plasma CXCL10 correlates with HAND in HIV-infected women

HIV-associated neurocognitive disorder (HAND) is characterized by chronic immune activation. We aimed to identify biomarkers associated with HAND and to investigate their association with cognitive function and sex, in a homogenous cohort of HIV-infected (HIV+) young adults, parenterally infected during early childhood. One hundred forty-four HIV+ Romanian participants (51% women) without major confounders underwent standardized neurocognitive and medical evaluation in a cross-sectional study. IFN-γ, IL-1β, IL-6, CCL2, CXCL8, CXCL10, and TNF-α were measured in plasma in all participants and in cerebrospinal fluid (CSF) in a subgroup of 56 study participants. Biomarkers were compared with neurocognitive outcomes, and the influence of sex and HIV disease biomarkers was assessed. In this cohort of young adults (median age of 24 years), the rate of neurocognitive impairment (NCI) was 36.1%. Median current CD4+ count was 479 cells/mm3 and 36.8% had detectable plasma viral load. Women had better HIV-associated overall status. In plasma, controlling for sex, higher levels of IL-6 and TNF-α were associated with NCI (p < 0.05). Plasma CXCL10 showed a significant interaction with sex (p = 0.02); higher values were associated with NCI in women only (p = 0.02). Individuals with undetectable viral load had significantly lower plasma CXCL10 (p < 0.001) and CCL2 (p = 0.02) levels, and CSF CXCL10 (p = 0.01), IL-6 (p = 0.04), and TNF-α (p = 0.04) levels. NCI in young men and women living with HIV was associated with higher IL-6 and TNF-α in plasma, but not in the CSF. CXCL10 was identified as a biomarker of NCI specifically in women with chronic HIV infection.

Zika virus infection in pregnant rhesus macaques causes placental dysfunction and immunopathology

Zika virus (ZIKV) infection during pregnancy leads to an increased risk of fetal growth restriction and fetal central nervous system malformations, which are outcomes broadly referred to as the Congenital Zika Syndrome (CZS). Here we infect pregnant rhesus macaques and investigate the impact of persistent ZIKV infection on uteroplacental pathology, blood flow, and fetal growth and development. Despite seemingly normal fetal growth and persistent fetal-placenta-maternal infection, advanced non-invasive in vivo imaging studies reveal dramatic effects on placental oxygen reserve accompanied by significantly decreased oxygen permeability of the placental villi. The observation of abnormal oxygen transport within the placenta appears to be a consequence of uterine vasculitis and placental villous damage in ZIKV cases. In addition, we demonstrate a robust maternal-placental-fetal inflammatory response following ZIKV infection. This animal model reveals a potential relationship between ZIKV infection and uteroplacental pathology that appears to affect oxygen delivery to the fetus during development.

Zika virus infection during pregnancy can result in birth defects, but underlying pathogenesis at the maternal-fetal interface is unclear. Here, the authors use non-invasive in vivo imaging of Zika-infected rhesus macaques and show that infection results in abnormal oxygen transport across the placenta.

Predicting the functional consequences of non-synonymous single nucleotide polymorphisms in IL8 gene

Here we report an in-silico approach for identification, characterization and validation of deleterious non-synonymous SNPs (nsSNPs) in the interleukin-8 gene using three steps. In first step, sequence homology-based genetic analysis of a set of 50 coding SNPs associated with 41 rsIDs using SIFT (Sorting Intolerant from Tolerant) and PROVEAN (Protein Variation Effect Analyzer) identified 23 nsSNPs to be putatively damaging/deleterious in at least one of the two tools used. Subsequently, structure-homology based PolyPhen-2 (Polymorphism Phenotyping) analysis predicted 9 of 23 nsSNPs (K4T, E31A, E31K, S41Y, I55N, P59L, P59S, L70P and V88D) to be damaging. According to the conditional hypothesis for the study, only nsSNPs that score damaging/deleterious prediction in both sequence and structural homology-based approach will be considered as 'high-confidence' nsSNPs. In step 2, based on conservation of amino acid residues, stability analysis, structural superimposition, RSMD and docking analysis, the possible structural-functional relationship was ascertained for high-confidence nsSNPs. Finally, in a separate analysis (step 3), the IL-8 deregulation has also appeared to be an important prognostic marker for detection of patients with gastric and lung cancer. This study, for the first time, provided in-depth insights on the effects of amino acid substitutions on IL-8 protein structure, function and disease association.

Aptamers Against Pro- and Anti-Inflammatory Cytokines: A Review

Inflammatory disorders result from continuous inflammation in injured sites. Many molecules are involved in this process; the inhibition of which could prevent the inflammation. Chemokines are a group of these biological mediators which are categorized into pro-, anti-, and pro-/anti-inflammatory. Thus, targeting these essential molecules can be an effective way for prevention and control of inflammatory diseases. Various therapeutic agents have been developed for primary and secondary prevention of these disorders, but each of them has its own limitations. Aptamers, as novel therapeutic agents, are a new generation of drugs which could replace other medications even antibodies. Aptamer can bind to its target molecule to trap it and prohibit its function. Among large group of inflammatory cytokines, only 11 aptamers have been selected either against cytokines or their related receptors. These cytokines include interleukin (IL)-2, IL-6, IL-10, IL-11, IL-17, IL-32, TGF-β, TNF-α, IFN-γ, CCL2, and IP-10. Most of the isolated aptamers are against pro-inflammatory or dual function cytokines, and it seems that they could be used for diagnosis, prevention, and treatment of the related inflammatory diseases. Most of the aptamers have been tested in vitro, but so far, none of them has been approved for in vivo use. Given a vast number of inflammatory cytokines, more aptamers against this group of biological molecules will be selected in the near future. The available aptamers will also be tested in clinical trials. Therefore, a significant improvement is expected for the prevention and control of inflammatory disorders.

Chemokines and immunity

Chemokines are a large family of small cytokines and generally have low molecular weight ranging from 7 to 15kDa. Chemokines and their receptors are able to control the migration and residence of all immune cells. Some chemokines are considered pro-inflammatory, and their release can be induced during an immune response at a site of infection, while others are considered homeostatic and are involved in controlling of cells migration during tissue development or maintenance. The physiologic importance of this family of mediators is resulting from their specificity − members of the chemokine family induce recruitment of well-defined leukocyte subsets. There are two major chemokine sub-families based upon cysteine residues position: CXC and CC. As a general rule, members of the CXC chemokines are chemotactic for neutrophils, and CC chemokines are chemotactic for monocytes and sub-set of lymphocytes, although there are some exceptions. This review discusses the potential role of chemokines in inflammation focusing on the two best-characterized chemokines: monocyte chemoattractant protein-1, a CC chemokine, and interleukin-8, a member of the CXC chemokine sub-family.

NLRP3 deficiency protects from type 1 diabetes through the regulation of chemotaxis into the pancreatic islets

Studies in animal models and human subjects have shown that both innate and adaptive immunity contribute to the pathogenesis of type 1 diabetes (T1D). Whereas the role of TLR signaling pathways in T1D has been extensively studied, the contribution of the nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing protein (NLRP) 3 inflammasome pathway remains to be explored. In this study, we report that NLRP3 plays an important role in the development of T1D in the nonobese diabetic (NOD) mouse model. NLRP3 deficiency not only affected T-cell activation and Th1 differentiation, but also modulated pathogenic T-cell migration to the pancreatic islet. The presence of NLRP3 is critical for the expression of the chemokine receptors CCR5 and CXCR3 on T cells. More importantly, NLRP3 ablation reduced the expression of chemokine genes CCL5 and CXCL10 on pancreatic islet cells in an IRF-1-dependent manner. Our results suggest that molecules involved in chemotaxis, accompanied by the activation of the NLRP3 inflammasome, may be effective targets for the treatment of T1D.

Oncogenic CXCL10 signalling drives metastasis development and poor clinical outcome

Background:

The CXCL10/CXCR3 signalling mediates paracrine interactions between tumour and stromal cells that govern leukocyte trafficking and angiogenesis. Emerging data implicate noncanonical CXCL10/CXCR3 signalling in tumourigenesis and metastasis. However, little is known regarding the role for autocrine CXCL10/CXCR3 signalling in regulating the metastatic potential of individual tumour clones.

Methods:

We performed transcriptomic and cytokine profiling to characterise the functions of CXCL10 and CXCR3 in tumour cells with different metastatic abilities. We modulated the expression of the CXCL10/CXCR3 pathway using shRNA-mediated silencing in both in vitro and in vivo models of B16F1 melanoma. In addition, we examined the expression of CXCL10 and CXCR3 and their associations with clinical outcomes in clinical data sets derived from over 670 patients with melanoma and colon and renal cell carcinomas.

Results:

We identified a critical role for autocrine CXCL10/CXCR3 signalling in promoting tumour cell growth, motility and metastasis. Analysis of publicly available clinical data sets demonstrated that coexpression of CXCL10 and CXCR3 predicted an increased metastatic potential and was associated with early metastatic disease progression and poor overall survival.

Conclusion:

These findings support the potential for CXCL10/CXCR3 coexpression as a predictor of metastatic recurrence and point towards a role for targeting of this oncogenic axis in the treatment of metastatic disease.

Local selection of human populations shapes complex evolution patterns of CXCL10 gene

CXC motif chemokine 10 (CXCL10) is a small cytokine belonging to the CXC chemokine family, and it is secreted by several cell types in response to IFN-γ and regulates immune responses through the recruitment and activation of lymphocytes. As CXCL10 is very important in T-cell immunity and infectious diseases, we studied the effect of natural selection on the CXCL10 locus. By sequencing 74 individuals from three human populations, we found a complex pattern of natural selection acting on the CXCL10 locus. We discovered a signature of balancing selection in the European population with a significant positive Tajima's D value (2.57, P=0.005) and an excess of intermediate frequency alleles. However, we observed an excess of high frequency-derived alleles and a significant Fay and Wu's test statistics (P=0.015) in the Chinese population, which suggests that recent selective sweeps under positive selection had occurred. Also, there are a lot of alleles showing great frequency difference among populations. These results demonstrate that local selection has shaped CXCL10 evolution and indicates that there exist different actions of natural selection on the CXCL10 locus in different populations. This study provides insights into the likely relative roles of natural selection and population history in shaping today's genetic variation at the CXCL10 locus, indicates the relationship between adaptation to past infection and predisposition to autoimmunity in modern populations, improves our understanding of CXCL10 evolution, and motivates further investigations of the role of CXCL10 in infectious diseases and autoimmune diseases.

A Sendai virus-derived RNA agonist of RIG-I as a virus vaccine adjuvant

The innate immune system is responsible for recognizing invading pathogens and initiating a protective response. In particular, the retinoic acid-inducible gene 1 protein (RIG-I) participates in the recognition of single- and double-stranded RNA viruses. RIG-I activation leads to the production of an appropriate cytokine and chemokine cocktail that stimulates an antiviral state and drives the adaptive immune system toward an efficient and specific response against the ongoing infection. One of the best-characterized natural RIG-I agonists is the defective interfering (DI) RNA produced by Sendai virus strain Cantell. This 546-nucleotide RNA is a well-known activator of the innate immune system and an extremely potent inducer of type I interferon. We designed an in vitro-transcribed RNA that retains the type I interferon stimulatory properties, and the RIG-I affinity of the Sendai virus produced DI RNA both in vitro and in vivo. This in vitro-synthesized RNA is capable of enhancing the production of anti-influenza virus hemagglutinin (HA)-specific IgG after intramuscular or intranasal coadministration with inactivated H1N1 2009 pandemic vaccine. Furthermore, our adjuvant is equally effective at increasing the efficiency of an influenza A/Puerto Rico/8/34 virus inactivated vaccine as a poly(I·C)- or a squalene-based adjuvant. Our in vitro-transcribed DI RNA represents an excellent tool for the study of RIG-I agonists as vaccine adjuvants and a starting point in the development of such a vaccine.

Expression of chemokine receptor CXCR3 on T cells affects the balance between effector and memory CD8 T-cell generation

Generation of a robust immunological memory response is essential for protection on subsequent encounters with the same pathogen. The magnitude and quality of the memory CD8 T-cell population are shaped and influenced by the strength and duration of the initial antigenic stimulus as well as by inflammatory cytokines. Although chemokine receptors have been established to play a role in recruitment of effector CD8 T cells to sites of inflammation, their contribution to determination of T-cell fate and shaping of the long-lived memory T-cell population is not fully understood. Here, we investigated whether reduced access to antigen and inflammation through alterations in expression of inflammatory and homeostatic chemokine receptors has an impact on generation of effector and memory CD8 T cells. We found that in mice infected with lymphocytic choriomeningitis virus, colocalization of virus-specific CD8 T cells with antigen in spleen is dependent on expression of the inflammatory chemokine receptor, CXCR3. In addition, absence of CXCR3 expression on CD8 T cells leads to formation of fewer short-lived effector cells and more memory precursor cells. Furthermore, the memory CD8 T-cell population derived from CXCR3-deficient cells has fewer cells of the effector memory phenotype and exhibits a recall response of greater magnitude than that of WT cells. These data demonstrate that CD8 T-cell positioning relative to antigen and inflammatory cytokines in secondary lymphoid organs affects the balance of effector and memory T-cell formation and has both a quantitative and qualitative impact on the long-lived memory CD8 T-cell population.

Transcription factor redundancy ensures induction of the antiviral state

The transcriptional response to virus infection is thought to be predominantly induced by interferon (IFN) signaling. Here we demonstrate that, in the absence of IFN signaling, an IFN-like transcriptome is still maintained. This transcriptional activity is mediated from IFN-stimulated response elements (ISREs) that bind to both the IFN-stimulated gene factor 3 (ISGF3) as well as to IFN response factor 7 (IRF7). Through a combination of both in vitro biochemistry and in vivo transcriptional profiling, we have dissected what constitutes IRF-specific, ISGF3-specific, or universal ISREs. Taken together, the data presented here suggest that IRF7 can induce an IFN-like transcriptome in the absence of type-I or -III signaling and therefore provides a level of redundancy to cells to ensure the induction of the antiviral state.

Disruption of Th2 immunity results in a gender-specific expansion of IL-13 producing accessory NK cells during helminth infection

Host gender has previously been identified as a determining factor in the resolution of Trichuris muris infection in mice lacking IL-4 (IL-4KO BALB/c). Worm expulsion in these mice is delayed, but occurs in females. In this study we were able to demonstrate delayed expulsion occurs at day 26 post infection and is associated with the production of the key Th2-associated cytokine IL-13 by both CD4(+) T cells and an auxiliary DX5(+) NK cell source, as well as a concurrent reduction in proinflammatory cytokines. NK cell number was comparably increased in both sexes, but NK cells from male mice were found to express higher levels of the chemokine receptor CXCR3. Depletion of CD4(+) T cells completely prevented parasite expulsion, whereas loss of NK cells resulted in a mild, but significant delay. Furthermore, IL-18 is a cytokine with the capacity to enhance both Th1 and Th2 responses found to be dispensable for worm expulsion in female mice but was a key factor for the suppression of the Th2 response in male IL-4KO mice. In contrast neutralization of IFN-gamma resulted in a complete restoration of typical wild-type BALB/c expulsion kinetics. This study sheds further light on the role of accessory NK cells in supplementing the IL-13-driven immune response when normal Th2 immunity is disrupted, and further identifies host gender as a key factor in determining the generation of "NK cell help".

New microbicidal functions of tracheal glands: defective anti-infectious response to Pseudomonas aeruginosa in cystic fibrosis

Tracheal glands (TG) may play a specific role in the pathogenesis of cystic fibrosis (CF), a disease due to mutations in the cftr gene and characterized by airway inflammation and Pseudomonas aeruginosa infection. We compared the gene expression of wild-type TG cells and TG cells with the cftr DeltaF508 mutation (CF-TG cells) using microarrays covering the whole human genome. In the absence of infection, CF-TG cells constitutively exhibited an inflammatory signature, including genes that encode molecules such as IL-1alpha, IL-beta, IL-32, TNFSF14, LIF, CXCL1 and PLAU. In response to P. aeruginosa, genes associated with IFN-gamma response to infection (CXCL10, IL-24, IFNgammaR2) and other mediators of anti-infectious responses (CSF2, MMP1, MMP3, TLR2, S100 calcium-binding proteins A) were markedly up-regulated in wild-type TG cells. This microbicidal signature was silent in CF-TG cells. The deficiency of genes associated with IFN-gamma response was accompanied by the defective membrane expression of IFNgammaR2 and altered response of CF-TG cells to exogenous IFN-gamma. In addition, CF-TG cells were unable to secrete CXCL10, IL-24 and S100A8/S100A9 in response to P. aeruginosa. The differences between wild-type TG and CF-TG cells were due to the cftr mutation since gene expression was similar in wild-type TG cells and CF-TG cells transfected with a plasmid containing a functional cftr gene. Finally, we reported an altered sphingolipid metabolism in CF-TG cells, which may account for their inflammatory signature. This first comprehensive analysis of gene expression in TG cells proposes a protective role of wild-type TG against airborne pathogens and reveals an original program in which anti-infectious response was deficient in TG cells with a cftr mutation. This defective response may explain why host response does not contribute to protection against P. aeruginosa in CF.

Liver transcriptome profiles associated with strain-specific Ehrlichia chaffeensis-induced hepatitis in SCID mice

Infection of humans with Ehrlichia chaffeensis, the etiologic agent of human monocytic ehrlichiosis, can cause hepatitis of various levels of severity. When the three human isolates of E. chaffeensis, each belonging to a different genogroup, are inoculated into severe combined immunodeficiency mice, the order of severity of clinical signs and bacterial burden detected in the liver is as follows (from greatest to least severity and highest to lowest burden): strain Wakulla, followed by strain Liberty, followed by strain Arkansas. In this article, we used microarray analysis to define transcriptional profiles characteristic of the histopathological features in the mouse liver. Cytokine and chemokine profiles and their receptor profiles were strikingly different among the three strains of E. chaffeensis: gamma interferon, CCL5, CXCL1, CXCL2, CXCL7, CXCL9, interleukin 2 receptor gamma (IL2Rgamma), IL21R, CCR2, and CXCR6 were highly upregulated with strain Arkansas; and tumor necrosis factor (TNF), CCL2, CCL3, CCL5, CCL6, CCL12, CCL20, CXCL2, CXCL7, CXCL9, CXCL13, TNF receptor superfamily 9 (TNFRSF9), TNFRSF13beta, IL1R2, IL2Rgamma, IL20Rbeta, IL21R, CCR1, CCR2, and CXCR4 were highly upregulated with strain Wakulla. With strain Liberty, only CXCL13 was highly upregulated, and IL13Ralpha2 was downregulated. In livers infected with the Arkansas strain, monocytes/macrophages and NK cells were enriched in the granulomas and an increase in NK cell marker mRNAs was detected. Livers infected with the Wakulla strain displayed infiltration of significantly more neutrophils and an increase in neutrophil marker mRNAs. Genes commonly upregulated in liver tissue infected with the three strains are other host innate immune and inflammatory response genes, including those encoding several acute-phase proteins. Genes downregulated commonly are related to host physiologic functions. The results suggest that marked modulation of host cytokine and chemokine profiles by E. chaffeensis strains underlies the distinct host liver disease.

CXCL10/IP-10: a missing link between inflammation and anti-angiogenesis in preeclampsia?

OBJECTIVE

Interferon (IFN)-gamma inducible protein, CXCL10/IP-10, is a member of the CXC chemokine family with pro-inflammatory and anti-angiogenic properties. This chemokine has been proposed to be a key link between inflammation and angiogenesis. The aim of this study was to determine whether preeclampsia and delivery of a small for gestational age (SGA) neonate are associated with changes in maternal serum concentration of CXCL10/IP-10.

STUDY DESIGN

This cross-sectional study included patients in the following groups: (1) non-pregnant women (N = 49); (2) women with normal pregnancies (N = 89); (3) patients with preeclampsia (N = 100); and (4) patients who delivered an SGA neonate (N = 78). SGA was defined as birth weight below the 10th percentile. Maternal serum concentrations of CXCL10/IP-10 were measured by sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

(1) Patients with normal pregnancies had a significantly higher median serum concentration of CXCL10/IP-10 than non-pregnant women (median 116.1 pg/mL, range 40.7-1314.3 vs. median 90.3 pg/mL, range 49.2-214.7, respectively; p = 0.002); (2) no significant correlation was found between maternal serum concentration of CXCL10/IP-10 and gestational age (between 19 and 38 weeks); (3) there were no differences in median serum CXCL10/IP-10 concentrations between patients who delivered an SGA neonate and those with normal pregnancies (median 122.4 pg/mL, range 37.3-693.5 vs. median 116.1 pg/mL, range 40.7-1314.3, respectively; p > 0.05); (4) patients with preeclampsia had a higher median serum concentration of CXCL10/IP-10 than normal pregnant women (median 156.4 pg/mL, range 47.4-645.9 vs. median 116.1 pg/mL, range 40.7-1314.3, respectively; p < 0.05); (5) patients with preeclampsia had a higher median concentration of CXCL10/IP-10 than those who delivered an SGA neonate (median 156.4 pg/mL, range 47.4-645.9 vs. median 122.4 pg/mL, range 37.3-693.5, respectively; p < 0.05).

CONCLUSIONS

Patients with preeclampsia have significantly higher serum concentrations of CXCL10/IP-10 than both normal pregnant women and mothers who have SGA neonates. These results are likely to reflect an anti-angiogenic state as well as an enhanced systemic inflammatory response in patients with preeclampsia. Alternatively, since preeclampsia and SGA share several mechanisms of disease, it is possible that a higher concentration of this chemokine may contribute to the clinical presentation of preeclampsia in patients with a similar intrauterine insult.

Maternal serum concentrations of the chemokine CXCL10/IP-10 are elevated in acute pyelonephritis during pregnancy

OBJECTIVE

Acute pyelonephritis is one of the most frequent medical complications of pregnancy, as well as a common cause of antepartum hospitalization. Interferon (IFN)-gamma inducible protein, CXCL10/IP-10, is a member of the CXC chemokine family with pro-inflammatory and anti-angiogenic properties. The purpose of this study was to determine whether maternal serum concentrations of CXCL10/IP-10 change in patients with acute pyelonephritis during pregnancy.

STUDY DESIGN

This cross-sectional study was conducted to determine the difference in maternal serum concentrations of CXCL10/IP-10 in pregnant women with acute pyelonephritis (N = 41) and normal pregnant women (N = 89). Pyelonephritis was defined in the presence of a positive urine culture, fever, and maternal clinical signs; blood cultures were performed in 36 cases. Maternal serum concentrations of CXCL10/IP-10 were measured by a sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

(1) The median serum concentration of CXCL10/IP-10 in pregnant patients with pyelonephritis was significantly higher than in normal pregnant women (median 318.5 pg/mL, range 78.8-2459.2 vs. median 116.1 pg/mL, range 40.7-1314.3, respectively; p < 0.001); (2) maternal median serum concentrations of CXCL10/IP-10 did not differ significantly among patients with acute pyelonephritis with and without bacteremia (positive blood cultures: median 362.6 pg/mL, range 100.2-2459.2 vs. negative blood cultures: median 298.9 pg/mL, range 108.5-1148.7, respectively; p = 0.3).

CONCLUSIONS

Pyelonephritis in pregnant women is associated with an increased maternal serum concentration of the chemokine CXCL10/IP-10.

Invariant NKT cells are essential for the regulation of hepatic CXCL10 gene expression during Leishmania donovani infection

Gamma interferon (IFN-gamma)-regulated chemokines of the CXC family have been implicated as key regulators of a variety of T-cell-dependent inflammatory processes. However, the cellular source(s) of IFN-gamma that regulates their early expression has rarely been defined. Here, we have directly addressed this question in mice after Leishmania donovani infection. Comparison of CXCL10 mRNA accumulation in normal and IFN-gamma-deficient mice confirmed an absolute requirement for IFN-gamma for sustained (24 h) expression of CXCL10 mRNA accumulation in this model. In normal mice, IFN-gamma was produced by both CD3int NK1.1+ NKT cells and CD3- NK1.1+ NK cells, as detected by intracellular flow cytometry. Strikingly, B6.Jalpha281-/- mice lacking NKT cells that express the invariant Valpha14Jalpha18 T-cell-receptor alpha chain, although retaining a significant population of IFN-gamma-producing NK cells and NKT cells, were unable to sustain CXCL10 mRNA accumulation. These data indicate that invariant NKT cells are indispensable for the regulation of hepatic CXCL10 gene expression during L. donovani infection.

Chemokines, chemokine receptors and adhesion molecules on different human endothelia: discriminating the tissue-specific functions that affect leucocyte migration

The selective accumulation of different leucocyte populations during inflammation is regulated by adhesion molecules and chemokines expressed by vascular endothelium. This study examined how chemokine production and the expression of adhesion molecules and chemokine receptors vary between endothelia from different vascular beds. Human saphenous vein endothelium was compared with lung and dermal microvascular endothelia and with umbilical vein endothelium and a bone-marrow endothelial cell line. All endothelia produced CCL2 and CXCL8 constitutively, whereas CXCL10 and CCL5 were only secreted after tumour necrosis factor (TNF)-alpha or interferon (IFN)-gamma stimulation. In combination with TNF-alpha, IFN-gamma suppressed CXCL8 but enhanced CCL5 and CXCL10, whereas transforming growth factor (TGF)-beta reduced secretion of all chemokines. Basal chemokine secretion was higher from umbilical vein than other endothelial cells. Chemokine receptors, CXCR1, CXCR3 and CCR3, were present on all endothelia but highest on saphenous vein. CCR4, CCR5, CCR6, CXCR2, CXCR4 and CXCR5 were also detected at variable levels on different endothelia. The variation between endothelia in chemokine secretion was much greater than the variations in adhesion molecules, both on resting cells and following cytokine stimulation. These results indicate that it is the tissue-specific variations in endothelial chemokine secretion rather than variations in adhesion molecules that can explain the different patterns of inflammation and leucocyte traffic seen in non-lymphoid tissues.

p48/STAT-1α-Containing Complexes Play a Predominant Role in Induction of IFN-γ-Inducible Protein, 10 kDa (IP-10) by IFN-γ Alone or in Synergy with TNF-α

Human IFN-γ-inducible protein, 10 kDa (hIP-10) and murine IP-10 (mIP-10) genes are induced by IFN-γ alone, and synergistically induced by TNF-α and IFN-γ. Upstream regions of the human and murine genes contain conserved regulatory motifs, including an IFN-stimulated response element (ISRE), which governs response of the mIP-10 gene to IFN-γ. Trans-acting factors mediating the IFN-γ response via ISRE remain incompletely defined. We examined ISRE-binding factors in the regulation of the hIP-10 gene. The requirement of p48 for hIP-10 induction by IFN-γ, with or without TNF-α, was demonstrated using p48-deficient U2A cells. An hIP-10 promoter-reporter mutant (mISRE3) that was relatively deficient for binding a related factor, IFN regulatory factor-1 (IRF-1) but competent for binding p48, was induced as well as the wild-type hIP-10 promoter, supporting the interpretation that p48 played a necessary and sufficient role in hIP-10 transcription. Genomic in vivo footprinting revealed IFN-γ/TNF-α-inducible binding at the ISRE consistent with the presence of p48 and associated factors, but not with IRF-1. Induction of hIP-10 by TNF-α/IFN-γ also required NFκB binding sites, which were protected in vivo and bound p65 homodimeric NFκB in vitro. These results documented the essential role of p48 (complexed with STAT-1α) for induction and sustained transcription of the IP-10 gene, strongly suggesting that IRF-1 is not required for IP-10 induction by these inflammatory cytokines.

CD8+ Myelin Peptide-Specific T Cells Can Chemoattract CD4+ Myelin Peptide-Specific T Cells: Importance of IFN-Inducible Protein 10

The demyelination process that occurs in the central nervous system (CNS) of patients with multiple sclerosis (MS) is due, in part, to an inflammatory response in which CD4+ and CD8+ T cells and macrophages infiltrate white matter. While it is thought that the inflammatory and demyelination process in MS is the product of Th1-associated cytokines secreted by CD4+ myelin protein-specific T cells present in the CNS, the mechanisms that are responsible for the recruitment and maintenance of these myelin-reactive CD4+ T cells in the CNS have not been elucidated. We have shown previously that CD8+CTL that recognize peptides derived from sequences of the myelin proteolipid protein (PLP) presented by HLA class I molecules can be generated in vitro, and that these PLP-specific CD8+CTL secrete the proinflammatory chemokines macrophage-inflammatory protein-1α and -1β, IL-16, and IP-10. In this study, we demonstrate that soluble products of these PLP-specific CD8+CTL can chemoattract CD4+ T cells that are specific for a myelin basic protein peptide and a PLP peptide, and that the majority of this chemotactic activity is mediated by IFN-inducible protein 10. These results demonstrate that PLP-specific CD8+ T cells can play a role in the recruitment and retention of myelin-derived peptide-specific CD4+ T cells, and indicate that they may play a proinflammatory role in the pathogenesis of MS.

A potent inhibitor of endothelial cell proliferation is generated by proteolytic cleavage of the chemokine platelet factor 4

Platelet factor 4 (PF-4) is an archetype of the "chemokine" family of low molecular weight proteins that play an important role in injury responses and inflammation. From activated human leukocyte culture supernatants, we have isolated a form of PF-4 that acts as a potent inhibitor of endothelial cell proliferation. The PF-4 derivative is generated by peptide bond cleavage between Thr-16 and Ser-17, a site located downstream from the highly conserved and structurally important CXC motif. The unique cleavage leads to a loss of one of the structurally important large loops in the PF-4 molecule and generation of an N terminus with basic residues that have the potential to interact with the acidic extracellular domain of the G-protein-coupled chemokine receptor. The N-terminal processed PF-4 exhibited a 30- to 50-fold greater growth inhibitory activity on endothelial cells than PF-4. Since endothelial cell growth inhibition is the only known cellular activity of the cleaved PF-4, we have designated this chemokine endothelial cell growth inhibitor. The N-terminal processing of PF-4 may represent an important mechanism for modulating PF-4 activity on endothelial cells during tissue injury, inflammation, and neoplasia.

Inhibition of endothelial cell proliferation by platelet factor-4 involves a unique action on S phase progression

Modulation of endothelial cell proliferation and cell cycle progression by the "chemokine" platelet factor-4 (PF-4) was investigated. PF-4 inhibited DNA synthesis, as well as proliferation of endothelial cells derived from large and small blood vessels. Inhibition by PF-4 was independent of the type and the concentration of stimuli used for the induction of endothelial cell proliferation. Inhibition of cell growth by PF-4 was reversible. The effects of PF-4 were antagonized by heparin. Cell cycle analysis using [3H]thymidine pulse labeling during traverse of synchronous cells from G0/G1 to S phase revealed that addition of PF-4 during G1 phase completely abolished the entry of cells into S phase. In addition, PF-4 also inhibited DNA synthesis in cells that were already in S phase. In exponentially growing cells, addition of PF-4 resulted in an accumulation of > 70% of the cells in early S phase, as determined by FACS (Becton-Dickinson Immunocytometry Systems, Mountain View, CA). In cells synchronized in S phase by hydroxyurea and then released, addition of PF-4 promptly blocked further progression of DNA synthesis. These results demonstrate that in G0/G1-arrested cells, PF-4 inhibited entry of endothelial cells into S phase. More strikingly, our studies have revealed a unique mode of endothelial cell growth inhibition whereby PF-4 effectively blocked cell cycle progression during S phase.

Inhibitors of serine/threonine phosphatases enhance phosphorylation of the interferon-gamma receptor while selectively attenuating interferon-gamma-induced gene expression in human peripheral-blood monocytes

Since many events following ligand-induced receptor clustering are controlled by serine and threonine (Ser/Thr) phosphorylation, we initiated an investigation into the role of Ser/Thr phosphatases in both phosphorylation of the interferon-gamma (IFN-gamma) receptor and IFN gamma-induced gene expression in human peripheral-blood monocytes. Whereas IFN gamma alone did not enhance phosphorylation of the IFN gamma receptor, treatment of monocytes with the Ser/Thr phosphatase inhibitors, okadaic acid and calyculin A, resulted in increased phosphorylation of the IFN gamma receptor. However, when these cells were analysed for IFN gamma-induced IP-10 gene expression, there was profound inhibition. Using three IFN gamma-induced early-response genes, IP-10, the Fc gamma receptor type I (Fc gamma RI) and ISG-54, we found selective sensitivity to pretreatment with okadaic acid and calyculin A. Whereas IFN gamma induction of IP-10 was blocked by both inhibitors, only calyculin A prevented Fc gamma RI-gene expression. Neither inhibitor prevented ISG-54 induction by IFN gamma. IFN-gamma-activated formation of the DNA-binding-protein complex FcRF gamma (which binds to the promoter of the Fc gamma RI gene) remained unaffected by okadaic acid or calyculin A. Therefore these data suggest that Ser/Thr phosphatases have no major part in IFN gamma-initiated signal transduction across the membrane, but selectively control the ultimate transcription of a set of early-response genes.

Constitutive expression of interferon gamma-inducible protein 10 in lymphoid organs and inducible expression in T cells and thymocytes

Interferon gamma-inducible protein 10 (IP-10), a member of a family of small proinflammatory chemotactic polypeptides, is expressed in interferon gamma-stimulated keratinocytes, macrophages, fibroblasts, and endothelial cells. Here we report that IP-10 is also expressed by activated but not resting T hybridoma cells, normal T cells, and thymocytes. Although resting lymphocytes did not synthesize IP-10, surprisingly high levels of IP-10 transcripts were found in lymphoid organs (spleen, thymus, and lymph nodes). Thymic and splenic stromal cells were found to express constitutively high levels of both IP-10 mRNA and protein, accounting for the high level of spontaneous expression in lymphoid tissue. Therefore, in addition to its role as a proinflammatory cytokine, IP-10 may participate in T cell effector function and perhaps T cell development.

Recognition DNA sequences of interferon regulatory factor 1 (IRF-1) and IRF-2, regulators of cell growth and the interferon system

Interferon (IFN) regulatory factor 1 (IRF-1) and IRF-2 were originally identified as transcription factors involved in the regulation of the IFN system. IRF-1 functions as a transcriptional activator, while IRF-2 represses IRF-1 function. More recently, evidence has been provided that IRF-1 and IRF-2 manifest antioncogenic and oncogenic properties, respectively, and that loss of one or both of the IRF-1 alleles may be critical for the development of human hematopoietic neoplasms. Both factors show a high degree of structural similarity in their N-terminal DNA-binding domains, and previous studies suggested that IRF-1 and IRF-2 bind to similar or identical cis elements within type I IFN (IFN-alpha and -beta) and IFN-inducible genes. However, the exact recognition sequences of these two factors have not yet been determined; hence, the spectrum of the IRF-responsive genes remains unclear. In this study, we determined the DNA sequences recognized by IRF-1 and IRF-2, using a polymerase chain reaction-assisted DNA-binding site selection method. We report that sequences selected by this method and the affinities for each sequence were virtually indistinguishable between IRF-1 and IRF-2. We confirm the presence of two contiguous IRF recognition sequences within the promoter region of the IFN-beta gene and of at least one such sequence in all of the IFN-inducible genes examined. Furthermore, we report the presence of potential IRF sequences in the upstream region of several genes involved in cell growth control.

Recognition DNA sequences of interferon regulatory factor 1 (IRF-1) and IRF-2, regulators of cell growth and the interferon system

Interferon (IFN) regulatory factor 1 (IRF-1) and IRF-2 were originally identified as transcription factors involved in the regulation of the IFN system. IRF-1 functions as a transcriptional activator, while IRF-2 represses IRF-1 function. More recently, evidence has been provided that IRF-1 and IRF-2 manifest antioncogenic and oncogenic properties, respectively, and that loss of one or both of the IRF-1 alleles may be critical for the development of human hematopoietic neoplasms. Both factors show a high degree of structural similarity in their N-terminal DNA-binding domains, and previous studies suggested that IRF-1 and IRF-2 bind to similar or identical cis elements within type I IFN (IFN-alpha and -beta) and IFN-inducible genes. However, the exact recognition sequences of these two factors have not yet been determined; hence, the spectrum of the IRF-responsive genes remains unclear. In this study, we determined the DNA sequences recognized by IRF-1 and IRF-2, using a polymerase chain reaction-assisted DNA-binding site selection method. We report that sequences selected by this method and the affinities for each sequence were virtually indistinguishable between IRF-1 and IRF-2. We confirm the presence of two contiguous IRF recognition sequences within the promoter region of the IFN-beta gene and of at least one such sequence in all of the IFN-inducible genes examined. Furthermore, we report the presence of potential IRF sequences in the upstream region of several genes involved in cell growth control.

The response of gamma interferon activation factor is under developmental control in cells of the macrophage lineage

Gamma interferon activation factor (GAF) rapidly induces transcriptional activation of gamma interferon (IFN-gamma)-responsive genes. Conversion of the GAF from a latent cytoplasmic to an activated, DNA-binding form is an immediate step in the cellular response to IFN-gamma. The amount of IFN-gamma-activated GAF, measured by exonuclease III protection or gel shift assays, increased strongly upon monocytic differentiation of U937 cells. Activated GAF contained the IFN-responsive 91-kDa protein as its DNA-binding activity in gel shift or exonuclease III assays could be inhibited through direct addition of specific antiserum, and it was not present in p91-immunodepleted extracts. There was a differentiation-induced increase in the amount of nonphosphorylated (latent) p91. Transcription rate measurement demonstrated a strong induction of the p91 gene during monocytic differentiation of U937 cells. The amount of p91 which was rapidly phosphorylated in response to IFN-gamma was found to be much higher in the differentiated cells and suggested a differentiation-controlled increase in the signaling leading to p91 phosphorylation. Concomitantly with a better GAF response, transcriptional activation of IFN-gamma-induced genes and the expression of GAF-dependent, transfected reporter plasmids increased in differentiated U937 monocytes. The promonocyte-monocyte transition also affected the IFN-alpha-responsive transcription factor ISGF-3. Differentiated U937 cells contained more of both the alpha-component p91 and the gamma-component p48, which constitutes the DNA-binding subunit of the complex. Our study thus provides evidence that the synthesis of specific transcription factors can be a regulated event to control the cytokine responsiveness of cells during development.

Recombinant human interferon-inducible protein 10 is a chemoattractant for human monocytes and T lymphocytes and promotes T cell adhesion to endothelial cells

The human cytokine interferon-inducible protein 10 (IP-10) is a small glycoprotein secreted by activated T cells, monocytes, endothelial cells, and keratinocytes, and is structurally related to a family of chemotactic cytokines called chemokines. Although this protein is present in sites of delayed-type hypersensitivity reactions and lepromatous leprosy lesions, the biological activity of IP-10 remains unknown. We report here that recombinant human IP-10 stimulated significant in vitro chemotaxis of human peripheral blood monocytes but not neutrophils. Recombinant human IP-10 also stimulated chemotaxis of stimulated, but not unstimulated, human peripheral blood T lymphocytes. Phenotypic analysis of the stimulated T cell population responsive to IP-10 demonstrated that stimulated CD4+ and CD29+ T cells migrated in response to IP-10. This resembles the biological activity of the previously described T cell chemoattractant RANTES. Using an endothelial cell adhesion assay, we demonstrated that stimulated T cells pretreated with optimal doses of IP-10 exhibited a greatly enhanced ability to bind to an interleukin 1-treated endothelial cell monolayer. These results demonstrate that the IP-10 gene encodes for an inflammatory mediator that specifically stimulates the directional migration of T cells and monocytes as well as potentiates T cell adhesion to endothelium.

The response of gamma interferon activation factor is under developmental control in cells of the macrophage lineage

Gamma interferon activation factor (GAF) rapidly induces transcriptional activation of gamma interferon (IFN-gamma)-responsive genes. Conversion of the GAF from a latent cytoplasmic to an activated, DNA-binding form is an immediate step in the cellular response to IFN-gamma. The amount of IFN-gamma-activated GAF, measured by exonuclease III protection or gel shift assays, increased strongly upon monocytic differentiation of U937 cells. Activated GAF contained the IFN-responsive 91-kDa protein as its DNA-binding activity in gel shift or exonuclease III assays could be inhibited through direct addition of specific antiserum, and it was not present in p91-immunodepleted extracts. There was a differentiation-induced increase in the amount of nonphosphorylated (latent) p91. Transcription rate measurement demonstrated a strong induction of the p91 gene during monocytic differentiation of U937 cells. The amount of p91 which was rapidly phosphorylated in response to IFN-gamma was found to be much higher in the differentiated cells and suggested a differentiation-controlled increase in the signaling leading to p91 phosphorylation. Concomitantly with a better GAF response, transcriptional activation of IFN-gamma-induced genes and the expression of GAF-dependent, transfected reporter plasmids increased in differentiated U937 monocytes. The promonocyte-monocyte transition also affected the IFN-alpha-responsive transcription factor ISGF-3. Differentiated U937 cells contained more of both the alpha-component p91 and the gamma-component p48, which constitutes the DNA-binding subunit of the complex. Our study thus provides evidence that the synthesis of specific transcription factors can be a regulated event to control the cytokine responsiveness of cells during development.

Two cis-DNA elements involved in myeloid-cell-specific expression and gamma interferon (IFN-gamma) activation of the human high-affinity Fc gamma receptor gene: a novel IFN regulatory mechanism

The human high-affinity receptor for the constant region of immunoglobulin G (human Fc gamma R1) is encoded by two mRNAs induced selectively by gamma interferon (IFN-gamma) and expressed in cells of myeloid lineage. The cis-DNA element (GRR) previously found to confer IFN-gamma responsiveness to this gene acts as an inducible enhancer and is the target of an IFN-gamma-activated factor(s) (GIRE-BP) in cells of different origins. Although the GRR motif is not related to the DNA elements involved in the regulation of other IFN-stimulated genes, GIRE-BP binding depends on the IFN-gamma-dependent activation of the 91-kDa protein known to be one of the factors of a transcriptional complex activated by IFN-alpha. Deletions of the Fc gamma R1 promoter allowed us to identify a 25-bp element, downstream from the GRR motif, conferring cell-type-specific expression. This element, called MATE (myeloid activating transcription element), is the DNA target for constitutive factors forming two complexes, MATE-BP1 and MATE-BP2. In accordance with the functional analysis, MATE-BP binding activities were detected in extracts prepared from myeloid cell lines such as THP-1, HL-60, and U-937 but not in HeLa cell extracts. The MATE motif is present not only in the promoter of other Fc receptor genes but also in several promoters of genes whose expression is restricted to monocytic cells. Our results suggest that human Fc gamma R1 gene expression in myeloid cells is initiated by the interaction of IFN-gamma-activated factors with cell-type-specific factors through their binding to the GRR and MATE motifs.

Two cis-DNA elements involved in myeloid-cell-specific expression and gamma interferon (IFN-gamma) activation of the human high-affinity Fc gamma receptor gene: a novel IFN regulatory mechanism

The human high-affinity receptor for the constant region of immunoglobulin G (human Fc gamma R1) is encoded by two mRNAs induced selectively by gamma interferon (IFN-gamma) and expressed in cells of myeloid lineage. The cis-DNA element (GRR) previously found to confer IFN-gamma responsiveness to this gene acts as an inducible enhancer and is the target of an IFN-gamma-activated factor(s) (GIRE-BP) in cells of different origins. Although the GRR motif is not related to the DNA elements involved in the regulation of other IFN-stimulated genes, GIRE-BP binding depends on the IFN-gamma-dependent activation of the 91-kDa protein known to be one of the factors of a transcriptional complex activated by IFN-alpha. Deletions of the Fc gamma R1 promoter allowed us to identify a 25-bp element, downstream from the GRR motif, conferring cell-type-specific expression. This element, called MATE (myeloid activating transcription element), is the DNA target for constitutive factors forming two complexes, MATE-BP1 and MATE-BP2. In accordance with the functional analysis, MATE-BP binding activities were detected in extracts prepared from myeloid cell lines such as THP-1, HL-60, and U-937 but not in HeLa cell extracts. The MATE motif is present not only in the promoter of other Fc receptor genes but also in several promoters of genes whose expression is restricted to monocytic cells. Our results suggest that human Fc gamma R1 gene expression in myeloid cells is initiated by the interaction of IFN-gamma-activated factors with cell-type-specific factors through their binding to the GRR and MATE motifs.

In vitro activation of the transcription factor gamma interferon activation factor by gamma interferon: evidence for a tyrosine phosphatase/kinase signaling cascade

Although it has been well documented that the biological activities of gamma interferon (IFN-gamma) are initiated through interaction with its cell surface receptor, the signal transduction mechanisms which mediate the effects of this cytokine have remained unclear. In order to facilitate a better understanding of IFN-gamma signaling, we have designed an assay using human fibroblast cell homogenates in which IFN-gamma activates the formation of the IFN-gamma activation factor (GAF) transcription complex. GAF mediates the rapid transcriptional activation of the guanylate-binding protein gene by IFN-gamma. Activation of GAF in homogenates required ATP, but not Ca2+ or GTP. Fractionation of homogenates indicated that both the pellet (18,000 x g) and the remaining cytoplasmic fraction were required for GAF activation by IFN-gamma. In intact cells and cell homogenates, the activation of GAF was prevented by the specific tyrosine kinase inhibitor genistein. Treatment of GAF-containing nuclear extracts with either monoclonal antiphosphotyrosine antibody or protein tyrosine phosphatase prevented the assembly of the transcription complex, indicating that its formation required phosphorylation of tyrosine residues. Furthermore, the tyrosine phosphatase inhibitors phenylarsine oxide and zinc chloride also inhibited GAF formation in vitro, but only if these agents were added to cell homogenates before IFN-gamma was added. The addition of either agent 5 min after IFN-gamma had no effect. These results provide the first evidence for an IFN-gamma-regulated tyrosine phosphatase/kinase signaling cascade that permits this cytokine to activate the transcription of an early-response gene.

In vitro activation of the transcription factor gamma interferon activation factor by gamma interferon: evidence for a tyrosine phosphatase/kinase signaling cascade

Although it has been well documented that the biological activities of gamma interferon (IFN-gamma) are initiated through interaction with its cell surface receptor, the signal transduction mechanisms which mediate the effects of this cytokine have remained unclear. In order to facilitate a better understanding of IFN-gamma signaling, we have designed an assay using human fibroblast cell homogenates in which IFN-gamma activates the formation of the IFN-gamma activation factor (GAF) transcription complex. GAF mediates the rapid transcriptional activation of the guanylate-binding protein gene by IFN-gamma. Activation of GAF in homogenates required ATP, but not Ca2+ or GTP. Fractionation of homogenates indicated that both the pellet (18,000 x g) and the remaining cytoplasmic fraction were required for GAF activation by IFN-gamma. In intact cells and cell homogenates, the activation of GAF was prevented by the specific tyrosine kinase inhibitor genistein. Treatment of GAF-containing nuclear extracts with either monoclonal antiphosphotyrosine antibody or protein tyrosine phosphatase prevented the assembly of the transcription complex, indicating that its formation required phosphorylation of tyrosine residues. Furthermore, the tyrosine phosphatase inhibitors phenylarsine oxide and zinc chloride also inhibited GAF formation in vitro, but only if these agents were added to cell homogenates before IFN-gamma was added. The addition of either agent 5 min after IFN-gamma had no effect. These results provide the first evidence for an IFN-gamma-regulated tyrosine phosphatase/kinase signaling cascade that permits this cytokine to activate the transcription of an early-response gene.

Functional analysis of the human neurofilament light chain gene promoter

We have carried out a structural and functional analysis on the human NF-L (H-NF-L) gene. It contains a methylation-free island, spanning the 5' flanking sequences and the first exon and a number of neuronal-specific DNase I hypersensitive sites have been identified in the upstream region as well as within the body of the gene. Analysis in cell lines and transgenic mice using a combination of these sites has revealed the presence of a conserved element(s) between -300bp and -190bp which is required for neuronal-specific expression.

Interferons induce xanthine dehydrogenase gene expression in L929 cells

Human interferon-alpha A/D (Bg/II) (IFN-alpha A/D) and mouse interferon-gamma (IFN-gamma) are shown to induce xanthine dehydrogenase (XD) mRNA in L929 fibroblastic cells. XD mRNA accumulation after IFN-alpha A/D treatment is relatively fast, being already evident after 4 h and reaching its maximum after 24 h. IFN-alpha A/D is active in inducing XD mRNA at 0.1 unit/ml and it is maximally active at 10(3) units/ml. The half-life of the XD message is unaffected by IFN-alpha A/D treatment, whereas the transcriptional activity of the XD gene and the concentrations of XD heterogeneous nuclear RNA are increased by 2- and 6-fold respectively. The effect of IFN-alpha A/D on XD mRNA is insensitive to cycloheximide, suggesting that protein synthesis de novo is not required. Experiments conducted with specific inhibitors suggest that protein kinase C, cyclic AMP and arachidonic acid metabolites derived from lipoxygenase or cyclooxygenase do not act as second-messenger molecules in the induction of XD mRNA by IFN-alpha A/D. XD mRNA is also induced in NIH3T3 fibroblastic cells, but not in F9 teratocarcinoma or B16 melanoma cells after treatment with IFN-alpha A/D. NIH3T3 are the only cells so far tested that have detectable XD and xanthine oxidase activities under basal conditions and after IFN-alpha A/D treatment, although their responsiveness to the cytokine is much less than that observed in L929 cells.

A lymphoid cell-specific nuclear factor containing c-Rel-like proteins preferentially interacts with interleukin-6 kappa B-related motifs whose activities are repressed in lymphoid cells

The proto-oncoprotein c-Rel is a member of the nuclear factor kappa B transcription factor family, which includes the p50 and p65 subunits of nuclear factor kappa B. We show here that c-Rel binds to kappa B sites as homodimers as well as heterodimers with p50. These homodimers and heterodimers show distinct DNA-binding specificities and affinities for various kappa B motifs. In particular, the c-Rel homodimer has a high affinity for interleukin-6 (IL-6) and beta interferon kappa B sites. In spite of its association with p50 in vitro, however, we found a lymphoid cell-specific nuclear factor in vivo that contains c-Rel but not p50 epitopes; this factor, termed IL-6 kappa B binding factor II, appears to contain the c-Rel homodimer and preferentially recognizes several IL-6 kappa B-related kappa B motifs. Although it has been previously shown that the IL-6 kappa B motif functions as a potent IL-1/tumor necrosis factor-responsive element in nonlymphoid cells, its activity was found to be repressed in lymphoid cells such as a Jurkat T-cell line. We also present evidence that IL-6 kappa B binding factor II functions as a repressor specific for IL-6 kappa B-related kappa B motifs in lymphoid cells.

A lymphoid cell-specific nuclear factor containing c-Rel-like proteins preferentially interacts with interleukin-6 kappa B-related motifs whose activities are repressed in lymphoid cells

The proto-oncoprotein c-Rel is a member of the nuclear factor kappa B transcription factor family, which includes the p50 and p65 subunits of nuclear factor kappa B. We show here that c-Rel binds to kappa B sites as homodimers as well as heterodimers with p50. These homodimers and heterodimers show distinct DNA-binding specificities and affinities for various kappa B motifs. In particular, the c-Rel homodimer has a high affinity for interleukin-6 (IL-6) and beta interferon kappa B sites. In spite of its association with p50 in vitro, however, we found a lymphoid cell-specific nuclear factor in vivo that contains c-Rel but not p50 epitopes; this factor, termed IL-6 kappa B binding factor II, appears to contain the c-Rel homodimer and preferentially recognizes several IL-6 kappa B-related kappa B motifs. Although it has been previously shown that the IL-6 kappa B motif functions as a potent IL-1/tumor necrosis factor-responsive element in nonlymphoid cells, its activity was found to be repressed in lymphoid cells such as a Jurkat T-cell line. We also present evidence that IL-6 kappa B binding factor II functions as a repressor specific for IL-6 kappa B-related kappa B motifs in lymphoid cells.

Isolation and characterization of a new mutant human cell line unresponsive to alpha and beta interferons

Previously we described human cell line 2fTGH, in which expression of guanine phosphoribosyltransferase is tightly controlled by the upstream region of interferon (IFN)-stimulated human gene 6-16. After mutagenesis of 2fTGH and selection with 6-thioguanine and IFN-alpha, we isolated 11.1, a recessive mutant that does not respond to IFN-alpha. We now describe U2, a second recessive mutant, selected similarly, that complements 11.1. U2 had no response to IFN-alpha or IFN-beta, and its response to IFN-gamma was partially defective. Although many genes did respond to IFN-gamma in U2, the 9-27 gene did not and the antiviral response of U2 cells to IFN-gamma was greatly reduced. Band shift assays showed that none of the transcription factors normally induced in 2fTGH cells by IFN-alpha (E and M) or IFN-gamma (G) were induced in U2. However, extracts of untreated U2 cells gave rise to a novel band that was increased by treatment with IFN-gamma but not IFN-alpha. Band shift complementation assays revealed that untreated and IFN-gamma-treated U2 cells lack the functional E gamma subunit of transcription factor E and that IFN-alpha-treated U2 cells do contain the functional E alpha subunit.

Isolation and characterization of a new mutant human cell line unresponsive to alpha and beta interferons

Previously we described human cell line 2fTGH, in which expression of guanine phosphoribosyltransferase is tightly controlled by the upstream region of interferon (IFN)-stimulated human gene 6-16. After mutagenesis of 2fTGH and selection with 6-thioguanine and IFN-alpha, we isolated 11.1, a recessive mutant that does not respond to IFN-alpha. We now describe U2, a second recessive mutant, selected similarly, that complements 11.1. U2 had no response to IFN-alpha or IFN-beta, and its response to IFN-gamma was partially defective. Although many genes did respond to IFN-gamma in U2, the 9-27 gene did not and the antiviral response of U2 cells to IFN-gamma was greatly reduced. Band shift assays showed that none of the transcription factors normally induced in 2fTGH cells by IFN-alpha (E and M) or IFN-gamma (G) were induced in U2. However, extracts of untreated U2 cells gave rise to a novel band that was increased by treatment with IFN-gamma but not IFN-alpha. Band shift complementation assays revealed that untreated and IFN-gamma-treated U2 cells lack the functional E gamma subunit of transcription factor E and that IFN-alpha-treated U2 cells do contain the functional E alpha subunit.

Organ specific cytokine therapy. Local activation of mononuclear phagocytes by delivery of an aerosol of recombinant interferon-gamma to the human lung

In the context of the central role of the alveolar macrophage in host defense of the respiratory epithelial surface, and the ability of IFN-gamma to activate mononuclear phagocytes, we have evaluated strategies to use rIFN-gamma to activate human alveolar macrophages in vivo. To accomplish this, rIFN-gamma was administered to nonsmoking normals, the amounts of IFN-gamma quantified in serum and respiratory epithelial lining fluid (ELF) and the status of IFN-gamma related activation of blood monocytes and alveolar macrophages was evaluated by quantifying the expression of mRNA transcripts of IP-10, a gene induced specifically by IFN-gamma. Systemic administration (subcutaneous) of maximally tolerated amounts of rIFN-gamma (250 micrograms) was followed by detectable levels of IFN-gamma in serum but not ELF, the expression of IP-10 transcripts in blood monocytes but not alveolar macrophages, and multiple systemic adverse effects. To circumvent the inability of systemic administration to reach respiratory ELF and activate alveolar macrophages, rIFN-gamma (250-1,000 micrograms) was inhaled as an aerosol once daily for 3 d. Strikingly, while IFN-gamma was not detected in serum it was detectable in respiratory ELF in a dose-dependent fashion. Further, alveolar macrophages, but not blood monocytes, expressed IP-10 mRNA transcripts and, importantly, inhalation of aerosolized rIFN-gamma was not associated with local or systemic adverse effects. Thus, it is feasible to use rIFN-gamma to activate alveolar macrophages by targeting the cytokine directly to the lung. These data suggest a potential strategy for targeted cytokine therapy, without systemic side effects, to augment respiratory tract defenses in individuals at risk for or with lung infection.

The immediate-early growth response in regenerating liver and insulin-stimulated H-35 cells: comparison with serum-stimulated 3T3 cells and identification of 41 novel immediate-early genes

Liver regeneration provides a unique system for analysis of mitogenesis in intact, fully developed animals. Cellular immediate-early genes likely play an important role in cell cycle regulation and have been extensively studied in mitogen-stimulated fibroblasts lymphocytes but not in liver. We have begun to characterize the immediate-early growth response genes of mitogen-stimulated liver cells, specifically, regenerating liver and insulin-stimulated Reuber H-35 hepatoma cells, and to address differences in growth response between different cell types. Through subtraction and differential screening of cDNA libraries from regenerating liver and insulin-treated H-35 cells, we have extensively characterized 341 differentially expressed clones and identified 52 immediate-early genes. These genes have been partially sequenced and subjected to Northern (RNA) blot analysis, and 41 appear to be novel. Surprisingly, two-thirds of these genes are also expressed in BALB/c 3T3 cells, but only 10 were identified in previous studies of 3T3 cells, and of these, 6 include well-known genes like jun and fos, and only 4 are novel. Approximately one-third of the immediate-early genes identified in mitogen-stimulated liver cells or serum-stimulated NIH 3T3 cells are expressed in a tissue-specific fashion, indicating that cell type-specific regulation of the proliferative response occurs during the immediate-early period. Our findings indicate that the immediate-early response is unusually complex for the first step in a regulatory cascade, suggesting that multiple pathways must be activated. The abundance of immediate-early genes and the highly varied pattern of their expression in different cell types suggest that the tissue specificity of the proliferative response arises from the particular set of these genes expressed in a given tissue.

Differential response of the human 6-16 and 9-27 genes to alpha and gamma interferons

9-27 mRNA is expressed to a high level in response to both alpha and gamma interferons. In contrast, 6-16 mRNA is expressed well in response to alpha but very poorly in response to gamma interferon in human cells. The factors governing these different levels of expression were investigated. For both genes the major effect of both interferons is on transcription. A transcriptional bias in the 6-16 promoter/enhancer accounts in large part for the differential response of 6-16 to the two interferons. No single DNA element appears responsible; the smaller the 5' region analysed the lower the absolute activity and the smaller the differential response to alpha and gamma interferons observed. Both the 6-16 and 9-27 mRNAs are very stable and no effect of the interferons on stability was detected. Nor was any direct evidence obtained for preferential processing of the 9-27 mRNA. Nevertheless, differentials between the transcription and accumulation of mature mRNAs, particularly for 6-16 mRNA in response to gamma interferon, suggest that post-transcriptional control(s) must additionally operate. The 9-27 5' promoter/enhancer is much less active than that from 6-16 when placed 5' of a marker gene, despite the similar response of the two genes to alpha interferon.

The immediate-early growth response in regenerating liver and insulin-stimulated H-35 cells: comparison with serum-stimulated 3T3 cells and identification of 41 novel immediate-early genes

Liver regeneration provides a unique system for analysis of mitogenesis in intact, fully developed animals. Cellular immediate-early genes likely play an important role in cell cycle regulation and have been extensively studied in mitogen-stimulated fibroblasts lymphocytes but not in liver. We have begun to characterize the immediate-early growth response genes of mitogen-stimulated liver cells, specifically, regenerating liver and insulin-stimulated Reuber H-35 hepatoma cells, and to address differences in growth response between different cell types. Through subtraction and differential screening of cDNA libraries from regenerating liver and insulin-treated H-35 cells, we have extensively characterized 341 differentially expressed clones and identified 52 immediate-early genes. These genes have been partially sequenced and subjected to Northern (RNA) blot analysis, and 41 appear to be novel. Surprisingly, two-thirds of these genes are also expressed in BALB/c 3T3 cells, but only 10 were identified in previous studies of 3T3 cells, and of these, 6 include well-known genes like jun and fos, and only 4 are novel. Approximately one-third of the immediate-early genes identified in mitogen-stimulated liver cells or serum-stimulated NIH 3T3 cells are expressed in a tissue-specific fashion, indicating that cell type-specific regulation of the proliferative response occurs during the immediate-early period. Our findings indicate that the immediate-early response is unusually complex for the first step in a regulatory cascade, suggesting that multiple pathways must be activated. The abundance of immediate-early genes and the highly varied pattern of their expression in different cell types suggest that the tissue specificity of the proliferative response arises from the particular set of these genes expressed in a given tissue.

Structures of human genes coding for cytokine LD78 and their expression

LD78 is a member of a newly identified superfamily of small inducible proteins involved in inflammatory responses, wound healing, and tumorigenesis. Southern blot analysis of the EcoRI-digested human genomic DNAs, using previously isolated LD78 cDNA as a probe, showed that in each individual there are 4.2- and 4.8-kilobase-pair (kb) fragments and that some have an additional 6.5-kb fragment. The 4.2-kb fragment contained genomic DNA sequences corresponding to the LD78 cDNA and was named the LD78 alpha gene. The 4.8-kb fragment contained similar sequences, showing 94% homology to the LD78 alpha gene, and was named the LD78 beta gene. The LD78 alpha gene was present in a single or a few copies per haploid genome, whereas the copy number of the LD78 beta gene and of the 6.5-kb fragment hybridizable to LD78 cDNA varied among the samples tested. Treatment of human myeloid cell lines HL-60 and U937 with phorbol 12-myristate 13-acetate (PMA) increased within 2 h cellular levels of the RNA hybridizable to LD78 cDNA. The human glioma cell line U105MG and primary culture of human fibroblasts also expressed the hybridizable RNA in response to PMA. Addition of cycloheximide had no apparent effect on this response in U937 cells and inhibited the response in fibroblasts, whereas it stimulated the response in HL-60 and U105MG cells. mRNA phenotyping experiments revealed that the LD78 alpha and LD78 beta genes were both transcribed in PMA-stimulated U937 cells.

Structures of human genes coding for cytokine LD78 and their expression

LD78 is a member of a newly identified superfamily of small inducible proteins involved in inflammatory responses, wound healing, and tumorigenesis. Southern blot analysis of the EcoRI-digested human genomic DNAs, using previously isolated LD78 cDNA as a probe, showed that in each individual there are 4.2- and 4.8-kilobase-pair (kb) fragments and that some have an additional 6.5-kb fragment. The 4.2-kb fragment contained genomic DNA sequences corresponding to the LD78 cDNA and was named the LD78 alpha gene. The 4.8-kb fragment contained similar sequences, showing 94% homology to the LD78 alpha gene, and was named the LD78 beta gene. The LD78 alpha gene was present in a single or a few copies per haploid genome, whereas the copy number of the LD78 beta gene and of the 6.5-kb fragment hybridizable to LD78 cDNA varied among the samples tested. Treatment of human myeloid cell lines HL-60 and U937 with phorbol 12-myristate 13-acetate (PMA) increased within 2 h cellular levels of the RNA hybridizable to LD78 cDNA. The human glioma cell line U105MG and primary culture of human fibroblasts also expressed the hybridizable RNA in response to PMA. Addition of cycloheximide had no apparent effect on this response in U937 cells and inhibited the response in fibroblasts, whereas it stimulated the response in HL-60 and U105MG cells. mRNA phenotyping experiments revealed that the LD78 alpha and LD78 beta genes were both transcribed in PMA-stimulated U937 cells.

An interferon gamma-regulated protein that binds the interferon-inducible enhancer element of major histocompatibility complex class I genes

Interferons (IFNs) induce transcription of major histocompatibility complex (MHC) class I genes through the conserved IFN consensus sequence (ICS) that contains an IFN response motif shared by many IFN-regulated genes. By screening mouse lambda ZAP expression libraries with the ICS as a probe, we isolated a cDNA clone encoding a protein that binds the ICS, designated ICSBP. Protein blot analysis with labeled oligonucleotide probes showed that ICSBP binds not only the MHC class I ICS but also IFN response motifs of many IFN-regulated genes, as well as a virus-inducible element of the IFN-beta gene. The ICSBP cDNA encodes 424 amino acids and a long 3' untranslated sequence. The N-terminal 115 amino acids correspond to a putative DNA-binding domain and show significant sequence similarity with other cloned IFN response factors (IRF-1 and IRF-2). Because of the structural similarity and shared binding specificity, we conclude that ICSBP is a third member of the IRF gene family, presumably playing a role in IFN- and virus-mediated regulation of many genes. Although IRF-1 and IRF-2 share some similarity in their C-terminal regions, ICSBP shows no similarity to IRF-1 or IRF-2 in this region, suggesting that it is more distantly related. We show that ICSBP mRNA is expressed predominantly in lymphoid tissues and is inducible preferentially by IFN-gamma. The induction by IFN-gamma appears to be predominant in lymphocytes and macrophages, implying that ICSBP plays a regulatory role in cells of the immune system. The presence of multiple factors that bind common IFN response motifs may partly account for the complexity and diversity of IFN action as well as IFN-regulated gene expression.

Alpha interferon suppresses hepatitis B virus enhancer activity and reduces viral gene transcription

Interferons inhibit replication of hepatitis B virus (HBV). The mechanism for this inhibition was investigated by analyzing the effect of interferons on transcription of a chloramphenicol acetyltransferase reporter gene under control of HBV regulatory sequences and by determining the steady-state level of viral mRNAs in permanently HBV-transfected HepG2 cells. Low doses (100 U/ml) of alpha interferon (IFN-alpha) but not IFN-gamma inhibited chloramphenicol acetyltransferase expression in cultured cells transfected with plasmids containing the HBV enhancer linked to either HBV or simian virus 40 promoters. IFN-alpha also lowered expression of HBV mRNA in HBV-transfected HepG2 cells actively replicating virus, suggesting that IFN-alpha inhibits HBV replication by reducing transcription of viral genes driven by the HBV enhancer.

Interferon gamma regulates binding of two nuclear protein complexes in a macrophage cell line

Interferon gamma (IFN-gamma) is a potent inducer of major histocompatibility complex (MHC) antigens during normal immune responses and in abnormal responses in autoimmune disease. In this report we identify two nuclear factors whose binding to the murine E beta class II MHC beta-chain gene is regulated by this cytokine. IFN-gamma stimulation of murine macrophages results in the appearance of increased binding of one protein complex, complex A, and decreased binding of a second, faster migrating protein complex, complex B. Although the contact residues for both of these proteins lie within the highly conserved Y-box transcriptional element, their binding specificity differs. The protein in complex B is a CCAAT-box-binding protein that may be similar or identical to NF-Y or YB1, previously identified class II Y-box-binding proteins. The DNA sequence requirements for the binding of the slower migrating complex, complex A, are not limited to CCAAT-box sequences but include sequences upstream of the Y box. These upstream sequences are required both for IFN-gamma-induced gene transcription and for IFN-gamma-induced modulation of binding activity. These data suggest a model in which upstream sequences contribute to formation of a lymphokine-regulated complex downstream. The IFN-gamma-induced binding protein described as complex A in this report differs from the IFN-gamma, -alpha, or -beta-induced nuclear factors previously identified.

In vivo evidence of interaction between interferon-stimulated gene factors and the interferon-stimulated response element

Constitutive and interferon-inducible DNase hypersensitive sites in vivo are located in interferon-stimulated gene promoters near sequences that specifically bind constitutive or interferon-inducible proteins in vitro. Induced sites and proteins are transient or maintained, depending on cell type. Interferon-stimulated gene transcription is transient or maintained in parallel.