Biomedical subjects

I Julkunen

Publications and source records attributed to I Julkunen.

At least 37 records · Page 2Linked to original sources

PubMed2000

Proteome analysis reveals ubiquitin-conjugating enzymes to be a new family of interferon-alpha-regulated genes.

Interferon (IFN)-alpha is a cytokine with antiviral, antiproliferative, and immunomodulatory properties, the functions of which are mediated via IFN-induced protein products. We used metabolic labeling and two-dimensional gel electrophoresis followed by MS and database searches to identify potentially new IFN-alpha-induced proteins in human T cells. By this analysis, we showed that IFN-alpha induces the expression of ubiquitin cross-reactive protein (ISG15) and two ubiquitin-conjugating enzymes, UbcH5 and UbcH8. Northern-blot analysis showed that IFN-alpha rapidly enhances mRNA expression of UbcH5, UbcH6 and UbcH8 in T cells. In addition, these genes were induced in macrophages in response to IFN-alpha or IFN-gamma stimulation or influenza A or Sendai virus infections. Similarly, IFNs enhanced UbcH8 mRNA expression in A549 lung epithelial cells, HepG2 hepatoma cells, and NK-92 cells. Cycloheximide, a protein synthesis inhibitor, did not block IFN-induced upregulation of UbcH8 mRNA expression, suggesting that UbcH8 is the primary target gene for IFN-alpha and IFN-gamma. Ubiquitin conjugation is a rate-limiting step in antigen presentation and therefore the upregulation of UbcHs by IFNs may contribute to the enhanced antigen presentation by macrophages. Our results show that proteome analysis of cells is a suitable method for identifying previously unrecognized cytokine-inducible genes.

Cells, Cultured↗

PubMed2000

Inhibition of human NK cell function by valinomycin, a toxin from Streptomyces griseus in indoor air.

Streptomyces griseus strains isolated from indoor dust have been shown to synthesize valinomycin. In this report, we show that human peripheral blood lymphocytes treated with small doses (30 ng ml(-1)) of pure valinomycin or high-pressure liquid chromatography-pure valinomycin from S. griseus quickly show mitochondrial swelling and reduced NK cell activity. Larger doses (>100 ng/ml(-1)) induced NK cell apoptosis within 2 days. Within 2 h, the toxin at 100 ng ml(-1) dramatically inhibited interleukin-15 (IL-15)- and IL-18-induced granulocyte-macrophage colony-stimulating factor and gamma interferon (IFN-gamma) production by NK cells. However, IFN-gamma production induced by a combination of IL-15 and IL-18 was somewhat less sensitive to valinomycin, suggesting a protective effect of the cytokine combination against valinomycin. Thus, valinomycin in very small doses may profoundly alter the immune response by reducing NK cell cytotoxicity and cytokine production.

Air Microbiology↗

PubMed1999

Impaired antiviral response in human hepatoma cells.

Hepatitis B, C, and D viruses can infect liver cells and in some individuals establish a chronic phase of infection. Presently, relatively little information is available on the antiviral mechanisms in liver cells. Because no good in vitro model infection systems for hepatitis viruses are available, we have used influenza A, Sendai, and vesicular stomatitis (VSV) viruses to characterize interferon (IFN) responses and IFN-induced antiviral mechanisms in human hepatoma cell lines. HepG2 or HuH7 cells did not show any detectable IFN-alpha/beta production in response to influenza A or Sendai virus infections. Treatment of cells with IFN-alpha resulted in upregulation of IFN-alpha-inducible Mx, 2',5'-oligoadenylate synthetase (OAS) and HLA class I gene expression but only with exceptionally high levels of IFN-alpha (>/=100 IU/ml). Accordingly, high pretreatment levels of IFN-alpha, 1000 IU/ml for influenza A and VSV and 100 IU/ml for Sendai virus, were required before any detectable antiviral activity against these viruses was seen. IFN-gamma had some antiviral effect against influenza A virus but appeared to be ineffective against VSV and Sendai virus. IFN-gamma upregulated HLA class I protein expression, whereas Mx or OAS expression levels were not increased. There was a modest upregulation of HLA class I expression during Sendai virus infection, whereas influenza A virus infection resulted, after an initial weak upregulation, in a clear decrease in HLA class I expression at late times of infection. The results suggest that hepatoma cells may have intrinsically poor ability to produce and respond to type I IFNs, which may contribute to their inability to efficiently resist viral infections.

2',5'-Oligoadenylate Synthetase↗

PubMed1999

Virus infection activates IL-1 beta and IL-18 production in human macrophages by a caspase-1-dependent pathway.

Monocytes and macrophages play a significant role in host's defense system, since they produce a number of cytokines in response to microbial infections. We have studied IL-1 beta, IL-18, IFN-alpha/beta, and TNF-alpha gene expression and protein production in human primary monocytes and GM-CSF-differentiated macrophages during influenza A and Sendai virus infections. Virus-infected monocytes released only small amounts of IL-1 beta or IL-18 protein, whereas 7- and 14-day-old GM-CSF-differentiated macrophages readily produced these cytokines. Constitutive expression of proIL-18 was seen in monocytes and macrophages, and the expression of it was enhanced during monocyte/macrophage differentiation. Expression of IL-18 mRNA was clearly induced only by Sendai virus, whereas both influenza A and Sendai viruses induced IL-1 beta mRNA expression. Since caspase-1 is known to cleave proIL-1 beta and proIL-18 into their mature, active forms, we analyzed the effect of a specific caspase-1 inhibitor on virus-induced IL-1 beta and IL-18 production. The release of IL-1 beta and IL-18, but not that of IFN-alpha/beta or TNF-alpha, was clearly blocked by the inhibitor. Our results suggest that the cellular differentiation is a crucial factor that affects the capacity of monocytes/macrophages to produce IL-1 beta and IL-18 in response to virus infections. Furthermore, the virus-induced activation of caspase-1 is required for the efficient production of biologically active IL-1 beta and IL-18.

Caspase 1↗

PubMed1999

Interferon-alpha activates multiple STAT proteins and upregulates proliferation-associated IL-2Ralpha, c-myc, and pim-1 genes in human T cells.

Interferon-alpha (IFN-alpha) is a pleiotropic cytokine that has antiviral, antiproliferative, and immunoregulatory functions. There is increasing evidence that IFN-alpha has an important role in T-cell biology. We have analyzed the expression of IL-2Ralpha, c-myc, and pim-1 genes in anti-CD3-activated human T lymphocytes. The induction of these genes is associated with interleukin-2 (IL-2)-induced T-cell proliferation. Treatment of T lymphocytes with IFN-alpha, IL-2, IL-12, and IL-15 upregulated IL-2Ralpha, c-myc, and pim-1 gene expression. IFN-alpha also sensitized T cells to IL-2-induced proliferation, further suggesting that IFN-alpha may be involved in the regulation of T-cell mitogenesis. When we analyzed the nature of STAT proteins capable of binding to IL-2Ralpha, pim-1, and IRF-1 GAS elements after cytokine stimulation, we observed IFN-alpha-induced binding of STAT1, STAT3, and STAT4, but not STAT5 to all of these elements. Yet, IFN-alpha was able to activate binding of STAT5 to the high-affinity IFP53 GAS site. IFN-alpha enhanced tyrosine phosphorylation of STAT1, STAT3, STAT4, STAT5a, and STAT5b. IL-12 induced STAT4 and IL-2 and IL-15 induced STAT5 binding to the GAS elements. Taken together, our results suggest that IFN-alpha, IL-2, IL-12, and IL-15 have overlapping activities on human T cells. These findings thus emphasize the importance of IFN-alpha as a T-cell regulatory cytokine.

CD3 Complex↗

PubMed1999

Maturation, activation, and protection of dendritic cells induced by double-stranded RNA.

The initiation of an immune response is critically dependent on the activation of dendritic cells (DCs). This process is triggered by surface receptors specific for inflammatory cytokines or for conserved patterns characteristic of infectious agents. Here we show that human DCs are activated by influenza virus infection and by double-stranded (ds)RNA. This activation results not only in increased antigen presentation and T cell stimulatory capacity, but also in resistance to the cytopathic effect of the virus, mediated by the production of type I interferon, and upregulation of MxA. Because dsRNA stimulates both maturation and resistance, DCs can serve as altruistic antigen-presenting cells capable of sustaining viral antigen production while acquiring the capacity to trigger naive T cells and drive polarized T helper cell type 1 responses.

Antigen Presentation↗

PubMed1999

Distinct patterns and kinetics of chemokine production regulate dendritic cell function.

Dendritic cells (DC) have been showed to both produce and respond to chemokines. To understand how this may impact on DC function, we analyzed the kinetics of chemokine production and responsiveness during DC maturation. After stimulation with LPS, TNF-alpha or CD40 ligand, the inflammatory chemokines MIP-1alpha, MIP-1beta and IL-8 were produced rapidly and at high levels, but only for a few hours, while RANTES and MCP-1 were produced in a sustained fashion. The constitutive chemokines TARC, MDC and PARC were expressed in immature DC and were up-regulated following maturation, while ELC was produced only at late time points. Activated macrophages produced a similar spectrum of chemokines, but did not produce TARC and ELC. In maturing DC chemokine production had different impact on chemokine receptor function. While CCR1 and CCR5 were down-regulated by endogenous or exogenous chemokines, CCR7 levels gradually increased in maturing DC and showed a striking resistance to ligand-induced down-regulation, explaining how DC can sustain the response to SLC and ELC throughout the maturation process. The time-ordered production of inflammatory and constitutive chemokines provides DC with the capacity to self-regulate their migratory behavior as well as to recruit other cells for the afferent and efferent limb of the immune response.

Chemokines↗

PubMed1999

Lack of induction by rhinoviruses of systemic type I interferon production or enhanced MxA protein expression during the common cold.

To study whether MxA protein expression is systemically upregulated during rhinovirus infection, blood specimens were collected from 40 patients with common cold and MxA expression in mononuclear cells analyzed by flow cytometry. None of the patients with a confirmed rhinovirus infection (n = 15) or with an infection of unknown etiology (n = 20) had elevated expression of the MxA protein (median fluorescence intensity, 549 and 582, respectively) when compared to healthy controls (n = 11, median 590). Patients with influenza infections had significantly elevated values (n = 5, median 750), and interferon could be detected only in serum samples from influenza patients. In conclusion, expression of MxA in blood lymphocytes and an apparently systemic type I interferon response is not induced during rhinovirus infection or during most other cases of common cold in young adult patients.

Adult↗

PubMed1999

Efficacy of PCR and other diagnostic methods for the detection of respiratory adenoviral infections.

Five methods were evaluated for the detection of adenovirus directly from nasopharyngeal aspirates (NPA), including conventional and rapid virus culture, two antigen detection tests, and the polymerase chain reaction (PCR). NPA specimens were obtained from 269 military conscripts suffering from an acute respiratory infection during an adenovirus outbreak. In 133 cases, paired blood specimens were also available. Virus culture followed by a hexon-specific immunofluorescence revealed 159 (59%) adenovirus-positive specimens and it was used as a reference method. In comparison to conventional culture, a rapid 2-day culture method had a sensitivity of 71%. The sensitivities of an enzyme immunoassay and time-resolved fluoroimmunoassay were 53% and 46%, respectively. The PCR method employing Ad7 hexon-specific primers showed a high sensitivity of 94%, and revealed an additional 15 (6%) specimens that could not be confirmed by virus culture. Serology based on significant adenovirus antibody rises had a diagnostic efficacy nearly equal to the virus culture and PCR methods, but a relatively high number of discordant results was found. The present study demonstrates that PCR is a very sensitive rapid diagnostic method for detecting adenovirus specific DNA in NPA specimens of adults.

Adenovirus Infections, Human↗

PubMed1998

Cells of the neuronal lineage play a major role in the generation of amyloid precursor fragments in gelsolin-related amyloidosis.

Gelsolin-related amyloidosis or familial amyloidosis, Finnish type (FAF) (OMIM No105120) is a hereditary amyloid disease caused by a mutation in a precursor protein for amyloid (gelsolin) and characterized by corneal dystrophy and polyneuropathy. In vitro expression of the FAF-mutant (Asp187 --> Asn/Tyr) secretory gelsolin in COS cells leads to generation of an aberrant polypeptide presumably representing the precursor for tissue amyloid. Here, we provide evidence that this abnormal processing results from defective initial folding of the secreted FAF gelsolin due to the lack of the Cys188-Cys201 disulfide bond, normally formed next to the FAF mutation site. We compared cells of different tissue origin and discovered a dramatic difference between the amount of cleavage of FAF gelsolin to the amyloid precursor in neuronal and non-neuronal cells. More than half of the mutant gelsolin was cleaved in PC12 and in vitro differentiated human neuronal progenitor cells. In contrast, human fibroblasts and Schwannoma cell cultures showed only a limited capacity to cleave FAF gelsolin, although the cleavage mechanism per se seems to be similar in the various cell types. The present findings of processing and distribution of secreted FAF gelsolin in the neuronal cells emphasize the role of neurons in the tissue pathogenesis of this amyloid polyneuropathy.

Amyloid Neuropathies↗

PubMed1998

Influenza A virus-induced IFN-alpha/beta and IL-18 synergistically enhance IFN-gamma gene expression in human T cells.

T cells contribute significantly the to host's early defense against viral and bacterial infections and are essential for clearance of the pathogen. IFN-gamma, a product of activated T and NK cells, has, in addition to its direct antimicrobial activity, a major role in activating cell-mediated immunity. Here we report that cytokines secreted by influenza A virus-infected macrophages are able to induce IFN-gamma synthesis in human T cells. Influenza A virus-infected human peripheral macrophages secreted IFN-alpha/beta, TNF-alpha, IL-1beta, and a recently identified cytokine, IL-18 (or IFN-gamma-inducing factor), whereas the production of IL-12 was not detected. Supernatants collected from virus-infected macrophages induced rapid IFN-gamma mRNA expression and protein production in T cells. This was down-regulated by the addition of neutralizing anti-IFN-alpha/beta Abs, whereas neutralizing anti-IL-12 Abs had no effect on IFN-gamma gene expression. Exogenously added IFN-alpha/beta also rapidly stimulated the synthesis of IFN-gamma mRNA in T cells independently of protein synthesis. IL-18 synergized with IFN-alpha to up-regulate IFN-gamma gene expression and protein production. The data suggest that IFN-alpha/beta and IL-18 produced by macrophages during virus infection may act together to induce IFN-gamma synthesis and, consequently, may play an important role for both of these cytokines in the development of Th1-type immune responses.

Cytokines↗

PubMed1998

Sudden deafness: lack of evidence for systemic viral infection.

The cause of sudden deafness remains unknown even though available evidence suggests that viral infection could be one factor involved. The presence of an interferon-inducible protein termed MxA in patients' leukocytes is a good marker of a systemic viral infection. This study included 20 patients with sudden deafness and 12 control subjects. Peripheral blood leukocytes obtained from the patients with sudden deafness did not express significantly higher levels of interferon-alpha/beta-inducible MxA protein than control subjects. In addition, no measurable interferon-alpha activity was detected in any of the serum specimens. These findings suggest that sudden deafness is not commonly associated with a systemic viral infection.

Adult↗

PubMed1998

Kinetics of cytokine and NFAT gene expression in human interleukin-2-dependent T lymphoblasts stimulated via T-cell receptor.

T cells respond to mitogenic or antigenic stimulation by proliferation and by turning on cytokine gene expression. Here we have analysed the kinetics and nature of cytokine production in human peripheral blood-derived T lymphoblasts stimulated with anti-CD3 antibodies or Lens culinaris lectin (LCL). T cells were purified from peripheral blood mononuclear cells (PBMC) and primarily activated with anti-CD3 antibodies and cultured in the presence of interleukin-2 (IL-2). Anti-CD3-restimulated T cells (mainly CD8+) produced IL-2, interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) and low levels of IL-4 and IL-10 transcripts and proteins. No IL-6 gene expression was observed. In LCL-stimulated cells the cytokine production pattern was very similar. Steady-state mRNA levels of IL-2, IL-10 and IFN-gamma peaked at 3 hr after anti-CD3 stimulation and declined rapidly thereafter. The kinetics of TNF-alpha mRNA expression was faster, being at its peak level 1 hr after stimulation. Anti-CD3-stimulated IL-2 gene expression was down-regulated by protein synthesis inhibitor, whereas IL-10, IFN-gamma and TNF-alpha genes were readily induced independent of ongoing protein synthesis. T-cell receptor stimulation also induced a very rapid expression of c-jun, c-fos and NFATc1 (NFATc) genes, the gene products of which are involved in cytokine gene expression. In conclusion, the cytokines synthesized by IL-2-dependent T cells were predominantly IL-2, IFN-gamma and TNF-alpha.

Antibodies↗

PubMed1998

The proximal interferon-stimulated response elements are essential for interferon responsiveness: a promoter analysis of the antiviral MxA gene.

Interferon (IFN)-inducible human MxA protein mediates resistance against influenza and several other RNA viruses. The MxA gene is under the control of type I IFN and, in certain cell types, is also directly activated by viruses. Here we show that in human macrophages, MxA mRNA levels are upregulated by very low doses of IFN-alpha in a dose-dependent manner. A similar, albeit much weaker, dose-dependent induction was seen with IFN-gamma. The induction was rapid and independent of protein synthesis. Interleukin-6 (IL-6) or tumor necrosis factor-alpha (TNF-alpha) did not influence MxA mRNA levels alone or in combination with IFNs, in spite of the presence of putative response elements of these cytokines in the MxA promoter. We show that the promoter of the MxA gene contains two functional IFN-stimulated response elements (ISRE) near the transcription start site and one homologous ISRE-like element, which is apparently nonfunctional, further upstream. The two proximal ISRE sites are essential for IFN-alpha-induced transcription and appear to be binding sites for IFN-stimulated gene factor 3 complex. In addition, EMSA and DNAse I footprinting analysis demonstrated that Spl binds with high affinity to a region encompassing nucleotides -25 and -50 and, thus, may provide means of interaction with the basal transcriptional machinery.

Antiviral Agents↗

PubMed1998

Lactobacilli and streptococci induce interleukin-12 (IL-12), IL-18, and gamma interferon production in human peripheral blood mononuclear cells.

Human peripheral blood mononuclear cells (PBMC) were stimulated with three nonpathogenic Lactobacillus strains and with one pathogenic Streptococcus pyogenes strain, and cytokine gene expression and protein production were analyzed. All bacteria strongly induced interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor alpha mRNA expression and protein production. S. pyogenes was the most potent inducer of secretion of IL-12 and gamma interferon (IFN-gamma), and two of three Lactobacillus strains induced IL-12 and IFN-gamma production. All strains induced IL-18 protein production. IL-10 and IL-4 production was induced weakly and not at all, respectively. Our data show that nonpathogenic lactobacilli and pathogenic streptococci can induce Th1 type cytokines IL-12, IL-18, and IFN-gamma in human PBMC.

Gram-Positive Bacteria↗

PubMed1998

Regulation of IRF and STAT gene expression by retinoic acid.

Retinoic acid has antiproliferative and differentiative effects on many cell types. However, the molecular mechanisms involved in ATRA (all-trans retinoic acid) -dependent growth inhibition and cell differentiation are poorly understood. On the other hand, several different cytokine specific transcription factors such as signal transducers and activators of transcription (STAT) and interferon regulatory factors (IRF) are known to be instrumental in mediating differentiative, growth regulatory and antiproliferative effects in cells. The IRF family consists of six different proteins, of which IRF-1 has been demonstrated to have antiproliferative and tumor suppressive functions. We have shown that ATRA activates IRF-1 gene expression in several myeloid leukemia cell lines (HL-60, NB4, THP-1, U937), all of which respond to ATRA by growth inhibition. In addition, during ATRA-induced myeloid differentiation, gene expression of STAT1, STAT2, and p48 was upregulated. These proteins are involved in IFN-alpha specific signaling. ATRA-induced expression of IRF and/or STAT transcription factors may be one of the molecular mechanisms mediating growth inhibition by ATRA.

DNA-Binding Proteins↗

PubMed1997

Nuclear cotransport mechanism of cytoplasmic human MxB protein.

Interferon-alpha/beta-inducible Mx proteins belong to the family of large GTPases and share high sequence homology with dynamins in their N-terminal GTP-binding domains. In addition, Mx proteins have a conserved C-terminal leucine zipper element that is involved in their oligomerization. Cytoplasmic human MxA protein mediates resistance to multiple RNA viruses, whereas no antiviral activity has been found for human MxB protein. We have previously shown that MxB protein exists as a nuclear 78-kDa and as a cytoplasmic 76-kDa form in interferon-alpha-induced human cells. Using various influenza hemagglutinin epitope-tagged MxB gene constructs in transient transfection experiments in COS-1 cells, we show that the cytoplasmic 76-kDa MxB protein forms hetero-oligomers with the nuclear 78-kDa MxB protein via the C-terminal leucine zipper element. This enables the cytoplasmic form of MxB protein to be translocated into the nucleus together with the nuclear form of MxB protein. This finding was confirmed in interferon-alpha-induced HEp-2 and T98G cells transfected with various MxB gene constructs. Cell fractionation studies also suggest that a considerable amount of the cytoplasmic MxB protein is also found in the nucleus. Using confocal laser microscopy, we also demonstrate that the cytoplasmic MxA and the nuclear MxB proteins do not colocalize/oligomerize with each other, and both of these proteins are retained in their specific cellular compartments.

Animals↗

PubMed1997

Interferons up-regulate STAT1, STAT2, and IRF family transcription factor gene expression in human peripheral blood mononuclear cells and macrophages.

IFN signaling is mediated by binding of IFNs to their receptors and subsequent activation of Janus tyrosine kinase (JAK)-STAT signaling pathway. Stimulation of cells with IFN-alpha leads to the assembly of IFN-stimulated gene factor 3 transcription factor complex formed by STAT1, STAT2, and p48 protein. IFN-gamma signaling is mediated by homodimeric STAT1 protein. Although these signaling molecules are expressed constitutively, there is also evidence of transcriptional regulation by IFNs. We have characterized the expression of STAT and IFN regulatory factor (IRF) family transcription factors in primary human blood mononuclear cells and macrophages in response to IFN-alpha and IFN-gamma stimulation. We show that IFN-alpha and IFN-gamma rapidly and efficiently enhanced STAT1, STAT2, p48, and IRF-1 gene expression. IFN-gamma induced IRF-1 gene expression more strongly than IFN-alpha. Stimulation experiments in the presence of protein synthesis inhibitor, cycloheximide, suggested that these genes were activated directly by IFNs. IRF-2 gene was apparently only weakly responsive to IFNs in these cells. When macrophages were pretreated with low doses of IFN-gamma and then stimulated with IFN-alpha, clearly enhanced formation of specific transcription factor complexes was detected. This suggests that higher intracellular levels of STAT1, STAT2, and p48 protein may result in enhanced signal transduction for cytokines utilizing these transcription factors.

Cells, Cultured↗