Lymphocytes, cytokines, inflammation, and immune trafficking

Detection of anti-topoisomerase I autoantibody in patients with silicosis

OBJECTIVES

The aim of this study was to detect anti-topoisomerase I (anti-topo I) autoantibodies, which are known to be limited in systemic sclerosis patients, in silicosis patients with no clinical symptoms of autoimmune disease.

METHODS

Serum anti-topo I autoantibodies were detected using ELISA. Differences in clinical parameters between patients with and without anti-topo I autoantibodies were analyzed.

RESULTS

Seven of 69 patients had anti-topo I autoantibodies. These 7 patients showed elevated PaCO(2) values (P=0.0212), and inverse correlations between serum soluble Fas levels and PaCO(2) values were found.

CONCLUSION

Anti-topo I autoantibodies were detected in 10.1% of silicosis patients without any clinical symptoms of autoimmune disease. The findings here suggest that the genesis of anti-topo I autoantibodies might be related to pulmonary involvement or lung fibrosis associated with progression of silicosis.

Role of CREM in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease. Immune complex, autoantibodies and autoreactive lymphocytes are involved in manifestations of SLE. Recently, investigations have indicated that expression of the transcription factor cAMP responsive element modulator (CREM) is abnormal in T cells and might play an important role in the pathogenesis of SLE. CREM has much influence on the promoters, such as IL-2, c-fos, TCR ζ, and SYK. Moreover, activity of CREM itself has been demonstrated, particularly with an auto-regulatory feedback mechanism. Therefore, we will discuss the association of CREM and SLE based on current knowledge to unravel the mechanism of CREM performance.

Association between variable number tandem repeats within the 3' flanking region of the interleukin-6 gene and systemic lupus erythematosus in Korean patients

Variable number tandem repeat (VNTR) polymorphism located in the 3' flanking region of the interleukin-6 (IL-6) gene was examined in Koreans with systemic lupus erythematosus (SLE). We identified 15 VNTR alleles (K1 to K15) in the 3' flanking region by Genescan analysis. The VNTR K8 allele, a 648-base pair (bp) allele, was most commonly found in Koreans, being present in 74.8% of the SLE patients and 70.3% of the normal controls. The VNTR K9 (642 bp) allele was associated with susceptibility to SLE. In addition, the VNTR K9 was significantly associated with leukopenia (p = 0.048), thrombocytopenia (p = 0.020), and elevated C-reactive protein (p = 0.019). These data suggest that the VNTR K9 in the 3' flanking region of the IL-6 gene may be associated with disease susceptibility and the clinical phenotypes of SLE.

Interleukin 6 gene polymorphisms are associated with systemic lupus erythematosus in Koreans

OBJECTIVE

Interleukin 6 (IL-6) gene polymorphisms are known to play a role in chronic inflammatory disorders. We searched for polymorphisms in the IL-6 gene and described their pathogenic role in Korean patients with systemic lupus erythematosus (SLE).

METHODS

Genomic DNA was extracted from 151 patients with SLE and 151 controls, and about 1.4 kb-sized IL-6 genes located between promoter region and exon 2 region were amplified by polymerase chain reaction. The promoter activity was analyzed by luciferase reporter assay in Hep3B cells and HeLa cells.

RESULTS

We identified 4 single-nucleotide polymorphisms (SNP; -572 C > G, -278 A > C in the promoter, and 330 T > G, and 334 A > T in exon 2) and a -373 A(n)T(n) tract polymorphism in the IL-6 gene. The genotype frequency, -373 A(10)T(11), -278 C, and 334 T allele were significantly associated with SLE (p < 0.001, p = 0.03 and p = 0.005, respectively). Patients with SLE carrying the -572 G allele had anti-dsDNA more frequently (p = 0.007). In addition, thrombocytopenia was significantly more common in patients carrying the -278 C allele (p = 0.006). In the haplotype analysis, patients with SLE had more frequently haplotype HT3 (CA(10)T(11)ATA, dominant model, p = 0.012) that was associated with arthritis, leukopenia, anti-dsDNA, and hypocomplementemia. Promoter reporter structures carrying the -278 C allele displayed significantly higher promoter activity than the -278 A allele in Hep3B cells (p < 0.001) and HeLa cells (p < 0.001).

CONCLUSION

These data suggest that IL-6 gene polymorphisms are associated with disease susceptibility and phenotype of SLE. In addition, promoter polymorphisms may be involved in regulation of IL-6 expression.

The cyclic AMP response element modulator {alpha} suppresses CD86 expression and APC function

The cAMP response element modulator (CREM)alpha is a widely expressed transcriptional repressor that is important for the termination of the T cell immune response and contributes to the abnormal T cell function in patients with systemic lupus erythematosus. We present evidence that APCs of Crem(-/-) mice express increased amounts of the costimulatory molecule CD86 and induce enhanced Ag-dependent and Ag-independent T cell proliferation. Similarly, human APCs in which CREMalpha was selectively suppressed expressed more CD86 on the surface membrane. CREMalpha was found to bind to the CD86 promoter and suppressed its activity. Transfer of APCs from Crem(-/-) mice into naive mice facilitated a significantly stronger contact dermatitis response compared with mice into which APCs from Crem(+/+) mice had been transferred. We conclude that CREMalpha is an important negative regulator of costimulation and APC-dependent T cell function both in vitro and in vivo.

Physiopathologie du lupus érythémateux systémique

Innate immunity is directly implicated in the pathophysiology of lupus through the dendritic cell system and the activation by immune complexes of some toll-like receptors (TLR). Interferon-alpha plays a key role in the pathophysiology of lupus and represents a promising target for immune therapy. Dendritic cells are activated and able to capture large quantities of nuclear antigen-containing bodies to stimulate specific adaptive immune response.

Association of deficient type II protein kinase A activity with aberrant nuclear translocation of the RII beta subunit in systemic lupus erythematosus T lymphocytes

Systemic lupus erythematosus (SLE) is an autoimmune disorder of indeterminate etiology characterized by abnormal T cell signal transduction and altered T cell effector functions. We have previously observed a profound deficiency of total protein kinase A (PKA) phosphotransferase activity in SLE T cells. Here we examined whether reduced total PKA activity in SLE T cells is in part the result of deficient type II PKA (PKA-II) isozyme activity. The mean PKA-II activity in SLE T cells was 61% of normal control T cells. The prevalence of deficient PKA-II activity in 35 SLE subjects was 37%. Deficient isozyme activity was persistent over time and was unrelated to SLE disease activity. Reduced PKA-II activity was associated with spontaneous dissociation of the cytosolic RIIbeta2C2 holoenzyme and translocation of the regulatory (RIIbeta) subunit from the cytosol to the nucleus. Confocal immunofluorescence microscopy revealed that the RIIbeta subunit was present in approximately 60% of SLE T cell nuclei compared with only 2-3% of normal and disease controls. Quantification of nuclear RIIbeta subunit protein content by immunoprecipitation and immunoblotting demonstrated a 54% increase over normal T cell nuclei. Moreover, the RIIbeta subunit was retained in SLE T cell nuclei, failed to relocate to the cytosol, and was associated with a persistent deficiency of PKA-II activity. In conclusion, we describe a novel mechanism of deficient PKA-II isozyme activity due to aberrant nuclear translocation of the RIIbeta subunit and its retention in the nucleus in SLE T cells. Deficient PKA-II activity may contribute to impaired signaling in SLE T cells.

Retinoic acid and its receptors repress the expression and transactivation functions of Nur77: a possible mechanism for the inhibition of apoptosis by retinoic acid

Nur77 (NGFI-B) is an orphan nuclear receptor that has been implicated in activation-induced T-cell apoptosis. Retinoids, potent immune modulators, were shown to inhibit the activation-induced apoptosis of immature thymocytes and T-cell hybridomas. To illustrate the mechanism of the inhibition, we examined the effects of retinoic acid (RA) on the expression and transactivation functions of Nur77 in the human peripheral blood mononuclear cells and the human T-cell leukemia, Jurkat. All-trans-RA remarkably repressed the DNA binding and transcriptional induction of Nur77. Among the two potential trans-acting factors that activate Nur77 gene promoter, i.e., AP-1 and related serum response factor (RSRF), all-trans-RA repressed DNA binding and reporter gene activity of AP-1 but not that of RSRF, suggesting that the inhibition may be mediated through AP-1. We also demonstrated a posttranscriptional regulation of Nur77 function by retinoid receptors by showing that transactivation activity of Nur77 was significantly inhibited by cotransfection of RARalpha or RXRalpha. Nur77 bound RARalpha or RXRalpha in both yeast and mammalian two-hybrid tests, suggesting that direct protein-protein interaction between these receptors may mediate the inhibition. Taken all together, we demonstrated that RA repressed Nur77 function through multiple mechanisms that may provide the basis for RA inhibition on the apoptosis of activated T-lymphocytes.

Serum levels of soluble Fas ligand in patients with silicosis

Certain patients with silicosis have been reported to exhibit immunological abnormalities such as the appearance of antinuclear antibodies and the occurrence of autoimmune diseases. Fas ligand (FasL) is a type II membrane protein which induces apoptosis by binding to its membrane receptor, Fas. FasL is converted to a soluble form by a metalloproteinase-like enzyme. We have already found serum soluble Fas (sFas) levels in silicosis patients as well as in patients with systemic lupus erythematosus (SLE) to be significantly higher than those in healthy volunteers. To examine further the role of the Fas/FasL system in silica-induced immunological abnormalities, we investigated serum soluble FasL (sFasL) levels in silicosis patients with no clinical symptoms of autoimmune diseases, using ELISA for sFasL. Although the serum sFasL levels in patients with SLE were significantly higher than those in healthy volunteers and showed a slight positive correlation with serum sFas levels, those in silicosis patients exhibited no significant difference from those in healthy volunteers, and there was no correlation with serum sFas levels. However, sFasL levels were elevated in silicosis patients with slight dyspnoea or normal PCO2 among various clinical parameters of silicosis. It may be speculated that the immunological disturbances presented by the abnormalities of apoptosis-related molecules in silicosis patients do not occur with a similar degree of respiratory involvement. Further studies are required to clarify which kinds of factors are involved in silicosis patients who exhibit immunological abnormalities.

Abnormal NF-κB Activity in T Lymphocytes from Patients with Systemic Lupus Erythematosus Is Associated with Decreased p65-RelA Protein Expression

Numerous cellular and biochemical abnormalities in immune regulation have been described in patients with systemic lupus erythematosus (SLE), including surface Ag receptor-initiated signaling events and lymphokine production. Because NF-κB contributes to the transcription of numerous inflammatory genes and has been shown to be a molecular target of antiinflammatory drugs, we sought to characterize the functional role of the NF-κB protein complex in lupus T cells. Freshly isolated T cells from lupus patients, rheumatoid arthritis (RA) patients, and normal individuals were activated physiologically via the TCR with anti-CD3 and anti-CD28 Abs to assess proximal membrane signaling, and with PMA and a calcium ionophore (A23187) to bypass membrane-mediated signaling events. We measured the NF-κB binding activity in nuclear extracts by gel shift analysis. When compared with normal cells, the activation of NF-κB activity in SLE patients was significantly decreased in SLE, but not in RA, patients. NF-κB binding activity was absent in several SLE patients who were not receiving any medication, including corticosteroids. Also, NF-κB activity remained absent in follow-up studies. In supershift experiments using specific Abs, we showed that, in the group of SLE patients who displayed undetectable NF-κB activity, p65 complexes were not formed. Finally, immunoblot analysis of nuclear extracts showed decreased or absent p65 protein levels. As p65 complexes are transcriptionally active in comparison to the p50 homodimer, this novel finding may provide insight on the origin of abnormal cytokine or other gene transcription in SLE patients.

Diminished Levels of Protein Kinase A RIα and RIβ Transcripts and Proteins in Systemic Lupus Erythematosus T Lymphocytes

Deficient type I protein kinase A phosphotransferase activity occurs in the T cells of 80% of subjects with systemic lupus erythematosus (SLE). To investigate the mechanism of this deficient isozyme activity, we hypothesized that reduced amounts of type I regulatory (RI) isoform transcripts, RIα and RIβ, may be associated with a diminution of RIα and/or RIβ protein. Sixteen SLE subjects with a mean (±1 SD) SLE disease activity index of 12.4 ± 7.2 were studied. Controls included 16 normal subjects, six subjects with primary Sjögren’s syndrome (SS), and three subjects with SS/SLE overlap. RT-PCR revealed that normal, SS, SS/SLE, and SLE T cells expressed mRNAs for all seven R and catalytic (C) subunit isoforms. Quantification of mRNAs by competitive PCR revealed that the ratio of RIα mRNA to RIβ mRNA in normal T cells was 3.4:1. In SLE T cells there were 20 and 49% decreases in RIα and RIβ mRNAs (RIβ; p = 0.008), respectively, resulting in an RIα:RIβ mRNA of 5.3:1. SS/SLE T cells showed a 72.5% decrease in RIβ mRNA compared with normal controls (p = 0.01). Immunoblotting of normal T cell RIα and RIβ proteins revealed a ratio of RIα:RIβ of 3.2:1. In SLE T cells, there was a 30% decrease in RIα protein (p = 0.002) and a 65% decrease in RIβ protein (p &lt; 0.001), shifting the ratio of RIα:RIβ protein to 6.5:1. T cells from 25% of SLE subjects lacked any detectable RIβ protein. Analysis of several lupus T cell lines demonstrated a persistent deficiency of both proteins, excluding a potential effect of disease activity. In conclusion, reduced expression of RIα and RIβ transcripts is associated with a decrement in RIα and RIβ proteins and may contribute to deficient type I protein kinase A isozyme activity in SLE T cells.

Protein Kinase C Regulates Fas (CD95/APO-1) Expression

Fas (CD95/APO-1) is a transmembrane protein of the TNF/neuron growth factor receptor family. Ligation of Fas by specific Abs or Fas ligand (FasL/CD95 ligand) induces rapid apoptotic cell death in a variety of cell types. Despite progress in understanding the death signals transduced from Fas, very little is known with regard to the mechanisms by which Fas expression is regulated. Using our previously established murine T cell hybridoma model A1.1, we show that specific protein kinase C (PKC) inhibitors could block activation-induced Fas expression and apoptosis. The activation of PKC with PMA or 1-oleoyl-2-acetyl-sn-glycerol could mimic the TCR signal by inducing the expression of Fas but not FasL. PKC-dependent Fas expression was also observed in several murine and human tumor cell lines. Since the inhibition of Ca2+ redistribution by an inhibitor of intracellular Ca2+ mobilization, 8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride, inhibited TCR-induced FasL but not Fas, the expression of Fas appears to be independent of Ca2+ mobilization. Significantly, expression of the newly identified Fas-regulatory gene, TDAG51, was found to be dependent upon the activity of PKC. PKC activation only induced Fas expression in cells expressing wild-type TDAG51. Thus, Fas expression is likely mediated by PKC through TDAG51.

Immunopathogenesis of SLE

Systemic lupus erythematosus (SLE) is an autoimmune rheumatic disease characterized by the deposition of autoantibodies and immune complexes, leading to tissue damage. The immunopathogenesis of SLE is like a jigsaw puzzle, some pieces of which are missing or have not fallen into place. In predisposed individuals, the initial stimulus is likely to be one or more of the environmental agents interacting with susceptibility genes. Once the critical threshold is breached there is a failure of the immune system to downregulate the ensuing abnormal immune response, involving polyclonal B cell activation and hyperactive T cell help. Key questions include, what are the processes behind the availability of autoantigens and the breakdown of tolerance that give rise to the pathogenic autoantibodies? Current areas of research also involve the roles played by cytokines, adhesion molecules, co-stimulatory molecules and apoptosis.