Analysis of proteins that interact with the IL-2 regulatory region in patients with rheumatic diseases

Therapeutic potential of interleukin-2 in autoimmune diseases

Autoimmune diseases are characterized by dysregulation and aberrant activation of cells in the immune system. Therefore, restoration of the immune balance represents a promising therapeutic target in autoimmune diseases. Interleukin-2 (IL-2) can promote the expansion and differentiation of different immune cell subsets dose-dependently. At high doses, IL-2 can promote the differentiation and expansion of effector and memory T cells, whereas at low doses, IL-2 can promote the differentiation, survival, and function of regulatory T (T_reg) cells, a CD4⁺ T cell subset that is essential for the maintenance of immune homeostasis and immune tolerance. Therefore, IL-2 exerts immunostimulatory and immunosuppressive effects in autoimmune diseases. The immunoregulatory role of low-dose IL-2 has sparked excitement for the therapeutic exploration of modulating the IL-2-T_reg axis in the context of autoimmune diseases. In this review, we discuss recent advances in the therapeutic potential of IL-2 or IL-2-derived molecules in the treatment of autoimmune diseases.

RGC32 Promotes Bleomycin-Induced Systemic Sclerosis in a Murine Disease Model by Modulating Classically Activated Macrophage Function

Systemic sclerosis (SSc) is a multisystem autoimmune disorder that is characterized by inflammation and fibrosis in the skin and internal organs. Previous studies indicate that inflammatory cells and cytokines play essential roles in the pathogenesis of SSc; however, the mechanisms that underlie the inflammation-driven development of SSc are not fully understood. In this study, we show that response gene to complement 32 (RGC32) is abundantly expressed in mouse macrophages in the early stage of bleomycin-induced SSc. Importantly, RGC32 is required to induce the inflammatory response during the onset of SSc, because RGC32 deficiency in mice significantly ameliorates skin and lung sclerosis and inhibits the expression of inflammatory mediators inducible NO synthase (iNOS) and IL-1β in macrophages. RGC32 appears to be a novel regulator for the differentiation of classically activated macrophages (M1 macrophages). IFN-γ and LPS stimulation induces RGC32 expression in primary peritoneal macrophages and bone marrow-derived macrophages. RGC32 deficiency impairs the polarization of M1 macrophages and attenuates iNOS and IL-1β production. Mechanistically, RGC32 interacts with NF-κB proteins and promotes iNOS and IL-1β expression by binding to their promoters. Collectively, our data reveal that RGC32 promotes the onset of SSc by regulating the inflammatory response of M1 macrophages, and it may serve as a promising therapeutic target for treating SSc.

Association of the Smad3 and NFATc2 gene polymorphisms and their serum levels with susceptibility to rheumatoid arthritis in Polish cohorts

One among many factors involved in induction of rheumatoid arthritis (RA) are T cells, the differentiation of which depends upon a unique combination of stimulants and subsequent activation of diverse transcription factors. The aim of this study was to identify polymorphic variants in Smad3 and NFATc2 genes and their possible association with susceptibility to and severity of RA. A total of 272 RA patients, 321 for Smad3 and 304 for nuclear factor of activated T cells (NFAT)c2 healthy individuals, were examined for rs6494629 C/T and rs2289263 T/G Smad3 and rs880324 NFATc2 gene polymorphisms using the polymerase chain reaction-fragment length polymorphism (PCR-RFLP) method and TaqMan single nucleotide polymorphism (SNP) genotyping assay, respectively. Serum Smad3 and NFATc2 levels in RA patients and controls were measured by enzyme-linked immunosorbent assay (ELISA). The rs6494629 C/T Smad3 gene polymorphism under the recessive (TT versus CC+CT) and over-dominant (CC+TT versus CT) models were associated with RA (P=0.014 and P=0.008, respectively). Smad3 rs2289263 T/G revealed differences in the case-control distribution in co-dominant, recessive and over-dominant models (P=0.037, P=0.010, P=0.034). Overall, rs6494629 C/T and rs2289263 T/G Smad3 gene polymorphisms were in a weak linkage disequilibrium (LD) with D'=0.116 and r(2)=0.004. After Bonferroni correction, the genotype-phenotype analysis showed no significant correlation of the Smad3 rs6494629 C/T and rs2289263 T/G and NFATc2 rs2289263 TT polymorphisms with disease activity, joint damage and extra-articular manifestation in RA patients. Serum Smad3 and NFATc2 levels were significantly higher in RA patients than in control groups (both P=0 0000). The present findings indicated that Smad3 genetic polymorphisms may be associated with the susceptibility to RA in the Polish population.

The c-Rel subunit of NF-κB regulates epidermal homeostasis and promotes skin fibrosis in mice

The five subunits of transcription factor NF-κB have distinct biological functions. NF-κB signaling is important for skin homeostasis and aging, but the contribution of individual subunits to normal skin biology and disease is unclear. Immunohistochemical analysis of the p50 and c-Rel subunits within lesional psoriatic and systemic sclerosis skin revealed abnormal epidermal expression patterns, compared with healthy skin, but RelA distribution was unaltered. The skin of Nfkb1(-/-) and c-Rel(-/-) mice is structurally normal, but epidermal thickness and proliferation are significantly reduced, compared with wild-type mice. We show that the primary defect in both Nfkb1(-/-) and c-Rel(-/-) mice is within keratinocytes that display reduced proliferation both in vitro and in vivo. However, both genotypes can respond to proliferative stress, with 12-O-tetradecanoylphorbol-13-acetate-induced epidermal hyperproliferation and closure rates of full-thickness skin wounds being equivalent to those of wild-type controls. In a model of bleomycin-induced skin fibrosis, Nfkb1(-/-) and c-Rel(-/-) mice displayed opposite phenotypes, with c-Rel(-/-) mice being protected and Nfkb1(-/-) developing more fibrosis than wild-type mice. Taken together, our data reveal a role for p50 and c-Rel in regulating epidermal proliferation and homeostasis and a profibrogenic role for c-Rel in the skin, and identify a link between epidermal c-Rel expression and systemic sclerosis. Modulating the actions of these subunits could be beneficial for treating hyperproliferative or fibrogenic diseases of the skin.

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.

Abnormal intracellular distribution of NFAT1 in T lymphocytes from patients with systemic lupus erythematosus and characteristic clinical features

Systemic lupus erythematosus (SLE) presents various clinical features; however, underlying mechanisms remain unclear. In the immunity of SLE, impaired T cell receptor (TCR) signaling and altered cytokine production are in the center of pathogenesis, although, little is known about NFAT (nuclear factor of activated T cells) in lupus T lymphocytes. TCR stimulation activates NFAT1 through Ca2+/calcineurin (Cn) pathway, facilitating nuclear translocation of NFAT1 from cytosol. Therefore, we investigated relationship of disease activity/features and intracellular NFAT1 localization in T lymphocytes from active lupus patients by fractionation. Results showed no significant relationship between disease activity and NFAT1 distribution. However, interestingly, we observed skewed NFAT1 distribution in pellet in patients with active lupus nephritis or pleuritis. In vitro cyclosporin A treatment suggested autonomously activated Ca2+/Cn pathway in lupus T lymphocytes. Considering these results, NFAT1 might be presenting the clinical heterogeneity in SLE.

Glucocorticoid receptor, nuclear factor kappaB, activator protein-1 and C-jun N-terminal kinase in systemic lupus erythematosus patients

OBJECTIVE

Due to the crucial role of the glucocorticoid receptor (GR), nuclear factor kappaB (NFkappaB), activator protein-1 (AP-1) and c-jun N-terminal kinase (JNK) in regulating inflammatory mediators and immune responses, we investigated their potential role in systemic lupus erythematosus (SLE).

PATIENTS AND METHODS

Whole cell and nuclear extracts from peripheral blood lymphocytes, isolated from 25 SLE patients and 25 controls, were immunoblotted using GR, p65/NFkappaB, c-fos and JNK1 antibodies. The electrophoretic mobility shift assay (EMSA) assessed GR, NFkappaB and AP-1-DNA binding in nuclear aliquots. Associations with the disease state and the doses of corticosteroids administered were studied.

RESULTS

(i) SLE patients had lower GR-DNA binding (p < 0.001), NFkappaB-DNA binding (p < 0.001) and whole cell c-fos (p < 0.01) but higher nuclear NFkappaB (p < 0.01). (ii) SLE patients and controls had similar AP-1-DNA binding, nuclear c-fos, GR and JNK, whole cell GR, NFkappaB and JNK. (iii) No differences were detected between active and non-active SLE or high- and low-dose corticosteroid patients. (iv) In SLE, increases in GR-DNA binding were associated with increases in NFkappaB-DNA binding (p < 0.0001), and increases in nuclear JNK were associated with increases in AP-1-DNA binding (p < 0.01). (v) In controls, increases in GR-DNA binding were associated with increases in AP-1-DNA binding (p < 0.001).

CONCLUSION

We suggest disturbed GR, NFkappaB, AP-1 and JNK signaling in SLE, characterized by a reduced GR- and NFkappaB-DNA binding, a significant association between GR-mediated and NFkappaB-driven pathways, and a significant correlation between nuclear JNK- and AP-1-driven pathways. These disturbances may contribute to abnormal cytokine production and the etiopathogenesis of SLE.

Decreased T cell ERK pathway signaling may contribute to the development of lupus through effects on DNA methylation and gene expression

T cells from patients with active lupus have multiple biochemical abnormalities. One of these is DNA hypomethylation, which in model systems alters gene expression and induces lupus-like autoimmunity. Recent reports indicate that DNA methylation is regulated in part by the ERK pathway, and that ERK pathway signaling is diminished in lupus T cells. This suggests a model in which defective T cell ERK pathway signaling contributes to the development of autoimmunity by decreasing DNA methyltransferase expression, modifying DNA methylation patterns and altering gene expression. This mechanism could contribute to idiopathic and drug-induced lupus.

Involvement of NF-kappaB signalling in skin physiology and disease

Transcription factors of the nuclear factor-kappaB (NF-kappaB)/Rel family play a crucial role in gene regulation during a variety of different cellular processes. This review focuses on the increasing knowledge of the role of NF-kappaB in skin physiology and pathology. Several studies demonstrate that NF-kappaB, or components of the system such as IkappaB kinase (IKK)-alpha, seem to be involved in epidermal development and differentiation. Furthermore, a dysregulation of NF-kappaB is suggested to play an important role in skin pathology, including proliferative disorders, e.g. psoriasis, inflammatory processes such as incontinentia pigmenti (IP), sunburn, Lyme disease, allergic contact dermatitis and autoimmune diseases, as well as also in skin carcinogenesis. However, although the knowledge concerning the role of NF-kappaB in the homeostasis of the skin is steadily increasing, many more questions need to be answered.

In vitro-activated human lupus T cells express normal estrogen receptor proteins which bind to the estrogen response element

We have shown that estrogen receptor (ERalpha, ERbeta) transcripts are expressed in SLE and normal T cells. In this study, T cell nuclear extracts from female lupus patients and normal donors were tested for biologically active ER proteins capable of binding to the human estrogen response element (hERE) by electrophoretic mobility shift assays. When peripheral blood T cells were stimulated with 17beta-estradiol (E2), PMA and ionomycin, two major retarded bands in T cell nuclear extracts exhibited a migration pattern similar to slow migrating protein-ERE complexes in human breast cancer cell extracts. T cells cultured only with E2 did not have these complexes. The formation of the complexes was inhibited by competition with the hERE cold oligonucleotide and partially with anti-ERalpha antibodies. There was no notable difference in the migration pattern of ERE-binding proteins between the SLE and normal T cell extracts. Together, these results suggest that activated human T cells, whether lupus-derived or normal-derived, contain biologically active ERalpha proteins. Other factors may be responsible for differential sensitivity of lupus T cells to estrogen.

Decreased Ras-mitogen-activated protein kinase signaling may cause DNA hypomethylation in T lymphocytes from lupus patients

OBJECTIVE

Previous studies have shown that inhibiting T cell DNA methylation causes a lupus-like disease by modifying gene expression. T cells from patients with lupus exhibit diminished levels of DNA methyltransferase (MTase) enzyme activity, hypomethylated DNA, and changes in gene expression similar to those exhibited by T cells treated with methylation inhibitors, suggesting that DNA hypomethylation may contribute to human lupus. Since it is known that DNA MTase levels are regulated by the ras-mitogen-activated protein kinase (MAPK) pathway, this study sought to determine whether decreased ras-MAPK signaling could account for the DNA hypomethylation in lupus T cells.

METHODS

DNA MTase messenger RNA (mRNA) from lupus patients and from healthy controls was quantitated by Northern analysis, and ras-MAPK signaling was determined by immunoblotting with antibodies to the activated forms of extracellular receptor-associated kinase (ERK). Results were compared with those in T cells in which ras-MAPK signaling was inhibited with a soluble inhibitor of MAPK ERK I (MEK1).

RESULTS

T cells from patients with active lupus had diminished DNA MTase mRNA levels and decreased signaling through the ras-MAPK pathway. Inhibiting signaling through the ras-MAPK pathway with the MEK1 inhibitor decreased DNA MTase mRNA and enzyme activity to the levels seen in lupus T cells, and resulted in DNA hypomethylation resembling that seen in lupus T cells.

CONCLUSION

These results suggest that a decrease in signaling through the ras-MAPK pathway may be responsible for the decreased MTase activity and DNA hypomethylation in patients with lupus.

Interleukin-10 signaling blocks inhibitor of kappaB kinase activity and nuclear factor kappaB DNA binding

The transcription factor nuclear factor kappaB (NF-kappaB) coordinates the activation of numerous genes in response to pathogens and proinflammatory cytokines and is, therefore, pivotal in the development of acute and chronic inflammatory diseases. In its inactive state, NF-kappaB is constitutively present in the cytoplasm as a p50-p65 heterodimer bound to its inhibitory protein IkappaB. Proinflammatory cytokines, such as tumor necrosis factor (TNF), activate NF-kappaB by stimulating the activity of the IkappaB kinases (IKKs) which phosphorylate IkappaBalpha on serine residues 32 and 36, targeting it for rapid degradation by the 26 S proteasome. This enables the release and nuclear translocation of the NF-kappaB complex and activation of gene transcription. Interleukin-10 (IL-10) is a pleiotropic cytokine that controls inflammatory processes by suppressing the production of proinflammatory cytokines which are known to be transcriptionally controlled by NF-kappaB. Conflicting data exists on the effects of IL-10 on TNF- and LPS-induced NF-kappaB activity in human monocytes and the molecular mechanisms involved have not been elucidated. In this study, we show that IL-10 functions to block NF-kappaB activity at two levels: 1) through the suppression of IKK activity and 2) through the inhibition of NF-kappaB DNA binding activity. This is the first evidence of an anti-inflammatory protein inhibiting IKK activity and demonstrates that IKK is a logical target for blocking inflammatory diseases.

High prevalence of T cell type I protein kinase A deficiency in systemic lupus erythematosus

OBJECTIVE

To estimate the prevalence of protein kinase A type I isozyme (PKA-I) deficiency in a cohort of systemic lupus erythematosus (SLE) patients, and to establish whether the isozyme deficiency is associated with SLE disease activity.

METHODS

Thirty-five SLE patients and 35 age-, sex-, and race-matched normal controls were studied. Fifteen subjects were restudied on at least 3 occasions over a 4-year interval. Clinical disease activity was estimated by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), and the T cell activation markers CD25+ and HLA-DR+ were quantified by flow cytometry. PKA-I isozyme activities were quantified in enriched T cells. Statistical analyses were performed by Student's t-test, Mann Whitney U test, and Pearson product moment test.

RESULTS

The mean PKA-I activity in SLE T cells (540 pmoles/minute/mg of protein) was significantly lower than that in control T cells (1,578 pmoles/ minute/mg of protein) (P<0.001). The prevalence of isozyme deficiency in this cohort was 80%. During a 4-year interval, PKA-I activities remained significantly reduced, whereas SLEDAI scores significantly improved. There was no relationship between deficient PKA-I activity and either SLEDAI scores or the proportion of T cells bearing CD25+ or HLA-DR+ activation markers.

CONCLUSION

There is a high prevalence of deficient T cell PKA-I isozyme activity in SLE that persists over time and is independent of SLE disease activity.

Gender differences in autoimmune diseases: estrogen increases calcineurin expression in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) predominantly affects women (9:1 compared to men) of childbearing age and often decreases its intensity in postmenopausal women, suggesting that sex hormones play a role in its pathogenesis. Comparison of steady-state levels of calcineurin mRNA using RNase protection assays revealed increased calcineurin expression in response to estradiol in cultured T cells from nine female lupus patients. Calcineurin mRNA levels did not increase significantly in T cells from eight age-matched normal control female volunteers. Estrogen-dependent calcineurin mRNA increased in a dose-dependent fashion, while progesterone and dexamethasone did not increase calcineurin mRNA in patient cells. Lupus T cell calcineurin mRNA increased in response to estradiol at 6 h but not at 3 h. Calcineurin phosphatase activity increased in lupus T cell extracts after incubation of cells with estradiol, while phosphatase activity in normal T cells was unaffected by estrogen. Calcineurin expression in T cells from patients with vasculitis and rheumatoid arthritis taking medications similar to those taken by the lupus patients was unaffected by estradiol. This study provides the first evidence for a molecular marker of estrogen action in lupus patients and suggests that estrogen-dependent changes in lupus T cell calcineurin could alter proinflammatory cytokine gene regulation and T-B cell interactions.

Interleukin-2 and systemic lupus erythematosus--fifteen years later

Systemic lupus erythematosus (SLE) is a highly heterogeneous disorder in which multiple immunologic abnormalities have been described. In this review, we thoroughly analyse the impaired T cell production of, and response to, interleukin-2 (IL-2) characteristic of patients with SLE. Since it was first reported, several articles have provided us with enlightening, but somewhat confusing, data that reveal the complexity of the subject. The IL-2 production by T cells is part of a complex network in which a discrete alteration is capable of disrupting the whole system. On the other hand, regulatory mechanisms exist that, in an attempt to compensate the primary alteration, provoke secondary defects. Evidence indicates that this defect is not intrinsic, but rather, results from multiple microenvironmental influences that act on the T cell and modify its activation state and its cytokine production. Abnormalities in co-stimulatory mechanisms and in cytokines that may be related to the IL-2 production deficiency, have been described in patients with SLE. We also consider the information derived from murine SLE models, IL-2 knockout models and reports concerning the immune dysregulation present in patients with SLE.

Direct evidence of high DNA binding activity of transcription factor AP-1 in rheumatoid arthritis synovium

OBJECTIVE

To investigate the possible activation of transcription factor AP-1 in rheumatoid arthritis (RA) and its involvement in the pathogenesis of RA.

METHODS

Synovial tissues and peripheral blood samples were obtained from 25 patients with RA and 5 patients with osteoarthritis (OA) during arthroplasty and synovectomy. The synovial tissue was digested with collagenase and separated into adherent and nonadherent cells by plastic-adhesion methods. Nuclear extracts obtained from each sample were examined by electrophoretic mobility shift assay to determine the DNA binding activity of AP-1. The expression of c-fos and c-jun messenger RNA (mRNA) was examined by in situ reverse transcription assay.

RESULTS

A markedly high DNA binding activity of AP-1 was detected in the synovial tissues of RA patients, while virtually no activity or only a little activity was observed in OA patients. Following separation of adherent and nonadherent cells, the AP-1 activity was mainly detected in adherent cells, which consisted of synovial cells and macrophages. However, the activity was significantly higher in the mononuclear cells infiltrating into RA synovium than in RA peripheral blood mononuclear cells. The high DNA binding activity of AP-1 in RA correlated with the expression of c-fos and c-jun mRNA in situ. Furthermore, AP-1 binding activity also correlated with disease activity.

CONCLUSION

In RA synovium, AP-1 DNA binding activity was constitutively up-regulated. These findings suggest that AP-1 may play an important role in the pathogenesis of RA, including synovial hyperplasia and abnormal immune responses.

Abnormality of Oct-1 DNA binding in T cells from Sjögren's syndrome patients

Primary Sjögren's syndrome (SS) is an autoimmune rheumatic disease characterized by T cell hypoactivity. To understand the diminished T cell response to activation signals, we measured nucleoprotein DNA-binding activities regulating gene expression during T cell activation using the electrophoretic mobility shift assay. Peripheral blood lymphocytes from 9/19 SS patients were found to be defective in their ability to bind an october sequence (Oct-1). This Oct-1-binding phenotype remained stable in culture for up to 3 days prior to activation. This abnormality was not seen in resting T cells nor T cells from patients with systemic lupus erythematosus, rheumatoid arthritis (RA), or SS accompanied by RA. The SS Oct-1 DNA-binding abnormality correlated significantly with an inability of cells to exit the Gzero/G1 cell cycle phase when stimulated in vitro. Importantly, nucleoprotein extracts showing decreased DNA-binding activity had normal amounts of Oct-1 proteins as determined by immunoprecipitation, implying a functional defect in the Oct-1 protein. Moreover, defective DNA binding was corrected by treatment with acid phosphatase.