Effect of trichostatin A on human T cells resembles signaling abnormalities in T cells of patients with systemic lupus erythematosus: a new mechanism for TCR zeta chain deficiency and abnormal signaling

Global histone modification analysis reveals hypoacetylated H3 and H4 histones in B Cells from systemic lupus erythematosus patients

OBJECTIVE

Histone modification is an epigenetic alteration which either activates or suppresses gene transcription. Studies revealed the association of altered global histone modification in T cells and monocytes with the pathogenesis of Systemic lupus erythematosus (SLE). Herein, we investigated the level of global histone 3 (H3) and histone 4 (H4) acetylation in B cells of SLE patients.

METHODS

Total 20 SLE patients and 10 healthy donors were recruited. Global H3 and H4 acetylation in B cells was assessed by Epigentek assay kits. Expression of DNA methyltransferase 1 (DNMT1) in B cells was analyzed by staining cells with anti-CD19/20 and anti-DNMT1 antibody. The concentration of BAFF and APRIL was measured using LegendPlex Human B cells panel and circulating ANAs were determined using indirect immunofluorescence.

RESULTS

Compared to healthy donors, B cells from SLE patients were found to be hypoacetylated on both H3 and H4 histones together with a decrease in the expression of DNMT1. Indeed, stratification of SLE patients on the basis of disease activity did not show any variation, as the amount of H3 and H4 acetylation in both inactive and active SLE patients was almost uniform.

CONCLUSION

These findings suggest that SLE-B cells were manifested with aberrant histone acetylation levels.

Post-translational modifications in T cells in systemic erythematosus lupus

Systemic erythematosus lupus (SLE) is a classic autoimmune disease characterized by multiple autoantibodies and immune-mediated tissue damage. The aetiology of this disease is still unclear. A new drug, belimumab, which acts against the B-lymphocyte stimulator (BLyS), can effectively improve the condition of SLE patients, but it cannot resolve all SLE symptoms. The discovery of novel, precise therapeutic targets is urgently needed. It is well known that abnormal T-cell function is one of the most crucial factors contributing to the pathogenesis of SLE. Protein post-translational modifications (PTMs), including phosphorylation, glycosylation, acetylation, methylation, ubiquitination and SUMOylation have been emphasized for their roles in activating protein activity, maintaining structural stability, regulating protein-protein interactions and mediating signalling pathways, in addition to other biological functions. Summarizing the latest data in this area, this review focuses on the potential roles of diverse PTMs in regulating T-cell function and signalling pathways in SLE pathogenesis, with the goal of identifying new targets for SLE therapy.

The Epigenetics of Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a life-threatening autoimmune disease that is characterized by dysregulated dendritic cells, T and B cells, and abundant autoantibodies. The pathogenesis of lupus remains unclear. However, increasing evidence has shown that environment factors, genetic susceptibilities, and epigenetic regulation contribute to abnormalities in the immune system. In the past decades, several risk gene loci have been identified, such as MHC and C1q. However, genetics cannot explain the high discordance of lupus incidence in homozygous twins. Environmental factor-induced epigenetic modifications on immune cells may provide some insight. Epigenetics refers to inheritable changes in a chromosome without altering DNA sequence. The primary mechanisms of epigenetics include DNA methylation, histone modifications, and non-coding RNA regulations. Increasing evidence has shown the importance of dysregulated epigenetic modifications in immune cells in pathogenesis of lupus, and has identified epigenetic changes as potential biomarkers and therapeutic targets. Environmental factors, such as drugs, diet, and pollution, may also be the triggers of epigenetic changes. Therefore, this chapter will summarize the up-to-date progress on epigenetics regulation in lupus, in order to broaden our understanding of lupus and discuss the potential roles of epigenetic regulations for clinical applications.

The Pathogenic Role of Dysregulated Epigenetic Modifications in Autoimmune Diseases

Autoimmune diseases can be chronic with relapse of inflammatory symptoms, but it can be also acute and life-threatening if immune cells destroy life-supporting organs, such as lupus nephritis. The etiopathogenesis of autoimmune diseases has been revealed as that genetics and environmental factors-mediated dysregulated immune responses contribute to the initiation and development of autoimmune disorders. However, the current understanding of pathogenesis is limited and the underlying mechanism has not been well defined, which lows the development of novel biomarkers and new therapeutic strategies for autoimmune diseases. To improve this, broadening and deepening our understanding of pathogenesis is an unmet need. As genetic susceptibility cannot explain the low accordance rate of incidence in homozygous twins, epigenetic regulations might be an additional explanation. Therefore, this review will summarize current progress of studies on epigenetic dysregulations contributing to autoimmune diseases, including SLE, rheumatoid arthritis (RA), psoriasis, type 1 diabetes (T1D), and systemic sclerosis (SSc), hopefully providing opinions on orientation of future research, as well as discussing the clinical utilization of potential biomarkers and therapeutic strategies for these diseases.

The Impact of Protein Acetylation/Deacetylation on Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease in which the body’s immune system mistakenly attacks healthy cells. Although the exact cause of SLE has not been identified, it is clear that both genetics and environmental factors trigger the disease. Identical twins have a 24% chance of getting lupus disease if the other one is affected. Internal factors such as female gender and sex hormones, the major histocompatibility complex (MHC) locus and other genetic polymorphisms have been shown to affect SLE, as well as external, environmental influences such as sunlight exposure, smoking, vitamin D deficiency, and certain infections. Several studies have reported and proposed multiple associations between the alteration of the epigenome and the pathogenesis of autoimmune disease. Epigenetic factors contributing to SLE include microRNAs, DNA methylation status, and the acetylation/deacetylation of histone proteins. Additionally, the acetylation of non-histone proteins can also influence cellular function. A better understanding of non-genomic factors that regulate SLE will provide insight into the mechanisms that initiate and facilitate disease and also contribute to the development of novel therapeutics that can specifically target pathogenic molecular pathways.

Association of SIRT-1 Gene Polymorphism and Vitamin D Level in Egyptian Patients With Rheumatoid Arthritis

Background

We investigated SIRT-1 genetic variant and its association with vitamin D level in Egyptian patients with rheumatoid arthritis (RA).

Methods

Seventy Egyptian subjects were enrolled in our study and divided into two groups: RA group (n = 50 patients) and healthy control group (n = 20 subjects). Five milliliter blood sample was withdrawn from each subject followed by laboratory investigation and DNA extraction for SIRT-1 gene polymorphism assessment (rs7895833 A>G, rs7069102 C>G and rs2273773 C>T) and vitamin D level expression.

Results

There was statistically significant difference between rheumatoid cases and controls with regard to vitamin D level with 88% of cases showing insufficient vitamin D versus all controls showing sufficient level. SIRT-1 different SNPs rs2273773, rs7895833and rs7069102 genotype frequencies were statistically significant in RA compared to control group (P = 0.001). There was no statistically significant difference between different genotypes of rs2273773, rs7895833 and rs7069102 with regard to vitamin D level.

Conclusion

We concluded that there is a strong association between SIRT-1 polymorphism genotyping and RA. Vitamin D level was insufficient in Egyptian patients with RA.

Translating epigenetics into clinic: focus on lupus

Systemic lupus erythematosus (SLE) is a chronic relapsing–remitting autoimmune disease with highly heterogeneous phenotypes. Biomarkers with high sensitivity and specificity are useful for early diagnosis as well as monitoring disease activity and long-term complications. Epigenetics potentially provide novel biomarkers in autoimmune diseases. These may include DNA methylation changes in relevant lupus-prone genes or histone modifications and microRNAs to upregulate and downregulate relevant gene expression. The timing and nature of epigenetic modification provide such changes. In lupus, DNA methylation alterations in cytokine genes, such as IFN-related gene and retrovirus gene, have been found to offer biomarkers for lupus diagnosis. Histone modifications such as histone methylation and acetylation lead to transcriptional alterations of several genes such as PTPN22, LRP1B, and TNFSF70. There are varieties of microRNAs applied as lupus biomarkers, including DNMT1-related microRNAs, renal function-associated microRNAs, microRNAs involved in the immune system, and microRNAs for phenotype classification. Thus, we conclude a wide range of promising roles of epigenetic biomarkers aiding in the diagnosing and monitoring of lupus diseases and the risk of organ damage.

Alterations in nuclear structure promote lupus autoimmunity in a mouse model

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by the development of autoantibodies that recognize components of the cell nucleus. The vast majority of lupus research has focused on either the contributions of immune cell dysfunction or the genetics of the disease. Because granulocytes isolated from human SLE patients had alterations in neutrophil nuclear morphology that resembled the Pelger-Huet anomaly, and had prominent mis-splicing of mRNA encoding the nuclear membrane protein lamin B receptor (LBR), consistent with their Pelger-Huet-like nuclear morphology, we used a novel mouse model system to test the hypothesis that a disruption in the structure of the nucleus itself also contributes to the development of lupus autoimmunity. The lupus-prone mouse strain New Zealand White (NZW) was crossed with c57Bl/6 mice harboring a heterozygous autosomal dominant mutation in Lbr (B6.Lbr(ic/+)), and the (NZW×B6.Lbr(ic))F1 offspring were evaluated for induction of lupus autoimmunity. Only female (NZW×B6.Lbr(ic))F1 mice developed lupus autoimmunity, which included splenomegaly, kidney damage and autoantibodies. Kidney damage was accompanied by immune complex deposition, and perivascular and tubule infiltration of mononuclear cells. The titers of anti-chromatin antibodies exceeded those of aged female MRL-Fas(lpr) mice, and were predominantly of the IgG2 subclasses. The anti-nuclear antibody staining profile of female (NZW×B6.Lbr(ic))F1 sera was complex, and consisted of an anti-nuclear membrane reactivity that colocalized with the A-type lamina, in combination with a homogeneous pattern that was related to the recognition of histones with covalent modifications that are associated with gene activation. An anti-neutrophil IgM recognizing calreticulin, but not myeloperoxidase (MPO) or proteinase 3 (PR3), was also identified. Thus, alterations in nuclear structure contribute to lupus autoimmunity when expressed in the context of a lupus-prone genetic background, suggesting a mechanism for the development of lupus autoimmunity in genetically predisposed individuals that is induced by the disruption of nuclear architecture.

The real culprit in systemic lupus erythematosus: abnormal epigenetic regulation

Systemic lupus erythematosus (SLE) is an autoimmune disease involving multiple organs and the presence of anti-nuclear antibodies. The pathogenesis of SLE has been intensively studied but remains far from clear. B and T lymphocyte abnormalities, dysregulation of apoptosis, defects in the clearance of apoptotic materials, and various genetic and epigenetic factors are attributed to the development of SLE. The latest research findings point to the association between abnormal epigenetic regulation and SLE, which has attracted considerable interest worldwide. It is the purpose of this review to present and discuss the relationship between aberrant epigenetic regulation and SLE, including DNA methylation, histone modifications and microRNAs in patients with SLE, the possible mechanisms of immune dysfunction caused by epigenetic changes, and to better understand the roles of aberrant epigenetic regulation in the initiation and development of SLE and to provide an insight into the related therapeutic options in SLE.

T cell receptor-associated protein tyrosine kinases: the dynamics of tolerance regulation by phosphorylation and its role in systemic lupus erythematosus

There are different abnormalities that lead to the autoreactive phenotype in T cells from systemic lupus erythematosus (SLE) patients. Proximal signaling, involving the T-cell receptor (TCR) and its associated protein tyrosine kinases (PTKs), is significantly affected in SLE. This ultimately leads to aberrant responses, which include enhanced tyrosine phosphorylation and calcium release, as well as decreased IL-2 secretion. Lck, ZAP70 and Syk, which are PTKs with a major role in proximal signaling, all present abnormal functioning that contributes to an altered T cell response in these patients. A number of other molecules, especially regulatory proteins, are also involved. This review will focus on the PTKs that participate in proximal signaling, with specific emphasis on their relevance in maintaining peripheral tolerance, their abnormalities in SLE and how these contribute to an altered T cell response.

Epigenetic dysregulation in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a prototypical systemic autoimmune disease that affects multiple organs and is characterized by episodic flares and elevated morbidity. The etiology of SLE is only partly known. In this context, recent attention has been paid to the importance of environmentally induced epigenetic modifications as significant contributors to the disease pathogenesis in genetically predisposed individuals. Here we review what is currently known on the role of epigenetics in SLE, and the investigations aimed at possibly targeting epigenetic mechanisms and/or related biomarkers to improve the monitoring, management and, ultimately, the prognosis of SLE.

Emerging and critical issues in the pathogenesis of lupus

Systemic lupus erythematosus (SLE) is a multisystemic, autoimmune disease, encompassing either mild or severe manifestations. SLE was originally labeled as being an immune complex-mediated disease, but further knowledge suggested its pathogenesis is motlier than that, involving complex interactions between predisposed individuals and their environment. People affected with SLE have their immune system skewed toward aberrant self-recognition usually after encountering a triggering agent. Defeats in early and late immune checkpoints contribute to tolerance breakdown and further generation and expansion of autoreactive cell-clones. B and T cells play a master role in SLE, however clues are emerging about other cell types and new light is being shed on SLE autoantibodies, since some of them display really harmful potential (pathogenic antibodies), while others are just connected with disease development (pathological antibodies) and may even be protective. Autoantibody generation is elicited by abnormal apoptosis and inefficient clearance of cellular debris causing intracellular autoantigens (e.g. nucleosomes) to persist in the extracellular environment, being further recognized by autoreactive cells. Here we explore the complexity of SLE pathogenesis through five core issues, i.e. genetic predisposition, B and T cell abnormalities, abnormal autoantigen availability, autoantibody generation and organ damage, relying on current knowledge and recent insights into SLE development.

Invasive fungal infection in patients with systemic lupus erythematosus: experience from a single institute of Northern China

Invasive fungal infection (IFI) is a life-threatening infection occurring most often in patients with systemic lupus erythematosus (SLE) and few data has been reported in SLE patients particularly in China. This present study was aimed to determine IFI prevalence, associated risk factors and patterns of infection in Chinese SLE patients. A retrospective study was conducted in a single institute of Northern China from July 2004 and October 2010. Demographic characteristics, clinical and laboratory data, and mycological examinations were collected. Among 1534 patients included, 20 (1.6%) were diagnosed with IFI, of whom there were 18 females and 2 males with the average age of 35.4 ± 15.1 years old. Involved sites included nine lungs, six central nervous system and five disseminated cases. 6 of 20 IFIs cases (30%) were non-survivors including 2 lungs, 2 central nervous system and 2 disseminated cases. Compared with survivors, non-survivors had significantly higher equivalent prednisone doses, elevated level of serum C reactive protein (CRP), higher erythrocyte sedimentation rate (ESR), higher thrombocytopenia rate and higher systemic lupus erythematosus disease activity index (SLEDAI) score. These results strongly demonstrated that prednisone doses, CRP, ESR, thrombocytopenia and SLEDAI could be associated risk factors in the prognosis of SLE patients with IFI.

cAMP-responsive element modulator (CREM)α protein induces interleukin 17A expression and mediates epigenetic alterations at the interleukin-17A gene locus in patients with systemic lupus erythematosus

IL-17A is a proinflammatory cytokine that is produced by specialized T helper cells and contributes to the development of several autoimmune diseases such as systemic lupus erythematosus (SLE). Transcription factor cAMP-responsive element modulator (CREM)α displays increased expression levels in T cells from SLE patients and has been described to account for aberrant T cell function in SLE pathogenesis. In this report, we provide evidence that CREMα physically binds to a cAMP-responsive element, CRE (-111/-104), within the proximal human IL17A promoter and increases its activity. Chromatin immunoprecipitation assays reveal that activated naïve CD4(+) T cells as well as T cells from SLE patients display increased CREMα binding to this site compared with T cells from healthy controls. The histone H3 modification pattern at the CRE site (-111/-104) and neighboring conserved noncoding sequences within the human IL17A gene locus suggests an accessible chromatin structure (H3K27 hypomethylation/H3K18 hyperacetylation) in activated naïve CD4(+) T cells and SLE T cells. H3K27 hypomethylation is accompanied by decreased cytosine phosphate guanosine (CpG)-DNA methylation in these regions in SLE T cells. Decreased recruitment of histone deacetylase (HDAC)1 and DNA methyltransferase (DNMT)3a to the CRE site (-111/-104) probably accounts for the observed epigenetic alterations. Reporter studies confirmed that DNA methylation of the IL17A promoter indeed abrogates its inducibility. Our findings demonstrate an extended role for CREMα in the immunopathogenesis of SLE because it contributes to increased expression of IL-17A.

cAMP-responsive element modulator (CREM)α protein signaling mediates epigenetic remodeling of the human interleukin-2 gene: implications in systemic lupus erythematosus

IL-2 is a key cytokine during proliferation and activation of T lymphocytes and functions as an auto- and paracrine growth factor. Regardless of activating effects on T lymphocytes, the absence of IL-2 has been linked to the development of autoimmune pathology in mice and humans. Systemic lupus erythematosus (SLE) is a multifactorial autoimmune disease and characterized by dysregulation of lymphocyte function, transcription factor and cytokine expression, and antigen presentation. Reduced IL-2 expression is a hallmark of SLE T lymphocytes and results in decreased numbers of regulatory T lymphocytes which play an important role in preventing autoimmunity. Reduced IL-2 expression was linked to overproduction of the transcription regulatory factor cAMP-responsive element modulator (CREM)α in SLE T lymphocytes and subsequent CREMα binding to a CRE site within the IL2 promoter (-180 CRE). In this study, we demonstrate the involvement of CREMα-mediated IL2 silencing in T lymphocytes from SLE patients through a gene-wide histone deacetylase 1-directed deacetylation of histone H3K18 and DNA methyltransferase 3a-directed cytosine phosphate guanosine (CpG)-DNA hypermethylation. For the first time, we provide direct evidence that CREMα mediates silencing of the IL2 gene in SLE T cells though histone deacetylation and CpG-DNA methylation.

Epigenetic mechanisms in systemic lupus erythematosus and other autoimmune diseases

The pathogenic origin of autoimmune diseases can be traced to both genetic susceptibility and epigenetic modifications arising from exposure to the environment. Epigenetic modifications influence gene expression and alter cellular functions without modifying the genomic sequence. CpG-DNA methylation, histone tail modifications and microRNAs (miRNAs) are the main epigenetic mechanisms of gene regulation. Understanding the molecular mechanisms that are involved in the pathophysiology of autoimmune diseases is essential for the introduction of effective, target-directed and tolerated therapies. In this review, we summarize recent findings that signify the importance of epigenetic modifications in autoimmune disorders while focusing on systemic lupus erythematosus. We also discuss future directions in basic research, autoimmune diagnostics and applied therapy.

HDAC inhibition in lupus models

Systemic lupus erythematosus (SLE) is a prototypic autoimmune inflammatory disease characterized by the production of autoantibodies directed against nuclear antigens such as nucleosomes, DNA and histone proteins found within the body's cells and plasma. Autoantibodies may induce disease by forming immune complexes that lodge in target organs or by crossreacting with targeted antigens and damaging tissue. In addition to autoantibody production, apoptotic defects and impaired removal of apoptotic cells contribute to an overload of autoantigens that initiate an autoimmune response. Besides the well-recognized genetic susceptibility to SLE, environmental and epigenetic factors play a crucial role in disease pathogenesis as evidenced by monozygotic twins typically being discordant for disease. Changes in DNA methylation and histone acetylation alter gene expression and are thought to contribute to the epigenetic deregulation in disease. In SLE, global and gene-specific DNA methylation changes have been demonstrated to occur. Additionally, aberrant histone acetylation is evident in individuals with SLE. Moreover, histone deacetylase inhibitors (HDACi) have been shown to reverse the skewed expression of multiple genes involved in SLE. In this review, we discuss the implications of epigenetic alterations in the development and progression of SLE, and how therapeutics designed to alter histone acetylation status may constitute a promising avenue to target disease.

Epigenetics in lupus

Accumulating epidemiological, clinical, and experimental evidence supports the conclusion of a critical role of epigenetic factors in immune programming. This understanding provides the basis for elucidating how the intricate interactions of the genome, epigenome, and transcriptome shape immune responses and maintain immune tolerance to self-antigens. Deciphering the precise contribution of epigenetic factors to autoimmunity, and in particular to lupus, has become an active research area. On one hand, it is well established that environmental factors have an impact on the epigenome and, therefore, on the transcriptional and translational machinery of specific cell types; on the other, the environment also plays an important role in the severity of lupus and other autoimmunity diseases. Determining how epigenetics "connects" the environment to cell biology and to autoreactivity will be key for advancing our understanding in this field and, possibly, for developing novel preventive strategies.

Global H4 acetylation analysis by ChIP-chip in systemic lupus erythematosus monocytes

Systemic lupus erythematosus (SLE) is a polygenic disorder affecting approximately 1 in 1000 adults. Recent data have implicated interferons (IFN) in the pathogenesis, and the expressions of many genes downstream of IFNs are regulated at the level of histone modifications. We examined H4 acetylation (H4ac) and gene expression in monocytes from patients with SLE to define alterations to the epigenome. Monocytes from 14 controls and 24 SLE patients were used for analysis by chromatin immunoprecipitation for H4ac and gene expression arrays. Primary monocytes treated with alpha-IFN were used as a comparator. Data were analyzed for concordance of H4ac and gene expression. Network analyses and transcription factor analyses were conducted to identify potential pathways. H4ac was significantly altered in monocytes from patients with SLE. In all, 63% of genes with increased H4ac had the potential for regulation by IFN regulatory factor (IRF)1. IRF1 binding sites were also upstream of nearly all genes with both increased H4ac and gene expression. alpha-IFN was a significant contributor to both expression and H4ac patterns, but the greatest concordance was seen in the enrichment of certain transcription factor binding sites upstream of genes with increased H4ac in SLE and genes with increased H4ac after alpha-IFN treatment.

Prevalence of Fc‐gammaR chain expression in CD4+T cells of patients with systemic lupus erythematosus

OBJECTIVE

To determine the upregulation of transcript and protein levels of the T cell receptor (TCR)/CD3-Fc-gammaR chain in CD4+ T cells of systemic lupus erythematosus (SLE) patients with different clinical disease activity scored on the SLE Disease Activity Index (SLEDAI) scale.

METHODS

CD4+ cells were isolated by the positive biomagnetic separation technique. Quantitative analysis of Fc-gammaR cDNA was carried out by using the real-time quantitative polymerase chain reaction (RQ-PCR) SYBR Green I system. Protein levels of Fc-gammaR in CD4+ T cells were determined by Western blotting analysis.

RESULTS

We observed significantly higher transcript and protein levels of the Fc-gammaR chain in CD4+ T cells of SLE patients (n = 45) than in healthy individuals (n = 26). The increase in Fc-gammaR expression was observed in 97.8% of SLE patients. Spearman statistical analysis suggests that the protein level of Fc-gammaR in CD4+ T cells may correlate with SLE activity scored by the SLEDAI scale (R = 0.556, p < 0.00006, respectively).

CONCLUSION

The high prevalence of the Fc-gammaR chain in CD4+ T cells of SLE patients may indicate an important role for this molecule in the pathogenesis of SLE.

The TNFalpha locus is altered in monocytes from patients with systemic lupus erythematosus

In systemic lupus erythematosus, TNFalpha is elevated in the serum and correlates with disease activity and triglyceride levels. The stimuli that drive TNFalpha in this setting are incompletely understood. This study was designed to evaluate monocyte chromatin at the TNFalpha locus to identify semi-permanent changes that might play a role in altered expression of TNFalpha. SLE patients with relatively quiescent disease (mean Physician Global Assessment=0.6) and healthy controls were recruited for this study. TNFalpha expression was measured by intracellular cytokine staining of different monocyte subsets in patients (n=24) and controls (n=12). Histone acetylation at the TNFalpha locus was measured by chromatin immunoprecipitation using a normalized quantitative PCR in patients (n=46) and controls (n=24). There were no differences in the overall fractions of cells expressing CD14 in SLE patients compared to controls; however, the fraction of DR+/CD16+ cells expressing CD14 was slightly higher as was true in the monocyte subset defined by DR+/CD11b+. Within the monocyte population defined by physical characteristics and DR+/CD14+, TNFalpha expressing cells were more frequent in SLE patients compared to controls. Both the fraction of positive cells and the mean fluorescence intensity were higher in patients than controls. Consistent with this was the finding that monocytes from patients had increased TNFalpha transcripts and more highly acetylated histones at the TNFalpha locus compared to controls. Furthermore, patients with the highest levels of TNFalpha histone acetylation were more likely to have had consistently elevated erythrocyte sedimentation rates, and to have required cytotoxic use. Histone acetylation, associated with increased transcriptional competence of TNFalpha, may play a role in certain inflammatory aspects of the disease.

Trichostatin A down-regulates ZAP-70, LAT and SLP-76 content in Jurkat T cells

We exploited Jurkat leukemia T cell clone E6-1 as a model of Trichostatin A (TSA) effect on cellular levels of ZAP-70, LAT and SLP-76 molecules involved in the signal transduction pathway from T cell receptor to nucleus. Using reverse transcription real-time quantitative PCR and Western blotting analysis we observed that TSA resulted in ZAP-70, LAT and SLP-76 transcript and protein down-regulation in Jurkat leukemia T cells. We also found that TSA reduced half-life of ZAP-70, LAT and SLP-76 mRNAs from 4.8, 3.5, and 4.8 to approximately 2.3, 1.9 and 1.7 h, respectively. Employing the protein biosynthesis inhibitor cycloheximide, we demonstrated the involvement of RNase and/or mRNA stabilization protein in ZAP-70, LAT and SLP-76 mRNAs stabilization. The effect of TSA on ZAP-70, LAT and SLP-76 content in T cells confirms an immunosuppressive effect by TSA, and the usefulness of this histone deacetylase inhibitor in the treatment of autoimmune diseases.

The epigenetic face of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an archetypical systemic, autoimmune inflammatory disease characterized by the production of autoantibodies to multiple nuclear Ags. Apoptotic defects and impaired removal of apoptotic cells contribute to an overload of autoantigens that become available to initiate an autoimmune response. Besides the well-recognized genetic susceptibility to SLE, epigenetic factors are important in the onset of the disease, as even monozygotic twins are usually discordant for the disease. Changes in DNA methylation and histone modifications, the major epigenetic marks, are a hallmark in genes that undergo epigenetic deregulation in disease. In SLE, global and gene-specific DNA methylation changes have been demonstrated to occur. Moreover, histone deacetylase inhibitors reverse the skewed expression of multiple genes involved in SLE. In the present study, we discuss the implications of epigenetic alterations in the development and progression of SLE and how epigenetic drugs constitute a promising source of therapy to treat this disease.

Histone acetylase inhibitor trichostatin A induces acetylcholinesterase expression and protects against organophosphate exposure

The biological effects of organophosphorous (OP) chemical warfare nerve agents (CWNAs) are exerted by inhibition of acetylcholinesterase (AChE), which prevents the hydrolysis of the neurotransmitter acetylcholine, leading to hypercholinergy, seizures/status epilepticus, respiratory/cardiovascular failure, and potentially death. Current investigations show that bioscavenger therapy using purified fetal bovine AChE in rodents and non-human primates and the more recently tested human butyrylcholinesterase, is a promising treatment for protection against multiple LD(50) CWNA exposures. Potential impediments, due to the complex structure of the enzyme, purification effort, resources, and cost have necessitated alternative approaches. Therefore, we investigated the effects of transcriptional inducers to enhance the expression of AChE to achieve sufficient protection against OP poisoning. Trichostatin A (TSA), an inhibitor of histone deacetylase that de-condenses the chromatin, thereby increasing the binding of transcription factors and mRNA synthesis, was evaluated for induction of AChE expression in various neuronal cell lines. Dose-response curves showed that a concentration of 333 nM TSA was optimal in inducing AChE expression. In Neuro-2A cells, TSA at 333 nM increased the extracellular AChE activity approximately 3-4 fold and intracellular enzyme activity 10-fold. Correlating with the AChE induction, TSA pre-treatment significantly protected the cells against exposure to the organophosphate diisopropylfluorophosphate, a surrogate for the chemical warfare agents soman and sarin. These studies indicate that transcriptional inducers such as TSA up-regulate AChE, which then can bioscavenge any organophosphates present, thereby protecting the cells from OP-induced cytotoxicity. In conclusion, transcriptional inducers are prospective new methods to protect against CWNA exposure.

Role of histone and transcription factor acetylation in diabetes pathogenesis

Globally, diabetes (and, in particular, type 2 diabetes) represents a major challenge to world health. Currently in the United States, the costs of treating diabetes and its associated complications exceed 100 billion US dollars annually, and this figure is expected to soar in the near future. Despite decades of intense research efforts, the genetic basis of the events involved in the pathogenesis of diabetes is still poorly understood. Diabetes is a complex multigenic syndrome primarily due to beta-cell dysfunction associated with a variable degree of insulin resistance. Recent advances have led to exciting new developments with regard to our understanding of the mechanisms that regulate insulin transcription. These include data that implicate chromatin as a critical regulator of this event. The 'Histone Code' is a widely accepted hypothesis, whereby sequential modifications to the histones in chromatin lead to regulated transcription of genes. One of the modifications used in the histone code is acetylation. This is probably the best characterized modification of histones, which is carried out under the control of histone acetyltransferases (HATs) and histone deacetylases (HDACs). These enzymes also regulate the activity of a number of transcription factors through acetylation. Increasing evidence links possible dysregulation of these mechanisms in the pathogenesis of diabetes, with important therapeutic implications.

Effect of 5-azacytidine and procainamide on CD3-zeta chain expression in Jurkat T cells

It has been observed that decrease of DNA methyltransferase 1 (DNMT1) activity is associated with low content of the CD3-zeta (zeta) chain in T cell receptor (TCR)/CD3 complex of T cells in systemic lupus erythematosus (SLE) patients. The CD3-zeta chain plays a pivotal role in intracellular signal transmission between TCR/CD3 complex and nuclei. The compounds 5'-azacytidine (AZC) and procainamide (PCA) belong to inhibitors of DNMT1, whose low activity correlates with increase in transcription of various genes. Using the reverse-transcription and real-time quantitative PCR (RQ-PCR) analysis, we indicated that AZC and PCA did not profoundly affect on CD3-zeta chain transcription in Jurkat T leukemia cells clone E6-1. However, the flowcytometric analysis revealed that AZC and PCA decreased intracellular contents of CD3-zeta chain in these cells in dose dependent manner. Our results suggest that decrease of DNMT1 activity may alter intracellular signal transmission without effect on transcription level of CD3-zeta chain.

Dissecting the molecular mechanisms of TCR zeta chain downregulation and T cell signaling abnormalities in human systemic lupus erythematosus

Abnormal expression of key signaling molecules and defective function of T lymphocytes play a significant role in the pathogenesis of systemic lupus erythematosus (SLE). Probing on altered expression of genes that may predispose to SLE revealed that the expression of TCR zeta chain is defective in the majority of SLE patients. Current research has been directed towards understanding the molecular basis of TCR zeta chain deficiency and dissecting the T cell signalling abnormalities in SLE T cells. Latest developments suggest that interplay of abnormal transcriptional factor expression, aberrant mRNA processing/editing, unbiquitination, proteolysis, and the effects of oxidative stress as well as changes in chromatin structure invariably contribute to TCR zeta chain deficiency in SLE T cells. On the other hand, multiple factors, including altered receptor structure, modulation of membrane clustering, lipid-raft distribution of signaling molecules, and defective signal silencing mechanisms, play a key role in delivering the increased TCR/CD3-mediated intracellular calcium response in SLE T cells.

Targeting combinatorial transcriptional complex assembly at specific modules within the interleukin-2 promoter by the immunosuppressant SB203580

The proximal promoter sequence of the interleukin-2 (IL-2) gene contains a series of composite sites or modules that controls much of its responsiveness to environmental stimuli. The integrated targeting of these modules is therefore a major mode of regulation. This report describes how multiple functional hierarchies, required for the recruitment of the p300 co-activator to the CD28RE/AP1 (TRE) module of the IL-2 promoter, are selectively disrupted in human T-cells by the immunosuppressive and anti-inflammatory actions of the p38 mitogen-activated protein kinase inhibitor (MAPK), SB203580. The molecular hierarchies targeted by SB203580 include the combinatorial interaction of NF-kappaB and CREB at the CD28RE/AP1 element coupled with the subsequent dynamic co-assembly and activation of p300. Several aspects of this targeting are linked to the ability of SB203580 to inhibit p38 MAPK-controlled pathways. Together, these results provide the molecular basis through which the combinatorial structure and context of the composite elements of the IL-2 promoter dictates mitogen responsiveness and drug susceptibility that are quantitatively and qualitatively distinct from the isolated action of single consensus sequences and/or transcriptional motifs.

Prevalence of T cell receptor zeta chain deficiency in systemic lupus erythematosus

T cells from patients with systemic lupus erythematosus (SLE) display antigen receptor-mediated signaling aberrations associated with defective T cell receptor (TCR) zeta chain expression. We determined the prevalence of TCR zeta chain deficiency in SLE from a large cohort of unselected racially diverse patients with different levels of clinical disease activity as determined by SLE Disease Activity Index (SLEDAI). Our data show that the occurrence of TCR zeta chain deficiency is 78% in SLE patients. There was no relationship between the deficiency of TCR zeta chain and the SLEDAI scores or theapy. TCR zeta chain deficiency was also not associated with age, race or gender and persisted over a 3 year follow-up period. Thus, there is a high prevalence of TCR zeta chain deficiency in SLE patients that is independent of disease activity, and persists over time indicating an important role for TCR zeta chain deficiency in SLE pathogenesis.

Histone deacetylase inhibitors modulate renal disease in the MRL-lpr/lpr mouse

Studies in human systemic lupus erythematosus (SLE) suggest a possible role for histone deacetylases (HDACs) in skewed gene expression and disease pathogenesis. We used the MRL-lpr/lpr murine model of lupus to demonstrate that HDACs play a key role in the heightened levels of both Th1 and Th2 cytokine expression that contribute to disease. The availability of specific HDAC inhibitors (HDIs) such as trichostatin A (TSA) and suberonylanilide hydroxamic acid (SAHA) permits the study of the role of HDACs in gene regulation. Our results indicate that HDIs downregulate IL-12, IFN-gamma, IL-6, and IL-10 mRNA and protein levels in MRL-lpr/lpr splenocytes. This effect on gene transcription is associated with an increased accumulation of acetylated histones H3 and H4 in total cellular chromatin. To elucidate the in vivo effects of TSA on lupuslike disease, we treated MRL-lpr/lpr mice with TSA (0.5 mg/kg/d) for 5 weeks. Compared with vehicle-treated control mice, TSA-treated mice exhibited a significant reduction in proteinuria, glomerulonephritis, and spleen weight. Taken together, these findings suggest that increased expression of HDACs leading to an altered state of histone acetylation may be of pathologic significance in MRL-lpr/lpr mice. In addition, TSA or other HDIs may have therapeutic benefit in the treatment of SLE.

Histone deacetylase inhibitors modulate renal disease in the MRL-lpr/lpr mouse

Studies in human systemic lupus erythematosus (SLE) suggest a possible role for histone deacetylases (HDACs) in skewed gene expression and disease pathogenesis. We used the MRL-lpr/lpr murine model of lupus to demonstrate that HDACs play a key role in the heightened levels of both Th1 and Th2 cytokine expression that contribute to disease. The availability of specific HDAC inhibitors (HDIs) such as trichostatin A (TSA) and suberonylanilide hydroxamic acid (SAHA) permits the study of the role of HDACs in gene regulation. Our results indicate that HDIs downregulate IL-12, IFN-gamma, IL-6, and IL-10 mRNA and protein levels in MRL-lpr/lpr splenocytes. This effect on gene transcription is associated with an increased accumulation of acetylated histones H3 and H4 in total cellular chromatin. To elucidate the in vivo effects of TSA on lupuslike disease, we treated MRL-lpr/lpr mice with TSA (0.5 mg/kg/d) for 5 weeks. Compared with vehicle-treated control mice, TSA-treated mice exhibited a significant reduction in proteinuria, glomerulonephritis, and spleen weight. Taken together, these findings suggest that increased expression of HDACs leading to an altered state of histone acetylation may be of pathologic significance in MRL-lpr/lpr mice. In addition, TSA or other HDIs may have therapeutic benefit in the treatment of SLE.