Protooncogene expression in peripheral blood mononuclear cells from patients with systemic lupus erythematosus as an indicator of the disease activity

Circular RNA circLOC101928570 suppresses systemic lupus erythematosus progression by targeting the miR-150-5p/c-myb axis

Background

Accumulating evidence supports the implication of circular RNAs (circRNAs) in systemic lupus erythematosus (SLE). However, little is known about the detailed mechanisms and roles of circRNAs in the pathogenesis of SLE.

Methods

Quantitative real-time PCR was used to determine the levels of circLOC101928570 and miR-150-5p in peripheral blood mononuclear cells of SLE. Overexpression and knockdown experiments were conducted to assess the effects of circLOC101928570. Fluorescence in situ hybridization, RNA immunoprecipitation, luciferase reporter assays, Western blot, flow cytometry analysis and enzyme-linked immunosorbent assay were used to investigate the molecular mechanisms underlying the function of circLOC101928570.

Results

The results showed that the level of circLOC101928570 was significantly downregulated in SLE and correlated with the systemic lupus erythematosus disease activity index. Functionally, circLOC101928570 acted as a miR-150-5p sponge to relieve the repressive effect on its target c-myb, which modulates the activation of immune inflammatory responses. CircLOC101928570 knockdown enhanced apoptosis. Moreover, circLOC101928570 promoted the transcriptional level of IL2RA by directly regulating the miR-150-5p/c-myb axis.

Conclusion

Overall, our findings demonstrated that circLOC101928570 played a critical role in SLE. The downregulation of circLOC101928570 suppressed SLE progression through the miR-150-5p/c-myb/IL2RA axis. Our findings identified that circLOC101928570 serves as a potential biomarker for the diagnosis and therapy of SLE.

Overall Downregulation of mRNAs and Enrichment of H3K4me3 Change Near Genome-Wide Association Study Signals in Systemic Lupus Erythematosus: Cell-Specific Effects

This study was designed to define gene expression and H3K4me3 histone modifications in T cells, B cells, and monocytes in systemic lupus erythematosus (SLE). Array studies of total peripheral blood mononuclear cells have demonstrated gene expression signatures related to neutrophils, interferon, and other inflammatory pathways. It is not clear how consistent these effects are across different cell types. In this study, RNA-seq and chromatin immunoprecipitation-seq were utilized to identify gene expression patterns and H3K4me3 histone modifications related to promoter activation in SLE. Across the three cell types, there was 55% concordance for gene expression changes related to SLE. Key conserved pathways were ribosome biogenesis among upregulated genes and heat shock response among downregulated genes. ETS family transcription factors (TFs) and STAT1 were revealed as common regulators by position weight matrices. When epigenetic changes were leveraged with gene expression, the pivotal TFs ATF3 and FOS were defined with ATF3 also cross-referencing with gene expression-identified TFs. Genome-wide association study (GWAS) single nucleotide polymorphisms associated with SLE were cross-referenced with both mRNA and H3K4me3 changes in SLE. Baseline mRNA expression and H3K4me3 peak height was higher at sites that cross-referenced with GWAS signals, however, all three cell types exhibited an overall decrease in expression of GWAS-associated RNAs differentially expressed in SLE. H3K4me3 changes in SLE were also enriched in GWAS-associated sites. In summary, the SLE disease process is associated with both shared and cell-specific changes in gene expression and epigenetics. Surprisingly, GWAS-associated RNAs were overall markedly decreased across all three cell types. TF analysis identified ATF3, FOS, STAT1, and ETS family members as critical, all pathways with a recognized relationship to the SLE disease process. GWAS signals clearly mark both cell-type specific changes in SLE as well as concordant changes across all three cell types. Interpretation of single nucleotide polymorphism effects in SLE will require tissue-specific mechanistic studies and therapeutics will require mechanistic studies in multiple cell types.

Cyclic adenosine 5'-monophosphate response element modulator is responsible for the decreased expression of c-fos and activator protein-1 binding in T cells from patients with systemic lupus erythematosus

T cells from patients with systemic lupus erythematosus express increased levels of the cAMP response element modulator (CREM) that has been shown to bind to the IL-2 promoter and suppress its activity. In this study, we demonstrate that CREM binds to the proximal promoter of the c-fos proto-oncogene in live systemic lupus erythematosus T cells and represses its expression following stimulation in vitro. Decreased levels of c-fos protein result in decreased AP-1 activity, as determined in shift assays. Blockade of the translation of CREM mRNA with an antisense CREM vector increases the expression of c-fos and the AP-1 activity. The levels of c-fos mRNA vary with disease activity. We conclude that CREM represses the expression of c-fos and limits the activity of the enhancer AP-1. Thus, CREM is involved indirectly in the modulation of transcriptional regulation of multiple genes including IL-2.

Decreased expression of the p21ras stimulatory factor hSOS in PBMC from inactive SLE patients

Expression of the p21 ras protooncogene is reported to be increased in animal models and in patients with SLE. However, the expression of p21ras regulatory elements has not been determined. We determined the expression of p21ras, and its regulatory elements p120-ras-GAP and hSOS, in PBMC of 10 patients with inactive SLE (mean SLEDAI score 1.8+/-0.53) and 10 age- and sex-matched healthy controls. No difference was found between the two groups in the levels of p21 ras (3760+/-513 and 3367+/-335, P=0.25) and ras-GAP (1048+/-261 and 1534+/-247, P=0.11) in patients and controls, respectively. In contrast, levels of hSOS were significantly decreased in patients as compared to controls: 955+/-218 and 2306+/-327, P = 0.002, respectively. The mitogen-induced proliferative response was comparable in the two groups: SI 20.8+/-4.2 and 15.03+/-4.9, P=0.135, in patients and controls, respectively. Taken together, our data demonstrate that nonactive SLE patients are characterized by reduced hSOS expression and underscore the need for a comprehensive evaluation of p21ras pathway in these patients.

Proto-oncogene expression in human glomerular diseases

The expression of the protein products and mRNA of c-fos, c-myc, p53, and c-raf was examined in normal renal tissues and biopsy specimens from 73 patients with various glomerular diseases. Immunofluorescent staining showed that there were cell nuclei stained for c-Fos, c-Myc, and p53, and cytoplasm positive for c-Raf, in the glomeruli of patients with proliferative types of glomerulonephritis, including IgA nephritis and lupus nephritis, and in patients with focal glomerular sclerosis. Glomerular expression of c-fos and c-myc mRNA was detected by in situ hybridization. The number of proto-oncogene-positive glomerular cells was significantly higher in lupus nephritis, IgA nephritis, and focal segmental sclerosis, as compared with minimal change nephrotic syndrome and normal specimens. In IgA nephritis, the population of glomerular cells positive for c-Fos and c-Myc and the grade of c-Raf immunoreactivity were significantly correlated with the proportion of proliferating cell nuclear antigen (PCNA)-positive glomerular cells, with histological grading of mesangial hypercellularity and matrix increase, and with the magnitude of proteinuria. These data indicate that proto-oncogene expression is associated with mesangial proliferation and matrix expansion in proliferative types of glomerulonephritis and in focal glomerular sclerosis.

Histological detection of c-myb and c-myc proto-oncogene expression in infiltrating cells in cutaneous lupus erythematosus-like lesions of MRL/l mice by in situ hybridization

A relationship between lymphocytic activation and the overexpression of proto-oncogenes such as c-myb or c-myc has been demonstrated in human autoimmune disease. In autoimmune-prone MRL/l mice, which spontaneously develop lupus erythematosus (LE)-like lesions on the back, increased expression of myb RNA has been found in the lymphoid organs. We detected the overexpression of c-myb and c-myc proto-oncogenes in infiltrating cells in the cutaneous lesions of MRL/l mice by using in situ hybridization. No specific hybridization signals of either of the probes used were seen in the nonlesional skin of MRL/l mice or in the apparently normal skin of aged MRL/n and young MRL/l mice. These results suggest that the increased expression of myb and myc proto-oncogenes in the cutaneous LE-like lesions of MRL/l mice is related to a state of activation in the infiltrating cells and is involved in the development of these lesions.

Tumour necrosis factor/cachectin plays a key role in autoimmune pulmonary inflammation in lupus-prone mice

The role of tumour necrosis factor-alpha (TNF-alpha) in the development of autoimmune pulmonary inflammation has been investigated in lupus-prone mice. An increase in TNF-alpha mRNA level from whole lung preparation of lupus-prone mice was evident, from 3 weeks to 12 weeks during growing process, as shown by Northern blot analysis, but not in control mice. Furthermore, it is also found that the major source of this increase in TNF-alpha mRNA was attributed to infiltrating mononuclear cells found within the lung. Treatment of lupus-prone mice with rabbit anti-mouse TNF-alpha IgG prevented the development of pulmonary inflammation lesions such as lung fibrosis and alveolitis. These results suggest that an increased TNF-alpha production by infiltrating mononuclear cells in the lungs of lupus-prone mice may play a role in the development of autoimmune pulmonary inflammation and in significant changes of cytokines and the immune responses in pulmonary inflammation lesions of lupus-prone mice.

Protooncogene (C-Myc) expression in the infiltrating cells of lesional skin from patients with systemic lupus erythematosus

Polyclonal activation of lymphocytes due to an unknown cause is considered to be one of the most important findings of systemic autoimmune disorders including systemic lupus erythematosus (SLE). In order to confirm the expression of the C-Myc protooncogene in lesional skin, tissue specimens from SLE were examined by the histo in situ hybridization method and a histochemical method using a specific antibody reactive with C-Myc related products. Twenty-two cases of SLE, six cases of DLE, one case of lupus erythematosus profundus, two cases of lichen planus, and five skin specimens from healthy volunteers were selected for the examination. In the SLE group, further comparative examination of diseased skin and normal skin from the same patient, and of diseased skin in an active stage and a stable stage in the same SLE patient with renal involvement, were carried out. In most of the active SLE cases, protooncogene expression had apparently increased as compared with the expression in the groups of inactive and treated SLE, active DLE, active lichen planus, and those with healthy skin. Even in normal-appearing skin from active SLE without other organic failure, the protooncogenes were not expressed very strongly.

Proto-oncogene expression in peripheral blood mononuclear cells in IgA nephropathy

We have investigated the expression of proto-oncogenes in mononuclear cells obtained from patients with IgA nephropathy using a RNA hybridization technique. Patients with IgA nephropathy expressed more c-myc, c-raf, c-fos, and c-jun proto-oncogene RNA than did normal controls. However, no significant expression of c-N-ras, c-mos or c-myb genes was found in the mononuclear cells of these patients. When the amount of urinary protein excretion was used as an indicator of disease activity (greater than 1 g/day), a positive correlation was found between c-myc, c-raf, c-fos, and c-jun expression and urinary protein excretion (P less than 0.01). The expression of these genes correlated also with the serum IgA concentration (P less than 0.01), IgA immune complex (P less than 0.01), and histopathological changes in renal tissues obtained from patients with IgA nephropathy (P less than 0.01). The results of this survey suggest that abnormally regulated proto-oncogene expression in mononuclear cells may play an important role in the progression of IgA nephropathy and may be useful as an indicator of disease activity and/or prognosis.

Enhanced expression of the tumour necrosis factor/cachectin gene in peripheral blood mononuclear cells from patients with systemic vasculitis

The expression of tumour necrosis factor-alpha (TNF-alpha) gene in peripheral blood mononuclear cells from patients with systemic vasculitis, periarteritis nodosa and Wegener's granulomatosis, has been studied by RNA dot blot and Northern blot assays. We further examined the transcriptional level of TNF-alpha gene in peripheral blood mononuclear cells from these patients by performing nuclear run on transcription assay. We demonstrate enhanced TNF-alpha gene expression in mononuclear cells from these patients compared with healthy subjects and patients with bronchial asthma. These findings suggest that the enhanced transcription of TNF-alpha gene in peripheral blood mononuclear cells from patients with systemic vasculitis may be involved in the pathophysiology/pathogenesis of these diseases by cytokine dysregulation.

Transcriptional and post-transcriptional mechanisms are responsible for the increased expression of c-myc protooncogene in lymphocytes from patients with systemic lupus erythematosus

Peripheral blood mononuclear cells (MNC) of patients with systemic lupus erythematosus (SLE) have increased expression of the c-myc protooncogene. The factors which are responsible for the accumulation of c-myc mRNA levels in SLE MNC, however, have not been determined. We have investigated the steady-state mRNA accumulation, nuclear transcription rate, rate of mRNA degradation as well as methylation status for the c-myc protooncogene in patients with SLE. Increased transcription rate of c-myc protooncogene and slow degradation rate of c-myc mRNA both appear to contribute to the accumulation of c-myc RNA in peripheral blood MNC of patients with SLE. Site-specific methylation of the human c-myc protooncogene in patients with SLE does not differ from that of normal controls. These findings provide evidence for both transcriptional and post-transcriptional alterations of c-myc protooncogene expression in human SLE.

Rheumatoid factor and Fc signaling: a tale of two Cinderellas

Signaling to lymphocytes depends not only upon the interaction of receptors with specific antigen, but also upon antigen nonspecific receptors which receive input from two classes of molecules, immunologically specific end products and lymphokines. These represent the central elements in the physiologic stimulation of immune responses to both self and foreign antigens. This review is dedicated primarily to describing the function of physiologically active receptors for end product which are central to end product feedback in normal immune responses. The emergence of autoimmunity as a pathologic process resultant from a defective end product signaling mechanism is described.

Increased proto-oncogene expression in peripheral blood T lymphocytes from patients with systemic sclerosis

The expression of c-myc, c-myb, and c-ras proto-oncogenes, determined using RNA hybridization techniques (slot-blot), was significantly increased in peripheral blood T lymphocytes, but not in B cells, from 17 patients with systemic sclerosis with diffuse scleroderma, compared with the expression in normal control subjects. The magnitude of expression of c-myc and c-myb tended to be higher in patients with early, active disease. These results demonstrate an in vivo activation of T cells from systemic sclerosis patients, which may play an important role in the pathogenesis of the disease.

Immune complex assays: diagnostic and clinical application

The presence of circulating immune complexes have been described in many different human disease states but the significance of their presence has always been a subject for debate. Improvements in the methods of detecting immune complexes have demonstrated a wide degree of heterogeneity, which accounts for the difficulty in obtaining accurate and reproducible measurements, even in the same individual. Techniques for isolating individual complexes, characterizing their pathophysiological properties, and biochemically analyzing the nature of the complexed antigen are now being used to provide data that is helping to clarify the role of immune complexes in the pathogenesis of disease. In addition, such studies are also providing data which is proving that immune complexes have a potential role in immune regulation.

Lupus-related transcript homologous to Abelson-murine leukemia virus

In the present study, we found the expression of transcripts homologous to Abelson murine leukemia virus (A-MuLV) in lupus-prone mice and nonautoimmune mice. One of them, as the lupus-related transcript, is expressed in only lupus-prone mice and induced by bacterial lipopolysaccharide (LSP). We could not induce the transcript by LSP in nonautoimmune mice that we examined. The significance of the transcript autoimmune events in lupus-prone mice is discussed.