Takashi Hishikawa

DNA methylation in systemic lupus erythematosus.

Recent studies on epigenetics, including DNA methylation and its regulatory enzymes, seem likely to contribute to elucidation of the pathogenesis of autoimmune diseases such as systemic lupus erythematosus (SLE), although the relationship between DNA methylation and SLE has long been the subject of investigation.To obtain a deeper understandingof the role of DNA methylation in the induction of SLE, we reviewed the relationship between DNA methylation and SLE based on findings reported in the literature and our own data. Various studies, including ours, have indicated the possible importance of DNA methylation, especially hypomethylation, in the etiology of SLE. These epigenetic studies may give us clues towards elucidation of the pathogenesis of SLE and development of new therapeutic strategies for this disease.

HLA-DP+ T cells and deficient interleukin-2 production in patients with systemic lupus erythematosus

In patients with systemic lupus erythematosus (SLE), frequency of the T cells positive for HLA-DP, one of the major histocompatibility complex (MHC) class II molecules, was markedly increased in peripheral blood lymphocytes (PBL), in association with an increase in the amount of specific cytoplasmic transcript of the HLA-DP gene segment. Cell cycle analysis showed that HLA-DP is an early activation marker of T cells and that the high ratios of HLA-DP+ T cells from SLE patients are associated with high frequency of T cells at early activation phases, mainly of G1A. Initial high ratios of HLA-DP+ T cells decreased to a great extent during 4 days of in vitro culture, in the absence of mitogens. This event was associated with decreases in the amount of HLA-DP transcript and the disappearance of activated T cells. Studies on the interleukin 2 (IL-2) production of T cells from patients with SLE demonstrated that while the PBL rich in HLA-DP+ T cells show a markedly low production of IL-2, preculture of these PBL restores the ability to produce IL-2. Thus, it appears that the T cells in patients with SLE are essentially intact with regard to the capacity to produce IL-2 and that T cell activation events continuously occurring in SLE patients are related to a deficiency in IL-2 production. The possible underlying mechanisms are discussed.

Immune Abnormalities Induced by Human Endogenous Retroviral Peptides: With Reference to the Pathogenesis of Systemic Lupus Erythematosus

P15E is a specific sequence among the envelope gene (env)-encoded transmembrane proteins of exogenous and endogenous retroviruses. A synthetic peptide (CKS-17) that shows homology to this p15E region in several species of retrovirus is known to induce immune abnormalities. In this study, we examined the effect of a synthetic peptide derived from a region of human endogenous retrovirus (HERV) clone 4-1 (λ 4-1) similar to sequences of CKS-17 on the induction of systemic lupus erythematosus (SLE)-related immune abnormalities. Our results indicated that this peptide could induce T-cell activation and anergy in normal peripheral blood mononuclear cells, and the peptide could also promote the production of interleukins IL-6 and IL-16. These phenomena are representative immune abnormalities observed in SLE patients. Thus, our findings support the possibility that HERV acts as a pathogen in human SLE.

Inhibitory effect of the immunosuppressant FK506 on apoptotic cell death induced by HIV-1 gp120

Human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein gp120 may play a central role in inducing immunoregulatory disorders after HIV infection. The apoptotic death of normal human peripheral blood mononuclear cells was induced by priming with gp120 followed by stimulation with an anti-T cell receptor (TCR) antibody. Tumor necrosis factor-α produced by gp120-binding macrophages may be important to induce this cell death. Treatment of gp120-primed cells with an immunosuppressant (FK506) before TCR signaling inhibited apoptotic cell death, and this blocking effect of FK506 was concentration dependent. FK506 did not have any influence on cell growth and viability over the range of concentrations tested. These findings suggest that FK506 is a potentially useful drug in delaying the onset of AIDS after HIV infection.

Sequence Analysis of Human Endogenous Retrovirus Clone 4-1 in Systemic Lupus Erythematosus

Human endogenous retroviruses (HERV) have emerged as a possible cause of systemic lupus erythematosus (SLE). We previously detected serum antibodies to the gag region of HERV clone 4-1 in patients with SLE, but not in normal volunteers. In the present study, we detected clone 4-1 messenger RNA (mRNA) in peripheral blood mononuclear cells (PBMC) from SLE patients and performed sequence analysis of the cDNA or genomic DNA from clone 4-1 in these patients. Clone 4-1 mRNA was detected in all of the SLE patients tested, although it was not found in normal controls. Sequence analysis of clone 4-1 in these SLE patients revealed inactivation of the stop codons in part of the gag region. In addition, a computer search of current sequence libraries revealed that the clone 4-1 gag genomic DNA from SLE patients was more highly homologous with the clone 4-1 sequence in chromosome 11 from normal individuals when compared with the sequence of clone 4-1 integrated in the other chromosomes. It is possible that transcription of clone 4-1 from chromosome 11 occurs in SLE, and that the stop codon inactivation contributes to the translation of clone 4-1 gag proteins in patients with this disease

Role of Curdlan Sulfate in the Binding of HIV-1 gp120 to CD4 Molecules and the Production of gp120-Mediated TNF-α

To clarify the mechanism by which curdlan sulfate (CRDS) inhibits human immunodeficiency virus (HIV)‐1 infection, we examined its influence on the binding of gp120 to CD4 molecules on T cells and macrophages, as well as on the production of TNF‐α by gp120‐stimulated macrophages (which promotes HIV‐1 replication). CRDS treatment of cells not only inhibited the binding of HIV‐1 gp120 to CD4+ cells, but also inhibited TNF‐α production induced by gp120. Inhibition of HIV‐1 infection by CRDS may be related to these two actions.

Role of tumour necrosis factor‐alpha (TNF‐α) in the induction of HIV‐1 gp120‐mediated CD4+ T cell anergy

The HIV‐1 envelope glycoprotein (gp120) is known to induce antigen‐specific and non‐specific CD4+ T cell anergy. We found that early T cell activation, as indicated by HLA‐DP expression in the early G1 (G1A) phase of the cell cycle, and the inhibition of mitogen‐mediated IL‐2 production induced by gp120, required TNF‐α produced by gp120‐stimulated macrophages. In the presence of an antibody to TNF‐α, these changes induced by gp120 were inhibited, while recombinant TNF‐α induced similar abnormalities of CD4+ T cells, even in the absence of gp120. On the other hand, inhibition of the mixed lymphocyte reaction (MLR) in CD4+ T cells by gp120, which may be related to gp120‐mediated down‐regulation of CD4 expression on T cells and activation of protein tyrosine kinase p56lck in CD4+ T cells, was observed even in the absence of macrophage‐derived TNF‐α induced by gp120. These observations indicate that both TNF‐α‐dependent and independent events contribute to gp120‐mediated CD4+ T cell anergy, and TNF‐α appears to play an important role in inducing CD4+ T cell anergy in HIV‐1 infection.

Very low-dose cyclosporin treatment of steroid-resistant interstitial pneumonitis associated with Sjögren's syndrome.

Cyclosporin is known to be effective for both transplantation and a spectrum of immune-mediated diseases. Because this agent also causes severe adverse effects, especially nephrotoxicity, careful monitoring is required for the development of such reactions. Here we report the successful treatment with extremely low-dose cyclosporin (1 mg/kg/day) of a patient who had steroidresistant interstitial pneumonitis and Sjögrens syndrome.

Effect of extremely low dose cyclosporine treatment on the thrombocytopenia in systemic lupus erythematosus

Cyclosporine is widely known to be effective in cases involving both transplantation as well as a spectrum of immune-mediated diseases, although careful monitoring is required for the preemptive detection of its adverse effects. Here we report the successful treatment by extremely low dose cyclosporine (1 mg/kg per day) of two patients with thrombocytopenia in systemic lupus erythematosus.

Subsets of Activated T Cells in Patients with Systemic Lupus Erythematosus: the Relation to Cell Cycle

The correlation among the various markers of activated T cells (soluble interleukin 2 receptor (sIL-2R), HLA-DR+ and HLA-DP+ T cells, proliferating cell nuclear antigen (PCNA) positive lymphocytes) were examined in patients with systemic lupus erythematosus (SLE), and related to the cell cycle. The concentration of sIL-2R and the proportion of HLA-DR+ T cells, HLA-DP+ T cells or PCNA+ lymphocytes were increased significantly as compared to that in normal subjects. And, the concentrations of sIL-2R correlated with the proportions of PCNA+ lymphocytes, but not with the proportions of HLA-DR+ T cells, HLA-DP+ T cells. The correlation between sIL-2R and PCNA+ lymphocytes was attributed to both indicators being increased during the G1B or S phase in normal T cells upon stimulation by phytohemagglutinin (PHA). Upon cell cycle analysis it was learned that activated T cells could be found in the G1A and the S phases.