Mycophenolic acid, the active form of mycophenolate mofetil, interferes with IRF7 nuclear translocation and type I IFN production by plasmacytoid dendritic cells

BACKGROUND

Both humoral and cellular immune mechanisms are involved in the onset and progression of autoimmune responses in systemic lupus erythematosus (SLE). Plasmacytoid dendritic cells (pDCs) play a central role in the pathogenesis of SLE via the dysregulation of type I interferon (IFN) production; these cells act together with activated myeloid DCs (mDCs) to amplify the vicious pathogenic spiral of autoimmune disorders. Therefore, control of aberrant DC activation in SLE may provide an alternative treatment strategy against this disease. Mycophenolate mofetil (MMF), which has been used to treat lupus nephritis, specifically blocks the proliferation of B and T lymphocytes via inhibition of inosine-5-monophosphate dehydrogenase. Here, we focus on the effects of MMF in targeting DC functions, especially the IFN response of pDCs.

METHODS

We isolated human blood pDCs and mDCs by flow cytometry and examined the effect of mycophenolic acid (MPA), which is a metabolic product of MMF, on the toll-like receptor (TLR) ligand response of DC subsets. Additionally, we cultured pDCs with serum from SLE patients in the presence or absence of MPA and then examined the inhibitory function of MPA on SLE serum-induced IFN-α production.

RESULTS

We found that treatment with 1-10 μM of MPA (covering the clinical trough plasma concentration range) dose-dependently downregulated the expression of CD80 and CD86 on mDCs (but not pDCs) without inducing apoptosis, in response to R848 or CpG-ODN, respectively. Notably, in pDCs, MPA significantly suppressed IFN-α production with IRF7 nuclear translocation and repressed the AKT activity. In addition, MPA inhibited IL-12 production with STAT4 expression in mDCs. We further identified that MPA had an inhibitory effect on SLE serum-induced IFN-α production by pDCs.

CONCLUSIONS

Our data suggest that MPA can interrupt the vicious pathogenic spiral of autoimmune disorders by regulating the function of DC subsets. This work unveiled a novel mechanism for the therapeutic ability of MMF against SLE.

Sporotrichal Tenosynovitis Diagnosed Helpfully by Musculoskeletal Ultrasonography

A 72-year-old man presented with persistent oligoarthritis and positive results for rheumatoid factor and was suspected of having rheumatoid arthritis (RA). However, the musculoskeletal ultrasonography (MSUS) findings were not consistent with those of typical RA. He had undergone surgery for carpal tunnel syndrome, which allowed both histopathological and microbiological examinations to be performed. A synovial tissue culture was positive for Sporothrix schenckii, and he was diagnosed with sporotrichal tenosynovitis. He received anti-fungal therapy, and the sporotrichal tenosynovitis resolved. This case suggests that MSUS is a useful modality, and sporotrichal tenosynovitis, though rare, should be considered in the differential diagnosis of RA.

AB0141 MYCOPHENOLATE MOFETIL, INHIBITOR OF INOSINE-5’-MONOPHOSPHATE DEHYDROGENASE, REGULATES DIFFERENTIATION, MATURATION AND FUNCTION OF HUMAN DENDRITIC CELL SUBSETS

Background:

Systemic lupus erythematosus (SLE) is a heterogeneous disease in which excessive inflammation, autoantibodies, and complement activation lead to multisystem tissue damage. Plasmacytoid dendritc cells (pDCs) play a central role in the pathogenesis of SLE through dysregulated type I IFN production, together with activated myeloid DCs (mDCs), amplifying vicious spiral of autoimmune disorders(1). Therefore, control of the aberrant DC activation may provide an alternative treatment strategy against SLE.

Objectives:

Mycophenolate mofetil (MMF), which has been used to treat lupus nephritis, specifically blocks proliferation of B and T lymphocytes by inhibition of inosine-5-monophosphate dehydrogenase (IMPDH). In addition, although there is evidence indicating the immunosuppressive effects of MMF on human monocyte-derived dendritic cells(2.3), there are no reports showing its effects on human blood DC subsets. Here we focused on the effects of MMF on the functions of the blood pDCs and mDCs.

Methods:

We isolated human blood DCs from healthy donors using cell sorting(4) and examined the function of mycophenolic acid (MPA), which is metabolic products of MMF, on DC subsets in response to TLR-ligands and serum from patients with active SLE. Written informed consent was obtained from all healthy adult donors and SLE patients.

Results:

We found that therapeutic plasma concentration range of MPA down-regulated expression of CD40, CD80 and CD86 dose-dependently on mDCs and pDCs without inducing apoptosis, in response to R848(TLR7/8 agonist) and CpG2216(TLR9 agonist), respectively. Of note, MPA profoundly suppressed IL-12 production and STAT4 expression in the mDCs and IFN-α production and IRF7 expression in the pDCs(Fig 1). We also obserbed inhibition of nuclear translocation of IRF-7 in pDCs treated with MPA by confocal microscopy(Fig 2). Furthermore,we identified that MPA had an inhibitory effect on SLE serum-induced IFN-α production by human PBMCs.

Conclusion:

Our data suggest that MMF can drive a wedge into the vicious spiral of autoimmune disorders through regulating the function of not only lymphocyte but also DC subsets. Thus, we unveiled a part mechanism of the therapeutic ability of MMF against SLE.

References:

[1]A Plasmacytoid Dendritic Cells-Type I Interferon Axis is Critically Implicated in the Pathogenesis of Systemic Lupus Erythematosus. Int. J. Mol. Sci. 2015: 16, 14158-14170.

[2]Mycophenolate mofetil inhibits differentiation, maturation and allostimulatory function of human monocyte-derived dendritic cells. Clin Exp Immunol. 2003;134:63-69.

[3]Mycophenolic acid inhibits maturation and function of human dendritic cells and B cells. Human Immunol. 2009;70: 692–700.

[4]Miyamoto et al. Arthritis Research & Therapy 2010, 12:R87.

Disclosure of Interests:

None declared

Anti-MDA-5 Antibody-positive Dermatomyositis after Allogeneic Bone Marrow Transplantation for Acute Transformation of Chronic Myelogenous Leukemia

Anti-melanoma differentiation-associated gene 5 (MDA-5) antibody-positive dermatomyositis is a disease with a poor prognosis associated with rapid progressive interstitial pneumonia. Autoimmune diseases have occasionally been reported to occur after hematopoietic stem cell transplantation (HSCT). We experienced a case of anti-MDA-5 antibody-positive dermatomyositis after HSCT. In this case, a sufficient dose of cyclophosphamide could not be administered due to an impaired bone marrow function. We discuss the complications of autoimmune diseases after HSCT.

FRI0550 CAN CYTOKINE GENE POLYMORPHISMS BE USEFUL FOR THE THERAPEUTIC CHOICE IN JAPANESE PATIENTS WITH RHEUMATOID ARTHRITIS?

Background:

Rheumatoid arthritis (RA) is a common autoimmune disease. It is characterized by systemic synovitis with bone erosion and joint cartilage degradation(1). Production of autoantibody is important for autoimmune disease. Cytokines play crucial roles in its pathogenesis(2). SNP distribution varies between races. Few studies have examined SNP targeted at Japanese patients. The analysis of cytokine gene polymorphisms is important factor of pathophysiology and treatment.

Objectives:

This analysis was aimed to investigate the association between cytokine gene polymorphisms and autoantibody and therapeutic response in Japanese RA patients.

Methods:

This study subjects consisted of 100 RA patients and 50 healthy controls. We extracted data on patient sex, age, disease duration, rheumatoid factor (RF), anti cyclic citrullinated peptide (anti-CCP) antibody and therapeutic response including methotrexate (MTX) and biological DMARDs. Genomic DNA was isolated from peripheral blood, these were genotyped for TNFα, TGFβ1, IL-6, IL-10 and IFNγ polymorphisms. We analyzed these data using a chi-square test.

Results:

IL-10 (-819 C/T and -592 C/A) revealed that there were significant decrease in the frequency of IL-10 (-819) CC genotype and (-592) CC genotype as compared to controls in RA patients. Genotyping of IL-10 showed that there was significant decrease ACC/ACC genotype (Table 1).

IFNγ (+874 A/T) revealed that there was significant decrease in the frequency of TT genotype as compared to controls (Table 1).

No significant differences in TNFα, TGFβ1and IL-6 genotypes and alleles frequency were observed between RA patients and control.

TGFβ1(+869 A/T) in patients with anti-CCP antibody positive revealed that there was significant decrease in the frequency of TT genotype as compared to patients with anti-CCP antibody negative (Table 2).

No significant association between RF and any cytokine gene polymorphism.

Analyzing cytokine gene polymorphisms could be useful for treatment with MTX and biological DMARDs.

Table 1.

Table 2.

Conclusion:

IL-10 (-819 C/T, -592 C/A) and IFNγ (+874 A/T) polymorphism might be related to RA in Japanese population. In addition, TGFβ1(+869 A/T) polymorphism might be associated with the production of anti-CCP antibody. These results suggest that the analyzing cytokine gene polymorphisms may offer promise as useful factors in the choice of treatment for Japanese RA patients.

References:

[1] Scott DL, Wolfe F, Huizinga TW. Rheumatoid arthritis. Lancet. 2010; 376: 1094–108.

[2] McInnes IB, Schett G. Cytokines in the pathogenesis of rheumatoid arthritis. Nat Rev Immunol. 2007 Jun;7(6):429-42.

Disclosure of Interests:

None declared