Mycophenolic acid and 6-mercaptopurine both inhibit B-cell proliferation in granulomatosis with polyangiitis patients, whereas only mycophenolic acid inhibits B-cell IL-6 production

• Published in: PloS one Vol. 15; no. 7; p. e0235743
• Main Authors: von Borstel, Anouk, Abdulahad, Wayel H, Dekkema, Gerjan, Rutgers, Abraham, Stegeman, Coen A, Veldman, Johanna, Heeringa, Peter, Sanders, Jan Stephan
• Format: Journal Article
• Language: English
• Published: San Francisco Public Library of Science 09.07.2020; Public Library of Science (PLoS)
• Subjects: 12-O-Tetradecanoylphorbol-13-acetate; 6-Mercaptopurine; Acetic acid; Antibodies; Antigens; Autoantibodies; Autoimmune diseases; Azathioprine; B cells; Biology; Biology and Life Sciences; Blood vessels; Calcium; Cell growth; Cell proliferation; CpG islands; Cytokines; Depletion; Disease; Drug dosages; Drugs; Granulomatosis; Health aspects; Hemopoiesis; Immune system; Immunological memory; Immunology; Immunosuppressive agents; Inflammatory diseases; Interleukin 10; Interleukin 6; Interleukins; Internal medicine; Lymphocytes B; Medicine and Health Sciences; Memory cells; Monoclonal antibodies; Mycophenolic acid; Nephrology; Oligonucleotides; Pathogenesis; Pathology; Phenols; Physiological aspects; Plasma; Remission; Rheumatology; Rituximab; Tumor necrosis factor-α; Vein & artery diseases; Wegener's granulomatosis; United States; United States > US; Netherlands
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0235743

Granulomatosis with polyangiitis (GPA) is an autoimmune disease affecting mainly small blood vessels. B-cells are important in the GPA pathogenesis as precursors of autoantibody-producing cells but likely also contribute (auto)antibody-independently. This has been underlined by the effectiveness of B-cell-depletion (with Rituximab) in inducing and maintaining disease remission. Mycophenolate-mofetil (MMF) and azathioprine (AZA) are immunosuppressive therapies frequently used in GPA-patients. Interestingly, MMF-treated GPA-patients are more prone to relapses than AZA-treated patients, while little is known about the influence of these drugs on B-cells. We investigated whether MMF or AZA treatment (or their active compounds) alters the circulating B-cell subset distribution and has differential effects on in vitro B-cell proliferation and cytokine production in GPA-patients that might underlie the different relapse rate. Circulating B-cell subset frequencies were determined in samples from AZA-treated (n = 13), MMF-treated (n = 12), untreated GPA-patients (n = 19) and matched HCs (n = 41). To determine the ex vivo effects of the active compounds of MMF and AZA, MPA and 6-MP respectively, on B-cell proliferation and cytokine production, PBMCs of untreated GPA-patients (n = 29) and matched HCs (n = 30) were cultured for 3-days in the presence of CpG-oligodeoxynucleotides (CpG) with MPA or 6-MP. After restimulation (with phorbol myristate acetate, calcium-ionophore), cytokine-positive B-cell frequencies were measured. Finally, to assess the effect of MMF or AZA treatment on in vitro B-cell proliferation and cytokine production, PBMCs of MMF-treated (n = 18), and AZA-treated patients (n = 28) and HCs (n = 41) were cultured with CpG. The memory B-cell frequency was increased in AZA- compared to MMF-treated patients, while no other subset was different. The active compounds of MMF and AZA showed in vitro that MPA decreased B-cell proliferation in GPA-patients and HCs. B-cell proliferation in MMF- and AZA-treated patients was not different. Finally, the IL-6.sup.+ B-cell frequency was decreased by MPA compared to 6-MP. No differences in IL-10.sup.+, IL-6.sup.+ or TNF[alpha].sup.+ B-cell proportions or proliferation were found in MMF- and AZA-treated patients. Our results indicate that MMF could be superior to AZA in inhibiting B-cell cytokine production in GPA-patients. Future studies should assess the effects of these immunosuppressive drugs on other immune cells to elucidate mechanisms underlying the potential differences in relapse rates.