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Arthritis Rheum. 1998 Nov;41(11):2032-8.

Effects of methotrexate on differentiation of monocytes and production of cytokine inhibitors by monocytes.

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1
Department of Rheumatology, University Hospital, Inselspital, Berne, Switzerland.

Abstract

OBJECTIVE:

To examine the potential of methotrexate (MTX) to act as a differentiation-stimulating factor for monocytes, which could explain the antiinflammatory properties of this agent in the treatment of rheumatoid arthritis (RA).

METHODS:

Fluorescence-activated cell sorter analysis was used to measure the changes in antigen expression (CD11b/c, CD16, CD64, CD14, CD68, and CD95) in response to MTX, 1,25-OH-cholecalciferol (1,25-OH-CCF), and granulocyte-macrophage colony-stimulating factor in the human monoblastic leukemia cell line U937, bone marrow mononuclear cells (BMMC), and peripheral blood mononuclear cells (PBMC). Release of interleukin-1beta (IL-1beta), IL-1 receptor antagonist (IL-1Ra), tumor necrosis factor a, and soluble tumor necrosis factor receptors (sTNFR) p55 and p75 during the differentiation in vitro was assessed by immunoassay in the culture supernatants.

RESULTS:

MTX alone and in combination with 1,25-OH-CCF markedly stimulated the differentiation of the monocytic U937 cells and simultaneously increased Fas-antigen expression. Differentiation was associated with enhanced IL-1Ra and sTNFR p75 release from U937 cells. MTX had fewer effects on phenotypic differentiation of human BMMC and PBMC, but did stimulate IL-1Ra release and inhibit IL-1beta synthesis in BMMC.

CONCLUSION:

MTX acts as a strong differentiation factor for immature and undifferentiated monocytic cells. Differentiation in vitro is associated with an increase in natural cytokine inhibitor release and a simultaneous down-regulation of IL-1beta. These findings may explain the marked clinical antiinflammatory effects of MTX when used in the treatment of RA.

[Indexed for MEDLINE]

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