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Methotrexate inhibits neutrophil function by stimulating adenosine release from connective tissue cells
B N Cronstein1, M A Eberle, H E Gruber
1Department of Medicine, New York University Medical Center, NY 10016.
Summary
Low-dose methotrexate increases adenosine release from cells, reducing neutrophil adherence. This mechanism, involving AICAR accumulation, may explain its anti-inflammatory effects and guide new drug development.
Area of Science:
- Pharmacology
- Immunology
- Cell Biology
Background:
- Low-dose methotrexate is widely used for inflammatory diseases, but its mechanism of action is not fully understood.
- Methotrexate accumulates intracellularly and may impact purine metabolism.
Purpose of the Study:
- To investigate whether methotrexate pretreatment affects adenosine release from human fibroblasts and umbilical vein endothelial cells.
- To determine if methotrexate-induced adenosine release influences neutrophil adherence to these cells.
Main Methods:
- Human fibroblasts and endothelial cells were pretreated with methotrexate.
- Adenosine release was measured using [14C]adenine labeling.
- Neutrophil adherence to treated cells was assessed, and the role of adenosine was confirmed using adenosine deaminase.
Main Results:
- Methotrexate significantly increased adenosine release from both fibroblasts and endothelial cells in a dose-dependent manner.
- Methotrexate treatment markedly inhibited neutrophil adherence to fibroblasts, an effect reversed by adenosine deaminase.
- The proposed mechanism involves methotrexate-induced accumulation of 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), leading to acadesine production and subsequent adenosine release.
Conclusions:
- Methotrexate's anti-inflammatory effects may stem from its ability to induce adenosine release, which inhibits neutrophil adherence.
- This mechanism provides a basis for developing novel anti-inflammatory drugs targeting adenosine pathways.