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In vitro effects of methotrexate on polyamine levels in lymphocytes from rheumatoid arthritis patients
G Nesher1, T G Osborn, T L Moore
1Department of Internal Medicine, Saint Louis University Health Sciences Center, Missouri 63104, USA.
Objective:
Several studies have documented increased levels of polyamines in rheumatoid arthritis (RA). We have suggested that one of the mechanisms of action of methotrexate (MTX) involves the inhibition of polyamine synthesis in lymphocytes. In this study, we sought to establish the inhibitory effect of MTX on polyamine synthesis and its specificity.
Methods:
Polyamine levels were determined in stimulated RA lymphocytes incubated in vitro with MTX and compared to levels in lymphocytes incubated with hydrocortisone, D-penicillamine, or medium alone. Lymphocyte polyamine levels were correlated with IgM-rheumatoid factor (RF) synthesis.
Results:
Incubation with MTX resulted in concentration-dependent decreased intracellular levels of spermidine and spermine, while putrescine levels were not affected. Addition of folinic acid or S-adenosyl-methionine (SAM) prevented this MTX-induced inhibition. Incubation with D-penicillamine or hydrocortisone had no significant effect on polyamine levels. There was a positive correlation between intracellular polyamine levels and the inhibition of IgM-RF synthesis by MTX.
Conclusion:
These data suggest that MTX inhibits the synthesis of spermidine and spermine in stimulated RA lymphocytes through inhibition of the SAM-dependent pathway. This inhibition may be related to the immune-modulating properties of MTX.
Insights
Methotrexate (MTX) significantly reduces spermidine and spermine levels in rheumatoid arthritis (RA) lymphocytes, suggesting a key mechanism for its immune-modulating effects. This inhibition is specific and linked to the S-adenosyl-methionine pathway.
Area of Science:
- Immunology
- Biochemistry
- Pharmacology
Background:
- Elevated polyamine levels are observed in rheumatoid arthritis (RA).
- Methotrexate (MTX) is a common RA treatment, and its mechanism may involve polyamine synthesis inhibition in lymphocytes.
Purpose of the Study:
- To investigate the inhibitory effect of MTX on polyamine synthesis in RA lymphocytes.
- To determine the specificity of MTX's effect on polyamine synthesis.
Main Methods:
- RA lymphocytes were stimulated and incubated with MTX, hydrocortisone, or D-penicillamine in vitro.
- Intracellular polyamine levels (spermidine, spermine, putrescine) were measured.
- Correlation between polyamine levels and IgM-rheumatoid factor (RF) synthesis was analyzed.
Main Results:
- MTX caused a concentration-dependent decrease in spermidine and spermine levels, but not putrescine.
- Folinic acid or S-adenosyl-methionine (SAM) reversed the MTX-induced inhibition.
- Hydrocortisone and D-penicillamine did not significantly affect polyamine levels.
- A positive correlation was found between polyamine levels and MTX's inhibition of IgM-RF synthesis.
Conclusions:
- MTX inhibits spermidine and spermine synthesis in RA lymphocytes via the SAM-dependent pathway.
- This polyamine synthesis inhibition is a potential mechanism for MTX's immune-modulating properties in RA.
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