Inhibition of leukotriene B4 synthesis in neutrophils from patients with rheumatoid arthritis by a single oral dose of methotrexate.
We studied the effects of a single, oral dose of methotrexate (MTX) on arachidonic acid metabolism in neutrophils from 6 patients with rheumatoid arthritis, which were obtained 1 day before and 1 day after their usual weekly MTX dose. The 6 patients had received a mean weekly MTX dose of 9.6 mg (range 5-15) for a mean of 61.7 months (range 58-64), and none received concomitant corticosteroids. Total generation of leukotriene B4 (LTB4) in neutrophils stimulated ex vivo with 10 microM calcium ionophore A23187 for 20 minutes was significantly suppressed, by a mean of 53%, after the MTX dose compared with the predose levels (mean +/- SEM 13.0 +/- 1.4 ng/10(6) cells versus 6.0 +/- 0.9 ng/10(6) cells; P = 0.0019), reflecting a comparable suppression of both released and cell-retained LTB4. A 49% decrease in omega-oxidation products of LTB4 demonstrates that decreased LTB4 synthesis, rather than increased degradation, is responsible for the decrease in LTB4 generation. The absence of a significant change in either 3H-labeled arachidonic acid release or platelet-activating factor generation indicates that the observed decrease in LTB4 synthesis was apparently not caused by diminished phospholipase A2 activity. A 28% decrease in the total formation of the 5-lipoxygenase products 5-hydroxyeicosatetraenoic acid and the 6-trans-LTB4 diastereoisomers, and a 48% suppression of production of LTB4 plus its omega-oxidation metabolites after the MTX dose suggest inhibition of 5-lipoxygenase activity and possible suppression of leukotriene A4 epoxide hydrolase activity.
Sperling
R I
RI
Department of Rheumatology and Immunology, Brigham and Women's Hospital, Boston, Massachusetts.
Coblyn
J S
JS
Larkin
J K
JK
Benincaso
A I
AI
Austen
K F
KF
Weinblatt
M E
ME
D000368:Aged; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D001172:Arthritis, Rheumatoid / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D000001:Calcimycin / Q000494:pharmacology; D002634:Chemotaxis, Leukocyte; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000096:biosynthesis; D007975:Leukotriene B4 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D008727:Methotrexate / Q000627:therapeutic use*; D008875:Middle Aged; D009504:Neutrophils / Q000378:metabolism* / Q000502:physiology; D010740:Phospholipases / Q000378:metabolism; D010972:Platelet Activating Factor / Q000096:biosynthesis
D001095:Arachidonic Acids; D006893:Hydroxyeicosatetraenoic Acids; D010972:Platelet Activating Factor; D007975:Leukotriene B4; D016718:Arachidonic Acid; D000001:Calcimycin; C022022:5-hydroxy-6,8,11,14-eicosatetraenoic acid; D010740:Phospholipases; D008727:Methotrexate