REGULATION OF FIBRINOLYSIS BY NONESTERIFIED FATTY-ACIDS

The ability of oleic acid to modulate fibrinolysis was measured by following the urokinase-mediated and plasminogen-dependent cleavage of I-125-labelled fibrin clots. Oleic acid levels within the physiological range exerted a concentration-dependent inhibition of urokinase-mediated fibrinolytic activity. SDS/PAGE revealed that oleic acid enhances urokinase activity but simultaneously increases the autolytic cleavage of the newly formed low-molecular-mass subunit of plasmin. Oleic acid-induced cleavage of this subunit containing the catalytic site of plasmin was suppressed by the plasmin substrate H-D-valyl-L-leucyl-L-lysine-p-nitroanilide (S-2251) and was prevented by alpha(2)-antiplasmin. A concentration-dependent inhibition of the activity of purified plasmin on I-125-labelled fibrin clot was also observed; 93 % and 50 % inhibition was noted with 150 mu M and 32 mu M oleic acid respectively. Oleic acid at 200 mu M also effectively displaced plasmin prebound to a polylysine-Sepharose column. Examination of the fatty acid specificity showed that a minimal chain length of 16 carbon atoms and the presence of at least one double bond, preferably in a cis configuration, were required for inhibition of the fibrinolytic activity of plasmin. Oleic acid at a concentration that produced only a minimal inhibition of plasmin activity induced a marked inhibition by palmitic acid, while palmitic acid alone is ineffective. The findings suggest that oleic acid stimulates plasminogen activation and modulates the fibrinolytic and autolytic activities of plasmin.