6-ketoprostaglandin-f1-alpha and ibudilast

A combination of low-dose aspirin (ASA) and a phosphodiesterase inhibitor has been clinically tried for the secondary prevention of atherothrombotic diseases. The in vivo antithrombotic property of ibudilast (CAS 50847-11-5), a phosphodiesterase 4 (PDE4) inhibitor, was evaluated in a photochemically-induced guinea pig carotid artery thrombosis model in combination with low-dose ASA. The time required to decrease the carotid artery blood flow to the reading "zero" was defined as the time to occlusion (TTO) of the artery through thrombogenesis. Each independent use of ASA (300 mg/kg, p.o.) and ibudilast (3 and 10 mg/kg, p.o.) significantly prolonged the TTO, and ASA (300 mg/kg) significantly increased bleeding time (BT) and gastric mucosal injury. A selective PDE4 inhibitor rolipram (1 and 5 mg/kg, p.o.) tended to prolong the TTO without extending BT. ASA (100 mg/kg) plus ibudilast (3 mg/kg) and ASA (100 mg/kg) plus rolipram (5 mg/kg) markedly prolonged the TTO compared with each agent alone. Interestingly, ASA (100 mg/kg) plus ibudilast (3 mg/kg) caused a longer TTO than ASA (300 mg/kg) alone, without significant extension of BT and gastric mucosal injury as observed in ASA (300 mg/kg). These results indicate that the combination of low-dose ASA and ibudilast has a more potent antithrombotic effect than ASA alone without increasing bleeding tendency and gastric mucosal injury. The potent in vivo antithrombotic effect of this combination may be brought about by an action that is associated with PDE4 inhibition of ibudilast.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Aspirin; Bleeding Time; Carotid Artery Thrombosis; Drug Therapy, Combination; Gastric Mucosa; Guinea Pigs; Immunoenzyme Techniques; Indicators and Reagents; Male; Mice; Phosphodiesterase Inhibitors; Photochemistry; Platelet Aggregation Inhibitors; Pyridines; Rolipram; Salicylic Acid; Stomach Diseases; Thromboxane B2

3-Isobutyryl-2-isopropylpyrazolo [1,5-a]pyridine (KC-404) at a concentration of greater than or equal to 4.34 X 10(-5) M inhibited adenosine diphosphate-, arachidonic acid- and collagen-induced aggregation of rabbit platelets. In rabbit, KC-404 (0.5 and 2 mg/kg, i.v.) caused a decrease in weight of collagen strip extracorporeally superfused with arterial blood, because of a disaggregation of deposited platelet aggregates. This disaggregatory effect of KC-404 was markedly diminished by the pretreatment of animals with aspirin. KC-404 (greater than or equal to 4.34 X 10(-6) M) and its major metabolite diOH-KD-404 (greater than or equal to 3.78 X 10(-7) M) significantly potentiated the anti-aggregatory action of prostacyclin on rabbit platelets. KC-404 (greater than or equal to (4.34 X 10(-8) M) exerted a similar effect in rat platelets. KC-404 had no significant effect on 6-keto-PGF1 alpha and thromboxane A2 formation by rat aortic segment and rabbit platelets, respectively. KC-404 inhibited cyclic AMP phosphodiesterase (Ki = 91 microM). The present results indicate that KC-404 exhibits its anti-platelet effect via the inhibition of cyclic AMP phosphodiesterase activity in platelets and via the potentiation of anti-aggregatory activity of prostacyclin on platelets.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; 6-Ketoprostaglandin F1 alpha; Animals; Epoprostenol; Female; In Vitro Techniques; Male; Muscle, Smooth, Vascular; Platelet Aggregation; Pyridines; Rabbits; Rats; Rats, Inbred Strains; Species Specificity; Thromboxane A2; Vasodilator Agents