The effects of TFC-612, a 7-THIA prostaglandin E1 derivative, on platelet function

Effect of TFC-612, a 7-thia prostaglandin E1 derivative, on a peripheral arterial occlusive disease model in rats

TFC-612, methyl 6-[((1R,2S,3R)-3-hydroxy-2-[(1E,3S,5R)-3-hydroxy-5- methyl-1-nonenyl)-5-oxocyclopentyl]-thio]-hexanoate, inhibited the progression of the lesion in a lauric acid-induced peripheral arterial occlusive model at 1.0 mg/kg p.o. or 1.0 microgram/rat/h s.c. in rats. Aspirin (32 mg/kg, p.o.), an anti-platelet drug, did not suppress the lesion growth. On the other hand, ketanserin (10 mg/kg, p.o.), a 5-HT2 antagonist, also inhibited the progression of the lesion. In vitro, TFC-612 inhibited rat platelet aggregation induced by collagen and ADP with IC50 values of 5.4 ng/mL and 9.5 ng/mL, respectively. Aspirin also inhibited collagen-induced aggregation with an IC50 value of 6.3 micrograms/mL, but not ADP-induced aggregation at 180 micrograms/mL. Ketanserin had no effect on either aggregation at 40 micrograms/mL. In ex vivo experiments, aspirin inhibited platelet aggregation induced by collagen at 10 and 32 mg/kg in rats. However, TFC-612 showed significant inhibition only at 10 mg/kg. TFC-612 and ketanserin increased dermal blood flow in the rat paw at 1.0 microgram/kg i.v. and 100 micrograms/kg i.v., respectively. Aspirin had no effect on blood flow at 3.2 mg/kg i.v. These results suggest that the improvement of microcirculation, in addition to anti-platelet action by TFC-612, contributes to its inhibitory effect in a peripheral arterial occlusive model in rats.

Effect of TFC-612, a 7-thia prostaglandin E1 derivative, on intimal thickening after endothelial injury with balloon catheter in rats

The effect of TFC-612, methyl-6-[(1R,2S,3R)-hydroxy-2-](1E,3S,5R)-3- hydroxy-5-methyl-1-nonenyl]-5-oxocyclopentyl)thio] hexanoate, on intimal thickening of carotid artery 14 days after endothelium denudation with a balloon catheter was examined in rats. This compound significantly suppressed the neointimal area and the ratio of intimal and medial layer by 41.1% and 31.4%, respectively, at 3.2 micrograms/rat/h s.c. infusion. At this dose, this compound did not inhibit platelet aggregation induced by either collagen or ADP. It did not inhibit bromodeoxyuridine incorporation into medial smooth muscle cells at 3 days after injury. In in vitro experiments, TFC-612 did not inhibit the [3H]thymidine uptake into cultured smooth muscle cells, but it showed significant inhibition of smooth muscle cell migration induced by platelet-derived growth factor (PDGF) at more than 10(-9) M. This compound increased cyclic AMP levels dose dependently in cultured smooth muscle cells at more than 10(-8) M. These results suggest that TFC-612 inhibits intimal thickening by inhibition of smooth muscle cell migration from media to intima through cyclic AMP elevation.

Experimental assessment of thrombogenicity in vascular prostheses before and during prostaglandin E1 treatment

The effect of prostaglandin E1 (PGE1; Prostavasin), a powerful platelet blocking agent, was assessed on various new synthetic or biological prostheses in a 6-min in vivo extra corporal arterio-venous (AV) shunt. In eight anaesthetised and heparinised minipigs (weight 25.1 +/- 1.9 kg) the following materials were tested before and during PGE1 infusion (alprostadil-alpha-CD; 40 micrograms/50 ml NaCl/50 min or 0.8 microgram/min): PTFE, (Gore-tex, TW, 4 mm ID); Xenograft, Biologic (Solcograft, 5 mm ID), (non-porous) and Dacron (Atrium, 4 mm ID); polyurethane 1 (Braun-Melsungen, 4 mm ID); polyurethane 2 (S. Gogolewski, 4 mm ID), (porous). Technetium-labelled platelet deposition and blood flow were measured; morphology was assessed by scanning electron microscopy (SEM) and histology. Compared to control levels, PGE1 infusion had a significant systemic effect on mean arterial pressure required by the protocol (MAP 82.6 vs. 66.6 mm Hg; p < 0.001) and flow (173.6 vs. 134.8 mm/min; p < 0.001). Standardised platelet counts per area showed a marked overall decrease from 197 to 130 counts/min/mm2; NS). The morphological assessment by SEM showed a slight increase of surface cellular deposition (score: 6.7 vs. 8.3), the histology score being unchanged (3.9 vs. 3.7). Looking at deposition of platelets for each prosthesis, the porous materials showed a net improvement after PGE1 treatment as compared to non-porous materials. We conclude that PGE1 may be of benefit by reducing platelet deposition in synthetic porous vascular prostheses in the early phase.

TFC-612, a prostaglandin E1 derivative, enhances fibrinolytic activity in rats

TFC-612 inhibited thrombus formation on wire coils inserted into the lumen of the inferior vena cava of rats after 5 oral doses of 1.0 and 3.2 mg/kg and subcutaneous doses of 1.0 and 3.2 micrograms/rat/hr. This compound showed slight inhibition of platelet aggregation induced by collagen at 1.0 and 3.2 mg/kg (po) and significant inhibition at 10 mg/kg. TFC-612 had no effect on the plasma coagulation system at 3.2 mg/kg. Conversely, oral doses of 0.32-3.2 mg/kg dose- dependently enhanced fibrinolytic activity as measured by euglobulin clot lysis time and lysis area on fibrin plates by euglobulin fraction. TFC-612 did not enhance fibrinolytic activity in vitro. These results suggest that the enhancement of fibrinolytic activity by TFC-612, which may be due to an increase in tissue plasminogen activator release or reduction of plasminogen activator inhibitors release, contributes to its inhibition of thrombus formation.