9-o-methanoprostaglandin-i and Brain-Ischemia

Isocarbacyclin is a valuable synthetic analogue of prostacyclin with potential neuroprotective effects for the treatment of ischemic stroke. Herein, we describe the synthesis of isocarbacyclin and bicyclic analogues in only 7-10 steps, with the ω-side chain diversified at a late stage. A combination of new reaction design, function-oriented synthesis, and late-stage diversification led to a series of compounds that were tested for their neuroprotective activities. Efforts toward the synthesis of tricyclic analogues of isocarbacyclin, using the same combination of metal-catalyzed reactions, is also described.

Topics: Animals; Brain Ischemia; Bridged Bicyclo Compounds; Epoprostenol; Mice; Neurons; Neuroprotective Agents; Stereoisomerism; Stroke

TTC-909 (Clinprost), a chemically stable PGI2 analog, isocarbacyclin methyl ester (TEI-9090 or Clinprost) incorporated in lipid microspheres, when administered intravenously after brain ischemia, prevents ischemic neuronal damage possibly by modulating cerebral blood flow and platelet aggregation. However, the possibility exists that TEI-7165, which is the free acid form and a central metabolite of TEI-9090, has direct neurotrophic action in vivo, since TEI-7165 has been shown to block neuronal voltage-dependent Ca2+ channels in vitro, and a novel prostacyclin receptor showing high affinity with TEI-7165 has been detected in a variety of brain regions including the hippocampus. In the present study, we infused TEI-7165 for 7 days into the lateral ventricle of gerbils starting 2 h before or just after 3-min forebrain ischemia. TEI-7165 infusion prevented significantly the ischemia-induced shortening of response latency time as revealed by a step-down passive avoidance task. Subsequent light and electron microscopic examinations showed that pyramidal neurons in the hippocampal CA1 region, as well as synapses within the strata moleculare, radiatum and oriens of the region, were significantly more numerous in gerbils infused with TEI-7165 than in those receiving vehicle infusion. TEI-7165 infusion did not affect hippocampal blood flow or temperature. These findings, together with the previously depicted accumulation of centrally administered [3H]TEI-7165 around hippocampal neurons, suggest that TEI-7165 has a direct neuroprotective action in brain ischemia.

Topics: Animals; Avoidance Learning; Brain; Brain Ischemia; Epoprostenol; Gerbillinae; Hippocampus; Male; Microscopy, Electron; Neurons; Neuroprotective Agents; Pyramidal Cells; Reaction Time; Synapses

Because the permeability of the blood-brain barrier to lipid microspheres (LMs) has not hitherto been demonstrated, blood-brain-barrier permeability to LM containing the prostaglandin I2 analogue clinprost has been evaluated for an in-vitro system of primary cultured monolayers of bovine brain capillary endothelial cells (BCECs), by a capillary depletion study in rats and by an in-situ brain perfusion study in normal and 4-vessel-occluded fore brain ischaemic rats. Although energy-dependency was not observed in [3H]clinprost uptake by BCECs, in accordance with results for simple diffusional transport, uptake of [3H]clinprost contained in lipid microspheres (denoted [3H]clinprost(LM)) was significantly inhibited by the endocytosis inhibitor, dansylcadaverine. The transport of LM into BCECs by endocytosis was also confirmed by fluorescence microscopy and flow-cytometric analysis using LM labelled with a fluorescent probe, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (Dil). The absolute uptake of Dil(LM) by BCECs, measured by HPLC, was, however, almost 1/10 that of [3H]clinprost(LM), results which suggest the superiority of simple diffusion of clinprost over endocytosis of its LM form in the uptake of clinprost(LM) by BCECs. In the capillary-depletion study with rat-brain-perfused [3H]clinprost(LM) from the internal carotid artery, the parenchyma apparent distribution volume was about 45 times larger than that of the capillary, showing that [3H]clinprost(LM) was transported through the blood-brain barrier into the brain. The permeability coefficients of [3H]clinprost and [3H]clinprost(LM) determined by insitu brain perfusion in normal rats were considerably higher than those of the active metabolite [3H]isocarbacyclin and its LM form. In addition, the Blood-brain-barrier permeabilities to [3H]clinprost, [3H]isocarbacyclin and their LM forms in ischaemic rats were almost identical to those in normal rats. It was concluded that clinprost(LM) was transported through the blood-brain barrier by endocytosis of LM, simple diffusion of clinprost released from LM, and transport of isocarbacyclin generated by hydrolysis of clinprost. The blood-brain-barrier permeability of clinprost(LM) is not reduced in ischaemic conditions, because the simple diffusion of clinprost released from LM contributed mainly to clinprost(LM) transport.

Topics: Animals; Blood-Brain Barrier; Brain Ischemia; Cattle; Cells, Cultured; Drug Carriers; Epoprostenol; Lipids; Microspheres; Permeability; Prostaglandins, Synthetic; Rats; Rats, Inbred F344