Protective effect of beraprost sodium, a new chemically stable prostacyclin analogue, against the deterioration of baroreceptor reflex following transient global cerebral ischaemia in dogs

Prostacyclin influences the pressure reactivity in patients with severe traumatic brain injury treated with an ICP-targeted therapy

BACKGROUND

This prospective consecutive double-blinded randomized study investigated the effect of prostacyclin on pressure reactivity (PR) in severe traumatic brain injured patients. Other aims were to describe PR over time and its relation to outcome.

METHODS

Blunt head trauma patients, Glasgow coma scale ≤8, age 15-70 years were included and randomized to prostacyclin treatment (n = 23) or placebo (n = 25). Outcome was assessed using the extended Glasgow outcome scale (GOSE) at 3 months. PR was calculated as the regression coefficient between the hourly mean values of ICP versus MAP. Pressure active/stable was defined as PR ≤0.

RESULTS

Mean PR over 96 h (PRtot) was 0.077 ± 0.168, in the prostacyclin group 0.030 ± 0.153 and in the placebo group 0.120 ± 0.173 (p < 0.02). There was a larger portion of pressure-active/stable patients in the prostacyclin group than in the placebo group (p < 0.05). Intra-individual changes over time were common. PRtot correlated negatively with GOSE score (p < 0.04). PRtot was 0.117 ± 0.182 in the unfavorable (GOSE 1-4) and 0.029 ± 0.140 in the favorable outcome group (GOSE 5-8). Area under the curve for prediction of death (ROC) was 0.742 and for favorable outcome 0.628.

CONCLUSIONS

Prostacyclin influenced the PR in a direction of increased pressure stability and a lower PRtot was associated with improved outcome. The individual PR varied substantially over time. The predictive value of PRtot for outcome was not solid enough to be used in the clinical situation.

Neuroprotective properties of prostaglandin I2 IP receptor in focal cerebral ischemia

We and others have identified that inhibition of cyclooxygenase might not be the optimal approach to limiting brain damage after stroke. Now we are investigating the unique properties of the various prostaglandin receptors to determine whether blocking those that mediate toxicity or stimulating those that reduce toxicity will improve neurological outcomes. Here, we determined the respective contribution of the prostaglandin I(2) (PGI(2)) receptor in transient middle cerebral artery (MCA) occlusion (tMCAO) and permanent MCAO (pMCAO) preclinical stroke models by using male wildtype (WT) and IP receptor knockout (IP(-/-)) C57Bl/6 mice. In addition, we investigated the putative preventive and therapeutic effects of the IP receptor agonist beraprost. The infarct volumes and neurological deficit scores (NDS) were significantly greater in IP(-/-) than in WT mice after both tMCAO and pMCAO. Interestingly, beraprost pretreatment (50 or 100 microg/kg p.o.) 30 min before tMCAO and post-treatment (100 microg/kg p.o.) at 2 or 4.5 h of reperfusion significantly reduced the neurological deficit score and infarct volume in WT mice. Post-treatment with beraprost (100 microg/kg p.o.) 4.5 h after pMCAO also significantly decreased neurological deficits and infarct volume in WT mice. Together, these novel findings suggest for the first time that PGI(2) IP receptor activation can attenuate anatomical and functional damage following ischemic stroke.

A systematic review of currently available pharmacological neuroprotective agents as a sole intervention before anticipated or induced cardiac arrest

We conducted a Medline search for controlled studies evaluating currently available drugs for pharmacological neuroprotection. They had to be administered prior to transient global cerebral ischaemia without further non-pharmacological measures. We deliberately excluded focal ischaemia since its pathophysiology is substantially different from global ischaemia. A total of 45 articles conducted exclusively in laboratory animals met these criteria. The following classes of agents were evaluated: anaesthetics, GABAergic drugs, calcium-antagonists, anticonvulsives, sodium-channel blockers, potassium-channel activators, NMDA-receptor antagonists, hormones, vasodilators, dopamine- and alpha2-agonists, magnesium, xanthine oxidase- and cyclooxygenase inhibitors, a nootropic, a protease inhibitor, and immunosuppressants. Some of them were applied chronically and others administered via clinically impracticable routes. The available literature favours isoflurane, phenytoin, lamotrigine, magnesium, and potentially, nimodipine, and flunarizine. If factors like costs, toxicity, side effects, route and mode of application are considered, isoflurane and MgSO4 that have also been safely applied to patients with compromised left ventricular pump function are advantageous but their true role in human neuroprotection remains unclear.

The intramolecular asymmetric Pauson-Khand cyclization as a novel and general stereoselective route to benzindene prostacyclins: synthesis of UT-15 (treprostinil)

A general and novel solution to the synthesis of biologically important stable analogues of prostacyclin PGI(2), namely benzindene prostacyclins, has been achieved via the stereoselective intramolecular Pauson-Khand cyclization (PKC). This work illustrates for the first time the synthetic utility and reliability of the asymmetric PKC route for synthesis and subsequent manufacture of a complex drug substance on a multikilogram scale. The synthetic route surmounts issues of individual step stereoselectivity and scalability. The key step in the synthesis involves efficient stereoselection effected in the PKC of a benzoenyne under the agency of the benzylic OTBDMS group, which serves as a temporary stereodirecting group that is conveniently removed via benzylic hydrogenolysis concomitantly with the catalytic hydrogenation of the enone PKC product. Thus the benzylic chiral center dictates the subsequent stereochemistry of the stereogenic centers at three carbon atoms (C(3a), C(9a), and C(1)).

Protection by nicorandil against the dysfunction of the central vagal baroreflex system following transient global cerebral ischaemia in dogs

1. A possible cerebroprotective effect of nicorandil was investigated in a canine model of 5 min global cerebral ischaemia, and compared with protective effects of nitroglycerin and nicardipine. 2. Cerebral ischaemia was produced by occlusion of the left subclavian and the brachiocephalic arteries with preceding ligation of the intercostal arteries. The decrease in baroreflex sensitivity (BRS), measured by phenylephrine-induced reflex bradycardia, was used to assess the cerebroprotective effect. 3. Nicorandil (10 or 30 micrograms kg-1 min-1, i.v.), nitroglycerin (3 micrograms kg-1 min-1, i.v.) or nicardipine (0.3 micrograms kg-1 min-1, i.v.) were infused for 60 min just before ischaemia. Nitroglycerin and nicardipine decreased mean arterial blood pressure to an extent similar to that induced by the lower dose of nicorandil. Blood flow in the dorsal medulla oblongata was increased by nicorandil and nicardipine, but not by nitroglycerin. 4. Nicorandil at both doses and nitroglycerin prevented the post-ischaemic decrease in BRS. In these cases, bilateral vagotomy during the reperfusion period decreased BRS, indicating that the vagal component of BRS was protected from ischaemia. On the other hand, nicardipine failed to exert a cerebroprotective effect. 5. The present study suggests that nicorandil may possess a direct cerebroprotective effect and that its property as a nitrate might, at least in part, be important for the observed cerebral protection.

The effects of beraprost Na, a stable prostacyclin analog, on animal models of stroke

We evaluated the effects of beraprost Na (Sodium (+-)-(1R*,2R*, 3aS*,8bS*)-2,3,3a,8b-tetrahydro-2-hydroxy-1-[(E)-(3S*)-3- hyd roxy-4-methyl-1- octen-6-ynyl]-1H-cyclopenta[b]benzofuran-5-butylate, beraprost), a stable and orally active prostacyclin (PGI2) analog with potent antiplatelet and vasodilating properties, on two stroke models, namely sudden death induced by arachidonate (AA) in rabbits and spontaneous stroke in stroke-prone spontaneously hypertensive rats (SHRSP). In the AA-induced sudden death model, 30 min after beraprost administration (1 or 3 mg/kg, po), AA was injected into the rabbit internal carotid artery, and incidence of convulsion and sudden death were assessed. Beraprost decreased both incidence of convulsion and mortality of rabbits. In SHRSP, orally administered beraprost (100 micrograms/kg, twice a day from 56-385 d of age) improved survival rate and decreased incidence of stroke. Preventive effects of beraprost on the two stroke models may have been caused mainly by the improvement of cerebral circulation. These results indicate that beraprost may have potential in the treatment and/or prevention of the cerebral circulatory disorders.