al-8810 and Brain-Ischemia

Spontaneous, recurrent spreading depolarizations (SD) are increasingly more appreciated as a pathomechanism behind ischemic brain injuries. Although the prostaglandin F2α - FP receptor signaling pathway has been proposed to contribute to neurodegeneration, it has remained unexplored whether FP receptors are implicated in SD or the coupled cerebral blood flow (CBF) response. We set out here to test the hypothesis that FP receptor blockade may achieve neuroprotection by the inhibition of SD. Global forebrain ischemia/reperfusion was induced in anesthetized rats by the bilateral occlusion and later release of the common carotid arteries. An FP receptor antagonist (AL-8810; 1 mg/bwkg) or its vehicle were administered via the femoral vein 10 min later. Two open craniotomies on the right parietal bone served the elicitation of SD with 1 M KCl, and the acquisition of local field potential. CBF was monitored with laser speckle contrast imaging over the thinned parietal bone. Apoptosis and microglia activation, as well as FP receptor localization were evaluated with immunohistochemistry. The data demonstrate that the antagonism of FP receptors suppressed SD in the ischemic rat cerebral cortex and reduced the duration of recurrent SDs by facilitating repolarization. In parallel, FP receptor antagonism improved perfusion in the ischemic cerebral cortex, and attenuated hypoemic CBF responses associated with SD. Further, FP receptor antagonism appeared to restrain apoptotic cell death related to SD recurrence. In summary, the antagonism of FP receptors (located at the neuro-vascular unit, neurons, astrocytes and microglia) emerges as a promising approach to inhibit the evolution of SDs in cerebral ischemia.

Topics: Animals; Brain Ischemia; Cerebral Cortex; Cerebral Infarction; Cerebrovascular Circulation; Cortical Spreading Depression; Dinoprost; Male; Prosencephalon; Prostaglandins; Rats, Sprague-Dawley; Signal Transduction

Bioactive lipids such as the prostaglandins have been reported to have various cytoprotective or toxic properties in acute and chronic neurological conditions. The roles of PGF(2α) and its receptor (FP) are not clear in the pathogenesis of ischemic brain injury. Considering that this G-protein coupled receptor has been linked to intracellular calcium regulation, we hypothesized that its blockade would be protective. We used FP antagonist (AL-8810) and FP receptor knockout (FP(-/-)) mice in in vivo and in vitro stroke models. Mice that were treated with AL-8810 had 35.7±6.3% less neurologic dysfunction and 36.4±6.0% smaller infarct volumes than did vehicle-treated mice after 48h of permanent middle cerebral artery occlusion (pMCAO); FP(-/-) mice also had improved outcomes after pMCAO. Blockade of the FP receptor also protected against oxygen-glucose deprivation (OGD)-induced cell death and reactive oxygen species formation in slice cultures. Finally, we found that an FP receptor agonist dose dependently increased intracellular Ca(2+) levels in cultured neurons and established that FP-related Ca(2+) signaling is related to ryanodine receptor signaling. These results indicate that the FP receptor is involved in cerebral ischemia-induced damage and could promote development of drugs for treatment of stroke and acute neurodegenerative disorders.

Topics: Animals; Brain; Brain Ischemia; Calcium; Cell Death; Cells, Cultured; Dinoprost; Dose-Response Relationship, Drug; Male; Mice; Mice, Knockout; Neurons; Neuroprotective Agents; Reactive Oxygen Species; Receptors, Prostaglandin