Intracerebral hemorrhage (ICH) is the deadliest form of stroke with frequent early neurological deterioration or death. Therefore, there is a desperate need for a medical treatment of ICH across the board. Dr. Dore and others have successfully demonstrated the role of prostaglandin receptors in ischemic stroke;however this remains to be elucidated in hemorrhagic stroke. Preliminary data have shown that activation of FP receptor with fluprostenol (FP receptor agonist) increased ischemic stroke brain damage and neurological deficit in WT but not in FP-/- mice. Also, deletion of FP receptors protects the brain from ischemic stroke-induced damage and enhances behavioral recovery. PGF2? when bound to its FP receptors, initiates a signaling cascade that results in the release of inositol-1,4,5-triphosphate and diacylglycerol and in turn activation of the calcium pathway, which has been associated with excitotoxicity following transient focal brain ischemia. To study the role of FP receptors in ICH, I propose to use the autologous blood injection ICH model in WT and FP-/- mice.
In Aim 1, I will measure PGF2? and FP receptor expression levels at different times after ICH and investigate the effect of FP deletion on ICH-induced neurological deficit score, brain injury, edema and blood brain barrier permeability. Therapeutic paradigms in ICH will be studied by post-treating WT mice with FP antagonist AL8810, suggesting potential drug treatment. The outcome and selectivity of this FP receptor antagonist drug will be further tested in the FP-/- mice. Using such pharmacological approaches extends our results from knockout animals to address potential compensatory effects. I hypothesize that blockade and deletion of FP receptor will significantly improve post-ICH outcomes. Following ICH, toxic blood components such as hemoglobin and heme are present in extravascular space and substantially contribute to morbidity. Preliminary data has shown that heme, a blood by-product, is neurotoxic to primary cortical neurons. Thus, in Aim 2, using an ICH-in vitro model, I will determine the cellular mechanism involved in FP receptor activation with and without heme and hemoglobin treatment. To elucidate FP receptor mediated neuroprotection I will focus on the survival of primary corticostriatal neurons after heme treatment because heme is derived mainly from hemoglobin after ICH. I will determine if heme- and/or Hgb- induced neurotoxicity can be rescued in postnatal neurons from WT and FP-/- mice and conclude FP receptor activated neuronal survival. I hypothesize that FP-/- and its blockade will protect or rescue neurons from heme/Hgb-induced toxicity. I anticipate that the use of AL8810 in WT cultures will corroborate and extend our in vivo results from the FP-/- studies. The second part of this aim is to begin investigating mechanisms of FP receptor related Ca2+ signaling. I expect increased [Ca2+]i response to heme/Hgb and compare with the free radical donor, tBuOOH toxicity. I hypothesize that FP receptor activation by PGF2? will affect changes in [Ca2+]i and that FP receptor blockade will attenuate those changes.
Spontaneous intracerebral hemorrhage (ICH) is more than twice as common as subarachnoid hemorrhage (SAH) and is more likely to result in death or major disability than cerebral infarction or SAH and further therapeutic strategies are desperately needed. The majority of experimental treatments have failed due to the fact that they are either administered prior to or at the time of ICH onset. The aims of my proposal are therefore highly relevant to public health as I will investigate mechanisms of ICH with special focus on prostaglandin PGF2alpha and its cognate FP receptor as a therapeutic target to reduce ICH-injury.