tg6-10-1 and Status-Epilepticus

This review describes an adult rat model of status epilepticus (SE) induced by diisopropyl fluorophosphate (DFP), and the beneficial outcomes of transient inhibition of the prostaglandin-E

Topics: Animals; Cholinesterase Inhibitors; Disease Models, Animal; Indoles; Isoflurophate; Organophosphate Poisoning; Rats; Receptors, Prostaglandin E, EP2 Subtype; Status Epilepticus

Topics: Animals; Blood-Brain Barrier; Brain; Brain Injuries; Cytokines; Dinoprostone; Disease Models, Animal; Gliosis; Hippocampus; Indoles; Inflammation; Kainic Acid; Male; Mice; Mice, Inbred C57BL; Neurons; Neuroprotective Agents; Receptors, Prostaglandin E, EP2 Subtype; Seizures; Signal Transduction; Status Epilepticus

Survivors of exposure to an organophosphorus nerve agent may develop a number of complications including long-term cognitive deficits (Miyaki et al., 2005; Nishiwaki et al., 2001). We recently demonstrated that inhibition of the prostaglandin E2 receptor, EP2, attenuates neuroinflammation and neurodegeneration caused by status epilepticus (SE) induced by the soman analog, diisopropylfluorophosphate (DFP), which manifest within hours to days of the initial insult. Here, we tested the hypothesis that DFP exposure leads to a loss of cognitive function in rats that is blocked by early, transient EP2 inhibition. Adult male Sprague-Dawley rats were administered vehicle or the competitive EP2 antagonist, TG6-10-1, (ip) at various times relative to DFP-induced SE. DFP administration resulted in prolonged seizure activity as demonstrated by cortical electroencephalography (EEG). A single intraperitoneal injection of TG6-10-1 or vehicle 1 h prior to DFP did not alter the development of seizures, the latency to SE or the duration of SE. Rats administered six injections of TG6-10-1 starting 90 min after the onset of DFP-induced SE could discriminate between a novel and familiar object 6-12 weeks after SE, unlike vehicle treated rats which showed no preference for the novel object. By contrast, behavioral changes in the light-dark box and open field assays were not affected by TG6-10-1. Delayed mortality after DFP was also unaffected by TG6-10-1. Thus, selective inhibition of the EP2 receptor may prevent SE-induced memory impairment in rats caused by exposure to a high dose of DFP.

Topics: Animals; Anxiety; Brain; Discrimination, Psychological; Disease Models, Animal; Electroencephalography; Exploratory Behavior; Indoles; Isoflurophate; Male; Memory Disorders; Nootropic Agents; Random Allocation; Rats, Sprague-Dawley; Receptors, Prostaglandin E, EP2 Subtype; Recognition, Psychology; Status Epilepticus

As a prominent inflammatory effector of cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2) mediates brain inflammation and injury in many chronic central nervous system (CNS) conditions including seizures and epilepsy, largely through its receptor subtype EP2. However, EP2 receptor activation might also be neuroprotective in models of excitotoxicity and ischemia. These seemingly incongruent observations expose the delicacy of immune and inflammatory signaling in the brain; thus the therapeutic window for quelling neuroinflammation might vary with injury type and target molecule. Here, we identify a therapeutic window for EP2 antagonism to reduce delayed mortality and functional morbidity after status epilepticus (SE) in mice. Importantly, treatment must be delayed relative to SE onset to be effective, a finding that could be explained by the time-course of COX-2 induction after SE and compound pharmacokinetics. A large number of inflammatory mediators were upregulated in hippocampus after SE with COX-2 and IL-1β temporally leading many others. Thus, EP2 antagonism represents a novel anti-inflammatory strategy to treat SE with a tightly-regulated therapeutic window.

Topics: Animals; Anti-Inflammatory Agents; Cyclooxygenase 2; Disease Models, Animal; Encephalitis; Hippocampus; Indoles; Kaplan-Meier Estimate; Mice; Mice, Inbred C57BL; Pilocarpine; Receptors, Prostaglandin E, EP2 Subtype; Signal Transduction; Status Epilepticus

Exposure to high levels of organophosphorus compounds (OP) can induce status epilepticus (SE) in humans and rodents via acute cholinergic toxicity, leading to neurodegeneration and brain inflammation. Currently there is no treatment to combat the neuropathologies associated with OP exposure. We recently demonstrated that inhibition of the EP2 receptor for PGE2 reduces neuronal injury in mice following pilocarpine-induced SE. Here, we investigated the therapeutic effects of an EP2 inhibitor (TG6-10-1) in a rat model of SE using diisopropyl fluorophosphate (DFP). We tested the hypothesis that EP2 receptor inhibition initiated well after the onset of DFP-induced SE reduces the associated neuropathologies. Adult male Sprague-Dawley rats were injected with pyridostigmine bromide (0.1 mg/kg, sc) and atropine methylbromide (20 mg/kg, sc) followed by DFP (9.5 mg/kg, ip) to induce SE. DFP administration resulted in prolonged upregulation of COX-2. The rats were administered TG6-10-1 or vehicle (ip) at various time points relative to DFP exposure. Treatment with TG6-10-1 or vehicle did not alter the observed behavioral seizures, however six doses of TG6-10-1 starting 80-150 min after the onset of DFP-induced SE significantly reduced neurodegeneration in the hippocampus, blunted the inflammatory cytokine burst, reduced microglial activation and decreased weight loss in the days after status epilepticus. By contrast, astrogliosis was unaffected by EP2 inhibition 4 d after DFP. Transient treatments with the EP2 antagonist 1 h before DFP, or beginning 4 h after DFP, were ineffective. Delayed mortality, which was low (10%) after DFP, was unaffected by TG6-10-1. Thus, selective inhibition of the EP2 receptor within a time window that coincides with the induction of cyclooxygenase-2 by DFP is neuroprotective and accelerates functional recovery of rats.

Topics: Acetylcholinesterase; Animals; Behavior, Animal; Body Weight; Chemokines; Cholinesterase Inhibitors; Cyclooxygenase 2; Disease Models, Animal; Gliosis; Hippocampus; Indoles; Isoflurophate; Male; Neurons; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Receptors, Prostaglandin E, EP2 Subtype; Recovery of Function; Status Epilepticus; Time Factors