Accumulating evidence in humans and in animal models indicates that inflammation of the brain that develops after status epilepticus (SE) may play a determinant role in long-term detrimental consequences, independent of an infection or auto-immune cause. The pathophysiological interactions among the various inflammatory molecules, and the sequence of events leading to their induction, have not yet been dissected. Previous work pointed to a role for cyclooxygenase-2 (COX-2) pathways in SE-induced inflammation, and showed that the EP2 receptor mediates much of the COX-2 effect. Our recent work suggests that PGE2 released from neurons after SE activates EP2 receptors on nearby neurons and myeloid cells, and that EP2 activation on neurons and myeloid cells might cause opposing effects. We hypothesize that EP2 activation on neurons after SE is neuroprotective, whereas EP2 activation on microglia or invading monocytes results in cytokine synthesis and subsequent development of epilepsy. Here we use a novel HaloTag technology to target neurons and myeloid cells separately with EP2 antagonists and agonists to test this hypothesis.
Our specific aims are: 1. To test the hypothesis that pharmacologic block of EP2 receptors on neurons and myeloid cells has opposing effects after SE. 2. To test the hypothesis that blocking EP2 receptors on myeloid cells interferes with the process of epileptogenesis. 3. To test the hypothesis that EP2-mediated neuroprotection involves neuronal EP2 receptors, utilizes a cAMP rather than ?-arrestin pathway, and requires CX3CL1 (fractalkine). To address these aims we employ in vitro culture models and in vivo SE models with novel EP2 antagonists and agonists targeted by HaloTag to neurons or microglia. Immunohistochemical, western blot, qRT-PCR, cell viability, EEG and behavioral assays are performed.
Inflammation of the brain accompanies many chronic neurologic disorders including epilepsy. A major inflammatory pathway, that mediated by activation of the EP2 receptor for prostaglandin E2, appears to exert a dual role during the development of epilepsy, both promoting and opposing neuropathology. We will identify the cell types underlying these opposing roles with the aim of developing more targeted anti-inflammatory therapies.