Targeting CNTF to increase adult forebrain neurogenesis

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Project Summary. CNTF mediates the increased SVZ neurogenesis that occurs in the mouse brain after ischemic stroke. We will follow up on our finding that JNK in astrocytes represses CNTF expression and neurogenesis in naïve mice, to test whether systemic treatment with JNK inhibitor can increase neurogenesis after stroke. We will also block the highly related pro-inflammatory ligand IL-6, which we found reduces stroke- induced neurogenesis, with a gp130 inhibitor. Secondly, we have discovered that blood levels of vitronectin (VTN), produced by the liver, only increase in females after stroke, and leaks into the SVZ to induce IL-6 and repress the neurogenic response. We will identify the mechanisms that regulate VTN, focusing on vagal nerve stimulated muscarinic receptors and FAK. Thirdly, we discovered in males that castration caused an unexpected and very robust effect by increasing basal levels of pro-neurogenic CNTF and decreasing detrimental IL-6, and that this was retained after MCAO. We will define the differential signaling pathways underlying this male-specific mechanism and test whether pharmacological blocking of testosterone would increase neurogenesis in males. Aim 1 will determine whether a gp130 inhibitor promotes neurogenesis when given at 6 h or 2 months after a stroke in adult and aged mice, and whether it acts by blocking IL-6. We will also determine whether JNK inhibition would increase neurogenesis after stroke by increasing CNTF, and/or whether JNK inhibitor would further enhance the neurogenic effects of SC144 after MCAO. Aim 2 will define potentially female-specific mechanisms that regulate liver VTN, including FAK and muscarinic acetylcholine receptors, testing pharmacological FAK inhibition and the role of the nervous system innervation of the liver after MCAO. Aim 3 will define the signaling pathways that mediate testosterone’s effects on CNTF, LIF and IL- 6 expression in the SVZ after MCAO, and using intracerebral injection of testosterone after castration, with or without FAK, JNK, ERK or p38 inhibitors, and whether a testosterone blocker can promote neurogenesis after MCAO. These studies will build on our previous work to define novel fundamental intracellular signaling mechanisms that repress and enhance the key cytokines CNTF and IL-6 involved in SVZ neurogenesis following stroke.