シンポジウム

シンポジウム Precise imaging and manipulation of gliopathy―are glial cells really required for brain function?―

1S6-1 Neurodegeneration promotes angiogenesis in the adult CNS Muramatsu Rieko^1,2 ¹Dept. Mol. Neurosci. Grad. Sch. Med. Osaka Univ.，²JST Presto Angiogenesis is a prominent feature of central nervous system（CNS）pathology and is crucial for regulating disease progression. Although neuronal damage is a primary process of CNS disease progression, the role of neuronal damage in pathological angiogenesis remains poorly understood. Here we show that lactate dehydrogenase A（LDHA）release from degenerating axons drives vascular endothelial cell proliferation in the spinal cord of mice with experimental autoimmune encephalomyelitis（EAE）, an animal model of multiple sclerosis. Silencing neuronal LDHA expression suppressed angiogenesis around EAE lesions and in response to controlled cortical impact（CCI）brain injury. LDHA-mediated angiogenesis was dependent on surface vimentin expression and p44/42 mitogen-activated protein kinase（MAPK）activation in vascular endothelial cells. Silencing of vimentin expression in vascular endothelial cells prevented angiogenesis around EAE. These results elucidate a novel aspect of pathological neurovascular interactions and provide a potential target for treating CNS diseases that involve angiogenesis.		1S6-2 Cortical astrocytes rewire somatosensory circuits for neuropathic pain Sun Kwang Kim¹，Koizumi Schuichi²，Nabekura Junichi³ ¹Department of Physiology, College of Korean Medicine, Kyung Hee University，²Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi，³Division of Homeostatic Development, National Institute for Physiological Sciences Neuropathic pain following peripheral nerve injury is characterized by mechanical allodynia, a painful response to innocuous tactile stimulation. Although this chronic pain is known to be induced by glial activation and altered nociceptive transmission within the spinal cord, an effective treatment is still insufficient, indicating that novel therapeutic targets are critically needed. One such target may be the synaptic rewiring in the primary somatosensory（S1）cortex that is correlated with the severity of neuropathic mechanical allodynia. However, its causal relationship to mechanical allodynia and its cellular/molecular mechanisms remain unknown. In addition, glial contribution to the S1 synaptic plasticity is unclear. Here we show that partial sciatic nerve ligation（PSL）injury induces an early re-emergence of immature metabotropic glutamate receptor 5（mGluR5）signaling in S1 astrocytes, which elicits spontaneous somatic Ca2+ transients, thrombospondin-1 release and synapse formation. Such activation of S1 astrocytes was apparent only during a critical period（~1w post-injury）, correlating with the temporal changes in S1 extracellular glutamate levels and dendritic spine turnover following PSL injury. Blocking this astrocytic signaling pathway suppressed mechanical allodynia, while activating this pathway in the absence of injury induced long-lasting（＞1 month）allodynia. Thus, these synaptogenic astrocytes are a key trigger for S1 synaptic circuit rewiring that causes neuropathic pain mechanical hypersensitivity.

1S6-3 Calcium signals in astrocyte processes：its visualization and manipulation Shigetomi Eiji¹，Koizumi Schuichi^1,2 ¹Dept. Neuropharmacol., Interdiscipl. Grad. Sch. of Med., Univ. Yamanashi，²CREST, JST Astrocytes are not electrically excitable, but are excitable in term of calcium signals. Such calcium excitability is observed throughout of the brain in both animals and humans. Calcium excitability is spatiotemporally dynamic phenomena. Thus, calcium signals in astrocytes are thought to be relevant to brain functions and brain disorders. It has been proposed that astrocytes regulate synapses using calcium via releasing gliotransmitters. However, the role of calcium excitability is still enigmatic since the mechanisms underlying the calcium signals are largely unknown due to the lack of the methods to analyze those calcium signals in astrocytes especially at peripheral processes where astrocytes intimately contact with synapses and may regulate synaptic transmission. To achieve better understanding of calcium signals in astrocyte processes, we used two novel methods. First, to visualize astrocytes processes, we expressed genetically encoded calcium indicator（GECI）, Lck-GCaMP3 or GCaMP3¹, into astrocytes. To introduce GECI into astrocytes, we injected adeno-associated viruses with GFAP minimal promoter into the brain or used transgenic mice generated by Cre-loxP mediated recombination. GECI successfully reports numerous calcium signals at processes in acute brain slices. Second, to manipulate calcium signals in astrocyte processes, we generated transgenic mice to overexpress P2Y1 receptors（P2Y1）, which is known to elevate calcium signals in astrocyte processes, using tetracycline inducible system. Astrocytes overexpressing P2Y1 showed ~3 fold increase in calcium signals in astrocytes from the dentate gyrus of acute brain slices. Astrocyte with P2Y1 overexpression displayed calcium signals highly correlated between neighboring astrocytes. Two approaches described above will give us an unique opportunity to analyze the role of astrocyte processes in neuronal circuits in（patho）physiology. Reference 1 Shigetomi et al. （2013）Imaging calcium microdomains within entire astrocyte territories and endfeet with GCaMPs expressed using adeno-associated viruses. J. Gen. Physiol. 141（5）：633-647.		1S6-4 The role of microglia in the adult CNS of systemic inflammation. WAKE Hiroaki National Institute for Physiological Sciences Microglia are haematopoietic-cell derived glial cells in the central nervous system（CNS）that function as the only resident immune cells of the CNS. Traditionally, effects of microglia as immune cell in CNS have been thought to be mainly in pathological conditions where they exert neuro-protective or neuro-toxic effects to modify disease progression. However, recent studies have reported that microglial cells play a role in brain homeostasis in the normal physiological state, promoting programmed cell death in both neural development and in adult neurogenesis, and monitoring and phagocytosing synapses. On the other hands, substantial evidence has demonstrated that immune condition can have effects on to the neuronal circuits. However little has been known whether those immune condition could affect on to the function of neuronal circuits. Here we use systemic inflammation model to study the interaction of systemic immune cells and microglia. And we also show the functional regulation of synapses by microglia contacts and the alteration of the synapse response in systemic inflammation model and their affect on the behavior responses. Those data indicate that microglia changes induced by the interaction with systemic immune cells can modulate function of neuronal circuits.