Symposium

Symposium 31 Roles of DAMPs in the regulation of neuropathology シンポジウム31 神経疾患の増幅と制御におけるDAMPsの役割

SY31-1 Prothymosin α has a robustness role to protect brain from ischemia-induced damages 脳虚血ストレスから脳を守るDAMPs/Alarminsプロサイモシン α Ueda Hiroshi（植田弘師），岩元隆征 Pharmacol and Ther Innov., Nagasaki Univ Grad Sch Bio Med Sci Nuclear acidic protein, prothymosin α (ProT α ) is released from neurons and astrocytes, but not from microglia upon the ischemic/starving stress. The manner of release is unique. ProT α is first released from the nucleus by ATP loss, followed by forming of a multiple protein complex with several Ca2+-binding protein. The complex is then extracellularly released by a series of machineries of membrane tethering through a SNARE protein interaction and flopping out. Released ProT α has two neuroprotective machineries. ProT α stimulates TLR4 and drives a cascade of TRIF-IRF3-mediated type 1 interferon gene expression, but not a cascade of MyD88-NFκB-mediated proinflammatory gene expression. In the retinal ischemia model, the preconditioning treatments with ProT α was found to stimulate microglial TLR4 and show beneficial actions in vivo. The post-ischemia treatment with ProT α has more potent neuroprotective actions. One of novel target which we have recently identified through affinity cross-linking study is F0/F1 ATPase. In HUVEC cells and microglial cells, ProT α produces ATP in a neutralizing antibody-reversible manner. This finding was also confirmed in vivo by the retinal ischemia model. The robustness role of ProT α was also observed in the study of heterozygous and brain region-specific conditional KO mice. Memory-learning deficit, anxiety and loss of neurogenesis were found in hetero KO mice.		SY31-2 Ultra-early phase pathology of dementias mediated by HMGB1 HMGB1を介した認知症の超早期病態と治療開発 Okazawa Hitoshi（岡澤均） Neuropatholpogy, Medical Research Institute, Tokyo Medical and Dental University Repeated failures of clinical trials in Alzheimer’s disease (AD) indicate necessity to elucidate early phase pathologies of dementias for development of radical therapeutics. We previously performed comprehensive phosphoproteome analyses of 4 genotypes of AD mouse models and human postmortem AD brains, and discovered that phosphorylation of some proteins are changed before formation of amyloid-beta aggregates. One of such proteins was MARCKS, which anchors actin-network to PIP2 in plasma membrane and regulates dendritic spines. In contrast to the previous report that phosphorylation within the PIP2 interaction domain increases elimination of dendritic spines, our proteome analysis detected a new phosphorylation site (pSer46) outside of the PIP2 interaction domain that was changed before formation of amyloid-beta aggregates. The MARCKS phosphorylation at Ser46 decreased affinity of MARCKS to actin and suppressed formation of dendritic spines. We next searched for extracellular factor to trigger MARCKS phosphorylation at Ser46, and finally discovered HMGB1 is a strongest cue. Moreover, anti-HMGB1 antibody suppressed MARCKS phosphorylation at Ser46, increased formation of dendritic spines, and ameliorated cognitive impairment of AD model mice when it was injected pericutaneously before the onset of symptoms. We also identified TLR4 is a responsible receptor for HMGB1 that mediates cell signaling to MARCKS phosphorylation at Ser46. Collectively, HMGB1-TLR4-MARCKS axis is a key pathway in pre-aggregation pathology, by which we propose “ultra-early phase pathology” occurring before formation of amyloid-beta aggregates. We have accumulated data suggesting the similar pathology in other types of dementias, and I would like to discuss on such new data if possible.

SY31-3 DAMPs and pain DAMPsと痛み Kawabata Atsufumi（川畑篤史） Lab. Pharmacol. Pathophysiol., Fac. Pharm., Kindai Univ., Higashi-Osaka, Japan High mobility group box 1 (HMGB1), a nuclear protein, once released from necrotic cells or secreted by certain types of cells including macrophages, plays a role as a protein of damage-associated molecular patterns (DAMPs). HMGB1 contains 3 cysteine residues, C²³, C⁴⁵ and C¹⁰⁶, and its active forms, all-thiol (at) HMGB1 and disulfide (ds) HMGB1, which has a C²3-C⁴⁵ disulfide bond, aggravate inflammatory responses. Peripheral atHMGB1 and dsHMGB1 promote pain signals via activation of the receptor for advanced glycation end-products (RAGE) and TLR4, respectively. TLR5 and/or NMDA receptors also contribute to the HMGB1-induced nociception. Our accumulating evidence suggest a critical role of macrophage-derived HMGB1 in chronic pain including chemotherapy-induced peripheral neuropathy (CIPN) and neuropathic pain caused by spinal nerve injury (SNI), and in visceral pain. Of interest is that paclitaxel, an anti-cancer agent, directly triggers release of HMGB1 from macrophages, which in turn participates in the development of CIPN. L5 SNI-induced neuropathic pain involves the Egr-1-dependent overexpression of Ca_v3.2 T-type Ca²⁺ channels in L4 dorsal root ganglion, which is a downstream event of macrophage-derived HMGB1 signaling. The macrophage-derived HMGB1/RAGE signals are also involved in the development of visceral pain accompanying pancreatitis and cystitis-related bladder pain. HMGB1 is now considered one of major pronociceptive messengers, and to play a central role in a neuroimmune crosstalk. We thus propose that targeting HMGB1 and its receptors may serve as a novel therapeutic strategy for prevention and treatment of various intractable pain.