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Synthetic excitatory synaptic organizer The human brain contains trillions of synapses within a vast network of neurons. Synapse remodeling is essential to ensure the efficient reception and integration of external stimuli and to store and retrieve information. Building and remodeling of synapses occurs throughout life under the control of synaptic organizer proteins. Errors in this process can lead to neuropsychiatric or neurological disorders. Suzuki et al. combined structural elements of natural synaptic organizers to develop an artificial version called CPTX, which has different binding properties (see the Perspective by Salinas). CPTX could act as a molecular bridge to reconnect neurons and restore excitatory synaptic function in animal models of cerebellar ataxia, familial Alzheimer's disease, and spinal cord injury. The findings illustrate how structure-guided approaches can help to repair neuronal circuits. Science , this issue p. eabb4853 ; see also p. 1052

Neuronal synapses undergo structural and functional changes throughout life, essential for nervous system physiology. However, these changes may also perturb the excitatory/inhibitory neurotransmission balance and trigger neuropsychiatric and neurological disorders. Molecular tools to restore this balance are highly desirable. Here, we report the design and characterization of CPTX, a synthetic synaptic organizer combining structural elements from cerebellin-1 and neuronal pentraxin-1 to interact with presynaptic neurexins and postsynaptic AMPA-type ionotropic glutamate receptors. CPTX induced the formation of excitatory synapses in vitro and in vivo and restored synaptic functions, motor coordination, spatial and contextual memories, and locomotion in mouse models for cerebellar ataxia, Alzheimer’s disease and spinal cord injury, respectively. Thus, CPTX represents a prototype for novel structure-guided biologics that can efficiently repair or remodel neuronal circuits.One Sentence SummaryStructural biology information was used to design CPTX, a synthetic protein that induces functional excitatory synapses and restores normal behaviors in mouse models of neurological diseases.

RATIONALE: CD69 is an immunomodulatory molecule induced during lymphocyte activation. Following stroke, T-lymphocytes upregulate CD69 but its function is unknown. OBJECTIVE: We investigated whether CD69 was involved in brain damage following an ischemic stroke. METHODS AND RESULTS: We used adult male mice on the C57BL/6 or BALB/c backgrounds, including wild-type mice and CD69-/- mice, and CD69+/+ and CD69-/- lymphocyte-deficient Rag2-/- mice, and generated chimeric mice. We induced ischemia by transient or permanent middle cerebral artery occlusion. We measured infarct volume, assessed neurological function, and studied CD69 expression, as well as platelet function, fibrin(ogen) deposition, and VWF (von Willebrand factor) expression in brain vessels and VWF content and activity in plasma, and performed the tail-vein bleeding test and the carotid artery ferric chloride-induced thrombosis model. We also performed primary glial cell cultures and sorted brain CD45-CD11b-CD31+ endothelial cells for mRNA expression studies. We blocked VWF by intravenous administration of anti-VWF antibodies. CD69-/- mice showed larger infarct volumes and worse neurological deficits than the wild-type mice after ischemia. This worsening effect was not attributable to lymphocytes or other hematopoietic cells. CD69 deficiency lowered the time to thrombosis in the carotid artery despite platelet function not being affected. Ischemia upregulated Cd69 mRNA expression in brain endothelial cells. CD69-deficiency increased fibrin(ogen) accumulation in the ischemic tissue, and plasma VWF content and activity, and VWF expression in brain vessels. Blocking VWF reduced infarct volume and reverted the detrimental effect of CD69-/- deficiency. CONCLUSIONS: CD69 deficiency promotes a prothrombotic phenotype characterized by increased VWF and worse brain damage after ischemic stroke. The results suggest that CD69 acts as a downregulator of endothelial activation., The study was funded by the Spanish Ministerio de Economía y Competitividad (MINECO; grant SAF2014-56279-R and SAF2017-87459-R to A.M. Planas), Acción Estratégica de Salud (grants AES 1366/13 and AESI 1346/16 to P. Lauzurica), and Fundació la Marató de TV3 (grants 474-082230 and 20153031 to P. Garcia-de-Frutos). F. Miró-Mur had a PERIS award by the Health Department of the Generalitat de Catalunya. A. Otxoa-de-Amezaga has an FPI fellowship (MINECO).

Acute stroke induces a local inflammatory reaction causing leukocyte infiltration. Circulating monocytes are recruited to the ischemic brain and become tissue macrophages morphologically indistinguishable from reactive microglia. However, monocytes are a heterogeneous population of cells with different functions. Herein, we investigated the infiltration and fate of the monocyte subsets in a mouse model of focal brain ischemia by permanent occlusion of the distal portion of the middle cerebral artery. We separated two main subtypes of CD11b monocytes according to their expression of the surface markers Ly6C and CD43. Using adoptive transfer of reporter monocytes and monocyte depletion, we identified the pro-inflammatory Ly6CCD43CCR2 subset as the predominant monocytes recruited to the ischemic tissue. Monocytes were seen in the leptomeninges from where they entered the cortex along the penetrating arterioles. Four days post-ischemia, they had invaded the infarcted core, where they were often located adjacent to blood vessels. At this time, Iba-1 and Iba-1 cells in the ischemic tissue incorporated BrdU, but BrdU incorporation was rare in the reporter monocytes. The monocyte phenotype progressively changed by down-regulating Ly6C, up-regulating F4/80, expressing low or intermediate levels of Iba-1, and developing macrophage morphology. Moreover, monocytes progressively acquired the expression of typical markers of alternatively activated macrophages, like arginase-1 and YM-1. Collectively, the results show that stroke mobilized immature pro-inflammatory Ly6CCD43 monocytes that acutely infiltrated the ischemic tissue reaching the core of the lesion. Monocytes differentiated to macrophages with features of alternative activation suggesting possible roles in tissue repair during the sub-acute phase of stroke., Financed by the Spanish Ministries of Economy MINECO (SAF2011-30492, SAF2014-56279) and Health (FIS PI12/01437), and the European Community FP7 (InMiND project n°278850). We acknowledge the Image and Cytometry platforms of IDIBAPS, and the Confocal Microscopy Unit of the Serveis Cientifico-Tècnics of the University of Barcelona for technical help. F.M.M. was supported by the ‘Red Invictus’ of the Instituto de Salud Carlos III (RD12/0014/0011).

Neutrophils are rapidly recruited in response to local tissue infection or inflammation. Stroke triggers a strong inflammatory reaction but the relevance of neutrophils in the ischemic brain is not fully understood, particularly in the absence of reperfusion. We investigated brain neutrophil recruitment in two murine models of permanent ischemia induced by either cauterization of the distal portion of the middle cerebral artery (c-MCAo) or intraluminal MCA occlusion (il-MCAo), and three fatal cases of human ischemic stroke. Flow cytometry analyses revealed progressive neutrophil recruitment after c-MCAo, lesser neutrophil recruitment following il-MCAo, and absence of neutrophils after sham operation. Confocal microscopy identified neutrophils in the leptomeninges from 6 h after the occlusion, in the cortical basal lamina and cortical Virchow–Robin spaces from 15 h, and also in the cortical brain parenchyma at 24 h. Neutrophils showed signs of activation including histone-3 citrullination, chromatin decondensation, and extracellular projection of DNA and histones suggestive of extracellular trap formation. Perivascular neutrophils were identified within the entire cortical infarction following c-MCAo. After il-MCAo, neutrophils prevailed in the margins but not the center of the cortical infarct, and were intraluminal and less abundant in the striatum. The lack of collaterals to the striatum and a collapsed pial anastomotic network due to brain edema in large hemispheric infarctions could impair neutrophil trafficking in this model. Neutrophil extravasation at the leptomeninges was also detected in the human tissue. We concluded that neutrophils extravasate from the leptomeningeal vessels and can eventually reach the brain in experimental animal models and humans with prolonged arterial occlusion. © 2014, Springer-Verlag Berlin Heidelberg, Supported by the Spanish Ministries of Economy (SAF2011-30492) and Health (FIS PI12/01437), and FP7 EU projects ERANET-NEURON (PRI-PIMNEU-2011-1342) and InMIND (grant agreement no 278,850)

El pdf del artículo es la versión post-print., Stroke induces inflammation that can aggravate brain damage. This work examines whether interleukin-10 (IL-10) deficiency exacerbates inflammation and worsens the outcome of permanent middle cerebral artery occlusion (pMCAO). Expression of IL-10 and IL-10 receptor (IL-10R) increased after ischemia. From day 4, reactive astrocytes showed strong IL-10R immunoreactivity. Interleukin-10 knockout (IL-10 KO) mice kept in conventional housing showed more mortality after pMCAO than the wild type (WT). This effect was associated with the presence of signs of colitis in the IL-10 KO mice, suggesting that ongoing systemic inflammation was a confounding factor. In a pathogen-free environment, IL-10 deficiency slightly increased infarct volume and neurologic deficits. Induction of proinflammatory molecules in the IL-10 KO brain was similar to that in the WT 6 hours after ischemia, but was higher at day 4, while differences decreased at day 7. Deficiency of IL-10 promoted the presence of more mature phagocytic cells in the ischemic tissue, and enhanced the expression of M2 markers and the T-cell inhibitory molecule CTLA-4. These findings agree with a role of IL-10 in attenuating local inflammatory reactions, but do not support an essential function of IL-10 in lesion resolution. Upregulation of alternative immunosuppressive molecules after brain ischemia can compensate, at least in part, the absence of IL-10. © 2013 ISCBFM., Work supported by the Spanish Ministry of Economy (SAF2011-30492), and the European Community (FP7, grant agreements: n°201024 ARISE and n°278850 InMiND), and the ERANET-NEURON project (PRI-PIMNEU-2011-1342). IPP and EBT had PhD fellowships from the Agència de Gestió d'Ajuts Universitaris i de Recerca (AGAUR) of the Generalitat de Catalunya and the FPU program of the Spanish Ministry of Economy, respectively.