Juliana M Rosa1,2, Víctor Farré-Alins3,2, María Cristina Ortega4, Marta Navarrete5, Ana Belen Lopez-Rodriguez3,2, Alejandra Palomino-Antolín3,2, Elena Fernández-López1, Virginia Vila-Del Sol6, Céline Decouty3,2, Paloma Narros-Fernández3,2, Diego Clemente4, Javier Egea3,2. 1. Experimental Neurophysiology and Neuronal Circuits Group, Hospital Nacional de Parapléjicos, Servicio de Salud de Castilla-La Mancha, SESCAM, Toledo, Spain. 2. Research Unit, Hospital Santa Cristina, Instituto de Investigación Sanitaria Princesa (IIS-IP), Hospital Universitario de la Princesa, Madrid, Spain. 3. Instituto Teófilo Hernando, Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain. 4. Neuroinmune-Repair Group, Hospital Nacional de Parapléjicos, Servicio de Salud de Castilla-La Mancha, SESCAM, Toledo, Spain. 5. Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain. 6. Flow Cytometry Service, Hospital Nacional de Parapléjicos, Servicio de Salud de Castilla-La Mancha, SESCAM, Toledo, Spain.
Abstract
BACKGROUND AND PURPOSE: Activation of astrocytes contributes to synaptic remodelling, tissue repair and neuronal survival following traumatic brain injury (TBI). The mechanisms by which these cells interact to resident/infiltrated inflammatory cells to rewire neuronal networks and repair brain functions remain poorly understood. Here, we explored how TLR4-induced astrocyte activation modified synapses and cerebrovascular integrity following TBI. EXPERIMENTAL APPROACH: To determine how functional astrocyte alterations induced by activation of TLR4 pathway in inflammatory cells regulate synapses and neurovascular integrity after TBI, we used pharmacology, genetic approaches, live calcium imaging, immunofluorescence, flow cytometry, blood-brain barrier (BBB) integrity assessment and molecular and behavioural methods. KEY RESULTS: Shortly after a TBI, there is a recruitment of excitable and reactive astrocytes mediated by TLR4 pathway activation with detrimental effects on post-synaptic density-95 (PSD-95)/vesicular glutamate transporter 1 (VGLUT1) synaptic puncta, BBB integrity and neurological outcome. Pharmacological blockage of the TLR4 pathway with resatorvid (TAK-242) partially reversed many of the observed effects. Synapses and BBB recovery after resatorvid administration were not observed in IP3 R2-/- mice, indicating that effects of TLR4 inhibition depend on the subsequent astrocyte activation. In addition, TBI increased the astrocytic-protein thrombospondin-1 necessary to induce a synaptic recovery in a sub-acute phase. CONCLUSIONS AND IMPLICATIONS: Our data demonstrate that TLR4-mediated signalling, most probably through microglia and/or infiltrated monocyte-astrocyte communication, plays a crucial role in the TBI pathophysiology and that its inhibition prevents synaptic loss and BBB damage accelerating tissue recovery/repair, which might represent a therapeutic potential in CNS injuries and disorders.
BACKGROUND AND PURPOSE: Activation of astrocytes contributes to synaptic remodelling, tissue repair and neuronal survival following traumatic brain injury (TBI). The mechanisms by which these cells interact to resident/infiltrated inflammatory cells to rewire neuronal networks and repair brain functions remain poorly understood. Here, we explored how TLR4-induced astrocyte activation modified synapses and cerebrovascular integrity following TBI. EXPERIMENTAL APPROACH: To determine how functional astrocyte alterations induced by activation of TLR4 pathway in inflammatory cells regulate synapses and neurovascular integrity after TBI, we used pharmacology, genetic approaches, live calcium imaging, immunofluorescence, flow cytometry, blood-brain barrier (BBB) integrity assessment and molecular and behavioural methods. KEY RESULTS: Shortly after a TBI, there is a recruitment of excitable and reactive astrocytes mediated by TLR4 pathway activation with detrimental effects on post-synaptic density-95 (PSD-95)/vesicular glutamate transporter 1 (VGLUT1) synaptic puncta, BBB integrity and neurological outcome. Pharmacological blockage of the TLR4 pathway with resatorvid (TAK-242) partially reversed many of the observed effects. Synapses and BBB recovery after resatorvid administration were not observed in IP3 R2-/- mice, indicating that effects of TLR4 inhibition depend on the subsequent astrocyte activation. In addition, TBI increased the astrocytic-protein thrombospondin-1 necessary to induce a synaptic recovery in a sub-acute phase. CONCLUSIONS AND IMPLICATIONS: Our data demonstrate that TLR4-mediated signalling, most probably through microglia and/or infiltrated monocyte-astrocyte communication, plays a crucial role in the TBI pathophysiology and that its inhibition prevents synaptic loss and BBB damage accelerating tissue recovery/repair, which might represent a therapeutic potential in CNS injuries and disorders.
Authors: Preston Stafford; Sanchayita Mitra; Margot Debot; Patrick Lutz; Arthur Stem; Jamie Hadley; Patrick Hom; Terry R Schaid; Mitchell J Cohen Journal: PLoS One Date: 2022-07-05 Impact factor: 3.752