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Astrocytes and pericytes attenuate severely injured patient plasma mediated expression of tight junction proteins in endothelial cells.

ABSTRACT: Blood Brain Barrier (BBB) breakdown is a secondary form of brain injury which has yet to be fully elucidated mechanistically. Existing research suggests that breakdown of tight junction proteins between endothelial cells is a primary driver of increased BBB permeability following injury, and intercellular signaling between primary cells of the neurovascular unit: endothelial cells, astrocytes, and pericytes; contribute to tight junction restoration. To expound upon this body of research, we analyzed the effects of severely injured patient plasma on each of the cell types in monoculture and together in a triculture model for the transcriptional and translational expression of the tight junction proteins Claudins 3 and 5, (CLDN3, CLDN5) and Zona Occludens 1 (ZO-1). Conditioned media transfer studies were performed to illuminate the cell type responsible for differential tight junction expression. Our data show that incubation with 5% human ex vivo severely injured patient plasma is sufficient to produce a differential response in endothelial cell tight junction mRNA and protein expression. Endothelial cells in monoculture produced a significant increase of CLDN3 and CLDN5 mRNA expression, (3.98 and 3.51 fold increase vs. control respectively, p<0.01) and CLDN5 protein expression, (2.58 fold change vs. control, p<0.01), whereas in triculture, this increase was attenuated. Our triculture model and conditioned media experiments suggest that conditioned media from astrocytes and pericytes and a triculture of astrocytes, pericytes and endothelial cells are sufficient in attenuating the transcriptional increases of tight junction proteins CLDN3 and CLDN5 observed in endothelial monocultures following incubation with severely injured trauma plasma. This data suggests that inhibitory molecular signals from astrocytes and pericytes contributes to prolonged BBB breakdown following injury via tight junction transcriptional and translational downregulation of CLDN5.

SUBMITTER: Stafford P

PROVIDER: S-EPMC9255734 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:While the accumulation and aggregation of amyloid-β and tau are central events in the pathogenesis of Alzheimer's disease, there is increasing evidence that cerebrovascular pathology is also abundant in Alzheimer's disease brains. In brain capillaries, endothelial cells are connected closely with one another through transmembrane tight junction proteins forming the blood-brain barrier. Because the blood-brain barrier tightly regulates the exchange of molecules between brain and blood and maintains brain homeostasis, its impairment is increasingly recognized as a critical factor contributing to Alzheimer's disease pathogenesis. However, the pathological relationship between blood-brain barrier properties and Alzheimer's disease progression in the human brain is not fully understood. In this study, we show that the loss of cortical tight junction proteins is a common event in Alzheimer's disease, and is correlated with synaptic degeneration. By quantifying the amounts of major tight junction proteins, claudin-5 and occludin, in 12 brain regions dissected from post-mortem brains of normal ageing (n = 10), pathological ageing (n = 14) and Alzheimer's disease patients (n = 19), we found that they were selectively decreased in cortical areas in Alzheimer's disease. Cortical tight junction proteins were decreased in association with the Braak neurofibrillary tangle stage. There was also a negative correlation between the amount of tight junction proteins and the amounts of insoluble Alzheimer's disease-related proteins, in particular amyloid-β40, in cortical areas. In addition, the amount of tight junction proteins in these areas correlated positively with those of synaptic markers. Thus, loss of cortical tight junction proteins in Alzheimer's disease is associated with insoluble amyloid-β40 and loss of synaptic markers. Importantly, the positive correlation between claudin-5 and synaptic markers, in particular synaptophysin, was present independent of insoluble amyloid-β40, amyloid-β42 and tau values, suggesting that loss of cortical tight junction proteins and synaptic degeneration is present, at least in part, independent of insoluble Alzheimer's disease-related proteins. Collectively, these results indicate that loss of tight junction proteins occurs predominantly in the neocortex during Alzheimer's disease progression. Further, our findings provide a neuropathological clue as to how endothelial tight junction pathology may contribute to Alzheimer's disease pathogenesis in both synergistic and additive manners to typical amyloid-β and tau pathologies.

Project description:Brain microvascular endothelial cells form a highly selective blood brain barrier regulated by the endothelial tight junctions. Cerebral ischemia selectively targets tight junction protein complexes, which leads to significant damage to cerebral microvasculature. Short noncoding molecules called microRNAs are implicated in the regulation of various pathological states, including endothelial barrier dysfunction. In the present study, we investigated the influence of microRNA-155 (miR-155) on the barrier characteristics of human primary brain microvascular endothelial cells (HBMECs). Oxygen-glucose deprivation was used as an in vitro model of ischemic stroke. HBMECs were subjected to 3 hours of oxygen-glucose deprivation, followed by transfections with miR-155 inhibitor, mimic, or appropriate control oligonucleotides. Intact normoxia control HBMECs and 4 oxygen-glucose deprivation-treated groups of cells transfected with appropriate nucleotide were subjected to endothelial monolayer electrical resistance and permeability assays, cell viability assay, assessment of NO and human cytokine/chemokine release, immunofluorescence microscopy, Western blot, and polymerase chain reaction analyses. Assessment of endothelial resistance and permeability demonstrated that miR-155 inhibition improved HBMECs monolayer integrity. In addition, miR-155 inhibition significantly increased the levels of major tight junction proteins claudin-1 and zonula occludens protein-1, while its overexpression reduced these levels. Immunoprecipitation and colocalization analyses detected that miR-155 inhibition supported the association between zonula occludens protein-1 and claudin-1 and their stabilization at the HBMEC membrane. Luciferase reporter assay verified that claudin-1 is directly targeted by miR-155. Based on these results, we conclude that miR-155 inhibition-induced strengthening of endothelial tight junctions after oxygen-glucose deprivation is mediated via its direct target protein claudin-1.

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Astrocytes and pericytes attenuate severely injured patient plasma mediated expression of tight junction proteins in endothelial cells.

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