Blood vessels in the central nervous system (CNS) form a specialized and critical structure, the blood-brain barrier (BBB). We present a resource to understand the molecular mechanisms that regulate BBB function in health and dysfunction during disease. Using endothelial cell enrichment and RNA sequencing, we analyzed the gene expression of endothelial cells in mice, comparing brain endothelial cells to peripheral endothelial cells. We also assessed the regulation of CNS Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

Gut microbiota modulates metabolic and immunoregulatory axes and contributes to the pathophysiology of diseases with inflammatory components, such as atherosclerosis, diabetes, and ischemic stroke. Inflammation is emerging as a critical player in the pathophysiology of intracranial aneurysm. Therefore, we hypothesized that the gut microbiota affects aneurysm formation by modulating inflammation. We induced intracranial aneurysms in mice by combining systemic hypertension and a single injection of elastase into the cerebrospinal fluid. Depletion of the gut microbiota was achieved via an oral antibiotic cocktail of vancomycin, metronidazole, ampicillin, and neomycin. Antibiotics were given three weeks before aneurysm induction and either continued until the end of the experiment or stopped one day before aneurysm induction. We also assessed the effects of the gut microbiota depletion on macrophage infiltration and mRNA levels of inflammatory cytokines. Gut microbiota depletion by antibiotics reduced the incidence when antibiotics were started three weeks before aneurysm induction and continued until the end of the experiment (83% vs. 6%, P < 0.001). Even when antibiotics were stopped one day before aneurysm induction, the gut microbiota depletion significantly reduced the incidence of aneurysms (86% vs. 28%, P < 0.05). Both macrophage infiltration and mRNA levels of inflammatory cytokines were reduced with gut microbiota depletion. These findings suggest that the gut microbiota contributes to the pathophysiology of aneurysms by modulating inflammation. Human studies are needed to determine the exact contribution of the gut microbiota to the pathophysiology of aneurysm formation and disease course in humans.

Background and Purpose Inflammation is emerging as a key component of the pathophysiology of intracranial aneurysms. Peroxisome proliferator-activated receptor-γ (PPARγ) is a nuclear hormone receptor of which activation modulates various aspects of inflammation. Methods Using a mouse model of intracranial aneurysm, we examined the potential roles of PPARγ in the development of rupture of intracranial aneurysm. Results A PPARγ agonist, pioglitazone (PGZ), significantly reduced the incidence of ruptured aneurysms and the rupture rate without affecting the total incidence aneurysm (unruptured aneurysms and ruptured aneurysms). PPARγ antagonist (GW9662) abolished the protective effect of PGZ. The protective effect of PGZ was absent in mice lacking macrophage PPARγ. PGZ treatment reduced mRNA levels of inflammatory cytokines (monocyte chemoattractant factor-1, interleukin-1, and interleukin-6) that are primarily produced by macrophages in the cerebral arteries. PGZ treatment reduced the infiltration of M1 macrophage into the cerebral arteries and the macrophage M1/M2 ratio. Depletion of macrophages significantly reduced the rupture rate. Conclusion Our data showed that the activation of macrophage PPARγ protects against the development of aneurysmal rupture. PPARγ in inflammatory cells may be a potential therapeutic target for the prevention of aneurysmal rupture.

Potential roles for neutrophils in the pathophysiology of intracranial aneurysm have long been suggested by clinical observations. The presence of neutrophil enzymes in the aneurysm wall has been associated with significant increases in rupture risk. However, the mechanisms by which neutrophils may promote aneurysm rupture are not well understood. Neutrophil extracellular traps (NETs) were implicated in many diseases that involve inflammation and tissue remodeling, including atherosclerosis, vasculitis, and abdominal aortic aneurysm. Therefore, we hypothesized that NETs may promote the rupture of intracranial aneurysm, and that removal of NETs can reduce the rate of rupture. We employed both pharmacological and genetic approaches for the disruption of NETs and used a mouse model of intracranial aneurysm to investigate the roles of NETs in the development of intracranial aneurysm rupture. Here, we showed that NETs are detected in human intracranial aneurysms. Both global and granulocyte-specific knockout of peptidyl arginine deiminase 4 (an enzyme essential for NET formation) reduced the rate of aneurysm rupture. Pharmacological blockade of the NET formation by Cl-amidine also reduced the rate of aneurysm rupture. In addition, the resolution of already formed NETs by deoxyribonuclease was effective against aneurysm rupture. Inhibition of NETs formation with Cl-amidine decreased mRNA expression of proinflammatory cytokines (intercellular adhesion molecule 1 (ICAM-1), interleukin 1 beta (IL-1β), monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor alpha (TNF-α)) in cerebral arteries. These data suggest that NETs promote the rupture of intracranial aneurysm. Pharmacological removal of NETs, by inhibition of peptidyl arginine deiminase 4 or resolution of already-formed NETs, may represent a potential therapeutic strategy for preventing aneurysmal rupture.