title: Increased blood-brain barrier permeability and alterations in perivascular astrocytes and pericytes induced by intracisternal glutaric acid.
abstract: BACKGROUND
  Glutaric acid (GA) is a dicarboxylic acid that accumulates in millimolar concentrations in glutaric acidemia I (GA-I), an inherited neurometabolic childhood disease characterized by extensive neurodegeneration. Vascular dysfunction is a common and early pathological feature in GA-I, although the underlying mechanisms remain unknown. In the present study, we have used a previously-validated rat model of GA-I to determine the effect of GA on the blood- brain barrier (BBB) and the neurovascular unit.
  
  
  METHODS
  Newborn rat pups received a single injection of GA (1 μmol/g) or vehicle into the cisterna magna. BBB permeability was analyzed at 14 and 30 days post injection (DPI) by assessing Evans blue (EB) and immunoglobulin G (IgG) extravasation. Blood vessels and microglia were labeled with tomato lectin. Characterization of EB positive cells was made by double labeling with antibodies to astrocyte and neuronal markers. Immunohistochemistry against aquaporin 4 (AQP4), β receptor of the platelet derived growth factor (PDGFRβ) and laminin was used to recognize astrocyte endfeet, pericytes and basal lamina. Zonula occludens 1 (ZO-1) and occludin striatal expression was assessed by Western blotting.
  
  
  RESULTS
  Perinatal intracisternal GA administration caused an increased extravasation of free EB, but not of IgG, into the striatal parenchyma at 14 and 30 DPI. EB extravasated through the BBB was internalized exclusively into neurons. GA-injected animals did not show significant changes in the area of small blood vessels in the striatum, but at 30 DPI there was a significant decrease in AQP4, PDGFRβ and laminin positive areas associated with small blood vessels. Occludin and ZO-1 expression in the striatal tissue was unchanged in all conditions analyzed.
  
  
  CONCLUSIONS
  The present study shows a previously-unknown effect of a perinatal administration of a single intracisternal GA injection on BBB permeability and on key components of the neurovascular unit. The results suggest BBB leakage is a pathogenic mechanism and a potential therapeutic target for patients with GA-I.
authors: Neurobiología Celular y Molecular, IIBCE, 3318 Italia Av., Montevideo, 11600, Uruguay.
authors: Eugenia
authors: E
authors: Isasi
authors: Institut Pasteur de Montevideo, Iguá s/n CP, Montevideo, 11400, Uruguay.
authors: Luis
authors: L
authors: Barbeito
authors: Neurobiología Celular y Molecular, IIBCE, 3318 Italia Av., Montevideo, 11600, Uruguay.
authors: Silvia
authors: S
authors: Olivera-Bravo
keywords: Astrocyte; Blood–brain barrier; Glutaric acid; Glutaric acidemia type I; Laminin; Neurons; Pericyte