In vitro Investigation of the Role of NCBE in Inflammation Induced Cerebrospinal Fluid Hypersecretion by the Choroid Plexus

Abstract

Post‐hemorrhagic hydrocephalus (PHH) can be the result of inflammation or deposition of FeCl3 in the choroid plexus (CP) after intraventricular hemorrhage (IVH). The hemorrhage leads to increased CSF secretion from the CP also known as the blood‐CSF‐barrier (BCSFB). The precise molecular mechanism is unknown, but the Na+ dependent Cl‐/HCO3‐ exchanger, NCBE, located in the basolateral membrane of the CP epithelia has been suggested as a possible facilitator of CSF hypersecretion.The aim of this study is to investigate the role of the NCBE located in the CP epithelia after inflammation or deposition of FeCl3in relation to the development of PHH. An in vitro model of the BCSFB was established and validated. The model was generated from mouse pup CP epithelial cells. The cells were treated with either TNF‐□, IL‐1□, LPS or FeCl3. NCBE protein expression of the CP epithelial cells was determined by immunoblotting.The CP epithelial cell cultures showed typical cobblestone‐like morphology, polarization and formed an intermediate tight barrier demonstrated by TEER values of ~ 100 Ω*cm2and expression of tight junctions. Compared with controls TNF‐□ decreased NCBE expression by 23.8 % after 24 h (p=0.0048, n=6/group). IL‐1□ had same effect with 28.3 % decrease after 24 h (p=0.0018, n= 6/group) persisting with a decrease of 88.5 % after 3 and 82.4 % after 7 days (p=0.0004 and p=0.0035, n=6/group). LPS had no effect on NCBE expression(n=5/group). FeCl3 increased NCBE expression by 52 % after 24 h (p=0.024, n=7/group) followed by a decrease of 57.8 % after 7 days (p=0.043, n=3/group).We hypothesized that IVH‐induced CP inflammation or FeCl3deposition leads to hydrocephalus by increasing the expression of the basolateral NCBE in the CP cells which leads to an increased rate of CSF secretion. However, the preliminary results suggest a decrease in expression of NCBE after inflammation whereas only an increase in NCBE expression was seen after FeCl3 deposition.In conclusion, NCBE expression of the CP epithelium in cultures decreases under pro‐inflammatory conditions and increases after FeCl3 deposition. Further studies are needed to define the pathways that lead to regulation of NCBE following hemorrhage.