Altered cellular localization of aquaporin-1 in experimental hydrocephalus in mice and reduced ventriculomegaly in aquaporin-1 deficiency

Hydrocephalus is a pathological accumulation of cerebrospinal fluid (CSF) in the cerebral ventricles that constitutes a significant cause of neurological morbidity and mortality. Surgical treatment involving shunt placement is associated with a high failure rate and complications due to infection, motivating the development of alternative, non-surgical therapies. Here, we investigated the role in hydrocephalus of water channel aquaporin-1 (AQP1), which is expressed at the apical membrane of choroid plexus epithelium and is believed to facilitate CSF production. AQP1 expression and subcellular localization were studied in a kaolin-induced hydrocephalus model in mice and the effect AQP1 deficiency on the severity of hydrocephalus was determined. While total choroidal AQP1 protein was not significantly altered in hydrocephalus, ~ 50% of AQP1 protein was redistributed from the apical membrane to intracellular vesicles. We found that the ventricular size in AQP1-deficient mice was smaller than in wild-type mice, both at baseline and following hydrocephalus. The reduced plasma membrane AQP1 localization following kaolin-induced hydrocephalus, which involves endocytosis, may be a compensatory mechanism to reduce CSF secretion. The reduced ventricular size in AQP1-deficient mice following kaolin-induced hydrocephalus suggests AQP1 inhibition or down-regulation as a potential adjunctive treatment for hydrocephalus.