Effect of Acetazolamide on Aquaporin-1 and Fluid Flow in Cultured Choroid Plexus
Acetazolamide (AZA), used in treatment of early or infantile hydrocephalus, is effective in some cases, while its effect on the choroid plexus (CP) remains ill-defined. The drug reversibly inhibits aquaporin-4 (AQP4), the most ubiquitous “water pore” in t
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Abstract Acetazolamide (AZA), used in treatment of early or infantile hydrocephalus, is effective in some cases, while its effect on the choroid plexus (CP) remains ill-defined. The drug reversibly inhibits aquaporin-4 (AQP4), the most ubiquitous “water pore” in the brain, and perhaps modulation of AQP1 (located apically on CP cells) by AZA may reduce cerebrospinal fluid (CSF) production. We sought to elucidate the effect of AZA on AQP1 and fluid flow in CP cell cultures. CP tissue culture from 10-day Sprague–Dawley rats and a TRCSF-B cell line were grown on Transwell permeable supports and treated with 100 mM AZA. Fluid assays to assess direction and extent of fluid flow, and AQP1 expression patterns by immunoblot, Immuncytochemistry (ICC), and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) were performed. Immunoblots and ICC analyses showed a decrease in AQP1 protein shortly after AZA treatment (lowest at 12 h), with transient AQP1 reduction mediated by mRNA expression (lowest at 6 h). Transwell fluid assays indicated a fluid shift at 2 h, before significant changes in AQP1 mRNA or protein levels. Timing of AZA effect on AQP1 suggests the drug alters protein transcription, while affecting fluid flow by a concomitant method. It is plausible that other mechanisms account for these phenomena, as the processes may occur independently. Keywords Acetazolamide • Aquaporin-1 • Hydrocephalus • Choroid plexus • TRCSF-B • Cerebrospinal fluid
P.A. Ameli, M. Madan, S. Chigurupati, A. Yu, S. Chan, and J.V. Pattisapu () Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, USA e-mail: [email protected]
Introduction Hydrocephalus is a disorder caused by an excessive accumulation of cerebrospinal fluid (CSF) within the cranial cavity, often causing developmental and functional deficits in the pediatric age group. Recent literature suggests that hydrocephalus accounts for 1.8% of days in children’s hospitals (0.6% of admissions) and 3.1% of all pediatric hospital charges [26]. Acetazolamide (AZA) is a carbonic anhydrase (CA) inhibitor used as an initial treatment in certain cases of early or infantile hydrocephalus, glaucoma, idiopathic intracranial hypertension, and seizures [3, 4, 12, 31]. Understanding the role of choroid plexus (CP) in CSF production or absorption is necessary to effectively treat hydrocephalus, and elucidating the effects of AZA on this structure may provide future therapeutic targets for such fluid disorders [7]. Aquaporins (AQPs) are ubiquitously expressed cellular pores capable of transporting water, ions, and small nonpolar molecules [1, 2]. The brain expresses 6 aquaporin isoforms (AQP1, AQP3, AQP4, AQP5, AQP8, and AQP9) [2, 14, 22, 32, 34], of which three have been significantly characterized (AQP1, AQP4, AQP9). AQP4 is predominant in the brain, while AQP1 is of particular interest for its abundance in CP cells [9, 36]. The high expression levels of AQP1 in the apical layer of CP cells implies a role in CSF production, flu
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