Wardman, J. H. | bioRxiv Science

bioRxiv2022

Transcriptional profiling of transport mechanisms and regulatory pathways in rat choroid plexus

BackgroundDysregulation of brain fluid homeostasis associates with brain pathologies in which fluid accumulation leads to elevated intracranial pressure. Surgical intervention remains standard care, since specific and efficient pharmacological treatment options are limited for pathologies with disturbed brain fluid homeostasis. Such lack of therapeutic targets originates, in part, from the incomplete map of the molecular mechanisms underlying cerebrospinal fluid (CSF) secretion by the choroid plexus. MethodsThe transcriptomic profile of rat choroid plexus was generated by RNA Sequencing (RNAseq) of whole tissue and epithelial cells captured by fluorescence-activated cell sorting (FACS), and compared to proximal tubules. The bioinformatic analysis comprised mapping to reference genome followed by filtering for type, location, and association with alias and protein function. The transporters and associated regulatory modules were arranged in discovery tables according to their transcriptional abundance and tied together in association network analysis. ResultsThe transcriptomic profile of choroid plexus displays high similarity between sex and species (human, rat, and mouse) and lesser similarity to another secretory epithelium, the proximal tubules. The discovery tables provide lists of transport mechanisms that could participate in CSF secretion and suggest regulatory candidates. ConclusionsWith quantification of the transport protein abundance in choroid plexus and their potentially linked regulatory modules, we envision a molecular tool to devise rational hypotheses regarding future delineation of choroidal transport proteins involved in CSF secretion and their regulation. Our vision is to obtain pharmaceutical targets towards modulation of CSF production in pathologies involving disturbed brain water dynamics.

neuroscience↗

bioRxiv2022

Acetazolamide modulates intracranial pressure directly by its action on the cerebrospinal fluid secretion apparatus

Elevated intracranial pressure (ICP) is observed in many neurological pathologies, e.g. hydrocephalus and stroke. This condition is routinely relieved with neurosurgical approaches, since effective and targeted pharmacological tools are still lacking. The carbonic anhydrase inhibitor, acetazolamide (AZE), may be employed to treat elevated ICP. However, its effectiveness is questioned, its location of action unresolved, and its tolerability low. Here, we employed in vivo and ex vivo approaches to reveal the efficacy and mode of action of AZE in the rat brain. The drug effectively reduced the ICP, irrespective of the mode of drug administration and level of anaesthesia. The effect occurred via a direct action on the choroid plexus and an associated decrease in cerebrospinal fluid secretion, and not indirectly via the systemic action of AZE on renal and vascular processes. Upon a single administration, the reduced ICP endured for approximately 10 h post-AZE delivery with no long-term changes of brain water content or choroidal transporter expression. However, a persistent reduction of ICP was secured with repeated AZE administrations throughout the day. Future specific targeting of choroidal carbonic anhydrases may limit the systemic side effects, and therefore enhance the treatment tolerability and effectiveness in select patient groups experiencing elevated ICP.

neuroscience↗