Idiopathic intracranial hypertension (IIH) is a condition characterised by raised intracranial pressure (ICP) that primarily affects obese women of reproductive age. The aetiology is poorly understood but involves imbalance of cerebrospinal fluid (CSF) secretion and absorption. IIH patients share similar phenotypic characteristics to PCOS patients, a condition with a distinct androgen signature. We hypothesise that obesity and androgen excess maybe pathogenic in IIH through dysregulation of CSF secretion and hence ICP.
In this study we aimed to develop an in vitro CSF secretion assay and then evaluate the impact of testosterone on CSF secretion. An immortalised rat choroid plexus epithelial cell line (Z310 cells) was infected with an adenoviral vector containing the ATP:ADP ratio sensor Perceval. Na+/K+ ATPase activity is the rate limiting step in CSF secretion and a validated surrogate for CSF secretion. Na+/K+ ATPase activity was determined following acute administration of the specific inhibitor ouabain (1 mM), the change in ATP:ADP ratio indicated Na+/K+ ATPase activity. The assay was validated and additionally challenged with acetazolamide (1 mM, 2 days), a drug used clinically to reduce CSF secretion. Acetazolamide reduced the ATP:ADP ratio (indicating a reduction in CSF secretion) (P<0.05) compared to control. Ultimately, Z310 cells were incubated with testosterone (100 nM, 2 days) and the ATP:ADP ratio was noted to be increased (P<0.0001) compared to vehicle, indicating increased Na+/K+ ATPase activity and hence increased CSF secretion. Furthermore real-time quantitative PCR demonstrated increased expression of carbonic anhydrase II and III (P<0.05), key components in generating the ion gradients required for CSF secretion.
We have developed a novel in vitro CSF secretion assay though quantification of Na+/K+ ATPase activity. Testosterone increased Na+/K+ ATPase activity, indicating increased CSF secretion. We speculate that testosterone may have a pathogenic role in IIH through modulation of CSF formation and increasing ICP.