Choroid plexus glutathione peroxidases are instrumental in protecting the brain fluid environment from hydroperoxides during postnatal development

Hydrogen peroxide, released at low physiological concentration, is involved in different cell signaling pathways during brain development. When released at supraphysiological concentrations in brain fluids following an inflammatory, hypoxic, or toxic stress, it can initiate lipid peroxidation, protein, and nucleic acid damage and contribute to long-term neurological impairment associated with perinatal diseases. We found high glutathione peroxidase and glutathione reductase enzymatic activities in both lateral and fourth ventricle choroid plexus tissue isolated from developing rats, in comparison to the cerebral cortex and liver. Consistent with these, a high protein expression of glutathione peroxidases 1 and 4 was observed in choroid plexus epithelial cells, which form the blood-cerebrospinal fluid barrier. Live choroid plexuses isolated from newborn rats were highly efficient in detoxifying H2O2 from mock cerebrospinal fluid, illustrating the capacity of the choroid plexuses to control H2O2 concentration in the ventricular system of the brain. We used a differentiated cellular model of the blood-cerebrospinal fluid barrier coupled to kinetic and inhibition analyses to show that glutathione peroxidases are more potent than catalase to detoxify extracellular H2O2 at concentrations up to 250 mu M. The choroidal cells also formed an enzymatic barrier preventing blood-borne hydroperoxides to reach the cerebrospinal fluid. These data point out the choroid plexuses as key structures in the control of hydroperoxide levels in the cerebral fluid environment during development, at a time when the protective glial cell network is still immature. Glutathione peroxidases are the main effectors of this choroidal hydroperoxide inactivation.