Table 5 Differential expression of water channels and peptide transporters at the BCSFB and BBB: Implications for CNS fluid and peptide homeostasis
From: Multiplicity of cerebrospinal fluid functions: New challenges in health and disease
A | |
|---|---|
Aquaporin 1 (Blood-CSF Interface) | Aquaporin 4 (Blood-Brain Interface) |
AQP1 is present at the CSF-facing pole of choroid plexus epithelium [70 – 73, 77, 78], and in the CSF-brain ependymal lining [281]. | AQP4 is located in astrocytic foot processes at the BBB. It is associated with fluid transfer across cerebral microvessels. |
Reduced expression in choroid plexus is associated with slower rates of CSF secretion and thus decreases ICP [77, 78]. | Elevated expression of AQP4 in the BBB occurs in chronic hydrocephalus [281 – 283]; may be associated with fluid reabsorption. |
Attenuated expression in aging [57] and in Alzheimer's disease is accompanied by slower fluid turnover rate [79]. | Diminished expression at BBB leads to a reduction in brain edema formation in some animal models. |
B | |
LRP-1 (Low density lipophilic receptor associated protein) | RAGE (Receptor for advanced glycation end products) |
Expressed in choroidal epithelium and capillary endothelium [229, 257]. | Expressed in choroidal epithelium and brain capillary endothelium [257]. |
Removes Aβ peptide from CSF and brain ISF [229, 243] for excretion via blood. | Transports Aβ from blood into brain ISF where the retained peptide may predispose to Aβ plaque formation in the interstitium. |
Sustained or increased expression in choroid plexus during aging, NPH and AD. | Enhanced expression of RAGE at BBB in aging, NPH [219] and AD [225] may destabilize BBB and precipitate plaque. |
Decreased expression of LRP-1 at the BBB in aging, NPH and AD likely interferes with Aβ removal [219, 225, 229]. | Expression of RAGE is generally opposite to that of LRP-1 at the barriers and in neurons [225]. |