Blood–brain and blood–cerebrospinal fluid passage of BRICHOS domains from two molecular chaperones in mice

Abstract

Edited by Ursula JakobTargeting toxicity associated with ␤-amyloid (A␤) misfolding and aggregation is a promising therapeutic strategy for preventing or managing Alzheimer's disease. The BRICHOS domains from human prosurfactant protein C (proSP-C) and integral membrane protein 2B (Bri2) efficiently reduce neurotoxicity associated with A␤42 fibril formation both in vitro and in vivo. In this study, we evaluated the serum half-lives and permeability into the brain and cerebrospinal fluid (CSF) of recombinant human (rh) proSP-C and Bri2 BRICHOS domains injected intravenously into WT mice. We found that rh proSP-C BRICHOS has a longer blood serum half-life compared with rh Bri2 BRICHOS and passed into the CSF but not into the brain parenchyma. As judged by Western blotting, immunohistochemistry, and ELISA, rh Bri2 BRICHOS passed into both the CSF and brain. Intracellular immunostaining for rh Bri2 BRI-CHOS was observed in the choroid plexus epithelium as well as in the cerebral cortex. Our results indicate that intravenously administered rh proSP-C and Bri2 BRICHOS domains have different pharmacokinetic properties and blood-brain/blood-CSF permeability in mice. The finding that rh Bri2 BRICHOS can reach the brain parenchyma after peripheral administration may be harnessed in the search for new therapeutic strategies for managing Alzheimer's disease.

Augmentation of Bri2 molecular chaperone activity against amyloid-β reduces neurotoxicity in mouse hippocampus in vitro

“…BRICHOS is a recently established molecular chaperone domain, which efficiently prevents fibrillar amyloid aggregation as well as its associated toxicity, as shown in vitro, in mouse hippocampal slice preparations, and in Drosophila models 19,23,26,27,32,34,35 . The dementia relevant Bri2 and its BBB permeable BRICHOS domain are associated with AD: Bri2 is produced in the CNS in the same cells as the Aβ precursor protein AβPP, colocalizes with senile plaques, interacts with Aβ in neurons, and increased amounts of different Bri2 forms have been found in human AD brains 38,39,48 . Further preclinical work that focus on the potential usefulness of Bri2 BRICHOS delivery and/or activation for prevention and treatment of AD should be pursued in relevant animal models.…”

“…To test this hypothesis, we coincubated rh Bri2 BRICHOS R221E monomers and rh wild-type Bri2 BRICHOS oligomers, after which the distribution of Bri2 BRICHOS assembly states, and effects on Aβ42 fibril formation and neurotoxicity were evaluated. To enable differentiation between wild-type and R221E rh Bri2 BRICHOS monomers, we used a rh wild-type Bri2 BRICHOS construct containing an AU1 tag, which behaves like the non-tagged wild-type protein and can be selectively immunodetected using an anti-AU1 antibody 48 . Native PAGE and western blot analysis showed that coincubation of rh wildtype Bri2 BRICHOS oligomers with rh Bri2 BRICHOS R221E monomer lead to the release of smaller species, especially monomers ( Fig.…”

Expression of the human molecular chaperone domain Bri2 BRICHOS on a gram per liter scale with an E. coli fed-batch culture

“…Rh Bri2 BRICHOS has emerged as an interesting biopharmaceutical candidate for treating AD, as the domain is a potent inhibitor of Aβ42 amyloid fibril formation and in particular its associated neurotoxicity in vitro, in hippocampal slice preparations ex vivo , and in Drosophila models in vivo [ 15 ] . In addition, rh Bri2 BRICHOS passes the blood-brain barrier [ 16 ].…”

“…For instance, Bri2 BRICHOS prevents amyloid formation and neurotoxicity of the 42-residue Aβ42, the main amyloidogenic species in AD, in transgenic fruit flies and mice and prevents Aβ42 neurotoxicity in mouse hippocampal slices in vitro [ 12 – 15 ]. Moreover, recombinant human (rh) Bri2 BRICHOS passes the blood-brain barrier in wild-type mice, making parenteral administration of rh Bri2 BRICHOS an interesting new potential treatment against AD [ 16 , 17 ]. Such application of rh Bri2 BRICHOS would require industrial protein production and purification protocols that result in a homogenous product at a reasonable cost.…”

Undiscovered Roles for Transthyretin: From a Transporter Protein to a New Therapeutic Target for Alzheimer’s Disease

“…The Bri2 protein is produced in the central nervous system, in the same cells as the Aβ precursor protein, APP, and colocalizes with senile plaques, interacts with Aβ in neurons, and increased amounts of different Bri2 forms have been found in human AD brains [81,82]. Interestingly, other researchers have found that the BRICHOS domain from the Bri2 chaperone is BBB permeable, reaching the brain parenchyma after peripheral administration [83]. A single point mutation of Bri2 BRICHOS, the mutant R221E, forms stable monomers and selectively blocks a main source of toxic species during Aβ42 aggregation.…”