Abstract TMP118: Potential Therapeutic Benefits of Perlecan Domain V in Preclinical Vascular Dementia and Cerebral Angiopathy

Abstract

Vascular contributions to cognitive impairment and dementia (VCID), the second leading cause of dementia behind Alzheimer’s disease (AD), is a broad term that encompasses a spectrum of initial asymptomatic cerebrovascular changes (seen in small vessel disease and cerebral amyloid angiopathy where pathologic Aβ1-42 protein accumulates around brain blood vessels) to the profound symptomatic damage following acute stroke(s). Cerebrovascular remodeling and new blood vessel growth (angiogenesis) may represent early compensatory changes to reduced cerebral blood flow that can initiate VCID. Angiogenesis, in turn, is supported by various growth factors and the proteolytic turnover of surrounding extracellular matrix. We have demonstrated that one such extracellular matrix protein, perlecan (a heparan sulfate proteoglycan), possesses a C terminal domain V (DV) protein that upon cleavage greatly enhances brain angiogenesis. We characterized VCID induced changes in DV expression in the human parietal cortex and a distinct mouse model (diabetic APP/PS1 knock in (db/AD)), that has a gradual cognitive decline by 9 months with microangiopathy, Aβ1-42 deposition, aneurysms, and microhemorrhages. We also utilized an in vitro model of the blood-brain barrier (BBB) to assess the transport of human Aβ1-42 in the presence of DV. In the human parietal cortex, dementia patients had increased expression of DV despite having fewer cells. In db/AD animals (3-6 months), we observed a decrease in BBB proteins (i.e. claudin-5), indicating that altered function correlated with an increase in brain DV expression during the asymptomatic angiogenic stage, which precedes cognitive changes (9-12 months). In vitro, DV doubled the transport of Aβ1-42 into the lumen of cerebral microvessels over 24 hours with increased activity and total protein expression of P-glycoprotein (P-gp), one of Aβ’s known transport proteins. Collectively, these data indicate that early cerebrovascular changes induce angiogenic-remodeling that correlates with increased expression of DV. DV, in turn, may further enhance angiogenesis and increase brain Aβ clearance into the vascular compartment through P-gp, suggesting that DV could represent a novel therapeutic for VCID.