Anti-malaria drug artesunate prevents development of amyloid-ß pathology in mice by upregulating PICALM at the blood-brain barrier.

ABSTRACT

BACKGROUND: PICALM is one of the most significant susceptibility factors for Alzheimer's disease (AD). In humans and mice, PICALM is highly expressed in brain endothelium. PICALM endothelial levels are reduced in AD brains. PICALM controls several steps in Aß transcytosis across the blood-brain barrier (BBB). Its loss from brain endothelium in mice diminishes Aß clearance at the BBB, which worsens Aß pathology, but is reversible by endothelial PICALM re-expression. Thus, increasing PICALM at the BBB holds potential to slow down development of Aß pathology. METHODS: To identify a drug that could increase PICALM expression, we screened a library of 2007 FDA-approved drugs in HEK293t cells expressing luciferase driven by a human PICALM promoter, followed by a secondary mRNA screen in human Eahy926 endothelial cell line. In vivo studies with the lead hit were carried out in Picalm-deficient (Picalm+/-) mice, Picalm+/-; 5XFAD mice and Picalmlox/lox; Cdh5-Cre; 5XFAD mice with endothelial-specific Picalm knockout. We studied PICALM expression at the BBB, Aß pathology and clearance from brain to blood, cerebral blood flow (CBF) responses, BBB integrity and behavior. RESULTS: Our screen identified anti-malaria drug artesunate as the lead hit. Artesunate elevated PICALM mRNA and protein levels in Eahy926 endothelial cells and in vivo in brain capillaries of Picalm+/- mice by 2-3-fold. Artesunate treatment (32 mg/kg/day for 2 months) of 3-month old Picalm+/-; 5XFAD mice compared to vehicle increased brain capillary PICALM levels by 2-fold, and reduced Aß42 and Aß40 levels and Aß and thioflavin S-load in the cortex and hippocampus, and vascular Aß load by 34-51%. Artesunate also increased circulating Aß42 and Aß40 levels by 2-fold confirming accelerated Aß clearance from brain to blood. Consistent with reduced Aß pathology, treatment of Picalm+/-; 5XFAD mice with artesunate improved CBF responses, BBB integrity and behavior on novel object location and recognition, burrowing and nesting. Endothelial-specific knockout of PICALM abolished all beneficial effects of artesunate in 5XFAD mice indicating that endothelial PICALM is required for its therapeutic effects. CONCLUSIONS: Artesunate increases PICALM levels and Aß clearance at the BBB which prevents development of Aß pathology and functional deficits in mice and holds potential for translation to human AD.