Inhibition of BACE1, the β-secretase implicated in Alzheimer’s disease, by a chondroitin sulfate extract from Sardina pilchardus

The pharmaceutical and anticoagulant agent heparin, a member of the glycosaminoglycan family of carbohydrates, has previously been identified as a potent inhibitor of a key Alzheimer’s disease drug target, the primary neuronal β-secretase, β-site amyloid precursor protein cleaving enzyme 1 (BACE1). The anticoagulant activity of heparin has, however, precluded the repurposing of this widely used pharmaceutical as an Alzheimer’s disease therapeutic. Here, a glycosaminoglycan extract, composed predominantly of 4-sulfated chondroitin sulfate, has been isolated from Sardina pilchardus, which possess the ability to inhibit BACE1 (IC(50) [half maximal inhibitory concentration] = 4.8 μg/mL), while displaying highly attenuated anticoagulant activities (activated partial thromboplastin time EC(50) [median effective concentration] = 403.8 μg/mL, prothrombin time EC(50) = 1.3 mg/mL). The marine-derived, chondroitin sulfate extract destabilizes BACE1, determined via differential scanning fluorimetry (ΔT(m) –5°C), to a similar extent as heparin, suggesting that BACE1 inhibition by glycosaminoglycans may occur through a common mode of action, which may assist in the screening of glycan-based BACE1 inhibitors for Alzheimer’s disease.