An Oligomannuronic Acid-Sialic Acid Conjugate Capable of Inhibiting Aβ42 Aggregation and Alleviating the Inflammatory Response of BV-2 Microglia

Oligomannuronic acid (MOS) from seaweed has antioxidant and anti-inflammatory activities. In this study, MOS was activated at the terminal to obtain three different graft complexes modified with sialic acid moiety (MOS-Sia). The results show that MOS-Sia addition can reduce the β-structure formation of Aβ42, and the binding effect of MOS-Sia3 is more obvious. MOS-Sia conjugates also have a better complexing effect with Ca(2+) while reducing the formation of Aβ42 oligomers in solutions. MOS-Sia3 (25–50 μg/mL) can effectively inhibit the activation state of BV-2 cells stimulated by Aβ42, whereas a higher dose of MOS-Sia3 (>50 μg/mL) can inhibit the proliferation of BV-2 cells to a certain extent. A lower dose of MOS-Sia3 can also inhibit the expression of IL-1β, IL-6, TNF-α, and other proinflammatory factors in BV-2 cells induced by Aβ42 activation. In the future, the MOS-Sia3 conjugate can be used to treat Alzheimer’s disease.