Aronia Bioactive Fraction–Alginic Acid Nanocomplex–Modulates Tau Phosphorylation and Aggregation in Cell Models of Alzheimer’s Disease

Preventing or reversing Tau hyperphosphorylation and aggregation represent critical objectives in the development of effective therapies for Alzheimer’s disease. The present study investigated the potential of a novel Aronia bioactive fraction—alginic acid nanocomplex (AANCP)—to simultaneously inhibit pathological features of Alzheimer’s disease. Evaluations of Aronia bioactive fraction (ABF) and low-molecular-weight alginic acid (LAA), utilized both individually and as AANCP, were conducted in HEK293-TauP301L and SH-SY5Y-TauP301L cell models of Alzheimer’s disease. Both ABF and LAA reduced the expression of total Tau and Tau phosphorylated at Ser396 in a concentration-dependent manner, with AANCP demonstrating significant synergistic activity of its components. Notably, the optimal AANCP ratio was 1:1 and 1:8 for inhibiting Tau phosphorylation and Tau aggregation, respectively. Mechanistically, AANCP inhibited Tau phosphorylation by upregulating p-Akt (phosphorylated protein kinase B) and p-GSK-3β (phosphorylated glycogen synthase kinase-3 beta), while also enhancing the activity of methylated PP2A, a key Tau phosphatase. Furthermore, AANCP exhibited superior efficacy in inhibiting heparin-induced Tau aggregation compared to the individual components. Analysis of autophagy markers indicated that the nanocomplex enhanced Tau clearance, as shown by increased LC3-II and Beclin-1 levels and reduced p62 levels. These results suggest AANCP as a promising therapeutic candidate that simultaneously reduces Tau phosphorylation and aggregation and facilitates autophagic Tau clearance, offering a potent, synergistic strategy for treating Alzheimer’s disease.