Wnt1 oversees microglial activation by the Wnt/LRP5/6 receptor signaling pathway during lipopolysaccharide-mediated toxicity.

Abstract

Background: The protective effects of autophagy-mediated microglial inflammatory regulation on diseases of the central nervous system (CNS) has been a recent field of interest. The canonical signaling pathway activated by Wnt1, the Wnt/β-catenin signaling cascade, also plays a crucial protective role in neurodegenerative diseases. However, the relationship between Wnt1/β-catenin signaling and microglial activation remains unclear. Our study focused on understanding the impact and mechanism of Wnt1 on microglial activation.

Methods and results: To simulate neuroinflammatory conditions in vitro, BV2 cells were exposed to 1 μg/mL lipopolysaccharide. CD86- and CD206-positive cells were identified by flow cytometry and immunofluorescence assays. Inflammatory and anti-inflammatory factors were measured using enzyme-linked immunosorbent assays. Autophagy was analyzed by expression of LC3B puncta, LC3, P62, and beclin1 expression. The inflammatory activation suppressed by rhWnt1 was restricted by DKK1, siRNA-β-catenin and siRNA-LKB1, respectively, with concomitant changes in β-catenin expression and phosphorylation of NFκB-p65, LKB1, and AMPK. Although the anti-inflammatory effect of Wnt1/LKB1 pathway was independent of β-catenin, Wnt1/LKB1 regulated β-catenin. The reduced inflammation caused by rhWnt1 is linked to its enhancement of autophagy, a process blocked by siRNA-LKB1 and 3-MA partially.

Conclusions: The anti-inflammatory effects of Wnt1 on BV2 cells improved autophagy, a mechanism partly dependent on the β-catenin pathway or the phosphorylation of LKB1. Furthermore, the Wnt1/LKB1 pathway was activated independently of β-catenin and participated in regulating its expression. Our research unveils a previously unknown method through which Wnt1 exerts its anti-inflammatory effects, which may have a potential protective role against CNS diseases.