Neuroinflammation induces aberrant activation of Wnt signaling in astrocytes and impairment of cholesterol homeostasis and myelin integrity.

Abstract

Neuroinflammation often disrupts cerebral cholesterol homeostasis and leads to white matter damage and demyelination. However, the molecular mechanisms underlying these defects have remained enigmatic. In this study, we report that inflammation is associated with aberrant activation of Wnt signaling in astrocytes. While Wnt signaling increases astrocytic expression of SREBF2 protein and intracellular cholesterol level, it simultaneously inhibits the expression of APOE and reduces cholesterol efflux from astrocytes. The extracellular cholesterol supply is essential for the activation of the expression of MYRF transcription factor and myelin-associated genes in oligodendrocytes. Moreover, the defective oligodendrocyte differentiation and myelin gene expression caused by astrocytic Wnt activation in transgenic mice can partially be rescued by chemical-enhanced ApoE expression. Our findings suggest a regulatory pathway of "inflammation → Wnt signaling → cholesterol metabolism → myelin integrity" and provide important insights into the molecular mechanisms underlying inflammation-induced demyelinating diseases and future therapeutic strategies.