Demyelination in cuprizone mice is ameliorated by calycosin mediated through astrocyte Nrf2 signaling pathway

Oxidative stress plays a pivotal role in multiple sclerosis (MS), triggering demyelination predominantly through excessive peroxide production and the depletion of antioxidants. The accumulation of oxidative damage can be caused by dysregulation of astrocytes, which are the brain's main regulators of oxidative homeostasis. Calycosin, an essential bioactive component extracted from Astragalus, is recognized for its neuroprotective properties. Although recent research has highlighted calycosin's neuroprotective capabilities, its role in demyelinating conditions like MS remains unclear. In this work, we examined the possible molecular mechanism of calycosin's neuroprotective effect on cuprizone (CPZ)-induced demylination in mice. According to our research, calycosin successfully reduced demyelination and behavioral dysfuction in CPZ mice. Calycosin also decreased the production of oxidative stress and enhanced the expression of antioxidants in CPZ mice and in astrocytes induced by hydrogen peroxide (H₂O₂). Furthermore, both in vivo and in vitro experiments demonstrated that calycosin promoted the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) along with the upregulation of heme oxygenase 1 (HO-1), NAD(P)H quinone dehydrogenase 1 (NQO1), and superoxide dismutase (SOD). Importantly, the application of all-trans retinoic acid (ATRA), a specific inhibitor of Nrf2, effectively reversed the myelin-protective and antioxidant effects conferred by calycosin. This study suggested that calycosin might exert neuroprotection by inhibiting oxidative stress and reducing demyelination via the activation of astrocyte Nrf2 signaling. These findings indicated that calycosin might be a potential candidate for treating MS.