Protective effect of Nrf2–ARE activator isolated from green perilla leaves on dopaminergic neuronal loss in a Parkinson's disease model
Parkinson's disease (PD) is a neurodegenerative disorder characterized by a selective loss of dopaminergic neurons in the substantia nigra (SN), and oxidative stress is thought to contribute to the pathogenesis. The nuclear factor erythroid 2-related factor 2 (Nrf2)–antioxidant response element (ARE) pathway, which is a cellular defense system against oxidative stress, is a promising target for therapeutics aimed at reducing neuronal death in PD. Previously, we have isolated 2′,3′-dihydroxy-4′,6′-dimethoxychalcone (DDC) from green perilla leaves as an activator of the Nrf2–ARE pathway. The present study showed the protective effect of DDC on PD models in vivo and in vitro. In a 6-hydroxydopamine (6-OHDA)-induced hemiparkinson's disease mouse model, intracerebral administration of DDC suppressed the dopaminergic neuronal loss and behavioral dysfunction. DDC upregulated the expression of heme oxygenase-1 (HO-1), one of the ARE-driven antioxidant enzymes, in astrocytes and microglia of the SN. In primary mesencephalic cultures, treatment with DDC also increased the HO-1 expression in astrocytes and microglia. DDC showed a protective effect against 6-OHDA-induced dopaminergic neuronal death, and the effect was suppressed by an HO-1 inhibitor. These results suggest that DDC prevents dopaminergic neurons from oxidative stress by upregulation of glial expression of HO-1.