Corynoxine B targets at HMGB1/2 to enhance autophagy for α-synuclein clearance in fly and rodent models of Parkinson's disease

Parkinson's disease (PD) is the most common neurodegenerative movement disease. It is featured by abnormal alpha-synuclein (α-syn) aggregation in dopaminergic neurons in the substantia nigra. Macroautophagy (autophagy) is an evolutionarily conserved cellular process for degradation of cellular contents, including protein aggregates, to maintain cellular homeostasis. Corynoxine B (Cory B), a natural alkaloid isolated from Uncaria rhynchophylla (Miq.) Jacks., has been reported to promote the clearance of α-syn in cell models by inducing autophagy. However, the molecular mechanism by which Cory B induces autophagy is not known, and the α-syn-lowering activity of Cory B has not been verified in animal models. Here, we report that Cory B enhanced the activity of Beclin 1/VPS34 complex and increased autophagy by promoting the interaction between Beclin 1 and HMGB1/2. Depletion of HMGB1/2 impaired Cory B-induced autophagy. We showed for the first time that, similar to HMGB1, HMGB2 is also required for autophagy and depletion of HMGB2 decreased autophagy levels and phosphatidylinositol 3-kinase III activity both under basal and stimulated conditions. By applying cellular thermal shift assay, surface plasmon resonance, and molecular docking, we confirmed that Cory B directly binds to HMGB1/2 near the C106 site. Furthermore, in vivo studies with a wild-type α-syn transgenic drosophila model of PD and an A53T α-syn transgenic mouse model of PD, Cory B enhanced autophagy, promoted α-syn clearance and improved behavioral abnormalities. Taken together, the results of this study reveal that Cory B enhances phosphatidylinositol 3-kinase III activity/autophagy by binding to HMGB1/2 and that this enhancement is neuroprotective against PD.

Research progresses in pharmacological effects of rhynchophylline and its isomers on nervous system / 药学学报

Uncaria rhynchophylla is one of the frequently used herbs in China, it is mainly used for heat-clearance, suppression of hyperactive liver, calming endogenous wind and arresting convulsion in traditional Chinese medicine (TCM). Alkaloids are the main active materials in Uncaria rhynchophylla, pharmacological studies have shown that Uncaria rhynchophylla and its alkaloids have comprehensive biological effects on the nervous system. Rhynchophylline is one of the most abundant alkaloids in Uncaria rhynchophylla. The recent studies demonstrate that rhynchophylline and its isomers (isorhynchophylline, corynoxine, corynoxine B) may be good drug candidates for treatment of Alzheimer's disease, Parkinson's disease, epilepsy, etc. Although the structures of the 4 alkaloids are very similar, they have different effects on nervous system. For example, corynoxine and corynoxine B exhibit better sedative effects than isorhynchophylline. Rhynchophylline and isorhynchophylline have been extensively studied. For development and utilization of rhynchophylline for nervous system disease, more studies are needed to unveil the structure-function relationship and the underlying mechanisms. Here, we summarizes the progresses the effects of rhynchophylline and its isomers on the nervous system.