A potent icaritin derivative ameliorates Parkinson's disease via GPER-mediated mitophagy restoration and dopaminergic neuroprotection.

Icaritin (ICT), a major prenylated flavone from Epimedium with anti-osteoporosis, anti-cancer, and anti-inflammatory properties, is limited clinically by poor water solubility and low bioavailability. In this study, ICT derivatives were prepared via multi-step chemical reactions and five ICT derivatives (ICTA, ICTB, ICTC, ICTD and ICTE) were successfully synthesized. Compared with ICT, most derivatives exhibited improved solubility and reduced cytotoxicity. Notably, ICTC showed a significant improvement in aqueous solubility (at least 12-fold higher), favorable lower cytotoxicity (at least 2-fold lower at 20 μM), and prominent neuroprotective effects. Mechanistically, in vitro studies revealed that ICTC targets the G protein-coupled estrogen receptor (GPER) to rescue defective mitophagy by restoring MPP+-suppressed expression of mitophagy-related proteins (PINK1, Parkin) and attenuating MPP+-induced accumulation of autophagic substrates (LC3-II, P62). In vivo, intraperitoneal injection of ICTC (0.3-3 mg/kg) effectively protected against MPTP-induced damage to dopaminergic neurons and attenuated neuroinflammation. Molecular docking, pharmacological blockade and studies in GPER knockout mouse models of Parkinson's disease (PD) confirmed that the effects of ICTC depend on GPER. Moreover, intravenous injection of ICTC also provided effective dopaminergic neuron protection, addressing the limitations of oral formulation. Overall, ICTC is a promising prodrug with enhanced solubility that exerts anti-inflammatory and neuroprotective effects in experimental PD by targeting GPER to ameliorate abnormal mitophagy.