Fucoxanthin protects retinal ganglion cells and promotes parkin-mediated mitophagy against glutamate excitotoxicity

Abstract

Objective To clarify whether fucoxanthin plays a protective role and regulates parkin-mediated mitophagy on retinal ganglion cells (RGCs) against glutamate excitotoxicity. Methods The excitotoxicity model of primary RGCs was carried out with glutamate. Mitochondrial membrane potential was measured by JC-1 kit (Abcam, USA). The apoptotic rate and cytotoxicity were detected by Hoechst staining and lactate dehydrogenase (LDH) kit (Takara, Japan). Mitochondria was assessed by MitoTracker staining and confocal microscopy. The mRNA levels and protein expression levels of Bax, Bcl-2, parkin, optineurin, LC3, and LAMP1 in RGCs were analyzed by quantitative PCR and immunoblotting. Finally, the mitochondrial health score and mitophagy were assessed by transmission electron microscopy. Results Fucoxanthin increased the mitochondrial membrane potential of RGCs, reduced cytotoxicity, and decreased apoptosis in RGCs under glutamate excitotoxicity. It also enhanced expression levels of parkin, optineurin, and LAMP1, and upgraded the ratio of LC3-II to LC3-I. Meanwhile, fucoxanthin increased LC3 and MitoTracker co-localization staining. In addition, up-regulated mitochondrial health score, and the number of autophagosomes and mitophagosomes were observed in fucoxanthin-treated RGCs under glutamate excitotoxicity. Conclusion Fucoxanthin may exert its neuroprotective effect on RGCs via promoting parkin-mediated mitophagy under glutamate excitotoxicity. The neuroprotective effect of fucoxanthin in glaucomatous neurodegeneration and ocular diseases characterized by impaired mitophagy warrants further investigation.