Algae-Derived C-Phycocyanin Mitigates AGE–RAGE-Induced ER Stress and Mitochondrial Apoptosis: Implications for Diabetes-Associated Neurodegeneration

Impaired glucose metabolism elevates the risk of neurodegenerative diseases by activating the receptor for advanced glycation end products (RAGE), thereby promoting oxidative and endoplasmic reticulum (ER) stress that leads to neuronal apoptosis. C-phycocyanin (C-PC), a natural pigment-protein complex derived from algae, possesses potent antioxidant and antiglycation properties; however, its capacity to modulate RAGE-mediated neurotoxicity remains to be fully elucidated. In this study, we established a RAGE-driven neuronal injury model by exposing differentiated SH-SY5Y cells to advanced glycation end products (AGEs; 300 μg/mL). Pretreatment with C-PC (15-50 μmol/L) improved cell viability, preserved neuronal morphology, and attenuated AGEs-induced oxidative stress, as indicated by reduced intracellular reactive oxygen species and mitochondrial superoxide levels. Furthermore, C-PC inhibited activation of the PERK-CHOP pathway, and upregulated Bcl-2 while downregulating Bax, thereby preventing cytochrome c release and reducing caspase-9/3 activation as well as apoptotic DNA fragmentation. These neuroprotective effects of C-PC were comparable to those observed with the selective RAGE antagonist FPS-ZM1. In conclusion, our findings demonstrate that C-PC confers robust protection against AGEs-induced neuronal injury by suppressing oxidative and ER stress pathways downstream of RAGE activation, highlighting its potential as a natural modulator of the AGE-RAGE axis for the prevention or treatment of diabetes-associated neurodegeneration.