Crude Saponins of Panax notoginseng Have Neuroprotective Effects To Inhibit Palmitate-Triggered Endoplasmic Reticulum Stress-Associated Apoptosis and Loss of Postsynaptic Proteins in Staurosporine Differentiated RGC‑5 Retinal Ganglion Cells

Increased apoptosis of retinal ganglion cells (RGCs) contributes to the gradual loss of retinal neurons at the early phase of diabetic retinopathy (DR). There is an urgent need to search for drugs with neuroprotective effects against apoptosis of RGCs for the early treatment of DR. This study aimed to investigate the neuroprotective effects of saponins extracted from Panax notoginseng, a traditional Chinese medicine, on apoptosis of RGCs stimulated by palmitate, a metabolic factor for the development of diabetes and its complications, and to explore the potential molecular mechanism. We showed that crude saponins of P. notoginseng (CSPN) inhibited the increased apoptosis and loss of postsynaptic protein PSD-95 by palmitate in staurosporine-differentiated RGC-5 cells. Moreover, CSPN suppressed palmitate-induced reactive oxygen species generation and endoplasmic reticulum stress-associated eIF2α/ATF4/CHOP and caspase 12 pathways. Thus, our findings address the potential therapeutic significance of CSPN for the early stage of DR.