Abstract
Excitotoxicity, resulting from excessive accumulation of glutamate in the extracellular space, leads to neuronal cell death. This study investigates the protective effects of Apelin-13 on D-glutamic acid-induced excitotoxicity in SH-SY5Y human neuroblastoma cells, an in vitro model for neurodegenerative diseases. Unlike the commonly studied L-glutamic acid, this research focuses on D-glutamic acid to understand its specific impacts. SH-SY5Y cells were treated with varying concentrations of D-glutamic acid and Apelin-13, followed by analyses at 12 and 24 hours to evaluate cell viability, oxidative stress markers, and inflammatory cytokine levels. Cell viability assays revealed significant cytotoxic effects of D-glutamic acid at doses of 10 mM and 20 mM, reducing viability by over 50%. However, Apelin-13 treatment mitigated these effects, especially at 2 µg/mL, enhancing cell viability and reducing inflammatory cytokine levels (IL-1β and TNF-α). Apelin-13 also increased anti-inflammatory cytokine levels (IL-10 and TGF-β1) and brain-derived neurotrophic factor (BDNF), indicating its neuroprotective role. Oxidative stress markers, including ROS, AGE, AOPP, DT, and T-SH, were significantly elevated by D-glutamic acid but effectively reduced by Apelin-13. The neuroprotective mechanisms of Apelin-13 involve modulation of cAMP/PKA and MAPK signaling pathways, enhancing BDNF synthesis and suppressing oxidative stress and inflammatory responses. This study is the first to demonstrate the effects of D-glutamic acid on SH-SY5Y cells. It highlights Apelin-13’s potential as a therapeutic agent against excitotoxicity-induced neuronal damage, emphasizing its ability to modulate key molecular pathways involved in inflammation and oxidative stress. Further in vivo studies are warranted to explore the long-term neuroprotective effects of Apelin-13 in treating neurodegenerative diseases.