Investigation of the neuroprotective effects of crocin via antioxidant activities in HT22 cells and in mice with Alzheimer's disease

Due to its complex pathogenesis, the prevention and therapization of Alzheimer's disease (AD) remains a serious challenge. Crocin, the main compound isolated from Crocus sativus L., demonstrates various pharmacological activities including anti‑apoptotic properties. The present study investigated the neuroprotective effect of crocin and the underlying mechanisms. In l‑glutamate‑damaged HT22 cells, 3‑h crocin pretreatment strongly enhanced the HT22 cell viability, reduced the apoptotic rate, mitigated mitochondrial dysfunction, suppressed intracellular reactive oxygen species (ROS) accumulation and Ca2+ overload compared with untreated cells. Additionally, crocin significantly decreased the expression levels of Bax, Bad and cleaved caspase‑3 and increased the expression levels of B‑cell lymphoma‑extra large, phosphorylated (P‑) protein kinase B and P‑mammalian target of rapamycin compared with untreated cells. In mice with AD induced by d‑galactose and aluminum trichloride, crocin substantially improved the cognition and memory abilities of the mice as measured by their coordination of movement in an open field test, and reduced their escape time in the Morris water maze test compared with untreated mice. Biochemical analysis confirmed that crocin was able to reduce the Aβ1‑42 content in the mouse brains, increase the levels of glutathione peroxidase, superoxide dismutase, acetylcholine and choline acetyltransferase, and reduce the levels of ROS and acetylcholinesterase in the serum, cerebral cortex and hypothalamus compared with untreated mice. Immunohistochemical analysis demonstrated that crocin reduced Aβ1‑42 deposition in the hippocampus of the brains of treated mice compared with untreated mice. In conclusion, crocin demonstrates good prospects in the treatment of AD through the oxidative stress‑associated apoptosis signaling pathway.