Involvement of PI3K/AKT Pathway in the Rapid Antidepressant Effects of Crocetin in Mice with Depression-Like Phenotypes.

The current first-line antidepressants have the drawback of slow onset, which greatly affects the treatment of depression. Crocetin, one of the main active ingredients in saffron (Crocus sativus L.), has been demonstrated to have antidepressant activities, but whether it has a rapid antidepressant effect remains unclear. This study aimed to investigate the onset, duration, and mechanisms of the rapid antidepressant activity of crocetin (20, 40 and 80 mg/kg, intraperitoneal injection) in male mice subjected to chronic restraint stress (CRS). The results of behavioral tests showed that crocetin exerted rapid antidepressant-like effect in mice with depression-like phenotypes, including rapid normalization of depressive-like behaviors within 3 h, and the effects could be maintained for 2 days. Hematoxylin-eosin (HE) and Nissl staining showed that crocetin ameliorated hippocampal neuroinflammation and nerve injuries in mice with depression-like phenotypes. The levels of inflammatory factors, corticosterone and pro brain-derived neurotrophic factor in crocetin-administrated mice serum were significantly reduced compared with those in the CRS group, as well as the levels of inflammatory factors in hippocampus. What's more, Western blot analyses showed that, compared to CRS-induced mice, the relative levels of mitogen-activated kinase phosphatase 1 and toll-like receptor 4 were significantly reduced after the administration of crocetin, and the relative expressions of extracellular signal-regulated kinase 1/2 (ERK1/2), cAMP-response element binding protein, phosphorylated phosphoinositide 3 kinase (p-PI3K)/PI3K, phosphorylated protein kinase B (p-AKT)/AKT, phosphorylated glycogen synthase kinase 3β (p-GSK3β)/GSK3β, phosphorylated mammalian target of rapamycin (p-mTOR)/mTOR were markedly upregulated. In conclusion, crocetin exerted rapid antidepressant effects via suppressing the expression of inflammatory cytokines and the apoptosis of neuronal cells through PI3K/AKT signaling pathways. The rapid antidepressant effect of crocetin (40 mg/kg) could be maintained for at least 2 days after single treatment.