Neuroprotective effects of crocin against Parkinson's disease in rats: association with the mTOR signaling pathway and inhibition of ferroptosis and apoptosis

Abstract

Parkinson's disease (PD) is a common neurodegenerative disorder with a complex pathogenesis linked to ferroptosis, apoptosis, inflammation, and oxidative stress. Mounting evidence has demonstrated that the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway is deeply involved in PD pathogenesis and acts as a key regulator of ferroptosis. Crocin, a carotenoid from saffron, exhibits potent neuroprotective effects in neurodegenerative diseases, particularly its anti-ferroptotic activity, alongside anti-apoptotic, anti-inflammatory, and antioxidant properties, though its precise molecular mechanisms remain unclear. Against this background, the present study aimed to explore the regulatory role of the mTOR pathway in rotenone (ROT)-induced ferroptosis and PD progression in rats, and to further investigate whether crocin exerts neuroprotection by targeting this signaling pathway and inhibiting ferroptosis. Male Sprague–Dawley rats were randomized into control, ROT, and Crocin + ROT groups. The ROT group received subcutaneous ROT (1.5 mg/kg/day) for 21 days to induce chronic PD; the Crocin + ROT group was gavaged with crocin (30 mg/kg) 2 h before each ROT injection. Subsequently, behavioral performance (open field, rotarod, and balance beam tests), striatal dopamine, reactive oxygen species (ROS), and 4-hydroxynonenal (4-HNE) levels (enzyme-linked immunosorbent assay, ELISA), substantia nigra (SN) histopathology (hematoxylin–eosin and Nissl staining), tyrosine hydroxylase (TH) immunohistochemistry, mitochondrial ultrastructure (transmission electron microscopy), glutathione (GSH), malondialdehyde (MDA), and Fe 2 ⁺ levels, and AKT/mTOR-related protein expression (Western blotting) were assessed. ROT induced motor dysfunction, reduced striatal dopamine levels, reduced TH-positive neurons in the SN, caused ferroptosis-like mitochondrial ultrastructural alterations, disrupted redox and iron homeostasis, and dysregulated the AKT/mTOR pathway ( P < 0.05 ). Crocin intervention significantly reversed these changes ( P < 0.05 ). Collectively, these findings suggest that crocin exerts neuroprotective effects in ROT-induced PD rats, possibly through modulation of the AKT/mTOR pathway and attenuation of ferroptosis and apoptosis.