Sericin alleviates restraint stress induced depressive- and anxiety-like behaviors via modulation of oxidative stress, neuroinflammation and apoptosis in the prefrontal cortex and hippocampus.

This study was aimed to examine the effects of sericin administration on restraint stress induced anxiety- and depressive-like behaviors, oxidative stress, inflammation and apoptosis in the prefrontal cortex (PFC) and hippocampus (HIP) of mice. Animals were subjected to chronic restraint stress (3 h/day for 21 days) to induce a depressive-like model. Sericin was administered at different doses (100, 150, and 200 mg/kg/day, gavage for 21 days) along with immobilization. Elevated plus maze (EPM) and open field test (OFT) were performed to assess anxiety; while, the forced swim test (FST) and tail suspension test (TST) were implemented to evaluate depressive-like behaviors. Mitochondrial membrane potential (MMP), and markers of oxidative stress, neuroinflammation, and apoptosis were evaluated in the PFC and HIP regions. Moreover, serum levels of corticosterone were measured. Results showed that sericin increased number of central entries in OFT and prolonged time spent in open arms of EPM apparatus, while it reduced immobility time in TST and FST. Moreover, sericin treatments decreased oxygen species (ROS) and lipid peroxidation levels, restored MMP, and enhanced total antioxidant capacity (TAC) and enzyme activity of GPx and SOD in both brain regions. Furthermore, sericin reduced serum corticosterone concentration and suppressed neuroinflammatory response in the HIP and PFC, shown by decreased NF-κB, TNF-α, and IL-1ß protein levels. Finally, sericin inhibited mitochondrial-dependent apoptosis pathway through down-regulation of Bax, cytochrome c, caspase-9 and -3, and up-regulation of Bcl-2 protein. These findings provide evidence for the protective effect of sericin therapy against psychopathological and behavioral changes induced by restraint stress.

Identification and applications of neuroactive silk proteins: a narrative review.

In traditional medicine, natural silk is regarded as a cognitive enhancer and a cure for ameliorating the symptoms of heart disease, atherosclerosis, and metabolic disorders. In this review, general characteristics of both silk proteins, fibroin and sericin, extracted from silkworm Bombyx mori and their potential use in the neuronal disorders was discussed. Evidence shows that silk proteins exhibit neuroprotective effects in models of neurotoxicity. The antioxidant, neuroprotective, and acetylcholinesterase inhibitory mechanisms of silk proteins could prove promising in the treatment of neurodegenerative diseases. Owing to their excellent neurocompatibility and physicochemical properties, silk proteins have been used as scaffolds and drug delivery materials in the neuronal tissue engineering. These data support the potential of silk proteins as an effective complementary agent for central and peripheral neurological disorders.