Identification of Peptides from Edible Pleurotus eryngii Mushroom Feet and the Effect of Delaying D-Galactose-Induced Senescence of PC12 Cells Through TLR4/NF-κB/MAPK Signaling Pathways

<i>Pleurotus eryngii</i> mushroom has been proven to have anti-aging bioactivities. However, few studies have focused on edible <i>Pleurotus eryngii</i> mushroom feet peptides (PEMFPeps). In this paper, the effects of delaying the senescence of D-Galactose-induced PC12 cells were evaluated, and the mechanisms were also investigated. PEMFPeps were prepared by alkaline protease enzymolysis of edible <i>Pleurotus eryngii</i> mushroom feet protein (PEMFP), which mainly consisted of a molecular weight of less than 1000 Da peptides, primarily occupying 89.15% of the total. Simulated digestion in vitro of <i>Pleurotus eryngii</i> mushroom feet peptides (SID-PEMFPeps) was obtained in order to further evaluate the bioactivity after digestion. The peptide sequences of PEMFPeps and SID-PEMFPeps were detected by LC-MS/MS subsequently. Five new peptides of PEMFPeps and one new peptide of SID-PEMFPeps were identified. The effects of PEMFP, PEMFPeps, and SID-PEMFPeps on D-Galactose-induced senescence of PC12 cells were evaluated. PEMFP, PEMFPeps, and SID-PEMFPeps could all enhance antioxidant enzyme activities significantly, such as superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT); decrease the intracellular levels of malondialdehyde (MDA) and reactive oxygen species (ROS); and inhibit the senescence-associated β-galactosidase (SA-β-gal) activity, among which SID-PEMFPeps showed the best effects. Western blotting analysis confirmed that SID-PEMFPeps significantly regulated the expressions of key proteins such as TLR4, IKKα, IκBα, p65, ERK, and JNK1/2/3, which indicated that SID-PEMFPeps could delay D-Gal-induced senescence of PC12 cells through TLR4/NF-κB/MAPK signaling pathways. This is the first time to investigate PEMFPeps and SID-PEMFPeps protective effects and mechanisms. Our study could lay a solid foundation for PEMFPeps to be used as nutritional supplementation to reduce aging-related damage. And the application of PEMFPeps could also provide optional solutions in exploring more edible protein resources for human beings.