Preparation and characterization of cysteine-rich collagen peptide and its antagonistic effect on microplastic induced damage to HK-2 cells

Cysteine (Cys) plays a significant role in the stability and antioxidant capacity of peptide. This study was to prepare Cys-rich collagen peptide and evaluate its preventive effect on microparticle (MPs)-induced HK-2 cell damage. The results showed that the Cys-rich peptides (AMP-C) were successfully prepared from collagen hydrolysate by plastein reaction in the presence of exogenous Cys. The scavenging activities of 2,2-Diphenyl-1-picrylhydrazyl and hydroxyl radical of AMP-C were significantly higher than those of original peptides without Cys. The fraction with molecular weight <3 kDa (AMP-CA) significantly improved MPs-induced damage and apoptosis of HK-2 cells. Compared with the same fractions lacking Cys (AMP-A), AMP-CA showed better performance in reducing reactive oxygen species and increasing the total superoxide dismutase and glutathione peroxidase levels, which may be related to its down-regulation of Kelch-like ECH-associated protein 1 (Keap1) expression. In addition, AMP-CA showed strong effects on inhibiting interleukin-6, tumor necrosis factor-α, monocyte chemoattractant protein-1, kidney injury molecule-1, and nuclear factor kappa-B levels. Finally, 330 Cys-containing peptides were isolated from AMP-CA, among which Leucine-Glycine-Asparagine-Glycine-Cysteine-Proline (LGNGCP) showed the lowest binding energy with Keap1 protein. In conclusion, the Cys-rich collagen peptide with higher antioxidant activity was successfully prepared by plastein reaction, which alleviated the HK-2 cells damage induced by MPs through antioxidant and anti-inflammatory. Our findings suggested that Cys-rich collagen peptide might be used as a functional food to mitigate health hazards associated with MPs accumulation.