Cytoprotective Effects of Antioxidant Peptides from Red Californian Worm (Eisenia foetida) Hydrolysate on Differentiated Caco-2 Cells

BACKGROUND/OBJECTIVES

When prooxidants outweigh antioxidants, oxidative stress can occur, causing an accumulation of reactive oxygen species (ROS). This process can lead to cellular damage and plays a role in the development of numerous health conditions. This study aimed to investigate the cytoprotective effects on differentiated Caco-2 cells of hydrolysates derived from the red Californian worm (WH) and their fractions, identify the peptides responsible for this effect, and elucidate the mechanisms involved.

METHODS

The WH was obtained through hydrolysis with Alcalase 2.4 L and subsequently fractionated to two fractions (F > 3 kDa and F < 3 kDa) using a ceramic membrane with a molecular weight cutoff of 3 kDa. The peptides found in the F < 3 kDa fraction, demonstrating the highest cytoprotective activity, were then sequenced via liquid chromatography-mass spectrometry analysis (LC-MS/MS), and molecular docking was conducted to elucidate the underlying antioxidant mechanisms.

RESULTS

The hydrolysate of Eisenia foetida and its F < 3 kDa fraction exhibited no cytotoxicity, protected the cells from H2O2-induced oxidative stress (50% increase viability), preserved cell viability by restoring their redox status (ROS: 20% decrease, and glutathione (GSH): recovered to basal control levels) and cell cycle distribution, and decreased apoptosis (16%). Twenty-eight peptides were identified, with five showing antioxidant activity through stable interactions with myeloperoxidase (MPO) and Kelch-like ECH-associated protein 1 (Keap-1), KPEDWDDR being the peptide that presented the highest affinity with both molecules (-7.9 and -8.8 kCal/mol, respectively).

CONCLUSIONS

These results highlight the WH as a potential source of bioactive peptides for the management of oxidative stress.

Evaluation of egg white hydrolysates on the hepatoprotective effect in vitro and in vivo

The small molecule characteristics and nutritional value of egg white hydrolysates have been widely used. In the present study, in vitro and in vivo models were used to investigate the hepatoprotective effect of egg protein hydrolysate (EWH) by regulating the expression of antioxidant enzymes. The in vitro experiment results showed that 0.1, 0.5, and 1 mg/mL of EWH enhanced antioxidant activity in HepG2 cells by increased glutathione peroxidase (GPx) activity and reduced glutathione (GSH) levels. The in vivo experiment results showed that EWH (L) (38.5 mg/kg BW) and EWH (H) (385 mg/kg BW) alleviated carbon tetrachloride (CCl4)-induced hepatotoxicity in SD rats through reduced levels of serum aspartate aminotransferase (AST) alanine aminotransferase (ALT), and lipid peroxidation products malondialdehyde (MDA). In addition, EWH also ameliorates CCl4-induced hepatotoxicity in SD rats by increasing the antioxidant activity of GSH levels with a decrease in oxidized glutathione (GSSG) levels. Besides, EWH ameliorates liver tissue injuries by CCl4-induction. EWH has the highest glutamic acid in free amino acid composition, the second highest was aspartic acid, and the third was cystine, 204, 141, and 125 mg/100 g, respectively. These results suggest EWH has hepatoprotective potential through reduced lipid peroxidation products and enhanced antioxidant activity.

Characterization and Genome Analysis of Cladobotryum mycophilum, the Causal Agent of Cobweb Disease of Morchella sextelata in China

Cobweb disease is a fungal disease that can cause serious damage to edible mushrooms worldwide. To investigate cobweb disease in Morchella sextelata in Guizhou Province, China, we isolated and purified the pathogen responsible for the disease. Through morphological and molecular identification and pathogenicity testing on infected M. sextelata, we identified Cladobotryum mycophilum as the cause of cobweb disease in this region. This is the first known occurrence of this pathogen causing cobweb disease in M. sextelata anywhere in the world. We then obtained the genome of C. mycophilum BJWN07 using the HiFi sequencing platform, resulting in a high-quality genome assembly with a size of 38.56 Mb, 10 contigs, and a GC content of 47.84%. We annotated 8428 protein-coding genes in the genome, including many secreted proteins, host interaction-related genes, and carbohydrate-active enzymes (CAZymes) related to the pathogenesis of the disease. Our findings shed new light on the pathogenesis of C. mycophilum and provide a theoretical basis for developing potential prevention and control strategies for cobweb disease.

Structural characteristics and improved in vitro hepatoprotective activities of Maillard reaction products of decapeptide IVTNWDDMEK and ribose

Here, a novel decapeptide IVTNWDDMEK with Maillard reactivity derived from scallop Chlamys farreri mantle was identified. The structural characteristics and in vitro hepatoprotective effects of IVTNWDDMEK conjugated with ribose were further investigated. The changes in decapeptide structures were determined by ultraviolet-visible (UV-vis), Fourier transform infrared (FTIR), and atomic force microscopy (AFM), and the modification sites induced by Maillard reaction of IVTNWDDMEK and ribose were monitored by high performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS). Maillard reaction products (MRPs) of IVTNWDDMEK-ribose demonstrate hepatoprotective benefits through the suppression of DNA damage and apoptosis induced by oxidative stress in human HepG2 cells in addition to enhancing the antioxidant activities. Moreover, after treatment with decapeptide-ribose MRPs, the activities of cellular antioxidative enzymes, such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and glutathione reductase (GSH-Rx) were remarkably increased, while the content of malondialdehyde (MDA) was decreased compared with H₂ O₂ ^- treated group, thereby enhancing the intracellular antioxidant defenses. These findings demonstrate the potential utilization of decapeptide IVTNWDDMEK-ribose MRPs as food antioxidants to suppress oxidative damage. PRACTICAL APPLICATION: In recent years, several food-derived bioactive peptides and their derivatives are regarded as good dietary antioxidants for reducing oxidative stress and improving liver function. Here, a novel Maillard reactive decapeptide IVTNWDDMEK, identified from scallop mantle hydrolysates by peptidomics in the previous study was synthesized. Then, the correlation between intercellular antioxidant activities and chemical structure changes of IVTNWDDMEK-ribose Maillard reaction conjugates was further studied. The preferable hepatoprotective activities of decapeptide IVTNWDDMEK-ribose MRPs indicated that these MRPs could be potentially utilized as food antioxidants or additives in the production of nutritional foods.