Long Ding

Transport of Egg White ACE-Inhibitory Peptide, Gln-Ile-Gly-Leu-Phe, in Human Intestinal Caco-2 Cell Monolayers with Cytoprotective Effect.

The purpose of this study was to investigate the transepithelial transport and cytoprotective effect of Gln-Ile-Gly-Leu-Phe (QIGLF), an ACE-inhibitory peptide derived from egg white ovalbumin, in human intestinal Caco-2 cell monolayers. The results showed that QIGLF could be absorbed intact through Caco-2 cell monolayers with a Papp value of (9.11 ± 0.19) × 10-7 cm/s (transport kinetic parameters: Km, 32.37 ± 12.59 mM; Vmax, 1.23 ± 0.49 μM/min cm2). The transport was not significantly decreased by sodium azide and Gly-Pro, an ATP synthesis inhibitor and a peptide transporter 1 (PepT1) substrate, respectively, suggesting that transport of QIGLF was not energy-dependent and carrier-mediated. In addition, wortmannin, a transcytosis inhibitor, had little effect on the transport, suggesting that endocytosis was not involved in the transport of QIGLF. However, the transport of QIGLF was increased significantly in the presence of cytochalasin D, a tight junction disruptor, suggesting that paracellular transport via tight junctions was the major transport mechanism for intact QIGLF across Caco-2 cell monolayers. Moreover, QIGLF was added to Caco-2 cells followed by addition of H2O2, and exhibited significant cytoprotective effect in Caco-2 cells against oxidative stress induced by H2O2.

Transport of Antihypertensive Peptide RVPSL, Ovotransferrin 328–332, in Human Intestinal Caco-2 Cell Monolayers

The objective of this study was to investigate the transepithelial transport of RVPSL (Arg-Val-Pro-Ser-Leu), an egg-white-derived peptide with angiotensin I-converting enzyme (ACE) inhibitory and antihypertensive activity, in human intestinal Caco-2 cell monolayers. Results revealed that RVPSL could be passively transported across Caco-2 cell monolayers. However, during the process of transport, 36.31% ± 1.22% of the initial RVPSL added to the apical side was degraded, but this degradation decreased to 23.49% ± 0.68% when the Caco-2 cell monolayers were preincubated with diprotin A (P < 0.001), suggesting that RVPSL had a low resistance to various brush border membrane peptidases. When transport from the apical side to the basolateral side was investigated, the apparent permeability coefficient (Papp) was (6.97 ± 1.11) × 10(-6) cm/s. The transport route of RVPSL appears to be the paracellular pathway via tight junctions, as only cytochalasin D, a disruptor of tight junctions (TJs), significantly increased the transport rate (P < 0.001). In addition, the relationship between the structure of RVPSL and transport across Caco-2 cell monolayers was studied by mutation of RVPSL. It was found that N-terminal Pro residues were more beneficial for transport of pentapeptides across Caco-2 cell monolayers than Arg and Val. Furthermore, RVPSL could be more easily transported as smaller peptides, especially in the form of dipeptides and tripeptides.

Intracellular ROS scavenging and antioxidant enzyme regulating capacities of corn gluten meal-derived antioxidant peptides in HepG2 cells

The objective of this study was to investigate the intracellular reactive oxygen species (ROS) scavenging activities and antioxidant enzyme regulating capacities of corn gluten peptide fractions (CPFs) in HepG2 cells. A cellular antioxidant activity (CAA) assay was used to assess their antioxidant activities and revealed that both CPF1 (molecular weight <1kDa) and CPF2 (molecular weight between 1 and 3kDa) exhibited high cellular antioxidant activities with EC50 values of 2.85±0.19mg/mL and 5.05±0.32mg/mL, respectively. Both CPFs also exhibited cytoprotective effects and intracellular ROS scavenging activities in HepG2 cells subjected to oxidative stress by oxidation with H2O2. In addition, at concentrations of 2.50mg/mL, the CPFs increased the activity levels of superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR), as well as the total glutathione (GSH) levels in oxidized HepG2 cells (from 86.54% to 114.14% (CPF1) or 109.72% (CPF2) for SOD activity; from 71.91% to 107.64% (CPF1) or 106.50% (CPF2) for CAT activity; from 70.52% to 103.01% (CPF1) or 104.10% (CPF2) for GR activity; and from 81.39% to 114.00% (CPF1) or 108.82% (CPF2) for total GSH levels). These results suggested that both CPF1 and CPF2 exhibited positive effects on the activities of the intracellular antioxidant enzymes SOD, CAT and GR, as well as on the total GSH levels in HepG2 cells under conditions of oxidative stress. Furthermore, size exclusion gel chromatography and MALDI-TOF/TOF mass spectrometry revealed that the molecular weights of the antioxidant peptides in CPF1 were between 500Da to 900Da, and a novel antioxidant peptide consisting of GLLLPH (Gly-Leu-Leu-Leu-Pro-His) was identified in CPF1.

Digestion and absorption of an egg white ACE-inhibitory peptide in human intestinal Caco-2 cell monolayers

Abstract The objective of this study was to investigate the digestion and absorption of egg white-derived angiotensin I-converting enzyme (ACE)-inhibitory peptide TNGIIR in human intestinal Caco-2 cell monolayers. Results showed that the digestion of TNGIIR to simulated gastrointestinal enzymes and brush border membrane peptidases were 5.87% ± 1.92% and 17.17% ± 0.64%, respectively (p < 0.05). The apparent permeability coefficients (Papp) of TNGIIR from the apical to basolateral side in Caco-2 cell monolayers was determined to be (4.92 ± 0.40) × 10−6 cm/s, indicating that TNGIIR can transport across Caco-2 cell monolayers in intact form. In addition, only cytochalasin D, a disruptor of tight junctions (TJs), changed TNGIIR transport rate significantly (p < 0.05), suggesting that the main transport route for TNGIIR across Caco-2 cell monolayers was paracellular pathway via TJs.

Short- and long-term antihypertensive effect of egg protein-derived peptide QIGLF

BACKGROUND The present study aimed to investigate the in vivo antihypertensive effect on spontaneously hypertensive rats (SHRs) induced by egg protein-derived peptide QIGLF, which has been previously characterized in vitro as a potent angiotensin-converting enzyme inhibitor. RESULTS In vivo antihypertensive effect of QIGLF orally administered was evaluated by the tail-cuff method. The systolic blood pressure and the diastolic blood pressure of rats were measured 0, 5, 10, 15 and 20 h after administration every day. Subsequently, the effect of QIGLF on angiotensin-converting enzyme mRNA expression in the kidney of SHRs was evaluated by a polymerase chain reaction. Systolic blood pressure was found to be reduced markedly in the SHRs after a single oral administration. CONCLUSION The results show that the effect of QIGLF (50 mg kg-1 body weight) was similar to that of captopril (10 mg kg-1 body weight) with respect to lowering systolic blood pressure in SHRs. Therefore, egg white protein-derived peptide QIGLF may be useful in the prevention or treatment of hypertension.

The enrichment and characterization of ginger-derived glycoprotein using magnetic particles

Ginger-derived glycoproteins are a widely distributed group of biological macromolecules with multiple functions. To date, the structure of ginger-derived glycoproteins has not been clarified with regard to their complexity, their sequence diversity and their uneven micro-distribution. In this study, a lectin microarray was used to evaluate 37 types of lectins and determine the optimal lectins that can conjugate with glycoproteins based on the fluorescence intensity. Subsequently, the lectins were immobilized on magnetic beads, coupled with glycoproteins to enrich ginger-derived glycoproteins, and evaluated using SDS-PAGE. Our results showed that five lectins (e.g. VVA, ConA, STL, LEL, and LCA) were selected by the lectin microarray and that VVA showed the highest fluorescence intensity. In addition, it is indicated that the structure of the carbohydrate chains might contain GlaNAc, mannose, GlcNAc, and LacNAc.

Novel Angiotensin-Converting Enzyme Inhibitory Peptides Derived from Oncorhynchus mykiss Nebulin: Virtual Screening and In Silico Molecular Docking Study: ACE inhibitory peptides derived from Oncorhynchus mykiss Nebulin…

Excessive concentrations of angiotensin-converting enzyme (ACE) can give rise to high blood pressure, and is harmful to the body. ACE inhibitory peptides from food proteins are considered good sources of function food. However, the preparation of ACE inhibitory peptides by classical method faces many challenges. Three novel ACE inhibitory peptides were identified by in silico methods, and showed potent activity against ACE in vitro. The simulation hydrolysis of nebulin was performed with ExPASy PeptideCutter program. Potential activity, solubility, and absorption, distribution, metabolism, excretion, and toxicity properties of generated peptides were predicted using program online. Molecular docking displayed that EGF, HGR, and VDF were docked into the S1 and S2 pockets of ACE. Meanwhile, Phe and Arg at the C-terminal enhance ACE affinity. The IC50 values of EGF, HGR, and VDF were 474.65 ± 0.08, 106.21 ± 0.52, and 439.27 ± 0.09 μM, respectively. Three peptides EGF, HGR, and VDF from Oncorhynchus mykiss nebulin were identified, and the molecular mechanism between ACE and peptides was clarified using in silico methods. The results suggested that Oncorhynchus mykiss nebulin would be an attractive raw material of antihypertensive nutraceutical ingredients. PRACTICAL APPLICATION This study has shown the potential of Oncorhynchus mykiss nebulin as good sources for producing ACE inhibitory peptides. According to this finding, in silico approach is the feasible way for prediction and identification of food-derived ACE inhibitory peptides in emerging nutraceutical field.

Individual and Synergistic Antioxidant Effects of Dipeptides in In Vitro Antioxidant Evaluation Systems

This study aimed to investigate the individual and synergistic antioxidant effects of dipeptides in vitro. Based on a study of amino acid antioxidant activities, 36 dipeptides were chosen. All their individual antioxidant effects were tested in in vitro antioxidant evaluation systems, including the DPPH, ABTS, ORAC, and FRAP assays. Based on the results of individual antioxidant effects of these dipeptides, some of them were chosen to study their synergistic antioxidant effects in the four antioxidant assays. The results of the DPPH assay showed that dipeptides containing Cys exhibited radical scavenging activity. The synergistic antioxidant assay indicated that LC and CH, LC and CN, LC and CE, CH and CN, CH and CE, and CN and CE have significant synergistic effects (p < 0.01) in the DPPH assay. Moreover, the results of the ABTS assay showed that 17 dipeptides have ABTS radical scavenging activities and that all of them contain Cys, Trp, and Tyr residues. Their synergistic antioxidant assay showed that CR and CH, YR and YK, YR and YN, and WK and IW showed highly significant synergistic antioxidant effects (p < 0.01). The results of the ORAC assay showed that 22 dipeptides possessed ORAC activities and that all of them have one or two Cys, His, Met, Trp, and Tyr residues. The synergistic effects of CH and HL, WK and WR, YK and WR, LC and FM, FM and CH, and WK and IW were significant (p < 0.01). Finally, in the FRAP assay, six dipeptides showed ferric reducing antioxidant activities and all of them contained the Cys residue. The synergistic antioxidant effects of HV and CN, CK and CN, CH and CN, and CE and CN were also significant (p < 0.01). These findings indicate that the individual and synergistic antioxidant effects of dipeptides are related to their constituent amino acids. These results may help study other individual and synergistic antioxidant effects of dipeptides.

Hydrolysis and transepithelial transport of two corn gluten derived bioactive peptides in human Caco-2 cell monolayers

The objective of this paper was to investigate the transepithelial transport of two novel corn gluten-derived antioxidant peptides, YFCLT and GLLLPH, using Caco-2 cell monolayers. Results showed that both of YFCLT and GLLLPH could transport in intact form across Caco-2 cell monolayers with apparent permeability coefficient (Papp) values of (1.10±0.16)×10-7cm/s and (1.98±0.23)×10-7cm/s, respectively. However, it was found that the two peptides were susceptible and easily hydrolyzed by brush border membrane peptidases. In the presence of diprotin A, an inhibitor of dipeptidyl peptidase IV (DPPIV), the hydrolysis of YFCLT and GLLLPH decreased and their permeabilities increased significantly compared to control group (P<0.05). The results of transport routes revealed that Gly-Sar, a peptide transporter 1 (PepT1) substrate, had little effects on the transepithelial permeability (P>0.05), suggesting that the transport of YFCLT and GLLLPH across Caco-2 cell monolayers was not mediated by PepT1. However, it was found that cytochalasin d, a tight junctions (TJs) disruptor, increased the permeability significantly (P<0.05). While wortmannin, a transcytosis inhibitor, and sodium azide, an ATP synthesis inhibitor, both decreased the permeability significantly (P<0.05). It indicated that the TJs-mediated paracellular pathway and energy-dependent transcytosis were involved in the transport of YFCLT and GLLLPH across Caco-2 cell monolayers.

Direct inhibition of Keap1–Nrf2 interaction by egg-derived peptides DKK and DDW revealed by molecular docking and fluorescence polarization

Egg-derived small peptides have various biological activities, including antioxidant properties. The Keap1–Nrf2 pathway is central to cell resistance to oxidative stress. In this study, we screened an egg-derived short peptide library to identify molecules with a potential to directly inhibit the Keap1–Nrf2 interaction, using molecular docking, fluorescence polarization assay, and a cytotoxicity model. Among the 20 small peptides selected by molecular docking, two tri-peptides, DKK and DDW, could directly inhibit the binding of the Keap1 Kelch domain to the FITC-labelled 9-mer Nrf2 peptide, as evidenced by increased Kd in fluorescence polarization experiments. Furthermore, in H2O2-treated cells, DKK and DDW promoted survival and upregulated the activity of catalase and superoxide dismutase, key enzymes involved in detoxification of reactive oxygen species. Our findings indicate that small egg-derived peptides DKK and DDW can exert antioxidant effects and protect cells against oxidative stress by directly inhibiting Keap1–Nrf2 interaction.