Peptide GEQQQQPGM derived from rice α-globulin reduces the risk of atherosclerosis in hamsters by improving vascular endothelial cells injury

Abstract

A previous study has confirmed that oral administration of rice α-globulin (100 mg per day per kg bodyweight) efficiently prevents atherosclerosis disease in male apolipoprotein E-deficient (ApoE^−/−) mice. However, the key peptide in rice α-globulin after gastrointestinal digestion and absorption as well as its anti-atherosclerosis mechanism still remain unclear. We obtained the absorbable part in the simulated digestive products of rice α-globulin by everting the intestinal sacs followed by purification using gel filtration chromatography and high performance liquid chromatography. The peptide GEQQQQPGM was confirmed to be one of the key fragments in rice α-globulin by LC-MS/MS (liquid chromatography-mass spectrometry/mass spectrometry). We investigated the hypocholesterolemic effect of the peptide in hamsters fed a hypercholesterolemic diet. The synthetic peptide GEQQQQPGM was orally administrated to hamsters at a dose of 100 mg per kg bodyweight, and deionized water was orally administrated to the normal and control hamsters for 30 days. In the peptide group, plasma total and LDL cholesterol concentrations and atherogenic index were significantly lower than those in the control group. To investigate the anti-atherosclerosis mechanism of the peptide, the effects of the GEQQQQPGM peptide derived from rice α-globulin on vascular endothelial cells injury were studied. The cell model was established using 10 ng mL⁻¹ of tumor necrosis factor-α (TNF-α). The study was performed on HUVECs that were pretreated with 50 μg mL⁻¹ of GEQQQQPGM. The cell viability and indicators of inflammation and oxidative stress were measured. The decreased viability of the HUVECs induced by TNF-α was significantly increased by GEQQQQPGM. The peptide obviously reduced the levels of monocyte chemoattractant protein-1 (MCP-1), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1). It also effectively affected the antioxidant indices such as it decreased the levels of nitric oxide (NO), inducible nitric oxide synthase (iNOS), malondialdehyde (MDA), and reactive oxygen species (ROS), whereas increased the activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD). Furthermore, GEQQQQPGM inhibited nuclear translocation and expression of p65 protein by decreasing the inhibitor of κB kinase α (IKKα) protein and up-regulating the inhibitor of nuclear factor κB kinase (IκB) protein. These results demonstrated that GEQQQQPGM reduced TNF-α-induced vascular endothelial cell injury by inhibiting the inflammatory response and oxidative stress, thereby reducing the risk of atherosclerosis.