To investigate the feasibility of using lumbrokinase as a protease in the development of bioactive peptides, and to study the antihypertensive activity of porcine blood protein ACE inhibitory peptides and explore their mechanisms of action, this study extracted and purified lumbrokinase with an enzyme activity of 43125.87 U/mg protein from earthworms, and used it to prepare porcine blood protein ACE inhibitory peptides. After separation and purification, an ACE inhibitory peptide with an ACE inhibition activity of 91.30% was obtained, named PBEP-M. A cell damage model was established by inducing HUVEC cells with Ang II. The toxicity of PBEP-M on HUVEC cells was determined using the CCK-8 assay, while the secretion levels of ET-1, NO, and ROS cytokines were measured using ELISA kits. Western Blot analysis was used to detect the expression of related proteins in the ACE - Ang II - AT1-R pathway. The experimental results indicated that when the mass concentration of PBEP-M ranged from 62.5 to 1000 μg/mL, it significantly promoted cell proliferation (P < 0.05). The 500 μg/mL PBEP-M treatment group significantly increased NO secretion (P < 0.05), which was 84.00% higher compared to the Ang II group. Additionally, PBEP-M significantly inhibited the secretion of ET-1 and ROS, reducing them by 53.66% and 36.94%, respectively, compared to the Ang II group. Furthermore, PBEP-M significantly inhibited the expression of ACE, Renin, and AT1-R (P < 0.05), reducing their levels by 76.76%, 83.96%, and 89.05%, respectively, compared to the Ang II group. Moreover, PBEP-M promoted the expression of eNOS protein (P < 0.05), which was increased by 8.77 times compared to the Ang II group. These findings suggest that the porcine blood protein ACE inhibitory peptide prepared using lumbrokinase can improve endothelial injury and exert a blood pressure-regulating effect.
