A Angiotensin ? Converting Enzyme Inhibitory Oligopeptide From Tilapia(Oreochromis Niloticus) Fish Skin And Its Mechanism Study

Objective: Essential hypertension is of great research value as a classic cardiovascular diseases whose pathogen is not clear.Angiotensin I converting enzyme(ACE)inhibitors,represented by captopril,have a significant antihypertensive effect but also with adverse reactions such as dry cough and palpitations.Therefore,it is a current research hotspots to find natural alternatives with fewer side effects from other sources.Studies have shown that oxidative stress and inflammatory stimulation of endothelial dysfunction are pathological features of hypertension,while tilapia fish skin oligopeptides have antioxidant and anti-aging effects,may have potential antihypertensive effects.Methods: This research aim to study the ACE inhibitory activity of Tilapia skin Oligopeptide(TSO)Leu-Ser-Gly-Tyr-Gly-Pro,human umbilical vein endothelial cells(HUVEC)stimulated by Angiotensin ? were used as a cell model to study the mechanism of hypotensive activity.Results:(1)The half-inhibition rate(IC50)of TSO was 2.57 ?M,which showed mixed non-competitive inhibition,TSO with a initial hypotensive trend in SHRs.(2)Leu-Ser-Pro in TSO has been identified as an ACE inhibitor.The difference in activity between TSO and captopril may be due to the different interaction forces on the ACE molecule docking.(3)TSO effectively inhibited(p < 0.001)Ang ? stimulated productions of nitric oxide(NO)and reactive oxygen species(ROS),expressions of inducible nitric oxide synthase(i NOS),cyclooxygenase-2(COX-2)and endothelin-1(ET-1)and other inflammatory factors.(4)Ang ? activated the phosphorylation of mitogen-activated protein kinases(MAPK),high-concentration TSO treatment group down-regulated phosphorylation of extracellular regulated protein kinases(ERK),p38,and c-Jun N-terminal kinase(JNK)(p < 0.001),TSO increased Bcl-2/Bax expression(p <0.001),increased RAC-? serine/threonine protein kinase(Akt)pathwayphosphorylation(p < 0.001).The above results indicate that Ang ? stimulation causes endothelial cell endothelial dysfunction,TSO can attenuate endothelial dysfunction to lowering blood pressure for protect blood vessels.(5)TSO can inhibit the phosphorylation and nuclear insertion of nuclear factor-kappa B(NF-?B)p65 by inhibiting the degradation of the nuclear factor kappa inhibitory protein(I?B),significantly reduced the DNA binding activity of NF-?B(p< 0.001),revealing that p65 may enter the nucleus based on the DNA binding activity.(6)In molecular docking analysis TSO inhibited phosphorylation of NF-?B p65 may be due to it binding with NF-?B p65 through multiple hydrogen bonds.(7)TSO attenuates the expression of ?-glutamyltransferase(GGT),increases superoxide dismutase(SOD),glutathione(GSH),nuclear factor E2 related factor 2(Nrf2),heme oxygenase 1(HO-1)and other cytokine expression(p < 0.001),alleviates Ang ? induction activation of Nrf2 pathway.The above results indicate that Ang ? stimulation causes oxidative stress in endothelial cells,TSO can inhibit oxidative stress to lowering blood pressure for protect blood vessels.Conclusion: Results show that TSO has good ACE inhibitory activity,it may play a hypotensive effect by inhibiting endothelial dysfunction caused by inflammation and oxidative stress with potential to treat hypertension-related diseases.