Protective Mechanism Of GSPE On Ouabain-Induced Hypertensive Target Organ Damage: On Rats

Essential hypertension is a major risk factor for cardiovascular mortality through its effect on the target organs including heart, brain, kidney and vessels. Therefore, treatment of hypertension is not only the blood pressure control, but also target organ protection.Ouabain, an inhibitor of Na+ pump secreted by adrenal gland, belongs to the family of steroid hormones. A lot of studies showed that ouabain plays a pivotal role in target organ impairment and cardiovascular remodeling during hypertension. Ouabain induced hypertensive rats are well established animal model to study the mechanism of hypertension. Here we also use this model to study the target organ changes during hypertension and the further mechanism.Grape seed proanthocyanidin extract (GSPE) is a potent antioxidant proved to be protective in cardiovascular system, not only due to its anti-oxidative but also anti-inflammation and endothelial cell protective effect. GPSE is well known in protecting ischemia heart from reperfusion injury. However, the role of GSPE in hypertension is not clear. In this study, we will investigate the effect of GSPE in ouabain induced hypertensive rats and the underlying mechanism.PartⅠOuabain induced hypertensive rats and target organ damage Nowadays, primary hypertetion is the main cause of cardiovascular mortality. The morbidity of primary hypertension increases in China recent years. There are about 160,000,000 hypertensive patients in China, compared to 1991, the prevalence of hypertension rises to 18.8%.Vascular remodeling and functional change is not only the secondary onset of hypertension, but also the possible cause of elevated blood pressure. It is reported that the target organ impairment may exist at the very beginning of hypertension, which is independent of blood pressure elevation. The mechanism and the pathophysiological results of hypertension, which comes first, is hardly to answer. Therefore, to define whether the vascular remodeling and target organ impairment happens before blood pressure elevation, is the burning question for hypertension prevention and treatment. In this part, we established hypertensive rat model by intraperitoneal injection of low dose ouabain, to see whether ouabaine leads to target organ damage directly, independent of blood pressure elevation.Method1.40 male SD rats were randomly divided into the oubain group (27.8μg·kg-1 of ouabaine injected intra-peritonealy everyday) and the N.S. control group (1ml saline injected peritonealy everyday).10 rats from each group were sacrificed at the end of 3th week and the rest at the end of 6th week, and the brain, heart, kidney and aortas were collected.2. The tail blood pressure and body weight were measured weekly.3. The organs collected were subjected for detection under microscope after H.E. staining, Nissl’s staining for neurons and Sirius red staining for aortas, and also for transmission electron microscope.Results1. The blood pressure of the ouabain group rise moderately during the first 3 weeks and elevated significantly since the 6th week, compared to almost no change of blood pressure in the N.S. group.2. The ultrastructure of the aortas from the ouabain rats changed from the 3th week and became notable since the 6th week while those in the control group remained the same.Conclusion 1. Lose dose ouabain can successfully induce hypertension in rats after 6 weeks peritoneal injection.2. The ultrastructure changed even before the blood pressure elevation, indicating that abnormally increased ouabain may lead to target organ damage directly and independently of the blood pressure elevation.3. Ouabain induced hypertensive rat model is an ideal hypertension model.PartⅡProtective mechanism of GSPE on the target organs of ouabain induced hypertensive ratsGSPE is a kind of natural polyphenol extracted from grape seeds. The cardiac protective effect of GSPE during atherosclerosis and reperfusion injury is well proved, not only for antioxidant but also anti-inflammation ability. In this section, the effect of GSPE during hypertension was studied in ouabain induced hypertensive rats model.Methods40 male SD rats were randomly divided into the oubain group (27.8μg·kg-1 of ouabain injected intra-peritonealy plus 1ml N. S. intragastrically everyday) and the GSPE group (27.8μg·kg-1 of ouabaine injected peritonealy plus GSPE 250mg·kg-1 intragastrically everyday). At the end of the experiments, all rats from each group were sacrificed, and aortas were collected for detection under microscope after H.E. staining, and also for transmission electron microscope. Immuno-staining, PCR and Western blot were carried out to detect the expression of NF-κB and TGF-β1.Results1. During the whole experiment, the rats in GSPE group only exhibited mild elevation of blood pressure, compared to significant increase in ouabain group. 2. GSPE reverse the aortic remodeling induced by ouabain.3. GSPE treatment significantly reduce the expression of NF-κB and TGF-β1 induced by ouabain (p<0.05 or 0.01).Conclusion1. GSPE can decrease the blood pressure and prevent vessel remodeling induced by ouabain.2. Ouabain induced hypertensive vessel remodeling was significantly increased, while GSPE can inhibit vessels remodeling in the aorta.3. Inhibition of NF-κB/TGF-. ipathway hence alleviate regional inflammation of GSPE may contribute to its target organ protective effect.