Effects Of Puerarin On Changes In The Responses To Hypoxia In Hypercholesterolemic Rats

Hypercholesterolemia (HC) is one of key risk factors forcardiovascular diseases. Previous studies have demonstrated HC maylead to chronic hypoxia or intermittent hypoxia at the early stage. Onepotential mechanism might be hypoxia may lead to oxidative stress,endothelial dysfunction and so on, or induce complicated damagesthrough adaptation reaction by upregulating expression of hypoxiainducible factor (HIF) and other hypoxia inducible genes. At present,the relationship between HC and HIF-1 remain unclear. So to study therelationship between them is very important for underlying mechanismof hypercholesterolemic damages and patho-physiologies, finding newtherapeutic measure and preventing cardiovascular diseases.This study was designed to investigate effects of Pur on changesindexes of HIF-1αand relative pathophysiology at the early differentages in hypercholesterolemic rats (ig with high cholesterol emulsion atdifferent periods: 10day and 28 day). SPF male Sprague-Dawley ratswere randomly divided into 6 groups, and treated with 3 treatments:normal control (NC) group (fed with normal feedstuffs), HC group(igwith high cholesterol emulsion 9 ml/kg twice a day on the basis of feeding with normal feedstuffs)and hypercholesterolemia plus Pur(HP) group(ip with Pur injection 40 mg/kg twice a day on the basis offeeding with high cholesterol emulsion). At the end of the experimentperiod, level of total serum cholesterol (TC), serum nitric oxide (NO)level before and after i.v. acetylcholine (ACh), thoracic aortic ringACh-induced endothelium-dependent relaxation, the content of themalondiadehyde (MDA), and superoxide dismutase (SOD), and thelevel of hypoxia inducible factor-1α(HIF-1α) (by western blotting) incerebral tissue were measured.At the end of experiment, there was no significant difference inserum TC level between NC_10d(1.17±0.19 mmol/L) and NC_28d(1.34±0.10mmol/L). Serum level of TC was 4.87±1.20 mmol/L in He_10d group(were significantly increased compared with NC_10d group, P＜0.01),7.33±0.97 mmol/L high in HC_28d(significantly increased comparedwith HC_10d, P＜0.01), 3.80±1.15 mmol/L in HP_10dgroup(P＞0.05), and6.16±0.52 mmol/L in HP_28d group(P＜0.05). All observed that ratmodels of HC were successfully designed, and Pur can decrease theserum level of TC on some extent. Endothelium-dependent relaxationof thoracic aortic rings were not obviously impaired in HC_10d group,however, 10^-7 mol/L ACh-induced endothelium-dependent relaxationof thoracic aortic rings were significantly decreased in HC_28d groupcompared with NC group (P＜0.05). Serum NO level were significantly decreased between HC_10d and HC_28dgroups compared with NC group,the same to Ach irritation. However, the level of serum NO in HC_28dgroup showed significantly less than that in HC_10d group (P＜0.05).Thoracic aortic ring was not obviously impaired on 10th days, butserum NO content was decreased than NC group; when it to 28th days,serum NO content was significantly decreased furtherly compared with10d and it showed obvious endothelial dysfunction. The experimentshows endothelium-dependent relaxation generally depends on thelevel of NO, it will induce endothelial dysfunction when NO wasdecreased to one level. The level of MDA in HC_10d group weresignificantly higher than NC group (P＜0.05), and SOD activity wasunchanged. HC_28d group showed the level of MDA increased furtherly(P＜0.01), and SOD activity was significantly less (P＜0.01). It showedno significant difference among 3 group of 10 days; after 4 weeks,protein expression of HIF-1αin rat's cerebral tissue was significantlymore than NC in HC_28d group(P＜0.05). All these indicated that at anearly age of HC, it showed decreased NO level, endothelial dysfunctionand oxidative stress; upregulared HIF-1 expression showed it may leadto hypoxia, oxidative stress and so on. Thus, chronic hypoxia orintermittent hypoxia resulted from an early stage of HC may be a keyfactor for HC damages.In all, at an early stage of HC, it upregulared HIF-1αexpression and the levels of MDA were higher than NC. The level of serum NOwere significantly decreased between HC_10d and HC_28d groupscompared with NC group, the same to Ach irritation. However, thelevel of serum NO in HC_28d group showed significantly less than HC_10dgroup. Pur might improve their dysfunction and enhance SOD activitydepended on the time. All these indicated that HC may lead to chronichypoxia or intermittent hypoxia at an early stage, and the organismshowed oxidative stress, endothelial dysfunction and upregularedHIF-1 expression. Pur can alleviate the diminish the damages in earlyHC because of its vasodilation,anti-oxidation,decreasing blood fat,protecting endothelial function and inducing HIF-1α. However, theeffects on inducing HIF-1αwill be researched further.