心肌缺血/再灌注损伤后的肺组织损伤

目的初步探讨心肌缺血／再灌注损伤对肺组织损伤的可能机制。方法选取雄性成年SD大鼠（4～6月龄）,体重130～160g,建立成年大鼠缺血／再灌注模型。运用CK和MPO试剂盒检测肌酸激酶（CK）和髓过氧化物酶（MPO）的含量,运用双抗体夹心ABC—ELISA法检测细胞间黏附分子-1（ICAM-1）的含量。结果与伪手术组相比,缺血／再灌注大鼠的AN／AAR比值明显增高（P〈0．05）,CK在心肌缺血／再灌注大鼠血清中的含量明显升高（P〈0．05）,MPO与ICAM-1在心肌缺血／再灌注组大鼠血清和肺组织中含量明显升高（P〈0．05）。结论大鼠心肌缺血再灌注损伤后肺组织受到一定的损伤,可能与体循环中炎性介质的作用及肺组织的炎性应激有关。     

Panax notoginseng saponins attenuate acute lung injury induced by intestinal ischaemia/reperfusion in rats

Background and objective:   Acute lung injury remains a challenge for both clinicians and scientists. The effects of Panax notoginseng saponins (PNS) on acute lung injury induced by intestinal ischaemia/reperfusion (II/R) were studied in rats.
Methods:   Forty-eight Wistar rats were randomly assigned to four groups: (1) a sham-operated group that received laparotomy without II/R ( n = 12); (2) a sham + PNS group, which was identical to group 1 except for PNS treatment ( n = 12); (3) an II/R group that had 1 h of intestinal ischaemia followed by 3 h of reperfusion ( n = 12); and (4) an II/R + PNS group that received 100 mg/kg of PNS, i.v., 15 min before reperfusion ( n = 12). The effects of PNS administration on lung tissue histology, activities of oxidant and antioxidant enzymes, levels of malondialdehyde, nitric oxide and inducible nitric oxide synthase activity were examined. Levels of surfactant protein B, cell numbers in BAL fluid and plasma levels of pro-inflammatory cytokines were also examined.
Results:   Compared with the II/R group, pulmonary parenchymal damage, activities of oxidant enzymes, levels of malondialdehyde and nitric oxide, inducible nitric oxide synthase activity in lung tissue, and plasma levels of pro-inflammatory cytokines were significantly reduced by PNS treatment. In addition, the decreases in antioxidant enzyme activities were prevented in the II/R + PNS group. Total leukocyte and neutrophil counts were significantly decreased by PNS treatment. The decline in surfactant protein B levels in BAL fluid was reduced in the II/R + PNS group compared with the II/R group.
Conclusions:   Administration of PNS before reperfusion injury alleviates acute lung injury induced by II/R, and this is attributable to the antioxidant and anti-inflammatory effects of PNS.     

肺源性一氧化氮过度表达在急性坏死性胰腺炎肺损伤中的作用

目的 探讨肺源性一氧化氮（NO）过度表达对急性坏死性胰腺炎（ANP）肺损伤的影响。方法 将72只成年SD大鼠随机分为三组各24只。ANP组、ANP预处理组（预处理组）逆行性胰胆管注射5％牛磺酸钠建立ANP大鼠模型，对照组注射等量生理盐水。造模前30min，预处理组腹腔注射N-硝基-L-精氨酸甲酯（L-NAME）10mg／kg。造模后1、3、6、12h分别处死大鼠各6只，取肺泡巨噬细胞（AM）检测NO水平及诱导型一氧化氮合成酶（iNOS）mRNA表达情况及TNF-a水平，并行肺组织病理学检查。结果 ANP组肺损伤随时间延长而逐渐加重；AM分泌TNF-a，NO水平逐渐升高，至6h达到高峰，12h回落。AMiNOS mRNA的表达情况与NO的变化趋势相似。预处理组各指标变化趋势与ANP组相似，但各指标均低于ANP组（P均〈0．05）；肺组织髓过氧化物酶（MPO）、支气管肺泡灌洗液（BALF）蛋白含量、肺组织湿／干重值逐渐升高，12h达最高值．动脉血氧分压值逐渐降低。结论 ANP发生后肺泡AM的iNOS表达增强，肺源性NO过量表达，并促进TNF-a大量分泌，加重肺损伤，应用iNOS抑制剂则能减轻肺损伤。     

一氧化氮合酶在N-乙酰半胱氨酸调控大鼠心肌冷缺血-再灌注损伤中的变化

目的:观察一氧化氮合酶(NOS)在N-乙酰半胱氨酸(NAC)调控大鼠心肌冷缺血-再灌注损伤中的变化。方法:将健康雄性Lewis大鼠60只随机分为3组。(1)对照组:摘取供心前30 min,经供体大鼠下腔静脉注射生理盐水0.5 mL;(2)供体预处理组:摘取供心前30 min,经供体大鼠下腔静脉注射NAC300 mg/kg,受体大鼠不作预处理;(3)受体预处理组:移植前30 min,经受体大鼠下腔静脉注射NAC300 mg/kg,供体大鼠不作预处理。将冷藏于4℃HTK液18 h的供心移植至受体大鼠腹腔,建立同种异体心脏移植模型。于再灌注24 h后取供心采用免疫组化方法检测诱导型一氧化氮合酶/内皮型一氧化氮合酶(iNOS/eNOS)蛋白表达水平,以免疫组化评分(IHS)表示。采用Real time-PCR法检测iNOS/eNOS mRNA表达。结果:与对照组相比,供、受体预处理组的iNOS蛋白表达降低,IHS评分分别为3.00±0.15、1.50±0.22、1.63±0.26,P<0.05;而eNOS蛋白表达升高,IHS评分分别为2.00±0.21,3.60±0.16,3.40±0.26,P<0.05。与对照组相比,受体预处理组iNOS mRNA表达降低(0.43±0.17对1.00±0.41,P<0.05),供体预处理组eNOS mRNA表达升高(3.06±1.47对1.00±0.65,P<0.05)。结论:NOS参与了NAC预处理减轻移植大鼠心肌缺血-再灌注损伤的过程。     

Splenectomy-reduced hepatic injury induced by ischemia/reperfusion in the rat

Abstract: In the present study, we investigated the role of the spleen in experimental hepatic ischemia/reperfusion in the rat. After a 90-min period of ischemia in the left and middle hepatic lobes, the ischemia was released and the liver was reperfused for up to 24 h. Plasma alanine aminotransferase reached a peak 3 h after the onset of reperfusion, and gradually decreased thereafter. A histological examination revealed evidence of hepatocellular necrosis and degeneration, especially 24 h after the onset of reperfusion. In addition, there was a noticeable accumulation of polymorphonuclear cells in the liver following ischemia/reperfusion. A splenectomy performed just prior to ischemia/reperfusion reduced both biochemical and histological hepatocellular injury. The number of polymorphonuclear cells in the liver following ischemia/reperfusion was significantly reduced in rats subjected to splenectomy, suggesting that the increase in polymorphonuclear cells may contribute to liver injury. The number of mononuclear cells also increased in the marginal zones of the spleen following ischemia/reperfusion, and appeared to be derived from the splenic monocyte/macrophage population, based on immunohistochemical studies. The spleen plays an important role in the pathogenesis of hepatic ischemia/reperfusion injury and the splenic monocyte/macrophage population contributes to liver damage.     

白细胞介素-17在心肌缺血再灌注损伤中的作用

目的:通过大鼠心肌缺血再灌注损伤(IRI)模型,分析白细胞介素-17(IL-17)在IRI中的作用。方法:用阻断大鼠冠状动脉左前降支的方法制作IRI模型。Realtime-PCR及Western blot方法动态观察IRI后不同时间点心肌组织IL-17的表达水平,流式细胞术进一步检测IL-17的来源。应用抗IL-17抗体体内干预,观察其对IRI的作用。结果:IRI后1h就有IL-17的表达,并且在24h的观察期内持续存在,未有峰值出现。流式细胞术检测结果显示心肌组织中IL-17的主要来源是CD4+T细胞。用抗IL-17的抗体体内干预后,血清肌钙蛋白T的水平降低,心肌梗死面积也明显减小。结论:IL-17参与大鼠IRI过程,中和IL-17能明显减轻心肌IRI。     

NLRP3炎性体加重小鼠脑缺血再灌注损伤的机制探讨

目的：探讨Nod样受体蛋白3（NLRP3）炎性体（NLRP3蛋白、IL-1β、IL-8）在小鼠脑缺血再灌注损伤中的作用和机制。方法将C57BL／6小鼠随机分为对照组和格列本脲（ NLRP3抑制剂）组各20只,每组中一半小鼠通过大脑中动脉栓塞法构建缺血再灌注（ IR）模型,其余接受假手术处理。格列本脲组术前30 min腹腔注射500 mg／kg格列本脲。造模成功后对小鼠进行神经学评分,2,3,5,-氯化三苯基四氮唑染色,并计算缺血梗死面积,HE染色观察病理变化,TUNEL染色观察各组神经元凋亡情况,Western Blot检测小鼠脑组织NLRP3蛋白表达,ELISA检测小鼠脑组织中IL-1β、IL-18浓度。结果各组IR小鼠脑损伤程度均重于假手术小鼠,但是对照组IR小鼠脑损伤程度比格列本脲组严重。 HE染色和TUNEL染色显示,IR小鼠脑组织出现明显损伤,神经元凋亡数量明显增多,格列本脲可减轻IR造成的病理损伤程度。与对照组相比,格列本脲组的脑组织NLRP3蛋白表达及IL-1β、IL-18升高程度明显降低（ P均＜0．05）。结论 NLRP3炎性体可促进小鼠脑IR损伤,主要通过增加细胞因子释放和促进神经元凋亡实现的。     

TNFα在心肌缺血／再灌注重塑期的保护作用

大量研究表明,肿瘤坏死因子d（TNFa）在心肌缺血／再灌注（I／R）损伤中,既能促进心肌损伤,又具有保护心肌的作用,这种看似相互矛盾的作用,系因在心肌I／R的不同时期由不同的信号转导通路所介导。在心肌I／R的急性期,缺血区冠脉血管床的内皮细胞受损,黏附血中巨噬细胞与淋巴细胞可释放大量可溶型TNFa（sTNFα）。高浓度的sTNFα可激活TNF的1型受体（TNFR1）及其下游信号转导通路,引起心肌细胞凋亡。在心肌I／R的重构期或修复期,虽然血中sTNFα的水平高于生理浓度,但血中可溶型TNFR的水平增加可中和sTNFa,阻止其对正常心肌组织的损害。心肌局部缺血可刺激心肌细胞与成纤维细胞合成TNFα,在细胞膜上装配为跨膜型TNFa,激活相邻细胞的2型TNF受体（TNFR2）及其下游信号转导通路,增强心肌细胞钙转运而增强其收缩功能,同时拯救缺血边界区可存活的心肌细胞。心肌局部跨膜型TNFα还能募集间充质干细胞,分泌多种细胞生长因子,改善心功能。TNFa可通过组蛋白去乙酰化酶1（HDAC1）调节核转录因子KB（NF-KB）的转录活性,保护心肌细胞在持续的TNFa作用下得以存活。跨膜型TNFα还可激活心肌中固有的干细胞向心肌细胞分化,修复受损的心肌组织。     

Melatonin abates liver ischemia/reperfusion injury by improving the balance between nitric oxide and endothelin

Introduction Melatonin (5-methoxy-N-acetyltryptamine) is a naturally occurring hormone derived from the amino acid tryptophan andproduced mainly by the pineal gland (pinealocytes) in the brain as well as in the retina and gastrointestinal tract. Although the major role of melatonin is in the sleep-wake cycle through its circadian fluctuation, a large body of literature has recently demonstrated that melatonin also exerts complex physiological and pharmacological effects on multiple systems and…     

脂质胞壁酸诱导的预适应对自发性高血压大鼠心肌缺血再灌注损伤的保护作用

目的:探讨脂质胞壁酸(LTA)诱导的延迟预适应对自发性高血压大鼠(SHR)心脏缺血/再灌注(I/R)损伤的保护作用及诱导型一氧化氮合酶(iNOS)是否参与其作用。方法:采用结扎左冠状动脉前降支30min,再灌注复制大鼠心肌I/R模型,结扎前24h注射LTA,检测心肌再灌注60min后血清心肌型肌酸激酶同工酶(CK-MB)、乳酸脱氢酶(LDH),并用dUTP缺口末端标记法检测心肌细胞凋亡,用Western Blot方法检测凋亡蛋白Bcl-2和Bax的蛋白表达。同时采用实时RT-PCR技术和Western Blot方法分别检测心肌再灌注末iNOS mRNA和蛋白的表达。结果:与I/R组比较,LTA预适应组能显著减少室性心律失常(VA)评分值(P<0.01);LTA预适应还能明显减少I/R后血清CK-MB和LDH的漏出(P<0.01,P<0.05),减少心肌细胞凋亡(P<0.01),凋亡相关蛋白Bcl-2表达明显上调(P<0.01),而Bax蛋白表达则下调(P<0.01)。再灌注末,预适应组iNOS mRNA的平均相对表达量较I/R组增加了0.71倍(P<0.01),LTA预适应组iNOS蛋白的表达量较I/R组增加了0.96倍(P<0.05)。不论在LTA预适应前或缺血前期给予iNOS抑制剂氨基胍或是单独给予氨基胍,上述观测指标均与I/R组比较差异无统计学意义。结论:LTA预适应能显著减轻SHRI/R导致肥厚心肌的坏死和细胞凋亡,iNOS/NO作为触发和效应环节在介导LTA预适应中发挥关键作用。     

Fish oil alleviates liver injury induced by intestinal ischemia/reperfusion via AMPK/SIRT-1/autophagy pathway

AIM To evaluate whether fish oil(FO) can protect liver injury induced by intestinal ischemia/reperfusion(I/R) via the AMPK/SIRT-1/autophagy pathway.METHODS Ischemia in wistar rats was induced by superior mesenteric artery occlusion for 60 min and reperfusion for 240 min. One milliliter per day of FO emulsion or normal saline was administered by intraperitoneal injection for 5 consecutive days to each animal. Animals were sacrificed at the end of reperfusion. Blood andtissue samples were collected for analyses. AMPK, SIRT-1, and Beclin-1 expression was determined in lipopolysaccharide(LPS)-stimulated HepG2 cells with or without FO emulsion treatment.RESULTS Intestinal I/R induced significant liver morphological changes and increased serum alanine aminotransferase and aspartate aminotransferase levels. Expression of p-AMPK/AMPK, SIRT-1, and autophagy markers was decreased whereas tumor necrosis factor-α(TNF-α) and malonaldehyde(MDA) were increased. FO emulsion blocked the changes of the above indicators effectively. Besides, in LPS-stimulated HepG2 cells, small interfering RNA(siRNA) targeting AMPK impaired the FO induced increase of p-AMPK, SIRT-1, and Beclin-1 and decrease of TNF-α and MDA. SIRT-1 siRNA impaired the increase of SIRT-1 and Beclin-1 and the decrease of TNF-α and MDA.CONCLUSION Our study indicates that FO may protect the liver against intestinal I/R induced injury through the AMPK/SIRT-1/autophagy pathway.     

Inhibition of Inducible Nitric Oxide Synthase Prevents Hepatic, but Not Pulmonary, Injury Following Ischemia-Reperfusion of Rat Liver

The aim of this study was to investigate the contribution of inducible nitric oxide synthase (iNOS)-derived nitric oxide on the liver and lung injury following hepatic ischemia-reperfusion (I/R) using a novel and potent iNOS inhibitor, ONO-1714. Rats were subjected to 90 min of partial hepatic ischemia followed by 3, 6, 12, and 24 hr of reperfusion. Expression of iNOS mRNA peaked at 3 hr of reperfusion in the liver and lung. Plasma nitric oxide levels were increased fourfold at 24 hr of reperfusion and plasma ALT was increased, reaching a peak at 12 hr of reperfusion; both were significantly inhibited by ONO-1714. Histological examination revealed extensive liver damage, whereas this was not seen in the ONO-1714 group. Lung injury was not significantly changed in groups with versus without ONO-1714. Nitrotyrosine expression was seen in regions similar to those of the histological injuries of the liver, while this staining was absent in the ONO-1714 group. These data show that generation of peroxynitrite could be involved in the pathogenesis of liver injury but not lung injury after hepatic I/R. Inhibition of iNOS could be applied for attenuation of liver injury following hepatic I/R.     

TNF-α and plasma D(-)-lactate levels in rats after intestinal ischemia and reperfusion

Objective To study the potential role of tumor necrosis factor-or(TNF-α)induction in the development ofmucosal barrier dysfunction in rats caused by acute intestinal ischemia-reperfusion injury,and to examine whetherpretreatment with monoclonal antibody against TNF-α(TNF-αMoAb)would affect the release of D(-)-lactate afterlocal gut ischemia followed by reperfusion.Methods Anesthetized Sprague-Dawley rats underwent superiormesenteric artery occlusion for 75 min followed by reperfusion for 6 hr.The rats were treated intravenonsly with eitherTNF-α MoAb(20 mg/kg)or albumin(20 mg/kg)30 min prior to the onset of ischemia.Plasma D(-)-lactate levelswere measured in both the portal and systemic blood by an enzymatic spectrophotometrie assay.Intestinal TNF-αmRNA expression as well as protein levels were also measured at various intervals.In addition,a postmortemexamination was performed together with a macropatholngical evaluation based on a four-grade scoring system.Results Intestinal ischemia resulted in a significant elevation in D(-)-lactate levels in the portal vein blood in boththe control and treatment groups(P<0.05).However,animals pretreated with TNF-α MoAb at 6 hr after reperfusionshowed significant attenuation of an increase in both portal and systemic D(-)-lactate levels when compared with thoseonly receiving albumin(P<0.05).In the control animals,a remarkable rise in intestinal TNF-α level was measuredat 0.5 hr after clamp release(P<0.01);however,prophylactic treatment with TNF-α MoAb completely annulled theincrease of local TNF-α levels seen in the control animals.Similarly,after anti-TNF-α MoAb administration,intestinalTNF-α mRNA expression was markedly inhibited,which showed significant differences when compared with the controlgroup at 0.5 hr,2 hr and 6 hr after the release of occlusion(P<0.05-0.01).In addition,the pathologicalexamination showed marked intestinal lesions that formed during ischemia,which were much worse upon reperfusion,particularly at the 6 hr time point.These acute injuries were obviously attenuated in animals receiving TNF-α MoAb.Conclusions It appeared that acute intestinal ischemia was associated with failure of the mucosal barrier,resulting inincreased plasma D(-)-lactate levels in both portal and systemic blood.These results suggest that TNF-α appears to beinvolved in the development of local damage associated with intestinal ischemic injury.Moreover,prophylactictreatment with TNF-α MoAb exerts preventive effects on ischemia/reperfusion-induced circulating D(-)-lactateelevation and gut injury.(J Geriatr Cardiol 2004;1(2):119-124.)     

氢气对脑缺血再灌注大鼠海马一氧化氮及其合酶的影响

目的探讨氢气治疗对急性脑缺血再灌注损伤大鼠海马NO和一氧化氮合酶(NOS)的影响。方法选择SD大鼠72只,随机分为3组:假手术组、模型组和治疗组(腹腔注射2%氢气饱和生理盐水),每组24只,每组又分为6、24h2个时间点。采用线栓法制作大鼠大脑中动脉缺血再灌注模型。免疫组织化学方法测定海马NOS的表达;硝酸还原酶法测定海马组织匀浆中NO含量;NOS检测试剂盒检测海马组织提取液中NOS的活性。结果模型组治疗6h海马NOS阳性细胞、NO含量及NOS活性明显高于假手术组,而治疗组上述指标较模型组明显下降(P<0.05);模型组治疗24h海马NOS阳性细胞、NO含量及NOS活性明显高于假手术组,差异有统计学意义(P<0.05),但治疗组与模型组比较,差异无统计学意义(P>0.05)。结论氢气治疗可减少缺血后海马组织中NO含量及NOS活性,对海马缺血再灌注损伤起到一定的保护作用。     

Role of P-selectin and anti-P-selectin monoclonal antibody in apoptosis during hepatic/renal ischemia reperfusion injury

AIM To evaluale the potential role of P-selectin and anti-P-selectin monoclonal antibody (mAb) in apoptosis during hepatic/renal ischemiareperfusion injury. METHODS Plasma P-selectin level, hepatic/renal P-selectin expression and cell apoptosis were detected in rat model of hepatic/ renal ischemia-reperfusion injury. ELISA, immunohistochemistry and TUNEL were used. Some ischemia-reperfusion rats were treated with antiP-selectin mAb. RESULTS Hepatic/ renal function insufficiency, up-regulated expression of P-selectin in plasma and hepatic/renal tissue, hepatic/renal histopathological damages and cell apoptosis were found in rats with hepatic/renal ischemiareperfusion injury, while these changes became less conspicuous in animals treated with anti-P selectin mAb. CONCLUSION P-selectin might mediate neutrophil infiltration and cell apoptosis and contribute to hepatic/renal ischemia-reperfusion injury, anti-P-selectin mAb might be an efficient approach for the prevention and treatment of hepatic/renal ischemia-reperfusion injury.     

Pretreatment with melatonin exerts anti-inflammatory effects against ischemia/reperfusion injury in a rat middle cerebral artery occlusion stroke model

Inflammatory response following cerebral ischemia/reperfusion plays a key pathogenic role in ischemic cerebral damage. Nitric oxide (NO), cyclooxygenase-2 (COX-2) and myeloperoxidase (MPO) are important inflammatory mediators. Neuronal NO synthase (nNOS) is a major initial source of excessive NO during ischemia/reperfusion. Induction of COX-2 and infiltration of polymorphonuclear cells expressing MPO are critical factors in delayed inflammatory damage. Previously, we demonstrated that administration of melatonin before ischemia significantly reduced the infarct volume in a rat middle cerebral artery occlusion (MCAO) stroke model. In this study, we examined the effect of pretreatment with melatonin at 5 mg/kg on the immunoreactivity (ir) for nNOS, COX-2, MPO, and glial fibrillary acidic protein (GFAP) at 24, 48, and 72 hr after right-sided endovascular MCAO for 1 hr in adult male Sprague-Dawley rats. Melatonin did not affect the hemodynamic parameters. When compared with rats with sham MCAO, ischemia/reperfusion led to an ipsilateral increase in cells with positive ir for nNOS (similar at all times) and in ir-GFAP (similar at all times). Ischemia/reperfusion led to appearance of cells with positive ir for COX-2 (greatest at 24 hr with a tendency to increase again at 72 hr) or MPO (greatest at 24 hr). A single dose of melatonin significantly lessened the ipsilateral increase in cells with positive ir for nNOS, COX-2 or MPO, but did not influence the ipsilateral change in ir-GFAP. Our results suggest that melatonin treatment mediates neuroprotection against ischemia/reperfusion injury partly via inhibition of the consequential inflammatory response.     

诱导型一氧化氮合酶在创伤性脑损伤后肠黏膜屏障损伤中表达的变化

目的观察创伤性脑损伤（TBI）后肠黏膜屏障损伤时诱导型一氧化氮合酶（iNOS）表达的变化及其可能的作用。方法 48只健康雄性W istar大鼠随机分为TBI组（n=24）和对照组（n=24）,各组动物分别在手术后3、6、12、24 h处死,每个时间点6只。动物处死后,抽门静脉血测血清内毒素、二胺氧化酶（DAO）,取脑组织和回肠黏膜,观察组织形态学改变,并测定肠黏膜组织DAO的含量和iNOS的表达情况。结果 TBI组肠黏膜受损,血中内毒素含量增加（P〈0.05）;肠黏膜DAO活性下降（P〈0.01）,而血中DAO活性则升高（P〈0.05）;iNOS的表达3h已经增高,12h达到最高,而后逐渐降低,但仍然高于对照组（P〈0.05）。结论 iNOS在TBI后肠黏膜屏障损伤时表达明显增加,参与了TBI后肠黏膜屏障损伤。     

线粒体钙单向转运体在远距预处理脑保护中的作用及其机制

目的探讨肢体缺血预处理（LIP）对脑缺血/再灌注（I/R）损伤保护作用中线粒体钙单向转运体（MCU）的作用及其作用机制。方法将50只I/R损伤模型大鼠随机分为五组。模型组不干预,钌红组、精胺组、LIP组及LIP＋精胺组分别于再灌注前予钌红、精胺、LIP及LIP＋精胺干预。再灌注24 h观察各组神经功能评分,血清丙二醛（MDA）、乳酸脱氢酶（LDH）、超氧化物歧化酶（SOD）水平及脑皮质区Bcl-2阳性细胞数。结果钌红组及LIP组神经功能评分及血清MDA、LDH水平明显低于另三组,SOD水平及Bcl-2细胞明显高于另三组,P均〈0.05。结论 CIP对I/R的脑保护作用可能与MCU有关;增强MCU活动可抑制LIP的脑保护作用。