Attenuation of myocardial ischemia/reperfusion injury in mice with myocyte-specific overexpression of endothelial nitric oxide synthase

OBJECTIVE: The role of nitric oxide (NO) in myocardial ischemia/reperfusion injury remains controversial as both NO donors and NO synthase (NOS) inhibitors have shown to be protective. We generated transgenic (TG) mice that overexpress endothelial NOS (eNOS) exclusively in cardiac myocytes to determine the effects of high cardiac NO levels on ischemia/reperfusion injury and cellular Ca(2+) homeostasis. Wild-type (WT) mice served as controls. METHODS: Hearts were perfused in vitro and subjected to 20 min of total no-flow ischemia and 30 min of reperfusion (n=5 per group). Left ventricular function, cGMP levels and intracellular Ca(2+) transients (Ca(2+)(i)) were determined. RESULTS: Left ventricular pressure was reduced (maximum, -33%) and basal cardiac cGMP was increased (twofold) in TG hearts, and the changes were reversed by NOS blockade with N(G)-nitro-L-arginine methyl ester (L-NAME). Relative to baseline, recovery of reperfusion contractile function was significantly better in hearts from TG (98%) than WT (51%) mice, and L-NAME abolished this effect. Heart rate and coronary perfusion pressure were not different between groups. Systolic and diastolic Ca(2+)(i) concentrations were similar in WT and TG hearts, but Ca(2+)(i) overload during early reperfusion tended to be less in TG hearts. Kinetic analysis of pressure curves and Ca(2+)(i) transients revealed a faster left ventricular diastolic relaxation and abbreviated aequorin light signals in TG hearts at baseline and during reperfusion. CONCLUSIONS: High levels of NO/cGMP strongly protect against ischemia/reperfusion injury, the protection is largely independent of changes in Ca(2+)(i) modulation, but relates to reduced preischemic performance. Myocyte-specific NO augmentation may aid in studies of the (patho)physiological roles of cardiac-derived NO.     

Myocardial reperfusion injury in neuronal nitric oxide synthase deficient mice

BACKGROUND: A substantial amount of data suggesting that endothelial cell nitric oxide synthase (eNOS) plays a cardioprotective role in animal models of ischemia-reperfusion injury has amassed. We have previously demonstrated that eNOS-deficient (-/-) mice exhibit significantly larger myocardial infarcts than do wild-type mice. Few investigations have examined the neuronal form of nitric oxide synthase in the heart. The two constitutive isoforms have been demonstrated to play differing roles in studies of cerebral ischemia-reperfusion. OBJECTIVE: To characterize the role of neuronal nitric oxide synthase (nNOS) in myocardial ischemia-reperfusion injury. METHODS: Wild-type and nNOS -/- mice were subjected to 20 min of coronary artery occlusion and 120 min of reflow. RESULTS: We found no significant difference between the two groups in terms of infarct size. Microscopic cross-sections from both groups were examined for infiltration of polymorphonuclear leukocyte. Hearts of nNOS -/- mice exhibited significantly (P < 0.05) more polymorphonuclear leukocytes than did hearts of wild-type mice. CONCLUSION: Despite the fact that eNOS plays a cardioprotective role in the ischemic-reperfused myocardium, we observed no change in size of myocardial infarcts when nNOS was genetically disrupted.     

鼠肝缺血再灌注损伤性别差异与一氧化氮有关

女性患者在肝移植或肝细胞肿瘤切除术后较男性患者有更好的生存率。雌激素可通过非基因和（或）基因反应增加内皮细胞一氧化氮合酶（eNOS），催化一氧化氮（NO）产生，而NO在限制全肝缺血再灌注损伤中起着重要作用，本实验观察NO在雌性大鼠肝缺血再灌注中的保护机制。     

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。     

一氧化氮抗心肌缺血再灌注损伤研究进展

心肌缺血再灌注损伤(MIRI)是指缺血期处于可逆损伤的心肌细胞恢复血液供应后产生更为严重的损伤,主要包括心肌梗死面积扩大、再灌注心律失常、心肌顿抑、冠状微循环障碍等。随着冠状动脉搭桥术、经皮冠状动脉内成形术等血管再通术的迅速开展,冠心病再灌注治疗出现了一个飞跃。但MIRI也成为阻碍缺血心肌从再灌注疗法获得最佳疗效的主要难题,如何减轻MIRI成为医学界新的挑战。自20世纪80年代首次发现一氧化氮(NO)能够产生较强的心肌保护作用以来,NO在缺血再灌注损伤中的作用一直备受关注,本文就NO的代谢及抗心肌缺血再灌注损伤的机制…     

一氧化氮与肺缺血再灌注损伤的研究进展

一氧化氮（nitricoxide，NO）是一种活性很强的自由基，具有广泛的生物学活性。多项研究提示NO在急性肺缺血／再灌注（ischemia／reperfusion，I／R）损伤中具有重要作用。本文重点描述有关一氧化氮在肺I／R损伤中作用的研究进展。     

Role of endothelial nitric oxide synthase in endothelial cell migration.

Endothelium-derived nitric oxide (NO) and its precursor L-arginine have been implied to promote angiogenesis, but little is known about the precise mechanism. The inhibition of endogenous NO formation by Nomega-nitro-L-arginine methyl ester (L-NAME) (1 mmol/L) but not its inactive enantiomer D-NAME (1 mmol/L) inhibited endothelial cell sprouting from the scratched edge of the cultured bovine aortic endothelial cell monolayer. Inhibition of endogenous NO release by L-NAME was confirmed by amperometric measurement using an NO-specific electrode. In the modified Boyden chamber, L-NAME (1 mmol/L) significantly inhibited endothelial cell migration, whereas L-NAME did not affect endothelial DNA synthesis as assessed by analysis of [3H]thymidine incorporation. We then examined alteration of endothelial cell adhesion molecule expression after the inhibition of NO by L-NAME in cultured human umbilical vein endothelial cells. In both normoxic and hypoxic conditions, L-NAME (1 mmol/L) inhibited surface expression of integrin alphavbeta3, which is an important integrin facilitating endothelial cell survival and angiogenesis. However, L-NAME did not affect the expression of platelet endothelial cell adhesion molecule-1, intercellular adhesion molecule-1, vascular endothelial adhesion molecule-1, gap junction protein connexin 43, and VE-cadherin, which have been reported to potentially affect angiogenesis. In summary, inhibition of endothelial NO synthase by L-NAME attenuated endothelial cell migration but not proliferation in vitro. Furthermore, endogenous endothelium-derived NO maintains the functional expression of integrin alphavbeta3, a mediator for endothelial migration, survival, and angiogenesis. Endothelium-derived NO, thus, may play an important role in mediating angiogenesis by supporting endothelial cell migration, at least partly, via an integrin-dependent mechanism.     

Gender differences in hepatic ischemic reperfusion injury in rats are associated with endothelial cell nitric oxide synthase-derived nitric oxide

AIM: This study was designed to examine the hypothesis that gender differences in I/R injury are associated with endothelial cell nitric oxide synthase (eNOS)-derived nitric oxide (NO). METHODS: Wistar rats were randomized into seven experimental groups (12 animals per group). Except for the sham operated groups, all rats were subjected to total liver ischemia for 40 min followed by reperfusion. All experimental groups received different treatments 45 min before the laparotomy. For each group, half of the animals (six) were used to investigate the survival; blood samples and liver tissues were obtained in the remaining six animals after 3 h of reperfusion to assess serum NO, alanine aminotransferase (ALT) and TNF-α levels, liver tissue malondialdehyde (MDA) content, and severity of hepatic I/R injury. RESULTS: Basal serum NO levels in female sham operated (FS) group were nearly 1.5-fold of male sham operated (MS) group (66.7±11.0 μmol/L vs45.3μ10.1 μmol/L, P<0.01). Although serum NO levels decreased significantly after hepatic I/R (P<0.01, vs sham operated groups), they were still significantly higher in female rat (F) group than in male rat (M) group (47.8±8.6 μmol/L vs 23.8±4.7 μmol/L, P<0.01). Serum ALT and TNF-α levels, and liver tissue MDA content were significantly lower in F group than in M group (370.5±46.4 U/L, 0.99±0.11 μg/L and 0.57±0.10 μmol/g vs668.7±78.7 U/L, 1.71±0.18μg/L and 0.86±0.11 μmol/g, respectively, P<0.01). I/R induced significant injury to the liver both in M and F groups (P<0.01 vs sham operated groups). But the degree of hepatocyte injury was significantly milder in F group than in M group (P<0.05 and P<0.01). The median survival time was six days in F group and one day in M group. The overall survival rate was significantly higher in F group than in M group (P<0.05). When compared with male rats pretreated with saline (M group), pretreatment of male rats with 17-β-estradiol (E2) (M+E2 group) significantly increased serum NO levels and significantly decreased serum ALT and TNF-α levels, and liver tissue MDA content after I/R (P<0.01). The degree of hepatocyte injury was significantly decreased and the overall survival rate was significantly improved in M+E2 group than in M group (P<0.01 and P<0.05). The NOS inhibitor Nw-nitro-L-arginine methyl ester (L-NAME) treatment could completely abolish the protective effects of estrogen in both male and female rats. CONCLUSION: The protective effects afforded to female rats subjected to hepatic I/R are associated with eNOS-derived NO.     

Inducible nitric oxide synthase is required in alcohol-induced liver injury: studies with knockout mice

BACKGROUND & AIMS : Oxidative stress contributes to early alcohol-induced liver injury, and superoxide (O(2)*-) production from NADPH oxidase plays a key role. However, the production of the free radical nitric oxide (NO*) by inducible nitric oxide synthase (iNOS) could also be involved. METHODS : To test this hypothesis, iNOS knockout (B6.129P2-Nos2 (tm1 Lau)) and wild-type mice were fed high-fat control or ethanol-containing diets for 4 weeks. RESULTS : Mean body weight gains were not significantly different between treatment groups, and average urine ethanol concentrations were similar in wild-type and iNOS knockout mice. After 4 weeks, serum alanine aminotransferase (ALT) levels were increased significantly about 4-fold over control values (29 +/- IU/L) by enteral ethanol (113 +/- 20) in wild-type mice; this effect of ethanol was significantly blunted in iNOS knockout mice (50 +/- 9). Similar protective effects against liver damage were observed if wild-type mice were treated with the iNOS inhibitor N -(3-aminomethyl)benzyl-acetamindine (1400W). Enteral ethanol also caused severe fatty accumulation, mild inflammation, and necrosis in the liver in wild-type mice but had no effect in iNOS knockout mice. The accumulation of 4-hydroxynonenal (lipid peroxidation) and 3-nitrotyrosine (reactive nitrogen species formation) protein adducts caused by alcohol was completely blocked in iNOS knockout mice. CONCLUSIONS : These data strongly support the hypothesis that iNOS is required for the pathogenesis of early alcohol-induced hepatitis by production of nitric oxide-derived pro-oxidants (e.g., peroxynitrite).     

Sinusoidal endothelial cell repopulation following ischemia/reperfusion injury in rat liver transplantation

We evaluated the kinetics by which rat liver sinusoidal endothelial cells (LSECs) are repopulated in the reperfused transplanted liver after 18 hours of cold ischemic storage. We found that the majority of LSECs in livers cold-stored for 18 hours in University of Wisconsin solution are seriously compromised and often are retracted before transplantation. Sinusoids rapidly re-endothelialize within 48 hours of transplantation, and repopulation is coincident with up-regulation of hepatocyte vascular endothelial growth factor expression and vascular endothelial growth factor receptor-2 expression on large vessel endothelial cells and repopulating LSECs. Although re-endothelialization occurs rapidly, we show here, using several high-resolution imaging techniques and 2 different rat liver transplantation models, that engraftment of bone marrow-derived cells into functioning LSECs is routinely between 1% and 5%. CONCLUSION: Bone marrow plays a measurable but surprisingly limited role in the rapid repopulation and functional engraftment of bone marrow-derived LSECs after cold ischemia and warm reperfusion.     

诱导型一氧化氮合酶在ConA诱发T细胞介导的小鼠肝损害中的表达

目的观察诱导型一氧化氮合酶（ｉＮＯＳ）在刀豆素Ａ（ＣｏｎＡ）诱发Ｔ细胞介导的小鼠肝损害中的表达及意义。方法应用黄递酶染色（ＮＡＤＰＨ－ｄ）技术观察ｉＮＯＳ表达。结果ＣｏｎＡ造成肝损害后，血浆中亚硝酸盐（ＮＯ－２）较正常对照组（ＰＢＳ组）显著升高，以Ｌ－ＮＡＭＥ抑制ＮＯ合成，肝细胞损害反而加重，且肝组织内丙二醛（ＭＤＡ）增加，肝窦内血细胞聚集加重；在ＣｏｎＡ造成肝损害时可见肝实质细胞表达ｉＮＯＳ，且越靠近中央静脉的肝细胞表达越多，推测这是肝细胞对缺血缺氧而产生的一种自身反映；用环孢霉素Ａ（ＣＳＡ）预先抑制Ｔ细胞活化，则未发现肝细胞表达ｉＮＯＳ。结论在ＣｏｎＡ性肝损害中，肝实质细胞通过启动自身的ＮＯ生物合成机制参与了炎症应答，并通过消除氧自由基和抑制血细胞在肝窦内聚集而起一定的保护作用，这一生物过程很可能是肝细胞参与机体免疫应答的一部分。     

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…     

糖原合成酶激酶-3β在肝脏热缺血再灌注损伤中的作用及其干预

目的 研究细胞内信号分子糖原合成酶激酶-3 β在肝脏缺血再灌注损伤中的作用.方法 以C57BL/6小鼠为研究对象,夹住肝脏动脉和门静脉以阻断肝脏向头侧肝叶血供90 min,随后建立不同灌注时间的小鼠热缺血再灌注损伤模型.动物实验组包括:假手术组,缺血再灌注模型组,SB216763干预组(SB216763溶于二甲基亚砜,质量分数为0.025,腹腔注射,缺血前2 h给予).通过Western blot检测肝脏组织中糖原合成酶激酶-3 β磷酸化的表达;检测血清ALT及组织病理学观察肝脏组织的损伤情况,实时定量PCR检测细胞炎症因子的基因表达.多组样本均数的两两比较采用one-way ANOVA分析(方差齐者用LSD-t检验,方差不齐者用Games-Howell法),P<0.05为差异具有统计学意义.结果 Western blot检测结果显示,在缺血再灌注的90 min缺血过程中,糖原合成酶激酶-3 β被去磷酸化而活性显著激活.抑制糖原合成酶激酶-3 β活性显著改善了肝脏的功能:ALT明显下降[干预组对模型组:(2046±513)U/L对比(5809±1689)U/L,P=0.0153],肝脏的组织病理损伤明显改善,并显著抑制了肝脏的炎症反应:促进肝脏组织中抗炎细胞因子白细胞介素10(IL-10)的基因高表达,并同时抑制了促炎细胞因子IL-12、IL-1 β、肿瘤坏死因子α、IL-6的基因表达.结论 肝脏缺血再灌注损伤过程中,缺血提高了糖原合成酶激酶-3 α活性,促进了炎症反应的发生并导致了肝脏组织的损伤.因此,以糖原合成酶激酶-3 α为靶点进行干预,有可能为肝移植患者提供一种新的、有效的治疗方法来改善肝脏缺血再灌注损伤.

Abstract：

Objective To investigate the role of the key intracellular signaling molecule glycogen synthase kinase-3 beta in the mechanism of liver ischemia reperfusion (IR). Methods C57BL/6 mice were subjected to 90 min warm liver cephalad lobe ischemia, followed by various length of reperfusion. Experiment groups included sham control group, liver IRI model group and glycogen synthase kinase-3 beta inhibitor-treated group (SB216763 in DMSO, 25 g/kg, i.p, 2 hour prior to the onset of liver ischemia). The expression of glycogen synthase kinase-3 beta protein was analysed by Western blotting. The serum ALT levels were determined to reflect the function of liver. The affected liver lobes were harvested for histology analysis. The inflammatory gene expression was detected by Quantitative PCR. Results By western blot analysis, we found that ischemia itself activated glycogen synthase kinase-3 beta by a significant decrease of its phosphorylation. Glycogen synthase kinase-3 beta inhibitor SB216763-pretreatment ameliorated the liver damages significantly as compared to the controls (sALT: 2046 ±513 U/L vs 5809 ± 1689 U/L, P = 0.0153), and suppressed the gene expressions of IL-12, TNF α, IL-1 β and IL-6. Conclusions This study demonstrated that the ischemia process modulated liver innate immune activation via a GSK-3-dependent mechanism which favored the development of a pro-inflammation response and lead to liver tissue damages. GSK-3β may be a new therapeutic target to ameliorate liver IRI in transplant patients.