Effect of ischemia and reperfusion without airway occlusion on vascular barrier function in the in vivo mouse lung.

Ischemia-reperfusion (I/R) lung injury causes increased vascular permeability and edema. We developed an in vivo murine model of I/R allowing measurement of pulmonary vascular barrier function without airway occlusion. The left pulmonary artery (PA) was occluded with an exteriorized, slipknotted suture in anesthetized C57BL/6J mice. The effect of ischemic time was determined by subjecting mice to 5, 10, or 30 min of left lung ischemia followed by 150 min of reperfusion. The effect of reperfusion time was determined by subjecting mice to 30 min of left lung ischemia followed by 30 or 150 min of reperfusion. Changes in pulmonary vascular barrier function were measured with the Evans blue dye (EBD) technique, dual-isotope radiolabeled albumin (RA), bronchoalveolar lavage (BAL) protein concentration, and wet weight-to-dry weight ratio (WW/DW). Increasing left lung ischemia with constant reperfusion time or increasing left lung reperfusion time after constant ischemic time resulted in significant increases in left lung EBD content at all times compared with both right lung values and sham surgery mice. The effects of left lung ischemia on lung EBD were corroborated by RA but the effects of increasing reperfusion time differed, suggesting binding of EBD to lung tissue. An increase in WW/DW was only detected after 30 min of reperfusion, suggesting edema clearance. BAL protein concentrations were unaffected. We conclude that short periods of I/R, without airway occlusion, increase pulmonary vascular permeability in the in vivo mouse, providing a useful model to study molecular mechanisms of I/R lung injury.     

High fat diet reduces the expression of miRNA-29b in heart and increases susceptibility of myocardium to ischemia/reperfusion injury

Several studies have shown the role of microRNAs (miRNAs) in myocardial dysfunction in response to ischemia/reperfusion (I/R). In this study, we investigated the impact of high fat (HF) diet in the myocardial susceptibility to I/R injury, as well as in the expression of miRNA-29b. Isolated heart experiments using the ex vivo Langendorff perfusion model were used to induce cardiac I/R injury. HF diet-induced cardiac hypertrophy and impaired cardiac functional recovery after I/R. miRNA-29b, which targets Col1, was reduced in the heart of HF diet-fed mice, whereas the cardiac expression of Col1 was increased. In addition, hypoxia–reoxygenation (H/R) reduced the expression of miRNA-29b in cardiomyoblasts cultures. However, the overexpression of miRNA-29b in cardiomyoblasts reduced p53 mRNA levels and H/R injury, suggesting that downregulation of miRNA-29b may be involved in I/R injury. Together, our findings suggest that the reduced expression of miRNA-29b may be involved in the deteriorated cardiac functional recovery following I/R in obese mice.     

A combination of ischemic preconditioning and allopurinol protects against ischemic injury through a nitric oxide-dependent mechanism

This study examined the cytoprotective mechanisms of a combination of ischemic preconditioning (IPC) and allopurinol against liver injury caused by ischemia/reperfusion (I/R). Allopurinol (50 mg/kg) was intraperitoneally administered 18 and 1 h before sustained ischemia. A rat liver was preconditioned by 10 min of ischemia, followed by 10 min of reperfusion, and then subjected to 90 min of ischemia, followed by 5 h of reperfusion. Rats were pretreated with adenosine deaminase (ADA), 3,7-dimethyl-1-[2-propargyl]-xanthine (DMPX), and N-nitro-l-arginine methyl ester (l-NAME) before IPC. Hepatic nitrite and nitrate and eNOS protein expression levels were increased by the combination of IPC and allopurinol. This increase was attenuated by ADA, DMPX, and l-NAME. I/R induced an increase in alanine aminotransferase activity, whereas it decreased the hepatic glutathione level. A combination of IPC and allopurinol attenuated these changes, which were abolished by ADA, DMPX, and l-NAME. The increase in the liver wet weight-to-dry weight ratio after I/R was attenuated by the combination of IPC and allopurinol. In contrast, hepatic bile flow was decreased after I/R, which was attenuated by the combination of IPC and allopurinol. These changes were restored by l-NAME. I/R induced a decrease in the level of mitochondrial dehydrogenase, whereas it increased mitochondrial swelling. A combination of IPC and allopurinol attenuated these changes, which were restored by ADA, DMPX, and l-NAME. Our findings suggest that a combination of IPC and allopurinol reduces post-ischemic hepatic injury by enhancing NO generation.     

钙网蛋白参与缺血后处理减轻大鼠骨骼肌缺血/再灌注损伤

本实验分别在整体和细胞水平观察缺血后处理（ischemic postconditioning,I-postC）对骨骼肌缺血／再灌注（ischemia／reperfusion,I／R）损伤的影响,并探讨钙网蛋白（calreticulin,CRT）介导的信号转导机制。（1）整体实验：健康雄性Wistar大鼠48只,无创动脉夹夹闭右侧股动脉4h,松夹再灌注12h或24h建立大鼠右后肢I／R损伤模型,随机分为I／R组、缺血预处理（ischemic preconditioning,IPC）组（5min缺血／5min再灌,3个循环）和I-postC组（1min再灌／1min缺血,3个循环）（n=16）,大鼠左后肢做对照处理。再灌注结束时测定血浆乳酸脱氢酶（1actate dehydrogenase,LDH）活性、骨骼肌湿干重比值（wet／dryweightratio,W／D）;电镜观察骨骼肌超微结构变化：Westernblot检测骨骼肌CRT、钙调神经磷酸酶（calcineurin,CaN）的表达。（2）细胞培养实验：原代培养Sprague-Dawley乳鼠骨骼肌细胞,随机分为6组：正常对照组、缺氧／复氧（hypoxia／reoxygenation,H／R）组、缺氧预处理（hypoxic preconditioning,HPC）组、缺氧后处理（hypoxic postconditioning,H-postC）组、CaN抑制剂环孢素A（cyclosporine,CsA）＋H／R组和CsA＋H-postC组。台盼蓝排斥实验、流式细胞仪检测细胞损伤情况：Westernblot检测骨骼肌细胞CRT和CaN的表达。结果显示：（1）在整体动物实验中,I-postC可显著降低血浆LDH活性和组织水肿,骨骼肌超微结构损伤减轻,无细胞核凋亡现象,与IPC组相比无显著差异。I-postC再灌注12h和24hCRT表达分别较I／R12h和24h组高4．39倍和1．02倍（P〈0．05）,CaN表达分别增高1．96倍和0．63倍（尸〈0．05）。相关分析显示CRT表达与CaN表达呈正相关（r-0．865,P〈0．01）。（2）在细胞培养实验中,H-postC可减轻H／R诱导的骨骼肌细胞凋亡,增加细胞存活率,与HPC组相比无显著差异,CsA可抑制H-postC的保护作用;H-postC可上调CRT和CaN的表达,分别较H／R组增加31．8％（P〈0．05）和6．02％,加入CsA后CaN表达降低44．02％（P〈0．05vsH-postC）。上述整体实验和细胞培养实验结果提示,I-postC与IPC保护作用相似,可显著减轻I／R损伤;CRT上调介导的CaN表达增加可能参与了I-postC的保护作用,抑制CaN表达可降低I-postC的保护作用。     

Cardiac mTOR protects the heart against ischemia-reperfusion injury

Cardiac mammalian target of rapamycin (mTOR) is necessary and sufficient to prevent cardiac dysfunction in pathological hypertrophy. However, the role of cardiac mTOR in heart failure after ischemic injury remains undefined. To address this question, we used transgenic (Tg) mice with cardiac-specific overexpression of mTOR (mTOR-Tg mice) to study ischemia-reperfusion (I/R) injury in two animal models: 1) in vivo I/R injury with transient coronary artery ligation and 2) ex vivo I/R injury in Langendorff-perfused hearts with transient global ischemia. At 28 days after I/R, mortality was lower in mTOR-Tg mice than littermate control mice [wild-type (WT) mice]. Echocardiography and MRI demonstrated that global cardiac function in mTOR-Tg mice was preserved, whereas WT mice exhibited significant cardiac dysfunction. Masson's trichrome staining showed that 28 days after I/R, the area of interstitial fibrosis was smaller in mTOR-Tg mice compared with WT mice, suggesting that adverse left ventricular remodeling is inhibited in mTOR-Tg mice. In the ex vivo I/R model, mTOR-Tg hearts demonstrated improved functional recovery compared with WT hearts. Perfusion with Evans blue after ex vivo I/R yielded less staining in mTOR-Tg hearts than WT hearts, indicating that mTOR overexpression inhibited necrosis during I/R injury. Expression of proinflammatory cytokines, including IL-6 and TNF-α, in mTOR-Tg hearts was lower than in WT hearts. Consistent with this, IL-6 in the effluent post-I/R injury was lower in mTOR-Tg hearts than in WT hearts. These findings suggest that cardiac mTOR overexpression in the heart is sufficient to provide substantial cardioprotection against I/R injury and suppress the inflammatory response.     

Release of tissue-specific proteins into coronary perfusate as a model for biomarker discovery in myocardial ischemia/reperfusion injury

Diagnosis of acute coronary syndromes is based on protein biomarkers, such as the cardiac troponins (cTnI/cTnT) and creatine kinase (CK-MB) that are released into the circulation. Biomarker discovery is focused on identifying very low abundance tissue-derived analytes from within albumin-rich plasma, in which the wide dynamic range of the native protein complement hinders classical proteomic investigations. We employed an ex vivo rabbit model of myocardial ischemia/reperfusion (I/R) injury using Langendorff buffer perfusion. Nonrecirculating perfusate was collected over a temporal profile of 60 min reperfusion following brief, reversible ischemia (15 min; 15I/60R) for comparison with irreversible I/R (60I/60R). Perfusate proteins were separated using two-dimensional gel electrophoresis (2-DE) and identified by mass spectrometry (MS), revealing 26 tissue-specific proteins released during reperfusion post-15I. Proteins released during irreversible I/R (60I/60R) were profiled using gel-based (2-DE and one-dimensional gel electrophoresis coupled to liquid chromatography and tandem mass spectrometry; geLC-MS) and gel-free (LC-MS/MS) methods. A total of 192 tissue-specific proteins were identified during reperfusion post-60I. Identified proteins included those previously associated with I/R (myoglobin, CK-MB, cTnI, and cTnT), in addition to examples currently under investigation in large cohort studies (heart-type fatty acid binding protein; FABPH). The postischemic release profile of a novel cardiac-specific protein, cysteine and glycine-rich protein 3 (Csrp3; cardiac LIM domain protein) was validated by Western blot analysis. We also identified Csrp3 in serum from 6 of 8 patients postreperfusion following acute myocardial infarction. These studies indicate that animal modeling of biomarker release using ex vivo buffer perfused tissue to limit the presence of obfuscating plasma proteins may identify candidates for further study in humans.     

大鼠肢体缺血预处理对肝缺血/再灌注损伤的保护作用

目的：研究肢体缺血预处理对大鼠肝缺血/再灌注损伤是否具有保护作用。方法：雄性SD大鼠32只,随机分为对照组（S组）;缺血/再灌注组（I/R组）;经典缺血预处理组（IPC组）;肢体缺血预处理组（远端缺血预处理组,RPC组）。S组仅行开腹,不作其他处理;IPC组以肝缺血5min作预处理;RPC组以双后肢缺血5min,反复3次作预处理,2个预处理组及I/R组均行肝缺血1h再灌注3h。取血用于血清谷丙转氨酶（ALT）与血清谷草转氨酶（AST）检测。切取肝组织用于测定湿干比（W/D）、中性粒细胞（PMN）计数及观察显微、超微结构的变化。结果：与I/R组比较,IPC组,RPC组ALT,AST,W/D值,及PMN计数均明显降低（P〈0.01）,肝脏的显微及超微结构损伤减轻。结论：肢体缺血预处理对大鼠肝脏I/R损伤有明显的保护作用,强度与经典缺血预处理相当,其机制可能与抑制肝脏炎症反应、减轻肝脏水肿、改善肝组织微循环有关。     

Kupffer cell-initiated remote hepatic injury following bilateral hindlimb ischemia is complement dependent

Intravital fluorescence microscopy was applied to the livers of male Wistar rats to test the hypothesis that complement mobilization stimulates Kupffer cells and subsequently initiates hepatic injury after hindlimb ischemia/reperfusion (I/R). Following 3 h of limb reperfusion, hepatocellular viability (serum levels of alanine transaminase and cell death via propidium iodide labeling) decreased significantly from levels in sham-operated animals. Inhibition of complement mobilization with soluble complement receptor type 1 (20 mg/kg body wt) and interruption of Kupffer cell function with GdCl(3) (1 mg/100g body wt) resulted in significant hepatocellular protection. Although the effects of hindlimb I/R on hepatic microvascular perfusion were manifest as increased heterogeneity, both complement inhibition and suppression of Kupffer cell function resulted in marked improvements. No additional hepatocellular protection and microvascular improvements were provided by combining the interventions. Furthermore, inhibition of complement mobilization significantly depressed Kupffer cell phagocytosis by 42% following limb reperfusion. These results suggest that the stimulation of Kupffer cells via complement mobilization is necessary but is not the only factor contributing to the early pathogenesis of hepatic injury following hindlimb I/R.     

大鼠肢体缺血/再灌注后肺损伤及一氧化氮合酶的变化与意义

目的：研究大鼠肢体缺血／再灌注后急性肺损伤时,内皮型一氧化氮合酶（eNOS）和诱导型一氧化氮合酶（i-NOS）的表达及其在急性肺损伤发生中的作用。方法：雄性Wistar大鼠于后肢根部阻断血流后松解（4h／4h）,分别给予L-Arg和氨基胍（AG）预先干预,分为control、IR、L-Arg和AG组,免疫组织化学方法检测肺组织中iNOS和eNOS的表达,同时检测肺组织中MDA、MPO、W／D和NO2^-／NO3^-值,肺组织形态学观察以评价肺损伤的程度。结果：与control组比较,I／R组eNOS表达降低,iNOS表达增强,MDA、MPO、W／D和NO2^-／NO3^-值增加。肺组织充血、炎细胞浸润,肺泡腔渗液;与I／R组比较,L-Arg组eNOS、iNOS表达无明显变化,NO2^-／NO3^-增加。MDA、MPO、W／D降低,肺组织损伤有减轻趋势,AG组eNOS表达无明显变化,iNOS活性降低,NO2^-／NO3^-减少,MDA、MPO、W／D增加,肺组织损伤有加重趋势。结论：肢体缺血／再灌注急性肺损伤过程中,iNOS表达增加,NO生成增多,在肺损伤发生中有一定的保护作用。     

吸入一氧化碳抗肢体缺血/再灌注损伤的实验研究

目的：观察吸入适量一氧化碳（CO）对大鼠肢体缺血/再灌注（I/R）损伤的防治作用。方法：SD大鼠44只,随机分为假手术（S）、I/R、I/R吸入CO（RC）组;通过夹闭股动脉4h、再开放48h,复制肢体I/R损伤模型;RC组行再灌注时,使动物吸入含有CO的医用空气（CO的体积分数为0.05%）,其余两组呼吸正常空气;对比观测缺血肢体大体及骨骼肌组织病理学、缺血肢体湿干重比值（W/D）的变化,流式细胞仪检测肌组织中Bax、Bcl-2的表达水平及细胞凋亡百分比,全自动生化分析仪检测血清乳酸脱氢酶（LDH）和肌酸激酶（CK）的变化。结果：与I/R组比较,RC组动物W/D、血清LDH及CK含量、肌组织中Bax表达水平及细胞凋亡百分比均显著降低,肌组织Bcl-2表达水平显著升高,缺血肢体大体观及肌组织病理学明显改善。结论：吸入适量浓度的外源性CO对肢体I/R损伤有防治作用。     

Disruption of Rac1 signaling reduces ischemia-reperfusion injury in the diabetic heart by inhibiting calpain

Diabetes increases myocardial ischemia/reperfusion (I/R) injury. However, the underlying mechanisms remain incompletely understood. This study investigated the role of Rac1 signaling and calpain in exacerbated I/R injury in diabetic hearts. Mice with cardiac-specific deletion of Rac1 (Rac1-ko) and transgenic mice with cardiac-specific superoxide dismutase-2 (SOD2) or calpastatin overexpression were rendered diabetic with streptozotocin. Isolated perfused hearts were subjected to global I/R. After I/R, Rac1 activity was significantly enhanced in diabetic compared with nondiabetic hearts. Diabetic hearts displayed more severe I/R injury than nondiabetic hearts, as evidenced by more lactate dehydrogenase release and apoptosis and decreased cardiac function. These adverse impacts of diabetes were abrogated in Rac1-ko hearts or by perfusion with the Rac1 inhibitor NSC23766. In an in vivo I/R mouse model, infarct size was much smaller in diabetic Rac1-ko compared with wild-type mice. Inhibition of Rac1 signaling prevented NADPH oxidase activation, reactive oxygen species production, and protein carbonyl accumulation, leading to inhibition of calpain activation. Furthermore, SOD2 or calpastatin overexpression significantly reduced I/R injury in diabetic hearts and improved cardiac function after I/R. In summary, Rac1 activation increases I/R injury in diabetic hearts and the role of Rac1 signaling is mediated, at least in part, through calpain activation.     

Murine model of gastrointestinal ischemia associated with complement-dependent injury.

Gastrointestinal ischemia-reperfusion (I/R) injury is often associated with remote tissue injury. Complement activation plays an important role in local and remote tissue injury associated with gastrointestinal I/R. We developed a new murine model of gastrointestinal I/R that has complement-dependent local and remote tissue injury. Twenty, but not thirty, minutes of gastrointestinal ischemia followed by 3 h of reperfusion induced a significant loss of intestinal lactate dehydrogenase that was significantly prevented by a murine anti-murine C5 monoclonal antibody. Anti-C5 also significantly decreased neutrophil infiltration into the gut and lung. Gastrointestinal I/R significantly increased pulmonary intercellular adhesion molecule-1 mRNA and protein expression that was significantly inhibited by anti-C5. Pulmonary macrophage inflammatory protein-2 mRNA was significantly induced by gastrointestinal I/R and inhibited by anti-C5 treatment. These data demonstrate that brief periods of murine gastrointestinal I/R activate complement, leading to tissue injury and neutrophil accumulation. Anti-C5 treatment attenuates tissue injury, neutrophil recruitment, and leukocyte adherence molecule and chemokine expression in the mouse. This model will be well suited to investigate the role of complement-mediated tissue injury and gene expression after gastrointestinal I/R.     

雌激素对去卵巢大鼠离体心脏缺血／再灌注损伤的保护作用

目的：探讨雌激素对去卵巢大鼠离体心脏缺血／再灌注损伤的保护作用。方法：成年SD雌鼠,随机分为假手术组（Sham）,双侧卵巢切除组（Ovx）和双侧卵巢切除后补充17β-雌二醇组（Ovx＋E2）。各组离体心脏再随机分为不同时间的缺血再灌注亚组。测量的指标包括冠脉流出液中LDH及CK含量、心室肌细胞存活率及产率、基础状态和异丙肾上腺素（ISO）刺激状态下收缩幅度。结果：30min缺血及其各复灌纽均显著增加冠脉流出液中LDH、CK的释放量。Ovx组LDH、CK漏出在30min缺血及再灌注条件下,显著高于正常灌注组,而Ovx＋E2组可减轻心肌损伤,减少LDH、CK的释放。10min和20min缺血对心肌细胞存活率、产率及冠脉流出液中LDH、CK含量影响均不明显。Sham、Ovx、Ovx＋E2各组心肌细胞基础收缩幅度在正常和10minⅠ＋30minR灌注条件下无显著差异。Ovx显著增加其他各组心肌细胞基础收缩和ISO刺激收缩幅度,Ovx＋E2可使其降至Sham水平。结论：雌激素对去卵巢大鼠心肌缺血／再灌注损伤具有保护作用。     

Human recombinant erythropoietin protects the striated muscle microcirculation of the dorsal skinfold from postischemic injury in mice

Erythropoietin (EPO) has been proposed as a novel cytoprotectant in ischemia-reperfusion (I/R) injury of the brain, heart, and kidney. However, whether EPO exerts its protection by prevention of postischemic microcirculatory deterioration is unknown. We have investigated the effect of EPO on I/R-induced microcirculatory dysfunctions. We used the mouse dorsal skinfold chamber preparation to study nutritive microcirculation and leukocyte-endothelial cell interaction in striated muscle of the dorsal skinfold by in vivo fluorescence microscopy before 3 h of ischemia and during 5 days of reperfusion. Animals were pretreated with EPO (5,000 U/kg body wt) 1 or 24 h before ischemia. Vehicle-treated I/R-injured animals served as controls. Additional animals underwent sham operation only or were pretreated with EPO but not subjected to I/R. I/R significantly (P < 0.05) reduced functional capillary density, increased microvascular permeability, and enhanced venular leukocyte-endothelial cell interaction during early reperfusion. These findings were associated with pronounced (P < 0.05) arteriolar constriction and diminution of blood flow during late reperfusion. Pretreatment with EPO induced EPO receptor and endothelial nitric oxide synthase expression at 6 h of reperfusion (P < 0.05). In parallel, EPO significantly (P < 0.05) reduced capillary perfusion failure and microvascular hyperpermeability during early reperfusion and arteriolar constriction and flow during late reperfusion. EPO pretreatment substantially (P < 0.05) diminished I/R-induced leukocytic inflammation by reducing the number of rolling and firmly adhering leukocytes in postcapillary venules. EPO applied 1 h before ischemia induced angiogenic budding and sprouting at 1 and 3 days of reperfusion and formation of new capillary networks at 5 days of reperfusion. Thus our study demonstrates for the first time that EPO effectively attenuates I/R injury by preserving nutritive perfusion, reducing leukocytic inflammation, and inducing new vessel formation.     

Tao-Hong-Si-Wu decoction reduces ischemia reperfusion rat myoblast cells calcium overloading and inflammation through the Wnt/IP3R/CAMKII pathway

Limb ischemia reperfusion (LIRI) injury is associated with serious local and systemic effects. Reperfusion may augment tissue injury in excess of that produced by ischemia alone. Calcium overloading and inflammation are considered to be two of the pathological mechanisms of limb ischemia/reperfusion (I/R) injury. Tao-Hong-Si-Wu decoction (THSWD) is a traditional Chinese herbal medicine with a powerful anti-inflammatory properties. We studied the probable restorative effect of THSWD on limb I/R-induced calcium overloading and inflammation in myoblast obtained from gastrocnemius muscle tissues of Sprague-Dawley rats (Frizzled Z5,a wnt5a blocker; KN-93, a calmodulin-dependent protein kinase II (CamkII) blocker; XeC, a IP3R blocker as positive controls). The simulated ischemia and reperfusion(I/R) solutions were used to imitate LIRI environment. The results showed that after I/R treatment, the secretion of proinflammatory factors (TNF-α and IL-1β) and Wnt5a/Ca²⁺ signal molecules (wnt5a, camkII, and IP3R) upregulated significantly, the Ca²⁺ concentration enhanced too in myoblast cells. THSWD pretreatment decreased the secretion of TNF-α and IL-1β, Ca²⁺ concentration; and abated the Wnt5a/Ca²⁺ signal molecules of wnt5a, camkII and IP3R expression activated by I/R injury; but could not abated the Wnt11 and protein kinase C (PKC) expression significantly, the results was similar with Frizzled Z5 treatment cells. Our research illustrated that THSWD may have a mitigating effect on LIRI targeting Wnt/IP3R/CAMKII but not Wnt/IP3R/PKC signaling pathway for the first time. This study may encourage the use of THSWD in the critical clinical settings with LIRI.     

Combined administration of naked DNA vectors encoding VEGF and bFGF enhances tissue perfusion and arteriogenesis in ischemic hindlimb

Few studies have examined in detail the combined effects of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) gene delivery on collateral development. Here, we evaluated the potential synergism of naked DNA vectors encoding VEGF and bFGF using a skeletal-muscle based ex vivo angiogenesis assay and compared tissue perfusion and limb loss in a murine model of hindlimb ischemia. In the ex vivo angiogenesis assay, the VEGF+bFGF combination group had a larger capillary sprouting area than those of the LacZ, VEGF, and bFGF groups. Consistent with these results, regional blood flow recovery on day 14 was also highest in the VEGF+bFGF combination group, followed by the bFGF, VEGF, and LacZ groups. The limb loss frequency was 0% in the combination group, whereas the limb loss frequencies of the other groups were 7-29%. The ischemic muscles of the combination group revealed evidence of increased angiogenesis and arteriogenesis and the upregulated expression of genes that may be associated with arteriogenesis, such as those for cardiac ankyrin repeat protein, early growth response factor-1, and transforming growth factor-beta1. Our study has implications for the development of a combined gene therapy for the vascular occlusive diseases.     

Sphingolipid therapy in myocardial ischemia-reperfusion injury

Sphingolipids are known to play a significant physiological role in cell growth, cell differentiation, and critical signal transduction pathways. Recent studies have demonstrated a significant role of sphingolipids and their metabolites in the pathogenesis of myocardial ischemia-reperfusion injury. Our laboratory has investigated the cytoprotective effects of N,N,N-trimethylsphingosine chloride (TMS), a stable N-methylated synthetic sphingolipid analogue on myocardial and hepatic ischemia-reperfusion injury in clinically relevant in vivo murine models of ischemia-reperfusion injury. TMS administered intravenously at the onset of ischemia reduced myocardial infarct size in the wild-type and obese (ob/ob) mice. Following myocardial I/R, there was an improvement in cardiac function in the wild-type mice. Additionally, TMS also decreased serum liver enzymes following hepatic I/R in wild-type mice. The cytoprotective effects did not extend to the ob/ob mice following hepatic I/R or to the db/db mice following both myocardial and hepatic I/R. Our data suggest that although TMS is cytoprotective following I/R in normal animals, the cytoprotective actions of TMS are largely attenuated in obese and diabetic animals which may be due to altered signaling mechanisms in these animal models. Here we review the therapeutic role of TMS and other sphingolipids in the pathogenesis of myocardial ischemia-reperfusion injury and their possible mechanisms of cardioprotection.     

The role of excessive versus acute administration of erythropoietin in attenuating hepatic ischemia-reperfusion injury

Ischemia-reperfusion injury (I/R) is the main cause of primary graft nonfunction. Our aim was to evaluate the effect of excessive versus acute administration of erythropoietin (EPO) in attenuating the hepatic injury induced by I/R in mice. The effect of segmental (70%) hepatic ischemia was evaluated in a transgenic mouse line with constitutive overexpression of human EPO cDNA and in wild-type (WT) mice. Mice were randomly allocated to 5 main experimental groups: (i) WT-sham, (ii) WT ischemia, (iii) WT ischemia + recombinant human erythropoietin (rhEPO), (iv) transgenic-sham, and (v) transgenic ischemia. The EPO-pretreated mice showed a significant reduction in liver enzyme levels and intrahepatic caspase-3 activity and fewer apoptotic hepatocytes (p < 0.05 for all) compared with the WT untreated I/R group. EPO decreased c-Jun N-terminal kinase (JNK) phosphorylation and nuclear factor-κB (NF-κB) expression during I/R. In transgenic I/R livers, baseline histology showed diffused hepatic injury, and no significant beneficial effect was noted between the WT untreated and the transgenic I/R mice. In conclusion, acute pretreatment with EPO in WT mice attenuated in vivo I/R liver injury. However, in excessive EPO overexpression, the initial liver injury abolished the beneficial effect of EPO. These findings have important implications for the potential use of acute EPO in I/R injury during liver transplantation.     

肢体缺血预适应的肝保护作用与一氧化氮／内皮素-1系统关系的研究

目的：观察肢体缺血／再灌注（I／R）后一氧化氮／内皮素-1（NO／ET-1）失衡与肝损伤的关系以及缺血预适应（1pc）对NO／ET-1系统的调节作用。方法：实验用雄性Wistar大鼠18只,随机分为3组（n=6）：对照组（control）、缺血／再灌注组（I／R）和缺血预适应组（IPC＋I／R）,分别测定血浆谷草转氨酶（ALT）、谷丙转氨酶（AST）;血浆和肝组织一氧化氮（NO）、内皮素-1（ET-I）的含量变化,一氧化氮／内皮素-1（NO／ET-1）比值及肝组织的总一氧化氮合酶（tNOS）、诱导型一氧化氮合酶（iNOS）、结构型一氧化氮合酶（cNOS）的水平;免疫组化法检测肝组织的诱导型一氧化氮舍酶（iNOS）、内皮型一氧化氮合酶（eNOS）的表达;HE染色,在光学显微镜下观察肝组织的形态学改变。结果：发现肢体再灌注期血浆和肝组织NO、ET-1均明显增加,而NO／ET-1的比值却明显降低,同时血浆ALT、AST升高,光学显微镜下肝细胞、内皮细胞肿胀,肝细胞变性及肝窦淤血,炎性细胞浸润,肝损伤加重,肢体I／R后肝组织iNOS的表达增强,而eNOS（主要为eNOS）的表达减少,伴有总NOS活性增强。说明肢体缺血再灌注后肝组织内皮源的NO产生减少,而非内皮源的NO产生增多;IPC减轻了肢体I／R后引起的NO／ET-1失衡。结论：肢体I／R后肝组织损伤与NO／ET-1失衡有关,IPC对肢体I／R继发的肝组织损伤的保护作用可能是通过对NO／ET-1系统的调节作用而介导的,此时内皮源的NO产生增加,非内皮源的NO产生减少。