Phagocyte activation in coronary artery disease

Abstract Recent studies suggest that granulocytes (PMNs) play a role in the pathogenesis of acute and chronic myocardial ischemia and extension of myocardial injury. Granulocytes can release a variety of molecules mediating tissue injury which act synergistically with other molecules and cells. The aim of our investigation was to evaluate the granulocyte function in patients affected by coronary artery disease (CAD) and during coronary angioplasty (PTCA). We studied 20 patients suffering from CAD. The PMN's aggregating activity was greater in the coronary sinus than in the aorta ( P <0.01). The increase in aggregating activity was evident in patients who were smokers: their cells release significantly lower quantities of leukotriene C₄ ( P <0.025). In the 20 patients who underwent coronary angioplasty we analyzed superoxide release after stimulation with phorbolmyristate-acetate (PMA). The results showed a greater decrease of PMN's superoxide production in the coronary sinus than in the aorta ( P <0.05). In all patients affected by CAD we evaluated the PMN's expression of CD11b/CD18 membrane integrins. In these patients the increase in expression of CD11b/CD18 was statistically significant in comparison with the controls ( P <0.01). This increase in expression correlates with a higher aggregation (r=0.87, P <0.001). The potential role of leukocytes, oxygen radicals, leukotrienes and granulocyte enzymes in the pathophysiology of myocardial injury due to regional ischemia and reperfusion is an area of intense investigation. This paper presents studies carried out in vivo which have been instrumental in demonstrating the role of granulocytes as mediators of myocardial ischemia.     

Studies on the interaction of leucocytes and the myocardial vasculature

Granulytes play an important role in increasing the infarct size after ischemia and reperfusion by the release of oxygen-derived free radicals (ODFR) and lysosomal enzymes. It has been shown that the number of granulocytes adhering to the vascular endothelium increases after occlusion of the coronary artery, and that the area of myocardial damage can be reduced by preventing granulocyte adherence with monoclonal antibodies directed against adhesion receptors. The underlying mechanism of granulocyte activation under these conditions is not yet known. We have investigated whether granulocytes can be activated directly by reduced oxygen tensions. Granulocytes were suspended in a hypoxic buffer and incubated on fibronectin and gelatin coated microtitre plates at 1–3% ambient oxygen to study their ability to adhere to these matrices. The results showed that the adherence of granulocytes to fibronectin was dependent on the duration of hypoxia. After 30 min of incubation under hypoxia granulocyte adherence increased 1.3 to 1.8 fold compared to the normoxic control. The adherence to fibronectin could be inhibited partially by anti-CD18 antibody, a monoclonal antibody to the common beta chain of a class of extracellular matrix receptors. This direct activation of granulocytes due to hypoxic conditions may have implications for the interaction of these cells with the vascular endotheliumin vivo, (Mol Cell Biochem116: 197–202, 1992)     

Augmentation of activities of peripheral granulocytes and of resistance against bacterial infection after administration of G-CSF into mice]

We evaluated the metabolic capability of murine peripheral granulocytes after administration of recombinant human granulocyte colony-stimulating factor (rhG-CSF) by quantitative flow cytometric assay for H2O2-dependent oxidative product formation. Intraperitoneal administration of a daily dose of 10 micrograms of rhG-CSF for 5 days induced doubling of the leukocyte population. Differential counting of peripheral leukocytes and scattergram by flow cytometry showed an increased mature granulocyte population. After stimulation with phorbol myristate acetate, the granulocytes of the rhG-CSF-administered mice demonstrated some hyperresponsive population and an increased H2O2 production. The hyperresponsive population showed H2O2 production 4-6 times higher than did normal cells. Granulocytes from the G-CSF-treated mice revealed an augmented phagocytic activity and an increased expression of Mac-1 molecules. Moreover, mice treated with G-CSF showed an enhanced resistance against intravenous infection with a lethal dose of E. coli. Granulocytes showing such markedly increased oxidative metabolism may be a significant component of the host defence to various infective organisms.     

Inflammatory responses to ischemia,and reperfusion in skeletal muscle

Skeletal muscle ischemia and reperfusion is now recognized as one form of acute inflammation in which activated leukocytes play a key role. Although restoration of flow is essential in alleviating ischemic injury, reperfusion initiates a complex series of reactions which lead to neutrophil accumulation, microvascular barrier disruption, and edema formation. A large body of evidence exists which suggests that leukocyte adhesion to and emigration across postcapillary venules plays a crucial role in the genesis of reperfusion injury in skeletal muscle. Reactive oxygen species generated by xanthine oxidase and other enzymes promote the formation of proinflammatory stimuli, modify the expression of adhesion molecules on the surface of leukocytes and endothelial cells, and reduce the bioavailability of the potent antiadhesive agent nitric oxide. As a consequence of these events, leukocytes begin to form loose adhesive interactions with postcapillary venular endothelium (leukocyte rolling). If the proinflammatory stimulus is sufficient, leukocytes may become firmly adherent (stationary adhesion) to the venular endothelium. Those leukocytes which become firmly adherent may then diapedese into the perivascular space. The emigrated leukocytes induce parenchymal cell injury via a directed release of oxidants and hydrolytic enzymes. In addition, the emigrating leukocytes also exacerbate ischemic injury by disrupting the microvascular barrier during their egress across the vasculature. As a consequence of this increase in microvascular permeability, transcapillary fluid filtration is enhanced and edema results. The resultant increase in interstitial tissue pressure physically compresses the capillaries, thereby preventing microvascular perfusion and thus promoting the development of the no-reflow phenomenon. The purpose of this review is to summarize the available information regarding these mechanisms of skeletal muscle ischemia/reperfusion injury.     

Alteration of purine metabolism by AICA-riboside in human B lymphoblasts.

The effect of 5-amino-4-imidazole-carboximide (AI-CA)-riboside on different pathways of purine metabolism (biosynthesis de novo, salvage pathways, adenosine metabolism, ATP catabolism) was studied in human B lymphoblasts (WI-L2). AICA-Riboside markedly decreased intracellular levels of 5-phosphoribosyl-1-pyrophosphate and in consequence affected purine biosynthesis de novo and purine salvage pathways. AICA-riboside inhibited incorporation of glycine into purine nucleotides, but when formate was used as the precursor of purine biosynthesis de novo, a biphasic effect was observed. The incorporation of formate into purine nucleotides was increased by AICA-riboside at concentrations up to 2 mM but decreased at higher concentrations. Salvage of the purine bases adenine, hypoxanthine, and guanine was markedly inhibited and utilization of extracellular adenosine in B lymphoblasts was reduced by AICA-riboside. AICA-riboside increased ribose 1-phosphate concentrations and increased degradation of prelabeled ATP. No effect on the intracellular levels of orthophosphate was found. Proliferation of WI-L2 lymphoblasts was only slightly affected at concentrations of AICA-riboside below 500 microM but markedly inhibited by higher concentrations.     

缺血预处理对缺血/再灌注离体心脏的保护作用

目的：探讨连续多次短暂缺血预处理对缺血/再灌注损伤心肌的保护作用及机制。方法：采用大鼠离体心脏Lan-gendorff灌流模型,观察缺血预处理对心肌缺血/再灌注后不同时间点冠脉流出液中AST、CPK、UDH及冠脉流量,心肌组织中SOD、LPO以及再灌注性心律失常的影响。结果：缺血预处理可以减少缺血/再灌注损伤的心肌冠脉流出液中AST、CPK、LDH的含量,提高心肌SOD活性,降低LPO水平,并且抑制再灌注性心律失常的发生,提高再灌注期间的冠脉流量。结论：缺血预处理对心肌缺血/再灌注损伤具有一定保护作用。     

Effects of exercise on collateral development in myocardial ischemia in pigs

To study the effects of exercise on collateral development in myocardial ischemia, we induced coronary arterial stenosis of the left circumflex coronary artery (LCCA) in 18 of 30 pigs. During that surgery, we identified the coronary bed at risk. Nine of these pigs were then subjected to 5 mo of exercise training on a treadmill. After exercise training, we determined regional collateral and myocardial blood flow using radiolabeled microspheres. At autopsy, all animals had complete occlusion of the LCCA. Infarct size in the exercise-trained pigs was significantly less than in the sedentary pigs (5.9 +/- 1.0 vs. 11.7 +/- 1.0% of the left ventricle). The exercise-trained animals had a greater increase in collateral flow, 35.1 +/- 3.0 vs. 28.7 +/- 4.1 ml X min-1 X 100 g-1, in the noninfarcted jeopardized zone of the LCCA bed. The major findings of the study were the following: 1) chronic coronary artery stenosis progressing to occlusion stimulated development of the collateral circulation and salvaged tissue in the jeopardized myocardium of an animal model with sparse collaterals; 2) development of the collateral circulation and tissue salvage is increased by exercise training; 3) collaterals develop primarily in or near the ischemic zone; and 4) all collateral beds develop a circumferential flow gradient following occlusion.     

MPG静注减轻清醒狗缺血后心肌顿抑

为了解自由基清除剂２巯基丙酰基甘氨酸（ＭＰＧ）能否减轻缺血后心肌顿抑,本文报告了在清醒狗模型中氧自由基清除剂ＭＰＧ对缺血后心肌顿抑的疗效。３９只清醒狗模型阻闭前降支１５ｍｉｎ后再灌注４８ｈ。治疗组（ｎ＝１７）于阻闭前１５ｍｉｎ始静脉给予ＭＰＧ（１００ｍｇ／ｋｇ·ｈ）,共持续６０ｍｉｎ,对照组（ｎ＝２２）给予生理盐水。结果表明,二组缺血区侧支血流、缺血区大小及血液动力学指标无显著差异,而治疗组室壁收缩增厚指数（一种局部心肌功能指标）于再灌注后２、３、４、５、６ｈ明显大于对照组,当侧支血流低于１０％时,改善更明显。指数回归分析结果显示,治疗组侧支血流越低,收缩功能恢复程度越明显。结论,ＭＰＧ可以促进缺血后心肌顿抑的恢复,这种有益的疗效在低侧支血流时更明显。     

中药抗心肌缺血再灌注损伤的信号通路研究进展

冠心病发生率、致死率高,严重危害人类健康。心肌缺血再灌注损伤是加重心肌损伤的主要病理机制,干预再灌注损伤挽救激酶、 单磷酸腺苷激酶、蛋白激酶 C 等信号传导通路保护心肌,成为减轻心肌损伤的重要途径之一。综述近 3 年国际期刊收录的中药有效成分、 提取物及复方制剂调节相关信号传导通路, 减轻心肌再灌注损伤的研究进展, 以期为阐释中药的作用特点, 有效防治心血管疾病提供参考。     

Protective effects of adenosine in rabbit sinoatrial node ischemia–reperfusion model in vivo: control of arrhythmia by hyperpolarization-activated cyclic nucleotide-gated (HCN)4 channels

Disturbance of cardiac rhythm is one of the consequences of myocardial ischemia/reperfusion injury. Many researchers have prompted considerable interests in developing therapeutic approaches for its control. In present study, we want to determine whether that adenosine pre- and postconditioning have protective effects on sinoatrial node ischemia/reperfusion injury on morphology, arrhythmia score, serological markers (CK-MB and cTnT), SOD activities, MDA levels and expression of HCN4 channels in SA node cells. According to the arrhythmia score recorded, whether adenosine used in terms of ischemia or reperfusion, the total number of arrhythmia was significantly reduced, as well as the number of its episodes was also markedly decreased. We have also shown a clear correlation between HCN4 channels expression and the dysfunction of SA node cells. HCN4 immunoreactivity decreased after adenosine pre- and postconditioning, but changes were significantly smaller in the cells of the SA node compared with cells of I/R group. The content of cTnT, CK-MB and MDA in adenosine pre- and postconditioning group reduced significantly; but the level of SOD increased significantly. Histological examination and electron microscopy observations found in adenosine pre- and postconditioning group sinoatrial node injury also mitigated. These findings suggested that adenosine pre- or postconditioning were to reduce the incidence of ischemia/reperfusion arrhythmias, reduce myocardial ischemia reperfusion injury. The mechanism was to stabilize the SA node cells membrane and one possible mechanism involves modulation of HCN4 channels in pacemaker cells of the sinoatrial node.     

Suppression of ischemic and reperfusion ventricular arrhythmias by inhalational anesthetic-induced preconditioning in the rat heart

Inhalational anesthetic-induced preconditioning (APC) has been shown to reduce infarct size and attenuate contractile dysfunction caused by myocardial ischemia. Only a few studies have reported the effects of APC on arrhythmias during myocardial ischemia-reperfusion injury, focusing exclusively on reperfusion. Accordingly, the aim of the present study was to examine the influence of APC on ventricular arrhythmias evoked by regional no-flow ischemia. APC was induced in adult male Wistar rats by 12-min exposures to two different concentrations (0.5 and 1.0 MAC) of isoflurane followed by 30-min wash-out periods. Ventricular arrhythmias were assessed in the isolated perfused hearts during a 45-min regional ischemia and a subsequent 15-min reperfusion. Myocardial infarct size was determined after an additional 45 min of reperfusion. The incidence, severity and duration of ventricular arrhythmias during ischemia were markedly reduced by APC. The higher concentration of isoflurane had a larger effect on the incidence of ventricular fibrillation than the lower concentration. The incidence of ventricular tachycardia and reversible ventricular fibrillation during reperfusion was also significantly reduced by APC; the same was true for myocardial infarct size. In conclusion, we have shown that preconditioning with isoflurane confers profound protection against myocardial ischemia- and reperfusion-induced arrhythmias and lethal myocardial injury.     

Capillary plugging by granulocytes and the no-reflow phenomenon in the microcirculation

Granulocytes are large, stiff viscoelastic cells that adhere naturally to the vascular endothelium. On their passage through the capillary network they have to be deformed, and recent evidence indicates that they may impose a significant hemodynamic resistance. The entry time of granulocytes into capillaries is about three orders of magnitude longer than that for red cells. Inside the capillary the granulocytes move with a lower velocity than red cells. Under conditions when the capillary perfusion pressure is reduced and/or elevated levels of inflammatory products are present that increase the adhesion stress to the endothelium, granulocytes may become stuck in the capillary. In such a situation, the granulocytes form a large contact area with the capillary endothelium, they obstruct the lumen, and they may initiate tissue injury. After the restoration of the perfusion pressure the granulocytes may not be removed from the capillary owing to the adhesion to the endothelium. Capillary plugging by granulocytes appears to be the mechanism responsible for the no-reflow phenomenon, and together with oxygen free radical formation and lysosomal enzyme activity may constitute the origin for ischemic injury as well as other microvascular occlusive diseases.     

Adenosine-enhanced ischemic preconditioning: adenosine receptor involvement during ischemia and reperfusion

Adenosine-enhanced ischemic preconditioning (APC) extends the cardioprotection of ischemic preconditioning (IPC) by both significantly decreasing myocardial infarct size and significantly enhancing postischemic functional recovery. In this study, the role of adenosine receptors during ischemia-reperfusion was determined. Rabbit hearts (n = 92) were used for Langendorff perfusion. Control hearts were perfused for 180 min, global ischemia hearts received 30-min ischemia and 120-min reperfusion, and IPC hearts received 5-min ischemia and 5-min reperfusion before ischemia. APC hearts received a bolus injection of adenosine coincident with IPC. Adenosine receptor (A(1), A(2), and A(3)) antagonists were used with APC before ischemia and/or during reperfusion. GR-69019X (A(1)/A(3)) and MRS-1191/MRS-1220 (A(3)) significantly increased infarct size in APC hearts when administered before ischemia and significantly decreased functional recovery when administered during both ischemia and reperfusion (P < 0.05 vs. APC). DPCPX (A(1)) administered either before ischemia and/or during reperfusion had no effect on APC cardioprotection. APC-enhanced infarct size reduction is modulated by adenosine receptors primarily during ischemia, whereas APC-enhanced postischemic functional recovery is modulated by adenosine receptors during both ischemia and reperfusion.     

Suppression of NF-κB Reduces Myocardial No-Reflow

No-reflow phenomenon is a risk factor which severely compromises the benefits of coronary revascularization in patients with acute myocardial infarction. Inflammatory response, as an essential component of cardiac ischemia/reperfusion (I/R) injury, has been suggested to contribute to the myocardial no-reflow. Since nuclear factor kappa B (NF-κB) is a key mediator of inflammation, we reasoned that inhibition of NF-κB might reduce the extent of no-reflow. To test this hypothesis, the left circumflex coronary arteries of New Zealand white male rabbits were ligated for 1.5 h, followed by reperfusion for 1 h to induce I/R injury. Pretreatment of the rabbits with a specific NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC), significantly attenuated neutrophil infiltration in the no-reflow area as well as the expansion of no-reflow. These beneficial effects were associated with a marked reduction in the serum levels of myocardial induced I/R tumor necrosis factor-α (TNF-α), intercellular adhesion molecule-1 (ICAM-1), and CXCL16. Consistently, simulative I/R culture of human umbilical vein endothelial cells (HUVECs) resulted in an increase of TNF-α, ICAM-1 and CXCL16, and all of these changes were significantly suppressed by pretreatment of the cells with PDTC or with siRNA-mediated p65 knockdown. Our data thus suggest that inhibition of NF-κB may reduce I/R-associated myocardial no-reflow through reduction of myocardial inflammation.     

Role of the locus coeruleus in the development of cerebrovascular disorders in acute myocardial ischemia

Experiments on rats were made to examine the total cerebral blood flow during locus coeruleus (LC) stimulation, acute myocardial ischemia and in the presence of acute myocardial ischemia after LC precoagulation . LC electric stimulation caused a decrease in the cerebral blood flow. The most profound cerebrovascular disorders were observed in animals with acute myocardial ischemia without LC precoagulation and were followed by cardiac arrhythmias. Cerebrovascular hemodynamic disorders occurring in acute myocardial ischemia were prevented by LC coagulation. It is suggested that the cerebrovascular disorders are consequent on the formation in the LC of the hyperactive determinant structure and play a role of a secondary pathogenetic factor in heart regulation disorders.     

Microdialysis study in vivo of the release of adenine nucleotide degradation products into intercellular space of canine myocardium during regional ischemia and reperfusion

Intercellular concentrations of adenine nucleotide degradation products (ANDP)--adenosine inosine and hypoxanthine--in ischemic and control regions of the canine myocardium were measured by microdialysis technique during 20- and 40-min coronary artery occlusion and reperfusion. In hearts that fibrillated on reperfusion during the ischemic 40-min period catabolism of adenine nucleotides was more intensive, which could be the min cause of the reperfusion ventricular fibrillation. Reperfusion ventricular fibrillation was accompanied by an increase in the intercellular ANDP level in the control region, that indicated the development of the total myocardial ischemia. During the initial period of reperfusion after 20-min, a sharp increase in the interstitial ANDP level was observed in the ischemic region as compared with the end of the ischemia which could be explained as a result of demasking of reperfusion damage in such a case. The 40-min reperfusion induced slow reduction of the intercellular ANDP level in the ischemic region, while the regional blood flow already 5 min after the reperfusion did not differ from the blood flow in the control region. It is supposed that a slow washout of ANDP could be caused by the "no-reflow" phenomenon.     

微血栓形成和纤维蛋白原、载脂蛋白比值与大鼠急性心肌缺血再灌注无再流现象的相关性

摘要 目的：探讨微血栓形成和纤维蛋白原、载脂蛋白比值与大鼠急性心肌缺血再灌注无再流现象的相关性。方法：选择70只SD大鼠构建大鼠急性心肌缺血再灌注模型,根据再灌注后有无再流分为2组,分别为无再流组（n=42）和有再流组（n=28）。分析各组大鼠血流动力学、微血栓形成、纤维蛋白原、载脂蛋白比值以及血清细胞因子水平,并分析微血栓形成和纤维蛋白原、载脂蛋白比值与大鼠急性心肌缺血再灌注无再流现象的相关性。结果：有再流组大鼠HR和LVEDP值、纤维蛋白原水平、VCAM-1值显著高于无再流组,而SBP、DBP和LVSP值、微血栓形成数量、ApoB值和ApoB/ApoA1值、P-selectin、ICAM-1、IL-6和IL-10值则显著低于无再流组,差异均有统计学意义（P<0.05）。微血栓形成（r=0.654,P=0.005）和载脂蛋白比值（r=0.582,P=0.004）与大鼠急性心肌缺血再灌注无再流现象之间存在正相关关系;纤维蛋白原（r=-0.552,P=0.002）与大鼠急性心肌缺血再灌注无再流现象之间存在负相关关系。结论：微血栓形成和纤维蛋白原、载脂蛋白比值与急性心肌缺血再灌注无再流现象之间存在一定的相关性,三者可作为急性心肌缺血再灌注无再流现象的预测因子。     

缺血后处理内源性心脏保护的研究进展

再灌注疗法是临床治疗心肌缺血最有效的措施,但会引起再灌注损伤,调动机体内源性保护机制可以减轻再灌注损伤,保护缺血心肌。缺血预处理（ischemic preconditioning,IPC）和后处理（ischemic postconditioning,I-postC）是缺血心脏有效的内源性保护现象,可以减轻缺血再灌注（ischemia／reperfusion,I／R）后心肌坏死与心肌功能障碍,减少恶性心律失常的发生。内源性心脏保护的机制主要是通过诱导触发因子释放,经多条细胞内信号转导途径的介导,作用于多种效应器,影响氧自由基产生、钙超载等I／R损伤的关键环节而发挥心肌细胞保护作用。特别是可以在缺血后实施的I-postC具有良好的临床应用前景。本文以I-postC为重点综述内源性心脏保护作用、机制及其临床应用现状。     

Intracoronary boluses of adenosine and sodium nitroprusside in combination reverses slow/no-reflow during angioplasty: a clinical scenario of ischemic preconditioning

No or slow reflow following percutaneous coronary intervention (PCI), despite the presence of a patent epicardial vessel, is a serious complication resulting in increased morbidity and mortality. In the present study, we have evaluated the combination therapy of adenosine and sodium nitroprusside administered as sequential intracoronary (IC) boluses on no-reflow during PCI. Seventy-five high risk acute coronary syndrome patients who underwent PCI with evidence of initial less than TIMI (thrombolysis in myocardial infarction) III flow or developed deterioration in TIMI flow during the procedure were randomized to prophylactic administration of multiple boluses of IC saline solution, adenosine (12 microg/bolus) or the combination of adenosine (12 microg/bolus) and sodium nitroprusside (50 microg/bolus), sequentially. Assessment of TIMI and the TMP (tissue myocardial perfusion) grade was done and major adverse cardiac events (MACE) were assessed at the end of 6 months. Slow or no-reflow was persistent in 70% patients receiving saline solution, 31% patients receiving adenosine, and 4% patient receiving the combination. IC injection with saline solution did not produce improvement in TIMI flow or TMP grade. IC injection with combination resulted in greater improvement of TIMI flow and TMP grade. The crossover of patients with no-reflow in saline solution group or adenosine with combination treatment was associated with reestablishment of TIMI II in 4 and TIMI III in 20 patients. Our data suggest that combination therapy of adenosine and nitroprusside is safe and provides better improvement in coronary flow and MACE as compared with IC adenosine alone in cases of impaired flow during coronary interventions.     

Effects of adenosine and acadesine on interstitial nucleosides and myocardial stunning in the pig.

5-Amino-4-imidazolecarboxamide riboside (AICAr) or acadesine has been proposed to exert cardioprotection by enhancing adenosine production in ischemic myocardium. However, there are conflicting reports on acadesine's effects in ischemic myocardium and few studies in which myocardial adenosine levels have been measured. The purpose of this study was to determine whether acadesine increases interstitial fluid adenosine levels and attenuates myocardial stunning or potentiates the effects of adenosine in the intact pig. In pentobarbital-anesthetized pigs, myocardial stunning was induced by 10 min left anterior descending coronary artery occlusion and 90 min reperfusion. Regional ventricular function was assessed by measuring systolic wall thickening, and interstitial nucleosides were estimated by cardiac microdialysis. Control hearts were compared with hearts treated with acadesine, adenosine, and adenosine plus acadesine. Adenosine pretreatment (100 microg x kg(-1) x min(-1), intracoronary) immediately prior to ischemia increased interstitial adenosine levels 9-fold and improved postischemic functional recovery from a control value of 17.6 +/- 4.1% to 43.6 +/- 3.4% of preischemic systolic wall thickening. In contrast, acadesine (20 mg/kg i.v. bolus 10 min prior to ischemia + 0.5 mg x kg (-1) x min(-1), i.v. infusion through 60 min reperfusion) had no effect on interstitial fluid adenosine levels or the recovery of regional function (21.5 +/- 5.9% recovery), nor were the functional effects of adenosine potentiated by acadesine. These findings indicate that acadesine does not enhance myocardial adenosine levels, attenuate myocardial stunning, or potentiate the cardioprotective effects of adenosine in the pig.