选择素在脑缺血再灌注损伤中的作用

选择素是黏附分子的一个家族,由P-选择索、L-选择素和E-选择素组成。这3种黏附分子均参与了脑缺血再灌注损伤的炎症过程。P-选择素在激活的血小板和内皮细胞表达,而E-选择素仅在血管内皮细胞表达,两者共同介导白细胞、血小板与内皮细胞的黏附。L-选择素主要在白细胞表达,介导白细胞在微血管内皮细胞上的滚动接触。     

针刺对大鼠脑缺血再灌注模型白细胞浸润及E-选择素mRNA和蛋白表达的调节

目的探讨针刺抗脑缺血再灌注(I/R)炎性损伤的机制。方法采用线栓法制作大鼠大脑中动脉缺血模型(MCAO),进行HE染色、白细胞髓过氧化物酶(MPO)活性、E-选择素mRNA和蛋白表达的测定。结果再灌注3h各实验组MPO活性均增加,24~48h达到峰值,白细胞浸润最普遍。E-选择素mRNA和蛋白表达均发生于脑I/R后3h,分别于12和24h达到高峰(组内比较,P<0.01)。针刺可显著降低MPO活性及E-选择素mRNA和蛋白表达(与模型组比较,P<0.01),明显减轻白细胞浸润。结论早期针刺治疗可能通过下调E-选择素mRNA和蛋白的表达,抑制黏附分子介导的内皮细胞与中性白细胞的黏附浸润,以防治脑I/R炎性损伤。     

急性心肌梗死时血浆可溶性E-选择素水平升高

急性心肌梗死 (AMI)的治疗 ,许多情况下应用心肌再灌注疗法。最近实验及临床研究均证实 ,再灌注后被激活的白细胞粘附在血管内皮细胞上 ,然后移行至心肌组织引起再灌注损伤。 E-选择素 (E- selectin)是一种细胞表面糖蛋白 ,属于选择素族 ,是炎症过程中白细胞初始粘附分子。最近 ,在人类血浆中发现可溶性 E-选择素 (s E- selectin)。Hwang等报道 ,血浆中 E-选择素水平是动脉硬化及冠心病的分子标志物。然而 ,AMI后心肌缺血及再灌注能否使可溶性 E-选择素水平升高尚不得而知。本研究通过测定 AMI时血浆可溶性 E-选择素水平 ,确定心肌缺…     

瑞舒伐他汀对兔心肌缺血再灌注损伤P选择素的影响

目的研究瑞舒伐他汀对兔心肌缺血再灌注损伤时P选择素的影响。方法将16只新西兰大白兔随机分为心肌缺血再灌注损伤组（对照组）和瑞舒伐他汀干预组（药物组）。建立心肌缺血再灌注模型,缺血40min,再灌注180min后取缺血区心肌组织,固定心肌,制作石蜡切片,采用免疫组化法检测缺血区心肌细胞P选择素的表达水平。结果与对照组比较,药物组的缺血区心肌细胞的P选择素表达显著下降（P〈0．01）。结论瑞舒伐他汀可有效抑制心肌缺血再灌注损伤时缺血区心肌细胞P选择素的表达水平,对损伤心肌有明显的保护作用。     

川芎嗪对肝缺血再灌注损伤大鼠P-选择素表达的影响

[目的]观察川芎嗪干预肝缺血再灌注损伤大鼠P-选择素表达,探索可能的病理机制,为预防治疗肝细胞缺血再灌注损伤提供依据.[方法]将64只SD大鼠随机分为4组,肉眼观察肝脏形态变化,光镜、电镜观察肝细胞形态变化,免疫组化SABC法检测肝组织中P-选择素表达.[结果]缺血再灌注组可见肝细胞水肿明显,伴空泡形成,间质充血水肿及炎性细胞浸润,再灌注6 h可见肝组织出现明显的点状坏死灶,并可见到灶性坏死;再灌注24 h肝组织可见多发性灶性坏死及片状坏死灶.川芎嗪干预组各时间点肝组织外观与正常肝相似,光镜下肝细胞无明显肿胀,有极少量空泡形成,但无变性或坏死,且间质无明显变化.免疫组化SABC法检测显示,缺血再灌注早期P-选择素即在肝组织中表达,与川芎嗪干预组及假手术组比较,差异有统计学意义(P＜0.01).缺血再灌注组P-选择素表达以1 h时最为明显,与再灌6 h及24 h相比,差异有统计学意义(P＜0.01).[结论]川芎嗪能有效抑制P-选择素的表达,减轻肝缺血再灌注损伤.P-选择素主要在缺血再灌注损伤早期表达.P-选择素介导中性粒细胞滚动黏附,可能是肝缺血再灌注损伤的主要机制之一.     

CD11/CD18在脑缺血再灌注损伤中的作用

粘附分子CD11 CD18是在白细胞上表达的糖蛋白 ,缺血 再灌注损伤时的作用是介导白细胞与内皮细胞的粘附及渗出到缺血组织 ,缺血性卒中患者和脑缺血动物模型中均发现其表达升高。通过降低CD11 CD18可以减少脑梗死的体积和白细胞在缺血组织中的数量 ,有望成为治疗缺血性卒中的一种方法。     

E-选择素介导的炎症反应与冠状动脉内支架术后再狭窄

再狭窄是限制冠状动脉内支架术远期成功的重要因素。它是一个由内皮损伤触发的多种因子参与的损伤修复过程,主要包括：机械损伤内皮处非阻塞性血栓形成、新生内膜增生及血管重构等反应。E-选择素仅表达于活化的内皮细胞表面,主要作用是在炎症发生时介导白细胞与血管内皮细胞的起始黏附,以及介导白细胞之间、白细胞与血小板之间的黏附形成血栓,从而对支架置入后损伤的内膜增生过程产生影响。E-选择素的研究对揭示再狭窄发生机制及寻找新的治疗途径均具有重要意义。     

CD11／CD18在脑缺血／再灌注损伤中的作用

粘附分子ＣＤ１１／ＣＤ１８是在白细胞上表达的糖蛋白，缺血／再灌注损伤时的作用是介导白细胞与内皮细胞的粘附及渗出到缺血组织，缺血性卒中患者和脑缺血动物模型中均发现其表达升高。通过降低ＣＤ１１／ＣＤ１８可以减少脑死的体积和白细胞在缺血组织中的数量，有望成为治疗缺血性卒中的一种方法。     

P—选择素与心肌缺血再灌注损伤及其单克隆抗体的应用研究

选择素（selectin)是一种细胞粘附分子，通过介导多形核白细胞与冠状血管内皮细胞之间粘附，对缺血心肌产生再灌注损伤。目前，应用其单克隆抗体的治疗正逐步显示出它的重要性。并将逐步从实验研究走向临床应用。     

P-选择素与心肌缺血再灌注损伤及其单克隆抗体的应用研究

选择素(selectin)是一种细胞粘附分子，通过介导多形核白细胞与冠状血管内皮细胞之间粘附，对缺血心肌产生再灌注损伤。目前，应用其单克隆抗体的治疗正逐步显示出它的重要性，并将逐步从实验研究走向临床应用。     

beta(2)-Integrin blockade driven by E-selectin promoter prevents neutrophil sequestration and lung injury in mice

Interaction of CD11/CD18 beta(2) integrins on polymorphonuclear leukocytes (PMNs) with their counterreceptor, intercellular adhesion molecule-1, on the surface of vascular endothelial cells is a critical event mediating stable PMN adhesion and migration across the pulmonary vascular endothelial barrier. Neutrophil inhibitory factor (NIF), a 41-kDa glycoprotein isolated from the canine hookworm (Ancylostoma caninum), binds to the I domain of CD11a and CD11b and inhibits beta(2) integrin-dependent PMN adhesion. We describe a novel strategy using the endothelial cell-specific E-selectin promoter to induce NIF expression in an inflammation-specific manner in pulmonary vascular endothelial cells. A construct containing NIF cDNA driven by the inducible endothelial cell-specific E-selectin promoter (pESNIF) was transfected into human pulmonary artery endothelial cells (HPAECs). Lipopolysaccharide challenge (known to activate E-selectin) resulted in NIF mRNA and protein expression in transfected HPAECs. NIF expression induced by the E-selectin promoter prevented PMN adhesion to the activated HPAECs, whereas PMNs adhered avidly to activated HPAECs in the absence of NIF expression. To address the utility of this approach in conditionally preventing in vivo PMN sequestration, we injected mice intravenously with cationic liposomes containing the pESNIF construct. Analysis of lung tissue showed that intraperitoneal challenge of Escherichia coli resulted in NIF expression. Inflammation-specific NIF expression induced by the E-selectin promoter prevented lung PMN sequestration and vascular injury induced by E coli challenge. These studies suggest the feasibility of conditionally blocking beta(2) integrin function at sites where the endothelium is activated and thereby of locally preventing PMN activation and migration responses that lead to tissue inflammation.     

Pathophysiologic importance of E- and L-selectin for neutrophil-induced liver injury during endotoxemia in mice

Neutrophils can cause parenchymal cell injury in the liver during ischemia-reperfusion and endotoxemia. Neutrophils relevant for the injury accumulate in sinusoids, transmigrate, and adhere to hepatocytes. To investigate the role of E- and L-selectin in this process, C3Heb/FeJ mice were treated with 700 mg/kg galactosamine and 100 microgram/kg endotoxin (Gal/ET). Immunogold labeling verified the expression of E-selectin on sinusoidal endothelial cells 4 hours after Gal/ET injection. In addition, Gal/ET caused up-regulation of Mac-1 (CD11b/CD18) and shedding of L-selectin from circulating neutrophils. Gal/ET induced hepatic neutrophil accumulation (422 +/- 32 polymorphonuclear leukocytes [PMN]/50 high power fields [HPF]) and severe liver injury (plasma alanine transaminase [ALT] activities: 4,120 +/- 960 U/L; necrosis: 44 +/- 3%) at 7 hours. Treatment with an anti-E-selectin antibody (3 mg/kg, intravenously) at the time of Gal/ET administration did not significantly affect hepatic neutrophil accumulation and localization. However, the anti-E-selectin antibody significantly attenuated liver injury as indicated by reduced ALT levels (-84%) and 43% less necrotic hepatocytes. In contrast, animals treated with an anti-L-selectin antibody or L-selectin gene knock out mice were not protected against Gal/ET-induced liver injury. However, E-, L-, and P-selectin triple knock out mice showed significantly reduced liver injury after Gal/ET treatment as indicated by lower ALT levels (-65%) and reduced necrosis (-68%). Previous studies showed that circulating neutrophils of E-selectin-overexpressing mice are primed and activated similar to neutrophils adhering to E-selectin in vitro. Therefore, we conclude that blocking E-selectin or eliminating this gene may have protected against Gal/ET-induced liver injury in vivo by inhibiting the full activation of neutrophils during the transmigration process.     

Increased expression of selectins in kidneys of patients with diabetic nephropathy

Summary In diabetic nephropathy leukocytes, mainly composed of monocytes/macrophages, which accumulate in the glomeruli and the interstitium, play an important part in the progression of glomerulosclerosis. The infiltration of leukocytes into inflammatory tissues or atherosclerotic lesions is mediated by adhesion molecules, which are expressed on the vascular endothelial cells, although little is known about the mechanism of leukocyte infiltration into diabetic renal tissues. P- and E-selectin are leukocyte adhesion molecules, which are expressed on the vascular endothelial cells and promote the adhesion of leukocytes to the endothelium. We investigated the expression of P- and E-selectin in the kidney tissue of patients with diabetic nephropathy and compared it with that of patients with other glomerular diseases (minimal change nephrotic syndrome, membranous nephropathy, IgA nephropathy, mesangioproliferative glomerulonephritis, and lupus nephritis). Expression of P- and E-selectin were both significantly increased in the glomeruli and the interstitium of patients with diabetic nephropathy as compared with those with other glomerular diseases. P- and E-selectin were both expressed along the glomerular capillaries and the peritubular capillaries in the interstitium. Neither P- nor E-selectin were correlated with the number of infiltrated leukocytes in the glomeruli, however, interestingly the E-selectin expression on peritubular capillaries was correlated with the number of infiltrated CD14 positive cells in the interstitium. These results suggest that E-selectin may play a key role in leukocyte infiltration into the renal interstitium in patients with diabetic nephropathy. [Diabetologia (1998) 41: 185–192] Received: 22 April 1997 and in final revised form: 29 September 1997     

Monocytes initiate a cycle of leukocyte recruitment when cocultured with endothelial cells

During the development of atherosclerotic plaque, monocytes and T-lymphocytes are recruited to the arterial intima by endothelial cells (EC) lining the vessel. This process is associated with chronic arterial inflammation and requires the activation-dependent expression of adhesion receptors and chemokines on EC. Here we show that monocytes can activate cocultured EC so that they support the adhesion, activation and transmigration of a secondary bolus of flowing peripheral blood monocytes or lymphocytes. The number of adherent leukocytes and their behaviour was comparable to that seen on EC activated with tumour necrosis factor-alpha (TNF-alpha). Depending upon the duration of endothelial cell/monocyte coculture different patterns of adhesion receptors were utilised by leukocytes. After 4 h coculture, antibodies against E-selectin, P-selectin and vascular cell adhesion molecule-1 (VCAM-1) reduced mononuclear leukocyte adhesion. After 24 h coculture, antibodies against E-selectin and VCAM-1 but not P-selectin were effective. Immunofluorescence analysis confirmed that monocyte coculture induced endothelial expression of E-selectin and VCAM-1, while P-selectin was at the limit of detection. We conclude that EC stimulated by monocytes can support the adhesion of flowing mononuclear leukocytes. We hypothesise that this mode of EC activation and leukocyte recruitment could initiate a self-perpetuating cycle of inflammation that could be relevant to atherogenesis and other chronic inflammatory disease states.     

Hypoxia enhances stimulus-dependent induction of E-selectin on aortic endothelial cells.

In many diseases, tissue hypoxia occurs in conjunction with other inflammatory processes. Since previous studies have demonstrated a role for leukocytes in ischemia/reperfusion injury, we hypothesized that endothelial hypoxia may "superinduce" expression of an important leukocyte adhesion molecule, E-selectin (ELAM-1, CD62E). Bovine aortic endothelial monolayers were exposed to hypoxia in the presence or absence of tumor-necrosis factor alpha (TNF-alpha) or lipopolysaccharide (LPS). Cell surface E-selectin was quantitated by whole cell ELISA or by immunoprecipitation using polyclonal anti-E-selectin sera. Endothelial mRNA levels were assessed using ribonuclease protection assays. Hypoxia alone did not induce endothelial E-selectin expression. However, enhanced induction of E-selectin was observed with the combination of hypoxia and TNF-alpha (270% increase over normoxia and TNF-alpha) or hypoxia and LPS (190% increase over normoxia and LPS). These studies revealed that a mechanism for such enhancement may be hypoxia-elicited decrements in endothelial intracellular levels of cAMP (<50% compared with normoxia). Addition of forskolin and isobutyl-methyl-xanthine during hypoxia resulted in reversal of cAMP decreases and a loss of enhanced E-selectin surface expression with the combination of TNF-alpha and hypoxia. We conclude that endothelial hypoxia may provide a novel signal for superinduction of E-selectin during states of inflammation.     

P-selectin induces the expression of tissue factor on monocytes.

P-selectin on activated platelets and stimulated endothelial cells mediates cell adhesion with monocytes and neutrophils. Since activated platelets induce tissue factor on mononuclear leukocytes, we examined the effect of P-selectin on the expression of tissue factor activity in monocytes. Purified P-selectin stimulated tissue factor expression on mononuclear leukocytes in a dose-dependent manner. Chinese hamster ovary (CHO) cells expressing P-selectin stimulated tissue factor procoagulant activity in purified monocytes, whereas untransfected CHO cells and CHO cells expressing E-selectin did not. Anti-P-selectin antibodies inhibited the effects of purified P-selectin and CHO cells expressing P-selectin on monocytes. Incubation of CHO cells expressing P-selectin with monocytes leads to the development of tissue factor mRNA in monocytes and to the expression of tissue factor antigen on the monocyte surface. These results indicate that P-selectin upregulates the expression of tissue factor on monocytes as well as mediates the binding of platelets and endothelial cells with monocytes and neutrophils. The binding of P-selectin to monocytes in the area of vascular injury may be a component of a mechanism that initiates thrombosis.     

Vascular adhesion protein-1, intercellular adhesion molecule-1 and P-selectin mediate leukocyte binding to ischemic heart in humans

OBJECTIVES: The expression of endothelial adhesion molecules and their functional significance in leukocyte adhesion to human myocardial blood vessels in acute myocardial infarction (AMI) were studied. BACKGROUND: Leukocyte extravasation, mediated by specific adhesion molecules, exacerbates tissue injury after restoration of blood supply to an ischemic tissue. Experimental myocardial reperfusion injury can be alleviated with antibodies that block the function of adhesion molecules involved in leukocyte emigration, but the relevant molecules remain poorly characterized in human AMI. METHODS: Semiquantitative immunohistochemistry and in vitro adhesion assays were used to study the expression and granulocyte binding abilities of different endothelial adhesion molecules in human AMI. Changes in the molecular nature of vascular adhesion protein-1 (VAP-1) were evaluated using immunoblotting. RESULTS: Certain endothelial adhesion molecules (intercellular adhesion molecule [ICAM-2], CD31 and CD73) were expressed in myocardial blood vessels homogeneously in normal and ischemic hearts, whereas others (E-selectin and peripheral lymph node addressin) were completely absent from all specimens. The synthesis of ICAM-1 was locally, and that of P-selectin regionally, upregulated in the infarcted hearts when compared with nonischemic controls. Vascular adhesion protein-1 showed ventricular preponderance in expression and alterations in posttranslational modifications during ischemia-reperfusion. Importantly, P-selectin, ICAM-1 and VAP-1 mediated granulocyte binding to blood vessels in the ischemic human heart. CONCLUSIONS: Human P-selectin, ICAM-1 and VAP-1 appear to be the most promising targets when antiadhesive interventions preventing leukocyte-mediated tissue destruction after myocardial ischemia are planned.     

Leukocyte ligands for endothelial selectins: specialized glycoconjugates that mediate rolling and signaling under flow

Reversible interactions of glycoconjugates on leukocytes with P- and E-selectin on endothelial cells mediate tethering and rolling of leukocytes in inflamed vascular beds, the first step in their recruitment to sites of injury. Although selectin ligands on hematopoietic precursors have been identified, here we review evidence that PSGL-1, CD44, and ESL-1 on mature leukocytes are physiologic glycoprotein ligands for endothelial selectins. Each ligand has specialized adhesive functions during tethering and rolling. Furthermore, PSGL-1 and CD44 induce signals that activate the β2 integrin LFA-1 and promote slow rolling, whereas ESL-1 induces signals that activate the β2 integrin Mac-1 in adherent neutrophils. We also review evidence for glycolipids, CD43, L-selectin, and other glycoconjugates as potential physiologic ligands for endothelial selectins on neutrophils or lymphocytes. Although the physiologic characterization of these ligands has been obtained in mice, we also note reported similarities and differences with human selectin ligands.