组织因子途径抑制物与无复流

缺血再灌注损伤在无复流病理生理中起核心作用。自噬在缺血再灌注损伤病理过程中起"双刃剑"作用。组织因子途径抑制物对组织因子介导的伴有炎症通路和凝血系统激活的无复流可能起到有效地预防及治疗作用。现就组织因子途径抑制物、心肌无复流与自噬的关系做一综述。     

自噬与心力衰竭的治疗

心力衰竭是由于各种原因导致心肌结构和功能异常,引起心室收缩和/或舒张功能受损的临床综合征。心力衰竭是一种进展性疾病,在其发生发展病程中,心肌细胞自噬起着至关重要的作用。心力衰竭时的"能量危机"刺激自噬激活,自噬激活可降解异常蛋白质及受损细胞器,从而为细胞的自我更新提供能量和物质材料。进一步揭示自噬在心力衰竭病程中的作用,通过调控自噬来预防和治疗心力衰竭,发现靶向自噬功能药物,正在成为心力衰竭治疗药物研发的热点领域。     

腺苷酸活化蛋白激酶在急性胰腺炎中的作用

腺苷酸活化蛋白激酶(AMPK)作为细胞内的一种重要能量及代谢调节酶,能够有效维持细胞及机体能量及代谢稳态,在人体健康和疾病中发挥重要作用。目前研究表明,AMPK能通过作用NF-κB、TNFα、IL-6等炎症细胞因子及信号通路调节机体炎症反应,成为多种炎症疾病重要潜在治疗靶点。急性胰腺炎是由于胰酶异常激活消化自身组织细胞,释放NF-κB、TNFα、IL-6等多种炎症因子,诱发全身炎症反应,导致全身组织器官损伤急性炎症疾病。目前研究表明激活AMPK能够一定程度上减轻急性胰腺炎炎症损伤。因此,AMPK及其信号通路有望成为急性胰腺炎的潜在治疗靶点。     

粘附分子与急性胰腺炎

粘附分子是位于细胞膜表面的糖蛋白分子,在机体免疫和炎症反应等过程中发挥重要作用。白细胞的过度激活是急性胰腺炎病理过程中的一个关键环节,而白细胞停滞并浸润式的血管外渗依赖于炎症部位白细胞和内皮细胞膜表面的粘附分子的表达及功能。实验证明,急性胰腺炎时血浆可溶性粘附分子、胰腺及胰外组织的粘附分子呈高表达状态,其值的高低与急性胰腺炎的严重程度、并发症的发生及死亡率的高低相关。人们试图通过粘附抑制及粘附阻滞的方法减轻急性胰腺炎过程中各组织的损害程度,目前研究证明应用单克隆抗体阻滞粘附分子是较有效的方法,通过抗粘附途径或许能成为急性胰腺炎多水平联合治疗的一个有效手段。     

线粒体障碍在非酒精性脂肪性肝炎中的作用机制

非酒精性脂肪性肝炎(NASH)是一种以肝脂肪变性、肝细胞炎症和肝纤维化为主要特征的常见慢性肝病。研究表明,线粒体内脂质代谢异常和活性氧生成、线粒体呼吸链受损、线粒体破裂以及线粒体自噬异常等线粒体障碍在NASH的发生、发展及转归过程中发挥重要作用。以NASH中肝脂肪代谢异常、肝炎发生和肝纤维化为主要线索,总结线粒体结构破坏、功能障碍以及线粒体自噬受损在NASH中的作用机制,以寻找相应靶点指导对NASH的治疗。     

线粒体与慢性气道疾病

支气管哮喘 (简称哮喘)和COPD是两大主要的慢性气道疾病.线粒体存在于大多数真核细胞的细胞浆内,是具有独特特性的细胞器.线粒体通过遗传学、动力学、自噬和 mtROS 等多个环节,参与炎症浸润、气道重塑等肺组织病理过程.越来越多的研究表明,线粒体功能异常或正常功能受损与慢性气道疾病的病理生理机制有关.故本文拟就线粒体在哮喘和 COPD中的作用及机制作一综述.     

自噬在肺部疾病中的研究进展

自噬作为一种维持细胞内环境稳定的重要机制,近年来成为一个研究热点。在受到氧化应激、饥饿诱导、炎症刺激等损伤因素作用后,细胞可以通过激活自噬完成对受损蛋白或细胞器的清除,从而维持细胞的稳态。但是自噬的过度激活也会导致细胞功能受损或自噬性死亡。自噬在肺部疾病发病机制所起的调控作用更加复杂,其中一些疾病的发病机制尚不明确,随着自噬与其关系研究的进一步深入,为临床治疗提供了一个新的思路。本文着重讨论自噬在一些常见肺部疾病发病机制中的作用及其临床运用前景。     

异常自噬在急性胰腺炎中的作用机制研究进展

急性胰腺炎(AP)作为临床上的重急症之一,是胰腺的一种潜在致命性疾病,其发病机制尚未明确。目前研究多认为胰腺的异常自噬作用参与了胰酶的提前活化过程,从而导致AP发生,研究胰腺自噬作用的机制有利于提供治疗AP的相关思路。最近研究表明,CCAAT增强子结合蛋白β(C/EBPβ)作为一种重要的转录因子,其基因的表达参与了自噬的调控。此文就异常自噬在AP中的相关作用及C/EBPβ调控自噬的相关机制展开综述。     

自噬在胆管癌中的相关研究进展

自噬是细胞利用溶酶体降解细胞质异常蛋白质及受损细胞器等以重新利用胞内的降解物质、降解胞内有害物质的过程,以维持细胞内环境稳定.正常情况下,自噬维持在较低水平,但当细胞处在不利因素条件下时,自身自噬也会被激活应对不利因素.自噬参与许多生理和病理过程,如细胞老化、细菌入侵、神经退行性疾病、细胞凋亡以及肿瘤的发生发展.自噬与包括胆管癌在内的多种肿瘤的发生、发展、转移、复发、耐药等方面有着重要作用,但自噬在这些方面的详细机制仍不清楚.探讨分析自噬在胆管癌中的发生、发展中的作用机制和调控途径,具有重要的意义和应用价值.本文对自噬在胆管癌中的研究进展进行综述.     

促炎性细胞因子调控自噬与神经系统变性疾病研究进展

自噬是真核细胞内受损的蛋白质或细胞器通过溶酶体途径及时被降解,降解的产物再重新利用的一种生理过程,自噬在维持细胞稳态、细胞生长和自我更新方面发挥重要作用[1]。但过度自噬可能导致细胞死亡,即自噬性细胞死亡或Ⅱ型程序性细胞死亡[2]。既往研究显示自噬功能异常与神经系统变性疾病、肿瘤、免疫和炎症性疾病等多种疾病密切相关[3]。了解自噬的调节机制有助于自噬的精准调控,为疾病提供新的治疗方向。     

Activation of trypsinogen in large endocytic vacuoles of pancreatic acinar cells

The intracellular activation of trypsinogen, which is both pH- and calcium-dependent, is an important early step in the development of acute pancreatitis. The cellular compartment in which trypsinogen activation occurs currently is unknown. We therefore investigated the site of intracellular trypsinogen activation by using an established cellular model of acute pancreatitis: supramaximal stimulation of pancreatic acinar cells with cholecystokinin. We used fluorescent dextrans as fluid phase tracers and observed the cholecystokinin-elicited formation and translocation of large endocytic vacuoles. The fluorescent probe rhodamine 110 bis-(CBZ-L-isoleucyl-L-prolyl-L-arginine amide) dihydrochloride (BZiPAR) was used to detect trypsinogen activation. Fluid phase tracers were colocalized with cleaved BZiPAR, indicating that trypsinogen activation occurred within endocytic vacuoles. The development of BZiPAR fluorescence was inhibited by the trypsin inhibitor benzamidine. Fluorescein dextran and Oregon Green 488 BAPTA-5N were used to measure endosomal pH and calcium, respectively. The pH in endocytic vacuoles was 5.9 +/- 0.1, and the calcium ion concentration was 37 +/- 11 microM. The caged calcium probe o-nitrophenyl EGTA and UV uncaging were used to increase calcium in endocytic vacuoles. This increase of calcium caused by calcium uncaging was followed by recovery to the prestimulated level within approximately 100 s. We propose that the initiation of acute pancreatitis depends on endocytic vacuole formation and trypsinogen activation in this compartment.     

Acute pancreatitis in Soweto,South Africa: relationship between trypsinogen load,trypsinogen activation,and fibrinolysis

OBJECTIVE: It is not known why acute pancreatitis in Soweto, South Africa, pursues an aggressive course. We sought clues from circulating trypsinogen load at admission as marker of initial acinar injury, trypsinogen activation using the carboxypeptidase B activation peptide as surrogate, proteinase inhibitors, the coagulation-fibrinolysis axis, indicators of inflammation, oxidative stress markers, and antioxidant status. This article reports on the first four aspects. METHODS: The study involved 24 consecutive patients with a first attack. All of them were admitted within 24 h, and 22 were alcoholic. Urine was analyzed for anionic trypsinogen and the carboxypeptidase B activation peptide. Serum was tested for anionic and cationic trypsinogen, alpha1 proteinase inhibitor and alpha2 macroglobulin. Plasma from a subset was assayed for soluble fibrin, cross-linked fibrin degradation products (surrogates for thrombin and plasmin activity, respectively), and tissue-type plasminogen activator and inhibitor. RESULTS: Soweto controls had higher serum anionic trypsinogen (p = 0.004) and plasminogen activator:inhibitor ratio (p = 0.047) than U.K. controls. The outcome of acute pancreatitis was mild in 17 but severe in seven with three deaths, two on day 2. In mild pancreatitis, intense plasmin activity (p < 0.001) accompanied the surge in trypsinogen, especially anionic (p < 0.001), but without increased thrombin activity and in five patients without trypsinogen activation. In severe pancreatitis, further significant increments in plasmin activity and trypsinogens were accompanied by increased thrombin activity (p = 0.013) and trypsinogen activation (p = 0.046). There was no correlation between surrogates of plasmin and thrombin activity, or between either and the carboxypeptidase B activation peptide, which showed a curvilinear relationship to total serum trypsinogen. CONCLUSIONS: The aggressive nature of alcoholic acute pancreatitis in Soweto seems to reflect early profound fibrinolysis, which precedes coagulation and is initially independent of trypsin. Subclinical acinar-cell injury and a profibrinolytic diathesis in outwardly healthy Sowetans may predispose to this problem.     

Prevention of experimental acute pancreatitis by intraduodenal trypsin inhibitor in rat

To confirm that trypsin activity is a most important initiating factor in closed duodenal loop pancreatitis in rats, we observed the course of acute pancreatitis when trypsinogen activation was inhibited by intraduodenal infusion of a potent synthetic trypsin inhibitor (TI, nafamostat mesilate) but the other conditions were left unchanged. Intraduodenal and intrapancreatic trypsinogen activation was inhibited for 16 hr after the intraduodenal infusion of the inhibitor, although elevation of serum amylase and immunoreactive trypsin and pancreatic trypsinogen remained similar both in the TI and control groups. The mortality decreased from 44% (control) to 4% (TI) at 48 hr after establishing the model. Active trypsin in duodenal reflux is an initiating factor for further development of acute pancreatitis in the closed loop model, and inhibition of the initial activation of trypsinogen has a favorable effect on acute pancreatitis even if other deleterious factors remain unchanged.Supported by a grant from the Intractable Pancreatic Disease Research Committee from the Health and Welfare Ministry of Japan.     

The effects of somatostatin on the microperfusion of the pancreas during acute necrotizing pancreatitis in rats

BACKGROUND/AIMS: Autodigestion and impairment of microcirculation of the pancreas play an important role in the pathogenesis of acute pancreatitis. Somatostatin with the reducing effect on the hepato-splanchnic blood flow decreases exocrine pancreatic secretion. Microcirculatory changes are central to the pathogenesis of acute pancreatitis. However, little is known about the effects of somatostatin on the pancreatic tissue oxygen pressure and acinar cell injury during acute pancreatitis. The aim was to evaluate somatostatin by measuring its effect on the pancreatic tissue oxygen pressure and acinar injury in acute pancreatitis. METHODOLOGY: Acute necrotizing pancreatitis was induced in rats by standardized intraductal bile acid infusion and cerulein hyperstimulation. Serum trypsinogen activation peptide was measured to verify comparable disease severity. After the induction of acute necrotizing pancreatitis, animals randomly received either ringer lactate or somatostatin. Monitoring included cardiorespiratory parameters, hematocrit, amylase, pancreatic tissue oxygen pressure, and trypsinogen activation peptide levels. At the end of the experiments the pancreas was removed for evaluation of acinar cell injury. RESULTS: The two study groups were comparable with regard to mean arterial pressure, heart rate, arterial blood gases, hematocrit, and serum amylase. The induction of pancreatitis resulted in the significant decrease of pancreatic tissue oxygen pressure in both groups. The use of somatostatin did not increase pancreatic tissue oxygen pressure. There were no significant differences in plasma trypsinogen activation peptide and serum amylase levels in the animals of two treatment groups. Only somatostatin decreased pancreatic damage significantly. CONCLUSIONS: The use of somatostatin did not improve pancreatic microcirculation or trypsinogen activation peptide level in acute necrotizing pancreatitis; however, it reduced pancreatic damage. Therefore, it has a limited value in the treatment of the acute pancreatitis.     

Etiology and pathogenesis of acute pancreatitis: current concepts

Acute pancreatitis is a disorder that has numerous causes and an obscure pathogenesis. Bile duct stones and alcohol abuse together account for about 80% of acute pancreatitis. Most episodes of biliary pancreatitis are associated with transient impaction of the stone in the ampulla (that causes obstruction of the pancreatic duct, with ductal hypertension) or passage of the stone though and into the duodenum. Other causes of acute pancreatitis are various toxins, drugs, other obstructive causes (such as malignancy or fibrotic sphincter of Oddi), metabolic abnormalities, trauma, ischemia, infection, autoimmune diseases, etc. In 10% of cases of acute pancreatitis, no underlying cause can be identified; this is idiopathic pancreatitis. Occult biliary microlithiasis may be the cause of two thirds of the cases of "idiopathic" acute pancreatitis. Intra-acinar activation of trypsinogen plays a central role in the pathogenesis of acute pancreatitis, resulting in subsequent activation of other proteases causing the subsequent cell damage. Ischemia/reperfusion injury is increasingly recognized as a common and important mechanism in the pathogenesis of acute pancreatitis and especially in the progression from mild edematous to severe necrotizing form. Increased intracellular calcium concentration also mediates acinar cell damage. Oxygen-derived free radicals and many cytokines (e.g., interleukin [IL]-1, IL-6, IL-8, tumor necrosis factor-alpha, platelet activating factor) are considered to be principal mediators in the transformation of acute pancreatitis from a local inflammatory process into a multiorgan illness.     

Hereditary pancreatitis: new insights, new directions.

Hereditary pancreatitis is an unusual form of acute and chronic pancreatitis with a familial predisposition. Recently, the gene mutations causing most cases of hereditary pancreatitis have been identified in the cationic trypsinogen gene. The known mutations are trypsinogen R117H and N211. These may predispose to acute pancreatitis by eliminating one of the fail-safe mechanisms used by the pancreas to eliminate prematurely activated trypsin. Accumulation of active trypsin mutants are hypothesized to initiate a digestive enzyme activation cascade in the pancreatic acinar cells leading to autodigestion, an intense inflammatory response, and acute pancreatitis. The observation that these patients also develop typical chronic pancreatitis and may later develop pancreatic cancer provides strong evidence that these conditions are linked. Knowledge of the pathophysiological conditions leading to acute and chronic pancreatitis and the development of a transgenic mouse expressing the mutant human trypsinogen genes will provide directions and tools necessary for the effective treatment or prevention of this human disease.     

Early prediction of severity in acute pancreatitis. Is this possible?

One out of ten cases of acute pancreatitis develops into severe acute pancreatitis which is a life threatening disorder with a high mortality rate. The other nine cases are self limiting and need very little therapy. The specificity of good clinical judgement on admission, concerning the prognosis of the attack, is high (high specificity) but misses a lot of severe cases (low sensitivity). The prediction of severity in acute pancreatitis was first suggested by John HC Ranson in 1974. Much effort has been put into finding a simple scoring system or a good biochemical marker for selecting the severe cases of acute pancreatitis immediately on admission. Today C-reactive protein is the method of choice although this marker is not valid until 48-72 hours after the onset of pain. Inflammatory mediators upstream from CRP like interleukin-6 and other cytokines are likely to react faster and preliminary results for some of these mediators look promising. Another successful approach has been to study markers for the activation of trypsinogen such as TAP and CAPAP. This is based on studies showing that active trypsin is the initial motor of the inflammatory process in acute pancreatitis. In the near future a combined clinical and laboratory approach for early severity prediction will be the most reliable. Clinical judgement predicts 1/3 of the severe cases on admission and early markers for either inflammation or trypsinogen activation should accurately identify 50-60% of the mild cases among the rest, thus missing only 2-4% of the remaining severe cases. One problem is that there is no simple and fast method to analyze any of these parameters.     

Trypsin-based laboratory methods and carboxypeptidase activation peptide in acute pancreatitis

Acute pancreatitis is a common disease varying widely in severity. At present, there is no "gold standard" for the diagnosis of acute pancreatitis. Currently, the diagnosis of acute pancreatitis is based on measurements of serum amylase and/or lipase activity, which are considered unsatisfactory due to their low level of accuracy. Early identification of acute pancreatitis and especially detection of patients with a severe form of the disease is of utmost importance. Premature intrapancreatic activation of trypsinogen is a crucial early event in the pathophysiology of acute pancreatitis. The conversion of trypsinogen to active trypsin is mediated by the release of its activation peptide (TAP). The active trypsin is then able to activate other pancreatic zymogens (i.e. procarboxypeptidase) leading to tissue damage and eventually to autodigestion of the pancreas. To improve the laboratory diagnostics of AP, new methods have been developed to measure this primary pancreatic proteolytic insult. Here we review the current knowledge and clinical implications of trypsin based laboratory methods and carboxypeptidase activation peptide (CAPAP) in the diagnosis and severity assessment of acute pancreatitis.     

Mechanisms of intracellular zymogen activation.

The pancreatic acinar cell is potentially the initial site of injury that begins the series of events leading to acute pancreatitis. Pathological intrapancreatic zymogen activation occurs in experimental pancreatitis in animals and in human pancreatitis. Intracellular activation has been clearly linked to aberrant zymogen processing in one form of hereditary pancreatitis; in this genetic disease a mutation in cationic trypsinogen may eliminate the degradation of any trypsin activated in the acinar cell. Recent studies have also provided the first direct evidence that trypsinogen activation takes place early in the course of caerulein-induced pancreatitis; parallel studies have used isolated pancreatic acini and conditions that simulate those that cause pancreatitis in vivo to demonstrate that zymogens can be pathologically activated in isolated cells. A unique acinar cell pathway regulates the intracellular proteinase processing of zymogens to their active forms. Stimulating the acinar cell with supramaximal concentrations of cholecystokinin (CCK) or carbamylcholine can activate this pathway. The activation depends on a low pH compartment within the acinar cell and activation of an intracellular serine protease. A marker of trypsinogen processing, the trypsinogen activation peptide (TAP), is generated in acinar cell compartments that do not overlap with secretory granules. This compartment overlaps with a marker of recycling endosomes and lysosomes. Thus, zymogen processing within the acinar cell proceeds in a distinct subcellular compartment and is dependent on a low pH environment and activation of serine proteases.