Ca2+与内质网途径的细胞凋亡

细胞Ca2+稳态的维持主要是通过内质网进行的，Ca2+在细胞内的活动多与内质网有关，胞内\[Ca2+\]的变化可以引起内质网应激，而过度的内质网应激则会导致细胞的凋亡。由于内质网和线粒体在细胞内空间结构上的接近，内质网释放的Ca2+又会引起线粒体途径的凋亡。一些内质网相关的因素也参与Ca2+所引起的细胞内质网途径的凋亡。     

细胞凋亡中Ca2+稳态失调机制的研究进展

Ca2+是重要的胞内信号传导因子,其稳态失调是细胞凋亡中的一个普遍现象.Ca2+稳态失调机制涉及胞外Ca2+内流,胞内钙库动员,Ca2+空间分布改变,细胞内活性氧及Bcl-2基因的调节等.研究凋亡过程中Ca2+稳态失调的发生机制,有助于阐明凋亡的启动及信号传导机制,为各种凋亡相关疾病的诊治及药物开发提供新的思路.     

钙网蛋白在心肌组织细胞氧化应激与缺血损伤构建中的表达与应用

背景：生物体内钙网蛋白具有调节细胞凋亡、应激、心血管炎症反应等多种生理和病理生理过程的功能。 目的：分析钙网蛋白在缺血再灌注损伤中的表达与应用。 方法：由作者检索1996/2010 PubMed数据库与中国知网数据库有关钙网蛋白结构、功能及在自身免疫、心脏发育中的作用、在缺血缺氧过程中表达的变化等方面的文献后,对钙网蛋白在氧化应激与缺血损伤中的表达变化进行了实验观察。 结果与结论：钙网蛋白通过协助蛋白质正确折叠和维持细胞内Ca2+稳态而参与调节细胞凋亡、黏附、类固醇敏感基因表达等,在心脏发生、发育和病理变化中发挥着重要作用。作者应用大鼠心肌缺血再灌注损伤模型,通过酶联免疫吸附试验、免疫组织化学及RT-PCR 3种不同的检测方法,观察了钙网蛋白在心肌缺血再灌注损伤中的表达,结果显示缺血再灌注损伤诱导钙网蛋白高表达,进而激活内质网凋亡信号途径,诱导细胞损伤,加重心肌损伤。     

BH3-only促调亡蛋白研究进展

细胞凋亡在多细胞生物的发育、组织稳态的维持等方面发挥重要的作用。近年来发现的BH3 only促凋亡蛋白是BCL 2家族促凋亡成员中的一大亚类 ,在不同凋亡刺激作用下 ,通过拮抗BCL 2和BCX Xl等抗凋亡蛋白及协助BAX和BAK等促凋亡蛋白参与凋亡反应 ,是细胞凋亡过程中重要的起始因子。     

内质网应激在糖尿病及糖尿病肾病中的研究进展

内质网（ER）是细胞内重要的细胞器,多种因素可导致ER内稳态失衡,功能发生改变,称为内质网应激（ERS）。ERS首先触发未折叠蛋白反应,增强细胞的存活能力。如果ERS持续存在,各种刺激超出了细胞处理能力,则将启动相关凋亡途径诱导细胞凋亡。越来越多的研究表明,ERS在糖尿病及其并发症脏器损害过程中普遍存在并发挥着重要作用。     

线粒体功能障碍与心血管疾病

 线粒体是真核细胞能量产生的重要细胞器,并在细胞钙稳态、信号传导和细胞凋亡调节中也发挥着举足轻重的作用。导致线粒体功能障碍的可能原因有氧化应激、Ca2+紊乱、线粒体生物合成减少以及线粒体DNA突变等,这些因素也与心血管疾病的发生发展密切相关。认识和研究线粒体功能障碍及其在心血管疾病中的重要作用,对阐明心血管疾病的发病机制、开拓其临床防治和药物研发新思路都具有重要意义。     

P53蛋白在蛛网膜下腔出血后早期脑损伤和血管痉挛中的作用

p53是重要的肿瘤抑制因子,在细胞内起着抑制细胞周期、促进基因组修复和诱导凋亡等多重作用。在蛛网膜下腔出血(subarachnoid hemorrhage,SAH)后,p53在缺氧等多种因素作用下被激活,并通过其靶蛋白、Bcl-2和Caspase家族蛋白等发挥促血管内皮细胞及脑内神经元凋亡的作用,并导致SAH后早期脑损伤和后期血管痉挛的发生。应用p53特异性的抑制剂可以阻断p53的活化,显著恢复SAH后的血脑屏障功能并缓解脑血管痉挛。本文讨论了p53在SAH后的血管内皮细胞和神经元凋亡中的作用机制,并进一步探讨应用p53抑制剂拮抗p53功能以治疗SAH后早期脑损伤和血管痉挛的可能性。     

线粒体损伤在创伤弧菌诱导树突状细胞凋亡中的作用

 目的：探讨线粒体损伤在创伤弧菌（Vibrio vulnificus,Vv）诱导树突状细胞（dendritic cell,DC）凋亡过程中的作用及其可能机制。方法：建立Vv 1.1758与DC2.4细胞混合培养模型。采用扫描电镜和透射电镜观察创伤弧菌侵入细胞方式和细胞线粒体病变情况。荧光探针DCFH-DA和Fluo-8/AM分别检测侵入细胞内活性氧（ROS）和Ca2+离子水平。流式细胞术检测细胞线粒体膜电位和细胞凋亡情况。采用Western blotting检测NF-κB p65和TNF-α蛋白的表达。结果：Vv 1.1758可诱导DC2.4细胞凋亡。Vv 1.1758以菌体一端与细胞表面结合的方式侵入细胞,侵入细胞的线粒体有明显病变,细胞内ROS和Ca2+水平升高,线粒体膜电位降低。共培育1 h,NF-κB p65蛋白即开始升高,5 h达高峰,6 h稍有下降;TNF-α蛋白则在共培育2 h开始增高,6 h达高峰。结论：线粒体损伤在Vv诱导DC凋亡中发挥作用,其作用机制可能与细胞内ROS和Ca2+水平升高、线粒体膜电位降低有关,NF-κB p65和TNF-α可能是细胞凋亡过程中的重要信号分子。     

钙网蛋白与肿瘤免疫关系的研究进展

钙网蛋白(CRT)是一种高度保守的内质网Ca2+结合伴侣蛋白,除了维持细胞内Ca2+平衡及负责糖蛋白的折叠外,还参与线粒体代谢、基因表达和细胞凋亡等过程。蒽环类化疗药物处理时,肿瘤细胞引起的内质网应激能导致肿瘤细胞内CRT的外翻,外翻的CRT可有效增强抗原提呈细胞对肿瘤细胞的识别与吞噬,由此引发抗同种肿瘤细胞的免疫杀伤效应,诱导肿瘤免疫原性细胞进入凋亡程序。由此说明,CRT是引起肿瘤细胞免疫原性凋亡的关键因子,其在肿瘤免疫治疗过程中具有潜在的应用价值。现就CRT在肿瘤免疫中的作用进行综述。     

内质网应激调控NLRP3炎症小体的研究进展

内质网是真核细胞中负责蛋白合成和折叠的重要细胞器,当未折叠或错误折叠蛋白在内质网腔内累积引起内质网应激时,内质网通过启动未折叠蛋白反应维持细胞稳态。炎症小体是细胞内的一种多蛋白复合物,活化后剪切Pro-Caspase-1,产生IL-1β等促炎因子,引发细胞焦亡,在固有免疫和适应性免疫中均发挥重要作用。在目前已知的多种炎症小体中,NLRP3炎症小体研究得最为深入。近年来研究表明,内质网应激与NLRP3炎症小体有密切联系,参与调控NLRP3炎症小体的活化,并在炎症性疾病的发生发展中起重要作用。本文对内质网应激参与调控NLRP3炎症小体的相关研究进展进行简要综述。     

Lithium-induced inhibition of Na-K ATPase and Ca ATPase activities in rat brain synaptosome.

To explore the action mechanism of lithium in the brain, the author investigated the effects of lithium on Na-K ATPase and Ca ATPase in rat brain synaptosomes prepared from forebrains by the method of Booth and Clark. The activities of Na-K ATPase and Ca ATPase were assayed by the level of inorganic phosphate liberated from the hydrolysis of ATP. Lithium at the optimum therapeutic concentration of 1 mM decreased the activity of Na-K ATPase from the control value of 19.08 +/- 0.29 to 18.27 +/- 0.10 micromoles Pi/mg protein/h and also reduced the activity of Ca ATPase from 6.38 +/- 0.12 to 5.64 +/- 0.12 micromoles Pi/mg protein/h. The decreased activity of Na-K ATPase will decrease the rate of Ca2+ efflux, probably via an Na-Ca exchange mechanism and will increase the rate of Ca2+ entry by the depolarization of nerve terminals. The reduced activity of Ca ATPase will result in the decreased efflux of Ca2+. As a Conclusion, it can be speculated that lithium elevates the intrasynaptosomal Ca2+ concentration via inhibition of the activities of Na-K ATPase and Ca ATPase, and this increased [Ca2+]i will cause the release of neurotransmitters and neurological effects of lithium.     

Prevention of tissue calcification on bioprosthetic heart valve by using epoxy compounds: a study of calcification tests in vitro and in vivo.

Calcification is the principal cause of the clinical failures of the bioprosthetic heart valves fabricated from glutaraldehyde pretreated porcine aortic valves or bovine pericardium. In this paper, we compared the calcification on various types of bovine pericardiums pretreated with two hydrophilic epoxy compounds adding GA post-treatment (EP 1 and EP 2), glutaraldehyde (GA)- and nontreated pericardium (Fresh), respectively, by in vitro and in vivo tests. Significant decrease of calcification was found by pretreatment with both epoxy compounds rather than with glutaraldehyde: 0.250 +/- 0.001 (Fresh), 0.276 +/- 0.058 (EP 1), 0.302 +/- 0.071 (EP 2), and 0.478 +/- 0.172 (GA) micrograms (Ca)/mg (dried tissue), respectively, after 20 days dipping in a simulating serum solution in vitro; 115.13 +/- 60.11 (Fresh), 129.84 +/- 51.08 (EP 1), 167.39 +/- 20.81 (EP 2), and 205.19 +/- 16.86 (GA) micrograms/mg, respectively, after 3 months subcutaneous implantation in rabbits. The in vitro method for evaluating calcification designed by us gave the similar order among four samples with that obtained by in vivo test. Because the bovine pericardium pretreated with the epoxy compounds adding GA post-treatment possesses the greater tenacity than that pretreated only with epoxy compounds or GA, meanwhile the calcification is also significantly decreased with this pretreatment, it may be expected that the bovine pericardium with this pretreatment will have the greater anticalcification and durability in dynamic stress.     

Oxidation of myofilament protein sulfhydryl groups reduces the contractile force and its Ca2+ sensitivity in human cardiomyocytes

This study sought to characterize the relation between the oxidation of protein sulfhydryl (SH) groups and Ca2+-activated force production in the human myocardium. Triton-permeabilized left ventricular cardiomyocytes from donor hearts were exposed to an oxidative (2,2'-dithiodipyridine, DTDP) agent in vitro, and the changes in isometric force, its Ca2+ sensitivity, the cross-bridge-sensitive rate constant of force redevelopment at saturating [Ca2+] (k(tr,max)), and protein SH oxidation were monitored. DTDP (0.1-10 mM for 2 min) oxidized the myocardial proteins and diminished the Ca2+-activated force with different concentration dependences (EC(50,SH) = 0.17 +/- 0.02 mM and EC(50,force) = 2.46 +/- 0.22 mM; mean +/- SEM). The application of 2.5 mM DTDP decreased the maximal Ca2+-activated force (to 64%), its Ca2+ sensitivity (DeltapCa(50) = 0.22 +/- 0.02), and the steepness of the Ca2+-force relation (n(Hill), from 2.01 +/- 0.08 to 1.76 +/- 0.08). These changes were paralleled by reductions in the free SH content of the proteins (to 15%) and in k(tr,max) (to 75%). SH-specific labeling identified SH oxidation of myosin light chain 1 and actin at DTDP concentrations at which the changes in the contractile parameters occurred. Our data suggest that SH oxidation in selected myofilament proteins diminishes the Ca2+-activated force and its Ca2+ sensitivity through an impaired Ca2+ regulation of the actin-myosin cycle in the human heart.     

Heparin coupling in inhibition of calcification of vascular bioprostheses.

Inhibitory effect of heparin coupling on calcification of bioprosthetic vascular grafts of different origin was studied. Heparin-bonded (Hep) and 0.625% glutaraldehyde-cross-linked (GA) segments of porcine thoracic aorta (AO), pulmonary artery (PA), jugular vein (JV) and rabbit aorta (RA) were implanted subcutaneously in weanling rats for 5 months. Heparin bonding is ineffective in prevention of calcification of JV (Hep: Ca, 159 +/- 32.26 mg g-1; GA: Ca, 193.55 +/- 17.81; p = 0.075) and RA (Hep: Ca, 150.17 +/- 14.78; GA: Ca, 192.12 +/- 26.61; p = 0.015). Calcium content of heparin-coupled PA and AO was significantly less when compared with their GA-treated counterparts. Calcification inhibition was achieved to a greater extent in heparin-bonded PA (Hep: Ca = 22.62 +/- 5.72, GA: Ca = 115.99 +/- 21.91, p < 0.0001) than in the AO coupled to heparin (Hep: Ca = 63.77 +/- 22.75, GA: Ca = 150.40 +/- 35.21, p < 0.0001). Elastin fibers were the predominant site of calcification in all explanted vascular grafts. Heparin-bonded porcine pulmonary artery is seemed to be the best among all vascular bioprostheses in this study.     

Lipoprotein PsaA in virulence of Streptococcus pneumoniae: surface accessibility and role in protection from superoxide

PsaA of Streptococcus pneumoniae, originally believed to be an adhesin, is the lipoprotein component of an Mn2+ transporter. Mutations in psaA cause deficiencies in growth, virulence, adherence, and the oxidative stress response. Immunofluorescence microscopy shows that PsaA is hidden beneath the cell wall and the polysaccharide capsule and only exposed to antibodies upon cell wall removal. A psaBC deletion mutant, expressing PsaA normally, was as deficient in adherence to Detroit 562 cells as were strains lacking PsaA. Thus, PsaA does not appear to act directly as an adhesin, but rather, psaA mutations indirectly affect this process through the disruption of Mn2+ transport. The deficiency in Mn2+ transport also causes hypersensitivity to oxidative stress from H2O2 and superoxide. In a chemically defined medium, growth of the wild-type strain was possible in the absence of Fe2+ and Mn2+ cations after a lag of about 15 h. Addition of Mn2+ alone or together with Fe2+ allowed prompt and rapid growth. In the absence of Mn2+, the addition of Fe2+ alone extended the 15-h lag phase to 25 h. Thus, while Fe2+ adversely affects the transition from lag phase to log phase, perhaps through increasing oxidative stress, this effect is relieved by the presence of Mn2+. A scavenger specific for superoxides but not those specific for hydroxyl radicals or H2O2 was able to eliminate the inhibition of growth caused by iron supplementation in the absence of Mn2+. This implies that superoxides are a key player in oxidative stress generated in the presence of iron.     

Concentration of TBA-reactive substances in type II pneumocytes exposed to oxidative stress

INTRODUCTION: Oxidative lung damage may be associated with the destruction of alveolar cells. Type II alveolar epithelial cells (AECs),as progenitors of type I cells, are indispensable for the renovation of alveolar structure after lung injury. Extensive damage to type II cells could be responsible for unfavorable outcome. However, the susceptibility of type II AECs to oxidative stress is unclear. MATERIAL/METHODS: We investigated the susceptibility of freshly isolated and cultured rat type II AECs to oxidative stress (H2O2 and Fe2+). Thiobarbituric acid reactive substances (TBARS)were measured as indices of lipid peroxidation and cytotoxicity was estimated by the MTT test. Aminotriazol (ATZ), an inhibitor of intracellular catalase, was used to estimate the protective role of catalase. RESULTS: TBARS concentration increased significantly in freshly isolated, oxidant-exposed cells (4.0 +/-1.3 vs.8.3 +/-2.2 nmol/g protein, p=0.0313)and insignificantly in cultured cells (1.7 +/-0.4 vs.4.4 +/-1.7 nmol/g protein).ATZ was toxic even to cells not exposed to oxidants. Inhibition of catalase in cells exposed to oxidants resulted in an insignificant increase in TBARs:4.5 +/-1.5 vs.16.2 +/-3.9 nmol/g protein, p=0.0625,and 4.0 +/-0.8 vs.7.6 +/-4.0 for freshly isolated and cultured cells, respectively. Oxidative stress itself did not increase cytotoxicity. CONCLUSIONS: Type II AECs are not resistant to oxidative stress. We cannot, however, explain why cells with evidence of lipid peroxidation do not show increased cytotoxicity. The toxicity of ATZ is not related to oxidative cell damage. In cells exposed to oxidants, TBARS may fur-ther increase when catalase is inhibited, which suggests an important protective role for catalase.     

Osteoclastogenesis: the role of calcium and calmodulin

Enhanced osteoclastogenesis is an important pathological feature in several aging-associated bone diseases. Thus, research activities on osteoclastogenesis have been intense during the last ten years. There has been great progress made in this field, however, and in this review, we will focus on current advances in understanding the role of Ca2+/calmodulin signaling in osteoclastogenesis. There are two major Ca2+/calmodulin signaling pathways emerging as important in osteoclastogenesis. The first is from our recent data, which has established a specific role for calmodulin in osteoclastogenesis and, more specifically, calmodulin-dependent kinase II (CaMKII). The other is that a pathway involving RANK-Ca2+-calmodulin-calcineurin-NFAT is critical for osteoclastogenesis. Collectively, these reports highlight the importance of Ca2+/calmodulin signaling in osteoclastogenesis, which may present novel targets for the new therapeutic agents to combat bone loss.     

Pmr1, a P-type ATPase, and Pdt1, an Nramp homologue, cooperatively regulate cell morphogenesis in fission yeast: the importance of Mn2+ homeostasis

Schizosaccharomyces pombe pmr1+ gene is homologous to Saccharomyces cerevisiae PMR1 gene, which encodes the P-type Ca2+/Mn2+-ATPase. Addition of Mn2+, as well as Ca2+, to the medium induced pmr1+ gene expression in a calcineurin-dependent manner. The pmr1 knockout (Deltapmr1) cells exhibited hypersensitivity to EGTA. A screen for high gene dosage-suppressors of the EGTA-hypersensitive phenotype of Deltapmr1 led to the identification of pdt1+ gene, which encodes an Nramp-related metal transporter. The Deltapmr1 cells showed round cell morphology. Although Deltapdt1 cells appeared normal in the regular medium, it showed round cell morphology similar to that of the Deltapmr1 cells when Mn2+ was removed from the medium. The removal of Mn2+ also exacerbated the round morphology of the Deltapmr1 cells. The Deltapmr1Deltapdt1 double mutants grew very slowly and showed extremely aberrant cell morphology with round, enlarged and depolarized shape. The addition of Mn2+, but not Ca2+, to the medium completely suppressed the morphological defects, while both Mn2+ and Ca2+ markedly improved the slow growth of the double mutants. These results suggest that Pmr1 and Pdt1 cooperatively regulate cell morphogenesis through the control of Mn2+ homeostasis, and that calcineurin functions as a Mn2+ sensor as well as a Mn2+ homeostasis regulator.