Identification and modulation of voltage-gated Ca2+ currents in zebrafish Rohon-Beard neurons

Electrically excitable cells have voltage-dependent ion channels on the plasma membrane that regulate membrane permeability to specific ions. Voltage-gated Ca(2+) channels (VGCCs) are especially important as Ca(2+) serves as both a charge carrier and second messenger. Zebrafish (Danio rerio) are an important model vertebrate for studies of neuronal excitability, circuits, and behavior. However, electrophysiological properties of zebrafish VGCCs remain largely unexplored because a suitable preparation for whole cell voltage-clamp studies is lacking. Rohon-Beard (R-B) sensory neurons represent an attractive candidate for this purpose because of their relatively large somata and functional homology to mammalian dorsal root ganglia (DRG) neurons. Transgenic zebrafish expressing green fluorescent protein in R-B neurons, (Isl2b:EGFP)(ZC7), were used to identify dissociated neurons suitable for whole cell patch-clamp experiments. Based on biophysical and pharmacological properties, zebrafish R-B neurons express both high- and low-voltage-gated Ca(2+) current (HVA- and LVA-I(Ca), respectively). Ni(+)-sensitive LVA-I(Ca) occur in the minority of R-B neurons (30%) and ω-conotoxin GVIA-sensitive Ca(V)2.2 (N-type) Ca(2+) channels underlie the vast majority (90%) of HVA-I(Ca). To identify G protein coupled receptors (GPCRs) that modulate HVA-I(Ca), a panel of neurotransmitters was screened. Application of GABA/baclofen or serotonin produced a voltage-dependent inhibition while application of the mu-opioid agonist DAMGO resulted in a voltage-independent inhibition. Unlike in mammalian neurons, GPCR-mediated voltage-dependent modulation of I(Ca) appears to be transduced primarily via a cholera toxin-sensitive Gα subunit. These results provide the basis for using the zebrafish model system to understanding Ca(2+) channel function, and in turn, how Ca(2+) channels contribute to mechanosensory function.     

Spatiotemporal analysis of programmed cell death during mouse cardiac septation

Cell death is thought to play an important role in mammalian cardiogenesis, although a precise map of its distribution during the crucial period of cardiac septation has so far been lacking. In this study, the spatiotemporal distribution of programmed cell death (PCD) during mouse cardiac septation is described between embryonic days 10.5 and 13.5. Two types of foci of cell death can be demonstrated in the developing heart. Those with high-intensity, with a PCD index greater than 1%, are clearly visible on individual TUNEL-assayed sections. Low-intensity foci, with a PCD index of less than 1%, become visible only following summation of data. High-intensity foci occur exclusively within the endocardial cushions of the outflow tract and atrioventricular region, appearing at the 52-54 somite stage (late E11.5), concomitant with the formation of the central mesenchymal mass. Low-intensity foci are present throughout the period of cardiac development from E10.5 to E13.5 and are frequently localized to regions of septation, such as the muscular ventricular septum and the mesenchymal cap of the primary atrial septum. Expression of Fas and FasL corresponds to these low-intensity foci, but not those with high-intensity, suggesting that activation of this death receptor may be specifically involved in molecular control of the low-intensity foci.     

Cell sheet integrity and nanomechanical breakdown during programmed cell death

Apoptosis is a critical physiological pathway required for the normal functioning, homeostasis, and development of many organisms. This process is highly regulated at the biochemical level and has been intensively studied. Recent evidence has demonstrated that apoptosis is also a controlled nanomechanical process which relies on feedback between biochemical signaling and the nanomechanical properties of the microenvironment. Deregulation of the nanomechanical breakdown of apoptotic cells results in the poorly timed release of cells and cell debris that leads to the pathogenesis of several inflammatory diseases. In this study, we investigate the nanomechanical consequences of early apoptosis in human fibroblasts grown as single cells and as cell monolayers. These fibroblasts are found within the body and are involved in many processes including wound healing and repair in which apoptosis plays a major role. We find that although the cells undergo massive morphological remodeling and nanomechanical breakdown, the extra-cellular matrix (ECM) acts to maintain monolayer integrity. Via strong interactions between fibronectin and F-actin (fibronexus junctions), the ECM maintains and reinforces cell monolayers during breakdown. This study sheds new insights on our understanding of apoptosis and how biological systems utilize multiple inter- and intra-cytoarchitectures to regulate nanomechanical breakdown.     

小鼠胚胎肾程序性细胞死亡行为的超微结构变化

目的:观察小鼠胚胎肾发育过程中程序性细胞死亡行为的超微结构变化.方法:应用透射电子显微镜技术对不同胚龄(E12、14、16、18 d)胎鼠的肾程序性细胞死亡进行系统观察.结果:在小鼠胚胎肾中,细胞凋亡多见,出现在肾发育的各个时期和各个结构中,程序性坏死和副凋亡少见,只出现在发育中的肾单位内.程序性细胞死亡的结局包括被吞噬、被血流带走和经尿液排出.结论:细胞凋亡、程序性坏死和副凋亡构成了小鼠胚胎肾发育过程中的程序性细胞死亡,以细胞凋亡为主,程序性坏死和副凋亡为辅.肾发育过程中程序性死亡的细胞尸骸经尿液排出是一个与肾结构特征有关的处理方式.     

吞噬作用能促进线虫的程序性细胞死亡

在后生动物的发育中 ,程序性细胞死亡 (ＰＣＤ)在组织的塑型、神经元间的精细连接、多余细胞或损伤细胞的消除等诸多方面扮演重要角色。通过ＰＣＤ方式 ,正在死亡的细胞迅速被吞噬细胞包裹清除。在线虫体内 ,ＰＣＤ需要杀手基因 (ｋｉｌｌｅｒｇｅｎｅｓ)ｅｇｌ- 1、ｃｅｄ - 4和ｃｅｄ - 3等的协同作用 ,而正在死亡细胞的吞噬过程 (ｅｎｇｕｌｆｍｅｎｔ)则由ｃｅｄ - 1、ｃｅｄ -2、ｃｅｄ - 5、ｃｅｄ - 6、ｃｅｄ - 7、ｃｅｄ - 10、ｃｅｄ - 12等吞噬基因 (ｅｎｇｕｌｆｍｅｎｔｇｅｎｅｓ)协同完成。根据基因相互作用的基础 ,将线虫的…     

The granule pathway of programmed cell death

The exocytosis of death-inducing granzymes stored in the granules of cytotoxic lymphocytes allows the immune system to rapidly eliminate intracellular pathogens and transformed cells. The membrane-disrupting protein perforin allows the entry of granzymes into a cell, where they induce apoptosis by cleaving target substrates in the cytoplasm and nucleus. Granzymes kill cells in a variety of ways. Recent work has demonstrated that granzymes induce mitochondrial dysfunction through caspase and caspase-independent pathways and destroy DNA and the integrity of the nucleus. Cytotoxic lymphocytes are susceptible to self-inflicted damage. Mice and humans defective in perforin and granzymes point to a role for self-inflicted damage in downregulating lymphocyte responses. Given the propensity for the granule pathway to inflict cellular damage, cytotoxic lymphocytes have developed a variety of mechanisms to protect themselves. In this regard, endogenous serine protease inhibitors have been suggested to protect cytotoxic lymphocytes from granzyme B. It would appear that certain viruses and possibly even tumor cells also use the same mechanism to escape destruction from the exocytosis pathway of programmed cell death.     

Inhibition of programmed cell death by cytomegaloviruses

The elimination of infected cells by programmed cell death (PCD) is one of the most ancestral defense mechanisms against infectious agents. This mechanism should be most effective against intracellular parasites, such as viruses, which depend on the host cell for their replication. However, even large and slowly replicating viruses like the cytomegaloviruses (CMVs) can prevail and persist in face of cellular suicide programs and other innate defense mechanisms. During evolution, these viruses have developed an impressive set of countermeasures against premature demise of the host cell. In the last decade, several genes encoding suppressors of apoptosis and necrosis have been identified in the genomes of human and murine CMV (HCMV and MCMV). Curiously, most of the gene products are not homologous to cellular antiapoptotic proteins, suggesting that the CMVs did not capture the genes from the host cell genome. This review summarizes our current understanding of how the CMVs suppress PCD and which signaling pathways they target.     

Ceramides modulate programmed cell death in plants

The balance between the bioactive sphingolipid ceramide and its phosphorylated derivative has been proposed to modulate the amount of programmed cell death (PCD) in eukaryotes. We characterized the first ceramide kinase (CERK) mutant in any organism. The Arabidopsis CERK mutant, called accelerated cell death 5, accumulates CERK substrates and shows enhanced disease symptoms during pathogen attack and apoptotic-like cell death dependent on defense signaling late in development. ACD5 protein shows high specificity for ceramides in vitro. Strikingly, C2 ceramide induces, whereas its phosphorylated derivative partially blocks, plant PCD, supporting a role for ceramide phosphorylation in modulating cell death in plants.     

Arrested differentiation and epithelial cell degeneration in zebrafish lens mutants.

In a chemical mutagenesis screen, we identified two zebrafish mutants that possessed small pupils. Genetic complementation revealed these two lines are due to mutations in different genes. The phenotypes of the two mutants were characterized using histologic, immunohistochemical, and tissue transplantation techniques. The arrested lens (arl) mutant exhibits a small eye and pupil phenotype at 48 hr postfertilization (hpf) and lacks any histologically identifiable lens structures by 5 days postfertilization (dpf). In contrast, the disrupted lens (dsl) mutants are phenotypically normal until 5 dpf, and then undergo lens disorganization and cell degeneration that is apparent by 7 dpf. Histology reveals the arl mutant terminates lens cell differentiation by 48 hpf, whereas the dsl lens exhibits a defective lens epithelial cell population at 5 dpf. Lens transplantation experiments demonstrate both mutations are autonomous to the lens tissue. Immunohistochemistry reveals the retinal cells may suffer subtle effects, possibly due to the lens abnormalities.     

骨关节炎软骨细胞的新型程序性死亡

背景:骨关节炎是一种常见的关节退行性疾病,其发生机制复杂,目前尚未阐明。但已有的研究表明,骨关节炎的发生发展与软骨细胞程序性死亡有关。目的:总结骨关节炎软骨细胞新型程序性死亡的研究进展。方法:“Osteoarthritis,Pyroptosis,Necroptosis,Ferroptosis,ROS,L-ROS,Iron-overload”为英文检索词,以“骨关节炎、细胞焦亡、坏死性凋亡、铁死亡、铁超载、脂质活性氧”为中文检索词,使用计算机在CNKI、万方数据库、PubMed、维普数据库检索2012年7月至2022年7月有关于程序性细胞死亡的相关文章,并进行系统地归纳、总结和分析。结果与结论:焦亡与骨关节炎的关系近年来备受关注,目前的研究重点仍是NLRP3炎性小体和脂多糖。有关坏死性凋亡的研究中,骨关节炎的发展也已被证明与受体相互作用蛋白激酶1密切相关,受体相互作用蛋白激酶1有可能是治疗骨关节炎的潜在靶点。铁死亡是一种最新发现的细胞死亡方式,研究发现其通过铁超载和脂质过氧化介导了软骨细胞的死亡,但铁死亡的发生涉及多个基因的表达和调控,具有复杂的信号通路和机制,目前尚未完全阐明。细胞焦亡、坏死性凋亡和铁死亡在骨关节炎的发生发展中具有重要作用,但其相关通路、基因、miRNA仍需进一步研究。     

RIP1在细胞程序性死亡中作用的研究进展

近期研究发现受体相互作用蛋白（receptor—interacting protein,RIP）是细胞生存和死亡的重要交叉点,在细胞的凋亡与存活、程序性坏死等过程中发挥着关键性的作用。RIP1为RIP家族中的第一个成员,是一种重要的细胞信号转导调控分子。RIP1的结构与生物学功能及在细胞程序性死亡中的作用具有重要意义。     

Intertwined pathways of programmed cell death in immunity

Summary: Programmed cell death (PCD) occurs widely in species from every kingdom of life. It has been shown to be an integral aspect of development in multicellular organisms, and it is an essential component of the immune response to infectious agents. An analysis of the phylogenetic origin of PCD now shows that it evolved independently several times, and it is fundamental to basic cellular physiology. Undoubtedly, PCD pervades all life at every scale of analysis. These considerations provide a backdrop for understanding the complexity of intertwined, but independent, cell death programs that operate within the immune system. In particular, the contributions of apoptosis, autophagy, and necrosis in the resolution of an immune response are considered.     

Apoptosis: a review of programmed cell death

The process of programmed cell death, or apoptosis, is generally characterized by distinct morphological characteristics and energy-dependent biochemical mechanisms. Apoptosis is considered a vital component of various processes including normal cell turnover, proper development and functioning of the immune system, hormone-dependent atrophy, embryonic development and chemical-induced cell death. Inappropriate apoptosis (either too little or too much) is a factor in many human conditions including neurodegenerative diseases, ischemic damage, autoimmune disorders and many types of cancer. The ability to modulate the life or death of a cell is recognized for its immense therapeutic potential. Therefore, research continues to focus on the elucidation and analysis of the cell cycle machinery and signaling pathways that control cell cycle arrest and apoptosis. To that end, the field of apoptosis research has been moving forward at an alarmingly rapid rate. Although many of the key apoptotic proteins have been identified, the molecular mechanisms of action or inaction of these proteins remain to be elucidated. The goal of this review is to provide a general overview of current knowledge on the process of apoptosis including morphology, biochemistry, the role of apoptosis in health and disease, detection methods, as well as a discussion of potential alternative forms of apoptosis.     

非凋亡性程序化细胞死亡的研究概况

细胞有2种基本死亡形式,即被动细胞死亡--细胞坏死和主动细胞死亡--程序化细胞死亡。凋亡是主动性细胞死亡,它是程序化细胞死亡的重要组成部分,但并非其唯一形式。最近研究表明还存在着其它的主动性细胞克亡,该细胞死亡过程中有RNA及蛋白质合成,为caspase非依赖性,形态学表现无细胞凋亡特征。由于有新的基因表达和新的蛋白质合成,因而称之为非凋亡性程序化细胞死亡。目前尚不知其确切的生物学意义,但近期研究表明它与发育和许多生理/病理现象有关。     

Biochemical evidence for programmed cell death in rabbit uterine epithelium.

Uterine epithelial cell proliferation, differentiation, and death are known to be regulated by estrogen and progesterone. The authors investigated a specific pattern of cell death called apoptosis, or programmed cell death, which is biochemically characterized by a specific pattern of DNA degradation. DNA isolated from endometrium of ovariectomized pseudopregnant rabbits showed a pattern of DNA cleavage at internucleosomal locations. In comparison, DNA from the endometrium of non-ovariectomized animals, as well as several other organs, did not exhibit that pattern. This biochemical evidence supports previous and present morphologic data and correlates with it. Under the experimental conditions used, only the uterine epithelial compartment of the endometrium shows apoptotic cell death, which is absent in the stromal compartment.     

Free radicals and reactive oxygen species in programmed cell death.

Oxidative stress, originating from reactive oxygen species and free radicals provides a constant challenge to eukaryotic cell survival. While implicated in a number of degenerative diseases, some associated with aging and with aging itself, the manner and extent to which oxidative stress contributes to the initiation or implementation of programmed-cell death is problematic. If oxidative stress is an important modulator of programmed-cell death, any ability intentionally to augment or inhibit it might ameliorate diseases in which the process is abnormally underactive or overactive.     

Heparin prevents programmed cell death in human trophoblast

Heparin is used clinically for the prevention of pregnancy complications associated with prothrombotic disorders, especially antiphospholipid antibody syndrome. Recent studies have suggested that heparin may exert direct effects on placental trophoblast, independently of its anticoagulant activity. We now demonstrate that heparin abrogates apoptosis of primary first trimester villous trophoblast in response to treatment with the pro-inflammatory cytokines interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha. This multifunctional glycosaminoglycan also inhibited apoptosis induced by other agents, including staurosporin, broad-spectrum kinase inhibitor and thrombin. Furthermore, heparin attenuated caspase-3 activity, a hallmark of apoptosis, in human first trimester villous and extravillous trophoblast cell lines treated with peptidoglycan, a Toll-like receptor-2 agonist isolated from Staphylococcus aureus. The ability of heparin to antagonize cell death induced by such diverse apoptotic signals suggested that it acts as a survival factor for human trophoblast. We demonstrate that heparin, like epidermal growth factor (EGF) and heparin-binding EGF (HB-EGF), elicits phosphorylation of the EGF receptor and activation of the phosphatidyl inositol 3-kinase (PI3K)-, the extracellular signal-related kinase 1/2 (ERK1/2)- and the c-Jun NH2 terminal kinase (JNK)-signal transduction pathways in primary villous trophoblast. In summary, we have demonstrated that heparin activates multiple anti-apoptotic pathways in human trophoblast. Our results suggest that heparin may be useful in the management of at-risk patients, even in the absence of an identifiable thrombophilic disorder.