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Pubmed Article
Histones-mediated lymphocyte apoptosis during sepsis is dependent on p38 phosphorylation and mitochondrial permeability transition.
PLoS ONE
PUBLISHED: 01-01-2013
Lymphocyte apoptosis is one reason for immunoparalysis seen in sepsis, although the triggers are unknown. We hypothesized that molecules in plasma, which are up-regulated during sepsis, may be responsible for this. In this study, peripheral lymphocyte apoptosis caused by extracellular histones was confirmed both in mouse and human primary lymphocytes, in which histones induced lymphocyte apoptosis dose-dependently and time-dependently. To identify which intracellular signal pathways were activated, phosphorylation of various mitogen-activated protein kinases (MAPKs) were evaluated during this process, and p38 inhibitor (SB203580) was used to confirm the role of p38 in lymphocyte apoptosis induced by histones. To investigate the mitochondrial injury during these processes, we analyzed Bcl2 degradation and Rhodamine 123 to assess mitochondrial-membrane stability, via cyclosporin A as an inhibitor for mitochondrial permeability transition (MPT). Then, caspase 3 activation was also checked by western-blotting. We found that p38 phosphorylation, mitochondrial injury and caspase 3 activation occurred dose-dependently in histones-mediated lymphocyte apoptosis. We also observed that p38 inhibitor SB203580 decreased lymphocyte apoptotic ratio by 49% (P<0.05), and inhibition of MPT protected lymphocytes from apoptosis. Furthermore, to investigate whether histones are responsible for lymphocyte apoptosis, various concentrations of histone H4 neutralization antibodies were co-cultured with human primary lymphocytes and plasma from cecal ligation and puncture (CLP) mice or sham mice. The results showed that H4 neutralization antibody dose-dependently blocked lymphocyte apoptosis caused by septic plasma in vitro. These data demonstrate for the first time that extracellular histones, especially H4, play a vital role in lymphocyte apoptosis during sepsis which is dependent on p38 phosphorylation and mitochondrial permeability transition. Neutralizing H4 can inhibit lymphocyte apoptosis, indicating that it could be a potential target in clinical interventions for sepsis associated immunoparalysis.
ABSTRACT
Breast cancer is one of the most common cancers amongst women in North America. Many current anti-cancer treatments, including ionizing radiation, induce apoptosis via DNA damage. Unfortunately, such treatments are non-selective to cancer cells and produce similar toxicity in normal cells. We have reported selective induction of apoptosis in cancer cells by the natural compound pancratistatin (PST). Recently, a novel PST analogue, a C-1 acetoxymethyl derivative of 7-deoxypancratistatin (JCTH-4), was produced by de novo synthesis and it exhibits comparable selective apoptosis inducing activity in several cancer cell lines. Recently, autophagy has been implicated in malignancies as both pro-survival and pro-death mechanisms in response to chemotherapy. Tamoxifen (TAM) has invariably demonstrated induction of pro-survival autophagy in numerous cancers. In this study, the efficacy of JCTH-4 alone and in combination with TAM to induce cell death in human breast cancer (MCF7) and neuroblastoma (SH-SY5Y) cells was evaluated. TAM alone induced autophagy, but insignificant cell death whereas JCTH-4 alone caused significant induction of apoptosis with some induction of autophagy. Interestingly, the combinatory treatment yielded a drastic increase in apoptotic and autophagic induction. We monitored time-dependent morphological changes in MCF7 cells undergoing TAM-induced autophagy, JCTH-4-induced apoptosis and autophagy, and accelerated cell death with combinatorial treatment using time-lapse microscopy. We have demonstrated these compounds to induce apoptosis/autophagy by mitochondrial targeting in these cancer cells. Importantly, these treatments did not affect the survival of noncancerous human fibroblasts. Thus, these results indicate that JCTH-4 in combination with TAM could be used as a safe and very potent anti-cancer therapy against breast cancer and neuroblastoma cells.
22 Related JoVE Articles!
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Cecal Ligation Puncture Procedure
Authors: Miguel G. Toscano, Doina Ganea, Ana M. Gamero.
Institutions: Temple University , Temple University .
Human sepsis is characterized by a set of systemic reactions in response to intensive and massive infection that failed to be locally contained by the host. Currently, sepsis ranks among the top ten causes of mortality in the USA intensive care units 1. During sepsis there are two established haemodynamic phases that may overlap. The initial phase (hyperdynamic) is defined as a massive production of proinflammatory cytokines and reactive oxygen species by macrophages and neutrophils that affects vascular permeability (leading to hypotension), cardiac function and induces metabolic changes culminating in tissue necrosis and organ failure. Consequently, the most common cause of mortality is acute kidney injury. The second phase (hypodynamic) is an anti-inflammatory process involving altered monocyte antigen presentation, decreased lymphocyte proliferation and function and increased apoptosis. This state known as immunosuppression or immune depression sharply increases the risk of nocosomial infections and ultimately, death. The mechanisms of these pathophysiological processes are not well characterized. Because both phases of sepsis may cause irreversible and irreparable damage, it is essential to determine the immunological and physiological status of the patient. This is the main reason why many therapeutic drugs have failed. The same drug given at different stages of sepsis may be therapeutic or otherwise harmful or have no effect 2,3. To understand sepsis at various levels it is crucial to have a suitable and comprehensive animal model that reproduces the clinical course of the disease. It is important to characterize the pathophysiological mechanisms occurring during sepsis and control the model conditions for testing potential therapeutic agents. To study the etiology of human sepsis researchers have developed different animal models. The most widely used clinical model is cecal ligation and puncture (CLP). The CLP model consists of the perforation of the cecum allowing the release of fecal material into the peritoneal cavity to generate an exacerbated immune response induced by polymicrobial infection. This model fulfills the human condition that is clinically relevant. As in humans, mice that undergo CLP with fluid resuscitation show the first (early) hyperdynamic phase that in time progresses to the second (late) hypodynamic phase. In addition, the cytokine profile is similar to that seen in human sepsis where there is increased lymphocyte apoptosis (reviewed in 4,5). Due to the multiple and overlapping mechanisms involved in sepsis, researchers need a suitable sepsis model of controlled severity in order to obtain consistent and reproducible results.
Medicine, Issue 51, sepsis, systemic inflammation, infection, septic shock, animal model
2860
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Activation of Apoptosis by Cytoplasmic Microinjection of Cytochrome c
Authors: Adam J. Kole, Elizabeth R.W. Knight, Mohanish Deshmukh.
Institutions: University of North Carolina , University of North Carolina .
Apoptosis, or programmed cell death, is a conserved and highly regulated pathway by which cells die1. Apoptosis can be triggered when cells encounter a wide range of cytotoxic stresses. These insults initiate signaling cascades that ultimately cause the release of cytochrome c from the mitochondrial intermembrane space to the cytoplasm2. The release of cytochrome c from mitochondria is a key event that triggers the rapid activation of caspases, the key cellular proteases which ultimately execute cell death3-4. The pathway of apoptosis is regulated at points upstream and downstream of cytochrome c release from mitochondria5. In order to study the post-mitochondrial regulation of caspase activation, many investigators have turned to direct cytoplasmic microinjection of holocytochrome c (heme-attached) protein into cells6-9. Cytochrome c is normally localized to the mitochondria where attachment of a heme group is necessary to enable it to activate apoptosis10-11. Therefore, to directly activate caspases, it is necessary to inject the holocytochrome c protein instead of its cDNA, because while the expression of cytochrome c from cDNA constructs will result in mitochondrial targeting and heme attachment, it will be sequestered from cytosolic caspases. Thus, the direct cytosolic microinjection of purified heme-attached cytochrome c protein is a useful tool to mimic mitochondrial cytochrome c release and apoptosis without the use of toxic insults which cause cellular and mitochondrial damage. In this article, we describe a method for the microinjection of cytochrome c protein into cells, using mouse embryonic fibroblasts (MEFs) and primary sympathetic neurons as examples. While this protocol focuses on the injection of cytochrome c for investigations of apoptosis, the techniques shown here can also be easily adapted for microinjection of other proteins of interest.
Cellular Biology, Issue 52, Microinjection, apoptosis, cytochrome c, fibroblasts, neurons
2773
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Human T Lymphocyte Isolation, Culture and Analysis of Migration In Vitro
Authors: Craig T. Lefort, Minsoo Kim.
Institutions: University of Rochester.
The migration of T lymphocytes involves the adhesive interaction of cell surface integrins with ligands expressed on other cells or with extracellular matrix proteins. The precise spatiotemporal activation of integrins from a low affinity state to a high affinity state at the cell leading edge is important for T lymphocyte migration 1. Likewise, retraction of the cell trailing edge, or uropod, is a necessary step in maintaining persistent integrin-dependent T lymphocyte motility 2. Many therapeutic approaches to autoimmune or inflammatory diseases target integrins as a means to inhibit the excessive recruitment and migration of leukocytes 3. To study the molecular events that regulate human T lymphocyte migration, we have utilized an in vitro system to analyze cell migration on a two-dimensional substrate that mimics the environment that a T lymphocyte encounters during recruitment from the vasculature. T lymphocytes are first isolated from human donors and are then stimulated and cultured for seven to ten days. During the assay, T lymphocytes are allowed to adhere and migrate on a substrate coated with intercellular adhesion molecule-1 (ICAM-1), a ligand for integrin LFA-1, and stromal cell-derived factor-1 (SDF-1). Our data show that T lymphocytes exhibit a migratory velocity of ~15 μm/min. T lymphocyte migration can be inhibited by integrin blockade 1 or by inhibitors of the cellular actomyosin machinery that regulates cell migration 2.
Immunology, Issue 40, T lymphocyte, Migration, Integrin, LFA-1, ICAM-1, Chemokine
2017
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Use of Animal Model of Sepsis to Evaluate Novel Herbal Therapies
Authors: Wei Li, Shu Zhu, Yusong Zhang, Jianhua Li, Andrew E. Sama, Ping Wang, Haichao Wang.
Institutions: North Shore – LIJ Health System.
Sepsis refers to a systemic inflammatory response syndrome resulting from a microbial infection. It has been routinely simulated in animals by several techniques, including infusion of exogenous bacterial toxin (endotoxemia) or bacteria (bacteremia), as well as surgical perforation of the cecum by cecal ligation and puncture (CLP)1-3. CLP allows bacteria spillage and fecal contamination of the peritoneal cavity, mimicking the human clinical disease of perforated appendicitis or diverticulitis. The severity of sepsis, as reflected by the eventual mortality rates, can be controlled surgically by varying the size of the needle used for cecal puncture2. In animals, CLP induces similar, biphasic hemodynamic cardiovascular, metabolic, and immunological responses as observed during the clinical course of human sepsis3. Thus, the CLP model is considered as one of the most clinically relevant models for experimental sepsis1-3. Various animal models have been used to elucidate the intricate mechanisms underlying the pathogenesis of experimental sepsis. The lethal consequence of sepsis is attributable partly to an excessive accumulation of early cytokines (such as TNF, IL-1 and IFN-γ)4-6 and late proinflammatory mediators (e.g., HMGB1)7. Compared with early proinflammatory cytokines, late-acting mediators have a wider therapeutic window for clinical applications. For instance, delayed administration of HMGB1-neutralizing antibodies beginning 24 hours after CLP, still rescued mice from lethality8,9, establishing HMGB1 as a late mediator of lethal sepsis. The discovery of HMGB1 as a late-acting mediator has initiated a new field of investigation for the development of sepsis therapies using Traditional Chinese Herbal Medicine. In this paper, we describe a procedure of CLP-induced sepsis, and its usage in screening herbal medicine for HMGB1-targeting therapies.
Medicine, Issue 62, Herbal therapies, innate immune cells, cytokines, HMGB1, experimental animal model of sepsis, cecal ligation and puncture
3926
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The Use of Carboxyfluorescein Diacetate Succinimidyl Ester (CFSE) to Monitor Lymphocyte Proliferation
Authors: Benjamin J. C. Quah, Christopher R. Parish.
Institutions: John Curtin School of Medical Research, Australian National University.
Carboxyfluorescein succinimidyl ester (CFSE) is an effective and popular means to monitor lymphocyte division1-3. CFSE covalently labels long-lived intracellular molecules with the fluorescent dye, carboxyfluorescein. Thus, when a CFSE-labeled cell divides, its progeny are endowed with half the number of carboxyfluorescein-tagged molecules and thus each cell division can be assessed by measuring the corresponding decrease in cell fluorescence via Flow cytometry. The capacity of CFSE to label lymphocyte populations with a high fluorescent intensity of exceptionally low variance, coupled with its low cell toxicity, make it an ideal dye to measure cell division. Since it is a fluorescein-based dye it is also compatible with a broad range of other fluorochromes making it applicable to multi-color flow cytometry. This article describes the procedures typically used for labeling mouse lymphocytes for the purpose of monitoring up to 8 cell divisions. These labeled cells can be used both for in vitro and in vivo studies.
Immunology, Issue 44, carboxyfluorescein diacetate succinimidyl ester (CFSE), labeling, lymphocytes, proliferation.
2259
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Monitoring Dynamic Changes In Mitochondrial Calcium Levels During Apoptosis Using A Genetically Encoded Calcium Sensor
Authors: Askar M. Akimzhanov, Darren Boehning.
Institutions: University of Texas Medical Branch.
Dynamic changes in intracellular calcium concentration in response to various stimuli regulates many cellular processes such as proliferation, differentiation, and apoptosis1. During apoptosis, calcium accumulation in mitochondria promotes the release of pro-apoptotic factors from the mitochondria into the cytosol2. It is therefore of interest to directly measure mitochondrial calcium in living cells in situ during apoptosis. High-resolution fluorescent imaging of cells loaded with dual-excitation ratiometric and non-ratiometric synthetic calcium indicator dyes has been proven to be a reliable and versatile tool to study various aspects of intracellular calcium signaling. Measuring cytosolic calcium fluxes using these techniques is relatively straightforward. However, measuring intramitochondrial calcium levels in intact cells using synthetic calcium indicators such as rhod-2 and rhod-FF is more challenging. Synthetic indicators targeted to mitochondria have blunted responses to repetitive increases in mitochondrial calcium, and disrupt mitochondrial morphology3. Additionally, synthetic indicators tend to leak out of mitochondria over several hours which makes them unsuitable for long-term experiments. Thus, genetically encoded calcium indicators based upon green fluorescent protein (GFP)4 or aequorin5 targeted to mitochondria have greatly facilitated measurement of mitochondrial calcium dynamics. Here, we describe a simple method for real-time measurement of mitochondrial calcium fluxes in response to different stimuli. The method is based on fluorescence microscopy of 'ratiometric-pericam' which is selectively targeted to mitochondria. Ratiometric pericam is a calcium indicator based on a fusion of circularly permuted yellow fluorescent protein and calmodulin4. Binding of calcium to ratiometric pericam causes a shift of its excitation peak from 415 nm to 494 nm, while the emission spectrum, which peaks around 515 nm, remains unchanged. Ratiometric pericam binds a single calcium ion with a dissociation constant in vitro of ~1.7 μM4. These properties of ratiometric pericam allow the quantification of rapid and long-term changes in mitochondrial calcium concentration. Furthermore, we describe adaptation of this methodology to a standard wide-field calcium imaging microscope with commonly available filter sets. Using two distinct agonists, the purinergic agonist ATP and apoptosis-inducing drug staurosporine, we demonstrate that this method is appropriate for monitoring changes in mitochondrial calcium concentration with a temporal resolution of seconds to hours. Furthermore, we also demonstrate that ratiometric pericam is also useful for measuring mitochondrial fission/fragmentation during apoptosis. Thus, ratiometric pericam is particularly well suited for continuous long-term measurement of mitochondrial calcium dynamics during apoptosis.
Cellular Biology, Issue 50, Ratiometric pericam, mitochondria, calcium, apoptosis, staurosporine, live cell imaging
2579
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Multi-parameter Measurement of the Permeability Transition Pore Opening in Isolated Mouse Heart Mitochondria
Authors: Raluca Marcu, Chris K. Neeley, Georgios Karamanlidis, Brian J. Hawkins.
Institutions: University of Washington, Seattle.
The mitochondrial permeability transition pore (mtPTP) is a non specific channel that forms in the inner mitochondrial membrane to transport solutes with a molecular mass smaller than 1.5 kDa. Although the definitive molecular identity of the pore is still under debate, proteins such as cyclophilin D, VDAC and ANT contribute to mtPTP formation. While the involvement of mtPTP opening in cell death is well established1, accumulating evidence indicates that the mtPTP serves a physiologic role during mitochondrial Ca2+ homeostasis2, bioenergetics and redox signaling 3. mtPTP opening is triggered by matrix Ca2+ but its activity can be modulated by several other factors such as oxidative stress, adenine nucleotide depletion, high concentrations of Pi, mitochondrial membrane depolarization or uncoupling, and long chain fatty acids4. In vitro, mtPTP opening can be achieved by increasing Ca2+ concentration inside the mitochondrial matrix through exogenous additions of Ca2+ (calcium retention capacity). When Ca2+ levels inside mitochondria reach a certain threshold, the mtPTP opens and facilitates Ca2+ release, dissipation of the proton motive force, membrane potential collapse and an increase in mitochondrial matrix volume (swelling) that ultimately leads to the rupture of the outer mitochondrial membrane and irreversible loss of organelle function. Here we describe a fluorometric assay that allows for a comprehensive characterization of mtPTP opening in isolated mouse heart mitochondria. The assay involves the simultaneous measurement of 3 mitochondrial parameters that are altered when mtPTP opening occurs: mitochondrial Ca2+ handling (uptake and release, as measured by Ca2+ concentration in the assay medium), mitochondrial membrane potential, and mitochondrial volume. The dyes employed for Ca2+ measurement in the assay medium and mitochondrial membrane potential are Fura FF, a membrane impermeant, ratiometric indicator which undergoes a shift in the excitation wavelength in the presence of Ca2+, and JC-1, a cationic, ratiometric indicator which forms green monomers or red aggregates at low and high membrane potential, respectively. Changes in mitochondrial volume are measured by recording light scattering by the mitochondrial suspension. Since high-quality, functional mitochondria are required for the mtPTP opening assay, we also describe the steps necessary to obtain intact, highly coupled and functional isolated heart mitochondria.
Cellular Biology, Issue 67, Mitochondria, respiration, mitochondrial permeability transition pore (mPTP), membrane potential, swelling, calcium, spectrofluorometer
4131
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Respirometric Oxidative Phosphorylation Assessment in Saponin-permeabilized Cardiac Fibers
Authors: Curtis C. Hughey, Dustin S. Hittel, Virginia L. Johnsen, Jane Shearer.
Institutions: University of Calgary, University of Calgary.
Investigation of mitochondrial function represents an important parameter of cardiac physiology as mitochondria are involved in energy metabolism, oxidative stress, apoptosis, aging, mitochondrial encephalomyopathies and drug toxicity. Given this, technologies to measure cardiac mitochondrial function are in demand. One technique that employs an integrative approach to measure mitochondrial function is respirometric oxidative phosphorylation (OXPHOS) analysis. The principle of respirometric OXPHOS assessment is centered around measuring oxygen concentration utilizing a Clark electrode. As the permeabilized fiber bundle consumes oxygen, oxygen concentration in the closed chamber declines. Using selected substrate-inhibitor-uncoupler titration protocols, electrons are provided to specific sites of the electron transport chain, allowing evaluation of mitochondrial function. Prior to respirometric analysis of mitochondrial function, mechanical and chemical preparatory techniques are utilized to permeabilize the sarcolemma of muscle fibers. Chemical permeabilization employs saponin to selectively perforate the cell membrane while maintaining cellular architecture. This paper thoroughly describes the steps involved in preparing saponin-skinned cardiac fibers for oxygen consumption measurements to evaluate mitochondrial OXPHOS. Additionally, troubleshooting advice as well as specific substrates, inhibitors and uncouplers that may be used to determine mitochondria function at specific sites of the electron transport chain are provided. Importantly, the described protocol may be easily applied to cardiac and skeletal tissue of various animal models and human samples.
Physiology, Issue 48, cardiac fibers, mitochondria, oxygen consumption, mouse, methodology
2431
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Finger-stick Blood Sampling Methodology for the Determination of Exercise-induced Lymphocyte Apoptosis
Authors: James Navalta, Brian McFarlin, Richard Simpson, Elizabeth Fedor, Holly Kell, Scott Lyons, Scott Arnett, Mark Schafer.
Institutions: Western Kentucky University, University of Houston.
Exercise is a physiological stimulus capable of inducing apoptosis in immune cells. To date, various limitations have been identified with the measurement of this phenomenon, particularly relating to the amount of time required to isolate and treat a blood sample prior to the assessment of cell death. Because of this, it is difficult to determine whether reported increases in immune cell apoptosis can be contributed to the actual effect of exercise on the system, or are a reflection of the time and processing necessary to eventually obtain this measurement. In this article we demonstrate a rapid and minimally invasive procedure for the analysis of exercise-induced lymphocyte apoptosis. Unlike other techniques, whole blood is added to an antibody panel immediately upon obtaining a sample. Following the incubation period, red blood cells are lysed and samples are ready to be analyzed. The use of a finger-stick sampling procedure reduces the volume of blood required, and minimizes the discomfort to subjects.
Immunology, Issue 48, Leukocyte phenotyping, programmed cell death, muscular activity, technique development
2595
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Viability Assays for Cells in Culture
Authors: Jessica M. Posimo, Ajay S. Unnithan, Amanda M. Gleixner, Hailey J. Choi, Yiran Jiang, Sree H. Pulugulla, Rehana K. Leak.
Institutions: Duquesne University.
Manual cell counts on a microscope are a sensitive means of assessing cellular viability but are time-consuming and therefore expensive. Computerized viability assays are expensive in terms of equipment but can be faster and more objective than manual cell counts. The present report describes the use of three such viability assays. Two of these assays are infrared and one is luminescent. Both infrared assays rely on a 16 bit Odyssey Imager. One infrared assay uses the DRAQ5 stain for nuclei combined with the Sapphire stain for cytosol and is visualized in the 700 nm channel. The other infrared assay, an In-Cell Western, uses antibodies against cytoskeletal proteins (α-tubulin or microtubule associated protein 2) and labels them in the 800 nm channel. The third viability assay is a commonly used luminescent assay for ATP, but we use a quarter of the recommended volume to save on cost. These measurements are all linear and correlate with the number of cells plated, but vary in sensitivity. All three assays circumvent time-consuming microscopy and sample the entire well, thereby reducing sampling error. Finally, all of the assays can easily be completed within one day of the end of the experiment, allowing greater numbers of experiments to be performed within short timeframes. However, they all rely on the assumption that cell numbers remain in proportion to signal strength after treatments, an assumption that is sometimes not met, especially for cellular ATP. Furthermore, if cells increase or decrease in size after treatment, this might affect signal strength without affecting cell number. We conclude that all viability assays, including manual counts, suffer from a number of caveats, but that computerized viability assays are well worth the initial investment. Using all three assays together yields a comprehensive view of cellular structure and function.
Cellular Biology, Issue 83, In-cell Western, DRAQ5, Sapphire, Cell Titer Glo, ATP, primary cortical neurons, toxicity, protection, N-acetyl cysteine, hormesis
50645
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A Restriction Enzyme Based Cloning Method to Assess the In vitro Replication Capacity of HIV-1 Subtype C Gag-MJ4 Chimeric Viruses
Authors: Daniel T. Claiborne, Jessica L. Prince, Eric Hunter.
Institutions: Emory University, Emory University.
The protective effect of many HLA class I alleles on HIV-1 pathogenesis and disease progression is, in part, attributed to their ability to target conserved portions of the HIV-1 genome that escape with difficulty. Sequence changes attributed to cellular immune pressure arise across the genome during infection, and if found within conserved regions of the genome such as Gag, can affect the ability of the virus to replicate in vitro. Transmission of HLA-linked polymorphisms in Gag to HLA-mismatched recipients has been associated with reduced set point viral loads. We hypothesized this may be due to a reduced replication capacity of the virus. Here we present a novel method for assessing the in vitro replication of HIV-1 as influenced by the gag gene isolated from acute time points from subtype C infected Zambians. This method uses restriction enzyme based cloning to insert the gag gene into a common subtype C HIV-1 proviral backbone, MJ4. This makes it more appropriate to the study of subtype C sequences than previous recombination based methods that have assessed the in vitro replication of chronically derived gag-pro sequences. Nevertheless, the protocol could be readily modified for studies of viruses from other subtypes. Moreover, this protocol details a robust and reproducible method for assessing the replication capacity of the Gag-MJ4 chimeric viruses on a CEM-based T cell line. This method was utilized for the study of Gag-MJ4 chimeric viruses derived from 149 subtype C acutely infected Zambians, and has allowed for the identification of residues in Gag that affect replication. More importantly, the implementation of this technique has facilitated a deeper understanding of how viral replication defines parameters of early HIV-1 pathogenesis such as set point viral load and longitudinal CD4+ T cell decline.
Infectious Diseases, Issue 90, HIV-1, Gag, viral replication, replication capacity, viral fitness, MJ4, CEM, GXR25
51506
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Ex vivo Culture of Drosophila Pupal Testis and Single Male Germ-line Cysts: Dissection, Imaging, and Pharmacological Treatment
Authors: Stefanie M. K. Gärtner, Christina Rathke, Renate Renkawitz-Pohl, Stephan Awe.
Institutions: Philipps-Universität Marburg, Philipps-Universität Marburg.
During spermatogenesis in mammals and in Drosophila melanogaster, male germ cells develop in a series of essential developmental processes. This includes differentiation from a stem cell population, mitotic amplification, and meiosis. In addition, post-meiotic germ cells undergo a dramatic morphological reshaping process as well as a global epigenetic reconfiguration of the germ line chromatin—the histone-to-protamine switch. Studying the role of a protein in post-meiotic spermatogenesis using mutagenesis or other genetic tools is often impeded by essential embryonic, pre-meiotic, or meiotic functions of the protein under investigation. The post-meiotic phenotype of a mutant of such a protein could be obscured through an earlier developmental block, or the interpretation of the phenotype could be complicated. The model organism Drosophila melanogaster offers a bypass to this problem: intact testes and even cysts of germ cells dissected from early pupae are able to develop ex vivo in culture medium. Making use of such cultures allows microscopic imaging of living germ cells in testes and of germ-line cysts. Importantly, the cultivated testes and germ cells also become accessible to pharmacological inhibitors, thereby permitting manipulation of enzymatic functions during spermatogenesis, including post-meiotic stages. The protocol presented describes how to dissect and cultivate pupal testes and germ-line cysts. Information on the development of pupal testes and culture conditions are provided alongside microscope imaging data of live testes and germ-line cysts in culture. We also describe a pharmacological assay to study post-meiotic spermatogenesis, exemplified by an assay targeting the histone-to-protamine switch using the histone acetyltransferase inhibitor anacardic acid. In principle, this cultivation method could be adapted to address many other research questions in pre- and post-meiotic spermatogenesis.
Developmental Biology, Issue 91, Ex vivo culture, testis, male germ-line cells, Drosophila, imaging, pharmacological assay
51868
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Cecal Ligation and Puncture-induced Sepsis as a Model To Study Autophagy in Mice
Authors: Ilias I. Siempos, Hilaire C. Lam, Yan Ding, Mary E. Choi, Augustine M. K. Choi, Stefan W. Ryter.
Institutions: Brigham and Women's Hospital, Brigham and Women's Hospital, Harvard Medical School, University of Athens Medical School, Evangelismos Hospital, Athens, Greece.
Experimental sepsis can be induced in mice using the cecal ligation and puncture (CLP) method, which causes polymicrobial sepsis. Here, a protocol is provided to induce sepsis of varying severity in mice using the CLP technique. Autophagy is a fundamental tissue response to stress and pathogen invasion. Two current protocols to assess autophagy in vivo in the context of experimental sepsis are also presented here. (I) Transgenic mice expressing green fluorescence protein (GFP)-LC3 fusion protein are subjected to CLP. Localized enhancement of GFP signal (puncta), as assayed either by immunohistochemical or confocal assays, can be used to detect enhanced autophagosome formation and, thus, altered activation of the autophagy pathway. (II) Enhanced autophagic vacuole (autophagosome) formation per unit tissue area (as a marker of autophagy stimulation) can be quantified using electron microscopy. The study of autophagic responses to sepsis is a critical component of understanding the mechanisms by which tissues respond to infection. Research findings in this area may ultimately contribute towards understanding the pathogenesis of sepsis, which represents a major problem in critical care medicine.
Infection, Issue 84, autophagosome, Autophagy, cecal ligation and puncture, mice, sepsis
51066
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Assessment of Mitochondrial Functions and Cell Viability in Renal Cells Overexpressing Protein Kinase C Isozymes
Authors: Grażyna Nowak, Diana Bakajsova.
Institutions: University of Arkansas for Medical Sciences .
The protein kinase C (PKC) family of isozymes is involved in numerous physiological and pathological processes. Our recent data demonstrate that PKC regulates mitochondrial function and cellular energy status. Numerous reports demonstrated that the activation of PKC-a and PKC-ε improves mitochondrial function in the ischemic heart and mediates cardioprotection. In contrast, we have demonstrated that PKC-α and PKC-ε are involved in nephrotoxicant-induced mitochondrial dysfunction and cell death in kidney cells. Therefore, the goal of this study was to develop an in vitro model of renal cells maintaining active mitochondrial functions in which PKC isozymes could be selectively activated or inhibited to determine their role in regulation of oxidative phosphorylation and cell survival. Primary cultures of renal proximal tubular cells (RPTC) were cultured in improved conditions resulting in mitochondrial respiration and activity of mitochondrial enzymes similar to those in RPTC in vivo. Because traditional transfection techniques (Lipofectamine, electroporation) are inefficient in primary cultures and have adverse effects on mitochondrial function, PKC-ε mutant cDNAs were delivered to RPTC through adenoviral vectors. This approach results in transfection of over 90% cultured RPTC. Here, we present methods for assessing the role of PKC-ε in: 1. regulation of mitochondrial morphology and functions associated with ATP synthesis, and 2. survival of RPTC in primary culture. PKC-ε is activated by overexpressing the constitutively active PKC-ε mutant. PKC-ε is inhibited by overexpressing the inactive mutant of PKC-ε. Mitochondrial function is assessed by examining respiration, integrity of the respiratory chain, activities of respiratory complexes and F0F1-ATPase, ATP production rate, and ATP content. Respiration is assessed in digitonin-permeabilized RPTC as state 3 (maximum respiration in the presence of excess substrates and ADP) and uncoupled respirations. Integrity of the respiratory chain is assessed by measuring activities of all four complexes of the respiratory chain in isolated mitochondria. Capacity of oxidative phosphorylation is evaluated by measuring the mitochondrial membrane potential, ATP production rate, and activity of F0F1-ATPase. Energy status of RPTC is assessed by determining the intracellular ATP content. Mitochondrial morphology in live cells is visualized using MitoTracker Red 580, a fluorescent dye that specifically accumulates in mitochondria, and live monolayers are examined under a fluorescent microscope. RPTC viability is assessed using annexin V/propidium iodide staining followed by flow cytometry to determine apoptosis and oncosis. These methods allow for a selective activation/inhibition of individual PKC isozymes to assess their role in cellular functions in a variety of physiological and pathological conditions that can be reproduced in in vitro.
Cellular Biology, Issue 71, Biochemistry, Molecular Biology, Genetics, Pharmacology, Physiology, Medicine, Protein, Mitochondrial dysfunction, mitochondria, protein kinase C, renal proximal tubular cells, reactive oxygen species, oxygen consumption, electron transport chain, respiratory complexes, ATP, adenovirus, primary culture, ischemia, cells, flow cytometry
4301
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The ChroP Approach Combines ChIP and Mass Spectrometry to Dissect Locus-specific Proteomic Landscapes of Chromatin
Authors: Monica Soldi, Tiziana Bonaldi.
Institutions: European Institute of Oncology.
Chromatin is a highly dynamic nucleoprotein complex made of DNA and proteins that controls various DNA-dependent processes. Chromatin structure and function at specific regions is regulated by the local enrichment of histone post-translational modifications (hPTMs) and variants, chromatin-binding proteins, including transcription factors, and DNA methylation. The proteomic characterization of chromatin composition at distinct functional regions has been so far hampered by the lack of efficient protocols to enrich such domains at the appropriate purity and amount for the subsequent in-depth analysis by Mass Spectrometry (MS). We describe here a newly designed chromatin proteomics strategy, named ChroP (Chromatin Proteomics), whereby a preparative chromatin immunoprecipitation is used to isolate distinct chromatin regions whose features, in terms of hPTMs, variants and co-associated non-histonic proteins, are analyzed by MS. We illustrate here the setting up of ChroP for the enrichment and analysis of transcriptionally silent heterochromatic regions, marked by the presence of tri-methylation of lysine 9 on histone H3. The results achieved demonstrate the potential of ChroP in thoroughly characterizing the heterochromatin proteome and prove it as a powerful analytical strategy for understanding how the distinct protein determinants of chromatin interact and synergize to establish locus-specific structural and functional configurations.
Biochemistry, Issue 86, chromatin, histone post-translational modifications (hPTMs), epigenetics, mass spectrometry, proteomics, SILAC, chromatin immunoprecipitation , histone variants, chromatome, hPTMs cross-talks
51220
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Setting-up an In Vitro Model of Rat Blood-brain Barrier (BBB): A Focus on BBB Impermeability and Receptor-mediated Transport
Authors: Yves Molino, Françoise Jabès, Emmanuelle Lacassagne, Nicolas Gaudin, Michel Khrestchatisky.
Institutions: VECT-HORUS SAS, CNRS, NICN UMR 7259.
The blood brain barrier (BBB) specifically regulates molecular and cellular flux between the blood and the nervous tissue. Our aim was to develop and characterize a highly reproducible rat syngeneic in vitro model of the BBB using co-cultures of primary rat brain endothelial cells (RBEC) and astrocytes to study receptors involved in transcytosis across the endothelial cell monolayer. Astrocytes were isolated by mechanical dissection following trypsin digestion and were frozen for later co-culture. RBEC were isolated from 5-week-old rat cortices. The brains were cleaned of meninges and white matter, and mechanically dissociated following enzymatic digestion. Thereafter, the tissue homogenate was centrifuged in bovine serum albumin to separate vessel fragments from nervous tissue. The vessel fragments underwent a second enzymatic digestion to free endothelial cells from their extracellular matrix. The remaining contaminating cells such as pericytes were further eliminated by plating the microvessel fragments in puromycin-containing medium. They were then passaged onto filters for co-culture with astrocytes grown on the bottom of the wells. RBEC expressed high levels of tight junction (TJ) proteins such as occludin, claudin-5 and ZO-1 with a typical localization at the cell borders. The transendothelial electrical resistance (TEER) of brain endothelial monolayers, indicating the tightness of TJs reached 300 ohm·cm2 on average. The endothelial permeability coefficients (Pe) for lucifer yellow (LY) was highly reproducible with an average of 0.26 ± 0.11 x 10-3 cm/min. Brain endothelial cells organized in monolayers expressed the efflux transporter P-glycoprotein (P-gp), showed a polarized transport of rhodamine 123, a ligand for P-gp, and showed specific transport of transferrin-Cy3 and DiILDL across the endothelial cell monolayer. In conclusion, we provide a protocol for setting up an in vitro BBB model that is highly reproducible due to the quality assurance methods, and that is suitable for research on BBB transporters and receptors.
Medicine, Issue 88, rat brain endothelial cells (RBEC), mouse, spinal cord, tight junction (TJ), receptor-mediated transport (RMT), low density lipoprotein (LDL), LDLR, transferrin, TfR, P-glycoprotein (P-gp), transendothelial electrical resistance (TEER),
51278
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Methods to Assess Beta Cell Death Mediated by Cytotoxic T Lymphocytes
Authors: Jing Chen, Scott Grieshaber, Clayton E. Mathews.
Institutions: University of Florida.
Type 1 diabetes (T1D) is a T cell mediated autoimmune disease. During the pathogenesis, patients become progressively more insulinopenic as insulin production is lost, presumably this results from the destruction of pancreatic beta cells by T cells. Understanding the mechanisms of beta cell death during the development of T1D will provide insights to generate an effective cure for this disease. Cell-mediated lymphocytotoxicity (CML) assays have historically used the radionuclide Chromium 51 (51Cr) to label target cells. These targets are then exposed to effector cells and the release of 51Cr from target cells is read as an indication of lymphocyte-mediated cell death. Inhibitors of cell death result in decreased release of 51Cr. As effector cells, we used an activated autoreactive clonal population of CD8+ Cytotoxic T lymphocytes (CTL) isolated from a mouse stock transgenic for both the alpha and beta chains of the AI4 T cell receptor (TCR). Activated AI4 T cells were co-cultured with 51Cr labeled target NIT cells for 16 hours, release of 51Cr was recorded to calculate specific lysis Mitochondria participate in many important physiological events, such as energy production, regulation of signaling transduction, and apoptosis. The study of beta cell mitochondrial functional changes during the development of T1D is a novel area of research. Using the mitochondrial membrane potential dye Tetramethyl Rhodamine Methyl Ester (TMRM) and confocal microscopic live cell imaging, we monitored mitochondrial membrane potential over time in the beta cell line NIT-1. For imaging studies, effector AI4 T cells were labeled with the fluorescent nuclear staining dye Picogreen. NIT-1 cells and T cells were co-cultured in chambered coverglass and mounted on the microscope stage equipped with a live cell chamber, controlled at 37°C, with 5% CO2, and humidified. During these experiments images were taken of each cluster every 3 minutes for 400 minutes. Over a course of 400 minutes, we observed the dissipation of mitochondrial membrane potential in NIT-1 cell clusters where AI4 T cells were attached. In the simultaneous control experiment where NIT-1 cells were co-cultured with MHC mis-matched human lymphocyte Jurkat cells, mitochondrial membrane potential remained intact. This technique can be used to observe real-time changes in mitochondrial membrane potential in cells under attack of cytotoxic lymphocytes, cytokines, or other cytotoxic reagents.
Immunology, Issue 52, cell, Type 1 Diabetes, Autoimmunity, Cytotoxic T Lymphocyte
2724
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A Colorimetric Assay that Specifically Measures Granzyme B Proteolytic Activity: Hydrolysis of Boc-Ala-Ala-Asp-S-Bzl
Authors: Magdalena Hagn, Vivien R. Sutton, Joseph A. Trapani.
Institutions: Peter MacCallum Cancer Centre.
The serine protease Granzyme B (GzmB) mediates target cell apoptosis when released by cytotoxic T lymphocytes (CTL) or natural killer (NK) cells. GzmB is the most studied granzyme in humans and mice and therefore, researchers need specific and reliable tools to study its function and role in pathophysiology. This especially necessitates assays that do not recognize proteases such as caspases or other granzymes that are structurally or functionally related. Here, we apply GzmB’s preference for cleavage after aspartic acid residues in a colorimetric assay using the peptide thioester Boc-Ala-Ala-Asp-S-Bzl. GzmB is the only mammalian serine protease capable of cleaving this substrate. The substrate is cleaved with similar efficiency by human, mouse and rat GzmB, a property not shared by other commercially available peptide substrates, even some that are advertised as being suitable for this purpose. This protocol is demonstrated using unfractionated lysates from activated NK cells or CTL and is also suitable for recombinant proteases generated in a variety of prokaryotic and eukaryotic systems, provided the correct controls are used. This assay is a highly specific method to ascertain the potential pro-apoptotic activity of cytotoxic molecules in mammalian lymphocytes, and of their recombinant counterparts expressed by a variety of methodologies.
Chemistry, Issue 93, Granzyme B, serine protease, peptide thioesters, BOC-Ala-Ala-Asp-S-Bzl, colorimetric substrate, hydrolysis, asp-ase activity
52419
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A Microplate Assay to Assess Chemical Effects on RBL-2H3 Mast Cell Degranulation: Effects of Triclosan without Use of an Organic Solvent
Authors: Lisa M. Weatherly, Rachel H. Kennedy, Juyoung Shim, Julie A. Gosse.
Institutions: University of Maine, Orono, University of Maine, Orono.
Mast cells play important roles in allergic disease and immune defense against parasites. Once activated (e.g. by an allergen), they degranulate, a process that results in the exocytosis of allergic mediators. Modulation of mast cell degranulation by drugs and toxicants may have positive or adverse effects on human health. Mast cell function has been dissected in detail with the use of rat basophilic leukemia mast cells (RBL-2H3), a widely accepted model of human mucosal mast cells3-5. Mast cell granule component and the allergic mediator β-hexosaminidase, which is released linearly in tandem with histamine from mast cells6, can easily and reliably be measured through reaction with a fluorogenic substrate, yielding measurable fluorescence intensity in a microplate assay that is amenable to high-throughput studies1. Originally published by Naal et al.1, we have adapted this degranulation assay for the screening of drugs and toxicants and demonstrate its use here. Triclosan is a broad-spectrum antibacterial agent that is present in many consumer products and has been found to be a therapeutic aid in human allergic skin disease7-11, although the mechanism for this effect is unknown. Here we demonstrate an assay for the effect of triclosan on mast cell degranulation. We recently showed that triclosan strongly affects mast cell function2. In an effort to avoid use of an organic solvent, triclosan is dissolved directly into aqueous buffer with heat and stirring, and resultant concentration is confirmed using UV-Vis spectrophotometry (using ε280 = 4,200 L/M/cm)12. This protocol has the potential to be used with a variety of chemicals to determine their effects on mast cell degranulation, and more broadly, their allergic potential.
Immunology, Issue 81, mast cell, basophil, degranulation, RBL-2H3, triclosan, irgasan, antibacterial, β-hexosaminidase, allergy, Asthma, toxicants, ionophore, antigen, fluorescence, microplate, UV-Vis
50671
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Quantitative In vitro Assay to Measure Neutrophil Adhesion to Activated Primary Human Microvascular Endothelial Cells under Static Conditions
Authors: Kevin Wilhelmsen, Katherine Farrar, Judith Hellman.
Institutions: University of California, San Francisco, University of California, San Francisco.
The vascular endothelium plays an integral part in the inflammatory response. During the acute phase of inflammation, endothelial cells (ECs) are activated by host mediators or directly by conserved microbial components or host-derived danger molecules. Activated ECs express cytokines, chemokines and adhesion molecules that mobilize, activate and retain leukocytes at the site of infection or injury. Neutrophils are the first leukocytes to arrive, and adhere to the endothelium through a variety of adhesion molecules present on the surfaces of both cells. The main functions of neutrophils are to directly eliminate microbial threats, promote the recruitment of other leukocytes through the release of additional factors, and initiate wound repair. Therefore, their recruitment and attachment to the endothelium is a critical step in the initiation of the inflammatory response. In this report, we describe an in vitro neutrophil adhesion assay using calcein AM-labeled primary human neutrophils to quantitate the extent of microvascular endothelial cell activation under static conditions. This method has the additional advantage that the same samples quantitated by fluorescence spectrophotometry can also be visualized directly using fluorescence microscopy for a more qualitative assessment of neutrophil binding.
Immunology, Issue 78, Cellular Biology, Infection, Molecular Biology, Medicine, Biomedical Engineering, Biophysics, Endothelium, Vascular, Neutrophils, Inflammation, Inflammation Mediators, Neutrophil, Leukocyte Adhesion, Endothelial cells, assay
50677
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Preparing T Cell Growth Factor from Rat Splenocytes
Authors: Christine Beeton, K. George Chandy.
Institutions: University of California, Irvine (UCI).
Maintenance of antigen-specific T cell lines or clones in culture requires rounds of antigen-induced activation separated by phases of cell expansion 1,2. Addition of interleukin 2 to the culture media during the expansion phase is necessary to prevent cell death and sufficient to maintain short-term T cell lines but has been shown to increase Th1 polarization 3. Replacement of interleukin 2 by T cell growth factor (TCGF) which contains a mix of cytokines is more effective than interleukin 2 in maintaining long-term T cell lines in vitro 3. Moreover, TCGF can easily be prepared in large amounts in the laboratory and is much cheaper than recombinant interleukin 2. Here, we show how to prepare TCGF from rat splenocyte culture supernatants. For this procedure, we harvest spleens from naive Lewis rats euthanized for thymus and blood collection. We prepare single-cell suspensions from the spleens, lyze the red blood cells by osmotic shock, and seed the splenocytes in culture medium. The cells are stimulated with concanavalin A, a mitogen that non-selectively activates all rat T lymphocytes, inducing the production of cytokines. The culture supernantant is collected 48 hours later andexcess concanavalin A is bound to alpha methyl mannoside to prevent it from activating T cell lines to which TCGF will be added. The TCGF is then sterile-filtered, aliquoted, and stored at -20°C.
Immunology, Issue 10, Rodent, Growth Factor, TCGF, Lymphocyte, Interleukin 2, Apoptosis, Survival, T cell line, Clone
402
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Enrichment of NK Cells from Human Blood with the RosetteSep Kit from StemCell Technologies
Authors: Christine Beeton, K. George Chandy.
Institutions: University of California, Irvine (UCI).
Natural killer (NK) cells are large granular cytotoxic lymphocytes that belong to the innate immune system and play major roles in fighting against cancer and infections, but are also implicated in the early stages of pregnancy and transplant rejection. These cells are present in peripheral blood, from which they can be isolated. Cells can be isolated using either positive or negative selection. For positive selection we use antibodies directed to a surface marker present only on the cells of interest whereas for negative selection we use cocktails of antibodies targeted to surface markers present on all cells but the cells of interest. This latter technique presents the advantage of leaving the cells of interest free of antibodies, thereby reducing the risk of unwanted cell activation or differenciation. In this video-protocol we demonstrate how to separate NK cells from human blood by negative selection, using the RosetteSep kit from StemCell technologies. The procedure involves obtaining human peripheral blood (under an institutional review board-approved protocol to protect the human subjects) and mixing it with a cocktail of antibodies that will bind to markers absent on NK cells, but present on all other mononuclear cells present in peripheral blood (e.g., T lymphocytes, monocytes...). The antibodies present in the cocktail are conjugated to antibodies directed to glycophorin A on erythrocytes. All unwanted cells and red blood cells will therefore be trapped in complexes. The mix of blood and antibody cocktail is then diluted, overlayed on a Histopaque gradient, and centrifuged. NK cells (>80% pure) can be collected at the interface between the Histopaque and the diluted plasma. Similar cocktails are available for enrichment of other cell populations, such as human T lymphocytes.
Immunology, issue 8, blood, cell isolation, natural killer, lymphocyte, primary cells, negative selection, PBMC, Ficoll gradient, cell separation
326
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