Liver Apoptosis Following Normothermic Ischemia-Reperfusion: In Vivo Evaluation of Caspase Activity by FLIVO Assay in Rats

Apoptosis (programmed cell death) and its signals - A review

Apoptosis is a sequential order of cell death occurring regularly to ensure a homeostatic balance between the rate of cell formation and cell death. However, a misplaced of this balancing function can contribute to an abnormal cell growth / proliferation or autoimmune disorders etc. Apoptosis is therefore said to be crucial from the point of development of an embryo throughout the growth of an organism contributing to the renewal of tissues and also the getting rid of inflammatory cells. This review seeks to elaborate on the recent overview of the mechanism involved in apoptosis, some element and signal contributing to its function and inhibition together with how their malfunction contribute to a number of cancer related cases.

Preconditioning methods in the management of hepatic ischemia reperfusion- induced injury: Update on molecular and future perspectives

Hepatic IR (ischemia reperfusion) injury is a commonly encountered obstacle in the post-operative management of hepatic surgery. Hepatic IR occurs during 'Pringle maneuver' for reduction of blood loss or during a brief period of cold storage followed by reperfusion of liver grafts. The stress induced during hepatic IR, triggers a spectrum of cellular responses leading to the varying degrees of hepatic complications which in turn affect the post operative care. Different preconditioning methods either activate or subdue different sets of molecular signals, resulting in varied levels of protection against hepatic IR injury. Yet, there is a serious lacuna in the knowledge regarding the choice of preconditioning methods and the resulting molecular changes in order to assess the efficiency and choice of these methods correctly. This review provides an update on the various preconditioning approaches such as surgical/ischemic, antioxidant, pharmaceutical and genetic preconditioning strategies published during last six years (2009-2015). Further, we discuss the attenuation or inhibition of specific inflammatory, apoptotic and necrotic markers in the various experimental models of liver IR subjected to different preconditioning strategies. While enlisting the controversies in the ischemic preconditioning strategy, we bring out the uncertainties in the existing molecular targets and their reliability in the attenuation of hepatic IR injury. Future research studies would include the novel preconditioning strategies employ i) the targeted gene silencing of key molecular targets inducing IR, ii) hyper expression of beneficial molecular signals against IR via gene transfer techniques. The above studies would see the combination of these latest techniques with the established preconditioning strategies for better post-operative hepatic management.

Fluorochrome-Labeled Inhibitors of Caspases: Expedient In Vitro and In Vivo Markers of Apoptotic Cells for Rapid Cytometric Analysis

Activation of caspases is a characteristic event of apoptosis. Various cytometric methods distinguishing this event have been developed to serve as specific apoptotic markers for the assessment of apoptotic frequency within different cell populations. The method described in this chapter utilizes fluorochrome labeled inhibitors of caspases (FLICA) and is applicable to fluorescence microscopy, flow- and imaging-cytometry as well as to confocal imaging. Cell-permeant FLICA reagents tagged with carboxyfluorescein or sulforhodamine, when applied to live cells in vitro or in vivo, exclusively label the cells that are undergoing apoptosis. The FLICA labeling methodology is rapid, simple, robust, and can be combined with other markers of cell death for multiplexed analysis. Examples are presented on FLICA use in combination with a vital stain (propidium iodide), detection of the loss of mitochondrial electrochemical potential, and exposure of phosphatidylserine on the outer surface of plasma cell membrane using Annexin V fluorochrome conjugates. FLICA staining followed by cell fixation and stoichiometric staining of cellular DNA demonstrate that FLICA binding can be correlated with the concurrent analysis of DNA ploidy, cell cycle phase, DNA fragmentation, and other apoptotic events whose detection requires cell permeabilization. The "time window" for the detection of apoptosis with FLICA is wider compared to the Annexin V binding, making FLICA a preferable marker for the detection of early phase apoptosis and therefore more accurate for quantification of apoptotic cells. Unlike many other biomarkers of apoptotic cells, FLICAs can be used to detect apoptosis ex vivo and in vivo in different tissues.

Noninvasive targeting delivery and in vivo magnetic resonance tracking method for live apoptotic cells in cerebral ischemia with functional Fe2O3 magnetic nanoparticles

Background

Apoptotic neuronal death is known as programmed cell death. Inhibition of this progression might contribute to a new treatment strategy. However, methods for in vivo detection of live apoptotic cells are in need to be developed and established.

Context and purpose

The purpose of this study is to develop a new method for in vivo brain imaging for live apoptotic lesions using magnetic resonance imaging (MRI). We focused on the specific accumulation of our recently developed functional magnetic nanoparticles (FMNPs) into apoptotic cells using a rat cerebral ischemia model. Sulphorhodamine B, fluorescent dye was linked to valylalanylaspartic acid fluoromethyl ketone as a pan-caspase inhibitor to form SR-FLIVO. SR-FLIVO was bound with FMNPs to develop SR-FLIVO-FMNP probe. Ischemic rat brains were scanned by 7T MRI before and after intravenous injection of SR-FLIVO-FMNP and the distribution was evaluated by subtraction images of T2* colored mapping. SR-FLIVO, intracellular FMNPs, and T2* reduction area were histologically analyzed. The distribution of SR-FLIVO-FMNP was evaluated by subtracting the T2* signal images and was significantly correlated with the histological findings by TUNEL staining.

Results

Our experimental results revealed several findings where our newly developed probe SR-FLIVO-FMNP was intravenously administered into ischemic rats and FLIVO expression was tracked and found in apoptotic cells in rat brains after cerebral ischemia. A remarkable T2* reduction within the ischemic lesion was recorded using MRI based SR-FLIVO-FMNP probe as a contrasting agent due to the specific probe accumulation in apoptotic cells whereas, no observation of T2* reduction within the non-ischemic lesion due to no probe accumulation in non-apoptotic cells. Histological analysis based on the correlation between FLIVO and TUNEL staining showed that almost all FLIVO-positive cells were positive for TUNEL staining. These findings suggest the possibility for establishment of in vivo targeting delivery methods to live apoptotic cells based on conjugation of magnetic and fluorescent dual functional probes.

Conclusion

A newly developed probe SR-FLIVO-FMNP might be considered as a useful probe for in vivo apoptotic detection, and FMNPs might be a strong platform for noninvasive imaging and targeting delivery.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-016-0173-1) contains supplementary material, which is available to authorized users.

Nanoparticle-based caspase sensors

Recent advances in nanotechnology have provided new tools for measuring enzymatic activities that are relevant for the assessment of physiological and pathological processes. Caspases, the enzymes intimately linked with cell death and inflammation, are cysteine-dependent aspartate-directed proteases. The measurement of caspase activity requires assays that can provide data with specificity, precision and sensitivity. Several nanoparticle-based assays are now beginning to emerge. This article will first provide a brief discussion of conventional methods of measuring caspase activity and their limitations, followed by an overview of the advantages and limitations of nanoparticle-based strategies for sensing caspase enzymatic activity in vitro and in vivo.

In vivo fluorescence imaging of apoptosis during foreign body response

Quantification of apoptotic tissues during inflammatory processes induced by biomaterials is challenging in vivo. Here we present a non-invasive method using a fluorescence imaging system which facilitates intermittent snap shots of the current state of local apoptotic tissue. For this purpose, apoptotic cells around two different subcutaneously implanted materials (titanium discs and copper-coated titanium discs) in hairless but immunocompetent mice were quantified after 4, 8 and 23 days of implantation. For validation, the results of fluorescence signals were compared to the histology of the inflammatory tissue using apoptotic-specific TUNEL-, macrophage-specific F4/80-, neutrophile-specific NIMP-R14- and chloroacetate esterase-staining. We could demonstrate that the fluorescence signals were well suited to quantify the extent of apoptosis in vivo and this is a good indication for the biocompatibility of biomaterials. This study shows that non-invasive monitoring of tissue processes following the implantation of biomaterials is possible in vivo and may help to reduce the number of animals in studies addressing biocompatibility.

Functional imaging of proteases: recent advances in the design and application of substrate-based and activity-based probes

Proteases are enzymes that cleave peptide bonds in protein substrates. This process can be important for regulated turnover of a target protein but it can also produce protein fragments that then perform other functions. Because the last few decades of protease research have confirmed that proteolysis is an essential regulatory process in both normal physiology and in multiple disease-associated conditions, there has been an increasing interest in developing methods to image protease activity. Proteases are also considered to be one of the few 'druggable' classes of proteins and therefore a large number of small molecule based inhibitors of proteases have been reported. These compounds serve as a starting point for the design of probes that can be used to target active proteases for imaging applications. Currently, several classes of fluorescent probes have been developed to visualize protease activity in live cells and even whole organisms. The two primary classes of protease probes make use of either peptide/protein substrates or covalent inhibitors that produce a fluorescent signal when bound to an active protease target. This review outlines some of the most recent advances in the design of imaging probes for proteases. In particular, it highlights the strengths and weaknesses of both substrate-based and activity-based probes and their applications for imaging cysteine proteases that are important biomarkers for multiple human diseases.

In vivo real-time imaging of the liver with confocal endomicroscopy permits visualization of the temporospatial patterns of hepatocyte apoptosis

Apoptosis is a dynamic process of programmed cell death and is involved in multiple diseases. However, its mechanisms and sequence of events are still incompletely understood, partly because of the inability to visualize single cells continuously in vivo. The aim of the present study was to monitor hepatocyte apoptosis with confocal endomicroscopy in living rodents. In 73 anaesthetized mice, apoptotic liver injury was induced by injection of the CD95-agonistic antibody Jo2. Individual hepatocytes were followed for up to 240 min with a handheld confocal probe (FIVE1; Optiscan) providing 0.7 μm resolution (1,000-fold magnification). Different fluorescence staining protocols were used for cellular staining, vascular and cellular barrier function imaging, and caspase activation visualization. The time course of apoptosis could be visualized in vivo while liver perfusion and tissue integrity were maintained. In contrast to most ex vivo studies, initial cell swelling was observed that coincided with early defects in barrier function of sinusoids and hepatocytes. Cytoplasmic vesicle formation, nuclear condensation, cellular disintegration, and macrophage infiltration were captured sequentially. Labeling of caspases allowed molecular imaging. Our study allowed for the first time to continuously follow distinct morphological, functional, and molecular features of apoptosis in a solid organ in vivo and at high resolution. Intravital confocal microscopy may be a valuable tool to study the effects of therapeutic intervention on apoptosis in animal models and humans.

Induction of different types of cell death after normothermic liver ischemia-reperfusion

Normothermic liver ischemia-reperfusion (I-R) may induce hepatocellular autophagy, apoptosis, and necrosis. The aim of this study was to investigate these three types of cell death in normothermic liver I-R in rats. A segmental normothermic ischemia of the liver was induced for 120 minutes. Liver autophagy was evaluated by transmission electron microscopy and LC3 (Light Chain 3) immunohistochemical studies. Liver apoptosis was assessed by FLIVO (FLuorescence in vIVO) and TUNEL (TdT-mediated dUTP nick end labeling) assays. Liver necrosis was determined by optical microscopic examination. Autophagy was increased in ischemic liver lobes at 6 hours after reperfusion, compared with nonischemic lobes. Fluorescence microscopy showed in situ caspase-3 and -7 specific activity to be increased in ischemic liver lobes after 6 hours of reperfusion, compared with nonischemic lobes. Quantitative analysis of apoptotic cells evaluated by the TUNEL method showed a clearly significant increase in ischemic liver lobes at 6 hours after reperfusion, compared with nonischemic lobes. Necrotic cell death was significantly increased in ischemic liver lobes at 6 hours after reperfusion, compared with nonischemic lobes (P < .005). In conclusion, 120 minutes normothermic liver I-R resulted in increased autophagic, apoptotic and necrotic cell death.

Fluorochrome-labeled inhibitors of caspases: convenient in vitro and in vivo markers of apoptotic cells for cytometric analysis

Activation of caspases is a hallmark of apoptosis. Several methods, therefore, were developed to identify and count the frequency of apoptotic cells based on the detection of caspases activation. The method described in this chapter is based on the use of fluorochrome-labeled inhibitors of caspases (FLICA) applicable to fluorescence microscopy, and flow- and image-cytometry. Cell-permeant FLICA reagents tagged with carboxyfluorescein or sulforhodamine when applied to live cells in vitro or in vivo, exclusively label cells that are undergoing apoptosis. The FLICA labeling methodology is simple, rapid, robust, and can be combined with other markers of cell death for multiplexed analysis. Examples are presented on FLICA use in combination with a vital stain (propidium iodide), detection of the loss of mitochondrial electrochemical potential, and exposure of phosphatidylserine on the outer surface of plasma cell membrane using Annexin V fluorochrome conjugates. Following cell fixation and stoichiometric staining of cellular DNA, FLICA binding can be correlated with DNA ploidy, cell cycle phase, DNA fragmentation, and other apoptotic events whose detection requires cell permeabilization. The "time window" for the detection of apoptosis with FLICA is wider compared to that with the Annexin V binding, making FLICA a preferable marker for the detection of early phase apoptosis and more accurate for quantification of apoptotic cells.

In vivo morphine treatment synergistically increases LPS-induced caspase activity in immune organs

Caspases are a family of proteins important for the elimination of infected cells through the induction of apoptosis as well as the initiation of inflammatory cytokines including IL-1β and IL-18. Morphine exposure to animals and/or cells has been associated with the induction of apoptosis. The most common practices of apoptosis detection have involved removing tissues from animal or humans and the analysis of apoptosis on cells or tissues. These methods can potentially induce spontaneous apoptosis that is unrelated to the actual treatment. The objective of this study was to develop an in vivo detection method for assessing caspase activity induced both by morphine directly and by morphine combined with lipopolysaccharide (LPS)-immune activation. Mice were administered saline, morphine, LPS, or a combination of morphine and LPS. Prior to sacrifice, mice were injected with a polycaspase-specific apoptosis detection probe to detect internal caspase activity in vivo. Results revealed that morphine alone did not directly induce caspase activity. However, morphine significantly enhanced the LPS-induced caspase activity in spleen, thymus, and bone marrow-derived immune cells. The use of a poly-caspase detection probe methodology to label caspase activity in vivo provides a powerful quantitative tool for the in vivo analysis of caspase activity.

Cytometry in cell necrobiology revisited. Recent advances and new vistas

Over a decade has passed since publication of the last review on "Cytometry in cell necrobiology." During these years we have witnessed many substantial developments in the field of cell necrobiology such as remarkable advancements in cytometric technologies and improvements in analytical biochemistry. The latest innovative platforms such as laser scanning cytometry, multispectral imaging cytometry, spectroscopic cytometry, and microfluidic Lab-on-a-Chip solutions rapidly emerge as highly advantageous tools in cell necrobiology studies. Furthermore, we have recently gained substantial knowledge on alternative cell demise modes such as caspase-independent apoptosis-like programmed cell death (PCD), autophagy, necrosis-like PCD, or mitotic catastrophe, all with profound connotations to pathogenesis and treatment. Although detection of classical, caspase-dependent apoptosis is still the major ground for the advancement of cytometric techniques, there is an increasing demand for novel analytical tools to rapidly quantify noncanonical modes of cell death. This review highlights the key developments warranting a renaissance and evolution of cytometric techniques in the field of cell necrobiology.

Histopathological and ultrastructural studies on the effects of electromagnetic fields on the liver of preincubated white Leghorn chicken embryo

There are several reports indicating a linkage between exposures to 50-60 Hz electromagnetic fields and abnormalities in the early stages of embryonic development of chicken embryos. The present study was designed to demonstrate whether electromagnetic fields could be an environmental factor invoking histopathological and ultra-structural changes in livers of preincubated chicken embryos exposed to EMFs. Following other researchers and our previous results from different groups of Developmental Biology at the Animal Sciences, Faculty of Biological Sciences, Shahid-Beheshti University, effects of most effective intensities (1.33, 2.66, 5.52, and 7.32 mT) of electromagnetic fields (EMFs, 50 Hz ) on livers of pre-incubated white leghorn chicken embryos were investigated . 150 healthy, fresh, and fertilized eggs (55-65 gr) were divided into 6 groups of experimental(1-4, n = 30), control (n = 60), and sham (n = 50). Experimental eggs (inside coil) were exposed to 4 different intensities (1.33, 2.66, 5.52, and 7.32 mT). Sham groups were located inside same coil, with no exposure, for 24 h before incubation. Control, sham, and experimental groups (1-4) were then incubated in an incubator (38 +/- 0.5 degrees C, 60% humidity) for 17 days. At the end of this period, livers of experimental, sham, and control groups were processed for light and transmission electrom microscopes (TEM and SEM) studies. So, livers of 17-day old chicken embryos were removed by C-sections, fixed in formalin 10%, stained with H&E and reticulin, and studied under light microscope. Others were prepared for electron microscopes (TEM and SEM) investigations. Morphological observations indicated exencephalic embryos, embryos with asymmetrical faces, crossed beak, shorter upper beak, deformed hind limbs, gastroschesis, anophthalmia, and microphthalmia. H&E and reticulin stainings, TEMS, and SEMs studies indicated EMFs would create hepato-cytes with fibrotic bands, severe steatohepatitis, vacuolizations, swollen and extremely electron-dense mitochondria, reduced invisible cristae, crystalized mitochondria with degenerated cristae, myelin-like figures, macrophages engulfing adjacent cells, dentated nuclei, nuclei with irregular envelopes, degenerated hepatocytes, abnormal lipid accumulations, lipid droplets pushing hepatocytes' nuclei to the corner of the cells, abundant cellular infiltrations cellular infiltrations inside sinusoid and around central veins, disrupted reticulin plexus, and release of chromatin into cytosol,, with partially regular water layers. An elevated oxyradical generation and, subsequently, cell membrane disruptions were the reasons for electromagnetic fields inducing cell damages.

Remote ischemic preconditioning by hindlimb occlusion prevents liver ischemic/reperfusion injury: the role of High Mobility Group-Box 1

INTRODUCTION

Hepatocellular injury caused by ischemia-reperfusion of the liver occurs in a number of clinical situations including major trauma, elective surgery of the liver, and liver transplantation. Several strategies have been used to prevent liver injury following ischemia-reperfusion (I/R). Among these, ischemic preconditioning has shown promise as a preventative approach. In this manuscript, we hypothesized that use of remote ischemic preconditioning by brief hindlimb ischemia might prevent liver dysfunction in a mouse model of liver I/R.

METHODS

C57/B mice were subjected to 60 minutes of partial liver ischemia with or without antecedent hindlimb vascular I/R. Blood was drawn for serum alanine aminotransferase levels at times following liver reperfusion. Liver inflammation was assessed by measuring serum and liver tumor necrosis factor (TNF)-alpha protein and mRNA. The role of toll-like receptor 4 (TLR4) in mediating protection was determined using the mouse strain HeJ, which has a mutated TLR4.

RESULTS

Antecedent hindlimb ischemia (10 minutes) lessened I/R-induced elevation of serum alanine aminotransferase compared with untreated I/R animals. This protection correlated with a reduction in serum TNF-alpha protein levels as well as liver TNF-alpha mRNA and apoptosis. High Mobility Group-Box 1 (HMG-B1) levels in the blood were elevated after hindlimb ischemia and injection of HMG-B1 prior to liver recapitulated the protective effect of hindlimb occlusion. TLR4-mutant HeJ mice did not demonstrate protection with hindlimb preconditioning.

CONCLUSIONS

Brief hindlimb occlusion prevents liver I/R injury. This effect appears to be related to release of HMG-B1 and is dependent on the presence of a functional TLR4. Remote ischemia preconditioning represents a novel approach to preventing distant organ injury.

Bicyclol protects HepG2 cells against D-galactosamine-induced apoptosis through inducing heat shock protein 27 and mitochondria associated pathway

AIM

To study the inducing effect of bicyclol on heat shock protein 27 (HSP27) and its role on anti-apoptosis in HepG2 cells intoxicated with D-galactosamine (D-GaIN).

METHODS

HepG2 cells were treated with various concentrations of bicyclol and then subjected to D-GaIN intoxication. Apoptosis was assayed by hoechst 33258 staining and flow cytometry analysis. HSP27, cytochrome c, apoptosis inducing factor (AIF) and c-Jun N-terminal kinase (JNK) were assayed by Western blot. Heat shock factor 1 (HSF1) was determined by electrophoretic mobility shift assay and the interactions of HSP27 with cytochrome c and AIF were detected by co-immunoprecipitation.

RESULTS

The results showed that bicyclol induced HSP27 protein and mRNA expression in HepG2 cells in both time- and dose-dependent manners (the maximal response: 1.23 fold increase at 100 micromol/L). Bicyclol treatment stimulated HSF1 activation and increased the HSF1-HSE binding activity (the maximal response: 2.1 fold increase at 100 micromol/L). This inducing effect of bicyclol on HSP27 and HSF1 was markedly blocked by quercetin. Pretreatment of the cells with bicyclol markedly attenuated D-GaIN-induced apoptosis and the release of cytochrome c and AIF from mitochondria. The induced HSP27 by bicyclol suppressed the activity of caspase-3 and the phosphorylation of JNK caused by D-GaIN in HepG2 cells. All the above effect of bicyclol against D-GaIN-induced hepatocytes apoptosis were significantly reversed by quercetin.

CONCLUSION

HSP27 is involved in the anti-hepatocytes apoptosis of bicyclol, and this effect of bicyclol-induced HSP27 is mainly through inhibition of mitochondria and JNK apoptotic pathways.