Molecular Mechanisms Of Cell Death Research Articles

Mechanisms of Action and Cell Death Associated with Clostridium perfringens Toxins.

Clostridium perfringens uses its large arsenal of protein toxins to produce histotoxic, neurologic and intestinal infections in humans and animals. The major toxins involved in diseases are alpha (CPA), beta (CPB), epsilon (ETX), iota (ITX), enterotoxin (CPE), and necrotic B-like (NetB) toxins. CPA is the main virulence factor involved in gas gangrene in humans, whereas its role in animal diseases is limited and controversial. CPB is responsible for necrotizing enteritis and enterotoxemia, mostly in neonatal individuals of many animal species, including humans. ETX is the main toxin involved in enterotoxemia of sheep and goats. ITX has been implicated in cases of enteritis in rabbits and other animal species; however, its specific role in causing disease has not been proved. CPE is responsible for human food-poisoning and non-foodborne C. perfringens-mediated diarrhea. NetB is the cause of necrotic enteritis in chickens. In most cases, host–toxin interaction starts on the plasma membrane of target cells via specific receptors, resulting in the activation of intracellular pathways with a variety of effects, commonly including cell death. In general, the molecular mechanisms of cell death associated with C. perfringens toxins involve features of apoptosis, necrosis and/or necroptosis.

Mutation in Rice Abscisic Acid2 Results in Cell Death, Enhanced Disease-Resistance, Altered Seed Dormancy and Development.

Lesion mimic mutants display spontaneous cell death, and thus are valuable for understanding the molecular mechanism of cell death and disease resistance. Although a lot of such mutants have been characterized in rice, the relationship between lesion formation and abscisic acid (ABA) synthesis pathway is not reported. In the present study, we identified a rice mutant, lesion mimic mutant 9150 (lmm9150), exhibiting spontaneous cell death, pre-harvest sprouting, enhanced growth, and resistance to rice bacterial and blast diseases. Cell death in the mutant was accompanied with excessive accumulation of H2O2. Enhanced disease resistance was associated with cell death and upregulation of defense-related genes. Map-based cloning identified a G-to-A point mutation resulting in a D-to-N substitution at the amino acid position 110 of OsABA2 (LOC_Os03g59610) in lmm9150. Knock-out of OsABA2 through CRISPR/Cas9 led to phenotypes similar to those of lmm9150. Consistent with the function of OsABA2 in ABA biosynthesis, ABA level in the lmm9150 mutant was significantly reduced. Moreover, exogenous application of ABA could rescue all the mutant phenotypes of lmm9150. Taken together, our data linked ABA deficiency to cell death and provided insight into the role of ABA in rice disease resistance.

Cell Death and Induced p53 Expression in Oral Cancer, HeLa, and Bone Marrow Mesenchyme Cells under the Exposure to Noncontact Electric Fields

Background: p53 acts as a transcription factor to regulate the expression of genes that modulate various cellular activities. The proliferation of cancer cells has been inhibited under the exposure to low-intensity (18 peak-to-peak voltage) and intermediate-frequency (100 KHz) electric fields generated between 2 capacitive electrodes. Therefore, the aims of this study were to observe the molecular mechanism of cell death caused by noncontact electric field exposure and to determine whether p53 protein can serve as a biomarker for this exposure or not. Methods: Oral squamous cell carcinoma, HeLa, and bone marrow mesenchyme cells were exposed to noncontact electric fields of Electro-Capacitive Cancer Therapy (ECCT) for 24 h. To observe the mechanism of cell death caused by ECCT, immunocytochemistry of p53 was performed, and the p53 expression was evaluated using immunoreactive score (IRS) calculation. Results: Electric field exposure by ECCT increased the percentage of dead cells in oral cancer cells (18.39%), HeLa cells (6.60%), and bone marrow mesenchyme cells (34.05%) with statistical significance using the independent t test compared to each control group. The IRS of p53 in oral cancer, HeLa, and bone marrow mesenchyme cultures were 10.50, 11.25, and 4.94, respectively. Conclusion: The high IRS shown in the treated oral cancer and HeLa culture cells may suggest that p53 expression in these culture cells is associated with the cell death mechanism induced by the exposure to noncontact electric fields, and the increased cell death in these culture cells may correlate with the IRS.

WEE1 inhibition by MK1775 as a single-agent therapy inhibits ovarian cancer viability.

Wee1-like protein kinase (WEE1) physiologically serves a key function in maintaining the integrity of the cell genome through mediating the activation of cyclin-dependent kinase (CDK)1 and CDK2. Increased expression of WEE1 has been associated with the poor prognosis of patients with ovarian cancer. The present study aimed at examining the in vitro and in vivo antitumor activity of MK1775, a potent pharmacological inhibitor of WEE1, as a single agent against ovarian cancer cells. The cytotoxicity of MK1775 was examined in a panel of tumor cells using MTT in vitro. Subsequently, a cell apoptosis assay was performed in ovarian cancer SKOV3 and ID8 cells to characterize the function of MK1775 in tumor cell apoptosis, under either wild-type tumor protein 53 (p53) or null p53 status. In addition, cell cycle analysis and a western blot analysis were performed to validate the effect of MK1775 on cell cycle progression and to elucidate the underlying molecular mechanism of cell death. Finally, the in vivo antitumor efficacy of MK1775 as a single agent at a clinical well-tolerated dose was determined. A dose-dependent inhibitory effect of MK1775 on tumor cell viability was determined in distinct cell lines, including B16F10, LLC1, BPS1, EG7, ID8 and SKOV3. Results from the cell cycle analysis and western blotting indicated that MK1775 abrogated the G2/M checkpoint through inhibiting the phosphorylation of CDK1 and inducing the apoptosis of ovarian cancer cells that lacked mutations in p53 and breast cancer 1 (BRCA1). Additionally, a significant antitumor effect of MK1775 was observed in C57BL/6 mice bearing syngeneic ID8 ovarian tumors. The results of the present study supported the use of MK1775 as a monotherapy agent in ovarian cancer. MK1775 was effective at inducing mitotic catastrophe, independent of p53 and BRCA1 mutations. Therefore, WEE1 inhibition by MK1775 requires additional investigation to identify novel combination approaches in ovarian cancer therapy with the current DNA damaging agents, including irradiation treatment and cell cycle checkpoint inhibitors.

Impact of combined treatment with nimesulide and cisplatin on oral carcinoma cells.

BackgroundDespite significant advances in diagnosis and therapy, the rate of survival of patients with oral cancers still remains poor as an appropriate treatment has not been found yet, due to side effects of chemo/radiotherapy.AimThis study aimed to identify molecular mechanisms of cell death of oral cancer cells caused by treatment with a nonselective Cox-2 inhibitor in combination with a low-dose chemotherapeutic drug.MethodsSquamous cell carcinoma (SCC) cells SCC9 and SCC25 were subjected to mono- and combination therapy with nimesulide and cisplatin. Fluorescence-activated cell sorting (FACS), immunohistochemistry, high-pressure liquid chromatography (HPLC), microarray gene chips, and isobaric tags for a relative and absolute quantitation (iTRAQ) system were used.ResultsIncreased numbers of apoptotic and necrotic SCC9/SCC25 cells were detected after combined exposure. ATP levels and the energy charge of SCC9 cells were significantly decreased after both individual and combined treatment. We detected and quantified a responsible gene, keratin 6a, and 540 relevant proteins. In SCC25 cells, ATP levels significantly decreased only after combination therapy. After combined treatment of SCC9 cells, significant upregulation of Histon-H2A/H2B/H4 was found, with a local discovery false rate of 0.003 for Histon-H2A and 0.0027 for Histon-H2B, respectively.ConclusionCompared to the single-drug treatment, combined treatment of the oral cancer cells with nimesulide and cisplatin increases and induces necrosis and apoptosis through different pathways. A significant effect of the cytoplasmic increase was also observed in histones of cell lines SCC9 and SCC25 that were previously treated with combined nimesulide and cisplatin therapy.

Catalase-imprinted Fe3O4/Fe@fibrous SiO2/polydopamine nanoparticles: An integrated nanoplatform of magnetic targeting, magnetic resonance imaging, and dual-mode cancer therapy

Recent advances in the research on the molecular mechanism of cell death and methods for preparation of nanomaterials make the integration of various therapeutic approaches, targeting, and imaging modes into a single nanoscale complex a new trend for the development of future nanotherapeutics. Hence, a novel ellipsoidal composite nanoplatform composed of a magnetic Fe3O4/Fe nanorod core (~120 nm) enwrapped by a catalase (CAT)-imprinted fibrous SiO2/ polydopamine (F-SiO2/PDA) shell with thickness 70 nm was prepared in this work. In vitro experiments showed that the Fe3O4/Fe@F-SiO2/PDA nanoparticles can selectively inhibit the bioactivity of CAT in tumor cells by the molecular imprinting technique. As a result, the H2O2 level in tumor cells was elevated dramatically. At the same time, the Fe3O4/Fe core released Fe ions to catalyze the conversion of H2O2 to ·OH in tumor cells. Eventually, the concentration of ·OH in tumor cells rapidly rose to a lethal level thus triggering apoptosis. Combined with the remarkable near-infrared light (NIR) photothermal effect of the CAT-imprinted PDA layer, the Fe3O4/Fe@F-SiO2/PDA nanoparticles can effectively kill MCF-7, HeLa, and 293T tumor cells but are not toxic to nontumor cells. Furthermore, these nanoparticles show good capacity for magnetic targeting and suitability for magnetic resonance imaging (MRI). Therefore, the integrated multifunctional nanoplatform opens up new possibilities for high-efficiency visual targeted nonchemo therapy for cancer.

VPS35 regulates parkin substrate AIMP2 toxicity by facilitating lysosomal clearance of AIMP2

Vacuolar protein sorting-associated protein 35 (VPS35) is involved in retrograde transport of proteins from endosomes to trans-Golgi network. Gene mutations in VPS35 are linked to autosomal dominant late-onset Parkinson’s disease (PD). Although the identification of VPS35 mutations has provided novel insight about its interactions with several PD-associated genes including leucine-rich repeat kinase 2 (LRRK2) and α-synuclein, little information is available about the molecular mechanisms of cell death downstream of VPS35 dysfunction. In this study, we showed that VPS35 has a role in the lysosomal degradation of parkin substrate aminoacyl tRNA synthetase complex-interacting multifunctional protein 2 (AIMP2), of which accumulation leads to poly(ADP-ribose) polymerase-1 (PARP1)-dependent cell death. VPS35 was co-immunoprecipitated with AIMP2, as well as lysosome-associated membrane protein-2a (Lamp2a). Interestingly, this association was disrupted by PD-associated VPS35 mutant D620N. VPS35 overexpression prevented AIMP2-potentiated cell death and PARP1 activation in SH-SY5Y cells. More importantly, knockdown of VPS35 led to PARP1 activation and cell death, which was AIMP2 dependent. These findings provide new mechanistic insights into the role of VPS35 in the regulation of AIMP2 levels and cell death. As AIMP2 accumulation was reported in PD patient’s brains and involved in dopaminergic cell death, identification of VPS35 as a novel regulator of AIMP2 clearance via lysosomal pathway provides alternative venue to control dopaminergic cell death in PD.

Novel Glycopyrrolidine Compounds Inhibit Human Cancer Cell Proliferation and Induce Apoptotic Mode of Cell Death

ABSTRACTSpirocyclic compounds, present in a number of bioactive natural alkaloids, are cyclic systems containing one carbon atom common to two rings. A highly regioselective glycopyrrolidine compound library was synthesized using 1,3-dipolar cycloaddition method, and its efficacy was tested on cell lines representing most commonly occurring cancers and the molecular mechanism of cell death deciphered. Results showed that among the 16 compounds screened, RPRR210 showed the most potent anticancer activity and induced cell cycle arrest, inhibited migration, caused cell death by inducing apoptosis through the intrinsic pathway, and were nontoxic to normal cells.

Proteasome inhibitors against amelanotic melanoma

The incidence of malignant melanoma, the most aggressive skin cancer, is increasing constantly. Despite new targeted therapies, the prognosis for patients with metastatic disease remains poor. Thus, there is a need for new combinational treatments, and antineoplastic agents potentially valuable in this approach are inhibitors of the ubiquitin-proteasome system (UPS). In this work, we analyze the cytotoxicity mechanisms of proteasome inhibitors (MG-132, epoxomicin, and lactacystin) in a specific form of melanoma which does not synthesize melanin—the amelanotic melanoma (Ab cells). We found that the most cytotoxic of the compounds tested was epoxomicin. Caspase-9 activation as well as cytochrome C and AIF release from mitochondria indicated that exposure to epoxomicin induced the mitochondrial pathway of apoptosis. Epoxomicin treatment also resulted in accumulation of Bcl-2 family members—proapoptotic Noxa and antiapoptotic Mcl-1, which were postulated as the targets for bortezomib in melanoma. Inhibition of caspases by BAF revealed that cell death was partially caspase-independent. We observed no cell cycle arrest preceding the apoptosis of Ab cells, even though cdk inhibitors p21Cip1/Waf1 and p27Kip1 were up-regulated. The cell cycle was blocked only after inactivation of caspases by the pan-caspase inhibitor BAF. In summary, this is the first study exploring molecular mechanisms of cell death induced by epoxomicin in melanoma. We found that Ab cells died on the mitochondrial pathway of apoptosis and also partially by the caspase-independent way of death. Apoptosis induction was fast and efficient and was not preceded by cell cycle arrest.

Phaleria macrocarpa (Boerl.) fruit induce G0/G1 and G2/M cell cycle arrest and apoptosis through mitochondria-mediated pathway in MDA-MB-231 human breast cancer cell

Ethnopharmacological relevancePhaleria macrocarpa (Scheff) Boerl, is a well-known folk medicinal plant in Indonesia. Traditionally, P. macrocarpa has been used to control cancer, impotency, hemorrhoids, diabetes mellitus, allergies, liver and hearth disease, kidney disorders, blood diseases, acne, stroke, migraine, and various skin diseases. Aim of the studyThe purpose of this study was to determine the in situ cytotoxicity effect P. macrocarpa fruit ethyl acetate fraction (PMEAF) and the underlying molecular mechanism of cell death. Materials and methodsMDA-MB-231 cells were incubated with PMEAF for 24h. Cell cycle and viability were examined using flow cytometry analysis. Apoptosis was determined using the Annexin V assay and also by fluorescence microscopy. Apoptosis protein profiling was detected by RayBio® Human Apoptosis Array. ResultsThe AO/PI staining and flow cytometric analysis of MDA-MB-231 cells treated with PMEAF were showed apoptotic cell death. The cell cycle analysis by flow cytometry analysis revealed that the accumulation of PMEAF treated MDA-MB-231 cells in G0/G1 and G2/M-phase of the cell cycle. Moreover, the PMEAF exert cytotoxicity by increased the ROS production in MDA-MB-231 cells consistently stimulated the loss of mitochondrial membrane potential (∆Ψm) and induced apoptosis cell death by activation of numerous signalling proteins. The results from apoptosis protein profiling array evidenced that PMEAF stimulated the expression of 9 pro-apoptotic proteins (Bax, Bid, caspase 3, caspase 8, cytochrome c, p21, p27, p53 and SMAC) and suppressed the 4 anti-apoptotic proteins (Bcl-2, Bcl-w, XIAP and survivin) in MDA-MB-231 cells. ConclusionThe results indicated that PMEAF treatment induced apoptosis in MDA-MB-231 cells through intrinsic mitochondrial related pathway with the participation of pro and anti-apoptotic proteins, caspases, G0/G1 and G2/M-phases cell cycle arrest by p53-mediated mechanism.

Naphthalene diimide-polyamine hybrids as antiproliferative agents: Focus on the architecture of the polyamine chains

Naphthalene diimides (NDIs) have been widely used as scaffold to design DNA-directed agents able to target peculiar DNA secondary arrangements endowed with relevant biochemical roles. Recently, we have reported disubstituted linear- and macrocyclic-NDIs that bind telomeric and non-telomeric G-quadruplex with high degree of affinity and selectivity. Herein, the synthesis, biological evaluation and molecular modelling studies of a series of asymmetrically substituted NDIs are reported. Among these, compound 9 emerges as the most interesting of the series being able to bind telomeric G-quadruplex (ΔTm = 29 °C at 2.5 μM), to inhibit the activity of DNA processing enzymes, such as topoisomerase II and TAQ-polymerase, and to exert antiproliferative effects in the NCI panel of cancer cell lines with GI50 values in the micro-to nanomolar concentration range (i.e. SR cell line, GI50 = 76 nM). Molecular mechanisms of cell death have been investigated and molecular modelling studies have been performed in order to shed light on the antiproliferative and DNA-recognition processes.

Molecular mechanisms of cell death in retina during development of age-related macular degeneration

Age-related macular degeneration (AMD) is a chronic progressive disease characterized by damage to the central retina zone. Changes in choriocapillaries, retinal pigment epithelium (RPE), and Bruch’s membrane (typical for aging) underlie AMD pathogenesis; however, the mechanisms launching the transfer of typical age-related changes in the pathological process are unknown. The death of photoreceptors and irreversible loss of vision become the results of pathological changes in RPE and choroid. In spite of intensive studies of AMD pathogenesis, information on molecular genetic preconditions of the events leading to the death of photoreceptors (as well as about the pathways of their death) is extremely limited; this complicates the search for efficient methods of AMD treatment (first of all, the most widely spread atrophic (“dry”) form of the disease). Recent studies demonstrated that not only apoptotic but also autophagic and necrotic signaling cascades are involved in the cellular death of retinal cells. The published data on three main forms of the programmed cell death (apoptosis, necrosis, and autophagy) and their role in AMD pathogenesis are summarized in the present review.

Molecular mechanisms of cell death in intervertebral disc degeneration (Review).

Intervertebral discs (IVDs) are complex structures that consist of three parts, namely, nucleus pulposus, annulus fibrosus and cartilage endplates. With aging, IVDs gradually degenerate as a consequence of many factors, such as microenvironment changes and cell death. Human clinical trial and animal model studies have documented that cell death, particularly apoptosis and autophagy, significantly contribute to IVD degeneration. The mechanisms underlying this phenomenon include the activation of apoptotic pathways and the regulation of autophagy in response to nutrient deprivation and multiple stresses. In this review, we briefly summarize recent progress in understanding the function and regulation of apoptosis and autophagy signaling pathways. In particular, we focus on studies that reveal the functional mechanisms of these pathways in IVD degeneration.

Inhibition of autophagy potentiates anticancer property of 20(S)-ginsenoside Rh2 by promoting mitochondria-dependent apoptosis in human acute lymphoblastic leukaemia cells.

Acute lymphoblastic leukaemia (ALL) is the most prevalent childhood malignancy. Although most children with ALL are cured, there is still a group of patients for which therapy fails owing to severe toxicities and drug resistance. Ginsenoside Rh2 (GRh2), a major bioactive component isolated from Panax ginseng, has been shown to have a therapeutic effect on some tumors. However, the molecular mechanisms of cell death induced by 20(S)-GRh2 in ALL cells remains unclear. In this study, we showed that 20(S)-GRh2 inhibited the cell growth and induced mitochondria-dependent apoptosis and autophagy. But it has no cytotoxic effect on human normal blood cells. Furthermore, autophagy plays a protective role in 20(S)-GRh2-induced apoptosis in ALL cell lines and human primary ALL cells. We demonstrated that either genetic or pharmacologic inhibition of autophagy could be more effective in reducing viability and enhancing 20(S)-GRh2-induced toxicity than 20(S)-GRh2 treatment alone. In addition, inhibition of autophagy could aggravate mitochondrial ROS generation and mitochondrial damage, and then accelerate mitochondria-dependent apoptosis. Taken together, these results suggest that inhibition of autophagy can sensitize ALL cells towards 20(S)-GRh2. The appropriate inhibition of autophagy could provide a powerful strategy to increase the potency of 20(S)-GRh2 as a novel anticancer agent for ALL therapy.

Investigation of cell death mechanisms in human lymphatic endothelial cells undergoing photodynamic therapy

BackgroundPhotodynamic therapy (PDT) has been shown to induce ablation and functional occlusion of tumor-associated lymphatic vessels. However, direct effects of PDT on lymphatic endothelial cells (LECs) have not been studied so far. The aim of this study was to elucidate molecular mechanisms of cell death induced by PDT in human LECs. MethodsVerteporfin was used as a photosensitizer to investigate PDT-mediated damage of lymphatic vessels in mice using immunofluorescent staining and stereomicroscopy. In vitro dose-response studies were carried-out with crystal violet staining. Immunofluorescence, flow cytometry, immunoblotting and DNA electrophoresis were used to investigate the mechanisms of cell death in human LECs undergoing PDT. ResultsPDT induced an increase in the number of propidium iodide positive lymphatic endothelial cells in the mouse dermis. In in vitro studies dose-dependent cytotoxic effects of PDT towards LECs were observed. Typical hallmarks of apoptotic cell death, including Annexin V binding, loss of mitochondrial membrane potential, caspase activation, cleavage of PARP as well as DNA fragmentation were observed in LECs when PDT was used at high irradiation conditions, causing >80% cell death. At lower light fluencies causing <50% cell death PDT induced autophagy rather than apoptosis, as revealed by conversion of LC3-I to the autophagosomal LC3-II and formation of LC3 puncta. Z-VAD-FMK, a caspase inhibitor, prevented cell death induced by high-dose PDT only, while 3-methyladenine, an autophagy suppressor, inhibited cell death induced by low-dose PDT. ConclusionsBoth apoptosis and autophagy are involved in cell death induced by verteporfin-PDT in LECs.

Mechanisms of cell death in neurodegenerative and retinal diseases: common pathway?

The review intends to draw the attention of researchers working in retinal degenerations on the fact that classical apoptosis, for example, apoptosis triggering caspase activation, may not be the main pathway of cellular demise in this tissue.Former work already showed the difficulty of proving the activation of apoptosis effectors in different models of retinal degeneration. However, these results were not really considered because of the lack of an alternative explanation for cell death. Nowadays, the description of many pathways of cellular demise is filling the gap and other forms of cell death are now described in the retina.The knowledge on the molecular mechanisms of cell death is very important for the development of new therapeutic strategies, as well as for the evaluation of cell death onset in retinal degeneration.

Gerald W. Dorn II: Thinker, Teacher, Tinkerer.

Cardiologist and molecular and cell biologist Gerald Dorn, MD, has built his research career crafting interesting questions and teaching himself techniques needed to find answers. Using approaches including genetic and physiological manipulation in animal models, development of mini-mouse technology to elucidate cardiac mysteries, and human genetics/genomics, Dorn is helping to unravel cellular and molecular mechanisms underlying cardiomyopathy and heart failure.1,2 Gerald W. Dorn II Dorn, 57, is founding director of the Center for Pharmacogenomics at the Washington University in St. Louis School of Medicine, where he joined the faculty in 2008. As a teenager Dorn sped through high school, starting college two years early. He earned his medical degree and trained in internal medicine, pharmacology, and clinical and interventional cardiology at the Medical University of South Carolina (MUSC) in Charleston, where two key mentors sparked in him a passion for patient care and research. After a couple of years at the University of Texas Health Science Center at San Antonio, Dorn moved to the University of Cincinnati, where an American Heart Association Established Investigator Award kick-started his research program. From 1990 to 2008 Dorn rose through the ranks at Cincinnati, capitalizing on the institution’s strength in mouse cardiac transgenesis. Dorn’s current interests include molecular mechanisms of cell death,3 microRNA regulation of cardiac genes,4 and mitochondrial dynamism5—work that has expanded to Parkinson’s disease. Building on an upbringing that valued lifelong growth, and drawing from his own broad experience, Dorn now leverages the holism of systems biology to fill in what he calls his field’s “infinitely large shades of gray.” My father was a career naval aviator. Whenever he moved, we moved. So I’m not really from anywhere. We spent a lot of time on both coasts. As a child I lived, in addition to …

RIP1 and RIP3 complex regulates radiation-induced programmed necrosis in glioblastoma.

Radiation-induced necrosis (RN) is a relatively common side effect of radiation therapy for glioblastoma. However, the molecular mechanisms involved and the ways RN mechanisms differ from regulated cell death (apoptosis) are not well understood. Here, we compare the molecular mechanism of cell death (apoptosis or necrosis) of C6 glioma cells in both in vitro and in vivo (C6 othotopically allograft) models in response to low and high doses of X-ray radiation. Lower radiation doses were used to induce apoptosis, while high-dose levels were chosen to induce radiation necrosis. Our results demonstrate that active caspase-8 in this complex I induces apoptosis in response to low-dose radiation and inhibits necrosis by cleaving RIP1 and RI. When activation of caspase-8 was reduced at high doses of X-ray radiation, the RIP1/RIP3 necrosome complex II is formed. These complexes induce necrosis through the caspase-3-independent pathway mediated by calpain, cathepsin B/D, and apoptosis-inducing factor (AIF). AIF has a dual role in apoptosis and necrosis. At high doses, AIF promotes chromatinolysis and necrosis by interacting with histone H2AX. In addition, NF-κB, STAT-3, and HIF-1 play a crucial role in radiation-induced inflammatory responses embedded in a complex inflammatory network. Analysis of inflammatory markers in matched plasma and cerebrospinal fluid (CSF) isolated from in vivo specimens demonstrated the upregulation of chemokines and cytokines during the necrosis phase. Using RIP1/RIP3 kinase specific inhibitors (Nec-1, GSK'872), we also establish that the RIP1-RIP3 complex regulates programmed necrosis after either high-dose radiation or TNF-α-induced necrosis requires RIP1 and RIP3 kinases. Overall, our data shed new light on the relationship between RIP1/RIP3-mediated programmed necrosis and AIF-mediated caspase-independent programmed necrosis in glioblastoma.

Molecular mechanism Of cell death induced by king cobra (Ophiophagus hannah) venom l-amino acid oxidase

Snake venom LAAOs have been reported to exhibit a wide range of pharmacological activities, including cytotoxic, edema-inducing, platelet aggregation-inducing/platelet aggregation-inhibiting, bactericidal and antiviral activities. A heat-stable form of l-amino acid oxidase isolated from king cobra (Ophiophagus hannah) venom (OH-LAAO) has been shown to exhibit very potent cytotoxicity against human tumorigenic cells but not in their non-tumorigenic counterparts, and the cytotoxicity was due to the apoptosis-inducing effect of the enzyme. In this work, the molecular mechanism of cell death induced by OH-LAAO was investigated. The enzyme exerts its apoptosis-inducing effect presumably via both intrinsic and extrinsic pathways as suggested by the increase in caspase-8 and -9 activities. Oligonucleotide microarray analysis showed that the expression of a total of 178 genes was significantly altered as a result of oxidative stress induced by the hydrogen peroxide generated by the enzyme. Of the 178 genes, at least 27 genes are involved in apoptosis and cell death. These alterations of gene expression was presumably caused by the direct cytotoxic effect of H2O2 generated during the enzymatic reaction, as well as the non-specific oxidative modifications of signaling molecules that eventually lead to apoptosis and cell death. The very substantial up-regulation of cytochrome P450 genes may also contribute to the potent cytotoxic action of OH-LAAO by producing excessive reactive oxygen species (ROS). In conclusion, the potent apoptosis inducing activity of OH-LAAO was likely due to the direct cytotoxic effect of H2O2 generated during the enzymatic reaction, as well as the non-specific oxidation of signalling molecules.

The End of the Beginning: Cell Death in the Germline.

Programmed cell death occurs in the germline of many organisms, both as an essential part of development and throughout adult life. Germline cell death can be apoptotic or nonapoptotic, depending on the stimulus or stage of development. Here, we focus on the Drosophila ovary, which is a powerful model for studying diverse types of cell death. In Drosophila, the death of primordial germ cells occurs normally during embryonic development, and germline nurse cells are programmed to die during oocyte development in adult flies. Cell death of previtellogenic egg chambers in adults can also be induced by starvation or other environmental cues. Mid-oogenesis seems to be particularly sensitive to such cues and has been proposed to serve as a checkpoint to avoid the energetically expensive cost of egg production. After the germline dies in mid-oogenesis, the remnants are engulfed by an epithelial layer of follicle cells; thus, the fly ovary also serves as a highly tractable model for engulfment by epithelial cells. These examples of cell death in the fly ovary share many similarities to the types of cell death seen in the mammalian germline. Recent progress in elucidating the molecular mechanisms of cell death in the germline is discussed.