Loss Of Plasma Membrane Asymmetry Research Articles

Systemic deficiency of mouse arachidonate 15-lipoxygenase induces defective erythropoiesis and transgenic expression of the human enzyme rescues this phenotype.

Arachidonic acid 15-lipoxygenases (ALOX15) are lipid peroxidizing enzymes, which has previously been implicated in the maturational breakdown of intracellular organelles and plasma membrane remodeling during reticulocyte-erythrocyte transition. Conventional Alox15-/- mice are viable, develop normally but do not exhibit a major defective erythropoietic phenotype. To characterize the putative in vivo relevance of Alox15 for red blood cell development, we explored the impact of systemic inactivation of the Alox15 gene on mouse erythropoiesis. We found that Alox15-/- mice exhibited reduced erythrocyte counts, elevated reticulocyte counts and red cell hyperchromia. The structure of the plasma membrane of Alox15-/- erythrocytes is altered and a significant share of the red cells was present as echinocytes and/or acanthocytes. An increased share of the Alox15-/- erythrocytes cells were annexin V positive, which indicates a loss of plasma membrane asymmetry. Erythrocytes of Alox15-/- mice were more susceptible to osmotic hemolysis and exhibited a reduced ex vivo life span. When we transgenically expressed human ALOX15 in Alox15-/- mice under the control of the aP2 promoter the defective erythropoietic system was rescued and the impaired osmotic resistance was normalized. Together these data suggest the involvement Alox15 in the maturational remodeling of the plasma membrane during red cell development.

Qianliening Capsule Promotes Mitochondrial Pathway Mediated the Apoptosis of Benign Prostatic Hyperplasia Epithelial-1 Cells by Regulating the miRNA-181a

Summary Background Our previous studies reported that Qianliening capsule (QC) has a significant therapeutic effect on BPH. Therefore, we investigated the effect QC on apoptosis of human prostatic hyperplasia epithelial-1 cells (BPH-1). Methods The BPH-1 cells were treated with various concentrations of QC in vitro. Morphology of BPH-1 cell was observed, and the cell viability was determined by the 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay. The levels of Cytochrome C, caspase-9 and caspase-3 were detected using the flow cytometry and colorimetric assay respectively. The Bax mRNA and the miRNA-221, -222, -15a, -16, -181a was determine by Real-time PCR analysis. Results The apoptosis of BPH-1 cells treated with QC increased than that of untreated cells, as evidenced by loss of plasma membrane asymmetry, the nuclear condensation and fragmentation, collapse of mitochondrial membrane potential in a dose depended manner. The levels of Cytochrome C and caspase-9, caspase-3 in the cells treated with QC increased using the flow cytometry and colorimetric assay respectively. The mRNA and protein expression of Bax and the expression of miRNA-181a in the cells treated with QC increased in a dose dependent manner. Conclusion QC could induce BPH-1 cells apoptosis by regulating miRNA-181a mediated mitochondrial dependent apoptosis pathway, which may be one of the important mechanisms that QC treated benign prostatic hyperplasia.

The Essential Neo1 Protein from Budding Yeast Plays a Role in Establishing Aminophospholipid Asymmetry of the Plasma Membrane

Eukaryotic organisms typically express multiple type IV P-type ATPases (P4-ATPases), which establish plasma membrane asymmetry by flipping specific phospholipids from the exofacial to the cytosolic leaflet. Saccharomyces cerevisiae, for example, expresses five P4-ATPases, including Neo1, Drs2, Dnf1, Dnf2, and Dnf3. Neo1 is thought to be a phospholipid flippase, although there is currently no experimental evidence that Neo1 catalyzes this activity or helps establish membrane asymmetry. Here, we use temperature-conditional alleles (neo1(ts)) to test whether Neo1 deficiency leads to loss of plasma membrane asymmetry. Wild-type (WT) yeast normally restrict most of the phosphatidylserine (PS) and phosphatidylethanolamine (PE) to the inner cytosolic leaflet of the plasma membrane. However, the neo1-1(ts) and neo1-2(ts) mutants display a loss of PS and PE asymmetry at permissive growth temperatures as measured by hypersensitivity to pore-forming toxins that target PS (papuamide A) or PE (duramycin) exposed in the extracellular leaflet. When shifted to a semi-permissive growth temperature, the neo1-1(ts) mutant became extremely hypersensitive to duramycin, although the sensitivity to papuamide A was unchanged, indicating preferential exposure of PE. This loss of asymmetry occurs despite the presence of other flippases that flip PS and/or PE. Even when overexpressed, Drs2 and Dnf1 were unable to correct the loss of asymmetry caused by neo1(ts) However, modest overexpression of Neo1 weakly suppressed loss of membrane asymmetry caused by drs2Δ with a more significant correction of PE asymmetry than PS. These results indicate that Neo1 plays an important role in establishing PS and PE plasma membrane asymmetry in budding yeast.

Jiedu Xiaozheng Yin decoction inhibits hepatoma cell proliferation by inducing apoptosis via the mitochondrial-mediated pathway.

Jiedu Xiaozheng Yin decoction (JXY) is a type of Chinese traditional medicine, which has been used to treat various types of cancer. The present study explored the mechanisms underlying the anticancer activity of JXY. The effects of ethyl acetate extraction of JXY (EE-JXY) were evaluated on the HepG2 human hepatoma cell line in vitro and in vivo. Following treatment of the HepG2 cells with EE-JXY for 24 h, cell viability, apoptosis, mitochondrial membrane potential, caspase enzyme activity and the expression levels of apoptotic-associated proteins (Bcl-2 and Bax) were detected by MTT, flow cytometry, ELISA and western blotting respectively. In addition, HepG2 cells were subcutaneously transplanted into BALB/c nude mice, and the tumor bearing mice were treated with either EE-JXY (0.06 g/kg) or normal saline for 21 days. Tumor volume and weight were measured and recorded. The apoptotic index, and the expression levels of Bax and cytochrome c were determined with immunohistochemical staining. Treatment with EE-JXY inhibited the proliferation of HepG2 cells, and reduced cell viability in a dose-and time-dependent manner. Furthermore, EE-JXY induced HepG2 cell apoptosis, as demonstrated by a loss of plasma membrane asymmetry and externalization of phosphatidylserine, collapse of mitochondrial membrane potential, activation of caspase-9 and caspase-3, and an increased ratio of pro-apoptotic Bax to anti-apoptotic Bcl-2. Furthermore, EE-JXY inhibited tumor growth and increased the apoptotic index of tumors in tumor-bearing mice. In conclusion, the results of the present study suggest that JXY inhibits HepG2 cell proliferation through mitochondrion-mediated apoptosis, which may partially explain its anticancer activity.

Millimeter Wave Treatment Inhibits Apoptosis of Chondrocytes via Regulation Dynamic Equilibrium of Intracellular Free Ca (2+).

The molecular mechanisms of TNF-α-induced apoptosis of chondrocyte and the role of Ca2+ mediating the effects of MW on TNF-α-induced apoptosis of chondrocytes remained unclear. In this study, we investigated the molecular mechanism underlying inhibiting TNF-α-induced chondrocytes apoptosis of MW. MTT assay, DAPI, and flow cytometry demonstrated that MW significantly increased cell activity and inhibited chromatin condensation accompanying the loss of plasma membrane asymmetry and the collapse of mitochondrial membrane potential. Our results also indicated that MW reduced the elevation of [Ca2+]i in chondrocytes by LSCM. Moreover, MW suppressed the protein levels of calpain, Bax, cytochrome c, and caspase-3, while the expressions of Bcl-2, collagen II, and aggrecan were increased. Our evidences indicated that MW treatment inhibited the apoptosis of chondrocytes through depression of [Ca2+]i. It also inhibited calpain activation, which mediated Bax cleavage and cytochrome c release and initiated the apoptotic execution phase. In addition, MW treatment increased the expression of collagen II and aggrecan of chondrocytes.

Listeria monocytogenes exploits efferocytosis to promote cell-to-cell spread.

Efferocytosis, the process by which dying/dead cells are removed by phagocytosis, plays an important role in development, tissue homeostasis and innate immunity1. Efferocytosis is mediated, in part, by receptors that bind to exofacial phosphatidylserine (PS) on cells or cellular debris after loss of plasma membrane asymmetry. Here we show that a bacterial pathogen, Listeria monocytogenes (Lm), can exploit efferocytosis to promote cell-to-cell spread during infection. These bacteria can escape the phagosome in host cells using the pore-forming toxin Listeriolysin O (LLO) and two phospholipases C2. Expression of the cell surface protein ActA allows Lm to activate host actin regulatory factors and undergo actin-based motility in the cytosol, eventually leading to formation of actin-rich protrusions at the cell surface. We show that protrusion formation is associated with plasma membrane damage due to LLO’s pore-forming activity. LLO also promotes the release of bacteria-containing protrusions from the host cell, generating membrane-derived vesicles with exofacial PS. The PS-binding receptor TIM-4 contributes to efficient cell-to-cell spread by Lm in macrophages in vitro and growth of these bacteria is impaired in TIM-4−/− mice. Thus, Lm promotes its dissemination in a host by exploiting efferocytosis. Our study suggests that PS-targeted therapeutics may be useful in the fight against infections by Lm and other bacteria that utilize similar strategies of cell-to-cell spread during infection.

Xiao Jin Wan, a traditional Chinese herbal formula, inhibits proliferation via arresting cell cycle progression at the G2/M phase and promoting apoptosis via activating the mitochondrial-dependent pathway in U-2OS human osteosarcoma cells

Xiao Jin Wan (XJW) is a well-known traditional Chinese folk-medicine, which is commonly used for the treatment of various types of diseases including cancers. However, the mechanism of the anticancer activity of XJW against U-2OS human osteosarcoma cells, have not yet been reported. In the present study, we investigated the cellular effects of the XJW on the U-2OS human osteosarcoma cell line. Our results showed that XJW induced cell morphological changes, reduced cell viability in a dose- and time-dependent manner and arrested in the G2/M phase of the cell cycle suggesting that XJW inhibited the proliferation of U-2OS cells. Hoechst 33258 staining and Annexin V/propidium iodide double staining exhibited the typical nuclear features of apoptosis and increased the proportion of apoptotic Annexin V-positive cells in a dose-dependent manner, respectively. In addition, XJW treatment caused loss of plasma membrane asymmetry, collapse of mitochondrial membrane potential, activation of caspase-9 and caspase-3, and increase of the ratio of pro-apoptotic Bax to anti-apoptotic Bcl-2. Taken together, the results indicate that the U-2OS cell growth inhibitory activity of XJW was due to cell cycle arrested and mitochondrial-mediated apoptosis, which may partly explain the anticancer activity of Xiao Jin Wan.

Qianliening capsule (前列宁胶囊) inhibits human prostate cell growth via induction of mitochondrion-dependent cell apoptosis

To investigate the molecular mechanisms by which Qianliening Capsule (, QC) treats benign prostatic hyperplasia (BPH). Human prostate stromal cell line WPMY-1 was treated with 0, 1, 3 and 5 mg/mL of QC for 24, 48 and 72 h, respectively, in the presence of 10 ng/mL basic fibroblast growth factor (bFGF). The viability of WPMY-1 cells was determined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell morphology was observed by phase-contrast microscopy. 4',6-diamidino-2-phenylindole (DAPI) staining and fluorescence activated cell sorting (FACS) analysis with Annexin-V/propidium iodide (PI) staining were performed to determine cell apoptosis. The loss of mitochondrial membrane potential was examined by FACS analysis with 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl-carbocyarine iodide (JC-1) staining. Activation of caspase-3 and -9 was evaluated by colorimetric assay. The mRNA and protein expression levels of Bcl-2 and Bax were measured by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting, respectively. Upon bFGF stimulation, the viability of WPMY-1 cells was increased to 122%-118% compared with the control cells (P <0.05). However, treatment with 1-5 mg/mL of QC for 24, 48 and 72 h decreased the viability of bFGF-stimulated cells to 80%-92%, 59%-82%, 36%-62% compared with the untreated cells (P <0.05). In addition, QC treatment reduced WPMY-1 cell density in a dose-dependent manner. Moreover, QC treatment dose-dependently induced the loss of plasma membrane asymmetry, the nuclear condensation and fragmentation, collapse of mitochondrial membrane potential, activation of caspase-9 and caspase-3, and increase of pro-apoptotic Bax/Bcl-2 ratio. Promoting mitochondrion-dependent apoptosis of prostate stromal cells might be one of the mechanisms by which QC treats BPH.

Enzymatic measurement of phosphatidylserine in cultured cells

Phosphatidylserine (PS) is a quantitatively minor membrane phospholipid involved in diverse cellular functions. In this study, we developed a new fluorometric method for measuring PS using combinations of specific enzymes and Amplex Red. The calibration curve for PS measurement was linear and hyperbolic at low (0-50 µM) and high (50-1000 µM) concentrations, respectively, and the detection limit was 5 µM (50 pmol in the reaction mixture). This assay quantified PS regardless of the chain length and the number of double bonds. We applied this new method to the determination of PS content in HEK293 cells, which was validated by a recovery study and comparison with TLC-phosphorus assay. We showed that the PS content was high in sparse cells. The overexpression of PS synthase 1 elevated not only the cellular PS content but also the phosphatidylcholine (PC) and phosphatidylethanolamine (PE) contents, suggesting the conversion of PS into PE and the enhancement of PC production. This new assay for PS measurement is simple, specific, sensitive, and high throughput, and it will be useful to clarify the metabolism and biological functions of PS.

Millimeter wave treatment induces apoptosis via activation of the mitochondrial-dependent pathway in human osteosarcoma cells

Millimeter wave (MW) is an electromagnetic wave with a wavelength between 1 and 10 mm and a frequency of 30-300 GHz that causes multiple biological effects and has been used as a major component in physiotherapies for the clinical treatment of various types of diseases including cancers. However, the precise molecular mechanism of the anticancer activity of millimeter wave remains to be elucidated. In the present study, we investigated the cellular effects of the MW in the U-2OS human osteosarcoma cell line. Our results showed that MW induced cell morphological changes and reduced cell viability in a dose- and time-dependent manner suggesting that MW inhibited the growth of U-2OS cells as demonstrated. Hoechst 33258 staining and Annexin V/propidium iodide double staining exhibited the typical nuclear features of apoptosis and increased the proportion of apoptotic Annexin V-positive cells in a dose-dependent manner, respectively. In addition, MW treatment caused loss of plasma membrane asymmetry, release of cytochrome c, collapse of mitochondrial membrane potential, activation of caspase-9 and -3, and increase of the ratio of pro-apoptotic Bax to anti-apoptotic Bcl-2. Taken together, the results indicate that the U-2OS cell growth inhibitory activity of MW was due to mitochondrial-mediated apoptosis, which may partly explain the anticancer activity of millimeter wave treatment.

Fucose-Containing Sulfated Polysaccharides from Brown Seaweeds Inhibit Proliferation of Melanoma Cells and Induce Apoptosis by Activation of Caspase-3 in Vitro

Fucose-containing sulfated polysaccharides (FCSPs) extracted from seaweeds, especially brown macro-algae, are known to possess essential bioactive properties, notably growth inhibitory effects on tumor cells. In this work, we conducted a series of in vitro studies to examine the influence of FCSPs products from Sargassum henslowianum C. Agardh (FSAR) and Fucus vesiculosus (FVES), respectively, on proliferation of melanoma B16 cells and to investigate the underlying apoptosis promoting mechanisms. Cell viability analysis showed that both FCSPs products, i.e., FSAR and FVES, decreased the proliferation of the melanoma cells in a dose-response fashion, with FSAR being more potent at lower dosages, and FVES being relatively more anti-proliferative than FSAR at higher dosages. Flow cytometric analysis by Annexin V staining of the melanoma cells exposed to the FCSPs products confirmed that both FSAR and FVES induced apoptosis. The FCSPs-induced apoptosis was evidenced by loss of plasma membrane asymmetry and translocation of the cell membrane phospholipids and was accompanied by the activation of caspase-3. The FCSPs bioactivity is proposed to be attributable to distinct structural features of the FCSPs, particularly the presence of sulfated galactofucans (notably in S. henslowianum) and sulfated fucans (notably in F. vesiculosus). This study thus indicates that unfractionated FCSPs may exert bioactive effects on skin cancer cells via induction of apoptosis through cascades of reactions that involve activation of caspase-3.

Initiation but no execution - modulation of peripheral blood lymphocyte apoptosis in rheumatoid arthritis - a potential role for heat shock protein 70

BackgroundRheumatoid arthritis (RA) is a chronic autoimmune disease, which causes synovial damage. Persistence of lymphocyte infiltrates in the rheumatoid synovium has been attributed to abnormal apoptosis. While not comprehensively investigated, perturbations in peripheral blood lymphocyte (PBL) apoptosis may also be involved in perpetuation of autoimmune processes in RA.MethodsWe investigated total, CD4+ and CD19+ PBL apoptosis in our study cohort by monitoring the translocation of phosphatidylserine using the Annexin-V assay. To examine the role of death receptor mediated apoptosis as well as activation-induced-cell-death (AICD), PBLs were labeled with CD95/Fas and CD69 markers and enumerated by flow cytometry. Proteolytic activity of initiator and executioner caspases was determined by luminometry. DNA fragmentation assays were used to examine whether apoptotic signals were transduced to the nucleus. Quantitative PCR arrays were used to investigate apoptotic pathways associated with RA-PBLs. Since heat-shock-protein-70 (HSP70) is an inducible protein which modulates apoptotic signals, we determined HSP70 levels by intra-cellular flow cytometry and western blots.ResultsThe RA-PBLs showed signs of elevated apoptosis whilst in circulation. These include increases in the loss of plasma membrane asymmetry, indicated by increased externalization of phosphatidylserine (especially in B-lymphocytes). RA-PBLs showed a bias to CD95/Fas mediated apoptotic pathways, but low levels of the CD69 marker suggested that this was not associated with immune activation. Although downstream markers of apoptosis such as caspase-3/7 activity, were increased, no DNA fragmentation was observed in RA-PBLs. Interestingly, elevated levels of apoptosis did not correlate with absolute lymphocyte counts in RA patients. Levels of HSP70 were highly elevated in RA-PBLs compared to controls.ConclusionThe results suggest that while apoptosis may be initiated in RA-PBLs, they may lack commitment to fully executing the apoptotic program. This may be related to inhibition on apoptotic transduction by HSP70. This study provides evidence that abnormalities in RA-PBLs apoptosis may occur whilst still in circulation and may contribute to pathogenesis of the disease.

Millimeter wave treatment inhibits the mitochondrion-dependent apoptosis pathway in chondrocytes

Millimeter wave (MW) is an electromagnetic wave with a wavelength between 1 and 10 mm and a frequency of 30-300 GHz that causes multiple biological effects, both locally and globally. MW has been widely used in clinical medicine. Although our previous work demonstrated that MW is capable of inhibiting sodium nitroprussiate (SNP)-induced apoptosis in chondrocytes, the precise mechanism of the anti-apoptotic activity remains to be elucidated. The purpose of this study was to investigate the effects of MW in SNP-induced apoptotic chondrocytes. Sprague Dawley rat chondrocytes were isolated and cultured, and the cells were counted. Cell viability was evaluated using MTT assay. Cells were then treated with SNP and MW, and flow cytometry was used to detect apoptosis. Our results showed that MW treatment inhibited a SNP-induced mitochondrion-dependent pathway of apoptosis. MW treatment inhibited the loss of plasma membrane asymmetry (externalization of phosphatidylserine), collapse of mitochondrial membrane potential, and activation of caspase-9 and caspase-3. Taken together, the results indicate that MW inhibits the mitochondrion-dependent pathway of apoptosis in chondrocytes and this may, in part, explain its clinical effect in the treatment of osteoarthritis.

Scutellaria barbata D. Don induces apoptosis of human colon carcinoma cell through activation of the mitochondrion-dependent pathway

Scutellaria barbata D. Don has long been used in China for the clinical treatment of various cancers including colorectal cancer. However, the precise mechanisms of its tumorcidal activity remain unclear. In the present study, we investigated the cellular effects of the ethanol extract of S. barbata D. Don (EESB) in the HT-29 human colon carcinoma cell line. We found that EESB inhibited the growth of HT-29 cells as demonstrated EESB-induced cell morphological changes and reduced cell viability in dose- and time-dependent manners. Furthermore, we observed that EESB treatment resulted in DNA fragmentation, loss of plasma membrane asymmetry, collapse of mitochondrial membrane potential, activation of caspase-9 and caspase-3, and increase of the ratio of pro-apoptotic Bax to anti-apoptotic Bcl-2. These results suggest that promotion of cancer cell apoptosis through activation of the mitochondrion-dependent pathway is one of the mechanisms by which S. barbata D. Don can be effective in the treatment of cancer. Key words: Scutellaria barbata D. Don, apoptosis, colorectal cancer, HT-29 cells, herbal medicine, mitochondria.

English

Spica Prunellae&nbsp;(Prunella vulgaris&nbsp;fruiting spikes) has long been used as an important component in formulated prescriptions of Chinese traditional medicine to treat various kinds of cancer. However, the precise mechanism of the anti-cancer activity of Spica Prunellae remains to be elucidated. In this report, we investigated the cellular effects of the ethanol extract of Spica Prunellae&nbsp;(EESP) in the HT-29 human colon carcinoma cell line. We found that EESP inhibited the growth of HT-29 cells as evidenced by EESP-induced cell morphological changes and reduced cell viability in dose- and time-dependent manners. Furthermore, we demonstrated that the HT-29 cell growth inhibitory activity of EESP was due to apoptosis, as EESP treatment resulted in the loss of plasma membrane asymmetry (externalization of phosphatidylserine), collapse of mitochondrial membrane potential, activation of caspase-9 and caspase-3, and increase in the ratio of pro-apoptotic Bax to anti-apoptotic Bcl-2. Taken together, these results suggest that Spica Prunellae inhibits the growth of HT-29 colon cancer cells through mitochondrion-mediated apoptosis, which may, in part, explain its anti-cancer activity. &nbsp; Key words:&nbsp;Apoptosis, anti-tumor, HT-29 cells, phytotherapy, mitochondria, Spica Prunellae.

Hedyotis Diffusa Willd extract induces apoptosis via activation of the mitochondrion-dependent pathway in human colon carcinoma cells

Hedyotis Diffusa Willd has been used as a major component in several Chinese medicine formulations for the clinical treatment of colorectal cancer. However, the molecular mechanism of the anti-cancer activity of Hedyotis Diffusa Willd remains unclear. In the present study, we investigated the cellular effects of the ethanol extract of Hedyotis Diffusa Willd (EEHDW) in the HT-29 human colon carcinoma cell line. We found that EEHDW inhibited the growth of HT-29 cells demonstrating EEHDW-induced cell morphological changes and reduced cell viability in a dose- and time-dependent manner. Furthermore, we observed that EEHDW treatment resulted in DNA fragmentation, loss of plasma membrane asymmetry, collapse of mitochondrial membrane potential, activation of caspase-9 and caspase-3, and increase of the ratio of pro-apoptotic Bax to anti-apoptotic Bcl-2, suggesting that the HT-29 cell growth inhibitory activity of EEHDW was due to mitochondrion-mediated apoptosis, which may partly explain the anti-cancer activity of Hedyotis Diffusa Willd.

Neutrophilic differentiation modulates the apoptotic response of HL-60 cells to sodium butyrate and sodium valproate

Differentiation of myeloid leukemic cells may result in less sensitivity to various apoptotic stimuli. We examined whether human leukemia HL-60 cells differentiating by all-trans retinoic acid (ATRA) acquired resistance to the apoptogenic activity of two histone deacetylase (HDAC) inhibitors, butyrate and valproate. In undifferentiated cells, the cytotoxicity of both butyrate and valproate was associated with activation of the intrinsic apoptotic pathway since we observed dissipation of mitochondrial membrane potential, induction of caspase-9 and caspase-3 activities, appearance of sub-G1 DNA and loss of plasma membrane asymmetry and/or integrity. Both HDAC inhibitors were also able to induce accumulation of undifferentiated cells in the G0/G1 phase of the cell cycle. ATRA was found to enhance the apoptotic effect of both butyrate and valproate in undifferentiated cells. This aside, ATRA appeared to synergize with butyrate in the induction of the G0/G1 cell cycle arrest. In cells pretreated for 72 h with ATRA, butyrate and valproate in combination with ATRA induced lower dissipation of mitochondrial membrane potential and weaker apoptotic and/or necrotic changes in plasma membrane, whereas DNA fragmentation was not diminished compared to undifferentiated cells. Similar results were also obtained when butyrate or valproate were combined with another neutrophilic differentiation inducer, dimethyl sulfoxide. We conclude that neutrophilic differentiation modulates but does not abrogate the apoptotic response of HL-60 cells to butyrate and valproate, and nuclei are preferentially affected during apoptosis in differentiated cells.

Cytotoxic activity of sanguinarine and dihydrosanguinarine in human promyelocytic leukemia HL-60 cells

The benzo[ c]phenanthridine alkaloid sanguinarine has been studied for its antiproliferative activity in many cell types. Almost nothing however, is known about the cytotoxic effects of dihydrosanguinarine, a metabolite of sanguinarine. We compared the cytotoxicity of sanguinarine and dihydrosanguinarine in human leukemia HL-60 cells. Sanguinarine produced a dose-dependent decline in cell viability with IC 50 (inhibitor concentration required for 50% inhibition of cell viability) of 0.9 μM as determined by MTT assay after 4 h exposure. Dihydrosanguinarine showed much less cytotoxicity than sanguinarine: at the highest concentration tested (20 μM) and 24 h exposure, dihydrosanguinarine decreased viability only to 52%. Cytotoxic effects of both alkaloids were accompanied by activation of the intrinsic apoptotic pathway since we observed the dissipation of mitochondrial membrane potential, induction of caspase-9 and -3 activities, the appearance of sub-G 1 DNA and loss of plasma membrane asymmetry. This aside, sanguinarine also increased the activity of caspase-8. As shown by flow cytometry using annexin V/propidium iodide staining, 0.5 μM sanguinarine induced apoptosis while 1–4 μM sanguinarine caused necrotic cell death. In contrast, dihydrosanguinarine at concentrations from 5 μM induced primarily necrosis, whereas apoptosis occurred at 10 μM and above. We conclude that both alkaloids may cause, depending on the alkaloid concentration, both necrosis and apoptosis of HL-60 cells.

The Antimicrobial Peptide NK-2, the Core Region of Mammalian NK-Lysin, Kills Intraerythrocytic Plasmodium falciparum

In a time of dramatically increasing resistance of microbes to all kinds of antibiotics, natural antimicrobial peptides and synthetic analogs thereof have emerged as compounds with potentially significant therapeutical applications against human pathogens. Only very few of these peptide antibiotics have been tested against protozoan pathogens that are a major cause of morbidity and mortality in large parts of the world. Here, we studied the effect of NK-2, a peptide representing the cationic core region of the lymphocytic effector protein NK-lysin, on the malaria parasite Plasmodium falciparum. Whereas noninfected red blood cells were hardly affected, human erythrocytes infected with the parasite were rapidly permeabilized by NK-2 in the micromolar range. Loss of plasma membrane asymmetry and concomitant exposure of phosphatidylserine upon infection appears to be the molecular basis for the observed target preference of NK-2, as can be demonstrated by annexin V binding. The peptide also affects the viability of the intracellular parasite, as evidenced by the drop in DNA content of cultured parasites. Accumulated evidence derived from permeabilization assays using parasites and liposomes as targets and from fluorescence microscopy of infected erythrocytes treated with fluorescently labeled NK-2 indicates that the positively charged peptide electrostatically interacts with the altered and negatively charged plasma membrane of the infected host cell and traverses this membrane as well as the parasitophorous vacuole membrane to reach its final target, the intracellular parasite. The apparent affinity for foreign membranes that resulted in the death of a eukaryotic parasite residing in human host cells makes NK-2 a promising template for novel anti-infectives.

Search for novel cell surface markers of apoptotic cells

Surface markers of apoptotic cells are of great interest as potential targets for non-destructive detection and study of these cells. They are also important for apoptotic cell recognition and subsequent clearance by cells of the immune system. Recently, it was found that apoptosis is accompanied by not only the loss of plasma membrane asymmetry detected by Annexin V, but also by changes in cell surface glycoconjugates. These novel markers of apoptosis are α-d-mannose and β-d-galactose-specific plasma membrane glycoproteins whose expression is substantially increased after induction of apoptosis. The glyconeoepitopes described in this article are proposed to be useful for both, the detection of apoptotic cells and the isolation of the latter, from mixed populations.