ATP6AP1 as a potential prognostic biomarker in CRC by comprehensive analysis and verification

The role of ATP6AP1 in colorectal cancer (CRC) remains elusive despite its observed upregulation in pan-cancer. Therefore, the current study aimed to assess the clinical significance of ATP6AP1 and its relationship with the immune infiltration in CRC. Transcriptome data of CRC were obtained from The Cancer Genome Atlas (TCGA) database and analyzed using the combination of R packages and tumor-related databases, including TIMER2, TISIDB, cBioPortal, and MethSurv. The tissue arrays and immunohistochemical staining were performed to verify the expression and clinical characteristics of ATP6AP1. The results revealed that ATP6AP1 expression was significantly elevated in CRC and associated with poor clinicopathological characteristics and prognosis. Furthermore, the analysis demonstrated ATP6AP1 expression was correlated with the infiltration of immune cells and cancer-associated fibroblasts in the microenvironment of CRC. Moreover, ATP6AP1 was found to be linked to various immune checkpoints and chemokines, with enrichment of cytoplasmic vesicle lumen, endopeptidase regulator activity, and endopeptidase inhibitor activity observed in the high ATP6AP1 expressional group. In conclusion, the findings of this study suggest that ATP6AP1 upregulation may serve as a biomarker for poor diagnosis in CRC and offer a potential target for immunotherapy in CRC.

Emerging insights into CP110 removal during early steps of ciliogenesis

The primary cilium is an antenna-like projection from the plasma membrane that serves as a sensor of the extracellular environment and a crucial signaling hub. Primary cilia are generated in most mammalian cells, and their physiological significance is highlighted by the large number of severe developmental disorders or ciliopathies that occur when primary ciliogenesis is impaired. Primary ciliogenesis is a tightly regulated process, and a central early regulatory step is the removal of a key mother centriole capping protein, CP110 (also known as CCP110). This uncapping allows vesicles docked on the distal appendages of the mother centriole to fuse to form a ciliary vesicle, which is bent into a ciliary sheath as the microtubule-based axoneme grows and extends from the mother centriole. When the mother centriole migrates toward the plasma membrane, the ciliary sheath fuses with the plasma membrane to form the primary cilium. In this Review, we outline key early steps of primary ciliogenesis, focusing on several novel mechanisms for removal of CP110. We also highlight examples of ciliopathies caused by genetic variants that encode key proteins involved in the early steps of ciliogenesis.

Fluorescence microscopy and correlative brightfield videos of mitochondria and vesicles in H9c2 cardiomyoblasts

This paper presents data acquired to study the dynamics and interactions of mitochondria and subcellular vesicles in living cardiomyoblasts. The study was motivated by the importance of mitochondrial quality control and turnover in cardiovascular health. Although fluorescence microscopy is an invaluable tool, it presents several limitations. Correlative fluorescence and brightfield images (label-free) were therefore acquired with the purpose of achieving virtual labelling via machine learning. In comparison with the fluorescence images of mitochondria, the brightfield images show vesicles and subcellular components, providing additional insights about sub-cellular components. A large part of the data contains correlative fluorescence images of lysosomes and/or endosomes over a duration of up to 400 timepoints (>30 min). The data can be reused for biological inferences about mitochondrial and vesicular morphology, dynamics, and interactions. Furthermore, virtual labelling of mitochondria or subcellular vesicles can be achieved using these datasets. Finally, the data can inspire new imaging experiments for cellular investigations or computational developments. The data is available through two large, open datasets on DataverseNO.

Preparation of Uniformly Oriented Inverted Inner (Cytoplasmic) Membrane Vesicles from Gram-Negative Bacterial Cells

The complex double-membrane organization of the envelope in Gram-negative bacteria places unique biosynthetic and topological constraints that can affect translocation of lipids and proteins synthesized on cytoplasm facing leaflet of cytoplasmic (inner) membrane (IM), across IM and between IM and outer membrane (OM). Uniformly oriented inside-out (ISO) vesicles became functional requisite for many biochemical reconstitution functional assays, vectorial proteomics, and vectorial lipidomics. Due to these demands, it is necessary to develop simple and reliable approaches for preparation of uniformly oriented IM membrane vesicles and validation of their sidedness. The uniformly ISO oriented membrane vesicles which have the cytoplasmic face of the membrane on the outside and the periplasmic side facing the sealed lumen can be obtained following intact cell disruption by a single passage through a French pressure cell (French press) at desired total pressure. Although high-pressure lysis leads to the formation of mostly inverted membrane vesicles (designated and abbreviated usually as ISO vesicles, everted or inverted membrane vesicles (IMVs)), inconclusive results are quite common. This uncertainty is due mainly by applying a different pressures, using either intact cells or spheroplasts and presence or absence of sucrose during rupture procedure. Many E. coli envelope fractionation techniques result in heterogeneity among isolated IM membrane vesicles. In part, this is due to difficulties in simple validation of sidedness of oriented membrane preparations of unknown sidedness. The sidedness of various preparations of membrane vesicles can be inferred from the orientation of residing uniformly oriented transmembrane protein. We outline the method in which the orientation of membrane vesicles can be verified by mapping of uniform or mixed topologies of essential protein E. coli protein leader peptidase (LepB) by advanced SCAM™. Although the protocol discussed in this chapter has been developed using Escherichia coli and Yersinia pseudotuberculosis, it can be directly adapted to other Gram-negative bacteria including pathogens.

Shedding of ciliary vesicles at a glance

Cilia sense and transduce sensory stimuli, homeostatic cues and developmental signals by orchestrating signaling reactions. Extracellular vesicles (EVs) that bud from the ciliary membrane have well-studied roles in the disposal of excess ciliary material, most dramatically exemplified by the shedding of micrometer-sized blocks by photoreceptors. Shedding of EVs by cilia also affords cells with a powerful means to shorten cilia. Finally, cilium-derived EVs may enable cell-cell communication in a variety of organisms, ranging from single-cell parasites and algae to nematodes and vertebrates. Mechanistic understanding of EV shedding by cilia is an active area of study, and future progress may open the door to testing the function of ciliary EV shedding in physiological contexts. In this Cell Science at a Glance and the accompanying poster, we discuss the molecular mechanisms that drive the shedding of ciliary material into the extracellular space, the consequences of shedding for the donor cell and the possible roles that ciliary EVs may have in cell non-autonomous contexts.

E. coli Membrane Vesicles as a Catalase Carrier for Long-Term Tumor Hypoxia Relief to Enhance Radiotherapy

Hypoxia is one of the most important factors that limit the effect of radiotherapy, and the abundant H₂O₂ in tumor tissues will also aggravate hypoxia-induced radiotherapy resistance. Delivering catalase to decompose H₂O₂ into oxygen is an effective strategy to relieve tumor hypoxia and radiotherapy resistance. However, low stability limits catalase's in vivo application, which is one of the most common limitations for almost all proteins' internal utilization. Here, we develop catalase containing E. coli membrane vesicles (EMs) with excellent protease resistance to relieve tumor hypoxia for a long time. Even treated with 100-fold of protease, EMs showed higher catalase activity than free catalase. After being injected into tumors post 12 h, EMs maintained their hypoxia relief ability while free catalase lost its activity. Our results indicate that EMs might be an excellent catalase delivery for tumor hypoxia relief. Combined with their immune stimulation features, EMs could enhance radiotherapy and induce antitumor immune memory effectively.

Functional characterization of four ATP-binding cassette transporter A3 gene (ABCA3) variants

ABCA3 transports phospholipids across lamellar body membranes in pulmonary alveolar type II cells and is required for surfactant assembly. Rare, biallelic, pathogenic ABCA3 variants result in lethal neonatal respiratory distress syndrome and childhood interstitial lung disease. Qualitative functional characterization of ABCA3 missense variants suggests two pathogenic classes: disrupted intracellular trafficking (type I mutant) or impaired ATPase-mediated phospholipid transport into the lamellar bodies (type II mutant). We qualitatively compared wild-type (WT-ABCA3) with four uncharacterized ABCA3 variants (c.418A>C;p.Asn140His, c.3609_3611delCTT;p.Phe1203del, c.3784A>G;p.Ser1262Gly, and c.4195G>A;p.Val1399Met) in A549 cells using protein processing, colocalization with intracellular organelles, lamellar body ultrastructure, and ATPase activity. We quantitatively measured lamellar body-like vesicle diameter and intracellular ABCA3 trafficking using fluorescence-based colocalization. Three ABCA3 variants (p.Asn140His, p.Ser1262Gly, and p.Val1399Met) were processed and trafficked normally and demonstrated well-organized lamellar body-like vesicles, but had reduced ATPase activity consistent with type II mutants. P.Phe1203del was processed normally, had reduced ATPase activity, and well-organized lamellar body-like vesicles, but quantitatively colocalized with both endoplasmic reticulum and lysosomal markers, an intermediate phenotype suggesting disruption of both intracellular trafficking and phospholipid transport. All ABCA3 mutants demonstrated mean vesicle diameters smaller than WT-ABCA3. Qualitative and quantitative functional characterization of ABCA3 variants informs mechanisms of pathogenicity.

The use of sonicated lipid vesicles for mass spectrometry of membrane protein complexes

Recent applications of mass spectrometry (MS) to study membrane protein complexes are yielding valuable insights into the binding of lipids and their structural and functional roles. To date, most native MS experiments with membrane proteins are based on detergent solubilization. Many insights into the structure and function of membrane proteins have been obtained using detergents; however, these can promote local lipid rearrangement and can cause fluctuations in the oligomeric state of protein complexes. To overcome these problems, we developed a method that does not use detergents or other chemicals. Here we report a detailed protocol that enables direct ejection of protein complexes from membranes for analysis by native MS. Briefly, lipid vesicles are prepared directly from membranes of different sources and subjected to sonication pulses. The resulting destabilized vesicles are concentrated, introduced into a mass spectrometer and ionized. The mass of the observed protein complexes is determined and this information, in conjunction with 'omics'-based strategies, is used to determine subunit stoichiometry as well as cofactor and lipid binding. Within this protocol, we expand the applications of the method to include peripheral membrane proteins of the S-layer and amyloid protein export machineries overexpressed in membranes from which the most abundant components have been removed. The described experimental procedure takes approximately 3 d from preparation to MS. The time required for data analysis depends on the complexity of the protein assemblies embedded in the membrane under investigation.

Peroxisome Biogenesis: A Union between Two Organelles

Peroxisomes are considered to form either by growth and division of existing peroxisomes or de novo from the endoplasmic reticulum. A recent study now demonstrates that mitochondria-derived vesicles are also required for de novo peroxisome biogenesis.

Mechanics of cellular packing of nanorods with finite and non-uniform diameters

To understand the mechanics of cellular/intracellular packing of one-dimensional nanomaterials, we performed theoretical analysis and molecular dynamics simulations to investigate how the morphology and mechanical behaviors of a lipid vesicle are regulated by encapsulated rigid nanorods of finite and non-uniform diameters, including a cylindrical rod, a rod with widened ends, a cone-shaped rod, and a screwdriver-shaped rod. As the rod length increases, the vesicle evolves from a sphere into different shapes, such as a lemon, a conga drum, a cherry, a bowling pin, or a tubular shape for long and thick rods. The contact between the vesicle protrusion and the rod plays an important role in regulating the vesicle tubulation, membrane tension, and axial contact force on the rod. Our analysis provides a theoretical basis to understand a wide range of experiments on morphological transitions that occur in cellular packing of actin or microtubule bundles, mitotic cell division, and intracellular packing of carbon nanotubes.

[Microvesicles derived from LPS-induced microglia aggravate the injury of tight junction in rat brain microvascular endothelial cells under oxygen-glucose deprivation]

Objective To study the effect of the administration of the circulating microvesicles (MV) obtained from lipopolysaccharide (LPS)-stimulated microglia supernatant into rat brain endothelial cells (RBECs) on the injury of tight junction in RBECs under the condition of oxygen-glucose deprivation (OGD) as well as the underlying mechanism. Methods The circulating MV was isolated from the supernatant of microglia stimulated with LPS 1 mg/L for 24 hours and subjected to morphological identification. The expression of miR-27a in MV was detected by real-time PCR. RBECs were randomly divided into control group, MV-RBECs control group, OGD 6-hour group and OGD-MV group. The expressions of occludin and claudin-5 were detected by immunofluorescence staining in the four groups. Western blot analysis was used to investigate the expressions of occludin, claudin-5, Toll-like receptor 4 (TLR4), NF-κBp65 and p38 proteins in RBECs, and ELISA was applied to detect the levels of interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α) in RBECs. Results The shape of MV was approximately circular double membrane vesicles, with an average diameter of 150 nm, in accordance with the morphological characteristics of MV. Under LPS stimulation, the level of miR-27a in the circulating MV was abnormally elevated. Compared with the control group, RBECs were not obviously influenced by the incubation of MV; under OGD condition, tight junction of RBECs was damaged with the decreasing expressions of occluding and claudin-5. The degree of injury was further damaged after the treatment with MV. Fluorescence intensity of occludin and claudin-5 were further reduced. Meanwhile, Western blot analysis showed the levels of occludin and claudin-5 proteins decreased in the OGD group after MV treatment, which was consistent with immunofluorescence staining. Compared with the control group, the expression of TLR4 protein and the phosphorylation of NF-κBp65 and p38 proteins increased in OGD group; after MV treatment, the level of TLR4 protein and the phosphorylation of NF-κBp65 and p38 proteins further increased, and the release of IL-1β and TNF-α increased as well. Conclusion Treatment with the circulating MV containing miR-27a obtained from LPS-stimulated microglia supernatant damages the tight junction of RBECs under the OGD condition. The mechanism may be related to up-regulation TLR4 and phosphorylation of NF-κBp65 and p38.

Polarity-Sensitive Probes for Superresolution Stimulated Emission Depletion Microscopy

The lateral organization of molecules in the cellular plasma membrane plays an important role in cellular signaling. A critical parameter for membrane molecular organization is how the membrane lipids are packed. Polarity-sensitive dyes are powerful tools to characterize such lipid membrane order, employing, for example, confocal and two-photon microscopy. The investigation of potential nanodomains, however, requires the use of superresolution microscopy. Here, we test the performance of the polarity-sensitive membrane dyes Di-4-ANEPPDHQ, Di-4-AN(F)EPPTEA, and NR12S in superresolution stimulated emission depletion microscopy. Measurements on cell-derived membrane vesicles, in the plasma membrane of live cells, and on single virus particles, show the high potential of these dyes for probing nanoscale membrane heterogeneity.

Small GTPase Rab1B is associated with ATG9A vesicles and regulates autophagosome formation

ATG9 is a membrane protein that is essential for autophagy and is considered to be directly involved in the early steps of autophagosome formation. Yeast Atg9 is mainly localized to small vesicles (Atg9 vesicles), whereas mammalian ATG9A is reportedly localized to the trans-Golgi network, the endosomal compartment, and other unidentified membrane structures. To dissect the ATG9A-containing membranes, we examined the subcellular localization of ATG9A and performed immunoisolation of those membranes. ATG9A-green fluorescent protein in human culture cells was observed as numerous puncta that move rapidly throughout the cytoplasm. We isolated these cytoplasmic membranes and found that they were small vesicles that resemble the yeast Atg9 vesicle. One of the proteins obtained via proteomic analyses of the mammalian ATG9A vesicle was Rab1, a small GTPase that is essential in endoplasmic reticulum-to-Golgi vesicle trafficking. Knockdown studies of Rab1B showed a suppression of autophagy. In these Rab1B-depleted cells, ATG9A accumulated in intermediate membrane structures at autophagosome formation sites. These results indicate that Rab1B is involved in regulating the proper development of autophagosomes.-Kakuta, S., Yamaguchi, J., Suzuki, C., Sasaki, M., Kazuno, S., Uchiyama, Y. Small GTPase Rab1B is associated with ATG9A vesicles and regulates autophagosome formation.

Small GTPase Rab1B is associated with ATG9A vesicles and regulates autophagosome formation

ATG9 is a membrane protein that is essential for autophagy and is considered to be directly involved in the early steps of autophagosome formation. Yeast Atg9 is mainly localized to small vesicles (Atg9 vesicles), whereas mammalian ATG9A is reportedly localized to the trans-Golgi network, the endosomal compartment, and other unidentified membrane structures. To dissect the ATG9A-containing membranes, we examined the subcellular localization of ATG9A and performed immunoisolation of those membranes. ATG9A-green fluorescent protein in human culture cells was observed as numerous puncta that move rapidly throughout the cytoplasm. We isolated these cytoplasmic membranes and found that they were small vesicles that resemble the yeast Atg9 vesicle. One of the proteins obtained via proteomic analyses of the mammalian ATG9A vesicle was Rab1, a small GTPase that is essential in endoplasmic reticulum-to-Golgi vesicle trafficking. Knockdown studies of Rab1B showed a suppression of autophagy. In these Rab1B-depleted cells, ATG9A accumulated in intermediate membrane structures at autophagosome formation sites. These results indicate that Rab1B is involved in regulating the proper development of autophagosomes.-Kakuta, S., Yamaguchi, J., Suzuki, C., Sasaki, M., Kazuno, S., Uchiyama, Y. Small GTPase Rab1B is associated with ATG9A vesicles and regulates autophagosome formation.

Removal of Vesicle Structures From Transmission Electron Microscope Images

In this paper, we address the problem of imaging membrane proteins for single-particle cryo-electron microscopy reconstruction of the isolated protein structure. More precisely, we propose a method for learning and removing the interfering vesicle signals from the micrograph, prior to reconstruction. In our approach, we estimate the subspace of the vesicle structures and project the micrographs onto the orthogonal complement of this subspace. We construct a 2D statistical model of the vesicle structure, based on higher order singular value decomposition (HOSVD), by considering the structural symmetries of the vesicles in the polar coordinate plane. We then propose to lift the HOSVD model to a novel hierarchical model by summarizing the multidimensional HOSVD coefficients by their principal components. Along with the model, a solid vesicle normalization scheme and model selection criterion are proposed to make a compact and general model. The results show that the vesicle structures are accurately separated from the background by the HOSVD model that is also able to adapt to the asymmetries of the vesicles. This is a promising result and suggests even wider applicability of the proposed approach in learning and removal of statistical structures.

In vivo volume and hemoglobin dynamics of human red blood cells

Human red blood cells (RBCs) lose ∼30% of their volume and ∼20% of their hemoglobin (Hb) content during their ∼100-day lifespan in the bloodstream. These observations are well-documented, but the mechanisms for these volume and hemoglobin loss events are not clear. RBCs shed hemoglobin-containing vesicles during their life in the circulation, and this process is thought to dominate the changes in the RBC physical characteristics occurring during maturation. We combine theory with single-cell measurements to investigate the impact of vesiculation on the reduction in volume, Hb mass, and membrane. We show that vesicle shedding alone is sufficient to explain membrane losses but not volume or Hb losses. We use dry mass measurements of human RBCs to validate the models and to propose that additional unknown mechanisms control volume and Hb reduction and are responsible for ∼90% of the observed reduction. RBC population characteristics are used in the clinic to monitor and diagnose a wide range of conditions including malnutrition, inflammation, and cancer. Quantitative characterization of cellular maturation processes may help in the early detection of clinical conditions where maturation patterns are altered.

GNOM regulates root hydrotropism and phototropism independently of PIN-mediated auxin transport

Plant roots exhibit tropisms in response to gravity, unilateral light and moisture gradients. During gravitropism, an auxin gradient is established by PIN auxin transporters, leading to asymmetric growth. GNOM, a guanine nucleotide exchange factor of ARF GTPase (ARF-GEF), regulates PIN localization by regulating subcellular trafficking of PINs. Therefore, GNOM is important for gravitropism. We previously isolated mizu-kussei2 (miz2), which lacks hydrotropic responses; MIZ2 is allelic to GNOM. Since PIN proteins are not required for root hydrotropism in Arabidopsis, the role of GNOM in root hydrotropism should differ from that in gravitropism. To examine this possibility, we conducted genetic analysis of gnom(miz2) and gnom trans-heterozygotes. The mutant gnom(miz2), which lacks hydrotropic responses, was partially recovered by gnom(emb30-1), which lacks GEF activity, but not by gnom(B4049), which lacks heterotypic domain interactions. Furthermore, the phototropic response of gnom trans-heterozygotes differed from that of the pin2 mutant allele eir1-1. Moreover, defects in the polarities of PIN2 and auxin distribution in a severe gnom mutant were recovered by gnom(miz2). Therefore, an unknown GNOM-mediated vesicle trafficking system may mediate root hydrotropism and phototropism independently of PIN trafficking.

ATG7 deficiency promote apoptotic death induced by Cisplatin in human esophageal squamous cell carcinoma cells

Cisplatin-(DDP)-based adjuvant chemotherapy is widely used for the treatment of esophageal cancer. However, DDP-based combinatorial treatments can eventually result in tumor resistance response. Therefore, new therapeutic strategies and/or new adjuvant drugs still need to be explored. In this study, we aimed to understand the role of autophagy in ESCC cells resistance to Cisplatin and discuss its potential therapeutic implication. We found that exposure to Cisplatin induced a significant increase in LC3 formation. While the proliferation of ESCC cells was inhibited upon Cisplatin exposure, inhibition of autophagy by ATG7 interference further increased the sensitivity to chemotherapy. Meanwhile, the Cisplatin-induced apoptotic cell death was significantly enhanced. These results suggest that autophagy may function importantly in ESCC cells resistance to Cisplatin. Intriguingly, the resistance could be recovered by autophagy inhibition. This also points to potential therapy for ESCC by perturbing autophagy.

Ectothiorhodospira variabilis sp. nov., an alkaliphilic and halophilic purple sulfur bacterium from soda lakes

During studies of moderately halophilic strains of Ectothiorhodospira from steppe soda lakes, we found a novel group of bacteria related to Ectothiorhodospira haloalkaliphila with salt optima at 50-80 g NaCl l(-1). Phylogenetic analysis using 16S rRNA gene sequences of strains from soda lakes in Mongolia, Egypt and Siberia revealed separation of the group of new isolates from other Ectothiorhodospira species, including the closely related Ect. haloalkaliphila. DNA-DNA hybridization studies demonstrated that the new isolates form a homogeneous group at the species level, but at the same time are distinct from related species such as Ect. haloalkaliphila, Ect. vacuolata, Ect. shaposhnikovii and Ect. marina. The new isolates are considered to be strains of a novel species, for which the name Ectothiorhodospira variabilis sp. nov. is proposed, with the type strain WN22(T) (=VKM B-2479(T) =DSM 21381(T)). Photosynthetic pigments of the novel species are bacteriochlorophyll a and carotenoids of the spirilloxanthin series with spirilloxanthin and derivatives thereof, together with small amounts of lycopene and rhodopin. Gas vesicles are formed by most of the strains, particularly in media containing yeast extract (0.5 g l(-1)) and acetate (0.5-2.0 g l(-1)). Sequence analysis of nifH (nitrogenase) and cbbL (RuBisCO) confirmed the assignment of the strains to the genus Ectothiorhodospira and in particular the close relationship to Ect. haloalkaliphila. The novel species Ect. variabilis is found in soda lakes separated by great geographical distances and is an alkaliphilic and halophilic bacterium that tolerates salt concentrations up to 150-200 g NaCl l(-1).

Evaluation of zebrafish (Danio rerio) ovarian follicle viability by simultaneous staining with fluorescein diacetate and propidium iodide

Reliable fish oocyte quality assessment methods are essential in developing protocols for cryopreservation as well as their in vitro maturation and fertilisation. Current ovarian follicle viability assessment methods either lack sensitivity (e.g. Trypan Blue staining-TB) or are stage dependent (e.g. in vitro maturation and observation of germinal vesicle breakdown-GVBD). The aim of the present study was to develop a new viability assessment method for zebrafish ovarian follicles that is reliable, sensitive and not-stage specific. Fluorescein Diacetate (FDA) and Propidium Iodide (PI) were used for the first time to assess viability of zebrafish ovarian follicles. After preliminary studies to evaluate the efficacy of FDA and PI, a combination of these two fluorochromes was subsequently chosen and compared with TB staining and GVBD test in a series of cryoprotectant toxicity studies and following cryopreservation using stage III ovarian follicles. In all cases the FDA-PI test proved to be more sensitive than TB staining but less sensitive than the GVBD test. Ovarian follicle survivals after 4M Methanol treatment for 30 min at 22 degree C were 67.4 +/- 4.4%, 43.9 +/- 3.8% and 19.6 +/- 1.9% using TB, FDA-PI and GVBD test respectively. Survivals after cryopreservation procedure were 38.9 +/- 4.0% and 28.9 +/- 2.5% using TB and FDA-PI respectively when Hank's solution was used as medium and 45.2 +/- 4.3% and 35.2 +/- 3.5% when KCl buffer was used. The results showed the method to be promising, and it may offer a new approach for viability assessment of fish ovarian follicles.

Dynamics of nearly spherical vesicles in an external flow

Tank-treading, tumbling, and trembling are different types of the vesicle behavior in an external flow. We derive a dynamical equation enabling us to establish a state of nearly spherical vesicles. For a 2D external flow, the character of the vesicle dynamics is determined by two dimensionless parameters, depending on the vesicle excess area, fluid viscosities, membrane viscosity and bending modulus, strength of the flow, and ratio of the elongational and rotational components of the flow. The tank-treading to tumbling transition occurs via a saddle-node bifurcation, whereas the tank-treading to trembling transition occurs via a Hopf bifurcation. A slowdown of vesicle dynamics should be observed in a vicinity of a point separating the transition lines. We show that the slowdown can be described by a power law with two different critical exponents 1/4 and 1/2 corresponding to the slowdown of tumbling and trembling cycles.

Halochromatium roseum sp. nov., a non-motile phototrophic gammaproteobacterium with gas vesicles, and emended description of the genus Halochromatium

A rod-shaped, marine, phototrophic, purple sulfur bacterium containing gas vesicles was isolated from a marine solar saltern at Kakinada, India. Cells of strain JA134T are Gram-negative, non-motile rods, with vesicular intracytoplasmic membranes, and the strain has an absolute requirement for NaCl for growth. Bacteriochlorophyll a and the carotenoid okenone are present as photosynthetic pigments. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that strain JA134T clusters with members of the genus Halochromatium, but is distinctly separated from the species reported so far. The morphological and physiological differences of strain JA134T from other Halochromatium species support the description of strain JA134T (=ATCC BAA-1363T =DSM 18859T =JCM 14151T) as the type strain of a novel species, Halochromatium roseum sp. nov.

Are Circulating Endothelial-Derived and Platelet-Derived Microparticles a Pathogenic Factor in the Cisplatin-Induced Stroke?

Background and Purpose— To evaluate whether cisplatin-induced stroke is mediated by vascular toxicity with release of prothrombotic endothelial and platelet-derived microparticles (MPs).

Methods— Endothelial (CD31 + CD41 − ), platelets (CD31 + CD41 + ) and prothrombotic (Annexin V + ) circulating MPs were quantified by flow cytometry in 18 patients with cancer, before and 3 days after administration of cisplatin, and compared with 18 healthy controls. Thrombin-antithrombin complex and prothrombin fragments (F 1+2 ) were measured as markers of the activation of the coagulation.

Results— In patients with cancer, baseline levels of circulating prothrombotic, endothelial and platelet-derived MPs were similar to healthy controls and decreased significantly after administration of cisplatin. High-baseline MPs levels were observed in 5 patients who received cisplatin for a second or third cycle. A high-baseline activation of the coagulation was observed in all patients without further increase after cisplatin infusion.

Conclusion— Cisplatin treatment is immediately followed by a decrease in circulating levels of endothelial and platelet-derived MPs. However, a transient increase in MPs is observed at the second and third infusion, and this may contribute to the cisplatin-induced stroke.

Rhodovulum imhoffii sp. nov

A yellowish-brown bacterium was isolated from photoheterotrophic enrichment cultures obtained from water samples of an aquaculture pond at Bhimunipatnam, India. Enrichment and isolation in a medium containing 2 % NaCl (w/v) yielded strain JA125T, the cells of which were rod-shaped and non-motile. On the basis of the 16S rRNA gene sequence, strain JA125T belongs to the class Alphaproteobacteria and is closely related to the type strains of Rhodovulum iodosum (96 %), Rhodovulum adriaticum (95 %), Rhodovulum robiginosum (95 %), Rhodovulum sulfidophilum (94 %) and Rhodovulum marinum (94 %). The cells of strain JA125T contained vesicular internal membranes and bacteriochlorophyll a and carotenoids of the spheroidene series. Strain JA125T grew optimally at 28 °C and at pH 7.0–8.0. The best growth occurred photoheterotrophically with a number of organic compounds serving as carbon sources and electron donors. The strain grew photoautotrophically, but chemoautotrophic growth did not occur. Strain JA125T was able to utilize sulfide, sulfate, thiosulfate and thioglycolate as sulfur sources. Biotin was required as a growth factor. The DNA G+C content was 58 mol%. On the basis of 16S rRNA gene sequence analysis and the morphological and physiological data, strain JA125T is significantly different from other species of the genus Rhodovulum and represents a novel species, for which the name Rhodovulum imhoffii sp. nov. is proposed. The type strain is JA125T (=JCM 13589T=DSM 18064T).

Methods to evaluate biliary excretion of drugs in humans: an updated review

Determining the biliary clearance of drugs in humans is very challenging because bile is not readily accessible due to the anatomy of the hepatobiliary tract. The collection of bile usually is limited to postsurgical patients with underlying hepatobiliary disease. In healthy subjects, feces typically are used as a surrogate to quantify the amount of drug excreted via nonurinary pathways. Nevertheless, it is very important to characterize hepatobiliary elimination because this is a potential site of drug interactions that might result in significant alterations in systemic or hepatic exposure. In addition to the determination of in vivo biliary clearance values of drugs, the availability of in vitro models that can predict the extent of biliary excretion of drugs in humans may be a powerful tool in the preclinical stages of drug development. In this review, recent advances in the most commonly used in vivo methods to estimate biliary excretion of drugs in humans are outlined. Additionally, in vitro models that can be employed to investigate the molecular processes involved in biliary excretion are discussed to present an updated picture of the new tools and techniques that are available to study the complex processes involved in hepatic drug transport.

Gas vesicles isolated fromHalobacteriumcells by lysis in hypotonic solution are structurally weakened

Analysis of pressure-collapse curves of Halobacterium cells containing gas vesicles and of gas vesicles released from such cells by hypotonic lysis shows that the isolated gas vesicles are considerably weaker than those present within the cells: their mean critical collapse pressure was around 0.049-0.058 MPa, as compared to 0.082-0.095 MPa for intact cells. The hypotonic lysis procedure, which is widely used for the isolation of gas vesicles from members of the Halobacteriaceae, thus damages the mechanical properties of the vesicles. The phenomenon can possibly be attributed to the loss of one or more structural gas vesicle proteins such as GvpC, the protein that strengthens the vesicles built of GvpA subunits: Halobacterium GvpC is a highly acidic, typically "halophilic" protein, expected to denature in the absence of molar concentrations of salt.

Enhanced photodynamic destruction of a transplantable fibrosarcoma using photochemical internalisation of gelonin

Photochemical internalisation (PCI) is a technique for releasing biologically active macromolecules from endocytic vesicles by light activation of a photosensitiser localised in the same vesicles of targeted cells. This study investigated the PCI of the toxin gelonin as a way of enhancing the effect of photodynamic therapy (PDT) on a human malignant fibrous histiocytoma transplanted into nude mice using the photosensitiser disulphonated aluminium phthalocyanine (AlPcS_2a). Pharmacokinetic studies after intraperitoneal administration showed that the serum level of AlPcS_2a fitted a biexponential model (half-lives of 1.8 and 26.7 h). The tumour concentration was roughly constant up to 48 h, although fluorescence microscopy showed that the drug location was initially mainly vascular, but became intracellular by 48 h. To compare PDT with PCI, 48 h after intraperitoneal injection of 10 mg kg⁻¹ AlPcS_2a, and 6 h after direct intratumour injection of 50 μg gelonin (PCI) or a similar volume of phosphate-buffered saline (PDT controls), tumour-bearing animals were exposed to red light (150 J cm⁻²). Complete response was observed for more than 100 days in 50% of the PCI tumours but only 10% of the PDT tumours (P<0.01). In tumours examined histologically 4 days after light delivery, the depth of necrosis was 3–4 mm after PDT, but 7 mm after PCI. The deeper effect after PCI demonstrates that the light fluence needed to kill tumour is less than with PDT. We conclude that PCI with gelonin can markedly enhance the effect of PDT on this type of tumour and may have a role clinically as an adjunct to surgery to control localised disease.

Human colorectal cancer cells induce T-cell death through release of proapoptotic microvesicles: role in immune escape

BACKGROUND & AIMS

Normal and neoplastic cells release microvesicles, whose effects on the immune system still need to be elucidated. Because human colorectal cancer cells are hypothesized to escape immune recognition by expressing proapoptotic molecules, we investigated whether microvesicles bearing Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand and inducing apoptosis of activated T cells are secreted by colorectal cancer cells both in vitro and in affected patients.

METHODS

Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand expression were analyzed in colorectal cancer cells and purified microvesicles by flow cytometry, Western blotting, and immunoelectron microscopy. Microvesicle tumor origin was assessed through simultaneous detection of lysosomal (CD63) and adenocarcinoma (carcinoembryonic antigen) markers. Proapoptotic activity of microvesicles was evaluated by annexin V/propidium iodide staining and caspase activation in T cells, including CD8+ T lymphocytes from colorectal cancer patients.

RESULTS

Colorectal cancer cells showed a granular pattern of tumor necrosis factor-related apoptosis-inducing ligand and Fas ligand expression, suggesting a secretory behavior. These proapoptotic molecules were detected on isolated microvesicles, together with class I HLA, CD63, and carcinoembryonic antigen. Microvesicles induced Fas ligand-mediated and tumor necrosis factor-related apoptosis-inducing ligand-mediated apoptosis of activated CD8+ T cells generated from colorectal cancer patients. Microvesicles with comparable phenotypes and functions were found in plasma from patients with advanced disease, whereas vesicular structures expressing Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand were also detected in colorectal cancer specimens.

CONCLUSIONS

These data show that colorectal cancer induces T-cell apoptosis through the release of Fas ligand-bearing and tumor necrosis factor-related apoptosis-inducing ligand-bearing microvesicles both in vitro and in vivo. This mechanism of immune escape has potential implications as a prognostic factor and could be targeted for the development of new antitumor therapies in colorectal cancer patients.

Salivary gland epithelial cell exosomes: A source of autoantigenic ribonucleoproteins

OBJECTIVE

Exosomes are membrane vesicles of endosomal origin that are distinct from apoptotic bodies and are thought to represent an acellular mechanism for antigen transfer to classic antigen-presenting cells, as well as for direct antigen presentation with the capacity to induce immune response or tolerance. Nevertheless, it is not known whether exosomes are involved in the induction or regulation of immune responses against intracellular autoantigens that characterize autoimmune diseases. Exosomes have been shown to be secreted by several types of cells, whereas studies of non-neoplastic epithelial cells are lacking. This study was undertaken to investigate the capacity of non-neoplastic salivary gland epithelial cells (SGECs) to release exosomes, and to determine whether epithelial exosomes contain RNPs, which are major autoantigens in systemic rheumatic diseases.

METHODS

Exosomes were isolated by ultracentrifugation from culture supernatants of 26 non-neoplastic SGEC lines established from patients with various rheumatic disorders. They were analyzed by electron microscopy, immunoblotting, or immunoprecipitation.

RESULTS

All SGEC lines were found to release comparable and significant amounts of exosomes. Similar to other cell systems, exosome secretion was constitutive and was unrelated to activation or apoptotic processes. SGEC-derived exosomes were found to contain the autoantigenic Ro/SSA, La/SSB, and Sm RNPs, as well as epithelial-specific cytokeratins.

CONCLUSION

SGECs constitutively secrete exosomes that contain the major autoantigens Ro/SSA, La/SSB, and Sm. This mechanism may represent a pathway whereby intracellular autoantigens are presented to the immune system with an immunogenic or tolerogenic outcome.

In vitro and in vivo gene transfer with poly(amino acid) vesicles

Non-viral gene delivery systems utilise either amine lipids or polyamines and although non-viral gene delivery systems are said to have a superior safety profile to viruses, the polyamines such as poly(L-lysine) are toxic when used without derivatisation and usually require specific receptor mediated uptake and/or endosomolytic agents to be effective. However, the conversion of poly(L-lysine) and poly(L-ornithine) polyamino acids into amphiphilic vesicle forming polymers reduces the toxicity of the polyamino acids and enables the resulting polyamino acid vesicles to deliver genes both in vitro and in vivo in the absence of receptor specific ligands and endosomolytic agents. The incorporation of a distearoylphosphatidylethanolamine poly(ethylene glycol)-galactosamine conjugate (with the galactosamine unit at the distal end of the poly(ethylene glycol) moiety) into the polyamino acid formulations improved in vitro gene transfer in the case of the amphiphilic poly(L-ornithine) (POP) although no in vivo targeting was detected with the galactosamine formulations. We conclude that the conversion of poly(L-lysine) and poly(L-ornithine) into amphiphilic colloid forming molecules reduces their toxicity, thus allowing these systems to be used for gene transfer in vivo. It is possible that this approach may be extended to other polyamines.

Expression of heterologous antigens in commensal Neisseria spp.: preservation of conformational epitopes with vaccine potential

Commensal neisseriae share with Neisseria meningitidis (meningococcus) a tendency towards overproduction of the bacterial outer envelope, leading to the formation and release during growth of outer membrane vesicles (OMVs). OMVs from both meningococci and commensal neisseriae have shown promise as vaccines to protect against meningococcal disease. We report here the successful expression at high levels of heterologous proteins in commensal neisseriae and the display, in its native conformation, of one meningococcal outer membrane protein vaccine candidate, NspA, in OMVs prepared from such a recombinant Neisseria flavescens strain. These NspA-containing OMVs conferred protection against otherwise lethal intraperitoneal challenge of mice with N. meningitidis serogroup B, and sera raised against them mediated opsonophagocytosis of meningococcal strains expressing this antigen. This development promises to facilitate the design of novel vaccines containing membrane protein antigens that are otherwise difficult to present in native conformation that provide cross-protective efficacy in the prevention of meningococcal disease.

Pulling tethers from adhered vesicles

The competition between adhesion and tether formation in bound vesicles is investigated. A theoretical model is developed in which tethers are induced by the application of a pulling force to the top of a strongly adhered vesicle. A critical onset force is identified where the tether spontaneously appears as part of a first order shape transition. Further growth of the tether initiates a detachment process that culminates in a continuous unbinding of the vesicle at a finite detachment force. Both critical forces, as well as all shape parameters, are calculated as a function of the reduced volume and the strength of adhesive potential.

Dispersal of Golgi matrix proteins during mitotic Golgi disassembly

During mitosis, the mammalian Golgi disassembles into numerous vesicles and larger membrane structures referred to as clusters or remnants. Following mitosis, the vesicles and clusters reassemble to form an intact Golgi in each daughter cell. One model of Golgi biogenesis states that Golgi matrix proteins remain assembled in mitotic clusters and then serve as a template for Golgi reassembly. To test this idea, we performed a 3D-computational analysis of mitotic cells to determine the extent to which these proteins remain in mitotic clusters. As a control we used brefeldin A-induced Golgi disassembly which causes dispersal of Golgi enzymes, but leaves matrix proteins in remnant structures. Unlike brefeldin A-treated cells, in which matrix proteins were clearly sorted from non-matrix proteins, we observed extensive dispersal of matrix proteins in metaphase cells with no evidence of differential sorting of these proteins from other Golgi proteins. The extensive disassembly of matrix proteins argues against their participation in a stable template and supports a self-assembly mode of Golgi biogenesis.

ATP-dependent vesiculation in red cell membranes from different hereditary stomatocytosis variants

The hereditary stomatocytoses are a group of dominant haemolytic anaemias that show two main features: invaginated, 'stomatocytic' morphology; and a membrane leak to the univalent cations Na and K. A patient with the most severe variant of these conditions was reported to show a defect in an in vitro process of ATP-dependent endocytic vesiculation (ADEV), which is found in normal red cells. We have examined this endocytosis process in 11 leaky red cell pedigrees available to us in the UK. ADEV in broken membranes was absent only in the two most severely affected, 'overhydrated' pedigrees studied, both of which showed a deficiency in the membrane raft protein, stomatin. The process was present, although typically diminished by about 10-20% compared with normal red cells, in all others. The cross-linker dimethyl adipimate (DMA), which could correct the cation leak in some of these patients, also corrected the ADEV defect in the same patients. In those patients in whom DMA had no effect on the ion leak, ADEV was not absent. In normal cells, this process of vesiculation was inhibited by inhibitors of membrane 'raft' function, by an antistomatin antibody and by vanadate and N-ethyl maleimide, but not by inhibitors of a number of kinases. These data highlight the heterogeneity of these conditions. A mechanism is discussed by which a defect in raft-based endocytosis could lead to the exaggerated surface exposure of an ion channel, which could then function constitutively, i.e. 'leak'.

The effects of oxidative stress and altered intracellular calcium levels on vesicular transport of apoE-EGFP

Apolipoprotein E (apoE) plays a role in the distribution of lipid within many organs and cell types in the human body, including the central nervous system (CNS). The apoE4 isoform is also an established risk factor for late-onset Alzheimer's disease (AD), however its role in the aetiology of the disease remains largely unknown. Therefore, as AD is a late-onset disease, we sort to investigate how conditions hypothesised to model ageing affect apoE metabolism, such as the transport of apoE along the secretory pathway. Two of these models include oxidative stress and calcium deregulation. Using apoE-EGFP-expressing astrocytoma cell lines we established that vesicle number and velocity are up-regulated under oxidative stress conditions, and slowed under KCl induced calcium deregulation. Although these findings apply to cells in general under these two stress conditions, the up-regulation of apoE in particular may be a response to cell injury with implications for neurodegeneration such as that found with late-onset AD.

Bid, Bax, and lipids cooperate to form supramolecular openings in the outer mitochondrial membrane

Bcl-2 family proteins regulate the release of proteins like cytochrome c from mitochondria during apoptosis. We used cell-free systems and ultimately a vesicular reconstitution from defined molecules to show that outer membrane permeabilization by Bcl-2 family proteins requires neither the mitochondrial matrix, the inner membrane, nor other proteins. Bid, or its BH3-domain peptide, activated monomeric Bax to produce membrane openings that allowed the passage of very large (2 megadalton) dextran molecules, explaining the translocation of large mitochondrial proteins during apoptosis. This process required cardiolipin and was inhibited by antiapoptotic Bcl-x(L). We conclude that mitochondrial protein release in apoptosis can be mediated by supramolecular openings in the outer mitochondrial membrane, promoted by BH3/Bax/lipid interaction and directly inhibited by Bcl-x(L).

Molecular topography imaging by intermembrane fluorescence resonance energy transfer

Fluorescence resonance energy transfer (FRET) between lipid-linked donor and acceptor molecules in two apposing lipid bilayer membranes is used to resolve topographical features at an intermembrane junction. Efficient energy transfer occurs when the membranes are apposed closely, which creates an image, or footprint, that maps the contact zone and reveals nanometer-scale topographical structures. We experimentally characterize intermembrane FRET by using a supported membrane junction consisting of a glass-supported lipid membrane, onto which a second membrane is deposited by rupture of a giant vesicle. A series of membrane junctions containing different glycolipids (phosphatidylinositol and ganglioside G(M1)), protein (cholera toxin), and lipid-linked polyethylene glycol are studied. The carbohydrate and protein components influence the intermembrane separation. Differential FRET efficiency is clearly distinguishable for each case. Quantitative analysis of the FRET efficiency yields measurements of intermembrane-separation distances that agree precisely with structural data on G(M1) and cholera toxin. The lateral arrangement of molecular species on the membrane surface thus can be discerned by their influence on membrane spacing without the need for direct labeling of the molecule of interest. In the case of polyethylene glycol lipid-containing membrane junctions, imaging by intermembrane FRET reveals spontaneously forming patterns that are not visible in conventional fluorescence images.

[Formation of giant and ultramicroscopic forms of Nostoc muscorum CALU 304 during cocultivation with Rauwolfia tissues]

The study of heteromorphic Nostoc muscorum CALU 304 cells, whose formation was induced by 6- to 7-week cocultivation with the Rauwolfia callus tissues under unfavorable conditions, revealed the occurrence of giant cell forms (GCFs) with a volume which was 35-210 times greater than that of standard cyanobacterial cells. Some GCFs had an impaired structure of the murein layer of the cell wall, which resulted in the degree of impairment of the cell wall ranging from the mere loss of its rigidity to its profound degeneration with the retention of only small peptidoglycan fragments. An analysis of thin sections showed that all GCFs had enlarged nucleoids. The photosynthetic membranes of spheroplast-like GCFs formed vesicles with the contents analogous to that of nucleoids (DNA strands and ribosomes). About 60% of the vesicles had a size exceeding 300 nm. With the degradation of GCFs, the vesicles appeared in the intercellular slimy matrix. It is suggested that the vesicles are analogous to elementary bodies, which are the minimal and likely primary reproductive elements of L-forms. The data obtained in this study indicate that such L-forms may be produced in the populations of the cyanobionts of natural and model syncyanoses. Along with the other known cyanobacterial forms induced by macrosymbionts, L-forms may represent specific adaptive cell forms generated in response to the action of plant symbionts.

Fluorescence probe properties of intramolecular charge transfer diphenylbutadienes in micelles and vesicles

This paper reports absorption and fluorescence spectral studies of methyl 4-[(1E,3E)-4-phenylbuta-1,3-dienyl]benzoate (1), N,N-dimethyl-N-[4-[(1E,3E)-4-phenylbuta-1,3-dienyl]phenyl]amine (2), methyl 4-[(1E,3E)-4-[4-(dimethylamino)phenyl]buta-1,3-dienyl]benzoate (3) and 1-methyl-4-[(1E,3E)-4-[4-methoxyphenyl]buta-1,3-dienyl]benzoate (4) in homogeneous media of 1,4-dioxane and 1,4-dioxane-water binary mixtures, and in microheterogeneous media of cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and Triton-X-100 micelles, and dipalmotoyl phosphatidylcholine (DPPC) vesicles. The binding site of the diene probes in micelles and vesicles has been determined and it has been found that while in micelles dienes occupy the polar interfacial regions, in vesicles the probes are located deep inside the hydrophobic bilayer. The binding of dienes to the vesicles is stronger than their binding to the micelles as indicated by the binding constant values. The fluorescence emission of the probe dienes in micelles is from a conformationally relaxed intramolecular charge transfer excited state. However, in vesicles, since the excited state conformational motions are restricted due to the rigidity of the alkyl chain, the dienes fluoresce from their planar locally excited states.

Separation of membrane vesicles and cytosol from cultured cells and bacteria in a preformed discontinuous gradient

There are many situations when it is necessary to separate rapidly and efficiently a cytosolic and a membrane vesicle fraction from either cultured cells or from bacteria. Flotation of the vesicles through a low-density barrier from a dense sample zone using the low viscosity medium iodixanol allows complete separation of these compartments. As the sample is exposed to the gmax the tendency of the proteins to sediment overcomes any diffusion in the opposite direction.

Comparison of the functional properties of murine dendritic cells generated in vivo with Flt3 ligand, GM-CSF and Flt3 ligand plus GM-SCF

Flt3 ligand (FL) and granulocyte-macrophage colony-stimulating factor (GM-CSF) are important growth factors for dendritic cells (DC). Substantial numbers of DC can be generated in vivo following the administration of either factor. We sought to extend our knowledge of the functional properties of these cells including their ability to prime naïve CD8(+) T cells. In addition, we compared the nature of the DC generated in vivo with the single cytokines to those generated with the combination of FL+polyethylene glycol-modified GM-CSF (pGM-CSF). Treatment with FL+pGM-CSF yielded greater numbers of both CD11b(low) and CD11b(high) DC than with either cytokine alone, and these DC were more efficient at antigen (Ag) capture. The FL+pGM-CSF-generated CD11b(low) DC lacked expression of CD8alpha. Following treatment with LPS in vivo, all DC subsets upregulated CD40, CD80, CD86, and MHC class II expression, but surprisingly Ag capture was not downregulated and some DC subsets retained expression of intracellular MHC class II vesicles. Thus, even after activation in vivo with LPS, DC retained Ag capture properties of immature DC, and Ag presentation/costimulation properties of mature DC. Though all DC subsets stimulated CD4(+) T cell proliferation equivalently, FL-generated DC were more efficient at priming Ag-specific CD8(+) cytolytic T cells than DC generated with either pGM-CSF alone or FL+pGM-CSF, and CD11b(high) DC were more efficient at priming CD8(+) T cells than CD11b(low) DC.

Isolation of calcifiable vesicles from aortas of rabbits fed with high cholesterol diets

Advanced arterial wall calcification in atherosclerosis imposes a serious rupturing effect on the aorta. However, the mechanism of dystrophic calcification linked to hyperlipidemia, that causes atherosclerosis remains unknown. Emerging morphological and biochemical evidence reveals that calcifiable vesicles may have a role in plaque calcification. To determine whether a high cholesterol diet can induce arterial calcification and produce or activate calcifiable vesicles in aortas, a rabbit model was used. After 2 months of daily high lipid feeding (supplemented with 2% cholesterol and 6% peanut oil), typical atherosclerotic lesions developed. However, the mineral, if present in aortas, was insufficient to be detected by Fourier transform-infrared spectroscopy (FT-IR) or alizarin red staining, indicative of a non-calcifying stage of atherosclerosis. Small segments of thoracic aortas were digested in a crude collagenase solution to release calcifiable vesicles. Vesicles were also isolated from normal aortas as control to consider the possibility that membrane vesicles may be produced by crude collagenase digestion, which could cause the degradation of some cells. Calcifiable vesicles were precipitated at 300,000 x g after subcellular particles were removed by centrifugation at 30,000 x g. Calcifiability of isolated vesicles was then tested using calcifying media containing physiological levels of Ca2+ and Pi and 1 mM ATP. Electron microscopic observations showed that the isolated vesicles were heterogeneous in size and shape and capable of depositing electron dense particles. Fourier transform infrared spectroscopic analysis of the deposited particles revealed the presence of an amorphous mineral phase. The spectroscopic mineral to matrix ratios, related to the amount of mineralization, indicated that vesicles from cholesterol-fed rabbits produced more minerals than control vesicles obtained from the normal aortas. Alizarin red staining for mineral further demonstrated substantially higher calcifiability of the experimental vesicles. A 3-5 h exposure of the vesicles to calcifying media caused significant deposition of 45Ca and 32Pi in a vesicle protein-concentration dependent manner. Similar to previously reported observations with human atherosclerotic aorta vesicles, rabbit vesicles were enriched in ATP-hydrolyzing enzymes including Mg2+- or Ca2+-ATPase and NTP pyrophosphohydrolase that are implicated in normal and pathological calcification. Altogether, these observations suggest that accumulation of the released calcifiable vesicles, as a result of high cholesterol diets, may have a role in dystrophic calcification in hyperlipidemia-related atherosclerosis.