Augmentation of low-frequency ultrasound-induced clot disruption by hydroxyethyl starch is dependent on the duration and intensity of ultrasound exposure; an in vitro study

We investigated the synergistic effect between low-frequency ultrasound (US) and hydroxyethyl starch (HAES) on blood clot disruption, using different HAES concentrations, US duration and intensity. Human blood clots, 200 to 400 mg in weight, were placed in tubes containing 10 mL of normal saline alone or with HAES 0.1%, 1% or 2%. Clots were randomized to four intensities of US exposure: none, low, medium and high (maximal amplitude of motion at the tip of the horn: 0, 96, 144 and 192 micro m, respectively), and for three durations of US exposure (10, 20 and 40 s). After treatment, the clots were reweighed, and the percent differences in weights were calculated. US intensity, US duration and HAES concentration had a significant effect on the blood clot dissolution (p < 0.001 for all three variables). HAES augmented clot dissolution only when US intensity was medium or high. With low intensity, HAES did not augment clot lysis.

CONCLUSIONS

microparticle-containing solutions, such as HAES, have a potential for augmenting clot disruption by US. This effect is highly dependent on US intensity.

Electron microscope and biochemical observations of the surface active phospholipids on the articular surfaces and in the synovial fluid of the temporomandibular joint: a preliminary investigation

PURPOSE

The goal of this article is to investigate the surface-active phospholipids located on the articular surfaces and in the temporomandibular joint (TMJ) synovial fluid (SF) by means of electron microscopy and biochemical analysis.

MATERIALS AND METHODS

Synovial fluids and articular cartilage samples taken from 6 normally functioning TMJs were studied. The osmiophilic lining of human TMJ articular surfaces has been studied by using special nondestructive fixation procedures. To study the SF, negative staining technique has been used. In addition, thin-layer chromatography has been used to identify the phospholipids extracted from synovial fluid of human TMJs.

RESULTS

In the SF, granular bodies were identified with diameter of between 170 and 280 nm. Their diameter decreased dramatically when exposed to phospholipase-A(2). The amorphous and highly osmophilic material on the articular surface include membrane-bound vesicles (270 nm in diameter) with lamellated pattern surrounding the amorphous-dense core. Biochemical extraction revealed phosphatidylcholine as the major component of the polar lipids.

CONCLUSIONS

This preliminary study presents findings that suggest that phospholipids present in the TMJ may provide an efficient boundary lubrication that enables the disc to slide down the slope of the eminence on joint function.

Superior sagittal sinus thrombosis: a rare complication in a child with nephrotic syndrome

A 2-year-old boy with new-onset nephrotic syndrome developed recurrent vomiting, apathy and papilloedema. Superior sagittal sinus thrombosis was diagnosed on cranial CT and MRI. He gradually recovered after treatment with heparin, fresh frozen plasma and warfarin with complete resolution of the thrombosis after 1 month. Superior sagittal sinus thrombosis is an extremely rare complication of nephrotic syndrome in children. Early diagnosis is essential for institution of anticoagulation therapy and a successful outcome.

Assessment of intestinal permeability in rats by permeation of inulin-fluorescein

The measurement of intestinal permeability is widely used to assess different aspects of mucosal barrier disorders and related disease states, and has been proposed for evaluation of disease activity. To provide a simple method for assessment of intestinal permeability, we examined the permeation of inulin-fluorescein (InFl) in rat models of small intestinal injury and colitis. Small intestinal or colonic inflammation was induced by either i.p. administration of indomethacin or rectal administration of trinitrobenzene sulfonic acid (TNBS), respectively. For monitoring of intestinal permeability, InFl was administered orally or rectally to rats with small intestinal or colonic inflammation, respectively, and its level in blood was determined by the fluorescence intensity in the plasma. In small intestinal injury, InFl reached its peak in plasma 3 h after oral administration, while in colitis the InFl peak was reached 1 h after rectal administration. The highest permeability was observed at 72 h or 12 h after induction of small intestinal or colonic inflammation, respectively. In small intestinal injury the InFl permeation, as measured by its plasma level prior to sacrifice, was in agreement with intestinal damage evaluated after sacrifice. In colitis, the permeability at 12 h after induction of the disease correlated well with mortality. These findings demonstrate that InFl can be used as a novel, safe and easy-to-use probe for the evaluation of gut permeation and follow-up of gastrointestinal injury.

Infusion of recombinant human acid sphingomyelinase into niemann-pick disease mice leads to visceral, but not neurological, correction of the pathophysiology

An inherited deficiency of acid sphingomyelinase (ASM) activity results in the Type A and B forms of Niemann-Pick disease (NPD). Using the ASM-deficient mouse model (ASMKO) of NPD, we evaluated the efficacy of enzyme replacement therapy (ERT) for the treatment of this disorder. Recombinant human ASM (rhASM) was purified from the media of overexpressing Chinese Hamster ovary cells and i.v. injected into 16 five-month-old ASMKO mice at doses of 0.3, 1, 3, or 10 mg/kg every other day for 14 days (7 injections). On day 16, the animals were killed and the tissues were analyzed for their sphingomyelin (SPM) content. Notably, the SPM levels were markedly reduced in the hearts, livers, and spleens of these animals, and to a lesser degree in the lungs. Little or no substrate depletion was found in the kidneys or brains. Based on these results, three additional 5-month-old ASMKO animals were injected every other day with 5 mg/kg for 8 days (4 injections) and killed on day 10 for histological analysis. Consistent with the biochemical results, marked histological improvements were observed in the livers, spleens, and lungs, indicating a reversal of the disease pathology. A group of 10 ASMKO mice were then i.v. injected once a week with 1 mg/kg rhASM for 15 wk, starting at 3 wk of age. Although anti-rhASM antibodies were produced in these mice, the antibodies were not neutralizing and no adverse effects were observed from this treatment. Weight gain and rota-rod performance were slightly improved in the treated animals as compared with ASMKO control animals, but significant neurological deficits were still observed and their life span was not extended by ERT. In contrast with these CNS results, striking histological and biochemical improvements were found in the reticuloendothelial system organs (livers, spleens, and lungs). These studies indicate that ERT should be an effective therapeutic approach for Type B NPD, but is unlikely to prevent the severe neurodegeneration associated with Type A NPD.

Antimalarial activities of dermaseptin S4 derivatives

The hemolytic antimicrobial peptide dermaseptin S4 was recently shown to exert antimalarial activity. In this study, we attempted to understand the underlying mechanism(s) and identify derivatives with improved antimalarial activity. A number of dermaseptin S4 derivatives inhibited parasite growth with a 50% inhibitory concentration (IC(50)) in the micromolar range. Among these, the substituted S4 analog K(4)K(20)-S4 was the most potent (IC(50) = 0.2 microM), while its shorter version, K(4)-S4(1-13)a, retained a considerable potency (IC(50) = 6 microM). Both K(4)K(20)-S4 and K(4)-S4(1-13)a inhibited growth of the parasites more at the trophozoite stage than at the ring stage. Significant growth inhibition was observed after as little as 1 min of exposure to peptides and proceeded with nearly linear kinetics. The peptides selectively lysed infected red blood cells (RBC) while having a weaker effect on noninfected RBC. Thus, K(4)K(20)-S4 lysed trophozoites at concentrations similar to those that inhibited their proliferation, but trophozoites were >30-fold more susceptible than normal RBC to the lytic effect of K(4)K(20)-S4, the most hemolytic dermaseptin. The same trend was observed with K(4)-S4(1-13)a. The D isomers of K(4)K(20)-S4 or K(4)-S4(1-13)a were as active as the L counterparts, indicating that antimalarial activity of these peptides, like their membrane-lytic activity, is not mediated by specific interactions with a chiral center. Moreover, dissipation of transmembrane potential experiments with infected cells indicated that the peptides induce damage in the parasite's plasma membrane. Fluorescence confocal microscopy analysis of treated infected cells also indicated that the peptide is able to find its way through the complex series of membranes and interact directly with the intracellular parasite. Overall, the data showed that dermaseptins exert antimalarial activity by lysis of infected cells. Dermaseptin derivatives are also able to disrupt the parasite plasma membrane without harming that of the host RBC.

Structure-activity relationship study of antimicrobial dermaseptin S4 showing the consequences of peptide oligomerization on selective cytotoxicity

To understand how peptide organization in aqueous solution might affect the activity of antimicrobial peptides, the potency of various dermaseptin S4 analogs was assessed against human red blood cells (RBC), protozoa, and several Gram-negative bacteria. Dermaseptin S4 had weak antibacterial activity but potent hemolytic or antiprotozoan effects. K(4)K(20)-S4 was 2-3-fold more potent against protozoa and RBC, yet K(4)K(20)-S4 was more potent by 2 orders of magnitude against bacteria. K(4)-S4 had similar behavior as K(4)K(20)-S4, but K(20)-S4 and analogous negative charge substitutions were as active as dermaseptin S4 or had reduced activity. Binding experiments suggested that potency enhancement was not the result of increased affinity to target cells. In contrast, potency correlated well with aggregation properties. Fluorescence studies indicated that K(20)-S4 and all negative charge substitutions were as aggregated as dermaseptin S4, whereas K(4)-S4 and K(4)K(20)-S4 were clearly less aggregated. Overall, the data indicated that N-terminal domain interaction between dermaseptin S4 monomers is responsible for the peptide's oligomerization in solution and, hence, for its limited spectrum of action. Moreover, bell-shaped dose-response profiles obtained with bacteria but not with protozoa or RBC implied that aggregation can have dramatic consequences on antibacterial activity. Based on these results, we tested the feasibility of selectivity reversal in the activity of dermaseptin S4. Tampering with the composition of the hydrophobic domains by reducing hydrophobicity or by increasing the net positive charge affected dramatically the peptide's activity and resulted in various analogs that displayed potent antibacterial activity but reduced hemolytic activity. Among these, maximal antibacterial activity was displayed by a 15-mer version that was more potent by 2 orders of magnitude compared with native dermaseptin S4. These results emphasize the notion that peptide-based antibiotics represent a highly modular synthetic antimicrobial system and provide indications of how the peptide's physico-chemical properties affect potency and selectivity.

Interaction of hyaluronic acid-linked phosphatidylethanolamine (HyPE) with LDL and its effect on the susceptibility of LDL lipids to oxidation

The amphiphilic polysaccharide hyaluronic acid-linked phosphatidylethanolamine (HyPE), synthesized by covalently binding dipalmitoyl-phosphatidylethanolamine (DPPE) to short chain hyaluronic acid (mol. wt. approximately = 30 000), interacts with low-density lipoproteins (LDL), to form a 'sugar-decoration' of the LDL surface. This results in an increase in the apparent size of the LDL particles, as studied by photon correlation spectroscopy, and in broadening of the 1H NMR signals of the LDL's phospholipids. Experiments conducted with fluorescently-labeled HyPE indicate that the interaction of HyPE with LDL involves incorporation of the hydrocarbon chains of this amphiphilic polysaccharide into the outer monolayer of the LDL. This interaction also inhibits the copper-induced oxidation of the LDL polyunsaturated fatty acids, avoiding oxidation altogether when the concentration of HyPE is higher than a tenth of the concentration of the LDL's phospholipids. This can not be attributed to competitive binding of copper by HyPE. We propose that the protection of LDL lipids against copper-induced oxidation is due to formation of a sugar network around the LDL.

A fluorescence-based high-performance liquid chromatographic assay to determine acid ceramidase activity

Acid ceramidase (N-acylsphingosine amidohydrolase) is the lysosomal enzyme required to hydrolyze the N-acyl linkage between the fatty acid and sphingosine moieties in ceramide. A deficiency of acid ceramidase activity results in the lipid storage disorder, Farber disease. This study reports a new assay method to detect acid ceramidase activity in vitro using Bodipy or lissamine rhodamine-conjugated ceramide (C12 ceramide; dodecanoylsphingosine). Using mouse kidney extracts as the source of acid ceramidase activity, this new method was compared with an assay using radioactive C12 ceramide (N-[(14)C]-dodecanoylsphingosine) as a substrate. The Bodipy C12 ceramide substrate provided data very similar to those of the radioactive substrate, but under the experimental conditions tested, it was significantly more sensitive. Using Bodipy C12 ceramide, femtomole quantities of the product, Bodipy dodecanoic acid, could be detected, providing an accurate measure of acid ceramidase activity as low as 0.1 pmol/mg protein/h. Acid ceramidase activities in skin fibroblasts and EBV-transformed lymphoblasts from Farber disease patients were around 7.8 and 10% of those in normal cells, respectively, confirming the specificity of this new assay method. Based on these results, we suggest that this fluorescence-based, high-performance liquid chromatographic technique is a reliable, rapid, and highly sensitive method to determine acid ceramidase activity, and that it could be useful wherever the in vitro detection of acid ceramidase activity is of importance.

Characterization of human acid sphingomyelinase purified from the media of overexpressing Chinese hamster ovary cells

A rapid purification method was developed to isolate milligram quantities of human acid sphingomyelinase from the media of overexpressing Chinese hamster ovary cells. The purified, recombinant enzyme (rhASM) had physical and kinetic characteristics that were consistent with those reported for the non-recombinant enzyme, including an acidic pH optimum and sensitivity to sulfhydryl reducing reagents and the zinc specific chelator, 1, 10-phenanthroline. A novel assay using fluorescently conjugated sphingomyelin was developed to explore the substrate binding properties of rhASM. Substrate binding required a fatty acid chain length of at least six carbons and the presence of the phosphocholine headgroup on sphingomyelin. Substrate binding also required an acidic pH, and was inhibited by pretreatment of the enzyme with sulfhydral reducing reagents or 1,10-phenanthroline. rhASM was rapidly internalized by cultured skin fibroblasts from Niemann-Pick disease (NPD) patients, and approximately 50% of this uptake was dependent on the mannose 6-phosphate receptor system. Studies using FITC-labeled rhASM revealed that by 1 h the internalized enzyme was localized to acidic compartments and could degrade sphingomyelin, the first demonstration that a lysosomal sphingolipid hydrolase can be fluorescently labeled and retain its biological activity. Intravenous injection of rhASM into ASM knock-out mice showed that the t(1/2) in the plasma was less than 5 min, and that the majority of the injected enzyme was taken up by the liver, followed by the spleen. Thus, these studies lay the foundation for future structure/function investigations of ASM, further investigations into this enzyme's role in ceramide mediated signal transduction, and the evaluation of enzyme replacement therapy for NPD using the mouse model.

Intracellular degradation of fluorescent glycolipids by lysosomal enzymes and their activators

Fluorescent glycolipids were utilized for detection of the intracellular, activator-dependent, activities of beta-glucocerebrosidase and arylsulphatase A. Activities were measured in primary skin fibroblasts from normal individuals, from patients with Gaucher disease who had mutations within the beta-glucocerebrosidase gene, and from a prosaposin-deficient patient. Fluorescent microscopy demonstrated that glucosylceramide or sulphatide labelled with a fluorescent probe (lissamine-rhodamine) were endocytosed and reached the lysosomes. There, in the presence of active enzyme and the corresponding saposin, they were hydrolysed to fluorescent ceramide, which changed its intracellular localization. When these substrates were labelled with pH-sensitive lissamine-rhodamine, which loses its fluorescence at neutral or alkaline pH, the transport of the product, i.e. fluorescent ceramide, from the lysosomes resulted in disappearance of the cellular fluorescence. In cells of patients having mutations within the genes encoding the glucocerebrosidase or the prosaposin, there was a considerable reduction in the intracellular rate of substrate hydrolysis that could be followed by fluorescence microscopy or measured quantitatively in cell extracts.

The structural requirements for the design of antiepileptic-glycine derivatives

Glycine is a major inhibitory neurotransmitter and recent reports have shown that certain lipophilic derivatives of glycine demonstrate anticonvulsant activity in intact animals. In these studies, glycinamide derivatives were found to be more potent than their corresponding glycine analogues. Consequently, the objective of the current study was to investigate the pharmacokinetics and pharmacodynamics (anticonvulsant activity and neurotoxicity) of the following phenyl derivatives of glycinamide: N'-benzyl glycinamide, N-benzyloxycarbonyl glycinamide (Z-glycinamide), Z-glycine, N-Z,N'-benzyl glycinamide and N-phenylacetyl glycinamide. The antiepileptic activity and neurotoxicity was carried out in classical animal models for antiepileptic screening. The pharmacokinetics of the active compounds were studied in dogs, a common animal model for comparative crossover pharmacokinetic studies. Of the compounds investigated in this study, Z-glycinamide, N'-benzyl glycinamide and N-Z,N'-benzyl glycinamide were found to be active. Therefore, the disposition of Z-glycinamide and N-Z,N'-benzyl glycinamide in comparison to Z-glycine was studied in plasma, brain, liver and urine of rats. The disposition of Z-glycinamide and N-Z,N'-benzyl glycinamide into the brain was better than that of Z-glycine. Unlike glycine or glycinamide, Z-glycinamide and N-Z,N'-benzyl glycinamide showed antiepileptic activity in animal models due to their better pharmacodynamic and pharmacokinetic properties. The pharmacokinetics of Z-glycinamide was similar in dogs and rats. Substitution of the Z group with the analogous phenylacetyl moiety led to inactive compounds. In an analogous series of compounds, the loss of the anticonvulsant activity may be due to pharmacodynamic and pharmacokinetic reasons. This study provides certain clues concerning the structural requirements for the design of antiepileptic-active glycine derivatives.

Importance of splicing for prosaposin sorting

The prosaposin gene encodes a 70 kDa protein. This protein might either reach the lysosomes and get processed there to four peptides, which are activators of known lysosomal enzymes, or be secreted by cells as a 70 kDa protein, recently anticipated to have several biological activities. The human prosaposin gene has a 9 bp exon (exon 8) that is alternatively spliced, thus encoding three prosaposin forms: one with an extra three amino acid residues, one with an extra two residues and a third form with no extra residues. With the aim of testing whether there is an association between the alternative splicing and the differential sorting of prosaposins, we cloned two human prosaposin cDNA forms in a T7/EMC/vaccinia virus-derived vector and expressed them in human cells. The results indicated that the prosaposin containing the three extra residues accumulated faster and in greater amounts in the medium, whereas the prosaposin with no extra residues was mainly destined for lysosomes. Point mutations created by mutagenesis in vitro in the 9 bp stretch had a diverse effect on prosaposin secretion. When supplied to cells in the medium, both prosaposins were endocytosed and reached the lysosomes, where they were processed to active saposin B and saposin C. The activities of the saposins were monitored qualitatively and quantitatively. Quantitatively, lipids were extracted from the cells, separated on TLC and measured fluorimetrically. Qualitatively, cells were detected by fluorescence microscopy.

Fluorescence-based selection of gene-corrected hematopoietic stem and progenitor cells from acid sphingomyelinase-deficient mice: implications for Niemann-Pick disease gene therapy and the development of improved stem cell gene transfer procedures

The general utility of a novel, fluorescence-based procedure for assessing gene transfer and expression has been demonstrated using hematopoietic stem and progenitor cells. Lineage-depleted hematopoietic cells were isolated from the bone marrow or fetal livers of acid sphingomyelinase-deficient mice, and retrovirally transduced with amphotropic or ecotropic vectors encoding a normal acid sphingomyelinase (ASM) cDNA. Anti-c-Kit antibodies were then used to label stem- and progenitor-enriched cell populations, and the Bodipy fluorescence was analyzed in each group after incubation with a Bodipy-conjugated sphingomyelin. Only cells expressing the functional ASM (ie, transduced) could degrade the sphingomyelin, thereby reducing their Bodipy fluorescence as compared with nontransduced cells. The usefulness of this procedure for the in vitro assessment of gene transfer into hematopoietic stem cells was evaluated, as well as its ability to provide an enrichment of transduced stem cells in vivo. To show the value of this method for in vitro analysis, the effects of retroviral transduction using ecotropic versus amphotropic vectors, various growth factor combinations, and adult bone marrow versus fetal liver stem cells were assessed. The results of these studies confirmed the fact that ecotropic vectors were much more efficient at transducing murine stem cells than amphotropic vectors, and that among the three most commonly used growth factors (stem cell factor [SCF] and interleukins 3 and 6 [IL-3 and IL-6]), SCF had the most significant effect on the transduction of stem cells, whereas IL-6 had the most significant effect on progenitor cells. In addition, it was determined that fetal liver stem cells were only approximately twofold more "transducible" than stem cells from adult bone marrow. Transplantation of Bodipy-selected bone marrow cells into lethally irradiated mice showed that the number of spleen colony-forming units that were positive for the retroviral vector (as determined by polymerase chain reaction) was 76%, as compared with 32% in animals that were transplanted with cells that were nonselected. The methods described within this manuscript are particularly useful for evaluating hematopoietic stem cell gene transfer in vivo because the marker gene used in the procedure (ASM) encodes a naturally occurring mammalian enzyme that has no known adverse effects, and the fluorescent compound used for selection (Bodipy sphingomyelin) is removed from the cells before transplantation.

Pharmacokinetic analysis and anticonvulsant activity of glycine and glycinamide derivatives

The objective of this study was to investigate the pharmacokinetics and pharmacodynamics (anticonvulsant activity and neurotoxicity) of a series of amide derivatives of glycinamide in order to explore their structure pharmacokinetic-pharmacodynamic relationship and to discover a glycinamide derivative which might have the potential to become a new antiepileptic agent. The following compounds were investigated: glycylglycine, glycylglycinamide, gaboylglycinamide, N-acetylglycine, N-acetylglycinamide, N-acetylglycylglycinamide, N-acetyl, N'-benzylglycinamide, N-benzyloxycarbonylglycine or Z-glycine, Z-glycinamide, Z-glycylglycine and Z-glycylglycinamide. The anticonvulsant activity and neurotoxicity study was carried out in classical animal models for anticonvulsant screening. The pharmacokinetics of the active compounds was studied in dogs, which is a common animal model for a comparative crossover pharmacokinetic studies. Of the compounds investigated in this study, all the dipeptides of glycinamide and the glycine derivatives were found to be inactive. The only two active compounds were: N-acetyl,N'-benzylglycinamide (VII) and Z-glycinamide (IX). These compounds demonstrated similar pharmacokinetic profiles. Unlike glycine or glycinamide, compounds VII and IX, being lipophilic derivatives of glycinamide, showed anticonvulsant activity in animal models due to their better pharmacodynamic and pharmacokinetic properties. The pharmacodynamics and pharmacokinetics of compounds VII and IX were similar to that of the potential new antiepileptics; N-valproylglycinamide and phthaloylglycinamide. This study provides certain clues concerning the structural requirements for the design of anticonvulsant-active glycine derivatives.

Inhibition of type I and type II phospholipase A2 by phosphatidyl-ethanolamine linked to polymeric carriers

We have previously shown that cell surface proteoglycans protect the cell membrane from the action of extracellular phospholipase A2 (PLA2) enzymes [Dan, P., Nitzan, D. W., Dagan, A., Ginsburg, I., and Yedgar, S. (1996) FEBS Lett. 383, 75-78]. Cell-impermeable PLA2 inhibitors (ExPLIs) were prepared by linking phosphatidylethanolamine (PE) to polymeric carriers, specifically, carboxymethylcellulose, heparin, or hyaluronic acid. The structure of these inhibitors enables the incorporation of their PE moiety into the membrane while the polymer remains at the membrane surface. In the present study, we show that the ExPLIs are effective inhibitors of the hydrolysis of different phospholipids in biological (Escherichia coli) and model (phospholipid vesicle) membranes, by diverse types of PLA2 enzymes, specifically human recombinant synovial fluid and C. atrox (type II), as well as Naja mocambique and porcine pancreatic (type I) PLA2. It is proposed that the external polymers of the ExPLIs, which are anchored to the membrane by the PE, mimic the naturally occurring cell surface proteoglycans and similarly protect membranes from the action of exogenous PLA2.

Natural ceramide is unable to escape the lysosome, in contrast to a fluorescent analogue

Since the generation upon cell stimulation of the second messenger ceramide has been reported to occur in an endosomal/lysosomal compartment, we investigated whether ceramide formed in the lysosomes can escape this compartment. The metabolic fate of radiolabelled ceramide produced by intralysosomal hydrolysis of LDL-associated [ceramide-3H]sphingomyelin or [stearoyl-1-(14)C]sulfatide was examined in fibroblasts from control individuals and a patient with inborn lysosomal ceramidase deficiency (Farber disease). The behavior of this radioactive ceramide was compared to that of a fluorescent (lissamine-rhodaminyl) ceramide analogue deriving from sulfatide degradation. While in Farber cells the natural, radiolabelled ceramide remained completely undegraded and accumulated in the lysosomes, the fluorescent derivative was rapidly converted to sphingomyelin. These findings strongly suggest that, in contrast to fluorescent derivatives, endogenous long-chain ceramide is unable to exit from lysosomes, therefore making the lysosomal ceramide unlikely to be a biomodulatory molecule.

Photochemically-activated electrodes: application in design of reversible immunosensors and antibody patterned interfaces

Antigen monolayers assembled onto Au electrodes associated with a quartz crystal act as electrochemical or microgravimetric quartz-crystal-microbalance (QCM) sensing interfaces for the complementary antibody. Electrochemical analysis of the antibody (Ab) is based on the insulation of the antigen monolayer electrode by the associated Ab towards a redox probe in the electrolyte solution. Ferrocene-modified glucose oxidase (Fc-GOx) and glucose are employed as redox probes for the amperometric transduction of the Ab association to the electrode. Bioelectrocatalyzed oxidation of glucose provides an electrochemical route to amplify the antigen-Ab complex formation. Electrochemical analysis of the dinitrophenyl antibody, DNP-Ab, by a dinitrophenyl-lysine monolayer electrode is presented. QCM analysis of the Ab is based on the frequency changes of the quartz crystal resulting from the association of the Ab to the crystal assembly. This method is discussed with the analysis of the fluorescein antibody, Flc-Ab, using a fluorescein monolayer-modified quartz crystal. A novel method to tailor reversible immunosensor devices by the application of photoisomerizable antigen monolayers on electrodes is presented. The antigen is modified by photoactive units exhibiting reversible photoisomerizable properties. In one photoisomer state, the antigen exhibits affinity for the Ab and enables its electrochemical or QCM analysis. Photoisomerization to the complementary state perturbs the antigen structure and the monolayer lacks affinity for the Ab. This enables the washing-off of the Ab and the regeneration of the actively sensing interface by a second illumination process that restores the antigen monolayer-modified surface. This method is exemplified by the development of a reversible DNP-Ab sensing electrode. N-Mercaptobutyl dinitrospiropyran was assembled as a photoisomerizable monolayer on a Au electrode. The dinitrospiropyran monolayer, SP-state, exhibits affinity for the DNP-Ab and enables the amperometric detection of the Ab using Fc-GOx and glucose as redox probe. The complementary photoisomerized protonated dinitromerocyanine monolayer, MRH(+)-state, lacks affinity for the DNP-Ab. By photoisomerization of the DNP-Ab associated with the SP-monolayer electrode to the MRH(+)-monolayer state, the DNP-Ab is washed-off, and by a second illumination process, the MRH(+)-monolayer is re-isomerized to the SP-monolayer assembly, which is the active interface for further analysis of the DNP-Ab. Cyclic amperometric detection of the DNP-Ab by the photoisomerizable dinitrospiropyran monolayer is demonstrated. The association of the DNP-Ab to the SP-monolayer electrode and the dissociation of the Ab from the MRH(+)-monolayer electrode are confirmed by QCM experiments using a dinitrospiropyran monolayer-modified quartz crystal. The insulating features of an antigen-Ab complex on a conductive surface and the photochemically controlled association of an antibody to a photoisomerizable monolayer assembled onto the surface were used to develop means for micropatterning of surfaces by the antibody. A dinitrospiropyran antigen monolayer was assembled onto conductive ITO glass. A DNP-Ab solution was used as 'ink solution' to pattern the surface. The Ab-pattern was imaged by electrochemical copper deposition onto the Ab-lacking surface domains. The dinitrospiropyran monolayer assembled onto ITO or Pyrex glass surfaces was employed as an active interface for the photolithographic patterning of the surface with the DNP-Ab. (ABSTRACT TRUNCATED)

Bone marrow transplantation in acid sphingomyelinase-deficient mice: engraftment and cell migration into the brain as a function of radiation, age, and phenotype

Types A and B Niemann-Pick disease (NPD) result from the deficient activity of the lysosomal hydrolase, acid sphingomyelinase (ASM). A long-term goal of our research is to evaluate the effects of bone marrow transplantation (BMT) and hematopoietic stem cell gene therapy (HSCGT) on the NPD phenotype. As an initial step toward this goal, we have undertaken a study aimed at optimizing hematopoietic cell engraftment in acid sphingomyelinase "knock-out" (ASMKO) mice. Several parameters were analyzed, including the effects of radiation and donor cell number on survival and engraftment of newborn and adult animals, the number of donor cells detected in the brain posttransplantation, and the levels of ASM activity achieved in the brain. A total of 202 ASMKO and normal animals were transplanted and studied, and the overall conclusions were: (1) newborn ASMKO animals were more susceptible to radiation-induced mortality than normal animals, (2) at low radiation doses, increasing the donor cell number improved engraftment, while this was less evident at the higher radiation doses, (3) engraftment was easier to achieve in normal as compared with ASMKO animals, (4) among newborn transplants, the number of donor cells detected in the brain was directly correlated with engraftment in the blood, (5) more donor cells were detected in the brains of newborn ASMKO animals as opposed to newborn normal animals, and (6) no donor cells were found in the brains of animals transplanted as adults, including those that were highly engrafted in the blood. These results provide important information regarding the design of future BMT and HSCGT studies in ASMKO mice and other mouse models and demonstrate the potential of altering the NPD phenotype by these therapeutic strategies.

Membrane lipid order of human red blood cells is altered by physiological levels of hydrostatic pressure

The effect of hydrostatic pressure at levels applied in diving or hyperbaric treatment (thus considered "physiological") on the order of lipid domains in human red blood cell (RBC) membrane was studied. Membrane order was determined by measuring 1) the fluorescence anisotropy (FAn) of lipid probes, 2) the resonance energy transfer from tryptophan to lipid probes, and 3) spectral shifts in Laurdan fluorescence emission. It was found that the application of mild pressure (< 15 atm) 1) increased, selectively, the FAn of lipid probes that monitor the membrane lipid core, 2) increased the tryptophan FAn, 3) increased the resonance energy transfer from tryptophan to lipid probes residing in the lipid core, and 4) induced changes in the Laurdan fluorescence spectrum, which corresponded to reduced membrane hydration. It is proposed that the application of pressure of several atmospheres increases the phase order of membrane lipid domains, particularly in the proximity of proteins. Because the membrane lipid order ("fluidity") of RBCs plays an important role in their cellular and rheological functions, the pressure-induced alterations of the RBC membrane might be pertinent to microcirculatory disorders observed in humans subjected to elevated pressure.

Photosensitized inactivation of Plasmodium falciparum- and Babesia divergens-infected erythrocytes in whole blood by lipophilic pheophorbide derivatives

BACKGROUND AND OBJECTIVES

Blood transfusions can transmit parasitic infections, such as those caused by Plasmodium (malaria), Trypanosoma cruzi (Chagas' disease), and Babesia (babesiosis). A higher degree of blood transfusion safety would be reached if methods were available for inactivating such parasites.

MATERIALS AND METHODS

We evaluated the effectiveness of photosensitization using lipophilic pheophorbide and red light illumination to eradicate red blood cells infected with Plasmodium falciparum, and with Babesia divergens, in whole blood. Fluorescence microscopy and conventional fluorometry showed the specific accumulation of pheophorbide derivatives in the RBC infected with either parasite, compared with uninfected RBC. The effectiveness of different derivatives in eradicating infected RBC was first estimated in parasite cultures.

RESULTS

The best photosensitizer was the N-(4-butanol) pheophorbide derivative (Ph4-OH) at 0.2 microM concentration and 5-min illumination. In whole blood, the eradication of RBC infected with B. divergens and P. falciparum was obtained with 2 microM Ph4-OH and 10 and 20 min illumination, respectively. Under these conditions of photosensitization, low levels of RBC hemolysis were noted even after 2 weeks of storage at 4 degrees C and a subsequent 48-hour incubation at 37 degrees C. No reduction of negative charges on treated RBC was noted and no increase in methemoglobin content.

CONCLUSIONS

In plasma, Ph4-OH is mainly transported by high-density lipoproteins (HDL). This high affinity for HDL may explain the selective accumulation of lipophilic pheophorbide derivatives in the intracellular parasites. Photosensitization with pheophorbide derivatives may be a promising approach to inactivation of transfusion-transmissible parasites and viruses in blood bank units.

Intracellular degradation of sulforhodamine-GM1: use for a fluorescence-based characterization of GM2-gangliosidosis variants in fibroblasts and white blood cells

A novel fluorescent ganglioside, sulforhodamine-GM1 was administered into cells derived from carriers and patients with different subtypes of GM2 gangliosidosis, resulting from various mutations in the gene encoding the lysosomal enzyme hexosaminidase (Hex) A. The cells used were skin fibroblasts and white blood cells, i.e. lymphocytes, monocytes and macrophages. In the severe infantile form of the GM2 gangliosidosis, Tay-Sachs disease, the sulforhodamine-GM1 was hydrolyzed within the lysosomes to the corresponding sulforhodamine-GM2 which, because of lack of Hex A activity, was not further degraded. In comparison, in the cells derived from GM2 gangliosidoses carriers, as well as pseudodeficient and adult forms of GM2 gangliosidosis, the sulforhodamine-GM2 was further processed and sequentially degraded by the lysosomal glycosidases to sulforhodamine-ceramide. The latter was converted to sulforhodamine-sphingomyelin, which was secreted into the culture medium. The fluorescence of the sulforhodamine ceramide in cell extracts and/or sulforhodamine-sphingomyelin in the culture medium was quantified and related to parallel data obtained using cells of normal individuals. This permitted distinguishing between the various GM2 gangliosidoses subtypes and relating the intracellular hydrolysis of sulforhodamine-GM1 to the genotypes of the respective GM2 gangliosidoses variants.

H2O2 renders cells accessible to lysis by exogenous phospholipase A2: a novel mechanism for cell damage in inflammatory processes

Phospholipase A2 (PLA2) and H2O2, secreted from activated inflammatory cells, play a central role in the tissue damage occurring in inflammatory processes. However, while exogenous PLA2 alone does not cause cell lysis, it readily does so when acting with H2O2. We have found that H2O2 degrades cell surface proteoglycans, thus rendering the membrane PL accessible to hydrolysis by exogenous PLA2. This novel mechanism introduces a role for cell surface proteoglycans in protection of cells from damage by pro-inflammatory agents, and may assign a central role for the combined action of H2O2 and PLA2 in inflammatory and bacteriocidal processes.

Uptake by cells and photosensitizing effectiveness of novel pheophorbide derivatives in vitro

Pheophorbide a prepared from the algae Spirulina was derivatized at the C(7)-carboxylic group by linking amino alkyls of various lengths and terminal functional groups. The compounds were purified by thin-layer chromatography (TLC) and by high-pressure liquid chromatography (HPLC). Solubilization of compounds by serum lipoproteins, the kinetics of compound uptake into mammalian cells, and photosensitizing effectiveness when activated by 673 nm laser light have been studied. Optimal photosensitizer uptake into cells and the greatest photosensitizing activity were observed with compounds having side-chain lengths of 4-6 carbon atoms which terminated in -OH and -CH3 groups. The most effective compounds were 3 orders of magnitude more potent than Photofrin in the degree of photoinactivation of cultured EMT-6 tumor cells. HDL and LDL significantly promoted the efflux of these photosensitizing drugs from cells, suggesting that their long-term retention in normal tissues in vivo would be minimal and produce little phototoxicity.

Abatement of bleomycin-induced pulmonary injury by cell-impermeable inhibitor of phospholipase A2

The mechanism of bleomycin (Bleo)-induced pulmonary injury is not fully understood. Elevated levels of lung phospholipase A2 (PLA2) have been previously reported following intratracheal (IT) instillation of Bleo, but the role of this enzyme in the pathogenesis of lung injury is not clear. In this pilot study, we have evaluated the effect of a cell impermeable inhibitor of PLA2 (CME) on Bleo-induced pulmonary inflammation in hamsters. Pulmonary injury was induced by a single IT instillation of Bleo (1 unit/0.5 ml saline). Three groups of male Syrian hamsters were evaluated: 1) BLEO-CME animals received IT Bleo and daily intraperitoneal (IP) injections of CME (1 mumole/kg), starting 1 day before IT instillation; 2) BLEO-SAL animals--received IT Bleo and IP injections of saline and 3) SAL-SAL animals--treated with IT and IP administrations of saline. Animals were sacrificed 14 days after IT treatment and lung injury was evaluated histologically by a semiquantitative morphologic index and by a differential cell count of bronchoalveolar lavage fluid. CME treatment significantly ameliorated Bleo-induced lung injury compared to BLEO-SAL animals (P < 0.05). The percentage of neutrophiles in bronchoalveolar lavage fluid was reduced from 17.7 +/- 3.2% (mean +/- S.E.) in BLEO-SAL group to 7.3 +/- 1.7% in BLEO-CME group (P < 0.05), achieving levels comparable to SAL-SAL control animals. These results suggest that treatment with an extracellular PLA2 inhibitor-CME abates Bleo-induced pulmonary injury. This may indicate an active role of PLA2 in the pathogenesis of interstitial pulmonary fibrosis.

Fluorescence-based selection of retrovirally transduced cells in the absence of a marker gene: direct selection of transduced type B Niemann-Pick disease cells and evidence for bystander correction

Types A and B Niemann-Pick disease (NPD) are lysosomal storage disorders resulting from the deficient activity of acid sphingomyelinase (ASM). Type A NPD is characterized by the absence of residual ASM activity, massive accumulation of sphingomyelin and cholesterol within lysosomes, and a rapid, neurodegenerative course that leads to death by 3 years of age. In contrast, type B NPD patients have low, but detectable, levels of residual ASM activity and little or no neurologic disease. Thus, individuals with type B NPD may survive into late adolescence or adulthood and are considered excellent candidates for somatic cell gene therapy. To facilitate the development of gene therapy for this disorder, a novel procedure was devised to isolate metabolically corrected type B NPD cells in the absence of marker gene expression. Type B NPD cells were transduced with retroviral vectors expressing ASM, labeled with lissamine rhodamine sphingomyelin (LR-SPM), and subjected to preparative fluorescence-activated cell sorting (FACS). Two non-overlapping cell populations were isolated, corresponding to enzymatically corrected (i.e., low fluorescence) and noncorrected (i.e., high fluorescence) cells. Quantitative PCR analysis demonstrated that the enzymatically corrected cells were enriched for vector sequences. Moreover, the corrected cells could be regrown and continued to express high levels of ASM activity after numerous passages, consistent with the fact that they were stably transduced. Notably, coculture of FACS-sorted, overexpressing cells with untreated type B NPD fibroblasts resulted in a homogeneous cell population with low fluorescence whose FACS distribution overlapped that of the corrected cells. Computerized fluorescence microscopy confirmed that nearly all of these cocultured cells expressed ASM activity and could hydrolyze LR-SPM.(ABSTRACT TRUNCATED AT 250 WORDS)

Control of inflammatory processes by cell-impermeable inhibitors of phospholipase A2

Cell-impermeable inhibitors of phospholipase A2 were prepared by linking inhibiting molecules to macromolecular carriers which prevent the inhibitor's internalization. These preparations inhibit the release of oxygen reactive species from neutrophils and cell death induced by inflammatory agents, as well as bleomycin-induced lung injury.

Sulforhodamine GM1-ganglioside: synthesis and physicochemical properties

A fluorescent derivative of GM1-ganglioside was synthesized by linking sulforhodamine 101 to the sphingosine moiety through amino dodecanoyl residue. The product (SR-12GM1) was quantitatively converted to SR-12GM2 by treatment with bovine testes beta-galactosidase and in intact cultured human skin fibroblasts was catabolized to sulforhodamine GM2, GM3 and ceramide; the latter product was further converted to sphingomyelin. In aqueous medium SR-12GM1 formed micelles. When transfer from micelles to vesicles and between vesicles was compared with that of pyrene-GM1, the transfer of SR-12GM1 occurred at higher rates, following in both cases a biexponential curve.

Synthesis and use of novel fluorescent glycosphingolipids for estimating beta-glucosidase activity in vitro in the absence of detergents and subtyping Gaucher disease variants following administration into intact cells

Two novel fluorescent glycolipids, LRO-glucosylceramide (LRO-GC) and LRO-trihexosylceramide (LRO-THC) were synthesized and utilized for estimating activities of the lysosomal, acid beta-glucosidase in cell extracts and intact skin fibroblasts, derived from normal individuals and patients with Gaucher disease subtypes. The uniqueness of the glycolipids is the fact that a fluorescent probe (lissamine rhodamine) is linked in a sulfonylamide linkage to the sphingosyl residue of the sphingolipid. Thus, the product of enzymatic hydrolysis, lissamine rhodamine sulfonylamido sphingosine (LRO-ceramide) cannot be further hydrolyzed and remains a metabolic end product. A unique property of LRO-GC as a substrate for the lysosomal, acid beta-glucosidase in vitro was the observation that enzymatic hydrolysis occurs in the absence of detergents and that hydrolytic rates are, in fact, reduced in the presence of Triton X-100 and/or sodium taurocholate. Also, both glycolipids penetrated the membrane of intact fibroblasts in the absence of serum and were hydrolyzed in lysosomes of the intact cells. The rates of intracellular hydrolysis decreased with the severity of the Gaucher disease subtypes. Using LRO-THC as substrate, the intracellular ratio of LRO-ceramide to LRO-glucosylceramide was an indicator for the specific GD-subtype.

Use of pyrenemethyl laurate for fluorescence-based determination of lipase activity in intact living lymphoblastoid cells and for the diagnosis of acid lipase deficiency

Pyrenemethyl laurate (PMLes), a fluorogenic substrate for determining in vitro lipase activity [Nègre, Salvayre, Dagan and Gatt (1989) Biochim. Biophys. Acta 1006, 84-88], has been administered to cultured lymphoblastoid cells from normal subjects and from a patient affected with Wolman disease, which is characterized by a deficiency of lysosomal acid lipase. The intracellular degradation of PMLes was dependent on the mode of administration of the substrate into the cells, and occurred by two separate pathways involving lysosomal and extra-lysosomal hydrolases. PMLes incorporated into LDL was taken up by normal lymphoblastoid cells through the apolipoprotein-B/E-receptor-mediated pathway and degraded in the lysosomal compartment, as suggested by the degradation block in Wolman cells. In contrast, when PMLes dissolved in 2% dimethyl sulphoxide was added directly to the culture medium, its hydrolysis was similar in lymphoblastoid cells from controls and from patients affected with Wolman disease, neutral lipid storage disease or familial hypercholesterolaemia. This suggested that the administered PMLes was degraded by a non-lysosomal enzyme which is not deficient in Wolman cells. This enzyme also differs from the neutral lipase system which is deficient in lymphoblastoid cells from patients with neutral lipid storage disease. When pyrenemethanol was administered directly to the cell culture, it was only poorly acylated and was rapidly released into the culture medium. These results and the fluorescence properties of PMLes ('monomeric' emission in a hydrophobic environment and 'excimeric' emission in a hydrophilic environment) and pyrenemethanol ('monomeric' emission in a hydrophilic environment) allowed us to design a 'direct reading' procedure by monitoring (without any lipid extraction) the fluorescence of intact living cells and that of the culture medium during pulse-chase experiments. This method allowed the direct evaluation of the time course of in situ degradation of PMLes. In pulse-chase experiments with LDL-PMLes, the fluorescence of normal cells decreased relatively rapidly with time whereas the fluorescence of the culture medium increased concomitantly. With Wolman cells, the cellular fluorescence decreased only very slightly, whereas that of the culture medium remained at the basal level; this demonstrates the catabolic block in intact living cells from patients with Wolman disease. In vitro degradation of PMLes indicated the existence of two PMLes-degrading enzymes in lymphoblastoid cell homogenates: one is the acid lipase which is involved in PMLes degradation in the lysosomal compartment (and is deficient in Wolman cells), while the second is a cytoplasmic enzyme (not deficient in Wolman cells).

Apolipoprotein B exhibits phospholipase A1 and phospholipase A2 activities

Low density lipoproteins (LDL) as well as isolated apolipoprotein B (ApoB) have been shown to exhibit phospholipase A2 (PLA2) activity toward phospholipids containing an oxidized or short fatty acyl chain at position 2. Some of these studies employed the fluorescent analogue of phosphatidyl choline (PC), C6-NBD-PC, containing NBD-caproic acid (C6-NBD-FA) at position 2 as a substrate, representative of short fatty acyl chains. The release of NBD-caproic acid from position 2 is attributed to PLA2-catalysed hydrolysis. However, this fatty acid can be released also by other enzymatic pathways. In the present study we examined, and ruled out, other enzymatic pathways which may be responsible for the hydrolysis of fatty acids from position 2 of phospholipids. On the other hand, we found that LDL as well as isolated ApoB hydrolyse C6-NBD-FA from both carbon 1 and carbon 2 of these phospholipids, thus exhibiting independent and simultaneous activities of phospholipase A1 and phospholipase A2.

Toward gene therapy for Niemann-Pick disease (NPD): separation of retrovirally corrected and noncorrected NPD fibroblasts using a novel fluorescent sphingomyelin

The neurologic (type A) and nonneurologic (type B) forms of Niemann-Pick disease (NPD) both result from deficiencies of acid sphingomyelinase (ASM) activity leading to the accumulation of sphingomyelin and other related lipids within lysosomes. Recently, the full-length cDNA and genomic sequences encoding ASM have been isolated and the nature of the molecular lesions causing NPD has been investigated. Although these developments have facilitated diagnosis for this debilitating disease, no effective treatment is currently available. Toward this latter goal, our laboratories recently reported the effectiveness of retroviral-mediated gene transfer for the in vitro correction of the cellular pathology in NPD fibroblasts (Suchi et al., 1992). In addition, novel selection procedures were developed to separate retrovirally corrected and noncorrected NPD fibroblasts based on the receptor-mediated delivery of a fluorescently (pyrene)-labeled sphingomyelin (P12-SPM) to the lysosomes of cells using liposomes coated with apolipoprotein E. In this study, we have used a different, fluorescent derivative of sphingomyelin (lissamine-rhodamine dodecanoyl sphingomyelin; LR12-SPM) to extend and improve this selection system. LR12-SPM offers a number of advantages over P12-SPM, including the facts that apolipoprotein E is not required for its efficient uptake and targeting to lysosomes and that the product of LR12-SPM degradation by ASM is efficiently transported out of cells. Thus, when analyzed in a fluorescence-activated cell sorter (FACS), there was complete separation (i.e., no overlap) of retrovirally corrected and noncorrected NPD cells after the administration of LR12-SPM.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration of pyrene lipids by receptor-mediated endocytosis and their degradation in skin fibroblasts

Sphingomyelin and seven glycosphingolipids were labeled with the fluorescent probe pyrene and administered into cultured fibroblasts by receptor-mediated endocytosis. For this purpose pyrene sphingomyelin or mixtures of pyrene glycolipid and unlabeled sphingomyelin were dispersed as small, unilamellar liposomes. Apolipoprotein E was then added and the receptor for this ligand on the cell surface was utilized for uptake of the liposomes and their transport to the lysosomes, where the respective pyrene lipids were degraded. Following incubation with each of the respective pyrene lipids, only the administered compound and the pyrene ceramide were present; intermediate hydrolysis products were not detected. This indicated that, in skin fibroblasts, the lysosomal ceramidase was limiting and controlled the rate of total degradation of the pyrene sphingolipids.

Synthesis, spectral properties and enzymatic hydrolysis of fluorescent derivatives of cerebroside sulfate containing long-wavelength-emission probes

Fluorescent derivatives of cerebroside sulfate (sulfogalactosyl ceramide, sulfatide) containing long-wavelength-emission fluorophores were synthesized. For this purpose a procedure was developed for preparing a cerebroside 3-sulfate derivative with an amino group on the terminal carbon atom of its fatty acyl residue. The latter compound has been used to prepare cerebroside 3-sulfate, coupled to lissamine-rhodamine, fluoresceine, eosine and NBD. The spectroscopic properties of these compounds, in different solvent systems and when incorporated into micelles of a non-ionic detergent or liposomes of a phospholipid, are reported. Incubation of these respective sulfatides with a human leukocyte preparation, resulted in the formation of the corresponding fluorescent cerebrosides.

Pyrenemethyl laurate, a new fluorescent substrate for continuous kinetic determination of lipase activity

A fluorescent acyl derivative of pyrenemethanol, pyrenemethyl laurate, was synthesized and used for the determination of several lipases by a continuous kinetic assay. The influence of the physical parameters of the substrate (pyrenemethyl laurate) and its hydrolysis product (pyrenemethanol), on the fluorescence emission was studied. The hydrolysis of pyrenemethyl laurate could be monitored directly in a spectrofluorometer because of the very high monomeric emission of pyrenemethanol at about 375 nm, whereas an aqueous dispersion of pyrenemethyl laurate emitted at 475 nm ('excimeric'). Pyrenemethyl laurate was hydrolyzed by gastric lipase, cellular lipases of haemopoietic cells, and the bacterial lipase of Rhizopus arrhizus.

Pyrene-methyl lauryl ester, a new fluorescent substrate for lipases: use for diagnosis of acid lipase deficiency in Wolman's and cholesteryl ester storage diseases

Fluorescent pyrene-methyl lauryl ester (PMLes) was synthesized and used for the determination of cellular lipase activities in lymphoblasts and fibroblasts from normal subjects and from patients affected with Wolman's or cholesteryl ester storage diseases (both exhibiting a deficiency of the lysosomal acid lipase). The hydrolysis of PMLes by acid lipase could be followed directly in a spectrofluorometer; this was possible because of the very high fluorescence emission of pyrene-methanol at 378 nm (monomeric form) in aqueous medium, whereas the substrate has practically no monomeric emission at 378 nm but emits only at 475 nm (excimeric form) in the experimental conditions used: this property permitted us to use PMLes as a fluorogenic substrate. In an alternative procedure, the enzymatic reaction could be determined after partition of the reaction mixture in a biphasic system of heptane and aqueous ethanol; the residual undegraded substrate partitioned into the upper heptane phase and the fluorescence of the product (i.e. pyrene-methanol) was read in the lower aqueous-ethanolic phase, at 378 nm. PMLes was hydrolyzed in extracts of normal lymphoblasts and fibroblasts by at least two lipases, one acidic lipase (pH 4.0) and a second more neutral enzyme (pH 6.5). The acidic lipase activity was practically absent in lymphoblasts and fibroblasts from Wolman's or cholesteryl ester storage diseases. This demonstrates that the fluorescent PMLes is hydrolyzed by the lysosomal acid lipase and can be used as a very sensitive fluorogenic substrate which permits direct recording of product formation and is suitable for the enzymatic diagnosis of either of these diseases.

A facile method for direct determination of phospholipase A2 activity in intact cells

The fluorescent phospholipid analogue 1-acyl-2-(N-4-nitrobenzo-2-oxa-1,3- diazole)aminocaproylphosphatidylcholine (C6-NBD-PC), which incorporates into cell membranes, is employed as a substrate for phospholipase A2 (PLA2) in intact cells. The interaction of this substrate with the cells produces only one fluorescent product; the fatty acid C6-NBD-FA, which does not incorporate into other lipids, and is not further metabolized. The product, a hydrophilic fatty acid, is separated from the substrate by aqueous: organic solvent phase separation. Using this method, the fatty acid produced is fully recovered and its amount, as measured by its fluorescence intensity, is a direct measure of the cell membrane PLA2 activity.

Diagnosis of arylsulfatase A deficiency in intact cultured cells using a fluorescent derivative of cerebroside sulfate

A fluorescent derivative of cerebroside sulfate (12-(1-pyrene)dodecanoyl-sphingosylgalactosyl-0-3-sulfate (P12-sulfatide) has been synthesized as a potential substrate for the determination of cerebroside sulfatidase (or arylsulfatase A) activity. It was administered into cultured human skin fibroblasts and thereby utilized for the diagnosis of arylsulfatase A deficiency. Cultured skin fibroblasts from normal individuals and healthy persons suffering from a pseudoarylsulfatase A deficiency (PD) degraded the P12-sulfatide, while in cells derived from a metachromatic leukodystrophy (MLD) patient it remained essentially intact. This contrasts with in vitro determinations of enzymatic activity, where the MLD or PD-derived arylsulfatase A exhibit similar deficiency, in spite of a profoundly different clinical course. Administration of the fluorescent sulfatide into the intact cells permitted a sensitive and rapid diagnosis of MLD and its distinction from the PD-phenomenon. This might be of particular importance for cases in which a rapid diagnosis is required and for prenatal diagnosis of fetuses from families afflicted with both MLD and pseudo-deficiency mutant genes.

Synthesis of cell-impermeable inhibitor of phospholipase A2

Phospholipase A2 (PLA2) in the cell surface membrane is considered a regulator of cellular secretion. The distinction between the role of the cell surface and the intracellular PLA2 is not clear, since it has not been possible to differentiate unequivocally the activity of the enzymes in the various organelles. The use of an extracellular inhibitor of PLA2 can greatly contribute to the understanding of cell surface PLA2 function. In this paper, the preparation of a cell-impermeable inhibitor of PLA2 is presented. This substance incorporates into lipid membranes and is capable of blocking the hydrolysis of membrane phospholipids by snake venom as well as by cell membrane PLA2.

New spectrophotometric assays of acid lipase and their use in the diagnosis of Wolman and cholesteryl ester storage diseases

Trinitrophenylaminolauric acid (TNPAL) was linked to glycerol or cholesterol and the resulting yellow compounds were used as substrates for several lipases and cholesteryl esterase in cells from normal individuals and patients with Wolman's or cholesteryl ester storage diseases. Normal cells (lymphoid cell lines or skin fibroblasts) showed two peaks of lipase or cholesteryl esterase activity at about pH 4.0 and 6.0 each. The activity of the most acidic enzyme, which hydrolyzed natural or synthetic triacylglycerols as well as cholesteryl esters, was considerably reduced in cells derived from patients with Wolman's or cholesteryl ester storage diseases. Simple spectrophotometric procedures were developed for using tri-TNPAL glycerol or TNPAL cholesterol to identify homozygotes of these two respective diseases.

Prenatal diagnosis of Krabbe disease using a fluorescent derivative of galactosylceramide

A fluorescent substrate 12-(N-methyl-N(7-nitro-2-oxa-1,3-diazol-4-yl) aminododecanoyl sphingosyl beta-D-galactoside ('NBD galactocerebroside') was synthesized and used for the detection of galactocerebrosidase activity. The enzyme determinations using this substrate were found to be extremely sensitive yielding unambiguous results. This substrate was used for the prenatal diagnosis of a fetus affected with Krabbe disease; the diagnosis was later confirmed in the aborted fetus.

Preparation and characterization of well defined D-erythro sphingomyelins

A simple semisynthetic procedure for the preparation of various D-erythro sphingomyelins (SPMs), differing in their acyl chains, is described. They were prepared by one-step condensation of the desired free fatty acid with sphingosyl phosphorylcholine (SPC) using dicyclohexylcarbodiimide. The D-erythro SPMs were obtained in high purity, high yields and resemble bovine brain SPM in their chromatographic behavior, infrared, circular dichroism (CD) and proton NMR (PMR) spectra as well as in their rate of hydrolysis by Staphylococcus aureus sphingomyelinase. Multilamellar vesicles can be prepared from the semisynthetic SPMs. Their thermotropic behavior is dependent mainly on the acyl chain though it is also affected by the heterogeneity of the sphingosine base composition. Intact sealed small unilamellar vesicles (SUV) cannot be prepared from a single semisynthetic saturated SPM but can be prepared from their mixtures. This acylation procedure can also be applied for preparing simple neutral glycosphingolipids. The sphingolipids prepared by this method can be used to study metabolism, enzymology and physicochemical properties of D-erythro well defined simple sphingolipids.

Human lysosomal beta-glucosidase: purification by affinity chromatography

Two Sepharose-bound substrate analogs, 6'-aminohexanoyl-(2-N-sphingosyl-O-beta-D-glucoside) and 6'-aminohexyl-dodecanedioyl-1-(2-N-sphingosyl-1-O-beta-D-glu coside), were synthesized and used sequentially for the affinity purification of lysosomal beta-glucosidase (N-acyl-sphingosyl-1-O-beta-D-glucoside:glucohydrolase, EC 3.2.1.45). The capacities of these nondegradable affinity supports were 0.1 and 0.15 mg enzyme/ml settled gel, respectively. The purified enzyme had a specific activity of 75 mumol min-1 mg-1. The preparation had a single protein band with a molecular weight of 67,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, evidencing its apparent homogeneity. Isoelectric focusing on granular gels revealed four molecular forms of the enzyme with pI values of 4.0, 4.5, 4.7, and 5.8 to 6.2. The purified enzyme hydrolyzed glucosyl ceramide and 4-methylumbelliferyl-beta-D-glucoside with Km and Vmax values of 0.6 and 2.5 mM, and 101 and 26.1 mumol min-1 mg-1, respectively. The enzyme also hydrolyzed octyl beta-glucoside, a linear mixed-type inhibitor of the enzyme. Binding constants (Ki) were determined for the inhibitors, sphingosyl-1-O-beta-D-glucoside (Ki = 20 microM) and its N-hexyl derivative (Ki = 0.3 microM). The enzyme had a half-life of 65 and 30 min at 50 degrees C and pH 5.0 or 6.0, respectively. In addition, two other classes of ligands were used for the purification of lysosomal beta-glucosidase, and their capacities and specificities were compared to those of the substrate analog affinity supports. These included (i) the alkyl amine inhibitors octylamine, decylamine, and tetradecylamine; and (ii) the inhibitors, 6-aminohexanoyl-beta-glucosylamine and aminododecanoyl-1-(2-N-sphingosyl-1-O-beta-D-glucoside). Compared to these other ligand columns, the substrate analog affinity supports had about 100- to 1000-fold greater capacities or afforded 8- to 40-fold greater purification of human lysosomal beta-glucosidase.

Enhancement of adriamycin delivery to liver metastatic cells with increased tumoricidal effect using liposomes as drug carriers

We have investigated the tissue distribution of liposome-entrapped Adriamycin (ADM) in mice with metastatic spread to the liver and spleen after inoculation of J-6456 lymphoma cells. Sonicated phosphatidylserine:phosphatidylcholine:cholesterol liposomes were used as carriers of ADM, based on previous studies on the drug entrapment, stability, and tissue distribution of ADM-containing liposomes of various compositions (A. Gabizon, A. Dagan, D. Goren, Y. Barenholz, and Z. Fuks. Cancer Res., 42: 4734-4739, 1982). Increased hepatic and splenic levels of ADM were found in tumor-bearing mice when the drug was injected in the liposome-entrapped form. Concomitantly, decreased cardiac uptake of ADM was observed in tumor-bearing mice treated with liposome-entrapped ADM. In order to measure the concentration of ADM directly in metastatic cells, J-6456 lymphoma cells were isolated from the liver by Percoll density gradients. It was found that the ADM levels were significantly augmented in tumor cells from mice given injections of liposome-entrapped ADM as compared to those given injections of free ADM at all time intervals checked after drug injection. In addition, the in vitro and in vivo growth ability of these isolated metastatic cells was significantly more impaired when they were obtained from mice receiving liposome-entrapped ADM as compared to mice which received free ADM. The histopathological damage to the normal liver parenchyma of mice treated with liposome-entrapped ADM was mild and confined to discrete foci and was not significantly different from that observed in mice treated with free ADM. These results indicate that liposome delivery may provide an efficient means of improving the therapeutic efficiency of ADM in certain forms of metastatic liver disease, while diminishing the potential hazard of cardiotoxicity.

Transport of fluorescent derivatives of fatty acids into cultured human leukemic myeloid cells and their subsequent metabolic utilization

Transport of fluorescent derivatives of fatty acids across the cell membrane of cultured human leukemic myeloid cells (HL 60) and their subsequent metabolic utilization were studied. The rates of uptake of these derivatives and their incorporation into cellular lipids wer compared with that of radioactively labelled palmitic acid. Three groups of fluorescent derivatives were observed: A, those transported into the cells and subsequently incorporated into neutral lipids and phospholipids, B, fatty acids which were taken up by the cells but not utilized metabolically, and C, fatty acids which were not transported across the cell membrane. Fatty acids of the latter group, except the hydrophobic probe, also contained functional groups such as hydroxy, acetylamino or sulfonylamino. When observed in fluorescence microscopy, cells incubated with group A fatty acids contained intracellular fluorescent granules, whereas those incubated with group B fatty acids showed diffuse fluorescence. HL 60 cells undergo differentiation into granulocytes or macrophages upon treatment with dimethylsulfoxide or a phorbol ester, respectively. When compared to the uninduced cells, the transport of the fluorescent fatty acids or palmitic acid as well as their subsequent incorporation into lipids were considerably lower in the granulocytes and higher in the macrophages. The use of the fluorescent derivatives as a tool for studying transport of fatty acids across the cell membrane is discussed.

Antineoplastic activity of poly(L-lysine) with some ascites tumor cells

We have found that poly(L-lysine) can be a very effective agent in preventing the growth of Ehrlich ascites tumors in mice. When given optimal doses of poly(L-lysine) (Mr 60 x 10(3)) intraperitoneally for 5 consecutive days, beginning on day 1 after inoculation with Ehrlich ascites cells. White Swiss mice show nearly a 100% remission from subsequent tumor growth. Rechallenge of "cured" animals with tumor cells, however shows no long-term immunological protection. In tissue culture, poly(L-lysine) shows a related potent cytotoxicity with HeLa cells; interestingly, the D isomer. In addition, there is a strong molecular weight dependence in that the small polylysine (Mr 3 x 10(3)) possesses less than 1/20th the cytotoxicity of large polymers (Mr 70 x 10(3)) on a weight basis in both cell culture and animal studies. At the same time, none of these lysine polymers gives any significant increase in life span to BDF1 mice infected with L1210 murine leukemia cells. We have also further explored the mechanism by which the polylysines express their cytotoxicity. These data indicate that lysine polymers show cell specificity in their action and in some cases they may be beneficial as potent antineoplastic agents, particularly when molecular weight is taken into consideration.