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.