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.