Comparative efficacy of liposomes containing synthetic bacterial cell wall analogues for tumoricidal activation of monocytes and macrophages

We examined the activation to the tumoricidal state of normal mouse peritoneal exudate macrophages, bone marrow macrophages, and human blood monocytes by liposomes containing either lipophilic muramyl tripeptide (CGP 19,835) or a new synthetic analogue of lipoprotein from gram-negative bacteria outer wall, CGP 31,362, or combinations of the two. The superiority of liposomes containing the synthetic lipopeptide over liposomes containing lipophilic muramyl tripeptide for in vitro activation of monocytes and macrophages was demonstrated in several experiments. First, liposome-CGP-19,835 activated monocytes only in the presence of interferon-gamma, whereas activation with liposome-CGP 31,362 was interferon-independent. Second, activation of both mouse macrophages and human blood monocytes by liposome-CGP 31,362 occurred at a lower liposomal concentration than that by liposome-CGP 19,835. Third, monocytes incubated with liposome-CGP 31,362 released both tumor necrosis factor (TNF) and interleukin-1 activities, whereas monocytes treated with liposome-CGP 19,835 (in the absence of interferon-gamma) released only TNF activity. These data suggest that liposomes containing the synthetic lipopeptide CGP 31,362 are superior to liposomes containing CGP 19,835 for systemic activation of macrophages.

Phosphatidylcholine stimulates the activity of UDP-Gal beta 1-4 galactosyltransferase in normal human kidney proximal tumour cells

Effects of various lipid components of low density lipoproteins (LDL) and serine on the regulation of UDP-Gal-beta 1-4-galactosyltransferase (GalT-2) activity have been investigated in normal proximal tubular (PT) cells. Addition of exogenous serine (0.1-0.75 mM), cholesterol (0-200 micrograms/ml medium), linoleic acid and oleic acid (0.1-0.75 mM) for 4 hr at 37 degrees C did not suppress the activity of GalT-2 in PT cells. Similarly, incubation of cells with glucosylceramide and lactosylceramide (25-50 micrograms/ml medium) did not alter GalT-2 activity in cells as compared to control. In contrast, palmitic acid (0-0.75 mM), phosphatidylethanolamine and sphingomyelin (0-200 micrograms/ml) stimulated GalT-2 activity by 20-36% as compared to control. Incubation of PT cells with D-alpha-dipalmitoyl phosphatidylcholine (0-200 micrograms/ml medium) also stimulated the activity of GalT-2, maximum stimulation (200%) occurring with 25 micrograms phosphatidylcholine/ml medium. However, at a higher concentration (200 micrograms/ml), the stimulation of the activity of GalT-2 was in the order of 27% compared to control. Dioleylphosphatidylcholine did not alter GalT-2 activity in PT cells. Thus, it is concluded that (i) various lipid components, sphingosine and serine present in LDL are not involved in the LDL-mediated suppression of GalT-2 activity in normal PT cells, and (ii) stringent structural requirements in the phosphatidylcholine molecule are necessary to exert a time and concentration dependent stimulation of GalT-2 activity.

The lipophilic muramyl peptide MTP-PE is a potent inhibitor of HIV replication in macrophages

Cultured monocyte-derived macrophages were productively infected with human immunodeficiency virus in vitro. Treatment of these cells shortly after infection and several times thereafter with the free form of MTP-PE had an inhibitory effect on virus production. When the liposomal formulation of MTP-PE was used, higher levels of protection were achieved. The drug was not only effective when added to cells immediately after infection, but it also reduced virus production by cells with an established infection. When the liposomal formulation of MTP-PE was used only one treatment was required to achieve maximal effects. During these studies it was noted that the placebo liposomes had some effect in reducing the reverse transcriptase levels found in the supernatants of infected cells. This reduction could not be explained by direct cytotoxic effect. Both free and liposomal MTP-PE lipid significantly prevented formation of giant cells during the course of infection as well as reduced the cell associated viral antigen.

Plasmid DNAs directly injected into mouse brain with lipofectin can be incorporated and expressed by brain cells

In this study, we demonstrated that lipofectin-treated DNAs which were injected into mouse brain could be incorporated and expressed by brain cells. When L7RH-beta gal plasmid DNA harboring E. coli beta-galactosidase gene fused with the nuclear location signal of SV40 T-antigen gene was injected into brains of 1-week-old mice, cells whose nuclei appeared to be densely stained with the chromogenic substrate X-gal were detected in several portions of the brain till 9 days after injection. Injection of pMLV-CAT plasmid DNA which contains the E. coli chloramphenicol acetyltransferase (CAT) gene also resulted in cells immunoreactive to the anti-CAT antibody.

Hydrolysis of lipid mixtures by rat hepatic lipase

The hydrolysis of phospholipid mixtures by purified rat hepatic lipase, also known as hepatic triglyceride lipase, was studied in a Triton X-100/lipid mixed micellar system. Column chromatography of the mixed micelles showed elution of Triton X-100 and binary lipid mixtures of phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine as a single peak. This indicated that the mixed micelles were homogenous and contained all components in the designated molar ratios. The molar ratio of Triton X-100 to lipid was kept constant at 4 to 1. Labeling one lipid with 3H and the other lipid with 14C enabled us to determine the hydrolysis of both components of these binary lipid mixed micelles. We found that the hydrolysis of phosphatidylcholine was activated by the inclusion of small amounts of phosphatidic acid (2.5-fold), phosphatidylethanolamine (1.5-fold) or phosphatidylserine (1.4-fold). The maximal activation of phosphatidylcholine hydrolysis was observed when 5 mol% of phosphatidylethanolamine, 7.5 mol% phosphatidic acid or 5 mol% phosphatidylserine was added to Triton X-100 mixed micelles. The hydrolysis of phosphatidic acid was activated 30%, and that of phosphatidylserine was inhibited 30% when the molar proportion of phosphatidylcholine was less than 50 mol%. The hydrolysis of phosphatidylethanolamine was slightly activated when the mol% of phosphatidylcholine was below 5. The hydrolysis of phosphatidylserine was inhibited by phosphatidylethanolamine when the mol% of the latter was 50 or less whereas phosphatidylethanolamine hydrolysis was not affected by phosphatidylserine. Under the conditions used sphingomyelin and cholesterol did not have a significant effect on the hydrolysis of the phospholipids studied. In agreement with our previous study (Kucera et al. (1988) J. Biol. Chem. 263, 1920-1928) these studies show that the phospholipid polar head group is an important factor which influences the action of hepatic lipase and that the interfacial properties of the substrate play a role in the expression of the activity of this enzyme. The molar ratios of phosphatidic acid, phosphatidylethanolamine and phosphatidylserine which activated phosphatidylcholine hydrolysis correspond closely to the molar ratios of these lipids found in the surface lipid film of lipoproteins e.g., high density lipoproteins.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of adriamycin and duramycin on calcium translocation in liposome systems modeled on the inner mitochondrial membrane

Adriamycin (doxorubicin, AdM) is a potent antineoplastic agent which binds specifically and with high affinity to the acidic phospholipid cardiolipin (CL) [Goormaghtigh et al. (1980) Biochim. Biophys. Acta 597, 1]. Duramycin (DM), a polypeptide antibiotic, has been reported to interact selectively with phosphatidylethanolamine (PE) and monogalactosyldiacylglycerol [Navarro et al. (1985) Biochemistry 24, 4645]. The selectivity of DM-PE interaction was confirmed. AdM and DM were then used to explore the roles of CL and PE in Ca2+ translocation in a phosphatidylcholine (PC)/PE/CL liposome system modeled on the inner mitochondrial membrane with the following results: (i) AdM (100-400 microM) altered Ca2+ uptake by PC/PE/CL (4/4/1, mol/mol) liposomes in a concentration-dependent fashion which varied with temperature, external Ca2+ concentration, and liposome PE content. (ii) Addition of AdM was qualitatively equivalent to increasing temperature, Ca2+ concentration, or liposome PE content, and cooperative interactions among these parameters were observed. An increase in any one factor generally enhanced Ca2+ uptake; simultaneous increases in several factors inhibited uptake. (iii) Inhibition of Ca2+ uptake was correlated with efflux of Arsenazo III. (iv) Ca2+ uptake by PC/PE/CL liposomes is biphasic [Kester and Sokolove (1989) Biochim. Biophys. Acta 980, 127]. DM suppressed the PE-dependent slow phase and stimulated the PE-independent initial phase. Ca2+ uptake by PC/PE/CL liposomes in the presence of DM resembled uptake by PC/CL liposomes. These data confirm the ability of PE to enhance the slow, highly temperature-dependent component of CL-mediated Ca2+ translocation and suggest that this process is sensitive to lipid phase behavior.

Phosphatidylethanolamine methyltransferase and phospholipid methyltransferase activities from Saccharomyces cerevisiae. Enzymological and kinetic properties

In the yeast Saccharomyces cerevisiae, two membrane-associated enzymes catalyze the three-step methylation of phosphatidylethanolamine (PE) to phosphatidylcholine (PC). Phosphatidylethanolamine methyltransferase (PEMT) catalyzes the first methylation reactions (PE----phosphatidylmonomethylethanolamine (PMME] and phospholipid methyltransferase (PLMT) catalyzes the second two methylation reactions (PMME----phosphatidyldimethylethanolamine (PDME)----PC). Using gene disruption mutants of the S. cerevisiae OP13 and CHO2 genes, we independently studied the enzymological properties of microsome-associated PEMT and PLMT, respectively. The enzymological properties of the enzymes differed with respect to their pH optima, cofactor requirements and thermal lability. For the PEMT reactions, the apparent Km values for PE and S-Adenosylmethionine (AdoMet) were 57 microM and 110 microM, respectively. For the PLMT reactions, the apparent Km values for PMME and PDME were 380 microM and 180 microM, respectively. The apparent Km values for AdoMet were 54 microM and 59 microM with PMME and PDME as substrates, respectively. S-Adenosylhomocysteine (AdoHcy) was a competitive inhibitor of PEMT (Ki = 12 microM) and PLMT (Ki = 57 microM and Ki = 54 microM for PMME and PDME, respectively) with respect to AdoMet. AdoHcy was a noncompetitive inhibitor of PEMT (Ki = 160 microM) and PLMT (Ki = 120 microM) with respect to PE and PMME and PDME, respectively.

Inhibition of actin regulatory activity of the 74-kDa protein from bovine adrenal medulla (adseverin) by some phospholipids

A 74-kDa protein (adseverin) derived from adrenal medulla severs actin filaments and nucleates actin polymerization in a Ca2(+)-dependent manner but does not form an EGTA-resistant complex with actin monomers, which is different from the gelsolin-actin interaction. The dissociation of gelsolin-actin complexes by phosphatidylinositol 4,5-bisphosphate (PIP2) and the inhibitory effect on actin filament severing by gelsolin was recently reported. This study shows that the activity of adseverin is inhibited not only by PIP2 but also by some common phospholipids including phosphatidylinositol (PI) and phosphatidylserine (PS). Other phospholipids such as phosphatidylcholine (PC) and phosphatidylethanolamine (PE) showed no effect. The addition of PC or PE to PI diminished the inhibitory effect of PI. Triton X-100 and neomycin were also found effective in suppressing the effect of PI, suggesting that the arrangement of polar head groups is important in exerting the inhibitory effect. Ca2(+)-dependent binding of adseverin to PS liposomes but not to PC or PE liposomes was observed by a centrifugation assay.

Further characterization of the diacylglycerol-phosphatidylethanolamine exchange reaction catalyzed by cell-free extracts of Escherichia coli

The conditions for phosphatidylethanolamine (PE)-diacylglycerol (DAG) exchange catalysed by cell-free extracts of Escherichia coli were studied using 14C- or 3H-analogues of both these lipids. The reaction, examined with either labelled PE or labelled DAG, occurred without co-factor addition and was inhibited by Ca2+ and Mg2+. Detergents such as Triton X-100 greatly enhanced the activity; however, the optimal concentration of this agent depended on the lipid substrate concentration. The exchange-catalysing enzyme involved in these extracts appeared to be very specific for DAG and PE, since no other labelled phospholipid or acylglycerol derivative formed radioactive product under the assay conditions tested. Again, endogenous [3H]PE present in the enzyme source, but no other endogenous lipid, was converted to labelled DAG in the presence of added 1,2-dioleoyl-sn-glycerol. The Vmax value for the conversion of labelled PE to DAG was very similar to the Vmax value found for the conversion of labelled DAG to PE as would be expected in the case of an exchange reaction being responsible for both conversions. However, the Km value for PE was appreciably larger than that for DAG. The enzyme involved, displayed a broad acyl chain specificity as could be judged from: (1) the ability of various species of DAG and PE to stimulate the exchange; (2) the suitability of lipid substrates prepared from widely different biological sources; and (3) the interchange of acyl groups that occurred between dimyristoyl PE and dilauroylglycerol. As would be expected for an exchange reaction, the incorporation of lauroyl groups into PE occurred without an increase in the total fatty acid content of this phospholipid. The results of the present study confirm and further characterize the PE-DAG exchange reaction of E. coli.

Introduction of large linear minichromosomes into Schizosaccharomyces pombe by an improved transformation procedure

The efficiency of transformation of Schizosaccharomyces pombe has been increased 10- to 50-fold over previously reported methods. By using 1 microgram of plasmid, 7.0 x 10(5) transformants are regularly obtained. This increased transformation efficiency is mainly due to the inclusion of the cationic liposome-forming reagent Lipofectin in the protocol. Various parameters affecting transformation of Sc. pombe in the presence of Lipofectin have been examined. Lipofectin can also be used to increase transformation efficiency in Saccharomyces cerevisiae. It is also demonstrated that by using this improved transformation procedure, linear minichromosomes of greater than 500 kilobases can be introduced into Sc. pombe with relative ease. These minichromosomes can replicate as stable linear molecules upon reintroduction into Sc. pombe, demonstrating that Sc. pombe telomeres retain function when reintroduced as naked DNA. The ability of Sc. pombe to admit large DNA molecules indicates that it should be feasible to clone large DNA from other organisms in Sc. pombe.

Effect of phosphatidylethanolamine on the properties of phospholipid-apolipoprotein complexes

Plasma high density lipoproteins (HDL) are synthesized in intestinal mucosal cells and hepatocytes and are secreted into the blood. Factors influencing the structure and function of these HDL, such as lipid and protein composition, are poorly understood. It appears, however, that intracellular, discoidal HDL are enriched, relative to plasma HDL, in phosphatidylethanolamine (PE), a phospholipid known to generate unusual, nonbilayer structures of putative physiological significance. Although incubation of dimyristoylphosphatidylcholine (DMPC) with apolipoprotein A-I at the gel-liquid crystalline phase transition temperature results in the spontaneous formation of lipid-protein complexes, the presence of proportionately small amounts of PE prevents the formation of such complexes, suggesting that PE profoundly alters the phase properties of the phospholipid bilayers. However, by using a detergent-mediated method for the formation of PE-rich model nascent HDL from phospholipids and apolipoprotein A-I, lipid-protein complexes containing as much as 75% DLPE could be formed, thus demonstrating that the presence of PE causes a kinetic, rather than a thermodynamic, barrier to spontaneous complex formation. The products contained a DLPE:DMPC molar ratio similar to that of the initial incubation mixture; however, as the mole percentage of DLPE increased, the products became less heterogeneous, the buoyant density of the products increased, and the Stokes diameter of the products decreased. Similar results were obtained when dimyristoylphosphatidylethanolamine (DMPE) and dipalmitoylphosphatidylethanolamine (DPPE) were employed in lieu of DLPE. Electron microscopy of complexes containing DLPE and DMPC at a 1:1 molar ratio showed that these particles possessed a discoidal, bilayer morphology similar to that seen with complexes containing only phosphatidylcholine.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of phospholipids on purified lipoamidase

Phospholipids were added to purified lipoamidase from porcine brain microsomal membranes, and changes in lipoamidase activity were examined. Approximately twofold activation of lipoamidase activity occurred upon the addition of phosphatidylethanolamine. On the other hand, phosphatidylserine, cardiolipin, and phosphatidic acid reduced the enzyme activity by approximately 80%. This pattern of the activation of lipoamidase by phosphatidylethanolamine and its inhibition by phosphatidylserine is similar to the pattern for adenylate cyclase, and contrasts with the pattern for ATPase.

Lipopolyamine-mediated transfection allows gene expression studies in primary neuronal cells

A simple and efficient transfection technique based on lipopolyamine-coated DNA that can be used for gene transfer in cerebellar granular neurons is described. Gene transfer is achieved by exposure of cells to a DNA/lipid complex obtained by simple mixing of lipopolyamine and plasmid DNA. This procedure may represent a general tool of physiological investigations in primary cells. We show that the promoters of the introduced chimera genes are regulated by their respective trans-acting factors and may be modulated via membrane receptors and second messengers. This procedure has no noticeable toxic effects, nor does it seem to interfere with complex physiological behavior like neuronal differentiation.

Separation of brain dolichol kinase from endogenous activating factors: evidence that phospholipid enhances the interaction between enzyme and dolichol

Porcine brain dolichol kinase activity is effectively solubilized by extracting salt-washed microsomes with 1% 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS). When the detergent-solubilized activity is chromatographed on Sepharose CL-6B, a low amount of dolichol kinase activity is recovered in the void volume, and a dolichol kinase activator (DKA) is eluted (Ve/Vo = 1.9-2.2) with the bulk of the membrane phospholipids. Although only approximately 20% of the activity applied to the Sepharose CL-6B column is detected in the column fractions, virtually all of the original activity is restored when the Vo fraction is recombined with DKA. Endogenous DKA, isolated from brain microsomes, is heat-stable, is extractable with CHCl3/CH3OH (2:1), and has the chemical and chromatographic properties of phosphatidylethanolamine (PE) and phosphatidylcholine (PC). Moreover, approximately 50% of the stimulatory activity is lost when the PC present in the DKA fraction is degraded by purified phospholipase C from Clostridium perfringens. Also consistent with a phospholipid co-factor requirement, the dolichol kinase activity recovered in the partially phospholipid-depleted fraction (Vo) is markedly stimulated by various molecular species of exogenous purified PC or PE, but not by phosphatidylinositol, phosphatidic acid, phosphatidylserine, phosphatidylglycerol, or sphingomyelin. A comparison of defined molecular species shows that PCs containing oleoyl or linoleoyl groups in the 1 and 2 positions are the most stimulatory, suggesting that the fatty acyl moieties are involved in the enzyme-phospholipid interaction. Kinetic analyses indicate that PC enhances the interaction between dolichol kinase and dolichol, the lipophilic substrate, but does not alter the apparent Km for CTP.(ABSTRACT TRUNCATED AT 250 WORDS)

The significance of high molecular weight kininogen for contact activation of rat blood coagulation, in vitro

The involvement of the high molecular weight rat kininogen in the activation of the rat contact system by kaolin-cephalin, kaolin, sulfatides and ellagic acid has been investigated, using a rat plasma congenitally devoid of this kininogen. Coagulation times induced by these activators were shorter in normal as well as in deficient rat plasma than in normal human plasma. Coagulation times were prolonged in deficient rat plasma, when the incubation times was three min or less. By kaolin or cephalin-kaolin, this prolongation disappeared when the incubation time reached ten min. The activation of plasma prekallikrein developed slowly in deficient plasma with all the triggers but reached control level after ten min of incubation. By kaolin-cephalin, the activation of Hageman factor was weak and slow in deficient plasma during the ten min of incubation. In rat, high molecular weight kininogen plays thus a role in the activation of the contact system by these triggers. But this role seems to be less important than in human plasma.

Phosphatidylcholine and phosphatidylethanolamine enhance the activity of the mammalian mitochondrial endonuclease in vitro

The purified endonuclease of bovine heart mitochondria extensively degrades a variety of DNA templates in vitro but shows a remarkably strong preference to nick within one specific evolutionarily conserved sequence block of 12 consecutive guanine residues which resides just upstream from the heavy strand origin of mitochondrial DNA replication (Low, R. L., Cummings, O. W., and King, T. C. (1987) J. Biol. Chem. 262, 16164-16170). If the enzyme serves to provide an important nicking function at this site in vivo, then mitochondrial factors likely exist which further enhance the enzyme's recognition of this locus and prevent cleavage at other less favored sites. In this study, we report that specific membrane phospholipids appear to exert such effects in vitro. In standard endonuclease assays, low levels of phosphatidylcholine or phosphatidylethanolamine (0.5 mM) stimulate the purified enzyme activity 10-20-fold. However, at moderate levels (20-40 mM), these phospholipids largely inhibit widespread degradation of duplex DNA while still allowing site-specific nicking at the conserved guanine target in the mitochondrial genome. These findings suggest that an interaction of the endonuclease with major lipid components of the inner membrane could be an important determinant of the enzyme's specificity for mitochondrial DNA.

Augmentation of macrophage growth-stimulating activity of lipids by their peroxidation

Previously, we reported that some kinds of lipids (cholesterol esters, triglycerides, and some negatively charged phospholipids) that are constituents of lipoproteins or cell membranes induce growth of peripheral macrophages in vitro. In this paper, we examined the effect of peroxidation of lipids on their macrophage growth-stimulating activity because lipid peroxidation is observed in many pathological states such as inflammation. When phosphatidylserine, one of the phospholipids with growth-stimulating activity, was peroxidized by UV irradiation, its macrophage growth-stimulating activity was augmented in proportion to the extent of its peroxidation. The activity of phosphatidylethanolamine was also increased by UV irradiation. On the other hand, phosphatidylcholine or highly unsaturated free fatty acids, such as arachidonic acid and eicosapentaenoic acid, did not induce macrophage growth irrespective of whether they were peroxidized. The augmented activity of UV-irradiated phosphatidylserine was not affected by the coexistence of an antioxidant, vitamin E or BHT. These results suggest that some phospholipids included in damaged cells or denatured lipoproteins which are scavenged by macrophages in vivo may induce growth of peripheral macrophages more effectively when they are peroxidized by local pathological processes.

Acidic phospholipids directly inhibit DNA binding of mammalian DNA topoisomerase I

Inhibition of mammalian DNA topoisomerase I by phospholipids was investigated using purified enzyme. Acidic phospholipids inhibited the DNA relaxation activity of topoisomerase I whereas neutral phospholipid, phosphatidylethanolamine, did not. Accumulation of a protein-DNA cleavable complex, an intermediate which is known to accumulate upon inhibition by a specific inhibitor camptothecin, did not occur. The filter binding assay revealed that the DNA binding activity of the enzyme was inhibited by acidic phospholipids. Moreover, direct binding of phosphatidylglycerol to topoisomerase I was demonstrated. These results indicated that the inhibitory effect of acidic phospholipids on topoisomerase I was due to the loss of the DNA binding of the enzyme as a result of direct interaction between phospholipids and the enzyme.

Synergistic activation of CTP:phosphocholine cytidylyltransferase by phosphatidylethanolamine and oleic acid

CTP:phosphocholine cytidylyltransferase present in rat liver cytosol was activated almost 30-fold when assayed in the presence of liposomes containing 60 mole % dioleoyl phosphatidylethanolamine (DOPE). During the assay, some of the DOPE was degraded to lysoPE and oleic acid. Whereas cytidylyltransferase activity was not affected when assayed in the presence of liposomes containing lysoPE, liposomes containing oleic acid activated the enzyme. Activation by oleic acid could be eliminated by the addition of fatty acid-free bovine serum albumin (BSA) to the assay. When cytidylyltransferase activity was measured in the presence of both BSA and liposomes containing DOPE, enzyme activity was increased almost 20-fold, as compared with assays performed in the absence of added lipid. The 1.5-fold difference in cytidylyltransferase activity observed when cytosol was assayed with DOPE containing liposomes in the absence or presence of BSA (30-fold stimulation vs 20-fold stimulation) cannot be explained by the loss of activation attributable to oleic acid alone. Activation of the enzyme in the presence of liposomes containing DOPE and oleic acid is several-fold greater than the sum of the activations caused by the individual compounds. These data suggest that PE and oleic acid act synergistically in activating the cytidylyltransferase.

A role for intracellular histamine in collagen-induced platelet aggregation

We previously demonstrated that newly formed intracellular histamine mediates platelet aggregation in response to phorbol-12-myristate-13-acetate (PMA). We now report further investigations of the role of histamine during physiological activation of platelets by collagen. Platelets stirred with collagen produced histamine; the rise in histamine precedes the onset of aggregation. The dose response for collagen stimulation of histamine synthesis and platelet aggregation is similar. Inhibitors of histidine decarboxylase (HDC) block both aggregation and histamine synthesis in parallel. Histamine production is not dependent on aggregation; both the intracellular histamine receptor antagonist, N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine-HCl (DPPE), and the cyclooxygenase inhibitors, aspirin and indomethacin, inhibit collagen-induced aggregation but not histamine synthesis. DPPE also inhibits collagen-induced serotonin secretion and thromboxane production. The effects of DPPE and HDC inhibitors are significantly reversed by the addition of histamine (0.1 to 10 mumol/L) to saponin-permeabilized platelets, though histamine alone has no pro-aggregatory effects. The results suggest that newly synthesized intracellular histamine has a role in collagen-induced platelet activation and that it may act to promote the generation of thromboxane and the secretion responses of platelet granules.

Effect of phospholipids on UDP-glucose: ceramide glucosyltransferase from Golgi membranes

1. The removal of phospholipids completely abolished the activity of the enzyme UDP-glucose:ceramide glucosyltransferase from Golgi membranes. 2. Modulation of enzyme activity by phospholipids was undertaken on the solubilized form of the enzyme. 3. Well-defined fatty acyl chains and polar head groups were necessary for maximal stimulation by phospholipids. 4. A specific requirement for phosphatidylcholine is suggested by preliminary experiments of reconstitution of enzyme activity with phosphatidylcholine vesicles.

Characterization with a simple clotting assay of the tissue factor inhibiting activity in serum

The serum inhibiting activity on tissue factor (TFI) was evaluated as follows: normal human serum was incubated at room temperature with highly diluted rabbit brain thromboplastin (TF) and calcium ions; after 30 min. rabbit brain cephalin, calcium and normal human plasma were added to a small aliquot of TF/serum mixture; the clotting time at 37 degrees C was then recorded. With this assay TFI activity is proportional to the serum level; it is low for incubation periods shorter than 30 min., is missing at TF concentrations higher than 8%, is strictly connected to the presence of F VII and F Xa in the serum sample, depends upon the presence of calcium ions and finally, is independent of antithrombin III. This inhibiting activity also seems to be saturable and reversible.

Tumor cytotoxicity and interleukin 1 production of blood monocytes of lung cancer patients

The effects of lung cancer on the abilities of blood monocytes to produce interleukin-1 and to mediate antitumor activity were examined. The functional integrity of blood monocytes was determined by their capacity to respond in vitro to a variety of activating agents and become tumoricidal, as assessed by a radioactive release assay and ability to produce interleukin-1 in vitro. The results show that the presence of lung cancer significantly increased the number of harvested blood monocytes and that the spontaneous tumoricidal activity of these monocytes was slightly high as compared to monocytes obtained from healthy donors. The production of interleukin-1 by monocytes of healthy donors and lung cancer patients was similar. Blood monocytes obtained from lung cancer patients were less cytotoxic against allogeneic A375 melanoma cells as compared with those of healthy donors subsequent to incubation with a soluble muramyl dipeptide analog or lipopolysaccharide, but were as tumoricidal as those from healthy donors when activated with lipophilic muramyl tripeptide (MTP-PE) entrapped in multilamellar liposomes. The finding that monocytes of patients with lung cancer can respond to MTP-PE encapsulated in liposomes, recommends the use of these liposomes in therapy of human lung cancer.

Membrane properties modulate the activity of a phosphatidylinositol transfer protein from the yeast, Saccharomyces cerevisiae

A phospholipid transfer protein from yeast (Daum, G. and Paltauf, F. (1984) Biochim. Biophys. Acta 794, 385-391) was 2800-fold enriched by an improved procedure. The specificity of this transfer protein and the influence of membrane properties of acceptor vesicles (lipid composition, charge, fluidity) on the transfer activity were determined in vitro using pyrene-labeled phospholipids. The yeast transfer protein forms a complex with phosphatidylinositol or phosphatidylcholine, respectively, and transfers these two phospholipids between biological and/or artificial membranes. The transfer rate for phosphatidylinositol is 19-fold higher than for phosphatidylcholine as determined with 1:8 mixtures of phosphatidylinositol and phosphatidylcholine in donor and acceptor membrane vesicles. If acceptor membranes consist only of non-transferable phospholipids, e.g., phosphatidylethanolamine, a moderate but significant net transfer of phosphatidylcholine occurs. Phosphatidylcholine transfer is inhibited to a variable extent by negatively charged phospholipids and by fatty acids. Differences in the accessibility of the charged groups of lipids to the transfer protein might account for the different inhibitory effects, which occur in the order phosphatidylserine which is greater than phosphatidylglycerol which is greater than phosphatidylinositol which is greater than cardiolipin which is greater than phosphatidic acid which is greater than fatty acids. Although mitochondrial membranes contain high amounts of negatively charged phospholipids, they serve effectively as acceptor membranes, whereas transfer to vesicles prepared from total mitochondrial lipids is essentially zero. Ergosterol reduces the transfer rate, probably by decreasing membrane fluidity. This notion is supported by data obtained with dipalmitoyl phosphatidylcholine as acceptor vesicle component; in this case the transfer rate is significantly reduced below the phase transition temperature of the phospholipid.