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Host response to Treponema pallidum infection. I. Quantitative changes of lipids in rabbit organs.

Levels of phospholipids, glycolipids and cardiolipin were determined in various organs of Treponema pallidum-infected rabbits. The phospholipid levels on the second week of infection decreased significantly in the spleen but remained unchanged in other organs. During the same time, glycolipids decreased significantly in both kidney and heart. 3 days after infection, a brief but significant increase of cardiolipin in the spleen was observed. Heat-killed T. pallidum but not Treponema reiteri caused a similar effect. The possible implication of these changes in the immunopathology of syphilis is discussed.

Animals↗

Specificity of mouse hybridoma antibodies to DNA. II. Phospholipid reactivity and biological false positive serological test for syphilis.

Using mouse hybridoma monoclonal antibodies to DNA from MRL/lpr and NZB X NZW (B/W F1) mice, the reactivity of anti-DNA antibodies to several phospholipids was analysed. The anti-DNA antibody which reacted with the common antigenic determinants on the phosphate-sugar backbone of nucleic acid could bind to the cardiolipin, but failed to bind to other phospholipids, including VDRL antigen. We tentatively conclude that the anti-cardiolipin antibody is identical with the anti-DNA antibody, but differs from the BFP reactor.

Animals↗

Lipidic particles.

A new type of lipid organization is observed in mixtures of phosphatidylcholine with cardiolipin in the presence of Ca++, monoglucosyldiglyceride and phosphatidylethanolamine (in the presence of cholesterol). This phase is characterized by an isotropic 31P NMR signal and is visualized by freeze fracturing as particles and pits on the fracture faces of the lipid bilayer. As the most favourable model for this phase we propose the inverted micelle sandwiched in between the two monolayers of the lipid bilayer. It will be shown that such particles and pits appear on the fusion site during fusion of unilamellar vesicles of an equimolar mixture of phosphatidylcholine and cardiolipin in the presence of Ca++.

Calcium↗

[Antigenic structure of the plasma membranes of mouse liver cells. III. Lipid haptens].

The total glycolipids, gangliosides, neutral lipids and some individual lipids of these fractions were isolated from the whole lipid extract of the mouse liver cell suspension. The antigenic activity of the isolated lipids was studied with the complement fixation test using the rabbit antisera against the liver cell ghosts. Active lipids were: glycosphingolipids, gangliosides, cardiolipin and fraction containing polar glyco- and phospholipid mixture. The cardiolipins isolated from animal cells of some species differed in their antigenic activity. With the immunofluorescence method, the absorbtion of antighost sera by lipid haptens resulted in a decreased fluorescence of plasma membranes of cells in the liver sections. This fact may evidence for the membrane localization of the studied haptens.

Animals↗

Function of phospholipids in Escherichia coli. Influence of changes in polar head group composition on the lipid phase transition and characterization of a mutant containing only saturated phospholipid acyl chains.

The cls mutation conferring a defect in cardiolipin synthesis (Pluschke, G., Hirota, Y., and Overath, P. (1978) J. Biol. Chem. 253, 5048-5055) has been introduced into an Escherichia coli strain defective in unsaturated fatty acid synthesis in order to study the effect of changes in polar head group composition on the ordered in equilibrium fluid phase transition of the membrane phospholipids. The defect in cardiolipin formation is compensated by an increase in phosphatidylglycerol content, resulting in a decrease of the midpoint of the phase transition by 6 degrees C. Starvation of the cls mutant strain for the unsaturated fatty acid supplement leads to the incorporation of saturated acyl chains of reduced average length into the phospholipids, and growth is inhibited although the membrane remains in a fluid state. A revertant of this strain is described which retains the parental fabB-, fadE-, and cls markers and grows in the absence of an unsaturated fatty acid supplement. A cls+ derivative of the revertant can multiply in a restricted temperature range (35-43 degrees C). It contains only saturated phospholipid acyl chains of an anomalously short average length of 14 carbon atoms but has the same polar head group composition as wild type E. coli. The results demonstrate that, under defined conditions, saturated acyl chains of reduced length are functionally equivalent to unsaturated chains.

Cardiolipins↗

Investigations of a new, highly negative liposome with improved biodistribution for imaging.

An attractive feature of liposomes is the wide range of lipid composition that can lead to liposome formation, coupled with the observation that liposome biodistribution may be altered by varying lipid composition. For instance, adding charged lipids to neutral lecithin will alter the biodistribution of the resulting charged liposomes. We have prepared highly negative liposomes by replacing lecithin with negatively charged cardiolipin. The liposomes have been labeled in the lipid phase with Ga-67 and Tc-99m oxine and their properties evaluated. The expected high negative charge of the resulting liposomes was confirmed by an ion-exchange chromatographic technique. Using paper chromatography, the stability of the label was determined during incubation in saline and serum. Finally, biodistributions were determined at 2 hr in mice, and the results compared with those for negative lecithin liposomes. Accumulated activities in liver and spleen were reduced by factors of five and 20, respectively, over lecithin liposomes. Since preferential accumulation of activity in these organs constitutes the biggest limitation to the use of lecithin liposomes, cardiolipin liposomes may prove to be more useful carriers of radioactivity in imaging applications. More importantly, however, these results illustrate the value of studying novel liposome types as potential radiopharmaceuticals.

Amines↗

Modulation of phospholipase A2 activity by membrane-active peptides on liposomes of different phospholipid composition.

To determine the influence of variations in both lipid species and lipid packing on phospholipase A2 (PLA2) hydrolytic activity, the activities of two PLA2 isolated from Crotalus molossus molossus venom, were followed on unilamellar liposomes modified by membrane-active peptides. Enzymatic activity was compared with cytolytic activity on human and mouse lymphocytes. Phosphatidylcholine liposomes were hydrolysed better than liposomes containing acidic phospholipids (phosphatidylserine, phosphatidic acid or cardiolipin) or phosphatidylethanolamine. Both membrane-active peptides, cardiotoxin and thionin, inhibited the PLA2 activity on phosphatidylcholine liposomes. The activities of the enzymes were profoundly enhanced on thionin-pretreated liposomes containing phosphatidylserine, and on cardiotoxin-pretreated liposomes containing cardiolipin or phosphatidic acid. Both cardiotoxin and thionin facilitated the cytolytic activities of PLA2 on both human and mouse lymphocytes. Cytolytic activity correlated well with esterase activity. It is proposed that the complex dynamic structure of cell membranes renders a variety of substrate configurations that transiently affect PLA2 activity.

Animals↗

[Different autoimmunity in Wegener's granulomatosis and microscopic polyangiitis].

Wegener's granulomatosis (WG) and microscopic polyangiitis (MP) are "small vessel" vasculitides which can serologically be discriminated measuring autoantibodies directed towards different target antigens (ANCA). In the present study we can demonstrate increased autoimmunity in patients with MP, as evaluated by measurement of thyroid microsomal and cardiolipin antibodies. Neither thyroid microsomal- nor myeloperoxidase-, nor cardiolipin antibodies were correlated to each other.

Adult↗

Do patients with antiphospholipid syndrome have autoantibodies to beta 2-glycoprotein I?

High positive anticardiolipin antibody tests have been associated with recurrent thrombosis and pregnancy loss. Although these antibodies were believed to bind negatively charged phospholipids, recent reports have suggested that a serum protein, beta 2-glycoprotein I (beta 2-GPI), may be the true antigen for these antibodies. To resolve this issue, we compared binding of 75 anticardiolipin-positive and 71 anticardiolipin-negative serum samples from patients with rheumatic diseases to beta 2-GPI by using an enzyme-linked immunosorbent assay (ELISA). Serum samples from 30 healthy blood donors and 10 laboratory personnel were used as normal controls. We found no difference in binding between the three groups of serum samples. In addition, when binding to beta 2-GPI coated plates was compared with binding to ELISA plates without beta 2-GPI (blank), no difference was observed. Finally, binding of anticardiolipin-positive serum samples to plates coated with cardiolipin-beta 2-GPI mixture varied directly with the cardiolipin concentrations. Based on these findings, we conclude that anticardiolipin-positive serum samples do not bind beta 2-GPI.

Antiphospholipid Syndrome↗

Phospholipid content and fatty acid composition in the rat heart after chronic diazepam treatment.

The effects of chronic diazepam treatment (10 mg/kg/day for 180 days) on the fractional distribution and fatty acid composition of heart phospholipids were studied in male Wistar rats. It was found that diazepam treatment increased the content of phosphatidylcholine and cardiolipin in the heart and slightly increased its phosphatidylcholine fraction. There were no significant changes in fatty acid composition after diazepam treatment in heart phospholipids, with the exception of significant decrease of 20:3n-6 and 20:5n-3 fatty acids. Our findings suggest that diazepam, probably through peripheral benzodiazepine binding sites, altered the content of heart cardiolipin and caused changes in the flux of oxidative phosphorylation in the heart.

Animals↗

alpha-d-glucopyranosyl-, d-alanyl- and l-lysylcardiolipin from gram-positive bacteria: analysis by fast atom bombardment mass spectrometry.

Cardiolipin species substituted on O2 of the middle glycerol moiety with alpha-d-glucopyranosyl, d-alanyl and l-lysyl residues were isolated from different gram-positive bacteria. There respective structures were elucidated by positive and negative mode fast atom bombardment mass spectrometry. The structural heterogeneity due to different fatty acid combinations was documented by up to seven molecular ions. General structural features were derived from diagnostic fragment ions, generated by single cleavage at the phosphodiester moieties in both positive and negative ion mode. A diagnostically important fragment ion for d-alanylcardiolipin was observed in the positive ion mode. It arose from double cleavage of the phosphodiester moieties yielding [NaH(Na) PO4-CH2.CH(OCO.CHNH2.CH3) CH2+]+. The fatty acid combinations in the phosphatidyl and diacylglycerol ions make it possible to recognize whether saturated and unsaturated fatty acids were selectively or randomly distributed on the two positions of the glycerol moieties. Molecular structures of cardiolipins, derived from mass spectrometric experiments, are in full agreement with those, elucidated by classical chemical analyses.

Cardiolipins↗

Effect of psychosine on mitochondrial function.

The effect of psychosine on the rate of respiration at different segments of the electron transport chain, respiratory control ratio and the efficiency of phosphorylation was studied. The transfer of electrons through site I, site II and site III was studied independently. The transfer through site I and site III was inhibited by psychosine, whereas the transfer through site II was not inhibited. Cardiolipin, which is essential for the electron transfer through site I and III, was implicated to be responsible for the inhibition of electron transfer by psychosine. Electron carriers of site II are not sensitive to cardiolipin, so psychosine could not inhibit the electron transfer through this site. The ADP/O ratio and respiratory control ratio were inhibited by psychosine showing that it has an uncoupler like effect. Mitochondria isolated from rat liver, kidney and brain behaved essentially the same way in their response to psychosine. Cytochrome c oxidase was significantly inhibited by psychosine and the degree of inhibition was almost same in mitochondria and sub mitochondrial particles. The preence of outer membrane in mitochondria did not make any difference with respect to the action of psychosine on electron transport chain. Psychosine interacts at site I and site III and a change in the lipid environment of the membrane is responsible for the mitochondrial dysfunctions induced by psychosine. This represents a possible mechanism for the destruction of cells in Gaucher's and Krabbe's disease.

Animals↗

Rapid detection of anticardiolipin antibodies.

A rapid screening method for the detection of antiphospholipid antibodies is described. Dense, red dyed polystyrene beads coated with cardiolipin were incubated with test sera for a short period of time, then added to a microtube containing anti-human IgG in a gel provided within a pre-cast card (DiaMed ID Microtyping System). The card was centrifuged at 150g for 5 min and then examined for movement of the beads through the gel. Beads without bound antibody travelled through the gel and formed a pellet on the bottom of the tube. Anti-human IgG within the gel matrix impeded cardiolipin-coated beads when antiphospholipid antibodies bound to the beads. Positivity was indicated by the formation of a layer of beads on the top of the gel matrix. Prospective analysis of 103 samples for the presence of antiphospholipid antibodies by flow cytometry and the gel-card technique showed good correlation between the two methods. All samples found to be positive by flow cytometry (23 of 103) were identified as positive by the gel-card technique. Two samples were identified as positive by the gel-card method but negative by flow cytometry. The technique is simple to perform and should prove useful as a rapid screening method for the detection of antiphospholipid antibodies.

Antibodies, Anticardiolipin↗

Hidden anti-phospholipid antibodies in normal human sera circulate as immune complexes whose antigen can be removed by heat, acid, hypermolar buffers or phospholipase treatments.

Heat treatment of normal human serum reveals otherwise masked anti-cardiolipin antibodies (aCL). We studied the mechanism of masking and the nature of the inhibitor of these aCL IgG. Other forms of treatment, besides heating for 30 min at 56 degrees C, can also unmask hidden aCL IgG. These include acid pH, hypermolar buffers and phospholipase digestion. When unmasked, these aCL recognize other anionic and zwitterionic phospholipids, but do not react with DNA, cell antigens or IgG. Using thin layer chromatography we demonstrate that the heat-labile inhibitor(s) of these aCL are phosphatidylserine, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine. These antibodies are not beta2-glycoprotein-I dependent and actually compete with this protein for phospholipid binding. The hidden antibodies are comprised of two populations of IgG autoantibodies: one reactive with cardiolipin, phosphatidylserine, phosphatidylinositol, phosphatidylglycerol, phosphatidylethanolamine and sphingomyelin, and the other reactive almost exclusively with phosphatidylcholine and phosphorylcholine on enzyme-linked immunosorbent assay plates or when exposed by bromelain on the erythrocyte surface. Our data suggest that hidden aCL are natural oligoreactive IgG anti-phospholipid autoantibodies that circulate masked by their antigen.

Antibodies, Antiphospholipid↗

Long-term remission from life-threatening hypercoagulable state associated with lupus anticoagulant (LA) following rituximab therapy.

Rituximab, a chimeric monoclonal CD20 antibody, is useful in the treatment of B-cell lymphomas and certain autoimmune diseases. We report a successful outcome of rituximab for life threatening hypercoagulable state associated with lupus anticoagulant (LA). A 30-year-old woman initially presented 10 years ago with DVT and positive serology for SLE and LA. While on Coumadin, she suffered from recurrent DVT in the legs and arms, pulmonary emboli, Budd-Chiari syndrome, mesenteric vein thrombosis, bone infarcts, recurrent strokes, and chronic ITP. All measures including plasmapheresis and monthly IV cyclophosphamide were of no benefit. She was recently admitted with spontaneous subdural hematoma with INR of 3.8. Upon discontinuation of anticoagulation for surgical drainage, she developed acute abdomen from thrombosis and recurrent DVT. Because she had failed prior standard measures, 4 weekly infusions of rituximab (375 mg/m2) were given following 2 rounds of plasmapheresis. Subsequently, she made a remarkable recovery over the next month and has been free of thrombosis on Coumadin for over 15 months. LA, IgM antibodies to cardiolipin, and B2GP1 were consistently positive. After rituximab therapy, LA became negative and IgM antibodies to cardiolipin decreased and ITP went into remission. Rituximab induced a lasting remission in a woman suffering from life-threatening hypercoagulable state associated with LA. Her clinical remission was associated with disappearance of LA.

Adult↗

Identification and characterization of a peptide mimetic that may detect a species of disease-associated anticardiolipin antibodies in patients with the antiphospholipid syndrome.

OBJECTIVE: To test the feasibility of applying a mimetic (specific for a patient-derived prothrombotic anticardiolipin antibody [aCL]) to study the homologous, disease-associated aCL in patients with antiphospholipid syndrome (APS). METHODS: We used the CL15 monoclonal aCL to screen 17 phage-display peptide libraries. Peptides (corresponding to recurrent peptide sequences) and their derivatives were synthesized and analyzed for binding to CL15 and for their abilities to inhibit CL15 from binding to cardiolipin. A peptide was chosen and used to study CL15-like IgG aCL in plasma samples from patients with APS, patients with systemic lupus erythematosus (SLE) but without APS, and normal healthy donors. RESULTS: Library screening with CL15 yielded 4 recurrent peptide sequences. Analyses of peptides showed that peptide CL154C reacted with antibody CL15 and inhibited binding of CL15 to cardiolipin, indicating that peptide CL154C may be a peptide mimetic for the CL15 aCL. Initial studies with plasma samples revealed that CL154C-reactive IgG was present (positivity defined as the mean + 3 SD optical density of the 25 normal controls) in 15 of 21 APS patients and 1 of 12 SLE patients. CONCLUSION: These findings suggest that it is feasible to develop a specific enzyme-linked immunosorbent assay for each immunologically and functionally distinct disease-associated aCL. Additional testing of CL154C with a larger number of APS patients and SLE patients, as well as identification of peptide mimetics for each distinct aCL, will reveal the diagnostic potential of CL154C and other mimetics in identifying patients with aCL who are at risk of developing life-threatening thrombosis.

Adolescent↗

Similarities of specificity and cofactor dependence in serum antiphospholipid antibodies from patients with human parvovirus B19 infection and from those with systemic lupus erythematosus.

OBJECTIVE: To assess the phospholipid specificity and immunoglobulin isotype of antiphospholipid (aPL) antibodies in patients with acute parvovirus B19 infection. METHODS: Specificity of aPL and isotype distribution in the negatively charged phospholipids, cardiolipin and phosphatidyl serine, and in the neutral phospholipid, phosphatidyl ethanolamine, were measured in the sera of patients with acute parvovirus B19 infections (n = 12), in those with other acute viral infections (n = 10), and in those with syphilis (n = 15) by enzyme-linked immunosorbent assays. The dependence of anticardiolipin (aCL) binding on the presence of beta 2-glycoprotein I (beta 2-GPI) as a binding cofactor was assessed in these same groups, and was compared with sera from systemic lupus erythematosus (SLE) patients (n = 11) with raised aCL antibody reactivity. RESULTS: Antibodies against any of the 3 phospholipids were found in all 3 groups of patients with infections (B19 in 11 of 12 patients, other viral infections in 8 of 10 patients, and syphilis in 14 of 15 patients). B19 patients' sera contained predominantly IgG antibodies against the negatively charged phospholipids, cardiolipin and phosphatidyl serine, and differed in their specificity and isotype distribution from those found in the other 2 patient groups. B19-associated aCL increased their binding to antigen in the presence of beta 2-GPI as a binding cofactor, similar to aCL found in SLE patients, but unlike antibodies from patients with other viral infections or from those with syphilis. CONCLUSION: The results show the remarkable similarity in specificity of aPL antibodies between B19-infected patients and SLE patients, and raise the question of whether parvovirus infection may be a trigger for the development of aPL antibodies in autoimmune diseases.

Antibodies, Anticardiolipin↗

Phosphorylation of mitochondrial phospholipid scramblase 3 by protein kinase C-delta induces its activation and facilitates mitochondrial targeting of tBid.

Phospholipid scramblase 3 (PLS3) is a member of the phospholipid scramblase family present in mitochondria. PLS3 plays an important role in regulation of mitochondrial morphology, respiratory function, and apoptotic responses. PLS3 is phosphorylated by PKC-delta at Thr21 and is the mitochondrial target of PKC-delta-induced apoptosis. Cells with overexpression of PLS3, but not the phosphoinhibitory mutant PLS3(T21A), are more susceptible to apoptosis induced by AD198, an extranuclear targeted anthracycline that activates PKC-delta. Here we report that the phosphomimetic mutant of PLS3(T21D) by itself can induce apoptosis in HeLa cells. Using proteoliposomes with addition of pyrene-labeled phosphatidylcholine (PC) at the outer leaflet, we measured the lipid flip-flop activity of PLS3 and its phosphorylation mutant. PLS3(T21D) is more potent than wild-type PLS3 or PLS3(T21A) to transfer pyrene-PC from the outer leaflet to the inner leaflet of liposomes. Based on our previous finding that PLS3 enhances tBid-induced mitochondrial damages, we tested the hypothesis that PLS3 enhances cardiolipin translocation to mitochondrial surface and facilitates tBid targeting. Fluorescein-labeled tBid(G94E) was used as a probe to quantify cardiolipin on the surface of mitochondria. Mitochondria from cells treated with AD198 or cells expressing PLS3(T21D) had a higher level of tBid-binding capacity than control cells or cells expressing wild-type PLS3. These findings indicate that phosphorylation of PLS3 by PKC-delta induces PLS3 activation to facilitate mitochondrial targeting of tBid and apoptosis.

Apoptosis↗