Phospholipid Analogues Research Articles

Interaction of fluorescent phospholipids with cyclodextrins

Fluorescent analogs of phospholipids are often employed to investigate the structure and dynamics of lipids in membranes. Some of those studies have used cyclodextrins e.g., to modulate the lipid phase. However, the role of the fluorescence moiety of analogs for the interaction between cyclodextrins and fluorescent lipids has not been investigated so far in detail. Therefore, in the present study the interaction of various fluorescent phospholipid analogs with methylated α-, β- and γ- cyclodextrins was investigated. The analogs differed in their structure, in the length of the fatty acyl chain, in the position of the fluorescence group, and in the attached fluorescence moiety (7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) or dipyrrometheneboron difluoride (BODIPY)). In aqueous buffer, cyclodextrins bind fluorescent lipids disturbing the organization of the analogs. When incorporated into lipid vesicles, analogs are selectively extracted from the membrane upon addition of cyclodextrins. The results show that the interaction of cyclodextrins with fluorescent phospholipids depends on the cyclodextrin species, the fluorescence moiety and the phospholipid structure. The presented data should be of interest for studies using fluorescent phospholipids and cyclodextrins, since the interaction between the fluorescence group and the cyclodextrin may interfere with the process(es) under study.

Retraction Note to: Erucylphosphocholine induces growth inhibition, cell cycle arrest, and apoptosis in human choriocarcinoma cells.

A membrane-targeted, lipophilic ether lipid of synthetic phospholipid analog, erucylphosphocholine (ErPC), induces apoptosis in some lines of human tumor cells. We investigated the effect of ErPC in the choriocarcinoma cell line, BeWo. BeWo cells were treated with various concentrations of ErPC, and changes in cell growth, the cell cycle, apoptosis, and related parameters were examined. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that BeWo cells were sensitive to the growth inhibitory effect of ErPC. Cell cycle analysis indicated that exposure to ErPC decreased the proportion of cells in the S phase and increased the proportion in the G0/G1 phases of the cell cycle. Induction of apoptosis was confirmed by Annexin V staining of externalized phosphatidylserine and by the loss of mitochondrial transmembrane potential. This induction occurred in conjunction with the altered expression of genes related to cell growth, malignant phenotype, and apoptosis. These results suggest that ErPC may serve as a therapeutic agent for the treatment of choriocarcinoma.

Miltefosine is active against Sporothrix brasiliensis isolates with in vitro low susceptibility to amphotericin B or itraconazole.

Sporotrichosis is a common mycosis caused by dimorphic fungi from the Sporothrix schenckii complex. In recent years, sporotrichosis incidence rates have increased in the Brazilian state of Rio de Janeiro, where Sporothrix brasiliensis is the species more frequently isolated from patients. The standard antifungals itraconazole and amphotericin B are recommended as first-line therapy for cutaneous/lymphocutaneous and disseminated sporotrichosis, respectively, although decreased sensitivity to these drugs in vitro was reported for clinical isolates of S. brasiliensis. Here, we evaluated the activity of the phospholipid analogue miltefosine - already in clinical use against leishmaniasis - towards the pathogenic yeast form of S. brasiliensis isolates with low sensitivity to itraconazole or amphotericin B in vitro. Miltefosine had fungicidal activity, with minimum inhibitory concentration (MIC) values of 1-2 µg ml(-1). Miltefosine exposure led to loss of plasma membrane integrity, and transmission electron microscopy (TEM) analysis revealed a decrease in cytoplasmic electron density, alterations in the thickness of cell wall layers and accumulation of an electron-dense material in the cell wall. Flow cytometry analysis using an anti-melanin antibody revealed an increase in cell wall melanin in yeasts treated with miltefosine, when compared with control cells. The cytotoxicity of miltefosine was comparable to those of amphotericin B, but miltefosine showed a higher selectivity index towards the fungus. Our results suggest that miltefosine could be an effective alternative for the treatment of S. brasiliensis sporotrichosis, when standard treatment fails. Nevertheless, in vivo studies are required to confirm the antifungal potential of miltefosine for the treatment of sporotrichosis.

Rapid access to phospholipid analogs using thiol-yne chemistry.

Phospholipids and glycolipids constitute an essential part of biological membranes, and are of tremendous fundamental and practical interest. Unfortunately, the preparation of functional phospholipids, or synthetic analogs, is often synthetically challenging. Here we utilize thiol-yne click chemistry methodology to gain access to phospho- and glycolipid analogs. Alkynyl hydrophilic head groups readily photoreact with numerous thiol modified lipid tails to yield the appropriate dithioether phospho- or glycolipids. The resulting structures closely resemble the structure and function of native diacylglycerolipids. Dithioether phosphatidylcholines (PCs) are suitable for forming giant unilamellar vesicles (GUV), which can be used as vessels for cell-free expression systems. The unnatural thioether linkages render the lipids resistant to phospholipase A2 hydrolysis. We utilize the improved stability of these lipids to control the shrinkage of GUVs composed of a mixture of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and dioleyl-dithioether PC, concentrating encapsulated nanoparticles. We imagine that these readily accessible lipids could find a number of applications as natural lipid substitutes.

Development of Photo-Controlled Molecular Shuttle Utilizing ATP Driven Motor Kinesin

The ATP driven motor kinesin has many possibilities for the application to the molecular machines. Previously, we introduced photochromic molecules into the functional key region of the kinesin as a photo-switch and tried to control the function of kinesin by ultraviolet (UV) and visible (VIS) light irradiations. The kinesin mutant S275C modified with thiol reactive azobenzene derivative exhibited photo-controlled ATPase activity correlating to photo isomerization of photochromic molecules.In this study, we tried to prepare the photo-controlled molecular shuttles using kinesin and liposome modified with photochromic molecule.We prepared the kinesin motor domain (K355) mutant that has a single cysteine at neck linker region and His-tag at C-terminal. Subsequently the kinesin mutant was dimerized with photochromic bifunctional cross-linker, azobenzene dimaleimide (ABDM). And the photo-reversible regulation of the ATPase and motor activities of the kinesin dimer cross-linked with ABDM was studied.We also tried to develop photo-responsive vesicle composed of photochromic molecules as a cargo for the photo-controlled kinesin. Diacyl glycerol was coupled with carboxypropyl-spiropyran to be phospholipid analogue using carbonyldiimidazole condensation reagent. The spiropyran moiety performs photo-reversible isomerization between hydrophobic spiro form and merocyanine zwitterion form upon visible light and ultraviolet light, respectively. Therefore, it is expected that the merocyanine form of the mimic phospholipid results in formation liposome like vesicle. The photo-reversible formation of the vesicle was studied using water-soluble fluorescent probe.

Cholesterol Bilayer Domain in Phospholipid Bilayer Membranes can be Detected by Confocal Microscope

The unique feature of the eye lens fiber-cell plasma membrane is its extremely high cholesterol content; cholesterol/phospholipid molar ratio can be as high as 4 in human lens nucleus. Cholesterol saturates bulk phospholipid bilayers and induces formation of immiscible cholesterol bilayer domains (CBDs) within membranes. The presence of CBDs plays crucial role ensuring that surrounding phospholipid bilayers are saturated with cholesterol which keeps the bulk physical properties of lens-lipid membranes consistent and independent of changes in phospholipid composition. Thus, CBDs help to maintain lens-membrane homeostasis when the membrane phospholipid composition changes significantly with age. Our previous experiments were based on electron paramagnetic resonance spin-labeling methods. They allowed to detect CBDs in model and lens lipid membranes at high cholesterol content (1,2). In current experiments the giant unilamellar vesicles made of cholesterol/distearoylphosphatidylcholine (Chol/DSPC) mixtures, with mixing ration from 0.5 to 5 and labeled with phospholipid analog (1,1′-Dioctadecyl-3,3,3’,3′-Tetramethylindocarbocyanine-5,5′-Disulfonic Acid) and cholesterol analog (23-(dipyrrometheneboron difluoride)-24-norcholesterol) fluorescent probes, were prepared using the electroformation method (3). Confocal microscopy experiment allowed us to confirm that membranes with higher Chol/DSPC molar ratio contain two distinct lipid environments, the bulk phospholipid-cholesterol domain (PCD) and the CBD. The amount of CBD was greater in membranes with higher Chol/DSPC ratio. According to these results, CBD is always located on the top of the giant vesicle. Rationale for this discovery is that CBD has smaller mass per unit area of the vesicle compared with PCD. Additionally, it can be concluded that vesicles with higher Chol/DSPC molar ratio are more rigid and show less wobbling motion in water environment.1. Raguz et al. CPL 2011 164(8):819-29.2. Mainali et al. BBA 2013 1828(6):1432-40.3. Veatch SL. Methods Mol Biol. 2007 398:59-72.AcknowledgementsSupported by NIH grants EY015526 and EY001931.

Scanning STED-FCS reveals spatiotemporal heterogeneity of lipid interaction in the plasma membrane of living cells.

The interaction of lipids and proteins plays an important role in plasma membrane bioactivity, and much can be learned from their diffusion characteristics. Here we present the combination of super-resolution STED microscopy with scanning fluorescence correlation spectroscopy (scanning STED-FCS, sSTED-FCS) to characterize the spatial and temporal heterogeneity of lipid interactions. sSTED-FCS reveals transient molecular interaction hotspots for a fluorescent sphingolipid analogue. The interaction sites are smaller than 80 nm in diameter and lipids are transiently trapped for several milliseconds in these areas. In comparison, newly developed fluorescent phospholipid and cholesterol analogues with improved phase-partitioning properties show more homogenous diffusion, independent of the preference for liquid-ordered or disordered membrane environments. Our results do not support the presence of nanodomains based on lipid-phase separation in the basal membrane of our cultured nonstimulated cells, and show that alternative interactions are responsible for the strong local trapping of our sphingolipid analogue.

Phospholipid lateral diffusion in phosphatidylcholine-sphingomyelin-cholesterol monolayers; Effects of oxidatively truncated phosphatidylcholines

Oxidative stress is involved in a number of pathological conditions and the generated oxidatively modified lipids influence membrane properties and functions, including lipid–protein interactions and cellular signaling. Brewster angle microscopy demonstrated oxidatively truncated phosphatidylcholines to promote phase separation in monolayers of 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine (POPC), sphingomyelin (SM) and cholesterol (Chol). More specifically, 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC), was found to increase the miscibility transition pressure of the SM/Chol-phase. Lateral diffusion of lipids is influenced by a variety of membrane properties, thus making it a sensitive parameter to observe the coexistence of different lipid phases, for instance. The dependence on lipid lateral packing of the lateral diffusion of fluorophore-containing phospholipid analogs was investigated in Langmuir monolayers composed of POPC, SM, and Chol and additionally containing oxidatively truncated phosphatidylcholines, using fluorescence correlation spectroscopy (FCS). To our knowledge, these are the first FCS results on miscibility transition in ternary lipid monolayers, confirming previous results obtained using Brewster angle microscopy on such lipid monolayers. Wide-field fluorescence microscopy was additionally employed to verify the transition, i.e. the loss and reformation of SM/Chol domains.

Modification of biomaterials surface by mimetic cell membrane to improve biocompatibility

Modification of biomaterials surface by mimetic cell membrane for improving biocompatibility, to imitate the excellent biological and physiological properties of the natural cell membrane, is an important research area in materials science. Numerous studies have been attempted to construct a mimetic cell membrane biointerface composed of phosphorylcholine (PC)-containing polymers or other phospholipid analogues on biomaterials surface. PC-containing biointerfaces show outstanding characteristics, especially in biological aspects such as blood compatibility and antifouling property. In this mini-review, the strategies of membrane mimetic modification of biomaterials and their antifouling applications are summarized.

Spin-label W-band EPR with seven-loop-six-gap resonator: Application to lens membranes derived from eyes of a single donor.

Spin-label W-band (94 GHz) EPR with a five-loop-four-gap resonator (LGR) was successfully applied to study membrane properties (L. Mainali, J.S. Hyde, W.K. Subczynski, Using spin-label W-band EPR to study membrane fluidity in samples of small volume, J. Magn. Reson. 226 (2013) 35-44). In that study, samples were equilibrated with the selected gas mixture outside the resonator in a sample volume ~100 times larger than the sensitive volume of the LGR and transferred to the resonator in a quartz capillary. A seven-loop-six-gap W-band resonator has been developed. This resonator permits measurements on aqueous samples of 150 nL volume positioned in a polytetrafluoroethylene (PTFE) gas permeable sample tube. Samples can be promptly deoxygenated or equilibrated with an air/nitrogen mixture inside the resonator, which is significant in saturation-recovery measurements and in spin-label oximetry. This approach was tested for lens lipid membranes derived from lipids extracted from two porcine lenses (single donor). Profiles of membrane fluidity and the oxygen transport parameter were obtained from saturation-recovery EPR using phospholipid analog spin-labels. Cholesterol analog spin-labels allowed discrimination of the cholesterol bilayer domain and acquisition of oxygen transport parameter profiles across this domain. Results were compared with those obtained previously for membranes derived from a pool of 100 lenses. Results demonstrate that EPR at W-band can be successfully used to study aqueous biological samples of small volume under controlled oxygen concentration.

Structural Determinants of the Transient Receptor Potential 1 (TRPV1) Channel Activation by Phospholipid Analogs

The transient receptor potential vanilloid 1 (TRPV1) ion channel is a polymodal protein that responds to various stimuli, including capsaicin (the pungent compound found in chili peppers), extracellular acid, and basic intracellular pH, temperatures close to 42 °C, and several lipids. Lysophosphatidic acid (LPA), an endogenous lipid widely associated with neuropathic pain, is an agonist of the TRPV1 channel found in primary afferent nociceptors and is activated by other noxious stimuli. Agonists or antagonists of lipid and other chemical natures are known to possess specific structural requirements for producing functional effects on their targets. To better understand how LPA and other lipid analogs might interact and affect the function of TRPV1, we set out to determine the structural features of these lipids that result in the activation of TRPV1. By changing the acyl chain length, saturation, and headgroup of these LPA analogs, we established strict requirements for activation of TRPV1. Among the natural LPA analogs, we found that only LPA 18:1, alkylglycerophosphate 18:1, and cyclic phosphatidic acid 18:1, all with a monounsaturated C18 hydrocarbon chain activate TRPV1, whereas polyunsaturated and saturated analogs do not. Thus, TRPV1 shows a more restricted ligand specificity compared with LPA G-protein-coupled receptors. We synthesized fatty alcohol phosphates and thiophosphates and found that many of them with a single double bond in position Δ9, 10, or 11 and Δ9 cyclopropyl group can activate TRPV1 with efficacy similar to capsaicin. Finally, we developed a pharmacophore and proposed a mechanistic model for how these lipids could induce a conformational change that activates TRPV1.

Peptidophospholipids: Synthesis, phospholipase A2 catalyzed hydrolysis, and application to development of phospholipid prodrugs

New phospholipid analogues incorporating sn-2-peptide substituents have been prepared to probe the fundamental structural requirements for phospholipase A2 catalyzed hydrolysis of PLA2-directed synthetic substrates. Two structurally different antiviral oligopeptides with C-terminal glycine were introduced separately at the sn-2-carboxylic ester position of phospholipids to assess the role of the α-methylene group adjacent to the ester carbonyl in allowing hydrolytic cleavage by the enzyme. The oligopeptide-carrying phospholipid derivatives were readily incorporated into mixed micelles consisting of natural phospholipid (dipalmitoyl phosphatidylcholine, DPPC) and Triton X-100 as surfactant. Hydrolytic cleavage of the synthetic peptidophospholipids by the phospholipase A2 occurred slower, but within the same order of magnitude as the natural substrate alone. The results provide useful information toward better understanding the mechanism of action of the enzyme, and to improve the design and synthesis of phospholipid prodrugs targeted at secretory PLA2 enzymes.

The Membrane-targeted Alkylphosphocholine Erufosine Interferes with Survival Signals from the Extracellular Matrix

Integrin-dependent adhesion of tumor cells to extracellular matrix proteins provides anchorage-dependent protection from cell death. In the present investigation we aimed to understand whether and how the paradigmatic membrane-targeted synthetic phospholipid analog erufosine is relevant for tumor cell adhesion to extracellular matrix proteins, cell survival and migration. The antineoplastic action of erufosine was analyzed with glioblastoma and prostate cancer cells adhering to fibronectin or collagen I using proliferation, adhesion and migration assays. The composition of adhesion contacts containing activated β1 integrins was studied using immunofluorescence. The importance of β1 integrins for the observed effects was analyzed in fibroblasts proficient or deficient in β1 integrin expression. Adhesion to collagen I and fibronectin increased the death threshold in serum-deprived tumor cells. Moreover, β1 integrin-deficient cells were more sensitive to erufosine-treatment compared to β1 integrin proficient cells suggesting a role of β1 integrins for matrix-mediated death resistance. Most importantly, erufosine disturbed the maturation of the cell adhesion complexes containing paxillin, activated β1 integrins and phosphorylated FAK, leading to a reduction of survival signals and inhibition of tumor cell adhesion and migration. These findings suggest that membrane-targeted synthetic phospholipids analogs may be of value for counteracting matrix-mediated treatment resistance in combined treatment approaches with radiotherapy or chemotherapy.

Synthesis of phospholipids on a glyceric acid scaffold: design and preparation of phospholipase A2 specific substrates

Synthesis of a new series of phospholipid analogues to serve as activity-based probes of secretory phospholipase A2 enzymes is reported. The synthesis is based upon (1) preparation of long-chain esters and amides of glyceric acid, followed by (2) regioselective derivatization of the diol function of the molecule to achieve phosphorylation at the primary hydroxyl group, and to introduce the incipient sn-2-ester group of the target compounds. The sequence has been shown to allow incorporation of fluorescent, paramagnetic, and redox-active reporter groups, leading to phospholipid analogues applicable to detect and measure enzyme activity, to develop highly specific, real-time spectroscopic assay of phospholipase A2 enzymes, as well as to track the metabolic fate of the hydrolysis products. The synthetic method has a great deal of flexibility to open the way to the design and synthesis of activity-probes for other phospholipid metabolizing enzymes as well.

Characterizing Pulmonary Surfactant Peptide and Lipid Interactions with Various Spectroscopic Techniques

In vitro studies of pulmonary surfactant peptides in vesicles of mixed lipid composition are examined using nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) and fluorescence spectroscopy. As KL4, a 21 residue mimetic of surfactant protein B (SP-B), has been used to restore lung compliance and promote gaseous exchange in premature babies with respiratory distress syndrome (RDS); and has served as a model in elucidating the mechanism by which lipids are trafficked to and from the air-fluid interface of alveoli. Here we utilize a pyrene phospholipid analog to investigate the effect of KL4 on lipid organization and acyl chain dynamics by monitoring changes in excimer-to-monomer (Ie/Im) ratio. This experiment probes the environment of the hydrophobic core of DPPC/POPG and POPC/POPG liposomes. An average decrease of ∼27-40% and ∼0-10% in Ie/Im was observed in the DPPC/POPG and POPC/POPG LUVs, respectively, with increasing peptide concentration (0.5 to 5 mol%). This decrease is directly proportional to a lowered probability of excimer formation, which is highly dependent on proximal interactions of an excited monomer with a pyrene moiety at ground state. The ability of the peptide to modify membrane fluidity properties was studied via anisotropy measurements of a rhodamine-labeled phospholipid. A steady increase in the order was observed in the DPPC/POPG liposomes with relatively constant fluorescence intensity, while collisional quenching was observed in the POPC/POPG liposomes. Further studies were performed on the SP-B N and C-terminal constructs for correlation with NMR and EPR observations, and proposed mechanisms of peptide-mediated lipid trafficking.

LABCG2, a New ABC Transporter Implicated in Phosphatidylserine Exposure, Is Involved in the Infectivity and Pathogenicity of Leishmania

Leishmaniasis is a neglected disease produced by the intracellular protozoan parasite Leishmania. In the present study, we show that LABCG2, a new ATP-binding cassette half-transporter (ABCG subfamily) from Leishmania, is involved in parasite virulence. Down-regulation of LABCG2 function upon expression of an inactive mutant version of this half-transporter (LABCG2K/M) is shown to reduce the translocation of short-chain analogues of phosphatidylserine (PS). This dominant-negative phenotype is specific for the headgroup of the phospholipid, as the movement of phospholipid analogues of phosphatidylcholine, phosphatidylethanolamine or sphingomyelin is not affected. In addition, promastigotes expressing LABCG2K/M expose less endogenous PS in the stationary phase than control parasites. Transient exposure of PS at the outer leaflet of the plasma membrane is known to be one of the mechanisms used by Leishmania to infect macrophages and to silence their immune response. Stationary phase/metacyclic promastigotes expressing LABCG2K/M are less infective for macrophages and show decreased pathogenesis in a mouse model of cutaneous leishmaniasis. Thus, mice infected with parasites expressing LABCG2K/M did not develop any lesion and showed significantly lower inflammation and parasite burden than mice infected with control parasites. Our results indicate that LABCG2 function is required for the externalization of PS in Leishmania promastigotes, a process that is involved in the virulence of the parasite.

A Novel Nontoxic Inhibitor of the Activation of NADPH Oxidase Reduces Reactive Oxygen Species Production in Mouse Lung

1-Hexadecyl-3-trifluoroethylglycero-sn-2-phosphomethanol (MJ33) is a fluorinated phospholipid analog that inhibits the phospholipase A2 (PLA2) activity of peroxiredoxin 6 (Prdx6). Prdx6 PLA2 activity is required for activation of NADPH oxidase 2 and subsequent generation of reactive oxygen species (ROS). In vitro, MJ33 inhibited agonist-stimulated production of ROS by the isolated perfused mouse lung, lung microvascular endothelial cells, and polymorphonuclear leukocytes. MJ33 (0.02-0.5 µmol MJ33/kg body weight) in mixed unilamellar liposomes was administered to C57BL/6 mice by either intratracheal (i.t.) or i.v. routes. Lung MJ33 content, measured by liquid chromatography/mass spectroscopy, showed uptake of 67-87% of the injected dose for i.t. and 23-42% for i.v. administration at 4 hours postinjection. PLA2 activity of lung homogenates was markedly inhibited (>85%) at 4 hours postadministration. Both MJ33 content and PLA2 activity gradually returned to near control levels over the subsequent 24-72 hours. Mice treated with MJ33 at 12.5-25 µmol/kg did not show changes (compared with control) in clinical symptomatology, body weight, hematocrit, and histology of lung, liver, and kidney during a 30- to 50-day observation period. Thus, the toxic dose of MJ33 was >25 µmol/kg, whereas the PLA2 inhibitory dose was approximately 0.02 µmol/kg, indicating a high margin of safety. MJ33 administered to mice prior to lung isolation markedly reduced ROS production and tissue lipid and protein oxidation during ischemia followed by reperfusion. Thus, MJ33 could be useful as a therapeutic agent to prevent ROS-mediated tissue injury associated with lung inflammation or in harvested lungs prior to transplantation.

Selective Modification of Lipid Bilayer Dynamics and Fluidity Properties by Kl4 (Mimetic of Surfactant Protein B)

KL4, a 21 residue mimetic of surfactant protein B, is effective in the treatment of infant respiratory distress syndrome (RDS) and functions by lowering aveolar surface tension and promoting oxygen exchange. Here we compare the results from previous NMR investigations to those of fluorescence characterization of the effects of KL4 on the lipid dynamics and organization in liposomes. We utilized a pyrene phospholipid analog to investigate the effect of KL4 on lipid organization and acyl chain dynamics by monitoring changes in excimer-to-monomer (Ie/Im) ratio. This experiment probes the environment of the hydrophobic core of DPPC/POPG and POPC/POPG liposomes. An average decrease of ∼27-40% and ∼0-10% in Ie/Im was observed in the DPPC/POPG and POPC/POPG LUVs, respectively, with increasing peptide concentration (0.5 to 5 mol%). This decrease is directly proportional to a lowered probability of excimer formation, which is highly dependent on proximal interactions of an excited monomer with a pyrene moiety at ground state.The ability of the peptide to modify membrane fluidity properties was studied via anisotropy measurements of a rhodamine-labeled phospholipid. A steady increase in the order was observed in the DPPC/POPG liposomes with relatively constant fluorescence intensity, while collisional quenching was observed in the POPC/POPG liposomes. These observations agree with NMR observations and proposed mechanisms of peptide-mediated lipid trafficking. Further studies on the orientation and penetration of the peptide were interrogated using power saturation SDSL EPR.

Hepatoprotective activity of essential phospholipids, licorice, and their combinations tested on experimental hepatitis

One of the most important problems in treating hepatitis is the choice and rational use of hepatoprotective agents. The goal of the work was to compare the hepatoprotective activity of licorice and essential phospholipids from different manufacturers. The completed investigation found that three of four licorice preparations (glycyrrhizic acid, decoction of licorice root, and liquiriton) showed similar effectiveness whereas licorice syrup did not exhibit hepatoprotective activity. This indicated that triterpene and flavonoid glycosides contributed approximately equally to the hepatoprotective activity of licorice root. Preparations of essential phospholipid analogs had different efficiencies. Essentiale had the greatest hepatoprotective activity. Then, eslidin and essliver forte followed in descending order. The combined preparation phosphogliv showed the greatest effectiveness in therapy of experimental toxic hepatitis.

Boronic Acid Based Inhibitors of Autotaxin: Understanding their Biological Role in Terms of Quantitative Structure Activity Relationships (QSAR)

Autotaxin (ATX or NPP2) is a newly discovered secreted glycoprotein lyso-phospholipase D (lysoPLD). Its main role is the lysoPLD activity, which transforms lyso-phosphatidylcholine (LPC) into lyso-phosphatidic acid (LPA). ATX contributes to tumor progression, inflammation, obesity and diabetes and constitutes a target for drug design. Various synthetic phospholipid analogues have been explored as ATX inhibitors. However, potent and selective non-lipid inhibitors of ATX are currently not available. Some new ATX inhibitors have been subjected to a Quantitative-Structure Activity Relationships (QSAR) analysis. CMR represents the calculated molar refractivity of the molecules and seems to govern the ATX inhibition. Steric factors are obviously important. No role for lipophilicity was found. Electronic parameters are not found to be present. Keywords: Boronic Acid based Autotaxin Inhibitors, Hydrophobicity, Molar Refractivity, QSAR, lyso-phosphatidic, cell proliferation, phospholipase, macromolecular systems