Location of the toxic molecule abietic acid in model membranes by MAS-NMR

Terpenes-Modified Lipid Nanosystems for Temozolomide, Improving Cytotoxicity against Glioblastoma Human Cancer Cells In Vitro

Currently, increasing the efficiency of glioblastoma treatment is still an unsolved problem. In this study, a combination of promising approaches was proposed: (i) an application of nanotechnology approach to create a new terpene-modified lipid system (7% w/w), using soybean L-α-phosphatidylcholine, N-carbonyl-methoxypolyethylene glycol-2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine for delivery of the chemotherapy drug, temozolomide (TMZ, 1 mg/mL); (ii) use of TMZ associated with natural compounds-terpenes (1% w/w) abietic acid and Abies sibirica Ledeb. resin (A. sibirica). Different concentrations and combinations of terpene-lipid systems were employed to treat human cancer cell lines T 98G (glioblastoma), M-Hela (carcinoma of the cervix) and human liver cell lines (Chang liver). The terpene-lipid systems appeared to be unilamellar and of spherical shape under transmission electron microscopy (TEM). The creation of a TMZ-loaded terpene-lipid nanosystem was about 100 nm in diameter with a negative surface charge found by dynamic light scattering. The 74% encapsulation efficiency allowed the release time of TMZ to be prolonged. The modification by terpenes of TMZ-loaded lipid nanoparticles improved by four times the cytotoxicity against human cancer T 98G cells and decreased the cytotoxicity against human normal liver cells. Terpene-modified delivery lipid systems are of potential interest as a combination therapy.

Stimulation of Hemolysis and Eryptosis by α-Mangostin through Rac1 GTPase and Oxidative Injury in Human Red Blood Cells

BACKGROUND

Chemotherapy-related anemia is prevalent in up to 75% of patients, which may arise due to hemolysis and eryptosis. Alpha-mangostin (α-MG) is a polyphenolic xanthonoid found in the mangosteen tree (Garcinia mangostana) whose antitumor medicinal properties are well-established. Nevertheless, the potential toxic effects of α-MG on red blood cells (RBCs) have, as of yet, not been as well studied.

METHODS

RBCs were exposed to 1-40 μM of α-MG for 24 h at 37 °C. Hemolysis and related markers were measured using colorimetric assays, eryptotic cells were identified through Annexin-V-FITC, Ca2+ was detected with Fluo4/AM, and oxidative stress was assessed through H2DCFDA using flow cytometry. The toxicity of α-MG was also examined in the presence of specific signal transduction inhibitors and in whole blood.

RESULTS

α-MG at 10-40 μM caused dose-dependent hemolysis with concurrent significant elevation in K+, Mg2+, and LDH leakage, but at 2.5 μM it significantly increased the osmotic resistance of cells. A significant increase was also noted in Annexin-V-binding cells, along with intracellular Ca2+, oxidative stress, and cell shrinkage. Moreover, acetylcholinesterase activity was significantly inhibited by α-MG, whose hemolytic potential was significantly ameliorated by the presence of BAPTA-AM, vitamin C, NSC23766, and isosmotic sucrose but not urea. In whole blood, α-MG significantly depleted intracellular hemoglobin stores and was selectively toxic to platelets and monocytes.

CONCLUSIONS

α-MG possesses hemolytic and eryptotic activities mediated through Ca2+ signaling, Rac1 GTPase activity, and oxidative injury. Also, α-MG leads to accelerated cellular aging and specifically targets platelet and monocyte populations in a whole blood milieu.

Synthesis and Antibacterial Activity of Polyalthic Acid Analogs

Polyalthic acid (PA) is a diterpene found in copaiba oil. As a continuation of our work with PA, we synthesized PA analogs and investigated their antibacterial effects on preformed biofilms of Staphylococcus epidermidis and determined the minimal inhibitory concentration (MIC) of the best analogs against planktonic bacterial cells. There was no difference in activity between the amides 2a and 2b and their corresponding amines 3a and 3b regarding their ability to eradicate biofilm. PA analogs 2a and 3a were able to significantly eradicate the preformed biofilm of S. epidermidis and were active against all the Gram-positive bacteria tested (Enterococcus faecalis, Enterococcus faecium, S. epidermidis, Staphylococcus aureus), with different MIC depending on the microorganism. Therefore, PA analogs 2a and 3a are of interest for further in vitro and in vivo testing to develop formulations for antibiotic drugs against Gram-positive bacteria.

Enhanced Antibacterial Activity of Ent-Labdane Derivatives of Salvic Acid (7α-Hydroxy-8(17)-ent-Labden-15-Oic Acid): Effect of Lipophilicity and the Hydrogen Bonding Role in Bacterial Membrane Interaction

In the present study, the antibacterial activity of several ent-labdane derivatives of salvic acid (7α-hydroxy-8(17)-ent-labden-15-oic acid) was evaluated in vitro against the Gram-negative bacterium Escherichia coli and the Gram-positive bacteria Staphylococcus aureus and Bacillus cereus. For all of the compounds, the antibacterial activity was expressed as the minimum inhibitory concentration (MIC) in liquid media and minimum inhibitory amount (MIA) in solid media. Structure activity relationships (SAR) were employed to correlate the effect of the calculated lipophilicity parameters (logP_ow) on the inhibitory activity. Employing a phospholipidic bilayer (POPG) as a bacterial membrane model, ent-labdane-membrane interactions were simulated utilizing docking studies. The results indicate that (i) the presence of a carboxylic acid in the C-15 position, which acted as a hydrogen-bond donor (HBD), was essential for the antibacterial activity of the ent-labdanes; (ii) an increase in the length of the acylated chain at the C-7 position improved the antibacterial activity until an optimum length of five carbon atoms was reached; (iii) an increase in the length of the acylated chain by more than five carbon atoms resulted in a dramatic decrease in activity, which completely disappeared in acyl chains of more than nine carbon atoms; and (iv) the structural factors described above, including one HBD at C-15 and a hexanoyloxi moiety at C-7, had a good fit to a specific lipophilic range and antibacterial activity. The lipophilicity parameter has a predictive characteristic feature on the antibacterial activity of this class of compounds, to be considered in the design of new biologically active molecules.

Isolation of cellular membranes from lignin-producing tissues of Norway spruce and analysis of redox enzymes

There are no earlier reports with successful isolation of plasma membranes from lignin-forming tissues of conifers. A method to isolate cellular membranes from extracellular lignin-producing tissue-cultured cells and developing xylem of Norway spruce was optimized. Modifications to the homogenization buffer were needed to obtain membranes from these phenolics-rich tissues. Membranes were separated by aqueous polymer two-phase partitioning. Chlorophyll a determination, marker enzyme assays and western blot analyses using antibodies for each membrane type showed that mitochondrial, chloroplastic and to a certain extent also ER and Golgi membranes were efficiently diminished from the upper phase, but tonoplast and plasma membranes distributed evenly between the upper and lower phases. Redox enzymes present in the partially purified membrane fractions were assayed in order to reveal the origin of H(2)O(2) needed for lignification. The membranes of spruce contained enzymes able to generate superoxide in the presence of NAD(P)H. Besides members of the flavodoxin and flavodoxin-like family proteins, cytochrome b5, cytochrome P450 and several stress responsive proteins were identified by nitroblue tetrazolium staining of isoelectric focusing gels and by mass spectrometry. Naphthoquinones juglone and menadione increased superoxide production in activity-stained gels. Some juglone-activated enzymes were preferentially using NADH. With NADH, menadione activated only some of the enzymes that juglone did, whereas with NADPH the activation patterns were identical. Duroquinone, a benzoquinone, did not affect superoxide production. Superoxide dismutase, ascorbate peroxidase, catalase and an acidic class III peroxidase isoenzyme were detected in partially purified spruce membranes. The possible locations and functions of these enzymes are discussed.

Antimicrobial activity of coronarin D and its synergistic potential with antibiotics

Coronarin D is a labdane-type diterpene from the rhizomes of Hedychium coronarium. In the view of our ongoing effort to explore its novel biological activity, antimicrobial activity study of coronarin D was performed. The results showed that coronarin D was active against tested Gram-positive bacteria, inactive for tested Gram-negative bacteria, and weakly active against tested fungi. The antibacterial effect of the combination of coronarin D with nine classical antibiotics against four Gram-positive bacteria was also evaluated. The fractional inhibitory concentration indices (FICI) of coronarin D-antibiotics combinations, calculated from the checkerboard assay, were used as synergism indicator. Out of 36 combinations, 47% showed total synergism, 33% had partial synergistic interaction, 17% showed no effect, and 3% showed antagonism. By combination with coronarin D at concentration of 0.25 minimal inhibitory concentration (MIC), the activities of antibiotics were boosted to 4- to 128-fold. These finding suggested an attractive approach to combat the infectious diseases by using coronarin D-antibiotic drug combination.

A structure-activity study of antibacterial diterpenoids

An analysis of the antibacterial activities of 15 terpenoids, eleven of which were previously described by us and four were extracted from the literature, suggested two structural requirements for activity of these and related compounds: a hydrophobic moiety, consisting of a substituted decalin skeleton, and a hydrophilic region possessing one hydrogen-bond-donor group. These structural requirements are responsible for an optimal insertion of these and related compounds into cell membranes, as suggested by the results of docking some of these compounds into a model phospholipid bilayer.

Labdane-type diterpenes: thermal effects on phospholipid bilayers, incorporation into liposomes and biological activity

Labd-13(E)-ene-8alpha,15-diol (1) and its derivative labd-13(E)-ene-8alpha-ol-15-yl-acetate (2) are water insoluble biological active molecules and their structures were elucidated using NMR and X-ray techniques. Differential scanning calorimetry (DSC) was applied to study the thermal effects of 1 and 2 on DPPC bilayers. Liposomes composed of egg phosphatidylcholine/dipalmytoylphosphatidylglycerol (9:0.1 molar ratio) were prepared by the thin-film hydration method and were used for incorporating 1 and 2. Free and liposomal 1 and 2 were tested for their activity against human cancer cell lines using the sulphorhodamine B assay. The effect of 1 and 2 on DPPC bilayers caused abolition of the pre-transition temperature, lowering of the main phase transition and reduction of the transition enthalpy only in the presence of cholesterol. The liposomes that have been designed and developed offer high incorporation efficiency; 62.4% (0.369 drug/lipid molar ratio) and 99.7% (0.661 drug/lipid molar ratio) for 1 and 2, respectively. Liposomal 2 showed growth-inhibiting activity against the majority of the tested cell lines.

Location and orientation of Triclosan in phospholipid model membranes

Triclosan is a hydrophobic antibacterial agent used in dermatological preparations and oral hygiene products. Although the molecular mechanism of action of this molecule has been attributed to inhibition of fatty acid biosynthesis, earlier work in our laboratories strongly suggested that the antibacterial action of Triclosan is mediated at least partly through its membranotropic effects. In order to assess its location in phospholipid membranes, high-resolution magic-angle spinning natural abundance (13)C NMR of Triclosan embedded within egg yolk lecithin model membranes has been used to obtain (13)C spin-lattice relaxation times for both Triclosan and lecithin carbon atoms in the presence of Gd(3+ )ions. The results indicate that Triclosan is localized in the upper region of the phospholipid membrane, its hydroxyl group residing in the vicinity of the C = O/C2 carbon atoms of the acyl chain of the phospholipid, and the rest of the Triclosan molecule is probably aligned in a nearly perpendicular orientation with respect to the phospholipid molecule. Intercalation of Triclosan into bacterial cell membranes likely compromises the functional integrity of those membranes, thereby accounting for at least some of this compound's antibacterial effects.

A MAS-NMR study of the location of (+)-totarol, a diterpenoid bioactive molecule, in phospholipid model membranes

(+)-Totarol, a diterpenoid isolated from Podocarpus spp., is a potent antioxidant and antibacterial agent. Although the mechanism of action of this hydrophobic molecule is poorly understood, recent work from our laboratories suggests that it could be due to membranotropic interactions. The location of (+)-totarol in membranes and its interaction with membrane components is therefore of considerable interest. High resolution magic angle spinning (MAS) natural abundance 13C nuclear magnetic resonance studies were undertaken to assess the location of (+)-totarol in model membranes composed of egg yolk phosphatidylcholine (EYL). 13C spin-lattice relaxation times (T(1)) of both the phospholipid and (+)-totarol molecules in the presence of Gd(3+) were measured to obtain information on molecular distances. Our results indicate that (+)-totarol is situated in the upper region of the membrane, with its hydroxyl group located in the vicinity of the C-3/4 carbon atoms of the phospholipid acyl chain, and nearly perpendicular with respect to the phospholipid acyl chain axis. Such a location of (+)-totarol in the membrane would be expected to compromise the functional integrity of the membrane and account, at least in part, for its antibacterial effects.

Effects of (+)-totarol, a diterpenoid antibacterial agent, on phospholipid model membranes

(+)-Totarol, a highly hydrophobic diterpenoid isolated from Podocarpus spp., is inhibitory towards the growth of diverse bacterial species. (+)-Totarol decreased the onset temperature of the gel to liquid-crystalline phase transition of DMPC and DMPG membranes and was immiscible with these lipids in the fluid phase at concentrations greater than 5 mol%. Different (+)-totarol/phospholipid mixtures having different stoichiometries appear to coexist with the pure phospholipid in the fluid phase. At concentrations greater than 15 mol% (+)-totarol completely suppressed the gel to liquid-crystalline phase transition in both DMPC and DMPG vesicles. Incorporation of increasing amounts of (+)-totarol into DEPE vesicles induced the appearance of the H(II) hexagonal phase at low temperatures in accordance with NMR data. At (+)-totarol concentrations between 5 and 35 mol% complex thermograms were observed, with new immiscible phases appearing at temperatures below the main transition of DEPE. Steady-state fluorescence anisotropy measurements showed that (+)-totarol decreased and increased the structural order of the phospholipid bilayer below and above the main gel to liquid-crystalline phase transition of DMPC respectively. The changes that (+)-totarol promotes in the physical properties of model membranes, compromising the functional integrity of the cell membrane, could explain its antibacterial effects.